EPA 560/6-77-007
ASSMEUI of m m
AND ECOliiC
on IMPIHK
THE
OF PUBS
JULY 1977
IfflENTAL PROTECTION AGENCY
u...JEOF TOXIC SUBSTANCES
WASHINGTON, D.C., 20460
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Document is available to the public through, the National
Technical Information Service, Springfield, Virginia, 22151. •
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EPA 560/6-77-007
ASSESSMENT OF THE ENVIRONMENTAL AND
ECONOMIC IFPACTS OF THE BAN ON TORTS OF PCBs
FINAL TASK REPORT
Submitted to:
U.S. Environmental Protection Agency
Office of Toxic Substances
Special Projects Branch
Washington, D.C.
Contract No. 68-01-3259
Task 6
Submitted by:
VEPSAR INC.
6621 Electronic Drive
Springfield, Virginia 22151
July 8, 1977
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This report has been reviewed by the Office of Toxic Substances,
U.S. Environmental Protection Agency, and approved for publication. Approval
does not signify that the contents necessarily reflect the views and policies
of the Environmental Protection Agency, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use. -
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' 'PREFACE
This report surmari2es an investigation into .the uses of imported poly-
chlorinated biphenyls CPCBs) in the United States. Imported PCBs are presently-
used only for the maintenance, of certain mining machinery. In addition, PCBs
are present as a significant impurity in polychlorinated terphenyls (PCTs)
imported for use in investment casting waxes. Importation of PCBs for these
uses will be banned after 1977 by the Toxic Substances Control Act, unless
exemptions are allowed in accordance with the provisions of the Act. Recent
PCB-related directives of the European Economic Community and the Organization
for Economic Co-Operation and Development, plus legislation in Canada, permit
at least temporarily the continued use of PCBs in mining applications but
prohibit Cor at least discourage) their use in tooling compounds and investment
casting waxes.
This report was prepared by Mr. Robert P. Burruss, Jr., P.E., Task
Manager. The author wishes to thank Thomas Kbpp of the Office of Toxic Substances
of the Environmental Protection Agency for his patience during the preparation
of this report. Many thanks are due Charles Gonzalez of the "off ice of U.S-. •
Representative Les Aspin (p-Wisc.) for ftis aid in the gathering of import
statistics, and to Les Aspin for forwarding the most recent import data. Grat-
itude is also extended to William Siegfried, Chief Chemist of the Freeman
Manufacturing Company in Cleveland, Ohio,, for answering many questipns concern-
ing components and fillers used in investment casting waxes; to Paul Solomon of
the Yates Manufacturing Company in Chicago, Illinois, for clarifying the current
status, of PCBs in the investment casting industry; to the American Society for
Metals for permitting the. use of diagrams from their Metals Handbook; and to
Henry Bidwell of the Investment Casting Institute in Dallas, Texas, for supply-
ing economic information on the investment casting industry and for generally
being available to answer questions as they arose. The. author is -also grateful
to James Barden of this office for his diligent data gathering efforts and to
Bruno Rey-Coquais of Prodelec for contributing to our awareness of international
efforts to control PCBs.
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TABLE OF CONTENTS
Page
1.0 INTRODUCTION 1
1.1 Uses of Imported PCBs and PCTs 1
1.1.1 Coolants for Mining Machinery 2
1.1.2 . Tooling Compounds 3
1.1.3 Investment Casting Waxes 3
1.2 Import Volume 1972 through 1976 4
1.3 Summary of Present Situation 4
1.4 Conclusions and Recommendations 5
2.0 IMPORTS 8
2.1 PCBs 8
2.2 PCTs 11
2.3 Importers 13
2.4 Discrepancies in Import Data . . . . 13
2.5 PCBs - What Other Nations are Doing 14
2.5.1 Canada 14
2.5.2 OECD 15
3.0 MINING MACHINERY COOLANTS 19
3.1 Portion of the Total Number of Mining Machines
Containing. PCBs . 21
3.2 Impact of the Toxic'Substances Control Act ........ 21
4.0 TOOLING COMPOUNDS . . . 24
5.0 THE INVESTMENT CASTING INDUSTRY 28
5.1 Introduction to Investment Casting 28
5.1.1 Making the Dies for the Production of Wax Patterns . 30
5.1.2 Production of the Wax Patterns . 31
5.1.3 Pattern Assembly 32
5.1.4 Investing the Wax Patterns and Producing the
Ceramic Molds 35
5.1.5 Removing Wax Patterns from the Ceramic Molds .... 36
5.1.5.1 Dewaxing of Shell Investment Molds .... 37
5.1.5.2 Dewaxing of Solid Investment Molds . . .'. 40
5.1.6 Firing and Preheating the Molds 41
5.1.6.1 .Furnace. Operation and Temperature 43
5.1.6.2 Mold Preheat Temperature 43
5.1.6.3 Wax Losses to the Environment During
Firing and Preheating 44
5.1.7 Metal Casting . 46
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TABLE OF CONTENTS, (Gon't)
5.2 Mvantages and Limitations of Investment Casting 46
5.2.1 Dimensional Accuracy 46
5.2.2 Surface Finish 48
5.2,3 Costs 50
5.2.3.1 Cost Comparison: Ceramic Shell vs Solid
Investment Processes 50
5.2.3.2 Cost as a Function of Investment Casting
Tolerance 55
5.2.4 Costs of Alternative Metal-Forming Processes .... 55
5.2.4.1 Sand Casting vs Investment Casting 57
5.2.4.2 One-Piece Investment Casting vs Welded
Assemblies 58
5.2.4.3 Investment Casting vs Machining from
Bar Stock 58
5.2.5 Discussion of Alternative Metal-Forming Methods to
Investment Casting 61
5.2.5.1 Shell Molding 62
5.2.5.2 Die Casting •; 63
5.2.5.3 Permanent Mold Casting 63
5.2.5.4 Powder Metallurgy (P/M) 64
5.2.6 Disadvantages of Investment Casting 65
5.3 Size of Investment Casting Industry . 65
. 5.3.1 Employment and Value of Shipments 65-
5.3.2 Growth of the Investment Casting Industry 68
6.0 INVESTMENT CASTING WAXES 72
6.1 Background 73
6.2 Desirable Wax Properties 75
6.3 Filled and Unfilled Waxes . 76
6.3.1 PCBs and PCTs in Waxes 77
6.3.1.1 Decachlorobiphenyl: History and Advantages 78
6.3.1.2 Polychlorinated Terphenyl: History
and Advantages 81
6.3.1.3 Current PCB/PCT Use and Current and
Impending Legislation 82
6.3.2 Disadvantages of PCB/PCT'Waxes "... 82
6.3.2.1 Environmental Stability of Decachlorobiphenyl
and Polychlorinated Terphenyl 84
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TABLE OF CONTENTS, (Can't)
6.3.2.2 Sources of PCB/PCT Loss to the Environ-
ment in the Investment Casting Industry 86
6.3.2.3 Sources of PCB/PCT Loss to the Environ-
ment in Wax Manufacturing SO
6;4 Wax Manufacturers 90
6.5 Sources of PCB/PCT Supply 92
6.5.1 Domestic Sources 92
6.5.2 Imports 93
6.6 Alternative Pattern Materials and Wax Fillers and
Components 93
6.6.1 Previously-Used Pattern Materials . 94
6.6.2 The Ideal Pattern Wax 96
6.6.3 Filled and Unfilled Waxes 96
6.6.3.1 PCBs 100
6.6.3.2 PCTs 100
' 6.6.3.2.1 Function of PCTs in Waxes ... 100
6.6.3.2.2 Dependency on the Investment
Casting Industry upon PCTs . . 101
6.6.4 Alternatives to PCTs in Investment Casting Waxes . . 103
6.6.5 Environmental and Toxicological Hazards of
Alternatives 106
7.0 PCBs AS IMPORT COMPONENTS . . . 110
8.0 CONCLUSIONS AMD RECOMMENDATIONS 112
APPENDIX A - METAL FORMING TECHNIQUES: COMPARED WITH INVESTMENT
CASTING
APPENDIX B - GLOSSARY OF WAXES, RESINS, AND CHEMICALS ASSOCIATED
WITH INVESTMENT CASTING WAXES
APPENDIX C - DIRECTIVES OF THE COUNCIL OF THE ORGANIZATION FOR
CO-OPERATION AND ECONOMIC DEVELOPMENT (OECD)
C-l: Decision of the Council of the Organization for
Economic Co-Operation and Development (OECD),
February 13, 1973
C-2: Directive of the Council of the European Economic
Community (EEC), July 27, 1976
IV.
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LIST OF TABLES
Table
2.1-1 PCS Imports 1971-1976 9
2.2-1 PCT Imports 1972-1976 12
5.1 Approximate Ranges of Surface Roughness for Steel Castings
Weighing up to 5 Ibs., Made by Four Processes 49
5.2 Typical Minimum and Maximum Roughness of Type 316 Stainless
Steel Fittings Cast by Three Different Processes 49
5.3 Ranges of Surface Roughness of Investment Casting of Five
Different Metals, as Measured in Two Different Plants 51
5.4 Cost Analysis of Typical Investment Casting 52
5.5 Comparison of Costs for Producing Castings by the Ceramic
Shell and Solid Investment Processes 54
6.5 Effect of the Tightening of Dimensional Tolerance on the
Cost of a Part Produced from a Steel Investment Casting 56
5.7 Machined Sand Casting vs Machined Investment Casting 59
5.8 Employment and Value of Shipments for the Investment
. Casting Industry 67
6.1 Status of State Legislation Restricting Manufacturing,
Use and Sale of PCBs and PCT Compounds 83
6.2 Lists of I.C. Wax Manufacturers 91
v.
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LIST OF FIGURES
Figure Page
5.1 Steps in the Production of a Casting by the Shell
Investment Molding Process . 33
5.2 Steps in the Production of a Casting by the Solid
Investment Molding Process 34
5.3 Typical Pieces for Two Brazing Fixtures that were Made at Less
Cost by Investment Casting than by Machining from Bar Stock ... 60
6.1 Flow Chart of Wax Usage in Investment Casting 87
6.2 Flow Chart Showing Probable Sources of Environmental
Pollution from a Typical Investment Casting Foundry 88
VI.
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1.0 INTEDDUCTICN
In April of 1971, the Monsanto Company voluntarily ceased production of
polychlorinated biphenyls (PCBs) destined for open-system uses - that is, those
uses where losses of PCBs to the environment can not be readily controlled. The
main uses for which Monsanto continues to produce PCBs are electrical capacitors
and transformers, closed systems where the PCBs are used as fire resistant
dielectric fluids and coolant fluids respectively. In these closed circuit
applications, the PCBs are completely contained and do not normally leak into
the environment during use of the equipment. It is therefore feasible to recover
the PCBs at the termination of the service life. Recovery of PCBs is not feasible
in such applications as carbonless copy paper, plasticizers, pesticide extenders,
hydraulic fluids, adhesives, inks, and lubricants. Thus, as of 1971, users of
PCBs in open-system applications have relied on imported PCBs. It is the purpose
of this report to examine the current uses of imported PCBs and the current eco-
nomic dependence on imported PCBs, and to recommend steps to control the imports
of PCBs and the consequent losses of this toxic chemical to the U.S. environment.
Related to the problem of polychlorinated biphenyls is that of polychlorinated .
terpehenyls (PCTs), some batches of which have been' found to contain over 0.5 .
percent PCBs as a by-product of their manufacture. PCTs, since they are closely
related chemically to .PCBs, may also be an environmental hazard in their own
right. In April of 1972, Monsanto ceased production of PCTs for all applications,
and users were forced to import PCTs. Tivian Laboratories of Providence, Rhode
Island, is the only U.S. distributor of PCTs. For the past several years, Tivian
Laboratories has been certifying that the PCTs which they have sold to M. Argueso
& Co., have contained less than 0.05% PCBs. Thus, in total, this report examines
the uses of and current economic dependence upon imported PCBs and PCTs.
1.1 Uses of Imported PCBs and PCTs
There is only one current use of imported PCBs: Pyralene 3010, a
French PCS compound, is used by the Joy Manufacturing Company of Pittsburgh as
a non-flammable cooling fluid in mining machinery. Sections 2.0 and 3.0 list
the volumes of PCBs imported during the years 1972 through 1976. Imports, of
Pyralene increased by a factor of nearly three in 1976 over the previous year.
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Polychlorinated terphenyls are used in investment casting waxes and in
tooling compounds. The latter application accounts for only-2 to 3 percent of the
terphenyl imported for use in investment casting waxes. Of the eleven domestic
investment casting wax producers, at least six have produced terphenyl waxes, and
three manufacturers are currently using PCTs in their wax formulations.
Since the bulk of the imported polychlorinated polycyclic compounds are
used in investment casting waxes, the investment casting industry and the wax manu-
facturing industry are the central topics of this report. Data on mining machinery
coolants and tooling compounds are scant; Sections 3.0 and 4.0 respectively summa-
rize current _information on these applications.
1.1.1. Coolants for Mining Machinery
Among the advantages of polychlorinated biphenyls in industrial
applications is their inertness and nonflammability. These properties make PCBs
useful as heat transfer fluids in high tsnperature applications, the most well-
known application being as a coolant for large electrical transformers. Electrical
transformers, however, are not included in this report because Monsanto still pro-
duces PCB fluids for closed applications where .there is a high probability the
material will eventually be recovered and properly destroyed. With regard to. ,
mining machinery, though, PCB fluids offer many of the same advantages they offer
in transformers; low combustion hazard in the event of a leak from or into a
high tsnperature environment, very low electrical conductivity, and inertness that
minimizes system corrosion even at continuous high operating temperatures.
Monsanto will cease producing all PCB formulations by the end
of 1977. Transformer manufacturers are in the process of finding cost-effective
alternative materials that provide adequate service. The fluid used in place of
PCBs will have to be nonflammable, inert at high temperatures, noncorrosive to the
containing systan, and reasonable in price. Section 3.0 shows import trends for
PCB mining machinery coolant for the period 1972 through 1976.
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1.1.2 Tooling Compounds
Tooling compounds are wax-like materials used to fill thin-walled
structures made of metal, plastic, glass or other materials so that machining can
be performed without bending or buckling or otherwise damaging the structure.
Aluminum or steel honeycomb structure of the kind used widely in aerospace applica-
tions is a prime example of the type of material in which tooling compounds are
used. Unless the honeycomb cells are filled with some easily removable but other-
wise rigid material during cutting or machining operations, the cell walls can be
easily damaged. Such damage to the cell walls will reduce the strength and rigidity
of the finished panel.
The properties of tooling compounds are similar to those of invest-
ment casting waxes: they must remain hard at temperatures close to the melting
temperature of the wax because machining operations cause localized heating, and they
should undergo minimal shrinkage during solidification and cooling. PCTs are used
in tooling compounds to provide all of these properties. PCT-type tooling compounds
*
contain 8 and 40 percent PCTs by weight. Alternatives to PCTs will have to provide
approximately these same properties. Section 4.0 summarizes information taken from
patents and from conversations-with the single PCT tooling-compound manufacturer.
r * (
1.1.3 Investment Casting Waxes
There are eleven domestic manufacturers of investment casting
wax, and there are about 150 investment casting foundries. Of the investment casting
wax manufacturers, only three currently produce PCT waxes for those foundries that
use PCT waxes. Of the remaining wax manufactures, one of the major ones voluntarily
ceased production of waxes containing chlorinated and nitrogenous components in the
early part of 1975; another stopped production of terphenyl waxes when Monsanto
stopped producing PCT in 1972; and a third producer stopped manufacturing terphenyl
waxes sometime within .the last seven years.
Section 5.0 characterizes the technique of investment casting and
the investment casting industry. Section 6.0 deals specifically with investment
casting waxes. Both these sections discuss the use of PCB filler material (decachloro-
biphenyl) which was used in one manufacturer's wax formulation until the middle of
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1976 when the passage of state legislation banning the use of all PCBs forced
termination of the manufacture of PCB-containing waxes. Import data shown in
Sections 2.0, 5.0 and 6.0 indicate an increase'in the imports of PCTs.
1.2 Import Volume 1972 through 1976
Data from U.S. Customs on the imports of PCBs and PCTs. are summarized
below. Domestic production of PCBs was terminated for most applications in
April 1971; terphenyl production was terminated the following year. Hence, PCB
and PCT imports began in earnest in 1972 and 1973 respectively. Shown in the table
are imports of PCTs and decachlorobiphenyl (both used in investment casting waxes)
and of other PCB formulations:
Year
1972
1973
1974
1975
1976
PCTs
(Ibs)
0
163,101
290,866
273,375
275,576
Decachlorobiphenyl
(Ibs)
3,547
109,060
0
149,914
0
Other FCBs
(Ibs)
394,912
36,420
50,795
48,501
113,581
In 1976, all the PCBs imported were from France and the port of entry,
according to Customs, was Pittsburgh, indicating that all of the PCB was destined
for use in mining machinery produced by the Joy Manufacturing Company. While it
is apparent from the above tabulation that PCB imports decreased significantly
between 1975 and 1976, two things should be noted: (1) the 1976 imports are more
than twice those of 1974, and (2) the volume of PCBs destined for Pittsburgh in 1976
are nearly three times the amount in 1975. (See Sections 2.0 and 3.0.)
Terphenyl imports increased to a maximum in 1974 and have held nearly
constant since. The bulk of imported terphenyls are used in investment casting
waxes, and the rest is used in tooling compounds.
1.3 Summary of Present Situation
At the present .time there are only four manufacturers who use imported
polychlorinated polycyclic materials; one of them is the sole user of imported PCBs
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for use in mining machinery; two of them use terphenyls in investment casting
waxes; and one uses terphenyls in investment casting waxes and tooling compounds.
There are, however, about 150 domestic investment casting foundries.
Not all of these foundries use PCT-containing waxes, but among those that do, the
feeling may prevail that PCT waxes offer the best properties for the particular
foundry's operations and types of objects being cast. Such a feeling may be without
foundation though, since there is ample evidence that precision investment casting
foundries can convert over to and rely entirely upon non-PCT waxes. The General
Electric foundry in Albuquerque, New Mexico, is an example; their primary product
is blades for gas turbine engines, parts which are very sensitive to deviations from
optimum surface finish and dimensional tolerances.
In early 1975, one wax manufacturer, the Freeman Manufacturing Company of
Cleveland, Ohio, voluntarily terminated production of waxes containing either PCTs
or nitrogenous components. While this company underwent some economic impact as
a result of their decision, suitable substitutes for PCTs were eventually found, -
and Freeman has retained its position among the largest wax manufacturers.
1.4 Conclusions and Recommendations
Imported polychlorinated biphenyls are currently used by only one manu-
facturer in the U.S. The specific PCS formulation is called Pyralene 3010 and it
is imported from France. It is used as a cooling fluid for mining machinery motors.
Imported terphenyls are used by three manufacturers of investment casting
waxes; one of the manufacturers also produces a line of terphenyl-containing tooling
compounds. The volume of terphenyl used in tooling compounds "is on the order of
only several percent of the terphenyl consumed in casting waxes; and terphenyl casting
waxes account for less than half the wax sales of at least two of the three terphenyl
casting wax producers.
Although one wax manufacturer has stated-that there are no adequate sub-
stitutes for polychlorinated terphenyl in waxes, at least three of the eleven wax
manufacturers in this country have terminated terphenyl wax production within the
last eight years. One of these companies voluntarily terminated production of
terphenyl waxes in early 1975; and though this company did not economically benefit
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by its decision, it is still very conpetitive and claims to have found alternatives
to PCTs that perform almost if not just as well as terphenyls in most applications.
With regard to the 150 or so investment casting foundries, at least one
has instituted a policy of using no casting waxes containing either PCBs or PCTs.
This foundry produces turbine blades for gas turbine engines, engines that are
used in commercial and military aircraft that are used throughout the world. That
such parts as turbine engine components - which must operate with the highest
reliability under conditions of extreme thermal and mechanical stress - can be
investment cast using wax patterns that do not contain PCTs makes one wonder what
exactly is meant by the phrase "there are no adequate substitutes for PCTs in invest-
ment casting waxes." This turbine-blade foundry is currently conducting a detailed
study of the economic and process effects of its decision against PCS and PCT waxes.
The problem of how to control the use of imported PCBs has to an extent
been obviated by the implementation of the Toxic. Substances Control Act, which
sets definite time limits on PCS importation. PCBs are currently imported for the
single purpose of maintenance of mining machinery that uses PCB fluids as coolants
for the electric drive motors. Depending upon the interpretation of the act, PCB-
containing machines may have to be put out of service at the end of 1977 unless.
either (1) the machinery is modified to dry-type drive motors,, or (2) the EPA,
in accordance with Section 6 (e) (2) (B) of TSCA, authorizes the continued use of
PCBs in the mining machinery based on a formal finding that such use will not pre-
sent an unreasonable risk of injury to health or the environment. The Feb. 13,
1973 Decision of the Organization for Economic Co-Operation and Development (CECD),
of which the U.S. is a member (Appendix C-l contains a copy of this Decision) ,
recommends that member nations ban the use of PCBs in all but four specific cate-
gories, one of which is mining machinery. This Decision might be cited by U.S.
mining machinery owners as a precedent in petitioning for an exemption from the
Toxic Substances Control Act. (Section 2.5 describes OECD).
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A Directive of .the Council of the EEC "{European Economic Conmunity,
or Common Market), dated' July 27, 1976, restricts, member nations from using
PCBs after January 1978 in all but six specific categories, one of which.
includes mining machinery. (Appendix C-2 contains a copy of this Directive.)
The United States is not, of course, a member of the. EEC, but owners and users
of PCB-containing mining machinery in this country might', cite the EEC Directive
of July 27, 1976 as evidence of the importance of allowing continued use of
currently operable PCB-containing mining machinery until the machinery is no
longer operable.
The control of PCT imports and PCT use presents, however, a slightly
different problem. Since it has been shown that polychlorinated terphenyls may
contain between 0.5 and 10 percent PCBs (probably arising as a by-product in the
manufacturing process), imports of PCTs might conceivably be treated as imports
of PCBs, and the appropriate provisions of the Toxic Substance Control Act could
then be applied to terminate importation.
A second control alternative for PCTs is to show that PCTs "present an
unreasonable risk of injury to health or the environment", in which case the Toxic
Substances Control Act would be applied as in the case of PCBs. The presence of
PCBs in imported PCTs might constitute sufficient evidence of unreasonable risk
of injury to the environment. It should be borne in mind, however, that pure
polychlorinated terphenyls have not been shown to be a serious hazard to human
health or to the environment, even though terphenyls are closely related to poly-
chlorinated biphenyls and are highly persistent in the environment.
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2.0 IMPORTS
Imports of polychlorinated biphenyls during the years 1972 through 1976 cams
primarily from France, Italy and Japan, with small amounts imported from Canada
and West Germany. All of the. decachlorobiphenyl used in one manufacturer's
casting waxes (until the middle of 1976) originated in Italy during these years,
and the port of entry was Chicago, except one relatively small shipment to Philadelphia
in 1972.
All of the polychlorinated terphenyl imported to the U.S. came from France
during the years 1973 through 1976. The main ports of entry were New York, Philadelphia,
Los Angeles and Baltimore.
In the following two sections, import data on PCBs and PCTs are discussed in
detail in terms of volume, source and destination.
2.1 PCBs
Data from the U.S. Customs on PCS imports is shown in chronological order
in Table 2.1-1. This.information can be broken down in the following way:
Decachlorobiphenyl
Total PCBs Imported Imported Comments '
1972 398,459 Ibs 3,547 Ibs 240 Ib deca to Chicago
3307 Ib deca to Philadelphia
1973 145,480. 109,060 all deca to Chicago
1974 50,795 0 — '
1975 198,415- 149,914 all deca to Chicago
1976 113,581 0 all imports to Pittsburgh,
Pyralene 3010
Since decachlorobiphenyl is no longer used in investment casting waxes,
it is unlikely that large volumes will ever be imported again. All the imports in
1976 were Pyralene 3010 shipped from France to Pittsburgh where it is used as a
motor coolant in mining machinery produced by Joy Manufacturing Company.
Imports of Pyralene 3000 and Pyralene 3010 to Pittsburgh have been as
follows:
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Table 2.1-1
PQ3 ImiJOfts 1972-1976
(2)
VO
I
QUANTITY
TRADE NAME
Pyralene 3000
Chemical Solvent K500
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Pyroclor
Cloresil 100
Decachlorobiphenyl
Decachlorobiphenyl
Chemical Solvent K500
Chemical Solvent K500
Chemical Solvent K700
Chemical Solvent K700
Pyralene 3000
Pyralene 3000
Decachlorobiphenyl
Decachlorobiphenyl
Pyralene 3000
Pyralene 3000
Decachlorobiphenyl
Dccachlorobiplienyl
Decachlorobiplvenyl
Docachlorobipl leny 1
pa wins
1,235
12,000
13,228
13,228
661
14,000
240
3,307
3,000
43,200
30, 000
115,200
13,580
13,580
2,205
11,023
13,500
22,840
40,013
15,784
22,399
17,636
METRIC 'TONS
0.560
5.44
6
6
0.30
14
0.24
.1.5
1.36
19.6
13.6
52.25
6.16
6.16
1.0
5
6.16
10.36
18.15
7.16
10.16
8
COUNTRY OF ORIGIN
France
Japan
• Japan
Japan
England
Italy
Italy
Italy
Japan
Jai-an
Japan
Japan
France
France
Italy
Italy
Frai ice
France
Italy
Italy
Italy
Italy
PORT OF ENTRY
Pittsburgh
Baltunore
New York
New York
New York
Chicago
Chiciigo
Philadelphia
los Angeles
Philadelphia
Philadelphia
Philadelphia
Pittsburgh
Pittsburgh
Chicago
Cliicago
Pittsburgh
Pittsburgh
Chicago
Chicago
Cliicago
Cliicago
ENTRY-NO.
102844
CE 137387
473422
506436
ID-N-4193
C-101860
C-101860
DC 102840
73-108967
DC 110107
DC 110107
111238
101898
101899
C-133511
C-135916
102607
103831
C-103875
C-104346
C-l 09141
C-109077
ENTRY DATK
4-4-72
5-15-72
5-23-72
6-22-72
7-2-72
7-13-72
7-13-72
7-18-72
7-31-72
8-23-72
8-23-72
8-30-72
12-14-72
12-14-72
1-9-73
1-24-73
2-15-73
5-21-73
7-25-73
7-26-73
8-22-73
8-22-73
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Table 2.1-1 (Con't)
O
TUADE NAME
Pyralene 3000
Pyralene 3000
Trichlorinated Diphenyl
Clophen Insulating Fluid
Pyralene 3000
Decachlorobiphenyl
Docachlorobiphcnyl
Decachlorobiphenyl
Decachloroblphenyl
Decachlorobiphenyl
Thermlnol FR1
Pyralene 3000
Pyralene 3010
Pyralene 3010
Pyralene 3010
POUNDS
25,926
20,988
1,235
2,646
20,988
17,637
39,683
13,228
39,683
39,683
6,525
20,988
20,988
30,864
61,729
METRIC TONS
11.76
9.52
.56
1.2
. 9.52
8.0
10
6.03
18
18
2.96
9.52
9.52
14
28
COUNTRY OF ORIGIN
France
France
France
W. Germany
France
Italy
Italy
Italy
Italy
Italy
Canada
France
France
France
France
POUT OF ENTRY
Pittslxirgh
Pittsburgh
New York
Jamaica
Pittsburgh
Chicago
Chicago
Chicago
Chicago
Chicago
Buffalo
Pittsburgh
Pittsburgh
Pittsburgh
Pittsburgh
ENTRY NO.
103140
100007
121619
K242989
102930
C-131926
C-134234
C-137905
C-142213
C-142938
CE 291970
100766
103693
. 105001
105855
ENTRY DATE
3-12-74
7-1-74
7-19-74
11-19-74
1-13-75
1-14-75
1-30-75
3-4-75
4-10-75
4-19-75
5-14-75
8-22-75
3-9-7C,
5-27-76
7-22-76
-------
Pyralene 3000
28,395 Ibs
36,420
46,914
41,976
Pyralene 3010
1972
1973
1974
.1975
1976 113,581 Ibs
That the amount imported in 1976 was almost three times the amount imported
in 1975, may indicate stockpiling in anticipation of an import ban. No other informa-
tion is available at this time with respect to the finding of alternative materials
for PCBs cooling fluids in mining machinery.
2.2 PCTs
PCT import data from U.S. Customs is shown in chronological order for the
years 1973 through 1976 in Table 2.2-1. Import volumes for each of the years listed
are as follows:
1972
1973
1974
1975
1976
Total PCTs Imported
163,101 Ibs
290,866
273,375
275,576
Electrophenyl T60
Imported
119,049 Ibs
three shipments to
New York
158,710
four shipments to
New York
218,212
four shipments to
New York; two to
Philadelphia
231,484
three shipments to
New York; two to
Los Angeles; one
to Philadelphia
Terphenyl Chlore T60
Imported
44,052 Ibs
one shipment to Baltimore
132,156
two shipments to Baltimore,
one to Los Angeles
44,052
one shipment to Los Angeles
44,092
one shipment to Los Angeles
Total terphenyl imports for the three years 1974 through 1976 have been
about constant, with the import rate of Electrophenyl T60 increasing steadily while
the import rate of Terphenyl Chlore T60 has correspondingly decreased.
-11-
-------
Table 2.2-1
PCf Imports 1972-1976
(1)
QUANTITY
TRADE NAME
Electrophenyl T60
Electrophenyl T60
Electrophenyl TCO
Terphenyl Chlore T60
Terphenyl dilore T60
Terphenyl Chlore T60
Electrophenyl T60
Electrophenyl T60
Terphenyl Clore TGO
Electrophenyl T60
Electrophenyl T60
Electrophenyl TGO
Electrophenyl T60
Electrophenyl T60
Terphenyl Chlore T60
Electrophenyl 801
Electroplienyl T60
Electrophenyl T60
Terphenyl Chlore T60
Electroplienyl T60
Electroplienyl T60
Electroplienyl T60
Electroplienyl T60
Electrophenyl T60
Electrophenyl T60
rCXMDS METRIC TONS
39,683
39,683
39,683
44,052
44,052
44,052
39,683
39,683
44,052
39,683
39,661
39,683
79,322
33,069
44,052
11,111
33,069
33,069
44,092
39,683
39,683
39,683
39,683
33,069
39,683
18 Mr
18
18
20
20
20
IB '
18
• 20
18
18
18
36
15
20
5
15 .
15
20
18
18
18
18
15
18
COUNTRY OF ORIGIN
France
Frarioe
France
France
France
France
France
France
France
France
France
France
France
France
France
France
France
France
France
France
France
France
France
France
France
POKI1 OF ENTRY
New York
New York
New York
Baltimore
Ins Angeles
Baltimore
New York
New York
Baltimore
New York
New York
New York
Now York
New York
Los Angeles
New York
Philadelphia
Philadelphia
I os Angeles
New York
New York
Jos Angeles
New York
Philadelphia
las Angeles
ENTRY NO.
102070
179326
236336
CK 121166
74-174095
(pre-entry)
385738
453564
03 109G37
171776
228680
289541
326189
427772
75-231060
531765
DC 11A274
DC-134BB9
76-209333
334666
338185
76-238985
607633
DC-114763
77-147176
BtrKt DATH:
7-5-73
9-10-73
103-1-73
11-30-73
1-16-74
2-27-74
3-19-74
5-22-74
8-26-74
8-27-74
10-15-74
1-17-75
2-14-75 .
4-18-75
6-2-75
6-26-75
10-6-75
12-11-75
3-18-76
3-18-76
3-23-76
5-19-76
9-10-76
12-6-76
12-27-76
-------
Assuming all of the imported terphenyl goes into investment casting
waxes, it is likely that all terphenyl entering the U.S. through Los Angeles pro-
bably goes to the single west coast terphenyl-wax manufacturer, J. F. McCoughlin
Co., in Rosemead, California, though this company also purchases terphenyl from
east coast importers. The remainder delivered to the east coast probably goes to
Yates Manufacturing in Chicago and M. Argueso & Co., in Mamaroneck, New York, with
a small amount going to Kindt-Collins in Cleveland, Ohio. West Coast terphenyl
imports have increased dramatically in 1976: 44,052 pounds in 1974 and 1975, and
123,458 pounds in 1976. Again, this may be evidence of stockpiling in view of a
possible import ban, but it might also indicate that either the other west coast
wax producer is now using terphenyl also, or that other terphenyl uses have been
initiated.
2.3 Importers
Pyralene for the Joy Manufacturing Company is purchased in France
by a Joy subsidiary, Joy Ville-Gozet, S.A., Paris, France, and shipped to
Pittsburgh. ^ . .
Electrophenyl T60 is imported by at least one company, Int;sel Corporation
in New York City. The single customer of Intsel Corporation is Tivian" Laboratories
in Providence, Rhode Island, which distributes the terphenyl to three large wax
producers: Yates in Chicago; J. F. McCoughlin, in Rosemead, California; and M.
Argueso in Mamaroneck, New York. ' '
2.4 Discrepancies in Import.Data
The import data reported above cones exclusively from the U.S. Customs.
Additional import data have been gathered in response to Section 308 letters, but
are not reported here since they do not cover the entire wax manufacturing industry.
However, it can be stated that the Section 308 (P.L. 92-500, FWPCD 1972) responses
contain information that is significantly different from the Customs data. For
instance, Yates Manufacturing Company, according to its 308 response, purchased
substantially more than 500,000 pounds of decachlorobiphenyl in 1974, though the
Customs data indicate that none was imported that year. Also the 308 response of
the single importer of terphenyl listed above, Intsel Corporation, indicates that
-13-
-------
the amount of terphenyl purchased in 1974 by M. Argueso & Co. was only one-third
the amount Argueso states it purchased in that year.
These discrepancies nay result from stockpiling of the material by the
import distributor or distributors, so that the final users (i.e., the wax manu-
facturers) are purchasing the material years after it is imported. However,, in the
case of decachlorobiphenyl, Yates Manufacturing Company reported purchasing over
one four-year period about five times the amount U.S. Customs reported was imported.
Thus either there is an error in the reported data, or the material was being
imported without it being recorded by Customs, or Yates was getting its material
from a supplier (importer) not on record with Customs. For the purposes of this
report, the Customs data is considered accurate.
2.5 PCBs - What Other Nations are Doing
All industrial, nations face the problem of PCBs to some, extent, and all
are taking steps to control the flow of PCBs into the environment. The following
is a discussion of PCB-related legislation and directives from Canada, the
European Economic Community (EEC), and the Organization of Economic Co-Cperation
and Development (OECD, of which the U.S. is a member).
2.5.1 Canada
In December, 1975, the Canadian Government enacted "an Act .to
protect human health and the environment fron substances that contaminate the
environment"; its short title is the Environmental Contaminants Act. It is the
Canadian equivalent of the Toxic Substances Control Act, though it does not
specifically address PCBs as does TSCA.
In February of this year, the Canadian Ministry of the Environ-
ment promulgated, in accordance with the provision of the Environmental
Contaminants Act, "Regulations Prescribing Certain Uses in Respect of Which.
Certain Chlorobiphenyls May Not Be Used". The Regulations was published in the
Canada Gazette, the equivalent of the Federal Register, and is cited as the
"Chlorobiphenyl Regulations.No. 1", part 3 of which, specifies that PCBs may not
be. used in the operation, .servicing or maintenance of any product, machinery or
-14-
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equipment other than heat transfer equipment, hydraulic equipment and vapor
diffusion pumps that were, in use in Canada before March 1, 1977. The Regulation
also allows, continued' use of PCBs: in certain electrical devices, including
f'A\
transformers and capacitors.v-
2.5.2 OECD
One of the. on-going out-growths', of the Marshall Plan is an
international agency known as the Organization for Economic Co-Operation and
Development (pECD). The. OECD is an independent body consisting of the main
industrial nations of Europe and North America (U.S. and Canada); it is the only
organization of non-communist industrial nations. .
The OECD was established in December 1960 and currently consists
of 24 members, primarily western European, but also including Japan, Australia,
New Zealand, Greece, Turkey, and, of course, the U.S. and Canada, with Yugoslavia
as an associate member. Funding contributions from member countries are based
on GNP, with the U.S. contributing about 25 percent of the operating costs.
Headquarters for the OECD is in Paris.^
«
The issue of PCBs has been before the OECD since the late '60s
when various incidents in Japan and the U.S. made it evident that international
controls were needed. PCBs are specifically addressed under the Chemicals Council
of the Environment Committee which meets three times each year and reports to
the Council of the OECD. Member nations submit information on imports, exports,
usages and disposal practices of PCBs to the Environment Committee, and the Council
of the OECD accordingly makes recommendations to the member countries.
According to an OECD document issued in 1973, member countries
other than the U.S. have been confronted with the same problems as the U.S. in
finding suitable substitutes for PCBs. The PCS applications deemed most difficult
to phase out and which the OECD considered temporarily permissible are:
Dielectric Fluids for transformers or large power
factor correction capacitors
-15-
-------
Heat Transfer 'Fluids (other than in installations for
processing of.foods, drugs, feeds.and veterinary
products)
Hydraulic 'Fluids in mining equipment
Small Capacitors, with, the provision that special efforts
be made in phasing them out most rapidly.
The single greatest advantage in using PCBs in the above applic-
ations is their combination of nonflairmability and high dielectric strength.
Appendix C-l contains copies, of the high points of the decision of the Council
of the OECD adopted February 13, 1973.
On July 27, 1976 the Council of the European Economic Coinnunity
(EEC1 issued a Directive "on the approximation of the laws, regulations and
administrative provision of the Member States relating to restriction on the
marketing and use of certain dangerous substances and preparations". The United
States is not, of course, a member of the EEC, but to the extent that the U.S.
and the EEC are confronted by similar problems — specifically, in this instance,
the problem of PCBs — the European efforts at controlling PCBs are worth noting
and comparing to our own efforts. .The July, 1976, Directive of the EEC makes the
following comments and restrictions:
• 1. That polychlorinated terphenyls have been shown through "detailed examination"
to entail risks similar to those presented by PCBs, and that the marketing of
PCTs should also be restricted;
2. That the ultimate objective with regard to PCBs and PCTs is a complete ban; and
3. That the "designation of the substance, of the group of substances or of the
preparation" shall include:
(a) PCBs except mono- and dichlorinated biphenyls. ,
(b) PCTs, and
(c) Preparations with PCB or PCT content higher than 0.1 percent by weight.
-16-
-------
The Council of .the EEC. directs..the restriction of the designated
*
PC3/PCT preparations in all uses' except the following-categories:
1. Closed-system electrical equipment -
2. Large capacitors (1 kg or more in.total weight 1
3. anall capacitors (provided .that the' PCS has a maxiitium
chlorine content of 43 percent and.does.'..not contain
more than' 3.5 percent of penta- or higher chlorinated
biphenyls); also, small capacitors not fulfilling this
requirement may still be marketed'., for one year from the
effective date of EEC Directive; and capacitors already
in service are not affected by the! directive
4. Heat-transfer fluids in closed-circuit heat-transfer
systems (except in installations for processing food,
animal feed, Pharmaceuticals and veterinary products;
if PCBs are used in these installations at the time of
the EEC Directive, the uses may continue till the end .
'of 1979. at the latest)
5. Hydraulic fluids used in:
(a) Underground mining machinery
(bl Machinery servicing cells for the electrolytic
production of aluminum, until the end of 1979 at
the latest.
A copy of the July 197 6 directive is included in Appendix C-2.
Neither the Canadian Government nor the two international
organizations, the EEC and the OECD, intend to permit the continued use of PCBs
Cor PCTs, in the case of the EEC), in tooling compounds or casting waxes. However,
they all permit the continued use of PCBs, at least temporarily, in heat transfer
applications of the type associated with. the. Joy mining machinery.
-17-
-------
Bibliography - Section 2.0
1. Unport records for PCBs.. and PCTs (including amounts, .countries of origin, and
ports of entry) for .the years.1972 through, 1976 were.gathered from U.S. Customs
through, the office of U.S. Representative Les Aspiri (D-Wisc.).
2. Telephone communication with: Frederick W. Steinberg, .Attorney with Rase,
Schmidt and Dixon of Pittsburgh, Pa., representing Joy Manufacturing Co.
3. Importers and import distributors were identified through responses to Section
308 letters.
4. Canada Gazette Part III, Vol. 1, No. 12, pp. 1-21, 1974-75.
5. Telephone comnunication with; Jack. Thompson, Head of Multilateral Organizations,
EPA Office of International Activities.
6. OECD and the Environment. Pamphlet published by the Organization for Economic
Co-Operation and Development, Paris, 1976.
-18-
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3.0 MINING MACHINERY COOLANTS
' The port of entry for all PCB's imported in 197C was Pittsburgh, Pennsyl-
vania, where the Joy Manufacturing Company is located.. The specific PC3
formulation is called Pyralene 3010 'and is imported from France where it is
marketed by Prodelec.
Pyralene 3010 is an intermediate-chlorinated biphenyl fluid. It is used
by the Joy Manufacturing Company in the maintenance of a line of mining ma-
chinery that is no longer being manufactured. There are two specific types of
machinery dependent upon PCB fluids, and in both types the function of the
fluids is that of a nonflammable coolant for large alternating-current electric
motors; a secondary function is that of bearing lubricant. The moving parts of
the motors are totally immersed in the fluid, which by convection and conduction
carries heat from the electrical windings to the external surfaces of the motor
casing.
The two types of mining machinery currently in the field are "loaders", .
of which a company spokesman estimated roughly about 350 are still operable,
and continuous miners, of which there are about 50 still operable. The loaders
use two motors and the continuous miners use three. Joy discontinued production
of loaders using PCB-filled motors in early 1973; the continuous miners haven't
C2)
been produced with PCB-filled motors since about 1970. Production of these
units was discontinued because of the PCB environmental issue.
An alternative fluid has not been found. The properties required are thermal
stability, low viscosity, good lubricity, and compatibility with the motor windings.
Joy currently sells, and is making an effort to market, a conversion kit for loaders.
The kit converts the inotor to a dry type requiring no heat transfer fluids. The
difficulty in marketing lies in convincing longer available for maintenance proce-
dures, as imports will soon be restricted by the Toxic Substances Control Act. The
conversion kit costs about $6,200 per loader to purchase and install, and though
sane operators have had satisfactory results, reliability is generally less, and
therefore overall operating costs have been higher. *• '
-19-
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There are no equivalent conversion kits for the continuous miners because
of space limitations. (The motors in continuous miners generate and must
dissipate more heat than do the motors in' the loaders; dry motors able to handle
the heat load would be too large to fit on the present PCB-containing miners.)
A Joy spokesman stated that the existing continuous miners might be fitted with
new cutting heads that do not use PCB-filled motors; cost is about $65,000 per
miner. Without such a modification, the 50 or so continuous miners using PCBs
may have to be put out of service unless a suitable alternative fluid is
found.(3)
Maintenance operations on PCB-filled mining machinery motors are performed
by Joy in Bluefield, West Virginia. Spent fluids are loaded into the steel drums
they arrive in and shipped to Monsanto in St. Louis where they are incinerated.
(4)
Information on volumes shipped is not available.
Joy also supplies machine owners with PCS fluids so that losses from the
motors in the field (due to leaky seals and fluid overflow resulting from over-
filling and subsequent heating and expansion of the fluids) can be replaced.
There are no data on the' amounts lost in mines.
All currently produced Joy mining machinery uses dry motors. The bulk of .
imports for the years 1972 through 1976 have been for maintenance of previously
built machinery. All current imports have been entirely for maintenance purposes.
The table below has been constructed from U.S. Customs data showing the amounts of
Pyralene 3000 and Pyralene 3010 imported from 1972 through 1976:(
% Increase Over
Pyralene 3000 Pyralene 3010• Previous Year
1972 28,395 Its'
1973 36,420 +28
1974 46,914 +29
1975 41,976 -11
1976 ' 113,581 Ibs +171
The large increase in 1976 over 1975 might be indicative of stockpiling in
anticipation of import restrictions.
-20-
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3.1 Portion of the Total Number of Mining Machines Containing PCBs
According to a publication of the National Mining Association, in
1971 there were 2065 loaders made by various manufacturers in service. In 1974
there were 2151 loaders and 1959 continuous miners in service. Thus, between
1971 and 1974, there was an increase of about 4 percent in the number of loaders;
assuming a similar increase between 1974 and the present (1977) for both miners
and loaders, the total numbers of loaders and miners currently in service are:
loaders - 2237
miners - 2037
Of these, the currently operable PCB-containing Joy units account for:
loaders - 350/2237 =15.6%
miners - 50/2037 =2.5%
.3.2 Impact of the Toxic Substances Control Act
Joy no longer produces PCB-containing mining machinery; therefore it
will not be adversely affected by the Toxic Substances Control Act. However, the
owners of the PCB-containing machinery will be affected, since, unless exemptions
are granted for mining machinery, the Act specifies that PCBs can no longer be ,
used for open-system applications past the end of 1977.
Owners of loaders have three options available: (1) petition for an
exemption, which,, depending upon the interpertation of the Act, will allow one
or more additional years of service from their loaders; (2) purchase and install
the Joy-manufactured dry-motor conversion kit; and (3) scrap the loaders at the
end of 1977. The second option will entail a certain initial cost (about $6,200
(2\
per machine ) and down-time for the machinery, but, except for a higher
maintenance cost thereafter, the loaders will still be useable.
. Owners of continuous miners also have three options: (1) scrap the
machinery at the end of 1977, in accordance with the Toxic Substances Control Act;
(2> obtain authorization from EPA for continued use of PCBs, assuming that it can
be shown that this use of PCBs presents no health or environmental risks; • or (3)
purchase and install new dry-motor cutting heads (about $65,000 per miner). The
practibility of the final option is a function of whether or not the installation
of new cutting heads can appreciably extend the service Life of the machinery.
-21-
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It is probable that any mining company or trade.association that
petitions for an exemption might.cite the July 27,.1976, Directive of the Council
of the EEC. The EEC is also moving toward an eventual bah on PCS'. Appendix C,
directs member nations to terminate the use and manufacture, of PCBs for all uses
except for five specific categories, within one of which.mining machinery is
included.
In the event exemptions from TSCA are petitioned for, provision must be
made for the maintenance of the PCB-containing machinery, which, means PCB fluids
will have to be available.' Importation and stockpiling of PCB for maintenance of
TSCA-exempt machinery will not be legal past the end of 1977'.
The cost of replacing the 50 PCB-containing continuous mining machines,
at an approximate cost of $300,000 each, will be about $15 million, which cost will
be borne by the machine owners.
The response of Joy Manufacturing Company to the. Section 308 question-
naire has been stipulated by Joy to be confidential. Thus the specific owners of
the currently operable mining machinery, and the number of machines owned by
each cannot be shown here. It should be noted, though, that the expected service
life of a continuous mining machine of the type at issue is 10 years or more, and
that the newest PCB-containing continuous miner is seven years old, and further,
(2)
that though, about 50 of these units are operable, not all are being operated.-
-22-
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Bibliography - Section 3.0
1. U.S. Custons data obtained through the office of U.S. Representative Les
Aspin (D-Wisc.).
2. Telephone communications with Prescott Green of the Joy Manufacturing
Company, Franklin, Pa. Green provided all information on Joy uses of PCBs
in mining machinery.
3. Telephone communications with C.W. Fitzgerald, Product Manager for Loaders
and Continuous Miners, Joy Manufacturing Company, Pittsburgh, Pa.
4. Telephone communication with Stanley Butler of the Joy Manufacturing
Company, Bluefield, West Virginia, Joy Maintenance. Disposal practices.
5. Telephone communications with David W. Pinkard, Editor, Mining Congress
Journal; the number of loaders in 1971 was quoted by Pinkard from the
publication of the National Coal Association, "1972 Bituminous Coal Data".
6. Telephone communication with Herbert Davis of the National Coal Association;
Davis's numbers, for continuous miners and loaders in 1974 were taken from
publications of the U.S. Bureau of Mines.
-23-
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4.0 TOOLING COMPOUNDS
Polychlorinated terphenyls are used in wax formulations known as tooling
compounds, which are used to provide support to thin-walled objects so that they
can be machined without buckling or otherwise being damaged. Most of the informa-
tion on terphenyl-containing tooling compounds has been obtained from a patent
held by the single manufacturer of terphenyl tooling compounds, from the response-
of this manufacturer to a Section 308 questionnaire, and from conversations with
this manufacturer. Since specific information on the volume of tooling-compound
sales might jeopardize this producers competitive position, no information will be
reported here relating directly to sales volume. Terphenyl consumption in tooling
compounds will be reported as an estimated percentage of terphenyl consumption in
investment casting waxes.
As far as is known at this time, the only producer of terphenyl tooling compounds
is M. Argueso & Co., Inc., of Mamaroneck, N.Y., which is also a major producer of
investment casting waxes. A patent on terphenyl tooling compounds was taken out by
Luis M. Argueso and Cyril S. Treacy, listed as assignors to M. Argueso & Co.
The patent application was filed in December 1961 and granted in April 1965. It is
entitled "Method of Machining a Thin-Walled Object" (U.S. Patent No. 3,176,387).
To quote from the patent: "... the method and compound of the present
invention may be utilized in the machining of any thin-walled.object where the
walls are subject to damage incident to the machining operation." An example of
such an object is honeycomb structure fabricated from strips of metal such as steel
or aluminum which are brazed or otherwise bonded into a hexagonal-cell honeycomb
shape that has remarkable rigidity and very low weight. The thin walls of the
cells of the honeycomb are, however, relatively fragile, and during cutting, routing,
grinding or other machining operations these walls can be damaged. Damage to the
cell walls will detract.from the strength and rigidity of the honeycomb in a
structural application. The function of a tooling compound is to provide support
of the walls so they will not be deformed during machining. In the case of honey-
comb structure, the tooling compound is used to fill the honeycomb cells until
the machining operations are completed, then the .compound is removed by heat or
solvents or by a combination of the two.
-24-
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Tooling compounds are not, of course, confined to use in the machining of
metal honeycomb. They can be used to support any thin-walled object made of
almost any material during machining, such as thin-walled tube made of plastic,
glass, and even .rubber or cardboard, according to the patent. The patent also
claims coverage of a tooling compound that can be removed after the machining
operation without the application of heat, as would be the method in the case of
tooling compounds formulated from high-melting waxes or low-melting alloys. The
tooling compound claimed in the Argueso patent is soluble in "aqueous solution at
substantially ambient temperature." Argueso's tooling compound is introduced
into the structure in a molten form, "which has no adverse effects on the unmachined
article." The advantage of this formulation is that it can be removed without the
application of heat to the machined object because of the potential adverse effects
of elevated temperature on the machined object. "Upon completion of the machining
operations, the compound within the interstices or cores may be removed by sub-
jecting the object to an aqueous acid solution at room temperature which effectively
removes all traces of the compound from the object and leaves no film of the com-
pound on the walls of the object with no-residual effect on brazing or other similar
properties."
The principle ingredient in Argueso's tooling compound is a water-soluble wax,
specifically polyethylene glycol having a molecular weight of from 4000 to 20,000.
Secondary ingredients are metallic carbonate (NaHCCL, CaCO, are two cited in"the
patent) and finely divided mica and/or spun glass fiber. The following sample
formulations are among ten recipes.listed in the patent:
Polyethylene glycol (6000 molecular weight) 70% (weight)
Very fine water-ground mica • 10
NaHCO., (precipitated, very fine) 20
Same as above, but with polyethylene glycol having a molecular weight of
4000
Polyethylene glycol (6000 molecular weight) 42%
Very fine water-ground mica 10
Chlorinated terphenyl (Acoclor 5460) 8
NaHCO., (precipitated, very fine) 40
-25-
-------
Polyethylene glycol (20,000 molecular weight) 14%
Polyethylene glycol (6,000molecular weight) 56
•Very fine water-ground mica. 10
CaCO., (precipitated, very fine) 20
Polyethylene glycol (20,000 molecular weight) 14%
Polyethylene glycol (6,000 molecular weight) • 56
Very fine water-ground mica and spun glass fiber 10
CaCCL (precipitated, very fine) 20
Polychlorinated terphenyl is cited in only one of the ten example formulations
given, and it is covered specifically only in claim 16 of the 22 claims made in
the patent. In the sample formulation, which is shown above, terphenyl is shown
as constituting only 8 percent of the mixture. This same 8 percent figure is also
stated specifically in claim #16.
Argueso's response to the Section 308 questionnaire states, however, a much
higher percentage of terphenyl, a percentage which would be stated here if it were
covered by the patent or otherwise public knowledge. It is likely that M. Argueso
& Co. produces several lines of tooling compounds, not only the aqueous-soluble
variety, but of the type that must be melted out of the work piece being machined.
The reason for saying this is that polychlorinated terphenyl ia insoluble in water,
and in the high percentages Argueso says is used in tooling compounds (much more
than 8 percent)-, dissolution of the tooling compound in aqueous solution at sub-
stantially room temperature would be extremely slow. ^ '
The amount of terphenyl sold in tooling compounds by Argueso is on the order
of about 2 or 3 percent of the volume of terphenyls sold in investment casting
(2)
waxes by the entire investment casting industry. Luis Argueso says there is no
adequate substitute for terphenyl in tooling compounds. Of the ten sample tooling
compound formulations shown in his patent though, only one lists terphenyl as an
ingredient, and only to an extent of 8 percent by weight.
-26-
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Bibliography - Section 4.0 .
1. U.S. Patent §3,176,387, Method of Machining a Thin-Walled Object. Luis Argueso,
April 6, 1965.
<2. Section 308 response: M. Argueso & Co., Mamaroneck, N.Y.
3. Telephone conmunications with Luis Argueso, Vice President, M. Argueso & Co.
-27-
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5.0 THE INVESTMENT CASTING INDUSTRY
In the following discussion the investment casting- industry is examined in
terms of the present state of the investment casting art, the advantages of in-
vestment casting and the limitations. The technology- of the investment casting
waxes is also examined, and alternative waxes and alternatives to wax are con- '
sidered.
5.1 Introduction to Investment Casting
Investment casting is a method of producing very precise metal cast-
ings; that is, castings having high surface finish and close dimensional toler-
ances. Investment casting is also known as lost-wax casting, lost-pattern
casting, hot investment casting and precision casting.
In general, casting consists of introducing molten or fluid materials
into a mold where, upon solidification, they acquire the internal shape of the
mold. The advantages of casting compared to other methods of metal forming
such as machining, forging, and extrusion is that casting can be used to mass
produce intricate shapes at a considerable cost savings over the other metal
forming methods. Materials can be cast in pieces weighing from fractions of an
ounce to tens of tons.
There are four types of casting processes: sand casting, permanent
mold casting, die casting, and centrifugal casting. Each method will be
touched upon briefly here; a more detailed discussion will be included later
when the various casting methods are compared to investment casting' on an
economic basis. Investment casting is considered a form of sand casting known
as aggregate molding.
The products produced by investment casting have the highest dimen-
sional accuracy and smoothest finish that can be produced by any casting process.
The process is also not limited by the melting point of the metal to be cast -
(2)
if a metal can be cast at all, it can be investment cast. The chief limita-
tion is weight of the casting; the process can be applied most advantageously
to castings weighing less than 10 pounds, though castings weighing as much as
100 pounds have been produced.
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The root of investment casting, i.e., to invest, means in this con-
text "to cover completely, to envelop". . That which is enveloped or invested is
-> f
the pattern out of which the investment casting mold is made. The pattern in
investment casting is referred to as expendable, because it is destroyed by the
time the mold is ready for the pouring of molten metal. The pattern material
is wax or some combination of wax and other ingredients, and it is invested with,
or covered with, a refractory coating that hardens at room temperature. The wax,
or in general, thermoplastic pattern material (including plastics such as poly-
styrene) , is then melted and/or burned out of the refractory mold which is then
raised to a high temperature in preparation for metal pouring; the cavities in
the mold duplicate the dimensions of the thermoplastic pattern to within several
thousandths of an inch. The products cast by the investment process are of such
high dimensional quality and surface finish that they require little or no ma-
chining once they are broken out of the mold and cut away from, the sprues, gates
and runners. (Appendix A contains a diagram in which such terms as sprue and
gate are defined. See also Figures 5.1 and 5.2.)
Investment casting can be viewed as two casting processes combined:
the patterns are made by a die casting process, and in that sense are themselves
castings, and then they are invested with ceramic material in order to make the
a
ceramic mold for the actual metal casting process. As a method of metal forming
lost-wax casting is among the oldest known. Whereas the oldest known sand mold
.has'been traced to 645 B.C., and it is known that the Chinese cast iron as long
ago as 800 to 700 B.C., investment or expendable pattern molding has been in use
in one culture or another for more than thirty-five hundred years. This is not
to imply, however, that investment casting is the oldest known casting method,
though it apparently did predate the casting of iron in sand, or in any medium
for that matter. There is evidence of copper casting in Mesopotamia some 6000
years ago.
(An interesting note on the casting of iron is that while in western
cultures castable iron was not melted until within the last'few centuries, the
Chinese developed a system of "box bellows" that could supply sufficient draft
and heat for the melting of iron more than 2500 years ago. The Chinese had also
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discovered that iron heated with carbon in a highly reducing atmosphere melts at
a much lower temperature (2138°F) than does purer iron having less carbon con-
(4)
tent (2786°F).){ '
Investment casting is best suited to the production of a large volume
of small (on the order of several ounces), intricate parts made of metals that
are otherwise difficult or impossible to machine. Examples are turbine blades,
gun and machine parts, nozzles for high temperature jets, and parts for house-
hold appliances. The high cost of producing the pattern dies (discussed below)
which must themselves be cast from metal or machined out of metal, and the high
capital cost of the investment casting support equipment, is offset by the
small amount of finishing operations and machining required for the final cast
product.(1'5)
The pattern is possibly the most critical part.in the investment cast-
ing process. As the alternative name for the process - i.e., lost-wax process -
indicates, wax is an essential ingredient in investment casting; specifically,
wax is the material from which the pattern or patterns are made. The wax - or,
in general, the pattern material - must have certain properties, the most
critical of which is dimensional stability as a function of temperature. Ordi-
nary wax shrinks upon cooling from a liquid to a solid, and it continues to
shrink in the solid phase as the temperature is" further- reduced. The main •.
function of polychlorinated biphenyls and polychlorinated terphenyls in invest-
ment casting waxes is to improve the dimensional properties of waxes as a func-
tion of temperature. ^ ' '•
5.1.1 Making the Dies for the Production of Wax Patterns
Dies for producing wax patterns can be made either by machining
cavities in two or more matching blocks of steel or by casting a low-melting-
point alloy around a higher-melting-point metal master pattern. Ordinarily the
dies consist of two parts, which separate in order to remove the wax pattern.
The life of a steel-machined die is considerably longer than that of a softer
low-melting-point alloy, .though once a metal master pattern has been made, low-
melting-point dies can be readily reproduced. To make such a die, the metal .
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master pattern is first imbedded in -plaster or clay to its' parting line, which
provides proper draft in each half of the die. After applying a parting
material and placing a "flask" over the upper, or exposed part of the roaster
pattern, to contain the metal to be poured, the low-melting-point alloy is poured,
thus producing one half of the pattern die. The other half is made by applying a
parting material and pouring molten alloy into a flask over the master pattern
resting in the previously completed die half. Alignment dowels and corresponding
holes in the die halves may be cast by first drilling two suitable holes in the
parting surface of the,first completed die half. When the opposite side is cast,
the corresponding pins will be cast. The gate through which the wax is to be in-
jected is then drilled or machined at the parting, providing draft for the open-
fO\
ing of the die and removal of the wax patterns.^ '
5.1.2 Production of the Wax Patterns
The two halves of the pattern die are clamped together and wax
is injected into the die cavity at pressures ranging from 100 to 2000 psi. De-
pending on the characteristics of the wax it may be injected in the liquid state,
the mushy or slush state (between liquidus and solidus), or in the solid state
at a temperature just below its melting point. To provide adequate venting, .
small shallow vents may have to be cut in the parting surface of one of the die
halves. Shrinkages in larger sections of the wax pattern during cooling may
cause surfaces to sink (a process called cavitation), because all wax formulations
shrink on cooling. Shrinkage problems may be overcome by the application of com-
pressed air at about 100 psi to the injection gate shortly after injecting the
wax, or by maintaining the injection pressure on the wax in the die until it is
sufficiently cooled for the pattern to be removed. Most^ quantity production
of wax patterns is by automatic injection machines offering close control of
temperature, pressure and speed of injection.
According to Beeley, polystyrene patterns are less expensive
to produce than wax patterns. Polystyrene patterns are also superior to wax in
that they are less fragile, they have better surface-finish properties, and
/2)
they can be. handled more readily without deterioration. The cost advantage
-31-
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of polystyrene has, however, (decreased since the 1973 rise in petroleum feed-
stock prices. The disadvantages of polystyrene compared to wax are: higher
injection pressures are required in making the patterns (up to 20,000 psi vs
about 400 psi for wax), steel pattern dies are required because of the higher
injection temperatures, higher pattern production rates are possible for wax
patterns and the pattern mold for plastic patterns must have and hold the
highest surface finishes because plastic patterns can hold a better surface
finish than wax.
The production of wax and polystyrene patterns has many problems
similar to those experienced in metal casting. Injection speed must be designed
to avoid flow marks or misrun patterns and mold-entrapped air. There is also the
possibility of deformation of the patterns because of residual cooling stresses.
5.1.3 Pattern Assembly
Figures 5.1 and 5.2 show the differences between the investment
shell and the investment block methods of investment casting. Investment shell
molds are precoated in a very fine ceramic slurry which is subsequently backed
by coa€ings of coarser ceramic materials, but in the investment block method a
fine-grain ceramic material is used throughout the entire investment. If the '.
pattern material is plastic (polystyrene), the investment block method is used
instead of the shell method, because the block mold is stronger and can better
withstand the stresses generated in the removal of the plastic pattern (poly-
(2 5)
styrene has a higher coefficient of thermal expansion than wax).
Most products cast by the investment casting process are small
enough that the patterns can be assembled in large numbers on a single "tree" so
that many castings can be poured simultaneously. The wax patterns can be easily
fastened to a gating system also made of wax. The fastening or "welding" process
is carried out with heated spatulate tools or small gas torches that heat and
melt the wax surfaces to be joined. To reduce the time required for this assembly
operation, an assembly fixture may be employed to hold the patterns in place while
molten wax, usually previously-used pattern wax, is poured into the fixture and
allowed to solidify thus producing the sprue and gating system as one unit with
the patterns. The assembled wax tree is removed from the fixture after the wax
solidifies. This fixture method entails a tooling cost that is greater than that
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Iftvasfmtnt Molalng
Paitcfn antneiy ituecacd
(c) ami truceotnq I d) art rtwotid until
rtouirttf *ail tfitckntts Jf moid it arodiKio.
(•I CoAolcf«4 maid dMtr *at ootli
nai Ofltt «n«it«d
(moid «»o»« in oounna o option I
(hi Ot»«o( rawrcntinqt at
front >gru*
Figxare 5.1
Steps in the Production of a Casting by the
Shell Investment Molding Process.*
*By permission from Metals Handbook Volume 5
Copyright American Society for Metals, 1970
-33-
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Solid Inwsfmtnf Molding
(e) Pstttfii «sumoiv « Matt ontr
mol4 ilurry no* QMi OOuftd-
(Pfteaannq of peritrn aucmoiy witn
HuffT 'I rtqui/f4 lor metal* »irn sgurmq
itmMrotufa aoow* 2000^.)
(f t On* of (aw casirnq* af ti
'tflwwl from igrw*
Figxure 5.2
Steps in the Production of a Casting by
the Solid Investment Molding Process.*
*By permission from Metals Handbook Volume 5
Copyright American Society for Metals, 1970
-34-
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of hand assembly of the patterns onto precast sprue and gating systems, but for
large quantities of parts the fixture method can be less labor intensive.^ ' .
Figures 5.1 and.5.2 show the pattern assembly process, but with-
out a holding fixture. Wax patterns can also be assembled by the "dip seal"
method whereby the gate lugs on the wax patterns are dipped in molten wax (which
is usually used wax from previous patterns) then quickly stuck to the lugs on the
sprue assembly. Polystyrene patterns can be glued with plastic cement or by
moistening with solvent. Patterns are packed as closely as possible for maximum
production, but not so close as to interfere with proper cooling of the castings.
. 5.1.4 Investing the Wax Patterns and Producing the Ceramic Molds
The assembled "tree" of wax patterns is surrounded with, or in-
vested with, refractory mold material, and, as mentioned above, the final mold
is either a monolithic block or a shell of built up layers of cermaic material.
The block-mold process, also called the solid-mold or flash-mold process, is the
more traditional one, but in the last few years automation has made the shell-
mold method predominant with the block-mold process being reserved mainly for
the casting-of parts requiring higher as-cast surface finish.
In general, the shell and solid mold processes do not differ
appreciably, if at all, in pattern preparation or pattern assembly. However,
patterns for the.shell process are always given a precoat of fine ceramic slurry,
whereas precoating of patterns for the solid process is generally not required
unless the properties of the backup refractory are inadequate for the special
application. Precoating methods for both processes are similar: the pattern is
dipped in a fine ceramic slurry, and a granulated refractory is applied by
sprinkling, by means of a fluidized bed, or by other suitable method.
In the shell investment process, after precoating, the pattern
assembly is alternately dipped in a coating slurry and "stuccoed" with granulated
refractory, either by sprinkling or by suspending it in a fluidized bed, until
the shell is built up to desired thickness. Usually, the refractory grain ranges
in size from 20 to 100-mesh, the fine material being used for the initial coat
and progressively coarser grains for subsequent coats. Since the fineness 'of the
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initial investment slurry determines the surface smoothness of the final cast-
ings, the precoatings are usually made of extremely fine refractory grains on the
order of 300 mesh suspended as a slurry in a suitable binder. Each coat of slurry
and grains is air dried before the following coats are applied. Shell' thicknesses
are on the order of 1/4 inch. .
In the solid investment process, the pattern assembly (precoated
if it is to be used for the casting of high-temperature alloys - i.e., above
2000°F).is encircled by a flash which, in"turn, is filled with a refractory
mold slurry. The mold slurry, called a "backup slurry", and the flask together
with the pattern assembly in it is vibrated for about an hour to settle the in-
vestment material and cause air bubbles to rise away from the pattern. After
/g\
air-drying for about 8 hours, the investment hardens.
The principle refractory used for investment materials is silica,
either quartz or Cristobalite. For metals with pouring temperatures below 2000°F
the commonly used binder is gypsum plaster. For higher pouring temperatures, a
(8)
high-temperature cement, or a binder such as ethyl silicate, must be used.
5.'1.5 Bemoving Wax Patterns from the Ceramic Molds
The most common method for removing patterns from molds is to
melt the pattern. However, the thermal expansion of the wax exceeds that of-the
/Q\
ceramic mold by a factor of about 10, and unless the melting is carried out in
the proper way, the mold can be cracked or broken. Although the amount of ex-
pansion varies among different waxes, the volume can increase as much as 10 per-
cent before the wax melts.
To increase the strength of the shell to prevent it from break-
ing under the wax pressure would be self-defeating. The thicker mold would be
harder to remove from the finished castings. A heavier mold would not dissipate
heat from the molten metal as well as would a thinner shell, possibly resulting
in hot tears in the castings. (Block-type molds can withstand considerably more
internal pressure during melt out than can the shell type). The only practical
methods for preventing mold breakage during wax removal are: (a) supplying ex-
ternal pressure to the shell to counterbalance the internal pressure of the wax;
-36-
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and (b) rapidly dissolving or melting a skin or surface layer of wax at the inter-
face of the ceramic shell mold and the wax pattern, thereby creating a cavity into
which the remaining wax can expand.
i
5.1.5.1 Dewaxing of Shell Investment Molds
In one method of external pressure application, the
ceramic shell mold and wax-pattern assembly is placed, pouring cup down, in a con-
tainer that has a hole in the bottom. The mold is positioned 'so that the pouring
cup is directly over this hole. Sand or some other granular or powder refractory
(or metal shot), heated to about 600°F is then poured around the shell, and the
container is vibrated to pack down the refractory medium as quickly as possible.
A continuous supply of hot refractory is required to operate the process on a
production basis. The container, filled with the hot refractory, is set aside
until the wax has melted out of the shell, after which the shell is ready to be
fired. The shell'may be fired in the container, supported by the backup re-
fractory, or it may be removed from the backup and fired unsupported. Less firing
time is required if the latter method is used. The wax collected from the mold
can be re-used after it has been filtered or centrifuged to remove refractory
(5)
particles.v '
The pressure applied to the shell depends on the depth
to which the shell is buried and the packed density of the refractory surrounding
it. The-shell must not cote in contact with the heated refractory at too high a
temperature if the packing is slow; otherwise, heat conducted through the shell
will'begin to .expand the wax before the full external pressure has been applied.
A temperature range of 500 to 750°F for the refractory or shot is suitable for
most normal vibrating methods of packing and produces crack-free shells. Wax
recovery by this method is high, because the wax is subjected to only moderate
heating and can be re-used after careful elimination of refractory particles.*• '
An alternative to the packed hot refractory method is
a heated fluidized bed. The bed is fluidized and the shell is placed in it with
the pouring cup up. The air is turned off to allow the refractory material in
the bed to settle and pack around the, shell. After the wax has melted, the bed
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is refluidized, and the shell is removed and rapidly inverted to pour out the
«ax.C5> . .
Flash dewaxing is widely used to remove .wax from shell-
type molds. In this method the shell molds are placed in a furnace hot enough
to establish a high thermal gradient across the ceramic shell, thus causing the •
wax to melt at the wax-ceramic interface before the volume of the wax heats and
expands appreciably. Low thermal conductivity of the wax is an advantage of this
phase of the ceramic mold manufacturing process. The temperature of the furnace
in flash dewaxing is 1800 to 2000°F. The time interval for loading shells into
the furnace must be regulated to avoid heating the shells too slowly. A slow
heating rate will expand the wax without melting it and may crack the shell mold.
For example, a shell produced under controlled conditions at SO°F will crack in
10 to 15 minutes at 100°F. In general, flash dewaxing takes 10 to 20 minutes,
depending on the shape and thickness of the mold. After dewaxing, the shells are
either transferred to a holding furnace for casting or they are cooled for in-
spection, patching, or additonal dips in the slurry.^)
Flash dewaxing generates considerable amounts of smoke,
so hooding and exhaust systems are essential. Often, the water container placed
under the furnace to collect molten wax overheats, boiling the water and igniting
the recovered wax. The fire hazard, the generation of smoke and the volatiliza-
tion of potentially dangerous wax components and fillers are major disadvantages
of flash dewaxing. '
The most commonly used method of dewaxing is by use of
a steam autoclave. As with the other thermal dewaxing methods, the object is to
deliver heat as rapidly as possible to the interface between the wax and the mold
so that melting can start there before the main body of the wax starts to heat
and expand. Autoclave dewaxing takes advantage of the latent heat of vaporization
of steam to deliver sudden heat to the surface of the mold.
A typical autoclave operates at 320 to 329°F and 90 to
100 psi. It is jacketed to maintain the temperature of the vessel during loading
and unloading operations. During the dewaxing cycle', shells are loaded onto a
sliding tray arid passed into the autoclave through a fast-operating door equipped
-38-
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with a safety lode to prevent accidental opening during the pressure
cycle. Loading the shells, closing the door, and pressurizing the
vessel to 50 psi is accomplished -in about 10. seconds. Average process-
ing tine for a complete cycle is about 10 minutes. Under normal condi-
tions, between 85 and 95 percent of the wax is recovered. .Since the
process is inherently low-temperature, and since the autoclave is sealed
until the dewaxing process is completed, the used wax is less likely to
be rendered unuseable by high temperatures and the amount of wax vola-
tilization and smoke generation is negligible.^'
Dewaxing can also be accomplished by use of a
hot-wax bath at 425 to 450°F. Ihe ceramic shell molds to be dewaxed are
placed, pouring cups down, on a wire or expanded-metal basket and are
lowered either inmediately or'in steps into the liquid wax bath. Com-
plete dewaxing takes place in 5 to 30 minutes', depending on the mold size
and shape and the type of loading sequence. Temperature control of the
liquid wax bath is important; if the bath temperature falls below 425°F,
a high percentage of shells will crack because, as mentioned above, too
much of the wax inside of the mold will heat and expand before melting
takes place at the wax-mold interface. Overheating of the wax bath can
cause fire/ '
Ihere are non-thermal methods of dewaxing in
which solvents are'used to dissolve the wax from the mold, or at least
from the wax-mold interface so that subsequent wax melting procedures
will not cause cracking of the mold if the absorption of heat into the
wax proceeds too-slowly. Heated trichlorethylene vapor, for example,
has been used to permeate the porous ceramic shell and dissolve the wax
at the interface; the remaining wax can then melt out without damaging
the mold. Ihe molds are normally supported in a wire tray with the
pouring cup down. During the latter stages of dewaxing, the wax patterns
(5 8}
malt and run into the reservoir of solvent. *• ' '
. Solvent dewaxing is slow, requiring about 30
minutes for large patterns, and if penetration of the ceramic is too
-39-
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slow, premature wax expansion can occur and crack the molds. Equipment
for solvent dewaxing consists of a conventional trichlorethylene vapor
machine of the type used for vapor degreasing. In time the wax accumu-
lates in the bottom of the tank in solution with the trichlorethylene.
When sufficiently concentrated, wax recovery is by distillation. This
is done in the same equipment used for dewaxing; the trichlorethylene,
which condenses on the cold-water pipes at the top of the tank, is
prevented from running back into the reservoir by collecting it in
gutters below the cold-water pipes .-^^
In a patented solvent dewaxing method, a cold
solvent is used for removing wax from the shell mold after the third or
fourth coat of ceramic material has been applied and dried. The solvent
penetrates the shell, and dissolves and removes a thin layer of wax at
the interface. Additional coats of ceramic are then applied. This
method was originally applied for removing plastic patterns (i.e., made
from a polystyrene thermoplastic composition) fran shell molds.
5.1.5.2 Dewaxing of Solid Investment Molds
m
Although shell-type molds are used far more •
than solid-type or flask-type molds these days, solid molds; are still
used for the casting, of very small and intricate pieces for which poly- '
styrene is the best pattern material. (Because polystyrene expands on
heating more than wax, the additional strength of the block-type molds
is required when using plastic patterns.) Mold cracking caused by expan-
sion of the wax is not a problem in dewaxing of solid molds, because of
the backing provided in the solid mold. In practice, solid molds are
dewaxed (or deplasticized), burned out (fired), and preheated for pouring
in a single cycle.
Initial heating is critical. Heating too
rapidly while large amounts of free water remain in the mold can cause
the formation of steam pockets between the precoat layer and the backup
investment. Pieces of precoat may break away from the backup coat,
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allowing molten metal to flow in between and form a "scab" on the
casting. 1b provide slow initial heating, the molds are placed in a
gas-fired or electric furnace, usually of the tunnel type. The molds .
are introduced at the low-temperature end (not more than 800°F) and are
slowly moved through the furnace to higher-heat zones (up to 2000°F).
The wax or plastic melts out of the mold and is burned off as the mold
advances through the furnace, and the mold emerges from the hot end pre-
heated and ready for pouring. Wax reclamation is possible with this
method, though it is not usually considered practical.^'
As with shell dewaxing, thorough burnout is
very important since any wax residue not removed shows up as carbon
black in the investment around the mold cavity and usually causes defec-
tive castings from failure of the mold to fill with metal. The mold
should remain at the maximum temperature for 2 to 4 hours depending on
the size of the mold and the amount of organic matter to be burned out/ '
5.1.6 Firing and Preheating the Molds
Most investment molds must be preheated prior to pouring
to: . • '
1. Burnout residues of wax and/or plastic
2. Permit metal filling of mold sections too thin
to be filled in a cold mold
3. Minimize the size of risers. (Risers are
internal reservoirs of molten metal in the
mold; they supply liquid metal to the actual
castings which, as they solidify from their
outer surfaces inward, shrink and must be fed
additional metal.)
4. Minimize hot tearing during cooling of the cast
metal
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Furnaces used for firing and preheating of molds are
either of the continuous type or batch type. Continuous furnaces of
either the pusher or rotary type provide a continuous supply of pre-
heated molds. They are efficient for high-production operations
because they can be divided into temperature zones that provide optimal
heating schedules. A typical continuous furnace used for heating solid
molds has four zones of heating:*• '
Zone 1. The mold is dewaxed, thus eliminating the
need for a previous dewaxing operation. The
temperature of this first zone may range from
300°F to 800°F.
Zone 2. Temperature is increased to an intermediate
range, usually from 1400°F to 150Q°F.
Zone 3. Maximum temperature, about 1800°F (steel
castings); wax residue is completely removed
in this stage.
Zone -4. Molds are' held at the same temperature or
slightly lower than in the previous zone
until pouring.
Batch-type furnaces for firing and preheating are gen-
erally similar to those used for metal heat treatment. Molds are
dewaxed in a previous operation (e.g., by autoclave). Batch-type fur-
naces are maintained at the desired preheat temperature. Molds are
loaded to the capacity of the furnace. When the furnace has stabilized
at the set preheat temperature and the molds have remained at temperature
for the required time (sufficient to burn out organic residues and to
achieve thermal equilibrium), pouring can begin. Preheated molds are
withdrawn from the furnace as they are required by the casting operation.
When the. furnace' has been completely emptied, it is reloaded with cold'
molds and the cycle is repeated. '
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5.1.6.1 Furnace Operation and Temperature
The same furnaces can be used for preheating
ceramic shell mold and solid molds, but the heating cycles are greatly
different. A shell mold will have been dewaxed prior to preheating and
will have a weight that is only a fraction of that of a comparable solid
mold; also, a shell is made of materials that can stand the thermal shock
of being placed in a preheated furnace at 1500° to 2000°F. Thus, the •
same furnace can preheat several times as many shell molds as solid molds.
Preheat time for shell molds ordinarily ranges
fran 1/2 to 2 hours. When shell molds are backed with a dry refractory
material, preheat time is on the order of 3 to 5 hours.
Furnace atmosphere must be oxidizing at all
times to ensure complete elimination of all organic material. It is
common to provide air 10 percent in excess of the amount theoretically
needed for complete combustion.
5.1.6.2 Mold Preheat Temperature
Although many investment molds are poured at
room temperature, more often the molds are preheated before pouring.
Preheat temperatures range from 200° to 190 0°F, depending on the type of
metal being poured.
For each casting metal,, there is a mold tempera-
ture range that is most commonly used, depending on casting size and
complexity. For instance, aluminum alloys are usually poured into molds
preheated to 400° to 650°F. But, depending on the particular casting,
mold temperature for aluminum alloys may range from 70° to 1000°F.
The advantages of high preheat temperatures
are:
1. Reduced possibility of misruns or cold shuts
in complex castings or those having extremely
-43-
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are:
thin sections, particularly when the castings
are gravity, fed.
2. Reduced thermal shock to the mold.
The disadvantages of high mold temperature
1. Increased possibility of local shrinkage,
especially in thick sections, because of the
slower cooling rate.
2. Greater possibility of evolved gases, which
are likely to cause porosity of the casting.
3. Adverse effect on mechanical properties for
sane alloys, because of the slower cooling
rate.
4. Longer cooling time required for removal of
the casting from the mold.
-5.1.6.3 Wax. Losses to the Environment During Firing
and Preheating
After the dewaxing process and prior to the
mold firing operation, the mold contains a certain amount of wax that
is either in the form of small puddles inside the mold or it is contained
within the porosity of the mold material. The amount of wax remaining
in the mold may vary from. 0.1 to 15 percent. ' ' Considering that the
ceramic molds are porous and that the wax acquires very low viscosity
during the melt-out process, it seems likely that the mold could well be-
come saturated with wax during meltout. Certainly the complexity of the
part being cast and the number of patterns making up a given mold would
influence the amount of wax that would not come out of the mold during
dewaxing. In any case, the highest industry estimates for wax remaining
in the molds prior to firing is about 15 percent, and of that wax remain-
ing, between 20 and 70 percent of it is filler materials or additives.
-44-
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Decachlorinated biphenyls were used till the middle of 1976 as a solid filler
material in many investment casting waxes. PCBs are no longer used-as such,
but polychlorinated terphenyls are being used and have been used for more than
20 years as a component of some wax formulations. Polychlorinated terphenyls
are no longer manufactured in the United States; all PCTs currently used in
this country originate in Europe. The sole distributor of PCTs in the U.S.,
however, is currently certifying that their PCTs contain less than 0.05% PCBs.
(The previously used American PCTs have been measured to contain about 0.5 per-.
cent PCS contamination.) Thus, to the extent that PCTs contain PCBs, they are
environmentally dangerous above and beyond the intrinsic hazard of PCTs alone.
The content of PCTs in PCT-containing waxs is on the order of 40 percent. ' '
Thus, 40 percent of whatever wax remains in the yet-to-be-fired molds is PCT, of
which a small percentage may be PCB of unspecified chlorination level.
The furnace temperatures at which molds are fired and
preheated range up to 2000°F. The amounts of PCTs and PCBs that can escape the
furnace range from zero or infinitesimally small to the full amount contained
in the mold prior to.firing. The low estimates are based on the premise that
the volatilized wax and its components and fillers are exposed to the highest
temperatures for periods of time sufficient to completely destroy the PCBs and
PCTs, and reference is made to the fact that the molds are heated for periods of
hours before removal from the furnace. (The long stay in the furnace is/_of
course, intended to assure complete oxidation of organic material in the mold.)
The higher estimates are based on the assumption that the bulk of the losses to
the environment take place during the initial mold heating phase, when the wax
and its components and fillers volatilize from the still-relatively-cool mold
and are carried upward through the flue in pockets of relatively cool gas. As
far as is known, no one has actually performed an analysis on the flue gases
emanating from investment foundry furnaces during firing and preheating.
Since most foundries use autoclave dewaxing these
• "" O *~C\
.days, ' the main process source of potential pollutant generation is the mold
firing operation where volatiles might be lost up the stack. Other sources of
environmental hazard from wax additives and fillers lie outside the foundry
-45-
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process - i.e., during wax disposal operations, which may include incineration
and non-secure landfilling, and during wax reclamation carried on by wax manu-
facturers,
5.1.7 Metal Casting
After the molds have been fired and preheated, molten metal is
poured into the molds while they are supported in suitable fixtures. After the
metal hardens and cools, the ceramic mold material is removed by various methods
including hydroblast, pressurized air blast or power chisels, or combinations
thereof, and in some instances powerful acids are used to dissolve small cores
out of the castings. (Silica cores as small as l/16th inch are dissolved out
with hydrofluoric acid.-) The individual castings are then cut from the cast
tree assembly and finishing operations are performed as needed - e.g., the grind-
ing off of gate lugs, machining, plating.
5.2 Advantages and Limitations of Investment Casting
Generally speaking, the advantage of investment casting is that it is
the most cost effective way to produce high quality castings out of any castable
(2)
alloy. If a metal can be cast, it can be investment cast. . Investment casting
is the only metal forming method currently available for producing large numbers
of complex-shaped parts cast to close tolerances in high-melting-point alloys.
In this section, the advantages and limitations of investment casting are dis-
cussed in terms of costs: costs of improving the capabilities of the investment
casting process itself (e.g., in taking care to assure close as^cast tolerances),
and costs of alternative methods of production.
5.2.1 Dimensional Accuracy
One of the main advantages of investment casting is the ability
to produce internal cavities and undercut features as integral parts of the mold.
This avoids the process of core placement and maintains the advantage of the
jointless mold. The two casting procedures having dimensional accuracy and sur-
face finish comparable to investment casting are permanent mold casting and die
casting, but^both of these alternative casting methods entail the joining of
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two or more dies to make a mold, and the joint, or parting, between the die
parts introduced an inherent inaccuracy because the thickness of the parting
interface can only be controlled to a tolerance of several thousandths of an
inch. Die casting and permanent mold casting are also limited by the melting
points of the metals that can be cast - high-temperature alloys cannot be cast .
by these methods.
The high accuracy of investment castings is due to the smooth
and inert mold surfaces and to the elimination of joints by the use of one-
piece molds. The only alignment operation is that of the pattern die assembly,
for which the metal components can be machined to fit with'high precision.
During pouring, ready flew in the preheated mold gives intricate detail and
fine finish. The process thus offers a degree of precision unrivalled except
in die casting. .
In investment casting, as in other metal shaping processes,
attainable tolerances depend partly upon design. Tolerances are close ± 0.001
to ± 0.003 inch may be feasible on certain small dimensions, but it is widely
accepted that values of ± 0.005 inch plus 0.5 percent of the dimension are more
•
realistic for general application. As in other manufacturing processes, toler-
ances can be allotted on a functional basis, with maximum precision specified
only for critical dimensions. '
casting are:^ *
Factors influencing the dimensional accuracy of investment
(a) Shrinkage of the pattern material
(b) Shrinkage of the metal and direction of maximum
shrinkage during solidification
(c) Shrinkage of the metal during cooling to room temper-
ature (most measurements are made at room temperature)
(d) Expansion of the mold in preheating
(e) Expansion of the mold when molten metal is poured into it.
-47-
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These factors are not additive because the shrinkages and ex-
pansions are not the same for all castings in all directions. The geometry of
the individual castings, of the clustered castings and of the mold are difficult
to compensate for analytically. Even if all the above listed shrinkages and
expansions were known, overall shrinkage allowances can only be estimated, and
finer tolerances (e.g., ± 0.002 in. /in.) must be established through experimen-
tation with the specific casting.^ ' '
To produce castings to the closest possible tolerances, it is
necessary to consider the effects of pattern tooling, cross-sectional thickness
of the pattern, location of pattern-die parting line, wax-injection conditions,
temperature control of stored patterns, pattern assembly, molding, and cleaning
and finishing of the casting. Since wax properties are the subject of this
report, the wax injection consideration will be discussed
The wax or plastic material must be consistent between runs and
homogeneous within each pattern. Temperature and dwell time during injection
must be accurately controlled. Deviations in these conditions can cause" vari-
ations from the anticipated shrinkage. In particular, temperature variation
should not be more than 2°F from an established optimum level.
When pattern dies are held together by clamping force during
injection, the injection pressure should not exceed the clamp pressure or the
die will be forced partially open. In large-area patterns for turbine engine
vanes, this may cause airfoil sections to be thicker than specified.
5.2.2 Surface Finish '
In most applications, investment castings have the best surface
finish of any casting process involving expendable molds. For the casting of
high-temperature alloys, investment casting offers the best surface finish of
any casting process. Tables 5.1 and 5.2 show -comparisons of surface finish for
several different casting procedures. (Shell molds, as listed in Tables 5.1 and
5.2, are not the same as investment shell molds; see Section 5.2.5.1 and Appen-
dix A.)
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Table 5.1
Approximate Ranges of Surface Roughness for Steel
Castings Weighing up to 5 Ibs., Made by Four Processes.*
Process
Green sand mold
Baked sand mold
Shell mold
Investment mold
Micro-in. (rms)
500 to 1000
250 to 500
125 to 250
80 to 125
Table 5.2
Typical Minimum and Maximum Roughness of Type 316
Stainless Steel Fittings Cast by Three Different Processes.*
Casting
Process
Sand
Shell
Investment
Measured, roughness, micro- in. (rms)
Minimum
Value
400
100
80
• Maximum Value
90% of Area
550
120
125
10% of Area
660
200
175
Measurements were made with a stylus-type tracer on all accessible
areas; however, parting lines and other major discontinuities were
not included in the traces. Before roughness was measured, all as-
cast surfaces of the castings were blasted with zircon sand (7% larger
than 100-mesh, the remainder smaller than 100-mesh but larger than
200-mesh).
*By permission, from Metals Handbook Volume 5, Copyright American Society
for Metals, 1970.
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Surface conditions of the wax or plastic pattern, condition of
the ceramic precoat, method of casting, the metal being cast, and the method of
cleaning are the variables controlling surface finish. The method of casting
affects the surface finish as a result of oxidation after pouring. Casting in
inert atmospheres or in a vacuum provides smooth cast surfaces. In general, non-
ferrous castings are smoother than ferrous castings. Table 5.3 compares surface
roughness of investment castings of five different metals.
5.2.3 Costs
Small intricate ferrous shapes are often most economically pro-
duced by investment casting. When investment castings costs for the production
of a specific item exceed costs by other production methods, the reason is
usually because there are a large number of operations in the process, especially
operations involving operator skill. A detailed per-unit cost analysis of a
typical investment cast part is shown on Table 5.4.
Costs may vary 50 percent or more among different investment
casting procedures. The two examples that follow show cost differences between
the use of ceramic shell and solid investment molds, arising from differences in
pattern material (wax patterns in the ceramic shell molds, plastic for the solid
molds), production rate and coring practice.
5.2.3.1 Cost Comparison; Ceramic Shell vs Solid Investment
Processes* -
Polystyrene patterns usually result in better surface
finish than do wax patterns. However, because polystyrene has a higher co-
efficient of thermal expansion than wax, polystyrene patterns are used exclu-
sively in solid investment molds while wax patterns can be used in both shell-
type and solid-type molds (solid molds .have the higher strength necessary to
withstand the greater stresses generated during the removal of plastic patterns).
Thus if high surface quality is desired in a casting, solid investment molds
would likely be used with plastic patterns. The trend these days, however, is
*By permission, from Metals Handbook Volume 5, Copyright American Society
for Metals, 1970.
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Table 5.3
Ranges of Surface Roughness of Investment Casting of
Five Different Metals, as Measured in Two Different Plants*
Casting Alloy
Aluminum
Magnesium
Copper
Steel
Stainless Steel
Surface roughness, micro-in.
Plant A
63 to 250
63 to 250
63 to 250
125 to 500
Plant B
100 to 200
70 to 225
100 to 200
(Castings were made in solid investment molds produced from
wax, plastic and mercury patterns. Data from plant A sum-
marize experience with aircraft castings "as received" from
foundries, and were taken by the visual-comparator method;
areas of unusual roughness, such as corners and fillets, were
not evaluated. Plant B measured roughness with a tracer in-
strument on about 50 different castings,for each alloy shown,
after .the castings had been abrasive blasted or cleaned by
tumbling.)
* By permission from Metals Handbook Volume 5, Copyright American Society
for Metals, 1970.
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Table 5.4
Cost Analysis of Typical Investment Casting
Item Oast per easting
T-a>vn- and Burden
Gores -(soluble-wax)
Core repair
Pattern (wax)
Chills (wax)
Pattern repair
Total pattern cost $ 2.68
Sprue and riser (wax)
Gate-and-chill assembly
Mechanical core supports
Total gating cost 0.72
Molding (a) 1.30
Mold baking; wax removal
Melt and pour metal
Total foundry cost 2.55
Pushout and vibrate
Waterblast (core removal)
Cutoff
Total cleaning cost 0.67
Grind 50.30
File 0.70
Sand' blast ' 0.25
Total finishing cost 1.25
Visual inspection
Dimensional inspection
Total, foundry inspection
Total cost, labor & burden
Materials
Soluble wax
Pattern wax
Investment
Metal
Total materials cost $ 1.29
Other Expenses
Rejects (15% scrap) •
teat treating (T6 tsnper)
Penetrant inspection
X-ray inspection (5 views)
Total Cost per Casting (b) $14.90
By permission, fron Metals Handbook Volume 5 Ccpyright
American Society for totals, 1970.
-52-
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toward shell-type investment casting, because the investment process has been
highly automated, furnace time for the molds is less (during burnout and pre-
heating) , dewaxing - or, in general, pattern removal - is faster and simpler,
and the capital outlay for wax handling equipment is less than for plastic
handling equipment (associated with block-type molds) which operates at higher
temperatures and pressures.
The following example illustrates how, in this one
instance at least, solid investment casting is more cost effective than shell
investment casting. The example is based on data nearly 10 years old, and cur-
rent methods of operation might give the opposite cost results, but the example
is included here because the details of the cost difference are edifying:
The Hastelloy C investment casting shown in Table 5.5
was evaluated for production by both the ceramic shell process and the solid
investment process. Wax patterns were used for the ceramic shell molds, and
plastic patterns for the solid mold.
The cost of patterns ($0.292 per casting for ceramic
shell vs $0.062 for solid investment) was a substantial contributor to the dif-
ference in cost. The difference in other.costs was considerably less, percent-
agewise. . .
Cost details for production by the two processes are
compared in Table 5.5. Production by the ceramic shell method cost almost
twice as much as by the solid investment method. The solid mold process, there-
fore was selected.
As shown in Table 5.5 several factors accounted for
the difference in cost. An explanation of the most important of these follows:
1. Pattern Molding. A total of 199 plastic patterns could be molded per hour,
as opposed to 46 wax patterns per hour.
2. Pattern Assembly. Only 132 wax patterns could be assembled per hour, as
opposed to 250 plastic patterns.
-53-
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Table 5.5
Comparison of Costs for Producing Castings by the
Ceramic Shell and Solid Investment Processes(a)*
—Cwi per cuunt .
Ctrunlc
•Hell Solid lorauunt
Pattern molding
Pattern inspection and
trimming .....••.••
Pattern material
Pattern assembly
Pattern cost
Dipping and Investing
Mold material
Pouring
Casting metal
finishing
Inspection
Rejects
fixed overhead
Cost per casting.
excluding pattern
cost
Total cost per
casting
Hotuiloy C
Rockwell 8 93
W.140
0.096
0.007
0.049
$0.292
0.039
0.018
0.044
0.217
0.151
0.042
0.067 (b)
0.460
$0.033
0.003
0.026
$0.062
0.032
0.040
0.036
0.177
0.070
0.022
0.019 (c)
0.244
(a) Casting, illustrated above, was produced
In ceramic shell molds made with wax patterns,
and la solid investment molds made with plas-
tic patterns. Costs (other than material costs)
Include labor and burden, (b) Based on 7%
scrap, (c) Based on 4% scrap.
*By permission, Mstals Handbook Volume 5, Copyright Anerican Society for
Metals, 1970.
-54-
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3. Pouring and casting metal cost more for the ceramic shell process, because
the wax assembly required large runners for mechanical strength during pro-
cessing of the clusters. In the ceramic shell, cluster weight was 16 Ib.
for 60 castings, as opposed to 14 Ib. for 64 castings in the solid mold.
4. Finishing costs were higher for the ceramic shell process because of the
cost of cleaning the residual refractory and the need to hold the 0.492/
0.498-in. diameter within tolerance. The plastic patterns in the solid
investment mold maintained this tolerance without secondary operations.
5. Inspection costs were higher for the ceramic shell process because of the
need for 100-percent inspection on the 0.492/0.498-in. diameter. Statis-
tical sampling sufficed for the solid investment mold.
5.2.3.2 Cost as a Function of Investment Casting Tolerance*
The assignment of tolerances closer than standard
entails higher production costs and longer production times because closer
tolerances increase both foundry time and the rejection rate. In some instances
pattern dies may have to be made more than once, or the gating of acceptable
dies may have- to be improved. Table 5.6 shows how costs are influenced by tol-
erances..
5.2.4 Costs of Alternative Metal-Forming- Processes
The value of investment casting is principally in the field of
small txnplex components', and especially of components requiring refractory or
high-melting-point metal composition. Since dimensional accuracy depends partly
on the magnitude of the dimensions, the advantage over other casting processes
(5)
diminishes with increasing size. Most investment castings are below 10 pounds
in weight, with the majority being less than 1 pound. Castings exceeding 100
(3 8)
pounds have been produced, however, with dimensions up to 18 inches. '
Despite the superlative technical capabilities of investment
casting, its application has been restricted by the relatively high production .
*By permission, from Metals Handbook Volume 5, Copyright American Society for
Metals, 1970.
-55-
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T
Table 5.6
Effect of the Tightening of Dimensional Tolerance on
the Cost of a Part Produced from a Steel Investment Casting.*
Tolerance
Original A. B and C
Revised A
Revised A and B
Revised A. B and C
Added operations
required
One inspection
One machining,
Two machinings,
three inspections
pnvvyr*xi'jy
-i, -)•••*• wi
|.jj"r*'!ifi,,q *,
1
..i, „,„ V.J ..j.^ ,. J-,
...J.ii'I.V» •;\'l,«.--~.T< jl\l,,.-,li
1
l_l
•l»l.9«^*«i-i
VTHEUl^
Dimension,
in.
A 0250
B 0060
C 1.000
Tolera
Original
* O.OIO
t 0.005
i 0.010
ice, in.
Revised
t 0.003
lO.OOl
t 0.003
r*
r^Sg
^Vi
-C-
j
S1«*l
r~""'^S^ rB
Cost per part, $
*By permission, from Metals Handbook Volume 5, Copyright American Society for Metals, 1970.
-------
costs to those products for which an overall economy can be achieved by the
elimination of machining, or for which there is no feasible alternative produc-
tion method. A prime example is turbine blades; machining of such complex
shapes on a mass production basis would be prohibitively expensive, and no other
casting process can be used with such high-melting-point metals. Other examples
are parts requiring accurate shaping in hard, wear resisting alloys that are
inherently difficult to machine, or in alloys which are difficult or impossible
(12)
to forge. In such cases any alternative to investment casting may be more ex-
pensive when the overall cost of the finished component is used as the criterion.
The adoption of investment casting usually requires appreciable
quantity production for amortization of die costs, although these are generally
much lower than in die casting. The minimum practicable output varies widely
according to the type of die, so that no general figures can be given. Die
costs are also usually less than for forgings and sintered compacts, for which
the hardest and least machinable die steels are required. For the mass pro-
duction of large quantities of simple, low-tolerance parts, however,- investment
casting is not price competitive with forging and powder metallurgy because of
their very low per-unit production costs.
Other applications of investment castings include impellers and
other pump valve components in stainless steel and nonferrous "alloys, wave- .
guides, die inserts and parts for gun mechanisms. Milling cutters and other
types of tools are also produced. Outside the engineering field,' investment
casting is used in dentistry, for surgical implants, and for jewelry and art
casting. In some of these cases the expendable patterns are individually
modelled rather than being produced by repetition from a
5.2.4.1 Sand Casting vs Investment Casting*
The cost of investment casting is sometimes competitive
with that of other casting methods especially when machining operations are
*By permission, from Mstals Handbook Volume 5, Copyright American Society for
Metals, 1970.
-57-
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eliminated by the use of the investment process. Investment casting also com-
petes with forging and with machining from bar stock.- The three examples that
follow compare costs of investment castings with costs of making the same part
by alternative methods.
When the part shown in Table 5.7 was produced as a
sand casting, the internal oil slot was milled in with a slotting cutter and
the hole leading to it was drilled. Producing the part as an investment cast-
ing permitted the slot to be cored, and it did not require machining. Casting
and machining costs for the sand and investment castings are compared in Table
5.7. Savings in the machining costs were possible because of the superior
dimensional accuracy attainable when the part was made as an investment casting.
The three concave reliefs required no machining when made by investment casting,
and only one-third as much stock removal was needed on all other machined sur-
faces.
.5.2.4.2 One-Piece Investment Casting vs Welded Assemblies*
A diffuser strut for an aircraft engine was originally
designed to be made of two forged halves, which were machined on mating surfaces
and then welded together. Alternative designs required that the feet of the
part be forged or cast, that the vane be formed from sheet metal, and that the
feet be welded on. All welding was done by the gas tungsten-arc method.
The strut was later produced as a one-piece investment
casting by the ceramic shell process. Producing the struts as castings reduced
the cost by $82 per strut, which represented a reduction of approximately 75 per-
cent, including machining costs.
5.2.4.3 Investment Casting vs Machining from Bar Stock*
Two sets of fixtures (one piece from, each is .shown in
Figure 5.3) used in the high-temperature brazing of stainless steel tubing were
originally made of Hastelloy X by machining from, bar stock. The cost of set A
was $58.00, and that of set B was $40.25.
*By permission, from Metals Handbook Volume 5, Copyright American Society for
Metals, 1970.
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Table 5.7
Machined Sand Casting vs Machined Investnent Casting*
Sand
1 Machine surfaces of casting .........
2 Mill-In oil groove (configuration must
be modified for slotting cutter) ----
3 Drill one 0.192-ln.-diam hole Into oil
groove ..........................
4 Remove burrs .................... .' .
Total machining cost
Cost of unmachlned casting . .
Total cost of
machined sand casting
Castlar
$5.97
Machine surfaces of casting
where required ..................
Total machining cost ...............
Cost of unmachlned casting .........
Total cost of machined Investment
casting ........................
Savings, using Investment casting . . .
Oil hole
l-t-0.192
| I diom
Section A-A
1970?'
M8talS Handb00k Voluite 5' Copyright toerican Society for
-59-
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Hastelloy X (bar Hock). HS-31 (costing)
^_a«is
O.J4J
'0,338
2.140
Sal A
Three-piece set
(I typical piece
shown)
Sat B
Two-piece set
(I typical pieca
shown)
Figure 5.3
Typical Pieces for Two Brazing Fixtures that were Made at
Less Cost by Investment Casting than by Machining from Bar Stock*
*By permission, from Metals Handbook Volume 5, Copyright American Society for
Metals, 1970.
-60-
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The same fixtures were later made of HS-31 (an accept-
able alternative material) by the ceramic shell invesbnent casting process, at
a cost of $4.47 for set A and $2.56 for set B. The investment cast fixtures also
had a longer service life.
5.2.5 Discussion of Alternative Metal-Forming Methods to Inves-bnent
Casting
The implications of the available tolerances and surface finish
are that while loose fits are attainable between as-cast components, machining
or grinding allowances are normally necessary for bearing surfaces, precision
threads and other close-tolerance needs.*• '
The minimum metal thickness that can be satisfactorily run
depends partly on the area of the section being cast. Although thicknesses of
0.010 to 0.015 inch have been obtained over very short distances, C.030 inch is
the practical minimum for appreciable areas - on the order of 1 square inch -
and 0.060 inch is the practical minimum for larger areas. The minimum diameter
for cast holes is also on the order of 0.060 inch.^ '
The general design capability of investment casting is high,
with few shape restrictions. Moid joint considerations are absent and components
can be produced without draft taper. Using the wide range of'-techniques avail-
able to the investment caster, virtually any shape can be formed.
Apart from dimensional errors, investment castings are subject
to a similar range of defects to those encountered in other processes - e.g.,
misrun (i.e., incomplete filling of the mold cavity) and non-metallic inclusions.
Defects with causes peculiar to investment casting include blowholes due to in-
complete removal of wax residues and surface defects resulting from local fail-
ure of the primary coating.
In the cost examples given above, investment casting was com-
pared to sand casting, welding, and machining, as alternative methods of manu-
facture. It is obvious from these examples that investment casting is more cost
effective, principally because of the relative simplicity of investment casting
-61-
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and the minimal need for finishing operations and machining. There are other
methods having more similarities to investment casting - namely, die casting,
permanent mold casting, shell molding, and powder metallurgy. Appendix A con-
tains detailed summaries of these alternative processes, but their advantages
and disadvantages .relative to investment casting are given here.
5.2.5.1 Shell Molding(8)
Aggregate molding is a term referring to traditional
sand casting, to shell molding, and even to investment casting. In each casting
method the mold material is aggregated refractory material; in virtually all
other respects the processes are entirely different from one another.
Shell molding is a casting method in which fine sand
(on the order of 100 to 150 mesh) is mixed with about 5 percent of a suitable
synthetic resin, such as phenol formaldehyde. Metal pattern plates (which are
permanent patterns - as opposed to the disposable patterns used in investment
casting) are heated to between 400 and 500°F. (The two pattern plates correspond
to the two halves of the shell mold to be produced.) They are sprayed with a
silicone release agent. The hot patterns - one at a time - .are fastened to a
"dump box" containing the sand/resin mixture, with the pattern surface facing
the opening of the dump box. When the dump box is inverted, the sand/resin.
mixture falls on the hot pattern surface. The heat penetrates the mixture and
softens the resin causing it"to bind the sand together. After 8 to 20 seconds,
depending on the desired shell thickness, the dump box is re-inverted and the
loose sand/resin mixture falls away from the pattern plate. Additional curing
of the resin is affected by further heating of the shell and pattern assembly,
'then the shell is stripped from the pattern plate. The complete shell mold
consists of two such shells fastened together sufficiently to withstand the
hydrostatic forces of the poured metal.
Shell molding produces surface finishes on the order
of 125 microinches, rms; tolerances of ±0.003 inch/inch are attainable, with
dimensions across the parting line being within ±0.010 inch. Such tolerances
-62-
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are not as close as those attainable with investment casting, but as with in-
vestment casting shell molding is amenable to the casting of almost any metal.
Casting sizes are typically on the order of that of automobile crankshafts,
which are produced by this method. The major disadvantage of shell molding
relative to investment casting is the level of complexity that can be achieved
in the castings - the nature of the method of shell mold manufacture necessi-
tates that in order for the shell molds to be removed from the pattern plates,
there must be no under, cuts in the cast design, and allowances must be made for
draft so that the molds can be removed from the pattern plates without breakage.
5.2.5.2 Die Casting '
In die casting (called pressure die casting in England
and Europe) metal is injected under pressure and at high velocity into a perma-
nent mold where it solidifies under externally applied pressure. The result is
a casting having good surface quality and good dimensional tolerance - except
for across the parting line of the dies.
Recent years have seen the rapid growth of die casting
in aluminum alloys , particularly the very fluid silicon containing -alloys . The
size of castings has also rapidly increased following the introduction of
heavier casting machines. Smaller but significant quantities '.of castings are
produced in magnesium alloys, in fusible alloys based on lead and tin, and in
copper alloys, especially 60/40 brass. Application of the process to alloys of
higher melting point is under development and not currently operational. Thus
it is not suited to the casting of high-temperature alloys, as is investment
casting.
5.2.5.3 Permanent ^ld Casting /
Permanent mold casting, (which in England and Europe is
referred to as gravity die casting) is notable for the very large output of
castings in aluminum alloys, for which the process is predominant as a mass pro-
duction technique. There is also a substantial production of copper alloys and
cast iron/ particularly in relatively simple shapes, and a limited output of
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magnesium alloys. The process is only suitable for fluid alloys owing to the
high freezing rates obtained in the permanent metal molds.
Except for the method of feeding the molten metal into
the two-part, hinged molds (sometimes additional mold parts called slides are
used for the permanent mold casting of more complex shapes) permanent mold cast-
ing is practically the same as die casting, though generally larger castings are
made in the permanent mold process.
Permanent mold casting produces castings having good
surface finish; but the existence of the parting surface in the molds does not
allow the close dimensional tolerances cannon to investment casting, and the
fact that the mold halves must be opened after casting restricts the level of
complexity of the shapes being cast. Permanent mold casting is also not amen-
able to the casting of the high temperature alloys.
5.2.5.4 Powder Metallurgy (P/M)t
Of the four alternative metal forming methods dis-
cussed here only powder metallurgy shares with investment casting the capability
of forming shapes out of high-temperature materials. In fact, P/M can be used
to manufacture parts out of uncastable materials such as tungsten, as well as
combinations of metals and ceramics.
The process of P/M consists of compressing metal-
powders, or combinations of metal powders and powders of other materials, in a
suitably shaped mold. After initial pressing, the parts are heated in an oven
to a temperature close to the fusion point of the metal components (sintering),
then repressed if necessary, or otherwise finished with machining, plating, or
whatever.
One disadvantage of P/M is the intrinsic porosity of
the parts produced. (In many respects this porosity is an advantage, such as
when the parts are to be impregnated with lubricants.) In finishing operations
such as plating and anodizing, corrosive chemicals invade the surface of the
porous parts and are difficult to remove. A further disadvantage of P/M is the
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relative simplicity of the parts that can be produced - undercut surfaces are
difficult if not impossible to produce in direct P/M processes and require sub-
sequent machining.
5.2.6 Disadvantages of Investment Casting
Q
In addition to the environmental hazard associated with the
volatilization of wax additives and fillers during the mold preparation pro-
cedures, investment casting is labor intensive, and the size of castings is
limited (the weight of wax or plastic required for a casting increases as the
cube of the characteristic linear dimensions of the casting). The majority
of investment castings weigh less than 1 pound.
5.3 Size of Investment Casting Industry
The Investment Casting Institute places the number of investment cast-
ing foundries in the United States at about 150. ' Uncertainty as to the exact
number derives from the fact that not all investment casting foundries are mem-
bers of the ICI. And, of course, there are many many types of business oper-
ations where investment casting is carried out as a nonspecialty - e.g., there
are probably thousands of jewelry manufacturers practicing investment casting.to
some, extent, and there are probably many foundries specializing in other types
of casting with investment casting as a small sideline.
• 5.3.1 Employment and Value of Shipments
«
Census Bureau data on foundries includes a listing of steel
investment foundries and a listing on nonferrous foundries not elsewhere.clas-
sified which includes nonferrous investment foundries. In Table 5,8.below,
showing the value of shipments from investment casting foundries, the figures
for nonferrous investment castings were derived on the basis of data frcm the
Investment Casting Institute - namely, that the ratio of dollar value of ferrous
to nonferrous investment castings is 3 to 1; that is, '75 percent of the value
of investment cast shipments are ferrous castings, and the remainder are non-
ferrous. (The ICI has also made a rough estimate that the ratio of the number
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of ferrous castings to nonferrous castings is on the order of 80/20 to 90/10;^ '
the difference between these estimated ratios and the ratio of values of ferrous
to' nonferrous castings probably results from the consideration that nonferrous
investment castings, are more likely specialty items for which the per-unit cost
is slightly higher because of smaller number of castings.) Thus it can be
assumed the dollar value of nonferrous investment castings is one-third of the
dollar value of ferrous investment castings. Employment figures in Table 5.8
are also from Census Bureau data, except that the employment in nonferrous in-
vestment casting production is also derived on the same basis as above - that
is, for each three people employed in ferrous investment casting, one is employed
in nonferrous investment casting.
According to the Investment Casting Institute the "adjusted net
(2)
sales" in the investment casting industry in 1975 were $230 million. The dif-
ference between the $230 million for 1975 and the $544 million shewn in Table
5.8 might be attributed to several factors:
1. The ICI figure for 1975 might not take into account the value of castings
produced for in-house operations - e.g., one jet engine manufacturing
company produces its own investment cast turbine blade and vanes, and these
may not be included in the ICI data.
2. Not all investment casting foundries are members of the ICI, and their
"adjusted net sales" might not be included in the $230 million estimate.
3. One information source - the publisher of a manufacturing trade journal -
said he.thought the Id estimates money value and production volumes were
probably on the low side and are "likely based on educated guesses", since
the investment casting industry is not as communicative within itself as
are other manufacturing industries.
4. The difference between the ICI's definition of "adjusted net sales" and the
Census Bureau's "Value of Shipments" might account for a large part of the
difference.
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Table 5.3
Employment and Value of Shipments for the Investment Casting
Industry (Note: Data for ferrous castings is from Census Bureau
sources; nonferrous employment and shipment value are taken as being
one-third of the ferrous numbers).
Value of Shipments
(millions)
of dollars)
Ferrous Castings $167.6
Nonferrous 55.8
Total $223.4
Snployment
Ferrous 11,600 13,900
Nonferrous 3,867-. 4,633
Total 15,467 18,533
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According to the ICI, the volume and dollar value of investment
castings can be broken down between "general engineering castings" and "gas
turbine blades and vanes" as follows:^ '
Weight basis:
general engineering castings 75%
gas turbine blades and vanes 25%
Dollar basis:
general engineering castings 50 to 55%
gas turbine blades and vanes 45 to 50%
The extra dollar value (per unit of weight of cast metal) of
gas turbine blades and vanes probably derives from the greater degree of care
heeded in the casting of these parts which in service are exposed to extreme
mechanical and thermal stresses. Turbine components are cast in alloys of pre-
cise composition, and they are cast in vacuum and in inert atmospheres to reduce
oxidation during pouring and solidification; extremely close tolerances are pro-
bably also important, which means a high reject rate.
5.3.2 Growth of the Investment Casting Industry
• (2) "'-••-
According to the Investment Casting Institute, investment
casting is growing and taking business from other techniques of manufacturing
such as forging/ powder metallurgy, and especially from machining. Sewing
machine parts (for which production volumes' are in terms of hundreds of thousands
of parts per year) and golf club heads are examples of products which used to be
produced by other methods'but which are now produced by investment casting. For
both sewing machine parts and golf club heads, investment casting offers the
potential for greater intricacy of design, greater manufacturing accuracy, and
it allows the designer a wide range of alloy types. The ICI spokesman says that
practically any alloy .- aluminum, magnesium, steel, cobalt, super alloys, beryl-
lium copper, copper, titanium - can be more economically cast by investment
casting except for lead, zinc and similar metals. Investment casting can typi-
cally save 50 percent-on overall manufacturing costs because the finishing
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operations are so minimal; even die casting entails more finishing operations,
has less intrinsic accuracy (due to parting line in the die), and has less
potential for design intricacy. With investment cast components, finishing
operations may consist simply of electropolishing and plating, with ho machining
other than the grinding away of the gate lug.
Growth rate of the industry is presently near zero, but the
figures for 1976 are expected to show a slight gain in profits. A bad year was
1973, but for the most part investment casting foundries have not had to lay off
personnel. The current slow growth is credited to the general recession,^ '
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Bibliography - Section 5.0
•1. McGraw-Hill Encyclopedia of Science and Technology, Vol. 8, Metal Forming.
McGraw-Hill Book Company, Inc., New York, 1971.-
2. Telephone communications with Henry Bidwell of the Investment Casting
Institute, Dallas, Texas.
3. Beeley, P.R., Foundry Technology. Halsted Press Division of John Wiley &
Sons, Inc., New York. . .
4. Simpson, Bruce L., History of the Metal Casting Industry. American Foundry-
men's Society.
5. Metals Handbook, Vol. 5, Forging and Casting, 8th edition. American Society
for Metals, Metals Park, Chio, 1970, pp. 237-261.
6. Telephone ccranunications with Paul Solomon, Yates Manufacturing Company,
Chicago, Illinois.
7. Telephone communications with Luis Argueso, Vice President of M. Argueso &
Co., Mamaroneck, New York.
8. Campbell, James S., Principles of Manufacturing Materials and Processes. ,
McGraw-Hill Book Company, Inc., New York, 1961.
9. Responses of foundries to a questionnaire distributed by Yates Manufacturing
Co. of Chicago; copies sent by Yates to EPA.
10. Responses of wax manufacturers to Section 308 questionnaries.
11. Versar in-house study of polychlorinated terphenyl (Aroclor 5460) measuring
PCB content.
i-
12. Taylor, Howard F., Merton C. Flemings and John Wolff, Foundry Engineering.
John Wiley & Sons, Inc., New York, 1959.
13. Metals Handbook, Vol. 5, Forging and Casting, 8th edition. American Society
for Metals,-Metals Park, Chio, 1970, pp. 285-313.
14. Metals Handbook, Vol. 5, Forging and Casting, 8th edition. American Society
for Metals, Metals Park, Ohio, 1970, pp. 265-284.
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15. Hirschhorn, Joel S., Introduction to Powder Metallurgy. American Powder
Metallurgy Institute, New YorH, 1969.
16. 1972 Census of Manufacturers, Ferrous and Nonferrous Foundries. U.S.
Department of Commerce, Bureau of the Census.
17. Telephone communication with Dave Veit, publisher of Precision Metal Magazine,
Cleveland, Ohio.
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6.0 INVESTMENT CASTING WAXES
The preceeding section dealt with the investment casting industry, its
size, its manufactioring capabilities and its limitations. This section deals
with the wax used in investment casting, the wax that is lost in the lost-
wax process, which is the older name of investment casting.
There are actually many types of wax that have been used in the lost-wax
process. In the earliest times, the waxes used obviously must have been of
some natural type, probably most commonly beeswax or some kind of vegetable
wax. Modern waxes are compositions of natural and synthetic components which
can, in general, be referred to as thermoplastic materials. Thermoplastic
materials in this context refers to natural and synthetic waxes as well as to
such unwaxy materials as polystyrene, which has been used widely in invest-
ment casting for several decades both by itself and as a filler material with-
in the more traditional wax compositions. The term thermoplastic, as applied
to both waxes and polystyrene (as well as to other materials discussed below),
indicate that these materials soften and liquify when heated, but regain their
room temperature properties when cooled. Polychlorinated biphenyls have been
used as fillers in these modern waxes. Polychlorinated polyphenyls, often -
contaminated with PCBs, have also been used because they perform well' as compo-
nents and fillers in investment casting waxes - that is, polychlorinated poly-
phenyls improve significantly the desirable properties of casting wax formu-
lations .
It should be noted that PCBs per se_ are no longer used in investment cast-
ing. The only chlorinated biphenyl that was used was the fully-chlorinated
decachlorobiphenyl, and it was used only during a period of several years ending
(2\
in the middle of 1976. ' Polychlorinated terphenyl, on the other hand, has
been in use as a wax component for more than 20 years and continues to be used
now. To the extent that polychlorinccted terphenyl (PCT) contains PCS con-
tamination, PCBs are still an issue in investment casting.
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6.1 Background
When lost-wax process was first practiced several thousand years
ago, practically any wax would suffice as a pattern material for wax expansion
on heating and shrinkage on freezing had little effect on the usefulness of
the casting as close tolerances were not required. Archeological evidence
indicates that most of the earliest lost-wax castings were of ornamental and
artistic significance. Also, the wax pattern was more than likely shaped or
carved by hand and at low temperature prior to the making of the mold, so
that the investment caster achieved a casting that was an accurate represen-
tation of his pattern. The main defects were likely to have been misrun cast-
ings (i.e., incompletely filled molds) , rough surface finish (the mold material
would probably have been bonded sand of a course grade by today's standards),
and nonmetallic inclusions in the casting (arising from impurities in the
melted metal to be poured, or from impurities in the wax which might not have
been entirely removed from the mold when the wax pattern itself was melted and
(4)
poured out). .
The only investment casting" operations for which patterns are presently
handmade at or near rocm temperature are in jewelry and dental work and in •
limited-edition ornamental or artistic castings. Most investment casting, how-
ever, is done on a mass-production basis. Because such mass-produced parts are
o'ften components in products of commercial or strategic value, close tolerances
and close dimensional similarities between the castings are very important,
which means that the patterns from which the molds are made must also fall with-
in certain design tolerances and must all be closely similar to one another.
It is in this mass production of thermoplastic patterns that wax properties be-
came critical, especially the property of thermally-induced expansion - -that is,
the coefficient of thermal expansion, and the expansion (or contraction) that
takes place during melting (or solidifying). Since the patterns are themselves
mass produced in die-type molds, dimensional allowance (as discussed in the
previous Section) must be made for the shrinkage of the pattern wax during
solidification in the pattern die, as well as for the further shrinkage that
takes place as the pattern cools to room temperature.
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Expansion of the wax during dewaxing of the investment mold is also a
problem. Within the last 5 years investment shell molds have become the type
most commonly used because this type of investment casting has become so auto-
mated. Shell investment molds are more fragile than the solid type, which
means that too much expansion of the wax during the process of pattern removal,
can cause the shell investment mold to fracture.
Since, the Second World War, when investment casting became popular
as a method of producing precision castings of high-melting-point alloys,
considerable effort has been paid to this problem of the dimensional changes
of wax as a function of temperature. Among the pattern materials used in
the past several decades with great success are tin and mercury. Both give
high surface quality in the product castings, better finishes than can be
obtained using the best of today's waxes, and both materials are less subject
to dimensional changes as a function of temperature than are waxes. However,
the problems of toxicity and special handling outweigh the benefits. With
tin as a pattern material, high-temperature equipment was needed for the in-
jection of molten tin into the pattern dies, which-themselves had to be made
of materials that could withstand the stresses of continual heating and
cooling cycles. Machinery and dies capable of withstanding temperatures
exceeding the melting point of tin 'cost more than do machines capable of •.
working at wax-melting temperatures, usually below 200°F. With mercury as a
pattern material, the problem was one of cold handling; the mercury pattern,
once cast in the pattern die, had to be maintained at low temperature (below
.-70°F for the pattern dies, and below -37°F for the rest of the process until
meltout). Removal of the mercury remaining after meltout was achieved by
treatment of the mold with successive solutions of nitric acid and sodium
hydroxide and acetone, all of which result in considerable process complexity.
/g\
Marcury toxicity was also a problem. '
Modern wax formulations allow the mold-snaking process to take place
at maximum temperatures below about 200°F, with minimum temperatures being
whatever is comfortable for the people making and assembling the patterns.
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Operating temperatures for pure polystyrene patterns are slightly higher,
except during pattern removal when the pattern is usually burned rather than
melted out of the mold.
6.2 Desirable Wax Properties
The expansion of a typical parrafin wax from 60°F to its melting
point 'is about 14 percent. Such a wax is usually too soft at an elevated
temperature, e.g., 100 to 110°F, to be used in investment casting. The ideal
wax would undergo no volume change as it was heated through its melting point.
Also, the ideal wax would remain hard at elevated temperatures that are less
than the wax's melting point.
There are other properties of an investment casting wax besides
high-temperature hardness and thermal expansion that are important, such as
the viscosity of the molten wax, which may change after more than one use;
and, in those investment casting operations where solvents are used to remove
the pattern from the mold, wax solubility is a consideration. Wetability is
a consideration too, as the investment slurry must be able to wet the wax
surface and adhere to it well enough to ensure a good surface on the product'.
castings. The following wax properties are also important: •
— Accurate Surface Finish - The pattern should reproduce the
internal surface details of the pattern die because such
detail is ultimately carried to the final metal casting.
— Minimal Ash Content - After the wax is melted out of the
ceramic mold, the mold is heated to a high temperature in
order to vaporize and melt out the remaining wax absorbed
in the ceramic mold structure; any ash or unbumed carbon
remaining in the mold can affect the surface qualities and
metallurgical properties of the finished casting.
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— Narrow Solidification Temperature Range - In order to reduce
the amount of time required to make an investment casting,
the speed at which the pattern can harden in its die must be
minimal; if the wax is injected into the pattern die at a
temperature very close to its melting point, the wax will
harden rapidly so the pattern can be removed quickly.
— Strength - At room temperature, investment casting waxes
should, if stressed mechanically, break before they will bend
plastically; this is not a property of ordinary waxes.
— Narrow Ductile-to-Brittle Transition Range - Upon cooling,
the faster the wax pattern becomes brittle and looses its
ductility, the sooner (and at higher temperature) the pattern
can-be.removed fron the pattern mold without the pattern
sagging or otherwise being deformed by handling.
— Resistance to Gum Formation - Some waxes are likely to
oxidize in the machine that injects the wax into the pattern
mold; the result is wax-insoluble gums that interfere with
. the injection process.
6.3 Filled and Unfilled Waxes
It is common practice to use finely divided solid filler materials
in the pattern wax in order to reduce^ the cooling shrinkage of the wax pat-
terns. However, fillers tend to separate from the melted wax due to differ-
ences in density between the wax and the filler material, and they tend to
increase the viscosity of the melted composition. Also, some filler materials
have undesirable thermal expansion characteristics, and some have undesirable
(8)
low melting points.
Various fillers or extenders have been added to base waxes in an
effort to inhibit or prevent shrinkage. Compositions formed by such additions
have not possessed the required non-shrinkage property, and frequently possess
other undesirable characteristics too. Inorganic fillers such as powdered
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mica or silica are left in the mold in small amounts subsequent to melting
and removal of the wax pattern material. Irregularly shaped particles, such
as -wood fiber, sugar or silica, inhibit the flow - i.e., increase the vis-
cosity - of the melted wax. Various plastic additives and sugar have a
higher specific gravity than pattern wax and settle out either during the
pre-casting operation or during casting, at which tine particles of the
additive settle into depressions within the mold. Polystyrene beads have
also been used as fillers but have disadvantages: the pattern wax melts
first and runs out of the mold, leaving a polystyrene residue; if heating
rates are not properly controlled, the polystyrene will char, .making it dif-
ficult to remove from the mold. In addition, even if the polystyrene is
melted properly, its viscous or tacky consistency often causes it to pull
away some of the refractory composition from the wall of the mold, thus'
(9)
causing defects in the final casting.
The difference between wax fillers and wax components is that
fillers are solid materials, usually in a powder form or in the form of small
beads, and they have a melting point that exceeds that of the rest of the wax
composition; components, on the other hand, can be and probably"usually are,
miscible in the wax matrix and melt with it.
6.3.1 PCBs and PCTs in Waxes
For a period of several years ending in the middle of 1976,
decachlorobiphenyl was used as a filler in investment casting waxes. As far
as can be determined, decachlorobiphenyl is the only FOB that has been used
in investment casting waxes, except for those PCBs which enter the waxes as
impurities in other chlorinated polyphenyls used as wax components or fillers.
No PCBs are currently being purposefully added to investment casting waxes.
PCBs constituted between 5 and 70 percent of the total casting wax formula-
tion, according to the patent covering its use in waxes/ ' though actual com-
mercial compositions of PCS wax contained on the order of 25 to 50 percent
of the decachlorobiphenyl.
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Polychlorinated terphenyls are added to waxes to the extent
of about 30 percent to 40 percent of the total wax weight, with the range
being from 30 to 60 percent. PCTs make up the resinous component, or a
portion of the resinous component of the wax formulation. Terphenyls make the
wax harder at all temperatures below the melting point, they cause the wax to
harden faster by improving the thermal conductivity, and they reduce the co-
efficient of thermal expansion of the wax, though not to the extent that deca-
chlorobiphenyl does.
6.3.1.1 Decachlorobiphenyl: History and Advantages
A patent for the use of decachlorobiphenyi was
applied for in October of 1972. In September of 1971 an application for
patent was filled by the same inventor on the use of cyanuric. acid as a wax
filler. Comparison of these two patents gives an insight into the purpose
of fillers in waxes, and shows the relative value of cyanuric-acid-filled wax,
decachlorobiphenyl-filled wax and unfilled wax. The following material comes
directly from these two patents:
"The composition of this invention comprises a
thermoplastic pattern material and decachlorobiphenyi in an amount of from 5 ''
percent 'to about 70 percent by weight of the total thermoplastic pattern form-
ing composition. For high, quality castings, the particle should not exceed
100 mesh. Decachlorobiphenyi does not appreciably expand or shrink in a range
from ambient room temperature to a temperature of 305°C. In pattern forming
compositions decachlorobiphenyi is inert, hence it'is not subject to shrinking
upon cooling as are the lower melting thermoplastic portions of the thermo-
plastic pattern forming compositions. '
In his patent on the cyanuric acid filler, the in-
ventor says virtually the same, except that the material is stable to its sub-
limation temperature which is about 330°C.
The following table lists the physical properties of
decachlorobiphenyi and 'cyanuric acid: '
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Decachloro- Cyanuric
Biphenyl Acid
f •
Molecular weight 499 129.08
Chlorine content 71.7% 0
Specific gravity 1.95 1.73
Melting point 305.0 to 305.5°C 330°C
(sublimates)
Boiling point (at 760 nrn Hg) 450 to 460°C
Dielectric constant . 3
• Coefficient of thermal
expansion per °C 52 to 63 x 10"*6
In both of these patents,' the inventor defines a
basic pattern wax of the following composition, then compares the thermal ex-
pansion characteristics of this wax to the same wax with 60 percent cyahuric
acid in one case and 60 percent decachlorobiphenyl in the other case. The
basic wax is:*
Parts by Volume
Terpene polymer (115°C m.p.)
Synthetic paraffinic mineral wax (200°C m.p.)
Paraffin (138 to 140°C m.p.)
Natural carnauba wax
Macrocrystalline wax (175 to 180°C m.p.)
In each of the cases where decachlorobiphenyl and
cyanuric acid are added to the above wax formulation, the fillers (i.e., the
cyanuric acid and the decachlorobiphenyl) retained their participate iden*-
tities.. The following table compares the thermal expansion characteristics
of the above wax with and without these two fillers:
*Appendix B is a glossary of names of different types of casting waxes and
wax components.
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Unfilled Wax with ' Wax with
Tenp. (°F) Wax Cyanuric Acid Decachlorobiphenyl
75 0% 0% 0%
85 ' 0.35 0.0 0.0
95 1.06 0.21 0.42
105 1.41 0.42 0.42
115 2.64 1.07 1.25
125 4.05 1.71 1.25
135 5.63 2.14 1.66
145 6.69 2.35 2.47
155 7.57 2.56 2.47
165 8.80 2.99 3.25
175 8.98 3.21 3.25
In spite of the incremental steps shewn for the
deca-filled wax, the method of measurement is supposed to have been within
±0.2 percent accurate. For all practical purposes, the cyanuric acid has
the same thermal 'expansion properties as the deca-filled wax.
Decachlorobiphenyl was used as a-wax filler by.
only one manufacturer and for a period of only several years (1973-1976).
To summarize its advantages: At the initiation of its use in'investment
casting wax it was a low-cost filler that performed well in controlling the
thermal expansion of the wax, and, during the firing of the investment mold,
it burned out cleanly leaving virtually zero ash and residue to contaminate
the cast metal. . >l
The use of decachlorobiphenyl was discontinued in
the middle of 1976. The reasons for the discontinuance were (1) controversy
over the use of PCS and the potential for adverse publicity for the wax pro-
ducer using the PCS in its product, (2) impending legislation on both the
state and Federal levels which would ban the use of PCBs, (3) the increasing
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cost of decachlorobiphenyl, which had to be imported because it was never
manufactured in the United States.^ '
6.3.1.2 Polychlorinated Terphenyl; History and Advantages
Polychlorinated terphenyls have been used in in-
vestment casting waxes for more than 20 years, and are still incorporated
into waxes by at least three of the eleven known wax manufacturers. PCT is
not a wax filler, as it is miscible with and melts with the total wax formu-
lation. In effect, PCTs constitute the resin component of the wax formula-
tion. (Resins have been used in investment casting waxes for at least as
long as PCTs, and likely longer; resin is defined in Appendix B, which is a
glossary of components, fillers and additives used in waxes.) There are no
patents covering the use of PCTs in waxes used in investment casting, but
there is a patent claiming the use of a specified proportion of PCT in waxes
used as tooling compound (see Section 4.0).
PCTs are incorporated into investment casting
waxes in amounts ranging from 30 to 60 percent, with the average being on the
order of 40 percent. The function of the terphenyls in waxes is generally
the same as that of the decachlorinated biphenyl: it improves the working
properties of the wax. Specifically, terphenyl reduces the -change in wax..
volume as a function of temperature and during solidification (and melting),
and it hastens solidification, probably by improving the conductive heat
transfer properties. According to one data source, terphenyls cause the wax
to rapidly form a shell in the pattern mold which allows quick removal of the
pattern from the mold, but it seems more likely this characteristic is a
result of improved heat transfer although the terphenyl may also increase the
hardness of the solidified wax, the wax still has a volume shrinkage upon
cooling which would result in excessive stresses on a thin shell of solidi-
fied wax. It therefore seems likely that terphenyls cause the wax to harden
faster, and to a greater hardness; the overall result being the achievement
of rapid production of high quality' patterns.
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Prior to 1972, polychlorinated terphenyl was
available from Monsanto. Terphenyl cost at. that time was about 20C/lb. In
April of 1972 terphenyl production was ended in the United States, and wax
manufacturers had to start importing it. Prices of imported terphenyl were
20C to 40
-------
Table 6.1
Status of State Legislation Restricting Manufacturing,
Use and Sale of PCBs and PCT Confounds
State Status of Legislation
Illinois Proposed; passed Senate and
may be voted on in 1977 in
House
Indiana Law
Michigan Law
Minnesota Law
New York Proposed ;• two bills are in
committee
Ohio Very little activity; may be
a year before legislation is
proposed
Wisconsin Law
Description of Legislation
PCB compounds or mixtures;
does not include PCTs
Includes both PCBs and
PCTs
Includes both PCBs and
PCTs
Includes only PCT compounds
Includes only PCBs
Includes only PCBs
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wax and the filler material, which, means that the melted wax must be contin-
ually aggitated prior to injection (into the pattern die) so that the filler .
material does not settle out (or rise to the top, if the specific gravity of
the filler is less than' that of the wax). This difference in specific
gravities might be one reason why, in some investment casting foundries, the
wax is injected into the pattern die in a semi-molten state, or even in a
soft/ but solid, state. (Another reason for such low-temperature injection
is to minimize the cooling shrinkage of the pattern after it has been in-
jected into the die.) A second industrial disadvantage of decachlorobiphenyl-
filled waxes was a trivial one:. The product wax was still not ideal in its
properties. This was not really a problem, of course, because the perform-
ance of decachlorobiphenyl waxes was apparently very satisfactory.
It is the environmental problems caused by PCBs that have
condemned both PCBs and PCTs in investment casting. Polychlorinated poly-
phenyls endure in the environment, and, though these chemicals are not
acutely toxic and though there is little data on their chronic toxicity,
evidence has been "found indicating a considerable potential for environmental
damage which can both directly and indirectly influence human beings. Such
evidence of the influence of chlorinated hydrocarbons on the life cycles of
fish and birds has been sufficiently covered elsewhere and need not be re- .
iterated here. Interested readers are referred to Benate Kimbrough's defini-
tive article, "The Toxicity of Polychlorinated Polycyclic Compounds and
Related Chemicals", published in the January, 1974 issue of QRC Critical
Reviews in Toxicology. There are more than 300 references cited in the
bibliography.
6.3.2.1 Environmental Stability of Decachlorobiphenyl and
Polychlorinated Terphenyl
It has been argued by persons both in the invest-
ment casting industry and outside of it that decachlorobiphenyl, by virtue of
its extreme stability (melting point: 480°F; boiling point: 850°F), is in
actuality an environmentally safe material. .The flaw in this argument, however,
-84-
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is that if it is so stable, and, indeed it is the most. stable of the poly-
chlorinated biphenyls,- it will •.accumulate in the., environment more than would
other members of the chlorinated', biphenyl family and .thereby have an effect over
long periods which, might exceed:.that of the less chlorinated', members of the family.
In other words, though the water solubility and vapor pressure of decachloro-
biphenyl may be less than that of any other chlorinated biphenyl, if there is
more decachlorobiphenyl in the environment than, other chlorinated biphenyls,
then it could have an effect on the environment out of proportion to its
relative inertness. Data on the environment endurance and degradation path-
ways of decachlorobiphenyl and of each mixture and pure species of chlorinated
biphenyls is scarce. .Among the few things known for certain aside from the
potential for, and reality of, environmental hazard - is that the higher
chlorinated forms endure longer than tiie lower chlorinated forms. But what-
ever the level of chlorination, PCBs in general can be accumulated in bio-
logical systans so that concentrated amounts of these materials can be passed
up the food chain.
With respect to chlorinated terphenyls, very little
is known about either the toxicology or the environment endurance. In ai
study by Allen, V commercial PCTs manufactured by Monsanto were fed to rhesus
monkeys in concentrations of 5000 ppm for three months. Physiological changes,
including morbidy, resulted. Subsequent testing by Versar Inc., of the terphenyl
formulation used by Allen indicated, however, that it was contaminated with PCB
(14)
to the extent of 0.56 percent, v ' sufficient concentration, according to Allen,
to account for the large portion of the damage noted in the test animals.
Thus little is known about terphenyl toxicology since so little study has been
done, and that work which has been done was likely influenced by PCB contamina-
tion of the PCTs tested.
As for environmental endurance, PCTs, like PCBs,
.are stable in direct relation to the degree of chlorination.
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6.3.2.2 Sources of PCB/PCT Loss to the Environment in the
Investment Casting Industry
The decachlorobiphenyl used in investment casting
waxes until the middle of 1976 was a very high melting, low volatility ma-
terial in comparison to the polychlorinated terphenyl formulations still
being added to ...some casting waxes. It is likely that any chlorinated bi-
phenyl contamination in the PCTs currently used is on the average not fully
chlorinated, which means such PCB contaminant would be more volatile than the
previously-used decachlorobiphenyl. Thus it is likely that on a pound-for-
pound basis more terphenyl and its contaminant biphenyls would be lost by
volatilization during the high temperature portions of the investment casting
foundry process than was the case with the .deca PCB. Figure 6.1 is a flow
chart of wax usage in a typical investment casting foundry. Figure 6.2 shows
an idealized flow chart of an investment foundry and the probable points of
PCB/PCT entry into the environment. The highest temperature part of the
process shown in Figure 6.2 is the mold firing and preheating phase where the
molds are heated to as high as 2000°F, and any residual wax remaining prior
to firing is volatilized into the atmosphere in this part of the process.
(The amount of wax remaining -in the molds prior to firing is in the' range of •
0.1 to 10 percent.) PCB fillers and PCT additives constitute an average qf
about 40 percent of the wax.
Losses to the atmosphere from the dewaxing process
are significantly less than from the firing process because most foundries
use autoclave dewaxing which, during- operation, is isolated from the air.
Opening of the autoclave might have contributed to release of decachloro-
biphenyl to the atmosphere, but probably only slightly since the autoclave
process does not reach sufficient temperature to even melt decachlorobiphenyl
(m.p. 580°F). The less chlorinated, lower-melting terphenyls with their
probable PCB contamination are, however, melted at autoclave temperatures and
significant volatilization of these PCTs and PCBs could take place during de-
waxing, or immediately upon opening of the autoclave, unless the autoclave is
allowed-to. cool thoroughly prior to .opening.
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IMPORTED PCBl
WAX-
PATTERN
WAX
PRODUCTION
PACKAGING AND SHIPMENT
(-30% PCBi, IN PLASTIC BAGS)
WAX- PRODUCTION
PATTERN
WAX
VIRGIN WAX
STORAGE
HEAT
EXCHANGER
HOT „
WAX "
REMOVAL OF
PATTERNS
FROM DIES
STEAM
T
.CLARIFIED WAX
DEWATERING IN
OPEN KETTLES
-»• BOTTOMS TO DISPOSAL
_£
FORMATION OF
CERAMIC MOLD
BY DIP-COATING
SPRUES AND GATES
FORMATION
ADDITION OF
SPRUES AND GATES
CERAMIC MOLDS
PSTACK GASES
MOLD
FURNACE
250O°F
METAL
POURING
COOLING
MOLD
REMOVAL
CASTING METAL
SPRUES AND GATES
REMOVAL
PACKING AND
DISTRIBUTION
OF CASTINGS
INVESTMENT CASTING PROCESS
Figure 6.1 - Flow Chart of Wax Usage in Investment Casting
-------
FOUNDRY
MAKE-UP
AIR
CD
00
r
i
MOLD
PRODUCTION
STACK
GAS
FOUNDRY
• AIR
EXHAUST
OEWAXING
WAX
RECLAMATION
' ' DISPOSAL
I ' SEWAGE
Figure 6.2 - Flow Chart Showing Probable Sources of Environmental
Pollution from a Typical Investment Casting Foundry.
-------
Volatilization during wax melting and pattern in-
jection into the pattern dies is probably insignificant since the melting
process takes place in closed kettles, and injection itself is done under
pressure and at a temperature not much higher than the melting point of the
wax. Further, the injected patterns are not removed from the pattern dies
until they have cooled and hardened sufficiently to be removed without
damage. .
losses during the wax reclamation phase of the
process would mostly be carried in the water removed from, the reclaimed wax.
Solubility of PCBs and PCTs in water is inversely related to the degree of
chlorination; thus terphenyls and any PCS contamination contained in the
terphenyls would more likely produce a higher concentration in the foundry
wastewater than would the decachlorobiphenyl.
The above comparisons of foundry losses of PCTs
and PCB contamination with decachlorobiphenyl may make the decachlorobiphenyl
appear preferable in terms of environmental pollution from investment casting
foundries, but though losses may be less for the decachlorobiphenyl in the
mold production, wax reclamation and dewaxing processes, the losses during the
mold firing were probably greater for the decachlorobiphenyl because its
greater chemical stability at high temperatures assures that if losses do 'take
place during the mold firing operation, decachlorobiphenyl would much more
likely escape destruction in the furnace and stack than the lower chlorinated
PCTs with their PCB contaminant. In other words, the greater thermal and
chemical stability of the decachlorobiphenyl may have minimized losses to the
environment during most of the foundry processes, but losses during the mold
firing operation are likely much greater for decachlorobiphenyl than for the
terphenyl and its PCB contaminant.
Detailed data on the losses from, the various parts
of the foundry process are not available. Industry sources claim, that
virtually all wax components are destroyed in the mold firing operation. No
known stack gas analysis has been performed to either substantiate or refute
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this claim; nor have analyses been performed to determine the level of PCS/
PCT contamination in foundry air or wastewater.
6.3.2.3 Sources of PG3/PCT Loss to the Environment in Wax
Manufacturing
Very little is known about the wax manufacturing
process. However, it is known that in the process fillers are added in
powdered form to the molten wax base. Processing to a desired particle size
may be performed, and losses of dust to the environment by air routes from
both size reduction and mixing would be expected. Chlorinated polycyclic
fillers are, however, no longer used in investment casting.
With regard to the use of chlorinated polycyclic
components, losses to the environment would probably result from'direct
volatilization of the ccmponent materials, which must be melted to be added
to the molten wax. No information is available on the process temperatures,
on whether the processing is done under pressure or within enclosed con-.
tainers, or on the volatility of polychlorinated terphenyl compounds except
for the 'single evaporation loss rate data point given "in Section 6.6.3.2.1 -
0.03 percent in 5 hours at 163°C. No analyses of plant air or water have
been performed to date.
6.4 Wax Manufacturers
Table 6.2 is a listing of investment casting wax manufacturers
indicating whether they have produced or currently produce waxes containing
PCBs or PCTs. Total production volumes cannot be derived from the data that
have been gathered; thus production data for the several companies that have
complied with requests for data are not included here since publication of
such information might jeopardize their competitive positions. If sufficient
information had been available to estimate the total annual volume of wax
production, such a total figure would have been stated.
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Table 6.2
Lists of I.C. Wax Manufacturers
Status of Usage of PCS end PCT in
Wax Foanulations
Wax Hanufaeturer
Alexander Saunders and Co.
P.O. Box 265
Coldspring, Mew York
M. Argueso £ Co., Inc.
441 •.•Overly Avenue
Mamaronedc, N.Y. 10543
Azuood Corporation
ftocklaiqh Industrial Par*
Sodciaiqh, New Jersey 07647
Caatshore Chemical
1221 East Barney Ave.
Musksgan. Michigan 49443
Freeman Manufacturing Co.
1315 Main Avenua
Cleveland, Ohio 44113
J. ?. McCOughlin Co.
2«2S North Payer Avenue
BOS€DI63d« f^a 11 ^PITU^
Kerr Manufacturing Co.
23200 Wide load
P.O. Box 455
Romulus, Michigan
Kindt-Collins
12651 Elowood Avenue
Cleveland, Chio 44Ul
Conpany Contact
Mr. Sauncers, Jr.
Lou Argueso
Mr. Nicolelis
Mr. (towy
Davidson
John McCouohlin
Oenisa Tandon
Robert Probst
Past
Currant
NO
NO
PCBs - YSS
PCTS - NO
PCSS - ^o
PCTS - '.is
PCTS - YES (before
Monsanto 's ban)
?CBs - NO
PCTS - NO
PCSs - NO
?CT3 - Y£S
PCBs - NO
PCTS - OS
No compliance with
information request
PCSs - NO NO
PCTs - Experimental • Sxperimaital
to
to
NO
YES
tenet Coiporaticn
P.O. Box 2D8
Bleachery Placa
Chadwidca, New York 13319
ttoqer Read Co.
161 Pleasant Street
Reading, Massachusetts
Precision Cast Parts Corp.
4600 South East Barney Dr.
Portland, Oregon 97206
Yates Manufacturing Co.
1615 West 15th Street
Chicago, Illinois 60608
10
John Newberry
Mrs. Griffin
Mite Hanslot
Paul Solcnen
Distributor (only) for M. Arguoso & Co., Inc.
PCBs - NO
PCTS - NO
PCBS - NO
PCTS - YES
PCBs - YES
PCTS - YES
NO
NO
to
NO
to
YES
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6.5 Sources of PCB/PCT Supply
6.5.1 Domestic Sources
Polychlorinated biphenyls were produced in the United States
primarily by Monsanto. Production commenced in the late 1920s and continued
without interruption until April of 1971 when Monsanto voluntarily ceased
production of PCBs intended for use in. other than closed systems such as
electrical capacitors and transformers (where they were used respectively as
dielectric fluids and cooling fluids). Between 1929 and '1975 the total U.S.
production of PCB formulations amounted to some 1400 million pounds, of which
it is estimated 758 million pounds are still in service in some form, 55
million pounds have been destroyed, 290 million pounds are in dumps and land-
fills, and 150 million pounds are contained in soil, air, water, sediment,
and in the bodies of animals, including humans.
By June of 1971, PCBs manufactured in the U.S. by Monsanto
were no longer available for use in open systems, (.there was a two-month
delay between curtailment of production and depletion of stocks.) Approxi-
mately one million pounds of PCB heat transfer liquid was manufactured by
Geneva Industries, Houston, Texas, from 1971 to 1973. The domestic pro-'
ducer of PCB-filled wax did not start-until after Monsantors voluntary
curtailment of production for open-ended uses. Further, it has been stated
by a Monsanto spokesman that the company has never produced a PCB product that
was more than 70 percent chlorinated, because high chlorination of biphenyl is
difficult (the material becomes thicker and harder and more difficult to
chlorinate at the higher chlorination levels)', and the resultant product would
(12)
be high in impurity, mainly in the form of lower chlorinated biphenyls.
Decachlorobiphenyl used in casting waxes has come exclusively from foreign
sources; no information is available on the degree of contamination of this
foreign decachlorobiphenyl.
Polychlorinated terphenyls, which have been used in invest-
ment casting waxes for more than two decades have at times been supplied to
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wax formulators "By Monsanto ..and its outlets." However, in April of 1972,
Monsanto ceased production of chlorinated terphenyls, and, as with PCBs, there
was a several-month delay between curtailment of production and cessation of
sales of PCI. At that time, Aroclor 5460 (the Monsanto PCT formulation used
in casting waxes) was selling to wax manufacturers for about 20£/lb. Once
donestic production ceased, wax formula-tors were forced to buy from foreign
sources at a cost of 20
-------
as pattern materials can be classified under the general heading of thermo-
plastics , though it is likely that the use of thentosetting resins has been
investigated and these materials could conceivably be used as .pattern ma-
terials (specifically/ as fillers) for seme casting applications. Generally
' the thermoplastics provide the greatest ease in handling and pattern pro-
duction since thermosetting resins require heat and pressure or the addition
of catalysts to affect curing, which is an exothermic process for most if not
all thermosetting resins; high temperature differentials and long cooling
periods influence the pattern's dimensional tolerances and increase the pat-
tern production cycle time.
6.6.1 Previously-Used Pattern Materials
In a special exhibit in the gem room of the Smithsonian
Institution several years ago were gemrstudded gold investment castings of
flowers and small shrubs. In addition to the monetary value, the exhibit was
technically interesting in that the patterns for the gold castings consisted
of the actual flowers and shrubs. The jeweler who made the castings had
apparently invested the flora in appropriate investment material, and then,
when the investment had hardened, he burned the organic -matter out of the
mold, and poured the gold in..
Generally twigs and flower petals do not make good pattern
materials because they "ash" when burned - that is, they leave behind the
non-volatile residues of the original organic structure. But for this one
special, application, in which production rate was not a consideration, the
jeweller/artist could take the time to use compressed air or some other gas
to blow the ash material frcm the crevices of the investment mold. Such
diligence in the inves-tment casting industry, however, would defeat the cost
effectiveness of the process; pattern materials must burn clean and leave no
residue, or minimal residue, in the investment mold.
Many thermoplastic pattern materials have been used and have
been suggested for use over the years. As the name "lost wax" indicates,
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true waxes, such as natural waxes, beeswax and the like, were originally used
as thermoplastic pattern materials. As other pattern materials were sought
to improve the properties of disposable patterns, other natural thermoplastic
materials, such as gum damar, gum esparto and other resins, plus mineral waxes
of the type extracted from soft coal, and petroleum waxes were adopted for
use. Modified waxes, such as micro-crystalline waxes were developed for use
and are currently used in investment cast procedures. (Appendix B is a
glossary of wax related terms.)
As has been mentioned in other parts of this report, mercury
and tin can be, and have been, used to make patterns. In the mercury process,
mercury is frozen into the desired shape in the pattern die; it is then re-
moved from the die and invested with appropriate material, and then the
mercury is melted out: Any mercury remaining in the mold is vaporized during
the mold-preheating process. The difficulties with mercury are toxicity, the
need for very low process working temperatures (-35° to -70°F), and the
hazards of the mercury cleaning process which entails acid handling. Also,
mercury is expensive. These disadvantages more than offset the advantage of
the mercury pattern process - namely, that the castings produced have ex-
tremely good surface finish, better than can be obtained with the best cast-..
ing waxes currently used, and, since mercury does not significantly change
volume in going from a solid to a molten state, no great stresses are put on
the mold during meltout, as with thermoplastic patterns. This latter advan-
tage assures very high tolerances of the cast product. According to the
Investment Casting Institute, mercury is no longer used as a pattern material
in the United States.
Tin patterns also result in high quality castings. Tin melts
at a higher temperature than do the currently-used thermoplastic materials,
which means that the pattern die material must have higher temperature capa-
bilities than.are necessary for the manufacture of wax patterns, and the tin-
handling and injection equipment must withstand the higher temperatures. The
result is higher capital cost for equipment and/or reduced pattern-die life.
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Modern investment casting procedures rely almost exclusively
on thermoplastic pattern formulations which, depend,ing upon the type of metal
to be cast and the shape of the casting, may be filled or unfilled.
6.6.2 The Ideal Pattern Wax
The ideal pattern material would have these properties:
- No change in volume during heating, cooling, melting or
solidifying
- High conductive heat transfer coefficient, for rapid
cooling after injection into the pattern mold
- Narrow temperature range over which melting and solidi-
fying take place
- Hardness at all temperatures up to the melting point
- Zero ash content; should burnout cleanly from the in-
vestment mold
— No toxic components, and no toxic byproducts produced •
during burnout
- No oxidation or gum formation potential in the injection
equipment
- Good surface .finish, accurately following the internal
surface finish of the pattern die
- Ceramic slurry should adhere well to it but not attack
or dissolve its surface
- Weldahility, so that multiple patterns can be affixed
to a. central pouring basin and sprue
6.6.3 Filled and Unfilled Waxes
The single greatest difficulty with investment casting waxes
is the change in volume that accompanies melting, solidification and, in
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general, temperature change. (This problem has been discussed in Section
5.0.) To reduce this temperature-induced volume change, filler materials of _
various kinds can be added to the wax formulation. Typical filler materials
are powders having the following properties:
- They melt or sublimate at a much higher temperature
then the basic wax formulation, which means they
remain in the solid phase throughout the entire in-
vestment casting process, except during mold burnout
and preheat
- They must have good heat transfer properties
- They must have a specific gravity that is close to
that of the wax, in order to minimize the need for
continuous agitation to keep the filler material in
suspension in the wax prior to injection into the
pattern die
- They must leave minimal ash or other residue in the
investment mold when the .pattern wax remaining in
the mold after the de-waxing operation is burned out
of the mold
- They should exhibit a very low volume change as a
function of temperature
- They should be safe to handle and should present
minimum toxic hazard to foundry workers, and to the
environment in general
The chief functions of fillers in waxes are to increase the
cooling rate and to control volume shrinkage during cooling and solidification
of the pattern. To the extent they serve these purposes, filled waxes sim-
plify the pattern making process and thereby reduce the process costs. Filled
waxes, however, cannot be used in all investment casting operations. Foundries
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having older equipment may not have the facilities for continuous agitation
of the melted wax prior to injectioa into the pattern die. If the wax is
not agitated the filler material will rise or sink (depending on its specific
relative to the liquid wax) and will not be uniformly distributed in the
pattern after the wax is injected into the pattern die. The result could in-
clude clogged injectors and poor-quality patterns, the latter being caused by
differential cooling and shrinkage within the pattern.
One other instance where filled waxes are not used is in
applications where the filler particles might be too large to allow the
pattern wax to flow into the finer crevices of the pattern die; a good example
is the casting of turbine engine blades where the edges of the blades have
very small radii of curvature and the use of filled waxes would cause a low-
(17)
quality edge to be produced on the pattern.
Filler materials that have been and are being used include:
- wood flour
- polystyrene beads or powder
- carbon microspheres
- urea powder
- polyols (e.g., pentaerythritol)
- various organic acids (e.g., cyanuric, fumaric,
isophthalic, adipic)
- decaciilorobiphenyl
Unfilled waxes contain no solid components vfaen the wax is
molten. All of the components melt together and are mutually miscible, and
continuous stirring of the wax is not necessary to maintain the components in
proper distribution. Unfilled waxes do contain resinous materials, and poly-
chlorinated terphenyl has been a commonly used resin component.
Typical wax. components of an unfilled wax are:*t
*By permission, from Metals Handbook Volume 5, Copyright American Society for
Metals, 1970.
tThe terms used in this list are defined in Appendix B.
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Hard Waxes
Vegetable wax (candelilla)
Vegetable wax (camauba)
Mineral wax. (montan)
Synthetic wax, nonchlorinated
Synthetic wax, chlorinated
Microcrystalline Waxes •
Petroleum origin, high m.p. (175°F)
Petroleum origin, low m.p. (145°F)
Insect'origin (beeswax, USP)
Soft Resinous Plasticizers
Rosin derivatives
Terpene resins
Coal-Tar resins
c
Petroleum hydrocarbon resins
Chlorinated resins
Elastomer polymers
Hard Resins
Rosin derivatives
Terpene resins (from plants)
Coal-tar resins
Petroleum hydrocarbon resins
Chlroinated resins
Modifiers
Synthetic wax, nonchlorinated
Elastomer polymers
Polyethylene resins
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A typical wax formulation would be:*
Hard wax „ . 40%
Microcrystalline wax 25%
Soft resinous plasticizers 15%
Hard resins . 20%
Antioxidant 0.05%
Polychlorinated terphenyl is classified under the headings
of Hard and Soft Resins, Chlorinated. PCT has been in use in waxes for more
than 20 years and is still being used. That hard and soft resins constitute
only 35 percent in the example cited above is on the low side, at least with
respect to the use of PCTs which usually constitute about 40 percent of the
wax composition.
6..6.3..1 PCBs
The only polychlorinated biphenyl used in invest-
ment casting waxes was decachlorobiphenyl, and it was used as a filler in
pattern waxes by only one manufacturer. Use of decachlorobiphenyl in waxes
ceased in the middle of 1976.
6.6.3.2 PCTs
6.6.3.2.1 Function of PCTs in Waxes
The polychlorinated biphenyl currently
used in waxes is a product imported from France called Electrophenyl T-60.
The number 60 apparently makes reference to the chlorine content, 60 percent
of the weight of the material, which indicates a rather high degree of
chlorination - sufficient to make the material solid at room temperature.
Prior to April of 1972, PCT formulations
could be purchased from Monsanto. As of that tine, however, Monsanto ceased
production of polychlorinated terphenyls for all open-system applications,
including investment casting since the bulk of the PCT eventually is either
*By permission, from Metals Handbook Volume 5, Copyright American Society for
Metals, 1970
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volatilized into the atmosphere or disposed of along with otherwise unre-
claimable wax. The Monsanto product used prior to 1972 was designated as
Aroclor 5460; the 54 designates terphenyl, the 60 designates the weight per-
(18)
cent of chlorine content. The following are the properties of Aroclor 5460:
Appearance: clear/ yellow to amber, brittle resin or flakes
Chlorine content: 58.5 to 60.6 percent
Acidity: 0.05 rag KOG/g (maximum)
Average Coefficient of Expansion: 0.00179 cc/cc/°C (25° to 124°C)
Specific gravity: 1.670
Density: 13.91 Ib/gal at 25°C
Evaporation loss: 0.03% in 5 hours at 163°C
• Flash point: none to boiling point
Fire point: none to boiling point
Softening point: 208° to 222°F
Refractive index: 1.660 to 1.665
As a resin component in investment cast-
ing waxes, PCTs serve the function of increasing the hardness of the wax
patterns and making the patterns cool faster and with less shrinkage in the .
pattern die.
6.6.3.2.2 Dependence of the Investment Casting
Industry upon PCTs
At the beginning of this study, the main,
issue was the extent-to which the investment casting industry was dependent
upon PCBs. The use of PCBs in waxes was discontinued in the middle of 1976,
after a period of about three years of use, and the impact on the industry as
a whole has been small. The single producer of PCS waxes was influenced by
state legislation controlling PCB use and by impending Federal legislation as
well as by the adverse publicity associated with PCBs. No data are available
on the economic impact on this one wax producer as a result of cessation of
PCB wax production.
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PCTs are more widely used in the industry
and have been used for several decades. Thus the industry is more dependent
upon the use of PCTs than it was upon PCBs. Of the 11 wax formulators listed
in Table 6.3 (12 are listed, but one is merely a distributor for one of the
others), three currently have product lines containing PCTs, whereas six manu-
facturers have at some time .produced PCT waxes. Of the three currently pro-
ducing PCT waxes, at least two are down-playing their PCT wax lines, because
they expect that pending environmental legislation might ban the use of PCTs.
One wax formulator, Freeman Manufacturing
Company in Cleveland, Ohio, terminated production of PCT waxes around the be-
ginning of 1975, a move that was apparently to some degree environmentally
altruistic since there were not any really adequate substitutes for the PCT
waxes at that tine and the company did loose a portion of its business until
adequate substitutes were found. Freeman also terminated its production of
wax lines containing nitrogen compounds because the nitrogen-containing waxes may
generate toxic compounds during the burnout and preheat phase of the invest-
ment casting-process. (The disadvantages of nitrogen-containing alternatives
to PCTs are discussed in Section 6.6.5, Environmental and Toxicological Con-
siderations of Alternatives.) The experience of the Freeman Manufacturing
Company shews that, at least as far as the wax formulators are concerned, -PCTs
are not an essential ingredient; and they have been able to cease production
even though PCT waxes continued .to be available from competitors. Thus it
• does not seem, unreasonable to surmise that an industry-wide restriction on the
use of PCTs would not have a significant, effect on the wax producers, except
insofar as such a restriction might impact on the wax formulators. through some
kind of feedback mechanism from the investment casting foundries, which, of
course, is where the final test of waxes is made.
In the 150 or so investment casting
foundries in this country the various wax formulations perform their functions
of providing patterns from, which molds can be made for the precision casting
of medium, to high temperature metals and alloys. Where the cast products are
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designed with generally small cross-sectional areas, cooling shrinkage of
waxes can have a negligible effect .on the final cast product, and lower-cost
waxes will serve the purpose adequately; but where section thicknesses are
large enough that wax shrinkage could cause surface "dishing" or "cavitation",
filled waxes or waxes that otherwise compensate for. cooling shrinkage are
essential to producing high-quality castings. Thus the question becomes one
of whether or not there exist unfilled non-PCT waxes that perform adequately.
Such waxes do exist and are being used. At least one foundry, the General
Electric Foundry in Albuquerque, New Mexico, has been able to produce its
(19)
cast products with waxes that contain neither PCBs or PCTs. (General
Electric is presently preparing a report on the economic and technical details
of their recent changeover to nonchlorinated waxes.)
6.6.4 Alternatives to PCTs in Investment Casting Waxes
Currently only three casting wax manufacturers produce waxes
containing PCTs as a resin component. One manufacturer is currently experi-
menting with PCTs in waxes, and the other seven wax producers shown in Table
6.2 produce waxes that do not contain PCTs. Of .these seven who do not pro.-
duce PCT waxes, one, Freeman Manufacturing Company, stopped production of PCT-
waxes in the early part of 1975 because of the environmental..controversy sur-
rounding chlorinated hydrocarbons. Freeman also terminated production of
waxes containing nitrogenous components which, during high temperature de-
.composition, generate cyanide or nitrogen oxides depending upon whether the
thermal environment is reducing or oxidizing. Freeman claims to have found
PCT alternatives that perform adequately in casting waxes, but details as to
the actual materials are proprietary and not available. Freeman is among the
largest of the investment casting wax producers,, and that this company was
able to. voluntarily cease production of PCT waxes tends to belie the claims of
other producers that there are no adequate substitutes for PCTs.
It is evident from the material covered thus-far that an
alternative material to PCTs must have nearly the same properties of PCTs in
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casting waxes; that is, the alternative material must produce a wax product
that has a narrow melting-temperature range, good heat transfer so that the
patterns solifidy rapidly in the pattern die, and the wax must be hard up to
temperatures close to the melting point.
To achieve these wax properties, the alternative material
must be a thermoplastic material that is miscible with and melts at about the
same temperature as the -other wax components. The properties of the domestic-
ally-produced terphenyl (Aroclor 5460) are listed in Section 6.6.3.2.1.. Since
the imported terphenyl is chlorinated to the same extent-, (i.e., 60 percent by
weight) it is likely the imported material has similar properties, unless it
contains additional components the Monsanto product was free of, or visa versa.
The relatively higher melting point of the terphenyl relative
to the other wax components, which typically melt at 20 to 50 degrees Fahren-
heit lower temperature, is not a concern once the components are mixed so long
as the product wax has suitable bulk melting properties. Similarly, terphenyl
alternatives need merely fulfill the bulk property requirements of the final
wax product.
Since polychlorinated terphenyl. constitutes a resin component
in the waxes, a suitable alternative would most likely be a -resin too - or, in
the more general sense, a thermoplastic, even though in camion usage this term.
is usually applied to synthetic high polymers and does not include natural
resins.
. Resins can be classified as natural or synthetic, and the
synthetics can be either thermoplastic or thermosetting, as shown in the fol-
lowing outline with examples (Appendix B is a glossary containing additional
information on these materials):
I. Natural Resins - rosin, balsam, kauri, congo, damar, mastic,
copal, sandarac, shellac
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II. Synthetic Resins
A. Thermoplastic Resins - acetal (copolymer, homopolymer),
acrylic, cellulosic resins (acetate, nitrate, butyrate,
propionate, ethylcellulose}, polycarbonate, polyolefin
(polyethylene, polypropylene, polybutylene), polystyrene,
polyvinyl haTide
B. Thermosetting Resins - amino-aldehyde (melamine), poly-
ester (allyl, alkyd), epoxy, ionomer, phenolic
Many of the resins listed above have been used in investment
casting waxes, especially the natural resins. The synthetic thermoplastic
resins are the most likely source of alternatives to PCTs since the synthetics
can be, to an extent, tailored to specific applications. Polyethylene, for
instance, has been and is being used to some, extent in waxes, and the prop-
erties it confers on the wax are a function of the-molecular weight of the poly-
ethylene. Polyethylene has a high coefficient of thermal expansion, however,
which makes it an unlikely substitute for PCTs. (Polyethylene serves to in-
crease the strength of the hardened wax.)
Ethylcellulose is another synthetic thermoplastic resin that
has been extensively tested in casting waxes, but it has a tendency to in-
crease the viscosity of the wax to unacceptable levels.
Polystyrene is a thermoplastic that is widely used by itself
as a pattern material. Polystyrene beads have been used as filler material in
waxes because its high melting temperature allows it to stay solid when the -
wax formulation is melted. Other high-melting thermoplastics can also serve
the function of wax filler, which does not qualify them as potential PCI
substitutes.
To the extent that molecular weight, can be controlled,
synthetic resins of both the thermoplastic and thermosetting kinds can be used
as fillers or components in waxes. Polyethylene has already been mentioned.
Acrylic resins can also be tailored in this manner.
-------
Thermosetting resins tend to harden irreversibly at high
temperatures because of molecular cross-linking, processes; however, it is
possible that high molecular weight polyester resins which might be solids
at room temperature but which might be meltable a sufficient number of times
to make them miscible with the other wax components and to be injected into
a pattern die might have some applicability in waxes, but they might also
cause problems in injection equipment as a result of hardening or gum form-
ation in the high-pressure molten-wax lines. Generally, thennosetting resins
probably have more applicability as fillers than as resinous components.
Alternatives to PCTs have been found and are being used by
at least one wax manufacturer. Specific infontation on the alternative
materials is proprietary and unavailable at this time. Since this information
is not patented, it might be that the material or materials that can replace
PCTs are already widely known in the wax manufacturing field as prior use
precludes patenting.
Potential alternatives to PCT will not likely come from the
class of thermosetting resins, except for the high molecular weight ester
resins which are solid at.room temperature but which melt at elevated temperr
ature.
There are many potential wax components. According to one
source, "all hydrocarbon resins and all ester resins, which number in the .
hundreds", have seme applicability in casting waxes. The problem is to find
the one material, or combination of materials that adequately serve the pur- •
pose of PCTs for the three manufacturers still producing PCT waxes.
6.6.5 Environmental and Toxicological Hazards of Alternatives
The general lack of concrete information on PCT alternatives
has not made it possible to cotment on the potential hazards of alternatives
to PCT waxes.
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In choosing to discontinue its production of PCT waxes,
Freeman Manufacturing. Company also decided not to produce any wax femulations
containing nitrogen in any significant amount, and the reasons are worthy of
consideration with respect to PCT alternatives. Nitrogenous components de-
compose during .the burnout phase of the ceramic mold preparation when the wax
remaining in the mold after dewaxing is volatilized and burned from the mold.
If the chemical environment of the furnace used, for burnout and mold preheat-
ing is oxidizing, the nitrogen compounds have a tendency to form nitrogen
oxides, some of which are acutely toxic and some of which contribute.to photo-
chemical smog problems in urban areas. If the furnace atmospheres are re-
ducing - which is actually rare in investaient casting furnaces since the
objective during' mold burnout is to oxidize the organic material from the
mold - nitrogenous compounds tend to form cyanide compounds, the hazards of
which are well known.
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Bibliography - Section 6.0
1. U.S. Patent #3,887,382, Disposable Pattern, Composition for Investment
Casting. Paul Solomon, June 3, 1975. . (Covering the use of decachloro-
biphenyl in investment casting waxes.)
2. Telephone communications with Paul Solomon, Yates Manufacturing Company,
Chicago, Illinois.
3. Telephone comtttunications with Luis Argueso, Vice President, M. Argueso &
Co., Mamaroneck, New York.
4. Simpson, Bruce L., History of the Metal Casting Industry. American
Foundrymen's Society.
5. Telephone communications with Henry Bidwell, Investment Casting Institute,
Dallas, Texas.
6. Metals Handbook, Vol. 5, Forging and Casting, p. 237, American Society for
Metals, Matals Park, Ohio, 1970.
7. U.S. Patent #3,667,979, Investment Casting Wax. John C. Merges, Jr.,
June 6, 1972.
8. U.S. Patent #3,822,138, Low Shrinkage Wax .Composition fo;r Investment
Casting, Kazuo Noguchi, July 2, 1974.
9. U.S. Patent #3,316,105, Pattern Wax Composition. Poy C. Feagin, April 25,
1967.
10. Responses to Section 308 questionnaires by wax manufacturers.
11. U.S. Patent #3,754,943, Disposable Pattern, Composition for Making Same
and Method of Investment Casting. Paul Solomon, August 28, 1973.
12. Telephone communication with Cole Weber, Monsanto Co., St. Louis,
Missouri.
13. Allen, J.R.., and D.H. Norback, Polychlorinated Biphenyl- and Triphenyl-
Induced Gastric Muscosal Hyperplasia in Primates. Science, Vol. 179,
pp. 498-499.
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14. Versar Inc., In-house study of Aroclor 5460 (terphenyl) used by J.R. Allen
and Versar Inc., December 1976. '(Measurement of PCB Contamination of
Aroclor 5460.)
15. Letter for J. R. Allen to Versar Inc., regarding Versar study of Aroclor
5460 used in Allen's test.
16. Versar Inc., Usage of PCBs in Open and Semi-Closed Systems and the Resulting
Losses of PCBs to the Environment. Springfield, Va., March 1977.
17. Telephone ccmmunications with William Siegfried, Freeman Manufacturing
Company, Cleveland, Ohio.
18. Monsanto data sheet on Aroclor products.
19. Telephone communications with Samuel Megantz, General Electric Company,
Schenectedy, New York.
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7.0 PCBs AS IMPORT COMPONENTS
Polychlorinated biphenyls may be components of imported machinery and
electrical equipment and thereby may not be registered with U.S. Customs as
PCBs. A specific recent instance involved the importation of transformers from
.Germany through Canada to the U.S. and entailed some 500,000 Ibs of askarel
In 1975, Wheelabrator-Frye, Inc., of Pittsburgh, Pa., took delivery of
256 transformers from Trafo Union (a division of Siemens, A German company)
located in Montreal. In 1976, Wheelabrator-Frye took delivery on 256
additional transformers. All of these 512 transformers were askarel filled
prior to importation; they were all the same model, and they were subsequently
sold by Wheelabrator-Frye to a utility company for installation and use in
electrostatic precipitators. Each transformer contained about 94 gallons of
askarel. In the early part of 1977, 256 more transformers of the same model
were inported to Wheelabrator-Frye for purchase and installation by the same
utility customer, but these last transformers, at the specification of the
utility company, were mineral oil cooled rather than askarel cooled. Wheela-
bratar-Frye says that the. importation of precipitator transformers for this
customer is completed. It is expected that none of the transformers will be ' •
in service until the ;end of 1977. Wheelabrator-Frye will supervise the
installation of the precipitators and the utility will maintain ownership of
the transformers after installation. According to Wheelabrator-Frye, the
importer is 1 isted with U.S. Customs as Siemens.
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Sources of Information - Section 7.0
1. Personal Oonntunication with one Mr. Hatch of Wheelabrator-Fr^e, Inc., of
Pittsburgh, Pa.
-Ill-
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8.0 CONCLUSIONS AND RECOMMENDATIONS
There are only four manufacturers that are currently directly reliant upon
imported polychlorinated polycyclic compounds. . They are:
Joy Manufacturing Company, Pittsburgh, Pennsylvania - Sole user of
heat transfer fluids for the cooling of mining machinery; the specific
PCS formulation is called' Pyralene and it is imported from France.
J. F. McCoughlin Company/ Rosemead, California - Uses imported poly-
chlorinated terphenyls in investment casting waxes.
Yates Manufacturing Company, Chicago, Illinois - Uses imported PCTs in
investment casting waxes.
M. Argueso & Company, Mamaroneck, New York - Uses imported PCTs in
investment casting waxes and tooling compounds.
Recommended steps to control the uses of imported PCBs need no longer be
considered since the Toxic Substances Control Act specifically addresses the
PCB problem (Section 6(e), Public Law 94-469), and states that imports must cease
as of one year after the effective date of the Act, except for those uses where the-
PCBs will be totally enclosed (specifically in electrical transformers and capacitors)
or where an exemption has been granted. Paragraph (2) subparagraph (A) states that
"effective one year after the effective date of this Act no person may manufacture,
process or distribute in comerce or use any polychlorinated biphenyl in any manner
other than in a totally enclosed manner." The Act became effective on January 1, 1977.
Importation is defined in the Act as manufacture.
The single use of imported PCBs is in the maintenance of a line of PCB-contain-
ing mining machinery that Joy Manufacturing Company produced up until several years
ago. (Production of PCB-containing Joy continuous miners terminated in 1970; PCB-
containing Joy loaders have not been produced since 1973). Since mining machinery
does not qualify as use of PCBs in "a totally enclosed manner", the currently oper-
able machinery will have to be either modified so. that it is not dependent upon
PCB cooling fluids or it will have to be put out of service at the end of 1977,
unless the EPA formally finds that continued use of PCBs will not present an un-
reasonable risk of injury to health or the environment in accordance with the provi-
sions of Section 6 (e)(2)(B) of the Act.
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As shown in Section 3.0 of this report, the PCB-containing Joy machinery
accounts for the following percentages of all equivalent mining machinery currently
operable:
loaders -15.6% (350 Joy loaders)
continuous miners - 2.5% (50 Joy miners)
FOB fluids- are used in the motors of the mining machinery (two motors in
each loader and three motors in each continuous miner) as heat transfer fluids.
For the loaders, dry-^notor conversion kits are available from Joy at a total
conversion cost of about $6,200 per loader. Thus the total conversion cost
for the approximately 350 currently operable loaders is on the order of $2.2
million and will have to be borne by the owners of the machinery.
No equivalent dry-motor conversion kits are available for the continuous miners
since the motors are larger and dissipate more heat than dry motors of the same
physical size could handle. However, if the entire cutting-head assemblies on
each miner are replaced - cost about $65,000 per miner - the total cost to the owners
of the 50 or so operable miners would be about $3,250,000. Otherwise, the replace-
ment cost for the 50 miners- at about $300,000 each would be $15 million.' '
The following considerations should be kept iri mind with regard to the con-
tinuous miners:
(a) The last of the PCB-containing continuous miners was built by Joy
in August 1970; thus most of these machines are more than 7
years old.
(2)
(b) The typical service life of these miners is at least 10 years.
(c) Although the number of miners considered currently operable is about 50 /
the number in actual operation is possibly considerably less than
this.'2'
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(d) The Organization for Economic Co-Operation and Development, of which
the U.S. is a member, issued a decision on February 13, 1973, (see
Appencix C-l) stipulating 'that member nations restrict the use of PCBs
in all but four categories of use, one of which includes mining machinery.
This OECD precedent might be useful to the owners of PCB-containing
Joy mining machinery in petitioning for a temporary exemption from
Toxic Substances Control Act.
With respect to imported polychlorinated terphenyls used in tooling compounds
and investment casting waxes, the following points should be noted:
(a) Terphenyl-containing investment casting waxes currently cost 15<= to
25£ per pound more than non-terphenyl waxes; manufacturers who
produce terphenyl waxes claim that their terphenyl wax sales are
less than half of their total wax sales.
(b) Of the eleven investment casting wax manufacturers, at least
six produced, terphenyl waxes.at the. beginning of this decade;
now only three do. . Of the three that ceased production of
terphenyl waxes, one stopped when domestic terphenyls became
no longer available, and one of the*remaining two, if not both,
voluntarily chose to stop using chlorinated and nitrogenous
components in its waxes. The companies that,have terminated
production of terphenyl waxes are still in business, and there is
no evidence that their competitive positions have been unfavorably
affected.
(c) Since some wax manufacturers have terminated production without
substantial adverse economic impact on sales^and operations, it
is reasonable to conclude that PCTs are not essential to the adequate
performance of investment casting waxes. One of the current manu-
facturers of 'terphenyl waxes says there are no suitable substitutes
for PCTs, even though'other manufacturers seem to have found some.
If terphenyl waxes perform in such a way as to, say, reduce the
number of rejected castings from 3 percent to 2 percent, then this
one producer who says there are no suitable alternatives to terphenyls
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may be speaking in the context of the 50-percent reduction of re-
jected castings terphenyls might afford. However, this same hypo-
thetical statistic can be also interpreted as meaning that terphenyl
waxes increase the number of successful castings by only slightly more
than 1 percent.
(d) Of the approximately 150 investment casting foundries, at least
one large foundry voluntarily terminated its use of waxes con-
taining PCBs or PCTs. This foundry is owned by the General Electric
Company and produces the highly precise components for the General
Electric line of turbine engines- that are widely used in commercial
and military applications, both domestically and internationally.
If there are applications that are more critically dependent upon
the accuracy and precision of the investment casting process, they
have not been uncovered in this study.
These above considerations, should be kept in mind in considering methods for
controlling the uses of imported PCTs. The following control options are suggested:
1. Since PCTs may contain PCBs in concentrations exceeding 0.5 percent,
PCTs might be treated as PCS mixtures and accordingly importation
could be banned under Section 6 (e) of the Toxic Substances Control
Act. However, imported PCTs currently being distributed in the U.S.
are certified by the distributor, as containing less than 0.05% PCBs.
2. If the concentration of PCBs in PCTs should be found to occasionally
exceed 0.05%, the EPA can take action under Section 6 .(b) of the Act
to assure adequate quality control. Actions authorized under this
section include requiring the manufacturer or processor to repurchase
contaminated material.
3. If, in accordance with Section 6 of the Toxic Substances Control Act,
PCTs are shown to "present an unreasonable risk, of injury to health or
the environment11, then imports of PCTs would be banned under Section 13
of the Toxic Substances Control Act.
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Sources of Information - Section 7.0
1. Telephone communications 'with C. W. Fitzgerald, Product Manager for
Loaders and Continuous Miners, Joy Manufacturing Company, Pittsburgh, Pa.
2. Telephone comiunication with Prescott Green, Joy Manufacturing Company,
Pittsburgh, Pa.
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APPENDIX A
METAL FOBMING TECHNIQUES: COMPARED WITH INVESTMENT CASTING
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APPENDIX A
METAL FORMING TECHNIQUES: COMPARED WITH INVESTMENT CASTING
Manufacturing processes by which parts or components are fabricated from
metal stock entail metal forming. The five major metal forming methods are
listed in. the outline below, which includes a further breakdown on the
.specific processes:
I. Metal Working
A. Forging
B. Extrusion
C. Rolling
D. Drawing
E. Sheet-forming processes
II. Powder and Fiber Forming Processes
III. Electroforming
IV. Joining Processes'
A. Welding and.brazing
. B. Mechanical joining - riveting, screwing, bolting, bending
V. Casting(2)
A. Sand casting (a.k.a. Aggregate Molding)
1. Shell molding
2. Carbon dioxide process
3. Investment casting
4. Ceramic molding
5. Plaster molding
B. Peunanent. mold casting
Cr Die casting
D. Centrifugal casting (also considered to be a permanent mold
' process)
A-l
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A given metal forming process is a factor in the satisfactory service
performance of a manufactured part in that' it affects the microstructure,
physical properties, and surface finish of the metal. The chosen process
may also introduce large residual stresses into the part and it may influence
final design which, in turn, influences service behavior. The more important
factors to be considered in choosing an optimum metal forming process (or
combination of processes) include: type of material, metallurgical structure
effect inherent in the process, size of the part, shape or complexity of the
part, tolerances or finish required, quantity to be produced, cost, and pro-
duction factors such as availability of equipment, rate of production, and
time required to initiate production.
The particular metal or alloy specified for a part is important in the
selection-of the forming process. Some aluminum or copper alloys may be
fabricated by practically any of the manufacturing processes; other alloys
may be brittle under cold-working conditions but may be hot-worked. Highly
refractory materials, such as tungsten and tungsten carbide, are not suitable
for casting and must be fabricated by powder-metallurgy (P/M) methods. P/M
is also used for making porous metal products, or parts requiring combinations'
of two or more materials (e.g., metals combined with ceramics). P/M combina-
tions of different metals are-not alloys in the traditional sense. Alloys .
that are extremely hard, and therefore unsuitable for machining operations,
can be precision cast (i.e., investment cast) and then ground if extremely
close tolerances are required. Higher-mel.t.ing-point alloys such as steel can
be fabricated by most of the major classes of processes but are not suitable
for all of the individual processes within'a major class. Where a specific
material must be used, the choice of the optimum fabricating process becomes
more limited. The formability of a material may be predicted either from the
reduction of area or the peroant elongation in a tension test: the higher
these values, the better is the formability. Other factors that influence
formability are rate of deformation, temperature, type of loading, environment,
impurities in the metal, and surface condition of the original stock.
A-2
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Each manufacturing process has a different effect on the raicrostructure
of the metal and, consequently, on its bulk mechanical properties. Casting
processes generally produce relatively coarse-grained microstructures and
random orientation of nonmetallie inclusions. The result is isotropic prop-
erties, but lower ductility than wrought products. Castings may also be
porous, particularly sand castings. Hot-working processes, such as forging,
align the inclusions (fiber ^structure) and thus impart anisotropic properties,
with the strength and ductility generally being higher in a direction parallel
to that of the .inclusions; such orientation may be an advantage or disadvan-
tage, depending upon the direction of the applied loads. Cold-working proc-
esses (such as cold rolling) also produce directional properties in the metal
because of the tendency of the grains (or crystals) to align in the direction
of maximum deformations. In addition the grains become distorted, and the
metal becomes harder and stronger but less ductile. Cold-working operations
(or any process causing nonuniform deformations) generally leave residual
stresses in the part. Residual stresses left in a. part arithmetically add to
the stresses induced by service loading, and in some instances residual
stresses are of major importance, either advantageous or disadvantageous de-
pending on the given application.
Metal -forming processes may be limited as to the size of the part they
can produce. Smong the processes that are limited to relatively small parts
are precision investment casting, die casting, and powder metallurgy. Large
parts are best produced by sand casting, forging, or fabrication of component
sections by welding or other joining processes. Parts with axial symmetry can
be produced by turning and spinning operations; other large parts, such as
domes, made of sheet or plate stock can be formed by explosive-forming tech-
niques.
The geometry of a part often dictates the process or combinations of
processes used in its. manufacture. Generally, castings can be more complex
'than parts made by most other fabrication processes; however, some casting
processes - sand and precision investment casting - are capable of producing
A-3
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parts of greater complexity. Parts produced by powder metallurgy have
definite restrictions as to design because of the inability of metal powder
to flow like a liquid. In some instances the complexity of a part may require
the fabrication by the welding or brazing of component sections. The change
from forming a part as a single piece to fabricating it from several sections
usually requires design modifications if optimum, servicability and cost
effectiveness are to be maintained.
Parts requiring close tolerances or smooth finishes' can be formed directly
by precision investment casting, die casting, permanent-mold casting, or such
cold-working processes as swaging, drawing, or stamping. If formed by other
processes, they can be finished by machining or grinding. Hot-working proc-
esses, such as forging, result in relatively rough, oxidized surfaces and lew
dimensional accuracies. Welding operations generally result in distortion or
dimensional change. Cost often governs whether the desired tolerances should
be attained in the original forming process or in secondary operations. For
instance, in hot-working operations, such as rolling, forging, and extrusion,
surface roughness ranges from about 100 to as high as 2000 microinches, while
in redlining operations, such as grinding and honing, surface finish can be
as fine as 1 microinch.
The number of parts to be produced is important in choosing the method of
manufacture. Seme processes are suitable only for large-quantity production
because of high tooling costs; examples are permanent-mold and die casting,
certain forging processes, deep drawing, and precision investment casting.
Processes such as sand casting, spinning, and welding are readily adaptable,
but not necessarily restricted to, small-quantity production.
If the quantity to be produced is large, the overall finished cost of the
product is usually the prime consideration in the selection of a process. In
most cases cost is the deciding factor in choosing both the material and the
fabrication process.
In some instances the time necessary to tool up. for production may be of
significance in selecting the fabrication process. Forming methods entailing
A-4
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extensive tooling require long lead times before production can commence.
Another important production factor is the required rate of production. Proc-
esses such as die casting, powder metallurgy, and deep drawing have high pro-
duction rates. Conversely, sand casting, spinning, hydraulic press forging
and welding are relatively slow processes.
Strength levels for metals range from as lew as 1000- psi to the order of
500,000 psi. Size of parts may range from a thousandth of an inch to a few
feet. Pates of deformation can be as high as 40,000 fpm, as in explosive
forming, while working temperatures can be as low as cyrogeriic to the range
of 4000 °F. Capacities of equipment for forming metal components are as high
as 50,000 tons, with a 200,000-ton hydraulic forging press presently in the
design stage.
Casting Techniques
(2)
Sand Castingv '
Sand casting has been and is currently the method by which the largest
number of castings are produced. Typical products include cast iron auto-
mobile engine blocks and crankshafts, furnace and- boiler parts, manhole
covers, aluminum pistons and bronze jewelry. The most common molding material
is known as green molding sand, which is a mixture of sand, clay, water, arid
other materials that add to the hot strength and thermal stability of the mold
and to the surface finish of the cast product. The pattern - that is, the
object used to make the impression to be cast in the sand is usually made of
wood, .plaster or metal and is used to make the two halves of the mold, the
cope (the upper portion of the mold) and the drag (the lower half). ' After
the pattern impressions have been made in the cope and drag, the two halves
are weighted down or fastened together to keep the cope from floating when the
molten metal is poured.
A-5
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OPEN RISER
POURING BASIN
DOTTED AREA
INDICATES
CASTING
COPE FLASH
DRAG FLASH
Section through a sand mold showing the various parts.
In the diagram the features shown are the oope, drag/ risers (blind and
open), gates, sprue and core. The meanings of these terms are applicable to
all forms of casting. A riser is a reservoir of molten metal which feeds
metal to the casting to compensate for shrinkage as the poured metal solidi-
fies . The sprue is a vertical connection between the pouring basin and the
gating system which distributes the metal in an optimum fashion to the volume
of the mold where the cast product will form. The design of the gating
system also controls the rate of entry of the metal into the 'mold cavity; it
minimizes turbulence, allows air and other gases to escape, and establishes
the proper temperature gradient to miniinize shrinkage cavities.
Sand casting can be used for almost all castable materials. Labor and
equipment costs are low so that sand casting is economical for small-quantity '
jobs. Minimum section thickness for objects cast in the traditional sand-
casting methods are on the order of l/8th inch. (Though investment casting
can be classed as a type of sand casting, section thicknesses of investment
castings are frequently less than l/8th of an inch.) Surface roughness ranges
between 25Q and 1000 microinches, rms.
Other casting methods that use aggregate molding materials, but which
otherwise are not referred to as sand casting, are shell molding, carbon
A-6
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dioxide process, ceramic molding/ plaster molding, and of course investment
casting.
Shell Molds(3)
Shell molding was developed in Germany during World War II and was un-
• known outside of Germany until after the war. It is sometimes referred to as
the "Craning", or "C", process, after its inventor. The process consists of
making molds and cores as relatively thin shells, about 1/4 inch thick. Fine
sand (usually silica), of 100 to 150 mesh, is used, and imparts smooth sur-
faces to the castings. The sand is thoroughly mixed with about 5 percent of
a suitable synthetic resin; a two-step phenol formaldehyde resin is ccmmonly
used. Metal pattern plates, similar to cope and drag pattern plates, are
heated to a temperature between 400 and 500 °F; to prevent the shell from
sticking to the pattern plate and thereby preventing its proper removal, a
silicone release agent is sprayed over the hot pattern surface. The hot
pattern is then fastened to a "dump box" containing the sand/resin mixture;
the pattern surface faces the opening of the dump box. When the dump box is
quickly inverted, the sand/resin mixture falls on the hot pattern surface.
The heat penetrates the mixture and softens the resin, making the binder
effective. After about 8 to 20 seconds, depending upon the shell thickness
desired and other variables, the dump box is rotated back to its normal
position. The powder mixture that has not been affected by the heat falls
away, leaving a shell adhering to the pattern. , Heat first causes the resin
to become sticky; additional heat cures or hardens it. For the additional
curing, the pattern plate and shell are removed together from the dump box
and heated for about 2 minutes at about 450°F. The shell is then stripped
from the pattern plate with the aid of the ejector pins which are an integral
part of the pattern plate. The tops of these pins, at the pattern-plate
surface, move upward simultaneously/ lifting the shell mold fron the pattern
plate. Two mating shells, produced as described above/ are securely fastened
together to form a complete mold. Shell molds may be poured either with the
parting surface vertical (standing on edge) or with the parting surface hori-
zontal as with ordinary sand molds.
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To produce shell cores, the sard/resin mixture is poured, or blown under
low pressures, into the interior, of a heated metal core box. After a suffi-
cient period of time, the loose mix is poured out, leaving a shell adhering
to the heated core-box surfaces. After heating for the additional curing, the
shell core is removed from the core box.
The advantages of shell molding include smooth surfaces (in the range of
125 micro-inches, rms) and close tolerances (±0.003 inch per inch are obtain-
able) . Dimensions which cross a parting line can be held to within.±0.010
inch per inch. The process is adaptable for mechanization, and several shell-
mold and shell-core machines are commercially available. Less skill is re-
quired of machine operators than for sand casting molds. Permeabilities of
shells are high, compared with other types of molds. Less sand is used com-
pared with sand molding, and it is feasible in larger plants to recover the
silica sand from the used shells. Shell molds may be made in advance and
stored indefinitely. Practically all metals including the high-temperature
alloy steels can be cast in shell molds.
The higher cost of the pattern manufacturing equipment. limits the use of
shell molding to sufficiently large production volumes to pay for pattern
production out of manufacturing savings. The patterns must be considerably
smoother and more accurate than the castings to be produced. Pesin costs are
also comparatively high, increasing the over-all process cost. Some casting
shapes are not suited for the shell molding process, because a suitable part-
ing and gating cannot be obtained. The size of the castings which can be cast
in shell molds is limited by the maximum shell size that can be feasibly pro-
duced and poured.
(2)
(>rhon Dixoide Process
The carbon dioxide process involves the use of sand plus 1.5 to 6 percent
liquid silicate as a binder. The mixture is packed around the pattern as in
shell molding, but instead of being hardened by the application of heat to the
tnermosetting resin used in shell molding, carbon dioxide is blown through the
sand/silicate mixture, thereby causing it to harden and to be gas permeable.
A-8
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Plaster Molding^2'3)
In plaster molding/ the mold material is a mixture of plaster of paris or
gypsum and such fillers as talc, asbestos and silica flour. The fillers im-
prove the mold strength and control the setting time of the plaster. The mold
ingredients are mixed with, water and poured over the pattern which is usually
situated inside of a container/ or flask, that confines the flow of the liquid
plaster. After the plaster sets/ the pattern is removed and the mold is dried
at 400°F. Plaster molds produce castings having high surface finish and diman-
sional. accuracy, plus faithful reproduction of fine detail and thin sections.
However, because plaster is not a high-temperature refractory, its use in
casting is limited to lew-melting-point nonferrous metals such as aluminum,
magnesium^ and some copper-base alloys.
Permanent-Mold Casting^ ' ^'
Another method giving smoother surface finish and closer tolerances than
sand casting is permanent-mold casting, a method which is also amenable to
higher production rates than sand casting. The mold material is cast iron,
steel, or bronze. Semi-permanent-mold materials include aluminum, silicon
carbide and graphite. The mold itself is a casting which, after its halves
have been cast over the pattern, is machined to the desired dimensions. Ma-
chining, in addition to producing the gating system in the mold halves, gives
a good surface finish and improves the dimensional accuracy of the casting.
To increase mold life and to make ejection of the casting easier, the surface
of the mold cavity is usually coated with carbon soot or a refractory slurry,
both of which also serve as heat barriers and control the rate of cooling of
the casting.
Permanent mold casting is particularly suitable for the high-volume pro-
duction of small, simple castings having fairly uniform wall thickness and no
undercuts or intricate internal coring. The process can also be used to pro-
duce moderately complex castings though production volumes should be high
enough to justify mold cost.
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Permanent mold casting has these limitations: (a) although, no maximum
size has been established, the process is.most applicable to small castings;
(b) not all alloys are suited to permanent mold casting (e.g., high-melting-
point alloys cannot be cast); (c) the process can be prohibitively expensive
for low production; and (d) some shapes cannot be made because of the location
of the parting line or difficulty in removing the casting from, the mold.
Limitations (b) and (d) offer no hindrance in investment casting.
Metals that can be cast, in permanent molds include aluminum., magnesium,
zinc and copper alloys, and hypereutectic gray iron. The metal being cast
must have a melting point that is less than that of the mold material.
Aluminum alloys have a low density, which, combined with their oxide-film-
forming characteristics, makes them flew somewhat sluggishly. The shrinkage
of aluminum alloys during solidification is relatively large, and allowances
must be made for metal feed during solidification. After solidification, the
aluminum alloys are soft at elevated temperature, and castings can be distorted
during removal from the mold.
Magnesium alloys- are less applicable to permanent mold casting than
aluminum alloys, and have relatively poor feeding characteristics in thin
sections. Also, magnesium castings are more sensitive to hot. shortness (brit-
tleness at elevated temperature) than aluminum alloy castings. Generous
fillets are required when the casting contains large bosses or when one section
of the casting is much larger than another. Sharp detail cannot be obtained
with magnesium alloy castings, and shapes that shrink onto mold sections are
susceptible to cracking.
Copper alloys solidify at high temperatures, and some have narrow solid-
ification ranges. They shrink onto cares and other mold elements and must be
rapidly ejected from the mold.
Zinc alloys can be cast in permanent molds, but because zinc castings are
usually made in large quantities, they are more often die cast.
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Gray iron is used successfully in the high-volume production of small
(1 oz. to 30 Ib.), simple castings. However, more complex gray iron castings,
with internal coring and marked changes in section, have also been successfully
made by the permanent mold process.
Practical sizes of permanent mold castings are limited by cost. Hie maxi-
mum sizes that have been cast differ among tiie casting alloys. In high pro-
duction, permanent mold castings weighing up to 30 Ib. can be made from alumi-
num alloys in casting machines. However, much larger castings have been
produced; for instance, aluminum alloy castings of relatively sinple • design
with a trimmed weight of 780 Ib. were produced in a three-section permanent
mold. The mold, of gray iron, had outside dimensions of 9 by 9 ft. and
weighed 25 tons. The castings with gates and risers weighed 1100 Ib. each.
Pouring time for each casting was 12 minutes. After pouring, castings were
held in the mold for 20 minutes before ejection.
Magnesium alloys, despite their relatively low castability, have been cast
in permanent or semipermanent molds to produce relatively large, complex cast-
ings. In one instance, a 17.7 pound magnesium casting was poured in a semi-
permanent mold. The mold utilized vertical parting and an oil-sand core to
develop vanes and internal surfaces in the casting. Surface finish of the
casting varied from about 250 to 500 microinches. In another instance, 53-
pound castings, 30 inches in diameter, were cast in a two-segment permanent
mold with vertical parting. These castings were used as ends for fiber rolls,
which have a heavy hub section and a thin peripheral rim and function like
spools for thread.
Saddle tanks, which function as 300-gal auxiliary fuel tanks and are com-
ponents of an aircraft wing structure, were successful cast in a magnesium
alloy in a two-segment, vertically-parted semipermanent mold using 42 expend-
able cores. The trimmed castings each weighed 30 pounds, and measured 1 by 4
feet. Wall thickness ranged from 5/16 to 5/8 inch.
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The dimensional accuracy of permanent mold castings is affected by short-
term and long-term variables. Short-term variables are those that prevail
regardless of the length of run:
1. Cycle-to-cycle variation in mold closure or in the position of
other moving elements of the mold
2. Variations in mold closure caused by foreign material on mold
faces or by distortion of the mold elements
3. Variations in thickness of mold coating
4. Variations in temperature distribution in the mold.
Long-term variables that occur over the life of the mold are caused by:
1. Gradual and progressive mold distortion resulting from stress
relief, growth and creep
2. Progressive wear of mold surfaces, caused mainly by cleaning
procedures.
Dimensional variations can be minimized by keeping rates of heating and
cooling at constant levels, operating on a fixed cycle and maintaining clean ,
parting faces. It is particularly important to select mold-cleaning procedures
that remove a minimum of mold material.
Mold thickness and the design of supporting ribs have an effect on the
warpage of the mold at operating temperatures. Supporting ribs on the back, of
a thick mold can warp the mold face in a concave way. The design error can
alter casting dimensions across the parting line as much as 1/16 inch. Adequate
mold lock-up can contribute to the control of otherwise severe warpage problems.
Mold erosion resulting from metal impingement and cavitation due to im-
proper gating design contribute to heat checking and rapid weakening of the
mold metal; this can contribute to rapid dimensional variation during a long
run.
Mechanical abrasion due to insufficient draft or to improperly designed
ejection systems also contributes to the rapid variation of casting dimensions.
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Sliding mold segments require clearance of up to 0.015 in. to function under
varying mold temperature. . The clearance and other mechanical problems, associ-
ated with sliding mold segments contribute to variation in casting dimensions.
Sand cores further aggravate the problem.
Surface finish on permanent mold castings depends mainly on:
1. Surface of the mold cavities - Surface of the castings can be
no better than that of the mold cavities; heat checks and other
imperfections can be reproduced on the casting surface.
2. Mold coating - Excessively thick coatings, uneven coatings, or
flaked coatings degrade casting finish.
3. Mold design - Enough draft must be provided to prevent galling
or cracking of casting surfaces; the location of the parting
line can also influence the surface finish of the casting.
Gating design and size have a marked effect on casting finish,
because they influence the rate and smoothness of flow on the
poured metal.
4. Venting - The removal of air entrapped in mold cavities is
important to insure smooth and complete fill.
5. Mold temperature - For optimum casting surface finish, mold
temperatures must be appropriate for the job and must be reason-
ably uniform.
6. Casting design - Severe changes of section, complexity, require-
ments for change in direction of metal flow, and large flat
areas all adversely affect surface finish.
Defects that can occur in permanent mold castings are porosity, dross,
non-metallic inclusions, misruns, cold shuts, distortion and- cracking.
Manually operated equipment is generally more economical for low pro-
duction quantities, but for medium to high production quantities machine mold-
ing invariably costs less.
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Die Casting(5/6)
Die castings are produced by forcing molten-metal under pressure into
metal molds called dies.
As a casting process it is closely related to permanent mold casting in
that in both processes reusable metal molds are used. The two processes
differ in mold-filling method; whereas in permanent mold casting mold filling
depends on the force of gravity, die casting involves metal injection under
high pressure (up to 100,000 psi) and high velocity. Because of this high-
velocity filling, die casting can produce shapes that are more complex than
those produced by permanent mold casting. (In Europe, die castings are
generally called "pressure die castings", and the term "gravity die casting"
is equivalent to permanent mold casting.)
In die casting, after the die has been closed and locked, molten metal
is delivered to a pump, which may be either cold (cold-chamber die casting)
or heated to the temperature of the molten metal (hot chamber). The pump
plunger is advanced to drive the metal quickly through the feeding system
while the air in the die escapes through vents. Sufficient metal is intro-
duced to overflow the die cavities, fill overflow wells and develop s"ome
flash. As the cast metal solidifies, pressure is maintained-.through a speci-
fied time while the casting solidifies and shrinks. The die is then opened
and the casting ejected. While the die is open, it is cleaned and lubricated
as needed, then it is closed and locked, and the cycle repeated.
The advantages of the die casting are:
1. More complex shapes can be made by die casting than by permanent
mold casting.
2. Because the dies are filled by pressure, castings with thinner
walls and greater dimensional accuracy can be produced than by
almost any other casting processes except investment casting.
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3. Production rates are higher in die casting, especially when
multiple-cavity dies are used, than in other casting processes.
4. Because die castings are produced by almost completely finished
parts, the investment in inventory and factory floor space is
reduced to a minimum.
5. Dies for die casting (as with molds for permanent mold casting)
can produce many thousands of castings without significant change
in casting dimensions.
6. Metal cost is often lower than in other casting processes, be-
cause die casting permits casting of thinner sections.
7. Many die castings can be plated (finished) with minimum surface
preparation.
8. Some aluminum alloy die castings can develop higher strength
than comparable sand castings.
9. Labor costs per unit of production are lower than in permanent
mold casting.
The principal limitations of die casting are:
1. Casting size is limited; casting weight seldom exceeds 50 Ib. and-.
normally is less than 10 Ib.
2. Depending on casting contours and gating, difficulty may be
encountered with air entrapped in the die; entrapped air is a
principal cause of porosity.
3. The facilities, consisting of the machine, the auxiliary equip-
ment, and the dies, are relatively expensive; because die castings
are small, large quantities of.castings are required for the
process to be economical.
4. With few exceptions, oaiiiiercial use of the process is limited to
metals having melting temperatures no higher than those of copper-
base alloys.
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Depending on degree of mechanization, process variables, and the part
being cast, hot-chamber machines generally operate at rates of 50 to 500 shots
per hour. Special machines greatly exceed these rates, ranging frcm 2000 to
5000 shots per hour up to 18,000 shots per hour for a zipper-casting machine.
Slides are the movable die parts needed to build up die surfaces; they
are used when it is impossible to avoid undercuts in a casting. The part of
the die-cavity wall that forms the undercut portion is made on the face of a
slide accurately fitted in a guide cut in the die block. The slide must be
retracted before the casting can be ejected. A separate locking mechanism
must be provided for each slide. The use of the slides adds considerably to
die cost.
The rate of die wear is influenced chiefly by the tonperature of the
casting metal and by the design of the die. When the metal has a casting .
temperature no higher than that of zinc alloys, and the die is of simple
design, it is possible to obtain more than 500,000 shots before there is sig-
nificant die wear. As metals with higher casting temperatures are used, pro-
gressing from zinc to aluminum and thence to copper alloys, die wear increases
«»
rapidly, regardless of die design. As the configuration of the casting and
gating system becomes more complex, wear in localized partitions of the die
also increases.
A good die casting has a uniform surface free of surface imperfections
due to uncontrolled flow of metal (imperfections such as heat-sink marks, pits,
porosity, swirls, cold shuts and misruns), and it exhibits no imperfections
caused by oil deposits and dross inclusions. A normal amount of buffing
seldom removes surface flaws. Excessive buffing can break through the dense
skin and expose underlying porosity.
Hardware finish is a term describing a die-casting surface finish that
will accept decorative plating. To obtain good hardware finish, dies must be
A
properly gated, overflow patterns must be correctly placed to remove trapped
gas and create heat balance, venting must be ample, and only a minimum of die
lubricant must be used. Polishing of the die cavities will greatly increase
A-16
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the number of shots that can be made with one lubrication. The location of
water lines for cooling the die is important; improper cooling can create
either hot spots that produce sink marks in the surface of the casting or
cold spots that cause metal to freeze prematurely. If openings from the die
cavity into overflows are too large, the casting metal will circulate in and
out of the overflows and produce swirls, which appear in the casting surface
and remain after plating. •
Factors influencing the cost of die castings, and the direction of their
influence, are:
1. Quantity - Unit cost decreases as the quantity increases, because
with a large production run fixed costs and tooling costs can be
spread over a large number of castings, and more-efficient tool-
ing can. be provided.
2. Tooling - Die more mold cavities in the die, the lower the unit
cost of each casting, because more castings can be produced per
unit of time; for large production runs, it may be economical to
use a more complex .die design and to. reduce the number of secondary
operations. .
3. Casting design - The more complex the casting, the higher are the-.
costs of cores and slides, removal of flash and gates, and die
maintenance.
4. Section thickness - Exceptionally thick or thin sections result in
higher-than-normal rejection rates.
5. Dimensional tolerance and surface finish - Unusually close toler-
ances and surface-finish requirements contribute to higher initial
tooling and tool-maintenance costs, and may slow production rates.
6. Cost of the casting metal - In addition to having a direct in-
fluence on over-all cost, the type of cast,ing metal used also
affects tooling cost.
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Processes that are competitive with die casting usually are other casting
processes. In some applications, machining, cold heading and welding may be
as economical as die casting, particularly when end use is noncritical or when
production quantity is small. Since die casting is a high-production process,
the quantity of reproductions to be made is often the deciding factor as to
which process is best.
Centrifugal Casting(3'5^
In centrifugal casting the inertial forces of rotation distribute the
molten metal into the mold cavities in such a way as to produce high-density
castings with low gas or air entrainment. There are essentially three types
of centrifugal casting: true centrifugal casting, semicentrifugal casting,
and centrifuging. The first two processes produce hollow cylindrical shapes
and parts having axial symmetry. In the third process, the mold cavities
are located at the ends of radially-located gates that feed the poured metal
into a centrally-located pouring basin and sprue. In true centrifugal cast-
ing, used for making cast iron and steel pipes and similarily shaped objects,
the mold material is sand, backed by a metal pipe called a flask which, with
the sand it contains, is rotated while the molten metal.is introduced at one • .
end of the flask. The other centrifugal casting processes may employ perma-
nent molds (or dies) made of forged steel or cast iron lined with graphite to
facilitate casting removal. Rotational speeds are chosen to produce acceler-
ations of between 40 and 60 gravities. In the semicentrifugal and centri-
fuging processes, the melting points of the materials to be cast are .limited
by the strength and temperature capabilities of the die material.
Powder Metallurgy (P/M) *1/7*
Powder Metallurgy (P/M) is a material processing technique used to con-
solidate particulate matter, both metals and/or nonmetals, into discrete
shapes. P/M methods also apply, with little modification, to ceramics and
other types of nonmetallic materials. Complex composites of both metallic and
A-18
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nonmetallic phases are being fabricated by (P/M) methods in increasing quan-
tities to provide the material properties required in the aerospace, electronic
and nuclear energy industries.
P/M. products are usually finished parts such as gears or cams. The tech-
nique employed consists essentially of subjecting the metal powders to pressure
and heat. The heat treatment, called sintering, is performed at some temper-
ature below the fusion point of the main constituents of the products. Instead
of pure metal powders, alloy powders may be used singly or as mixtures. Also,
metal powders may be used in mixtures with metallic or nonmetallic components.
Powder metallurgy thus permits the production of metallic, or metal-like, bodies
of many shapes without the use of standard metal-forming techniques such as>
melting and casting.
Many refractory metals have such high melting points that conventional
melting and casting is difficult, if not impossible. Powder metallurgy is the
ideal method, for example, of producing tungsten filaments. Metal combinations
in which the characteristics of each constituent are retained are of particular
interest for certain electrical applications, and they can be produced by P/M
•
methods. For instance, heavy-duty electrical contacts and welding electrodes
combine a skeleton of refractory metal, highly resistant to abrasion and arcing,
with a second metal of low melting point and high conductivity. Alloying be-
tween the constituents is negligible so that the original properties of the
individual metals are preserved. •
Other examples are cemented-carbide high-speed cutting tools, cermets, and
dispersion alloys. Cermets are predominantly nonmetallic, or ceramic, with a
metallic binder phase. Dispersion alloys contain minute nonmetallic particles
dispersed in a metallic matrix. Cermets are important as nuclear reactor com-
ponents, such as fuel elements which consist of combinations of uranium oxide
and binder metals, and control or moderator elements which contain fine dis-
persions of boron and other neutron-capturing elements in aluminum, stainless
steel, or zirconium, matrices.
A-19
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The largest application of P/M is in the production of small metal parts,
gears, cams, and other components for machines and instruments requiring
closely controlled dimensions and properties. These parts can often be pro-
duced at lower cost by powder metallurgy than by other metal-forming methods.
The parts may be steel, brass, or alloys of iron with copper, nickel, or
chromium.
The development of metallic bodies of closely controlled porosity has
made possible so-called self-lubricating bronze and iron-base bearings which
can be impregnated with oil and used in places inaccessible to external
lubrication. Porous metal is also used effectively in oil-pump gears, metal
filters, and diaphragms.
Current-collector brushes in electrical machinery are laminated P/M
products. Copper-lead bearings whose constituents are not miscible in the
liquid or solid state are typical of metal powder alloys of unusual components.
After sintering the part may be ready for use or secondary operations
such as repressing, resintering, infiltration with a molten metal or impregna-
tion with plastic or liquid lubricant, or a combination of these may be per-
formed to achieve specific properties. More conventional operations such as • ,
machining, tumbling, plating and heat treatment may also be carried out. A
number of applications require joining operations; brazing, soldering, or
welding of these parts onto other metal bases is common practice in the hard
metal and refractory metal industries. Finishing and joining operations must
frequently be adapted to the specific properties of P/M products: care must
be taken in machining because of the porosity, plating methods must be adjusted
to prevent corrosion caused by the porosity; special fluxes or inert or re-
ducing gaseous media must be used to prevent excessive oxidation during brazing
and welding. Two very important factors should be noted: (1) the process
offers the greatest economic advantages when very few, if any secondary oper-
ations are necessary, and large quantities of a part may be mass produced at
rapid rates; and (2) the process variables may be adjusted to produce parts
with, controllable types and amounts of useful porosity or with densities
A-20
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approaching the theoretical value that was analogous to and competitive with
conventional cast and wrought materials, including forgings. Additionally,
many alloys and complex multiphase materials can be economically manufactured
only by P/M techniques.
A comparison of P/M with, the more conventional metal forming methods
reveals the advantages and limitations.
Powder metallurgy does not make up a preponderant segment of the metal-
lurgical industries. In spite of the accelerated growth of its different
branches, P/M has remained a limited and specialized field. The reasons for
this .are both economic and technical. Powdered starting materials, with the
exception of most iron powders, are more expensive than other raw materials.
Tools and dies must be durable, and usually return their cost only when many
thousands of the same part are produced. Special tools are required for the
forming of complex shapes because the powder does not flow readily into
lateral protrusions. Powders of high specific volume require long compression
strokes, which in turn impose slow production rates. Also, the large surfaces
of the powders are prone to gas adsorption, leading to brittleness of the end
product.
Beryllium products are made exclusively of P/M and in the electronics,
nuclear, and rocket fields, P/M dispersion alloys, refractory metals, and
cermets with unusual properties are being developed. High-density forging
preforms from powders of titanium alloys, nickel-chromium heat-resistant alloys,
and high alloy and tool steel are also new developments in P/M, which offers
economic advantages due to reduced machining time and scrap as well as to
potentially superior properties that can be obtained because of grain size con-
trol and tailor-made special compositions.
The increasing use of large P/M parts for structural applications by the
automobile industry represents a very important contemporary development. At
the outset all P/M parts were small, less than a few square inches in cross
section, and tine mechanical properties were considered barely comparable to
more conventional materials. Today the size has increased many times -and large
A-21
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parts of a foot or more in diameter and veighing ten to fifty pounds are being
produced in large quantities. Materials with mechanical properties far ex-
f •
ceeding those of more conventional materials have been developed by using new
alloying elements for iron-base materials, by improving heat treatments, by
using improved powders and by achieving higher densities. Not only can high
strengths be obtained but also high levels of ductility and toughness in P/M
parts are available. The notion that P/M parts are brittle and fragile is
completely invalid today.
The disadvantages of P/M. center on tooling costs and on the toxicities
and flammabilities of the metal powders. Handling of certain fine powders
can present severe health hazards. Pyrophoricity (spontaneous ignition or
oxidation) is a potential danger for many metals, including the more common
types when they are in a finely divided form with large surface-area-to-volume
ratios. Toxicity of powders is normally related to inhalation or ingestion,
the basic cause of which is not merely the property of the material but the
ability of small particles to remain suspended in air and resist collection
and removal. A 100-micron particle will settle at a rate of about 60 ft/min;
a 50-micron particle at a rate of about 10 ft/min; and a 10-micron particle at
about 0.5 ft/min. In normal situations air has a turbulent velocity of about '
25 ft/min. Consequently, particles in the 50-micron range float easily for
extended periods in the air stream.
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Bibliography - Appendix A
1. McGraw-Hill Encyclopedia of Science and Technology, Vol. 8, p. 337, Metal
Forming.
2. McGraw-Hill Encyclopedia of Science and Technology, Vol. 2, p. 567, Cast-
ing. McGraw-^Iill Book Company, New York, 1971.
3. Campbell, James S., Principles of Manufacturing. Materials and Processes.
McGraw-Hin Book Company, New York, 1961, pp. 240-242.
4. Metals Handbook, Vol. 5, Forging and Casting. 8th edition, p. 265,
Permanent Mold Casting, American Society for Metals, Metals Park, Ohio, 1970.
5. Taylor, Howard F., Merton C. Flemings and John Wulff, Foundry Engineering.
John Wiley & Sons, Inc., New York, 1959, pp. 57-63.
6. Metals Handbook, Vol. 5, Forging and Casting. 8th edition, Die Casting.
American Society for Metals, Metals Park, Ohio, 1970, p. 285.
7. Hirschhorn, Joel S., Introduction to Powder Metallurgy. American Powder
Meta-lurgy Institute, New York, 1969.
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APPENDIX B
GLOSSARY OF WAXES, EESINS, AND CHEMICALS ASSOCIATED
WITH INVESTMENT CASTING WAXES
-------
APPENDIX B
Glossary of Waxes, Resins, and Chemicals Associated
with. Investment Casting Waxes*
Acetal Resin - Also called polyacetal. A polyoxymethylene thermoplastic polymer
obtained by anionic polymerization of formaldehyde; hard, rigid, strong, tough
and resilient; specific gravity 1.425; nontoxic, even when thermally decomposed.
Acrylic Resin - A thermoplastic polymer or copolymer of acrylic acid, methacrylic
acid, esters of these acids, or acrylonitrile; they can be converted to thermo-
setting resins by adding acrylic anhydride, acrylamide, or glycol esters or acrylic
acid.
Adipic Acid - An organic-acid casting wax filler material; white crystalline solid;
melting point 152°C; boiling point 265°C; specific gravity 1.360; low toxicity;
used also in manufacture of nylon and polyurethane foams, is also a food additive.
Balsam - A resinous mixture of varying composition obtained from several species
of evergreen trees or shrubs. Contains oleoresins, terpenes, and usually cinnamic
and benzoic acids. All types are soluble in organic liquids and insoluble in water.
Ihey are combustible and in general non-toxic. A component of investment casting
waxes.
Carnauba Wax - Also known as Brazil wax, it is a vegetable wax 'and is the hardest
and most expensive commercial wax. Hard, amorphous, light yellow to greenish brown
with a specific gravity of 0.995 (at 15°C) and a melting point of 84 to 86°C, it is
soluble in ether and boiling alcohol and alkalies, but not in water. It is com-
bustible and nontoxic. Its uses are in shoe polish, leather finishes, waterproofing,
and confectionary, among others.
Cellulosic Plastics - A group of semisynthetic thermoplastic polymers based on
cellulose; examples are cellulose acetate, cellulose nitrate (nitrocellulose),
carboxymethl-cellulose, and ethylcellulose, the latter being at least one member
of this group that has been used as a component in investment casting waxes.
Coal-Tar Resin - See Coumarone-Indene Resin
*The bulk of the terms defined and/or discussed in this glossary were taken from
patents and trade association publications. Definitions and other information
came from the sources listed in the bibliography at the end of this Appendix.
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Component - A casting wax component is an ingredient, and is usually either a resin
or a wax and can be of either natural or synthetic origin. (See Filler)
Congo Resin - A possible casting wax component. A variety of copal fossil resins,
the natural, product is insoluble in organic solvents, but when thermally processed
(cracked) it is soluble in all organic solvents, fatty acids, and vegetable oils.
Copal - A group of fossil resins used to some extent in varnishes and lacquers.
Insoluble in oils and water. Most important types are congo, kauri and manila. •
Coumarone - Benzofuran; A bicyclic ring compound derived from coal-tar naphtha.
Coumarone-Indene Resin - A thermosetting resin derived by heating a mixture of
coumarone and indene with sulfuric acid, which induces polymerization. At room
temperature it is soft and sticky; on heating it hardens to a resinous solid.
Cumar Resin - Cumar is a trademark for a series of neutral, stable, synthetic
resins of the coumarone-indene type, manufactured from selected distillates or
tar. It is used as a softener and tackifier in varnishes, floor tile, rubber
products, printing ink, adhesives, and water-proofing materials.
OH
N - C
» . *
Cyanuric Acid - go - C N
\ /
N = C .
OH
Cyanuric acid has been used as a filler in the past but is not presently used be-
cause of its relatively high price (about SOC/lb). It is odorless, and decomposes
to cyanic acid (HOCN) at 320 to 350°C before melting. Cyanuric acid is soluble in
water and hot mineral acids, and is insoluble in alcohol and acetone. Its specific
gravity is 1.768. Both cyanuric acid and cyanic acid are highly toxic by ingestion
or inhalation. Despite this fact, one industry source stated that cyanuric acid
is safe for wax filling applications as it "does not evolve toxic gases in the
temperature range used in casting operations." Cyanic acid is a severe explosion
risk, and cyanuric acid vapors are also quite flammable.
B-2
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N,N' Ethylene Bis Stearimide - At least one. manufacturer used this material in pro-
duction of filled waxes. No information is available on the chemical or toxicological
properties.
Dammar - A group of tree-derived resins soluble in hydrocarbon and chlorinated
solvents; partially soluble in alcohol; insoluble in water.
Epoxy Resin - A thermosetting resin having potential application as an investment
casting wax filler; very low toxicity in cured state, but emits highly toxic fumes
when heated to decomposition. Not currently used in waxes. Expensive.
Filler - A casting wax filler is usually an organic material that melts at a
significantly higher temperature than the wax; its functions are mainly to reduce
the cooling and solidification shrinkage of the wax and to increase the heat trans-
fer rate of the wax; fillers should be able to burn without leaving ash or residue,
and the products of decomposition should be nontoxic. (See Component)
Fischer-Tropsch .Wax - A wax made by the catalytic process known as the Fischer-
Tropsch process in which, water gas or other synthetic gas mixtures containing carbon
monoxide are reacted with hydrogen to produce aliphatic straight-chain hydrocarbons
and oxygenated derivatives.
Fumaric Acid - An organic-acid casting wax filler material; colorless crystalline
solid; specific gravity 1.635; melting point 287°C; low toxicity; used also as
modifier for polyester, alkyd, and phenolic resins, and as a food additive.
Indene - A component of crude coal-tar distillates.
lonomer Resin - A thermoplastic crosslinked copolymer of ethylene and a vinyl monomer
with an acid group such as methacrylic acid. Cannot be completely dissolved in any
commercial solvent;
COCK
Isophthalic Acid - l^J-CCOH isophthalic acid is one of the most widely used wax
fillers in the investment casting industry. It is combustible, and has a melting point o
B-3
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345 to 348°C; it also sublimes. Isophthalic acid is slightly soluble in water; is
soluble in alcohol and acetic.acid, and insoluble in benzene and petroleum ether.
Acute local toxicity by ingestion, inhalation, or skin contact is slight. The LD_Q
of isophthalic acid by interperitoneal injection in mice is 4,200 mg/kg. The
acute systemic and chronic toxicology of isophthalic acid is not known.
Kauri - See Copal
Mastic - A resinous exudation of a tree found in the Mediterranean, area; used in
chewing gum, varnishes, and to some extent in adhesives and dentistry.
Microcrystalline Wax - A wax, usually consisting of branched chain paraffins and
characterized by a crystal structure much smaller than normal wax and by higher
viscosity than normal wax. It is obtained by dewaxing tank bottoms, refiner
residues and other petroleum waste products. Average molecular weight is about
twice that of ordinary paraffin; that is, about 500 to 800. Uses include: adhesives,
paper coating, cosmetic creams, floor wax, electrical insulation, glass fabric
impregnation, leather treatment and emulsions. Two naturally occurring micro-
crystalline waxes are chlorophyll and beeswax, of which the latter still finds some
use in investment casting.
Mcntan Wax - Also called lignite wax; melting point 80° to 90°C; a hard white '.
wax; soluble in carbon tetrachloride, benzene, and chloroform,•insoluble in water.
Derived from lignite. Substitute for carnauba and beeswax. Nbntoxic.
Nylon - Used as a filler in waxes; not likely currently used; contains nitrogen,
which can evolve cyanide or nitrogen oxides at high temperatures.
Paraffin Wax - A white translucent, tasteless, odorless solid consisting of a
mixture of solid hydrocarbons of high molecular weight (e.g., C,,-H74). Paraffin
waxes are soluble in benzene, warm alcohol, chloroform, turpentine, carbon disulfide,
and olive oil; insoluble in water and acids. Specific gravity is 0.880 to 0.915;
melting point range is 47 to 65°C generally, though a narrow melting range of only
2 or 3 degrees.is more desirable in paraffin waxes used in investment casting.
Pentaerythritol C(CH^OH). - Although a patent exists for the use of polyhydric
alcohols as a wax filler, pentaerythritol is apparently the only member of this
group to be used on a commercial scale. Pentaerythritol melts at 262°C and boils
B-4
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at 276°C. It is soluble in water; slightly soluble in alcohol; and insoluble in
benzene, carbon tetrachloride, ether, and petroleum ether. The specific gravity
of pentaerythritol is 1.399 Cat 25°C) . It is combustible and is a moderate fire
hazard. Its toxicity is unknown. The toxicity of pentaerythritol derivatives
listed in the Registry of Toxic Effects of Chemical Substances by oral applica-
tion. in rats ranges widely, with LD5Q of diphanyl phosphito tetra pentaerythritol
at 1.5 mg/kg and ID-, of pentaerythritol triacrylate at 2460 mgAg-
Phenolic Resin - Any of several types of synthetic thermosetting resin obtained
by the condensation of phenol or substituted phenols with aldehydes such as for-
maldehyde, acetaldehyde, and furfural. Phenol-formaldehyde resins are typical and
constitute the chief class of phenolics.
Phthalimide - O
Phthalimide is structurally similar to isophthalic acid, and exhibits some similar
properties. Its melting point is 233 to 238 °C; it also sublimes. Like isophthalic
acid, it is combustible and is slightly soluble in water and insoluble in cold
benzene; it is slightly soluble in ether and is soluble in aqueous alkalies and
boiling benzene. Phthalimide may emit toxic fumes when heated; hydrogen cyanide
or nitrogen oxides 'may be produced by. phthalimide-containing waxes during wax .
burnout, depending on the temperatures and oxygen concentration in the furnace.
Cyanide fumes would not be expected from a properly operating furnace. Little
is. known about the toxicity of phthalimide.
Polycarbonate - A synthetic thermoplastic resin derived from bisphenol A and phos-
gene; a linear polyester of carbonic acid; nontoxic; combustible but self-
extinguishing .
Polyester Resin - Any of a group of thermosetting synthetic resins, which are
polycondensation products of dicarboxylic acids with dihydroxy alcohols. They
are a special class of alkyd resin, but, unlike other types, are not usually
modified with fatty acids or drying oils. Their outstanding characteristic is
their ability, when catalyzed, to harden at room temperature under little or no
pressure.
B-5
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Polyethylene (C-HJ - Polyethylene is widely used as a casting wax conponent. Its
molecular weight varies depending on the degree of polymerization. It is a thermo-
setting white resinous solid, highly resistant to temperature and chemical stresses.
It is insoluble in organic solvents, and does not stress-crack. Polyethylene is
combustible. Although polyethylene is non-toxic, apparently little research has
been done on this ubiquitous substance. It is an unintentional food additive,
resulting from contact of food with, polyethylene packaging materials. Toxicity
studies in which polyethlene was surgically impanted in mice and rats yielded
contrasting results. Tumors were produced in mice by a dosage as low as 330 mgAg
but the lowest dosage causing this effect in rats was 2,120 mg/kg.
Polyhydric Alcohols - Polyhydric alcohols are alcohols containing three or more
hydroxyl groups. Those having three OH groups (trihydric) are glycerols; those.
with more than three are called sugar alcohols. In investment casting, the preferred
polyhydric alcohol is pentaerythritol, which is a polyhydric alcohol of tetra
substituted methane having alcohol groups of up to and including six carbon atoms
with OH groups on at least half of the carbon atoms.
Polyol - A polyhydric alcohol.
Polyolefin - A class or group for thermoplastic polymers derived from simple olefins;
among the more important are polyethylene, polyporpylene, polybutenes, polyisoprene,
and their co-polymers. This group comprises the largest tonnage of all thermoplastics
produced. Polyethylene is used to some extent as a wax component; different mole-
cular weights give different performances in wax.
Polypole Resin Ester - Proprietary trade name of a resin presently used by at least
one wax manufacturer. Its chemical composition is unknown, as are its chemical and
toxicological properties.
Polystyrene -
Polystyrene is possibly the most widely used filler in the industry. It is a thermo-
plastic synthetic resin with high strength and impact resistance. The molecular
weight of polystyrene is variable depending on the degree of polymerization. It is
an excellent electrical insulator. Polystyrene is attacked by hydrocarbon solvents,
B-6
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but is resistant to organic acids, alkalies, and alcohols. It is combustible and
is not self-extinguishing. Polystyrene generally contains styrene monomer
approximately as 0.1 percent of the total weight. Polystyrene is considered non-
toxic, although surgical implantations of as low as 19 mg/kg have caused neoplastic
effects (production of tumors) in rats.
Polyvinyl Chloride - A synthetic thermoplastic polymer; combustible but self-
extinguishing; nontoxic, except when burned releases HC1 fumes and phosgene and
possibly unpolymerized vinyl chloride monomer which, is toxic and has been linked
to cancer of the liver.
Resin - Resins are classed as either natural or synthetic. Natural resins are
vegetable derived; they are amorphous mixtures of carboxylic acids, essential oils
and terpenes occurring as exudations on the.bark of many varieties of trees and
shrubs. They are combustible and electrically nonconductive. When cold they are
hard and glassy with a conchoidal fracture; at higher temperatures they are soft
and sticky. Rosin is a natural resin. Synthetic resins are high polymers resulting
from a chemical reaction between two or more substances, usually with heat or
catalyst. Examples are synthetic rubber, siloxanes, and silicones. (Water-soluble
modified polymers often referred to as resins are not really synthe-CLc resins.)
Polystyrene is a thermoplastic synthetic resin used in investment casting. Plastics
are resins, but with such additives as fillers, colorants and plasticizers. .•Poly-
chlorinated terphenyl serves the function of a resin in investment casting waxes.
The preferred resins in investment casting are polymers and copolymers of cyclic
alkenes; for example, terpenes and naphthenes which solidify into a hard state such
as occurs with rosins and the petroleum-base higher melting naphthenes. Typical
higher thermoplastic resins used in pattern waxes include terpene phenolics, methyl
ester of rosin, hydrogenated rosins, polymerized rosins, rosin derivatives, cold tar
derivatives, petroleum derivatives, styrene derivatives, alkyds, polyesters,
chlorinated polyphenyls, polyamides, coumarone-indene resin, and diphenyl bis
steramide.
B-7
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A. Natural Pesins
rosin
balsam
kauri
congo
damar
mastic
copal
sandarac
shellac
B. Synthetic Pesins
1. Thermoplastic resins
acetal (copolymer, homopolymer)
acrylic
cellulosic (e.g., acetate, nitrate, butyrate, propionate,
ethylcellulose)
polycarbonate
polyolefin (polyethylene, polypropylene, polybutylene)
polystyrene
polyvinyl halide
2. Thermosetting resins
amino-aldehyde (melamine)
polyester (allyl, alkyd)
epoxy.
ionomer
phenolic
Rosin - A natural resin, rosin derives from pine tree sap; gum rosin is the residue
obtained after the distillation of turpentine oil from the oleoresin tapped from
living .trees; wood rosin is obtained by extracting pine stumps with naphtha and
distilling off the volatile fraction. In general, rosin comes in angular, trans-
lucent, amber-colored fragments; specific gravity is about 1.08, melting point is
between 100°C and 150°C. Though insoluble in water, it is freely soluble in
alcohol, benzene, ether, glacial acetic acid and carbon disulfide. The toxicity
of rosin is low. At room temperature, rosin is hard and friable; when warmed it
becomes soft and sticky.
B-8
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Sandarac - A natural resin obtained from Morocco. Its commercial form is yellow,
brittle, amorphous lumps or powder; soluble in alcohol; insoluble in benzene and
water. ' ' •
Shellac - A natural resin secreted by the insect Laccifer lacca and deposited on
the twigs of trees in India.
Styrene (monomer)
Styrene monomer is used to a limited basis by the investment-casting industry as
a filler. Styrene has a melting point of -31°C and boiling point of 141°C. Its
lower explosive limit is 1.1 percent; upper explosive limit is 6.1 percent. Flash
point is 31°C and autoignition temperature is 490°C. Styrene is moderately toxic
by inhalation, ingestion, or skin irritation. Inhalation of concentrations as low
as 20 mg/m have caused toxic glandular effects in humans and a concentration of
10,000 ppm over 30 minutes has been lethal to humans. Data on the toxicity of
2
styrene by ingestion is not conclusive with LD,-n for rats being 5,000 mg/kg and
2
IID50 for mice being 316 mg/kg • The U.S. Occupational Standard for styrene is
that the time-weighted average concentration is not to exceed 100 ppm and peak
concentration is not to exceed.600 ppm.
Terpene Polymer - A resinous synthetic thermoplastic material made by the poly-•
merization of beta-pinene and dipentene (which are the monocyclic and dicyclic
forms of terpene, which is itself an unsaturated hydrocarbon having the empirical
formula C. QH.. g). Terpene resin is used in paper coating, and hot-melt adhesive
compounds. Two trade names are Nirez and Piccolyte.
Urea - Also known as carbamide, CO(NH_)-, a white crystalline powder; specific
gravity 1.335; melting point 132.7°C; decomposes before boiling; soluble in water,
alcohol, and benzene; has been used as a filler in investment casting waxes;
synthesized from liquid ammonia and liquid carbon dioxide at high pressure; low
toxicity except when heated, in which case with sufficient temperature and an
oxidizing atmosphere nitrogen oxides are generated, and in a reducing atmosphere
hydrogen cyanide can be generated.
B-9
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Wax - A low-melting mixture or compound of high molecular weight, solid at room
temperature and generally similar in composition to fats and oils, except that it
contains no glycefides. Some are hydrocarbons; others are. esters of fatty
acids and alcohols. They are classed among the lipids; they are thermoplastic,
but since they are not high polymers, they are not considered in the family of
plastics. Waxes are classed as follows:
I. Natural
a. Animal - beeswax, spermaceti, lanolin, shellac wax
b. Vegetable - carnauba, candelilla, bayberry, sugarcane
c. Mineral
1. Fossil earth waxes - ozocerite, ceresin, montan
2. Petroleum waxes - paraffin, microcrystalline, petrolatum
II. Synthetic
a. Ethylenic polymers and polyol ether-esters - "Carbowax", sorbitol
b. Chlorinated naphthalenes - "Halowax"
c. Hydrocarbon type via Fischer-Tropsch synthesis
B-10
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Information Sources - Appendix JB
1. Hawley, Gessner G., editor, The Condensed Chemical Dictionary. 3th edition,
Van Nbstrand Iteinhold Company, 1971.
2. Sax, N". Irving, Dangerous Properties of Industrial Materials. 3rd edition,
Van Nbstrand Rsinhold Company, New York, 1968.
3. Christensen, Herbert E. and Thomas T. Luginbyhl, Registry of Toxic Effects of
Chemical Substances. U.S. Dept. of HEW, Public Health Service, Center for
Disease Control, NIOSH, Rockville, Mi., June 1975.
4. Modern Plastics Encyclopedia. Vol. 49, No. 10A, McGraw-Hill Publications
Co., October 1972.
5. Telephone coirnunications with William Siegfried of the Freeman Manufacturing
Company, Cleveland, Ohio.
6. Telephone communications with Paul Solomon of the Yates Manufacturing Company,
Chicago, Illinois.
7. Patent #3,884,708, Thermoplastic Pattern Material. Edward F. Burkert,
May 20, 1975.
B-ll
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APPENDIX C
INTERNATIONAL AGREEMENTS CN THE USE OF PCBs
C-l: DECISION OF THE COUNCIL OF THE ORGANIZATION FOR
ECONOMIC CO-OPERATION AND DEVELOPMENT (OECD),
FEBRUARY 13, 1973
C-2: DIRECTIVE OF THE COUNCIL OF THE EUROPEAN ECONOMIC
COMMUNITY (EEC), JULY 21, 1976
-------
APPENDIX C (C-l)
COUNCIL
DECISION OF THE COUNCIL
ON PROTECTION OF THE ENVIRONMENT BY CONTROL
OP POLTCH10RDTATED BIPHENYLS
(Adopted by the Council at its 315th Meeting
on 13th February, 1973)
The Council,
Having regard to Articles 5(a)., 5(b) and 12(c) of the
Convention on the Organisation for Economic Co-operation and
Development of 14th December, 1360;
Having regard to the Recommendation cf the Council of
26th May, 1972, on Guiding Principles concerning International
Economic Aspects of Environmental Policies ,/C"(72) 12§7;
Having regard to the Note by the Secretary-General of
7th February, 1973, • concerning Proposals for Concerted Action _
with respect to • Polychlorinated Biphenyls AX 73)1 (2nd R'evisionJ_7:
Considering -that the use of Polychlorinated Biphenyls • ,
(PCBs)should be controlled by international action in order to
minimise their escape, into the environment'pending the realisa- .
tion of the ultimate objective of .eliminating entirely their'
escape into the.environment;
On the proposal of the Environment Committee;
I. DECIDES:
1. Member countries shall ensure that in their respective-
territories, Polychlorinated Biphenyls (PCBs) shall not be used
for industrial or commercial purposes, except in the following
categories -~;f use: ,
Dielectric fluids for transformers or large power factor
correction capacitors;
Heat transfer fluids (other than in installations for
processing of foods, drugs, feeds and veterinary products);
Hydraulic, fluids in mining equipment;
Smal1 canacitors (subject to the provisions of Section
II.2 below);
C-l
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rand, as regards the foregoing categories, .i?C3s niay be used only
in those applications in which the requirements for non-
inflammability outweigh .the need for environmental protection
and in which Member countries are satisfied that sufficient
controls are exercised in order to minimise risk to the
environment.
2. In pursuance of paragraph 1.1 above, Member countries
shall:
(a) control the manufacture, import and exnort of bulk
£C3s; • '*
(b) institute adequate arrangements for the recovery,
regeneration, adequate incineration or other safe
disposal of surplus and waste materials;
(c) institute a special, uniform labelling system for
both bulk PCBs and PCB-containing manufactured product:
and
(d) establish safety specifications for containers and
transport.
II. RECOMMENDS that Member countries in implementing the
Decisions set -forth in Section I above:'
1. control and manufacture, import and export of PCS-' •
containing products;
2. work tov/ards the elimination of the use of PCBs
in small capacitors;
J>. -give priority attention to the • elimination of the
following applications of PCBs: '' ...
(a) heat transfer fluids in the food, phamiaceuticals>
feed and vetinary industries;
(b) plasticizers for paints, inks, copying paper,
adhesives, sealants;
(c) hydraulic liquids (other than in mining) and
lubricating oils;
(d) vacuum pump fluids and cutting oils;
(e) pesticides;
4-. request firms to use, as PCB replacements, materials
which are less hazardous to human health and the environment
than the range of PCBs now in use.'
C-2
-------
1 -L _L .
At the beginning of 1974, 1975 and 1976 within the frane-
worlc of . the Environment 'Committee , Member countries shall exchan^
information on the main statistical data concerning FC3s , notably
on:
(1) amounts of PC3s, including:
amounts manufactured by FOB type,
amounts imported " " " and by country,
amounts exported " " " and by country,
amounts incinerated " " "
amounts consumed " " . " and by use;
(2) PCS replacements supplied by manufacturers, including
the folio-wing points:
identification,
total amounts for each chemical type and for each
use,
known toxicity and environmental hazard of each
. chemical type;
(3) disposal of surplus PCBs by incineration (including
evaluation of incinerator efficiency) or by other
efficient means.
IV. tfOTSS the "Technical JTote on Polychlorinated B'iphenyls"1
contained in the Appendix to this Decision.
V. INVITES Member countries to report to the Organisation
at the' beginning of 1974, 1975 and 1976 on measures taken in
application of .this Decision.
VI. INSTRUCTS the Environment Committee to follow the
implementation of this- Decision, to report at regular intervals
to the Council on the information exchanges provided for in
Section III of this Decision and to make such proposals to
further improve and strengthen the control of production and use
of -PCBs as" may seem appropriate in the light of experience
gained and the continued work of the Organisation in this field.
03
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Technical Note on
Polychlorinated Biohenyls
INTRODUCTION
Polychlorinated biphenyls (PCBs) are a group of stable
substances comprising theoretically^ more than 200 individual
compounds, many of which are widely used particularly because
of their dielectric properties and non-flanreability. At present
they are obtained through chlorina.tion of diphenyl, resulting in
mixtures that are characterised by their average content of
chlorine. Due to the persistence and toxicity of some of these
compounds(1), effects have been observed in the environment and
accidents reported over the last few years, which have given rise
to serious concern in Member countries. In view of this concern..
the Sector Group on Unintended Occurrence of Chemicals in the
Environment has investigated, on a priority basis, the need for,
and feasibility of, concerted action to control the use and
emissions of PCBs. The results of this enquiry,.lead to the
folloving conclusions:
(a) Because of unacceptable levels of FCBs found in the
environment and' because of a number of incidents
involving human health, some countries have taken,
or are considering taking action to control the use"
of PCBs;
(b) There are (1972) -only six companies in O.S.C.D.
Member countries that manufacture PCBs; five of
them have already taken steps to reduce production
to the supply for a few approved uses;
(c) PCBs can be replaced except for some users where
their dielectric properties and non-flaminability
are essential;
(d) The technology for destruction of PCBs exists;
(e) Because of the many applications of PCBs in the wide
range of consumer products moving in international
trade, the situation will almost certainly become
complicated unless international agreement is reached
on allowable uses;
(1) As'of the time of the preparation of this Note, limited
research studies with certain selected PCB-compounds seem
to indicate that some of these compounds could eventually
safely be used for certain applications.
04
-------
(f) A rough estimate(l) indicates that consumption of
PC3s in O.E.C.D. countries is matched by production.
Considering in addition that import of chemicals
from non-0.E.G.13. to O.E.C.D. countries is still re-
stricted to basic chemicals, import of bulk PCBs is
unlikely. It is, therefore, reasonable to suggest
that the major part of'the problem-of unintended
occurrence of PCBs can be solved through concerted
action between O.S.C.D. Member countries.
USES OP PCBs'
The applications of PCBs fall mainly into two categories:
uses in closed systems;
dissipative uses.
CLOSES SYSTEMS
The use of PCBs in closed systems can be defined as
applications from which the PCEs are recoverable. PCBs in
transformers, capacitors, heat transfer systems, hydraulic equip-
ment, and vacuum pumps are in principle recoverable, since during
use, the PCBs are not generally dispersed into the environment.
It is, however, important to distinguish between closed
.system uses that are controllable in practice and those where
control cannot be guaranteed either:
w • »
because frequent replacement of relatively small ••
quantities vfi.II lead to disposal rather than
recovery, or '• .
because a large number of small units widely dispersed
will make collection extremely difficult, or
because accidental leakage will cause imminent danger
to human health.
A truly controllable use may therefore be defined as an
application where:
the PG3s are contained in a sealed circuit in large,
long-life units; ^ .
the quantities involved are such that there is an
incentive for regeneration.
(1) Production in 1971 amounted to about 48,400-metric tons and
consumption in the 13 countries that provided numerical
information to about 35,300 tons.
c-s
-------
Following what has-been said above, the only truly
controllable uses of JfCBs are in dielectrics for t r an s f o rm_ers
and for large capacitors for power factor correction. Pre-
venting escape of PCBs from these applications- is mainly a
problem of engineering design and of collection and destruction
of used liquids, or, in the case of capacitors, of removal and
destruction of PCs-impregnated material. These uses also being
essential for safety reasons, it would be unreasonable to suggest
that they be discontinued at the present time.
In all other closed systems, recovery o-f ?CBs, although
theoretically possible, would not be practical. Such applica-
tions should, therefore, be discontinued, unless safety require-
ments prevent the use of substitute products:
(i) Heat transfer system's
There may be some installations where the risk of
explosion or fire must be avoided at all cost, and
the danger of some escape of PCBs therefore is of
less importance. Because. of the risk of leakage,
which can never be totally guarded against, the use
of PCBs as heat transfer media in the food, drugs
and feed industries should, however, be prohibited.
r ' * -!•
(ii) Hydraulic equipment > vacuum pumps
Although the quantities invoi.-.^ j_n -t^e individual'
case are relatively small, they ^.-\i > unless
recovered, add significantly to the «— .rironmente.1
burden of PCBs. ' Theoretically, used flux^ could
be recovered, but in view of the difficulty 02
establishing a system- to collect small quantities
from many users, these applications should be dis-
continued.. Furthermore, PCBs are generally not
essential in hydraulic and pumping fluids, with the
possible exception of hydraulic equipment in under-
ground mining.
(iii) Small capacitors
These are typical examples of an application of PGBs
in sealed units that are almost completely non- .
recoverable. Considering, for example, the many
domestic electrical appliances in which capacitors
are used, the cost of recovery- would probably be
prohibitive. A warning' label showing that the
equipment must hot be disposed of as ordinary waste .
has been suggested; it is however, not likely to
be sufficient, unless manufacturers and retailers
C-6
-------
would accept return of appliances that are out of
use. The problem of recovery remains unresolved-
at the present time, but it has to be noted that
Japan has stopped the use of PCBs in the manufacture
of- small capacitors.
DISSIPATIVE USES '
The dissipative uses are those where recovery of used
PCBs is not possible, sinca they are not contained in closed
systems but in direct contact with the environment:
(i) Lubricating and-cutting oils
The conditions under which these oils are used are
such that there is continuous emission of small
quantities into the environment. These applications,
not being essential, should be discontinued;
(ii) ?_esticige Use
This use has fortunately been abandoned in most
countries already; if not, it should be banned with
immediate effect. Since all O.S.C. D. countries
require registration of pesticides, such a measure
can easily be taken under existing legislation;
(iii) P'lasticizers
The most important category„ by volume of dis-
sipative 'use is-in the field of plasticisers. They
are or have been used in most countries in a wide
variety of consumer products including paints,', inks,
copying paper, adhesives, sealants, plastic products,
•etc., many"of which are traded internationally. The
• - major applications seem to be. in the printing and
paint industries.
The Printing; Industry; Because of the risk of contamina-
tion of paper,""which after recycling may be used in food packaging,
the use of PCBs in the printing industry should be banned.. In
view of the fact that printing inks can be produced without
PCBs and that in any case the amount used probably represents a
total value of only about £>3o,000 in O.E.C.D. countries, such a
measure should not cause serious economic damage. Assuming that
copying paner is usually provided by the copying machine manu-
facturers ^relatively few and big companies;, any economic effects
should be small.
The Paint Industry poses a somewhat different problem.
Over the last decade, production has increased by 3.5 per cent - .
5 per cent annually and the trend is rising in the O.S.C.D. area.
C-7
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The over 2,000 million dollar Vest European paint industry alone
accounts for some 40'per cent of the world output. Production
is assured by a few large and a great many small companies
(United Kingdom = 430, Italy and France = 350 etc.)." This
picture'suggests that an overall ban on PCBs in paints could
have some economic consequences.
It appears, however, that where used (e.g. in stoving
applications) PCBs constitute something like 5-10 per cent of
the paint. Pew details are available in respect of the amounts
used in paints', but taking one example (Prance) where 250 tons
were used (1971) in a, paint industry that produced something
like 700,000 tons of paint, presumably only 2500-5000 tons would •
contain PCBs. Considering in addition that small paint manufac-
turers are generally highly specialised, and that the manufac-
turing process would not have"to undergo-a major change to re-
place the use of PCBs, a ban on PCBs should not cause any serious
disturbance. The use of PCBs-in paints has, in fact, been
discontinued in some countries already. Figures for production
(8,654:200 tons in 1969) and consumption (3,517,500 tons) in
0.E.G.ID. countries again suggest that import of paints from non-
O.E.C.D.. producers may be of. minor significance.
In practice, none of. the products 'where PCBs have been
used as plasticizers can be recovered. -Unless the use is totally
eliminated, there will be continuous emissions into.the environ-
ment due - to evaporation, insufficient incinceration etc. •
Judging by the action already taken in several countries, sub-
s'titutes can readily be found for the whole category of plas.ti-
cizer use of PC3s, which should, therefore, be banned.
It follows from what has been said above that for adequate
protection of health and environment, but also to avoid undue
competition in international trade, agreement is necessary on
allowed uses of PCBs. In order to ensure- that home production
is not substituted by import, control action by governments,
through licencing or other means, is essential. Measures are
further necessary to ensure collection of used material, safety
in transport of raw PCBs,-and assessment of substitute materials:
(a) A uniform labelling system, internationally
recognisable, should be developed for use on
containers of raw PCBs as well as on any equip-
ment or product containing PCBs.
(b) Suppliers (i.e. manufacturers and importers)
should further provide containers for the trans-
port of PCB-containing liquids: such containers
must meet the appropriate specifications that have
been laid down to ensure safety in transport of
dangerous chemicals.
C-8
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(c) Development of substitutes .that are less hazardous
than persistent ?CBs(l) should be encouraged, but
in view of the fact that no system for pre-market
control of new chemicals has been introduced,
testing for environmental effects is so far entirely
the responsibility of the manufacturers. Informa-
tion on replacement products should,, therefore,
be collected .and reviewed.
(.1) See footnote on page 10
C-9
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9.76
27.9. 76
Official journal of the European Communities
No L 262/201
APPENDIX C (C-2)
COUNCIL DIRECTIVE
of 27 July 1976
on the approximation of the laws, regulations and administrative provisions of the
Member States relating to restrictions on the marketing and use of certain dangerous
substances and preparations
(76/769/EEC)
THE COUNCIL OF THE EUROPEAN COMMUNITIES,
Having regard to the Treaty establishing the European
Economic Community, and in particular Article 100
thereof,
Having regard to the proposal from rhe Commission,
Having regard to the opinion r>( rhc European
Parliament ('),
Whereas provisions relating to certain dangerous sub-
stances and preparations have already been laid down
in Community Directives; whereas it is still necessary
to establish rales for other products, in .particular for
those in respect of which international organizations
have decided on restrictions such as polychlorinared
biphenyils (PCS), a decision restricting the production
and use of which was adopted by the CouncH of the
OECD on 13 February 1973; whereas such a measure
is necessary to prevent the absorption of PCB by the
human body and the resultant danger to human
health;
Having -regard to the opinion of the Economic and
Social Committee (•), •
Whereas any rules concerning the placing on the
market of dangerous" substances and preparations
must aim at protecting the public, and particular
persons using such substances and preparations;
Whereas they shotfld contribute to the protection of
the environment from ail substances and preparations
which have characteristics of ecotoxicity or which
could pollute the environment;
•
Whereas they should also aim to restore, preserve
and improve the quality of human life;
Whereas detailed examinations have shown that
polychlorinated terphenyls (PCT) entail risks similar
to .those presented by PCBs; whereas rhe mar-
keting and use of such substances should also be
restricted;
Whereas it wiB be necessary, moreover, periodically
to review the whole problem with a view to moving
gradually towards a complete ban on PCBs and PCTs;
Whereas die use of chloro-l-«thylene (monomer vinyl
chloride) as an aerosol propeflant involves dangers
to human health and the use thereof should be pro-
hibited,
Whereas dangerous substances and preparations are
governed by rules in the Member States; whereas
these rules differ as to the conditions of their market-
ing and use; whereas diese differences constitute an
obstacle to trade and directly affect the establishment
and functioning of the common market;
HAS ADOPTED THIS DIRECTIVE:
Whereas this obstacle should therefore be removed;
whereas this entails approximating the laws
governing the matter in the iMember States;
(') OJ No C 60, 13. 3. 1975, p. 49.
(*} OJ No C 16, 23. 1. 1975, pi 25.
Article i
1. Without prejudice to die application of other
relevant Community provisions, this Directive--is
concerned with restricting die marketing and use in
the Member States of the Community, of the
dangerous substances and preparations listed in the
Annex.
C-10
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.7.9.76
Official Journal of the European Communities
No L 262/203
' ANNEX
Designation of the substance, of the groups
of substances or of the preparation
1. — Polychlorinared biphenyls (PCS),
except mono- and dichlorinated
biphenyls.
— Polychlorinated terphenyls (PCT).
— Preparations with a PCB or PCT
content higher than 0-1% by weight.
Conditions of restriction
May not be used except for the following
categories:
1. closed-system electrical equipment: trans-
formers, resistors .and inductors;
2. large condensers (^ 1 kg total weight);
3. small condensers (provided that' the
PCB has a maximum chlorine content of
43% and does not contain more than
3-5% of penra- and higher chlorinated
biphenyls).
Small condensers which do not fulfil the
above requirements may still be marketed
for one year from the date of entry into
force of this Directive. This restriction
does not apply to small condensers
already in use;
4. heat-transmitting fluids in closed-circuit
heat-transfer installations (except in
installations for processing foodstuffs,
feedingstuffs, pharmaceutical and veteri-
nary products; however, if PC3s are
used in the abovementioned installations
at the time of notification of this Directive,
they may continue to be used until 31
December 1979 at the latest);
5. hydraulic fluids utilized in:
(a) underground mining equipment;
(b) machinery servicing cells for the
electrolytic production of aluminium, •
in use when this Directive is" adopted,
until 31 December 1979 at the latest;
6. primary and intermediate .products, for
further processing into other products
which are not prohibited under this
Directive.
2. Chloro-l-cthylene (monomer vinyl
chloride)
May not be used as aerosol propellant for
any use whatsoever.
Oil
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No L 262/202
Official Journal of the European Communities
27. 9.76
2. This Directive shall not apply to:
(a) the carriage of dangerous substances and prep-
arations by rail, road, inland waterway, sea or
air;
(b) dangerous substances and preparations exported
to non-member countries;
(c) substances and preparations in transit and subject
to customs inspection, provided chat they undergo
no processing.
3. For the purposes of this Directive:
(a) 'substances' means
chemical elements and their compounds as they
occur in -the natural state or as produced by
industry;
(b) 'preparations' means
mixtures or solutions composed of two.or more
substances.
Article 2
Member States shall take all neccessary measures to
ensure that the dangerous substances and preparations
listed in the Annex may only be placed on the market
or used subject to the conditions specified therein.
Such restrictions shall not apply to marketing or use
for Research and Development or analysis purposes.
Article 3 •
1. Member States shadl bring into force the pro-
visions necessary to comply with this Directive
within 18 months of its notification and snail forth-
with inform the Commission thereof.
2. Member States shall communicate to the Com-
mission the text of the provisions of national law
which they adopt in the field covered by this
Directive.
Article 4
This Directive is addressed co the Member States."
Done at Brussels, 27 July 1976.
For the Council
The President
M. van der STOEL
C-12
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BIBLIOGRAPHIC DATA
SHEET
Kcpori No.
EPA 560/6-77-007
3. Recipient's Accession No.
4. Title and Subtitle
ASSESSMENT OF THE ENVIRONMENTAL AND ECONOMIC IMPACTS
OF THE BAN CN IMPORTS OF PCBs
5. Report Date
July,'1977
6.
7. Authot(s)
Robert P. Burruss, Jr., P.E.
8. Performing Organization Kept.
N°- 474-5B '
9. Performing Organization Name and Address
VERSAR INC.
6621 Electronic Drive
Springfield, Virginia
10. Project/Task/Work Unit No.
Task 6
22151
11. Contract/Grant No.
68-01-3259
12. Sponsoring Organization Name and Address
U.S. Environmental Protection Agency
Office of Toxic Substances
Washington, D.C. 20460
13. Type of Report & Pcriou
Covered
Final Task Reoort
14.
15. Supplementary Notes
Project Officer: Thomas Kopp
16. Abstracts
This report summarizes an investigation into the uses of imported polychlorinated
biphenyls (PCBs) in the United States. Imported PCBs are presently used only for
the maintenance of certain mining machinery. In addition, PCBs are present as a
significant impurity in polychlorinated terphenyls (PCTs) imported for use in
investment casting waxes. Importation of PCBs"for these uses will be banned after
1977 by the Toxic Substances Control Act, unless exemptions are allowed in accord-
ance with the provisions of the Act. The recent Directive of the Council of the
European Communities (EEC) prohibits use of PCBs and PCTs in investment casting
waxes, but allows continued use of PCBs in mining machinery in Europe.
17. Key Words and Document Analysis. ]7a. Descriptors
Polychlorinated Biphenyls
Polychlorinated Terphenyls
Mining Machinery
Investment Casting Wax
Tooling Compounds
Imports
17b. Identifiers/Open-Ended Terms
Chlorine Organic Compounds
Toxic Substances Control Act
Casting Technology
Foundries
Metal Forming
Investment Casting
Toxicity
17e. COSATI Field/Group
18. Availability btatement
Distribution Unlimited
19.. Security Class (This
Report)
UNCLASSIFIED
20. Security Class (This
Page
"
21. No. of Pages
176
22. Price
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(e.g., date of issue, date of approval, date of preparation, date published).
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:!.-. !n
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