ASTM B631-93(1998)
(Specification)Standard Specification for Silver-Tungsten Electrical Contact Materials
Standard Specification for Silver-Tungsten Electrical Contact Materials
SCOPE
1.1 This specification covers electrical contact components made from silver-tungsten by powder-metallurgical procedures.
1.2 This specification covers compositions within the silver-tungsten system normally specified by users of contacts.
1.3 This standard does not purport to address all the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
1.4 It is the responsibility of the user to become familiar with all hazards including those identified in the appropriate Material Safety Data Sheet for this product/material as provided by the manufacturer.
General Information
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Standards Content (Sample)
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Designation: B 631 – 93 (Reapproved 1998)
Standard Specification for
Silver-Tungsten Electrical Contact Materials
This standard is issued under the fixed designation B 631; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4.2 The chemical analysis shall be made in accordance with
the methods prescribed in the newest edition of the Annual
1.1 This specification covers electrical contact components
Book of ASTM Standards, or by any other approved method
made from silver-tungsten by powder-metallurgical proce-
agreed upon between the manufacturer and purchaser.
dures.
1.2 This specification covers compositions within the silver-
5. Other Requirements
tungsten system normally specified by users of contacts.
5.1 The manufacturer and purchaser shall agree on qualifi-
1.3 This standard does not purport to address all the safety
cation tests for determination of physical properties.
concerns, if any, associated with its use. It is the responsibility
5.2 The tests shall be performed on production parts,
of the user of this standard to establish appropriate safety and
wherever practical or applicable (small size contacts do not
health practices and determine the applicability of regulatory
lend themselves to accurate conductivity measurement).
limitations prior to use.
5.3 The tests shall be determined after consideration of the
1.4 It is the responsibility of the user to become familiar
function of the part.
with all hazards including those identified in the appropriate
5.4 The typical properties of the four most common types of
Material Safety Data Sheet for this product/material as pro-
silver-tungsten contacts are given in the appendix.
vided by the manufacturer.
6. Finishing of Contacts
2. Referenced Documents
6.1 The material shall be finished by such operations as
2.1 ASTM Standards:
necessary to meet requirements agreed upon by the maker and
B 328 Test Method for Density, Oil Content, and Intercon-
user of the contacts (braze alloy backing, tumbling to polish
nected Porosity of Sintered Metal Structural Parts and
2 surfaces, special surface finish, silver-rich surface layer, clean-
Oil-Impregnated Bearings
ing, etc.).
3. Ordering Information
7. Permissible Variations in Dimensions
3.1 Orders for this material under this specification shall
7.1 Permissible variations in dimensions shall be within the
include the following information:
limits specified on drawings describing the contacts and
3.1.1 Dimensions (see Section 7).
accompanying the order, or shall be within the limits specified
3.1.2 Chemical composition (see reference tables in the
in the purchase order.
Appendix X1 as a possible guide).
3.1.3 Physical properties (see Section 6 and Appendix X1 as
8. Workmanship
guideline).
8.1 The parts shall be free of defects in material or process-
3.1.4 Certification (see Section 13).
ing that would seriously affect their performance.
3.1.5 Other features as agreed upon between the purchaser
9. Significance and Use
and manufacturer.
9.1 Proprietary methods for manufacture of these materials
vary significantly among suppliers, and these methods influ-
4. Chemical Composition
ence such properties as arc erosion, contact resistance, and
4.1 The material shall conform to composition limits as
tendency to weld in service. Since the performance of contacts
agreed upon between the manufacturer and purchaser.
in a device depends on numerous factors outside the contact
itself (opening speed, closing speed, contact pressure, contact
This specification is under the jurisdiction of ASTM Committee B-2 on bounce, environmental variations, assembly technique and
Nonferrous Metals and Alloys and is the direct responsibility of Subcommittee
variations, etc.) this specification cannot ensure performance
B2.05 on Precious Metals.
control in the application. As part of the qualification on initial
Current edition approved Aug. 15, 1993. Published October 1993. Originally
published as B 631 – 77. Last previous edition B 631 – 88.
Annual Book of ASTM Standards, Vol 02.05.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B 631
samples it is recommended that the user functionally electri- agreement between manufacturer and purchaser for both limits
cally test the materials for all devices applicable to the and methods of analysis should be required for elements not
material’s use. This specification will provide a means for the specified.
contact manufacturer and contact user to reach agreement on 10.3 Physical Tests—The manufacturer and purchaser shall
the details of material to be supplied for a specific use and agree on a representative number of specimens for physical
reasonable assurance that future lots will be similar in proper- tests including microstructure.
ties and microstructure to the initial test or sample contacts
11. Inspection
supplied.
11.1 Unless otherwise specified, inspection of parts supplied
on contract shall be made by the purchaser.
10. Sampling
10.1 Lot—Unless otherwise specified, a lot shall consist of
12. Rejection
parts of the same form and dimensions, made of powders of the
12.1 Unless otherwise specified, rejections based on tests
same particle size range and composition, processed under the
made in accordance with the specification shall be reported to
same conditions, and submitted for inspection at one time.
the manufacturer within 30 days of the receipt of shipment.
10.2 Chemical Analysis—At least one sample for chemical
analysis shall be taken from each lot. A representative sample 13. Certification
of chips may be obtained by milling, drilling, or crushing at
13.1 A certification, when requested by the purchaser, based
least two pieces with dry tools, without lubrication. In order to
on the manufacturer’s quality control, that the material con-
obtain oil-free chips, the parts selected for test shall have the
forms to the requirements of this specification, shall be
oil extracted in accordance with Test Method B 328.
furnished upon request of the purchaser, provided the request is
10.2.1 These specification limits do not preclude the pos-
made at the time of cost quotation and at the time of order
sible presence of other unnamed elements, impurities or
placement.
additives. Analysis shall be regularly made only for the minor
14. Keywords
elements listed in the table. However, if a user knows of
elements that might be detrimental to their application or has 14.1 contacts; powder metallurgy; silver; silver–tungsten;
other reasons for requiring analysis for specific elements, then tungsten; tungsten–silver
APPENDIX
(Nonmandatory Information)
X1. Typical Property Values
NOTE X1.1— Table X1.1, Table X1.2, Table X1.3, and Table X1.4
X1.1 Scope
represent the major manufacturing techniques used in industry. The size
X1.1.1 The following information provides guidelines for
and shape of the part is important in choosing the optimum technique as
users and manufacturers of silver-tungsten contact material.
well as other considerations such as frequency of operation of the device,
Typical ranges of chemistry and properties are given for the
and how crucial is its application.
three most popular compositions, 27 silver/73 tungsten, 35
silver/65 tungsten, and 50 silver/50 tungsten. These proper
...
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