ASTM B476-90(1995)e1

NOTICE: This standard has either been superseded and replaced by a new version or
withdrawn. Contact ASTM International (www.astm.org) for the latest information.
e1
Designation: B 476 – 90 (Reapproved 1995) An American National Standard
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Specification for
General Requirements for Wrought Precious Metal
Electrical Contact Materials
This standard is issued under the fixed designation B 476; 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.
This standard has been approved for use by agencies of the Department of Defense. Consult the DoD Index of Specifications and
Standards for the specific year of issue which has been adopted by the Department of Defense.
e NOTE—Section 17 was added editorially in June 1995.
1. Scope E 3 Methods of Preparation of Metallographic Specimens
E 8 Test Methods of Tension Testing of Metallic Materials
1.1 This specification covers general requirements common
E 29 Practice for Using Significant Digits in Test Data to
to wrought precious metal electrical contact alloy products in
Determine Conformance with Specifications
the form of sheet, strip, wire, and rod. Unless otherwise
E 55 Practice for Sampling Wrought Nonferrous Metals and
specified in the purchase order or in an individual specification,
Alloys for Determination of Chemical Composition
these general requirements shall apply to wrought electrical
E 112 Test Methods for Determining Average Grain Size
contact materials where indicated in the applicable product
specifications issued by ASTM.
3. Terminology
1.2 In case of conflict, the requirements on the purchase
3.1 Definition:
order, the individual specification, and this general specifica-
3.1.1 lot—the quantity of material of the same type, size,
tion shall prevail in the sequence named.
and finish produced at one time from the same cast or heat, and
1.3 The values stated in inch-pound units are to be regarded
heat treated in the same heat-treatment cycle.
as the standard. The metric equivalents of inch-pound units
4. Ordering Information
may be approximate.
1.4 This standard does not purport to address all of the
4.1 Orders for material to this specification shall include the
safety concerns, if any, associated with its use. It is the
following information:
responsibility of the user of this standard to establish appro-
4.1.1 Designation and revision date of this specification.
priate safety and health practices and determine the applica-
4.1.1.1 If a revision date is not designated, the latest revision
bility of regulatory limitations prior to use.
should be used.
1.5 It is the responsibility of the user to become familiar
4.1.2 Designation and revision date of the applicable prod-
with all hazards including those identified in the appropriate
uct specification.
Material Safety Data Sheet for this product/material as pro-
4.1.2.1 If a revision date is not designated, the latest revision
vided by the manufacturer.
of the product specification should be used.
4.1.3 Description of material form,
2. Referenced Documents
4.1.4 Dimensions of the material,
The following documents of the issue in effect, on the date
4.1.5 Total quantity of each size,
of material purchase, form a part of this specification to the
4.1.6 Temper of the material (annealed, cold worked, etc.),
extent referenced herein:
4.1.7 Temper test (hardness or tensile) (Section 10),
2.1 ASTM Standards:
4.1.8 Special requirements (if any), and
B 63 Test Method for Resistivity of Metallically Conduct-
4.1.9 Certification (Section 14).
ing Resistance and Contact Materials
4.2 Specify the following, if required:
B 277 Test Method for Hardness of Electrical Contact
4.2.1 Certificate of compliance of physical and chemical
Materials
requirement.
4.2.2 Test Data—Specify tests and analyses to be performed
and reported.
This specification is under the jurisdiction of ASTM Committee B-4 on
4.2.3 Special packaging, if required.
Metallic Materials for Thermostats and for Electrical Resistance, Heating, and
Contacts and is the direct responsibility of Subcommittee B04.02 on Electrical
Contact Materials.
Current edition approved May 25, 1990. Published July 1990. Originally Annual Book of ASTM Standards, Vol 03.01.
published as B476 –68. Last previous edition B476 – 85. Annual Book of ASTM Standards, Vol 14.02.
2 5
Annual Book of ASTM Standards, Vol 03.04. Annual Book of ASTM Standards, Vol 03.05.
B 476
5. Materials and Manufacture shall be that the maximum deviation from the flat surface shall
be less than 1 % of the measurement distance specified for the
5.1 The raw material shall be of such quality and purity that
product, such as diameter for circles, length or width of blanks,
the finished product shall have the properties and characteris-
or any specific measurement length; that is, maximum of 0.20
tics prescribed in the applicable product specification issued by
in. (5.08 mm) deviation in any 20 in. (508 mm) length in any
ASTM.
direction.
5.2 The product shall be produced by a combination of hot
or cold working operations. it shall be finished, unless other-
7. Workmanship
wise specified, by such cold working, annealing, or heat
treatment as may be necessary to meet the specified properties.
7.1 Surfaces of all material furnished to this specification
shall be smooth, clean, and free from scratches, stains, rough
6. Dimensions and Permissible Variations
spots, slivers, laps, scale, pits, and any other injurious defects
6.1 General—For the purpose of determining conformance
within limits consistent with the best possible practice.
with the dimensional requirements prescribed in this specifi-
cation, any measured value outside the specified limiting
8. Sampling
values for any dimension may be cause for rejection.
8.1 Sampling—The portion size and selection of pieces
6.2 Tolerance tables to cover all forms of products can
shall be as follows:
become quite voluminous. For this reason, it is recommended
8.1.1 Chemical Analysis—Samples for chemical analysis
that tolerances be established and agreed upon between the
shall be taken and prepared in accordance with Practice E 55.
producer and user at the time of placing an order or an inquiry
The minimum weight of the composite sample that is to be
for quotation of price and delivery. Refer to Section 16
divided into three equal parts shall be 6 g.
(Supplementary Requirements). Details of form and tolerances
8.1.2 Physical Tests—For physical tests, a test specimen
for products not covered by this specification, such as, the
shall be taken from each of four randomly selected individual
types of materials listed below, and means of measurement,
units of finished product from a lot. If the lot consists of less
should be established between producer and user.
than four units, a piece shall be taken from each individual unit.
6.2.1 Sawed products,
6.2.2 Square sheared products,
9. Number of Tests and Retests
6.2.3 Flat wire, thickness, width and edge radius tolerances,
6.2.4 Edge rolled flat wire, thickness, width and corner
9.1 If any specimen tested shows a defective test method or
radius tolerances.
extraneous flaws, it may be discarded and another specimen
6.3 Wire and Rod:
substituted.
6.3.1 The standard tolerances applied to the diameter of
9.2 If the chemical analysis fails to conform to the specified
wire and rod shall be as prescribed in Table 1.
limits, analysis shall be made on a new composite sample,
6.3.2 The rod straightness and length tolerance shall be
prepared from samples selected in accordance with Practice
those prescribed in Table 2.
E 55 or 8.1.2 after the physical tests have been performed. The
6.4 Strip and Sheet—Supplied in the form of coils, flat
results of this retest shall comply with the specified require-
lengths or on spools.
ments.
6.4.1 The thickness tolerances shall be those prescribed in
9.3 The required physical tests shall be performed on 2 of 4
Table 3.
of the pieces selected in accordance with 8.1.2.
6.4.2 The width standard tolerance for slit products shall be
9.3.1 If one of the two tests made to determine any of the
those prescribed in Table 4.
physical properties fails to meet a specified limit, this test shall
6.4.3 The straightness (camber or edgewise curvature) tol-
be repeated on each of the two remaining pieces selected in
erance for slit strip is prescribed in Table 4 also.
accordance with 8.1.2 and the results of both of these tests shall
6.5 Flatness—The flatness of blanks, shims, circles, or
comply with the specified requirements.
other forms should be
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