ASTM B277-95

NOTICE: This standard has either been superseded and replaced by a new version or
withdrawn.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.
Designation: B 277 – 95 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 Test Method for
1
Hardness of Electrical Contact Materials
This standard is issued under the fixed designation B 277; 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 3.2 The microhardness test is of questionable significance
when the metallic phases in a material are so large that the
1.1 This test method covers the determination of the hard-
indentation does not represent an accurate average hardness.
ness of metallic materials used for electrical contacts. Rock-
Sintered contact materials usually contain segregates differing
well, Rockwell superficial, Brinell, and microhardness tests are
greatly in hardness from the matrix hardness and may destroy
included, along with information on the limitations and use of
the validity of microhardness readings.
these tests.
3.3 Other aspects of significance and use shall be as
1.2 The values stated in inch-pound units are to be regarded
described in the particular ASTM test method used, as listed in
as the standard. The SI units in parentheses are for information
Section 2.
only.
1.3 This standard does not purport to address all of the
4. Sampling
safety concerns, if any, associated with its use. It is the
4.1 Prepare test samples in accordance with the method
responsibility of the user of this standard to establish appro-
selected from those listed in Section 2 and, where applicable,
priate safety and health practices and determine the applica-
supplemented with the requirements in 5.3.
bility of regulatory limitations prior to use.
5. Procedure
2. Referenced Documents
5.1 Determine the hardness in accordance with one of the
2.1 ASTM Standards: following:
5.1.1 Test Methods E 18 subject to the additional require-
E 10 Test Method for Brinell Hardness of Metallic Materi-
2
als ments and precautions in 3.1, 5.2, and 5.3.
5.1.2 Test Method E 384 subject to the additional require-
E 18 Test Methods for Rockwell Hardness and Rockwell
2
Superficial Hardness of Metallic Materials ments and precautions in 3.2 and 5.4.
2
5.1.3 Test Method E 10.
E 384 Test Method for Microhardness of Materials
5.2 When employing the Rockwell superficial hardness test
3. Significance and Use
(Test Methods E 18) the specimen hardness shall be within the
range of the selected scale, as shown in Table 1.
3.1 The Rockwell hardness and Rockwell superficial tests
5.3 When using the Rockwell or Rockwell superficial hard-
are useful when the test specimens are sufficiently thick (in
ness tests on contacts which are in rivet form, the shanks of
relation to the indentor load) to ensure that the results are not
such rivets may have insufficient cross-sectional area to sup-
affected by the flow of metal on the surface of the anvil. On a
port the test pressure. In such cases the shank shall be removed
solid piece the flow of metal on the under surface may be
to form a flat surface for placement against the anvil. The
detected by a bulge or marking. On composite pieces where the
welding projection on contacts designed for assembly by
contact materials are attached to backings of a different
pro
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