ASTM B277-95(2001)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:B277–95(Reapproved 2001)
Standard Test Method for
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.
NOTE 1—As a matter of information, it may be stated that tests on fine
1. Scope
silver showed that on annealed samples having a Rockwell 15T hardness
1.1 This test method covers the determination of the hard-
of 27, the readings were not affected on thicknesses ⁄16 in. (1.6 mm) or
ness of metallic materials used for electrical contacts. Rock-
over. On thicknesses of ⁄32 in. (0.8 mm) Rockwell 15T scale readings of
well, Rockwell superficial, Brinell, and microhardness tests are
72 and higher were not affected.
included, along with information on the limitations and use of
3.2 The microhardness test is of questionable significance
these tests.
when the metallic phases in a material are so large that the
1.2 The values stated in inch-pound units are to be regarded
indentation does not represent an accurate average hardness.
as the standard. The SI units in parentheses are for information
Sintered contact materials usually contain segregates differing
only.
greatly in hardness from the matrix hardness and may destroy
1.3 This standard does not purport to address all of the
the validity of microhardness readings.
safety concerns, if any, associated with its use. It is the
3.3 Other aspects of significance and use shall be as
responsibility of the user of this standard to establish appro-
described in the particularASTM test method used, as listed in
priate safety and health practices and determine the applica-
Section 2.
bility of regulatory limitations prior to use.
4. Sampling
2. Referenced Documents
4.1 Prepare test samples in accordance with the method
2.1 ASTM Standards:
selected from those listed in Section 2 and, where applicable,
E 10 Test Method for Brinell Hardness of Metallic Materi-
supplemented with the requirements in 5.3.
als
E 18 Test Methods for Rockwell Hardness and Rockwell
5. Procedure
Superficial Hardness of Metallic Materials
5.1 Determine the hardness in accordance with one of the
E 384 Test Method for Microhardness of Materials
following:
5.1.1 Test Methods E 18 subject to the additional require-
3. Significance and Use
ments and precautions in 3.1, 5.2, and 5.3.
3.1 The Rockwell hardness and Rockwell superficial tests
5.1.2 Test Method E 384 subject to the additional require-
are useful when the test specimens are sufficiently thick (in
ments and precautions in 3.2 and 5.4.
relation to the indentor load) to ensure that the results are not
5.1.3 Test Method E 10.
affected by the flow of metal on the surface of the anvil. On a
5.2 When employing the Rockwell superficial hardness test
solid piece the flow of metal on the under surface may be
(Test Methods E 18) the specimen hardness shall be within the
detectedbyabulgeormarking.Oncompositepieceswherethe
range of the selected scale, as shown in Table 1.
contact materials are attached to backings of a different
5.3 When using the Rockwell or Rockwell superficial hard-
material, the thickness limitations imposed for a solid piece
ness tests on contacts which are in rivet form, the shanks of
shall apply to the contact material portion of such composite
such rivets may have insufficient cross-sectional area to sup-
pieces
...