ASTM B277-95(2012)
(Test Method)Standard Test Method for Hardness of Electrical Contact Materials
Standard Test Method for Hardness of Electrical Contact Materials
SIGNIFICANCE AND USE
The Rockwell hardness and Rockwell superficial tests are useful when the test specimens are sufficiently thick (in relation to the indentor load) to ensure that the results are not affected by the flow of metal on the surface of the anvil. On a solid piece the flow of metal on the under surface may be detected by a bulge or marking. On composite pieces where the contact materials are attached to backings of a different material, the thickness limitations imposed for a solid piece shall apply to the contact material portion of such composite pieces.
Note 1—As a matter of information, it may be stated that tests on fine silver showed that on annealed samples having a Rockwell 15T hardness of 27, the readings were not affected on thicknesses 1/16 in. (1.6 mm) or over. On thicknesses of 1/32 in. (0.8 mm) Rockwell 15T scale readings of 72 and higher were not affected.
The microhardness test is of questionable significance when the metallic phases in a material are so large that the indentation does not represent an accurate average hardness. Sintered contact materials usually contain segregates differing greatly in hardness from the matrix hardness and may destroy the validity of microhardness readings.
Other aspects of significance and use shall be as described in the particular ASTM test method used, as listed in Section 2.
SCOPE
1.1 This test method covers the determination of the hardness of metallic materials used for electrical contacts. Rockwell, Rockwell superficial, Brinell, and microhardness tests are included, along with information on the limitations and use of these tests.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to become familiar will all hazards including those identified in the appropriate Material Safety Data Sheet (MSDS) for this product/material as provided by the manufacturer, to establish appropriate safety and health practices, and determine the applicability of regulatory limitations prior to use.
General Information
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Standards Content (Sample)
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Designation: B277 − 95 (Reapproved 2012)
Standard Test Method for
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Hardness of Electrical Contact Materials
This standard is issued under the fixed designation B277; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope detectedbyabulgeormarking.Oncompositepieceswherethe
contact materials are attached to backings of a different
1.1 This test method covers the determination of the hard-
material, the thickness limitations imposed for a solid piece
ness of metallic materials used for electrical contacts.
shall apply to the contact material portion of such composite
Rockwell, Rockwell superficial, Brinell, and microhardness
pieces.
tests are included, along with information on the limitations
and use of these tests.
NOTE 1—As a matter of information, it may be stated that tests on fine
silver showed that on annealed samples having a Rockwell 15T hardness
1.2 The values stated in inch-pound units are to be regarded
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of 27, the readings were not affected on thicknesses ⁄16 in. (1.6 mm) or
as standard. The values given in parentheses are mathematical
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over. On thicknesses of ⁄32 in. (0.8 mm) Rockwell 15T scale readings of
conversions to SI units that are provided for information only 72 and higher were not affected.
and are not considered standard.
3.2 The microhardness test is of questionable significance
1.3 This standard does not purport to address all of the when the metallic phases in a material are so large that the
safety concerns, if any, associated with its use. It is the
indentation does not represent an accurate average hardness.
responsibility of the user of this standard to become familiar Sintered contact materials usually contain segregates differing
will all hazards including those identified in the appropriate
greatly in hardness from the matrix hardness and may destroy
Material Safety Data Sheet (MSDS) for this product/material the validity of microhardness readings.
as provided by the manufacturer, to establish appropriate
3.3 Other aspects of significance and use shall be as
safety and health practices, and determine the applicability of
described in the particularASTM test method used, as listed in
regulatory limitations prior to use.
Section 2.
2. Referenced Documents
4. Sampling
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2.1 ASTM Standards:
4.1 Prepare test samples in accordance with the method
E10 Test Method for Brinell Hardness of Metallic Materials
selected from those listed in Section 2 and, where applicable,
E18 Test Methods for Rockwell Hardness of Metallic Ma-
supplemented with the requirements in 5.3.
terials
E384 Test Method for Knoop and Vickers Hardness of
5. Procedure
Materials
5.1 Determine the hardness in accordance with one of the
following:
3. Significance and Use
5.1.1 Test Methods E18 subject to the additional require-
3.1 The Rockwell hardness and Rockwell superficial tests
ments and precautions in 3.1, 5.2, and 5.3.
are useful when the test specimens are sufficiently thick (in
5.1.2 Test Method E384 subject to the additional require-
relation to the indentor load) to ensure that the results are not
ments and precautions in 3.2 and 5.4.
affected by the flow of metal on the surface of the anvil. On a
5.1.3 Test Method E10.
solid piece the flow of metal on the under surface may be
5.2 When employing the Rockwell superficial hardness test
(Test Methods E18) the specimen hardness shall be within the
range of the selected scale, as shown in Table 1.
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This test method is under the jurisdiction of ASTM Committee B02 on
Nonferrous Metals and Alloys and is the direct responsibility of Subcommittee
5.3 When using the Rockwell or Rockwell superficial hard-
B02.11 on Electrical Contact Test Methods.
ness tests on contacts which are in rivet form, the shanks of
Current edition approved May 1, 2012. Published May 2012. Originally
such rivets may have insufficient cross-sectional area to sup-
approved in 1952. Last previous edition approved in 2006 as B277 – 95 (2006).
DOI: 10.1520/B0277-95R12.
port the test pressure. In such cases the shank shall be removed
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
to form a flat surface for placement against the anvil. The
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
welding projection on contacts designed for assembly by
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. projection welding shall also be removed. Some rivet contacts
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