1、Designation: B 277 95 (Reapproved 2006)Standard Test Method forHardness of Electrical Contact Materials1This standard is issued under the fixed designation B 277; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last rev
2、ision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the hard-ness of metallic materials used for electrical contacts. Rock-well, Roc
3、kwell superficial, Brinell, and microhardness tests areincluded, along with information on the limitations and use ofthese tests.1.2 The values stated in inch-pound units are to be regardedas the standard. The SI units in parentheses are for informationonly.1.3 This standard does not purport to addr
4、ess all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to become familiarwill all hazards including those identified in the appropriateMaterial Safety Data Sheet (MSDS) for this product/materialas provided by the manufacturer, to establis
5、h appropriatesafety and health practices, and determine the applicability ofregulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E10 Test Method for Brinell Hardness of Metallic Materi-alsE18 Test Methods for Rockwell Hardness and RockwellSuperficial Hardness of Metallic Ma
6、terialsE 384 Test Method for Microindentation Hardness of Ma-terials3. Significance and Use3.1 The Rockwell hardness and Rockwell superficial testsare useful when the test specimens are sufficiently thick (inrelation to the indentor load) to ensure that the results are notaffected by the flow of met
7、al on the surface of the anvil. On asolid piece the flow of metal on the under surface may bedetected by a bulge or marking. On composite pieces where thecontact materials are attached to backings of a differentmaterial, the thickness limitations imposed for a solid pieceshall apply to the contact m
8、aterial portion of such compositepieces.NOTE 1As a matter of information, it may be stated that tests on finesilver showed that on annealed samples having a Rockwell 15T hardnessof 27, the readings were not affected on thicknesses116 in. (1.6 mm) orover. On thicknesses of132 in. (0.8 mm) Rockwell 15
9、T scale readings of72 and higher were not affected.3.2 The microhardness test is of questionable significancewhen the metallic phases in a material are so large that theindentation does not represent an accurate average hardness.Sintered contact materials usually contain segregates differinggreatly
10、in hardness from the matrix hardness and may destroythe validity of microhardness readings.3.3 Other aspects of significance and use shall be asdescribed in the particular ASTM test method used, as listed inSection 2.4. Sampling4.1 Prepare test samples in accordance with the methodselected from thos
11、e listed in Section 2 and, where applicable,supplemented with the requirements in 5.3.5. Procedure5.1 Determine the hardness in accordance with one of thefollowing:5.1.1 Test Methods E18subject to the additional require-ments and precautions in 3.1, 5.2, and 5.3.5.1.2 Test Method E 384 subject to th
12、e additional require-ments and precautions in 3.2 and 5.4.5.1.3 Test Method E10.5.2 When employing the Rockwell superficial hardness test(Test Methods E18) the specimen hardness shall be within therange of the selected scale, as shown in Table 1.5.3 When using the Rockwell or Rockwell superficial ha
13、rd-ness tests on contacts which are in rivet form, the shanks ofsuch rivets may have insufficient cross-sectional area to sup-port the test pressure. In such cases the shank shall be removedto form a flat surface for placement against the anvil. Thewelding projection on contacts designed for assembl
14、y by1This test method is under the jurisdiction of ASTM Committee B02 onNonferrous Metals and Alloys and is the direct responsibility of SubcommitteeB02.05 on Precious Metals and Electrical Contact Materials.Current edition approved June 1, 2006. Published June 2006. Originallyapproved in 1952. Last
15、 previous edition approved in 2001 as B 277 95 (2001).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyri
16、ght ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.projection welding shall also be removed. Some rivet contactsare too small for the use of Rockwell superficial hardnesstesting, in which case the microhardness tests may be used.5.4 When emplo
17、ying the microhardness test (Test MethodE 384) the minimum indentor load shall be 100 gf, except forspecimens that have a thickness or diameter less than 0.005 in.(0.13 mm) in which case a 25 or 50 gf load shall be used.5.4.1 When microhardness tests (Test Method E 384) areemployed at 100 gf or less
18、 load, make a minimum of fiveindentations. Obtain the reported microhardness value byaveraging these indentations.6. Reports6.1 In addition to the requirements of the applicable hard-ness method used, the report shall include the following:6.1.1 When it is necessary to make measurements on thinsecti
19、ons of material where results will be affected, this factshall be stated in reporting the results, stating the thickness ofthe material tested.6.1.2 When tests are made on surfaces having a spherical orcylindrical curvature, the radius of curvature shall be given inthe report.7. Precision and BiasTh
20、e precision and bias of this test method are as stated in theparticular ASTM Test Method used (see 2.1 and Note 1).NOTE 2Interlaboratory Knoop hardness tests at 100 gf on noble alloysin the range of approximately 170 to 230 HK indicate that measureddiagonal lengths have a standard deviation of appro
21、ximately 1.4 m thatcorresponds to 5.3 to 7.5 Knoop numbers respectively.8. Keywords8.1 contacts; electrical contact materials; hardness;microhardnessASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users
22、 of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every f
23、ive years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical
24、 committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken,
25、PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).TABLE 1 Permissible Hardness RangesScale Permitted Range15T 209030T 209045T 109015N 7010030N 4010045N 20100B 277 95 (2006)2
