ASTM_C_748_-_98_2015.pdf

Designation:C74898(Reapproved 2015)An American National StandardStandard Test Method forRockwell Hardness of Graphite Materials1This standard is issued under the fixed designation C748;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers Rockwell L scale hardnesstesting of graphite materials with grain size less than 0.8 mmand a hardness range between 0 and 120.1.2 Test Methods E18 shall be followed except whereotherwise indicated.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2E18 Test Methods for Rockwell Hardness of Metallic Ma-terialsE171 Practice for Conditioning and Testing Flexible BarrierPackaging3.Summary of Test Method3.1 The specimen is held in position and the load is applied.Final position of the indicator on the scale is observed andrecorded as the hardness number.4.Significance and Use4.1 A Rockwell L scale hardness number is a numberderived from the net increase in depth of impression as the loadon a 6.3500 mm 6 0.0025 mm diameter steel-ball indenter isincreased from a fixed 10 kg minor load to a 60 kg major loadand then returned to the minor load.4.2 A Rockwell hardness number is directly related to theindentation hardness of a material;the higher the Rockwell Lscale reading,the harder the material.The test is useful in theevaluation and the manufacturing control of carbon and graph-ite materials.5.Apparatus5.1 Rockwell Hardness Tester,calibrated in accordance withthe requirements of Section 7.5.2 Rockwell Hardness Tester Anvil,appropriate for thematerial shall be used as the specimen base plate.6.Test Specimen6.1 The recommended test specimen shall be flat and have aminimum thickness of 6.35 mm.6.2 The test surface roughness shall not exceed 3175 nmarithmetical average.6.3 The test surface to opposite face parallelism for flatspecimens shall be within 1%.For all other specimen shapes,the test surface must be maintained normal to the direction ofload application.7.Verification of Calibration7.1 Level the Rockwell hardness tester in accordance withthe manufacturers instructions.7.2 The adjustment of speed-of-load application is of greatimportance.Adjust the dashpot on the Rockwell tester so thatthe operating handle completes its travel in 4 s to 7 s with nospecimen on the machine or no load applied by the indenter tothe anvil.The major load shall be 60 kg for this calibration.When so adjusted,the period taken for the mechanism to cometo a stop with the specimen in place will vary from 5 s to 15 s,depending upon the particular specimen,the indenter,and theload used.The operator should check the instrument manualfor this adjustment.7.3 Select a test block for Rockwell L scale ball-typeindenters and make five impressions on the test surface of theblock.Compare the average of these five tests against thehardness calibration of the block.If the error is more than 62hardness numbers,the machine or penetrator,or both,must bechecked to determine and correct the cause of error.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products,Liquid Fuels,and Lubricants and is the direct responsibility ofSubcommittee D02.F0 on Manufactured Carbon and Graphite Products.Current edition approved Oct.1,2015.Published December 2015.Originallyapproved in 1973.Last previous edition approved in 2010 as C748 98(2010)1.DOI:10.1520/C0748-98R15.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 8.Conditioning8.1 Allow the specimen(s)to reach equilibrium with room-temperature air,and test under the same conditions in accor-dance with Specification E171.8.2 Keep specimens free from contamination.9.Procedure9.1 Before using the Rockwell hardness tester,calibrate it asdescribed in Section 7.9.2 Select the proper anvil for the specimen used.9.3 Clean the shoulder of the screw and seat the anvilsecurely.9.4 Record the Rockwell L scale hardness values(theposition of the pointer of the red dial after the major load hasbeen removed and while the minor load is still applied).Estimate the readings to the nearest full-scale division within15 s after removi