1、Designation: C748 98 (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 rev
2、ision, 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
3、 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 t
4、hesafety 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 Rockw
5、ell 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
6、 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 num
7、ber 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 wi
8、ththe 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 nmarith
9、metical 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 wit
10、hthe 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 loa
11、d 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
12、.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 bec
13、hecked 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,
14、 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 vo
15、lume 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 States18. Conditioning8.1 Allow the specimen(s) to reach equilibrium with room-temperature air, and test under
16、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 an
17、vilsecurely.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 removing the major load.9.5 At least five
18、hardness tests shall be made on isotropicmaterial in accordance with 11.1.9.9.6 For anisotropic material, at least five hardness tests shallbe made on the surface perpendicular to the molding orextrusion direction unless otherwise specified and in accor-dance with 11.1.9.10. Report10.1 Report the fo
19、llowing information:10.1.1 Material identification;10.1.2 Total thickness of the specimen;10.1.3 Shape and surface condition; for example, flat orround, molded or machined;10.1.4 Orientation of test with respect to materialanisotropy, for example, parallel or perpendicular;10.1.5 Average hardness re
20、ading to the nearest full divisionand indicating the Rockwell scale use;10.1.6 The standard deviation when applicable; and10.1.7 The testing conditions including test date, test ma-chine serial number, operators name, and environmentalconditions.11. Precision and Bias311.1 The precision and bias in
21、11.2 and 11.3 are affected bythe following factors:11.1.1 If the table on which a Rockwell hardness tester ismounted is subject to vibration, such as is experienced in thevicinity of other machines, the tester should be effectivelyprotected. Mounting the hardness tester on a metal plate with25 mm th
22、ick sponge rubber pads is recommended.11.1.2 Indenters that show rust, nicks, burrs, or are out ofround will cause erroneous readings.11.1.3 The condition of the test equipment is an importantfactor in the accuracy of the tests. Dust, dirt, grease, or heavyoil act as a cushion to the load supporting
23、 members of the testequipment and cause erroneous readings. The shoulders of theinstrument housing, indenter chuck, ball seat in the instrumenthousing, capstan, capstan screw, and anvil shoulder seat shouldbe kept clean and true. Only the capstan screw should belightly oiled.11.1.4 Geometry of the s
24、pecimens may have a marked effecton the readings obtained in a test. Tubular or unsupportedcurved specimens are not recommended for hardness testing;such shapes have a tendency to deform with the load andinfluence the reading.11.1.5 Many graphites have anisotropic characteristicswhich may cause hard
25、ness to vary with the orientation of thespecimen.11.1.6 Rockwell hardness tests should be made on speci-mens of sufficient thickness so that the Rockwell reading is notaffected by the supporting anvil.11.1.7 Specimen surface finish and surface parallelism mayinfluence the readings.11.1.8 Contaminant
26、s like water, oil, and so forth, absorbedin the specimen pores may influence the readings.11.1.9 Do not make the tests near the edge of the specimenor too close together. In no case shall the clearance between theedge of the specimen and between individual indentations beless than 6.35 mm. Never tes
27、t on the opposite face of a singlespecimen; if a specimen is turned over and retested on theopposite face, the indentation ridges on the first face may affectthe reading on the opposite face.11.1.10 Rockwell L scale hardness readings over 120 shallnot be reported. Readings between 0 and 100 arerecom
28、mended, but readings up to 120 are permissible.11.2 Precision among eight laboratories is 62 hardnessnumbers.11.3 Bias of a properly calibrated instrument is 62 hardnessnumbers.12. Keywords12.1 carbon; graphite; hardness; indenter; Rockwell L3Supporting data have been filed at ASTM International Hea
29、dquarters and maybe obtained by requesting Research Report RR:C05-1007.C748 98 (2015)2ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of t
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32、s 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, PA 19428-2959,United States. Individual reprints (single or mul
33、tiple 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). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 98 (2015)3
