1、Designation: C748 98 (Reapproved 2010)1An 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.1NOTEUpdated units of measurement throughout editorially in May 2010.1. Scope1.1 This test method covers Rockwe
3、ll 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 i
4、n 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.
5、2. Referenced Documents2.1 ASTM Standards:2E18 Test Methods for Rockwell Hardness of Metallic Ma-terialsE171 Specification for Atmospheres for Conditioning andTesting Flexible Barrier Materials3. Summary of Test Method3.1 The specimen is held in position and the load is applied.Final position of the
6、 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 6 0.0025-mm diameter steel-ball indenter isincreased from a fixed 10-kg minor lo
7、ad 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 gr
8、aph-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 ami
9、nimum 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
10、.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 to 7 s with no
11、specimen 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 to 15 s,depending upon the particular specimen, the indenter, a
12、nd 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
13、error is more than 621This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.F0 on Manufactured Carbon and Graphite Products.Current edition approved May 1, 2010. Published November 2010. Originallyappr
14、oved in 1973. Last previous edition approved in 2005 as C74898(2005). DOI:10.1520/C0748-98R10E01.2For 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 Docum
15、ent Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.hardness numbers, the machine or penetrator, or both, must bechecked to determine and correct the cause of error.8. Conditioning8.1 Allow the specime
16、n(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 t
17、he 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
18、division within15 s after removing the major load.9.5 At least five 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 s
19、pecified and in accor-dance with 11.1.9.10. Report10.1 Report the following 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 material anisot-r
20、opy, for example, parallel or perpendicular;10.1.5 Average hardness reading 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 environm
21、entalconditions.11. Precision and Bias311.1 The precision and bias in 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 effectivel
22、yprotected. Mounting the hardness tester on a metal plate with25-mm thick 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. D
23、ust, dirt, grease, or heavyoil act as a cushion to the load supporting 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.
24、Only the capstan screw should belightly oiled.11.1.4 Geometry of the specimens 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
25、.5 Many graphites have anisotropic characteristicswhich may cause hardness 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 finis
26、h and surface parallelism mayinfluence the readings.11.1.8 Contaminants 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 speci
27、men and between individual indentations beless than 6.35 mm. Never test 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 readi
28、ngs over 120 shallnot be reported. Readings between 0 and 100 are recom-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; indent
29、er; Rockwell L3Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:C05-1007.C748 98 (2010)12ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this stand
30、ard. Users 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 review
31、ed every five 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
32、 technical 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 Cons
33、hohocken, 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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).C748 98 (2010)13
