1、Designation: C 748 98 (Reapproved 2005)An American National StandardStandard Test Method forRockwell Hardness of Graphite Materials1This standard is issued under the fixed designation C 748; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re
2、vision, the year of last revision. 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 Rockwell L scale hardnesstesting of graphite materials with grain size le
3、ss than 0.8 m(0.032 in.) and 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 as thestandard. The values given in parentheses are provided forinformation purposes only.1.4 This standard does
4、 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 Stand
5、ards:2E18 Test Methods for Rockwell Hardness and RockwellSuperficial Hardness of Metallic MaterialsE 171 Specification for Standard Atmospheres for Condi-tioning and Testing Flexible Barrier Materials3. Summary of Test Method3.1 The specimen is held in position and the load is applied.Final position
6、 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- 6 0.0025-mm (0.2500- 6 0.0001-in.) diametersteel-ball indenter is increa
7、sed from a fixed 10-kg minor loadto a 60-kg major load and 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 manufac
8、turing 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 spec
9、imen shall be flat and have aminimum thickness of 6.35 mm (14 in.).6.2 The test surface roughness shall not exceed 3175-nm(125-in.) arithmetical 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 mai
10、ntained 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 operati
11、ng handle completes its travel in 4 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 to 15 s,depen
12、ding 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 aga
13、inst 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.8. Conditioning8.1 Allow the specimen(s) to reach equilibrium with room-temperature air, and test under the same con
14、ditions in accor-dance with Specification E 171.1This 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, 2005. Published Ma
15、y 2005. Originallyapproved in 1973. Last previous edition approved in 1998 as C 748 98.2For 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 Summar
16、y page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.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 prop
17、er 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 neare
18、st full-scale 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 unle
19、ss otherwise specified 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 mat
20、erial anisot-ropy, 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
21、, and environmentalconditions.11. Precision and Bias311.1 The precision and bias in 11.2and 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
22、be effectivelyprotected. Mounting the hardness tester on a metal plate with25-mm (1-in.) 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 acc
23、uracy of the tests. Dust, 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
24、kept clean and true. 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 andinflu
25、ence the reading.11.1.5 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 S
26、pecimen surface finish 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
27、 theedge of the specimen and between individual indentations beless than 6.35 mm (14 in.). Never test on the opposite face ofa single specimen; if a specimen is turned over and retested onthe opposite face, the indentation ridges on the first face mayaffect the reading on the opposite face.11.1.10 R
28、ockwell L scale hardness readings 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 points.11.3 Bias of a properly calibrated instrument is 62 points.12. Keywords12.1 carbon; graphite; hard
29、ness; indenter; Rockwell LASTM 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 the validity of any such patent rights, and the riskof infrin
30、gement 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 five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard
31、 or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views
32、 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 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).3Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: C05-1007.C 748 98 (2005)2
