1、Designation: B 294 92 (Reapproved 2006)1Standard Test Method forHardness Testing of Cemented Carbides1This standard is issued under the fixed designation B 294; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis
2、ion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEAdded research report footnote to Section 8 editorially in June 2009.1. Scope1.1 This test method covers the hardness testing of ce-men
3、ted carbides by use of the Rockwell hardness tester withthe Rockwell A scale (diamond indenter and 588.4 N (60 kgf)load) in the range of Rockwell A80 and above. Also coveredare the procedures for the testing and selection of diamondindenters, the management and traceability of the four levels ofstan
4、dard test blocks, the acquisition of secondary standard testblocks, and the making and calibration of working standard testblocks.1.2 The Rockwell hardness tester is a convenient andreliable means of measuring the hardness of cemented car-bides. A hardness value is obtained easily, but it is subject
5、 toconsiderable error unless certain precautions are observed.1.3 Test Methods E18 shall be followed except whereotherwise indicated in this test method.1.4 The values stated in SI units are to be regarded asstandard. The values given in parentheses are for informationonly.1.5 This standard does not
6、 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
7、:2E18 Test Methods for Rockwell Hardness of MetallicMaterialsE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with Specifications2.2 ISO Standard:3ISO 3738-2 HardmetalsRockwell hardness test (ScaleA)Part 2, Preparation and calibration of standard testblocks3. Significan
8、ce and Use3.1 Rockwell hardness is one of the more important prop-erties used to evaluate cemented carbides. For compositionalgroups of cemented carbides, hardness is an indication of wearresistance and toughness. Lower hardness grades usuallyindicate less wear resistance but greater toughness. For
9、aspecific grade of cemented carbide, hardness is an indication ofthe metallurgical quality of the material. In no case is hardnessthe only property to be considered in evaluating cementedcarbides.4. Apparatus4.1 ScaleAll hardness tests shall be made on the regular(as opposed to superficial) Rockwell
10、 tester, using a 588.4 N (60kgf) load (Rockwell A scale).4.2 Effect of VibrationThe Rockwell hardness testershould be located in a vibration-free area in order to avoiderroneous results. If this is not possible, the tester shall bemounted so as to minimize vibrations, since vibrations tend tocause e
11、rratic readings.4.3 IndenterThe standard indenter shall be selected, inaccordance with the Annex to this test method, from diamondcone indenters specified for Rockwell A scale use and inconformance with Test Methods E18.4.3.1 The indenter, and an indentation made with it, inhardened steel or cemente
12、d carbide should be examinedoptically at approximately 50-diameter magnification for de-fects, conformance to shape, and mounting of the diamond.Examination should be made when selecting an indenter,occasionally during use, and whenever some event may besuspected of having damaged the diamond or its
13、 mounting.4.4 AnvilsSelect an anvil suitable for the specimen to betested. The shoulder of the screw and the mating surface of theanvil should be clean. Seat the anvil securely. For the bestaccuracy, flat test pieces should be tested on a flat anvil ofapproximately 6-mm (14-in.) diameter. The bearin
14、g surface ofthis anvil, with a Rockwell C hardness of at least 60, shall bepolished smooth and be free of pits and heavy scratches. The1This test method is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcom-mittee B09.06
15、on Cemented Carbides.Current edition approved April 1, 2006. Published April 2006. Originallyapproved in 1954. Last previous edition approved in 2001 as B 294 92 (2001).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annua
16、l Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken,
17、 PA 19428-2959, United States.test piece should be supported suitably, with the test surfaceperpendicular to the line of travel of the indenter. Dust, dirt,grease, or scale should not be allowed to accumulate on anypart of the apparatus, as this will affect the results.4.5 Test BlocksSecondary stand
18、ard test blocks or workingstandard test blocks that have been prepared and calibrated inaccordance with the Annex to this test method shall be used.5. Test Specimens5.1 Size of SpecimensA minimum thickness of 1.6 mm(116 in.) is recommended. With thinner specimens, breakagemay occur, resulting in dam
19、age to the anvil, the indenter, orboth. Specimens that have enough overhang to cause imbal-ance shall be supported properly. The 6-mm (14-in.) anvil willsupport flat test specimens up to approximately 113 g (14 lb)and will also support the standard test blocks recommendedpreviously.5.2 Preparation o
20、f Test SpecimensThe finish of the testsurface is of major importance. The surface to be tested shouldbe prepared to obtain a roughness of Ra #0.2 m (8 in.) Acoarser finish will provide a wider range of readings. Prepara-tion shall be conducted in such a way that alteration of thesurface due to heat
21、or cold-working is minimized. A 220-gritmedium hardness resinoid bond diamond wheel, downfed 0.01mm (0.0005 in.) per pass with abundant flow of coolant, shouldprovide the desired surface. The thickness of the layer removedfrom an as-sintered surface to be tested shall be not less than0.2 mm (0.008 i
22、n.).5.3 The surfaces of the test specimen shall be flat andparallel within one part per hundred parts in general practice,but within one part per thousand parts when critical compari-sons are being made. The surface in contact with the anvil shallbe free of any irregularity (for example, a previous
23、hardnessindentation). Taper that results in the test surface not beingnormal to the axis of the indenter, or irregularity that causesinstability during the test, will result in error.5.4 When determining the hardness of a test specimen witha curved surface, the radius of curvature shall not be less
24、than15 mm (916 in.). If less, then a flat surface at least 3-mm (18-in.)wide shall be prepared on which to conduct the test, and thereshall be an opposite flat surface such that the specimenconforms to the requirements of 5.2 and 5.3. If the test surfaceis curved or the opposite surface must be supp
25、orted in aV-anvil, the repeatability and reproducibility limits of 8.2 and8.3 may not apply.5.5 Preparation of Mounted CarbidesRemove mountedcarbides from the steel body by heating or some otherconvenient method. All braze metal or other bond materialshall be removed from both the test surface and t
26、he oppositeface. The specimen should then be prepared as described in 5.1through 5.4.6. Procedure6.1 Procedures that are not described in this test methodshall conform to those of Test Methods E18.6.2 Disregard the first two readings after an indenter hasbeen newly mounted.6.3 Limit the speed of app
27、lying the major load so that themovement of the weights is completed in 4 to 6 s, with no testpiece on the testing equipment and with the machine set toapply a major load of 60 Kg. Verification should be by directobservation of the weight motion, if visible.6.4 Do not permit the time of maintaining
28、the major loadafter the motion of the needle or the changing of the digitalreadout has ceased to exceed 2 s. Removal of the major loadshould be gradual by operating lever in manual machines or bymotor in automatic machines, and should not exceed twoadditional seconds. On manual machines, abrupt actu
29、ation ofthe major load trip lever may affect the hardness valueobtained.Abrupt actuation of the major load removal lever willsignificantly affect the hardness value obtained.6.5 The Rockwell A hardness value is read after the majorload has been removed and while the minor load is stillapplied.6.6 Th
30、e distance between the centers of any two adjacentindentations, and the distance between the center of anyindentation and the edge of a test specimen, shall be at least 1.5mm (0.06 in.).6.7 Hardness should be read or estimated to the nearest 0.1HRA. Calculations should be carried to two decimal plac
31、es.6.8 Make two trial determinations of the hardness of the testspecimen. This action also reassures that the indenter is seatedproperly.6.8.1 Select the standard test block having a value closest tothe trial hardness of the test specimen. Determine the RockwellA hardness at three points on the bloc
32、k.6.8.2 If the arithmetic mean of the three determinationsdiffers from the certified hardness value of the standard testblock by more than 60.5 HRA, check the diamond indenterand the testing equipment, and eliminate the cause of the error.Repeat the determinations.6.8.3 If the arithmetic mean of the
33、 three determinationsdiffers from the certified hardness value of the standard testblock by 60.5 HRA or less, record the difference, giving dueregard to the algebraic sign. This difference will be used tocorrect the arithmetic mean of the hardness of the testspecimens.6.8.4 Determine the Rockwell A
34、hardness of the test speci-men, with determinations at three or more locations chosen atrandom, or as dictated by the purpose of the test.6.8.5 Calculate the arithmetic mean of the hardness deter-minations. Apply the correction determined as in 6.8.3, givingdue regard to the algebraic sign.6.8.6 Rep
35、ort the corrected arithmetic mean of the hardnessdeterminations, rounded in accordance with Practice E294tothe nearest 0.1 HRA.7. Report7.1 Report the following information:7.1.1 All details necessary for identification of the testspecimen,7.1.2 The corrected mean hardness,4When the second decimal p
36、lace is less than 0.05, leave the first decimal placeunchanged. When the second decimal place is more than 0.05, increase the firstdecimal place by 0.1. When the second decimal place is exactly 5 and the firstdecimal place is odd, increase the first decimal by 0.1. If the first decimal place iseven,
37、 leave it unchanged.B 294 92 (2006)127.1.3 The range of hardness determinations,7.1.4 The number of hardness determinations,7.1.5 The smallest division of readout or graduation of thehardness test machine and whether it is digital or analog,7.1.6 The identification and original source of calibration
38、for the standard test blocks used,7.1.7 A reference to this test method, and7.1.8 Details of any deviations from this test method, ofoptional procedures used, and of any conditions and occur-rences that may have affected the results.8. Precision and Bias58.1 The following statements regarding the re
39、peatability andreproducibility of hardness (HRA) measurements of cementedcarbide test specimens shall apply only within the hardnessrange established for the indenter in accordance with A1.8.2 orA1.8.3. See Table A1.1.68.2 The repeatability limit (r) is 0.3 HRA. On the basis oftest error alone, the
40、difference in absolute value of two testresults obtained in the same laboratory on the same testspecimen will be expected to exceed 0.3 HRA only approxi-mately 5 % of the time. The repeatability standard deviation(Sr) is 0.1 HRA.8.3 The reproducibility limit (R) between or among labora-tories is 0.4
41、 HRA when each has calibrated its machine,indenter, and operator system with a standard test block thathas itself been calibrated to the same superior test block usedto calibrate the test blocks of the other laboratories. On thebasis of test error alone, the difference in absolute value of thetest r
42、esults obtained in different laboratories on the same testspecimen will be expected to exceed 0.4 HRA only approxi-mately 5 % of the time. The reproducibility standard deviation(SR) is 0.14 HRA.8.4 Neither the data of the interlaboratory study nor theo-retical considerations suggest a bias in this t
43、est procedure.8.5 If the test specimens are of a hardness substantiallyoutside the hardness ranges of the standard test blocks onwhich the indenter has been performance tested, and if inter-laboratory reproducibility is critical, the same indenter andstandard test blocks should be used by each labor
44、atory.9. Keywords9.1 cemented carbides; hardness; indenters; Rockwell hard-ness test; Scale A; test blocksANNEX(Mandatory Information)A1. PREPARATION, CALIBRATION, AND CONTROL OF STANDARD TEST BLOCKS AND SELECTION OF SCALE AINDENTERS USED IN THE PERFORMANCE OF THE PROCEDURES OF THIS TEST METHODA1.1
45、Scope and Field of ApplicationThis Annex speci-fies the control of master, primary, secondary, and workingstandard test blocks. It specifies the preparation and calibrationof primary, secondary, and working standard test blocks. It alsospecifies the procedure for selecting indenters having therequir
46、ed precision from standard Scale A indenters. Both testblocks and indenters complying with this Annex are requiredfor Rockwell hardness testing of cemented carbides by theprocedures of this test method.A1.2 Hierarchy and Availability of Standard Test Blocks:A1.2.1 Secondary standard test blocks, and
47、 the calibrationor recalibration services for secondary standard test blocks, areavailable from the authorized calibrating agency. To providetraceability to the master standard test blocks, the CementedCarbide Producers Association (CCPA) has released Set 2,master standard test blocks, to the author
48、ized calibratingagency.7A1.3 Master Standard Test Blocks:A1.3.1 Of three sets of five master standard test blocks, Set1 is retained by the CCPA. Set 2 has been released by theCCPA to Wilson Instruments, so that Wilson Instruments mayserve as the calibrating agency for secondary standard testblocks t
49、raceable through primary standard test blocks to the setof master standard test blocks. Set 3 is retained by theSecretariat of ISO/TC 119.A1.3.2 The sets of master standard test blocks retained bythe CCPA and ISO/TC 119 shall be kept as permanentstandards and shall be used only when calibration of a newmaster standard is required.A1.3.3 Blocks retained by ISO/TC 119 shall be retained asunused international standards. Only in the event of destruction5The statements of repeatability and reproducibility in this section are based onan interlaboratory study conduct
