1、Designation: B294 10B294 17Standard Test Method forHardness Testing of Cemented Carbides1This standard is issued under the fixed designation B294; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number
2、in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 This test method covers the hardness testing of cemented carbides by use of a Rockwell hardness tester performing testsin the Rockwell
3、HRA scale (regular scale, diamond indenter, 10 kgf (98.07 N) preliminary test force, and 60 kgf (588.4 N) load)total test force in the range of Rockwell 80 HRA and above. Also covered are the procedures for the testing and selection ofdiamond indenters, the management and traceability of the four le
4、vels of standardized test blocks, and the making and calibrationof Primary, Secondary, and Working standardized test blocks.1.2 The Rockwell hardness tester is a convenient and reliable means of measuring the hardness of cemented carbides. Ahardness value is obtained easily, but it is subject to con
5、siderable error unless certain precautions are observed.1.3 The latest version of Test Methods E18 shall be followed except where otherwise indicated in this test method.1.4 The values stated in SI units are to be regarded as standard except that force and length values associated with the Rockwellh
6、ardness testers will comply with E18 with force values specified as N (kgf) and indenter length values specified as mm.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropri
7、ate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.6 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for th
8、e Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E18 Test Methods for Rockwell Hardness of Metallic MaterialsE29 Practice for Using Significant Digits in T
9、est Data to Determine Conformance with Specifications2.2 ISO Standards:3ISO/IEC 17011 Conformity AssessmentGeneral Requirements for Accreditation Bodies Accrediting Conformity AssessmentBodiesISO/IEC 17025 General Requirements for the Competence of Testing and Calibration Laboratories3. Significance
10、 and Use3.1 Rockwell hardness testing is one of the more important methods used to evaluate cemented carbides. For compositionalgroups of cemented carbides, hardness is an indication of wear resistance and toughness. Lower hardness grades usually indicateless wear resistance but greater toughness. F
11、or a specific grade of cemented carbide, hardness is an indication of the metallurgicalquality of the material. In no case is Rockwell hardness testing the only test method to be considered in evaluating cementedcarbides.1 This test method is under the jurisdiction ofASTM Committee B09 on Metal Powd
12、ers and Metal Powder Products and is the direct responsibility of Subcommittee B09.06on Cemented Carbides.Current edition approved May 1, 2010Nov. 1, 2017. Published June 2010February 2018. Originally approved in 1954. Last previous edition approved in 20092010 asB294 09B294 10. (2009). DOI: 10.1520
13、/B0294-10.10.1520/B0294-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American National
14、 Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically pos
15、sible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCo
16、pyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Principles of Test Apparatus4.1 TesterAll hardness tests shall be performed using a Rockwell hardness tester that meets the requirements defined in thelatest version of Test Method E18
17、except where otherwise indicated in this test method. Testers shall comply with the requirementsof Annex A3 of this test method.4.2 ScaleAll tests shall be performed using the carbide Rockwell HRA scale (a carbide diamond indenter, 10 kgf (98.07 N)preliminary force, and 60 kgf (588.4 N) total test f
18、orce.4.3 Effect of VibrationThe Rockwell hardness tester should be located in a vibration-free area in order to avoid erroneousresults. If this is not possible, the tester shall be mounted so as to minimize vibrations, since vibrations tend to cause erraticreadings.4.4 IndenterThe indenters used sha
19、ll conform to the requirements defined in Annex A2 of this test method.4.5 AnvilsSelect an anvil suitable for the specimen to be tested.The test piece should be supported rigidly, with the test surfaceperpendicular to the line of travel of the indenter. For the best accuracy, flat test pieces should
20、 be tested on a flat spot anvil ofapproximately 6-mm diameter. The surface of the anvil that contacts the sample should have a Rockwell hardness of at least 58HRC, and shall be polished smooth and be free of pits and heavy scratches that could affect the test results. The mounting surfaceof the anvi
21、l support and the mating surface of the anvil should be clean. Dust, dirt, grease, or scale should not be allowed toaccumulate on any part of the apparatus, as this will affect the results. Seat the anvil securely.4.6 Test BlocksStandardized test blocks used to verify the performance of the tester s
22、hall comply with the requirements inAnnex A1 of this test method.5. Test Specimens5.1 Size of SpecimensA minimum thickness of 1.6 mm is recommended. With thinner specimens, breakage may occur,resulting in damage to the anvil, the indenter, or both. Specimens that have enough overhang to cause imbala
23、nce shall be supportedproperly. The 6-mm anvil will support flat test specimens up to approximately 113 g and will also support the standard test blocksrecommended previously.5.2 Preparation of Test Specimens:5.2.1 The finish of the test surface is of major importance. The surface to be tested shoul
24、d be prepared to obtain a roughnessof Ra 0.2 m.Acoarser finish will provide a wider range of readings. Preparation shall be conducted in such a way that alterationof the surface due to heat or cold-working is minimized.A220-grit medium hardness resinoid bond diamond wheel, downfed 0.01mm per pass wi
25、th abundant flow of coolant, should provide the desired surface. The thickness of the layer removed from anas-sintered surface to be tested shall be not less than 0.2 mm.5.2.2 The test and anvil surfaces of the test specimen shall be parallel within 0.01 mm/mm in general practice, but within 0.001mm
26、/mm when critical comparisons are being made. The surface in contact with the anvil shall be free of any irregularity (forexample, a previous hardness indentation). Taper that results in the test surface not being normal to the axis of the indenter, orirregularity that causes instability during the
27、test, will result in error.5.2.3 When determining the hardness of a test specimen with a curved surface, the radius of curvature shall not be less than 15mm. If less, then a flat surface at least 3 mm wide shall be prepared on which to conduct the test, and there shall be an oppositeflat surface suc
28、h that the specimen conforms to the requirements of 5.2 and 5.3. If the test surface is curved or the opposite surfacemust be supported in a V-anvil, the repeatability and reproducibility limits of 8.2 and 8.3 may not apply.5.3 Preparation of Mounted CarbidesRemove mounted carbides from the steel bo
29、dy by heating or some other convenientmethod. All braze metal or other bond material shall be removed from both the test surface and the opposite face. The specimenshould then be prepared as described in 5.1 and 5.2.6. Procedure6.1 Rockwell hardness tests should be carried out at an ambient temperat
30、ure within the limits of 10 to 35C. Users of theRockwell hardness test are cautioned that the temperature of the test material and the temperature of the hardness tester may affecttest results. Consequently, users should ensure that the test temperature does not adversely affect the hardness measure
31、ment.6.2 Procedures that are not described in this test method shall conform to those of Test Method E18.6.3 Disregard the first two readings after an indenter or anvil has been newly mounted.6.4 Test Cycle Time6.4.1 The application time for the additional test force (major load) shall be 2 to 6 s.6
32、.4.2 The total test force (major load) shall be maintained for 2 to 4 s.NOTE 1On manual machines, the abrupt actuation of the total test force (major load) application trip lever may affect the hardness value obtained.In addition the abrupt actuation of the total test force (major load) removal leve
33、r may significantly affect the hardness value obtained.B294 1726.5 The Rockwell HRAhardness value is read after the total test force (major load) has been removed and while the preliminarytest force (minor load) is still applied.6.6 Hardness should be read or estimated to at least the nearest 0.1 HR
34、A. Calculations should be carried to two decimal places.6.7 The distance between the centers of any two adjacent indentations, and the distance between the center of any indentationand the edge of a test specimen, shall be at least 1.5 mm.6.8 Make two trial determinations of the hardness of the test
35、 specimen. This action also reassures that the indenter is seatedproperly. Disregard the results and perform the following steps.6.8.1 Select a standardized test block that complies with Annex A1 having a value closest to the trial hardness of the testspecimen. Determine the Rockwell HRA hardness at
36、 three points on the block.6.8.2 If the arithmetic mean of the three determinations differs from the certified hardness value of the standardized test blockby more than 60.5 HRA, check the diamond indenter and the testing equipment, and eliminate the cause of the error. Repeat thedeterminations.6.8.
37、3 If the arithmetic mean of the three determinations differs from the certified hardness value of the standardized test blockby 60.5 HRA or less, record the difference, giving due regard to the algebraic sign. This difference will be used to correct thearithmetic mean of the hardness of the test spe
38、cimens.6.8.4 Determine the Rockwell HRA hardness of the test specimen, 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 determinations. Apply the correction determined as in 6.8.3, giving due
39、regard to the algebraic sign.6.8.6 Report the corrected arithmetic mean of the hardness determinations, rounded in accordance with Practice E294 to thenearest 0.1 HRA.7. Report7.1 Report the following information:7.1.1 All details necessary for identification of the test specimen,7.1.2 The corrected
40、 mean hardness and the amount of correction including the algebraic sign,7.1.3 The range of hardness determinations,7.1.4 The number of hardness determinations,7.1.5 The smallest division of readout or graduation of the hardness test machine and whether it is digital or analog,7.1.6 The identificati
41、on and original source of calibration for the standardized test blocks used,7.1.7 A reference to this test method, and7.1.8 Details of any deviations from this test method, of optional procedures used, and of any conditions and occurrences thatmay have affected the results.8. Precision and Bias58.1
42、The following statements regarding the repeatability and reproducibility of hardness (HRA) measurements of cementedcarbide test specimens shall apply only within the hardness range established for the indenter in accordance withA2.3.4.5A2.4.2.4 (5) or A2.3.4.6A2.4.2.4. (6).8.2 The repeatability limi
43、t (r) is 0.3 HRA. On the basis of test error alone, the difference in absolute value of two test resultsobtained in the same laboratory on the same test specimen will be expected to exceed 0.3 HRAonly approximately 5 % of the time.The repeatability standard deviation (Sr) is 0.1 HRA.8.3 The reproduc
44、ibility limit (R) between or among laboratories is 0.4 HRAwhen each has calibrated its machine, indenter, andoperator system with a standard test block that has itself been calibrated to the same superior test block used to calibrate the testblocks of the other laboratories. On the basis of test err
45、or alone, the difference in absolute value of the test results obtained indifferent laboratories on the same test specimen will be expected to exceed 0.4 HRA only approximately 5 % of the time. Thereproducibility standard deviation (SR) is 0.14 HRA.8.4 Neither the data of the interlaboratory study n
46、or theoretical considerations suggest a bias in this test procedure.8.5 If the test specimens are of a hardness substantially outside the hardness ranges of the standard test blocks on which theindenter has been performance tested, and if interlaboratory reproducibility is critical, the same indente
47、r and standard test blocksshould be used by each laboratory.4 When the second decimal place is less than 0.05, leave the first decimal place unchanged. When the second decimal place is more than 0.05, increase the first decimalplace by 0.1. When the second decimal place is exactly 5 and the first de
48、cimal place is odd, increase the first decimal by 0.1. If the first decimal place is even, leave itunchanged.5 The statements of repeatability and reproducibility in this section are based on an interlaboratory study conducted by the Cemented Carbide Producers Association.Supporting data have been f
49、iled at ASTM International Headquarters and may be obtained by requesting Research Report RR:B09-1016.B294 1739. Keywords9.1 cemented carbides; hardness; indenters; Rockwell hardness test; Scale HRA; test blocksANNEXES(Mandatory Information)A1. PREPARATION, CALIBRATION, AND CONTROL OF STANDARDIZED TEST BLOCKS USED IN THE PERFORMANCEOF THE PROCEDURES OF THIS TEST METHODA1.1 Scope and Field of ApplicationA1.1.1 The Rockwell hardness levels of cemented carbides are established by sets of Master test blocks that were developed bythe Cemented Carbide ProducersAssociat
