ASTM_A_956_-_12.pdf

Designation:A95612Standard Test Method forLeeb Hardness Testing of Steel Products1This standard is issued under the fixed designation A956;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,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 the determination of the Leebhardness of steel,cast steel,and cast iron(Part A),includingthe methods for the verification of Leeb hardness testinginstruments(Part B),and the calibration of standardized testblocks(Part C).NOTE1The original title of this standard was“Standard Test Methodfor Equotip Hardness Testing of Steel Products.”11.2 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 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.2.Referenced Documents2.1 ASTM Standards:2E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 Definitions:3.1.1 calibrationdetermination of the values of the sig-nificant operating parameters of the instrument by comparisonwith values indicated by a reference instrument or by a set ofreference standards.3.1.2 Leeb hardness numbera number equal to the ratio ofthe rebound velocity to the impact velocity of a 3-mm or 5-mm(based on the type of impact device)diameter sphericallyshaped tungsten carbide,silicon nitride,or diamond tippedimpact body,multiplied by 1000.L 5Rebound VelocityImpact Velocity31000The Leeb hardness number is followed by the symbol HLwith one or more suffix characters representing the type ofimpact device.3.1.3 Leeb hardness testa dynamic hardness test methodusing a calibrated instrument that impacts a spherically shapedtungsten carbide,silicon nitride,or diamond tipped body witha fixed velocity(generated by a spring force)onto a surface ofthe material under test.The ratio of the rebound velocity to theimpact velocity of the impact body is a measure of the hardnessof the material under test.3.1.4 surface finishall references to surface finish in thistest method are defined as surface roughness(that is,Ra=average roughness value,AA=arithmetic average).3.1.5 verificationchecking or testing the instrument toensure conformance with this test method.4.Summary of Test Method4.1 During a hardness test,an impact body with a spheri-cally shaped tungsten carbide,silicon nitride,or diamond tipimpacts under spring force,the test surface from which itrebounds.The impact and rebound velocities are measuredwhen the impact body is approximately 1 mm from the testsurface.This is accomplished by means of a permanent magnetmounted in the impact body which,during the test,movesthrough a coil in the impact device and induces an electricvoltage on both the impact and rebound movements.Theseinduced voltages are proportional to the respective impact andrebound velocities.The quotient of these measured voltagevalues derived from the impact and rebound velocities,multi-plied by the factor 1000 produces a number which constitutesthe Leeb hardness value.5.Significance and Use5.1 Hardness of a material is a poorly defined term that mayhave many meanings depending on the type of test performedand the expectations of the person involved.The Leeb hardnesstest is of the dynamic or rebound type,which primarilydepends both on the plastic and on the elastic properties of the1This test method is under the jurisdiction of ASTM Committee A01 on Steel,Stainless Steel and Related Alloys and is the direct responsibility of SubcommitteeA01.06 on Steel Forgings and Billets.Current edition approved Nov.15,2012.Published December 2012.Originallyapproved in 1996.Last previous edition approved in 2006 as A956 06.Leeb and Equotip are registered trademarks used with permission of Proceq SA.DOI:10.1520/A0956-12.2For 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 Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 material being tested.The results obtained are indicative of thestrength and dependent on the heat treatment of the materialtested.5.2 The Leeb hardness test is a superficial determinationonly measuring the condition of the surface contacted.Theresults generated at that location do not represent the part atany other surface location and yield no information about t