Guidelines to Hardness Testing

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<ul><li><p>10/28/2015 Guidelinestohardnesstesting</p><p>http://www.hegewaldpeschke.com/interestingfacts/guidelinestohardnesstesting.html#c274 1/22</p><p>Home|Contact|Sitemap|Imprint</p><p>Suche </p><p>ProductsUniversaltestingmachines</p><p>StatictestingmachinesDynamictestingmachinesSpecialtestingmachinesModernisationofuniversaltestingmachinesTestingsoftwareApplicationsAccessoriesforuniversaltestingmachines</p><p>FurnituretestingmachinesTestingofseatingfurniture,upholsteredfurniture,tables,cabinetsTestingofdrawers,drawerguidingsandfunctionalfittingsTestingofbeds,mattresses,slattedframes,cushionframesAccessoriesfurnituretesting</p><p>SpecialtestingplantShocktestingReversebendtestingmachinesFrictionteststandsMechanicalcreepbehaviourtestingequipmentTorsionteststand</p><p>HardnesstestingmachinesBasichardnesstestersHardnesstestbenchesModernisationofHardnessTestersHardnesstestingsoftwareAccessoriesforhardnesstesters</p><p>LengthmeasurementtechnologyMagnescaledigitalgaugeSonydigitalmeasuringtechnologyMeasurementequipmentModernisationofmachinetools</p><p>TestingmachinesforAutomationAutomatedtestingsystemwithuniversaltestingmachineandrobotorAutomatedhardnesstestingsystemwithrobotor</p><p>adinaiText Boxreference</p></li><li><p>10/28/2015 Guidelinestohardnesstesting</p><p>http://www.hegewaldpeschke.com/interestingfacts/guidelinestohardnesstesting.html#c274 2/22</p><p>ServicesInstallationandinstructionAdviceCustomerserviceMaintenanceoftestingmachinesDAkkScalibrationTrainingandworkshopsContracttesting</p><p>TheCompanyPortraitCustomersandpartnersCertifications</p><p>NewsandPressLatestnewsDatesPressandpublicationsWillypresentsJobs</p><p>InterestingfactsGuidelinestohardnesstestingGlossar</p><p>ContactandSpecialsContact</p><p>ContactusformularGermanyInternational</p><p>ServiceServiceFormMagnescaleProductInformationToolSitemapSearchImprint</p><p>InterestingfactsGuidelinestohardnesstesting</p></li><li><p>10/28/2015 Guidelinestohardnesstesting</p><p>http://www.hegewaldpeschke.com/interestingfacts/guidelinestohardnesstesting.html#c274 3/22</p><p>Contents:</p><p>1.Generalnotesonhardnesstesting2.TheRockwellprocedure2.1StandardRockwell2.2SuperficialRockwell2.3FieldsofapplicationwithdifferentRockwellscales2.4Testsoncylindricandsphericalsurfaces2.5ProsandconsoftheRockwellprocedure2.6VariationsoftheRockwellprocedure</p><p>3.TheBrinellmethod3.1ThelabellingofBrinelltests3.2DifferentapplicationsofBrinelltests3.3ProsandconsoftheBrinellprocedure3.4RockwelltestswithBrinellloadsandBrinellpenetrators</p><p>4.TheVickersmethod4.1ApplicationsofdifferentVickerstestloads4.2ProsandconsoftheVickersprocedure</p><p>5.Otherhardnesstestingprocedures5.1TheShoreprocedure(formetals)5.2TheKnoopmethod</p><p>6.Revaluationtablesandhardnesscomparisonplates6.1Theuseofrevaluationtables6.2Theuseofhardnesscomparisonplates</p><p>1.GeneralNotesonHardnessTesting</p><p>Amongthedifferentkindsofmeasurementsthatarecarriedoutinalaboratory,hardnesstestingisoneofthemostcomplexones.Ontheonehand,therearedifferentmeasurementproceduresontheotherhand,itisnecessarytomeasurelarge,small,hard,soft,thinorthickmetalparts.Consideringthedifferentproceduresandthelargenumberofscales,itisunderstandablethatevenveryexperiencedpersonscanbechallengedbyhardnesstestingtasks.</p><p>Asinsomanyotherareasofapplication,electronicdevelopmenthasledtoasignificantsimplificationofhardnesstesting.Withcomputeraidedhardnesstesters,ahigherprecisionduringresultreadout,datastorageandthepossibilityofdataprocessingtostatistics,graphicrepresentations,documentation,etc.havebecomeamatterofcourse.</p><p>However,electronicsarestillonlyusedforresultsreadout(and,ifnecessary,automationofthemeasuring/drive),whilethedifferentmechanictestingresultsarestillapplicable.</p></li><li><p>10/28/2015 Guidelinestohardnesstesting</p><p>http://www.hegewaldpeschke.com/interestingfacts/guidelinestohardnesstesting.html#c274 4/22</p><p>Althoughlaterwewillbetalkingaboutdefinitions,advantagesanddisadvantagesoftheRockwell,Brinell,andVickersprocedures,itisstillbeneficialtodealbrieflywiththemostimportantfeaturesthatshouldbeconsideredbeforebuyingsuchadevice,hereintheintroduction:1)thetotaltestload2)thehardnessrange3)accuracy,4)theflexibilityofthedevicewithregardtoformsanddimensionsofspecimens,and5)economicaspects.</p><p>1. Totaltestload</p><p>Ontheonehand,thereisthegeneralruletouseatestloadashighaspossible.Thisallowsforhigheraccuracy(becausethemeasurementislesssensitivetothesurfacetexturewithahighertestload).</p><p>Ontheotherhand,theindentationshouldnotbedeeperthan1/10ofthethicknessofthespecimenorthehardenedsurface.</p><p>Thedegreeofhomogeneityofthematerialisalsoanimportantcriterion:atypicalexampleiscastiron,whichisusuallyonlytestedwithahightotalload,exceptintherangeswhereithasbeeninductionhardened,e.g.machinetoolbases.</p><p>2. HardnessrangeAboveahardnessofapproximately650HB/30,adiamondpenetratorshouldbeusedbelowthatvalueitisalsopossibletouseapenetratormadeofsteelorhardmetal.</p><p>TheBrinellmethod,whichdoesnotallowdiamondpenetrators,cannotbeusedforhardenedsteel.</p><p>TheRockwellmethodismoreuniversal,becauseitallowsfortheusedofdiamondconeandsteelballpenetrators.</p><p>TheVickersmethod,whichonlyallowsforadiamondpyramidpenetrator,canbeemployedintheentirehardnessrange.However,itismostsuitablefortestsinlaboratoriescomparedtotestsinworkshops.</p><p>3. AccuracyTheprecisionofthemeasurementisheavilydependentontheaccuracyemployedbytheoperator.Thisalsoincludeswellgroundsurfaces,sufficientmeasurementperiodsandfrequentrevisionsofthetestingdevicewithreliabletestplates.Ifpossible,theuseofstaticsystemsshouldbepreferredtodynamicsystems.Usingverylowtestingloadsisaparticularrestrictiontotheprecisionofthemeasurements</p><p>4. FlexibilityofthedevicewithregardtoformsanddimensionsofspecimensThespecimencanbeputonthedevice,orthedevicecanbeputonthespecimen.Thefirstcasedescribesstationarydevices,whichhaveenoughcapacitytoholdthespecimen.Stationarydevicesare,thus,primarilysuitablefortestsonsmallandmediumsizedspecimens.</p><p>Portabledevicescanbeclampedtothespecimens(clampingjaw,chain,etc)orwhentestinglargeorbulkyspecimensjustputonthespecimens.</p><p>Portabledevicescanonlybedynamicwhenusinghightestingloads.Whenthetestingloadsaresmaller,theycanalsobestatic.Itispossibletofindcustomerspecificsolutionsforspecialcases.</p><p>5. EconomicaspectsThisincludesthefollowingelements:thepurchasepriceofthedevice,theuniversalismoftheapplication,themeasurementperiod,andthequalificationneededtooperatethedevice.</p><p>Thefirsttwoaspectsareimportantwhenspecimensofdifferentformsandwithdifferentsurfacetreatmentsare</p></li><li><p>10/28/2015 Guidelinestohardnesstesting</p><p>http://www.hegewaldpeschke.com/interestingfacts/guidelinestohardnesstesting.html#c274 5/22</p><p>tested.Thisisusuallythecaseintechnicalcompaniesandinsmallscaleindustries.</p><p>Incompaniesthatdotheirtestsseriallythequicknessofthemeasurementsandthepossibilitytoemployunskilledstaffareveryimportant.Here,suchdevicesarepreferredthatdonotneedspecialclampingequipment.</p><p>Top Content</p><p>2.TheRockwellmethod</p><p>Forabetterunderstanding,thesequenceoftheRockwellmethod,whichisdescribedbelow,isalsoshowninthenumberedimagesbelow(figure1).Themeter,whichisconnectedtothepenetratoranddisplaysthepenetratorsshiftsonalargerscale,isalsoincludedinthefigure.</p><p>1. ThetestedsurfaceisexposedtothepenetratorandthefirsttestloadFo(preload)isapplied.Asmallindentation</p><p>appears.Atthispoint,themeterissettozero.</p><p>2. SlowlyandwithoutshockstheloadF1isappliedadditionally.TogetherwiththepreloadthisisdefinedastotaltestloadF.Withthisloadthepenetratorentersthematerialmoreorlessdeep,dependingonthehardnessofthematerial.Thispositionneedstobekepttoreachthefinalpenetration(whentestinghardmaterialsthepenetrationisalmostimmediatewithsoftmaterialsitisnecessarytowaitforanumberofseconds).Thepenetrationprocedurecanalsobeobservedontheindicatorofthemeter.</p><p>3. Whentheindicatorofthemeterfinallystopsmoving,theadditionalloadF1isremoveduntilthepreloadisapplied</p><p>respectively.Thisway,thepenetratorremainsintheimprintandallelasticdeformations,whichwerecausedbytheapplicationofthetotaltestload,areeliminatedthus,themeteronlyshowstheremainingpenetrationdepth(asdifferencebetweenpreloadandtotaltestload).</p><p>Thepenetrator,preloads,testloads,andtheunitsarestandardisedintheRockwellmethodandcanbedividedintotwogroups:standardRockwell(methodN)andsuperficialRockwell(methodT).</p><p>Top Content</p></li><li><p>10/28/2015 Guidelinestohardnesstesting</p><p>http://www.hegewaldpeschke.com/interestingfacts/guidelinestohardnesstesting.html#c274 6/22</p><p>2.1StandardRockwell</p><p>ThestandardRockwellprocedureisintendedfortheuseofonesinglediamondconepenetratorof120witharoundedoffpeakof0.2mmradius(seefigure2),ordifferentballpenetratorsmadefromhardmetalwithdiametersof1/16"1/8"1/4"1/2"(inch).</p><p>Figure2profileoftheRockwellpenetratorwithdiamondcone</p><p>Thepreloadisunchanging:98.07N.Thetotaltestloadsare(preload+additionalload):588.4N980.7N1,471N.ThemeasuringunitinstandardRockwellcorrespondsto0.002mmpenetration.Thehardnessvalueincreaseswiththehardnessofthematerial,butatthesametimethepenetrationdifferencebetweenthepreloadandthetotaltestingloaddecreasestheharderthematerialis.Thus,Rockwellhardnessvaluesarecalculatedbysubtractingthepenetrationdepth(per0.002mm)from100(whenusingthediamondpenetrator)orfrom130(whenusinganyballpenetrator).</p><p>Example:withadiamondpenetratorandapenetrationdepthof0.082mmthismakes1000.082/0.002=59Rockwellthesamepenetrationdepthmeasuredwithaballpenetratormakes1300.082/0.002=89Rockwell</p><p>Whenusinganaloguedeviceswithdialgauges,whichusuallyhave100partitions(onerotation=0.2mm),theRockwellvaluescanbereaddirectlyfromthedial.Thedialthenusuallyhas2seriesofnumbers:theblackonesarefordiamondpenetratorsandtherednumbersaremadeforballpenetrators.Forthezeropositionalwaysusetheblack0(orthered30).Whenusingadigitaldevice,thedataaredisplayedafterthecompletemeasuringcyclewasrunthrough.Duetothedifferentcombinationsofpenetratorsandtestloads,thereisagreatnumberofscales,whicharelabelledwithdifferentletters(seeTable1).</p><p>HRSCALE</p><p>Penetrator:</p><p>DiamondCone</p><p>Ball1/16"1,5875mm</p><p>Ball1/8"3,175mm</p><p>Ball1/4*</p><p>Ball1/2"*</p><p>Numbers:</p><p>black</p><p>red</p></li><li><p>10/28/2015 Guidelinestohardnesstesting</p><p>http://www.hegewaldpeschke.com/interestingfacts/guidelinestohardnesstesting.html#c274 7/22</p><p>F=1471N</p><p>C</p><p>G</p><p>K</p><p>P</p><p>V</p><p>F=980,7N</p><p>D</p><p>B</p><p>E</p><p>M</p><p>S</p><p>F=588,4N</p><p>A</p><p>F</p><p>H</p><p>L</p><p>R</p><p>Table2superficialRockwellscales,F=totaltestload(Newton)*)W,X,Yarenotstandardised</p><p>TheERNSTdevicesNR3SR,AT130ASRandAT130DSRallworkwiththesuperficialRockwellprocedure.</p><p>Top Content</p><p>2.2SuperficialRockwell</p><p>AlthoughthesuperficialRockwellmethodusesthesamepenetratorsasthestandardRockwellprocedure,themethodrequiresamorepreciselyshapeddiamondconepenetrator.Thisregardsnotonlytheconicityofthe120conepeak,butalsoitsroundingoffof0.2mm.Withthismethod,smallertotalloadsareusedtocreatesmallerindentations,sothatthesmallestshapedefectsonthepeakwouldfalsifythemeasuringresults.Thepreloadisunchanging:29.42NThetotaltestloadsare(preload+additionalload):147.1N294.2N441.3NThemeasuringunitinsuperficialRockwellcorrespondsto0.001mmpenetrationdepth.IncontrasttostandardRockwell,thezeropointissetto100(0onthedialgauge)inthesuperficialRockwellprocedure(bothwiththediamondpenetratorandwiththeballpenetrator).Thedialonlyhasoneseriesofnumbersand100partitions.Onerotationoftheindexequals0.1mm.</p><p>Example:Withadiamondorballpenetratorandapenetrationdepthof0.082mmthismakes1000.082/0.001=18superficialRockwell.Duetothedifferentcombinationsofpenetratorsandtestloads,thereisagreatnumberofsuperficialRockwellscales,whicharelabelledwithdifferentletters.Therespectiveletterisalsoprecededbyanumberwhichindicatesthetotalloadusedinthetest(seeTable2).</p><p>HRScale</p><p>Penetrator</p><p>DiamondCone</p><p>Ball1/16"1,5875mm</p><p>Ball1/8"*</p><p>Ball1/4"*</p><p>Ball1/2"*</p></li><li><p>10/28/2015 Guidelinestohardnesstesting</p><p>http://www.hegewaldpeschke.com/interestingfacts/guidelinestohardnesstesting.html#c274 8/22</p><p>F=441,3N 45N 45T 45W 45X 45Y</p><p>F=294,2N</p><p>30N</p><p>30T</p><p>30W</p><p>30X</p><p>30Y</p><p>F=147,1N</p><p>15N</p><p>15T</p><p>15W</p><p>15X</p><p>15Y</p><p>superficialRockwellscales,F=totaltestload(Newton)*)W,X,Yarenotstandardised</p><p>TheERNSTdevicesNR3SR,AT130ASRandAT130DSRallworkwiththesuperficialRockwellprocedure.</p><p>Top Content</p><p>2.3FieldsofapplicationwithdifferentRockwellscales</p><p>Aswehaveseen,thereisaconsiderablenumberofRockwellscales.Whichscaletochooseisaquestiondependingonthehardnessofthematerial,andthethicknessofthespecimenorhardenedsurface(incaseswheretherehavebeensurfacetreatmentssuchascarburisation,nitridingetc.).Thehardnessofthematerialdeterminesthechoiceofthepenetrator:diamondconeorball.</p><p>Thediamondconeissolelyusedfortemperedorhardenedsteelandhardmetal.Itisnotrecommendableforsteelwithasoliditybelow785N/mm2(20HRC,230HB/30).</p><p>Thesteelballpenetratorisusedforsoftermaterials.Thesofterthematerial,thelargershouldbethediameteroftheballand/orthesmallershouldbethetotaltestload.Forinstance,thematerialsthatcanbetestedwiththeHRBscale(ball1/16"totaltestload980.7N)areharderthanthematerialstestedwiththeHRLscale(ball1/4"totaltestload588.4N).</p><p>Thelargeballsaresolelyusedforthetestingofplasticsandmaterialsalike.Flowingplasticscanbemeasuredaswell,ifcertainstepsaretaken,withthehelpofthetotaltestload.</p><p>Again,wewouldliketomentionthattheHRhardnesstestingalsorequiresaminimumthicknessofthesample.However,thereisnohardruleforthisminimumthickness.Itisusuallyestimatedbycalculating10xthepenetrationdepth(seeTable3).Thisprincipleisalsovalidforhardenedsurfaces(carburisationetc.),whichareusuallymeasuredwiththesmallesttotaltestload(scaleHRA).</p><p>F</p><p>HRC</p><p>20</p><p>30</p><p>40</p><p>50</p><p>60</p><p>70</p></li><li><p>10/28/2015 Guidelinestohardnesstesting</p><p>http://www.hegewaldpeschke.com/interestingfacts/guidelinestohardnesstesting.html#c274 9/22</p><p>147,1N</p><p>0.41</p><p>0.33</p><p>0.26</p><p>0.19</p><p>0.14</p><p>0.09</p><p>294,2N</p><p>0.69</p><p>0.58</p><p>0.47</p><p>0.36</p><p>0.26</p><p>0.17</p><p>441,3N</p><p>0.91</p><p>0.77</p><p>0.63</p><p>0.50</p><p>0.37</p><p>0.25</p><p>588,4N</p><p>1.0</p><p>0.9</p><p>0.8</p><p>0.7</p><p>0.6</p><p>0.5</p><p>1471N</p><p>1.8</p><p>1.6</p><p>1.4</p><p>1.2</p><p>1.0</p><p>0.8</p><p>Table3measurableminimumthicknessforRockwelltestswithdiamondpenetrators</p><p>MostfrequentlyusedarethefollowingRockwellscales:</p><p>1.HRC(diamondcone1471N)HRCisthemostcharacteristicalRockwellscalefortestinghardened,temperedandcarburisedsamples.Whentalkingabout"Rockwellhardness"ingeneral,thisusuallymeanstheHRCscale.Thismightcauseacertainconfusion,becausesometimesahardnessoftheHRCscaleisordered,althoughthesmalldimensionsofthesamplemaketestswithatotaltestloadof1471Nimpossible.Insuchcases,otherRockwellscalesorothermeasuringproceduresareusedtodeterminethehardness,whichisthenrevaluedtoHRCwiththehelpofcharts.Aswewillseelater,thoserevaluationtablescanonlygiveapproximatedvalues.Thatiswhyitisrecommendedtouseonlyhardnessvaluesthatcanbemeasuredinrealitywhenenteringthemintodrafts,orders,etc.</p><p>2.HRA(diamondcone588.4N)Mainlyusedforcarburisedmaterialsandhardmetals,whosehighcarbidehardnessmightdamagethediamond.</p><p>3.HRB(ball1/6"980.7N)InEurope,thisscaleisusuallyusedforcopperalloys(brass,bronzeetc.)intheU.S.,itisalsousedforsteeluptoapprox.686N/mm.</p><p>4.RockwellNandT(superficialRockwell)ThescalesHR15N,HR30N,HR45N(diamondcone)areusedforsampleswiththincarburisationthescalesHR15T,HR30T,HR45T(ball1/16")areusedforthinmetalsheets.Thegeneralnotesconcerningthechoiceofthetotaltestloadalwayshavetobeattendedto.</p><p>Top Content</p><p>2.4Testsoncylindricandsphericalsurfaces</p><p>Itisclearthattheconditionsforhardnessmeasurementsoncylindricorsphericalsurfacesare</p></li><li><p>10/28/2015 Guidelinestohardnesstesting</p><p>http://www.hegewaldpeschke.com/interestingfacts/guidelinestohardnesstesting.html#c274 10/22</p><p>differentfromthoseonflatsurfaces.Thedifferencesarenotascrucialwithlargerdiametersbecausethenthebendingofthesurfaceissmallandapproximatesaflat.</p><p>Whenworkingwithsmallerdiameters(withhigherbending)itisn...</p></li></ul>

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