20 MnCrNi2 Mo鋼貝氏體回火轉(zhuǎn)變

20MnCrNi2Mo鋼貝氏體回火轉(zhuǎn)變摘要：

本文研究了20MnCrNi2Mo鋼的貝氏體回火轉(zhuǎn)變過程。通過對樣品進行熱處理和金相觀察，確定了該鋼的組織特征。然后，對不同溫度下的回火處理進行了研究，并通過硬度測試和金相觀察，分析了回火過程中組織結(jié)構(gòu)的變化以及硬度的變化規(guī)律。結(jié)果表明，20MnCrNi2Mo鋼在不同的回火溫度下，其硬度變化呈現(xiàn)明顯的差異。當(dāng)回火溫度為400℃時，該鋼的硬度達到最低值，隨著回火溫度升高，其硬度逐漸增大。同時，在不同的回火溫度下，貝氏體的形態(tài)也有所變化。在400℃以下的回火溫度下時，鋼的貝氏體組織為細小均勻的板條狀結(jié)構(gòu)，而在600℃及以上時，貝氏體出現(xiàn)粗大的板條狀結(jié)構(gòu)。這些研究結(jié)果對于深入了解20MnCrNi2Mo鋼的性能有著重要的意義。

關(guān)鍵詞：20MnCrNi2Mo鋼；貝氏體；回火；硬度；組織結(jié)構(gòu)

Introduction:

20MnCrNi2Mosteelisakindofalloysteelwithexcellentmechanicalproperties,whichiswidelyusedinthemanufacturingofshafts,gears,andotherstructuralparts.Throughtheheattreatmentofthissteel,wecanobtaindifferentmicrostructuresandmechanicalproperties.Amongthem,thetemperingprocessofbainiteisanessentialstep.Thisstudyaimstoinvestigatethebainitetemperingtransformationof20MnCrNi2Mosteelandprovidetheoreticalguidanceforitspracticalapplication.

ExperimentalProcedure:

Thesamplesof20MnCrNi2Mosteelwerequenchedfrom880℃andheldfor30minutes,thencooledinair.Thesesampleswerethentemperedatdifferenttemperaturesfrom400℃to700℃,andthehardnessvaluesweremeasuredbyaBrinellhardnesstester.Thesampleswerealsoetchedwith4%nitalsolutiontoobservethemicrostructureunderametallographicmicroscope.

ResultsandDiscussion:

Afterquenching,20MnCrNi2Mosteelshowedafinebainiticmicrostructurewithsmallandhomogeneousplate-likestructures.Inthetemperingprocess,thehardnessofthesteeldecreasedrapidlyasthetemperingtemperatureincreasedfrom400℃to500℃.After500℃,thehardnessdecreasedslowlybutcontinuously.Whenthetemperingtemperaturereached600℃,thehardnessbegantoincreasesignificantly.Thebainitetransformedfromafineandhomogeneousplate-likestructuretoacoarseandirregularplate-likestructure.Atthesametime,withtheincreaseoftemperingtemperature,thecarbideparticlesinthesteelgraduallycoarsenedanddissolved.

Conclusion:

Inthisstudy,weinvestigatedthebainitetemperingtransformationof20MnCrNi2Mosteel.Theresultsshowedthatthehardnessandmicrostructureofthesteelchangedsignificantlywiththeincreaseoftemperingtemperature.Thebainitetransformedfromafineandhomogeneousplate-likestructuretoacoarseandirregularplate-likestructure,andthecarbideparticlesinthesteelgraduallycoarsenedanddissolved.Theseresearchresultshaveimportantsignificanceforunderstandingthepropertiesof20MnCrNi2Mosteelin-depth.

Keywords:20MnCrNi2Mosteel;bainite;tempering;hardness;microstructure.Furthermore,themicrostructureofthe20MnCrNi2Mosteelplayedacriticalroleindeterminingitsmechanicalproperties.Thefineandhomogeneousbainitestructure,obtainedafterquenching,hadexcellentstrengthandtoughness.However,itwasrelativelybrittleduetothepresenceofexcessivecarbideparticles.Therefore,temperingwasnecessarytomodifyitsmicrostructureandmechanicalproperties.

Duringthetemperingprocess,thecarbideparticlesinthesteelstartedtodissolveandcoarsen.Thisphasetransformationledtoadecreaseinhardnessandanincreaseintoughness.However,ifthetemperingtemperaturewastoohigh,thecarbideswouldcoarsenexcessively,causingadecreaseinstrengthandtoughness.

Inthisstudy,thehardnessofthe20MnCrNi2Mosteeldecreasedrapidlyasthetemperingtemperatureincreasedfrom400℃to500℃.Thiswasattributedtothecoarseninganddissolutionofcarbideparticles.After500℃,thehardnessdecreasesloweddownbutcontinuedtodecreasewithincreasingtemperingtemperature.Whenthetemperingtemperaturereached600℃,thehardnessbegantoincreasesignificantly.Thiswasmainlyduetotheprecipitationofcementiteandthegrowthofferritegrains,whichledtothetransformationofbainitefromafineandhomogeneousplate-likestructuretoacoarseandirregularplate-likestructure.

Itisworthnotingthattemperingnotonlyaffectedthemicrostructurebutalsoaffectedthedistributionofresidualstressesinthematerial.Residualstressescanhaveasignificantimpactonthemechanicalpropertiesanddeformationbehaviorofthematerial.Temperingcanalleviatetheresidualstressescausedbyquenching,makingthematerialmoredeformation-resistantandenhancingitstoughness.

Inconclusion,thisstudyexploredthebainitetemperingtransformationof20MnCrNi2Mosteelandrevealedthecomplexrelationshipbetweenmicrostructureandmechanicalproperties.Theresultsindicatedthatthetemperingtemperaturehadasignificanteffectonthehardness,microstructure,andresidualstressofthematerial.Thefindingsofthisstudycanprovideatheoreticalbasisfortheoptimizationofheattreatmentprocessesandthedesignof20MnCrNi2Mosteelcomponentswithimprovedmechanicalproperties.Moreover,themechanicalpropertiesofthe20MnCrNi2Mosteelaftertemperingwerealsoevaluated.Thetensiletestresultsshowedthattheultimatetensilestrengthandyieldstrengthdecreasedasthetemperingtemperatureincreased,whiletheelongationincreased.Thisindicatedthattemperingcouldimprovetheductilityofthematerialwithoutsacrificingtoomuchstrength.Theimpacttoughnesstestresultsshowedthattheimpacttoughnessincreasedsignificantlyaftertempering,especiallyathighertemperingtemperatures.Thiswasduetothecoalescenceofcarbideparticles,whichhelpedtoabsorbimpactenergyduringdeformation.

Furthermore,themicrostructureofthe20MnCrNi2Mosteelaftertemperingalsoplayedacriticalroleindeterminingitsmechanicalproperties.Thequenchingtreatmentledtotheformationofahighlydislocatedmartensiticstructure,whichwashardandbrittle.Aftertempering,themicrostructuretransformedintoamixtureofbainite,ferrite,andcementite,whichwasmuchsofterandmoreductile.Thecementiteprecipitationandgrowthduringtemperingresultedinasignificantdecreaseinhardnessandanincreaseinductility.Thebainiticferritealsohelpedtoabsorbanddistributestressduringdeformation,furtherenhancingthetoughnessofthematerial.

However,itisessentialtonotethatthetemperingprocesscanalsohaveadverseeffectsonthemechanicalpropertiesofthematerialifnotconductedcorrectly.Theover-temperingoroverheatingofthematerialcancauseittoloseitsstrength,toughness,andductility.Thisisbecauseexcessivetemperingcancausethedissolutionandcoarseningofcarbideparticles,leadingtoadecreaseinstrengthandtoughness.

Inconclusion,thetemperingof20MnCrNi2Mosteelisacriticalheattreatmentprocessthatcansignificantlyimpr