CLASS11工业用钢.

SteelforEngineering工程用钢CharpterVISteelforEngineering第6章工程用钢1)Steelscanbedividedintotwomaingroups:Plaincarbonsteels碳钢Alloysteels合金钢2）AccordingtocarbonconcentrationLowcarbonsteels低碳钢:≤0.25%Mediumcarbonsteels中碳钢:0.25~0.6%Highcarbonsteels高碳钢:0.63)AccordingtotheirtotalcontentofalloyingelementsLowalloysteels低合金钢:(totalalloyingcontent5%)Mediumalloysteels中合金钢：(totalalloyingcontent5%-10%)Highalloysteels高合金钢:(totalalloyingcontent10%)一、ClassificationofcarbonSteels钢的分类1一、ClassificationofcarbonSteels钢的分类2•PlainCarbonSteels：普通碳钢DefinitionofAmericanIronandSteelInstitute（AISI）AplaincarbonsteelstobeanalloyofironwhichcontainsspecifiedamountsofMnbelowamaximumamountof1.65%,lessthan0.6%Si,lessthan0.6%Cuandwhichdoesnothaveanyspecifiedminimumcontentofanyotherdeliberatelyaddedalloyingelement.Itisusualformaximumamounts(e.g.,0.05%)ofSandPtobespecified.一、ClassificationofcarbonSteels钢的分类3•Alloysteels:合金钢~arethosesteelsthatcontainminimumspecifiedamountsofalloyingelementsinadditiontothosefoundinplaincarbonsteels.Alloyingelement:Cr,Ni,Mo,Nb,Ti,W,Co,Cu,V,Si,AlandB.Theseelementproduceavarietyofchangesinthebehaviorandpropertiesofsteel.4)Accordingtotheirapplicationsintothreemaingroups:a)Constructionalsteels结构钢whicharegenerallyusedformachinepartshighlystressedintensionorcompression.b)Toolsteels工具钢whichrequiregreathardnessand,insomecases,resistancetosofteningbyheat.c)Specialsteels特殊用途钢(e.g.stainlesssteelsandheat-resistingsteels)4一、ClassificationofcarbonSteels钢的分类二、钢的编号（1）钢材编号原则：化学符号、数字及汉语拼音字母并用（2）合金元素用元素符号表示：Si,Mn,Cr,Ni（3）稀土元素用“RE”表示其总含量（4）在牌号首部用数字标明钢的含碳量结构钢以万分之一为单位的数字(两位数)：08Al、45、40Cr工具钢和特殊性能钢以千分之一为单位的数字(一位数)来表示含碳量：5CrNiMo工具钢含碳量超过1%时，含碳量不标出：CrWMn钢，为工具钢，平均含碳量大于1.0%5在表明含碳量的数字之后，用元素符号表明主要合金元素，含量由其后数字标明，平均含量少于1.5%时不标数，平均含量为1.5%~2.49%,2.5%~3.49%…时，相应地标以2,3….。如：20Cr2Ni4举例：1)40Cr钢为结构钢，平均含碳量为0.4%;主要合金元素为Cr，其含Cr量在1.5%以下2)5CrNiMo钢为工具钢，平均含碳量为0.5%，含有Cr,Ni,Mo三种主要合金元素，含量皆在1.5%以下3)CrWMn钢，也为工具钢，平均含碳量大于1.0%，含有Cr,W,Mn合金元素，合金元素含量都少于1.5%6二、钢的编号•专用钢用其用途的汉语拼音字首来标明。例如，滚珠轴承钢钢号前标以“G”字,GCr15•表示含碳量约1.0%、铬约1.5%(含铬量以千分之一为单位的数字表示1)的滚珠轴承钢•对于高级优质钢，则在钢号的末尾加“A”字表明，例如20Cr2Ni4A等7二、钢的编号三、Low-alloysteels低合金钢Plain-carbonsteelscanbeusedsuccessfullyifthestrengthandotherengineeringrequirementsarenottoosevere.Thesesteelsarerelativelylowincostbuthavesomelimitations,whichincludethefollowing:1.~cannotbestrengthenedbeyondabout690MPawithoutasubstantiallossinductilityandimpactresistance.2.Large-sectionthicknessesof~cannotbeproducedwithamartensiticstructurethroughout,i.e.,theyarenotdeep-hardenable.3.~havelowcorrosionandoxidationresistance.4.Medium-carbon~mustbequenchedrapidlytoobtainafullymartensiticstructure.Rapidquenchingleadstopossibledistortionandcrackingoftheheat-treatedpart.5.Plain-carbonsteelshavepoorimpactresistanceatlowtemperatures.8•Alloysteelshavebeendevelopedthatcontainalloyingelementstoimprovetheirproperties.•Alloysteelsingeneralcostmorethanplain-carbonsteels,butformanyapplicationstheyaretheonlymaterialsthatcanbeusedtomeetengineeringrequirements.•Theprincipalalloyingelementsaddedtomakealloysteelsaremanganese,nickel,chromium,molybdenum,andtungsten.•Otherelementsthataresometimesaddedincludevanadium,cobalt[kəu‘bɔ:lt]钴,boron['bɔ:rɔn]硼,copper,aluminum,lead,andtitanium.9三、Low-alloysteels低合金钢（一）ClassificationofAlloySteels合金钢的分类Alloysteelsmaycontainupto50percentofalloyingelementsandstillbeconsideredalloysteels.Inthisbooklow-alloysteelscontainingfromabout1to4percentofalloyingelementswillbeconsideredalloysteels.Thesesteelsaremainlyautomotive-andconstruction-typesteelsandarecommonlyreferredto把...归类simplyasalloysteels.10（二）DistributionofAlloyingElementsinAlloySteels合金元素对合金钢的贡献Thewayinwhichalloyelementsdistributethemselvesincarbonsteelsdependsprimarilyonthecompound-andcarbide-formingtendenciesofeachelement.•Nickel镍dissolvesintheaferriteofthesteelsinceithaslesstendencytoformcarbidesthaniron.•Silicon硅combinestoalimitedextentwiththeoxygeninthesteeltoformnonmetallicinclusionsbutotherwisedissolvesintheferrite.•Mostofthemanganese锰addedtocarbonsteelsdissolvesintheferrite.Someofthemanganese,however,willformcarbidesbutwillusuallyenterthecementiteas(Fe,Mn)3C.11•Chromium铬,whichhasasomewhatstrongercarbide-formingtendencythaniron,partitionsbetweentheferriteandcarbidephases.Thedistributionofchromiumdependsontheamountofcarbonpresentandonwhetherotherstrongercarbide-formingelementssuchastitaniumandcolumbiumareabsent.•Tungsten钨andmolybdenum钼combinewithcarbontoformcarbidesifthereissufficientcarbonpresentandifotherstrongercarbide-formingelementssuchastitaniumandcolumbiumareabsent.•Vanadium钒,titanium钛,andcolumbium钴arestrongcarbide-formingelementsandarefoundinsteelsmainlyascarbides.•Aluminum铝combineswithoxygenandnitrogentoformthecompoundsAl203andAlN,respectively.12（二）DistributionofAlloyingElementsinAlloySteels合金元素对合金钢的贡献•ThevariousalloyingelementscausetheeutectoidtemperatureoftheFe-Fe3Cphasediagramtoberaisedorlowered(Fig.9.35).•Manganeseandnickelbothlowertheeutectoidtemperatureandactasaustenite-stabilizingelementsenlargingtheausteniticregionoftheFe-Fe3Cphasediagram.Insomesteelswithsufficientamountsofnickelorm