Unit13HeatTreatmentofMetalUnit13HeatTreatmentofMeta1ContentsNewWords&Expressions

Text&TranslationComplexSentenceAnalysisKeytoExercisesContentsNewWords&Expression2NewWords&Expressionsforge[f?:d?]v.鑄造,偽造transformation[?tr?nsf?'mei??n]n.變換，轉(zhuǎn)換，相變eutectoid[ju:'tekt?id]adj.類似共熔體的，共析的austenite['?stinait]n.奧氏體pearlite['p?:lait]n.珠光體cementite[si'mentait]n.滲碳體NewWords&Expressionsforge3NewWords&Expressionsmartensitic['mɑ:t?n?zaitik]adj.馬氏體的stressrelieving消除應(yīng)力，低溫退火tempering['temp?ri?]n.回火normalizing['n?:m?laizi?]n.正火ferrousalloy鐵合金still[stil]adj.不動(dòng)的，靜止的 fullannealing完全退火 notably['n?ut?bli]adv.顯著地,特別是NewWords&Expressionsmarten4NewWords&Expressionsaustenitize['?stinitaiz]v.奧氏體化，使成奧氏體denote[di'n?ut]v.指示，表示，概述machinability[m?'?i:n?biliti]n.切削加工性，機(jī)械加工性能facilitation[f??sili'tei?n]n.容易化，助長(zhǎng)，便于in-process['pr?uses]adj.(加工、處理)過(guò)程中的qualification[?kw?lifi'kei??n]n.資格,條件,限制,限定quenching[kwent?]n.淬火NewWords&Expressionsausten5NewWords&Expressionsbrine[brain]n.鹽水caustic['k?:stik]adj.腐蝕性的,堿性的aqueous['eikwi?s]adj.水的,水成的warp[w?:p]n.翹曲，變形fogquenching噴霧淬火interruptedquenching分級(jí)淬火selectivequenching局部淬火quench-hardened['kwent??hɑ:dnd]adj.淬硬的processannealing中間退火，工序間退火NewWords&Expressionsbrine[6Text&TranslationThegenerallyaccepteddefinitionforheattreatingmetalsandmetalalloysis“heatingandcoolingasolidmetaloralloyinawaysoastoobtainspecificconditionsand/orproperties.”Heatingforthesolepurposeofhotworking(asinforgingoperations)isexcludedfromthisdefinition.Likewise，thetypesofheattreatmentthataresometimesusedforproductssuchasglassorplasticsarealsoexcludedfromcoveragebythisdefinition.Text&TranslationThegenerall7Text&Translation1.TransformationCurvesHeattreatmentbasesonthetime—temperature—transformationcurvesorTTTcurves;allthethreeparametersareplottedinasinglediagram.Becauseoftheshapeofthecurves，theyarealsosometimescalledC-curvesorS-curves.Fig.13.1showstheisothermaldecompositiondiagramofT80steel.Text&Translation1.Transforma8Text&TranslationToplotTTTcurves，theparticularsteelisheldatagiventemperatureandthestructureisexaminedatpredeterminedintervalstorecordtheamountoftransformationtakenplace.［1］Itisknownthattheeutectoidsteel(T80)underequilibriumconditionscontains，allausteniteabove723℃,whereasbelow，itispearlite.Toformpearlite，thecarbonatomsshoulddiffusetoformcementite.Thediffusionbeingarateprocess，wouldrequiresufficienttimeforcompletingtransformationofaustenitetopearlite.Fromdifferentsamples，itispossibletonotetheamountofthetransformationtakingplaceatanytemperature.［2］Thesepointsarethenplottedonagraphwithtimeandtemperatureastheaxes.Throughthesepoints，transformationcurvescanbeplottedasshowninFig.13.1foreutectoidsteel.Text&TranslationToplotTTT9Text&TranslationThecurveatextremeleftrepresentsthetimerequiredforthetransformationofaustenitetopearlitetostartatanygiventemperature.Similarly，thecurveatextremerightrepresentsthetimewhichisrequiredforcompletingthetransformation.Thepointsrepresentingpartialtransformationarebetweenthetwocurves.ThestartandfinishofmartensitictransformationarerepresentedbythehorizontallinesMsandMf.Text&TranslationThecurveat10Fig.13-1IsothermalDecompositionDiagramofT80SteelFig.13-1IsothermalDecompos11Text&Translation2.ClassificationofHeatTreatingProcessesInsomeinstances，heattreatmentproceduresareclearcutintermsoftechniqueandapplication，whileinotherinstances，descriptionsorsimpleexplanationsareinsufficientbecausethesametechniquefrequentlymaybeusedtoobtaindifferentobjectives.Forexample，stressrelievingandtemperingareoftenaccomplishedwiththesameequipmentandbyuseofidenticaltimeandtemperaturecycles.Theobjectives，however，aredifferentforthetwoprocesses.Thefollowingdescriptionsoftheprincipalheattreatingprocessesaregenerallyarrangedaccordingtotheirinterrelationships.Text&Translation2.Classifica12Text&Translation1)NormalizingNormalizingmeansheatingaferrousalloytoasuitabletemperature(usually50°Fto100°For28°Cto56°C)aboveitsspecificuppertransformationtemperature.［3］Thisisfollowedbycoolinginstillairtoatleastsometemperaturewellbelowitstransformationtemperaturerange.Forlowcarbonsteels，theresultingstructureandpropertiesarethesameasthoseachievedbyfullannealing；formostferrousalloys，normalizingandannealingaredifferent.Text&Translation1)Normalizin13Text&TranslationNormalizingusuallyisusedasaconditioningtreatment，notablyforrefiningthegrainsofsteelsthathavebeensubjectedtohightemperaturesforforgingorotherhotworkingoperations.Thenormalizingprocessusuallyissucceededbyanotherheattreatingoperationsuchasaustenitizingforhardening，annealing，ortempering.Text&TranslationNormalizing14Text&Translation2)AnnealingAnnealingisagenerictermdenotingaheattreatmentthatconsistsofheatingtoandholdingatasuitabletemperaturefollowedbycoolingatasuitablerate.Itisusedprimarilytosoftenmetallicmaterials，butalsotosimultaneouslyproducedesiredchangesinotherpropertiesorinmicrostructure.Thepurposeofsuchchangesmaybe，butisnotconfinedto，improvementofmachinability，facilitationofcoldwork(knownasinprocessannealing)，improvementofmechanicalorelectricalproperties，ortoincreasedimensionalstability.Whenappliedsolelytorelievestresses，itcommonlyiscalledstressreliefannealing，synonymouswithstressrelieving.Whentheterm“annealing”isappliedtoferrousalloyswithoutqualification，itmeansfullannealing.Thisisachievedbyheatingabovethealloy’stransformationtemperature，thenapplyingacoolingcyclewhichprovidesmaximumsoftness.Thiscyclemayvarywidely，dependingoncompositionandcharacteristicsofthespecificalloy.Text&Translation2)Annealing15Text&Translation3)QuenchingQuenchingistherapidcoolingofasteeloralloyfromtheaustenitizingtemperaturebyimmersingtheworkpieceinaliquidorgaseousmedium.Quenchingmediacommonlyusedincludewater，5%brine，5%causticinanaqueoussolution，oil，polymersolutions，orgas(usuallyairornitrogen).Selectionofaquenchingmediumdependslargelyonthehardenabilityofthematerialandthemassofthematerialbeingtreated(principallysectionthickness).Text&Translation3)Quenching16Text&TranslationThecoolingcapabilitiesoftheabovelistedquenchingmediadiffersalot.Inselectingaquenchingmedium，itisbesttoavoidasolutionthathasmorecoolingpowerthanisneededtoachievetheresults，thusminimizingthepossibilityofcrackingandwarpofthepartsbeingtreated.Modificationsofthetermquenchingincludedirectquenching，fogquenching，hotquenching，interruptedquenching，selectivequenching，sprayquenching，andtimequenching.Text&TranslationThecooling17Text&Translation4)TemperingInheattreatingofferrousalloys，temperingconsistsofreheatingtheaustenitizedandquenchhardenedsteelorirontosomepreselectedtemperaturethatisbelowthelowertransformationtemperature(generallybelow1300°For705°C).Temperingoffersameansofobtainingvariouscombinationsofmechanicalproperties.Temperingtemperaturesusedforhardenedsteelsareoftennohigherthan300°F(150°C).Theterm“tempering”shouldnotbeconfusedwitheitherprocessannealingorstressrelieving.Eventhoughtimeandtemperaturecyclesforthethreeprocessesmaybethesame，theconditionsofthematerialsbeingprocessedandtheobjectivesmaybedifferent.Text&Translation4)Tempering18Text&Translation5)StressrelievingLiketempering，stressrelievingisalwaysdonebyheatingtosometemperaturebelowthelowertransformationtemperatureforsteelsandirons.Fornonferrousmetals，thetemperaturemayvaryfromslightlyaboveroomtemperaturetoseveralhundreddegrees，dependingonthealloyandtheamountofstressreliefthatisdesired.Text&Translation5)Stressrel19Text&TranslationTheprimarypurposeofstressrelievingistorelievestressesthathavebeenimpartedtotheworkpiecefromsuchprocessesasforming，rolling，machiningorwelding.Theusualprocedureistoheatworkpiecestothepreestablishedtemperaturelongenoughtoreducetheresidualstresses(thisisatimeandtemperaturedependentoperation)toanacceptablelevel；thisisfollowedbycoolingatarelativelyslowratetoavoidcreationofnewstresses.Text&TranslationTheprimary20Text&Translation普遍認(rèn)同的對(duì)金屬及合金熱處理的定義是，以一定的方式加熱或和冷卻固態(tài)金屬或合金以達(dá)到一定的條件和/或獲得某些性能。以熱加工(如鍛造)為目的的加熱，不在此定義之列。同樣地，有時(shí)用于生產(chǎn)諸如玻璃或塑料制品的熱處理也不屬于該定義的范疇。Text&Translation普遍認(rèn)同的對(duì)金屬及合金熱21Text&Translation1.相變曲線熱處理的基礎(chǔ)分別是時(shí)間-溫度-相變曲線，即TTT曲線，3個(gè)參數(shù)都繪制在一個(gè)圖中。根據(jù)曲線的形狀特點(diǎn)，分別稱為C曲線或S曲線。如圖13-1所示為共析鋼的等溫轉(zhuǎn)變曲線圖。Text&Translation1.相變曲線22Text&Translation為了繪制TTT曲線，將特定的鋼置于給定溫度下，以預(yù)先確定的時(shí)間間隔檢查其結(jié)構(gòu)，記錄發(fā)生相變的量。我們知道共析鋼(C80)在平衡條件下，在723

℃以上時(shí)全為奧氏體，而低于此溫度，則為珠光體。為了形成珠光體，碳原子將產(chǎn)生擴(kuò)散形成滲碳體。擴(kuò)散是一種漸進(jìn)過(guò)程，需要足夠的時(shí)間完成奧氏體向珠光體的轉(zhuǎn)變。對(duì)于不同的樣品，可以記錄下在任一溫度時(shí)產(chǎn)生相變的量。然后把這些點(diǎn)繪制在一條以時(shí)間和溫度為坐標(biāo)軸的曲線上。通過(guò)這些點(diǎn)就可以得到圖13-1所示的共析鋼的相變曲線。左邊的曲線表示任一給定溫度下奧氏體開(kāi)始轉(zhuǎn)變?yōu)橹楣怏w所需要的時(shí)間。類似地，右邊的曲線表示相變完成所需要的時(shí)間。兩條曲線之間是表示部分相變的點(diǎn)。兩條水平線Ms和Mf表示馬氏體轉(zhuǎn)變的開(kāi)始和結(jié)束。Text&Translation為了繪制TTT曲線，將23Text&Translation圖13-1共析鋼的等溫轉(zhuǎn)變曲線圖Text&Translation圖13-1共析鋼的等溫24Text&Translation2.熱處理工藝的分類在某些場(chǎng)合熱處理過(guò)程可以根據(jù)其工藝和應(yīng)用明確地區(qū)分開(kāi)來(lái)。而在另一些場(chǎng)合，因?yàn)橥瑯拥墓に嚦３？梢杂脕?lái)達(dá)到不同的目的，因此對(duì)該術(shù)語(yǔ)的說(shuō)明和簡(jiǎn)單的解釋是不夠的。例如：消除應(yīng)力的熱處理和回火處理常常使用同樣的設(shè)備、同樣的時(shí)間和溫度循環(huán)來(lái)實(shí)現(xiàn)，但這兩種工藝的目的是不同的。下面對(duì)主要熱處理工藝的描述大體上是按其相互關(guān)系來(lái)安排的。Text&Translation2.熱處理工藝的分類25Text&Translation1）正火把鐵類合金加熱到指定的相變溫度上限以上(通常50～100F或28～56°C)的合適溫度。接下來(lái)在不流動(dòng)的空氣中冷卻到至少比相變溫度低得多的某一溫度。對(duì)于低碳鋼，得到的結(jié)構(gòu)和性能與完全退火相同。而對(duì)于大多數(shù)鐵類合金，正火和退火意義不同。正火一般作為起調(diào)節(jié)作用的熱處理工藝，特別是用于細(xì)化在鍛造或其他熱加工工藝中經(jīng)受了高溫的鋼的晶粒。正火處理之后通常還要接著進(jìn)行淬火、退火或回火等進(jìn)行奧氏體化。Text&Translation1）正火26Text&Translation2）退火熱處理的一個(gè)通用術(shù)語(yǔ)，指的是加熱到一定溫度并保溫，然后以合適的速度冷卻，主要用于降低金屬材料的硬度，同時(shí)在其他性能或顯微組織方面產(chǎn)生一些理想的變化。這種變化的目的是改善其機(jī)械加工性、便于冷加工(被稱為中間退火)，改善機(jī)械或電性能，或增加工件的尺寸穩(wěn)定性，但也不僅僅局限于此。如果僅僅用于消除應(yīng)力，就叫做去應(yīng)力退火，與應(yīng)力消除(stressrelieving)熱處理是同義詞。Text&Translation2）退火27Text&Translation當(dāng)“退火”這個(gè)術(shù)語(yǔ)用于鐵類合金而又無(wú)其他限制條件時(shí)，指的是完全退火。這種處理是把合金加熱到其相變溫度以上，再進(jìn)行循環(huán)冷卻以使硬度下降最大。冷卻過(guò)程的變化范圍較大，要看具體合金的成分和特性。3）淬火把鋼或合金浸沒(méi)在液體或氣體介質(zhì)中，從奧氏體化溫度下快速冷卻。常用的淬火介質(zhì)有水、5%的鹽水、5%的堿性水溶液、油、聚合物溶液或氣體(常為空氣或氮?dú)?。對(duì)淬火介質(zhì)的選擇主要取決于材料的淬透性以及被處理的材料的質(zhì)量(主要是淬火部分的厚度)。Text&Translation當(dāng)“退火”這個(gè)術(shù)語(yǔ)用于鐵28Text&Translation上面列出的各種淬火介質(zhì)的冷卻能力有很大的區(qū)別。在選擇淬火介質(zhì)時(shí)，最好避免選擇比達(dá)到預(yù)期效果所需的冷卻能力更強(qiáng)的溶液，從而盡量降低處理零件開(kāi)裂或變形的可能性。淬火包括直接淬火、噴霧淬火、熱淬火、分級(jí)淬火、局部淬火、噴射淬火和限時(shí)淬火。4）回火在鐵類合金的熱處理中，回火指的是把奧氏體化和淬硬的鋼或鐵再加熱到預(yù)先設(shè)定的相變溫度下限以下的某一溫度(通常低于1300F或705°C)。回火提供了獲得各種綜合機(jī)械性能的方法。用于淬硬鋼的回火溫度通常低于300F(150°C)。不要把回火與中間退火或去應(yīng)力退火混淆。即使3種處理方法的時(shí)間和溫度循環(huán)可能相同，但是被處理的材料的狀態(tài)和目的可能是不同的。Text&Translation上面列出的各種淬火介質(zhì)的29Text&Translation5）去應(yīng)力退火與回火相似，去應(yīng)力退火總是把鋼和鐵加熱到相變溫度下限以下的某一溫度。對(duì)于有色金屬，這個(gè)溫度可以是稍高于室溫，也可以達(dá)到幾百度，取決于合金的種類和期望去除的應(yīng)力的大小。去應(yīng)力退火的主要目的是消除在模鑄、軋制、機(jī)加工、焊接等過(guò)程中在工件中產(chǎn)生的應(yīng)力。通常這一過(guò)程是把工件加熱到預(yù)先設(shè)定的溫度并保持足夠長(zhǎng)的時(shí)間來(lái)降低殘留的應(yīng)力(這是一個(gè)與時(shí)間和溫度有關(guān)的工序)。接下來(lái)，以比較慢的速度冷卻以避免產(chǎn)生新的應(yīng)力。Text&Translation5）去應(yīng)力退火30ComplexSentenceAnalysis[1]Itisknownthattheeutectoidsteel(T80)underequilibriumconditionscontains，allausteniteabove723℃，whereasbelow，itispearlite．我們知道共析鋼(T80)在平衡條件下，在723℃以上時(shí)全為奧氏體，而低于此溫度，則為珠光體。①that：引導(dǎo)主語(yǔ)從句，itisknownthat譯為“我們知道”。②eutectoidsteel：共析鋼③below：指低于723℃。whereasbelow句是個(gè)省略句，完整的句子為whereasitisbelow723℃。ComplexSentenceAnalysis[1]I31ComplexSentenceAnalysis[2]Thesepointsarethenplottedonagraphwithtimeandtemperatureastheaxes．然后把這些點(diǎn)繪制在一條以時(shí)間和溫度為坐標(biāo)軸的曲線上。Axes:軸，此處為坐標(biāo)軸。ComplexSentenceAnalysis[2]T32ComplexSentenceAnalysis[3]Thisisfollowedbycoolinginstillairtoatleastsometemperaturewellbelowitstransformationtemperaturerange．接下來(lái)在不流動(dòng)的空氣中冷卻到至少比相變溫度低得多的某一溫度。①follow：接著，跟著②this：代替上一句話的內(nèi)容，先heatingaferrousalloy...，接下來(lái)，再cooling...ComplexSentenceAnalysis[3]T33KeytoExercisesⅠ.TranslatethefollowingphrasesintoChineseorEnglish.1.金屬的熱處理2.Transformationcurves3.奧氏體4.pearlite5.滲碳體6.normalizing7.退火8.quenching9.回火10.stressrelievingKeytoExercisesⅠ.Translatet34KeytoExercisesⅡ.MarkthefollowingstatementwithTrue(T)orFalse(F)accordingtothetext.1.T2.F3.T4.T5.TKeytoExercisesⅡ.Markthefo35KeytoExercisesⅢ.Fillintheblankswiththesuitablewordsorphrasesgivenbelow.1.atagiventemperature2.Itisknown3.Toformpearlite4.itispossible5.Throughthesepoints6.SimilarlyKeytoExercisesⅢ.Fillinthe36KeytoExercisesⅣ.TranslatetheChinesepartsgiveninthebracketsintoEnglish.1.coolingatasuitablerate2.inaliquidorgaseousmedium3.Serruptedquenchingselectivequenching，sprayquenching,andtimequenching5.theaustenitizedandquench-hardenedsteelorironKeytoExercisesⅣ.Translateth37Theend!Theend!38Unit13HeatTreatmentofMetalUnit13HeatTreatmentofMeta39ContentsNewWords&Expressions

Text&TranslationComplexSentenceAnalysisKeytoExercisesContentsNewWords&Expression40NewWords&Expressionsforge[f?:d?]v.鑄造,偽造transformation[?tr?nsf?'mei??n]n.變換，轉(zhuǎn)換，相變eutectoid[ju:'tekt?id]adj.類似共熔體的，共析的austenite['?stinait]n.奧氏體pearlite['p?:lait]n.珠光體cementite[si'mentait]n.滲碳體NewWords&Expressionsforge41NewWords&Expressionsmartensitic['mɑ:t?n?zaitik]adj.馬氏體的stressrelieving消除應(yīng)力，低溫退火tempering['temp?ri?]n.回火normalizing['n?:m?laizi?]n.正火ferrousalloy鐵合金still[stil]adj.不動(dòng)的，靜止的 fullannealing完全退火 notably['n?ut?bli]adv.顯著地,特別是NewWords&Expressionsmarten42NewWords&Expressionsaustenitize['?stinitaiz]v.奧氏體化，使成奧氏體denote[di'n?ut]v.指示，表示，概述machinability[m?'?i:n?biliti]n.切削加工性，機(jī)械加工性能facilitation[f??sili'tei?n]n.容易化，助長(zhǎng)，便于in-process['pr?uses]adj.(加工、處理)過(guò)程中的qualification[?kw?lifi'kei??n]n.資格,條件,限制,限定quenching[kwent?]n.淬火NewWords&Expressionsausten43NewWords&Expressionsbrine[brain]n.鹽水caustic['k?:stik]adj.腐蝕性的,堿性的aqueous['eikwi?s]adj.水的,水成的warp[w?:p]n.翹曲，變形fogquenching噴霧淬火interruptedquenching分級(jí)淬火selectivequenching局部淬火quench-hardened['kwent??hɑ:dnd]adj.淬硬的processannealing中間退火，工序間退火NewWords&Expressionsbrine[44Text&TranslationThegenerallyaccepteddefinitionforheattreatingmetalsandmetalalloysis“heatingandcoolingasolidmetaloralloyinawaysoastoobtainspecificconditionsand/orproperties.”Heatingforthesolepurposeofhotworking(asinforgingoperations)isexcludedfromthisdefinition.Likewise，thetypesofheattreatmentthataresometimesusedforproductssuchasglassorplasticsarealsoexcludedfromcoveragebythisdefinition.Text&TranslationThegenerall45Text&Translation1.TransformationCurvesHeattreatmentbasesonthetime—temperature—transformationcurvesorTTTcurves;allthethreeparametersareplottedinasinglediagram.Becauseoftheshapeofthecurves，theyarealsosometimescalledC-curvesorS-curves.Fig.13.1showstheisothermaldecompositiondiagramofT80steel.Text&Translation1.Transforma46Text&TranslationToplotTTTcurves，theparticularsteelisheldatagiventemperatureandthestructureisexaminedatpredeterminedintervalstorecordtheamountoftransformationtakenplace.［1］Itisknownthattheeutectoidsteel(T80)underequilibriumconditionscontains，allausteniteabove723℃,whereasbelow，itispearlite.Toformpearlite，thecarbonatomsshoulddiffusetoformcementite.Thediffusionbeingarateprocess，wouldrequiresufficienttimeforcompletingtransformationofaustenitetopearlite.Fromdifferentsamples，itispossibletonotetheamountofthetransformationtakingplaceatanytemperature.［2］Thesepointsarethenplottedonagraphwithtimeandtemperatureastheaxes.Throughthesepoints，transformationcurvescanbeplottedasshowninFig.13.1foreutectoidsteel.Text&TranslationToplotTTT47Text&TranslationThecurveatextremeleftrepresentsthetimerequiredforthetransformationofaustenitetopearlitetostartatanygiventemperature.Similarly，thecurveatextremerightrepresentsthetimewhichisrequiredforcompletingthetransformation.Thepointsrepresentingpartialtransformationarebetweenthetwocurves.ThestartandfinishofmartensitictransformationarerepresentedbythehorizontallinesMsandMf.Text&TranslationThecurveat48Fig.13-1IsothermalDecompositionDiagramofT80SteelFig.13-1IsothermalDecompos49Text&Translation2.ClassificationofHeatTreatingProcessesInsomeinstances，heattreatmentproceduresareclearcutintermsoftechniqueandapplication，whileinotherinstances，descriptionsorsimpleexplanationsareinsufficientbecausethesametechniquefrequentlymaybeusedtoobtaindifferentobjectives.Forexample，stressrelievingandtemperingareoftenaccomplishedwiththesameequipmentandbyuseofidenticaltimeandtemperaturecycles.Theobjectives，however，aredifferentforthetwoprocesses.Thefollowingdescriptionsoftheprincipalheattreatingprocessesaregenerallyarrangedaccordingtotheirinterrelationships.Text&Translation2.Classifica50Text&Translation1)NormalizingNormalizingmeansheatingaferrousalloytoasuitabletemperature(usually50°Fto100°For28°Cto56°C)aboveitsspecificuppertransformationtemperature.［3］Thisisfollowedbycoolinginstillairtoatleastsometemperaturewellbelowitstransformationtemperaturerange.Forlowcarbonsteels，theresultingstructureandpropertiesarethesameasthoseachievedbyfullannealing；formostferrousalloys，normalizingandannealingaredifferent.Text&Translation1)Normalizin51Text&TranslationNormalizingusuallyisusedasaconditioningtreatment，notablyforrefiningthegrainsofsteelsthathavebeensubjectedtohightemperaturesforforgingorotherhotworkingoperations.Thenormalizingprocessusuallyissucceededbyanotherheattreatingoperationsuchasaustenitizingforhardening，annealing，ortempering.Text&TranslationNormalizing52Text&Translation2)AnnealingAnnealingisagenerictermdenotingaheattreatmentthatconsistsofheatingtoandholdingatasuitabletemperaturefollowedbycoolingatasuitablerate.Itisusedprimarilytosoftenmetallicmaterials，butalsotosimultaneouslyproducedesiredchangesinotherpropertiesorinmicrostructure.Thepurposeofsuchchangesmaybe，butisnotconfinedto，improvementofmachinability，facilitationofcoldwork(knownasinprocessannealing)，improvementofmechanicalorelectricalproperties，ortoincreasedimensionalstability.Whenappliedsolelytorelievestresses，itcommonlyiscalledstressreliefannealing，synonymouswithstressrelieving.Whentheterm“annealing”isappliedtoferrousalloyswithoutqualification，itmeansfullannealing.Thisisachievedbyheatingabovethealloy’stransformationtemperature，thenapplyingacoolingcyclewhichprovidesmaximumsoftness.Thiscyclemayvarywidely，dependingoncompositionandcharacteristicsofthespecificalloy.Text&Translation2)Annealing53Text&Translation3)QuenchingQuenchingistherapidcoolingofasteeloralloyfromtheaustenitizingtemperaturebyimmersingtheworkpieceinaliquidorgaseousmedium.Quenchingmediacommonlyusedincludewater，5%brine，5%causticinanaqueoussolution，oil，polymersolutions，orgas(usuallyairornitrogen).Selectionofaquenchingmediumdependslargelyonthehardenabilityofthematerialandthemassofthematerialbeingtreated(principallysectionthickness).Text&Translation3)Quenching54Text&TranslationThecoolingcapabilitiesoftheabovelistedquenchingmediadiffersalot.Inselectingaquenchingmedium，itisbesttoavoidasolutionthathasmorecoolingpowerthanisneededtoachievetheresults，thusminimizingthepossibilityofcrackingandwarpofthepartsbeingtreated.Modificationsofthetermquenchingincludedirectquenching，fogquenching，hotquenching，interruptedquenching，selectivequenching，sprayquenching，andtimequenching.Text&TranslationThecooling55Text&Translation4)TemperingInheattreatingofferrousalloys，temperingconsistsofreheatingtheaustenitizedandquenchhardenedsteelorirontosomepreselectedtemperaturethatisbelowthelowertransformationtemperature(generallybelow1300°For705°C).Temperingoffersameansofobtainingvariouscombinationsofmechanicalproperties.Temperingtemperaturesusedforhardenedsteelsareoftennohigherthan300°F(150°C).Theterm“tempering”shouldnotbeconfusedwitheitherprocessannealingorstressrelieving.Eventhoughtimeandtemperaturecyclesforthethreeprocessesmaybethesame，theconditionsofthematerialsbeingprocessedandtheobjectivesmaybedifferent.Text&Translation4)Tempering56Text&Translation5)StressrelievingLiketempering，stressrelievingisalwaysdonebyheatingtosometemperaturebelowthelowertransformationtemperatureforsteelsandirons.Fornonferrousmetals，thetemperaturemayvaryfromslightlyaboveroomtemperaturetoseveralhundreddegrees，dependingonthealloyandtheamountofstressreliefthatisdesired.Text&Translation5)Stressrel57Text&TranslationTheprimarypurposeofstressrelievingistorelievestressesthathavebeenimpartedtotheworkpiecefromsuchprocessesasforming，rolling，machiningorwelding.Theusualprocedureistoheatworkpiecestothepreestablishedtemperaturelongenoughtoreducetheresidualstresses(thisisatimeandtemperaturedependentoperation)toanacceptablelevel；thisisfollowedbycoolingatarelativelyslowratetoavoidcreationofnewstresses.Text&TranslationTheprimary58Text&Translation普遍認(rèn)同的對(duì)金屬及合金熱處理的定義是，以一定的方式加熱或和冷卻固態(tài)金屬或合金以達(dá)到一定的條件和/或獲得某些性能。以熱加工(如鍛造)為目的的加熱，不在此定義之列。同樣地，有時(shí)用于生產(chǎn)諸如玻璃或塑料制品的熱處理也不屬于該定義的范疇。Text&Translation普遍認(rèn)同的對(duì)金屬及合金熱59Text&Translation1.相變曲線熱處理的基礎(chǔ)分別是時(shí)間-溫度-相變曲線，即TTT曲線，3個(gè)參數(shù)都繪制在一個(gè)圖中。根據(jù)曲線的形狀特點(diǎn)，分別稱為C曲線或S曲線。如圖13-1所示為共析鋼的等溫轉(zhuǎn)變曲線圖。Text&Translation1.相變曲線60Text&Translation為了繪制TTT曲線，將特定的鋼置于給定溫度下，以預(yù)先確定的時(shí)間間隔檢查其結(jié)構(gòu)，記錄發(fā)生相變的量。我們知道共析鋼(C80)在平衡條件下，在723

℃以上時(shí)全為奧氏體，而低于此溫度，則為珠光體。為了形成珠光體，碳原子將產(chǎn)生擴(kuò)散形成滲碳體。擴(kuò)散是一種漸進(jìn)過(guò)程，需要足夠的時(shí)間完成奧氏體向珠光體的轉(zhuǎn)變。對(duì)于不同的樣品，可以記錄下在任一溫度時(shí)產(chǎn)生相變的量。然后把這些點(diǎn)繪制在一條以時(shí)間和溫度為坐標(biāo)軸的曲線上。通過(guò)這些點(diǎn)就可以得到圖13-1所示的共析鋼的相變曲線。左邊的曲線表示任一給定溫度下奧氏體開(kāi)始轉(zhuǎn)變?yōu)橹楣怏w所需要的時(shí)間。類似地，右邊的曲線表示相變完成所需要的時(shí)間。兩條曲線之間是表示部分相變的點(diǎn)。兩條水平線Ms和Mf表示馬氏體轉(zhuǎn)變的開(kāi)始和結(jié)束。Text&Translation為了繪制TTT曲線，將61Text&Translation圖13-1共析鋼的等溫轉(zhuǎn)變曲線圖Text&Translation圖13-1共析鋼的等溫62Text&Translation2.熱處理工藝的分類在某些場(chǎng)合熱處理過(guò)程可以根據(jù)其工藝和應(yīng)用明確地區(qū)分開(kāi)來(lái)。而在另一些場(chǎng)合，因?yàn)橥瑯拥墓に嚦３？梢杂脕?lái)達(dá)到不同的目的，因此對(duì)該術(shù)語(yǔ)的說(shuō)明和簡(jiǎn)單的解釋是不夠的。例如：消除應(yīng)力的熱處理和回火處理常常使用同樣的設(shè)備、同樣的時(shí)間和溫度循環(huán)來(lái)實(shí)現(xiàn)，但這兩種工藝的目的是不同的。下面對(duì)主要熱處理工藝的描述大體上是按其相互關(guān)系來(lái)安排的。Text&Translation2.熱處理工藝的分類63Text&Translation1）正火把鐵類合金加熱到指定的相變溫度上限以上(通常50～100F或28～56°C)的合適溫度。接下來(lái)在不流動(dòng)的空氣中冷卻到至少比相變溫度低得多的某一溫度。對(duì)于低碳鋼，得到的結(jié)構(gòu)和性能與完全退火相同。而對(duì)于大多數(shù)鐵類合金，正火和退火意義不同。正火一般作為起調(diào)節(jié)作用的熱處理工藝，特別是用于細(xì)化在鍛造或其他熱加工工藝中經(jīng)受了高溫的鋼的晶粒。正火處理之后通常還要接著進(jìn)行淬火、退火或回火等進(jìn)行奧氏體化。Text&Translation1）正火64Text&Translation2）退火熱處理的一個(gè)通用術(shù)語(yǔ)，指的是加熱到一定溫度并保溫，然后以合適的速度冷卻，主要用于降低金屬材料的硬度，同時(shí)在其他性能或顯微組織方面產(chǎn)生一些理想的變化。這種變化的目的是改善其機(jī)械加工性、便于冷加工(被稱為中間退火)，改善機(jī)械或電性能，或增加工件的尺寸穩(wěn)定性，但也不僅僅局限于此。如果僅僅用于消除應(yīng)力，就叫做去應(yīng)力退火，與應(yīng)力消除(stressrelieving)熱處理是同義詞。Text&Translation2）退火65Text&Translation當(dāng)“退火”這個(gè)術(shù)語(yǔ)用于鐵類合金而又無(wú)其他限制條件時(shí)，指的是完全退火。這種處理是把合金加熱到其相變溫度以上，再進(jìn)行循環(huán)冷卻以使硬度下降最大。冷卻過(guò)程的變化范圍較大，要看具體合金的成分