机械工程材料双语课件第五章.ppt

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1、§5Heattreatmentprocessofsteels-Phasetransformationinsteels钢的热处理—钢中的相变1.IntroductionHeattreatmentisanimportantwaytoenhancepropertiesofmetalmaterials.Threestages:heating,heatpreservationandcooling.Byvaryingthemannerinwhichsteelsareheatedandcooled,differentcombinationsofmechanicalpropertie

2、sforsteelscanbeobtained.加热与冷却的方式不同，可得到具有不同力学性能的钢。Inthissection,weshalldiscusssomeofthestructuralandpropertychangesthattakeplaceduringsomeoftheimportantheattreatmentsgiventoplain-carbonsteels.（普碳钢热处理过程中的结构与性能的变化。）2.Transformationofsteelsinheatingandcoolingprocesses(钢在加热和冷却时的组织转变)Austeniti

3、zing:steelsareusuallyheatedtogetaustenitewhensubjectedtoheattreatment.Thenaustenitetransformsintodifferentstructureswhencooling.奥氏体化(Austenitizing):热处理过程中将钢加热得到奥氏体的过程。Ld’Ld图2.4简化的Fe—Fe3C相图0.02180.772.114.36.69Wc%15001400130012001100100090070010000.20.40.60.81.01.52.02.53.03.54.04.55.05.5

4、6.0温度t/℃FF+Fe3CIIIQ912GF+AA+Fe3CIILC1538A1227DL+AL+Fe3CI1148EFAA+Fe3CII+LdFe3CI+LdS727PKPF+PP+Fe3CⅡP+Fe3CⅡ+Ld’Fe3CI+Ld’过冷奥氏体Supercooledaustenite:theunstable,temporallyexistentaustenitebelowtheeutectoidtemperature.过冷奥氏体：共析温度下暂存的、不稳定的奥氏体。过冷奥氏体冷却方式Amongthethreestagesofsteelheattreatment,the

5、coolingstageisthemostvitalone.Twocoolingways:isothermalcoolingtransformation;continuous-coolingtransformation<1>Isothermalcoolingtransformation(等温冷却转变)IsothermaltransformationdiagramisalsocalledCcurve.CcurveindicateswhatproductsformwhenAofeutectoidsteelsisrapidlycooledtothetemperaturesbe

6、lowtheeutectoidtemperaturesandthenisothermallytransformed.Ld’Ld图2.4简化的Fe—Fe3C相图0.02180.772.114.36.69Wc%15001400130012001100100090070010000.20.40.60.81.01.52.02.53.03.54.04.55.05.56.0温度t/℃FF+Fe3CIIIQ912GF+AA+Fe3CIILC1538A1227DL+AL+Fe3CI1148EFAA+Fe3CII+LdFe3CI+LdS727PKPF+PP+Fe3CⅡP+Fe3CⅡ+Ld

7、’Fe3CI+Ld’①ConstructionandanalysisofCcurve(C曲线的建立与分析)共析钢，若干小试样，加热奥氏体化，保温后等温冷却，分别测出过冷奥氏体转变的开始、终止时间和产物转变量。A1—临界温度左—转变开始线右—转变终了线MS（Mf）—马氏体转变开始（终了线）奥氏体MSA→MⅠ-PⅡ-SⅢ-T转变开始点转变终止点A1时间lgτ温度/℃9008007006005004003002001000曲线的测定与绘制Determinationandrenderingofthecurve·····Criticaltemper