P46Chapterunit5Heattreatingoftoolsteels工具钢的热处理Thepurposeofheattreatmentistocontrolthepropertiesofametaloralloythroughthealterationofthestructureofthemetaloralloybyheatingittodefinitetemperaturesandcoolingatvariousrates.Thiscombinationofheatingandcontrolledcoolingdeterminesnotonlythenatureanddistributionofthemicroconstituents,whichinturndeterminetheproperties,butalsothegrainsize.热处理的目的是通过把金属或合金加热到预定的温度并以不同的速率冷却，来改变金属或合金的结构，从而控制它们的性质。加热和可控的冷却相结合不仅决定着材料中微观组织的性质和分布（这些反过来也决定了材料的性质），也决定着内部晶粒的大小。Heattreatmentshouldimprovethealloyormetalfortheserviceintended.Someofthevariouspurposesofheattreatingareasfollows:热处理将会改善合金或金属需要的性能。一些各种各样的热处理的目的如下：1.Toremovestrainsaftercoldworking.2.Toremoveinternalstresssuchasthoseproducedbydrawing,bending,orwelding.3.Toincreasethehardnessofthematerial.4.Toimprovemachinability.5.Toimprovethecuttingcapabilitiesoftools.6.Toincreasewear-resistingproperties.7.Tosoftenthematerial,asinannealing.Toimproveorchangepropertiesofamaterialsuchascorrosionresistance,heatresistance,magneticproperties,orotherssuchasrequired.1.去除冷加工后的应变。2.去除内应力，如用冲压、完全或焊接成型的工件。3.增加材料的硬度。4.增加机械加工性能。5.增加工具的切割性能。6.增加抗磨性。7.软化材料，如退火。改善或改变某种材料的性能，比如抗腐蚀，耐高温，磁性或者其它需要的性能。TreatmentofFerrousMaterials.Ironisthemajorconstituentinthesteelusedintooling,towhichcarbonisaddedinorderthatthesteelmayharden.Alloysareputintosteeltoenableittodeveloppropertiesnotpossessedbyplaincarbonsteel,suchastheabilitytohardeninoilorair,increasedwearresistance,highertoughness,andgreatersafetyinhardening.铁材料的热处理铁是用于制作工具的钢材的主要成分，其中加入碳是为了使钢变硬。加入合金是为了使其具有其它性能而不是普通的碳素钢，比如在油或空气中硬化的性能，耐磨性的提高，高的韧性和在淬火中的良好安全性.Heattreatmentforferrousmaterialsinvolvesseveralimportantoperationswhicharecustomarilyreferredtoundervariousheadings,suchasnormalizing,spheroidizing,stressrelieving,annealing,hardening,tempering,andcasehardening.铁材料的热处理包括一些重要的操作，这些操作一般涉及到各种类别，比如：正火，球化，应力消除，退火，淬火，回火及表面硬化等。Normalizinginvolvesheatingthematerialtoatemperatureofabout100~200°F(55~100°C)abovethecriticalrangeandcoolinginstillair.Thisisabo