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1、附录1：外文原文ThemachinabilityofmaterialThemachinabilityofamaterialusuallydefinedintermsoffourfactors:（1）.Surfacefinishandintegrityofthemachinedpart;（2）.Toollifeobtained;（3）.Forceandpowerrequirements;（4）.Chipcontrol.Thus,goodmachinabilitygoodsurfacefinishandintegrity,longtoollif
2、e,andlowforceAndpowerrequirements.Asforchipcontrol,longandthin(stringy)curedchips,ifnotbrokenup,canseverelyinterferewiththecuttingoperationbybecomingentangledinthecuttingzone.Becauseofthecomplexnatureofcuttingoperations,itisdifficulttoestablishrelationshipsthatquantitative
3、lydefinethemachinabilityofamaterial.Inmanufacturingplants,toollifeandsurfaceroughnessaregenerallyconsideredtobethemostimportantfactorsinmachinability.Althoughnotusedmuchanymore,approximatemachinabilityratingsareavailableintheexamplebelow.1.MachinabilityOfSteelsBecausesteel
4、sareamongthemostimportantengineeringmaterials,theirmachinabilityhasbeenstudiedextensively.Themachinabilityofsteelshasbeenmainlyimprovedbyaddingleadandsulfurtoobtainso-calledfree-machiningsteels.ResulfurizedandRephosphorizedsteels.Sulfurinsteelsformsmanganesesulfideinclusio
5、ns(second-phaseparticles),whichactasstressraisersintheprimaryshearzone.Asaresult,thechipsproducedbreakupeasilyandaresmall;thisimprovesmachinability.Thesize,shape,distribution,andconcentrationoftheseinclusionssignificantlyinfluencemachinability.Elementssuchastelluriumandsel
6、enium,whicharebothchemicallysimilartosulfur,actasinclusionmodifiersinresulfurizedsteels.Phosphorusinsteelshastwomajoreffects.Itstrengthenstheferrite,causingincreasedhardness.Hardersteelsresultinbetterchipformationandsurfacefinish.Notethatsoftsteelscanbedifficulttomachine,w
7、ithbuilt-upedgeformationandpoorsurfacefinish.Thesecondeffectisthatincreasedhardnesscausestheformationofshortchipsinsteadofcontinuousstringyones,therebyimprovingmachinability.LeadedSteels.Ahighpercentageofleadinsteelssolidifiesatthetipofmanganesesulfideinclusions.Innon-resu
8、lfurizedgradesofsteel,leadtakestheformofdispersedfineparticles.Leadisinsolubleiniron,copp
