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1、附錄1：外文原文TheimpregnabilityofmaterialTheimpregnabilityofamaterialusuallydefinedintermsoffourfactors:（1）.Surfacefinishandintegrityofthemachinedpart;（2）.Toollifeobtained;（3）.Forceandpowerrequirements;（4）.Chipcontrol.Thus,goodimpregnabilitygoodsurfacefinishandintegrity,longtoollife,andlo
2、wforceAndpowerrequirements.Asforchipcontrol,longandthin(stringy)curedchips,ifnotbrokenup,canseverelyinterferewiththecuttingoperationbybecomingentangledinthecuttingzone.Becauseofthecomplexnatureofcuttingoperations,itisdifficulttoestablishrelationshipsthatquantitativelydefinetheimpreg
3、nabilityofamaterial.Inmanufacturingplants,toollifeandsurfaceroughnessaregenerallyconsideredtobethemostimportantfactorsinimpregnability.Althoughnotusedmuchanymore,approximateimpregnabilityratingsareavailableintheexamplebelow.1.ImpregnabilityOfSteelsBecausesteelsareamongthemostimporta
4、ntengineeringmaterials,theirimpregnabilityhasbeenstudiedextensively.Theimpregnabilityofsteelshasbeenmainlyimprovedbyaddingleadandsulfurtoobtainso-calledfree-machiningsteels.SulfuricandReauthorizedsteels.Sulfurinsteelsformsmanganesesulfideinclusions(second-phaseparticles),whichactass
5、tressraisersintheprimaryshearzone.Asaresult,thechipsproducedbreakupeasilyandaresmall;thisimprovesimpregnability.Thesize,shape,distribution,andconcentrationoftheseinclusionssignificantlyinfluenceimpregnability.Elementssuchastelluriumandselenium,whicharebothchemicallysimilartosulfur,a
6、ctasinclusionmodifiersinSulfuricsteels.Phosphorusinsteelshastwomajoreffects.Itstrengthensthedeterring,causingincreasedhardness.Hardersteelsresultinbetterchipformationandsurfacefinish.Notethatsoftsteelscanbedifficulttomachine,withbuilt-upedgeformationandpoorsurfacefinish.Thesecondeff
7、ectisthatincreasedhardnesscausestheformationofshortchipsinsteadofcontinuousstringyones,therebyimprovingmachinability.LeadedSteels.Ahighpercentageofleadinsteelssolidifiesatthetipofmanganesesulfideinclusions.Innon-resulfurizedgradesofsteel,leadtakestheformofdispersedfineparticles.Lead
8、isinsolubleiniron,c
