完整版机械制造及自动化毕业设计外语文献翻译.docx
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完整版机械制造及自动化毕业设计外语文献翻译.docx
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完整版机械制造及自动化毕业设计外语文献翻译
攀枝花学院本科毕业设计(论文)
外文译文
院(系):
机电工程学院
专业:
机械设计制造及其自动化
姓名:
王中蔚
学号:
ZJD02043
指导教师评语:
签名:
年月日
外语文献翻译
摘自:
《制造工程与技术(机加工)》(英文版)
《ManufacturingEngineeringandTechnology—Machining》
机械工业出版社2004年3月第1版
美s.卡尔帕基安(Seropekalpakjian)
s.r施密德(StevenR.Schmid)著
原文:
20.9MACHINABILITY
Themachinabilityofamaterialusuallydefinedintermsoffourfactors:
1、Surfacefinishandintegrityofthemachinedpart;
2、Toollifeobtained;
3、Forceandpowerrequirements;
4、Chipcontrol.
Thus,goodmachinabilitygoodsurfacefinishandintegrity,longtoollife,andlowforceAndpowerrequirements.Asforchipcontrol,longandthin(stringy)curedchips,ifnotbrokenup,canseverelyinterferewiththecuttingoperationbybecomingentangledinthecuttingzone.
Becauseofthecomplexnatureofcuttingoperations,itisdifficulttoestablishrelationshipsthatquantitativelydefinethemachinabilityofamaterial.Inmanufacturingplants,toollifeandsurfaceroughnessaregenerallyconsideredtobethemostimportantfactorsinmachinability.Althoughnotusedmuchanymore,approximatemachinabilityratingsareavailableintheexamplebelow.
20.9.1MachinabilityOfSteels
Becausesteelsareamongthemostimportantengineeringmaterials(asnotedinChapter5),theirmachinabilitystudiedextensively.Themachinabilityofsteelsmainlyimprovedbyaddingleadandsulfurtoobtainso-calledfree-machiningsteels.
ResulfurizedandRephosphorizedsteels.Sulfurinsteelsformsmanganesesulfideinclusions(second-phaseparticles),whichactasstressraisersintheprimaryshearzone.Asaresult,thechipsproducedbreakupeasilyandaresmall;thisimprovesmachinability.Thesize,shape,distribution,andconcentrationoftheseinclusionssignificantlyinfluencemachinability.Elementssuchastelluriumandselenium,whicharebothchemicallysimilartosulfur,actasinclusionmodifiersinresulfurizedsteels.
Phosphorusinsteelsbetterchipformationandsurfacefinish.Notethatsoftsteelscanbedifficulttomachine,withbuilt-upedgeformationandpoorsurfacefinish.Thesecondeffectisthatincreasedofshortchipsinsteadofcontinuousstringyones,therebyimprovingmachinability.
LeadedSteels.Asteelssolidifiesatthetipofmanganesesulfideinclusions.Innon-resulfurizedgradesofsteel,leadtakestheformofdispersedfineparticles.Leadisinsolubleiniron,copper,andaluminumandtheiralloys.Becauseofitslowshearstrength,therefore,leadactsasasolidlubricant(Section32.11)andissmearedoverthetool-chipinterfaceduringcutting.Thisbehaviorverifiedbythepresenceofthetool-sidefaceofchipswhenmachiningleadedsteels.
Whenthetemperatureissufficiently20.6)—theleadmeltsdirectlyinfrontofthetool,actingasaliquidlubricant.Inadditiontothiseffect,leadlowerstheshearstressintheprimaryshearzone,reducingcuttingforcesandpowerconsumption.Leadcanbeusedineverygradeofsteel,suchas10xx,11xx,12xx,41xx,etc.LeadedsteelsareidentifiedbytheletterLbetweenthesecondandthirdnumerals(forexample,10L45).(Notethatinstainlesssteels,similaruseoftheletterLmeans“lowcarbon,”aconditionthatimprovestheircorrosionresistance.)
However,becauseleadisawell-knowntoxinandapollutant,thereareseriousenvironmentalconcernsaboutitsuseinsteels(estimatedat4500tonsofleadconsumptioneveryyearintheproductionofsteels).Consequently,thereisacontinuingtrendtowardeliminatingtheuseofleadinsteels(lead-freesteels).Bismuthandtinarenowbeinginvestigatedaspossiblesubstitutesforleadinsteels.
Calcium-DeoxidizedSteels.Animportantdevelopmentiscalcium-deoxidizedsteels,inwhichoxideflakesofcalciumsilicates(CaSo)areformed.Theseflakes,inturn,reducethestrengthofthesecondaryshearzone,decreasingtool-chipinterfaceandwear.Temperatureiscorrespondinglyreduced.Consequently,thesesteelsproducelesscraterwear,especiallyatbesproblem,necessitatingmachinetoolswith--resistanttoolmaterials.
TheEffectsofOtherElementsinSteelsonMachinability.Thepresenceofaluminumandsiliconinsteelsisalwaystoformaluminumoxideandsilicates,whicharesteels.
Carbonandmanganesethemachinabilityofsteels,dependingontheircomposition.Plainlow-carbonsteels(lessthan0.15%C)canproducepoorsurfacefinishbyformingabuilt-upedge.Caststeelsaremoreabrasive,althoughtheirmachinabilityissimilartothatofwroughtsteels.Toolanddiesteelsareverydifficulttomachineandusuallyrequireannealingpriortomachining.Machinabilityofmoststeelsisimprovedbycoldworking,which.
Otheralloyingelements,suchasnickel,chromium,molybdenum,andvanadium,whichimprovethepropertiesofsteels,generallyreducemachinability.Theeffectofboron
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