Vibyga机械制造及自动化毕业设计外语文献翻译.doc

Vibyga机械制造及自动化毕业设计外语文献翻译.doc

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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）,theirmachinabilityhasbeenstudiedextensively.Themachinabilityofsteelshasbeenmainlyimprovedbyaddingleadandsulfurtoobtainso-calledfree-machiningsteels.

ResulfurizedandRephosphorizedsteels.Sulfurinsteelsformsmanganesesulfideinclusions（second-phaseparticles）,whichactasstressraisersintheprimaryshearzone.Asaresult,thechipsproducedbreakupeasilyandaresmall;thisimprovesmachinability.Thesize,shape,distribution,andconcentrationoftheseinclusionssignificantlyinfluencemachinability.Elementssuchastelluriumandselenium,whicharebothchemicallysimilartosulfur,actasinclusionmodifiersinresulfurizedsteels.

Phosphorusinsteelshastwomajoreffects.Itstrengthenstheferrite,causingincreasedhardness.Hardersteelsresultinbetterchipformationandsurfacefinish.Notethatsoftsteelscanbedifficulttomachine,withbuilt-upedgeformationandpoorsurfacefinish.Thesecondeffectisthatincreasedhardnesscausestheformationofshortchipsinsteadofcontinuousstringyones,therebyimprovingmachinability.

LeadedSteels.Ahighpercentageofleadinsteelssolidifiesatthetipofmanganesesulfideinclusions.Innon-resulfurizedgradesofsteel,leadtakestheformofdispersedfineparticles.Leadisinsolubleiniron,copper,andaluminumandtheiralloys.Becauseofitslowshearstrength,therefore,leadactsasasolidlubricant（Section32.11）andissmearedoverthetool-chipinterfaceduringcutting.Thisbehaviorhasbeenverifiedbythepresenceofhighconcentrationsofleadonthetool-sidefaceofchipswhenmachiningleadedsteels.

Whenthetemperatureissufficientlyhigh-forinstance,athighcuttingspeedsandfeeds（Section20.6）—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,especiallyathighcuttingspeeds.

StainlessSteels.Austenitic（300series）steelsaregenerallydifficulttomachine.Chattercanbesproblem,necessitatingmachinetoolswithhighstiffness.However,ferriticstainlesssteels（also300series）hav