《制造工程与技术(机加工)》

《制造 工程 路基工程安全技术交底工程项目施工成本控制工程量增项单年度零星工程技术标正投影法基本原理 与技术(机加工)》《制造工程与技术(机加工)》《制造工程与技术(机加工)》摘自:《制造工程与技术（机加工）》（英文版）ManufacturingEngineeringandTechnology—Machining》机械工业第一版社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：20.9MACHINABILITYThemachinabilityofamaterialusuallydefinedintermsoffourfactors:1、Surfacefinishandintegrityofthemachinedpart;2、Toollifeobtained;3、Forceandpowerrequirements;4、Chipcontrol.Thus,goodmachinabilitygoodsurfacefinishandintegrity,longtoollife,andlowforceandpowerrequirements.Asforchipcontrol,longandthin(stringy)curedchips,ifnotbrokenup,canseverelyinterferewiththecuttingoperationbybecomingentangledinthecuttingzone.Becauseofthecomplexnatureofcuttingoperations,itisdifficulttoestablishrelationshipsthatquantitativelydefinethemachinabilityofamaterial.Inmanufacturingplants,toollifeandsurfaceroughnessaregenerallyconsideredtobethemostimportantfactorsinmachinability.Althoughnotusedmuchanymore,approximatemachinabilityratingsareavailableintheexamplebelow.20.9.1MachinabilityOfSteelsBecausesteelsareamongthemostimportantengineeringmaterials(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.non-resulfurizedgradesofsteel,leadtakestheformofdispersedfineparticles.Leadisinsolubleiniron,copper,andaluminumandtheiralloys.Becauseofitslowshearstrength,therefore,leadactsasasolidlubricant(Section32.11)andissmearedoverthetool-chipinterfaceduringcutting.Thisbehaviorhasbeenverifiedbythepresenceofhighconcentrationsofleadonthetool-sidefaceofchipswhenmachiningleadedsteels.Whenthetemperatureissufficientlyhigh-forinstance,athighcuttingspeedsandfeeds(Section20.6)—theleadmeltsdirectlyinfrontofthetool,actingasaliquidlubricant.Inadditiontothiseffect,leadlowerstheshearstressintheprimaryshearzone,reducingcuttingforcesandpowerconsumption.Leadcabeusedineverygradeofsteel,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.Chattercanbeaproblem,necessitatingmachinetoolswithhighstiffness.However,ferriticstainlesssteels(also300series)havegoodmachinability.Martensitic(400series)steelsareabrasive,tendtoformabuilt-upedge,andrequiretoolmaterialswithhighhothardnessandcrater-wearresistance.Precipitation-hardeningstainlesssteelsarestrongandabrasive,requiringhardandabrasion-resistanttoolmaterials.TheEffectsofOtherElementsinSteelsonMachinability.Thepresenceofaluminumandsiliconinsteelsisalwaysharmfulbecausetheseelementscombinewithoxygentoformaluminumoxideandsilicateswhicharehardandabrasive.Thesecompoundsincreasetoolwearandreducemachinability.Itisessentialtoproduceandusecleansteels.Carbonandmanganesehavevariouseffectsonthemachinabilityofsteels,dependingontheircomposition.Plainlow-carbonsteels(lessthan0.15%C)canproducepoorsurfacefinishbyformingabuilt-upedge.Caststeelsaremoreabrasive,althoughtheirmachinabilityissimilartothatofwroughtsteels.Toolanddiesteelsareverydifficulttomachineandusuallyrequireannealingpriortomachining.Machinabilityofmoststeelsisimprovedbycoldworking,whichhardensthematerialandreducesthetendencyforbuilt-upedgeformation.Otheralloyingelements,suchasnickel,chromium,molybdenum,andvanadium,whichimprovethepropertiesofsteels,generallyreducemachinability.Theeffectofboronisnegligible.Gaseouselementssuchashydrogenandnitrogencanhaveparticularlydetrimentaleffectsonthepropertiesofsteel.Oxygenhasbeenshowntohaveastrongeffectontheaspectratioofthemanganesesulfideinclusions;thehighertheoxygencontent,thelowertheaspectratioandthehigherthemachinability.Inselectingvariouselementstoimprovemachinability,weshouldconsiderthepossibledetrimentaleffectsoftheseelementsonthepropertiesandstrengthofthemachinedpartinservice.Atelevatedtemperatures,forexample,leadcausesembrittlementofsteels(liquid-metalembrittlement,hotshortness;seeSection1.4.3),althoughatroomtemperatureithasnoeffectonmechanicalproperties.Sulfurcanseverelyreducethehotworkabilityofsteels,becauseoftheformationofironsulfide,unlesssufficientmanganeseispresenttopreventsuchformation.Atroomtemperature,themechanicalpropertiesofresulfurizedsteelsdependontheorientationofthedeformedmanganesesulfideinclusions(anisotropy).Rephosphorizedsteelsaresignificantlylessductile,andareproducedsolelytoimprovemachinability..20.9.2MachinabilityofVariousOtherMetalsAluminumisgenerallyveryeasytomachine,althoughthesoftergradestendtoformabuilt-upedge,resultinginpoorsurfacefinish.Highcuttingspeeds,highrakeangles,andhighreliefanglesarerecommended.Wroughtaluminumalloyswithhighsiliconcontentandcastaluminumalloysmaybeabrasive;theyrequirehardertoolmaterials.Dimensionaltolerancecontrolmaybeaprobleminmachiningaluminum,sinceithasahighthermalcoefficientofexpansionandarelativelylowelasticmodulus.Berylliumissimilartocastirons.Becauseitismoreabrasiveandtoxic,though,itrequiresmachininginacontrolledenvironment.Castgrayironsaregenerallymachinablebutare.Freecarbidesincastingsreducetheirmachinabilityandcausetoolchippingorfracture,necessitatingtoolswithhightoughness.Nodularandmalleableironsaremachinablewithhardtoolmaterials.Cobalt-basedalloysareabrasiveandhighlywork-hardening.Theyrequiresharp,abrasion-resistanttoolmaterialsandlowfeedsandspeeds.Wroughtcoppercanbedifficulttomachinebecauseofbuilt-upedgeformation,althoughcastcopperalloysareeasytomachine.Brassesareeasytomachine,especiallywiththeadditionpflead(leadedfree-machiningbrass).Bronzesaremoredifficulttomachinethanbrass.Magnesiumisveryeasytomachine,withgoodsurfacefinishandprolongedtoollife.Howevercareshouldbeexercisedbecauseofitshighrateofoxidationandthedangeroffire(theelementispyrophoric)Molybdenumisductileandwork-hardening,soitcanproducepoorsurfacefinish.Sharptoolsarenecessary.Nickel-basedalloysarework-hardening,abrasive,andstrongathightemperatures.Theirmachinabilityissimilartothatofstainlesssteels.Tantalumisverywork-hardening,ductile,andsoft.Itproducesapoorsurfacefinish;toolwearishigh.Titaniumanditsalloyshavepoorthermalconductivity(indeed,thelowestofallmetals),causingsignificanttemperatureriseandbuilt-upedge;theycanbedifficulttomachine.Tungstenisbrittle,strong,andveryabrasive,soitsmachinabilityislow,althoughitgreatlyimprovesatelevatedtemperatures.Zirconiumhasgoodmachinability.Itrequiresacoolant-typecuttingfluid,however,becauseoftheexplosionandfire.20.9.3MachinabilityofVariousMaterialsGraphiteisabrasive;itrequireshard,abrasion-resistant,sharptools.Thermoplasticsgenerallyhavelowthermalconductivity,lowelasticmodulus,andlowsofteningtemperature.Consequently,machiningthemrequirestoolswithpositiverakeangles(toreducecuttingforces),largereliefangles,smalldepthsofcutandfeed,relativelyhighspeeds,andpropersupportoftheworkpiece.Toolsshouldbesharp.Externalcoolingofthecuttingzonemaybenecessarytokeepthechipsfrombecomingstickingtothetools.Coolingcanusuallybeachievedwithajetofair,vapormist,orwater-solubleoils.Residualstressesmaydevelopduringmachining.Torelievethesestresses,machinedpartscanbeannealedforaperiodoftimeattemperaturesrangingfromtoto(),andthencooledslowlyanduniformlytoroomtemperature.Thermosettingplasticsarebrittleandsensitivetothermalgradientsduringcutting.Theirmachinabilityisgenerallysimilartothatofthermoplastics.Becauseofthefiberspresent,reinforcedplasticsareveryabrasiveandaredifficulttomachine.Fibertearing,pulling,andedgedelaminationaresignificantproblems;theycanleadtoseverereductionintheload-carryingcapacityofthecomponent.Furthermore,machiningofthesematerialsrequirescarefulremovalofmachiningdebristoavoidcontactwithandinhalingofthefibers.Themachinabilityofceramicshasimprovedsteadilywiththedevelopmentofnanoceramics(Section8.2.5)andwiththeselectionofappropriateprocessingparameters,suchasductile-regimecutting(Section22.4.2).Metal-matrixandceramic-matrixcompositescanbedifficulttomachine,dependingonthepropertiesoftheindividualcomponents,i.e.,reinforcingorwhiskers,aswellasthematrixmaterial.20.9.4ThermallyAssistedMachiningMetalsandalloysthataredifficulttomachineatroomtemperaturecanbemachinedmoreeasilyatelevatedtemperatures.Inthermallyassistedmachining(hotmachining),thesourceofheat—torch,inductioncoil,high-energybeam(suchaslaserorelectronbeam),orplasma—arcisforces,(b)increasedtoollife,(c)useofinexpensivecutting-toolmaterials,(d)highermaterial-removalrates,and(e)reducedtendencyforvibrationandchatter.Itmaybedifficulttoheatandmaintainauniformtemperaturedistributionwithintheworkpiece.Also,theoriginalmicrostructureoftheworkpiecemaybeadverselyaffectedbyelevatedtemperatures.Mostapplicationsofhotmachiningareintheturningofhigh-strengthmetalsandalloys,althoughexperimentsareinprogresstomachineceramicssuchassiliconnitride.SUMMARYMachinabilityisusuallydefinedintermsofsurfacefinish,toollife,forceandpowerrequirements,andchipcontrol.Machinabilityofmaterialsdependsnotonlyontheirintrinsicpropertiesandmicrostructure,butalsoonproperselectionandcontrolofprocessvariables.译文：切削加工性一种资料的切削加工性往常从四个方面来定义：1、已切削部分的 表 关于同志近三年现实表现材料材料类招标技术评分表图表与交易pdf视力表打印pdf用图表说话 pdf 面光洁度和表面完好性。2、刀具的寿命。3、切削力和切削的功率需求。4、切屑控制。由上述可知，好的切削加工性指的是好的表面光洁度和完好性，长的刀具寿命，低切削力和功率需求。至于切屑控制，修长而卷曲的切屑，假如没有实时清理，就会在切削区环绕，严重影响切削工序。因为切削工序的复杂性，所以很难成立一个定量确立一种资料切削加工性的关系式。在制造厂里，刀具寿命和表面粗拙度往常被以为是切削加工性中最重要的影响要素。只管切削性能指数使用的其实不多，但基本的切削性能指数在下边的资猜中仍旧被使用。钢的切削加工性因为钢是最重要的工程资料之一（如第5章所示），所以它的切削加工性已经被宽泛地研究过。经过加入铅和硫磺，能够使钢的切削加工性获得大幅度地提升。进而获得了所谓的高速切削钢。二次硫化钢和二次磷化钢硫在钢中形成硫化锰夹杂物（第二相粒子），这些夹杂物在第一剪切区形成应力集中元。其结果是使切屑简单断开而变小，进而改良了切削加工性。这些夹杂物的大小、形状、散布和集中程度明显的影响切削加工性。化学元素如碲和硒，其化学性质与硫近似，在二次硫化钢中起杂质改性作用。钢中的磷有两个主要的作用。第一它增强铁素体，增添硬度。越硬的钢，就会对切屑的形成和表面光洁度越有益。需要注意的是软钢是很难加工的，因为软钢加工简单产生积削瘤并且表面光洁度差。第二个作用是硬度增添会惹起短切屑的形成而不是连续修长的切屑的形成，所以提升切削加工性。铅钢钢中高含量的铅在硫化锰杂质尖端析出。在非二次硫化钢中，铅呈渺小而分别的颗粒。铅在铁、铜、铝和它们的合金中是不可以溶解的。因为它的低抗剪强度，铅在切削时充任固体润滑剂，被涂在刀具和切屑的分界处。这一特征已经被证明--在切削加工铅钢时，在刀具横向表面的切屑上有高浓度的铅存在。当温度足够高时——比如，在高的切削速度和进刀速度下——铅在刀具前直接融化，并且充任液体润滑剂。除了这个作用外，铅还能够降低第一剪切区中的剪应力，减小切削力和降低功率耗费。铅能用于各样型号的钢，比如10XX，11XX，12XX，41XX等等。铅钢由型号中第二和第三数码中的字母L辨别（比如，10L45）。（需要注意的是在不锈钢中，字母L指的是低碳，这是提升不锈钢耐腐化性的先决条件）。但是，因为铅是尽人皆知的毒素和污染物，所以在钢的使用中存在着严重的环境隐患（在钢产品中每年大概有4500吨的铅耗费）。于是，除去铅在钢中使用是一个必定的趋向（无铅钢）。铋和锡现正作为最可能代替钢中铅的物质而被人们所研究。脱氧钙钢一个重要的发展是脱氧钙钢，在脱氧钙钢中能够形成硅酸钙的氧化物片。这些片状物，能够减小第二剪切区中的应力，降低刀具和切屑分界处的摩擦和磨损。温度也相应地降低。于是，这类钢产生更小的月牙洼磨损，特别是在高速切削时更是这样。不锈钢往常奥氏体钢很难进行切削加工。振动可能是一个问题，这必需要求机床有足够的刚度。但是，铁素体不锈钢有很好的切削加工性。马氏体钢易磨蚀，易于形成积屑瘤，并且要求刀具资料有高的热硬性和耐月牙洼磨损性。经积淀硬化的不锈钢强度高、磨蚀性强，所以要求刀具资料硬度高而耐磨。钢中其余元素对切削加工性能的影响钢中铝和硅元素的存在老是有害的，因为这些元素联合氧会生成氧化铝和硅酸盐，而氧化铝和硅酸盐硬度高且拥有磨蚀性。这些化合物会加速刀具磨损，降低切削加工性。因今生产和使用净化钢是特别必需的。依据它们的组成，碳和锰在钢的切削加工性方面有各样不一样的影响。低碳钢（少于0.15%的碳）简单形成积屑瘤而使毛坯的表面光洁度很低。铸钢的切削加工性和锻钢的大概同样，但铸钢更简单磨蚀。工具钢和模具钢很难用于切削加工，往常是在切削加工以行进行退火办理。大部分钢的切削加工性在冷加工后都有所提升，冷加工能使资料变硬而减少积屑瘤的形成。其余合金元素，比如镍、铬、钼和钒，能改良钢的特征，而往常会钢减小切削加工性。硼的影响能够忽略。气态元素比方氢和氮在钢的特征方面有特别有害的影响。氧已经被证了然在硫化锰夹杂物的纵横比方面有很强的影响。含氧量越高，纵横比越低且切削加工性越好。在选择各样元素以改良切削加工性时，我们应当考虑这些元素对已加工零件在使用中的性能和强度的不利影响。比如，当温度高升时，铅会使钢变脆（液态金属的脆化，热缩性，见节），只管其在室温下对机械性能没有影响。因为硫化铁的组成，硫元素能严重的降低钢的热加工性，除非有足够的锰元向来防备这类构造的形成。在室温下，二次硫化钢的机械性能取决于变形的硫化锰夹杂物的定位（各向异性）。二次磷化钢拥有更小的延展性，被独自生成来提升切削加工性。其余不一样金属的切削加工性只管越软的资料更易于生成积屑瘤而致使很差的表面光洁度，但铝往常很简单进行切削加工。这需要高的切削速度，高的前角和后角。铸铝合金和高含量硅的锻铝合金可能拥有磨蚀性，它们要求刀具资料硬度更高。在加工铝资料的工件时尺寸公差控制可能会是一个难题，这是因为它拥有高热膨胀系数和相对较低的弹性模数。铍和铸铁相像。因为它更具磨蚀性和毒性，于是它需要在可控环境下进行加工。灰铸铁往常是可进行切削加工的，但也有磨蚀性。铸件中的游离碳化物降低它们的切削加工性，简单致使刀具破碎或裂口，所以它需要拥有强韧性的刀具。在刀具拥有足够硬度的状况下球墨铸铁和可锻铸铁是可加工的。钴基合金有磨蚀性和高度的加工硬化性。这要求刀具一定尖利并且拥有耐蚀性，并且在加工时进给速度要低。铸铜合金是很简单进行切削加工的，与此相反的是锻铜因为简单产生积屑瘤而很难进行切削加工。黄铜易进行切削加工，特别是在增添了必定量铅的状况下更简单。而青铜比黄铜更难进行切削加工。镁是很简单加工的，加工后的镁件拥有很好的表面光洁性并且使加工零件的刀具寿命更长。但是，因为镁极易氧化而焚烧（这类元素易燃），所以我们应当要特别当心的使用它。钼有很好的延展性和加工硬化性，所以加工后它的表面光洁性很差。所以尖利的刀具是很很有必需的。镍基合金拥有加工硬化性和磨蚀性，且在高温下特别坚硬。它的切削加工性和不锈钢相像。钽拥有特别好的加工硬化性，延展性和柔性。加工后零件的表面光洁性很差且刀具磨损特别大。钛和钛的合金导热系数很低(确实，是全部金属中最低的)，所以在加工时会惹起显然的温度高升和还会产生积屑瘤。它们是很难进行切削加工的。钨易脆，坚硬，且拥有磨蚀性，所以只管它的性能在高温下能大幅提升，但它的切削加工性仍很低。锆切削加工性很好。但是，因为有爆炸和起火的危险，锆在加工时要求切削液冷却性能特别好。各样资料的机加工性石墨拥有磨蚀性。它要求刀具硬度高、尖利和拥有必定的耐蚀性。热塑性塑料往常热导性都很差且弹性模数小、融化温度低。所以，加工热塑性塑料时要求刀具拥有正前角（以此降低切削力），较大的后角，较小的切削和进给深度，相对较高的切削速度和适合的工件支承。此外还要求刀具应当足够尖利。切削区外面的冷却也是很必需的，这能够防备切屑变的有黏性而粘在刀具上。实现冷却往常是利用空气流，汽雾或水溶性油。在切削加工时，可能会产生剩余应力。为了减小这些应力，已加工的部分需要在（）的温度范围内进行一段时间的退火，而后迟缓而均一地冷却到室温。热固性塑料在切削时易脆，并且对热梯度很敏感。它的切削加工性能和热塑性塑料的基真同样。因为有纤维状切屑的存在，加固塑料拥有很强的磨蚀性并且很难进行切削加工。切屑的扯破、拉长和界限分层是特别严重的几个问题。它能致使组件的承载能力大大降落。并且，这些资料的切削加工需要对加工碎屑进行认真清理，进而防止接触而吸入纤维。跟着纳米陶瓷（见节）的发展和适合的参量办理的选择，比如塑性切削（见节），陶瓷器的切削加工性能已大大地提升了。金属基复合资料和陶瓷基复合资料很难进行切削加工，它们依靠于独立零件的特征，也就是包含基质资料在内纤维或金属须的增强。20.9.4热协助加工有些在室温下很难进行切削加工的金属和其合金在高温下却能更简单地进行加工。在热协助加工时（高温切削），热源——一个火源，感觉线圈，高能束流（比如雷射或电子束），或等离子弧——被集中在切削刀具前的一块地区内。作用是：（a）降低切削力。（b）增添刀具寿命。（c）减少切削刀具资料使用成本。（d）提升资料切除率。（e）减少振动。或许很难在工件内加热和保持均一的温度散布。并且高温可能会对工件的最先微观构造产生不利的影响。只管加工陶瓷（如氮化硅）实验在进行中，，但高温切削仍大部分应用在高强度金属及其合金的加工中。小结切削加工性往常从以下几个方面来定义：已切削部分的表面粗拙度，刀具的寿命，切削力和切削功率的需求以及切屑的控制。资料的切削加工性能不单取决于其固有特征和微观构造，也取决于工艺参数的适入选择与控制。Whenyouareoldandgreyandfullofsleep,Andnoddingbythefire,takedownthisbook,Andslowlyread,anddreamofthesoftlookYoureyeshadonce,andoftheirshadowsdeep;Howmanylovedyourmomentsofgladgrace,Andlovedyourbeautywithlovefalseortrue,Butonemanlovedthepilgrimsoulinyou,Andlovedthesorrowsofyourchangingface;Andbendingdownbesidetheglowingbars,Murmur,alittlesadly,howlovefledAndpaceduponthemountainsoverheadAndhidhisfaceamidacrowdofstars.ThefurthestdistanceintheworldIsnotbetweenlifeanddeathButwhenIstandinfrontofyouYetyoudon'tknowthatIloveyou.ThefurthestdistanceintheworldIsnotwhenIstandinfrontofyouYetyoucan'tseemyloveButwhenundoubtedlyknowingthelovefrombothYetcannotbetogether.ThefurthestdistanceintheworldIsnotbeingapartwhilebeinginloveButwhenIplainlycannotresisttheyearningYetpretendingyouhaveneverbeeninmyheart.ThefurthestdistanceintheworldIsnotstrugglingagainstthetidesButusingone'sindifferentheartTodiganuncrossableriverFortheonewholovesyou.