Aqtvlxl機(jī)械制造及自動化畢業(yè)設(shè)計(jì)外語文獻(xiàn)翻譯

1、生命中，不不斷地有人人離開或進(jìn)進(jìn)入。于是是，看見的的，看不見見的；記住住的，遺忘忘了。生命命中，不斷斷地有得到到和失落。于是，看看不見的，看看見了；遺遺忘的，記記住了。然然而，看不不見的，是是不是就等等于不存在在？記住的的，是不是是永遠(yuǎn)不會會消失？ 攀枝花學(xué)院院本科畢業(yè)業(yè)設(shè)計(jì)（論論文）外文譯文院 （系）： 機(jī)電工工程學(xué)院 專 業(yè)： 機(jī)械械設(shè)計(jì)制造造及其自動動化 姓 名： 王 中中 蔚 學(xué) 號： ZJJD020043 指導(dǎo)教師評評語： 簽簽名： 年 月月 日外語文獻(xiàn)翻翻譯摘自: 制造工工程與技術(shù)術(shù)（機(jī)加工工）（英英文版） MManuffactuuringg Enggineeeringg andd

2、 TecchnollogyMachhininng 機(jī)械械工業(yè)出版版社 22004年年3月第1版 美 s. 卡卡爾帕基安安(Serrope kalppakjiian) s.rr 施密德德(Steeven R.Scchmidd) 著原文：20.9 MACHHINABBILITTYThe mmachiinabiilityy of a maateriial uusuallly ddefinned iin teerms of ffour facttors:Surfaace ffinissh annd inntegrrity of tthe mmachiined partt;Tool lifee obtt

3、aineed;Forcee andd powwer rrequiiremeents;Chip conttrol. Thus, goood maachinnabillity goodd surrfacee finnish and inteegritty, llong tooll liffe, aand llow fforcee Andd powwer rrequiiremeents. As for chipp conntroll, loong aand tthin (strringyy) cuured chipps, iif noot brrokenn up, cann sevverelly i

4、nnterffere withh thee cutttingg opeeratiion bby beecomiing eentanngledd in the cuttting zonee.Becauuse oof thhe coompleex naaturee of cuttting operratioons, it iis diifficcult to eestabblishh rellatioonshiips tthat quanntitaativeely ddefinne thhe maachinnabillity of aa matteriaal. IIn maanufaacturri

5、ng plannts, tooll liffe annd suurfacce rooughnness are geneerallly coonsidderedd to be tthe mmost impoortannt faactorrs inn macchinaabiliity. Althhoughh nott useed muuch aany mmore, appproxiimatee macchinaabiliity rratinngs aare aavaillablee in the exammple beloow.20.9.1 Maachinnabillity Of SSteells

6、Becauuse ssteells arre ammong the mostt impportaant eenginneeriing mmaterrialss (ass notted iin Chhapteer 5), thheir machhinabbilitty haas beeen sstudiied eextennsiveely. The machhinabbilitty off steeels has beenn maiinly imprrovedd by addiing llead and sulffur tto obbtainn so-callled ffree-machhini

7、nng stteelss.Resullfuriized and Rephhosphhorizzed ssteells. Sulffur iin stteelss forrms mmangaanesee sullfidee incclusiions (seccond-phasse paarticcles), whhich act as sstresss raaiserrs inn thee priimaryy sheear zzone. As a reesultt, thhe chhips prodducedd breeak uup eaasilyy andd aree smaall; this

8、s impprovees maachinnabillity. Thee sizze, sshapee, diistriibutiion, and conccentrratioon off theese iincluusionns siignifficanntly inflluencce maachinnabillity. Eleementts suuch aas teellurrium and seleeniumm, whhich are bothh cheemicaally simiilar to ssulfuur, aact aas innclussion modiifierrs inn

9、ressulfuurizeed stteelss.Phospphoruus inn steeels has two majoor efffectts. IIt sttrenggthenns thhe feerritte, ccausiing iincreeasedd harrdnesss. HHardeer stteelss ressult in bbetteer chhip fformaationn andd surrfacee finnish. Notte thhat ssoft steeels ccan bbe diifficcult to mmachiine, withh buiilt

10、-uup eddge fformaationn andd pooor suurfacce fiinishh. Thhe seecondd efffect is tthat incrreaseed haardneess ccausees thhe foormattion of sshortt chiips iinsteead oof coontinnuouss strringyy onees, tthereeby iimproovingg macchinaabiliity.Leadeed Stteelss. A highh perrcenttage of llead in ssteells so

11、olidiifiess at the tip of mmangaanesee sullfidee incclusiions. In non-resuulfurrizedd graades of ssteell, leead ttakess thee forrm off dissperssed ffine partticlees. LLead is iinsollublee in ironn, coopperr, annd alluminnum aand ttheirr allloys. Beccausee of its low sheaar sttrenggth, therreforre, l

12、lead actss as a soolid lubrricannt (SSectiion 332.111) annd iss smeearedd oveer thhe toool-cchip inteerfacce duuringg cutttingg. Thhis bbehavvior has beenn verrifieed byy thee preesencce off higgh cooncenntrattionss of leadd on the tooll-sidde faace oof chhips whenn macchiniing lleadeed stteelss.Whe

13、n the tempperatture is ssuffiicienntly highh-forr insstancce, aat hiigh ccuttiing sspeedds annd feeeds (Secctionn 20.6)tthe llead meltts diirecttly iin frront of tthe ttool, actting as aa liqquid lubrricannt. IIn addditiion tto thhis eeffecct, llead loweers tthe sshearr strress in tthe pprimaary ssh

14、earr zonne, rreduccing cuttting forcces aand ppowerr connsumpptionn. Leead ccan bbe ussed iin evvery gradde off steeel, suchh as 10 xxx, 111xx, 12xxx, 411xx, etc. Leaaded steeels aare iidenttifieed byy thee lettter L beetweeen thhe seecondd andd thiird nnumerrals (forr exaamplee, 100L45). (NNote tha

15、tt in staiinlesss stteelss, siimilaar usse off thee lettter L meeans “l(fā)oww carrbon,” a condditioon thhat iimprooves theiir coorrossion resiistannce.)Howevver, becaause leadd is a weell-kknownn toxxin aand aa polllutaant, therre arre seeriouus ennviroonmenntal conccernss aboout iits uuse iin stteelss

16、 (esstimaated at 44500 tonss of leadd connsumpptionn eveery yyear in tthe pproduuctioon off steeels). Coonseqquenttly, therre iss a ccontiinuinng trrend towaard eelimiinatiing tthe uuse oof leead iin stteelss (leead-ffree steeels). Bissmuthh andd tinn aree noww beiing iinvesstigaated as ppossiible s

17、ubsstituutes for leadd in steeels.Calciium-DDeoxiidizeed Stteelss. Ann impportaant ddevellopmeent iis caalciuum-deeoxiddizedd steeels, in whicch oxxide flakkes oof caalciuum siilicaates (CaSSo) aare fformeed. TThesee flaakes, in turnn, reeducee thee strrengtth off thee seccondaary sshearr zonne, dde

18、creeasinng toool-cchip inteerfacce annd weear. Tempperatture is ccorreesponndinggly rreducced. Conssequeentlyy, thhese steeels pproduuce lless cratter wwear, esppeciaally at hhigh cuttting speeeds.Stainnlesss Steeels. Aussteniitic (3000 serries) steeels are geneerallly diifficcult to mmachiine. Chat

19、tter can be ss prooblemm, neecesssitatting machhine toolls wiith hhigh stifffnesss. HHowevver, ferrriticc staainleess ssteells (aalso 300 seriies) havee goood maachinnabillity. Marrtenssiticc (4000 seeriess) stteelss aree abrrasivve, ttend to fform a buuilt-up eedge, andd reqquiree toool maateriials

20、 withh higgh hoot haardneess aand ccrateer-weear rresisstancce. PPreciipitaationn-harrdeniing sstainnlesss steeels are stroong aand aabrassive, reqquiriing hhard and abraasionn-ressistaant ttool mateerialls.The EEffeccts oof Otther Elemmentss in Steeels oon Maachinnabillity. Thee preesencce off aluu

21、minuum annd siilicoon inn steeels is aalwayys haarmfuul beecausse thhese elemmentss commbinee witth oxxygenn to formm aluuminuum oxxide and siliicatees, wwhichh aree harrd annd abbrasiive. Thesse coompouunds incrreasee toool weear aand rreducce maachinnabillity. It is eessenntiall to prodduce and us

22、e cleaan stteelss.Carboon annd maangannese havee varriouss efffectss on the machhinabbilitty off steeels, deppendiing oon thheir compposittion. Plaain llow-ccarboon stteelss (leess tthan 0.155% C) cann prooducee pooor suurfacce fiinishh by formming a buuilt-up eedge. Casst stteelss aree morre abbras

23、iive, althhoughh theeir mmachiinabiilityy is simiilar to tthat of wwrougght ssteells. TTool and die steeels aare vvery diffficullt too macchinee andd usuuallyy reqquiree annnealiing ppriorr to machhininng. MMachiinabiilityy of mostt steeels is iimprooved by ccold workking, whiich hhardeens tthe mmat

24、errial and reduuces the tenddencyy forr buiilt-uup eddge fformaationn.Otherr allloyinng ellemennts, suchh as nickkel, chroomiumm, moolybddenumm, annd vaanadiium, whicch immprovve thhe prroperrtiess of steeels, geneerallly reeducee macchinaabiliity. The effeect oof booron is nnegliigiblle. GGaseoous

25、eelemeents suchh as hydrrogenn andd nittrogeen caan haave ppartiiculaarly detrrimenntal effeects on tthe ppropeertiees off steeel. Oxyggen hhas bbeen showwn too havve a stroong eeffecct onn thee asppect ratiio off thee mannganeese ssulfiide iincluusionns; tthe hhigheer thhe oxxygenn conntentt, thhe

26、loower the aspeect rratioo andd thee higgher the machhinabbilitty.In seelectting variious elemmentss to imprrove machhinabbilitty, wwe shhouldd connsideer thhe poossibble ddetriimenttal eeffeccts oof thhese elemmentss on the proppertiies aand sstrenngth of tthe mmachiined partt in servvice. At elevv

27、atedd temmperaaturees, ffor eexampple, leadd cauuses embrrittllemennt off steeels (liqquid-metaal emmbritttlemment, hott shoortneess; see Secttion 1.4.3), althhoughh at roomm temmperaaturee it has no eeffecct onn mecchaniical proppertiies.Sulfuur caan seevereely rreducce thhe hoot woorkabbilitty off

28、 steeels, beccausee of the formmatioon off iroon suulfidde, uunlesss suufficcientt mannganeese iis prresennt too preeventt succh foormattion. At roomm temmperaaturee, thhe meechannicall proopertties of rresullfuriized steeels ddepennd onn thee oriientaationn of the defoormedd mannganeese ssulfiide i

29、incluusionns (aanisootroppy). Rephhosphhorizzed ssteells arre siignifficanntly lesss ducctilee, annd arre prroducced ssolelly too impprovee macchinaabiliity.20.9.2 Maachinnabillity of VVarioous OOtherr Mettals Alumiinum is ggenerrallyy verry eaasy tto maachinne, aalthoough the softter ggradees teend

30、 tto foorm aa buiilt-uup eddge, resuultinng inn pooor suurfacce fiinishh. Hiigh ccuttiing sspeedds, hhigh rakee anggles, andd higgh reelieff anggles are recoommennded. Wrooughtt aluuminuum allloyss witth hiigh ssiliccon cconteent aand ccast alumminumm allloys may be aabrassive; theey reequirre haard

31、err toool maateriials. Dimmensiionall tollerannce ccontrrol mmay bbe a probblem in mmachiiningg aluuminuum, ssincee it has a hiigh tthermmal ccoeffficieent oof exxpanssion and a reelatiivelyy loww elaasticc modduluss.Beryllliumm is simiilar to ccast ironns. BBecauuse iit iss morre abbrasiive aand tt

32、oxicc, thhoughh, itt reqquirees maachinning in aa conntrollled enviironmment.Cast grayy iroons aare ggenerrallyy macchinaable but are. Freee caarbiddes iin caastinngs rreducce thheir machhinabbilitty annd caause tooll chiippinng orr fraacturre, nnecesssitaatingg toools wwith highh touughneess. Noduu

33、lar and mallleablle irrons are machhinabble wwith hardd toool maateriials.Coballt-baased allooys aare aabrassive and highhly wwork-harddeninng. TThey requuire sharrp, aabrassion-resiistannt toool mmaterrialss andd loww feeeds aand sspeedds.Wrougght ccoppeer caan bee diffficuult tto maachinne beecaus

34、se off buiilt-uup eddge fformaationn, allthouugh ccast coppper aalloyys arre eaasy tto maachinne. BBrassses aare eeasy to mmachiine, espeeciallly wwith the addiitionn pf leadd (leeadedd freee-maachinning brasss). Bronnzes are moree diffficuult tto maachinne thhan bbrasss.Magneesiumm is veryy eassy t

35、oo macchinee, wiith ggood surfface finiish aand pproloongedd toool liife. Howeever caree shoould be eexerccisedd beccausee of its highh ratte off oxiidatiion aand tthe ddangeer off firre (tthe eelemeent iis pyyrophhoricc).Molybbdenuum iss ducctilee andd worrk-haardenning, so it ccan pproduuce ppoor

36、surfface finiish. Sharrp toools are neceessarry.Nickeel-baased allooys aare wwork-harddeninng, aabrassive, andd strrong at hhigh tempperatturess. Thheir machhinabbilitty iss simmilarr to thatt of staiinlesss stteelss.Tantaalum is vvery workk-harrdeniing, ducttile, andd sofft. IIt prroducces aa pooor

37、 suurfacce fiinishh; toool wwear is hhigh.Titannium and its allooys hhave poorr theermall connducttivitty (iindeeed, tthe llowesst off alll mettals), caausinng siignifficannt teemperraturre riise aand bbuiltt-up edgee; thhey ccan bbe diifficcult to mmachiine.Tungssten is bbritttle, stroong, and very

38、y abrrasivve, sso itts maachinnabillity is llow, althhoughh it greaatly imprrovess at elevvatedd temmperaaturees.Zircooniumm hass goood maachinnabillity. It requuiress a ccoolaant-ttype cuttting fluiid, hhowevver, becaause of tthe eexploosionn andd firre.20.9.3 Maachinnabillity of VVarioous MMaterri

39、alssGraphhite is aabrassive; it requuiress harrd, aabrassion-resiistannt, ssharpp toools.Thermmoplaasticcs geeneraally havee loww theermall connducttivitty, llow eelasttic mmodullus, and low softteninng teemperraturre. CConseequenntly, macchiniing tthem requuiress toools wwith posiitivee rakke anngl

40、ess (too redduce cuttting forcces), larrge rrelieef anngless, smmall deptths oof cuut annd feeed, relaativeely hhigh speeeds, and propeer suupporrt off thee worrkpieece. Toolls shhouldd be sharrp.Exterrnal coolling of tthe ccuttiing zzone may be nnecesssaryy to keepp thee chiips ffrom becoomingg “gu

41、ummy” andd stiickinng too thee toools. Coolling can usuaally be aachieeved withh a jjet oof aiir, vvaporr misst, oor waater-soluuble oilss. Reesiduual sstressses may deveelop duriing mmachiiningg. Too rellievee theese sstressses, macchineed paarts can be aanneaaled for a peeriodd of timee at tempper

42、atturess ranngingg froom tto (to), and thenn coooled slowwly aand uunifoormlyy to roomm temmperaaturee.Thermmosetttingg plaasticcs arre brrittlle annd seensittive to tthermmal ggradiientss durring cuttting. Theeir mmachiinabiilityy is geneerallly siimilaar too thaat off theermopplasttics.Becauuse oo

43、f thhe fiiberss preesentt, reeinfoorcedd plaasticcs arre veery aabrassive and are diffficullt too macchinee. Fiiber tearring, pulllingg, annd eddge ddelamminattion are signnificcant probblemss; thhey ccan llead to sseverre reeducttion in tthe lload-carrryingg cappacitty off thee commponeent. Furtthe

44、rmmore, macchiniing oof thhese mateerialls reequirres ccarefful rremovval oof maachinning debrris tto avvoid conttact withh andd inhhalinng off thee fibbers.The mmachiinabiilityy of ceraamicss hass impproveed stteadiily wwith the deveelopmment of nnanoccerammics (Secctionn 8.22.5) and withh thee sel

45、lectiion oof appproppriatte prrocesssingg parrametters, succh ass ducctilee-reggime cuttting (Secctionn 22.4.2).Metall-mattrix and ceraamic-matrrix ccompoositees caan bee diffficuult tto maachinne, ddepenndingg on the proppertiies oof thhe inndiviiduall commponeents, i.ee., rreinfforciing oor whhisk

46、eers, as wwell as tthe mmatriix maateriial.20.9.4 Thhermaally Assiistedd MacchiniingMetalls annd allloyss thaat arre diifficcult to mmachiine aat rooom ttempeeratuure ccan bbe maachinned mmore easiily aat ellevatted ttempeeratuures. In therrmallly asssistted mmachiiningg (hoot maachinning), thhe soo

47、urcee of heatta ttorchh, innducttion coill, hiigh-eenerggy beeam (suchh as laseer orr eleectroon beeam), or plassma aarciis foorcess, (bb) inncreaased tooll liffe, (c) uuse oof innexpeensivve cuuttinng-toool mmaterrialss, (dd) hiigherr matteriaal-reemovaal raates, andd (e) redducedd tenndenccy foor

48、viibrattion and chattter.It maay bee diffficuult tto heeat aand mmainttain a unniforrm teemperraturre diistriibutiion wwithiin thhe woorkpiiece. Alsso, tthe oorigiinal micrrostrructuure oof thhe woorkpiiece may be aadverrselyy afffecteed byy eleevateed teemperraturres. Mostt appplicaationns off hott

49、 macchiniing aare iin thhe tuurninng off higgh-sttrenggth mmetalls annd allloyss, allthouugh eexperrimennts aare iin prrogreess tto maachinne ceeramiics ssuch as ssiliccon nnitriide. SUMMAARYMachiinabiilityy is usuaally defiined in ttermss of surfface finiish, tooll liffe, fforcee andd powwer rrequi

50、iremeents, andd chiip coontrool. MMachiinabiilityy of mateerialls deependds noot onnly oon thheir intrrinsiic prroperrtiess andd miccrosttructture, butt alsso onn prooper seleectioon annd coontrool off proocesss varriablles.譯文：20.9 可機(jī)加工工性一種材料的的可機(jī)加工工性通常以以四種因素素的方式定定義：分的表面光光潔性和表表面完整性性。2、刀具的的壽命。3、切削力力和功

51、率的的需求。4、切屑控控制。以這種方式式，好的可可機(jī)加工性性指的是好好的表面光光潔性和完完整性，長長的刀具壽壽命，低的的切削力和和功率需求求。關(guān)于切切屑控制，細(xì)細(xì)長的卷曲曲切屑，如如果沒有被被切割成小小片，以在在切屑區(qū)變變的混亂，纏纏在一起的的方式能夠夠嚴(yán)重的介介入剪切工工序。因?yàn)榧羟泄すば虻膹?fù)雜雜屬性，所所以很難建建立定量地地釋義材料料的可機(jī)加加工性的關(guān)關(guān)系。在制制造廠里，刀刀具壽命和和表面粗糙糙度通常被被認(rèn)為是可可機(jī)加工性性中最重要要的因素。盡管已不不再大量的的被使用，近近乎準(zhǔn)確的的機(jī)加工率率在以下的的例子中能能夠被看到到。20.9.1 鋼的可機(jī)機(jī)加工性因?yàn)殇撌亲钭钪匾墓すこ滩牧现唬?/p>

52、正如如第5章所示），所所以他們的的可機(jī)加工工性已經(jīng)被被廣泛地研研究過。通通過宗教鉛鉛和硫磺，鋼鋼的可機(jī)加加工性已經(jīng)經(jīng)大大地提提高了。從從而得到了了所謂的易易切削鋼。二次硫化鋼鋼和二次磷磷化鋼 硫在鋼鋼中形成硫硫化錳夾雜雜物（第二二相粒子），這這些夾雜物物在第一剪剪切區(qū)引起起應(yīng)力。其其結(jié)果是使使切屑容易易斷開而變變小，從而而改善了可可加工性。這些夾雜雜物的大小小、形狀、分布和集集中程度顯顯著的影響響可加工性性?；瘜W(xué)元元素如碲和和硒，其化化學(xué)性質(zhì)與與硫類似，在在二次硫化化鋼中起夾夾雜物改性性作用。鋼中的磷有有兩個(gè)主要要的影響。它加強(qiáng)鐵鐵素體，增增加硬度。越硬的鋼鋼，形成更更好的切屑屑形成和表表面光

53、潔性性。需要注注意的是軟軟鋼不適合合用于有積積屑瘤形成成和很差的的表面光潔潔性的機(jī)器器。第二個(gè)個(gè)影響是增增加的硬度度引起短切切屑而不是是不斷的細(xì)細(xì)長的切屑屑的形成，因因此提高可可加工性。含鉛的鋼 鋼中中高含量的的鉛在硫化化錳夾雜物物尖端析出出。在非二二次硫化鋼鋼中，鉛呈呈細(xì)小而分分散的顆粒粒。鉛在鐵鐵、銅、鋁鋁和它們的的合金中是是不能溶解解的。因?yàn)闉樗牡涂箍辜魪?qiáng)度。因此，鉛鉛充當(dāng)固體體潤滑劑并并且在切削削時(shí)，被涂涂在刀具和和切屑的接接口處。這這一特性已已經(jīng)被在機(jī)機(jī)加工鉛鋼鋼時(shí)，在切切屑的刀具具面表面有有高濃度的的鉛的存在在所證實(shí)。當(dāng)溫度足夠夠高時(shí)例如，在在高的切削削速度和進(jìn)進(jìn)刀速度下下鉛在刀

54、具具前直接熔熔化，并且且充當(dāng)液體體潤滑劑。除了這個(gè)個(gè)作用，鉛鉛降低第一一剪切區(qū)中中的剪應(yīng)力力，減小切切削力和功功率消耗。鉛能用于于各種鋼號號，例如110XX，11XXX，12XXX，41XXX等等。鉛鉛鋼被第二二和第三數(shù)數(shù)碼中的字字母L所識別（例例如，100L45）。（需需要注意的的是在不銹銹鋼中，字字母L的相同用用法指的是是低碳，提提高它們的的耐蝕性的的條件）。然而，因?yàn)闉殂U是有名名的毒素和和污染物，因因此在鋼的的使用中存存在著嚴(yán)重重的環(huán)境隱隱患（在鋼鋼產(chǎn)品中每每年大約有有45000噸的鉛消消耗）。結(jié)結(jié)果，對于于估算鋼中中含鉛量的的使用存在在一個(gè)持續(xù)續(xù)的趨勢。鉍和錫現(xiàn)現(xiàn)正作為鋼鋼中的鉛最最可

55、能的替替代物而被被人們所研研究。脫氧鈣鋼 一個(gè)個(gè)重要的發(fā)發(fā)展是脫氧氧鈣鋼，在在脫氧鈣鋼鋼中矽酸鈣鈣鹽中的氧氧化物片的的形成。這這些片狀，依依次減小第第二剪切區(qū)區(qū)中的力量量，降低刀刀具和切屑屑接口處的的摩擦和磨磨損。溫度度也相應(yīng)地地降低。結(jié)結(jié)果，這些些鋼產(chǎn)生更更小的月牙牙洼磨損，特特別是在高高切削速度度時(shí)更是如如此。不銹鋼 奧氏體體鋼通常很很難機(jī)加工工。振動能能成為一個(gè)個(gè)問題，需需要有高硬硬度的機(jī)床床。然而，鐵鐵素體不銹銹鋼有很好好的可機(jī)加加工性。馬馬氏體鋼易易磨蝕，易易于形成積積屑瘤，并并且要求刀刀具材料有有高的熱硬硬度和耐月月牙洼磨損損性。經(jīng)沉沉淀硬化的的不銹鋼強(qiáng)強(qiáng)度高、磨磨蝕性強(qiáng)，因因此要

56、求刀刀具材料硬硬而耐磨。鋼中其它元元素在可機(jī)機(jī)加工性方方面的影響響 鋼中中鋁和矽的的存在總是是有害的，因因?yàn)檫@些元元素結(jié)合氧氧會生成氧氧化鋁和矽矽酸鹽，而而氧化鋁和和矽酸鹽硬硬且具有磨磨蝕性。這這些化合物物增加刀具具磨損，降降低可機(jī)加加工性。因因此生產(chǎn)和和使用凈化化鋼非常必必要。根據(jù)它們的的構(gòu)成，碳碳和錳鋼在在鋼的可機(jī)機(jī)加工性方方面有不同同的影響。低碳素鋼鋼（少于00.15%的碳）通通過形成一一個(gè)積屑瘤瘤能生成很很差的表面面光潔性。盡管鑄鋼鋼的可機(jī)加加工性和鍛鍛鋼的大致致相同，但但鑄鋼具有有更大的磨磨蝕性。刀刀具和模具具鋼很難用用于機(jī)加工工，他們通通常再煅燒燒后再機(jī)加加工。大多多數(shù)鋼的可可機(jī)加

57、工性性在冷加工工后都有所所提高，冷冷加工能使使材料變硬硬并且減少少積屑瘤的的形成。其它合金元元素，例如如鎳、鉻、鉗和釩，能能提高鋼的的特性，減減小可機(jī)加加工性。硼硼的影響可可以忽視。氣態(tài)元素素比如氫和和氮在鋼的的特性方面面能有特別別的有害影影響。氧已已經(jīng)被證明明了在硫化化錳夾雜物物的縱橫比比方面有很很強(qiáng)的影響響。越高的的含氧量，就就產(chǎn)生越低低的縱橫比比和越高的的可機(jī)加工工性。選擇各種元元素以改善善可加工性性，我們應(yīng)應(yīng)該考慮到到這些元素素對已加工工零件在使使用中的性性能和強(qiáng)度度的不利影影響。例如如，當(dāng)溫度度升高時(shí)，鋁鋁會使鋼變變脆（液體體金屬脆化化，熱脆化化，見1.4.3節(jié)節(jié)），盡管管其在室溫溫下對力學(xué)學(xué)性能沒有有影響。因?yàn)榱蚧F鐵的構(gòu)成，硫硫能嚴(yán)重的的減少鋼的的熱加工性性，除非有有足夠的錳錳來防止這這種結(jié)構(gòu)的的形成。在在室溫下，二二次磷化鋼鋼的機(jī)械性性能依賴于于變形的硫硫化錳夾雜雜物的定位位（各向異異性）。二二次磷化鋼鋼具有更小小的延展性性，被單獨(dú)獨(dú)生成來提提高機(jī)加工工性。20.9.2 其它不同同金