Thaum tshav kub kub khong yogpua erformed rau change paub chyam ntxwvof metal ibnd tag nrhooyus in ordua to make thua emmore haum rau a tshwj xeeb zoo ntawm daim ntawv thov. Hauv dav dav, kub khoment yog the lub sij hawm rau tej txheej txheem employed, los ntawm eithua cua sov los yog cua txias, rau hloov the physical zog ntawm a metal. Cov lub hom phiaj ntawm kub khoment yog hloov the qauv ntawm the material rau a raum, uas paub rau muaj the xav tau
khoom. Cov khoments induce theem hloovmations thntawmgreat kuvnfluencemechanical khoom zoo li
raws li lub zog, hardness, ductility, toughness, thiab hnav tsis kam ntawm cov alloys. Cov loj nujmua ber ntawm xav tau kev pabments thiab amunt ntawm tag nrhooys muaj mua ake for a considerable amunt ntawm kev kho cua sov kev ua haujlwm.
Kub Kev kho mob ntawm Cov pa roj carbon Cov hlau thiab Cov pa roj carbon Alloy Cov hlau
Cov pa roj carbon hlau thiab carbon tag nrhooy hlau ua tau ua kub kho rau the lub hom phiaj ntawm imua pov thawj khoom zoo li raws li hardness, tensile thiab tawm los zog. Cov xav tau tshwm sim yog ua accomplis los ntawm cua sov hauv kojmperature ranges qhov twg a theem los yog combinations ntawm theem yog ruaj khov, thiab/los yog cua sov los yog cua txias nruab nrab kojmperature thaj tsam
hauv uas txawv theem yog ruaj khov.
Cov qauv ntawm steel yog composed ntawm ob sib txawv:
1. Nplej Qauv - Cov npajment ntawm ib atoms hauv a metal.
2. Grain Size - Qhov loj ntawm tus kheej muaju ntawmmthiabal. Cov nplej loj loj yog feem ntau txuam nrog low kevngth, hardnes, anddukev ctility.
Tom qabbib eing formed, the material yogusuphooj ywgua quenched and kojmpua ered rau produ uace ibmarte uansiv structure thntawm cov khoom the most nrhiav mechanical zog hauv steel fasteners. Martensite yog raumed los ntawm kev ua kom txias sai los yog quenching los ntawm austenizing kojmperatures pebing a quenching medu uam, zoo li raws li roj, dej los yog air, thnyob tranua sferhnoj from the hot parts a sufficie uant nqi. The ua quenched marte uansiv structure,
whib ich yoghardua but blus, then kojmpua ered hauv ordua to inqob the ductility ibnd drov the hardnes tau teev qib. Thaum the quenching khoment, yog imua tau rau zoo the tshwj xeebmen ntawm a khaub ncaws tus nqi thoob plaws. Cov nto ntawm tus tshwj xeebmen yuav ib txwm cool ua more ceev ceev tshaj qhov sab hauv cheeb tsam.
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Theref uaore, the austennws yuav tranua sfoua rm ovua range of kojmpuaures, ywjding a possiblevkevon of mib icrostructure ibnd properties nrogposition txawj ntsehhauv the material.
Kev kho cua sov ua tiavment ntawm hlau rau tsim tawm a ua ntejmua tsis ncaj martensitic mkev tsim kho thoob the ntoo khaub lig ntu nyob ntawm mib ainly nws three yam:
1. the composition of the cwboy
2. the type thiab tus cwj pwm ntawm the quenching medium
3. tus qhov loj thiab puab ntawm tus tshwj xeebmen
Hardenabkev muaj peev xwm
The influenceof tag nrhooy composition on the abkev muaj peev xwmof ib steel poboy rau tranua sfoua rm rau marte uansite for a particularua quenching khoment yog hais txog rau a pua aramnpe eter hardenabkev muaj peev xwm. For everydyog hais tiasnt steel poboy thyog aspecific relati uantawmshib ip bib nrab thua eirmib echanicalproperty ibnd thyog coo ualing tus nqi. Hardenability yogtsis muajt
"hardnes" whib ich yog resistance ua indentatintawm; nashyog,hardnesmyoojurements yoguua tsaug rau determine the exkojnt of a marte uansib tranua sformib ation hauv the interior of the material. Ib steel tag nrhooy thntawmhas ahigh
hardenability yog ib uas hardens, los yog raums martensite, tsis tsuas yog nyob rau saum npoo tab sis kuj mus rau ib tug loj degree thoob plaws tus tag nrho sab hauv. Hauv lwm yam lus, hardenability yog amyooj yim ntawm qhov tob uas ib qho tshwj xeeb alloymyog yuav hardened.
Cov ua rawsotis elemcov muaj paub teebmeem ntawm the khoom ntawm hlau:
Carbon (C): Primary poboua ying element: pibnciplehardening element: Esntias for the formib ation of martensite thaum lub sij hawm tawv
Manganese (Mn ): Hauvcreases strngth and hardnes :indaim tawv nqaijhardenabkev muaj peev xwm
Phosphorus (P): Considua ered ib impuarit, tau causebrittlenes ua low kojmpuauresSulfur (S): Sibua ered ib imdawb huvy, ua tau lower tensile zog ntawm siab kojmperature: kuvmua pov thawjmachinability hauv dawbmachining hlau
Silicon(Si)Tom ntej: Deoxidizer
Nickel (Ni): Imua pov thawj toughness: Simplub neej Thaum tshav kub kub kho: Nce hardenability: Txo distortion: Imua pov thawj corrosion tsis kam
Chromyam (Cr): Improveshardenabkev: Provides hnav and abrasion resistance: improves coua rrosion tiv
Molybdenum ua (Mo): Improveshardenabkev: Nntawm-ua oxidib zing
Boron ( B ): Trace ibmouts nce hardenpeev: Promotes raummuaj peev xwm
Aluminu uam ( Al ): Tswj cov nplejLoj: Deoxidizer
Tempering
Hauv tus raws li-quenched xeev, martensite, hauv ntxiv rau ua heev nyuaj, yog ntxivmely nkig thiab tsis tuaj yeem siv rau most daim ntawv thov. Tsis tas li ntawd, ib inkev nyuaj siab thntawmmay muaj ua innthuav tawm thaum quenching muaj ib qho tsis muaj zog nyhuv.
Yog tus hlau muaj ua tag nrho hardened los ntawm ua quenched los ntawm saum nws qhov tseem ceeb tempkev, tempering tau
ua siv rau txhim khu tus ductility thiab tawv ntawm martensite thiab daws tus sab hauv kev nyuaj siab. Hauv kojmping, cov hlau yog reheated rau ib qho tshwj xeeb kojmperature hauv qab nws qhov tseem ceeb temperatua ur rau a meej lub sij hawm ntawm kojme thiab tom qab ntawd txias ntawm a sau ntawv tus nqi.
The folloua wing example yuavdemntawmtxoj kev thua effevenesof kojmpib ering:
ASTM A193 Cov khoom lag luam Qib B7, SAE J429 Qib 8 thiab ASTM A574 Cov Lus Qhia Tshwj Xeeb Lub taub hau Cap Ntsia hlau yog tag nrhomua ade los ntawm txhua tusoy hlau. Hauv qhov tseeb li ntawdme cwboy qib steel ua tau ua siv rau mtsim khoom ib yam ntawm the three cov khoom kawg:
zoo li raws li 4140 thiab 4142 tag nrhooy steel. Cov kawgmechanical zog yog the ua rawsoQauv: ASTM A193 B7
• Tensile zog: 125, 000 PSI mib inimum (2-1/2- nti thiab hauv qab)
• Yield Lub zog: 105, 000 PSI mib inimum (2-1/2- nti thiab hauv qab)
• Hardness: HRC 35 Maxismum
SAE J429 Qib 8
• Tensile zog: 150, 000 PSI mib inimum
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• Pov thawj Lub zog: 120, 000 PSI
• Yield Lub zog: 130, 000 PSI mib inimum
• Hardness: HRC 33-39
ASTM A574 Cov Lus Qhia Tshwj Xeeb Lub taub hau Cap Ntsia hlau
• Tensile zog: 180, 000 PSI mib inimum (los ntawm ½"), 170,000 PSI mib inimum (saum toj no ½")
• Pov thawj Lub zog: 140, 000 PSI (los ntawm ½"), 135,000 PSI (saum toj no ½")
• Yield Lub zog: 153, 000 PSI mib inimum
• Hardness: HRC 39-45 (los ntawm ½"), HRC 37-45 (saum toj no ½")
Thawj qhov kev kho cua sov yog relative same rau tag nrho peb cov khooms. Cov khoom raug kho cua sov kom txog thaum tag nrho austenitized. Cov ntu yog ces quenched thiab kojmpua ered hauv ib liua quid (oib). Thyog final kojmpib ering kojmperature yog dab tsi yuav dictate peb cov khoom kawg. Cov raws li yog tus mib inimum kojmpkev kojmperatures
rau txhua qhov specification:
• ASTM A193 Cov khoom lag luam B7: 1150degreeF
• SAE J429 Qib 8: 800degreeF
• ASTM A574: 65 Cov0degreeF
Raws li ua tau ua pom los ntawm tus tshwm sim, a qis kojmpkev kojmperature yuav tsim tawm a nyuaj dua thiab siab dua tensile zogngth part for thyog e cwboy hlau. Hopebvua, the loua tempib ering kojmpuaures kuj mean loua service ua condnwsntawms, ductility, ibmpua strngth andpossible fatiua gue liv. For exampua b7 has ahigh-temperature limkev xav ntawm kwv yeesmnoj mov 750-800degreeF. Cov lub qhov (socket). taub hau cap ntsia hlau thiab qib 8's muaj ib limnwson ofkwv yeesimnoj400-500degreeF.
Annealing
Annua ealing yoguua sed rau soften previkojloj cold-worked metalby poboua wing nws rau rov ua crystallize. The lub sij hawm annealing hais txog rau a kub khomua in uas a material yog nthuav tawm rau ib nce kojmperature rau ib ncua kojme lub sij hawm thiab then maj mam txias. Ordinarily, annealing yog nqa tawm kom (1) txo kev ntxhov siab;
(2) nce softness, ductility thiabtughness; thiab/los yog (3) tsim tawm a microstrkev kawm. A ntau yam ntawm annealing tshav kub khomua tau.
Ib qho annealing txheej txheem muaj three theem:
1. cua sov rau the xav tau kojmperature
2. tuav los yog "soaking" ntawm thob temperature
3. maj mam txias, feem ntau rau chav kojmperature
Time yog the importa uant pua arameter hauv thyogprocedures
Txheej txheem Annealing
Txheej txheem annealing yog kev kho cua sovment uas siv nerooj vag tus teebmeem ntawm txias ua haujlwm that yog soften and inqob the dukev ctilityof a previkojsly lojn-hardened metal.
Kev ntxhov siab
Internal residual stressesmua develop inmetal pieces hauv teb rau zoo li yam raws li txias ua haujlwm.
Distortion thiab warpage mua result if thyog residual stresses tsis remua oved. Lawvmua eliminated los ntawm kev ntxhov siab nyem annealing tshav kub khoment nyob rau hauv uas daim yog rhuab mus tus recommxaus kojmperature, tuav
thib ere ntev txaus rau ua tau a khaub ncaws kojmperature, thiab Thaum kawg txias rau a chav kojmperature hauv huab cua. Kev ntxhov siab ua tau eliminnoj yog li ntawdme inkev nyuaj siab tsis muaj qhov hloov pauv loj the qauv ntawm the material.
Noua rmalisng
Cov hlau thntawm muaj ua plastically deformed by, rau exa uample, a dov kev ua haujlwm, muaj nplej ntawm
pearli, wbhib ich ua irreua gulaj shaped and kev sib thamvely lajge, ua but vary substantib in qhov loj. Normalizi uang yog annealing kub khomsiv rau kho kom zoo the nplej thiab tsim tawm a more khaub ncaws thiab ntshaw qhov loj
kev faib tawm.
Tsis yogmalizing yog accomplished los ntawm cua sov lubmaterial rau ib temperature saum nws lub siab tseem ceeb temperature. Tom qab sufficie uant tsime hraws libib een tag nrhoowed for the cwboy rau comploj tranua sfoua rm rau austenib, aprocedure
termed austenkevng, the metal yog tag nrhoowed rau coo ual hauv thua air.
Tag Nrho Anneal
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A kub khoment paub raws li puv annealing yog feem ntau utilized nyob rau hauv qis- thiabmedu uam- carbon hlau uas yuav yogmachined or yuav exp uaerienceem exkojnsive pyasdua eformib ationduri ibng a formingoptsimntawm. The full ib anncua txias txheej txheem yog time consumhauv,
Spherodkev
Medium- thiab high-carbon hlau muaj a mkev tsim kho muaj ntxhib pearlitemay tseem yuav nyuaj heev kom yooj yimmua achine los yog plastically deform. Cov no steels, thiab hauv qhov tseeb, tej steel, mua be kub kho los yog annua eal rau develop the sphuaoidua structure. Sphuaoidua ized hlauhave a maximum softnib es anddukev ctility
thiab yog yooj yim mmob siab los yog deformed.
