Kev kho cua sov ntawm cov hlau yog qhov muaj zog tshaj plaws rau kev cuam tshuam nws cov qauv thiab cov khoom. Nws yog raws li kev hloov kho ntawm cov siv lead ua lattices nyob ntawm qhov kev ua si ntawm qhov kub thiab txias. Ferrite, pearlite, cementite, thiab austenite tuaj yeem muaj nyob hauv cov hlau-carbon alloy nyob rau hauv ntau yam mob. Lub tom kawg ua lub luag haujlwm tseem ceeb hauv txhua qhov kev hloov pauv thermal hauv steel.
Definition
Steel yog ib qho alloy ntawm hlau thiab carbon, nyob rau hauv uas cov pa roj carbon ntsiab lus yog mus txog 2.14% theoretically, tab sis technologically siv muaj nyob rau hauv tus nqi ntawm tsis ntau tshaj 1.3%. Raws li, tag nrho cov qauv uas tau tsim nyob rau hauv nws nyob rau hauv lub zog ntawm sab nraud influences kuj muaj ntau yam ntawm alloys.
Txoj kev xav nthuav tawm lawv qhov muaj nyob hauv 4 qhov kev hloov pauv: kev nkag mus rau cov khoom siv tshuaj, kev cais tawm cov kua, cov khoom sib xyaw ntawm cov nplej lossis cov tshuaj lom neeg.
Austenite yog cov tshuaj tov ntawm carbon atom nkag mus rau hauv lub ntsej muag-centric cubic crystal lattice ntawm hlau, hu ua γ. Cov pa roj carbon atom tau nkag mus rau hauv kab noj hniav ntawm γ-lattice ntawm hlau. Nws qhov ntev tshaj qhov sib thooj pores ntawm Fe atoms, uas piav qhia txog kev txwv ntawm lawv los ntawm "phab ntsa" ntawm cov qauv tseem ceeb. Tsim nyob rau hauv cov txheej txheemKev hloov pauv kub ntawm ferrite thiab perlite nrog nce cua sov siab tshaj 727˚С.
Daim duab ntawm hlau-carbon alloys
Ib daim duab hu ua hlau-cementite lub xeev daim duab, tsim kev sim, yog qhov ua qauv qhia meej ntawm txhua qhov kev xaiv tau rau kev hloov pauv hauv cov hlau thiab cam khwb cia hlau. Qhov tshwj xeeb kub qhov tseem ceeb rau qee cov pa roj carbon monoxide cov ntsiab lus tseem ceeb ntawm cov txheej txheem kev hloov pauv tseem ceeb tshwm sim thaum cov txheej txheem cua sov lossis cua txias, lawv kuj tsim cov kab tseem ceeb.
GSE kab, uas muaj cov ntsiab lus Ac3 thiab Acm, sawv cev rau qib ntawm cov pa roj carbon solubility thaum tshav kub nce.
| Cov lus ntawm cov pa roj carbon solubility hauv austenite piv rau qhov kub thiab txias | |||||
| Kub, ˚C | 900 | 850 | 727 | 900 | 1147 |
| kwv yees solubility ntawm C hauv austenite, % | 0, 2 | 0, 5 | 0, 8 | 1,3 | 2, 14 |
Txoj kev kawm
Austenite yog cov qauv tsim thaum cov hlau raug cua sov. Thaum ncav cuag qhov kub thiab txias, pearlite thiab ferrite tsim ib yam khoom.
xaiv cua sov:
- Uniform, kom txog rau thaum tus nqi yuav tsum tau mus txog, luv luv,cua txias. Nyob ntawm cov yam ntxwv ntawm cov hlau, austenite tuaj yeem ua tiav lossis tsim ib nrab.
- Nyob rau hauv qhov kub thiab txias, lub sij hawm ntev ntawm kev tswj kom mus txog theem ntawm cov cua sov thiaj li yuav tau cov ntshiab austenite.
Cov khoom ntawm cov khoom siv hluav taws xob ua kom sov, nrog rau qhov uas yuav tshwm sim los ntawm kev ua kom txias. Ntau yam nyob ntawm qhov ntsuas kub ua tiav. Nws yog ib qho tseem ceeb los tiv thaiv overheating los yog overheating.
Microstructure thiab khoom
Txhua theem yam ntxwv ntawm cov hlau-carbon alloys muaj nws tus kheej cov qauv ntawm lattices thiab nplej. Cov qauv ntawm austenite yog lamellar, muaj cov duab nyob ze rau ob qho tib si acicular thiab flaky. Nrog kev ua tiav ntawm cov pa roj carbon monoxide hauv γ-hlau, cov nplej muaj lub teeb pom kev zoo yam tsis muaj qhov tsaus nti cementite inclusions.
Hardness yog 170-220 HB. Lub thermal thiab hluav taws xob conductivity yog ib qho kev txiav txim ntawm qhov loj me dua li cov ferrite. Tsis muaj cov khoom sib nqus.
Variants ntawm txias thiab nws ceev ua rau tsim ntawm ntau yam kev hloov kho ntawm lub xeev "txias": martensite, bainite, troostite, sorbite, perlite. Lawv muaj cov qauv acicular zoo sib xws, tab sis sib txawv hauv cov khoom tawg, qhov loj me thiab cov cementite hais.
Txoj kev ua kom txias ntawm austenite
Decomposition ntawm austenite tshwm sim ntawm tib lub ntsiab lus tseem ceeb. Nws txoj kev ua tau zoo nyob ntawm cov hauv qab no:
- Tus nqi txias. Muaj feem xyuam rau qhov xwm ntawm carbon inclusions, tsim cov nplej, tsim ntawm qhov kawgmicrostructure thiab nws cov khoom. Nyob ntawm qhov nruab nrab siv los ua lub coolant.
- Lub xub ntiag ntawm ib qho isothermal tivthaiv ntawm ib qho ntawm cov theem ntawm decomposition - thaum txo qis rau qee qhov ntsuas kub, cov cua sov ruaj khov yog khaws cia rau qee lub sijhawm, tom qab ntawd cov cua txias txuas ntxiv mus, lossis nws tshwm sim ua ke nrog ib lub sijhawm. Cov khoom siv cua sov (lub qhov cub).
Yog li, kev hloov pauv tsis tu ncua thiab isothermal ntawm austenite yog qhov txawv.
Ntawm tus yam ntxwv ntawm kev hloov pauv. Chart
C-puab daim duab, uas qhia txog qhov kev hloov pauv hauv microstructure ntawm cov hlau hauv lub sijhawm luv, nyob ntawm qhov ntsuas kub hloov pauv - qhov no yog austenite transformation daim duab. Kev txias tiag yog txuas ntxiv. Tsuas yog qee cov theem ntawm kev quab yuam cua sov tuaj yeem ua tau. Daim duab piav qhia txog cov xwm txheej isothermal.
Tus cwj pwm tuaj yeem sib kis thiab tsis sib kis.
Ntawm tus nqi txo cov nqi hluav taws xob, cov nplej austenite hloov pauv los ntawm kev sib kis. Nyob rau hauv cheeb tsam ntawm thermodynamic instability, atoms pib txav ntawm lawv tus kheej. Cov uas tsis muaj sij hawm nkag mus rau hauv cov hlau lattice daim ntawv cementite inclusions. Lawv koom nrog cov pa roj carbon monoxide nyob sib ze tso tawm los ntawm lawv cov muaju. Cementite yog tsim nyob rau hauv ciam teb ntawm decaying nplej. Purified ferrite crystals tsim cov ntawv sib xws. Ib tug dispersed qauv yog tsim - ib tug sib tov ntawm nplej, qhov loj thiab concentration ntawm uas nyob ntawm seb qhov ceev ntawm txias thiab cov ntsiab lus.carbon hlau alloy. Perlite thiab nws cov theem nruab nrab kuj tseem tsim: sorbite, troostite, bainite.
Ntawm qhov tseem ceeb ntawm qhov kub thiab txias, qhov decomposition ntawm austenite tsis muaj qhov sib txawv. Complex distortions ntawm crystals tshwm sim, nyob rau hauv uas tag nrho cov atoms ib txhij tsiv nyob rau hauv ib tug dav hlau yam tsis hloov lawv qhov chaw. Tsis muaj diffusion ua rau lub nucleation ntawm martensite.
Kev cuam tshuam ntawm hardening ntawm cov yam ntxwv ntawm decomposition ntawm austenite. Martensite
Hardening yog hom kev kho cua sov, qhov tseem ceeb ntawm cov cua kub ceev kom kub siab tshaj qhov tseem ceeb Ac3 thiab Acm, ua kom txias sai. Yog tias qhov ntsuas kub qis dua nrog kev pab ntawm cov dej ntawm tus nqi ntau dua 200˚С ib ob, tom qab ntawd cov txheej txheem acicular tau tsim, uas yog hu ua martensite.
Nws yog ib qho kev daws teeb meem supersaturated ntawm kev nkag mus ntawm cov pa roj carbon rau hauv cov hlau nrog cov siv lead ua lattice ntawm hom α. Vim muaj zog txav ntawm atoms, nws yog distorted thiab tsim ib tug tetragonal lattice, uas yog ua rau hardening. Cov qauv tsim muaj lub ntim loj dua. Raws li qhov tshwm sim, cov muaju uas khi los ntawm lub dav hlau yog compressed, koob zoo li daim hlau yug.
Martensite muaj zog thiab nyuaj heev (700-750 HB). Tsim tshwj xeeb vim yog kev kub ceev quenching.
Ntxhais. Diffusion structures
Austenite yog ib qho tsim los ntawm bainite, troostite, sorbite thiab perlite tuaj yeem tsim tawm. Yog hais tias qhov txias ntawm hardening tshwm sim ntawmqis dua speeds, diffusion transformations yog nqa tawm, lawv mechanism yog piav saum toj no.
Troostite yog perlite, uas yog tus cwj pwm los ntawm kev sib cais siab. Nws yog tsim thaum tshav kub txo 100˚С ib ob. Ntau cov nplej me me ntawm ferrite thiab cementite raug faib thoob plaws lub dav hlau. Cov "hardened" cementite yog tus cwj pwm los ntawm daim ntawv lamellar, thiab cov troostite tau txais los ntawm qhov kev sib tw tom ntej muaj qhov pom kev pom. Hardness - 600-650 HB.
Bainite yog theem nrab, uas yog qhov sib xyaw ua ke ntau dua ntawm cov muaju ntawm cov pa roj carbon ferrite thiab cementite. Nyob rau hauv cov nqe lus ntawm mechanical thiab technological zog, nws yog inferior rau martensite, tab sis tshaj troostite. Nws yog tsim nyob rau hauv qhov kub thiab txias ntau yam thaum diffusion yog tsis yooj yim sua, thiab lub zog ntawm compression thiab txav ntawm crystal qauv rau transformation mus rau hauv ib tug martensitic tsis txaus.
Sorbitol yog ib rab koob zoo li ntau yam ntawm pearlite theem thaum txias ntawm tus nqi ntawm 10˚С ib ob. Cov khoom siv tshuab yog nruab nrab ntawm pearlite thiab troostite.
Perlite yog kev sib xyaw ntawm cov nplej ntawm ferrite thiab cementite, uas tuaj yeem ua granular lossis lamellar. Tsim los ntawm kev lwj ntawm austenite nrog qhov txias ntawm 1˚C ib ob.
Beitite thiab troostite muaj feem cuam tshuam rau cov txheej txheem hardening, thaum sorbite thiab perlite tuaj yeem tsim tau thaum lub sij hawm tempering, annealing thiab normalization, cov yam ntxwv uas txiav txim siab cov duab ntawm cov nplej thiab lawv loj.
Kev cuam tshuam ntawm annealing rauaustenite lwj nta
Xyaum txhua yam kev sib tsoo thiab kev ua kom zoo yog raws li kev hloov pauv ntawm austenite. Tag nrho thiab tsis tiav annealing yog siv rau hypoeutecoid steels. Cov khoom yog rhuab nyob rau hauv lub cub tawg saum toj no cov ntsiab lus tseem ceeb Ac3 thiab Ac1 feem. Thawj hom yog tus cwj pwm los ntawm kev muaj lub sijhawm tuav ntev, uas ua kom tiav kev hloov pauv: ferrite-austenite thiab pearlite-austenite. Qhov no yog ua raws li kev ua kom txias qeeb ntawm cov workpieces hauv qhov cub. Ntawm cov zis, qhov sib xyaw ua kom zoo ntawm ferrite thiab pearlite tau txais, tsis muaj kev ntxhov siab sab hauv, yas thiab ruaj khov. Tsis tiav annealing yog tsawg zog siv zog thiab tsuas yog hloov cov qauv ntawm pearlite, tawm hauv ferrite zoo tsis hloov. Normalization implies qhov kub ntawm qhov txo qis dua, tab sis kuj yog coarser thiab tsawg dua cov qauv yas ntawm qhov tawm. Rau cov hlau alloys nrog cov ntsiab lus carbon ntawm 0.8 mus rau 1.3%, thaum txias, ua ib feem ntawm normalization, decomposition tshwm sim nyob rau hauv cov kev taw qhia: austenite-pearlite thiab austenite-cementite.
Lwm hom kev kho cua sov raws li cov qauv kev hloov pauv yog homogenization. Nws muaj feem xyuam rau qhov loj. Nws txhais tau hais tias qhov ua tiav tiav ntawm lub xeev austenitic coarse-grained ntawm qhov kub ntawm 1000-1200 ° C thiab raug rau hauv qhov cub rau txog 15 teev. Cov txheej txheem isothermal txuas ntxiv nrog kev ua kom txias qeeb, uas pab kom txawm tias tawm ntawm cov txheej txheem hlau.
Isothermal annealing
Txhua txoj kev teev tseg ntawm kev cuam tshuam cov hlau kom nkag siab yooj yimsuav tias yog isothermal transformation ntawm austenite. Txawm li cas los xij, txhua tus ntawm lawv tsuas yog nyob rau qee theem muaj cov yam ntxwv tshwj xeeb. Hauv kev muaj tiag, kev hloov pauv tshwm sim nrog qhov txo qis hauv cov cua sov, qhov ceev uas txiav txim siab qhov tshwm sim.
Ib txoj hauv kev ze tshaj plaws rau cov xwm txheej zoo tshaj plaws yog isothermal annealing. Nws cov ntsiab lus tseem muaj nyob rau hauv cua sov thiab tuav kom txog rau thaum tag nrho cov txheej txheem rau hauv austenite. Kev ua kom txias yog siv nyob rau hauv ob peb theem, uas ua rau qeeb qeeb, ntev dua thiab ntau thermally ruaj khov decomposition.
- Qhov kub poob sai sai rau 100˚C hauv qab tus taw tes Ac1.
- Kev tuav pov hwm tus nqi tiav (los ntawm kev tso rau hauv lub qhov cub) kom ntev mus txog thaum cov txheej txheem ntawm kev tsim cov ferrite-pearlite theem tiav.
- Coj hauv huab cua.
Txoj kev kuj tseem siv tau rau cov hlau alloy, uas yog tus cwj pwm los ntawm qhov muaj cov austenite seem hauv lub xeev txias.
Retained austenite thiab austenitic steels
Qee zaum kev lwj tsis tiav tuaj yeem ua tau thaum muaj cov austenite khaws cia. Qhov no tuaj yeem tshwm sim hauv cov xwm txheej hauv qab no:
- Cov nrawm dhau thaum ua tiav kev lwj tsis tshwm sim. Nws yog ib feem ntawm bainite los yog martensite.
- High-carbon lossis low-alloy steel, uas cov txheej txheem ntawm austenitic dispersed transformations yog qhov nyuaj. Yuav tsum muaj kev kho cua sov tshwj xeeb xws li homogenization lossis isothermal annealing.
rau siab-alloyed -tsis muaj cov txheej txheem ntawm kev piav qhia txog kev hloov pauv. Alloying steel nrog npib tsib xee, manganese, chromium txhawb kev tsim ntawm austenite ua lub ntsiab muaj zog, uas tsis tas yuav muaj kev cuam tshuam ntxiv. Austenitic steels yog tus cwj pwm los ntawm lub zog siab, kev tiv thaiv corrosion thiab kub tsis kam, kub tsis kam thiab tsis kam ua haujlwm hnyav hnyav.
Austenite yog cov qauv uas tsis muaj kev tsim uas tsis muaj qhov kub thiab txias ntawm cov hlau tuaj yeem ua tau thiab koom nrog yuav luag txhua txoj hauv kev kho cua sov txhawm rau txhawm rau txhim kho cov khoom siv thiab thev naus laus zis.
