Austenite - dab tsi yog qhov no?

Thaum tshav kub kub kev kho mob ntawm steel - yog ib tug haib mechanism rau ua raws li nws tus qauv thiab cov khoom. Nws yog raws li nyob rau hauv kev hloov kho ntawm tus siv lead ua ntxaij ntoo raws li ib tug muaj nuj nqi ntawm qhov kub ntawm qhov kev ua si. Qhov ntau yam tej yam kev mob nyob rau hauv hlau-cov hlau yuav ua tau tam sim no ferrite, pearlite, cementite thiab austenite. Cov yav tas plays ib tug luag hauj lwm loj nyob rau hauv tag nrho cov ntawm thermal hloov nyob rau hauv lub hlau.

txhais

Steel - ib tug hlau hlau thiab cov pa roj carbon, nyob rau cov pa roj carbon cov ntsiab lus yog li 2,14% ntawm kev tshawb xav, tab sis nws yog ib technologically siv muaj nyob rau hauv tus nqi tsis ntau tshaj li 1.3%. Raws li, tag nrho cov lug uas yog tsim nyob rau therein nyob rau hauv lwm influences, yog tseem variants alloys.

Qhov kev tshawb xav yog lawv lub neej nyob rau hauv 4 variations: allergic khoom tov, ib tug khoom tov ntawm ib qho kev zam, ib tug txhua yam sib tov los yog ib tug tshuaj compound nplej.

Austenite - ib tug khoom carbon atom granetsentricheskuyu allergic daws nyob rau hauv ib tug nyhav siv lead ua ntxaij ntoo ntawm hlau, raug xa mus rau raws li γ. carbon atom yog nkag tau rau hauv cov kab noj hniav ntawm γ-hlau ntxaij ntoo. Nws qhov ntev tshaj cov neeg pores ntawm Fe atoms, uas piav txog cov tsawg dua lawv los ntawm lub "phab ntsa" ntawm lub hauv paus qauv. Tsim thaum lub sij hawm transformation kub ntawm ferrite thiab pearlite los ntawm kev ua lub tshav kub 727˚S saum toj no.

Daim duab ntawm cov hlau-carbon alloys

Teeb hu ua theem daim duab ntawm cov hlau-cementite lub tsev los experimentation, yog ib tug ntshiab ua qauv qhia ntawm tag nrho cov tau variants ntawm transformations nyob rau hauv steels thiab cam khwb cia irons. Cov qhov tseem ceeb rau ib tug muab kub tus nqi ntawm cov carbon nyob rau hauv lub hlau tsim ib tug tseem ceeb heev taw tes nyob rau hauv uas muaj ib qho tseem ceeb cov yam ntxwv hloov nyob rau hauv cov cua kub lossis cua txias dab, lawv kuj tsim tau ib cov tseem ceeb heev line.

GSE kab uas muaj point thiab Ac ₃ Ac _m, qhia txog cov theem ntawm cov pa roj carbon solubility nrog ua tshav kub ntau.

kev kawm nta

Austenite - ib tug qauv uas yog tsim nyob rau thaum lub sij hawm steel cua kub. Thaum lub tseem ceeb heev kub tsim perlite thiab ferrite ib cov ntaub ntawv uas.

cua kub variations:

1. Uniform, kom txog thaum xeeb cov yam nqi, ib tug nyuag excerpt txias. Nyob ntawm seb cov yam ntxwv ntawm cov hlau, lub austenite tej zaum yuav tsim raws li ib tug tag nrho los yog.
2. Qeeb sawv nyob rau hauv kub, ib tug ntev lub sij hawm ntawm kev tswj cov tiav qib ntawm tshav kub mus rau tsim ib tug dawb huv austenite.

Lub zog ntawm cov rhuab cov ntaub ntawv uas, raws li zoo raws li uas yuav tshwm sim raws li ib tug tshwm sim ntawm txias. Ntau nyob ntawm lub theem tiav los ntawm lub tshav kub. Nws yog ib qho tseem ceeb kom tsis txhob overheating los yog perepal.

Microstructure thiab khoom

Txhua yam ntawm cov theem, ntse hlau-carbon alloys, yuav muaj cov qauv ntawm cov arrays thiab nplej. austenite qauv - phaj muaj ib tug duab nyob ze rau qhov koob li thiab lub hlwb, thiab flaky. Thaum siab yaj carbon nyob rau hauv lub γ-hlau nplej muaj ib tug duab tsis muaj ib lub teeb tsaus cementite inclusions.

Lub hardness ntawm 170-220 HB. Thermal thiab hluav taws xob conductivity yog qis dua hais tias ntawm ferrite. Sib Nqus zog yog tsis muaj.

Variants thiab cua txias npaum li cas ua rau yus mus rau tsim ntawm txawv versions ntawm lub "khaub thuas" xeev: martensite, bainite, troostite, sorbitol, perlite. Lawv muaj koob zoo li tus qauv, tab sis txawv particle dispersion, lub grain loj thiab cov cementite particle.

Cawv ntawm txias austenite

austenite lwj tshwm sim nyob rau hauv tib qho tseem ceeb cov ntsiab lus. Nws cov hauj lwm zoo nyob rau yam nram qab no:

1. Tus nqi ntawm txias. Muaj feem xyuam rau qhov xwm ntawm cov pa roj carbon impurities, tus tsim ntawm cov nplej, tsim ntawm lub kawg microstructure thiab nws cov khoom. Nws nyob rau ntawm ib puag ncig, uas yog siv raws li ib tug coolant.
2. Muaj isothermal tivthaiv rau ntawm ib cov theem kev lwj - yog lowered mus rau ib tug tej yam kub theem, lub tshav kub yog khaws cia ruaj khov thaum lub sij hawm ib tug tej lub sij hawm, tom qab uas sai txias yog txuas ntxiv, los yog hais tias nws tshwm sim nyob rau hauv nrog ib tug cua kub apparatus (cub).

Yog li, cais thiab tas mus li isothermal transformation ntawm austenite.

Nta ntawm cov ua cim transformations. daim ntawv

C-zoo li tus teeb uas qhia tau hais tias cov qauv ntawm cov kev hloov ntawm cov hlau microstructure nyob rau hauv lub sij hawm luv nyob rau hauv lub kub hloov - qhov no austenite transformation daim duab. Lub sij txias tsis tu ncua. Muaj tsuas yog tej yam theem yuam tshav kub tuav tseg. Lub teeb qhia txog cov isothermal tej yam kev mob.

Ximxoo yuav ua tau diffuse thiab Diffusionless.

Thaum txheej txheem ceev kev hloov txo tshav kub diffusion austenite nplej tshwm sim. Lub thermodynamic instability tsam atoms pib txav ua ke. Cov neeg uas tsis tswj kom penetrate lub hlau ntxaij ntoo, tsim cementite inclusions. Lawv tuaj koom los ntawm lub nyob sib ze hais txog cov pa roj carbon, tso nws muaju. Cementite yog tsim nyob rau thaj tsam ntawm lub nplej disintegrating. Lim muaju roos duas ferrite phaj. Dispersed qauv yog tsim - sib tov ntawm grain, qhov luaj li cas thiab concentration ntawm uas yog nyob rau hauv lub rapidity ntawm txias thiab cov ntsiab lus ntawm cov pa roj carbon nyob rau hauv lub hlau. Tsim raws li perlite thiab nws intermediate theem: sorbitol, troostite, bainite.

Nrog tseem ceeb ceev yuav txo tau kub austenite decomposition tsis diffusive xwm. Complex siv lead ua distortion tshwm sim tsis pub dhau uas tag nrho cov atoms ib txhij txav mus rau hauv lub dav hlau tsis muaj kev hloov qhov chaw. Qhov uas tsis muaj diffusion muaj txhawb rau rov tshwm sim ntawm martensite.

Cov nyhuv ntawm quenching rau austenite decomposition yam ntxwv. martensite

Hardening - ib hom ntawm tshav kub kev kho mob, uas yeej tseem zoo muaj nyob rau hauv ib tug ceev ceev cua kub mus rau siab kub saum toj no tseem ceeb heev taw tes thiab lub Ac ₃ Ac _m, ua raws li los ntawm ceev ceev txias. Yog hais tias lub txo nyob rau hauv kub yuav siv sij hawm qhov chaw nrog dej rau tus ceev ntawm ntau tshaj 200 ° C rau ib tug thib ob, ces ib tug khoom acicular theem muaj martensite lub npe.

Nws yog ib tug supersaturated khoom tov ntawm cov pa roj carbon nyob rau hauv allergic hlau hom siv lead ua ntxaij ntoo nrog α. Vim hais tias ntawm cov haib taw atoms yog distorted thiab ntaub ntawv ib tug tetragonal lattice uas ua hauj lwm pab ua hardening. Cov tsim qauv muaj ib tug loj ntim. Cov uas ua muaju tau ciaj dav hlau compressed nucleate acicular daim hlau.

Martensite - check thiab nyuaj heev (700-750 HB). Tsim heev dua lwm yam raws li ib tug tshwm sim ntawm high-ceev quenching.

Tempering. diffusion qauv

Austenite - yog lub tsim ntawm uas yuav artificially ua bainite, troostite, sorbite, thiab perlite. Yog hais tias lub quenching txias tshwm sim rau sab velocities, lub conversion nqa tawm diffusion, lawv mechanism piav saum toj no.

Troost - yog perlite, uas yog yus muaj los ntawm ib tug high degree ntawm dispersion. Tsim nyob rau ntawm 100 ° C txo nyob rau hauv lub tshav kub ntawm lub caij. Ib tug loj tus naj npawb ntawm zoo nplej ntawm ferrite thiab cementite yog faib nyob rau hauv tag nrho lub dav hlau. "Hardened" peculiar cementite phaj zoo thiab troostite uas ua los ntawm tom ntej tempering, muaj ib tug granular visualization. Hardness - HB 600-650.

Bainite - ib nrab theem, uas yog ib tug txawm ntau dua muaju ntawm high-dispersed sib tov ntawm ferrite thiab cementite. Raws li tus neeg kho tshuab thiab hauj zog ua tsis tau zoo rau martensite, tab sis ntau tshaj troostite. Tsim nyob rau hauv lub kub ntau qhov chaw uas lub diffusion yog tsis yooj yim sua thiab cov compression quab yuam thiab tsiv mus nyob rau crystalline qauv kom hloov mus rau martensite - tsis txaus.

Sorbitol - lub ntxhib acicular ntau yam pearlitic theem ntawm txias npaum li cas ntawm 10 ° C rau ib ob. Neeg kho tshuab hauj lwm cov khoom yog intermediate ntawm troostite thiab pearlite.

Perlite - ib tug plurality cov nplej ntawm ferrite thiab cementite, uas tej zaum yuav granular, los yog phaj lawm. Tsim raws li ib tug tshwm sim ntawm cov smooth decomposition ntawm austenite ntawm ib tug txias npaum li cas 1S ib ob.

Beit troostite thiab - xa mus rau ib tug tua lug, thaum sorbitol thiab perlite peev xwm yuav tsim thiab tempering, annealing thiab normalizing nta uas txhais tau lub zoo thiab loj cov nplej.

Nyhuv ntawm annealing rau cov austenite decomposition

Yuav luag tag nrho cov hom ntawm annealing thiab normalization raws li nyob rau hauv lub reciprocal transformation ntawm austenite. Tag nrho thiab yog ib feem-lub sij hawm annealing yog siv los doevtektoidnyh steels. Paub meej rhuab nyob rau hauv ib qhov cub saum toj no tseem ceeb heev cov ntsiab lus Ac ₁ thiab Ac _3, ntsig txog. Rau thawj lub hom yog yus muaj los ntawm ib lub caij nyoog raug lub sij hawm, uas saib kuas tiav hloov dua siab tshiab: austenite-ferrite-austenite thiab pearlite. Raws li los ntawm qeeb txias billets nyob rau hauv lub cub tawg. Thaum cov qhov tso zis muab zoo sib tov ntawm ferrite thiab pearlite, tsis muaj nrog txhawj xeeb thiab yas khoom. Mos annealing tsawg zog-intensive, tsuas hloov cov qauv ntawm cov perlite, ferrite tawm hauv zoo unchanged. Normalization implies ib tug ntau dua tus nqi ntawm kub poob, txawm li cas los, ntau yas thiab tsawg ntxhib qauv ntawm cov qhov hluav taws xob. Rau steel hlau nrog ib tug carbon cov ntsiab lus ntawm los ntawm 0.8 mus 1.3% thaum txias nyob rau hauv lub normalization lwj tshwm sim mus rau: austenite, pearlite, austenite-cementite.

Lwm yam ntawm tshav kub kev kho mob uas yog raws li nyob rau hauv structural transformations, yog homogenisation. Nws yog muaj feem xyuam rau ntau qhov chaw. Nws implies tsis tau raws li ntxhib austenitic lub xeev nyob kub 1000-1200˚S thiab endurance nyob rau hauv ib tug cub tawg nyob rau hauv ib lub sij hawm txog li 15 teev. Isothermal dab tseem qeeb cua txias, uas muaj txhawb rau equalization ntawm cov hlau lug.

isothermal annealing

Txhua yam ntawm cov kev ntawm influencing hlau rau facilitation ntawm kev nkag siab ntshai li isothermal transformation ntawm austenite. Txawm li cas los, lawv txhua tus tsuas yog nyob rau ib qho kev theem muaj yam ntxwv. Nyob rau hauv kev muaj tiag, kev hloov tshwm sim nrog ib tug neeg twg txo ntawm tshav kub, lub ceev uas txiav txim tshwm sim.

Ib txoj kev uas yog ze tshaj rau tus zoo tagnrho tej yam kev mob - isothermal annealing. Nws essence kuj muaj nyob rau hauv cov cua kub thiab raug mus rau lub tiav cev qhuav dej ntawm tag nrho cov lug nyob rau hauv lub austenite. Lub cua txias yog pom tau hais nyob rau hauv ob peb theem, uas muaj txhawb rau ib tug qeeb qeeb, ntau heev thiab ntau thermally ruaj khov ntawm nws cov hniav lwj.

1. Lub ceev ceev nco nyob rau hauv kub mus rau ib tug nqi hauv qab no 100 ° C rau Ac ₁ point.
2. Yuam tuav tiav nqi (muab tso rau hauv lub cub tawg) rau ib ntev lub sij hawm kom txog rau thaum kawm tiav ntawm tsim ntawm ib tug ferritic-pearlitic theem.
3. Cua txias nyob rau hauv tseem huab cua.

Cov qauv no yog muaj feem xyuam rau alloy steels, uas yog tsiag ntawv los ntawm xub ntiag ntawm residual austenite nyob rau hauv ib tug tub yees xeev.

Qhov seem austenite thiab austenitic steels

Tej zaum nws yog tau ib nrab lwj, thaum muaj ib tug residual austenite. Qhov no yuav tshwm sim nyob rau hauv lub nram qab no:

1. Dhau sai txias thaum ua tiav rhuav tshem tshwm sim. Nws yog ib tug yam ntxwv feem ntawm bainite los yog martensite.
2. High carbon steel los yog tsawg hlau, rau cov uas dab yog nyuab dispersed austenite transformations. Nws yuav tsum tau siv tshwj xeeb thaum tshav kub kub kho mob txoj kev, xws li, piv txwv li, homogenization los yog isothermal annealing.

Rau high-- Tsis yog piav los ntawm transformations. Alloying steel nrog npib tsib xee, manganese, chromium txhawb lub tsim ntawm austenite li cov thawj cov khoom qauv uas tsis yuav tsum tau ntxiv influences. Austenitic steels yog yus muaj los ntawm siab zog, corrosion kuj thiab tshav kub tsis kam, Thaum tshav kub kub kuj thiab kuj mus txhoj puab heev ua hauj lwm tej yam kev mob tsis yooj yim.

Austenite - yog ib tug qauv uas yog tsis yooj yim sua yam uas tsis tau txoj kev tsis muaj high-kub cua sov ntawm hlau thiab uas yog muab kev koom tes nyob rau hauv yuav luag tag nrho nws cov tshav kub kev kho mob txoj kev los txhim kho txhua yam thiab ua zog.