Decarburization Qhov tob ntawm Rail Surface thiab Cov Txheej Txheem Tseem Ceeb rau Rail Head Fatigue Crack Initiation
Vim li cas cov txheej txheem decarburized dhau los ua qhov zoo tshaj plaws pib qhov chaw rau kev qaug zog tawg hauv lub taub hau tsheb ciav hlau, thiab nws cov micro- tshuab yog dab tsi?
Vim yog cov pa roj carbon poob, cov txheej decarburized hloov pauv los ntawm siab - lub zog pearlite mus rau qhov sib xyaw mos ntawm ferrite thiab pearlite, nrog hardness 30% -50% qis dua cov matrix. Nyob rau hauv lub log-rail rolling kev sib cuag, cov mos decarburized txheej tsis tuaj yeem tiv taus kev ntxhov siab heev thiab ua rau cov yas ntws hnyav, ua rau cov kab nrib pleb. Cov yas deformation hauv zos no ua rau muaj kev ntxhov siab tseem ceeb ntawm qhov sib cuam tshuam ntawm cov txheej txheem decarburized thiab cov matrix nyuaj, uas ua rau "kev nyuaj siab teeb meem" vim tsis sib haum xeeb deformation. Nyob rau hauv cyclic loading, microcracks pib ntawm no interface, propagate parallel mus rau qhov chaw khiav, thiab nws thiaj li tsim nto qaug zog tawg.
Dab tsi yog qhov sib txawv ntawm cov kev cai tseem ceeb rau kev tsheb ciav hlau lub taub hau decarburized txheej tob ntawm Suav thiab thoob ntiaj teb cov qauv?
Tuam Tshoj tus GB/T 2585 qhia meej meej qhov pib: rau siab -ceev thiab hnyav- tsheb ciav hlau, tag nrho decarburized txheej qhov tob (tag nrho + ib nrab) yuav tsum tsis pub tshaj0.5 hli, nrog xoom tag nrho decarburization. UIC 860 yog nruj dua, txwv tsis pub decarburized txheej dhau0.3mm ib for UIC 60 and above rails, with no continuous full decarburization allowed. AREMA standards grade by axle load: the threshold is 0.4mm for heavy-haul rails (>35t) thiab 0.6mm rau cov pa tsheb ciav hlau. Cov kev sib txawv no qhia txog kev sib txawv ntawm kev tswj lub log- kev tsheb ciav hlau tiv thaiv kev qaug zog.
Dab tsi tshwj xeeb rail defects tshwm sim thaum lub decarburized txheej tob tshaj qhov tseem ceeb pib?
Ntau dhau decarburization feem ntau ua raurail taub hau nto spalling, pib tshwm li ntses- nplai- zoo li flaking. Cov spalls tom qab ntawd dhau los ua kev ntxhov siab concentrators, accelerating rolling contact fatigue crack formation. Qhov thib ob, nws ua raurail taub hau corrugation, raws li qhov tsis sib xws ntawm cov txheej txheem decarburized cuam tshuam lub log -rail kev sib cuag smoothness thiab induces tus kheej -zoo siab co. Hauv hnyav- cov kab tsheb,rail taub hau yas ntwstej zaum yuav tshwm sim, qhov twg decarburized hlau extrudes sideways los ua "bulges," hnyav heev rau lub log -rail kev taw qhia kev ua tau zoo.
Yuav ua li cas kom tswj tau cov txheej txheem decarburized qhov tob los ntawm kev kho cua sov thaum lub caij tsheb ciav hlau?
Lub hauv paus tswj yog nyob rau hauv "oxidation cais + ceev ceev. "Thaum kev kho cua sov hauv online, ua ntej lub taub hau tsheb ciav hlau nkag mus rau hauv lub thawv quenching,inert roj tiv thaivlos yogtiv thaiv - oxidation txheejyog siv los cais cov tsheb ciav hlau kub taub hau los ntawm huab cua, tiv thaiv cov pa roj carbon diffusion ntawm qhov chaw. Hauv quenching,siab -siab dej pos huab cua txiasua kom txias sai sai ntawm qhov chaw tsheb ciav hlau los ntawm thaj chaw austenitizing mus rau thaj chaw pearlite hloov pauv hauv tsawg dua 2 vib nas this, txo cov sijhawm carbon diffusion tsawg. Tsis tas li ntawd, optimizing lub quenching kub teb kom zoo ib yam ntawm qhov kub thiab txias, tsis txhob overheating nyob rau hauv lub zos overheating thiab hnyav decarburization, stably tswj qhov tob nyob rau hauv qhov chaw pib.
Nyob rau hauv - qhov chaw kuaj pom qhov tsis zoo, yuav ua li cas kom raug txiav txim siab yog tias cov txheej txheem decarburized ntau dhau los ntawm kev sib txuas cov tshuaj ntsuam xyuas saum npoo thiab kev tshuaj ntsuam metallographic?
Ncaj nraim ntawm - qhov chaw ntsuas tsis yooj yim sua; ib "nto qhov xwm txheej ua ntej kev txiav txim + sampling metallographic tshuaj xyuas" txoj kev yog siv. Ua ntej, siab -txhais qhov chaw imaging systems ntawm txoj kev tsheb ciav hlau tsis pom kev tsheb txheeb xyuas cov ntses thaum ntxov- nplai spalling lossis txawv txav ntawm cov yas deformation, kos cim qhov chaw xav tau. Tom qab ntawd, cov qauv tsheb ciav hlau raug coj los ntawm cov cim cim rau kev npaj metallographic. Hauv chav kuaj, ib txheej txheej metallographic microscope ntsuas ntawm 50x decarburized. pearlite) thiab ib nrab decarburization (refined pearlite lamellae) yog qhov txawv;