Austenitic stainless hlaufeem ntau muaj microstructure uas muaj cov ntshiab austenite ntawm chav tsev kub; Txawm li cas los xij, qee qhov sib txawv muaj me me ntawm ferrite, uas pab tiv thaiv kub tawg. Vim lawv cov weldability zoo heev, austenitic stainless hlau tau dav siv hauv kev lag luam xws li kev ua tshuaj lom neeg thiab kev tsim cov hlab ntsha siab rau cov roj av. Txawm li cas los xij, yog tias kev ua haujlwm vuam tau ua tsis raug, austenitic stainless hlau muaj qhov cuam tshuam rau ntau yam teeb meem, nrog rau kev cuam tshuam ntawm intergranular, kub tawg, kev nyuaj siab corrosion cracking, thiab tsis zoo weld hlaws tsim.
Dab tsi yog cov teeb meem vuam cuam tshuam nrog austenitic stainless hlau?
I. Intergranular corrosion
a. Ua rau ntawm Intergranular Corrosion
Intergranular corrosion tshwm sim ntawm cov ciam teb nplej; Yog li ntawd, nws yog hu ua intergranular corrosion. Nws sawv cev rau ib qho ntawm cov ntaub ntawv txaus ntshai tshaj plaws ntawm degradation rau austenitic stainless hlau. Nws yog tus cwj pwm los ntawm kev xeb uas nkag mus tob rau hauv cov hlau raws li cov ciaj ciam ntawm cov qoob loo, uas ua rau muaj kev poob qis hauv ob qho tib si cov khoom thiab corrosion kuj ntawm cov hlau.
Thaum austenitic stainless hlau tuav nyob rau hauv qhov kub ntawm 450℃mus rau 850℃rau ib lub sij hawm, chromium carbides (Cr23C6) precipitate ntawm grain ciam teb. Cov chromium xav tau rau cov nag lossis daus no feem ntau yog los ntawm cov txheej txheej ntawm cov nplej; Yog hais tias cov chromium los ntawm cov nplej sab hauv tsis tuaj yeem nthuav tawm sab nraud sai txaus los ntxiv cov txheej txheem saum npoo av, cov ntsiab lus chromium ntawm cov ciam teb nplej -tshwj xeeb hauv cov txheej txheej ntawm cov nplej- yuav poob, tsim kom muaj "chromium-depleted zone." Raws li kev cuam tshuam ntawm kev tawm dag zog corrosive, cov chromium -depleted aav ntawm cov ciam teb ua rau muaj kev cuam tshuam rau kev tawm tsam, ua rau muaj kev cuam tshuam ntawm intergranular. Stainless hlau cuam tshuam los ntawm intergranular corrosion tuaj yeem pom tsis pom kev hloov pauv ntawm nws qhov chaw; Txawm li cas los xij, thaum raug kev nyuaj siab, nws yuav tawg raws li cov qoob loo ciam teb, uas ua rau yuav luag tag nrho cov qauv ntawm lub zog.
b. Kev ntsuas los tiv thaiv Intergranular Corrosion
Xaiv stainless hlau vuam electrodes nrog ultra- cov ntsiab lus carbon tsawg (C Tsawg dua lossis sib npaug li 0.03%) lossis cov uas muaj cov khoom ruaj khov xws li titanium lossis niobium.
Ua haujlwm "low-heat-input" welding parameters. Lub hom phiaj yog kom txo qis lub sijhawm nyob hauv qhov ntsuas kub tseem ceeb (450℃-850 degree). Qhov no yog ua tiav los ntawm kev siv cov vuam tam sim no qis, kev mus ncig siab ceev, luv luv arc lengths, thiab tsis txhob hla txoj kev sib tw. Kev ua kom txias txias (piv txwv li, siv tooj liab rov qab daim hlau los yog dej txias) tuaj yeem siv rau hauv vuam seam kom ceev cov cua txias ntawm qhov sib koom ua ke thiab txo qhov kub ntawm qhov kub- thaj tsam cuam tshuam (HAZ).
Hauv ntau- hla vuam, inter- kis kub yuav tsum tau tswj nruj me ntsis; cov hlaws weld ua ntej yuav tsum tau tso cai kom txias kom qis dua 60℃ua ntej qhov kev xa mus tom ntej yog tso. Lub weld seam nyob rau sab ntawm cov khoom uas yuav nyob rau hauv kev sib cuag nrog corrosive nruab nrab yuav tsum tau welded kawg. Ib qho kev tshaj tawm -weld tov kev kho yuav tsum tau ua: lub workpiece yog rhuab mus rau ib tug kub ntawm 1050℃thiab 1150 degree, ua raws li los ntawm quenching. Cov txheej txheem no ua rau Cr23C6 precipitates ntawm cov ciam teb ntawm cov nplej kom rov ua dua rau hauv cov nplej sab hauv, yog li rov ua kom lub cev tsis zoo austenitic microstructure.
II. Kub Cracking
Ua rau Kub Cracking
Lub sijhawm kub kub loj ntawm cov kua dej thiab cov kab mob solidus- txhais tau tias muaj qhov kub thiab txias thaum lub sij hawm ua tiav cov txheej txheem solidification- ua rau muaj kev sib cais hnyav ntawm qis - melting - taw tes impurities, uas nyiam mloog zoo ntawm cov ciam teb. Tsis tas li ntawd, lub siab coefficient ntawm thermal expansion ua rau muaj kev ntxhov siab loj thaum lub sij hawm txias thiab shrinkage.
Kev ntsuas los tswj kub tawg
Tswj lub microstructure ntawm lub vuam hlau; Qhov zoo tshaj plaws, cov hlau vuam yuav tsum muaj cov qauv duplex, nrog cov ntsiab lus ferrite khaws cia ntawm lossis qis dua 3% -5%. Qhov no yog vim hais tias ferrite muaj peev xwm ua kom yaj cov khoom tsis zoo xws li sulfur (S) thiab phosphorus (P). Tswj cov tshuaj muaj pes tsawg leeg; txo cov ntsiab lus ntawm npib tsib xee, carbon, sulfur, thiab phosphorus hauv cov hlau vuam-thaum nce qib ntawm cov ntsiab lus xws li chromium, molybdenum, silicon, thiab manganese- tuaj yeem txo qhov tshwm sim ntawm kub tawg.
Xaiv ib hom electrode txheej uas tsim nyog. Kev siv qis -hydrogen- hom coated electrodes txhawb cov nplej refinement nyob rau hauv cov hlau weld, txo impurity segregation, thiab txhim khu kev tiv thaiv tawg. Hloov pauv, acidic - hom coated electrodes muaj zog oxidizing zog, ua rau muaj kev kub nyhiab heev - tawm ntawm cov ntsiab lus alloying thiab ua rau txo qis hauv kev ua haujlwm tawg; Ntxiv mus, lawv ua rau ntxhib- cov qauv nplej, ua rau cov weld raug kub kub tawg. Siv cov txheej txheem vuam tsim nyog thiab cov nqi cua txias. Siv qhov ntsuas "txias" vuam txwv tsis pub-tshwj xeeb, tsis tshua muaj tam sim no thiab kev mus los nrawm- txhawm rau tiv thaiv kom tsis txhob muaj cua sov ntawm lub pas dej welding thiab pab kom txias sai; Qhov no txo qis kev sib cais thiab txhim kho kev sib tsoo. Hauv ntau- hla vuam, nruj me ntsis tswj qhov kub ntawm qhov sib cuam tshuam; xyuas kom meej tias cov hlaws weld ua ntej tau txias rau 60℃ua ntej tso cov hlaws tom ntej.
III. Kev nyuaj siab Corrosion Cracking
Ua rau Stress Corrosion Cracking
Kev ntxhov siab corrosion cracking (SCC) yog ib qho tshwm sim ntawm ncua kev tawg uas tshwm sim hauv cov pob qij txha thaum raug kev ntxhov siab nyob rau hauv ib qho chaw corrosive. Nyob rau hauv austenitic stainless hlau welded pob qij txha, SCC sawv cev rau ib tug tshwj xeeb hom ntawm tsis ua hauj lwm, manifesting li brittle fracture unaccompanied los ntawm tej macroscopic yas deformation.
Kev ntsuas tiv thaiv kev ntxhov siab Corrosion Cracking
Tsim kom tsim nyog tsim, ua, thiab sib dhos cov txheej txheem kom txo tau qhov txias txias -induced deformation ntau npaum li sai tau; tsis txhob yuam kev sib dhos; thiab tiv thaiv qhov kev taw qhia ntawm ntau yam defects nyob rau hauv cov txheej txheem los ua ke (vim ntau yam sib dhos- cuam tshuam cov khawb thiab arc ntaus tuaj yeem ua qhov chaw pib tawg rau SCC thiab muaj kev txhim kho rau hauv qhov corrosion). Xaiv vuam consumables judiciously. Cov hlau vuam thiab lub hauv paus hlau yuav tsum zoo- sib txuam kom tiv thaiv kev tsim ntawm cov khoom siv tsis zoo- xws li cov nplej coarsening lossis tawv, nkig martensite. Siv cov txheej txheem vuam tsim nyog. Xyuas kom meej tias cov hlaws hlaws nthuav tawm zoo morphology, tsis muaj qhov tsis xws luag uas tuaj yeem ua rau muaj kev ntxhov siab los yog pitting (xws li, undercut); Tsis tas li ntawd, txais yuav ib qho kev sib txuas ntawm kev sib txuas kom txo tau qhov seem welding stresses. Ua raws li kev ntxhov siab{11}}kev kho mob. Qhov no feem ntau suav nrog tom qab-weld kev kho cua sov, xws li tag nrho annealing lossis annealing; Nyob rau hauv rooj plaub uas kev kho cua sov yog qhov nyuaj rau kev ua tiav, lwm txoj hauv kev-xws li ncej- vuam peening lossis tua blasting- tuaj yeem ua haujlwm.
IV. Poor Weld Bead Formation
a. Ua rau tsis zoo Weld Bead Formation
Thaum vuam austenitic stainless hlau, cov ntsiab lus siab ntawm cov ntsiab lus alloying nyob rau hauv cov hlau weld ua rau cov dej tsis zoo ntawm lub pas dej ua ke, uas feem ntau ua rau tsis zoo ntawm cov hlaws hlaws. Qhov no yog feem ntau manifested raws li deteriorated tsim nyob rau sab nraum qab ntawm lub hauv paus pass thiab ib tug ntxhib nto tiav rau lub hau hla. Txawm hais tias qhov kev cuam tshuam ntawm qhov tsis zoo ntawm qhov kev ua haujlwm ntawm vuam tsis yog tshwj xeeb tshaj yog pom nyob rau hauv ib puag ncig lossis siab - qhov kub thiab txias ua haujlwm, nyob rau hauv qis - qhov kub thiab txias, qhov kev ntxhov siab vim los ntawm qhov tsis xws luag tuaj yeem cuam tshuam rau qhov vuam qhov qis - qhov kub thiab txias kev ua haujlwm ib yam li qhov tsis xws luag hauv weld.
b. Kev ntsuas rau qhov tsis zoo Weld Bead tsim
Cov teeb meem hais txog kev tsim cov hlaws tsis zoo- nrog rau cov teeb meem ntawm intergranular corrosion nyob rau hauv tshav kub- cuam tshuam cheeb tsam (HAZ)- tuaj yeem daws tau zoo los ntawm kev ua kom zoo ntawm cov txheej txheem vuam. Tshwj xeeb, ua haujlwm Gas Tungsten Arc Vuam (GTAW) rau cov hauv paus hla, ua ke nrog kev siv cov khoom siv hluav taws xob qis qis, tso cai rau kev tswj tau zoo ntawm qhov HAZ raug rau qhov kub thiab txias ntau yam.
xaus
Austenitic stainless hlau yog cov khoom siv dav siv hauv kev lag luam tshuaj thiab petrochemical; Txawm li cas los xij, nws txoj kev vuam yog ua rau plaub hom kev tsis xws luag-xws li intergranular corrosion thiab kub tawg- lub hauv paus ua rau muaj feem cuam tshuam rau kev tswj qhov kub thiab txias, kev sib cais ntawm lub hauv paus, thiab kev ntxhov siab seem. Qhov zoo tshaj plaws, cov teeb meem no tsuas yog cuam tshuam cov weld morphology; Qhov phem tshaj plaws, lawv degrade cov ntaub ntawv ua tau zoo heev lossis txawm tias precipitate brittle puas. Yog li ntawd, kev tiv thaiv zoo thiab kev tswj xyuas cov tswv yim yuav tsum muaj kev tswj hwm thoob plaws ntau theem- suav nrog kev xaiv electrode, vuam parameter optimization, thiab tom qab-weld kev kho mob- nrog rau kev tswj xyuas cov cua kub tawm los ua qhov tseem ceeb focal point.