Austenitic stainless hlau nyob rau hauv cov yam ntxwv welding: cov txheej txheem vuam ntawm elastic, yas kev nyuab siab thiab kev ntxhov siab hloov pauv loj heev, tab sis tsis tshua muaj tshwm sim txias tawg. Tsis muaj qhov tawv tawv thiab ntxhib nplej hauv cov welded sib koom ua ke, yog li lub zog tensile ntawm lub vuam yog siab.
Cov teeb meem tseem ceeb ntawm austenitic stainless hlau vuam: loj vuam deformation; Vim nws cov yam ntxwv ciam teb thiab rhiab heev rau qee cov kab mob tsis huv (S, P), nws yooj yim los tsim cov tawg kub.
Tsib qhov teeb meem vuam thiab kev kho mob ntawm austenitic stainless hlau
01 Kev tsim ntawm chromium carbide txo qhov kev cuam tshuam ntawm intergranular corrosion ntawm welded pob qij txha
Intergranular corrosion: Raws li chrome-tsis zoo txoj kev xav, chromium carbide precipitates ntawm cov ciam teb nplej thaum lub vuam thiab tshav kub-cuam tshuam cheeb tsam yog rhuab mus rau rhiab kub cheeb tsam ntawm 450-850 degree C, ua rau chrome- pluag grain ciam teb. tsis txaus los tiv thaiv qib ntawm corrosion.
(1) Rau weld intergranular corrosion thiab corrosion nyob rau hauv qhov kub thiab txias cheeb tsam ntawm lub mesh, cov kev ntsuas hauv qab no tuaj yeem siv los txwv:
a. Txo cov pa roj carbon ntsiab lus ntawm lub hauv paus hlau thiab vuam, thiab ntxiv stabilizing cov ntsiab lus Ti, Nb thiab lwm cov ntsiab lus rau lub hauv paus hlau kom nyiam ua MC kom tsis txhob tsim cov Cr23C6.
b. Lub weld yog tsim rau hauv cov qauv biphase ntawm austenite thiab ib qho me me ntawm ferrite. Thaum muaj qee qhov nyiaj ntawm ferrite nyob rau hauv weld, cov nplej loj tuaj yeem ua kom zoo dua qub, thaj tsam ntawm cov nplej tuaj yeem nce ntxiv, thiab cov nyiaj ntawm chromium carbide nag lossis daus ntawm cov qoob loo ciam teb cheeb tsam tuaj yeem txo.
Chromium muaj siab solubility nyob rau hauv ferrite, Cr23C6 nyiam cov ntaub ntawv nyob rau hauv ferrite, thiab tsis ua rau chromium deficiency nyob rau hauv austenite grain ciam teb. Cov ferrite, uas taug kev ntawm cov austenites, tiv thaiv corrosion los ntawm kev sib kis mus rau sab hauv raws li cov ciam teb.
c. Tswj lub sij hawm nyob rau hauv qhov sensitized kub ntau. Kho qhov vuam thermal voj voog, txo lub sijhawm nyob ntawm 600 ~ 1000 degree kom ntau li ntau tau, thiab xaiv txoj kev vuam nrog lub zog siab ntom ntom (xws li ntshav argon arc vuam).
Xaiv cov vuam kab me me zog, argon roj nyob rau sab nraum qab ntawm lub vuam lossis tooj liab ncoo kom txias ceev ntawm cov welded sib koom ua ke, txo cov arcs thiab arcs kom tsis txhob rov qab cua sov, thiab kev sib cuag ntawm ntau txheej vuam nrog qhov nruab nrab corrosive yog welded kom deb li deb tau.
d. Tom qab vuam, cov khoom siv kho mob los yog kev ruaj ntseg annealing (850 ~ 900 degree) tom qab kev txuag hluav taws xob thiab cua txias, kom cov carbide tag nrho precipitated, thiab chromium yog nrawm diffusion).
(2) Riam corrosion ntawm welded pob qij txha, vim li no, cov kev tiv thaiv hauv qab no tuaj yeem raug coj los siv:
Vim tias muaj peev xwm diffusion muaj zog ntawm cov pa roj carbon monoxide, nws yuav raug polarized nyob rau hauv cov ciam teb los tsim ib lub xeev supersaturated thaum lub sij hawm txias, thaum Ti thiab Nb nyob twj ywm hauv cov siv lead ua vim muaj peev xwm diffusion tsawg. Thaum cov welded sib koom ua ke rov ua kom sov nyob rau hauv qhov kub thiab txias, cov pa roj carbon monoxide yuav ua rau hauv daim ntawv ntawm Cr23C6 ntawm cov muaju.
a. Txo cov ntsiab lus carbon. Rau cov hlau stainless uas muaj cov khoom ruaj khov, cov ntsiab lus carbon yuav tsum tsis pub tshaj 0.06 feem pua.
b. Txais cov txheej txheem vuam tsim nyog. Xaiv ib qho me me vuam kab hluav taws xob kom txo tau lub sij hawm nyob rau hauv lub overheated cheeb tsam ntawm qhov kub thiab txias, thiab ua tib zoo saib xyuas kom tsis txhob muaj qhov "kub kub sensitization" tshwm sim thaum lub sij hawm vuam txheej txheem.
Thaum vuam ntawm ob sab, lub vuam nyob rau hauv kev sib cuag nrog cov corrosive nruab nrab yuav tsum tau welded thaum kawg (qhov no yog vim li cas vim li cas lub vuam sab hauv thiab sab nraud ntawm lub loj-inch tuab phab ntsa welding yog nqa tawm), yog hais tias nws tsis ua hauj lwm, lub vuam. specification thiab weld puab yuav tsum tau kho, thiab overheated cheeb tsam nyob rau hauv kev sib cuag nrog corrosive nruab nrab yuav tsum tau rhiab heev dua li deb li deb tau.
c. Kev kho cua sov tom qab vuam. Solid tov los yog stabilization tom qab vuam.
02 Kev nyuaj siab corrosion cracking
Cov kev ntsuas hauv qab no tuaj yeem raug coj los tiv thaiv kev ntxhov siab corrosion tawg:
a. Kev xaiv cov ntaub ntawv raug thiab tsim nyog hloov ntawm weld muaj pes tsawg leeg. High purity chromium-nickel austenitic stainless hlau, siab silicon chromium-nickel austenitic stainless hlau, ferritic-austenitic stainless hlau, siab chromium ferritic stainless hlau, thiab lwm yam., muaj zoo tiv thaiv kev nyuaj siab corrosion, thiab zoo tiv thaiv corrosion thaum lub vuam hlau yog austenite-ferrite duplex steel qauv.
b. Tshem tawm lossis txo cov kev ntxhov siab uas seem. Cov residual deg kev nyuaj siab yog txo los ntawm mechanical txoj kev xws li polishing, txhaj blasting thiab hammering.
c. Tsim nyog tus qauv tsim. Kom tsis txhob muaj kev ntxhov siab loj.
03 Vuam kub tawg (weld crystallization tawg, kub cuam tshuam cheeb tsam liquefaction tawg)
Lub thermal tawg rhiab heev yog nyob ntawm cov tshuaj muaj pes tsawg leeg, qauv thiab cov khoom ntawm cov khoom. Ni yog ib qho yooj yim los tsim cov ntsiab lus qis melting los yog eutectic nrog impurities xws li S thiab P, thiab kev sib cais ntawm boron thiab silicon yuav txhawb kev tsim cov kub tawg.
Lub weld yog ib qho yooj yim los tsim ib tug muaj zog directional coarse columnar siv lead ua qauv, uas yog conducive rau lub segregation ntawm teeb meem impurities thiab hais. Yog li, ib tug nruam intergranular kua zaj duab xis yog tsim thiab rhiab heev ntawm thermal tawg yog nce. Yog hais tias lub vuam tsis sib xws, nws yog ib qho yooj yim los tsim ib tug loj tensile kev nyuaj siab thiab txhawb cov tiam ntawm vuam kub tawg.
Kev tiv thaiv:
a. nruj me ntsis tswj cov ntsiab lus ntawm teeb meem impurities S thiab P.
b. Kho cov qauv ntawm cov hlau weld. Lub weld muaj kev ua haujlwm zoo tawg. Lub δ theem nyob rau hauv lub weld tuaj yeem kho cov nplej, tshem tawm cov kev ncaj qha ntawm ib-theem austenite, txo cov kev sib cais ntawm cov khoom tsis zoo ntawm cov ciam teb, thiab theem δ tuaj yeem yaj ntau S thiab P, txo lub zog sib cuam tshuam, thiab txhim kho lub zog. tsim ntawm intergranular kua zaj duab xis.
c. Kho weld hlau alloy muaj pes tsawg leeg. Lub thermal tawg rhiab heev tuaj yeem raug txo los ntawm kev tsim cov ntsiab lus ntawm Mn, C thiab N nyob rau hauv ib-theem austenitic steel thiab ntxiv ib qho me me ntawm cov kab mob xws li cerium, hlau, tantalum (uas tuaj yeem kho cov qauv weld thiab purify cov nplej. ciam teb).
d. Txheej txheem ntsuas. Txo cov cua sov ntawm lub pas dej molten kom tiv thaiv kev tsim ntawm cov kab nrib pleb tuab, thiab siv cov kab me me zog thiab me me hla ntu weld. Piv txwv li, 25-20 austenitic steel yog nquag ua liquefaction tawg. Los ntawm nruj txwv tsis pub cov ntsiab lus impurity thiab grain loj ntawm cov khoom siv hauv paus, lub zog siab ceev vuam txoj kev, cov kab me me zog thiab kev txhim kho cov cua txias ntawm qhov sib koom ua ke tuaj yeem saws.
04 Embrittlement ntawm welded pob qij txha
Thermal zog steel yuav tsum xyuas kom meej lub plasticity ntawm welded pob qij txha los tiv thaiv kub kub embrittlement; Cov hlau tsis tshua muaj kub yuav tsum muaj qhov kub tsis tshua muaj zog los tiv thaiv qhov kub tsis tshua muaj qhov tawg ntawm cov pob qij txha welded.
05 Loj vuam deformation
Vim tsis tshua muaj thermal conductivity thiab loj expansion coefficient, vuam deformation yog loj, thiab fixture yuav siv tau los tiv thaiv deformation. Xaiv txoj kev vuam thiab vuam cov ntaub ntawv rau austenitic stainless hlau:
Austenitic stainless hlau tuaj yeem welded los ntawm tungsten argon arc vuam (TIG), molten argon arc vuam (MIG), plasma argon arc vuam (PAW) thiab submerged arc vuam (SAW).
Vim nws qhov qis melting point, me me thermal conductivity thiab loj resistivity, vuam tam sim no ntawm austenitic stainless hlau yog me me. Qhov nqaim weld thiab nqaim weld dhau yuav tsum tau siv los txo qhov kub ntawm qhov chaw nyob, tiv thaiv carbide nag lossis daus, txo weld contraction kev nyuaj siab, thiab txo thermal tawg rhiab heev.
Vuam cov khoom muaj pes tsawg leeg, tshwj xeeb tshaj yog Cr, Ni alloy cov ntsiab lus siab dua cov khoom siv hauv paus. Vuam cov ntaub ntawv uas muaj me me (4 ~ 12 feem pua ) ntawm ferrite yog siv los xyuas kom meej zoo cracking kuj (txias cracking, kub cracking, kev nyuaj siab corrosion cracking) ntawm lub vuam.
Thaum lub sij hawm ferrite tsis raug tso cai los yog tsis muaj nyob rau hauv lub vuam, cov khoom siv vuam yuav tsum tau xaiv nrog Mo, Mn thiab lwm yam alloying ntsiab.
C, S, P, Si, Nb nyob rau hauv cov khoom siv vuam yuav tsum tsawg li sai tau, Nb nyob rau hauv cov ntshiab austenite weld yuav ua rau solidification tawg, tab sis ib tug me me ntawm ferrite nyob rau hauv lub weld tuaj yeem zam tau zoo.
Vuam cov qauv uas yuav tsum tau stabilized los yog kev ntxhov siab tom qab vuam yog feem ntau welded cov ntaub ntawv uas muaj Nb. Submerged arc vuam yog siv los vuam nruab nrab phaj. Kev kub hnyiab ntawm Cr thiab Ni tuaj yeem ntxiv los ntawm kev hloov pauv ntawm cov ntsiab lus alloying hauv flux thiab hlau.
Vim qhov tob tob tob, yuav tsum tau them nyiaj rau kev tiv thaiv qhov tshwm sim ntawm kub tawg nyob rau hauv nruab nrab ntawm lub vuam thiab txo cov corrosion kuj ntawm tshav kub cuam tshuam cheeb tsam. Kev saib xyuas yuav tsum tau them rau kev xaiv cov hlau nyias nyias thiab lub zog vuam me me, thiab cov hlau yuav tsum tsis tshua muaj Si, S, thiab P.
Cov ntsiab lus ferrite nyob rau hauv lub tshav kub-resistant stainless hlau weld yuav tsum tsis txhob ntau tshaj 5 feem pua. Rau austenitic stainless hlau nrog Cr thiab Ni cov ntsiab lus ntau dua 20 feem pua, siab Mn (6-8} feem pua) hlau yuav tsum raug xaiv, thiab alkaline lossis nruab nrab flux yuav tsum raug xaiv los tiv thaiv Si los ntawm kev ntxiv rau qhov vuam los txhim kho nws qhov tawg. tsis kam.
Qhov tshwj xeeb flux rau austenitic stainless hlau nce Si me ntsis, uas tuaj yeem hloov pauv cov hlau mus rau qhov vuam thiab them nyiaj rau qhov kub ntawm cov hlau alloying kom tau raws li qhov yuav tsum tau ua ntawm vuam kev ua tau zoo thiab tshuaj muaj pes tsawg leeg.
