Taw Qhia Rau Ntau Hom Vuam Cracks

Vuam cov kab nrib pleb ntawm nws qhov xwm txheej rau cov ntsiab lus, tuaj yeem muab faib ua cov tawg kub, rov ua kom tawg, tawg tawg, laminated tearing thiab lwm yam. Cov hauv qab no tsuas yog nyob rau ntawm qhov ua rau ntawm ntau yam kab nrib pleb, yam ntxwv thiab kev tiv thaiv txoj hauv kev tshwj xeeb elaboration.
1. Cov cua kub tawg
Nws yog tsim los ntawm qhov kub thiab txias thaum lub sij hawm vuam, yog li hu ua thermal cracking, uas yog tus cwj pwm los ntawm kev tawg raws cov thawj austenite lis ciam teb. Raws li cov khoom siv hlau welded (tsawg-alloy high-strength steel, stainless hlau, cam khwb cia hlau, aluminium alloys thiab qee cov hlau tshwj xeeb, thiab lwm yam), daim ntawv ntawm thermal cracking, kub ntau yam thiab lub ntsiab yog vim li cas kuj txawv. Tam sim no, cov thermal tawg tau muab faib ua peb pawg loj xws li crystallization tawg, liquefaction tawg thiab ntau kab nrib pleb.
(1) crystallization tawg yog tsuas yog tsim nyob rau hauv carbon steel uas muaj ntau impurities, tsawg alloy steel weld (muaj S, P, C, Si yog siab) thiab ib-theem austenitic steel, nickel-raws li alloys thiab ib co aluminium alloy weld. Qhov no tawg yog nyob rau hauv cov txheej txheem vuam ntawm crystallization, nyob rau hauv ib ncig ntawm cov khoom theem kab, vim lub solidification ntawm cov hlau contraction, cov residual kua hlau yog tsis txaus, yuav tsis tau ntxiv nyob rau hauv lub sij hawm, nyob rau hauv qhov kev txiav txim ntawm kev nyuaj siab. tshwm sim raws li crystal cracking.
Kev tiv thaiv kev tiv thaiv yog: nyob rau hauv metallurgical yam, tsim nyog kev hloov kho ntawm weld hlau muaj pes tsawg leeg, luv luv ntawm qhov kub thiab txias cheeb tsam los tswj cov weld nyob rau hauv sulfur, phosphorus, carbon thiab lwm yam teeb meem impurities; refine lub weld hlau grain, uas yog, qhov tsim nyog ntxiv ntawm cov ntsiab lus xws li Mo, V, Ti, Nb, thiab lwm yam.; nyob rau hauv cov nqe lus ntawm kev siv tshuab, tuaj yeem preheated ua ntej vuam, tswj cov kab ntawm lub zog, txo cov pob qij txha thiab lwm yam kev tiv thaiv thiab tswj.
(2) Ze-seam cheeb tsam liquefaction tawg yog ib yam ntawm microcrack uas tawg raws li austenite lis ciam teb, uas yog heev me me thiab tshwm sim nyob rau hauv lub ze-seam cheeb tsam ntawm lub HAZ los yog interlayer. Nws ua rau feem ntau yog vim vuam nyob ze seam cheeb tsam hlau los yog weld interlayer hlau, nyob rau hauv high kub kom cov cheeb tsam ntawm lub austenite grain ciam teb nyob rau hauv qis-melting eutectic constituents re-melted, nyob rau hauv qhov kev txiav txim ntawm tensile kev nyuaj siab nyob rau hauv lub austenite intergranular cracking thiab tsim ntawm liquefaction tawg.
Hom kev tiv thaiv kab mob no thiab kev tswj xyuas thiab cov kab nrib pleb crystallization yog qhov zoo ib yam. Tshwj xeeb tshaj yog nyob rau hauv metallurgy, kom deb li deb raws li qhov ua tau kom txo tau cov sulfur, phosphorus, silicon, boron thiab lwm yam tsawg-melting eutectic constituent ntsiab ntawm cov ntsiab lus yog zoo heev; nyob rau hauv cov txheej txheem, koj tuaj yeem txo cov kab hluav taws xob, txo qhov concavity ntawm cov kab melting ntawm lub pas dej ua ke.
(3) Polygonization tawg yog tshwm sim los ntawm plasticity tsawg heev ntawm qhov kub thiab txias thaum lub sij hawm tsim ntawm polygonization. Qhov kev tawg no tsis yog ib txwm muaj, thiab nws cov kev tiv thaiv thiab kev tswj xyuas tuaj yeem ntxiv rau qhov vuam los txhim kho lub zog ntawm polygonization excitation ntawm cov ntsiab lus xws li Mo, W, Ti, thiab lwm yam.
2. Reheating tawg
Feem ntau tshwm sim hauv qee qhov uas muaj nag lossis daus ntxiv cov ntsiab lus ntawm cov hlau thiab cov hlau kub kub (xws li cov hlau tsis tshua muaj hlau tsis muaj zog, pearlitic tshav kub-resistant steel, nag lossis daus ntxiv dag zog rau high-temperature alloys, nrog rau qee qhov austenitic stainless hlau), lawv tsis pom. tawg tom qab vuam, tab sis nyob rau hauv cov txheej txheem kev kho cua sov tawg. Reheat cov kab nrib pleb tshwm sim nyob rau hauv weld tshav kub cuam tshuam cheeb tsam ntawm lub superheated ntxhib siv lead ua qhov chaw, cov kev taw qhia ntawm uas yog nyob rau hauv lub fusion kab ntawm lub austenite ntxhib crystal grain ciam extension.
Kev tiv thaiv thiab kev tswj ntawm reheat cracking los ntawm kev xaiv cov ntaub ntawv, koj tuaj yeem xaiv cov hlau zoo. Nyob rau hauv cov nqe lus ntawm cov txheej txheem, xaiv ib tug me me kab hluav taws xob, xaiv ib tug ntau dua preheating kub thiab nrog rau cov tom qab kub ntsuas, xaiv ib tug tsawg sib piv cov khoom siv vuam kom tsis txhob muaj kev ntxhov siab concentration.
3. Txias tawg
Feem ntau tshwm sim nyob rau hauv siab, nruab nrab carbon steel, qis, nruab nrab alloy steel vuam tshav kub cuam tshuam cheeb tsam, tab sis ib co hlau, xws li ib co ultra-siab zog steel, titanium thiab titanium alloys, thiab lwm yam. Qee zaum txias cracking kuj tshwm sim nyob rau hauv lub weld. Feem ntau, lub hardening nyiam ntawm qib steel, cov ntsiab lus hydrogen thiab kev faib tawm ntawm cov pob qij txha welded, nrog rau cov pob qij txha raug rau lub xeev ntawm kev ntxhov siab yog peb lub ntsiab tseem ceeb ntawm lub zog steel vuam los tsim cov kab nrib pleb txias. Lub koom haum martensitic tsim tom qab vuam nyob rau hauv qhov kev txiav txim ntawm elemental hydrogen, ua ke nrog lub tensile kev nyuaj siab, txias tawg yog tsim. Nws tsim yog feem ntau los ntawm cov siv lead ua los yog raws li cov siv lead ua. Cov kab nrib pleb txias yog feem ntau categorized li ntiv taw tawg, hauv qab-weld tawg, thiab hauv paus tawg.
Kev tiv thaiv thiab tswj cov kab mob khaub thuas tuaj yeem yog los ntawm cov tshuaj muaj pes tsawg leeg ntawm cov khoom ua haujlwm, kev xaiv cov khoom siv vuam thiab cov txheej txheem ntsuas hauv peb yam. Yuav tsum sim xaiv cov khoom siv nrog qis carbon sib npaug; welding consumables yuav tsum tau xaiv nrog tsawg hydrogen electrodes, welds yuav tsum tau txuam nrog tsis muaj zog, rau siab txias cracking nyiam ntawm cov khoom kuj yuav xaiv austenitic vuam consumables; tsim nyog tswj cov kab hluav taws xob, preheating thiab tom qab kev kho cua sov yog los tiv thaiv thiab tswj qhov txias tawg ntawm cov txheej txheem ntsuas.
Nyob rau hauv vuam ntau lawm vim yog siv cov hlau, vuam cov ntaub ntawv, ntau hom qauv, steel, raws li zoo raws li kev tsim kho ntawm txawv tej yam kev mob, tej zaum yuav muaj ntau yam ntaub ntawv ntawm cov kab nrib pleb. Txawm li cas los xij, qhov tseem ceeb uas feem ntau ntsib hauv kev tsim khoom yog ncua kev tawg.

Muaj peb hom kev ncua sijhawm tawg:
(1) Weld ntiv taw tawg - Hom kab nrib pleb no tshwm sim ntawm qhov sib txuas ntawm lub hauv paus hlau thiab vuam, thiab muaj qhov pom tseeb ntawm qhov kev ntxhov siab. Cov kev taw qhia ntawm cov kab nrib pleb yog feem ntau sib npaug mus rau lub vuam channel, feem ntau pib los ntawm qhov chaw ntawm cov ntiv taw weld mus rau qhov tob ntawm cov khoom siv niam txiv.
(2) Cov kab nrib pleb nyob rau hauv weld channel - qhov tawg no feem ntau tshwm sim nyob rau hauv lub hardening tendency, siab dua hydrogen cov ntsiab lus ntawm lub weld tshav kub-cuam tshuam cheeb tsam. Feem ntau cov kev taw qhia tawg yog parallel mus rau fusion kab.
(3) lub hauv paus tawg - qhov tawg no yog ntau hom kev ncua kev tawg, feem ntau tshwm sim nyob rau hauv cov ntaub ntawv ntawm cov ntsiab lus hydrogen ntau dua thiab tsis txaus preheating kub. Hom kab nrib pleb no zoo ib yam li cov ntiv taw ntiv taw tawg thiab tshwm sim nyob rau hauv ib feem ntawm qhov vuam qhov twg qhov kev ntxhov siab ntau tshaj plaws ntawm cov hauv paus hniav. Cov kab nrib pleb tuaj yeem tshwm sim hauv cov pob zeb ntxhib ntawm thaj chaw tshav kub lossis hauv cov hlau welding.
Lub hardening nyiam ntawm cov qib steel, cov ntsiab lus hydrogen ntawm cov welded sib koom ua ke thiab nws qhov kev faib tawm, nrog rau lub xeev ntawm kev sib koom ua ke raug rau qhov kev ntxhov siab yog peb lub ntsiab lus tseem ceeb uas ua rau cov kab mob khaub thuas thaum welding high-strength steel. Peb yam no muaj kev cuam tshuam thiab kev sib koom ua ke nyob rau hauv qee yam xwm txheej.
Lub hardening nyiam ntawm qib steel yog tsuas yog txiav txim los ntawm cov tshuaj muaj pes tsawg leeg, phaj thickness, vuam txheej txheem thiab txias txias. Thaum welding, qhov ntau dua qhov hardening nyiam ntawm qib steel, qhov ntau yuav ua rau tawg. Vim li cas steel hardening ua rau tawg? Nws tuaj yeem raug sau tseg hauv ob yam hauv qab no.
a: kev tsim ntawm nkig nyuaj martensite lub koom haum - martensite yog carbon nyob rau hauv ɑ hlau supersaturated khoom tov, carbon atoms nrog interstitial atoms muaj nyob rau hauv lub lattice, thiaj li hais tias cov hlau atoms deviate los ntawm qhov sib npaug ntawm txoj hauj lwm, cov lattice undergoes ib tug loj aberration, ua rau cov hlau atom. lub koom haum nyob rau hauv lub xeev hardened. Tshwj xeeb tshaj yog nyob rau hauv welding tej yam kev mob, nyob ze ntawm lub seam cheeb tsam ntawm cov cua kub kub yog siab heev, thiaj li hais tias lub austenite grain loj hlob tshwm sim tiag tiag, thaum lub ceev ceev txias, ntxhib austenite yuav hloov mus rau hauv coarse martensite. Los ntawm txoj kev xav ntawm lub zog ntawm cov hlau tuaj yeem paub, martensite yog ib lub koom haum nkig thiab tawv, qhov tshwm sim ntawm pob txha yuav siv zog tsawg, yog li ntawd, cov pob qij txha welded nrog lub xub ntiag ntawm martensite, cov kab nrib pleb yog yooj yim tsim thiab nthuav.
b: Hardening yuav tsim ntau cov lattice defects - Ntau cov lattice defects yog tsim thaum cov hlau raug thermally unbalanced tej yam kev mob. Cov lattice defects no feem ntau yog qhov chaw ua haujlwm thiab dislocations. Nrog rau qhov nce ntawm thermal stress nyob rau hauv welded tshav kub cuam tshuam cheeb tsam, nyob rau hauv cov kev mob ntawm kev nyuaj siab thiab thermal imbalance, ob qhov chaw thiab dislocations yuav tsiv mus nyob thiab sib sau ua ke, thiab thaum lawv concentration mus txog ib tug tej yam tseem ceeb tus nqi, ib tug tawg qhov chaw yuav tsim. Nyob rau hauv qhov kev txiav txim txuas ntxiv ntawm kev ntxhov siab, kev nthuav dav yuav tshwm sim tsis tu ncua thiab tsim cov kab nrib pleb macroscopic.
Hydrogen yog ib qho tseem ceeb uas ua rau txias tawg ntawm lub zog siab steel vuam, thiab muaj cov yam ntxwv ntawm kev ncua, yog li ntawd, nyob rau hauv ntau cov ntaub ntawv, ncua kev tawg los ntawm hydrogen hu ua "hydrogen cracking". Cov kev tshawb fawb soj ntsuam tau ua pov thawj tias qhov siab dua cov ntsiab lus hydrogen ntawm cov hlau steel welded pob qij txha, qhov ntau dua qhov cuam tshuam rau kev tawg, thaum cov ntsiab lus hydrogen hauv zos nce mus txog qhov tseem ceeb, cov kab nrib pleb yuav pib tshwm, thiab qhov txiaj ntsig no hu ua hydrogen tseem ceeb. cov ntsiab lus ntawm tawg [H]cr.
Ntau yam steel txias cracking [H] cr tus nqi sib txawv, nws muaj feem xyuam rau cov tshuaj muaj pes tsawg leeg ntawm steel, steel, preheating kub, thiab txias txias.
1: Thaum vuam, noo noo nyob rau hauv cov khoom siv vuam, xeb thiab roj ntawm lub bevel ntawm lub weldment, thiab ambient humidity yog tag nrho cov ua rau hydrogen enrichment nyob rau hauv lub weld. Feem ntau cov hydrogen nyob rau hauv cov khoom siv hauv paus thiab hlau yog me me, thaum cov dej noo hauv cov tawv nqaij ntawm cov electrode thiab cov dej noo hauv huab cua tsis tuaj yeem tsis quav ntsej, thiab dhau los ua qhov tseem ceeb ntawm hydrogen enrichment.
2: Hydrogen nyob rau hauv ntau lub koom haum hlau nyob rau hauv lub solubility thiab diffusion muaj peev xwm sib txawv, hydrogen nyob rau hauv lub austenite solubility yog ntau loj dua li ferrite solubility. Yog li ntawd, thaum vuam los ntawm austenite mus rau ferrite hloov, solubility ntawm hydrogen tshwm sim sai li sai tau. Nyob rau tib lub sijhawm, qhov diffusion tus nqi ntawm hydrogen yog qhov sib txawv, los ntawm austenite mus rau ferrite hloov dheev nce.
Vuam ntawm qhov kub thiab txias, yuav muaj ntau cov hydrogen yaj nyob rau hauv lub pas dej molten, nyob rau hauv lub tom ntej txias thiab solidification txheej txheem, vim lub ntse txo nyob rau hauv solubility, hydrogen sim khiav, tab sis vim hais tias ntawm lub txias yog ceev heev, yog li hais tias cov hydrogen lig dhau los khiav tawm thiab khaws cia hauv cov hlau hlau hauv kev tsim cov diffusion hydrogen.

4. Laminar kua muag
Nws yog ib qho internal low-temperature cracking. Txwv rau lub hauv paus hlau ntawm cov phaj tuab los yog vuam tshav kub-tshem tawm tsam, feem ntau tshwm sim hauv "L", "T", "+" hom pob qij txha. Txhais raws li dov tuab steel phaj raws lub thickness ntawm cov kev taw qhia ntawm plasticity yog tsis txaus los tiv thaiv cov kev taw qhia ntawm vuam contraction strain thiab tshwm sim nyob rau hauv lub hauv paus hlau ntawm ib tug step-like txias tawg. Feem ntau vim yog cov hlau phaj tuab hauv cov txheej txheem dov, qee qhov tsis yog xim hlau inclusions nyob rau hauv cov hlau dov thaum uas tig mus rau dov kev taw qhia ntawm cov qhab inclusions, cov inclusions tshwm sim los ntawm cov hlau phaj nyob rau hauv lub mechanical zog ntawm lub conductivity ntawm txhua. Kev tiv thaiv thiab kev tswj ntawm laminar tearing nyob rau hauv cov kev xaiv ntawm cov ntaub ntawv yuav raug xaiv los ntawm refined steel, uas yog, kev xaiv ntawm z mus rau qhov kev ua tau zoo ntawm cov hlau phaj, koj muaj peev xwm kuj txhim kho cov kev sib koom tsim daim ntawv, kom tsis txhob unilateral weld, los yog mus rau lub siab ntawm cov hlau phaj. dais z rau sab ntawm kev ntxhov siab tawm ntawm bevel.
Laminar tearing thiab txias cracking yog txawv, nws tsim thiab steel lub zog theem tsis muaj dab tsi ua, feem ntau nrog cov nqi ntawm inclusions nyob rau hauv cov hlau thiab kev faib ntawm morphology. Feem ntau dov tuab steel phaj, xws li cov pa roj carbon tsawg, tsis tshua muaj hlau alloy high-strength steel, thiab txawm tias aluminium alloy phaj yuav tshwm sim hauv cov kua muag laminar. Raws li qhov chaw ntawm laminar tearing tuaj yeem muab faib ua peb pawg:
Thawj qeb yog tsim ntawm laminar tearing induced los ntawm txias tawg nyob rau hauv lub vuam ntiv taw los yog weld cag nyob rau hauv lub tshav kub cuam tshuam cheeb tsam ntawm vuam.
Qhov thib ob qeb yog qhov vuam kub cuam tshuam cheeb tsam raws cov kev sib xyaw ua ke, yog qhov feem ntau engineering laminar tearing.
Cov qeb thib peb yog nyob deb ntawm thaj chaw muaj kev kub ntxhov nyob rau hauv cov khoom siv hauv paus raws li cov khoom sib xyaw ua ke, feem ntau ntau hauv cov phaj tuab nrog ntau MnS flake inclusions.
Laminar tearing morphology thiab inclusions ntawm hom, zoo li, tis, raws li zoo raws li qhov chaw ntawm kev sib raug zoo. Thaum cov kev taw qhia dov raws cov flaky MnS suav nrog yog qhov tseem ceeb, laminar tearing muaj cov kauj ruam meej, thaum cov silicate inclusions yog qhov tseem ceeb hauv txoj kab ncaj nraim, xws li Al inclusions yog qhov tseem ceeb hauv cov kauj ruam tsis xwm yeem.

Thick phaj qauv welding, tshwj xeeb tshaj yog T-hom thiab lub kaum sab xis pob qij txha, nyob rau hauv lub nruj constrained tej yam kev mob, lub weld contraction yuav nyob rau hauv cov kev taw qhia ntawm lub thickness ntawm lub hauv paus cov ntaub ntawv los tsim ntau tensile kev nyuaj siab thiab strain, thaum lub strain tshaj cov yas. deformation muaj peev xwm ntawm lub hauv paus hlau, cov inclusions thiab cov hlau matrix yuav raug sib cais los ntawm cov hlau matrix thiab microcracking tshwm sim, nyob rau hauv cov kev nyuaj siab tseem mus ua si lub luag hauj lwm ntawm tawg. ntxeev raws lub dav hlau ntawm expansion ntawm inclusions nyob, tsim ntawm thiaj li hu ua "platform".
Muaj ntau yam cuam tshuam rau laminar tearing, feem ntau ntawm cov hauv qab no:
1: non-metallic inclusions ntawm hom, kom muaj nuj nqis thiab kev faib tawm ntawm morphology yog qhov tseem ceeb ua rau laminar tearing, nws yog tshwm sim los ntawm cov anisotropy ntawm hlau, txhua yam khoom ntawm lub hauv paus sib txawv.
2: Z-txoj kev confinement kev ntxhov siab tuab-walled welded qauv hauv cov txheej txheem vuam kom tiv taus qhov sib txawv Z-txoj kev kaw qhov kev ntxhov siab, tom qab vuam seem kev ntxhov siab thiab thauj khoom, lawv yog tshwm sim los ntawm cov neeg kho tshuab ntawm laminar tearing.
3: Cov nyhuv ntawm hydrogen feem ntau ntseeg tau tias nyob ib puag ncig ntawm thaj chaw muaj kev cuam tshuam los ntawm tshav kub, cuam tshuam los ntawm qhov txias txias los ua laminar tearing, hydrogen yog qhov tseem ceeb cuam tshuam.
Vim tias qhov cuam tshuam ntawm laminar tearing yog qhov loj heev, qhov kev puas tsuaj kuj loj heev, yog li nws yuav tsum tau txiav txim siab txog qhov cuam tshuam ntawm cov hlau rau laminar tearing ua ntej kev tsim kho.
Feem ntau siv cov kev ntsuam xyuas yog Z-kev taw qhia tensile seem shrinkage thiab tus pin Z-kev taw qhia tseem ceeb txoj kev nyuaj siab. Txhawm rau tiv thaiv laminar tearing, ntu shrinkage yuav tsum tsis pub tsawg dua 15%, feem ntau cia siab tias=15 ~ 20% yog qhov tsim nyog, thaum 25%, tias cov tshuaj tiv thaiv laminar tearing zoo heev.
Txhawm rau tiv thaiv laminar tearing, kev ntsuas yuav tsum tau coj los ntawm cov hauv qab no:
Ua ntej, refining steel dav siv hlau desulfurization txoj kev, thiab lub tshuab nqus tsev degassing, yuav smelted tawm ntawm cov sulfur ntsiab lus ntawm tsuas yog {{0}}.003 ~ 0.005% ntawm ultra-low-sulfur steel, nws seem shrinkage ( Z kev taw qhia) tuaj yeem ncav cuag 23 ~ 25%.
Qhov thib ob, kev tswj cov sulfide inclusions yog tig MnS mus rau lwm cov ntsiab lus ntawm sulfide, yog li ntawd nws yog ib qho nyuaj rau elongate nyob rau hauv kub dov, yog li txo anisotropy. Tam sim no, cov khoom siv dav siv ntxiv yog calcium thiab cov ntsiab lus tsis tshua muaj hauv ntiaj teb. Nrog rau cov kev kho mob saum toj no, cov hlau tuaj yeem tsim nrog Z-kev taw qhia seem shrinkage ntawm 50 mus rau 70% los tiv thaiv laminated tearing steel phaj.
Thib peb, los ntawm qhov pom ntawm kev tiv thaiv laminar tearing, tus tsim thiab kev tsim kho txheej txheem yog tsuas yog kom tsis txhob Z-kev taw qhia kev ntxhov siab thiab kev ntxhov siab concentration, thiab cov kev ntsuas tshwj xeeb raug xa mus rau hauv cov piv txwv hauv qab no:
(1) yuav tsum tau sim kom tsis txhob unilateral weld, es tsis txhob ntawm ob sab weld yuav yooj yim lub xeev kev nyuaj siab ntawm lub hauv paus cheeb tsam ntawm lub weld, thiaj li yuav tiv thaiv kev nyuaj siab concentration.
(2) Kev siv cov symmetrical fillet welds nrog tsawg vuam es tsis txhob welded loj npaum li cas ntawm tag nrho cov weld los ntawm weld, thiaj li tsis mus tsim kev nyuaj siab heev.
(3) Lub bevel yuav tsum tau ua nyob rau sab uas raug Z-kev taw qhia kev nyuaj siab.
(4) Rau T-hom pob qij txha, ib txheej ntawm cov khoom siv vuam uas tsis muaj zog tuaj yeem ua ntej-stacked rau ntawm tus ntoo khaub lig phaj kom tiv thaiv weld cag tawg, thiab tseem ua rau cov vuam strain.
(5) Txhawm rau tiv thaiv laminar tearing los ntawm qhov txias txias, qee qhov kev ntsuas los tiv thaiv kev sib tsoo yuav tsum tau txais ntau li ntau tau, xws li txo cov hydrogen, ua kom lub preheat thiab tswj cov interlayer kub.