Sigma Phase Embrittlement nyob rau hauv Duplex Stainless Steel: Lub Sijhawm -Tsuas Kub-Ntxhais Khaub Ncaws

Sigma theem cov ntaub ntawv nyob rau hauv duplex stainless hlau ceev tshaj ntawm kwv yees li 700℃thiab 900 degree, nrog rau lub qhov ntswg ntawm lub sij hawm -kub- nag lossis daus (TTP) nkhaus feem ntau nyob ib ncig ntawm 800-850℃- txhais tau hais tias nqaim band, tsis siab dua los yog qis dua kub, yog qhov chaw ceev tshaj plaws, feem ntau precipitation dams. Sigma feem me me li 1-3% los ntawm ntim tuaj yeem ua rau muaj qhov hnyav, tsis sib haum xeeb hauv kev cuam tshuam thiab pitting corrosion tsis kam, uas yog vim li cas kev tswj lub sijhawm siv nyob rau hauv qhov ntau no thaum vuam thiab kev kho cua sov yog qhov yuav tsum tau ua nruj me ntsis, tsis yog cov txheej txheem me me.

Duplex stainless hlau khwv tau nws lub koob npe nrov - siab zog, zoo heev chloride kuj - los ntawm ib tug sib npaug microstructure ntawm roughly sib npaug qhov chaw austenite thiab ferrite. Qhov sib npaug ntawd yog qhov tsis yooj yim ntawm qhov kub siab. Tuav ntev dhau ntawm lub qhov rais kub tsis ncaj ncees lawm, lub ferrite theem ib nrab hloov mus rau hauv ib qho intermetallic compound hu ua sigma theem, thiab cov hlau alloy cov khoom tseem ceeb tshaj plaws poob. Kab lus no piav qhia seb lub sijhawm sigma yog dab tsi, nws lub sijhawm -kub- nag lossis daus zoo li cas, thiab cov neeg tsim khoom yuav tsum ua dab tsi kom nyob twj ywm.

Dab tsi yog Sigma Phase, thiab Vim Li Cas Nws Ua Rau Duplex Stainless Hlau?

Sigma theem yog ib qho nyuaj, brittle intermetallic compound nplua nuj nyob rau hauv chromium thiab molybdenum uas tsim thaum lub ferrite nyob rau hauv duplex stainless hlau decomposes ntawm siab kub - thiab vim hais tias nws strips chromium thiab molybdenum los ntawm ib puag ncig matrix, nws puas ob leeg toughness thiab corrosion kuj nyob rau tib lub sij hawm.

Sigma theem tsim los ntawm eutectoid- hom tshuaj tiv thaiv uas ferrite decomposes rau hauv sigma theem ntxiv rau theem nrab austenite. Nws nucleates nyiam tshaj plaws ntawm ferrite-austenite theem ciam teb thiab ferrite-ferrite grain ciam teb - feem ntau ua ntej los ntawm kev cuam tshuam intermetallic, chi theem, uas ua ntej ntawm ferrite-ferrite ciam teb thiab tom qab ntawd noj raws li sigma theem loj hlob.

Vim hais tias sigma theem yog intrinsically nyuaj thiab nkig, thiab vim hais tias nws tsim tau rub chromium thiab molybdenum tawm ntawm ib puag ncig matrix, nws tsim ob qho teeb meem ib txhij: lub cev nqaij daim tawv theem nrab zaum ntawm grain ciam teb, thiab chromium / molybdenum{0}} depleted cheeb tsam nyob ib ncig ntawm nws uas yog nyob deb dua corrosion. Qhov kev puas tsuaj dual no yog vim li cas sigma theem embrittlement raug kho raws li qhov kev pheej hmoo tseem ceeb ntawm kev tsim khoom ntau dua li kev xav paub ntawm cov khoom siv hlau zoo nkauj.

Lub Sijhawm -Tsuas Kub-Ntshav nag (TTP) Curve Qhia rau Sigma Phase yog dab tsi?

TTP nkhaus taw qhia qhov kub thiab txias ntawm lub alloy yog tuav ntawm qhov ntev npaum li cas nws yuav siv sij hawm rau ib tug npaum li cas ntawm sigma theem tshwm sim, ua ib tug yam ntxwv C-zoo li tus nkhaus uas nws 'lub qhov ntswg' cim qhov ceev tshaj tau los nag - rau duplex stainless hlau, lub qhov ntswg feem ntau zaum ntawm 800–850 degree.

Cov kws tshawb fawb tsim cov kab nkhaus no los ntawm kev tuav cov kev daws teeb meem-annealed cov qauv ntawm cov ntsuas kub ruaj khov, tom qab ntawd ntsuas seb qib sigma tau tsim ntau npaum li cas tom qab tuav lub sijhawm sib txawv, txij li feeb mus rau ntau tshaj li ib txhiab teev. Plotted ntawm ib lub sij hawm (log scale) piv rau qhov kub thiab txias axis, qhov tshwm sim nkhaus zoo li ib sab "C": nag lossis daus yog qeeb ntawm ob qhov siab thiab qis kawg ntawm qhov kev pheej hmoo ntau, thiab ceev tshaj plaws nyob rau hauv nruab nrab.

Kev tshawb fawb ntawm wrought UNS S31803 (2205) duplex stainless hlau tau txheeb xyuas ncov sigma- tsim kinetics nyob ib ncig ntawm 850 degree, nrog luam tawm TTP ua hauj lwm spanning tuav lub sij hawm mus txog thiab tshaj 1,000 teev kom tag nrho tus yam ntxwv nkhaus. Kev ywj pheej ua hauj lwm ntawm cam khwb cia duplex qib, super duplex qib, thiab lean duplex compositions tsis tu ncua tso lub qhov ntswg ntawm lub nkhaus nyob rau hauv tib lub dav dav 800-850℃band, txawm tias lub caij nyoog zoo thiab sij hawm hloov me ntsis nrog alloy muaj pes tsawg leeg.

Qhov ntsuas kub dab tsi yog qhov txaus ntshai tshaj plaws rau Sigma Phase Tsim?

Qhov chaw txaus ntshai tshaj plaws yog kwv yees li ntawm 700℃txog 950℃thoob plaws qib duplex thiab super duplex, nrog rau qhov kub thiab txias tshaj plaws - nag lossis daus ceev tshaj - tsis tu ncua qhia txog 800–850 degree.

Sab nraum cov kab no, daim duab hloov pauv: hauv qab li ntawm 700 degree, diffusion qeeb txaus uas sigma tsim ua qeeb heev, txawm tias ntev ntev tseem tuaj yeem tso cai rau nws, thiab sib cais, qis dua -kub embrittlement mechanism - 475℃embrittlement los ntawm spinodal decomposition ntawm {3} ferrite muaj feem cuam tshuam ntau dua. Tshaj li ntawm 950-1000 degree, sigma theem ua thermodynamically tsis ruaj khov thiab zoo li yaj rov qab rau hauv matrix, uas yog lub hauv paus rau kev daws annealing raws li kev kho cua sov kho.

Me Sigma Phase Yuav Ua Li Cas Thiaj Ua Tau Teeb Meem?

Ib qho me me zoo kawg nkaus - feem ntau hais txog qis li 1% mus rau 3% los ntawm ntim - yog txaus los ua rau muaj kev cuam tshuam loj heev, tsis sib haum xeeb poob rau hauv kev cuam tshuam toughness, uas yog dab tsi ua rau sigma theem tswj tsis tu ncua nruj piv nrog ntau lwm yam metallurgical tsis xws luag.

Qhov no yog qhov nthuav dav uas feem ntau surprises engineers tshiab rau duplex stainless hlau: sigma theem tsis tas yuav sau mus rau ib feem loj ua ntej nws yuav txaus ntshai. Ntau cov kev tshawb fawb ywj pheej ntawm 2205 duplex stainless hlau qhia tias sigma cov ntsiab lus nyob rau hauv qis ib tus lej los ntawm qhov ntim yog twb txaus los ua rau lub cim toughness vau, thiab qhov cuam tshuam lub zog nkhaus taug qab ze nrog cov duab ntawm sigma nag lossis daus nkhaus nws tus kheej - tib yam 800-850℃ntau yam uas precipitates sigma ceev tshaj plaws yog qhov tsawg tshaj plaws tom qab kev cuam tshuam. Raws li tuav lub sij hawm thiab sigma cov ntsiab lus nce ntxiv, toughness tseem mus degrade, tab sis lub steepest, feem ntau consequential poob tshwm sim thaum ntxov, nyob rau hauv feem ntau ib tug xws li kev soj ntsuam xyuas yuav yooj yim nco.

Puas yog Sigma Phase Tseem Mob Corrosion Resistance, lossis Tsuas Toughness?

Ob leeg. Sigma theem nag lossis daus ntsuas txo qis pitting peev xwm thiab ua rau muaj kev cuam tshuam rau intergranular thiab pitting corrosion, vim hais tias cov chromium - thiab molybdenum- depletion nyob ib ncig ntawm txhua sigma particle undermines passive zaj duab xis raws nraim qhov nws xav tau tshaj plaws.

Qhov tshwm sim ntawm corrosion ua raws li ncaj qha los ntawm cov txheej txheem sigma: raws li chromium thiab molybdenum diffuse mus rau hauv cov loj sigma particle, tam sim ntawd ib puag ncig matrix ua rau hauv zos depleted nyob rau hauv cov ntsiab lus uas stabilize lub passive oxide zaj duab xis. Kev ntsuam xyuas hluav taws xob hluav taws xob ntawm cov laus duplex stainless hlau qhia pom tias muaj peev xwm poob qis thaum cov ntsiab lus sigma nce, nrog rau thaj tsam passive nqaim thiab thaum kawg ua tsis ruaj khov ntawm ntau dua sigma feem.

Cov pits tau pom tias muaj qhov tshwj xeeb hauv cov chromium - cov cheeb tsam depleted ib puag ncig sigma hais, thiab cov nplais hnyav nrog rau ob qho tib si cov nyiaj thiab kev faib tawm ntawm sigma tam sim no - ntxhib, concentrated sigma hais feem ntau puas ntau dua li tib lub ntim feem cuam tshuam zoo. Nyob rau hauv luv luv, ib feem yuav ua tsis tau ib tug corrosion test nyob rau hauv raws nraim tib yam welded los yog cua sov- cuam tshuam cheeb tsam uas nws kuj yuav ua tsis tau tej yam kev sim.

Vim li cas Vuam Muab Duplex Stainless Hlau Risk ntawm Sigma Phase?

Lub tshav kub- cuam tshuam thaj tsam ntawm ib sab ntawm ib qho weld inevitably dhau los ntawm 700-950℃txaus ntshai band thaum lub sij hawm cua sov thiab cua txias, thiab ntau qhov weld hla los yog qeeb interpass txias tuaj yeem ua rau lub sij hawm txaus nyob rau hauv qhov band kom precipitate puas sigma theem txawm tias tsis muaj ib qho dhau los zoo li pom tseeb dhau los.

Txhua qhov arc vuam dhau los tsim qhov kub thiab txias gradient tawm ntawm lub pas dej welding, thiab qhov chaw raws qhov gradient, lub hauv paus hlau luv luv zaum hauv sigma - tsim ntau yam. Ib qho kev nrawm nrawm yuav tsis nyob rau ntawd ntev txaus los teeb meem. Ntau- hla vuam, cov khoom siv hluav taws xob siab, kev tswj qhov kub tsis txaus, lossis kev ua kom txias qeeb hauv cov ntu tuab tuaj yeem txuas ntxiv lub sijhawm siv nyob rau hauv qhov txaus ntshai band zoo dhau los ntawm cov hlau alloy TTP nkhaus tso cai ua ntej ua rau cov ntsiab lus sigma tshwm sim. Qhov no yog vim li cas cov txheej txheem vuam rau duplex stainless hlau qhia qhov siab tshaj plaws ntawm cov khoom siv hluav taws xob, tswj kev sib tshuam ntawm qhov kub thiab txias, thiab - nyob rau hauv ntau zaus - qhov yuav tsum tau ua kom txias txias los ntawm qhov tseem ceeb, es tsis tso cua txias rau lub caij nyoog.

Sigma Phase ua tau sai npaum li cas - feeb, lossis teev?

Nyob rau ntawm lub qhov ntswg ntawm qhov nkhaus, lub sij hawm kuaj pom tau tuaj yeem pib tsim nyob rau hauv ob teev, thiab hauv qee qhov cam khwb cia thiab cov khoom sib xyaw ua ke, nyob rau hauv kwv yees li 100 feeb lossis tsawg dua - nrawm txaus uas qeeb weld cooldown lossis kev tswj tsis raug tom qab-weld heat treatment yog tiag tiag, tsis yog theoretical, pheej hmoo.

Tshaj tawm TTP cov ntaub ntawv rau cam khwb cia CD3MN duplex stainless hlau tso lub qhov ntswg ntawm qhov nkhaus ntawm kwv yees li 800℃nrog kuaj pom qhov tsim tawm pib ntawm 100 feeb ntawm lub sijhawm tuav. Kinetic cov kev tshawb fawb ntawm wrought 2205 qhia txog kev hloov pauv sai tshaj plaws kinetics ntawm 850 degree, nrog rau tag nrho cov cwj pwm kev tshawb fawb txuas ntxiv tuav lub sij hawm tawm mus rau ntau tshaj 1,000 teev los qhia txog qhov nkhaus tiav, suav nrog cov nqi tsim qeeb qeeb ntawm cov npoo ntawm qhov txaus ntshai band. Qhov kev cuam tshuam zoo yog asymmetric: qhov nrawm tshaj plaws ntawm qhov nkhaus ua haujlwm ntawm lub sijhawm kwv yees li ib teev mus rau ob peb teev, uas yog qhov zoo nyob rau hauv lub sijhawm tuab -section weldment lossis lub voj voog tsis zoo ntawm lub tshuab hluav taws xob tuaj yeem siv sijhawm dhau los ntawm qhov ntsuas kub.

Dab tsi txias npaum li cas yuav tsum tau tom qab tshuaj Annealing kom tsis txhob Sigma Phase?

Txias tus nqi nrawm dua li ntawm 0.25 K / s los ntawm sigma- tsim ntau yam tau tshaj tawm los txhawm rau txo qis sigma theem tsim thaum lub sij hawm tas li txias los ntawm kev daws teeb meem -annealing kub, uas yog vim li cas dej quenching los yog yuam- cua txias - tsis qeeb, tseem -cua txias {6} stainless hlau seem yog du.

Cov tshuaj annealing ntawm qhov kub thiab txias (feem ntau tshaj li 1000-1050 degree) dissolves ib theem sigma uas twb muaj lawm thiab rov pib dua austenite-ferrite tshuav nyiaj li cas, tab sis cov txiaj ntsig tsuas yog khaws cia yog tias qhov txias tom ntej dhau los ntawm sigma- tsim ntau yam sai txaus los tiv thaiv nag lossis daus tshiab. Nruam -txias- kev hloov pauv kev tshawb fawb ua ke nrog TTP cov ntaub ntawv lees paub tias cov cua txias txaus txaus - nrog cov pib tshaj tawm nyob rau hauv thaj tsam ntawm kwv yees li ib feem peb ntawm ib℃Celsius ib thib ob - zam kev tsim muaj txiaj ntsig sigma txawm tias cov khoom siv tib yam yuav yooj yim tsim sigma yog tuav isothermally nyob rau hauv qhov txaus ntshai. Qhov no yog qhov tseeb yog vim li cas tuab -section duplex Cheebtsam yuav tsum nruj quenching tom qab cov tshuaj annealing: huab hwm coj ib leeg tuaj yeem ua rau qeeb tus nqi cua txias ntawm cov khoom tseem ceeb hauv qab qhov pib no txawm tias qhov chaw txias sai sai.

Sigma Phase Pom tau li cas hauv kev ua tiav lossis hauv -Cov Chaw Pabcuam?

Kev tshuaj xyuas metallographic nrog kev xaiv etching tseem yog txoj kev siv, tab sis cov txheej txheem tsis muaj kev puas tsuaj - suav nrog cov txheej txheem sib nqus thiab electrochemical uas siv sigma theem cov khoom sib txawv los ntawm ferrite - tau nce siv los tshuaj xyuas cov khoom yam tsis muaj cov qauv txiav.

Metallography: polished seem nrog xaiv etchants qhia sigma theem morphology thiab faib ncaj qha, thiab nyob twj ywm tus qauv rau qhov tseeb ntim - feem quantification.

Kev ntsuam xyuas qhov cuam tshuam: Charpy kuaj yog qhov taw qhia tsis muaj zog, txij li qhov cuam tshuam lub zog nkhaus tau taug qab cov ntsiab lus sigma hauv cov laus duplex stainless hlau.

Sib nqus thiab electromagnetic txoj kev: vim hais tias sigma theem tsis yog -sib nqus thaum ferrite yog ferromagnetic, nws tsim ntsuas hloov cov khoom sib nqus teb, ua kom tsis muaj kev cuam tshuam kev tshuaj ntsuam.

Kev ntsuam xyuas hluav taws xob: potentiodynamic polarization tuaj yeem kuaj pom qhov poob hauv pitting muaj peev xwm cuam tshuam nrog sigma- cuam tshuam txog chromium thiab molybdenum depletion, muab kev tsis ncaj ncees tab sis rhiab corrosion-raws li kev tshuaj ntsuam.

Rau qhov tseem ceeb fabricated Cheebtsam, kev sib xyaw ua ke ntawm txoj hauv kev - es tsis yog ib qho kev sim ib zaug - muab cov duab txhim khu kev qha tshaj plaws, txij li kev poob qis, kev tiv thaiv corrosion, thiab cov ntsiab lus ncaj qha sigma tsis tas yuav txav mus rau hauv qhov ntsuas phoo ntawm qhov qis sigma feem ntau.

Dab tsi yuav tsum Fabricators ua los tiv thaiv Sigma Phase Embrittlement?

Tswj cov khoom siv hluav taws xob thiab kev sib tshuam ntawm qhov kub thiab txias thaum lub vuam, txias sai heev los ntawm 700-950℃ntau tom qab muaj kev kub siab -, thiab txheeb xyuas qhov tshwm sim nrog kev sim cuam tshuam es tsis yog cia siab rau kev soj ntsuam pom ib leeg.

Qhia thiab tswj qhov siab tshaj plaws ntawm qhov kub thiab txias input txwv nyob rau hauv cov txheej txheem vuam specification, vim hais tias cov no ncaj qha tswj ntev npaum li cas lub tshav kub - cuam tshuam cheeb tsam dwells nyob rau hauv lub txaus ntshai band.

Siv cov cua txias sai sai - dej quenching los yog yuam- cua txias raws li qhov tsim nyog rau ntu tuab - tom qab cov tshuaj annealing los yog ib qho siab - kub thermal voj voog, es tsis pub qeeb, tseem - cua txias.

Tus account rau seem thickness qhia meej: cov khoom tuab txias dua maj mam ntawm lawv cov tub ntxhais thiab tej zaum yuav xav tau kev quenching ntau dua kom ua tiav qhov kev ua kom txias zoo ib yam li cov ntu nyias.

Yuav tsum tau Charpy cuam tshuam kev soj ntsuam ntawm cov txheej txheem kev tsim nyog cov ntaub ntawv thiab, qhov ua tau zoo, ntawm cov welds ntau lawm, vim toughness poob yog ib qho ntawm cov rhiab heev qhia ntawm incipient sigma tsim.

Qhov twg cov kev pabcuam cuam tshuam nrog kev rov ua dua lossis ntev ntev nyob ze ntawm qhov phom sij, ntsuas kev xaiv alloy nws tus kheej - qee qhov kev sib xyaw ua ke thiab cov tswv yim alloying ncua kev tsim sigma zoo dua li lwm tus.

Cov lus nug nquag

Thaum twg qhov kub thiab txias ua sigma theem sai tshaj plaws hauv duplex stainless hlau?

Feem ntau cov sij hawm luam tawm -kub- nag lossis daus kev tshawb fawb tso qhov nrawm tshaj plaws sigma tsim - 'qhov ntswg' ntawm qhov nkhaus - nyob ib ncig ntawm 800-850 degree, txawm hais tias tus nqi tseeb hloov me ntsis nrog cov alloy muaj pes tsawg leeg.

Sigma theem puas txaus ntshai?

Kuj ceeb tias me me. Ntau cov kev tshawb fawb qhia txog qhov poob qis ntawm qhov sib txawv ntawm qhov sib txawv ntawm thaj tsam li ntawm 1% mus rau 3% los ntawm qhov ntim, zoo ua ntej theem yuav yooj yim rau pom yam tsis muaj kev kuaj xyuas metallographic.

Puas yog sigma theem cuam tshuam rau kev tiv thaiv corrosion lossis tsuas yog cov neeg kho tshuab toughness?

Ob leeg. Sigma theem tsim depletes chromium thiab molybdenum los ntawm ib puag ncig matrix, uas ntsuas qhov qis pitting muaj peev xwm thiab nce intergranular thiab pitting corrosion susceptibility, ntxiv rau txo qhov cuam tshuam toughness.

Puas tuaj yeem tshem tawm theem sigma thaum nws tau tsim?

Yog lawm, feem ntau los ntawm kev daws teeb meem ntawm qhov kub siab txaus (feem ntau tshaj li ntawm 1000-1050 degree) ua raws li cov cua txias sai, uas ua rau cov theem sigma rov qab rau hauv matrix thiab rov ua kom muaj qhov sib npaug ntawm microstructure - muab qhov tom ntej cooldown yog ceev txaus los tiv thaiv kev hloov kho.

Vim li cas welding feem ntau ua rau cov theem sigma hauv thaj teb?

Vim tias cov cua sov- cuam tshuam thaj tsam ib puag ncig ib puag ncig weld inevitably dhau los ntawm sigma- tsim qhov kub thiab txias thaum lub sij hawm cua sov thiab txias, thiab ntau- hla vuam los yog cov cua kub siab tuaj yeem sau sijhawm txaus hauv qhov ntau los ua kom puas cov ntsiab lus sigma.