Stainless Hlau Phaj 304 vs 316: Tshuaj Chemical thiab Weldability rau Siab Vessel Fabrication

Ob qib yog austenitic chromium-nickel stainless hlau, thiab ob qho tib si tau teev nyob rau hauv ASTM A240 rau siab hlab ntsha phaj. Tag nrho qhov sib txawv los mus rau ib lub caij: molybdenum. 316 nqa 2.00 txog 3.00 feem pua ​​ntawm nws thiab 304 tsis muaj. Ib kab ntawm daim ntawv pov thawj zeb kuaj hloov chloride pitting tus cwj pwm, kev hloov pauv uas cuam tshuam nrog kev kuaj corrosion, hloov tus nqi, thiab - yog tias koj tab tom tsim rau ASME Tshooj VIII - hloov yuav luag tsis muaj dab tsi txog cov txheej txheem vuam. Phau ntawv qhia no cais cov chemistry uas tseem ceeb ntawm chemistry uas yog kev lag luam.

Dab tsi yog qhov txawv ntawm 304 thiab 316 stainless hlau phaj?

Ib lub ntsiab lus: molybdenum. 316 thiab 316L muaj 2.00 txog 3.00 feem pua ​​molybdenum thiab 304 thiab 304L tsis muaj. Chromium thiab nickel ranges txav me ntsis nyob rau hauv qhov kev coj rov qab - 304 muaj cov chromium ntau dua, 316 ntau dua nickel ntau - thiab cov pa roj carbon tsawg ntawm ob lub hau carbon ntawm 0.030 feem pua. Txhua yam koj mob siab rau hauv kev pabcuam thiab hauv cov vuam ua raws li plaub kab ntawd.

Txoj kev nrawm tshaj plaws los nyeem cov lus qhia tshwj xeeb yog kom tsis txhob xav txog304thiab316raws li ob yam khoom sib txawv thiab pib xav txog lawv ua ib qho khoom siv nrog kev xaiv alloying. Ob leeg yog austenitic, uas txhais tau hais tias ob qho tib si muaj lub ntsej muag-centred cubic crystal qauv ntawm chav tsev kub, ob qho tib si tsis yog hlau nplaum nyob rau hauv cov mob annealed, ob qho tib si tsis tuaj yeem hardened los ntawm kev kho cua sov, thiab ob qho tib si tawv tag nrho mus rau qhov kub thiab txias. 300 series stainless hlau cov hauv paus yog zoo tib yam rau ob qib.

ASTM A240 / ASME SA-240 cov khoom siv tshuaj, qhov hnyav feem pua

Ob lub ntsiab lus nyob rau hauv lub rooj surprise neeg. Ua ntej, 304 muaj cov chromium ntau dua - 17.5 mus rau 19.5 feem pua ​​​​ tiv thaiv 16.0 mus rau 18.0 feem pua ​​​​rau 316. Qhov ntxiv corrosion kuj ntawm 316 tsis ntau chromium; nws yog molybdenum. Qhov thib ob, cov npib tsib xee yog qhov dav txaus uas qhov muab cov cua sov ntawm 316 tuaj yeem ua tau ze li cov npib tsib xee-nplua nuj ntau npaum li cov nickel-cov kabmob tshwj xeeb, uas yog ib feem ntawm vim li cas molybdenum surcharge ib leeg tsis piav qhia tus nqi sib txawv.

Qhia meej los ntawm kev ntsuas cua sov ntawm daim ntawv pov thawj zeb xeem, tsis txhob los ntawm cov nqi raug luam tawm hauv daim ntawv qhia zeb.

Ib qho 316 cua sov ntawm 2.02 feem pua ​​​​molybdenum thiab ib qho ntawm 2.95 feem pua ​​​​yog ob qho tib si hauv cov ntsiab lus thiab lawv tsis coj tus cwj pwm zoo ib yam hauv qhov kub chloride crevice. Yog hais tias lub nkoj nyob rau hauv ib qho kev pab cuam uas pitting yog tus tswj mechanism, qhia ib tug tsawg kawg nkaus molybdenum ntawm 2.5 feem pua ​​raws li ib tug ntxiv yuav tsum tau ntawm daim ntawv yuav khoom.

Yuav ua li cas molybdenum hloov tus cwj pwm corrosion ntawm 316 phaj?

Molybdenum slows down qhov pib thiab thaum ntxov loj hlob ntawm pits thiab crevice nres nyob rau hauv chloride-cov kabmob ib puag ncig. Nws ua qhov no los ntawm kev ntxiv dag zog rau hauv cov yeeb yaj kiab passive thiab hauv kev daws teeb meem hauv qhov loj hlob, uas ua rau cov tshuaj lom neeg hauv zos tsis tshua muaj zog thiab muab lub sijhawm ntau dua los rov ua dua. Nws tsis ua rau 316 tiv thaiv kab mob, thiab nws tsis yuav cov tshuaj tiv thaiv chloride kev nyuaj siab corrosion tawg.

Stainless hlau tiv thaiv nws tus kheej nrog ib tug chromium oxide zaj duab xis ob peb nanometers tuab. Hauv cov dej uas muaj chlorides uas zaj duab xis raug tawm tsam ntawm cov ntsiab lus tsis muaj zog - kev suav nrog, khawb, sulphide stringer - thiab lub qhov pib pib. Thaum lub qhov dej qhib, cov chemistry nyob rau hauv nws ua acidic thiab concentrated nyob rau hauv cov tshuaj chloride, thiab lub qhov dej khawb sai dua li nws tau ua thaum pib. Molybdenum cuam tshuam ntawm ob lub ntsiab lus: molybdate hom nyob rau hauv zaj duab xis ua rau nws nyuaj rau tawg nyob rau hauv thawj qhov chaw, thiab molybdenum yaj los ntawm cov hlau nyob rau hauv ib tug active pit buffers lub zos acidity thiab pab lub qhov dej phab ntsa repassivate ua ntej nws ua nws tus kheej-sustaining.

Qhov twg molybdenum nyob rau hauv 316 pab, thiab qhov twg nws tsis

Ib qho kev to taub kim tshaj plaws hauv cov lus no yog cov tshuaj chloride kev nyuaj siab corrosion cracking kab. Molybdenum tsis pab. Ib lub nkoj 316 nyob rau hauv kev rwb thaiv tsev ntawm ntug dej hiav txwv tuaj yeem tawg los ntawm sab nraud hauv ib qho yooj yim li 304, vim tias lub tshuab xav tau chlorides, oxygen, tensile stress thiab kub siab tshaj li 60 C - thiab molybdenum hloov tsis muaj plaub. Kev kho yog txheej txheej, tsis tshua muaj chloride rwb thaiv tsev, thiab ua kom cov hlau qhuav. Yog tias koj xav tau lub nkoj kom ciaj sia lub luag haujlwm hauv cov hlau liab qab, koj xav tauwb 2205los yog ntau dua alloyed khoom.

PREN qhov tseem ceeb ntawm 304 thiab 316 yog dab tsi, thiab lawv ua tau li cas?

Siv PREN=feem pua Cr + 3.3 x feem pua Mo + 16 x feem N, feem ntau 304 av ntawm roughly 18 mus rau 20 thiab raug 316 ntawm kwv yees li 23 mus rau 26. Qhov ntawd yog qhov sib txawv ntawm qhov sib txawv ntawm li 25 feem pua, thiab nws yog ib txoj hauv kev zoo los sib piv cov cua sov ntawm cov hlau tsis muaj steel thiab PREN. ntawm nws tus kheej nws tsis yog tus lej tsim rau lub nkoj siab.

Lub molybdenum coefficient ntawm 3.3 yog vim li cas qhov sib txawv tshwm sim: ntawm 2.1 feem pua ​​molybdenum, lub sij hawm ib leeg pab txhawb txog 6.9 cov ntsiab lus, ntau tshaj li tshem tawm cov chromium deficit. Nitrogen txhawb ib yam nkaus, uas yog vim li cas 316LN - nitrogen-alloyed variant - zaum saum 316L dawb rau tib cov ntsiab lus molybdenum. SaibStainless hlau 316LNrau cov nitrogen-muaj zog version.

PREN ua haujlwm los ntawm kev ntsuas cua sov

Dab tsi PREN tsis qhia koj tseem ceeb npaum li cas. Nws tsis hais dab tsi txog qhov tseem ceeb ntawm qhov kub thiab txias, uas yog ib txwm qis dua qhov tseem ceeb pitting kub thiab yog tus naj npawb uas tswj hwm lub flange gasketed lossis lub puab tsaig. Nws hais tias tsis muaj dab tsi txog cov hlau weld, qhov twg kev sib cais thaum lub sij hawm solidification tuaj yeem tso cov hlau kawg kom khov nrog ib qho sib txawv ntawm cov khoom. Thiab nws yog qhov ntsuas ntsuas, tsis yog qhov pib: PREN ntawm 24 tsis qhia koj txog cov tshuaj chloride concentration lossis qhov kub thiab txias ntawm lub nkoj tshwj xeeb yuav pit. Rau qhov koj xav tau ntsuas qhov ntsuas kub tseem ceeb ntawm cov ntaub ntawv rau ib puag ncig tiag tiag, lossis keeb kwm kev pabcuam.

Vim li cas cov ntsiab lus carbon thiaj txiav txim siab seb koj yuav 304L lossis 316L phaj?

Vim tias cov pa roj carbon yog qhov ua rau thaj chaw muaj kev kub ntxhov poob nws qhov kev tiv thaiv corrosion. Tshaj li ntawm 0.03 feem pua ​​​​ carbon muaj qhov txaus los ua ke nrog chromium thiab precipitate chromium carbide ntawm cov ciam teb thaum cov hlau hla 425 txog 815 C. Carbide rub chromium tawm ntawm cov hlau tam sim ntawd nyob ib ncig ntawm nws, cov hlau poob qis dua li ntawm 12 feem pua ​​​​chromium xav tau kom nyob twj ywm corrosion, thiab intergran.

Ib lub vuam ua rau thaj chaw uas muaj kev cuam tshuam los ntawm qhov cua sov yuav ua li cas. Hlau ob peb millimeters los ntawm fusion kab yog rhuab mus rau hauv cov carbide nag lossis daus ntau thiab tuav ntev txaus rau qhov teeb meem, ces txias. Nyob rau hauv ib tug multipass weld nyob rau hauv tuab phaj cheeb tsam yog reheated ob peb zaug. Hauv qib nrog 0.06 feem pua ​​carbon, chromium carbide nag lossis daus tuaj yeem pib hauv feeb ze 675 C. Hauv qib nrog 0.02 feem pua ​​​​ carbon, tib lub voj voog thermal tsis tsim lub network txuas ntxiv carbide, vim tias tsuas yog tsis muaj cov pa roj carbon ntau txaus hauv kev daws rau ib qho.

Cov pa roj carbon monoxide, rhiab heev thiab qhov ua tau zoo

Qib L tsis yog noj su dawb. Nws lub zog tawm los yog 170 MPa tiv thaiv 205 MPa rau qib ncaj, thiab Tshooj II Tshooj D teev nws qhov kev cia siab ntawm 16.7 ksi tiv thaiv 20.0 ksi. Koj them kwv yees li ntawm 17 feem pua ​​​​ntawm kev tsim lub zog rau qhov weldability. Thiab qhov kev zam tsis tas mus tas li: tuav qib L ntawm kwv yees li 500 thiab 800 C rau xyoo thiab nws tseem yuav hnov ​​​​qab, ib qho tshwm sim hu ua qhov kub thiab txias. Qhov ntawd tseem ceeb rau cov hlab ntsha uas sov sov, thiab nws yog ib qho ntawm cov laj thawj 316H muaj nyob - saibStainless hlau 316Hrau high-carbon variant.

Dab tsi yog dual-certified 304/304L lossis 316/316L phaj thiab nws puas pab tau?

Dual-certified phaj yog ib qho cua sov uas ua tau raws li txhua qhov yuav tsum tau ua ntawm ob qib ncaj thiab qib L - carbon ntawm 0.030 feem pua ​​lossis qis dua, thiab tensile thiab tawm los ntawm qib qis qis. Nws yog tus txheej txheem mills muab cov phaj stainless hnub no, thiab nws cia ib qho khoom lag luam ua haujlwm ob qho tib si L-qib vuam specification thiab tus qauv ncaj-qib tso cai.

Tsis muaj metallurgical ua kom yuam kev ntawm no. Cov cua sov tsuas yog cov cua kub uas tsis tshua muaj carbonated uas tau tshwm sim los ntsuas saum toj ntawm cov khoom siv hluav taws xob ncaj nraim, uas feem ntau niaj hnub melts ua thaum tswj nitrogen. Lub zeb ua pov thawj nws rau ob qho tib si specifications thiab daim ntawv pov thawj npe ob qho tib si.

Dab tsi dual ntawv pov thawj ua thiab tsis muab rau koj

Rau lub nkoj uas yuav tsum tau welded thiab tsis nyob rau hauv high-kub creep kev pab cuam, qhia dual-certified 304/304L los yog 316/316L thiab tsim rau cov qib ncaj tso cai qhov twg koj tso cai soj ntsuam pom zoo. Nws yog qhov pheej yig tshaj plaws kom tau txais L-qib weldability yam tsis tau muab 17 feem pua ​​​​ntawm cov kev ntxhov siab tso cai. Paub meej tias daim ntawv pov thawj qhia tias carbon ntawm lossis qis dua 0.030 feem pua ​​​​ua ntej koj lees txais nws, thiab xyuas kom meej tiasstainless hlau phaj muas phau ntawv qhiacov kev cai rau kev cim thiab traceability yog sau rau hauv qhov kev txiav txim.

Dab tsi yog cov yam ntxwv ntawm 304 thiab 316 phaj rau ASTM A240?

304 thiab 316 zoo ib yam: 515 MPa (75 ksi) yam tsawg kawg nkaus tensile, 205 MPa (30 ksi) yam tsawg kawg nkaus 0.2 feem pua ​​yield, 40 feem pua ​​tsawg kawg elongation . 304L thiab 316L kuj zoo tib yam rau ib leeg thiab qis dua: 485 MPa (70 tensile) (70 MPa) ksi) yield. Molybdenum hloov tus cwj pwm corrosion; nws tsis hloov lub zog. Tsuas yog qhov sib txawv ntawm txhua qhov sib piv yog qhov tshwm sim los ntawm carbon.

ASTM A240 yam khoom yam tsawg kawg nkaus, annealed mob

Ob kab kawg yog qhov tseem ceeb hauv lub khw tshaj li ntawm daim duab. Austenitic stainless ua rau kwv yees li ib feem peb ntawm cov cua kub ntau npaum li cov pa roj carbon steel thiab nthuav dav li 40 mus rau 50 feem pua ​​​​ntau dua rau tib qhov kub thiab txias. Ob qhov tseeb ua ke yog vim li cas lub nkoj stainless distorts nyob rau hauv txoj kev ntawm carbon steel hlab ntawm zoo tib yam geometry tsis, thiab lawv yog tib yam rau 304 thiab rau 316 - xaiv ntawm cov qib yuav tsis hloov koj distortion teeb meem.

Qib twg muab lub plhaub nyias nyias thiab pheej yig dua lub plhaub?

Tsis yog . 304 thiab 316 nqa tib yam ASME tso cai rau kev ntxhov siab ntawm qhov kub thiab txias, yog li qhov ntsuas lub plhaub tuab yog tib yam. Dab tsi hloov thickness yog cov pa roj carbon variant: tsim rau 304L los yog 316L ntawm 16.7 ksi es tsis txhob 304 los yog 316 ntawm 20.0 ksi ua rau lub plhaub txog 20 feem pua ​​thicker. Molybdenum yuav corrosion kuj; nws yuav tsis muaj zog kiag li.

Ua hauj lwm nws los ntawm ib tug neeg sawv cev plhaub. Siv lub siab sab hauv ntawm 150 psi, sab hauv vojvoog ntawm 30 hauv, thiab hom 1 ob-welded taub qab sib koom nrog tag nrho cov duab hluav taws xob muab kev sib koom ua haujlwm ntawm 1.0 ib UW-12. Qhov sib npaug ntawm UG-27 qhov sib npaug ntawm qhov ntev yog t=PR / (SE - 0.6P).

Ua haujlwm UG-27 plhaub xam: P=150 psi, R=30 hauv, E=1.00

Qhov kev ntxhov siab uas tso cai rau nws tus kheej yog muab los ntawm tib txoj kev rau txhua kab hauv lub rooj. Tshooj II Ntu D teev S raws li qhov qis dua ntawm ob feem ntawm cov khoom tsawg kawg nkaus ntawm qhov kub thiab txias: ob feem peb ntawm lub zog tawm los, thiab ib qho 3.5th ntawm lub zog tensile. Ntawm ambient uas muab 2/3 x 30=20.0 ksi tiv thaiv 75 / 3.5=21.4 ksi rau cov qib ncaj, yog li 20.0 tswj hwm; thiab 2/3 x 25=16.7 ksi tiv thaiv 70 / 3.5=20.0 ksi rau qib L, yog li 16.7 kav. Saum toj no kwv yees li 540 C lub creep thiab kev ntxhov siab rupture zog coj mus thiab ob tsev neeg sib txawv, yog li nyeem Table 1A rau qib pes tsawg thiab tsim qhov kub thiab txias es tsis yog interpolating.

Qhov kev coj ua tiag tiag yog tias cov pa roj carbon sib txawv yog qhov tsim qauv sib txawv thiab cov molybdenum tsis yog. Yog tias koj lub nkoj tau tsim los rau 304L thiab koj mam li pauv mus rau 316L rau qhov laj thawj corrosion, lub plhaub tuab tsis hloov pauv thiab tsuas yog daim nqi txav yog tus nqi phaj. Yog tias koj pauv ntawm 316 mus rau 316L, lub plhaub loj hlob li ntawm ib feem tsib. Paub meej tias qhov kev sib koom ua tau zoo uas koj muaj cai nyob rau hauv UW-12 ua ntej koj ua tiav cov phab ntsa, vim tias tag nrho cov duab hluav taws xob ntawm E=1.00 muaj nqis ntau dua li qhov kev xaiv qib feem ntau yog.

Thaum twg koj yuav tsum tsis txhob siv 304L lossis 316L?

Peb qhov txwv tsis pub siv thiab qhov qis tshaj yog tswj hwm. Tsawg-kub rhiab heev pib muaj teeb meem siab dua li ntawm 500 C hauv kev pabcuam ntev, qhov kev cia siab tau poob qis tshaj li ntawm 540 C thaum nkag mus, thiab molybdenum-cov kabmob 316L yog qhov ntau sigma-nrawm ntawm ob hauv 550 txog 900 C band. Rau cov hlau ruaj khov kub siab tshaj li 540 C, txav mus rau 304H lossis 316H, lossis mus rau qib ruaj khov.

Qhov ntsuas kub txwv thiab dab tsi tswj ntawm txhua pawg

Sigma theem tsim nyog tau txais kev ceeb toom vim tias nws tshwj xeeb rau molybdenum sab ntawm qhov kev sib piv no. Sigma yog ib qho nyuaj, nkig intermetallic uas tsim los ntawm ferrite nyob rau hauv kwv yees li 550 txog 900 C ntau, thiab molybdenum accelerates nws. Nyob rau hauv 316L puag hlau muaj ib txwm tsis muaj ferrite los hloov, yog li qhov kev pheej hmoo zaum hauv cov hlau vuam, qhov twg 3 mus rau 10 tus lej ferrite tau txhob txwm muab tso rau hauv kom tsis txhob kub tawg. Yog hais tias lub nkoj 316L yuav khiav hauv qhov kub thiab txias, tuav lub vuam hlau ferrite nyob rau hauv qab ntawm qhov kev pom zoo thiab ua kom cov cua sov ntawm cov ferrite tsawg.

Puas yog 316 zoo dua 304 rau chloride kev nyuaj siab corrosion tawg?

Tsis yog. Qhov no yog qhov yuam kev ntau tshaj plaws thiab kim tshaj plaws hauv tag nrho 304 piv rau 316 kev txiav txim siab. Molybdenum txhim kho pitting thiab crevice kuj; nws tsis txhim kho kev tiv thaiv rau chloride kev nyuaj siab corrosion cracking. Ob qib tawg, thiab lub nkoj 316 nyob rau hauv rwb thaiv tsev ntawm qhov chaw sov, chloride-cov kabmob yuav ua tsis tau zoo ib yam li 304 ib qho ua.

Chloride stress corrosion cracking xav tau plaub yam ib zaug: chlorides, yaj oxygen, tensile stress, thiab kub siab tshaj li 50 mus rau 60 C. Tshem tawm ib qho thiab koj tsis tau tawg. Molybdenum tsis cuam tshuam rau ib qho ntawm plaub. Qhov nws hloov pauv yog qhov pitting uas feem ntau ua ntej qhov tawg, thiab hauv qhov chaw kuaj nqaim uas tuaj yeem hloov qhov pib me ntsis - tab sis kev hloov pauv hauv qhov chaw kuaj mob tsis yog daim ntawv tso cai rau lub nkoj siab.

Dab tsi tiag tiv thaiv chloride kev nyuaj siab corrosion cracking

Yog tias koj tab tom sau cov ntaub ntawv kab rau lub nkoj uas yuav raug rwb thaiv tsev thiab nyob sab nraum zoov lossis ntawm ntug dej hiav txwv, tsis txhob sau 316 raws li kev txo qis rau sab nraud chloride kev nyuaj siab corrosion cracking. Sau cov txheej txheem txheej txheem, qhov yuav tsum tau muaj cov tshuaj tiv thaiv chloride tsawg thiab cov ntsiab lus tiv thaiv huab cua, thiab kev siv nyiaj rau kev tswj xyuas lawv. Cov khoom siv kho dua tshiab uas ua haujlwm hauv lub luag haujlwm yog kev hloov pauv ntawm tsev neeg hlau, tsis yog kev hloov pauv hauv 304 thiab 316 khub.

316 phaj nqi ntau npaum li cas tshaj 304, thiab nws puas tseem ceeb ntawm lub nkoj?

316 phaj feem ntau nqa 25 mus rau 45 feem pua ​​​​ntau tshaj 304, uas tau tsav los ntawm molybdenum thiab npib tsib xee alloy surcharges. Ntawm lub nkoj siab tiav qhov kev nplua me dua li qhov sib txawv qhia, vim tias phaj tsuas yog ib feem ntawm tus nqi xa thiab vuam, kev kuaj xyuas thiab kev kho cua sov yog zoo tib yam rau ob qib.

Qhov twg tus nqi sib txawv tshwm sim, thiab qhov twg nws tsis

Cov kab kawg tsis yog lus tso dag. Thaum 304 lub nkoj pits vim tias cov txheej txheem tau muab cov tshuaj chlorides, cov hauv paus ntsiab lus yog yooj yim mus nrhiav thiab kho - txhim kho cov khoom - yog ncaj nraim. Thaum lub nkoj 316 tawg nyob rau hauv rwb thaiv tsev, tus neeg tsim khoom feem ntau yog thawj tus neeg xav tias txawm tias cov khoom siv tsis muaj peev xwm tiv thaiv cov txheej txheem ntawd. Them tus nqi them rau 316 thiab tom qab ntawd siv nws los daws qhov teeb meem molybdenum tsis nyob yog qhov phem tshaj ntawm ob qhov txiaj ntsig.

Rau cov kev xaiv alloy tshaj qhov khub no,904L vs 254 SMO vs 316Lnpog qhov twg cov qib super austenitic coj mus, thiabStainless hlau 904Lmuab cov muaj pes tsawg leeg thiab cov khoom ntawm feem ntau siv los ntawm lawv.

Koj siv cov khoom siv hlau twg rau 304 piv rau 316 phaj?

Sib piv cov qib thiab ua kom cov pa roj carbon tsawg. Weld 304 thiab 304L nrog ER308L rau GTAW thiab GMAW lossis E308L rau SMAW; Weld 316 thiab 316L nrog ER316L lossis E316L. Siv silicon-cov kabmob variants rau GMAW los txhim kho kev ntub dej. Ob lub hauv paus hlau zaum hauv P-No. 8 Pawg 1 thiab tag nrho cov khoom siv no zaum hauv F-No. 6, yog li ib tus txheej txheem tsim nyog suav nrog tag nrho tsev neeg.

Filler xaiv rau 304 thiab 316 phaj welds

Qhov muab tub lim yog txhob txwm tsis ua kom zoo meej rau lub hauv paus hlau. ER308L khiav txog 19.5 mus rau 22.0 feem pua ​​​​chromium tiv thaiv 17.5 txog 19.5 feem pua ​​​​hauv phaj, thiab ER316L khiav txog 18.0 txog 20.0 feem pua ​​​​chromium tawm tsam 16.0 txog 18.0 feem pua ​​​​hauv phaj. Qhov chromium enrichment yog dab tsi tso cov hlau weld rau ntawm txoj kev ferritic-austenitic solidification es tsis txhob muaj cov austenitic tag nrho, uas yog cov lus nug tom ntej - thiab nws kuj yog vim li cas lub weld deposited nrog qhov tsis ncaj ncees lawm muab tub lim yuav saib zoo meej ntawm radiography thiab tseem yog ib qho teeb meem tawg.

Cov qauv tsim nyog yog ib txwm muaj rau ob qib. ASME Tshooj IX muab 304, 304L, 316 thiab 316L rau P-No. 8 Pawg 1, muab tag nrho cov austenitic stainless fillers rau F-No. 6, thiab npog cov vuam hlau muaj pes tsawg leeg raws li A-Number system. Cov txiaj ntsig zoo: kev tsim nyog rau tus txheej txheem ntawm 316L feem ntau tsim nyog rau cov kev hloov pauv tseem ceeb rau tag nrho tsev neeg, yog vim li cas cov khw feem ntau tsim nyog rau 316L thiab ua haujlwm qis dua tsis tsim nyog txhua qib sib cais.

Vim li cas ferrite tooj tseem ceeb hauv austenitic stainless weld hlau?

Vim tias ib qho me me ntawm delta ferrite yog tib yam uas sawv ntawm austenitic weld thiab solidification cracking. Lub hom phiaj 3 txog 10 ferrite tooj. Hauv qab no txog 3 FN cov hlau weld solidifies li coarse columnar austenite nplej nrog impurity-nplua nuj kua zaj duab xis ntawm lawv thiab tuaj yeem tawg thaum nws txias; saum toj no txog 10 FN cov ferrite tuaj yeem hloov mus rau nkig sigma theem hauv kev pabcuam sov.

Ferrite yog sib nqus thiab austenite tsis yog, uas yog vim li cas tag nrho cov kev ntsuas yuav ua tau nrog ib tug calibrated sib nqus ntsuas ntawm lub tiav weld. Ferrite tooj yog txhais los ntawm AWS A4.2 thiab tsis yog raws nraim qhov ntim feem pua ​​- hauv qab no txog 8 mus rau 10 ob yog nyob ze, saum toj no uas lawv diverge - uas yog ib qho ntxiv vim li cas lub hom phiaj pom zoo nyob qhov twg nws ua.

Ferrite tooj bands thiab dab tsi txhua tus txhais tau tias

Kev kwv yees ua ntej koj welding ua tiav nrog WRC-1992 daim duab kos duab, uas siv cov chromium thiab npib tsib xee sib npaug suav los ntawm diluted weld hlau muaj pes tsawg leeg: Cr sib npaug sib npaug li feem pua ​​​​Cr ntxiv rau feem pua ​​Mo plus 0.7 zaug feem pua ​​Nb, thiab Ni sib npaug sib npaug Ni plus 35 zaug feem pua ​​​​C ntxiv rau 20 zaug feem pua. Lub sij hawm nitrogen yog vim li cas WRC-1992 tshem tawm cov laus Schaeffler daim duab rau niaj hnub qis-carbon, nitrogen-cov kabmob heats.

Predicted ferrite tus lej yog suav; ntsuas ferrite tooj yog cov ntaub ntawv txais. Ntsuas nws ntawm tus txheej txheem daim coupon tsim nyog nrog ib tug calibrated ntsuas thiab dua nyob rau hauv ntau lawm xeem daim coupons yog lub muab tub lim hloov. Nco ntsoov tias qhov kev ntsuas cuam tshuam cryogenic nyob rau hauv UHA-51 nqa lawv tus kheej ferrite txwv uas zaum qis dua 3 mus rau 10 band. Yog tias koj lub nkoj xav tau ob qho tib si tawg-resistant welds thiab qhov kub ntawm cov hlau tsim qis heev, daws qhov teeb meem ntawm PQR nrog koj Tus Kws Tshuaj Ntsuam Xyuas es tsis pom nws tom qab cov welds nyob hauv.

Koj puas xav tau preheat los yog tom qab vuam kub kho rau 304 thiab 316 hlab ntsha welds?

Tsis yog rau ob leeg, nyob rau hauv qhov kev nkag siab ib txwm. Tsis muaj hydrogen cracking mechanism rau preheat tiv thaiv, vim hais tias austenite tsis hloov mus rau martensite ntawm txias thiab muaj siab hydrogen solubility. Thiab ASME Tshooj VIII-1 Table UHA-32 hais tias tom qab kev kho cua sov rau P-No. 8 austenitic stainless hlau tsis tas yuav tsum tau lossis txwv tsis pub - tsis muaj qhov ua kom tuab tuab.

Thermal kho ntawm austenitic stainless hlab ntsha welds

Txoj haujlwm UHA-32 yog qhov sib txawv ntawm lub ntiaj teb carbon steel thiab nws ntes cov neeg tsim khoom tawm. Rau P-No. 1 carbon steel nkoj muaj qhov nyuaj thickness pib - 38 hli (1.5 in) rau P-No. 1 Pab Pawg 1 - saum toj no uas PWHT yuav tsum tau ua. Rau austenitic stainless tsis muaj qhov pib, tsis muaj lub sijhawm tuav thiab tsis muaj qhov kub thiab txias. Yog tias tus neeg siv qhia txog kev kho cua sov lawm, lub voj voog txoj cai yog kev daws teeb meem ua raws li kev ua kom txias sai, tsis yog kev ntxhov siab subcritical. A 650 C kev ntxhov siab nyem rau ntawm lub nkoj welded los ntawm cov tsis-L phaj yog ib txoj hauv kev zoo rau rhiab rau tag nrho cov cua sov.

Cov taub hau tsim yog qhov tshwj xeeb tsim nyog paub txog. Cold forming strain and any hot forming cycle ob leeg hloov cov khoom, thiab hnyav heev-tsim austenitic hau yog nquag tov annealed tom qab tsim kom tshem tawm cov strain thiab restore corrosion kuj. Qhov ntawd yog kev kho cua sov ua haujlwm, tsis yog vuam PWHT, thiab nws tshwm sim ua ntej lub taub hau yog welded rau hauv lub plhaub.

Yuav ua li cas koj nres rhiab heev nyob rau hauv lub tshav kub-cuam tshuam cheeb tsam ntawm lub nkoj weld?

Tswj cov pa roj ua ntej, tom qab ntawd lub sijhawm thiab kub. Order L qib lossis dual-certified cov ntaub ntawv yog li tsis muaj cov pa roj carbon txaus los tsim ib qho kev sib txuas txuas ntxiv carbide, tom qab ntawd ua kom qhov sib txawv ntawm qhov kub thiab txias input nruab nrab yog li HAZ siv sij hawm tsawg li tsawg tau ntawm 425 thiab 815 C. Qhov twg lub nkoj yuav sov so rau ntau xyoo, xav txog qib stabilized, thiab qhov twg qhov tshwm sim yog siab, xyuas nrog ib qho kev ntsuam xyuas ntawm ASTM A2.

Lub tshuab tsim nyog nkag siab ib zaug kom cov tswj kom nkag siab. Chromium carbide precipitates ntawm grain ciam teb vim carbon diffuses rau ciam teb sai tshaj li chromium diffuse tawm ntawm ib ncig ntawm cov hlau. Cov carbide uas cov ntaub ntawv yog nplua nuj nyob rau hauv chromium, yog li lub nqaim band ntawm hlau tam sim ntawd ib sab ntawm ciam teb yog depleted. Hauv qab no kwv yees li 12 feem pua ​​​​ntawm chromium uas band tsis muaj stainless lawm, thiab hauv cov kua dej corrosive nws dissolves nyiam, tawm hauv txoj kev txuas ntxiv mus. Qhov dej nag ceev tshaj plaws tshwm sim nyob ze 650 txog 750 C, uas yog squarely hauv qhov ntau ntawm qhov vuam HAZ hla dhau.

Sensitization tswj, nyob rau hauv qhov kev txiav txim lawv yuav tsum tau siv

Qhov twg A262 xyaum hu tawm yog nyob ntawm qib, thiab qhov no yog ib qho ntawm ob peb qhov chaw uas qhov kev xaiv 304 piv rau 316 tiag tiag hloov txoj kev sim. Xyaum B, ferric sulfate-sulfuric acid xeem, yog qhov tsim nyog rau qib molybdenum-cov kabmob austenitic, yog li qhia nws rau 316 thiab 316L. Xyaum C, nitric acid lossis Huey test, yog qhov kev xaiv zoo rau 304 thiab 304L. Xyaum A yog qhov ceev oxalic acid etch siv rau kev tshuaj ntsuam, thiab Practice E yog qhov ntsuas tooj liab-tooj ​​liab sulfate-sulfuric acid siv thaum xav tau kev ntsuam xyuas dav dav austenitic.

Vim li cas austenitic stainless hlab welds distort ntau dua carbon steel welds?

Ob lub cev muaj zog, ob qho tib si rau 304 thiab 316. Austenitic stainless ua rau kwv yees li ib feem peb ntawm cov cua kub ntau npaum li cov hlau, yog li cov cua sov nyob hauv qhov sib koom ua ke es tsis txhob nthuav tawm; thiab nws nthuav dav li ntawm 40 mus rau 50 feem pua ​​​​ntau dua ib degree, yog li tib qhov kub thiab txias ua rau thermal strain ntau dua. Ntau hom kev mob siab rau hauv ib cheeb tsam nqaim txhais tau hais tias muaj kev cuam tshuam ntau dua, ntau dua shrinkage thiab ntau dua kev ntxhov siab.

Lub cev muaj zog uas tsav kev coj tus cwj pwm

Cov tswj ua raws ncaj qha los ntawm physics. Siv cov khoom siv hluav taws xob nruab nrab ntau dua li qhov kev tso nyiaj siab uas koj xav siv ntawm cov hlau. Siv tooj liab los yog aluminium backing tuav kom rub cov cua sov tawm ntawm lub hauv paus. Siv qhov sib npaug ntawm qhov sib npaug - rov qab los yog sib npaug - yog li shrinkage yog faib ntau dua li cov khoom sib sau. Clamp mus rau qhov muaj zog rov qab qhov twg cov duab geometry tso cai, thiab nco ntsoov tias kev txwv tsis pub nce kev ntxhov siab txawm tias nws txo qis qhov pom kev cuam tshuam.

Ib qho ntxiv yog qhov tshwj xeeb rau cov hlab ntsha nyias nyias. Lub plhaub nyob rau hauv li 6 hli yog nruj-txheej es tsis muaj zog-limited, yog li distortion thiab tuav kev puas tsuaj, tsis yog lub UG-27 xam, teem lub tswv yim yam tsawg kawg nkaus. Tias yog vim li cas nyias cov hlab ntsha austenitic feem ntau yog ua nrog cov rings stiffening los yog nce nominal phab ntsa ntau dua li qhov tsawg kawg nkaus, thiab vim li cas cov thickness kev taw qhia hauvyuav ua li cas xaiv stainless hlau phaj thicknesstsim nyog nyeem ua ntej koj ua tiav lub plhaub.

ASME Tshooj VIII xav tau dab tsi ntawm austenitic stainless hlab welds?

Radiography per UW-11 nyob rau theem xav tau kom tau txais kev sib koom ua haujlwm uas koj tsim los, ntxiv rau kev tshuaj xyuas cov kua dej ntawm txhua qhov austenitic chromium-nickel welds nrog lub nominal thickness tshaj 19 hli (3/4 hauv) raws li xav tau los ntawm UHA-34. Yog tias muaj kev kho cua sov ua tiav, kev tshuaj xyuas tom qab ua tiav. Txoj cai penetrant yog ib txoj cai tshwj xeeb ntawm austenitic uas tsis muaj carbon steel sib npaug.

Kev xeem yuav tsum tau siv rau 304 thiab 316 nkoj welds

Txoj cai UHA-34 yog ib qho uas feem ntau tsis nco qab lawm. Tus neeg tsim khoom uas nws tus cwj pwm los ntawm cov hlau yuav siv hluav taws xob, tej zaum yuav kuaj ultrasonic, thiab yuav tsis xav txog kev tshuaj ntsuam xyuas ntawm lub plhaub 25 hli. The Code requires it, and it matters: austenitic weld metal solidifies with coarse columnar grains, and a radiograph taken through coarse columnar grains is poor at finding the planar, tightly closed lack-of-fusion defects those grains tend to hide.

Dab tsi yog hydrostatic test trap rau stainless hlau siab hlab ntsha?

Cov dej. Ib lub nkoj uas dhau nws qhov kev sim hydrostatic tuaj yeem raug puas tsuaj los ntawm qhov ntsuas dej sab laug sawv hauv nws, vim tias cov dej tsis muaj tshuaj chloride-cov kabmob pits austenitic stainless sai dua li feem ntau ntawm cov kua dej hauv lub nkoj yuav pom. Txwv cov tshuaj chloride, ntws tam sim ntawd, qhuav kom huv si, thiab tsis txhob tawm hauv ib nrab ntawm cov hlab ntsha zaum hauv ib lub lis piam.

Hydrostatic xeem tswj rau austenitic stainless hlab ntsha

Muaj ib tug thib ob, ntsiag to cuab nyob rau hauv tib cheeb tsam. Cov nkoj feem ntau yog hydrotested, drained, thiab ces sab laug nrog lub nozzle blanks rau thiab manway kaw rau lub lis piam ua ntej commissioning. Cov zaj duab xis ntawm cov dej evaporates thiab recondenses, tsom txhua yam chloride nyob rau hauv qhov chaw sov tshaj plaws thiab txias tshaj plaws. Yog tias lub nkoj yuav tsum zaum, cia nws qhib thiab qhuav, lossis khaws cia nrog cov nitrogen qhuav. Fabricators uas tau tuavstainless hlaurau xyoo yuav paub txog tus qauv no: qhov kev puas tsuaj yeej tsis yog qhov twg dej tob tshaj plaws, nws yog nyob ntawm cov kab dej.

Koj yuav ua li cas thiaj paub tseeb tias koj tau txais 316 thiab tsis yog 304?

Kev txheeb xyuas cov khoom zoo nrog lub xov tooj ntawm tes X-ray fluorescence analyzer, kuaj xyuas molybdenum. Nws yuav siv sij hawm vib nas this, nws ua hauj lwm ntawm lub phaj thiab nyob rau hauv lub tiav weld, thiab nws yog tib lub tswv yim txoj kev mus ntes ib tug mix-up nyob rau hauv lub khw, vim hais tias 304 thiab 316 yog visually, magnetically thiab dimensionally zoo tib yam.

Kev txheeb xyuas cov kauj ruam los ntawm kev yuav khoom mus rau daim ntawv teev npe

Molybdenum yog qhov kev ntxub ntxaug vim nws yog tib lub ntsiab lus hauv cov lus qhia uas ib qib muaj thiab lwm yam tsis muaj. Chromium thiab npib tsib xee sib tshooj sib tshooj txaus uas lawv tsis tuaj yeem daws cov lus nug, thiab tsis muaj qhov muag pom lossis sib nqus tau. Ib tug tsib-thib ob PMI txhaj rau txhua phaj ua ntej nws mus rau hauv yob, thiab nyob rau hauv txhua txhua seam tom qab vuam, tshem tawm ib tug yuam kev hom uas txwv tsis pub nto xyoo tom qab raws li unexplained corrosion. Tib daim tshev yog tsim nyog ua rau ntawm qhov muab tub lim hlau spool, vim hais tias cov hlau yog lwm qhov chaw sib xyaw tuaj yeem nkaum.

Thaum twg yuav tsum tau tsim lub nkoj siab los ntawm 304 tsis yog 316?

Thaum twg tsis muaj lub hauv paus kev txhim kho corrosion rau molybdenum los teb. Yog tias cov kua dej tsis muaj cov ntsiab lus chloride, qhov ntsuas kub qis dua li 60 C thaum muaj cov tshuaj chloride tag nrho, qhov kev pabcuam yog oxidising, lossis lub nkoj qhuav, huv si thiab sab hauv tsev, 304L yog cov khoom raug thiab pheej yig dua thiab molybdenum yog nyiaj siv tsis muaj dab tsi.

Kev xaiv matrix rau 304L piv rau 316L siab nkoj phaj

Qhov twg cov lus teb tsis yog, txoj kev txhim kho tau tsim tau zoo.TIAB SA 2205roughly doubles lub zog tawm los thiab tuav cov chloride kev nyuaj siab corrosion cracking deb zoo dua li qib.254 SMOthiab904Lcoj mus rau qhov twg pitting tsis kam yog qhov yuav tsum tau muaj kev tswj hwm, thiab rau lub luag haujlwm hnyav tshaj plaws kev sib piv yuav dhau los uaInconel 625 thiab 316L. Vuam cov ntaub ntawv yog kev qhuab qhia sib txawv dua - saibHastelloy C276 vuam qhiathiabInconel 625 vuam qhiarau cov txheej txheem hloov li cas.

Yuav ua li cas koj qhia 304 piv rau 316 phaj rau lub nkoj siab?

Ua haujlwm raws li kev txiav txim: txhais ib puag ncig, xaiv cov pa roj carbon sib txawv, paub meej cov npe Code thiab ntawv pov thawj, tsim nrog kev tso cai rau cov qib uas koj tau yuav, tsim nyog cov txheej txheem nrog ntsuas tus lej ferrite, tswj kev cuam tshuam thiab tiv thaiv, qhia txog kev kuaj xyuas thiab kev ntsuas kev sib tshuam, tom qab ntawd tswj cov dej hydrotest thiab ntxuav lub nkoj tom qab.

Kauj Ruam 1. Sau cov txheej txheem ib puag ncig ua ntej koj sau qib:Sau cov ntsiab lus chloride, qhov kub thiab txias, pH, txawm tias cov kua dej oxidising los yog txo, dab tsi tshwm sim thaum kaw, thiab dab tsi nyob rau hauv cov rwb thaiv tsev . 304 thiab 316 yog ob qho tib si austenitic chromium-nickel qib; molybdenum nyob rau hauv 316 tsuas yog yuav koj txhua yam yog hais tias ib tug localized corrosion mechanism yog tam sim no. Saib304 vs 316 stainless hlau khoom thiab kev sivrau daim duab dav dav.

Kauj ruam 2. Xaiv cov pa roj carbon variant ntawm vuam thiab kev pabcuam kub ua ke:Rau lub nkoj welded uas yuav tsis pom kev pabcuam siab tshaj li 425 C, xaj qib L. Yog tias qhov ntsuas kub tsim nyob hauv qhov tob tob, txav mus rau 316H lossis 304H es tsis txhob sim ncab qib L. Yog tias koj xav tau ib qho khoom lag luam los ua haujlwm rau ob qho tib si, yuav cov ntaub ntawv pov thawj dual thiab ua kom daim ntawv pov thawj zeb teev ob qho kev qhia tshwj xeeb.

Kauj ruam 3. Paub meej tias lub phaj yog Code khoom thiab tau txais daim ntawv pov thawj ua ntej nws txiav:Lub phaj yuav tsum yog SA-240 (ASME txais yuav ntawm ASTM A240) thiab tau teev tseg rau Tshooj VIII-1 siv, nrog tus lej xov tooj cua sov tuaj yeem nkag mus rau lub phaj cim thiab daim ntawv EN 10204 3.1 lossis 3.2. Nyeem cov ntsuas kub, tsis yog tus nqi ib txwm: xyuas cov pa roj carbon monoxide 0.030 feem pua ​​​​rau qib L thiab molybdenum tiv thaiv 2.00 feem pua ​​​​rau 316.ASTM A 240 Cov Lus Qhiateev tag nrho chemistry thiab mechanical xav tau.

Kauj Ruam 4. Tsim lub plhaub nrog qhov tso cai rau kev ntxhov siab rau qib pes tsawg uas koj yuav:Siv t=PR / (SE - 0.6P) los ntawm UG-27 rau lub longitudinal joint thiab t=PR / (2SE + 0.4P) rau lub circumferential joint, nrog S nyeem los ntawm Tshooj II Tshooj D Table 1A ntawm qhov ntsuas kub thiab E los ntawm UW-12 rau koj hom kev sib koom tes thiab kev kuaj xyuas. Tsis txhob tsim nrog 304 tso cai thiab tom qab ntawd yuav 304L phaj.

Kauj Ruam 5. Ua kom tiav cov txheej txheem vuam nrog txoj cai muab tub lim thiab ntsuas tus lej ferrite:Tsim nyog rau ASME Tshooj IX siv P-No. 8 Pab Pawg 1 cov khoom siv nrog ER308L lossis ER316L hauv qab F-No. 6. Txiav txim siab tus lej ferrite nrog WRC-1992 daim duab ntawm cov khoom siv hluav taws xob tiag tiag, tom qab ntawd lees paub nws ntawm daim coupon tsim nyog nrog lub ntsuas ntsuas sib nqus thiab tuav 3 rau 1.

Kauj Ruam 6. Tswj cov cua kub nkag, cuam tshuam qhov kub thiab txias hauv paus:Khaws interpass ntawm 175 C (350 F) siab tshaj plaws rau kev ua haujlwm dav dav thiab 150 C (300 F) qhov siab tshaj plaws qhov kev tiv thaiv corrosion tseem ceeb. Rov qab tshem tawm cov hauv paus hniav nrog argon kom cov ntsiab lus oxygen nyob qis qis kom tsis txhob muaj suab thaj, thiab siv qhov sib npaug sib npaug nrog tooj liab lossis aluminium backing tuav kom rub tawm ntawm qhov sib koom ua ke.

Kauj Ruam 7. Sau qhov kev ntsuam xyuas thiab kev ntsuam xyuas qhov sib txawv ntawm qhov sib tsoo rau hauv qhov kev txiav txim:Qhia meej radiography ib UW-11 rau kev sib koom ua haujlwm uas koj tsim los, kua nkag mus rau ib UHA-34 ntawm welds tshaj 19 mm nominal thickness, thiab ib qho kev xeem ASTM A262 ntawm daim coupon weld ntau lawm thaum lub nkoj yuav pom sensitizing kub los yog corrosive kua. Siv Practice B rau 316L thiab xyaum C rau 304L.

Kauj Ruam 8. Tswj cov dej ntsuas hydrostatic thiab tom qab ntawd qhuav lub nkoj:Txwv cov tshuaj chloride rau kwv yees li 50 ppm, ntws lub nkoj sai li sai tau thaum qhov kev xeem tiav, thiab qhuav tag nrho cov chaw sab hauv. Tshem tawm cov cua sov los ntawm pickling rau ASTM A380 lossis los ntawm kev siv tshuab nrog cov cuab yeej stainless siab, passivate rau ASTM A967, thiab ua tiav nrog cov ntaub ntawv zoo ntawm cov welds ua tiav kom paub meej tias molybdenum nyob qhov twg 316 tau teev tseg.

Ob tus cwj pwm ua rau qhov sib txawv ntawm qhov kev qhia tshwj xeeb uas muaj sia nyob sib cuag nrog lub khw thiab ib qho uas tsis yog. Ua ntej, sau cov kev xav tau ntxiv ntawm kev yuav khoom, tsis yog nyob rau hauv lub cev ntawm daim ntawv kos duab - yam tsawg kawg nkaus molybdenum, tsawg kawg ferrite tooj, intergranular corrosion test, thiab daim ntawv pov thawj hom yog tag nrho cov khoom xaj. Qhov thib ob, ua kom cov ntaub ntawv txheeb xyuas qhov chaw tuav hauv qhov kev tshuaj ntsuam xyuas thiab cov phiaj xwm sim es tsis yog qhov kev thov. Rau tag nrho txoj kev los ntawm phaj mus rau spool thiab nkoj sib dhos,tubing spool fabricationnpog qhov fabrication sequence thiabprefabrication tiv thaiv teb weldingnpog qhov chaw ua haujlwm zoo tshaj plaws.

Cov lus nug nquag

Molybdenum. 316 thiab 316L muaj 2.00 txog 3.00 feem pua ​​molybdenum thiab 304 thiab 304L tsis muaj. Cov chromium sib txawv me ntsis nyob rau lwm qhov kev taw qhia - 304 khiav 17.5 mus rau 19.5 feem pua ​​chromium tiv thaiv 16.0 txog 18.0 feem pua ​​​​rau 316 - thiab 316 nqa cov nickel ntau dua ntawm 10.0 txog 14.0 feem pua. Txhua yam ntxiv, suav nrog txhua yam khoom siv tshuab, yog tib yam.

Molybdenum ntau npaum li cas hauv 316 stainless hlau phaj?

ASTM A240 xav tau 2.00 txog 3.00 feem pua ​​​​rau 316 thiab 316L. Lub tshav kub ntawm 2.02 feem pua ​​​​thiab ib qho ntawm 2.95 feem pua ​​​​yog ob qho tib si ua raws tab sis tsis ua zoo ib yam hauv qhov kub chloride crevice, yog li qhia qhov tsawg kawg nkaus molybdenum raws li qhov yuav tsum tau ua ntxiv thaum pitting yog txoj cai tswj hwm.

Puas yog 316 muaj zog dua 304?

No. ASTM A240 teev zoo tib yam yam tsawg kawg nkaus txhua yam khoom: 515 MPa (75 ksi) tensile thiab 205 MPa (30 ksi) tawm los rau ob qho tib si, thiab 485 MPa (70 ksi) tensile thiab 170 MPa (25 ksi) tawm los rau ob qib L. Molybdenum hloov tus cwj pwm corrosion, tsis muaj zog.

PREN ntawm 304 piv rau 316 yog dab tsi?

Siv PREN=feem pua ​​Cr + 3.3 x feem pua ​​Mo + 16 x feem pua ​​N, feem ntau 304 yog li ntawm 18 txog 20 thiab 316 feem pua ​​​​yog li ntawm 23 txog 26. Qhov sib txawv yuav luag tag nrho los ntawm lub sij hawm molybdenum. PREN yog qhov ntsuas ntsuas, tsis yog qhov pib tsim - nws tsis muab rau koj qhov ntsuas kub tseem ceeb lossis qhov ntsuas kub tseem ceeb.

Qhov twg zoo dua rau lub nkoj siab, 304 lossis 316?

Nws nyob ntawm seb puas muaj kev txhim kho corrosion hauv zos. Yog tias tsis muaj cov tshuaj chlorides, lossis cov tshuaj chlorides qis dua li 50 ppm ntawm qhov kub thiab txias, 304L yog qhov tseeb thiab pheej yig dua. Yog tias muaj cov chlorides los yog cov kua dej yog cov kua qaub diluted, xaiv 316L. Yog tias cov tshuaj chlorides nyob saum toj li 60 C, qhov tsis txaus vim tias cov tshuaj chloride kev ntxhov siab corrosion yog qhov kev pheej hmoo ntawm kev tswj hwm.

Vim li cas 316L nyiam dua 316 rau welded siab hlab ntsha?

Cov pa roj carbon . 316 tso cai txog li 0.08 feem pua ​​carbon, uas yog txaus los tsim chromium carbide ntawm grain ciam teb nyob rau hauv lub tshav kub-cuam tshuam cheeb tsam thaum vuam, depleting cov hlau uas nyob ib sab ntawm chromium thiab tsim ib txoj kev rau intergranular corrosion. 316L caps carbon ntawm 0.030 feem pua, uas yog me ntsis dhau los ua ib lub tsheb sib txuas mus tas li.

Koj puas tuaj yeem txuas 304 rau 316?

Yog lawm. Siv ER316L lossis E316L muab tub lim, uas phim cov alloyed siab dua ntawm ob lub hauv paus hlau. Tsis txhob downgrade rau 308L muab tub lim rau ntawm 304 mus rau 316 sib koom ua ke, vim tias cov hlau diluted weld yuav ces nqa molybdenum tsawg dua li niam txiv. Ob qib yog P-No. 8 Pawg 1, yog li kev sib koom ua ke yog nyob rau hauv ib qho kev tsim nyog tus qauv.

Dab tsi muab cov hlau koj siv los vuam 316 phaj?

ER316L rau GTAW thiab GMAW, E316L rau SMAW, thiab ER316LSi rau GMAW thaum koj xav tau zoo dua ntub dej thiab hlaws zoo li ntawm silicon. Rau 316L rau carbon steel siv ER309LMo yog li thaj chaw hloov pauv khaws molybdenum. Target 3 mus rau 10 ferrite tooj nyob rau hauv lub as-deposited weld hlau.

Dab tsi yog qhov tseeb ferrite tooj rau 308L thiab 316L vuam hlau?

Lub hom phiaj 3 txog 10 FN, nrog 3 txog 8 qhov zoo tshaj plaws li niaj zaus. Hauv qab no txog 3 FN qhov kev pheej hmoo ntawm solidification cracking nce sharply vim cov weld solidifies li ntxhib columnar austenite nrog impurity films ntawm cov nplej. Tshaj li ntawm 10 FN, thiab tshwj xeeb tshaj yog saum toj no 12 FN, delta ferrite tuaj yeem hloov mus rau nkig sigma theem nyob rau hauv 550 rau 900 C band, thiab molybdenum accelerates qhov kev hloov.

Koj puas xav tau kev kho cua sov tom qab vuam rau 304 lossis 316 lub nkoj welds?

Tsis yog. ASME Tshooj VIII-1 Table UHA-32 hais tias PWHT rau P-No. 8 austenitic stainless hlau tsis tas yuav tsum tau lossis txwv tsis pub, yog li tsis muaj qhov ua kom tuab raws li muaj rau cov hlau. Yog tias tus neeg siv qhia txog kev kho cua sov lawm, lub voj voog txoj cai yog kev daws teeb meem ntawm 1040 txog 1095 C ua raws li kev ua kom txias sai - tsis yog kev ntxhov siab subcritical, uas yuav ua rau cov khoom tsis yog L.

Koj puas preheat stainless hlau ua ntej vuam?

Tsis txhob tiv thaiv kev tawg, thiab tsis mus rau qhov kub thiab txias siv ntawm carbon steel. Austenite tsis hloov mus rau martensite ntawm qhov txias thiab tuav hydrogen yooj yim, yog li tsis muaj hydrogen cracking mechanism rau preheat tiv thaiv. Preheat tsuas yog siv los tshem tawm cov dej noo los yog thaw ib qho kev sib koom ua ke, thiab ntau dhau preheat ua rau distortion zuj zus.

Dab tsi yog qhov siab tshaj plaws interpass kub rau austenitic stainless hlau?

175 C (350 F) yog qhov siab tshaj plaws rau kev tsim khoom, thiab 150 C (300 F) yog siv qhov kev tiv thaiv corrosion tseem ceeb. Interpass yog tswj tau raws li qhov siab tshaj plaws es tsis yog qhov tsawg kawg nkaus vim tias tuav thaj chaw muaj kev kub ntxhov hauv 425 txog 815 C band yog dab tsi ua rau rhiab heev.

Dab tsi yog rhiab heev thiab koj tiv thaiv nws li cas?

Sensitization yog nag lossis daus ntawm chromium carbide ntawm cov ciam teb thaum cov hlau tuav ntawm li 425 thiab 815 C, uas depletes chromium los ntawm cov hlau tam sim ntawd ib sab ntawm tus ciam teb thiab tso cai rau intergranular corrosion. Tiv thaiv nws los ntawm kev siv qib L lossis ob daim ntawv pov thawj nrog 0.030 feem pua ​​​​cov pa roj carbon siab tshaj plaws, txwv kev cuam tshuam ntawm qhov kub thiab txias, thiab siv qib ruaj khov xws li 347 rau kev pabcuam sov.

Dab tsi kub ua rau rhiab heev hauv stainless hlau?

Nyob nruab nrab ntawm li 425 thiab 815 C (800 thiab 1500 F), nrog rau nag lossis daus sai tshaj plaws nyob ze 650 txog 750 C. Ib qho chaw weld tshav kub cuam tshuam dhau los ntawm cov qhab no hauv feeb, uas yog vim li cas cov ntsiab lus carbon - tsis yog chromium cov ntsiab lus - txiav txim siab seb lub vuam puas muaj corrosion resistant.

Qhov twg ASTM A262 xyaum xeem 316L rau rhiab heev?

Xyaum B, ferric sulfate-sulfuric acid xeem, yog qhov kev xyaum tsim nyog rau molybdenum-cov kabmob austenitic stainless xws li 316 thiab 316L. Xyaum C, nitric acid lossis Huey test, yog qhov kev xaiv zoo rau 304 thiab 304L. Xyaum A yog qhov ntsuas oxalic acid nrawm, thiab Xyaum E yog qhov ntsuas tooj liab-tooj ​​liab sulfate-sulfuric acid.

Dab tsi yog qhov tso cai kev ntxhov siab ntawm SA-240 304 piv rau 316?

Zoo tib yam ntawm ambient kub: 20.0 ksi (138 MPa) rau ob qho tib si 304 thiab 316, thiab 16.7 ksi (115 MPa) rau ob qho tib si 304L thiab 316L, rau ASME Tshooj II Tshooj D Table 1A. Qhov ntawd txhais tau hais tias 316 tsis cia koj tsim lub nkoj nyias dua li 304 - molybdenum yuav corrosion kuj, tsis muaj zog.

Puas yog 316 resistant rau chloride kev nyuaj siab corrosion cracking?

Tsis yog. Molybdenum txhim kho pitting thiab crevice tsis kam tab sis tsis muaj txiaj ntsig zoo rau chloride kev nyuaj siab corrosion tawg, uas xav tau chlorides, oxygen, tensile stress thiab kub siab tshaj li 60 C. Molybdenum tsis muaj ib qho ntawm plaub. Txoj kev kho yog tshem tawm ib qho ntawm plaub yam xwm txheej lossis hloov cov tsev neeg hlau rau duplex, 6Mo lossis npib tsib xee alloy.

316 puas tuaj yeem siv rau kev pabcuam dej hiav txwv?

Tsis yog rau kev nqhis dej tas mus li lossis ib lub luag haujlwm creviced . 316L pits thiab crevice corrodes nyob rau hauv dej hiav txwv, tshwj xeeb tshaj yog nyob rau hauv qhov chaw ruaj khov los yog shielded. Siv super duplex xws li S32750, qib 6Mo xws li 254 SMO, lossis cov nickel alloy nyob ntawm qhov nrawm, qhov kub thiab txias geometry.

Dab tsi yog qhov ntsuas hydrostatic kuaj dej chloride txwv rau cov hlab ntsha stainless?

Feem ntau teev ntawm 50 ppm siab tshaj plaws, thiab 25 ppm lossis qis dua qhov twg lub nkoj tsis tuaj yeem ntseeg tau qhuav. Txawm li cas los xij, tso lub nkoj sai sai tom qab kuaj thiab qhuav tag nrho cov chaw sab hauv. Stagnant chloride dej pits austenitic stainless sai dua li cov txheej txheem dej feem ntau nws yuav puas muaj, thiab qhov kev puas tsuaj feem ntau tshwm ntawm cov kab dej.

Koj qhia 304 ntawm 316 hauv khw li cas?

Kev txheeb xyuas cov khoom zoo nrog lub xov tooj ntawm tes X-ray fluorescence analyzer, kuaj xyuas molybdenum. Ob qib yog qhov pom kev, sib nqus thiab qhov sib npaug, thiab cov chromium thiab npib tsib xee sib tshooj, yog li molybdenum yog tib qho kev ntxub ntxaug. Xyuas nws ntawm txhua lub phaj thaum tau txais, ntawm txhua daim tom qab txiav, thiab ntawm qhov ua tiav welds.

Puas yog 316 stainless hlau phaj sib nqus?

Tsis yog, tsis yog nyob rau hauv tus mob annealed - ob qho tib si 304 thiab 316 yog austenitic thiab tsis-magnetic. Weld hlau hauv ob qib muaj cov delta ferrite txaus los muab cov lus teb tsis muaj zog sib nqus, uas yog raws nraim li qhov ntsuas ferrite ntsuas. Kev ua haujlwm txias kuj tuaj yeem ua rau cov hlau nplaum me ntsis hauv qhov chaw tsim.

Thaum twg koj yuav tsum tsis txhob siv 304L lossis 316L?

Peb txwv. Tsawg-kub sensitization teeb meem saum toj no txog 500 C nyob rau hauv ntev kev pab cuam, tso cai rau kev ntxhov siab ntog saum toj no roughly 540 C raws li creep tswj, thiab molybdenum-bearing 316L yog qhov ntau sigma-nrhiav qib nyob rau hauv 550 mus rau 900 C band. Rau cov hlau ruaj khov kub siab tshaj li 540 C, txav mus rau 304H lossis 316H, lossis mus rau qib ruaj khov xws li 347.

Dual certified 316/316L phaj yog dab tsi?

Ib qho cua sov uas ua tau raws li txhua qhov yuav tsum tau ua ntawm ob qho kev qhia tshwj xeeb: carbon ntawm 0.030 feem pua ​​​​siab tshaj plaws ua ke nrog cov qib ncaj tensile thiab tawm los tsawg kawg nkaus. Nws tso cai rau ib qho khoom lag luam txaus siab rau qib L-qib vuam specification thiab tus qauv tsim ncaj nraim, raws li kev txiav txim yuav khoom, phaj cim thiab daim ntawv pov thawj tag nrho cov npe qib uas koj tab tom tsim rau.

Puas yog 316 vuam hlau xav tau kev ntxhov siab?

Tsis yog. Tsis muaj Code yuav tsum muaj kev ntxhov siab los daws cov austenitic stainless welds, thiab subcritical kev nyuaj siab nyem nyob rau hauv lub 600 mus rau 700 C ntau yog nquag tsim teeb meem vim hais tias nws sensitises non-L cov ntaub ntawv thiab yuav loj hlob sigma theem nyob rau hauv molybdenum-cov kabmob weld hlau. Residual stress yog tswj los ntawm kev sib koom tsim, weld sequence thiab, qhov tsim nyog, mechanical txoj kev.

316 phaj nqi ntau npaum li cas tshaj 304?

Feem ntau 25 mus rau 45 feem pua ​​​​ntawm cov nqi phaj, uas tau tsav los ntawm molybdenum thiab npib tsib xee alloy surcharges thiab txav nrog cov kev lag luam alloy. Ntawm lub nkoj tiav lawm qhov kev nplua me me, vim tias vuam, kev kuaj xyuas thiab kev kho cua sov raug nqi tib yam rau cov qib thiab phaj tsuas yog ib feem ntawm tus nqi xa khoom.

Puas yog 316 zoo dua 304 rau kev pabcuam nitric acid?

Tsis yog, nws yog qhov phem dua. Molybdenum dissolves nyiam nyob rau hauv muaj zog oxidising acids, yog li 304L yog tus qauv xaiv rau nitric acid kev pab thiab 316L yog zam. Qhov no yog ib qho ntawm ob peb rooj plaub uas qib kim dua yog qhov tsis ncaj ncees lawm.