Ntawm Qhov Kev Sib Txuas Tshwj Xeeb ntawm Sulfuric Acid Concentration thiab Kub Puas Yog 1.2 Millimeter 316 Stainless Steel Sheath Yuav Tsum Tau Tshaj Tawm - Weld Annealing los Tiv Thaiv Intergranular Corrosion nyob rau hauv Hluav Taws Xob Immersion Heaters?

Vuam ntawm kev txuas ntawm mounting flanges thiab fittings rau 316 stainless hlau sheath yuav tsum tau ua rau cov engineers tsim thiab cov neeg ua haujlwm ruaj ntseg hauv tus nqi hluav taws xob rau cov cua sov rau kev siv sulfuric acid. Vuam tsim cov cua sov uas tuaj yeem tsim kev puas tsuaj, tsim cov chromium carbides ntawm cov ciaj ciam ntawm cov qoob loo hauv tshav kub - thaj chaw cuam tshuam . 316 sensitized poob nws cov corrosion tsis kam thiab ua rau muaj kev cuam tshuam rau intergranular corrosion uas nyiam tshaj tawm tsam cov ciam teb ua rau cov khoom poob sai thiab ua rau lub tshuab cua sov tsis ua haujlwm. Phab ntsa thickness ntawm lub sheath tswj cov pace ntawm txias tom qab vuam thiab qhov yuav tsum tau rau post-weld annealing. Hauv kev ua haujlwm no peb tau txiav txim siab qhov pib ntawm sulfuric acid concentration uas yuav tsum tau tshaj tawm -weld annealing kom tsis txhob muaj kev cuam tshuam ntawm intergranular corrosion nyob rau hauv 1.2 hli 316 sheath.

rhiab heev thiab mechanism ntawm intergranular corrosion nyob rau hauv 316
Thaum 316 stainless hlau yog rhuab mus rau qhov kub ntawm 450 ° C thiab 850 ° C, qhov rhiab heev ntau yam, chromium carbides precipitate ntawm cov ciam teb grain. Cov dej lwg li no- taw tes nag lossis daus chromium los ntawm thaj chaw nyob ib sab ntawm cov ciam teb, ua rau lawv depleted tsawg dua li 12% chromium xav tau los ua ib zaj duab xis passive. Nyob rau hauv ib puag ncig corrosive, cov cheeb tsam ntawm chromium depletion yog qhov zoo tshaj plaws corroded, ua rau cov nplej ciam teb nres thiab thaum kawg ntawm kev tshem tawm cov khoom. Lub 1.2 hli nyias-walled sheath muaj cov cua sov tsawg thiab cov cua sov yuav sai sai sai tom qab vuam. Qhov no ua rau kom txias ceev ceev. Cov phab ntsa nyias ua kom txias sai sai ntawm qhov kub ntawm qhov vuam mus rau qis dua 450 ° C thiab siv sij hawm me ntsis hauv thaj chaw rhiab heev. Lub tuab-walled sheath> 3 mm muaj qhov ua kom txias qeeb qeeb, uas ua rau muaj kev pheej hmoo ntawm rhiab heev. Txawm li cas los xij, rau phab ntsa 1.2 hli, qhov cua txias feem ntau yog ceev txaus kom tsis txhob muaj kev kub ntxhov nyob rau hauv cov pa roj tungsten arc vuam xwm txheej. Nws tsis yog tsuas yog phab ntsa thickness uas yog qhov tseem ceeb, nws yog cov ntsiab lus carbon ntawm 316 cov khoom. Cov pa roj carbon tsawg 316L (max 0.03% C) tshwj xeeb tshaj yog tiv taus rau kev nkag siab ntawm phab ntsa tuab. Standard 316 (max 0.08% carbon) tuaj yeem sensitized yog tias txias heev.

Tseem ceeb Concentration ntawm Sulfuric Acid rau Kev Tshawb Fawb Txog Kev Tshawb Fawb
Lub intergranular corrosion ntawm sensitized 316 yog tshwj xeeb tshaj yog hnyav nyob rau hauv tej yam concentrations sulfuric acid. Kev sim Strauss (ASTM A262 Practice E) ua ke nrog boiling 16% sulfuric acid nrog tooj liab sulphate los kuaj rau rhiab heev. Intergranular nres feem ntau yuav tshwm sim hauv kev pabcuam hauv 10 txog 40% sulfuric acid ntawm qhov kub tshaj 50 ° C. Tsawg dua 10% cov kua qaub tsis muaj zog txaus rau lub hom phiaj ntawm cov qoob loo zoo dua. Ntawm 40% cov kua qaub ua oxidising thiab repassivates saum npoo, npog qhov rhiab heev. Qhov chaw pib concentration rau kev pheej hmoo ntawm intergranular corrosion rau 1.2 hli 316 sheath nyob rau hauv sulfuric acid yog li ntawm 15-25% ntawm qhov kub thiab txias ntawm 60-80 ° C. Hauv qab 15% ib sensitized sheath muaj peev xwm nyob tau rau xyoo tsis muaj pov thawj tshwm sim. Ntawm qhov siab tshaj 25% cov kua qaub yuav ua rau oxidising txaus los nres intergranular nres tab sis pitting ces dhau los ua teeb meem. Nyob rau hauv qhov tseem ceeb 15-25% ntau yam, ib qho sensitized sheath tuaj yeem poob 0.5-2.0 hli ntawm cov khoom txhua xyoo raws li cov ciam teb, tho ib phab ntsa 1.2 hli hauv lub hlis. Yog li, rau cov ntawv thov nrog sulfuric acid concentration ntawm 15% thiab 25% thiab kub siab tshaj 50 ° C, tom qab vuam annealing yog pom zoo heev tshwj tsis yog siv 316L.

Annealing Requirements Matrix rau Welded 316 Sheaths
Cov lus hauv qab no teev cov lus pom zoo rau kev tshaj tawm -weld annealing ntawm 1.2 mm 316 sheaths rau txawv sulfuric acid concentrations, kev khiav hauj lwm kub thiab tej 316 qib ua hauj lwm. Annealing yog cua sov lub welded los ua ke rau 1050 ° C rau 15 feeb, ces txias txias (dej quench los yog yuam gas).

Sulfuric Acid Concentration Operating Temperature Grade 316 Post-Yuav tsum tau Weld Annealing? Kev pom zoo
Tsawg dua 10 feem pua ​​​​ntawm Txhua qhov kub thiab txias 316 lossis 316L Tsis muaj txheej txheem vuam OK
10 - 15% Hauv qab 60 ° C 316L Tsis nyiam 316L
10 - 15% Hauv qab 60 ° C 316 Tsis yog, tab sis 316L pom zoo Pom tau yam tsis muaj annealing
10 - 15% 60 - 90 ° C 316L Tsis muaj kev saib xyuas kev tawm tsam 10 - 15% 60 - 90 ° C 316 Yog Annealing lossis siv 316L 15 - 25% Hauv qab 50 ° C 316L Tsis muaj 316L tau txais 15 - 515% Annealing 25% 50 - 80 ° C 316 los yog 316L Yog Annealing yuav tsum tau rau qib 15 - 25% Saum toj no 80 ° C Ib 316 Yog, ntxiv rau xav txog kev txhim kho hlau alloy siab txaus ntshai; siv Alloy 20 25 - 40% Txhua qhov kub thiab txias Ib qho 316 Tsis siv tau Sensitization tsis yog thawj hom tsis ua haujlwm; pitting dominates
Ntau tshaj 40 feem pua ​​​​Qhov kub ntawm 316 Tsis siv rau Oxidising acid; intergranular nres improbable
Yog tias tus qauv 316 siv, tom qab-weld annealing yog xav tau rau 1.2 hli 316 sheath nyob rau hauv qhov tseem ceeb concentration ntau ntawm 15-25% ntawm qhov kub thiab txias tshaj 50 ° C. Nrog 316L, annealing yog ib qho kev nyab xeeb ntxiv. Intergranular corrosion tuaj yeem permeate phab ntsa nyias hauv 3-12 lub hlis, ua rau flange detachment lossis sheath to, tsis muaj annealing ntawm welded flange txuas cheeb tsam.

Tswv yim xav txog Annealing rau nyias -Walled Tubes
Cov teeb meem hauv kev xyaum tshwm sim nrog kev tshaj tawm -weld annealing ntawm 1.2 mm 316 sheath. Qhov kub ntawm 1,050 ° C tuaj yeem ua rau oxidation ntawm cov hlau tsis muaj zog yog tias lub rooj sib txoos tsis zoo tiv thaiv. Annealing yuav tsum tau ua nyob rau hauv ib puag ncig tswj qhov cub nrog argon los yog dissociated ammonia kom tsis txhob oxidation. Xwb, thaj tsam weld tuaj yeem ua rau hauv zos annealed los ntawm induction cua sov yam tsis muaj cua sov tag nrho lub rhaub. MgO rwb thaiv tsev nyob rau hauv lub cua sov swages nthuav txawv ntawm cov hlau thiab tuaj yeem tawg lub plhaub, yog li tag nrho cov cua sov annealing ntawm cov cua sov uas yav tas los tau swaged nrog MgO rwb thaiv tsev yog tsis tau. Annealing yuav tsum tau ua tom qab vuam, tab sis ua ntej swaging, los yog nyob rau hauv cheeb tsam weld nkaus xwb. Cov kws ua haujlwm yuav tsum tau hais kom meej tias cov welds ntawm 316 sheaths rau 15-25% sulfuric acid kev pabcuam yuav tsum tau ua raws li qhov chaw induction annealing ntawm tshav kub- thaj tsam cuam tshuam. Qhov annealed cheeb tsam yuav tsum yog yam tsawg kawg 10 mm ntawm ob sab ntawm weld. Kev kho kom zoo tuaj yeem kuaj xyuas siv lub ntsuas ferrite lossis xa cov qauv weld rau ASTM A262 Practice E xeem. Ib tus neeg muag khoom uas tsis tuaj yeem ua tom qab-weld annealing lossis muab kev kuaj xyuas pov thawj yuav tsum tsis txhob ua haujlwm rau kev pabcuam sulfuric acid nyob rau hauv qhov tseem ceeb ntawm cov concentration ntau. Tus nqi ntawm ib qho intergranular corrosion tsis ua hauj lwm, uas feem ntau yog npaj txhij txog thiab tsis muaj kev ceeb toom, yog ntau dua li tus nqi ntawm cov txheej txheem zoo annealing. Rau kev txhim kho tshiab, xaiv 316L, ntau dua li tus qauv 316, tshem tawm lub peev xwm ntawm rhiab heev rau 1.2 hli phab ntsa nyob rau hauv tag nrho tab sis cov xwm txheej hnyav tshaj plaws thiab tau pom zoo rau txhua qhov kev pabcuam sulfuric acid siab dua 10%.