321 vs 347 Stainless Steel: Stabilized High-Tsub Alloys Piv

 

Dab tsi yog cov tshuaj muaj pes tsawg leeg, cov yam ntxwv tseem ceeb, thiab kev siv ib txwm?
Ob lub alloys yog raws li 18% chromium thiab 9-11% npib tsib xee. Qib 321 (UNS S32100) ruaj khov nrog titanium, thaum qib 347 (UNS S34700) siv niobium (columbium) kom ruaj khov. Qhov no tiv thaiv chromium carbide nag lossis daus thaum vuam. Lawv muaj kev tiv thaiv oxidation zoo txog li 900℃. 321 feem ntau yog siv nyob rau hauv lub dav hlau tso cua tshuab, thermal oxidizers, thiab expansion bellows . 347 yog nyiam nyob rau hauv refinery heaters, high-temperature chemical reactors, thiab lub zog tsim khoom rau nws creep zog.

Qhov kev xaiv ntawm stabilizing element cuam tshuam li cas rau lawv qhov kev ua tau zoo?
Titanium hauv 321 thiab niobium hauv 347 ob leeg ua ke nrog carbon, tiv thaiv chromium depletion. Txawm li cas los xij, niobium carbides ruaj khov dua ntawm qhov kub siab heev (siab dua 800 degree). Qhov no muab 347 superior tiv thaiv rau creep thiab "kub hardening" nyob rau lub sij hawm ntev. Nyob rau hauv cyclic cua sov thiab cua txias, 347 lub stabilized qauv kuj resists grain ciam degradation zoo dua 321, ua rau nws ntau txhim khu kev qha nyob rau hauv xav tau thermal cycling daim ntaub ntawv.

Hauv qhov chaw twg yog 347 qhov kev xaiv meej thiab tsim nyog tshaj 321?
Xaiv 347 thaum cov khoom siv yuav ua haujlwm tsis tu ncua siab tshaj 800℃hauv kev ntxhov siab, xws li hauv cov raj superheater, cov raj hluav taws xob hluav taws xob, lossis siab - siab boiler qhov chaw. Nws kuj tseem nyiam nyob rau hauv cov huab cua oxidizing thiab kev siv nrog nitric acid. Rau kev sib cuam tshuam siab - qhov kev pabcuam kub lossis tsawg dua thermal cycles, xws li hauv cov pa hluav taws xob lossis qee yam khoom siv hluav taws xob, 321 muab kev ua haujlwm txaus ntawm tus nqi qis dua.

Dab tsi yuav tsum fabricators nco ntsoov thaum vuam cov qib no?
Vuam ob qib yuav tsum muaj cov txheej txheem austenitic, tab sis nrog kev saib xyuas rau cov cua sov. Rau 321, tsis txaus tiv thaiv roj tuaj yeem ua rau titanium oxidation, txo nws cov nyhuv stabilizing ntawm vuam. Rau 347, tus qauv niobium-stabilized fillers (xws li, ER347) yog siv. Tom qab-weld kev kho cua sov feem ntau tsis tas yuav tsum tau rau cov ntu nyias, tab sis rau tuab welds nyob rau hauv ib puag ncig hnyav, kev daws teeb meem yuav raug pom zoo los kho kom zoo dua corrosion.

Dab tsi zaum kawg yuav tsum coj cov kev xaiv ntawm 321 thiab 347?
Ua raws li kev txiav txim siab ntawm qhov kev pabcuam kub, kev ntxhov siab, thiab huab cua. Rau qhov kub thiab txias tsis tu ncua tshaj 800℃nrog txhua yam load, qhia 347. Rau nruab nrab kub (600-800 degree) thiab qhov twg tus nqi yog qhov tseem ceeb, 321 feem ntau txaus. Ib txwm tshuaj xyuas cov tshuaj lom neeg thiab thermal ib puag ncig ntawm daim ntawv thov, thiab sab laj nrog cov lej hauv kev lag luam (piv txwv li, ASME) rau cov ntaub ntawv pom zoo hauv siab thiab siab - kev pabcuam kub.