304 vs 316 Stainless Hlau: Qhov Kev Xaiv Tseem Ceeb rau Corrosion Resistance

 

Dab tsi yog qhov sib txawv tseem ceeb hauv kev sib xyaw, cov khoom, thiab kev siv ib txwm?
Qib 304 (UNS S30400, EN 1.4301) yog cov classic 18/8 stainless (18% Cr, 8% Ni). Qib 316 (UNS S31600, EN 1.4401) muaj qhov zoo sib xws tab sis ntxiv 2-3% Molybdenum. Qhov sib ntxiv no ua rau muaj kev tiv thaiv corrosion tag nrho, tshwj xeeb tshaj yog tiv thaiv chlorides. Ob leeg muaj kev tsim tau zoo thiab weldability. 304 yog qhov kev xaiv thoob ntiaj teb rau cov khoom siv, kev ua zaub mov, thiab kev tsim vaj tsev. 316 tau teev tseg rau cov khoom siv hauv hiav txwv, cov chaw ua tshuaj, thiab cov khoom siv kho mob uas muaj cov tshuaj chlorides.

Yuav ua li cas molybdenum tshwj xeeb txhim kho kev ua tau zoo hauv cov ntsiab lus?
Molybdenum dramatically txhim kho kev tiv thaiv rau localized corrosion. Nyob rau hauv ib puag ncig uas muaj chlorides (xws li, dej ntsev, de-icing ntsev, tshuaj dawb), 316's molybdenum ntxiv dag zog rau passive oxide txheej. Qhov no ua rau qeeb qhov pib thiab kev loj hlob ntawm pitting thiab crevice corrosion. Piv txwv li, 304 tuaj yeem pom cov pob xeb hauv cov huab cua ntawm ntug hiav txwv, thaum 316 feem ntau tseem tsis cuam tshuam. Qhov no ua rau 316 qhov tseem ceeb rau kev ua neej nyob ntev hauv hnyav, ntub dej, lossis dej ntsev.

Hauv cov kev lag luam tshwj xeeb lossis daim ntawv thov twg yog 316 qhov tsim nyog?
316 yog qhov yuav tsum tau ua nyob rau hauv offshore thiab marine engineering rau cov khoom raug dej hiav txwv txaws los yog tshuaj tsuag. Nws yog tus qauv hauv cov khoom siv tshuaj thiab tshuaj ua cov tshuaj chlorides lossis acids. Cov ntug dej hiav txwv architecture, pas dej da fittings, thiab nkoj fittings kuj yuav tsum tau 316. Txhua daim ntawv thov uas muaj kev sib cuag nrog ntsev, hws, los yog cov tshuaj muaj tshuaj yuav tsum default rau 316 tshaj 304 kom ruaj khov.

Puas muaj tus nqi lossis kev tsim khoom lag luam- tawm thaum xaiv 316 dhau 304?
Yog lawm, kev lag luam tseem ceeb - tawm yog tus nqi. Cov ntsiab lus molybdenum thiab npib tsib xee ua rau 316 tseem kim tshaj ib tuj tshaj 304. Fabrication zoo sib xws, tab sis vuam 316 yuav tsum tau ceev faj muab tub lim xaiv hlau (xws li, 316L) los tiv thaiv corrosion. Nws lub zog me ntsis siab dua tuaj yeem xav tau ntau lub zog rau kev tsim. Kev nqis peev yog qhov ncaj ncees thaum ib puag ncig tswj hwm nws txoj kev siv, zam kev ua tsis tiav ntxov ntxov ntawm 304 cov khoom.

Dab tsi yog txoj cai yooj yim, txhim khu kev qha rau engineers thiab buyers ua raws li?
Siv cov tshuaj chloride no-raws li txoj cai: yog tias daim ntawv thov yuav raug rau cov dej ntsev, dej chlorinated, de- cov ntsev ntsev, cov tshuaj hnyav, lossis tsis tu ncua siab - cov av noo ntawm ntug dej hiav txwv, qhia 316 stainless hlau. Rau qhov chaw qhuav hauv av, kev siv sab hauv, cov dej tsis huv, lossis kev sib cuag nrog cov khoom noj uas tsis muaj chlorides, 304 yog qhov tsim nyog thiab kev lag luam ntau dua. Ib txwm txheeb xyuas qhov tseeb qhov chaw pabcuam hauv koj qhov kev qhia tshwj xeeb.