Yuav Ua Li Cas Kom Tsis Txhob Ua Taug Kev Puas Ntawm Cov Hlau Thiab Me Alloy Hlau?

Caustic Cracking, tseem hu ua alkali brittleness, yog qhov tawg ntawm cov hlau thiab alloys hauv alkaline kev daws teeb meem vim muaj kev ntxhov siab ntau dhau los thiab xov xwm corrosive. Nws yog ib hom kev ntxhov siab corrosion cracking (SCC). Caustic cracking ntawm siab txog ntsha feem ntau tshwm sim hauv chav thiab lwm qhov chaw nquag rov ua dua evaporation thiab concentration lossis nyob rau hauv siab-kub cov hlab hauv kev sib cuag nrog caustic soda. Tej zaum nws yuav tshwm sim hauv cov khoom siv ntawm cov pa roj carbon steel, tsis tshua muaj lub zog steel, hlau tsis zoo thiab austenitic stainless hlau nyob rau hauv kev sib cuag nrog caustic sis dej qab zib. Alkali caustic kev ua txhaum kev sib tsoo kuj tshwm sim nyob rau hauv cov hlab siab ntawm high voltage autoclapper, pov tseg tshav kub rov qab system ntawm petrochemical kev lag luam, Al2O3 evaporator ntawm electrolytic aluminium qhauj, siab txog ntsha ntawm chlor-alkali tshuaj nroj tsuag, ntawv mills thiab nuclear zog lag luam los ntawm Na {{{4 }} mloog lus. Yog li ua cas caustic cracking tshwm sim?


Lub tshuab ntawm alkali caustic cracking tseem tsis tau to taub tag nrho, piv txwv li, lis ciam ciam Ferrite lossis intercrystalline carbides yog qhov zoo dua, cov neeg tseem siv cov txheej txheem SCC classical los piav qhia qhov tshwm sim ntawm kev tawg hauv alkaline ib puag ncig. Feem ntau hais lus, qhov tshwm sim ntawm alkali caustic tawg ntawm carbon hlau thiab qis alloy steel yuav tsum muaj peb yam:

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1. Ntau qhov ntau ntawm lye. NaOH yuav tsum muaj ntau dua 5% hauv cov pa roj carbon tsawg kawg ntawm qhov taw tes kub.

2. Tshaj siab kub. Alkali caustic cracking muaj qhov kub thiab dav, qhov kev nyuaj siab alkali kev txhim kho ntawm cov pa roj carbon hlau feem ntau tshwm sim hauv 50 ~ 80 ℃ lossis siab dua, thiab txog 60 ℃ yog qhov kub tshaj qhov tseem ceeb, uas cuam tshuam nrog kev mloog zoo ntawm alkali. Qhov feem ntau yuav ua rau alkali brittle kub yog nyob ze qhov kub taw tes ntawm kev daws.

3. Muaj kev ntxhov siab ntau dua. Raws li txoj kev xav, SCC mechanism ntawm cov pa roj carbon steel tsawg nyob rau hauv kev kub siab alkali daws yog intercrystalline anodic dissolution, thiab SCC muaj peev xwm nyob rau hauv qhov ntau ntawm kev ua kom hloov-passivation kev hloov pauv. Thaum lub zos NaOH ntau dua 10%, tiv thaiv oxide zaj duab xis ntawm cov hlau yuav yaj thiab ntxiv kev cuam tshuam nrog lub hauv paus. Qhov nruab nrab yog:


Caustic cracking feem ntau intergranular thiab bifurcate. Txawm li cas los xij, kev sib kis transgranular kuj tseem yuav tshwm sim. Piv txwv li, qhov tawg morphology ntawm Austenitic stainless hlau hauv 50% NaOH daws tsis muaj dab tsi ua nrog kev kho cua sov, tab sis yog transgranular cracking. Nws cov khoom ua xeb yog xoob, ntxeem tau, tsis-txheej ua kom cov hlau nplaum, thiab nws cov kua aqueous yog alkaline. Ntev npaum li muaj 10 ~ 20mg · l-1 NaOH hauv dej ntawm lub rhaub dej kub lossis cua sov, qhov kev tso zis hauv zos yuav ua rau muaj qhov ua kom cov kua dej alkali nyob rau hauv kev txo qis lossis tawg, ua rau lub zos alkali xeb. Alkali brittleness cracking tuaj yeem tshwm sim thaum alkali corrosion thiab tensile kev ntxhov siab nyob ib txhij. Kev tshawb xav yog qhov ntawd ntawm xeb H + diffuses rau cov hlau ua rau hydrogen embrittlement. Yog li no, alkali embrittlement cracking tuaj yeem ua kom hydrogen-ntxias ua kom tawg, los yog nws tuaj yeem ua anodes yaj los yog sib xyaw tawg. Yog li koj yuav ua li cas thiaj zam dhau kev tawg?


  • Kev xaiv khoom siv

Xav txog lub zog, plasticity thiab alkali embrittlement rhiab heev, carbon steel ntim siv tau los ntim cov dej qab caustic. Hauv qhov kub tshaj plaws ntawm 46 ℃ caustic daws qhov chaw ib puag ncig, kuj tuaj yeem xaiv 0.20% C sedative carbon steel. Txawm li cas los xij, thaum lub caustic kub siab tshaj 46 ℃, carbon hlau welds yuav tsum muaj cua sov tom qab welding kom tsis txhob muaj alkali brittleness. Ntxiv Ti thiab lwm cov ntsiab lus sib xyaw ua ke nrog cov pa roj carbon steel thiab cov cua sov ua kom zoo dua tuaj yeem ua tau zoo tiv thaiv kev tawg. Piv txwv li, cov qauv hlau muaj 0.73% Ti (0.105% C) yog cov rwb thaiv tsev ntawm 650 ~ 750 ℃, thiab tom qab ntawd ces cov cua sov kom txias kom txuas lub sijhawm ntawm 150h txog 1000h.

  • Txo kev ntxhov siab

Qhov kev ntxhov siab nyob rau lub ntsiab yog qhov tseem ceeb ntawm alkali embrittlement, yog li nws raug nquahu kom txais yuav cov txheej txheem vuam ntsuas xws li qis kab lub zog, preheating ua ntej vuam, txoj haujlwm vuam tsim nyog, kev taw qhia thiab rauj tawm tsam ntawm txheej kom txo cov naj npawb thiab qhov ntev ntawm vuam nqaws kom ntau li ntau tau thiab txo vuam vuam kev nyuaj siab ntawm welded pob qij txha. Cov ntawv txias thiab tom qab - vuam kev kho cua sov kom tshem tawm kev ntxhov siab yog qhov ntsuas tau zoo los tiv thaiv kev tawg.

Txo tsis tshua muaj cov khoom sab hauv kev ntxhov siab thaum tsim khoom thiab sib dhos, xws li sab tsis ncaj ncees, lub kaum tsis deformation, thiab tiv thaiv voids thiab lwm yam. Riveting qauv kuj tseem tuaj yeem siv qee qhov kev ntsuas xws li kev teeb tsa ntawm qhov riveting qhov kom tsis txhob muaj lub siab riveting ntau dhau. Hauv kev xyaum, lub workpiece yog rhuab mus rau qhov ntsuas kub thiab qhov tau npaj tseg thiab tau tuav ntev txaus kom txo cov kev ntxhov siab mus rau qib uas tsim nyog. Nws nyob ntawm lub sijhawm thiab qhov kub thiab txias, thiab ib txwm koj txias rau nws ntawm qhov qeeb dua kom tsis txhob muaj kev ntxhov siab tshiab. Tom qab welding, qhov de-kev nyuaj siab annealing kub ntawm carbon hlau thiabtsawg hlau alloyyuav tsum tsis txhob qis dua 620 ℃, thiab lub sij hawm rwb thaiv tsev yuav tsum tau txiav txim siab raws li 1h / 25mm (tuab) .Qhov rooj hauv qab no qhia txog kev siv ntau ntawm kev tiv thaiv tom qab cua sov kho kub ntawm cov hlau siv rau hauv qhov chaw kho, thiab tus nqi hardness tau siv los ua tus txheej txheem ntawm cov nyhuv kho cua sov.

Cov khoom siv

Ntsig Kub

Lub Zog

Cov hlau

593-648

200

Cr-0.5Mo

593-718

225

1-1 / 4Cr-0.5Mo

704-746

225

2-1 / 4Cr-1Mo

704-760

241

5Cr-1Mo

704-760

241

  • Corrosion inhibitor ntxiv rau

Kev siv tshuaj tiv thaiv tsis haum yog Na3PO4, NaNO3, NaNO2, Na2SO4, thiab lwm yam kev noj tshuaj tuaj yeem txiav txim siab raws li cov kev sim, piv txwv li, qhov piv ntawm NaNO3 / NaOH yog ntau dua 0.4, thiab Na2SO4 / NaOH ntau dua 5 los tiv thaiv caustic tawg.

Ntxiv rau, txo qhov kub thiab txias ntawm kev ua haujlwm, xws li sib quas ntus siv cov cua sov sib xyaw, ua kom qhov kub ≤46 ℃, lossis hauv kev tsim qauv los txo lossis tiv thaiv qhov chaw hauv zos ntawm lye sawv los lossis rov ua dua evaporation concentration yog cov kev ntsuas zoo los tiv thaiv alkali brittleness.