316Lmod vs Standard 316L: Optimized Chemistry rau Urea thiab Nitric Acid Service

Urea ntau lawm thiab nitric acid tuav yog ob qho ntawm cov kev pabcuam metallurgically unforgiving nyob rau hauv cov txheej txheem tshuaj lom neeg kev lag luam - tsis yog vim tus qauv 316L tsis muaj corrosion kuj feem ntau, tab sis vim hais tias cov chaw tshwj xeeb no tawm tsam stainless hlau los ntawm cov txheej txheem uas cov txheej txheem zeb - ntawv pov thawj 316L tshav kub tsis tau lees tias yuav tiv taus.

316Lmod vs Standard 316L

316 LWMyog ib qho kev lag luam teb rau qhov sib txawv: tib lub hauv paus alloy tsev neeg raws li tus qauv 316L, tab sis ua rau nruj zog muaj pes tsawg leeg thiab microstructural tswj tshwj xeeb validated tiv thaiv tsis ua hauj lwm hom ntawv sau tseg nyob rau hauv urea synthesis loops thiab nitric acid khoom. Phau ntawv qhia no piav qhia qhov tseeb qhov txawv ntawm 316Lmod los ntawm tus qauv 316L, vim li cas cov kev sib txawv tshwj xeeb tseem ceeb, thiab yuav ua li cas qhia qib zoo rau kev pabcuam urea thiab nitric acid.

316Lmod tsis yog ib tsev neeg sib txawv ntawm 316L - nws yog tib yam austenitic muaj pes tsawg leeg ua rau nruj dua, daim ntawv thov - tshwj xeeb ntawm cov ntsiab lus ferrite, cov khoom seem, thiab intergranular corrosion kuj, tsim tshwj xeeb vim cov qauv zeb- xyaum 316L tsis tau lees tias kev ua haujlwm hauv acid urea.

Txheem 316Lyog tsim rau ib tug kuj dav compositional ntau yam nyob rau hauv specifications xws li ASTM A240, uas yog kiag li tsim nyog rau feem coob ntawm nws cov kev siv. Urea synthesis thiab nitric acid tuav, txawm li cas los xij, nthuav tawm qhov tshwj xeeb qhov tsis zoo uas tus qauv zeb xyaum tsis tswj rau: muaj cov delta ferrite thiab qee cov khoom seem nyob rau hauv ib qho kev txwv tsis pub ua raws li 316L tshav kub tuaj yeem tsim qhov chaw hauv cheeb tsam corrosion pib hauv ob qhov tshwj xeeb chemistry, txawm tias cov khoom ua tau raws li cov qauv kev txwv.

316Lmod hais txog kev lag luam xyaum - tsim thiab ua kom zoo zoo los ntawm cov txheej txheem urea cov ntawv tso cai thiab cov khoom siv fabricators tom qab cov ntaub ntawv ua haujlwm corrosion tsis ua hauj lwm - ntawm kev qhia ntxiv, nruj dua tswj nyob rau sab saum toj ntawm lub hauv paus 316L tus qauv, ntau dua li kev hloov pauv hauv cov khoom siv hlau. Qhov no yog ib qho tseem ceeb sib txawv: 316Lmod yog qhov zoo tshaj plaws to taub raws li ib tug stricter zoo thiab microstructural specification txheej txheej rau 316L, tsis yog ib tug tshiab proprietary alloy.

Ib sab-los ntawm- sab piv ntawm cov ntsiab lus tseem ceeb uas paub qhov txawv ntawm ob:

Parameter	Txheem 316L	316Lmod (urea / nitric acid qib)	Vim Li Cas Nws Tseem Ceeb
Delta ferrite cov ntsiab lus	Kev tswj tsis tau; feem ntau ob peb feem pua ntawm cov cua sov thiab kev ua haujlwm	Tightly tswj, feem ntau tsom zoo hauv qab 1%	Ferrite theem corrode nyiam nyob rau hauv kub ammonium carbamate tov, pib xaiv nres
Compositional kam rau ua band	Txheem ASTM A240 ntau yam (kwv yees)	Narrowed internal ranges nyob rau hauv tus txheej txheem specification, feem ntau nrog tighter carbon, silicon, thiab residual ntsiab tswj	Ib txoj kab nqaim ua rau muaj qhov sib xws, kwv yees microstructure cua sov kom sov
Residual/trace elements (S, P, Si)	Tswj rau tus qauv specification siab tshaj plaws xwb	Tuav kom nruj me ntsis hauv kev txwv ntau dua li tus qauv siab tshaj plaws	Cov seem seem tuaj yeem txhawb nqa kev sib cais, kev tawm tsam intergranular, lossis qhov chaw pib qhov chaw corrosion.
Intergranular corrosion (IGC) kuaj	Tsis tas yuav tsum tau ua los yog ua ib qho cua sov	Txhua zaus tsim nyog los ntawm kev sim boiling nitric acid immersion test (xws li ASTM A262 Practice C)	Qhia ncaj qha rau kev tiv thaiv rau hom kev tawm tsam tshwj xeeb cuam tshuam rau nitric acid thiab carbamate kev pabcuam
Hom kev tsim nyog hauv paus	General ASTM / ASME cov khoom specification ua raws	Tus tsim khoom lossis kawg- cov neeg siv kev qhia tshwj xeeb (feem ntau xa mus rau urea kev lag luam koom haum kev taw qhia) ntxiv rau cov qauv ASTM	Cov neeg tsim khoom urea thiab nitric acid keeb kwm tau tsim cov kev xav tau ntxiv tshaj li tus qauv tsim tom qab sau tseg qhov ua tsis tiav

Table 1. Tus neeg sawv cev tsis sib piv ntawm tus qauv 316L thiab 316Lmod (urea/nitric acid qib) kev xyaum. Cov nqi thiab cov kev xav tau yog cov lus piav qhia thiab kev lag luam-tus neeg sawv cev; Cov txheej txheem lees paub tseeb txawv ntawm tus txheej txheem tso cai, tus tsim khoom, thiab qhov kawg - cov neeg siv tshwj xeeb thiab yuav tsum tau lees paub tawm tsam qhov tsim nyog siv lossis kev koom tes hauv kev lag luam.

Delta ferrite theem nyob rau hauv austenitic 316L microstructure corrode preferentially nyob rau hauv kub ammonium carbamate tov - corrosive intermediate tsim thaum lub sij hawm urea synthesis - yog li tswj ferrite cov ntsiab lus mus rau ib tug heev tsawg theem yog ib qho tseem ceeb tshaj qhov sib txawv ntawm cov qauv 316L thiab daim ntawv thov no.

Standard austenitic stainless hlau castings thiab weldments feem ntau khaws cia me me ntawm delta ferrite, theem nrab uas tsim thaum lub sij hawm solidification thiab feem ntau suav hais tias tsis muaj teeb meem lossis txawm tias muaj txiaj ntsig hauv ntau daim ntawv thov, vim nws tuaj yeem pab tiv thaiv kub tawg thaum vuam. Nyob rau hauv ib puag ncig ammonium carbamate tam sim no nyob rau hauv urea reactors thiab siab - siab synthesis voj khoom, txawm li cas los xij, ferrite coj electrochemical txawv ntawm ib puag ncig austenite, thiab qhov sib txawv ntawm corrosion muaj peev xwm ua rau ferrite theem corrode xaiv thiab sai, undermining cov khoom nyob ib puag ncig txawm tias lub suab matrix tseem nyob.

Qhov kev xaiv corrosion no yog tshwj xeeb rau carbamate chemistry - nws tsis yog qhov tsis muaj zog ntawm ferrite- muaj cov hlau tsis muaj steel hauv feem ntau lwm cov kev pabcuam - uas yog vim li cas urea kev lag luam xyaum tsim ib qho tshwj xeeb, nruj tswj ferrite txwv rau 316Lmod es tsis yog kev cia siab rau tus qauv 316L, ferrite.

316Lmod txoj kev tswj xyuas nruj dua ntawm cov khoom seem thiab nws cov kev tsim nyog niaj hnub los ntawm kev ntsuam xyuas kev sib xyaw ua ke muab kev ntseeg tau ntau dua, zoo dua -cov ntaub ntawv tiv thaiv rau lub intergranular thiab xaiv nres mechanisms uas concentrated los yog kub nitric acid tuaj yeem ua rau hauv qhov tsis txaus tswj 316L cua sov.

Nitric acid yog ib qho oxidizing acid, thiab stainless hlau qhov kev ua tau zoo nyob rau hauv ib puag ncig yog hnyav heev ntawm kev tswj kom tag nrho passive, tsis xws luag -dawb nto thiab microstructure - tej yam kev mob uas yuav cuam tshuam los ntawm grain ciam carbide nag lossis daus, tej yam residual element cais, los yog lwm yam microstructural inconsistors tsis soj ntsuam cov txheej txheem ib txwm muaj. acid kev pab xav tau.

316Lmod qhov kev coj ua ntawm cov khoom tsim nyog niaj hnub los ntawm kev ntsuam xyuas kev sib xyaw ua ke ncaj qha hais txog qhov sib txawv no, muab cov lus pom zoo, rau - cov pov thawj kub ntawm kev tiv thaiv rau hom kev tawm tsam tshwj xeeb ntawm kev txhawj xeeb es tsis yog kev cia siab rau kev ua raws li kev sib xyaw ua ke raws li qhov tsis ncaj ncees rau kev ua haujlwm. Qhov no yog qhov muaj txiaj ntsig zoo sib txawv: ob lub tshav kub ntawm cov hlau tuaj yeem raug lees paub tias yog "316L" thaum qhov sib txawv ntawm lawv qhov tseeb tiv thaiv intergranular nres hauv nitric acid, uas yog raws nraim qhov sib txawv ntawm 316Lmod cov kev tsim nyog ntxiv yog tsim los tshem tawm.

Kev xeem Huey (ASTM A262 Practice C) yog ib qho kev ntsuas kub siab nitric acid immersion test siv los kuaj xyuas qhov cuam tshuam rau intergranular corrosion, thiab nws niaj hnub siv hauv 316Lmod kev tsim nyog yog qhov tseem ceeb vim li cas qib no muaj kev ntseeg siab dua, kev ua tau zoo hauv nitric acid thiab carbamate kev pabcuam tshaj li tus qauv 316L cov ntawv pov thawj nkaus xwb.

Hauv kev sim Huey, cov qauv npaj tau raug rov ua dua cov nthwv dej kub npau npau, thiab qhov tshwm sim corrosion tus nqi yog ntsuas thiab muab piv rau qhov kev lees paub; cov ntaub ntawv uas qhia tau hais tias qhov kev npaj txhij txog siab corrosion qhia tau tias muaj kev cuam tshuam rau intergranular nres, feem ntau cuam tshuam nrog chromium carbide nag lossis daus ntawm cov ciam teb lossis lwm yam microstructural sensitization.

Vim tias qhov kev ntsuam xyuas no ncaj qha ntsuas cov khoom siv tus cwj pwm tiag tiag hauv kev txhoj puab heev, oxidizing acid ib puag ncig zoo sib xws rau cov kev pabcuam nitric acid tiag tiag, nws yog txoj kev tsim nyog tshaj plaws tshaj li kev tshuaj ntsuam xyuas ib leeg, uas tuaj yeem tsuas yog qhov kev ua tau zoo es tsis lees paub nws. Yuav tsum tau kuaj Huey (los yog qhov sib npaug sib npaug ntawm kev ntsuas kev sib xyaw ua ke) raws li tus qauv ntawm 316Lmod cov ntaub ntawv lees paub yog ib qho ntawm qhov tseeb tshaj plaws, qhov tseeb tshaj qhov sib txawv ntawm qib no qhov kev tsim nyog nruj thiab tus qauv 316L cov ntawv pov thawj zeb raug, uas tsis niaj hnub suav nrog qhov kev xeem no.

316Lmod yog tsim nyob rau hauv ib tug nqaim internal compositional bands - tshwj xeeb tshaj yog rau cov pa roj carbon, silicon, thiab residual ntsiab xws li sulfur thiab phosphorus - ntau tshaj li qhov sib txawv ntau tau tso cai nyob rau hauv lub hauv paus 316L specification, txo tshav kub- mus rau - kub variability nyob rau hauv microstructure thiab corrosion cwj pwm.

How Do Compositional Tolerances Differ Between 316Lmod and Standard 316L

Standard 316L's ASTM specification ranges yog txhob txwm broad txaus kom haum raws li ib txwm steelmaking variation nyob rau hauv ntau manufacturers thiab daim ntawv thov, uas yog tsim nyog rau nws lub luag hauj lwm raws li ib tug general - lub hom phiaj corrosion- qib resistant. Rau kev pabcuam urea thiab nitric acid tshwj xeeb, txawm li cas los xij, qhov dav dav ntawm qhov kev tso cai no tuaj yeem txhais ua qhov muaj txiaj ntsig, daim ntawv thov - qhov sib txawv ntawm tus kheej cov cua sov - ob daim ntawv pov thawj zeb tuaj yeem ua ob qho tib si qhia tau raws li 316L chemistry thaum sawv cev muaj txiaj ntsig sib txawv ntawm kev ua haujlwm corrosion hauv carbamate lossis nitric acid raug.

316Lmod specifications nqaim no variability los ntawm imposing nruj nreem txwv nyob rau hauv cov ntsiab lus feem ntau zoo sib xws nrog cov kev ua hauj lwm tsis ua hauj lwm hom uas tau tham saum toj no, ua tau zoo txo qhov kev ua tau zoo ntawm cov neeg yuav khoom yuav cia siab tias yuav tau txais raws li 316Lmod kev xaiv piv nrog tus qauv 316L kev yuav khoom uas tshwj xeeb tsuas yog lub hauv paus ASTM txwv.

Qhov tseem ceeb corrosion mechanisms ntawm kev txhawj xeeb rau tus qauv 316L nyob rau hauv urea nroj tsuag yog xaiv ferrite nres nyob rau hauv ammonium carbamate tov thiab intergranular corrosion, ob qho tib si ntawm uas yog microstructural es tsis yog purely compositional tsis ua hauj lwm hom - lub ntsiab lus ib tug tag nrho specification-raws li 316L tshav kub tseem tuaj yeem ua raws li cov ntsiab lus tshwj xeeb los yog tsis muaj kev cuam tshuam cov ntsiab lus tshwj xeeb yog tias nws cov ntsiab lus tsis zoo

Qhov no yog lub hauv paus kev pom zoo uas piav qhia tias yog vim li cas 316Lmod tshwm sim raws li qhov tshwj xeeb kev coj ua es tsis yog tsuas yog rov ua dua nrog tus qauv 316L: ob qho tib si xaiv ferrite corrosion thiab intergranular nres tuaj yeem tshwm sim hauv cov khoom uas txaus siab rau lub hauv paus ASTM compositional specification, vim hais tias cov specification tsis ncaj qha tswj ferrite cov ntsiab lus los yog yuav tsum tau intergranular corrosion testing.

Cov ntaub ntawv kev paub dhau los thoob plaws kev lag luam urea - suav nrog kev ua tsis tiav corrosion tau taug qab mus rau tus qauv- xyaum 316L cov khoom hauv carbamate cov kev pabcuam - yog dab tsi ua rau muaj kev txhim kho ntxiv, daim ntawv thov- cov kev cai tshwj xeeb tam sim no feem ntau hu ua 316Lmod, es tsis yog cov kev xav tau no yog autorary los yog kev ua tau zoo.

Cov kws ua haujlwm yuav tsum tau qhia 316Lmod cov kev cai kom meej thiab nthuav dav - ferrite cov ntsiab lus txwv, intergranular corrosion test method thiab kev lees paub, thiab cov kev txwv nruj nruj - es tsis yog kev cia siab rau lo lus "316Lmod" ib leeg, vim nws yog kev lag luam xyaum ntau dua li ib qho kev tsim qauv thoob ntiaj teb, thiab cov txheej txheem yuav tsum muaj peev xwm varied.

Daim ntawv teev cov kev qhia tshwj xeeb:

1. Qhia qhov txwv cov ntsiab lus ferrite kom meej,suav nrog txoj kev ntsuas (piv txwv li, kev ntsuas magnetic ferrite lossis metallographic point suav), es tsis xav tias tus nqi pib siv.

2. Qhia meej txog cov txheej txheem kev ntsuas kev sib tsoo ntawm intergranular thiab kev lees paub(xws li ASTM A262 Practice C los yog lwm txoj kev tsim nyog), suav nrog cov khoom siv twg thiab cov khoom siv welded yuav tsum tau kuaj.

3. Siv cov txheej txheem tso cai los yog kev lag luam koom haum kev caiqhov twg qhov project ua raws li daim ntawv tso cai tshwj xeeb urea technology, txij li cov no feem ntau codify lawv tus kheej cov ncauj lus kom ntxaws cov ntaub ntawv xav tau tshaj li "316Lmod" kev lag luam lub sij hawm.

4. Yuav tsum tau cua sov- ntawv pov thawj tshwj xeebUa kom pom kev ua raws li cov kev cai nruj rau txhua qhov kub ntawm cov khoom siv, tsis yog daim ntawv pov thawj qib dav dav.

5. Paub meej tias cov txheej txheem vuam tsim nyogkom tswj tau qhov xav tau ferrite thiab IGC kev ua tau zoo thoob plaws qhov vuam thiab cua sov- thaj tsam cuam tshuam, txij li kev vuam tuaj yeem hloov kho ob qho tib si ferrite cov ntsiab lus thiab cov ciam teb txawm tias nyob rau hauv cov ntaub ntawv raug cai.

316Lmod yog tus nqi -kev xaiv zoo tshwj xeeb rau urea synthesis voj thiab nitric acid kev pabcuam, qhov uas cov ntaub ntawv muaj feem cuam tshuam ntawm corrosion tsis ua hauj lwm ntxov nyob rau hauv tus qauv 316L ua rau cov kev ntsuam xyuas ntxiv thiab nruj dua tus nqi me me piv rau tus nqi ntawm qhov tsis tau npaj tseg lossis hloov khoom siv, tab sis nws yog tus nqi tsis tsim nyog rau kev siv tshuaj lom neeg sab nraud.

Is 316Lmod a Cost-Effective Upgrade Over Standard 316L

Tus nqi ntxiv ntawm 316Lmod txheeb ze rau tus qauv 316L feem ntau yog los ntawm qhov kev sim ntxiv (tshwj xeeb yog kev ntsuas kev sib xyaw ua ke ua ib qho cua sov lossis ib qho ntau) thiab kev tswj xyuas nruj dua uas yuav tsum tau ua kom ntseeg tau raws li cov kev txwv nqaim thiab ferrite, tsis yog los ntawm cov ntsiab lus sib txawv los yog kim dua cov ntsiab lus raw khoom.

Nyob rau hauv cov ntsiab lus tshwj xeeb ntawm urea synthesis loop khoom thiab nitric acid tuav - qhov kev paub dhau los tau pom tias muaj kev pheej hmoo corrosion tiag tiag hauv tus qauv - xyaum 316L - tus nqi ntxiv no feem ntau yog me ntsis cuam tshuam rau tus nqi ntawm kev poob qis, kev hloov khoom siv, lossis kev nyab xeeb muaj feem cuam tshuam nrog corrosion tsis ua hauj lwm nyob rau hauv siab - kev pab cuam siab. Sab nraum cov chaw tshwj xeeb no, txawm li cas los xij, tus qauv 316L tseem tsim nyog, thiab qhia txog 316Lmod yam tsis muaj cov carbamate lossis nitric acid cuam tshuam uas ua rau nws ntxiv tus nqi yam tsis muaj txiaj ntsig kev ua tau zoo.

Puas yog 316Lmod yog tus qauv ASTM lossis UNS?

Tsis yog. 316Lmod yog ib qho kev xyaum ua lag luam uas piav txog kev nruj, daim ntawv thov- cov kev cai tshwj xeeb muab tso rau hauv tus qauv 316L specification (xws li ASTM A240), feem ntau cuam tshuam nrog urea kev lag luam kev taw qhia; nws tsis yog nws tus kheej ib qho cais ASTM lossis UNS- npe rau npe alloy, uas yog vim li cas qhov kev qhia tshwj xeeb yuav tsum tau hais txog cov kev xav tau tshwj xeeb ntxiv kom meej meej es tsis yog cia siab rau lub sijhawm ib leeg.

Puas yog 316Lmod tshem tawm tag nrho cov kev pheej hmoo corrosion hauv urea thiab nitric acid kev pabcuam?

Tsis muaj cov khoom tshem tawm kev pheej hmoo corrosion nkaus; 316Lmod txo qhov kev pheej hmoo ntawm cov kev xaiv tshwj xeeb ferrite thiab intergranular nres mechanisms tau tham txog ntawm no piv rau tus qauv- xyaum 316L, tab sis tsim nyog tsim, tsim, vuam txheej txheem tsim nyog, thiab kev soj ntsuam txuas ntxiv tseem yog qhov tseem ceeb ntawm kev ua tiav kev tswj xyuas corrosion hauv cov kev pabcuam xav tau.

Tus qauv 316L tuaj yeem siv tau nyob txhua qhov chaw hauv urea cog, lossis puas 316Lmod siv thoob plaws?

Standard 316L tseem tsim nyog rau ntau qhov sib npaug - ntawm - cov khoom cog tsis raug rau cov tshuaj ammonium carbamate ntau; 316Lmod feem ntau yog tshwj tseg rau lub voj voog synthesis thiab lwm yam khoom siv nrog kev raug carbamate ncaj qha, qhov twg cov txheej txheem corrosion tshwj xeeb no cov chaw nyob qib yog tam sim no.

Cov ntsiab lus ferrite feem ntau ntsuas thiab txheeb xyuas li cas hauv 316Lmod cov khoom?

Cov ntsiab lus ferrite feem ntau ntsuas siv cov ntsuas ntsuas sib nqus ferrite los yog, qee zaum, metallographic point suav, nrog rau cov qauv tshwj xeeb thiab kev lees paub txwv tau teev tseg hauv qhov project lossis daim ntawv tso cai kev qhia tshwj xeeb es tsis yog ib qho kev lag luam thoob ntiaj teb.

Puas yog vuam cuam tshuam rau 316Lmod qhov corrosion kuj zoo ib yam li nws cuam tshuam tus qauv 316L?

Vuam xav tau kev saib xyuas tshwj xeeb hauv 316Lmod daim ntawv thov vim tias nws tuaj yeem ua rau hauv zos nce ferrite cov ntsiab lus lossis hloov pauv cov ciam teb hauv qhov vuam thiab cua sov- thaj tsam cuam tshuam, yog li cov txheej txheem vuam rau 316Lmod feem ntau tsim nyog nrog tib lub ferrite thiab intergranular corrosion txheej txheem siv rau cov khoom siv hauv paus, tsis yog rau qhov pom kev zoo thiab kev siv tshuab.