Peb tab tom tsim cov tshuab ntxhua khaub ncaws rau cov nroj tsuag sulfuric acid siv Incoloy 825 phaj thiab yeeb nkab. Dab tsi muab cov hlau uas peb yuav tsum tau siv los xyuas kom meej cov hlau vuam sib tw rau corrosion kuj ntawm lub hauv paus hlau?

1. Khoom Siv Chemistry & Qhov "Titanium Stabilization" Advantage

Q: Peb cov sulfuric acid cog piping specification hu rau UNS N08825. Dab tsi yog lub luag haujlwm tshwj xeeb ntawm titanium hauv cov hlau no, thiab vim li cas nws tseem ceeb heev rau welded yeeb nkab hauv kev pabcuam acid?

A: Qhov sib ntxiv ntawm titanium (0.6-1.2%) hauv Incoloy 825 tsis yog ib qho kab ke; nws yog ib tug txhob txwm metallurgical tswj mechanism tsim los tiv thaiv intergranular corrosion tom qab vuam los yog thermal raug.

Nyob rau hauv cov qauv stainless hlau, thaum cov khoom yog rhuab mus rau hauv lub rhiab heev ntau yam (kwv yees li 900-1500℃F / 450-800 degree), carbon combines nrog chromium los tsim chromium carbides ntawm lub grain ciam teb. Qhov no depletes thaj chaw uas nyob ib sab ntawm chromium, ua rau lawv yooj yim rau kev tawm tsam sai hauv qhov chaw acidic-ib qho tshwm sim hu ua "weld decay."

Hauv UNS N08825, titanium muaj kev sib raug zoo rau cov pa roj carbon ntau dua li chromium. Thaum tshav kub kub kho los yog lub voj voog kub ntawm vuam, titanium nyiam ua ke nrog cov pa roj carbon monoxide los tsim cov khoom me me, innocuous titanium carbides (TiC). Cov txheej txheem no hu ua "stabilization."

Vim li cas qhov no tseem ceeb rau cov kav dej acid:
Vim hais tias cov titanium "scavenes" cov pa roj carbon, cov chromium tseem nyob rau hauv cov khoom tov, tswj cov corrosion{0}}resistant passive txheej txoj cai mus txog rau lub grain ciam teb. Qhov no txhais tau hais tias Incoloy 825 seamless yeeb nkab lossis tubing tuaj yeem siv tau raws li -welded mob rau cov kev pabcuam acid feem ntau yam tsis tas yuav tsum muaj kev tshaj tawm -weld tov anneal los kho corrosion kuj. Rau cov khoom siv pickling thiab acid ntau lawm kab uas welds yog inevitable, no stabilization ua kom tag nrho cov txheej txheem - puag hlau thiab tshav kub- cuam tshuam cheeb tsam - nthuav tawm cov kev tawm tsam tsis zoo.

2. Sulfuric & Phosphoric Acid Service

Q: Vim li cas Incoloy 825 tau teev tseg rau cov kav dej hauv sulfuric thiab phosphoric acid ntau dua li tus qauv 316L stainless hlau lossis siab dua -qib nickel alloys xws li C-276?

A: Kev xaiv ntawm Incoloy 825 rau cov kav dej ua kua qaub los ntawm qhov sib npaug ntawm kev tiv thaiv corrosion thiab kev lag luam, tshwj xeeb tshaj yog nyob rau hauv "nruab nrab-ntau" ntawm cov kua qaub thiab kub.

Mechanism:

Sulfuric Acid (H₂SO₄): Standard 316L stainless hlau ua tau zoo txaus nyob rau hauv heev dilute los yog heev concentrated sulfuric acid ntawm ambient kub, tab sis nws tsis sai heev nyob rau hauv lub intermediate concentration range (20-60%) ntawm elevated kub. Cov tooj liab (1.5–3.0%) thiab molybdenum (2.5–3.5%) cov ntsiab lus hauv 825 ua haujlwm sib koom ua ke los muab kev tiv thaiv rau qhov txo qis acid ib puag ncig. Tooj liab tshwj xeeb txhim kho passivation nyob rau hauv sulfuric acid, ib tug yam ntxwv tsis muaj nyob rau hauv 316L.

Phosphoric Acid (H₂PO₄): Hauv "cov txheej txheem ntub dej" rau kev tsim cov phosphoric acid (siv rau cov chiv), cov kua qaub muaj cov khoom tsis zoo xws li chlorides, fluorides, thiab gypsum . 316L raug kev txom nyem los ntawm pitting thiab crevice corrosion nyob rau hauv qhov chaw no. Alloy 825 cov ntsiab lus siab nickel (~ 42%) tiv thaiv chloride kev nyuaj siab corrosion tawg, thaum cov ntsiab lus molybdenum resists pitting los ntawm halides.

Vim li cas ho tsis C-276?
Alloys zoo li C-276 muab kev tiv thaiv corrosion ntau dua, tab sis lawv tseem kim dua vim muaj cov ntsiab lus molybdenum thiab tungsten ntau dua. Rau feem ntau ntawm phosphoric acid evaporators, cov kav dej, thiab cov hlab ntsha, 825 muab "qhov chaw qab zib"-kev ua tau zoo tshaj plaws rau cov hlau tsis muaj steel ntawm tus nqi qis dua qhov siab -kawg nickel alloys. Nws feem ntau suav hais tias yog "workhorse" nkag-theem nickel alloy rau cov kev pabcuam acid.

3. Cov Khoom Siv Pickling & Kev Kho Hniav

Q: Peb cov kab pickling siv cov khoom sib tov ntawm nitric acid (HNO₃) thiab hydrofluoric acid (HF) kom descale stainless hlau. Peb tab tom qhia Incoloy 825 rau cov cua sov coils thiab cov kav dej tank. Dab tsi ua rau nws tsim nyog rau qhov sib xyaw ua ke ntawm -acid puag ncig?

A: Pickling nrog kev sib xyaw ntawm nitric thiab hydrofluoric acid (HNO₃ / HF) yog ib qho ntawm cov chaw ua haujlwm hnyav tshaj plaws hauv cov khoom siv hlau. Qhov sib tov no yog tsim los tua thiab tshem tawm nplai, yog li nws tseem yuav tawm tsam cov cuab yeej uas muaj nws. Incoloy 825 raug xaiv rau qhov kev pabcuam no vim nws muaj peev xwm ua rau muaj kev phom sij: tiv thaiv oxidizing acids (nitric) thiab txo cov kua qaub (hydrofluoric).

Dual Mechanism:

Chromium rau Oxidizing Resistance (HNO₃): Cov ntsiab lus chromium (19.5-23.5%) tsim ib qho chaw ruaj khov, tsis muaj zog oxide zaj duab xis uas tiv taus cov oxidizing zoo heev ntawm nitric acid.

Nickel & Molybdenum rau Txo Kev Tiv Thaiv (HF): Hydrofluoric acid yog txo cov kua qaub uas tawm tsam cov ntaub ntawv los ntawm kev rhuav tshem cov yeeb yaj kiab passive. Cov ntsiab lus siab nickel hauv 825 muab kev tiv thaiv rau HF nres. Molybdenum kuj tseem pab tiv thaiv cov kab mob hauv zos uas HF tuaj yeem ua rau.

Pickling Hardware Considerations:
Rau cov khoom siv pickling, xws li immersion cua sov coils los yog circulating twj, lub alloy yuav tsum tau tiv thaiv thermal cycling thiab yaig los ntawm kev txav ntawm cov tshuaj pickling. Thaum 825 muaj peev xwm ua haujlwm tau zoo, cov neeg tsim khoom yuav tsum nco ntsoov tias vim nws qhov kev tiv thaiv corrosion siab, oxide nplai tsim thaum lub sij hawm kub sib sau yog me ntsis nyuaj rau tshem tawm dua li ntawm 304 stainless hlau. Pickling lubfabricated khoom nws tus kheej(kom tshem tawm cov txheej txheem tsim) yuav tsum muaj cov nitric muaj zog -hydrofluoric da dej los yog, zoo dua, ua ke ntawm alkaline descaling ua raws li cov kua qaub pickling kom huv si, passive nto.

4. Cov Lus Qhia Tshwj Xeeb (ASTM B423 vs. ASTM B163)

Q: Peb tab tom yuav seamless UNS N08825 yeeb nkab rau cov khoom siv hluav taws xob hauv cov txheej txheem tshuaj. Qhov txawv ntawm kev txiav txim rau ASTM B423 piv rau ASTM B163 yog dab tsi, thiab peb yuav tsum qhia qhov twg?

A: Qhov no yog qhov tseem ceeb ntawm kev yuav khoom sib txawv. Ob qho kev qhia tshwj xeeb npog cov raj seamless ntawm UNS N08825, tab sis lawv siv rau kev siv kawg thiab muaj qhov sib txawv ntawm kev tshuaj xyuas.

ASTM B423 (Nickel-Iron-Chromium-Molybdenum-Copper Alloy Seamless Pipe thiab Tube): Qhov no yog cov lus qhia dav dav rau seamless raj ntawm Alloy 825

. Nws feem ntau yog siv rau cov kav dej dav dav, xws li kev sib txuas cov kav dej hauv cov nroj tsuag tshuaj los yog cov kab pickling. Nws npog ntau qhov dav ntawm txoj kab uas hla thiab phab ntsa tuab haum rau cov kav dej siab ntawm ASME B31.3.

ASTM B163 (Seamless Nickel thiab Nickel Alloy Condenser thiab Thaum tshav kub kub-Exchanger Tubes): Qhov kev qhia tshwj xeeb no yog tsim tshwj xeeb rau cov raj siv hauv cov condensers, evaporators, thiab cov khoom siv hluav taws xob.

. Qhov sib txawv tseem ceeb yog nyob rau hauv qhov nruj dua qhov kam rau ua thiab feem ntau nruj dua qhov yuav tsum tau ua.

Tolerances: B163 feem ntau yuav tsum nruj dua tswj ntawm sab nraud txoj kab uas hla (OD) thiab phab ntsa tuab kom tso cai rau cov raj xa mus rau hauv cov ntawv raj.

Kev Ntsuas: B163 feem ntau tswj hwm qhov tsis yog- kev kuaj kev puas tsuaj (eddy tam sim no lossis ultrasonic) kom ntseeg tau tias lub raj haum rau nyias - phab ntsa, siab - kev ncaj ncees xav tau ntawm kev pab cuam cua sov.

Qhov twg los qhia?

Rau kev sib txuas cov yeeb nkab (hloov kab, manifolds) hauv cov nroj tsuag acid: Qhia ASTM B423.

Rau cov raj kub exchanger (cov raj tiag tiag hauv lub plhaub & lub raj sib hloov): Qhia ASTM B163. Yog tias koj xaj B423 yeeb nkab rau cov khoom siv hluav taws xob sib txuas, koj tuaj yeem pom OD kam rau ua yog qhov dav dhau los ua kom muaj qhov xau- pov thawj hydraulic expansion sib koom ua ke hauv cov ntawv raj.

5. Vuam & Fabrication rau Acid Service

Q: Peb tab tom tsim cov tshuab ntxhua khaub ncaws rau cov nroj tsuag sulfuric acid siv Incoloy 825 phaj thiab yeeb nkab. Dab tsi muab cov hlau uas peb yuav tsum tau siv los xyuas kom meej cov hlau vuam sib tw rau corrosion kuj ntawm lub hauv paus hlau?

A: Thaum vuam Incoloy 825 rau cov kua qaub, txoj cai dav dav yog "dhau-alloy" lub vuam. Koj yuav tsum tsis txhob siv cov khoom sib xyaw ua ke hlau. Kev lag luam- qauv pom zoo yog siv ERNiCrMo-3 (Alloy 625) muab tub lim hlau.

Vim li cas Alloy 625 Filler?

Segregation nyob rau hauv Weld pas dej ua ke: Thaum lub sij hawm solidification ntawm weld pas dej ua ke, alloying ntsiab yuav cais. Yog tias koj siv cov hlau muab tub lim sib piv nrog 825 chemistry (Ni-Cr-Fe-Mo-}Cu), qhov kev tso nyiaj ntawm weld yuav xaus nrog cov cheeb tsam hauv cheeb tsam depleted hauv molybdenum lossis tooj liab, tsim kom muaj qhov zoo tshaj plaws corrosion nres qhov chaw.

Cov ntsiab lus Nickel siab dua: ERNiCrMo-3 (Alloy 625) muaj cov ntsiab lus nickel ntau dua (~64%) thiab siab dua molybdenum (9%) dua li cov hlau hauv qab. Qhov no "tshaj-match" chemistry ua kom ntseeg tau tias cov nyiaj tso nyiaj muaj kev tiv thaiv corrosion tsawg kawg yog sib npaug, thiab feem ntau zoo dua, 825 lub hauv paus hlau hauv acidic ib puag ncig. Nws ua raws li "corrosion buffer."

Theem Stability: Lub 625 muab tub lim chemistry yog ntau metallurgically ruaj khov nyob rau hauv raws li -welded mob thiab resists lub tsim ntawm deleterious theem uas yuav raug tua nyob rau hauv kub acid.

Fabrication Cov kev coj ua zoo tshaj plaws:

Kev huv huv: Nickel alloys raug rau embrittlement los ntawm cov kab mob. Xyuas kom qhov chaw vuam tsis muaj roj, roj, thiab cov khoom sib txuas. Kev sib tsoo cov cim yuav tsum huv si, vim tias cov hlau tsis huv tuaj yeem ua rau cov txheej txheem tsis zoo.

Thaum tshav kub kub Input: Tswj cov cua sov input kom tsis txhob muaj cua sov ntau dhau. Kev siv hluav taws xob nruab nrab nrog qhov ntsuas kub sib txawv (feem ntau hauv qab 300℃F / 150 degree) yog pom zoo kom tiv thaiv kub tawg.