Vim li cas 316 Stainless Hlau Sheath Hluav Taws Xob Hluav Taws Xob Hluav Taws Xob Hluav Taws Xob Hluav Taws Xob nrog Mill-Annealed Surfaces Outperform Pickled lossis Electropolished tiav nyob rau hauv siab - Kub Siab -Purity Water Oxidation Service saum toj 250℃?

Xaiv qhov chaw tiav ntawm 316 stainless hlau sheaths nyob rau hauv cov tshuab raug dej kub, xws li supercritical water oxidation (SCWO) reactors, pressurized water reactor (PWR) auxiliary circuits thiab ultra-supercritical boiler feedwater heaters, yuav tsum tau thim rov qab ntawm cov kev paub txog kev txhim kho corrosion. Electropolished los yog pickled nto muab zoo pitting kuj nyob rau hauv uas tsis muaj kub chloride uas muaj kua, los ntawm kev tshem tawm cov imbedded hlau hais thiab passive zaj duab xis flaws. Txawm li cas los xij, ntawm qhov kub siab tshaj 250℃hauv cov dej purity siab (conductivity <0.1 µS / cm, yaj oxygen < 10 ppb) cov txheej txheem corrosion hloov los ntawm thaj chaw pitting mus rau oxidation dav thiab muaj peev xwm corrosion corrosion. Cov nyias nyias, chromium-nplua nuj zaj duab xis uas tshwm sim nyob rau hauv zeb-annealed nto (tau los ntawm annealing zaum kawg nyob rau hauv ib qho chaw tswj los yog huab cua ua raws li cua txias) muaj zoo adhesion, thermal stability thiab tsis kam mus spallation dua li cov khoom tuab tuab los yog cov tshuaj hloov kho oxide txheej uas tau txais los ntawm kev khaws cov khoom siv hluav taws xob. Daim ntawv no ntsuas tus cwj pwm oxidation ntawm 316 stainless hlau sheaths nrog peb qhov chaw tiav ntawm 280-320℃hauv deaerated siab purity dej thiab muab cov ntaub ntawv xaiv tiav rau kev kub siab nuclear thiab supercritical dej siv.

Mechanisms ntawm Oxide Film Formation sib txawv nrog kev npaj nto
Cov oxide deposit ib txwm nyob rau ntawm 316 stainless hlau loj hlob los ntawm ob peb lub tswv yim nyob ntawm seb qhov kev npaj nto tom qab lub raj kawg tsim. Kev kho cua sov zaum kawg yog ua nyob rau hauv ib puag ncig oxidising (cua lossis tswj kev sib xyaw ntawm nitrogen nrog cov pa oxygen) ntawm 1010-1120℃thiab lub zeb-annealed nto yog txias ntawm tus nqi uas tsim cov duplex oxide ntawm li 50-150 nm hauv thickness. Cov txheej sab nrauv feem ntau yog hlau oxides (Fe₂O₃ thiab Fe₃O₄ - haematite thiab magnetite, feem) thaum txheej sab hauv yog nplua nuj nyob rau hauv chromium (Cr₂O₃ lossis FeCr₂O₄ spinel). Cov oxide no loj hlob ntawm qhov kub thiab txias ua rau lub lattice zoo sib xws nrog cov hlau hauv qab thiab qis qis ntawm cov hlau - oxide contact.

Pickled nto yog kho nrog sib tov ntawm nitric thiab hydrofluoric acid tom qab annealing. Qhov kub siab oxide raug tshem tawm tag nrho los ntawm cov kua qaub sib tov kom tawm cov hlau liab qab. Tom qab ntawd cov hlau passivates spontaneously nyob rau hauv cov huab cua ntawm ambient kub, tsim ib tug ntau thinner oxide (1.5-3 nm) uas yog feem ntau chromium- nplua nuj nrog me ntsis hlau. Cov zaj duab xis nyias nyias no muaj kev tiv thaiv zoo heev tiv thaiv chloride nres ntawm qhov kub thiab txias, tab sis nws tsis muaj qhov yuav tsum tau thermal stability thiab thickness rau high-kub dej oxidation kev pab cuam.

Electropolishing yog anodic dissolving ntawm nto nyob rau hauv ib tug electrolyte (feem ntau yog ib tug sib tov ntawm phosphoric thiab sulfuric acids) uas dissolves ib tug nyias txheej ntawm hlau (20-50 µm) thiab ua ib tug du, ci ntsa iab nto nrog ib tug passive zaj duab xis zoo ib yam li cov pickled nto tab sis txawm ntau chromed {{4}. Electropolished nto muaj qhov qis tshaj qhov roughness (Ra tsawg li 0.1 µm) thiab siab tshaj chromium- rau - hlau piv nyob rau hauv cov zaj duab xis passive, feem ntau yog 1.8-2.2, piv rau 1.2-1.5 rau qhov chaw pickled thiab 0.8-1.0 rau mills.annealed nto.

Kev kub siab dej oxidation cwj pwm ntawm 280-320 degree
Kev tswj xyuas corrosion tau ua nyob rau hauv recirculating siab -purity dej loops (0.06 µS / cm conductivity, 5 ppb yaj oxygen, pH 6.5 ntawm 25 degree, ntws tshaj tawm 0.5 m / s) ntawm 300℃mus txog 5000 teev. Kev ntsuas qhov hnyav nce thiab tus cwj pwm ntawm oxide txheej los ntawm grazing tshwm sim X-ray diffraction (GIXRD) thiab scanning electron microscopy muab cov ntaub ntawv sib piv.

Nto Finish Initial Surface Roughness Ra (µm) Oxide Thickness ntawm 5000 Teev ntawm 300℃(µm) Oxide Spallation (yuag poob vim flaking, mg/cm²) Hlau poob (µm nkag mus) Dominant Oxide Phase Mill-annealed (6 {cua txias) - 8.<0.05 0.8 – 1.2 Spinel (FeCr2O4) + haematite
Magnetite (Fe₃O₄) chromium depleted Pickled (HNO₃/HF) 0.4 – 0.8 2.2 – 3.1 0.12 – 0.25 1.6 – 2.4
Electropolished 0.1 - 0.3 2.8 - 3.8 0.30 - 0.55 2.1 - 3.0 Chromium- nplua nuj nodules embedded nyob rau hauv ib tug magnetite matrix
Mill-annealed + post-polish (mechanical rau Ra 0.2 um) 0.2 - 0.3 1.4 - 2.0 0.06 - 0.10 0.9 - 1.4 Spinel + minor magnetite
Lub thinnest thiab feem ntau nplaum oxide yog ib txwm ua nyob rau hauv lub zeb -annealed nto tom qab lub sij hawm ntev ntawm kub kub raug. Qhov sib txawv tseem ceeb yog cov qauv pib ntawm cov oxides. Lub siab- kub zeb oxide muab cov qauv uas txhawb kev tsim cov txheej txheem ntom ntom ntom ntom ntom ntom ntom ntom ntom nti (FeCr₂O₄) thaum lub sijhawm ua haujlwm yav tom ntej. Lub coefficient ntawm thermal expansion (CTE) ntawm spinel yog nyob ib ncig ntawm 8.5 × 10⁻⁶ / K, uas yog ib tug zoo match nrog lub CTE ntawm 316 stainless hlau (16 × 10⁻⁶ / K ntawm 300℃nyob rau hauv cov nqe lus ntawm kev hloov pauv, tab sis crystallographically sib xws). Nyob rau hauv sib piv, pickled thiab electropolished nto ua rau cov tsim ntawm magnetite (Fe3O4) muaj ib tug CTE ntawm ~ 12 × 10-6 / K, uas induces ntau thermal stresses thaum lub sij hawm thermal cycling thiab muaj zog spallation nyiam.

Stress Corrosion Cracking Susceptibility nyob rau hauv dej kub
Thaum pib ntawm kev ntxhov siab corrosion cracking (SCC) nyob rau hauv 316 stainless hlau nyob rau hauv siab - purity dej ntawm 300-350℃yog zoo-cov ntaub ntawv nyob rau hauv lub boiling dej reactor (BWR) ib puag ncig thiab muaj zog cuam tshuam los ntawm nto tag ntxiv rau oxidation dav dav. U- khoov cov qauv nrog txhua qhov chaw tiav tau sim los ntawm kev sim qeeb qeeb (SSRT) ntawm 300℃hauv dej deaerated (solved oxygen 20 ppb). Kev tawg qhov tob thiab lub sijhawm rau SCC tawg pib raug ntsuas.

Nto tiav Lub Sijhawm rau SCC Initiation (teev, 300 degree) Crack Depth Tom qab 2000 Teev (µm) Residual Surface Stress (MPa) Crack Morphology
Mill-annealed >3000 (tsis muaj pib pom) 0 Tsis muaj +25 (compressive)
Pickled 1800 – 2400 50 – 90 Intergranular, branched +10 (tensile)
Electropolished 1100 - 1600 120 - 200 Transgranular, ntse +50 rau +80 (tensile)
Electropolishing ua rau muaj qhov nce ntawm tensile residual kev ntxhov siab ntawm txheej txheej vim qhov sib txawv ntawm qhov sib txawv ntawm cov hlau tsis muaj zog thiab tsis muaj zog. Cov kev ntxhov siab tensile (feem ntau yog 50-80 MPa) yog ntxiv rau kev siv thiab thermal stresses, uas ua rau qhov tshwm sim ntawm SCC. Pickling feem ntau ua rau cov chaw yuav luag nruab nrab lossis me ntsis compressed, thaum lub zeb annealing feem ntau ua rau cov chaw nyob rau hauv ib qho kev nyuaj siab me ntsis vim yog cov oxide ntau lawm thaum txias. Kev ua haujlwm ntawm lub zeb-annealed sheaths rau SCC pib tshaj qhov chaw pickled thiab electropolished nyob rau hauv qhov kub thiab txias, dej purity siab, yog vim muaj qhov ruaj khov spinel oxide ua ke nrog compressive residual stress.

Daim ntawv thov -Tshwj xeeb Finish Choices rau High- Kev Pabcuam Dej Kub
Cov kev txiav txim siab hauv qab no rau kev xaiv qhov chaw tiav rau 316 stainless hlau sheaths, raws li kev ua haujlwm ntawm qhov kub thiab txias, kev huv huv ntawm cov dej thiab cov txheej txheem kev xav tau zoo tshaj plaws yog muab.

Kev khiav hauj lwm kub (degree) Dej Purity / Chemistry Dominant Corrosion Mechanism Pom Zoo Nto Ua tiav Rationale < 100 Txhua qib ntawm chloride Pitting, crevicePolished los yog pickledMaximum pitting kuj Negligible oxidation
100 - 200 < 50 ppm chloride Pitting + nruab nrab oxidation Pickled lossis mechanically polishedBalanced, tiv thaiv electropolish> 180℃200 - 250High purity (< 0.5 µS/cm) Oxidation + possible SCS Mill-annealed or mill-annealed + light mechanical polished Transition zone; mill-annealed preferred
250 - 350 Nuclear qib siab purity General oxidation + SCCElectropolish thiab pickle contraindicated, tsuas yog zeb-annealed
350 - 500 (supercritical H2O) Txhua yam purity Spallation, tuab oxide growthGrain loj tswj, zeb annealedPreferred oxide adhesion coarse grain tseem ceeb
Txhua qhov kub thiab txias Chlorides> 500 ppmPitting tsis hais txog qhov ua tiav Upgrade rau super-austenitic lossis Ni alloy 316 stainless hlau tsis tau txais
Rau cov txheej txheem pabcuam hauv cov twj tso kua dej siab (kwv yees li 280-320 degree) thiab supercritical dej oxidation reactors (400-600 degree), cov lus qhia tshwj xeeb yuav tsum tau hais meej meej zeb-annealed nto tiav uas tsis muaj ntxiv los yog electropolishing. Thaum kawg annealing yuav tsum nyob rau hauv huab cua los yog nyob rau hauv ib tug tswj oxidising cua thiab yuav tsum tau ua raws li los ntawm cua txias rau chav tsev kub. Tsis muaj kev ntxuav cov kua qaub yuav tsum tau ua tom qab annealing tsuas yog tshem tawm tag nrho cov kab mob sib kis uas yuav ua tiav los ntawm me me alkaline lossis citric acid ntxuav tsis tawm tsam lub hauv paus oxide.

Specification Language for High Temperature Water Heaters (Tswj)
Thaum xaj 316 stainless hlau sheathed hluav taws xob cua sov raj rau siv siab tshaj 250℃hauv dej purity siab, engineers yuav tsum qhia cov qauv hauv qab no. Qhov saum npoo ntawm lub sheath yuav tsum nyob rau hauv cov xwm txheej ntawm zeb-annealed raws li tsim los ntawm lub kawg raj annealing txheej txheem. Sab nraud sheath nto yuav tsum tsis txhob muab pov tseg, electropolished los yog chemically brightened tom qab annealing kawg. Yog tias tom qab- kev tshem tawm yuav tsum tau ntxuav kom tshem tawm cov roj nplua nyeem lossis tuav cov cim, tsuas yog cov tshuaj alkaline me me lossis 5-10% citric acid daws ntawm qhov kub qis dua 50 degree, thiab kev ntxuav yuav tsum tsis txhob tshem tawm cov haiv neeg siab -kub oxide. Tus kws kho mob yuav tsum sau qhov kawg ntawm qhov chaw annealing (cua lossis nitrogen nrog 2-5% oxygen) thiab tus nqi cua txias (cua txias, tsis dej quenched). Qhov saum npoo roughness yuav tsum yog Ra 0.5-1.5 µm. Ua tiav smoother dua Ra 0.4 µm tsis tau vim lawv yog cov txiaj ntsig ntawm kev siv tshuab lossis tshuaj polishing uas tshem tawm cov txiaj ntsig zeb oxide. Rau cov ntawv thov uas muaj thermal cycling ntau dua 1000 lub voj voog ntawm ambient thiab 300 degree, lub zeb-annealed sheath yuav tsum tau ua ntej -kev kho oxidation (500 teev ntawm 300℃hauv chav lossis siab -} dej purity) ua ntej kev sib dhos zaum kawg, uas ntxiv cov stabil oxide. Yog tias cov engineers tsis lees txais qhov kev xaiv ib txwm siv ntawm cov khoom siv hluav taws xob hauv qhov qis -kub chloride kev pabcuam thiab qhia cov zeb-annealed tiav nyob rau hauv siab -kub high-purity dej, sheath kev pab cuam nyob rau hauv ntau tshaj 50,000 teev yuav tau txais nyob rau hauv tej yam kev mob uas polished heaters poob los ntawm oxide spallation nyob rau hauv 10 teev thiab tawg.