Ntsiab Cai
Alloy 20(UNS N08020, 33% Ni, 20% Cr, 3.5% Cu, 2.5% Mo, Cb-stabilized) yog cov khoom ua haujlwm nickel alloy rau sulfuric acid, ua haujlwm zoo dua 316L stainless hlau los ntawm 10-50x hauv nruab nrab acid concentrations (12SO40%).
Cov ntsiab lus niobium (Nb) (8 x C min) yog lub ntsiab lus ntawm Alloy 20 - nws tiv thaiv vuam rhiab heev thiab ua kom cov cua sov- cuam tshuam cheeb tsam (HAZ) khaws tag nrho corrosion tsis kam tom qab fabrication vuam.
Alloy 20 excels hauv 10-80% H2SO4 ntawm qhov kub txog li 80C. Nws tsis pom zoo rau dilute acid (<10%) at elevated temperatures (where 316L may suffice) or concentrated acid (>95%) ntawm qhov kub siab (qhov twg Hastelloy B-3 los yog titanium yuav tsum tau).
For intermediate concentrations (50-80% H2SO4) at temperatures >80C, hloov mus rau Hastelloy G-30 (UNS N06030) lossis Sanicro 28 (UNS N08028) - cov hlau no muaj 2-3x siab dua corrosion dua li Alloy 20 nyob rau hauv thaj tsam hnyav tshaj plaws.
Cov "Alloy 20Cb-3" variant (nrog 0.5-1.0% Si) muab kev tiv thaiv zoo rau sulfuric acid ntawm nruab nrab concentrations thiab siab kub piv rau cov qauv Alloy 20.
Taw qhia rau Alloy 20 hauv Sulfuric Acid Service
Sulfuric acid (H₂SO₄) yog cov khoom lag luam dav dav tshaj plaws hauv ntiaj teb, nrog rau kev tsim khoom thoob ntiaj teb ntau tshaj 260 lab metric tons hauv ib xyoos. Nws yog siv nyob rau hauv txhua qhov kev lag luam: chiv tsim (phosphate ua), roj av refining (alkylation), hlau pickling thiab hydrometallurgical leaching, tshuaj synthesis (tsim hydrochloric acid, phosphoric acid, thiab titanium dioxide), kev kho dej, thiab explosives manufacturing.
Qhov kev sib tw nrog kev pabcuam sulfuric acid yog tias nws tsis yog ib puag ncig ib puag ncig - nws yog ib qho spectrum ntawm cov xwm txheej uas hloov pauv loj nrog cov concentration thiab kub. Qhov no yog tib txoj hauv kev tseem ceeb tshaj plaws hauv kev xaiv cov khoom siv sulfuric acid: tsis muaj cov khoom siv thoob ntiaj teb uas ua tau zoo thoob plaws txhua qhov ntau thiab qhov kub thiab txias.
Alloy 20 (UNS N08020, tseem hu ua Carpenter 20, ASTM Qib CN-7M hauv daim ntawv cam khwb cia, thiab muag raws li cov npe lag luam suav nrog Marca 20, ATI 20, thiab Nicrill 20) tau tsim tshwj xeeb los daws qhov kev sib tw corrosion hauv nruab nrab - concentration ntau ntawm sulfuric acid - kwv yees li 8% H₂SO₄ qhov twg feem ntau austenitic stainless hlau tsis ua puas tsuaj.Cov hlau chemistry yog txhob txwm sib npaug los muab:
Niobium (Nb) stabilization:Cov pa roj carbon yog txhob txwm khaws cia qis dua 0.07% thiab niobium ntxiv ntawm 8 npaug ntawm cov ntsiab lus carbon (Nb Ntau dua lossis sib npaug ntawm 8 x C) los tsim NbC (niobium carbide) thaum lub sij hawm solidification. Qhov no tiv thaiv Cr₂₃C₆ chromium carbide nag lossis daus ntawm cov ciam teb thaum lub sij hawm vuam los yog siab - qhov kev pab kub, uas yuav txwv tsis pub chromium los ntawm cov cheeb tsam uas nyob ib sab thiab ua rau intergranular nres (IGA). Qhov no yog qhov txhais cov yam ntxwv ntawm Alloy 20 piv rau tus qauv austenitic stainless hlau.
Copper (Cu) ntxiv:3.0-4.0% tooj liab muab tshwj xeeb tsis kam rau sulfuric acid los ntawm kev tsim ib tug passive tooj liab sulfate nto zaj duab xis uas ruaj khov nyob rau hauv txo (tsawg-oxygen) acid tej yam kev mob. Tooj liab yog qhov laj thawj tseem ceeb ntawm Alloy 20 outperforms 316L hauv sulfuric acid.
Molybdenum (Mo) ntxiv:2.0-3.0% molybdenum txhim kho kev tiv thaiv rau pitting thiab crevice corrosion nyob rau hauv cov kua qaub sib tov uas muaj chloride (Cl-) ions - ib txwm muaj nyob rau hauv mining leach solutions thiab pickling da dej.
Chromium (Cr) cov ntsiab lus:19.0-21.0% chromium muab kev tiv thaiv corrosion thiab passivity nyob rau hauv oxidising tej yam kev mob. Cov ntsiab lus chromium qis dua 316L (16%) ntawm qhov hnyav tab sis yog siv tag nrho vim niobium tiv thaiv nws cov depletion.
Nickel (Ni) cov ntsiab lus:32.0-38.0% npib tsib xee stabilizes lub austenitic (lub ntsej muag-centred cubic, FCC) microstructure, muab chloride kev nyuaj siab corrosion cracking (SCC), thiab tswj ductility thiab toughness nyob rau hauv tag nrho cov kub ntau yam ntawm cryogenic mus 450C.
Cov ntsiab lus tseeb:Alloy 20 yog cov khoom siv tseem ceeb rau kev pabcuam sulfuric acid hauv 10-80% concentration ntau ntawm qhov kub txog li 80℃. Nws niobium-stabilized chemistry (Nb Ntau dua los yog sib npaug ntawm 8 × C) yog qhov kev paub txog kev tsim vaj tsev - nws tiv thaiv kev sib txhuam rhiab heev, tshem tawm cov kev sib txhuam ntawm cov hniav hauv HAZ, thiab ua kom cov khoom siv vuam ua kom muaj kev tiv thaiv corrosion sib npaug ntawm cov hlau puag. Tsis muaj stainless hlau tuaj yeem muab qhov kev lees paub no.
Chemical Composition thiab Mechanical Properties
Chemical Composition los ntawm Qib Variant
Table 1: Tshuaj muaj pes tsawg leeg ntawm Alloy 20 thiab Variants - Wrought Sheet/Plate (Weight %)
| Element | Alloy 20 (N08020) | Alloy 20Cb-3 (N08020, Si-modified) | Alloy 20 Mod. (N08020, qis Si) | Alloy 20 Cast (CN-7M) | Qhov tseem ceeb ntawm Txhua Yam |
| Nickel (Ni) | 32.0-38.0 (nrog rau Co) | 32.0-38.0 (nrog rau Co) | 32.0-38.0 | 38.0-44.0 | Stabilizes austenitic FCC qauv; tiv thaiv chloride SCC; Ni muab kev tiv thaiv kom txo cov kua qaub; siab dua Ni nyob rau hauv daim ntawv cam khwb cia rau txhim kho sulfuric acid kuj |
| Chromium (Cr) | 19.0-21.0 | 19.0-21.0 | 19.0-21.0 | 19.0-22.0 | Muab passivity thiab dav corrosion kuj; lub ntsiab tseem ceeb rau oxidizing tej yam kev mob; Cr yuav tsum nyob twj ywm hauv cov kua (tsis yog precipitated li Cr23C6) los muab kev tiv thaiv corrosion |
| Hlau (Fe) | Sib npaug (~35) | Sib npaug (~35) | Sib npaug (~35) | Sib npaug (~30-34) | Base matrix element; Fe cov ntsiab lus yog sib npaug los ntawm Ni thiab Cr; muab cov qauv muaj zog thiab txo cov nqi raw khoom vs cov nickel alloys ntshiab |
| Copper (Cu) | 3.0-4.0 | 3.0-4.0 | 3.0-4.0 | 3.0-4.0 | PRIMARY anti-corrosion element for sulfuric acid; forms passive Cu2+ surface film in reducing conditions; 3.5% is the optimum for 10-80% H2SO4; excess Cu (>5%) txo qhov kub - ua haujlwm tau |
| Molybdenum (hli) | 2.0-3.0 | 2.0-3.0 | 2.0-3.0 | 2.0-3.0 | Txhim khu kev tiv thaiv pitting thiab crevice corrosion; tseem ceeb nyob rau hauv chloride- bearing pickling thiab mining leach daws; Mo txhim kho passivity hauv oxidising acid sib tov |
| Niobium (Nb) | 8 x C min (typ. 0.5-1.0) | 8 x C min (typ. 0.5-1.0) | 8 x C min (typ. 0.5-1.0) | 8x c miv | CEEB TOOM: Nb khi tag nrho cov pa roj carbon li NbC (niobium carbide), tiv thaiv Cr23C6 nag lossis daus ntawm cov ciam teb; tshem tawm cov vuam rhiab heev thiab HAZ intergranular nres; tsis muaj Nb, Alloy 20 yuav coj zoo li tsis ruaj khov 316L hauv HAZ |
| Cov pa roj carbon (C) | 0.07 max | 0.07 max | 0.04 max (tsawg-carbon variant) | 0.07 max | Tswj rau 0.07% max; Nb / C piv ntawm 8: 1 ua kom tag nrho C yog sequestered li NbC; qis- carbon variant (0.02-0.04%) muaj rau kev txhim kho IGC tsis kam nyob rau hauv cov kua qaub tshaj plaws |
| Manganese (Mn) | 2.0 max | 2.0 max | 2.0 max | 1.5 max | Deoxidizer thaum melting; txhim kho kub- ua haujlwm tau zoo; khi nrog S los tsim MnS suav nrog (tab sis S yog twb tswj tau qis heev hauv Alloy 20) |
| Silicon (Si) | 1.0 max | 0.5-1.0 (ntxiv) | 0.3 max (tsawg) | 1.0 max | Cb-3 variant txhob txwm ntxiv Si (0.5-1.0%) los txhim kho corrosion kuj nyob rau hauv nruab nrab H2SO4 concentrations (50-80%) ntawm siab kub; low-Si variant rau kev txhim kho toughness hauv kev pabcuam cryogenic |
| Sulfur (S) | 0.035 max | 0.035 max | 0.035 max | 0.035 max | Tswj kom qis qis los tiv thaiv MnS stringers uas ua raws li qhov chaw pib rau crevice thiab pitting corrosion hauv acid; Tsawg S txhim kho kev txhim kho corrosion tag nrho |
| Phosphorus (P) | 0.045 max | 0.045 max | 0.045 max | 0.045 max | Controlled; high P (>0.04%) accelerates intergranular nres hauv Alloy 20 hauv oxidising acid ib puag ncig |
Tau qhov twg los: ASTM B463-23: Standard Specification rau UNS N08020, UNS N08026, UNS N08024, thiab UNS N08926 Phaj, Sheet, thiab Sawb; ASME SB-463; SAE AMS 5550 (Alloy 20 Sheet thiab Sawb); Special Metals Corporation "Alloy 20" Tshaj tawm SMC-064; Rolled Alloys Alloy 20 Cov ntaub ntawv qhia kev; Cabot Corporation "Alloy 20 Product Data" 2023
Table 2: Mechanical and Physical Properties of Alloy 20 (UNS N08020) - Wrought and Cast Forms
| Khoom | Annealed (Daim ntawv / phaj) | Kev daws -Kho (Plate) | Cam khwb cia CN-7M | Sau ntawv |
| Tensile zog, UTS (MPa) | 550-690 | 550-690 | 530-690 | Yam tsawg kawg nkaus: 515 MPa rau ASTM B463; cam khwb cia yam tsawg kawg nkaus: 450 MPa |
| Yield zog, 0.2% offset (MPa) | 240-345 | 240-345 | 240-310 | Yam tsawg kawg nkaus: 241 MPa rau ASTM B463 |
| Elongation hauv 50 mm (%) | 25-50 | 25-50 | 25-35 | Yam tsawg kawg nkaus: 30% rau ASTM B463 rau daim ntawv |
| Hardness (Rockwell B) | B 75-88 | B 75-88 | B 75-88 | Yam khoom muaj nqis; tsis yog kev yuav khoom |
| Modulus ntawm elasticity (GPa) | 200 | 200 | 200 | Ntawm 20C; txo mus rau 175 GPa ntawm 400C |
| Qhov ceev (g / cm3) | 8.14 | 8.14 | 8.14 | Me ntsis qis dua 316L (8.00) vim siab dua Ni thiab Cu |
| Melting ntau (C) | 1350-1400 | 1350-1400 | 1350-1400 | Solidus: 1350C; dej kub: 1400C |
| Thermal conductivity (W / m·K ntawm 100C) | 13.5 | 13.5 | 13.5 | Tsawg dua 316L (16 W / m·K); cuam tshuam rau kev tsim hluav taws xob hloov hluav taws xob |
| Coefficient ntawm thermal expansion (um / m·C, 20-200C) | 14.7 | 14.7 | 14.7 | Zoo ib yam li austenitic stainless; yuav tsum suav rau thermal expansion hauv nkoj tsim |
| Hluav taws xob tiv taus (µΩ·cm ntawm 20C) | 108 | 108 | 108 | Siab dua 316L (75 µΩ·cm) vim Ni cov ntsiab lus siab dua |
| Sib nqus permeability | <1.02 (essentially non-magnetic) | <1.02 | <1.02 | Austenitic qauv yog ruaj khov; tsis muaj ferrite-induced magnetism |
| Charpy V-qhov cuam tshuam (J ntawm 20C) | 100-160 | 100-160 | 80-130 | Zoo heev toughness; haum rau cryogenic thiab dynamic load daim ntaub ntawv |
| Charpy V-qhov cuam tshuam (J ntawm -196C) | 70-120 | 70-120 | 60-100 | Khaws zoo toughness ntawm kua nitrogen kub |
| PREN (Pitting Resistance Eq. Number) | 28-33* | 28-33* | 28-33* | Cr + 3.3(Mo + 0.5W) + 16N; PREN 28-33 yog nruab nrab vs 316L (PREN 24-28) tab sis Cu zaj duab xis muab kev ua tau zoo H2SO4 |
| Tus nqi txheeb ze (x 316L phaj) | 5-7x | 5-7x | - | Raws li 2024 tus nqi lag luam thoob ntiaj teb; raw Ni thiab Cu nqe volatility cuam tshuam rau Alloy 20 nqi |
Tau qhov twg los: ASTM B463-23; ASME SB-463; SAE AMS 5550; Special Metals Corporation "Alloy 20" Tshaj tawm SMC-064; Rolled Alloys Technical Data Sheet; Cabot Corporation Cov Khoom Siv Khoom 2023; *PREN=Cr + 3.3(Mo + 0.5W) + 16N - PREN tsis yog thawj qhov taw qhia rau H2SO4 tsis kam; Cu cov ntsiab lus yog qhov tseem ceeb tshaj plaws
Cov ntsiab lus tseeb:Alloy 20 yog ib qho niobium-stabilized 33% Ni-Cr-Fe alloy nrog 3.5% Cu thiab 2.5% Mo - tsis yog nickel alloy tiag tiag hauv tsev neeg Hastelloy/Inconel. Lub Nb Ntau dua lossis sib npaug rau 8 × C qhov yuav tsum tau ua yog daim ntawv cog lus engineering uas ua rau Alloy 20 weldable yam tsis muaj kev xav. Cov cam khwb cia sib txawv CN-7M muaj ntau dua Ni (38-44%) thiab qis dua Fe rau kev txhim kho sulfuric acid tsis kam, tab sis qis dua cov khoom siv kho tshuab.
Vim li cas Sulfuric Acid yog Corrosion Npau suav phem
Kev nkag siab yog vim li cas sulfuric acid tawm tsam hlau yuav tsum paub tias cov kua qaub muaj nyob rau hauv ob lub ntsiab lus tshuaj, txhua tus tsim cov txheej txheem sib txawv:
Qhov txo qis (0-85% H₂SO₄)
Ntawm cov concentrations qis dua li ntawm 85% H₂SO₄, cov kua qaub ua rau txo cov kua qaub. Cov hom tseem ceeb yog H⁺ (hydrogen ions) thiab HSO₄⁻ (bisulfate ions). Cov hlau tawg tshwm sim los ntawm cov tshuaj tiv thaiv electrochemical qhov twg cov hlau yog oxidized thiab hydrogen gas yog hloov zuj zus: Fe + H₂SO₄ → FeSO₄ + H₂↑ (kev xeb dav dav) Hauv cheeb tsam no, tus nqi corrosion yog tswj los ntawm tus nqi ntawm hydrogen evolution.
Cov kua qaub yog thermally ruaj khov - nws tsis decompose los yog tsim oxidising hom. Qhov no yog thaj chaw uas tooj liab, Monel 400, thiab Alloy 20 ua tau zoo vim tias lawv tsim cov yeeb yaj kiab tsis muaj zog tiv thaiv kom txo tau cov xwm txheej. Austenitic stainless hlau (304L, 316L) ua haujlwm tsis zoo ntawm no vim tias lawv cov chromium oxide passive zaj duab xis tsis ruaj khov thaum tsis muaj oxidizing hom.
The Oxidising Zone (>85% H₂SO₄)
At concentrations above 85% H₂SO₄, the acid undergoes thermal decomposition to produce sulfur trioxide (SO₃), water, and oxygen - creating strongly oxidising conditions:2H₂SO₄ → 2SO₂ + O₂ + 2H₂O (thermal decomposition at >250℃) H₂SO₄ → SO₃ + H₂O (vapor theem ntawm qhov kub thiab txias Nyob rau hauv cheeb tsam no, SO₃ thiab O₂ tsim muaj zog oxidisers.
Stainless hlau (tshwj xeeb tshaj yog 316L nrog nws cov molybdenum ntxiv) ua tau zoo dua ntawm no vim tias lawv cov chromium oxide zaj duab xis yog ruaj khov los ntawm oxidising tej yam kev mob.
Nickel alloys with high copper content (Alloy 20, Monel) perform POORLY because copper is oxidatively attacked - copper sulfate forms on the surface and spalls off, providing no protective barrier. For concentrated (>95%) kub sulfuric acid, tantalum, iav -lined carbon steel, los yog cam khwb cia hlau feem ntau yuav tsum tau.
Thaj Chaw Hloov Pauv (50-85% H₂SO₄): Thaj Chaw Txaus Ntshai Tshaj Plaws
Cov concentration ntau ntawm 50-85% H₂SO₄ ntawm qhov kub thiab txias yog universally lees paub tias yog qhov kev nruj tshaj plaws corrosion ib puag ncig rau cov pa alloys. Hauv cheeb tsam no:
· Cov kua qaub yog concentrated txaus rau oxidising (SO₃ pib tsim saum toj no 85%, tab sis sub-stoichiometric SO₃ hom muaj nyob rau hauv 50-85% ntau yam) · Kub yog feem ntau nce siab (60-150℃hauv feem ntau cov txheej txheem)
· Cov khoom siv hlau sulfate corrosion (FeSO₄) uas ua rau cov hlau thiab stainless hlau nto yog soluble - nws tsis ua raws thiab tsis tiv thaiv
· Kev cuam tshuam nrawm yog qhov tseem ceeb: kev kub ntxhov ntawm cov khoom siv, cov twj tso kua mis, thiab cov phaj hauv qhov chaw ua kom nrawm nrawm heev -corrosion
· Chloride ions (los ntawm cov khoom siv raw, dej txias, lossis cov txheej txheem ntxiv) feem ntau tshwm sim, sib txuas nrog cov oxidising acid los tsim ib txhij pitting thiab crevice corrosion.
Table 3: Sulfuric Acid Concentration Zones - Corrosion Character, Best Materials, and Temperature Limits for each Range
| H2SO4 Concentration | Corrosion Cim | Oxidising vs Txo | Qhov ntsuas kub tseem ceeb | Cov ntaub ntawv zoo tshaj plaws | Cov ntaub ntawv uas yuav tsum zam |
| 0-10% (dilute acid) | Txo; H+ tseem ceeb | Ntshiab txo | >60℃accelerates dav corrosion | 316L (txog 60 degree); Alloy 904L (txog 80 degree); Alloy 20 (txog 100 degree) | Carbon steel (ceev dav dav corrosion); cam khwb cia hlau (tsis pub tshaj 10% ntawm ib qho temp) |
| 10-50% (intermediate, dilute kawg) | Txo kom me ntsis oxidising; H+ and HSO4- | Txo me ntsis; pib qhia oxidation saum 30% | >50℃nrawm nrawm nrawm ntawm SS | Alloy 20 (txog 80 degree); 316L tau txais yog Cl-<50 ppm and T<50°C | 304L tsis siab tshaj 40 degree; carbon steel txwv rau<10% at room temp only |
| 50-85% (intermediate, concentrated kawg) | ZOO TSHAJ PLAWS ZONE; sib xyaw txo / oxidizing; sub-stoichiometric SO3 hom tam sim no | Sib tov; feem ntau unpredictable | >80℃ua rau muaj kev tawm tsam sai rau tag nrho SS alloys | Alloy 20Cb-3 (up to 90°C); Hastelloy G-30 or Sanicro 28 (up to 120°C); Tantalum or SiC for >130 degree | Standard Alloy 20 txwv rau 80℃max; 316L / 904L FAIL siab dua 50℃hauv qhov ntau |
| 85-98% (concentrated acid) | Muaj zog oxidizing; SO3 thiab O2 los ntawm thermal decomposition | Muaj zog oxidizing siab tshaj 85% | >120°C requires special materials; >200℃nruj heev | 316L / 310S (txog 120 degree); tantalum, iav -lined carbon steel (txog 300 degree) | Alloy 20 thiab Monel: tooj liab yog oxidatively tawm tsam; Tsis pom zoo tshaj 60℃hauv cov kua qaub |
| >98% (Fuming acid, oleum) | Super{0}}oxidising; pub dawb SO3 gas | oxidizing heev | Txhua qhov kub siab tshaj ambient yog txhoj puab heev | Tantalum (only practical material for >98% kub acid); borosilicate iav; cam khwb cia hlau (txog 240℃rau 93% acid) | Alloy 20: NYIAJ TXIAV TXIM NYIAJ; tooj liab thiab npib tsib xee oxidized |
| Vapor chaw / condensing acid | Qhov siab tshaj plaws corrosion: condensing acid droplets cuam tshuam qhov chaw nrog tag nrho cov cua sov ntawm condensation | Sib tov; phem tshaj ntawm condensation interface | Txhua qhov kub siab tshaj ambient yog txhoj puab heev | Alloy 20 lossis Hastelloy G-30 rau tag nrho qhov chaw vapor; HRS plhaub-sab yuav tsum yog Alloy 20 lossis Hastelloy | Carbon steel thiab cam khwb cia hlau tsis nyob rau hauv vapor qhov chaw siab tshaj 40 degree; 316L tsis txaus siab tshaj 10% condensate |
Source: ASM Handbook Vol. 13C: Corrosion - Ib puag ncig thiab kev lag luam (ASM International, 2006); NACE Publication 34103: Cov Lus Qhia rau Kev Xaiv Cov Khoom Siv rau Sulfuric Acid; ASTM G1-17: Tus Qauv Cwj Pwm rau Kev Npaj, Tu, thiab Kev Ntsuas Kev Ntsuas Corrosion Test; Cov ntaub ntawv tseem ceeb ntawm Corrosion hauv Sulfuric Acid, Avestor / IIT Research Institute; Jones, DA, Cov Ntsiab Cai thiab Kev Tiv Thaiv Corrosion (3rd ed., Prentice Hall, 1996); Cronin, J. thiab Sridhar, N., "Corrosion of Nickel Alloys in Sulfuric Acid," NACE Corrosion 2000, Ntawv 00247
Cov ntsiab lus tseeb:The 50-85% H₂SO₄ concentration range at temperatures above 80°C is the most aggressive corrosion environment for conventional engineering alloys. Standard Alloy 20 reaches its performance limit in this zone at approximately 80°C - beyond this, Alloy 20Cb-3, Hastelloy G-30, or Sanicro 28 must be specified. For concentrated acid (>85%) ntawm qhov kub siab, Alloy 20 yog contraindicated vim nws cov ntsiab lus tooj liab yog oxidatively tawm tsam - 316L los yog Tantalum yog lawm.
Alloy 20 Corrosion Performance in Sulfuric Acid
Cov kab nkhaus isocorrosion hauv qab no sawv cev rau qhov kub siab tshaj plaws ntawm Alloy 20 tswj qhov corrosion qis dua 0.5 hli / xyoo (0.020 ipy) hauv quiescent, aerated sulfuric acid. Cov txiaj ntsig no tau muab los ntawm kev sim ntsuas qhov ntsuas dej rau hauv ASTM G31 (72-teev raug) thiab yuav tsum suav tias yog kev saib xyuas rau cov dej ntws los yog muaj kev kub ntxhov.
Table 4: Isocorrosion Curves rau Alloy 20 thiab Reference Alloys hauv Sulfuric Acid - Qhov Kev Pab Cuam Tshaj Plaws rau Corrosion Rate<0.5 mm/year (Aerated, Quiescent Conditions)
| H2SO4 concentration (%) | Max Temp rau<0.5 mm/yr (Alloy 20) | Max Temp rau<0.5 mm/yr (Alloy 20Cb-3) | Max Temp rau<0.5 mm/yr (316L) | Max Temp rau<0.5 mm/yr (904L) | Cov lus ceeb toom ntawm Alloy 20 Performance |
| 0.5 (zoo heev) | 90 degree | 90 degree | 60 degree | 80 degree | Alloy 20 muab kev ua tau zoo tshaj plaws hauv cov kua qaub diluted ntawm qhov kub siab |
| 1.0 | 90 degree | 90 degree | 60 degree | 80 degree | Zoo ib yam li 0.5%; 316L thiab 904L tsim nyog rau<40°C |
| 5.0 | 90 degree | 90 degree | 50 degree | 80 degree | 316L pib poob siab tshaj 50℃vim Cl- hauv acid |
| 10.0 | 85 degree | 90 degree | 40 degree | 80 degree | Alloy 20 tuav<0.5 mm/yr at 85°C; 316L marginal at 40°C |
| 20.0 | 80 degree | 90 degree | 35 degree | 75 degree | Alloy 20 yog txhim khu kev qha rau 80 degree; 316L FAIL saum 35 degree |
| 30.0 | 80 degree | 85 degree | 30 degree | 70 degree | Core daim ntawv thov cheeb tsam rau Alloy 20 |
| 40.0 | 80 degree | 85 degree | FAIL (>30 degree) | 70 degree | 316L: FAIL hauv 40% H2SO4 ntawm txhua qhov kub siab tshaj 30 degree |
| 50.0 | 75 degree | 85 degree | FAIL | 65 degree | Most aggressive zone begins: Alloy 20 must be Cb-3 for >75 degree |
| 60.0 | 70 degree | 80 degree | FAIL | 60 degree | Standard Alloy 20 reaches its limit; Cb-3 required for >75 degree |
| 70.0 | 65 degree | 75 degree | FAIL | 55 degree | Hloov mus rau oxidising cheeb tsam: Hastelloy G-30 nyiam tshaj 80 degree |
| 78.0 (cov roj teeb acid) | 60 degree | 70 degree | FAIL | 50 degree | 78% H2SO4 yog daim ntawv thov kev lag luam loj; Alloy 20 dav siv rau roj teeb phaj pluaj |
| 80.0 | 55 degree | 70 degree | FAIL | 45 degree | Sab saum toj ntawm qhov txo qis: Hastelloy G-30 pom zoo siab tshaj 80℃kev pabcuam |
| 90.0 (kwv yees) | 30 degree | 40 degree | 60 degree | 45 degree | Alloy 20 Tsis pom zoo siab tshaj 40 degree; 316L nyiam nyob rau hauv concentrated acid |
| 96.0 (cov roj ntawm vitriol) | 25 degree | 25 degree | 80 degree | 40 degree | Alloy 20 tooj liab yog oxidatively tawm tsam; 316L yog qhov kev xaiv raug rau cov kua qaub siab tshaj 80 degree |
| 98.0 (Fuming ntau) | TSIS MUAJ | TSIS MUAJ | 90 degree | 30 degree | Alloy 20 thiab 904L contraindicated; tantalum xav tau rau kub fuming acid |
Source: Special Metals Corporation "Alloy 20" Publication SMC-064 (Isocorrosion curves, 0.5 mm/xyoo kab); Rolled Alloys Alloy 20 Daim Ntawv Qhia Cov Ntaub Ntawv; Cabot Corporation "Corrosion Resistance of Nickel-Copper and Nickel-Chromium-Iron Alloys in Sulfuric Acid" Tshaj tawm; NACE Tshaj tawm 34103; ASTM G31-21a: Cov Qauv Txuj Ci rau Kev Ntsuas Kev Ntsuas Kev Ntsuas Cov Hlau; Jones, DA thiab Sridhar, N., "Kev kwv yees ntawm Corrosion hauv Sulfuric Acid Ib puag ncig," NACE Corrosion 2001; Corrosion Data Survey - Metals Section (NACE, 2015 ib tsab); Cov ntaub ntawv siv tau los ntawm cov ntaub ntawv txheeb xyuas cov phooj ywg: Heaney, MD et al., "Corrosion of Nickel Alloys in Sulfuric Acid," NACE International, 2000
Table 5: Flow Velocity Effects on Alloy 20 Corrosion Rate in Sulfuric Acid - Quiescent vs Turbulent Conditions
| Acid Concentration | Flow condition | Kub (degree) | Alloy 20 Corrosion Rate (mm / xyoo) | Pass/Fail (<0.5 mm/yr) | Qhov tseem ceeb |
| 10% H2SO4 | Quiescent (tsis muaj ntws) | 60 | 0.08 | PASS | Base rooj; zoo nyob rau hauv muaj peev xwm |
| 10% H2SO4 | Tawg (2 m / s) | 60 | 0.15 | PASS | Yooj yim nce los ntawm kev yaig; tseem txais tau |
| 30% H2SO4 | Tsis tshua muaj | 60 | 0.12 | PASS | Core acid concentration ntau |
| 30% H2SO4 | Tawg (2 m / s) | 60 | 0.25 | PASS | Cov nyhuv ntws: ~ 2x vs quiescent; tseem txais tau |
| 50% H2SO4 | Tsis tshua muaj | 70 | 0.18 | PASS | Kev hloov chaw pib; txoj kev txwv |
| 50% H2SO4 | Tawg (2 m / s) | 70 | 0.45 | PASS (marginal) | 2.5x nce; ntawm qhov pib ntawm kev lees paub |
| 50% H2SO4 | Tawg (4 m / s) | 70 | 0.80 | FAIL | Siab - nrawm yaig- xeb: Alloy 20 tsis tuaj yeem lees txais siab dua 3 m / s |
| 70% H2SO4 | Tsis tshua muaj | 65 | 0.30 | PASS | Sab saum toj kev ua haujlwm cheeb tsam rau tus qauv Alloy 20 |
| 70% H2SO4 | Tawg (2 m / s) | 65 | 0.65 | FAIL (marginal) | Cov nyhuv nrawm yog qhov hnyav hauv siab -concentration acid |
| 78% H2SO4 | Tsis tshua muaj | 60 | 0.25 | PASS | Roj teeb acid concentration; loj Alloy 20 daim ntawv thov |
| 78% H2SO4 | Tsis tshua muaj | 80 | 0.48 | PASS (marginal) | Alloy 20 ntawm nws qhov txwv rau 78% acid ntawm 80 degree |
| 90% H2SO4 | Tsis tshua muaj | 60 | 0.90 | FAIL | Alloy 20 tooj liab tawm tsam oxidatively; 316L xav |
| 96% H2SO4 | Tsis tshua muaj | 80 | 1.50 | FAIL | Concentrated acid: Alloy 20 TSIS pom zoo siab tshaj 40 degree |
Source: ASM Phau Ntawv Qhia Vol. 13C (Corrosion: Ib puag ncig thiab kev lag luam); NACE Tshaj Tawm 34103: Cov Lus Qhia rau Kev Xaiv Cov Khoom Siv Hauv Kev Pabcuam Sulfuric Acid; EPRI NP-2813: Cov Khoom Siv Ua Haujlwm hauv Sulfuric Acid Ib puag ncig; Baboian, R. (ed.), Corrosion Tests and Standards: Application and Interpretation (2nd ed., ASTM, 2005); flow velocity multiplier raws li EPRI cov ntaub ntawv qhia 1.5-2.5x corrosion tus nqi nce ntawm 2 m / s vs quiescent; turbulence data validated tiv thaiv Schweitzer, PA, Corrosion Resistance Tables (6th ed., CRC Press, 2011)
Cov ntsiab lus tseeb:Alloy 20 is the definitive material for 10-80% H₂SO₄ at temperatures up to 80°C in quiescent conditions. In turbulent flow (>2 m / s) nyob rau hauv 50-80% concentration ntau, tus nqi corrosion tuaj yeem nce 2-3x - hem kom tshaj 0.5 mm / xyoo. Rau cov ntawv thov siab tshaj plaws hauv cov kua qaub nruab nrab, qhia meej Hastelloy G-30 lossis siv cov qauv kev txo qis (txoj kab uas hla loj dua, ntws ncaj).
Alloy 20 vs Competing Materials
Xaiv cov khoom raug rau sulfuric acid yuav tsum tau muab piv rau Alloy 20 tiv thaiv tag nrho spectrum ntawm lwm txoj kev - los ntawm carbon steel mus rau kab txawv tantalum. Cov lus hauv qab no muab kev sib piv sib piv thoob plaws chemistry, kev ua tau zoo, nqi, thiab fabricability.
Table 6: Kev sib piv ntawm Alloy 20 vs Competing Materials in Sulfuric Acid Service
| Khoom / Parameter | Alloy 20 (N08020) | 316L Stainless hlau | 904L Stainless hlau (N08904) | Hastelloy G-30 (N06030) | Sanicro 28 (N08028) Cov. | Monel 400 (N04400) |
| Primary alloy tsev neeg | Ni-Cr-Fe-Cu-Mo-Nb (stabilized austenitic) | Fe-Cr-Ni-Mo (unstabilized austenitic) | Fe-Cr-Ni-Mo-Cu (austenitic super-SS) | Ni-Cr-Mo-Cu-W (Hastelloy G tsev neeg) | Fe-Ni-Cr-Mo-Cu (siab-alloy SS) | Ni-Cu binary (khoom-kev daws teeb meem) |
| Nickel cov ntsiab lus (%) | 32-38 | 10-12 | 23-28 | 43-53 | 30-32 | 63 nqi |
| Cov ntsiab lus tooj liab (%) | 3.0-4.0 | <1.0 | 1.0-2.0 | 1.5-2.5 | 0.8-1.5 | 28-34 |
| Molybdenum cov ntsiab lus (%) | 2.0-3.0 | 2.0-3.0 | 4.0-5.0 | 5.5-7.0 | 1.0-1.5 | - |
| Niobium (Nb ntau dua lossis sib npaug rau 8 × C) | YOG - ruaj khov | TSIS MUAJ - tsis ruaj khov | TSIS MUAJ - stabilized (L) | TSIS MUAJ - Hastelloys siv W/Cb | TSIS MUAJ - qis-carbon L- qib | |
| Max temp rau<0.5 mm/yr in 50% H2SO4 | 75-80 degree | FAIL at >30 degree | FAIL at >50 degree | 110-120 degree | 85-95 degree | 50-60 degree |
| Max temp rau<0.5 mm/yr in 78% H2SO4 | 60-70 degree | FAIL | FAIL | 95-100 degree | 75-80 degree | 40-50 degree |
| Max temp rau<0.5 mm/yr in 10% H2SO4 | 90 degree | 60 degree | 80 degree | 100 degree | 85 degree | 90 degree |
| Chloride SCC kuj | Zoo (33% Ni) | Tsis zoo (10% Ni) | Nruab nrab (23% Ni) | Zoo heev (43% Ni) | Nruab nrab (30% Ni) | Zoo heev (63% Ni - tiv thaiv) |
| Weldability (GTAW/MIG) | Zoo heev nrog ER320LR lossis ERNiCrMo-3 muab tub lim | Standard 316L muab tub lim | 316LMod lossis ERNiCrMo-3 muab tub lim | ERNiCrMo-3 yuav tsum tau muab tub lim | 316LMod los yog ERNiCrMo-3 | ERNiCu-7 muab tub lim; no PWHT |
| Max nruam kev pab temp (degree) | 450 | 425 | 400 | 500 | 400 | 400 |
| Tus nqi txheeb ze (vs 316L=1x) | 5-7x | 1 x (lub hauv paus) | 3-4x | 10-15x | 5-6x | 3-4x |
| Muaj (daim ntawv / phaj) | Muaj dav thoob ntiaj teb | Standard cov khoom | Muaj dav | Txwv tsis pub dhau - 4-8 lub lim tiam | Muaj nyob nruab nrab | Muaj dav |
| NACE MR0175 / ISO 15156 | YOG (nrog kev txwv) | Txwv rau tej yam kev mob | YOG | YOG (nrog kev txwv) | YOG | YOG |
| ASTM tus qauv | B463 / SB-463 IB | A240/SA-240 | B625 / SWB-625 | B582 / SWB-582 | B625 / SWB-625 | B127 / SWB-127 |
| PREN | 28-33 | 24-28 | 34-38 | 42-52 | 24-28 | 29-32 (tsis yog Mo-based) |
Tau qhov twg los: ASTM B463-23 (Alloy 20); ASTM A240-22 (316L); ASTM B625-22 (904L thiab Sanicro 28); ASTM B582-23 (Hastelloy G-30); ASTM B127-23 (Monel 400); Cov Hlau Tshwj Xeeb SMC-064 (Alloy 20); Haynes International H-2000 (Hastelloy G-30); Rolled Alloys Sanicro 28 Daim Ntawv Teev Npe; NACE MR0175/ISO 15156-3:2015; Schweitzer, PA, Corrosion Resistance Tables (6th ed., CRC Xovxwm, 2011)
Table 7: Cov Khoom Xaiv Kev Txiav Txim Matrix - Sulfuric Acid Service Scenarios vs Recommended Alloys
| Scenario | Pom zoo cov khoom tseem ceeb | Alternative (yog tias qhov tseem ceeb tsis muaj) | Cia siab tias Corrosion Rate | Kev ntseeg siab |
| Dilute acid (0.5-10%) ntawm T<60°C, low Cl- | 316L stainless hlau | 904L (if T >60 degree) | 0.05-0.15 hli / xyoo | HIGH - 316L zoo- pov thawj hauv dilute H2SO4 |
| Dilute acid (0.5-10%) ntawm T 60-90 degree, qis Cl- | Alloy 20 | 904L | 0.05-0.20 hli / xyoo | HIGH - Alloy 20 zoo- pov thawj |
| Dilute acid with Cl- >200 ppm (pickling, mining) | Alloy 904L los yog Alloy 20 | 316L nrog roj hmab hauv ob sab phlu | 0.10-0.30 hli / xyoo | MODERATE - Cl- nyuaj rau txhua qhov kev xaiv |
| Intermediate acid 10-50% ntawm T<80°C | Alloy 20 (tus qauv) | Alloy 20Cb-3 (if T >75 degree) | 0.05-0.25 hli / xyoo | HIGH - core Alloy 20 daim ntawv thov |
| Intermediate acid 50-80% ntawm T 80-100 degree | Alloy 20Cb-3 los yog Hastelloy G-30 | Sanicro 28 (rau<95°C) | 0.10-0.40 hli / xyoo | HIGH - Cb-3 thiab G-30 ua pov thawj hauv qhov no |
| Intermediate acid 50-80% ntawm T 100-130 degree | Hastelloy G-30 | Sanicro 28 (marginal at T>110 degree) | 0.15-0.50 hli / xyoo | MODERATE - G-30 nyiam; paub meej nrog kev sim ntsuas |
| Concentrated acid 85-98% ntawm T<80°C | 316L lossis 310S stainless hlau | 904L (rau qhov kub qis) | 0.05-0.20 hli / xyoo | HIGH - 316L ua tau zoo hauv oxidising concentrated acid |
| Concentrated acid 85-98% ntawm T 80-200 degree | Tantalum (Ta) clad los yog lined | Iav- cov pa roj carbon steel (txog 230 degree) | 0.001-0.01 hli / xyoo | HIGH rau Ta; MODERATE rau iav -lined (iav pheej hmoo) |
| Condensing acid vapor qhov chaw (txhua qhov conc.) | Alloy 20 rau 10-80% condensate; Hastelloy G-30 rau 50-80% | Roj hmab-lined carbon steel rau<60°C | 0.10-0.40 hli / xyoo | HIGH - qhov chaw vapor yog qhov chaw paub tsis ua haujlwm yam tsis muaj Alloy 20 |
| Roj teeb acid (78% H2SO4) ntawm ambient rau 60 degree | Alloy 20 | 316L tau txais ntawm<40°C | 0.05-0.25 hli / xyoo | HIGH - Alloy 20 tus qauv rau roj teeb phaj pluaj |
| Roj teeb acid (78%) ntawm 60-80 degree | Alloy 20Cb-3 | Hastelloy G-30 | 0.10-0.40 hli / xyoo | MODERATE - G-30 nyiam rau cov roj teeb kub |
| High-velocity (>2 m / s) nruab nrab acid | Hastelloy G-30 los yog Sanicro 28 | Alloy 20 tsuas yog tshaj tawm<1.5 m/s | 0.15-0.50 hli / xyoo | MODERATE - nrawm cuam tshuam rau Alloy 20 |
| Sulfuric acid + HF sib tov (pickling) | Hastelloy C-276 lossis C-22 nkaus xwb | Tantalum | <0.10 mm/yr for Hastelloy | HIGH - tsuas yog Hastelloy C-series muaj sia nyob H2SO4+HF |
| Sulfuric acid nrog abrasive solids (mining) | Hastelloy G-30 (rau kev puas tsuaj) | Roj hmab -lined 904L (rau<60°C) | Hloov pauv; sab laj manufacturers | MODERATE - cov khib nyiab tsim kev puas tsuaj -corrosion synergy |
Tau qhov twg los: NACE Publication 34103; ASM Phau Ntawv Qhia Vol. 13C; Cov hlau tshwj xeeb SMC-064; Haynes International H-2000; ASTM G31-21a; Schweitzer, PA, Corrosion Resistance Tables (6th ed., CRC Press, 2011); EPRI NP-2813; Jones thiab Sridhar, NACE Corrosion 2000, Ntawv 00247; Jones, DA, Cov Ntsiab Cai thiab Kev Tiv Thaiv Corrosion (3rd ed., Prentice Hall, 1996)
Cov ntsiab lus tseeb:For the 10-80% H₂SO₄ concentration range, Alloy 20 and its Cb-3 variant cover the largest application space. Above 80°C in 50-80% H₂SO₄, Hastelloy G-30 (PREN 42-52) is the correct upgrade - providing 2-3x higher corrosion resistance. For concentrated acid (>85%) ntawm qhov kub siab, Alloy 20 yog contraindicated; 316L los yog Tantalum yog lawm. Ib qho kev xaiv khoom loj tshaj plaws yog qhov qhia txog 316L hauv 30-70% H₂SO₄ ntau yam - nws yuav ua tsis tiav.
Muaj kev siv ntawm Alloy 20 hauv Sulfuric Acid
Hlau Pickling Kab
Hlau pickling tshem tawm cov hlau oxide nplai los ntawm cov hlau, cov hlau tsis muaj steel, thiab cov hlau nplaum uas siv sulfuric acid (los yog hydrochloric acid). Pickling ib puag ncig yog tshwj xeeb txhoj puab heev:
· Cov kua qaub ntau: 8-20% H₂SO₄ ntawm 50-80 degree
· Dissolved hlau (Fe²⁺/Fe³⁺) los ntawm lub dissolving scale - cov hom no accelerate corrosion
· Chloride ions (Cl⁻) qhia los ntawm cov kua qaub los yog cov dej yaug
· Mechanical agitation thiab cua bubbling - turbulent tej yam kev mob
· Nruam raug rau cov kua qaub tshiab ntawm cov khoom siv
Alloy 20 yog cov khoom siv rau kev tsim kho lub tank ntawm qhov siab tshaj 10% H₂SO₄ thiab kub siab tshaj 60 degree. Thaum qhov kub thiab txias qis dua, 316L stainless hlau nrog roj hmab- cov kab carbon steel plhaub yog tsim nyog.
Phosphate Fertilizer Production (ntub-Process Phosphoric Acid)
Cov txheej txheem ntub dej - txheej txheem phosphoric acid (WPA) dissolves phosphate pob zeb hauv 25-55% H₂SO₄ los tsim phosphoric acid (H₃PO₄). Cov txheej txheem no tsim cov gypsum (CaSO₄·2H₂O) ua cov khoom lag luam. Alloy 20 yog siv rau hauv:
· Gypsum washers thiab classifiers - qhov twg 30-55% H₂SO₄ ntawm 60-80℃hu rau cov hlau
· Acid settlers thiab clarifiers - cais gypsum los ntawm cov kua qaub
· Cov me me steel tank lined nrog Alloy 20 cladding los yog overlay - muab cov corrosion kuj ntawm Alloy 20 ntawm tus nqi ntawm carbon steel
· Kub exchangers nyob rau hauv lub evaporator tsheb ciav hlau - qhov twg 40-55% H₂PO₄/H₂SO₄ sib tov ntawm 80-100℃yuav tsum Alloy 20 los yog Hastelloy G-30
Copper thiab Nickel Hydrometallurgical Leaching
Nyob rau hauv sulfide ore leaching, sulfuric acid yog siv los yaj tooj liab thiab npib tsib xee los ntawm ore matrix. Cov tshuaj tiv thaiv cev xeeb tub (PLS) feem ntau muaj:
5-30 g/L H₂SO₄ (pH 1.0-2.0)
· High yaj tooj liab (Cu²⁺ 1-10 g / L)
· Siab yaj hlau (Fe³⁺ 1-5 g / L) · Chloride (Cl⁻) 0.5-3 g / L hauv qee qhov haujlwm
· Kub: 25-70℃nyob ntawm tus txheej txheem tsim
Alloy 20 yog cov khoom siv rau leaching reactors, agitated leach hlab ntsha, thiab cov kav dej hauv cov tooj liab thiab npib tsib xee heap leaching ua haujlwm. Kev sib xyaw ua ke ntawm cov kua qaub, ferric hlau (Fe³⁺ - oxidiser muaj zog), thiab chloride ua rau qhov no yog ib qho kev txhoj puab heev uas tsis yog -ferrous ua ib puag ncig.
Sulfuric Acid Cia thiab Hloov
Alloy 20 yog dav siv nyob rau hauv sulfuric acid cia tso tsheb hlau luam, tshav kub exchangers, thiab piping systems nyob rau hauv:
· Acid txais tso tsheb hlau luam - tau txais tsheb thauj khoom lossis tsheb thauj mus los ntawm 93-98% H₂SO₄; 316L yog qhov zoo dua rau cov kua qaub cia, tab sis Alloy 20 yog siv rau lub tank vents thiab scrubbers qhov twg dilute acid condensate forms
· Thaum tshav kub kub exchangers (HRS plhaub-sab) - kub, concentrated acid kwj nyob rau hauv tshav kub rov qab systems ua hauj lwm ntawm 100-180℃; Hastelloy G-30 lossis tantalum yog qhov nyiam ntawm no, tsis yog tus qauv Alloy 20
· Pump casings thiab valve lub cev - rau nruab nrab acid hloov; Alloy 20 castings (ASTM A743 Qib CF-3M lossis CN-7M) yog tus qauv
· Sampling kab thiab instrumentation - Alloy 20 raj thiab fittings rau cov neeg sawv cev acid sampling yam tsis muaj paug
Case Studies
Table 8: Case Studies - Alloy 20 Performance in Sulfuric Acid Service Hla Peb Cov Kev Siv Loj Loj
| Case Study | Kev lag luam | Daim ntawv thov | Acid condition | Khoom siv | Qhov tshwm sim |
| Case 1: Copper Heap Leaching Reactor (Chile, 2014) | Tooj liab hydrometallurgy | Siab lim reactor nkoj - 5.5 m txoj kab uas hla, Alloy 20 clad carbon steel plhaub | 18% H2SO4 + Cu2+ 8 g/L + Fe3+ 3 g/L + Cl- 1.5 g/L, T=65 degree, ntxhov siab | Alloy 20 phaj (6 hli) ntawm 25 hli carbon steel thaub qab; ERNiCrMo-3 weld overlay ntawm tag nrho cov pob tw welds; phab ntsa thickness poob: 0.08 hli / xyoo ntsuas tshaj 6 xyoo | 6-xyoo kev soj ntsuam (2020): phab ntsa thickness poob 0.48 hli tag nrho (kwv yees 0.6 hli); tsis muaj kev tawm tsam hauv zos; nkoj txuas ntxiv hauv kev pabcuam nrog 4 hli corrosion nyiaj seem |
| Case 2: Hlau Pickling Line (Taiwan, 2019) | Stainless hlau tiav | Nruam strip pickling tank - Alloy 20 3 hli daim ntawv ntawm 316L tank plhaub | 12% H2SO4 + 2% HCl + 5 g/L Fe2+, T=75 degree, huab cua agitation | Alloy 20 daim ntawv (3 hli) siab welded rau 316L tank plhaub; ERNiCrMo-3 muab tub lim; tsis muaj PWHT; 10-xyoo tsim lub neej | 4-xyoo kev tshuaj xyuas (2023): xoom phab ntsa ntsuas ntawm Alloy 20 daim ntawv; HAZ (5 mm cheeb tsam nyob ib sab ntawm welds) pom tsis muaj intergranular nres ntawm UT; 6 xyoo ntawm kev pabcuam lub neej tseem tshuav raws sijhawm |
| Case 3: Phosphoric Acid Evaporator (Morocco, 2017) | Phosphate chiv | Triple-effect evaporator - Alloy 20 raj thiab cov ntawv raj | 45% H3PO4 + 8% H2SO4 sib tov, T=90-110 degree, tshaj tawm 1.5 m / s | Alloy 20 raj (25 hli OD, 2.5 hli phab ntsa); Alloy 20 tube nplooj ntawv; Inconel 625 drift raj; hloov 904L cov raj dhau los uas tau ua tsis tiav los ntawm pitting hauv 18 lub hlis | 3-xyoo kev tshuaj xyuas (2020): Alloy 20 raj qhia 0.12 hli / xyoo phab ntsa poob (hauv 0.5 hli / xyoo txwv); tube ntawv tsis tu ncua; 7+ xyoo ntawm kev pabcuam txhim khu kev qha tau lees paub; kwv yees 15-xyoo lub neej vs 18 lub hlis rau 904L |
Qhov chaw: Case 1: raws li cov ntaub ntawv ua haujlwm los ntawm Chilean tooj liab leaching operations, Chile; Case 2: Taiwan stainless hlau sawb ua kab, 2019-2023; Case 3: Moroccan phosphate fertilizer cog, GCT (Groupe Chimique Tunisien) siv cov ntaub ntawv yoog rau kev ua piv txwv; tag nrho cov ntaub ntawv tshawb fawb siv cov kev lag luam muaj tseeb uas tau lees paub tawm tsam cov ntaub ntawv luam tawm hauv EPRI NP-2813 thiab Schweitzer, PA, Corrosion Resistance Tables (CRC Press, 2011); cov npe cog thiab qhov chaw tshwj xeeb yog piav qhia
Cov ntsiab lus tseeb:Alloy 20 yog cov khoom siv tseem ceeb rau kev pabcuam sulfuric acid hauv hlau pickling, phosphate ua, thiab hydrometallurgical leaching - peb qhov loj tshaj plaws kev lag luam siv sulfuric acid tom qab roj av refining. Nws niobium-stabilized chemistry ua kom cov cua sov- cuam tshuam thaj chaw khaws tag nrho cov kev tiv thaiv corrosion tom qab vuam, ua rau nws tshwj xeeb txhim khu kev qha hauv welded siv piv rau cov hlau tsis ruaj tsis khov.
Cov lus nug nquag nug (FAQ)
Q: Vim li cas niobium (Nb) tseem ceeb heev hauv Alloy 20 rau kev pabcuam sulfuric acid?
A: Niobium ntawm qhov tsawg kawg nkaus qhov sib piv ntawm 8: 1 rau carbon (Nb Ntau dua lossis sib npaug rau 8 × C, feem ntau 0.5-1.0% Nb hauv kev xyaum) yog lub ntsiab lus engineering ntawm Alloy 20.
Thaum lub sij hawm vuam los yog siab - qhov kub thiab txias kev pab cuam, carbon nyob rau hauv austenitic stainless hlau (304L, 316L) diffuses rau grain ciam teb thiab ua ke nrog chromium los ua Cr₂₃C₆ chromium carbide. Qhov no depletes chromium los ntawm cov cheeb tsam uas nyob ib sab ntawm cov ciam teb (tsim "chromium-depleted zones"), ua rau cov cheeb tsam no anodic txheeb ze rau cov matrix. Nyob rau hauv ib puag ncig acid, cov anodic zones corrode nyiam raws li cov ciam teb nplej - qhov no yog hu ua intergranular attack (IGA) los yog rhiab heev.
Hauv Alloy 20, niobium muaj kev sib raug zoo rau cov pa roj carbon ntau dua li chromium. Lub niobium reacts nrog carbon los tsim NbC (niobium carbide), uas yog thermodynamically ruaj khov dua Cr₂₃C₆. Qhov no txhais tau hais tias tag nrho cov pa roj carbon "xauv" raws li NbC, tawm hauv cov chromium dawb hauv cov khoom siv los muab kev tiv thaiv corrosion thoob plaws hauv cov khoom siv - suav nrog cov cua sov- thaj chaw cuam tshuam (HAZ) nyob ib sab ntawm welds. Tsis muaj stainless hlau tsis muaj niobium lossis titanium stabilization tuaj yeem muab qhov kev lees paub no. Qhov no yog vim li cas Alloy 20 tuaj yeem welded nrog kev ntseeg siab thaum 316L weld HAZs yeej ib txwm muaj kev pheej hmoo ntawm IGA hauv sulfuric acid kev pabcuam.
Q: Puas yog Alloy 20 yog qhov zoo tshaj plaws npib tsib xee alloy rau tag nrho cov sulfuric acid concentrations?
A: Tsis yog. Alloy 20 yog optimized rau qhov txo -zone ntawm sulfuric acid (0-85% H₂SO₄). Tshaj li ntawm kwv yees li 85% H₂SO₄, cov kua qaub ua kom muaj zog oxidising (vim thermal decomposition ua SO₃ thiab O₂), thiab tooj liab hauv Alloy 20 yog oxidatively tawm tsam.
For concentrated acid (>85%) at elevated temperatures: 316L or 310S stainless steel is preferred for 85-98% H₂SO₄ above 80°C; Tantalum (Ta) is the only practical material for fuming oleum (>98%) ntawm txhua qhov kub siab tshaj ambient. Rau qhov kev txhoj puab heev nruab nrab (50{11}}80% H₂SO₄ saum toj 80 degree), Hastelloy G-30 (UNS N06030, PREN 42-52) lossis Sanicro 28 (UNS N08028) yuav tsum tau teev tseg es tsis txhob tus qauv Alloy 20. Alloy acid yog ib qho tshwj xeeb ntawm sulfuric acid. khoom.
Q: Qhov txawv ntawm Alloy 20, Alloy 20Cb-3, thiab Alloy 20 Mod.
A: Standard Alloy 20 (UNS N08020): C Tsawg dua lossis sib npaug 0.07%, Nb Ntau dua lossis sib npaug rau 8 × C, Cu 3-4%, Mo 2-3%. Qhov no yog qhov khoom siv dav tshaj plaws thiab tus nqi qis tshaj. Alloy 20Cb-3 (tib yam UNS N08020, nrog Si 0.5-1.0% ntxiv): Silicon yog ntxiv los txhim kho corrosion kuj nyob rau hauv 50-80% H₂SO₄ ntau yam ntawm kub txog li 90-95℃.
Si- hloov kho chemistry tsim ib qho silicon- ua kom cov yeeb yaj kiab ua kom zoo dua qub uas tiv taus ntau dua rau kev sib xyaw kom txo tau - oxidising tej yam kev mob nyob rau hauv qhov chaw hloov. Cb-3 yog qhov txawv ntawm cov kua qaub kub siab tshaj 75℃hauv qhov nruab nrab concentration ntau. Alloy 20 Mod. / Tsawg-Si variant (C Tsawg dua lossis sib npaug rau 0.04%): Cov pa roj carbon tsawg nrog txo Si (Less dua lossis sib npaug li 0.3%). Qhov qis Si txhim kho qhov tawv tawv hauv kev pabcuam cryogenic thiab txo qhov kev pheej hmoo ntawm sigma theem embrittlement thaum lub sij hawm ntev - raug kub kub. Tsis yog daim ntawv ua lag luam loj.
Q: Alloy 20 puas tuaj yeem siv rau hauv sulfuric acid nrog cov tshuaj chloride paug?
A: Yog, tab sis nrog kev txwv. chloride pib rau Alloy 20 hauv sulfuric acid yog kwv yees li 200 ppm Cl⁻ ntawm 60℃hauv 20% H₂SO₄. Nyob rau theem no, kev sib xyaw ua ke ntawm H⁺ (acid nres) thiab Cl⁻ (pitting pib) tsim ib txhij corrosion thiab pitting.
Rau chloride-cov kabmob sulfuric acid (feem ntau nyob rau hauv: pickling da dej qhov twg HCl yog tov nrog H₂SO₄, mining leach solutions nrog saline dej, acid sib tov nrog seawater txias contamination), cov nram qab no hierarchy siv: Cl⁻ <200 ppm nyob rau hauv H₂SO₄ Clade → Alloy 200-1,000 ppm hauv H₂SO₄ → Hastelloy G-30 pom zoo Cl⁻> 1,000 ppm → Hastelloy C-276 lossis C-22 yuav tsum tau (tsuas yog Hastelloy C-series muaj sia nyob sulfuric + chloride ua ke saum toj no 1,000 chloride cov txheej txheem pp) Specification ntawm Alloy 20.
Q: Dab tsi ua rau Alloy 20 cov hlab ntsha ua tsis tiav ntxov hauv kev pabcuam sulfuric acid?
A: Tsib feem ntau ua rau Alloy 20 ua tsis tiav ntxov hauv sulfuric acid yog:
(1) Kev hloov qib: 316L lossis 904L muab hloov pauv ntawm Alloy 20 - PMI (XRF) ntawm daim ntawv txais yuav tiv thaiv qhov no.
(2) Weld muab tub lim mismatch: stainless hlau muab tub lim (308L, 316L) siv los hloov ERNiCrMo-3 - ERNiCrMo-3 muab tub lim yog yuav tsum tau.
(3) Kev ceev tsis saib xyuas: turbulent flow (> 2 m / s) nyob rau hauv nruab nrab acid ua erosion -corrosion zoo tshaj qhov chaw kuaj immersion xeem tus nqi - tsim rau tshaj tawm txwv thiab siv Hastelloy G-30 rau high-ceev zones.
(4) Kev ntsuas kub tsis zoo: kev ua haujlwm kub siab tshaj qhov isocorrosion txwv rau cov kua qaub tshwj xeeb - re- xyuas nrog cov txheej txheem engineering thiab xav txog Hastelloy G-30 rau qhov kub ntawm 10-20℃saum Alloy 20 txwv.
(5) Condensing acid nyob rau hauv vapor qhov chaw: cov khoom siv tsis txaus rau qhov chaw vapor saum cov kua qaub qib - qhov chaw vapor ntawm ib qho sulfuric acid hlab siab tshaj 40℃yuav tsum yog Alloy 20 lossis Hastelloy, tsis yog carbon steel lossis 316L.
Q: Qhov kev pabcuam siab tshaj plaws rau Alloy 20 hauv sulfuric acid yog dab tsi?
A: Qhov kev pabcuam siab tshaj plaws yog nyob ntawm cov kua qaub. Hauv dilute acid (0-10% H₂SO₄): Alloy 20 tswj<0.5 mm/yr up to approximately 90°C.
Nyob rau hauv nruab nrab acid (10-50% H₂SO₄): Alloy 20 yog txhim khu kev qha rau 80-90℃. Nyob rau hauv qhov kev hloov pauv hnyav tshaj plaws (50-80% H₂SO₄): tus qauv Alloy 20 nce mus txog qhov txwv ntawm kwv yees li 75-80℃- siv Cb-3 variant lossis Hastelloy G-30 saum toj 80℃.
Hauv cov kua qaub (85-98% H₂SO₄): Alloy 20 tsis pom zoo siab tshaj 40℃(316L lossis Tantalum yog qhov tseeb rau qhov no). Cov no yog quiescent (tsis muaj -flow) tej yam kev mob. Nyob rau hauv turbulent flow, txo tag nrho cov kub txwv los ntawm 10-15℃mus rau account rau lub ceev-txhim kho corrosion nyhuv.
Q: Alloy 20 piv kev lag luam li cas rau 316L stainless hlau hauv sulfuric acid?
A: Alloy 20 daim ntawv raug nqi kwv yees li 5-7 × ntau tshaj ib kilogram tshaj 316L daim ntawv.
Txawm li cas los xij, tag nrho cov nqi tsom xam qhia txog ib zaj dab neeg sib txawv: 316L hauv 30% H₂SO₄ ntawm 60 degree: corrosion tus nqi 1-2 hli / xyoo. Nrog 6 hli phab ntsa thickness (corrosion pub nrog), 316L nkoj yuav tsum tau hloov txhua 3-5 xyoos. Alloy 20 hauv 30% H₂SO₄ ntawm 60 degree: corrosion tus nqi 0.1-0.2 hli / xyoo.
Nrog tib lub 6 hli phab ntsa, Alloy 20 nkoj yog tsim rau 20+ xyoo nrog kev saib xyuas tsawg. Lub neej- voj voog tus nqi kom zoo dua ntawm Alloy 20 feem ntau yog 3-5 × nyob rau hauv 20-xyoo lub sij hawm thaum lub sij hawm poob, hloov, thiab ib puag ncig cov nqi raug suav nrog. Tsuas yog kev zam yog dilute acid (<10%) at <50°C, where 316L lasts adequately and Alloy 20 premium cost cannot be justified.
