1. Dab tsi yog qhov sib txawv hauv qhov chaw ua haujlwm thiab kev tsim metallurgical ntawm Incoloy alloys UNS N08811 (800HT) thiab UNS N08825 (825) rau kev siv yeeb nkab?
Qhov kev sib txawv yog lub hauv paus thiab tswj hwm lawv txoj kev siv tag nrho. UNS N08811 (800HT) yog engineered raws li siab -kub, creep- resistant alloy rau siv nyob rau hauv qhuav, gaseous ib puag ncig. Nws cov qauv tsim tseem ceeb suav nrog kev tswj hwm, nce siab carbon cov ntsiab lus (0.06-0.10%), siab ua ke titanium thiab txhuas cov ntsiab lus, thiab yuav tsum tau ua cov qauv ntxhib ntxhib. Cov ntsiab lus no ua haujlwm sib koom ua ke los muab qhov tshwj xeeb creep thiab kev ntxhov siab tawg lub zog ntawm qhov kub thiab txias feem ntau siab dua 700℃(1292℃F), nrog rau kev ua haujlwm zoo rau oxidation thiab carburization. Nws tsis muaj molybdenum lossis tooj liab.
Conversely, UNS N08825 (825) yog engineered raws li ib tug corrosion{2}}resistant alloy rau aggressive aqueous thiab ntub dej tshuaj ib puag ncig. Nws cov qauv tsim tseem ceeb yog kev txhob txwm tshaj tawm ntawm molybdenum (2.5-3.5%) thiab tooj liab (1.5-3.0%), nrog rau titanium stabilization. Qhov no chemistry muab kev tiv thaiv zoo rau pitting, crevice corrosion, thiab kev ntxhov siab corrosion tawg hauv cov chloride-muaj cov xov xwm, nrog rau txo cov acids xws li sulfuric thiab phosphoric acid. Nws cov ntsiab lus siab nickel (38-46%) ntxiv stabilizes nws tiv thaiv chloride nres.
Txoj Cai Xaiv: Siv N08811 yeeb nkab rau cua sov (piv txwv li, cov raj rauv, cov kab hloov pauv). Siv N08825 yeeb nkab rau corrosion (piv txwv li, acid kab, seawater piping).
2. Nyob rau hauv cov kev lag luam tshwj xeeb thiab cov kav dej siv cov kav dej yog N08811 thiab N08825 cov kav dej uas suav tias yog cov qauv lossis cov khoom nyiam?
Lawv daim ntawv thov diverge sharply raws li lawv cov yam ntxwv tseem ceeb:
UNS N08811 (800HT) Yeeb Nkab Daim Ntawv Thov:
Petrochemical (Ethylene Production): Radiant and convection coil tubing in pyrolysis furnaces, transfer line exchangers (TLEs), where it withstands temperatures >900℃thiab carburizing hydrocarbon ntws.
Steam Methane Reforming: Lub hauv paus hloov kho qhov hluav taws xob qhov hluav taws xob headers thiab pigtails hauv cov nroj tsuag hydrogen / ammonia, tuav siab -siab chav / hydrocarbon sib tov ntawm qhov kub thiab txias.
Cov Cuab Yeej Cuab Yeej & Lub Hwj Chim: Siab -kub kub exchanger tubing, superheater kev txhawb nqa, thiab cov txheej txheem roj kab hauv cov tshuab uas nkag tau lub neej yog qhov tsim qauv txwv.
UNS N08825 (825) Yeeb Nkab Daim Ntawv Thov:
Roj & Roj (Sour Service): Flowlines, sib sau ua ke, thiab txhaj piping rau qaub (H₂S{0}}muaj) roj thiab roj, qhov uas nws tiv thaiv sulfide kev nyuaj siab tawg thiab chloride pitting.
Kev Siv Tshuaj: Cov kav dej rau kev tsim cov sulfuric thiab phosphoric acid, acid rov qab, thiab cov txheej txheem hnyav. Nws yog tus qauv rau kev tuav cov kua qaub thiab chloride sib xyaw.
Marine & Offshore: Seawater txias thiab cov kav dej tua hluav taws, qhov chaw tiv thaiv pitting nyob rau hauv qhov chaw ruaj khov yog qhov tseem ceeb.
Kev Tswj Kev Ua Phem: Slurry thiab effluent piping hauv Flue Gas Desulfurization (FGD) scrubbers, uas muaj chlorides, sulfates, thiab acidic condensates.
3. Dab tsi yog qhov sib txawv tseem ceeb hauv cov txheej txheem vuam thiab muab tub lim hlau xaiv rau N08811 piv rau N08825 yeeb nkab kom ntseeg tau tias kev pabcuam ncaj ncees?
Kev siv vuam yuav tsum khaws cia txhua qhov sib txawv ntawm cov khoom sib txawv, yuav tsum muaj kev sib txawv.
Rau UNS N08811 (800HT):
Lub Hom Phiaj: Khaws cia siab - qhov kub thiab txias thiab tiv thaiv kev tawg tawg.
Filler Hlau: Rau siab - qhov kev pabcuam kub, qhov sib txuam lossis dhau - sib txuam creep- lub zog muab tub lim yog siv. Cov kev xaiv feem ntau suav nrog ERNiCr-3 (kev sib txuam) lossis, rau lub zog zoo dua thiab muaj zog, ERNiCrCoMo-1 (xws li, Inconel 617 hom).
Kev coj ua tseem ceeb: Kev tswj nruj ntawm kev sib tshuam ntawm qhov kub thiab txias (<150°C) and the mandatory use of a post-weld heat treatment (PWHT). A stress relief at ~899°C is essential to reduce residual stresses that could lead to stress relaxation cracking during high-temperature operation.
UNS N08825 (825):
Lub Hom Phiaj: Khaws kev tiv thaiv corrosion, tshwj xeeb tshaj yog nyob rau hauv vuam thiab tshav kub- cuam tshuam cheeb tsam (HAZ).
Filler Hlau: Kom phim lossis tshaj qhov pitting tsis kam ntawm lub hauv paus hlau, ERNiCrMo-3 (xws li, Inconel 625 muab tub lim) yog tus qauv kev lag luam. Nws cov molybdenum siab dua thiab cov ntsiab lus niobium kom ntseeg tau tias cov hlau weld resists rhiab heev thiab kev tawm tsam hauv zos.
Kev xyaum tseem ceeb: kev tu kom zoo, siv siab -purity argon rov qab- tshem tawm kom tsis txhob muaj qhov sib txuas hauv oxidation ("sugaring"), thiab tswj cov cua kub tawm kom txo tau lub sij hawm nyob rau hauv qhov rhiab heev. PWHT feem ntau tsis tas yuav tsum tau vim yog titanium stabilization, tab sis cov tshuaj anneal tuaj yeem siv rau kev pabcuam hnyav.
4. Dab tsi yog kev tswj hwm cov khoom siv ASTM / ASME, thiab qhov kev kuaj tshwj xeeb lossis ntawv pov thawj yuav tsum tau ua rau N08811 thiab N08825 yeeb nkab hauv kev tsim cov hlab ntsha siab?
Ob lub alloys yog tswj hwm los ntawm cov qauv nruj, tab sis nrog cov kev xav tau tseem ceeb sib txawv.
UNS N08811 (800HT):
Specification: ASTM B407 / ASME SB407 rau seamless yeeb nkab thiab raj.
Daim ntawv pov thawj tshwj xeeb: Daim Ntawv Pov Thawj Zeb Xeem (MTC) yuav tsum lees paub tias nws ua tau raws li qib "H": Cov ntsiab lus carbon tsis pub dhau 0.06-0.10%, cov ntsiab lus tsawg kawg nkaus (Ti + Al) cov ntsiab lus, thiab lav qhov ntxhib austenitic grain loj (ASTM No. 5 lossis coarser). Daim ntawv pov thawj ntawm cov tshuaj annealing kev kho mob kuj tseem ceeb heev. Cov ntaub ntawv pov thawj ntawm kev ntxhov siab-rupture xeem cov ntaub ntawv feem ntau yog hais txog.
UNS N08825 (825):
Specification: ASTM B423 / ASME SB423 rau seamless yeeb nkab thiab raj.
Daim ntawv pov thawj tshwj xeeb: MTC yuav tsum txheeb xyuas cov chemistry tag nrho, tshwj xeeb yog cov ntsiab lus molybdenum thiab tooj liab. Rau corrosion- kev pabcuam tseem ceeb, cov ntawv tshaj tawm ntxiv rau kev kuaj kev sib xyaw ua ke (piv txwv li, ASTM G28 Txoj Kev A, lossis ASTM A262 Practice E) tej zaum yuav raug teev los ua pov thawj tias cov khoom nyob rau hauv qhov zoo rhiab heev- tiv taus.
5. Nyob rau hauv qhov xwm txheej uas muaj qhov kub thiab txias thiab huab cua corrosive (piv txwv li, pov tseg- rau- lub tshuab hluav taws xob boiler superheater raug cov pa roj flue uas muaj chlorides), tus engineer yuav ua li cas xaiv cov khoom siv ntawm N08811 thiab N08825?
Qhov no complex scenario yuav tsum tau ib tug tsis ua hauj lwm hom tsom xam thiab feem ntau ua rau xav txog ib tug thib peb, ntau alloyed kev xaiv.
Assess the Dominant Threat: If the metal temperature is high enough that creep rupture is the primary life-limiting factor (typically >600-650 degree), N08811 lub zog zoo tshaj plaws ua rau nws yog qhov pib. Txawm li cas los xij, nws tsis muaj molybdenum tawm nws yooj yim rau chloride-induced pitting thiab kev ntxhov siab corrosion tawg los ntawm flue gas condensate, uas tuaj yeem ua rau ntxov ntxov tsis ua hauj lwm los ntawm sab nraud.
Ntsuas N08825: Thaum N08825 muaj cov tshuaj chloride zoo heev, nws qhov kub siab tshaj plaws rau cov khoom siv hauv siab yog qis dua (~ 550℃rau ntev -lub zog). Nws lub zog creep ntog tawm ntawm qhov siab tshaj qhov no, ua rau nws tsis haum rau lub siab - kub superheater los ntawm kev tsim qauv tsim qauv.
Txoj kev daws teeb meem: Hauv qhov xav tau ob qho tib si - kev hem thawj ib puag ncig, tsis muaj hlau yuav zoo dua. Ib tug engineer feem ntau yuav saib rau cov khoom siv alloyed ntau dua uas sib xyaw ua ke siab - qhov kub thiab txias nrog cov tshuaj chloride. Qhov no feem ntau ua rau kev xaiv cov nickel -chromium- molybdenum alloy xws li UNS N06617 (Inconel 617) lossis UNS N10276 (Hastelloy C-276), uas muaj qhov sib npaug zoo dua ntawm kev nkag siab thiab pitting tsis kam, txawm tias tus nqi siab dua.
Xaus: Qhov kev xaiv ntawm N08811 thiab N08825 yeeb nkab tsis tshua muaj kev cuam tshuam; nws yog qhov kev txiav txim siab binary raws li seb puas muaj kev ntxhov siab thermal lossis tshuaj lom neeg corrosion yog qhov tseem ceeb tsim kev sib tw. Nkag siab txog qhov tseem ceeb dichotomy no yog qhov tseem ceeb rau kev xaiv cov khoom zoo thiab kev lag luam.
