304H vs 321H: Cov ntsiab lus Carbon thiab Creep Strength rau siab -Tsuas Kub Siab Nkoj

Taw qhia

Thaum tsim cov hlab ntsha siab rau siab -kev pabcuam kub-refinery heaters, boiler superheaters, catalytic crackers, thiab heat exchangers-cov engineers pheej ntsib ib lo lus nug: lawv puas yuav tsum qhia 304H lossis 321H? Ob leeg yogaustenitic stainless hlaunqa cov lus "H" uas tsim los tswj cov pa roj carbon zoo rau kev ua haujlwm zoo dua. Txawm li cas los xij lawv sib txawv hauv cov tswv yim ruaj khov, weldability, thiab ntev - kev ntseeg tau ntev. Qhov kev sib piv no rhuav tshem cov ntsiab lus ntawm cov pa roj carbon monoxide, lub zog nkag mus, thiab cov txheej txheem xaiv hauv cov lus yooj yim, yog li cov neeg qhia tshwj xeeb tuaj yeem ua kom muaj kev ntseeg siab, kev cai- kev txiav txim siab ua raws.

Dab tsi yog 304H thiab 321H Stainless Hlau?

304H thiab 321H yog ob qho tib si austenitic, chromium-nickel stainless hlau hauv 18Cr-8Ni tsev neeg; cov lus "H" qhia txog kev tswj hwm cov pa roj carbon ntau (0.04–0.10%) ua kom zoo rau cov kev pabcuam kub kub. 321H kuj tseem muaj titanium rau carbide stabilization.

Ob qib sib koom tib yam 17.0–19.0% chromium thiab 9.0–13.0% nickel base chemistry. Qhov sib txawv yog nyob rau hauv yuav ua li cas txhua tus tuav cov pa roj carbon ntawm qhov kub thiab txias:

304H (UNS S30409) yog qhov siab -carbon variant ntawm tus qauv 304. Nws tswj cov ntsiab lus carbon (0.04–0.10%) ntxiv dag zog rau cov hlau ntawm qhov kub siab los ntawm kev nce cov tshuaj- ntxiv dag zog rau carbon yaj hauv austenite matrix.

321H (UNS S32109) yog qhov siab -carbon variant ntawm 321, uas yog qhov tseem ceeb 304 chemistry ntxiv rau titanium. Titanium khi nyiam nrog cov pa roj carbon monoxide los tsim cov titanium carbides ruaj khov (TiC), tiv thaiv chromium carbide nag lossis daus ntawm cov ciam teb.

Ob lub alloys poob rau hauv ASTM A240 / A240M (phaj, ntawv, sawb), ASTM A312 (seamless thiab welded yeeb nkab), thiab ASME Boiler thiab Pressure Vessel Code (BPVC) Tshooj II.

Lawv qhov sib txawv ntawm Cr thiab Ni ua rau lawv sib hloov tau yooj yim hauv kev tiv thaiv corrosion rau tsis yog -welded, stabilized, los yog post- kev daws teeb meem -annealed tej yam kev mob.

Cov ntsiab lus carbon sib txawv li cas ntawm 304H thiab 321H?

Cov pa roj carbon ntau yog nominally zoo tib yam -0.04% rau 0.10% rau ob qho tib si-tab sis 321H's titanium "locks" carbon li TiC, yog li cov pa roj carbon monoxide muaj txiaj ntsig zoo rau kev ntxiv dag zog yog qis dua hauv 321H dua li hauv 304H.

Raws li ASTM A240, ob qho tib si 304H thiab 321H xav tau carbon ntawm 0.04% thiab 0.10%. Qhov qis dua ua kom muaj kev nkag siab tsawg kawg nkaus - ua kom muaj zog; lub sab sauv khi tiv thaiv ntau tshaj carbide network tsim uas embrittles lub matrix. Txawm li cas los xij, qhov sib txawv ntawm carbon behaves li cas:

Nyob rau hauv 304H, feem ntau carbon tseem yaj nyob rau hauv lub austenite tom qab kev daws annealing, pab ncaj qha mus rau solid- kev daws teeb meem thiab rau carbide nag lossis daus uas pins grain ciam thaum lub sij hawm kev pab cuam.

Nyob rau hauv 321H, titanium (5 × C yam tsawg kawg nkaus, feem ntau 0.15-0.70%) reacts nrog carbon los tsim TiC ruaj khov. Qhov no txo ​​cov pa roj carbon uas muaj rau chromium carbide (Cr₂₃C₆) nag lossis daus thiab tseem txo cov pa roj carbon monoxide rau cov matrix ncaj qha.

Cov txiaj ntsig zoo: 304H feem ntau xa tawm me ntsis luv dua - lub sijhawm nce siab - kub tawm lub zog vim tias cov pa roj carbon ntau nyob hauv cov tshuaj, thaum 321H txi qee qhov kev ntxiv dag zog rau kev sib pauv rau kev tiv thaiv rau kev nkag siab.

Cov Carbon cuam tshuam li cas rau Creep Strength ntawm Kub Kub?

Cov pa roj carbon nyob rau hauv austenitic stainless hlau nce creep zog los ntawm ob lub tswv yim -khoom- kev daws teeb meem ntawm matrix thiab grain - ciam teb los ntawm carbides- thiab ob qho tib si cuam tshuam loj heev thaum carbon txav los ntawm 0.04% mus rau 0.10%.

Creep yog qhov qeeb, lub sijhawm- nyob ntawm deformation uas tshwm sim thaum cov hlau tuav hauv qhov kev ntxhov siab ntawm qhov kub siab. Cov pa roj carbon monoxide nkag mus rau ob sab pem hauv ntej:

Khoom- daws teeb meem. Cov pa roj carbon monoxide distorts lub austenite lattice, tiv thaiv kev txav mus los nce - cov txheej txheem nkag siab tshaj 0.5 Tₘ (kub kub hauv Kelvin). Rau 18Cr-8Ni austenite, kev pabcuam kub ntawm 600-800℃muab cov hlau sib npaug rau hauv txoj cai no.

Grain - ciam teb carbide pinning. M₂₃C₆ (feem ntau Cr₂₃C₆) precipitates ntawm grain ciam thaum lub sij hawm kev pab cuam. Ib tug tswj dispersion pins grain ciam teb, slows zawv zawg, thiab ncua lub neej rupture. Txawm li cas los xij, carbide ntau dhau, ua rau cov nplej tsis tu ncua - ciam teb zaj duab xis uas ua rau cov hlau tsis huv thiab depletes chromium uas nyob ib sab.

Kev ntxhov siab - cov ntaub ntawv tawg (ASME Tshooj II, Table 1A) lees paub qhov kev them nyiaj. Ntawm 700℃thiab 100,000 teev, tso cai rau kev ntxhov siab rau 304H phaj (ASTM A240) feem ntau tshaj li ntawm 321H phaj los ntawm kwv yees li 5-15%, nyob ntawm seb cov khoom tsim thiab qhov sib npaug carbon / titanium. Qhov no yog qhov ncaj, ntsuas tau ntawm cov pa roj carbon ntau dua hauv 304H.

Dab tsi yog Titanium Ua Si hauv 321H?

Titanium nyob rau hauv 321H ua raws li cov pa roj carbon scavenger, tsim TiC ruaj khov uas tiv thaiv Cr₂₃C₆ nag lossis daus, yog li tiv thaiv cov nplej - ciam teb chromium thiab tshem tawm rhiab heev hauv tshav kub- thaj chaw cuam tshuam (HAZ) tom qab vuam.

Qhov sib piv ruaj khov yog txhais tias Ti Ntau dua lossis sib npaug rau 5 × C (ASTM A240). Nrog cov pa roj carbon monoxide ntawm 0.06% (nruab nrab-ntau), qhov tsawg kawg nkaus titanium yuav tsum yog 0.30%, thiab cov ntsiab lus tshwj xeeb lub hom phiaj yog 0.30-0.60% kom ntseeg tau tias muaj kev ruaj khov.

TiC yog thermodynamically ruaj khov dua Cr₂₃C₆. Nws tsim thaum cov tshuaj annealing (1050-1100 degree) thiab txuas ntxiv los ntawm kev pabcuam, yog li chromium carbide tsis tuaj yeem tsim ntawm 450-850℃rhiab qhov qhov rai qhov alloy ntsib hauv kev pabcuam lossis hauv HAZ.

Qhov no yog vim li cas 321H tsis xav tau tom qab-weld tov annealing los kho intergranular corrosion kuj-ib qho kom zoo dua rau daim teb-erected hlab thiab loj- txoj kab uas hla piping qhov cub annealing yog impractical.

Kev lag luam tawm -tawm: titanium kuj khi cov pa roj carbon monoxide uas yuav ua rau muaj zog ntxiv, thiab titanium nitride / carbonitride suav nrog tuaj yeem txo qis qhov tawv nqaij ntawm chav tsev kub.

Cov hlau twg muaj zog dua Creep: 304H lossis 321H?

304H tau ntsuas qhov nkag siab ntau dua - tawg lub zog ntau dua 321H ntawm 600℃thiab siab dua hauv cov hlau hauv paus, vim tias ntau ntawm nws cov pa roj carbon tseem muaj rau cov khoom ruaj khov- kev daws teeb meem thiab nplej- ciam teb pinning; Txawm li cas los xij, 321H khaws nws lub zog zoo dua hauv qhov vuam HAZ, qhov twg 304H tuaj yeem poob cov pa roj carbon - txhawb zog los ntawm kev nkag siab.

Qhov kev sib piv faib ua ob txoj kev tswj hwm -cov hlau thiab vuam HAZ- thiab lawv nyiam cov qib sib txawv:

Base-hlau creep-rupture. ASME Code Case thiab Tshooj II tso cai rau kev ntxhov siab tsis tu ncua muab 304H sib npaug lossis siab dua qhov kev ntxhov siab tshaj 321H ntawm 538℃(1000℃F) txog 816℃(1500℃F). Ntawm 704℃(1300℃F) thiab 100,000 teev, 304H phaj tso cai rau kev ntxhov siab feem ntau yog 10-12% siab dua 321H phaj.

Weld-HAZ tus cwj pwm. Hauv 304H, HAZ ntsib carbide dissolution thaum vuam thiab rov- nag lossis daus thaum txias. Yog tias qhov txias txias qeeb (cov ntu tuab), cov ntaub ntawv sensitized cheeb tsam, hauv zos depleted hauv chromium thiab tsis muaj zog hauv creep. Nyob rau hauv 321H, titanium re-forms TiC nyiam, khaws cia nplej- ciam teb ruaj khov thiab HAZ creep zog.

Cov tswv yim coj mus siv: Rau seamless, nyias- cov khoom siv phab ntsa (tubing, nyias cov yeeb nkab), 304H lub hauv paus siab dua- hlau creep zog feem ntau yeej. Rau tuab-phab ntsa, welded, los yog teb-fabricated siab hlab ntsha, 321H's weld-HAZ stability feem ntau yeej lub neej- voj voog sib cav.

Lawv Sib piv li cas hauv kev hnov ​​​​mob thiab kev cuam tshuam ntawm intergranular Corrosion Resistance?

321H yog ntau tiv taus rau sensitization thiab intergranular corrosion (IGC) tshaj 304H, vim titanium stabilization tiv thaiv chromium{2}}depletion mechanism uas tsav 304H rhiab heev nyob rau hauv 425-900℃ntau yam.

Sensitization yog qhov poob ntawm corrosion kuj tshwm sim los ntawm chromium carbide nag lossis daus ntawm lis ciam teb. Ob qib tswj nws txawv heev:

rhiab heev mechanism. Thaum 304H qeeb-txias los ntawm 425-900 degree, Cr₂₃C₆ precipitates ntawm grain ciam teb. Cov chromium uas nyob ib sab poob qis dua 10.5% passivation pib, ua rau cov cheeb tsam muaj kev cuam tshuam rau IGC hauv acidic lossis chloride-cov kabmob media.

321H tiv thaiv kab mob. TiC cov ntaub ntawv ntawm qhov kub thiab txias dua thiab ruaj khov dua li Cr₂₃C₆, yog li chromium carbides tsis tuaj yeem tsim thiab lis ciam teb khaws cov ntsiab lus chromium tag nrho. Cov hlau hla dhau ASTM A262 Xyaum A / E kev xeem txawm tias tom qab kev kho cua sov.

Qhov kev pabcuam. Hauv kev ua haujlwm qaub qaub, polythionic acid (PTA) tawg thaum lub sijhawm kaw yog ib qho kev lees paub tsis ua haujlwm rau sensitized 304H. NACE SP0170 qhia meej meej cov qhab nia ruaj khov (321H, 347H) tshaj 304H rau cov cuab yeej raug PTA tawg.

Huey xeem (ASTM A262 Xyaum C). 304H feem ntau xav tau cov tshuaj annealing tom qab vuam kom dhau; 321H kis tau raws li -welded mob.

Dab tsi yog ASME thiab ASTM Standards rau 304H thiab 321H?

Ob lub alloys yog tswj hwm los ntawm qhov tseem ceeb ntawm tib cov txheej txheem ntawm ASTM cov khoom specifications thiab ASME BPVC Tshooj II tso cai rau - cov lus ntxhov siab, tab sis qhov tshwj xeeb UNS lub npe, kev ruaj khov, thiab cov khoom siv - daim ntawv muaj txawv.

Cov lus hauv qab no qhia txog cov qauv kev tswj hwm thiab cov kev cai tseem ceeb rau txhua qib:

Lub ASME tso cai rau- kev ntxhov siab (Tshooj II, Cov Ntawv Ntxiv 1) rau ob qib yog qis dua ntawm: (1) ob-feem peb ntawm 0.2% tawm los ntawm qhov kub thiab txias, (2) 100% ntawm qhov nruab nrab kev ntxhov siab los tsim 1% creep hauv 100,000 teev, lossis (3) mus rau 670% ntawm kev ntxhov siab, nruab nrab ntawm 670 xuaj moos Ntawm qhov kub siab tshaj li 538 degree, qhov creep-rupture criterion dominates- yog li qhov siab dua creep zog ntawm 304H ncaj qha txhais mus rau siab dua tso cai nyob rau hauv lub hauv paus hlau.

Vuam kev xav txawv li cas?

321H yog yooj yim dua rau weld rau cov ntu tuab thiab kev tsim teb vim nws tiv thaiv qhov kev xav tsis tau tom qab-weld heat treatment (PWHT), hos 304H yuav xav tau cov tshuaj annealing tom qab vuam los kho corrosion kuj; 321H kuj xav tau ib qho tshwj xeeb muab tub lim.

Vuam siab -carbon austenitic stainless hlau yog qhov twg ob qib sib txawv tshaj plaws:

Filler hlau. 304H yog feem ntau welded nrog ER308H muab tub lim, sib piv cov niam txiv hlau cov pa roj carbon ntau. 321H yog welded nrog ER347 (niobium-stabilized) muab tub lim, tsis yog ER321, vim titanium tsis hloov zoo nyob rau hauv arc; niobium muab qhov sib npaug stabilization hauv cov hlau vuam.

Kev hnov ​​​​mob tom qab vuam. 304H HAZ rhiab heev yog tias cua txias los ntawm 425-900℃qeeb (phab ntsa tuab, cov cua kub siab). Kev txo qis: cov tshuaj anneal ntawm 1050-1100℃tom qab nrawm nrawm- lub tshuab ua haujlwm tsis zoo rau cov hlab ntsha loj . 321H HAZ tsis hnov ​​​​qab vim TiC re- cov ntaub ntawv nyiam dua.

PWHT xav tau. ASME Tshooj VIII tsis tso cai rau PWHT rau ob qib, tab sis qhov chaw pabcuam (kub, PTA, caustic) feem ntau xav tau. Rau 304H, qhov xav tau PWHT yog tag nrho cov tshuaj anneal; rau 321H, ib qho kev ntxhov siab- nyem ntawm 850-900℃feem ntau txaus thiab zam qhov kev pheej hmoo ntawm kev cuam tshuam ntawm tag nrho cov anneal.

Kub cracking txaus ntshai. Ob qib yog austenitic nrog 5-10% ferrite nyob rau hauv cov hlau weld, yog li kub tawg yog me me . 321H's titanium nitride inclusions tuaj yeem ua tus pib tawg hauv cov pob qij txha hnyav heev -yuav tsum tau tswj cov cua sov nkag thiab sib cuam tshuam kub.

Qhov twg yog qhov zoo dua rau kev siv lub nkoj siab?

Tsis muaj universal yeej; 304H yog qhov zoo dua rau nyias-phab ntsa, siab- qhov kub thiab txias qhov chaw nyob qhov twg lub hauv paus- hlau creep zog tswj kev tsim (superheater raj, rauv coils), hos 321H yog nyiam rau tuab- phab ntsa, welded, los yog qaub- kev pab cuam siab hlab ntsha griern}} kev tiv thaiv corrosion nyob rau hauv HA 7. drums, reactor internals, catalytic cracker regenerator plhaub).

Txoj kev xaiv yog nyob ntawm seb hom twg tsis ua haujlwm tiag tiag tswj tus qauv tsim. Siv cov lus qhia txog kev txiav txim siab hauv qab no:

Xaiv 304H thaum:

Kev tsim qauv yog tswj hwm los ntawm creep- kev ntxhov siab tawg thiab cov khoom sib txuas tsis sib xws los yog muaj ob peb welds (tube, yeeb nkab, coil).

Tshaj tawm -weld tov annealing yog ua tau (khoom fabrication, me me nkoj).

Kev pabcuam yog oxidizing, qis-sulfur, thiab tsis muaj polythionic acid raug.

Qhov tsawg kawg nkaus phab ntsa thickness thiab qhov hnyav yog cov hom phiaj tsim qauv (siab dua tso cai rau cov phab ntsa thinner).

Xaiv 321H thaum:

Lub nkoj yog tuab-phab ntsa, teb-welded, lossis loj dhau rau qhov cub-anneal.

Cov kev pabcuam suav nrog kev kaw qhov raug rau polythionic acid (refinery FCC, coker, hydrotreater).

Tus qauv tsim yuav tsum muaj sia nyob rau qhov kev pabcuam kub kub yam tsis muaj kev hnov ​​​​mob -tsav tawg.

Code lossis kawg-tus neeg siv tshwj xeeb (piv txwv li, NACE SP0170, API RP 939-A) tswj hwm qib ruaj khov.

Txoj cai ntawm tus ntiv tes xoo: Hauv qab kwv yees li 538 degree, ob qib dhau los -tseem ceeb- tus qauv 304/321 lossis 316L txaus. Nruab nrab ntawm 538℃thiab kwv yees li 750 degree, 304H feem ntau yog qhov creep{10}}kev xaiv zoo. Tshaj 750 degree, xav txog 800H / HT, 310S, lossis npib tsib xee alloys (600/601).

Cov Nqi Them Sib txawv yog dab tsi?

321H feem ntau raug nqi 15-30% ntau dua 304H ib chav tsev qhov hnyav vim titanium ntxiv, qis zeb ntau lawm ntim, thiab nruj dua qhov zoo- tswj cov kev xav tau rau qhov sib piv; Txawm li cas los xij, lub neej- kev ntsuas tus nqi voj voog feem ntau nyiam 321H thaum PWHT, kev tshuaj xyuas, thiab kev pheej hmoo hluav taws xob raug suav nrog.

Tus nqi ntawm cov khoom siv tsuas yog ib feem ntawm tag nrho cov nqi ntawm cov tswv cuab. Kev tawg:

Raw-khoom kim heev. Titanium- bearing ferroalloys thiab lub qhov rais chemistry nqaim (Ti yuav tsum muaj ntau dua lossis sib npaug li 5 × C tab sis tsis siab li ua rau TiN suav nrog) nce nqi melting.

Mill muaj. 304H yog tsim nyob rau hauv ntau dua tonnage thoob ntiaj teb, yog li lub sij hawm ua cov hmoov txhuas thiab cov nqi sib tw ntau dua . 321H yog qib tshwj xeeb nrog tsawg tus tsim nyog tsim nyog.

Tus nqi Fabrication. 304H yuav xav tau kev daws teeb meem tag nrho tom qab vuam- lub voj voog hluav taws xob ntxiv, kev thauj mus los, thiab muaj peev xwm cuam tshuam kev ua haujlwm rov ua dua. 321H feem ntau yog li -welded lossis kev ntxhov siab-relieved, txiav nqi fabrication.

Lub neej- tus nqi voj voog. Ib qho kev lag luam uas tsis tau npaj tseg los ntawm 304H PTA tawg tuaj yeem raug nqi ntau lab ib hnub. Cov khoom siv zoo tshaj plaws rau 321H feem ntau rov qab tau ntau zaus dhau los ntawm kev zam kom tsis txhob tawg.

Yuav Ua Li Cas Xaiv Ntawm 304H thiab 321H: Daim Ntawv Txiav Txim Siab

Ua qhov kev xaiv nyob rau hauv plaub kauj ruam txiav txim-(1) txheeb xyuas txoj kev tswj tsis ua haujlwm, (2) xyuas qhov kub thiab txias, (3) ntsuas qhov weldability thiab PWHT qhov ua tau, (4) paub meej cov cai thiab xaus-cov neeg siv cov cai-ces teev UNS, daim ntawv khoom, thiab stabilization los yog cov pa roj carbon xeem yuav tsum tau.

Ib txoj hauv kev ua kom tsis txhob muaj qhov yuam kev tshwj xeeb tshaj plaws:

Kauj Ruam 1 - Txheeb xyuas qhov kev tswj hwm tsis ua haujlwm. Yog creep-rupture kav (nyias-phab ntsa, siab-kub), lean 304H. Yog hais tias IGC/PTA cracking tswj (thick-phab ntsa, raug kaw), lean 321H.

Kauj ruam 2 - Kos lub qhov rais kub. Hauv qab 538 degree, tsis xav tau qib H-. Los ntawm 538℃mus rau 750 degree, ob leeg haum; saum toj 750 degree, txhim kho tsev neeg hlau.

Kauj ruam 3 - Ntsuam xyuas weldability/PWHT. Yog tias post-weld solution anneal yog impractical (loj teb-fabricated nkoj), xaiv 321H. Yog khw-fabricated nyias- phab ntsa, xaiv 304H.

Kauj ruam 4 - Paub meej cov lej thiab xaus- cov neeg siv cov cai. NACE SP0170 (PTA cracking), API RP 939-A (refinery heater tubes), thiab ntau tus neeg teb xov tooj specs yuam kev xaiv.

Tom qab ntawd qhia meej ntawm daim duab kos thiab kev yuav khoom: UNS tus lej, ASTM cov khoom specification, H-qib carbon ntau, stabilization piv (rau 321H), thiab yuav tsum tau kuaj corrosion (ASTM A262).

Xaus

304H thiab 321H yog nyob ze cov kwv tij metallurgical: ob qho tib si yog 18Cr-8Ni austenitic stainless hlau nrog tswj elevated carbon rau siab - kub lub zog. Qhov kev txiav txim siab ntawm lawv hloov mus rau ib qho kev lag luam tawm ib zaug - tawm - siab dua puag - hlau creep zog (304H) piv rau superior weld -HAZ stability thiab corrosion resistance (321H). Rau nyias-phab ntsa, seamless, high-temperature tubing qhov twg creep kav tsim, 304H feem ntau yog txoj cai hu.

Rau tuab-phab ntsa, teb-welded, los yog kaw- cov hlab ntsha uas muaj siab, 321H feem ntau them rov qab nws cov nqi them rov qab rau kev ntseeg siab thiab lub neej- tus nqi mus ncig. Cov kws tshaj lij uas ua qhov kev xaiv no txhob txwm tshaj tawm- siv ASME tso cai rau- cov lus ntxhov siab, NACE thiab API cov lus qhia, thiab cov kev pabcuam-ib puag ncig profile-yuav qhia cov alloy zoo thawj zaug thiab zam qhov kev xav tsis thoob ntawm kev tawm ntawm - ntawm - kev pabcuam nkoj.