Yuav Ua Li Cas Ua Ntej Austenite Grain Size Number nyob rau hauv 316 Stainless Steel Heater Sheath Tubing Control Creep Cavitation Nucleation Rate ntawm 550 degree

Grain Boundary Density raws li qhov tseem ceeb ntawm Creep Life

Rau 316 stainless hlau sheathed hluav taws xob cua sov raj ua haujlwm ntawm qhov kub siab (550 degree, raug rau cov cua kub kub lossis roj cua sov), qhov ua ntej austenite grain loj qhia raws li ASTM grain loj naj npawb (G) yog thawj microstructural hloov pauv tswj cov creep cavitation nucleation tus nqi. Fine- cov khoom siv nplej (ASTM G=8-10, grain inch 15-}25 µm) muaj thaj tsam ntau dua ntawm cov qoob loo ntawm ib lub ntim ntau dua li cov khoom siv ntxhib (ASTM G=3-5, grain diameter 50-80 µm). Txawm hais tias cov nplej nplua nuj qhia tau hais tias muaj zog yield zog ntawm qhov kub thiab txias, lawv qhia tau sai dua nucleation ntawm creep cavitation ntawm qhov kub thiab txias vim tias cov ciam teb yog qhov chaw nyiam rau kev tsim kab noj hniav. Coarse grainy 316 (ASTM G=4-5) muaj lub neej nkag 3-5 zaug ntev dua ntawm 550℃dua li cov khoom zoo ntawm cov khoom sib xws thiab qhov kub thiab txias.
Rephrase kab lus

Rov qab mus rau qhov qub kab lus

Luam kab lus

Tsis muaj tswv yim

Txoj kev tshawb no soj ntsuam kev sib raug zoo ntawm ASTM grain loj naj npawb, cavitation nucleation tus nqi thiab creep rupture lub neej rau 316 sheaths, thiab tawm tswv yim ib tug specification rau siab -kub siv.

Crack Initiation ntawm Grain Boundary Cavitation Thaum Creep

Lub ntsiab mechanism ntawm creep deformation ntawm 316 stainless hlau ntawm 550℃yog grain ciam zawv zawg. zawv zawg ntawm cov nplej uas nyob ib sab dhau los ua rau muaj kev ntxhov siab ntawm peb lub ntsiab lus thiab nyob rau theem thib ob cov khoom (carbides, suav nrog) vim qhov tsis sib xws ntawm geometric incompatibilities, uas nucleate voids. Lub nucleation tus nqi yog inversely proportional rau grain loj; qhov me me ntawm cov nplej loj qhov loj ntawm cov qoob loo ciam teb junctions ib chav tsev ntim thiab yog li qhov loj dua qhov chaw nucleation. Thaum nucleated, voids nthuav dav los ntawm qhov tsis muaj qhov sib txawv raws li thaj tsam ntawm cov qoob loo (Coble creep) thiab los ntawm lub hwj chim- txoj cai creep ntawm ib puag ncig matrix. Lub neej nkag mus tag nrho yog qhov suav ntawm lub sijhawm los ua kom muaj cov kab noj hniav tseem ceeb (feem ntau yog 5-10% thaj tsam ntawm thaj tsam kab noj hniav) thiab lub sijhawm rau cov kab noj hniav kom coalesce rau hauv qhov tawg. Ntau tus ciam teb ceev kuj tseem cuam tshuam ntau qhov chaw nucleation, yog li qhov feem pua ​​​​ntawm cov kab noj hniav tseem ceeb tuaj yeem ua tiav ua ntej rau cov ntaub ntawv zoo txawm hais tias qhov kev loj hlob qeeb qeeb ntawm ib kab noj hniav vim qhov ntev diffusion luv.

Quantitative Correlation ntawm ASTM Grain Size thiab Creep Life ntawm 550 degree

Kev ntsuam xyuas rupture ntawm 316 tubing nrog tswj qhov ntau thiab tsawg (los ntawm kev kho cov tshuaj annealing lub sij hawm thiab qhov kub thiab txias) ntawm 550℃thiab ib qho kev siv kev ntxhov siab ntawm 100 MPa (feem ntau ntawm cov hoop stress los ntawm thermal expansion txwv) tau tsim cov kev sib raug zoo hauv qab no.

ASTM Grain Size Number (G) Grain Diameter (µm) Grain Boundary Area per mm3 (mm2/mm3) Time to 1% Cavitated Boundary Area (teev, 550 degree, 100 MPa)Creep rupture life (h, 550 degree, 100 MPa)Relative Creepmen 5}degree rau kev pab cuam (G{8}) (zoo heev) 10-15 150-200 100-200 500-1,000 0.3× Tsis muaj 8-9 (zoo) 15-25 100-150 200-400 1,000-2,000 0.5 × Tsis pom zoo 7-8 (nruab nrab-nplua) 25-35 70-100 300-600 1,500-3,000 0.8 × Marginal 6-7 (nruab nrab) 35-45 50-70 500-1,000 2,500-4,500 1.0-1.2× Tau txais kev sib tshuam
5-6 (nruab nrab-coarse) 45-55 40-50 800-1,500 4,000-6,500 1.5-2.0 × Pom zoo
4-5 (coarse) 55-70 30-40 1,200-2,500 6,000-10,000 2.5-3.5 × Zoo tagnrho rau kev pabcuam tsis tu ncua
3-4 (coarse) 70-85 25-30 1,500-3,500 7,000-12,000 3.0-4.0 × Txais tau tab sis qis dua
Kev cuam tshuam ntawm Grain Size thiab Carbide Distribution

Lub creep cavitation tsis kam ntawm coarse grained 316 yog qhov tseem ceeb nyob ntawm seb muaj ob qho tib si intragranular thiab grain ciam carbides. Cov cua txias thaum lub sij hawm cov tshuaj annealing uas tsim kom zoo, intragranular carbides (M 23 C 6, MC) muab nag lossis daus ntxiv dag zog rau cov nplej sab hauv, txo cov matrix creep. Cov cua txias qeeb ua rau cov ntxhib, tsis tu ncua ntawm cov ciam teb carbides, uas ua rau lub neej poob qis vim tias lawv qhov chaw zoo nkauj ntawm cov kab noj hniav nucleation. Qhov zoo tshaj plaws microstructure rau creep kev pab cuam ntawm 550℃yog coarse nplej (ASTM G=4-6) nrog ib tug zoo dispersion ntawm intragranular carbides thiab discontinuous grain ciam carbides. Microstructure: Cov tshuaj annealed ntawm 1040-1060 C, txias txias (cua cua, tsis dej quench), ces stabilization annealed ntawm 850-900 C rau 2-4 teev. Lub stabilization anneal precipitates carbides nyob rau hauv ib tug tswj yam tsis muaj sensitization (rau 316L los yog stabilized qib).

Grain Size Specification rau siv hauv Kev Pabcuam Kub Kub Kub

Raws li kev kwv yees lub neej kev pab cuam, cov qauv hauv qab no yog npaj rau 316 sheathed heaters rau kev ua haujlwm tas li ntawm 550℃sheath kub (sab hauv phab ntsa).

Kev Pabcuam Lub Neej ntawm 550 C (teev) Yam tsawg kawg nkaus ASTM Grain Size (tus lej qis dua=coarser) (ASTM) qhov siab tshaj plaws grain loj (ntau dua=me dua) Pom zoo kho cua sov<2,000 (intermittent duty) 3 6 Standard solution anneal + quench 2,000-5,000 4 6 Controlled anneal + forced air cool 5,000-10,000 5 (max, indicating coarser than G=5 is permitted) 5 Extended anneal + stabilisation
Grain loj thiab creep puas validation 10,000-20,000 4 (tsawg kawg coarseness) 5 High-temperature anneal (1100 degree) + qeeb txias

Cov khoom siv kub kub ua kom sov cov qoob loo loj tuaj yeem txiav txim siab los ntawm metallographic tsom xam ntawm tus ntoo khaub lig- ntu, tom qab etching nrog glyceregia (15 mL HCl, 10 mL glycerol, 5 mL HNO3). ASTM grain loj naj npawb yog tau los ntawm kev sib piv nrog cov qauv kab kos raws li ASTM E112 . Creep cavitation puas (me ntsis dub me ntsis (kab noj hniav) nyob rau hauv grain ciam teb ntawm magnification ntawm 500-1000x) feem ntau tshwm sim thaum 50-60% ntawm lub creep lub neej tag lawm. Rau lub tshuab cua sov (G=5), kab noj hniav raug pom ntawm ~ 4,000-6,000 teev ntawm lub neej 8,000 teev. Rau cov khoom zoo (G=8), kab noj hniav pom nyob ib ncig ntawm 200-400 teev, muab kev ceeb toom tsawg dua ua ntej tawg. Kev kuaj ib ntus (ib lub rhaub rau ib pob hauv ib xyoos) rau kev ntsuam xyuas metallographic ntawm cavitation feem muab cov ntaub ntawv saib xyuas rau cov cua sov tseem ceeb.

Xav txog grain loj rau welded thiab khoov Cheebtsam

Cov qoob loo loj yuav tsum raug soj ntsuam nrog rau qhov kawg hau vuam thiab khoov. Vuam tsim ib cheeb tsam cuam tshuam nrog cov hmoov nplej zoo (ASTM G=9-11) raws txoj kab welding. Thaum qhov kub thiab txias qhov nplua no - cheeb tsam cov nplej tuaj yeem yog qhov chaw tsis muaj zog rau kev nkag mus cavitation. Nyob rau hauv cov ntaub ntawv ntawm cov cua sov khiav saum toj 500 degree, lub weld cheeb tsam yuav nyiam dua ua tsis tau tejyam txawm tias lub hauv paus hlau grain loj yog ntxhib. Ib qho kev txo qis yog ua ib qho kev tshaj tawm -weld tov anneal, uas coarsens HAZ nplej. Qhov no tej zaum yuav siv tsis tau. Lwm txoj hauv kev yog siv cov hlau tsis muaj zog ntxiv xws li 310 stainless hlau lossis Inconel 600 rau tag nrho lub tshuab cua sov uas yuav tshem tawm cov nplej loj nyob ntawm qhov sib txawv hauv lub neej nkag.

Xaus: Specification ntawm Coarse Grains rau High Temperature Creep Strength

Rau 316 stainless hlau encased heaters ntawm 550 degree, tus lej ua ntej austenite grain loj yog qhov tseem ceeb rau cov creep cavitation nucleation tus nqi thiab yog li tag nrho cov creep rupture lub neej. Cavitation nucleation yog 3-5 npaug sai dua nyob rau hauv cov khoom zoo grained (ASTM G=8-10) dua nyob rau hauv coarse grained khoom (ASTM G=4-5) nrog creep lub neej txo los ntawm 10,000 teev mus rau 2,000 teev nyob rau tib qhov kev ntxhov siab thiab kub. Cov kws kho tsheb yuav tsum tau qhia txog G=5 lossis G=6, txheeb xyuas los ntawm metallography ASTM E112, rau qhov siab tshaj plaws ASTM grain loj naj npawb (coarser grains) rau 316 sheaths rau kev siv kub kub tsis tu ncua. Cov txheej txheem tau piav qhia hais txog cov qoob loo loj rau qhov muaj peev xwm cavitation tus nqi thiab lub neej tawg, ua rau cov neeg yuav khoom tuaj yeem xaiv 316 sheath tube nrog qhov zoo tshaj plaws tiv thaiv kev nkag mus tsis ua haujlwm hauv cov ntawv thov kub.