304 vs 304L Stainless Hlau: Thaum Tsawg Carbon Matters rau Vuam thiab Corrosion Resistance

Yog tias koj tau txiav txim siab stainless hlau rau lub tank welded, lub nkoj siab, lossis cov kav dej tshuaj, koj tau ntsib cov lus nug: "304 lossis 304L?" Tus nqi sib txawv zoo li me me ntawm daim ntawv - tej zaum $ 200 ntawm $ 5,000 xaj. Tus neeg muag khoom yuav hais tias, "Lawv yeej zoo ib yam." Tab sis qhov kev txiav txim siab $ 200 txiav txim siab seb koj cov welds tseem yuav zoo li cas rau tsib xyoos tom qab ntawd - lossis seb puas muaj kev cuam tshuam intergranular yuav tau noj los ntawm tshav kub- cuam tshuam thaj tsam ntawm txhua qhov sib koom ua ke, tig lub nkoj siab mus rau hauv lub foob pob tawg.

Tag nrho qhov sib txawv ntawm 304 thiab 304L los rau ib tus lej: cov ntsiab lus carbon . 304 tso cai rau 0.08% carbon. 304L - "L" sawv rau "Low Carbon" - caps carbon ntawm 0.03%. Qhov sib txawv ntawm 0.05% yog qhov tsis pom ntawm qhov muag liab qab, tsis tuaj yeem kuaj pom los ntawm cov hlau nplaum, thiab tsis cuam tshuam rau lub zog tensile. Tab sis thaum lub sij hawm vuam - nyob rau hauv feeb thaum cov hlau txias los ntawm 1,500℃mus rau 400℃- uas 0.05% ntxiv carbon nyob rau hauv 304 precipitates tawm raws li chromium carbides ntawm lub grain ciam teb, depleting lub puag ncig hlau ntawm chromium thiab tsim microscopic paths rau corrosion mus tua. Qhov tshwm sim no yog hu ua rhiab heev, thiab qhov tshwm sim tsis ua hauj lwm hom - intergranular corrosion, los yog "weld decay" - tau ua rau ntau stainless steel khoom ua tsis tau tejyam dua li tag nrho lwm yam corrosion mechanisms ua ke.

Txoj cai txiav txim yog yooj yim: yog tias koj vuam, xaiv 304L. 3-8% tus nqi them nqi rau 304L yog qhov tsis tseem ceeb piv rau tus nqi ntawm ib qho kev sib tsoo. Yog tias koj tsis welding - piv txwv li, qhia qhov txias - ua cov ntawv hlau, fasteners, lossis annealed bar Tshuag rau machining - 304 yog technically txaus thiab me ntsis kim. Tab sis nyob rau hauv cov khoom siv niaj hnub no, dual{13}}cov ntaub ntawv pov thawj 304/304L tau dhau los ua ntau yam uas tus nqi hwm tau zoo ploj mus rau feem ntau cov qauv khoom. Thaum tsis ntseeg, qhia dual - ntawv pov thawj 304/304L - koj tau txais cov pa roj carbon tsawg ntawm 304L yam tsis tau them nyiaj ntxiv.

Chemical Composition - Qhov 0.05% Uas Hloov Txhua Yam

304 thiab 304L sib koom tib lub hauv paus chemistry - 18-20% chromium thiab 8-10.5% npib tsib xee - thiab txawv tsuas yog nyob rau hauv lawv cov ntsiab lus siab tshaj plaws tso cai: 304 tso cai txog 0.08% carbon, thaum 304L caps nws ntawm 0.03%. Qhov sib txawv ib leeg no tsis muaj qhov cuam tshuam rau cov khoom siv kho tshuab ntawm chav tsev kub, tab sis yog qhov txiav txim siab rau weld corrosion kuj.

Ob leeg 304 thiab 304L belongs rau 300-series austenitic stainless hlau tsev neeg. Lawv tsis yog-sib nqus nyob rau hauv cov mob annealed, muaj zoo formability thiab weldability, thiab muab zoo corrosion kuj nyob rau hauv atmospheric, aqueous, thiab me ntsis acidic ib puag ncig. Lub npe "18-8" yog hais txog lawv qhov kwv yees li ntawm 18% chromium + 8% nickel muaj pes tsawg leeg - ib qho qauv uas tau ua 304 qib siv stainless hlau ntau tshaj plaws hauv ntiaj teb, suav txog ntau dua 50% ntawm lub ntiaj teb stainless hlau ntau lawm.

Vim li cas 0.05% Carbon tseem ceeb heev? - Tus Txheej Txheem Kev Ntsuas

Thaum twg304 stainless hlauyog rhuab mus rau 425-870℃- qhov kub ntawm qhov kub tau mus txog hauv tshav kub- thaj chaw muaj kev cuam tshuam (HAZ) nyob ib sab ntawm lub vuam - cov pa roj carbon atoms uas tau yaj hauv cov hlau matrix ua txawb thiab tsiv mus rau cov ciam teb, qhov chaw uas lawv hnov ​​​​mob nrog chromium los ua chromium₂₆ carbide. Txhua chromium carbide particle siv kwv yees li 16 chromium atoms rau txhua 6 carbon atoms, depleting thaj tsam ntawm cov qoob loo uas nyob ib sab ntawm chromium qis dua 12% qhov yuav tsum tau ua kom muaj cov yeeb yaj kiab oxide passive. Qhov tshwm sim: microscopic chromium{10}}depleted cheeb tsam ntawm txhua tus ciam teb, uas corrodes nyiam dua thaum raug electrolyte - hom tsis ua hauj lwm hu ua intergranular corrosion (IGC) lossis "weld decay."

Kom nkag siab tias yog vim li cas 0.05% carbon ua rau qhov sib txawv ntawm corrosion kuj thiab corrosion tsis ua hauj lwm, xav txog carbon atoms li "chromium tub sab." Hauv 304, nrog txog 0.08% carbon, muaj cov pa roj carbon txaus hauv cov hlau los nyiag chromium los ntawm kwv yees li 1.3% ntawm tag nrho cov ntsiab lus chromium thaum carbides tsim. Qhov no tso tseg cov qoob loo ciam teb chromium qis dua 12% - qhov tseem ceeb passive zaj duab xis pib. Hauv 304L, nrog tsuas yog 0.03% carbon, tus nqi ntawm chromium uas tuaj yeem "kho tau" tsawg dua 0.5% ntawm tag nrho cov chromium - tsis txaus los tso tseg ib thaj tsam hauv qab ntawm 12% qhov pib. Cov ciam teb hauv welded 304L khaws lawv cov kev tiv thaiv corrosion tag nrho, txawm tias tsis muaj kev tshaj tawm -weld heat treatment.

Qhov ntsuas kub ntawm qhov ntsuas ntawm 425-870℃(800-1,600℃F) yog qhov tseem ceeb vim tias qhov no yog qhov ntsuas kub raws nraim li qhov kub ntawm qhov kub- thaj tsam cuam tshuam ntawm lub vuam hla dhau thaum lub caij txias. Ib tug raug GTAW (TIG) weld ntawm 3mm-thick 304 daim ntawv khaws HAZ nyob rau hauv lub rhiab heev ntau yam rau kwv yees li 30-60 vib nas this - ntev txaus rau carbide nag los pib nyob rau hauv 304, tab sis tsis ntev txaus yuav ua rau sensitization ntsuas nyob rau hauv 304L. Rau cov seem thicker (10mm +), qhov qis qis qis txuas ntxiv lub sij hawm nyob rau hauv qhov rhiab heev rau ob peb feeb, ua 304L qhov tseem ceeb.

Dual -Certified 304/304L - Tus Qauv Niaj Hnub No

Hauv kev xyaum, feem ntau cov hlau tsis muaj steel uas ua rau niaj hnub no - tshwj xeeb yog tiaj- cov khoom dov (daim ntawv, phaj, coil) thiab cov khoom siv tubular (pipe, raj) - yog dual- ntawv pov thawj raws li kev sib ntsib 304 thiab 304L chemistry. Qhov no txhais tau hais tias cov khoom muaj cov pa roj carbon tsawg dua lossis sib npaug li 0.03% (lub rooj sib tham 304L), chromium 18.0-20.0%, thiab npib tsib xee 8.0-10.5% (sib ntsib ob leeg). Dual-cov ntaub ntawv pov thawj tshem tawm qhov yuav tsum tau xaiv - koj tau txais lub weldability ntawm 304L ntawm tus nqi ntawm 304. Nco ntsoov nug koj tus neeg muag khoom yog tias cov khoom muaj ntawv pov thawj dual; Yog tias nws yog, qhov kev sib cav 304 vs 304L raug daws.

Daim ntawv pov thawj dual tau dhau los ua qhov dav vim tias niaj hnub argon- oxygen decarburization (AOD) refining, uas ua rau ntau tshaj 95% ntawm lub ntiaj teb stainless hlau, ib txwm ua tiav cov pa roj carbon qis dua 0.03% yam tsis muaj nqi ntxiv. Cov txheej txheem AOD txhaj tshuaj sib xyaw ntawm argon thiab oxygen rau hauv cov hlau molten kom tshem tawm cov pa roj carbon - thiab nws yooj yim dua thiab pheej yig dua kom tshem tawm cov pa roj carbon mus rau 0.02-0.03% dua li kom tsis txhob muaj tseeb ntawm 0.08%. Qhov no txhais tau tias rau niaj hnub steelmaker, tsim 304L chemistry yog qhov ua tau raws li - thiab tsim 304 nrog cov pa roj carbon ntau dua yuav tsum txhob txwm ntxiv cov pa roj rov qab rau hauv cov yaj. Qhov no yog vim li cas ob daim ntawv pov thawj 304/304L tau dhau los ua cov qauv kev lag luam es tsis yog qhov zam.

[Source] ASTM A240/A240M - Txheem Specification rau Chromium thiab Chromium-Nickel Stainless Hlau Phaj, Ntawv, thiab Sawb. ASTM A312/A312M - Txuj Specification rau Seamless, Welded, thiab hnyav hnyav ua haujlwm Austenitic Stainless hlau kav.

Mechanical Properties - Puas yog 304 thiab 304L tib lub zog?

Nyob rau hauv chav tsev kub nyob rau hauv lub annealed mob, 304 thiab 304L muaj zoo tib yam tensile zog. Ob qib ua tau raws li qhov xav tau ntawm ASTM A240 yam tsawg kawg nkaus: tensile zog Ntau dua lossis sib npaug ntawm 515 MPa (75 ksi), yield zog Ntau dua lossis sib npaug rau 205 MPa (30 ksi), thiab elongation Ntau dua lossis sib npaug li 40%. Txhua qhov sib txawv ntawm lub zog ntawm ob daim ntawm 304 thiab 304L yog tshwm sim los ntawm cov qoob loo loj, keeb kwm ua haujlwm txias, thiab kev xyaum ua kom zoo - tsis yog qhov sib txawv ntawm cov ntsiab lus carbon.

Siab -Tsub Muaj Zog: Qhov sib txawv me me ntawm qhov ntsuas kub siab

Tshaj li ntawm 425℃(800℃F), 304 khaws lub zog me ntsis siab dua 304L vim tias cov pa roj carbon ntau dua muab cov nag lossis daus me me- ua kom muaj zog ntawm cov carbide dispersions zoo. Txawm li cas los xij, qhov kom zoo dua no los nrog kev lag luam loj heev -tawm: ntawm tib qhov kub thiab txias, 304 yog qhov yooj yim rau kev nkag siab yog tias nws tau welded yav dhau los. Rau siab -kev siv kub siab tshaj 425℃qhov yuav tsum tau vuam, xav txog 304H (0.04-0.10% C, UNS S30409) es tsis txhob - uas ua ke nrog lub siab kub siab zog ntawm cov pa roj carbon ntau dua nrog kev tswj cov nplej loj rau kev nkag siab, raws li ASME Boiler Code yuav tsum.

ASME Boiler thiab Pressure Vessel Code Tshooj II, Ntu D muab cov txiaj ntsig kev ntxhov siab rau ob qib ntawm qhov kub siab. Ntawm 500℃(932℃F), 304 muaj qhov tso cai kev ntxhov siab ntawm kwv yees li 102 MPa vs 94 MPa rau 304L - qhov sib txawv ntawm li 8%. Ntawm 600℃(1,112℃F), qhov txawv txav mus txog li 5%. Rau feem ntau cov ntawv thov kev lag luam qis dua 400℃- uas suav nrog feem ntau ntawm kev ua tshuaj lom neeg, khoom noj khoom haus thiab dej haus, tshuaj, kev kho dej, thiab kev siv vaj tse - qhov siab - qhov kub ntawm qhov sib txawv ntawm qhov sib txawv tsis cuam tshuam, thiab qhov zoo ntawm corrosion ntawm 304L outweighs tej theoretical zog 3.

[Source] ASME Boiler thiab Pressure Vessel Code, Tshooj II, Ntu D - Cov Khoom (Metric), 2023 Tsab. ASTM A240 / A240M tso cai rau kev ntxhov siab.

Welding Performance - Qhov Tseem Ceeb ntawm 304 vs 304L Kev Txiav Txim

Weld decay (intergranular corrosion nyob rau hauv tshav kub- cuam tshuam cheeb tsam) tshwm sim nyob rau hauv plaub kauj ruam: (1) lub hauv paus hlau nyob rau hauv lub weld yog rhuab mus rau 425-870℃; (2) carbon atoms diffuse mus rau ib thaj tsam ntawm grain thiab react nrog chromium los tsim chromium carbides; (3) cov qoob loo ciam teb nyob ib sab ntawm cov carbides yog depleted ntawm chromium hauv qab 12%; (4) thaum raug rau ib puag ncig corrosive - txawm me ntsis acids los yog noo noo - chromium{13}}depleted grain ciam teb corrode preferentially, thiab cov hlau cia poob sib nrug raws li grain ciam teb. Hauv 304L, kauj ruam 2 yeej tsis ncav cuag qhov tseem ceeb tshaj plaws vim tias tsis muaj cov pa roj carbon txaus los tsim ib qho kev sib txuas txuas ntxiv ntawm cov nplej-txheej carbides.

Txhawm rau pom cov txheej txheem no, xav txog ib phab ntsa cib. Cov nplej stainless hlau yog cov cib - muaj zog, corrosion- tiv taus, thiab ib tus zuj zus. Cov ciam teb yog cov mortar nruab nrab ntawm cov cib. Hauv un-welded 304 lossis welded 304L, lub mortar muaj zog npaum li cov cib. Tab sis nyob rau hauv welded 304, sensitization dissolves lub chromium tawm ntawm lub mortar, tig nws mus rau hauv xuab zeb. Phab ntsa tseem zoo li phab ntsa - cov cib tseem nyob ntawd, cov duab kos tsis hloov pauv - tab sis lub teeb thawb (ib puag ncig corrosive) ua rau cov cib sib cais, vim cov mortar uas tuav lawv ua ke ploj mus. Qhov no yog vim li cas weld lwj yog insidious heev: cov tivthaiv zoo li qub kom txog thaum nws tsis dheev.

Vuam 304 vs 304L - Cov Cai Siv Tau

Txoj cai rau TAG NRHO welding: Siv 308L muab tub lim hlau (ER308L rau TIG, E308L rau stick), tsis hais seb koj puas vuam 304 txog 304, 304L rau 304L, lossis 304 txog 304L. Qhov qis-carbon muab tub lim kom ntseeg tau tias cov hlau vuam nws tus kheej yog resistant rau rhiab heev. Txawm hais tias lub hauv paus hlau yog tus qauv 304, cov hlau tso rau hauv cov hlau yuav muaj kev tiv thaiv corrosion ntawm304l hlau.

Tshaj tawm -Kev kho cua sov - Thaum 304 Yuav Tsum Tau thiab 304L Tsis

Qhov tseem ceeb sib txawv ntawm 304 thiab 304L yog qhov no: ib qho welded 304 tivthaiv uas yuav pom cov kev pabcuam corrosive yuav tsum yog kev daws teeb meem-annealed tom qab vuam kom rov ua dua-kho cov chromium carbides thiab rov ua kom corrosion. Kev daws annealing yuav tsum tau cua sov rau tag nrho cov Cheebtsam rau 1,040-1,150℃(1,900-2,100℃F) thiab tom qab ntawd sai sai quenching hauv dej - tus txheej txheem uas kim, zog{17}}intensive, thiab feem ntau lub cev tsis yooj yim sua rau loj fabricated lugs (cov kav dej, cov kav dej, cov kav dej, cov kav dej, thiab lwm yam). Ib qho welded 304L tivthaiv ua tau zoo ib yam corrosion kuj nyob rau hauv raws li -welded mob - tsis muaj tom qab-weld kev kho cua sov yuav tsum tau.

Qhov no yog kev sib cav txog kev lag luam rau 304L hauv ib kab lus: tus nqi ntawm kev daws teeb meem annealing loj welded fabrication ($ 2,000-10,000 rau ib lub voj voog rau lub cub tawg ntxiv rau qhov kev pheej hmoo ntawm kev cuam tshuam) yog 10-50 npaug ntawm tus nqi rau kev siv 304L es tsis txhob 304 ($ 200-5 qhov project). Thaum PWHT tsis yooj yim sua - rau thaj chaw welds ntawm cov piping ntsia, rau cov tso tsheb hlau luam loj, rau kev kho cov cuab yeej uas twb muaj lawm - 304L tsis yog nyiam xwb; nws yuav tsum tau.

Vuam Parameters rau 304 thiab 304L

[Source] AWS A5.9/A5.9M - Specification for Bare Stainless Steel Welding Electrodes and Rods. AWS D1.6/D1.6M - Structural Welding Code - Stainless Steel.

Corrosion Resistance - Qhov Chaw Tsawg -Carbon Advantage Pom Pom

Intergranular corrosion (IGC) is the primary corrosion mechanism that differentiates 304 from 304L. In the unwelded, annealed condition, both grades have identical general corrosion resistance to atmospheric exposure, fresh water, mild chemicals, and food products. But after welding, 304 becomes susceptible to IGC in even mildly corrosive environments - including tap water, rainwater, and humid air - because the chromium-depleted grain boundaries in the HAZ are anodic to the surrounding grains, creating microscopic galvanic cells. 304L after welding remains resistant to IGC because its grain boundaries retain >12% chromium.

Intergranular corrosion yog qhov txaus ntshai tshwj xeeb vim nws nyuaj rau kev kuaj pom los ntawm kev kuaj pom. Ib qho sensitized 304 weld zoo li ib txwm nyob ntawm qhov chaw - nws tuaj yeem dhau qhov kev ntsuas dye penetrant, vim tias qhov chaw txuas mus ntxiv. Tab sis thaum raug cov kua conductive - txawm me ntsis acidic txheej txheem dej - lis ciam teb, thiab cov hlau poob lub zog yam tsis poob seem thickness. Lub sensitized 304 yeeb nkab uas tau hydrotested rau 1.5x tsim siab nyob rau hnub 1 yuav poob ntawm 0.3x tsim siab tom qab rau lub hlis ntawm kev pab cuam, vim hais tias intergranular corrosion tau hloov nruam hlau mus rau hauv xoob sib txuas nplej uas tsis muaj zog ntawm lawv.

Corrosion Resistance los ntawm Ib puag ncig - 304 vs 304L Tom qab Vuam

Standard Test rau Intergranular Corrosion Susceptibility

Peb qhov kev ntsuam xyuas yog siv los xyuas kom meej tias 304L (los yog ib qho qis -carbon stainless hlau) yog resistant rau intergranular corrosion tom qab vuam: ASTM A262 Xyaum A (oxalic acid etch test - nrawm, 15 feeb), Xyaum C (nitric acid / Huey test {{5}4}} poob ntau tshaj tsib zaug lub sij hawm), thiab xyaum E (tooj liab- tooj liab sulfate-sulfuric acid / Strauss xeem - khoov xeem tom qab 15- teev boil). 304L nyob rau hauv raws li-welded mob kis tag nrho peb; 304 nyob rau hauv raws li -welded mob ua tsis tau tag nrho peb - ​​muab quantitative, standard-based pov thawj ntawm qhov tseem ceeb sib txawv ntawm cov qib.

Kev xeem Huey (ASTM A262 Practice C) yog qhov hnyav tshaj plaws thiab qhov ntau ntawm peb. Ib qho welded 304 cov qauv boiled nyob rau hauv 65% nitric acid rau tsib 48-teev lub sij hawm feem ntau poob 0.5-5.0 mm / xyoo (20-200 mils ib xyoos) nyob rau hauv lub HAZ - ib tug corrosion tus nqi siab tshaj 10{{18.} lub hauv paus ntawm 10 zaug Ib qho zoo sib xws welded 304L cov qauv kuaj nyob rau hauv cov xwm txheej zoo tib yam poob qis dua 0.05 hli / xyoo (2 mils ib xyoos) - nce mus txog qhov kev txwv ntawm qhov ntsuas. Qhov kev sib txawv ntawm qhov sib txawv ntawm cov qoob loo ntawm cov ciam teb corrosion yog cov pov thawj engineering tom qab txoj cai yooj yim: "weld=siv L-qib."

Daim ntawv qhia - Thaum twg xaiv 304 vs 304L

Tsib Txoj Cai Kev Xaiv Ntawm 304 thiab 304L

Txoj cai 1Cov khoom puas yuav welded? - Yog tias YOG, siv 304L lossis dual- tau ntawv pov thawj 304/304L. Ib lo lus nug no daws ntau dua 80% ntawm 304 vs 304L kev txiav txim siab. Txhua qhov vuam - txawm tias ib qho tack weld, ib daim ntawv txuas nrog, ib qho kev txhawb nqa - tsim HAZ uas muaj kev cuam tshuam rau kev nkag siab ntawm tus qauv 304.

Txoj cai 2Puas yog phab ntsa thickness ntau dua 3 hli (1/8 nti)? - Yog tias YOG, siv 304L. Thicker seem txias qeeb qeeb los ntawm vuam kub, ncua sij hawm siv nyob rau hauv qhov rhiab heev (425-870℃). 25mm- phaj tuab yuav nyob twj ywm hauv qhov kev xav tau rau 5-10 feeb tom qab vuam, piv rau 30-60 vib nas this rau daim ntawv 1.5mm - ntau dua 10 npaug ntev dua rau carbide nag los tsim.

Txoj cai 3Cov khoom puas yuav pom ib puag ncig corrosive? - Yog tias YOG thiab welded, siv 304L. "Corrosive" suav nrog ib puag ncig uas zoo li me me: dej kais dej, dej nag, huab cua ntub, cov khoom noj acids (kua txiv hmab txiv ntoo, kua txiv hmab txiv ntoo), tshuaj ntxuav, txheej txheem condensate. IGC tsis xav tau cov kua qaub ntau ntau - nws tsuas yog yuav tsum muaj cov khoom siv hluav taws xob los tsim cov galvanic cell ntawm chromium -depleted grain ciam (anode) thiab cov nplej nyob ib puag ncig (cathode).

Txoj cai 4Puas yog post-weld solution annealing ua tsis tau lossis siv tsis tau? - Yog tias YOG, siv 304L. Kev daws annealing yuav tsum tau cua sov mus rau 1,040-1,150℃tom qab dej ceev ceev. Qhov no yog tsis yooj yim sua rau: teb-welded piping, tank loj, ntsia khoom, kho, nyias-wall Cheebtsam uas yuav distort, thiab cov khoom uas machined nto uas yuav oxidize. Rau cov xwm txheej no, 304L yog tib txoj kev xaiv.

Txoj cai 5Puas yog kev ua haujlwm kub siab tshaj 425℃(800℃F)? - Yog tias YOG, xav txog 304H hloov pauv. 304 muaj qhov zoo me ntsis siab dua - qhov kub thiab txias tshaj li 304L, tab sis yog tias cov khoom siv welded thiab ua haujlwm siab tshaj 425℃, 304H (UNS S30409, 0.04-0.10% Ceeper tshaj li 7 lub zog loj thiab sib npaug rau SME) Kev ua raws cai. Tsis txhob siv 304 lossis 304L rau ASME-coded siab hlab ntsha siab tshaj 425℃yam tsis tau txheeb xyuas qhov kev ntxhov siab.

Cov lus nug nquag

Q: Dab tsi yog "L" hauv 304L sawv cev rau?

A: "L" sawv cev rau "Low Carbon." 304L stainless hlau muaj cov ntsiab lus siab tshaj plaws ntawm 0.03%, piv rau 0.08% rau tus qauv 304. Cov ntsiab lus qis dua no tiv thaiv chromium carbide nag lossis daus ntawm cov ciam teb thaum vuam, uas yog lub hauv paus ua rau intergranular corrosion (weld lwj). Lub npe "L" tau qhia los ntawm ASTM hauv xyoo 1950s tshwj xeeb los hais txog qhov tsis ua haujlwm ntawm cov khoom siv tshuaj lom neeg.

Q: Puas yog 304L tsis muaj zog dua li 304?

A: Tsis yog - nyob rau hauv chav tsev kub, 304 thiab 304L muaj qhov tseem ceeb zoo tib yam tensile thiab yield zog (ob leeg raws li ASTM A240 yam tsawg kawg nkaus: 515 MPa tensile, 205 MPa yield). Ntawm qhov kub siab tshaj 425℃(800℃F), 304 khaws lub zog siab dua me ntsis (kwv yees 5-8% siab dua tso cai rau kev ntxhov siab ntawm 500℃ib ASME Code), tab sis rau cov ntawv thov qis dua 400℃- uas suav nrog feem ntau siv kev lag luam - ob qib sib pauv tau ntawm lub zog.

Q: Kuv puas tuaj yeem txuas 304 txog 304L?

A: Yog - 304 thiab 304L yog tag nrho rau vuam. Siv ER308L (TIG) lossis E308L (stick) muab tub lim hlau. Qhov qis -carbon muab tub lim kom ntseeg tau tias cov hlau welding yog resistant rau rhiab heev txawm hais tias lub hauv paus hlau carbon cov ntsiab lus. Qhov kev txiav txim siab nkaus xwb yog tias 304 sab ntawm HAZ tseem tuaj yeem cuam tshuam rau kev nkag siab yog tias cov khoom siv yuav pom cov kev pabcuam corrosive.

Q: Puas yog 304L xav tau kev tshaj tawm -weld kev kho cua sov?

A: Tsis yog - qhov no yog qhov zoo ntawm 304L. Nyob rau hauv raws li -welded mob, 304L resists intergranular corrosion tsis muaj post-weld heat treatment. 304, los ntawm kev sib piv, yuav tsum tau tov annealing ntawm 1,040-1,150℃+ dej quenching tom qab welding los kho corrosion kuj yog hais tias cov khoom yuav pom corrosive kev pab cuam.

Q: Dual -certified 304/304L yog dab tsi?

A: Dual - ntawv pov thawj 304/304L yog cov khoom siv ib txhij ua tau raws li cov tshuaj muaj pes tsawg leeg ntawm ob qib: carbon Tsawg dua lossis sib npaug li 0.03% (sib ntsib 304L), chromium 18.0-20.0%, nickel 8.0-10.5% (me ntsis). Nws tau dhau los ua cov khoom lag luam los ntawm cov hlau tsis muaj steel feem ntau vim tias niaj hnub AOD refining ib txwm ua tiav cov qib carbon qis dua 0.03%. Dual-certified khoom muab koj lub weldability ntawm 304L ntawm tus nqi ntawm 304 - thiab yuav tsum nco ntsoov yog koj thawj xaiv thaum muaj.

Q: Puas yog 304 xeb?

A: 304 thiab 304L yog "stainless" - tsis yog "stain- pov thawj." Ob qib tiv thaiv xeb nyob rau hauv feem ntau sab hauv tsev thiab sab nraum zoov ib puag ncig, tab sis tuaj yeem tsim cov xeb xeb (tshuaj yej staining) hauv chloride- thaj chaw nplua nuj - tshwj xeeb yog thaj chaw ntug dej hiav txwv nrog ntsev tsuag. Qhov no yog qhov kev txwv dav dav ntawm 304 tsev neeg, tsis yog qhov sib txawv ntawm 304 thiab 304L. Rau chloride- thaj chaw nplua nuj ( dej hiav txwv, ntug dej hiav txwv, de- cov ntsev ntsev), hloov mus rau 316L, uas ntxiv 2-3% molybdenum los tiv thaiv pitting corrosion.

Q: 304 vs 304L vs 316L - Kuv yuav xaiv li cas?

A: Xaiv 304/304L (dual{2}} ntawv pov thawj) rau kev dav dav - lub hom phiaj welded fabrication, kev ua zaub mov, kev siv vaj tse, thiab kev pabcuam tshuaj me me uas tsis muaj chlorides. Xaiv 316L thaum ib puag ncig muaj chlorides (seawater, ntug hiav txwv dej, de-icing ntsev, tshuaj txheej txheem nrog Cl⁻) - 316L ntxiv 2-3% molybdenum rau pitting kuj. Xaiv 304H rau ASME cov hlab ntsha siab ua haujlwm siab tshaj 425℃qhov twg lub zog nkag yog qhov tseem ceeb. Tsis txhob xaiv tsis yog -L-qib 304 rau welded Cheebtsam uas yuav pom tej corrosive ib puag ncig.

Q: Kuv yuav ua li cas thiaj paub tseeb tias kuv cov khoom yog 304L tiag tiag thiab tsis yog 304?

A: Txheeb xyuas Cov Khoom Siv Xeem Xeem (MTR) - nws yuav tsum qhia Carbon Tsawg dua lossis sib npaug li 0.03%. PMI (Positive Material Identification) siv handheld XRF tsis tuaj yeem paub qhov txawv ntawm 304 los ntawm 304L vim tias XRF tsis tuaj yeem ntsuas cov pa roj carbon (cov pa roj carbon ntau dhau lub teeb rau XRF kuaj pom). Tib txoj kev tshawb xyuas kev ntseeg tau tsuas yog Optical Emission Spectroscopy (OES), uas tuaj yeem ntsuas cov ntsiab lus carbon. Yog tias kev txheeb xyuas cov ntsiab lus ntawm cov pa roj carbon monoxide yog qhov tseem ceeb, thov kev kuaj tshuaj lom neeg los yog cia siab rau lub zeb MTR (EN 10204 Hom 3.1).