Q1: Dab tsi tshwm sim yuav tsum ua ntej vuam A335 steel yeeb nkab?
Ua ntej vuam, cov roj thiab xeb nyob rau hauv 25mm ntawm kev zawj thiab ob tog yuav tsum tau huv thiab impurities los ntawm kev sib xyaw rau hauv weld. Rau cov hlau loj xws li P91, nws yog qhov tsim nyog yuav txo tus nqi txias thiab zam kev martensitic hardening thiab tawg. Lub zawj lub zawj yog feem ntau tsim los ua 60℃± 5 degree, thiab lub blunt ntug yog 1.5 ~ 2 hli los xyuas kom nkag mus. Lub Vuam tus pas nrig yuav tsum tau qhuav ntawm 350℃rau 2 teev thiab coj tawm raws li xav tau. Yuav tsum muaj kev tsim cov txheej txheem vuam tsim nyog (WPS) kuj yuav tsum tau lees paub tias cov tsis muaj peev xwm phim cov niam txiv cov khoom kawm.
Q2: Uas Vuam Qws yog haum rau vuam A335 P91 Hlau?
P91 Hlau pom zoo siv E9015-B9 lossis E9018-B9 Bio-Rad Fox B9), uas yog muaj pes tsawg-rad fox b9), uas muaj pes tsawg ntawm cov niam txiv cov khoom (9Clo-v-NB). Cov hluav taws xob yuav tsum yog qhov yooj yim los tswj cov kab sib txawv hydrogen cov ntsiab lus rau<5mL/100g. For TIG root welding, ER90S-B9 welding wire can be selected. Note that the electrode needs to be controlled in coordination with the preheating temperature (200~250°C) and the interlayer temperature (≤300°C). Post-heat insulation (300~350°C/2h) is required immediately after welding to drive out hydrogen.
Q3: Vim li cas thiaj yog kev kho cua sov tom qab Weld (PWtht) qhov tseem ceeb rau A335 steel yeeb nkab?
PWHT can eliminate welding residual stress (usually required to be reduced to ≤30% yield strength) and prevent stress corrosion cracking. For P91 steel, it is necessary to keep it at 740~760°C for 2~4 hours to fully temper the martensite and improve toughness. Insufficient temperature will cause the hardness to exceed the standard (such as >250HB), thiab kev kub siab dhau yuav ua rau lub zog kub siab. Kev kuaj tawv tawv (xws li Brinell hardness HB Tsawg dua lossis sib npaug nrog 250) thiab cov xov xwm hauv zos thiab hauv zos yuav tsum tau kev kho kom sov. ASME B31.3 cov ceg tawv tawv uas yog qhov yuav tsum tau ua rau A335 steel yeeb nkab vuam.
Q4: Yuav ua li cas kom tsis txhob muaj hydrogen-inducts nrib pleb hauv weld cheeb tsam ntawm A335 steel yeeb nkab?
Kev tswj cov khoom siv hydrogen yog qhov tseem ceeb: Siv Ultra-muaj ultra-muaj ultra-tsawg cov ntaub ntawv vuam, thiab zam kev tsim kho hauv huab cua. Qhov ntsuas kub ua ntej yuav tsum tau txaus (xws li 150 ~ 200℃rau tus nqi txias, thiab tso cai rau hydrogen kom diffuse thiab khiav dim. Tus interlayer kub tsis tshaj 300℃los tiv thaiv hydrogen txuam. Tom qab tshav kub dehydrogenation kev kho mob ntawm 350℃/ 1h yog ua tam sim ntawd tom qab vuam. Ib qho ntxiv, tsim cov ntawv sib koom ua ke tsawg (xws li U-puab grooves) tuaj yeem txo cov nyiam ua kom tawg.
Q5: Yuav ua li cas cov kev kuaj yuav tsum muaj nyob hauv cov txheej txheem vuam (PQR)?
PQR yuav tsum muaj cov kev sim siab tensile (cov khoom lag luam yuav tsum muaj nyob hauv cov khoom siv ntawm niam txiv), thiab cuam tshuam rau sab nraud) Metallographic kev ntsuam xyuas kuj yuav tsum tau rau P91 Hlau (Martensite hloov dua siab tshiab> 90%). Txhua qhov kev sim yuav tsum ua raws li ASME IX lossis EN ISO 15614 tus qauv. Kev ntsuas kev ntsuas yuav tsum npog txhua qhov tsis muaj nyob rau hauv kev tsim tiag tiag (xws li tam sim no, voltage, tawm tswv yim tshav kub).
