post heating of P91
post heating of P91
(OP)
Hi,
After welding P91 steel (P No. 5B), we perform post heat treatment at 300 deg.C for 4hr and then PWHT at 745deg.C for 2hr. If we perform PWHT exactly after welding (without any delay), post heat is required or not?
Why shall we perform post heat treatment?
Regards
After welding P91 steel (P No. 5B), we perform post heat treatment at 300 deg.C for 4hr and then PWHT at 745deg.C for 2hr. If we perform PWHT exactly after welding (without any delay), post heat is required or not?
Why shall we perform post heat treatment?
Regards





RE: post heating of P91
Typically for Grade 91 steels, welding is performed and the joint is cooled to below 100 deg C. Once this operation is completed, you PWHT. All welding consumables should be low hydrogen and follow proper bake-out procedure before welding.
RE: post heating of P91
RE: post heating of P91
RE: post heating of P91
Why would a weld filler with high nickel content make it more crucial to allow martensite conversion? Is martensite not strictly an iron base material phenomenon?
Thanks.
RE: post heating of P91
Hi nickel also lowers the 1st and 2nd critical temp, so if you PWHT at too high a temp you may overtemper the piece and lose creep stength properties, so the max PWHT will be lowered by about 30 F compared to the optimum PWHT for a matching electrode. See papers by Jeff Henry and Eur-weld
RE: post heating of P91