What‘re thickness involved. You’ve to respect the materials engineering requirements, otherwise pay the price. For example it’s not advisable to weld P-91 steel without any provision for immediate PWHT. Better try when you’re ready with PWHT facilities.
You may delay PWHT for the other grade by adopting Post Heating or DHT, but may not have much luck with Garde-91 steel.
For P-91 a DHT @ 300-350 Deg C / 4 hrs is recommended as an alternative. Mind you NON-heat treated hardness of grade-91 steel would be easily over 350 HV, hence any impact loading, rough handling could crack the welds. Hence sooner the PWHT done, it’s better.
Also note DHT for grade -91 steel must be done after cooling the steel to room temperature for the whole martensitic transformation to occur. DHT should follow next. Without this the creep properties would be bad.
It’s better to know the full details first.
Shell DEP’s are exhaustive , read thoroughly & you’ll have the answer.
Thanks.
Pradip Goswami, P.Eng,IWE
Independent Welding & Metallurgical Engineering Specialist ,
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Prasu Cutie
Sent: Saturday, August 06, 2016 10:33 PM
To: materials-welding@googlegroups.com
Subject: [MW:25208] Reg. post heating for low alloy steels
Dear experts,
We are going to start pqr for low alloy steels i.e. A335 Gr P11, P22, P5, P91 etc, it suppose to be post weld heat treated immediately after welding. As per literature if pwht is not possible immediately after welding, intermediate PWHT recommende .i.e pos heating.
Now the question is is there any code reference for the same? What is the heating time n temp???
The codes we r following here are shell dep's n asme b 31.3
Project: refinery
Awaiting for your reply
Thanks n regards
Prasad
0096594122634
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