P91 welding

by nuno
(setubal, portugal)

I am doing an exam of P91 6g pipe.
I have never welded this chromium nickel alloy, only carbon steel and stainless.
Do we use purge gases?
What preheat and PHWT?

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sorry, but I do not have first hand experience with this alloy...I have welded similar alloys but not p91.

i did locate an excellent paper on welding p91 steel.

copy and paste this link in your browser.
http://www.steamforum.com/pictures/Grade%2091%20R%2010-05.pdf