ASME B31.3 – 2002 paragraph 331.1.3(b)(2) does not require PWHT for socket welded pipe connections of NPS 2 and smaller when the fillet throat is 13mm (1/2 in) and smaller, with the recommended preheat applied and specified minimum tensile strength is 71 ksi and less, for P 3, 4, 5 and 10A. This means P5 B’s such as 5Cr, 9Cr can be welded without PWHT within the about constraints. I was always under the impression that these materials, containing more than 3% Cr should be PWHT regardless; does anybody have experience with this?
Cheers
Joe