Stainless sensitisation
Stainless sensitisation
(OP)
Can anyone explain the circumstances in which PWHT of 321 SS is appropriate? A customer has recently asked my shop to prepare a WPS for welding SA-312 TP321 pipe to itself and apply 1100 deg F PWHT for 1 hour. This seems like a recipie for carbide precipitation to me. The base metal thickness is 0.432", welded with GTA root and SMA fill and cap, using 321 rod. My stainless weld prcoedures are usually designed to keep the heat input as low as possible and keep the interpass temp are 375 F. The customers primary concern seems to be ductility in the as-welded condition, but I believe the proposed "cure" is going to make things worse.





RE: Stainless sensitisation
We made thousands of butt welds in 321 SS piping fabricating serpentine heat exchangers that operate at 600°F. We had a number of 321 SS storage tanks and associated piping.
There was never any thought of PWHT.
RE: Stainless sensitisation
I would agree with unclesyd. I see no real benefit for the cost and time related to stress relieve unless you have specific concerns over residual stresses from welding related to the performance of the component under ambient temperature service. Keep in mind that at elevated temperature service any residual stresses will diminish.
RE: Stainless sensitisation
RE: Stainless sensitisation
RE: Stainless sensitisation
RE: Stainless sensitisation
Is this for prevention of SCC by polythionic acid?
RE: Stainless sensitisation