PWHT loading temperature

[pwtomlin]

I have a question regarding the furnace temperature when a load is placed in it for PWHT. It is generically about any stainless steel, but more specifically cast pumps/valves in CA6NM (wrought equivalent 415). Metallurgically speaking, is there anything detrimental placing a load in the furnace at the tempering (stress relief) temperature of 1100 degrees F versus loading at a lower temperature (~800 F) and ramping up to 1100?

I believe the purpose of the ramp up is to avoid cracking, but are there any other issues that could be potentially caused by loading the furnace at the higher temperature?

 

[metengr]

pwtomlin;
If this is for non-ASME Code work I really do not see a problem other than risk of excessive thermal gradients and distortion. In most cases, there are no adverse effects. Materials that are air hardenable may be at greater risk for distortion and cracking (depending on geometry and thickness) with a rapid temper.

For Code work we have to provide more conservative requirements to assure low thermal gradients for all approved materials. If this is a heat treatment procedure violation, there would need to be a nonconformance and final disposition. This would be some form of dimensional check and perhaps NDT.