QW 407.1 & .2 PWHT of 304 Stainless 1

[jrupert24]

We want to do a low level stress relief for stainless steel. Our current WPS shows a range of 1650-2000F PWHT. The pqr used the 1650F. The way I read it, we can determine that range for this P number. Can I just revise the WPS with a new range? It appears that it is not that important for P8 materials. Can someone help?

 

[metengr]

jrupert24;
Do not perform a low temperature stress relief for P-No 8 material (304). It will not serve any useful purpose. Your PWHT for 304 weldments in your WPS is actually a solution anneal post weld heat treatment to remove the effects of sensitization from welding. The 1650 deg F for your PWHT needs to be much higher in temperature, more like a range of 1900-1950 deg F, followed by rapid cooling to avoid the temperature range of 850-1400 deg F.

Any low temperature thermal treatment is a waste of time and money. Plus, you can undo the solution anneal heat treatment that was required in your WPS.

 

[jrupert24]

We were just looking for options to stay outside the sensitization range, but I agree with you that it probably won't do much. I think in the end we will go with the 1950 solution anneal. The issue is that it is a very thick weldment (5.5" thick) with branch connections, etc. and we are wondering how we will cool it fast enough.

Do you happen to know what kind of a cooling rate I would need in degrees per hour through that range?

 

[metengr]

jrupert24;
I am going to ask a stupid question, why are you even considering any form of thermal treatment after welding 5.5" thick material. You would need one heck of a furnace and quench tank.

Why are you having any thermal treatment after welding such thick section components. Do you need a re-solution heat treatment? Can you get by with controlled welding and live with some sensitization?