CrNi attachment on C.Steel shell before PWHT 1

[termoguven]

WE HAVE A PRESSURE VESSEL. SHELL MATERIAL IS SA516GR70.
WE SHALL DO HEAT TREATMENT AT 593C(1100F) TEMPERATURE.
WE HAVE SOME SA304L ATTACHMENTS ON SHELL.

HOW DOES HEAT TREATMENT AT 593C EFFECT THOSE CRNI ATTACHMENTS?
SHOULD I WELD PADS ON SHELL AND WELD THOSE ATTACHMENTS AFTER PWHT?

 

[ijzer]

If Inconel weldfiller metal was used for this dissimilar weld there will be no problem with respect to difference in thermal expansion. The stainless itself won't have a problem since L quality is specified , so with short PWHT time no sensitizing is expected.

 

[rustbuster1]

Your first option - welding the 304L to the CS and then PWHTing the whole thing - is common in many industries. 309 electrodes are commonly used to do this. Make sure however, if the service is in SCC-causing environments, that the 304L is clean before the PWHT. C from oils and organic matter will tend to migrate into the SS at 1100+F

 

[ijzer]

I would not advice to use 309 electrodes for a 304L to CS weld that needs PWHT. The difference in thermal expansion between 309 and CS is to large and can cause cracking. Better to use Inconel electrode which has a thermal expansion coefficient that lays between CS and Stainless steel.