Metallurgy. The presence of chromium affects the formation of crystalline structures in different ways from other steels where chromium levels are much less.

to be more accurate, Post weld heat treatment is seldom required on austenitic stainless steel, as this material as a high resistance to brittle fracture; occasionally stress relief is carried out to reduce the risk of stress corrosion cracking.

it may be required in pressurized devices temperatures exceeding 550° C.

for martensitic stainless steel, PWHT can have different effects. see this doc.

check out the following references:

Go Welding

Patent Docs

Stainless Steel Fabrication <-- see the table!

HTH!

it depends on the stainless steel...austenitic stainless steel are not susceptible to martensite formation like for example carbon steel or martensitic SS so PWHT is not necessary to reduce hardness due to rapid cooling. the heat treatment when is performed is usually a solution annealing at approx 1050°c but this is done to dissolve the carbides (sensitization of SS) that reduce the corrosion resistance.

http://www.industrialheating.com/Articles/Column/62087467d24db010VgnVCM100000f932a8c0____

http://www.corrosionist.com/Materials_Stainless_Steel_Welding.htm

S