Why PWHT Not Required in SS
Post Weld Heat Treatment (PWHT) is typically not required in stainless steel. This is because stainless steel has a different microstructure compared to carbon steel, which makes it less susceptible to cracking and hydrogen induced cracking during welding. Additionally, stainless steel has a higher resistance to corrosion, which means it is less likely to degrade over time due to the heat generated during welding. Since stainless steel has austenitic microstructure which is stable at room temperature, so no microstructure impact during welding. So PWHT is not recommended.
However, in certain situations, PWHT may be required for stainless steel, such as when the application involves high-stress loading, corrosive environments, or when welding procedures are performed under strict codes and standards. In such cases, the specific requirements for PWHT may vary and should be specified by the relevant codes and standards.
The necessity for any type of heat treatment of austenitic chromium-nickel steel weldments depends largely on the service conditions encountered. For some applications, heat treatment is used to impart the greatest degree of corrosion resistance possible, e.g. by solution treating to homogenize the composition or stabilizing, to minimize the risk of sensitization during subsequent elevated temperature exposure.
It’s important to note that in some applications, PWHT may still be recommended for stainless steel, even if it’s not technically required, in order to optimize the material’s properties and ensure the highest level of performance and safety.
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