PWHT is typically required for which conditions?

• A. For all welds
• B. For certain high-strength or austenitic stainless steels, or thick sections
• C. Never required
• D. Only for aluminum

Answer: (C)

Post-weld heat treatment is used to relieve the residual stresses and adjust the weld’s microstructure in ways that improve ductility and reduce cracking risk. It’s not required for every weld; it’s typically specified for materials where welding induces significant hardening and stress, such as certain high-strength steels, austenitic stainless steels, or when the weld is in a thick section. Aluminum welding, in contrast, generally doesn’t rely on PWHT and has different heat-treatment considerations, so PWHT isn’t typical there. So the condition under which PWHT is usually required is for specific high-strength steels or thick sections (and some grades of stainless steel), not universally or for aluminum.