Why is PWHT needed after welding?

Question

Accepted Answer

PWHT is needed after welding to relieve residual stresses and improve the mechanical properties of the welded joint.

PWHT helps to reduce residual stresses that are generated during welding.
It improves the mechanical properties of the welded joint, such as toughness and ductility.
PWHT can prevent cracking and distortion in the welded structure.
It helps to achieve the desired microstructure and hardness in the heat-affected zone.
PWHT is commonly used in industries like oil and gas, power generation, and construction.

Accepted Answer

Post-weld heat treatment (PWHT) is applied to steel assemblies primarily to reduce the likelihood of brittle fracture by reducing the level of tensile welding residual stresses and by tempering hard, potentially brittle, microstructural regions.