Purpose of post-weld heat treatment

1. Relax the welding residual stress.

2. Stabilize the shape and size of the structure and reduce distortion.

3. Improve the performance of base metal and welded joints, including:

a. Improve the plasticity of the weld metal.

b. Reduce the hardness of the heat-affected zone.

c. Improve fracture toughness.

d. Improve fatigue strength.

e. Restore or increase the yield strength reduced during cold forming.

4. Improve the ability to resist stress corrosion.

5. Further release the harmful gases in the weld metal, especially hydrogen, to prevent the occurrence of delayed cracks.