There are mainly the following kinds.
From an organizational point of view
The purpose of heat treatment is to soften the hardened brittle structure of the material, form an annealed structure with good strength and toughness, and improve the ductility and fracture toughness of the welded joint material.
(2) From the stress state.
In order to eliminate the uneven stress state between cold and hot, realize the relaxation of welding stress and stabilize the size and shape of the structure, it is necessary to use stress-relieving annealing or artificial aging heat treatment to restore the properties of the material.
(3) improve corrosion resistance.
For austenitic stainless steel products, the welding structure and stress will reduce the corrosion resistance of the material, so the welding area must be stress relieved.
(4) preventing thermal strain aging embrittlement
Heat treatment and annealing are required after welding.
(5) Dehydrogenation after welding
Mainly to accelerate the escape of hydrogen in the weld, especially for low alloy steel weldments.
Therefore, artificial aging is only a method to eliminate welding stress in post-weld heat treatment.