Brief introduction to post weld heat treatment (PWHT)
We often receive inquiry from our customers detailed as below:
API 602 Gate Valves, Bolted Bonnet, Rising Stem, Socket Weld with 100mm Long Plain End Nipples Welded at Both Ends, PWHT.
So have you heard of PWHT? What’s PWHT? Well, it is short for post weld heat treatment, which means the heat treatment carried out for the material after welding process.
The main purpose of PWHT is to repair the micro structure of the welded material, and thus maintain or improve material strength and mechanical properties, also to relieve residual stresses. That’s because, during welding process, enough heat is introduced to melt the base material. This temperature causes micro-structural changes of the material and leads to material properties changes, like tensile strength, hardness, etc.
Based on the above, PWHT is critical process needed for welded material, which should be paid enough attention during production.