Stress Relief Annealing Prior to Post-Treatment

You do stress relief annealing to remove the internal stresses that occur during welding. If you don't do it, the part can warp or even crack. You heat the component evenly to a high temperature and let it sit there for a while so the structure can settle. Then it must cool slowly and controlled, otherwise you build the stresses back up. It's important that heating and cooling happen evenly everywhere, especially with thick or complex parts.