Joint Zone Plasticization

During welding, the material in the joint zone becomes plastic due to the heat, i.e., soft and deformable. Only then can the materials properly bond and a load-bearing weld form. If the zone doesn't get plastic enough, you won't get a clean penetration and the weld won't hold. Adjust the heat input to the material so that the zone becomes nicely soft but doesn't burn or overheat. For steel, a post-weld heat treatment may be necessary to restore the correct properties to the structure.