Welding is a fabrication process that uses heat, pressure, or both to fuse two or more parts together, forming a joint as the parts cool. Welding is typically used on metals and thermoplastics, but can also be used on wood. The completed welded joint can be referred to as a weldment .Welding is a fabrication process whereby two or more parts are fused together by means of heat, pressure or both forming a join as the parts cool. Welding is usually used on metals and thermoplastics but can also be used on wood.