Basically, the welding process consists of solidly joining two or more metal pieces or different parts to form a final piece. In this process the surfaces to be welded are heated, both in contact, until the metal melts and becomes malleable. Once both parts have cooled down, the joint solidifies and becomes a single piece.
In this casting process no external substances are added to keep the structure of the metal intact. Different tools are usually used as a source of energy, such as an electric arc, a gas flame, an electron beam, laser or ultrasound processes. Their use will depend on the type of metal the piece is made of as well as the type of finish it is to be given.