The process of welding is a fabrication or sculptural that joins materials, usually metals or thermoplastics, by merging. This is often done by melting and adding a filler material to form a pool of molten material (the weld pool) this cools to become a strong joint, with pressure sometimes used in combining with heat, or by itself, to produce the weld. This is in contrast with soldering and brazing, which involve melting a lower-melting-point material between the workpieces to form a bond between them, without melting the workpieces.
Up until the end of the 19th century, the only welding process was forge welding, which blacksmiths had used for centuries to join iron and steel by heating and hammering them.
Gas metal arc welding
Different energy sources can be used for welding, including a gas flame, an electric arc, a laser, an electron beam, friction, and ultrasound. While often an industrial process, welding can be done in many different environments, including open air, under water. Welding remains dangerous, and precautions are taken to avoid burns, electric shock, eye damage, poisonous fumes, and overexposure to ultraviolet light.