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Welding is a process that joins two materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material (the weld puddle) that cools to become a strong joint, but sometimes pressure is used in conjunction 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.
Many different energy sources can be used for welding, including a gas flame, an electric arc and a laser. While it is often an industrial process, welding can actually be done in many different environments, including open air and even underwater. Regardless of location however, welding remains dangerous and precautions must always be taken to avoid burns, poisonous fumes, electric shock, and overexposure to ultraviolet light. Until the end of the 19th century, the only available welding process was forge welding which blacksmiths had used for many centuries to join metals by heating and pounding them together. Arc welding and oxyfuel welding were among the first processes to develop during the 1800s, and resistance welding followed soon after. Welding technology advanced quickly during the early 20th century as the two world wars increased the demand for reliable and inexpensive methods of joining materials together. Following the wars, several modern welding techniques were developed, including manual methods like shielded metal arc welding, now one of the most popular welding methods, as well as semi-automatic and automatic processes such as gas metal arc welding, submerged arc welding and flux-cored arc welding. Developments continued with the invention of laser beam welding and electron beam welding in the latter half of the century. Today, the science continues to advance. Today,. robot welding is becoming more commonplace in industrial settings.
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