<P> After the discovery of the short pulsed electric arc in 1800 by Humphry Davy and of the continuous electric arc in 1802 by Vasily Petrov, arc welding developed slowly . C.L. Coffin had the idea of welding in an inert gas atmosphere in 1890, but even in the early 20th century, welding non-ferrous materials such as aluminum and magnesium remained difficult because these metals react rapidly with the air and result in porous, dross - filled welds . Processes using flux - covered electrodes did not satisfactorily protect the weld area from contamination . To solve the problem, bottled inert gases were used in the beginning of the 1930s . A few years later, a direct current, gas - shielded welding process emerged in the aircraft industry for welding magnesium . </P> <P> Russell Meredith of Northrop Aircraft perfected the process in 1941 . Meredith named the process Heliarc because it used a tungsten electrode arc and helium as a shielding gas, but it is often referred to as tungsten inert gas welding (TIG). The American Welding Society's official term is gas tungsten arc welding (GTAW). Linde Air Products developed a wide range of air - cooled and water - cooled torches, gas lenses to improve shielding, and other accessories that increased the use of the process . Initially, the electrode overheated quickly and, despite tungsten's high melting temperature, particles of tungsten were transferred to the weld . To address this problem, the polarity of the electrode was changed from positive to negative, but the change made it unsuitable for welding many non-ferrous materials . Finally, the development of alternating current units made it possible to stabilize the arc and produce high quality aluminum and magnesium welds . </P> <P> Developments continued during the following decades . Linde developed water - cooled torches that helped prevent overheating when welding with high currents . During the 1950s, as the process continued to gain popularity, some users turned to carbon dioxide as an alternative to the more expensive welding atmospheres consisting of argon and helium, but this proved unacceptable for welding aluminum and magnesium because it reduced weld quality, so it is rarely used with GTAW today . The use of any shielding gas containing an oxygen compound, such as carbon dioxide, quickly contaminates the tungsten electrode, making it unsuitable for the TIG process . In 1953, a new process based on GTAW was developed, called plasma arc welding . It affords greater control and improves weld quality by using a nozzle to focus the electric arc, but is largely limited to automated systems, whereas GTAW remains primarily a manual, hand - held method . Development within the GTAW process has continued as well, and today a number of variations exist . Among the most popular are the pulsed - current, manual programmed, hot - wire, dabber, and increased penetration GTAW methods . </P> <P> Manual gas tungsten arc welding is a relatively difficult welding method, due to the coordination required by the welder . Similar to torch welding, GTAW normally requires two hands, since most applications require that the welder manually feed a filler metal into the weld area with one hand while manipulating the welding torch in the other . Maintaining a short arc length, while preventing contact between the electrode and the workpiece, is also important . </P>

Gas tungsten arc welding should be used to weld uhss