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​Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding, is an arc welding process that uses a non-consumable tungsten electrode to produce the weld. The weld area and electrode are protected from oxidation or other atmospheric contamination by an inert shielding gas (argon or helium). A filler metal is normally used, though some welds, known as autogenous welds, or fusion welds do not require it. When helium is used, this is known as heliarc welding. A constant-current welding power supply produces electrical energy, which is conducted across the arc through a column of highly ionized gas and metal vapors known as a plasma. GTAW is most commonly used to weld thin sections of stainless steel and non-ferrous metals such as aluminum, magnesium, and copper alloys. The process grants the operator greater control over the weld than competing processes such as shielded metal arc welding and gas metal arc welding, allowing for stronger, higher quality welds. However, GTAW is comparatively more complex and difficult to master, and furthermore, it is significantly slower than most other welding techniques. A related process, plasma arc welding, uses a slightly different welding torch to create a more focused welding arc and as a result is often automated.

Lincoln (/ˈlɪŋkən/) is a cathedral city and county town of Lincolnshire in the East Midlands of England. The non-metropolitan district of Lincoln had a 2012 population of 94,600. The 2011 census gave the urban area of Lincoln, which includes North Hykeham and Waddington, a population of 130,200.

Roman Lindum Colonia developed from an Iron Age settlement on the River Witham. The city's landmarks include Lincoln Cathedral, an example of English Gothic architecture and the tallest building in the world for over 200 years, and the 11th-century Norman Lincoln Castle. The city is home to the University of Lincoln and Bishop Grosseteste University, and to Lincoln City FC and Lincoln United FC.