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.
Coalville is an industrial town in the district of North West Leicestershire, Leicestershire in the East Midlands of England, with a population at the 2011 census of 34,575. It lies on the A511 trunk road between Leicester and Burton upon Trent, close to junction 22 of the M1 motorway where the A511 meets the A50 between Ashby-de-la-Zouch and Leicester. It borders the upland area of Charnwood Forest to the east of the town.
Coalville is twinned with Romans-sur-Isère in southeastern France.