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.
The East Midlands is one of nine official regions of England at the first level of NUTS for statistical purposes. It consists of Derbyshire, Leicestershire, Lincolnshire (except North and North East Lincolnshire), Northamptonshire, Nottinghamshire and Rutland.
The region has an area of 15,627 km2 (6,034 sq mi), with a population over 4.5 million in 2011. The most populous settlements in the region are Derby, Leicester, Lincoln, Mansfield, Northampton and Nottingham. Other notable settlements include Boston, Chesterfield, Corby, Grantham, Hinckley, Kettering, Loughborough, Newark-on-Trent, Skegness, Wellingborough, and Worksop.
Relative proximity to London and its position on the national motorway and trunk road networks help the East Midlands to thrive as an economic hub. Nottingham and Leicester are each classified as a sufficiency-level world city by the Globalization and World Cities Research Network.
The region is primarily served by East Midlands Airport, which lies between Derby, Loughborough and Nottingham.