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.
Nottingham (/ˈnɒtɪŋəm/ (About this soundlisten) NOT-ing-əm) is a city and unitary authority area in Nottinghamshire, England. Part of the East Midlands region, it is 128 miles (206 km) north of London and 45 miles (72 km) northeast of Birmingham. To the west lies Derby, separated by the M1 motorway.
Nottingham has links to the legend of Robin Hood and to the lace-making, bicycle (notably Raleigh bikes) and tobacco industries. It was granted its city charter in 1897, as part of Queen Victoria's Diamond Jubilee celebrations. Nottingham is a tourist destination; in 2018, the city received the second highest amount of overnight visitors in the Midlands and the highest amount in the East Midlands.
In 2017, Nottingham had an estimated population of 329,200. The population of the city proper, compared to its regional counterparts, has been attributed to its historical and tightly-drawn city boundaries. The wider conurbation, which includes many of the city's suburbs, has a population of 768,638. It is the largest urban area in the East Midlands and the second-largest in the Midlands. Its Functional Urban Area, also the largest in the East Midlands, has a population of 919,484. The population of the Nottingham/Derby metropolitan area is estimated to be 1,610,000.
Its metropolitan economy is the seventh largest in the United Kingdom with a GDP of $50.9bn (2014). The city was the first in the East Midlands to be ranked as a sufficiency-level world city by the Globalization and World Cities Research Network.
Nottingham's public transport system won awards prior to 2015, including the largest publicly owned bus network in England, and is also served by Nottingham railway station and the modern Nottingham Express Transit tram system.
It is also a major sporting centre and, in October 2015, was named 'Home of English Sport'. The National Ice Centre, Holme Pierrepont National Watersports Centre and Trent Bridge international cricket ground are all based in or around the city, which is also the home of two professional football teams; the former world's oldest professional league club Notts County and Nottingham Forest, famously two-time winners of the UEFA European Cup under Brian Clough and Peter Taylor in 1979 and 1980. The city also has professional rugby, ice hockey and cricket teams, and the Aegon Nottingham Open, an international tennis tournament on the ATP and WTA tours. This accolade came just over a year after Nottingham was named as the UK's first City of Football.
On 11 December 2015, Nottingham was named a "City of Literature" by UNESCO, joining Dublin, Edinburgh, Melbourne and Prague as one of only a handful in the world. The title reflects Nottingham's literary heritage, with Lord Byron, D. H. Lawrence and Alan Sillitoe having links to the city, as well as a contemporary literary community, a publishing industry and a poetry scene.
The city is served by three universities: the University of Nottingham, Nottingham Trent University and the University of Law; hosting the highest concentration of higher education providers in the East Midlands.