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.
Cambridge (/ˈkeɪmbrɪdʒ/ KAYM-brij) is a university city and the county town of Cambridgeshire, England, on the River Cam approximately 55 miles (89 km) north of London. At the United Kingdom Census 2011, the population of the Cambridge built-up area (which is larger than the remit of Cambridge City Council) was 158,434 including 29,327 students. Cambridge became an important trading centre during the Roman and Viking ages, and there is archaeological evidence of settlement in the area as early as the Bronze Age. The first town charters were granted in the 12th century, although modern city status was not officially conferred until 1951.
The University of Cambridge was founded in 1209. The buildings of the university include King's College Chapel, Cavendish Laboratory, and the Cambridge University Library, one of the largest legal deposit libraries in the world. The city's skyline is dominated by several college buildings, along with the spire of the Our Lady and the English Martyrs Church, and the chimney of Addenbrooke's Hospital. Anglia Ruskin University, which evolved from the Cambridge School of Art and the Cambridgeshire College of Arts and Technology, also has its main campus in the city.
Cambridge is at the heart of the high-technology Silicon Fen with industries such as software and bioscience and many start-up companies born out of the university. Over 40 per cent of the workforce have a higher education qualification, more than twice the national average. The Cambridge Biomedical Campus, one of the largest biomedical research clusters in the world, is soon to house premises of AstraZeneca, a hotel, and the relocated Royal Papworth Hospital.
The first game of association football took place at Parker's Piece. The Strawberry Fair music and arts festival and Midsummer Fair are held on Midsummer Common, and the annual Cambridge Beer Festival takes place on Jesus Green. The city is adjacent to the M11 and A14 roads. Cambridge station is less than an hour from London King's Cross railway station.