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.
Market Harborough is a market town within the Harborough district of Leicestershire, England. It is situated in the far southeast of the county, forming part of the border with Northamptonshire.
Harborough District has a population of 91,461 (2017) and Market Harborough is the district's administrative headquarters. It sits on the Northamptonshire-Leicestershire border. The town was formerly at a crossroads for both road and rail; however the A6 now bypasses the town to the east and the A14 which carries east-west traffic is 6 miles (9.7 km) to the south. Market Harborough railway station is served by East Midlands Railway services on the Midland Main Line with direct services north to Leicester, Nottingham, Derby and Sheffield and south to London St Pancras. Rail services to Rugby and Peterborough ended in 1966.
Market Harborough is located in an area which was formerly a part of the Rockingham Forest, a royal hunting forest used by the medieval monarchs starting with William I. Rockingham Road takes its name from the forest. The forest's original boundaries stretched from Market Harborough through to Stamford and included the settlements at Corby, Kettering, Desborough, Rothwell, Thrapston and Oundle.
The steeple of St Dionysius' Church rises directly from the street, as there is no churchyard. It was constructed in grey stone in 1300 with the church itself a later building of about 1470. Next to the church stands the Old Grammar School, a small timber building dating from 1614. The ground floor is open, creating a covered market area and there is a single room on the first floor. It has become a symbol of the town. The nearby square is largely pedestrianised and surrounded by buildings of varying styles. The upper end of the High Street is wide and contains mostly unspoiled Georgian buildings.
Market Harborough has two villages within its confines: Great Bowden lies over a hill about a mile from the town centre; Little Bowden is less than half a mile from the town centre. The three centres have largely coalesced through ribbon development and infill, although Great Bowden continues to retain a strong village identity.