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.
Northampton /nɔːrˈθæmptən/ (About this soundlisten) is a large market town and the county town of Northamptonshire in the East Midlands of England. It lies on the River Nene, 60 miles (97 km) north-west of London and 50 miles (80 km) south-east of Birmingham. One of the largest towns (as opposed to cities) in England, it had a population of 212,100 at the 2011 census (223,000 est. 2019).
Archaeological evidence of settlement in the area dates to the Bronze Age, Romans and Anglo-Saxons. In the Middle Ages, the town rose to national significance with the establishment of Northampton Castle, an occasional royal residence which regularly hosted the Parliament of England. Medieval Northampton had many churches, monasteries and the University of Northampton, all enclosed by the town walls. It was granted a town charter by Richard I in 1189 and a mayor was appointed by King John in 1215. The town was also the site of two medieval battles, in 1264 and 1460.
Northampton supported the Parliamentary Roundheads in the English Civil War, and Charles II ordered the destruction of the town walls and most of the castle. The Great Fire of Northampton in 1675 destroyed much of the town. It was soon rebuilt and grew rapidly with the industrial development of the 18th century. Northampton continued to grow with the arrival of the Grand Union Canal and the railways in the 19th century, becoming a centre for footwear and leather manufacture.
Northampton's growth was limited until it was designated as a New Town in 1968, accelerating development in the town. It unsuccessfully applied for city status in 2000.