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.
Boston is a port and market town in Lincolnshire, on the east coast of England, about 100 miles (160 km) north of London. It is the largest town of the wider Borough of Boston local government district. The town itself had a population of 35,124 at the 2001 census, while the borough had a total population of 66,900, at the ONS mid-2015 estimates. It is north of Greenwich on the Prime Meridian.
Boston's most notable landmark is St Botolph's Church ("The Stump"), the largest parish church in England, visible for miles around from the flat lands of Lincolnshire. Residents of Boston are known as Bostonians. Emigrants from Boston named several other settlements around the world after the town, most notably Boston, Massachusetts, in the United States.