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.
March is a Fenland market town and civil parish in the Isle of Ely area of Cambridgeshire, England. It was the county town of the Isle of Ely which was a separate administrative county from 1889 to 1965. It is now the administrative centre of Fenland District Council.
The town grew by becoming an important railway centre. Like many Fenland towns, March was once an island surrounded by marshes. It occupied the second largest "island" in the Great Level. As the land drained, the town grew and prospered as a trading and religious centre. It was also a minor port before, in more recent times, a market town and an administrative and railway centre. March is situated on the banks of the navigable old course of the River Nene, today mainly used by pleasure boats.