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.
Downham Market, sometimes simply referred to as Downham, is a market town and civil parish in Norfolk, England. It lies on the edge of the Fens, on the River Great Ouse, approximately 11 miles south of King's Lynn, 39 miles west of Norwich and 30 miles north of Cambridge.
The civil parish has an area of 5.2 km² and in the 2011 census had a population of 9,994 in 4,637 households.
Fire Station in 2006, now a heritage centre
It was an agricultural centre, developing as a market for the produce of the Fens with a bridge across the Ouse. During the Middle Ages, it was famed for its butter market and also hosted a notable horse fair. The market is now held Fridays and Saturdays.
Notable buildings in the town include its mediaeval parish church, dedicated to St Edmund, and the Victorian clock tower, constructed in 1878. The town is also known as the place where Charles I hid after the Battle of Naseby. In 2004 the town completed a regeneration project on the Market Place, moving the market to the town hall car park. The decorative town sign depicts the crown and arrows of St Edmund with horses to show the importance of the horse fairs in the town's history.
A heritage centre, Discover Downham, opened in a former fire station in 2016. The town is twinned with Civray, Vienne, France.