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.
Norwich (/ˈnɒrɪdʒ, -ɪtʃ/ (About this soundlisten)) is a city in Norfolk, England, situated on the River Wensum in East Anglia, about 100 miles (160 km) north-east of London. A city since 1094, Norwich is the county town of Norfolk and unofficially seen as East Anglia's capital. From the late Middle Ages until the Industrial Revolution, Norwich was the largest city in England after London and one of the most important. The present-day population of the city is about 142,000.