Gas tungsten arc welding is an arc welding process that uses a nonconsumable tungsten electrode to produce the weld. The weld area is protected from atmospheric contamination by a shielding gas (usually an inert gas such as argon), and a filler metal is normally used, though some welds, known as autogenous welds, do not require it. A constant-current welding power supply produces 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 light metals such as aluminum, magnesium, and copper alloys. The process grants the operator greater control over the weld than competing procedures 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.

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_______________________________ Today's selected anniversaries:

105 BC: The Cimbri and the Teutons inflicted a major defeat on the Roman Republic in the Battle of Arausio. (http://en.wikipedia.org/wiki/Battle_of_Arausio)

1927: The first successful talking movie The Jazz Singer, starring Al Jolson, was released. (http://en.wikipedia.org/wiki/The_Jazz_Singer_(1927_film))

1976: Premier Hua Guofeng ordered the arrest of the Gang of Four and their associates, putting an end to the Cultural Revolution in China. (http://en.wikipedia.org/wiki/Gang_of_Four_(China))

1981: Egyptian President Mohamed Anwar el-Sadat was assassinated while attending a parade in Cairo to mark the eighth anniversary of the Crossing of the Bar Lev Line at the start of the 1973 Arab-Israeli War. (http://en.wikipedia.org/wiki/Anwar_Sadat)

1995: An article in the journal Nature reported the discovery of a planet orbiting 51 Pegasi as the first known extrasolar planet around a main-sequence star. (http://en.wikipedia.org/wiki/51_Pegasi)

_____________________ Wikiquote of the day:

Behold, we know not anything; I can but trust that good shall fall At last — far off — at last, to all, And every winter change to spring. So runs my dream; but what am I? An infant crying in the night; An infant crying for the light, And with no language but a cry. -- Alfred, Lord Tennyson (http://en.wikiquote.org/wiki/Alfred_Tennyson)