Materials Science Forum, Vol.426-4, 4105-4110, 2003
Arc behavior under extreme condition
Principle of Gas Tungsten Arc Welding is quite simple. Electron, which is emitted from Tungsten electrode, hits into the metal, and the heat from this impingement produce enough heat for fusion welding. However, actual behaviors are quite complicated. Electron emission is much influenced by physical condition of cathode and ambient circumstance. Considerable electron emits from unbelievable location of the cathode, especially at the stage of the cathode is not enough hot. The anode spot, where main electrons hit into the metal, is also much influenced by surface condition. The anode spot is usually appeared at the center of molten pool where the temperature seems to be maximum value. But, it sometimes moves irregularly or hits on the solid surface. This situation is mainly caused by oxidized layer on the metal or molten pool. Some minor elements in/on the metal act as a kind of catalytic agent. It sometimes drastically changes weld geometry.