Analysis on TIG Arc During Welding of Magnesium Alloy Sheet by a Combination of Spectral Diagnosing and Langmuir Probe Detection

To identify the discharge features of tungsten inert gas (TIG) welding arc on magnesium alloy workpiece, spectral diagnosing and a self-developed Langmuir probe detection were jointly performed on the welding arc. Results show that during welding, Mg atoms with low ionization energy rush into the burning arc and replace Ar atoms to discharge, which gives influences on arc discharge. The arc plasmas have a normal space potential distribution. Reflected by both of the two diagnosing methods, region near arc anode (magnesium alloy workpiece) has the lowest electron temperature and the highest electron density. The variations of electron temperature and density with the position have similar trends measured by the two diagnosing methods, indicating that the self-developed probe detection system is effective and reliable in diagnosing the welding arc. It is also found that the diagnosing error of probe detection is a little larger than that of spectral diagnosing, especially in the region near cathode. This research gives a new method to diagnose the welding arc, and the results can give experimental indication and support to researchers in arc welding area from another view sight.