Identification of Ionization Region Profile and Potential Distribution in Welding Arc Plasma by Direct Probe Detection

A special probe detection system and analyzing method were designed for estimating the ionization region in welding arc. Results showed that ionization region in gas tungsten welding arc is in spindle shape. Arc plasma prefers to contract near anode workpiece. The arc volume increases with the increase of welding arc current accordingly. With the decrease of arc length, the arc expands in radius direction. Electrical equipotential lines nearly parallel the anode surface and tend to bend to the tungsten electrode in the region near cathode. Voltage drop near the cathode dominates the arc voltage when arc current changes.