Space charge in plasma arc welding and cutting

Abstract

In transferred arc plasma arc welding, the plasma is not electrically neutral. Some simple mathematical models are constructed to demonstrate this fact and orders of magnitude are obtained. The relevance of these models to plasma arc welding and cutting is considered; quite long arcs can be achieved if the flow rate is sufficiently high, and an arc from a consumed tubular field emitting cathode of 75 mm length is described. In keyhole welding it is found that the current earths at the surface of the workpiece, or close to the top of the keyhole.