Initiation Of A Tungsten Inert Gas Arc By High Voltage DC

TWI Industrial Member Report Summary 31/1976

By M J Brown

Background

The problems of initiating a TIG arc across an open gap are briefly discussed, particularly with respect to high voltage high frequency spark starting. Also a high voltage DC system is proposed, and its potential advantages outlined.

The DC breakdown voltages of electrode-workpiece gaps in argon are determined for pure, thoriated and zirconiated tungsten electrodes and for 60 degree pointed and balled (melted) electrode tips. The arc voltage and current requirements immediately following high voltage breakdown are also studied. The safety aspects of arc initiation are discussed and recommendations made as to the relative utilisation of DC and high voltage starting in practice.