Evolution rules for cathode erosion and corresponding arc behaviour in tungsten inert gas welding

Abstract

Cathode erosion is a serious problem in long hours of Tungsten Inert Gas (TIG) welding. The evolution of electrode end shape and corresponding arc behaviour was studied at different welding currents and cathode parameters. The results illustrate that slow erosion, shedding, and expansion are three typical erosion modes. Slow erosion is an inevitable mode, causing the arc root width ( Ra) and arc diameter ( Rb) to slowly increase by 2.1% and 2.6%, respectively. With the increasing welding current or the decreasing cone angle and diameter, Ra and Rb are increased in shedding mode by 6.3% and 1.0%, respectively. Expansion appears when the electrode end has a truncated cone shape, causing gradual decrease of 5.7% and 2.3% in Ra and Rb, respectively.