Studies on Characteristics of Tungsten Electrode for TIG arc Welding (Report 2)

Consumption Characteristics

Abstract

As to the consumption of tungsten electrode the following phenomena are observed.
The consumption of pure and thoriated tungsten shows a remarkable difference at arc starting as shown in Fig. 2. The explosive expansion of gas in intercrystal zone of sintered electrode is presumed as the main cause of the consumption at arc starting. Experiment shows the minimum consumption at 1.5% ThO₂ content. Thoria acts to decrease the arc starting period of cold cathode state and at the same time acts to increase the number of sintered defects as shown in Fig. 3.
It is observed that the metal vapour in arc atmosphere little affects the consumption in stationary period, while iron particle spattered on the electrode acts to increase the consumption of electrode. Photo 5 shows a remarkable change of electrode shape when the electrode is contaminated by carbon vapour.
Oxygen and nitrogen affect also the consumption; the former decreases the surface tension and the latter produces gas holes in the molten electrode tip. See Photo XI .