Abstract :
WITH THE increased use of inert-gas arc welding, especially in automatic welding machines, problems of arc ignition and stability become important. New electrodes much more satisfactory than the conventional type have been developed by using the highly refractory oxides, thoria and zirconia, in combination with tungsten and other materials. The conventional welding electrode is of some nonconsumable material, usually tungsten, and starting is accomplished either by contact or by a high-frequency spark. When spark starting is used, ignition may be quite erratic, depending on the previous history of the tungsten electrode. If the electrode is cold, the arc may not form immediately or at all, and, when formed, it may be extremely mobile, with the footpoint moving rapidly over the tungsten surface. In an automatic setup, this type of behavior can lead to losses in both time and material. See Figure 1. This shows the effect on the work of slow starting and arc wander. Also, the welding torch may be damaged. With the new electrode, instant starting and a highly stable arc are obtained. The arc picks up at lower open-circuit voltage and the current ranges are extended.
