Rare Earth Effect in Tungsten Electrode

Among tungsten electrodes, thoriated tungsten electrode, having good weldability, is the most widely used tungsten electrodes. But because thorium has radioactive contamination so in the production and using process will endanger human health and pollute the environment. Through continuous research and development, the researchers developed multiple composite rare earth tungsten electrodes, and it is considered the best material to replace thoriated tungsten electrodes.

Rare earth doped as the active material doped to tungsten matrix can effectively reduce the work function of the tungsten electrode material to improve the welding performance. In multiple composite rare earth tungsten electrodes, the doped rare earth elements include La, Y and Ce. These three different rare earth elements at different temperatures have diffusion rates. Among these elements, Ce first diffused to the surface, reducing the work function of the surface, so click arc easy. When arc burning stable, La has largest surface coverage, and plays an important role at this process. While working in high current, Y timely migration to the surface, so the electrode can stably operate at high current conditions. Synergy of these three rare earth elements, so that the performance of multiple composite rare earth electrodes better than thoriated tungsten electrode.

On the other hand, the rare earth is conducive to refine reduction powder, and easy to promote the β-W formation. β-W makes the sintering process not easy to control. In the tungsten electrode sintering process, not only the rare earth will impede tungsten grain growth, but it will improve the recovery and recrystallization temperature of tungsten electrode such that the deformation resistance increases of electrode will increase, resulting in sintering process not easy to control. This is also one of reasons that multiple composite rare earth tungsten electrode has low finished produced rate and high production costs.

In the future, studies should toward production technology development direction to research. To improve the multiple composite rare earth tungsten electrodes finished produced rate and to reduce production costs make it more widely used.