Tungsten Electrode Material and the Effect of Rare-earth Metallic Oxides on It

The development and research status of tungsten electrode materials are introduced The requirements of electrode materials are analyzed in terms of the characteristics of the welding tip A comparative study is made between W-ThO2 and pure tungsten electrode materials In particular, the influence of rare-earth metallic oxides adding to tungsten electrode materials as replacements for ThO2 addition are discussedThe studies show that tungsten electrodes activated with 2wt% of rare earth metallic oxides have good form ability The operating characteristics of electrodes depend strongly on the rare-earth oxide additions; their presence affects the operating, electrode temperature, work function, and the arc stability The equilibrium between the supply and diffusion due to surface evaporation of rare-earth metallic oxides is essential to arc stability, electrode lifetime The rare-earth metallic oxides form tungstate or oxy-tungstate during arc burning These newly formed relatively low melting point compounds melt, migrate, as well as evaporate, during arc burning Rare-earth metallic oxides with various components and ratios in the tungsten electrodes have different effects on this migration and evaporation of the tungstate and oxy-tungstate compounds At the same time, they affect the crystal structure upon recrystallization All of the above factors combine to influence arc burning, electrode consumption, and arc stability Among the tungsten electrodes activated with two or three types of rare-earth metal oxides(CeO2, La2O3 and Y2O3), the electrodes with the ratio of CeO2∶La2O3∶Y2O3=1∶1∶3 show the lowest electrode temperature and the best thermal emission, and have the best properties in terms of arc starting and electrode consumption