稀土钨电极材料及稀土氧化物的作用

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

介绍了焊接钨电极材料的发展历史和研究现状。从焊接工作特性分析了对电极材料的要求，比较了纯钨、钍钨电极材料的特点。着重对近年来代钍钨稀士钨电极材料研究及稀土氧化物的作用等有关理论研究问题进行了讨论。有关研究表明：添加２％稀土氧化物的钨电极材料具有可加工性能。电极的使用性能强烈地依赖于稀土金属氧化物，燃弧过程中它们的行为是影响电极使用、电极温度、逸出功和电弧稳定性的最重要因素。稀土氧化物的补给与表面蒸发之间的平衡是实现稳定和长寿命工作的关键。一般情况下稀土氧化物与钨反应生成钨酸盐或氧化钨酸盐，这些盐的熔点低于稀土氧化物和钨的熔点，在燃弧过程中熔化、迁移和蒸发。不同成分和配比的稀土氧化物，对它们与钨反应生成的钨酸盐和氧化钨酸盐的迁移与蒸发的平衡调节作用各异，同时也影响燃弧后钨的再结晶晶粒组织，这些因素综合影响了电极的燃弧特性、抗烧损性和电弧的稳定性。在复合稀土钨电极中，比例为１∶１∶３的ＣｅＯ２－Ｌａ２Ｏ３－Ｙ２Ｏ３－Ｗ电极的工作温度最低，热发射最高。

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