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在完全稳定的规范参数条件下,等离子弧焊缝的成型未必能保持稳定,其原因之一是所用钨极在使用过程中发生了变化。在一般钨极氩弧自动焊时,这一问题也已引起了人们的注意。本文作者们对不同冷却情况及包敷的十四支钨阴极进行了烧损量对比和形状变化的对比。试验表明;(1)铈钨极和钍钨极的性能基本相同,(2)冷却不够的裸钨极烧损量最大。这是由于圆柱表面的氧化及氧化钨升华之故;(3)钨极尖的“开花”、“结瘤”损坏与此升华过程亦有关;(4)包敷及强冷均可提高电极尖端之稳定性,而未发现对电弧稳定性之不利影响;(5)一个重要的现象是,在完全相同的条件下秃钨极比尖钨极的成份变化及熔化程度严重得多。作者们认为这是由于阴极斑飘荡、阳离子在阴极导电中所占比例增大之故。因此建议阴极尖应有恰当的形状和钝头大小,(6)包敷有可能以细钨丝代替粗钨丝作钨极、提高稳定性、减少修磨次数。如果是用钍钨极的话,这可以大大减少放射性钍对环境的污染。
One of the reasons that the formation of plasma arc welds may not be stable under completely stable specifications is that the tungsten electrodes used have changed during use. In the general TIG welding, this issue has also attracted people’s attention. In this paper, the authors compared the burn-off and shape changes of fourteen tungsten cathodes under different cooling conditions and their application. Experiments show that: (1) cerium tungsten and thorium tungsten performance is basically the same, (2) the cooling is not enough of the largest amount of tungsten burning. This is due to the oxidation of the surface of the cylinder and the sublimation of tungsten oxide; (3) The “flowering” and “nodulation” damage of the tungsten tip are also related to this sublimation process; (4) (5) An important phenomenon is that under the same conditions, the composition of the bald tungsten pole is more serious than that of the tip tungsten pole and the degree of melting is much more serious. The authors think this is due to the cathode spot floating, the proportion of cations in the cathode conductivity increases. Therefore, it is suggested that the cathode tip should have the proper shape and blunt tip size. (6) It is possible to wrap the thin tungsten wire instead of the thick tungsten wire for the tungsten electrode to improve the stability and reduce the number of grinding. If it is thorium tungsten, this can greatly reduce the radioactive thorium pollution of the environment.