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等离子弧焊钨阴极稳定性的研究
吴望周1, 林谦生2, 罗天虎2
1.南京化工学院;2.西北工业大学
摘要:
本文对不同冷却情况及包敷的13只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所致;3.钨极尖的"开花"、"结瘤"损坏也与升华过程有关;4.包敷及强冷均可提高电极尖端的稳定性,而未发现对电弧稳定性产生不利影响;5.在其他条件相同的情况下,秃钨极的成分变化及熔化程度都严重得多,这是由于阴极斑点飘荡、阳离子在阴极区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;6.如果对电极实行包敷,有可能以细钨丝代替粗钨丝作阴极,能提高稳定性,减少修磨次数。如果是用钍钨极的话,可以大大地减少放射性钍对环境的污染。
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AN INVESTIGATION ON TUNGSTEN CATHODE STABILITY IN PLASMA ARC WELDING
Wu Wangzhou1, Lin Oiansheng2, Luo Tianhu2
1.Nanjing Chemical Engineering Institute;2.North-West Polytechnic Institute
Abstract:
Experiments have been carried out to compare the burn-weight-loss and the deformation at the tips of 14 tungsten cathodes with different packed and cooling conditions. The test results revealed that:<1> Welding characteristics of the ceriated-tungsten electrode is almost the same as the thoriated electrode.<2> Bare electrode with insufficient cooling has the most burn-weight-loss due to tungsten oxidizing on the electrode cylindric surface and the consequent sublimation of the wolfram oxide. <3> Electrode damage by "flowering" at the cathode tip ("umbrella-like-halo" forming) and by "tumour-condense-forming" are also related to the sublimation prcess.<4> Electrod packed with copper,for example,or intensive cooling can improve the cathode tip steadiness without any harmful effect on the arc stability.<5> There is an important phenomenon that the melting of blunt tungsten cathode and the change of its chemical compositions are far more severe than those of the sharped one under the same conditions.It is considered to be a result of the cathode-spot-floating and increasing the ion-conducting-fraction in the cathode zone.Therefore,it is suggested that the selected cathode should have a satisfactory geometry at the tip. <6> Packed electrode is possible to take thin tungsten wire in place of the thick nonpacked one,which will increase the cathode stability and decrease the electrode grinding frequency.On the other hand,it will greatly minimize the contamination of surrounding environment by thorium radiation,if the thoriated electrode is selected.
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