中文摘要：

随着国家对具有放射性危害的钍资源有计划性的管理,钍的价格不断上升,推动了焊接领域环保钨电极替代钍的发展。对市场上现有替代钍钨的Ce-W,三元稀土W电极（La-Ce-Y）以及美国市场上积极推广的E3电极的焊接性能进行研究,采用钨极氩弧焊（TIG）直流正接（DCSP）的方法研究了几种电极的高温抗烧损性能,尺寸稳定性以及静特性曲线,并对燃弧后电极尖端的表面形貌进行了扫描电镜（SEM）观察,对稀土添加相La2O3,Y2O3,CeO2在电极尖端轴向分布进行了能谱分析（EDX）。对比试验结果发现,在焊接电流200 A工作5 h后,E3和WX电极的烧损量明显小于Th-W,Ce-W电极,且质量损失随时间呈近似的线性关系,尺寸稳定性好。从金相组织可以看出Th-W,Ce-W电极再结晶晶粒粗大,E3和WX电极的再结晶晶粒小,再结晶程度较弱,从侧面说明E3和WX电极工作温度较低,电子发射能力强。几种稀土氧化物的行为揭示了电极性能差异的本质原因,多元电极中,CeO2的扩散速率最快,使得其在小电流焊接和起弧过程中作用明显。Y2O3和La2O3热稳定性好,只有在较高温度时其扩散速率才明显增加,因此它们在大电流长时间焊接时作用突出。由于几种元素的协同作用,降低了电极表面的逸出功,并使得电子发射过程稳定。因此,三元稀土钨电极（WX）具有优异的焊接性能。

英文摘要：

As the top-down management on the radioactive element Th,its price became more expensive,which promoted the development of environment-friendly electrodes to replace Th-W. The welding performance of Th-W,Ce-W,（ La-Ce-Y）-W and E3 electrodes widely used in US was investigated. The erosion,morphological stability and U-I curve at high temperature and heavy current were considered by direct current straight polarity tungsten inert gas welding（ DCSP TIG） welding. The morphology of erosion on the electrode surface was explored by scanning electron microscopy（ SEM）,and energy-dispersive X-ray spectrometer（ EDX） was used to study the distribution of oxide additions on electrode tip. The results suggested that when the welding current I0= 200 A,after loading5 h,the property of anti-erosion of E3 and WX electrodes was superior to that of Th-W and Ce-W and the mass loss was approximately linear with time with fine thermal stability. The metallographic structure of the electrode tips showed that the recrystallized grain sizes of E3 and WX were much smaller than those of Th-W and Ce-W,which was largely due to the lower working temperature and suggested a better electron emission ability. The behavior of rare earth oxides on the electrode tip revealed the nature of the difference in working performances. CeO2,which had the highest diffusion rate,had a magical effect during low current welding and arcing; Y2O3 and La2O3,which had a higher thermal stability,diffused slowly unless the temperature elevated to higher degree. So,they played an important role in the condition of heavy current long time welding. Owing to the synergy of three rare earth elements,the work function of the electrode decreased significantly,the electron emission process became more stable. As a result,the ternary rare earth tungsten electrodes（ WX） had superiority in welding performances.