A Fundamental Study on Chemical Metallurgy in Welding Processes

对金属材料电弧焊过程中气体-金属反应和渣-金属反应进行了理论研究。研究结果如下：（1）采用钨极氩弧焊和GTA两种焊接工艺，研究了不同保护气氛（包括氮气）对铁合金焊接过程中吸氮量的影响。铁合金在电弧熔炼或电弧焊过程中的吸氮行为不符合西弗定律。电弧熔化金属的氮含量高于平衡溶解度。焊缝金属的氮含量低于平衡溶解度，只有当溶解度高时，如高铬合金或加压氮气气氛的情况下。这些事实表明，高温电弧的存在和反应时间的不足影响焊缝金属的氮含量。而合金元素对电弧熔炼或电弧焊态铁合金吸氮量的影响与平衡吸氮量基本相当。(2)在包括氧气在内的各种气氛下，对铁合金进行钨极气体保护电弧熔炼和GMA焊接。系统地研究了合金元素（硅、锰、铝、钛）对焊缝金属吸氧量的影响。通过对焊缝金属中氧化物夹杂物的成分、形貌、数量和含量的分析，探讨了吸氧脱氧机理。(3)采用简化的焊剂成分对钢进行埋弧焊，研究焊接过程中渣-金反应。系统地研究了焊剂成分对焊缝金属氧含量的影响。

Gas-and slag-metal reactions during arc-welding processes of metallic materials were studied thermodynamically. The results are as follows:(1) Iron alloys were gas-tungsten-arc-melted and GTA welded under various atmospheres including nitrogen gas to study the nitrogen absorption of molten iron alloys during welding processes. The nitrogen absorption behaviour of iron alloy during arc-melting or arc-welding did not obey sieverts' law. The nitrogen contents of arc-melted metals were higher than the equilibrium solubilities. The nitrogen content of weld metal was lower than the equilibrium solubility, only when the solubility is high, such as the cases of high chromium alloys or pressurized nitrogen atmospheres. These facts suggest that the presence of high temperature arc and the shortage of reaction time affect the nitrogen content of weld metal. However, the effects of alloying elements on the nitrogen absorption of arc-melted or arc-welded iron alloys were roughly equal to equilibrium ones.(2) Iron alloys were gas-tungsten-arc-melted and GMA welded under various atmospheres including oxygen. The effects of alloying elements ('silicon, manganese, aluminium, titanium) on the oxygen absorption of weld metal were systematically studied. The mechanisms of oxygen absorption and deoxidation were discussed by examining the composition, morphology, number and amount of oxide inclusions in the weld metals.(3) Steels were submerged-arc-welded with simplified flux compositions to study slag-metal reactions during welding processes. The effect of flux composition on the oxygen content of weld metal was examined systematically.