中文摘要：

针对铝合金穿孔型等离子弧横向焊接,开展新型变极性等离子电弧热-力特性及横焊成形研究。通过设计变极性等离子弧喷嘴,控制电弧热-力特性来提高横焊穿孔稳定性。对不同热-力特性进行研究,比较三种喷嘴的电弧形态、电弧力和电弧阳极电流密度的数值与分布,分析认为新型电弧的热-力特性在横焊穿孔成形稳定性方面具有优势。依据电弧压力波形稳定性和穿孔稳定性进一步验证新型等离子电弧的作用效果,验证得出新型等离子电弧瞬间电弧压力波动较小,背面穿孔形状似圆形,且穿孔面积变化较小。通过分析穿孔熔池宏观轮廓,得到新型热-力特性对熔池行为的直接影响。利用高速摄像捕捉横焊穿孔熔池的稳定形成过程,证明较高电弧能量、较低电弧压力相配合更有利于穿孔熔池形成和稳定;同时观察到横焊熔池的稳定流动过程,并对熔池金属进行受力分析,认为新型热-力特性容易满足横焊熔池金属在流动过程中达到受力平衡,最终实现了8 mm铝合金穿孔等离子弧横焊稳定成形。

英文摘要：

In view of the horizontal plasma welding of thick aluminum alloy, the thermal-mechanical characteristics and weld forming process of new type variable polarity plasma arc（VPPA） welding are studied. New kinds of VPPA nozzle were designed to control the arc thermal force characteristics and to improve the stability of horizontal welding. Arc shape, arc force and anodic current density of three kinds of nozzles are compared. It is concluded that the thermal force characteristics of the new type arc have obvious advantages in the horizontal welding forming stability. According to the stability of instantaneous arc pressure waveform and the stability of perforation, it is also found that the arc pressure and the perforation area of the new plasma arc are smaller than those of the normal plasma welding arc, and the shape of the back perforation under the action of the new kind arc is circular and symmetrical. By analyzing the macroscopic contours of perforated welding pool, the direct influence of new arc thermal-force characteristics on the behavior of molten pool is obtained. High-speed photography is used to capture the formation process of the horizontal weld pool, and the results indicated that the higher arc energy and lower arc pressure are more favorable for the formation and stabilization of the molten pool. By observing the flow process and analyzing the force balance of the horizontal molten pool, it is found that the new arc thermo-force character make it easy to balance the molten metal in the flow process. Under the action of the new type plasma arc, it is easy to realize the stable horizontal welding of 8mm aluminum alloy.