Abstract In contrast to other welding processes of aluminum alloys, variable polarity plasma arc (VPPA) nonvertical-up welding produces pores in specific positions (on the upper side of the welded joint) rather than throughout the whole welded joint due to the effect of gravity. In horizontal welding, the porosity area percentage on the upper side of the welded joint reached about ∼20%. Asymmetric metal flow in the keyhole molten pool caused either side of the weld to have different cooling rates. This difference in cooling caused the metal on this side of the weld to rapid crystallization, leading to higher concentrations of copper and manganese around the weld that are conducive to higher porosity. The Cu content reached ∼50% around the pores but was only ∼7% in the filler wire and ∼5% in the base metal. The root reason for porosity is the asymmetric metal flow. To correct this, the free point was found according to the force balance on the leading side of the keyhole. A proposed method to produce symmetric metal flow was used, and the resulting welds were determined to be of high quality via X-ray phase-contrast imaging.

中文翻译：

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铝合金变极性等离子弧焊过程中重力对焊缝气孔分布的控制

摘要 与铝合金的其他焊接工艺相比，可变极性等离子弧（VPPA）非垂直向上焊由于重力作用在特定位置（焊接接头的上侧）而不是整个焊接接头产生气孔。 . 在水平焊接中，焊接接头上侧的气孔面积百分比达到约 20%。锁孔熔池中的不对称金属流动导致焊缝两侧的冷却速率不同。这种冷却差异导致焊缝这一侧的金属快速结晶，导致焊缝周围铜和锰的浓度更高，从而导致更高的孔隙率。Cu 含量在孔周围达到 50%，但在填充焊丝中仅为 7%，在母材中为 5%。孔隙率的根本原因是不对称的金属流动。为了纠正这个问题，根据锁孔前侧的力平衡找到了自由点。使用了一种产生对称金属流的建议方法，并通过 X 射线相衬成像确定所得焊缝具有高质量。