基于斑点簇定向控制的VPPA穿孔熔池动态行为与气孔缺陷抑制机理研究

针对铝合金复杂结构变极性等离子弧焊接过程出现的气孔缺陷问题，以控制穿孔熔池稳定并实现气泡原位消除为目标，提出阴极斑点簇定向扫掠与定点质量补偿的组合式气孔缺陷抑制措施：利用脉冲弱磁场控制斑点簇定向移动，靶向作用于氧化膜和小孔周围气泡富集区域，利用阴极斑点的高温特性原位蒸发释放气泡；通过定点填丝的方式补充高温金属延缓熔池凝固时间，增加气泡逸出机率。充分利用非电弧主体的作用消除气孔缺陷，可以有效解除兼顾成形稳定和缺陷抑制的工艺参数限制，拓宽工艺窗口。课题首先从阴极斑点定向控制下的穿孔熔池绕流行为出发，以多驻点信息为目标量建立熔池稳定性判据；在稳定绕流基础上，通过研究阴极斑点集群效应、气泡运动路径与气泡在凝固过程的变化规律，揭示斑点簇热力定向作用下气泡的释放机制以及质量填充对气孔的影响机理；并基于铝合金复杂材料与结构的穿孔焊接试验全面评价这一新措施的控制效果，为铝合金高质量焊接提供新方案。

Addressing the porosity defects problem in variable polarity plasma arc welding of complex aluminum alloy structure, the technical goal to control the keyhole weld pool stable and realizing bubble in situ release is figured out. The combined suppressive measure of porosity defects by cathode spot cluster directional sweeping and mass compensation with certain point is proposed. The cathode spot group is moved directional using pulse weak magnetic field, and targeted working on the oxide layer and bubble enriched area. The bubble release in situ by the inherent characteristics of high temperature of cathode spots. Replenishing high temperature metal with fixed-point wire filling is applied to delay the solidification time of weld pool, then increase the probability of bubble release. Fully utilizing the role of non-main body of arc to eliminate the porosity defects can effectively remove the parameters adjust limitation for balancing form stability and defect suppression, thereby expanding the welding process margin. This subject starts from the study of detouring flow behavior of keyhole weld pool under the directional moving control of cathode spot. The keyhole weld pool criterion is established with multi-station information as the target parameter. Based on the stable detouring flow, the cluster effect of cathode spot, bubble moving path and changing of bubble in solidification process are investigated to reveal the bubble releasing mechanism with the thermal-mechanical directional effect of spot cluster, and the influence mechanism of targeted mass filling on porosity. Based on the keyhole welding test of complex materials component and structure of aluminum alloy, the control effect of this new measure is comprehensively evaluated to provide a new solution for high-quality welding of aluminum alloys.