不同焊接位置对5A90铝锂合金激光焊接质量的影响(英)

针对铝锂合金激光焊接产生的成形不良和气孔缺陷，探究不同焊接位置对焊缝成形及气孔的影响，并对比分析不同焊接位置熔池受力状态、熔融金属流动和小孔动态行为，解释缺陷形成及其抑制机理。研究发现:不同焊接位置熔池受力状态和熔融金属流动决定焊缝成形。平焊时焊缝成形差、下榻严重；横焊时背面焊缝不连续，有飞溅；立向上焊时背面焊缝内凹严重；立向下焊可得到最优焊缝成形和最优的气孔缺陷。焊缝气孔受小孔动态行为影响，不同焊接位置气孔随热输入的变化规律一致，气孔先增后减，在仅熔池透状态下有气孔最大值。立上焊时小孔不稳定，焊缝气孔多且分布杂乱；立向下焊时小孔稳定性高，气孔最少，主要分布在焊缝中心线上。

Effects of welding positions on welding quality in CO2 laser welding of 5A90 aluminum-lithium alloy

Autogenous laser welding of aluminum-lithium alloy often results in bad weld appearance and serious porosity. This paper investigates the influence of different laser welding positions on the welding quality of 5A90 Al-Li alloy. The weld appearance and the porosity are compared with the flat welding, the horizontal welding and the vertical welding respectively. The formation and suppression mechanism of defects in different welding positions are analyzed and discussed considering the force state of the melt pool, the liquid metal flow and the keyhole behavior. The experimental results show that the weld seams suffer from excessive penetration in the flat welding, and serious metallic spatters, discontinuous weld bead in the horizontal welding, the concave defects in the back weld in the vertical-up welding. The optimal weld appearance and least porosity defects could be obtained in the vertical-down welding position. The porosity is closely related to the welding positions due to the change of dynamic characteristics of the keyhole and the flow behavior of the melt pool. The porosity changes in a similar trend with the increase of the heat input in different welding positions. The pores increase at first then decrease, and a maximum value is reached when the weld is incompletely penetrated. The number of pores and their average size could both be suppressed into minimums in the vertical-down welding, and the pores formed mainly in the centerline of the seam while they distribute chaotically around the weld seam in other welding positions.