气孔缺陷是铝合金T型接头双侧激光焊接面临的主要问题, 基于其工艺特点, 文中系统研究了表面处理状态、光束入射角度、焊接速度、热输入和光束间距对气孔缺陷的影响规律。研究结果表明: 铝合金表面保留一定厚度的纯铝包覆层才能最大程度地降低气孔缺陷; 采用较大的光束入射角度和较高的焊接速度可以有效降低气孔缺陷, 主要原因是小孔上方金属流动趋势由对流变为流向小孔内部更有利于气泡的逃逸; 降低焊接热输入和增加光束间距均不利于降低气孔缺陷, 造成小孔形状和贯通性改变并引起熔池流动行为的改变是其本质原因, 保证双侧小孔对称和贯通才能利于气泡逸出并降低气孔缺陷。

Porosity defect is the main problem for the double-sided laser beam welding of aluminum alloy T-joints. Based on its technology characteristics, the effects of the surface states, laser incident angles, welding speeds, heat inputs and laser distances on the porosity defects were studied in this work. The results indicate that the pure aluminium cladding layer is beneficial for reducing porosity defects. Using larger laser incident angle and welding speed are good for reducing porosity defects, the reason is that the fluid flow changes from convection to toward to keyhole, which can help pores escape from the weld pool. And, reducing heat input and increasing laser distance are bad for reducing porosity defects, the change of the keyhole shape and fluid flow are the essential reasons. It is necessary to ensure keyhole symmetry and pass-through, which can help the pores escape from the weld pool and reduce the number of the porosity defects.