Transient behavior and influence factors of keyhole in laser deep penetration spot welding
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摘要: 通过数值模拟的方法对激光深熔点焊过程中小孔瞬态行为进行了研究。建立了二维瞬态小孔激光点焊数值模型，分别对连续激光点焊和脉冲激光点焊过程中小孔演化规律和瞬态行为进行了分析，并通过改变计算条件，对影响小孔生长的多种物理因素进行了探究。结果表明，在连续激光点焊过程中，小孔深度随着热输入的积累不断增长，并且始终处于不断的振荡中；在脉冲激光点焊过程中，小孔的演化具有明显的周期性且与脉冲周期一致。当激光关闭时，小孔深度减小甚至闭合；当激光开启时，小孔迅速增大至激光关闭前的深度。反冲压力是形成小孔的必要因素，而表面张力是阻碍小孔形成的作用力。粘度增大熔池宽度减小，小孔和熔池深度增大。Abstract: The transient behavior of keyhole in laser deep penetration spot welding was studied by method of numerical simulation. A numerical model of two-dimensional transient keyhole in laser spot welding was established. The evolution and transient behavior of keyhole in the process of both continuous and pulse laser spot welding were analyzed respectively. The various factors that affected the growth of keyhole were studied by applying different calculation conditions. The results showed that depth of the keyhole increased with the accumulation of heat input and the keyhole oscillated constantly in the continuous laser spot welding. However,the evolution of the keyhole was periodic and consistent with the pulse period in the pulse laser spot welding. When the laser was turned off,the depth of the keyhole decreased or even closed. When the laser was turned on,the keyhole increased quickly to the depth before the laser was turned off. The recoil pressure was the necessary factor to form the keyhole,while the surface tension was the force to hinder the formation of the keyhole. With the increase of viscosity,the width of weld pool decreased and the depth of keyhole and weld pool increased.
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Keywords:
- laser welding /
- keyhole /
- transient behavior /
- numerical simulation
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