焊接位置对激光-电弧复合焊接底部驼峰的影响

目的 通过改变焊接位置来抑制底部驼峰的形成进而降低生产成本。方法 使用高速摄像机观察平向焊接和横向焊接2种不同焊接位置下熔池的匙孔和底部驼峰的形成过程，并对底部凸起受到的金属蒸气反冲压力、熔融金属重力以及表面张力进行受力分析。结果 在S355J2W耐候钢的激光-电弧复合焊接平焊过程中，受金属蒸气反冲作用力的影响，熔融金属迅速从匙孔底部排出，流入匙孔底部凸起区域，底部凸起的增长速度极快，仅需7.5 ms即可形成大尺寸的驼峰。而在横向焊接中，匙孔前壁凸起数量减少，导致金属蒸气反冲压力减小，匙孔排出的熔融金属量减少，底部凸起的增速减缓，在13.6 ms时才达到最大高度，使驼峰在底部熔池凝固之前难以形成。结论 采用横向焊接的方式可以有效避免驼峰的产生，降低生产成本。同时，该方式在焊缝背部成形效果方面也表现良好，为优化焊接工艺提供了重要参考。

Effect of Welding Position on Bottom Hump of Laser-arc Composite Welding

The work aims to mitigate bottom hump by altering the welding position, thereby achieving cost reduction in the production process. A high-speed camera was used to observe the formation process of keyholes and bottom hump in the weld pool under both flat and horizontal welding positions. A force analysis was conducted to examine the impact on the bottom protrusion, considering forces such as metal vapor recoil pressure, molten metal gravity, and surface tension. During the laser-arc hybrid welding process of S355J2W weathering steel with a flat welding position, influenced by the metal vapor recoil force, molten metal swiftly evacuated from the bottom of the keyhole, streaming into the region of the bottom protrusion. The bottom protrusion exhibited rapid growth, forming a substantial hump in a mere 7.5 ms. Contrastingly, in the case of transverse welding, the reduced number of front-wall protrusions in the keyhole resulted in diminished metal vapor recoil pressure. This led to a decrease in the amount of molten metal expelled from the keyhole, consequently slowing down the growth rate of the bottom protrusion. The maximum height was reached at 13.6 ms, making it challenging for the hump to form before solidification of the bottom weld pool. The utilization of the horizontal welding method proves effective in preventing hump and thereby reducing production costs. Simultaneously, it has demonstrated favorable outcomes in shaping the back of the weld seam, offering crucial insights for optimizing the welding process.