研究了厚板低碳钢窄间隙激光-MIG复合焊接，分析了焊接工艺参数对焊缝表面成形的影响规律，深入讨论了焊缝内部缺陷的形成原因。结果表明，通过激光-MIG复合焊接工艺参数优化和合理设计坡口形式可以获得成形良好的焊接接头。焊缝表面形成的缺陷主要有未焊透、咬边、背部下塌等，除了与材料本身的焊接特性相关外，还与不匹配的焊接工艺参数有关。而焊缝的内部缺陷主要是气孔，气孔的形成主要是由于焊前试样表面的清洗不彻底与焊接过程中的匙孔不稳定造成的。研究还发现，通过焊前彻底的表面清洗和加大熔池的保护可以有效消除气孔并获得良好的焊缝质量。

Laser-MIG hybrid welding of thick mild steel plates with a narrow gap was researched. The influence of process parameters on the weld surface appearance was analyzed. And the reasons of producing defects in weld were deeply discussed. The results show that a joint with good formation can be obtained by optimizing process parameter and designing reasonable grooves. The defects on the surface of the weld consisted of incomplete penetration, undercut, back depression, etc, which related to welding characteristics of material itself as well as the mismatch of welding process parameters. Porosities are also produced in the weld because of incomplete surface cleaning before welding and the instability of keyhole during welding process. In addition, it is also found that porosities can be effectively prevented and a good joint can be achieved via complete surface cleaning before welding and proper protection of the molten pool during welding.