为实现20 mm 厚16MnDR 钢板的窄间隙焊接，设计实验探究了钝边尺寸和坡口角度对焊缝成形及焊接效率的影响，并对坡口尺寸进行优化。在此基础上，采用单激光自熔焊打底，多层多道激光-电弧复合焊填充的工艺实现了20 mm 厚16MnDR 钢板的窄间隙焊接。结果表明，在该工艺条件下，焊缝表面成形良好，焊缝内部也没有明显缺陷产生，与传统工艺相比，焊接线能量降低45%，焊接效率提高155%，具有明显优势。对接头力学性能进行测试发现，接头的抗拉强度略高于母材的抗拉强度，满足强度要求，且将接头弯曲至180°时，接头处没有明显裂纹产生，满足弯曲性能要求。

In order to realize the narrow-gap welding of 20 mm thick plate 16MnDR steel, experiments are designed to study the effect of root faces and groove angles on welding process stability, weld appearances and welding efficiency, then optimize the size of the groove, on this basis, using autogenous laser as bottom welding, multi-pass multi-layer laser-MIG hybrid welding to fill the gap. The results indicate that the weld appearance is pretty good and there is no defects of internal weld. Comparing the welding heat input and welding efficiency of laser-MIG hybrid welding with traditional arc welding, the welding heat input of laser-MIG hybrid welding decreases by 45%, and the welding efficiency of laser-MIG hybrid welding increases by 155%. The tensile strength of the joint is slightly higher than that of the base metal, satisfying the strength requirement, and there is no crack while the joints are bent to 180°, meeting the yield strength.