Study on high speed laser-MIG hybrid welding for large gap joint of stainless steel sheet

Fiber laser-MIG hybrid welding using ER316 filler metal was applied to join the 1mm thickness SUS444 ferrite stainless steel sheet by butt joint and lap joint with a gap of 0.5 mm. In this study, the process window has been successfully obtained for acquiring butt joint and lap joint with good formation. Both dye-penetrant inspection and tensile experiment have been conducted on those joints. The results show that the proper match of welding speed and welding current is a key factor for acquiring large gap joint with good appearance. When welding speed is too low or welding current is too high, the excessive heat input leads to excessive penetration of the weld resulting in bad weld formation. When welding speed is too high or welding current is too low, the heat input is not capable to penetrate the joint. In addition, the highest welding speed can reach 12 m/min and 5 m/min for butt joint and lap joint with good formation with full penetration. In dye-penetrant inspections, no surface crack was found for all the joint with good formation. Meanwhile, in tensile experiments, all the butt joint fractured at the base metal, and most of the lap joint fractured near the fusion line. The tensile strength of the lap joint reached 84.2 % of the strength of base metalunder the highest welding speed (5m/min).