Microstructure and properties of laser-arc hybrid welding thick bainitic steel joints with different arc position

The realization of 12mm thick laser-arc hybrid welding technology is the prerequisite for efficient production of new high-speed train bogies. In this work, for the laser-leading hybrid welding, the problem of hump defects in the root of the weld is easy to occur. The arc-leading mode is chosen to obtain the welded joint of high-strength bainitic steel with no hump, no unfilled and no porosity defects. Then the microstructure distribution of the welds of the high-strength bainitic steel is analyzed, which the weld metal is mainly composed of acicular ferrite and lath bainite and the heat affected zone mainly concludes coarse-grained bainite and granular bainite. Then, under the optimal process, the hardness distribution, arc action area size and weld impact performance of the laser-leading and arc-leading welds were compared. It was found that the arc-leading weld hardness distribution was more uniform and stable, and the hardness peaks both appear in the HAZ(coarse lath bainite), and the valleys both appear in partial phase-change zones (Bulk ferrite). Meanwhile, the arc-leading weld impact performance is 21.49% higher than that of laser-leading.