Research on Microstructure and Mechanical Properties of Hot-wire Laser Narrow-gap Welding Joint of Q460 Steel

The hot-wire laser narrow-gap welding technology of Q460 mine rescue cabin steel was studied.Metallographic microscope, SEM, tensile testing machine, impact testing machine and microhardness tester were used for microstructure analysis and property test of the welded joint. The results show that when the welding speed is 0.003 m/s, the laser power is 2 kW, the defocus amount is 20 mm and the wire feeding speed is 1.5 m/s, the weld formation is the best. The weld mirostructure is composed of ferrite side-plate, bainite and a large amount of acicular ferrite, and the mirostructure of the coarse grain heat-affected zone is composed of massive ferrite and granular bainite. The strength of the weld zone is the lowest, the tensile fracture is the weld zone. The average impact absorption energy of the weld zone and the heat-affected zone is 98.18,180.76 J, respectively and the impact fracture mode is ductile fracture. The microhardness of the weld is the highest with average hardness of 275 HV, followed by the welding heat affected zone, with average hardness of 225 HV.