Abstract: The galvanized steel is commonly used in car body manufacturing for its excellent corrosion resistance, so its weldability has been widely studied. CMT welding has less splash when welding galvanized steel plate, which can reduce the possibility of pores.CMT has great advantages in galvanized steel plate welding application. The DP590 galvanized steel with a thickness of 1.0 mm is taken as the welding base material, and the BHG-2M welding wire with a diameter of 1.0 mm is used as the welding material. The CMT digital welder is used for lap welding. Wire feeding speed and welding speed are adjusted as the welding process parameters to study the porosity and zinc layer of welding joint under different welding process parameters. The composition of zinc layer is analyzed by energy dispersive spectrometer and the width of zinc layer is measured. The results show that the generation of pores in the weld is closely related to the welding heat input. The higher the heat input, the lower the porosity. The center of the upper surface of the weld is severely burned. Zn is almost completely evaporated. The degree of burn on both sides gradually decreases. The closer to the center of the weld, the greater the oxidation degree of the zinc layer on the lower surface. Increasing the welding speed or reducing the wire feeding speed will reduce the burning degree of the zinc coating in the weld.

Key words: DP590 galvanized dual-phase steel, cold metal transfer welding, pore, zinc coating