Characteristics and mechanisms of weld formation during oscillating arc narrow gap vertical up GMA welding

Large metal structures are applied increasingly in manufacturing industry, such as ship building industry, pressure vessel, pipeline engineering, and ocean engineering. Narrow gap vertical up GMA welding has been applied in such large metal structures with the advantage of higher production efficiency. In this paper, the characteristics and mechanisms of weld formation during oscillating arc narrow gap vertical up GMA Welding were investigated by experiment and simulation, and the influences of the oscillating parameters on weld formation were analyzed, such as oscillating angle and oscillating speed. The results show that the weld formation of vertical up GMA welding is apt to appear convex shape, due to the molten liquid metal accumulating at the middle of pool with the action of gravity, and oscillating arc is beneficial to reduce convex degree. The desired weld bead with little convex degree has been achieved by using the optimization parameters.