Influence factors and control methods of droplet transfer in narrow gap P-GMAW overhead welding position

When conducting narrow gap all position welding of pipelines, welding defects are easy to occur near the overhead welding position, which restricts the quality and efficiency of pipeline construction. Aiming at the problem of poor formation and low reliability of overhead welding position in automatic pipe welding, this paper studies the influence of wire feeding speed, arc length correction, contact nozzle distance to molten pool and other factors on droplet transfer in P-GMAW process. It is found that increasing the arc length correction coefficient can increase the heat input of the arc to the side wall, which can alleviate the problem of poor side wall fusion, but will make the droplet transfer path difficult to control, Therefore, when the welding gun moves to the overhead welding position, short arc welding shall be adopted and the heat input to the side wall shall be supplemented by increasing the side stop time and swing; Increasing the wire feeding speed is conducive to obtaining smaller droplets, higher transfer frequency, reducing the distance between the contact tip and the molten pool, increasing the electromagnetic force and reducing the droplet size, which is more conducive to the transfer of droplets to the molten pool in overhead welding position. The research results have certain guiding significance for the process design of pipe narrow gap welding.