Stability analysis of CO2 gas shielded welding short-circuit transition process based on GMAW dynamic model

Based on the arc phase and short-circuit phase and their relationship, the paper considers the changes of the extension length of the welding wire, the arc length, liquid bridge resistance and mass of liquid bridge, combines the improved "mass-spring" model with the loop model of welding power system, puts forward the critical judgment condition of droplet transition, and establishes a more accurate dynamic model for describing the short-circuit transition process. Through the dynamic model, the short-circuit transition frequency, welding current and voltage, contact droplet and residual droplet equivalent radius (including mean and statistical distribution) and the dynamic changes of droplet equivalent radius at different wire feeding speeds were calculated and analyzed, and compared with the experimental results, they were in good agreement. The dynamic changes of droplet displacement, velocity, welding wire extension length and liquid bridge shape are discussed. The results show that the fluctuations of droplet displacement, velocity, and extension length of welding wire is the smallest at the optimal arc point, and the smaller the radius of curvature of the initial liquid bridge is, the better the stability of short-circuit transition is.