Numerical analysis of arc parameters and droplet behaviors for underwater flux-cored arc welding

In our previous work, a non-axisymmetric 3D numerical model with the arc and droplet behaviors coupled for underwater flux-cored arc welding (FCAW) was developed for the first time, several qualitative results of arc and droplet were given. Based on that, this work further focuses on the quantitative analysis, mainly discussing in detail the distribution and value of physical quantities including current density, electromagnetic force, temperature, velocity, pressure and heat flux. The influence of the droplet offset angle from the wire on the welding process was also analyzed. The results show that the droplet offset angle is random under the action of multiple complex forces. Due to the non-axisymmetric distribution of the droplet, the arc current density is concentrated on one side, which makes the electromagnetic force, temperature and velocity in the arc area also present asymmetrical distributions. The rotation of the droplet makes the asymmetric distribution of physical quantities change in real time relative to the position of the workpiece, which finally affects the weld formation. The flow field inside the droplet presents a non-uniform distribution, the symmetrical vortex in the initial stage will gradually disappear and only one side of it remains. The current density at the bottom and neck of the droplet is higher and the rest is relatively low. The variation trend of current density and electromagnetic force at the neck of the droplet are consistent with that of the droplet offset angle from the wire.