The Research Of Droplet Transfer Behavior And Arc Shape Of Narrow Gap GMAW

The narrow gap GMAW is a kind of efficient and low thermal input new type welding method, it has a extensive application prospect in the field of middle and thick plate welding. During the process of the narrow gap GMAW, the climbing behavior of arc and the droplet transfer mode have an important influence on the welding quality. Therefore, according to the arc of interval constraint conditions and the droplet transfer behavior, the research was undertaked from the following three aspects:Firstly, the process research of narrow gap GMAWAiming at the characteristics of the narrow gap GMAW process, the rapid prototyping experiment system and the high-speed video acquisition system were established, the narrow gap GMAW real-time control, the electrical signals synchronous acquisition, and the acquisition and treatment of the arc and the droplet behaviors were undertook.Secondly, the research of arc behavior under the gap constraint condition.Aiming at the climbing behavior of arc during the narrow gap GMAW process, this paper analyzed the arc automatic adjustment process under the gap constraint conditions and the reasons of the climbing phenomenon of arc; Meanwhile, according to the change of the narrow gap GMAW arc load characteristics, the mathematical analytical model was set up to describe the current distribution forms of the narrow gap GMAW.The above research results showed that under the narrow gap constraint conditions, as the principle of minimum voltage, the arc would firstly choose a shortest path conductive, when the distance of the welding wire ends to the gap sidewall less than the distance of welding wire ends to the gap base, the arc would burn by choosing the shorter conductive path, the stem elongation also reduced, as the effect of self-adjusting of the arc, the length of the arc also would increase, but the distance of the welding wire ends to the gap sidewall was certain, the length of the arc couldn’t increase, so only through melting the welding wire to increase the length of the arc, so that stem elongation of the welding wire decreased, leading to the phenomenon of arc climbes along the gap sidewall.Thirdly, the research of droplet transfer behavior under the gap constraint conditions.Aiming at the unstable problem of droplet transfer during the narrow gap GMAW process, the static equilibrium theory was used to analyze the stress forms on the surface of the molten droplets, and theoretically analyzed the droplet transfer behavior under the gap constraint conditions. The results showed that when the arc is on the condition of narrow gap constraint, the arc shape changed, so that the droplets had the radial electromagnetic force, which made the arc root area extented, thereby promoted the droplet transfer.