Characteristics of CMT lap joint process for thin galvanized sheet for vehicles

In order to further reduce the spatter generated during cold metal transfer (CMT), the characteristics of CMT lap welding process of thin galvanized sheet were studied and analyzed for automotive thin galvanized sheet materials. Baumer HX 13 industrial high-speed camera was used to capture the CMT welding droplet transition images, and the CMT welding current and voltage signals were collected using NI PXI data acquisition system. The influence of current and voltage on the droplet transfer of CMT in the early stage and late stage of short circuit is mainly studied, and the influence of welding gun inclination on the droplet transfer behaviour of CMT lap welding of thin galvanized sheet was analysed. The results show that when the current in the short-circuit stage of CMT is less than the base stage current, there is no disturbance in the current and voltage waveform, and the welding process is stable. When the current at the later stage of short circuit is reduced by about 5 A, the spatter generated by the CMT lap can be effectively reduced. A smooth droplet transition can be obtained with minimum welding spatter, maximum weld depth of fusion and best weld formation when the torch is at an angle of 30° to the vertical plane. Therefore, when the short-circuit phase current is less than the base stage current and the short-circuit current is reduced by about 5 A, the welding process with 30° welding gun inclination can achieve less metal splash, providing a theoretical basis for production practice.