Jianguo Gao

A novel plasma-pulsed GMAW hybrid welding (plasma-GMAW-P) process is proposed for joining 6061 aluminum and zinc-coated steel. The results show that the change in welding heat input has little effect on the microstructure of the joint and the composition of the intermetallic compounds (IMCs) but only changes the thickness of the reaction layer (increased from 5 μm to 12 μm). when the plasma arc current is 20 A and the MIG current is 80 A, the welded joint obtained has the highest tensile-shear force. With the optimal process parameters, the weld strength obtained by filling ER4043 welding wire is the highest, accounting for 65% of the tensile-shear force of the base material. The effect of the plasma arc acting on the joint properties is studied through the microstructure and a tensile-shearing test. The action position of the plasma arc plays a significant role in the Al/steel interface, which directly influences the strength of the welded joints. Regardless of the plasma-GMAW-P style used to obtain the joints, Fe-Al IMCs appear at the interface. When the plasma arc is in front of the welding direction and the GMAW-P arc is in the rear, the tensile-shear force reaches the maximum of 3322 N.

Keyholes are very important to the Plasma-MIG hybrid welding process, weld formation, and quality. With the purpose of studying the effect of the main welding parameters (plasma current, MIG current, magnetic field intensity, and welding velocity) on keyhole depth and the interaction among parameter factors, the experiment was designed by the response surface method. In addition, the prediction model with keyhole depth as the response value was obtained. The model shows the important degree of influence of each factor on keyhole depth. It shows that there is an obvious interaction between plasma current and MIG current, while there is no obvious correlation between other parameters. The temperature field of the Plasma-MIG welding process under certain parameters was obtained by using Fluent software for numerical simulation, and the evolution behavior of the keyhole was analyzed. Based on the simulation results, the metal flow mode and the movement mechanism of the keyhole are described.

In the magnetically controlled Plasma-GMAW welding process, the composite arc forms a keyhole in the workpiece to be welded. In order to explore the effect of process parameters on arc coupling, weld pool and keyhole, and the behavior characteristics of keyhole, the arc behavior and side weld pool information were collected using a welding arc acquisition system and a high-speed camera during bead-on-plate welding. The arc image is processed by pseudo-color enhancement technology, and the collected molten pool information is analyzed by boundary extraction algorithm and coordinate conversion algorithm, and the molten pool boundary and keyhole entrance width are obtained. It is found that the coupling degree of the two arcs increases with the increase in plasma current, GMAW current and magnetic field intensity. With the increase in plasma current, the size of keyhole inlet increases; with the increase of GMAW current, the size of keyhole inlet decreases, and the wave crest increases. With the increase of magnetic field intensity, the intensity of metal oscillation between the two arcs increases, and so does the wave crest.