Study On Metal Transfer Behavior During Ultrasonic Assisted Metal Avtive Gas Welding Process

Significant improvement of the stability of the whole welding process wasachieved in ultrasonic-assisted metal inert gas welding （U-MIG）. However, theapplication of MIG is not widely which is limited by its own characteristics. Attempt ofusing ultrasonic wave to promote the detachment of droplet during metal active gaswelding （MAG） process was made, referred to as ultrasonic assisted metal active gaswelding （U-MAG）.The ultrasound’s role of promoting metal transfer in welding process which haddifferent components of shielding gas was studied. As is well known, the behaviors ofshort-circuiting transfer and globular transfer are respectively determined by arc lengthand forces acted on the droplet. The arc and conducting zone on the droplet wererecorded by high-speed camera system. Comprehensive study on arc length and thechanges of the conducting zone were carried out under different shielding gas.Compression ratio of arc length under different shielding gas was studied to clarify theimpact of short-circuiting transfer by ultrasonic wave. The change of electromagneticforce impacted by conducting zone was investigated. The suitable range of carbondioxide content was proposed that the droplet detachment was accelerated during theU-MAG process.The metal transfer map and the characteristics of different metal transfer modeswere researched in comparison with the conventional MAG under Ar-8%CO₂shieldinggas. As shown in the metal transfer map, the short-circuiting transfer mode of U-MAGshowed better adapt to welding current and voltage than conventional MAG, thetransition frequency increased in U-MAG. The droplet’s size decreased and the shapeobserved approximately to be ellipsoid rather than sphere in globular transfer mode. Inthe spray mode, the welding process changed to be stable under low welding voltagewhen combined with ultrasonic wave. On the contrary, the welding process becamemore stable when under higher welding voltage. Generally speaking, the weldingprocess was improved in U-MAG compared with conventional MAG.The forces acting on the droplet were modified to be accurately. The detaching forces was found decreasing in U-MAG because of the deformation of droplet.According to the static forces balance theory, the ultrasonic radiation force plays alarger role in detachment than it was thought in the former times. At last, a method werecarried out to calculate the ultrasonic radiation force basing on the energy balanceprinciple.