Development of novel MIG welding process with duplex current feeding

Abstract

MIG welding under pure argon shielding gas atmosphere (pure argon MIGW) is suitable to obtain a high-strength and high toughness welded joint. However, pure argon MIGW is difficult to be applied practically to welding structure because of arc instability as well as low wettability and shallow penetration of weld bead. For solving the above problems, a novel MIG welding process with a duplex current feeding (DCF-MIGW) has been developed. The DCF-MIGW enables to control the wire feeding speed and the welding current independently by additionally feeding secondary current near the wire tip. In this paper, the basic characteristics of DCF-MIGW were clarified. As a result, under the same wire feeding speed, the DCF-MIGW was able to feed larger welding current than that of the conventional MIG welding. Accordingly, the quantity of heat of droplets in the DCF-MIGW was found to increase with the increase in the secondary current, leading to improved wettability and deeper penetration. The increased welding current also contributed to the arc stability. The multi-layer welding using the DCF-MIGW enabled to avoid the weld defects to prove the practical effectiveness of the DCF-MIGW.