Characteristics of bypass coupling twin-wire indirect arc welding with high-speed welding mode

Abstract The welding characteristics in the process of bypass coupling twin-wire indirect arc welding (BC-TWIAW) with high-speed welding mode was comprehensively investigated. Under the condition of the total current of 300 A, the direct arc and indirect arc mainly periodically burned alternately. Its alternating frequency increased with cathode wire feeding speed increase. Nevertheless, it is also found that these two arc burned simultaneously for a very short duration. The indirect arc between the twin wires was principally used for melting the wire while the direct arc was beneficial for deepening the molten pool. Overall, the alternating burning of two arcs could remarkably reduce the heat input into the workpiece. Irrespective of the cathode wire feeding speed, the arc voltage and total welding current generally remained stable. Meanwhile, the droplet transfer patterns changed periodically accompanying with the alternative burning between the two arcs. The droplets of cathode wire mainly transferred into the molten pool globularly. When the cathode wire feeding speed was slow, the droplets of anode wire was mainly in stable spray transfer mode. The anode wire droplet successively experienced spray transfer, short circuiting transfer and globular transfer in turn with the acceleration of cathode wire feeding. Even though the deposition efficiency was improved with a faster cathode wire feeding speed, too fast feeding speed might lead to frequent short circuit explosion and impair the weld formation. Considering both the deposition efficiency and weld formation, the feeding speed of cathode wire should be adjusted at 40%–50% of the anode wire.