Effect of phase on the behavior of metal transfer in double-wire pulsed GMAW

High-speed photography was used to record metal transfer during double-wire pulsed gas metal arc welding (GMAW) in the synchronous, alternating and independent phases, while the voltage and current waveforms were recorded simultaneously. According to the relationships between voltage, current, and metal transfer, the effect of phase on the behavior of metal transfer was analyzed. The experimental results demonstrated that metal transfer was all a "one drop per pulse" (ODPP) spray transfer mode in the three phases. ODPP was easier to achieve and metal transfer was more stable in the alternating phase. The deviation distance of droplets in the synchronous phase was larger than that in the alternating and independent phases, and the deviation distance of droplets in the alternating phase was minimum. The surfaces of weld beads acquired showed a desirable weld bead appearance that resembled fish scales. The weld bead in the alternating phase exhibited more obvious fish scales. Phase had little effect on weld width and reinforcement, though it had a significant effect on penetration. Penetration in the alternating phase was significantly deeper than penetration in the synchronous or independent phases, and penetration was minimum in the synchronous phase. The alternating phase facilitated the growth of columnar grains to be inhibited and the directions of ferrites to be disrupted. The columnar grains were discontinuous and the directions of ferrites were more chaotic in the alternating phase when compared with in the synchronous phase. And the anisotropic microstructure in the independent phase was between the synchronous and alternating phases.