Arc and keyhole behavior in narrow-gap oscillating laser-MIG hybrid welding of thick aluminum alloys

Narrow-gap oscillating laser-MIG hybrid welding was developed to weld thick aluminum alloys. Weld formation and porosity defect with various oscillating laser parameters were systematically analyzed. Furthermore, the corresponding influencing factors, i.e., arc and keyhole dynamic behaviors were discussed. The difference between both sidewall penetrations was small while wire feeding speed was high and oscillating laser diameter was lower than 3 mm. When laser oscillating frequency was higher than 300 Hz, porosity was less than 0.5 %. Arc burnt stably and the deflection angles were small while laser oscillating frequency was 300–450 Hz and diameter was 1–2 mm. The small fluctuation of arc resulted in small difference between both sidewall penetrations. With the action of oscillating laser, the charged particles increased and diffused to the upper part of the groove. Therefore, arc was attracted by the charged particles and struck at the center bottom of groove. While the arc burnt stably, the difference between both sidewall penetrations was small. The pore formation was significantly inhibited by oscillating laser, as the keyhole opening size increased and fluctuation degree decreased. With the action of oscillating laser, the ratio of keyhole opening width to depth increased, the probability of Rayleigh jet instability on the keyhole wall was reduced.