Research On The Mechanism Of Laser In Laser-Low Power MIG Hybrid Welding Of Aluminum Alloys

The MIG welding methods commonly used for aluminum alloys sheet are short-circuiting transfer MIG welding and pulsed MIG welding. The welding process of short-circuiting transfer MIG welding of aluminum alloys is not stable, and the weld appearance is poor. To pulsed welding of aluminum alloys, the welding quality and welding efficiency need to be improved. Laser-arc hybrid welding has the advantages of stable welding process, high welding efficiency, good welding quality, and it is an ideal welding to aluminum alloys.In this study, the arc behavior, droplets transfer process, welding electrical signals in welding process were observed exploiting high-speed imaging and welding electrical signals collecting. Bead-on-plate welding experiments were conducted using Al 6061 plates with a thickness of 3mm, and welding process characteristics of low power MIG welding of alumnium alloys and the effect of laser on it were studied.The obtained results are as follows:It took less time to strike the arc in Laser-MIG hybrid welding, and the stability of arc striking was increased.The arc shape was improved after introducing laser into the arc atomosphere. The arc plasma was attracted by the laser, and the arc cathode spot was fixed to the laser beam impinging spot, so the arc could burn stably. There were interactions between laser plasma and arc plasma, and a more stable conductive channel was built. Plasma distribution was decided by the relative strength of the two plasmas. When the arc plasma is stronger, the plasma mainly distributed at the end of wire. When the laser plasma is stronger, the plasma mainly distributed at the laser spot.Laser influenced the droplets transfer process of aluminum alloys MIG welding. When the laser power is blow the threshold value, the droplets transfer became more stable, and the shape of weld are significantly improved. While the laser power exceeds the threshold value, the droplets transfer becomes instable. When the distance between the end of wire and the laser beam was too close or too far, the droplets transfer process was unstable. An analysis method of judging droplet transfer stability based on mathematical statistics is proposed. By this method, it can be concluded quantitatively that welding process in Laser-MIG hybrid welding is more stable than that in conventional MIG welding of aluminum alloys.There are three droplet transfer modes in Pulsed MIG welding of aluminum alloy: Pulsed Short Circuiting transfer, Pulsed Meso-spray transfer, Pulsed Spray transfer. The droplet transfer behaviors were changed when the Laser was introduced into the arc atmosphere. Pulsed Meso-spray transfer mode changed to Pulsed Spray transfer mode gradually with the laser power increasing. When the Laser power was above a threshold level, Pulsed Meso-spray transfer mode turned into Pulsed Spray transfer mode totally. The arc length and the wire melting rate increased in Laser-Pulsed Spray transfer MIG hybrid welding.Compared with MIG welding and laser welding, Laser-MIG hybrid welding obtained better weld appearance and deeper weld penetration. With similar welding line energy, hybrid welding has the highest welding efficiency.