Abstract
The simulation method in laser-MIG hybrid welding, which involves two heat sources and multiple welding parameters, is beneficial to reveal the complex physical phenomena and dynamic behavior of molten pool keyhole during the welding process. In this investigation, laser-MIG hybrid welding for 6-mm-thick 6061 aluminum alloy was performed under different heat input by the high-power disc laser, MIG welding system, and KUKA robot. The high-speed camera system was used to observe the droplet transition phenomenon in the welding process. Besides, a thermal-fluid coupling model was established to simulate the temperature field and flow field, which was changed by the droplet transfer during laser-MIG hybrid welding. The experimental and simulated results showed that the droplet transition behavior affected the formation of the keyhole. The keyhole was the smallest when the droplet contacted the molten pool. In addition, the droplet transition brought external momentum and energy to the molten pool, which was conducive to the increase of the flow rate of the molten pool.
Highlights
Contemporary aerospace is based on the goal of improving the carrying capacity through weight reduction[1, 2]
3.6 Droplet transition model The mass, energy and momentum brought by the droplet transition behavior, which impacts on the temperature field and flow field of the molten pool as well as the dynamic evolution behavior of the keyhole
The contact surface gradually increased under the action of the surface tension of the molten pool and gravity, the molten droplet was completely separated from the end of the welding wire at t0+6 ms
Summary
Contemporary aerospace is based on the goal of improving the carrying capacity through weight reduction[1, 2]. Laser-arc hybrid welding with the characteristics of high welding energy, strong gap bridging ability and high joint quality[14], makes up for the deficiencies in the single processing heat source, effectively combines the advantages of the two welding methods[15]. Many researches have been carried out to observe the morphology of the molten pool during the laser-MIG hybrid welding process by high-speed cameras. Liu et al [17] observed the droplet transfer and the keyhole in the molten pool during laser-arc hybrid welding by high speed camera. It revealed that the laser had a compressive effect on the arc pressure with the surface of the molten pool. With the help of high-speed camera and the establishment of a thermal-fluid coupling model, the droplet transition behavior is studied
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