Study Of Technique On Hybrid CO₂ Laser-MIG Welding Of 5083 Aluminium Alloy For Shipbuilding

With the development of weldable aluminum alloy and global light-duty trend of transport facility, aluminum alloys have been applied widely in the shipbuilding industry. Aluminum alloy traditional welding method of MIG is facing some problems such as slower welding speed, bigger distortion and inferior weld joint performance. While the laser welding method with the high reflectivity by aluminum alloy will also have other problems that the welding process of stability is difficult to control and prone to some weld defections, affecting its application. A new method of CO₂ laser-MIG hybrid welding involving two heat sources (CO₂ laser and MIG arc) together can complement each other, so as to achieve the best effect of energy utilization, especially for thick aluminum alloy plate welding.In this paper, the effect of complex process parameters, including laser and arc process parameters such as welding speed, heat source distance, laser power, arc voltage, wire speed and defocus position on welding electrical signals, the quality of weld seam surface and the weld bead geometry were studied by using CO₂ laser-MIG hybrid welding 5083H116 aluminum alloy. The microstructure and mechanical properties of the sound welds are also be evaluated.The CO₂ laser-MIG hybrid welding process parameters experiments on 5083H116 aluminum alloy were conducted, with the electrical signals collected. The signals typical characteristics of different voltage were analyzed, as well as the signals characteristics changes under different source distance and the different match of laser power and wire speed. The results show that only the two sources in a certain distance can the signals maintain stable and distance too larger or smaller would give rise to fluctuations. Both laser power and wire speed have influence on the stability of electrical signals, and the match of these two factors is the key point.The effect of source distance and the match of laser and arc power on the quality of weld seam surface were analyzed by the rate judgment of the weld surface appearance. The results show that well-sound weld can be obtained under the certain source distance in which the electrical signals maintain stable. With the voltage increased, the range of the source distance value will be wider. Laser linear energy has a great impact on the quality of weld seam surface, and this influence becomes more evident when the wire speed increased.The effect of source distance, the match of laser and arc power under different welding speed and defocus position on the weld bead geometry were analyzed. The results show that the biggest weld penetration can be obtained under the certain appropriate source distance in which the best effect of the two heat source achieved. The match of laser power and wire speed under different welding speed has different weld penetration.At last, based on the results above, 5083 aluminum alloy CO₂ laser-MIG hybrid butt welding have been made using optimized weld parameters, and well-sound weld can be obtained. The microstructure analysis, micro hardness and mechanical properties test of tensile and bending have been made. The results show that clutter arborescent crystal is found in the weld center and the micro hardness in the center is lower than the base material due to the lost of lower melting point elements like magnesium. The weld joints tensile properties are above 95% than the base material and bending properties are good according to the shipbuilding standard.