Research On Welding Process Of Laser-Arc Hybrid Welding Of The 5083 Aluminum Alloy

Recently, the broad prospect has been showed in the laser-MIG hybrid welding of thick high strength aluminum, due to the process of the lightweight high-speed trains. By the maturity of high power fiber laser, fiber laser-MIG hybrid welding, which integrates fiber laser and MIG arc and obtains advantages including higher welding speed and stronger "bridge" capability, has become a hotpot. However, up to now, bad weld appearance, serious porosity defects and poor joint mechanical properties readily occurred during thick high strength aluminum plates. Therefore, the topic investigates the technological characteristics, through analyzing the welding shaping characteristics, microstructure characters, porosity defects, tensile properties and residual stress distribution, in fiber laser-MIG hybrid welding of 5083 aluminum alloy structure. The followings are the results:The technological characteristics of different welding methods were studied comparatively. The experimental results demonstrated that laser-MIG hybrid welding is superior to laser welding and MIG arc welding, whether in welding shaping, penetration ability, production efficiency and stability of the welding process or in tensile properties.The process characteristics were investigated comparatively during laser-MIG hybrid welding high strength aluminum with different thickness. The consequences founded that the 6mm thick aluminum alloy was welded with worse joint appearance and more pores than 4mm aluminum, so that further study on hybrid wielding 6mm aluminum was carried out essentially. However, the joint tensile strength of 6mm aluminum plate reached a higher level, which indicated that the presence of stomata may not necessarily weaken the tensile properties of welded joints. Meanwhile, the number of stomata can be actually reduced with proper characteristics in the welding process.The technological characteristics of 6mm aluminum plate were obtained by laser-MIG hybrid welding experiments. It was thought that two main effects of welding speed and wire feed rate were significant to weld width; the interaction effect of laser power and welding speed was significant to both weld reinforcement and coefficient of weld reinforcement; the main effect of welding speed was significant to porosity and tension strength.The laser-MIG hybrid welding process characteristics of different joint forms were studied comparatively. It was found that the better weld shaping was obtained when welding with a U-groove bevel, but the prevention of porosity and tensile strength went poor.The welding longitudinal residual stress distribution was analyzed separately by different testing methods and welding techniques. The test result obtained by traditional machine-cut method was always the maximum, on the contrary, that by the X-ray diffraction method was the minimum. The result also showed that the residual stressfluctuated the most in laser-MIG hybrid welding, and the value of residual tensile stress in its welding seam center is the maximum, compared with the other two welding methods.The longitudinal residual stress distributionof laser-MIG hybrid welding was discussed. It was experimentally proved that the distribution of residual stress in 6mm aluminum plate is consistent with that value of residual stress in 4mm plate and the value in the middle of the joint is higher than the positions of arc starting and suppressing. Meanwhile, the peak and fluctuation of the residual stress was increased and the high residual tensile stress range was widened when the heat input was higher. The residual tensile stressdistribution of the plate with a U-groove bevel was narrower but more variable.