Welding Process Analysis And Distortion Control Of Mig Welding For Metro Aluminum Alloy Traction Beam

High strength aluminum alloys with low density and resistant corrosion are widely used to manufacture car body of metro vehicles. Aluminum alloys are easy to cause residual deformation for large thermal diffusivity and thermal expansion coefficient, so they usually need adjustment and rectification. The productivity of welding aluminum alloy is limited for those reasons above. This thesis focuses on optimizing the welding process for aluminum alloy traction beams with the help of numerical simulation and experiment to reduce welding distortion and increase the productivity.Firstly, the unsymmetrical welding sequence for the X weld seam is the main reason of traction beam welding deformation with analyzing the feature and shortage of the common MIG welding process according to the structure featur e and quality requirement of the traction beam.Secondly, numerical simulation was done for plate specimen. The welding heat source model in simulation was verified by experiment. Numerical simulation was done for traction beam by common MIG welding process to obtain the magnitude of distortion. Comparing and analyzing simulated and experiment results was also done. Research results show that the distortion was 1.5°or so.Finally, flip cross welding, double-sided arc welding and preset reverse-deformation method were put forward according to the actual situation of our workshop. Numerical simulation was done for the three schemes. The results show that flip cross welding and double-sided arc weld are relatively better and combination of the two schemes is the best by analyzing the three schemes. The optimization was verified by welding experiment. The experimental results show that the angle distortion is under the reasonable tolerance range and can be ignored in actual production. This small angle distortion has no effect on flatness of traction beam.The Research has been applied to welding traction beam by using special preset deformation jigs. The qualified rate of traction beams is more than 98%, which increases the productivity and reduces the cost.Experience is accumulated in success of distortion control on aluminum alloy traction beams.