Research Of Parameters Optimization And Numerical Simulation Of Laser Brazing Of Flange Joints

Laser brazing is a widely established technology for joining zinc-coated steel plates in the body-shop, as one of the modern welding technology. Successful applications are the zero-gap joint, which represents the joint between the side panel and the roof-top of the body-in-white. These joints in the body appearance visual display to the user, therefore have to meet higher forming quality requirements. The main parameters for laser brazing are the laser power, the filler wire speed and the brazing speed. In this paper, from the point of view of laser brazing for galvanized sheet summarizing the different factors affecting the brazing seam forming, focusing on the effect of welding parameters on seam forming, And summarizing the measures adopted at home and abroad in view of the different factors.In order to optimized the process of laser brazing of the flange butt joint, the experiments of laser brazing were carried out, in which the base metal is galvanized steel sheets and CuSi3 is used as filler metal. The influence of laser power, defocus and wire feeding speed on the morphology of brazed joints were analysed by changing the single factor. Response surface methodology was applied to the data, and mathematical models was built based on Box-Behnken Design using linear and quadratic polynomial equations. The results indicate that the proposed models predict the responses adequately within the limits of brazing parameters being used.In order to study the heat phenomenon of laser brazing of the flange butt joint, the numerical simulation of temperature field was carried on by the finite element method, based on the forming characteristics of the flange butt joint and the principle of laser brazing. The heat transfer behavior of the solder spreading flow was simulated by the composite heat source model of gauss double ellipsoid. The model considered the thermal physical properties of material with temperature changing and the effects of the latent heat, radiation and convection on heat transfer. Temperature field of different process parameters have been calculated. The results show that: The peak temperature and temperature gradient on the joint are lower when the laser power is 1600 W, the welding speed is 0.96m/min, defocusing amount is 30 mm. It is more favorable to form the brazed joint of good quality. Temperature field thermal cycle curve measurement system was built. The thermal cycling curves of different positions near the weld were measured, based on Labview software through the data acquisition card and thermocouple. The experimental results were in agreement with the simulation results. The accuracy of the simulation result of the temperature field was verified.In order to obtain stress field and residual stress distribution in laser brazing process. The finite element analysis is used to calculate and analyze the generation and distribution of stress and deformation. Based on the accurate thermal analysis, the temperature field simulation is applied to the stress analysis model by means of therm mechanical order coupling. The stress field of laser power 1600 W, weld speed 0.96m/min, defocusing amount 30 mm was calculated. The stress and residual stress distribution in different directions of the three coordinates are analyzed, and The evolution of the deformation of the galvanized sheet in the process of laser brazing was analyzed.