| Due to its own characteristics,galvanized steel sheet caused defect during the laser welding,while it improved the corrosion-proof of Body-in-White.Multi-spot beam,as a new type of laser welding beam,can effectively reduce the influence of zinc vapor generated by galvanized steel on the welding quality during welding.It has great development potential in the laser welding field of the automotive industry,especially in the Body-in-White.The researsh contents are as follows:(1)A solution that multi-spot beam especially the triple-spot beam(panda beam)has been proposed to replace the original welding beam.Aiming at the status quo of zinc vapor generated by the melting and evaporation of zinc coating during the laser welding of automotive galvanized steel plates into the weld area,which caused the disturbance of the molten pool and reduced the welding quality.(2)Based on the theory of grating diffraction,Multi-spot beam laser beam splitting simulation in Zemax has been achieved by using Dammann Grating and Bragg Grating respectively.The Panda beam was obtained by splitting the 4k W incident laser through the Bragg grating and achieved a good beam splitting effect.The single front beam radius is0.6mm with power is 1.1261 k W,and the distance between the front beams is 3.8mm;The radius of the main beam is 1mm,the power is 1.7168 k W,and the distance from the front beam is 9.7mm.(3)Based on the geometric optics beam splitting theory and Zemax,the simulation model of laser beam splitting has been based on the two different beams of the roof mirror multipoint beam and the panda beam is implemented.Described the advantages of the laser beam splitting based on geometric optics.And by establishing a panda beam simulation model composed of three independent light sources,the huge advantage of the laser beam splitter over the multi-light source structure in practical applications is illustrated.(4)A laser welding temperature field simulation model of the panda beam has been established in Matlab and Comsol by using the theory of the finite element analysis.The radius of the main beam is 1mm with the power is 2.8 k W in order to molten solder,and the radius of the front beam is 0.5mm with the power is 600 W in order to gasify zinc coating.At the welding speed of 3m/min,there was a time interval of about 0.3s between the vaporization of the zinc coating and the melting of the solder,which is sufficient to achieve the escape of zinc vaporThis research work validated the advantages of multi-spot beams in the laser welding process of Body-in-White galvanized steel sheet,and proposed another idea of ?implementing multi-spot beams based on the laser beam splitter.Avoided the problem that the structure of the laser welding joint is too complicated caused by using multiple light sources to form multi-spot beam.Among them,Bragg gratings and roof mirrors are more suitable for this field.This research work has certain reference value in the field of laser welding of galvanized steel for Body-in-White. |
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