Research On Flow Field Of Invar Steel Molten Pool By Laser-MIG Hybrid Welding

Invar steel die is widely used in the process of the current aircraft composite structure hot press forming,The main problem of the percentage of home-made parts is that the welding process of Invar steel with large thickness.This paper used the method of combining experiment and simulation to study on the flow field in the-MIG die steel Invar composite welding as well as the related problems of the flow field.Firstly,5mm thick Invar steel was welded by laser-MIG hybrid welding,observed the macro morphology of weld joint would find that the laser-MIG hybrid welding seam was presented as the funnel shape. Using 19.05 mm thick Invar steel to design three sets of laser-MIG hybrid welding experiments,from the weld center to the base material,the metallographic is made from equiaxed grain to columnar crystal,and then to coarse grain size. The appearance of pores in the weld,centered at the bottom of the weld edge, or at the bottom of the weld. In the Invariant case of other welding processes,with the increase of laser power and welding current,the hardness distribution of weld seam is more uniform.Secondly,5mm thick Invar steel-MIG composite welding was used as the research object,researched on the selection of heat source model in the process of thesimulation of laser-MIG hybrid welding of Invar steel. The simulation results of the Gauss rotary body heat source and the double ellipsoid heat source were compared with the experimental results of the laser-MIG welding,which showed that the local area of the weld has a certain consistency,but it can not be completely identical. However,with the combination of the new heat source model,the Invar steel laser-MIG hybrid welding pool numerical simulation results showed that the simulation of the weld pool shape could well match the actual weld area.Finally,the 19.5mm thick Invar steel laser-MIG composite multilayer welding was used as the research object,and the finite element numerical simulation method is adopted,using the new combination of heat sources to analysis the causes of welding results from the flow field in the weld pool,the flow velocity of molten pool is small,so the flow of the molten pool is not good,which is difficult to generate the gas in time to drive the escape,so as to cause weld porosity. The better the flow velocity in the laser-MIG hybrid welding,the better the uniformity of the hardness of the weld,and the speed of the flow field in the molten pool has little effect on the maximum value of the weld hardness.In this paper,the combination of experimental study and simulation analysis of Invar steel laser-MIG hybrid welding was adopted,From the welding experiment,the welding heat source and the flow field form of the weld pool were studied,and the welding process of laser-MIG hybrid welding was studied in detail,which lays the foundation for the research on the welding technology of laser-MIG hybrid welding.