Numerical Simulation And Experiment Investigation On Laser-MIG Hybrid Welding Angle Structural Sheet

Due to the insufficient promotion of advanced and efficient welding technology in China,the related welding technology in the field of automobile manufacturing has been greatly restricted.At present,the efficient welding technology is mainly used in the connection of butt joints and the overlapping structure of the medium and heavy plates,but the application in the angle structure sheet is very limited.Laser-MIG hybrid welding technology is an efficient welding technology that combines the advantages of laser welding and MIG welding.When the technology is used for welding 1.5 mm spcc(steel plate cold common)sheet,it not only has high welding efficiency,but also have few defects.And it can improve the microstructure and mechanical properties of the weld joint.In this paper,the distribution of temperature field and the flow characteristics of molten pool during laser-MIG hybrid welding of1.5 mm angle structural spcc sheet are simulated by software Fluent.At the same time,the hybrid welding experiment is carried out.From the perspective of welding process parameters,the weld forming law of aangle structural sheet laser-MIG hybrid welding is studied,and the microstructure and mechanical properties of the weld joint are analyzed.The distribution of the temperature field and flow field of the molten pool during laser-MIG hybrid welding process of angle structural sheet is calculated.In the depth direction of the weld,the farther away from the surface of the weld,the lower the temperature,the maximum temperature gradient appears at the edge of the weld pool.A slight "temperature rebound" occurs during the cooling phase of the melt pool.Under the effect of Marangoni,melt flow from the center of the heat source to the edge of the pool,and the maximum rate of the molten pool appears at the edge.Comparing the molten pool cross-section by calculating and weld cross-section by experimenting,it is found that the numerical simulation results are in good agreement with the experimental results.It indicats that the new heat source model combined by the double ellipsoid heat source and the rotating Gaussian heat source has high accuracy for simulating laser-MIG hybrid welding.The effects ofthree process parameters of groove angle(?),laser power(P)and welding speed(V)on welding temperature field and molten pool flow field are studied and discussed.The results show that the instantaneous temperature and flow velocity of the molten pool increase with the increase of the groove angle and the laser power.The instantaneous temperature and flow velocity of the molten pool decrease with the increase of the welding speed.It is also found that the influence of laser power and welding speed on the temperature field and flow field of the molten pool is greater than those of the groove angle.The experimental results show that weld joints can be clearly divided into weld zone?heat affected zone and substrate zone.The weld zone is mainly composed of granular bainite and lath martensite.The heat affected zone is mainly composed of irregular ferrite and a small amount of retained austenite,and a large number of dislocation structures are found in weld zone.The higher the laser power,the finer the grain structure of the weld bead and the higher the microhardness.The larger the welding speed,the larger the grain size and the lower the microhardness.The angle of the groove only affects the geometry of the weld pool,which is no significant effect on the microstructure of the weld.When the welding parameters is: P=2.0 kW;V=20 mm/s;?=45 o(the current is 105A),good quality fillet joints can be obtained.In the path of the vertical weld,as the distance from the center of the weld increases,the residual stress gradually changes from tensile stress to compressive stress.And the turning point of the longitudinal residual stress into compressive stress is about20 mm from the center of the weld,the turning point of the transverse residual stress into compressive stress is about 18 mm from the center of the weld.At the same time,as the groove angle increases,the value of residual stress increases.