Laser Welding Process Optimization And Finite Element Simulation Of 20Mn2 And Q345D Steel

This article focuses on the laser welding process of material 20Mn2 and material Q345D through the combination of theory and experiment,and through the modification experiment to remelt the weldment to make the mechanical properties of the weld area improve the weld quality and through the metallurgical microscope,Scanning electron microscopy,micro hardness tester,tensile performance test,energy dispersive spectrometer(EDS)and other analysis methods,the structure and performance of the weld are studied,and the temperature field and stress field of the welding process are analyzed using finite element analysis software Simulation.The corresponding conclusions of the process parameters on the weld seam morphology of the weldment,the changes in the organization of the weld seam,the hardness change of the weld fusion zone,the heat affected zone and the adjacent base metal and the improvement of the mechanical properties are as follows:In this paper,the finite element software is first used for laser welding simulation analysis,and the temperature field and stress during the welding of dissimilar steel are simulated,which lays a theoretical foundation for laser welding.The results indicate that the center of the heat source has the highest temperature in the welding simulation,the isotherm looks like an ellipse,and the heat affected zone is small.It is concluded that the molten pool is not completely symmetrical,and there is a difference between the left and right molten pools.When the laser power is 1800 w,the weld depth is 2.51 mm.When the laser power is adjusted to 2700 w,the simulated value of the weld depth is 4.31 mm.After the power exceeds2700,the weld depth is not Will get bigger.The peak time of the temperature at 5mm on both sides of the weld is relatively short,and the time for the temperature to reach the peak is different due to the physical parameters of the material.The stress in the weld and its vicinity is high,and stress relaxation is found in laser weldingThrough research,we found a single change of laser process parameters,and studied the change of hardness,mechanical properties and microstructure of weld area.The results show that the microstructure of the different areas of the weld is plane crystal,cell crystal,dendrite,equiaxed crystal,and the hardness gradually decreases to both sides,and the laser depth and mechanical properties of the weld seam vary with a single change within a certain range.Change into a positive correlation.When the welding power is 1600 W,the welding seam value is 2.73 mm,and the welding depth is increased to 5.01 mm when the welding power is adjusted to 2800 W.The welding width is increased to 6.75 mm.The tensile strength withstood to reach 18 kN is about 399 Mpa.When the welding speed is 1mm/s,the welding depth is5.03 mm.When the welding speed increases from 2mm/s to 2.5mm/s,the welding depth begins to decrease.After 3.5mm/s,the performance of the material decreases after fusion.The welding speed is plastic fracture before 2mm/s.The maximum breaking force value is16.83 kN when the welding speed value is 1mm/s.And compared with the simulation results,the weld pool is verified and found that the morphology is very similar and the center temperature of the weld is the highestFinally,in order to further improve the quality of the weld seam,welding cladding and ultrasonic auxiliary methods were adopted on the basis of the original laser welding process,and the welding area was grooved and filled with Ni60 powder.It was found through experiments that the welding cladding area had better mechanical properties and weld structure They are equiaxed crystals,dendrites and cell crystals,and observation shows that the cladding layer and the substrate can form a better metallurgical combination.It is also found that the microstructure of the welded cladding layer is related to the temperature gradient difference,cooling time,supercooling and the time for the crystal to form crystal nuclei,and the weld microstructure of the ultrasonic-assisted laser cladding welding is significantly higher than that without the ultrasonic-assisted Refine.This study provides new experimental ideas and experimental methods for laser welding of two dissimilar materials.