Numerical Simulation Of Q345D/304 Laser-MAG Hybrid Welding

Laser-MAG hybrid welding has the characteristics of deep penetration and low assembly precision requirements,which makes up for the shortcomings of single laser welding and arc welding.Therefore,it has stronger welding adaptability and it is suitable for welding various kinds of metallic materials.The welding of dissimilar metals is widely used in petrochemical industry,energy transmission and pressure vessel manufacturing and other fields.However,due to the different thermophysical properties of the dissimilar material,different degrees of deformation will occur during the welding process and welding process will produce the welding stress.The high residual tensile stress concentration region is more vulnerable to destroy,and the deformation affect the usage effect.At present,research on welding of dissimilar materials are often used experiment methods,this process is time-consuming,and once the welding process is changed,the experiment could be redone.The numerical simulation can simulate the deformation of the workpiece and the stress concentration area after welding.The numcrical simulation can reduce the test times,cut down the cost of the test and shorten the test period,so it has guiding significance to engineering practice.Surfacing layer on Q345D surface is produced by laser welding,MAG welding and laser—MAG hybrid welding,and the results show that the depth of fusion and weld width have a positive correlation with laser welding power(PL=1.5-3.5KW)and MAG welding wire feeding speed(V=5.7-7.7mm/s);In the process of laser—MAG hybrid welding(PL=1.5-3.5KW,wire feeding speed V=5.7-7.7mm/s),with the increase of laser power,the depth of fusion can improve,but the laser power has little influence on weld width and excess weld metal;In addition,with the increase of wire feeding speed,the weld width can improve.In this paper,the welding numerical simulation is based on Simufact.welding software.A numerical simulation model is established to analyze the influence of heat source parameters and multi heat source combination on the weld molten pool morphology,and the simulation results show that the cross-section morphology of weld molten pool by Goldak heat source is circular arc,not suitable for high current MAG welding and laser-MAG hybrid welding.The method of combining the Goldak+ laser volumetric heart source and laser surface + laser volumetric heart source can be suitable for high current MAG welding and laser—MAG hybrid welding,and the cross-section morphology of the weld molten pool obtained by simulation can exhibit "wine cup like".The simulation experiment of Q345D/304 dissimilar steel single layer welding with different welding method by different heart source shows that the workpiece can be fully welded by laser welding,laser-arc hybrid welding,and small power laser-arc hybrid welding except arc welding.Moreover,the workpiece has the deeper depth of fusion and narrower weld width with small power laser-arc hybrid welding.The workpieces have different peak value of residual equivalent stress after welding.The small power laser-arc hybrid welding is 581.07Mpa,laser-arc hybrid welding is 560.81Mpa,laser welding is 515.84.In the upper and lower surfaces,the vertical and horizontal stress have the same trend in each welding method;especially the stress distribution and trend of small power laser-arc hybrid welding and laser welding are very close.The simulation results of Q345D/304 dissimilar steel multi-layer welding with laser—MAG hybrid welding process show that the simulated weld molten pool morphology and deformation could be in good agreement with the measured results.Therefore,the laser ?MAG hybrid welding can be simulated by numerical simulation.The test results of changing the welding direction of multi-layer welding show that the peak values of residual equivalent stress have not been changed significantly after welding,in which Case A is 584.49MPa,Case B is 580.65 MPa,Case C is 591.55 MPa and Case D is 589.84 MPa,but the peak values and distribution of residual equivalent stress in the constrained area have been changed significantly;The test results of changing the constraint condition of workpiece show that the constraint condition has little influence on peak value of residual equivalent stress after welding,in which the stress of the constrained workpiece is 584.49MPa,and unconstrained workpiece is 583.6MPa.