Numerical Simulation Analysis On Thermal Deformation And Residual Stress Of Stainless Steel T-joint Of Laser-arc Hybrid Welding

Civil air defense engineering generally refers to the underground buildings that can effectively cover personnel and materials in wartime,and has been used as underground malls and underground parking lots in daily life,which provides great convenience for people's life.The frame of the steel protective door in civil air defense equipment is welded by combination of I-beam and channel steel.The welding quality directly affects the performance of the protective equipment.The traditional arc welding causes large welding deformation,and laser welding requires higher machining precision of the joint.The laser-arc hybrid welding process which combines two kinds of welding heat sources can make up for the deficiency and improve the welding quality.In order to fully understand the process of laser-arc hybrid welding,numerical simulation technology is used in this paper.Firstly,the laser-arc hybrid welding platform is built to carry out the laser arc hybrid overlaying welding experiment of 3 mm thick 304 stainless steel sheet.Metallographic corrosion test is carried out to obtain the cross-section topography of the welds.The residual stress of the welds is measured with X-ray stress meter and the out-of-plane deformation is measured with vernier caliper.The test results provide a basis for verifying the simulation results.Secondly,considering the high temperature properties and geometric nonlinearity of materials,a heat source model combining Gaussian surface heat source and Gaussian conical body heat source is established to simulate the laser-arc hybrid overlaying welding process,and the simulation results of temperature field,residual stress and thermal deformation are obtained.The results show that the simulation results of weld pool morphology are in good agreement with the experimental results.The results of the longitudinal residual stress distribution and value of laser-arc hybrid welding are in good agreement with the simulation results.The out-of-plane deformation results obtained by numerical simulation of 304 stainless steel plate in laser-arc hybrid overlaying welding are in saddle shape,which is consistent with the test results,and the results of welding deformation at the welding edge are also consistent with each other.It shows that the established numerical analysis model can better simulate the laser-arc hybrid welding process.Finally,the finite element analysis model of overlaying welding is improved and applied to the hybrid welding simulation of T-joint.Nine groups of orthogonal experiments are designed to study the temperature field and structure field of the hybrid welding of T-joint under different parameters.According to the index of reducing residual stress and welding deformation,range analysis is carried out to get the optimal parameter combination.Applying the optimal parameter combination to the test of changing the welding sequence,the effect of welding sequence on temperature field and structure field of T-joint laser-arc hybrid welding is analyzed.The results show that the temperature distribution of different parameters in temperature field analysis has little difference.The range analysis of residual stress under different parameters shows that the influence of laser power is the largest.The range analysis of deformation under different parameters shows that the welding speed has the greatest influence.According to the test index of reducing residual stress and welding deformation,the optimal parameter combination obtained by range analysis is 150 A,arc voltage is 20 V,laser power is 1400 W,and welding speed is 0.05m/s.The welding sequence affects the maximum temperature at the weld,and the temperature of the two welds on the T-joint affects each other.Two welds welding in sequence can effectively reduce the residual stress,the residual stress of reverse sequence welding is the minimum.Simultaneous reverse welding is the best method to reduce welding deformation.