Experimental And Simulation Study On Welding Residual Stress Of High Strength Structural Steel Full Penetration T-joint

With the development of large-scale,high parameters and complicated service condition of steel structure engineering,the requirement of steel structure performance is higher andhigher,and the yield strength of steel is higher and higher.At the same time,the problems of high strength steel are more serious,especially the welding problems.Welding is an indispensable process in modern manufacturing industry.Due to the serious inhomogeneous heating,the welding residual stress and deformation of the steel plate greatly affect the manufacturing process and performance of the joint.Therefore,effective prevention and reduction of residual stress and deformation are of great significance to the actual production.In this paper,the residual stress of welded T-joint of Q690 high strength steel is studied by combining experimental research and simulation,and the main research contents are as follows:(1)The influence of heat input on the residual stress is studied through the combination of experiment and simulation.The results show that when the heat input is in the range of 0.75～2.04 kJ/mm,the transverse residual stress decreases and the longitudinal residual stress increases with the increases of heat input.However,from the change range of residual stress,the longitudinal residual stress increases greatly.Therefore,with the increases of heat input,the overall residual stress level increases,and the welding deformation increases gradually.(2)By setting up the control group,the weld sequence optimization analysis of the two-sided two-layer two pass welding mode of T-joint was carried out.The results show that under the same welding current and voltage,the scheme of welding one side first and then the other side produces the smallest overall residual stress level,and the high stress range of the weld area is also smaller,while the overall stress level of the alternative welding scheme of both sides is slightly larger.The range of high stress in weld zone is also large.For welding residual deformation,the alternative welding of both sides has smaller deformation,and the deformation of both sides is more symmetrical.The scheme of welding one side first and then the other side has the largest deformation,accompanied by the overall tilt deformation.(3)The results show that under the same welding current and voltage conditions,the opposite welding method can reduce the residual stress to a certain extent,but compared with the optimization of weld sequence,the reduction effect is not obvious.The segmented welding has a more significant effect on reducing the residual stress and deformation.(4)Through the study of the length size effect(i.e.end effect)of the welded plate,it is concluded that the residual stress and deflection increase with the increases of the length of the steel plate.Therefore,combined with the results of the segmented welding process,the segmented welding method can be used to reduce the residual stress and deflection for the long welded T-shaped members under the actual working conditions.(5)Combined with XRD and electrolytic corrosion,the distribution of residual stress along the depth direction of T-joint flange was obtained,and compared with the simulation results.In addition,in the simulation analysis of thin and wide seam,a method of setting zigzag swing heat source path to simulate the welding of thin and wide seam is proposed,and good results are achieved.