Investigations On Welding Residual Stress And Distortion In Dissimilar Metal Joints By Means Of Numerical Simulation

Dissimilar metal welded joints are becoming widely used in nuclear power and engineering machinery and equipment to meet the requirement employed in complicated and rigorous conditions in recent years. During the welding process, it is inevitably to produce residual stress and distortion because of the non-uniform temperature field. Due to the differences of thermal physical properties and mechanical properties between two dissimilar metal materials, it is easy to generate large thermal stresses which are not easily to be eliminated. Moreover, the residual stress distribution and deformation produced in dissimilar metal joint are more complex than those in the similar metal joint. Both welding residual stress and distortion have negative influences on the static strength, fatigue strength and structural stability and manufacturing precision. Therefore, how to control and reduce the welding residual stress and deformation of the structure is a very hot topic in welding community.As a fundamental research, based on ABAQUS software, a computational approach was developed to simulate welding temperature field, residual stress distribution and deformation for Q345/SUS304 dissimilar steel multi-pass joint with 10 mm thickness. Meanwhile, experiments were carried out to measure welding residual stresses, transverse shrinkage and angular distortion in the butt weld. Through comparing the simulated results with the measured data, it was found that both residual stresses and deformation predicted by the numerical model were in good agreement with the experimental measurements. The influences of groove shape on welding residual stress and deformation in a Q345/SUS304 dissimilar steel butt welded joint were investigated by means of both numerical simulation and experiment.1) The simulation results show that the longitudinal residual stress distribution is discontinuous near the fusion line between Q345 and weld metal, and the longitudinal stresses next to the fusion line in the Q345 steel side are significantly lower than those in the both sides of this region. Also, another interesting phenomenon is that the region with high tensile stress in SUS304 side is wider than that in Q345 side. In addition, both the finite element model and the experiment indicate that a relatively large angular distortion produced in the joint after welding.2) Comparing K-groove welded joints of opening toward the Q345 side with opening toward the SUS304 side, the peak value of residual stress and the high tensile residual stresses near the intersection area of the Q345/weld were significantly smaller. Both the measured data and the simulated results indicate that the angular distortion of the butt joint is significantly affected by groove type.3) Comparing the welded joints of V-groove and X-groove, the simulation results show that the longitudinal residual stress distribution is discontinuous near the fusion line between Q345 and weld metal, and the region with high tensile stress in SUS304 side is wider than that in Q345 side. The shape of residual stress distribution, transverse shrinkage and angular distortion of V-groove are significantly larger than X-groove, while groove type has small influence on the peak value of longitudinal residual stress.In addition, on the basis of previous studies, we calculated the residual stress distribution in a plant nozzle component through using the developed thermoselastic-plastic finite element method. The simulated results predicted by the numerical model will be useful and helpful in assessing the structural integrity for the components used in nuclear power plants.