Research On Residual Stress Of Dissimilar Steel Welding

The welding structure of dissimilar steels can fulfill the performance advantage of each material fully and save the noble metal. Thus result in a cost advantage. With the development of the shipbuilding technology, the application of dissimilar steels welding has become more and more widely.The influence of welding residual stress is an important factor of the quality of the shipbuilding. The residual stresses are complex and difficult to predict because of the differences between mechanical and physical properties of the different materials. Therefore, it is necessary to do researches on the residual stress distribution of the dissimilar steels welding structure, providing a theoretical basis for improving the welding process, raising the level of shipbuilding and reducing the residual stress of welding.Firstly, in this paper Elasto-plastic finite element method is used for measuring the welding temperature field and the residual stress in butt-welded Q235 and 304 Stainless Steel. The results indicate that differences between their physics property caused the inhomogeneous distribution of the welding temperature field and the residual stress. And the peaks of the residual stress show on 304 Stainless Steel side, and the peak value is slightly less than the yield strength of 304 Stainless Steel.Secondly, the welding parameters were changed in this paper to explore the influences of the offsetting of heat resources and the changing of heat input on the welding residual stress. When the heat source was moved towards Q235, the peak value has small changes, but the high-stress was reduced as well as the welding distortion. On the contrary, when the heat source was moved towards 304 Stainless Steel, the high-stress area would be expanded with higher welding heat, and the peak value of the residual stress was slightly decreased.Finally, an infrared thermal imager was also applied to measure surface temperature changing of welding materials during welding, the results are accordant with that drawn from elasto-plastic finite element measurement. Meanwhile the same finite element model were used on residual stresses in dissimilar butt-welded pipes, the results indicate that the residual stress on inner surface is larger than outer surface of dissimilar joint. And the axial and hoop distribution of residual stress were shown in the results.