Numerical Simulation Of Welding Temperature Fields And Stress Fields Of T91 Steel In Power Boilers

ANSYS software is used here to simulate the temperature fields and the residual stress fields in T91/12CrlMoV and T91/G102 dissimilar joints ,and in T91/T91 similar joint. The finite element model is built by aiming at the characteristics in geometry of the welding joints and pyrogenation of the welding process. The function of Gauss is chosen as heat source model, and the function command is used to apply load of moving heat source. The uneven grid of meshes are used , also the impact of phase change latent is considered adequately. Besides, the varying thermal and mechanical properties with temperature varying are taken into account in detail, and the high temperature material physical property parameters are properly selected and adjusted. The sequential coupled method is introduced to calculate the effect of thermo-mechanical coupling. Because of material nonlinear and geometry nonlinear, the small time step is adopted to improve convergence of the calculation, and the full New-Raphson iterative method is also introduced.The content of study in this paper: the distribution rule is discussed here after the simulation of temperature fields in three different kinds of welding joints. Three kinds of filler materials are selected in discussing the dissimilar steel joints which are composed by two different level's steels in intensity. Preheating before welding and heat treat after welding are also discussed in their effect to the distribution residual stress. And by simulation of the actual work load role on the various joints, the effect the distribution of stress on the joints to their useful life is also studied.Simulation results indicate: in order to reduce welding residual stress, it is reasonable that medium alloy material H10Cr5Mo is used as the filler metal of weld in the dissimilar steel joints. Preheating has little significance in reducing residual stress of small-calibre thin wall pipe. Simultaneously the important effects of heat treatment after welding on the degradation of welding residual stress are validated. Finally, by the numerical simulation of stress distribution in the dissimilar steel joints which undergone actual work load for long time ,we can find 12CrlMoV and G102 HAZ which are the low sides of joints are the weakest parts in the joints.Finally, by using the test method of boring when measuring the residual stress, the distribution rule of welding residual stress on the surface of joints is checked.it is validated that the finite element model and simulation results are exact, and simulation methods are reasonable.