Influence of Phase Transformation on Thermo-mechanical Analysis of Modified 9Cr-1Mo Steel

Abstract

The aim of this study is to examine influence of phase transformation in modified 9Cr-1Mo steel on residual stress induced due to Gas Tungsten arc Welding(GTA) process. Modified 9Cr-1Mo steel is one of the candidate material used in Indian Test Blanket Module mockup trial for ITER fusion reactor. In this paper, to simulate temperature field and stress distribution in an autogenous GTA welding of 3mm thick Modified 9Cr-1Mo steel plate a 3D meshed model based on finite element method is developed using commercial welding software SYSWELD. Two types of material database are used for simulation, considering with and without phase transformation. Thermo-mechanical analysis of GTA welding is simulated by applying double ellipsoidal heat distribution model. Effects of the heat source distribution on change in temperature were investigated by bead-on-plate welding, further same heat input parameters are used for welding of square butt joint plate. Temperature history during welding was recorded using thermocouples placed nearer to weld line and induced residual stresses in weld plate were measured using X- ray diffraction method. Comparison of thermal analysis with experimental results showed a good agreement for both cases. In case of thermo mechanical analysis, the predicted residual stress using phase transformation properties in material database showed a good agreement with experimental results, whereas in second case considering without phase transformation, there is a large difference in predicted numerical results.