Experimental and finite element analysis of residual stress and distortion in GTA welding of modified 9Cr-1Mo steel

In this paper, investigation of residual stress and distortion induced in 3 mm thick Modified 9Cr-1Mo steel plates during GTA welding is carried out. SYSWELD software is used for the thermo-mechanical analysis. A 3D meshed model is created for the simulation and double ellipsoidal heat source distribution is used for the thermal analysis. Thermal cycles predicted near the fusion zone are compared with experimentally measured thermal cycles using thermocouples. Predicted residual stress profile across the fusion zone is compared with the measured profile using X-ray diffraction method. There is a good agreement between measured and predicted thermal cycles and residual stress profile. Distortion of the weld joint is measured using vertical electronic height gauge. Finite element analysis of distortion of the weld joint is carried out by applying both large and small distortion theories. Comparison of experimental and numerical results showed better accuracy if large distortion theory is applied.