Numerical Simulation and Experimental Validation of A-TIG Welding of 2.25Cr–1Mo Steel

Localized heating and cooling during welding introduces residual stress in the weld joints due to the thermal gradients. The microstructure formation in 2.25Cr–1Mo steel is very much sensitive to the rate of cooling and eventually, the austenite may transform to pearlite/bainite/martensite. A variant of Tungsten Inert Gas (TIG) welding called Activated-TIG (A-TIG) welding was made use of in this study. Here, we have tried to develop a numerical model based on the finite element method to predict the thermo-mechanical behavior of 6 mm thick 2.25Cr–1Mo steel weld joints, with accounting solid-state phase transformation. The heat energy supplied to the workpiece is determined and calibrated in the heat source model. Simulated thermal cycle showed a peak temperature of 1377 °C at 8 mm distance away from the weld centerline, whereas, the experimental result showed 1371 °C. A k-type thermocouple was used to measure the temperature distribution during welding. The simulated thermal distributions were sequentially coupled to mechanical analysis. The evolution of stress and ultimately the locked-in residual stresses were determined. X-ray diffraction studies showed the peak residual stress near heat affected zone of 592 MPa and the vertical height gauge was used to measure the distortion before and after welding. The predicted residual stresses and distortion showed good agreement with the experimental measurements.