Numerical and experimental analysis of temperature and residual stress of GTA and LASER welding for grade 91 steel

The amount of heat input in welding plays a crucial role in stress and distortion and these two are most effective parameters for life of weld plate. Minimization or elimination of distortion and refinement of the residual stresses in the thin plates of Grade 91 steel entails management of the heat input parameters that usually depends on the welding process to be undertaken. GTA and LASER welding process are most popular and preferred welding process for welding of P91 steel material. The purpose of this study to conduct FEM based thermo-mechanical analysis on 2 mm thick plates of Grade 91 steel. Finite element analysis is carried out for the both the welding process using SYSWELD software to adjust the heat source model for full depth of penetration to fit for different bead on plates. Thereafter, thermo-mechanical analysis of the square butt joint weld is conducted by incorporating the validated heat source model onto the developed numerical model and within the determined optimum heat input parameters for both the welding processes. The stresses thus induced were measured and estimated, using X-ray diffraction testing along the longitudinal axis. This paper provides a detailed and comprehensive coverage of the predicted and the measured values of thermal cycles, distortion and longitudinal residual stresses caused by these two different welding processes. Therefore from the results and comparison, it can be evidence that for the same thickness of plate LASER welding was able to provide less value stress and distortion as compare to GTA welding process.