Welding is a complex process where localized and intensive heat is imposed to a piece promoting mechanical and metallurgical changes. Phenomenological aspects of welding process involve couplings among different physical processes and its description is unusually complex. Basically, three couplings are essential: thermal, phase transformation and mechanical phenomena. Welding processes can generate residual stress due to the thermal gradient imposed to the workpiece in association to geometric restrictions. The presence of tensile residual stresses can be especially dangerous to mechanical components submitted to fatigue loadings. The present work regards on study the residual stress in welded superduplex stainless steel pipes using experimental and a numerical analysis. A parametric nonlinear elastoplastic model based on finite element method is used for the evaluation of residual stress in superduplex steel welding. The developed model takes into account the coupling between mechanical and thermal fields and the temperature dependency of the thermomechanical properties. Thermocouples are used to measure the temperature evolution during welding stages. Instrumented hole drilling technique is used for the evaluation of the residual stress after welding process. Experimental data is used to calibrate the numerical model. The methodology is applied to evaluate the behavior of two-pass girth welding (TIG for root pass and SMAW for finishing) in 4 inch diameter seamless tubes of superduplex stainless steel UNS32750. The result shows a good agreement between numerical experimental results. The proposed methodology can be used in complex geometries as a powerful tool to study and adjust welding parameters to minimize the residual stresses on welded mechanical components.
