Microstructure and transverse shrinkage stress analysis in GTA welds of P91 steel pipe

Abstract

In a steam power plant, several components such as boiler tube, condenser and steam lines are made of high creep resistant steel. The P91 steel pipes are generally used in steam power plant because of high creep strength at service temperature of approximately 600oC. In the present research work, the study about shrinkage stresses and their distribution in the four quadrants of P91 pipe weld of 11 mm thickness is reported. The conventional-V and narrow-groove welds were prepared by using the gas tungsten arc welding (GTAW) process. Welding current, arc voltage, groove design, and straining length were the main parameters that affect the transverse shrinkage stresses. In the present research work, the effect of groove design on transverse shrinkage stresses has been evaluated. It also describes the effect of the number of passes on shrinkage. It is concluded that, for a given heat input, the narrow groove pipe weld joint exhibits comparatively less transverse shrinkage stress. Scanning electron microscope (SEM) with field emission gun and optical microscope has been used to characterize the weld fusion zone and HAZs of P91 pipe weldments. � 2017, Korean Society of Steel Construction and Springer-Verlag GmbH Germany.