Microstructural Evolution and Mechanical Property Analysis of Weldox-700 Steel: Effect of Welding and Post-Weld Heat Treatments

This work presents the effect of welding and post-weld heat treatments on the microstructure and mechanical properties of Weldox 700 steel used for structural applications. Welding results in the microstructural heterogeneity across the section due to the high thermal gradient. The heterogeneity in microstructure is examined using optical and scanning electron microscope. Post-weld heat treatment (PWHT) of 450, 520, and 580 °C, results in the softening of the microstructure within the heat-affected zone due to the formation of tempered martensite. The PWHT does not have a significant effect on the mechanical properties of the joint, rather it enhances the percentage elongation up to some extent. Further, PWHT results in a reduction in the size of inclusions which acts as a barrier for crack propagation. The PWHT at 450 and 520 °C increases the impact toughness and percentage elongation, whereas the PWHT at 580 °C decreases the impact toughness and percentage elongation. The PWHT significantly influences the mechanical property by changing the phase of individual microstructures.