Impact of post weld heat treatment on structural and mechanical properties of dissimilar high strength steels

This study explores the influence of Submerged Arc Welding (SAW) parameters on the microstructural evolution, mechanical properties, and residual stresses in dissimilar welds of A516 Gr70 and A106 GrB high-strength carbon steels. Through a comprehensive experimental approach, the research delineates the direct relationship between welding heat input, determined by voltage, current, and speed, and its profound impact on the heat-affected zone (HAZ) size, microstructure, and mechanical properties such as hardness and tensile strength. The investigation reveals that optimal welding parameters play a critical role in controlling bead geometry and HAZ size, which in turn significantly affects the mechanical integrity and performance of the welded joint. Notably, the study uncovers that higher heat input does not necessarily lead to a larger HAZ, challenging conventional assumptions in welding practices.

Further, the research delves into the effects of post-weld heat treatment (PWHT) techniques, including normalizing, quenching, and annealing, on reversing the microstructural alterations induced by welding and restoring the initial mechanical properties of the base metals. Microstructural analyses employing stereo microscopy, optical microscopy, scanning electron microscopy, and X-ray diffraction technique provide insight into the granular details of the morphological changes across different regions of the weld, highlighting the formation of martensitic lathes in the weld bead region and variations in the pearlite-ferrite matrix.