Microstructural Evolution and Resulting Mechanical Properties of WeldJoints upon Flux Cored Arc Welding and Post-weld Heat Treatment

摘要

The objective of this study is to determine the mechanism of the dramatic increase ofimpact toughness at low temperatures after post-weld heat treatment on weld joints. In this study,weld joints using two semi-automatic welding consumables were fabricated by flux cored arc weldingwith subsequent PWHT at 660°C for 65 min and 195 min, respectively. Tests of the tensile and yieldstrength, microhardness and impact toughness, were carried out. The microstructure was inspected byoptical, scanning electron, and transmission electron microscopy in addition to compositionalanalysis using energy dispersive spectrometry. PWHT was observed to result in grain coarsening,sub-grain structure formation and decrease of the dislocation density. The increase of impacttoughness is attributed to the relieved thermal stress, the inclusions and precipitations, softening ofthe structure, dislocation recovery and sub-grain structure.