The effects of post weld heat treatment for welded high-Mn austenitic steels using the submerged arc welding method

The high-Mn austenitic steels exhibit fully austenitic structure at room temperatures while showing twinning mechanisms during deformations. In the SAW welding process, the microstructure and mechanical properties of heat affected zone (HAZ) and weld metal (WM) are affected by the welding heat causing potential degradation of mechanical properties due to the segregation and depletion of Mn in HAZ and WM regions. In this study, post weld heat treatment (PWHT) was performed at 800 °C, 900 °C and 1000 °C to improve the mechanical properties of welded high-Mn austenitic steels. We examined electron backscattered diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDS) analysis to investigate the relationship between microstructure and mechanical properties after heat treatment. In particular, mechanisms of impact toughness improvement was identified by analyzing the microstructure and deformation behavior such as mechanical twin and grain size through the instrumented Charpy impact test and EBSD analysis.