Tensile and Microstructural Characteristics of Fe-24Mn Steel Welds for Cryogenic Applications

Herein, we investigated the weldability and relationship between microstructure and tensile properties in 24 wt% Mn steel welds and, specifically, submerged arc welds (SAWs) were produced using these welds for cryogenic applications. The base metal (BM) and weld metal (WM) exhibited a stacking fault energy (SFE) that maintained a stable austenite phase for 27.1 and 17.0 mJ/m², respectively. Deformation twins were observed after tensile testing of the BM and WM at 298 K. Weld metals using undermatched fillers showed a lower SFE and coarser grain size (~ 86 μm) compared to that of the BM (~ 12 μm). Therefore, the tensile testing at 110 K produced deformation twins and ε-martensite. The formation of ε-martensite with deformation twins antedated necking during tensile testing and elongation decreased at 110 K. However, the SAWs of high Mn steels maintained excellent low-temperature mechanical properties such as elongation, tensile strength, and yield strength with values of 20%, 1150 MPa, and 617 MPa, respectively.