5th International High Manganese Steel Conference - HMNS 2022

A novel medium Mn steel with 8 wt% Mn was developed and processed through hot rolling and intercritical annealing. The steel possessed tensile properties of 1 GPa yield strength, 1.13 GPa tensile strength and ductility of 41%. The TWIP+TRIP mechanism was found to be operative in this steel. By further cold rolling the steel after intercritical annealing, the strain hardening rate was found to increase with increasing cold reduction but without a significant loss in ductility. It was found that cold rolling activated additional twinning systems as compared to uniaxial tension and also increased the amount of nucleation sites for strain-induced martensite. The large number of nucleation sites then led to an enhanced TRIP effect in subsequent tensile tests of the cold rolled steel. A scale up study from a laboratory 400 g to 5 kg ingot was also conducted on this alloy to determine the effects of segregation and delta-ferrite dissolution on the resulting tensile properties. It was found that the Mn segregation range could be reduced from 6.2 to 1.5 wt% but delta ferrite could not be fully dissolved within a standard reheating cycle of 1250 ˚C for 2 h. Nevertheless, the tensile properties were not significantly affected, demonstrating the increasing industrial readiness of medium Mn steels.