5th International High Manganese Steel Conference - HMNS 2022

In the past decade, many efforts have been paid to improve the product of strength and elongation of medium Mn steels (containing 3~12 wt% Mn). Due to smelting difficulty and cost reasons, the application of higher Mn steels is limited. In this paper, an Nb-microalloyed 4Mn medium Mn steel, Fe-4Mn-2Al-0.2C-0.02Nb (0.02Nb steel), was prepared and short-time annealing toughening was achieved. The best mechanical properties of 0.02Nb steel were obtained at 720 oC for 5 min, with tensile strength of 902 MPa, total elongation of 39.1%, and product of strength and elongation of 35.3 GPa·%. With the increase of holding time, the coarsening of grain and the decrease of austenite stability occur together, which worsens the plasticity of the material. When the Nb content is increased to 0.1 wt% (0.1Nb steel), the strength of 0.1Nb steel can be improved by 30~40 MPa due to the finer grain size, but the excessive addition of Nb will hinder the migration of grain boundaries and delay the occurrence of recrystallization during annealing. After annealing for 10min, the properties of 0.1 steel are similar to that of 0.02 steel. Therefore, better comprehensive mechanical properties, combined with lower alloying element addition and shorter annealing time, make the application of 0.02 steel more advantageous.