Investigation on the Micro-Segregation Behaviors of a High-Mn Austenitic Cryogenic Steel Continuous Casting Slab Through Thermodynamic Calculations and Homogenization Experiments

This study systematically investigated the mechanism of micro-segregation reduction in a high-Mn austenitic cryogenic steel continuous casting slab using thermodynamic calculations and homogenization experiments. The high-Mn austenitic cryogenic steel continuous casting slab exhibits obvious non-equilibrium solidification characteristics, with severe interdendritic segregation of C and Mn. The solidus temperatures of equilibrium, Scheil, and Scheil–Back solidification are 1324 °C, 953 °C, and 1272 °C, respectively. According to thermodynamic calculations, there is only a slight decrease in the highest segregation C content when the homogenization temperature is 900 °C. When the specimens were homogenized at 1000 °C, the segregation of C and Mn was significantly alleviated, and the segregation degree further decreased when the homogenization temperature was 1100 °C. Two feasible and industrially applicable strategies for alleviating the micro-segregation of a high-Mn steel continuous casting slab are proposed. First, reduce the cooling intensity of the secondary cooling stage during continuous casting, slow down the cooling rate around 1000 °C, and promote the limited diffusion of solute elements to reduce initial segregation. Second, introduce a holding stage at around 1000 °C during slab reheating prior to hot rolling, eliminating residual segregation and stabilizing the local solidus temperature above 1200 °C.