Optimizing Microstructure and Mechanical Properties of Cold-Rolled Medium-Mn Steel Through Intercritical Annealing and Warm Rolling

This study investigates the influence of intercritical annealing (IA) and warm-rolling (WR) parameters on the microstructure and mechanical properties of a cold-rolled medium-Mn steel (CR-MMnS). IA was conducted between temperatures of 620°C and 740°C, while warm rolling was carried out after IA to improve mechanical properties. To calculate the parameters for the IA and IA + WR treatments, thermodynamic model calculations were conducted using the ThermoCalc database, TCFE9. The microstructural analysis of CR-MMnS revealed that IA promoted the formation of globular morphology of ferrite/martensite and retained austenite along with the formation of carbides, while warm rolling resulted in refined grain sizes and the breakup of coarser carbides with lamellar morphology. Mechanical testing demonstrated that the combination of intercritical annealing and warm rolling (IA + WR) achieved improved tensile strength and yield strength compared to the individual intercritical annealing. The findings provide valuable insights into the optimization of intercritical annealing and warm-rolling parameters for enhancing microstructure and mechanical properties in medium-Mn steel. This research contributes to the development of advanced steel materials with enhanced performance for various engineering applications.