Mn‐Alloyed High‐Strength Steels with a Reduced Austenitization Temperature: Thermodynamic Calculations and Experimental Investigations

High‐strength steels (e.g., 1.5528–22MnB5), processed by direct press‐hardening, are widely used for security‐relevant structures in automotive bodyworks. In this study, the austenitization temperature A C3 of the steel 22MnB5 (approx. 840 °C) is decreased to enable a reduction in the heat‐treatment temperature. Thermodynamic calculations using the CALPHAD method are used to assess the effect of alloying elements on the α – γ transformation temperatures. On this account, 22MnB5 steel is alloyed with 6 to 9.5 mass% manganese, which decreases the α–γ transformation temperature to 744 °C. Simultaneously, the martensite finish temperature decreases below room temperature, which is accompanied by the presence of retained austenite after hardening. Furthermore, ϵ ‐martensite is formed. High Mn‐alloyed steel 22MnB5 (9.5 mass% Mn, A C3  = 744 °C) possesses a high strength of R m  = 1618 MPa, similar to the initial material 22MnB5. Elongation‐to‐fracture decreases to A 5  = 3.5% due to the formation of ϵ ‐martensite. The material strength of the steel alloyed with 6 mass% manganese ( A C3  = 808 °C) strongly increases to R m  = 1975 MPa as a result of α ‐martensite and solid‐solution strengthening by the element manganese. This steel possesses a higher elongation‐to‐fracture of A 5  = 7%.