Prediction of the hot flow behaviour of a third generation advanced high-strength hot-formable steel

Medium manganese steels provide numerous benefits in hot forming, including reduced blank reheating temperatures and critical quenching rates compared to conventional boron-added steels. Moreover, their enhanced strength and ductility make them a promising material for lightweight components in the mobility sector. In this study, the flow behaviour of a novel medium manganese steel is characterised and modelled to enable the simulation of hot forming processes. A forming and quenching dilatometer is utilised for isothermal tensile tests at different forming temperatures and strain rates. The specimens undergo heat treatment prior to forming, following a process route that includes annealing, cooling, and reheating to replicate the heat treatment at the steel producer and the hot forming at the parts manufacturer. An in-situ optical measurement system is used to determine the strains with digital image correlation. The experimental flow curves are modelled using various phenomenological hardening laws. Finally, the applicability of the hardening laws is verified by the simulation of a tensile test that was not used for modelling. The best prediction accuracy was achieved by the modified Norton-Hoff law, which provided a root mean square error of 14.4% during model calibration and a low mean absolute percentage error of 1.3% during validation.