High manganese steels are able to deform by the TRIP effect, TWIP effect and microbanding formation. These steels are quite promising materials for mechanical construction, once they show an unusual combination of high ductility and high tensile strength. The casting of these steels represents a technological challenge, because they are extremely prone to macro- and microsegregation. Segregation, on its turn, may locally impair the desired mechanical properties. Simulations by the phase-field method may be utilized to investigate microstructure formation and the development of microsegregation patterns during solidification. Nevertheless, performing reliable microstructure simulations is only possible when reliable values for the solid–liquid interface energy are available. Through utilization of the sessile-drop method, first measurements of the interface energy in the Fe–Mn–C alloy system were performed. By utilizing the obtained values for the interface energy as an input, phase-field simulations were run aiming at investigating both the effect of the value for the interface energy and of the steel composition on the dendrite morphology.