Grain refinement of high-Mn wear-resistant cast steel by means of heterogeneous nucleation

Understanding and controlling the primary solidification, particularly the formation of first grains, is of significant relevance. Generally, high-Mn steels, such as alloy Mn13, exhibit a coarse-grained microstructure in the millimeter range and are known for their high strain hardening ability and thus, excellent cyclic deformation resistance. To further improve the cyclic mechanical properties, this study aims to increase the strength of the alloy via grain refinement. From a comprehensive literature research, the nonmetallic inclusions AlCeO 3 , CeO 2 , Ce2O 3 and Ce 2 O 2 S were identified as the most promising particles for the heterogeneous nucleation of austenite. Based on this literature review, various grain refining agents were evaluated and finally the grain refining agent from ELKEM (WearSeed™) was selected for test melts. This resulted in a successful grain refinement and the grain size was reduced by over 80% (from 1550μm to 285μm). However, the process window for a successful grain refinement is only very small. For a deeper understanding, thermodynamic calculations with FactSage on the interaction of O-S-Ce-Al in high-Mn steel melts and particle analyses of the potential nuclei by automated SEM-EDS were carried out. The framework conditions for a successful grain refinement were systematically developed depending on the casting temperature, dissolved O and S, and the addition of Al and Ce. Finally, the static and cyclic mechanical properties of the grain refined high-Mn steel cast were determined using tensile and low cycle fatigue testing and showed very promising results.