5th International High Manganese Steel Conference - HMNS 2022

To control the production processes and design product properties of promising medium and high Mn steels, reliable solidification and material models are essential. High precision and experimentally validated thermodynamic data are essential data sources for all these models. As manganese is a segregating element, it is crucial to describe high manganese concentrations well, e.g. for the final stage of solidification.

But especially with higher manganese contents, there is a significant lack of experimental data. All published thermodynamic Calphad descriptions from Huang(1990), Djurovic(2011) and Kim(2015) refer to the solid-liquid transformations exclusively on the measurement data from Schuermann (1977). No other data/publications are available, and even Schuermann(1977) measure the solidus temperatures of high Mn steels only rarely.

As the mentioned thermodynamic descriptions show significant differences at higher Mn contents, an own data set of reliable data is necessary for the evaluation, selection, and if required for the assessment of the Calphad models. For this purpose, an own experimental study has been performed, and model alloys with Fe-Mn (up to 30 w.t.-% Mn), Fe – 10%Mn – C (up to 2.5 w.t.-% C) and Fe – 20%Mn – C (up to 2.5 w.t.-% C) were produced by induction melting and subsequent centrifugal spin casting. Since manganese has a strong tendency to evaporate when it melts and can quickly destroy measuring devices, a new measuring method was developed. Using a micro-DTA-protected setup with closed crucible by tantalum lids (local-getter and Mn “catcher”), all high-temperature phase transformations (TLiquid, TPeritectic, TSolid, TEutectic, TGamma-Delta) can be measured in equilibrium conditions. Based on these new experimental results, the thermodynamic description of Djurovic(2011) is identified as the most accurate one. Nevertheless, there are still significant deviations with Mn contents above 10 w.t.-% and further research is necessary and ongoing.