In the last decades, great efforts were made in computational thermodynamics to develop new model descriptions. A large number of CALPHAD-based optimizations were published considering recent experimental data. Nowadays, most steel grades are well described by commercial databases enabling to perform reliable calculations of thermodynamic properties and phase diagrams over a wide composition range. However, in order to further improve databases for advanced steels, e.g. electrical steels and medium Mn-steels, there is still a need to provide new phase equilibrium data obtained by modern laboratory techniques.
In this work, we present an overview of more than ten years of research experience at the Chair of Ferrous Metallurgy at Montanuniversitaet Leoben with particular relevance to the continuous casting process. Taking the example of the Fe-C-P and Fe-C-Mn ternary systems, the detailed experimental procedure will be demonstrated. The investigations started with the melting of high-purity alloys by induction melting, followed by the systematic determination of phase transitions up to the liquidus temperature using DSC/DTA methods. Solid-state phase equilibria were additionally characterized by HT-XRD and high-temperature laser scanning confocal microscopy (HT-LSCM). The results clearly indicate, that existing deviations between the experimental data and the thermodynamic calculations can be addressed to the binary Fe-P and Fe-Mn phase diagrams. Both elements, phosphorus and manganese, are well-known to significantly influence the phase transformation behavior in the casting machine, e.g. transformation sequences and final point of solidification. The measured phase equilibrium data for the binary Fe-P and Fe-Mn systems support more accurate calculations of CALPHAD-based process models to simulate solidification and temperature fields in the caster.