Because of the problems with 1st and 2nd generations of Advanced High-Strength Steels (AHSS),
a 3rd generation of AHSS steels has become prominent and these steels have properties in between
the 1st and 2nd generations of AHSS. However, although the 3rd generation of AHSS is a promising
candidate as a replacement for its predecessors, there remain some challenges in processing these
steels which are essentially medium Mn (Mn content ~ 5–7 wt per cent) and high Al (Al content ~ 1–
3 wt per cent) steels. The use of conventional casting powders based on the CaO-SiO2 system is
unsuitable for high and medium Mn/Al steels. This work investigates the development of CaO-Al2O3-
based mold fluxes for casting third-generation AHSS steel. Mold fluxes, with otherwise similar
compositions but different C/A ratios, are tested and their crystallisation behaviour is examined using
differential scanning calorimetry (DSC). A calcium aluminate phase having a composition
Ca12Al14O33 was found to be the main crystalline phase in the mold fluxes. A decrease in
crystallisation temperature was observed as the CaO/Al2O3 ratio increased from 1.00 to 1.33. The
effective crystallisation rate constant exhibited an increase with decreasing crystallisation
temperature, indicating a potential influence of nucleation rate on the overall crystallisation rate and
suggesting an anti-Arrhenius behaviour in the crystallisation process of these mold fluxes.