Abstract:
Advanced high-strength steels (AHSS) are sophisticated materials being developed by the steel industry
to mitigate challenges related to the performance of motor vehicles. To meet the requirements of
AHSS, the ferromanganese alloys (FeMn) utilized in the production of the steel are required to contain
acceptable levels of unwanted impurities, i.e. P, S, N, H, and C. The focus of the current study was to
investigate dephosphorization of ferromanganese to produce a low-P alloy that could be effectively
utilized in the production of AHSS. The study involved conducting laboratory-scale testwork to study
the efficiency of CaO-based slag systems to dephosphorize FeMn alloys. The addition of Na2O, CaF2,
and BaO to MnO-CaO-SiO2 slag was considered. The test work was carried out in a 25 kW induction
furnace at temperatures of 1350°C, 1400°C, and 1450°C. The P partition coefficient (Lp) remained
small at <1, which is an indication that dephosphorization had not been achieved. The baseline slag,
comprising 40%CaO-40%SiO2-20%MnO, reported higher Lp values. Addition of Na2O and CaF2 did not
show any further benefit. Substituting half of the CaO by BaO, resulted in similar Lp values to those of the
baseline slag under conditions of 1350°C and 1450°C at 30 minutes. In summary, based on the Lp values
obtained, the conditions investigated with the CaO-based slags appeared to have been unfavourable for
dephosphorization of FeMn alloys, as most of this impurity element remained in the alloy.
