Dephosphorization equilibria between pure molten iron and CaO‐saturated FeO n –CaO–SiO 2 and FeO n –CaO–Al 2 O 3 slags

Metal‐slag refining reactions have been investigated to determine dephosphorization equilibria in steelmaking using CaO‐saturated slags, low in P 2 O 5 –content, based on the systems FeO n –CaO–SiO 2 and FeO n –CaO–Al 2 O 3 . Slag compositions have been optimized with respect to basicity and oxygen potential to achieve maximum partition ratios wt.%(P 2 O 5 )/wt.%[P] and minimum phosphorus contents in pure molten iron at 1550, 1600 and 1700°C. Both slag systems prove to be effective dephosphorizers. Optimal slag compositions are around 10 wt.% SiO 2 near the CaO–3CaO · SiO 2 double saturation in the case of FeO n –CaO–SiO 2 slags and at Al 2 O 3 contents tending to zero in the case of FeO n –CaO–Al 2 O 3 slags. Attempts were also made to present phosphate capacities C PO4 3− , fractions of free oxygen ions x O 2− and theoretical optical basicities Λ as a function of the FeO n content of slags.