Coupling relationship between dephosphorisation and desulphurisation abilities or potentials for CaO–FeO–Fe 2 O 3 –Al 2 O 3 –P 2 O 5 slags over a large variation range of slag oxidisation ability during secondary refining process of molten steel

The coupling relationships between dephosphorisation and desulphurisation abilities or potentials for CaO–FeO–Fe₂O₃–Al₂O₃–P₂O₅ slags during secondary refining process of molten steel have been proposed as or in reducing zone at oxygen potential less than 2.27 × 10⁻⁶ Pa as well as or in oxidising zone at oxygen potential greater than 2.27 × 10⁻⁶ Pa through deleting slag oxidisation ability expressed by the comprehensive mass action concentration of iron oxides based on the ion and molecule coexistence theory (IMCT). The proposed coupling relationships between dephosphorisation and desulphurisation abilities or potentials of the slags have been verified to be valid using reported data of oxygen, phosphorus and sulphur distribution equilibria between the slags and liquid iron over a temperature range from 1811 to 1927 K (1538–1654 °C) and predicted results of dephosphorisation and desulphurisation abilities or potentials. Not only the proposed coupling relationships between dephosphorisation and desulphurisation potentials but also the correlated coupling relationships between dephosphorisation and desulphurisation abilities for the slags in reducing and oxidising zones have been verified to be indeed independent of slag oxidisation ability.