Phosphorus Removal Properties of the Fe–C–Si–Mn–P–S Metallic Melts Based on the Atom–Molecule Coexistence Theory: Mutual Verification by Industrial and Laboratorial Experiments

In order to quantify the reaction ability of phosphorus containing compounds in iron-based alloys such as hot metal or molten steel, and accurately evaluate their phosphorus removal degree, a thermodynamic prediction model for scientifically characterizing the reaction ability of structural units in the Fe–C–Mn–Si–P–S metallic melts has been established based on the Atom–Molecule Coexistence Theory (AMCT), macroscopic experiments, physical chemistry in metallurgy and computer science. Within the present studied metallic system and composition range, there is a strong linear correlation between the equilibrium mass percents of different atoms and molecules in the melt and their mass action concentration N_i calculated based on AMCT, of which iron phosphide compounds are the main phosphorus transport units. The mass action concentration of Fe₂P shows a continuous linear strong correlation with the [mass pct P] in the initial and dephosphorized hot metal in the range of 0.02 to 0.31 pct. The equilibrium phosphorus removal ratio between the Fe–C–Si–Mn–P–S metallic melts and slag calculated based on AMCT shows a perfect linear relationship of 1:1 with the measured values. Iron phosphide compounds contribute the most to the total equilibrium phosphorus removal ratio, up to 99.9 pct, of which Fe₂P contributes 68.7 pct. The dephosphorization ratio of hot metal measured based on industrial and laboratorial experiments shows a consistent linear trend with the equilibrium phosphorus removal ratio calculated based on AMCT, which indicates that AMCT can be correctly applied to study the phosphorus removal properties of hot metal or molten steel during the dephosphorization process.