Phosphate enrichment mechanism in CaO–SiO₂–FeO–Fe₂O₃–P₂O₅ steelmaking slags with lower binary basicity

Abstract

The addition of silica to steelmaking slags to decrease the binary basicity can promote phosphate enrichment in quenched slag samples. In this study, we experimentally investigated phosphate enrichment behavior in CaO–SiO₂–FeO–Fe₂O₃–P₂O₅ slags with a P₂O₅ content of 5.00% and the binary basicity B ranging from 1.0 to 2.0, where the (%Fe _tO)/(%CaO) mass percentage ratio was maintained at 0.955. The experimental results are explained by the defined enrichment degree $R_{C_2 S - C_3 P}$ of solid solution 2CaO·SiO₂–3CaO·P₂O₅ (C₂S–C₃P), where $R_{C_2 S - C_3 P}$ is a component of the developed ion and molecule coexistence theory (IMCT)–N _i model for calculating the mass action concentrations N _i of structural units in the slags on the basis of the IMCT. The asymmetrically inverse V-shaped relation between phosphate enrichment and binary basicity B was observed to be correlated in the slags under applied two-stage cooling conditions. The maximum content of P₂O₅ in the C₂S–C₃P solid solution reached approximately 30.0% when the binary basicity B was controlled at 1.3.

Keywords

phosphates enrichment / mechanisms / steelmaking / slags / basicity

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