Effect of P₂O₅ and Fe_tO on the Viscosity and Slag Structure in Steelmaking Slags

The present paper investigates the influence of P₂O₅ and Fe_tO on the viscosity and structure of steelmaking slags. An understanding of the viscous behavior and structure of Fe_tO-bearing smelting slags is essential to control the dephosphorization in steelmaking process and to efficiently recycle the phosphorus from steelmaking slags. It is found that the viscosity of CaO-SiO₂-Al₂O₃-MgO-Fe_tO-P₂O₅ slags slightly increases with increasing P₂O₅ content, while the viscosity decreases with increasing Fe_tO content. The degree of the polymerization of quenched slags, determined from Raman spectra, is found to increase with increasing P₂O₅ content and decrease with increasing Fe_tO content. It is also noted that the peaks of Raman spectra between 800 and 1200 cm⁻¹ were nearly absent at the Fe_tO content of 22.46 wt pct; whereas according to ²⁹Si MAS-NMR and FTIR analysis, it is clearly seen that the [SiO₄]-tetrahedra-related peaks existed even for the same slag. This may confirm that small quantities of extra-framework iron species can absorb the Raman scattering and damp the Raman signal intensity and the presence of Fe_tO in the slag does not necessarily eliminate [SiO₄]-tetrahedra.