Selective Crystallization Behavior of CaO-SiO₂-Al₂O₃-MgO-Fe_tO-P₂O₅ Steelmaking Slags Modified through P₂O₅ and Al₂O₃

In this study, the selective crystallization behavior of synthetic Fe_tO-rich steelmaking slags modified by P₂O₅ and Al₂O₃ additions was explored using non-isothermal differential scanning calorimetry, X-ray diffraction, and field emission scanning electron microscopy techniques. Continuous cooling transformation diagrams of Fe-enriched and P-enriched phases were constructed. It was found that P₂O₅ addition can suppress the crystallization due to the increasing viscosity caused by increasing degree of polymerization; however, an increase of Al₂O₃ content accelerated the precipitation of dystectic MgFeAlO₄, copolymerized by [AlO₄]-tetrahedra and [FeO₄]-tetrahedra units. It was also noted that the content of phosphorus in P-enriched phase can reach a high value as 28.71 wt pct for the slags modified by 15.17 wt pct Al₂O₃. The non-isothermal crystallization kinetics derived from activation energy and the structure of the slags explained by Raman spectra were further analyzed, which was well in accordance with the above analysis.