Analysis of the Phase Composition and Microstructure of Slag from a Semi-Steel Converter

To clarify the phase composition, microstructural characteristics, and phosphorus retention mechanisms of semi-steel converter slag, this study employed characterization techniques such as XRD, SEM-EDS, FTIR, and Raman spectroscopy to systematically compare the mineral composition, phosphorus retention patterns, and microstructure of semi-steel converter slag with those of single-slag converter slag. The results show that the main mineral phases in both types of slag are C2F, C2S, and the RO phase; in single-slag converter slag, phosphorus primarily exists as n-dicalcium silicate-tricalcium phosphate solid solutions, with a small amount tending to be fixed in the glass phase and other phosphates; in semi-steel converter slag, phosphorus is enriched in the form of nC2S-C3P solid solutions and C3P, with a small amount present in the glass phase and phosphorus-containing solid solutions; Both types of slag are composed of phosphates, silicates, and iron-aluminum coordination structures, with relatively low siloxane polymerization degrees, and P-O-P and P-O-Si are not major structural units. However, there are significant differences in the iron coordination environment: in semi-steel converter slag, iron primarily exists as FeO4 tetrahedra and FeO6 octahedra, whereas in single-slag converter slag, iron tends to form FeO4 tetrahedra; furthermore, the silicon and phosphorus group content and network polymerization degree in single-slag converter slag are significantly higher than those in semi-steel converter slag. This study provides a theoretical basis for the resource utilization of converter slag and the optimization of smelting process parameters.