Metallogenic mechanisms of three typical high-basicity sinter: Hematite-type, magnetite-type and vanadium-titanium magnetite-type

Abstract

The mineral composition and microstructure critically affect high-basicity sinter quality. Using analytical grade reagents, the formation mechanisms of main minerals and microstructures in high-basicity sinter (hematite-type, magnetite-type, and vanadium-titanium magnetite-type) during mineralization were analyzed via polarized light microscopy and FactSage. The results indicated that hematite appeared as primary and secondary forms in different sinter types at 900°C. In the heating process, calcium ferrite, magnetite, and perovskite formed at 1150, 1280, and 1400°C, respectively, while olivine formed at 1200°C during cooling. From room temperature to 1400°C, microstructures evolved from powder-like to porphyritic and skeletal crystal forms. During cooling (1280 to 1100°C), an interlaced-erosion structure was observed. FactSage simulations show that in the low-temperature phase, the liquid composition is closer to the high-basicity CaO–Fe₂O₃ liquid phase region, where silica-ferrite of calcium and aluminum (SFCA) binds with magnetite and hematite to form an interlaced-erosion structure. The porphyritic structure resulted from SFCA melting into the liquid phase, hematite decomposing, and the glass phase cementing magnetite upon quenching. The skeletal crystal structure forms during the high-temperature phase as the high silicate content in the liquid phase increases melting viscosity, reduces local medium concentration, and leads to incomplete crystal growth. This research aims to advance high-basicity sinter metallogenic theory and guide sintering quality improvement.

Keywords

high-basicity sinter / mineralization process / interlaced-erosion structure / porphyritic structure / skeletal crystal structure

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