In Situ Method to Study the Dissolution of Ti(C,N) Inclusion in Molten Mold Flux

Mold flux plays a critical role in absorbing the inclusions floating from the liquid steel. However, this dissolution process is hard to observe in situ because the mold is a “black box”. This paper used the in-situ single hot thermocouple technique (SHTT) combined with high definition microscope to investigate the dissolution behavior of Ti(C,N) inclusion in molten CaO–SiO₂–B₂O₃-based mold flux, as well as the dissolution mechanism was explored by scanning electron microscope (SEM) equipped with X-ray energy spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). The results suggest that Ti(C,N) inclusion was oxidized and then dissolved in molten slag as [TiO₄] tetrahedra and [TiO₆] octahedra, which is accompanied by the generation of N₂ and CO₂ gas. In addition, CaTiO₃ crystals tend to precipitate and stabilize in the molten slag, leading to the final solid–liquid mixed state of the melt. In addition, the precipitated CaTiO₃ crystals are greater in number but smaller in size because the dissolution of Ti(C,N) releases more gases that can provide more nucleation sites, thereby increasing the nucleation of the crystal.