Effects of CaF 2 , B 2 O 3 , and Li 2 O Additions on Crystallization Kinetics and Phase Evolution of Multicomponent Mold Fluxes

The crystallization behavior of mold fluxes is critical for controlling heat transfer and lubrication during high‐speed thin slab casting. In this study, the effects of CaF 2 , B 2 O 3 , and Li 2 O were systematically compared within a common compositional framework using M0 as the reference composition. The crystallization behavior was investigated by the single hot thermocouple technique under continuous cooling transformation and time–temperature transformation conditions, combined with Raman spectroscopy, X‐ray diffraction, scanning electron microscopy, and thermodynamic calculations.Increasing CaF 2 raises the crystallization temperature, shortens the incubation time and crystallization duration, and promotes cuspidine formation through silicate‐network depolymerization. In contrast, increasing B 2 O 3 lowers the crystallization temperature and delays crystallization despite reducing melt viscosity, owing to enhanced structural complexity, glass‐forming tendency, and liquid‐phase stability. Li 2 O exhibits a nonmonotonic effect: 0–2 wt% Li 2 O promotes crystallization and silicate‐network depolymerization, whereas 3 wt% Li 2 O retards the overall crystallization process and modifies the relative stability of cuspidine and B‐containing phases. These results demonstrate that crystallization behavior is governed by the combined effects of kinetics, melt structure, and phase stability, providing guidance for mold flux design in high‐speed thin slab casting.