Effect of rare earth oxide on the crystallization behavior of CaO-Al2O3-based mold flux for rare earth heat-resistant steel continuous casting

New CaO-Al2O3-based mold flux for rare earth steel continuous casting was devised to restrain the slag-steel interface reaction. The effect of Ce2O3 on the crystallization behavior were investigated. The continuous cooling transformation tests show that the addition of Ce2O3 not only reduces the critical cooling rate of the mold flux but also reduces the initial crystallization temperature. Besides, the distribution of the initial crystallization temperature became more stable. The temperature time transformation tests show that the crystallization incubation time is slightly increased, the addition of Ce2O3 inhibit the isothermal crystallization process to a certain extent. The crystalline phases changed from LiAlO2+CaO to LiAlO2+CaCeAlO4. The precipitation of CaO was restrained by adding Ce2O3. With the combination of Ca2+, Ce3+, and [AlO6(9)(-)]octahedron units, CaCeAlO4 formed and precipitated in the crystallization process. Besides inhibiting the crystallization of CaO-Al2O3-based mold flux, adding rare earth oxide also can reduce the viscosity and the breaking temperature.

Automated summary

The new CaO-Al2O3-based mold flux with Ce2O3 addition showed reduced critical cooling rate and initial crystallization temperature, as well as more stable distribution of initial crystallization temperature. Ce2O3 incorporation slightly increased crystallization incubation time and inhibited isothermal crystallization process. The formation of CaCeAlO4 phase was observed, contributing to the inhibition of CaO crystallization and reduction in viscosity and breaking temperature.