Agglomeration Characteristics of Various Oxide Inclusions in Molten Steel Containing Rare Earth Element under Different Deoxidation Conditions

Abstract

Comprehensive investigation of agglomeration behavior of oxide inclusions in steel-containing rare earth (RE) under different deoxidation conditions is essential for improving the nozzle-clogging problem during continuous casting. The present study first optimized the thermodynamic model by supplementing thermodynamic data of the RE-compound to study the formation of various inclusions in the Ce–Si–Al–O system. On this basis, laboratory-scale experiments with different deoxidation conditions were designed to obtain samples containing one single type of inclusions, viz., SiO₂, SiO₂–Ce₂O₃ or SiO₂–Al₂O₃–Ce₂O₃, respectively. Subsequently, the agglomeration behavior of inclusions was observed in situ by confocal laser scanning microscopy (CLSM), and the corresponding attractive forces were calculated to compare the agglomeration tendency of various inclusions. The results indicate that, in the Si deoxidized samples, SiO₂–Ce₂O₃ inclusions agglomerate to form clusters with the attractive force of 4.3 × 10⁻¹⁷N to 4.2 × 10⁻¹⁵N, which is weaker than that of Al₂O₃ and Al₂O₃–Ce₂O₃ inclusions after Al deoxidation. Although SiO₂ inclusions can agglomerate, their attractive force is only 6.3 × 10⁻¹⁹N to 1.2 × 10⁻¹⁶N, which is the weakest of the above inclusions. In the case of Si/Al complex deoxidization, spherical SiO₂–Al₂O₃–Ce₂O₃ liquid inclusions are formed after Ce treatment, and no agglomeration of such inclusions was observed in situ. The study could provide theoretical guidance for improving the nozzle-clogging problem of RE-containing steel from inclusion-controlling perspective under different deoxidation conditions.