Quantitative characterization of reaction behavior between La-bearing FeCrAl melt and CaO–Al₂O₃–La₂O₃-based slags and its guidance for design of mold flux

The reaction behavior between CaO–Al₂O₃–La₂O₃-based slags and La-bearing FeCrAl melt was quantitatively characterized, which was further compared with the reaction behavior of CaO–SiO₂-based slags. Based on this, the new type of mold flux for La-bearing FeCrAl alloy continuous casting was designed and its basic properties were evaluated. The results showed that the order of reaction degree of fluxing agents in CaO–Al₂O₃–La₂O₃-based slags is (Na₂O) > (B₂O₃) > (Li₂O), and the percentages of mass change of fluxing agents were 85.8, 54.29 and 42.35 wt.%, respectively. Moreover, the addition of (Li₂O) and (Na₂O) promoted the reaction between (CaO) and [Al], and the reaction degree of the former was weaker than that of the latter, which was due to the greater effect of (Na₂O) on the activity of (CaO) and (Al₂O₃) than (Li₂O). Compared with the reactivity of CaO–SiO₂-based slags, the percentages of mass change of Al and La caused by slag–steel reaction decreased by 10.63–14.36 and 39.78–50.49 wt.%, respectively. The percentages of mass change of (Al₂O₃), (La₂O₃) and (CaO) in slags highest increased by 17.71, 17.98, and 7.81 wt.%, respectively. The reactivity of CaO–Al₂O₃–La₂O₃-based slags was significantly weakened. Ultimately, the new type of mold flux was designed and the composition range was determined. The fundamental properties of new mold flux basically meet the theoretical requirements for La-bearing FeCrAl alloy continuous casting.