Original Article

Effect of Ce₂O₃-bearing slag on inclusions in a low-carbon Al-killed steel

¹ School of Mechanical Engineering, Yanshan University, Qinhuangdao 066004, China
² School of Mechanical and Materials Engineering, North China University of Technology, Beijing 100144, China

* e-mail: renqiang@ysu.edu.cn
** e-mail: zhanglifeng@ncut.edu.cn

Received: 12 November 2024
Accepted: 21 January 2025

Abstract

In this paper, the effect of Ce₂O₃ bearing slag on inclusions was investigated in laboratory scale experiments by slag-steel reaction. The morphology and chemical composition of inclusions were analyzed using an automatic scanning electron microscope equipped with energy dispersive spectroscopy. In the case of the ratio of steel and slag was 10:1, dissolved cerium generated from the reaction between Ce₂O₃ in slag and [Al] in steel was transferred to molten steel. As the content of Ce₂O₃ in the slag increased, the average content of Al₂O₃ in inclusions decreased initially and then increased, the average content of MgO in inclusions showed an opposite trend compared with that of Al₂O₃. The content of [Ce] was too low to form pure cerium oxides and sulfides but just reacted with the existing inclusions in steel to generate a small number of multi-phase inclusions containing Ce₂O₃ and CeS. The CeAlO₃ inclusion was generated from the reaction between [Ce] and Al₂O₃ and existed inside inclusions. While CeS precipitated outside the inclusions during solidification. The activity of CaO, Al₂O₃, MgO, Ce₂O₃ in the slag was calculated using Ion-Molecule Coexistence Theory. As the content of Ce₂O₃ in slag increased, the activity of Ce₂O₃ increased slightly and the activity of CaO and MgO increased significantly while the activity of Al₂O₃ decreased. According to the calculated result of [Al]-[Ce] equilibrium relation, the content of [Ce] generated from the reaction between Ce₂O₃ in slag and [Al] in steel was less than 1 ppm. Then the Gibbs free energy of possible chemical reactions of inclusions were calculated. The thermodynamic calculations were in good agreement with the experimental results.