Original Article

Control of steel cleanliness and non-metallic inclusions in an Al-killed steel through CaO-Al₂O₃ powder injection during RH refining process

¹ School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing (USTB), Beijing 100083, China
² School of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004, China
³ School of Mechanical and Materials Engineering, North China University of Technology, Beijing 100144, China

^* e-mail: yingren@ustb.edu.cn
^** e-mail: zhanglifeng@ncut.edu.cn

Received: 26 November 2024
Accepted: 13 April 2025

Abstract

In the current study, an industrial trial of the CaO-Al₂O₃ powder injection during RH refining process was carried out to investigate the control of steel cleanliness and non-metallic inclusions in an Al-killed steel. At the refining start, main inclusions were Al₂O₃. During the refining process, inclusions gradually changed from Al₂O₃ to calcium aluminate. Meanwhile, the number density and diameter increased first due to the CaO-Al₂O₃ powder injection and then decreased due to the floating of inclusions. The coagulation coefficient and adhesion work can reflect the aggregation and removal ability of inclusions, respectively. The higher liquid fraction of inclusions lowered their coagulation coefficient, decreasing the aggregation ability of the inclusions. Meanwhile, the adhesion work of inclusions increased with the increased liquid fraction, retarding the removal of inclusions from the steel.