Regular Article

Study on the control of inclusions in Al-deoxidized steel during LF-RH refining and the influence of calcium treatment in ladle furnace

¹ School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, PR China
² Zenith Steel Co. Ltd, Changzhou 213002, Jiangsu Province, PR China

^* e-mail: jiangmin@ustb.edu.cn

Received: 9 February 2022
Accepted: 4 April 2022

Abstract

In this paper, evolution of inclusions in an Al deoxidized specialty steel with basic slag refining in the LF-RH process were studied, taking into account of the influence of calcium treatment in the ladle furnace. It was found that inclusions would be modified from alumina into spinel then mainly into solid calcium magnesia aluminates after LF refining, and finally into calcium aluminates at the end of RH refining, irrespective of calcium treatment. When calcium treatment was carried out in the ladle furnace, solid calcium magnesia aluminates largely produced in the LF refining would be mostly modified into liquid calcium aluminates during the afterwards RH refining. By comparison, without calcium treatment, solid and liquid calcium aluminates were both formed in the RH refining. Importantly, when calcium treatment was used, big calcium aluminates as large as 40–50 μm were more frequently observed in steel and with a number density about 0.09–0.015 /mm², which were bad to fatigue resistance.