Original Article

Removal behavior of MgO-Al₂O₃ spinel inclusions in steel during RH vacuum process

¹ State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, PR China
² Zenith Steel Group Co., LTD, Changzhou, Jiangsu 213011, PR China

^* e-mail: wangkunpeng@zt.net.cn

Received: 10 December 2024
Accepted: 11 February 2025

Abstract

MgO · Al₂O₃ inclusions in steel not only deteriorate the castability of steel, but also may lead to macroscopic defects in finished products, and RH vacuum treatment is an important step to remove the inclusions in steel. Many studies have indicated that MgO · Al₂O₃ inclusions could be removed efficiently by RH. Therefore, investigating the removal mechanism of MgO · Al₂O₃ inclusions in RH refining is of paramount importance. Based on industrial experiments and thermodynamic calculations for low-carbon 20CrMnTi, medium-carbon 42CrMo, and high-carbon GCr15, a new removal mechanism of MgO · Al₂O₃ inclusions during RH process is put forward: 4[C] + MgO · Al₂O₃= [Mg] + 2[Al] + 4CO. The removal efficiency of MgO · Al₂O₃ inclusions for these steels at 5 kPa is 3.5%, 56.1%, and 94.6%, respectively. Vacuum pressure and [C] content are two key factors to determine the removal efficiency of MgO · Al₂O₃ inclusions during RH process.