Regular Article

Metallurgical characteristics of refining slag used for high manganese steel

¹ School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, PR China
² State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, PR China

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

Received: 30 April 2019
Accepted: 2 September 2019

Abstract

High manganese steel has excellent mechanical properties, which has garnered much attention. Whereas the research on the refining slag used for high Mn steel is very limited. In this study, the metallurgical characteristics of refining slag for high Mn steel were investigated based on thermodynamic calculation with FactSage 6.3 and slag-metal equilibrium reaction in MgO crucible. The calculated liquid zones of T ≤ 1873 K of CaO-SiO₂-Al₂O₃-8%MgO-5%MnO system are located in the middle region of pseudo-ternary CaO-SiO₂-Al₂O₃. For CaO-SiO₂-Al₂O₃-8%MgO-MnO system, the apparent liquid zone at 1873 K enlarges with MnO content in slag increasing, and moves toward the direction of SiO₂ and Al₂O₃ content increasing. For CaO-SiO₂-Al₂O₃-MgO-MnO system, the liquidus zone shrinks with the basicity increasing, and moves toward the direction of Al₂O₃ content increasing. The measured MnO content in top slag reacted with high Mn steel was much higher than that reacted with conventional steels. In present experiments, the MnO content was around 5% when CaO-SiO₂-Al₂O₃-MgO slag with basicity of 4 was in equilibrium with high Mn steel (Mn = 10, 20%) at 1873 K. The inclusions in master high Mn steel were mainly MnO type. After reaction with top slag, most inclusions transformed to MnO-SiO₂ system and MnO-Al₂O₃-MgO system, in which the MnO content still shared the majority. Thermodynamic calculations show that SiO₂ in top slag can be reduced by [Mn] in steel to supply [Si] under present experimental condition, which subsequently reacts with [O] in steel bath to form SiO₂.