Effect of addition of Al-based slag deoxidizer on MgO.Al₂O₃ inclusions in 3Si-Fe steels

¹ School of Metallurgical and Ecological Engineering at University of Science and Technology Beijing (USTB), Beijing 100083, P.R. China
e-mail: zhanglifeng@ustb.edu.cn
² CISDI R&D Co., Ltd, Chongqing, Chongqing 401122, P.R. China

Received: 24 May 2016
Accepted: 15 July 2016

Abstract

In the current study, laboratory experiments between CaO-Al₂O₃-SiO₂-MgO-TiO₂- MnO-Fe₂O₃ slags and 3Si-Fe melts with the addition of an Al-based slag deoxidizer with the main composition of 45% metallic Al, 25% CaO, 13% Al₂O₃, 4% SiO₂ and 2.3% MgO were carried out at 1873 K. The addition of an Al-based slag deoxidizer increased not only Al but also Mg in the steel due to the reduction of MgO in slag and crucible by Al, which was responsible for the evolution of inclusions from MgO.Al₂O₃ to pure MgO. log(a._Mg/a²_Al . a²_O) in steel linearly increases by increasing log(a^s_MgO/a^s_Al2O3) in slag with the slope close to unity. In addition, the relationship between log(X_MgO/X_Al2O3) in the inclusions and log(a._Mg/a²_Al . a²_O) in steel exhibits a linear correlation with a slope close to 1. Consequently, the prediction of compositions of slag, steel and inclusions can be achieved based on the relationships in the present study. The calculated stability diagram of inclusions in Mg-Al-O-0.035% C-0.04 % Mn-3-Si-Fe melts at 1873K can be used to predict the formation of Al₂O₃, MgO.Al₂O₃ and MgO inclusions based on the steel composition.