The effect of carbon in slag on steel reoxidation and carbon analysis by X-ray photoelectron spectroscopy in the CaO-SiO2-Al2O3-MgO-MnO-FetO system

Abstract

An equilibrium experiment was carried out at 1873 K to investigate the effect of carbon in CaO-SiO2-Al2O3-MgO-MnO-FetO slag systems on their FetO and MnO activity coefficients, representing the slag's thermodynamic potential for steel reoxidation. The activity coefficients of FetO and MnO showed not only a sharp increment but also a simultaneous slow decrement with increasing carbon content in slag, suggesting opposite roles of the carbon in slag according to its stable forms. X-ray photoelectron spectroscopy (XPS) was introduced to determine the stable forms of carbon in slag. The XPS results proved that carbon dissolves in slag as carbonate, and carbide ions under oxidizing and reducing atmospheres, respectively. The simultaneous consideration of the activity coefficients of FetO and MnO and stable carbon forms showed that carbonate ions increase the activity coefficients of FetO and MnO, but that carbide decreases them. This article suggests an application method. of the present results to actual ladle refining processes, in order to enhance steel cleanliness with maintaining (FetO + MnO) in slag to some allowable amount.