THERMODYNAMIC MODELING OF PHASE EQUILIBRIA DURING DEOXIDATION OF THE LOW AND MEDIUM CARBON STEELS BY SILICOMANGANESE

Abstract

To create digital twins of steelmaking production, it is necessary to develop programs for calculating all stages of smelting and secondary treatment of steel and alloys, including the process of deoxidation. The aim of this work was to construct a phase stability diagram in the form of a surface of solubility of components in a metal (SSCM) of the Fe–Si–Mn–O–C system for carbon concentrations [C] = 0; 0.1; 0.4 wt. % and a temperature of 1600 °C. SSCM will make it possible to establish the stability boundaries of non-metallic inclusions (NI) formed during deoxidation and the degree of deoxidation of low- and medium-carbon steel, depending on the introduced concentrations of silicon and manganese. It is noted that in the system under study, during absence of carbon ([C] = 0 wt. %) an oxide melt of variable composition (FeO, MnO, SiO2) with a minimum concentration of iron oxide prevails as nonmetallic inclusions. With the appearance of carbon in the melt, the region of equilibrium of the liquid metal with the gas phase {CO, CO2} was established, and with an increase in the concentration of carbon, this region increased. For low-carbon steels ([C] = 0.1 wt. %) at industrially significant concentrations of silicon (0.1–0.3 wt. %) and manganese (about 1.0 wt. %), NI in steel also represent oxide melt. In medium-carbon steels ([C] = 0.4 wt. %) at the same silicon and manganese concentrations, the deoxidation product is in the gas phase. In the course of modeling, the isotherms of oxygen solubility in the system under study were also constructed. The simulation results are in good agreement with the literature data. The constructed SSCM can be used to create a digital twin of the deoxidation process of steels.