Carbon Distribution Behavior Between Molten Iron and CaO-Al₂O₃-FeO-SiO₂-MgO Slag at 1873 K

The carbon solubility of the CaO-Al₂O₃-FeO-SiO₂-MgO slag, the main system during the Ruhrstahl-Heraeus (RH) vacuum degasser process, has been measured at 1873 K (1600 °C) to understand the impact of slag composition on the solubility of carbon in molten slag during ultra-low-carbon (ULC) steel production. The stable form of carbon was demonstrated as a carbonate \(\left(C{O}_{3}^{2-}\right)\) $\left(C,O_3^{2-}\right)$ by plotting the \({log}[(mass\,pct\,C)/{a}_{C}]\) $\mathit{log}[(masspctC)/a_C]$ ratio against \({log}{p}_{{\text{O}}_{2}}\) $\mathit{log}{p}_{{\text{O}}_2}$ in the range of \(-11<{log}\left[{p}_{{\text{O}}_{2}},atm\right]<-9\) $-11<\mathit{log}\left[p_{{\text{O}}_2},,,a,t,m\right]<-9$ . The carbon solubility of the CaO-Al₂O₃-FeO-SiO₂-MgO slag was estimated using the Pelton-Eriksson-Serrano model. The distribution ratio of carbon increased with increasing FeO content due to the higher oxygen potential and the increased basicity of slag. The carbonate capacity of the CaO-Al₂O₃-FeO-SiO₂-MgO slag could be expressed as a linear function of the activity of lime and optical basicity.