Abstract
The standard Gibbs free energy of formation of MnO-saturated MnO·Cr2O3 solid solution (stoichiometric MnO·Cr2O3), which is one of important thermodynamic properties of the MnO-SiO2-CrOx inclusion system to clarify the equilibrium relation among molten stainless steel and the inclusions formed during the stainless steel Si-deoxidation process, was determined at 1873 K. By equilibrating molten iron or copper with MnO-saturated MnO·Cr2O3 crucible under controlled oxygen partial pressure, Po2´, the standard Gibbs free energy changes of the following reactions at 1873 K were determined to be:
Mn (mass%, in molten Fe)+2Cr (mass%, in molten Fe)+2O2 (g)
= MnO·Cr2O3 (MnO-satd.): ΔG°/kJ = −755±4 (PO2 = 2×10−6−6×10−5 Pa)
Mn (mass%, in molten Cu)+2Cr (mass%, in molten Cu)+2O2 (g)
= MnO·Cr2O3 (MnO-satd.): ΔG°/kJ = −807±7 (PO2 = 3×10−5−1.5×10−4 Pa)
Mn (l)+2Cr (s)+2O2 (g) = MnO·Cr2O3 (MnO-satd.):
ΔG°f, MnO · Cr2O3/kJ·mol−1 = −958±8 (PO2 =2×10−6−1.5×10−4 Pa)
The values of ΔG° and ΔG°f, MnO · Cr2O3 are independent of the oxygen partial pressure within the PO2 range in the present study.
