Standard Gibbs Free Energy of Formation of MnO-saturated MnO - Cr_2O_3 Solid Solution at 1873 K

摘要

The standard Gibbs free energy of formation of MnO-saturated MnO·Cr_2O_3 solid solution (stoichiometric MnO·Cr_2O_3), which is one of important thermodynamic properties of the MnO-SiO_2-CrO_x 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 1 873 K. By equilibrating molten iron or copper with MnO-saturated MnO·Cr_2O_3 crucible under controlled oxygen partial pressure, P_(O_2), the standard Gibbs free energy changes of the following reactions at 1 873 K were determined to be: Mn(mass%, in molten Fe)+2Cr (mass%, in molten Fe)+2O_2(g) = MnO·Cr_2O_3(MnO-satd.): ΔG°/kJ = -755+-4 (P_(O_2)=2x10~(-6)-6x10~(-5)Pa) Mn (mass%, in molten Cu)+2Cr (mass%, in molten Cu)+2O_2(g) = MnO·Cr_2O_3(MnO-satd.): ΔG°/kJ = -807+-7 (P_(O_2)=3x10~(-5)-1.5x10~(-4)Pa) Mn (l) + 2 Cr (s)+2O_2(g) = MnO·Cr_2O_3 (MnO-satd.): ΔG°(_f,MnO·Cr_2O_3)/kJ·mor1 = -958+-8 (P_(O_2)=2x10~(-6)-1.5x10~(-4)Pa) The values of ΔG° and ΔG°_(f,MnO·Cr_2O_3) are independent of the oxygen partial pressure within the P_(O_2) range in the present study.