Thermodynamics of Zirconium Deoxidation Equilibrium in Liquid Iron by EMF Measurements

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Thermodynamics of Zr deoxidation equilibrium in liquid iron has been studied at 1873 K by using ZrO2–9mol%MgO and mullite (3Al2O3·2SiO2) electrolytes coupled with the quantitative alalysis of soluble Zr and insoluble Zr as ZrO2 by using a potentiostatic electronic extraction method. The soluble O content for a given soluble Zr content is lower than the previously reported values in the plot of soluble O vs. soluble Zr contents, and the oxygen activity for a given soluble Zr content is higher than the previously reported values. The free energy change of solid Zr dissolution into iron melt: Zr(s)=Zr at 1873 K is obtained as ΔG°=−153±10 kJ. The interaction coefficients for eOZr, rOZr and rOZr,O are estimated as −70±15, 901±131 and 10300±1500, respectively. However, the following interaction coefficients are represented by using a continuous function of logarithms of X, where X=[%sol.Zr]+5.7[%sol.O]+17.1[%sol.Zr]·[%sol.O]/(2[%sol.Zr]+5.7[%sol.O]):eOZr=−3.70−2.20 ln X−2.07(ln X)2+(ln X)3rOZr=dY/dX={−0.33+1.87 ln X+3.01(ln X)2}/XrOZr,O<11.4rOZr={−3.72+21.4 ln X+34.3(ln X)2}/X
社団法人日本鉄鋼協会の論文
2008-09-15