論文
溶鉄/ZrO2系溶融スラグ/固体ZrO2の多相平衡における酸素ポテンシャル測定による溶鉄中Zr活量係数の評価
2019 年 105 巻 3 号 p. 382-388
詳細
2019 年 105 巻 3 号 p. 382-388
Rare earth metals are generally used as a deoxidizer of molten steel due to its high reactivity with oxygen content in the steel. To produce high-grade steel by efficient steel refining, information on thermodynamic interaction between these rare earth metals and major alloying elements in molten steel are important, although these information are very limited. In the present study, activity coefficient of Zr element in molten iron-based alloy was experimentally determined through oxygen potential in gas / molten Fe-Zr alloy / ZrO2-containing molten slag / solid ZrO2 multi-phase equilibrium, measured by an solid electrolyte oxygen sensor. Solid Nb / liquid Nb2O5 phase equilibrium was used to determine the referenced oxygen potential. The ZrO2-containing liquid slag was provided on the liquid Fe-Zr alloy to achieve good wettability with the solid electrolyte oxygen sensor, so that stable electromotive force (EMF) measurement of the oxygen sensor was enabled. The slag composition was selected so as to be equilibrated with the ZrO2 cubic solid phase at the treated temperature. A quite low value of Zr activity coefficient in the molten iron was evaluated, which indicated highly attractive interaction between Fe and Zr in the liquid phase. In addition, the oxygen potential in molten Fe-Zr-Cr alloy in equilibrium with solid ZrO2 and ZrO2-containing slag was evaluated to determine the effect of Cr addition on dissolved O activity in molten Fe-Zr alloy.
