Determination of activity interaction parameters of Nb in Fe-C-Nb melts at 1873 K

The interaction parameters of Nb in Fe-C-Nb melts at 1873 K were measured using the chemical equilibrium method.The Fe-C melts were equilibrated with the CaO-MgO-Al_(2)O_(3)-NbO_(2) slags under a controlled oxygen potential for 24 h.In addition to acting as the protective gas,argon was adopted to control the oxygen potential.Based on the data obtained in the experiments,the activity interaction parameters were obtained by the multiple linear regression method.The first-order interaction parameters e_(Nb)^(C)and e_(Nb)^(Nb)are determined to be−0.035 and−0.134,respectively.The second-order interaction parameters r_(Nb)^(C),r_(Nb)^(Nb,C),and r_(Nb)……(Nb)are determined to be 0.011,−0.0063,and 0.0023,respectively.The thermodynamic data obtained are more reliable than those in previous publications for the Fe-C-Nb system when the Nb content range was 0.92-4.62 wt.%.