Abstract: The liquid iron containing elements Nb,Mn and Si has been equilibrated with MgO-SiO_2-MnO slag melts at 1600℃ in a Mo wire-wound resistance furnace with a duration of 4h.The oxygen activities in liquid iron were measured with oxygen sensors.Using the known equilibrium constants of concerning reactions and the oxygen activities in liquid iron,the activities of components in the slag melts can be calculated.It was found that the par- tition ratios of Nb.Mn and Si have a close linear relationship with α_(FeO) in logarithmic scale.The dependence of Nb partition ratio on mole fractions of the slag components was al- so obtained.

Key words: MgO-SiO_2-MnO slag, equilibrating partition ratio