Behavior of Vanadium and Niobium during Hot Metal Dephosphorization by CaO–SiO<sub>2</sub>–Fe<sub>t</sub>O Slag

Abstract

V and Nb are key elements for the production of high-grade steel. These elements are produced by few countries, and V has been nominated as a national stockpile element in Japan. Despite the importance of these elements, there are no strategies to obtain stable resources for them. Some types of iron ore that contain V and Nb can be used as sources of these elements. This study clarified the possibility of extracting V and Nb by means of a conventional hot metal dephosphorization process without using CaF2 as a flux. First, the influences of V and Nb oxides on the distribution ratio of P2O5 between the solid solution and liquid phases in slag were measured. Then, the behaviors of V and Nb in hot metal dephosphorization by CaO–SiO2–FetO slag were investigated. Finally, a previously described hot metal simulation model was modified and the behaviors of various elements, including V and Nb, during hot metal dephosphorization were simulated, and the results were compared with experimental ones. The results are summarized as follows: (1) The addition of V and Nb oxides slightly increases the distribution ratio of P2O5 between the solid solution and liquid phases in slag. (2) The decreasing rate of the elements by the flux addition can be expressed as Nb > Mn > P > V, and these decreasing rates increase as the basicity increases. (3) The simulation results for the behavior of P and V or Nb are in good agreement with the experimental results; that is, the decreasing rate for Nb is greater than that for P, and the separation of Nb leaving P in the hot metal is easier than the separation of V.