Viscosity of niobium oxide systems for production of complex ferroalloys

Abstract

The relevance of the development of modern technological solutions for the processing of niobium ore materials used for the production of complex ferroalloys of domestic deposits is shown. The need to develop new technological processes of processing is caused by the fact that when switching to new types of niobium concentrates, the chemical and phase compositions of the starting materials change, and, consequently, this leads to a change in the composition and properties of the melting products (both metallic and oxide). Using an electrovibration viscometer, the temperature dependences of viscosity were studied and the crystallization temperatures of oxide melts of the Nb2O5 – SiO2 – CaO – TiO2 – Al2O3 system were calculated. The compositions of the studied samples correspond to phosphorless niobium slags, which can be obtained by carbothermic method from rough concentrates. The samples were obtained by fusing oxide materials in a high-temperature laboratory electric furnace. On the basis of the obtained data, graphical dependences of viscosity – temperature are constructed. It was experimentally established that oxide melts containing 15 – 26 % Nb2O5 are more “long” (having a wide crystallization range) and unfavorable according to the characteristic viscosity – temperature dependence. An increase in the concentration of niobium pentoxide to 40 % translates slags into the category of “short” (with a high crystallization rate). It is shown that an increase in the concentration of niobium oxide Nb2O5 from 15 to 40 % leads to a decrease in the crystallization temperature of melts by 200 °C and a decrease in the viscosity of melts from 1.32 to 0.24 Pa·s at 1350 °C. The improvement of the physico-chemical characteristics of oxide melts with an increase in the concentration of niobium pentoxide can favorably affect the technical and economic indicators of ferroalloy production.