Vatolin Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences (Ekaterinburg, Russia)

K. V. Pikulin, Candidate of Technical Sciences, Senior Researcher, pikulin.imet@gmail.com
L. I. Galkova, Candidate of Technical Sciences, Senior Researcher
R. I. Gulyaeva, Candidate of Chemical Sciences, Senior Researcher
L. Yu. Udoeva, Candidate of Technical Sciences, Leading Researcher
S. V. Sergeeva, Candidate of Technical Sciences, Senior Researcher
S. N. Tyushnyakov, Candidate of Technical Sciences, Leading Researcher

The phase formation mechanisms during the metallothermic reduction of natural wolframite from the Akchatau Deposit using aluminum and a calcium-aluminum master alloy was investigated in this study. Thermodynamic simulation demonstrates that, regardless of the reducing agent employed (Al or Ca – Al master alloy), the equilibrium composition of the metallic phase consists of tungsten and ferrotungsten. The application of the Ca – Al master alloy increases the thermal effect of the process by 4.3% and raises the adiabatic temperature by 390 °C compared to the conventional aluminothermic route, while also enhancing the separation of the metallic and oxide phases due to the formation of low-melting calcium aluminates. Using differential scanning calorimetry (DSC), X-ray diffraction (XRD), and X-ray microanalysis (EPMA), it was established that both processes proceed in a stepwise manner; however, their underlying mechanisms differ fundamentally. In the aluminothermic process, the iron-bearing component of the mineral is reduced first, yielding aluminum-based intermetallic compounds, which subsequently react with the manganese-enriched residual wolframite fraction. When the Ca – Al master alloy is employed, the initial stage involves the formation of calcium tungstates (CaWO₄, Ca₃WO₆, Ca₂WMnO₆) and aluminides of the principal metals; these intermediates, together with calcium vapor, subsequently reduce the complex oxides formed in the preceding step. It is shown that, in both cases, the final products of natural wolframite reduction are metallic tungsten and its solid solutions with iron and manganese. The results obtained may contribute to the optimization of out-of-furnace metallothermic processing technologies for tungstencontaining raw materials.

The work was carried out according to the State Assignment for the Vatolin Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences (IMET UB RAS) using the equipment of the Collaborative Usage Center “Ural-M”.

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