Thermodynamic and Pilot-Scale Experimental Analysis of Medium-Carbon Ferromanganese Production

This study investigates the thermodynamic and technological aspects of smelting medium-carbon ferromanganese from Zhezdinsky manganese ore using ferrosilicomanganese and lime. The equilibrium distribution of components in the oxide-metal system was calculated using HSC Chemistry 10.0 within the temperature range of 573–2073 K. The modeling results revealed the effect of lime and ore consumption on slag phase composition as well as on manganese and silicon contents in the metallic phase. Experimental validation was performed in a laboratory Tamman resistance furnace and in a 100 kVA large-scale laboratory electric arc furnace. The chemical compositions of metal and slag were determined by bulk chemical analysis, while microstructure and local elemental distribution were examined using SEM-EDS. An increase in slag basicity was found to promote the transfer of silicon into the silicate phase while simultaneously reducing manganese losses to the slag. The large-scale laboratory smelting experiments, with a duration of 100–120 min per heat, enabled the establishment of a stable processing regime and the production of a metal with an average composition of 88.1 wt.% Mn, 1.6 wt.% C, and 0.03 wt.% Si. The corresponding slag contained approximately 15 wt.% MnO and 21 wt.% SiO2. SEM-EDS analysis showed that the alloy possesses a heterogeneous microstructure consisting of an Fe-Mn metallic matrix with finely dispersed silicide microphases. Local silicon concentrations in these phases reach 15–24 wt.%, which explains the discrepancy between local and bulk chemical compositions. The experimental data are in good quantitative agreement with the thermodynamic modeling results, confirming that slag basicity and composition control are key factors for improving manganese recovery and stabilizing metal composition. The identified relationships can be applied in the development of industrially oriented smelting regimes for producing medium-carbon ferromanganese from Kazakhstan manganese raw materials.