Abstract
With the depletion of rich manganese ore resources, plentiful manganese ore powders with various Mn/Fe mass ratios are produced. The physicochemical aspects of oxidative consolidation behavior of manganese ores with various Mn/Fe mass ratios were investigated in this work to determine whether manganese ore powders with high iron content (Fe-Mn ore) can be prepared as high-quality pellets. Physicochemical properties of the pellets were investigated, including cold compression strength (CCS), phase transformation, microstructural evolution, Vickers hardness (HV), porosity, and lattice parameter. CCS testing indicated that the strength of roasted Fe-Mn ore pellets was observably lower than that of pure hematite or manganese ore pellets. Phase and morphology results showed that in Fe-Mn ore pellets, an Mn ferrite phase was generated between hematite and pyrolusite particles. However, newborn Mn ferrites and hematite had an obvious crystal boundary in the crystallographic particles. Moreover, poorly crystallized Mn ferrite particles were evident, along with Mn and Fe element concentration gradients, due to the inadequate diffusion of metal ions. This resulted in poor mechanical properties of the Fe-Mn ore pellets. A temperature over 1275 °C and a roasting time of 15 min is required for the oxidative consolidation of Fe-Mn ores. In such optimized cases, Mn, Fe, O, and Al elements were uniformly distributed in the well-crystallized Mn ferrite grains, which provided favorable mineralogy for the consolidation of Fe-Mn ore powders.
Highlights
Previous research has mainly concentrated on the characterization, as well as pelletizing and sintering behaviors, of pure iron ores and manganese ores with very high Mn/Fe mass ratios [15–19]
We investigated the optimization of sintering parameters and consolidation behavior of Fe-Mn ore fines with an Mn/Fe mass ratio of 0.74 and natural basicity [13,23]
During the HV hardness test, diamond pyramid heads were pressed on the phases of recrystallization hematite, hausmannite, and Mn ferrites
Summary
Manganese and iron are strategic metal elements, and 90–95% of manganese, in the form of Mn alloys, is consumed in steel production [1]. Pyrometallurgical smelting of manganese ores in blast furnaces and electric furnaces constitutes the mainstream production process for Mn alloys in factories [9–13] In these processes, manganese ore fines or powders are first agglomerated to sinters or pellets, which have superior mechanical and metallurgical properties. Previous research has mainly concentrated on the characterization, as well as pelletizing and sintering behaviors, of pure iron ores and manganese ores with very high Mn/Fe mass ratios [15–19]. Sintering of ore fines and pelletization of ore powders are the two main processes for the preparation of qualified burdens for blast-furnace or electric-furnace smelting. We investigated the optimization of sintering parameters and consolidation behavior of Fe-Mn ore fines with an Mn/Fe mass ratio of 0.74 and natural basicity [13,23]. The average grain sizes of the hem aofti1t3e and manganese ore powders are 14.2 μm and 24.2 μm, respectively
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