Abstract
Direct Reduction of Chromite (DRC) is a promising new technology that does not require the high (>1600 °C) temperatures used in smelting. In the DRC process, chromite (Mg,Fe)(Cr,Al)2O4 ore is combined with a carbon reductant and CaCl2 flux then heated to 1300 °C where Fe and Cr oxides from chromite incongruently dissolve and reduced to M7C3-type ferrochrome. A major benefit of the DRC process is that ferrochrome can be produced at temperatures below the chromite latent heat of fusion leaving a residual refractory magnesian aluminum spinel. The resulting ferrochrome is distributed as particles similar in size to the original reductant. Therefore, it is important to understand the 3D relationships between ferrochrome, residual spinel, and porosity to quantitatively assess the product quality.
X-ray computed microtomography is an emerging analytical tool for investigating the 3D microstructure of materials. In this work we digitally segregate ferrochrome, spinel, reductant, and pore space in DRC products. We then investigate the 3D relationships between different phases by calculating individual particle volumes, sizes, shapes, spatial organization, porosity, and network connectivity. We then use this information to assess localized and bulk metallization of ferrochrome from experimental samples. The results demonstrate how non-destructive X-ray computed microtomography can be used to rapidly assess ferrochrome metallization and product quality.