Characterization of Multi Component Calcium-ferrites in Iron Ore Sinter by EBSD Method

Abstract

Multi component calcium-ferrites (CFs) including in iron ore sinter are key component of sinter properties, such as strength and reducibility. Those in a sinter are crystallized from oxide melts and form various morphologies such as columnar, needle, and fine textures depending on the formation process. Ca₂(Fe,Ca)₆(Fe,Al,Si)₆O₂₀ (SFCA), Ca₃(Ca,Fe)(Fe,Al)₁₆O₂₈ (SFCA-I) and SFCA-III phases are representative multicomponent CFs, which are included in a sinter. Those texture and types of the crystal structure are not matched one by one. Since their compositional ranges and chemical properties have not yet been fully clarified, and they have micron ordered grain size, it is difficult to determine CF phases only by EPMA chemical composition analysis. In this study, phase determination of CFs in sinter was conducted by Electron backscatter diffraction (EBSD) analysis, which has better spatial resolution than Electron Probe Micro Analyzer (EPMA). Needle like CFs in the sinter with size of several microns were analyzed and confirmed presence of SFCA, SFCA-I and SFCA-III with the needle like texture. Crystal grains determined as SFCA showed higher Si content compared to those of SFCA-I, and this result is consistent with phase diagram. Mg concentration of SFCA-III found in sinter was in the range of 0.6－2.6mass%, which was lower than that of previously reported single crystal structure analysis sample.