Article ID: ISIJINT-2022-375
Silico-ferrite of calcium and aluminum (SFCA) is the primary bonding phase of iron ore sinter, the world's most popular artificial feed material for ironmaking. However, fundamental questions about its crystal structure and the atomic occupancy at each site remain unanswered. To date, the quantitative phase analysis (QPA) of SFCA has mostly been conducted using two-dimensional information and only provided information regarding phase fractions. In contrast, Rietveld analysis uses bulk data and provides lattice information in addition to phase fraction information. This study investigates the effects of basicity and Al2O3 concentration on the crystal structure and atomic site occupancy of SFCA through Rietveld analysis of the X-ray diffraction patterns. Raman spectroscopy and micro-Vickers hardness tests are used to verify the analytical results. Changes in the chemical composition affect the atomic occupancies at sites Si1 (Si-Al), Ca2 (Ca-Fe), Ca3 (Ca-Fe), Fe4 (Fe-Al), Fe5 (Fe-Al), and Fe7 (Fe-Al). With increasing basicity or Al2O3 content, the microhardness increases linearly, which can be attributed to the modification of atomic site occupancies. The crystalline structure obtained in this study is essential for developing a thermodynamic model of SFCA that can be used to predict its phase stability. This information can then be used to design a novel high-performance iron ore sinter.