Influence of Grade on the Splitting Mechanical Properties of Iron Ore: Insights from Microstructure Analysis

Abstract

The grade of iron content in ore was measured using X-ray fluorescence, and three iron ore grades (i.e., 28%, 34%, and 40%) were selected to prepare disk specimens. The Brazilian splitting test was performed, and acoustic emission and digital image correlation methods were used to capture the surface strain distribution and crack propagation behavior. The microscopic morphology of the fracture surfaces of specimens was analyzed using scanning electron microscopy, and the PFC (particle flow code) simulation was used to analyze the type of discrete fracture network in the specimens. The results showed that as the grade increased, the fracture zone shifted from the center to both sides, along with specimen tensile strength. This occurred because the iron oxide enrichment strength increases microscopically and is affected by the gradual increase in shear cracks and decrease in tensile cracks with increasing grade. Moreover, both the strain value of specimens and the speed of crack propagation increased with higher grades. Scanning electron microscopy revealed that microcracks on the fracture surface gradually change from pulse failure to transgranular failure, with the latter primarily comprising microcracks. By extending numerical simulations to 22% and 46% grades, it was found that the fracture surface became more prone to bilateral damage as the grade increased. The proportion of transgranular cracks increased from 8.9% to 33.8%. Additionally, the increase in the number of cracks accelerated microcrack propagation, leading to more severe fracture of the specimens.