Influence of the Iron Ore Pellets Macrostructure on Their Strength

The quality of iron ore pellets significantly affects the efficiency of pig iron and HBI production. The purpose of the work is to assess the potential for increasing the strength of iron ore pellets based on their macrostructure control. As a result of the study, it is found that the compressive strength of the pellets decreases monotonically at 20 daN/pel for each percentage of porosity. The external manifestations of structural defects (small crack, large crack, pellet fragments, pellet adhesions) are studied. It is revealed that the bulk of industrial pellets have optically detectable structural defects. At the same time, there is a lower content of fractured pellets and a higher proportion of aggregations in samples from a rich in iron concentrate. The crack orientation also depends on the degree of concentrate enrichment: in pellets with a higher iron content, the cracks are predominantly concentric, and with a decrease in the mass fraction of iron in the pellets, radial cracks predominate. Controlling the macrostructure parameters and the pellet strength is possible by forming a given porosity by adding fluxes and using polymer binders, minimizing the number and height of raw pellet overloads, obtaining dense row pellets with minimal porosity, organization of heat treatment of pellets with limited conditions for the defect formation—drying and firing rate, uniform thermal field across the width and height of the layer; cooling rate.