ABSTRACT
The Chapter describes the induration reactions with respect to the magnetite- and hematite-bearing pellets and the phases formed. The formation of minerals as consequence of oxidation of magnetite at different stages of induration is discussed. The factors affecting the oxidation kinetics are outlined. The characteristics of pellet induration in terms of recrystallization of hematite grains and its growth are discussed. The hematite pellets require a higher temperature and longer firing time than that of magnetite. The various bonding and phases in the indurated pellets that take place through a sequence of chemical reactions, and are responsible for its strength, are outlined. First, the silicates and ferrites are formed, which then react with each other and with alumina to form silicoferrites of calcium and aluminum (SFCAs). The effect of pellet basicity and MgO in the formation of ferrite-oriented minerals and oxide bonding is discussed. These minerals are conducive for higher strength, lesser swelling index, improved reduction parameters, and also better softening-meltdown characteristics. The mechanism and process of formation of duplex structures in fired pellets are described. The effects of pellet size and MgO addition on the formation of duplex structure are also described.
