In this study, pot sinter tests were carried out to study the sintering properties of iron ores of different alumina (2-4-6%) level. It was observed that the 6% alumina level ores have a higher RDI values and decreased tumbler index (TI) compared to its other two counterparts. It was observed that an increase in composite fracture toughness (CFT) of sinter improves the Tumbler as well as RDI of the sinter. Beyond 4 CFT there is remarkable improvement in TI, RDI and RI values. The mechanical strength parameters of sinter phases were further correlated and analysed with respect to the chemistry of sinter and mineralogy of sinter phases. There is strong evidence which suggests that the Al 2 O 3 deteriorates the strength of the phases by making them hard and thus generating cracks in them. Unlike alumina, CaO and SiO 2 tend to stabilise and improve the strength of the phase.

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The softening and melting properties of ferrous materials are controlled by reduction degree, basicity, amount of gangue and flux, phase chemistry and their distribution in the microstructure. Design of laboratory softening-melting tests simulating blast furnace conditions greatly affects the reduction degree of the ferrous materials, since heating rate and reduction gas profile are key parameters affecting reduction degree of burden. Softening-melting behaviors of different blast furnace burden were compared by running laboratory tests under modified conditions. Comparing conventional and modified softening-melting test conditions, it can be said that modified test conditions are more practical adaptation of blast furnace conditions. SEM analysis indicated the primary mechanism for softening is due to presence of wustite as primary liquid slag former under modified test conditions, which is more close to blast furnace situation.

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Though sintering is controlled by kinetics of various reactions and is far from equilibrium, a thermodynamic analysis can provide useful inputs on melt formation and helps understand deviation from actual process conditions. The thermodynamic software 'FACTSAGE™' was used for this study. The general sequence of reactions during the heating cycle is as follows: decomposition of calcium carbonate to calcined lime; formation of calcium ferrites/silicates; decomposition of calcium ferrites, reduction of haematite to magnetite and formation of spinel and silicates; assimilation of ferrites, silicates, spinel and magnetite into the melt. During the cooling stage, the amount of melt decreased with subsequent precipitation of phases such as magnetite, ferrites, silicates, spinel and formation of haematite. It is very much clear that the sinter made by using higher alumina levels generate fewer amounts of oxides and more slag phase compared to its low alumina counterpart.