Development of a bonding phase within titanomagnetite-coal compacts
The development of the bonding phase within reduced ironsand-coal compacts was studied to investigate the reduction of ironsand-coal compacts and to understand how the oxide bonding phase develops during reduction. Ironsand ore and sub-bituminous coal were mixed and pressed into compacts which were reduced by heating in a thermogravimetric furnace (TGA) to 1 350°C under argon. The reduced compacts were characterised in terms of their composition, strength and microstructure. The strength in the reduced compacts is brought about by slag bonding between the relict ironsand particles. Formation of a metallic network was limited, and seen only in relatively few samples. As the ironsand particles reduce, oxides surrounding the sponge iron structure form a slag. Slags from different particles then join to form a slag network between the particles. The formation of a slag and the bonding between the particles is aided by inherent silica and added lime. Reducing the spacing between ironsand particles in the green compacts was found to be important in increasing inter-particle bonding. Increasing the coal-iron ratio in the compacts increased the spacing and decreased the bonding. Decreasing the ironsand particle size decreased the spacing between ironsand particles, and increased the bonding in the reduced compacts.