Effect on the Microstructure of Carbonized BF Slag with Different Cooling Methods

The phase compositions,microstructure and Ti C distribution of carbonized blast furnace slag（BF slag） obtained separately using air cooling and water quenching were studied by polarization microscope,SEM-EDS and MLA analysis,etc.The results show that there’s a large difference on the main mineral compositions between air cooling and water quenching slag.The air cooling slag is mainly composed of ordinary pyroxene,titanaugite,Ti C and perovskite,while the water quenching slag is principally made up of titanaugite,Ti-rich green pyroxene and Ti C.The distribution of Ti in air cooled slag is more concentrated than that of water quenching slag.Ti without forming Ti C in water quenching slag is almost distributed in the silicate phases evenly.The content of Ti and O in Ti C is 72% ~87% and 3% ~9%,respectively. It has a higher O content and lower Ti concentration for water quenching slag probably due to the counterreaction of Ti C during water quenching process.The phase microstructures of air cooling and water quenching slag are similar,mainly composed of silicates,Ti C and small amount of perovskite and Fe. The Ti C grains in water quenching slag are smaller,with about 80% of the Ti C particles having 0 ~20 μm of particle size.There’s a comparative distribution of Fe phase for both of the slags,and a spot of Ti C is concentrated at the boundary and inner of Fe phase.