Effect of cooling methods on the mineralogical composition and microstructure of low titanium-containing blast furnace slag

The mineralogical composition,microstructure and TiO₂ distribution rule of low titanium-containing blast furnace slags after water cooling and air cooling were investigated by X-ray diffraction,polarization microscopy and scanning electron microscopy.The results show that main mineralogical compositions in these slags are all vitreous,gehlenite,perovskite and merwinite,but the contents of mineral components in the two kinds of slags have much larger differences. The average contents of gehlenite and perovskite in the air-cooled slag are 62.5% and 12.5%,which are 2.27 and 1.92 times as large as those in the water-cooled slag,respectively.The content of vitreous in the air-cooled slag is less than a third of that in the water-cooled slag. The mineralogical microstructure of the water-cooled slag is pretty different from that of the air-cooled slag. Gehlenite in the water-cooled slag is dentate,but in the watercooled slag it is feathery and needle-shaped,and its grain size is smaller. Perovskite forms as star points and dendritic in the watercooled slag and the air-cooled slag,respectively. Merwinite is spindle-shaped both in the water-cooled slag and the air-cooled slag. It could be concluded that TiO₂ in the water-cooled slag mainly distributes in perovskite,vitreous glassy and gehlenite,but TiO₂ in theair-cooled slag mainly distributes in perovskite and gehlenite,and the distribution ratio of TiO₂ in the air-cooled slag is 8.41% higher than that in the water-cooled slag. Air cooling is more beneficial to increase TiO₂ content in perovskite.