Crack generation in blast furnace slag bearing high titanium by microwave cyclic heating

In order to facilitate grinding a blast furnace (BF) slag bearing high TiO₂ (Ti-BF slag) for extracting CaTiO₃ (TiO₂ containing phase) from it, microwave (MW) cyclic heating was attempted to induce cracks. In this study, MW heating behavior of Ti-BF slag, general BF slag and sintered perovskite (CaTiO₃) body were examined. Under the same heating conditions, Ti-BF slag was heated better than the general BF slag. And the sintered perovskite powder compact was heated best among them. Considering the measured large permittivity of Ti-BF slag, the perovskite phases in the Ti-BF slag are responsible for heating of the whole slag. Cracks were induced in the Ti-BF slag by cyclic irradiation of MW. They extended and opened as an increase of the cycle number. In order to examine the effect of the induced cracks on the strength of Ti-BF slags, compression test of the specimens was performed after the treatment. It was demonstrated that MW treatment caused reduction in the compressive strength, such that the strength decreased about 35% after 10 cycles of heating for 5 min. It was also shown that while the treatment with longer heating time caused a smaller decrease in the compressive strength, increasing of cyclic number decreased the strength more effectively.