Influence of Al2O3 content on crystallization behaviors of blast furnace slags in directional solidification process

Focusing on the heat recovery of BF slag by dry granulation technology, an improved directional solidification method combines with X-ray diffraction (XRD) is promoted to explore the influence of Al2O3 content on crystallization behaviors of BF slags in a phase-change cooling process. In the current research, the crystallization process is on real-time reflected by the temperature distribution inside the slag. Moreover, the type and content evolutions of crystal phase were obtained by analyzing the XRD patterns. Furthermore, Scanning Electron Microscope (SEM) was adopted to investigate the morphology evolution of the crystal phase. The results indicated that with an increase in Al2O3 content, the primary crystal structure transformed from Akermanite to Gehlenite. Moreover, the transformation of the crystal structure led to a decrease of critical cooling rate and an increase in critical supercooling degree. Furthermore, the crystal phase precipitated in a varying temperature interval, which was governed by the average cooling rate and primary crystal structure. In addition, the growth mode of the crystal phase transformed from columnar pattern to equiaxed pattern with a decrease in average cooling rate. Furthermore, the transformational cooling rate of growth mode decreased with increasing the Al2O3 content.