Crystallization behavior of blast-furnace slag by single hot thermocouple technique

Abstract

The crystallization behavior of blast-furnace slag under isothermal and continuous-cooling conditions was studied using the single hot thermocouple technique. The crystallization phases were obtained using FactSage software and X-ray diffractometry. The crystallization kinetic parameters were calculated by combining these results with the Johnson–Mehl–Avrami model. Under isothermal conditions, the shortest crystallization incubation time was 24 and 18 s when the temperatures were 1300 and 1150 °C, and the corresponding critical cooling rates were 4.5 and 14.3 °C/s, respectively. At 1270 °C, the slag was difficult to crystallize and the fiber-forming rate improved. When the continuous-cooling rate was 6.5 °C/s, the slag solidified into a glassy state. The main crystallization phases, gehlenite, akermanite, anorthite, and melangite, were most easily precipitated. The growth factors of melangite and anorthite were approximately 1.63 and 1.68, respectively, which indicated that the crystals nucleated on the surface and grew in two dimensions.