Crystallization of molten blast furnace slag directly affects the fibre forming rate and stability of fibre. The single hot thermocouple technique was used to investigate the crystallization behaviour of modified blast furnace slag. The results revealed that, with increasing acidity coefficient of modified blast furnace slag during the isothermal process, the initial crystallization temperature of modified blast furnace slag gradually decreased, which were at 1390°C, 1330°C and 1180°C, respectively, and TTT curves changed from double C-type curve to single C-type curve. Through a continuous cooling process, the critical cooling rate decreased from 6°C s −1 to 0.5°C s −1 when the acidity coefficient of modified blast furnace slag increased from 1.05 to 1.40. Based on these findings, we conclude that, the crystal growth rate is controlled by diffusion driving force and undercooling driving force.
The forming of rings was a key problem of magnesian flux pellets in rotary kiln, which seriously limited production efficiency. Pellet powder and flux were the raw materials of the ring. Based on this, the bonding strength, melting behavior and microstructure of pellet powder and its mixed powder with flux were investigated. The influence of basicity (R = CaO/SiO2) on ring behavior of pellet powder was analyzed, and ring formation mechanism of magnesian flux pellets was clarified. The results showed that acid pellet powder was not easy to form rings due to lower bonding strength of briquettes. Due to changes in bonding process after mixing of flux, magnesian flux pellet powder produced ferrite and silicate liquid phase with lower melting point, which promoted diffusion and recrystallization of hematite and enhanced compressive strength of briquettes, then finally caused rings to form. Moreover, it is required to control roasting temperature below 1200 °C, which is a necessary condition for magnesian flux pellet powder to form an initial ring which was easy to be destroyed.
The forming of rings was a key problem of magnesian flux pellets in rotary kiln, which seriously limited production efficiency. Pellet powder and flux were the raw materials of the ring. Based on this, the bonding strength, melting behavior and microstructure of pellet powder and its mixed powder with flux were investigated. The influence of basicity on ring behavior of pellet powder was analyzed, and ring formation mechanism of magnesian flux pellets was clarified. The results showed that acid pellet powder was not easy to form rings due to lower bonding strength of briquettes. Due to changes in bonding process after mixing of flux, magnesian flux pellet powder produced ferrite and silicate liquid phase with lower melting point, which promoted diffusion and recrystallization of hematite and enhanced compressive strength of briquettes, then finally caused rings to form. Moreover, it is required to control roasting temperature below 1200℃, which is a necessary condition for magnesian flux pellet powder to form an initial ring which was easy to be destroyed.
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