Effect of Mild-calcined Coal Gangue Addition on Hot Strength and Thermal Shock Resistance of ULC Castables in Al_2O3-SiO_2 System

摘要

This work explored the way to improve hot strength and thermal shock resistance (TSR) by adding mild-calcined coal gangue (MCG) in Al_2O_3-SiO_2 ULC castables, making use of the in situ effect of the MCG during heating-up. The influence of respective additions of 5%, 10% and 15% of the MCG powders calcined at 700 ℃ was investigated on HMOR at 1400℃ and thermal shock resistance, by 1100 ℃-water quenching, of the castables. With increased addition of the MCG, the HMOR and the TSR become significantly enhanced. At 10% of the MCG addition, the HMOR is around 3MPa, as compared to 0.27MPa in the case of no MCG addition. At 5% of the MCG addition, the residual CMOR ratio after 1 cycle of the thermal shock remains around 45%, in comparison to 12% when without any MCG addition. The microstructure of the heated castable samples was also investigated by SEM. The in situ formed needle-like and interlaced mullite in the matrix is contributive to the improvement.