关键词: 刚玉质浇注料, Al₂O₃微粉, 粒度, 中低温强度

Abstract: During baking and service,alumina castables generally suffer strength degradation after medium- and low-temperature heat treatment compared with their cohesive bonding strength at room temperature and sintering strength at high temperatures.To overcome this medium- and low-temperature strength defect,alumina castables were prepared using tabular corundum aggregates and fine powder,and alumina ultra-fines as main raw materials,and calcium aluminate cement as the binder.All specimens were dried at 110 ℃ for 24 h and subsequently heat-treated at different temperatures for 3 h:400,600,800,900,1 000,1 100 and 1 200 ℃.The cold modulus of rupture,cold compressive strength,phase composition and microstructure of castables containing Al₂O₃ micropowders with different average particle sizes (about 4,2,1 and 0.8 μm) were investigated.The results show that the strength of the specimens increases with the decreasing particle size of Al₂O₃ micropowder.In the temperature range of 110-1 200 ℃,the specimens with 0.8 μm Al₂O₃ micropowder exhibit the most stable cold modulus of rupture,which effectively avoids the medium- and low-temperature strength degradation of the castables.

Key words: alumina castables, alumina ultra-fines, particle size, medium- and low-temperature strength