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

摘要： 刚玉质浇注料在烘烤和使用过程中,相比于常温的凝聚结合强度和高温烧结强度,中低温度热处理后强度往往有所降低。为了避开刚玉质浇注料的中低温强度缺陷,以板状刚玉颗粒和细粉、Al₂O₃微粉为主要原料,以铝酸钙水泥为结合剂制备了刚玉质浇注料。研究添加不同粒度(平均粒度分别约为4、2、1和0.8 μm)Al₂O₃微粉的刚玉质浇注料经110 ℃干燥24 h,再经400、600、800、900、1 000、1 100、1 200 ℃保温3 h热处理后的常温抗折强度和常温耐压强度及其物相组成和显微结构。结果表明:随着Al₂O₃微粉粒度变细,试样的强度变大;在110~1 200 ℃温度范围内,添加平均粒度约为0.8 μm的Al₂O₃微粉的试样常温抗折强度最稳定,避免了浇注料中低温强度降低。

关键词: 刚玉质浇注料, Al₂O₃微粉, 粒度, 中低温强度