Effect of fused magnesia on properties of bauxite based castables

Abstract: In this study, special grade bauxite and fused magnesia were used as the main raw materials to investigate the effect of the addition form and amount of fused magnesia on the properties of bauxite based castables. The flexural strength at high temperature from 1000 ℃ to 1400 ℃ and the properties after sintering at 1550 ℃ were tested. The results of high-purity magnesia show that with the increase of the amount of fused magnesia, the amount of magnesia-alumina spinel in bauxite based castables increases after sintering at 1550 ℃; Compared with the samples added with fused magnesia powder, the samples added with fused magnesia particles produce less liquid phase at high temperature, more magnesia-alumina spinel, larger apparent porosity and lower strength after sintering at 1550 ℃. At 1000 ℃, the high temperature bending strength is high, at 1200 ℃, the high temperature strength is reduced due to the liquid phase, and at 1400 ℃, there is basically no high temperature strength due to the large amount of liquid phase.

Refractory castables are the main varieties of unshaped refractory materials, which are made by mixing aggregates with a certain size grading with powder, binder and additives. They have the advantages of simple production process, convenient construction and long service life. Bauxite-based castables have excellent high temperature strength, creep resistance, thermal shock resistance, high operating temperature, low production cost and wide range of application, and are often widely used as lining materials for thermal kilns and metallurgical equipment. Lei Zhongxing et al. added fine magnesia powder into bauxite based castables, and found that with the addition of fine magnesia powder, the sample strength first increased and then decreased after drying, and the linear change rate after burning increased, but the strength after burning decreased. Liu Xinhong and others added SiO2 micro-powder into the bauxite based castable, and found that the normal temperature strength and high temperature bending strength of the sample increased with the addition of SiO2 micro-powder. Li Peijia and others added sillimanite to the bauxite based castables, and found that with the increase of sillimanite addition, the normal temperature strength and bulk density of the castables decreased. When the mass fraction of sillimanite was 4%~8%, the comprehensive performance of the castables was better. In this paper, the effects of different amounts and ways of adding fused magnesia on the sintering properties, normal temperature properties and high temperature properties of aluminum castables were studied.