Effects of CaO content on sintering and lightweight of Al₂O₃–MgO–CaO refractories

Abstract

The effects of CaO content on phase evolution, sintering behaviour and densification process of Al₂O₃–MgO–CaO refractories were investigated. The addition of CaO decreased the initial sintering temperature of Al₂O₃–MgO refractory from 1300 to 1100°C associated with a reinforcement of grain–grain bonding and significant grain growth of calcium dialuminate (CA₂) from 1100 to 1200°C. Calcium hexaluminate (CA₆) grains with typical planar structures were formed, and the bulk density decreased with the addition of 8% CaO after firing at 1600°C because of the stabilised existence of the CA₂. Meanwhile, the relative density increased because of the resorption of porosity in the initial sintering stage and the promotion of grain growth at high temperatures, indicating that the lightweight, as well as the densification, of the Al₂O₃–MgO refractory was effectively improved.

Keywords:

• Al₂O₃–MgO–CaO
• Refractory
• Reaction
• Sintering
• Lightweight
• Densification