PROPERTIES IMPROVEMENT OF LIGHTWEIGHT Al_2O_3-SiO_2 CASTABLES BY ANDALUSITE ADDITION

摘要

High performance light weight castables (LWC) in Al_2O_3-SiO_2 system are increasingly needed for energy saving, for which concerns in terms of shrinkage, insufficient strength, etc must be eliminated by improving properties. This work investigated the role of andalusite addition in improving properties of LWC using mullite based hollow balls as aggregates. The effect of andalusite additions up to 30% at an interval of 6% was investigated on bulk density, permanent linear change (PLC), hot modulus of rupture (HMOR), refractoriness under load (RUL) and thermal conductivity (TC). By means of SEM, microstructure of the related samples was also characterized. The mullitization effect of the added andalusite leads to improved PLC, cold strength, HMOR and RUL of the LWC without degrading TC. The improvement by andalusite addition is attributed to the favorable matrix microstructure featured by interlaced mullite derived from andalusite, dotted with SiO2-rich liquid phase within the mullite based network.