The effect of additives on Al2O3–SiO2–SiC–C ramming monolithic refractories

Abstract

The aim of this study is to describe the effect of containing additives on increasing cold crushing strength (CCS) and bulk density (BD) of Al2O3–SiO2–SiC–C monolithic refractories. Two series of carbon containing monolithics were prepared from Iranian chamotte (Samples A) and Chinese bauxite (Samples B), as 65 wt.% in each case together with, 15wt.% SiC-containing material regenerates (crushed sagger), 10 wt.% fine coke (a total of 90% aggregate) and 10 wt.% resole (phenol formaldehyde resin) as a binder. Different types of additives (such as silicon and ferrosilicon metal) are added to a batch of 100 g of mixture and the physical and mechanical properties (such as BD, apparent porosity and CCS) are measured after tempering at 200°C for 2 h and firing at 1100°C and 1400°C for 2h. After low temperature tempering at 200°C, silicon and ferrosilicon contribute to the formation of stronger cross linking in the resulting structure and provides CCS values as high as 65 MPa. After high temperature sintering, at 1400°C, SiC whiskers of nano sized diameter are formed due to the presence of Si and FeSi2 and increases the CCS values of the refractories as high as 3–4 times in sample containing 6wt.% ferrosilicon metal as additive, compared to the material without additive. The temperature of 1100°C is a transient temperature, used in high temperature sintering.