Study on structure and properties of low carbon spinel-C refractory composites

The formation mechanism (gas-gas, gas-solid) of magnesia-alumina spinel was investigated under carbon-containing atmosphere. Meanwhile, the influence of in-situ spinel formation and additives on structure and properties of low carbon spinel-C was researched. Mg(g) was formed by carbon thermal reaction which reacted with alumina (gas-solid) and Al2O(g) (gas-gas). The presence of carbon promoted the formation of spinel by gas-phase reaction. Spinel of in-situ formation strongly improved strength performance, thermal shock resistance and slag corrosion resistance of low carbon spinel-C materials. The addition of superfine graphite and expanded graphite was beneficial to thermal shock and room/high temperature flexure strength respectively. Al-Si alloy and B4C worked together obviously improving flexure strength of spinel-C materials in a wide temperature range. The synergistic interaction of Al-Si and B4C provided the higher oxidation resistance for low carbon spinel-C materials than that of single component. Si powder significantly improved thermal shock resistance for all spinel-C samples. However, the excessive Si powder was adverse to slag corrosion resistance. So the magnesia and α-Al2O3 were added which obviously enhanced slag corrosion resistance of low carbon (8% graphite) spinel-C materials.