Thermal characteristics of Al 2O 3–MgO and Al 2O 3–spinel castables for steel ladles

Abstract

The hot properties of the Al 2O 3–MgO castables containing 5.5 wt.% MgO and 1.36 wt.% CaO with and without the addition of 0.75 wt.% microsilica and the Al 2O 3–spinel castables containing 20 wt.% Al 2O 3–rich spinel of 90 wt.% Al 2O 3 and 1.70 wt.% CaO, respectively, were investigated. The thermal shock damage test using the prism quench into water technique indicated that the retained modulus of rupture of the Al 2O 3–MgO castables after three cycles was down to 5%, while that of the Al 2O 3–spinel castables was 51%. The combined test of slag and thermal shock attack on castables using the rotary slag test furnace showed that the Al 2O 3–MgO castables had 0% penetration and 24% erosion, while the Al 2O 3–spinel castables had 10% penetration and 30% erosion. The field trials confirmed that Al 2O 3–MgO castables have better slag resistance and a longer service life for use in steel ladles, compared to Al 2O 3–spinel castables. The importance of thermal shock damage resistance of castables for use in steel ladles should be de-emphasized, based on the lab and field tests. There is no correlation between hot strengths and slag resistance for castables. The magnitude of specific surface area of pores is more important than pore size and porosity for governing the slag resistance of Al 2O 3–MgO castables, with and without microsilica addition.