The microporous corundum material was prepared using alumina micro-powder as the main raw material,alumina sol and starch as binders by a wet process,achieving the bulk density of 3. 05 g·cm^(-3),the apparent porosity of 9. 1%,the closed porosity of 12. 3%,the median pore diameter of 0. 43 μm,and the thermal conductivity of 6. 5 W·m^(-1)·K^(-1)at 800 ℃ which is41. 6% lower than that of common corundum. The slag resistance of the microporous corundum material was studied by immersion and compared with that of the common corundum aggregate, and the slag resistant mechanism of microporous corundum material was revealed. The results show that the slag resistance of the microporous corundum material is superior to that of the common corundum aggregate,the SEM and EDX show that on the reaction interface between microporous corundum and molten slag,a continuous isolation layer with a large quantity of CA_2 and CA_6columnar crystals is formed; while the common corundum aggregate reacts with the molten slag interface to form a discontinuous isolation layer of columnar crystals,through which a lot of molten slag corrodes or permeates into the aggregate. The mechanism is mainly that the microporous structure is more advantageous to nucleation and growth of CA_2 and CA_6 columnar crystals; in the reaction with the aggregate,the molten slag gets saturated and the critical solution thickness of the microporous corundum and the common corundum is 0. 16 μm and 0. 34 μm,respectively,this is caused by the smaller microporous corundum aggregate pores; and the smaller pores also increase the second phase ripening rate of microporous corundum,which is 9. 7 times of that of the common corundum.
FU LyupingHUANG AoGU HuazhiZHANG MeijieLI ZhengkunZHAO Yi
Corundum-spinel castables containing lightweight aggregates have drawn many attentions due to their potential for energy-saving,especially when applied in the high-temperature region,such as the work lining of refining ladle. One main aspect that restricts their application is the slag corrosion performance. In this study,one dense tabular corundum and three kinds of lightweight corundum were chosen as aggregates to prepare four different corundum-spinel castables. The slag resistance was compared through the induction furnace corrosion test. SEM-EDS,XRD,and thermodynamic and kinetics analysis were adopted for the discussion of the corrosion mechanism. Results show that the crystal grain size and shape of aggregates are important for the slag corrosion resistance of lightweight corundum-spinel castables under dynamic condition( enforced convection),yet the effects of pore characteristics are not dominated. Aggregates with large flake-like crystal grains show a thicker dissolution diffusion boundary layer and a lower dissolution rate,resulting in a favorable corrosion resistance of the castable. The poor microstructure of the aggregates,namely,larger pores and small and spherical grains,would cause deterioration of castables ' slag resistance.
