| Corundum-spinel castables are widely used as working linings of steel ladles dueto their excellent high temperature service performance. However, its high thermalconductivity usually results in a striking decrease of temperature of the molten steel inthe steel ladles and leads to high temperature of the shell at the external surface ofsteel ladles, which increased energy consumption to meet the smelting smoothly. It iswell known that the low thermal conductivity of the heat insulation material need tohave high porosity. However, for refractories material, it should bring the highapparent porosity and decline the performance of resistance against slag corrosion.Hence, this work means to take advantage of the characteristics of foaming method,which produces uniform pore size distribution, high closed porosity, and controllablebulk density only through changing the foam dosage. Then, introduced the foam tomatrix and aggregate corundum-spinel castable, porous corundum-spinel castableswere designed and prepared, which ambitiously aimed at reduce the thermalconductivity and improve the thermal shock resistance on the premise that themechanical strength and slag resistance could be maintained. The work providestheoretical basis for the lightweight of working linings of steel ladles refractorycastable. Specific studies and results are as follows:(1) Porous corundum-spinel castable was prepared through introducing the foamto matrix corundum-spinel castable. A systematical investigation on differentproperties of samples, such as room temperature physical properties, high temperatureservice performance and thermal conductivity has been taken in this paper andscanning electron microscopy (SEM) was used to characterize the microstructure ofsamples. The results showed that when the addition foam content is200mL/kg, thecomprehensive performance was most close to conventional sample, but the thermalconductivity of samples have a sharp decrease. After110°C×24h, its bulk density is3.03g·cm-3; cold modulus of rupture (CMOR) and cold crushing strength (CCS) is10.1MPa and67MPa. After1550°C×3h, its bulk density is2.94g·cm-3; CMOR andCCS is27.1MPa and144MPa. Its retained strength ratio is29.0%and16.6%afteronce water quenching test and three times water quenching test, respectively. Its slagresistance is almost unchanged and compared with specimen without foam. Itsthermal conductivity is0.788W/m·K at1000oC and decreased by10%comparingwith specimen without foam.(2) Porous corundum spheres (PCS) that possess core-shell structure have been fabricated by foaming and wet granulation method. The results showed that themedian pore diameter of PCS is6.47μm. Unbroken PCS possess apparent porosity of10.9%and closed porosity of13.6%; broken PCS possess apparent porosity of15.5%and closed porosity of6.6%. The cylinder compressive strength of PCS is443.3MPa.(3) PCS that replaced the tabular corundum have been used as aggregates toprepare the porous corundum-spinel castables. It present micro expansionphenomenon. After110°C×24h, its bulk density is2.96g·cm-3; CMOR and CCS is10.3MPa and87MPa. After1550°C×3h, its bulk density is2.90g·cm-3; CMOR andCCS is28.7MPa and172MPa. It showed the higher corrosion index thancorundum-spinel castables which tabular corundum used as aggregates and showedbetter resistance to slag penetration. Its thermal conductivity is0.753W/m·K at1000oC and decreased by13.9%comparing with corundum-spinel castables which tabularcorundum used as aggregates. |
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