Research On Properties Of MgO-Al₂O₃ Based Castable For Ladle Slag Line

With the progress of metallurgical technology, increment of high-quality steel and continuous casting rate, the technology of secondary refining was used widely. For the requirements of continuous casting and clean steel, the capability of ladle enlarged, the temperature of molten steel raised and its stay prolonged, which made the ladle's service environment worse than before. The refractory in slag line had become one of the most severely damaged parts in the ladle because it was flushed severely by molten steel and corroded strongly by molten slag. Its service life dismatched with side wall of the ladle, which increased the consumption of refractory and the labour of workers, so it was important to develop carbon-free and long-life castable for the ladle slag line. MgO based refractory is one of the most important candidate materials for slag line, but its slag infiltration resistance was bad, what decreased the service life of MgO based refractory, so the paper emphasized how to improve the properties of slag infiltration resistance of MgO based refractory. What had been done in this paper was divided three parts:The first part focused on the influences of binders on properties of MgO based castable, to find the suitable binder and addition. The influences of microsilica and calcium aluminate cement on the properties of MgO based castable were studied. The experimental results indicated that the MgO based castable had the best comprehensive properties when the additions of microsilica were 3%. The properties of slag infiltration resistance of MgO based castable became very bad when calcium aluminate cement was used as binder.The second part focused on the influences of compositions of matrix on properties of MgO based castable, to find the suitable compositions of matrix. The influences of MA spinel powder and microfine α-Al₂O₃ on the properties of MgO based castable were studied. The experimental results indicated that the slag infiltration resistance of samples became better and slag corrosion resistance became feebleness, with the increasement of additions of MA spinel power, the cold modulus of rupture and crushing strength of the samples at 1100℃×3h and 1550℃×3h decreased at first and increased later. It also showed the similar tendency that the properties of slag resistance with the increasement of additions of microfine α -Al₂O₃, but the cold modulus of rupture and crushing strength of the samples at 1100℃ ×3h and 1550℃ ×3h always decreased. The samples adding microfine α-Al₂O₃ had better properties of slag infiltration resistance and worse properties of slag corrosion resistance than adding MA spinel powder at the same additions.The third part focused on the influences of additives on properties of MgO-Al₂O₃ based castable, to find the suitable additives to improve the properties of slag resistance of castable. The influences of additions of zircon powder,TiO₂ powder, Cr₂O₃ powder, white corundum and ferric oxide powder on the properties of MgO-Al₂O₃ based castable were studied. Theexperimental results indicated that the ferric oxide powder and white corundum were beneficial to the properties of slag infiltration resistance of samples, but the zircon powder, TiO2 powder and Cr2O3 powder were disadvantageous to the properties. With the increasement of additions of ferric oxide powder in the matrix, the cold modulus of rupture and crushing strength of samples at 1100°C><3h and 1550°C><3h were improved, but the thermal shock resistance were weakened, slag corrosion resistance of samples became a little feeble and slag infiltration resistance became better apparently.