Chromite sand for ladle filler
Chromite sand is a kind of chilling material, and 46% Cr2O3 Chromite sand is the main material for producing chrome-based ladle filler sand (Drainage sand). Chromite sand for ladle filler is one of the main applications of natural chromite sand.
In continuous casting production, the automatic pouring rate of molten steel is very important. The pouring rate refers to the volume rate of molten steel entering the mold. If the speed is too slow, the metal will cool and solidify before filling the mold cavity. Therefore, it is particularly important to improve the automatic pouring rate of continuous casting. The quality of ladle filler sand has a direct impact on the pouring rate.
The filler sand is located in the gap between the ladle bottom protector and the nozzle. It fills in the whole nozzle to the bottom of the ladle. At the initial stage of molten steel smelting, the filler sand above the nozzle contacts the molten steel and then rapidly sinters to form a sintering layer with molten steel infiltration. The filler sand below the nozzle shall withstand the static pressure of molten steel without being damaged. When the pouring starts, the part of the drainage sand that is not sintered falls due to its own weight, and the sintering layer loses its support and breaks so that the molten steel flows out and the pouring is realized. If adopt siliceous drainage sand with quartz sand as the main raw material, the open pouring rate will decrease significantly after the open pouring time exceeds 1 hour. This is because the sintering layer of siliceous drainage sand will gradually thicken and be difficult to break, and the molten steel cannot break through and flow out normally.
However, with the wide application of secondary refining and continuous casting process in iron and steel production enterprises, the procedure of pouring will be up to more than 2 hours, and the siliceous filler sand cannot meet the requirements of maintaining the rate of pouring. Chrome filler sand gradually replaces silica filler sand.
The main component of chrome filler sand is natural chromite sand with Cr2O3 content higher than 46%. It can keep the casting rate above 95% even the standing time of molten steel exceeds 100 minutes. The excellent performance of chrome filler sand comes from the superior thermal properties of chrome ore sand:
The specific gravity of chromite sand is high, up to 4.0-4.8g/cm3. It can drop from the nozzle easily after pouring.
Chromite sand has strong slag resistance. It can prevent corrosion and penetration of molten steel.
Chromite sand has strong chilling properties and high sintering temperatures. The sintering temperature is min.1800°C. The sintering layer of the drainage sand can be rapidly formed. In the meantime, it chilled down without affecting the solidification of unsintered filler sand. Thus, the sintering layer is thin and the pouring rate is increased.
The grain shape of chromite sand is sub-granule even after crushing. There are no obvious edges and corners, and the fluidity is good.
Therefore, chrome filler sand is popular for many iron and steel production enterprises. The generally used specifications of chromite sand for filler sand are AFS30-35, AFS35-40, AFS40-45, AFS45-50, etc.
