The deep-bed filter is a new type of filter device developed in recent years. It is composed of multiple layers of alumina balls and a layer of alumina grit of appropriate size. The size and stacking method of alumina balls and gravel are determined according to the quality requirements of the final product. The combination of deep bed filter device and ceramic foam filter has a better filtering efficiency for molten metal.
The filter bed is a porous medium. The bed body is designed and calculated according to the requirements to ensure that the aluminum liquid achieves laminar flow and prevent secondary pollution from destroying the alumina layer. Under the action of gravity, the path of the liquid aluminum flowing through the tortuous filter layer is as long as possible, so that the impurity particles are trapped or deposited on the filter bed. It is suitable for the needs of high-demand semi-continuous casting production, and the single casting-rolling production line with smaller output is currently used less.
The use of a deep bed filter device must make the molten aluminum completely soak the filter bed. Otherwise, the temperature of some parts will be too low, causing the aluminum liquid to solidify, reducing the flow area, shortening the flow path, and affecting the effect and service life of the filter bed. Therefore, before the bed is filtered, on the one hand, it must be fully preheated to keep the bed heated evenly. On the other hand, it is necessary to fill the filter bed with a proper temperature of molten aluminum and a proper flow rate. The filling process is: inject liquid aluminum from the outlet of the filter bed, so that the aluminum liquid rises from the bottom of the filter bed, and slowly spreads over the top of the filter bed to ensure that the filter bed is 100% immersed in the liquid aluminum.