CFF filtration purification is to remove the large inclusions and some suspended fine inclusions carried in the molten aluminum through the filter medium, reduce the gas content in the molten aluminum and remove some harmful elements in the molten aluminum, and change the physical properties and solidification characteristics of the molten aluminum. CFF filtration purification is a technology to improve the mechanical properties of aluminum. At present, the CFF (ceramic foam filter) filtration is the most effective and most widely used technology in the filtration and purification technology.
The ceramic foam filter is a three-dimensional continuous network structure composed of fine ceramic branch skeletons. The filtering mechanism has three aspects:
1. Block debris particles at each hole of the filter plate, and in some places even accumulate into “filter cake”, and the “filter cake” can block some smaller inclusions.
2. When the metal melt passes through the filter plate, due to the tortuous channels inside the filter plate, the flow rate of the melt changes greatly, and some very small impurity particles settle in some corners of the filter plate.
3. Because the filter skeleton has a huge surface, and the ceramic skeleton itself is also a porous ceramic body with interconnected pores and micro channels inside. The ceramic surface is not wetted by molten metal and has a strong adsorption capacity, which can absorb inclusions in the alloy that are not wetted by molten metal.
The combined effect of the above three mechanisms can not only filter out fine inclusion particles as small as 10-20um in the aluminum melt, but also filter out liquid flux inclusions and some harmful metal elements that are difficult to filter with ordinary filter media.
When the foam ceramic filter plate is working, it is responsible for filtering the aluminum melt by placing it on the production line of semi-continuous casting or continuous casting and rolling.
Therefore, the foam ceramic filter board should have the performance:
1. Have sufficient mechanical strength;
2. It has high thermal shock resistance and scouring performance;
3. Have sufficient porosity and metal liquid permeability;
4. Has extremely low gassing properties;
5. Has high chemical stability.
In the casting process, foam ceramic filter plates should be selected according to different filtration precisions, different flow sizes and flow rates. Under normal circumstances, the 30PPI foam ceramic filter plate meets the requirements.