The ceramic foam filter is a grid of curved holes, and the molten metal must pass through the tortuous channel to enter the cavity. Large inclusions, which are too large to pass through the channel, are caught on the surface of the filter. As the increase of inclusion, the inclusions accumulate on the surface of the filter sheet and gradually form a filter cake so that only very fine particles can pass.
The molten metal flows through the filter cake and enters the tortuous channel of the lower layer. The mechanism of foam filtration is to change the direction of the molten metal many times and reduce the flow rate, resulting in smaller particles being adhered to the surface of the filter by the inside of the filter. The foam filter is also very effective in removing non-metallic inclusions generated during melting.
The ceramic foam filter prevents the formation of secondary oxidation slag by changing the flow state of the molten metal, reducing turbulence into the cavity, and effectively preventing air entrainment.
For all alloys, especially alloys that are prone to oxidation, turbulence must be eliminated as much as possible during the casting process. Turbulence will cause entrainment of gas and slag, producing secondary oxides, and new oxidation slag will be generated due to the exposure of clean molten metal to the atmosphere.
Choosing the molten metal filter correctly and applying it correctly can play a very important role in preventing secondary oxidation. In a sense, the correct use of ceramic foam filters is more important than the role of the filter itself.
The ceramic foam filter has the performance of making the molten metal stable, but this is only the characteristic of the filter. To make it fully utilize this characteristic, it must be matched with a reasonably designed filter box to achieve stable filling, reduce turbulence and The role of entrainment. The filter has such excellent characteristics, but if the design of the entire filter system is unreasonable and the placement of the filter is unreasonable, it will not play such a role.