Ceramic foam materials are particularly suitable for filtering molten metals, mainly due to their excellent filtering efficiency, low cost, and ease of use.
Since the filter is designed as a disposable item, it is necessary to provide an effective sealing method for the filter to be fixed in its bracket, which is easy to assemble, disassemble and clean. The bracket or filter chamber itself is usually a component of the tank, pouring tray or tundish, etc., and should be made of refractory material resistant to molten metal, similar to the refractory material used in standard launder structures. We provide fire-resistant filter linings for placing ceramic foam filters.
It is very preferable to seal the filter using elastic sealing gaskets on the oblique plate of the filter. The gasket-type seal ensures leak-free installation and provides an effective separation medium, which is essential for easy disassembly. In addition, because the gasket prevents metal from entering the sealing surface of the bracket unit, their use greatly simplifies the cleaning work and effectively extends the service life of the unit by eliminating the problem of metal corrosion. In addition, due to its elasticity, the gasket can provide sufficient friction to fix the filter body in the bracket without the need for other types of pressing devices. The elastic sealing device should be non-wetting to the specific molten metal, resist chemical attack from it, and have sufficient fire resistance to withstand high operating temperatures.
So far, ceramic foam materials for filtering have been sealed with pre-cut low-density ceramic fiber strips with organic binders. After the filter is baked and fired, the straight pre-cut strips are simply glued to the beveled edge of the filter.
Another gasket technology for foam ceramic filters involves applying an expandable gasket material with an adhesive release backing to the filter. The material is manually cut and installed around the filter.