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Application of Foamed Ceramics: Filtration of Molten Metal
2022-09-22

Foamed Ceramics is a porous material. It has the material characteristics of three-dimensional network structures and high porosity. Its pore size ranges from nanometer to micrometer. It has the advantages of high porosity, large specific surface area, thermal shock resistance, and high-temperature resistance.

Application of Foamed Ceramics

Foam ceramics have been widely used in many fields. In addition to purifying the metallurgical industry and filtering molten metal, it is also used in thermal insulation materials, chemical catalyst substrates, and other applications.

foamed  ceramics

Filtration of Molten Metals

Foam ceramic filters are mainly used in casting processes to purify liquid casting alloys. It reduces or eliminates various non-metallic inclusions and outgassing problems in castings.

Casting scraps due to casting defects such as non-metallic inclusions account for up to 50%-60% of the total scrap. At the same time as various costs increase, the outflow of excess waste products can cause damage to the external environment. Inclusion defects not only seriously drag down the mechanical properties and casting properties of the castings, but also have a detrimental effect on the machining and appearance of the castings.

The history of solving non-metallic inclusions

To solve this problem, people initially used barbed wire, perforated steel plates, etc., to make simple filters inserted into the gating system to remove inclusions. Later, two-dimensional structures such as silicate pin fibers and boron nitride fibers were used. Nowadays, ceramic foam filters use pore size to mechanically intercept large particles of mixed oxides, and use filter cake to filter small particles of mixed oxides. And with adsorption and rectification ability.

The production line using ceramic foam filters has significantly improved the casting yield. For example, after an automobile foundry used foam ceramic filters, the yield increased from 65.3% to 71.5%. Only from the weight of the pouring riser, the molten iron is saved by 6%. Filtered castings are also significantly harder, which in turn extends the life of the cutting tool.

How to make a foamed ceramics filter?

The ceramic foam filter generally uses polyurethane foam as a carrier, immersed in a ceramic slurry made of refractory aggregate sintering aids, binders, and other micro powders and water, and then extrudes excess slurry, and the rest is wrapped in The ceramic material around the foam fiber is dried, fired and sintered at a high temperature. Finally, the foam-like ceramic product is left.

The pouring temperature of the casting alloy is different, and the foam ceramic filter of the refractory material should be selected differently for the casting. In recent decades, according to the properties of different material alloys, a variety of material foam ceramic filters have been developed.