Foam Ceramic Filters Used in Metal Casting Processes to Filter and Purify Molten Metal

Foam ceramic filter is a porous ceramic device used to purify molten metal. Its core function is to efficiently remove non-metallic inclusions, bubbles, and oxides from molten metal during the casting process, thereby significantly improving the yield and internal quality of castings.

It uses polyurethane foam as a carrier and is manufactured through processes such as impregnation with ceramic slurry (e.g., alumina, silicon carbide, zirconium oxide, etc.), drying, and high-temperature firing, ultimately forming a ceramic product with a three-dimensional interconnected curved porous network skeleton structure.

This structure gives it an open porosity of 80%-90%, enabling deep purification of molten metal through multiple mechanisms such as mechanical interception, scum rectification, deep adsorption, and filter cake sieving.

Foam ceramic filters achieve high-efficiency purification through four mechanisms:

1.Filter cake screening: intercepting large particulate impurities;

2.Deep bed filtration: adsorbing tiny suspended solids within the pores;

3.Rectifying effect: converting turbulent flow into laminar flow, reducing molding impact;

4.Scum separation: promoting the flotation and separation of impurities.

Experiments show that its filtration efficiency can reach 95%, far exceeding the 67% of traditional fiber filters.

1. Foundry Industry: Molten Metal Purification.

The primary application of foam ceramic filters is in the casting processes of aluminum alloys, cast iron, cast steel, and copper alloys. They are used to filter non-metallic inclusions (such as oxides, slag, and sand particles) from the molten metal, significantly improving casting quality.

1) Aluminum Alloy Casting: Alumina (AlO) foam ceramic filters effectively remove micron-sized inclusions from molten aluminum, reducing porosity and slag defects. They are widely used in the production of precision components such as automotive wheel hubs and engine blocks.

2) Cast Iron and Cast Copper: Made of silicon carbide (SiC), these filters withstand temperatures up to 1550°C and are suitable for filtering high-density, high-thermal-shock molten copper and iron. They are particularly useful in high-requirement castings such as marine turbines and chemical valves, extending their service life.

3) Cast Steel and Stainless Steel: Zirconia (ZrO) is used, with a temperature resistance exceeding 1700°C. It efficiently filters out minute inclusions in molten steel, reduces surface defects, minimizes subsequent processing allowances, and improves yield.

2. Automotive Exhaust Purification: Catalyst Carrier.
Foam ceramics, due to their large specific surface area and good thermal stability, are widely used as carrier materials for automotive exhaust catalytic converters.

1) After coating with precious metal catalysts, CO, HC, and NOx can be converted into harmless gases, with a conversion rate exceeding 90%;

2) In diesel vehicles, the purification rate of carbon particles exceeds 50%, and regeneration can be achieved through catalytic oxidation or electronically controlled combustion, enabling long-term use.

3. Environmental Protection and Waste Gas Treatment:

1) Used as a high-temperature filter medium in industrial flue gas dust removal, desulfurization, and denitrification systems;

2) Removes suspended solids and oil in wastewater treatment, improving effluent quality.

4. Other High-Tech Fields

1) Catalyst Supports: Used in petrochemical refining, organic waste gas treatment, and other reaction processes;

2) Thermal and Sound Insulation Materials: Utilizing their porous structure to achieve heat preservation and noise absorption in high-temperature furnaces;

3) Biochemistry and Medicine: Serving as bioreactor supports or drug release carriers.