STELEX ZR zirconia filters
Stelex ZRSTELEX ZR filters smooth metal flow in the mold when used in a conventional gating system. They also remove non-metallic inclusions such as furnace and ladle slag, furnace and ladle refractory materials, molding sand, products of deoxidation, and products of reoxidation. Filtration reduces internal re-work costs in welding and cleaning, reduces the rate of casting returns, improves machinability, improves machine tool life, and increases casting yield. Proper filter use provides improved quality, productivity, and profitability.

STELEX ZR ceramic foam filters are ideally suited to the filtration of steel castings. They are produced from partially stabilized zirconia, a highly stable refractory material offering a unique combination of thermal shock resistance, resistance to chemical attack, hot strength and creep resistance. STELEX ZR filters are intended for use in all grades of steel at pouring temperatures up to1680°C.

The effectiveness of STELEX ZR foundry filters is due to their foam structure. Some 90% of the volume consists of open, reticulated, interconnected pores. This produces many changes in direction and velocity, leading to intensive contact with the filter surface that allows small non-metallic particles to be retained within the foam structure.

Due to the open pore structure and large surface area, STELEX ZR filters are highly effective in the removal of slag, sand, refractories and deoxidation products suspended in the metal stream.

STELEX ZR foam filters enable smooth, non-turbulent mold filling, thereby reducing the risk of reoxidization defects and molding sand erosion problems.

Filtration effectiveness is largely dependent on the correct application and positioning of the filter. Foseco Product Application Engineers are able to provide technical application support for the calculation and design of gating systems. For correct filter positioning, Foseco’s standard filter print designs are recommended.

STELEX ZR filters are available in a variety of sizes and 3 porosities:

• coarse (10 ppi);
• coarse-medium (15 ppi);
• medium (20 ppi).
*ppi = Average number of pores per linear inch.

STELEX ZR filters are routinely tested to ensure compliance with specifications for physical dimensions, weight, cold compression strength and porosity.

The benefits of foam filtration are seen throughout the foundry. Depending on the alloy and the application, many of the following benefits are achievable:

Scrap Control
• lower levels of scrap produced;
• improved ability to diagnose scrap problems due to a clearer separation of metal and mold factors;
• reduction in expensive machine scrap;
• running systems and downsprues fill smoothly and remain full, reducing the risk of gas bubbles entering the mold cavity.

Productivity Improvements
• higher tons shipped to tons melted ratio (yield) due to the elimination of long running systems;
• simplified gating systems since the filter itself will reduce velocity and smooth the flow of liquid metal
• simplified pattern plate designs can allow a foundry to reduce mold sizes or increase castings per mold;
• more molds per melted ton;
• lower levels of cash tied up in work-in-progress.

Casting Quality Improvements
• greater consistency in casting cleanliness;
• reduction in the variability of metal flow of hand-poured castings leading to increased casting consistency;
• improved mechanical properties due to greater metallurgical consistency;
• increased fluidity of the metal improves casting finish, appearance and surface details.

After Cast Operations
• reduced welding, repair and heat treatment costs,
• improved machinability and reduced tool wear;
• machining allowances can be reduced with confidence due to a lower level of inclusions;
• reduction in inspection and expensive, time-consuming non-destructive testing operations;
• faster cycle times and increased work schedule flexibility and foundry competitiveness.