Zirconia ceramic foam filter is a high-performance porous reticulated ceramic component specially developed for high-temperature molten metal purification in foundry industry.

It is manufactured via the replica method: polyurethane open-cell foam is impregnated with zirconia slurry, followed by drying, sintering and phase stabilization treatment.

The finished product features an interconnected 3D tortuous pore network, which captures non-metallic inclusions and slag while homogenizing molten metal flow during pouring.

The base raw material is zirconium dioxide (ZrO₂), commonly partially stabilized by magnesia (MgO) or yttria (Y₂O₃).

Stabilization eliminates destructive volume expansion of pure zirconia during rapid heating, drastically improving fracture toughness and thermal shock resistance, preventing cracking under severe thermal stress when contacting molten steel.

Typical colour is pale yellow / cream yellow, visually distinguishable from white alumina filters and grey silicon carbide filters to avoid mixing on-site.

Core Working Principle

Two filtration mechanisms work simultaneously:

1. Mechanical interception: Blocks large slag, dross and macroscopic solid particles on the inlet surface.

2. Adsorption capture: The large specific surface area of the 3D pore skeleton adsorbs tiny micro-inclusions via surface wetting effect as molten metal flows through winding channels.

Meanwhile, the porous structure breaks turbulent flow and converts it into stable laminar flow, reducing secondary oxidation of molten metal and minimizing new inclusion formation during pouring.

Key Physical & Chemical Properties

● Main composition: Partially stabilized ZrO₂, ZrO₂ ≥95%

● Max continuous operating temperature: 1700–1760 °C

● Open porosity: 80%–90%

● Pore specification: 10–30 PPI (Pores Per Inch, standard choice for steel casting; fine grades up to 40 PPI for precision castings)

● Bulk density: 0.8–1.0 g/cm³

● Room-temperature compressive strength: ≥1.5 MPa

● Thermal shock resistance: No cracking after ≥6 cycles from 1100 °C to room temperature

● Chemical property: Chemically inert to molten carbon steel, alloy steel, stainless steel, nickel-based and cobalt-based superalloys; no dissolution or secondary contamination into molten metal.

Product Specifications

Standard shapes: square, rectangular, circular plates; thickness commonly 22 mm, custom thickness available. Standard dimensions: 40×40×22 mm, 50×50×22 mm, 75×75×22 mm, 100×100×22 mm; circular sizes Φ50, Φ75, Φ100 mm. Custom sizes are acceptable upon drawing. PPI selection guide:

● 10–15 PPI: Large steel castings, high pouring throughput, coarse slag removal

● 20 PPI: General stainless steel & alloy steel, balance of flow rate and filtration precision

● 25–30 PPI: Aerospace superalloy, high cleanliness precision investment castings

Application Fields

Designed for high melting-point ferrous and superalloy casting where alumina and SiC filters cannot withstand the temperature.

● Carbon steel, low-alloy steel, stainless steel, tool steel castings

● Nickel-base & cobalt-base superalloys (gas turbine blades, aerospace structural parts)

● Power equipment, hydraulic high-pressure steel components, high-value precision investment castings Applicable casting processes: sand casting, investment casting, gravity casting, bottom pouring casting.

Main Advantages

1. Ultra-high temperature resistance, suitable for steel pouring temperature range 1550–1680 °C; no softening or collapse under high heat.

2. Outstanding thermal shock resistance, can endure sudden thermal impact from hot molten metal without crack or spalling.

3. Excellent chemical inertness, no reaction with molten steel, avoids introducing foreign impurities.

4. Dual purification function: remove inclusions + stabilize metal flow, reduce casting defects such as slag inclusion, porosity, shrinkage and surface blemishes.

5. Improve mechanical performance of finished castings, reduce scrap rate and post-machining workload, raise production yield.

Installation & Notes

Installed inside the gating system (runner bar) before pouring.

Preheating is recommended for large castings to reduce thermal shock risk.

Calculate filtration area according to pouring weight and melt viscosity; avoid overloading which causes clogging and cold shut defects.