Corundum Mullite Brick for Blast Furnace Belly, Stoves & Kilns

Corundum mullite brick exists because two desirable properties pull in opposite directions. Corundum gives you refractoriness and slag resistance but spalls under repeated thermal cycling. Mullite gives you thermal shock tolerance and low thermal expansion but creeps under sustained load. Corundum-mullite carries enough of each to be usable where both matter — which turns out to be a lot of real furnace zones.

Reading the Grade Series

Our CM series runs 80 to 90% Al₂O₃, and the trade is explicit:

• XZK-CM90 — most corundum, best slag resistance and density (3.00 g/cm³), selected where chemical attack and temperature dominate.
• XZK-CM85 — the balance point, and the grade with the best documented thermal shock rating at 15 cycles (1100 °C water quench). The usual default for cycled high-temperature zones.
• XZK-CM80 — lower peak temperature and moderate load, where the mullite contribution is doing most of the work.

Note that CM90 carries no published thermal shock figure. That is deliberate: we do not publish a number we do not test consistently. If shock resistance is your controlling property, we will steer you to CM85.

Creep Is the Property People Forget

Corrosion gets the attention, but deformation ends more long campaigns than chemistry does. Under sustained compressive load at temperature, refractory slowly changes shape; joints open, arches flatten, and the structure loses stability while the brick still has most of its thickness. Holding creep to ≤0.3% at 1500 °C is what keeps geometry intact over a multi-year campaign, and it is the number worth asking any supplier for when the zone is loaded.

Typical Zones

• Blast furnace bosh and belly — high heat load plus cycling, usually evaluated alongside Si₃N₄-bonded SiC.
• Hot blast stove domes and combustion chambers — low creep plus changeover cycling.
• Ladle working and safety linings — where cycling rules out pure corundum.
• Tunnel and shuttle kiln hot faces — car linings, burner zones and crowns.

Manufacturing and Documentation

XZK corundum mullite bricks are pressed on 2,000-ton class CNC hydraulic presses and fired on controlled curves to develop the mullite bond. Bulk density and porosity per ASTM C830, crushing strength per ASTM C133, RUL per ISO 1893, creep per ISO 3187 and chemistry per GB/T 6900 are tested per batch, with a Certificate of Analysis on every shipment. Custom shapes and precast blocks are produced to drawing with ground seating faces and dry trial-fitting.

Where This Grade Sits in the Lining System

Corundum and high-alumina grades earn their place on hot strength and creep resistance, and those properties only pay back if the surrounding zones survive as long as they do. Putting the strongest brick into the harshest zone and leaving the rest to habit is how most of the refractory budget is actually lost.

XZK supplies corundum mullite brick as one zone of a zoned package rather than as a standalone item: the grades normally zoned alongside it — among them corundum brick — are documented on the corundum and high-alumina refractories page, and the vessel-level architecture — where each zone starts and ends, and which mechanism actually limits the campaign — is set out on the blast furnace and hot blast stove pages.

For a complete vessel programme built on this class of material, including the wear survey that set the zoning, see the MMK Magnitogorsk No.10 BF and 375 t ladle programme project reference.