SiALON-Bonded Corundum Brick for Blast Furnace Bosh & Belly

SiALON-bonded corundum brick is what you specify when the bosh and belly of a blast furnace are being destroyed by alkali, not by slag. In the lower furnace, alkali metals circulate and condense, and they attack the oxide bonds that hold conventional alumina bricks together. The lining does not wear away so much as lose its structure — a process usually described as alkali disintegration.

The Bond Is the Product

SiALON is a silicon-aluminium-oxynitride phase. Replacing part of the oxide bond with it changes three things that matter in the bosh:

• Alkali resistance — the nitride phase is far less reactive to circulating alkali, so the brick keeps its surface integrity.
• Thermal conductivity — nitride bonding conducts heat better, so more heat reaches the cooling staves instead of accumulating in the lining.
• Hot strength — hot modulus of rupture ≥20 MPa at 1400 °C, with cold crushing strength ≥110 MPa, handles burden abrasion and thermal load together.

Thermal shock is rated at 30 cycles at 1100 °C water quench, roughly double a typical corundum-mullite grade, which is what lets the lining survive burden movement and cooling fluctuations without spalling.

Verify the Nitrogen, Not the Marketing

SiALON bonding is easy to claim and impossible to confirm visually. The measurable indicator is nitrogen content: if the nitride phase has genuinely formed, the brick contains bound nitrogen. XZK-SACOR grades are specified at ≥4.5–5.0% N and the figure appears on the batch Certificate of Analysis. If a supplier quotes a nitride-bonded product without a nitrogen number on the test report, they are quoting a name, not a specification.

SiALON-Corundum or Si₃N₄-SiC?

Both are nitride-bonded and both target the bosh and belly, so the question comes up constantly. Silicon carbide offers higher thermal conductivity and excellent abrasion resistance. SiALON-corundum offers different slag and oxidation behaviour and is often preferred where oxidation risk or specific slag chemistry argues against a high-SiC body. In practice the decision depends on your cooling design, alkali load and whether oxidation or abrasion dominates — which is why we ask for the furnace drawing and cooling configuration before recommending either.

Quality and Supply

Minimum order 20 metric tons with 20–35 day lead time. Bulk density and porosity per ASTM C830, cold crushing strength per ASTM C133, hot modulus of rupture per ASTM C583, RUL per ISO 1893 and chemistry including nitrogen per GB/T 6900 are tested per batch, with a Certificate of Analysis on every shipment. Large bosh and belly blocks are produced to drawing with dimensional tolerance confirmed at drawing approval.

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 sialon-bonded corundum 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 page.

The MMK Magnitogorsk No.10 BF and 375 t ladle programme reference documents how this class of material performed in full service, with the measured campaign figures rather than datasheet values.