High-Alumina Refractory Brick (55–82% Al₂O₃) for Steel & Industrial Furnaces

High-alumina brick is the workhorse of the furnace world, and it is also the most commonly over-specified material on the market. In zones that are not chemically aggressive and not at extreme temperature, a 55–82% Al₂O₃ body will deliver perfectly adequate life at a fraction of the cost of corundum or silicon carbide. Buying a premium grade for those zones is one of the most reliable ways to waste a refractory budget.

Grade by Temperature, Then by Load

Our SK series covers four steps:

• XZK-SK36 — 55% Al₂O₃, RUL 1450 °C, CCS ≥45 MPa. Backup courses, lower-temperature zones.
• XZK-SK37 — 65% Al₂O₃, RUL 1480 °C, CCS ≥50 MPa. General furnace linings.
• XZK-SK38 — 70% Al₂O₃, RUL 1530 °C, CCS ≥60 MPa. Hotter working zones.
• XZK-SK40 — 82% Al₂O₃, RUL 1550 °C, CCS ≥70 MPa. The top of the range, for hot or heavily loaded zones.

All grades hold Fe₂O₃ to 2.0%, which limits low-melting iron-bearing phase formation and reduces iron pickup risk in sensitive applications.

RUL Matters More Than SK

Refractoriness, reported as a pyrometric cone equivalent (SK), is measured with no mechanical load. Refractoriness under load (RUL) is measured under a specified compressive stress. Real linings carry load, so RUL is the figure that should drive design — and it is the one we publish for every grade. A supplier quoting only SK is giving you the easier number, not the more useful one.

Where High-Alumina Stops Being Enough

Step up to corundum-mullite or corundum when continuous temperature exceeds roughly 1550 °C, when slag penetration becomes the controlling mechanism, or when the zone is heavily loaded for long periods. Below those thresholds, high-alumina is almost always the better economic decision. We will tell you which zones genuinely need the upgrade and which do not — because a lining where every course is premium is not a better lining, it is just a more expensive one.

Supply and Documentation

Minimum order 10 metric tons for standard shapes (7–14 days) and 20 metric tons for custom shapes (20–35 days). Bulk density per ASTM C830, cold crushing strength per ASTM C133, RUL per ISO 1893, refractoriness per ISO 528 and chemistry per GB/T 6900 are tested per batch, with a Certificate of Analysis on every shipment. Matching refractory mortar is supplied so that the joint is not the weakest part of the lining.

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 high-alumina 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.