SiC-Mullite Brick (High-Alumina Silicon Carbide) for Blast Furnace & Kilns

SiC-mullite brick — also known as high-alumina silicon carbide brick — is the answer to a specific economic question: how do you get most of silicon carbide’s abrasion resistance across a large lining area without paying for a full SiC body?

The Economic Argument

Silicon carbide is expensive. On a lining course where the duty is moderate, the extra life it buys often costs more than it saves. But plain high-alumina brick may not have enough abrasion resistance. SiC-mullite occupies the middle ground: silicon carbide additions raise surface hardness and wear resistance, while the alumina-mullite matrix keeps the material at a fraction of the cost of a nitride-bonded SiC body.

Over a large stack area or a long kiln transition zone, that difference per ton compounds into a significant number — which is why this grade is specified far more often than its modest datasheet would suggest.

What It Does and Does Not Do

It gives you abrasion resistance, decent refractoriness under load (to 1650 °C on XZK-GM1650) and reasonable thermal shock behaviour (10–12 cycles at 1100 °C water quench). It does not give you the thermal conductivity of a SiC body, and it does not give you nitride-level alkali resistance. Those are the properties you pay for when the zone genuinely needs them.

Being clear about this boundary is the whole point: over-specifying a large area with a premium grade is one of the most common ways refractory budgets are wasted, and under-specifying the bosh is one of the most common ways campaigns are shortened. Knowing which is which is the specification job.

Grade Selection

• XZK-GM1650 — 65% Al₂O₃, RUL 1650 °C, density 2.65 g/cm³. Hottest courses.
• XZK-GM1600 — 63% Al₂O₃, RUL 1600 °C, CCS ≥90 MPa. General duty.
• XZK-GM1550 — 60% Al₂O₃, RUL 1550 °C, thermal shock 12 cycles. Cooler or more heavily cycled zones.

Note that GM1550 carries the best thermal shock rating despite the lowest RUL — where cycling dominates rather than peak temperature, it is often the correct pick.

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 and porosity per ASTM C830, crushing strength per ASTM C133, RUL per ISO 1893, thermal shock cycles and chemistry are tested per batch, with a Certificate of Analysis on every shipment. Matching mortar is available so that the joint does not become the weak point.

Where This Grade Sits in the Lining System

Silicon carbide and carbon grades are selected for what they do with heat rather than for what they resist. Thermal conductivity decides whether the cooling system ever sees the load, and the bonding system decides how long the material survives alkali attack and oxidation once it does.

XZK supplies sic-mullite brick as one zone of a zoned package rather than as a standalone item: the grades normally zoned alongside it — among them si₃n₄ bonded sic brick — are documented on the silicon carbide and carbon 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.