Silicon Carbide & Carbon Refractories for Long Blast Furnace Campaigns

Designing the Blast Furnace Defence Line

Blast furnace refractory design is a thermal management problem before it is a materials problem. The lining survives when heat is conducted into the cooling system fast enough to keep the 1150 °C isotherm — the temperature at which molten iron solidifies — inside the refractory. Every material choice below follows from that principle.

Zone-by-Zone Material Logic

• Hearth and bottom — microporous carbon brick plus a ceramic cup barrier, backed by high-conductivity carbon ramming mass against the cooling staves. Carbon provides the thermal pathway; the ceramic cup protects it during start-up and against alkali and zinc attack.
• Bosh and belly — Si₃N₄-bonded or SiALON-bonded SiC brick. These zones carry the highest heat load and the worst alkali vapour attack, which is exactly where nitride bonding earns its cost.
• Lower and mid stack — SiC-mullite or high-strength high-alumina brick, balancing abrasion resistance from the burden against thermal cycling.
• Upper stack — dense high-alumina or fireclay grades, where abrasion rather than chemical attack controls.
• Taphole and casthouse — ASC castables and waterless taphole clay, covered in our monolithic range.

Why Conductivity Beats Thickness

Adding refractory thickness without adding conductivity is counterproductive: it moves the hot face further from the cooling system and can actually raise the temperature at the isotherm. Where hearth temperatures are climbing, the correct response is usually higher conductivity in the carbon build-up and a verified cooling circuit — not simply more brick.

Carbon Oxidation: The Main Life Limiter Outside the Hearth

In the stack and bosh, carbon-containing materials can be lost to oxidation if the cooling system or gas flow allows oxygen ingress. Selecting oxidation-protected grades, controlling the ramming and jointing materials, and monitoring shell temperature are all part of the package we specify.

What to Send Us

Furnace volume and drawing, cooling configuration, campaign history, hearth temperature trend, and the alkali and zinc load if known. We will return a full zonal build-up with a material schedule, thermal rationale and installation guidance.