Silicon Carbide Refractories — Kiln Furniture and Blast Furnace Lining
title: "Silicon Carbide Refractories — Kiln Furniture and Blast Furnace Lining" description: "SiC bricks, kiln furniture, and blast furnace lining materials: grades, manufacturing, and applications in high-temperature industrial processes." section: "downstream"
SiC in Refractory Applications
Silicon carbide refractories occupy a unique position in high-temperature industrial processes. Their combination of extreme hardness (Mohs 9.5), high thermal conductivity (60–120 W/m·K), low thermal expansion (4.0 × 10⁻⁶/K), and excellent resistance to thermal shock makes them irreplaceable in applications where alumina and fireclay refractories fail.
Global SiC refractory consumption is estimated at 300,000–400,000 tonnes/year, serving ceramics kilns, steel blast furnaces, aluminium smelters, and waste incineration plants.
Key SiC Refractory Product Categories
Kiln furniture — Batts, setters, saggers, and posts for supporting ceramic ware during firing in tunnel kilns and periodic kilns. Silicon nitride-bonded SiC (Si₃N₄–SiC) and recrystallised SiC (RSiC) are preferred because they resist the oxidising atmosphere at 1200–1400°C, accept heavy load cycling, and exhibit very low creep.
Blast furnace lining — The bosh, belly, and lower stack of iron blast furnaces are lined with SiC bricks bonded with silicon nitride or sialon. These zones experience thermal shock from hot metal tapping, alkali attack from coke ash, and abrasion from descending burden — SiC outperforms graphite and fireclay in this environment.
Aluminium reduction cell lining — Nitride-bonded SiC bricks line the sidewalls of Hall-Héroult electrolytic cells. SiC's resistance to cryolite melt attack and electrical conductivity enables the "cold ledge" protective freeze to form efficiently.
| SiC refractory type | Bond phase | Max use temp | Key advantage |
|---|---|---|---|
| Si₃N₄-bonded SiC | Silicon nitride | 1400°C | Oxidation resistance |
| Sialon-bonded SiC | Sialon | 1650°C | Alkali resistance |
| RSiC (recrystallised) | None (direct bond) | 1650°C | Very low impurity |
| Oxide-bonded SiC | Mullite/silica | 1300°C | Low cost |
Raw Material Quality Requirements
Silicon carbide for refractories uses coarser black SiC grain (F16–F100 grit) with SiC content ≥98%. The balance is free silicon and SiO₂ skin on particles. Green SiC is used where minimum iron contamination is critical (advanced ceramics).