What Is Silicon Carbide Brick and What Is It Used For?

Overview: Silicon carbide brick is a special refractory with good wear and corrosion resistance, suited to high-temperature furnaces.

Introduction to silicon carbide brick

Silicon carbide brick is a refractory brick for high-temperature furnaces used in non-ferrous smelting, iron and steel, and metallurgical smelters. It offers good corrosion resistance, good wear resistance, high thermal conductivity and thermal shock resistance. We can supply various specifications and grades of high-quality refractory brick at competitive prices—contact us or email us for a free quote.

Properties of silicon carbide brick

Corrosion resistance

Good wear resistance

High thermal conductivity

High-temperature strength

Good thermal shock resistance

Low coefficient of thermal expansion

Applications of silicon carbide brick

1. Non-ferrous smelting: Silicon carbide withstands high temperatures, has high strength, good thermal conductivity and impact resistance, and is used for high-temperature indirect heating, such as in vertical retort distillation furnaces, rectifier trays, aluminum electrolysis cells, copper furnace linings, arc plates for zinc powder furnaces and thermocouple protection tubes.

2. Iron and steel: Uses the corrosion resistance of silicon carbide. SiC refractory bricks have good thermal shock and wear resistance, and their good thermal conductivity in large blast furnace linings extends service life.

3. Metallurgical and mineral processing: Silicon carbide is second only to diamond in hardness and is highly wear-resistant. SiC bricks are ideal for wear-resistant pipes, impellers, pump chambers, cyclones and mine linings. [The original sentence ending here is incomplete.]

4. Building ceramics and grinding wheels: Uses its thermal conductivity. Thin kiln furniture dissipates heat well and has high hot strength, which reduces kiln furniture load, increases kiln capacity and product quality, and shortens production cycles—an ideal material for indirect firing such as ceramic glaze firing.

5. Energy saving: Thanks to good thermal stability, when used in heat exchangers it reduces fuel consumption by 20%, saves 35% fuel and raises productivity by 20–30%. In particular, discharge pipes used in concentrators last 6–7 times longer than ordinary wear-resistant materials.

Types of silicon carbide brick

1. Clay-bonded silicon carbide brick

Clay-bonded SiC brick is a refractory made with silicon carbide as the main raw material and clay as the binder. It features high thermal conductivity, low thermal expansion, and good thermal shock and wear resistance, and was one of the earliest SiC bricks developed.

Clay-bonded SiC brick is made from black silicon carbide. Typical chemistry: SiC 98.0%, free C 0.5%, Fe 0.2%, free SiO2 0.6%, with soft clay and pulp waste liquor as binders for good bonding. Clay additions used to be relatively high, usually 10%–15%; now 3% clay and 5% pulp waste liquor are used. SiC brick with less clay has 3–4 times the thermal conductivity of clay-bonded SiC brick, and higher refractoriness under load and slag resistance. To make 3% clay-bonded SiC brick, coarse, medium and fine SiC are graded to obtain high packing density. After uniform dry mixing, clay is added; after 3 minutes of dry mixing, 4% pulp waste liquor (density 1.26–1.289/cm³) is added and the mix kneaded. Mix moisture is about 1.5%. After 12 hours of aging, the mix is passed through a 4 mm screen and formed on a brick press. Brick bulk density is 2.5–2.79/cm³. Bricks are air-dried for 2–4 days and fired in a tunnel kiln at 1400°C.

Many buyers of SiC bricks and products lack experience and cannot tell good quality from bad, and end up with substandard products that greatly shorten kiln life, increase refractory spending and cause unnecessary losses. So how can you tell the quality of SiC brick?

First, check that dimensions are correct. The specific gravity of SiC brick is generally 2.45–2.6; a value that is too low or too high indicates impure material with other refractories added, which lowers the SiC content and impairs heat transfer. When buying, check the brick surfaces for chipped corners and cracks, which should be within national standard tolerances; if they seriously exceed the standard, the batch is unqualified. We recommend supervising packing and loading on site to avoid rough handling that damages the products.

Popular uses of SiC brick include ceramic kiln furniture (shelves, supports, rafts, etc.), muffle covers for muffle furnaces, lining bricks for aluminum refining furnaces, retorts for zinc distillation furnaces, and cement rotary kiln coolers.

2. Silicon nitride bonded silicon carbide brick

Silicon nitride bonded SiC brick is a refractory sintered by nitriding SiC and Si powders, characterized by Si3N4 as the bonding phase. Si3N4 forms needle-like or fibrous crystals between SiC grains, making it an important new refractory.

A SiC body containing silicon powder is reaction-sintered by nitridation, with firing completed in a closed furnace where nitrogen supply is easily controlled. Furnace temperature, pressure and atmosphere are strictly controlled. Key process parameters: nitriding gas pressure 0.02–0.04 MPa; O2 content in the furnace atmosphere below 0.01%; final nitriding temperature 1350–1450°C; total nitriding time varies with product shape and size.

Silicon nitride bonded SiC brick offers good resistance to alkali corrosion and molten cryolite, oxidation resistance, wear resistance, high thermal conductivity, thermal shock resistance and very low electrical conductivity.

It is mainly used as lining for the lower furnace body, lasting more than twice as long as traditional refractories. It can also be used for aluminum reduction cell linings and ceramic kiln furniture, offering energy savings and longer life.

3. Recrystallized silicon carbide products

Recrystallized SiC products are refractories in which silicon carbide grains are directly bonded to each other. They contain no second phase and consist of 100% α-SiC. Raw material chemistry: SiC 99.5%, free C 0.2%, Fe 0.08%, free SiO2 0.08%.

Recrystallized SiC products are mainly used as kiln furniture, offering energy savings, larger effective kiln volume, shorter firing cycles, higher kiln productivity and strong economic returns. They can also be used for burner nozzles, ceramic radiant heating tubes and components, and protection tubes (especially for atmosphere furnaces).

Energy-saving performance of silicon carbide brick

SiC bricks currently sell well in the enamel, ceramics, glass, non-ferrous, power, chemical and environmental protection industries. Their energy-saving effect is excellent and can lower production costs, and this performance is attracting growing industry attention.

Because SiC brick has high thermal conductivity, it transfers heat very quickly. Furnaces today burn coal, biomass pellets, natural gas, LPG, heavy oil, electricity and other energy sources. With greater emphasis on environmental protection, coal use is declining and most companies use natural gas or electric heating—both relatively expensive. Since fuel cost directly drives production cost, reducing it has become a common concern, and production cost plays a very important role in a product's market competitiveness.

Using SiC bricks fully addresses enterprises' fuel cost problem. When SiC bricks or plates are used for furnace hearths, linings and burners, they save more than 50% energy compared with ordinary refractory bricks. SiC bricks are therefore vital to product competitiveness, and their energy-saving benefits are increasingly recognized.