Silicon Carbide Brick

Introduction

Silicon carbide brick is a refractory product made with silicon carbide (SiC) as the main raw material. The SiC content is usually between 72% and 99%. Black silicon carbide (SiC content above 96%) is generally selected as the raw material, with or without binders, and is produced through batching, mixing, forming, and firing processes. The main crystal phase is silicon carbide.

Silicon carbide is covalently bonded and does not have the usual sinterability. Sintering is achieved by chemical reactions that generate new phases. Its main varieties include oxide-bonded silicon carbide brick (clay-bonded), silicon nitride-bonded silicon carbide brick, Sialon-bonded silicon carbide brick, recrystallized silicon carbide brick, and self-bonded silicon carbide brick. Silicon carbide products are not only essential refractory materials for vertical retort zinc smelting but are also widely used in industrial furnaces in steel metallurgy, chemicals, and ceramics, as well as in corrosion-resistant and wear-resistant pump and pipeline linings.

Specification

Classification by Bonding Method and Typical Grades

Clay-Bonded Silicon Carbide Brick
Made with silicon carbide as the main raw material and clay as the binder. Early clay binder proportions were generally 10%~15%. The thermal conductivity of modern low-clay bonded products (about 3% clay) is 3~4 times higher than that of high-clay bonded products, and the refractoriness under load and slag resistance are also higher.

Item	SiC80	SiC90
SiC (%) ≥	80	90
Refractoriness under load (0.2MPa) (℃) ≥	1600	1600
Bulk density (g/cm³) ≥	2.5	2.65
Apparent porosity (%) ≤	18	18
Cold compressive strength (MPa) ≥	85	90

Silicon Nitride-Bonded Silicon Carbide Brick
With Si₃N₄ as the bonding phase, it is the best refractory material for the middle and lower stack, belly, and bosh of blast furnaces. It has good high-temperature chemical stability, high high-temperature strength, and excellent alkali erosion resistance. Typical indicators: SiC≥72%, Si₃N₄≥21%, apparent porosity≤16%, bulk density≥2.68g/cm³, cold compressive strength≥180MPa, 1400℃ flexural strength≥55MPa.
Sialon-Bonded Silicon Carbide Brick
Used for blast furnace maintenance. Typical procurement technical indicators: SiC≥71%, Al₂O₃≥5%, N≥5.5%, Fe₂O₃≤0.7%, apparent porosity≤16%, bulk density≥2.65t/m³, cold compressive strength≥150MPa, 1400℃ flexural strength≥45MPa, thermal shock resistance (1100℃ water cooling) ≥30 cycles.
Recrystallized Silicon Carbide Brick
Composed of 100% α-SiC with no second phase, it is a new energy-saving kiln furniture material developed in the 1980s. Manufacturing requires firing in a 2500℃ high-temperature electric furnace with isolated air. Above 2100℃, SiC evaporates and condenses, forming a shrinkage-free self-bonded structure.

Dimensional Specifications

The standard brick shape for silicon carbide brick is 230×114×65mm (T-3 type). Shapes and dimensions can be implemented according to GB/T 2992.1, and special-shaped products can also be customized according to buyer drawings.

MORE DETAILS

Product Advantages

High thermal conductivity
The thermal conductivity of silicon carbide products is about 10~14 timesthat of clay products. This is one of the most significant advantages of silicon carbide brick, widely used in parts requiring efficient heat conduction, such as muffle furnaces, heat exchangers, and retorts.
Low thermal expansion coefficient, excellent thermal shock resistance
Silicon carbide has a low thermal expansion coefficient (about 4.5~5.5×10⁻⁶/℃) and good thermal stability. The thermal shock resistance (1100℃ water cooling) of Sialon-bonded silicon carbide brick can reach more than 30 cycles, and composite silicon carbide brick for coke dry quenching inclined flues can reach 100 cycles.
High high-temperature strength
Ordinary ceramic materials significantly decrease in strength at 1200~1400℃, while silicon carbide still maintains a relatively high flexural strength of 500~600MPa at 1400℃, with a working temperature of up to 1600~1700℃. The cold compressive strength of silicon nitride-bonded silicon carbide brick can reach above 180MPa.
Good wear resistance and erosion resistance
Silicon carbide brick has excellent wear resistance and erosion resistance, with outstanding mechanical strength and wear resistance over a wide temperature range. It is suitable for parts subjected to severe wear such as cyclones, dust collectors, pipes, and chutes.
Stable chemical properties
Silicon carbide has stable chemical properties and resists erosion by various acids and alkalis. In recent years, continuous improvement of binders has overcome the weaknesses of easy oxidation and alkali corrosion.
Good high-temperature chemical stability
Silicon nitride-bonded silicon carbide brick has excellent alkali erosion resistance. Results from use in Angang No. 6 blast furnace show that the lining life can be extended to more than 8 years.

Applications

Silicon carbide brick is widely used in the following industrial fields:

Steel Metallurgy

Blast furnace: The best refractory material for the middle and lower stack, belly, and bosh. Abroad, 61% of blast furnace linings already use silicon carbide products
Ironmaking: Linings for iron troughs and iron ladles
Coke dry quenching furnace: Composite silicon carbide brick for the inclined flue area, with a service life of 4~5 years
Aluminum electrolytic cell: Side wall lining

Non-Ferrous Metallurgy

Vertical retort zinc smelting: Essential refractory material for retorts
Aluminum refining furnace: Lining bricks
Zinc distillation furnace: Retorts
Non-ferrous metal melting furnace: Lining

Ceramics Industry

Kiln furniture: Batts, supports, saggers, etc.
Recrystallized silicon carbide products: Energy-saving kiln furniture, which can increase the effective volume of the kiln and shorten the firing cycle
Chemicals and Environmental Protection
Chemical reaction tanks: Corrosion-resistant reaction vessels
Organic waste liquid incinerators: Lining
Waste incineration furnaces: Silicon carbide brick is the first choice among brick-type refractories for waste incineration furnaces

Others

Muffle furnace: Muffle covers

Cement rotary kiln: Clinker coolers

Heating furnace, soaking pit: Lining

Steam boiler: High-temperature parts