Silicon-Carbide Refractories

articles produced from silicon carbide (carborundum) and additives, containing between 20-35 and 70-98 percent SiC.

Silicon-carbide refractories are classified, according to the method of bonding the silicon-carbide granules, as siliceous (formed in the oxidation of carbide), nitride (Si₃N₄), oxynitride (Si₂ON₂), and aluminosilicate, as well as recrystallized and self-bonded. The products are formed on presses (or by other methods) from powdered mixtures containing silicon carbide and subsequently fired at 1300°-1550°C (certain types at 2000°-2200°C).

Silicon-carbide refractories exhibit high thermal conductivity: 7-17 watts per (m.°K) at 800°C. As a result, they show good thermal stability. They are also resistant to deformation at elevated temperatures. At 130O°-1500°C in an oxidizing medium they undergo gradual oxidation, particularly in the presence of an excess of oxygen and of water vapor. Silicon-carbide refractories are used in recuperators, retort furnaces, nonferrous-metal-lurgy plant units, shelves of tunnel wagons (in firing porcelain and ceramics), and boilers.