Silica brick

Silica brick is a fired brick composed of mullite (3Al2O3.2SiO2) and silicon carbide (SiC) as the main minerals. Its characteristics are not only the high temperature resistance of mullite, but also the wear resistance, corrosion resistance, and good thermal conductivity of silicon carbide. When Baosteel was built in the 1980s, the refractory materials introduced from Nippon Steel, which looked like torpedo tanks, were similar to current silicon-moulded bricks. In fact, it is a modified material of aluminum silicate products. The original material of the iron ladle is refractory bricks mainly made of high aluminum. In the technological progress of the iron and steel industry, in order to speed up the steelmaking speed, a certain amount of Calcium oxide (CaO) undergoes so-called pretreatment. In this way, the refractory material in the tank has to withstand the high-temperature corrosion of molten iron and resist strong alkaline corrosion. Obviously, the high-aluminum material cannot withstand it, so adding an appropriate amount of silicon carbide to the high-aluminum material forms a new variety. The metallurgical industry calls it a fired brick of aluminum silicate combined with silicon carbide.

The performance of the silicon carbide brick comes from its process. Firstly, it is necessary to select the special grade alumina with Al2O3 higher than 80% in the raw material. The silicon carbide should be pure and the Mohs hardness requirement is close to 9.5. The company’s selection of silicon carbide is very strict. This kind of mineral is extremely rare. Most of the products use SiO2 and C to synthesize SiC at high temperature in an electric furnace. Different raw materials will produce quality differences. At present, in the production process of SiC, the SiO2 in the raw materials comes from natural silica, and C is derived from coal coke and coal. Petroleum coke, according to our research results, silicon carbide synthesized with petroleum coke and SiO2 has high indicators in terms of hardness and wear resistance, and is suitable for use as silicon carbide bricks. The main crystal phases of the fired bricks made from these raw materials are mullite, silicon carbide and corundum. These minerals have high hardness, which lays the foundation for dense and high-strength refractory products.