Introduction to Common Refractory Bricks From Material Composition (3)

7. Zirconium-containing refractory bricks are acidic materials made of natural zircon sand (ZrSiO4). Zirconium refractory bricks are different from aluminum-silicon refractory bricks and carbon-containing refractory bricks. Good slag resistance, a low thermal expansion rate, the thermal conductivity decreases with increasing temperature, high load softening temperature, and high wear resistance. It has good thermal shock resistance and has become an important material in various industrial fields. With the development of continuous casting and vacuum degassing technology in the metallurgical industry, the application of zircon refractory bricks is becoming more and more extensive. Typical examples are zircon bricks, AZS fused bricks, AZS sintered bricks, and zircon mullite fused bricks.

(1) Zircon brick, a refractory material with zirconium silicate (zircon) as the main crystal phase. The theoretical composition and structure of zircon are 67.1% ZrO2; 32.9% SiO2. Zircon bricks contain more than 90% zircon, 65-72% zirconia, and 25-33% silicon oxide. The Mohs hardness is about 7.5, and the bulk density is 3.60-4.40g/cm3. The apparent porosity is 0% to 18%. Softening temperature under load>1500℃. Zircon refractories have good corrosion resistance and thermal shock resistance to slag and molten steel and are very stable in oxidizing atmosphere conditions. Widely used in the metallurgical industry to build degassed ladle linings, as well as stainless steel ladle linings, continuous casting ladle linings, cast bricks, plug bricks, sleeve bricks, high-temperature induction furnace linings, etc. Zirconia products are close to acidic refractory materials, have good corrosion resistance to acidic or neutral slag, and are resistant to acid slag and glass, so they are also widely used in severely damaged parts of glass furnaces to melt bright glass. Zircon refractories also have no oxidation of metallic aluminum and aluminum. The slag has good permeability, so it has a good effect on the bottom of the aluminum smelting furnace;

(2) AZS fused bricks, also known as fused zirconia corundum bricks, with the development of the glass industry, AZS fused bricks have become a key component of glass melting furnaces. Resistant to the corrosion of molten glass; AZS sintered bricks are mainly used in the construction of thermal equipment such as glass kiln bottoms, kiln walls, and heat storage checker bricks; zirconium mullite fused bricks are characterized by fine crystal structure and high load softening temperature. Good thermal shock resistance, high mechanical strength at room temperature and high temperature, good wear resistance, good thermal conductivity, and excellent slag corrosion resistance. This type of product is more widely used in metallurgical heating furnaces, soaking furnaces, discharge ports of calcium carbide furnaces, and furnace walls of glass melting furnaces. It has a good application effect.

(3) Sintered zircon-mullite brick is a high-grade refractory brick made by introducing ZrO2 into the mullite matrix through the reaction sintering process by using industrial alumina and zircon concentrate as raw materials. The reaction equation is: 3Al2O3+2ZrSiO4→3Al2O3•2SiO2+2ZrO2 mullite ceramics have many excellent characteristics. Zirconium mullite bricks have a dense crystal structure, high packing density, high softening temperature under load, good thermal stability, and mechanical properties at room temperature and high temperature. High strength, good wear resistance, good thermal conductivity, excellent corrosion resistance, good thermal shock stability, low secondary combustion shrinkage and high-temperature creep, and extremely high chemical stability. Corrosion resistance in alkaline media. Zircon mullite bricks are mainly used in large-scale glass furnace furnaces corroded by solutions, picture tube furnaces, regenerator partition walls, and chemical and metallurgical industrial furnaces.