Introduction To Lightweight Castables

A granular and powdery material made by adding a certain amount of binder to refractory materials. Has high fluidity and is suitable for amorphous refractory materials formed by casting.
Compared with other amorphous refractory materials, the binder and moisture content are higher, and the flowability is better. Therefore, amorphous refractory materials have a wider range of applications, and the materials and binders used can be selected according to the usage conditions. It can be directly poured into a lining for use, or prefabricated blocks can be made by pouring or compacting methods.
Brief History: Refractory castables are the main variety of amorphous refractory materials. During World War II, refractory castables were used as a substitute for irregular bricks in boilers or oil production equipment in the United States. Japan began researching and producing such materials in 1950. In the early 1950s, the Soviet Union began using silicate cement refractory castables. Since the 1960s, the development of amorphous refractory materials has been rapid. By the 1990s, the production of amorphous refractory materials in countries such as Japan, the United States, and Germany had accounted for more than one-third of the total refractory material production, and refractory castables accounted for 40% to 50% of amorphous refractory materials. In the early 1950s, China began to use silicate cement refractory castables, which were then called heat-resistant concrete and mainly used for thermal structures below 700 ℃ (sometimes 700-1200 ℃). From 1965 to 1975, calcium aluminate cement and phosphate refractory castables were widely used, which were then called refractory concrete. The operating temperature was increased to 1400-1600 ℃, and during this period, product production bases were built. In early 1976, product standards were established. After 1976, the variety of products rapidly increased and the quality gradually improved. In the mid-1980s, China developed a new generation of refractory castables, including low cement, ultra-low cement, and cementless refractory castables, whose quality was close to the international advanced level.
The castable mixture made of lightweight refractory aggregate, powder, binder, and admixture is called lightweight castable. Due to its low bulk density and thermal conductivity, lightweight castable is also known as insulation refractory castable. In terms of classification, lightweight castables can be divided into two categories: semi lightweight refractory castables, lightweight refractory castables, and ultra lightweight refractory castables based on their bulk density; According to the usage temperature, it is divided into low-temperature insulation (lightweight) refractory castables, medium temperature insulation (lightweight) refractory castables, and high-temperature insulation (lightweight) refractory castables.
The application range of lightweight insulation castables is very wide. In the lining of kilns, thermal equipment, flues, and smoke windows in industrial sectors such as metallurgy, machinery, petrochemicals, power, and building materials, lightweight insulation refractory castables are commonly used as insulation layers. But with the improvement of lightweight insulation refractory castable materials and the advancement of preparation technology, there are also many occasions where they are directly used as working linings for atmosphere furnaces. Low temperature and medium temperature lightweight castables are mainly used as insulation liners and do not come into direct contact with flames. And a large part of high-temperature lightweight castables are directly used as working liners that do not come into contact with the molten or solid medium inside the furnace. Especially for use as working lining in various heating furnaces and heat treatment furnaces, it can greatly save energy consumption.