In many fields of modern industry, high temperature environment is an indispensable part of many production processes. Whether it is steel smelting, glass manufacturing or cement production, it is inseparable from a special material-refractory. As the cornerstone of high-temperature industry, refractory provides reliable protection for various high-temperature equipment with its excellent high-temperature resistance and stability, ensuring the smooth progress of industrial production.

I. Definition and Classification of Refractory Materials

Refractory refers to a material that can keep its physical and chemical properties stable at high temperature. They usually have high melting point, low thermal conductivity, good chemical stability and mechanical strength. According to their shapes and uses, refractories can be divided into two categories: fixed refractories and unshaped refractories.

Shaped refractories refer to products with fixed shapes, such as refractory bricks and insulating brick. Refractory brick is one of the most common forms of refractory materials, including clay brick, high alumina brick, silicon brick, magnesium brick and many other types. These bricks have different fire-resistant temperature and performance characteristics according to their composition and manufacturing technology, and are suitable for different high-temperature environments. For example, because of its high aluminum content, high refractory temperature and good corrosion resistance, high alumina brick is often used as the lining of iron and steel smelting furnace; Insulating brick is mainly used to reduce heat transfer and heat loss of equipment.

Amorphous refractory refers to materials without fixed shape, such as refractory castable, plastic refractory, high temperature refractory mud, etc. These materials can be formed on site as needed during construction, which has better adaptability and flexibility. Refractory castable is a commonly used amorphous refractory material, which is composed of refractory aggregate, powder and binder. It has high strength and good corrosion resistance, and is suitable for various complex high-temperature equipment structures. Plastic refractory, on the other hand, has good plasticity, can be easily molded during construction, and is suitable for repair and local protection.

II. Raw materials and production technology of refractory materials

The performance of refractories depends largely on the quality of raw materials and production technology. Common refractory raw materials include clinker, sintered corundum and sintered mullite. These raw materials have good fire resistance and chemical stability after high temperature sintering and other processes. For example, sintered corundum is a kind of high-purity alumina material with extremely high refractory temperature and good corrosion resistance, and it is one of the important raw materials for producing high-alumina bricks and refractory castables.

In terms of production technology, the production process of refractory materials usually includes the steps of crushing, screening, mixing, forming and firing of raw materials. Taking the production of refractory bricks as an example, various raw materials are first crushed and screened according to a certain proportion, and then the mixed raw materials are put into the mold for molding. The formed green brick needs to be fired at high temperature to achieve the required fire resistance. The control of sintering temperature and time is a key link in the production process, and different refractories need different sintering processes. For example, the firing temperature of clay brick is generally around 1300℃, while the firing temperature of high alumina brick needs to reach above 1500℃.

III. Application fields of refractory materials

Refractory materials are widely used, covering almost all industrial fields involving high temperature. In metallurgical industry, refractories are the key materials for lining of ironmaking and steelmaking furnaces, which can withstand the erosion of high-temperature slag and molten metal and protect the structural integrity of the furnace body. For example, in the process of steelmaking, the lining of ladle and tundish usually adopts high alumina brick or magnesia brick to ensure the purity and fluidity of molten steel at high temperature. In the glass industry, refractories are used to make the furnace body and tank wall of glass melting furnace, which can withstand the high temperature corrosion and chemical corrosion of glass liquid. Insulating brick also plays an important role in glass melting furnaces, which can improve energy efficiency and reduce production costs by reducing heat loss.

In the cement industry, refractories are used as the lining of cement rotary kiln, which can withstand the chemical reaction and physical action of cement clinker at high temperature. In addition, refractories are widely used in the fields of ceramics, chemical industry, machining, architecture and military affairs. For example, in the production of ceramics, refractory materials are used to make the body and kiln furniture of ceramic firing kiln; In the field of chemical industry, refractories are used to make the lining of high-temperature reactors and pipelines to prevent the corrosion and leakage of chemicals.

IV. Quality Control and Standards of Refractory Materials

The quality of refractory is directly related to its service life and performance in high temperature environment. Therefore, strict quality control is the principle that refractory manufacturers must follow. Generally speaking, the quality control of refractories includes chemical analysis, physical performance testing and appearance inspection. Chemical analysis mainly detects whether the composition of the material meets the design requirements, such as the content of main components such as alumina and silica. Physical properties testing includes the tests of refractoriness, compressive strength, flexural strength, thermal conductivity and other indicators, which can reflect the stability and mechanical properties of materials in high temperature environment. Appearance inspection mainly checks the dimensional tolerance, deformation, cracks, corner defects, etc. of the product to ensure that the appearance quality of the product meets the standard requirements.

In order to standardize the production and quality control of refractories, various countries have formulated a series of standards and specifications. For example, ASTM standard in the United States, DIN standard in Germany, JIS standard in Japan, etc., these standards have made detailed provisions on the classification, performance indicators, testing methods and other aspects of refractories. In our country, there are also corresponding national standards and industry standards, such as GB/T 2997-2015 "Dense shaped refractory products" and GB/T 22586-2008 "unshaped refractory materials". These standards provide important basis and guidance for the production and application of refractories.

V. Development trend of refractories

With the continuous development of modern industry, higher requirements are put forward for the performance and quality of refractories. Refractory industry is also constantly carrying out technological innovation and product upgrading to meet market demand. On the one hand, the research and development of new refractories has become the focus of industry development. For example, nano-refractories have excellent high temperature performance and thermal shock resistance, and can remain stable in extreme high temperature environment; Composite refractories combine different types of refractories, which integrates the advantages of many materials and improves the comprehensive properties of materials. On the other hand, energy saving and environmental protection of refractories have also become an important development direction. By improving the production process and material formula, the energy consumption and pollutant emission of refractories can be reduced and sustainable development can be realized.

In addition, intelligent production and quality control is also a development trend of refractory industry. Using advanced sensor technology and automatic control system to monitor and control the production process of refractories in real time can improve production efficiency and product quality stability. At the same time, through the establishment of quality traceability system, the production process and quality data of products are recorded and analyzed to provide support for the continuous improvement of product quality.

VI. Conclusion

As an important supporting material of high temperature industry, refractories play an irreplaceable role in modern industry. It is rich in variety and excellent in performance, and can meet the needs of various complex high-temperature environments. With the continuous progress of science and technology and the continuous development of industry, the refractory industry will continue to develop in the direction of high performance, energy saving, environmental protection and intelligence, providing a solid guarantee for the efficient, stable and sustainable development of industrial production.