Refractory Properties, Testing Methods, and Repair Processes
2025-10-28 13:59:39
When considering refractory materials as solid materials, their material properties can be broadly categorized into physical and chemical properties. However, in reality, refractory properties are not strictly defined, so a more practical classification approach is to categorize them into basic properties (groups) and application properties (groups).
Basic properties, as the literal meaning suggests, are the fundamental material properties of refractory materials. These properties are independent of the refractory's form or application. Examples include microstructure density, structural composition, high-temperature strength, and thermal conductivity.
Application properties are important properties related to the refractory's application, such as CO resistance when used in a CO atmosphere or high-temperature creep resistance when used under prolonged high-temperature loads. Application properties are often closely related to these basic properties and can be inferred from them. For example, thermal shock resistance (spalling resistance) is a crucial application property in environments subject to drastic temperature fluctuations. Methods for estimating these properties from basic properties such as tensile strength, elastic modulus, linear expansion coefficient, and thermal conductivity are widely used.
Table 1-6 is a list of the main characteristics divided into basic characteristics. According to their use, there are many examples of application characteristics, especially the application characteristics that have not yet been standardized. The above characteristics are ultimately the characteristics of the finished refractory products (commodities). In the actual manufacturing process, characteristics are indispensable for production management. These characteristics range from the original quality characteristics (composition, particle size) to the strength of the formed product or the sintering shrinkage. In addition, as one of the characteristics of refractory materials, indicators such as the shape and size accuracy and smoothness of the finished product are extremely important in some cases. This aspect is omitted here. For products with basic characteristics, most of the test methods for refractory materials have been standardized and normalized. For products with high frequency of application characteristics, they are standardized or similar to make them universal. The test methods for refractory materials have changed with the development of the times. As discussed in the main text, they are also of great significance to the history of technological development. The test methods for refractory materials currently used are roughly divided into the following points: (1) Tests for production management and quality management during the manufacturing process (including raw material analysis, defect inspection, etc.). (2) Testing of basic and application characteristics of finished products.
(3) Simulation test of finished products.
(4) Testing of finished products in actual furnaces.
Regarding the quality specifications of refractory materials, governments and non-governmental organizations have already started to formulate and revise them, and this aspect will be discussed in the following. Recently, the integration of international standards ISO for refractory materials and quality specifications is a good opportunity.
Furnace design and construction and repair of refractory materials
Refractory materials are used in furnaces (or other high-temperature processing equipment). The order of their use is first the design of the furnace body. This process determines the type, shape, size, etc. of refractory materials that must be used. The basic conditions of the construction method are also largely determined during the design stage. It is generally believed that the design stage determines more than half of the effect of refractory materials. However, it is affected by construction conditions and furnace operating conditions (usage conditions). In particular, the furnace operating conditions are very different from the initial design premise conditions. The greater the difference, the greater the impact.
The construction of refractory materials and the operation of furnace repair (furnace building and furnace repair) were previously carried out in a high-temperature and dusty working environment. However, with the progress of mechanized operations, the working environment has greatly improved. In particular, the expanded use of amorphous refractory materials has greatly promoted the mechanized operations of construction and repair.
Basic properties, as the literal meaning suggests, are the fundamental material properties of refractory materials. These properties are independent of the refractory's form or application. Examples include microstructure density, structural composition, high-temperature strength, and thermal conductivity.
Application properties are important properties related to the refractory's application, such as CO resistance when used in a CO atmosphere or high-temperature creep resistance when used under prolonged high-temperature loads. Application properties are often closely related to these basic properties and can be inferred from them. For example, thermal shock resistance (spalling resistance) is a crucial application property in environments subject to drastic temperature fluctuations. Methods for estimating these properties from basic properties such as tensile strength, elastic modulus, linear expansion coefficient, and thermal conductivity are widely used.
Table 1-6 is a list of the main characteristics divided into basic characteristics. According to their use, there are many examples of application characteristics, especially the application characteristics that have not yet been standardized. The above characteristics are ultimately the characteristics of the finished refractory products (commodities). In the actual manufacturing process, characteristics are indispensable for production management. These characteristics range from the original quality characteristics (composition, particle size) to the strength of the formed product or the sintering shrinkage. In addition, as one of the characteristics of refractory materials, indicators such as the shape and size accuracy and smoothness of the finished product are extremely important in some cases. This aspect is omitted here. For products with basic characteristics, most of the test methods for refractory materials have been standardized and normalized. For products with high frequency of application characteristics, they are standardized or similar to make them universal. The test methods for refractory materials have changed with the development of the times. As discussed in the main text, they are also of great significance to the history of technological development. The test methods for refractory materials currently used are roughly divided into the following points: (1) Tests for production management and quality management during the manufacturing process (including raw material analysis, defect inspection, etc.). (2) Testing of basic and application characteristics of finished products.
(3) Simulation test of finished products.
(4) Testing of finished products in actual furnaces.
Regarding the quality specifications of refractory materials, governments and non-governmental organizations have already started to formulate and revise them, and this aspect will be discussed in the following. Recently, the integration of international standards ISO for refractory materials and quality specifications is a good opportunity.
Furnace design and construction and repair of refractory materials
Refractory materials are used in furnaces (or other high-temperature processing equipment). The order of their use is first the design of the furnace body. This process determines the type, shape, size, etc. of refractory materials that must be used. The basic conditions of the construction method are also largely determined during the design stage. It is generally believed that the design stage determines more than half of the effect of refractory materials. However, it is affected by construction conditions and furnace operating conditions (usage conditions). In particular, the furnace operating conditions are very different from the initial design premise conditions. The greater the difference, the greater the impact.
The construction of refractory materials and the operation of furnace repair (furnace building and furnace repair) were previously carried out in a high-temperature and dusty working environment. However, with the progress of mechanized operations, the working environment has greatly improved. In particular, the expanded use of amorphous refractory materials has greatly promoted the mechanized operations of construction and repair.