What are the performance aspects of refractory materials?

2023-08-21 15:25


1、 What are the physical properties of refractory materials?


1. Physical performance: structural performance, thermal performance, mechanical performance, usage performance, and operational performance.


2. Structural performance: porosity, bulk density, water absorption, air intake, pore size distribution, etc.


3. Thermal performance: thermal conductivity, thermal expansion coefficient, specific heat, heat capacity, thermal conductivity, thermal emissivity, etc.


4. Mechanical properties: compressive strength, tensile strength, flexural strength, torsional strength, shear strength, impact strength, wear resistance, creep resistance, withering strength, elastic modulus, etc.


5. Usage performance: fire resistance, load softening degree, change in firing line, resistance to thermal expansion, resistance to flow, resistance to shipping, resistance to alkalinity, pit hydration, corrosion resistance to CO, conductivity, and corrosion resistance.


6. Job performance: slump, flowability, plasticity, adhesiveness, resilience, condensation, hardening, etc.


2、 Porosity of refractory materials


1. The ratio of pore volume to the total volume of a material can be divided into true porosity, closed porosity, and apparent porosity. It is commonly referred to as apparent porosity in the refractory industry in China. The pores in refractory materials can be roughly divided into three types: closed pores, open pores, and through pores.


2. Merge the above three types of pores into two categories, namely open pores (including through pores) and closed pores. Apparent porosity refers to the volume density of all open pores in the material, which is the ratio of the dry mass of the refractory material to its total volume (the total volume of solid, open pores, and closed pores), that is, the mass per unit volume of the material, expressed in g/cm3 or kg/m3. The volume density of dense shaped refractory products should be measured in accordance with the national standard GB/T2997-2000. The volume density of shaped insulation refractory products should be measured in accordance with the national standard GB/t2998-2001. The volume density of dense refractory castable should be measured according to YB/t5200-1993.


3. Porosity is the basic technical indicator of most refractory materials, which almost affects all the properties of refractory products, especially strength, thermal conductivity, corrosion resistance, thermal shock resistance, etc. Generally speaking, as porosity increases, strength decreases, thermal conductivity decreases, and corrosion resistance decreases.


4. The porosity of refractory materials is influenced by various factors such as all raw materials and process conditions. Generally speaking, selecting dense raw materials, using a reasonable grain size distribution based on the principle of tight stacking, selecting appropriate binders, fully mixing the materials, high-pressure forming, increasing firing temperature, and extending insulation time are all beneficial for reducing the porosity of the materials.


3、 Water absorption rate of refractory materials

Water absorption rate is the ratio of the mass of all open pores in a material that are filled with water to its dry mass, expressed as a percentage. It is essentially a technical indicator that reflects the amount of open pores in a product. Due to its simplicity in measurement, it is often used in production to identify the quality of raw material satin firing. A well sintered raw material should have a lower water absorption value.



4、 Volume density of refractory materials


1 Volume density refers to the dry mass and total volume of refractory materials The ratio of the total volume of solids, open pores, and closed pores. It refers to the mass per unit volume of the material. It is expressed in g/cm3 or kg/m3. The volume density of dense shaped refractory products should be measured in accordance with the national standard GB 62997-2000. The volume density of shaped insulation refractory products should be measured in accordance with the national standard GB/t2998-2001. The volume density of dense refractory castables should be measured in accordance with YB/t5200-1993.


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2. Volume density is a characterization of the density of refractory materials and is one of the basic indicators in the quality standards of all refractory raw materials and refractory products. The volume density of materials has a significant impact on many other properties, such as porosity, strength, corrosion resistance, load softening temperature, wear resistance, thermal shock resistance, etc. For lightweight insulation materials, such as insulation bricks, lightweight castables, etc, The volume density is also closely related to its thermal conductivity and thermal capacity. Generally speaking, a high volume density of a material is beneficial for its strength, corrosion resistance, wear resistance, and load softening temperature.


5、 True density of refractory materials

True density is the ratio of the solid mass in refractory materials to its true volume (the volume of the solid part), expressed in g/cm3 or kg/m3. The true density of refractory products and refractory raw materials should be determined in accordance with the national standard GB/t5071-1997 (equivalent to iso5018-1983).


6、 Permeability of refractory materials


1. Permeability is the performance of a material that allows gas to pass through under pressure difference. Permeability is related to the size, quantity, structure, and state of the through-hole, and varies with the direction of pressure applied during the molding of refractory products. The permeability of dense shaped refractory products should be measured in accordance with the national standard GB/T3000-1999 (equivalent to the international standard IS08841-1991).


3. The permeability of refractory materials directly affects their corrosion resistance, oxidation resistance, and breathability of corrosive media such as slag, molten steel, molten iron, and various gases (vapors). For products used for isolating flames or high-temperature gases or directly contacting slag or molten metal, they are required to have very low air permeability; And some functional materials must also have a certain degree of air intake.




7、 Pore size distribution of refractory materials

The distribution of pore size is the frequency of pore volume distribution under different pore sizes in refractory materials. The distribution of pore size of refractory materials should be determined in accordance with YB/T118-1997. The pore size distribution of refractory materials is directly influenced by raw materials, particle size distribution, powder and micro powder, binder, molding and firing systems, etc. The pore size distribution has a certain impact on the corrosiveness, strength, thermal conductivity, thermal shock resistance, etc. of the material.


8、 Thermal and electrical properties of refractory materials

The thermal properties of refractory materials include heat capacity, thermal expansion, thermal conductivity, temperature conductivity, etc. The thermal properties of refractory materials are the basis for measuring whether products can adapt to specific thermal process needs, and are the basic data required for structural design of industrial kilns and high-temperature equipment. The thermal properties of refractory materials are related to the raw materials and processes used in their manufacturing, as well as their chemical composition The mineral composition and microstructure are closely related. The electrical properties of refractory materials mainly depend on their conductivity.


9、 Thermal expansion of refractory materials

The thermal expansion of refractory materials refers to the physical properties of their volume or length increasing with temperature. The thermal expansion of refractory materials can be expressed by linear expansion rate and coefficient of linear expansion, or by volume expansion rate and coefficient of volume expansion. The relative change rate of sample length (%). Linear expansion rate refers to the relative change rate of sample length for every 1 ° C increase from room temperature to test temperature.


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