Indicators which determine the high temperature performance of the refractory materials
1. Refractory: refractoriness refers to a material’s resistance to melting at high temperatures. The chemical composition of the refractory and the content of fusible impurities (such as FeO, NaO, and others) in the material determine its refractoriness. Because the high temperature load under the softening temperature of the refractory material will be reduced, the actual permissible use of refractory temperature is higher than the refractory, refractory does not represent the actual use of refractories humidity. Experimentation is usually used to determine refractoriness. Refractory materials have a refractor temperature of greater than 1580 °C.
2. High temperature structural strength: high temperature structural strength refers to the ability of refractory products to withstand pressure without deformation of the resistance when exposed to high temperatures. It’s common to estimate the weight of softening temperature. The so-called weight softening temperature refers to refractory items that began to deform of the temperature and compression deformation of 4 percent or 40 percent of the temperature at 0.2 pressure and a particular heating rate of heating. Weight loss softening start humidity refers to the temperature of the former, while weight softening 4 percent or 40 percent softening point refers to the temperature of the latter.
3. Thermal stability, also known as rapid cooling resistance, is the ability to change resistance to humidity quickly without breaking or flaking. It is calculated by heating refractory insulation goods to a certain temperature (850° C) and then cooling them with cold water until the part’s weight is reduced by 20% of its original weight. Indicators of thermodynamic stability are being assessed.
Volume stability: volume stability refers to the percentage change in volume of refractory products when heated and cooled repeatedly at a specific temperature. Refractory products within the composition of the occurrence of recrystallization and additional sintering, in general, will create residual expansion or contraction phenomena when subjected to repeated high temperatures. The maximum amount of residual expansion or contraction that can be tolerated is 0.5–1.0 percent.
Temperature high temperature chemical stability Chemical stability relates to the capacity of refractory materials to withstand high temperatures, as well as resistance to metal oxides, molten salt, and furnace gas erosion. This attribute, which is commonly used to assess slag resistance, is primarily determined by the composition of refractory products, as well as chemical and physical parameters such as porosity, bulk density, and so on.
Bulk density, porosity, and permeability: Bulk density refers to the total unit of refractory products, including weight, and is measured in g / cm3.
Porosity (percentage) is split into two categories: porosity and actual porosity. The apparent porosity is the proportion of the hole volume to the total volume of refractory product exposed to the environment. True porosity is defined as the ratio of the hole’s volume to the whole volume that is not in contact with the atmosphere.
The air permeability coefficient is 9.8Pa under pressure difference, passing through the thick 1m, surface 1m2 refractory products of the amount of air in 1h.
Thermal conductivity, specific heat capacity, and thermal expansion: thermal conductivity refers to the thermal conductivity of refractory materials, which is frequently denoted by the symbol “λ”. Its physical meaning is W / m2 when the temperature difference is 1K, the unit time is 1m, and the area of refractory products of heat is 1m2 (m.K)
The thermal storage capacity of refractories is measured in kJ / (kg * °C), and its value increases as the temperature rises.
The proportion of linear expansion “α”is a term used to describe the proportion of linear expansion that occurs in The coefficient of thermal expansion is generally expressed as the length L of the refractory material at t ° C and the length L at 0 ° C. The difference between the value of L and the ratio’s percentage.
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