2023

Composition and Properties of Refractory Materials (Ⅰ)

Source: Network

Refractory refers to non-metallic materials with physical and chemical properties suitable for use at high temperatures, but it is not excluded that certain products may contain a certain amount of metallic materials (CB/T 18930-2002). Generally refers to the refractoriness of not less than 1580 ℃ inorganic non-metallic materials or products. Refractory materials have an iconic indicator-refractoriness, which refers to the characteristics of refractory materials that resist high temperatures without melting under load conditions. It can also be understood as the temperature at which the refractory material reaches a certain degree of softening under the action of high temperature. It is an indicator of material resistance to high temperature and can be used as a basic guarantee for the use of kilns at high temperatures. In the process of using refractory materials, in addition to being affected by high temperature (generally 1000~1800 ℃), it is also affected by physical, chemical, mechanical and other aspects, such as: bearing the load of furnace body and materials at high temperature; External stress in the operation process; Due to the rapid change of temperature, the great temperature difference caused by uneven heating and the resulting internal stress; Scour of various high temperature fluids, slag and smoke; the erosion of liquid metal, slag and impurity elements, the transformation and function of environmental atmosphere, etc. Therefore, the selection of refractory materials in addition to considering the refractoriness, but also need to consider the nature of the refractory material to fully resist the above effects, so that the refractory material can be applied under various operating conditions as much as possible.

Refractory materials due to the material, shape, manufacturing methods and the use of complex objects, such as not a reasonable division will not be conducive to (or not easy to) research, production and selection, therefore, it is necessary to scientific classification of refractory materials. It is usually divided according to the commonality and characteristics of refractory materials, and can also be classified according to the chemical and mineral composition of the materials, and can also be classified according to the preparation method of the materials, the shape and size of the materials, and the application of the materials. We only introduce the main classification methods of refractory materials.

Classification of 1.1 refractory materials

1.1.1 Classification by chemical properties

In addition to the use of refractory materials in the process of high temperature, often accompanied by slag (liquid) and gas chemical erosion. In order to ensure that the refractory material has sufficient erosion resistance in use, the chemical properties of the selected refractory material should be the same as or close to the chemical properties of the erosion medium. Classification by chemical properties is of great significance for understanding the chemical properties of refractory materials and judging the chemical interaction between refractory materials and contacts in actual use. Refractory materials according to chemical properties can be divided into acid refractory materials, neutral refractory materials and alkaline refractory materials.

1.1. 1.1 acid refractories

Usually refers to the SiO, the main component of the refractory material. At high temperatures, it is easy to react with alkaline refractories, alkaline slag, alkali-containing compounds or high alumina refractories. Generally siliceous refractories (acidic), clayey refractories (weak acid) and semi-siliceous refractories (acidic between the above two). There are also zircon refractory materials and silicon carbide refractory materials classified as acidic refractory materials, because such materials contain high SiO, or can be converted into SiO at high temperature,. Acid refractory materials have strong resistance to the erosion of acid medium.

1.1.1.2 Neutral refractories

Refractories that do not react significantly with acidic refractories, alkaline refractories, acidic or alkaline slag or fluxes at high temperatures are called neutral refractories. In the strict sense refers to the carbonaceous refractory material. Generally, high alumina, corundum, zirconium corundum and chromium refractory materials with trivalent oxides as the main body are also classified as neutral refractory materials. Because such materials contain more amphoteric oxides such as Al,0, Cr,O, and so on. This kind of refractory material has certain stability to the chemical attack of acid and alkaline medium at high temperature, especially to the attack of weak acid and weak base.

1. 1.1.3 Alkaline Refractory

Alkaline refractories are refractory materials that are easy to react with acidic refractories, acidic slag, acidic flux or high alumina refractories at high temperatures. Generally refers to the MgO, CaO or MgO · Ca0 as the main component of the refractory material, such as magnesium, lime, magnesium chromium, magnesium silicon, dolomite refractory material. Magnesia, lime and dolomite refractories are strong alkaline refractories; magnesia-chrome, magnesia-silica and spinel refractories are weak alkaline refractories. The refractoriness of this kind of refractory material is relatively high, and it has strong resistance to the chemical attack of alkaline medium.

1.1.2 Classification by chemical composition

This classification method can directly characterize the basic composition and characteristics of various refractory materials, and is a common classification method in production, use and scientific research, and has strong practical application significance.

1.1.2.1 Siliceous Refractory

Refractory materials with SiO as the main component are usually called siliceous refractories, mainly including silica bricks and fused silica products. The silica content (mass fraction) is not less than 93%, and the refractory material with natural quartzite as the main raw material is silica refractory. Silica brick to silica as the main raw material production, its SiO. The content (mass fraction) is generally not less than 85% and less than 93%. The main mineral composition is tridymite and cristobalite, which is mainly used for the construction of thermal equipment such as coke ovens and glass kilns. Fused quartz products are produced with fused quartz as the main raw material, and its main mineral composition is quartz glass. Because the expansion coefficient of quartz glass is very small, fused quartz products have excellent thermal shock resistance. For example, the fused quartz immersion nozzle is used in steelmaking and continuous casting, which has a good use effect.

1.1.2.2 Aluminosilicate refractories

Refractory materials with Si02-AI2O3 and series minerals as the main raw materials are aluminosilicate refractories. According to the different content of AL2O3, aluminosilicate refractories can be divided into different types,

Key words:

Composition and properties of refractory materials