1. Acid raw material

They are mainly siliceous raw materials, such as quartz, tridymite, cristobalite, chalcedony, chert, opal, quartzite, silica sand and diatomite. These siliceous raw materials contain at least 90% SiO2 and 99% pure raw materials. When the silicates are in contact with the silicates at high temperature, they are chemically active. Therefore, if a small amount of metal oxide is contained in the silicon material, its heat resistance will be seriously affected.

Application and function of five kinds of natural refractory raw materials

2. Semi acid raw materials (mainly refractory clay)

In the past classification, clay was listed as acidic raw materials, which was not suitable. The acidity of refractory materials is mainly based on free silica (SiO2), because according to the chemical composition of refractory clay and silica raw material, the free silica in refractory clay is much less than that in siliceous raw material. Because there are 30% ~ 45% alumina in general refractory clay, and alumina is rarely in free state, so it must be combined with silica to form kaolinite (Al2O3 · 2SiO2 · 2H2O). Even if there is excess silica, the amount is very small and the effect is very small. Therefore, the acid property of refractory clay is much weaker than that of siliceous material. Some people think that the refractory clay decomposes into free silica and free alumina at high temperature, but this is not the same. When the refractory clay is heated continuously, the free silica and free alumina will combine to form mullite (3Al2O3 · 2SiO2). In addition, the alkali resistance of clay to alkali or alkali silica is 50% and the resistance to alkali and alkali silica is very low. In terms of its erosivity, Yinglai stone is also very slow, so we think it is appropriate to list refractory clay as semi acid raw material. Refractory clay is the most basic and widely used raw material in refractory industry.

3. Neutral raw materials

The neutral raw materials are mainly chromite, graphite and silicon carbide (manufactured artificially), which do not react with acid or alkaline slag at any temperature. At present, there are two kinds of raw materials in nature, namely chromite and graphite. In addition to natural graphite, there are also artificial graphite. These neutral raw materials have significant resistance to slag, and are most suitable to be used as the interlayer of basic refractory and acid refractory.

4. Basic refractory materials

The main raw materials are magnesite (magnesite), dolomite, lime, olivine, serpentine and high alumina oxygen (sometimes neutral). These raw materials have strong resistance to alkaline slag and are mostly used to build alkaline furnaces, but they are particularly easy to react with acid slag to form salts.

5. Special refractory

They are mainly zirconia, titanium oxide, beryllium oxide, cerium oxide, thorium oxide, yttrium oxide, etc. These raw materials have different degrees of resistance to various slag, but due to the limited source of raw materials, they can not be widely used in refractory industry, and can only be used in special circumstances, so they are generally called special refractory materials.