1. Acidic raw materials
Mainly siliceous raw materials, such as: quartz, tridymite, cristobalite, chalcedony, flint, opal, quartzite, white silica sand, diatomaceous earth, these siliceous raw materials contain silicon oxide (SiO2) at least 90% , The pure raw material contains silicon oxide as high as 99%. Siliceous raw materials are acidic in the high-temperature chemical dynamics. When metal oxides are present or in contact with them, they play a chemical role and combine to form fusible silicates. Therefore, if the silicon material contains a small amount of metal oxide, its heat resistance will be seriously affected.
Uses and functions of five types of natural refractory raw materials
2. Semi-acidic raw materials (mainly refractory clay)
In the past classification, clay was listed in acidic raw materials, which is actually inappropriate. The acidity basis of refractory raw materials is based on free silica (SiO2), because in terms of the chemical composition of refractory clay and siliceous raw materials, the free silica in refractory clay is much less than that of siliceous raw materials. Because there is 30%~45% alumina in general refractory clay, and alumina is rarely in a free state, it must combine with silica to form kaolinite (Al2O3·2SiO2·2H2O), even if there is excess silica Very few and very small. Therefore, the acidic nature of refractory clay is much weaker than that of siliceous raw materials. Some people believe that refractory clay decomposes into free silicic acid and free alumina at high temperature, but it does not remain the same. Free silicic acid and free alumina will combine to form enlite (3Al2O3·2SiO2) when heated. Ying Laite has good acid resistance to alkaline slag. At the same time, due to the increase of alumina content in refractory clay, its acidic substance gradually weakens. When alumina reaches 50%, it will appear alkaline or neutral. It is a clay brick made under ultra-high pressure. It has high density, fineness and compactness, low porosity, and is more resistant to alkaline slag under high temperature conditions than silica. In terms of its corrosivity, Ying Lai stone is also very slow, so we think it is more appropriate to list refractory clay as a semi-acid raw material. Refractory clay is the most basic and most versatile raw material in the refractory industry.
3. Neutral raw materials
The neutral raw materials are mainly chromite, graphite, and silicon carbide (manually manufactured), which will not chemically react with acidic or alkaline slag under any temperature conditions. There are currently two such 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 for use as a barrier between alkaline refractories and acid refractories.
4. Alkaline refractory materials
Mainly magnesite (magnesite), dolomite, lime, olivine, serpentine, high alumina raw materials (sometimes neutral), these raw materials have strong resistance to alkaline slag and are mostly used for masonry Build an alkaline furnace, but it is particularly easy to chemically react with acidic slag to become salts.
5. Special refractory materials
Mainly zirconium oxide, titanium oxide, beryllium oxide, cerium oxide, thorium oxide, yttrium oxide, etc. These raw materials have varying degrees of resistance to various slags, but due to the limited source of raw materials, they cannot be widely used in the refractory industry and can only be used under special circumstances, so they are generally called special refractory raw materials.
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