- Acidic raw materials
Mainly siliceous raw materials, such as: quartz, quartz scale, square quartz, chalcedony, flint, opal, quartzite, white silica sand, diatomaceous earth, these siliceous raw materials contain silicon oxide (SiO2) at least 90%, pure raw materials have silicon oxide up to 99% or more. Siliceous raw materials in the high temperature chemical dynamics is acidic in nature, when the presence of metal oxides, or its contact with the chemical effect, and combined into a fusible silicate class. Therefore, if the silica raw material contains a small amount of metal oxides, seriously affect its resistance to heat.
- Semi-acidic raw materials (mainly refractory clay)
In the past, the classification of clay are listed in the acidic raw materials, the actual is not appropriate. The acidic basis of refractory raw materials is based on free silica (SiO2) as the main body, because according to the chemical composition of refractory clay and siliceous raw materials, the free silica in refractory clay is much less than siliceous raw materials. Because in the general refractory clay there are 30% to 45% of alumina, and alumina is rarely free state, inevitably combined with silica into kaolinite (Al2O3-2SiO2-2H2O), even if there is excess silica amount is very little, the role is also very small. Therefore, the acidic nature of refractory clay is much weaker than siliceous raw materials. Some people believe that the refractory clay decomposition at high temperatures into free silicic acid, free alumina, but not on this unchanged, in the continued heat free silicic acid and free alumina will be combined into Yinglai stone (3Al2O3-2SiO2). Yinglaiite has good acid resistance to alkaline slag, and at the same time, due to the increase of alumina content in refractory clay, its acid gradually becomes weaker, and when alumina reaches 50%, it will appear alkaline or neutral nature, especially the clay bricks made under ultra-high pressure force, with high density, meticulous and compact, low porosity, and stronger resistance to alkaline slag than silica under high temperature conditions. As far as its aggressiveness is concerned, inlay stone is also very sluggish, so we think it is more appropriate to classify refractory clay as a semi-acidic raw material. Refractory clay is the most basic and most versatile raw material in the refractory industry.
- Neutral raw materials
Neutral raw materials are mainly chromite, graphite, silicon carbide (artificially manufactured), at any temperature conditions are not chemically reactive with acidic or alkaline slag. At present, there are two such raw materials in nature, namely chromite and graphite. Graphite in addition to natural, there are artificial graphite, these neutral raw materials, all have significant resistance to slag, the most suitable for use as alkaline refractories and acidic refractory compartments.
- Alkaline refractories raw materials
Mainly magnesite (rhodochrosite), dolomite, lime, olivine, serpentine, high alumina oxygen raw materials (sometimes neutral), these raw materials have a strong resistance to alkaline slag, more for masonry alkaline furnace, but especially easy and acidic slag chemical reaction and become salts.
- Special refractory materials
Mainly zirconium oxide, titanium oxide, beryllium oxide, cerium oxide, thorium oxide, yttrium oxide, etc.. These raw materials have different degrees of resistance to a variety of slag, but due to the source of raw materials are not available, can not be used in the refractory industry in large quantities, only in special circumstances, so commonly known as special refractory materials.