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What are refractories' main components
The main component of refractory materials is the basis for the properties of refractory materials and is the main component of refractory raw materials. The properties of refractory materials are determined by its content and properties. The main component can be an oxide with a high melting point, such as magnesium oxide, zirconium oxide, alumina and silica. It can also be a composite oxide, typically magnesia-aluminum spinel (MgO·Al2O3), dolomite (MgO·CaO), etc.; it can also be some elemental and non-oxides. Refractories can be divided into two types according to their main constituent content:
1.Acid refractory materials
Acid refractories include siliceous refractories, clay refractories and semi-felsic refractories.
2.Refractory materials which are rather neutral
From a chemical point of view, neutral refractories are strictly speaking only carbonaceous refractories that have no application in the steelmaking process. The main types of neutral refractories are
1) high aluminium refractories Al2O3>45% in this type of product is a weakly acidic refractory that tends to be neutral.
2) Chromium refractories are alkaline but tend to be neutral.
3.Alkaline refractories
Refractory materials in which MgO and CaO make up the absolute majority of the product are called alkaline refractories, which mainly include magnesia-carbon bricks, dolomite bricks, magnesia-calcium sand, magnesia-chromium bricks, forsterite and spinel refractories. Strong alkaline refractories are mainly magnesia and dolomite refractories.
What are refractory additives?
In the production process of refractory materials, a small amount of other ingredients is added to promote some performance changes of a particular type of refractory material and to simplify the production process. For example, to reduce the sintering temperature and sintering range, optimise the cost structure and improve the performance of refractory materials, some small amounts of added ingredients are called additive ingredients. Additives can significantly improve the performance of refractory materials and reduce production costs.
What are impurities in refractories?
Impurities refer to the fact that during the production and processing of refractory materials, due to the limited purity of the raw materials, some small amounts of components are introduced into the refractory materials which have a negative effect on the performance of the refractory materials. These small amounts of components are called impurities. In general, iron oxide or ferrous oxide, potassium oxide (K20) and sodium oxide (Na20) are harmful impurities in refractory materials. Impurities have a strong fluxing effect at high temperatures. They interact with each other or with the main components, causing the temperature of the eutectic liquid phase to decrease or the amount of liquid phase to increase, thereby reducing the performance of the refractory. For example, if the Fe2O3 content in magnesia-chromium bricks is high, when the molten steel refining atmosphere changes from oxidation to reduction, magnesium ferrite (MgO-Fe2O3) and magnesia-floustite will transform, causing the magnesia-chromium bricks to crack.
In the case of alkaline refractories based on oxides, the acidic oxides contained, and in the case of acidic refractories based on oxides, the alkaline oxides contained, are considered impurities.
