The raw materials used in the production of magnesia-chrome bricks include: natural raw materials, artificial synthetic raw materials, industrial chromium oxide and industrial alumina, etc. The natural raw materials of magnesia-chrome brick heat storage bricks: such as various grades of sintered magnesia, ordinary chrome ore and chrome concentrate with low impurity content. Synthetic raw materials: co-sintered magnesia-chromium material obtained by fine grinding, mixing, and compacting of magnesia and chromium concentrate, and then calcined at high temperature; Fused magnesia chrome material; and fused magnesia. Synthetic materials should generally be raw materials with low impurity content.
The above raw materials are used in different ways. The combination and formula can be made into magnesia-chrome bricks with various names, and the manufacturer is unwilling to explain more about its formula, so the varieties and names of magnesia-chrome bricks are confusing and confusing. According to the existing names of magnesia-chrome bricks at home and abroad, it can be roughly standardized as follows.
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(1) Ordinary magnesia-chrome brick (ie, silicate combined magnesia-chrome brick), which is made of chrome ore and magnesia with more impurities (SiO2 and CaO). The firing temperature is not high at about 1550 ℃. The microstructure of the brick is characterized by: the refractory grains are combined by silicate.
The fine powder of this refractory brick is made of magnesia-chromium material which is ground, mixed, compacted and calcined by ordinary chrome ore and magnesia, which is still combined with silicate. But the performance is improved compared with ordinary magnesia bricks.
(2) Directly combined magnesia bricks are made of chromium concentrate with low impurity content and relatively pure magnesia. The firing temperature is above 1700°C. The structural feature of this kind of refractory brick is that most of the refractory grains are in direct contact. Therefore, its high temperature performance, corrosion resistance and erosion resistance are better than ordinary magnesia-chrome bricks.
(3) Recombined magnesia-chrome bricks, and magnesia-chrome bricks made of artificial synthetic raw materials co-sintered magnesia-chromium materials or fused magnesia-chromium materials (or with some fused magnesia) are often called recombined magnesia-chrome bricks. brick. In China, only magnesia-chrome bricks made of fused magnesia-chrome materials are called recombined magnesia-chrome bricks. In order to be more consistent with the international community, it is advisable to use co-sintered magnesia-chrome bricks and electrofused materials to combine magnesia-chrome bricks or fused particles to combine magnesia-chrome bricks.