It is the alkaline refractory products. It is generally produced by the sintered magnesia sand (MgO content 89%~92%) and the chrome ore as the raw material.
The content of Cr2O3 ≥ 8% is called magnesia chrome brick. When the Cr2O3 content no less than 20%,they are called chrome magnesia bricks.
The magnesia chrome brick we are known, commonly refers the magnesia bricks sintered by the light burned magnesia and imported chrome ore, it is also be known as ordinary sintered magnesia chrome brick, magnesia chrome brick in short.
The main crystalline phases of it is magnesite and magnesium-chromium spinel, it is burned at 1600~1800℃ in oxidizing atmosphere, it can also make the unfired brick with the binder such as sodium silicate.
Magnesium-chrome brick is the largest characterized of it is strong resistance to chemical erosion, high refractoriness resistance (fire resistance), high temperature strength, they are suitable for the burning part of the stable rotation thermal condition rotary kiln. But it also have the weaknesses. Such as large coefficient of thermal expansion, poor cold and heat resistance, difficulty in masonry and discomfort in the new production of rotary kiln or frequently running and off kiln.
There also different kinds of magnesia chrome bricks, According to the binding mode, it can be divided into ordinary, directly bonded, re-bonded, semi-re-bonded, etc.
- Commom: Raw material purity is not high, using light burned magnesia, and the sintering temperature at 1550℃.Made directly from magnesia and chrome ore. The strength is low at the high temperature, the slag resistance also not good enough. with the developing of the enhanced smelting technology of non-ferrous metals, the ordinary magnesia chrome brick have phased out.
- Directly bonded: The lower content of impurity SiO2 and CaO in brick. and the sintering temperature also higher at 1700℃.Directly bonded magnesia chrome brick with the characteristic of high melting point minerals, and the high temperature performance, erosion resistance and scouring resistance are all better than ordinary magnesia chrome brick.
- Fused Rebonded: Made by the fused magnesia chrome materials, the much less impurity content, and the higher sintering temperature above 1750℃,Effectively improve the scouring resistance ability.
- Fused Semi-rebond: It made of synthetic raw materials as aggregate, chrome ore concentrate and magnesia as the fine powder has a good thermal shock resistance performance.