Microstructure of magnesia chromium refractories

Microstructure of Magnesium Chromium Refractory Materials

The microstructure of magnesium chromium refractory materials is a key factor affecting their physical and chemical properties. Magnesium chromium refractory materials are usually composed of magnesia and chromite. Their microstructure characteristics, such as crystalline microstructure and grain size, etc., significantly influence the properties of the material.

Microstructure of Magnesia-Chromite Refractory Materials

Magnesia-chromite refractory material is composed of two oxides, MgO and Cr2O3, and their microstructure reflects the ratio of the two oxides. When MgO content is more than 90%, there will be few crystal particles of Cr2O3, and the structure is mainly composed of flake crystalline magnesia and combined with a small amount of amorphous Cr2O3. The MgO content is reduced, and the amount of amorphous Cr2O3 increases. That is, primary magnesia crystals are decorated by secondary Cr2O3 crystalline particles. When the MgO content is reduced to 70%, the amount of amorphous Cr2O3 will reach a maximum and the MgO crystalline grains become smaller. The reduction of the MgO content does not significantly affect the crystal structure of Cr2O3.

With the increase of chromite content, the primary magnesia crystalline grain size decreases and the matrix of the material becomes finer. Therefore, the magnesia-chromite refractory material can be seen as having a fine matrix structure with primary magnesia crystals and secondary chromium oxide crystalline particles.

Impact of Grain Size on the Property of Magnesia-Chromite

Grain size is one of the important characteristics of a materials microstructure. The grain size of magnesia-chromite refractory materials has a significant influence on their properties. Generally speaking, the higher the content of magnesia-chromite, the finer the grain size.

The grain size of magnesia-chromite affects its compression strength and thermal shock resistance. As the grain size decreases, the compression strength increases, while its thermal shock resistance decreases. In addition, when the content of magnesia-chromite is higher and the grain size is finer, its thermal conductivity, electrical conductivity and corrosion resistance will increase.

Conclusion

The microstructure of magnesium chromium refractory material is a very important factor affecting its properties. It is composed of primary magnesia crystals and secondary chromium oxide crystalline particles, which are surrounded by an ultra-fine matrix. The grain size of magnesium chromium refractory materials has a significant influence on its compression strength and thermal shock resistance. Increasing the grain size of the material can improve its compression strength, while decreasing its thermal shock resistance.

Magnesium-chrome refractory is a type of refractory material that is widely used in industrial furnaces due to its high temperature resistance and heat insulation properties. The microstructure of magnesium-chrome refractory is composed of two basic components, namely magnesia (MgO) and chrome (Cr203), as well as certain other components such as alumina (Al2O3), calcium carbonate (CaCO3), etc.

The magnesia particles in magnesium-chrome refractory are spherical or ellipsoidal in shape. The main elements of magnesia particles are magnesium oxide and silica. The internal structure of magnesia particles consists of a layered plate geometric structure and a network structure. The layers formed by the plate geometric structure are dense and have a larger area of contact with the adjacent layers, thereby improving the strength and thermal stability of the magnesia particles. The network structure is composed of many interconnected channels and voids, which are beneficial to the formation of liquid phases and gas phases during the sintering process, thereby improving the working performance of the magnesia particles.

The chrome particles in magnesium-chrome refractory are usually in the form of short fibers with a smooth surface. The main elements of the chrome particles are chrome, silicon and oxygen. The particle internal structure consists of rib-like structures and layers of cubic crystals. The rib-like structure of chrome particles has better thermal stability and higher temperature resistance. The layers of cubic crystals are formed by the diffusion of oxygen between the adjacent chrome particles, which has a beneficial effect on the reduction and oxidation of the system.

In summary, the microstructure of magnesium-chrome refractory is composed of two main components, magnesia and chrome particles, both of which possess unique characteristics that contribute to its high temperature resistance and heat insulation properties.