The raw materials used to produce fired magnesia bricks mainly include sintered natural magnesia and seawater magnesia. The fired magnesia bricks produced in my country are mainly made of the first two types of magnesia. The requirements for magnesia are mainly chemical composition and sintering degree.
Magnesia Chrome Brick
Combined with the raw material of magnesia bricks is fused magnesia.
Directly combined with mid-range magnesia brick raw materials, high-purity sintered magnesia.
Burnt magnesia brick raw materials are reburned and fused skin sand. Due to the high impurity content of raw materials, raw material control is the key to firing magnesia bricks.
From the chemical composition of raw materials, in addition to the main component MgO, there are Ca0, Fe2O3, melting point and chemical stability, but when they coexist, it is possible to form new compounds, and the new compounds form a lower eutectic point , thereby reducing fire resistance and chemical stability.
Magnesia Iron Spinel Brick
The chemical composition of dead-burned magnesia should be controlled at Mg0>87%, Ca0<3.5%, Si02<5.0%, burning reduction less than 0.3%, no nodules, and the less black lumps, the better. It can also be judged and graded according to the appearance and color of magnesium stone. Pure magnesite is white after calcination, and is dyed brown, tan or tea-brown due to the influence of iron oxides. When the content of Si02 is high, it is white and yellow, and when the content of Ca0 is high, it is black. The higher the Fe2O3 content, the greater the density, and the higher the SiO2 content, the lower the density.
Dead-burned magnesia has a high calcium content, which will cause the bricks to crack when they are dry. The raw materials need to be sorted out before use, to pick out nodules and black blocks, or to digest them with water.
The hydration of the underburned material in the leather sand will also cause the cracking of the adobe.
When Ca0/Si02 is greater than 2, the melting point of the combined phase dicalcium silicate is 2150C. It has good high temperature performance and has good corrosion resistance when used in metallurgical furnaces and lime kilns, but glass kilns and magnesium-aluminum products will be produced when used. low melt. The former requires low Si02, and the latter requires low Ca0/Si02, and calcium is a harmful impurity.
