Introduction：
The experience of using magnesia-carbon bricks in converters, electric furnaces and ladle shows that because of its excellent high temperature resistance, slag corrosion resistance and good thermal shock stability, it is very suitable for the requirements of iron and steel smelting. Carbon materials are difficult to be wetted by slag and molten steel, and magnesia has high refractory properties, high slag resistance and solubility resistance, and low high temperature creep. and other parts.
So far, huge economic benefits have been created due to its extensive use in the steelmaking process and the improvement of the steel smelting process. At present, it shows the disadvantages of high-priced graphite consumption, increased heat consumption, and continuous addition of carbon to molten steel, thereby polluting molten steel. In order to reduce the cost of raw materials and pure molten steel, low carbon magnesia carbon bricks can solve these problems well.
Mainly reflected in the following aspects:
1) Tissue density
The compactness of magnesia-carbon bricks depends on the type and amount of binders and antioxidants, the type of magnesia, the particle size and amount of graphite, etc. In addition, molding equipment, brick pressing technology and heat treatment conditions have certain influences. In order to achieve the apparent porosity below 3.0%, ensure that the molding pressure is 2t/cm2, and strengthen the bulk density of the matrix part to improve its corrosion resistance, magnesia-carbon bricks with a particle size of less than 1mm are used in wind eye bricks and tapping bricks. Different binders also have a certain influence on its compactness, and the binder with high carbon residue rate is selected for its higher bulk density.
The effect of adding different antioxidants on its compactness is obviously different. Below 800 degrees, the apparent porosity increases with the oxidation of the antioxidants. Above 800 degrees, the apparent porosity of metal-free magnesia-carbon bricks does not increase. However, the apparent porosity of the metal containing metal dropped significantly, and it was only half of that of 800 degrees at 1450 degrees, and the apparent porosity of adding metal aluminum was the lowest.
The heating speed during use will also affect the change of its apparent porosity. Therefore, when using it for the first time, try to heat up at a low speed so that the binder can be completely decomposed at a lower temperature. The effect of porosity is also obvious, the greater the temperature difference, the faster the increase of porosity.
2) Tissue density
High temperature mechanical properties Different additives have different effects on improving their high temperature strength. Research shows that for high temperature flexural strength above 1200 ℃, no additives < calcium boride < aluminum < aluminum magnesium < aluminum + calcium boride < aluminum magnesium + calcium boride, where aluminum magnesium + boron carbide is between aluminum magnesium and aluminum magnesium + calcium boride.
Thermal expansion performance The participating expansion value of it without metal added is much lower than that of adding metal, and the participating expansion value increases with the increase of the amount of metal added.
The thermal expansion and high-temperature flexural strength in different directions of anisotropy are different, mainly due to the orientation of flake graphite. Determine the principles and methods of working lining bricks. High temperature strength in the vertical direction is higher and thermal expansion is lower
