Main properties of magnesia carbon bricks

Magnesia-carbon bricks are carbon-bonded refractories with magnesia and carbon materials as the main components. The main feature of magnesia-carbon bricks is the formation of a combination of carbon on the microstructure. This combination of magnesia-chromium bricks is formed by the coking of organic binders at high temperatures.

Magnesia-carbon brick is a non-burning product, and the process factors affecting the performance of magnesia-carbon brick mainly include raw materials, binders, additives, etc.

 The experience of using magnesia-carbon bricks in converters, electric furnaces and ladle shows that magnesia-carbon bricks have excellent high temperature resistance, slag corrosion resistance, and thermal shock stability, which meet the requirements of iron and steel smelting. Taking advantage of the fact that carbon materials are not easily wetted by slag and molten steel, as well as magnesia's high refractoriness, good slag resistance, solubility resistance, and low high temperature creep, magnesia-carbon bricks are used in slag lines and outflows with severe corrosion damage. Steel mouth and other parts. So far, magnesia-carbon bricks have been widely used in the steelmaking process, and the steel smelting process has been improved, which has created huge economic benefits. Magnesia brick manufacturers currently have shortcomings in the application of magnesia-carbon bricks such as high price of graphite, large consumption, increased heat consumption, and continuous increase of carbon into molten steel resulting in pollution of molten steel. In order to reduce the cost of raw materials and pure molten steel, magnesium The low carbonization of carbon bricks can solve these problems very well.

The characteristics of magnesia carbon bricks are mainly reflected in the following aspects:

1. Microstructure density of magnesia carbon bricks

The compactness of magnesia-carbon bricks depends on the type and amount of binder and antioxidant, the type of magnesia, and the particle size and amount of graphite. 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 the compactness of magnesia-carbon bricks, and the binder with high carbon residue rate is selected for its higher bulk density. The effect of adding different antioxidants on the compactness of magnesia-carbon bricks is obviously different. Below 800 °C, the apparent porosity increases with the oxidation of antioxidants. After 800 °C, the metal-free magnesia-carbon bricks show pores The apparent porosity of the metal-containing bricks does not change, and the apparent porosity of the metal-containing bricks decreases significantly, and is only half of that at 800°C at 1450°C.

The heating speed of magnesia-carbon bricks during use will also affect the change of its apparent porosity. Therefore, when using magnesia-carbon bricks, try to heat up at a low speed to make the binder completely decompose at a lower temperature. During the use of magnesia-carbon bricks, the temperature difference The effect of the change on the porosity is also obvious. The larger the temperature difference, the faster the porosity increases.

2. High temperature performance of magnesia carbon bricks

2.1 High-temperature mechanical properties: Different additives have different effects on improving the high-temperature strength of magnesia-carbon bricks. Studies have shown that for high-temperature flexural strength above 1200 °C, no additives < calcium boride < aluminum < aluminum magnesium < aluminum + boron Calcium < aluminum magnesium + calcium boride, where aluminum magnesium + boron carbide is between aluminum magnesium and aluminum magnesium + calcium boride.

2.2 Thermal expansion performance: The participating expansion value of magnesia-carbon bricks without metal added is far lower than that of adding metal, and the participating expansion value increases with the increase of the amount of metal added.

2.3 The thermal expansion and high temperature flexural strength of magnesia-carbon bricks in different directions of anisotropy are different, mainly due to the orientation of flake graphite, determine the principles and methods of working lining brick masonry. The magnesia-carbon brick in the vertical direction has higher high temperature strength and lower thermal expansion.