Erosion mechanism of magnesia carbon brick in slag in LF

In the ladle, the chemical composition of?slag is complex and variable, and the temperature changes frequently, especially in the ladle slag line. Therefore, the magnesia carbon brick with excellent performance is often applied to the slag line. At demostic and abroad, the erosion mechanism of magnesia-carbon bricks in ladle in slag has been deeply studied. The detailed summary is as follows:

(1) Erosion of slag on magnesia carbon bricks:
In the ladle, due to the complex physical and chemical environment of the slag line, the lining of slag is most easily damaged. The chemical erosion of magnesia by the slag mainly through the dissolution of magnesium oxide and the oxidation of carbon in the matrix of magnesia carbon brick. Under the combined effect of the following factors, the damage of magnesia carbon bricks is caused:

1. The effect of alkalinity: the lower the alkalinity of the slag, the more favorable the erosion of the magnesia carbon brick. If the alkalinity of the slag is increased, the activity of SiO2 in the slag is lowered, the oxidation of carbon can be reduced, and the alkali degree increases, the activity of FeO in the slag decreases, which relatively slows the erosion behavior of the slag on the magnesia carbon brick.

2. The influence of MgO: When the composition analysis of the LF slag line was carried out, it was found that the content of MgO in the slag layer was as high as 30%, and the higher the content of MgO in the slag, the slower the erosion of the magnesia carbon brick and the higher the alkalinity. Also, the erosion of the slag on the magnesia carbon bricks is slowed down.

3. The influence of Al2O3: Al2O3 in the slag will reduce the melting point and viscosity of the slag, increase the wettability of the slag and the refractory material, make the slag more easily penetrate from the grain boundary of the magnesia, and remove the magnesite from the magnesia carbon brick matrix.

4. The influence of FeO: Firstly, FeO in the slag is easily oxidized with graphite in magnesia carbon brick at high temperature, and produces bright white iron beads to form a decarburized layer; then the periclase in the magnesia carbon brick is also in the same slag. The FeO reaction produces a low melting point product. During the repeated heating and cooling of the ladle, the thermal expansion coefficient between the formed magnesium iron composite low melting point product and the mafic iron is inconsistent, causing the magnesium oxide on the surface of the refractory material to be broken, thereby causing the dissolution of the brick body. Foreign scholars also believe that the increase of iron content in steel slag is not good for the life of magnesia carbon brick. First, iron FeO accelerates the oxidation of carbon on the surface of magnesia carbon brick, followed by FeO reaction with MgO, which makes the structure of magnesium carbon brick work surface loose. The combination of points will accelerate the erosion of magnesia carbon bricks.
(2) Oxidation of carbon in magnesia carbon bricks:
When the magnesia carbon bricks is in contact with the slag, the carbon will decarburize with the oxide such as FeO in the slag, and the decarburization layer is formed under certain conditions, so that the structure of the working surface of the magnesia carbon brick is loose, which is damaged by the magnesia carbon brick. main reason. The carbon reacts with oxides such as CO2, O2 and SiO2 and is continuously oxidized by the iron oxides in the slag; the loose structure formed by the second decarburization layer generates larger cracks and voids under the action of thermal expansion and slag, so that the slag is easily infiltrated. And forming a low melting point phase with MgO, and at the same time, the surface layer structure of the magnesia carbon brick changes under the action of the mechanical agitation of the molten pool and the violent erosion of the steel slag, and eventually the outer layer is gradually damaged, causing the magnesia carbon brick to be seriously damaged. After the temperature exceeds a certain value, the brick structure will be damaged and then sharply eroded, which is due to the self-consumption of MgO and graphite at high temperature.
(3) Influence of stomata
The erosion of magnesia carbon bricks is more likely to occur due to the presence of micropores inside and on the magnesia carbon brick. During the use of magnesia carbon bricks, the pores play an accelerating role in the formation of the decarburization layer, which in turn makes the erosion of the slag on the refractory polishing of the magnesia carbon bricks more serious. The outside air enters the pores in the magnesia carbon brick for cooling, and the oxygen in the air reacts with the surrounding carbon to produce CO gas and is discharged through the micropores. The continuous occurrence of the two processes causes the porosity and the pore size to gradually increase. The most important factor in the generation of pores is the choice of binder in magnesia carbon bricks. The binder is generally selected from phenolic resins. If a small amount of phenolic resin is added to the magnesia carbon brick, the porosity will not be too high in the cold state of about 3%, but the phenolic resin will decompose to produce water, argon, methane, carbon monoxide, carbon dioxide and the like after heating. And pores are formed under the flow of these gases, increasing the porosity. Therefore, the magnesia carbon brick is eroded by the slag passing through the pores, so that the oxidation of carbon and the dissolution of MgO are more intense, thereby causing damage to the magnesia carbon brick. Due to the repetitive nature of the gas generation process, the damage of magnesia carbon bricks is increasing.
Changxing refractory provides refractory products, calcium silicate products, castable & mortar, china refractory brick, ceramic fiber felt, ladle & tundish nozzle, ceramic fiber with high quality for you. Such as high alumina refractory bricks, magnesia carbon brick, clay refractory bricks and other refractory products.
Article Source:Erosion mechanism of magnesia carbon brick in slag in LF
Company name:Henan Xinmi Changxing Refractory Materials Co.,Ltd
Email: sales1@chinafirebrick.com
Website:http://www.chinafirebrick.com/

Application of MgO-C bricks in ladle

Currently, inhibition of steel temperature droping has become a major issue for many steel plants. Therefore, in order to suppress temperature drop of molten steel, there has a test to study insulation problem of refractory lining in 185t ladle, by comparing three different measures.

First: Reducing the heat transfer effect of sidewall castables (30% reduction). This method is by reducing coarse particles in refractory castable, increasing porosity and other measures to reduce the thermal conductivity, to suppress heat dissipation.

Second: Using insulation materials in the backlayer of wall castable. This method is to use one layer insulating bricks with less than 1W (m℃) thermal conductivity between ladle steel shell and wall castable, to inhibit heat dissipationheat.

Thrid: Reducing the heat transfer of slag line MgO-C brick heat transfer (30% reduction). This method is developed in recent years, to select lower thermal conductivity of MgO-C brick from the high thermal conductivity of magnesia carbon brick for slag line, to suppress heat dissipation.

After comparing, the results found that: only in reducing the thermal conductivity of slag line magnesia carbon bricks , the effect of suppressing steel temperature dropping is significant, up to 2℃. The durability is same or higher than ordinary ladle, less cracks, the residual condition after use is also very good.

Changxing refractory provides refractory products, calcium silicate products, castable & mortar, china refractory brick, ceramic fiber felt, ladle & tundish nozzle, ceramic fiber with high quality for you. Such as high alumina refractory bricks, magnesia carbon brick, clay refractory bricks and other refractory products.

Article Source：Application of MgO-C bricks in ladle
Company name:Henan Xinmi Changxing Refractory Materials Co.,Ltd
Email: sales1@chinafirebrick.com
Website:http://www.chinafirebrick.com/

Effect of magnesia on refractory materials

Magnesia properties are divided into chemical and physical properties. The chemical properties of magnesia mainly refer to MgO as the main component. Periclase MgO is one of the common minerals in cement clinker, therefore, periclase has good corrosion resistance to cement clinker.

The physical properties of magnesia make refractory materials in cement rotary kiln often exhibit the following phenomena:
1. The Periclase MgO has a high melting point, so many magnesia refractories have quite high temperature resistance;
2.The magnesia has good thermal conductivity. When the high-MgO refractory raw material is used and the kiln skin is not attached, then the surface temperature of the kiln body rises. At this time, not only the heat loss is large, but also the kiln body is easily burned out;
3.The Periclase MgO has a high thermal expansion coefficient, which causes the insufficient thermal shock resistance of the magnesia refractory material. During use, the magnesia refractory material often peels off.

Changxing refractory provides refractory products, calcium silicate products, castable & mortar, china refractory brick, ceramic fiber felt, ladle & tundish nozzle, ceramic fiber with high quality for you. Such as high alumina refractory bricks, magnesia carbon brick, clay refractory bricks and other refractory products.

Article Source: Effect of magnesia on refractory materials
Company name: Henan Xinmi Changxing Refractory Materials Co.,Ltd
Email: sales1@chinafirebrick.com
Website:http://www.chinafirebrick.com/

The details of magnesia carbon brick

Magnesia carbon brick is a refractory consisting of MgO at 80-85% or more, with magnesite as the main mineral. The raw material of Magnesia carbon brick is mainly magnesite, the basic component is MgC03, after high temperature calcination into sintered magnesite, and then broken into a certain size after sintering magnesia (also known as metallurgical magnesia). Magnesia is widely used as a furnace material, refractory ramming material, containing less magnesium magnesia, as the manufacture of refractory raw materials of magnesia fire brick. Natural magnesite resources are few, China's reserves and production rank the forefront of the world. Many countries that lack magnesite rely on magnesia made from seawater, and the cost is high.

Magnesia carbon bricks according to their different production processes, divided into two kinds of sintered magnesia and chemical combination of magnesia brick. Sintered magnesia is used to burn, the size of particles with the appropriate proportion of magnesia, adding brine (MgCl2 aqueous solution) and sulfite pulp waste as a binder, press molding, in the 1550-1650 ℃ high temperature firing. In the firing process, the impurities in the magnesite and the addition of liquid phase, the magnesia carbon brick bonded together. And the chemical combination of magnesia carbon brick is not through the firing process, the sintered magnesite according to the proportion of grain with a good amount, adding the right amount of mineralizer and binder, press molding, after drying is finished. Chemical combination of magnesia carbon brick strength is low, the performance is not as good as sintered magnesia, but the price is cheap, less than half the price of sintered magnesia. It is used in the performance requirements are not too high parts, such as heating furnace and soaking furnace bottom.

Chinafirebrick provides refractory products, calcium silicate products, castable & mortar, china refractory brick, ceramic fiber felt, ladle & tundish nozzle, ceramic fiber with high quality for you. Such as high alumina refractory bricks, Magnesia Carbon Brick, clay refractory bricks and other refractory.

Article Source:Magnesia Carbon Brick
Company name: Henan Xinmi Changxing Refractory Materials Co.,Ltd
Email: sales1@chinafirebrick.com
Website:http://www.chinafirebrick.com/

Why is crystalline flake graphite a raw material of magnesia carbon brick？

1.The melting point of high temperature resistant graphit is 3850℃±50℃, and boiling point 4250℃, after burnt by ultrahigh temperature arc, the mass loss is small, and the coefficient of linear expansion is small. The strength of graphit will get higher with the increase of temperature, it will be doubled at 2000℃; If you need any refractory products, such as fire brick for sale, refractory raw materials, refractory nozzle and other refractory products.

2.Electrical conductivity and thermal conductivity. The electrical conductivity of graphit is one time higher than normal nonmetallic ore. Its thermal conductivity is even higher than some metals like steel, iron, lead, etc.. Thermal conductivity goes lower as temperature increase. Graphit can become thermal insulator at superhigh temperature;

3.Lubricating property. The lubricating property of graphit depends on the size of flake, the biger the flake, the smaller the friction coefficient, the better the lubricating property;

4.Chemical stability. Graphit has excellent chemical stability under normal temperature, it is resistant to the erosion of acid, alklai and organic solvent;

5.Plasticity. Graphit has good plasticity, can be grinded very thin;

6.Thermal shock resistance. Graphit is able to endure the drastic changes of temperature, volume change is small and there will be no crack.There have many kinds of refractory products in our factory. Such as fire brick, Magnesia Carbon brick, refractory raw materials, refractory nozzle and other refractory products.

Article source: Why is crystalline flake graphite a raw material of magnesia carbon brick