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
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Refractory design effect for EAF lining performance

Refractory design is one of the most fundamental factor in furnace construction. Its details and proven technology consideration is of paramount importance to come up with an optimum furnace life and to maintain productivity in the life span of the furnace lining.

The failure to produce a technically or operationally durable refractory design lining could give rise to premature deterioration of the refractory lining and furnace shell.

The premature failure of the furnace lining will lead to extensive heat losses, furnace bath shift, change in taphole orientation and alteration of the Pitch Circle Diameter. In this way, the pre-design of refractory lining is very important, we must pay attention to every details, finding out the most suitable refractories for each part.
If you want to learn more about this, please contact us. 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.
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How to distinguish the quality of high alumina refractory bricks

Application
High-alumina bricks are commonly used for industrial furnaces such as steel, steel making, hot blast stoves, electric furnace tops, blast furnaces, reverberatory furnaces, rotary kiln linings, etc., which are mainly composed of high alumina bauxite; sillimanite minerals (including Kyanite, red sill, sillimanite, etc.; artificial composition of materials, such as industrial alumina, mullite, fused corundum and so on.)
Characteristics
1.Strong wear resistance
2. Excellent thermal conductivity
3. Great resistance to impact
4. Great slag resistance
Factors affecting quality

Color
When buying high-alumina bricks, the first thing to look at is color. The excellent high-aluminum brick surface is lubricated, the color is yellow and white, the four sides are flat, no break angle, no cracks.
Appearance impurity
In addition, it is to look at the content of impurities on the surface of refractory bricks. In high-aluminum bricks, we often see some black spots on the surface. These are the impurities in the raw materials. In theory, the less impurities, the better, because most of these impurities are the iron oxide is simply reduced to molten iron in the high temperature environment of the kiln, which forms the damage of the refractory brick structure and then affects the service life of the refractory brick.
Weight
To weigh the weight of a single brick, take the T-3 standard brick as an example. The weight of the first grade high aluminum brick is 4.5kg or so. The second-grade high-alumina brick has a single weight of around 4.2kg, and the third-grade high-aluminum brick has a single weight of about 4.0 kg. The equal grade, the equal parameter type can reach this specification and can be regarded as an excellent high-aluminum brick. On the contrary, the quality of this component cannot be achieved.
Article Source:China ladle lining materials development
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Converter Lining Repair with Bricks

In the process of steelmaking in converter, due to the impact of molten iron and scrap on the lining, the scouring of the lining in the smelting of molten steel and slag, and the chemical erosion of the slag to the lining, the converter lining will be damaged to varying degrees during use. The lining is gradually thinned. When the lining is thinned to a certain thickness, the damaged part of the lining must be repaired in time.
In order to improve the converter operation rate, the principle of rapid sintering of magnesium carbide ladle bricks and residual slag of the converter at high temperature is utilized, and the existing furnace technology is boldly innovated and improved, and the bricks are used instead of materials to fix the converter. Fixing with firebricks saves more time and cost when compared to ramming mass.
Brick repair is a kind of furnace protection method with low cost and short sintering period. After the steel is finished, the steel can be repaired by pouring the residual bricks that meet the requirements of the furnace into the converter. By pouring it to the position need being repaired, using the residual heat in the slag after tapping, where the converter is damaged, the slag and the ladle are quickly sintered and formed to achieve the purpose of repairing the lining.
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Refractory design concept on reheating furnace

1. The plastic refractories can have high refractoriness and high flexural strength. Its function is to directly contact the flame in the furnace and resist the erosion of the furnace gas. According to the difference of working temperature of various parts inside the furnace body, different grades of plastic can be selected to reduce the construction cost.
2. The thermal insulation coefficient of the lightweight thermal insulation brick is between the plastic and the fiber refractory material, and its working position is also between the two. However, because there are many parts in the furnace body that are in direct contact with the plastic and fiber refractory materials, the calculation of the heat dissipation of the furnace body is based on the refractory material with the smallest thermal conductivity, so its chemical composition and physical properties can be neglected.
3. Because of the large thermal conductivity of plastics, in order to reduce the energy loss of the reheating furnace and improve the resource use efficiency, a fiber refractory material with very low thermal conductivity is designed and used together. Compared to plastics, fiber refractories can be considered as 0, ie insulation materials.
4. According to the particularity of the furnace body and the convenience of construction, fiberboard is used in the furnace wall, and the fiber blanket is used at the top of the furnace. Because of the limited space in the roof, a thin ceramic fiber blanket with a lower thermal conductivity is used.

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Steel-making

Steel is made by pig iron produced by blast furnace and DRI sponge iron and scrap as raw material, using different melting methods into steel, which include converter steelmaking method, open hearth furnace, electric arc furnace steelmaking etc. three categories. All the three kinds of steel-making process can meet the general quality requirements of steel users.

In order to meet requirements for higher quality and more varieties of high-grade steel, there has a variety of handling methods for molten steel outside of the furnace (also known as refining), such as blowing argon, vacuum degassing and desulfurization outside of furnace etc. By additional refining processing of molten steel produced from converter, open-hearth furnace and electric arc furnace etc., we can get advanced steel grades.

For some high-quality steel for special purpose and special requirements, if further processing outside of furnace still can not meet requirements, then we will use a special method for steel refining, such as ESR, which is a complicate refining process need secondary refining. After got molten steel from converter, open-hearth furnace or electric arc furnace steel smelting, do casting for forging to make it as electrode, then start secondary refining by heating with remelting slag.

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.
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.
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Refractory properties

The physical functions of refractory materials include structural function, thermal function, mechanical function, function of use and homework function.
The structural functions of the refractory include porosity, bulk density, water absorption, transthoracic, stomatal pore size distribution, and the like.
The thermal function of the refractory materials includes thermal conductivity, thermal expansion coefficient, specific heat, heat capacity, temperature coefficient, thermal emissivity, and the like.

The mechanical properties of refractory raw materials include compressive strength, tensile strength, flexural strength, torsional strength, shear strength, impact strength, wear resistance, creep, bond strength, modulus of elasticity, and the like.
Refractory use functions include refractoriness, load softening temperature, re-firing line change, thermal shock resistance, slag resistance, acid resistance, alkali resistance, hydration resistance, CO corrosion resistance, electrical conductivity, oxidation resistance wait.

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.
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