The process flow of magnesia carbon brick production

1. Broken to pieces

Crushing is the process of processing bulk materials into ideal particle size materials. It is an indispensable process in the production of refractory materials. Although it is simple, it is very important. It has an important impact on the stability of product quality. At the same time, the crushing equipment consumes a lot of power, wears a lot, and has a high maintenance rate, so the maintenance cost is high. Pay attention to crushing, stabilize product quality, save energy and reduce consumption.
The purpose of crushing in the process of producing magnesia carbon bricks is mainly to prepare raw materials of various particle sizes. Increase the specific surface area of the material and destroy the crystal lattice of the material to cause defects, thereby accelerating the physical and chemical reaction speed of the material.

2. Ingredients (weighing)

Batching is the process of combining different raw materials and different particles according to product formula design. The method of batching varies according to the type and state of the raw material.
The weight batching method is usually used in the production of magnesia carbon bricks, because the weight batching method has high accuracy and generally does not exceed 2%. Commonly used weight batching equipment includes manual weighing scales, automatic weighing scales, weighing vehicles, etc., and the corresponding equipment is selected according to the requirements and automatic control level.

3. Preparation of mud (mixing, kneading)

The purpose of mixing materials is to make the composition of the materials uniform and to maximize the contact surface between different materials. The kneading of refractory materials is a method of homogenizing materials accompanied by extrusion, kneading, and exhaust processes. Like the mixing of any powder, the mixing of refractory materials is also carried out step by step, and the mixing process is more complicated due to the different components, particle sizes, binders and admixtures of the materials.

There are many types of magnesia carbon bricks. According to the different parts used, the formula is also different, mainly the taste of magnesia, the amount of graphite added, and the type and quantity of additives will change. For example, in the slag line of the ladle, in order to improve the slag resistance and thermal shock resistance of magnesia carbon bricks, the grade and amount of graphite must be increased. If the carbon content is less than 10%, the continuous carbon network cannot be formed inside the magnesia-carbon brick, and the characteristics of carbon cannot be fully exerted, which will affect the slag resistance and thermal shock resistance of the magnesia-carbon brick. And if the carbon content is too high, it will not only bring difficulties to the production of magnesia carbon bricks, but also make the magnesia carbon bricks easy to oxidize. Therefore, the carbon content in magnesia carbon bricks is generally controlled between 10% and 20%.

In order to make the magnesia particles evenly wrapped by graphite, the following steps are generally followed when mixing the materials. Firstly, the granules are added, then resin is added, graphite is added, and fine powder and various additives are finally added. Graphite has a low density, is easy to float, and is added in a large amount, so it is not suitable for mixing, and the amount of additives added is very small, so if you want to mix the whole material evenly, you must stir for a long time with high intensity. However, the binder will volatilize and become dry during the stirring process. If the time is too long, the graphite and fine powder wrapped on the particles will fall off, so the mixing time must be well controlled.

Magnesia Carbon Brick
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4. Forming

Forming is an essential process for the production of shaped refractory products. It is a process in which refractory mud becomes a green body with a certain shape and strength under the joint action of pressure equipment and molds.

There are a variety of molding methods for refractory materials, and the magnesia carbon brick is formed by semi-dry pressing. The semi-dry method has less strict requirements on the mud material, and the process is simple. During the pressurization process, due to the low moisture content of the mud material, a large pressure must be used to force the particles to be tightly combined. Under the action of external force, the particles are rearranged, the gas is discharged, and the particles are combined to generate strength and form a green body with a certain shape. The most important factor in semi-dry forming is the external pressure. Within a certain pressure range, the external pressure directly determines the various properties of the magnesia carbon brick. As the pressure increases, the green body density increases, the porosity decreases, and the strength increases.

Magnesia-carbon bricks with excellent performance have one thing in common, that is, the bulk density of magnesia-carbon bricks is high and the porosity is low. Magnesia-carbon bricks with an open porosity lower than 4% have a very low corrosion rate.

The purpose of molding is to densify the structure of magnesia-carbon bricks. Since the magnesia-carbon bricks are formed by a semi-dry method, they must be formed under high pressure. Since the mud used for molding has a small particle size and high graphite content, the molding must be operated strictly according to the regulations, otherwise cracks or lamellar cracks will easily occur. It should be light first and then heavy, and the pressure should be increased several times. The light hammer is exhausted slowly, and the heavy hammer is kept under pressure and lifted slowly.

If conditions permit, a vacuum pumping pressurized brick machine can be used to vacuumize the mud in the mold cavity before pressurizing, and there is no need to exhaust when pressurizing, so that even if the speed of light hammer pressurization is accelerated, it will hardly be used. Magnesia carbon bricks produce cracks or laminations. Especially for high-carbon magnesia-carbon bricks, which are prone to spalling, it is especially useful.

5. Heat treatment

The heat treatment of magnesia carbon bricks is usually called drying in the factory. In fact, drying is not accurate enough here, because drying generally refers to the process of discharging the moisture contained in the product. In addition to the discharge of water, the heat treatment process of magnesia carbon bricks is accompanied by a series of physical and chemical changes, so we call this process heat treatment.

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