Do you know how to use magnesium carbon brick in ladle?

At present, the working lining used in ladle, especially the slag line, is mostly made of carbon-containing refractories. The newly laid ladle, before being put into the use of molten steel, must be baked to about 1000 ° C in accordance with the order of small fire, medium fire to large fire, and the whole process generally takes 20 to 30 hours, and some even longer. At present, quite a number of ladle use sites have not taken anti-oxidation measures for the carbon-containing working lining in the baking process, resulting in the working layer of magnesia carbon brick has produced about 20mm of oxidation and decarburization layer when the baking is finished. There are also a small number of ladle working layer magnesia carbon bricks after the laying of anti-oxidation coating, but because the coating needs to be added water in the field, the use of inconvenient, and other reasons lead to the anti-oxidation effect is greatly reduced. This is also the main reason why most ladle sites have abandoned the use of anti-oxidation coatings for a long time. The anti-oxidation coating of magnesium-carbon brick in this test is a pre-prepared slurry, which has good adhesion, is easy to paint and has a long storage period.

The bonding agent of magnesia carbon brick is phenolic resin carbonaceous material, when the temperature exceeds 450℃, the phenolic resin as bonding agent will be significantly oxidized, resulting in a significant reduction in the strength of magnesia carbon brick. The graphite in the magnesia-carbon brick material will also be significantly oxidized when it is above 800℃, resulting in a large increase in the porosity of magnesia-carbon brick and loose structure. The higher the carbon content of magnesia-carbon brick, the more obvious the porosity increase and the looser the structure after oxidation. In Figure 2, the decarburized layer of the uncoated part is basically the same as the loose layer, because after a long enough time above 800 ° C, the carbon and graphite of the resin bond eventually reach the same oxidation depth. The part of the paint and the internal body of the sample block are uniform black, and there is no loose phenomenon and decarburization phenomenon, indicating that the paint has a good anti-oxidation effect on the resin carbon and graphite in the magnesia carbon brick at each temperature point of 1100℃ and below.

In the baking process of new masonry ladle, when the temperature reaches more than 800℃, the oxidation rate of graphite and resin in magnesium-carbon brick is very fast. With the progress of oxidation, the oxidized part can also play a certain protective role on the unoxidized part, so the oxidation rate will be slowed down in the later baking period. The whole baking process results in a fully decarburized layer of around 20 mm of magnesium-containing carbon bricks, which is characterized by almost no bonding strength, high porosity and loose structure. When loaded with molten steel, under the scouring and erosion of molten steel and slag, the decarburization layer will soon fall off, and the furnace lining material of this part is almost wasted. Generally, the thickness of the new masonry working lining of the ladle is about 200mm, the residual working lining after the line is generally about 60mm, and then subtract the oxidized 20mm, the effective thickness of the working lining is about 120mm. The oxidized part accounts for about 15% of the effective use part. By brushing the anti-oxidation coating, the effective thickness of magnesia carbon brick can be increased by about 20mm on the original basis, which is equivalent to increasing the service life of the furnace lining by about 15%.

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