In the process of using ladle breathable bricks by steel manufacturers, the main reasons for the damage of breathable bricks are thermal stress, mechanical stress, mechanical abrasion, and chemical erosion.

 

The air-permeable brick consists of two parts: air-permeable core and air-permeable seat brick. When the bottom blowing gas is turned on, the working surface of the air-permeable core will be in direct contact with the high temperature molten steel. As the number of times of use increases, due to the rapid heat and cold it receives, the deeper the erosion of the ventilated brick core is, and it is easy to produce cracks.

 

The working surface of the bottom air-permeable brick is in direct contact with the high-temperature molten steel, and the temperature of the non-working surface is relatively low. The volume of the air-permeable brick and nearby refractory materials changes due to temperature changes during the recycling process of steel joining, pouring, and hot repair. The volume change, due to the existence of the temperature gradient and the difference in thermal expansion coefficient between the metamorphic layer and the original layer, the degree of volume change from the working surface of the ventilating brick to the non-working surface gradually changes, which will cause shearing of the ventilating brick. The shear force causes the ventilating brick to have cracks in the transverse direction, and in severe cases, the ventilating brick will break in the transverse direction.

During the tapping process, the molten steel will scour the bottom of the ladle with high strength, which will accelerate the erosion of the breathable brick. When the upper surface of the air-permeable brick is higher than the bottom of the bag, it will be sheared and washed by the flow of molten steel, and the part higher than the bottom of the bag will generally be washed away after one use. In addition, after refining, if the valve is quickly closed, the reverse impact of molten steel will also accelerate the erosion of the breathable brick.

 

The working surface of the air-permeable brick core is in contact with steel slag and molten steel for a long time. The steel slag and molten steel contain iron oxide, ferrous oxide, manganese oxide, magnesium oxide, silicon oxide, etc., while the components of the air-permeable brick include alumina, silicon oxide, etc. , It will react to generate low-melting substances (such as FeO·Al2O3, 2(MnO)·SiO2·Al2O3, etc.) and be washed away.

 

Increasing the service life of ventilating bricks can increase the output of steel to a certain extent. The main methods include bottom blowing asymmetric air supply, replacement of vent cores, control of reasonable bottom blowing parameters and maintenance.

 

1. In the bottom-blowing asymmetric air supply method, two sets of air-permeable bricks work alternately in production. Generally speaking, the two sets of air-permeable bricks are fully functional, and the bag age can be greatly increased, and the large-flow air supply of the air-permeable bricks when the ladle is not very large is not too problematic. In comparison, the use of this method will increase the cost, but it is insufficient compared with the promotion effect and the economic benefit produced by the increase of the package age.

 

2. Use split ventilating bricks to replace the ventilating core. After the ventilating core sees an alarm, break the pad under the ventilating brick and replace with a new ventilating core. This method can make full use of other refractory materials in the bag and improve The purpose of package age.

 

3. By controlling reasonable bottom blowing parameters and frequent maintenance, it is not only beneficial to improve the bag age, but also maintains good metallurgical effects. In the process of using ventilating bricks, when the bottom blowing pressure is too high, the molten steel will roll violently. After contact with the air, the molten steel will be re-oxidized; if the pressure is too small, the molten steel cannot be blown and the bottom blowing will fail and affect the metallurgical effect. In addition, the bottom blowing device has been neglected for a long time and may have air leakage, which not only causes the loss of bottom blowing gas and increases production costs, but also causes the bottom blowing pressure to be too small and affects the production process.