Do you know how the breathable brick is damaged?

The breathable brick is a high-end functional refractory material and does not work continuously during the entire ladle turnover cycle, so different physical and chemical corrosion damage will occur at different times. From the perspective of sales and use practice, the damage of breathable bricks can be divided into the following categories:

1, the effect of burning oxygen

The ladle will be hot-repaired in the hot-repair area after the ladle is tapped and before the next steel connection. At this moment, the air-permeable bricks need to be burnt and purged with oxygen to clean up the remaining steel and slag. Oxygen lance purge It is beneficial to the normal use of breathable bricks. This measure ensures the cleaning of the working surface of breathable bricks and the smooth flow of gas passages, so that the ladle turnover can be carried out smoothly. The thickness of the steel and slag depends on the thickness of the steel and slag, so after removing the residue, the air-permeable brick will be burned by mistake or more. When the bottom of the package is in poor condition or the operator in the hot repair area makes a mistake, the situation may become more serious. When it reaches above 2000 degrees Celsius, the high temperature airflow is very fatal to the breathable brick, and the melting loss in these few minutes is often 23 times higher than the corrosion loss during normal use.

2, the effect of thermal stress

The refractory material of the working surface of the breathable brick, especially the refractory material of the air outlet of the breathable brick, has a large temperature gradient due to the direct contact with the high-temperature molten steel and the influence of the high-temperature molten steel and the continuous outflow of cold air. Because After repeated use, the ventilation bricks are subject to a large rapid cooling and rapid heating effect, especially near the air outlet, which is subject to greater thermal stress, and it is easy to produce annular cracks and then crack.

3, mechanical wear effect

During the tapping process, the high speed of molten steel and the strong scouring of the bottom of the ladle will also accelerate the damage of the permeable bricks. After the hydraulic model test on the damage of the permeable bricks, it is found that: when the low-speed flowing airflow is injected into the liquid phase molten pool , the airflow hits back and hits the front of the air-permeable brick, giving a certain impact force to the refractory material around the air outlet of the air-permeable brick. When the gas flow rate is further increased, the reverse pulse frequency decreases, but the reverse impact strength further increases; other , When the argon blowing enters the normal eruption state, the intense bubbles form a gas eruption beam, the eruption beam strengthens the stirring at the bottom of the ladle, the liquid phase movement at the bottom of the ladle is aggravated, and the 2-phase plume makes the permeable brick subjected to intense shear and impact stress Effect. When the breathable brick is higher than the seat brick, it is sheared by this plume, and the scouring is particularly obvious. The part higher than the seat brick is generally washed away after one use. Therefore, under the condition of newly replacing the breathable brick, this kind of The situation is often very simple; in addition, if the valve is quickly closed after the purification is completed, the reverse impact of the molten steel will also accelerate the damage of the breathable brick.

4, chemical erosion effect

The working surface of the breathable brick is in contact with the slag and molten steel for a long time. During the whole contract, the molten slag continuously infiltrates and penetrates into the brick. The oxides MnO, MgO, SiO2, FeO, Fe2O3, etc. It reacts to generate low melt and metamorphic layer, and part of the low melt will be washed away. When the stoppage time is long, because the temperature difference between hot and cold is too large, the performance of the metamorphic layer and the breathable brick body will change greatly, and the effect of thermal stress will be reduced. It will lead to the fault and fall off of the breathable brick, which will seriously affect the production efficiency and may even cause an accident.