- Time:Feb 07, 2023
The wear of refractories used in cement kilns is mainly divided into three types: adhesive wear, abrasive wear and corrosion wear. Adhesive wear is the main failure mode at high temperature. Adhesive wear is the damage caused by the relative sliding of the contact surface of kiln material and refractory under the action of normal load. This kind of damage mainly occurs in the pouring material of cement kiln kiln mouth. The damage process is: the kiln material and the refractory material are in contact; to some extent, the kiln material and the refractory material are bonded; the kiln material and the refractory material are separated, and the kiln material is torn refractory material. Adhesive wear is directly proportional to the normal load and inversely proportional to the yield strength of the material being worn. Therefore, improving the thermal strength of refractories helps to improve the ability to resist high temperature wear.
At low temperatures, abrasive wear is the main form of damage. Abrasive wear can be divided into chisel wear, high stress rolling wear and low stress abrasion wear. The characteristic of chiseling wear is that the abrasive grains chisel into the material. During the relative sliding, the abrasive grains cut off a certain amount of tissue from the surface of the material, and plow out grooves on the surface of the refractory material. The characteristics of high-stress rolling wear are: the maximum stress on the abrasive grains exceeds the strength of the abrasive grains, the abrasive grains are continuously crushed, and the surface of the refractory material is also cracked and peeled off. The characteristics of low-stress abrasion wear are: the maximum stress on the abrasive grains does not exceed the strength of the abrasive grains, the abrasive grains are not crushed but blunted, and the surface of the refractory material is slowly worn due to low-stress abrasion. Under low stress galling wear, failure often starts from the interface of particles in the refractory material. Usually, the cracks in the cross-section of the particles expand after fatigue, followed by interface fracture and particle shedding. The general law of mechanical wear is: the higher the hardness of the abrasive grains and the greater the number, the lower the hardness of the refractory material, the greater the relative speed of the abrasive grains and the refractory material, and the more serious the wear.
Abrasive wear results from the simultaneous action of wear and corrosion. The damage to the material is greatly accelerated in the presence of aggressive media. The process of corrosion and wear is: First, the surface of the refractory is subjected to the action of the abrasive medium to produce grooves or microcracks. Secondly, the corrosive medium invades the surface of the worn material along the microcracks, and a corrosion reaction occurs. Next, the material is degraded in the areas subjected to wear, and these areas lose their ability to resist wear due to weakened properties. Finally, the abrasive media removes the deteriorating material from the refractory surface.
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