The rolling mill bearing is an important part in the rolling mill stand. Its main function is to support the rotating roll, bear the rolling force transmitted by the roll, and maintain the correct position of the roll in the stand. The working conditions of rolling mill bearings are very harsh and are affected by factors such as high temperature, heavy load, water and dust. Although the consumption of bearings only accounts for about 5% of the total consumption, the impact on the rolling output is as high as 20%. Therefore, special attention must be paid to the use and performance indicators of rolling mill bearings. Typical Application of Rolling Mill Bearings Analysis of Factors Affecting Rolling Mill Bearing Failure by Bearings Used in Rolling Mill Auxiliary Devices Rolling mill bearings are precision parts with large load and poor working environment. The common failure modes of rolling mill bearings are: fatigue spalling, wear, corrosion, etc. of the working face. The failure causes are intricate and often crossed in one or more forms. There are many factors that are difficult to quantitatively express the existence of bearing failure. contact directly. According to the fishbone diagram (Fig. 1), the factors affecting the service life of rolling mill bearings are mainly divided into two aspects: internal factors and external factors. Internal factors include bearing materials, structural design, processing and manufacturing, etc. speed conditions, load conditions, lubrication, cooling, etc. Figure 1 Analysis of factors affecting the service life of rolling mill bearings Figure 1) The metallurgical quality of raw materials fundamentally affects the service life of rolling mill bearings, and it is necessary to strictly control material defects such as pores, porosity, carbide accumulation, inclusions, etc. In the case of inclusions, cracks first formed and propagated at the junction of the inclusions and the matrix, resulting in early fatigue spalling (Fig. 2, Fig. 3). Fig. 2 Peeling of the raceway surface caused by looseness and holesFig. 3 Fatigue microcracks formed along the boundary of inclusions have poor cleanliness, which will destroy the continuity of the metal matrix and reduce the plasticity, toughness and fatigue properties of the material. Under the action of variable stress, stress concentration occurs near the inclusions, resulting in pitting corrosion. After the pitting corrosion expands, fatigue spalling will be formed. The later stage of fatigue spalling damage is fatigue cracking. 2) Heat treatment The heat treatment of bearing steel is very important, and a reasonable heat treatment process is the key to ensuring the performance of the material. The metallographic structure of heat treatment is unqualified, the structure is not dense and uneven, the decarburization layer is too deep, the amount of retained austenite is too much, the stress is too large, etc., resulting in the unqualified strength of the material. Low hardness is easy to cause wear or indentation, and high hardness is easy to cause chipping. After quenching and low temperature tempering, the structure of high carbon bearing steel will become undissolved carbide, acicular martensite and retained austenite, the content of undissolved carbide and carbide morphology distribution, the size and The retained austenite will affect the apparent properties of the bearing. The lower the undissolved carbide content of the bearing steel, the higher the hardness of the bearing steel. The reason is that the less the undissolved carbide content, the lower the carbon concentration of the martensite matrix. The higher the hardness, the higher the hardness. A small amount of undissolved carbides in the quenched bearing steel helps to improve the wear resistance of the bearing, and also helps to obtain fine-grained cryptocrystalline martensite, thereby improving the toughness and fatigue strength of the bearing; carbonization The particle size of the material also has a great influence on the bearing life. The carbide particles of bearing steel are less than 0.6 μm, and its service life will be significantly improved. The distribution of material particles is also more uniform and will not be presented in a banded distribution; the distribution of network carbides will affect the connection between the matrix grains, thereby reducing the fatigue resistance limit of the bearing. If the stress exceeds the fatigue limit, cracks will gradually occur and the bearing life will be shortened. The characteristics of bainite structure will improve the proportional limit, flexural strength, yield strength and area reduction rate of carbon-chromium bearing steel, improve the toughness of bearing steel, and enhance the bearing's ability to withstand impact force, fracture force, and friction force. Contributes to good retention of bearing dimensions. 3) Load conditions The bearing of the rolling mill has a large load. For example, the radial bearing of the roll adopts a multi-row bearing. The design idea of ​​the multi-row bearing is to rely on the multi-row rolling elements to evenly carry the load and thereby enhance the bearing capacity of the bearing. However, in the rolling mill use In the actual process, the load of multi-row rolling elements cannot be completely uniform or even has a large deviation. The main factors causing the deviation include deviation from the design and manufacture of the bearing itself, the installation accuracy of the bearing seat and the wear of the rolling mill components, etc. At the same time, the bearing The load distribution is also affected by the rolling axial force and the overturning moment.