Causes of Abnormal Wear of Double Row Angular Contact Ball Bearing Cage

Double row angular contact ball bearings can withstand radial and axial loads acting in both directions. It can limit the axial displacement of the shaft or housing in both directions. The contact angle is 30 or 35 degrees. It can provide a high stiffness bearing structure and can withstand overturning moments. Therefore, axial positioning at the rolling mill (operation side) is usually chosen. Generally consists of inner ring, outer ring, rolling elements and cage. Among them, the cage is mainly used to make the rolling elements equidistant and restrict the rolling elements to run correctly in the channel. During the use of the 4024D (double row angular contact ball bearing) bearing on the working side of the intermediate roll of a customer's six-high cold rolling mill, the bearing cage is often damaged abnormally, which seriously affects the normal production.

1. Damage phenomenon of double row angular contact ball bearing.

The main reason is that the cage wears and breaks during high-speed operation (the position of the bearing gland exceeds 80 degrees), which eventually leads to locking and adhesion. In severe cases, the roller diameter and bearing box holes will be damaged, resulting in huge economic losses and waste of human and material resources.

2. Analysis of damage causes of double row angular contact ball bearings.

• Consider the double row angular contact ball bearing itself.

Generally speaking, the double row angular contact ball bearing has low rotation accuracy and small clearance. When the linear speed of the rolling mill is high, when it is close to the limit speed of the bearing or exceeds the limit speed, the bearing temperature will be high, and then there will be problems such as abnormal noise, locking and sticking. . The damage of the angular ball bearings is all concentrated on the running side, while the bearings on the transmission side use the same batch of bearings. Under the same rotational speed and lubrication conditions, the above problems do not exist, and they can operate normally. Therefore, it can be temporarily ruled out that the bearing is damaged due to its own problems.

• Double row angular contact ball bearing size matching.

The double row angular contact ball bearing is installed on the working side of the roller system, which mainly restricts the axial movement of the shaft and does not bear any radial load. The outer diameter matches the box bore diameter F7, and the inner diameter matches the shaft diameter e6. The main bearing is C3 radial clearance. Taking into account this fit, all bearings are distributed to the main bearing after being subjected to radial forces during operation. Double row angular contact ball bearings do not bear any negative radial loads, only axial loads. Therefore, it can be temporarily ruled out that the bearing is damaged due to the size matching problem.

• Fitting of end contacts of double row angular contact ball bearings.

Carefully check the end faces of the inner and outer rings of the bearing. All damaged double row angular contact ball bearing end faces have abnormal wear, and the cage also has serious wear marks. Further check the end faces of the mating parts in contact with them, mainly including the end face of the outer ring gland, the end face of the spacer ring connecting the inner ring, and the end face of the inner hole boss of the box that locates the outer ring of the bearing, all of which are abnormally worn, with pits and protrusions on the surface . Therefore, it can be judged that there is serious relative sliding friction between the bearing and each mating contact part during operation. When the bearing is subjected to an axial force in a certain direction, the end face rests on the mating part in the opposite direction (in this case, the end face). Therefore, the faster the speed is, the irregular running of the rolling elements will produce a larger clamping force and frequent impact force on the cage, which will lead to the wear and fracture of the cage.