Reasons and improvement measures for roller end face wear of high speed cylindrical roller bearing
The roller end wear of high-speed short cylindrical roller bearings is a typical case. In order to avoid repeated failures, we share relevant examples of end wear, to find out the actual wear causes and make corresponding improvement measures.
1. Case of roller end face wear of high-speed cylindrical roller bearings
When a certain type of bearing is working in the external field, the alarm of excessive metal chips occurs, and the bearing fails. Its typical failure characteristics are as follows:
The roller end face appears wear, both ends of the outer diameter appear high temperature discoloration, the cage pocket hole inside the grinding beam and side beam have occurred serious high temperature wear deformation, the outer raceway guard wear deformation. Spalling occurred in the inner raceway, and the phenomenon of secondary quenching at high temperature appeared in the spalling area.
From the above failure characteristics, serious deviation of bearing rollers has occurred, resulting in the wear of roller end face, cage pocket hole, outer raceway guard edge, as well as fatigue spalling of inner raceway and high temperature secondary quenching phenomenon.
In recent years, a number of similar failures have occurred in this type of bearing, with serious wear of the outer ring retaining edge, serious wear of the roller end face, contact fatigue spalling of the inner and outer raceway and other fault characteristics.
2. Cause analysis of bearing failure
When the bearing is running at high speed, if there is any small interference or change (such as lubricating oil carbon particles caused by high temperature), the high-speed roller will produce dynamic instability, swing, the result will be abnormal sliding wear between the end face of the roller and the outer ring guard. The outer surface of the roller will also slide against the surface of the raceway of the inner ring. The result of the swing of the roller will also cause the sliding or wear on the inner surface of the cage pocket hole in contact with it. A series of sliding and wear will be accompanied by the rise of temperature. With the change of time, wear and temperature rise will increase until bearing failure is caused.
The main factors that cause roller dynamic instability and side swing are as follows:
(a) Roller accuracy. It mainly includes straightness of straight section of roller, symmetry of arc slope and chamfer, diameter difference and length difference, parallel difference and vertical difference of roller end face, surface roughness, etc.
(b) straightness of the raceway of the ring;
(c) Parallel difference of outer ring guard edge;
(d) Cage pocket hole accuracy. It mainly includes the vertical difference between the beam and the side beam, the bottom to the cage end wall thickness difference, etc.
(e) Clearance between roller end face and outer ring guard;
(f) Interference by foreign bodies.
If the roller precision is not good, it will directly affect the dynamic balance of the roller under the condition of high-speed rolling, thus destroying the running stability of the roller. In the early stage of dynamic instability of roller, if the precision such as parallel difference of outer ring guard, straightness of ring raceway and cage hole is high enough, it will play a constrains role in dynamic instability of roller, so as to keep it in normal operating state. Otherwise, it will increase dynamic instability of roller. When sliding friction occurs between the roller and the rim of the ring at a very high rotation speed, the friction heat is also very high. At this time, if the clearance between the end face of the roller and the rim of the ring is too small, it is difficult to form lubricating oil film, and the cooling effect here will be seriously affected, and eventually lead to high temperature wear of the end face of the roller and the rim of the ring. Therefore, the roller end wear failure of a high-speed short cylindrical roller bearing is the result of the above factors. The straightness of the raceway and roller of the faulty bearing ring was tested by the profiler, and the original straightness of each part was confirmed to meet the requirements, and the influence of this factor could be eliminated. Through the design review, it is found that the roller length difference requirement is low, the arc slope surface is grinding surface, roughness and accuracy are low. The parallel difference of the reference end face of the outer ring retaining edge is also required to be low. These factors should be the main factors affecting the dynamic stability of the bearing roller when it is rotating at high speed.
3. Improvement measures
According to the failure cause analysis results, the following technical improvement measures are formulated:
(1) the parallel difference between the outer ring guard edge and the reference end face is increased from 5m to 3m;
(2) Increase the length difference of each group of rollers from 8m to 4m, and the diameter difference from 0.7131 to 0.5m;
(3) Increase the requirement of the cage end wall thickness difference at the bottom of the cage pocket hole (no more than 0.05mm);
(4) Increase the superfinishing requirements of the arc slope surface on both sides of rollers.
(5) Increase the requirement of measuring the clearance between the roller end face and the outer ring guard.
The improvement effectively improves and enhances the dynamic stability when the roller rotates at high speed, the quality of the bearing in the later production is greatly improved, so as to improve the life and reliability of the bearing, and ensure the safety of the main engine. The improved bearing, after the installation of the machine, the same kind of failure did not happen again, the improvement effect is good.