At present, many machines require high speed, high load and high rotation accuracy. Therefore, the quality of materials used to manufacture rolling bearings has a great impact on the performance of rolling bearings. The basic material requirements are determined by the failure mode of the bearing. Under the action of alternating stress, the main failure form of rolling bearing is fatigue spalling, and the bearing accuracy is lost due to friction and wear. In addition, there are problems such as indentation, crack and corrosion. Therefore, the production of rolling bearing steel has the following characteristics.
When the rolling bearing is running, the rolling between the inner ring and the raceway of the outer ring of the rolling bearing, and the contact part of the rolling bearing is subjected to periodic alternating load. It can reach hundreds of thousands of times per minute. Under the action of periodic variable stress, the fatigue and peeling of the metal on the contact surface will cause bearing vibration, increase noise and rapidly increase the working temperature, resulting in the final damage of the bearing, which is called contact fatigue failure. Contact fatigue damage is the main form of normal bearing failure. The high fatigue strength of the material means that it has strong fatigue resistance, so the steel for rolling bearing should have high contact fatigue strength.
In addition to the friction of rolling bearings, the sliding friction of rolling bearings will also occur at the same time. Sliding friction mainly occurs in rolling body, raceway, rolling body and cage pocket. Rolling bearing not only has rolling friction, but also has sliding friction. Sliding friction will occur in the following parts: rolling bearing and cage, retaining ring guide groove, roller end face and annular guide baffle, etc. Both macro and micro sliding friction will cause the wear of bearing contact surface. The existence of sliding friction in rolling bearing will cause the wear of bearing parts. If the bearing steel has poor resistance, the bearing life is reduced due to the increase of wear or bearing vibration and the decrease of rotation accuracy. The rolling bearing is caused by the premature loss of accuracy. Therefore, bearing steel should have good wear resistance.
Because the contact area between the rolling element and the ring raceway is relatively small, the contact pressure on the contact surface of the bearing is very large under relatively large load. In order to prevent excessive plastic deformation under high contact pressure, loss of bearing accuracy or surface crack, bearing steel is required to have relatively high elastic limit.
Hardness has a direct impact on contact fatigue strength, wear resistance and elastic limit. Therefore, the hardness of rolling bearing will also directly affect the service life of rolling bearing. The hardness of rolling bearing steel is not the higher the better, and the size should be appropriate. Too large or too small will affect the service life of the bearing.
The hardness of materials reflects the ability to resist impact load. Many rolling bearings will bear certain impact load in use, so bearing steel is required to have certain toughness to ensure that the bearing will not be damaged by impact.
Rolling bearing is a kind of precision mechanical part, and its precision is calculated in microns (? M). In long-term storage and use, the change of part size caused by the change of internal structure of material will lose the accuracy of bearing. Therefore, in order to ensure the dimensional accuracy of bearing, bearing steel needs to have good dimensional stability.
Rolling bearings have many production processes, long production cycle, and some need to be stored for a long time. Therefore, bearings are prone to corrosion during production and storage of finished products, especially in humid air. Therefore, bearing steel is required to have certain anti rust ability.
In addition, for the bearing used under special working conditions, the steel must put forward corresponding special performance requirements, such as high temperature resistance, high speed performance, corrosion resistance, etc.