High contact fatigue strength

Contact fatigue damage is the main form of bearing normal damage. When the rolling bearing is running, the rolling element rolls between the raceways of the inner and outer rings of the bearing. The contact part of the rolling element bears periodic alternating load, which can reach hundreds of thousands of times per minute. Under the repeated action of periodic alternating stress, the contact surface appears fatigue spalling. When the rolling bearing begins to peel off, it will cause the vibration and noise of the bearing to increase, and the working temperature to rise sharply, resulting in the ultimate damage of the bearing, which is called contact fatigue damage. Therefore, it is required that the steel used for rolling bearings should have high contact fatigue strength.

High wear resistance

When the rolling bearing works normally, besides rolling friction, it is accompanied by sliding friction.The main parts of sliding friction are the contact surface between rolling body and raceway, between rolling body and cage pocket, between cage and ring guide edge, between roller end face and ring guide edge, etc. The existence of sliding friction in rolling bearings inevitably causes wear of bearing parts. If the wear resistance of bearing steel is poor, the rolling bearing will lose its accuracy prematurely due to wear or reduce its vibration and service life due to the decrease of rotational accuracy. Therefore, bearing steel is required to have high wear resistance.

High elastic limit

When a rolling bearing works, because the contact area between the rolling element and raceway is very small, the contact pressure on the contact surface of the bearing is very high when it bears a load, especially when it bears a large load. In order to prevent excessive plastic deformation under high contact stress, loss of bearing accuracy or surface crack, it is required that bearing steel should have high elastic limit.

Appropriate hardness

Hardness is one of the important indexes of rolling bearing. It has a close relationship with material contact fatigue strength, wear resistance and elastic limit, and directly affects the life of rolling bearings. The hardness of bearings is usually determined by the way and size of bearing load, bearing size and wall thickness. The hardness of rolling bearing steel should be appropriate, too large or too small will affect the service life of bearings. It is well known that the main failure modes of rolling bearings are contact fatigue failure, and bearing accuracy loss due to poor wear resistance or dimensional instability. If bearing parts lack certain toughness, brittle fracture will occur when bearing under large impact load. Therefore, it is necessary to determine the hardness of bearings according to the specific conditions of bearings and the way of damage. For bearing precision loss due to fatigue spalling or poor wear resistance, higher hardness should be selected for bearing parts; for bearings bearing bearing larger impact load (such as rolling mill, railway bearings and some automobile bearings), it is necessary to reduce the hardness appropriately to improve the toughness of bearings.

Certain impact toughness

Many rolling bearings will be subjected to a certain impact load in the use process, so bearing steel is required to have a certain degree of toughness to ensure that the bearing is not damaged by impact. For bearings with large impact load, such as rolling mill bearings and railway bearings, the required materials have relatively high impact toughness and fracture toughness. Some of these bearings are treated by bainite quenching heat treatment process, and some are made of carburized steel, in order to ensure that these bearings have good impact toughness.

Good dimensional stability

Rolling bearing is a precise mechanical part whose accuracy is calculated in micron. In the long-term storage and use process, changes in internal structure or stress will cause changes in bearing size, resulting in loss of accuracy of bearings. Therefore, in order to ensure the dimensional accuracy of bearings, bearing steel should have good dimensional stability.

Good rust resistance

There are many production processes and long production cycle of rolling bearings. Some semi-finished or finished parts need to be stored for a long time before assembly. Therefore, bearing parts are prone to corrosion in the production process or in the preservation of finished products, especially in humid air. Therefore, bearing steel is required to have good anti-rust performance.

Good process performance

In the production process of rolling bearing, its parts have to go through many cold and hot processing processes. This requires that bearing steel should have good technological properties, such as cold and hot forming properties, cutting, grinding and heat treatment properties, etc. to meet the needs of rolling bearing mass production, high efficiency, low cost and high quality.