Basic Performance Requirements Of Steel For Rolling Bearings

In actual use, rolling bearing parts often have to work at high speed and for a long time under complex stress states and high stress values such as tension, compression, bending, shearing, and alternating. Whether the material used to manufacture rolling bearings is suitable will have a great impact on its performance and life. The basic method of selecting materials is determined based on the damage (failure) form of the bearing. Generally speaking, the main damage form of rolling bearings is fatigue peeling under the action of alternating stress.
Falling, and the loss of bearing accuracy due to friction and wear. In addition, there are also cracks, pits, rust and other reasons that cause abnormal damage to the bearings. Therefore, in general, rolling bearings should have high resistance to plastic deformation, low friction and wear, good rotational accuracy, high dimensional accuracy, good dimensional stability, and long contact fatigue life. And many of these properties are determined by the material and heat treatment process. Therefore, the materials for manufacturing rolling bearings are required to have the following properties after a certain heat treatment in the post-process.
1High contact fatigue performance
When a rolling bearing is running, when the rolling elements roll between the raceways of the inner and outer rings of the bearing, their contact parts are subjected to periodic alternating loads, which can reach tens of thousands or hundreds of thousands of times per minute. Under the repeated action of periodic alternating stress, fatigue spalling occurs on the contact surface. After peeling begins, the vibration and noise of the bearing increase, and the operating temperature continues to rise, causing the bearing to eventually fatigue and fail and become unusable. Contact fatigue damage is the main form of rolling bearing damage.
Therefore, the steel used for rolling bearings is required to have high contact fatigue strength.
2High wear resistance
When rolling bearings work normally, in addition to rolling friction, there is also sliding friction. The main parts where sliding friction occurs are: the contact surface between the rolling element and the raceway, the contact surface between the rolling element and the cage pocket, the contact surface between the cage and the ferrule guide rib, the end surface of the roller and The contact surface of the ferrule rib. The existence of sliding friction in rolling bearings inevitably causes wear of bearing parts. If the wear resistance of the bearing steel is poor, the rolling bearing will lose its accuracy prematurely due to wear or the vibration of the bearing will increase and its life will decrease due to the decrease in bearing rotation accuracy. Therefore, bearing steel is required to have high wear resistance.
3 high elastic limit
When the rolling bearing is working, due to the small contact area between the rolling elements and the inner and outer rings, the contact stress on the contact surface is very large when the bearing is under load, especially when it is under heavy load. In order to prevent plastic deformation from occurring under high contact stress Deformation may cause damage to the bearing accuracy and surface cracks, so the steel used for the bearing should have a high elastic limit.
4 Suitable hardness
Hardness has a very close relationship with contact fatigue life, wear resistance, and elastic limit. Therefore, the hardness of rolling bearings also directly affects the life of rolling bearings, so hardness is one of the important indicators of rolling bearings. The hardness of rolling bearings is usually determined based on the way and size of the bearing bearing load, the bearing size and wall thickness. Too high or too low hardness will affect the life of the bearing. As we all know, the main failure mode of rolling bearings is contact fatigue.
fatigue damage; poor wear resistance or dimensional instability leading to loss of bearing accuracy; bearing parts lacking a certain degree of toughness and brittle fracture when subjected to large impact loads, leading to bearing damage. The hardness of the bearing must be determined based on the specific conditions of the bearing and the mode of failure. For the loss of bearing precision due to fatigue spalling damage or poor wear resistance of bearing parts, bearing parts should be selected with higher hardness; for bearings withstanding large impact loads (such as rolling mills)
machine bearings, some automobile bearings, etc.), it is necessary to appropriately reduce the hardness to improve the toughness of the bearings.
5 A certain degree of resilience
Many bearings are subject to certain impact loads during use, so the bearing steel is required to have a certain degree of toughness to ensure that the bearings are not damaged due to impact loads. Bearings that bear large impact loads, such as rolling mill bearings and railway bearings, require materials with relatively high impact toughness and fracture toughness. Some of these bearings are quenched with bainite and some are made of carburized steel to ensure that these bearings have Better impact resistance.
6Good dimensional stability
Rolling bearings are precision mechanical parts, and their accuracy is measured in microns. During the long-term storage and use of bearings, the accuracy of the bearing must not be lost due to changes in bearing dimensions caused by changes in the internal structure or stress of bearing parts. Therefore, bearing steel is required to have good dimensional stability.
7 Certain anti-rust properties
Due to the numerous 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 certain corrosion during the production process or during the storage of finished products, especially It’s in humid air. Therefore, the steel used for rolling bearings is required to have certain anti-rust properties.
8Good process performance
During the production process of rolling bearings, parts need to go through multiple cold and hot processing processes, which requires that the steel used for bearings should have good processing properties, such as cold and hot forming properties, cutting performance, grinding performance, heat treatment performance, etc. To meet the needs of high-volume, high-efficiency, low-cost and high-quality production of rolling bearings. In addition, in addition to the above basic requirements, bearing steel used under special working conditions should also have corresponding special performance requirements, such as high temperature resistance, high speed performance, corrosion resistance and non-magnetic properties.