Follow me on: 
Basic Performance Requirements of Bearing Steel
The vast majority of rolling bearings and their parts are made of bearing steel. Bearing steel is usually high carbon chromium steel and carburized steel. With the development of modern science and technology and the increasing use of rolling bearings, the requirements for bearings are getting higher and higher, such as high precision, long life and high reliability. For some special-purpose bearings, bearing materials are also required to have properties such as high temperature resistance, corrosion resistance, non-magnetic, ultra-low temperature, and radiation resistance. In addition, bearing materials also include alloy materials, non-ferrous metals and non-metallic materials. In addition, bearings made of ceramic materials are now used in locomotives, automobiles, subways, aviation, aerospace, chemical industry and other fields.
The basic material requirements for rolling bearings depend to a large extent on the working performance of the bearings. Whether the material used to manufacture rolling bearings is suitable will have a great impact on its performance and life. In general, the main damage forms of rolling bearings are fatigue spalling under the action of alternating stress, and loss of bearing accuracy due to friction and wear. In addition, there are cracks, indentations, rust and other reasons that cause abnormal damage to bearings. Therefore, rolling bearings should have high resistance to plastic deformation, low friction and wear, good rotation accuracy, good dimensional accuracy and stability, and long contact fatigue life, and many of these properties are achieved by medium materials and thermal external treatment processes. decided jointly. Since the basic requirements for bearing materials are determined by the damage mode of the bearing, the materials used to manufacture rolling bearings should have the following properties after heat treatment:
Contact fatigue damage is the main form of bearing damage. When a rolling bearing is running, the rolling elements roll between the raceways of the inner and outer rings of the bearing, and their contact parts are subjected to periodic alternating loads, which can reach hundreds of thousands of times per minute. Under the repeated action of periodic alternating stress, fatigue spalling occurs on the contact surface. Once the rolling bearing begins to peel off, it will cause the bearing to vibrate, increase noise, and the operating temperature to rise sharply, causing the bearing to eventually be damaged. This form of damage is called contact fatigue damage. Therefore, bearing steel is required to have high contact fatigue strength.
High 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 hole, the cage and the ferrule guide rib, and the roller end surface and the ferrule guide rib. Wait between sides. 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 precision prematurely due to wear or the rotation accuracy will decrease, resulting in increased bearing vibration and reduced service life. Therefore, bearing steel is required to have high wear resistance.
When the rolling bearing is working, since the contact area between the rolling element and the ring raceway is very small, when the bearing is bearing load, especially when bearing a large load, the contact pressure on the contact surface is very large. In order to prevent excessive plastic deformation from occurring under high contact stress, resulting in loss of bearing accuracy or occurrence of surface cracks, the bearing steel is required to have a high elastic limit.
Suitable hardness
Hardness is one of the important indicators of rolling bearings. It is closely related to the material contact fatigue strength, wear resistance, and elastic limit, and directly affects the life of the rolling bearing. The hardness of the bearing is usually determined based on the way and size of the bearing’s load, the bearing size, and the overall situation of the wall thickness. The hardness of the steel used for rolling bearings must be appropriate. If it is too large or too small, it will affect the service life of the bearing.
Good toughness
It is well known that the main failure modes of rolling bearings are contact fatigue damage and loss of bearing accuracy due to poor wear resistance or dimensional instability. If the bearing parts lack a certain degree of toughness, they will be damaged due to brittle fracture when subjected to large impact loads. Therefore, the hardness of the bearing must be determined based on the specific conditions of the bearing and the mode of damage. For bearing accuracy loss due to fatigue spalling or poor wear resistance, bearing parts should be selected with higher hardness; for bearings that bear larger impact loads (such as rolling mill bearings, railway bearings and some automobile bearings, etc.), the hardness should be appropriately reduced. Hardness is necessary to improve the toughness of the bearing.
Good impact resistance
Many bearings will be 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 by impact. Bearings that bear large impact loads, such as rolling mill bearings, railway bearings, etc., require materials with relatively high High impact toughness and fracture toughness. Some of these bearings use bainite quenching heat treatment process, and some use carburizing steel materials, in order to ensure that these bearings have better impact resistance and toughness.
Good dimensional stability
Bearings are precision mechanical parts, and their accuracy is measured in microns. During long-term storage and use, changes in the internal structure or stress will cause changes in the size of the bearing, causing the bearing to lose accuracy. Therefore, in order to ensure the dimensional accuracy of the bearing, the bearing steel should have good dimensional stability.
Rolling bearings have many production processes and a long production cycle. Some semi-finished products 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, bearing steel is required to have good anti-rust properties.
Good manufacturing performance
In the process of manufacturing bearings, their parts undergo multiple cold and hot processing processes. This requires that bearing steel should have good process properties, such as cold and hot forming properties, cutting, grinding processing properties and heat treatment properties, etc., to meet the needs of large-volume, high-efficiency, low-cost and high-quality production of rolling bearings.
For bearings used under special working conditions, in addition to the above basic requirements, corresponding special performance requirements must be put forward for the steel used, such as high temperature resistance, high speed performance, corrosion resistance and antimagnetic properties.