Properties And Requirements Of Bearing Steel（1）

Rolling bearing materials include rolling bearing parts materials and cages, rivets and other auxiliary materials. The vast majority of rolling bearings and their parts are made of steel, and the steel used for rolling bearings 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 high temperature resistance, corrosion resistance, non-magnetic, ultra-low temperature, radiation resistance and other properties. In addition, bearing materials also include alloy materials, non-ferrous metals and non-metallic materials. In addition, bearings made of ceramic materials have been used in locomotives, automobiles, subways, aviation, aerospace, chemical and other fields.

     The basic material requirements of rolling bearings depend to a large extent on the working performance of the bearing. Whether the material used to manufacture rolling bearings is suitable will have a great influence on its performance and life. In general, the main failure forms of rolling bearings are fatigue spalling under alternating stress and loss of bearing accuracy due to friction and wear. In addition, there are also cracks, indentations, rust and other reasons that cause abnormal damage to the bearing. Therefore, rolling bearings should have high resistance to plastic deformation, less friction and wear, good rotational accuracy, good dimensional accuracy and stability, and long contact fatigue life. And many of these properties are jointly determined by the material and the heat treatment process. Since the basic requirements of rolling bearings for materials are determined by the damage form of the bearings, the materials required to manufacture rolling bearings should have the following properties after a certain heat treatment in the post-process:

 a, high contact fatigue strength

      Contact fatigue failure is the main form of normal bearing failure. When the rolling bearing is running, the rolling elements roll between the raceways of the inner and outer rings of the bearing, and the contact part is subjected to periodic alternating loads, which can reach hundreds of thousands of times per minute. Under the repeated action of periodic alternating stress, the contact surface Fatigue spalling occurs. After the rolling bearing begins to peel, it will cause the bearing vibration and noise to increase and the working temperature will rise sharply, resulting in the final damage of the bearing. This damage form is called contact fatigue damage. Therefore, the steel for rolling bearings is required to have high contact fatigue strength.

 b, high wear resistance

       When rolling bearings work normally, in addition to rolling friction, there is also sliding friction. The main parts of sliding friction are: the contact surface between the rolling element and the raceway, the contact surface between the rolling element and the cage pocket, between the cage and the ring guide ribs, and the roller end face and the ring guide etc. between the sidewalls. 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 increase the vibration of the bearing and reduce the service life due to the decrease of the rotation accuracy. Therefore, the bearing steel is required to have high wear resistance.