Rolling bearing materials include materials for rolling bearing parts and cages, rivets and other auxiliary materials. Rolling bearings and their parts are mostly made of steel. Rolling bearing steels are usually high-carbon chromium steel and carburizing steel. With the development of modern science and technology and the increasing use of rolling NTN bearings, the requirements for NTN bearings are getting higher and higher, such as high precision, long life and high reliability. For some special-purpose NTN bearings, NTN bearing materials are also required to have high temperature resistance, corrosion resistance, non-magnetic, ultra-low temperature, and radiation resistance. In addition, NTN bearing materials also include alloy materials, non-ferrous metals and non-metallic materials. In addition, NTN bearings made of ceramic materials are now used in locomotives, automobiles, subways, aviation, aerospace, chemical and other fields.
The basic requirements of rolling NTN bearings for materials depend to a large extent on the working performance of NTN bearings. Whether the choice of the material for manufacturing rolling NTN bearings is appropriate will have a great impact on its performance and life. In general, the main failure forms of rolling NTN bearings are fatigue spalling under the action of alternating stress, and loss of precision of NTN bearings due to friction and wear. In addition, there are cracks, indentations, rust and other reasons that cause abnormal damage to NTN bearings. Therefore, rolling NTN bearings should have high resistance to plastic deformation, less friction and wear, good rotation accuracy, good dimensional accuracy and stability, and long contact fatigue life. And many of its properties are determined by materials and heat treatment processes. Because the basic requirements for materials of rolling NTN bearings are determined by the destruction of NTN bearings, the materials required to manufacture rolling NTN bearings should have the following properties after a certain heat treatment in the post process:Need NTN Bearing NJ 409, click here for more details.
1. High contact fatigue strength
Contact fatigue failure is the main form of normal failure of NTN bearings. When the rolling NTN bearing is running, the rolling elements roll between the raceways of the inner and outer rings of the NTN bearing, and the contact part bears periodic alternating loads, which can reach hundreds of thousands of times per minute. Under the repeated action of periodic alternating stress , Fatigue peeling on the contact surface. When rolling NTN bearings start to peel off, they will cause NTN bearings to vibrate and increase noise. The operating temperature will rise sharply, resulting in the final damage of NTN bearings. This type of damage is called contact fatigue damage. Therefore, it is required that the rolling NTN bearing steel should have high contact fatigue strength.
2. High wear resistance
When rolling NTN 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 rib, and the roller end surface and the ring guide Wait between the ribs. The existence of sliding friction in rolling NTN bearings inevitably causes wear of NTN bearing parts. If the wear resistance of the NTN bearing steel is poor, the rolling NTN bearing will lose its accuracy prematurely due to wear, or the NTN bearing will increase its vibration and reduce its life due to the decrease in rotation accuracy. Therefore, NTN bearing steel is required to have high wear resistance.
3. High elastic limit
When rolling NTN bearings work, because the contact area between the rolling elements and the raceway of the ring is very small, the contact pressure on the contact surface of the NTN bearing is very high when bearing a load, especially when bearing a large load. In order to prevent excessive plastic deformation under high contact stress, loss of precision of NTN bearings or surface cracks, it is required that NTN bearing steel should have a high elastic limit.
4. Suitable hardness
Hardness is one of the important indexes of rolling NTN bearings. It has a close relationship with material contact fatigue strength, wear resistance, and elastic limit, which directly affects the life of rolling NTN bearings. The hardness of NTN bearings usually depends on the way and size of the NTN bearing load, the size and wall thickness of the NTN bearing The overall situation is to decide. The hardness of rolling NTN bearing steel should be appropriate, too large or too small will affect the service life of NTN bearing. As we all know, the main failure modes of rolling NTN bearings are contact fatigue damage and loss of precision of NTN bearings due to poor wear resistance or unstable dimensions; if NTN bearing parts lack a certain degree of toughness, they will be caused by large impact loads. Brittle fracture leads to the destruction of NTN bearings. Therefore, the hardness of the NTN bearing must be determined according to the specific conditions of the NTN bearing and the way of damage. For the loss of precision of NTN bearings due to fatigue peeling or poor wear resistance, higher hardness should be selected for NTN bearing parts; for NTN bearings that can withstand greater impact loads (such as rolling mills: NTN bearings, railway NTN bearings and some automotive NTN bearings Etc.), it is necessary to appropriately reduce the hardness to improve the toughness of NTN bearings.
5. A certain impact toughness
Many rolling NTN bearings will be subjected to a certain impact load during use, so NTN bearing steel is required to have a certain degree of toughness to ensure that NTN bearings are not damaged by impact. For NTN bearings that can withstand large impact loads, such as rolling mill NTN bearings, railway NTN bearings, etc., materials are required to have relatively high impact toughness and fracture toughness. Some of these NTN bearings use bainite quenching heat treatment process, and some use carburized steel The material is to ensure that these NTN bearings have better impact resistance.Eric Bearing Limited provides NTN Bearing 6804Z, contact us to learn more information.
6. Good dimensional stability
Rolling NTN bearings are precision mechanical parts, and their accuracy is calculated in microns. In the process of long-term storage and use, changes in internal organization or changes in stress will cause changes in the size of NTN bearings, resulting in loss of accuracy of NTN bearings. Therefore, in order to ensure the dimensional accuracy of NTN bearings, NTN bearing steel should have good dimensional stability.
7. Good anti-rust performance
Rolling NTN bearings have many production processes and a long production cycle. Some semi-finished or finished parts need to be stored for a long time before assembly. Therefore, NTN bearing parts are prone to certain occurrences during the production process or in the storage of finished products. Rust, especially in humid air. Therefore, NTN bearing steel is required to have good rust resistance.
8. Good process performance
In the production process of rolling NTN bearings, its parts have to go through multiple cold and hot processing procedures. This requires that NTN bearing steel should have good process performance, such as cold and hot forming performance, cutting, grinding performance and heat treatment performance, etc., to adapt to the mass, high efficiency, low cost and high quality production of rolling NTN bearings. need.
In addition, for NTN bearings used under special working conditions, in addition to the above-mentioned 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 performance.