Rolling bearing parts timber including timber and cage, rivets and other supporting material. The vast majority of rolling bearings and parts made of steel, bearing steel is usually high carbon chromium steel and hardened steel. With the increasing amount of development and the use of modern science and technology of rolling bearings, bearing the increasingly high demand, such as precision, long life and high reliability. For some special purpose bearings, bearing materials also requires a high temperature, corrosion-resistant, non-magnetic, ultra-low temperature, radiation and other properties. In addition, the bearing material further includes alloys, non-ferrous metals and non-metallic materials. In addition, the ceramic material of the bearing has been applied to locomotives, cars, subways, aviation, aerospace, chemical and other fields.
Rolling basic material requirements depends largely on the performance of the bearing. Select the manufacturer of rolling bearings material is appropriate, it will have a significant impact on its performance and life. Under normal circumstances, the main damage is in the form of a rolling bearing deposit under varying stress fatigue spalling, and wear due to friction loss leaving precision bearings. In addition, crack, indentation, corrosion and other causes of non-normal damage bearings. Therefore, the bearing should have a 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 the performance is made of a material and heat treatment of the common decision. Because of the basic requirements for Rolling material damage in the form of the bearing by the decision, it requires material rolling bearings after a certain heat treatment process should have the following properties:
1, high contact fatigue strength
Contact fatigue damage is the main form bearing normal damage. When Rolling running, rolling in the bearing outer ring raceway between the rolling contact portions bear cycle alternating loads, more are up to hundreds of thousands of times per minute, in alternating cycles under repeated stress, the contact surface fatigue spalling. Rolling start after peeling will cause bearing vibration, noise increases sharply rising operating temperature, resulting in a final bearing damage, destroy this form known as contact fatigue damage. Therefore, the requirements of the rolling bearing steel should have a high contact fatigue strength.
2, high wear resistance
When Rolling normal operation, in addition to rolling friction occurs, but also with sliding friction. The main parts of the sliding friction is: the contact surface between the rolling elements and raceway, the rolling elements and to maintain contact between the surface of the cage pockets, between the cage and the ring guide ribs and roller end ferrule guide etc. between the ribs. Rolling in the presence of sliding friction bearing parts inevitably produces wear. If the difference in wear resistance of the bearing steel, bearing will wear prematurely due to loss of precision or accuracy decreased due to the rotation leaving the bearing vibration increase, decrease life expectancy. Therefore, the required bearing steel should have a high abrasion resistance.
3, high elastic limit
When working at the rolling bearing, the rolling bodies rolling between the track and the ring contact area is small, when subjected to a load bearing, particularly in the case to bear large load, the contact pressure of the contact surface is large. To prevent contact stress at high plastic deformation is too large, the bearing accuracy or the occurrence of surface cracks loss, therefore, requires bearing steel should have a high elastic limit.
4, a suitable hardness
Hardness is an important indicator of rolling bearings. It is in contact with the material fatigue strength, wear resistance, the elastic limit has a close relationship, a direct impact on the life of rolling bearings, bearing hardness is usually to be determined according to the way the bearing load and size, bearing size and thickness of the overall situation. Rolling steel hardness to be appropriate, too large or too small will affect bearing life. It is well known that the main failure mode Rolling contact fatigue damage, as a result of poor or unstable wear size leaving lose precision bearings; bearing parts if certain lack of toughness when subjected to large impact loads will lead to brittle fracture due bearing damage. Therefore, we must determine the hardness of the bearing according to the specific circumstances and manner of bearing damage. In the case of wear due to fatigue spalling or errand bearing precision loss, bearing parts should be used in high hardness; to withstand greater shock loads (eg mill: bearing, railway bearing and some car bearings, etc.), should be appropriately reduced hardness to improve the toughness of the bearing is necessary.
5, a certain degree of toughness
Many Rolling in the course will be subject - given the impact load, thus requiring bearing steel has a certain toughness, to ensure that the bearing is not due to impact damage. To withstand greater shock loads such as rolling bearings, railway bearings and other requirements of a material having a relatively high impact toughness and fracture toughness, these bearing some with bainite hardening heat treatment process, some with hardened steel material, is to ensure that these bearings have good resistance to impact toughness.
6, good dimensional stability
Rolling is a precision machine parts, its accuracy is micron for the unit. In the long-term storage and use, due to changes in internal tissue changes or stress can cause changes in the size of the bearing, resulting in loss of precision bearings. Therefore, to ensure the dimensional accuracy of the bearing, bearing steel should have good dimensional stability.
7, good rust resistance
Rolling variety of production processes, production cycle is longer, and some semi-finished or finished parts need to be stored a long time before assembly, therefore, bearing parts in the production process or are prone to corrosion in the finished product must be stored in special in humid air. Therefore, the requirements of bearing steel to have good anti-corrosion properties.
8, good process performance
Rolling in the production process, the parts to go through multi-channel cold, heat processing operations. This requires bearing steel should have good technological properties, such as cold and hot forming performance, cutting and grinding properties and heat treatment performance, etc., in order to adapt the rolling bearing large-volume, high efficiency, low cost and high quality production.
In addition, under special working conditions for bearings used in addition to the few basic requirements, it must also be made of steel corresponding special performance requirements, such as high temperature performance, high-speed performance, corrosion resistance and magnetic properties and the like.
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