Steel for ball bearings should have the properties

Modern machines require bearings that work with high reliability under high loads, high rotational speeds, high rotational accuracy and over a wide range of operating temperatures. Therefore the appropriateness of the material chosen when manufacturing ball bearings has a great influence on their serviceability. And the basic requirements for the material are determined by the form of damage to the bearing. In general, the main damage form of ball bearings is in the alternating stress under the action of fatigue spalling, and due to frictional wear and loss of bearing accuracy. In addition, there are cracks, indentation, rust and so on. Therefore, the manufacture of ball bearings with steel should have the following properties:

A. Have high contact fatigue strength

Ball bearing operation, rolling body in the bearing inner and outer ring between the raceway rolling, the contact part of the periodic alternating load, more than every minute can reach hundreds of thousands of times, in the cyclic alternating stress repeatedly, the contact surface metal fatigue spalling, causing bearing vibration, noise increases, the working temperature rises sharply, resulting in the final damage to the bearing, known as contact fatigue damage. Contact fatigue damage is the main form of normal bearing damage. The high contact fatigue strength of the material means that its fatigue resistance, so the requirements of ball bearing steel, should have a high contact fatigue strength.

Two. Have good wear resistance

Ball bearing work, in addition to rolling friction, but also sliding friction, the main parts of sliding friction is: rolling body and raceway between, rolling body and keep frame pocket hole between, keep frame and ring guide edge between and roller end face and ring guide edge between, etc.. Whether macroscopic or microscopic sliding friction will bring contact surface wear, ball bearings in the existence of sliding friction inevitably make the bearing parts wear. If the bearing steel wear resistance is poor, ball bearings will be prematurely lost due to wear and precision or due to the decline in rotational accuracy and bearing vibration increase, life reduced. Therefore, the requirement of bearing steel should have good wear resistance.

Three. Have high elastic limit

As the rolling body and the contact area between the ring raceway is very small, bearing in the load, especially in the larger load, the contact surface contact pressure is very large. In order to prevent excessive plastic deformation under high contact pressure, so that the bearing accuracy loss or surface cracking, so the requirements of bearing steel should have a high elastic limit.

IV. Have a suitable hardness

Hardness of contact fatigue strength, wear resistance, elastic limit, have a direct impact on the relationship, therefore, the hardness of the ball bearing also directly affects the life of the ball bearing of all kinds. Ball bearing steel hardness is not the higher the better, the size should be appropriate, too big or too small will affect the contact fatigue strength, wear resistance, elastic limit, thus affecting the bearing life. Ball bearing in the national standards: when bearing rings and rollers with GCr15 bearing steel manufacturing, its hardness should be HRC61 ~ 65; with GCr15SiMn manufacturing, should be HRC60 ~ 64, a large number of tests show that in the above hardness range, the material contact fatigue strength, wear resistance and elasticity limit are high.

V. A certain degree of toughness

The hardness of the material reflects the ability to resist the impact load, many ball bearings in use will be subjected to a certain impact load, so the requirements of bearing steel has a certain toughness, to ensure that the bearing is not damaged by impact.

VI. Have good dimensional stability

Ball bearing is a precision mechanical parts, its precision is to micron (μm) to measure. In the long-term storage and use, because the material inherent organization changes and cause changes in the size of the parts, will make the bearing loss of precision, therefore, in order to ensure the dimensional accuracy of the bearing, bearing steel should have good dimensional stability.

VII. A certain degree of rustproof performance

Ball bearing production processes are numerous, the production cycle is long, some finished products also need to be stored for a long time, therefore, the bearing in the production process and finished products are very easy to rust, especially in the humid air, so, require bearing steel has a certain anti-rust performance.

Eight. Have good process performance

Ball bearing in the production, its parts to go through a number of cold, hot processing process. This requires bearing steel should have good process performance, such as cold, hot forming performance, cutting, grinding and heat treatment performance, in order to adapt to the needs of high-volume, low-cost and high-quality production.

In addition, for the special working conditions of the bearing, the steel must also put forward the corresponding special performance requirements, such as high temperature resistance, high-speed performance, corrosion resistance and anti-magnetic properties, etc.