Due to different uses and working conditions, the structure of rolling bearings varies a lot, but the basic structure is composed of four parts: inner ring, outer ring, rolling elements (steel balls or rollers) and cage.

(1) Inner ring (also known as inner sleeve or inner ring). Usually fixed on the journal, the inner ring rotates with the shaft. There are grooves on the outer surface of the inner ring for steel balls or rollers to roll, which are called inner grooves or inner raceways.

(2) Outer ring (also known as coat or outer ring). It is usually fixed on the bearing seat or the casing of the machine to support the rolling elements. There are also grooves on the inner surface of the outer ring for steel balls or rollers to roll, called inner grooves or inner raceways.

(3) Rolling body (steel ball or roller). Each set of bearings is equipped with one or several sets of rolling elements, which are installed between the inner ring and the outer ring, and play the role of rolling and transmitting forces. The dynamic body is the part that bears the load, and its shape, size and quantity determine the bearing's ability to bear the load and the performance of high-speed operation.

(4) Cage (also known as retainer or isolator). The rolling elements in the bearing are evenly spaced from each other so that each rolling element rolls normally between the inner and outer rings. In addition, the cage has the function of guiding the movement of the rolling elements, improving the lubrication conditions inside the bearing, and preventing the rolling elements from falling off.

In the thrust bearing, the ring matched with the shaft is called the shaft ring, the ring matched with the bearing seat or the machine shell is called the seat ring, and the shaft ring and the seat ring are collectively called the washer. In addition to the above four parts, bearings of various structures also have other matching parts. For example, rivets, dust caps, sealing rings, snap washers, retaining rings and adapter sleeves, etc.

Basic requirements of steel for rolling shafts:

I. Contact fatigue strength

Under the action of cyclic load, the contact surface of the bearing is prone to fatigue damage. That is, cracking and spalling occur, which is the main form of damage to the bearing. Therefore, in order to improve the service life of the bearing, the bearing steel must have high contact fatigue strength.

Second, wear resistance

When the bearing is working, not only rolling friction but also sliding friction occurs between the ring, the moving body and the cage, so that the bearing parts are constantly ground wear. In order to reduce the wear of bearing parts, maintain the stability of bearing accuracy and prolong the service life, bearing steel should have good wear resistance.

III. Hardness

Hardness is one of the important qualities of bearing quality, which has a direct impact on contact fatigue strength, wear resistance and elastic limit. The hardness of bearing steel in use state generally needs to reach HRC61~65, so that the bearing can obtain higher contact fatigue strength and wear resistance.

Four. Anti-rust performance

In order to prevent the bearing parts and finished products from being corroded and rusted during processing, storage and use, it is required that the bearing steel should have good anti-rust performance.

V. Machining performance

In the production process of shaft parts, many cold and hot working processes are required. In order to meet the requirements of large quantities, high efficiency and high quality, bearing steel Should have good processing properties. For example, cold and hot formability, machinability, hardenability, etc.

In addition to the above basic requirements, bearing steel should also meet the requirements of appropriate chemical composition, uniform internal structure, less non-metallic inclusions, internal surface defects that meet the standards, and surface decarburization layers that do not exceed the specified concentration. Items are clearly defined in the raw material standards.

The commonly used materials for bearing parts are: high carbon chromium bearing steel, carburized steel (such as 20Cr2Ni4A, 15Mn, 20Cr2MnMoA), high temperature bearing steel (such as Cr4Mo4V, Cr14Mo4, Cr15Mo4V, W18Cr4V), stainless bearing steel (9Cr18, 9Cr18Mo, 1Cr18Ni9Ti), vacuum degassed steel, antimagnetic bearing steel, etc., of which the most commonly used is high carbon chromium bearing steel. The basic steel grades of high carbon chromium bearing steel are GCr6, GCr9, GCr9SiMn, GCr15, GCr15SiMn. It is the most widely used and used steel in my country's bearing manufacturing industry. It has good wear resistance and contact fatigue performance. Ideal processing properties, with certain elasticity and toughness.