Bearing Heat Treatment Technology And Equipment
Bearing Heat Treatment Technology And Equipment
2022年1月4日
Common Miniature Bearing Models
Common Miniature Bearing Models
2022年1月4日

Accuracy And Grade Of Bearing

Accuracy And Grade 

The accuracy of rolling bearings is divided into (main) dimensional accuracy and rotational accuracy. The accuracy grade has been Accuracy And Grade standardized and divided into five grades: P0, P6, P5, P4 and P2.

The accuracy shall be improved successively from level 0. Level 0 is sufficient for general purposes, but Accuracy And Grade level 5 or higher accuracy is required for the conditions or occasions shown in Table 1.

Although the above accuracy levels are based on ISO standards, their Accuracy And Grade names are different in national standards.

Table 2 lists the accuracy levels applicable to various bearing types Accuracy And Grade and the comparison between national standards.

Accuracy And Grade Of Bearing

Dimensional accuracy (items related to shaft and Housing installation)

1. Allowable deviation of inner diameter, outer diameter, width and assembly width

2. Allowable deviation of inner and outer diameter of roller set

3. Allowable limit value of chamfer size

4. Allowable variation of width

Rotation accuracy (items related to the runout of the rotating body)

1. Allowable radial runout and axial runout of inner ring and outer ring

2. Allowable lateral runout of inner ring

3. Allowable variation of inclination of outer diameter surface

4. Allowable variation of thrust bearing raceway thickness

5. Allowable deviation and allowable variation of conical hole

Fracture Causes Of Imported Bearing Cage And Factors Affecting Bearing Performance

Prolonging Method And Installation Of Industrial Skf Bearing Life

Bearing plays an important role in social life. Bearing is composed of cage, outer ring, rolling element and inner ring. The components of bearing vary with different bearing types. Accuracy And Grade What are the reasons for the fracture of imported bearing cage?

Creep is also one of the causes of cage fracture. The so-called creep mostly refers to the sliding phenomenon of the ferrule. When the interference of the mating surface is insufficient, the load point moves to the surrounding direction due to sliding, resulting in the deviation of the ferrule from the axis or shell to the circumferential direction.

Once creep occurs, the mating surface will be significantly worn, and the wear powder may enter the Accuracy And Grade bearing to form a process of abnormal wear, raceway peeling, cage wear and additional load, which may even cause cage fracture.

Abnormal load of cage. If the installation is not in place, the inclination and the interference amount are too large,

it is easy to reduce the clearance, aggravate the friction and heat generation, soften the surface, and premature abnormal spalling. With the expansion of spalling, the spalling foreign matter enters the cage pocket, resulting in the operation block of the cage and additional load, which intensifies the wear of the cage. Such a deteriorated cyclic effect may cause the cage fracture.

Cage material defects and riveting defects may cause cage fracture. The countermeasures are to strictly control in the manufacturing process. The invasion of foreign matters is a common mode of cage fracture failure. Due to the intrusion of foreign hard foreign matters, the wear of cage and abnormal additional load may also lead to cage fracture.

Poor lubrication mainly refers to that the shaft is in poor oil state, which is easy to form adhesive wear and Accuracy And Grade deteriorate the working surface state. The tears caused by adhesive wear are easy to enter the cage, resulting in abnormal load on the cage, which may cause cage fracture.

Bearing plays an important role in the field of machinery. Bearing can not Accuracy And Grade only be used in machinery, but also be made into some craft toys. Bearing has had a great impact on our life.

What are the factors affecting bearing performance? The following is the analysis. The smelting quality and basic requirements of bearing steel  the service life and reliability of rolling bearings are closely related to the smelting quality of bearing steel to a great extent. The smelting requirements of bearing steel are much stricter than those of general industrial steel.

High precision dimension requires steel for rolling bearings, which Accuracy And Grade requires high dimensional accuracy, because most bearing parts have to be pressure formed. In order to save materials and improve labor productivity, most bearing rings are forged,

steel balls are formed by cold heading or hot rolling, and small-size rollers are also formed by cold heading. If the dimensional accuracy of steel is not high, the blanking size and weight can not be calculated accurately, the Accuracy And Grade product quality of bearing parts can not be guaranteed, and it is easy to cause damage to equipment and molds.

Especially strict requirements for carbide non-uniformity.

In bearing steel, if there is serious uneven carbide distribution, it is easy to cause non-uniformity of Accuracy And Grade microstructure and hardness in the process of heat treatment.

The structural non-uniformity of steel has a great impact on the contact fatigue strength. In addition, the serious non-uniformity of carbide is also easy to cause cracks in the bearing parts during quenching and cooling, and the non-uniformity of carbide will also reduce the service life of the bearing.

Therefore, in the bearing material standard, there are clear special requirements for steels of different specifications. Strict chemical composition requirements. The general bearing steel is mainly high carbon chromium bearing steel, that is, hypereutectoid steel with carbon content of about 1%, chromium of about 1.5% and a small amount of manganese and silicon.

Chromium can not only improve heat treatment performance, hardenability, microstructure uniformity and tempering stability, but also improve rust prevention and grinding performance of steel.

However, when the chromium content exceeds 1.65%, the residual austenite in the steel will be increased after quenching, the hardness and dimensional stability will be reduced, the heterogeneity of carbide will be increased, and the impact toughness and fatigue strength of the steel will be reduced.

Therefore, the chromium content in high carbon chromium bearing steel is generally controlled below 1,65%. Only by strictly controlling the chemical composition in the bearing steel can the microstructure and hardness meeting the bearing properties be obtained through the heat treatment process.

Particularly strict requirements for surface defects and internal defects for bearing steel, surface defects include cracks, slag inclusions, burrs, scabs, oxide scales, etc., and internal defects include shrinkage, bubbles, white spots, serious porosity and segregation, etc.

These defects have a great impact on the processing, performance and service life of the bearing. It is clearly stipulated in the bearing material standard that these defects are not allowed.