What Is Bearing Steel?
Bearing steel is steel used for bearings.
Bearing steel is required to have “load carrying capacity,” “wear resistance,” “hardenability,” and “corrosion resistance.”
Depending on the environmental conditions in which it is used, carbon and chromium are added, and heat treatment and rolling are used to achieve high cleanliness, reduce the oxygen content in the steel, and refine non-metallic inclusions to increase the service life of bearings.
Applications of Bearing Steel
Bearings are used to support rotating parts and are mainly classified into roller bearings and ball bearings. Rollers are cylindrical and balls are spherical and roll in a cylindrical shape to support a rotating body.
The rollers and balls make linear or point contact with the weight of the rotating body, but the contact area is subject to high loads. Bearing Steel was developed to withstand high loads. The main processing methods are as follows:
- After the coarse cementite mesh structure is crushed by forging or rolling, it is heated to refine the crystal grains by recrystallization.
- Further spheroidizing annealing is followed by quenching or tempering at low temperature.
Other Information on Bearing Steel
Types of Materials Used in Bearings
The types of materials used for bearings are as follows:
1. High Carbon Chromium Bearing Steel
This material, called SUJ, is hardened not only on the surface but also internally. It is easy to temper, and its machinability is improved by spheroidizing and annealing.
SUJ2 is used for more than 90% of high-carbon chromium steels. SUJ3 is a type of SUJ2 with improved hardenability by increasing the ratio of Si and Mn and reducing the amount of Cr. It is suitable for large-sized balls, rollers, and races.
2. Hardened-Skin Alloy Steel for Bearings
By carburizing, this type of steel maintains the same hardness and wear resistance as high-carbon chromium bearings, but has an internal toughness.
3. Corrosion-Resistant Steel Bearing Steel
This type of steel has excellent corrosion and wear resistance and is used in chemical plants where materials are prone to corrosion.
4. Heat-Resistant Steel Bearing Steel
This is used in high-temperature environments with good dimensional stability.
5. Medium Carbon Steel Bearing Steel
Parts requiring high hardness are subjected to high-frequency quenching and are often used in hub unit bearings and linear motion bearings for automobiles.