Bearing Steel Material Type and Grade

There are two main types of materials commonly used in bearing steel: carburized bearing steel (G20Cr2Ni4A) and high carbon chromium bearing steel (GCr15/GCr15SMn/GCr18Mo).

Carburized bearing steel (G20Cr2Ni4A) is a high-quality alloy carburized carbon steel (low-carbon C: 0.17-0.23) used for manufacturing bearing. Bearing made from this type of steel have high hardness (hardness>HRC60), certain wear resistance, and high contact fatigue strength after heat treatment processes such as carburization, quenching, and tempering, Low carbon C: 0.17-0.23 ensures good toughness at the core (hardness>HRC33-48). This surface hardened core has the characteristic of toughness, making carburized bearing steel particularly suitable for stable operation under high impact loads. In summary, the advantages of carburized steel bearings are:

1. After carburizing and quenching, the surface retains a compressive stress state and has good fatigue resistance.

2. Strong ability to withstand impact loads, with microcracks on the surface hardening layer that are not easy to propagate inward. The surface has higher hardness while the core hardness is lower (generally 35HRC~40HRC), and compared with high carbon chromium bearing steel, it has better core impact toughness.

3. The depth and concentration of carburization can be adjusted as needed.

4. Not limited by the size and wall thickness of bearing parts.

High carbon chromium bearing steel (GCr15/GCr15SMn/GCr18M0) is a high carbon alloy steel containing 1.30-1.65% chromium. Its characteristics are: the microstructure after heat treatment is relatively uniform and stable, the hardness is high and uniform, the wear resistance is good, the contact fatigue strength is high, and it has good dimensional stability and corrosion resistance. After spheroidization annealing, its cutting performance is good. This type of steel can meet the usage requirements of bearings operating under normal working conditions.

1. High carbon chromium bearing steel is widely used worldwide, with the most commonly used grades being GCr15 and GCr15SiMn, which account for over 80% of the total amount of bearing steel used in China. The properties of these two steels are basically the same, but GCr15SiMn steel has better hardness than GCr15 steel. Therefore, for large-sized bearing parts, GCr15SiMn steel is recommended.

2. GCr15 bearing steel is widely used in the manufacturing of engine bearings for automobiles, tractors, tanks, airplanes, spindle bearings for machine tools, motors, as well as bearings for railway vehicles, mining machinery, and general machinery.

3. GCr15SiMn bearing steel is mainly used to manufacture bearings with large wall thickness, such as various large and extra large bearings, and is often used in heavy-duty machine tools and rolling mills under working conditions without significant impact loads.

4. Due to the high crack sensitivity and poor impact toughness of GCr15SiMn steel, it cannot fully meet the usage requirements for thick walled bearings with impact loads. The Ministry of Railways first proposed that GCr15SiMn steel should not be used for passenger car bearings, and also restricted the use of GCr15SiMn steel for rolling mills and mining bearings with large wall thicknesses under high impact loads. GCr18Mo high hardenability steel and wear resistance have been developed. Its performance is superior to GCr15SiMn steel and can be used as a substitute for GCr15SiMn steel in railway bearings, rolling mill bearings, and mining bearings.