Bearings are produced worldwide and used in applications ranging from conveyors to aerospace applications. Each country or region has their own “Bearing Steel Standard.” Based on where the company is located and where its bearings are manufactured, the steel is coded as one of the following:
- North America: SAE 52100
- Europe: 100Cr6
- China: GCr15
- Japan: SUJ2
In theory, all steel grades are comparable, however, the standard chemical composition of chromium steel will vary depending on the country where it is produced. Although it is similar to all standards, GCr15 is generally viewed as a different grade of steel. The belief is that the Chinese steel is not as clean as the other standards, which is why reliable companies that produce bearings in China buy steel that uses the finest melt sources available.
Reputable bearing manufacturers test steel using a spectrometer to measure the properties of incoming steel deliveries.
What is a Spectrometer?
A spectrometer is a machine that excites atoms in the sample steel by creating a spark between the sample and an electrode. This spark causes electrons to emit light, which is converted into a spectral pattern. The quality and quantity of the material composition is measured using the intensity of peaks in the spectrum. Test results are then compared against the proper composition for the material.
Differences in Chinese Steel
Some Chinese steels will have different manganese and/or phosphor, while others can have higher sulfur. It is important for the bearing producer to select the right melt source in order for it to be equal to European and North American steels. Doing so increases the cost of the material by 30%, but yields a better product.
How to Verify Bearing Steel
Insist on viewing the bearing manufacturer’s certifications or incoming steel inspection reports. If your supplier is ISO9001 or TS16949, as is CCTY, such information should be readily available.