- Carbon Chromium Steel
- 1% carbon and 1.5% chromium
- Hardness between 59 and 65 HRC
- Can be used at temperature up to +125 degree C
Bearings can be divided into small, medium, large and extra large ones according to their performance and size. Bearing rings, outer rings and rollers are made of special bearing steel. The cage is usually made of carbon steel, usually 20 carbon steel.
1. Chromium bearing steel: this kind of steel is specially used for making bearings, and has special requirements for inclusions and grain size. The general small bearing can be GCr9, GCr15, medium bearing using GCr15, GCr15SiMn, large use of GCr15SiMn, and the large bearing because of hardenability, the use of carburized bearing steel.
2. Carburizing bearing steel: steel rolling machinery or mine machinery and other problems that need impact resistance are carburized bearing steel, medium and small bearings use 20Cr, 20CrMo, 20CrMnMo and other carbonized steel, large and extra large use 20Cr2Ni4A, 20Cr2Mn2MoA and so on.
3. Stainless bearing steel: in the areas where corrosion resistant, such as sulfuric acid, hydrochloric acid, chemical fertilizer and other industries need stainless bearing steel, high carbon and high chromium stainless steel, such as 9Cr18 steel, is generally used.
4. High temperature bearing steel: high temperature bearing needs high temperature bearing steel, such as high speed steel 18-4-1, 6-5-4-2 and so on, Cr4Mo4V and Cr15Mo4 steel.
The heat treatment of bearing steel varies according to the material, purpose, type, size and technical requirements of bearing. Usually through the following heat treatment:
1. Chromium bearing steel: spheroidizing annealing, quenching + low tempering. For example, GCr15, annealing temperature is 770~810 degrees, furnace cooling. Quenching uses 840 degrees, tempering uses 155~165 degree, precision bearing also uses cold treatment. The heat treatment process of other chromium bearing steels is in principle the same as that of GCr15, but the specific process parameters are different.
2. Carburizing bearing steel: carburizing, high-temperature tempering, two quenching + low tempering. The specific process is different according to the use of steel.
3. Stainless bearing steel: anneal after forging, quenching, cold treatment, low temperature tempering. For example, 9Cr18 steel is annealed at 850~870 degree, quenching 1050~1100, – 75 degree cold treatment (of course, cryogenic treatment), and 150~160 tempering at low temperature.
4. High temperature bearing steel: this kind of steel is annealed, Quenched and tempered. The quenching temperature is different according to the steel used. Tempering is usually more than 500 degrees, that is to say, the tempering temperature must be higher than the use temperature.