Bearing steel is mainly used to manufacture rolling elements and rings of rolling bearings. Since the bearing should have the characteristics of long life, high precision, low calorific value, high speed, high rigidity, low noise, high wear resistance, etc., it is required that the bearing steel should have: high hardness, uniform hardness, high elastic limit, high contact fatigue Strength, necessary toughness, certain hardenability, and corrosion resistance in atmospheric lubricants. In order to meet the above performance requirements, the uniformity of the chemical composition of the bearing steel, the content and type of non-metallic inclusions, the particle size and distribution of carbides, and decarburization are strictly required. Bearing steel is generally developing in the direction of high quality, high performance and variety. Bearing steels are classified according to their characteristics and application environment: high-carbon chromium bearing steel, carburized bearing steel, high-temperature bearing steel, stainless bearing steel and special special bearing materials.
In order to meet the requirements of high temperature, high speed, high load, corrosion resistance and radiation resistance, a series of new bearing steels with special properties need to be developed. In order to reduce the oxygen content of bearing steel, smelting technologies for bearing steel such as vacuum smelting, electroslag remelting, and electron beam remelting have been developed. The smelting of large quantities of bearing steel is smelted by electric arc furnaces and developed into various types of primary smelting furnaces plus external refining. At present, bearing steel is produced by primary furnace with a capacity of more than 60 tons + LF/VD or RH + continuous casting + continuous rolling to achieve high quality, high efficiency and low energy consumption. In terms of heat treatment process, heat treatment has been developed from car bottom furnace and bell furnace to continuous controllable atmosphere annealing furnace. At present, the longest continuous heat treatment furnace is 150m, and the spheroidized structure of the bearing steel processed and produced is stable and uniform, the decarburization layer is small, and the energy consumption is low.
Bearing steel should have the following properties:
1. High contact fatigue strength.
2. High wear resistance.
3. High elastic limit and yield strength.
4. High and uniform hardness.
5. Certain impact toughness.
6. Good dimensional stability.
7. Good corrosion inhibition performance.
8. Good process performance.
Common materials of bearing steel:
The selection of bearing steel material also needs to be purchased according to specific requirements. For bearing materials working under special conditions, according to their specific requirements, they should also have special properties suitable for their conditions, such as: high temperature resistance, low temperature resistance, corrosion resistance, Anti-radiation, anti-magnetic and other characteristics.
Fully hardened bearing steel is mainly high-carbon chromium steel, such as GCr15, with a carbon content of about 1% and a chromium content of about 1.5%. In order to improve hardness, wear resistance and hardenability, some silicon, manganese, molybdenum, etc., such as GCr15SiMn, are properly added. This type of bearing steel has the largest output, accounting for more than 95% of all bearing steel output.
Carburized bearing steel is a chromium, nickel, molybdenum alloy structural steel with a carbon content of 0.08 to 0.23%. After the bearing parts are made, the surface is carbonitrided to improve its hardness and wear resistance. This steel is used in manufacturing Large bearings subject to strong impact loads, such as large rolling mill bearings, automobile bearings, mining machinery bearings and railway vehicle bearings, etc.
High-temperature bearing steel is used at high temperature (300-500°C), and the steel is required to have certain red hardness and wear resistance at the service temperature. Most of them are replaced by high-speed tool steel, such as W18Cr4V, W9Cr4V, W6Mo5Cr4V2, Cr14Mo4 and Cr4Mo4V, etc.