In the huge system of modern industry, bearings, as indispensable key components in various mechanical equipment, play an important role in supporting, guiding rotational motion and transmitting loads. Special steel for bearings, as the core material for manufacturing bearings, directly determines the quality, reliability and service life of bearings, and thus profoundly affects the operating efficiency and stability of the entire industrial equipment.
1. Characteristics and requirements of special steel for bearings
High hardness and wear resistance: During the operation of bearings, there is strong friction and contact stress between the raceway and the rolling element. Therefore, special steel for bearings must have a sufficiently high hardness to resist wear and plastic deformation. Generally speaking, the hardness of bearing steel is required to be between HRC60-65, which enables bearings to maintain good working conditions under long-term high-speed and heavy-load conditions, reducing dimensional changes and loss of precision caused by wear.
High strength and toughness: In addition to bearing huge radial and axial loads, bearings may also face complex working conditions such as impact and vibration. Therefore, special steel for bearings must not only have high strength to bear the load, but also have a certain toughness to prevent brittle fracture under impact. Good strength and toughness match to ensure the reliable operation of bearings under various harsh conditions.
High contact fatigue strength: Under the repeated action of alternating contact stress, fatigue peeling is prone to occur on the bearing surface. In order to extend the service life of the bearing, special steel for bearings must have excellent contact fatigue strength and be able to withstand millions or even billions of alternating stresses without fatigue failure. This requires special steel to have a uniform organizational structure and pure chemical composition to reduce the adverse effects of internal defects on fatigue performance.
Good dimensional stability: During the processing and use of bearings, factors such as temperature changes and heat treatment may cause changes in material size. In order to ensure the accuracy and matching performance of bearings, special steel for bearings needs to have good dimensional stability, and its dimensional changes should be controlled within a very small range under different working environments. This is especially important for high-precision bearings, such as those used in aerospace, precision machine tools and other fields.
Good corrosion resistance: In some special working environments, such as moisture, acid and alkali and other corrosive media, bearings need to have a certain corrosion resistance to prevent rust and corrosion of materials, thereby ensuring the normal operation of bearings. For this reason, some special-purpose bearings will use special steel materials with corrosion resistance, such as stainless steel bearing steel.
2. Common types of special steel for bearings
High carbon chromium bearing steel: This is the most widely used special steel for bearings, and its typical representative steel types include GCr15, etc. High carbon chromium bearing steel has a high carbon content (generally 0.95% - 1.10%) to ensure the hardness and wear resistance of the steel; at the same time, it contains an appropriate amount of chromium (generally 1.30% - 1.65%), which can improve the hardenability, hardness and wear resistance of the steel, and can also improve the contact fatigue strength and dimensional stability of the steel. High carbon chromium bearing steel has a relatively low price and good comprehensive performance. It is widely used in many fields such as automobiles, machine tools, motors, metallurgy, etc.
Carburized bearing steel: For some bearings that are subjected to large impact loads and surface wear, such as aircraft engine bearings, railway locomotive bearings, etc., carburized bearing steel is often used. The carbon content of this type of steel is generally between 0.15% - 0.25%, which belongs to low carbon steel. Through carburizing treatment, a high carbon layer is obtained on the surface of the steel, so that after quenching and tempering, the surface has high hardness, wear resistance and contact fatigue strength, while the core maintains good toughness and strength. Common carburized bearing steels include 20CrMnTi, 20Cr2Ni4, etc.
Stainless bearing steel: In an environment with corrosive media, stainless bearing steel plays an important role. Its main alloying elements are chromium and nickel. Chromium can form a dense oxide film on the surface of steel to prevent further oxidation and corrosion, while nickel can improve the corrosion resistance and toughness of steel. Common stainless bearing steels include 9Cr18, 9Cr18Mo, etc., which are widely used in food machinery, medical equipment, marine engineering and other fields.
High-temperature bearing steel: As modern industry develops towards high temperature and high speed, the performance requirements for bearings in high temperature environments are getting higher and higher. High-temperature bearing steel can maintain good hardness, strength, wear resistance and dimensional stability at higher temperatures. For example, high-temperature bearing steels such as Cr4Mo4V are often used in bearing manufacturing in high-temperature equipment such as aerospace engines and gas turbines.
3. Application fields of special steel for bearings
Automobile industry: Bearings are widely used in automobile engines, transmissions, wheels and other parts. The quality of special steel for bearings directly affects the performance, reliability and safety of automobiles. In automobile engines, high-speed rotating crankshafts, camshafts and other parts require high-precision and high-reliability bearings to support them. These bearings are usually made of high-carbon chromium bearing steel or carburized bearing steel. In automobile wheels, in order to bear the weight of the vehicle and various forces during driving, bearings with good wear resistance and dimensional stability are required. High-carbon chromium bearing steel is a commonly used material.
Machine tool industry: As the mother machine of the manufacturing industry, machine tools have extremely high requirements for the accuracy and performance of bearings. The spindle bearings of precision machine tools need to have extremely high rotation accuracy, rigidity and speed performance to ensure the accuracy and surface quality of machined parts. High-carbon chromium bearing steel can meet the requirements of spindle bearings of precision machine tools after special refining and processing technology. In addition, various types of bearings are also widely used in the feed system, workbench and other parts of machine tools. The quality of special steel for bearings directly affects the processing accuracy and production efficiency of machine tools.
Aerospace industry: The aerospace field has extremely stringent requirements on the performance of bearings, and they need to operate reliably under extreme conditions such as high temperature, high pressure, high speed and high vacuum. Key components such as the main shaft bearings and turbine bearings of aircraft engines are usually made of high-performance materials such as high-temperature bearing steel and carburized bearing steel. These materials must not only have excellent mechanical properties, but also meet the requirements of lightweight to improve the performance and fuel efficiency of aerospace vehicles. At the same time, aerospace bearings have extremely high requirements for the purity, dimensional accuracy and surface quality of materials, and any minor defects may lead to serious consequences.
Energy industry: Bearings are also widely used in energy industries such as electricity, oil, and natural gas. For example, the main shaft bearings and gearbox bearings of wind turbines need to operate stably for a long time in harsh natural environments, and withstand huge loads and alternating stresses. In order to ensure the reliability and service life of wind turbines, these bearings usually use high-strength and high-toughness special steel for bearings, and carry out special surface treatment and protection. In oil extraction equipment, such as drilling rigs and pumping units, bearings need to work in high temperature, high pressure, and high corrosion environments. Stainless bearing steel and special alloy bearing steel are widely used.
Other fields: In addition to the above-mentioned major industries, special steel for bearings is also widely used in many fields such as metallurgy, mining, textiles, printing, medical equipment, etc. In the rolling mills of the metallurgical industry, a large number of heavy-duty bearings are needed to support the rollers. These bearings are subjected to huge rolling forces and friction forces, and the strength and wear resistance of the materials are extremely high. In mining machinery, bearings of equipment such as crushers and ball mills need to work under harsh working conditions, which also puts high demands on the performance of special steel for bearings.
4. Development trend of special steel for bearings
High performance: With the continuous advancement of industrial technology, the performance requirements for bearings are getting higher and higher. In the future, special steel for bearings will develop towards higher strength, hardness, toughness, contact fatigue strength and dimensional stability to meet the stringent requirements of high-end equipment manufacturing industry for bearings. For example, by optimizing alloy composition design, improving smelting and processing technology, and developing new high-performance bearing steel materials, the reliability and service life of bearings under extreme working conditions can be improved.
Improved purity and uniformity: The purity and uniformity of the organizational structure of special steel for bearings have a vital impact on its performance. Reducing the content of impurity elements (such as sulfur, phosphorus, oxygen, etc.) in steel, reducing the number and size of inclusions, and improving the purity of steel can significantly improve the contact fatigue strength and service life of bearings. At the same time, through advanced metallurgical technology and processing technology, ensuring the uniformity of the steel structure and reducing component segregation are also important directions for improving the performance of special steel for bearings.
Green and environmental protection: Under the background of sustainable development, the production process of special steel for bearings will pay more attention to energy conservation, emission reduction and environmental protection. On the one hand, by improving the smelting process, energy consumption and pollutant emissions can be reduced; on the other hand, recyclable bearing steel materials can be developed to reduce resource waste and realize the recycling of materials. In addition, in the surface treatment process of bearing steel, environmentally friendly treatment methods will gradually be adopted to replace traditional treatment processes containing heavy metals and harmful substances.
Integration with advanced manufacturing technology: With the rapid development of advanced manufacturing technologies such as intelligent manufacturing and additive manufacturing, the production and processing of special steel for bearings will also be deeply integrated with them. For example, using digital simulation technology, the composition design and processing technology of bearing steel can be optimized to improve production efficiency and product quality. Additive manufacturing technology (3D printing) makes it possible to manufacture bearings with complex structures. Through customized design and manufacturing, it can meet the special needs of bearings in different fields.