The inner and outer rings and steel balls of the bearing are made of bearing steel (vacuum heat treatment). Most bearings use SUJ2 made of JIS steel, that is, domestic chromium steel (GCr 15). The chemical composition of SUJ2 has been standardized as bearing material all over the world. For example, it is the same steel as AISL52 100 (USA), DIN 100Cr6 (West Germany) and BS535A99 (UK). Using this material, the torque performance of the bearing is effectively improved, the noise is reduced and the service life is prolonged. However, in humid or high temperature environment, martensitic stainless steel should be used.
The material of bearing steel is high-purity iron-carbon alloy steel! Because bearing steel is mainly used to manufacture rolling bodies and rings of rolling bearings. Bearing steel requires high hardness, uniform hardness, high elastic limit, high contact fatigue strength, necessary toughness, certain hardenability and corrosion resistance in atmospheric lubricants, because bearings should have the characteristics of long life, high precision, low calorific value, high speed, high rigidity, low noise and high wear resistance. In order to meet the above performance requirements, there are strict requirements on the chemical composition uniformity of bearing steel, the content and types of non-metallic inclusions, the particle size and distribution of carbides and decarbonization. Bearing steel generally develops in the direction of high quality, high performance and various varieties. Bearing steel can be divided into high carbon chromium bearing steel, carburized bearing steel, high temperature bearing steel, stainless steel bearing steel and special bearing materials according to its characteristics and application environment.
In order to meet the requirements of high temperature, high speed, high load, corrosion resistance and radiation resistance, it is necessary to develop a series of new bearing steels with special properties. In order to reduce the oxygen content of bearing steel, vacuum smelting, electroslag remelting and electron beam remelting are developed. However, a large number of smelting of bearing steel has developed from electric arc furnace smelting to various types of primary smelting furnace plus external refining. At present, bearing steel is produced by primary smelting furnace +LF/VD or RH+ continuous casting+continuous rolling, and the production capacity is over 60 tons, so as to achieve the purpose of high quality, high efficiency and low energy consumption. In terms of heat treatment technology, it has developed from trolley furnace and bell furnace to continuous controllable atmosphere annealing furnace for heat treatment. At present, what is the longest continuous heat treatment furnace type? 150m, the ball-spheroidized structure of the bearing produced by processing is stable and uniform, with small decarburized layer and low energy consumption.
Since 1970s, with the development of economy and industrial technology, the application scope of bearings has been expanding. The development of international trade has promoted the internationalization of bearing steel standards and the development and application of new technologies, new processes and new equipment, and supporting technologies and equipment with high efficiency, high quality and low cost have emerged. Japan and Germany built bearing steel production lines with high cleanliness and high quality, which greatly increased the output, quality and fatigue life of steel. Japan and? The oxygen content of bearing steel produced in Sweden dropped below 10ppm. In the late 1980s, the advanced level of Yang Shan Special Steel Company was 5.4ppm, reaching the level of vacuum remelting bearing steel.
The contact fatigue life of bearings is very sensitive to the uniformity of steel structures. Improving the cleanliness (reducing the content of impurity elements and inclusions in steel) and promoting the fine and uniform distribution of nonmetallic inclusions and carbides in steel can improve the contact fatigue life of bearing steel. The microstructure of bearing steel in use should be that fine carbide particles are evenly distributed on tempered martensite matrix, so as to give bearing steel the required properties. The main alloying elements in high carbon bearing steel are carbon, chromium and chromium. Silicon, manganese, vanadium, etc.
How to obtain spheroidized structure is an important problem in the production of bearing steel, and controlled rolling and controlled cooling are important production processes of advanced bearing steel. By controlling rolling or rapid cooling after rolling, the network carbide can be eliminated and the appropriate preliminary structure can be obtained, which can shorten the annealing time of bearing ball rolling, refine carbide and improve fatigue life. In recent years, Russia and Japan have adopted low-temperature controlled rolling (below 800℃ ~ 850℃), followed by air cooling and short-time annealing, or completely canceled spheroidizing annealing process to obtain qualified bearing steel structure. Bearing steel processing at 650℃ is also a new technology. * * * If the precipitated steel or high carbon steel has a fine grain structure before hot working or can form fine grains during processing, it will be sintered at (0.4 ~ 0.5). 6) It presents superplasticity at a certain strain rate within the melting temperature range. The United States Naval Research Institute (NSP) was established in 5? The processing test of 2 100 steel at 650℃ shows that the true strain at 650℃? 2.5 No fracture occurs. Therefore, it is possible to replace high temperature processing with warm processing at 650℃ and combine it with spheroidizing annealing process, which is of great significance to simplify equipment and processes, save energy and improve quality.
In terms of heat treatment, progress has been made in improving the quality of spheroidizing annealing, obtaining fine, uniform and spherical carbides, shortening annealing time or canceling spheroidizing annealing process, that is, wire rod production adopts twice microstructure annealing, and recrystallization annealing after drawing is changed from 720℃ to 730℃ to 760? The annealing temperature of the microstructure is 100℃, so that the microstructure with low hardness, good spheroidization and no network carbide can be obtained. The key is to ensure that the area shrinkage during intermediate stretching is ≥ 14%. This process can improve the efficiency of heat treatment furnace by 25% ~ 30%. Continuous spheroidizing annealing technology is the development direction of bearing steel heat treatment.
All countries are developing new bearing steel, expanding its application range and replacing traditional bearing steel. Such as rapid carburizing bearing steel, the carburizing speed is improved by changing the chemical composition, in which the carbon content is increased from the traditional 0.08% ~ 0.20% to about 0.45%, and the carburizing time is shortened from 7 hours to 30? Minutes. High frequency quenched bearing steel was developed. Using ordinary medium carbon steel or medium carbon manganese chromium steel instead of ordinary bearing steel for high frequency heating quenching not only simplifies the production process, but also reduces the cost and prolongs the service life. What is the fatigue life ratio of GCr465 and SCM465 developed in Japan? 2 2 ~ 4 times higher. Bearing steels such as M50(CrMo4V) and 440C(9Cr 18Mo) used in the past can no longer meet the requirements due to the increasing use of bearings in harsh environments such as high temperature, corrosion and lubrication. There is an urgent need to develop bearing steels with good machinability, low cost and long fatigue life, such as high-temperature carburized steels that can adapt to different purposes and uses. M50NiL, easy-to-process stainless steel bearing steel 50X 18M and ceramic bearing material.
Aiming at the weakness of low hardenability of GCr 15SiMn steel, China has developed high hardenability and high hardenability bearing steel GCr 15SiMo, with hardenability HRC≥60 and hardenability J60≥25mm. The contact fatigue life of GCr 15SiMo L 10 and L50 is higher than that of GCr 15Si? Manganese increased by 73% and 68% respectively. Under the same service conditions, the service life of bearings made of G0 15SiMo steel is twice as long as that of GCr 15SiMo steel. In recent years, China has also developed energy-saving, resource-saving and impact-resistant GCr4 bearing steel. Compared with GCr 15, the impact value, fracture toughness and contact fatigue life of GCr4 are increased by 66% ~ 104%, 67% and 12% respectively. Is GCr4 steel bearing heated at high temperature? Surface quenching heat treatment process. Compared with the fully hardened GCr 15 steel bearing, the service life of GCr4 steel bearing is obviously prolonged, and it can be used for heavy-duty high-speed train bearings.
In the future, bearing steel will mainly develop in two directions: high cleanliness and diversified properties. Improving the cleanliness of bearing steel, especially reducing the oxygen content in steel, can obviously prolong the life of bearings. When the oxygen content is reduced from 28ppm to 5ppm, the fatigue life can be extended by 1 order of magnitude. In order to prolong the service life of bearing steel, people have been committed to developing and applying refining technology to reduce the oxygen content in steel for many years. After unremitting efforts, the minimum oxygen content in bearing steel is from 60? 28ppm in the s? It dropped to 5ppm in the 1990s. At present, China can control the minimum oxygen content in bearing steel at? About 10ppm. The change of bearing service environment requires bearing steel to have diversified properties. If the rotating speed of equipment is increased, bearing steel (below 200℃) for quasi-high temperature is needed (usually used in? On the basis of SUJ2 steel, softening resistance and dimensional stability can be achieved by increasing Si content and adding V and Nb. Corrosion application requires the development of stainless steel bearing steel; In order to simplify the process, high-frequency quenching bearing steel and short-time carburizing bearing steel should be developed; In order to meet the needs of aerospace, high temperature bearing steel should be developed.
1. Precision plastic bearing
Compared with traditional plastic bearings, precision plastic bearings have higher precision and tolerance. The whole inner ring and outer ring are made of materials suitable for precision machining. On the basis of maintaining the traditional advantages of plastic bearings, rolling bodies and cages can be applied to precise and high-speed operating conditions. Generally, the inner and outer rings are made of POM, PPS or PEEK, the cage is made of glass fiber reinforced nylon 66(RPA66-25) or PEEK, and the rolling elements are glass balls, stainless steel balls or ceramic balls.
2. Corrosion-resistant plastic bearings
There are many material solutions for different application conditions, which can work freely even under the worst acid/alkali/salt/solvent/oil/gas/seawater erosion. Ensure ideal durability and life expectancy.
3. Acid and alkali resistant plastic bearings
Hdpe, pe and UHMWPE materials have been proved to be used in relatively weak acid-base cross environment (30% CuCl2 solution and 30%NaOH solution can be used), PVDF and PTFE materials can be used in strong acid-base environment, and PTFE can be used in all concentrated acid-base occasions, including HF, fuming sulfuric acid and nitric acid (above 98%).
4. High temperature resistant plastic bearing
PVDF, PTFE (polytetrafluoroethylene), PPS (polyphenylene sulfide), PEEK (polyetheretherketone) and PI (polyetherimide) have all been proved to be ideal materials for manufacturing high-temperature plastic bearings, among which PI can be used at the temperature of 290℃ for a long time and can withstand the temperature of 350℃ for a short time. It has the best high-temperature performance among all known engineering plastics.
5. Plastic bearing seat and plastic outer spherical bearing
Plastic seat bearing has the advantages of light weight, simple installation, corrosion resistance, maintenance-free, etc. At the same time, it has the ability of vibration reduction and impact resistance that ordinary cast iron seats or stamping seats do not have. With the continuous development of new materials, they are more and more widely used in engineering.
Through the introduction of Bian Xiao, do you know more about the material of bearing steel? The chemical composition of bearing steel is very strict, and the dimensional accuracy is not lower than the chemical composition. The manufactured bearing steel must have strict purity, and it will not be used if it is defective. In China, the label of bearing steel also has a strict auditing status. The above is the main content that Bian Xiao brought to you today. Through the material of bearing steel, everyone can buy it with the target nature. I hope Bian Xiao's introduction today will help you!