As an important part of modern mechanical equipment, bearings are precision products and are often referred to as the "joints" of machinery. In the fields of industry and agriculture, national defense and military science, home appliances and other fields, the accuracy, performance, life, reliability and various economic indicators of bearings directly or indirectly affect the operation of the host equipment, and the development of the bearing industry is also closely related to the manufacturing level of major technical equipment and the export capacity of machinery and equipment on the mainland. In recent years, the export volume of bearings in the mainland has shown a trend of rising year by year, and bearing exports have also become one of the important factors driving the rapid development of the domestic bearing industry. The development of bearing materials also shows advanced, composite, diversified, of which metal bearing materials include high carbon chromium steel, carburized steel, stainless steel, heat-resistant steel, tool steel and other materials, non-metallic materials such as ceramics, engineering plastics, graphite and carbon fiber. The types of bearing materials are gradually enriched, and the advantages of their finished products are different, and this article introduces the bearing characteristics of metal, engineering plastics and ceramics.
The timeline of bearing development
(The world bearing industry arose in the late 19th century to the beginning of the 20th century)
In 1880, the earliest bearings were produced by the United Kingdom
In 1883, Germany established the world's first bearing company (FAG GeorgesChafer Company)
In 1889, the United States opened an ND bearing factory (now General Motors Bearing Company)
In 1910, SKF sweden supplied bearing samples to Japan
Japan NSK established in 1914
1918 Established NTN Japan
1. Ceramic bearings
(1) Advantages:
(1) Ceramic materials have strong corrosion resistance, so ceramic bearings are almost not afraid of corrosion and can operate in a special harsh environment full of corrosive media.
(2) On the ceramic rolling bearing, because the density of the ceramic rolling ball is lower than that of steel, the weight is lighter, and the centrifugal effect on the outer ring can be reduced by 40% when rotating, so that the service life of the product can be greatly extended.
(3) The influence of ceramic materials on thermal expansion and contraction is smaller than that of metals, and reasonable arrangement of the clearance between each ceramic bearing can be applied to the bearing in an environment with large fluctuations in temperature difference.
(4) The fatigue life of all-ceramic bearings is 10 to 50 times longer than that of all-steel bearings, and the life of hybrid bearings is about 3 to 5 times higher than that of all-steel bearings, and the service life of ceramic bearings is much higher than that of metal bearings.
(5) The wear resistance and modulus of elasticity of ceramic bearings are higher than that of metal bearings, and the coefficient of friction is low, so the lubrication performance of ceramic bearings running with lubricating oil will not be lower than that of traditional lubricants commonly used in traditional steel bearings in the case of dilution or lack of oil.
(2) Disadvantages:
The processing method of preparing finished ceramic bearings is highly demanding and costly, which greatly hinders the popular application of ceramic bearings.
2. Metal bearings
The biggest advantage of metal bearings is that it is convenient to process, compared with the processing cost of ceramic and engineering plastic bearings, and the price advantage is obvious; secondly, the impact resistance is good, and the variety of metal materials is diverse, which is suitable for the application needs of most conventional bearing equipment.
The service life is short and the lubricating oil consumption required for operation is large.
3. Engineering plastic bearings
(1) The finished product has low density, light volume, small starting torque during high-speed operation, and can also reduce the energy consumption of rotation, which is suitable for application in modern lightweight structural product design.
(2) Its preparation method is open mold injection molding method, the production cycle of the finished product is short, the speed is fast, the manufacturing cost is low, and the flexibility of the design product is large, which can be designed into a more complex structural form, the overall economy is good, which is convenient for large-scale and large-scale production, which can improve production efficiency and save manufacturing costs.
(3) Engineering plastic bearings themselves have excellent self-lubrication effects, which can meet the engineering conditions that cannot use lubricating oil (such as: food, packaging, medical machinery, etc.), and the product maintenance cost is low.
(4) With the characteristics of wear resistance, low friction, anti-bite, etc., wear-resistant elements can be added according to the needs of the required cost, and the friction coefficient can be reduced to a lower level, so that the reduction of frictional heat can maintain better performance.
(5) Based on its own material characteristics, engineering plastic bearings have the performance of cushioning and vibration damping, which can greatly reduce the occurrence of running noise during operation and can be applied to special environments.
(6) It has stable high heat resistance and stable specification size, and the temperature difference range is generally -250 °C ~ +320 °C, which can meet the operating temperature of most engineering states.
(7) The preparation flexibility of engineering plastic bearings is high, and different raw materials can be selected according to different performance requirements to enhance toughness, thereby increasing toughness to enhance the impact resistance and fracture resistance of the product, and the same reason can also increase the stiffness to improve the hardness standard.
The disadvantages of engineering plastic bearings are poor mechanical properties, low speed, low load, and not resistant to high temperatures, and the upper limit of high temperature tolerance is low.
Compared with foreign countries, the mainland's research and development and use of engineering plastic bearings started late, and it is relatively lacking in raw material production and product application. However, according to incomplete statistics from relevant parties, in the past five years, the domestic general PC, POM, PA, thermoplastic resin, modified polyphenylene ether and other five major engineering plastics and market demand has maintained a rapid growth of 30.3%, but the mainland has a strong dependence on the import of raw materials for bearing engineering plastics, if the relevant plastics enterprises can seize the market opportunity, insight into the market, and vigorously develop related bearing products, the prospect is considerable.