Bearing is an essential component in mechanical equipment, playing a crucial role in supporting and reducing friction for rotating parts. It is a result of the combination of mathematical physics, material science, heat treatment technology, precision machining, and numerical control technology. Whether it's airplanes, cars, high-speed trains, or high-precision machine tools, bearings are necessary for all rotating parts.
When different parts move in relation to each other on a shaft, bearings are used to maintain the central position of the shaft and control the movement. They enable the smooth rolling of rotating shafts, minimizing friction during rotation.
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In the past, linear motion bearings consisted of a row of wooden poles placed under the skid. Although there is no concrete evidence, this technology can be traced back to the construction of the Kavla Pyramid. Modern linear motion bearings operate on the same principle but use balls instead of rollers.
Rotary bearings are necessary in a variety of situations, ranging from heavy-duty wheel shafts to precision clock parts. The most basic type of rotary bearing is the sleeve bearing, which was later replaced by rolling bearings. Rolling bearings replaced the original bushing with multiple cylindrical rollers. The very first rolling bearing was created by watchmaker John Harrison in 1760 for his H3 timer.
Evidence of early ball bearings can be found on an ancient Roman ship discovered on the Italian Lake Nami. A wooden ball bearing was used to support the rotating table on the ship, which was constructed in 40 BC. One significant drawback of ball bearings at that time was the tendency for the balls to collide with each other, resulting in additional friction.
The first patent for a bearing ball raceway was obtained by Philip Vaughn in 1794. In 1883, Friedrich Fisher proposed the use of specialized production machines to grind steel balls with consistent size and precise roundness, which became the foundation for the bearing industry. In 1907, Sven Winquist, an engineer at the SKF ball bearing factory, designed the earliest modern self-aligning ball bearing.
According to the contact form of relative motion, bearings are divided into ball bearings, needle bearings, tapered roller bearings, sliding bearings, flexible bearings, air bearings, magnetic levitation bearings, gem bearings and oil-bearing bearings.
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Even though the design of the bearing is straightforward and can be produced by many small workshops, it requires advanced technical knowledge and can serve as a significant measure of a country's technological and industrial prowess. Currently, the leading countries in science, technology, and industry are also leaders in bearing research and manufacturing.
The top ten multinational bearing groups, which include companies from the United States, the European Union, and Japan, control over 70% of the global bearing market. Specifically, the United States holds a 23% share, the European Union has 21%, and Japan has 19%. Five companies, such as NSK in Japan, SKF in Sweden, FAG in Germany, and Timken in the United States, largely dominate the global bearing market.
Furthermore, these aforementioned enterprises monopolize the high-end segment of the bearing industry worldwide, while China primarily dominates the low-end market. However, the top ten bearing enterprises in China, such as bearing shaft, only account for 24.7% of the total industry sales. Additionally, the top 30 enterprises in terms of production concentration only make up 37.4% of the market.
Over the past few years, China has successfully developed a self-sufficient and comprehensive industrial system in the bearing industry. China has now become one of the leading countries in this field, securing the third position globally. According to statistics from 2017, the total revenue generated by large-scale bearing enterprises in China reached 178.8 billion yuan, with a staggering production of 21 billion sets of bearings. Furthermore, China has the capability to manufacture over 90,000 different types and sizes of bearings, ranging from 0.6 mm to 11 m in diameter.
From 2006 to 2017, the growth of China's bearing exports was relatively stable, and the growth rate was higher than that of imports. The trade surplus between imports and exports showed a growing trend. In 2017, the trade surplus reached 1.55 billion US dollars. Compared with the unit price of import and export bearings, the price difference between import and export bearings in China has been large in recent years, but the range of price difference has decreased year by year, reflecting that although there is still a certain gap between the technical content of China's bearing industry and the advanced level, it is catching up. At the same time, it reflects the current situation of overcapacity of middle and low-end bearings and insufficient capacity of high-end bearings in China.
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Top-notch equipment like high-speed trains, jumbo jets, and heavy-duty weapons all require high-quality bearings. These bearings must meet strict standards in terms of precision, performance, durability, and reliability. The quality and reliability of the materials used in these bearings play a crucial role.
Maintenance of F110 engine fan bearing
Due to the rapid rotation of objects, different parts of the bearing experience varying levels of stress and high-frequency impacts. Typically, the pressure per unit area can reach up to 1500 to 5000 N per square millimeter. These factors make the bearing susceptible to stress fatigue, resulting in fatigue peeling and rendering the bearing ineffective. Additionally, rolling bearings must also endure centrifugal force, friction, high temperatures, corrosion, and other elements. This is why it is essential to construct a robust bearing using high-quality steel.
In the moving bearing, apart from the retainer, the inner and outer rings, as well as the rolling element (ball, roller, or needle), are all made of bearing steel. Bearing steel, which is known as the superior steel, is the most demanding type of steel in the production process.
The quality of bearing steel mainly relies on the following four factors: firstly, the content, shape, distribution, and size of inclusions within the steel; secondly, the content, shape, distribution, and size of carbides in the steel; thirdly, the presence of porosity shrinkage cavity and segregation at the center of the steel; fourthly, the consistency of the performance of bearing steel products. These four factors can be summarized as indicators of purity and uniformity.
In high-quality bearing steel, there is a uniform and fine carbide structure, which remains evenly distributed even after undergoing heat treatment.
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