Bearing is an indispensable core component of the mechanical equipment, the main function is to support the mechanical rotating body, reduce the friction coefficient and ensure rotation accuracy. It is the product of mathematical physics and other theories plus material science, heat treatment technology, precision processing, and numerical control technology. No matter aircraft, cars, high-speed rail, or high-precision machine tools, all rotating parts, usually need bearings.
When other components produce relative movement on the axis, the unit is used to maintain the central position of the axis and control the movement, known as a bearing. It can be used for the mutual rolling of the shaft to minimize the friction of the shaft.
Early linear movement bearings, were a row of wooden rods under the skid. This technique dates back to the construction of the Kafra Pyramid, although there is no clear evidence. Modern linear motion bearings use the same working principle, but use roller balls instead of rollers.
According to the relative movement of the contact form bearing, ball bearing, needle bearing, conical roller bearing, sliding bearing, flexible bearing, air bearing, magnetic suspension bearing, gem bearing, and oil-bearing, etc.
Although the bearing structure is simple and many small workshops can be made, the bearing has a high technical content and can even be used as an important standard to measure a country’s science and technology, and industrial strength. Today’s world science and technology and industry powers without exception are bearing research and development and manufacturing power.
In recent years, China’s bearing industry has formed a complete set of independent and complete industrial systems, whether, from the bearing output or bearing sales, China has entered the bearing industry power, ranking third in the world.
Between 2006 and 2017, China’s bearing exports increased steadily, higher than imports, the import and export trade surplus showed a growth trend, and the 2017 trade surplus reached $1.550 billion. Compared with the unit price of import and export bearings, the price difference of Chinese import and export bearings in recent years is large, but the price difference has decreased year by year, reflecting that although the technical content is still a certain gap between the bearing industry in China and the advanced level, it is catching up. At the same time, it reflects the current situation of low-end bearing capacity and low-end bearing capacity.
Take the most common deep groove ball bearing as an example, the actual life of foreign advanced products is generally more than 8 times the calculated life, up to more than 30 times, the reliability is more than 98%.
The life of the domestic bearing is generally 3~5 times the calculated life, the reliability is about 96%, the gap is very significant. This is not too big a problem for ordinary motor machinery.
To meet the high quality and reliability of the high-end bearing in precision, performance, life, and reliability, the bearing material is the decisive factor.
Due to the high-speed rotation of the object, each part of the bearing should bear the role of variable stress and high frequency. Generally, the unit area pressure is up to 1500 to 5000N per square mm. Under these factors, the bearing can easily produce stress fatigue, thus causing fatigue peeling, making the bearing lose its function. Meanwhile, the rolling bearing should bear centrifugal force, friction, high temperature, corrosion, and other factors, which also makes steel to be made.
Among the four components of the rolling bearing, in addition to the holder, the inner, coat ring, roll body (roller, roller, or needle) are composed of bearing steel, and the bearing steel is known as the “king of steel”, is the most stringent steel type in steel production.
The quality of bearing steel mainly depends on the following four factors: the content, form, distribution, and size of inclusion in steel; the content, form, distribution, and size of carbide in steel; the loose center hole and center segregation in steel; the consistency of product performance of bearing steel. These four factors can be summarized as purity and uniformity indicators.
Purity requires the inclusions in the material as little as possible. The purity can directly affect the fatigue life of the bearing; while the uniformity requires the inclusion and carbide particles in the material, which affects the deformation and tissue uniformity after heat treatment in the bearing manufacturing.
The addition of rare earth in the process of steel can make the original quality steel become more “strong”. But how to add, this is the core secret of the world’s bearing giants.
China has been able to build good steel, the next thing to do is how to use it to bearings, High-end bearings also involve technical problems in materials, design, high-precision processing, bearing manufacturing, and other on, there are some cross disciplines such as fatigue and destruction, lubrication, etc., so there is still a certain gap in China from high-end bearing technology.