26

2022

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07

"Ten years to grind a sword" has made a major breakthrough in bearing steel technology, and the bearing industry is welcoming new changes

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During an interview with Northwestern Polytechnical University recently, the reporter learned that the Power Rotating Rolling Technology (PTR) developed by Professor Liu Dong and his team from the School of Materials Science and Technology of the school has made a major breakthrough and solved the problems in the development of related industries in my country.
From automobiles, high-speed trains, airplanes, instruments, and mechanical equipment, almost all rotating machinery can find a common core component-bearing. Bearing steel, the material needed to manufacture bearings, is known as the "King of Steel" because it is directly related to the life and reliability of bearings.

Finished product produced by powerful spinning technology. Photo courtesy of Northwestern Polytechnical University

"The working environment of bearings is severe and complex. It not only requires high-speed and stable rotation, but also withstands strong extrusion, friction, and even ultra-high temperature experience." Professor Liu Dong told reporters that because of this, the quality and reliability of bearing steel , has very strict requirements.

How to improve the quality of bearing steel? According to Professor Liu Dong, firstly, the interior should be pure enough, with as few inclusions as possible; secondly, it should be uniform enough that the particles in the material should be as fine and dispersed as possible. However, it is regrettable that the quality of bearing steel produced in my country has always been far behind the international advanced level. Taking inclusions as an example, the size of inclusions in foreign products is completely less than or equal to 10 microns, while the largest domestic particle size is 50-52 microns, "the difference in size is five times as much".

Compared with the traditional technology, the strong spinning technology can obtain finer and more dispersed carbides. Photo courtesy of Northwestern Polytechnical University
Due to the inability to find bearing steels that meet high-quality needs from domestic manufacturers, many companies have to pay high prices to import them. This means: every time we make a set of products, we need to buy a bearing from abroad.

As a "steel power", how can it become a "steel power"? After decades of efforts of scientific researchers in our country, technical problems such as oxygen content and inclusions in bearing steel have been effectively solved. The last "big problem" in the industry - "carbide" was also overcome by Professor Liu Dong and his team.

Since bearing steel is a high carbon steel, its carbon content is relatively high among all steels. If the carbides are unevenly distributed and in large chunks, the quality will be severely affected. Professor Liu Dong made an analogy: "It's like sprinkling a handful of salt when kneading dough. If the dough is not kneaded and kneaded evenly, the dough will be full of salty and hard lumps." "Make the salt finer and more uniform. distribution in the surface" is the goal pursued by Professor Liu Dong and his team.

"Take kneading as an example. The larger the deformation, the more uniform the kneading will be. The key to good kneading is how to 'knead'." Professor Liu Dong's team innovatively proposed the "powerful spinning technology"—— "This technique is to deform the dough in three directions when kneading the dough, and the deformation value is very large. It can be said that the dough is kneaded thoroughly and vigorously."

It sounds simple logic, but it contains the tireless exploration of Professor Liu Dong's team. The team "honed a sword in ten years", and after continuous research and testing, finally broke through the technical bottleneck, developed 3 "world's first" technologies, and applied for 66 invention patents. Power spinning technology is one of them.

According to Professor Liu Dong, China's bearing industry has formed an industry sales scale of nearly 200 billion yuan, and the annual growth rate is 12%-15%, but the bearings produced are still mainly medium and low-end bearings and small and medium-sized bearings. Among them, the proportion of automobile bearings is about 40%, and the quality control level of inclusions and carbides in bearing steel is low, which seriously affects the life and reliability of domestic automobile bearings. "The emergence of powerful spinning technology may forcefully change this status quo."

Compared with the traditional technology, the average grain size of the power spinning technology is more optimized. Photo courtesy of Northwestern Polytechnical University
Laboratory data show that: using the strong spinning technology, the grain size is refined from the original 50 microns to 10 microns, and the carbide size is only 1/10 of the original. At the same time, the hardness of bearing steel has been greatly improved, and it is at the top level in the world. In addition, the life and reliability of the bearings are greatly improved. This technology can also significantly improve material utilization and greatly shorten the production process.