China’s manufacturing industry is short of high-end bearing steel
Core technologies to be tackled urgently
“High end bearings depend on imports. Why can’t we make them ourselves?” after investigating five or six provinces such as the three eastern provinces, Zhejiang and Shandong, Wang Dongsheng, executive deputy director of Shandong technology transformation center of Chinese Academy of Sciences, found the answer: the biggest problem lies in the material, “without good steel, we can never make high-end bearings”.
As an indispensable core component in mechanical equipment, bearing supports mechanical rotating body, reduces its friction coefficient and ensures its rotation accuracy. In his opinion, no matter aircraft, automobiles, high-speed railways, high-precision machine tools and instruments, “all rotating parts need bearings”.
It is no exaggeration to say that the bearing in the engine has been working in “Purgatory” – it not only has to run at a speed of tens of thousands of revolutions per minute for a long time, but also bears various forms of stress extrusion, friction and ultra-high temperature. This puts forward high requirements for the accuracy, performance, service life and reliability of the bearing, and the key factor determining these four points lies in its material.
Unfortunately, although China’s shaft making technology is close to the world’s top level, the material, that is, high-end bearing steel, is almost entirely imported.
Recently, a reporter from science and technology daily interviewed a large state-owned iron and Steel Group in East China and learned about the embarrassment of the latter. As a “top 100 Chinese enterprises”, this iron and Steel Group has its own high-quality steel base, but it can not produce high-end steel for bearings and can only rely on imports. Not long ago, it spent nearly 100 million yuan to import bearing steel.
“Ppm” is the unit of oxygen content in steelmaking, which means parts per million or parts per million. Experts from the Institute of metals of the Chinese Academy of Sciences told the science and Technology Daily that generally speaking, in the iron and steel industry, 8 ppm steels belong to good steels; 5 ppm steel is the top steel, which is needed for high-end bearings. The R & D, manufacturing and sales of high-end bearing steel are basically monopolized by the world bearing giants Timken of the United States and SKF of Sweden. A few years ago, they established bases in Yantai and Jinan, Shandong respectively, purchased low-end materials from China, made high-end bearings with their core technology, and sold them to the Chinese market at ten times the price.
The addition of rare earth in the steelmaking process can make the original high-quality steel more “strong”. But how to add, this is the core secret of the world’s bearing giants.
Rare earth is called “industrial vitamin”, and rare earth steel refers to steel containing a certain amount of rare earth. In the 1980s, China set off a climax of R &D and application of rare earth steel. Scientists generally believe that adding rare earth in the steelmaking process is the technical direction to solve the problem of high-end bearing steel. However, after adding rare earth to the steel, the performance of the steel becomes good and bad, and it is also very easy to block the gate in the process of large-scale production. Although it has been tackling key problems for many years, it has failed to break through the technical bottleneck, This also leads to the change of rare earth from heat to cold in the application of iron and steel industry.
Like a drop of ink in a basin of water, how many trace rare earths are more appropriate to add to a ton of steel? How?
The problem remains unsolved, resulting in the following consequences: at present, except for a small number of steel grades, iron and steel enterprises almost give up the application of rare earth in actual production.
However, on the road of developing high-end bearing steel, it is not all bad news.
In the previous stage, the material processing simulation research team of the Institute of metals of the Chinese Academy of Sciences found that impurities were the main cause of uneven composition through physical anatomy and calculation of large steel ingots with a single weight of 100 tons. Based on this, a new defect formation mechanism in steel was proposed, which caused great repercussions in the industry and was quickly applied. Since then, the team has developed the purified preparation technology of commercial rare earth alloys and the special addition technology of rare earth in steel, thus breaking through the technical bottleneck of industrial application of rare earth in steel and realizing the smooth process and stable performance after adding rare earth in steel.
