Current situation and development direction of bearing steel

Bearings are widely used in mining machinery, precision machine tools, metallurgical equipment, heavy equipment and high-end cars and other major equipment fields, wind power generation, high-speed rail bullet train and aerospace and other emerging industries.Bearings produced in China are mainly low-end bearings and small and medium-sized bearings, showing low-end surplus and high-end lack.Compared with foreign countries, there is a big gap in high-end bearings and large bearings.

China high-speed railway passenger car special matching wheelset bearings all need to be imported from abroad.In the key bearings used in aerospace, high-speed railway, high-end cars and other industrial fields, there is a big gap between Chinese bearings and advanced ones in terms of service life, reliability, Dn value and bearing capacity.For example, the service life of foreign automobile transmission bearings is at least 500,000 kilometers, while the service life of domestic similar bearings is about 100,000 kilometers, and the reliability and stability are poor.

1. Aviation

As the key basic component of aero-engine, the second generation aero-engine bearing with thrust ratio of 15-20 is being developed abroad, which is ready to be assembled into the fifth generation fighter around 2020.In the past 10 years, the United States has developed the second-generation bearing steel for aero-engine, whose representative steel types are CSS-42L, a high strength corrosion resistant bearing steel with 500℃ resistance, and X30 (Cronidur30), a high nitrogen corrosion resistant bearing steel with 350℃ resistance. China is developing the second-generation bearing for aero-engine.

2. Cars

For automobile hub bearings, the first and second generation hub bearings (ball bearings) are widely used in China, while the third generation hub bearings have been widely used in Europe.The main advantages of the third generation hub bearings are reliability, short payload spacing, easy installation, no adjustment, compact structure and so on.At present, most imported models in China use such lightweight and integrated structure hub bearings.

3. Railway rolling stock

At present, bearings used in China's railway heavy-haul trains are made of domestic electroslag remelting G20CrNi2MoA carburized steel.And foreign has the ultra high purity of bearing steel (EP) steel smelting and vacuum degassing inclusion homogenization technology (IQ) steel, long life steel technology (TF) steel, fine quality, and the heat treatment technology, surface hardening treatment technique and advanced sealing lubrication technology applied to the bearing production and manufacturing, thus greatly enhance the service life of bearing and reliability.The quality of Chinese electroslag bearing steel is not only low, but also the cost is 2000-3000 yuan/ton higher than that of vacuum degassing steel. In the future, China needs to develop vacuum degassing bearing steel with ultra-high purity, fine quality, homogenization and stable quality to replace the current use of electroslag bearing steel.

Future research and development direction of Bearing steel in China

It is mainly reflected in four aspects:

1. Economic cleanliness

Under the premise of considering economy, the cleanliness of steel is further improved, the content of oxygen and titanium in steel is reduced, and the mass fraction of oxygen and titanium in bearing steel is less than 6×10-6 and 15×10-6, respectively. The content and size of inclusions in steel are reduced, and the distribution uniformity is improved.

2. Organization refinement and homogenization

Through the application of alloying design and controlled rolling and controlled cooling process, the uniformity of inclusions and carbides is further improved, the reticulated and banded carbides are reduced and eliminated, the average size and maximum particle size are reduced, and the average size of carbides is less than 1μ m.The grain size of bearing steel is further refined by improving the grain size of matrix structure.

3. Reduce low-power tissue defects

Further reduce the central porosity, central shrinkage cavity and central component segregation in bearing steel, improve the uniformity of low-power structure.

4. High toughness of bearing steel

The toughness of bearing steel was improved by new alloying, hot rolling process optimization and heat treatment process research.(China Steel Research & Development Strategy Institute)

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