Reprinted from: CIMES Beijing Machine tool Exhibition
In 2004, there is no one-inch high-speed rail in China; by the end of 2018, China’s high-speed rail traffic has reached 30,000 km, accounting for more than two-thirds of the world’s total mileage, and the commercial operation speed is 350 km/ h and the world is the highest. China’s high-speed rail has achieved the gorgeous turn from “catch-up” to “runner”, and high-speed rail technology has entered the world’s leading ranks.
However, our country can build the best high-speed train in the world, build the world’s largest high-speed railway network, with the ability to install the road and go to sea, but rely on foreign guns and foreign guns in a few key technologies. In order to maintain their technological advantages, western enterprises often have reservations about the export of equipment and technology, which poses a potential constraint on the future development of China’s high-speed rail.
Although the whole vehicle of high-speed railway train unit with independent intellectual property rights has been produced in the country, the axle box bearing of the high-speed motor train unit as the key technology of the nine-large key technology of the motor train unit is the commonly used high-speed rail bearing, and all the imported bearings are used, The axle box bearing has always been a short board that restricts the formation of a fully autonomous intellectual property unit and its associated components. At the same time, the axle box bearing is also one of the most damaged parts of the high-speed railway passenger car. The service life and reliability of the axle box bearing of high-speed railway passenger car directly affect its performance, quality and safety.
The bearing is an important component in the high-speed rail gear box. The high-speed rail gear box is mainly composed of gear, box body, bearing and lubricating mechanism. It is the power transmission of the high-speed rail train. It is responsible for transmitting the power of the motor to the train, so that the train can run at high speed, it is one of the core components of the high-speed rail train. The hub bearing has eight sets of high-speed rail trains at a cost of ten million. The bearing belongs to the wear piece, and it needs to be replaced once every 1 million kilometers.
The line speed of the driven gear will jump from 35 meters per second to 70 meters per second when the train is lifted up to 380 km/ h from 200 km/ h. In general, a gear with a linear velocity of more than 25 meters per second may be referred to as a high-speed gear box. Such high speed, the performance of the gear itself, the meshing between the gears, the sealing of the box body and the like, and the great challenge is put forward.
The high-speed rail bearing spindle is the key component of the precision optical coordinate boring machine. in the bearing, the radial swing error of the jacket cannot exceed 2/1000 mm. in the case of high speed operation, the temperature rise of the bearing cannot exceed 15°C.
For a long time, high-speed rail bearings because of high risk, great impact, the main engine users lack of confidence in the choice of domestic bearings. In order to avoid the risk, some users only purchase and use imported bearings, which sets the threshold for the entry of domestic bearings and limits the development of domestic high-end bearings such as high-speed rail bearings. The death of imports is expensive, which also responds to that sentence. What China can make is very cheap!
At present, the main companies that produce high-speed railway bearings in the world are SKF, of Sweden, FAG, of Germany, TIMKEN of the United States, NTN and NSK. of Japan. These companies have carried out very systematic research on bearings for high-speed railways.
In the aspect of design, SKF applies the finite element analysis method to the shaft box bearing design, and develops the compact tapered roller bearing assembly, which is also equipped with sensors to monitor the speed and bearing state. NTN adopts the dynamic analysis of cage motion and the advanced finite element analysis and design method to develop the plastic cage. The life span of the compact tapered roller bearing developed by SKF company is more than three times that of the ordinary material. The compact tapered roller bearing developed by SKF company has built-in low contact seal, which adopts built-in non-contact or light contact seal, combines labyrinth seal and lip seal, reliably isolates pollution and greatly improves pollution. And the service life of the bearing is effectively improved. The sealing seat and the gasket are eliminated in the bearing design, the seal is arranged in the bearing, the middle of the outer ring is in the middle of the outer ring, the space is saved, and the bending of the axle is restrained.
In terms of materials, the vacuum degassing smelting technology of inclusion homogenization technology (IQ steel), ultra-high purity bearing steel (EP steel) and ultra-long life steel (TF steel) have been systematically and deeply studied abroad to improve the service life of bearing steel. In the aspect of manufacturing, foreign bearing enterprises have solved the heat treatment and manufacturing problems of high-speed iron bearings, bearings generally reach P4 grade accuracy, some key position accuracy reaches P2 class.
Domestic high-speed rail bearing research and development started relatively late. At present, the finite element method has been used to analyze the dynamics of bearings and optimize the structure. In terms of materials, domestic smelting technology is relatively backward, including electroslag remelting G20CrNi2MoA Carburizing steel and electroslag remelting GCrl 5 bearing steel. At present, it is necessary to explore and study the vacuum refining technology of bearing steel and the process method of improving the purity of bearing steel material, so as to replace the electroslag remelting method with 360000 square data, so as to realize the high reliability, long life and low cost of high speed iron bearing. With regard to the cage, the bearing of the axle box of the railway in our country has protected the plastic. The holder is used as a standard component.
High-speed rail bearing is the core key component of high-speed EMU, and it is the comprehensive embodiment of a national high-tech development level, equipment manufacturing ability and independent innovation ability. Therefore, it is urgent to carry out independent research and development of axle box bearings of high speed EMU. The research and development of high-speed rail shaft box bearing involves a series of technical problems, such as design, manufacture, material, lubrication, detection and test, condition monitoring and so on. Domestic bearing related enterprises have carried out the corresponding technical research and development basis.
Luoyang LYC Company started to develop high-speed rail bearing from the “the 11th Five-” period, and solved a series of key technical problems such as product design process and heat treatment process. Starting in 2006, the first batch of railway passenger car bearings, such as 140 km/ h,160 km,200 km,250 km,350 km and the like, has been developed and produced by the Laxis, and is tested by the national authorities.
Large-scale high-speed rail bearing tester
In the domestic public bidding for “2014 Industrial Transformation and upgrading strong Foundation Project” organized by the Ministry of Industry and Information Technology and the Ministry of Finance, this is the first domestic tender for high-speed rail bearings in China. Luoyang LYC Company won the bid for the axle box bearing project of railway passenger cars from 200km / h to 350km / h. The accuracy of the bearing products of the winning axle box reaches grade 5, and the limit speed is 3000 revolutions per minute, which meets the requirements of high speed EMU from 200km / h to 350km / h, service life of 2 million km / h and reliability of 1 million km / h to 99 per cent.
By 2019, Luoyang bearing Factory has completed the product design, process research and sample manufacturing of 250 km / h and 350 km / h high speed railway bearings. The product has passed the 1.2 million km durability bench test, and the test results show that the bearing is in good condition and meets the requirements of the standard. Luo shaft has opened the high-speed rail bearing development technology channel, basically has the high-speed rail bearing mass production condition. It is also worth mentioning that the price of high-speed rail bearings developed and produced by Luo shaft is only 1% of that of similar foreign products.
China’s high-speed rail technology ranks at the forefront of the world, but in the advanced “made in China” system, there are some “shortcomings” in which some core technologies are controlled by foreign countries. Our country should make great efforts to overcome a number of shortcomings in the fields of basic materials, key components and so on, and greatly improve the manufacturing level in the field of basic technology and materials. At the same time to provide domestic equipment to provide more trial production, application space.