The people's network reporter learned from the Chinese Academy of Sciences, recently, by the Chinese Academy of Sciences Institute of Metals LiDianzhong researcher, Li YiYi academician team led the research and development of super large shield machine with a diameter of 8 meters main bearing successfully. This marks China has mastered the shield machine main bearing independent design, material preparation, precision machining, installation and commissioning and testing and evaluation of integrated technology.

The main bearing is the first set of the largest diameter and the largest single weight shield machine with the main bearing manufactured in China, weighing 41 tons, and will be installed in the super-large shield machine with a diameter of 16 meters for tunneling works. Tested by the National Bearing Quality Inspection and Testing Center and evaluated by the expert group, the technical performance index of the main bearing is comparable to that of imported similar main bearings and meets the application requirements of super-large shield machine installation.

Shield machine is a major equipment for national economic construction, carrying the heavy responsibility of crossing mountains and rivers across the sea. China has achieved the localisation of shield machines, but its core component, the main bearing, is dependent on imports, and there is an urgent need to break the "last mile" of independent and controllable manufacturing.

The main bearing is the core key component of the shield machine's blade drive system. During the shield machine's tunneling process, the main bearing "holds" the blade to rotate and cut the palm surface and provide rotational support for the blade. According to the introduction, the 8m diameter main bearing carries a maximum axial force of 100,000 kN (equivalent to the gravity of 2,500 Asian elephants), a radial force of 10,000 kN and an overturning moment of 100,000 kN-m during operation. The large shield machine can only move forward, not backward, during the tunneling process, and once the main bearing fails, it will cause serious losses. Therefore, in order to ensure the high bearing capacity and high reliability of the main bearings, it is especially required that the bearing steel for manufacturing the main bearings should be highly pure, highly homogeneous, highly tough and highly wear-resistant, and at the same time, high requirements are put forward for the complete set of design, processing accuracy and grease of the main bearings.

Chinese Academy of Sciences in 2020 launched a "high-end bearing independent controlled manufacturing" strategic pioneering science and technology special project, the Chinese Academy of Sciences Institute of Metals, the Chinese Academy of Sciences Lanzhou Institute of Chemical Physics and other seven research units within the institution to form an establishment team, joint CCCC Tianhe Machinery Equipment Manufacturing Co. Ltd. and other 20 units to carry out collaborative research, has solved 12 core key technical problems in the main bearing material preparation, precision processing and complete set design, and developed a total of 10 sets of shield machine main bearings from 3m to 8m in diameter. At present, the 3m diameter main bearings have been successfully applied in the Shenyang Metro project.

Previously, China's shield machine with large diameter main bearing manufacturing for a long time but the main reason is: manufacturing bearing materials and large roller processing accuracy is not pass, the whole process technology chain is not coherent. After more than a decade of research, the team from the Institute of Metals of the Chinese Academy of Sciences developed the key technology of "low oxygen rare earth steel", and developed a rare earth bearing steel with more than 40 times higher tensile fatigue life and 40% higher rolling contact fatigue life, and the relevant basic research results were published this year in the international famous journal Nature The relevant basic research results were published in the internationally renowned journal Nature (Materials) this year.