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The main bearing of the shield machine with the largest diameter in my country has been successfully

Date: 本站原创 From: Internet Browse:755 ADD Date:2023-01-05
Brief introduction: On December 15, the reporter learned from the Institute of Metal Research, Chinese Academy of Sciences that the research team led by Li Dianzhong,

On December 15, the reporter learned from the Institute of Metal Research, Chinese Academy of Sciences that the research team led by Li Dianzhong, a researcher at the Institute, and Li Yiyi, an academician of the Chinese Academy of Sciences, has successfully developed the 8-meter-diameter main bearing for super-large shield machines. The main bearing is currently the first set of main bearings for shield machines with the largest diameter and the largest single weight manufactured in my country. It will be installed on the self-developed domestic super large shield machine with a diameter of 16 meters.


15 years of tackling key problems and breaking through key problems

High-end equipment such as aero-engines, shield machines, and high-end CNC machine tools are inseparable from bearings. At present, although my country has realized the localization of shield machines, the core and key components of its cutter head drive system - the main bearing, still relies on imports. During the excavation process of the shield machine, the main bearing "holds" the cutter head, rotates and cuts the excavation face and provides rotational support for the cutter head. Its speed is very slow when it works, less than 3 revolutions per minute, which means that during this process, the maximum axial force and radial force of the main bearing with a diameter of 8 meters will reach 100,000 kN and 10,000 kN during operation. , the overturning moment reaches 100,000 kN·m.


"If the weight of an adult Asian elephant is 4 tons, the axial force of the main bearing will be equivalent to the weight of 2,500 Asian elephants." Li Dianzhong said that the main bearing with a diameter of 8 meters is the largest diameter class. , weighing 41 tons. And more importantly, once the main bearing is loaded into the shield machine and starts digging, it cannot be "reversed". "The shield machine can only move forward, not backward. Once the bearing fails, the loss will be huge."

Such high load-carrying capacity and high reliability standards require that the bearing steel used to manufacture the main bearings should be of high purity, high homogeneity, high strength and toughness, and high wear resistance. Very demanding.

In 2020, the Chinese Academy of Sciences launched the "Independent and Controllable Manufacturing of High-end Bearings" strategic science and technology pilot project. Seven research institutes, including the Institute of Metal Research, Chinese Academy of Sciences and the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, formed an institutionalized team. More than 20 units, including Jiaotianhe Machinery Manufacturing Co., Ltd. and Luoyang Xinqianglian Slewing Bearing Co., Ltd., worked together to tackle key problems.

Previously, in the research and development of bearings, our country has been facing two main problems-the materials for manufacturing bearings and the processing accuracy of large rollers are not up to standard, and the technical chain of the whole process is not connected. In order to make a breakthrough, it is necessary to solve the problem of material manufacturing at the source. Therefore, the research team focused on rare earth bearing steel.


A large number of existing studies have shown that adding trace amounts of rare earths to steel can significantly improve the ductility, wear resistance, heat resistance, and corrosion resistance of steel. "We also call rare earths 'industrial vitamins'. Only more than 100 grams of rare earths are needed in 1 ton of rare earth steel." The research and application of it have been repeatedly frustrated. After adding rare earth to molten steel, it is easy to cause serious clogging of the gate, and it will lead to violent fluctuations in the performance of the steel and poor stability.


After 15 years, the research team of the Institute of Metal Research, Chinese Academy of Sciences finally found the answer to this question - the oxygen content. As long as the oxygen content in rare earth steel and rare earth metals is reduced, its performance is exceptionally stable. The key technology of "low-oxygen rare earth steel" has increased the tension and compression fatigue life of rare earth bearing steel by more than 40 times, and the rolling contact fatigue life has increased by 40%. With the help of this technology, domestic enterprises have manufactured tens of millions of sets of high-quality bearings.


Excellent performance in multiple indicators of the product


However, it is not enough to rely on high-quality rare earth bearing steel. Issues such as bearing machining accuracy, grease material, and bearing heat treatment are also crucial.


Due to the limitation of processing equipment, the machining accuracy of large rollers in my country can only reach the second level before, which is still far behind the more stringent first-level precision machining. Hu Xiaoqiang, the chief engineer of the main bearing development technology of the shield machine and a researcher at the Institute of Metals, Chinese Academy of Sciences, jointly carried out research with the company, which enabled my country's bearing industry to break through the first-level precision machining technology for large rollers, and realized the processing and manufacturing, assembly and debugging of the main bearing of the shield machine. The whole process such as testing and evaluation is independently controllable, and at the same time it drives the development of related domestic equipment.

The stable operation of bearings is inseparable from good lubricating materials. The Lanzhou Institute of Chemical Physics of the Chinese Academy of Sciences has formed its own main bearing lubricating grease ratio and composition through the structural design of core additives and the development of controllable preparation technology, and has developed a lubricant that can still maintain good lubrication under impact loads. Lubricating grease with less wear.


"Our team was born in materials, but in the development process of the main bearing of the shield machine, we jumped out of the 'comfort zone' of scientific research and completed the transformation from 'what to do' to 'what to do'. Materials need to be made, The material must be made into a tool, and the tool must be easy to use.” Li Dianzhong said that through the multidisciplinary team and the joint venture of the enterprise, the team broke the industry barriers of materials and machinery manufacturing. Concentration of ability."


At present, the 8-meter-class main bearing is my country's first set of main bearings for shield machines with the largest diameter and largest single weight. Many of its indicators are superior to similar foreign products. The content of a non-metallic inclusion inside the material is only a few parts per 100,000, which is an order of magnitude lower than that of imported products; the inclusions of rare earth steel materials are small and round, and the size is smaller than imported products. The fatigue strength of bearing steel is also improved by more than 100 MPa compared with imported products.


The National Bearing Quality Inspection and Testing Center's inspection and expert group review believe that the technical performance indicators of the main bearing are equivalent to those of imported similar main bearings, and meet the installed application requirements of super-large-scale machinery. The successful development of the main bearing marks that my country has mastered the integrated technology of independent design, material preparation, precision machining, installation and debugging, and testing and evaluation of the main bearing of the shield machine.


At present, the pilot special project has successively solved 12 core key technical problems in the main bearing material preparation, precision machining, and complete set design, and developed a total of 10 sets of shield machine main bearings with a diameter of 3 meters to 8 meters. Previously, the main bearing of the shield machine with a diameter of 3 meters has been installed on the shield machine produced by North Heavy Industry Group, and it has been successfully applied in the Shenyang subway project in April 2022. In the future, the 8-meter-class main bearing will be installed on a super-large shield machine with a diameter of 16 meters for tunnel excavation.

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