A reporter from People's Daily Online learned from the Chinese Academy of Sciences, recently, a team led by researcher Li Dianzhong and academician Li Yiyi from the Institute of Metal Research, Chinese Academy of Sciences has successfully developed the main bearing with a diameter of 8 meters for super-large shield machines. This indicates that China 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.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 our country. It weighs 41 tons and will be installed on a super-large shield machine with a diameter of 16 meters for tunnel engineering excavation. After the inspection by the National Bearing Quality Inspection and Testing Center and the review of the expert group, it is believed that the technical performance indicators of the main bearing are equivalent to the imported main bearings of the same kind, and meet the installed application requirements of super-large shield machines.

The shield machine is a major piece of equipment for the construction of the national economy. The main bearing is the core and key component of the cutter head drive system of the shield machine. During the excavation process of the shield machine, the main bearing "handholds" the cutter head to rotate and cut the tunnel face and provide rotational support for the cutter head.

According to reports, the main bearing with a diameter of 8 meters can carry a maximum axial force of 100,000 kN (equivalent to the gravity of 2,500 Asian elephants) and a radial force of 10,000 kN during operation. However, during the excavation process of a large shield machine, it can only move forward and cannot go backward. Once the main bearing fails, it will cause serious losses. Therefore, to ensure the high load-carrying capacity and high reliability of the main bearing, it is especially required that the bearing steel used for manufacturing the main bearing should be of high purity, high homogeneity, high strength and toughness, and high wear resistance. etc. put forward very high demands.

Previously, the main reason why the manufacture of super-large-diameter main bearings for shield machines in our country has been pending for a long time is that 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. After more than ten years of research, the team of the Institute of Metal Research of the Chinese Academy of Sciences has developed the key technology of "low-oxygen rare earth steel". The results were published in the internationally renowned journal Nature Materials this year.

(Source: People's Daily Online)

Shield machine

 the main bearing of the ultra-large shield machine with a diameter of 8 meters