CCTV Focus

On October 12, the main bearing of an 8.61-meter-diameter shield machine independently developed by CRCHI (China Railway Construction Heavy Industry) rolled off the production line in Changsha. This is the world's largest-diameter, heaviest single-unit, and highest-load-capacity integral shield machine main bearing to date. Its successful development marks that China's capability in developing and industrializing domestically produced super-large-diameter main bearings has reached a world-leading level, meaning that shield machine main bearings have achieved full domestic production and that domestically produced shield machine main bearings now cover the full spectrum from small and medium diameters to super-large diameters.

Roll-off ceremony site

Wang Lixin, President and Deputy Party Secretary of China Railway Construction Corporation, delivers a speech

Su Zimeng, President of the China Construction Machinery Association, delivers a speech

Zhao Hui, Party Secretary and Chairman of CRCHI, delivers a speech

Liu Feixiang, Chief Scientist of CRCHI and Director of the Enterprise Technology Center, introduces the independent innovation of tunnel boring machine main bearings

Leaders and guests pose for a group photo at the site

This main bearing was independently developed by China Railway Construction Heavy Industry Group and can be used to drive an 18-meter super-large-diameter shield machine. The product weighs 62 tons, stands three stories tall, and can withstand loads of over ten thousand tons; within the raceway plane of more than 8 meters in diameter, the flatness is less than 20 micrometers, making it no less difficult to manufacture than carving flowers on a grain of rice.

8.61-meter shield machine main bearing

As the "heart" component of a shield machine, the main bearing must withstand extreme and harsh operating conditions such as ultra-heavy loads, large eccentric loads, and frequent variable loads. Its service life and reliability are constrained by multiple key factors including materials, design, manufacturing, and testing, and the development difficulty multiplies as size increases. Previously, the key technology for super-large-diameter shield machine main bearings was monopolized by foreign enterprises for a long time.

It is understood that in order to overcome the weak links in the full independent industrialization of the entire shield machine industry chain, with the support of national ministries and commissions, local governments, and China Railway Construction's key science and technology special projects, CRCHI joined forces with upstream and downstream enterprises and higher education institutions to carry out collaborative research. A research and development team led by CRCHI Chief Scientist Liu Feixiang was formed, and the largest and internationally leading shield machine main bearing production line in China was built at CRCHI's Changsha Second Industrial Park. A full series of main bearings from 3 meters to 7.6 meters has been successfully developed, and the world's largest main bearing operating condition simulation test bench has been built, solving the worldwide problem of difficult test verification for large low-speed heavy-load main bearings. 

The world's largest main bearing operating condition simulation test bench

In the process of developing the 8.61-meter shield machine main bearing, the development team made concerted efforts and comprehensive breakthroughs in design, materials, manufacturing, testing, and other links, ultimately achieving a breakthrough in the 8.61-meter-diameter shield machine main bearing. In terms of independent design, the development team developed specialized calculation software for large-diameter heavy-load main bearings, tried hundreds of materials and processes, carried out thousands of theoretical verifications and design optimizations, and went through closed-loop verification and improvement in the design, manufacturing, and testing of main bearings of multiple specifications from 3 meters to 7.6 meters in diameter.

At the same time, in the materials breakthrough, CRCHI partnered with steel mills to successfully develop high-performance, long-life bearing steel; in manufacturing processes, it effectively solved manufacturing challenges such as deformation control of thin-walled rings under super-large dimensions, hard milling of high-precision large-module gears, and heat treatment of complex profiles; and in test verification, through operating condition simulation tests of main bearings of multiple specifications, it fully verified the highly reliable service capability under complex and harsh operating conditions.

It is reported that the shield machine main bearing is listed among the 35 "bottleneck" key technologies constraining China's industrial development and is the "last link" in the independent industrialization of the entire shield machine industry chain. With the successful roll-off of the 8.61-meter domestically produced super-large-diameter shield machine main bearing, CRCHI has thoroughly overcome and independently mastered the key core technologies of the entire process—from design and materials to manufacturing and testing—for the full series of shield machine main bearing products, giving domestically produced shield machines a full series of Chinese "hearts."