A thousand-layer cake is a cake with many layers on top of each other. The thousand-layer cake is just an exaggeration. In fact, it does not have so many layers, and this thousand-layer cake really has tens of thousands of layers!

The Baihetan Hydropower Station, located in Ningnan County, Liangshan Prefecture, Sichuan Province, and Qiaojia County, Zhaotong City, Yunnan Province, has a freshly baked "Wan Layer Cake", which is nearly 4 meters high and over 15 meters in diameter. Weighing 1274 tons.

This is not a piece of cake, but the heaviest and largest core component of the generator set - the rotor. It is made up of more than 20,000 yoke steel sheets.

　This "10,000-layer cake" is not simple. The 20,000-layer behemoth will eventually spin up, and the speed will reach 111 revolutions per minute, which is equivalent to spinning at a speed of 345 kilometers per hour, which is similar to the speed of high-speed rail.
If the 20,000-layer yoke steel sheets are uneven and uneven, the weight of the entire rotor will be uneven, and the huge centrifugal force during high-speed rotation will cause damage to related parts and threaten the safety of the entire generator set. However, in order to make the 20,000 layers of steel sheets still evenly and evenly stacked, each layer must be made extremely evenly and evenly, which is a difficult technology.
Twenty years ago, the Three Gorges Dam could only import the "layers" of this "thousand-layer cake" from abroad, and foreign manufacturers could control the unevenness of each layer within 6mm. But now, our generator sets are getting bigger and bigger. The motor of Baihetan Hydropower Station has the largest rotor in the world. The bigger the rotor is, the higher the flatness requirement of each layer is. The foreign yoke steel sheet cannot meet our requirements. Require.
In order to completely solve this "stuck neck" problem, Taiyuan Iron and Steel Group went up to the challenge and through numerous tests, found the best ratio of the composition of the yoke steel sheet, overcame a number of technical problems, and made the yoke steel sheet in one fell swoop. The unevenness is reduced by 5mm to within 1mm. Not only that, the high-strength seismic steel, large-thickness high-grade hydropower steel plate, and high-grade silicon steel of my country's large-scale hydropower stations have all gotten rid of the situation of relying on imports. The steel industry has become a strong backing for the million-kilowatt hydropower unit to climb to the top of the world.
Because yoke steel has the characteristics of high strength, high precision and high magnetic properties, not only the technical indicators of the steel are very strict, but also the processing requirements are extremely high. Taiyuan Taiyuan Iron & Steel Daming Taiyuan Machining Center CTL25.4 cross-cutting unit, as the main processing equipment for the yoke steel of the rotor part of the Baihetan project, processes materials with a thickness range of 3.0~25.4mm and a maximum yield strength of 1200MPa. In addition, the unit is equipped with two sets of levelers and three sets of roller systems, which successfully achieved the target requirement of "unevenness ≤ 1mm" for the finished product.
After the yoke steel is flattened, it is then cut and punched by a fiber laser cutting machine. The accuracy error of cutting and punching is within 0.03mm, and the error of cutting flatness is less than 1mm.
The processed products have undergone a series of inspections by the company's quality personnel, manual inspections, three-coordinate inspections and other links to ensure that the products meet customer requirements and ensure the final pass for the high-quality distribution of products.