This project belongs to product manufacturing technology in the field of materials science and technology.
Nuclear power is a clean and efficient energy source and an important measure to optimize my country's power supply structure and achieve low-carbon development. The key equipment products of the nuclear island are the basis for supporting the implementation of my country's nuclear power "active development" and "going global" strategies. The 690 alloy U-shaped heat transfer tube of the steam generator is the core component for heat exchange in the primary and secondary circuits of the nuclear island, and is a key guarantee for the safe and reliable operation of nuclear power plants.
Before 2009, my country's nuclear power steam generator U-shaped heat transfer tubes completely relied on imports. Foreign technology monopolized and the prices were extremely high. Only three companies, Valinox of France, Sumitomo of Japan and Sandvik of Sweden, could produce them, which seriously restricted the development of my country's nuclear power. Nuclear power heat transfer pipes must be in long-term stable service in high temperature and high pressure special corrosive environments (~60 years), its technical requirements are very high and manufacturing is extremely difficult. To this end, the state has set up major scientific and technological special projects, and Baosteel has joined forces with the General Steel Research Institute to carry out research on the full-process manufacturing process and control technology of 690 alloy U-shaped heat transfer pipes for nuclear power steam generators, and has achieved the following main innovative results:

1. Independently develop high-precision carbon control, high-uniformity, ultra-pure smelting and control technologies. Stabilize control the C content at 0.019-0.021%, develop a proprietary desulfurization and environmentally friendly slag system to stably control the S content at 4-6ppm, develop special casting control technology, and obtain highly uniform and ultra-pure steel ingots, which is superior to foreign levels.
2. The first high-signal-to-noise ratio and high-precision tolerance surface cold working control technology for 690 alloy pipes. By studying key factors affecting the signal-to-noise ratio, the problem of high signal-to-noise ratio was solved, and the signal-to-noise ratio control of finished pipes was concentrated at 30-50, ensuring the uniformity and consistency of high-precision size tolerances.
3. Independent research and development of online degreasing control technology for ultra-long, thin-walled and small-diameter 690 alloy pipes. Online heating, pressurizing, cyclic internal and external degreasing equipment was designed and developed to achieve good degreasing of the finished pipe of Φ17.48×1.01×29000 mm and ensure corrosion resistance.
4. Independently developed high-precision control technology for 690 alloy U-bend. A special bending mold has been designed to stably control the ovality of the minimum bend of the finished pipe at 90 degrees ≤2.5%, the outer diameter of the bend is 17.48-17.51mm, and the wall reduction amount is <0.10mm.
5. A full-process size accuracy and organizational performance control technology has been formed from internal control component matching-high-precision smelting-fine pipe manufacturing-TT heat treatment, and a full-process dedicated production line for heat transfer pipes has been established, realizing 690 heat transfer pipes. Stable batch manufacturing.
   This project has obtained 17 authorized patents (5 invention patents and 12 utility models), 9 corporate technical secrets, 13 papers have been published, and more than 40 engineering manufacturing process documents have been formed. After the implementation of the project, the project products have been used in batches in second-generation plus and third-generation nuclear power plants. A total of 1.53 million meters/690 tons of 690 alloy U-shaped pipes have been delivered. The domestic market share has ranged from zero to 40%, and sales revenue of 530 million yuan has been achieved. The new profits and taxes have been increased by 230 million yuan, forcing the price of foreign imported pipes to drop significantly, from a maximum of 2 million yuan/ton to 800,000 yuan/ton, saving the country 520 million yuan in foreign exchange expenditures, with huge economic and social and environmental benefits. The overall technical and performance indicators of the project products have reached international advanced, and some technical performances are superior to foreign levels, allowing my country to reach the world advanced level in terms of the production capacity of high-precision and high-requirement alloy pipes, filling domestic technical gaps, breaking foreign monopolies, and improving The international competitiveness of my country's nuclear power. In the next 10 years, combined with the rapid development of my country's nuclear power and "going global", the technology of this project will have broader application space.