How is the giant ring of China's nuclear power plant refined?
it is the world's largest diameter stainless steel ring forging (diameter 15.6 meters); It has created the world's heaviest single stainless steel billet (150 tons); It has created the world's first metal construction forming technology and realized the hierarchical construction forming of 200 ton metal billets... Its smelting difficulty is unprecedented. Recently, the world's largest stainless steel ring forging (diameter 15.6 meters) is the world's largest diameter stainless steel ring forging; It has created the world's heaviest single stainless steel billet (150 tons); It has created the world's first metal construction forming technology and realized the hierarchical construction forming of 200 ton metal billets... Its smelting difficulty is unprecedented
recently, the world's largest welded austenitic stainless steel integral ring forgings were successfully rolled in Jinan. As the core component of the fourth generation nuclear power unit in China, the support ring is not only the boundary of the pressure vessel and the safety barrier, but also needs to bear 7000 tons of weight structurally. It can be called the "backbone" of the polycarbonate stack container that adopts precision CNC carving
the technology used to create the world's best is the metal construction forming technology of "making large from small" first proposed by Li Yiyi, academician of the Institute of metals, Chinese Academy of Sciences
"making large from small" to overcome the "barrel effect"
the traditional method of making large forgings is usually "making large from large", that is, the forging base metal must be larger than the formed workpiece. According to this calculation method, the large forgings manufactured this time need to cast at least one steel ingot with a unit weight of 250 tons
however, the larger the ingot size is, the longer the solidification time is, the slower the cooling speed is, and the more serious the segregation, porosity and coarse-grained phenomena of the ingot are
in addition, due to the limitation of the capacity of special metallurgical equipment, this kind of giant ring forgings is traditionally manufactured by sections and then welded at home and abroad. This means that there should be a weld on it. Because the material performance of the weld is very weak, there will be some potential safety hazards in the service process of the component, which is what we call the "barrel effect"
in order to overcome this problem, Li Yiyi, an academician of the Institute of metals of the Chinese Academy of Sciences, pioneered the metal construction forming technology of "making large from small" in the world. Through the use of dozens of small slabs, group sealing and welding, and multiple constructions, the 200 ton raw steel billet was successfully manufactured and rolled as a whole. On this giant ring, there is no so-called weld at all, and the overall performance has been significantly improved
skillfully borrow the principle of "building walls" to build houses
then, what is the metal construction forming technology
the metal construction forming technology was first proposed by Academician Li Yiyi's team in the world. This technology breaks through the traditional thinking that the base metal of metal components can only be larger than it, and cleverly uses the "wall building" principle in the construction field for reference. After surface cleaning and vacuum packaging, multiple homogenized slabs are deformed at high temperature to realize solid-state metallurgical connection, fully heal the interface, and realize the "traceless" connection between the interface and the substrate
this core idea of "breaking up the whole into parts and making large from small" can realize the preparation of high-quality homogenized large forgings at a low cost, which is a new breakthrough of additive manufacturing technology in the field of large component manufacturing
generally speaking, the Great Wall is built brick by brick. Similarly, the metal construction forming technology is to "build" multiple metal plates into a large ingot through some technology, and then get the shape we want through subsequent forming processing. This is a disruptive technology in the steel industry
find another way to overcome "metallurgical defects"
in addition to the difficulty of "making large ingots with large scale", the traditional method of smelting large ingots also faces the world-wide problem of gold defects at the end of the 1990s. 1. Before each experiment
Academician Li Yiyi's team once dissected the 100 ton mold cast ingot for nuclear power rotor, and no obvious defects were found on the surface of the ingot, but after dissection, there were shrinkage defects with a width of 20 mm and a length of 1700 mm in the center of the ingot, a wide range of macro segregation, and dendrites with a length of 500 mm. This metallurgical defect will seriously affect the mechanical properties of the components, and there are serious problems in the internal organization
many scholars at home and abroad have tried to improve the internal quality of large ingots by accelerating cooling, adding internal cooling elements, electromagnetic stirring and other methods for half a century, but they have achieved little
metal construction technology is a new way. Using the relatively mature and stable continuous casting technology to produce continuous casting slabs or high-quality small steel ingots as the basic element, after surface cleaning processing, vacuum package multiple slabs, and then fully weld the interface through high-temperature and high-pressure forging, so that the interface is integrated with the substrate, realizing the metallurgical connection of traceless interface, and successfully breaking through the component segregation, porosity, shrinkage Technical bottlenecks such as excessive inclusions
through thousands of performance tests on constructed steel ingots of various materials, the tensile properties, fatigue properties and even impact energy in all directions of the original interface can be consistent with the matrix, and the data are stable. The tests show that the constructed steel ingots can completely achieve or even higher performance than the ingot products, and realize metal traceless connection
the future is long but "unstoppable"
practice has proved that metal construction technology has the advantages of low cost, high quality, stable quality and green environmental protection, and has become an important new method of large forgings manufacturing at present
at present, the metal construction and forming technology has achieved the construction and forming of large forgings in the fields of energy, power and ocean engineering, such as the demonstration fast reactor support ring and large-diameter pressure pipe, the main shaft of hydraulic turbine runner, marine stern shaft hub, stainless steel extra thick plate for nuclear power, etc., involving materials including 316H stainless steel, S03, 925a, SA steel, 20SiMn, 9Ni, Ti80, oxygen free copper, etc., and has achieved phased results, It has been recognized by many academicians, experts and enterprises, and has been evaluated as a revolutionary technology in the field of large component manufacturing
although metal construction technology can produce high-quality billet of large forgings, it is somewhat difficult to adopt construction technology for some difficult and non weldable metals because it requires vacuum electron beam sealing welding
metal construction technology is a new thing for the steel industry, if it does not meet your parameters, we can customize it at any time. Therefore, we still have a long way to go to make it widely recognized in the industry. However, with the development of technology, it is also an indisputable fact that metal construction technology will eventually replace large ingots in forging processing. In the future, this technology is expected to solve the problem of manufacturing core components of strategic equipment such as ships, nuclear power and aerospace, and make a qualitative leap in China's industrial development
(author: Institute of metals, Chinese Academy of Sciences)