China Made the World's Largest Weldless Integral Stainless Steel Ring Forging

On March 12, the world's largest seamless integral stainless steel ring forging was successfully rolled using the metal construction forming technology developed by Institute of Metal Research, Chinese Academy of Sciences.

Observers'Network learned from the Institute of Metals, Academy of Sciences that the ring has a diameter of 15.6 meters and a weight of 150 tons. It is the first time that a 100-ton grade metal billet has been constructed by stages. It is also the largest forged stainless steel ring with the largest diameter and weight in the world.

With the entrustment and support of China Nuclear Group, the Institute of Metals, CAS, has set up a production, teaching and research team. By using high purity continuous casting slab of Taiyuan Iron and Steel Company, a 15.6m diameter ring forging has been developed by Yilaite Heavy Industries, Shandong Province. Its characteristics are that there is no weld on the whole, its homogenization degree is high, and its structure is uniform. The giant ring will be applied to the fourth generation nuclear power units in China, and its successful development will strongly guarantee the implementation of major equipment in the nuclear industry.

As the core component of the fourth generation nuclear power unit in China, the supporting ring is not only the boundary and safety barrier of pressure vessel, but also the backbone of the whole reactor vessel, which bears 7000 tons of weight in structure. In the past, this kind of giant forgings were manufactured by multi-stage billet assembly welding abroad, which not only has a long processing cycle and high cost, but also has a weak material structure and performance at the welding seam position, which buries a potential safety hazard for the operation of nuclear power units.

After more than ten years of hard work, the researchers of Institute of Metal Sciences of Chinese Academy of Sciences have developed the original metal construction forming technology and revealed the healing mechanism and organization evolution mechanism of the construction interface. They have broken through the limitation of the idea of "large forging" and developed a series of key technologies, such as surface activation, vacuum packaging, multi-direction forging, hierarchical construction and integral rolling ring, and completely eliminated the multi-layers. The interface between metals makes the position of the interface of supporting ring forgings exactly consistent with that of matrix metals in composition, structure and performance, realizes a new type of processing and manufacturing with small size, greatly improves the quality and reduces the manufacturing cost.

This technology has been evalsuated by many academician experts as a revolutionary innovation in the field of large component manufacturing. It has been applied in the fields of hydropower, wind power, nuclear power, etc. It has played an important role in promoting the rapid development of high-end equipment in China and guaranteeing the autonomy and controllability of core materials of major equipment.