The world’s largest weldless stainless steel forging ring was rolled successfully on March 12, 2019, using the additive forging technology developed by Institute of Metal Research (IMR) of Chinese Academy of Sciences.

The ring piece has a diameter of 15.6 meters and weighs 150 tons. It is the largest and heaviest integral forged stainless steel ring in the world.

This ring piece will be applied as the support ring of the core component in China’s fourth generation nuclear power unit. As the boundary and back bone of the reactor vessel, the support ring needs to bear 7000 tons of weight from the whole reactor vessel and the reactor internals.

Traditionally, such giant forgings were manufactured by welding of multiple small billets, which has a long processing cycle and costs high. Moreover, the security and stability of the support ring will be greatly reduced due to several longitudinal welds, which pose a safety hazard to the operation of the nuclear power unit.

IMR scientists initiates the additive forging technology, and reveals the interface healing mechanism and microstructure evolution mechanism.

By implementing several key technologies, the bonding interface can be eliminated completely, and the microstructure and properties of the bonding zone can restore to the same level of the matrix.

This revolutionary technology improves the quality and reduces costs in manufacturing of such large component. It has been successfully applied in fields of wind power, hydropower and nuclear power.

Figure 1: The weldless stainless steel forging ring (Image by IMR) 

Figure 2: The weldless stainless steel forging ring (Image by IMR)