Ring forging is a technology for forming metal materials into a ring shape through plastic deformation. In particular, "ring rolling," which involves piercing a heated billet and then rotating and rolling it while it is clamped between a mandrel and a main roll, is a typical processing method. This process continuously refines the material's grain structure, resulting in seamless ring products with high strength, toughness, and fatigue resistance. It achieves excellent mechanical properties and dimensional accuracy with few internal defects. It is a fundamental technology indispensable for manufacturing critical components that require high reliability and durability, such as races for large bearings, gears, flanges, bodies and nozzles of pressure vessels, aircraft engine components, and wind power generation components.