ringformning

Ringformning, or ring rolling, is a metal forming process used to manufacture hollow circular components such as rings and gear rings by plastic deformation of a preform. The process is usually performed hot, though cold or warm forming is used for some alloys, and it yields parts with accurate circularity and controlled cross-sections.

In operation, a preform ring, hollow or solid, is placed between rolls in a ring-rolling stand; a mandrel inside defines the bore. As the rolls press and rotate, the ring expands radially and the length increases, producing a larger outer diameter while preserving or adjusting wall thickness. The rolling may use two or three rolls and can involve multiple passes to reach the final geometry. Ring rolling is chosen for producing large rings that would be difficult to forge as a single piece.

Variants include hot ring rolling, which is most common, and cold ring rolling for certain nonferrous alloys to achieve tight tolerances. Some processes combine ring rolling with upsetting to create thicker sections.

Materials commonly processed include steel and stainless steel, aluminum, titanium alloys, and copper alloys. Ring rolling can handle very large diameters and thick walls, depending on equipment.

Applications span aerospace components (bearing rings, turbine engine rings), automotive parts (ring gears, valve rings), power generation equipment, wind turbines, and mechanical seals. The technique offers high dimensional accuracy, good surface finish, and refined microstructure due to controlled deformation, enabling near-net-shape parts.

Limitations include the need for specialized rolling mills, high capital costs, and restriction to axisymmetric cross-sections. Quality control involves dimensional surveys, metallurgical examination, residual-stress relief through post-heat treatment, and non-destructive testing as required.