Rolled Rings Information
Rolled rings (also known as seamless forged rings) have a toroidal or donut shape. Rolled ring products can range in size from small, washer-like rings to large parts over 9 feet in diameter. Rolled rings are typically near net shape or starting blank products, which undergo additional forming, machining, and grinding to produce finished products.
Rings machined from a solid forged or wrought blank may have similar properties (sans circumferential grain flow). However, the near net rolled ring forging process reduces scrap compared to cutting and machining rings from a solid wrought block or blank, resulting in machining and material cost savings for the customer. The ring rolling process can manufacture parts to specific geometries and tight tolerances with excellent concentricity and surface smoothness. These attributes can sometimes result in additional cost savings if the forged surface and tolerances meet the design needs of the engineer.
For many product applications requiring a ring shape, a casting or powder metal part can have sufficient properties. However, castings and powder metal parts often have internal porosity, causing reduced fatigue, creep, and toughness problems compared to a 100% dense wrought form. The solidification process during casting results in compositional in-homogeneities, which can impact mechanical properties and corrosion resistance. In certain demanding applications with high stress, elevated temperatures, and cyclic loading, a high-integrity material with a dense, homogeneous structure is a design requirement.
Rolled ring manufacturers use a special open die forging process which aligns the grain flow of the metal with the die and closes any internal porosity, producing parts with predictable grain structures and consistent material properties. This process ensures a finished ring that is homogeneous, strong, and possesses excellent fatigue, creep, and impact resistance characteristics. Mandrel ring forging is another process for production of high integrity parts for small order or very heavy rings. The rolled ring forging process involves upsetting to produce the initial disc shape, piercing and shearing the disc shape to form a donut preform, then forming the preform into the rolled ring shape with a mandrel and cones in mill.
Rolled rings may be rectangular, in which the cross section of the rolled ring has a plain, rectangular shape; or profiled, in which the cross section has specific contours or profiles per drawing or design requirements.
Manufacturers typically provide rolled rings in one or more of the following metals or alloys:
- Alloy steel
- Aluminum or aluminum alloys
- Carbon steel
- Cobalt alloy
- Copper or copper alloys
- Nickel alloys
- Stainless steel
- Titanium or titanium alloys
- Tool steel
As-rolled: The rolled ring is provided in the as-rolled condition where the purchaser will provide additional heat treating, machining, grinding, and finishing.
Coating / surface treatment: The rolled ring or machined rolled ring has been coated, plated, peened, case hardened.
Finished part: The rolled ring blank has been heat treated, machined, ground, and surface treated to meet the requirement of the customer’s part drawings and specifications.
Heat treated: The rolled ring has been heat treated such as annealing, homogenization, quench and temper, or aging to improve material properties and component performance.
Rough machined: The rolled ring has been rough machined to bring the blank closer to the final geometry and finish required.
Hollow metal rings are used as starting stock or near net shape blanks for wheels or rail tires, housings, bearings, gears, valve seats, ring gaskets, and coupling. Common applications include:
- Boiler parts
- Heavy wall couplings or connectors
- High pressure piping
- Missile housings
- Pump components
- Reactor / pressure vessel parts
- Ring gaskets
- Valve seats / plungers
Rolled ring manufacturers typically provide testing and certification that their products meets the specific standards required by their customers. The rolled ring product undergo inspection, materials testing, and nondestructive evaluation or testing (NDE/NDT) to certify and verify the products meet the required materials standards and specifications. A certification document is typically provided with the components. Rolled rings or rolled ring products may be manufactured and certified to ASTM, ASME, API, AMS / SAE, MSS, DIN, PED, BS, ISO, and NACE standards such as:
- ANSI/NACE MR0175/ISO 15156—These standard provide guidance on materials selection to mitigate or prevent stress corrosion cracking in alloys exposed to H2S (sour gas) in oil and gas applications.
- ASME/ANSI B16.47, B16.48, and B16.5—American Society of Mechanical Engineers boiler code pressure vessels codes (ASME BPVC).
- ASTM B247-15—Standard specification for aluminum and aluminum-alloy die forgings, hand forgings, and rolled ring forgings.
- BS 3293:1960—British Standard (BS) 3293 is a specification for carbon steel pipe flanges (over 24 inches nominal size) for the petroleum industry.
- Pressure Equipment Directive (PED)—European standards for boilers, pressure vessels, pressure piping, pressure relief valves, and high pressure equipment.