Specifications

Chemical composition and mechanical properties

Low-carbon grades F304L and F316L have a lower carbon limit; nitrogen and other elements as given in the standard.

Values for solution-annealed forgings.

Background on stainless steel grades is on the stainless steel page.

Seamless rolled, forged and plate-cut rings

Seamless rolled rings are made by piercing a forged billet and rolling it between a driven roll and an idler roll, which expands the diameter and gives a continuous circumferential grain flow. They are used for large flange blanks, girth flanges and rings where strength and soundness matter. Open-die forged rings are forged over a mandrel and suit thick-walled and smaller rings. Plate-cut rings are cut from A240 plate by plasma or water-jet and used for flat rings, spacers, stiffeners and low-stress parts; they do not have the grain flow of forged rings and are not used where the design calls for forgings.

How we manufacture stainless steel rings

We manufacture forged and rolled rings from certified billets: the billet is heated, upset and pierced, then forged or rolled to the required outside diameter, inside diameter and height. Rings are solution annealed and quenched to restore corrosion resistance, then rough or finish machined to drawing. Test pieces are taken from the ring or a prolongation as the specification requires. Each ring is marked with grade, heat number and identification.

Choosing the grade

F304L and F316L rings are used for welded vessel and heat-exchanger flanges in chemical, pharmaceutical and food equipment; F316L where chlorides or acids are present. F321 and F347 are used for high-temperature components, and duplex F51 and F53 for seawater and chloride service with higher strength. For welded assemblies, the low-carbon L grades or dual-certified material avoid sensitisation.

Inspection and testing

Rings for pressure parts are usually ordered with ultrasonic testing to detect internal defects, and with dye penetrant testing of machined surfaces. Intergranular corrosion testing to ASTM A262 Practice E can be added for chemical service. Dimensional inspection is carried out against the drawing, and the mill test certificate reports chemistry, mechanical properties and heat treatment.

Ordering stainless steel rings

Please send a drawing or the finished and as-supplied dimensions, with the grade and specification, forged or plate-cut, condition, testing and quantity.

Machining and tolerances

Rough-machined rings are supplied with an allowance on all surfaces for the customer's final machining, which removes the forging skin. Finish-machined rings are machined to the drawing tolerances, with bolt holes, grooves and faces as specified. Austenitic stainless steels work-harden during machining, so rings are machined with sharp tools and steady feeds to avoid surface hardening and distortion. For large thin rings, machining sequences are planned to control ovality.

Weight and supply

Ring weight is calculated from the outside and inside diameters and the height, using a density of about 7.9–8.0 g/cm³ for stainless steel; our weight calculator includes a ring option. Forged rings start from a heavier billet to allow for the machining allowance and test material. Please send drawings early for large or heavy rings so that forging and testing can be planned.

Applications and related products

Stainless steel rings are used for flange blanks, vessel and heat-exchanger body flanges, valve seats and bodies, pump wear rings and casings, bearing and seal rings, and machined components. All ring materials are on the rings page. In stainless steel we also supply seamless pipes, welded pipes, tubes, flanges, pipe fittings, sheets, plates, round bars, fasteners, coils, circles, wires, angles, channels, flats. Grade information is on the stainless steel page.