ASTM A290 / A290M

Scope of ASTM A290

A290/A290M applies to one product: a steel ring, forged or rolled, that will be used in or machined into a reduction gear.

The specification governs the material and its processing, not the gear geometry. It sets out how the steel is melted and forged, how it is heat treated, what chemistry it must hold, and which mechanical tests it must pass before release. Tooth cutting, case hardening after delivery and gear rating to AGMA or ISO 6336 fall outside its scope.

Rings are ordered by grade and class together. The grade fixes the chemical composition, that is, whether the ring is plain carbon steel, a chromium-molybdenum steel, a nickel-chromium-molybdenum steel, a nitriding steel or a nickel-chromium-molybdenum-vanadium steel. The class fixes the strength and hardness level reached within that chemistry by tempering. An order that states a grade but no class is incomplete.

Values are given in SI units or in inch-pound units. The two systems are treated as independent standards and are not exact equivalents, so an order must state which system applies. Values from the two systems must not be combined.

Grades and classes

ASTM A290 defines six grades containing fifteen classes: two carbon steel grades and four alloy steel grades.

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Grade 4 carries six classes because it is the most widely used chemistry in the specification. A single nickel-chromium-molybdenum composition is tempered to six different strength levels, so a designer can move up or down the strength range without changing the steel or the supply route. Grade 6 has one class only, tighter phosphorus and sulfur limits of 0.015 % maximum, and a vanadium addition. It is used where through-hardened toughness in heavy sections is the controlling requirement.

Chemical composition by grade

Composition limits are set per grade rather than per class. The two classes of Grade 1 share one chemistry and differ only in tempered strength, and the same applies within every other grade.

Scroll the table sideways to see every grade.

Where vacuum carbon deoxidation is used, the silicon maximum drops to 0.10 %. Both a heat analysis and a product analysis are required. These limits are given for buyer reference. The purchased copy of ASTM A290/A290M governs in every case.

Notes on the composition limits

Grade 5 contains 0.85 to 1.30 % aluminium. Aluminium forms hard, stable nitrides, which is why Grade 5 is specified when the ring gear is to be nitrided rather than through hardened.

Grade 6 limits phosphorus and sulfur to 0.015 %, less than half the level permitted in the other grades. Lower residuals support transverse toughness in thick sections.

Grade 4 contains 1.65 to 2.00 % nickel, which raises hardenability. This is why one composition can cover six classes across a wide strength range.

Comparable steel grades

A290 grades are defined by the specification itself, but each one is close in composition to a steel most gear engineers already work with. The table below is a selection aid, not a list of substitutions. An A290 order is satisfied only by material certified to A290, because the standard also controls melting practice, heat treatment, test location and acceptance criteria that a bare AISI or EN grade designation does not.

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We forge all of these related grades as bar and ring: AISI 4140, 42CrMo4, AISI 4340, 34CrNiMo6 and 18CrNiMo7-6.

Testing and acceptance requirements

Every A290 ring is released on three mechanical tests and two chemical analyses.

Chemical analysis

A heat analysis is reported by the steelmaker. A product analysis is taken from the forging itself. Both cover carbon, manganese, phosphorus, sulfur, silicon, nickel, chromium, molybdenum, vanadium, copper and aluminium, and both must fall inside the Table 2 limits with the permitted product analysis tolerances applied.

Mechanical testing

• Tension test. Tensile strength, yield strength, elongation and reduction of area, each against the per-class minimum.
• Charpy V-notch impact test. Absorbed energy at the specified temperature. This is the main control on toughness in a gear rim carrying shock load.
• Brinell hardness test. A per-class range. In practice it also confirms that the body of the ring reached the intended temper, rather than the coupon alone.

Supplementary requirements

These are not automatic. If they are needed, they belong on the purchase order.

• Ultrasonic examination to ASTM A388/A388M with the acceptance standard named. On a large rolled ring this is usually the first supplementary requirement to add.
• Magnetic particle examination for surface and near-surface indications.
• Additional or specifically located test coupons, particularly mid-wall in heavy sections.
• Impact testing at a temperature below the default, for cold-service gearboxes.
• Grain size, hardenability, or additional hardness survey points across the rim face.

Manufacturing route

The route below applies to open-die forged rings and to seamless rolled rings alike.

1. Melting. Steel is melted to the grade chemistry. Secondary refining by ladle treatment and vacuum degassing is normal practice for Grade 6 and for heavy Grade 4 rings, and is what makes the tight phosphorus and sulfur limits achievable.
2. Forging or ring rolling. The ingot or billet is upset, punched and expanded. A seamless rolled ring is produced by piercing a forged preform and rolling it on a radial-axial ring mill until the target diameter and section are reached. Grain flow then follows the ring circumference, which is the orientation a gear rim requires.
3. Cooling. Forgings are allowed to cool below the transformation range before reheating. Properties therefore come from a controlled heat treatment cycle, not from residual forging heat.
4. Heat treatment. Normalize and temper for Grade 1 Classes A and B. Quench and temper for all other grades and classes. Tempering temperature separates the classes within a grade.
5. Machining. Optional under the standard. It is usually agreed as a rough-machined or proof-machined ring with an allowance for the gear cutter.
6. Testing and certification. Coupons are taken, tests are run, results are certified.

All grades and classes are considered weldable under proper conditions. The standard states that welding technique is fundamental and presupposes that the procedure and inspection follow methods appropriate to the class in question. In practice that means qualified preheat, interpass temperature control and post-weld heat treatment, since carbon content across the specification runs from 0.25 % to 0.50 %.

Applications

A290 rings are used wherever a large through-hardened steel ring transmits torque in a speed reducer.

• Marine propulsion reduction gears, the application the specification was originally written around.
• Wind turbine gearbox ring gears and annulus blanks, where Grade 4 and Grade 6 chemistries are preferred for section toughness.
• Mining and cement mill girth gear rims and segments.
• Industrial and process plant gearboxes: extruders, kilns, crushers, sugar mills and rolling mill drives.
• Steel mill drive trains and heavy-duty planetary gear carriers.
• Nitrided internal ring gears in Grade 5, where a hard flank is required without a full carburizing cycle.

The shapes we most often supply against A290 enquiries are seamless rolled rings, gear rim blanks, internal ring gear blanks, annulus blanks, forged sleeves and hollow cylinders, and proof-machined ring segments for large girth gears.

ASTM A290, A291 and A668

A290 covers the ring. A291 covers the pinion and shaft. A668 covers general forgings where no gear-specific requirement applies.

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A single gearbox commonly draws on two of these at once. We quote A290 rings and A291 pinion and shaft forgings on the same enquiry so that the heat treatment route and the certification package stay consistent across the assembly.

Ordering information

The following information is needed before an A290 ring can be priced.

• Specification and edition, for example ASTM A290/A290M-16(2021).
• Grade and class, both of them, for example Grade 4 Class J. Grade alone is not enough.
• Unit system, SI or inch-pound, since the standard treats them as independent.
• Dimensions: outside diameter, inside diameter, height, and whether the figures are finished, rough-machined or as-forged with allowance.
• Quantity and delivery condition: as-forged, rough-machined or proof-machined.
• Certification: EN 10204 3.1 as standard, or 3.2 with a named inspection body.
• Supplementary requirements: ultrasonic examination and acceptance class, magnetic particle examination, coupon location, impact test temperature.
• Marking and packing: heat number marking method, and packing for sea freight.

ASTM A290 ring supply from Jiangyin Jiangnan Metal

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, producing seamless rolled rings and open-die forgings to ASTM A290/A290M for gearbox manufacturers and gear cutters worldwide.

Jiangyin sits in the Yangtze River delta about two hours from the Port of Shanghai, inside one of China's main concentrations of forging and special steel capacity. We forge in carbon, alloy, tool and stainless steel and in nickel alloys, and we supply against ASTM, EN, DIN, JIS and GB specifications.

Forming

Open-die forging and radial-axial seamless ring rolling

Heat treatment

Normalizing, normalizing and tempering, quenching and tempering, annealing

Non-destructive examination

Ultrasonic to ASTM A388/A388M, magnetic particle examination

Machining

Rough machining and proof machining to drawing

Certification

EN 10204 3.1 as standard, 3.2 third-party witnessed on request

Traceability

Heat number marking, records from ingot to shipped ring

Ring diameter, height, wall thickness and single-piece weight are confirmed against each enquiry, since the workable envelope depends on the grade, the section and the heat treatment route. Send the outside diameter, inside diameter, height and estimated weight with your drawing and we will confirm feasibility before quoting.

Documents supplied with the ring

• EN 10204 3.1 mill test certificate listing heat number, heat and product analysis, heat treatment record and mechanical test results against the ordered class.
• 3.2 third-party witnessed inspection on request, by SGS, BV, TUV, Lloyd's Register or your own inspector.
• Ultrasonic examination report to ASTM A388/A388M with the acceptance class recorded, when invoked on the order.
• Dimensional report for rough-machined and proof-machined rings.

Contact the factory

Send a drawing, or the grade, class and size, to sales@steelforgepieces.com, or call +86-189-2135-9659. Enquiries in English and Chinese are both handled by the sales engineering team.

Frequently asked questions

Referencing this page

If you are quoting this page in a specification or a report, please attribute it as follows.

Primary source

The controlling document is ASTM A290/A290M-16(2021), Standard Specification for Carbon and Alloy Steel Forgings for Rings for Reduction Gears, ASTM International, West Conshohocken, PA. This page summarises and interprets that standard for buyers. It does not replace it, and any conflict is resolved in favour of the purchased copy.

Related specifications and grades

Other forging materials we produce, frequently quoted alongside A290 rings:

• AISI 4140
• 42CrMo4
• 1.7225
• AISI 4340
• 34CrNiMo6
• 1.6582
• 18CrNiMo7-6
• 17CrNiMo6
• 30NiCrMo8
• SCM440
• 817M40
• All alloy steel