Forging billets

Billet describes an input, not finished properties

An ideal round billet 100 mm in diameter and 200 mm long contains 1.571 L of metal. At an assumed 80% accepted-part volume, allow 1.257 L for the part and 0.314 L for combined loss and allowance. Set actual allowances for flash, scale, crop, machining and rejects separately.

A forging billet is stock intended for further deformation. Preserve the alloy/grade, manufacturing route, supplied condition and geometry separately. A material designation and billet diameter do not establish the finished forging's strength, grain structure, fatigue life or inspection acceptance.

Metallus's glossary distinguishes a hot-worked solid round/square billet from the broader bloom/billet category, which can be as-cast or wrought and is destined for further hot working. It also notes that the size distinction is somewhat arbitrary. Specify the actual route instead of assuming every product called billet has already received the same amount of working. Metallus steel terminology

Product specification and purchase record

ASTM's active A711/A711M-17(2022), last updated March 7, 2022, covers carbon/alloy steel forging stock including cast and semi-wrought ingots/strand castings and rolled or forged blooms, billets and slabs. Its scope describes approximate cross-sectional dimensions and says optional supplementary requirements apply only when specified by the purchaser. This is a steel-stock specification, not a universal specification for aluminum, titanium or nickel-alloy forging inputs. ASTM A711/A711M scope and record

The order should resolve the following information together:

Additional requirements need explicit acceptance criteria. A supplier capability statement or the presence of a familiar specification number on its website does not demonstrate that a particular heat was supplied to it.

For example, Metallus lists multiple steel quality levels on its SBQ page and identifies Parapremium with AMS 2304. That illustrates why “steel billet” is an incomplete quality description; it does not make AMS 2304 applicable to every billet or forging. The same page's stated round/square size ranges are labelled as bar offerings and should not be copied into a universal billet-size limit. Metallus SBQ products and quality levels

Surface, ends and traceability

Resolve surface condition with the material producer and forger before cutting. Specify permitted imperfections, any conditioning/removal allowance and the inspection stage. The public A711 abstract requires freedom from injurious surface imperfections and describes conditioning of defects; the actual order and full specification control acceptance. ASTM A711/A711M abstract

A turned, ground, peeled or otherwise conditioned surface is a processing description, not proof of internal soundness. Establish internal inspection method, coverage and acceptance separately when required. Retain heat identity through cutting, surface removal and reheating, including identification of child charges and rejected pieces.

The Forging Industry Association's gear case study describes turned/polished bar cut to precise lengths to control the volume entering closed dies. This is a specific near-net gear process example, not a demand that every billet receive that finish. FIA, Case Study 9, High Performance Gears

Check cut-face condition, squareness and dimensional tolerance against the charge plan. Separate saw kerf, crop ends and unusable material from the volume assigned to an individual charge. Do not treat nominal purchased length as entirely usable stock.

Original volume-planning example

Assume an ideal solid cylindrical charge, 100 mm diameter and 200 mm length. Its volume is

V = π × 100² × 200 / 4 = 1,570,796 mm³, approximately 1.571 litres.

Apply the 80% assumption only to this example. Actual yield needs measured flash, scale, crop, machining and reject losses.

This geometry does not establish billet mass without an applicable density. It also does not establish forming load, die fill, required reduction or defect closure. Dimensional variation and radiused corners must be included when those features materially affect charge-volume control.

Heating and forging qualification

Carpenter's guidance for difficult-to-forge alloys says heating cycles depend on section size and alloy, and recommends working within the alloy manufacturer's temperature limits. It identifies cracking/tearing below the range and incipient melting or harmful phases above it. Its temperature charts are guidance with additional equipment and process qualifications, rather than universal recipes. Carpenter Technology, Forging Difficult Alloys

Establish the actual starting condition, heating uniformity, transfer/reheat sequence and deformation route with the producer/forger. Record the process stage at which required properties and inspection results must be achieved. A furnace setpoint is not a measurement of the whole billet, and a surface-temperature reading cannot alone establish its center temperature.

Qualification of a finished forging must address its required geometry, property locations, treatment and inspections. Do not approve a substitution merely because the replacement has the same nominal chemistry and gross volume. The prior route, supplied quality and intended process can change the qualification basis.

Release record and source versions

Retain producer, heat/lot, material specification/edition, supplied condition and route, section/length, conditioning and inspection evidence, cut-charge identity and downstream process record. Review handling and heating against the actual equipment instructions; this reference supplies no universal stacking height, soak time or forging-temperature range.

ASTM's public record identifies A711/A711M-17(2022) as active. The cited Metallus, Carpenter and FIA webpages have no independently verified technical revision date. Confirm binding requirements with the supplier rather than treating retrieval or search-index dates as source editions.

See Stock forms and dimensions.