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Forging Specifications
A forging order usually cites four kinds of document: a product specification for the grade, a general requirements specification behind it, a tolerance standard and test methods. This page sorts the common ones by role.
Forging specifications by role
Typical uses. Always cite the edition the drawing or the project specification names.
| Specification | Role | Covers | Typical products |
|---|---|---|---|
| ASTM A788/A788M | General requirements | Steel forgings: ordering, melting, testing, certification rules that product specs call up | Referenced by A668, A266, A336 and other forging specs |
| ASTM A961/A961M | General requirements | Common rules for steel flanges, forged fittings, valves and parts for piping | Referenced by A105, A182, A350, A694 |
| ASTM A668/A668M | Product | Carbon and alloy steel forgings for general industrial use, ordered by strength class | Shafts, blocks, rings, machinery parts |
| ASTM A105/A105M | Product | Carbon steel forgings for piping at ambient and higher temperature | Flanges, fittings, valve bodies |
| ASTM A182/A182M | Product | Alloy and stainless steel forged piping components for high temperature service | F11, F22, F91, F304L, F316L, F51 flanges and fittings |
| ASTM A350/A350M | Product | Carbon and low alloy forgings for piping with impact testing at low temperature | LF2, LF3 flanges and fittings |
| ASTM A266, A336 | Product | Carbon (A266) and alloy (A336) steel forgings for pressure vessel components | Shell rings, nozzles, heads |
| EN 10250-1 to -4 | Product | Open die steel forgings for general engineering: general rules, non-alloy, alloy and stainless grades | C45E, 42CrMo4, 34CrNiMo6 shafts and blocks |
| EN 10222-1 to -5 | Product | Steel forgings for pressure purposes | Pressure equipment parts for the EU market |
| API 20B, API 20C | Qualification | Open die (20B) and closed die (20C) forgings for the petroleum and gas industry | Supplier qualification by level |
| EN 10243-1, -2 | Tolerances | Dimensional tolerances of closed die forgings, grades F and E | Hammer, press and upset forgings |
| ASTM A388, EN 10228-3 | Testing | Ultrasonic examination of steel forgings | Shafts, rings, blocks, pressure parts |
| ASTM A275, EN 10228-1 | Testing | Magnetic particle examination of steel forgings | Surface crack checks |
| EN 10204 | Certificates | Types of inspection document: 2.1, 2.2, 3.1, 3.2 | Every metal product order |
| ASTM B381, B564, B247 | Product, non-ferrous | Titanium (B381), nickel alloy (B564) and aluminum (B247) forgings | Aerospace, chemical and process parts |
| JIS G 3201 | Product | Carbon steel forgings for general use, SF grades | Parts for buyers working to JIS |
Check the current edition of each standard before you quote. Several of these specifications were revised in 2024 to 2026.
How the documents fit together
A product specification such as ASTM A105 or A182 sets the grade: chemistry, heat treatment, tensile and hardness limits and marking. It points to a general requirements specification, A961 for piping parts or A788 for most other steel forgings, for the rules every grade shares: test lot definition, retests, repair welding and certification.
Tolerances sit in separate standards. Closed die forgings usually follow EN 10243-1 or the supplier tolerance table written on the drawing. Open die forgings carry machining allowances agreed per part.
Test methods such as ASTM A388 for ultrasonic testing describe how to test, not what passes. The buyer writes the acceptance level on the order. The certificate type, usually EN 10204 3.1 or 3.2, says who signs the results.
Qualifications of the supplier, such as ISO 9001, API Q1 or Nadcap, sit beside these documents and are mapped on the supplier qualifications hub.
Questions buyers ask
Which forging specification should I put on my drawing?
Start from the service. Pressure piping parts take a piping product specification such as ASTM A105, A182 or A350. General machinery parts often take ASTM A668 or EN 10250 with a grade and strength class. Add the test method, acceptance level and certificate type.
What is the difference between ASTM A788 and ASTM A668?
A788 is a general requirements specification. It sets shared rules for steel forgings and is called up by product specifications. A668 is a product specification for carbon and alloy steel forgings for general industrial use, ordered by class.
Do EN and ASTM forging grades match one to one?
Rarely. Close equivalents exist, for example 42CrMo4 and 4140, but chemistry limits, test units and certificates differ. Name one standard on the order and ask the supplier to confirm any dual certification in writing.
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