Meeting forging MTC requirements is critical: a pressure vessel forging rejection during ASME U-stamp final inspection is one of the most expensive events in a fabrication project. By the time the forging is machined, heat-treated, and presented for NDE acceptance, it has accumulated 6 to 14 weeks of lead time and significant value-added cost. If the MTC cannot be produced, is missing required fields, or shows values outside the specified range — and if the forging shop did not catch this at incoming inspection — the options are remedial retesting (if test samples were retained), rejection with replacement order, or engineering concession with documented risk assessment. None are fast, and none are cheap.
The forging MTC requirements that most often cause this scenario are not obscure: they are documented in ASTM A788, EN 10228, ASME Section VIII, and the applicable product-specific ASTM standards (A182, A105, A694, etc.). The problem is that these requirements are more numerous and more interconnected than most plate or pipe MTC requirements, and the verification checklist is longer and less familiar to receiving teams that primarily handle rolled product.
This guide covers the complete documentation requirements for industrial forgings, field by field, with the specific standards that mandate each requirement.
Why Forging MTCs Are More Complex Than Rolled Product Certificates
A plate or pipe certificate documents chemistry from the ladle and mechanical properties from a standard test coupon taken transverse to the rolling direction. The test is standardized, the coupon location is defined, and the result is straightforward to interpret.
Forgings are more complex because the forging process itself alters the material's properties in ways that depend on: the degree of forging reduction (how much the original ingot or billet was reduced), the forging direction (grain flow orientation relative to the part geometry), and the heat treatment applied after forging. For large or complex forgings, mechanical properties in the longitudinal and transverse directions may be specified separately — and the MTC must document which orientation was tested and what results were obtained.
Additionally, forgings for pressure service typically require ultrasonic examination (UT) — not just visual and dimensional inspection — because UT is the only method that can detect internal discontinuities (laps, folds, cracks, porosity, inclusions) in the forging body that would not be visible at the surface. The UT acceptance criteria and examination coverage must appear on the MTC or a referenced NDE report.
Governing Standards for Forging Certification
ASTM A788 / A788M — General Requirements for Steel Forgings
ASTM A788 is the umbrella general requirements standard for steel forgings in the same way that A6 and A20 govern structural steel and pressure vessel plate. Any ASTM forging product standard (A105, A181, A182, A335, A470, A508, etc.) operates under A788 as the parent document.
Key A788 certificate requirements:
- Heat analysis: all elements including residuals where applicable to the grade
- Product (ladle) analysis at the option of the purchaser — must be specified at the time of order
- Tensile test results: yield strength (0.2% offset), ultimate tensile strength, elongation (with gage length), reduction of area
- Charpy V-notch impact test results when specified, including test temperature and individual/average values
- Hardness test results when specified
- Heat treatment condition and temperature documentation where controlled heat treatment was performed
- Forging reduction ratio where specified by the applicable product standard or purchaser
- Identification of test coupon location (longitudinal or transverse) relative to the forging
A788 also requires that every forging be marked with the manufacturer's name or brand, grade designation, heat number, and specification number. The MTC must correlate to these markings — a forging with no legible heat number cannot be accepted regardless of how complete the certificate is.
EN 10228 — Non-Destructive Testing of Steel Forgings
EN 10228 is the European standard series for NDE of steel forgings. Parts 1 through 4 cover magnetic particle testing (MT), penetrant testing (PT), ultrasonic testing (UT), and eddy current testing. For pressure-containing forgings, EN 10228-3 (UT) is the most commonly specified.
The UT acceptance class (Class 1 through 6 per EN 10228-3) must be specified at the time of order and appear on the MTC or the referenced NDE report. Class 3 is the default for most pressure service forgings; Class 4 or higher for critical subsea or pressure-retaining items where tighter discontinuity acceptance applies.
ASME Section VIII — Pressure Vessel Forgings
For ASME Code pressure vessels, forgings must comply with:
- ASME Section II Part A (material specifications for ferrous materials) for the applicable ASTM forging standard
- UG-11 (material requirements for pressure parts) and UG-93 (certification and marking of materials)
- The Authorized Inspector must review and accept the forging MTC before final Code sign-off
For SA-105 carbon steel flanges, the MTC must show compliance with A105 including minimum yield of 250 MPa (36 ksi), minimum tensile of 485 MPa (70 ksi), and minimum elongation of 22% in 50 mm. All of these must appear on the MTC with test method references. Where the project specification invokes supplementary requirements (e.g., S58 for impact testing in accordance with ASME Section VIII), these results must also be documented.
Field-by-Field MTC Checklist for Forgings
| Field | Standard Requiring It | Pass Criterion |
|---|---|---|
| Heat number | ASTM A788 mandatory | Matches physical forging marking |
| Material grade and specification | All applicable standards | Exact match to PO specification |
| Specification edition | A788, ASME Section II | Edition matches PO or later |
| Heat analysis — all specified elements | A788 | All values within specification limits |
| Product analysis | A788 / per order requirement | Within product analysis tolerances if required |
| Yield strength (0.2% offset) | A788 | At or above specification minimum |
| Tensile strength | A788 | At or above specification minimum |
| Elongation | A788 with gage length noted | At or above minimum; gage length specified |
| Reduction of area | A788 | At or above minimum if required |
| Charpy impact energy and test temperature | A788 / customer order | Both values present; test temp matches service requirement |
| Hardness (HB, HRC as applicable) | Grade-specific, NACE where required | Within specified range |
| Heat treatment condition and temperature | A788 where applicable | Condition matches specification (N, QT, A, etc.) |
| Test coupon orientation | A788 | Longitudinal or transverse as specified |
| Forging reduction ratio | Some product specs | Meets minimum reduction per applicable standard |
| UT results and acceptance criteria | EN 10228-3 / purchaser spec | Class stated; acceptance criteria documented |
| MT/PT surface examination results | EN 10228-1/2 or equivalent | If required by spec |
| Signatory | EN 10204 type; A788 | Correct EN 10204 type per PO; authorized signatory identified |
| Certificate type | EN 10204 | Matches PO requirement (3.1 or 3.2) |
Heat Analysis vs. Product Analysis for Forgings
The distinction between heat (ladle) analysis and product analysis is especially important for forgings because of the potential for segregation in large ingots. In a 50-tonne ingot that is subsequently forged into multiple large pressure vessel heads, the chemistry at the ingot center may vary from the chemistry at the ingot surface — a phenomenon called macro-segregation — because alloying elements tend to concentrate in the last-solidifying portions of the ingot.
ASTM A788 allows purchasers to require product analysis of the finished forging, in addition to heat analysis. Product analysis is conducted on chips machined from the actual forging surface or from a test coupon cut from the forging body. For large pressure vessel forgings (reactor shells, thick-walled heads) in safety-critical applications, requiring product analysis is good practice and is often mandated by the engineering specification.
If only heat analysis is present on the MTC and product analysis was specified on the PO, the certificate is incomplete. This is a hold condition.
Forging Reduction Ratio and Grain Flow
Some specifications — particularly for aerospace forgings and high-integrity pressure vessel items — require documentation of the forging reduction ratio: the ratio of the original billet or ingot cross-sectional area to the final forging cross-sectional area. A minimum reduction ratio is specified because adequate reduction is needed to break down the as-cast dendritic structure, close internal porosity, and align the grain flow for optimum mechanical properties.
AMS 2750 (pyrometry for aerospace heat treating) and some ASTM pressure vessel specifications specify minimum forging reduction ratios of 4:1 to 10:1 depending on the grade and application. If the MTC or the forge shop's process documentation cannot demonstrate the specified reduction ratio was achieved, the forging may need to be rejected regardless of its measured mechanical properties — because the grain flow and inclusion distribution may be inadequate even if tensile coupon values meet minimums.
Ultrasonic Testing as Part of the MTC Package
For pressure vessel and oil and gas forgings, UT is typically mandatory and its results must either appear on the MTC or in a referenced NDE report that is formally attached to the MTC. The key elements that must be documented:
- The UT standard used (EN 10228-3, ASTM A388, or purchaser's own written procedure)
- The acceptance class or discontinuity acceptance criteria
- The scan coverage (100% volumetric is the norm for pressure-retaining forgings)
- The calibration block standard and sensitivity level
- Any indications found, their location, size, and disposition (accepted within criteria or rejected)
- The NDE technician qualification level (UT Level II or III per ISO 9712 or ASNT SNT-TC-1A)
A forging MTC that says "UT: Per EN 10228-3, Class 3, No Rejectable Indications" without the supporting NDE report documentation is insufficient — the test method, calibration, and technician qualification are part of the compliance evidence.
Common Forging MTC Non-Conformances
The non-conformances that most frequently trigger forging holds at receiving or during Authorized Inspector review:
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Missing UT report or incomplete UT data — The MTC states UT was performed but no report is attached and no reference to a retrievable report number is provided.
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Charpy test temperature not stated — The MTC reports impact energy values but omits the test temperature. For low-temperature service forgings, this makes the data meaningless.
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EN 10204 type mismatch — 3.1 supplied where 3.2 was specified (or vice versa where 3.2 specification coverage would be wasted cost).
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Missing or wrong specification edition — The forging was tested per an older ASTM edition with different limits for a specific element.
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No heat number on the physical forging — The certificate is complete but the forging has no legible marking. This triggers a complete hold until PMI and re-marking or rejection.
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Product analysis required but only heat analysis provided — Common with distributors who re-sell from stock and can only provide the original mill heat analysis.
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Forging reduction ratio not documented — Required by the engineering specification but absent from the MTC and not documented in the forger's process records.
How TestCert Handles Forging Certification
Forging MTCs are among the most data-rich and format-variable certificates in the metals industry. They arrive from forge shops in multiple countries, in formats ranging from well-structured digital documents to handwritten test records attached to a typed declaration. They reference test methods and acceptance standards that vary by continent. And they must be verified not just against chemistry and mechanical property limits but against requirements — such as UT acceptance class, test coupon orientation, and forging reduction ratio — that are not on standard incoming inspection checklists for rolled product.
TestCert's extraction engine handles forging certificate formats specifically — pulling UT acceptance class, NDE reference report numbers, Charpy test temperatures, heat treatment condition codes, and test coupon orientation alongside the standard chemistry and mechanical fields. Validation rules are configurable per material grade and product form: a pressure vessel flange under ASME Section VIII, an aerospace titanium forging under AMS 4928, and an oil and gas subsea valve body under EN 10228 Class 4 each have different validation requirements that the system applies automatically.
Non-conformances — missing UT documentation, wrong EN 10204 type, absent Charpy temperature, missing forging reduction ratio — are flagged at receiving before the forging enters any downstream process. The audit trail linking the forging MTC to its inspection outcome and purchase order reference is available for ASME Authorized Inspector review without manual document assembly.