Checklist: Verifying Forging Mill Certs and NDT

Start with the heat, not the part

Before a forging mill cert leaves the supplier’s office, the heat number must be linked to a specific pour, a specific mill, and a specific chemical analysis. Procurement teams often request a “certificate” as if it is a single document. In practice, verifying forging mill certs means assembling a paper trail that proves the metal in the part came from the declared heat.

A forged component may pass dimensional checks and still contain the wrong alloy. The mill cert is the first control. The NDT report is the second. Both must align.

Begin every verification with the purchase order. The PO should name the alloy, the heat treatment requirement, the NDT method, and the acceptance criteria. If those fields are missing, the audit starts with a documentation gap.

Check the material certification forging documents

Material certification forging documents vary by supplier, but a reliable set includes:

1. Mill certificate or heat analysis certificate
2. Furnace test report, if separate from the mill cert
3. Chemical analysis (as cast and as heat treated)
4. Mechanical test report
5. Heat treatment certificate
6. NDT report
7. Traceability record linking heat number to part serial or batch

Each document should carry the same heat number. If the chemical analysis references heat number A, the mechanical test report must reference heat number A. If the heat treatment certificate references a furnace charge that does not match the heat number, stop.

A common issue is the use of a “copy” of a mill cert that lacks the supplier’s quality seal or the mill’s quality assurance signature. A copy is acceptable for internal file reference, but the original or a certified duplicate from the mill should be retained. Ask the supplier to state whether the document is an original, a certified copy, or a photocopy.

The chemical analysis should list the elements that matter for the alloy. For common forging steels, that means carbon, manganese, silicon, chromium, molybdenum, and any alloying elements that define the grade. Out-of-tolerance values are not acceptable. If a value is near the limit, request the raw furnace test data.

Verify the NDT forging inspection method selection

NDT forging inspection is not one test. It is a set of methods, each with strengths and limits. Ultrasonic testing detects internal flaws. Radiography shows internal and some surface flaws. Magnetic particle and eddy current focus on surface and near-surface defects. The method must match the defect type the part is at risk for.

A typical forged steel part may need more than one method. A large structural forging may receive ultrasonic testing for internal porosity or inclusions. A smaller precision part may receive eddy current for surface cracks. A part with tight tolerances and high stress concentration may receive magnetic particle after machining.

The NDT report should name the method, the standard or specification used, the operator qualification, the equipment calibration date, and the acceptance criteria. If the report says “NDT performed” without naming the method, it is not useful.

The following table shows how to read the NDT method line on a supplier report:

NDT Method	What It Detects	Typical Use in Forging	What to Verify on the Report
Ultrasonic (UT)	Internal voids, inclusions, cracks	Large sections, critical cores	UT level, scan coverage, reference block used
Radiography (RT)	Internal flaws, porosity, hot tears	High-stress areas, welds, thick sections	Exposure parameters, film or digital image reference
Magnetic Particle (MT)	Surface and near-surface cracks	Ferromagnetic parts after machining	Powder type, contrast, demagnetization record
Eddy Current (ET)	Surface and near-surface cracks	Non-ferromagnetic or thin sections	Probe type, lift, coverage diagram
Dye Penetrant (PT)	Open surface cracks	Final surface inspection	Penetrant type, developer time, reference standard

A red flag is a method that does not match the part. Eddy current on a thick ferromagnetic section is unlikely to be the primary internal defect detector. Radiography on a small, complex geometry may miss certain orientations. If the selected method is weak for the risk, ask the supplier to justify the selection in writing.

Review the NDT report details

The NDT forging inspection report should be more than a pass/fail line. It should describe what was inspected and how.

Check the following:

• Part identification: drawing number, revision, serial number, or batch number
• Heat number: must match the mill cert
• NDT method: named and referenced to a standard
• Operator: name or ID, and qualification level
• Equipment: calibrated date and calibration certificate reference
• Coverage: percentage or diagram showing scanned area
• Reference standard: block or specimen used for calibration
• Acceptance criteria: the standard or specification used
• Date: inspection date and report date
• Signature: operator and reviewer

If the report says 100 percent coverage, ask what that means. Does it include all critical surfaces? Are the corners scanned? Is the entire volume covered by UT, or only selected planes? A coverage diagram is more useful than a percentage.

For ultrasonic testing, the report should state the scan type, such as phased array, pulse echo, or shear wave, and the scan angle or beam orientation. If the part has a complex shape, a single scan plane may miss defects. The report should reference a scan plan or inspection procedure.

For radiography, ask whether the image is retained. A pass/fail report without the digital image or film reference is weak. If a defect is found and reworked, the rework area must be re-inspected and documented.

Look for red flags in the documentation

Red flags are not always failures. Some are gaps that can be corrected with follow-up. Others are indicators of a supplier that does not manage quality effectively.

Watch for:

• Heat number missing or inconsistent across documents
• Chemical analysis values that are out of specification without an explanation
• NDT method not named or described in vague terms
• No operator qualification or calibration date
• Report date before the heat treatment date
• “As received” material certification that does not match the part
• Missing rework records after a rejected NDT
• Supplier refusing to provide raw NDT data or heat traceability
• Certificate issued by the supplier rather than the mill, with no mill reference
• Generic acceptance criteria with no standard number or internal specification

If a supplier provides a copy of a mill cert but will not share the original heat traceability, treat that as a risk. You may be able to accept the copy for a low-risk part, but not for a safety-critical or high-stress component.

Another red flag is a heat treatment certificate that lists a furnace number but not a heat number. If the heat is mixed with other heats in the furnace, the traceability is broken. Ask the supplier to clarify whether the heat was treated alone or with other heats. If mixed, request the heat treatment log for that furnace charge.

Build a repeatable checklist for your team

Procurement managers need a standard way to file and audit every lot. Keep a folder per lot with the following items:

1. Purchase order
2. Mill certificate
3. Chemical analysis
4. Mechanical test report
5. Heat treatment certificate
6. NDT report
7. Receiving inspection record
8. First article inspection record, if applicable

Use a simple scoring method. Assign a pass, fail, or question to each item. A “question” is not a fail. It is a prompt for follow-up. For example, if the NDT report is missing the operator qualification, mark it as a question and request the operator card or qualification record.

Do not rely on a single person to remember the checklist. Build it into your receiving process. The person who accepts the goods should be the same person who checks the documents, or a second person should verify the first person’s sign-off.

For high-risk parts, require the supplier to provide the NDT data in a format that allows review. For ultrasonic, that may be a scan map or a reference standard image. For radiography, that may be a digital image file. For surface methods, that may be a coverage diagram. The level of data depends on the part’s criticality and your contract.

Close the loop with the supplier

Verification is not a one-time event. If a lot has a documentation gap, record it in a supplier quality action. If the gap is minor, such as a missing calibration date, request a corrective action and a follow-up document. If the gap is major, such as a broken heat traceability or an unqualified NDT operator, reject the lot or require rework and re-inspection.

Ask the supplier to confirm the standard it follows for material certification forging and NDT forging inspection. Some suppliers follow internal procedures. Others follow recognized industry standards. The standard matters because it defines what “pass” means. Without a shared standard, pass/fail is subjective.

If you qualify a new forging vendor, include the verification checklist in the qualification process. A vendor that can produce clean, traceable, and complete quality documents is easier to work with than a vendor that is fast but sloppy on paper. The cost of a missing document is usually a delayed shipment, a rejected lot, or a field failure.

Keep the checklist short enough to use. If it is too long, people will skip it. Focus on the items that break traceability or hide defects. A five-item check on the heat number, NDT method, operator qualification, acceptance criteria, and coverage is enough to catch most problems.

Final audit point

The goal of verifying forging mill certs is not to create a file. The goal is to know what metal you received and whether it was inspected for the defects that matter. If the heat number is real, the NDT method is right, and the report is specific, you have a defensible record. If any of those are missing, you have a gap. Close the gap before the part goes into service.