EN 10204 3.1 vs 3.2 is the material-certificate choice that causes more arguments between buyers and sheet metal suppliers than any tolerance callout. Two lines on a drawing sit behind most of them: "material certificate to EN 10204 3.1 required" and "parts traceable to heat number". Both are reasonable. Both are routinely misunderstood, usually in opposite directions — the buyer thinks the certificate covers the finished part, and the supplier thinks issuing the certificate is the whole job. This guide separates the two, lists what a useful certificate actually contains, and shows where the traceability chain breaks in a real fabrication shop.
Key takeaways
- An EN 10204 certificate describes the coil or sheet the mill delivered. It says nothing about the formed, welded and finished part.
- 2.1 and 2.2 are declarations; 3.1 is specific inspection on the delivered material by an inspection representative independent of production; 3.2 adds validation by a party independent of the manufacturer.
- 3.1 and 3.2 differ in who vouches for the result, not in what is tested.
- Heat-number traceability is a four-link chain — receiving, issue to production, through the process including subcontractors, and shipment mapping. Auditors test the weakest link.
- Certificate of Conformance is not a material certificate. A CoC states compliance and carries no test data.
- Ask at RFQ stage. A certificate promised after production is the most common failure mode in this whole topic.
What an inspection certificate is — and what it is not
EN 10204 is the framework that defines types of inspection documents for metallic products. It does not define the steel grade; the product standard does that. EN 10204 defines who tested the material and who is vouching for the result.
That distinction matters because a certificate travels with a delivery of flat product — coil, sheet, plate. Everything on it is true of that flat product. After the certified material is cut, bent, welded, annealed or coated, the certificate still identifies the base material only if traceability has been preserved. It does not certify the fabrication steps or the finished part. It remains the first piece of evidence in a quality package, never the last one.
EN 10204 3.1 vs 3.2: how the four document types differ
EN 10204 3.1 and 3.2 both report specific inspection results for the delivered material. A 3.1 certificate is validated by the manufacturer's inspection representative independent of production; a 3.2 certificate adds validation by the purchaser's representative or by an inspector designated under the applicable regulation.
| Type | Who issues it | Basis | What you actually get |
|---|---|---|---|
| 2.1 | Manufacturer | Declaration of compliance, no test results | "This meets the order." No data. Rarely sufficient as quality evidence. |
| 2.2 | Manufacturer | Non-specific inspection | Test results from the manufacturer's general production, not from the specific heat you received. Useful commercially, weak in an audit. |
| 3.1 | Manufacturer's authorised inspection representative, independent of the manufacturing department | Specific inspection of the material actually delivered | Heat or cast number, chemical composition, mechanical properties, delivery condition, the standard it is certified against. The default industrial requirement. |
| 3.2 | Manufacturer plus an independent inspector — a third party or the buyer's own representative | Specific inspection, witnessed or validated externally | The same content as 3.1 with an outside signature behind it. Costs more and needs scheduling. |
Type 3.1 is commonly specified for general industrial sheet metal work. Type 3.2 is used where the purchase specification, applicable regulation or quality plan explicitly requires independent validation — confirm that requirement before ordering, because it affects inspection planning, cost and the possibility of re-testing.
What should a usable EN 10204 certificate contain?
A usable EN 10204 certificate should identify the mill, certificate number, heat or cast number, grade, product standard, dimensions, quantity, chemical composition, mechanical properties, delivery condition, document type and validating signature. Check the first three before material is released for cutting. The order matters, because those are the fields that catch wrong material while it is still cheap to reject:
- Mill name and site — matches who you think you bought from.
- Certificate number and date — present, unique, traceable.
- Heat or cast number — matches the number on the coil tag or label. If it does not match, stop before the coil enters stock.
- Grade and governing product standard — EN, ASTM, JIS or GB, matching the drawing callout.
- Product form and dimensions — thickness and width, matching both the coil and the tooling setup.
- Quantity or mass — covers what was delivered.
- Chemical composition — the elements required by the grade, including residuals. Unexpected carbon is a forming problem, not just a paperwork problem.
- Mechanical properties — yield, tensile, elongation; hardness or impact when ordered. For forming work, check that the values sit inside your process window, not merely above the grade minimum.
- Delivery condition — annealed, as-rolled, hardened and tempered, coating specification for pre-coated or galvanised product.
- Certificate type — confirm it is the type you ordered. A 2.2 arriving in place of a 3.1 is a real and common substitution.
- Signature or stamp — consistent with the declared type.
For coated coil, coating mass and paint system details may sit on the same document or on a companion coating certificate. Confirm what your receiving procedure accepts before you need it.
How does heat-number traceability work?
Heat-number traceability links the mill certificate to the shipped part through four recorded handoffs: receiving, issue to production, every internal or subcontract process, and shipment mapping. Holding a 3.1 certificate and being able to answer "which heat is in this box" are different capabilities — a supplier can have one without the other. The chain has four links:
- Receiving. Coil booked in against its heat number, certificate filed against that number rather than in a general quality folder.
- Issue to production. The heat number travels with the material to the machine, on the lot traveller or job card, so the record knows which heat ran in which lot.
- Through the process. Cutting, forming, welding, heat treatment, finishing and any outsourced operation recorded against the same lot identity.
- Shipment. Delivery documentation maps boxes back to heats, so a claim or a recall can be bounded to the affected batches instead of to a year of output.
Where the chain breaks
- Mixed stock at the machine. Two heats of the same grade are interchangeable in the part, so they get used interchangeably, and then nothing can be attributed to either.
- Remnants and offcuts. A part-cut coil goes back to storage without a label, and the next job inherits an unknown heat — the same scrap-and-yield problem we describe in nesting and material yield, except here the loss is documentation rather than steel.
- Subcontract operations. Annealing, plating, anodising and coating are the classic gaps: material leaves the plant and comes back with a different container identity. Insist the lot identity travels on the packaging.
- Rework and top-up lots. A shortage part way through a production run is filled from a different coil, and the lot record is never updated.
If you only audit one thing, audit the subcontract link.
The certificate is one leg, not the whole package
A material certificate proves the steel was what the drawing asked for. It does not prove the part is. Forming changes thickness locally, work-hardens the material, and produces a dimensional result the mill never saw. Welding adds a heat-affected zone — see our welding process and weld records. Coating adds a thickness.
A first article or PPAP submission for a sheet metal enclosure needs at least:
- Material certificate with heat traceability (this document)
- Dimensional results on the finished part, including the features that matter in assembly, against the tolerance guide callouts on the drawing
- Coating or finish records — thickness, adhesion, and the specification used
- Weld records where welds are structural or sealing
- Functional results where applicable — leak test, continuity and bonding test, ingress test — planned with the enclosure qualification test plan
We set out how those fit together in first article inspection, FAI and PPAP, and the in-process side in quality control and inspection. Where a certificate is the only evidence offered, the submission is incomplete.
When to ask
| Stage | What to do | Why it matters |
|---|---|---|
| RFQ | State the certificate type in writing, with the product standard | Suppliers price differently when documentation is required; asking later invites disputes |
| Purchase order | Make the certificate a contractual deliverable, tied to acceptance | Keeps quality leverage intact under flexible payment terms |
| Before first cut | Ask for the certificate when material lands at the supplier's plant | Last cheap chance to reject wrong material |
| At delivery | Certificate travels with the shipment or arrives before it | Receiving inspection should not release a lot without it |
| With the FAI package | Include it, mapped to the part number and lot | Expected as standard in automotive and industrial programs |
The failure mode is always timing: a certificate promised after production, requested after a quality problem appears, or treated as a customs formality. Fix the requirement early, in writing, and enforce it at receiving.
Related documentation that often gets bundled
Three neighbouring requirements show up on the same PO and are frequently confused with the material certificate:
- PMI (positive material identification). Portable XRF confirms the alloy on the piece itself. Useful when a part has been separated from its paperwork, and standard practice for high-alloy grades.
- Coating and finish certificates. Separate documents. See corrosion resistance coatings.
- Substance and origin declarations. RoHS, REACH and SCIP obligations are a different compliance stream from EN 10204 — see RoHS and REACH compliance. Carbon-related declarations and EPDs sit in another stream again; see low-carbon and recycled steel, CBAM and EPD.
Material choice itself is a separate decision — grade, temper, formability and cost are covered in sheet metal material selection.
What to put on the drawing and the PO
`` Material: [grade] to [product standard] Inspection document: EN 10204 [3.1 / 3.2] <-- state the type explicitly Traceability: heat number to be recorded and reported per lot Certificate to be provided: before first cut, and again with delivery Additional evidence: coating record, dimensional report, [weld / leak / bonding] Subcontract operations to carry lot identity: [anneal / plate / anodise / coat] Retention: [years] ``
For EN 10204 3.1 vs 3.2, two lines prevent most disputes: state the certificate type as a number, and require the certificate before first cut rather than only with the shipment. Put both into your sheet metal RFQ checklist.
Frequently Asked Questions
What is the difference between EN 10204 3.1 and 3.2?
Both report specific inspection results on the material actually delivered. The difference is who validates them: 3.1 is issued by the manufacturer's inspection representative independent of the manufacturing department, while 3.2 is additionally validated by an inspector independent of the manufacturer — a third party or the buyer's own representative. What is tested is essentially the same; who vouches for it is not.
Does a 3.1 certificate cover the finished part?
No. It covers the coil, sheet or plate the mill delivered. Forming changes thickness locally and work-hardens the material, welding adds a heat-affected zone, and coating adds thickness. A part made from certified material still needs dimensional, coating and functional evidence on the finished item.
Is a Certificate of Conformance the same as a material certificate?
No. A CoC states that the product complies with the order and carries no test data. It will not survive a serious supplier audit on its own. Insist on the EN 10204 type you need, named as a number.
When should I ask for the material certificate?
At RFQ stage, written into the purchase order, and then again before the first cut at the supplier's plant. The worst time to ask is after the container has shipped, because by then your leverage is gone.
What is a heat number and why does it matter?
It is the unique production identifier for a melt. It connects the certificate to the physical steel, and it is what lets you bound a claim, a recall or a forming problem to the specific batches affected rather than to all material received that year.
Why can a supplier hold a valid certificate and still fail a traceability audit?
Because the certificate and the traceability are different things. A supplier can file a perfect 3.1 and still be unable to say which heat is in the box, usually because heat numbers were not carried on the job card, offcuts lost their labels, or outsourced operations such as plating or coating returned material under a new container identity.