Sooner or later a drawing pack arrives with a line that says the material must be certified to EN 10204 3.1, and the part must be traceable to heat number. Both requirements are reasonable, and both are frequently misunderstood at the same time. The certificate and the traceability are two different things: one is a document about a coil of steel, the other is a discipline about what happens to that coil after it leaves the mill. A supplier can hold a perfect 3.1 certificate and still be unable to tell you which heat number is in the parts in the box, and a supplier with excellent traceability can be handing over a 2.2 test report that an auditor will not accept.
EN 10204 3.1 vs 3.2: what is the difference?
EN 10204 defines three inspection documents that matter on a drawn part. A 2.2 test report is a declaration of compliance based on non-specific inspection — it is not tied to the metal you actually received. A 3.1 inspection certificate is issued by the manufacturer's inspection representative who is independent of the manufacturing department, and it reports the results of specific inspection on the delivered material: heat number, chemical composition, mechanical properties, condition and the standard it is certified against. A 3.2 certificate is the same document validated by an inspection representative independent of the manufacturer, in practice a third party or the buyer's own inspector. So 3.1 and 3.2 differ in who validates the result, not in what is tested, and neither of them certifies the drawing operation that turns the coil into a housing.
The three documents, side by side
| Document | Who issues it | Based on | What it typically tells you |
|---|---|---|---|
| 2.2 test report | The manufacturer | Non-specific inspection | The material meets the order. Useful for commercial confirmation, weak as evidence for an audit. |
| 3.1 inspection certificate | The manufacturer's inspection representative, independent of production | Specific inspection of the delivered material | Heat number, chemistry, mechanical properties, delivery condition and the standard certified against — for the coil or sheet actually supplied. |
| 3.2 inspection certificate | An inspection representative independent of the manufacturer | Specific inspection, validated by the third party | The same content as 3.1, with an outside signature behind it. Asked for where the buyer or the end customer requires third-party release. |
A 3.1 certificate describes the coil, not the drawn part
Everything a 3.1 certificate states is true of the flat product the mill delivered. It says nothing about the housing that comes out of the press. The drawing operation changes the wall thickness locally, work-hardens the material, may need an inter-stage anneal, and ends with a dimensional result that the mill never saw. A part can be made from certified 316L coil and still fail the requirement that matters, which is the finished wall thickness at a specific height, or the hardness left in the material after forming.
That is why a material certificate should never be the only evidence in a PPAP or first article submission. It is one leg: the steel is what the drawing asked for. The other legs are dimensional results on the drawn part, the wall thickness in the places that matter, a surface and cleanliness result if the part is brazed or welded, and — where the part carries fluid — a leak test. Reading a 3.1 certificate as if it covered the forming step is how a supplier ends up shipping certified material in an uncertified part.
What heat-number traceability has to mean in practice
Traceability is a chain of custody, and on a stamped or drawn part it has four links. Each one has to hold, because an auditor will test the weakest link, not the strongest.
- Receiving: the coil or sheet is booked in against its heat number, and the 3.1 certificate is filed against that number rather than in a general quality folder.
- Release to production: the heat number travels with the material to the press, on the lot traveller or the job card, so the operator knows which heat is running — and the records know which heat was used for which production lot.
- Through the process: drawing, anneal, deburring and any outsourced finishing are recorded against the same lot identity. This is the link that breaks most often, because material that leaves the plant for annealing or plating is easy to lose track of if the container is not labelled with the lot.
- To the customer: the shipment documentation maps the delivered parts back to the heat, so a claim or a recall can be bounded to the batches that used that heat instead of the whole year's output.
The three places the chain usually breaks
- Mixed bins at the press. Two heats of the same grade are interchangeable in a part, so they get used interchangeably — and then the finished parts cannot be attributed to either. If the requirement is per-heat traceability, the heats cannot be mixed during production, even though the material is identical.
- Outsourced finishing without a lot identity. Annealing, passivation and plating are often carried out by partner companies. If the lot card does not travel with the parts, the returning parts are certified to a heat nobody can name.
- Rework from an unlabelled container. Parts pulled for rework and put back without their lot card are the classic finding in an audit: the parts are fine, the identity is gone.
What to write in the purchase order
The requirement is only enforceable if it is specific. A purchase order line that says “3.1 certificate required” leaves the supplier to guess the rest, and the guesses will not match what the auditor asks for six months later. These are the fields that remove the ambiguity.
- The document type and the standard it is issued against: EN 10204 3.1, and the steel specification the certificate must state — for stainless, typically EN 10088 or ASTM A240, with grade and delivery condition named.
- The scope of traceability: certificate for the delivered material, or per-heat identification of the finished parts. These are different requirements with different production discipline, and the second costs more.
- Whether 3.2 is required, and if so who the independent inspector is, because the supplier cannot choose the third party that the buyer's auditor will accept.
- Which characteristics must be reported on the certificate: chemistry, mechanical properties, hardness, surface finish, and any inter-stage anneal.
- What is delivered with the shipment: certificate copies, lot mapping, and whether the parts are marked, labelled or bagged by heat.
- The retention period for the records, since the requirement usually outlives the order by several years.
When 3.2 is worth the extra cost
A 3.2 certificate adds a third signature to a document that already reports real test results, and it adds cost and lead time because an outside inspector has to be scheduled. It earns that cost in three situations: where the part goes into a pressure or safety-related assembly and the end customer's own quality system demands independent release; where the material is difficult and the buyer does not want to rely on the mill's own inspection; and where the buyer is qualifying a new supplier and wants one independent confirmation before moving to routine 3.1 supply. Outside those three, 3.1 with a disciplined traceability chain usually serves an automotive or industrial programme better than a 3.2 certificate attached to parts whose heat numbers cannot be reconstructed.
Key point
A 3.1 or 3.2 certificate proves what the mill delivered. What the customer receives is a drawn part, so the submission needs both: the certificate for the material, and dimensional, wall-thickness and functional results for the part made from it. Traceability is a production discipline — if heats are mixed at the press or the lot card does not travel to outsourced finishing, no certificate can restore the link afterwards.
Frequently asked questions
Does a 3.1 certificate prove the finished part meets the drawing?
No. It reports specific inspection results on the delivered material — heat number, chemistry, mechanical properties and condition. It says nothing about wall thickness after drawing, dimensional accuracy, hardness after forming or leak tightness. Those are proven by first article inspection and the dimensional report on the part itself.
What is the difference between 3.1 and 3.2 in practice?
Who validates the result. A 3.1 certificate is issued by the manufacturer's inspection representative, independent of the manufacturing department. A 3.2 certificate is validated by an inspection representative independent of the manufacturer — a third party or the buyer's inspector. The tests reported are the same; the signature behind them is not.
Can several heats be used in one production lot?
They can be used, but then the parts cannot be attributed to a single heat. If the requirement is per-heat identification of finished parts, the heats have to be run and stored separately through every operation, including outsourced finishing. If the requirement is only a certificate for the material supplied, mixing is acceptable and cheaper.
Which stainless standards are normally named on the certificate?
For stainless flat product, EN 10088 or ASTM A240 with the grade and delivery condition stated — for example 1.4404 / 316L, or 1.4845 / 310S in the annealed condition. The certificate should also name the heat number, the chemical composition and the mechanical properties actually measured on that heat.