Mill certificates from Korea: 3.1 or 3.2, and what arrives when you don't say
The purchase order says "material certificates required". The shipment arrives with a document that lists a chemical analysis and a heat number, and your inspection department rejects it because the project needed 3.2. Nobody was wrong. The order never said which type, and the supplier issued what they normally issue.
The difference is who signs, not what is measured
Under EN 10204, the distinction between certificate types is about independence of verification rather than about the tests themselves.
A 3.1 certificate reports results on the actual product, validated by the manufacturer's own inspection representative — someone independent of the production department, but employed by the manufacturer. A 3.2 certificate carries a second signature: an inspector from the purchaser or an independent third party, who witnesses or verifies the same results.
The chemical and mechanical data on both can be identical. What differs is who attests to it, and that is precisely what a project specification is selecting when it names one or the other.
There is also 2.2, a non-specific test report covering the production run rather than your item. It is common for general-purpose material and is not interchangeable with 3.1, because it cannot be tied to the piece you received.
What you get if you do not specify
Korean manufacturers supply against many different export markets, and their default varies with the material and the shop. Ask for "material certificates" without a type and you may receive 3.1, a 2.2 report, or a works certificate of the supplier's own format.
This matters most for material bought from stock. A shop holding bar or plate across several heats can issue a certificate for the heat if the traceability was maintained — and cannot if it was not. The question of which you will get is settled long before your order, by how the material was received and stored.
So the practical rule is to state the type in the enquiry rather than the order. By order stage, the supplier has priced a certificate they can produce cheaply, and upgrading the requirement becomes a commercial discussion.
When 3.2 is worth the cost and delay
A 3.2 certificate requires a third party or your own inspector present or verifying, which costs money and inserts a scheduling dependency into the manufacturing sequence.
| Situation | Typical requirement |
|---|---|
| Pressure-retaining parts under a design code | 3.2 where the code or client specification calls for it |
| Structural or load-bearing components | 3.1 commonly sufficient |
| Corrosion-critical wetted parts | 3.1, with the relevant corrosion test reported |
| General machined parts, non-critical | 3.1 or 2.2 depending on client requirements |
Two points make this decision easier. First, the requirement often comes from outside your company — a design code, a client specification, a regulatory regime — and is therefore not negotiable internally. Establish which before debating cost. Second, requiring 3.2 across an entire bill of material, rather than on the items that need it, generates expense and delay without adding assurance.
The timing consequence is worth stating plainly. A 3.2 certificate has to be arranged while the material is still at the stage being witnessed, which means the inspection has to be booked into the manufacturing schedule rather than added at the end. Deciding you need 3.2 after the parts are machined does not produce a 3.2 certificate; it produces a request to re-make the parts or to substitute sample testing. This is why the certificate type belongs in the enquiry, alongside the inspection and test plan, and not in a later email.
Specify the standard as well as the type
"3.1" is a European designation. Korean suppliers work with it routinely for export, but they also work to KS, ASTM and JIS, and certificate formats differ accordingly.
An ASTM material test report contains comparable information without carrying an EN 10204 designation. If your inspection procedure keys on the phrase "EN 10204 3.1", a perfectly adequate ASTM report gets rejected at goods-in by someone following a checklist.
State both: the material standard and grade, and the certificate type or its equivalent. If you accept an equivalent, say so in the order, because that sentence is what lets your own inspector release the shipment without a query.
Traceability is the part that actually fails
A certificate with correct data is of limited use if it cannot be tied to the item in front of you.
The link is the heat or cast number, and it has to survive machining. A plate marked at the mill can lose its marking when cut and machined, and the shop transfers it by hand or by a tag. If that transfer is not specified, the piece arrives unmarked and the certificate becomes a document about some material rather than about this part.
What to require: hard stamping or a durable mark of the heat number on the part, and the same number on the certificate. Where the part is too small or the surface too critical, require the marking on the packaging with a per-piece record. This is the single most effective line to add to a purchase order, and it is usually absent.
Ask also for the format in which certificates will be delivered and when. Electronic copies sent with the shipping advice let you check the documents before the container arrives; paper originals travelling by courier routinely arrive after the goods, and goods-in cannot release material it has no paperwork for. Unless your own retention policy requires wet-signed originals, asking for scanned copies at shipment and originals to follow removes a common source of demurrage and storage cost.
Reading what arrives
Receiving the certificate is not the same as checking it. Four checks take a few minutes and catch nearly everything.
- Grade and standard match the order, including the edition where it matters.
- Values sit inside the specified range — not merely present, but within limits.
- Heat number matches the part, physically verified on at least a sample.
- Dates are consistent: the certificate should not predate the material or postdate shipment implausibly.
Values clustered at the edge of a range are not non-conforming, but for fatigue-loaded or low-temperature applications they are worth a second look before the part goes into service.
One more habit pays off years later: file the certificate against the part number and the order, not only in a document folder. The question that eventually arrives is never "do you have the certificates" — it is "how did you verify the material in this component", and answering it requires the link between the paper and the item, which is exactly what an undated folder of PDFs cannot provide.
When the supplier says it cannot be issued
This happens, and the reasons differ enough that the response should differ too. Material drawn from mixed stock may genuinely not be traceable. Material bought through a trader may have the original certificate held by the trader. Sometimes the reluctance is that the certificate names the mill, and the supplier does not want the source disclosed.
The last case is the easiest to resolve: a redacted certificate showing composition and properties without the mill's name satisfies the technical purpose, since what you are verifying is the material, not their supply chain.
Where traceability is truly lost, testing a sample from the delivered item is the remaining option. It costs more than the certificate and may be destructive, which for small quantities means ordering an extra piece. At that point, comparing the cost against sourcing from a supplier who can certify is a straightforward calculation.
Once the type is settled, the constraint moves to timing
Specifying the certificate type removes the argument about which document is owed. What it does not remove is the question of when it arrives, and that is where shipments sit next.
The sequence matters more than people expect. Goods-in cannot release material it has no paperwork for, so a container that arrives ahead of its certificates occupies storage and accrues charges while everyone waits for a courier. On a witnessed certificate the dependency runs the other way: the inspection has to be slotted into the manufacturing schedule, and if it slips, the certificate slips with it and the shipment waits for a document rather than for a part.
Two lines in the order handle both. State that scanned certificates are sent with the shipping advice, with originals to follow if your retention policy needs them. And require a minimum notice period for any witnessed inspection, so a moved date is contained rather than discovered.
Beyond that, the remaining variable is the calendar the supplier is working to — which is a separate subject, and the one that most often explains a date that moved for no visible reason. Send us the item and its service conditions and we can look at which certificate type your application actually requires and where it sits on the schedule — documentation requirements are worth reconciling at the same time. Talk to us about sourcing.