Key takeaways
- An EN 10204 3.1 certificate reports tests on a specific heat and is validated by a mill inspector independent of production; 2.1 and 2.2 documents are not batch-specific.
- For scrap, a certificate only counts when the heat number on the metal matches the certificate character for character.
- Check that the chemistry has the shape of the named grade: iron, niobium, tungsten, aluminium or copper often give a mismatch away.
- Present each certificate beside a photograph of the matching marking, and confirm the metal with XRF or PMI readings.
Picture a pipe-spool shop clearing out a rack: Inconel 625 offcuts, a few plate crops, and a ring binder of mill certificates from the original order. The paperwork looks convincing, but an EN 10204 3.1 certificate describes a heat of metal as it left the mill, not the pile in front of you. Reading it well means knowing what each block on the page says and, more to the point, whether the metal can still be tied back to it.
This guide reads a 3.1 certificate the way a scrap buyer or a melt-shop quality engineer does: who signed it, which heat it covers, whether the chemistry fits the grade, and how much weight it can carry once the material has become scrap.
What Is an EN 10204 3.1 Certificate?
An EN 10204 3.1 certificate is an inspection certificate issued by the manufacturer, reporting tests on the delivered product or on test units from the same heat or lot, and validated by the mill’s authorised inspection representative who is independent of the production department. That independence is the whole point. The people who made the metal do not sign off their own work.
EN 10204 is the European standard that defines the types of inspection document for metallic products. The current edition, from 2004, recognises four types: 2.1, 2.2, 3.1 and 3.2. Older paperwork may still print "3.1.B", a designation from the 1991 edition that the 2004 revision folded into the single type 3.1. People in the trade call the document an MTC (mill test certificate) or, in North America, an MTR (mill test report). The name matters less than the EN 10204 type printed on it.
| Type | Name | Validated by | Results from the actual heat or lot? | Weight as scrap evidence |
|---|---|---|---|---|
| 2.1 | Declaration of compliance | Manufacturer | No results at all | Very little: a statement without numbers |
| 2.2 | Test report | Manufacturer | No: typical, non-specific results | Low: describes the grade, not your heat |
| 3.1 | Inspection certificate | Mill inspector independent of production | Yes | Good, if the heat number is still on the metal |
| 3.2 | Inspection certificate | Mill inspector plus the purchaser’s or an officially designated inspector | Yes, with a second signature | The same as a 3.1 once the metal is scrap |
A 3.1 certificate is a statement about a heat. Without that heat number on the metal, even a perfect certificate describes some other piece of metal.
Is a 3.2 Certificate Better than a 3.1 for Scrap?
For scrap, a 3.2 certificate is not meaningfully better than a 3.1. The second signature mattered to the original purchaser, who wanted their own inspector, or one named by regulation, to witness the tests. It does not make the heat any more traceable once the pipe has been cut into offcuts. Both types report tests on the delivered heat. The line that matters in a scrap sale runs between the 3.x types, which carry batch-specific results, and the 2.x types, which do not.
What Is on a 3.1 Certificate, Block by Block?
Every mill lays out the page differently, but a 3.1 certificate for nickel alloy pipe, plate or bar carries the same building blocks. Read them top to bottom, and check each one against the metal or the grade rather than against what you expect to see.
- Headerissuing mill, certificate number, date and the EN 10204 type
- Order and productcustomer, order number, product specification, grade, UNS number, size and quantity
- Heat and lotheat or cast number and, where used, lot or piece numbers
- Chemical analysisthe heat analysis, element by element, against specification limits
- Mechanical and other teststensile, yield, elongation and hardness, plus any corrosion, flattening or NDT results
- Condition and declarationheat treatment, statement of conformity, inspector’s name, signature and stamp
Header and Certificate Type
Look for "EN 10204" and the type number printed on the certificate itself, not written in by hand or claimed in a covering email. A certificate number that also appears on the mill’s dispatch documents is a good sign.
Specification, Grade and UNS Number
The product line should name a specification and a grade together, for example ASTM B444 with UNS N06625 for Inconel 625 pipe. Many certificates print an ASME SB number beside the ASTM B number; that dual marking is normal for pressure-equipment material and is explained under ASME SB and SA specifications. If you are unsure which product form a B number covers, the ASTM B specifications for nickel alloys list them grade by grade. Trust the UNS number over the trade name; how UNS numbers work explains why.
Heat Number
The heat (or cast) number identifies one melt, and everything in the chemistry block belongs to that melt. Some mills add a lot number for a heat-treatment batch, or a piece number for each length. If those appear on the certificate, they should appear in the marking on the metal too.
Chemistry, Mechanical Results and Declaration
The chemistry block gives measured values for the heat, usually beside the specification’s minimum and maximum. The mechanical results show the material passed its tests in the delivered condition. At the foot, the declaration states that the material complies with the order, signed by the named inspection representative.
How Do You Match a Heat Number to the Metal?
You match a heat number by reading it off the metal itself, from the mill’s stencil, ink-jet line or hard stamp, and finding the same number on the certificate, character for character. Close is not a match. A transposed digit or a different suffix letter can mean a different heat.
- 1Find the markingstencil, ink-jet line or hard stamp, often near a pipe end or plate corner
- 2Read the heat numbercopy it exactly, letters and suffixes included
- 3Match the certificatesame heat, specification and UNS number, and a 3.1 or 3.2 type
- 4Check the chemistryvalues fit the grade and the defining elements are reported
- 5Spot-check the metalan XRF reading confirms the piece matches the paper
- 6Record itphotograph marking and certificate together and file them with the lot
Fabrication scrap is where this works best. Shops doing traceable pressure work commonly transfer the heat number onto each length before cutting, which leaves offcuts that can be matched one by one. Plate crops often keep the mill stencil along one edge. Bar ends lose their marking fastest, because the stamped end of a bar is usually the first piece sawn off and the rest of the bar carries nothing.
Where only some pieces in a bundle carry a readable heat number, keep the marked pieces apart from the unmarked ones. A buyer will judge a mixed bundle by its weakest piece.
Does the Chemistry on the Certificate Fit the Grade?
The chemistry fits the grade when each element sits inside the specification limits printed beside it and the elements that define the grade are actually reported. Measured values will not equal the nominal figures on a grade page, because a real heat lands somewhere inside the range. What you are checking is that the shape of the analysis matches the alloy named at the top of the page.
Iron is the quickest sanity check on a nickel alloy certificate, because it varies widely between grades that look alike on paper.
A certificate for Inconel 625 should show iron below 5%, molybdenum near 9% and niobium in the 3–4% region. If the same page shows iron near 18% and niobium near 5%, the chemistry belongs to Inconel 718, whatever the header says; the Inconel 625 vs 718 comparison lists the separating elements. In the same way, a "C-276" certificate with no tungsten reported, or a "K-500" with no aluminium or titanium, is missing the elements that make those grades what they are. The nominal composition tables give a reference point for every grade we list.
Some dual designations are normal and should not worry you. Duplex is routinely certified to both UNS S31803 and S32205, and 316 stainless is often certified as 316/316L. The chemistry then has to satisfy both sets of limits at once, which you can check on the page.
What Does a 3.1 Certificate Prove About Scrap?
A 3.1 certificate proves what a specific heat was when it left the mill: its chemistry, its tested properties and the specification it met. It proves nothing about a piece of scrap unless that piece can still be traced to that heat, and even then it says nothing about what happened to the metal afterwards.
It Can Show
- The heat’s measured chemistry element by element
- The specification and UNS number what the mill made it to
- An independent mill signature the condition for a 3.1
- A link to the metal only through a matching heat number
It Cannot Show
- That an unmarked piece came from that heat paper does not travel with offcuts
- That nothing was added later bins and bags get topped up
- What happened in service repairs, overlays, coatings and welds
- What a drum of turnings holds chips from several jobs share one drum
That is why a buyer reads a certificate as supporting evidence and then confirms the metal itself. For new fabrication offcuts with clear heat numbers, a certificate plus a few XRF readings is strong evidence. For service scrap, the original certificate may describe the parent pipe accurately while a later repair weld or overlay is a different alloy altogether.
Which Scrap Forms Keep Their Certificate Value?
Certificates keep their value for fabrication scrap that still carries mill marking, and lose it for anything machined to chips, run in service or mixed. The table sets out what to expect, form by form.
| Scrap form | Chance the heat number survives | How to use the certificate |
|---|---|---|
| Pipe and tube offcuts | Good where the shop transfers markings to each length | Match length by length and list heat numbers on the packing list |
| Plate crops and burning skeletons | Fair: the stencil often runs along one edge only | Keep the marked edge on each crop and photograph it before further cutting |
| Bar ends | Poor: the stamped end is cut off first | Useful only where the shop bins ends heat by heat |
| Turnings | Lost unless chips are kept job by job | Background only; a composite sample carries the weight |
| Service scrap and plant dismantling | Rare: paint, scale and wear cover the marks | Background only; piece-by-piece testing decides |
What Are the Warning Signs on a Mill Certificate?
The warning signs are mismatches and gaps: a heat number that does not match the metal, a type that is not 3.1, a missing inspector, or chemistry that looks too tidy. None of these proves a certificate is false, but each one means the metal should be tested before the paper is relied on.
- Heat number matches the metalcharacter for character, suffixes included
- Type printed as 3.1 or 3.2not a 2.2 test report presented as a 3.1
- Specification and UNS agreethe B number covers that grade and product form
- Defining elements reportedNb in 625, W in C-276, Al and Ti in K-500, Cu in 825
- Values look like a real heatnot every element sitting exactly on a round nominal figure
- Inspector named and signedwith the mill stamp, not an empty signature block
- Quantities add upthe scrap claimed cannot outweigh the certificate quantity
Watch, too, for photocopies of photocopies where the heat number is the only sharp line on the page, one certificate offered against material from several sources, and mixed fonts inside the chemistry block. If a certificate covers a few hundred kilograms of bar and a scrap lot claims two tonnes from that heat, the arithmetic is the problem. The PMI inspection checklist covers what to record when you test the metal to settle any of these.
How Should You Present Certificates with a Scrap Lot?
Present certificates so that each one points to identifiable metal: the heat number on the packing list, a photograph of the marking beside the certificate, and the matching pieces kept together. A thick folder of certificates that match nothing in the lot does not help, and it can make a buyer more cautious, not less.
- Heat number legible on every piece and matched to a 3.1?YesStrong evidence. Add XRF spot checks and send both
- Heat number on some pieces only?YesSplit marked from unmarked pieces and describe them as two lots
- Certificates on file but no marking on the metal?YesTreat them as background and rely on test readings
- No certificates and no markings: piece-by-piece PMI is the evidence
For the testing side, see positive material identification for scrap lots and how handheld XRF sorts nickel alloys. When a lot is going overseas, certificates sit beside the shipping paperwork rather than replacing it; the export documents guide covers that side.
When you send us an enquiry, include the certificates you have, photographs of the markings and any readings. We ask sellers for that grade evidence, and we’ll review your enquiry against it.
Submit a requirement with the grade, form, quantity and delivery location.
Source a GradeFAQ
Is a mill test certificate the same as an EN 10204 3.1 certificate?
Not always. "Mill test certificate" (MTC) and "mill test report" (MTR) are general names for the paperwork that ships with metal. The document could be a 2.2 test report, a 3.1 or a 3.2 inspection certificate. Look for the EN 10204 type printed on the certificate itself. Only types 3.1 and 3.2 report tests on the actual heat and carry an inspector’s validation independent of production.
Can a scrap seller issue an EN 10204 3.1 certificate?
No. A 3.1 certificate can only come from the manufacturer of the product, because it reports that manufacturer’s tests on the heat it made. A scrap seller can pass on copies of the original certificates, and can add a PMI report or laboratory analysis of the scrap itself. Those are separate documents and should be labelled as such, never presented as a mill certificate.
What is a heat number on nickel alloy pipe or plate?
A heat number, also called a cast number, identifies a single melt of metal. All the product made from that melt shares the chemistry reported on its certificate. The mill marks the heat number on the pipe, plate or bar by stencil, ink-jet or stamp, and it is the only reliable link between a piece of metal and its paperwork.
Does a 3.1 certificate expire?
No. A 3.1 certificate describes a heat at the time of manufacture and has no expiry date. What fades is its usefulness. Once markings are cut off, painted over or worn away, or the metal has been repaired and overlaid in service, the certificate no longer tells you much about the piece in front of you.
What if my XRF reading does not match the certificate chemistry?
Small differences are normal, because handheld XRF and mill laboratory analysis are different methods. Clean the test spot and look at the elements that define the grade. If one of those is clearly wrong, such as low niobium on a piece certified as Inconel 625, trust the metal and take a laboratory sample. See XRF, OES or laboratory analysis.
Do I need mill certificates to sell nickel alloy scrap?
No. Most nickel alloy scrap is bought on the evidence of testing, not paperwork. Certificates help most with clean fabrication offcuts whose heat numbers are still legible, because they back up the readings. If you have none, describe the grade, form and quantity with photographs and readings on the sell your scrap page and the enquiry can still be reviewed.
What does 3.1.B mean on an old certificate?
3.1.B is a certificate type from the 1991 edition of EN 10204. The 2004 revision simplified the list to 2.1, 2.2, 3.1 and 3.2, folding the old 3.1 sub-types into the single type 3.1. A certificate marked 3.1.B is still an inspection certificate on the actual heat, so read it with the same checks as a current 3.1.
