How to read a mill test certificate
A test certificate is the only thing that ties the bolt in your hand to a batch of steel that was actually tested. Most people file it without reading it. Click any part of the sample certificate to see what that field is telling you, what the standard requires it to say, and what a bad one looks like. The certificate below is a sample with illustrative values — it is not a real document.
Inspection certificate 3.1 · EN 10204:2004
Certificate No. IC-26-04417 · Date 12-Sep-2026Product: Hex bolt ISO 4014 · M20 × 100 · property class 8.8 · hot-dip galvanized ISO 10684 · Qty 1 200 pcs
Specification: ISO 898-1:2013 · ISO 4014 · ISO 10684
| C | Si | Mn | P | S | Cr | Mo | B |
|---|---|---|---|---|---|---|---|
| 0.36 | 0.24 | 0.72 | 0.014 | 0.009 | 0.98 | 0.19 | <0.0005 |
| Rm MPa | Rp0.2 MPa | A % | Z % | Proof load kN | Wedge test |
|---|---|---|---|---|---|
| 896 | 752 | 15.5 | 54 | 147.0 · held | Fracture in shank · pass |
(independent of production)
[name] · QA/QC · signed · stamped
not required for 3.1
Values on the sample are illustrative and were chosen to comply with ISO 898-1 class 8.8 above M16. Field order, headings and layout vary between manufacturers; the content required does not.
Which certificate you have, and which you should ask for
| EN 10204 type | What it is | Who signs | Tested on your batch? |
|---|---|---|---|
| 2.1 Declaration of compliance | A statement that the goods meet the order. No test results. | Manufacturer | No |
| 2.2 Test report | Results from non-specific inspection — the manufacturer's usual production, not necessarily this heat. | Manufacturer | Not necessarily |
| 3.1 Inspection certificate | Results from specific inspection of the actual products or test units of the batch supplied. | Manufacturer's authorised inspection representative, independent of the production department | Yes |
| 3.2 Inspection certificate | As 3.1, additionally witnessed and countersigned. | Manufacturer's independent representative and the purchaser's representative or an official inspector | Yes, witnessed |
For structural and pressure work, 3.1 is the working minimum. A 2.2 is not a certificate for your bolts; it is a description of the factory. Ask for 3.2 where the specification, the client or the regulator requires third-party witnessing. EN 10204 also allows a manufacturer to transfer results from the incoming bar's own 3.1 onto its certificate, provided traceability is maintained — which is exactly how an anchor bolt certificate from MF carries the bar mill's heat analysis.
Questions we are asked
The tensile figure is above the maximum — is that a problem?
ISO 898-1 sets minimums for tensile and yield, not maximums, so a high Rm is not a non-conformance in itself. What it sets both ways is hardness: 255–335 HV for 8.8 above M16. A tensile result that looks too good for the class, alongside a hardness at the top of the band, is worth a second look — an over-hardened 8.8 loses ductility, and the elongation and wedge test results are where that shows.
What is the wedge test and why does it matter more than the tensile?
A full-size bolt is pulled to failure with a wedge of a specified angle under the head, so the head is loaded off-axis. The bolt must fail in the shank or the thread, never at the head-to-shank junction. It is the test that catches a poorly formed head radius or a hardened, brittle head — the machined tensile test piece tells you about the steel; the wedge test tells you about the bolt.
Does a galvanized bolt need anything extra on the certificate?
Three things: the coating thickness, local and mean, against the ISO 1461 or ISO 10684 minimum; confirmation the nuts were tapped oversize after galvanizing and are marked Z or X; and, for class 8.8 and above, that the embrittlement relief the coater is required to manage was carried out. A bolt certificate that ends at the mechanical properties is only half a certificate for a galvanized product.
Can I accept a certificate that references a different edition of the standard?
Only with care. ISO 898-1:2013 tightened the phosphorus and sulphur limits from 0.035 to 0.025 for the quenched-and-tempered classes, among other changes. A certificate quoting the 1999 edition may be reporting compliance with the looser limits. Check the edition on the certificate against the one your specification calls for, and read the actual numbers rather than the word "conforms".
Related
Inspecting a delivery · Head markings chart · Galvanizing & thread fit · Back to the Bolt Lab