A mill test certificate (MTC) is the mill's document certifying that a steel batch meets its specified grade — chemical composition and mechanical properties. Under EN 10204, demand a type 3.1 (inspected and signed by the mill's independent QA), not a 2.1/2.2 self-declaration. Cross-check the heat/cast number on the coil against the cert, and verify the mill.
You are a trader, metal stockist, construction company or manufacturer importing steel from China by the container load — 20 tonnes and up. You paid for a specific grade — Q235B, DX51D+Z, 304 — but how do you prove the coil or bundle in the container is actually that grade, and not a cheaper "same colour" substitute? The answer is one document: the mill test certificate (MTC), also called a mill certificate or steel quality certificate. The catch is that a PDF is trivially easy to forge or borrow from a different heat. Below is how to read an MTC and, more importantly, how to verify it is genuine rather than just filing it away.
What a mill test certificate is and why it matters
A mill test certificate (mill certificate, MTC, steel quality certificate) is a document from the steel mill that certifies the chemical composition and mechanical properties of a specific batch of metal. It is tied to a heat number (heat / cast number) — the unique "passport" of the melt the slab or coil was cast from. In essence, the MTC is proof that you received the exact grade you paid for, not a visually similar lower-grade steel.
For a wholesale importer the MTC is not paperwork — it is a financial instrument. Grade substitution is the classic quality-fade play: the sample is flawless, then the batch is quietly cheapened. Thinner zinc on galvanized, less manganese in structural steel, "almost 304" instead of 304 — none of this is visible by eye, but it surfaces on site or during certification. The MTC is your first line of defence — but only if you can read and verify it.
EN 10204 inspection-document types: why you need 3.1
The thing most buyers miss: MTCs differ by level of independence. The European standard EN 10204 defines four types of inspection document, and the difference is fundamental:
- 2.1 (Declaration of compliance) — the mill simply declares "conforms to the order." No test results, no actual figures. The weakest document.
- 2.2 (Test report) — the mill states test results, but not necessarily from your heat — they may be typical/average product data. Better than 2.1, but still not about your specific batch.
- 3.1 (Inspection certificate 3.1) — test results from your actual heat, validated by a mill QC representative independent of the manufacturing department (not the sales office). This is the B2B standard: the values are real, tied to your heat number, and someone at the mill signed off on them.
- 3.2 (Inspection certificate 3.2) — the same as 3.1, but also countersigned by an independent third party (a classification society or a buyer-appointed inspector). Required for critical applications — shipbuilding, pressure, energy.
The rule is simple: for container-scale orders, demand 3.1 as a minimum. If a supplier offers only 2.1 or 2.2, that is either a trader with no access to mill data or an attempt to leave room for grade substitution.
MTC fields: what each one means
A genuine MTC is a dense table of numbers. Here is what it should contain and what each field means:
- Heat / cast / lot number — the unique melt identifier. This is what stitches the document to the physical metal. No heat number, no certificate.
- Chemical composition — mass fractions of elements: C (carbon), Mn (manganese), Si (silicon), S (sulphur), P (phosphorus). For stainless, additionally Cr (chromium), Ni (nickel), Mo (molybdenum); for galvanized, the zinc coating mass (Zn, g/m², e.g. Z100, Z275).
- Mechanical properties — yield strength, tensile strength, elongation (%). For structural steel these are the critical numbers.
- Dimensions and tolerances — thickness, width, and actual deviation from nominal.
- Standard and grade — which standard it was tested against (GB, EN, ASTM, JIS) and the grade claimed.
- Mill name, stamp and signature — producer details, seal and the signature of the responsible QC.
How to verify an MTC is authentic: 5 steps
Receiving a PDF counts for nothing. Verification starts here:
- 1. Heat number = physical marking. The heat number on the certificate must match the tag/marking on the coil, bundle or edge. This is the single most important check: if the numbers differ, the certificate belongs to different metal.
- 2. Values inside the grade's spec limits. The figures must sit within the specification of the claimed grade. Example: for Q235B, carbon C is typically ≤ 0.22%, manganese Mn ≤ 1.40%, with sulphur and phosphorus tightly capped. If C = 0.30%, it is no longer Q235B, whatever the header says.
- 3. Confirm the mill is a real licensed producer. Cross-check the mill's legal entity in China's national business registry, gsxt.gov.cn. A steel plant and a trading company are not the same thing; a certificate "from a trader" guarantees nothing.
- 4. Beware recycled or edited PDFs. Reused scans, altered figures, a "pasted-in" heat number — all of this is common. Request the original directly from the mill, not a file forwarded by the trader.
- 5. Confirm at pre-shipment inspection. An independent inspector with a portable spectrometer (PMI test) verifies the actual metal composition against the MTC on the spot. This is the only way to prove the paper matches the steel.
An MTC does not prove that paper exists — it proves the steel matches that paper, and only a spectrometer at the mill's warehouse confirms it.
Forgery red flags
- The same heat number on different batches/coils.
- Values suspiciously "dead centre" of the spec for every element (a sign of a made-up table).
- No QC signature/seal, or signed off by the sales department.
- Certificate format that doesn't match a known mill's house style; a low-quality logo.
- A supplier who refuses to provide the original directly from the mill or blocks independent verification.
How this fits full-cycle verification
The MTC is one link in a chain we run from sourcing to warehouse: supplier checks before the deposit, verifying a manufacturer rather than a trader, independent pre-shipment quality inspections with a PMI test, and only then logistics. That is the difference between full-cycle sourcing and "just shipping," where the container is accepted blind. For the wider procurement picture see our guide on importing steel from China, and for specific products galvanized GI coils and stainless steel.
Send us your supplier's details and a scan of the MTC — we will match the heat number, check the grade against spec, verify the mill's legal entity and confirm the composition by spectrometer at pre-shipment inspection. Reach us at contact@silkwaysourcing.com or on WhatsApp +380 97 883 4765.
