Article
A mill test certificate, usually shortened to MTC or MTR, is the document that ties a piece of steel to the tests that were done on it. It is the only thing that proves a pipe marked ASTM A106 Grade B actually is A106 Grade B. Stamping and paint can be applied to anything; a certificate that matches the heat number on the material cannot be faked without someone noticing.
This guide goes through a certificate from top to bottom, explains the certificate types in EN 10204, and ends with the checks worth making on receipt.
What a certificate is for
A certificate answers three questions. Which heat of steel did this material come from? What was that heat made of? And how did samples from it behave under test? If all three answers are on the page and they agree with the material in front of you, the certificate has done its job.
The parts of a mill test certificate
The header
The manufacturer's name and address, the certificate number, the date of issue, and the certificate type under EN 10204. The customer and order reference usually appear here too.
Product description
The standard and grade the material is certified to (for example ASTM A312 / ASME SA312 TP316L), the product form, the size, the wall thickness or schedule, the delivery condition (solution annealed, normalised, as rolled) and the quantity. A certificate that names two standards, such as A312 and SA312, certifies the material to both.
Heat number
The heat number identifies one melt of steel. It is the single most important entry on the certificate, because it is what links the paper to the pipe. The same number must be hard-stamped or stencilled on the material itself. If the numbers do not match, the certificate does not belong to that material, however correct everything else looks.
Chemical composition
The percentage by weight of each element, measured on a sample from the heat (the heat analysis) and sometimes also on the finished product (the product analysis). Compare each figure against the limits in the standard, not against the limits printed on the certificate itself; the certificate is what you are checking.
Mechanical properties
Tensile strength, yield strength and elongation are always given. Depending on the product and the order, you may also see hardness, reduction of area, and Charpy impact values with the test temperature. For low-temperature materials such as ASTM A333 Grade 6 the impact test and its temperature are not optional; a certificate without them does not certify the grade.
Other tests and conditions
Hydrostatic or non-destructive testing (ultrasonic, eddy current), flattening and flaring tests for pipe, intergranular corrosion tests for stainless steel where ordered, heat treatment details, and a statement that the material is free of mercury contamination or radioactive contamination where the order asked for it.
Signature and stamp
The person who signs is certifying the results. On a 3.1 certificate that is the manufacturer's authorised inspection representative, independent of the manufacturing department. On a 3.2 certificate there is a second signature from an independent inspector.
EN 10204 certificate types
| Type | Who confirms it | What it contains |
|---|---|---|
| 2.1 | Manufacturer | A declaration that the product complies with the order. No test results. |
| 2.2 | Manufacturer | Compliance with the order, with results of non-specific tests (tests on the same type of product, not necessarily this heat). |
| 3.1 | Manufacturer's inspection representative, independent of production | Results of specific tests on the delivered product or its heat. |
| 3.2 | Manufacturer's representative and a purchaser's or third-party inspector | As 3.1, with both parties confirming the results. |
For most process piping, 3.1 is the normal requirement. A 3.2 certificate is asked for where a client, a classification society or a third-party agency must witness testing: offshore work, critical pressure equipment, and some export orders. It adds cost and time, because an inspector has to attend, so it should be specified when it is genuinely needed rather than by default.
Five checks before accepting material
- The heat number on the material matches the certificate. Check several pieces, not one.
- The standard, grade and size match the order. TP316 and TP316L are not interchangeable where low carbon was specified for welding.
- Every chemical and mechanical value is inside the standard's limits. Pay attention to carbon on "L" grades and to molybdenum on 316.
- Any test the order asked for is reported. Impact tests, intergranular corrosion tests, hardness for sour service.
- The certificate is signed and legible. A photocopy of a photocopy that cannot be read is not evidence of anything.
When a certificate is re-issued by a stockist
Material bought from a stockist often arrives with the original mill certificate and, sometimes, a stockist's own certificate referring to it. The mill's document is the one that certifies the steel. A stockist's document can add traceability for cutting or processing, but it cannot replace the mill's test results. Ask for the mill certificate by heat number if it is missing.
What we supply with material
Every consignment from Sawariya Metal Industries goes with the certificate for the heat it came from, and the heat number stays on the material through cutting and preparation. If your order needs a 3.2 certificate or a witnessed test, tell us at the enquiry stage so the inspection can be arranged before dispatch rather than after.
See our pipes and tubes and flanges, or send an enquiry with the certificate type your project calls for.
Frequently asked questions
What is the difference between EN 10204 3.1 and 3.2?
A 3.1 certificate is validated by the manufacturer's independent inspection department; a 3.2 is also validated by the purchaser's or a third-party inspector.
How is an MTC linked to the material?
Through the heat number marked on the material and printed on the certificate.
What should I check first on an MTC?
Specification and grade, heat number, chemical composition, mechanical properties and heat treatment against the order.
Key takeaways
- The MTC proves the material meets its specification.
- Match heat numbers on material and certificate.
- Check chemistry, mechanicals, heat treatment and extra tests.
Need these products?
Sawariya Metal Industries supplies stainless steel pipes, flanges and buttweld pipe fittings from Mumbai to buyers in India and overseas. Send your size, grade, standard and quantity through our enquiry form and we will reply with a clear quotation and the test documents you need. You can also browse our stainless steel pipes, flanges and buttweld fittings.