A mill test certificate (MTC) is the document that ties a batch of stainless steel pipe or tube to its test results: which heat of steel it came from, what its chemical composition and mechanical properties actually measured, and which tests it passed. For most industrial orders the certificate requested is an EN 10204 3.1 inspection certificate. This guide explains what the EN 10204 document types mean, walks through a real 3.1 certificate line by line, and lists the checks a buyer should make before accepting one.

1. What EN 10204 is

EN 10204 is the European standard that defines the types of inspection documents a supplier can provide for metallic products. It does not set any material requirements itself; the limits for chemistry, strength and testing come from the product standard (for example ASTM A312, ASTM A269 or EN 10216-5). EN 10204 only defines how much testing the document reports and who is responsible for confirming it.

Document type	What it contains	Who validates it
2.1 Declaration of compliance	A statement that the products comply with the order, without any test results	The manufacturer
2.2 Test report	A statement of compliance with results of non-specific inspection — typical results for the production, not necessarily from the delivered batch	The manufacturer
3.1 Inspection certificate	Results of specific inspection carried out on the delivered products (or the test units they belong to)	The manufacturer’s authorised inspection representative, independent of the manufacturing department
3.2 Inspection certificate	Results of specific inspection, as for 3.1	Both the manufacturer’s independent inspection representative and the purchaser’s representative or an inspector designated by official regulations

In practice: 3.1 is the normal requirement for pressure piping, heat exchanger tube, sanitary tube and most project work. 3.2 is requested when the end user, a classification society or a regulation requires an independent party to witness testing — common on offshore, nuclear and some oil & gas and pressure-equipment projects. A 2.1 or 2.2 document is not enough wherever traceability to the actual delivered heat is required.

2. How to read a 3.1 mill test certificate — a real example

Below is how to read one of our own certificates: a 3.1 MTC for seamless 316L stainless steel tube coils to ASTM A269 (customer name hidden). You can open the full sample certificate (PDF) and follow along.

Header: what was ordered

Certificate, contract and order numbers — these link the certificate to your purchase order. Check they match.
Product description — here, seamless austenitic stainless steel tube coils.
Material specification — grade and standard, here 316L to ASTM A269. This must match your order, including the grade designation.
Delivery condition — here solution annealed and bright annealed.

A) Chemical analysis

The first row shows the limits of the specification; the next row shows the actual heat analysis. On the sample certificate, heat N250508AV06 measured:

Element	Limit shown on certificate	Measured
C	max 0.030%	0.018%
Mn	max 2.00%	0.9%
P	max 0.045%	0.038%
S	max 0.030%	0.001%
Si	max 1.00%	0.37%
Cr	16.00–18.00%	16.46%
Ni	10.00–14.00%	10.01%
Mo	2.00–3.00%	2.01%

What to check: every measured value sits inside its limit, the carbon value confirms the low-carbon “L” grade, and molybdenum is present — that is what distinguishes 316L from 304L.

B) Mechanical properties

The certificate lists the heat-treatment temperature (1080 °C) and the results of tensile and hardness testing against the minimums shown: yield strength min. 175 MPa, tensile strength min. 480 MPa and elongation min. 35%. The measured results were yield strength 252–277 MPa, tensile strength 553–578 MPa, elongation 60–66% and hardness 71–75 HRB. Every result must meet the minimum; a result exactly on the limit is acceptable but worth noticing.

C) Extent of delivery

This section lists each size and quantity covered by the certificate — on the sample, four sizes from 6 × 1 mm to 12 × 1 mm, all from the same heat. Compare it with your packing list: every size you received should appear here with a heat number.

D) Hydrostatic test, NDT and dimensional checks

The tests carried out and their results. On the sample: visual and dimensional inspection, a hydrostatic test at 30 MPa held for 10 seconds, a flattening test and a drift-expanding (flare) test, each marked satisfactory against ASTM A269. If your order requires eddy-current or ultrasonic testing, PMI or intergranular-corrosion testing, it must appear in this section — a test that is not listed should be treated as not performed.

E) Statement and approval

A declaration that the material complies with the contract and the material specification, with the date, the inspector and the QC manager’s approval and company stamp.

3. Checklist before you accept an MTC

The heat number on the certificate matches the heat number marked on the pipe or tube and on the packing.
The standard, grade and edition match your purchase order, including dual certification (for example 316/316L) if you ordered it.
Every chemical and mechanical result is within the limits of the product standard you ordered — not only the limits printed on the certificate.
Every test you specified (hydrostatic, eddy current, ultrasonic, PMI, corrosion, surface roughness) is listed with a result.
Sizes and quantities match the packing list and invoice.
The certificate is dated, signed and stamped, and is the document type you asked for (3.1 or 3.2).

Warning signs

No heat number, or one heat number covering sizes that could not plausibly come from one heat.
Identical chemistry or test values copied across different heats or orders.
Tests required by the order that are missing from the certificate.
A “3.1” certificate with no identifiable inspection representative or approval.

If any of these appear, ask for clarification before the goods are shipped — it is far easier to resolve at the mill than after delivery.

4. How TeCarve supplies inspection documents

TeCarve is the sole export arm of two stainless steel tube factories in Foshan and Wenzhou, China. Every order ships with an EN 10204 3.1 mill test certificate traceable to the heat number. Where your project needs witnessed testing, we arrange EN 10204 3.2 certification or third-party inspection by SGS, Bureau Veritas or TÜV on request.

Ask for a sample certificate for the grade and standard you need before you order.
Specify any extra tests (eddy current, ultrasonic, PMI, intergranular corrosion, Ra) in the enquiry so they are performed and reported.
Book a live video audit of either partner factory on our verify our factories page.
Response within 24 hours at sales@tecarve.com.

Frequently asked questions

Is an EN 10204 3.1 certificate enough?

For most industrial, sanitary and heat exchanger orders, yes. Request 3.2 when your contract, the end user or a regulation requires an independent inspector to witness testing.

What is the difference between 2.2 and 3.1?

A 2.2 test report gives typical results from production, not necessarily from your batch. A 3.1 certificate reports results of specific inspection on the delivered products and is validated by an inspection representative independent of manufacturing.

Who signs a 3.2 certificate?

Both the manufacturer’s independent inspection representative and the purchaser’s representative or an inspector designated by official regulations, such as a third-party inspection agency or classification society.

Does the MTC prove that NDT was carried out?

Only if the test is listed with a result. If eddy-current or ultrasonic testing is required, write it into the purchase order and check that it appears on the certificate.

Can I see a sample certificate before ordering?

Yes — you can download our sample 3.1 MTC, or ask us for one in the grade and standard you need.

Mill Test Certificate (MTC) Explained: EN 10204 3.1 for Stainless Steel Pipe and Tube