Every steel or aluminium bar that enters your shop should come with a piece of paper that is easy to ignore: the mill test certificate (MTC). When a customer asks "which certificate did you get for this material?", the answer is usually an EN 10204 type, most often 2.2 or 3.1. Getting this right matters for traceability, PPAP material evidence, and for defending yourself if a part fails.

This guide explains what the EN 10204 types mean, what to check on an MTC before you cut the bar, and how to write the certificate requirement into your purchase order.

What EN 10204 is

EN 10204 is the European standard that defines the types of inspection documents supplied with metallic products. According to Material Welding, it was revised in 2004, and the current version keeps four types: 2.1, 2.2, 3.1 and 3.2. Indian buyers and export customers commonly use these type numbers even when the material is to an IS, ASTM or DIN grade.

2.1, 2.2, 3.1 and 3.2 in plain words

  • Type 2.1 – declaration of compliance. The manufacturer states the material meets the order. No test results are given.
  • Type 2.2 – test report. The manufacturer certifies compliance using non-specific test results, meaning tests on the same grade but not necessarily on the heat or lot you received. Projectmaterials notes that heat traceability is not guaranteed with a 2.2.
  • Type 3.1 – inspection certificate. Results come from specific inspection of the actual delivered product, and the document is validated by the manufacturer's authorised inspection representative, who is independent of the manufacturing department. Chemistry and mechanical properties relate to the specific heat, and the heat number is traceable.
  • Type 3.2 – inspection certificate with third-party verification. Like 3.1, but also verified by an independent inspector appointed by the purchaser or named by regulation.
For most automotive and export machining work, ask for 3.1 unless the customer's drawing or PO says something else.

Why 3.1 vs 2.2 matters for a machine shop

Say your drawing calls for EN8 / 080M40 or 42CrMo4, hardened and tempered, and a part cracks in the customer's assembly. With a 3.1 certificate you can show the actual chemistry and tensile results for that heat, and link the heat number to your job card and dispatch lot. With a 2.2 you can only show typical values for the grade. In a customer complaint or an 8D, that difference decides who carries the cost.

A 3.1 also gives you real numbers to plan with: actual carbon and alloy content help your heat treater set the cycle, and actual hardness or tensile strength tells you whether the bar is in the condition the drawing assumes.

What to check on an MTC before cutting the bar

A quick incoming check at the stores takes five minutes:

  1. Certificate type – the document should state the EN 10204 type, and it should match your PO.
  2. Material grade and standard – exactly as the drawing specifies, including condition (annealed, normalised, hardened and tempered).
  3. Heat number – it must match the marking or tag on the bar, and you should carry it onto your traveller or job card.
  4. Size and quantity – section size and weight should match the delivery.
  5. Chemical composition – compare each element against the limits in the grade standard, not just against the supplier's own "specified" column.
  6. Mechanical properties – tensile, yield, elongation, hardness, and impact if your drawing calls for it.
  7. Signature and validation – for 3.1, the authorised inspection representative; for 3.2, the third-party inspector as well.

Illustrative example: a bar of 42CrMo4 arrives with a 3.1 certificate, but the heat number stamped on the bar end differs by one digit from the MTC. Do not issue it to production until the supplier clarifies in writing. A five-minute hold at stores is far cheaper than a lot of finished parts with no traceability.

Writing it into your purchase order

Most MTC problems start with a vague PO. Spell out:

  • grade, standard and delivery condition,
  • the certificate type, for example "MTC to EN 10204 3.1",
  • that the heat number must be marked on each bar or bundle,
  • any extra tests your customer needs (hardness, impact, ultrasonic testing).

The Indian context: BIS and stainless steel QCOs

Indian steel buyers also need to watch Quality Control Orders (QCOs) that require BIS-certified material for some steel products. As one recent example, KNN India reported that the steel ministry suspended a stainless steel QCO on 27 April 2026, and that MSME stainless steel associations later sought its reinstatement after imports rose. These rules change, so check the current notification before you rely on imported material without BIS certification. A BIS mark is not a replacement for an MTC; you still need heat-level test data for traceability.

This is a general guide, not legal or regulatory advice.

How SpecReview helps

When you upload a drawing, SpecReview flags unclear or missing material, heat treatment and certificate notes as spec gaps to clarify before quoting. Its quality plan can then include incoming material checks, with each item tagged as coming from the spec or from an assumption.