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Material Certificates for Stainless Parts: EN 10204 3.1 and the JIS Mill Sheet

Choosing a Shop / 15 Sept 2026

A certificate is the only evidence that the metal in your part is the metal on your drawing. It is also one of the easiest things to specify badly, because the words look interchangeable and are not.

The EN 10204 types

EN 10204 defines four document types. Two of them mean very little and two of them mean something.

Type Name What it contains Who signs it
2.1 Declaration of compliance A statement that the product meets the order. No results The manufacturer
2.2 Test report Results from non specific inspection, often typical values The manufacturer
3.1 Inspection certificate Actual results for the batch supplied The manufacturer’s inspection department, independent of production
3.2 Inspection certificate Actual results for the batch supplied As 3.1, plus the purchaser’s or a third party inspector

The important distinction is between the 2 series and the 3 series. A 2.2 can legitimately report values from a different heat that happens to be representative. A 3.1 reports the results from the material you actually received.

If you need to know what is in your part, you need a 3.1. If you only need someone to confirm they sold you what you ordered, a 2.1 does that and costs nothing.

What a 3.1 actually contains

For stainless bar it will normally give:

  • Heat number. The identifier for the melt. This is what traceability hangs on
  • Chemical composition. Actual percentages for each specified element, from the ladle analysis
  • Mechanical properties. Tensile strength, yield strength, elongation, sometimes hardness
  • Product form and dimensions
  • Delivery condition. Annealed, solution annealed, cold drawn, condition A
  • The standard it is certified against. EN 10088-3, ASTM A276, JIS G 4303
  • Any supplementary test. Intergranular corrosion test, ultrasonic test, ferrite content

That last group matters on specific parts. Intergranular corrosion testing to ASTM A262 is worth asking for on welded 316L in aggressive service. Ferrite content matters on parts where magnetic permeability is specified.

The JIS mill sheet

Japanese mills issue a mill sheet, or inspection certificate, against the relevant JIS product standard: G 4303 for bar, G 4304 and G 4305 for plate and sheet.

Content is broadly equivalent to a 3.1. Heat number, chemistry, mechanical results, delivery condition, the JIS standard and grade.

What differs is the reference framework. The mill sheet certifies against JIS. The 3.1 certifies against whatever standard the order named, usually EN or ASTM. Neither document is wrong. They simply answer different questions, and an incoming inspector working from a checklist that says “JIS G 4303 certificate required” will stop when handed a certificate that names EN 10088-3.

This is not pedantry on the inspector’s part. In a regulated supply chain the certificate is the audit trail, and an audit trail that does not match the specification is a finding.

How to write the requirement

Bad:

Material certificate required

Every shop reads that differently. Some will send a 2.1. Some will send a delivery note.

Better:

SUS316L per JIS G 4303
EN 1.4404 acceptable
Mill certificate to EN 10204 3.1 minimum, heat number stated

Best, when it matters:

SUS316L
Acceptable standards: JIS G 4303, EN 10088-3, ASTM A276
Certificate: EN 10204 3.1 or equivalent mill inspection certificate
Heat number to be recorded on the certificate and marked on the parts
Certificate to be supplied with the delivery, not on request

That last line is worth including. A certificate that exists somewhere and arrives three weeks after the parts is a certificate that holds up your goods inwards.

Traceability, and how far down it goes

Certificate and traceability are different requirements.

A certificate says what the heat was. Traceability says which parts came from which heat. On a single batch job they are the same thing. On a repeat order machined from two bars bought months apart, they are not.

Levels, from loose to strict:

  1. Certificate supplied. You know the heat. You do not know which parts came from it
  2. Batch traceability. The delivery is tied to a heat number on the packing note
  3. Part marking. Each part carries a heat or batch identifier, etched, laser marked or stamped
  4. Full traceability. Part marking plus records tying each piece to its heat, its operator and its inspection record

Each level up costs more. Level 2 is reasonable on most engineered parts. Level 3 and 4 belong in aerospace, medical and pressure equipment, and they should be specified because a standard demands them, not because they sound thorough.

If you need part marking, say where. An etched heat number on a sealing face is a defect.

Where certificates go wrong

Asked for late. A certificate requested after the bar has been cut may not be recoverable. The shop bought from stock, the stock was mixed, and there is no honest answer. Ask before the order, not at delivery.

Specified against the wrong standard. The drawing says JIS G 4303, the shop buys EN 1.4404 bar, the certificate says EN 10088-3, the inspector rejects it. Everybody was reasonable and the lot is stuck. Naming acceptable standards up front prevents this entirely.

Requested by default. A 3.1 on every part, including the ones nobody will ever question, is a quiet tax on the whole order. It narrows which stock the shop can use, which raises the price and lengthens the lead time.

Confused with a test report. A 2.2 looks like a certificate. It is a report on non specific inspection. If it matters, the type number has to be in the requirement.

The short version

Ask three questions before you write the note:

  1. Does anyone audit this part? If yes, 3.1 and name the acceptable standards
  2. Will it be reordered against the same revision? If yes, ask for heat numbers on the packing note
  3. Is it safety or pressure related? If yes, check whether the governing standard demands 3.2 or a specific supplementary test

If all three are no, a 2.1 is enough and you have saved money on every piece.

For the grade and standard mapping, see the JIS to AISI equivalents table. For the rest of the enquiry, see the JIS drawing checklist.

Have a part where the paperwork matters? Get a quote with the certificate requirement stated. We buy the material against the right standard and the certificate ships with the parts. Priced quote within 24 business hours.

Questions

What is an EN 10204 3.1 certificate?

An inspection certificate issued by the manufacturer's own inspection department, which must be independent of the production department. It states the actual test results for the specific batch supplied, not typical values.

What is the difference between 3.1 and 3.2?

A 3.1 is validated by the manufacturer's independent inspection representative. A 3.2 is additionally validated by the purchaser's representative or an independent third party inspector. A 3.2 costs substantially more and is normally required only in regulated sectors.

Is a JIS mill sheet the same as a 3.1?

In practice they carry similar information, actual heat chemistry and mechanical results. They are written against different standards and are not formally interchangeable. If your inspector was told to expect one, the other will be questioned.

Do I need a certificate on every part?

No. Ask for one when the part is safety related, regulated, audited, or will be reordered against a traceable revision. On a bracket it is paperwork nobody reads.

Have a drawing for a stainless part?

Send it and an engineer reads the title block, quotes it within 24 business hours, and if you order we place, manage, inspect and ship the parts on one PO and one invoice.

Get a quote

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