Reading an EN 10204 3.1 certificate without being fooled

The certificate is the only document that ties a heat to your parts. Here is what a 3.1 must contain, the four checks that catch most problems, and where 3.2 differs.

Every nickel alloy shipment arrives with a certificate. Very few buyers read it line by line, which is why the same problems keep appearing at incoming inspection. This note is the checklist we would use if we were the buyer.

What a 3.1 certificate must carry

• The manufacturer's name and address — the party that melted and processed the material.
• The purchaser and the order reference.
• Product description, form, dimension and the standard the product is supplied to, including the edition year.
• The heat number, and the number of pieces or bundles it covers.
• Chemical composition, with the values for each element specified by the standard.
• Mechanical properties: tensile, yield, elongation, and hardness or impact where the specification requires them.
• The heat treatment condition and the temperatures used, where properties depend on it.
• The signature of the manufacturer's authorised inspection representative — independent of the production department.

Four checks that catch most problems

1. Heat number against the stamping

Compare the certificate heat number with the number stamped, engraved or tagged on the goods. If they differ, stop. Everything else on the document is unverifiable until they match.

2. Standard edition

"ASTM B166" is not a specification; "ASTM B166-18" is. Superseded editions carry different chemistry limits for some grades, and a certificate quoting an old edition may be correct to a standard you did not order.

3. Test piece orientation and location

Mechanical results depend on where the test piece came from. For plate, transverse properties are lower than longitudinal. For bar, properties vary with distance from the centre. A certificate that does not state orientation is reporting a number you cannot compare with your design allowables.

4. Chemistry that adds up

Check the balance element and the residual limits. A 718 certificate that shows 58% nickel is not 718. A C276 certificate that reports 0.02% carbon fails the ≤ 0.010% limit that gives the grade its welded-service corrosion resistance.

Where 3.2 differs

A 3.1 is issued by the manufacturer's own inspection function. A 3.2 is countersigned by an independent inspector appointed by the purchaser or a nominated body, who witnesses the tests. The numbers are usually identical; the difference is who is prepared to sign them. Pressure-retaining and safety-critical parts are specified as 3.2 for that reason, and the price reflects the inspector's time.

What we put on ours

Every heat we ship carries the melt route and the heat number, chemistry by element, mechanical results with test piece orientation, the heat treatment condition, and the standard edition. If a customer needs a 3.2, we schedule the third-party inspection into the production plan rather than after it.

Values quoted here follow the ASTM / EN edition named in each paragraph. For a specific heat, the governing numbers are those printed on the EN 10204 certificate that ships with the material. Written by the technical desk at Shanghai Hangbo Alloy Group.