Understanding Mill Test Certificates: EN 10204 3.1 Explained

When you buy steel, copper or alloy products for an industrial or medical project, the material itself is only half of what you receive. The other half is the paperwork that proves what the material is. The most important document is the mill test certificate, often called an MTC or material test certificate. This guide explains what it contains, what the EN 10204 certificate types mean, and how to check one before you accept a delivery.

What is a mill test certificate?

A mill test certificate is a document issued by the manufacturer that certifies the material’s chemical composition and mechanical properties, and confirms that it meets the specified standard and grade. It links a specific batch of material, identified by a heat or cast number, to the test results for that batch. Without it, a buyer has no reliable way of knowing whether a pipe marked 316L really is 316L.

What a certificate usually shows

• Manufacturer details and the certificate number and date.
• Product description: type, size, wall thickness or thickness, and quantity.
• Standard and grade, for example a specific ASTM or EN standard and material grade.
• Heat or cast number that traces the material back to the melt it came from.
• Chemical composition, listing the percentage of each element.
• Mechanical properties such as tensile strength, yield strength, elongation and hardness.
• Other tests where required, such as impact tests, hydrostatic tests, non-destructive testing or corrosion tests.
• Heat treatment condition, such as annealed or normalised.
• A signed declaration of compliance from the authorised person.

The EN 10204 certificate types

EN 10204 is the European standard that defines the types of inspection documents for metallic products. It is widely used around the world, including on projects that otherwise follow American standards. It defines four main types:

Type 2.1: Declaration of compliance

The manufacturer states that the products comply with the order, but provides no test results.

Type 2.2: Test report

The manufacturer states compliance and includes test results based on non-specific inspection, meaning tests on products of the same type, not necessarily the exact batch supplied.

Type 3.1: Inspection certificate

The manufacturer states compliance and provides results of specific inspection carried out on the actual products supplied, or the batch they came from. The certificate is validated by the manufacturer’s authorised inspection representative, who is independent of the manufacturing department. This is the most commonly requested type for industrial, pressure and medical applications.

Type 3.2: Inspection certificate with third-party validation

The same as 3.1, but the results are also validated by an independent inspector appointed by the purchaser or by the authorities. This is used for the most critical applications, such as certain pressure equipment, nuclear and offshore projects. It adds cost and time, so it is specified only where it is genuinely required.

How to check a certificate on delivery

1. Match the heat number. Check that the heat or cast number on the certificate matches the marking on the material itself.
2. Check the standard and grade against your purchase order and project specification.
3. Compare the chemistry with the limits in the standard. Pay particular attention to key elements, such as molybdenum in 316 stainless steel.
4. Review mechanical properties against minimum requirements.
5. Confirm the certificate type, for example 3.1, matches what was ordered.
6. Check sizes and quantities against the delivery note.
7. Look for signatures and dates, and file the certificate with your quality records.

Why certificates matter

Certificates protect everyone in the supply chain. They allow inspectors to accept material, give the end client confidence in what has been installed, and provide traceability if a problem ever arises years later. On export orders, they are also often required by customs, banks and the buyer’s quality department before payment is released.

Our approach

Nefton Exports Industries is an ISO 9001:2015 certified company and supplies Materials Test Certificates with its copper, steel and alloy products. Tell us the certificate type your project requires when you request a quotation, and we will confirm what will accompany your order.