A mill certificate connects the steel in a fabricated member to the heat it came from. On an overseas steel structure project it is one of the documents the inspector, the engineer and sometimes the certification body will ask for.
EN 10204 is the standard that defines the inspection document types. The number after the type, 3.1 or 3.2, changes who issues the document, who validates it and how much independent testing stands behind it. The material grade and its acceptance criteria come from a different standard.
What EN 10204 does and does not cover
EN 10204 defines the form of the inspection document. It does not set the steel grade, the impact class, the thickness limits or the acceptance values. Those come from the material standard named in the order, for example GB/T 1591, EN 10025 or ASTM A572.
| Document type | Who issues it | Typical use |
|---|---|---|
| 2.1 | Manufacturer's declaration of compliance, without test results | Non-structural or low-risk items where a declaration is enough |
| 2.2 | Manufacturer's test report, based on non-specific inspection | General verification where the purchaser accepts the manufacturer's routine test results |
| 3.1 | Manufacturer's inspection representative independent of the manufacturing department, with specific test results | Common requirement for structural steel in fabricated building projects |
| 3.2 | The same specific test results, validated by an inspector nominated by the purchaser or by a recognized independent body | Projects with third-party inspection, higher execution classes or client QA requirements |
What a 3.1 certificate usually contains
- The manufacturer and the works that produced the heat.
- The material standard, grade and impact class.
- The heat number and the product description, including dimensions and thickness.
- Chemical composition, including the elements the standard limits.
- Mechanical test results: yield strength, tensile strength, elongation and impact energy at the specified temperature.
- Heat treatment condition, where the standard requires it.
- The date, the inspection representative and the signature.
The certificate is only useful when it can be traced to the delivered steel. Fabricators normally map each heat number to the member marks that used it, and keep that mapping with the inspection records. If one heat is split across several members, the mapping is what lets an inspector select a member and follow it back.
When 3.2 or independent inspection is specified
3.2 is common on projects where the purchaser wants an inspector who does not report to the fabricator. The requirement is normally written into the inspection and test plan, together with the witness and hold points.
- Name the inspection body, or say who nominates it.
- State which tests are witnessed, which are reviewed as records, and which are hold points.
- Agree who pays for the inspector, travel and any repeat testing.
- State the language and the number of document copies required.
- Confirm whether the certificate package is a condition of shipment or a payment milestone.
How to write the certificate requirement into the enquiry
- Name the material standard, grade, impact class and thickness range.
- State the EN 10204 document type: 2.2, 3.1 or 3.2.
- Say whether certificates are required for plates, sections, bolts, welding consumables and coatings, or only for the main steel.
- State whether the certificate has to be traceable to member marks or only to the delivery lot.
- Say whether a third-party inspector is required, who nominates the inspector, and which points are witnessed.
- State the document language, the number of copies and whether electronic copies are acceptable.
- Put the document list in the purchase order and in the inspection and test plan, not only in the quotation.
This guide describes general practice for steel structure projects. It is not a design, and it does not replace the specification or the engineer responsible for your project.