The Mill Test Certificate (MTC) is the most important quality document in special alloy procurement. It evidences the chemistry, mechanical properties and heat treatment condition of the batch and provides a complete chain of traceability from finished product back to the melt heat.
1. EN 10204 certificate types
| Type | Name | Issued by | Typical use |
|---|---|---|---|
| 2.1 | Declaration of compliance with the order | Manufacturer | General parts with no special requirements |
| 2.2 | Declaration of compliance (non-specific testing) | Manufacturer | Routine structural parts |
| 3.1 | Declaration of compliance with specific testing | Manufacturer's authorised inspector | Most industrial and pressure equipment |
| 3.2 | Declaration of compliance — third-party witnessed | Third-party inspector or customer representative | Nuclear, defence, critical pressure parts |
2. Fields you must verify on an MTC
- Heat or cast number: unique per batch and the only key to melt records
- Grade and standard: both the commercial name (e.g. Inconel 625) and the specification (ASTM B443 / UNS N06625)
- Heat analysis: the actual chemistry of that heat, element by element with measured values
- Mechanical properties: tensile, yield, elongation and hardness, with sampling direction and heat treatment condition stated
- Heat treatment record: solution/ageing temperature, holding time and cooling method
- NDT: acceptance level and results for UT, ET or PT
- Dimensions and weight: size, piece count and weight for goods-in checking
- Referenced standards: special requirements such as NACE MR0175 or ASME SB-443
- Signature or stamp of the authorised signatory plus date
- Certificate number: enables later verification and re-testing
3. Common fraud and risk points
- Heat number on the certificate does not match the stamp or label on the goods — the most frequent issue; check every piece on receipt
- Only specification ranges are listed with no measured values: the batch chemistry cannot be evidenced
- Mechanical properties given without the heat treatment condition: data cannot be matched to design conditions
- Illegible copies, missing pages or missing signature: request the original or manufacturer e-verification
- Certificate type below the order requirement — for example 2.2 supplied where 3.1 was specified
4. Hangbo's certification capability
Hangbo issues EN 10204 3.1 mill test certificates. Independent inspection by the customer or third-party bodies (SGS, BV, LR, DNV, TÜV and others) can be arranged on request. Every certificate is traceable by heat number through melting, forging, heat treatment and inspection records.
Frequently asked questions
What is the core difference between EN 10204 3.1 and 3.2?
3.1 is issued by the manufacturer's own authorised inspector with testing done in-house; 3.2 is witnessed and signed by an inspection body independent of the works or by the customer's authorised representative. 3.2 carries higher independence and credibility and is normally required for nuclear, defence and critical pressure equipment.
Which certificate should I request when purchasing?
3.1 is sufficient for general industrial equipment and routine pressure parts. Specify 3.2 and name the witnessing body for nuclear, defence, subsea pipelines, critical pressure vessels or wherever the owner's specification demands it.
What is the heat number on a certificate for?
The heat number is the unique identifier for traceability. Through it you can trace back to the melt, the original chemistry records, the forging and heat treatment batches and the corresponding NDT reports. When a quality dispute arises, the heat number is the basis for determining responsibility.