EN 10204 3.1 Material Test Certificates: How to Read a Foundry's MTC

An EN 10204 3.1 certificate for castings is a document issued and validated by the foundry's own quality department, independent of the production line, confirming that a specific batch of parts meets the chemical composition and mechanical properties specified on the purchase order. Reading it correctly, not just filing it, is what separates buyers who catch a bad heat before it reaches assembly from buyers who find out after a failure in the field.

Key Takeaways

• 3.1 means independent validation: the certificate must be signed by a qualified representative separate from the production department, not simply printed by the machine operator.
• Heat number is the anchor: every mechanical and chemical result on the certificate must trace back to a heat or lot number physically stamped on the parts themselves.
• Round numbers are a warning sign: tensile, yield, and impact values that repeat identically across multiple batches usually indicate a template certificate, not actual test data.
• 3.1 differs from 3.2: 3.2 requires validation by an inspector nominated by the purchaser or an official body, which adds cost and lead time that most castings don't need.
• Ask before you order, not after: requesting a sample MTC from a prior batch during supplier qualification catches formatting or traceability gaps before your PO is on the line.

At a Glance: EN 10204 Certificate Types for Castings

Certificate Type	Who Validates It	Typical Use Case	Extra Cost/Lead Time
2.1	Manufacturer (declaration of compliance)	Low-criticality general engineering parts	None
2.2	Manufacturer, with test results shown	Non-critical parts where some data is useful	Minimal
3.1	Manufacturer's authorized inspector, independent of production	Pump & valve, oil & gas, mining, automotive, rail & defence castings	Standard practice, usually built into quoted price
3.2	Manufacturer's inspector plus purchaser-nominated or official inspector	Pressure vessels, nuclear, some defence programs	Adds cost and 1-3 weeks for third-party witness
Heat/lot traceability	Physical stamp cross-referenced to certificate	All 3.1/3.2 certified castings	Included in 3.1 process
Chemical analysis method	Spectrometer (OES) in-house or subcontracted lab	All ferrous and non-ferrous castings	Included
Mechanical test method	UTM, Charpy impact, hardness tester	Structural and pressure-retaining castings	Included

1. Why the EN 10204 3.1 Certificate Matters for Cast Components

EN 10204 is a European standard, but it has become the default reference document type requested by pump, valve, oil & gas, mining, automotive, and railway & defence buyers worldwide, regardless of where the casting is poured. The standard defines four inspection document types: 2.1, 2.2, 3.1, and 3.2. A 2.1 certificate is a simple declaration of compliance, signed by the manufacturer with no test data attached. A 3.1 certificate is validated by someone in the foundry's quality function who is organizationally independent from the manufacturing department, and it must show actual chemical and mechanical test results tied to the specific batch shipped.

That independence matters more than most buyers realize. A production supervisor under schedule pressure has an incentive to pass a batch. A quality manager reporting through a separate chain does not carry the same pressure, which is exactly why EN 10204 3.1 certificate castings are the accepted minimum for pressure-containing and safety-related components across pump, valve, and oil & gas supply chains.

For readers comparing overall supplier reliability rather than just paperwork, our guide on how to qualify an overseas investment casting supplier covers the wider audit process that a strong MTC practice usually sits inside.

2. The Header Block: Order and Traceability Data

Before you look at a single number, check that the header fields tie your specific order to a specific production batch. A properly completed EN 10204 3.1 certificate should show:

• Your purchase order number and line item, matching your internal PO exactly
• The part number and drawing revision, so a design change doesn't slip through unnoticed
• A heat number or lot number, which must also be physically stamped or tagged on the casting itself
• The quantity of pieces covered by that specific heat
• The date of casting and the date of certificate issue

If the heat number on the certificate does not match a stamp you can find on the actual part, the document is disconnected from the metal in front of you. That single gap has caused real recalls: a rail bracket or valve body that fails inspection months later cannot be traced back to its melt, and the entire lot in the field becomes suspect instead of just the bad heat.

3. Chemical Composition: Reading the Spectrometer Results

The chemistry section lists each element in the specified grade, usually carbon, manganese, silicon, phosphorus, sulfur, chromium, nickel, and molybdenum for stainless and alloy steels, alongside the acceptable range from the material specification (ASTM A351, A216, A995, or the equivalent EN standard) and the actual result from that heat. A foundry running its own in-house spectrometer, rather than sending samples out to a third-party lab, can report results within hours of the pour and correct a heat before it moves to the next stage.

Watch for two things here. First, results that sit suspiciously close to the midpoint of the range for every single element on every single certificate, which suggests the numbers were copied rather than measured. Second, missing elements: a certificate for a duplex stainless grade that omits nitrogen content, for example, is incomplete no matter how good the rest of it looks.

4. Mechanical Properties: Tensile, Yield, Elongation, Impact, Hardness

This is the section most sourcing engineers care about most, and it's also where template certificates are easiest to spot. A complete mechanical properties table should report:

• Tensile strength and yield strength in MPa or ksi, from a Universal Testing Machine (UTM), against the minimum required by the material spec
• Elongation percentage, showing ductility rather than just strength
• Charpy impact values at the specified test temperature, critical for oil & gas and low-temperature service castings
• Hardness (Brinell or Rockwell), which correlates with wear resistance for mining and earthmoving components

Real test data has natural variation between heats. If tensile strength reads exactly 520 MPa on ten consecutive certificates for the same grade, that is not a coincidence, it's a copy-paste. Genuine results cluster around a value but shift slightly heat to heat, the way actual metallurgy behaves.

5. Heat Treatment and Process Records

Many casting grades, especially duplex and super-duplex stainless steels used in pump and valve bodies, depend entirely on the heat treatment cycle to achieve their final properties. The certificate should state the heat treatment applied, solution annealing, normalizing, or tempering, along with the temperature and hold time. If the certificate lists a heat treatment cycle that doesn't match what the material specification requires for that grade, the mechanical properties reported elsewhere on the same document become questionable, because grain structure and corrosion resistance are a direct result of that thermal cycle.

6. Signatures, Stamps and Authorized Inspector Details

An EN 10204 3.1 certificate needs a named, qualified signatory representing the manufacturer's quality function, along with a company stamp or seal and the date of signature. This is different from a 3.2 certificate, which additionally requires validation by an inspector nominated by the purchaser, or by an official body such as a classification society. Most industrial castings for pump, valve, general engineering, and mining applications only need 3.1. Reserve 3.2 for pressure vessel components, nuclear-adjacent work, or specific defence programs that explicitly call for third-party witness testing, since it adds both cost and one to three weeks of lead time for scheduling the outside inspector.

7. Red Flags: Signs of a Weak or Falsified MTC

Sourcing engineers who have been burned once tend to develop a checklist. Here is what experienced buyers look for:

• Repeated exact values across multiple certificates for different heats, the clearest sign of a template document
• No heat number stamped on the physical part, breaking the chain between paper and metal
• Certificate issued by a trading company or agent rather than the actual manufacturing foundry, which strips out the independence requirement entirely
• Missing test method standards, such as no reference to ASTM E8 for tensile testing or ASTM E23 for impact testing
• Inconsistent units or grade names that don't match your drawing or purchase order
• No date, or a certificate dated before the casting's actual pour date

Our related article on red flags when sourcing castings from an overseas foundry expands on these signals in the context of a full supplier audit, not just the paperwork.

8. How to Verify and Integrate MTCs into Your Sourcing Workflow

Don't wait for the first shipment to see what a foundry's certificate actually looks like. Ask for a sample MTC from a recent batch of a comparable part during your RFQ stage, before you commit tooling costs. Compare it against a checklist covering every item above. Once a supplier is qualified, build MTC verification into your receiving process rather than treating it as a filing task:

1. Match the heat number on the certificate to the physical stamp on a sample of parts from each pallet, not just one piece
2. Confirm chemical and mechanical results fall within your drawing's callout range, not just the generic material spec range
3. Store the certificate against the part number and heat number in your quality management system, so it's retrievable during a customer audit or a warranty claim years later
4. Flag any certificate with formatting different from prior shipments for a follow-up call with the foundry's quality manager

This is also where a single-source, line-ready machined supply chain saves real administrative time. When the same foundry handles casting and machining, one MTC package covers the whole component instead of two separate documents from two separate vendors that have to be reconciled by hand. Our post on how to choose the right investment casting foundry covers what else to weigh alongside documentation quality when you're narrowing down suppliers.

9. What to Ask Your Foundry Before You Order

A short, direct list of questions during supplier qualification tells you more than a glossy brochure. Ask:

• Is chemical and mechanical testing done in-house, or subcontracted to an outside lab, and what is the turnaround time?
• Who signs the 3.1 certificate, and what is their reporting line relative to production?
• Can you provide a sample certificate for a part in the same grade before we place an order?
• How is the heat number physically marked on parts under 1 kg, where stamping space is limited?
• What happens if a heat fails testing, is it scrapped, re-melted, or does it get separated for a lower-spec application?

Wellmake Technocast operates its own in-house lab in Rajkot, Gujarat, with a spectrometer, Universal Testing Machine, Charpy impact tester, and hardness tester on site, alongside ISO 9001, ISO 14001, and ISO 45001 certification across the plant. Because casting and machining happen under one roof, a single EN 10204 3.1 certificate package covers the finished, line-ready component rather than requiring buyers to reconcile documents from a casting house and a separate machine shop. That matters for pump & valve, oil & gas, mining, automotive, railways & defence, and fire safety buyers who need traceability that holds up under their own end-customer audits, not just a document that looks correct on first read.

For readers evaluating whether in-house testing capability actually changes lead time and reliability, our deep dive on how investment casting works step by step shows where in-process quality checks fit into the eight-stage ceramic shell process, well before the final MTC is even issued.

FAQ

Is an EN 10204 3.1 certificate mandatory for castings?

It isn't mandated by law, but it's the de facto minimum expected for pump, valve, oil & gas, mining, and defence-related castings. Most technical purchase specifications for these sectors reference EN 10204 3.1 explicitly, and buyers who accept 2.1 declarations for critical parts take on traceability risk they usually don't need to accept.

What's the real difference between 3.1 and 3.2 certificates?

Both require test results tied to a specific heat, validated by someone independent of production. A 3.2 certificate adds a second validation step from an inspector nominated by the purchaser or an official body, which is why it costs more and takes longer to schedule. Most industrial castings only need 3.1; reserve 3.2 for pressure vessels or contracts that explicitly specify it.

Can a casting have both EN 10204 3.1 documentation and NACE MR0175 compliance?

Yes, and for sour service oil & gas components these are usually requested together. NACE MR0175 governs material selection and hardness limits for sour service, while EN 10204 3.1 governs how the test results and traceability are documented and signed off. They address different questions and are not substitutes for one another.

Does requesting a 3.1 certificate cost extra?

For most established foundries, 3.1 certification is standard practice built into the quoted unit price rather than a line-item add-on, since the in-house testing infrastructure already exists to support it. Ask your foundry directly during quoting rather than assuming, as practices vary supplier to supplier.

What if my drawing doesn't specify a certificate type?

Default to requesting 3.1 for any pressure-retaining, structural, or safety-related casting. It costs little to nothing extra with a foundry that already runs in-house testing, and it gives you a documented, traceable record if a warranty or field failure question ever comes up.

Reading an EN 10204 3.1 certificate for castings carefully, checking heat numbers against physical parts, confirming test methods, and watching for round-number template data, is one of the fastest ways to catch a quality gap before it becomes a production line problem. If you're evaluating a new casting supplier and want to see what a complete, traceable MTC package looks like before you commit to tooling, explore Wellmake's product range across pump & valve, oil & gas, mining, automotive, and railways & defence components, or get in touch to request a sample certificate from a recent batch in your grade. For buyers still comparing tooling and machining costs before placing a first order, our guide on investment casting tooling costs is a useful next read, and if pricing certainty across quantities is the bigger open question, contact us today to discuss your specific drawing and required certification level.