In most projects, nobody complains about heat numbers and material traceability—until something goes wrong.
A missing heat stamp, a mismatched certificate, or a mixed bundle can turn a simple delivery into an NCR, a rework job, or a serious safety risk. For QA/QC and vendor inspectors, heat numbers and certificate matching are the backbone of material traceability.
This guide explains, in practical QA/QC language:
- What heat numbers are and how they’re used
- How different levels of traceability (lot, piece-mark, piece) actually work
- What your Mill Test Certificates (MTCs) must contain for traceability
- A step-by-step method to match heat numbers, certificates and items
- Typical nonconformities and how to fix them
- How digital tools and QR codes are changing material traceability
Quick Answer – What Are Heat Numbers and Why Do They Matter?
A heat number is a unique identifier assigned to a batch of metal produced in one melting operation at the mill. Think of it as the DNA of your material:
- It links a physical plate, pipe, forging or bar back to one specific melt or “heat” at the steel mill.
- It appears both on the physical item (stamp, stencil, tag) and on the MTC/MTR for that heat.
- Through the heat number, you can find the chemical composition, mechanical properties, heat treatment and test results recorded on the certificate.
Material traceability means you can follow a material:
- From supplier and heat
- Through receiving inspection and storage
- Into fabrication, welding, assembly and installation
and prove at any time that the item installed in a system corresponds to a particular heat and certificate.
Certificate matching is the QA/QC act of:
- Checking that the heat numbers and descriptions on the MTC
- Match the heat numbers and markings on the physical items
- And match the PO line item, drawing and project spec
If any link is broken, your traceability is broken.
How Heat Numbers Are Created and Used in Practice
From Melt to Heat Number
At the mill or foundry:
- A batch of steel is melted and cast – this batch is the heat.
- The heat is given a heat number (for example 713845, or a longer alphanumeric code).
- As the heat is processed into plates, pipes, bars or forgings, the heat number is carried forward into production records and certificates.
When the mill issues an MTC/MTR for an order, each line in the certificate table is tied to a heat number, with associated:
- Material grade and product form
- Dimensions and quantity
- Chemical analysis and mechanical test results
- Heat treatment information and sometimes NDE results
Heat, Lot, Batch – Why the Terminology Matters
In projects you’ll also see:
- Heat number – tied to the melting operation.
- Batch / lot number – tied to a grouping for manufacturing or shipping (a subset of a heat, or a combination of heats).
- Coil or plate numbers – internal identifiers for particular products from that heat.
Understanding these distinctions is critical when you interpret certificates and trace materials through fabrication.
Levels of Material Traceability (Heat, Lot, Piece-Mark, Piece)
Not all projects require the same level of traceability. Typical levels include:
- Heat / lot traceability
- You can say: “All these plates or pipes come from heat 713845.”
- Suitable for many structural and non-critical applications.
- Piece-mark traceability
- Each fabrication drawing has piece marks (for example B12-01, B12-02).
- Each piece mark is mapped to one or more heat numbers in a traceability register.
- You can say: “Piece B12-01 is made from plate P-002, heat 713845.”
- Full piece traceability
- Each individual item (valve body, forging, fastener, etc.) has a unique ID or serial.
- That ID maps to a single heat (or combination for welds/cladding).
- Required for pressure-retaining items, critical bolting, safety-related hardware and regulated equipment in many industries.
The right level is defined by:
- Codes and standards (for example API 20E bolting, ASME requirements)
- Project specification and risk level
- Client and regulatory expectations
As an inspector, you need to know what traceability level the project demands, so you can judge whether the supplier’s system is adequate.
What Must Be on the Certificate for Traceability to Work
For heat numbers and traceability to mean anything, the MTC itself must support them.
A good MTC typically includes:
- PO number and line item
- Manufacturer name and works location
- Product description and form (plate, pipe, bar, forging…)
- Grade and referenced standards/editions
- Dimensions and quantities
- Heat or batch numbers and clear mapping to delivered items
- Chemical composition and mechanical properties, plus impact/hardness/NDE where required
- EN 10204 certificate type (3.1 or 3.2) and signatories
- Certificate ID, issue date, page count and any attachments
For a detailed breakdown of what to expect and how to check it in the context of EN 10204, see
EN 10204 3.1 vs 3.2: Differences Explained.
For a deeper, step-by-step approach to reading and verifying MTCs, use the
MTC Interpretation Guide + Checklist (PDF).
If the certificate is weak (missing heat mapping, wrong standard, incomplete tests), you cannot build reliable traceability on top of it.
Step-by-Step – How to Match Heat Numbers, Certificates and Items
This is the practical part: how to do certificate matching during receiving inspection or vendor visits.
Step 1 – Start from the PO and Item List
Before you look at steel:
- Take the PO and line item list.
- Note the material grade, dimensions, standards and project spec references.
- Check whether the project or PO calls for a particular EN 10204 certificate type.
This tells you what you should expect to see on the certificate and on the delivered items.
Step 2 – Find the Heat Numbers on the MTC
On the MTC:
- Locate the table where the heats are listed.
- Each row should show:
- Heat number
- Product description and dimensions
- Quantity
- Test results linked to that heat
If several heats are listed on one MTC, there must be a clear mapping between each heat and the quantities shipped.
If the heat number format is long or coded, keep the certificate handy when you go to the material.
Step 3 – Check Heat Numbers on the Physical Material
On the material itself:
- For plates and pipes, look for stamped or stencilled markings along the edge or body.
- For bars and small items, look for tags, bands or labels.
- For finished components (valves, fittings, forgings) you may see:
- Casting numbers
- Heat numbers
- Serial IDs that must be mapped to heat numbers via a manufacturer’s traceability list.
If the vendor has used an internal short code instead of the full heat number, ask them for the heat mapping document that links these short IDs to the full heat numbers on the MTC.
Any item without a legible marking or reliable mapping is, from a QA/QC perspective, orphaned until traceability is restored.
Step 4 – Match Heat → Item → Certificate
For each lot or bundle:
- Match the physical markings (heat or short ID) to the heat numbers or IDs on the MTC.
- Confirm that the dimensions, grade and product form on the MTC match the actual items and the PO line.
- Where drawing or piece-mark numbers exist, ensure there is a traceability register mapping:
- Piece mark or tag → plate or pipe ID → heat number → MTC ID.
If you are using an incoming inspection form (for example, the template described in the article Incoming Inspection Form Template (XLSX/PDF)), record:
- MTC IDs and heat numbers
- Which packages, plates or pipes correspond to which heats
- Any gaps or doubts in the mapping
Step 5 – What to Do When Things Don’t Match
Common mismatch scenarios include:
- Heat number on material doesn’t appear on the MTC
- MTC lists multiple heats, but packages are not labelled to show which is which
- Material is marked with a lot number only, with no link to the heat number
- Nameplate or tag shows a different grade or standard than the certificate
In these cases, good practice is to:
- Stop and segregate the affected items (do not mix with accepted stock).
- Request a corrected MTC or clear mapping document from the manufacturer.
- If necessary, perform PMI testing or extra mechanical tests to re-establish confidence in the material.
- Raise an IR or NCR where traceability cannot be proven or where tests show nonconformity.
For the technical and documentation side of this process, see:
Typical Nonconformities in Heat Numbers & Traceability (And How to Fix Them)
Here are some of the most common heat and traceability nonconformities seen in vendor and receiving inspections:
- Heat numbers on MTC and material don’t match
- Risk: you cannot be sure the tested heat is the one installed.
- Fix: corrected MTC referencing the actual heat mark, or re-marking material plus proper certificate issuing; NCR as required.
- Mixed heats in one bundle without identification
- Risk: good and bad heats may be used together; traceability destroyed.
- Fix: split and re-identify the bundle by heat, update documentation; use AQL or extra sampling and tests if there is any doubt.
- Missing or illegible heat markings
- Risk: orphaned items with no link to any certificate.
- Fix: attempt reconciliation via dimensional checks, PMI and vendor records; if successful, re-mark with the correct heat and document; if not, scrap or treat as nonconforming stock.
- Wrong standard or edition on the MTC vs PO
- Risk: tests might not meet the actual project requirements.
- Fix: request re-documentation or re-testing to the correct standard or edition as defined by the project specification.
- Internal short codes without clear mapping
- Risk: mapping depends on undocumented vendor knowledge; not auditable.
- Fix: require a heat mapping list that ties every short ID to a heat number on the MTC, and file it in the dossier.
A disciplined use of checklists—such as those in the MTC Interpretation Guide + Checklist (PDF)—greatly reduces both the frequency and impact of these nonconformities.
Digital Material Traceability – From Hand-Stamps to QR Codes
Many mills and fabricators are moving beyond hand-stamped heat numbers and paper logs. While the basic principles of traceability haven’t changed, digital tools are changing how they’re implemented:
- Barcodes and QR codes on tags or plates that encode heat number, grade and PO
- Digital MTCs linked directly to ERP or QMS records instead of scanned PDFs in random folders
- Traceability registers maintained in structured databases rather than spreadsheets passed around by email
The benefits:
- Faster and more reliable retrieval of MTCs during inspections and audits
- Reduced risk of transcription errors when heat numbers are copied by hand
- Easier integration of material data into AQL sampling, NCR reporting and supplier KPIs
The risks:
- Over-reliance on systems without proper validation and backups
- Poor data entry still leading to garbage-in/garbage-out situations
- Cybersecurity concerns when supplier data is cloud-based
Digital traceability doesn’t change your responsibility as QA/QC or inspector; it just gives you better tools—as long as you verify that the data behind them is correct.
How Heat Numbers & Traceability Fit into the NTIA QA/QC Toolkit
Heat numbers and certificate matching are not standalone tasks. They form part of a wider QA/QC and vendor inspection system:
- Certificate verification and red flags:
- Sampling and incoming inspection:
- Verification testing when documentation is not enough:
- The article PMI Testing: What, When & How to Document, for using PMI as a final traceability check.
- Nonconformity and dossier control:
- Standardised templates and registers:
Used together, these tools turn heat numbers from “numbers on steel” into a coherent traceability system that survives audits and supports safe, efficient operation.
Make Heat Numbers Truly Traceable in Your Projects
If you want heat numbers and MTCs to do more than just fill folders:
- Standardise your MTC checks
- Use a checklist-based approach for every receiving inspection.
- Clarify what certificate types and content you expect in your POs and ITPs.
- Tighten your incoming inspection forms and logs
- Always record heat numbers, MTC IDs and any mapping files.
- Make it easy to trace from an installed item back to its certificate.
- Treat traceability failures as serious NCRs
- Segregate any orphaned or mismatched items.
- Restore traceability through documentation and/or testing, or reject.
- Plan your move towards digital traceability
- Start with structured Excel or database registers.
- Gradually integrate barcodes, QR codes and digital MTC management.
By integrating these practices into your NTIA-based workflows—MTC checklists, incoming inspection forms and master QA/QC templates—you turn “checking heat numbers” from a stressful last-minute scramble into a routine, auditable part of your QA/QC system.
