What Is a Heat Number on a Steel Mill Test Certificate?
You receive two steel plates with the same grade, thickness, and dimensions. Their MTCs also look similar.
So how do you know which test results belong to the actual plates you received?
The answer is the Heat Number — the link between production, testing, the Mill Test Certificate (MTC), and the physical steel.
1. What Is a Heat Number in Steel?
A heat number is a unique identification code assigned to a specific batch of steel produced during a single melting operation — known as a "heat."
- ✔ Each heat receives its own number
- ✔ The number links the steel to its chemical composition and production records
- ✔ It appears on the MTC and often on the physical plate marking
- ✔ It is not the same as a plate number
💡 Key distinction: A steel plate may carry several markings at once — Heat No., Plate No., Grade, Thickness, and Manufacturer. These are not the same identifiers.
2. How Is a Heat Number Created?
Raw Materials → Melting → One Heat → Continuous Casting / Ingot → Rolling → Steel Plates → Testing → MTC
During melting, the steel receives its chemical composition. The mill assigns a unique number to that heat. This number then appears in the production and quality documents associated with the plates produced from that heat.
3. What Information Can Be Traced Through a Heat Number?
⚠️ Important: The exact records available for traceability depend on the steel grade, purchase specification, mill quality system, and order requirements. Not every document is traceable through the heat number alone.
4. Where Can You Find the Heat Number?
On the Steel Plate
Markings may include: Grade, Heat No., Plate No., Manufacturer.
On the Mill Test Certificate
Look for: Heat No., Cast No., or Heat Identification.
On Other Quality Documents
Depending on the order: inspection reports, UT reports, impact test reports, HIC test reports, and third-party inspection documents.
5. Heat Number vs Plate Number: What Is the Difference?
- Heat Number — represents the production heat / melting batch
- Plate Number — represents an individual plate or product identification
Example:
Heat No. H12345
→ Plate No. 001
→ Plate No. 002
→ Plate No. 003
→ Plate No. 004
These plates share the same Heat Number but have different Plate Numbers.
6. How to Check a Heat Number Against an MTC
- ✓ Step 1: Find the Heat No. on the MTC
- ✓ Step 2: Check the steel plate marking
- ✓ Step 3: Compare the two numbers
- ✓ Step 4: Check grade and dimensions
- ✓ Step 5: Check the required tests
💡 Key point: Don't check the heat number alone. Check it together with the grade, dimensions, and required test results.
7. Why Is Heat Number Traceability Important for Pressure Vessel Steel?
For grades like SA516 Gr.70, buyers may require more than the grade:
- ✔ Normalized condition
- ✔ Impact testing
- ✔ UT
- ✔ HIC / NACE requirements
- ✔ Supplementary requirements
The link between the MTC and the physical plate becomes more important when additional tests and inspection requirements are involved.
8. What If the Heat Number on the Plate and MTC Do Not Match?
Do not assume the steel is defective. First, pause use or shipment and contact the supplier to verify.
Possible causes:
- ✔ Typing error
- ✔ Plate marking issue
- ✔ MTC revision
- ✔ Multiple heats in the same order
- ✔ Incorrect document attached
- ✔ Re-identification or cutting records
⚠️ Important: A mismatch should be clarified before the material is accepted for a critical application.
9. Heat Number, Cast Number and MTC: Are They the Same?
📌 Note: Terminology can vary between mills and standards. Buyers should check the specific identification system used by the manufacturer.
10. A Simple Steel Plate Traceability Example
Heat No.: H240815
↓
Chemical Analysis
↓
Rolling
↓
Plate No.: P001 / P002 / P003
↓
Mechanical Testing
↓
MTC
↓
Physical Steel Plate
11. What Should Steel Buyers Check on an MTC?
Before accepting the material, check:
- ☐ Heat Number
- ☐ Steel Grade
- ☐ Plate Number / Identification
- ☐ Thickness and dimensions
- ☐ Chemical composition
- ☐ Yield strength
- ☐ Tensile strength
- ☐ Elongation
- ☐ Impact test, if required
- ☐ Heat treatment condition
- ☐ UT, if required
- ☐ HIC/SSC testing, if specified
- ☐ Applicable standard / specification
12. Frequently Asked Questions
❓ What is a heat number in steel?
A heat number is a unique identification code assigned to a specific batch of steel produced during a single melting operation.
❓ Where can I find the heat number on a steel plate?
It is typically marked on the steel plate along with the grade, plate number, and manufacturer's mark. It also appears on the Mill Test Certificate.
❓ Is the heat number shown on the MTC?
Yes. The heat number is a standard field on the Mill Test Certificate and is used to link the certificate to the physical steel.
❓ Is a heat number the same as a plate number?
No. A heat number identifies the melting batch. A plate number identifies an individual plate. One heat can produce multiple plates, each with its own plate number.
❓ Can steel plates from the same heat have different plate numbers?
Yes. Plates rolled from the same heat share the same heat number but receive different plate numbers for individual identification.
❓ Why is heat number traceability important?
Heat number traceability links the physical steel plate to its production and test records. This is especially important for pressure vessel and critical applications.
❓ What should I do if the heat number on the plate does not match the MTC?
Pause use or shipment and contact the supplier to verify. Possible causes include typing errors, plate marking issues, MTC revisions, or incorrect document attachment. A mismatch should be clarified before acceptance.
13. Final Thoughts
A heat number may look like a small code on a steel plate or MTC, but it plays an important role in material traceability.
For buyers, checking the number against the physical plate and the MTC is a simple step that can help avoid documentation and identification problems later.
💡 Our view: When purchasing pressure vessel, structural, marine, or other carbon steel plates, clear material identification and complete MTC documentation should be confirmed before shipment.
📚 Further Reading & Related Content
- 🔗 How to Read a Steel Plate Mill Test Certificate (MTC)
- 🔗 Heat Analysis vs Product Analysis: What Is the Difference in Steel?
- 🔗 Q345R vs SA516 Grade 70 – Comparison Guide
- 📄 ASTM A20/A20M, ASTM A516/A516M, GB/T 713.2-2023
Need Steel Plates with Full Traceability?
CEHE STEEL supplies carbon steel plates with complete MTC documentation, including heat number traceability. Send us your specification — we'll confirm the material identification and inspection records before shipment.