What Is an MTC?
A Material Test Certificate — commonly called an MTC, Mill Certificate, or Test Report — is the document that proves the stainless steel you received is what you ordered. In quality-critical industries like pharmaceutical, chemical, food processing, and oil and gas, an MTC is mandatory. Even for general engineering, a good MTC protects you if the material ever fails in service.
An MTC certifies:
- The chemical composition of the heat from which your bars were produced
- The mechanical properties (tensile strength, yield strength, elongation)
- The standard the material conforms to
- Traceability information — heat number, size, quantity
The key word is heat. A heat is a single melting batch — typically 6 to 30 tonnes of steel produced in one furnace cycle. Every bar produced from a single heat has the same chemistry. The MTC represents that.
The Heat Number — Most Important Field
The heat number (also called charge number or cast number) is the unique identifier of the melting batch. Every bar should be tagged or stamped with the heat number. When you receive material, check that the heat number on the physical bars matches the heat number on the MTC.
If they do not match — stop. Do not use the material until the discrepancy is explained and resolved.
The heat number gives you full traceability. If a component fails in service two years later, you can trace it back to the exact heat, the exact chemistry, and the exact production batch.
Chemical Composition Section
This is the core of the MTC. It shows the actual percentage of each element in the steel, as measured by the manufacturer's spectrometer (SPECTRO or OES analysis).
For each element, compare the actual value against the standard limits:
For SS304 per ASTM A276:
| Element | Standard Limit | What to Check |
|---|---|---|
| Carbon (C) | 0.08% max | Must be at or below 0.08% |
| Manganese (Mn) | 2.00% max | Must be at or below 2.00% |
| Silicon (Si) | 0.75% max | Must be at or below 0.75% |
| Chromium (Cr) | 18.00–20.00% | Must be within this range |
| Nickel (Ni) | 8.00–10.50% | Must be within this range |
| Phosphorus (P) | 0.045% max | Lower is better |
| Sulfur (S) | 0.030% max | Lower is better |
For SS316 per ASTM A276, additionally check:
| Element | Standard Limit | What to Check |
|---|---|---|
| Molybdenum (Mo) | 2.00–3.00% | This is the key element — must be present |
| Nickel (Ni) | 10.00–14.00% | Higher than SS304 |
For SS316L, additionally check:
Carbon (C) must be 0.030% maximum. If your MTC shows carbon above 0.030% for material labelled SS316L, the material is not genuine SS316L. Reject it.
Mechanical Properties Section
This section shows the results of tensile testing performed on a sample from the heat.
| Property | SS304/SS316 Minimum (ASTM A276) |
|---|---|
| Ultimate Tensile Strength | 515 MPa |
| 0.2% Proof Strength (Yield) | 205 MPa |
| Elongation in 50mm | 40% |
Check that all three values meet or exceed the minimums. If any value is below the minimum, the material does not meet the standard.
Standard and Specification Reference
The MTC should state which standard the material is certified to. Common standards you will see:
- ASTM A276 — Standard for stainless steel bars and shapes (most common for round bars, hex bars, square bars)
- ASTM A479 — Standard for stainless steel bars for boilers, pressure vessels, and general service
- IS 6911 — Indian Standard for stainless steel bars and flats
- EN 10088 — European standard for stainless steel
Check that the standard cited on your MTC matches what you specified in your purchase order.
Size, Quantity and Manufacturer Details
The MTC should state the size (diameter or dimensions) and quantity (number of bars, weight in kg) to which it applies. Verify this matches your delivery. The MTC should clearly show the name and address of the steel manufacturer.
Red Flags — When to Question an MTC
Be cautious if:
- Heat number on MTC does not match heat number on material tags
- Chemistry values are "round numbers" — real SPECTRO results have decimal precision (e.g., Cr: 18.42%, not Cr: 18.00%)
- Molybdenum (Mo) is absent or shows zero on a document claiming SS316
- Carbon shows 0.08% exactly on a document claiming SS316L (the L grade limit is 0.030%)
- The MTC has no manufacturer address or certification details
- You cannot cross-reference the heat number with the manufacturer
Verify at Source
A legitimate manufacturer's MTC will show actual heat chemistry with full decimal precision from their SPECTRO analyser. If you ever want to verify a Navkardeep Steel MTC, contact us directly with the heat number at steel@navkardeep.com.
Every consignment from Navkardeep Steel includes a full MTC with SPECTRO-verified chemistry. No additional charge. No request needed — it comes with every order.