How to Read a Steel Mill Test Certificate (MTC)

A Mill Test Certificate (MTC, sometimes called a mill certificate or test report) is your proof that the steel you received is the grade you paid for. Here is how to read one.

What it is

A document issued by the steel manufacturer recording the chemical composition and mechanical properties of a specific production batch, identified by a heat number.

The key sections

1. Heat / batch number

The unique ID of that melt. It should be traceable back to the material you received — often stamped or marked on the product.

2. Grade and standard

Confirms the grade (e.g. SS 304) and the standard it was made to. Check this matches your order exactly — 304 and 304L are not the same thing.

3. Chemical composition

Percentages of key elements. For stainless, the ones that matter most:

• Chromium (Cr) — around 18% in 304; the source of corrosion resistance
• Nickel (Ni) — around 8% in 304; much lower in 202
• Molybdenum (Mo) — around 2% in 316, essentially absent in 304
• Carbon (C) — lower in 304L, which improves weldability

This section is how you can tell whether you actually received 304 or a cheaper grade.

4. Mechanical properties

Tensile strength, yield strength, elongation and sometimes hardness — relevant for structural work.

What to check when you receive one

1. Does the grade match your purchase order?
2. Does the heat number correspond to the delivered material?
3. Is molybdenum present if you ordered 316?
4. Is nickel at the expected level if you ordered 304?
5. Is the certificate from the mill, not just a typed dealer note?

When you should insist on one

Structural work, coastal and pool projects, commercial contracts and anything where a rust failure would be expensive. This is how you avoid paying for 304 and receiving 202.

Kiran Steel India provides grade certificates on request.