How to Read a Mill Test Certificate (MTC) for Steel

• Mill name, certificate number and date.
• The standard and grade the steel was made to (for example ASTM A615 Grade 60, ASTM A36 or API 5L Grade B).
• The heat number — the batch of steel the material was rolled from.
• Product, size and quantity or weight covered by the certificate.
• Chemical composition: usually carbon (C), manganese (Mn), phosphorus (P), sulphur (S) and silicon (Si), sometimes with copper, chromium, nickel and a carbon equivalent (CE) value that indicates weldability.
• Mechanical test results: yield strength, tensile strength and elongation, and for rebar a bend test result.
• The mill's stamp or signature. Certificates issued to EN 10204 state their type, for example 3.1.

1. Match the heat number on the certificate to the tags on the bundles, plates or pipes you received.
2. Confirm the standard and grade on the certificate are the ones in your drawings or purchase order.
3. Check that yield and tensile strength are at or above the minimums for that grade.
4. Check that elongation and the bend test meet the standard for that size.
5. Check that chemistry is within the standard's limits, especially phosphorus and sulphur, and the carbon equivalent if the steel will be welded.

• No heat number on the certificate or on the material.
• A heat number on the tags that does not appear on any certificate supplied.
• A certificate for a different standard, grade or size from the one ordered.
• Identical test values on certificates for different heats.
• Copies that are unreadable or have the mill details cut off.

An MTC is issued by the mill. For critical structures, or when the consultant asks for it, samples are also tested by an independent accredited laboratory. Plan this before delivery so samples can be taken from the same heats that are listed on the certificate.