How to read a mill test certificate

TL;DR

• It is the steel maker's record of one batch: its chemistry and its strength.
• The heat number ties the certificate to the metal in front of you.
• EN 10204 type 3.1 is the type most often asked for.

What it is

A mill test certificate (MTC), also called a mill test report, comes from the mill that made the steel. It records the tests on one batch, called a heat.

It lets a buyer confirm that the material matches the grade and standard on the order.

A certificate is only as good as the heat number that ties it to the steel.

What it shows

Four entries carry most of what a buyer needs.

• Heat number: the batch the steel was poured in, also marked on the material.
• Grade and standard: what the steel was made to, such as IS 2062 E250.
• Chemical composition: the share of carbon, manganese and other elements.
• Mechanical properties: yield strength, tensile strength and elongation.

The EN 10204 types

EN 10204 sets out four kinds of document. Types 2.1 and 2.2 are the maker's declaration, without test results from your own batch.

Type 3.1 carries results from the batch supplied, signed off by the mill's own inspector, who is independent of production. Type 3.2 adds an outside inspector.

Four checks

Before the steel is cut, look at four things.

• Heat number: the same on the certificate and on the steel.
• Grade: the one the drawing or order names.
• Values: each inside the limits of the standard.
• Type: 3.1 or 3.2, as the order asked.