How do you know whether the steel you have ordered truly meets the standard specification and grade you specified?

You may hope that the mill test certificate will verify grade compliance and that the mechanical and chemical composition properties reported are reliable.

However unless the steel manufacturer uses a testing laboratory that is accredited by a recognised testing body, the mill test certificate should be treated with caution.

Particular care should be exercised when a mill test certificate claims compliance with multiple and varying international specifications and grades.

A reliable mill test certificate will typically show that it has been prepared by a testing laboratory accredited by a signatory to the International Laboratories Agreement Cooperation (ILAC) through their Mutual Recognition Agreement (MRA) or a Ships Classification Society.

The ILAC Arrangement provides significant technical underpinning to the international trade in engineering products. The key to the Arrangement is the developing global network of accredited testing and calibration laboratories that are assessed and recognised as being competent by ILAC Arrangement signatory accreditation bodies. The signatories have, in turn, been peer-reviewed and shown to meet ILAC’s criteria for competence.

International Accreditation New Zealand (IANZ) is the New Zealand ILAC MRA signatory and the National Association of Testing Authorities (NATA) is the equivalent body in Australia. A full listing of signatories may be downloaded at the ILAC website.

Compliance with a standard specification and grade of steel is no easy matter, and requires a steel mill to show product conformance through the use of consistent raw material inputs, manufacturing processes and settings, backed up by scientifically robust testing methods and records. It is not simply a matter of showing that a mill test certificate shows results within the bounds of a particular standard specification.

The mill test certificate is a single piece of evidence of compliance with a particular specification and grade. It gains importance in the context of the population of tests that have built up the evidence of the mill’s ability to produce steel conforming to that grade. On its own it does not prove grade compliance.

The reliabile history of a steel mill to produce steel to a specification and grade as attested to by an appropriately recognised testing laboratory is what makes the mill test certificate compelling evidence.