Reading a mill certificate

Most buyers file the certificate and never read it. That is usually fine, and occasionally expensive. Here is what each part means.

The heat number

This identifies the melt. Everything else on the page describes that melt, so if the heat number on the certificate does not match the stamp on the material, nothing else on the document applies to what you received. Check this one.

Chemistry

The elements that matter depend on the grade. For commercially pure titanium the number to watch is oxygen: it raises strength and lowers ductility, and a Grade 2 near the top of its oxygen range will form differently from one near the bottom even though both are in specification.

Mechanical results

Tensile and yield strength are reported from actual test pieces, not from a table. A result far above the minimum is not automatically good news — it can mean the material will be harder to form than you planned for.

What 3.1 means

It means the results were certified by the manufacturer's own inspection department, independent of the production department. A 3.2 certificate adds a third-party inspector. For most orders 3.1 is what you want and what you get.