How to Read a Mill Test Report Without Getting Lost
A certificate is not a quality pass. It is a set of specific measurements against a specific specification. Here is how to check the three things that actually matter.
Check one, two and three
Most disputes about material documentation come from a buyer accepting a certificate without checking that it answers three specific questions. These are the three.
- Is the heat analysis against the standard you ordered? A certificate quoting the right elements but against a different specification proves nothing. Check the standard number and edition, not just the grade name.
- Are the mechanical properties measured on your section size? Yield strength falls as section increases. A minimum quoted for a small bar says nothing about a large forging.
- Are the product form and the condition what you specified? Solution annealed and aged material are different products with different certificates. A certificate for the right alloy in the wrong condition is not a certificate for your order.
The columns that tell you how the material was made
Modern certificates separate the heat analysis from the product analysis. The heat analysis comes from the ladle and represents the melt. The product analysis is taken from the finished material and carries permitted variations. For anything where segregation matters — large forgings, heavy sections, or grades prone to centreline segregation — the product analysis is the number that reflects what you will machine.
What a supplementary requirement adds
EN 10204 Type 3.1 certification means the inspection document was verified by an independent party. Type 3.2 means it was additionally witnessed by an inspection body acting on your instruction. Neither is a quality grade — both describe who checked the paperwork, not how good the material is. If your customer requires 3.2, ask for it on the order rather than after the goods are made.
Traceability is the part worth insisting on
Heat number continuity is what lets a problem be traced. The heat number on the certificate should appear on the material, on the cutting list and on the parts. When a customer asks for a document package years later, this chain of numbers is what makes the answer possible. It is much easier to insist on at order stage than to reconstruct afterwards.