A mill cert tells you what's actually in the metal and how it tested. If your customer, inspector or engineer asks for one, you need it tied to the exact pieces you used. Mill certs are available on request with our material. The key is to ask for them when you request the quote, because traceability is hard to rebuild after the metal is cut.
What an MTR is
A mill test report, also called a material test report or MTR, is the document the producing mill issues for a batch of metal. It lists the specification the material was made to, such as ASTM A36, A500 Grade C or B209 for aluminum sheet, along with the chemical composition and the mechanical test results: yield strength, tensile strength and elongation, sometimes hardness or impact values.
A certificate of conformance is different. It states that material meets a specification, without the actual test numbers. Many jobs accept one. Anything with a weld procedure, pressure boundary or customer inspection usually wants the real MTR.
Heat numbers and lots
Steel is made in heats, one melt of metal cast together. Every piece from that heat carries the same heat number, stenciled or stamped on the bar, plate or tube, and the MTR references it. Aluminum works the same way with lot or cast numbers. The heat number is the link between a physical piece and its paperwork. Without it, a cert is just a sheet of paper about some metal somewhere.
EN 10204 3.1 in plain terms
EN 10204 is a European standard that grades inspection documents, and it's widely used in the U.S. oil, gas and process world. A 2.1 is a declaration that the product complies, with no test results. A 2.2 adds typical test results, not from your specific material. A 3.1 is the one most buyers mean: an inspection certificate from the manufacturer with test results from the actual heat or lot, signed by an inspection representative independent of production. A 3.2 adds sign-off by a third-party or purchaser's inspector, which has to be arranged before the material is made.
When you need certs
- Pressure piping, vessels and skids built to code
- Structural work where the engineer or inspector asks for material records
- Oilfield parts, especially anything going into sour service
- Aerospace, defense and medical machining, where the customer's PO calls for traceability
- Any job where you'll need to prove what grade you used if something fails
How certs follow cut pieces
When a bar or plate is cut into pieces, the heat number stamped on it ends up on one piece at most. Traceability survives only if the heat number is transferred to each cut piece, or the pieces are bagged and tagged by heat, at the time of cutting. That's why it has to be requested up front. Once pieces from mixed heats sit on your rack unmarked, no one can say which cert goes with which part.
When you ask for cut-to-size material with certs, we arrange heat marking on the pieces and send the matching MTRs with the order. Add it to your RFQ as one line: "MTRs required, heat numbers marked on each piece."