Material certs are documents that show the chemistry, mechanical properties, and specification of the raw material used to make your parts, traced back to the mill heat. The most common is the mill test report, and buyers often pair it with a certificate of conformance from the machine shop stating that the parts were made from that documented material.
For regulated, defense, or safety-related parts, material traceability is part of acceptance. This page explains the common types of material certs, what each contains, and how heat-lot traceability connects the cert to the finished part.
Common types of material certs
| Document | Issued by | What it shows |
|---|---|---|
| Mill test report (MTR) | Producing mill | Heat number, chemistry, mechanical test results, specification |
| EN 10204 3.1 certificate | Mill, with independent inspection department sign-off | Actual test results for the specific heat or lot |
| EN 10204 2.1 or 2.2 | Manufacturer | Statement of compliance, with or without non-specific test results |
| Certificate of conformance (CoC) | Machine shop | Parts conform to the drawing and PO requirements |
| DFARS specialty metals statement | Mill, distributor, or shop | Melt origin compliant with DFARS 252.225-7009 |
| Outside processing certificate | Heat treater, plater, or finisher | Process, specification, and results for that operation |
What is on a mill test report
A mill test report identifies the material by grade and specification, such as ASTM A276 for stainless bar or AMS specifications for aerospace alloys. It lists the heat number, the product form and size, the chemical analysis, and mechanical properties such as tensile strength, yield strength, elongation, and hardness. Depending on specification, it may also show grain size, heat treatment condition, and country of melt.
Heat-lot traceability
A cert only matters if the material in your parts can be traced to it. Heat-lot traceability means the shop records which heat of material was used for each job, keeps the MTR on file, and can connect every shipped part to that heat. Good practice includes:
- Recording the heat number when material is received and verifying it against the MTR.
- Keeping heats separated in storage and on the shop floor.
- Carrying the heat number on the job traveler through machining and outside processing.
- Referencing the heat number on the CoC and packing documentation.
When to require material certs
Most buyers of industrial machined parts request material certs as a standard line on the PO. They are especially important for pressure-containing parts, structural parts, defense and government parts, parts made from high-nickel alloys or titanium, and any part where the material specification is called on the drawing. If your contract flows down DFARS specialty metals or Buy American clauses, state it on the RFQ so compliant material is quoted.
Reading a cert against your drawing
- Confirm the grade and specification match the drawing callout.
- Check the condition, such as annealed, solution treated, or T6.
- Confirm the product form and size are consistent with the part.
- Check that mechanical properties meet the specification minimums.
- Match the heat number to the one on the CoC.
Material certs and outside processing
When parts go to heat treat, plating, or passivation, the processor issues its own certificate. That certificate should reference the specification, the lot or job number, and the results, such as hardness after heat treat or thickness after plating. The machine shop keeps the processor certificate with the job record and ties it to the same heat number as the material. For the buyer, the complete record for a lot is typically the mill test report, the processor certificates, the inspection report, and the shop's certificate of conformance. Keep these records with the part lot, since they are often requested again during audits or failure investigations.
Material certs at Wexmar
Wexmar machines carbon and alloy steels, 300 and 400-series and PH stainless, Nitronic 50, Inconel, Monel, Hastelloy, aluminum, brass, bronze, copper, titanium, and engineered plastics. Material certs and heat-lot traceability are available, and DFARS 252.225-7009 specialty-metals-compliant sourcing is available on request. Certificates from outside processors for heat treat, plating, or passivation are passed through with the shipment. See our materials and inspection and quality pages.
Material cert checklist for your RFQ
- Material specification and condition on the drawing.
- MTR or EN 10204 3.1 requirement stated on the RFQ.
- CoC requirement stated.
- DFARS or Buy American sourcing requirement stated if applicable.
- Outside processing certs required with shipment.
Getting a quote
List your cert requirements with the drawing so they are priced from the start. You can upload a drawing for an instant estimate or call (315) 400-2654 to confirm documentation requirements.