A mill test report — also called a mill test certificate or material test report — is the mill's sworn statement that a specific heat of steel was made, tested and found to meet a specification. Every inspector, QA engineer and auditor will ask for it. Here is how to read one in under two minutes.
1. Header: who, what and which standard
Check the manufacturer, the product description and the specification and grade — for example API 5L X52 PSL2 or ASTM A106 Gr. B. Dual-certified material lists every standard it meets. Make sure the one on your purchase order is there.
Look for the inspection document type under EN 10204. A 3.1 certificate is issued by the manufacturer's authorized inspection representative, independent of production. A 3.2 adds verification by a third-party or purchaser's inspector.
2. Heat number: the traceability key
The heat number links the paper to the steel. It must match the stencil or stamp on the pipe, flange or fitting. If it does not match, the MTR does not belong to that material — full stop.
3. Chemical analysis
The chemistry table lists elements by weight percent: carbon, manganese, phosphorus, sulfur, silicon and micro-alloys such as niobium, vanadium and titanium. Compare each against the specification maximums. For weldable grades, check the carbon equivalent (CE) — PSL2 line pipe has CE limits that affect weldability.
4. Mechanical properties
- Yield strength — must meet the grade minimum (and maximum, for PSL2 and sour grades).
- Tensile strength — within the specified range.
- Elongation — minimum percentage per the specification.
- Yield-to-tensile ratio — limited for PSL2 line pipe.
5. Toughness and hardness
Charpy V-notch (CVN) impact results show absorbed energy at a stated test temperature. PSL2 line pipe and low-temperature flanges require them. For sour-service material, the hardness results are critical — check them against NACE MR0175 limits.
6. Hydrostatic and NDE
The MTR should confirm hydrostatic test pressure and duration, and any nondestructive examination performed (ultrasonic, electromagnetic, radiographic) on the weld seam or body.
Common red flags
- Heat number on the MTR does not match the material.
- Grade on the MTR is lower than ordered, or the PSL level is missing.
- Results are blank where the specification requires a test.
- Photocopied or edited certificates with no mill signature or stamp.
At Oltorf, every MTR is reviewed against the order before release and matched to the heat numbers on the material. If you ever receive a document from us that raises one of these flags, call us.