The MTR is the birth certificate of the steel you are welding. Without it, you cannot confirm that the base metal on the shop floor matches the base metal specification written into your WPS — and a WPS that does not match the actual material is not a valid procedure. Every CWI who has walked into a fabrication shop mid-project has seen steel stacked without MTRs in reach. Making that a correctable nuisance rather than a costly shutdown requires understanding what the MTR must contain, how it connects to the WPS, and what the inspection hold points are.
Why the MTR-to-WPS connection matters
AWS D1.1:2025 permits two paths for WPS qualification: prequalified and procedure-qualified. Both paths start with the same requirement — the base metal must be an acceptable specification.
For prequalified WPS procedures, AWS D1.1 defines which base metals are permitted directly. If your WPS says SMAW on A36, the MTR must confirm the material is ASTM A36. If the MTR shows A1011 Grade 50 sheet steel, that material may not qualify on the same prequalified WPS. The wrong material means the wrong minimum preheat, the wrong filler metal group, and possibly a joint type that is not prequalified for that base metal.
For procedure-qualified WPS procedures, the PQR records the actual base metal specification tested. When you run production welds, the production base metal must fall within the qualified base metal group. The MTR is the document that proves it does.
What a complete MTR must show
A structurally adequate MTR covers five areas:
Identity
- Mill name and location
- Heat number (unique to the melt)
- Lot or coil number when applicable
- ASTM or other specification designation (e.g., ASTM A572/A572M Grade 50)
- Thickness, width, and product form (plate, W-shape, HSS)
Chemistry
The certified ladle analysis lists every required element plus any supplemental elements. For high-strength steels, carbon equivalent (CE) is often calculated from the ladle chemistry using the IIW formula. That CE number feeds directly into the preheat calculation on your WPS.
Mechanical properties
Tensile strength, yield strength, and percent elongation from the tension test. For fracture-critical members that invoke Table 6.8 supplementary essential variables, Charpy V-notch (CVN) energy values at the required test temperature must also appear.
Heat treatment record (when applicable)
A913 Grade 65 and other thermomechanically treated steels include the treatment condition (TMCP or QT). That condition is an essential variable under Table 6.6 — a different heat treatment on the same base metal can trigger requalification.
Certification statement
A physically or digitally signed statement that the material meets the cited specification, from the certifying laboratory or the producing mill. A photocopy of a photocopy that cannot be traced to a specific heat number is not adequate for audit purposes.
Tracing the MTR to the material in the shop
An MTR that sits in a binder on the QC manager's desk but cannot be connected to the steel on the fit-up table is not serving its function. The traceability chain runs from the MTR to the physical material through the heat number.
Mill stencil check. Every structural shape and plate product has the specification designation, grade, and heat number stenciled at the mill. When material arrives, receiving inspection should verify the stencil matches what is on the purchase order and MTR. Missing stencils should be flagged before the material enters the cutting queue.
Cut list tracking. When the shop cuts pieces from a plate or shape, the heat number must follow the cut pieces. Some shops stencil the heat number on every piece; others maintain a cut log that links each piece number to the original heat. Either method is acceptable as long as the trail is unbroken from MTR to finished weld joint.
Weld map integration. A weld map ties each joint on the fabricated assembly to the base metal heat numbers, the applicable WPS number, and the welder ID. When the AISC auditor or the engineer's third-party inspector walks the floor, the weld map should answer, for any joint: what is the base metal, what was the procedure, and who welded it. For shops managing MTR traceability in a spreadsheet, maintaining this linkage is error-prone. Software that ties the WPS directly to the material heat number and generates the weld map automatically removes that error source.