What makes a base metal 'unlisted' under AWS D1.1:2025?

A base metal is unlisted if it does not appear in AWS D1.1:2025's prequalified base metal table. Listed steels — A36, A572, A992, A709, and others — can be used in prequalified WPS under Clause 5 without a PQR test. Any steel not on that list cannot use the prequalified pathway and must be qualified by testing under Clause 6.

Can a fab shop weld unlisted base metals under AWS D1.1?

Yes, provided the WPS is qualified by testing. There is no prohibition on welding unlisted steels — the code simply removes the prequalified shortcut and requires a PQR demonstrating acceptable mechanical properties. The engineer of record must approve the base metal for the application.

Does the PQR test coupon need to use the actual unlisted steel?

Yes. The test coupon must be made using the actual unlisted base metal. Using a substitute prequalified steel for the coupon and applying the results to an unlisted steel is not permitted.

How do you select filler metal for an unlisted base metal?

Start with the mill certificate. Identify the tensile strength range and chemistry limits. Select a filler metal that meets or overmatches the specified minimum tensile strength, and choose a hydrogen-designated electrode appropriate to the material's carbon equivalent and preheat sensitivity.

WPS Qualification for Unlisted Base Metals in AWS D1.1:2025

When a steel grade isn't prequalified under AWS D1.1:2025, the WPS requires a tested PQR. Here's how to qualify procedures for unlisted base metals.

The prequalified WPS shortcut in AWS D1.1:2025 depends entirely on the base metal being on the approved list. When the steel is not there, the shortcut disappears — and many fab shops discover this during an audit rather than during project planning.

What "prequalified" means for base metals

AWS D1.1:2025 maintains a table of prequalified base metals — steels that the code committee has vetted for use under the prequalified WPS provisions of Clause 5. These are steels with established weldability records, predictable preheat requirements, and known mechanical properties. When a WPS meets all the geometric, process, and consumable requirements in Clause 5 and uses a listed base metal, no PQR test coupon is required. The WPS can go directly into production.

The prequalified list includes most common structural steels used in North American construction: A36, A572 (Grades 42 through 65), A992 wide-flange shapes, A500 and A1085 hollow structural sections, A588 weathering steel, A709 bridge steels, A53 Grade B pipe, A913 high-performance shapes, and others with long service histories in structural applications.

What happens when the steel is not on the list

If the base metal is not in the prequalified table, the prequalified pathway is closed. The shop must qualify the WPS by testing under Clause 6 — which means designing and running a PQR test weld, having mechanical test specimens prepared and tested by a qualified laboratory, and documenting all results in a completed PQR record.

This is not a prohibition on welding unlisted steels. Unlisted does not mean unweldable. It means the code committee has not pre-validated the combination of that steel's chemistry, mechanical properties, and weldability for prequalified use. The onus shifts to the fabricator to demonstrate adequate welded joint properties through testing.

When unlisted base metals reach structural fab shops

Several scenarios regularly put unlisted steels on the shop floor:

International structural grades. When a project uses steel procured overseas — European EN 10025 S355, S460, or Australian AS/NZS 3678 grades — those designations do not appear in the AWS D1.1:2025 prequalified table. An EPC contractor or owner may specify these steels for availability or cost reasons. The shop must qualify WPS procedures for them from scratch.

Older steels in repair and modification work. Buildings and bridges constructed before the 1970s may contain A7, A441, or other retired ASTM grades. These are not in the current prequalified table. Structural modification, attachment welding, or repair on these structures requires testing to establish qualified procedures. The requirement to match the WPS to the base metal in service cannot be circumvented by treating the unknown steel as though it were A36. See: Welding existing structures under AWS D1.1 Clause 8

Proprietary HSLA and quenched-tempered grades. Some steel mills produce proprietary structural grades — typically in the 80–100 ksi tensile range — that carry trade names or non-standard ASTM references. If the applicable ASTM designation is not in the prequalified table, the qualification-by-testing path applies regardless of the material's commercial familiarity.

New ASTM grades that lag the code cycle. AWS D1.1 is updated on a multi-year cycle. New ASTM grades that have achieved market acceptance may not yet be in the prequalified table of the edition in use. A steel comparable to a listed grade but carrying a different designation is still unlisted until the next code revision adds it.

The Clause 6 tested qualification pathway

Qualifying a WPS for an unlisted base metal follows the same Clause 6 process as for any procedure requiring PQR testing:

Design the test weld. Select the joint configuration representative of the production joints the WPS will cover. The test coupon must use the actual unlisted base metal — the base metal type and heat/lot are recorded on the PQR. Substituting a standard prequalified steel to "get the test done" and then applying the PQR to the unlisted material is not code-compliant.

Draft a preliminary WPS. Before running the PQR, document the proposed welding conditions: process, current, polarity, travel speed, preheat, and all other applicable variables. Preheat for an unlisted steel requires engineering judgment — use the carbon equivalent calculation or the steel mill's weldability data as the starting point. If in doubt, increase preheat conservatively; underpreheat with an unlisted steel is a worse outcome than running hot.

Weld and test. The test weld is made under the preliminary WPS conditions. Mechanical test specimens are prepared and submitted to a qualified testing laboratory. Required tests for groove weld qualification include reduced-section tensile specimens, guided bend tests (face, root, or side bends depending on thickness), and visual examination. Some applications require Charpy V-notch impact testing as a supplementary essential variable under AWS D1.1:2025 Table 6.8. See: PQR tensile and bend test requirements under AWS D1.1

Record and issue. All test results are recorded on the PQR form. The base metal identity, the heat/lot, and the mill certificate reference are explicit PQR entries. The completed WPS references the PQR record number and lists the unlisted base metal as the covered material.

Carbon equivalent and mill certificate review

Before committing to a PQR program for an unlisted base metal, review the mill test report (MTR/CMTR) to assess weldability. The carbon equivalent by the IIW formula — CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 — is the primary indicator of heat-affected zone cold cracking susceptibility. Steels with CE above 0.43 are prone to hydrogen-induced cracking and require elevated preheat. For lower-carbon microalloyed grades, the Pcm formula (C + Si/30 + Mn/20 + Cu/20 + Ni/60 + Cr/20 + Mo/15 + V/10 + 5B) may give a more accurate cracking risk assessment.

The mill certificate should confirm: yield and tensile strength (to determine filler metal selection), Charpy V-notch results if required by the project specification, and any supplementary chemistry guarantees relevant to preheat planning. See: CMTR verification for structural welding

Filler metal selection for unlisted steels

For an unlisted base metal, there is no prequalified matching filler metal table entry. Select a filler metal that:

Meets or overmatches the minimum specified tensile strength of the base metal
Carries a low-hydrogen designation appropriate to the material's CE — typically H8 for CE below 0.43, H4 or lower for higher CE steels
Is classified under the applicable AWS A5-series specification for the welding process in use

Overmatching tensile strength is generally acceptable for structural applications and is the conservative default when the base metal tensile range is wide or not tightly specified. See: Overmatching filler metal in structural WPS

EOR approval and documentation

AWS D1.1:2025 places responsibility for accepting unlisted base metals with the engineer of record. Written EOR concurrence that the unlisted steel is acceptable for the structural application should be obtained before starting PQR testing. Without that approval, the fabricator may qualify a WPS that the EOR ultimately rejects for the job.

The completed WPS and PQR for an unlisted base metal belong in the WPS submittal package to the EOR and inspector of record, with the mill certificate attached as supporting documentation. See: WPS submittal package for EOR review

Common audit findings with unlisted base metals

The most frequent nonconformance involving unlisted base metals: a shop uses a prequalified WPS for a project that included steels the shop assumed were prequalified — but were not. This surfaces during WPS review when an auditor checks the base metal specification against the prequalified table. The result is a WPS that does not technically cover the production welds. Retroactive PQR testing creates schedule pressure and raises questions about welds already in place.

A pre-project WPS review — confirming that every specified base metal is either in the prequalified table or covered by an existing tested WPS — prevents this outcome. A centralized WPS library with explicit base metal coverage tracking makes the check routine rather than reactive. WPS Welding maintains that coverage map against your qualified WPS and PQR inventory so gaps surface before production, not during audits.

Rule library based on AWS D1.1:2025; verify against your governing edition.