Filler Metal Classification: AWS D1.1 vs. ASME IX F-Numbers

Steel fabrication projects rarely follow a single welding code. A petrochemical module might have structural steel under AWS D1.1:2025 and process piping under ASME B31.3 (which adopts ASME Section IX for welding qualifications). A power plant expansion might combine structural frames under D1.1 with pressure vessel attachments under ASME Section VIII. In these dual-code environments, filler metal documentation is where confusion most often surfaces — because AWS D1.1 and ASME IX use entirely different frameworks to classify and group electrodes.

How AWS D1.1 References Filler Metals

AWS D1.1 does not use a grouping number for filler metals. Instead, the code references each electrode or wire directly by its A5-series specification and classification. The A5 series is AWS's family of filler metal specifications:

• AWS A5.1: Carbon Steel Electrodes for SMAW (e.g., E6010, E7018)
• AWS A5.18: Carbon Steel Electrodes and Rods for GMAW and GTAW (e.g., ER70S-6)
• AWS A5.20: Carbon Steel Electrodes for FCAW (e.g., E71T-1C)
• AWS A5.36: Carbon and Low-Alloy Steel Flux Cored Electrodes (classification system introduced for newer designators)
• AWS A5.5: Low-Alloy Steel Electrodes for SMAW (e.g., E8018-C3)
• AWS A5.23: Low-Alloy Steel Electrodes and Fluxes for SAW
• AWS A5.28: Low-Alloy Steel Electrodes and Rods for GMAW and GTAW

The WPS must list the A5 specification and the full electrode classification. A change in classification — for example, from E7018 to E7018-H4R — is evaluated under Table 6.6 of AWS D1.1:2025 to determine whether it constitutes an essential variable requiring PQR requalification (Rule library based on AWS D1.1:2025; verify against your governing edition). Some classification suffix changes (particularly H-suffix hydrogen designations and the –G designator rules introduced in 2025) are essential variables; others are not.

AWS D1.1 does not provide substitution tables that allow one electrode classification to stand in for another without requalification. If a shop runs E7018 and wants to add E7016 as an alternate, it needs a PQR with E7016 or must demonstrate the change is not an essential variable under Table 6.6. See AWS D1.1:2025 Table 6.6 Explained for the complete essential variable framework.

How ASME Section IX Uses F-Numbers

ASME Section IX takes a different approach. QW-431 assigns every electrode, wire, or rod an F-number (F1 through F6 for shielded metal arc, F6 for most solid wires used in GMAW and GTAW, F7 for SAW flux/wire combinations, and additional designations for specialty processes). The F-number groups electrodes by similar usability characteristics and weld deposit behavior.

The practical effect is cross-qualification within an F-number group: a welder who qualifies with an F3 electrode (e.g., E6010 cellulosic SMAW) is also qualified to weld with F1 and F2 electrodes under QW-433. This saves considerable testing time when a shop stocks multiple electrode types across the same F-number range.

The F-number groupings are:

Beyond F-numbers, ASME IX also uses A-numbers to group weld metal by chemical composition, which matters for procedure qualification (not welder qualification). A-numbers are a distinct concept from F-numbers and from the AWS A5 designation system — A1 is a carbon steel weld metal group, A2 a carbon-molybdenum group, and so on through A10 and beyond. See ASME IX A-Numbers and Weld Metal Analysis for a detailed breakdown.

Where the Two Systems Diverge in Practice

The most operationally significant difference between the two codes is how they handle welder qualification coverage. Under ASME IX, a welder who passes a groove weld test with F3 electrodes is qualified for F1 through F3 electrodes. Under AWS D1.1, there is no equivalent automatic cross-qualification — the welder's WPQ (Welder Performance Qualification) is tied to the process, position, and base metal group tested, and the filler is not a standalone qualification category in the same way.

For procedure qualification, ASME IX allows a single PQR tested with one classification within an F-number group to support a WPS covering any classification in that group (within other essential variable limits). AWS D1.1 does not have a parallel provision — the procedure is qualified on the specific classification used in the PQR, and changes must be evaluated case by case against Table 6.6.

This matters most for dual-code projects where the same welder needs to work on both structural steel joints (AWS D1.1) and piping or pressure equipment (ASME IX). The welder must hold valid qualifications under both codes. The test coupons may or may not satisfy both simultaneously depending on the position, thickness, and base metal requirements of each code.

Running a Dual-Code WPS Library

Shops that work across both codes typically maintain two parallel WPS libraries — one formatted for AWS D1.1 (using AWS B4.0 test methods and the Annex M WPS form) and one formatted for ASME IX (using QW-482 and QW-483 forms). The underlying welding parameters can be identical, but the documentation format, essential variable checklist, and record-keeping requirements differ.

Key administrative practices for dual-code shops:

Separate PQR records by code: A single test coupon may generate both a D1.1 PQR and an ASME IX PQR if the test satisfies both codes simultaneously — but the two records must be maintained separately, signed by the appropriate qualified individual (CWI or responsible engineer for D1.1; Authorized Inspector or designated representative for ASME IX), and filed under the correct code.

Filler metal traceability: Because the two codes reference filler metals differently (A5 classification for D1.1, F-number for ASME IX), the purchasing and receiving records for consumables should capture both designations for electrodes used on dual-code projects. This avoids confusion during audits when an inspector asks for the F-number of an electrode whose WPS was written for D1.1.

Welder log segregation: A welder continuity log maintained for AWS D1.1 Clause 6.4.1 (the six-month continuity rule) is a different document from an ASME IX QW-322 welder log, even if the same welder appears in both. Keep them separate and ensure the applicable code is identified on each record. See AWS D1.1 Welder Continuity Six-Month Rule for the D1.1 requirements.

When Dual Qualification on One Coupon Makes Sense

Qualifying a single test coupon to satisfy both codes simultaneously is attractive when project schedules are tight. To do so, the coupon must meet the more restrictive test requirements of both codes in terms of:

• Test position (both codes recognize standard positions, but the allowable ranges covered may differ)
• Base metal specification and thickness
• Filler metal classification
• Acceptance criteria for tensile, bend, and any required toughness tests
• Documentation: both sets of forms must be fully completed

The coupon itself is one piece of steel. What differs is the documentation generated from it. In practice, the shop's quality manager should confirm with the ASME Authorized Inspector that simultaneous qualification is acceptable for the specific scope before investing in the test. See Dual Qualification PQR for AWS D1.1 and ASME IX for a detailed walkthrough.

Avoiding Common Mix-Ups

A recurring audit finding on dual-code projects is a WPS that cites ASME IX F-numbers in the filler metal field when the WPS is formatted for AWS D1.1 — or vice versa. AWS D1.1 WPS forms should list the A5 specification and classification (e.g., AWS A5.1 / E7018); ASME IX forms list the F-number and A-number (F4 / A1 for the same electrode). Using the wrong framework on the wrong form creates ambiguity about what condition was qualified.

A related issue: listing only a trade name (e.g., a manufacturer's branded name) with no specification or classification reference. AWS D1.1 and ASME IX both require the AWS classification to appear on the WPS. A trade name with no specification citation is not a qualified filler metal entry.

For shops building out their WPS and WPQ library to cover both structural and pressure work, the wpswelding.com pricing page describes how the WPS editor manages multi-code procedure sets with process-specific essential variable tracking.

Rule library based on AWS D1.1:2025; verify against your governing edition. The AHJ or contract may specify 2020 or an earlier edition with different table numbering. ASME Section IX requirements are edition-dependent; confirm the applicable edition with the Authorized Inspector.