Does a PQR on A36 (P1) automatically cover A516-70 (also P1)?

Generally yes for the base metal grouping—both are P1, so a WPS qualified on one covers the other within P1, subject to thickness and other essential variable limits. Check QW-200.2 for the specific range rules.

Are AWS D1.1 procedure qualifications accepted under ASME IX?

No. AWS D1.1 does not use P-numbers and operates under a separate qualification framework. A PQR prepared for D1.1 structural work is not accepted as ASME IX qualification evidence.

What is the difference between F4 and F6 filler metals?

F4 covers low-hydrogen covered electrodes (E7016, E7018, E8018, etc.) used in SMAW. F6 covers bare solid wire and rods used in GTAW, GMAW, and SAW. A welder or WPS qualified with F4 does not cover F6 work—separate PQR required.

Do P-numbers apply to aluminum?

Yes. Aluminum alloys have their own P-numbers: P21 covers 1xxx and 3xxx series, P22 covers 5xxx series (Al-Mg), and P23 covers 6xxx series (Al-Mg-Si). These are separate from the steel P-numbers and require independent qualification.

ASME IX P-Numbers and F-Numbers: What They Mean for Your WPS

How ASME Section IX groups base metals by P-number and filler metals by F-number—and why those groupings determine your WPS qualification range.

Before you cut the first test coupon for an ASME Section IX procedure qualification, you need to understand two classification systems: P-numbers for base metals and F-numbers for filler metals. Both are defined in QW-400 of ASME IX, and both directly determine the qualification range of your WPS. Misread them and your PQR may not support the production welds you need.

Why ASME IX Groups Materials

Writing a separate PQR for every base metal and filler combination a shop uses would be prohibitively expensive. ASME IX solves this by grouping materials with similar weldability, heat treatment response, and mechanical properties. A WPS and PQR developed with one material in a group can, within the rules of QW-200, support production welds on other materials in the same or a specifically permitted related group.

The grouping is metallurgically based — materials in the same P-number share similar pre-weld and post-weld heat treatment windows, similar notch toughness behavior, and similar susceptibility to hydrogen-assisted cracking. That shared behavior is the evidence basis for using one PQR to support multiple materials.

P-Numbers: Base Metal Groups

P-numbers are assigned in QW-422 and the referenced material tables. The groups a typical fab shop running pressure vessel or piping work will encounter:

P1 — Carbon and Low-Alloy Steels The most common group. Covers most carbon steel plate, pipe, and forgings: ASTM A36, A53, A106 Grade B, A516 Grades 60 and 70, A572, SA-516, SA-106, and dozens more. A single PQR on P1 base metal covers an enormous range of production materials. If you're building process piping or pressure vessels from standard carbon steel, you're working entirely within P1.

P3 — Alloy Steels Low-alloy steels in the 1Cr and 1.25Cr range. Requires a separate PQR from P1 — the higher alloy content changes preheat requirements and HAZ behavior enough that P1 test results don't transfer.

P4 — Chromium-Molybdenum, Low Alloy C-0.5Mo and 1.25Cr-0.5Mo types. Common in heat exchangers and moderate-temperature service piping. Separate qualification from P3.

P5A — 2.25Cr-1Mo (P22 Pipe and Fittings) The standard chrome-moly alloy for high-temperature service — boiler tubing, steam headers, high-pressure process piping. Most P5A applications require post-weld heat treatment. Separate PQR from P4.

P8 — Austenitic Stainless Steel 304, 316, 321, 347, and their low-carbon and stabilized variants. Sensitization risk, intergranular corrosion, and interpass temperature restrictions make P8 behavior quite different from carbon steel. P8 does not cross-qualify with P1 for anything other than overlay work under specific code provisions.

P21–P25 — Aluminum Alloys Subdivided by alloy series. P21 covers commercially pure aluminum and Al-Mn alloys (1xxx, 3xxx); P22 covers Al-Mg alloys (5xxx series); P23 covers Al-Mg-Si alloys (6061, 6062). A qualification on P22 5086 does not cover P23 6061 — they are different groups.

Group Numbers Within P-Numbers Materials within P1 are further divided into Group 1, Group 2, and Group 3. Group numbers matter when supplementary essential variables apply — primarily for CVN impact testing requirements. A PQR done on P1 Group 1 material may not automatically support P1 Group 3 if notch toughness testing is required by the application. Shops doing pressure vessel work subject to impact testing requirements need to verify their test material matches the required group, not just the P-number.

F-Numbers: Filler Metal Groups

F-numbers are defined in QW-432. They group welding consumables by usability characteristics — arc stability, coating type, position capability. The underlying logic is that welders trained on one F-number electrode have transferable technique across the group, and weld deposits within the group share enough chemistry and mechanical behavior to support the same mechanical test evidence.

F-numbers affect both WPS qualification range and welder/operator qualification range.

F4 — Low-Hydrogen Covered Electrodes E7016, E7018, E7018-1, E8018-C1, E9018-D1, and similar low-hydrogen SMAW electrodes. The most common choice for structural-to-pressure-vessel work on carbon and low-alloy steel. A WPS qualifying with F4 filler does not cover F3 or F6 applications — they are separate essential variable entries.

F6 — Bare Solid Wire and Bare Electrodes ER70S-6, ER308L, ER316L, ER4043, and all bare wire and rod products used in GTAW, GMAW, and SAW. This group covers the majority of GTAW and GMAW work in a typical fab shop. An F6 GTAW rod qualification does NOT cover F4 SMAW electrodes — different essential variable, separate PQR required.

F5 — Austenitic Stainless Covered Electrodes E308, E309, E316, and similar SMAW stainless electrodes. Separate from F6 even though both groups are used for stainless welding. F5 is specifically for covered SMAW stainless electrodes; F6 is for bare stainless wire used in GTAW and GMAW.

F1–F3 — Other Carbon Steel Covered Electrodes These groups cover cellulosic, rutile, and iron oxide coated electrodes. Less common in industrial pressure vessel and structural shops that have moved to low-hydrogen practice, but still encountered in pipeline work and light structural fabrication.

A-Numbers: Weld Metal Chemistry Groups

Less commonly misunderstood than P- and F-numbers, but still an essential variable for most process qualifications: A-numbers (QW-442) group deposited weld metal by chemical analysis. A-1 covers carbon steel weld metal; A-2 covers carbon-molybdenum; A-8 covers austenitic stainless. A change in A-number is an essential variable in QW-250 through QW-290 for most processes. Shops that run multiple filler chemistries need to verify whether a proposed filler substitution changes the A-number — if it does, a new PQR is required.

How P- and F-Numbers Determine Qualification Range

When you qualify a WPS with a PQR, the test locks in the P-number and F-number used during testing. Your WPS qualification range follows the essential variable tables in QW-250 through QW-290 (process-specific) plus QW-200.2 (general rules):

Change the P-number → new PQR required (with limited exceptions for materials in the same P-number group)
Change the F-number → new PQR required
Change from F4 SMAW to F6 GTAW → two essential variable changes (process and filler group), definitely a new PQR

This is a frequent source of unintentional scope creep when shops add a new process. If you've been doing SMAW on P1 with F4 and want to switch to GMAW with ER70S-6 (F6), the process change and the filler group change are both essential variables. One PQR won't cover both.

No P-Numbers in AWS D1.1

AWS D1.1 structural welding does not use P-numbers. D1.1 has its own prequalified and qualified base metal tables. Shops running both structural fabrication under D1.1 and pressure equipment under ASME IX need separate WPS qualification paths for each code — a D1.1 PQR does not satisfy ASME IX requirements, and vice versa.

For a side-by-side look at how these two codes approach procedure qualification, see D1.1 vs. ASME Section IX: which code governs your weld? and how to qualify a welding procedure under AWS D1.1.

ASME Section IX procedure qualification support is included in the Pro and Shop plans at wpswelding.com/pricing, alongside AWS D1.1:2025 WPS, PQR, WPQ, NDE reports, and code interpretations search.

Rule library based on AWS D1.1:2025; verify against your governing edition. For ASME IX compliance, verify all P-number, F-number, and essential variable requirements against the current edition of ASME Boiler and Pressure Vessel Code Section IX.