ASME IX F-Number and A-Number tables: a reference guide

If the P-Number groups base metals, the F-Number and the A-Number do the same job on the consumable side. Together the three form the classification tripod of a WPS to ASME IX - and getting any one of them wrong means qualifying a range different from the one your production actually needs, or failing an audit.

This article summarises the two consumable groupings. If you are not yet comfortable with the P-Number concept, start with this article and with our interactive P-Number table.

What the F-Number is (QW-432)

The F-Number groups electrodes and filler rods by usability - the operational characteristic that determines the skill required of the welder. The logic is simple: someone who welds well with a cellulosic electrode (difficult) will probably weld well with a rutile one (easier), but the reverse is not true.

That is why the F-Number is an essential variable both for procedure qualification and for welder qualification.

Summary table of F-Numbers

F-Number	Consumable group	Example AWS classifications
F-1	High-deposition covered electrodes (iron powder)	EXX20, EXX24, EXX27, EXX28
F-2	Rutile covered electrodes	EXX12, EXX13, EXX14
F-3	Cellulosic covered electrodes	EXX10, EXX11
F-4	Basic covered electrodes (low hydrogen)	EXX15, EXX16, EXX18, EXX48
F-5	Stainless steel covered electrodes	E308-16, E316-15, E309-17
F-6	Wires and rods (solid, flux-cored and metal-cored) for steels	ER70S-X, E71T-X, ER308
F-21 to F-26	Aluminium and its alloys	ER4043, ER5356
F-31 to F-37	Copper and its alloys	ERCu, ERCuSi-A
F-41 to F-46	Nickel and its alloys	ERNiCrMo-3, ENiCrFe-3
F-51 to F-56	Titanium and its alloys	ERTi-2, ERTi-5
F-61	Zirconium and its alloys	ERZr-2
F-71 and F-72	Hardfacing	-

One detail that is worth real money in welder qualification: under QW-433, qualification with an F-4 electrode also covers F-1, F-2 and F-3 (subject to the conditions in the table, such as the use of a backing strip). Planning the test with the right consumable reduces the number of qualifications you need.

What the A-Number is (QW-442)

The A-Number classifies the chemical composition of the deposited weld metal in ferrous alloys. Where the F-Number looks at the operation, the A-Number looks at the metallurgical result of the deposit.

Summary table of A-Numbers

A-Number	Deposited metal family
A-1	Carbon steel
A-2	Carbon-molybdenum steel
A-3	Chromium-molybdenum steel (low Cr)
A-4	Chromium-molybdenum steel (intermediate Cr)
A-5	Chromium-molybdenum steel (high Cr)
A-6	Martensitic chromium steel
A-7	Ferritic chromium steel
A-8	Austenitic chromium-nickel steel (300 series)
A-9	Chromium-nickel steel (high alloy content)
A-10	Nickel steel (up to ~4% Ni)
A-11	Manganese-molybdenum steel
A-12	Nickel-chromium-molybdenum steel

The exact composition ranges for each A-Number are given in table QW-442 of the code - use the official values when classifying, particularly for deposits whose alloy content sits close to the boundary between families.

Where this lands in your WPS

In the QW-404 block (filler metal) of the WPS you declare the SFA specification, the AWS classification, the F-Number and the A-Number of the consumable. Those fields define part of the procedure’s qualified range: changing F-Number or A-Number will, as a rule, require requalification.

I have seen a WPS fail an audit over something trivial: the procedure qualified with ER70S-3 correctly declared “F-6 / A-1”, but production bought flux-cored wire of a different classification on the assumption that “wire is wire”. It is not - and the F/A-Number is what formalises that.

Put it into practice

Download our free WPS template in Excel to ASME IX 2025 ed. - bilingual, with the F-Number and A-Number fields already structured in the QW-404 block and a worked example.

And to master the complete writing and qualification process, from the P-Number to the PQR, take a look at the course Writing a WPS - ASME IX (2025 ed.) or talk to XP about WPS qualification as a service.