P-Number, F-Number, and A-Number in Welding

To ease welding procedure creation and welding procedure management, the ASME Weld Number tables provide a well-defined numbering system methodology. These numbers are assigned to the Weld base metals and filler metals. Grouping materials reduces the number of welding procedures and welder performance qualification tests for a wide range of materials. ASME Boiler and Pressure Vessel Code (ASME BPVC Section IX) has assigned a grouping scheme for base metals that consists of the P numbers and Group Numbers. Earlier there were ASME S Numbers that were removed by the code from the year 2009. Similarly, the filler metal grouping scheme consists of the F-Numbers and A-Numbers. Refer to Fig. 1, which clarifies what these numbers relate to.

What is the P Number in Welding?

Depending on the material characteristics like composition, weldability, brazeability, design consideration, heat treatment, and mechanical properties, ASME BPVC assigned P-Numbers to the base metals. The code assigned the same P-number for the materials with similar material characteristics. These are listed in Table QW/QB-422 of ASME. While changing the base metal from a qualified WPS to a new base metal, requalification or a new PQR is not required if the new base metal falls in the same P-Number.

These base metals are grouped by material and the assigned P-Numbers are constant for that specific material group. For example, the base metals of Low Carbon Steel or Carbon Manganese material fall in P-Number 1. The following table (Table-1) provides the P-number ranges for various metals and alloys.

Sr. No.	Type of  Steel, Metal, Alloy	P-Number
1.	Carbon Steel (C-Mn )	1
2.	Low Alloy Steel (Cr-Mo Steels)	4, 5A, 5B, 5C, 15E
3.	Stainless  Steels (Cr-Ni steels)	8, 10H
4.	Nickel & Ni-base alloys	41 to 49
5.	Aluminum & Aluminum alloys	21 to 26
6.	Copper & copper alloys	31 to 35
7.	Titanium & titanium alloys	51 to 53
8.	Zirconium & zirconium alloys	61 and 62

From the ASME Sec IX table, QW/QB-422 can find the P-number of a specific grade of material, i.e. which material falls under which P-number and what is product form i.e. plate, forging, sheets, fittings, etc.

P-number is generally mentioned in WPS & PQR for procedure qualification and in WPQ for performance qualification.

What is the F-Number in Welding?

As the name suggests, F stands for Filler number. Depending on the composition, the microstructure of the material F-number is assigned to welding consumables i.e. filler wires, and electrodes to reduce the procedure and performance qualifications. F-number is generally mentioned in WPS & PQR for procedure qualification and in WPQ for performance qualification. The ASME Sec IX (QW-432 assigned the F-number on the basis of type of consumable, usability of consumable, metallurgical compatibility, heat treatment, and other mechanical properties. The same F no is assigned to carbon steel as well as stainless steel filler wires. For example. ER70S-6 & ER308 have the same F no. i.e. F no. 6. The following table (Table-2) provides the F-number ranges for various consumables as classified in ASME Section.

Sr. No.	Type of  Steel consumables	F-Number
1.	Carbon Steel	1 to 6
2.	Low Alloy Steel (Cr-Mo Steels)	1 to 6
3.	Stainless  Steels (Cr-Ni steels)	5, 6
4.	Nickel & Ni-base alloys	41 to 46
5.	Aluminum & Aluminium alloys	21 to 26
6.	Copper & copper alloys	31 to 37
7.	Titanium & titanium alloys	51 to 56
8.	Zirconium & zirconium alloys	61
9.	Hard-facing weld metal overlays	71 and 72

From the ASME Sec IX, table QW-432 can find the F-number of specific consumables classified as per ASME Sec IIC. With the F-number there is a reduction of procedure and performance qualification as the same F-number of material does not require requalification.

From the ASME Sec IX, table QW-433 can be referred to for the welder performance qualification range. A snapshot is given below:

What is the A-Number in Welding?

As from the name, A stands for analysis. A-number is designated by ASME to weld metal deposition composition analysis to reduce the number of procedure qualifications in Welding. From the ASME Sec IX table QW-442 can be referred to for different A  number is given to different groups of metals/alloys. A-number is generally mentioned in WPS & PQR. It is not essential for performance qualification i.e. not mentioned in WPQ.

Note that the A-Number gives the chemical composition of the weld metal in the “as-welded” state, not of the filler metal product in its raw form.

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Video Courses in Welding

To learn more about welding the following video courses you can refer to:

• Introduction to MIG Welding
• Understanding Welding Codes and Procedures
• The Basics of Gas Tungsten Arc Welding
• Certification in Welding Technology
• Understand Welding Symbols
• AWS-Certified Welding Inspector