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, 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. Same F no is assigned to carbon steel as well as stainless steel filler wires. For example. For 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 for different A number is given to a different group 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.