What is P numbers, Group Numbers, F-Numbers and A-Numbers in Welding...?
ASME boiler and pressure vessel Code (BPVC) has assigned Certain numbers to base metals in order to minimize the number of procedure and qualification in WPS and PQR.
Base Metal : Base metal is parent metal It is that metal in the welding practice that has been cut by the various forms of cutting and other activities, then prepared and is to be welded. Base metal is categorized as P Number and P number is further divided in group numbers based on base metal characteristics.
The diagrammatical view of base metal as shown in Pic.001
Pic.001
Filler Metals : A filler metal is a metal added in the making of a joint through welding, brazing, or soldering. Filler Metals - Electrodes are as categorized as per F- Number same as per the characteristics of filler metal.
Weld Metal : Weld Metal is the composition designated on PQR to form of A-Number.
The diagrammatical view of P-Number, F-Number,A-Number as shown in Pic.000
Pic.002
The categorization of P-Numbers, Group Numbers, F-Numbers and A-Numbers can be found in ASME Section IX in different tables as shown the below,
For P-Number - See Table QW-422 In ASME SEC IX
For Group Number - See Table QW-422 In ASME SEC IX
For F-Number - See Table QW-432 In ASME SEC IX
For A-Number - See Table QW-442 In ASME SEC IX
P-Number :
To reduce the number of Procedure Qualification Required ASME has assigned P-Numbers to different types of materials. This numbers are assigned as per base metal characteristics , this characteristics consisting Mechanical properties, Weldability, Composition and other different parameters. Same type of P-Numbers allows us to use the one qualified PQR on different grades of material which process same type of P-Number on which PQR is qualified.
Any change P-Number shall be required to requalification of WPS.
We can obtain the P-Numbers for different metals from the Table mentioned in ASME SEC IX QW-422 so the PQR shall be determined as per ASME table. One thing is noted that before using qualified PQR on other grade material on shall consider the other different properties like Heat Treatment, mechanical properties, design considerations etc.
Example : PQR qualified for P-Number 1 (SA 106 GR.B to SA 106 GR.B) the welding procedure shall qualify for P-Number 1 (SA 333 GR.6 or SA 234 GR. WPB or SA 516 GR. 60/70 to any of the same P-Number. Different material have different P-Numbers for ex for SA 106 GR, B P-Number 1 and for SA 312 TP 304 P-Number is 8.
Same materials with P-Numbers shown below,
P-Number Material
1 Carbon Steel
3 Low alloy steel (Up to 1/2% Cr and up to 1/2% Mo)
4 Low alloy steel (1 to 2% Cr and up to 1/2% Mo)
5A Low alloy steel (2 to 3% Cr, 1% Mo Alloy Steel)
5B Intermediate Allot Steel (5 to 10% Cr, 1% Mo)
5C All 5A and 5B Materials heat treated to 85ksi+
6 Martensitic Stainless Steel
7 Ferritic Stainless Steel
8 Austenitic Stainless Steel
9 2 to 5% Ni Alloy Steel
10 Mn-V, Cr-V, 9%Ni, High Cr Alloy Steels
11 Low Alloy Steel, Quenched and Tempered to 95ksi+
21 1.2% Mg or Mn alloy Aluminum
22 1.2% Mn, 2,5% Mg, 0.25% Cu Aluminum
23 1.3% Mg, 0.7% Si, 0.25% Cr Aluminum
25 1.5% Mg, 0.8% Mn, 0.15% Cr Aluminum
31 Copper
32 Admiralty, Naval, Aluminum Brass, Muntz Metal
33 Cu-Si Alloys
34 Cu-Ni Alloys
41 Nickel
51 Titanium
61,62 Zirconium
Group Number : The P-Number are further categorized as Group Number. Group number is applicable when toughness requirements applies to materials. This is sub-grouping of the P-Number materials by the similarity of metallurgical properties except impact requirements.
Shown below the examples of different grades to understand the group subgrouping under P-Numbers from the Table from ASME SEC IX Table QW-422 as
Grade P-Number Group Number
For SA 516 Gr. 60 1 1
For SA 516 Gr. 70 1 2
F-Number : The grouping of electrodes and welding rods is mentioned in ASME SEC IX Table QW-432 is based essentially on their usability characteristics, which fundamentally determine the ability of welders to make satisfactory welds with a given filler metal. This grouping is made to reduce the number of welding procedure and performance qualifications, where this can logically be done.
F-Numbers of filler metals can be found in ASME Section IX’s Number Table QW-432 an extract is shown as following:
Electrodes/Welding rods F-Number
Steel and steel Alloys F-Number 1 To F-Number 6
Aluminum and Aluminum Base Alloys F-Number 21 to 23 7 F-Number 25,26
Copper and Copper Base Alloys F-Number 31 to F-Number 37
Nickel and Nickel Base Alloys F-Number41 to F-Number46
Titanium and Titanium Base Alloys F-Number 51 to F-Number 56
Zirconium and Zirconium base Alloys F-Number 61
Hard Facing Weld Metal Weld Overlay F-Number 71 to F-Number 72
A-Number : For Identification of Chemical Composition of weld metal the another type of grouping consisting in welding on PQR and WPS is done as per A-Number. The A-Number can be found in ASME SEC. IX Table QW-442.Please note the A number in WPS does not refer to the filler wire or electrode chemical composition; it refers to the deposited weld metal chemical composition.
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