Posted by: heatsschoolofweldingtechnology | December 12, 2008

What is P-Numbers?

You might be asking, what is P-Numbers? P-Number is often used in WPS and Welder’s Qualification.


In accordance to QW-420.1 of ASME IX, to reduce the numbers of welding and brazing procedure qualification required, base metals have been assigned P-Numbers, and for ferrous base metals which have specified impact test requirements, Group Numbers within P-Numbers. These assignments are based essentially on comparable base metal characteristics, such as composition, weldability, brazeability and mechanical properties, where this can logically be done. These assignments do not imply that base metal maybe indiscriminately substituted for a base metal which was used in the qualification test without consideration of compatability from the stand point of metallurgical properties, and service requirements. Where notch-toughness is a consideration, it is presupposed that the base metals meet the specific requirements.



Base Metal



Steel and Steel Alloys

P-No. 1 through P-No. 11 incl. P-No. 5A, 5B and 5C

P-No. 101 through P-No. 103

Aluminum and Aluminum-base Alloys

P-No.21 through P-No. 25

P-No. 104 and P-No. 105

Copper and Copper-Base Alloys

P-No. 31 through P-No. 35

P-No. 107 and P-No. 108

Nickel and Nickel base Alloys

P-No. 41 through P-No. 47

P-No. 110 through P-No. 112

Titanium and Titanium base Alloys

P-No. 51 through P-No. 53

P-No. 115

Zirconium and zirconium base Alloys

P-No. 61 through P-No. 62

P-No. 117



The P-Numbers of each specific materials are listed in QW/QB-422 of ASME IX.


  1. Hi there,
    Thanks for article. Everytime like to read you.


  2. HI Hobosic, thanks for coming by and being our reader. you are welcome here and feel free to read and learn whatevetever you can learn here

  3. Hi,
    Thanks for article. Everytime like to read you.

    Thank you

  4. Hi eremeef thanks for coming by. you are welcome to read and learn in our site.

  5. Hi! I was surfing and found your blog post… nice! I love your blog. 🙂 Cheers! Sandra. R.

  6. i love your blog.thanx

  7. Bagong sikat kpatid ni inang

  8. What is P No for P355NH material ?

  9. Plz I need how to implement p numbe

  10. Can you please tell me From P.Number what is P stands for..

  11. Can you please tell me what P stands for

  12. thnx ur explain…
    can i ask….
    So, what’s mean that the alphabet of the tail??
    i.g p-no : 10H what ‘s mean..H??


  13. What does it mean if in a table in ASME III div2 there is a material that says “not assigned” in the welding p number field? thanks!

  14. what is the p number for IS 3589 Fe 410

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