ASME IX P-Number Table
ASME BPVC Section IX uses P-Numbers (QW-422) to group base metals with similar weldability characteristics. This reduces the number of welding procedure qualifications needed — if you qualify on one P-Number, it generally covers all materials within that group. Group Numbers further subdivide P-Numbers for impact testing requirements.
What P-Number is 304 stainless steel?
304 stainless steel (UNS S30400) is assigned P-Number 8, Group 1 per ASME IX QW-422. This P-Number covers all austenitic stainless steels in the 300 series, including 304L, 316, 316L, 321, and 347.
Ask WeldIQ for the full answerWhat P-Number is A36 carbon steel?
ASTM A36 is assigned P-Number 1, Group 1 per ASME IX QW-422. P-1 covers carbon steels and carbon-manganese steels with a minimum tensile strength up to 70 ksi. Other P-1 materials include A106 Grade B, A53 Grade B, and A516 Grade 70.
Ask WeldIQ for the full answerCan I weld P-1 to P-8 with one WPS?
Yes, but it requires separate qualification. Per ASME IX QW-202.2, a WPS for a dissimilar P-Number combination (e.g., P-1 to P-8) must be supported by a PQR qualified on that specific combination. A procedure qualified on P-1 alone does not cover P-1 to P-8 joints.
Ask WeldIQ for the full answerWhat's the difference between P-Number and Group Number?
P-Numbers group metals by weldability; Group Numbers subdivide them for notch toughness. Per QW-403.1, when impact testing is not required, qualification on any Group Number within a P-Number covers all Group Numbers in that P-Number. When impact testing is required, you must test the specific Group Number.
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