P-Number & F Number List with Charts| ASME Section IX Base Metal Groupings

Grade 91 (SA-335 P91 pipe, SA-213 T91 tube, SA-182 F91 forgings) is assigned P-Number 15E, not P-5B despite being a 9% chromium steel similar in bulk composition to Grade 9. ASME separated it into its own P-Number because its vanadium-modified, creep-strength-enhanced ferritic microstructure behaves differently enough from conventional Cr-Mo steel to need its own, more restrictive qualification requirements — a WPS qualified on P-5B material does not automatically qualify P-15E material, and vice versa.

Copper and copper alloys are covered by P-Numbers 31 through 35 (P-31 pure copper, through P-35 copper-aluminum bronze) under the welding qualification table QW-422. This is a completely different range from P-11, which is reserved for certain high-strength quenched and tempered alloy steels. Brazing qualification (QB-422) for copper uses its own separate numbering system starting around P-101, distinct from the welding P-Numbers entirely.

Titanium and titanium alloys are covered by P-Numbers 51 through 54. P-15E, which is sometimes confused with titanium because of the similar-looking number, is actually assigned to Grade 91 (9Cr-1Mo-V) steel — a completely unrelated ferrous material. Nickel and nickel alloys sit in the P-41 to P-46 range, and zirconium alloys are P-61 and P-62, following the same general non-ferrous numbering pattern as titanium.

P-6 covers martensitic stainless steel (Types 410, 420, 431), P-7 covers ferritic stainless steel (Types 409, 430, 446), and P-8 covers austenitic stainless steel (304, 316, 321). P-10 is reserved for various specialty and proprietary high-alloy steels, including certain duplex stainless steel grades, and should not be confused with the general martensitic stainless steel category, which is P-6.

Generally yes, for essential variable purposes — a PQR qualified using P-1 base metal qualifies WPS use across all P-1 graded materials. However, the responsible welding engineer still needs to separately evaluate metallurgical compatibility, PWHT requirements, and toughness (Group Number) requirements before applying that qualification broadly, since P-Number coverage alone does not guarantee every practical aspect of the joint is addressed.

Group Number becomes a Supplementary Essential Variable specifically when the governing Code Section requires WPS qualification by impact (toughness) testing, such as under ASME Section VIII Division 1 UG-84. In that situation, a change in Group Number — even within the same P-Number — requires WPS requalification with toughness testing at the applicable test temperature. Where toughness testing is not required, Group Number generally does not affect qualification scope.

P-Numbers classify base metals by composition, weldability, and mechanical properties. F-Numbers classify filler metals — electrodes, wire, and rod — by usability characteristics that affect a welder’s ability to produce a sound weld, found in Table QW-432. The two systems serve related but distinct purposes: P-Number governs which base metals a qualified WPS covers, while F-Number governs which filler metals a qualified welder (WPQ) is permitted to use.

If the weld metal’s actual chemical composition does not correspond to any A-Number listed in Table QW-442, the complete chemical composition must be recorded directly on both the PQR and the WPS rather than referencing an A-Number. A-Number itself remains an essential variable regardless — any change in A-Number (or, where no A-Number applies, any change in the recorded full composition) requires WPS requalification.