What is P-Number?

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.

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