P-Numbers are assigned to base metals for the purpose of reducing the number
of welding and brazing procedure qualifications required.
P-Numbers are alphanumeric designations: accordingly, each P-Number shall be
considered a separate P-Number.
P-No. 中的 P 英文全拼是什么?
没有全拼,就是一个英文字母。
We had a discussion on this at the ASME Section IX Subcommittee meeting a year or two ago. Dr. D'or Doty, who probably was the longest subcommittee member at that time said that the "P" originally designated materials approved for welded "pressure" applications. The "S" numbers were developed sometime after P-Numbers and originally referred to materials approved by Code Cases for "structural" applications. That description would no longer be correct today, as there are many S-number materials that are used for pressure applications, such as piping.