This is an issue of debate in some welding circles.  The applicable section of the code is QW-424.1, which states that the unassigned base metal shall be identified "by specification type and grade, or by chemical analysis and mechanical properties."  If an  base metal is defined by chemical analysis and mechanical properties, the code does not say who is defining these.  Some people will not recognize definitions that are not an industry standard, while others say it is up to the writer of the PQR/WPS, (and acceptance of the customer if required).  I have thought about sending an inquiry in on this subject, but haven't yet.  I am also interested to know what others think on this subject.

Okay, I guess I didn't know the answer, maybe there is a possible out.

But, if there are no limits defined for the chemical analysis, one could conceivably design the weld procedure with chemical limits so broad as to encompass every known material. Or, is the intent to be able to define an unknown material by analysis and therefore be able to generate a WPS and PQR good for only that specific heat lot.

As heard from a ASME Section IX committe member, Section IX is intended to be used with sound engineering judgment.  Obviously, as you know the incoperation of every known metal would be irresponsible and dangerous.  On the other hand, a PQR/WPS that would only be good for one heat of material would be rather restrictive.  What I try to do is find relavent industry standards and see how a material not listed in Section IX is handled by other codes, such as D1.1, ASTM A488, MIL-STD-248, or other ones relavent to your industry.  Just remember that Section IX is based on leak before break train of mind, so many materials that could be grouped together for qualification are not included because they aren't suitable for pressure vessels, (or piping for S No.s)