It would then be considered an UNDEFINED material. You can still qualify as per Sec IX but your WPS will be specific to the exact base metals you qualified with since there is no way to group the base metal.
Dear Sirs Just a point of caution If ASTM A519 Grade 4130 Piping belong to high pressure piping (example- 6000psi) pls ensure WPS/PQRs and Welder Qualified meeting ASME B31.3 Chapter IX apart from ASME IX Requirements