As SteveBraune mentioned, ASTM materials are often acceptable for B&PV fabrication. For a Code reference, see II-A Appendix A on page xlv. A quick quote: "... however, material produced under an ASTM Specificaiton may be used in lieu of the corresponding ASME Specificaiton as listed in this Appendix." Common materials such as SA515 and SA516 are listed as identical to A515 and A516 on page l (that's Roman 50, not one). Its usually easy to order material to the SA spec, and it is the "preferred" way, and it will most often avoid annoyed AI's and customers, so given a choice, just order the SA spec.
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