The equivalency of material specifications have long been an area of much debate. As such, there are both much disagreement and a lot of resources to help with this.

If there is one thing that I can say with certainty, it is that there is infact no such thing as totally equivalent specifications. (The only exceptions here being specifications that are essentially copies of each other, as is often found in ASTM and ASME material specifications.) This is so because the different specifications not only look at the materials properties, but also the product forms and applications. In addition, different material specifications use different materials testing specifications. This however is all theoretical and from a practical point of view, there are many specifications that are close enough to be given the label of "equivalent" or at least similar.

From your question it appears that you are interested in equivalent American specifications, and in particular, that you are interested in chemical and properties issues. If this is the case, then the easiest approach is to use the UNS numbers of the materials in question. The UNS designations appear to be quite widespread in the American specs.

My own preferance for finding "equivalent" materials is to use the German Werkstoff designations. The best reference source for these is the "Stahlslussel". (could have the spelling wrong)

Hope this is what you were looking for. If not, let me know.

Regards
Niekie Jooste