I need additional info for the above to satisfy a run in Caesar II: modulus of elasticity at different temperatures and correspondingly, hot and cold allowable stress at different temperatures. Any data resources known other than ASME B31.3? Any known mathematical formulas that would predict a pipe material physical properties as mentioned above?

As you pointed out, the B31.3 code does not list allowables for these materials. Therefore, this data is not in the CAESAR II material database.

Your best course of action is to contact the vendor and request this information.

I would have a look at the UKOAA Standard and the BS7159, both implemented in Caesar II for code stress computations. These codes take into account the orthotropic material properties, what B31.3 does not.

Best Regards,
Veit Bockemühl