Yes the allowable is from B16.5. The allowable decreases with increasing temperature, so what you state above makes sense. You can see the data used by viewing the file: "\ProgramData\Intergraph CAS\CAESAR II\6.10\System\ASME-2003.flg". This is a text file, so you can use NotePad to view the data. (The first column is temperature, then moving to the right you have the allowables for the various material classes.