Not quite sure of your question.... Steel is an alloy of iron... steel is iron combined with carbon and also may have several metals like vanadium, molybdenum, etc. depending on the composition required by the manufacturer... However, most brake rotors/discs are usually made of a kind of cast iron called gray iron... which is tougher than your ordinary cast iron...
Sintered pads are harder on the rotors because of the metallic content but rotor wear would be negligible if you ask me...
