What bars to Superheat?

[Wub to craft]

Hey everyone, I was alching.. But then, I thought of Superheating, which I believe is a better option.

However, I'm only 21 Smithing. What bar should I superheat?
Should I just do iron, or should I quickly get 30, and do steel?
Thanks,
wub.

 

[Treyarch]

Iron is faster - I'd do iron.