Let's start with a torch and a piece of titanium. What is the fastest way to get the titanium up to red hot? I am not going for getting the Titanium malleable, just red hot.

Whenever I ask my science-y friends they like to point out that the bright blue tip is the hottest point in the torch flame.

But this doesn't take into account heat transfer. Aren't we better off with having more flame spread out on the metal transferring heat over a larger area even if that flame isn't at the most extreme possible temperature? What is the optimum balance between heat transfer area and temperature?