When carbon reacts with oxygen to form carbon mono oxide the heat is absorbed from the surroundings , thus the temperature in that area falls, this is an endothermic reaction.
I think this is how to extract iron, a pure metal. Steels are alloys (mixtures of different metals) which can be made by adding other elements, such as carbon, to molten iron. As far as I know, they're made in a separate process, using a different type of furnace called an oxygen furnace. I could be wrong though since I've only just learnt this :/
