in real life, iron is often refined into steel by blowing air or oxygen across molten high-carbon iron (pig iron) to reduce the carbon content. maybe you could make some kind of alternative steel recipe.
it might make the most sense in factorio to just make a faster recipe that needs hot iron but but less time to smelt because there's no need to reheat hot iron.
this might encourage more interesting iron smelting setups than the typical furnace stack.
if it's too needlessly complicated with no reward, you could adjust the recipes a little
maybe it could take only 3 iron plates in stead of 4 to add more of an incentive to smelt steel plates with the hot iron recipe. or change the non-hot steel recipe to make steel plates cost 6 iron plates so people will have a reason to try to use the recipe that uses 4 hot plates