I worked on top of Coke ovens back in 1979.
They heat coal making it into Coke, Coke burns hotter, hot enough to melt the iron out of iron ore. Of course you have to blast oxygen into it to really get it going, which is why they have those Blast Furnaces.
Coke Oven
Coke Oven
The Larry Car is on top, dumps the coal down into the ovens. The Pusher pulls off the side doors and pushes the Coke into train cars on the other side.
Very dangerous and hard work, happy to have survived it for five months.
Blast Furnace
Iron
And you know what steel is.