My uncle Bob works for a Nucor steel mill in Decatur, AL. He was kind enough to take me and a couple friends on a tour while I was in town for work, but we weren't allowed to bring cameras. They recently had a photographer come in for a newspaper piece on the plant and sent along a few pics of what we saw there.
The coil box is a piece of the process that I don't understand. The red-hot steel comes in flat, gets wound up into a coil... and then immediately gets unwound back into something that is approximately flat. But I must admit, I am 100% ignorant of what goes on at this mill other than A) it's really hot B) it's really big and C) it's really loud. The end result is rolls of steel sheeting with tailorable thickness, length, and composition. The guys who crank this stuff out were really cool to talk to, and the process itself was fascinating, even if the details were mostly lost on me.
Photo by Jeronimo Nisa