U.S. Steel's last open hearth furnace

450-ton open hearth installed in the 1970s when everyone else had moved to BOFs. Probably world's largest steel furnace ever made. Symbol of US Steel conservatism.

That wasn't very efficient. Then came the basic open hearth — what Andrew Carnegie used — where you just had a big furnace with a layer of liquid iron about three feet thick. You start figuring out the density of that iron. We used open hearths from the 1880s to the 1970s. When everyone else was going to the basic oxygen furnace, U.S. Steel — being the conservative people they were — in the 1970s put in the world's last open hearth furnace at 450 tons, probably the world's largest steel furnace ever made. They were going bigger and bigger in scale.