Linz BOF development (Austria)

1950s Linz, Austria — replaced air-blown Bessemer with pure-oxygen blow using Linde liquefaction. 300 tons of steel in 20 minutes vs. 24–48 hours in open hearth. By the 1970s had taken over the global industry. U.S. Steel built the last open hearth in the early 70s — "they were stupid to build that one."

In the 1950s, there was a guy at Linz in Austria who decided, all you're doing in the open hearth and the other furnace is basically the Bessemer process of passing hot air over cast iron to burn the carbon off, to turn it into a lower-carbon version, which is basically steel. He decided, why don't we just use pure oxygen? The Germans had developed the Linde process for liquefying air, and you could get pure oxygen. So they built a basic oxygen furnace. In the old open hearth process, it would be 400 tons of steel in the furnace, and it used to take anywhere from 24 to 48 hours to process those 400 tons of steel. The BOF furnace, which they started building around 1960, by the 1970s had taken over the entire industry. The last basic open hearth was built by U.S. Steel in the early 70s, and they were stupid to build that one. The BOF process is 300 tons of steel in 20 minutes.