The Bessemer Process and Modern Steelmaking

It’s the mid-1800’s and the United States was beginning to make its name in the steel production industry. The growth of railroads during the 19th century in both Europe and America put pressure on the iron industry to produce more, but the steel industry was still struggling with inefficient production processes. Steel still hadn’t proved yet to be a structural metal and the production was both slow and costly. This changed in 1856 when Henry Bessemer discovered a process that had an effective way to add oxygen to molten iron that reduced the carbon content. This was also the same year that Sabel Steel was founded.

Now formally known as the Bessemer Process, Bessemer invented a pear-shaped receptacle—referred to as a ‘converter’—in which the iron could be heated, and oxygen could be blown through the molten metal. When oxygen passes through the molten metal, it would react with the carbon, releasing carbon dioxide and creating a purer iron.

The process was both inexpensive and fast, it removed carbon and silicon from iron in only a few minutes but was still strong. There was still a problem, though. By the end of the process, too much carbon was being removed and too much oxygen remained in the final product. Bessemer ultimately found that if he added the right quantities of manganese, it would provide a solution, so he began adding it to his conversion process with great success.

There was still only one problem, Bessemer had failed to find a way to remove phosphorus from his end product, which made the steel brittle. This was problematic because the only phosphorus-free ores that could be used were from Sweden and Wales. In 1876 Welshman Sidney Gilchrist Thomas came up with the solution by adding limestone to the Bessemer process. This discovery meant that iron ore from anywhere in the world could be used to make steel. Production costs decreased immediately and prices for steel rail dropped more than 80% by 1884.