Bessemer converter was a squat, ugly, clay-lined crucible that simplified the problem of removing impurities — excess manganese and carbon, mostly — from pig iron through the process of oxidation. Once the impurities were removed, either as gas or as solid slag, the molten iron was bolstered with other elements to create steel alloys, then poured into molds and given shape.

Depending on the size of the converter, as much as 30 tons of molten iron could be processed in one go. Air was blown into the converter through a number of small channels and forced through the liquid to remove the impurities.

The Bessemer process, which could take as little as 30 minutes to complete, resulted in better quality steel that could be mass-produced. This made steel a viable (read: cheaper) building material, and it soon became the standard in heavy construction projects, like skyscrapers and bridges.

The first Bessemer steel mill in the United States opened outside Detroit in 1855, a year before the U.S. patent was issued. As a Great Lakes port city, and given its proximity to the fertile iron-ore-producing fields in the upper Midwest, Detroit became an early steel-producing town.

Bessemer, meanwhile, moved his mill operations to Sheffield in England’s industrial Midlands, which became the British equivalent of Germany’s Essen, seat of the Krupp steel dynasty.

Bessemer wasn’t alone in working on this process. In fact, an American, William Kelly, developed a similar oxidation technique a few years earlier. He held a patent but was forced through bankruptcy to eventually sell it to Bessemer.

The Bessemer process was used into the 1960s, when it was finally replaced by newer technologies, including the Linz-Donawitz process.

Source: Various

Photo: Henry Bessemer/Courtesy Wikipedia

This article first appeared on Wired.com Nov. 11, 2008.

See Also:

• April 26, 1812: Birthday of Alfred Krupp, Germany's 'Cannon King'
• Aug. 13, 1913: Great Alloyed Victory for Stainless Steel
• Guns, Germs, Steel and Now, TV
• July 9–10, 1856: Visionary Tesla Born at Midnight
• Nov. 11, 1930: Einstein Gets Ice Cold

Authors: Tony Long

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