Day 45/365 of Steel – Henry Cort

Today a nice little story from the old days, but with a sad end.
Henry Cort (c. 1740 – died 23 May 1800) British discoverer of the puddling process for converting pig iron into wrought iron. In 1784, he patented an improved version of the puddling process for refining cast iron although its commercial viability was only accomplished by innovations introduced by the Merthyr Tydfil ironmasters Crawshay and Homfray, who used coke smelted pig iron instead of iron from charcoal furnaces.

Rolling mill and puddling furnace

Henry Cort's puddling furnace, 1766
Fig 1: Henry Cort’s puddling furnace, 1766

Cort developed his ideas resulting in a 1783 patent for a simple reverberatory furnace to refine pig iron followed by a 1784 patent for his puddling furnace, with grooved rollers which mechanised the formerly laborious process. His work built on the existing ideas of the reverberatory furnace (where heat is applied from above, rather than through the use of forced air from below) and Peter Onions’ puddling process where iron is stirred to separate out impurities and extract the higher quality wrought iron. The furnace effectively lowered the carbon content of the cast iron charge through oxidation while the “puddler” extracted a mass of iron from the furnace using an iron “rabbling bar”. The extracted ball of metal was then processed into a “shingle” by a shingling hammer, after which it was rolled in the rolling mill.

Patents and royalties

Schematic drawing of a puddling furnace
Fig 2: Schematic drawing of a puddling furnace

The discovery that his partner had invested stolen funds in the enterprise led to Cort’s being deprived of his patents and forced into bankruptcy. In 1787, Cort came to an agreement with South Wales ironmaster Richard Crawshay whereby all iron manufactured according to the former’s patents would result in a royalty of 10 shillings per ton. His business ventures did not bring him wealth, even though vast numbers of the puddling furnaces that he developed were eventually used (reportedly 8,200 by 1820), they used a modified version of his process and thus avoided payment of royalties. He was later awarded a government pension, but died a ruined man.

About the Author:

Bruno Dursin – Managing Director at Believe in Steel. Bruno has more than 30 years of experience in promoting steel & steel solutions. His clients benefit from his extensive network within the building industry.

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