Bessemer Converter changed the Industry

bessemer converter

The Industrial Revolution was characterized by enormous growth in many areas of industry: mining, transport, and construction to name but a few. This growth set up a demand for more raw materials, and in many cases, for new materials with better properties that did not yet exist.

As these new materials were developed, by design or by chance, new applications sprang up to make use of them, creating further demands and so on. One of the features of the Industrial Revolution is the plethora of new materials that became available, and the upsurge in manufacturing methods that made use of them. Metals, fibers and even the early precursors of modern plastics were available in unprecedented variety and quantity.

In the early years of the industrial revolution the production of steel was restricted by a slow, small-scale and labor-intensive process, so wrought iron was an expensive commodity. A way had to be found of making iron and steel on a large scale.

The critical step forward was made by Henry Bessemer in 1856, in a series of classic experiments with various designs of furnace for burning off the carbon in the iron. At one point in his work, he suddenly realized that he didn’t need to heat or supply fuel to the charge of molten iron when trying to make steel: the 4% carbon present in the cast iron would burn, and produce heat, if an air stream was directed through the molten metal, so keeping the metal hot and fluid as well as reducing the carbon content! The result was the Bessemer furnace.

After selling (expensive) licenses to clamoring iron masters from all over the country and abroad, all initial trials were disastrous.

The problem was again one of chemistry: the other iron producers used ore contaminated with phosphorus, which Bessemer later realized by careful chemical analysis of the ores and cast irons (after the event) prevented the production of high quality steel. In his original experiments, he had fortunately used uncontaminated iron. As a result, he set up his own steel works in Sheffield, but persuaded his suppliers to ensure the purity of the feedstock. The problem with the phosphorus-containing ores was solved by changing the lining of the furnace, the chemistry of which caused the phosphorus to be removed from the steel in the slag.

Bessemer was sued by the patent purchasers who couldn’t get it to work. In the end Bessemer set up his own steel company because he knew how to do it, even though he could not convey it to his patent users. Bessemer’s company became one of the largest in the world and changed the face of steel making.

Henry Bessemer

The solution was first discovered by English metallurgist Robert Forester Mushet, who had carried out thousands of experiments in the Forest of Dean. His method was to first burn off, as far as possible, all the impurities and carbon, then reintroduce carbon and manganese by adding an exact amount of spiegeleisen. This had the effect of improving the quality of the finished product, increasing its malleability—its ability to withstand rolling and forging at high temperatures and making it more suitable for a vast array of uses. Mushet’s patent ultimately lapsed due to Mushet’s inability to pay the patent fees and was acquired by Bessemer. Bessemer earned over 5 million dollars in royalties from the patents.

Göran Fredrik Göransson, the founder and Sandvikens Jernverk AB in 1857 to acquire a steam engine for the Edske furnace but after a change in business plans, bought one-fifth of Henry Bessemer’s patent to produce steel from pig-iron. Upon his return, the Royal Swedish Academy of Sciences gave him a sum of 50,000 Swedish crowns for financing steel production using the Bessemer process. The Bessemer method involved blasting a strong current of air through molten iron to burn off the carbon and other impurities. However, it proved difficult to keep the temperature high enough throughout the process.

The story goes that the solution came to Fredrik in a nightmare. At this point he was facing serious financial difficulties and getting the Bessemer converter to work was paramount. Fredrik had a recurring nightmare in which he was suffocated due to lack of enough oxygen in his surroundings. He realized that introducing more oxygen to the converter would allow them to hold the temperature at the high level needed to achieve a melt with the quality needed. After making modifications, Göransson successfully managed to produce steel on an industrial scale using the new process on 18 July 1858.

The rest, as they say, is history.

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