Bessemer process

• 1. Introduction

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  The Bessemer process changed the price of steel from forty pounds per long ton to six or seven pounds - in a single generation. Before Henry Bessemer filed his patent in 1856, steel was a precious material. It made cutlery and tools, but it was far too expensive to cast into artillery or span a river. The world's bridges and building frames ran on wrought iron instead. What Bessemer invented was not simply a better furnace. It was a way to convert three to five tons of molten pig iron into steel in ten to twenty minutes, a task that had previously taken at least a full day of heating, stirring, and reheating. The questions worth sitting with are these: how did a conversation with Napoleon III spark that invention, why did the process nearly collapse before it succeeded, and who actually deserves credit for making it work?

• 2. A Cab Ride from Vincennes

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  Henry Bessemer described the birth of his idea in an autobiography written in 1890, and the setting he chose was not a laboratory. It was a wartime dinner. During the Crimean War, English industrialists and inventors turned their attention to military technology, and Bessemer was among them. A conversation with Napoleon III in 1854 about steel requirements for improved artillery was, in Bessemer's own words, "the spark which kindled one of the greatest revolutions that the present century had to record." He recalled that during his ride alone in a cab that night from Vincennes to Paris, he resolved to find a way to improve the quality of iron in the manufacture of guns. Starting in January 1855, he began that work in earnest. By October of that year he had filed his first patent related to the process, and he secured the full method patent in 1856. The American inventor William Kelly had been experimenting with a similar process in the early to mid-1850s, and Kelly later wrote a letter to Scientific American claiming that he had experimented with the process first and that Bessemer had known of his discovery. Kelly noted that English iron workers had visited his operation to observe the new process and may have reported it back home. Historians have regarded the parallel-invention claim as controversial, with Kelly's version considered less developed and less successful than Bessemer's.

• 3. The Rotten Steel Problem

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  Bessemer licensed his patent to four ironmasters for a combined total of twenty-seven thousand pounds, and the results were a disaster. The steel they produced was, in the words of his friend William Clay, "rotten hot and rotten cold." Bessemer bought those licenses back for thirty-two thousand five hundred pounds - a net loss before the process had earned a penny. The technical culprit took time to identify. Certain grades of steel are sensitive to the nitrogen that made up seventy-eight percent of the air blast, and impurities in the iron created further problems. Bessemer spent tens of thousands of pounds on experiments without finding the answer. The solution came from English metallurgist Robert Forester Mushet, working in the Forest of Dean. Mushet had conducted thousands of experiments and arrived at a two-step remedy. First, burn away as much carbon and other impurities as possible. Then reintroduce carbon and manganese by adding a precise quantity of spiegeleisen, an alloy of iron and manganese with trace amounts of carbon and silicon. The result was steel that could withstand rolling and forging at high temperatures and suited a far wider range of uses. Mushet's patent eventually lapsed because he could not pay the renewal fees, and Bessemer acquired it. Bessemer ultimately earned over five million dollars in royalties from the combined patents.

• 4. Sheffield, Sweden, and First Steel

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  The Manchester firm of W & J Galloway was actually the first company to license the process, doing so before Bessemer made his public announcement at Cheltenham in 1856. They are not listed among the four licensees who received refunds. In 1858 they exchanged their license for an investment stake in a new partnership with Bessemer and others, and that partnership began manufacturing steel in Sheffield using imported charcoal pig iron from Sweden. This was the first commercial production anywhere. Across the North Sea, a Swedish trader and consul named Goran Fredrik Goransson had purchased a twenty-percent share of the Bessemer patent during a visit to London in 1857. He and a small group of engineers ran experiments at Edsken, near Hofors, Sweden, through the first half of 1858. After achieving success, Goransson returned to London and convinced Bessemer that the process was working, then negotiated the right to sell his steel in England. Production at Edsken proved too limited for industrial scale, and in 1862 Goransson built a new factory on the shore of Lake Storvsjon for his Hogbo Iron and Steel Works. The town of Sandviken was founded around that plant. The company eventually became Sandvik in the 1970s.

• 5. Carnegie and American Steel

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  Alexander Lyman Holley arrived at Bessemer's Sheffield works in 1862, and what he saw changed American industry. His book, A Treatise on Ordnance and Armor, had already established him as a serious student of steel-making; now he wanted to bring the process to the United States. He returned home and connected with two iron producers from Troy, New York, John F. Winslow and John Augustus Griswold, who sent him back to the United Kingdom to negotiate a license. Holley secured the agreement and returned to the US in late 1863. By 1865 the three men were building a mill in Troy. The factory included a number of Holley's own innovations, and its public debut in 1867 drew immediate attention from the Pennsylvania Railroad, which funded Holley's second mill through its Pennsylvania Steel subsidiary. Between 1866 and 1877, the partners licensed a total of eleven Bessemer steel mills across the country. Andrew Carnegie visited Bessemer in 1872 and saw in the process an extension of his existing businesses, the Keystone Bridge Company and the Union Iron Works. Holley built Carnegie's new mill, the Edgar Thomson Steel Works, which opened in 1875. Carnegie Steel drove the price of steel railroad rails from one hundred dollars per ton in 1873 down to fifty dollars per ton by 1875, and kept cutting until rails sold for eighteen dollars per ton by the 1890s. Before Thomson Works opened, US steel output totaled roughly one hundred fifty-seven thousand tons per year. By 1910, American companies were producing twenty-six million tons annually.

• 6. The Phosphorus Fix

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  Industrial chemist Sidney Gilchrist Thomas identified one of the process's remaining weak points: phosphorus in the iron. High phosphorus content produced low-grade steel, and the original clay linings used in the converter could not remove it. Thomas believed he had found a solution and contacted his cousin Percy Gilchrist, who worked as a chemist at the Blaenavon Ironworks. The manager there, Edward Martin, offered Thomas test equipment and helped him draw up a patent issued in May 1878. Thomas's fix was to replace clay linings with dolomite or limestone, creating what became known as the basic Bessemer process in contrast to the acid Bessemer process. An added benefit was that the basic process generated more slag inside the converter, and that slag could be recovered and sold profitably as fertilizer. The basic process, also called the Thomas-Gilchrist process, outlasted the acid version by decades in Continental Europe, where iron ores typically contained high levels of phosphorus and the open-hearth process could not strip them all away. Almost all inexpensive construction steel in Germany was still produced by this method in the 1950s and 1960s.

• 7. Rise and Decline

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  Steel rails made from the Bessemer process lasted ten times longer than iron rails and could carry heavier locomotives pulling longer trains. Steel rail cars grew longer and shifted the freight-to-car-weight ratio from one-to-one to two-to-one. In 1898, Scientific American republished an 1890 speech by politician and ironmaking industrialist Abram S. Hewitt titled Bessemer Steel and its Effect on the World, which traced how cheap steel had opened sparsely inhabited regions of the country to settlement and made the transport of goods that had previously been too costly to ship suddenly profitable. Yet Hewitt had also been a skeptic of the material for certain uses. In 1877 he wrote a letter urging against its use in the construction of the Brooklyn Bridge, arguing for crucible steel instead. The contract ultimately went to J. Lloyd Haigh Co. rather than to John A. Roebling's Sons, which had submitted the lowest bid for Bessemer steel. By 1895 in the United Kingdom, the Iron and Coal Trades Review was describing the process as being in "a semi-moribund condition," saying it had "not only ceased to make progress, but it has absolutely declined." Observers at the time attributed the decline less to any flaw in the process itself and more to a failure to invest in training and technology. The giant ironmaking firm Bolckow Vaughan of Middlesbrough was cited as an example: its unwillingness to upgrade its equipment hastened its fall. In the US, commercial steel production using the Bessemer method stopped in 1968, replaced by the basic oxygen Linz-Donawitz process, which gave steelmakers better control over final chemistry. Henry Bessemer had understood the advantage of a pure oxygen blast over air as early as the nineteenth century; the technology to produce the large quantities of pure oxygen needed simply did not exist in his lifetime.