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Puddling was one step in one of the most important processes of making the first appreciable volumes of high-grade bar iron (malleable wrought iron) during the Industrial Revolution. In the original puddling technique, molten iron in a reverberatory furnace was stirred with rods, which were consumed in the process. It was one of the first processes for making bar iron without charcoal in Europe, although much earlier coal-based processes had existed in China. Eventually, the furnace would be used to make small quantities of specialty steels. Though it was not the first process to produce bar iron without charcoal, puddling was by far the most successful, and replaced the earlier potting and stamping processes, as well as the much older charcoal finery and bloomery processes. This enabled a great expansion of iron production to take place in Great Britain, and shortly afterwards, in North America. That expansion constitutes the beginnings of the Industrial Revolution so far as the iron industry is concerned. Most 19th century applications of wrought iron, including the Eiffel Tower, bridges, and the original framework of the Statue of Liberty, used puddled iron. Later the furnaces were also used to produce a good-quality carbon steel; this was a highly skilled art, but both high-carbon and low-carbon steels were successfully produced on a small scale, particularly for the gateway technology of tool steel as well as high quality swords, knives and other weapons. ==History== Puddling was one of several processes developed in the second half of the 18th century in Great Britain for producing bar iron from pig iron without the use of charcoal. It gradually replaced the earlier charcoal-fuelled process, conducted in a finery forge. It was invented by Henry Cort at Fontley in Hampshire in 1783–84 and patented in 1784. A superficially similar (but probably less effective) process was patented the previous year by Peter Onions. Cort's process consisted of stirring molten pig iron in a reverberatory furnace in an oxidising atmosphere, thus decarburising it. When the iron "came to nature", that is, to a pasty consistency, it was gathered into a puddled ball, shingled, and rolled (as described below). This application of the rolling mill was also Cort's invention. Ninety years after Cort's invention, an American labor newspaper recalled the advantages of his system:
Cort's process (as patented) only worked for white cast iron, not grey cast iron, which was the usual feedstock for forges of the period. This problem was resolved probably at Merthyr Tydfil by combining puddling with one element of a slightly earlier process. This involved another kind of hearth known as a 'refinery' or 'running out fire'.〔Referred to as a "finery" and "run-out fire" by Overman, but not to be confused with the finery in the finery forge.〕 The pig iron was melted in this and run out into a trough. The slag separated, and floated on the molten iron, and was removed by lowering a dam at the end of the trough. The effect of this process was to desiliconise the metal, leaving a white brittle metal, known as 'finers metal'. This was the ideal material to charge to the puddling furnace. This version of the process was known as 'dry puddling' and continued in use in some places as late as 1890. The alternative to refining gray iron was known as 'wet puddling', also known as 'boiling' or 'pig boiling'. This was invented by a puddler named Joseph Hall at Tipton. He began adding scrap iron to the charge. Later he tried adding iron scale (in effect, rust). The result was spectacular in that the furnace boiled violently. This was a chemical reaction between the oxidised iron in the scale and the carbon dissolved in the pig iron. To his surprise, the resultant puddle ball produced good iron. One big problem with puddling was that almost 50% of the iron was drawn off with the slag because sand was used for the bed. Hall substituted roasted tap cinder for the bed, which cut this waste to 8%, declining to 5% by the end of the century.〔 〕 Hall subsequently became a partner in establishing the Bloomfield Iron Works at Tipton in 1830, the firm becoming Bradley, Barrows and Hall from 1834. This is the version of the process most commonly used in the mid to late 19th century. Wet puddling had the advantage that it was much more efficient than dry puddling (or any earlier process). The best yield of iron achievable from dry puddling is a ton of iron from 1.3 tons of pig iron, but the yield from wet puddling was close to 100%. The production of mild steel in the puddling furnace was only achieved in about 1850 in Westphalia, Germany and was patented in Great Britain on behalf of Lohage, Bremme and Lehrkind. It worked only with pig iron made from certain kinds of ore. The cast iron had to be melted quickly and the slag to be rich in manganese. When the metal came to nature, it had to be removed quickly and shingled before further carburisation occurred. The process was taken up at the Low Moor Ironworks at Bradford in Yorkshire (England) in 1851 and in the Loire valley in France in 1855. It was widely used. The puddling process began to be displaced with the introduction of the Bessemer process, which produced steel. This could be converted into wrought iron using the Aston process for a fraction of the cost and time. For comparison, an average size charge for a puddling furnace was 〔 while a Bessemer converter charge was (13,600 kg). The puddling process could not be scaled up, being limited by the amount that the puddler could handle. It could only be expanded by building more furnaces. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Puddling (metallurgy)」の詳細全文を読む スポンサード リンク
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