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During the Han dynasty (202 BC – 220 AD), most, if not all, iron smelted in the blast furnace was remelted in a cupola furnace; it was designed so that a cold blast injected at the bottom traveled through tuyere pipes across the top where the charge (i.e. of charcoal and scrap or pig iron) was dumped, the air becoming a hot blast before ...
Bessemer converter, schematic diagram. The Bessemer process was the first inexpensive industrial process for the mass production of steel from molten pig iron before the development of the open hearth furnace. The key principle is removal of impurities from the iron by oxidation with air being blown through the molten iron. The oxidation also ...
The cupola furnace is ideally suited to this task, but since one reason for the existence of direct reduction processes is the non-use of coke, other melting furnaces have emerged. The COREX process , in operation since 1987, consists of a direct-reduction shaft reactor feeding a blast furnace crucible, in which the pre-reduced ore is brought ...
The advantage of the induction furnace is a clean, energy-efficient and well-controlled melting process, compared to most other means of metal melting. Most modern foundries use this type of furnace, and many iron foundries are replacing cupola furnaces with induction furnaces to melt cast iron, as the former emit much dust and other pollutants ...
Open hearth furnace workers at the Zaporizhstal steel mill in Ukraine taking a steel sample, c. 2012 Tapping open-hearth furnace, VEB Rohrkombinat Riesa, East Germany, 1982. An open-hearth furnace or open hearth furnace is any of several kinds of industrial furnace in which excess carbon and other impurities are burnt out of pig iron to produce ...
The furnace is charged with slag, scrap iron, limestone, coke, oxides, dross, and reverberatory slag. The coke is used to melt and reduce the lead. Limestone reacts with impurities and floats to the top. This process also keeps the lead from oxidizing. The molten lead flows from the blast furnace into holding pots.
This is because carbon must diffuse out of the graphite until it has reached the equilibrium concentration dictated by the temperature and the phase diagram. This step may be done in many types of furnaces, in a high-temperature salt bath, or via direct flame or induction heating. Numerous patents describe specific methods and variations.
The Chinese are thought to have skipped the bloomery process completely, starting with the blast furnace and the finery forge to produce wrought iron; by the fifth century BC, metalworkers in the southern state of Wu had invented the blast furnace and the means to both cast iron and to decarburize the carbon-rich pig iron produced in a blast ...