Building America and Making Steel: The Bessemer Process

The Bessemer steelmaking process was the first low-cost industrial process for the mass production of general steel from molten pig iron. Its inventor, Henry Bessemer, obtained a patent on the process in 1855. The process was also discovered independently in 1851 by William Kelly. The process had also been used in other countries for hundreds of years, but not in industrial use. The main principle involved is the removal of impurities from iron by oxidation through the use of air that is forced through the molten iron. Oxidation also raises the temperature of the mass of iron and maintains its molten state.

The basic Bessemer process: A certain amount of lime is loaded with the iron, and the process is carried out in much the same way as acid until the flame goes down. Here, instead of turning the bowl upside down, you continue to blow (sometimes a little more lime is added) for about four to five minutes, during which time the phosphorus and some of the sulfur are removed. The end of the operation is determined by taking a test ingot that is forged, quenched in water and broken; the fracture and also the malleability indicate the state of the process. The period before the flame falls is called the frontal blow, and the latter blow is called a posterior blow (rarely an excessive blow). When ready, the container is turned over, as much slag is poured in as much as possible, and the metal is decarburized in the container or ladle. As a small percentage of phosphorus always returns to the metal from the slag, the heat must be blown out, that is, reducing the phosphorus to a percentage lower than that required in steel. A heating takes between 20 and 25 minutes and a container can produce between 1000 and 5000 tons per day, depending on the size, which varies between 15 and 25 tons.

Modifications to the Bessemer process have focused almost exclusively on basic practice, as will be seen below. Champin’s pneumatic process was a modification for the manufacture of wrought iron whose advantages would appear to be very doubtful. Pig iron was blown into a converter in the usual way, and then the blown metal was distributed, by ladle, into heated rotating cylinders, called ballers, and when solidified into balls, it was taken to a juicer, and then given a heat wash, and then work as usual on the desired product. Flohr adds (basic process) iron ore briquettes, flakes, etc., joined with about 10% slaked lime, and claims that thereby the slag becomes thinner and dephosphorization much faster.

The Harmet process consists of treating the molten pork, first in an acid container to remove the silicon, and then in a basic container to remove the phosphorus and remaining impurities, taking care that none of the siliceous slag from the first container enters In a second; This is also called the “refueling” process or the transfer process. Massenez’s modification of the basic process for the treatment of metals with high silicon content consists in charging only a part of the lime at the beginning of the process, and when the coal flame appears (showing that the silicon has been removed) the as much slag as possible. off; then the rest of the lime is added and the blowing is completed. In the Pettitt process, iron oxide (basic) was used to remove phosphor, regardless of the converter coating. The Rochussen and Daelen process consisted of loading the converter rich iron ore (acid) with the molten pig and coating the converter with it prior to the hit. It was claimed that the amount of blasting required was greatly decreased while the amount of steel was increased, but the excessive corrosion that must occur would more than outweigh those advantages. The Schiebler process involves loading the metal and part of the lime into the container, and both the metal and the slag are poured out when the first phosphoric slag is formed. The treatment is completed in a basic or neutral hearth furnace, with the addition of the rest of lime or flux.

In the United States, commercial general steel production using this method stopped in the late 1960s. It was superseded by processes like the Linz-Donawitz, which offered better control of the final chemistry of the steel.

Leave a Reply

Your email address will not be published. Required fields are marked *