| steel://Bessemer & further processing | |
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Bessemer Process
Developed in 1847 by William Kelly of USA and Sir Henry Bessemer of England. The Bessemer Process allows the same process as described previously. However, it allows mass production of steel by quick and effective refining processes. Oxygen is pumped into the molten steel via an air burst. The high temperatures allow the oxygen to react with all the impurities. The main impurity that gets removed from the iron is sulphur.
2FeS + 3O2 -->2Fe02 + 2S02
The extra oxygen also helps the iron retain its carbon content. The impurities reacting with the oxygen are caught in a slag and removed in vast quantities. The schematic diagram to the right illustrates how oxygen is injected into the system.
Later Processing
The primitive processes of creating steel from refined iron probably resulted in wrought iron. Heating iron ore and charcoal in a furnace sometimes created true steel. Steel could also then be made by heating wrought iron and charcoal in clay boxes. In this manner, the iron could absorb carbon to become steel. Today, giant steel mills utilize the Bessemer furnace to refine the molten iron with air. Iron ore remains an essential component of these mills. Smelting is key in creation of proper steel. Working the steel as to refine the crystalline structure makes the steel stronger. Hot rolling is the process used to work steel. The steel is essentially reduced to a very large thin sheet, and then it is molded by rollers. Afterwards, the steel is sometimes run through molten tin, which may coat the steel to create a cheap and light solution. Steel is also sometimes heat-treated to change the amount, size, shape, and distribution of cementite in the ferrite. The steel is sometimes heated with carbon or nitrogen to get only a hard surface. |
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