The Bessemer process was the first inexpensive industrial process for the mass-production of steel from molten pig iron. Industrial processes are procedures involving chemical or mechanical steps to aid in the Manufacture of an item or items usually carried out on a very Steel is an Alloy consisting mostly of Iron, with a Carbon content between 0 Pig iron is the intermediate product of Smelting Iron ore with coke, usually with Limestone as a flux The process is named after its inventor, Henry Bessemer, who took out a patent on the process in 1855. Sir Henry Bessemer ( January 19, 1813 – March 15, 1898) English Engineer and Inventor. Year 1855 ( MDCCCLV) was a Common year starting on Monday (link will display the full calendar of the Gregorian Calendar (or a Common year The process was independently discovered in 1851 by William Kelly. William Kelly ( August 22, 1811 - February 11, 1888) born in Pittsburgh Pennsylvania, was an American Inventor ^[1][2] The process had also been used outside of Europe for hundreds of years, but not on an industrial scale. ^[3] The key principle is removal of impurities from the iron by oxidation with air being blown through the molten iron. Steelmaking is the second step in producing Steel from Iron ore. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state The oxidation also raises the temperature of the iron mass and keeps it molten.

Bessemer converter, schematic diagram

The details of the process

Bessemer converter components.

Bessemer Converter

The process is carried on in a large ovoid steel container lined with clay or dolomite called the Bessemer converter. Clay is a naturally occurring material composed primarily of fine-grained Minerals which show plasticity through a variable range of Water content, and Dolomite (ˈdɒləmaɪt is the name of a Sedimentary Carbonate rock and a Mineral, both composed The capacity of a converter was from 8 to 30 tons of molten iron with a usual charge being around 15 tons. At the top of the converter is an opening, usually tilted to the side relative to the body of the vessel, through which the iron is introduced and the finished product removed. The bottom is perforated with a number of channels called tuyères through which air is forced into the converter. The converter is pivoted on trunnions so that it can be rotated to receive the charge, turned upright during conversion, and then rotated again for pouring out the molten steel at the end. A trunnion is a cylindrical protrusion used as a mounting and/or pivoting point

Oxidation

The oxidation process removes impurities such as silicon, manganese, and carbon as oxides. Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 Manganese (ˈmæŋgəniːz is a Chemical element, designated by the symbol Mn. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 These oxides either escape as gas or form a solid slag. The refractory lining of the converter also plays a role in the conversion - the clay lining is used in the acid Bessemer, in which there is low phosphorus in the raw material. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are Phosphorus, (ˈfɒsfərəs is the Chemical element that has the symbol P and Atomic number 15 Dolomite is used when the phosphorus content is high in the basic Bessemer (limestone or magnesite linings are also sometimes used instead of dolomite) - this is also known as a Gilchrist-Thomas converter, named after its inventor, Sidney Gilchrist Thomas. In Chemistry, a base is most commonly thought of as an aqueous substance that can accept Protons This refers to the Brønsted-Lowry theory of acids and Limestone is a Sedimentary rock composed largely of the Mineral Calcite ( Calcium carbonate: CaCO3 Magnesite is not to be confused with Magnetite or Magnemite. Magnesite is Magnesium carbonate, Mg[[carbon Sidney Gilchrist Thomas ( April 16, 1850 - February 1, 1885) was an English inventor In order to give the steel the desired properties, other substances could be added to the molten steel when conversion was complete, such as spiegeleisen (an iron-carbon-manganese alloy). Spiegeleisen ( German: Spiegel &mdash Mirror or Specular; Eisen &mdash Iron) is a Ferromanganese Alloy

Managing the process

When the required steel had been formed, it was poured out into ladles and then transferred into moulds and the lighter slag is left behind. The conversion process called the "blow" was completed in around twenty minutes. During this period the progress of the oxidation of the impurities was judged by the appearance of the flame issuing from the mouth of the converter: the modern use of photoelectric methods of recording the characteristics of the flame has greatly aided the blower in controlling the final quality of the product. After the blow, the liquid metal was recarburized to the desired point and other alloying materials are added, depending on the desired product.

Predecessor processes

Bessemer converter at Station Square, Pittsburgh

Before the Bessemer process Britain had no practical method of reducing the carbon content of pig iron. Station Square is a 52 acre indoor and outdoor shopping dining and entertainment complex located in the South Shore neighborhood of Pittsburgh, Pennsylvania The United Kingdom of Great Britain and Ireland was the formal name of the United Kingdom from 1 January 1801 until 12 April 1927 Decarburization is the process opposite to Carburization, namely aimed at decreasing the content of Carbon in Metals (usually Steel) Pig iron is the intermediate product of Smelting Iron ore with coke, usually with Limestone as a flux Steel was manufactured by the reverse process of adding carbon to carbon-free wrought iron, usually imported from Sweden. QtubIronPillarJPG|thumb|right| Iron pillar at Delhi India containing 98% wrought iron]] Wrought iron is commercially pure Iron. "Sverige" redirects here For other uses see Sweden (disambiguation and Sverige (disambiguation. The manufacturing process, called cementation process, consisted of heating bars of wrought iron together with charcoal for periods of up to a week in a long stone box. The cementation process is an obsolete technique for making Steel by Carburization of Iron. Charcoal' is the blackish residue consisting of impure Carbon obtained by removing water and other volatile constituents from Animal and Vegetation This produced blister steel. The cementation process is an obsolete technique for making Steel by Carburization of Iron. Up to 3 tons of expensive coke was burnt for each ton of steel produced. Coke is a solid Carbonaceous material derived from Destructive distillation of low-ash low-sulfur Bituminous coal. Such steel when rolled into bars was sold at £50 to £60 a long ton. The most difficult and work-intensive part of the process was however the production of wrought iron done in finery forges in Sweden. Iron tapped from the Blast furnace is Pig iron, and contains significant amounts of Carbon and Silicon.

This process was refined in the 1700s with the introduction of Benjamin Huntsman's crucible steel making technique, which added an additional three hours firing time, and additional massive quantities of coke. Benjamin Huntsman ( 4 June 1704 – 20 June 1776) was an English inventor and manufacturer of Crucible steel. Crucible steel describes a number of different techniques for making Steel Alloy by slowly heating and cooling pure Iron and Carbon (typically In making crucible steel, the blister steel bars were broken into pieces and melted in small crucibles each containing 20 kg or so. This produced higher quality crucible steel, and increased the cost. Crucible steel describes a number of different techniques for making Steel Alloy by slowly heating and cooling pure Iron and Carbon (typically The Bessemer process reduced to about ½ hour the time to make steel of this quality, while requiring only the coke needed initially to melt the pig iron. Pig iron is the intermediate product of Smelting Iron ore with coke, usually with Limestone as a flux The earliest Bessemer converters produced steel for £7 a long ton, although they priced it initially at around £40 a ton.

Bessemer converter, Kelham Island Museum, Sheffield, England (2002)

History

Historian Robert Hartwell points out that the 11th century Chinese of the Song Dynasty innovated a "partial decarbonization" method of repeated forging of cast iron under a cold blast. The Song Dynasty ( Wade-Giles: Sung Ch'ao was a ruling dynasty in China between 960&ndash1279 CE it succeeded the Five Dynasties and Ten Kingdoms Cast iron usually refers to grey cast iron, but identifies a large group of Ferrous Alloys which solidify with a Eutectic. ^[4] The historians Joseph Needham and Wertime acknowledged that this was the predecessor to the Bessemer process of making steel. This process was first described by the prolific scholar and polymath government official Shen Kuo (1031–1095) in 1075 when he visited Cizhou. Shen Kuo or Shen Kua ( (1031&ndash1095 style name Cunzhong and pseudonym Mengqi Weng, was a Polymathic Chinese ^[4] Hartwell states that perhaps the earliest center where this was practiced was the great iron-production district along the Henan-Hebei border during the 11th century. Henan ( is a province of the People's Republic of China, located in the central part of the country ( Postal map spelling: Hopeh) is a northern province of the People's Republic of China. ^[4]

Both Bessemer and Huntsman were based in the city of Sheffield, England. Sheffield ( is a city and Metropolitan borough in South Yorkshire, England England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland Sheffield has an international reputation for steel-making, which dates from 1740, when Benjamin Huntsman discovered the crucible technique for steel manufacture, at his workshop in the district of Handsworth. Steelmaking is the second step in producing Steel from Iron ore. Year 1740 ( MDCCXL) was a Leap year starting on Friday (link will display the full calendar of the Gregorian calendar (or a Leap Handsworth is a Suburb of south eastern Sheffield, in South Yorkshire, England. This process had an enormous impact on the quantity and quality of steel production and was only made obsolete, a century later, in 1856 by Henry Bessemer's invention of the Bessemer converter which allowed the true mass production of steel. Year 1856 ( MDCCCLVI) was a Leap year starting on Tuesday (link will display the full calendar of the Gregorian Calendar (or a Leap year Bessemer had moved his Bessemer Steel Company to Sheffield to be at the heart of the industry. The city's Kelham Island Museum still maintains one of the UK's last examples of a working Bessemer converter [from Workington, Cumbria] for public viewing. The Kelham Island Museum is an industrial museum on Alma Street alongside the River Don, in the centre of The City of Sheffield, England.

Importance

The Bessemer process revolutionized steel manufacture by decreasing its cost, and greatly increasing the scale and speed, while also decreasing the labour requirements. Prior to its introduction, steel was far too expensive to make bridges or the framework for buildings and wrought iron had been used throughout the Industrial Revolution. QtubIronPillarJPG|thumb|right| Iron pillar at Delhi India containing 98% wrought iron]] Wrought iron is commercially pure Iron. The Industrial Revolution was a period in the late 18th and early 19th centuries when major changes in agriculture manufacturing and transportation had a profound effect on the After its introduction, steel and wrought iron became similarly priced, and most manufacturers turned to steel.

Obsolescence

In the U. S. , commercial steel production using this method stopped in 1968. It was replaced by processes such as the Linz-Donawitz process, which offered better control of final chemistry. Basic oxygen steelmaking ( BOS BOF Linz-Donawitz-Verfahren LD-converter) is a method of Steelmaking in which carbon-rich molten iron is made into Steel The Bessemer process was so fast (10-20 minutes for a heat) that it allowed little time for chemical analysis or adjustment of the alloying elements in the steel. Bessemer converters did not remove phosphorus efficiently from the molten steel; as low-phosphorus ores became more expensive, conversion costs increased. Phosphorus, (ˈfɒsfərəs is the Chemical element that has the symbol P and Atomic number 15 The process only permitted a limited amount of scrap steel to be charged, further increasing costs, especially when scrap was inexpensive. Scrap is a term used to describe Recyclable materials left over from every manner of product consumption such as parts of vehicles building supplies and surplus materials Certain grades of steel were sensitive to the nitrogen which was part of the air blast passing through the steel. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14

See also

• Henry Bessemer
• William Kelly
• Linz-Donawitz process
• Siemens-Martin process
• Basic oxygen steelmaking
• Sandvik
• 1862
• Ladle Analysis Formula

References

• A retrospective of 20th century steel making technology

Notes

External links

• The Engineer, 15 August 1856. Bessemer's explanation of his process