steel making

25/3/2014 Steelmaking - Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/Steelmaking 1/4

Steel mill with two arc furnaces.

SteelmakingFrom Wikipedia, the free encyclopedia

Steelmaking is the process for producingsteel from iron and ferrous scrap. Insteelmaking, impurities such as nitrogen,silicon, phosphorus, and excess carbon areremoved from the raw iron, and alloyingelements such as manganese, nickel,chromium and vanadium are added toproduce different grades of steel. Limitingdissolved gases such as nitrogen andoxygen, and entrained impurities (termed"inclusions") in the steel is also important toensure the quality of the products cast from

the liquid steel.[1] There are two majorprocesses for making steel, namely basicoxygen steelmaking which has liquid pig-iron from the blast furnace and scrap steel as the main feed materials, and electric arc furnace (EAF) steelmakingwhich uses scrap steel or direct reduced iron (DRI) as the main feed materials. Oxygen steelmaking is fuelledpredominantly by the exothermic nature of the reactions inside the vessel where as in EAF steelmaking, electricalenergy is used to melt the solid scrap and/or DRI materials. In recent times, EAF steelmaking technology has

evolved closer to oxygen steelmaking as more chemical energy is introduced into the process.[2]

Contents

1 History2 Modern processes

2.1 Primary steelmaking

2.2 Secondary steelmaking

2.3 HIsarna steelmaking

3 See also

4 References

5 External links

History

Steelmaking has played a crucial role in the development of modern technological societies. Cast iron is a hardbrittle material that is difficult to work, whereas steel is malleable, relatively easily formed and a versatile material.For much of human history, steel has only been able to be made in small quantities but since the invention of theBessemer process in the 19th century and subsequent technological developments in injection technology andprocess control, mass production of steel has become an integral part of the world's economy and a key indicator

of technological development.[3] The earliest means of producing steel was in a bloomery.



Bethlehem Steel in Bethlehem,

Pennsylvania was one of the

world's largest manufacturers

of steel before its 2003

closure.

Early modern methods of producing steel were often labour-intensive and highly skilled arts. See:

finery forge, in which the German finery process could be managed to produce steel.

blister steel and crucible steel.

An important aspect of the industrial revolution was the development of large-scale methods of producing forgeablemetal (bar iron or steel). The puddling furnace was initially a means of producingwrought iron, but was later applied to steel production.

The real revolution in steelmaking only began at the end of the 1850s when theBessemer process became the first successful method of steelmaking inquantity, followed by the open-hearth furnace.

Modern processes

Modern steelmaking processes can be broken into two categories: primary andsecondary steelmaking. Primary steelmaking involves converting liquid iron froma blast furnace and steel scrap into steel via basic oxygen steelmaking or meltingscrap steel and/or direct reduced iron (DRI) in an electric arc furnace.Secondary steelmaking involves refining of the crude steel before casting andthe various operations are normally carried out in ladles. In secondary metallurgy, alloying agents are added,dissolved gases in the steel are lowered, inclusions are removed or altered chemically to ensure that high-quality

steel is produced after casting.[4]

Primary steelmaking

Main article: Basic oxygen steelmaking

Basic oxygen steelmaking is a method of primary steelmaking in which carbon-rich molten pig iron is made intosteel. Blowing oxygen through molten pig iron lowers the carbon content of the alloy and changes it into steel. Theprocess is known as basic due to the chemical nature of the refractoriescalcium oxide and magnesium oxidethat line the vessel to withstand the high temperature and corrosive nature of the molten metal and slag in the vessel.The slag chemistry of the process is also controlled to ensure that impurities such as silicon and phosphorus areremoved from the metal.

The process was developed in 1948 by Robert Durrer and commercialized in 195253 by Austrian VOEST andAMG. The LD converter, named after the Austrian towns of Linz and Donawitz (a district of Leoben) is a refinedversion of the Bessemer converter where blowing of air is replaced with blowing oxygen. It reduced capital cost ofthe plants, time of smelting, and increased labor productivity. Between 1920 and 2000, labor requirements in theindustry decreased by a factor of 1,000, from more than 3 worker-hours per tonne to just 0.003. The vast majorityof steel manufactured in the world is produced using the basic oxygen furnace; in 2011, it accounted for 70% ofglobal steel output. Modern furnaces will take a charge of iron of up to 350 tons and convert it into steel in less than

40 minutes, compared to 1012 hours in an open hearth furnace.[5]

Main article: Electric arc furnace



Electric arc furnace steelmaking is predominantly used for producing steel from scrap and involves melting scrap ordirect reduced iron using electric arcs (either in AC or DC mode). It is common to start the melt with a "hot heel"(molten steel from a previous heat) and use gas burners to assist with the melt down of the scrap pile in the furnace.As in basic oxygen steelmaking, fluxes are also added to protect the lining of the vessel and help improve theremoval of impurities. Electric arc furnace steelmaking typically involves furnaces of capacity around 100 tonnes

that produce steel every 40 to 50 minutes for further processing.[6]

By-product gases from the steel making process can be used to generate electricity through the use of reciprocating

gas engines.[7]

Secondary steelmaking

Secondary steelmaking is most commonly performed in ladles and often referred to as ladle (metallurgy). Some ofthe operations performed in ladles include de-oxidation (or "killing"), vacuum degassing, alloy addition, inclusionremoval, inclusion chemistry modification, de-sulphurisation and homogenisation. It is now common to performladle metallurgical operations in gas stirred ladles with electric arc heating in the lid of the furnace. Tight control ofladle metallurgy is associated with producing high grades of steel in which the tolerances in chemistry and

consistency are narrow.[8]

HIsarna steelmaking

Main article: HIsarna steelmaking process

The HIsarna steelmaking process is a process for primary steelmaking in which iron ore is processed almostdirectly into steel. The process is based around a new type of blast furnace called a Cyclone Converter Furnace,which makes it possible to skip the process of manufacturing pig iron pellets that is necessary for the basic oxygensteelmaking process. Without the necessity for this preparatory step the HIsarna process is more energy-efficientand has a lower carbon footprint than traditional steelmaking processes.

See also

History of the steel industry (18501970)History of the steel industry (1970present)

Argon oxygen decarburizationDecarburization

FINEXFlodin process

Steel mill

Carbon Additive

References

1. ^ B. Deo and R. Boom, Fundamentals of Steelmaking Metallurgy, Prentice and Hall, 1993

2. ^ E.T. Turkdoagn, Fundamentals of Steelmaking, IOM, 1996

3. ^ S. Sass, The Substance of Civilization, Arcade Publishing, 1998

4. ^ A. Gosh, Secondary Steelmaking, Principles and Applications, CRC Press, 2001



5. ^ R. Fruehan, The Making, Shaping and Treating of Steel, 11th Edition, AIST, 1999

6. ^ R. Fruehan, The Making, Shaping and Treating of Steel, 11th Edition, AIST, 1999

7. ^ Steel Production Gas to Power (http://www.clarke-energy.com/gas-type/steel-production-gas/), www.clarke-energy.com

8. ^ A. Gosh, Secondary Metallurgy, Principles and Applications, CRC Press, 2001

External links

The short film The Drama of Steel (1946) (http://www.archive.org/details/gov.archives.arc.12505) is

available for free download at the Internet Archive [more]

U.S. Steel Gary Works Photograph Collection, 1906-1971 (http://www.dlib.indiana.edu/collections/steel/)"Steel For The Tools For Victory" , December 1943, Popular Science (http://books.google.com/books?

id=fScDAAAAMBAJ&pg=PA122&dq=popular+science+1943+there%27s+one+thrill+no+soldier&hl=en

&ei=NlvOTJj2EIPMnAeRwYT-Dw&sa=X&oi=book_result&ct=result&resnum=1&ved=0CC4Q6AEwAA#v=onepage&q&f=true) large

detailed article with numerous illustrations and cutaways on the modern basics of making steel

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