Basic oxygen steelmaking (BOS, BOF, Linz-Donawitz-Verfahren, LD-converter) is a method of primary steelmaking Steelmaking is the second step in producing steel from iron ore. In this stage, impurities such as sulfur, phosphorus, and excess carbon are removed from the raw iron, and alloying elements such as manganese, nickel, chromium and vanadium are added to produce the exact steel required in which carbon-rich molten pig iron Pig iron is the intermediate product of smelting iron ore with coke, usually with limestone as a flux. Pig iron has a very high carbon content, typically 3.5–4.5%, which makes it very brittle and not useful directly as a material except for limited applications is made into steel Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten. Carbon and other elements act as a hardening agent, preventing. The LD-converter is named after the Austrian Austria /ˈɒstriə/ or /ˈɔːstriə/ (German: Österreich (help·info)), officially the Republic of Austria (German: Republik Österreich), is a landlocked country of roughly 8.3 million people in Central Europe. It borders Germany and the Czech Republic to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and placenames Linz Linz is the third-largest city of Austria and capital of the state of Upper Austria . It is located in the north centre of Austria, approximately 30 km south of the Czech border, on both sides of the river Danube. The population of the city is 189,284 (2009), and that of the Greater Linz conurbation is 271,000 and Donawitz (a district of Leoben Leoben is a city in Styria, in central Austria, located on the Mur river. With a population of about 25,000, Leoben is a local industrial center and hosts the University of Leoben which specialises in mining. The Peace of Leoben, an armistice preliminary to the Treaty of Campo Formio, was signed in Leoben in 1797). The vast majority of steel manufactured in the world is produced using the basic oxygen furnace. Modern furnaces will take a charge of iron of up to 350 tons and convert it into steel in less than 40 minutes. The LD converter is a refined version of the Bessemer converter The Bessemer process was the first inexpensive industrial process for the mass-production of steel from molten pig iron. The process is named after its inventor, Henry Bessemer, who took out a patent on the process in 1855. The process was independently discovered in 1851 by William Kelly. The process had also been used outside of Europe for where blowing of air is replaced with blowing oxygen Oxygen (pronounced /ˈɒksɨdʒɨn/, OK-si-jin, from the Greek roots ὀξύς (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter), is the element with atomic number 8 and represented by the symbol O. It is a member of the chalcogen group on the periodic table, and is a highly.

Blowing oxygen through molten pig iron lowers the carbon content of the alloy An alloy is a partial or complete solid solution of one or more elements in a metallic matrix. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may be homogeneous in distribution depending on thermal history. Alloys usually have different properties from those of the and changes it into low-carbon steel Carbon steel, also called plain carbon steel, is steel where the main alloying constituent is carbon. The AISI defines carbon steel as: "Steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt, columbium [niobium], molybdenum, nickel, titanium, tungsten, vanadium or zirconium, or any other.

The process is known as basic due to the pH In chemistry, pH is a measure of the acidity or basicity of a solution. It approximates but is not equal to p[H], the negative logarithm of the molar concentration of dissolved hydronium ions (H3O+); a low pH indicates a high concentration of hydronium ions, while a high pH indicates a low concentration. Crudely, this negative of the logarithm of the refractories A refractory material is one that retains its strength at high temperatures. ASTM C71 defines refractories as "non-metallic materials having those chemical and physical properties that make them applicable for structures, or as components of systems, that are exposed to environments above 1,000 °F " - calcium oxide Calcium oxide , commonly known as quicklime, is a widely used chemical compound. It is a white, caustic and alkaline crystalline solid at room temperature and magnesium oxide Magnesium oxide, or magnesia, is a white solid mineral that occurs naturally as periclase and is a source of magnesium . It has an empirical formula of Mg - that line the vessel to withstand the high temperature of molten metal.

Process

The basic oxygen steel-making process is as follows:

1. Molten iron from a blast furnace A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally iron is poured into a large refractory A refractory material is one that retains its strength at high temperatures. ASTM C71 defines refractories as "non-metallic materials having those chemical and physical properties that make them applicable for structures, or as components of systems, that are exposed to environments above 1,000 °F "-lined container called a ladle;
2. The metal in the ladle is sent directly for basic oxygen steelmaking or to a pretreatment stage. Pretreatment of the blast furnace metal is used to reduce the refining load of sulfur Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant, multivalent non-metal. Sulfur, in its native form, is a bright yellow crystalline solid. In nature, it can be found as the pure element and as sulfide and sulfate minerals. It is an essential element for life and is found in, silicon Silicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. A tetravalent metalloid, silicon is less reactive than its chemical analog carbon. It is the eighth most common element in the universe by mass, but silicon very rarely occurs as the pure free element in nature. Silicon is more widely, and phosphorus Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus is commonly found in inorganic phosphate rocks. Elemental phosphorus exists in two major forms – white phosphorus and red phosphorus. Although the term "phosphorescence", meaning glow after. In desulfurising pre treatment, a lance is lowered into the molten iron Iron is the most common element in the earth as a whole, and the fourth most common in the Earth's crust. It is produced as a result of stellar fusion in high-mass stars, and it is the heaviest stable element produced by stellar fusion because the fusion of iron is the last nuclear fusion reaction that is exothermic. Iron is the most widely used in the ladle and several hundred kilograms of powdered magnesium Magnesium is a chemical element with the symbol Mg, atomic number 12 and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust, where it constitutes about 2% by mass, and ninth in the known Universe as a whole. This preponderance of magnesium is related to the fact that it is easily are added. Sulfur impurities are reduced to magnesium sulfide in a violent exothermic In thermodynamics, the term exothermic describes a process or reaction that releases energy usually in the form of heat, but also in the form of light (e.g. a spark, flame, or explosion), electricity (e.g. a battery), or sound(e.g. burning hydrogen). Its etymology stems from the Greek prefix ex- (meaning "outside") and the Greek word reaction. The sulfide is then raked off. Similar pretreatment is possible for desiliconisation and dephosphorisation using mill scale (iron oxide) and lime as reagents. The decision to pretreat depends on the quality of the blast furnace metal and the required final quality of the BOS steel.
3. Filling the furnace A furnace is a device used for heating. The name derives from Latin fornax, oven. The earliest furnace was excavated at Balakot, a site of the Indus Valley Civilization, dating back to its mature phase . The furnace was most likely used for the manufacturing of ceramic objects with the ingredients is called charging. The BOS process is autogenous: the required thermal energy is produced during the process. Maintaining the proper charge balance, the ratio of hotmetal to scrap, is therefore very important. The BOS vessel is one-fifth filled with steel scrap. Molten iron Iron is the most common element in the earth as a whole, and the fourth most common in the Earth's crust. It is produced as a result of stellar fusion in high-mass stars, and it is the heaviest stable element produced by stellar fusion because the fusion of iron is the last nuclear fusion reaction that is exothermic. Iron is the most widely used from the ladle is added as required by the charge balance. A typical chemistry of hotmetal charged into the BOS vessel is: 4% C, 0.2-0.8% Si, 0.08%-0.18% P, and 0.01-0.04% S.
4. The vessel is then set upright and a water-cooled lance is lowered down into it. The lance blows 99% pure oxygen Oxygen (pronounced /ˈɒksɨdʒɨn/, OK-si-jin, from the Greek roots ὀξύς (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter), is the element with atomic number 8 and represented by the symbol O. It is a member of the chalcogen group on the periodic table, and is a highly onto the steel and iron, igniting the carbon dissolved in the steel and burning it to form carbon monoxide Carbon monoxide , also called carbonic oxide, is a colorless, odorless and tasteless gas which is slightly lighter (M = 28.0) than air (M = 28.8). It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal biological functions and carbon dioxide Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state. CO2 is a trace gas comprising 0.039% of the atmosphere, causing the temperature to rise to about 1700°C. This melts the scrap, lowers the carbon Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. There are three naturally occurring isotopes, with 12C and 13C being stable, while 14C is radioactive, decaying with a half-life of content of the molten iron and helps remove unwanted chemical elements A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons. Common examples of elements are iron, copper, silver, gold, hydrogen, carbon,. It is this use of oxygen instead of air that improves upon the Bessemer process The Bessemer process was the first inexpensive industrial process for the mass-production of steel from molten pig iron. The process is named after its inventor, Henry Bessemer, who took out a patent on the process in 1855. The process was independently discovered in 1851 by William Kelly. The process had also been used outside of Europe for, for the nitrogen (and other gases) in air do not react with the charge as oxygen does. High purity oxygen Oxygen (pronounced /ˈɒksɨdʒɨn/, OK-si-jin, from the Greek roots ὀξύς (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter), is the element with atomic number 8 and represented by the symbol O. It is a member of the chalcogen group on the periodic table, and is a highly is blown into the furnace or BOS vessel through a vertically oriented water-cooled lance with velocities faster than Mach 1.^[1]
5. Fluxes In metallurgy, a flux is a chemical cleaning agent that facilitates soldering, brazing, and welding by removing oxidation from the metals to be joined. Common fluxes are: ammonium chloride or rosin for soldering tin; hydrochloric acid and zinc chloride for soldering galvanized iron ; and borax for brazing or braze-welding ferrous metals. Different (burnt lime Lime is a general term for calcium-containing inorganic materials, in which carbonates, oxides and hydroxides predominate. Strictly speaking, lime is calcium oxide or calcium hydroxide. It is also the name for a single mineral of the CaO composition, occurring very rarely.[citation needed] The word 'lime' originates with its earliest use as or dolomite Dolomite is the name of a sedimentary carbonate rock and a mineral, both composed of calcium magnesium carbonate Ca ) are fed into the vessel to form slag Slag is a partially vitreous by-product of smelting ore to separate the metal fraction from the unwanted fraction. It can usually be considered to be a mixture of metal oxides and silicon dioxide. However, slags can contain metal sulfides and metal atoms in the elemental form. While slags are generally used as a waste removal mechanism in metal which absorbs impurities of the steelmaking process. During blowing the metal in the vessel forms an emulsion with the slag, facilitating the refining process. Near the end of the blowing cycle, which takes about 20 minutes, the temperature is measured and samples are taken. The samples are tested and a computer analysis of the steel given within six minutes. A typical chemistry of the blown metal is 0.3-0.6% C, 0.05-0.1% Mn, 0.01-0.03% Si, 0.01-0.03% S and P.
6. The BOS vessel is tilted again and the steel is poured into a giant ladle. This process is called tapping the steel. The steel is further refined in the ladle furnace, by adding alloying An alloy is a partial or complete solid solution of one or more elements in a metallic matrix. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may be homogeneous in distribution depending on thermal history. Alloys usually have different properties from those of the materials to give the steel special properties required by the customer. Sometimes argon Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table (noble gases). Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide. The complete octet (eight electrons) in the outer atomic shell makes it or nitrogen Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere gas is bubbled into the ladle to make sure the alloys mix correctly. The steel now contains 0.1-1% carbon. The more carbon in the steel, the harder it is, but it is also more brittle and less flexible.
7. After the steel is removed from the BOS vessel, the slag, filled with impurities, is poured off and cooled.

History

The first basic oxygen steelmaking process was the LD process developed in 1952 by voestalpine AG voestalpine AG is an international steel company based in Linz, Austria. The company is active in steel, automotive, railway systems, profilform and Tool Steel industries in Linz Linz is the third-largest city of Austria and capital of the state of Upper Austria . It is located in the north centre of Austria, approximately 30 km south of the Czech border, on both sides of the river Danube. The population of the city is 189,284 (2009), and that of the Greater Linz conurbation is 271,000, Austria Austria /ˈɒstriə/ or /ˈɔːstriə/ (German: Österreich (help·info)), officially the Republic of Austria (German: Republik Österreich), is a landlocked country of roughly 8.3 million people in Central Europe. It borders Germany and the Czech Republic to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and.^[2] Some major steelmaking companies in the US did not convert to this process for some years, with the last Bessemer converter The Bessemer process was the first inexpensive industrial process for the mass-production of steel from molten pig iron. The process is named after its inventor, Henry Bessemer, who took out a patent on the process in 1855. The process was independently discovered in 1851 by William Kelly. The process had also been used outside of Europe for still operating commercially until 1968. The LD process replaced both the previously common Siemens-Martin process, also known as the open-hearth process Open hearth furnaces are one of a number of kinds of furnace where excess carbon and other impurities are burnt out of the pig iron to produce steel. Since steel is difficult to manufacture due to its high melting point, normal fuels and furnaces were insufficient and the open hearth furnace was developed to overcome this difficulty. Most open, and the Bessemer process The Bessemer process was the first inexpensive industrial process for the mass-production of steel from molten pig iron. The process is named after its inventor, Henry Bessemer, who took out a patent on the process in 1855. The process was independently discovered in 1851 by William Kelly. The process had also been used outside of Europe for. European companies replaced open hearth furnaces Open hearth furnaces are one of a number of kinds of furnace where excess carbon and other impurities are burnt out of the pig iron to produce steel. Since steel is difficult to manufacture due to its high melting point, normal fuels and furnaces were insufficient and the open hearth furnace was developed to overcome this difficulty. Most open with BOF rapidly after WWII, but US companies were reluctant to give up the old and tried open hearths. The first company in the U.S. to use this type of furnace was McLouth Steel McLouth Steel is a former integrated steel company. The company had three locations. The first plant was in Detroit, Michigan, the second in Trenton, Michigan and the third, a cold mill, in Gibraltar, Michigan. The Detroit plant is currently owned by Jones & Laughlin Steel Company. Around half of the Trenton plant remains, including the in Trenton, Michigan.

The first BOF in North America was installed at Dofasco in Hamilton, Ontario Hamilton (2006 population 504,559; UA population 647,634; CMA population 692,911) is a port city in the Canadian province of Ontario. Conceived by George Hamilton when he purchased the Durand farm shortly after the War of 1812, Hamilton has become the centre of a densely populated and industrialized region at the west end of Lake Ontario known as, Canada The land occupied by Canada was inhabited for millennia by various groups of Aboriginal peoples. Beginning in the late 15th century, British and French expeditions explored, and later settled, along the Atlantic coast. France ceded nearly all of its colonies in North America in 1763 after the Seven Years' War. In 1867, with the union of three.^{[citation needed]}

References

1. ^ McGannon, p 486
2. ^ McGannon, p 26

Bibliography

• McGannon, Harold E. editor (1971). The Making, Shaping and Treating of Steel: Ninth Edition. Pittsburgh, Pennsylvania: United States Steel Corporation.

External links

• Basic Oxygen Steelmaking module at steeluniversity.org, including a fully interactive simulation

Categories: Industrial processes An industrial process is a procedure that alters materials or substances. Some processes make the production of a rare material vastly cheaper, thus changing it into a commodity; i.e. the process makes it economically feasible for society to use the material on a large scale | Metallurgy Categories: Chemistry | Materials science | Metals | Mining | Steelmaking

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• Steelmaking
• Oxygen: Encyclopedia
• Steelmaking: Encyclopedia
• Basic (Chemistry): Encyclopedia
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