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 process is an improvement over the historically important Bessemer process. The LD-converter is named after the Austrian placenames Linz and Donawitz (a district of Leoben). A base in chemistry is a chemical substance which has a free pair of electrons to bind a hydrogen ion commonly referred to as a proton (IUPAC definition). ... Steelmaking is the second step in producing steel from iron ore. ... The steel cable of a colliery winding tower. ... Bessemer converter, schematic diagram The Bessemer process was the first inexpensive industrial process for the mass-production of steel from molten pig iron. ... Map of Austria, locating Linz Linz is a city and Statutarstadt in northeast Austria, on the Danube river. ... The toll tower (1280) and the church of Holy Xaver (1660-1665). ...

By blowing oxygen through molten pig iron, the carbon content of the alloy is lowered and changes the material into low-carbon steel. General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... Pig iron is raw iron, the immediate product of smelting iron ore with coke and limestone in a blast furnace. ... An alloy is a combination, either in solution or compound, of two or more elements, at least one of which is a metal, and where the resulting material has metallic properties. ... The steel cable of a colliery winding tower. ...

A typical BOS vessel holds about 280 tonnes of steel. The vessel is lined with heat-resistant refractory bricks that can withstand the high temperature of molten metal. A tonne or metric ton (symbol t), sometimes referred to as a metric tonne, is a measurement of mass equal to 1,000 kilograms. ... Fig. ...

The basic oxygen steel-making process is as follows:

1. Molten iron from a blast furnace is poured into a large refractory-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 sulphur, silicon, and phosphorus. In desulphurising pre treatment, a lance is lowered into the molten iron in the ladle and several hundred kilograms of powdered magnesium are added. Sulphur impurities are reduced to magnesium sulphide in a violent exothermic reaction. The sulphide 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 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 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 onto the steel and iron, causing the temperature to rise to about 1700°C. This melts the scrap, lowers the carbon content of the molten iron and helps remove unwanted chemical elements. It is this use of oxygen instead of air that improves upon on the Bessemer process, for the nitrogen (and other gases) in air do not react with the charge as oxygen does.
5. Fluxes (burnt lime or dolomite) are fed into the vessel to form slag 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, a 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, .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 materials to give the steel special properties required by the customer. Sometimes argon or nitrogen 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.

The first basic oxygen steelmaking process was the LD process developed in 1952 by VOEST ALPINE in Linz, Austria. Some major steelmaking companies in the US did not convert to this process for decades, with the last Bessemer converter still operating commercially until 1968. Blast furnace in Sestao, Spain. ... The term refractory can refer to multiple things: A refractory clergyman is one who refused to swear an oath to the French Revolution-era French state under the Civil Constitution of the Clergy. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white Atomic mass 24. ... For the chemical element see: sulfur. ... In thermodynamics, the word exothermic describes a process or reaction that releases energy in the form of heat. ... A furnace is a device for heating air or any other fluid. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... The periodic table of the chemical elements (this version outdated on October 13, 2006) A chemical element, or element for short, is a pure substance that cannot be decomposed into any simpler substance. ... Bessemer is the name, or part of the name, of several places in the United States: Bessemer, Alabama Bessemer, Michigan Bessemer Township, Michigan Bessemer City, North Carolina Bessemer, Pennsylvania Bessemer Bend, Wyoming Other things or people named Bessemer include: Bessemer process, a method of making steel Henry Bessemer, the inventor... In metallurgy, flux is a substance which removes passivating oxides from the surface of a metal or alloy. ... Lime is a general term for various naturally occurring minerals and materials derived from them in which carbonates, oxides and hydroxides of calcium predominate. ... Dolomite crystals from Touissite, Morocco Dolomite is the name of both a carbonate rock and a mineral consisting of calcium magnesium carbonate (formula: CaMg(CO3)2) found in crystals. ... A path through a slag heap in Clarkdale, Arizona, showing the striations from the now rusting corrugated sheets used to hold it back. ... LADLE ... An alloy is a combination, either in solution or compound, of two or more elements, at least one of which is a metal, and where the resulting material has metallic properties. ... General Name, Symbol, Number argon, Ar, 18 Chemical series noble gases Group, Period, Block 18, 3, p Appearance colorless Atomic mass 39. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless gas Atomic mass 14. ... 1952 (MCMLII) was a Leap year starting on Tuesday (link will take you to calendar). ... Voestalpine AG is an international steel company based in Linz, Austria. ... Map of Austria, locating Linz Linz is a city and Statutarstadt in northeast Austria, on the Danube river. ... Bessemer converter, schematic diagram The Bessemer process was the first inexpensive industrial process for the mass-production of steel from molten pig iron. ... 1968 (MCMLXVIII) was a leap year starting on Monday. ...

The LD process replaced both the previously common Siemens-Martin process, also known as the open-hearth process, and the Bessemer process. ... Open hearth furnaces are one of a number of kinds of furnace where excess carbon and other impurities are burnt out of pig iron to produce steel. ... Bessemer converter, schematic diagram The Bessemer process was the first inexpensive industrial process for the mass-production of steel from molten pig iron. ...

External links

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