Steel is an 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 that consists mostly of 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 and has a 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 between 0.2% and 2.1% by weight, depending on the grade Steel grades to classify various steels by their composition and physical properties have been developed by a number of standards organizations. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature (often in combination with iron), and in many minerals. As a free element, manganese is a metal with important industrial metal alloy uses, particularly in stainless steels, chromium Chromium is a chemical element which has the symbol Cr and atomic number 24, first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable. The name of the element is derived from the Greek word "chrōma" (χρώμα), meaning color,, vanadium Vanadium is the chemical element with the symbol V and atomic number 23. It is a soft, silvery gray, ductile transition metal. The formation of an oxide layer stabilizes the metal against oxidation. Andrés Manuel del Río discovered vanadium in 1801 by analyzing the mineral vanadinite, and named it erythronium. Four years later, however, he was, and tungsten Tungsten , also known as wolfram (/ˈwʊlfrəm/, WOOL-frəm), is a chemical element with the chemical symbol W and atomic number 74.[1] Carbon and other elements act as a hardening agent, preventing dislocations In materials science, a dislocation is a crystallographic defect or irregularity, within a crystal structure. The presence of dislocations strongly influences many of the properties of materials. The theory was originally developed by Vito Volterra in 1905. Some types of dislocations can be visualized as being caused by the termination of a plane in the iron atom crystal lattice In mineralogy and crystallography, crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid. A crystal structure is composed of a pattern, a set of atoms arranged in a particular way, and a lattice exhibiting long-range order and symmetry. Patterns are located upon the points of a lattice, which is an array from sliding past one another. Varying the amount of alloying elements and the form of their presence in the steel (solute elements, precipitated phase) controls qualities such as the hardness Hardness refers to various properties of matter in the solid phase that give it high resistance to various kinds of permanent shape change when force is applied. Hard matter is contrasted with soft matter, ductility Ductility is a mechanical property used to describe the extent to which materials can be deformed plastically without fracture, and tensile strength Tensile strength is indicated by the maxima of a stress-strain curve and, in general, indicates when necking will occur. As it is an intensive property, its value does not depend on the size of the test specimen. It is, however, dependent on the preparation of the specimen and the temperature of the test environment and material of the resulting steel. Steel with increased carbon content can be made harder and stronger than iron, but is also less ductile Ductility is a mechanical property that describes the extent in which solid materials can be plastically deformed without fracture.

Alloys with a higher carbon content are known as cast iron Cast iron usually refers to grey iron, but also identifies a large group of ferrous alloys, which solidify with a eutectic. The colour of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due to its carbide impurities which allow cracks to pass straight through. Grey cast iron is because of their lower melting point The melting point of a solid is the temperature at which the vapor pressure of the solid and the liquid are equal. At the melting point the solid and liquid phase exist in equilibrium. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point. Because of the ability of some substances to and castability Castability is the ease of forming a casting. Castability can be thought of as how easy is it to cast a quality part. A very castable part design is easily developed, incurs minimal tooling costs, requires minimal energy, and has few rejections.[1] Steel is also distinguishable from wrought iron Wrought iron is an iron alloy with a very low carbon content, in comparison to steel, and has fibrous inclusions, known as slag. This is what gives it a "grain" resembling wood, which is visible when it is etched or bent to the point of failure. Wrought iron is tough, malleable, ductile and easily welded. Historically, it was known as &, which can contain a small amount of carbon, but it is included in the form of 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 inclusions. Two distinguishing factors are steel's increased rust Rust is a general term for a series of iron oxides. Colloquially, the term is applied to red oxides, formed by the reaction of iron and oxygen in the presence of water or air moisture. Yet, there are also other forms of rust, such as the result of the reaction of iron and chlorine in an environment deprived of oxygen, such as rebar used in resistance and better weldability The weldability, also known as joinability, of a material refers to its ability to be welded. Many metals and thermoplastics can be welded, but some are easier to weld than others. It greatly influences weld quality and is an important factor in choosing which welding process to use.

Though steel had been produced by various inefficient methods long before the Renaissance The Renaissance was a cultural movement that spanned roughly the 14th to the 17th century, beginning in Florence in the Late Middle Ages and later spreading to the rest of Europe. The term is also used more loosely to refer to the historic era, but since the changes of the Renaissance were not uniform across Europe, this is a general use of the, its use became more common after more-efficient production methods were devised in the 17th century. With the invention of 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 in the mid-19th century, steel became an inexpensive mass-produced Mass production is the production of large amounts of standardized products, including and especially on assembly lines. The concepts of mass production are applied to various kinds of products, from fluids and particulates handled in bulk (such as food, fuel, chemicals, and mined minerals) to discrete solid parts (such as fasteners) to assemblies material. Further refinements in the process, such as basic oxygen steelmaking Basic oxygen steelmaking is a method of primary steelmaking in which carbon-rich molten pig iron is made into steel. The LD-converter is named after the Austrian placenames Linz and Donawitz (a district of Leoben). The vast majority of steel manufactured in the world is produced using the basic oxygen furnace. Modern furnaces will take a charge of, further lowered the cost of production while increasing the quality of the metal. Today, steel is one of the most common materials in the world, with more than 1300 million tons produced annually. It is a major component in buildings, infrastructure, tools, ships, automobiles An automobile, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor. Most definitions of the term specify that automobiles are designed to run primarily on roads, to have seating for one to eight people, to typically have four wheels, and to be constructed principally for the, machines, appliances, and weapons. Modern steel is generally identified by various grades defined by assorted standards organizations A standards organization, standards body, standards development organization or SDO is any entity whose primary activities are developing, coordinating, promulgating, revising, amending, reissuing, interpreting, or otherwise maintaining standards that address the interests of a wide base of users outside the standards development organization.

The steel cable of a colliery The goal of coal mining is to economically remove coal from the ground. Coal is valued for its energy content, and since the 1880s is widely used to generate electricity. Steel and cement industries use coal as a fuel for extraction of iron from iron ore and for cement production. In the United States, United Kingdom, and South Africa, a coal mine winding tower A Headframe or Gallows Frame or Winding Tower or Hoist Frame or Pit Frame or Shafthead Frame or Headgear is the structural frame above an underground mine shaft. Modern headframes are built out of steel, concrete or a combination of both. Timber headframes are no longer used in industrialized countries, but are still used in developing nations

Contents

Material properties

Iron-carbon phase diagram A phase diagram in physical chemistry, engineering, mineralogy, and materials science is a type of chart used to show conditions at which thermodynamically distinct phases can occur at equilibrium. In mathematics and physics, "phase diagram" is used with a different meaning: a synonym for a phase space, showing the conditions necessary to form different phases

Iron, like most metals, is found in the Earth Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets. It is sometimes referred to as the World, the Blue Planet,[note 6] or by its Latin name, Terra.[note 7]'s crust In geology, a crust is the outermost solid shell of a rocky planet or moon, which is chemically distinct from the underlying mantle. The crusts of Earth, our Moon, Mercury, Venus, Mars, Io, and other planetary bodies have been generated largely by igneous processes, and these crusts are richer in incompatible elements than their respective mantles only in the form of an ore, i.e., combined with other elements such as 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 or 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.[2] Typical iron-containing minerals A mineral is a naturally occurring solid chemical substance that is formed through geological processes and that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not have a specific chemical composition include Fe2O3—the form of iron oxide Iron oxides are chemical compounds composed of iron and oxygen. Altogether, there are sixteen known iron oxides and oxyhydroxides found as the mineral A mineral is a naturally occurring solid chemical substance that is formed through geological processes and that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not have a specific chemical composition hematite Hematite, also spelled as hæmatite, is the mineral form of iron oxide (Fe2O3), one of several iron oxides. Hematite crystallizes in the rhombohedral system, and it has the same crystal structure as ilmenite and corundum. Hematite and ilmenite form a complete solid solution at temperatures above 950°C, and FeS2—pyrite The mineral pyrite, or iron pyrite, is an iron sulfide with the formula Fe (fool's gold).[3] Iron is extracted from ore An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element by removing oxygen and combining the ore with a preferred chemical partner such as carbon. This process, known as smelting Smelting is a form of extractive metallurgy; its main use is to produce a metal from its ore. This includes iron extraction from iron ore, and copper extraction and other base metals from their ores. Smelting uses heat and a chemical reducing agent and heat to change the oxidation state of the metal ore; the reducing agent is commonly a source of, was first applied to metals with lower melting Melting, or fusion, is a physical process that results in the phase change of a substance from a solid to a liquid. The internal energy of a substance is increased, typically by the application of heat or pressure, resulting in a rise of its temperature to the melting point, at which the rigid ordering of molecular entities in the solid breaks points, such as tin Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead, like the two possible oxidation states +2 and +4. Tin is the 49th most abundant element and has, with 10 stable isotopes, the largest, which melts at approximately 250 °C (482 °F) and copper Copper is a chemical element with the symbol Cu (Latin: cuprum) and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is rather soft and malleable, and a freshly exposed surface has a pinkish or peachy color. It is used as a thermal conductor, an electrical conductor, a building material, and a, which melts at approximately 1,000 °C (1,830 °F). In comparison, cast iron melts at approximately 1,370 °C (2,500 °F). All of these temperatures could be reached with ancient methods that have been used since the Bronze Age The Bronze Age of a culture is the period when the most advanced metalworking in that culture used bronze. This could either have been based on the local smelting of copper and tin from ores, or trading for bronze from production areas elsewhere. Many, though not all, Bronze Age cultures flourished in prehistory. Since the oxidation rate itself increases rapidly beyond 800 °C, it is important that smelting take place in a low-oxygen environment. Unlike copper and tin, liquid iron dissolves carbon quite readily. Smelting results in an alloy (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) containing too much carbon to be called steel.[4] The excess carbon and other impurities are removed in a subsequent step.

Other materials are often added to the iron/carbon mixture to produce steel with desired properties. Nickel Nickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four ferromagnetic elements that exist around room temperature, the other three being iron, cobalt and gadolinium and manganese in steel add to its tensile strength and make austenite more chemically stable, chromium Chromium is a chemical element which has the symbol Cr and atomic number 24, first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable. The name of the element is derived from the Greek word "chrōma" (χρώμα), meaning color, increases hardness and melting temperature, and vanadium Vanadium is the chemical element with the symbol V and atomic number 23. It is a soft, silvery gray, ductile transition metal. The formation of an oxide layer stabilizes the metal against oxidation. Andrés Manuel del Río discovered vanadium in 1801 by analyzing the mineral vanadinite, and named it erythronium. Four years later, however, he was also increases hardness while reducing the effects of metal fatigue In materials science, fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The maximum stress values are less than the ultimate tensile stress limit, and may be below the yield stress limit of the material. To prevent corrosion, at least 11% chromium is added to steel so that a hard oxide forms on the metal surface; this is known as stainless steel. Tungsten interferes with the formation of cementite, allowing martensite to form with slower quench rates, resulting in high speed steel. On the other hand, sulfur, nitrogen, and phosphorus make steel more brittle, so these commonly found elements must be removed from the ore during processing.[5]

The density of steel varies based on the alloying constituents, but usually ranges between 7.75 and 8.05 g/cm3 (0.280–0.291 lb/in3).[6]

Even in the narrow range of concentrations which make up steel, mixtures of carbon and iron can form a number of different structures, with very different properties. Understanding such properties is essential to making quality steel. At room temperature, the most stable form of iron is the body-centered cubic (BCC) structure α-ferrite. It is a fairly soft metallic material that can dissolve only a small concentration of carbon, no more than 0.021 wt% at 723 °C (1,333 °F), and only 0.005% at 0 °C (32 °F). If the steel contains more than 0.021% carbon then it transforms into a face-centered cubic (FCC) structure, called austenite or γ-iron. It is also soft and metallic but can dissolve considerably more carbon, as much as 2.1%[7] carbon at 1,148 °C (2,098 °F)), which reflects the upper carbon content of steel.[8]

When steels with less than 0.8% carbon, known as a hypoeutectoid steel, are cooled from an austenitic phase the mixture attempts to revert to the ferrite phase, resulting in an excess of carbon. One way for carbon to leave the austenite is for cementite to precipitate out of the mix, leaving behind iron that is pure enough to take the form of ferrite, resulting in a cementite-ferrite mixture. Cementite is a hard and brittle intermetallic compound with the chemical formula of Fe3C. At the eutectoid, 0.8% carbon, the cooled structure takes the form of pearlite, named after its resemblance to mother of pearl. For steels that have more than 0.8% carbon the cooled structure takes the form of pearlite and cementite.[9]

Perhaps the most important polymorphic form is martensite, a metastable phase which is significantly stronger than other steel phases. When the steel is in an austenitic phase and then quenched it forms into martensite, because the atoms "freeze" in place when the cell structure changes from FCC to BCC. Depending on the carbon content the martensitic phase takes different forms. Below approximately 0.2% carbon it takes an α ferrite BCC crystal form, but higher carbon contents take a body-centered tetragonal (BCT) structure. There is no thermal activation energy for the transformation from austenite to martensite. Moreover, there is no compositional change so the atoms generally retain their same neighbors.[10]

Martensite has a lower density than austenite does, so that transformation between them results in a change of volume. In this case, expansion occurs. Internal stresses from this expansion generally take the form of compression on the crystals of martensite and tension on the remaining ferrite, with a fair amount of shear on both constituents. If quenching is done improperly, the internal stresses can cause a part to shatter as it cools. At the very least, they cause internal work hardening and other microscopic imperfections. It is common for quench cracks to form when water quenched, although they may not always be visible.[11]

Heat treatment

Main article: Heat treating carbon steel

There are many types of heat treating processes available to steel. The most common are annealing and quenching and tempering. Annealing is the process of heating the steel to a sufficiently high temperature to soften it. This process occurs through three phases: recovery, recrystallization, and grain growth. The temperature required to anneal steel depends on the type of annealing and the constituents of the alloy.[12]

Quenching and tempering first involves heating the steel to the austenite phase, then quenching it in water or oil. This rapid cooling results in a hard and brittle martensitic structure.[10] The steel is then tempered, which is just a specialized type of annealing. In this application the annealing (tempering) process transforms some of the martensite into cementite or spheroidite to reduce internal stresses and defects, which ultimately results in a more ductile and fracture-resistant metal.[13]

Steel production

Iron ore pellets for the production of steel Main article: Steelmaking See also: Steel production by country

When iron is smelted from its ore by commercial processes, it contains more carbon than is desirable. To become steel, it must be melted and reprocessed to reduce the carbon to the correct amount, at which point other elements can be added. This liquid is then continuously cast into long slabs or cast into ingots. Approximately 96% of steel is continuously cast, while only 4% is produced as cast steel ingots.[citation needed] The ingots are then heated in a soaking pit and hot rolled into slabs, blooms, or billets. Slabs are hot or cold rolled into sheet metal or plates. Billets are hot or cold rolled into bars, rods, and wire. Blooms are hot or cold rolled into structural steel, such as I-beams and rails. In modern foundries these processes often occur in one assembly line, with ore coming in and finished steel coming out.[14] Sometimes after a steel's final rolling it is heat treated for strength, however this is relatively rare.[15]

History of steelmaking

Bloomery smelting during the Middle Ages Main article: History of ferrous metallurgy

Ancient steel

Steel was known in antiquity, and may have been produced by managing bloomeries — iron-smelting facilities — so that the bloom contained carbon.[16]

The earliest known production of steel is a piece of ironware excavated from an archaeological site in Anatolia (Kaman-Kalehoyuk ) and is about 4,000 years old.[17] Other ancient steel comes from East Africa, dating back to 1400 BC.[18] In the 4th century BC steel weapons like the Falcata were produced in the Iberian Peninsula, while Noric steel was used by the Roman military.[19] The Chinese of the Warring States (403–221 BC) had quench-hardened steel,[20] while Chinese of the Han Dynasty (202 BC – 220 AD) created steel by melting together wrought iron with cast iron, gaining an ultimate product of a carbon-intermediate steel by the 1st century AD.[21][22]

Wootz steel and Damascus steel

Main articles: Wootz steel and Damascus steel

Evidence of the earliest production of high carbon steel in the Indian Subcontinent was found in Samanalawewa area in Sri Lanka.[23] Wootz steel was produced in India by about 300 BC.[24] Along with their original methods of forging steel, the Chinese had also adopted the production methods of creating Wootz steel, an idea imported into China from India by the 5th century AD.[25] In Sri Lanka, this early steel-making method employed the unique use of a wind furnace, blown by the monsoon winds, that was capable of producing high-carbon steel.[26] Also known as Damascus steel, wootz is famous for its durability and ability to hold an edge. It was originally created from a number of different materials including various trace elements. It was essentially a complicated alloy with iron as its main component. Recent studies have suggested that carbon nanotubes were included in its structure, which might explain some of its legendary qualities, though given the technology available at that time, they were produced by chance rather than by design.[27] Natural wind was used where the soil containing iron was heated up with the use of wood. The ancient Sinhalese managed to extract a ton of steel for every 2 tons of soil[citation needed], a remarkable feat at the time. One such furnace was found in Samanalawewa and archaeologists were able to produce steel as the ancients did long ago.[26][28]

Crucible steel, formed by slowly heating and cooling pure iron and carbon (typically in the form of charcoal) in a crucible, was produced in Merv by the 9th to 10th century AD.[24] In the 11th century, there is evidence of the production of steel in Song China using two techniques: a "berganesque" method that produced inferior, inhomogeneous steel and a precursor to the modern Bessemer process that utilized partial decarbonization via repeated forging under a cold blast.[29]

Modern steelmaking

A Bessemer converter in Sheffield, England

Since the 17th century the first step in European steel production has been the smelting of iron ore into pig iron in a blast furnace.[30] Originally using charcoal, modern methods use coke, which has proven to be a great deal cheaper.[31][32][33]

Processes starting from bar iron

Main articles: Blister steel and Crucible steel

In these processes pig iron was "fined" in a finery forge to produce bar iron (wrought iron), which was then used in steel-making.[30]

The production of steel by the cementation process was described in a treatise published in Prague in 1574 and was in use in Nuremberg from 1601. A similar process for case hardening armour and files was described in a book published in Naples in 1589. The process was introduced to England in about 1614.[34] It was produced by Sir Basil Brooke at Coalbrookdale during the 1610s. The raw material for this were bars of wrought iron. During the 17th century it was realised that the best steel came from oregrounds iron from a region of Sweden, north of Stockholm. This was still the usual raw material in the 19th century, almost as long as the process was used.[35][36]

Crucible steel is steel that has been melted in a crucible rather than being forged, with the result that it is more homogeneous. Most previous furnaces could not reach high enough temperatures to melt the steel. The early modern crucible steel industry resulted from the invention of Benjamin Huntsman in the 1740s. Blister steel (made as above) was melted in a crucible or in a furnace, and cast (usually) into ingots.[36][37]

Processes starting from pig iron

A Siemens-Martin steel oven from the Brandenburg Museum of Industry White-hot steel pouring out of an electric arc furnace

The modern era in steelmaking began with the introduction of Henry Bessemer's Bessemer process in 1858. His raw material was pig iron.[38] This enabled steel to be produced in large quantities cheaply, so that mild steel is now used for most purposes for which wrought iron was formerly used.[39] The Gilchrist-Thomas process (or basic Bessemer process) was an improvement to the Bessemer process, because it lined the converter with a basic material to remove phosphorus. Another improvement in steelmaking was the Siemens-Martin process, which complemented the Bessemer process.[36]

These were rendered obsolete by the Linz-Donawitz process of basic oxygen steelmaking (BOS), developed in the 1950s, and other oxygen steelmaking processes. Basic oxygen steelmaking is superior to previous steelmaking methods because the oxygen pumped into the furnace limits impurities.[40] Now, electric arc furnaces (EAF) are a common method of reprocessing scrap metal to create new steel. They can also be used for converting pig iron to steel, but they use a great deal of electricity (about 440 kWh per metric ton), and are thus generally only economical when there is a plentiful supply of cheap electricity.[41]

Steel industry

A Corus Group plant in the United Kingdom Steel production by country in 2007 See also: History of the modern steel industry, Global steel industry trends, Steel production by country, and List of steel producers

It is common today to talk about "the iron and steel industry" as if it were a single entity, but historically they were separate products. The steel industry is often considered to be an indicator of economic progress, because of the critical role played by steel in infrastructural and overall economic development.[42]

The economic boom in China and India has caused a massive increase in the demand for steel in recent years. Between 2000 and 2005, world steel demand increased by 6%. Since 2000, several Indian [43] and Chinese steel firms have risen to prominence like Tata Steel (which bought Corus Group in 2007), Shanghai Baosteel Group Corporation and Shagang Group. ArcelorMittal is however the world's largest steel producer.

In 2005, the British Geological Survey stated China was the top steel producer with about one-third of the world share; Japan, Russia, and the US followed respectively.[44]

In 2008, steel started to be traded as a commodity in the London Metal Exchange. At the end of 2008, the steel industry faced a sharp downturn that led to many cut-backs.[45]

Recycling

A pile of steel scrap in Brussels, waiting to be recycled

Steel is one of the most recycled materials in the world,[46] and, as of 2008, more than 83% of steel was recycled in the United States.[47] In the United States, it is the most widely recycled material; in 2000, more than 60 million metric tons were recycled.[46][48]

The most commonly recycled items are containers, automobiles, appliances, and construction materials. For example, in 2008, more than 97% of structural steel and 106% of automobiles were recycled, comparing the current steel consumption for each industry with the amount of recycled steel being produced (the late 2000s recession and the associated sharp decline in automobile production explains the over-100% calculation).[47] A typical appliance is about 75% steel by weight[49] and automobiles are about 65% steel and iron.[50]

The steel industry has been actively recycling for more than 150 years, in large part because it is economically advantageous to do so. It is cheaper to recycle steel than to mine iron ore and manipulate it through the production process to form new steel. Steel does not lose any of its inherent physical properties during the recycling process, and has drastically reduced energy and material requirements compared with refinement from iron ore. The energy saved by recycling reduces the annual energy consumption of the industry by about 75%, which is enough to power eighteen million homes for one year.[51]

Steel from the World Trade Center is poured for construction of USS New York (LPD-21)

The BOS steelmaking uses between 25 and 35% recycled steel to make new steel. BOS steel usually has less residual elements in it, such as copper, nickel and molybdenum and is therefore more malleable than EAF steel so it is often used to make automotive fenders, soup cans, industrial drums or any product with a large degree of cold working. EAF steelmaking uses almost 100% recycled steel. This steel contains more residual elements that cannot be removed through the application of oxygen and lime so it is used to make structural beams, plates, reinforcing bar and other products that require little cold working.[52] Recycling one ton of steel saves 1,100 kilograms of iron ore, 630 kilograms of coal, and 55 kilograms of limestone.[53]

Because steel beams are manufactured to standardized dimensions, there is often very little waste produced during construction, and any waste that is produced may be recycled. For a typical 2,000-square-foot (200 m2) two-story house, a steel frame is equivalent to about six recycled cars, while a comparable wooden frame house may require as many as 40–50 trees.[54]

Contemporary steel

See also: Steel grades

Modern steels are made with varying combinations of alloy metals to fulfill many purposes.[5] Carbon steel, composed simply of iron and carbon, accounts for 90% of steel production.[1] High strength low alloy steel has small additions (usually < 2% by weight) of other elements, typically 1.5% manganese, to provide additional strength for a modest price increase.[55] Low alloy steel is alloyed with other elements, usually molybdenum, manganese, chromium, or nickel, in amounts of up to 10% by weight to improve the hardenability of thick sections.[1] Stainless steels and surgical stainless steels contain a minimum of 11% chromium, often combined with nickel, to resist corrosion (rust). Some stainless steels are magnetic, while others are nonmagnetic.[56]

Some more modern steels include tool steels, which are alloyed with large amounts of tungsten and cobalt or other elements to maximize solution hardening. This also allows the use of precipitation hardening and improves the alloy's temperature resistance.[1] Tool steel is generally used in axes, drills, and other devices that need a sharp, long-lasting cutting edge. Other special-purpose alloys include weathering steels such as Cor-ten, which weather by acquiring a stable, rusted surface, and so can be used un-painted.[57]

Many other high-strength alloys exist, such as dual-phase steel, which is heat treated to contain both a ferritic and martensitic microstructure for extra strength.[58] Transformation Induced Plasticity (TRIP) steel involves special alloying and heat treatments to stabilize amounts of austentite at room temperature in normally austentite-free low-alloy ferritic steels. By applying strain to the metal, the austentite undergoes a phase transition to martensite without the addition of heat.[59] Maraging steel is alloyed with nickel and other elements, but unlike most steel contains almost no carbon at all. This creates a very strong but still malleable metal.[60] Twinning Induced Plasticity (TWIP) steel uses a specific type of strain to increase the effectiveness of work hardening on the alloy.[61] Eglin Steel uses a combination of over a dozen different elements in varying amounts to create a relatively low-cost metal for use in bunker buster weapons. Hadfield steel (after Sir Robert Hadfield) or manganese steel contains 12–14% manganese which when abraded forms an incredibly hard skin which resists wearing. Examples include tank tracks, bulldozer blade edges and cutting blades on the jaws of life.[62]

Most of the more commonly used steel alloys are categorized into various grades by standards organizations. For example, the Society of Automotive Engineers has a series of grades defining many types of steel.[63] The American Society for Testing and Materials has a separate set of standards, which define alloys such as A36 steel, the most commonly used structural steel in the United States.[64]

Though not an alloy, galvanized steel is a commonly used variety of steel which has been hot-dipped or electroplated in zinc for protection against rust.[65]

Uses

A roll of steel wool

Iron and steel are used widely in the construction of roads, railways, other infrastructure, applicances, and buildings. Most large modern structures, such as stadiums and skyscrapers, bridges, and airports, are supported by a steel skeleton. Even those with a concrete structure will employ steel for reinforcing. In addition to widespread use in major appliances and cars. Despite growth in usage of aluminium, it is still the main material for car bodies. Steel is used in a variety of other construction materials, such as bolts, nails, and screws.[66] Other common applications include shipbuilding, pipeline transport, mining, offshore construction, aerospace, white goods (e.g. washing machines), heavy equipment such as bulldozers, office furniture, steel wool, tools, and armour in the form of personal vests or vehicle armour (better known as rolled homogeneous armour in this role).

Historical

A carbon steel knife

Before the introduction of the Bessemer process and other modern production techniques, steel was expensive and was only used where no cheaper alternative existed, particularly for the cutting edge of knives, razors, swords, and other items where a hard, sharp edge was needed. It was also used for springs, including those used in clocks and watches.[36] With the advent of speedier and thriftier production methods, steel has been easier to obtain and much cheaper. It has replaced wrought iron for a multitude of purposes. However, the availability of plastics in the latter part of the 20th century allowed these materials to replace steel due to their lower cost and weight.[67]

Long steel

A steel pylon suspending overhead powerlines

Flat carbon steel

Stainless steel

A stainless steel gravy boat Main article: Stainless steel

See also

References

  1. ^ a b c d e Ashby, Michael F.; David R. H. Jones (1992) [1986]. Engineering Materials 2 (with corrections ed.). Oxford: Pergamon Press. ISBN 0-08-032532-7.
  2. ^ Winter, Mark. "Periodic Table: Iron". The University of Sheffield. http://www.webelements.com/iron/. Retrieved 2007-02-28.
  3. ^ F. Brookins, Theo (November 1899). "Common Minerals and Valuable Ores". Birds and All Nature (A. W. Mumford) 6 (4). http://birdnature.com/nov1899/ores.html. Retrieved 2007-02-28.
  4. ^ "Smelting". Britannica. Encyclopedia Britannica. 2007.
  5. ^ a b "Alloying of Steels". Metallurgical Consultants. 2006-06-28. http://materialsengineer.com/E-Alloying-Steels.htm. Retrieved 2007-02-28.
  6. ^ Elert, Glenn. "Density of Steel". http://hypertextbook.com/facts/2004/KarenSutherland.shtml. Retrieved 2009-04-23.
  7. ^ Sources differ on this value so it has been rounded to 2.1%, however the exact value is rather academic as plain-carbon steel is very rare made with this level of carbon. See:
  8. ^ Smith & Hashemi 2006, p. 363.
  9. ^ Smith & Hashemi 2006, p. 365–372.
  10. ^ a b Smith & Hashemi 2006, pp. 373–378.
  11. ^ "Quench hardening of steel". http://steel.keytometals.com/default.aspx?ID=CheckArticle&NM=12. Retrieved 2009-07-19.
  12. ^ Smith & Hashemi 2006, p. 249.
  13. ^ Smith & Hashemi 2006, p. 388.
  14. ^ Smith & Hashemi 2006, pp. 361–362.
  15. ^ Bugayev et al. Savin, p. 225
  16. ^ Wagner, Donald B.. "Early iron in China, Korea, and Japan". http://www.staff.hum.ku.dk/dbwagner/KoreanFe/KoreanFe.html. Retrieved 2007-02-28.
  17. ^ "Ironware piece unearthed from Turkey found to be oldest steel". http://www.hindu.com/thehindu/holnus/001200903261611.htm. Retrieved 2009-03-27.
  18. ^ "Civilizations in Africa: The Iron Age South of the Sahara". Washington State University. http://www.wsu.edu/~dee/CIVAFRCA/IRONAGE.HTM. Retrieved 2007-08-14.
  19. ^ "Noricus ensis," Horace, Odes, i. 16.9
  20. ^ Wagner, Donald B. (1993). Iron and Steel in Ancient China: Second Impression, With Corrections. Leiden: E.J. Brill. p. 243. ISBN 9004096329.
  21. ^ Needham, Joseph (1986). Science and Civilization in China: Volume 4, Part 3, Civil Engineering and Nautics. Taipei: Caves Books, Ltd.. p. 563.
  22. ^ Gernet, 69.
  23. ^ Wilford, John Noble (1996-02-06). "Ancient Smelter Used Wind To Make High-Grade Steel". The New York Times. http://www.nytimes.com/1996/02/06/science/ancient-smelter-used-wind-to-make-high-grade-steel.html?n=Top%2FNews%2FScience%2FTopics%2FArchaeology%20and%20Anthropology.
  24. ^ a b Ann Feuerbach, 'An investigation of the varied technology found in swords, sabres and blades from the Russian Northern Caucasus' IAMS 25 for 2005, 27-43 at 29, apparently ultimately from the writings of Zosimos of Panopolis.
  25. ^ Needham, Volume 4, Part 1, 282.
  26. ^ a b G. Juleff (1996). "An ancient wind powered iron smelting technology in Sri Lanka". Nature 379 (3): 60–63. doi:10.1038/379060a0.
  27. ^ Sanderson, Katharine (2006-11-15). "Sharpest cut from nanotube sword". News nature (Nature). doi:10.1038/news061113-11.
  28. ^ Wayman, M L and Juleff, G (1999). "Crucible Steelmaking in Sri Lanka". Historical Metallurgy 33 (1): 26.
  29. ^ Robert Hartwell (966). "Markets, Technology and the Structure of Enterprise in the Development of the Eleventh Century Chinese Iron and Steel Industry". Journal of Economic History 26: 53–54.
  30. ^ a b R. F. Tylecote, A history of metallurgy 2 edn, Institute of Materials, London 1992, 95-99 and 102-105.
  31. ^ A. Raistrick, A Dynasty of Ironfounders (1953; York 1989)
  32. ^ C. K. Hyde, Technological Change and the British iron industry (Princeton 1977)
  33. ^ B. Trinder, The Industrial Revolution in Shropshire (Chichester 2000)
  34. ^ K. C. Barraclough, Steel before Bessemer: I Blister Steel: the birth of an industry (The Metals Society, London, 1984), 48-52.
  35. ^ P. W. King (2003). "The Cartel in Oregrounds Iron: trading in the raw material for steel during the eighteenth century". Journal of Industrial History 6 (1): 25–49.
  36. ^ a b c d "Iron and steel industry". Britannica. Encyclopaedia Britannica. 2007.
  37. ^ K. C. Barraclough, Steel before Bessemer: II Crucible Steel: the growth of technology (The Metals Society, London, 1984).
  38. ^ James Moore Swank (1892). History of the Manufacture of Iron in All Ages. ISBN 0833734636.
  39. ^ "Bessemer process". Britannica. 2. Encyclopedia Britannica. 2005. pp. 168.
  40. ^ "Basic oxygen process". Britannica. Encyclopedia Britannica. 2007.
  41. ^ J.A.T. Jones, B. Bowman, P.A. Lefrank, Electric Furnace Steelmaking, in The Making, Shaping and Treating of Steel, 525–660. R.J. Fruehan, Editor. 1998, The AISE Steel Foundation: Pittsburgh.
  42. ^ "Steel Industry". http://bx.businessweek.com/steel-industry/. Retrieved 2009-07-12.
  43. ^ "India's steel industry steps onto world stage". http://csmonitor.com/2007/0212/p07s02-wosc.html. Retrieved 2009-07-12.
  44. ^ "Long-term planning needed to meet steel demand". The News. 2008-03-01. http://www.thenews.com.pk/daily_detail.asp?id=98951.
  45. ^ Uchitelle, Louis (2009-01-01). "Steel Industry, in Slump, Looks to Federal Stimulus". The New York Times. http://www.nytimes.com/2009/01/02/business/02steel.html?_r=1&partner=permalink&exprod=permalink. Retrieved 2009-07-19.
  46. ^ a b Hartman, Roy A. (2009). "Recycling". Encarta. Archived from the original on 2008-04-14. http://web.archive.org/web/20080414215636/http://encarta.msn.com/encyclopedia_761556346/Recycling.html.
  47. ^ a b "Steel Recycling Rates at a Glance". Archived from the original on 2010-02-20. http://www.webcitation.org/5nge7f632. Retrieved 2010-02-20.
  48. ^ "2005 Minerals Handbook" (PDF). February 2007. http://minerals.usgs.gov/minerals/pubs/commodity/recycle/recycmyb05.pdf. Retrieved 2008-06-15.
  49. ^ "Recycling steel appliances". http://recycle-steel.org/appliances.html. Retrieved 2009-07-13.
  50. ^ "Steel: Driving auto recycling success". http://recycle-steel.org/cars.html. Retrieved 2009-07-13.
  51. ^ "Facts About Steel Recycling". http://earth911.com/metal/steel/facts-about-steel-recycling/. Retrieved 2009-07-18.
  52. ^ "Steel". http://www.epa.gov/waste/conserve/materials/steel.htm. Retrieved 2009-07-13.
  53. ^ "Information on Recycling Steel Products". WasteCap of Massachusetts. Archived from the original on 2007-10-11. http://web.archive.org/web/20071011205459/http://wastecap.org/wastecap/commodities/steel/steel.htm#Benefitssteel. Retrieved 2007-02-28.
  54. ^ "Steel: the clear cut alternative for building homes". http://recycle-steel.org/PDFs/brochures/residenfram.pdf. Retrieved 2009-07-13.
  55. ^ "High strength low alloy steels". Schoolscience.co.uk. http://resources.schoolscience.co.uk/Corus/16plus/steelch3pg1.html. Retrieved 2007-08-14.
  56. ^ "Steel Glossary". American Iron and Steel Institute (AISI). http://steel.org. Retrieved 2006-07-30.
  57. ^ . American Institute of Steel Construction Inc. (AISC). Archived from on 2007-12-22. . Retrieved 2007-02-28.
  58. ^ "Dual-phase steel". Intota Expert Knowledge Services. http://www.intota.com/experts.asp?strSearchType=all&strQuery=dual%2Dphase+steel. Retrieved 2007-03-01.
  59. ^ Werner, Prof. Dr. mont. Ewald. "Transformation Induced Plasticity in low alloyed TRIP-steels and microstructure response to a complex stress history". http://www.wkm.mw.tum.de/Forschung/projekte_html/transtrip.html. Retrieved 2007-03-01.
  60. ^ "Properties of Maraging Steels". http://steel.keytometals.com/default.aspx?ID=CheckArticle&NM=103. Retrieved 2009-07-19.
  61. ^ Mirko, Centi; Saliceti Stefano. "Transformation Induced Plasticity (TRIP), Twinning Induced Plasticity (TWIP) and Dual-Phase (DP) Steels". Tampere University of Technology. Archived from the original on 2008-03-07. http://web.archive.org/web/20080307200557/http://www.dimet.unige.it/resta/studenti/2002/27839/26/TWIP,TRIPandDualphase+mirko.doc. Retrieved 2007-03-01.
  62. ^ Hadfield manganese steel. Answers.com. McGraw-Hill Dictionary of Scientific and Technical Terms, McGraw-Hill Companies, Inc., 2003. Retrieved on 2007-02-28.
  63. ^ Bringas, John E. (2004) (PDF). Handbook of Comparative World Steel Standards: Third Edition (3rd. ed.). ASTM International. p. 14. ISBN 0-8031-3362-6. http://astm.org/BOOKSTORE/PUBS/DS67B_SampleChapter.pdf.
  64. ^ Steel Construction Manual, 8th Edition, second revised edition, American Institute of Steel Construction, 1986, ch. 1 page 1-5
  65. ^ "Galvanic protection". Britannica. Encyclopedia Britannica. 2007.
  66. ^ Ochshorn, Jonathan (2002-06-11). "Steel in 20th Century Architecture". Encyclopedia of Twentieth Century Architecture. http://www.ochshorndesign.com/cornell/writings/steel.html. Retrieved 2010-04-26.
  67. ^ "Materials science". Britannica. Encyclopedia Britannica. 2007.

Bibliography

Further reading

External links

Wikimedia Commons has media related to: Steel
Look up steel in Wiktionary, the free dictionary.
Recycling by material
aluminum • batteries • computers • concrete • glass • paper • plastic • rubber • steel • textiles • timber

Categories: Building materials | Recyclable materials | Steel | Steelmaking

 

The above information uses material from Wikipedia and is licensed under the GNU Free Documentation License.
Some facts may not have been fully verified for accuracy. [Disclaimers]
This page was last archived by our server on Fri Jul 30 21:44:33 2010. [ refresh local cache ]
Displaying this page or its contents does not use any Wikimedia Foundation's resources.
The owners of this site proudly support the Wikimedia Foundation.

[Hide]▼
'Steel' News
Usha Martin expects to complete expansion in 30 months - Hindustan Times
hindustantimes.com
Usha Martin expects to complete expansion in 30 months - Hindustan Times
Tue, 27 Jul 2010 15:10:58 GMT+00:00
Hindustan Times Speciality steel and wire rope manufacturer Usha Martin Limited expects to complete its planned Rs 1200-crore capital expenditure in the next 30 months, ...
Google News Search: Steel,
Tue Jul 27 10:38:19 2010
'Steel' Images
steel
img3.pcgames.com.cn
steel
376px x 502px | 27.10kB

[source page]



Yahoo Images Search: Steel,
Fri Jul 30 21:46:46 2010
'Steel' Blogs
Chewing Gum For The Ears: You Should Know: Steel Train
chewinggumfortheears.blogspot.com
Chewing Gum For The Ears: You Should Know: Steel Train

Chris N

Mon, 28 Jun 2010 02:14:00 GM

Steel. Train is a name that isn't completely unknown, I suppose, but I find it is mentioned less often than I would expect, at least now that I'm familiar with the band's music. Though I'd heard of the group before a couple years ago, ...

Google Blogs Search: Steel,
Fri Jul 16 06:00:08 2010
'Steel' Answers
I have many stainless steel appliances that need major cleaning. What is the best cleaner or home remedy?
Q. All of my small appliances are stainless steel and they all have spots on them. I have tried a variety of cleaners but nothing seems to work. What is the best cleaner or home remedy that will work for this? I would like for them to look like new. Thanks!
Asked by Liz - Tue Jun 17 12:00:45 2008 - - 7 Answers - 0 Comments

A. Stainless steel kitchen appliances look best when they're clean and shiny. To clean tough stains and cooking grease, and give them a dazzling shine, try the same detergent you would use when washing the dishes. One formulated to cut grease works especially well.This also works well for general kitchen cleaning.Waterless hand soap also works great as a polish, simply rub on, and polish - no rinsing...
Answered by @y - Tue Jun 17 13:44:28 2008

Yahoo Answers Search: Steel,
Fri Jul 30 22:12:22 2010
[Hide]▲