Some of the most commonly used iron alloys are:. Iron, in general, was heavily used for tools and weapons in the past; for example, iron ore that contained vanadium was used to create Damascene steel, perfect for sword-making if you want more interesting facts about iron, including its role in medieval weaponry, our Game of Tonnes infographic may be right up your alley!

Nowadays, we tend to use iron to create steel, often used in manufacturing and civil engineering. Uses of iron in daily life include machinery and tools, as well as vehicles, hulls of ships, structural elements for buildings, bridges and aircraft.

But can iron be recycled? The answer is yes; recycling your vehicle, including the iron in it, has many environmental benefits. By doing this, you are actively helping to reduce the use of natural resources, contributing to lower levels of carbon emissions, and reducing the amount of energy needed to make more metal from virgin ore.

More specifically, for every tonne of steel recycled , you can save 1. This means that, by scrapping end-of-life vehicles , you are contributing to less air pollution, less water pollution and less mining waste, which means increased sustainability. At Morecambe Metals , we love everything metal, and we also love recycling it!

Being aware of the properties of metals that you make use of in your day-to-day can help you to gain a deeper understanding of their applications and carbon footprint, for example. This is crucial, especially in a society where sustainability has gained more importance in recent decades.

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Iron has low cost and high strength. It is used in automobiles, rails, ship hulls, machining tools, etc. The load carrying framework of buildings is majorly supported by iron. September 12, by CEW · Published September 12, August 21, by CEW · Published August 21, · Last modified August 11, September 1, by CEW · Published September 1, Pump Performance Curve.

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Conversely, many human induced problems, especially vandalism , are random in occurrence; can produce catastrophic results; are difficult to prevent, and require emergency action to mitigate.

Some human induced problems, however, are predictable and occur routinely. Selective Attack: When a metal is not homogenous throughout, certain areas may be attacked in preference to others. Stress corrosion cracking: Attacks areas in a metal which were stressed during metal working and were later exposed to a corrosive environment.

Old, hand wrought iron items are more likely to be affected than are machine rolled wrought iron pieces. Rust: Probably the most common form of chemical corrosion of wrought iron.

It occurs when unprotected metal is exposed to oxygen in the atmosphere in the presence of moisture. Moisture can be in the form of normal humidity, rain, dew, condensation, etc.

Other gases, such as carbon dioxide, sulfur compounds, soot and fly ash will exacerbate the corrosion of the iron, as will airborne salts. Galvanic or Electro-Chemical Corrosion: Galvanic corrosion occurs when two dissimilar metals are in contact with one another and an electrolyte, such as rainwater, condensation, dew, fog, etc.

is present. Such a reaction will cause one or the other of the metals to corrode. In the case of wrought iron, direct contact with copper or zinc, and to a lesser extent galvanized iron or steel, will cause galvanic corrosion.

Wrought iron is generally fatigue resistant because it is so tough. It will deform considerably, within its elastic limit, without failure.

Even if past overloading has caused deformation, wrought iron fixings will usually continue to function.

Heat: Usually in the form of fire, will cause wrought iron features to become plastic, distort, and fail. Distortion: Permanent deformation or failure may occur when a metal is overloaded beyond its yield point because of increased live or dead loads, thermal stresses, or structural modifications altering a stress regime.

Chemical and mechanical processes can breakdown or reduce the effectiveness of structural metal fixings such as bolts, rivets, and pins. Stress failure is often a contributor to breakdown situations. Iron water traps are particularly susceptible.

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Rates for Alaska, Hawaii, U. Economically workable reserves of iron ores exceed billion tonnes. The main mining areas are China, Brazil, Australia, Russia and Ukraine, with sizeable amounts mined in the USA, Canada, Venezuela, Sweeden and India.

Iron can be found in meat, whole meal products, potatoes and vegetables. The human body absorbs iron in animal products faster than iron in plant products. Iron is an essential part of hemoglobin; the red colouring agent of the blood that transports oxygen through our bodies.

Iron may cause conjunctivitis, choroiditis, and retinitis if it contacts and remains in the tissues. Chronic inhalation of excessive concentrations of iron oxide fumes or dusts may result in development of a benign pneumoconiosis, called siderosis, which is observable as an x-ray change.

No physical impairment of lung function has been associated with siderosis. Inhalation of excessive concentrations of iron oxide may enhance the risk of lung cancer development in workers exposed to pulmonary carcinogens.

LD Lethal dose A more common problem for humans is iron deficency, which leads to anaemia. A man needs an average daily intake pf 7 mg of iron and a woman 11 mg; a normal diet will generally provided all that is needed.

Iron III -O-arsenite, pentahydrate may be hazardous to the environment; special attention should be given to plants, air and water. It is strongly advised not to let the chemical enter into the environment because it persists in the environment.

Read more on iron in water Back to the periodic table of elements. As molten iron cools past its freezing point of °C, it crystallizes into its δ allotrope, which has a body-centered cubic bcc crystal structure.

As it cools further to °C, it changes to its γ-iron allotrope, a face-centered cubic fcc crystal structure, or austenite. At °C and below, the crystal structure again becomes the bcc α-iron allotrope. The physical properties of iron at very high pressures and temperatures have also been studied extensively, [11] [12] because of their relevance to theories about the cores of the Earth and other planets.

Above approximately 10 GPa and temperatures of a few hundred kelvin or less, α-iron changes into another hexagonal close-packed hcp structure, which is also known as ε-iron. The higher-temperature γ-phase also changes into ε-iron, but does so at higher pressure.

Some controversial experimental evidence exists for a stable β phase at pressures above 50 GPa and temperatures of at least K. It is supposed to have an orthorhombic or a double hcp structure.

The inner core of the Earth is generally presumed to consist of an iron- nickel alloy with ε or β structure. The melting and boiling points of iron, along with its enthalpy of atomization , are lower than those of the earlier 3d elements from scandium to chromium , showing the lessened contribution of the 3d electrons to metallic bonding as they are attracted more and more into the inert core by the nucleus; [15] however, they are higher than the values for the previous element manganese because that element has a half-filled 3d sub-shell and consequently its d-electrons are not easily delocalized.

This same trend appears for ruthenium but not osmium. The melting point of iron is experimentally well defined for pressures less than 50 GPa. For greater pressures, published data as of still varies by tens of gigapascals and over a thousand kelvin. Below its Curie point of °C 1, °F; 1, K , α-iron changes from paramagnetic to ferromagnetic : the spins of the two unpaired electrons in each atom generally align with the spins of its neighbors, creating an overall magnetic field.

y 2 do not point toward neighboring atoms in the lattice, and therefore are not involved in metallic bonding. In the absence of an external source of magnetic field, the atoms get spontaneously partitioned into magnetic domains , about 10 micrometers across, [20] such that the atoms in each domain have parallel spins, but some domains have other orientations.

Thus a macroscopic piece of iron will have a nearly zero overall magnetic field. Application of an external magnetic field causes the domains that are magnetized in the same general direction to grow at the expense of adjacent ones that point in other directions, reinforcing the external field.

This effect is exploited in devices that need to channel magnetic fields to fulfill design function, such as electrical transformers , magnetic recording heads, and electric motors.

Impurities, lattice defects , or grain and particle boundaries can "pin" the domains in the new positions, so that the effect persists even after the external field is removed — thus turning the iron object into a permanent magnet. Similar behavior is exhibited by some iron compounds, such as the ferrites including the mineral magnetite , a crystalline form of the mixed iron II,III oxide Fe 3 O 4 although the atomic-scale mechanism, ferrimagnetism , is somewhat different.

Pieces of magnetite with natural permanent magnetization lodestones provided the earliest compasses for navigation. Particles of magnetite were extensively used in magnetic recording media such as core memories , magnetic tapes , floppies , and disks , until they were replaced by cobalt -based materials.

Iron has four stable isotopes : 54 Fe 5. Twenty-four artificial isotopes have also been created. The nuclide 54 Fe theoretically can undergo double electron capture to 54 Cr, but the process has never been observed and only a lower limit on the half-life of 3. In the last decade, advances in mass spectrometry have allowed the detection and quantification of minute, naturally occurring variations in the ratios of the stable isotopes of iron.

Much of this work is driven by the Earth and planetary science communities, although applications to biological and industrial systems are emerging.

In phases of the meteorites Semarkona and Chervony Kut, a correlation between the concentration of 60 Ni, the granddaughter of 60 Fe, and the abundance of the stable iron isotopes provided evidence for the existence of 60 Fe at the time of formation of the Solar System.

Possibly the energy released by the decay of 60 Fe, along with that released by 26 Al , contributed to the remelting and differentiation of asteroids after their formation 4. The abundance of 60 Ni present in extraterrestrial material may bring further insight into the origin and early history of the Solar System.

The most abundant iron isotope 56 Fe is of particular interest to nuclear scientists because it represents the most common endpoint of nucleosynthesis. This 56 Ni, which has a half-life of about 6 days, is created in quantity in these stars, but soon decays by two successive positron emissions within supernova decay products in the supernova remnant gas cloud, first to radioactive 56 Co, and then to stable 56 Fe.

As such, iron is the most abundant element in the core of red giants , and is the most abundant metal in iron meteorites and in the dense metal cores of planets such as Earth. Although a further tiny energy gain could be extracted by synthesizing 62 Ni , which has a marginally higher binding energy than 56 Fe, conditions in stars are unsuitable for this process.

Element production in supernovas greatly favor iron over nickel, and in any case, 56 Fe still has a lower mass per nucleon than 62 Ni due to its higher fraction of lighter protons. In the far future of the universe, assuming that proton decay does not occur, cold fusion occurring via quantum tunnelling would cause the light nuclei in ordinary matter to fuse into 56 Fe nuclei.

Fission and alpha-particle emission would then make heavy nuclei decay into iron, converting all stellar-mass objects to cold spheres of pure iron.

Iron's abundance in rocky planets like Earth is due to its abundant production during the runaway fusion and explosion of type Ia supernovae , which scatters the iron into space. Metallic or native iron is rarely found on the surface of the Earth because it tends to oxidize.

Electric currents in the liquid outer core are believed to be the origin of the Earth's magnetic field. The other terrestrial planets Mercury , Venus , and Mars as well as the Moon are believed to have a metallic core consisting mostly of iron.

The M-type asteroids are also believed to be partly or mostly made of metallic iron alloy. The rare iron meteorites are the main form of natural metallic iron on the Earth's surface.

Items made of cold-worked meteoritic iron have been found in various archaeological sites dating from a time when iron smelting had not yet been developed; and the Inuit in Greenland have been reported to use iron from the Cape York meteorite for tools and hunting weapons.

This is known as telluric iron and is described from a few localities, such as Disko Island in West Greenland, Yakutia in Russia and Bühl in Germany. In the literature, this mineral phase of the lower mantle is also often called magnesiowüstite.

While iron is the most abundant element on Earth, most of this iron is concentrated in the inner and outer cores. Most of the iron in the crust is combined with various other elements to form many iron minerals.

An important class is the iron oxide minerals such as hematite Fe 2 O 3 , magnetite Fe 3 O 4 , and siderite FeCO 3 , which are the major ores of iron. Many igneous rocks also contain the sulfide minerals pyrrhotite and pentlandite.

Both of these are oxidized in aqueous solution and precipitate in even mildly elevated pH as iron III oxide. Large deposits of iron are banded iron formations , a type of rock consisting of repeated thin layers of iron oxides alternating with bands of iron-poor shale and chert. The banded iron formations were laid down in the time between 3, million years ago and 1, million years ago.

Materials containing finely ground iron III oxides or oxide-hydroxides, such as ochre , have been used as yellow, red, and brown pigments since pre-historical times. They contribute as well to the color of various rocks and clays , including entire geological formations like the Painted Hills in Oregon and the Buntsandstein "colored sandstone", British Bunter.

from Donzdorf in Germany [49] and Bath stone in the UK, iron compounds are responsible for the yellowish color of many historical buildings and sculptures. Significant amounts of iron occur in the iron sulfide mineral pyrite FeS 2 , but it is difficult to extract iron from it and it is therefore not exploited.

According to the International Resource Panel 's Metal Stocks in Society report , the global stock of iron in use in society is 2, kg per capita. More-developed countries differ in this respect from less-developed countries 7,—14, vs 2, kg per capita.

Ocean science demonstrated the role of the iron in the ancient seas in both marine biota and climate. Iron shows the characteristic chemical properties of the transition metals , namely the ability to form variable oxidation states differing by steps of one and a very large coordination and organometallic chemistry : indeed, it was the discovery of an iron compound, ferrocene , that revolutionalized the latter field in the s.

Iron also occurs in higher oxidation states , e. The oxidation states and other bonding properties are often assessed using the technique of Mössbauer spectroscopy. As such, iron, cobalt, and nickel are sometimes grouped together as the iron triad.

Unlike many other metals, iron does not form amalgams with mercury. As a result, mercury is traded in standardized 76 pound flasks 34 kg made of iron. However, it does not react with concentrated nitric acid and other oxidizing acids due to the formation of an impervious oxide layer, which can nevertheless react with hydrochloric acid.

Iron forms various oxide and hydroxide compounds ; the most common are iron II,III oxide Fe 3 O 4 , and iron III oxide Fe 2 O 3. Iron II oxide also exists, though it is unstable at room temperature.

Despite their names, they are actually all non-stoichiometric compounds whose compositions may vary. They are also used in the production of ferrites , useful magnetic storage media in computers, and pigments.

The best known sulfide is iron pyrite FeS 2 , also known as fool's gold owing to its golden luster. The binary ferrous and ferric halides are well-known. The ferrous halides typically arise from treating iron metal with the corresponding hydrohalic acid to give the corresponding hydrated salts.

Iron reacts with fluorine, chlorine, and bromine to give the corresponding ferric halides, ferric chloride being the most common. The standard reduction potentials in acidic aqueous solution for some common iron ions are given below: [10].

The red-purple tetrahedral ferrate VI anion is such a strong oxidizing agent that it oxidizes ammonia to nitrogen N 2 and water to oxygen [66]. As pH rises above 0 the above yellow hydrolyzed species form and as it rises above 2—3, reddish-brown hydrous iron III oxide precipitates out of solution.

Thus, all the above complexes are rather strongly colored, with the single exception of the hexaquo ion — and even that has a spectrum dominated by charge transfer in the near ultraviolet region.

Carbon dioxide is not evolved when carbonate anions are added, which instead results in white iron II carbonate being precipitated out. In excess carbon dioxide this forms the slightly soluble bicarbonate, which occurs commonly in groundwater, but it oxidises quickly in air to form iron III oxide that accounts for the brown deposits present in a sizeable number of streams.

Due to its electronic structure, iron has a very large coordination and organometallic chemistry. Many coordination compounds of iron are known. For example, the trans - chlorohydridobis bis-1,2- diphenylphosphino ethane iron II complex is used as a starting material for compounds with the Fe dppe 2 moiety.

The dihydrate of iron II oxalate has a polymeric structure with co-planar oxalate ions bridging between iron centres with the water of crystallisation located forming the caps of each octahedron, as illustrated below. Iron III complexes are quite similar to those of chromium III with the exception of iron III 's preference for O -donor instead of N -donor ligands.

The latter tend to be rather more unstable than iron II complexes and often dissociate in water. Many Fe—O complexes show intense colors and are used as tests for phenols or enols. For example, in the ferric chloride test , used to determine the presence of phenols, iron III chloride reacts with a phenol to form a deep violet complex: [69].

Like manganese II , most iron III complexes are high-spin, the exceptions being those with ligands that are high in the spectrochemical series such as cyanide. This value is always half the number of unpaired electrons.

Complexes with zero to two unpaired electrons are considered low-spin and those with four or five are considered high-spin. They have a tendency to be oxidized to iron III but this can be moderated by low pH and the specific ligands used.

Organoiron chemistry is the study of organometallic compounds of iron, where carbon atoms are covalently bound to the metal atom. They are many and varied, including cyanide complexes , carbonyl complexes , sandwich and half-sandwich compounds.

Prussian blue or "ferric ferrocyanide", Fe 4 [Fe CN 6 ] 3 , is an old and well-known iron-cyanide complex, extensively used as pigment and in several other applications.

Another old example of an organoiron compound is iron pentacarbonyl , Fe CO 5 , in which a neutral iron atom is bound to the carbon atoms of five carbon monoxide molecules.

The compound can be used to make carbonyl iron powder, a highly reactive form of metallic iron. Thermolysis of iron pentacarbonyl gives triiron dodecacarbonyl , Fe 3 CO 12 , a complex with a cluster of three iron atoms at its core. A landmark in this field was the discovery in of the remarkably stable sandwich compound ferrocene Fe C 5 H 5 2 , by Pauson and Kealy [77] and independently by Miller and colleagues, [78] whose surprising molecular structure was determined only a year later by Woodward and Wilkinson [79] and Fischer.

Iron-centered organometallic species are used as catalysts. The Knölker complex , for example, is a transfer hydrogenation catalyst for ketones. The iron compounds produced on the largest scale in industry are iron II sulfate FeSO 4 ·7 H 2 O and iron III chloride FeCl 3.

The former is one of the most readily available sources of iron II , but is less stable to aerial oxidation than Mohr's salt NH 4 2 Fe SO 4 2 ·6H 2 O.

Iron II compounds tend to be oxidized to iron III compounds in the air. Iron is one of the elements undoubtedly known to the ancient world. However, iron artefacts of great age are much rarer than objects made of gold or silver due to the ease with which iron corrodes. Beads made from meteoric iron in BC or earlier were found in Gerzeh , Egypt by G.

Meteoric iron was highly regarded due to its origin in the heavens and was often used to forge weapons and tools. Meteoritic iron is comparably soft and ductile and easily cold forged but may get brittle when heated because of the nickel content.

The first iron production started in the Middle Bronze Age , but it took several centuries before iron displaced bronze. Samples of smelted iron from Asmar , Mesopotamia and Tall Chagar Bazaar in northern Syria were made sometime between and BC.

They appear to be the first to understand the production of iron from its ores and regard it highly in their society. Artifacts of smelted iron are found in India dating from to BC, [92] and in the Levant from about BC suggesting smelting in Anatolia or the Caucasus.

The rigveda term ayas metal refers to copper, while iron which is called as śyāma ayas , literally "black copper", first is mentioned in the post-rigvedic Atharvaveda. Some archaeological evidence suggests iron was smelted in Zimbabwe and southeast Africa as early as the eighth century BC. The spread of ironworking in Central and Western Europe is associated with Celtic expansion.

According to Pliny the Elder , iron use was common in the Roman era. During the Industrial Revolution in Britain, Henry Cort began refining iron from pig iron to wrought iron or bar iron using innovative production systems.

In he patented the puddling process for refining iron ore. It was later improved by others, including Joseph Hall. Cast iron was first produced in China during 5th century BC, [] but was hardly in Europe until the medieval period. Cast iron was used in ancient China for warfare, agriculture, and architecture.

For all these processes, charcoal was required as fuel. Medieval blast furnaces were about 10 feet 3. In , Abraham Darby I established a coke -fired blast furnace to produce cast iron, replacing charcoal, although continuing to use blast furnaces.

The ensuing availability of inexpensive iron was one of the factors leading to the Industrial Revolution. Toward the end of the 18th century, cast iron began to replace wrought iron for certain purposes, because it was cheaper.

Carbon content in iron was not implicated as the reason for the differences in properties of wrought iron, cast iron, and steel until the 18th century.

Since iron was becoming cheaper and more plentiful, it also became a major structural material following the building of the innovative first iron bridge in This bridge still stands today as a monument to the role iron played in the Industrial Revolution.

Following this, iron was used in rails, boats, ships, aqueducts, and buildings, as well as in iron cylinders in steam engines. French chemin de fer , German Eisenbahn , Turkish demiryolu , Russian железная дорога , Chinese, Japanese, and Korean 鐵道, Vietnamese đường sắt.

Steel with smaller carbon content than pig iron but more than wrought iron was first produced in antiquity by using a bloomery. Blacksmiths in Luristan in western Persia were making good steel by BC. These methods were specialized, and so steel did not become a major commodity until the s.

New methods of producing it by carburizing bars of iron in the cementation process were devised in the 17th century. In the Industrial Revolution , new methods of producing bar iron without charcoal were devised and these were later applied to produce steel.

In the late s, Henry Bessemer invented a new steelmaking process, involving blowing air through molten pig iron, to produce mild steel.

This made steel much more economical, thereby leading to wrought iron no longer being produced in large quantities. In , Antoine Lavoisier used the reaction of water steam with metallic iron inside an incandescent iron tube to produce hydrogen in his experiments leading to the demonstration of the conservation of mass , which was instrumental in changing chemistry from a qualitative science to a quantitative one.

Iron plays a certain role in mythology and has found various usage as a metaphor and in folklore. The Greek poet Hesiod 's Works and Days lines — lists different ages of man named after metals like gold, silver, bronze and iron to account for successive ages of humanity.

The Virtues, in despair, quit the earth; and the depravity of man becomes universal and complete. Hard steel succeeded then.

An example of the importance of iron's symbolic role may be found in the German Campaign of Frederick William III commissioned then the first Iron Cross as military decoration.

Berlin iron jewellery reached its peak production between and , when the Prussian royal family urged citizens to donate gold and silver jewellery for military funding.

The inscription Ich gab Gold für Eisen I gave gold for iron was used as well in later war efforts. For a few limited purposes when it is needed, pure iron is produced in the laboratory in small quantities by reducing the pure oxide or hydroxide with hydrogen, or forming iron pentacarbonyl and heating it to °C so that it decomposes to form pure iron powder.

Nowadays, the industrial production of iron or steel consists of two main stages. In the first stage, iron ore is reduced with coke in a blast furnace , and the molten metal is separated from gross impurities such as silicate minerals.

This stage yields an alloy — pig iron — that contains relatively large amounts of carbon. In the second stage, the amount of carbon in the pig iron is lowered by oxidation to yield wrought iron, steel, or cast iron.

The blast furnace is loaded with iron ores, usually hematite Fe 2 O 3 or magnetite Fe 3 O 4 , along with coke coal that has been separately baked to remove volatile components and flux limestone or dolomite. This reaction raises the temperature to about °C. The carbon monoxide reduces the iron ore to metallic iron [].

Some iron in the high-temperature lower region of the furnace reacts directly with the coke: []. The flux removes silicaceous minerals in the ore, which would otherwise clog the furnace: The heat of the furnace decomposes the carbonates to calcium oxide , which reacts with any excess silica to form a slag composed of calcium silicate CaSiO 3 or other products.

At the furnace's temperature, the metal and the slag are both molten. They collect at the bottom as two immiscible liquid layers with the slag on top , that are then easily separated.

Steelmaking thus remains one of the largest industrial contributors of CO 2 emissions in the world. This high level of carbon makes it relatively weak and brittle.

Reducing the amount of carbon to 0. A great variety of steel articles can then be made by cold working , hot rolling , forging , machining , etc. Steel products often undergo various heat treatments after they are forged to shape.

Annealing consists of heating them to — °C for several hours and then gradual cooling. It makes the steel softer and more workable. Owing to environmental concerns, alternative methods of processing iron have been developed.

Natural gas is partially oxidized with heat and a catalyst : []. Iron ore is then treated with these gases in a furnace, producing solid sponge iron: []. Silica is removed by adding a limestone flux as described above. Ignition of a mixture of aluminium powder and iron oxide yields metallic iron via the thermite reaction :.

Various processes have been used for this, including finery forges , puddling furnaces, Bessemer converters , open hearth furnaces , basic oxygen furnaces , and electric arc furnaces. In all cases, the objective is to oxidize some or all of the carbon, together with other impurities.

On the other hand, other metals may be added to make alloy steels. Molten oxide electrolysis uses an alloy of chromium, iron and other metals that does not react with oxygen and a liquid iron cathode while the electrolyte is a mixture of molten metal oxides into which iron ore is dissolved.

The current keeps the electrolyte molten, and reduces the iron oxide. In addition to pure liquid iron, put oxygen is also produced, which can be sold to offset part of the cost. Production cell size is variable and can be much smaller than conventional furnaces.

The only cardon dioxide emissions come from the electricity used to heat and reduce the metal. Its low cost and high strength often make it the material of choice to withstand stress or transmit forces, such as the construction of machinery and machine tools , rails , automobiles , ship hulls , concrete reinforcing bars , and the load-carrying framework of buildings.

Since pure iron is quite soft, it is most commonly combined with alloying elements to make steel. The mechanical properties of iron and its alloys are extremely relevant to their structural applications. Those properties can be evaluated in various ways, including the Brinell test , the Rockwell test and the Vickers hardness test.

The properties of pure iron are often used to calibrate measurements or to compare tests. An increase in the carbon content will cause a significant increase in the hardness and tensile strength of iron.

Maximum hardness of 65 R c is achieved with a 0. α-Iron is a fairly soft metal that can dissolve only a small concentration of carbon no more than 0. This form of iron is used in the type of stainless steel used for making cutlery, and hospital and food-service equipment.

Commercially available iron is classified based on purity and the abundance of additives. Pig iron has 3. Pig iron is not a saleable product, but rather an intermediate step in the production of cast iron and steel. The broken surface of a white cast iron is full of fine facets of the broken iron carbide, a very pale, silvery, shiny material, hence the appellation.

Cooling a mixture of iron with 0. Rapid cooling, on the other hand, does not allow time for this separation and creates hard and brittle martensite. The steel can then be tempered by reheating to a temperature in between, changing the proportions of pearlite and martensite.

The end product below 0. In gray iron the carbon exists as separate, fine flakes of graphite , and also renders the material brittle due to the sharp edged flakes of graphite that produce stress concentration sites within the material.

Wrought iron contains less than 0. If honed to an edge, it loses it quickly. Wrought iron is characterized by the presence of fine fibers of slag entrapped within the metal. Wrought iron is more corrosion resistant than steel. It has been almost completely replaced by mild steel for traditional "wrought iron" products and blacksmithing.

Mild steel corrodes more readily than wrought iron, but is cheaper and more widely available. Carbon steel contains 2. Alloy steels contain varying amounts of carbon as well as other metals, such as chromium , vanadium , molybdenum , nickel, tungsten , etc. Their alloy content raises their cost, and so they are usually only employed for specialist uses.

One common alloy steel, though, is stainless steel. Recent developments in ferrous metallurgy have produced a growing range of microalloyed steels, also termed ' HSLA ' or high-strength, low alloy steels, containing tiny additions to produce high strengths and often spectacular toughness at minimal cost.

Alloys with high purity elemental makeups such as alloys of electrolytic iron have specifically enhanced properties such as ductility , tensile strength , toughness , fatigue strength , heat resistance, and corrosion resistance. Apart from traditional applications, iron is also used for protection from ionizing radiation.

Although it is lighter than another traditional protection material, lead , it is much stronger mechanically. The attenuation of radiation as a function of energy is shown in the graph.

The mechanism of the rusting of iron is as follows: []. The electrolyte is usually iron II sulfate in urban areas formed when atmospheric sulfur dioxide attacks iron , and salt particles in the atmosphere in seaside areas.

Because Fe is inexpensive and nontoxic, much effort has been devoted to the development of Fe-based catalysts and reagents.

Iron is however less common as a catalyst in commercial processes than more expensive metals. Iron catalysts are traditionally used in the Haber—Bosch process for the production of ammonia and the Fischer—Tropsch process for conversion of carbon monoxide to hydrocarbons for fuels and lubricants.

Iron III oxide mixed with aluminium powder can be ignited to create a thermite reaction , used in welding large iron parts like rails and purifying ores.

Iron III oxide and oxyhydroxide are used as reddish and ocher pigments. Iron III chloride finds use in water purification and sewage treatment , in the dyeing of cloth, as a coloring agent in paints, as an additive in animal feed, and as an etchant for copper in the manufacture of printed circuit boards.

Iron II sulfate is used as a precursor to other iron compounds.