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8 décembre 2011 4 08 /12 /décembre /2011 03:42

Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal.HP Pavilion DV4-1199EA Battery

Cobalt-based blue pigments have been used since ancient times for jewelry and paints, and to impart a distinctive blue tint to glass, but the color was later thought by alchemists to be due to the known metal bismuth. Miners had long used the namekobold ore(German for goblin ore) for some of the blue-pigment producing minerals;HP Pavilion DV4-1199EE Battery

they were named because they were poor in known metals and gave poisonous arsenic-containing fumes upon smelting. In 1735, such ores were found to be reducible to a new metal (the first discovered since ancient times), and this was ultimately named for the kobold.HP Pavilion DV4-1199EF Battery

Nowadays, some cobalt is produced specifically from various metallic-lustered ores, for example cobaltite (CoAsS), but the main source of the element is as a by-product of copper and nickel mining. The copper belt in the Democratic Republic of the Congo and Zambia yields most of the cobalt metal mined worldwide.HP Pavilion DV4-1199EO Battery

Cobalt is used in the preparation of magnetic, wear-resistant and high-strength alloys. Cobalt silicate and cobalt(II) aluminate (CoAl2O4, cobalt blue) give a distinctive deep blue color to glass, smalt, ceramics, inks, paints and varnishes. Cobalt occurs naturally as only one stable isotope, cobalt-59.HP Pavilion DV4-1199EP Battery

Cobalt-60 is a commercially important radioisotope, used as aradioactive tracer and in the production of gamma rays.

Cobalt is the active center of coenzymes called cobalamins, the most common example of which is vitamin B12. As such it is an essential trace dietary mineral for all animals. Cobalt in inorganic form is also an active nutrient for bacteria, algae andfungi.HP Pavilion DV4-1199ER Battery

Cobalt is a ferromagnetic metal with a specific gravity of 8.9. Pure cobalt is not found in nature, but compounds of cobalt are common. Small amounts of it are found in most rocks, soil, plants and animals. The Curie temperature is 1115 °C[4] and the magnetic moment is 1.6–1.7 Bohr magnetons per atom.HP Pavilion DV4-1199ES Battery

In nature, it is frequently associated with nickel, and both are characteristic minor components of meteoric iron. Cobalt has arelative permeability two thirds that of iron.Metallic cobalt occurs as twocrystallographic structures: hcp and fcc. The ideal transition temperature between the hcp and fcc structures is 450 °C, but in practice, the energy difference is so small that random intergrowth of the two is common.HP Pavilion DV4-1199ET Battery

Cobalt is a weakly reducing metal that is protected from oxidation by a passivating oxide film. It is attacked by halogens and sulfur. Heating in oxygen produces Co3O4 which loses oxygen at 900 °C to give the monoxide CoO.HP Pavilion DV4-1200 CTO Battery

Common oxidation states of cobalt include +2 and +3, although compounds with oxidation states ranging from ?3 to +4 are also known. A common oxidation state for simple compounds is +2. Cobalt(II) salts form the red-pink [Co(H2O)6]2+ complex in aqueous solution. Addition of chloride gives the intensely blue [CoCl4]2?.HP Pavilion DV4-1200 Battery

Oxygen and chalcogen compounds

Several oxides of cobalt are known. Green cobalt(II) oxide (CoO) has rocksalt structure. It is readily oxidized with water and oxygen to brown cobalt(III) hydroxide (Co(OH)3). At temperatures of 600–700 °C, CoO oxidizes to the blue cobalt(II,III) oxide (Co3O4), which has a spinel structure.HP Pavilion DV4-1201AU Battery

Black cobalt(III) oxide (Co2O3) is also known.[11] Cobalt oxides areantiferromagnetic at low temperature: CoO (Neel temperature 291 K) and CHP Pavilion DV4-1201TU Battery

The principal chalcogenides of cobalt include the black cobalt(II) sulfides, CoS2, which adopts a pyrite-like structure, andCo2S3. Pentlandite (Co9S8) is metal-rich.HP Pavilion DV4-1201TX Battery

Halides

The four dihalides of cobalt(II) are known: cobalt(II) fluoride (CoF2, pink), cobalt(II) chloride (CoCl2, blue), cobalt(II) bromide (CoBr2, green), cobalt(II) iodide (CoI2, blue-black). These halides exist as anhydrous and hydrates. Whereas the anhydrous dichloride is blue, the hydrate is red.HP Pavilion DV4-1202AU Battery

The reduction potential for the reaction

Co3+ + e? ? Co2+

is +1.92 V, beyond that for chlorine to chloride, +1.36 V. As a consequence cobalt(III) and chloride would result in the cobalt(III) being reduced to cobalt(II).HP Pavilion DV4-1202TU Battery

Because the reduction potential for fluorine to fluoride is so high, +2.87 V, cobalt(III) fluoride is one of the few simple stable cobalt(III) compounds. Cobalt(III) fluoride, which is used in some fluorination reactions, reacts vigorously with water.HP Pavilion DV4-1202TX Battery

Coordination compounds

As for all metals, molecular compounds of cobalt are classified as coordination complexes, that is molecules or ions that contain cobalt linked to several ligands. The principles of electronegativity and hardness–softness of a series of ligands can be used to explain the usual oxidation state of the cobalt.HP Pavilion DV4-1203AU Battery

For example Co+3 complexes tend to have ammine ligands. As phosphorus is softer than nitrogen, phosphine ligands tend to feature the softer Co2+ and Co+, an example being tris(triphenylphosphine)cobalt(I) chloride ((P(C6H5)3)3CoCl). The more electronegative (and harder) oxide and fluoride can stabilize Co4+ derivatives, e.g.HP Pavilion DV4-1203TU Battery

caesium hexafluorocobaltate (Cs2CoF6) and potassium percobaltate (K3CoO4).

Alfred Werner, a Nobel-prize winning pioneer in coordination chemistry, worked with compounds of empirical formulaCoCl3(NH3)6. One of the isomers determined was cobalt(III) hexammine chloride.HP Pavilion DV4-1203TX Battery

This coordination complex, a "typical" Werner-type complex, consists of a central cobalt atom coordinated by six ammine ligands orthogonal to each other and three chloridecounteranions. Using chelating ethylenediamine ligands in place of ammonia gives tris(ethylenediamine)cobalt(III) chloride([Co(en)3]Cl),HP Pavilion DV4-1204AU Battery

which was one of the first coordination complexes that was resolved into optical isomers. The complex exists as both either right- or left-handed forms of a "three-bladed propeller". This complex was first isolated by Werner as yellow-gold needle-like crystals.HP Pavilion DV4-1204TU Battery

Organometallic compounds

Cobaltocene is a structural analog to ferrocene, where cobalt substitutes for iron. Cobaltocene is sensitive to oxidation, much more than ferrocene. Cobalt carbonyl (Co2(CO)8) is a catalyst in carbonylation reactions. Vitamin B12 (see below) is an organometallic compound found in nature and is the only vitamin to contain a metal atom.HP Pavilion DV4-1204TX Battery

59Co is the only stable cobalt isotope and the only isotope to exist in nature. 22 radioisotopes have been characterized with the most stable being 60Co with a half-life of 5.2714 years, 57Co with a half-life of 271.79 days, 56Co with a half-life of 77.27 days, and 58Co with a half-life of 70.86 days.HP Pavilion DV4-1205AU Battery

All of the remainingradioactive isotopes have half-lives that are shorter than 18 hours, and the majority of these are shorter than 1 second. This element also has 4 meta states, all of which have half-lives shorter than 15 minutes.

The isotopes of cobalt range in atomic weight from 50 u (50Co) to 73 u (73Co).HP Pavilion DV4-1205TU Battery

The primary decay mode for isotopes with atomic mass unit values less than that of the most abundant stable isotope, 59Co, is electron capture and the primary mode of decay for those of greater than 59 atomic mass units is beta decay. The primary decay products before 59Co are element 26 (iron) isotopes and the primary products after are element 28 (nickel) isotopes.HP Pavilion DV4-1205TX Battery

Cobalt compounds have been used for centuries to impart a rich blue color to glass, glazes and ceramics. Cobalt has been detected in Egyptian sculpture and Persian jewelry from the third millennium BC, in the ruins of Pompeii (destroyed in 79 AD), and in China dating from the Tang dynasty (618–907 AD) and the Ming dynasty (1368–1644 AD).HP Pavilion DV4-1206TU Battery

Cobalt has been used to color glass since the Bronze Age. The excavation of the Uluburun shipwreck yielded an ingot of blue glass, which was cast during the 14th century BC. Blue glass items from Egypt are colored with copper, iron, or cobalt. The oldest cobalt-colored glass was from the time of the Eighteenth dynasty in Egypt (1550–1292 BC).HP Pavilion DV4-1206TX Battery

The location where the cobalt compounds were obtained is unknown.

The word cobalt is derived from the German kobalt, from kobold meaning "goblin", a superstitious term used for the ore of cobalt by miners. The first attempts at smelting these ores to produce metals such as copper or nickel failed, yielding simply powder (cobalt(II) oxide) instead.HP Pavilion DV4-1207TU Battery

Also, because the primary ores of cobalt always contain arsenic, smelting the ore oxidized the arsenic content into the highly toxic and volatile arsenic oxide, which also decreased the reputation of the ore for the miners.

Swedish chemist Georg Brandt (1694–1768) is credited with discovering cobalt circa 1735, showing it to be a new previously unknown element different from bismuth and other traditional metals, and calling it a new "semi-metal."HP Pavilion DV4-1207TX Battery

He was able to show that compounds of cobalt metal were the source of the blue color in glass, which previously had been attributed to thebismuth found with cobalt. Cobalt became the first metal to be discovered since the pre-historical period, during which all the known metals (iron, copper, silver, gold, zinc, mercury, tin, lead and bismuth) had no recorded discoverers.HP Pavilion DV4-1208TU Battery

During the 19th century, a significant part of the world's production of cobalt blue (a dye made with cobalt compounds and alumina) and smalt (cobalt glass powdered for use for pigment purposes in ceramics and painting) was carried out at the Norwegian Blaafarveværket.HP Pavilion DV4-1208TX Battery

The first mines for the production of smalt in the 16th to 18th century were located in Norway, Sweden, Saxony and Hungary. With the discovery of cobalt ore in New Caledonia in 1864 the mining of cobalt in Europe declined. With the discovery of ore deposits in Ontario,HP Pavilion DV4-1209TU Battery

Canada in 1904 and the discovery of even larger deposits in the Katanga Province in the Congo in 1914 the mining operations shifted again. With the Shaba conflict starting in the 1978 the main source for cobalt the copper mines of Katanga Province nearly stopped their production.HP Pavilion DV4-1209TX Battery

The impact on the world cobalt economy from this conflict was smaller than expected, because industry established effective ways for recycling cobalt materials and in some cases was able to change to cobalt-free alternatives.

In 1938, John Livingood and Glenn T. Seaborg discovered cobalt-60. This isotope was famously used at Columbia University in the 1950s to establish parityviolation in radioactive beta decay.HP Pavilion DV4-1210EA Battery

Occurrence

The stable form of cobalt is created in supernovas via the r-process. It comprises 0.0029% of the Earth's crust and is one of the first transition metal series.

Cobalt occurs in copper and nickel minerals and in combination with sulfur and arsenic in the sulfidic cobaltite (CoAsS), safflorite (CoAs2) and skutterudite (CoAs3) minerals.HP Pavilion DV4-1210EF Battery

The mineral cattierite is similar to pyrite and occurs together with vaesite in the copper deposits of the Katanga Province.[37] Upon contact with the atmosphere, weathering occurs and the sulfide minerals oxidize to form pink erythrite ("cobalt glance": Co3(AsO4)2·8H2O) and sphaerocobaltite (CoCO3).HP Pavilion DV4-1210EO Battery

Cobalt is not found as a native metal but is mainly obtained as a by-product of nickel and copper mining activities. The main ores of cobalt are cobaltite,erythrite, glaucodot and skutterudite.HP Pavilion DV4-1210ER Battery

Production

In 2005, the copper deposits in the Katanga Province (former Shaba province) of the Democratic Republic of the Congo were the top producer of cobalt with almost 40% world share, reports theBritish Geological Survey.[42] The political situation in the Congo influences the price of cobalt significantly.HP Pavilion DV4-1210TU Battery

The Mukondo Mountain project, operated by the Central African Mining and Exploration Company in Katanga, may be the richest cobalt reserve in the world. It is estimated to be able to produce about one third of total global production of cobalt in 2008.HP Pavilion DV4-1210TX Battery

In July 2009 CAMEC announced a long term agreement under which CAMEC would deliver its entire annual production of cobalt in concentrate from Mukondo Mountain to Zhejiang Galico Cobalt & Nickel Materials of China.

Several methods exist for the separation of cobalt from copper and nickel. They depend on the concentration of cobalt and the exact composition of the used ore.HP Pavilion DV4-1211EA Battery

One separation step involves froth flotation, in which surfactants bind to different ore components, leading to an enrichment of cobalt ores. Subsequent roasting converts the ores to the cobalt sulfate, whereas the copper and the iron are oxidized to the oxide. The leaching with water extracts the sulfate together with the arsenates.HP Pavilion DV4-1211TU Battery

The residues are further leached with sulfuric acid yielding a solution of copper sulfate. Cobalt can also be leached from the slag of the copper smelter.

The products of the above-mentioned processes are transformed into the cobalt oxide (Co3O4). This oxide is reduced to the metal by the aluminothermic reaction or reduction with carbon in a blast furnace.HP Pavilion DV4-1211TX Battery

Applications

The main application of cobalt is as the metal in alloys.

Alloys

Cobalt-based superalloys consume most of the produced cobalt. The temperature stability of these alloys makes them suitable for use in turbine blades for gasturbines and jet aircraft engines, though nickel-based single crystal alloys surpass them in this regard.HP Pavilion DV4-1212LA Battery

Cobalt-based alloys are also corrosion and wear-resistant. This makes them useful in the medical field, where cobalt is often used (along with titanium) for orthopedic implants that do not wear down over time. The development of the wear-resistant cobalt alloys started in the first decade of the 19th century with the stellite alloys, which are cobalt-chromium alloys with varying tungsten and carbon content.HP Pavilion DV4-1212TU Battery

The formation of chromium and tungsten carbides makes them very hard and wear resistant.[48] Special cobalt-chromium-molybdenumalloys like Vitallium are used for prosthetic parts such as hip and knee replacements.[49] Cobalt alloys are also used for dental prosthetics, where they are useful to avoid allergies to nickel.HP Pavilion DV4-1212TX Battery

Some high speed steels also use cobalt to increase heat and wear-resistance. The special alloys of aluminium, nickel, cobalt and iron, known as Alnico, and of samarium and cobalt (samarium-cobalt magnet) are used in permanent magnets. It is also alloyed with 95% platinum for jewelry purposes, yielding an alloy that is suitable for fine detailed casting and is also slightly magnetic.HP Pavilion DV4-1213LA Battery

Batteries

Lithium cobalt oxide (LiCoO2) is widely used in lithium ion battery cathodes. The material is composed of cobalt oxide layers in which the lithium is intercalated. During discharging the lithium intercalated between the layers is set free as lithium ion.HP Pavilion DV4-1213TU Battery

Nickel-cadmium  (NiCd) and nickel metal hydride (NiMH) batteries also contain significant amounts of cobalt; the cobalt improves the oxidation capabilities of nickel in the battery.

Catalysis

Several cobalt compounds are used in chemical reactions as oxidation catalysts.HP Pavilion DV4-1213TX Battery

Cobalt acetate is used for the conversion of xylene to terephthalic acid, the precursor to the bulk polymer polyethylene terephthalate. Typical catalysts are the cobalt carboxylates (known as cobalt soaps). They are also used in paints, varnishes, and inks as "drying agents" through the oxidation of drying oils.HP Pavilion DV4-1214LA Battery

The same carboxylates are used to improve the adhesion of the steel to rubber in steel-belted radial tires.

Cobalt-based catalysts are also important in reactions involving carbon monoxide. Steam reforming, useful in hydrogen production, uses cobalt oxide-base catalysts.HP Pavilion DV4-1214TU Battery

Cobalt is also a catalyst in the Fischer-Tropsch process, used in the hydrogenation of carbon monoxide into liquid fuels. The hydroformylation of alkenes often rely on cobalt octacarbonyl as the catalyst, although such processes have been partially displaced by more efficient iridium- and rhodium-based catalysts, e.g. the Cativa process.HP Pavilion DV4-1214TX Battery

The hydrodesulfurization of petroleum uses a catalyst derived from cobalt and molybdenum. This process helps to rid petroleum of sulfur impurities that interfere with the refining of liquid fuels.

Pigments and coloring

Before the 19th century, the predominant use of cobalt was as pigment. Since the Middle Ages, it has been involved in the production of smalt, a blue colored glass.HP Pavilion DV4-1215EF Battery

Smalt is produced by melting a mixture of the roasted mineralsmaltite, quartz and potassium carbonate, yielding a dark blue silicate glass which is ground after the production. Smalt was widely used for the coloration of glass and as pigment for paintings. In 1780, Sven Rinman discovered cobalt green and in 1802 Louis Jacques Thénard discovered cobalt blue.HP Pavilion DV4-1215TU Battery

The two varieties of cobalt blue, cobalt aluminate and cobalt green (a mixture of cobalt(II) oxide and zinc oxide), were used as pigments for paintings because of their superior stability.

Radioisotopes

Cobalt-60 (Co-60 or 60Co) is useful as a gamma ray source because it can be produced in predictable quantity and high activity by bombarding cobalt with neutrons.HP Pavilion DV4-1215TX Battery

It produces two gamma rays with energies of 1.17 and 1.33 MeV.

Its uses include external beam radiotherapy, sterilization of medical supplies and medical waste, radiation treatment of foods for sterilization (cold pasteurization), industrial radiography (e.g. weld integrity radiographs), density measurements (e.g. concrete density measurements), and tank fill height switches.HP Pavilion DV4-1216TU Battery

The metal has the unfortunate habit of producing a fine dust, causing problems withradiation protection. Cobalt from radiotherapy machines has been a serious hazard when not disposed of properly, and one of the worst radiation contamination accidents in North America occurred in 1984,HP Pavilion DV4-1216TX Battery

after a discarded radiotherapy unit containing cobalt-60 was mistakenly disassembled in a junkyard in Juarez, Mexico.

Cobalt-60 has a radioactive half-life of 5.27 years. This decrease in activity requires periodic replacement of the sources used in radiotherapy and is one reason why cobalt machines have been largely replaced by linear accelerators in modern radiation therapy.HP Pavilion DV4-1217LA Battery

Cobalt-57 (Co-57 or 57Co) is a cobalt radioisotope most often used in medical tests, as a radiolabel for vitamin B12 uptake, and for the Schilling test. Cobalt-57 is used as a source in Mössbauer spectroscopy and is one of several possible sources in X-ray fluorescence devices.HP Pavilion DV4-1217TX Battery

Nuclear weapon designs could intentionally incorporate 59Co, some of which would be activated in a nuclear explosion to produce 60Co. The 60Co, dispersed as nuclear fallout, creates what is sometimes called a cobalt bomb.HP Pavilion DV4-1218TX Battery

Other uses

Other uses of cobalt are in electroplating, owing to its attractive appearance, hardness and resistance to oxidation, and as ground coats for porcelainenamels.

Biological role

Cobalt is essential to all animals, including humans. It is a key constituent of cobalamin, also known as vitamin B12, which is the primary biological reservoir of cobalt as an "ultratrace" element.HP Pavilion DV4-1219TX Battery

Bacteria in the guts of ruminant animals convert cobalt salts into vitamin B12, a compound which can only be produced by bacteria. The minimum presence of cobalt in soils therefore markedly improves the health of grazing animals, and an uptake of 0.20 mg/kg a day is recommended.HP Pavilion DV4-1220BR Battery

Non-ruminant herbivores produce vitamin B12 from bacteria in their colons, from which the vitamin cannot be absorbed, and thus some of them ingest feces to obtain the nutrient. Animals that do not follow these methods of getting vitamin B12 from their own gastrointestinal bacteria must obtain the vitamin from animal products in their diet,HP Pavilion DV4-1220TX Battery

and they cannot benefit from ingesting simple cobalt salts.

The cobalamin-based proteins use corrin to hold the cobalt. Coenzyme B12 features a reactive C-Co bond, which participates in its reactions.HP Pavilion DV4-1220US Battery

In humans, B12 exists with two types of alkyl ligand: methyl and adenosyl. MeB12 promotes methyl (-CH3) group transfers. The adenosyl version of B12 catalyzes rearrangements in which a hydrogen atom is directly transferred between two adjacent atoms with concomitant exchange of the second substituent,HP Pavilion DV4-1221TX Battery

X, which may be a carbon atom with substituents, an oxygen atom of an alcohol, or an amine. Methylmalonyl coenzyme A mutase (MUT) converts MMl-CoA to Su-CoA, an important step in the extraction of energy from proteins and fats.

Although far less common than other metalloproteins (e.g. those of zinc and iron), cobaltoproteins are known aside from B12.HP Pavilion DV4-1222LA Battery

These proteins include methionine aminopeptidase 2 an enzyme that occurs in humans and other mammals which does not use the corrin ring of B12, but binds cobalt directly. Another non-corrin cobalt enzyme is nitrile hydratase, an enzyme in bacteria that are able to metabolizenitriles.HP Pavilion DV4-1222NR Battery

Precautions

Cobalt is an essential element for life in minute amounts. The LD50 value for soluble cobalt salts has been estimated to be between 150 and 500 mg/kg. Thus, for a 100 kg person the LD50 would be about 20 grams.HP Pavilion DV4-1222TX Battery

After nickel and chromium, cobalt is a major cause of contact dermatitis. In 1966, the addition of cobalt compounds to stabilize beer foam in Canada led tocardiomyopathy, which came to be known as beer drinker's cardiomyopathy.HP Pavilion DV4-1223LA Battery

Recovery from copper-cobalt sulfide concentrates

The ores are treated by a sulfatizing roast in a fluidized bed furnace to convert copper and cobalt sulfides into soluble oxides andiron into insoluble hematite. The calcine is subsequently leached with sulfuric acid from the spent copper recovery electrolyte. Oxide concentrates are introduced at this leaching step to maintain the acid balance in the circuit.HP Pavilion DV4-1223TX Battery

Iron and aluminum are removed from the leach solution by the addition of lime, and copper iselectrowon on copper cathodes. A part of the spent electrolyte enters the cobalt recovery circuit and is purified by the removal of iron, copper, nickel, and zincprior to the precipitation of cobalt as its hydroxide.HP Pavilion DV4-1224LA Battery

This is accomplished by the addition of more lime to raise the pH until the remaining copper precipitates. This copper is sent back to the copper circuit. As more lime is then added, a copper-cobaltite precipitates and is fed back to the leaching process.HP Pavilion DV4-1224TX Battery

Sodium hydrosulfide (NaHS) is added (along with some metallic cobalt as a catalyst) to precipitate nickel sulfide (NiS). Hydrogen sulfide (H2S) and sodium carbonate(Na2CO3) are then added to precipitate zinc sulfide (ZnS). Lime is then added to saturation to precipitate cobalt(II) hydroxide (Co(OH)2).HP Pavilion DV4-1225DX Battery

In the final stages, this cobalt hydroxide is redissolved and the metal is refined by electrolysis. The resulting cobalt cathodes are crushed and vacuum degassed to obtain a pure cobalt metal.

Recovery from nickel-cobalt sulfide concentrates (Sherritt process)

The Sherritt process is a hydrometallurgical process named for Sherritt Gordon Mines Ltd.HP Pavilion DV4-1225EE Battery

(now Sherritt International) of Sherridon and Lynn Lake Manitoba Canada, based on the older Forward process developed by Dr. Frank Forward for the recovery of copper and nickel form those same mines. Nickel sulfide concentrates can be treated by either roasting or flash smelting to produce matte from which nickel and cobalt can be recovered hydrometallurgically,HP Pavilion DV4-1225LA Battery

or they may be treated by anammonia solution pressure leach. The residue is removed. A feed of matte and sulfide concentrate containing approximately 0.4% cobalt and 30% sulfur is pressure leached at elevated temperature and pressure in an ammoniacal solution to produce a solution of nickel, copper and cobalt.HP Pavilion DV4-1225TX Battery

By boiling away the ammonia; copper is precipitated as a sulfide and sent to a smelter. Hydrogen sulfide is added to the autoclave to remove nickel sulfide and copper sulfide which is fed back to the leaching process. Air is then passed through the solution in the autoclave for oxyhydrolysis.HP Pavilion DV4-1226TX Battery

The solution is then reduced with hydrogen, again at high temperature and pressure, to precipitate nickel powder (>99%). The remaining solution (containing approximately equal proportions of nickel and cobalt sulfides), is then adjusted (to a lower temperature and pressure) to precipitate the mixed sulfides and the fluid is concentrated and crystallized into ammonium sulfate ((NH4)2SO4).HP Pavilion DV4-1227LA Battery

The mixed sulfides are pressure leached with air and sulfuric acid. Ammonia is then added to remove potassium and iron as jarosite (KFe3+3 (OH)6(SO4)2). More ammonia and air is added for oxidation. The solution is removed from the autoclave and sulfuric acid added to remove nickel as nickel(II) sulfate-ammonium sulfatehexahydrate?HP Pavilion DV4-1227TX Battery

((NiSO4)•((NH4)2SO4)•6H2O) which is then sent to have its nickel recovered. The solution is then further reduced with more sulfuric acid and cobalt metal powder is added to aid in the nucleation of precipitants (seeding). Addition of hydrogen gas to saturation precipitates cobalt powder with a purity of approximately 99.6%.HP Pavilion DV4-1227US Battery

Recovery from copper-cobalt oxide concentrates

The ore is comminuted and the cobalt rich oxides are separated by froth flotation. The cobalt-bearing concentrate is then mixed with lime and coal, and then meltedin a reducing atmosphere. Iron and lighter impurities float to the surface as solid dross or are expelled from the melt as gas.HP Pavilion DV4-1228CA Battery

The remaining liquid is composed of a heavier copper smelt containing approximately 5% cobalt that is processed for its copper and a lighter slag that is approximately 40% cobalt that is further refined by hydrometallurgical and electrolytic processing. Concentrations of cobalt oxide (Co3O4) may also be reduced by the aluminothermic reaction or with carbon in ablast furnace.HP Pavilion DV4-1228LA Battery

Recovery from laterite ores

Nickel-cobalt lateritic ores can be treated by either hydrometallurgical processes or pyrometallurgical processes, such as matte or ferronickel smelting, which require the entire ore to be melted and the metal values to be separated from the residual components of the ore. The hydrometallurgical process for laterite ore can use sulfuric acid or ammonia leach solutions.HP Pavilion DV4-1228TX Battery

Recovery from arsenide ores

Arsenic containing concentrates are roasted in a fluidized bed to remove 60% to 70% of the arsenic present as arsenic oxide (As2O5).HP Pavilion DV4-1229LA Battery

The roasted ores can be treated with hydrochloric acid and chlorine or with sulfuric acid to give a leach solution that can be purified by hydrometallurgical methods and from which cobalt can be recovered by electro refining or by carbonate precipitation.HP Pavilion DV4-1229TX Battery

If hydrochloric acid is used then cobalt may be extracted using alamine 336 in meta-xylene.Cobalt can be extracted also using Cyanex 272 {bis-(2,4,4-trimethylpentyl) phosphinic acid}. When Cobalt carbonate (CoCO3) is heated (calcined) above 400 °C it decomposes into carbon dioxide (CO2) and Cobalt(II) oxide (CoO) and can be refined as an oxide concentrate (see above).HP Pavilion DV4-1230BR Battery

Electro refining

If purifying by electrolysis, an aqueous sulfate solution at 50° to 70°C is usually used with a lead anode (corrosion products from which will not contaminate the cobalt oxy-hydroxide (CoOOH) electrolyte solution) and a stainless steel cathode which will allow for the easy removal of the deposited cobalt.HP Pavilion DV4-1230TX Battery

Electro refining in a chloride or sulfate medium at -0.3 V will make a cathode coating of 99.98% Cobalt.

Extractive metallurgy is the study of the processes used in the separation and concentration (benefaction) of raw materials.HP Pavilion DV4-1231TX Battery

The field is an applied science, covering all aspects of the physical and chemical processes used to produce mineral-containing and metallic materials, sometimes for direct use as a finished product, but more often in a form that requires further physical processing which is generally the subject of physical metallurgy, ceramics, and other disciplines within the broad field of materials science.HP Pavilion DV4-1232TX Battery

The field of extractive metallurgy encompasses many specialty sub-disciplines, each concerned with various physical and chemical processes that are steps in an overall process of producing a particular material. These specialties are generically grouped into the categories of mineral processing, hydrometallurgy,pyrometallurgy, and electrometallurgy.HP Pavilion DV4-1233TX Battery

The distinctions among these groups of sub-disciplines within extractive metallurgy is far from clear, and many commercially important metallurgical processes involve considerable overlap.

The theoretical basis of extractive metallurgy is underpinned by the more general sciences of physics, chemistry, and geology.HP Pavilion DV4-1234TX Battery

Additionally, the practice of extractive metallurgy nearly always involves contributions from other scientific fields such as analytical chemistry and mineralogy.

Mineral processing

Mineral processing involves the processes used to manipulate the particle size of solid raw materials and to separate valuable materials from materials of no value, referred to as gangue.HP Pavilion DV4-1235EE Battery

Usually, particle size reduction, also referred to as comminution, is required to permit efficient separation of the valuable materials from gangue. Separation processes take advantage of physical properties of the materials in order to separate them from each other.HP Pavilion DV4-1235EI Battery

These physical properties can include density, particle size and shape, electrical and magnetic properties, and surface properties. Since many size reduction and separation processes involve the use of water, solid-liquid separation processes are also a subject of mineral processing.HP Pavilion DV4-1235TX Battery

Hydrometallurgy

Hydrometallurgy is concerned with processes involving aqueous solutions to extract metals from ores. The most common hydrometallurgical process is leaching, which involves dissolution of the valuable metals into the aqueous solution.HP Pavilion DV4-1236TX Battery

After the solution is separated from the ore solids, the solution is often subjected to various processes of purification and concentration before the valuable metal is recovered either in its metallic state or as a chemical compound. The solution purification and concentration processes may include precipitation, distillation, adsorption, and solvent extraction.HP Pavilion DV4-1237TX Battery

The final recovery step may involve precipitation, cementation, or an electrometallurgical process. Sometimes, hydrometallurgical processes may be carried out directly on the ore material without any pretreatment steps. More often, the ore must be pretreated by various mineral processing steps, and sometimes by pyrometallurgical processes.HP Pavilion DV4-1238TX Battery

Pyrometallurgy

Pyrometallurgy involves high temperature processes where chemical reactions take place among gases, solids, and molten materials. Solids containing valuable metals are reacted to form intermediate compounds for further processing or converted into their elemental or metallic state.HP Pavilion DV4-1239TX Battery

Pyrometallurgical processes that involve gases and solids are typified by calcining and roastingoperations. Processes that produce molten products are collectively referred to as smelting operations. The energy required to sustain the high temperature pyrometallurgical processes may come entirely from the exothermic nature of the chemical reactions taking place,HP Pavilion DV4-1240TX Battery

usually oxidation reactions. Often, however, energy must be added to the process by combustion of fuel or, in the case of some smelting processes, by the direct application of electrical energy.

Ellingham Diagrams are a useful way of analysing the possible reactions, and so predicting their outcome.HP Pavilion DV4-1241TX Battery

Electrometallurgy

Electrometallurgy involves metallurgical processes that take place in some form of electrolytic cell. The most common types of electrometallurgical processes are electrowinning and electro-refining. Electrowinning is an electrolysis process used to recover metals in aqueous solution, usually as the result of an ore having undergone one or more hydrometallurgical processes.HP Pavilion DV4-1242TX Battery

The metal of interest is plated onto the cathode, while the anode is an inert electrical conductor. Electro-refining is used to dissolve an impure metallic anode (typically from a smelting process) and produce a high purity cathode. Fused salt electrolysis is another electrometallurgical process whereby the valuable metal has been dissolved into a molten salt which acts as the electrolyte,HP Pavilion DV4-1243TX Battery

and the valuable metal collects on the cathode of the cell. The fused salt electrolysis process is conducted at temperatures sufficient to keep both the electrolyte and the metal being produced in the molten state. The scope of electrometallurgy has significant overlap with the areas of hydrometallurgy and (in the case of fused salt electrolysis) pyrometallurgy.HP Pavilion DV4-1244TX Battery

Additionally, electrochemical phenomena play a considerable role in many mineral processing and hydrometallurgical processes.

Metallurgy is a domain of materials science that studies the physical and chemical behavior of metallic elements, theirintermetallic compounds, and their mixtures, which are called alloys. HP Pavilion DV4-1245BR Battery

It is also the technology of metals: the way in which science is applied to their practical use. Metallurgy is distinguished from the craft of metalworking.

Etymology and pronunciation

The word was originally (1593) an alchemist's term for the extraction of metals from minerals: the ending -urgy signifying a process, especially manufacturing: it was in this sense it was used by the 1797 Encyclopaedia Britannica.HP Pavilion DV4-1245TX Battery

In the late 19th century it was extended to the more general scientific study of metals and alloys and related processes. The roots are borrowed from Ancient Greek: ????????????, matallourgos, "worker in metal", from ????????, metallon, "metal" + ?????, ergon, "work". In English, the /me?tæl?d?i/ pronunciation is the more common one in the UK and Commonwealth.HP Pavilion DV4-1246TX Battery

The /?met?l?rd?i/ pronunciation is the more common one in the USA, and is the first-listed variant in various American dictionaries (e.g., Merriam-Webster Collegiate, American Heritage).

The first evidence of human metallurgy dates from the 5th and 6th millennium BC, and was found in the archaeological sites ofMajdanpek, Yarmovac and Plocnik all three in Serbia.HP Pavilion DV4-1247TX Battery

To date, the earliest copper smelting is found at the Belovode site,[2] these examples include a copper axe from 5,500BC belonging to the Vin?a culture.[3] Other signs of human metallurgy are found from the third millennium BC in places like Palmela (Portugal), Cortes de Navarra (Spain), and Stonehenge (United Kingdom).HP Pavilion DV4-1248TX Battery

However, as often happens with the study of prehistoric times, the ultimate beginnings cannot be clearly defined and new discoveries are continuous and ongoing.

Silver, copper, tin and meteoric iron can also be found native, allowing a limited amount of metalworking in early cultures.HP Pavilion DV4-1249TX Battery

Egyptian weapons made from meteoric iron in about 3000 B.C. were highly prized as "Daggers from Heaven".[4] However, by learning to get copper and tin by heating rocks and combining those two metals to make an alloy called bronze, the technology of metallurgy began about 3500 B.C. with the Bronze Age.HP Pavilion DV4-1250TX Battery

The extraction of iron from its ore into a workable metal is much more difficult. It appears to have been invented by theHittites in about 1200 B.C., beginning the Iron Age. The secret of extracting and working iron was a key factor in the success of the Philistines.HP Pavilion DV4-1251TX Battery

Historical developments in ferrous metallurgy can be found in a wide variety of past cultures and civilizations. This includes the ancient and medieval kingdoms and empires of the Middle East and Near East, ancient Iran, ancient Egypt, ancient Nubia, andAnatolia (Turkey),HP Pavilion DV4-1252TX Battery

Ancient Nok, Carthage, the Greeks and Romans of ancient Europe, medieval Europe, ancient and medieval China, ancient and medieval India, ancient and medieval Japan, amongst others. Many applications, practices, and devices associated or involved in metallurgy were established in ancient China,HP Pavilion DV4-1253TX Battery

such as the innovation of the blast furnace, cast iron, hydraulic-powered trip hammers, and double acting piston bellows.

A 16th century book by Georg Agricola called De re metallica describes the highly developed and complex processes of mining metal ores, metal extraction and metallurgy of the time. Agricola has been described as the "father of metallurgy".HP Pavilion DV4-1254TX Battery

Extraction

Extractive metallurgy is the practice of removing valuable metals from an ore and refining the extracted raw metals into a purer form. In order to convert a metal oxide or sulfide to a purer metal, the ore must be reduced physically, chemically, orelectrolytically.HP Pavilion DV4-1255TX Battery

Extractive metallurgists are interested in three primary streams: feed, concentrate (valuable metal oxide/sulfide), and tailings(waste). After mining, large pieces of the ore feed are broken through crushing and/or grinding in order to obtain particles small enough where each particle is either mostly valuable or mostly waste.HP Pavilion DV4-1256TX Battery

Concentrating the particles of value in a form supporting separation enables the desired metal to be removed from waste products.

Mining may not be necessary if the ore body and physical environment are conducive to leaching. Leaching dissolves minerals in an ore body and results in an enriched solution. The solution is collected and processed to extract valuable metals.HP Pavilion DV4-1257TX Battery

Ore bodies often contain more than one valuable metal. Tailings of a previous process may be used as a feed in another process to extract a secondary product from the original ore. Additionally, a concentrate may contain more than one valuable metal. That concentrate would then be processed to separate the valuable metals into individual constituents.HP Pavilion DV4-1258TX Battery

Alloys

Common engineering metals include aluminium, chromium, copper, iron, magnesium, nickel, titanium and zinc. These are most often used as alloys. Much effort has been placed on understanding the iron-carbon alloy system, which includes steels and cast irons.HP Pavilion DV4-1259TX Battery

Plain carbon steels are used in low cost, high strength applications where weight and corrosion are not a problem. Cast irons, including ductile iron are also part of the iron-carbon system.

Stainless steel or galvanized steel are used where resistance to corrosion is important. Aluminium alloys and magnesium alloys are used for applications where strength an

d lightness are required.HP Pavilion DV4-1260TX Battery

Copper-nickel alloys (such as Monel) are used in highly corrosive environments and for non-magnetic applications. Nickel-basedsuperalloys like Inconel are used in high temperature applications such as turbochargers, pressure vessel, and heat exchangers. For extremely high temperatures, single crystal alloys are used to minimize creep.HP Pavilion DV4-1265DX Battery

Production

In production engineering, metallurgy is concerned with the production of metallic components for use in consumer or engineering products. This involves the production of alloys, the shaping, the heat treatment and the surface treatment of the product.HP Pavilion DV4-1272CM Battery

The task of the metallurgist is to achieve balance between material properties such as cost, weight, strength, toughness, hardness, corrosion, fatigue resistance, and performance in temperature extremes. To achieve this goal, the operating environment must be carefully considered.HP Pavilion DV4-1275MX Battery

In a saltwater environment, ferrous metals and some aluminium alloys corrode quickly. Metals exposed to cold orcryogenic conditions may endure a ductile to brittle transition and lose their toughness, becoming more brittle and prone to cracking. Metals under continual cyclic loading can suffer from metal fatigue.HP Pavilion DV4-1280US Battery

Metals under constant stress at elevated temperatures can creep.

Cold working processes, where the product’s shape is altered by rolling, fabrication or other processes while the product is cold, can increase the strength of the product by a process called work hardening. Work hardening creates microscopic defects in the metal, which resist further changes of shape.HP Pavilion DV4-1281US Battery

Various forms of casting exist in industry and academia. These include sand casting, investment casting (also called the “lost wax process”), die casting andcontinuous casting.

Heat treatment

Metals can be heat treated to alter the properties of strength, ductility, toughness, hardness or resistance to corrosion.HP Pavilion DV4-1282CM Battery

Common heat treatment processes includeannealing, precipitation strengthening, quenching, and tempering . The annealingprocess softens the metal by heating it and then allowing it to cool very slowly, which gets rid of stresses in the metal and makes the grain structure large and soft-edged so that when the metal is hit or stressed it dents or perhaps bends, rather than breaking;HP Pavilion DV4-1283CL Battery

it is also easier to sand, grind, or cut annealed metal. Quenching is the process of cooling a high-carbon steel very quickly after you have heated it, thus "freezing" the steel's molecules in the very hard martensite form, which makes the metal harder. There is a balance between hardness and toughness in any steel,HP Pavilion DV4-1287CL Battery

where the harder it is, the less tough or impact-resistant it is, and the more impact-resistant it is, the less hard it is. Temperingrelieves stresses in the metal that were caused by the hardening process; tempering makes the metal less hard while making it better able to sustain impacts without breaking.HP Pavilion DV4-1290BR Battery

Often, mechanical and thermal treatments are combined in what is known as thermo-mechanical treatments for better properties and more efficient processing of materials. These processes are common to high alloy special steels, super alloys and titanium alloys.HP Pavilion DV4-1290EL Battery

Plating

Metallurgists study the microscopic and macroscopic properties using metallography, a technique invented by Henry Clifton Sorby. In metallography, an alloy of interest is ground flat and polished to a mirror finish. The sample can then be etched to reveal the microstructure and macrostructure of the metal.HP Pavilion DV4-1292CM Battery

The sample is then examined in an optical or electron microscope, and the image contrast provides details on the composition, mechanical properties, and processing history.

Crystallography, often using diffraction of x-rays or electrons, is another valuable tool available to the modern metallurgist.HP Pavilion DV4-1299EE Battery

Crystallography allows identification of unknown materials and reveals the crystal structure of the sample. Quantitative crystallography can be used to calculate the amount of phases present as well as the degree of strain to which a sample has been

Smelting is a form of extractive metallurgy; its main use is to produce a metal from its ore.HP Pavilion DV4-1300 CTO Battery

This includes iron extraction fromiron ore, and copper extraction and other base metals from their ores. Smelting uses heat and a chemical reducing agent to change the oxidation state of the metal ore; the reducing agent is commonly a source of carbon such as coke, or in earlier timescharcoal.HP Pavilion DV4-1301TU Battery

The carbon or carbon monoxide derived from it removes oxygen from the ore to leave the metal. The carbon is thus oxidized in two stages, producing first carbon monoxide and then carbon dioxide. As most ores are impure, it is often necessary to use flux, such as limestone, to remove the accompanying rock gangue as slag.HP Pavilion DV4-1301TX Battery

Plants for the electrolytic reduction of aluminium are also generally referred to as smelters. These do not melt aluminum oxide but instead dissolve it in aluminum fluoride. They normally use carbon electrodes, and conversion of carbon to carbon dioxide provides an important part of deoxydation energy,HP Pavilion DV4-1302TU Battery

rest of energy being provided by electricity, but novel smelter designs use electrodes that are not consumed in the process. The end product is molten aluminum.

Smelting involves more than just "melting the metal out of its ore".HP Pavilion DV4-1302TX Battery

Most ores are a chemical compound of the metal with other elements, such as oxygen (as anoxide), sulfur (as a sulfide) or carbon and oxygen together (as a carbonate). To produce the metal, these compounds have to undergo a chemical reaction. Smelting therefore consists of using suitable reducing substances that will combine with those oxidizing elements to free the metal.HP Pavilion DV4-1303TU Battery

Roasting

In the case of carbonates and sulfides, a process called "roasting" drives off the unwanted carbon or sulfur, leaving an oxide, which can be directly reduced. Roasting is usually carried out in an oxidizing environment. A few practical examples:HP Pavilion DV4-1303TX Battery

  • Malachite, a common ore of copper, is primarily copper carbonate (CuCO3). This mineral undergoes thermal decomposition to CuO and CO2 in several stages between 250°C and 350°C. The carbon dioxide is expelled into the atmosphere, leaving copper oxide which can be directly reduced to copper as shown below.HP Pavilion DV4-1304TU Battery
  • Galena, the most common mineral of lead, is primarily lead sulfide (PbS). The sulfide is oxidized to a sulfite (PbSO3) which thermally decomposes into lead oxide and sulfur dioxide gas. (PbO and SO2) The sulfur dioxide (like the carbon dioxide in the example above) is expelled, and the lead oxide is reduced as below.HP Pavilion DV4-1304TX Battery

Reduction

Reduction is the final, high-temperature step in smelting. It is here that the oxide becomes the elemental metal. A reducing environment, (often provided by carbon monoxide in an air-starved furnace) pulls the final oxygen atoms from the raw metal.HP Pavilion DV4-1305TU Battery

The required temperature varies over a very large range, both in absolute terms, and in terms of the melting point of the base metal. A few examples:

  • iron oxide becomes metallic iron at roughly 1250°C, almost 300 degrees below iron's melting point of 1538°C
  • mercuric oxide becomes vaporous mercury near 550°C, almost 600 degrees above mercury's melting point of -38°CHP Pavilion DV4-1305TX Battery

Fluxes

Fluxes are used in smelting for several purposes, chief among them catalyzing the desired reactions and chemically binding to unwanted impurities or reaction products. Calcium oxide, in the form of lime, was often used for this purpose, since it could react with the carbon dioxide sulfur dioxide produced during roasting and smelting to keep them out of the working environment.HP Pavilion DV4-1306TU Battery

Historically, the first smelting processes used carbon (in the form of charcoal) to reduce the oxides of tin (cassiterite, SnO2), copper (cuprite, CuO) and lead (Lead(II) oxide, PbO), and eventually iron (hematite, Fe2O3) In all these reactions the reducing agent was actually carbon monoxide, as the charcoal and oxides remained solid and therefore could not react directly with each other.HP Pavilion DV4-1306TX Battery

For copper and lead, important ores were actually the sulfides, chalcocite (CuS2) and galena (PbS); these first had to be converted to oxides by roasting them in air.

Silver was generally found in the form of sulfides mixed with galena; it was smelted together with lead and was afterwards separated from it by cupellation.HP Pavilion DV4-1307TU Battery

The primary source of mercury was the sulfide ore (cinnabar, HgS). This was roasted to produce the oxide HgO, which decomposed into oxygen and mercury, which both left the furnace as a (highly toxic) vapor, that was condensed in appropriate containers.

In the Old World, humans learned to smelt metals in prehistoric times, more than 8000 years ago.HP Pavilion DV4-1307TX Battery

The discovery and use of the "useful" metals — copper and bronze at first, then iron a few millennia later — had an enormous impact on human society. The impact was so pervasive that scholars traditionally divide ancient history into Stone Age, Bronze Age, and Iron Age.HP Pavilion DV4-1308TU Battery

In the Americas, pre-Inca civilizations of the central Andes in Peru had mastered the smelting of copper and silver at least six centuries before the first Europeans arrived in the 16th century.

Tin and lead

In the Old World, the first metals smelted were tin and lead. The earliest known cast lead beads were found in the Çatal Höyük site in Anatolia (Turkey), and dated from about 6500 BC, but the metal may have been known earlier.HP Pavilion DV4-1308TX Battery

Since the discovery happened several millennia before the invention of writing, we have no evidence about how it was made. However, tin and lead can be smelted by placing the ores in a wood fire, so it is possible that the discovery may have occurred by accident.HP Pavilion DV4-1309TU Battery

Although lead is a common metal, its discovery had relatively little impact in the ancient world. It is too soft to be used for weapons (except possibly as slingprojectiles) or for structural elements. However, being easy to cast and shape, it came to be extensively used in the classical world of Ancient Greece and Ancient Rome for piping and storage of water.HP Pavilion DV4-1309TX Battery

It was also used as a mortar in stone buildings, and as a writing material for commemorative plaques and curses.

Tin was much less common than lead and is only marginally harder, and had even less impact by itself.

Copper and bronze

After tin and lead, the next metal to be smelted appears to have been copper. How the discovery came about is a matter of much debate.HP Pavilion DV4-1310TU Battery

Campfires are about 200 °C short of the temperature needed for that, so it has been conjectured that the first smelting of copper may have been achieved in pottery kilns. The earliest known instances in Europe and the Near East were found in Iran, dated about 6000 BC.HP Pavilion DV4-1310TX Battery

The first smelted copper artifact was thought to be a mace head found in Can Hasan, Turkey and dated to 5000 BC. However, this now appears to be hammered native copper. The earliest current evidence of copper smelting, dating from between 5500 BC and 5000 BC, has been found in Plo?nik and Belovode, Serbia.HP Pavilion DV4-1311TU Battery

The development of copper smelting in the Andes, which is believed to have occurred independently of that in the Old World, may have occurred in the same way.

By combining copper with tin and/or arsenic in the right proportions one obtains bronze, an alloy which is significantly harder than copper.HP Pavilion DV4-1311TX Battery

The first copper/arsenic bronzes date of 4200 BC from Asia Minor. The Inca bronze alloys were also of this type. Arsenic is often an impurity in copper ores, so the discovery could have been made by accident; but eventually arsenic-bearing minerals were intentionally added during smelting.HP Pavilion DV4-1312TU Battery

Copper/tin bronzes, harder and more durable, were developed around 1500 BC or 3200 BC,also in Asia Minor.

The discovery of copper smelting and bronze manufacture had a significant impact on the history of the Old World.HP Pavilion DV4-1312TX Battery

The metal was hard enough to make weapons that were heavier, stronger, and more resistant to impact-related damage than their wood, bone, or stone equivalents. For several millennia, bronze was the material of choice for weapons such as swords, daggers, battle axes, and spear and arrow points, as well as protective gear such as shields, helmets, shin guards, and other body armor.HP Pavilion DV4-1313DX Battery

Bronze also supplanted stone, wood, and organic materials in all sorts of tools and household utensils, such as chisels, saws, adzes, nails, blade shears, knives,sewing needles and pins, jugs, cooking pots and cauldrons, mirrors, horse harnesses, and much more.HP Pavilion DV4-1313TU Battery

In turn, bronze tools brought about an increase in the quantity, quality, and complexity of manufactured products, from buildings to leather goods. Tin and copper also contributed to the establishment of trade networks spanning large areas of Europe and Asia, and had a major effect on the distribution of wealth among individuals and nations.HP Pavilion DV4-1313TX Battery

The process through which the smiths learned to produce copper/tin bronzes is once again a mystery. The first such bronzes were probably a lucky accident from tin contamination of copper ores, but by 2000 BC, we know that tin was being mined on purpose for the production of bronze.HP Pavilion DV4-1314TU Battery

This is amazing, given that tin is a semi-rare metal, and even a rich cassiterite ore only has 5% tin. Also, it takes special skills (or special instruments) to find it and to locate the richer lodes. But, whatever steps were taken to learn about tin, these were fully understood by 2000 BC.HP Pavilion DV4-1314TX Battery

Early iron smelting

The earliest evidence to date for the bloomery smelting of iron is found at Tell Hammeh, Jordan (see also external link), and dates to 930 BC (C14 dating). However, based on the archaeological record of iron artifacts,HP Pavilion DV4-1315TU Battery

it is clear that intentional reduction of iron metal from terrestrial ores (in the case of Hammeh a Haematite ore), must have started near the end of the Late Bronze Age (ca. 1600–1150 BC). Where and how iron smelting was discovered is widely debated, and remains uncertain due to the significant lack of production finds.HP Pavilion DV4-1315TX Battery

Nevertheless, there is some consensus  that iron technology originated in the Near East, perhaps in Eastern Anatolia.

In Ancient Egypt, somewhere between the Third Intermediate Period and 23rd Dynasty (ca. 1100–750 BC), there are indications of iron working.HP Pavilion DV4-1316TU Battery

Significantly though, no evidence for the smelting of iron from ore has been attested to Egypt in any period. There is a further possibility of iron smelting and working in West Africa by1200 BC. In addition, very early instances of carbon steel were found to be in production around 2000 years before the present in northwest Tanzania, based on complex preheating principles.HP Pavilion DV4-1316TX Battery

These discoveries are significant for the history of metallurgy.

Most early processes in Europe and Africa involved smelting iron ore in a bloomery, where the temperature is kept low enough so that the iron does not melt. This produces a spongy mass of iron called a bloom, which then has to be consolidated with a hammer.HP Pavilion DV4-1317TU Battery

Later iron smelting

From the medieval period, the process of direct reduction in bloomeries began to be replaced by an indirect process. In this, a blast furnace was used to make pig iron, which then had to undergo a further process to make forgeable bar iron.HP Pavilion DV4-1317TX Battery

Processes for the second stage include fining in a finery forge and, from theIndustrial Revolution, puddling. However both processes are now obsolete, and wrought iron is now hardly made. Instead, mild steel is produced from a bessemer converter or by other means.HP Pavilion DV4-1318TU Battery

Base metals

The ores of base metals are often sulfides. In recent centuries, reverberatory smelters (sometimes called cupolas) have been used. These keep the fuel and the charge being smelted separate. Traditionally these were used for carrying out the first step:HP Pavilion DV4-1318TX Battery

formation of two liquids, one an oxide slag containing most of the impurity elements, and the other a sulfide matte containing the valuable metal sulfide and some impurities. Such "reverb" furnaces are today about 40 m long, 3 m high and 10 m wide.HP Pavilion DV4-1319TU Battery

Fuel is burned at one end and the heat melts the dry sulfide concentrates (usually after partial roasting), which is fed through the openings in the roof of the furnace. The slag floats on top of the heavier matte, and is removed and discarded or recycled. The sulfide matte is then sent to the converter.HP Pavilion DV4-1319TX Battery

However the precise details of the process will vary from one furnace to another depending on the mineralogy of the orebody from which the concentrate origninates.

More recent furnaces have been designed based upon bath smelting, top jetting lance smelting, flash smelting and blast furnaces.HP Pavilion DV4-1320CA Battery

Some examples of bath smelters include, the noranda furnace, the teniente reactor, the vunyukov smelter and the SKS technology to name a few. Top jetting lance smelters include the mitsubishi smelting reactor. The flash smelters consist of over 50% of the worlds copper smelters.HP Pavilion DV4-1320TX Battery

There are many more varies smelters as well, including the kievset, Ausmelt, Isasmelt, Tamano, EAF, and BF.

Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrousalloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy.HP Pavilion DV4-1321TX Battery

White cast ironis named after its white surface when fractured, due to its carbide impurities which allow cracks to pass straight through.Grey cast iron is named after its grey fractured surface, which occurs because the graphitic flakes deflect a passing crack and initiate countless new cracks as the material breaks.HP Pavilion DV4-1322TX Battery

Carbon (C) and silicon (Si) are the main alloying elements, with the amount ranging from 2.1 to 4 wt% and 1 to 3 wt%, respectively. Iron alloys with less carbon content are known as steel. While this technically makes these base alloys ternary Fe-C-Si alloys, the principle of cast iron solidification is understood from the binary iron-carbon phase diagram.HP Pavilion DV4-1322US Battery

Since the compositions of most cast irons are around the eutectic point of the iron-carbon system, the melting temperatures closely correlate, usually ranging from 1,150 to 1,200 °C (2,102 to 2,192 °F), which is about 300 °C (572 °F) lower than the melting point of pure iron.HP Pavilion DV4-1323TX Battery

Cast iron tends to be brittle, except for malleable cast irons. With its relatively low melting point, good fluidity,castability, excellent machinability, resistance to deformation and wear resistance, cast irons have become an engineering material with a wide range of applications and are used in pipes,HP Pavilion DV4-1324TX Battery

machines and automotive industry parts, such as cylinder heads (declining usage), cylinder blocks and gearbox cases (declining usage). It is resistant to destruction and weakening by oxidation (rust).

Cast iron is made by re-melting pig iron, often along with substantial quantities of scrap iron and scrap steel and taking various steps to remove undesirable contaminants.HP Pavilion DV4-1325TX Battery

Phosphorus and sulphur may be burnt out of the molten iron, but this also burns out the carbon, which must be replaced. Depending on the application, carbon and silicon content are adjusted to the desired levels, which may be anywhere from 2 to 3.5% and 1 to 3% respectively.HP Pavilion DV4-1326TX Battery

Other elements are then added to the melt before the final form is produced by casting.

Iron is sometimes melted in a special type of blast furnace known as a cupola, but more often melted in electric induction furnaces.After melting is complete, the molten iron is poured into a holding furnace or ladle.HP Pavilion DV4-1327TX Battery

Alloying elements

Cast iron's properties are changed by adding various alloying elements, or alloyants. Next to carbon, silicon is the most important alloyant because it forces carbon out of solution. Instead the carbon forms graphite which results in a softer iron, reduces shrinkage, lowers strength, and decreases density.HP Pavilion DV4-1328TX Battery

Sulfur, when added, forms iron sulfide, which prevents the formation of graphite and increases hardness. The problem with sulfur is that it makes molten cast iron sluggish, which causes short run defects. To counter the effects of sulfur, manganese is added because the two form into manganese sulfide instead of iron sulfide.HP Pavilion DV4-1329TX Battery

The manganese sulfide is lighter than the melt so it tends to float out of the melt and into the slag. The amount of manganese required to neutralize sulfur is 1.7×sulfur content+0.3%. If more than this amount of manganese is added, thenmanganese carbide forms, which increases hardness and chilling, except in grey iron, where up to 1% of manganese increases strength and density.HP Pavilion DV4-1330TX Battery

Nickel is one of the most common alloyants because it refines the pearlite and graphite structure, improves toughness, and evens out hardness differences between section thicknesses. Chromium is added in small amounts to the ladle to reduce free graphite, produce chill, and because it is a powerful carbide stabilizer; nickel is often added in conjunction.HP Pavilion DV4-1331TX Battery

A small amount of tin can be added as a substitute for 0.5% chromium. Copper is added in the ladle or in the furnace, on the order of 0.5 to 2.5%, to decrease chill, refine graphite, and increase fluidity. Molybdenum is added on the order of 0.3 to 1% to increase chill and refine the graphite and pearlite structure;HP Pavilion DV4-1332TX Battery

it is often added in conjunction with nickel, copper, and chromium to form high strength irons. Titanium is added as a degasser and deoxidizer, but it also increases fluidity. 0.15 to 0.5% vanadium are added to cast iron to stabilize cementite, increase hardness, and increase resistance to wear and heat. 0.1 to 0.3% zirconium helps to form graphite, deoxidize, and increase fluidity.HP Pavilion DV4-1365DX Battery

In malleable iron melts, bismuth is added, on the scale of 0.002 to 0.01%, to increase how much silicon can be added. In white iron, boron is added to aid in the production of malleable iron; it also reduces the coarsening effect of bismuth.[1]

Grey cast iron

Grey cast iron is characterized by its graphitic microstructure, which causes fractures of the material to have a grey appearance.HP Pavilion DV4-1400 CTO Battery

It is the most commonly used cast iron and the most widely used cast material based on weight. Most cast irons have a chemical composition of 2.5 to 4.0% carbon, 1 to 3% silicon, and the remainder is iron. Grey cast iron has less tensile strength and shock resistance than steel, but its compressive strength is comparable to low and medium carbon steel.HP Pavilion DV4-1404TX Battery

White cast iron

It is the iron that displays white fractured surface due to the presence of cementite. With a lower silicon content and faster cooling, the carbon in white cast ironprecipitates out of the melt as the metastable phase cementite, Fe3C, rather than graphite.HP Pavilion DV4-1405TX Battery

The cementite which precipitates from the melt forms as relatively large particles, usually in a eutectic mixture, where the other phase is austenite (which on cooling might transform to martensite). These eutectic carbides are much too large to provide precipitation hardeningHP Pavilion DV4-1406TX Battery

(as in some steels, where cementite precipitates might inhibit plastic deformation by impeding the movement of dislocationsthrough the ferrite matrix). Rather, they increase the bulk hardness of the cast iron simply by virtue of their own very high hardness and their substantial volume fraction, such that the bulk hardness can be approximated by a rule of mixtures.HP Pavilion DV4-1407TX Battery

In any case, they offer hardness at the expense of toughness. Since carbide makes up a large fraction of the material, white cast iron could reasonably be classified as a cermet. White iron is too brittle for use in many structural components, but with good hardness and abrasion resistance and relatively low cost,HP Pavilion DV4-1408TX Battery

it finds use in such applications as the wear surfaces (impeller and volute) of slurry pumps, shell liners and lifter bars in ball mills and autogenous grinding mills, balls and rings in coal pulverisers, and the teeth of a backhoe's digging bucket (although cast medium-carbon martensitic steel is more common for this application).HP Pavilion DV4-1409TX Battery

It is difficult to cool thick castings fast enough to solidify the melt as white cast iron all the way through. However, rapid cooling can be used to solidify a shell of white cast iron, after which the remainder cools more slowly to form a core of grey cast iron. The resulting casting, called a chilled casting, has the benefits of a hard surface and a somewhat tougher interior.HP Pavilion DV4-1413LA Battery

High-chromium white iron alloys allow massive castings (for example, a 10-tonne impeller) to be sand cast, i.e., a high cooling rate is not required, as well as providing impressive abrasion resistance.

Malleable cast iron

Malleable iron starts as a white iron casting that is then heat treated at about 900 °C (1,650 °F).HP Pavilion DV4-1414LA Battery

Graphite separates out much more slowly in this case, so thatsurface tension has time to form it into spheroidal particles rather than flakes. Due to their lower aspect ratio, spheroids are relatively short and far from one another, and have a lower cross section vis-a-vis a propagating crack or phonon.HP Pavilion DV4-1416LA Battery

They also have blunt boundaries, as opposed to flakes, which alleviates the stress concentration problems faced by grey cast iron. In general, the properties of malleable cast iron are more like mild steel. There is a limit to how large a part can be cast in malleable iron, since it is made from white cast iron.HP Pavilion DV4-1425LA Battery

Ductile cast iron

Because cast iron is comparatively brittle, it is not suitable for purposes where a sharp edge or flexibility is required. It is strong under compression, but not under tension. Cast Iron was first invented in China in the 4th century BC (see also: Du Shi) and poured into moulds to make ploughshares and pots as well as weapons and pagodas.HP Pavilion DV4T Battery

In the west, where it did not become available till the late 14th century, its earliest uses included cannon and shot. Henry VIII initiated the casting of cannon in England. Soon, English iron workers using blast furnaces developed the technique of producing cast iron cannons,HP Pavilion DV4T-1000 CTO Battery

which, while heavier than the prevailing bronze cannons, were much cheaper and enabled England to arm her navy better. The ironmasters of the Weald continued producing cast irons until the 1760s and armament was one of the main uses of irons after the Restoration.HP Pavilion DV4T-1100 CTO Battery

Cast iron pots were made at many English blast furnaces at the time. In 1707, Abraham Darby patented a method of making pots (and kettles) thinner and hence cheaper than his rivals could. This meant that his Coalbrookdale furnaces became dominant as suppliers of pots, an activity in which they were joined in the 1720s and 1730s by a small number of other coke-fired blast furnaces.HP Pavilion DV4T-1200 CTO Battery

The development of the steam engine by Thomas Newcomen provided further market for cast iron, since cast iron was considerably cheaper than the brass of which theengine cylinders were originally made. John Wilkinson was a great exponent of cast iron, who,HP Pavilion DV4T-1200SE CTO Battery

amongst other things, cast the cylinders for many of James Watt's improved steam engines until the establishment of the Soho Foundry in 1795.

Cast iron bridges

The use of cast iron for structural purposes began in the late 1770s, when Abraham Darby III built the Iron Bridge, although short beams had already been used, such as in the blast furnaces at Coalbrookdale.HP Pavilion DV4T-1300 CTO Battery

Other inventions followed, including one patented by Thomas Paine. Cast iron bridges became commonplace as the Industrial Revolution gathered pace. Thomas Telford adopted the material for his bridge upstream at Buildwas, and then for a canal trough aqueduct at Longdon-on-Tern on theShrewsbury Canal.HP Pavilion DV4T-1300SE CTO Battery

It was followed by the Chirk Aqueduct and the Pontcysyllte Aqueduct, both of which remain in use following the recent restorations. Cast iron beam bridges were used widely by the early railways, such as the Water Street Bridge at the Manchester terminus of the Liverpool and Manchester Railway.HP Pavilion DV4T-1400 CTO Battery

Problems arose when a new bridge carrying the Chester and Holyhead Railway across the River Dee in Chester collapsed in May 1847, less than a year after it was opened. The Dee bridge disaster was caused by excessive loading at the centre of the beam by a passing train, and many similar bridges had to be demolished and rebuilt, often in wrought iron.HP Pavilion DV4Z Battery

The bridge had been erroneously designed, being trussed with wrought iron straps, which were wrongly thought to reinforce the structure. The centres of the beams were put into bending, with the lower edge in tension, where cast iron, like masonry, is very weak.HP Pavilion DV4Z-1000 CTO Battery

The best way of using cast iron for bridge construction was by using arches, so that all the material is in compression. Cast iron, again like masonry, is very strong in compression. Wrought iron, like most other kinds of iron and indeed like most metals in general, is strong in tension, and also tough - resistant to fracturing.HP Pavilion DV4Z-1100 CTO Battery

The relationship between wrought iron and cast iron, for structural purposes, may be thought of as analogous to the relationship between wood and stone.

Nevertheless, cast iron continued to be used in inappropriate structural ways, until the Tay Rail Bridge disaster of 1879 cast serious doubt on the use of the material. HP Pavilion DV4Z-1200 CTO Battery

Crucial lugs for holding tie bars and struts in the Tay Bridge had been cast integral with the columns and they failed in the early stages of the accident. In addition, the bolt holes were also cast and not drilled, so that all the tension from the tie bars was placed on a corner, rather than being spread over the length of the hole.HP Pavilion DV4 Battery

The replacement bridge was built in wrought iron and steel.

Further bridge collapses occurred, however, culminating in the Norwood Junction rail accident of 1891. Thousands of cast iron rail underbridges were eventually replaced by steel equivalents.HP Pavilion DV4-1000 Battery

Cast iron columns enabled architects to build tall buildings without the enormously thick walls required to construct masonry buildings of any height. Such flexibility allowed tall buildings to have large windows. In urban centres like SoHo-Cast Iron Historic District in New York City,HP Pavilion DV4-1000EA Battery

manufacturing buildings and early department stores were built with cast iron columns to allow daylight to enter. Slender cast iron columns could also support the weight that would otherwise require thick masonry columns or piers, opening up floor spaces in factories, and sight lines in churches and auditoriums.HP Pavilion DV4-1000ET Battery

The historic Iron Building in Watervliet, New York, is a cast iron building.

Textile mills

Another important use was in textile mills. The air in the mills contained flammable fibres from the cotton, hemp, or wool being spun. As a result, textile mills had an alarming propensity to burn down.HP Pavilion DV4-1001 Battery

The solution was to build them completely of non-combustible materials, and it was found convenient to provide the building with an iron frame, largely of cast iron, replacing flammable wood. The first such building was at Ditherington in Shrewsbury, Shropshire.HP Pavilion DV4-1001AX Battery

Many other warehouses were built using cast iron columns and beams, although faulty designs, flawed beams or overloading sometimes caused building collapses and structural failures.HP Pavilion DV4-1001TU Battery

During the Industrial Revolution, cast iron was also widely used for frame and other fixed parts of machinery, including spinning and later weaving machines in textile mills. Cast iron became widely used, and many towns had foundries producing industrial and agricultural machinery.HP Pavilion DV4-1001TX Battery,HP Pavilion DV4-1002 Battery,HP Pavilion DV4-1002AX Battery,HP Pavilion DV4-1002TU Battery,HP Pavilion DV4-1002TX Battery,HP Pavilion DV4-1003AX Battery,HP Pavilion DV4-1003TU Battery,HP Pavilion DV4-1003TX Battery,HP Pavilion DV4-1004AX Battery,HP Pavilion DV4-1004TU Battery

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