Metallurgy encompasses both thescience and thetechnology of metals, including the production ofmetals and the engineering of metal components used in products for both consumers and manufacturers. Metallurgy is distinct from thecraft ofmetalworking. Metalworking relies on metallurgy in a similar manner to howmedicine relies on medical science for technical advancement. A specialistpractitioner of metallurgy is known as a metallurgist.
Historically, metallurgy has predominately focused on the production of metals. Metal production begins with the processing ofores to extract the metal, and includes the mixture of metals to makealloys. Metal alloys are often a blend of at least two different metallic elements. However, non-metallic elements are often added to alloys in order to achieve properties suitable for an application. The study of metal production is subdivided intoferrous metallurgy (also known asblack metallurgy) andnon-ferrous metallurgy, also known as colored metallurgy.
Ferrous metallurgy involves processes and alloys based oniron, while non-ferrous metallurgy involves processes and alloys based on other metals. The production of ferrous metals accounts for 95% of world metal production.[3]
Metallurgy derives from theAncient Greekμεταλλουργός,metallourgós, "worker in metal", fromμέταλλον,métallon, "mine, metal" +ἔργον,érgon, "work" The word was originally analchemist's term for the extraction of metals from minerals, the ending-urgy signifying a process, especially manufacturing: it was discussed in this sense in the 1797Encyclopædia Britannica.[4]
In the late 19th century, metallurgy's definition was extended to the more general scientific study of metals, alloys, and related processes. InEnglish, the/mɛˈtælərdʒi/ pronunciation is the more common one in theUnited Kingdom. The/ˈmɛtəlɜːrdʒi/ pronunciation is the more common one in theUS and is the first-listed variant in various American dictionaries, includingMerriam-Webster Collegiate andAmerican Heritage.
Artefacts from theVarna Necropolis in present-dayBulgariaThe mining areas of the ancientMiddle East witharsenic (in brown),copper (in red),tin (in grey), iron (in reddish brown), gold (in yellow), silver (in white),lead (in black),arsenic bronze (in yellow), and tin (in bronze)
The earliest metal employed by humans appears to begold, which can be found "native". Small amounts of natural gold, dating to the latePaleolithic period,40,000 BCE, have been found in Spanish caves.[5]Silver,copper,tin andmeteoric iron can also be found in native form, allowing a limited amount ofmetalworking in early cultures.[6] Early cold metallurgy, usingnative copper not melted from mineral has been documented at sites inAnatolia and at the site ofTell Maghzaliyah inIraq, dating from the 7th~6th millennia BCE.[7][8][9]
The earliest archaeological support ofsmelting (hot metallurgy) in Eurasia is found in theBalkans andCarpathian Mountains, as evidenced by findings of objects made by metal casting and smelting dated to around6,200 ~ 5,000 BCE, with the invention of copper metallurgy.[10][11][8][9] Certain metals, such as tin, lead, and copper can be recovered from their ores by simply heating the rocks in a comparatively moderate-temperature fire orblast furnace in a process known assmelting. The first evidence of copper smelting, dating from the6th millennium BCE,[12] has been found at archaeological sites inMajdanpek,Jarmovac, andPločnik, in present-daySerbia.[13][8] The site of Pločnik has produced a smelted copper axe dating from5,500 BCE, belonging to theVinča culture.[14] The Balkans and adjacentCarpathian region were the location of majorChalcolithic cultures includingVinča,Varna,Karanovo,Gumelnița andHamangia, which are often grouped together under the name of 'Old Europe'.[15] With the Carpatho-Balkan region described as the 'earliest metallurgical province in Eurasia',[9][11] its scale and technical quality of metal production in the6th~5th millennia BCE totally overshadowed that of any other contemporary production centre.[9][16][a][b]
The earliest documented use of lead (possibly native or smelted) in the Near East dates from the6th millennium BCE, is from the lateNeolithic settlements ofYarim Tepe andArpachiyah inIraq. The artifacts suggest that lead smelting may have predated copper smelting.[17] Metallurgy of lead has also been found in the Balkans during the same period.[8]
Copper smelting is documented at sites inAnatolia and at the site of Tal-i Iblis in southeasternIran fromc. 5,000 BCE.[7]
Copper smelting is first documented in theDelta region of northernEgypt inc. 4,000 BCE, associated with theMaadi culture. This represents the earliest evidence for smelting in Africa.[18][c]
TheVarna Necropolis,Bulgaria, is a burial site located in the western industrial zone ofVarna, approximately 4 km from the city centre, internationally considered one of the key archaeological sites in world prehistory. The oldestgold treasure in the world, dating from4,600 BC – 4,200 BCE, was discovered atVarna.[19] The gold piece dating from4,500 BCE, found in 2019 inDurankulak, nearVarna is another important example.[20][21] Other signs of early metals are found from the3rd millennium BCE inPalmela, Portugal,Los Millares, Spain, andStonehenge, United Kingdom. The precise beginnings, however, have not be clearly ascertained and new discoveries are both continuous and ongoing.
In approximately1,900 BCE, ancient iron smelting sites existed inTamil Nadu.[22][23]
In theNear East, about3,500 BCE, it was discovered that by combining copper and tin, a superior metal could be made, analloy calledbronze. This represented a major technological shift known as theBronze Age.
The extraction ofiron from its ore into a workable metal is much more difficult than for copper or tin. The process appears to have been invented by theHittites in about1,200 BCE, beginning theIron Age. The secret of extracting and working iron was a key factor in the success of thePhilistines.[24][25]
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 theMiddle East andNear East, ancientIran, ancientEgypt, ancientNubia, andAnatolia in present-dayTurkey,Ancient Nok,Carthage, theCelts,Greeks andRomans of ancientEurope, medieval Europe, ancient and medievalChina, ancient and medievalIndia, ancient and medievalJapan, amongst others.
A 16th century book byGeorg Agricola,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".[26]
Extractive metallurgy is the practice of removing valuable metals from anore and refining the extracted raw metals into a purer form. In order to convert a metaloxide orsulphide to a purer metal, the ore must bereduced physically,chemically, orelectrolytically. Extractivemetallurgists are interested in three primary streams: feed, concentrate (metal oxide/sulphide) andtailings (waste).
After mining, large pieces of the ore feed are broken through crushing or grinding in order to obtain particles small enough, where each particle is either mostly valuable or mostly waste. 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 toleaching. Leaching dissolves minerals in an ore body and results in an enriched solution. The solution is collected and processed to extract valuable metals. 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.
Iron, the most common metal used in metallurgy, is shown in different forms, including cubes, chips, and nuggets
Much effort has been placed on understandingiron–carbon alloy system, which includessteels andcast irons.Plain carbon steels (those that contain essentially only carbon as an alloying element) are used in low-cost, high-strength applications, where neither weight norcorrosion are a major concern. Cast irons, includingductile iron, are also part of the iron-carbon system. Iron-Manganese-Chromium alloys (Hadfield-type steels) are also used in non-magnetic applications such as directional drilling.
Inproduction engineering, metallurgy is concerned with the production of metallic components for use in consumer orengineering products. This involves production of alloys, shaping, heat treatment and surface treatment of product. The task of the metallurgist is to achieve balance between material properties, such as cost,weight,strength,toughness,hardness,corrosion,fatigue resistance and performance intemperature extremes. To achieve this goal, the operating environment must be carefully considered.[citation needed]
Determining the hardness of the metal using the Rockwell, Vickers, and Brinell hardness scales is a commonly used practice that helps better understand the metal's elasticity and plasticity for different applications and production processes.[27] In a saltwater environment, most ferrous metals and some non-ferrous alloys corrode quickly. Metals exposed to cold orcryogenic conditions may undergo a ductile to brittle transition and lose their toughness, becoming more brittle and prone to cracking. Metals under continual cyclic loading can suffer frommetal fatigue. Metals under constantstress at elevated temperatures cancreep.
An open-die drop forging with two dies of an ingot, which is then further processed into a wheel
Casting – molten metal is poured into a shapedmold. Variants of casting includesand casting,investment casting, also called the lost wax process,die casting, centrifugal casting, both vertical and horizontal, and continuous castings. Each of these forms has advantages for certain metals and applications considering factors like magnetism and corrosion.[28]
Laser cladding – metallic powder is blown through a movable laser beam (e.g. mounted on a NC 5-axis machine). The resulting melted metal reaches a substrate to form a melt pool. By moving the laser head, it is possible to stack the tracks and build up a three-dimensional piece.
3D printing – Sintering or melting amorphous powder metal in a 3D space to make any object to shape.
Cold-working processes, in which 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 calledwork hardening. Work hardening createsmicroscopic defects in the metal, which resist further changes of shape.
Metals can beheat-treated to alter the properties of strength, ductility, toughness, hardness and resistance to corrosion. Common heat treatment processes include annealing,precipitation strengthening, quenching, and tempering:[29]
Annealing process 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; it is also easier to sand, grind, or cut annealed metal.
Quenching is the process of cooling metal very quickly after heating, thus "freezing" the metal's molecules in the very hard martensite form, which makes the metal harder.
Tempering relieves 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.
Often, mechanical and thermal treatments are combined in what are known as thermo-mechanical treatments for better properties and more efficient processing of materials. These processes are common to high-alloy special steels,superalloys and titanium alloys.
A simplified diagram of electroplating copper on a metal
Electroplating is a chemical surface-treatment technique. It involves bonding a thin layer of another metal such asgold,silver,chromium orzinc to the surface of the product. This is done by selecting the coating material electrolyte solution, which is the material that is going to coat the workpiece (gold, silver, zinc). There needs to be two electrodes of different materials: one the same material as the coating material and one that is receiving the coating material. Two electrodes are electrically charged and the coating material is stuck to the work piece. It is used to reduce corrosion as well as to improve the product's aesthetic appearance. It is also used to make inexpensive metals look like the more expensive ones (gold, silver).[30]
Shot peening is a cold working process used to finish metal parts. In the process of shot peening, small round shot is blasted against the surface of the part to be finished. This process is used to prolong the product life of the part, prevent stress corrosion failures, and also prevent fatigue. The shot leaves small dimples on the surface like a peen hammer does, which cause compression stress under the dimple. As the shot media strikes the material over and over, it forms many overlapping dimples throughout the piece being treated. The compression stress in the surface of the material strengthens the part and makes it more resistant to fatigue failure, stress failures, corrosion failure, and cracking.[31]
Thermal spraying techniques are another popular finishing option, and often have better high temperature properties than electroplated coatings. Thermal spraying, also known as a spray welding process,[32] is an industrial coating process that consists of a heat source (flame or other) and a coating material; the coating can be in a powder or wire form, either of which is melted and then sprayed at a high velocity onto the surface of the material being treated. The spray treating process is known by many different names such as HVOF (high velocity oxygen fuel), plasma spray, flame spray, arc spray and metalizing.
Electroless deposition (ED) orelectroless plating is defined as theautocatalytic process, through which metals and metal alloys are deposited onto nonconductive surfaces. These nonconductive surfaces include plastics, ceramics, glass, etc., which can then become decorative, anti-corrosive, and conductive, depending on the method of deposition and the designed use. Electroless deposition is a chemical processes that createmetal coatings on various materials byautocatalyticchemical reduction of metalcations in a liquid bath.
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. The sample is then examined in an optical orelectron microscope, and the image contrast provides details on the composition, mechanical properties, and processing history.
Crystallography, often usingdiffraction ofX-rays orelectrons, is another valuable tool available to the modern metallurgist. 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 subjected.
^The scale and technical quality of the Carpathian-Balkan copper industry totally overshadows that of any other contemporary production centre. This, together with the late sixth-millennium date for its beginning, gives strong support to the suggestion that the art of copper smelting was first perfected in the Balkans. The region can also claim to be the first to produce gold, beginning in the mid-fifth millennium, five hundred years or more before the earliest gold objects appear in the Near East. —Cunliffe (2015), p. 105[16]
^The general area of the Carpatho-Balkan Metallurgical Province (CBMP) equaled approximately 1.5 million sq. km spread from the Danubian basin in the Western flank to the Mid and Lower Volga basin in the Eastern flank of this province. The most characteristic features of the CBMP are (1) casting and hammering of various heavy tools and weapons made from chemically pure copper;(2) a big number of gold decorations and ornaments. Metallurgical revolution and CBMP formation emerged independently from centers of the Proto-Metal area [in the Middle East] where in the5th millennium BCE there continued a limited production of primitive handmade copper goods. —Chernykh (2014)[9]
^Egypt and adjacent regions closely mimic the metallurgical trajectories of the nearby Middle East. Egyptian metallurgy started with the working of copper around4,000 BCE.(p17) The earliest evidence for metallurgy in Africa comes from theNile Delta, inEgypt, and is associated with theMaadi culture dating between 4,000 ~ 3,200 BCE.(p19) —Chirikure (2015), pp. 17, 19[18]
^abRosenstock, Eva; Scharl, Silviane; Schier, Wolfram (February 2016)."Ex oriente lux? – Ein Diskussionsbeitrag zur Stellung der frühen Kupfermetallurgie Südosteuropas" ['Light out of the east?' – A contribution to discussion of the situation of early copper metallurgy in southeast Europe]. In Bartelheim, Martin; Horejs, Barbara; Krauß, Raiko (eds.).Von Baden bis Troia: Ressourcennutzung, Metallurgie, und Wissenstransfer [From Baden to Troy: Resource use, metallurgy, and knowledge transfer]. Oriental and European Archaeology (in Latin and German). Vol. 3. Leidorf. pp. 59–122.ISBN978-3-86757-010-7 – via researchgate.net.eine Jubiläumsschrift für Ernst Pernicka [a jubilee publication for Ernst Pernicka]
^Haiko, H.I.; Biletskyi, V.S. (2015). "First metals discovery and development the sacral component phenomenon". In Bondarenko, V.; Kovalevska, I.; Pivnyak, G. (eds.).Theoretical and Practical Solutions of Mineral Resources Mining. New Developments in Mining Engineering. Vol. 2015. London, UK: Balkema Books. pp. 227–233.ISBN9781-1380-2883-8. Archived fromthe original on 8 December 2015 – via crcpress.com.
^Grande, Lance; Augustyn, Allison (2009)."Precious metals (primarily gold)".Gems and Gemstones: Timeless natural beauty of the mineral world.Field Museum of Chicago[popular publications]. McCarter, John W., Jr. (foreward); Weinstein, John (gem photography); Augustyn, Allison (contributor). Chicago, IL / London, UK: University of Chicago Press. p. 290.ISBN978-0-226-30511-0. Archived fromthe original on 12 February 2020 – via Google.
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