Metallurgy is a domain of material science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are known as alloys.
Metallurgy encompasses both the science and the technology of metals, including their production and the engineering of metal components used in products for both consumers and manufacturers. Metallurgy is distinct from the craft of metalworking by providing it with a scientific foundation, much as medical science supports the practice of medicine. A specialist practitioner of metallurgy is known as a metallurgist.
The science of metallurgy is further subdivided into two broad categories: chemical metallurgy and physical metallurgy. Chemical metallurgy is chiefly concerned with the reduction and oxidation of metals, and the chemical performance of metals. Subjects of study in chemical metallurgy include mineral processing, the extraction of metals, thermodynamics, electrochemistry, and chemical degradation (corrosion). In contrast, physical metallurgy focuses on the mechanical properties of metals, the physical properties of metals, and the physical performance of metals. Topics studied in physical metallurgy include crystallography, material characterization, mechanical metallurgy, phase transformations, and failure mechanisms.
Historically, metallurgy has predominantly focused on the production of metals. Metal production begins with the processing of ores to extract the metal, and includes the mixture of metals to make alloys. Metal alloys are often a blend of two or more 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 into ferrous metallurgy (also known as black metallurgy) and non-ferrous metallurgy, also known as colored metallurgy.
Ferrous metallurgy involves processes and alloys based on iron, while non-ferrous metallurgy involves processes and alloys based on other metals. The production of ferrous metals accounts for 95% of world metal production."Металлургия" . in The Great Soviet Encyclopedia. 1979.
Modern metallurgists work in both emerging and traditional areas as part of an interdisciplinary team alongside material scientists and other engineers. Some traditional areas include mineral processing, metal production, heat treatment, failure analysis, and the joining of metals (including welding, brazing, and soldering). Emerging areas for metallurgists include nanotechnology, superconductors, composites, biomedical materials, electronic materials (semiconductors) and surface engineering.
Etymology and pronunciation Metallurgy derives from the Ancient Greek , , "worker in metal", from , , "mine, metal" + , , "work" The word was originally an alchemist'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 1797 Encyclopædia Britannica.
In the late 19th century, metallurgy's definition was extended to the more general scientific study of metals, alloys, and related processes. In English, the pronunciation is the more common one in the United Kingdom while pronunciation is the more common one in the United States and is the first-listed variant in various American dictionaries, including Merriam-Webster Collegiate and American Heritage.
History
The earliest metal employed by humans appears to be gold, which can be found "native". Small amounts of natural gold, dating to the late Paleolithic period, have been found in Spanish caves. Silver, copper, tin and meteoric iron can also be found in native form, allowing a limited amount of metalworking in early cultures. Early cold metallurgy, using native copper that was not smelted from ore has been documented at sites in Anatolia and at the site of Tell Maghzaliyah in Iraq, dating from the 7th~6th millennia BCE.
The earliest archaeological support of smelting (hot metallurgy) in Eurasia is found in the Balkans and Carpathian Mountains, as evidenced by findings of objects made by metal casting and smelting dated to around with the invention of copper metallurgy. 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 or blast furnace in a process known as smelting. The first evidence of copper smelting, dating from the has been found at archaeological sites in Majdanpek, Jarmovac, and Pločnik, in present-day Serbia. The site of Pločnik has produced a smelted copper axe dating from belonging to the Vinča culture. The Balkans and adjacent Carpathian region were the location of major Chalcolithic cultures including Vinča, Varna, Karanovo, Gumelnița and Hamangia, which are often grouped together under the name of 'Old Europe'. With the Carpatho-Balkan region described as the 'earliest metallurgical province in Eurasia', its scale and technical quality of metal production in the totally overshadowed that of any other contemporary production centre.
The earliest documented use of lead (possibly native or smelted) in the Near East dates from the is from the late Neolithic settlements of Yarim Tepe and Arpachiyah in Iraq. The artifacts suggest that lead smelting may have predated copper smelting. Metallurgy of lead has also been found in the Balkans during the same period.
Copper smelting is documented at sites in Anatolia and at the site of Tal-i Iblis in southeastern Iran from
Copper smelting is first documented in the Delta region of northern Egypt in associated with the Maadi culture. This represents the earliest evidence for smelting in Africa.
The Varna Necropolis, Bulgaria, is a burial site located in the western industrial zone of Varna, approximately 4 km from the city centre, internationally considered one of the key archaeological sites in world prehistory. The oldest gold treasure in the world, dating from was discovered at Varna. The gold piece dating from found in 2019 in Durankulak, near Varna is another important example. Other signs of early metals are found from the in Palmela, Portugal, Los Millares, Spain, and Stonehenge, United Kingdom. The precise beginnings, however, have not been clearly ascertained and new discoveries are both continuous and ongoing.
In approximately ancient iron smelting sites existed in Tamil Nadu.
In the Near East, about it was discovered that the superior metal bronze could be made by combining copper and tin. This represented a major technological shift known as the Bronze Age.
The extraction of iron from its ore into a workable metal is much more difficult than for copper or tin. The process appears to have been invented by the Hittites in about beginning the Iron Age. The ability to extract and work iron was a key factor in the success of the Philistines.
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, and Anatolia in present-day Turkey, Ancient Nok, Carthage, the Celts, Greeks and Romans of ancient Europe, medieval Europe, ancient and medieval China, ancient and medieval India, ancient and medieval Japan, amongst others.
Wootz process was developed and practiced in the Indian subcontinent as early as 300 BCE—although certainly by 200 BCE—high quality steel was being produced in southern India, by what Europeans would later call the crucible technique. Golconda steel, also called Wootz steel is an ultra-high carbon steel, with a natural inclusion of carbide forming Vanadium (~0.005%), resulting in the formation of nanomaterials in its microstructure and characterised by exhibiting properties such as superplasticity and high impact hardness. Archaeological and Tamil language literary evidence suggests that this manufacturing process was already in existence in South India well before the common era, with wootz steel exported from the Chera dynasty and called Seric Iron in Rome, and later known as Damascus steel in Europe. Reproduction research undertaken by Prof. J.D Verhoeven and Al Pendray identified the role of impurities within the local ore, in carbide formation, and repeated thermal cycling of blades, in the pattern creation, and reproduced Wootz steel blades with patterns microscopically and visually identical to ancient blade patterns.Juleff, G (1996). "An ancient wind powered iron smelting technology in Sri Lanka". Nature. 379 (6560): 60–63. Bibcode:1996Natur.379...60J. doi:10.1038/379060a0. S2CID 205026185"WOOTZ STEEL: AN ADVANCED MATERIAL OF THE ANCIENT WORLD". materials.iisc.ernet.in. Archived from the original on 11 February 2019. Retrieved 23 July 2008.Sasisekaran, B; Raghunatha Rao, B (1999). "Technology of Iron and Steel in Kodumanal – An Ancient Industrial Centre in Tamilnadu" (PDF). Indian Journal of History & Science. 34 (4): 263–272. Archived from the original (PDF) on 23 September 2015.
A 16th century book by Georg 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".
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 sulphide to a purer metal, the ore must be reduced physically, chemically, or electrolytically. Extractive metallurgists are interested in three primary streams: feed, concentrate (metal oxide/sulphide) and tailings (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 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. 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.
Metal and its alloys
Much effort has been placed on understanding the iron–carbon alloy system, which includes steels and cast 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 nor corrosion are a major concern. Cast irons, including ductile 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.
Other engineering metals include aluminium, chromium, copper, magnesium, nickel, titanium, zinc, and silicon. These metals are most often used as alloys with the noted exception of silicon, which is not a metal. Other forms include:
Stainless steel, particularly Austenitic stainless steels, galvanized steel, nickel alloys, titanium alloys, or occasionally copper alloys are used where resistance to corrosion is important. Aluminium alloys and magnesium alloys are commonly used when a lightweight strong part is required such as in automotive and aerospace applications. Copper-nickel alloys (such as Monel) are used in highly corrosive environments and for non-magnetic applications.