What is metallurgy technology



metallurgy (synonymous Metallurgy) refers to the entirety of the processes for the extraction and use of metals, as well as metallurgically important semi-metals and non-metals from ores, earths, salts and waste materials.

The extraction of metallurgically valuable chemical elements from their natural deposits is the task of mining-driven mining, which is made use of by metallurgy. In addition, metallurgy can never be restricted to the mere extraction of material; it needs markets for its products in the long term. In order to insist on this, the smelting process must be adapted to the growing amounts of material, and further processing must correspond to the current state of the art.

From early history to the state of the art

The word metallurgy is of Greek origin (μέταλλονmetal "The found") and suggests an already recognized "technical skill". Translated logically, metallurgy or metallurgist means “to work with found (metal) works” or to be a skilled or industrial “metalworker”, to work in a “metalworks”.

Copper or bronze tools, after which historical epochs were named, are the first evidence of targeted metallurgical work, its preliminary stage - you can also find a rare one Intermediate product see - which is ore lump accidentally separated from heated rock and recognized as workable. From this point of view, it will be a long way until the “tapped” pig iron is finally available in large quantities when the first blast furnace is put into operation Intermediate product for iron casting and from the 18th century for steel production. The Steel age and the one that appeared alongside them in the 20th century Earth metal time today determine in many ways the living conditions of mankind. It can be so for a long time, but the history of metallurgy remains linked to that of its deposits. The traditional German, such as the zinc-rich Goslarer Rammelsberg, the Hessian-Siegerland iron ore mines, as well as the centuries-old mines in the Slovakian Ore Mountains and other European deposits are largely exploited. In consideration of the continuing growth of the earth's population and its increasing demand, new deposits are sought in advance worldwide and developed under conditions that were still unimaginable in the 19th century.

In this way, metallurgy has grown from old experiences and new knowledge into a technology (science of the techniques used). Increasingly broader, it was divided into manageable sub-areas as early as the 19th century. The most important are ferrous and non-ferrous metallurgy, if raw materials and production quantities are used as criteria.

The main and secondary disciplines not only ensure the latest state of the art for their own research. She finds support in the independent sciences that accompany the entire process from raw materials to ready-to-use goods, which include metallurgy, closely linked to materials science, chemistry and a variety of techniques, such as plant engineering.

   

Timetable

The following timeline provides an overview of the development of metallurgy from the Neolithic to the beginning of "modernity".

until 12000 BC Chr. Ending Neolithic (Neolithic) Early high cultures emerge, settled settlements, jewelry from precious metal finds, first experiences in metal extraction and processing
until 4000 BC Chr. Copper Age Copper hatchets
until 2500 BC Chr. Early bronze age Advance of bronze from the Caucasus into the Mediterranean and Egypt
1700-800 BC Chr. Bronze age Bronze chariots and weapons, swords, monuments, jewelry (bronze brooches), coins, tools (axes), construction (brackets to connect marble parts)
until 1100 BC Chr. Immigration from the north brings technical progress - not uncontroversial in terms of type and timing. Doric cavalry warriors, already with iron weapons, are said to have prevailed against bronze swords and chariots.
until 800 BC Chr. Early Iron Age Hallstatt culture, first iron objects in Central Europe
up to 600 BC Chr. Beginning of the Iron Age in China
up to 500 BC Chr. The heyday of Hellenic-Roman antiquity
until 450 BC Chr. Younger Iron Age, La Tène culture advanced use of iron
Turning point Roman smelting plants are built in areas close to ore, Siegerland
200 AD Late antiquity Fabricae (manufactories) appear alongside handicrafts in metalworking
200–600 AD Time of the Great Migration, end of late antiquity Further development in the use of iron (weapons, technical equipment). Bronze for coins, small portraits, reliefs, monuments
around 1180 Beginning of the settlement of the Bohemian-Saxon Ore Mountains for the time being only targeted silver mining
in the 14th century first "high shaft furnaces" instead of previous "low shaft furnaces", see blast furnace
in the 15. century increasing early industrial iron extraction and processing
in the 16th century Beginning of the modern age with Georgius Agricola (XII Libri) technical aids for ore extraction and processing take the place of mere manual labor;
The first Joachimsthalers were minted from Bohemian silver mining in 1519

From the copper ax to the Bronze Age

 

Looking back, the history of the development of metallurgy began a little more than 10,000 years ago, in the Neolithic, the Neolithic Age, which was drawing to a close (see the above table of times). Recent research in Anatolia has already discovered the first metallurgical approaches in 12,000 year old settlements. They confirm the view that early metallurgy was decisively determined by the conversion of nomadic “hunters and gatherers” to arable farmers and settlers with “fixed stoves” instead of changing, open fireplaces. Maybe it starts with an accidental find of dignified (Pure) metal, probably river gold from the mountains, or because an ore that was very rich in metal struck people at the time due to its weight or a special, reddish hue (see red copper ore). It is conceivable that a solid stove built from such stone with a natural draft will reach 1000 ° C with prolonged use and use of resinous wood and suddenly sweat copper or a natural alloy of copper and tin and thus stimulate metallurgical considerations. This assumption is obvious, because a dull fire can be "refreshed" by supplying air (blowing) and at the same time can become hot enough to reach a corresponding temperature. Pictorial representations show the use of blowguns for this technique, which was only called "stove freshening" much later. The supplied oxygen from the air oxidizes the sulfur content in the ore, as does the carbon, which is a hindrance to the machinability of iron, into volatile, gaseous sulfur dioxide (SO2), as well as carbon dioxide (CO2), whereby additional heat of reaction arises.

The first purpose-built smelting furnaces can be found as early as the early Copper Age (4500-3500 BC) (copper axes). It is followed by the "late Copper Age", which dates from around 3000-2500 BC. Chr. Passes into the "early Bronze Age". In very long periods of time and in partially overlapping cultures, but with a clear reference to local and regional ore deposits (Bohemian Ore Mountains), centers of metallurgical development emerge over time, which are connected by trade routes. This happens in Central Europe, in southern Spain, in England, in the Carpathian region and in the Balkans. This circle flows around 3000 BC. BC, at the beginning of the Early Bronze Age, knowledge from the Caucasus and Anatolia, which also reached Mycenae, Crete and Egypt and found its way into works of art and everyday life in the advanced cultures there. For the Mediterranean area, copper, in Greek "chalkos" (Chalkidike), called "aes cyprium" ("ore from Cyprus") by the Romans, is the basis for a now comprehensive metallurgical development that not only turns small parts and weapons into commercial items the Phoenician makes, but also produces large bronzes. Even then, the Colossus of Rhodes was counted among the "wonders of the world". The processing of gold as a store of value was already recognized by Pharaoh Menes from the first dynasty of the “old empire”, he had small gold bars stamped with a kind of “guarantee stamp”. One can deduce from this that already 3000 BC Knew how to melt and work gold. Driven and cast everyday objects and pieces of jewelry made of gold and silver, as well as numerous parts made of pure copper, were found by Heinrich Schliemann in 1873 during his search for the Homeric Troy and mistakenly assigned to a much younger culture as the “treasure of Priam”.

The Scythians, an equestrian people without writing or coinage, in so far not yet a high culture, are already very skillful in making gold jewelry, as the tombs of princes (Kurgane) show. The Celts also use gold for jewelry and regalia. As a means of controllable store of value, gold is used around 600 BC. BC struck into coins by King Croesus of Lydia ("gold stater"). It also becomes a means of payment. The Egyptian Ptolemies mined gold in mines leading to gold ore in pre-Christian times, the Romans exploited the Spanish silver ore deposits to produce coins, statues, vessels and other proofs of wealth.

Middle East, India, China, Southeast Asia, Japan

In the Near East there are bronzes, for example that of a king's head, from the time of the Akkadian Empire (Mesopotamia) around 2300 BC. BC Although the knowledge was available, the subsequent empires preferred to depict their rulers again in stone or alabaster.

In parts of the Indian subcontinent, towards the end of the 4th millennium BC, The use of copper and bronze can be proven at the same time as the development of “urban life” (Indus cultures). Southeast Asia has known copper and bronze since around 3000 BC. From China this only becomes apparent around 1600 BC. Chr. Reported. Workable alloys (with lowered melting points), such as gold-colored brass, are invented. The influence of the 1700 to 1100 BC in this area is documented. Ruling Shang dynasty. The bronze drums (dong son), which were built around 1000 BC, are traced back to them. Are numerous in the southern provinces.

Culturally, Japan is first under the influence of China and the Shintoism that is widespread there. Buddhism gained a foothold around 500 AD. The figure of the Daibutsu of Nara, cast from a low-tin bronze, is said to weigh 380 tons. Bronze mirrors from the period between 3000 and 710 BC are evidence of earlier metallurgical activity. The Yayoi period from 350 BC. BC is also visible through mirrors, as well as bells and weapons.

Overall, the Asian region with its metallurgical knowledge does not lag behind the European one, although only since 600 BC. A beginning Iron Age is spoken of. Caravan routes, such as the Silk Road, and perhaps even more so the trade by sea, increasingly favor the exchange of knowledge and the products that have arisen from such. This includes a 200 BC In Europe still unknown, shiny white copper alloy, which is called "Packfong" in China.

Biblical traditions

They cannot always be precisely timed, but they are facts that were recorded in very old documents.

He will sit and melt and cleanse the silver;
he will cleanse and purify the children of Levi like gold and silver.

Malachi 3, verse 3 (Old Testament)

Melting, refining (cleaning the melt of foreign substances) and driving work (for defleading) are professionally correct in various places in the Old Testament Bible. Tubal-Cain (Genesis 4:22) and Malachi describe early metallurgists and their pyrometallurgical techniques. They differ only slightly from today's basics. Jewelry and utensils made of gold, silver and bronze are manufactured. Iron is not unknown and - based on the findings - is still used very rarely.

In Jeremiah 6, verses 27-30, a metallurgist becomes the judge of apostates whom he describes as "rejected silver" in a comparison with inadequately chased silver. In Exodus, 32: 1-4, the "golden calf" is narrated as having been cast from melted jewelry by the Israelites who turned away from Yahweh.

From the early to the late Bronze Age and the beginning of the Early Iron Age

Because of the Greek word “chalkos” (χαλκὀς), which does not differentiate between copper and bronze, the early Bronze Age is also late Copper Age called,[1] The knowledge gained from experience of a targeted improvement of the properties of copper objects by adding tin and zinc to the alloy asserts itself relatively quickly by today's standards. Brass as a copper-zinc alloy is either of Chinese or Persian-Indian origin.

Figurative finds prove the almost simultaneous development of lead. The widespread occurrence of lead gloss is initially only sought as a silver carrier, the lead that occurs during its extraction is considered "waste". Its low melting point of only 334 ° C favors, once recognized, considerations that lead to a wide range of uses. Very early figurative objects are known (Hallstatt finds), followed by objects of daily use - (Roman times with vessels, tubes, plates). Lead casting still achieves a late bloom in monuments of the Baroque period, whereby the toxicity of the lead vapors occurring during melting was not taken into account for a very long time.

Another “historic” metal is nickel. As a component of copper-zinc alloys (brass), it was first found around 200 BC. In China. The nickel-containing nickel silver is still the basic type for cutlery alloys today.

The long way to the Iron Age

 

Already in the Middle Bronze Age from 1200 BC. The gradual displacement of bronze by iron begins, the extraction of which became possible - even if by today's standards in a very simple way - because the necessary basic principles had been learned. This became visible in around 700 BC. BC fully developed Hallstatt culture, which is referred to as the "early Iron Age". Celts, Slavs, Italians and Illyrians had an equal share in this. From around 450 BC. The second stage is the La Tène period, an Iron Age epoch that extends to the turn of the ages and beyond. Weapons, tools and utensils are made of iron for the first time.

From today's perspective, the transition from the Bronze Age to the Iron Age is slow progress, because apart from the time around 5000 BC. Backdated individual finds from Egypt do not appear until 1600 BC. Chr. (Hyksos) repeated incursions of equestrian peoples fighting with iron weapons contributed to the spread of iron. Interesting in this context is the use of the Indo-European word “brazen”, ie “of great durability” (compare “Aera”). North of the Alps it was understood to be “iron”, for Italians and Iberians it was “bronzenes”.

Iron for weapons came from 660 BC. On trade routes from Asia to North Africa, however, surprisingly, it was not found until 700 years later (100 AD) in southern Africa. The Central American civilizations give evidence for the use of iron only for the time around 500 AD.

How dominance influences influence the metallurgical development of Europe

The representation of metallurgical development in the course of cultural epochs, which by no means abruptly, but often followed one another with long transition periods, is overlaid by historical periods of rule. The ancient world left its mark on us most sustainably. It begins around 2500 BC. Seen and equated with the early Bronze Age. The influence becomes clearer with the beginning of the “Doric migration”, which is disputed in terms of origin and effects, around 1100 BC. During the course of this period, mounted "warriors with iron weapons" coming from the north prevail against opponents still fighting with bronze swords and two-wheeled chariots. But they do not only bring advances in this area (Balkan or “Carpathian technology”). The Cretan Minoan influence that had prevailed up to that point, including places like Mycenae and Tiryns, was finally replaced after many local and regional wars by the Hellenic antiquity (Magna Graecia), which extended over large parts of the Mediterranean (temple building with the help of bronze brackets and Doric, Ionic and Corinthian capitals).

Gold and silver are found as solid metals, especially easily accessible river gold, or as deposits containing silver, as well as from visibly silver-rich ore veins. As a valuable commodity, gold and silver are not only used for trading, but also for booty on military expeditions.The regional and supraregional exchange, whether wanted or forced, contributes to the refinement of the craftsmanship handed down from Mycenae and early layers of Troy in the production of ornamental jewelry and cult objects. From 700 BC onwards, The first gold or silver coinage. Sparta as an exception leads around 660 BC. Chr. Iron in bar form as the "domestic currency".

The Hellenic determined antiquity reached a climax around 500 BC. In New Greece, after that it is dated from around 1000 BC. Beginning of the rise of the Etruscans and from 700 BC Determined by that of Rome. It stayed that way for almost a millennium, in which, after all, it was considered noble for an upper class to be "Greek" for a long time.

In Roman times, the importance of bronze extends beyond figurative representations (statues) and cult objects. It remains indispensable in the construction industry when connecting marble parts (cast or forged bronze brackets), as well as in roofing and in car construction. Iron is still comparatively difficult to manufacture. Until the time of the Merovingians (Merowech), the founders of the Frankish empire that replaced the Romans and their Western and Eastern Gothic successors, its use was limited to tools and, above all, weapons. Damascus steel became famous at that time with its special hardening process, which was kept secret for a long time.

Late antiquity coincides with the migration of peoples from the 2nd to the 6th century AD. Rome becomes a Christian empire under Emperor Constantine. Not yet completely detached from the bronze culture (monuments), the Western Roman Empire was first occupied in 476 by Odoacer and a little later in 486 by the Merovingian Clovis I. 565 AD not only put an end to the Roman Empire and thus the period called late antiquity. The already acquired knowledge of bronze casting - with the exception of bell casting - is lost again for several centuries. Only the invention of gunpowder brought the ancient art to mind. "Piece casters" are said to have cast the first cannons from ore - that is, from bronze - in 1372.

From medieval blast furnace to electric steel mill

Europe lags behind China and Egypt for a long time in terms of the “industrial” extraction and processing of metals, not just iron. The iron objects found in excavations in Egypt, probably 5000 years old and still well preserved, do not allow any reliable conclusions to be drawn about the type of iron extraction. After all, old and newer reference works (Meyer, Brockhaus) indicate that as early as 1200 BC. The Philistines (valley dwellers in contrast to the mountain dwelling Israelites) have knowledge of iron extraction. Bronze can still be produced in a low-shaft furnace made of clay with a natural draft, but the extraction and processing of iron is inconceivable without the use of a powerful bellows. Only through the abundant supply of atmospheric oxygen is it possible to increase the temperature from 1100 ° C, which is sufficient for bronzes, to the more than 1600 ° C required for iron extraction. In the Bronze Age, so-called "lobes" - unformed lumps of forgeable iron (because it is low in carbon) - were made from a mixture of iron-rich ores - such as hematite / red iron ore and charcoal - and the air supply by means of still very simple bellows (racing freshness) in racing furnaces (racing fire) - won and used for weapons, armor and tools. However, this first step into the Iron Age does not yet produce any significant amounts of iron. An improvement leads to the so-called wolf or piece furnaces, forerunners of today's blast furnace. They deliver liquid pig iron to the bottom (bottom of the furnace), the "wolf" above it releases carbon during annealing and refining and becomes steel or malleable iron.

 

Although contemporary records of the first high shaft furnaces (blast furnaces in today's parlance) are reported as early as the 14th century and early industrial iron production in the 15th century, there is one in technical The so-called “Iron Age” was rightly only spoken of when, towards the end of the 16th century, it was possible for the first time to achieve temperatures of more than 1400 ° C with bellows powered by water power. This enabled the first conceptually real blast furnace, which was still dependent on charcoal, to be set in motion, which could produce pig iron in appreciable quantities. Medieval gunsmiths - instead of the earlier "piece casters" - process it as "castings" into guns and cannonballs, and later into various "cast goods" such as the Siegerland furnace plate casting, which founded an entire industry.

Georgius Agricola (1494–1555), mineralogist, geologist and author of the basic work on ore mining and smelting "De re metallica libri XII“ („twelve books on mining and metallurgy"), With precise descriptions and engravings of technical facilities and processes, such as" driving art "," water art ", tunnel construction, melting furnace construction, or roasting and driving work, gives his successors the foundations for a" modern "metallurgy that are still valid today.

 

A blast furnace no longer powered by charcoal but by coke went into operation in England in 1781, followed by Silesian Gleiwitz in 1796. In 1837 the hot blast furnace gases were made usable for the first time (Faber-du-Faur process). Since the early pig iron with a carbon content of up to 10% can neither be forged nor welded, various methods of “freshening”, i.e. carbon removal, are being developed. Starting from the historical “stove freshening” approach, via the labor-intensive “puddling oven”, a solution can be found in the “wind freshening” invented by Henry Bessemer in 1855, in which compressed air flows from below through a large, pear-shaped vessel (Bessemer pear lined with acidic (silicate) mass) ) is blown. In the process, carbon - and with it other undesirable, oxidizable admixtures of the pig iron, such as silicon (which provides process heat) - is oxidized, in fact burned, to such an extent that the iron treated in this way can now be forgiven. In 1878 the process by Sidney Thomas and Percy Gilchrist was decisively improved by an alkaline lining of the "pear", which also reduced the phosphorus content. With this process, the brown iron ores (30–55% Fe) with a lower iron content, as well as the very fine-grained, Lorraine ores, are produced Minette belongs (only 20–40% Fe), and German lawn iron ore (Salzgitter) can be processed into cast and forged steel. The slag, which predominates in the blast furnace process in a ratio of 2: 1, is - ground - as "Thomas flour" now containing phosphorus, making it the first "artificial fertilizer" for agriculture. (A next step here in the 20th century is the ammonia synthesis according to Haber-Bosch). The above-mentioned blow-steel processes are further improved with the LD process, which introduces pure oxygen for refining in steel production and, after a good four hundred years of history of the blast furnace, which however still retains its technical justification under the appropriate conditions, becomes the state of the art.

The classic blast furnace loses its unique position as a pig iron supplier for steel production with the introduction of the Siemens-Martin furnace with Martin's regenerative furnace. In it, at a temperature of 1700 ° C, pig iron is transformed into low-carbon steel together with scrap containing oxides (scrap recycling as the first recycling process). The electric steel process goes one step beyond the Siemens-Martin process. Scrap and sponge iron (pellets) produced by direct reduction from rich ores are turned into steels or cast iron types in an electric arc furnace.

A conventional blast furnace plant designed for maximum throughput is dependent on the use of location advantages in order to be economical because of its large demand for input materials. Local and regional ore or coal deposits as well as the infrastructure are essential for blast furnace operation. An important German plant in Duisburg uses the local coal and at the same time Germany's largest inland port. An Austrian plant was built near the ore on the Danube major shipping lane. Expanded inland and sea ports make it possible to operate a blast furnace even in locations that are poor in ore and coal. The electric steelworks (mini-steelworks), for which a mere transport connection by land or water is sufficient, is increasingly taking its place. It can adapt flexibly to the available quantities of its raw material scrap and, unlike a blast furnace, work discontinuously and with less environmental pollution. In return, the classic pig iron production in the blast furnace including the attached steelworks migrates to the basic raw materials, primarily deposits with high-quality iron ore (Brazil, Belo Horizonte). The advantage achieved in this way favors the globally oriented transport of the products.

The return of copper

Since the middle of the 19th century and the onset of industrialization, a kind of new era for copper and copper alloys has begun in Europe: the bronzes are no longer in the foreground. The return of copper is clearly determined by a new alloy based on copper, it is called "Gun Metal" or "Cannon Bronze" and is a copper-tin-zinc-lead alloy that met military requirements at that time, mainly for guns. Later and until today it is called machine bronze or gunmetal and is used especially for fittings.

Equally important for the consumption of copper is the rediscovery of historical brass as a particularly versatile cast and wrought alloy (cartridge cases, cartridges, sheet metal, wires and wire mesh made from them). Sieves made from fine brass wires for house and trade are called Leonische Waren. Today it is the "cable harnesses" manufactured in highly specialized factories that modern electronics not only require in motor vehicles and large aircraft.

With the introduction of telegraphy and later the telephone, the civil sector required highly conductive copper wires to bridge greater distances. The same applies to the armature winding, since Werner von Siemens discovered the dynamo-electric principle in 1866 and the use of the electromagnet made possible by it at the end of the 19th century made small, high-speed electric drives (electric motors) available for working machines and gradually replacing steam engines and drive belts. At the same time, for other inventors, the impetus to generate high-voltage electricity and thus again a need for the overhead lines made of copper that is necessary for transmission is given.

There is a need for copper pipes for public and individual heating systems and water supply (fittings). A tubular cooler made of copper (radiator) is used for water-cooled internal combustion engines in automobiles.

In shipbuilding, the corrosion-resistant copper, which protects against mussel growth, is used below the waterline (fouling), while above it, brass dominates in equipment, fittings and instruments. The proven resistance to the effects of the weather creates numerous possible uses in construction and in traffic. The bactericidal property of brass handles and handles has proven to be beneficial in public transport.

The "earth metals" are coming

In addition to the "Iron Age", which adapted to the requirements of modern times (steel structures, Eiffel Tower), something completely new in metallurgy has appeared since the end of the 19th century, the "Earth Metal Age". The elements that determine them are called earth metals because they do not occur as metal-bearing ore, but only in compounds that are called Earth are designated. Usually this is the oxidic form, in the case of aluminum, the best known of all earth metals in group IIIa of the periodic system of elements, the bauxite. The rare earth metals belonging to the same group are by no means insignificant industrially. Cer in the form of its mischmetal is an important element of this group for metallurgy because it is used to influence the structure, not only of steels.

When it comes to aluminum, the beginning is modest. Friedrich Wöhler reduced it for the first time in 1828 as a gray powder, although aluminum as an element was discovered by Hans Christian Ørsted as early as 1825. The production of molten spheres from aluminum only succeeded in 1845. In 1854 Robert Wilhelm Bunsen proposed fused-salt electrolysis for the recovery of usable quantities. Henri Etienne Sainte-Claire Deville presented it for the first time in a trial in 1855 and called it “silver made of clay” because of the cost of its presentation at the time. In 1886 Charles Martin Hall and Paul Héroult applied for a patent at the same time, which is the basis of aluminum production to this day and paved the way for a utility metal for him. It takes another 10 years until the world's first aluminum smelter in Schaffhausen, Switzerland, starts operations with the help of powerful turbines that use the water power of the Rhine Falls. Today, more than 20 million tons of raw aluminum are produced annually worldwide (energy-rich Russia is aiming for market leadership).

The designation as "earth metal" comes first of all to aluminum. Scandium, which also belongs to group IIIa, is another light metal with a density of 2.98 and only finds interest in the age of space technology. Boron is a non-metal that only occurs in the form of oxidic compounds; in metallurgy it is used in the hardening of steels, as an additive in aluminum alloys and as a neutron brake in nuclear technology.

As earth metal, other elements can be assigned to aluminum that do not belong to the same group, but are metallurgically comparable insofar as they never occur in the wild as minerals and in ore deposits, but only as chemical compounds, mostly chlorides and silicates , Carbonates. One example is magnesium, which is obtained in nature (Dead Sea) as chloride, but far more abundantly from magnesite worldwide.

Cerium and other rare earth metals are extracted from monazite sand, a mineral weathering product. Titan has an exceptional position. It occurs as ore in the form of rutile, anatase or ilmenite and this seldom, it is extracted in bulk from ilmenite and rutile sands and can be put to the side of the earth metals. With a density of only 4.5, it is still one of the light metals.

The "light metal age" begins with the earth metals and elements related to them. In any case, it must be seen as a metallurgical epoch and is increasingly taking its place alongside the still dominant “Iron Age”. In a foreseeable period of time, the light metals will not displace iron in the same way as it displaced bronze and this previously displaced copper and that in turn the stone ax and hand ax.

State of metallurgy at the beginning of the 21st century

Extraction of the raw materials

 

Finding “solid”, i.e. pure metal, is always an exception. The metal is sought in ore. The geoscience of geosciences deals with the origin of the deposits. The sciences around mining (prospecting) deal with the exploration and extraction of deposits that are as "prospective" as possible (promising a good ore yield) - whereby the technology and further processing are heavily dependent on the metal content of the deposit. It is located underground in the tunnel (historical examples: silver mining on Cerro Rico in the Bolivian town of Potosí until 1825, today only copper, tin and lead can be found there). The historical gold mining in Austria ("Rauriser Tauerngold") is also known. Other European examples typical of opencast mining can be found in Falun in Sweden (lead, zinc, copper), in Erzberg (iron) in Austria and not far away in Mittersill (tungsten). In addition to open ore deposits ("outcrops"), the important deposits include not only ore, but also "solid" geologically so-called "sands" and "soaps". They are differentiated according to the way in which they arise. Most metallurgically significant are the residuals left over after the weathering of surrounding rock (e.g. magnetite or magnetic iron ore), and the alluvial, washed ashore by water going down into the valley (e.g. discovered very rich in gold on the American River in California in 1848), as well as geologically comparable , the tin-containing, marine, coastal soaps of Malaysia and Indonesia with 30% share of world production, as well as the cerium-containing Monazite sands of Western Australia) and the titanium-containing Ilmenite sands (black sands). Nickel laterite ores, which are geologically only found in lower latitudes close to the equator, are considered to be “residual rocks”, close to the “sands”.

Post-classical, as it is tied to processes developed in the modern era, metallurgy is still assigned:

  • the electrolytic extraction of alkali metals from the mining of their chlorides and the mining of uranium ore as a mineral containing uranium, which is also operated.
  • the production of magnesium, which represents the state of the art, from the breakdown of magnesite (Australia) via the intermediate stage magnesium chloride, which can still be obtained to a lesser extent from its share in seawater.
  • the open mining of bauxite, a reddish sedimentary rock, which - converted to pure clay - is the basic material for aluminum production.
  • A future task with great metallurgical benefits is the deep-sea mining of manganese nodules with up to 27% manganese and other metals, including up to 1% nickel, which has been prospected for decades and has not yet been technically solved satisfactorily. This applies even more to the deposits of minerals, crude oil and natural gas that have been suspected to be under the North Pole at a depth of 4000 m since 2007.

Classification of metals according to their metallurgical importance

A common classification is based on the percentage of the elements in the earth's crust, i.e. without taking into account the nickel-iron earth core. However, it says nothing about the metallurgical meaning. Beryllium has a share of only 0.006% and yet without its addition as an oxidation inhibitor the magnesium, which is abundant with 1.95%, cannot be melted and cast.

In practice, it tends to stick to the distinction between main metals - that is, metals that are widely used as the basis of alloys - and secondary metals. Aluminum has become a main metal, only recognized as such in the 20th century because, like silicon, it does not occur as a metal in nature. The clay mineral bauxite (formerly often referred to as "aluminum ore") is processed into alumina and has been electrolytically extracted from aluminum since the end of the 19th century. The main metals also include the metallurgically and chemically important alkali and alkaline earth metals sodium, potassium, calcium and magnesium. Since they never occur metallic, but only in the form of non-metallic compounds, as salts, carbonates and silicates, they were assigned to the earth metals at an earlier point (section The “earth metals”), also because of the comparability of the extraction process.

This is especially true for silicon, which has several functions. It is a semi-metal that occurs naturally only as rock or quartz sand (SiO2), from which it is obtained "carbothermally" in an electrochemical reduction process in an electric arc furnace with carbon electrodes. When iron scrap is added at the same time, ferrosilicon (FeSi), which is used, among other things, for calming the steel after refining, is created “in situ” (during the process). Like aluminum and manganese, it has a deoxidizing (oxygen-removing) effect.

In the case of aluminum-silicon alloys, silicon determines the alloy properties of wrought alloys as well as cast alloys. An additional melt treatment (refinement / refinement) prevents the disadvantageous primary coarse separation of the silicon when the melts slowly solidify, be it in sand casting, such as engine parts (e.g. crankcases, cylinder heads), but also with heavy die casting.

In the case of very specialized copper alloys (silicon bronze) it is an alloy companion and in semiconductor technology it has achieved its own position. Manufactured in an elaborate process of "pure metallurgy" (that is, the achieved degree of purity of a metal in the range of 99.999, so-called "five-nine metal"), it is the basis for chips that are indispensable in computer technology. The German share of world production is considerable (for example chip production in Dresden / "Elbe-Valley"). Silicon is also used as a semiconductor in the manufacture of solar cells.


Another possibility of classification separates the heavy from the light metals. Heavy metals have a density greater than 5. Platinum is at the top with a density of 21.45. Copper 8.93, iron 7.86, zinc 7.14 follow at a distance. Among the light metals, lithium is the lightest with 0.54, followed by magnesium with 1.74 and aluminum with 2.70. Titanium with a density of 4.5 is still assigned to light metals.

There is also a widespread division into "base metals" and "alloy companions", which includes numerous elements that are often only added in traces and yet are important. Copper, iron, lead, tin, zinc, and nickel are considered to be base metals - due to their evolutionary history. However, aluminum, magnesium and titanium are now equated with the historical base metals in terms of their economic and metallurgical importance.

A distinction already mentioned in the introduction sees iron and its metallurgy, which are more important in terms of quantity, in the first place. The non-ferrous metals follow at a distance.

Main metals

     

copper is extracted as the main metal either on the "dry route" for the richer ores, or the "wet route" for the poorer ores. The process leading to pure copper is multi-stage. It begins with the roasting of the ore, which is followed by the crude smelting with further operations, either in the shaft furnace ("German way") or in the flame furnace ("English way"). The product is now black copper with more than 85% copper content. Its further refining is now rarely done in the flame furnace. Rather, it is customary to refine black copper plates electrolytically. The pure copper that arises is a hydrogen-containing oneCathode copper, also known as blister copper (blistered copper). It is “conductive copper” (pure copper with defined electrical conductivity) for the electrical industry, being highly pure and free of oxygen.

The bulk of the available refined copper is - mostly alloyed - into kneading or casting material. When rolled into sheet metal, pure copper is particularly noticeable in construction. Very stable against the effects of the weather, copper sheets are increasingly being used for roofing and rain gutters. The patina (green color) that develops over time was valued earlier. Wrongly referred to as toxic verdigris, it is actually made up of non-toxic copper sulfate and carbonate.

Bell bronze with 20–24% tin has been known as a copper alloy for centuries. All alloys with the main component copper are considered to be Copper alloys between bronzes and special bronzes (compare beryllium bronze) and brass (alpha or beta brass with 63/58% zinc), there are clear differences in appearance and mechanical properties. One example is the “nickel silver”, which is completely different in color from the reddish copper tone, formerly also known as white copper and even more recently with the term “Packfong”, which originated in its country of origin, China.

Pure copper is more numerous than the “master alloy” in non-ferrous metallurgical processes of added elements. In cast iron, copper is an alloying element that has positive properties.

tin has been the most important metal accompanying copper since the Bronze Age. As pure tin, it is only rarely processed (crockery tin, tin figures); it is indispensable for tinplate production (tin cans). Soldering tin is a tin alloy with a melting point below 330 ° C. Like lead, tin is an important component of bearing materials (plain bearings).

lead is historically (Roman times) a main metal, today it is no longer used because of its toxicity for drinking water systems (lead pipes). It is seen as one of the causes of the fall of the Roman Empire.[2] Paints made on the basis of lead oxide ("white lead", red lead) and children's toys on or in which it is contained are also toxic.

As a result of modern printing technology, lead-antimony alloys as font metals have become largely insignificant. For the time being, lead is still indispensable for accumulators and as a component of lead-containing bearing metals. Here it is especially lead bronze, a copper-lead-tin alloy with up to 26% lead, which is used for highly stressed slide bearings in automobile engines.

In wrought brass alloys, lead is an additive that promotes machining (maximum 3%). With up to 7% it is an alloy companion of copper-tin-zinc cast alloys (machine bronze).

iron becomes cast iron or steel solely through its accompanying elements (iron companions), which, although indispensable in steel production, remain minor metals in terms of quantity. The best known are manganese (mirror iron with 50% also as manganese carrier ferromanganese or FeMn50. Comparable in their meaning are chromium, nickel, molybdenum, vanadium, cobalt, titanium, the semimetal silicon (added as ferrosilicon / FeSi) and the nonmetals carbon, phosphorus and Sulfur.

zinc is called Pure zinc Alloyed with 0.5% copper when galvanizing steel used in large quantities as corrosion protection. Zinc sheets and strips made from very “low-alloy pure zinc or titanium zinc” with 0.1% copper or titanium are used in construction. Furthermore, zinc is the base metal for fine zinc casting alloys with copper and aluminum components. Zinc is an important companion in copper alloys (see above), especially in brass for more than two millennia.

aluminum is available as pure metal (achieved degree of purity in the range of 99.99, so-called "four-o'clock metal") or as pure metal (in the range of 99.999), but its actual importance as a wrought and cast material is determined by numerous alloy-forming accompanying elements, including the base metal copper. In 1909 Alfred Wilm developed the patented duralumin (brand name DURAL), the first hardenable alloy consisting of aluminum, copper and magnesium (Al95 / Cu 4 / Mg 1). This alloy is mainly used in aircraft construction, initially at Junkers / Dessau. In 1920, Aladár Pácz succeeded in “refining” the eutectic aluminum-silicon two-component alloy (legally protected as “ALPAX”, “SILUMIN”) by adding less than 150 ppm sodium. In the range of 7–13% silicon, this becomes the group of alloys most processed as castings today. A little later, aluminum-magnesium alloys follow (legally protected as "HYDRONALIUM", seawater-proof; with the addition of titanium, particularly seawater-proof). In terms of quantity, the universal wrought alloy AlMg0.5Si0.5 and numerous other alloys with copper, titanium, zinc, manganese, iron, nickel, chromium and others are of greatest importance, with the increasingly more specified properties required of the alloys, the accompanying elements according to type and quantity determine. If not available as a finished alloy, they can be added to a base melt of pure aluminum as an “alloying agent” or “master alloy based on aluminum”.

Accompanying metals

In addition to the term "accompanying metals" (synonymous: "alloy companions") there is the more comprehensive term "accompanying elements". These are regularly used to manufacture alloys. The proportion of these accompanying elements is between tenths of a percent and less and the double-digit percentage range. Examples: AlCuTi with 0.15-0.30% titanium; AlSi 12 with 10.5-13.5% silicon. Materials development now only knows a few elements, for example radioactive ones, which are not suitable for potentially improving the properties of newly developed alloys.

Examples of other important companions are the non-metal phosphorus in hypereutectic AlSi piston alloys, or beryllium, a light metal with a density of 1.84, which is very toxic in the form of its vapors. Beryllium is used for hardenable bronzes (beryllium bronze), for spark-free tools in mining, as a deoxidation additive for conductive copper (here via a 5 percent master alloy) and in the ppm range (also dosed via master alloy) in aluminum alloys to improve quality and to reduce oxidation of the melt which is essential for magnesium alloys. The annual world production is given as 364 t (source: Google alerts).

Basic metallurgical processes

After this first process stage, the elements described in the section “Extraction of the raw materials” with regard to occurrence and extraction go through a further process stage, the treatment, before they become pure or alloyed usable metals and semi-metals through smelting.

A first divorce or sighting is still assigned to the mining area, which can be tunnels as well as open-cast mining. The subsequent processing stage is already considered "metallurgical" work. The necessary measures are as diverse as the starting materials themselves. A basic distinction is made between dry and wet Procedure, each with the aim of “enrichment”. "Heap" mined in the tunnel requires the separation of the valuable, ore-rich from the worthless, ore-poor, "deaf" material, which is referred to as "gangue". For the separation, the rock is crushed further by grinding, followed by sieving, sifting and, if necessary, magnetic separation. When mining in opencast mines, overburden of different thicknesses usually has to be removed beforehand.

The further processing of the prepared substances is carried out using the basic techniques described below.

Pyrometallurgy

Pyrometallurgy is the further thermal processing of ores or already extracted metal, be it oxidizing, i.e. heated with oxygen supply (roasting), or reducing in an oxygen-free furnace atmosphere. This includes fire refining (oxidation and slagging of undesired elements), as well as segregation, which means the segregation of a melt using differences in density in the melt (example: above its solubility limit in copper, lead segregates from a copper alloy melt and sinks to the bottom of the melting vessel). The situation is similar with distillation, which uses different vapor pressures of the substances at a given temperature to separate them into fractions (example zinc extraction from roasted zinc ore in muffle furnaces).

Hydrometallurgy

Hydrometallurgy originally means the preparation of ores for smelting by cold or warm separation processes (cold or hot extraction) using water. The historical flotation, further developed for sink-swim separation, makes it possible to further enrich the ore extracted in the mining process. Leaching and boiling serve the same purposes. Extraction by acids, alkalis, organic solutions and bacteria is also part of hydrometallurgy. In addition, the elements contained in less than one percent concentration, such as precious metals, are obtained from poor ores by chemical precipitation processes or by means of electrolysis. In these cases hydrometallurgy is referred to as "electrometallurgy by the wet route".

Electrometallurgy

 

Electrometallurgy includes electrothermal and carbothermal (see silicon production