Copper

Copper (from the Latin cuprum , and this one from the Greek kýpros ). Whose symbol is Cu, it is the chemical element with atomic number 29. It is a transition metal with a reddish color and metallic luster that, together with silver and gold, is part of the so-called copper family, it is characterized by being one of the best conductors of electricity (second only to silver). Thanks to its high electrical conductivity, ductility and malleability , it has become the most widely used material to manufacture electrical cables and other electrical and electronic components. It is the third most used metal in the world , after iron andaluminum .

Summary

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• 1 General characteristics
• 2 Names and symbols
• 3 History
  • 1 Copper in ancient times
  • 2 Middle Ages and Modern Age
  • 3 Contemporary Age
  • 4 Chile
• 4 Isotopes
• 5 Properties and characteristics of copper
  • 1 Physical properties
  • 2 Mechanical properties
  • 3 Chemical characteristics
  • 4 Biological properties
  • 5 Sanitary precautions for copper
    • 5.1 Poisoning
  • 6 Copper alloys and types
    • 1 Brass Cu-Zn
    • 2 Bronze (Cu-Sn)
    • 3 Alpaca (Cu-Ni-Zn)
    • 4 Other alloys
  • 7 Industrial copper processes
    • 1 Copper mining
    • 2 Copper metallurgy
    • 3 Heat treatments of copper
  • 8 Applications and uses of copper
    • 1 Metallic copper
    • 2 Electricity and telecommunications
    • 3 Means of transport
    • 4 Construction and ornamentation
    • 5 Coins
    • 6 Other applications
    • 7 Non-metallic copper
  • 9 Copper products
    • 1 Foundry: blister and anodes
    • 2 Refinery: cathodes
    • 3 Smelter and refinery by-products
    • 4 Wire rod
    • 5 Bare copper wire
    • 6 Wire drawing
    • 7 Pipes
    • 8 Lamination
    • 9 Casting of parts
    • 10 Forged
    • 11 Machining
    • 12 Welding
    • 13 Boilerwork
    • 14 Stuffing
    • 15 Stamping
    • 16 Die cutting
  • 10 Recycled
  • 11 Production and trade
    • 1 Mining production
    • 2 Reservations
    • 3 Trade and consumption
  • 12 Sources

General characteristics

This metal is part of a very high amount of alloys that generally have better mechanical properties, although they have lower electrical conductivity. The most important are known by the name of bronzes and brass. It is also a durable metal because it allows it to be recycled an unlimited number of times without losing its mechanical properties.

It was one of the first metals to be used by humans in prehistory . Copper and its alloy with tin , bronze , acquired great importance, which is why historians gave the names of the Copper Age and the Bronze Age to two periods in Antiquity. Its use lost relative importance with the development of the steel industry, but copper and its alloys continued to be used to make objects as diverse as coins, bells and cannons. From the 19th century , specifically from the invention of the Electric Generator in 1831 by Faraday, copper once again became a strategic metal, being the main raw material for cables and electrical installations.

Copper also has an important biological role in the process of photosynthesis of plants , although not part of the composition of the Chlorophyll . It also contributes to the formation of red blood cells and the maintenance of blood vessels , nerves , immune system and bones , therefore it is an essential trace element for human life .

Copper is found in a large number of common foods in the diet such as oysters, shellfish , legumes , organ meats and nuts, among others, in addition to drinking water and therefore it is very rare for a copper deficiency to occur in the body . The copper imbalance causes a liver disease known as Wilson’s disease .

Copper is the third most widely used metal in the world, behind iron and aluminum . World refined copper production was estimated at 15.8 Mt in 2006 , with a deficit of 10.7% compared to the projected global demand of 17.7 Mt.

Names and symbols

• Etymology. The word “copper” comes from the Latin cuprum (with the same meaning) and this in turn from the expression aes cyprium which literally means “from Cyprus” due to the great importance of the copper mines on the island of Cyprus in the Greco-Roman world.
• Acronyms and abbreviations. The current chemical symbol for copper is “Cu.” Centuries ago, alchemists represented it with the symbol? , which also represented the planet Venus , the Greek goddess Aphrodite and the female gender. The reason for this relationship may be that the Phoenician goddess Astarte , partly equivalent to Aphrodite, was highly revered on Cyprus , an island famous for its copper mines. The symbol ? It bears in turn similar to the Egyptian hieroglyph Ankh , which represented life or perhaps also sexual union.
• Adjective. The particular qualities of copper, specifically with regard to its color and luster, have generated the root of the term copper. The same particularity of the material has been used when colloquially naming some snakes from India , Australia and the United States as “copper head”

History

Copper in ancient times

Copper is one of the few metals that can be found in nature in a “native” state, that is, without combining with other elements. For this reason it was one of the first to be used by humans. The other native metals are Gold , Platinum , Silver and Iron from Meteorites .

Native copper utensils dating from around 7000 BC have been found in Çayönü Tepesí (in present-day Turkey ) and in Iraq . The copper from Çayönü Tepesí was annealed but the process was not yet perfected. At this time, in the Middle East copper carbonates ( Malachite and Azurite ) were also used with ornamental motifs. In the Great Lakes region of North America, where native copper deposits were abundant, from 4000 BC the indigenous people used to beat them into an arrowhead, although they never discovered the fusion.

The first crucibles to produce metallic copper from carbonates by reduction with carbon date from the 5th millennium BC. It is the beginning of the so-called Copper Age , with crucibles appearing throughout the area between the Balkans and Iran , including Egypt . Evidence of copper carbonate mining has been found since ancient times in both Thrace (Ai Bunar) and the Sinai Peninsula. In an endogenous way, not connected with the civilizations of the Old World, in pre-Columbian America , around the 4th century BC. C. the Moche culture developed the metallurgy of already refined copper from malachite and other copper carbonates.

Around 3500 BC , copper production in Europe went into decline due to the depletion of carbonate deposits. Around this time there was the emergence from the east of some peoples, generically called Kurgans, which carried a new technology: the use of arsenical copper. This technology, perhaps developed in the Middle East or the Caucasus, made it possible to obtain copper by oxidizing copper sulfide.

To prevent copper from oxidizing, arsenic was added to the mineral. Arsenical copper (sometimes also called “arsenical bronze”) was sharper than native copper and could also be obtained from the very abundant sulfide deposits. Combining it with the also new technology of the two-piece mold, which allowed the mass production of objects, the Kurgans equipped themselves with tomahawks and spread rapidly.

Ötzi , the corpse found in the Alps and dated around 3300 BC , carried a copper ax with 99.7% copper and 0.22% arsenic. The Los Millares deposit ( Almería , Spain ), a metallurgical center near the copper mines of the Sierra de Gádor, also dates from this period .

It is not known how or where the idea of ​​adding tin to copper, producing the first bronze, came about. It is believed that it was an unforeseen discovery, since tin is softer than copper and, however, adding it to copper gave a harder material whose edges were preserved longer. The discovery of this new technology triggered the beginning of the Bronze Age, dated around 3000 BC for the Middle East, 2500 BC for Troy and the Danube and 2000 BC for China . At the Bang Chian field in ThailandBronze objects have been dated to before 2000 BC. Bronze played a leading role for many centuries and tin deposits, often far from the large urban centers of that time, gained great importance.

The decline of bronze began around 1000 BC , when a new technology emerged in the Middle East that made it possible to produce metallic iron from ferrous ores. Iron weapons were replacing copper weapons throughout the space between Europe and the Middle East . In areas like China the Bronze Age lasted several more centuries. There were also regions of the world where bronze was never used. For example, sub-Saharan Africa went directly from stone to iron. However, the use of copper and bronze did not disappear during the Iron Age.

Replaced in weapons, these metals came to be used essentially in construction and in decorative objects such as statues. Brass, an alloy of copper and zinc, was invented around 600 BC. Also around this time the first coins were made in the state of Lydia, in present-day Turkey . While the most valuable coins were minted in Gold and Silver , the most commonly used coins were made of copper and bronze.

The search for copper and precious metals in the Mediterranean led the Carthaginians to exploit the great deposit of Río Tinto , in the current province of Huelva . After the Punic Wars, the Romans seized these mines and continued to exploit them until all the copper oxide was exhausted. Beneath it was a large vein of copper sulfide, which the Romans did not know how to use effectively. By the fall of the Roman Empire the mine had been abandoned and was only reopened when the Andalusians invented a more efficient process to extract copper from sulfur.

Middle Ages and Modern Age

The resistance to corrosion of copper, bronze and brass allowed these metals to have been used not only as decorative but also as functional from the Middle Ages to the present day. Between the 10th and 12th centuries, large deposits of silver and copper were found in Central Europe, mainly Rammelsberg and Joachimsthal . From them arose a large part of the raw material to make the great Bells, Doors and Statues of the European Gothic Cathedrals. In addition to the warlike use of copper for the manufacture of objects, such as Axes , Swords , Helmetso Shells; copper was also used in the Middle Ages in lamps such as lamps or candelabra; in braziers and in storage objects such as chests or cases.

The first European wrought iron cannons date from the fourteenth century , but by the sixteenth century bronze was imposed as the almost unique material for all artillery and maintained that dominance well into the nineteenth century . In the BaroqueDuring the 17th and 18th centuries, copper and its alloys acquired great importance in the construction of monumental works, the production of clockwork machinery and a wide variety of decorative and functional objects. The authoritarian monarchies of the Old Regime used copper in alloy with silver (called fleece) to carry out repeated currency devaluations, leading to the issuance of purely copper coins, characteristic of the difficulties of the Treasury of the Spanish Monarchy of the seventeenth century (which He used it in such quantity that he had to resort to importing it from Sweden ).

Contemporary age

During 1831 and 1832 , Michael Faraday discovered that an Electric Conductor moving perpendicular to a Magnetic Field generated a potential difference. Taking advantage of this, he built the first electrical generator , the Faraday Disc , using a copper disc that rotated between the ends of a horseshoe-shaped magnet, inducing an electric current . The subsequent development of electric generators and their use in the history of Electricity has led to copper having obtained a prominent importance in humanity, which has increased its demand significantly.

During much of the 19th century , Great Britain was the world’s largest copper producer, but the importance that copper was acquiring motivated mining exploitation in other countries, with production in the United States and Chile standing out , in addition to the opening of mines. in Africa . Thus, in 1911 world copper production exceeded one million tons of fine copper.

The appearance of the processes that allowed the massive production of steel in the mid- nineteenth century , such as the Thomas-Bessemer Converter or the Martin-Siemens Furnace, led to the replacement of the use of copper and its alloys in some specific applications where it required a tougher and more resistant material. However, technological development that followed the Industrial Revolution in all branches of human activity and advances in copper metallurgy have made it possible to produce a wide variety of alloys. This has led to an increase in the fields of application of copper, which, added to the economic development of several countries, has led to a notable increase in world demand.

Chile

In 1810 , the year of its first national meeting, Chile produced some 19,000 tons of copper per year. Throughout the century the figure grew to make the country the world’s leading producer and exporter. However, a period of decline began at the end of the 19th century, due on the one hand to the depletion of high-grade deposits and, on the other, to the fact that the exploitation of nitrate monopolized mining investments. By 1897 production had fallen to 21,000 tons, about the same as in 1810 .

The situation changed at the beginning of the 20th century , when large American mining groups, endowed with technological advances that allowed the recovery of copper in low concentration deposits, began the exploitation of Chilean deposits. The Chilean state received few benefits from copper mining throughout the first half of the 20th century . The situation began to change in 1951 with the signing of the Washington Agreement , which allowed it to have 20% of the production. In 1966 the National Congress of ChileIt imposed the creation of Mixed Mining Societies with foreign companies in which the State would have 51% ownership of the deposits. The process of “chilenización of copper” culminated in July of 1971 , under President Salvador Allende , when Congress unanimously approved the nationalization of the big mining of copper.

… because the national interest demands it and in exercise of the sovereign and inalienable right of the State to freely dispose of its wealth and natural resources, the foreign companies that constitute the great copper mining.

Transitory provision added in 1971 to article 10 of the Constitution of Chile .

In 1976 , already under the military regime of Pinochet , the State founded the National Copper Corporation of Chile ( Codelco ) to manage the large copper mines. The Chuquicamata mine , in which evidence of copper extraction by pre-Columbian cultures has been found, began its construction for industrial exploitation in 1910 and exploitation began on May 18 , 1915 . Chuquicamata is the largest open pit mine in the world and was for several years the copper mine with the highest production in the world. In 2002 the divisions of Chuquicamata and Radomiro Tomic were merged, creating the Codelco Norte mining complex, which consists of two open pit mines, Chuquicamata and Mina Sur. Although the Radomiro Tomic deposit was discovered in the 1950s , its operations began in 1995 , once the technical and economic feasibility studies were updated.

In 1995 , the construction of the Minera Escondida mine began in Antofagasta Region II , and extraction operations began in 1998 . It is the largest producing mine in the world. The Minera Escondida Strike in 2006 paralyzed production for 25 days and altered world copper prices. Minera Escondida’s production in 2007 reached 1,483,934 t. This production represents 9.5% of world production and 26% of Chilean copper production, according to estimates for 2007.

In recent decades, Chile has established itself as the main copper producer, going from 14% of world production in 1960 to 36% in 2006 .

Isotopes

Stable: 63Cu and 65Cu. The lightest of them is the most abundant (69.17%). Up to now, 25 radioactive isotopes have been characterized, of which the most stable are 67Cu, 64Cu and 61Cu with half – lives of 61.83 hours, 12.70 hours and 3,333 hours respectively. Other radioisotopes with atomic masses from 54.966 Uma (55Cu) to 78.955 amu (79Cu), have half lives of less than 23.7 minutes and most do not reach 30 seconds. The 68Cu and 70Cu isotopes present metastable states with a half-life longer than the ground state.

The isotopes lighter than stable 63Cu disintegrate mainly by positive beta emission , giving rise to Nickel isotopes , while those heavier than the stable 65Cu isotope disintegrate by negative beta emission, giving rise to zinc isotopes . The 64Cu isotope disintegrates generating 64 Zn , by electronic capture and positive beta emission in 69% and by negative beta disintegration it generates 64Ni in the remaining 31%.

Properties and characteristics of copper

Physical properties

Copper has several physical properties that promote its industrial use in multiple applications, being the third most consumed metal in the world. It is reddish in color and has a metallic luster and, after Silver , it is the element with the highest electrical and thermal conductivity. It is an abundant material in nature; It has an accessible price and is Recycled indefinitely; It forms Alloys to improve mechanical performance and is resistant to Corrosion and Oxidation . The electrical conductivity of pure copper was adopted by the International Electrotechnical Commission in 1913 as the standard reference for this quantity, establishing the International Annealed Copper Standard or IACS.

By this definition, the conductivity of annealed copper measured at 20 ° C is equal to 58.1086 S / m. This conductivity value is assigned a 100% IACS index and the conductivity of the rest of the materials is expressed as a percentage of IACS. Most metals have conductivity values ​​below 100% IACS but there are exceptions such as silver or special very high conductivity coppers designated C-103 and C-110.

Mechanical properties

Both copper and its alloys have good machinability, ie, they are easy Machining . Copper has very good ductility and malleability , which allows it to produce very thin and fine sheets and wires. Is a soft metal with a hardness 3 on the Mohs Scale (50 in the Vickers scale ) and its resistance to traction is 210 MPa, with an elastic limit of 33.3 MPa. It supports deformation manufacturing processes such as rolling or forging, and welding processes and their alloys acquire different properties with heat treatments such as quenching and annealing. In general, its properties improve at low temperatures, which allows it to be used in cryogenic applications.

Chemical characteristics

In most of its compounds, copper has low oxidation states, the most common being +2, although there are also some with a +1 oxidation state.

Exposed to air, the initial salmon-red color turns violet-red due to the formation of cuprous oxide (Cu2O) to later blacken due to the formation of cupric oxide (CuO). [40] The blue coloration of Cu + 2 is due to the formation of the Ion [Cu (OH2) 6] +2.

Exposed for a long time to humid air, it forms an adherent and impermeable layer of basic carbonate ( cupric carbonate ) of a green and poisonous color. Verdigris patina can also form, a poisonous mixture of greenish or bluish copper acetates that forms when copper oxides react with Acetic Acid , which is responsible for the flavor of Vinegar and is produced in acetic fermentation processes. When using copper utensils for cooking food, precautions should be taken to avoid poisoning by verdigris which, despite its bad taste, can be masked with sauces and condiments and be ingested.

The halogens readily attack on copper, especially in the presence of moisture. When dry, Chlorine and Bromine have no effect and Fluorine only attacks it at temperatures above 500 ° C. The cuprous chloride and cupric chloride , combined with oxygen in the presence of moisture produce hydrochloric acid , causing spots of Atacamite or Paratacamita , pale green to greenish, soft and dusty blue which are not fixed on the surface and produce more copper chlorides, starting the Erosion cycle again .

Oxacid acids attack copper, which is why these acids are used as strippers (sulfuric acid) and brighteners ( nitric acid ). Sulfuric acid reacts with copper to form a sulfide, CuS (covelina) or Cu2S ( Chalcocite ) of black color and water. Cupric sulfate salts ( Antlerite ) with colors from green to blue-green can also form.

These salts are very common in the anodes of lead batteries used in automobiles.

The citric acid dissolves copper oxide, so it is applied to clean copper surfaces, polishing the metal and forming copper citrate . If after cleaning copper with citric acid, the same cloth is used again to clean lead surfaces, the lead will be coated with an outer layer of copper citrate and lead citrate with a reddish and black color.

Biological properties

In plants, copper plays an important role in the photosynthesis process and is part of the composition of Plastocyanin . About 70% of the copper in a plant is present in Chlorophyll , mainly in Chloroplasts . The first symptoms in plants of copper deficiency appear in the form of narrow and twisted leaves, in addition to whitish tips. The panicles and pods empty may appear severe copper deficiency, causing serious economic losses in agriculture.

Copper contributes to the formation of red blood cells and to the maintenance of blood vessels , nerves , immune system and bones and therefore is essential for human life. Copper is found in some enzymes such as cytochrome c oxidase , the lysyl oxidase and superoxide dismutase .

The copper imbalance in the body when it is produced excessively causes a liver disease known as Wilson’s disease , the origin of this disease is hereditary, and apart from the liver disorder that it causes, it also damages the nervous system. It is a rare disease.

Copper deficiency can occur in children with a diet low in Calcium , especially if they have Diarrhea or Malnutrition . There are also diseases that decrease the absorption of copper, such as celiac disease , cystic fibrosis or when eating restrictive diets.

Copper is found in a large number of common foods in the diet such as Oysters , Seafood , Legumes , Organ meats and Nuts among others, in addition to drinking water and therefore it is very rare for a copper deficiency to occur in the body.

Copper health precautions

Despite the fact that copper is a trace element necessary for life, high levels of this element in the body can be harmful to health. Inhaling high levels of copper can irritate the respiratory tract. Ingesting high levels of copper can cause nausea, vomiting, and diarrhea. Too much copper in the blood can damage the liver and kidneys, and even cause death. Orally ingesting 30 g of Copper Sulfate is potentially fatal in humans.

For work activities in which copper products are made and handled, it is necessary to use collective protection measures that protect workers. The tolerated limit value is 0.2 Mg / m³ for smoke and 1 mg / m³ for dust and mist. Copper reacts with strong oxidants such as chlorates, bromates and iodides, creating an explosion hazard. In addition, it may be necessary to use personal protective equipment such as gloves, glasses and masks. Additionally, it may be advisable for workers to shower and change clothes before returning home each day.

The World Health Organization ( WHO ) in its Guide to drinking water quality recommends a maximum level of 2 mg / l. The same value has been adopted in the European Union as the limit value for copper in drinking water, while in the United States the Environmental Protection Agency has established a maximum of 1.3 mg / l. Water with copper concentrations higher than 1 mg / l can make clothes dirty when washed and have an unpleasant metallic taste. The Agency for Toxic Substances and Disease Registry of the United States recommends that to lower copper levels in drinking water through copper pipes, the water be flushed for at least 15 seconds before drinking or using it for the first time in the morning.

Mining activities can cause the contamination of rivers and groundwater with copper and other metals during their exploitation as well as once mining has been abandoned in the area. The turquoise color of the water and rocks is due to the action that copper and other metals develop during mining.

Poisoning

Copper and its salts are almost non-toxic to mammalian tissues . You need to ingest a large amount of soluble salts, such as copper sulfate, for poisoning to occur. Nausea, vomiting, diarrhea, abdominal cramps, melena, coma, and death may occur. Copper solutions not only cause vascular congestion of the digestive tract, but are irritating and cause focal necrosis, microscopic thrombi in the capillaries of the intestinal wall, and liver necrosis. Death is usually caused by vascular collapse (shock). The ingestion of small amounts of dissolved copper salts, from the walls of pots and glasses by the action of citrus juices, rarely produces symptoms and is not life-threatening; symptoms are mild (nausea and vomiting) and are due togastroenteritis . Inhalation of copper salt dusts, vapors, or fumes can cause congestion and upper respiratory irritation, but generalized symptoms do not occur. Chronic copper poisoning is not a great health hazard.

Chronic toxicity in humans is extremely rare, except in those who inherit a group of autosomal recessive genes that cause an abnormal increase in body copper (a syndrome called hepatolenticular degeneration or Wilson’s disease). Normal individuals absorb low amounts of copper, which are sufficient to meet the essential needs of the body and the excess is easily eliminated. Copper, in small quantities, is an element of the least abundant in the body, essential for the activity of mammalian metalloenzymes such as ceruloplasmin, cytochrome or oxidase, dopamine and tyrosinase.

Copper alloys and types

From the physical point of view, pure copper has a very low elastic limit (33 MPa ) and a low hardness (3 on the Mohs Scale or 50 on the Vickers Scale ). On the other hand, when joined in alloy with other elements, it acquires much higher mechanical characteristics, although its conductivity decreases. There is a wide variety of copper alloys, the compositions of which depend on the technical characteristics obtained, which is why they are used in a multitude of objects with very diverse technical applications. Copper is mainly alloyed with the following elements: Zn , Sn , Al , Ni , Be , Si , Cd, Cr and others to a lesser extent.

According to the purposes for which they are used in the industry, they are classified into alloys for forging and alloys for molding. To identify them, they have the following general nomenclatures according to the ISO 1190-1: 1982 standard or its equivalent UNE 37102: 1984. Both standards use the UNS (Unified Numbering System) system.

Brass Cu-Zn

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The Brass , also known as cuzin, is a copper alloy, zinc (Zn) and, to a lesser extent, other metals. It is obtained by melting its components in a crucible or by melting and reducing sulfurous ores in a reverberatory or cupola furnace.

In industrial brasses, the Zn percentage is always kept below 50%. Its composition influences the mechanical characteristics, the fusibility and the formability by casting, forging and machining. When cold, the ingots obtained are plastically deformed producing sheets, rods or cut into strips that can be stretched to make wires. Its density depends on its composition and is generally between 8.4 G / cm3 and 8.7 g / cm3.

The characteristics of the brass depend on the proportion of elements that intervene in the alloy in such a way that some types of brass are malleable only when cold, others exclusively when hot, and some are not so at any temperature. All types of brass become brittle when heated close to the melting point.

Brass is harder than copper, but easy to machine, engrave, and cast. It is resistant to oxidation, saline conditions and is malleable, so it can be rolled into thin plates. Its malleability varies with temperature and with the presence, even in minute quantities, of other metals in its composition.

A small contribution of Lead in the composition of Brass improves machinability because it facilitates chip fragmentation during machining. Lead also has a lubricating effect due to its low melting point, which slows down wear on the cutting tool.

Brass admits few heat treatments and only Homogenization and Recrystallization anneals are carried out . Brass has a bright yellow color, similar to gold , a characteristic that is used in jewelery , especially in costume jewelery , and in the galvanizing of decorative elements. Brass applications cover a wide range of other fields, such as weaponry, boilermaking, welding, wire manufacturing, condenser tubes and electrical terminals. As it is not attacked by salt water, it is also used in shipbuilding and in fishing and marine equipment.

Brass does not produce sparks from mechanical impact, an unusual property for alloys. This characteristic makes brass an important material in the manufacture of containers for handling flammable compounds , metal cleaning brushes and lightning rods.

Bronze (Cu-Sn)

The alloys in whose composition copper and Tin (Sn) predominate are known by the name of bronze and have been known since ancient times. There are many types of bronzes that also contain other elements such as Aluminum , Beryllium , Chromium or Silicon . The percentage of Tin in these alloys is between 2 and 22%. They are yellowish in color and bronze castings are of better quality than brass castings, but they are more difficult to machine and more expensive.

The metallurgical technology of the manufacture of bronze is one of the most important milestones in the history of mankind as it gave rise to the so-called Bronze Age. Bronze was the first alloy made voluntarily by man: it was made by mixing copper ore ( Chalcopyrite , Malachite , etc.) and tin ore ([[Cassiterite) in a furnace fired with charcoal. The carbon dioxide resulting from the combustion of coal, reduced copper and tin ores to metals. The copper and tin that were melted were alloyed between 5 and 10% by weight of tin.

Bronze is used especially in heat conducting alloys, in electric batteries and in the manufacture of valves , pipes and plumbing unions . Some bronze alloys are used in sliding joints, such as bearings and bearings, friction discs; and other applications where high resistance to corrosion is required, such as turbine impellers or pump valves, among other machine elements. In some electrical applications it is used in Springs .

Alpaca (Cu-Ni-Zn)

The alpacas or German Plates are copper alloys, Nickel (Ni) and zinc (Zn). in a proportion of 50-70% copper, 13-25% nickel, and 13-25% zinc. Their properties vary continuously depending on the proportion of these elements in their composition, going from maximum hardness to minimum conductivity, these alloys have the property of rejecting marine organisms (antifouling). If small amounts of Aluminum or Iron are added to these copper-nickel-zinc alloys, are alloys that are characterized by their resistance to marine corrosion, which is why they are widely used in shipbuilding, mainly in capacitors and pipes, as well as in the manufacture of coins and electrical resistances.

Alpaca alloys have good corrosion resistance and good mechanical qualities. Its application covers Telecommunications materials , instruments and accessories for plumbing and electricity, such as taps, clamps, springs, connectors.

It is also used in construction and hardware, for decorative elements and in the chemical and food industries, as well as tableware and goldsmith materials .

Monel is an alloy that is obtained directly from Canadian minerals, and has a composition of Cu = 28-30%, Ni = 66-67%, Fe = 3-3.5%. This material has great resistance to corrosive agents and high temperatures.

Platinoid is a white metal composed of 60% copper, 14% nickel, 24% zinc and 1-2% Tungsten .

Other alloys

Other copper alloys with technical applications are the following:

• Copper-cadmium (Cu-Cd): these are copper alloys with a small percentage of Cadmium and have a higher resistance than pure copper. They are used in overhead power lines subject to strong mechanical stresses such as Catenaries and contact cables for trams.
• Copper-chromium (Cu-Cr) and Copper-chromium-zirconium (Cu-Cr-Zr): have high electrical and thermal conductivity. They are used in resistance welding electrodes , bus bars, power contactors, [iron and steel equipment]] and conductive springs.
• Copper-iron-phosphorus (Cu-Fe-P): For the manufacture of elements that require good electrical conductivity and good thermal and mechanical properties, iron and phosphorus particles are added to copper . These alloys are used in integrated circuits because they have good electrical conductivity, good mechanical properties, and have high resistance to temperature.
• Copper- Aluminum(Cu-Al) : also known as aluminum bronzes and Duralumin , they contain at least 10% aluminum. These alloys are very similar to gold and highly valued for artistic work. They have good mechanical properties and high resistance to corrosion. They are also used for Landing gear of aircraft , in certain mechanical constructions.
• Copper- Beryllium(Cu-Be) : it is an alloy consisting essentially of copper. This alloy has important mechanical properties and great resistance to corrosion. It is used to make springs, plastic molds , resistance welding electrodes, and explosion-proof tools.
• Constantán (Cu55Ni45): it is an alloy made up of 55% copper and 45% nickel. It is characterized by having an electrical resistivity of 4.9 • 10-7 O m almost constant in a wide range of temperatures, with a temperature coefficient of 10-5 K-1. It is used in the manufacture of Thermocouples , Strain Gauges and Coins .
• Manganin (Cu86Mn12Ni2): is another alloy with a very low temperature coefficient and is used in strain gages and Resistors high stability. Furthermore, its thermoelectric potential in contact with copper by the Seebeck Effect is very small (+0.6 mV / 100 K). Its electrical resistivity is about 4.9 • 10-7 O • m and its temperature coefficient is 10-8 K-1 .

Some copper alloys have small percentages of Sulfur and Lead that improve the machinability of the alloy. Both lead and sulfur have very low solubility in copper, separating respectively as lead (Pb) and as cuprous sulfide (Cu2S) at the grain edges and facilitating chip breakage in machining processes, improving machinability of the alloy.

Industrial copper processes

Copper mining

Native copper usually accompanies its minerals in bags that rise to the surface being exploited in open-pit mines. Copper is obtained from sulfur minerals (80%) and oxidized minerals (20%), the former are treated by a process called Pyrometallurgy and the latter by another process called Hydrometallurgy .

Generally, oxidized minerals ( Cuprite , Melaconite ) are found in the upper layer , together with native copper in small quantities, which explains its millenary elaboration since the metal could be easily extracted in pit furnaces. Next, below the water table, are the primary Pyrites (sulfides) Calcosina (CuS2), Covellina (CuS) and Aikinite. Finally, the secondary Chalcopyrite (FeCuS2) whose exploitation is more profitable than the previous ones. Accompanying these minerals are others such as bornite (Cu5FeS4), gray coppers and carbonates Azurite and Malachite. that tend to form important masses in copper mines because they are the way in which sulfides are usually altered.

The technology for obtaining copper is very well developed although it is laborious due to the poverty of the mineral grade. Copper deposits generally contain very low concentrations of the metal. This is why many of the various stages of production are aimed at removing impurities.

Copper metallurgy

The metallurgy of copper depends on whether the mineral is in the form of sulfides or oxides.

For sulfides, the path called pyrometallurgy is used to produce cathodes, which consists of the following process: Mineral comminution -> Concentration (flotation) -> furnace smelting -> conversion to converters -> refining -> anode molding -> electrorefining -> cathode. The refining process produces cathodes with a 99.9% copper content. The cathodes are plates of one square meter and a weight of 55 kg.

Other components obtained from this process are iron (Fe) and sulfur (S), in addition to very small amounts of silver (Ag) and gold (Au). As impurities in the process, lead (Pb), arsenic (As) and mercury (Hg) are also extracted.

As a general rule, a copper metallurgical facility that produces 300,000 t / year of anodes, consumes 1,000,000 t / year of copper concentrate and as by-products produces 900,000 t / year of sulfuric acid and 300,000 t / year of slag.

When it comes to taking advantage of mineral waste, the small concentration of copper in them is found in the form of oxides and sulfides, and to recover this copper, the technology called hydrometallurgy is used, better known by its Anglo-Saxon nomenclature Sx-Ew.

The process that this technique follows is as follows: Copper ore-> leaching-> extraction-> electrolysis-> cathode

This technology is used very little because almost all copper concentrates are forming sulfides, with the estimated global production of waste recovery being around 15% of all copper produced.

Copper heat treatments

Copper and its alloys allow certain heat treatments for very specific purposes, the most common being annealing, refining and tempering.

Hard annealed copper performs very well for cold operations such as: bending, stamping and drawing. Annealing occurs by heating the copper or brass to a suitable temperature in a controlled atmosphere electric furnace, and then allowing it to cool in air. Care must be taken not to exceed the annealing temperature because then the copper burns and becomes brittle and is rendered useless.

The refining is a controlled oxidation followed by a reduction process which aims to volatilize or reduce slags all impurities contained in the copper in order to obtain high purity copper.

The heat treatments carried out on the brass are mainly Homogenization , Recrystallization and Stabilization anneals . Brass with more than 35% Zn can be tempered to make them softer.

Bronzes are commonly subjected to homogenization annealing treatments for casting alloys; and annealed against workmanship and recrystallization for forging alloys. The tempering of bronzes of two constituent elements is analogous to the tempering of steel: it heats up to about 600 ° C and cools rapidly. This reduces the hardness of the material, contrary to what happens when tempering steel and some bronzes with more than two components.

Applications and uses of copper

Whether considering the amount or value of the metal used, the industrial use of copper is very high. It is an important material in a multitude of economic activities and has been considered a strategic resource in conflict situations.

Metallic copper

Copper is used both with a high level of purity, close to 100%, and alloyed with other elements. Pure copper is used mainly in the manufacture of electrical cables.

Electricity and telecommunications

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Copper is the non-precious metal with the best electrical conductivity . This, together with its ductility and mechanical resistance , have made it the most widely used material to manufacture electrical cables, both for industrial and residential use. Copper conductors are also used in many electrical equipment such as generators, motors, and transformers. The main alternative to copper in these applications is aluminum.

Most telephone cables are also made of copper, which also allow access to the Internet . The main alternatives to copper for telecommunications are fiber optics and wireless systems . On the other hand, all computer and telecommunications equipment contains copper to a greater or lesser extent, for example in its integrated circuits, transformers and internal wiring.

Means of transport

Copper is used in various components of cars and trucks, mainly radiators (thanks to its high thermal conductivity and resistance to corrosion), brakes and bearings, as well as, naturally, cables and electric motors. A small car contains in total around 20 kg of copper, raising this figure to 45 kg for larger ones.

Trains also require large amounts of copper in their construction: 1 – 2 tons in traditional trains and up to 4 tons in high-speed trains. In addition, the catenaries contain about 10 tons of copper per kilometer on high-speed lines. Finally, ship hulls often include copper and nickel alloys to reduce fouling from marine life.

Construction and ornamentation

A large part of the water transport networks are made of copper or brass , due to its resistance to corrosion and its antibacterial properties, the lead pipes having been left in disuse due to its harmful effects on human health. Compared to plastic pipes, copper pipes have the advantage that they do not burn in the event of a fire and therefore do not release potentially toxic fumes and gases.

Copper and, above all, bronze are also used as architectural elements and coatings on roofs, facades, doors and windows. Copper is also often used for the doorknobs of public places, as its antibacterial properties prevent the spread of epidemics .

Two classical applications of bronze in construction and ornamentation are the making of statues and bells. The construction sector currently consumes ( 2008 ) 26% of world copper production.

Coins

Since the beginning of the minting of Coins in the Ancient Age, copper is used as their raw material, sometimes

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pure and, more often, in alloys such as bronze and cupronickel .

Examples of coins that include pure copper:

• The one, two and five cent euro coins are made of copper-coated steel. The US one cent coin is made of copper-coated zinc.

Examples of cupro-nickel coins:

• Inner disk of the one euro coin and outer part of the two euro coin. Coins of 25 and 50 cents of US dollar. Spanish coins of 5, 10, 25, 50 and 200 pesetas minted since 1949.

Examples of coins made of other copper alloys:

• The ten, twenty and fifty euro cent coins are made of Nordic gold, an alloy containing 89% copper. The Argentine coins of 1/2, 1, 5, 10 and 50 austral centavos are made of brass.

Other apps

The copper participates in the raw materials of a lot of different and varied components of all kinds of machinery, such as bushings , bearings , trims , etc. It is part of the elements of Costume Jewelery , Fluorescent Bulbs and Tubes , Boilermaking , Electromagnets , Wind Musical Instruments , Microwaves , Heating Systems and Air Conditioning . Copper, bronze and brass are suitable for galvanizing treatments to coat other metals.

Non-metallic copper

The copper sulfate (II) also known as cupric sulfate is the copper compound of greater industrial importance and is used as fertilizer and pesticide in agriculture, algaecide in water purification and as a wood preservative.

Copper sulfate is especially indicated to supply the main functions of copper in the plant, in the field of enzymes: Ascorbic Acid , Polyphenol , Cytochrome oxidases , etc. Also part of the Plastocyanin contained in chloroplasts and participating in the chain transfer electrons of Photosynthesis . Its absorption is carried out through a metabolically active process. It is practically not affected by the competition of other cations but, on the contrary, it affects the other cations. This product can be applied to all types of crops and in any climatic zone in greenhouses.

For the decoration of tiles and ceramics, glazes are made that provide a metallic shine of different colors. To decorate the piece once it has been fired and glazed, mixtures of copper oxides and other materials are applied and then the piece is fired again at a lower temperature. By mixing other materials with copper oxides, different shades can be obtained. For ceramic decorations , silver and copper metallic films are also used in colloidal mixtures of ceramic varnishes that provide tones similar to the metallic iridescence of gold or copper.

A pigment widely used in paint for green tones is verdigris, also known in this field as verdigris, which consists of a mixture formed mainly by copper acetates, which provides greenish or bluish tones.

Copper products

Foundry: blister and anodes

Anodic blister (blister) copper is a metallic material with a purity level of around 98 to 99.5%, used in turn as raw material to produce high-quality products, especially copper cathodes . If it is of good quality, it can be used occasionally in the production of copper sulfate and other derived chemical products. Its main application is its transformation into copper anodes. Copper anodes, already semi-refined, with close to 99.6% purity, are the raw material of the electrolytic refining process that allows their transformation into copper cathodes with 99.99% purity. A copper anode has dimensions of approximately 100×125 cm, a thickness of 5 cm and an approximate weight of 350 kg.

Refinery: cathodes

Copper cathode is the ideal raw material for the production of high specification copper wire rod. It is a product, with a content higher than 99.99% of copper, it is the result of the electrolytic refining of the copper anodes. Its quality is within the designation Cu-CATH-01 under the EN 1978: 1998 standard. It is presented in corrugated packages and strips, whose plate has dimensions of 980×930 mm and a thickness of 7mm with an approximate weight of 47 kg. Its main use is the production of high quality copper wire rod, although it is also used for the production of other highly demanding semi-transformed materials.

Smelter and refinery by-products

After the process of making copper anode and copper cathode, the following by-products are obtained: Sulfuric acid , Granulated slag . Electrolytic sludge , Nickel sulfate , Gypsum .

Wire rod

Copper wire rod is a product resulting from the transformation of cathode in continuous casting. Its production process is carried out according to the ASTM B49-92 and EN 1977 standards . The essential characteristics of the wire rod produced by the Atlantic-copper company are:

• Diameter and tolerance: 8mm +/- 0.4mm. Cu: 99.97% min. Oxygen: 200 ppm. Electrical conductivity:> 101% (IACS. Spiral elongation test:> 450 m (200 ° C). The wire rod is sold in coils strapped on wooden pallets and protected with a plastic sheath. Its dimensions are: Coil weight 5000 kg, external diameter 1785 mm, internal diameter 1150 mm and height 900 mm The applications of the wire rod are for the manufacture of electric cablesthat require high quality, whether they are enameled or multi-stranded with diameters of 0.15 / 0.20 mm.

Bare copper wire

Bare copper wire is produced from wire rod and through a roughing process and an annealing furnace. Bare wire formed by an electrolytic copper wire is obtainedin three tempers, hard, medium hard and soft and is used for electrical purposes it is produced in a range of diameters from 1 mm to 8 mm and in coils that can weigh in the order of 2250 kg. This wire is used in overhead electrical distribution lines, in substation neutrals, equipment and system grounding, and to manufacture flat, enameled and multi-stranded wires that can have a diameter of 0.25 / 0.22 mm. It is made from high purity copper with a minimum content of 99.9% Cu. This type of wire has high conductivity, ductility and mechanical resistance as well as great resistance to corrosion in brackish environments.

Drawing

Drawing is called the process of thinning copper through the mechanical stretching that is exerted on it when starting from 6 or 8 mm diameter wire rod with the aim of producing flexible electric cables with the required section. An electric cable is made up of several wires that, through an extrusion process, are applied the outer insulation with a plastic compound of PVC or Polyethylene . Generally, the entry gauge is 6 to 8 mm, to later thin it to the required diameter. As wire drawing is a continuous process, different Coils are formedor rolls that are being cut to the lengths required or established by the standards and are duly labeled with the corresponding technical data of the cable. Shielding is called the covering of a central conductor duly insulated by several copper conducting wires, which interlaced around them form a screen. When it is necessary to insulate a conductive wire by enamelling, a layer of varnish (polyesterimide) is applied to it. These resin mixtures are used to coat the metallic conductor, being isolated from the environment that surrounds it and thus managing to conduct the electrical flow without problems.

Tubes

Copper tube coil

A tube is a hollow product, whose section is normally round, having a periphery which is continuous and used in Gasfitería , Plumbing and Mechanical Systems for transporting liquids or gases . Copper tubes due to the characteristics of this metal with high resistance to corrosionand their resistance and adaptability mean that they are used massively in residences, buildings, condominiums, offices, commercial and industrial premises. For the manufacture of tubes, generally a mixture of refined copper and scrap of controlled quality is started, it is melted in a furnace and by means of copper casting, ingots known as “billets” are obtained, which have a cylindrical shape. , with dimensions that are generally 300 mm in diameter and 8 m long and weighing approximately 5 metric tons. These metal blocks are used to manufacture seamless tubes by means of a series of plastic deformations.

The stages are as follows:

• Cut: Billetsare cut into pieces of around 700mm long, taking into account the capacity of the plant’s production facilities.
• Heating: The billet is then heated in a tunnel oven at a temperature between 800 and 900 ° C. Here, the metal achieves a higher degree of plastic deformation capacity, thereby reducing the pressure required for subsequent transformation operations.
• Extrusion: In this operation, a large diameter piece or pre-pipe with very thick walls is obtained in a single pass. In practice the Extruderis a press in which the billet, previously heated, is forced to pass through a matrix The piston that exerts the pressure has a mandrel that pierces the billet. As this operation is carried out at a high temperature, the copper undergoes oxidation that impairs subsequent operations (which are carried out in controlled atmospheres with rapid cooling to prevent surface oxidation of the pre-pipe).
• Lamination: It is a “cold” operation that consists of passing the pre-tube through two cylinders that rotate in the opposite direction. In addition to the rotary movement, the two cylinders have a reciprocating movement in the longitudinal direction, while the pre-tube, to which a mandrel has been inserted, advances in a helical manner. With this, a reduction in the thickness of the tube wall is obtained, keeping the perfectly circular section. The cold rolling operation produces tubes of high hardness, also called hard hardening.
• Wire drawing: The successive reduction of diameters to obtain the various commercial products is carried out in a cold operation called wire drawing, which consists of stretching the tube forcing it to pass through a series of external dies and an internal gauge known as a floating mandrel. The industrial operation is carried out in a machine called “Bull Block” where the end of the tube is squeezed by a clamp mounted on a rotating cylinder that produces traction.
• Annealing: Cold plastic deformation causes a hardening of the metal that results in a loss of plasticity. Successive wire drawing increases this hardening and gives rise to a greater danger of tube breakage. For this reason, a heat treatment called annealing is used for a crystallization of the copper that allows to recover its plasticity characteristics.
• Finishing: At the end of the production cycle an annealed tube is obtained; presented in high quality rolls. These tubes can be coated with an external protective or insulatingcoating for various uses, or with a very smooth internal finish for special applications.
• Quality Control: The finished tube is subjected to tests to determine imperfections, the usual ones being electromagnetic induction by Eddy Currents, which allow the detection of cracks and other imperfections inside the tube wall.
• Packaging: Annealed copper tubes or soft tempered copper tubes are presented in rolls that are carefully packed to avoid deformation due to movements. Hard-tempered cold-rolled tubes are presented in strips, generally 6m long, which are packed in bundles for transport to places of use. As copper tubes do not experience aging due to the action of ultraviolet rays, Ozone or other chemical and physical agents, they do not require special storage and packaging characteristics. After a long period, a slight surface oxidation may form, but this does not present major disadvantages for later use.

Lamination

One of the fundamental properties of copper is its malleability, which makes it possible to produce all types of sheets from very small thicknesses, both in continuous roll form and in plates of various dimensions, using the appropriate lamination facilities.

Casting of parts

Pure copper is not very suitable for casting because it produces galleo. Galleo is produced when oxygen from the air is absorbed by the metal at high temperatures forming bubbles and, as it cools, the air is released from the bubbles creating a large number of tiny holes in the surface of the castings. manufacture parts by any of the part casting processes that exist depending on the type of part and the quantity that has to be produced.

The most common casting methods are casting and spinning. It is called casting by molding the process of manufacturing parts, commonly metallic but also plastic, consisting of melting a material and introducing it into a cavity, called a mold, where it solidifies. The traditional process is casting in sand, as this is a very abundant refractory material in nature and that, mixed with Clay, acquires cohesion and moldability without losing the permeability that makes it possible to evacuate the gases from the mold while pouring the molten metal. The centrifugal casting process consists of depositing a layer of liquid cast iron in a revolution mold rotating at high speed and rapidly solidifying the metal by means of continuous cooling of the mold or shell . The applications of this type of foundry are very varied.

Wrought

The hot forging of a piece consists of shaping a metal plug previously brought to a suitable temperature and plastically deformed between two dies in which the mold of the desired piece has been made in intaglio by means of the power provided by a machine called press. Forging is done hot with the intention of minimizing the mechanical power required to produce the plastic deformation required to obtain the desired shape. The starting metal is, originally, a round section bar or other profile, cut so that it has the exact volume of the part in the case of the closed die, or adding a surplus to it to create a burr in the case of the open die . Copper products and their alloys meet very good conditions to produce parts by hot stamping processes, allowing the design of extremely complex pieces thanks to the great ductility of the material and the low resistance to deformation it opposes, thus providing a long life to the dies. A copper alloy is “hot forgeable” if there is a wide enough temperature range in which the ductility and resistance to deformation are acceptable. This range of temperatures depends on its chemical composition, which is influenced by added elements and impurities. A copper alloy is “hot forgeable” if there is a wide enough temperature range in which the ductility and resistance to deformation are acceptable. This range of temperatures depends on its chemical composition, which is influenced by added elements and impurities. A copper alloy is “hot forgeable” if there is a wide enough temperature range in which the ductility and resistance to deformation are acceptable. This range of temperatures depends on its chemical composition, which is influenced by added elements and impurities.

Machining

The pieces of copper or its alloys that are going to undergo machining work by chip removal have in their chemical composition a small contribution of Lead and Sulfurwhich causes a better fracture of the cut chip. Currently the machining of copper components, is carried out under the concept of fast dry machining with the tool cooled by air if necessary. This type of fast machining is characterized by the fact that the machine heads rotate at very high speeds, achieving high cutting speeds in small diameter tools. Likewise, the tools used are usually integral hard metal, with special coatings that make it possible to work with very high cutting feeds. The coatings and materials of these tools are very resistant to wear, they can work at high temperatures, hence their refrigeration is not necessary many times, they have a coefficient of friction very low and achieve very fine and precise surface finishes

Welding

Two different types of solder are used to solder copper or copper alloy joints: soft soldering and brazing.

Soft soldering is one that is carried out at a temperature of about 200 ° C and is used to join the components of printed and electronic circuits , tin soldering irons are used and the filler material is an alloy of tin and lead in the form of coiled wire that has deoxidizing resin in its soul. It is a not very resistant solder and it serves to ensure the continuity of the electric current through the circuit. Gas and Water Pipe Weldsmade by plumbers are of various types depending on the materials to be joined and the tightness to be achieved from welding. Currently, most water installations are made with copper pipes, although flexible pipes and plastic pipes are also used for certain connections.

The welding of copper pipes is done with gas torches that provide the flame to melt the brazing material. There are torches fired with Butane or Propane gas .

Plumbing brazing uses copper or silver as a binder . It is used for complex heating pipes and gas pipes .

Boilermaking

Boilermaking is a professional specialty of the metal manufacturing branch whose main function is the construction of tanks suitable for the storage and transport of solids in the form of grains or aggregates, liquids and gas, as well as all types of shipbuilding and metal structures. . Thanks to the excellent thermal conductivity that copper plate has, it is used to make alembics , boilers , coils , covers , etc.

Stuffing

Drawing is called the cold-forming process by which a disc or cut pieces are transformed, depending on the material, into hollow pieces, and even starting from previously drawn pieces, stretch them to a smaller section with greater height.

The objective is to achieve a hollow part according to the shape defined by the drawing die used, through the pressure exerted by the press. The drawing die is also known as Mold . It is a process of forming sheet metal by plastic deformation in the course of which the sheet undergoes simultaneously stretching and upsetting transformations, producing variations in its thickness. Hydraulic presses are used almost exclusively for drawing .

Copper sheet and its alloys have very good properties to be cold formed. Deep drawing is a good process for manufacturing thin sheet metal parts with complex surfaces and high dimensional demands, successfully replacing parts traditionally manufactured by casting and machining.

Stamping

It is known by the name of stamping to the mechanical operation that is carried out to engrave a Drawing or a legend on the flat surface of a piece that is generally made of sheet metal. Copper sheets and their alloys meet very good conditions for making all kinds of engravings on them.

The key elements of the stamping is a press that can be mechanical, pneumatic or hydraulic; of very varied size, shape and power, and a matrix called stamp or die , where the drawing to be struck on the sheet is engraved, and when a sharp blow is made on it, it remains engraved.

Metal stamping is done by pressure or impact, where the sheet adapts to the shape of the mold. Stamping is one of the easiest machining tasks that exist, and allows a great level of automation of the process when it comes to making large quantities of parts.

The stamping can be done cold or hot, the stamping of hot parts is called forging, and it has a different operation than the cold stamping that is generally done on sheets. Steel, aluminum, silver, brass and gold sheets are best suited for stamping. One of the best known stamping tasks is the one that performs the stamping of the faces of the Coins in the minting process of the same.

Die cutting

It is called Die cuttingto the mechanical operation that is performed to produce sheet metal parts or where it is necessary to make various holes in them. To accomplish this task, they use from simple manual override mechanisms to sophisticated high-powered mechanical presses. The basic elements of a die-cutting press are the die that has the shape and exterior dimensions of the part or the holes to be made, and the cutting die through which the die is inserted when it is energetically driven by power. provided by the press by means of an eccentric drive that it has and that provides a dry and forceful blow on the sheet, producing a clean cut of it. Depending on the work to be done, this is how the presses are designed and built.

When the cut deteriorates due to wear of the die and the die, they are dismounted from the machine and are rectified in a flat grinding machine establishing a new cut. A die and a die allow many regrinds until they are completely worn out.

There are stamping machines that work with a head where several dies of different sizes can be inserted, and a wide table where the sheet to be machined is placed. This table is activated by CNC and moves the length and width of it at high speed, producing the pieces with speed and accuracy.

Recycling

Copper is one of the few materials that does not degrade or lose its chemical or physical properties in the recycling process. It can be recycled an unlimited number of times without losing its properties, making it impossible to distinguish whether a copper object is made from primary or recycled sources. This means that copper has been, since ancient times, one of the most recycled materials.

Recycling provides a critical part of the total metallic copper needs. It is estimated that in 2004 9% of world demand was met by recycling old copper objects. If the recasting of the wastes from the mineral refining process is also considered “recycling”, the percentage of recycled copper amounts to 34% in the world and up to 41% in the European Union.

The recycling of copper does not require as much energy as its mining extraction . Although recycling requires collecting, sorting and melting metal objects, the amount of energy required to recycle copper is only about 25% of that required to convert copper ore into metal. The efficiency of the recycling system depends on technological factors such as the design of economic products such as the price of copper and social factors such as the awareness of the population about sustainable development. Another key factor is legislation. Currently there are more than 140 national and international laws, regulations, directives and guides that try to favor the responsible management of the end of the life cycle of products that contain copper, such as for exampleAppliances , Telephones and Vehicles. In the European Union, directive 2002/96 / CE on waste electrical and electronic equipment ( WEEE , or WEEE from English Waste Electrical and Electronic Equipment) promotes a waste minimization policy, which includes a mandatory and drastic reduction of waste industrial and residential, and incentives for producers who produce less waste. The objective of this initiative was to recycle 4 kilos per inhabitant per year by the end of 2006 .

An example of the massive recycling of copper was the replacement of the national currencies of twelve European countries by the euro in 2002 , the largest currency exchange in history. Some 260,000 tons of coins were removed from circulation, containing approximately 147,496 tons of copper, which were melted down and recycled for use in a wide range of products, from new coins to different industrial products.

Production and trade

Mining production

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Evolution of world copper production. World copper production during 2009 reached a total of 15.87 million metric tons of fine copper. The main producing country is Chile , with more than a third of the total, followed by Peru and the United States .

Of the ten largest copper mines in the world, five are in Chile ( Escondida , Codelco Norte , Collahuasi , El Teniente and Los Pelambres ), two in Indonesia , one in the United States , one in Russia and another in Peru ( Antamina ) .

Bookings

According to information provided in the annual report of the United States Geological Survey ( USGS ), estimates indicate that known copper reserves in 2009 worldwide would reach 540 million metric tons of fine copper. And according to USGS estimates, Chile would have around 160 million economically exploitable tons, equivalent to 30% of the total world mineral reserves; followed by Peru with 63 million economically exploitable tons, equivalent to 12% of the total world mineral reserves.

Trade and consumption

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Copper is the third most used metal in the world, behind Steel and Aluminum . There is an important world trade in copper that moves about 30,000 million dollars annually.

The three main copper markets are LME of London , the COMEX in New York and Metal Exchange Shanghai . These markets set the price of copper and futures contracts on the metal on a daily basis. The price of is usually expressed in dollars / pound and in the last decade has fluctuated between the 0.65 $ / lb of the end of 2001 and the more than 4.00 $ / lb reached in 2006 and 2008 . The sharp rise in copper prices since 2004 , mainly due to increased demand from China and other emerging economies, has caused a wave of theft of copper objects (especially cables) around the world, with consequent risks to the electrical infrastructure.

The main producers of copper ore are also the main exporters of both ore and refined copper. The main importers are the industrialized countries: Japan , China , India , South Korea and Germany for ore and the United States , Germany , China , Italy and Taiwan for refining.