Properties and application of copper. Metallic copper: element description, properties and applications

In the periodic system of elements of D.I. Mendeleev, copper is located in group I of the 4th period, its serial number is 29. The atomic mass is 63.54. As an element of the first group, copper is monovalent. In this state, it is widely represented in ore minerals, mattes, slags, and other products of pyrometallurgy. In the products of their oxidation in nature and in technological processes, the divalent state is more stable.

The melting point of copper is 1083 0 C. The boiling point is 2325 0 C.

Copper is a soft, ductile and malleable red metal that can be easily machined. Easily rolled into thin sheets and drawn into wire.

The most important property is electrical conductivity (second only to silver). Impurities reduce electrical conductivity, so high-purity copper is used in electrical engineering.

Copper also has a high thermal conductivity.

In chemical terms, copper is inactive, although it can directly combine with oxygen, sulfur, halogens and some other elements.

At ordinary temperatures and dry air, copper remains inert, but in humid air containing CO 2, copper oxidizes and becomes covered with a protective film of basic carbonate СuCO 3 ·Cu (OH) 2, which is a toxic substance.

In solutions of hydrochloric and sulfuric acids in the absence of an oxidizing agent, copper does not dissolve. In acids that are simultaneously oxidizing agents (nitric or hot concentrated sulfuric), copper dissolves easily.

At high temperatures in pyrometallurgical processes, stable copper compounds are Cu 2 O and Cu 2 S.

Copper and its sulfide Cu 2 S are good collectors (solvents) of gold and silver, which makes possible their high recovery in copper production.

An important property of copper is to form alloys with other metals. These are bronze (Cu + Sn), brass (Cu + Zn) copper-nickel alloys.

In modern bronzes, aluminum, silicon, beryllium, and lead are used as additives. These bronzes are used for the manufacture of critical parts and cast products.

For example, beryllium bronzes (2% Be) are superior in mechanical properties to many grades of steel and have good electrical conductivity. Aluminum bronzes (5-10% Al) are very durable and are used in the manufacture of aircraft engines.

In special brass, in addition to zinc, aluminum, iron, silicon, nickel are added. Brass is used for the manufacture of radiators, pipes, flexible hoses, cartridge cases, art products.

Of the copper-nickel alloys, the best known are cupronickel (used in shipbuilding, as it is resistant to sea water) and nickel silver - resistant to solutions of salts and organic acids (medical instruments are made).

About 50% of all copper is used by the electrical industry. Also, copper is used in mechanical engineering, rocket technology, in the production of building materials, in transport, the chemical industry, agriculture.

1.3 Raw materials for copper production

Copper clarke, i.e. its content in the earth's crust is 0.01%. However, it forms numerous deposits. Characteristic for copper is the presence in nature of all 4 types of ores. However, the main copper raw materials are sulfide ores. 85-90% of all primary copper is currently smelted from sulfide ores.

In Russia, copper ores are mined in the Urals - Kirovgrad, Krasnouralsk, Mednogorsk, Guy, etc., in the Arctic - on the Kola Peninsula and Taimyr.

The sources of obtaining copper are ores, products of their enrichment - concentrates - and secondary raw materials. The share of secondary raw materials currently accounts for about 40% of the total output of copper.

Copper ores are almost completely classified as polymetallic. There are no monometallic ores of copper in nature. About 30 elements are valuable companions of copper in ore raw materials. The most important of them: zinc, lead, nickel, cobalt, gold, silver, platinum group metals, sulfur, selenium, tellurium, cadmium, germanium, rhenium, indium, thallium, molybdenum, iron.

More than 250 copper minerals are known. Most of them are rare. The greatest industrial importance is a small group of minerals, the composition of which is given in Table 2.

Table 2 - Industrial copper minerals

Most of the copper ores are currently mined in an open pit. In Russia, underground mining accounts for about 30%.

In modern practice, ores are usually developed with a content of 0.8-1.5% copper, sometimes higher. But for large deposits of disseminated ores, the minimum copper content suitable for development is 0.4-0.5%. If the rock contains less than the specified amount of copper, its processing is unprofitable.

The value of copper ores increases significantly due to the presence of noble metals and a number of rare metals - selenium, tellurium, rhenium, bismuth, etc.

Due to the low content of copper in the ore and the complex nature of the ores, the raw material is preliminarily subjected to flotation enrichment. When enriching copper ores, the main product is copper concentrates containing up to 55% Cu (usually 10-30%). Pyrite concentrates and concentrates of other non-ferrous metals, such as zinc, are also obtained. Flotation concentrates are fine powders with a particle size of 74 microns and a moisture content of 8-10%.

Copper ores and concentrates have the same mineralogical composition and differ only in the quantitative ratios between various minerals. The physical and chemical bases of their metallurgical processing are exactly the same.

COPPER and COPPER ROLL

Grades and chemical composition of technical copper

Copper grades and their chemical composition are defined in GOST 859-2001. abbreviated information on copper grades is given below (the minimum content of copper and the maximum content of only two impurities - oxygen and phosphorus are indicated):

The first group of grades refers to cathode copper, the rest reflect the chemical composition of various copper semi-finished products (copper ingots, wire rod and products from it, rolled products).

Specific Features copper, inherent in different grades, are determined by the absence of copper (differences are no more than 0.5%), but by the content of specific impurities (their amount can vary by 10 - 50 times). The classification of copper grades by oxygen content is often used:

Oxygen-free copper (M00 , M0 and M1 ) with oxygen content up to 0.001%.

Refined copper (M1f, M1r, M2r, M3r) with oxygen content up to 0.01%, but with

high phosphorus content.

High purity copper (M00, M0, M1) with an oxygen content of 0.03-0.05%.

General purpose copper (M2, M3) with oxygen content up to 0.08%.

Approximate the correspondence of copper grades produced according to different standards is given below:

Different grades of copper have different applications, and differences in the conditions of their production determine significant price differences.

For the production of cable and wire products, cathodes are remelted according to a technology that excludes the saturation of copper with oxygen during the manufacture of products. Therefore, copper in such products corresponds to the grades M00, M0 , M1 .

The requirements of most technical tasks are satisfied by the relatively cheap brands M2 and M3. This determines the mass production of the main types of rolled copper from M2 and M3.

Rolled products from the M1, M1f, M1r, M2r, M3r brands are produced mainly for specific consumers and are much more expensive.

Physical properties of copper

The main property of copper, which determines its predominant use, is a very high electrical conductivity (or low electrical resistivity). Impurities such as phosphorus, iron, arsenic, antimony, tin significantly worsen its electrical conductivity. The value of electrical conductivity is significantly affected by the method of obtaining a semi-finished product and its mechanical state. This is illustrated in the table below:

Differences in the resistance of wire rod grades M00, M0 and M1 are due to different amounts of impurities and amount to about 1%. At the same time, differences in resistance due to different mechanical conditions reach 2–3%. The resistivity of products made of copper grade M2 ​​is approximately 0.020 μOhm * m.

The second most important property of copper is its very high thermal conductivity.

Impurities and alloying additives reduce the electrical and thermal conductivity of copper, so copper-based alloys are significantly inferior to copper in these indicators. The values ​​of the parameters of the main physical properties of copper in comparison with other metals are given in the table (the data are given in two different systems of units):

In terms of electrical and thermal conductivity, copper is slightlysecond only to silver.

The influence of impurities and features of the properties of copper of various grades

Differences in the properties of copper of different grades are associated with the influence of impurities on the basic properties of copper. The influence of impurities on the physical properties (thermal and electrical conductivity) was discussed above. Let's consider their influence on other groups of properties.

Effect on mechanical properties .

Iron, oxygen, bismuth, lead, antimony impair plasticity. Impurities poorly soluble in copper (lead, bismuth, oxygen, sulfur) lead to brittleness at high temperatures.

The recrystallization temperature of copper for different grades is 150-240 o C. The more impurities, the higher this temperature.A significant increase in the recrystallization temperature of copper gives silver, zirconium. For example, the introduction of 0.05% Ag increasesrecrystallization temperature twice, which manifests itself in an increase in the softening temperature and a decrease in creep at high temperatures, and without loss of thermal and electrical conductivity.

Impact on technological properties .

Technological properties include 1) the ability to process by pressure at low and high temperatures, 2) solderability and weldability of products.

Impurities, especially fusible, form brittle zones at high temperatures, which makes hot working difficult. However, the level of impurities in grades M1 and M2 provide the necessary technological plasticity.

During cold deformation, the influence of impurities is noticeably manifested in the production of wire. For the same tensile strength (? V = 16 kgf/mm 2) wire rods from M00, M0 and M1 grades have different relative elongation? (38%, 35% and 30% respectively). Therefore, class A wire rod (it corresponds to grade M00) is more technologically advanced in the production of wire, especially of small diameters. The use of oxygen-free copper for the production of current conductors is due not so much to the magnitude of the electrical conductivity as to the technological factor.

The processes of welding and soldering are significantly hampered by an increase in the content of oxygen, as well as lead and bismuth.

Influence of oxygen and hydrogen on operational properties .

At normal conditions The operational properties of copper (primarily the durability of operation) are almost the same for different grades. At the same time, at high temperatures, the harmful effect of oxygen contained in copper can appear. This possibility is usually realized when copper is heated in a medium containing hydrogen.

Oxygen is initially contained in copper grades M0, M1, M2, M3. In addition, if oxygen-free copper is annealed in air at high temperatures, then due to oxygen diffusion, the surface layer of the product will become oxygen-containing. Oxygen in copper is present in the form of cuprous oxide, which is localized along the grain boundaries.

In addition to oxygen, copper may contain hydrogen. Hydrogen enters copper during electrolysis or during annealing in an atmosphere containing water vapor. Water vapor is always present in the air. At high temperature, it decomposes to form hydrogen, which readily diffuses into copper.

In oxygen-free copper, hydrogen atoms are located in the interstices of the crystal lattice and do not particularly affect the properties of the metal.

In oxygen-containing copper at high temperatures, hydrogen interacts with cuprous oxide. In this case, high-pressure water vapor is formed in the thickness of the copper, which leads to swelling, ruptures and cracks. This phenomenon is known as "hydrogen sickness" or "hydrogen embrittlement". It manifests itself during the operation of a copper product at temperatures above200 o C in an atmosphere containing hydrogen or water vapor.

The degree of embrittlement is the stronger, the greater the oxygen content in copper and the higher the operating temperature. At 200 o Cservice life is 1.5 years, at 400 ° C- 70 hours.

It is especially pronounced in products of small thickness (tubes, tapes).

When heated in vacuum, the hydrogen initially contained in copper interacts with cuprous oxide and also leads to embrittlement of the product and deterioration of the vacuum. Therefore, products that are operated at high temperatures are made from oxygen-free (refined) copper grades M1r, M2r, M3r.

Mechanical properties of rolled copper

Most of the copper rolled products available for free sale are produced from the M2 grade. Rolled steel from the M1 brand is produced mainly on order, in addition, it is about 20% more expensive.

Cold rolled steel- these are drawn (rods, wire, pipes) and cold-rolled (sheets, tape, foil) products. It is available in hard, semi-hard and soft (annealed) states. Such rental is marked with the letter "D", and the state of delivery with the letters T, P or M.

Hot rolled steel- the result of pressing (rods, pipes) or hot rolling (sheets, plates) at temperatures above the recrystallization temperature. Such rental is marked with the letter "G". In terms of mechanical properties, hot-rolled steel is close (but not identical) to cold-rolled steel in a soft state.

High compressive strength (55 - 65 kgf / mm 2) in combination with high ductility determines the widespread use of copper as gaskets in the seals of fixed joints with operating temperatures up to 250 ° C (pressure 35Kgs \ cm 2 for steam and 100 Kgs \ cm 2 for water).

Copper is widely used in the technology of low temperatures, up to helium. At low temperatures, it retains the strength, ductility and toughness characteristic of room temperature. The most commonly used property of copper in cryogenic engineering is its high thermal conductivity. At cryogenic temperatures, the thermal conductivity of grades M1 and M2 becomes significant, therefore, in cryogenic technology, the use of grade M1 becomes fundamental.

Copper bars are produced pressed (20 - 180 mm) and cold-formed, in solid, semi-solid and soft states (diameter 3 - 50 mm) according to GOST 1535-2006.

flat copper general purpose is produced in the form of foil, tape, sheets and plates in accordance with GOST 1173-2006:

Copper foil - cold rolled: 0.05 - 0.1 mm (only available in solid state)

Copper strips - cold rolled: 0.1 - 6 mm.

Copper sheets - cold rolled: 0.2 - 12 mm

Hot rolled: 3 - 25 mm (mechanical properties are regulated up to 12 mm)

Copper plates - hot rolled: over 25 mm (mechanical properties are not regulated)

Hot-rolled and soft cold-rolled copper sheets and strips pass the bending test around a mandrel with a diameter equal to the thickness of the sheet. With a thickness of up to 5 mm, they withstand bending until the sides touch, and with a thickness of 6 - 12 mm - until the sides are parallel. Cold rolled semi-rigid sheets and strips withstand a 90 degree bend test.

Thus, the permissible bending radius of copper sheets and tapes is equal to the thickness of the sheet (tape).

Copper pipes general purpose are made cold-formed (in soft, semi-solid and solid states) and pressed (large sections) in accordance with GOST 617-2006.

Copper pipes are used not only for process fluids, but also for drinking water. Copper is inert to chlorine and ozone, which are used to purify water, inhibits the growth of bacteria, and when water freezes, copper pipes deform without breaking. Copper pipes for water are produced in accordance with GOST R 52318-2005, the content of organic substances on the inner surface is limited for them. The minimum bending radii and allowable pressures for soft copper pipes are given below:

Corrosion properties of copper .

At normal temperatures copper stable in the following environments:

dry air

Fresh water (ammonia, hydrogen sulfide, chlorides, acids accelerate corrosion)

In sea water at low water velocities

In non-oxidizing acids and salt solutions (in the absence of oxygen)

Alkaline solutions (except ammonia and ammonium salts)

Dry halogen gases

Organic acids, alcohols, phenolic resins

Copper unstable in the following environments:

Ammonia, ammonium chloride

Oxidizing mineral acids and acid salt solutions

The corrosive properties of copper in some environments noticeably worsen with an increase in the amount of impurities.

contact corrosion.

Contact of copper with copper alloys, lead, tin in a humid atmosphere, fresh and sea water is allowed. At the same time, contact with aluminum and zinc is not allowed due to their rapid destruction.

The high thermal and electrical conductivity of copper makes its electric welding (spot and roller) difficult. This is especially true for massive products. Thin parts can be welded with tungsten electrodes. Parts with a thickness of more than 2 mm can be welded with a neutral oxy-acetylene flame. A reliable way to connect copper products is soldering with soft and hard solders. For details on copper welding, see www.weldingsite.com.ua

Technical copper has low strength and wear resistance, poor casting and anti-friction properties. Copper-based alloys are deprived of these shortcomings -brass And bronze . True, these improvements are achieved due to the deterioration of thermal and electrical conductivity.

There are special cases when it is necessary to maintain the high electrical or thermal conductivity of copper, but to give it heat resistance or wear resistance.

When copper is heated above the recrystallization temperature, a sharp decrease in the yield strength and hardness occurs. This makes it difficult to use copper in resistance welding electrodes. Therefore, for this purpose, special copper alloys with chromium, zirconium, nickel, cadmium (BrKh, BrKhTsr, BrKN, BrKd) are used. Electrode alloys retain relatively high hardness and satisfactory electrical and thermal conductivity at temperatures of the welding process (about 600C).

Heat resistance is also achieved by alloying with silver. Such alloys (MA) have lower creep at a constant electrical and thermal conductivity.

For use in moving contacts (collector plates, contact wire), copper with a low level of alloying with magnesium or cadmium BrKd, BrMg is used. They have increased wear resistance with high electrical conductivity.

For crystallizers, copper with additions of iron or tin is used. Such alloys have high thermal conductivity with increased wear resistance.

Low-alloy copper grades are essentially bronzes, but they are often referred to the group of rolled copper with the appropriate marking (MS, MK, MF).

Approximately the III millennium BC is considered a transition from stone as the main industrial substance to bronze. The period of perestroika is considered to be the copper age. After all, it was this connection that at that time was the most important in construction, in the manufacture of household items, utensils and other processes.

To date, copper has not lost its relevance and is still considered a very important metal, often used in various needs. Is copper a body or a substance? What properties does it have and what is it for? Let's try to figure it out further.

General characteristics of the copper element

Physical properties

Is copper a substance or a body? You can be completely convinced of the correctness of the answer only by considering its physical properties. If we talk about a given element as a simple substance, then it is characterized by the following set of properties.

1. Red metal.
2. Soft and very malleable.
3. Excellent thermal and electrical conductor.
4. Not refractory, melting point is 1084.5 0 C.
5. The density is 8.9 g/cm 3 .
6. In nature, it is found mainly in native form.

Thus, it turns out that copper is a substance, moreover, known from antiquity. Since ancient times, many architectural structures have been created on the basis of it, dishes and household items have been made.

Chemical properties

From the point of view of chemical activity, copper is a body or substance that has a low ability to interact. There are two main oxidation states of this element that it exhibits in compounds. This:

It is very rare to find substances in which these values ​​are replaced by +3.

So, copper can interact with:

• air;
• carbon dioxide;
• hydrochloric acid and some other compounds only at very high temperatures.

All this is explained by the fact that a protective oxide film is formed on the metal surface. It is she who protects it from further oxidation and gives stability and low activity.

Of the simple substances, copper is able to interact with:

• halogens;
• selenium;
• cyanides;
• gray.

Often forms complex compounds or Almost all complex compounds of this element, except for oxides, are toxic substances. Those molecules that monovalent copper forms are easily oxidized to divalent representatives.

Areas of use

Copper is a mixture or which, in any of these states, is widely used in industry and everyday life. It is possible to identify several main industries for the use of copper and pure metal compounds.

1. in which some salts are used.
2. Production of fur and silk.
3. Manufacture of fertilizers, plant protection products against pests
4. Copper alloys are widely used in the automotive industry.
5. Shipbuilding, aircraft construction.
6. Electrical engineering in which copper is used due to its good corrosion resistance and high electrical and thermal conductivity.
7. Various instrumentation.
8. Manufacture of dishes and household items of economic importance.

Obviously, despite the long hundreds of years, the metal in question only strengthened its position and proved its viability and indispensability in application.

Copper alloys and their properties

There are many alloys based on copper. She herself is distinguished by high technical specifications, as it can be easily forged and rolled, it is light and strong enough. However, when certain components are added, the properties are significantly improved.

In this case, the question should be asked: "Is copper a substance or a physical body when it comes to its alloys?" The answer will be: it is a substance. All the same, it is just that until some physical body, that is, a certain product, is made from the alloy.

What are copper alloys?

1. An almost equal combination of copper and zinc in one composition is commonly called brass. This alloy is characterized by high strength and chemical resistance.
2. Tin bronze is a combination of copper and tin.
3. Cupronickel - nickel and copper in a ratio of 20/80 out of 100. Used to make jewelry.
4. Constantan is a combination of nickel, copper and manganese additive.

biological significance

It is not so important whether copper is a substance or a body. Significantly different. What role does copper play in the life of living organisms? It turns out to be very important. Thus, the ions of the metal under consideration perform the following functions.

1. They are involved in the conversion of iron ions to hemoglobin.
2. They are active participants in the processes of growth and reproduction.
3. They allow the absorption of the amino acid tyrosine, therefore, they affect the manifestation of hair and skin color.

If the body does not receive this element in the right amount, then unpleasant diseases can occur. For example, anemia, baldness, painful thinness, and so on.

History of copper

Copper is called one of the first metals that man mastered in antiquity and uses it to this day. Copper mining was affordable because the ore needed to be smelted at a relatively low temperature. The first ore from which copper was mined was malachite ore (calorizator). The Stone Age in the history of mankind has changed precisely copper, when household items, tools and weapons made of copper were most widely used.

Copper is an element of the XI group of the IV period of the periodic system of chemical elements of D.I. Mendeleev, has an atomic number of 29 and an atomic mass of 63.546. The accepted designation is Cu(from the Latin Cuprum).

Being in nature

Copper is quite widely represented in the earth's crust, in sedimentary rocks, in the waters of marine and fresh water bodies, and in shales. It is distributed both in the form of compounds, and in an independent version.

Physical and chemical properties

Copper is a ductile, so-called transition metal, has a golden-pink color. Upon contact with air, an oxide film forms on the copper surface, giving the metal a yellowish-red hue. The main alloys of copper are known - with zinc (brass), with tin (bronze), with nickel (cupronickel).

Daily requirement for copper

The need for copper in an adult is 2 mg per day (about 0.035 mg / 1 kg of body weight).

Copper is one of the most important trace elements for the body, so foods rich in copper should be in everyone's diet. This:

• nuts, cereals,
• fish,
• cereals (especially and),
• dairy products
• , berries and

Signs of Copper Deficiency

Signs of an insufficient amount of copper in the body are: anemia and worsening of breathing, loss of appetite, indigestion, nervousness, depressive states, fatigue, skin and hair pigmentation disorders, brittleness and hair loss, skin rashes, frequent infections. Possible internal bleeding.

Signs of excess copper

An excess of copper is characterized by insomnia, impaired brain activity, epilepsy, problems with the menstrual cycle.

Interactions with others

It is assumed that copper and compete with each other in the process of assimilation in the digestive tract, so an excess of one of these elements in food can cause a deficiency of another element.

Copper is of great importance in the national economy, its main application is electrical engineering, but the metal is widely used for minting coins, often in works of art. Copper is also used in medicine, architecture and construction.

Useful properties of copper and its effect on the body

Required to convert the body into hemoglobin. Enables the use of the amino acid tyrosine, allowing it to act as a factor in hair and skin pigmentation. After absorption of copper by the intestines, it is transported to the liver with the help of albumin. Copper is also involved in the processes of growth and reproduction. It takes part in the formation of collagen and elastin and the synthesis of endorphins - hormones of "happiness".

Copper

Copper(lat. Cuprum) - a chemical element of group I of the periodic system of Mendeleev (atomic number 29, atomic mass 63.546). In compounds, copper usually exhibits oxidation states +1 and +2, and a few compounds of trivalent copper are also known. The most important copper compounds: oxides Cu 2 O, CuO, Cu 2 O 3; hydroxide Cu (OH) 2, nitrate Cu (NO 3) 2. 3H 2 O, sulfide CuS, sulfate (copper sulfate) CuSO 4. 5H 2 O, CuCO 3 Cu(OH) 2 carbonate, CuCl 2 chloride. 2H2O.

Copper- one of the seven metals known from ancient times. The transitional period from the Stone Age to the Bronze Age (4th - 3rd millennium BC) was called copper age or chalcolithic(from the Greek chalkos - copper and lithos - stone) or Chalcolithic(from Latin aeneus - copper and Greek lithos - stone). During this period, copper tools appear. It is known that copper tools were used in the construction of the pyramid of Cheops.

Pure copper is a malleable and soft metal of reddish color, in a pink fracture, in places with brown and variegated tint, heavy (density 8.93 g / cm 3), an excellent conductor of heat and electricity, second only to silver in this respect (melting point 1083 ° C). Copper is easily drawn into a wire and rolled into thin sheets, but is relatively little active. In dry air and oxygen under normal conditions, copper does not oxidize. But it reacts quite easily: already at room temperature with halogens, for example, with wet chlorine, it forms CuCl 2 chloride, when heated with sulfur, it forms Cu 2 S sulfide, with selenium. But copper does not interact with hydrogen, carbon and nitrogen even at high temperatures. Acids that do not have oxidizing properties do not act on copper, for example, hydrochloric and dilute sulfuric acids. But in the presence of atmospheric oxygen, copper dissolves in these acids with the formation of the corresponding salts: 2Cu + 4HCl + O 2 = 2CuCl 2 + 2H 2 O.

In an atmosphere containing CO 2, H 2 O vapors, etc., it becomes covered with a patina - a greenish film of basic carbonate (Cu 2 (OH) 2 CO 3)), a toxic substance.

Copper is included in more than 170 minerals, of which only 17 are important for industry, including: bornite (variegated copper ore - Cu 5 FeS 4), chalcopyrite (copper pyrites - CuFeS 2), chalcocite (copper luster - Cu 2 S) , covelline (CuS), malachite (Cu 2 (OH) 2 CO 3). There is also native copper.

Density of copper, specific gravity of copper and other characteristics of copper

Density - 8.93 * 10 3 kg / m 3;
Specific gravity - 8.93 g/cm3;
Specific heat at 20 °C - 0.094 cal/deg;
Melting temperature - 1083°C;
Specific heat of fusion - 42 cal/g;
Boiling temperature - 2600°C;
Linear expansion coefficient(at a temperature of about 20 ° C) - 16.7 * 10 6 (1 / deg);
Coefficient of thermal conductivity - 335 kcal / m * hour * hail;
Resistivity at 20 °C - 0.0167 Ohm * mm 2 / m;

Elastic modulus of copper and Poisson's ratio

COPPER COMPOUNDS

Copper (I) oxide Cu 2 O 3 and cuprous oxide (I) Cu2O, like other copper (I) compounds, are less stable than copper (II) compounds. Copper (I) oxide, or copper oxide Cu 2 O, occurs naturally in the form of the mineral cuprite. In addition, it can be obtained as a precipitate of red copper (I) oxide by heating a solution of copper (II) salt and alkali in the presence of a strong reducing agent.

Copper(II) oxide, or copper oxide, CuO- a black substance found in nature (for example, in the form of the mineral tenerite). It is obtained by calcining copper (II) hydroxocarbonate (CuOH) 2 CO 3 or copper (II) nitrate Cu(NO 2) 2 .
Copper(II) oxide is a good oxidizing agent. Copper hydroxide (II) Cu (OH) 2 precipitated from solutions of copper (II) salts under the action of alkalis in the form of a blue gelatinous mass. Already at low heating, even under water, it decomposes, turning into black oxide of copper (II).
Copper(II) hydroxide is a very weak base. Therefore, solutions of copper (II) salts in most cases are acidic, and with weak acids, copper forms basic salts.

Copper (II) sulfate CuSO 4 in the anhydrous state, it is a white powder, which turns blue when water is absorbed. Therefore, it is used to detect traces of moisture in organic liquids. An aqueous solution of copper sulfate has a characteristic blue-blue color. This color is characteristic of hydrated 2+ ions, therefore all dilute solutions of copper (II) salts have the same color, unless they contain any colored anions. From aqueous solutions, copper sulfate crystallizes with five molecules of water, forming transparent blue crystals of copper sulphate. Copper sulphate is used for the electrolytic coating of metals with copper, for the preparation of mineral paints, and also as a starting material in the preparation of other copper compounds. In agriculture, a dilute solution of copper sulphate is used to spray plants and dress grains before sowing to kill spores of harmful fungi.

Copper (II) chloride CuCl 2 . 2H2O. Forms dark green crystals, easily soluble in water. Very concentrated solutions of copper chloride (II) are green, dilute - blue-blue.

Copper (II) nitrate Cu (NO 3) 2. 3H2O. Obtained by dissolving copper in nitric acid. When heated, blue crystals of copper nitrate first lose water, and then easily decompose with the release of oxygen and brown nitrogen dioxide, turning into copper (II) oxide.

Copper (II) hydroxocarbonate (CuOH) 2 CO 3. It occurs naturally in the form of the mineral malachite, which has a beautiful emerald green color. It is artificially prepared by the action of Na 2 CO 3 on solutions of copper (II) salts.
2CuSO 4 + 2Na 2 CO 3 + H 2 O \u003d (CuOH) 2 CO 3 ↓ + 2Na 2 SO 4 + CO 2
It is used to obtain copper chloride (II), for the preparation of blue and green mineral paints, as well as in pyrotechnics.

Copper (II) acetate Cu (CH 3 COO) 2. H2O. Obtained by treating metallic copper or copper (II) oxide with acetic acid. Usually it is a mixture of basic salts of various composition and color (green and blue-green). Under the name verdigris, it is used for the preparation of oil paint.

Complex compounds of copper are formed as a result of the combination of doubly charged copper ions with ammonia molecules.
Various mineral paints are obtained from copper salts.
All copper salts are poisonous. Therefore, in order to avoid the formation of copper salts, copper dishes are coated from the inside with a layer of tin (tinned).

COPPER PRODUCTION

Copper is mined from oxide and sulfide ores. 80% of all mined copper is smelted from sulfide ores. As a rule, copper ores contain a lot of waste rock. Therefore, an enrichment process is used to obtain copper. Copper is obtained by smelting it from sulfide ores. The process consists of a number of operations: roasting, melting, converting, fire and electrolytic refining. During the roasting process, most of the impurity sulfides are converted into oxides. So, the main impurity of most copper ores pyrite FeS 2 turns into Fe 2 O 3. The gases generated during roasting contain CO 2 , which is used to produce sulfuric acid. The oxides of iron, zinc and other impurities obtained during the roasting process are separated in the form of slag during smelting. Liquid copper matte (Cu 2 S with an admixture of FeS) enters the converter, where air is blown through it. During the conversion, sulfur dioxide is released and blister or raw copper is obtained. To extract valuable (Au, Ag, Te, etc.) and to remove harmful impurities, blister copper is first subjected to fire and then electrolytic refining. During fire refining, liquid copper is saturated with oxygen. In this case, impurities of iron, zinc and cobalt are oxidized, pass into slag and are removed. And copper is poured into molds. The resulting castings serve as anodes for electrolytic refining.
The main component of the solution during electrolytic refining is copper sulfate - the most common and cheap copper salt. To increase the low electrical conductivity of copper sulfate, sulfuric acid is added to the electrolyte. And to obtain a compact precipitate of copper, a small amount of additives is introduced into the solution. Metallic impurities contained in crude ("blister") copper can be divided into two groups.

1) Fe, Zn, Ni, Co. These metals have much more negative electrode potentials than copper. Therefore, they dissolve anode together with copper, but do not precipitate on the cathode, but accumulate in the electrolyte in the form of sulfates. Therefore, the electrolyte must be replaced periodically.

2) Au, Ag, Pb, Sn. Noble metals (Au, Ag) do not undergo anodic dissolution, but during the process they settle at the anode, forming, together with other impurities, anode sludge, which is periodically removed. Tin and lead dissolve together with copper, but in the electrolyte they form poorly soluble compounds that precipitate and are also removed.

COPPER ALLOYS

Alloys, which increase the strength and other properties of copper, are obtained by introducing additives into it, such as zinc, tin, silicon, lead, aluminum, manganese, nickel. More than 30% of copper goes to alloys.

Brass- alloys of copper with zinc (copper from 60 to 90% and zinc from 40 to 10%) - stronger than copper and less susceptible to oxidation. When silicon and lead are added to brass, its anti-friction qualities increase, and when tin, aluminum, manganese and nickel are added, anti-corrosion resistance increases. Sheets and cast products are used in mechanical engineering, especially in chemical engineering, in optics and instrumentation, and in the production of nets for the pulp and paper industry.

Bronzes. Previously, bronzes were called alloys of copper (80-94%) and tin (20-6%). Currently, tinless bronzes are produced, named after the main component after copper.

Aluminum bronzes contain 5-11% aluminum, have high mechanical properties combined with anti-corrosion resistance.

Lead bronzes, containing 25-33% lead, is used mainly for the manufacture of bearings operating at high pressures and high sliding speeds.

silicon bronzes containing 4-5% silicon are used as cheap substitutes for tin bronzes.

Beryllium bronzes, containing 1.8-2.3% beryllium, are distinguished by hardness after hardening and high elasticity. They are used for the manufacture of springs and spring products.

Cadmium bronzes- copper alloys with a small amount of cadmium (up to 1%) - are used for the manufacture of fittings for water and gas lines and in mechanical engineering.

Solders- non-ferrous metal alloys used in soldering to obtain a monolithic brazed seam. Among hard solders, a copper-silver alloy is known (44.5-45.5% Ag; 29-31% Cu; the rest is zinc).

COPPER APPLICATIONS

Copper, its compounds and alloys are widely used in various industries.

In electrical engineering, copper is used in its pure form: in the production of cable products, bare and contact wire tires, power generators, telephone and telegraph equipment and radio equipment. Heat exchangers, vacuum apparatuses, pipelines are made of copper. More than 30% of copper goes to alloys.

Alloys of copper with other metals are used in mechanical engineering, in the automotive and tractor industries (radiators, bearings), and for the manufacture of chemical equipment.

The high viscosity and ductility of the metal make it possible to use copper for the manufacture of various products with a very complex pattern. Red copper wire in the annealed state becomes so soft and ductile that all kinds of cords can be easily twisted from it and the most complex elements of the ornament can be bent. In addition, copper wire is easily soldered with scanned silver solder, it is well silvered and gilded. These properties of copper make it an indispensable material in the production of filigree products.

The coefficient of linear and volumetric expansion of copper during heating is approximately the same as that of hot enamels, and therefore, when cooling, the enamel adheres well to the copper product, does not crack, does not rebound. Due to this, masters for the production of enamel products prefer copper to all other metals.

Like some other metals, copper is one of the vital trace elements. She is involved in the process. photosynthesis and assimilation of nitrogen by plants, promotes the synthesis of sugar, proteins, starch, vitamins. Most often, copper is applied to the soil in the form of pentahydrate sulfate - copper sulfate CuSO 4. 5H 2 O. In large quantities, it is poisonous, like many other copper compounds, especially for lower organisms. In small doses, copper is necessary for all living things.