Section 1. Name and history of the discovery of aluminum.

Section 2. General characteristics aluminum, physical and chemical properties.

Section 3. Obtaining castings from aluminum alloys.

Section 4 Application aluminum.

Aluminum- this is an element of the main subgroup of the third group, the third period of the periodic system of chemical elements of D. I. Mendeleev, with atomic number 13. It is designated by the symbol Al. Belongs to the group of light metals. The most common metal and the third most abundant chemical element in earth's crust(after oxygen and silicon).

Simple substance aluminum (CAS number: 7429-90-5) - light, paramagnetic metal silver- white color, easily molded, cast, machined. Aluminum has a high thermal and electrical conductivity, resistance to corrosion due to the rapid formation of strong oxide films that protect the surface from further interaction.

The achievements of industry in any developed society are invariably associated with the achievements of the technology of structural materials and alloys. The quality of processing and the productivity of manufacturing items of trade are the most important indicators of the level of development of the state.

The materials used in modern designs, in addition to high strength characteristics, must have a set of properties such as increased corrosion resistance, heat resistance, thermal and electrical conductivity, refractoriness, as well as the ability to maintain these properties under conditions long work under loads.

Scientific developments and production processes in the field of foundry production of non-ferrous metals in our country correspond to the advanced achievements of scientific and technological progress. Their result, in particular, was the creation of modern chill casting and pressure casting workshops at the Volga Automobile Plant and a number of other enterprises. Large injection molding machines with a mold locking force of 35 MN are successfully operating at the Zavolzhsky Motor Plant, which produce aluminum alloy cylinder blocks for the Volga car.

At the Altai Motor Plant, an automated line for the production of castings by injection molding has been mastered. In the Union of Soviet Socialist Republics() for the first time in the world developed and mastered process continuous casting of ingots from aluminum alloys in an electromagnetic mold. This method significantly improves the quality of ingots and reduces the amount of waste in the form of chips during their turning.

The name and history of the discovery of aluminum

The Latin aluminium comes from the Latin alumen, meaning alum (aluminum and potassium sulfate (K) KAl(SO4)2 12H2O), which has long been used in leather dressing and as an astringent. Al, a chemical element of group III of the periodic system, atomic number 13, atomic mass 26, 98154. Due to the high chemical activity, the discovery and isolation of pure aluminum dragged on for almost 100 years. The conclusion that "" (a refractory substance, in modern terms - aluminum oxide) can be obtained from alum was made back in 1754. German chemist A. Markgraf. Later it turned out that the same "earth" could be isolated from clay, and it was called alumina. It was only in 1825 that he was able to obtain metallic aluminum. Danish physicist H. K. Oersted. He treated aluminum chloride AlCl3, which could be obtained from alumina, with potassium amalgam (an alloy of potassium (K) with mercury (Hg)) and, after distilling off mercury (Hg), isolated a gray powder of aluminum.

Only a quarter of a century later, this method was slightly modernized. The French chemist A. E. St. Clair Deville in 1854 suggested using metallic sodium (Na) to produce aluminum, and obtained the first ingots of the new metal. The cost of aluminum was then very high, and it was used to make Jewelry.

An industrial method for the production of aluminum by electrolysis of a melt of complex mixtures, including oxide, aluminum fluoride and other substances, was independently developed in 1886 by P. Eru () and C. Hall (USA). The production of aluminum is associated with a high cost of electricity, so it was realized on a large scale only in the 20th century. AT Union of Soviet Socialist Republics (CCCP) the first industrial aluminum was obtained on May 14, 1932 at the Volkhov aluminum plant, built next to the Volkhov hydroelectric power station.

Aluminum with a purity of over 99.99% was first obtained by electrolysis in 1920. In 1925 in work Edwards published some information about the physical and mechanical properties of such aluminum. In 1938 Taylor, Wheeler, Smith, and Edwards published an article that gives some of the properties of 99.996% purity aluminum, also obtained in France by electrolysis. The first edition of the monograph on the properties of aluminum was published in 1967.

In subsequent years, due to the relative ease of preparation and attractive properties, many works on the properties of aluminum. Pure aluminum has found wide application mainly in electronics - from electrolytic capacitors to the pinnacle of electronic engineering - microprocessors; in cryoelectronics, cryomagnetics.

Newer methods for obtaining pure aluminum are the zone purification method, crystallization from amalgams (alloys of aluminum with mercury) and isolation from alkaline solutions. The degree of purity of aluminum is controlled by the value of electrical resistance at low temperatures.

General characteristics of aluminum

Natural aluminum consists of one nuclide 27Al. The configuration of the outer electron layer is 3s2p1. In almost all compounds, the oxidation state of aluminum is +3 (valency III). The radius of the neutral aluminum atom is 0.143 nm, the radius of the Al3+ ion is 0.057 nm. The successive ionization energies of a neutral aluminum atom are 5, 984, 18, 828, 28, 44, and 120 eV, respectively. On the Pauling scale, the electronegativity of aluminum is 1.5.

Aluminum is soft, light, silvery-white, the crystal lattice of which is face-centered cubic, parameter a = 0.40403 nm. Melting temperature pure metal 660°C, boiling point about 2450°C, density 2, 6989 g/cm3. The temperature coefficient of linear expansion of aluminum is about 2.5·10-5 K-1.

Chemical aluminum is a fairly active metal. In air, its surface is instantly covered with a dense film of Al2O3 oxide, which prevents further access of oxygen (O) to the metal and leads to the termination of the reaction, which leads to high anti-corrosion properties of aluminum. A protective surface film on aluminum is also formed if it is placed in concentrated nitric acid.

Aluminum actively reacts with other acids:

6HCl + 2Al = 2AlCl3 + 3H2,

3Н2SO4 + 2Al = Al2(SO4)3 + 3H2.

Interestingly, the reaction between aluminum and iodine (I) powders begins at room temperature, if a few drops of water are added to the initial mixture, which in this case plays the role of a catalyst:

2Al + 3I2 = 2AlI3.

The interaction of aluminum with sulfur (S) when heated leads to the formation of aluminum sulfide:

2Al + 3S = Al2S3,

which is easily decomposed by water:

Al2S3 + 6H2O = 2Al(OH)3 + 3H2S.

Aluminum does not interact directly with hydrogen (H), however, indirectly, for example, using organoaluminum compounds, it is possible to synthesize solid polymeric aluminum hydride (AlH3)x - the strongest reducing agent.

In the form of a powder, aluminum can be burned in air, and a white refractory powder of aluminum oxide Al2O3 is formed.

The high bond strength in Al2O3 determines the high heat of its formation from simple substances and the ability of aluminum to reduce many metals from their oxides, for example:

3Fe3O4 + 8Al = 4Al2O3 + 9Fe and even

3СаО + 2Al = Al2О3 + 3Са.

This method of obtaining metals is called aluminothermy.

Being in nature

In terms of prevalence in the earth's crust, aluminum ranks first among metals and third among all elements (after oxygen (O) and silicon (Si)), it accounts for about 8.8% of the mass of the earth's crust. Aluminum is included in a huge number of minerals, mainly aluminosilicates, and rocks. Aluminum compounds contain granites, basalts, clays, feldspars, etc. But here is the paradox: with a huge number minerals and rocks containing aluminum, bauxite deposits - the main raw material for industrial production aluminum are quite rare. AT Russian Federation there are bauxite deposits in Siberia and the Urals. Alunites and nephelines are also of industrial importance. As a trace element, aluminum is present in the tissues of plants and animals. There are organisms - concentrators that accumulate aluminum in their organs - some club mosses, mollusks.

Industrial production: at the index of industrial production, bauxites are first subjected to chemical processing, removing from them impurities of oxides of silicon (Si), iron (Fe) and other elements. As a result of such processing, pure aluminum oxide Al2O3 is obtained - the main one in the production of metal by electrolysis. However, due to the fact that the melting point of Al2O3 is very high (more than 2000°C), it is not possible to use its melt for electrolysis.

Scientists and engineers found a way out in the following. Cryolite Na3AlF6 is first melted in an electrolysis bath (melt temperature slightly below 1000°C). Cryolite can be obtained, for example, by processing nephelines from the Kola Peninsula. Further, a little Al2O3 (up to 10% by mass) and some other substances are added to this melt, improving the conditions for the subsequent process. During the electrolysis of this melt, aluminum oxide decomposes, the cryolite remains in the melt, and molten aluminum is formed on the cathode:

2Al2O3 = 4Al + 3O2.

Aluminum alloys

Most metal elements are alloyed with aluminum, but only a few of them play the role of the main alloying components in industrial aluminum alloys. However, a significant number of elements are used as additives to improve the properties of alloys. The most widely used:

Beryllium is added to reduce oxidation at elevated temperatures. Small additions of beryllium (0.01 - 0.05%) are used in aluminum casting alloys to improve fluidity in the production of internal combustion engine parts (pistons and cylinder heads).

Boron is introduced to increase electrical conductivity and as a refining additive. Boron is introduced into aluminum alloys used in nuclear power engineering (except for reactor parts), because it absorbs neutrons, preventing the spread of radiation. Boron is introduced on average in the amount of 0.095 - 0.1%.

Bismuth. Low melting point metals such as bismuth, cadmium are added to aluminum alloys to improve machinability. These elements form soft fusible phases that contribute to chip breakage and cutter lubrication.

Gallium is added in the amount of 0.01 - 0.1% to the alloys from which the consumable anodes are further made.

Iron. In small quantities (>0.04%) it is introduced during the production of wires to increase strength and improve creep characteristics. Same way iron reduces sticking to the walls of molds when casting into a mold.

Indium. The addition of 0.05 - 0.2% strengthens aluminum alloys during aging, especially at low cuprum content. Indium additives are used in aluminum-cadmium bearing alloys.

Approximately 0.3% cadmium is introduced to increase the strength and improve the corrosion properties of the alloys.

Calcium gives plasticity. With a calcium content of 5%, the alloy has the effect of superplasticity.

Silicon is the most used additive in foundry alloys. In the amount of 0.5 - 4% reduces the tendency to cracking. The combination of silicon and magnesium makes it possible to heat seal the alloy.

Magnesium. The addition of magnesium significantly increases strength without reducing ductility, improves weldability and increases the corrosion resistance of the alloy.

Copper strengthens alloys, maximum hardening is achieved when the content cuprum 4 - 6%. Alloys with cuprum are used in the production of pistons for internal combustion engines, high-quality cast parts for aircraft.

Tin improves cutting performance.

Titanium. The main task of titanium in alloys is grain refinement in castings and ingots, which greatly increases the strength and uniformity of properties throughout the volume.

Although aluminum is considered one of the least noble industrial metals, it is quite stable in many oxidizing environments. The reason for this behavior is the presence of a continuous oxide film on the surface of aluminum, which immediately re-forms on the cleaned areas when exposed to oxygen, water and other oxidizing agents.

In most cases, melting is carried out in air. If the interaction with air is limited to the formation of compounds insoluble in the melt on the surface, and the resulting film of these compounds significantly slows down further interaction, then usually no measures are taken to suppress such interaction. Melting in this case is carried out with direct contact of the melt with the atmosphere. This is done in the preparation of most aluminum, zinc, tin-lead alloys.

The space in which melting of alloys takes place is limited by a refractory lining capable of withstanding temperatures of 1500 - 1800 ˚С. In all melting processes, the gas phase is involved, which is formed during the combustion of fuel, interacting with the environment and the lining of the melting unit, etc.

Most aluminum alloys have high corrosion resistance in the natural atmosphere, sea water, solutions of many salts and chemicals, and in most foods. Aluminum alloy structures are often used in sea water. Sea buoys, lifeboats, ships, barges have been built from aluminum alloys since 1930. At present, the length of ship hulls made of aluminum alloys reaches 61 m. There is experience of aluminum underground pipelines, aluminum alloys are highly resistant to soil corrosion. In 1951, a 2.9 km long pipeline was built in Alaska. After 30 years of operation, no leaks or serious damage due to corrosion have been found.

Aluminum is used in large volumes in construction in the form of cladding panels, doors, window frames, electrical cables. Aluminum alloys are not subject to severe corrosion for a long time in contact with concrete, mortar, plaster, especially if the structures are not frequently wet. When wet frequently, if the surface of the aluminum trade items has not been further processed, it may darken, up to blackening in industrial cities with a high content of oxidizing agents in the air. To avoid this, special alloys are produced to obtain shiny surfaces by brilliant anodizing - applying an oxide film to the metal surface. In this case, the surface can be given a variety of colors and shades. For example, alloys of aluminum with silicon allow you to get a range of shades, from gray to black. Aluminum alloys with chromium have a golden color.

Industrial aluminum is produced in the form of two types of alloys - casting, parts of which are made by casting, and deformation - alloys produced in the form of deformable semi-finished products - sheets, foil, plates, profiles, wire. Castings from aluminum alloys are obtained by all possible casting methods. It is most common under pressure, in chill molds and in sandy-clay molds. In the manufacture of small political parties, it is used casting in gypsum combined forms and casting for investment models. Cast alloys are used to make cast rotors of electric motors, cast parts of aircraft, etc. Wrought alloys are used in automotive production for interior decoration, bumpers, body panels and interior parts; in construction as a finishing material; in aircraft, etc.

AT industry aluminum powders are also used. Used in metallurgical industry: in aluminothermy, as alloying additives, for the manufacture of semi-finished products by pressing and sintering. This method produces very durable parts (gears, bushings, etc.). Powders are also used in chemistry to obtain aluminum compounds and as catalyst(for example, in the production of ethylene and acetone). Given the high reactivity of aluminum, especially in the form of a powder, it is used in explosives and solid propellants for rockets, using its ability to quickly ignite.

Given the high resistance of aluminum to oxidation, the powder is used as a pigment in coatings for painting equipment, roofs, paper in printing, shiny surfaces of car panels. Also, a layer of aluminum is covered with steel and cast iron trade item to prevent their corrosion.

In terms of application, aluminum and its alloys are second only to iron (Fe) and its alloys. The widespread use of aluminum in various fields of technology and everyday life is associated with a combination of its physical, mechanical and chemical properties: low density, corrosion resistance in atmospheric air, high thermal and electrical conductivity, ductility and relatively high strength. Aluminum is easily processed in various ways - forging, stamping, rolling, etc. Pure aluminum is used to make wire (the electrical conductivity of aluminum is 65.5% of the electrical conductivity of cuprum, but aluminum is more than three times lighter than cuprum, so aluminum is often replaced in electrical engineering) and foil used as packaging material. The main part of the smelted aluminum is spent on obtaining various alloys. Protective and decorative coatings are easily applied to the surface of aluminum alloys.

The variety of properties of aluminum alloys is due to the introduction of various additives into aluminum, which form solid solutions or intermetallic compounds with it. The bulk of aluminum is used to produce light alloys - duralumin (94% aluminum, 4% copper (Cu), 0.5% magnesium (Mg), manganese (Mn), (Fe) and silicon (Si)), silumin ( 85-90% - aluminum, 10-14% silicon (Si), 0.1% sodium (Na)) and others. In metallurgy, aluminum is used not only as a base for alloys, but also as one of the widely used alloying additives in alloys based on cuprum (Cu), magnesium (Mg), iron (Fe), >nickel (Ni), etc.

Aluminum alloys are widely used in everyday life, in construction and architecture, in the automotive industry, in shipbuilding, aviation and space technology. In particular, the first artificial Earth satellite was made of aluminum alloy. An alloy of aluminum and zirconium (Zr) is widely used in nuclear reactor building. Aluminum is used in the manufacture of explosives.

When handling aluminum in everyday life, you need to keep in mind that only neutral (in acidity) liquids (for example, boil water) can be heated and stored in aluminum dishes. If, for example, sour cabbage soup is boiled in aluminum dishes, then aluminum passes into food, and it acquires an unpleasant “metallic” taste. Since the oxide film is very easy to damage in everyday life, the use of aluminum cookware is still undesirable.

Silver-white metal, light

density — 2.7 g/cm

melting point for technical aluminum - 658 °C, for high purity aluminum - 660 °C

specific heat of fusion — 390 kJ/kg

boiling point - 2500 ° C

specific heat of evaporation - 10.53 MJ / kg

tensile strength of cast aluminum - 10-12 kg / mm², deformable - 18-25 kg / mm², alloys - 38-42 kg / mm²

Brinell hardness — 24…32 kgf/mm²

high ductility: technical - 35%, clean - 50%, rolled into a thin sheet and even foil

Young's modulus - 70 GPa

Aluminum has high electrical conductivity (0.0265 μOhm m) and thermal conductivity (203.5 W / (m K)), 65% of the electrical conductivity of cuprum, and has a high light reflectivity.

Weak paramagnet.

Temperature coefficient of linear expansion 24.58 10−6 K−1 (20…200 °C).

The temperature coefficient of electrical resistance is 2.7·10−8K−1.

Aluminum forms alloys with almost all metals. The best known are alloys with cuprum and magnesium (duralumin) and silicon (silumin).

Natural aluminum consists almost entirely of the only stable isotope, 27Al, with traces of 26Al, a radioactive isotope with period a half-life of 720 thousand years, formed in the atmosphere during the bombardment of argon nuclei by cosmic ray protons.

In terms of prevalence in the earth's crust, the Earth occupies the 1st place among metals and the 3rd place among elements, second only to oxygen and silicon. aluminum content in the earth's crust data various researchers is from 7.45 to 8.14% of the mass of the earth's crust.

In nature, aluminum, due to its high chemical activity, occurs almost exclusively in the form of compounds. Some of them:

Bauxites - Al2O3 H2O (with admixtures of SiO2, Fe2O3, CaCO3)

Alunites - (Na,K)2SO4 Al2(SO4)3 4Al(OH)3

Alumina (mixtures of kaolins with sand SiO2, limestone CaCO3, magnesite MgCO3)

Corundum (sapphire, ruby, emery) - Al2O3

Kaolinite - Al2O3 2SiO2 2H2O

Beryl (emerald, aquamarine) - 3BeO Al2O3 6SiO2

Chrysoberyl (alexandrite) - BeAl2O4.

However, under certain specific reducing conditions, the formation of native aluminum is possible.

In natural waters, aluminum is found in the form of low-toxic chemical compounds such as aluminum fluoride. The type of cation or anion depends, first of all, on the acidity of the aqueous medium. Aluminum concentrations in surface water bodies Russian Federation range from 0.001 to 10 mg/l, in sea water 0.01 mg/l.

Aluminum (Aluminum) is

Obtaining castings from aluminum alloys

The main challenge facing the foundry in our country, consists in a significant overall improvement in the quality of castings, which should find expression in a decrease in wall thickness, a decrease in machining allowances and gating systems while maintaining proper operational properties trade items. The end result of this work should be to meet the increased needs of mechanical engineering with the necessary number of cast billets without a significant increase in the total monetary emission of castings by weight.

Sand casting

Of the above methods of casting into disposable molds, the most widely used in the manufacture of castings from aluminum alloys is casting into wet sand molds. This is due to the low density of the alloys, the small force effect of the metal on the mold, and low casting temperatures (680-800C).

For the manufacture of sand molds, molding and core mixtures are used, prepared from quartz and clay sands (GOST 2138-74), molding clays (GOST 3226-76), binders and auxiliary materials.

The type of gating system is chosen taking into account the dimensions of the casting, the complexity of its configuration and location in the mold. Casting molds for castings of complex configuration of small height is carried out, as a rule, with the help of lower gating systems. At high altitude castings and thin walls, it is preferable to use vertically slotted or combined gating systems. Molds for castings of small sizes can be poured through the top gating systems. In this case, the height of the metal scab falling into the mold cavity should not exceed 80 mm.

To reduce the speed of the melt at the entrance to the mold cavity and to better separate the oxide films and slag inclusions suspended in it, additional hydraulic resistances are introduced into the gating systems - meshes (metal or fiberglass) are installed or poured through granular filters.

Sprues (feeders), as a rule, are brought to thin sections (walls) of castings dispersed around the perimeter, taking into account the convenience of their subsequent separation during processing. The supply of metal to massive units is unacceptable, as it causes the formation of shrinkage cavities in them, increased roughness and shrinkage "failures" on the surface of the castings. In cross section, the sprue channels most often have a rectangular shape with a wide side of 15-20 mm, and a narrow side of 5-7 mm.

Alloys with a narrow crystallization interval (AL2, AL4, AL), AL34, AK9, AL25, ALZO) are prone to the formation of concentrated shrinkage cavities in the thermal units of castings. To bring these shells out of the castings, the installation of massive profits is widely used. For thin-walled (4-5 mm) and small castings, the mass of the profit is 2-3 times the mass of the castings, for thick-walled castings, up to 1.5 times. Height arrived chosen depending on the height of the casting. When the height is less than 150 mm, the height arrived H-adj. take equal to the height of the casting Notl. For higher castings, the ratio Nprib / Notl is taken equal to 0.3 0.5.

The greatest application in the casting of aluminum alloys is found in the upper open profits of a round or oval section; lateral profits in most cases are made closed. To improve work efficiency profits they are insulated, filled with hot metal, topped up. Warming is usually carried out by a sticker on the surface of the form of sheet asbestos, followed by drying with a gas flame. Alloys with a wide crystallization range (AL1, AL7, AL8, AL19, ALZZ) are prone to the formation of scattered shrinkage porosity. Impregnation of shrinkage pores with profits ineffective. Therefore, in the manufacture of castings from the listed alloys, it is not recommended to use the installation of massive profits. To obtain high-quality castings, directional solidification is carried out, widely using the installation of refrigerators made of cast iron and aluminum alloys for this purpose. Optimum conditions for directional crystallization are created by a vertical slot gate system. To prevent gas evolution during crystallization and to prevent the formation of gas-shrinkage porosity in thick-walled castings, crystallization under a pressure of 0.4–0.5 MPa is widely used. To do this, the casting molds are placed in autoclaves before pouring, they are filled with metal and the castings are crystallized under air pressure. For the manufacture of large-sized (up to 2-3 m high) thin-walled castings, a casting method with successively directed solidification is used. The essence of the method is the successive crystallization of the casting from the bottom up. To do this, the casting mold is placed on the table of a hydraulic lift and metal tubes 12–20 mm in diameter, heated to 500–700°C, are lowered inside it, performing the function of risers. The tubes are fixedly fixed in the gating cup and the holes in them are closed with stoppers. After the gating cup is filled with melt, the stoppers are lifted, and the alloy flows through the tubes into the gating wells connected to the mold cavity by slotted sprues (feeders). After the level of the melt in the wells rises by 20-30 mm above the lower end of the tubes, the mechanism for lowering the hydraulic table is turned on. The lowering speed is taken such that the filling of the mold is carried out under the flooded level and the hot metal continuously flows into the upper parts of the mold. This provides directional solidification and makes it possible to obtain complex castings without shrinkage defects.

Filling sand molds with metal is carried out from ladles lined with refractory material. Before filling with metal, freshly lined ladles are dried and calcined at 780–800°C to remove moisture. The temperature of the melt before pouring is maintained at the level of 720-780 °C. Molds for thin-walled castings are filled with melts heated to 730-750°C, and for thick-walled castings up to 700-720°C.

Casting in plaster molds

Casting in gypsum molds is used in cases where increased requirements are placed on castings in terms of accuracy, surface cleanliness and reproduction of the smallest details of the relief. Compared to sand molds, gypsum molds have higher strength, dimensional accuracy, better resistance to high temperatures, and make it possible to obtain castings of complex configuration with a wall thickness of 1.5 mm according to the 5-6th accuracy class. Forms are made according to wax or metal (brass,) chrome-plated models. Model plates are made of aluminum alloys. To facilitate the removal of models from the molds, their surface is covered with a thin layer of kerosene-stearin lubricant.

Small and medium molds for complex thin-walled castings are made from a mixture consisting of 80% gypsum, 20% quartz sand or asbestos and 60-70% water (by weight of the dry mixture). The composition of the mixture for medium and large forms: 30% gypsum, 60% sand, 10% asbestos, 40-50% water. To slow down the setting, 1-2% slaked lime is added to the mixture. The necessary strength of the forms is achieved by hydration of anhydrous or semi-aqueous gypsum. To reduce strength and increase gas permeability, raw gypsum molds are subjected to hydrothermal treatment - they are kept in an autoclave for 6-10 hours under a water vapor pressure of 0.13-0.14 MPa, and then for a day in air. After that, the forms are subjected to stepwise drying at 350-500 °C.

A feature of gypsum molds is their low thermal conductivity. This circumstance makes it difficult to obtain dense castings from aluminum alloys with a wide range of crystallization. Therefore, the main task in the development of a sprue-profitable system for gypsum molds is to prevent the formation of shrinkage cavities, looseness, oxide films, hot cracks and underfilling of thin walls. This is achieved by using expanding gating systems that provide a low speed of movement of melts in the mold cavity, directed solidification of thermal units towards the risers with the help of refrigerators, increasing the compliance of molds by increasing the content quartz sand in the mixture. Thin-walled castings are poured into molds heated to 100–200°C by the vacuum suction method, which makes it possible to fill cavities up to 0.2 mm thick. Thick-walled (more than 10 mm) castings are obtained by pouring molds in autoclaves. Crystallization of the metal in this case is carried out under a pressure of 0.4–0.5 MPa.

Shell casting

Casting into shell molds is expedient to use in serial and large-scale production of castings of limited dimensions with increased surface finish, greater dimensional accuracy and less machining than when casting into sand molds.

Shell molds are made using hot (250–300 °C) metal (steel,) tooling in a bunker way. Model equipment is performed according to the 4th-5th accuracy classes with molding slopes from 0.5 to 1.5%. The shells are made two-layer: the first layer is from a mixture with 6-10% thermosetting resin, the second from a mixture with 2% resin. For better removal of the shell, the model slab is covered with a thin layer of separating emulsion (5% silicone fluid No. 5; 3% laundry soap; 92% water) before filling the molding sand.

For the manufacture of shell molds, fine-grained quartz sands containing at least 96% silica are used. The half-molds are connected by gluing on special pin presses. Glue composition: 40% MF17 resin; 60% marshalite and 1.5% aluminum chloride (hardening). Filling of the assembled forms is carried out in containers. When casting into shell molds, the same gating systems and temperature conditions are used as when casting into sand molds.

The low rate of metal crystallization in shell molds and the lower possibilities for creating directed crystallization result in the production of castings with lower properties than when casting in raw sand molds.

Investment casting

Investment casting is used to manufacture castings of increased accuracy (3rd-5th class) and surface finish (4-6th roughness class), for which this method is the only possible or optimal one.

Models in most cases are made from pasty paraffin stearin (1: 1) compositions by pressing into metal molds (cast and prefabricated) on stationary or carousel installations. In the manufacture of complex castings with dimensions of more than 200 mm, in order to avoid deformation of the models, substances are introduced into the composition of the model mass that increase the temperature of their softening (melting).

As a refractory coating in the manufacture of ceramic molds, a suspension of hydrolyzed ethyl silicate (30–40%) and powdered quartz (70–60%) is used. Sprinkling of model blocks is carried out with calcined sand 1KO16A or 1K025A. Each coating layer is dried in air for 10-12 hours or in an atmosphere containing ammonia vapor. The necessary strength of the ceramic mold is achieved with a shell thickness of 4–6 mm (4–6 layers of a refractory coating). To ensure smooth filling of the mold, expanding gating systems are used with metal supply to thick sections and massive nodes. Castings are usually fed from a massive riser through thickened sprues (feeders). For complex castings, it is allowed to use massive profits to power the upper massive units with the obligatory filling of them from the riser.

Aluminum (Aluminum) is

Models are melted from molds in hot (85–90°C) water acidified with hydrochloric acid (0.5–1 cm3 per liter of water) to prevent saponification of stearin. After melting the models, the ceramic molds are dried at 150–170°C for 1–2 hours, placed in containers, filled with dry filler, and calcined at 600–700°C for 5–8 hours. Filling is carried out in cold and heated molds. The heating temperature (50-300 °C) of the molds is determined by the thickness of the walls of the casting. The filling of molds with metal is carried out in the usual way, as well as using vacuum or centrifugal force. Most aluminum alloys are heated to 720-750°C before pouring.

Die casting

Chill casting is the main method of serial and mass production of castings from aluminum alloys, which makes it possible to obtain castings of the 4th-6th accuracy classes with a surface roughness Rz = 50-20 and a minimum wall thickness of 3-4 mm. When casting into a mold, along with defects caused by high speeds of the melt in the mold cavity and non-compliance with the requirements of directional solidification (gas porosity, oxide films, shrinkage looseness), the main types of rejects and castings are underfills and cracks. The appearance of cracks is caused by difficult shrinkage. Cracks occur especially often in castings made from alloys with a wide crystallization interval, which have a large linear shrinkage (1.25–1.35%). Prevention of the formation of these defects is achieved by various technological methods.

In the case of supplying metal to thick sections, provision should be made for feeding the supply point by installing a supply boss (profit). All elements of the gating systems are located along the chill mold connector. The following cross-sectional area ratios of the gate channels are recommended: for small castings EFst: EFsl: EFpit = 1: 2: 3; for large castings EFst: EFsl: EFpit = 1: 3: 6.

To reduce the rate of melt entry into the mold cavity, curved risers, fiberglass or metal meshes, and granular filters are used. The quality of castings from aluminum alloys depends on the rate of rise of the melt in the mold cavity. This speed should be sufficient to guarantee the filling of thin sections of castings under conditions of increased heat removal and at the same time not cause underfilling due to incomplete release of air and gases through the ventilation ducts and profits, swirling and flowing of the melt during the transition from narrow sections to wide ones. The rate of rise of the metal in the mold cavity when casting into a mold is taken somewhat higher than when casting into sand molds. The minimum allowable lifting speed is calculated according to the formulas of A. A. Lebedev and N. M. Galdin (see section 5.1, “Sand casting”).

To obtain dense castings, as in sand casting, directional solidification is created by proper positioning of the casting in the mold and control of heat dissipation. As a rule, massive (thick) casting units are located in the upper part of the mold. This makes it possible to compensate for the reduction in their volume during hardening directly from the profits installed above them. The regulation of the intensity of heat removal in order to create directional solidification is carried out by cooling or insulating various sections of the mold. To locally increase heat removal, inserts from heat-conducting cuprum are widely used, they provide for an increase in the cooling surface of the mold due to fins, local cooling of the molds with compressed air or water is carried out. To reduce the intensity of heat removal, a layer of paint 0.1–0.5 mm thick is applied to the working surface of the mold. For this purpose, a layer of paint 1-1.5 mm thick is applied to the surface of the sprue channels and profits. The slowdown in the cooling of the metal in the risers can also be achieved by local thickening of the mold walls, the use of various low-heat-conductive coatings and the insulation of the risers with an asbestos sticker. The coloring of the working surface of the mold improves appearance castings, contributes to the elimination of gas shells on their surface and increases the resistance of molds. Before painting, the molds are heated to 100-120 °C. An excessively high heating temperature is undesirable, since this reduces the rate of solidification of the castings and the duration deadline mold service. Heating reduces the temperature difference between the casting and the mold and the expansion of the mold due to its heating by the casting metal. As a result, the tensile stresses in the casting, which cause cracks, are reduced. However, heating the mold alone is not enough to eliminate the possibility of cracking. It is necessary to timely remove the casting from the mold. The casting should be removed from the mold before the moment when its temperature equals the temperature of the mold, and the shrinkage stresses reach the maximum value. Usually, the casting is removed at the moment when it is strong enough that it can be moved without destruction (450-500 ° C). By this time, the gating system has not yet acquired sufficient strength and is destroyed by light impacts. The holding time of the casting in the mold is determined by the rate of solidification and depends on the temperature of the metal, the temperature of the mold, and the rate of pouring.

To eliminate metal sticking, increase service life and facilitate extraction, metal rods are lubricated during operation. The most common lubricant is a water-graphite suspension (3-5% graphite).

Parts of the molds that perform the external outlines of the castings are made of gray cast iron. The wall thickness of the molds is assigned depending on the wall thickness of the castings in accordance with the recommendations of GOST 16237-70. Internal cavities in castings are made using metal (steel) and sand rods. Sand rods are used to decorate complex cavities that cannot be made with metal rods. To facilitate the extraction of castings from molds, the outer surfaces of the castings should have a casting slope of 30" to 3 ° towards the parting. Internal surfaces castings made with metal rods must have a slope of at least 6 °. In castings, sharp transitions from thick to thin sections are not allowed. Curve radii must be at least 3 mm. Holes with a diameter of more than 8 mm for small castings, 10 mm for medium and 12 mm for large castings are made with rods. The optimal ratio of the hole depth to its diameter is 0.7-1.

Air and gases are removed from the mold cavity with the help of ventilation ducts placed in the parting plane and plugs placed in the walls near deep cavities.

In modern foundries, molds are installed on single-station or multi-station semi-automatic casting machines, in which the closing and opening of the mold, insertion and removal of cores, ejection and removal of the casting from the mold are automated. Automatic control of the mold heating temperature is also provided. Filling molds on machines is carried out using dispensers.

To improve the filling of thin mold cavities and remove air and gases released during the destruction of binders, the molds are evacuated, poured under low pressure or using centrifugal force.

Squeeze casting

Squeeze casting is a type of die casting. It is intended for the manufacture of large-sized castings (2500x1400 mm) of panel type with a wall thickness of 2-3 mm. For this purpose, metal half-moulds are used, which are mounted on specialized casting-squeezing machines with one-sided or two-sided convergence of the half-moulds. Distinctive feature This method of casting is the forced filling of the mold cavity with a wide melt flow when the half-moulds approach each other. There are no elements of a conventional gating system in the casting mold. Data This method is used to make castings from AL2, AL4, AL9, AL34 alloys, which have a narrow crystallization range.

The melt cooling rate is controlled by applying a heat-insulating coating of various thicknesses (0.05–1 mm) to the working surface of the mold cavity. Overheating of alloys before pouring should not exceed 15-20°C above the liquidus temperature. The duration of the convergence of the half-forms is 5-3 s.

Low pressure casting

Low pressure casting is another form of die casting. It has been used in the manufacture of large-sized thin-walled castings from aluminum alloys with a narrow crystallization interval (AL2, AL4, AL9, AL34). As in the case of mold casting, the outer surfaces of the castings are made with a metal mold, and the inner cavities are made with metal or sand cores.

For the manufacture of rods, a mixture consisting of 55% quartz sand 1K016A is used; 13.5% bold sand P01; 27% powdered quartz; 0.8% pectin glue; 3.2% resin M and 0.5% kerosene. Such a mixture does not form a mechanical burn. Forms are filled with metal by pressure of dried compressed air (18–80 kPa) supplied to the surface of the melt in a crucible heated to 720–750°C. Under the action of this pressure, the melt is forced out of the crucible into the metal wire, and from it into the gating system and further into the mold cavity. The advantage of low-pressure casting is the ability to automatically control the rate of metal rise in the mold cavity, which makes it possible to obtain thin-walled castings of better quality than gravity casting.

Crystallization of alloys in the mold is carried out under a pressure of 10–30 kPa until a solid metal crust is formed and 50–80 kPa after the formation of a crust.

Denser aluminum alloy castings are produced by low-pressure casting with back pressure. The filling of the mold cavity during casting with back pressure is carried out due to the pressure difference in the crucible and in the mold (10–60 kPa). Crystallization of the metal in the form is carried out under a pressure of 0.4-0.5 MPa. This prevents the release of hydrogen dissolved in the metal and the formation of gas pores. High blood pressure contributes better nutrition massive casting units. In other respects, back-pressure casting technology is no different from low-pressure casting technology.

Back pressure casting successfully combines the advantages of low pressure casting and pressure crystallization.

Injection molding

Die-casting from aluminum alloys AL2, ALZ, AL1, ALO, AL11, AL13, AL22, AL28, AL32, AL34, castings of complex configuration of the 1st-3rd accuracy classes with a wall thickness of 1 mm and more, cast holes with a diameter of up to 1, 2 mm, cast external and internal thread with a minimum pitch of 1 mm and a diameter of 6 mm. The surface cleanliness of such castings corresponds to 5-8 roughness classes. The production of such castings is carried out on machines with cold horizontal or vertical pressing chambers, with a specific pressing pressure of 30–70 MPa. Preference is given to machines with a horizontal bale chamber.

The dimensions and weight of the castings are limited by the capabilities of the Injection Molding Machines: the volume of the pressing chamber, the specific pressing pressure (p) and the locking force (0). The area of ​​projection (F) of the casting, the gate channels and the pressing chamber on the movable mold plate should not exceed the values ​​determined by the formula F = 0.85 0/r.

The optimum slope values ​​for outdoor surfaces are 45°; for internal 1°. The minimum radius of curvature is 0.5—1mm. Holes larger than 2.5 mm in diameter are made by casting. Castings from aluminum alloys, as a rule, are machined only along the seating surfaces. The processing allowance is assigned taking into account the dimensions of the casting and ranges from 0.3 to 1 mm.

Various materials are used to make molds. Parts of the molds in contact with the liquid metal are made of steel ZKh2V8, 4Kh8V2, 4KhV2S; steels 35, 45, 50, pins, bushings and guide columns - from U8A steel.

The supply of metal to the cavity of the molds is carried out using external and internal gating systems. The feeders are brought to the parts of the casting that are subjected to machining. Their thickness is assigned depending on the thickness of the wall of the casting at the point of supply and the given nature of the filling of the mold. This dependence is determined by the ratio of the Feeder thickness to the wall thickness of the casting. Smooth, without turbulence and air entrapment, the filling of molds takes place if the ratio is close to one. For castings with wall thickness up to 2 mm. feeders have a thickness of 0.8 mm; with a wall thickness of 3mm. the thickness of the feeders is 1.2 mm; with a wall thickness of 4-6 mm-2 mm.

To receive the first portion of the melt enriched with air inclusions, special wash tanks are located near the mold cavity, the volume of which can reach 20–40% of the casting volume. Washers are connected to the cavity of the mold by channels, the thickness of which is equal to the thickness of the feeders. The removal of air and gas from the cavity of the molds is carried out through special ventilation channels and gaps between the rods (pushers) and the mold matrix. Ventilation channels are made in the split plane on the fixed part of the mold, as well as along the movable rods and ejectors. The depth of the ventilation ducts when casting aluminum alloys is assumed to be 0.05-0.15 mm, and the width is 10-30 mm in order to improve ventilation, the cavity of the washers with thin channels (0.2-0.5 mm) is connected to the atmosphere .

The main defects of castings obtained by injection molding are air (gas) subcrustal porosity due to air entrapment at high speeds of metal inlet into the mold cavity, and shrinkage porosity (or shells) in thermal nodes. The formation of these defects is greatly influenced by the parameters of the casting technology, the pressing speed, the pressing pressure, and the thermal regime of the mold.

The pressing speed determines the mold filling mode. The higher the pressing speed, the faster the melt moves through the gating channels, the greater the melt inlet speed into the mold cavity. High pressing speeds contribute to better filling of thin and elongated cavities. At the same time, they are the cause of air capture by the metal and the formation of subcrustal porosity. When casting aluminum alloys, high pressing speeds are used only in the manufacture of complex thin-walled castings. The pressing pressure has a great influence on the quality of castings. As it increases, the density of castings increases.

The value of the pressing pressure is usually limited by the value of the locking force of the machine, which must exceed the pressure exerted by the metal on the movable matrix (pF). That's why big interest acquires local pre-pressing of thick-walled castings, known as the Ashigai process. The low rate of metal entry into the mold cavity through large-section feeders and the effective pre-pressing of the crystallizing melt with the help of a double plunger make it possible to obtain dense castings.

The quality of castings is also significantly affected by the temperatures of the alloy and the mold. In the manufacture of thick-walled castings of a simple configuration, the melt is poured at a temperature of 20–30 °C below the liquidus temperature. Thin-walled castings require the use of a melt superheated above the liquidus temperature by 10–15°C. To reduce the magnitude of shrinkage stresses and prevent the formation of cracks in castings, the molds are heated before pouring. The following heating temperatures are recommended:

Casting wall thickness, mm 1—2 2—3 3—5 5—8

Heating temperature

molds, °С 250—280 200—250 160—200 120—160

The stability of the thermal regime is provided by heating (electric) or cooling (water) molds.

To protect the working surface of the molds from sticking and erosive effects of the melt, to reduce friction during the extraction of the cores and to facilitate the extraction of castings, the molds are lubricated. For this purpose, fatty (oil with graphite or aluminum powder) or aqueous (salt solutions, aqueous preparations based on colloidal graphite) lubricants are used.

The density of castings from aluminum alloys increases significantly when casting with vacuum molds. To do this, the mold is placed in a sealed casing, in which the necessary vacuum is created. Good results can be obtained using the "oxygen process". To do this, the air in the cavity of the mold is replaced with oxygen. At high speeds of metal inlet into the mold cavity, which cause the capture of oxygen by the melt, subcrustal porosity in castings is not formed, since all the trapped oxygen is spent on the formation of finely dispersed aluminum oxides, which do not noticeably affect mechanical properties castings. Such castings can be subjected to heat treatment.

Depending on the requirements of technical specifications, castings from aluminum alloys can be subjected to various types of control: X-ray, gamma-ray flaw detection or ultrasonic to detect internal defects; markings for determining dimensional deviations; luminescent to detect surface cracks; hydro- or pneumocontrol to assess tightness. The frequency of the listed types of control is specified in the technical conditions or determined by the department of the chief metallurgist of the plant. Identified defects, if allowed by the technical specifications, are eliminated by welding or impregnation. Argon-arc welding is used for welding of underfills, shells, looseness of cracks. Before welding, the defective place is cut in such a way that the walls of the recesses have a slope of 30 - 42 °. Castings are subjected to local or general heating up to 300-350C. Local heating is carried out by an oxy-acetylene flame, general heating is carried out in chamber furnaces. Welding is carried out with the same alloys from which the castings are made, using a non-consumable tungsten electrode with a diameter of 2-6 mm at expense argon 5-12 l/min. The strength of the welding current is usually 25-40 A per 1 mm of the electrode diameter.

Porosity in castings is eliminated by impregnation with bakelite varnish, asphalt varnish, drying oil or liquid glass. Impregnation is carried out in special boilers under a pressure of 490-590 kPa with preliminary holding of castings in a rarefied atmosphere (1.3-6.5 kPa). The temperature of the impregnating liquid is maintained at 100°C. After impregnation, the castings are subjected to drying at 65-200°C, during which the impregnating liquid hardens, and repeated control.

Aluminum (Aluminum) is

Application of aluminum

Widely used as a structural material. The main advantages of aluminum in this capacity are lightness, ductility for stamping, corrosion resistance (in air, aluminum is instantly covered with a strong Al2O3 film, which prevents its further oxidation), high thermal conductivity, non-toxicity of its compounds. In particular, these properties have made aluminum extremely popular in the manufacture of cookware, aluminum foil in Food Industry and for packaging.

The main disadvantage of aluminum as a structural material is its low strength, therefore, to strengthen it, it is usually alloyed with a small amount of cuprum and magnesium (the alloy is called duralumin).

The electrical conductivity of aluminum is only 1.7 times less than that of cuprum, while aluminum is approximately 4 times cheaper per kilogram, but, due to 3.3 times lower density, to obtain equal resistance, it needs approximately 2 times less weight . Therefore, it is widely used in electrical engineering for the manufacture of wires, their shielding, and even in microelectronics for the manufacture of conductors in chips. The lower electrical conductivity of aluminum (37 1/ohm) compared to cuprum (63 1/ohm) is compensated by an increase in the cross section of aluminum conductors. The disadvantage of aluminum as an electrical material is the presence of a strong oxide film that makes soldering difficult.

Due to the complex of properties, it is widely used in thermal equipment.

Aluminum and its alloys retain strength at ultra-low temperatures. Because of this, it is widely used in cryogenic technology.

The high reflectivity combined with the low cost and ease of deposition makes aluminum an ideal material for making mirrors.

In the production of building materials as a gas-forming agent.

Aluminizing gives corrosion and scale resistance to steel and other alloys, such as piston engine valves, turbine blades, oil rigs, heat exchange equipment, and also replaces galvanizing.

Aluminum sulfide is used to produce hydrogen sulfide.

Research is underway to develop foamed aluminum as a particularly strong and lightweight material.

As a component of thermite, mixtures for aluminothermy

Aluminum is used to recover rare metals from their oxides or halides.

Aluminum is an important component of many alloys. For example, in aluminum bronzes, the main components are copper and aluminum. In magnesium alloys, aluminum is most often used as an additive. For the manufacture of spirals in electric heaters, Fechral (Fe, Cr, Al) is used (along with other alloys).

aluminum coffee" height="449" src="/pictures/investments/img920791_21_Klassicheskiy_italyanskiy_proizvoditel_kofe_iz_alyuminiya.jpg" title="(!LANG:21. Classic Italian aluminum coffee producer" width="376" />!}

When aluminum was very expensive, a variety of jewelry trade items were made from it. So, Napoleon III ordered aluminum buttons, and in 1889 Dmitry Ivanovich Mendeleev was presented with scales with bowls made of gold and aluminum. The fashion for them immediately passed when new technologies (developments) for its production appeared, which reduced the cost many times over. Now aluminum is sometimes used in the manufacture of jewelry.

In Japan, aluminum is used in the manufacture of traditional jewelry, replacing .

Aluminum and its compounds are used as a high performance propellant in bipropellant propellants and as a propellant in solid propellants. The following aluminum compounds are of the greatest practical interest as rocket fuel:

Powdered aluminum as a fuel in solid rocket propellants. It is also used in the form of powder and suspensions in hydrocarbons.

aluminum hydride.

aluminum borane.

Trimethylaluminum.

Triethylaluminum.

Tripropylaluminum.

Triethylaluminum (usually, together with triethylboron) is also used for chemical ignition (i.e., as a starting fuel) in rocket engines, as it ignites spontaneously in oxygen gas.

It has a slight toxic effect, but many water-soluble inorganic aluminum compounds remain in a dissolved state for a long time and can have a harmful effect on humans and warm-blooded animals through drinking water. The most toxic are chlorides, nitrates, acetates, sulfates, etc. For humans, the following doses of aluminum compounds (mg/kg of body weight) have a toxic effect when ingested:

aluminum acetate - 0.2-0.4;

aluminum hydroxide - 3.7-7.3;

aluminum alum - 2.9.

First of all, it acts on the nervous system (accumulates in the nervous tissue, leading to severe disorders of the central nervous system function). However, the neurotoxic property of aluminum began to be studied since the mid-1960s, since the accumulation of the metal in the human body is hindered by the mechanism of its excretion. Under normal conditions, up to 15 mg of an element per day can be excreted in the urine. Accordingly, the greatest negative effect is observed in people with impaired renal excretory function.

According to some biological studies, the intake of aluminum in the human body was considered a factor in the development of Alzheimer's disease, but these studies were later criticized and the conclusion about the connection of one with the other was refuted.

The chemical features of aluminum are determined by its high affinity for oxygen (in minerals aluminum is included in oxygen octahedra and tetrahedra), constant valence (3), poor solubility of most natural compounds. In endogenous processes during the solidification of magma and the formation of igneous rocks, aluminum enters the crystal lattice of feldspars, micas and other minerals - aluminosilicates. In the biosphere, aluminum is a weak migrant; it is scarce in organisms and the hydrosphere. In a humid climate, where the decaying remains of abundant vegetation form a lot of organic acids, aluminum migrates in soils and waters in the form of organomineral colloidal compounds; aluminum is adsorbed by colloids and precipitated in the lower part of soils. The connection of aluminum with silicon is partially broken and in some places in the tropics minerals are formed - aluminum hydroxides - boehmite, diaspore, hydrargillite. Most of the aluminum is part of the aluminosilicates - kaolinite, beidellite and other clay minerals. Weak mobility determines the residual accumulation of aluminum in the weathering crust of the humid tropics. As a result, eluvial bauxites are formed. In past geological epochs, bauxites also accumulated in lakes and the coastal zone of the seas of tropical regions (for example, sedimentary bauxites of Kazakhstan). In the steppes and deserts, where there is little living matter, and the waters are neutral and alkaline, aluminum almost does not migrate. The migration of aluminum is most vigorous in volcanic areas, where highly acidic river and underground waters rich in aluminum are observed. In places of displacement of acidic waters with alkaline - marine (at the mouths of rivers and others), aluminum is deposited with the formation of bauxite deposits.

Aluminum is part of the tissues of animals and plants; in the organs of mammals, from 10-3 to 10-5% of aluminum (per crude substance) was found. Aluminum accumulates in the liver, pancreas and thyroid glands. AT herbal products aluminum content ranges from 4 mg per 1 kg of dry matter (potato) to 46 mg (yellow turnip), in animal products - from 4 mg (honey) to 72 mg per 1 kg of dry matter (). In the daily human diet, the content of aluminum reaches 35-40 mg. Known organisms are aluminum concentrators, for example, club mosses (Lycopodiaceae), containing up to 5.3% aluminum in ash, mollusks (Helix and Lithorina), in whose ash 0.2-0.8% aluminum. Forming insoluble compounds with phosphates, aluminum disrupts the nutrition of plants (phosphate absorption by roots) and animals (phosphate absorption in the intestines).

The main purchaser is aviation. The most heavily loaded elements of the aircraft (skin, power reinforcing set) are made of duralumin. And they took this alloy into space. He even landed on the Moon and returned to Earth. And the stations "Luna", "Venus", "Mars", created by the designers of the bureau, which for many years was headed by Georgy Nikolayevich Babakin (1914-1971), could not do without aluminum alloys.

Alloys of the aluminum-manganese and aluminum-magnesium system (AMts and AMg) are the main material for the hulls of high-speed "rockets" and "meteors" - hydrofoils.

But aluminum alloys are used not only in space, aviation, sea and river transport. Aluminum occupies a strong position in land transport. The following data speaks of the widespread use of aluminum in the automotive industry. In 1948, 3.2 kg of aluminum was used per one, in 1958 - 23.6, in 1968 - 71.4, and today this figure exceeds 100 kg. Aluminum also appeared in railway transport. And the Russkaya Troika superexpress is more than 50% made of aluminum alloys.

Aluminum is being used more and more in construction. New buildings often use strong and lightweight beams, ceilings, columns, railings, railings, elements ventilation systems made of aluminum based alloys. In recent years, aluminum alloys have entered the construction of many public buildings, sports complexes. There are attempts to use aluminum as roofing material. Such a roof is not afraid of impurities of carbon dioxide, sulfur compounds, nitrogen compounds and other harmful impurities, which greatly enhance atmospheric corrosion of roofing iron.

As casting alloys, silumins are used - alloys of the aluminum-silicon system. Such alloys have good fluidity, give low shrinkage and segregation (heterogeneity) in castings, which makes it possible to obtain parts of the most complex configuration by casting, for example, engine cases, pump impellers, instrument cases, internal combustion engine blocks, pistons, cylinder heads and jackets piston engines.

Fight for decline cost aluminum alloys also met with success. For example, silumin is 2 times cheaper than aluminum. Usually, on the contrary, alloys are more expensive (to obtain an alloy, it is necessary to obtain a pure base, and then by alloying - an alloy). Soviet metallurgists at the Dnepropetrovsk Aluminum Plant in 1976 mastered the smelting of silumins directly from aluminosilicates.

Aluminum has long been known in electrical engineering. However, until recently, the scope of aluminum has been limited to power lines and, in rare cases, power cables. The cable industry was dominated by copper and lead. The conductive elements of the cable structure were made of cuprum, and the metal sheath was made of lead or lead-based alloys. For many decades (for the first time, lead sheaths for protecting cable cores were proposed in 1851) was the only metal material for cable sheaths. He is excellent in this role, but not without flaws - high density, low strength and scarcity; these are just the main ones that made a person look for other metals that can adequately replace lead.

They turned out to be aluminum. The beginning of his service in this role can be considered 1939, and work began in 1928. However, a serious shift in the use of aluminum in cable technology occurred in 1948, when the technology for manufacturing aluminum sheaths was developed and mastered.

Copper, too, for many decades was the only metal for the manufacture of current-carrying conductors. Studies of materials that could replace copper have shown that aluminum should and can be such a metal. So, instead of two metals, essentially different purposes, aluminum entered the cable technology.

This substitution has a number of advantages. Firstly, the possibility of using an aluminum shell as a neutral conductor is a significant savings in metal and weight reduction. Secondly, higher strength. Thirdly, facilitating installation, reducing transportation costs, reducing the cost of the cable, etc.

Aluminum wires are also used for overhead power lines. But it took a lot of effort and time to make an equivalent replacement. Many options have been developed, and they are used based on the specific situation. [Produced aluminum wires increased strength and increased creep resistance, which is achieved by alloying with magnesium up to 0.5%, silicon up to 0.5%, iron up to 0.45%, hardening and aging. Steel-aluminum wires are used, especially for the implementation of large spans required at the intersection of various obstacles with power lines. There are spans of more than 1500 m, for example, when crossing rivers.

Aluminum in transfer technology electricity over long distances, they are used not only as a conductor material. A decade and a half ago, aluminum-based alloys began to be used for the manufacture of power transmission towers. They were first built in our country in the Caucasus. They are about 2.5 times lighter than steel and do not require corrosion protection. Thus, the same metal replaced iron, copper and lead in electrical engineering and electricity transmission technology.

And so or almost so it was in other areas of technology. Tanks, pipelines and other assembly units made of aluminum alloys have proven themselves well in the oil, gas and chemical industries. They have supplanted many corrosion-resistant metals and materials, such as iron-carbon alloy containers enameled inside to store aggressive liquids (a crack in the enamel layer of this expensive design could lead to losses or even an accident).

Over 1 million tons of aluminum is spent annually in the world for the production of foil. The thickness of the foil, depending on its purpose, is in the range of 0.004-0.15 mm. Its application is extremely varied. It is used for packaging various food and industrial products - chocolate, sweets, medicines, cosmetics, photographic products, etc.

Foil is also used as a structural material. There is a group of gas-filled plastics - honeycomb plastics - cellular materials with a system of regularly repeating regular cells. geometric shape, the walls of which are made of aluminum foil.

Encyclopedia of Brockhaus and Efron

ALUMINUM- (clay) chem. zn. AL; at. in. = 27.12; beats in. = 2.6; m.p. about 700°. Silvery white, soft, sonorous metal; is in combination with silicic acid the main integral part clays, feldspar, micas; found in all soils. Goes to…… Dictionary of foreign words of the Russian language

ALUMINUM- (symbol Al), silver-white metal, element of the third group periodic table. It was first obtained in pure form in 1827. The most common metal in the crust of the globe; its main source is bauxite ore. Process… … Scientific and technical encyclopedic dictionary

ALUMINUM- ALUMINUM, Aluminum (chemical sign A1, at. weight 27.1), the most common metal on the surface of the earth and, after O and silicon, the most important component of the earth's crust. A. occurs in nature, mainly in the form of silicic acid salts (silicates); ... ... Big Medical Encyclopedia

Aluminum- is a bluish-white metal, characterized by particular lightness. It is very ductile and can be easily rolled, drawn, forged, stamped, and cast, etc. Like other soft metals, aluminum also lends itself very well to ... ... Official terminology

Aluminum- (Aluminium), Al, a chemical element of group III of the periodic system, atomic number 13, atomic mass 26.98154; light metal, mp660 °С. The content in the earth's crust is 8.8% by weight. Aluminum and its alloys are used as structural materials in ... ... Illustrated Encyclopedic Dictionary

ALUMINUM- ALUMINUM, aluminum male., chem. alkali metal clays, alumina base, clays; as well as the basis of rust, iron; and yari copper. Aluminite male. an alum-like fossil, hydrous alumina sulphate. Alunit husband. fossil, very close to ... ... Dictionary Dalia

aluminum- (silver, light, winged) metal Dictionary of Russian synonyms. aluminum n., number of synonyms: 8 clays (2) … Synonym dictionary

ALUMINUM- (lat. Aluminum from alumen alum), Al, a chemical element of group III of the periodic system, atomic number 13, atomic mass 26.98154. Silvery white metal, light (2.7 g/cm³), ductile, with high electrical conductivity, mp 660 .C.… … Big Encyclopedic Dictionary

Aluminum- Al (from lat. alumen the name of alum, used in ancient times as a mordant in dyeing and tanning * a. aluminium; n. Aluminium; f. aluminium; and. aluminio), chem. group III element periodic. Mendeleev systems, at. n. 13, at. m. 26.9815 ... Geological Encyclopedia

ALUMINUM- ALUMINUM, aluminum, pl. no, husband. (from lat. alumen alum). Silvery white malleable light metal. Explanatory Dictionary of Ushakov. D.N. Ushakov. 1935 1940 ... Explanatory Dictionary of Ushakov

Lesson Objectives: consider the distribution of aluminum in nature, its physical and chemical properties, as well as the properties of the compounds it forms.

Progress

2. Learning new material. Aluminum

The main subgroup of group III of the periodic system is boron (B), aluminum (Al), gallium (Ga), indium (In) and thallium (Tl).

As can be seen from the above data, all these elements were discovered in the 19th century.

Discovery of metals of the main subgroup III groups

1806	1825	1875	1863	1861
G. Lussac,	G.H. Oersted	L. de Boisbaudran	F. Reich,	W. Crooks
L. Tenard	(Denmark)	(France)	I. Richter	(England)
(France)			(Germany)

Boron is a nonmetal. Aluminum is a transition metal, while gallium, indium and thallium are full metals. Thus, with an increase in the atomic radii of the elements of each group of the periodic system, the metallic properties of simple substances increase.

In this lecture, we will take a closer look at the properties of aluminum.

Download:

Preview:

MUNICIPAL BUDGET EDUCATIONAL INSTITUTION

GENERAL EDUCATIONAL SCHOOL № 81

Aluminum. The position of aluminum in the periodic system and the structure of its atom. Finding in nature. Physical and chemical properties of aluminum.

chemistry teacher

MBOU secondary school №81

2013

Lesson topic: Aluminum. The position of aluminum in the periodic system and the structure of its atom. Finding in nature. Physical and chemical properties of aluminum.

Lesson Objectives: consider the distribution of aluminum in nature, its physical and chemical properties, as well as the properties of the compounds it forms.

Progress

1. Organizational moment of the lesson.

2. Learning new material. Aluminum

The main subgroup of group III of the periodic system is boron (B),aluminum (Al), gallium (Ga), indium (In) and thallium (Tl).

As can be seen from the above data, all these elements were discovered in the 19th century.

Discovery of metals of the main subgroup of group III

1806	1825	1875	1863	1861
G. Lussac,	G.H. Oersted	L. de Boisbaudran	F. Reich,	W. Crooks
L. Tenard	(Denmark)	(France)	I. Richter	(England)
(France)			(Germany)

Boron is a nonmetal. Aluminum is a transition metal, while gallium, indium and thallium are full metals. Thus, with an increase in the atomic radii of the elements of each group of the periodic system, the metallic properties of simple substances increase.

In this lecture, we will take a closer look at the properties of aluminum.

1. The position of aluminum in the table of D. I. Mendeleev. The structure of the atom, the oxidation states shown.

The element aluminum is located in group III, main “A” subgroup, 3rd period of the periodic system, serial number No. 13, relative atomic mass Ar (Al) \u003d 27. Its neighbor on the left in the table is magnesium - a typical metal, and on the right - silicon - already a non-metal . Therefore, aluminum must exhibit properties of some intermediate nature and its compounds are amphoteric.

Al +13) 2 ) 8 ) 3 , p is an element,

Basic state 1s 2 2s 2 2p 6 3s 2 3p 1
excited state 1s 2 2s 2 2p 6 3s 1 3p 2

Aluminum exhibits an oxidation state of +3 in compounds:

Al 0 - 3 e - → Al +3

2. Physical properties

Free form aluminum is a silvery-white metal with high thermal and electrical conductivity. Melting point 650 about C. Aluminum has a low density (2.7 g/cm 3 ) - about three times less than that of iron or copper, and at the same time it is a durable metal.

3. Being in nature

In terms of prevalence in nature, it occupies1st among metals and 3rd among elementssecond only to oxygen and silicon. The percentage of aluminum content in the earth's crust, according to various researchers, ranges from 7.45 to 8.14% of the mass of the earth's crust.

In nature, aluminum occurs only in compounds(minerals).

Some of them:

Bauxites - Al 2 O 3 H 2 O (with impurities SiO 2, Fe 2 O 3, CaCO 3)

Nephelines - KNa 3 4

Alunites - KAl(SO 4 ) 2 2Al(OH) 3

Alumina (mixtures of kaolins with sand SiO 2 , limestone CaCO 3 , magnesite MgCO 3 )

Corundum - Al 2 O 3

Feldspar (orthoclase) - K 2 O × Al 2 O 3 × 6 SiO 2

Kaolinite - Al 2 O 3 ×2SiO 2 × 2H 2 O

Alunite - (Na,K) 2 SO 4 × Al 2 (SO 4 ) 3 × 4Al (OH) 3

Beryl - 3BeO Al 2 O 3 6SiO 2

Bauxite
Al2O3	Corundum
	Ruby
	Sapphire

4. Chemical properties of aluminum and its compounds

Aluminum easily interacts with oxygen under normal conditions and is covered with an oxide film (it gives a matte appearance).

Its thickness is 0.00001 mm, but thanks to it, aluminum does not corrode. To study the chemical properties of aluminum, the oxide film is removed. (Using sandpaper, or chemically: first by dipping into an alkali solution to remove the oxide film, and then into a solution of mercury salts to form an aluminum-mercury alloy - an amalgam).

I. Interaction with simple substances

Aluminum already at room temperature actively reacts with all halogens, forming halides. When heated, it interacts with sulfur (200 °C), nitrogen (800 °C), phosphorus (500 °C) and carbon (2000 °C), with iodine in the presence of a catalyst - water:

2Al + 3S \u003d Al 2 S 3 (aluminum sulfide),

2Al + N 2 = 2AlN (aluminum nitride),

Al + P = AlP (aluminum phosphide),

4Al + 3C \u003d Al 4 C 3 (aluminum carbide).

2 Al + 3 I 2 = 2 AlI 3 (aluminum iodide)

All these compounds are completely hydrolyzed with the formation of aluminum hydroxide and, accordingly, hydrogen sulfide, ammonia, phosphine and methane:

Al 2 S 3 + 6H 2 O \u003d 2Al (OH) 3 + 3H 2 S

Al 4 C 3 + 12H 2 O \u003d 4Al (OH) 3 + 3CH 4

In the form of shavings or powder, it burns brightly in air, releasing a large amount of heat:

4Al + 3O 2 = 2Al 2 O 3 + 1676 kJ.

II. Interaction with complex substances

Interaction with water:

2 Al + 6 H 2 O \u003d 2 Al (OH) 3 + 3 H 2

without oxide film

Interaction with metal oxides:

Aluminum is a good reducing agent, as it is one of the active metals. It is in the activity series right after the alkaline earth metals. That's whyrestores metals from their oxides. Such a reaction - aluminothermy - is used to obtain pure rare metals, such as tungsten, vanadium, etc.

3 Fe 3 O 4 + 8 Al \u003d 4 Al 2 O 3 + 9 Fe + Q

Thermite mixture Fe 3 O 4 and Al (powder) - also used in thermite welding.

Cr 2 O 3 + 2Al \u003d 2Cr + Al 2 O 3

Interaction with acids:

With sulfuric acid solution: 2 Al + 3 H 2 SO 4 \u003d Al 2 (SO 4) 3 + 3 H 2

It does not react with cold concentrated sulfuric and nitrogenous (passivates). Therefore, nitric acid is transported in aluminum tanks. When heated, aluminum is able to reduce these acids without releasing hydrogen:

2Al + 6H 2 SO 4 (conc) \u003d Al 2 (SO 4) 3 + 3SO 2 + 6H 2 O,

Al + 6HNO 3 (conc) \u003d Al (NO 3) 3 + 3NO 2 + 3H 2 O.

Interaction with alkalis.

2 Al + 2 NaOH + 6 H 2 O \u003d 2 NaAl (OH) 4 + 3 H 2

Na [Al (OH) 4] - sodium tetrahydroxoaluminate

At the suggestion of the chemist Gorbov, during the Russo-Japanese War, this reaction was used to produce hydrogen for balloons.

With salt solutions:

2Al + 3CuSO 4 \u003d Al 2 (SO 4) 3 + 3Cu

If the surface of aluminum is rubbed with mercury salt, then the following reaction occurs:

2Al + 3HgCl 2 = 2AlCl 3 + 3Hg

The released mercury dissolves the aluminum, forming an amalgam.

5. Application of aluminum and its compounds

The physical and chemical properties of aluminum have led to its widespread use in technology.The aviation industry is a major consumer of aluminum.: 2/3 aircraft is made of aluminum and its alloys. An aircraft made of steel would be too heavy and could carry far fewer passengers.Therefore, aluminum is called the winged metal.Cables and wires are made from aluminum: with the same electrical conductivity, their mass is 2 times less than the corresponding copper products.

Considering the corrosion resistance of aluminum, itmanufacture parts of apparatuses and containers for nitric acid. Aluminum powder is the basis for the manufacture of silver paint to protect iron products from corrosion, as well as to reflect heat rays, such paint is used to cover oil storage facilities and firefighters' suits.

Aluminum oxide is used to produce aluminum and also as a refractory material.

Aluminum hydroxide is the main component of the well-known drugs Maalox, Almagel, which lower the acidity of gastric juice.

Aluminum salts are highly hydrolyzed. This property is used in the process of water purification. Aluminum sulfate and a small amount of slaked lime are added to the water to be purified to neutralize the resulting acid. As a result, a volumetric precipitate of aluminum hydroxide is released, which, settling, takes with it suspended particles of turbidity and bacteria.

Thus, aluminum sulfate is a coagulant.

6. Obtaining aluminum

1) The modern cost-effective method for producing aluminum was invented by the American Hall and the Frenchman Héroux in 1886. It consists in the electrolysis of a solution of aluminum oxide in molten cryolite. Molten cryolite Na 3 AlF 6 dissolves Al 2 O 3, how water dissolves sugar. The electrolysis of a "solution" of aluminum oxide in molten cryolite proceeds as if cryolite were only a solvent, and aluminum oxide was an electrolyte.

2Al 2 O 3 electric current → 4Al + 3O 2

In the English Encyclopedia for Boys and Girls, an article about aluminum begins with the following words: “On February 23, 1886, a new metal age began in the history of civilization - the age of aluminum. On this day, Charles Hall, a 22-year-old chemist, showed up in his first teacher's laboratory with a dozen small balls of silvery-white aluminum in his hand, and with the news that he had found a way to manufacture this metal cheaply and in large quantities". So Hall became the founder of the American aluminum industry and an Anglo-Saxon national hero, as a man who made a great business out of science.

2) 2Al 2 O 3 + 3 C \u003d 4 Al + 3 CO 2

IT IS INTERESTING:

• Metallic aluminum was first isolated in 1825 by the Danish physicist Hans Christian Oersted. By passing gaseous chlorine through a layer of hot alumina mixed with coal, Oersted isolated aluminum chloride without the slightest trace of moisture. To restore metallic aluminum, Oersted needed to treat aluminum chloride with potassium amalgam. After 2 years, the German chemist Friedrich Wöller. He improved the method by replacing potassium amalgam with pure potassium.
• In the 18th and 19th centuries, aluminum was the main jewelry metal. In 1889, in London, D.I. Mendeleev was awarded a valuable gift for his services to the development of chemistry - scales made of gold and aluminum.
• By 1855, the French scientist Saint-Clair Deville had developed a process for producing aluminum metal on an industrial scale. But the method was very expensive. Deville enjoyed the special patronage of Napoleon III, Emperor of France. As a sign of his devotion and gratitude, Deville made for Napoleon's son, the newborn prince, an elegantly engraved rattle - the first "consumer product" made of aluminum. Napoleon even intended to equip his guardsmen with aluminum cuirasses, but the price was prohibitive. At that time, 1 kg of aluminum cost 1000 marks, i.e. 5 times more expensive than silver. It wasn't until the invention of the electrolytic process that aluminum became as valuable as conventional metals.
• Did you know that aluminum, entering the human body, causes disorder nervous system. With its excess, metabolism is disturbed. And protective agents are vitamin C, calcium, zinc compounds.
• When aluminum burns in oxygen and fluorine, a lot of heat is released. Therefore, it is used as an additive to rocket fuel. The Saturn rocket burns 36 tons of aluminum powder during its flight. The idea of ​​using metals as a component of rocket fuel was first proposed by F.A. Zander.

3. Consolidation of the studied material

No. 1. To obtain aluminum from aluminum chloride, calcium metal can be used as a reducing agent. Make an equation for this chemical reaction, characterize this process using electronic balance.
Think! Why can't this reaction be carried out in an aqueous solution?

No. 2. Complete the equations of chemical reactions:
Al+H 2 SO 4 (solution) ->
Al + CuCl 2 ->
Al + HNO 3 (conc) - t ->
Al + NaOH + H 2 O ->

Number 3. Solve the problem:
An aluminum-copper alloy was exposed to an excess of concentrated sodium hydroxide solution while being heated. 2.24 liters of gas (n.o.s.) were released. Calculate the percentage composition of the alloy if its total mass was 10 g?

4. Homework slide 2

AL Element III (A) of the table group D.I. Mendeleev Element with serial number 13, its Element of the 3rd period The third most common in the earth's crust, the name is derived from lat. "Aluminis" - alum

Danish physicist Hans Oersted (1777-1851) For the first time, aluminum was obtained by him in 1825 by the action of potassium amalgam on aluminum chloride, followed by distillation of mercury.

Modern production of aluminum The modern production method was developed independently by the American Charles Hall and the Frenchman Paul Héroux in 1886. It consists in dissolving alumina in a cryolite melt followed by electrolysis using consumable coke or graphite electrodes.

As a student at Oberlin College, he learned that you can get rich and get the gratitude of mankind if you invent a way to produce aluminum on an industrial scale. Like a man possessed, Charles conducted experiments on the production of aluminum by electrolysis of a cryolite-alumina melt. On February 23, 1886, a year after graduating from college, Charles produced the first aluminum by electrolysis. Hall Charles (1863 - 1914) American chemical engineer

Paul Héroux (1863-1914) - French chemical engineer In 1889 he opened an aluminum plant in Fron (France), becoming its director, he designed an electric arc furnace for steel smelting, named after him; he also developed an electrolytic method for producing aluminum alloys

8 Aluminum 1. From the history of the discovery Main Next During the discovery of aluminum, the metal was more expensive than gold. The British wanted to honor the great Russian chemist D.I. Mendeleev with a rich gift, they gave him a chemical balance, in which one cup was made of gold, the other - of aluminum. A cup made of aluminum has become more expensive than gold. The resulting "silver from clay" interested not only scientists, but also industrialists and even the emperor of France. Further

9 Aluminum 7. Content in the earth's crust main Next

Finding in nature The most important aluminum mineral today is bauxite. The main chemical component of bauxite is alumina (Al 2 O 3) (28 - 80%).

11 Aluminum 4. Physical properties Color - silver-white t pl. = 660 °C. t b.p. ≈ 2450 °C. Electrically conductive, thermally conductive Lightweight, density ρ = 2.6989 g/cm 3 Soft, ductile. home Next

12 Aluminum 7. Found in nature Bauxite – Al 2 O 3 Alumina – Al 2 O 3 main Next

13 Aluminum main Insert the missing words Aluminum is an element of group III, the main subgroup. The charge of the nucleus of an aluminum atom is +13. There are 13 protons in the nucleus of an aluminum atom. There are 14 neutrons in the nucleus of an aluminum atom. There are 13 electrons in an aluminum atom. The aluminum atom has 3 energy levels. The electron shell has a structure of 2e, 8e, 3e. At the outer level, there are 3 electrons in an atom. The oxidation state of an atom in compounds is +3. The simple substance aluminum is a metal. Aluminum oxide and hydroxide are amphoteric in nature. Further

14 Aluminum 3 . The structure of a simple substance Metal Bond - metallic Crystal lattice - metallic, cubic face-centered main More

15 Aluminum 2. Electronic structure 27 A l +13 0 2e 8e 3e P + = 13 n 0 = 14 e - = 13 1 s 2 2 s 2 2p 6 3s 2 3p 1 Short electronic record 1 s 2 2 s 2 2p 6 3s 2 3p 1 Filling order main Next

Aluminum \u003d 2AlCl 3 4Al + 3C \u003d Al 4 C 3 C non-metals (with halogens, with carbon) (Remove the oxide film) 2 Al + 6 H 2 O \u003d 2Al (OH) 2 + H 2 C with water 2 Al + 6 HCl \u003d 2AlCl 3 + H 2 2Al + 3H 2 SO 4 \u003d Al 2 (SO 4) 3 + H 2 C acids and 2 Al + 6NaOH + 6H 2 O \u003d 2Na 3 [Al (OH ) 6] + 3H 2 2Al + 2NaOH + 2H 2 O \u003d 2NaAlO 2 + 3H 2 C with alkalis and 8Al + 3Fe 3 O 4 \u003d 4Al 2 O 3 + 9Fe 2Al + WO 3 \u003d Al 2 O 3 + W C oxi d a m e t a l l

17 Aluminum 8. Obtaining 1825 H. Oersted: AlCl 3 + 3K = 3KCl + Al: Electrolysis (t pl. = 2050 ° C): 2Al 2 O 3 = 4 Al + 3O 2 Electrolysis (in melting cryolite Na 3 AlF 6, t pl ≈ 1000 ° С): 2Al 2 O 3 \u003d 4 Al + 3O 2 main Next

Natural aluminum consists of one nuclide 27Al. The configuration of the outer electron layer is 3s2p1. In almost all compounds, the oxidation state of aluminum is +3 (valency III).

The radius of the neutral aluminum atom is 0.143 nm, the radius of the Al3+ ion is 0.057 nm. The sequential ionization energies of a neutral aluminum atom are 5.984, 18.828, 28.44, and 120 eV, respectively. On the Pauling scale, the electronegativity of aluminum is 1.5.

The simple substance aluminum is a soft, light, silvery-white metal.

Properties

Aluminum is a typical metal, the crystal lattice is face-centered cubic, parameter a = 0.40403 nm. The melting point of pure metal is 660°C, the boiling point is about 2450°C, the density is 2.6989 g/cm3. The temperature coefficient of linear expansion of aluminum is about 2.5·10-5 K-1 Standard electrode potential Al 3+/Al is 1.663V.

Chemically, aluminum is a fairly active metal. In air, its surface is instantly covered with a dense film of Al 2 O 3 oxide, which prevents further access of oxygen (O) to the metal and leads to the termination of the reaction, which leads to high anti-corrosion properties of aluminum. A protective surface film on aluminum is also formed if it is placed in concentrated nitric acid.

Aluminum actively reacts with other acids:

6HCl + 2Al \u003d 2AlCl 3 + 3H 2,

3H 2 SO 4 + 2Al \u003d Al 2 (SO 4) 3 + 3H 2.

Aluminum reacts with alkali solutions. First, the protective oxide film is dissolved:

Al 2 O 3 + 2NaOH + 3H 2 O \u003d 2Na.

Then the reactions take place:

2Al + 6H 2 O \u003d 2Al (OH) 3 + 3H 2,

NaOH + Al (OH) 3 \u003d Na,

or in total:

2Al + 6H 2 O + 2NaOH \u003d Na + 3H 2,

and as a result, aluminates are formed: Na - sodium aluminate (Na) (sodium tetrahydroxoaluminate), K - potassium aluminate (K) (potassium tetrahydroxoaluminate) or others. Since the aluminum atom in these compounds is characterized by a coordination number of 6, not 4 , then the actual formulas of these tetrahydroxo compounds are as follows:

Na and K.

When heated, aluminum reacts with halogens:

2Al + 3Cl 2 \u003d 2AlCl 3,

2Al + 3Br 2 = 2AlBr 3 .

Interestingly, the reaction between aluminum and iodine (I) powders begins at room temperature, if a few drops of water are added to the initial mixture, which in this case plays the role of a catalyst:

2Al + 3I 2 = 2AlI 3 .

The interaction of aluminum with sulfur (S) when heated leads to the formation of aluminum sulfide:

2Al + 3S \u003d Al 2 S 3,

which is easily decomposed by water:

Al 2 S 3 + 6H 2 O \u003d 2Al (OH) 3 + 3H 2 S.

Aluminum does not interact directly with hydrogen (H), however, indirectly, for example, using organoaluminum compounds, it is possible to synthesize a solid polymeric aluminum hydride (AlH 3) x - the strongest reducing agent.

In the form of a powder, aluminum can be burned in air, and a white refractory powder of aluminum oxide Al 2 O 3 is formed.

The high bond strength in Al 2 O 3 determines the high heat of its formation from simple substances and the ability of aluminum to restore many metals from their oxides, for example:

3Fe 3 O 4 + 8Al = 4Al 2 O 3 + 9Fe and even

3CaO + 2Al \u003d Al 2 O 3 + 3Ca.

This method of obtaining metals is called aluminothermy.

Amphoteric oxide Al 2 O 3 corresponds to amphoteric hydroxide - an amorphous polymer compound that does not have a constant composition. The composition of aluminum hydroxide can be conveyed by the formula xAl 2 O 3 yH 2 O, when studying chemistry at school, the formula of aluminum hydroxide is most often indicated as Al (OH) 3.

In the laboratory, aluminum hydroxide can be obtained in the form of a gelatinous precipitate by exchange reactions:

Al 2 (SO 4) 3 + 6NaOH \u003d 2Al (OH) 3 + 3Na 2 SO 4,

or by adding soda to an aluminum salt solution:

2AlCl 3 + 3Na 2 CO 3 + 3H 2 O \u003d 2Al (OH) 3 + 6NaCl + 3CO 2,

and also by adding an ammonia solution to an aluminum salt solution:

AlCl 3 + 3NH 3 H2O = Al(OH) 3 + 3H 2 O + 3NH 4 Cl.

Name and history of the discovery: Latin aluminum comes from the Latin alumen, meaning alum (aluminum and potassium sulfate (K) KAl (SO 4) 2 12H 2 O), which have long been used in leather dressing and as an astringent. Due to the high chemical activity, the discovery and isolation of pure aluminum dragged on for almost 100 years. The conclusion that "earth" (a refractory substance, in modern terms - aluminum oxide) can be obtained from alum was made back in 1754 by the German chemist A. Marggraf. Later it turned out that the same "earth" could be isolated from clay, and it was called alumina. It was only in 1825 that the Danish physicist H. K. Oersted could obtain metallic aluminum. He treated aluminum chloride AlCl 3 , which could be obtained from alumina, with potassium amalgam (an alloy of potassium (K) with mercury (Hg)) and, after distilling off mercury (Hg), isolated a gray powder of aluminum.

Only a quarter of a century later, this method was slightly modernized. The French chemist A. E. St. Clair Deville in 1854 suggested using metallic sodium (Na) to produce aluminum, and obtained the first ingots of the new metal. The cost of aluminum was then very high, and jewelry was made from it.

An industrial method for the production of aluminum by electrolysis of a melt of complex mixtures, including oxide, aluminum fluoride and other substances, was independently developed in 1886 by P. Eru (France) and C. Hall (USA). The production of aluminum is associated with a high consumption of electricity, so it was realized on a large scale only in the 20th century. In the Soviet Union, the first industrial aluminum was obtained on May 14, 1932 at the Volkhov aluminum plant, built next to the Volkhov hydroelectric power station.

>> Chemistry: Aluminum

Structure and properties of atoms. Aluminum Al is an element of the main subgroup of group III of the Periodic Table of D. I. Mendeleev. Atom aluminum contains three electrons at the external energy level, which it easily gives up during chemical interactions. The ancestor of the subgroup and the upper neighbor of aluminum, boron, has a smaller atomic radius (for boron it is 0.080 nm, for aluminum it is 0.143 nm). In addition, the aluminum atom has one intermediate eight-electron layer (2e-; 8e-; Ze-), which prevents the attraction of external electrons to the nucleus. Therefore, the reducing properties of aluminum atoms are much more pronounced than those of boron atoms, which exhibit non-metallic properties.

In almost all of its compounds, aluminum has an oxidation state of +3.

Aluminum is a simple substance. Silvery white light metal. Melts at 660 °C. It is very plastic, easily drawn into a wire and rolled into a foil 0.01 mm thick. It has very high electrical and thermal conductivity. It forms light and strong alloys with other metals.

What chemical reaction did he base the story on? sparklers» its author N. Nosov?

On what physical and chemical properties based on the use of aluminum and its alloys in technology?

Write in ionic form the equations of reactions between solutions of aluminum sulfate and potassium hydroxide with a deficiency and an excess of the latter.

Write the reaction equations for the following transformations: Al -> AlCl3 -> Al(0H)3 -> Al2O3 -> NaAl02 -> Al2(SO4)3 -> Al(OH)3 -> AlCl3 -> NaAlO2

Reactions involving electrolytes, write in ionic form. Consider the first reaction as a redox process.

Lesson content lesson summary support frame lesson presentation accelerative methods interactive technologies Practice tasks and exercises self-examination workshops, trainings, cases, quests homework discussion questions rhetorical questions from students Illustrations audio, video clips and multimedia photos, pictures graphics, tables, schemes humor, anecdotes, jokes, comics, parables, sayings, crossword puzzles, quotes Add-ons abstracts articles chips for inquisitive cheat sheets textbooks basic and additional glossary of terms other Improving textbooks and lessonscorrecting errors in the textbook updating a fragment in the textbook elements of innovation in the lesson replacing obsolete knowledge with new ones Only for teachers perfect lessons calendar plan for the year methodological recommendations of the discussion program Integrated Lessons

Chemical element of group III of the periodical system of Mendeleev.

Latin name— Aluminium.

Designation— Al.

atomic number — 13.

Atomic mass — 26,98154.

Density- 2.6989 g / cm 3.

Melting temperature- 660 °С.

Simple, light, paramagnetic metal of light gray or silvery white color. It has high thermal and electrical conductivity, corrosion resistance. Distribution in the earth's crust - 8.8% by mass - it is the most common metal and the third most common chemical element.

It is used as a structural material in the construction of buildings, aircraft and shipbuilding, for the manufacture of conductive products in electrical engineering, chemical equipment, consumer goods, the production of other metals using aluminothermy, as a component of solid rocket fuel, pyrotechnic compositions, and the like.

Metallic aluminum was first obtained by the Danish physicist Hans Christian Oersted.

In nature, it occurs exclusively in the form of compounds, as it has a high chemical activity. Forms a strong chemical bond with oxygen. Due to the reactivity, it is very difficult to obtain metal from ore. Now the Hall-Heroult method is used, which requires large amounts of electricity.

Aluminum forms alloys with almost all metals. The most famous are duralimium (an alloy with copper and magnesium) and silumin (an alloy with silicon). Under normal conditions, aluminum is covered with a strong oxide film, therefore it does not react with classical oxidizing agents water (H 2 O), oxygen (O 2) and nitric acid (HNO 3). Due to this, it is practically not subject to corrosion, which ensured its demand in the industry.

The name comes from the Latin "alumen", which means "alum".

The use of aluminum in medicine

traditional medicine

The role of aluminum in the body is not fully understood. It is known that its presence stimulates the growth of bone tissue, the development of epithelium and connective tissues. Under its influence, the activity of digestive enzymes increases. Aluminum is related to the recovery and regeneration processes of the body.

Aluminum is considered a toxic element for human immunity, but nevertheless, it is part of the cells. At the same time, it has the form of positively charged ions (Al3 +), which affect the parathyroid glands. AT different types cells, a different amount of aluminum is observed, but it is known for sure that the cells of the liver, brain and bones accumulate it faster than others.

Medicines with aluminum have analgesic and enveloping effects, antacid and adsorbent effects. The latter means that when interacting with hydrochloric acid, drugs can reduce the acidity of gastric juice. Aluminum is also prescribed for external use: in the treatment of wounds, trophic ulcers, acute conjunctivitis.

The toxicity of aluminum is manifested in its replacement of magnesium in the active centers of a number of enzymes. Its competitive relationship with phosphorus, calcium and iron also plays a role.

With a lack of aluminum, weakness in the limbs is observed. But such a phenomenon in the modern world is almost impossible, since the metal comes with water, food and through polluted air.

With an excess of aluminum in the body, changes in the lungs, convulsions, anemia, disorientation in space, apathy, and memory loss begin.

Ayurveda

Aluminum is considered to be poisonous and therefore should not be used for treatment. Just as you should not use aluminum utensils for preparing decoctions or storing herbs.

The use of aluminum in magic

Due to the difficulty of obtaining a pure element, the metal was used in magic along with it, jewelry was made from it. When the process of obtaining was simplified, the fashion for aluminum crafts immediately passed.

Protective Magic

Only aluminum foil is used, which has the properties of shielding energy flows, preventing them from spreading. Therefore, as a rule, objects are wrapped in it that can spread negative energy around them. Very often dubious magical gifts are wrapped in foil - wands, masks, daggers, especially those brought from Africa or Egypt.

They do the same with unknown objects thrown up, found in the yard or under the door. Instead of lifting it with your hands or through a cloth, it is better to cover it with foil without touching the object itself.

Sometimes foil is used as a protective screen for amulets and talismans that are not currently needed, but may be needed in the future.

Aluminum in astrology

Zodiac sign: Capricorn.