The concept of alloy, their classification and properties. To eliminate such large losses in mechanical engineering, parts are coated with varnishes, paints, chemically resistant metals, and oxide films.

The metallic state is explained by the electronic structure. Metal elements, entering into a chemical reaction with elements that are non-metals, give them their outer, so-called valence electrons. This is a consequence of the fact that in metals the outer electrons are loosely bound to the nucleus; in addition, there are few electrons on the outer shells (only 1-2), while non-metals have a lot of electrons (5-8).

All elements located to the left of gallindium and thallium are metals, and to the right of arsenic, antimony and bismuth are non-metals.

In technology, a non-metal is understood as substances that have a "metallic luster" and plasticity - characteristic properties.

In addition, all metals have high electrical and thermal conductivity.

The peculiarity of the structure of metallic substances is that they are all built mainly from light atoms, in which the outer electrons are weakly bound to the nucleus. This causes a special nature of the interaction of metal atoms and metallic properties. Metals are good conductors of electricity.

Of the known (by 1985) 106 chemical elements, 83 are metals.

Metal classification

Each metal differs in structure and properties from the other, however, according to some features, they can be combined into groups.

This classification was developed by the Russian scientist Gulyaev A.P. and may not coincide with the generally accepted.

All metals can be divided into two large groups - ferrous and non-ferrous metals.

Ferrous metals most often have a dark gray color, high density (except for alkaline earth), high melting point, relatively high hardness. The most typical metal of this group is iron.

Non-ferrous metals most often have a characteristic color: red, yellow and white. They have high plasticity, low hardness, relatively low melting point. The most typical element of this group is copper.

Ferrous metals, in turn, can be subdivided as follows:

1. Iron metals- iron, cobalt, nickel (the so-called ferromagnets) and manganese close to them in properties. Co, Ni, Mu are often used as additives to iron alloys, and also as a base for the corresponding alloys, similar in their properties to high-alloy steels.

2. Refractory metals, whose melting point is higher than that of iron (i.e., above 1539C). It is used as an additive to alloyed steels, and also as a base for the corresponding alloys. These include: Ti, V, Cr, Zr, Nb, Mo, Tc (technetium), Hf (hafium), Ta (tantalum), W, Re (rhenium).

3. Uranium metals- actinides, which are mainly used in alloys for nuclear power engineering. These include: Ac (actinium), Th (thorium), U (uranium), Np (neptunium), Pu (plutonium), Bk (berkelium), Cf (californium), Md (mendelevium), No (nobelium), etc. .

4. Rare earth metals(REM) - La(lanthanum), Ce(cerium), Nd(neodymium), Sm(sanarium), Eu(europium), Dy(dysprosium), Lu(lutetium), Y(yttrium), Sc(slandium), etc. ., united under the name of lanthanides. These metals have very similar chemical properties, but rather different physical properties (Typ., etc.). They are used as additives to alloys of other elements. Under natural conditions, they occur together and are difficult to separate into separate elements. Usually a mixed alloy is used - 40-45% Ce (cerium) and 40-45% of all other REMs.

5. Alkaline earth metals- in the free metallic state are not used, except for special cases, for example, coolants in nuclear reactors. Li(lithium), Na, K(potassium), Rb(rubidium), Cs(cesium), Fr(francium), Ca(calcium), Sr(strontium), Ba(barium), Ra(radium).

Non-ferrous metals are divided into:

1. Light metals - Be (beryllium), Mg (magnesium), Al (aluminum), which have a low density.

2. Noble metals - Ag (silver), Pt (platinum), Au (gold), Pd (palladium), Os (osmium), Ir (iridium), etc. Cu is a semi-noble metal. They have high corrosion resistance.

3. Low-melting metals - Zn (zinc), Cd (cadmium), Hg (mercury), Sn (tin), Bi (bismuth), Sb (antimony), Pb (lead), As (arsenic), In (indium) and etc., and elements with weakened metallic properties - Ga (gallium), Ge (germanium).

The use of metals began with copper, silver and gold. Since they are found in nature in a pure (native) form.

Later, metals began to be restored from ores - Sn, Pb, Fe, etc.

The most widely used in technology are alloys of iron with carbon: steel (0.025-2.14% C); cast iron (2.14-6.76% C); The reason for the widespread use of Fe-C alloys is due to a number of reasons: low cost, the best mechanical properties, the possibility of mass production and the high prevalence of Fe ores in nature.

More than 90% of the metals produced are steel.

Production of metals for 1980:

Iron - 718,000 thousand tons (in the USSR up to 150 million tons per year)

Manganese - > 10,000 thousand tons

Aluminum - 17,000 thousand tons

Copper - 9,400 thousand tons

Zinc - 6200 thousand tons

Tin - 5400 thousand tons

Nickel - 760 thousand tons

Magnesium - 370 thousand tons

Gold - > 1.2 thousand tons

The cost of metal is a factor in the possibility and expediency of its use. The table shows the relative cost of different metals (the cost of iron, more precisely, simple carbon steel, is taken as a unit).

noble metals:

Au, Ag, Pt and their alloys.

They got their name because of their high corrosion resistance. These metals are plastic. They have a high cost.

Used in jewelry and dentistry. Pure gold is not used because of its softness. To increase the hardness, gold is alloyed (other elements are added). Commonly used ternary alloys: Au - Ag - Cu.

The most common are alloys of 375, 583, 750 and 916 samples - this means that in these alloys per 1000 g of the alloy there are 375, 583, 750 and 916 g of gold, and the rest is copper, silver, the ratio of which can be various.

Alloys of the 916th sample are the softest, but also the most corrosion resistant. As the sample index decreases, the corrosion resistance decreases.

The highest hardness (hence wear resistance) is possessed by alloys of the 583rd sample, with a ratio of Cu and Ag of about 1:1.

The alloys of these samples have the color of gold.

Indian Bulat

The end of the 4th century BC, the troops of Alexander the Great first encountered unusual Indian steel during a campaign through Mesopotamia (Iraq) and Afghanistan to India.

"Chakra" - a heavy flat steel ring sharpened like a blade, spun on two fingers, and thrown at the enemy. It rotated at a terrible speed and cut off the heads of the Macedonians like the heads of flowers.

Sword parameters:

length - 80-100 cm

width at the crosshairs - 5-6 cm

thickness - 4 mm

weight - 1.2-1.8 kg

Blade properties:

High hardness, strength and at the same time high elasticity and viscosity. The blades freely cut nails and at the same time easily bent into an arc. Easily cut gas light handkerchiefs.

When assessing the quality of damask weapons, the drawing on the blade played an important role. In the pattern, the shape, size and color of the base metal (background) mattered.

The shape of the pattern is divided into striped, jet, wavy, mesh and cranked. The most highly valued cranked damask steel.

The damask blade was also tested for elasticity: it was placed on the head, after which both ends were pulled to the ears and released. After that, no permanent deformation was observed.

Real bulat was made by forging from cast steel with natural patterns.

Welding steel (fake)- obtained by forging pieces of wire twisted into a rope with different carbon content and therefore different hardness. After etching, a pattern appeared.

They also forged damask steel from sheets of sheet steel - up to 320 layers: or: scattered at different levels get a different pattern.

The Don Cossacks used weapons from all over the world - they captured them in battles. The weapons were made mainly by the craftsmen of the Caucasus.

Baltic Bulat:

Opened by Prof. Ivanov G.P., and Admiral Makarov S.O. found a new application: when testing armor plates

The plate easily made its way from the soft low-carbon side, then an armor-piercing projectile with a soft tip was invented:

Therefore, because of this, the old master blacksmiths sewed a soft strip on a very hard blade to pierce steel plate.

The production of damask steel is associated with traditions and secrets. It is very difficult to weld strips and rods of different composition to each other and provide the required properties: flexibility, hardness, sharpness of the blade. It is necessary to withstand the temperature, forging speed, the order of joining the strips, the removal of oxides, the application of fluxes.

Japanese Bulat

Japanese damask steel was harder and stronger than Damascus steel. This is due to the presence of molybdenum (Mo) in the composition of the steel. Mo is one of the few elements whose addition to steel causes an increase in its toughness and hardness at the same time. All other elements, increasing strength and hardness, increase fragility.

Production: smelted iron (with Mo) was forged into rods and hardened for 8-10 years in the ground. In the process of corrosion, particles enriched with harmful impurities were eaten out of the metal, falling out. The blanks looked like cheese with holes. Then the bars were carburized and forged repeatedly. The number of the thinnest layers reached several tens of thousands.

Steel materials, structures, parts must have high corrosion resistance. This is facilitated by the presence in the composition of steel: copper, Cr, Ni, especially phosphorus. (Example: weather-resistant low-carbon building steel - "corten" - has a noble color due to surface oxides. But this steel has increased brittleness, especially at low temperatures).

Corrosion is the most dangerous enemy of steel structures. According to scientists, to date, man has smelted at least 20 billion tons of iron and steel, 14 billion tons of this metal has been “eaten” by rust and dispersed in the biosphere…

Eiffel Tower - 1889 - it was predicted that it would stand for no more than 25 years (Eiffel considered 40 years for strength). The tower has been standing in Paris for over 100 years, but that's only because it's constantly covered in thick layers of paint. It takes 52 tons of paint to paint the tower. Its cost has long exceeded the cost of the building itself.

There are a large number of examples of steel and iron structures that do not corrode over time: beams in the Katav-Ivanovsk church, the railing of the stairs of the Fontanka River in Leningrad, an iron column in Delhi (1500 years old). Corrosion is resisted by surface oxides and high content of Cu and P, as well as by natural alloying.

Non-ferrous metals include all metals, except for iron and alloys based on it - steels and cast irons, which are called ferrous. Alloys based on non-ferrous metals are mainly used as structural materials with special properties: corrosion-resistant, bearing (having a low coefficient of friction), heat- and heat-resistant, etc.

There is no single system for marking non-ferrous metals and alloys based on them. In all cases, an alphanumeric system is adopted. The letters indicate that the alloys belong to a certain group, and the numbers in different groups of materials have different meanings. In one case, they indicate the degree of purity of the metal (for pure metals), in the other, the number of alloying elements, and in the third, they indicate the number of the alloy, which according to the state. the standard must comply with a certain composition or properties.
Copper and its alloys
Technical copper is marked with the letter M, after which there are numbers associated with the amount of impurities (show the degree of purity of the material). Copper grade M3 contains more impurities than M000. The letters at the end of the brand mean: k - cathodic, b - oxygen-free, p - deoxidized. The high electrical conductivity of copper determines its predominant use in electrical engineering as a conductor material. Copper is well deformed, well welded and soldered. Its disadvantage is poor machinability.
The main copper-based alloys are brass and bronze. In alloys based on copper, an alphanumeric system is adopted that characterizes the chemical composition of the alloy. Alloying elements are designated by the Russian letter corresponding to the initial letter of the element name. Moreover, often these letters do not coincide with the designation of the same alloying elements when marking steel. Aluminum - A; Silicon - K; Manganese - Mts; Copper - M; Nickel - H; Titanium -T; Phosphorus - F; Chrome -X; Beryllium - B; Iron - F; Magnesium - Mg; Tin - O; Lead - C; Zinc - C.
The procedure for marking cast and wrought brass is different.
Brass is an alloy of copper and zinc (Zn from 5 to 45%). Brass with a content of 5 to 20% zinc is called red (tompac), with a content of 20-36% Zn - yellow. In practice, brasses are rarely used, in which the zinc concentration exceeds 45%. Usually brass is divided into:
- two-component brass or simple, consisting only of copper, zinc and, in small quantities, impurities;
- multi-component brass or special - in addition to copper and zinc, there are additional alloying elements.
Deformable brass are marked according to GOST 15527-70.
The brand of simple brass consists of the letter "L", indicating the type of alloy - brass, and a two-digit number characterizing the average copper content. For example, grade L80 is brass containing 80% Cu and 20% Zn. All two-component brasses work well with pressure. They are supplied in the form of pipes and tubes of various section shapes, sheets, strips, tapes, wires and bars of various profiles. Brass products with high internal stress (for example, hard-worked) are prone to cracking. During long-term storage in air, longitudinal and transverse cracks form on them. To avoid this, before long-term storage, it is necessary to remove the internal stress by low-temperature annealing at 200-300 C.
In multicomponent brasses, after the letter L, a number of letters are written indicating which alloying elements, in addition to zinc, are included in this brass. Then numbers follow through hyphens, the first of which characterizes the average copper content in percent, and the subsequent ones characterize each of the alloying elements in the same sequence as in the letter part of the brand. The order of letters and numbers is established according to the content of the corresponding element: first comes the element, which is more, and then descending. The zinc content is determined by the difference from 100%.
Brass is mainly used as a deformable corrosion-resistant material. Sheets, pipes, rods, strips and some parts are made from them: nuts, screws, bushings, etc.
Cast brass are marked in accordance with GOST 1711-30. At the beginning of the brand, they also write the letter L (brass), after which they write the letter C, which means zinc, and a number indicating its content as a percentage. In alloyed brass, letters are additionally written corresponding to the introduced alloying elements, and the numbers following them indicate the percentage of these elements. The rest, missing up to 100%, corresponds to the content of copper. Cast brass is used for the manufacture of fittings and parts for shipbuilding, bushings, liners and bearings.
Bronzes (copper alloys with various elements, where zinc is not the main one). They, like brass, are divided into foundry and wrought. Marking of all bronzes begins with the letters Br, which means bronze for short.
In foundry bronzes, after Br, letters are written followed by numbers, which symbolically designate the elements introduced into the alloy (in accordance with Table 1), and the following numbers indicate the percentage of these elements. The rest (up to 100%) is copper. Sometimes, in some brands of foundry bronzes, the letter “L” is written at the end, which means foundry.
Most bronzes have good casting properties. They are used for various shaped castings. Most often they are used as a corrosion-resistant and anti-friction material: fittings, rims, bushings, gears, valve seats, worm wheels, etc. All copper-based alloys have high cold resistance.
Aluminum and alloys based on it
Aluminum is produced in the form of ingots, ingots, wire rod, etc. (primary aluminum) in accordance with GOST 11069-74 and in the form of a deformable semi-finished product (sheets, profiles, rods, etc.) in accordance with GOST 4784-74. According to the degree of contamination, both aluminum is divided into aluminum of special purity, high purity and technical purity. Primary aluminum according to GOST 11069-74 is marked with the letter A and a number by which the content of impurities in aluminum can be determined. Aluminum is well deformed, but poorly processed by cutting. It can be rolled into foil.

Alloys based on aluminum are divided into cast and wrought.
Aluminum-based casting alloys are marked according to GOST 1583-93. The brand reflects the main composition of the alloy. Most casting alloy grades begin with the letter A, which stands for aluminum alloy. Then letters and numbers are written, reflecting the composition of the alloy. In some cases, aluminum alloys are marked with the letters AL (which means cast aluminum alloy) and a number indicating the number of the alloy. The letter B at the beginning of the grade indicates that the alloy is high-strength.
The use of aluminum and alloys based on it is very diverse. Technical aluminum is mainly used in electrical engineering as a conductor of electric current, as a substitute for copper. Aluminum-based casting alloys are widely used in the refrigeration and food industries in the manufacture of complex-shaped parts (by various casting methods) that require increased corrosion resistance in combination with low density, for example, some compressor pistons, levers and other parts.
Wrought aluminum-based alloys are also widely used in food and refrigeration technology for the manufacture of various parts by pressure treatment, which are also subject to increased requirements for corrosion resistance and density: various containers, rivets, etc. An important advantage of all aluminum-based alloys is their high cold resistance.
Titanium and alloys based on it
Titanium and alloys based on it are marked in accordance with GOST 19807-74 according to the alphanumeric system. However, there is no pattern in the labeling. The only feature is the presence of the letter T in all brands, which indicates belonging to titanium. The numbers in the grade indicate the conditional number of the alloy.
Technical titanium is marked: VT1-00; VT1-0. All other grades refer to titanium-based alloys (VT16, AT4, OT4, PT21, etc.). The main advantage of titanium and its alloys is a good combination of properties: relatively low density, high mechanical strength and very high corrosion resistance (in many aggressive environments). The main disadvantage is the high cost and scarcity. These shortcomings hinder their use in food and refrigeration engineering.

Titanium alloys are used in rocket, aviation, chemical engineering, shipbuilding and transport engineering. They can be used at elevated temperatures up to 500-550 degrees. Products from titanium alloys are made by pressure treatment, but can also be made by casting. The composition of cast alloys usually corresponds to the composition of the wrought alloys. At the end of the cast alloy brand is the letter L.
Magnesium and alloys based on it
Due to its unsatisfactory properties, technical magnesium is not used as a structural material. Alloys based on magnesium in accordance with the state. The standard is divided into foundry and deformable.
Cast magnesium alloys in accordance with GOST 2856-79 are marked with the letters ML and a number that indicates the conditional number of the alloy. Sometimes lowercase letters are written after the number: pch - high purity; it is general purpose. Wrought magnesium alloys are marked in accordance with GOST 14957-76 with the letters MA and a number indicating the conditional number of the alloy. Sometimes after the number there may be lowercase letters pch, which means high purity.

Magnesium-based alloys, like aluminum-based alloys, have a good combination of properties: low density, increased corrosion resistance, relatively high strength (especially specific) with good technological properties. Therefore, both simple and complex parts are made from magnesium alloys, which require increased corrosion resistance: necks, gasoline tanks, fittings, pump housings, brake wheel drums, trusses, steering wheels and many other products.
Tin, lead and alloys based on them
Lead in its pure form is practically not used in food and refrigeration engineering. Tin is used in the food industry as a coating for food packaging (for example, tinning of cans). Tin is marked in accordance with GOST 860-75. There are grades O1pch; O1; O2; O3; O4. The letter O stands for tin, and the numbers - a conditional number. As the number increases, the amount of impurities increases. The letters pch at the end of the brand mean - high purity. In the food industry, tin is most often used for tinning canning sheets of grades O1 and O2.
Alloys based on tin and lead, depending on the purpose, are divided into two large groups: babbits and solders.
Babbits are complex alloys based on tin and lead, which additionally contain antimony, copper and other additives. They are marked according to GOST 1320-74 with the letter B, which means babbit, and a number that shows the tin content as a percentage. Sometimes, in addition to the letter B, there may be another letter that indicates special additives. For example, the letter H denotes the addition of nickel (nickel babbit), the letter C denotes lead babbit, etc. It should be borne in mind that it is impossible to determine its complete chemical composition by the brand of babbit. In some cases, the tin content is not even indicated, for example, in the BN grade, although it contains about 10% here. There are also tinless babbits (for example, lead-calcium), which are marked according to GOST 1209-78 and are not studied in this work.

Babbits are the best antifriction material and are mainly used in plain bearings.
Solders in accordance with GOST 19248-73 are divided into groups according to many criteria: according to the method of melting, according to the melting temperature, according to the main component, etc. According to the melting temperature, they are divided into 5 groups:

1. Particularly fusible (melting point tmelt ≤ 145 °C);

2. Low-melting (melting point tmelt > 145 °С ≤ 450 °С);

3. Medium-melting (melting point tmelt > 450 °С ≤ 1100 °С);

4. High-melting (melting point tmelt > 1100 °С ≤ 1850 °С);

5. Refractory (melting point tmelt > 1850 °C).

The first two groups are used for low-temperature (soft) soldering, the rest - for high-temperature (hard) soldering. According to the main component, solders are divided into: gallium, bismuth, tin-lead, tin, cadmium, lead, zinc, aluminum, germanium, magnesium, silver, copper-zinc, copper, cobalt, nickel, manganese, gold, palladium, platinum, titanium , iron, zirconium, niobium, molybdenum, vanadium.

The concept of alloy, their classification and properties.

In engineering, all metallic materials are called metals. These include simple metals and complex metals - alloys.

Simple metals consist of one basic element and a small amount of impurities of other elements. For example, commercially pure copper contains from 0.1 to 1% impurities of lead, bismuth, antimony, iron and other elements.

Alloys- these are complex metals, representing a combination of a simple metal (alloy base) with other metals or non-metals. For example, brass is an alloy of copper and zinc. Here the basis of the alloy is copper.

A chemical element that is part of a metal or alloy is called a component. In addition to the main component that prevails in the alloy, there are also alloying components introduced into the composition of the alloy to obtain the required properties. So, to improve the mechanical properties and corrosion resistance of brass, aluminum, silicon, iron, manganese, tin, lead and other alloying components are added to it.

According to the number of components, alloys are divided into two-component (double), three-component (triple), etc. In addition to the main and alloying components, the alloy contains impurities of other elements.

Most alloys are obtained by fusing components in a liquid state. Other ways of preparing alloys: sintering, electrolysis, sublimation. In this case, the substances are called pseudoalloys.

The ability of metals to mutually dissolve creates good conditions for obtaining a large number of alloys with a wide variety of combinations of useful properties that simple metals do not have.

Alloys are superior to simple metals in strength, hardness, machinability, etc. That is why they are used in technology much more widely than simple metals. For example, iron is a soft metal, almost never used in its pure form. But the most widely used in technology are iron-carbon alloys - steels and cast irons.

At the present stage of development of technology, along with an increase in the number of alloys and the complication of their composition, metals of special purity are of great importance. The content of the main component in such metals ranges from 99.999 to 99.999999999%
and more. Metals of high purity are needed by rocket science, nuclear, electronic and other new branches of technology.

Depending on the nature of the interaction of the components, alloys are distinguished:

1) mechanical mixtures;

2) chemical compounds;

3) solid solutions.

1) mechanical mixture two components is formed when they in the solid state do not dissolve in each other and do not enter into chemical interaction. Alloys - mechanical mixtures (for example, lead - antimony, tin - zinc) are heterogeneous in structure and represent a mixture of crystals of these components. In this case, the crystals of each component in the alloy completely retain their individual properties. That is why the properties of such alloys (for example, electrical resistance, hardness, etc.) are defined as the arithmetic mean of the magnitude of the properties of both components.

2) Solid solutions are characterized by the formation of a common spatial crystal lattice by the atoms of the base metal-solvent and the atoms of the soluble element.
The structure of such alloys consists of homogeneous crystalline grains, like a pure metal. There are substitution solid solutions and interstitial solid solutions.

Such alloys include brass, copper-nickel, iron-chromium, etc.

Alloys - solid solutions are the most common. Their properties differ from those of the constituent components. For example, the hardness and electrical resistance of solid solutions are much higher than those of pure components. Due to their high ductility, they lend themselves well to forging and other types of pressure treatment. The casting properties and machinability of solid solutions are low.

3) Chemical compounds, like solid solutions, are homogeneous alloys. When they solidify, a completely new crystal lattice is formed, which is different from the lattices of the components that make up the alloy. Therefore, the properties of a chemical compound are independent and do not depend on the properties of the components. Chemical compounds are formed at a strictly defined quantitative ratio of the alloyed components. The alloy composition of a chemical compound is expressed by a chemical formula. These alloys usually have high electrical resistance, high hardness, and low ductility. So, the chemical compound of iron with carbon - cementite (Fe 3 C) is 10 times harder than pure iron.

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Municipal educational institution secondary Gorodishchenskaya school No. 2

Essay on chemistry on the topic

Work completed

middle school student #2

Yablochkina Ekaterina

Settlement 2011

• Introduction
• Alloy
• Alloy classification
• Alloy properties
• Physical properties of alloys
• Receiving alloys
• ELEMENTS CHEMICALLY E
• Alloys of gold
• Conclusion
• Used Literature and Websites
• Introduction
• Ancient metal craftsmen did not leave descriptions of processing methods and compositions of alloys used to make various items. Such literature appears only in the Middle Ages, but in it the names of alloys and terminology are not always decipherable, so the source of information is exclusively the things themselves. There are many works devoted to the results of research on ancient objects. From them we learn that archaeologists attribute the first appearance of copper products to the 7th millennium BC. These were forged objects from native copper. Then metallurgical copper and copper alloys with other metals appear. For several millennia, various items were made mainly from copper and its alloys: tools, weapons, jewelry and mirrors, dishes, coins. The compositions of ancient alloys are very diverse; in the literature they are conditionally called bronze. Arsenic and tin bronzes belong to the earliest ones. In addition to tin and arsenic, ancient alloys often contain lead, zinc, antimony, iron and other elements in the form of microimpurities that got into the metal with ore. The composition of the alloy was selected very rationally, depending on the functional purpose of the object and the manufacturing technique used. So, for casting art products, a recipe for a triple copper-tin-lead alloy was chosen, which was used in ancient Greece, in the Roman Empire, in the Near and Middle East, in India; in China, bronze was one of the most common alloys. On cast objects made of such bronze, a beautiful patina develops over time, which in some cases is preserved on archaeological objects.

Alloy

Alloys, macroscopic homogeneous systems consisting of two or more metals (rarely metals and non-metals) with characteristic metallic properties. In a broader sense, alloys are any homogeneous systems obtained by fusion of metals, non-metals, inorganic compounds, etc. Many alloys (for example: bronze, steel, cast iron) were known in ancient times and even then had extensive practical application. The technical significance of metal alloys is explained by the fact that many of their properties (strength, hardness, electrical resistance) are much higher than those of their pure metals.

Alloys are named based on the name of the element contained in them in the largest amount (main element, base), for example: iron alloy, aluminum alloy. Elements introduced into the alloy to improve their properties are called alloying elements, and the process itself is called alloying.

Alloying is the process of introducing additional elements into the melt that improve the mechanical, physical and chemical properties of the base material. Alloying is a general concept of a number of technological procedures carried out at various stages of obtaining a metallic material in order to improve the quality of metallurgical products.

Alloy classification

According to the nature of the base metal, there are ferrous alloys (base - iron (Fe), non-ferrous alloys (base - non-ferrous metals), alloys of rare metals, alloys of radioactive metals.

b According to the number of components, alloys are divided into double, triple, etc.;

b in structure - into homogeneous (homogeneous) and heterogeneous (mixtures), consisting of several;

b according to characteristic properties - into refractory, low-melting, high-strength, heat-resistant, hard, anti-friction, corrosion-resistant;

l alloys with special properties and others.

b According to the production technology, foundry (for the manufacture of parts by casting) and deformable (subjected to forging, stamping, rolling, pressing and other types of pressure treatment) are distinguished.

Alloy properties

The properties of alloys depend not only on the composition, but also on the methods of their thermal and mechanical processing: hardening, forging, etc. Until the end of the 19th century, the search for new practical useful alloys was carried out by trial and error. Only at the turn of the XIX-XX centuries. As a result of fundamental discoveries in the field of physical chemistry, a doctrine arose about the regularity between the properties of metals and the properties of alloys formed from them, about the influence of mechanical, thermal and other influences on them.

There are three types of alloys in metal science:

b solid solution (if the atoms that make up the alloy of elements differ slightly in structure and size, they can form a common crystal lattice);

b mechanical mixture (if each element of the alloy crystallizes independently);

b chemical compound (if the elements of the alloy interact chemically, forming a new substance).

Physical properties of alloys

Mechanical properties of metals and alloys

The main mechanical properties include strength, toughness, ductility, hardness, endurance, creep, wear resistance. They are the main characteristics of a metal or alloy.

Physical properties of metals and alloys

The physical properties of metals and alloys are determined by the specific gravity, to coefficients of linear and volume expansion, electrical conductivity, thermal conductivity, melting point, etc.

Chemical resistance of metals and alloys

The chemical resistance of metals and alloys is determined by their ability to resist the chemical attack of various aggressive environments. These properties are of great importance for mechanical engineering and have to be taken into account when designing machines and parts. Corrosion (oxidation of metals) is a typical example of the chemical action of a medium.

The destruction of metals from corrosion causes enormous damage to the industry, which is expressed in the annual loss of millions of tons of metal.

To eliminate such large losses in mechanical engineering, parts are coated with varnishes, paints, chemically resistant metals, and oxide films.

In some cases, various alloys with high chemical resistance are used, for example, stainless cast irons, stainless steels and a number of chemically resistant alloys based on copper and nickel. Titanium is beginning to be widely used.

Technological properties of metals

Technological properties of metals and alloys are characterized by their ability to succumb to various methods of hot and cold working (easy to melt and fill the form, forge, weld, process with cutting tools, etc.). In this regard, they are divided into foundry

Casting properties of metals and alloys

Casting properties of metals and alloys are determined by fluidity, shrinkage and a tendency to segregation. Fluidity - the ability of the alloy to fill the mold. Shrinkage refers to the reduction in volume and dimensions of the casting metal during solidification and subsequent cooling. Segregation is the process of formation of heterogeneity of the chemical composition of the alloy in different parts of the casting during its solidification.

Malleability of metal

Malleability of metal - the ability to deform at the lowest resistance resistance and take the necessary form under the influence of external forces without violating integrity. Metals can be malleable both when cold and when heated. Steel has good malleability when heated. Single-phase brass and aluminum alloys have good cold ductility. Bronze is characterized by low malleability. Cast irons have practically no malleability.

Metal weldability

Metal weldability - the ability to create strong connections of metal parts by welding methods. Mild steel is well welded, cast iron, copper and aluminum alloys are much worse.

Receiving alloys

Consider the process of obtaining alloys using the example of cast iron and steel.

Production of iron and steel. The technological process for obtaining ferrous metals includes the smelting of cast iron from iron ores with its subsequent processing into steel.

The main method of producing pig iron is blast-furnace. The blast furnace process consists of three stages: reduction of iron from oxides contained in the ore, carburization of iron and slag formation. The raw materials are iron ores, fuels and fluxes.

Before smelting, iron ores are usually subjected to preliminary preparation: crushing, enrichment and agglomeration. The crushed ore is often enriched by magnetic separation. Wash with water to remove sand and clay particles. Small and silty ores are agglomerated by agglomeration - by sintering on grates of sintering machines or pelletizing in a granulator, followed by drying and roasting. The main fuel in the smelting of cast iron is coke, which is a source of heat and is directly involved in the reduction and carburization of iron. Fluxes (limestone, dolomite or sandstone) are used to lower the melting point of the waste rock and bind it with fuel ash to slag.

The blast furnace is a vertical shaft with a height of up to 35 m or more with walls made of refractory bricks enclosed in a steel casing. Prepared raw materials are loaded into the furnace from above in layers. As a result of the combustion of coke, due to the oxygen of the air injected into the lower part of the furnace, carbon monoxide is formed, which reduces iron from the ore and can interact with it, thus forming Fe3C carbide - cementite.

Simultaneously with the reduction of iron, silicon, phosphorus, manganese and other impurities are reduced.

Molten at a temperature of 1380--1420 ° C, cast iron and slag are released through tapholes. Cast iron is poured into molds, and the slag is recycled. In blast furnaces, pig iron is smelted, which is used for processing into steel, foundry iron, used to produce a variety of cast iron products, and special cast irons (ferrosilicon, ferromanganese), used in steel production as deoxidizers or alloying additives.

Steel is obtained from pig iron by oxidation using open-hearth, converter and electrosmelting methods. The main method of steel production in the USSR and other countries of the world is the open-hearth method, but in recent years the oxygen-converter method, which has significant technical and economic advantages, has become widespread.

With the open-hearth method, steel is obtained in open-hearth furnaces, in the melting space of which gas or fuel oil is burned, and in special chambers - regenerators, the air and gaseous fuel entering the furnace are prepared due to the accumulated heat of the exhaust combustion products. The charge includes pig iron and scrap metal - scrap or liquid pig iron, scrap and iron ore. The process of obtaining steel consists in the melting of the charge, in which a large amount of ferrous oxide is formed, the oxidation of carbon and other impurities with ferrous oxide and deoxidation - the reduction of iron from oxide with the addition of ferrosilicon, ferromanganese or aluminum.

Chemical elements

Many metals, such as magnesium, are produced in high purity so that the composition of the alloys made from it can be precisely known. The number of metal alloys used today is very large and is constantly growing. They are usually divided into two broad categories: iron-based alloys and non-ferrous alloys. The most important alloys of industrial importance are listed below and their main areas of application are indicated.

Steel. Alloys of iron with carbon containing up to 2% of it are called steels. Alloy steels also contain other elements - chromium, vanadium, nickel. Steels are produced much more than any other metals and alloys, and it would be difficult to enumerate all kinds of their possible applications. Mild steel (less than 0.25% carbon) is consumed in large quantities as a structural material, while steel with a higher carbon content (more than 0.55%) is used to make low-speed cutting tools such as razor blades and drills. Alloy steels are used in mechanical engineering of all kinds and in the production of high-speed tools.

Cast iron. Cast iron is an alloy of iron with 2-4% carbon. Silicon is also an important component of cast iron. A wide variety of very useful products can be cast from cast iron, such as manhole covers, pipe fittings, engine blocks. In correctly made castings, good mechanical properties of the material are achieved.

Alloys based on copper. Basically it is brass, i.e. copper alloys containing from 5 to 45% zinc. Brass with a content of 5 to 20% zinc is called red (tompac), and with a content of 20-36% Zn - yellow (alpha brass). Brass is used in the manufacture of various small parts where good machinability and formability are required. Alloys of copper with tin, silicon, aluminum or beryllium are called bronzes. For example, an alloy of copper and silicon is called silicon bronze. Phosphor bronze (copper with 5% tin and trace amounts of phosphorus) has high strength and is used to make springs and membranes.

lead alloys. Common solder (tretnik) is an alloy of about one part lead to two parts tin. It is widely used for connecting (soldering) pipelines and electrical wires. Sheaths of telephone cables and battery plates are made from antimony-lead alloys. Pewter, from which cutlery (forks, knives, plates) was previously cast, contains 85-90% tin (the rest is lead). Lead-based bearing alloys, called babbits, typically contain tin, antimony, and arsenic.

light alloys. Modern industry needs high strength light alloys with good high temperature mechanical properties. The main metals of light alloys are aluminum, magnesium, titanium and beryllium. However, alloys based on aluminum and magnesium cannot be used in high temperature and aggressive environments.

aluminum alloys. These include cast alloys (Al - Si), die casting alloys (Al - Mg) and high strength self-hardening alloys (Al - Cu). Aluminum alloys are economical, readily available, strong at low temperatures and easily machined (they are easily forged, stamped, suitable for deep drawing, drawing, casting, well welded and processed on machine tools). Unfortunately, the mechanical properties of all aluminum alloys begin to noticeably deteriorate at temperatures above about 175°C. But due to the formation of a protective oxide film, they exhibit good corrosion resistance in most common corrosive environments. These alloys conduct electricity and heat well, are highly reflective, non-magnetic, harmless in contact with food (because corrosion products are colorless, tasteless and non-toxic), explosion-proof (because they do not produce sparks), and absorb shock loads well. Due to this combination of properties, aluminum alloys serve as good materials for light pistons, are used in car, automobile and aircraft construction, in the food industry, as architectural and finishing materials, in the production of lighting reflectors, technological and household cable ducts, when laying high-voltage power lines. The impurity of iron, which is difficult to get rid of, increases the strength of aluminum at high temperatures, but reduces corrosion resistance and ductility at room temperature. Cobalt, chromium and manganese weaken the embrittlement effect of iron and increase corrosion resistance. When lithium is added to aluminum, the modulus of elasticity and strength increase, which makes such an alloy very attractive for the aerospace industry. Unfortunately, despite their excellent strength-to-weight ratio (specific strength), aluminum-lithium alloys have poor ductility.

magnesium alloys. Magnesium alloys are light, have high specific strength, good casting properties and excellent machinability. Therefore, they are used for the manufacture of parts for rockets and aircraft engines, housings for automotive equipment, wheels, gas tanks, portable tables, etc. Some magnesium alloys, which have a high coefficient of viscous damping, are used in the manufacture of moving parts of machines and structural elements operating in conditions of unwanted vibrations. Magnesium alloys are quite soft, resist wear poorly, and are not very ductile. They are easily formed at elevated temperatures, are suitable for arc, gas and resistance welding, and can also be connected by soldering (hard), bolts, rivets and adhesives. Such alloys are not particularly corrosion resistant to most acids, fresh and salt water, but are stable in air. They are usually protected from corrosion by surface coating - chrome etching, dichromate treatment, anodizing. Magnesium alloys can also be brightened or plated with copper, nickel and chromium by pre-plating with molten zinc dipping. Anodizing magnesium alloys increases their surface hardness and abrasion resistance. Magnesium is a chemically active metal, and therefore it is necessary to take measures to prevent the ignition of chips and welded parts made of magnesium alloys.

titanium alloys. Titanium alloys are superior to both aluminum and magnesium in terms of tensile strength and modulus of elasticity. Their density is greater than all other light alloys, but in terms of specific strength they are second only to beryllium. With a sufficiently low content of carbon, oxygen and nitrogen, they are quite plastic. The electrical conductivity and thermal conductivity of titanium alloys are low, they are resistant to wear and abrasion, and their fatigue strength is much higher than that of magnesium alloys. The creep strength of some titanium alloys at moderate stresses (on the order of 90 MPa) remains satisfactory up to about 600°C, which is well above the temperature allowed for both aluminum and magnesium alloys. Titanium alloys are sufficiently resistant to the action of hydroxides, salt solutions, nitric and some other active acids, but not very resistant to the action of hydrohalic, sulfuric and orthophosphoric acids. Titanium alloys forging up to temperatures around 1150 ° C. They allow arc welding in an inert gas atmosphere (argon or helium), spot and roller (seam) welding. They are not very amenable to cutting (seizing of the cutting tool). The melting of titanium alloys must be carried out in a vacuum or controlled atmosphere to avoid contamination with oxygen or nitrogen impurities that cause embrittlement. Titanium alloys are used in the aviation and space industries for the manufacture of parts operating at elevated temperatures (150-430 ° C), as well as in some special-purpose chemical apparatus. Titanium-vanadium alloys are used to make light armor for the cockpits of combat aircraft. Titanium-aluminum-vanadium alloy is the main titanium alloy for jet engines and airframes. In table. 3 shows the characteristics of special alloys, and in table. 4 shows the main elements added to aluminum, magnesium and titanium, indicating the resulting properties.

beryllium alloys. A ductile beryllium alloy can be obtained, for example, by interspersing brittle grains of beryllium into a soft, ductile matrix such as silver. It was possible to bring the alloy of this composition by cold rolling to a thickness of 17% of the original. Beryllium surpasses all known metals in specific strength. Combined with its low density, this makes beryllium suitable for missile guidance devices. The modulus of elasticity of beryllium is greater than that of steel, and beryllium bronzes are used for making springs and electrical contacts. Pure beryllium is used as a neutron moderator and reflector in nuclear reactors. Due to the formation of protective oxide layers, it is stable in air at high temperatures. The main difficulty associated with beryllium is its toxicity. It can cause serious respiratory problems and dermatitis.

Alloys of gold

Gold is a noble yellow metal, soft and rather heavy. Gold is found both in the earth's crust and in water, and although its content in the earth is quite low (3 µg/kg), there are very numerous areas highly enriched in this metal. Such areas, which are the primary gold deposit, are called placers.

Of the physical and chemical properties of gold, it should be noted, first of all, its exceptionally high thermal conductivity and low electrical resistance. Under normal conditions, it does not interact with most acids and does not form oxides, does not oxidize in air and is resistant to moisture, alkalis and salts, due to which it was classified as a noble metal. Gold is very malleable and ductile. From a piece of gold weighing one gram, you can stretch a wire three and a half kilometers long or make gold foil 500 times thinner than a human hair. Gold is a very heavy metal, which is a big plus in its mining. Its density is high - 19.3 g / cm3, Brinell hardness - 20. Gold is also the most inert metal, but when the ability of aqua regia (a mixture of hydrochloric and nitric acids in a ratio of 3/1) to dissolve gold was discovered, confidence in its inertia was shaken. The metal melts at a very high temperature - 1063 ° C. Soluble in hot selenic acid. These physical and chemical properties of gold are widely used for its production.

Gold is mined most often by washing, which is based on its high density (other metals, with a density less than gold, are washed out in a stream of water). But natural gold is rarely pure, it contains silver, copper and many other elements, therefore, after washing, all gold undergoes deep cleaning - refining. In Russia, the purity of gold is measured by breakdown.

There are gold alloys that are becoming very popular nowadays.

Pink gold

Rose gold is an alloy of pure gold and copper; jewelry alloy of an unusually delicate shade.

Pink alloy jewelry is becoming more and more popular, rings and pendants are becoming more and more common.

Green (olive) gold

Green (olive) gold can be obtained as an alloy of gold and potassium.

Such compounds are also called metallides.

In general, metallides are compounds of gold with aluminum (purple gold), rubidium (dark green), potassium (violet and olive), indium (blue gold). Such alloys are very beautiful and exotic, but at the same time they are fragile and not ductile. As a precious metal, they cannot be processed. But sometimes such jewelry metal alloys are used as inserts in jewelry, like stones.

By the way, sometimes green gold is also obtained by fusing pure gold with silver. A small inclusion of silver in the composition of the jewelry alloy will give a greenish color, a slightly larger proportion will make gold yellowish green, increasing the silver content even more, we get a yellow-white tint, and finally completely white.

blue gold

It is an alloy of pure gold with indium. But such a jewelry alloy is also a metallide, it is unstable and cannot be used like ordinary gold.

Only as inserts in jewelry, i.e. like stones.

Gold also "turns blue" if it is covered with rhodium.

Or if it is the brainchild of the Argentine jeweler Antoniassy. It is still a mystery how he managed to get a blue alloy with almost 958 fineness (90% pure gold in the alloy). The jeweler is in no hurry to reveal his secrets.

blue gold

Blue gold is an alloy of gold with iron and chromium. Like green and purple gold, blue gold can only be used as inlays in jewelry.

By itself, the blue alloy is fragile and it will not work to make a jewel only from it.

purple gold

In fact, it is an alloy of gold and aluminum. Such gold can be "awarded" 750 samples (the gold content in the alloy is even more than 75%).

Another type of purple gold is an alloy of gold and potassium.

Purple jewelry alloy is beautiful. But, unfortunately, it is fragile and non-plastic. Sometimes it can be found in jewelry in the form of inserts, as if it were a precious stone and not metal.

brown gold

Brown gold - gold 585 or 750, with a larger proportion of copper in the ligature (the addition of impurities to pure gold in the alloy). Jewelers subject such gold to a special chemical treatment.

black gold

Black gold is an unusually refined metal with a deep and soft color. There are several ways to get black gold.

This is alloying with cobalt and chromium with oxidation at high temperature, and coating with black rhodium or amorphous carbon ...

alloy cast iron steel alloying gold

Conclusion

The metal objects around us rarely consist of pure metals. Only aluminum pans or copper wire are about 99.9% pure. In most other cases, people are dealing with alloys. Thus, various types of iron and steel contain, along with metal additives, small amounts of carbon, which have a decisive influence on the mechanical and thermal behavior of the alloys. All alloys have a special marking, because. alloys with the same name (for example, brass) may have different mass fractions of other metals.

Used literature and websites

b Chemistry for the Curious - E. Grosse.

b Soviet Encyclopedic Dictionary. - M.: Soviet Encyclopedia, 1983.

o Brief Chemical Encyclopedia edited by I.A. Knuyants et al. Soviet Encyclopedia, 1961-1967, Vol.2.

o Encyclopedic Dictionary of a Young Chemist compiled by V.A. Kritzman and V.V. Stanzo Publishing house "Pedagogy", 1982.

The Great Encyclopedia of the Modern Schoolchild.

b General chemistry. Glinka N.L., USSR, 1985

o Wikipedia website

b www.erudition.ru- report "Alloys"

b dic.academic.ru - site "Akademik", topic "Alloys"

b www.chemport.ru alloys

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DEFINITION

Alloys are mixtures of two or more elements, among which metals predominate. The metals included in the alloy are called the base. Often, non-metal elements are added to the alloy, which give the alloys special properties, they are called alloying or modifying additives. Among alloys, alloys based on iron and aluminum are of the greatest importance.

Alloy classification

There are several ways to classify alloys:

• according to the manufacturing method (cast and powder alloys);
• according to the method of obtaining the product (cast, wrought and powder alloys);
• by composition (homogeneous and heterogeneous alloys);
• by the nature of the metal - bases (ferrous - base Fe, non-ferrous - base non-ferrous metals and alloys of rare metals - base radioactive elements);
• by the number of components (double, triple, etc.);
• by characteristic properties (refractory, low-melting, high-strength, heat-resistant, hard, anti-friction, corrosion-resistant, etc.);
• by purpose (structural, instrumental and special).

Alloy properties

The properties of alloys depend on their structure. Alloys are characterized by structurally insensitive (determined by the nature and concentration of the elements that make up the alloys) and structure-sensitive properties (depending on the characteristics of the base). The structurally insensitive properties of alloys include density, melting point, and heat of vaporization. thermal and elastic properties, coefficient of thermal expansion.

All alloys exhibit properties characteristic of metals: metallic luster, electrical and thermal conductivity, ductility, etc.

Also, all properties characteristic of alloys can be divided into chemical (the ratio of alloys to the effects of active media - water, air, acids, etc.) and mechanical (the ratio of alloys to the effects of external forces). If the chemical properties of alloys are determined by placing the alloy in an aggressive environment, then special tests are used to determine the mechanical properties. So, in order to determine strength, hardness, elasticity, plasticity and other mechanical properties, tensile, creep, impact strength, etc. tests are carried out.

Main types of alloys

Various steels, cast iron, alloys based on copper, lead, aluminum, magnesium, as well as light alloys have found wide application among various alloys.

Steels and cast irons are alloys of iron with carbon, and the carbon content in steel is up to 2%, and in cast iron 2-4%. Steels and cast irons contain alloying additives: steels - Cr, V, Ni, and cast iron - Si.

There are different types of steels, so, according to their purpose, structural, stainless, tool, heat-resistant and cryogenic steels are distinguished. According to the chemical composition, carbon (low, medium and high carbon) and alloyed (low, medium and high alloyed) are distinguished. Depending on the structure, austenitic, ferritic, martensitic, pearlitic and bainitic steels are distinguished.

Steels have found application in many sectors of the national economy, such as construction, chemical, petrochemical, environmental protection, transport energy and other industries.

Depending on the form of carbon content in cast iron - cementite or graphite, as well as their quantity, several types of cast iron are distinguished: white (light color of the fracture due to the presence of carbon in the form of cementite), gray (gray color of the fracture due to the presence of carbon in the form of graphite). ), malleable and heat resistant. Cast irons are very brittle alloys.

The areas of application of cast iron are extensive - artistic decorations (fences, gates), body parts, plumbing equipment, household items (pans) are made from cast iron, it is used in the automotive industry.

Copper-based alloys are called brasses, as additives they contain from 5 to 45% zinc. Brass with a content of 5 to 20% zinc is called red (tompac), and with a content of 20–36% Zn - yellow (alpha brass).

Among lead-based alloys, there are two-component (lead alloys with tin or antimony) and four-component alloys (lead alloys with cadmium, tin and bismuth, lead alloys with tin, antimony and arsenic), and (typically for two-component alloys) with different contents of the same components receive different alloys. So, an alloy containing 1/3 lead and 2/3 tin - tretnik (ordinary solder) is used for soldering pipe and electric wires, and an alloy containing 10-15% lead and 85-90% tin - pewter, was previously used for casting cutlery.

Aluminum-based alloys are two-component - Al-Si, Al-Mg, Al-Cu. These alloys are easy to obtain and process. They have electrical and thermal conductivity, non-magnetic, harmless in contact with food, explosion-proof. Aluminum-based alloys have found application for the manufacture of light pistons, are used in car, automobile and aircraft construction, the food industry, as architectural and finishing materials, in the production of technological and household cable ducts, and when laying high-voltage power lines.

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Exercise	Under the action of an excess of HCl on a mixture of Al and Fe weighing 11 g, 8.96 liters of gas were released. Determine the mass fractions of metals in the mixture.
Solution	Both metals enter into an interaction reaction, as a result of which hydrogen is released: 2Al + 6HCl = 2AlCl 3 + 3H 2 Fe + 2HCl \u003d FeCl 2 + H 2 Find the total number of moles of hydrogen released: v(H 2) \u003d V (H 2) / V m v (H 2) \u003d 8.96 / 22.4 \u003d 0.4 mol Let the amount of substance Al be x mol, and Fe - y mol. Then, based on the reaction equations, we can write an expression for the total number of moles of hydrogen: 1.5x + y = 0.4 We express the mass of metals in the mixture: Then, the mass of the mixture will be expressed by the equation: 27x + 56y = 11 We got a system of equations: 1.5x + y = 0.4 27x + 56y = 11 Let's solve it: (56-18) y \u003d 11 - 7.2 v(Fe) = 0.1 mol x = 0.2 mol v(Al) = 0.2 mol Then, the mass of metals in the mixture: m(Al) = 27×0.2 = 5.4 g m(Fe) \u003d 56 × 0.1 \u003d 5.6 g Find the mass fractions of metals in the mixture: ώ =m(Me)/m sum ×100% ώ(Fe) \u003d 5.6 / 11 × 100% \u003d 50.91% ώ(Al) = 100 - 50.91 = 49.09%
Answer	Mass fractions of metals in the mixture: 50.91%, 49.09%