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 many electrons (5-8).

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

In technology, a non-metal is understood as a substance that has 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 determines the special nature of the interaction of metal atoms and metallic properties. Metals are good conductors of electric current.

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

Metal classification

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

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

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 metals), a high melting point, and relatively high hardness. The most typical metal in this group is iron.

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

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

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

2. Refractory metals, the melting point of which is higher than that of iron (i.e. above 1539C). Used as additives to alloy steels, and also as a base for 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 primarily used in alloys for nuclear power. 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. ., grouped under the name lanthanides. These metals have very similar chemical properties, but quite 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 individual elements. Usually a mixed alloy is used - 40-45% Ce (cerium) and 40-45% all other rare earth metals.

5. Alkaline earth metals- in a free metallic state are not used, with the exception of 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 (berylium), Mg (magnesium), Al (aluminum), which have 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 are highly resistant to corrosion.

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 they began to recover metals from ores - Sn, Pb, Fe, etc.

The most widespread in technology are alloys of iron and 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, 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.

Metal production 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 the metal is a factor in the possibility and feasibility of its use. The table shows the relative cost of different metals (the cost of iron, or 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 ductile. They have a high cost.

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

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

916 alloys are the softest, but also the most corrosion-resistant. As the sample index decreases, corrosion resistance decreases.

Alloys of the 583rd sample have the greatest hardness (and therefore wear resistance), with a ratio of Cu and Ag of about 1:1.

The alloys of these samples have the color of gold.

Indian damask steel

The end of the 4th century BC, the troops of Alexander the Great first encountered extraordinary Indian steel while marching 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 through nails and at the same time easily bent into an arc. Light gauze scarves were easily cut.

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

According to the shape, the pattern is divided into striped, streamed, wavy, mesh and cranked. The most highly valued item was 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 this, no residual deformation was observed.

Real damask steel was made by forging cast steel with natural patterns.

Welding damask 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 packages of sheet steel - up to 320 layers: or: scattered at different levels, they 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 craftsmen from the Caucasus.

Baltic damask steel:

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

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

Consequently, because of this, the old master blacksmiths sewed a soft strip onto a very hard blade to pierce the steel armor.

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

Japanese damask steel

Japanese damask steel was harder and stronger than Damascus steel. This is due to the presence of molybdenum (Mo) in the steel composition. 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, while increasing strength and hardness, also increase fragility.

Manufacturing: smelted iron (with Mo) was forged into rods and hardened into the ground for 8-10 years. During the corrosion process, the metal was eaten away and particles enriched with harmful impurities fell out. The blanks resembled cheese with holes. Then the rods were carburized and forged many times. The number of thinnest layers reached several tens of thousands.

Steel materials, structures, parts must have high corrosion resistance. This is facilitated by the presence in the steel composition: copper, Cr, Ni, especially phosphorus. (Example: weather-resistant low-carbon construction 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 are “eaten” by rust and scattered in the biosphere...

Eiffel Tower - 1889 - predicted that it would last no more than 25 years (Eiffel considered 40 years for durability). The tower has stood in Paris for over 100 years, but this is only because it is constantly covered with a thick layer of paint. It takes 52 tons of paint to paint the tower. Its cost has long exceeded the cost of the structure 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, railings of the stairs of the Fontanka River in Leningrad, an iron column in Delhi (1500 years). Surface oxides and increased content of Cu and P, as well as natural alloying, resist corrosion.

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

There is no unified system for marking non-ferrous metals and alloys based on them. In all cases, the alphanumeric system is adopted. Letters indicate that the alloys belong to a specific group, and 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 another - the number of alloying elements, and in the third they indicate the number of the alloy, which according to the state. the standard must meet a certain composition or properties.
Copper and its alloys
Technical copper is marked with the letter M, followed by numbers associated with the amount of impurities (indicating the degree of purity of the material). M3 grade copper contains more impurities than M000. The letters at the end of the mark mean: k - cathodic, b - oxygen-free, p - deoxidized. The high electrical conductivity of copper determines its primary use in electrical engineering as a conductor material. Copper deforms well, welds and solders well. Its disadvantage is poor machinability.
The main copper-based alloys include brass and bronze. In copper-based alloys, an alphanumeric system is adopted that characterizes the chemical composition of the alloy. Alloying elements are designated by a Russian letter corresponding to the initial letter of the element's 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 - N; Titan -T; Phosphorus - F; Chrome -X; Beryllium - B; Iron - F; Magnesium - Mg; Tin - O; Lead - C; Zinc - C.
The marking procedure for cast and wrought brasses 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 (tompak), with a content of 20-36% Zn - yellow. In practice, brasses with a zinc concentration exceeding 45% are rarely used. 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 brasses are marked according to GOST 15527-70.
The grade 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 are highly pressure-treatable. They are supplied in the form of pipes and tubes of various cross-sectional shapes, sheets, strips, tape, wire and rods of various profiles. Brass products with high internal stress (for example, cold-worked) are susceptible to cracking. When stored in air for a long time, longitudinal and transverse cracks form on them. To avoid this, before long-term storage it is necessary to relieve internal stress by performing low-temperature annealing at 200-300 C.
In multi-component brasses, after the letter L, a series of letters are written indicating which alloying elements, other than zinc, are included in this brass. Then numbers follow through hyphens, the first of which characterizes the average copper content as a percentage, and the subsequent ones - each of the alloying elements in the same sequence as in the letter part of the brand. The order of letters and numbers is determined by the content of the corresponding element: first comes the element that has more, and then descending. The zinc content is determined by the difference from 100%.
Brasses are mainly used as a deformable, corrosion-resistant material. Sheets, pipes, rods, strips and some parts are made from them: nuts, screws, bushings, etc.
Casting brasses are marked in accordance with GOST 1711-30. At the beginning of the stamp they also write the letter L (brass), after which they write the letter C, which means zinc, and a number indicating its percentage content. In alloyed brasses, letters are additionally written corresponding to the entered alloying elements, and the numbers following them indicate the content of these elements as a percentage. The remainder missing up to 100% corresponds to the copper content. Casting brass is used for the manufacture of fittings and parts for shipbuilding, bushings, liners and bearings.
Bronze (alloys of copper with various elements, where zinc is not the main one). They, like brass, are divided into cast and wrought. All bronzes are marked with the letters Br, which is short for bronze.
In cast bronzes, after Br, letters are written followed by numbers, which symbolically indicate the elements introduced into the alloy (in accordance with Table 1), and the subsequent numbers indicate the content of these elements as a percentage. The rest (up to 100%) means copper. Sometimes in some brands of cast bronzes they write the letter “L” 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 pigs, ingots, wire rods, etc. (primary aluminum) according to GOST 11069-74 and in the form of a deformable semi-finished product (sheets, profiles, rods, etc.) according to 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, which can be used to determine the content of impurities in aluminum. Aluminum deforms well, but is difficult to cut. By rolling it you can make foil.

Aluminum-based alloys are divided into cast and wrought.
Aluminum-based casting alloys are marked according to GOST 1583-93. The grade 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 that reflect 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 alloy number. The letter B at the beginning of the mark indicates that the alloy is high-strength.
The use of aluminum and alloys based on it is very diverse. Technical aluminum is used mainly 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 (using various casting methods), which require increased corrosion resistance in combination with low density, for example, some compressor pistons, levers and other parts.
Wrought alloys based on aluminum are also widely used in food and refrigeration technology for the manufacture of various parts by pressure processing, 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 using an alphanumeric system. However, there is no pattern in the labeling. The only peculiarity is the presence in all brands of the letter T, which indicates that they belong to titanium. The numbers in the mark indicate the conditional number of the alloy.
Technical titanium is marked: VT1-00; VT1-0. All other grades belong 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 disadvantages hinder their use in food and refrigeration technology.

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

Magnesium-based alloys, like aluminum-based alloys, have a good combination of properties: low density, increased corrosion resistance, relatively high strength (especially specific strength) with good technological properties. Therefore, both simple and complex-shaped parts that require increased corrosion resistance are made from magnesium alloys: 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 equipment. Tin is used in the food industry as coatings for food containers (for example, tinning tin plates). Tin is marked in accordance with GOST 860-75. There are O1pch brands; O1; O2; O3; O4. The letter O stands for tin, and the numbers represent a conventional number. As the number increases, the amount of impurities increases. The letters pch at the end of the brand mean increased purity. In the food industry, tin of the O1 and O2 grades is most often used for tinning tin plates.
Alloys based on tin and lead, depending on their purpose, are divided into two large groups: babbits and solders.
Babbitts 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 babbitt, 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 babbitt), the letter C - lead babbitt, etc. It should be borne in mind that the brand of babbitt cannot determine its full chemical composition. In some cases, the tin content is not even indicated, for example in the BN brand, although it contains about 10%. There are also tin-free babbits (for example, lead-calcium), which are marked according to GOST 1209-78 and are not studied in this work.

Babbitts 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 characteristics: 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 low-melting (melting point tmelt ≤ 145 °C);

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

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

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

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 main element and a small amount of impurities of other elements. For example, technically 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 some simple metal (alloy base) with other metals or non-metals. For example, brass is an alloy of copper and zinc. Here the base 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 predominates in the alloy, there are also alloying components introduced into the alloy to obtain the required properties. Thus, 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 (ternary), etc. In addition to the main and alloying components, the alloy contains impurities of other elements.

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

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

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

At the present stage of technological development, along with an increase in the number of alloys and the complication of their composition, metals of special purity are becoming of great importance. The content of the main component in such metals ranges from 99.999 to 99.999999999%
and more. Metals of special purity are needed in rocket science, nuclear, electronics 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 are formed when they do not dissolve in each other in the solid state and do not enter into chemical interaction. Alloys are mechanical mixtures (for example, lead - antimony, tin - zinc) are heterogeneous in their 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 determined as the arithmetic average of the properties of both components.

2) Solid solutions characterized by the formation of a common spatial crystal lattice by atoms of the main solvent metal and atoms of the soluble element.
The structure of such alloys consists of homogeneous crystalline grains, like pure metal. There are substitutional 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 the properties of the constituent components. For example, the hardness and electrical resistance of solid solutions is much higher than that of pure components. Due to their high ductility, they lend themselves well to forging and other types of forming. 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, 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 fused 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. Thus, the chemical compound of iron and carbon - cementite (Fe 3 C) is 10 times harder than pure iron.

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Municipal educational institution secondary Gorodishche school No. 2

Chemistry essay on the topic

Completed the work

high school student No. 2

Yablochkina Ekaterina

Settlement 2011

• Introduction
• Alloy
• Alloy classification
• Properties of alloys
• Physical properties of alloys
• Preparation of alloys
• ELEMENTS CHEMICALLY E
• Gold alloys
• Conclusion
• Literature and sites used
• Introduction
• Ancient metal craftsmen did not leave descriptions of processing techniques and compositions of alloys used to make various objects. 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 into ancient objects. From them we learn that archaeologists date the first appearance of copper products to the 7th millennium BC. These were forged objects made of native copper. Then metallurgical copper and alloys of copper with other metals appear. For several millennia, various objects 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 conventionally called bronze. The earliest ones include arsenic and tin bronzes. In addition to tin and arsenic, ancient alloys often contain lead, zinc, antimony, iron and other elements in the form of trace impurities that got into the metal with the ore. The composition of the alloy was selected very rationally, depending on the functional purpose of the item and the manufacturing technique used. Thus, for the casting of artistic products, a recipe was chosen for a ternary alloy of copper-tin-lead, which was used in ancient Greece, the Roman Empire, the Near and Middle East, and India; In China, bronze was one of the most common alloys. Cast objects made from such bronze develop a beautiful patina 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 fusing 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 applications. The technical importance of metal alloys is explained by the fact that many of their properties (strength, hardness, electrical resistance) are much higher than those of their constituent pure metals.

Alloys are named based on the name of the element contained in them in the largest quantity (main element, base), for example: iron alloy, aluminum alloy. Elements introduced into an alloy to improve their properties are called alloying, 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 metal material with the aim of improving the quality of metallurgical products.

Alloy classification

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

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

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

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

b alloys with special properties and others.

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

Properties of alloys

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.

In metallurgy, three types of alloys are distinguished:

b solid solution (if the atoms that make up an 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 chemically interact to form 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 their specific gravity, coefficients of linear and volumetric 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 effects 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. A typical example of the chemical influence of the environment is corrosion (oxidation of metals).

The destruction of metals from corrosion causes enormous damage to industry, 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 iron, stainless steel and a number of chemically resistant alloys based on copper and nickel. Titanium is beginning to find widespread use.

Technological properties of metals

Technological properties of metals and alloys are characterized by their way Easily amenable to various methods of hot and cold working (easily melted and filled into a mold, forged, welded, processed with cutting tools, etc.). In this regard, they are divided into foundries

Casting properties of metals and alloys

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

Malleability of metal

Malleability of a metal - the ability to deform with the least resistance resistance and take the required shape under the influence of external forces without violating its 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 reduced malleability. Cast irons have virtually no malleability.

Metal weldability

Weldability of metal - the ability to create strong connections between metal parts using welding methods. Low-carbon steel welds well, cast iron, copper and aluminum alloys are much worse.

Preparation of alloys

Let's consider the process of producing alloys using the example of cast iron and steel.

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

The main method of producing cast 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. Crushed ore is often enriched by magnetic separation. To remove sand and clay particles, wash with water. The agglomeration of fine and dusty ores is carried out by agglomeration - by sintering on the grates of sintering machines or by rolling in a granulator, followed by drying and roasting. The main fuel when melting cast iron is coke, which is a source of heat and is directly involved in the reduction and carburization of iron. Fluxes (limestones, dolomites or sandstones) are used to reduce the melting point of waste rock and bind it with fuel ash into slag.

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

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

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

Steel is produced from pig iron by oxidation using open-hearth, converter and electric melting 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 produced 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 using the accumulated heat of waste combustion products. The charge includes pig iron and metal scrap - scrap or liquid iron, scrap and iron ore. The process of producing steel consists of melting the charge, which produces a large amount of ferrous oxide, the oxidation of carbon and other impurities with ferrous oxide, and deoxidation - the reduction of iron from the 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 accurately known. The number of metal alloys used today is very large and is constantly growing. They are usually divided into two large 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 and carbon containing up to 2% are called steels. Alloy steels also contain other elements - chromium, vanadium, nickel. There are far more steels produced than any other metals and alloys, and it would be difficult to list all of their possible uses. Low-carbon steel (less than 0.25% carbon) is consumed in large quantities as a structural material, while steel with 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 types 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, pipeline fittings, and engine cylinder blocks. Correctly executed castings achieve good mechanical properties of the material.

Copper-based alloys. These are mainly brass, i.e. copper alloys containing from 5 to 45% zinc. Brass containing 5 to 20% zinc is called red (tompak), and brass containing 20-36% Zn is called yellow (alpha brass). Brasses are used in the production 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. Conventional solder (tertiary) is an alloy of approximately one part lead to two parts tin. It is widely used for connecting (soldering) pipelines and electrical wires. Antimony-lead alloys are used to make shells of telephone cables and battery plates. Pewter, from which cutlery (forks, knives, plates) were previously cast, contains 85-90% tin (the rest is lead). Lead-based bearing alloys, called babbitts, 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 at high temperatures and in aggressive environments.

Aluminum alloys. These include casting alloys (Al - Si), die-casting alloys (Al - Mg) and self-hardening high-strength alloys (Al - Cu). Aluminum alloys are economical, easily accessible, strong at low temperatures and easy to process (they are easily forged, stamped, suitable for deep drawing, drawing, casting, well welded and machined on metal-cutting machines). Unfortunately, the mechanical properties of all aluminum alloys begin to deteriorate noticeably at temperatures above approximately 175° C. However, due to the formation of a protective oxide film, they exhibit good corrosion resistance in most common aggressive environments. These alloys conduct electricity and heat well, are highly reflective, non-magnetic, harmless in contact with food (since the corrosion products are colorless, tasteless and non-toxic), explosion-proof (since they do not produce sparks) and absorb shock loads well. Thanks to this combination of properties, aluminum alloys serve as good materials for lightweight pistons; they are used in carriage, automobile and aircraft construction, in the food industry, as architectural and finishing materials, in the production of lighting reflectors, technological and household cable ducts, and in the laying of high-voltage power lines. The iron impurity, 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 embrittling effect of iron and increase corrosion resistance. When lithium is added to aluminum, the elastic modulus and strength increase, making the alloy very attractive to the aerospace industry. Unfortunately, despite their excellent strength-to-weight ratio (specific strength), aluminum-lithium alloys have low ductility.

Magnesium alloys. Magnesium alloys are lightweight, characterized by high specific strength, as well as good casting properties and excellent cutting properties. Therefore, they are used to make parts for rockets and aircraft engines, car body housings, wheels, gas tanks, portable tables, etc. Some magnesium alloys, which have a high viscous damping coefficient, are used for the manufacture of moving machine parts and structural elements operating under conditions of unwanted vibrations. Magnesium alloys are quite soft, have poor wear resistance and are not very ductile. They are easily formed at elevated temperatures, are suitable for arc, gas and resistance welding, and can also be joined by soldering (solder), 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 given a shiny surface or clad with copper, nickel and chromium after being dipped into molten zinc. 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 alloys in terms of tensile strength and elastic modulus. Their density is greater than that of all other light alloys, but in terms of specific strength they are second only to beryllium. With a fairly 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 limit of some titanium alloys at moderate stresses (about 90 MPa) remains satisfactory up to about 600° C, which is significantly higher than the temperature permissible for both aluminum and magnesium alloys. Titanium alloys are quite 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 are forged up to temperatures of about 1150° C. They allow electric 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). Melting of titanium alloys must be done 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. Light armor for the cockpits of combat aircraft is made from titanium-vanadium alloys. Titanium-aluminum-vanadium alloy is the primary titanium alloy for jet engines and airframes. In table Table 3 shows the characteristics of special alloys, and table. Figure 4 shows the main elements added to aluminum, magnesium and titanium, indicating the resulting properties.

Beryllium alloys. A ductile beryllium alloy can be produced, for example, by embedding brittle grains of beryllium into a soft ductile matrix such as silver. The alloy of this composition was brought to a thickness of 17% of the original by cold rolling. Beryllium surpasses all known metals in specific strength. Combined with its low density, this makes beryllium suitable for missile guidance systems. The elastic modulus of beryllium is greater than that of steel, and beryllium bronzes are used to make 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 with beryllium is its toxicity. It can cause serious respiratory problems and dermatitis.

Gold alloys

Gold is a noble metal of yellow color, soft and quite heavy. Gold is contained 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 that are highly enriched in this metal. Such areas, which are the primary gold deposits, 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. Dissolves in hot selenic acid. These physical and chemical properties of gold are widely used for its production.

Gold is most often mined 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, so after washing, all gold undergoes deep cleaning - refining. In Russia, the purity of gold is measured by its fineness.

There are gold alloys that are becoming very popular nowadays.

Rose gold

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

Jewelry made from pink alloy is becoming more and more popular, rings and pendants are becoming 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 (violet 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. They cannot be processed as a precious metal. But sometimes such jewelry metal alloys are used as inserts in jewelry, like stones.

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

Blue gold

It is an alloy of pure gold and indium. But such a jewelry alloy is also a metallic metal; it is unstable and cannot be used like ordinary gold.

Only as inserts into decorations, i.e. like stones.

Gold also turns blue if it is plated with rhodium.

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

Blue gold

Blue gold is an alloy of gold with iron and chromium. Just like green and purple, blue gold can only be used as jewelry inserts.

The blue alloy itself is fragile and it will not be possible to make a jewel from it alone.

Purple gold

Essentially it is an alloy of gold and aluminum. Such gold can be “awarded” 750 fineness (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 not plastic. Sometimes it can be found in jewelry in the form of inserts, as if it were a precious stone rather than a metal.

Brown gold

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

Black gold

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

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

alloy cast iron steel alloy gold

Conclusion

The metal objects around us rarely consist of pure metals. Only aluminum pans or copper wire have a purity of about 99.9%. In most other cases, people deal 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 special markings, because... alloys with the same name (for example, brass) may have different mass fractions of other metals.

Literature and websites used

b Chemistry for the curious - E. Grosse.

ь Soviet encyclopedic dictionary. - M.: Soviet Encyclopedia, 1983.

o Concise chemical encyclopedia edited by I.A. Knuyants et al. Soviet Encyclopedia, 1961-1967, T.2.

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

ь Great encyclopedia of modern schoolchildren.

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

o Wikipedia website

b www.erudition.ru- report "Alloys"

ь dic.academic.ru - “Academician” website, topic “Alloys”

b www.chemport.ru- alloys

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DEFINITION

Alloys- These 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, giving the alloys special properties; they are called alloying or modifying additives. Among alloys, the most important are those based on iron and aluminum.

Alloy classification

There are several ways to classify alloys:

• by manufacturing method (cast and powder alloys);
• by the method of obtaining the product (cast, wrought and powder alloys);
• by composition (homogeneous and heterogeneous alloys);
• according to the nature of the metal - base (ferrous - Fe base, non-ferrous - base, non-ferrous metals and alloys of rare metals - radioactive elements base);
• 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).

Properties of alloys

The properties of alloys depend on their structure. Alloys are characterized by structure-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 evaporation. 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 the properties characteristic of alloys can be divided into chemical (the relationship of alloys to the effects of active media - water, air, acids, etc.) and mechanical (the relationship 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, to determine strength, hardness, elasticity, ductility 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 are widely used among all kinds of alloys.

Steels and cast irons are alloys of iron and carbon, with the carbon content in steel 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; for example, structural, stainless, tool, heat-resistant and cryogenic steels are distinguished according to their intended purpose. Based on their chemical composition, they are divided into carbon (low-, medium- and high-carbon) and alloyed (low-, medium- and high-alloy). 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), cabinet parts, plumbing equipment, household items (frying pans) are made from cast iron, and it is used in the automotive industry.

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

Among lead-based alloys, 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) are distinguished, and (typical of two-component alloys) with different contents of the same components different alloys are obtained. Thus, an alloy containing 1/3 lead and 2/3 tin - tertiary (ordinary solder) is used for soldering pipes and electrical wires, and an alloy containing 10-15% lead and 85-90% tin - pewter, was previously used for casting cutlery.

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

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Exercise	When a mixture of Al and Fe weighing 11 g was exposed to excess HCl, 8.96 liters of gas were released. Determine the mass fractions of metals in the mixture.
Solution	Both metals react, resulting in the release of hydrogen: 2Al + 6HCl = 2AlCl3 + 3H2 Fe + 2HCl = FeCl 2 + H 2 Let's find the total number of moles of hydrogen released: v(H 2) =V(H 2)/V m v(H 2) = 8.96/22.4 = 0.4 mol Let the amount of substance Al be x mol, and Fe be y mol. Then, based on the reaction equations, we can write the expression for the total number of moles of hydrogen: 1.5x + y = 0.4 Let us express the mass of metals in the mixture: Then, the mass of the mixture will be expressed by the equation: 27x + 56y = 11 We received a system of equations: 1.5x + y = 0.4 27x + 56y = 11 Let's solve it: (56-18)y = 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 is: m(Al) = 27×0.2 = 5.4 g m(Fe) = 56×0.1 = 5.6 g Let's find the mass fractions of metals in the mixture: ώ =m(Me)/m sum ×100% ώ(Fe) = 5.6/11 ×100%= 50.91% ώ(Al) = 100 – 50.91 = 49.09%
Answer	Mass fractions of metals in the mixture: 50.91%, 49.09%