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A method for doping silicon with phosphorus and growing oxide on silicon in the presence of steam. Nuclear-doped silicon for power electronics An alternative version of the above




Under certain operating conditions of steel products and structures, the usual physical and mechanical characteristics of the material do not meet the requirements. In such cases, steels are alloyed - other chemical elements are added to the initial composition during smelting (mostly also metals, although, as will be shown below, there are exceptions). As a result, the steel becomes stronger, harder, more resistant to external adverse factors, although it loses its ductility, which in most situations worsens its machinability.

Technical requirements for alloy steels are regulated by GOST 4543 (GOST 1542 also applies to thin sheet steel). At the same time, a number of complex and complexly alloyed steels are produced in accordance with the specifications of metallurgical enterprises.

From a formal point of view, some chemical elements contained in ordinary steels, both structural and ordinary quality, can also be called alloying. These include, for example, copper (up to 0.2%), silicon (up to 0.37%), etc.

Constant companions of any steel are phosphorus and sulfur. Nonetheless, metallurgists refer for the most part not to alloying additives, but to impurities, although sometimes the percentage of another alloying element may be even lower.


The reason is that any impurity is a consequence of either the purity of the original ore (manganese) or the specifics of the metallurgical smelting processes (sulfur, phosphorus). Theoretically, steel smelted without copper, phosphorus and sulfur would have the same mechanical properties. Alloying, on the other hand, has as its ultimate goal precisely the increase in certain technical characteristics of steel. Wherein phosphorus and sulfur definitely are harmful but unavoidable impurities. The presence of copper increases ductility, but contributes to sticking of the metal surface having an excessive (more than 0.3%) concentration of copper on the surface of the adjacent part. When the structure is operating under conditions of intense friction, this is a major drawback.

The presence of a chemical element with a concentration of more than 1% gives reason to introduce its symbol into the steel grade. In addition to the aforementioned 65G steel, aluminum is also honored with a similar honor (present, in particular, in O8Yu steel). In this case aluminum is introduced into conventional structural O8 steel for the purpose of its deoxidation, and the fact that, in this case, the indicators of its plasticity somewhat increase, is only a fortunate concomitant circumstance. Steel boriding provides her increased subsequent deformability, therefore, even microadditives of boron in the chemical composition of steel are marked with a correspondingly changed marking (for example, only 0.001 ... 0.005% of boron is present in 20R steel).

It is generally accepted that:

  • Steels containing only one, intentionally introduced into the composition of the element;
  • Steels containing chemical elements other than carbon and manganese in an amount not exceeding 1%

— are not considered alloyed. On the other hand, if the percentage of iron in the composition of the melted alloy does not exceed 55%, then such material can no longer be called alloyed steel.

General classification of alloying elements in steels

Metals dominate the list of alloying elements. The exceptions are silicon and boron.

The presence of alloying elements has a predominant effect on the form of the state diagram of the "iron-carbon" system, and on the presence / absence of chemical compounds in the final product (nitrides, carbides and components more complex in formula). The latter, in turn, significantly modify the microstructure of the steel.

In this regard, steel alloying metals are divided into two groups:

  1. Metals that increase the region of solid solutions based on γ-iron(austenitic region in the state diagram), which leads to an increase in the diversity of the final microstructure of the alloyed steel after its hardening heat treatment). These elements include nickel, manganese, cobalt, copper, and nitrogen.
  2. Metals and chemical elements, the presence of which narrows the γ-region, but increases the strength of steel. These include chromium, tungsten. vanadium, molybdenum, titanium.

In the process of obtaining alloyed steels, the following regularities in its properties change.

As you know, different elements have different crystal structures (for metals, this is face-centered and body-centered). Iron itself has a body-centered lattice.

When a metal with a similar type of lattice is introduced into steel, the region of existence of an α-solution (ferrite) increases due to a corresponding decrease in the austenitic region. As a result, the microstructure is stabilized, which allows a wider choice of technological processes for subsequent heat treatment.
On the contrary, if there is a metal with a different type of lattice in the steel, the austenitic region narrows. Such steel, during its subsequent machining, will be more ductile.
Alloying of steel with some metals is generally impossible. This happens if the difference in the atomic diameters of the elements exceeds 15%.


It is for this reason that such a metal as zinc is introduced as an alloying additive only in non-ferrous metals and alloys. Limited use for steel alloying purposes is also found by chemical elements that are unable to form stable chemical compounds with carbon, iron and nitrogen during smelting.

The dependence of the characteristics of steel on its saturation with certain chemical elements has not yet been finally studied. This is explained by the fact that with complex doping, each component can interact differently with others, and such changes often cannot be explained in a natural way. Therefore, the questions of the expediency of using one or another alloying element are resolved experimentally.

The following statements are considered proven:

  • The efficiency of the process increases with an increase in the solubility of nitrogen and carbon in the dopant and in the base iron;
  • The stability of the final properties of the steel increases with an increase in the size of the austenitic zone;
  • The quality of steel alloyed with metals and elements with a lower serial number than iron (in the table of chemical elements of D. Mendeleev) is worse than in the opposite case;
  • More refractory, compared with iron, metals increase the strength of steel in any options for its further heat treatment.

However, secondary interactions, which strongly depend on the method of steel smelting, can significantly correct these provisions. Therefore, at this stage, we can speak with confidence only about the influence of specific alloying elements on the properties of steel.

Influence of chromium

Chromium is a metal most often used for alloying purposes. It is added both to structural steels (for example, 20X, 40X) and tool steels (9XC, X12M). In this case, the final properties of steel alloyed with chromium strongly depend on its content in it. At low (less than 0.5 ... 0.7%) concentrations steel structure becomes more rough, and sensitive to the direction of its subsequent processing, especially when cold rolling and bending. The uniformity of the distribution of the main components of the microstructure also deteriorates.

As noted above, one of the main purposes of alloying is the formation of metal carbides in steel, the strength and hardness of which are noticeably higher than the base metal. Chromium forms two types of carbides: hexagonal Cr 7 C 3 and cubic Cr 23 C 6, and in both cases, the strength and cold resistance of steel increase. A feature of chromium carbides is the presence in their structure also of other elements - iron and vanadium. As a result, the effective dissolution temperature decreases, which, in turn, leads to such positive features of steels alloyed with chromium as hardenability, the possibility of secondary precipitation hardening and heat resistance. Therefore, chromium-alloyed steels have increased service life under severe operating conditions.

However, an increase in the chromium content in steel also leads to negative consequences. When it concentrations over 5…10% the carbide homogeneity of the material deteriorates sharply, which is accompanied by undesirable phenomena during its mechanical processing: even when heated, the ductility of steel is low, therefore, when forged with large degrees of deformation, high-chromium steels are prone to cracking.

With excessive carbide formation the number of stress concentrators also increases, which negatively affects the resistance of such steels to dynamic loads. Considering this, the content chromium in steels should not exceed 5..6%.

Influence of tungsten and molybdenum

The action of these alloying additives in steels is approximately the same, therefore they are considered together. Tungsten and molybdenum improve the precipitation hardening of steels, which increases their heat resistance, especially during prolonged operation at elevated temperatures. Maraging steels have a unique set of properties: they combine sufficient ductility and toughness with high surface strength, and therefore are wide application as tool steels designed for cold forging with high degrees of deformation. The reason for this is the formation of Fe 2 W and Fe 2 Mo 3 intermetallic compounds, which contribute to the subsequent appearance of special carbides (more often, chromium and vanadium). Therefore, often, together with tungsten and molybdenum, steels are also alloyed with these metals. An example is tool steels of the Kh4V2M1F1 type, structural steels 40KhVMFA, etc.

Such alloying is most effective for steels containing a relatively large amount of carbon. This explains the predominant the use of steels containing tungsten and molybdenum for the production responsible gears, shafts and other parts machines operating under complex, sharply cyclic loads. The presence of the considered alloying components improves the hardenability of steels and contributes to more stable final characteristics of products made from them.

There are also negative aspects of overdoping these metals. For example, raising molybdenum concentrations over 3% contributes to the decarburization of steel when heated, causes brittle fracture(especially if silicon is present in the composition of such steel in an increased - more than 2% - amount). The limiting content of tungsten in steel - 10 ... 12% - is mainly associated with a sharp increase in the cost of the finished product.

Influence of vanadium

Vanadium is more often used as a component of complex alloying. Its presence gives alloy steels more uniform and favorable structure, which changes little even with heat treatment. In addition, vanadium stabilizes the γ-phase, which increases the resistance of steel to shear stresses (as is known, it is under shear deformations that metals have the lowest strength).

Vanadium has virtually no effect on the hardness of steel., this is especially noticeable for structural steels containing less carbon than tool steels. In complex alloyed steels, vanadium increases heat resistance, which increases their resistance to brittle fracture. In this sense, the influence of vanadium is opposite to that of molybdenum. A feature of the heat treatment of alloyed steels containing vanadium is the impossibility of high tempering after hardening, since the subsequent ductility of the steel decreases. Therefore, in steels intended for the manufacture of large parts or forgings, the percentage of vanadium is limited to 3..4%.

Influence of silicon, manganese and cobalt

Silicon is the only non-metal "admitted" to alloying processes. This is explained by two factors - the low cost of the element and the unambiguous dependence of hardness on the percentage of silicon in steel. That is why silicon is often used in the smelting of low-cost low-alloy building steels, as well as steels, for the operational durability of which an optimal combination of strength and elasticity is important. Most often, manganese is also used together with silicon - examples can be steel 09G2S, 10GS, 60S2, etc.

In tool steels, silicon is rarely used as an alloying component, and, moreover, only in combination with other metals that neutralize its negative properties are low operational ductility and viscosity. Of these steels - in particular, 9XC, 6X3C, etc. — manufacture cutting and stamping tools, which requires a combination of high hardness and resistance to sudden loads.

Like silicon, cobalt when introduced into the steel structure, it does not form its own carbides, but in complex alloyed steels it intensifies their formation during tempering. That's why cobalt is not used alone, but in combination with metals such as vanadium, chromium, tungsten, while, due to the scarcity of cobalt, its content usually does not exceed 2.5 ... 3%.

Nickel influence

Nickel- the only alloying component of steels, which increases its plasticity and reduces hardness. Therefore, steel is not alloyed with one nickel. But in combination with manganese, nickel leads to a noticeable increase in the hardenability of steel, which is very important in the manufacture of large machine parts, for which high operational durability is important. At the same time, the presence of nickel reduces the requirements for the accuracy of observing the temperature intervals of heat treatment.

Alloying with nickel also has a number of features. In particular, nickel, without forming its own carbides, contributes to an increase in accumulations of "foreign" carbides along the grain boundaries, as a result, heat resistance decreases, and brittleness in the range of 20 ... manganese and chromium: in their presence, the maximum concentration of nickel is 2%, and in their absence - no more than 0.5 ... 1%.

Alloy steels for special areas of use contain a number of other metals (for example, titanium, aluminum, etc.). The choice of steel type is dictated by operational and financial considerations.

The second high-tech area of ​​work using the research nuclear reactor VVR-ts is nuclear (neutron-transmutation) doping and radiation modification of semiconductor materials.

It is well known that in order to impart the desired electrical properties to semiconductor silicon, it is necessary to introduce impurity atoms into the crystal. A necessary condition for this is the homogeneity of the distribution of impurity atoms over the volume of the crystal, which, in turn, ensures the homogeneity of the distribution of electrical resistivity. Conventional doping methods cannot provide the required level of dopant distribution uniformity in the volume of a single crystal, especially when growing large single crystals. Only the method of nuclear (neutron transmutation) doping makes it possible to obtain high-quality single-crystal silicon that meets the modern requirements of power electronics and power industry in terms of uniformity, stability and reproducibility of properties.

The method is based on nuclear transformations that occur when thermal neutrons are captured by nuclei of the silicon-30 isotope, followed by the formation of an isotropically distributed phosphorus-31 dopant in a silicon single crystal.

The domestic technology of nuclear (neutron transmutation) doping was developed on the basis of the VVR-ts research reactor.

The main methods for irradiating long single-crystal silicon workpieces were developed, providing a uniform and precise "introduction" of a dopant, depending on
parameters of the irradiation zone and design features of the type of nuclear reactor used: static mode, reciprocating movement of the container with simultaneous rotation, continuous passage of the column of containers along the core with simultaneous rotation, post-processing methods and annealing modes of irradiated crystals. At present, a line for irradiating silicon ingots with a diameter of up to 85 mm is operating with a full cycle of post-processing technological operations. The deviation from the uniform distribution of impurity atoms over the diameter of the ingot does not exceed 3-5%. The electrical resistivity, depending on the degree of doping, which is determined by the neutron fluence, ranges from 15 to 600 Ohm*cm. The lifetime of minority charge carriers in this case exceeds 100 μs.

Nuclear-doped silicon (YALS) of the NIFHI branch is certified by a number of foreign companies: Wacker, Freiberger (Germany), Topsil (Denmark), SKD (Czech Republic). For some of them, we make regular deliveries on a contract basis.

At the same time, two new technological lines for the production of NLK are being created on the basis of the VVR-ts reactor: a line for doping high-purity single-crystal silicon with a diameter of up to 105 mm for photodetectors and detectors of nuclear and cosmic radiation, and a line for producing NLK with a diameter of up to 156 mm.

The second semiconductor material for which the doping and modification technology has been developed is gallium arsenide. The doping method is based on nuclear reactions:

Nuclear-doped gallium arsenide finds application in solar energy and microelectronics, and is also used to manufacture radiation detectors.

Radiation modification of semi-insulating gallium arsenide is based on the optimal combination of irradiation conditions and subsequent heat treatment. In this case, the inhomogeneity of the electrical and optical properties over the volume of the crystal decreases several times and does not exceed 5%, and the thermal stability and radiation stability of the material increase. In the same way, it is possible to obtain gallium arsenide with an optical absorption coefficient of less than 60 at a wavelength of 10.6 μm, which is two times less than that of the original. Such material is used for optical systems of lasers. Samples of this material have been certified by a number of US firms, with which a contract has been concluded for the creation of a production technology with subsequent deliveries of products.

Technical characteristics of the YALK, produced according to the technology developed in the branch of the NIFHI named after. L.Ya. Karpov.

Pure semiconductors are an object of mainly theoretical interest. Major research in semiconductors is concerned with the effect of adding impurities to pure materials. Without these impurities, most semiconductor devices would not exist.

Pure semiconductor materials such as germanium and silicon contain a small amount of electron-hole pairs at room temperature and can therefore conduct very little current. To increase the conductivity of pure materials, a process called doping is used.

alloying is the process of adding impurities to a semiconductor material. Two types of impurities are used. The first, which is called pentavalent, consists of atoms with five valence electrons. Examples are arsenic and antimony. The second, called trivalent, consists of atoms with three valence electrons. Examples are indium and gallium.

When a pure semiconductor material is doped with a pentavalent material such as arsenic (As), some semiconductor atoms are replaced by arsenic atoms. The arsenic atom places its four valence electrons in covalent bonds with neighboring atoms. Its fifth electron is weakly bound to the nucleus and can easily become free.

The arsenic atom is called donor atom because it donates its extra electron. There are many donor atoms in the doped semiconductor material. This means that there are many free electrons to support the current.

At room temperature, the number of additional free electrons exceeds the number of electron-hole pairs. This means that the material has more electrons than holes. Hence, electrons are called majority carriers. The holes are called minority carriers. Because the majority carriers have a negative charge, the material is called a semiconductor. n-type.

If a voltage is applied to an n-type semiconductor, then free electrons added by donor atoms will begin to move towards the positive terminal. In addition, electrons will begin to move towards a positive conclusion, which will be able to destroy their covalent bonds. These electrons, destroying covalent bonds, will create electron-hole pairs. The corresponding holes will move towards the negative terminal.

When a semiconductor material is doped with a trivalent material such as indium (In), the indium atoms will place their three valence electrons among three neighboring atoms. This will create a hole in the covalent bond.

The presence of additional holes will allow electrons to easily drift from one covalent bond to another. Since holes easily accept electrons, atoms that introduce additional holes into a semiconductor are called acceptors.

Under normal conditions, the number of holes in such a material greatly exceeds the number of electrons. Therefore, holes are majority carriers and electrons are minority carriers. Since the majority carriers have a positive charge, the material is called a semiconductor. p-type.

If to a semiconductor p-type voltage is applied, the holes begin to move towards the negative terminal, and the electrons move towards the positive terminal. In addition to the holes that created the acceptor atoms, there are holes formed due to the breaking of covalent bonds, creating electron-hole pairs.

semiconductor materials p-type and p-type have significantly higher conductivity than pure semiconductor materials. This conductivity can be increased or decreased by changing the amount of impurities. The stronger the semiconductor material is doped, the lower its electrical resistance.

Semiconductor materials have half-filled valence shells. Crystals are formed from atoms that share their valence electrons by forming covalent bonds.

Semiconductor materials have a negative temperature coefficient of resistance: as the temperature rises, their resistance decreases. Heat creates problems in semiconductor materials by allowing electrons to break covalent bonds. As the temperature rises, electrons in a semiconductor material drift from one atom to another.

A hole is the absence of an electron in the valence shell.

A potential difference applied to a purely semiconductor material creates a stream of electrons moving towards the positive terminal and a stream of holes moving towards the negative terminal. The current in semiconductor materials consists of the directed motion of electrons and the directed motion of holes.

alloying is the process of adding impurities to a semiconductor material.

Trivalent materials have atoms with three valence electrons and are used to make p-type semiconductors.

Pentavalent materials have atoms with five valence electrons and are used to make n-type semiconductors.

in semiconductor n-type electrons are majority carriers and holes are minority carriers. in semiconductor p-type holes are majority carriers and electrons are minority carriers. n- and p-type semiconductor materials have a significantly higher conductivity than pure semiconductor materials.

The property of semiconductors that makes them most useful for making electronic devices is that their conductivity can be easily changed by introducing impurities into their crystal lattice. The process of adding impurities to a semiconductor is known as doping. The amount of impurity or dopant added to an intrinsic (pure) semiconductor changes the level of its conductivity. Doped semiconductors are often referred to as doped semiconductors.

alloying elements

The materials that are selected as an alloying element depend on the atomic properties of both the alloying element and the material to be alloyed. In general, alloying elements that produce the desired controlled changes are classified as electron acceptors or donors. The donor atom that is activated donates weakly bound valence electrons to the material, creating excess negative charge carriers. These loosely bound electrons can move relatively freely in the crystal lattice and can facilitate electrical conduction in the presence of an electric field. Conversely, an activated acceptor leaves a hole. The semiconductors doped with donor impurities are called semiconductors. n-type, and those doped with acceptor impurities are known as semiconductors R-type. Notation n and p- types indicate which charge carrier acts as the main carrier in the material. The opposite carrier is called the minor carrier, which exists as a result of thermal excitation at a much lower concentration than the major carrier.

For example, the pure semiconductor silicon has four valence electrons. For silicon, the most suitable alloying elements are group 13 (known as group III) and IUPAC group 15 (known as group V). All Group 13 elements contain three valence electrons, which causes them to behave as acceptors when doped with silicon. Group 15 elements have five valence electrons which allow them to act as donors. Consequently, a silicon crystal doped with boron creates a hole semiconductor, and a semiconductor doped with phosphorus with electronic conductivity.

Charge carrier concentration

The concentration of alloying elements introduced into an intrinsic semiconductor determines its concentration and indirectly affects many of its electrical properties. The most important factor directly affected by doping is the concentration of charge carriers in the material. In a pure semiconductor at thermal equilibrium, the concentration of electrons and holes is the same. That is n=p=n i .

Where n - concentration of conducting electrons, p - hole concentration, and n i is the concentration of carriers in a pure material. The concentration of carriers in an intrinsic semiconductor varies with material temperature. n i silicon approximately 1×10 10 cm -3 at 300 kelvins (room temperature).

In general, an increase in impurity concentration allows an increase in electrical conductivity due to a higher concentration of charge carriers available for conduction. Heavily doped semiconductors have conductivity levels comparable to metals and are often used in modern integrated circuits as a replacement for metal. Superscripts plus and minus are often used to indicate the relative concentration of an impurity in semiconductors. For example, n+ denotes a semiconductor n-type with high impurity concentration. Similarly, p − indicates a lightly doped material with hole electrical conductivity. It should also be noted that even high doping levels imply low impurity concentrations relative to the base semiconductor. In its own crystalline silicon approximately 5×10 22 atoms/cm 3 . The impurity concentration for silicon semiconductors can vary from 10 13 cm -3 to 10 18 cm -3 . An impurity concentration above 10 18 cm -3 is considered high at room temperature. Highly alloyed silicon contains a ratio of impurity to silicon as parts per thousand. This ratio can be reduced to parts per billion in lightly doped silicon. Typical concentration values ​​are in this range and are adjusted to embody the desired properties in the device for which this semiconductor is intended.

Physical and chemical properties of the alloy. Various types of surface alloying are also used to change various properties (increase in hardness, wear resistance, corrosion resistance, etc.) of the near-surface layer of metals and alloys. Alloying is carried out at various stages of obtaining a metallic material in order to improve the quality of metallurgical products and metal products.

In the manufacture of special types of glass and ceramics, surface alloying is often performed. Unlike sputtering and other types of coating, the added substances diffuse into the alloyed material, becoming part of its structure.

Doping goals

The main goal is to change the type of conductivity and the concentration of carriers in the bulk of the semiconductor to obtain the desired properties (conductivity, obtaining the required smoothness of the pn-junction). The most common dopants for silicon are phosphorus P and arsenic As (allow to obtain n-type conductivity) and boron B (p-type).

Doping methods

Currently, doping is technologically performed in three ways: ion implantation, neutron transmutation doping (NTL) and thermal diffusion.

Ion implantation

Ion implantation makes it possible to control device parameters more accurately than thermal diffusion and to obtain sharper pn junctions. Technologically, it goes through several stages:

  • Driving (implantation) of impurity atoms from plasma (gas).
  • Impurity activation, control of the depth and smoothness of the pn-junction by annealing.

Ion implantation is controlled by the following parameters:

  • dose - the amount of impurity;
  • energy - determines the depth of the impurity (the higher, the deeper);
  • annealing temperature - the higher, the faster the redistribution of impurity carriers;
  • annealing time - the longer, the stronger the impurity redistribution occurs.

Neutron transmutation doping

In neutron transmutation doping, dopants are not introduced into the semiconductor, but are formed (“transmuted”) from the atoms of the original substance (silicon, gallium arsenide) as a result of nuclear reactions caused by irradiation of the original substance with neutrons. NTL makes it possible to obtain single-crystal silicon with a particularly uniform distribution of impurity atoms. The method is mainly used for substrate doping, especially for power electronics devices.

When the irradiated substance is silicon, under the influence of a stream of thermal neutrons from the silicon isotope 30 Si, a radioactive isotope 31 Si is formed, which then decays to form a stable isotope of phosphorus 31 P. The resulting 31 P creates n-type conductivity.

In Russia, the possibility of neutron-transmutation doping of silicon on an industrial scale at nuclear power plant reactors and without prejudice to electricity production was shown in 1980. By 2004, the technology for alloying silicon ingots with a diameter of up to 85 mm was brought to industrial use, in particular, at the Leningrad NPP. .

Thermal diffusion

Thermal diffusion contains the following steps:

  • Deposition of alloying material.
  • Heat treatment (annealing) for impurity driving into alloyed material.
  • Removal of alloying material.

Alloying in metallurgy

Story

Alloying has become purposefully used relatively recently. This was partly due to technological difficulties. The alloying additives simply burnt out when using the traditional steelmaking technology. Therefore, to obtain Damascus (damask) steel, a rather complicated technology for those times was used.

It is noteworthy that the first steels that people met were naturally alloyed steels. Even before the beginning of the Iron Age, meteorite iron was used, containing up to 8.5% nickel.

Naturally alloyed steels made from ores originally rich in alloying elements were also highly valued. The increased hardness and toughness of Japanese swords, with the ability to provide sharp edges, may be due to the presence of molybdenum in the steel.

Modern views on the influence of various chemical elements on the property of steel began to take shape with the development of chemistry in the second quarter of the 19th century.

Apparently, the invention in 1858 by Muschette of steel containing 1.85% carbon, 9% tungsten and 2.5% manganese can be considered the first successful use of targeted alloying. The steel was intended for the manufacture of cutters for machine tools and was the prototype of the modern line of high-speed steels. Industrial production of these steels began in 1871.

It is generally accepted that the first mass-produced alloy steel was Hadfield Steel, discovered by the English metallurgist Robert Abbott Hadfield in 1882. The steel contains 1.0 - 1.5% carbon and 12 - 14% manganese, has good casting properties and wear resistance. Without any significant changes in the chemical composition, this steel has been preserved to this day.

Influence of alloying elements

To improve the physical, chemical, strength and technological properties, metals are alloyed by introducing various alloying elements into their composition. Chromium, manganese, nickel, tungsten, vanadium, niobium, titanium and other elements are used to alloy steels. Small additions of cadmium to copper increase the wear resistance of wires, zinc additions to copper and bronze increase strength, ductility, and corrosion resistance. Alloying of titanium with molybdenum more than doubles the temperature limit of operation of the titanium alloy due to a change in the crystal structure of the metal. Alloy metals may contain one or more alloying elements that give them special properties.

Alloying elements are introduced into steel to increase its structural strength. The main structural component in structural steel is ferrite, which occupies at least 90% by volume in the structure. Dissolving in ferrite, alloying elements strengthen it. The hardness of ferrite (in the state after normalization) is most strongly increased by silicon, manganese and nickel. Molybdenum, tungsten and chromium have less effect. Most alloying elements, strengthening ferrite and having little effect on ductility, reduce its toughness (with the exception of nickel). The main purpose of alloying is to increase the strength of steel without the use of heat treatment by strengthening ferrite by dissolving alloying elements in it; an increase in hardness, strength and toughness as a result of an increase in the stability of austenite and thereby an increase in hardenability; imparting special properties to steel, of which for steels used in the manufacture of boilers, turbines and auxiliary equipment, heat resistance and corrosion resistance are of particular importance. Alloying elements can dissolve in ferrite or austenite, form carbides, give intermetallic compounds, be located in the form of inclusions without interacting with ferrite and austenite, as well as with carbon. Depending on how the alloying element interacts with iron or carbon, it affects the properties of steel in different ways. All elements dissolve to a greater or lesser extent in ferrite. Dissolution of alloying elements in ferrite leads to hardening of steel without heat treatment. In this case, the hardness and tensile strength increase, and the impact strength usually decreases. All elements that dissolve in iron change the stability of ferrite and austenite. The critical points of alloyed steels shift depending on which alloying elements and in what quantities are present in it. Therefore, when choosing temperatures for hardening, normalization and annealing or tempering, it is necessary to take into account the shift of critical points.

Manganese and silicon are introduced during the steelmaking process for deoxidation, they are technological impurities. Manganese is introduced into steel up to 2%. It is distributed between ferrite and cementite. Manganese noticeably increases the yield strength, cold brittleness threshold, and hardenability of steel, but makes the steel sensitive to overheating. In this regard, carbide-forming elements are introduced into steel to grind grain with manganese. Since the content of manganese is approximately the same in all steels, its effect on steel of different composition remains imperceptible. Manganese increases strength without reducing the ductility of the steel.

Alternative version of above:

Silicon is not a carbide-forming element, and its amount in steel is limited to 2%. It significantly increases the yield strength and strength of steel and, at a content of more than 1%, reduces toughness, ductility and increases the cold brittleness threshold. Silicon is not structurally detectable, since it is completely soluble in ferrite, except for that part of silicon that did not have time to float into the slag in the form of silicon oxide and remained in the metal in the form of silicate inclusions.

Alloy steel marking

The brand of high-quality alloy steel in Russia consists of a combination of letters and numbers indicating its chemical composition. Alloying elements have the following designations: chromium (X), nickel (H), manganese (G), silicon (C), molybdenum (M), tungsten (B), titanium (T), tantalum (TT), aluminum (U) , vanadium (F), copper (D), boron (R), cobalt (K), niobium (B), zirconium (C), selenium (E), rare earth metals (H). The number after the letter indicates the content of the alloying element in percent. If the figure is not indicated, then the alloying element contains 0.8-1.5%, with the exception of molybdenum and vanadium (the content of which in salts is usually up to 0.2-0.3%), as well as boron (in steel with the letter P it should be up to 0.010% ). In structural high-quality alloy steels, the first two digits show the carbon content in hundredths of a percent.

Example: 03Kh16N15M3B - high-alloy quality steel, which contains 0.03% C, 16% Cr, 15% Ni, up to 3% Mo, up to 1.0% Nb

Separate groups of steels are designated somewhat differently:

  • Ball bearing steels are marked with letters (ШХ), after which the chromium content is indicated in tenths of a percent;
  • High-speed steels (complex alloyed) are indicated by the letter (P), the next figure indicates the tungsten content in percent;
  • Automatic steels are designated by the letter (A) and the carbon content in hundredths of a percent is indicated by a number.

Examples of using

  • Become
    • Chrome steels;
    • Well-known ShKh15 steels (obsolete brand designation) used as a material for bearings;
    • The so-called "stainless steels";
    • Steels and alloys alloyed with molybdenum, tungsten, vanadium;
    • Heat-resistant steels and alloys.
  • Aluminum
  • Bronzes
  • Brass
  • glass

see also

Notes

Links

  • "Doping" - an article in the "Chemical Encyclopedia"
  • "Alloying" - an article in the Metallurgical Dictionary
  • "Doping" - an article in the "Encyclopedia of Cyril and Methodius"

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Synonyms:

See what "Doping" is in other dictionaries:

    - (German legieren to fuse from Latin ligo I connect, I connect), 1) Introduction to the composition of metal alloys of the so-called. alloying elements (for example, in steel Cr, Ni, Mo, W, V, Nb, Ti, etc.) to give the alloys certain physical, chemical or ... ... Big Encyclopedic Dictionary

    - (German Legirung, from Latin ligare to bind). The fusion of a noble metal with another. Dictionary of foreign words included in the Russian language. Chudinov A.N., 1910. ALLOYING German. Legirung, from lat. ligare, bind. Fusion… … Dictionary of foreign words of the Russian language

    - (German legieren to alloy, from the Latin ligo I connect, I connect), the introduction of elements into a metal melt or charge (for example, chromium, nickel, molybdenum, tungsten, vanadium, niobium, titanium in steel) that increase mechanical, physical and ... ... Modern Encyclopedia

    ALLOY, rue, rue; this; owls. and nonsov., that (special). Add (infuse) other metals, alloys into the composition of the metal to impart certain properties. alloying elements. Alloy steel. Explanatory dictionary of Ozhegov. S.I. Ozhegov, N.Yu. Shvedova… … Explanatory dictionary of Ozhegov