Tungsten is a metal with unique properties. It has the highest boiling point (5555 °C - the same temperature in the solar photosphere) and melting point (3422 °C) among metals, while having the lowest coefficient of thermal expansion.
In addition, it is one of the hardest, heaviest, stable and dense metals: The density of tungsten is comparable to that of uranium and is 1.7 times higher than that of lead.
Its electrical conductivity is almost 3 times lower than that of copper, but it is quite high. In its purified form, tungsten is silvery-white, reminiscent of steel or platinum in appearance, with significant heating - up to 1600 ° C - it is perfectly forged.
History of discovery and application
The metal got its name from wolframite, a mineral whose name is translated from Latin as “wolf foam”, and from German as “wolf cream”. Such a strange name is associated with the behavior of the mineral: it interfered with the smelting of tin when it accompanied the mined tin ore, turning the material valuable in the Middle Ages into slag foam. Then they said about him: "the wolf eats tin like a sheep."
The discovery of pure tungsten occurred in two places at the same time. In 1781, the chemist Scheele (Sweden) received a "heavy stone" by influencing nitric acid for scheelite. And in 1783, the chemists of Eluard (Spain) also reported the isolation of pure tungsten. 
The main metal reserves were found in Kazakhstan, Canada, China, and the USA.
The use of tungsten Wolfram carbide.
Approximately 50% of tungsten is used to produce hard materials, especially tungsten carbide with a melting point of 2770 °C.
Wolfram carbide - chemical compound equal in number of tungsten and carbon atoms. It is 2 times stiffer than steel and has a stiffness factor of 9 on the Mohs scale (factor 10).
Tungsten carbide is used to make:
– cutting tools that are extremely resistant to abrasion and high temperatures;
- armor-piercing ammunition;
- tank armor; 
- aircraft and engine parts;
- details spaceships and rockets;
— equipment for the nuclear industry;
— ballasts, commercial aircraft, racing cars;
- surgical instruments intended for open (cavitary) surgery and laparoscopic (scissors, tweezers, grippers, cutters, etc.) - they are more expensive than medical steel, but they have better performance;
— jewelry especially wedding rings: the popularity of tungsten in wedding rings is due to physical properties metal (strength, refractoriness, as if symbolizing the same strength of relationships) and its appearance- polished, tungsten retains a shining, mirror-like appearance for an indefinitely long time, since in ordinary life it is impossible to scratch it with something;
- a ball in expensive ballpoint pens;
- calibration blocks used, in turn, for the production of precision lengths in dimensional metrology.
Other Uses for Tungsten
Tungsten is used in the production of heating elements for high-temperature vacuum furnaces, incandescent filaments in a variety of lighting devices. 
Tungsten sulfide has found application as a high temperature lubricant that can withstand temperatures up to 500 °C. Tungstate single crystals are used in nuclear physics and medicine.
Tungsten- the most refractory of metals. Only the non-metallic element, carbon, has a higher melting point. Under standard conditions, chemically resistant. The name Wolframium was transferred to the element from the mineral wolframite, known as far back as the 16th century. called lat. Spuma lupi ("wolf foam") or German. Wolf Rahm ("wolf cream", "wolf cream"). The name was due to the fact that tungsten, accompanying tin ores, interfered with the smelting of tin, turning it into foam of slag (“it devours tin like a wolf a sheep”).
See also:
STRUCTURE
The tungsten crystal has a body-centered cubic lattice. Tungsten crystals in the cold are characterized by low plasticity, therefore, in the process of pressing the powder, they practically do not change their basic shape and size, and the compaction of the powder occurs mainly through the relative movement of particles. In body-centered cubic cell tungsten atoms are located at the vertices and in the center of the cell, i.e. There are two atoms per cell. The bcc structure is not the closest packing of atoms. The compactness factor is 0.68. The space group of tungsten is Im3m.
PROPERTIES
Tungsten is a shiny light gray metal with the highest proven melting and boiling points (it is assumed that seaborgium is even more refractory, but so far this cannot be firmly stated - the lifetime of seaborgium is very short). Melting point - 3695 K (3422 °C), boils at 5828 K (5555 °C). The density of pure tungsten is 19.25 g/cm³. It has paramagnetic properties (magnetic susceptibility 0.32 10−9). Brinell hardness 488 kg/mm², electrical resistivity at 20 °C - 55·10−9 Ohm·m, at 2700°C - 904·10−9 Ohm·m. The speed of sound in annealed tungsten is 4290 m/s. It is paramagnetic.
Tungsten is one of the heaviest, hardest and most refractory metals. In its pure form, it is a silver-white metal, similar to platinum, at a temperature of about 1600 ° C it lends itself well to forging and can be drawn into a thin thread.
RESERVES AND PRODUCTION
The clarke of tungsten in the earth's crust is (according to Vinogradov) 1.3 g/t (0.00013% by content in earth's crust). Its average content in rocks, g/t: ultrabasic - 0.1, basic - 0.7, medium - 1.2, acidic - 1.9.
The process of obtaining tungsten passes through the substage of separation of trioxide WO 3 from ore concentrates and subsequent reduction to a metal powder with hydrogen at a temperature of about 700 °C. Due to the high melting point of tungsten, powder metallurgy methods are used to obtain a compact form: the resulting powder is pressed, sintered in a hydrogen atmosphere at a temperature of 1200-1300 ° C, then passed through it electricity. The metal is heated to 3000 °C, and sintering into a monolithic material occurs. For subsequent purification and obtaining a single-crystal form, zone melting is used.
ORIGIN
Tungsten occurs in nature mainly in the form of oxidized complex compounds formed by tungsten trioxide WO 3 with oxides of iron and manganese or calcium, and sometimes lead, copper, thorium and rare earth elements. Wolframite (iron and manganese tungstate nFeWO 4 * mMnWO 4 - respectively, ferberite and hübnerite) and scheelite (calcium tungstate CaWO 4) are of industrial importance. Tungsten minerals are usually interspersed in granitic rocks, so that the average concentration of tungsten is 1-2%.
Kazakhstan, China, Canada and the USA have the largest reserves; deposits are also known in Bolivia, Portugal, Russia, Uzbekistan and South Korea. World production of tungsten is 49-50 thousand tons per year, including 41 in China, 3.5 in Russia; Kazakhstan 0.7, Austria 0.5. Main exporters of tungsten: China, South Korea, Austria. Main importers: USA, Japan, Germany, UK.
There are also deposits of tungsten in Armenia and other countries.
APPLICATION
The refractoriness and plasticity of tungsten make it indispensable for filaments in lighting devices, as well as in kinescopes and other vacuum tubes.
Due to its high density, tungsten is the basis of heavy alloys, which are used for counterweights, armor-piercing cores of sub-caliber and arrow-shaped feathered artillery shells, cores of armor-piercing bullets and high-speed gyroscope rotors to stabilize the flight of ballistic missiles (up to 180 thousand rpm).
Tungsten is used as electrodes for argon arc welding. Alloys containing tungsten are characterized by heat resistance, acid resistance, hardness and abrasion resistance. They are used to make surgical instruments (amaloy alloy), tank armor, shells of torpedoes and shells, the most important parts of aircraft and engines, and storage containers. radioactive substances. Tungsten is an important component of the best grades of tool steels. Tungsten is used in high-temperature vacuum resistance furnaces as heating elements. An alloy of tungsten and rhenium is used in such furnaces as a thermocouple.
For mechanical processing of metals and non-metallic structural materials in mechanical engineering (turning, milling, planing, chiselling), well drilling, in the mining industry, hard alloys and composite materials based on tungsten carbide are widely used (for example, Pobedite, consisting of WC crystals in a cobalt matrix; grades widely used in Russia - VK2, VK4, VK6, VK8, VK15, VK25, T5K10, T15K6, T30K4), as well as mixtures of tungsten carbide, titanium carbide, tantalum carbide (TT grades for especially difficult processing conditions, for example, chiselling and planing forgings from heat-resistant steels and rotary percussion drilling of strong material). It is widely used as an alloying element (often in conjunction with molybdenum) in steels and iron-based alloys. High-alloy steel, classified as "high-speed" with a marking starting with the letter P, almost always contains tungsten. (Р18, Р6М5. from rapid - fast, speed).
Tungsten sulfide WS 2 is used as a high temperature (up to 500 °C) grease. Some tungsten compounds are used as catalysts and pigments. Tungstate single crystals (lead, cadmium, calcium tungstates) are used as scintillation detectors x-ray radiation and other ionizing radiation in nuclear physics and nuclear medicine.
Tungsten ditelluride WTe 2 is used to convert thermal energy into electrical energy (thermo-EMF about 57 μV/K). The artificial radionuclide 185 W is used as a radioactive label in the study of matter. Stable 184 W is used as a component of uranium-235 alloys used in solid-phase nuclear rocket engines, since it is the only common tungsten isotope that has a low thermal neutron capture cross section (about 2 barns).
Tungsten - W
CLASSIFICATION
| Nickel-Strunz (10th edition) | 1.AE.05 |
| Dana (7th edition) | 1.1.38.1 |
The history of the discovery of tungsten
The word "tungsten" existed long before the discovery of this metal. Another German physician and metallurgist Georgius Agricola (1494-1555) called some metals tungsten. The word "tungsten" had many shades of meaning; it, in particular, meant both "wolf saliva" and "wolf foam", i.e. foam at the mouth of an angry wolf. Metallurgists of the 14th-16th centuries noticed that during the smelting of tin, the admixture of some mineral causes significant losses of the metal, turning it into “foam” - into slag. A harmful impurity was the mineral wolframite (Mn, Fe)WO4, similar in appearance to tin ore - cassiterite (SnO2). Medieval metallurgists called wolframite "tungsten" and said that "it steals and devours tin like a wolf a sheep."
For the first time tungsten was obtained by the Spanish chemists brothers de Eluyar in 1783. Even earlier - in 1781. - The Swedish chemist Scheele isolated tungsten trioxide WO3 from the mineral with the composition CaWO4, later called "scheelite". Therefore, tungsten was called sheel for a long time.
In England, France and the USA, tungsten is called differently - tungsten, which means "heavy stone" in Swedish. In Russia in the 19th century, tungsten was called "wolf".
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Radon, its effect on humans
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Pharmaceutical analysis of furan derivatives (furagin)
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Physical properties of Tungsten.
Tungsten.
Tungsten(Wolframium) W - element of group VI, 6th period periodic system D. I. Mendeleev, p. s. 74, atomic mass 183.85. Opened in 1781 by K. Scheele. Tungsten is not widely distributed in nature. Forms its own minerals - wolframite and scheelite; contained as an impurity in the minerals of tin, molybdenum, titanium. Tungsten is a light gray metal, in normal conditions chemically resistant. At elevated temperatures, it reacts with oxygen, carbon and other elements. It reacts with fluorine at 20°C, with other halogens - when heated. Acids, with the exception of hydrofluoric and nitric acids, do not affect Tungsten. In compounds, it exhibits variable valency. Compounds of 6-valent Tungsten are the most stable. Tungsten is used for alloying steels, for the manufacture of hard alloys for incandescent electric lamps, heaters in electric furnaces, welding electrodes, generator lamp cathodes, and high voltage rectifiers.
Tungsten crystallizes in a body-centered cubic lattice with a period a = 3.1647Å; density 19.3 g/cm3, mp 3410°C, tbp 5900°C. Thermal conductivity (cal/cm sec °C) 0.31 (20°C); 0.26 (1300°C). Electrical resistivity (ohm cm 10-6) 5.5 (20°C); 90.4 (2700°C). Electron work function 7.21 10-19 J (4.55 eV), radiation energy power at high temperatures (W/cm2): 18.0 (1000°C); 64.0 (2200°C); 153.0 (2700°C); 255.0 (3030°C). The mechanical properties of Tungsten depend on the previous processing. Tensile strength (kgf/mm2) for sintered ingot 11, for pressure-treated from 100 to 430; modulus of elasticity (kgf/mm1) 35000-38000 for wire and 39000-41000 for single-crystal thread; Brinell hardness (kgf/mm2) for sintered ingot 200-230, for forged ingot 350-400 (1 kgf/mm2 = 10 MN/m2). At room temperature, tungsten has low plasticity.
Under normal conditions Tungsten is chemically resistant. At 400–500°C, the compact metal is noticeably oxidized in air to WO3. Water vapor intensively oxidizes it above 600°C to WO3. Halogens, sulfur, carbon, silicon, boron interact with Tungsten at high temperatures (fluorine with powdered Tungsten - at room temperature). Tungsten does not react with hydrogen up to the melting point; with nitrogen above 1500°C forms nitride. Under normal conditions, Tungsten is resistant to hydrochloric, sulfuric, nitric and hydrofluoric acids, as well as to aqua regia; at 100°С, weakly interacts with them; dissolves rapidly in a mixture of hydrofluoric and nitric acids. In alkali solutions, when heated, tungsten dissolves slightly, and in molten alkalis with access to air or in the presence of oxidizing agents - quickly; in this case, tungstates are formed. In compounds, tungsten exhibits a valency of 2 to 6; compounds of higher valency are the most stable.
Tungsten forms four oxides: the highest - WO3 (tungsten anhydride), the lowest - WO2 and two intermediate ones W10O29 and W4O11. Tungstic anhydride is a lemon-yellow crystalline powder that dissolves in alkali solutions to form tungstates. When it is reduced with hydrogen, lower oxides and tungsten are successively formed. Tungstic anhydride corresponds to tungstic acid H2WO4 - a yellow powder, practically insoluble in water and acids. When it interacts with solutions of alkalis and ammonia, solutions of tungstates are formed. At 188°C, H2WO4 splits off water to form WO3. With chlorine, tungsten forms a series of chlorides and oxychlorides. The most important of them: WCl6 (mp 275°C, bp 348°C) and WO2Cl2 (mp 266°C, sublimates above 300°C), are obtained by the action of chlorine on tungsten anhydride in the presence of coal. With sulfur, tungsten forms two sulfides WS2 and WS3. Tungsten carbides WC (tmelt 2900°C) and W2C (tmelt 2750°C) are hard refractory compounds; obtained by the interaction of Tungsten with carbon at 1000-1500°C.
Tungsten is a chemical element of the periodic system of Mendeleev, which belongs to the VI group. In nature, tungsten occurs as a mixture of five isotopes. In its normal form and under normal conditions, it is a silvery-gray hard metal. It is also the most refractory of all metals.
Main properties of tungsten
Tungsten is a metal with remarkable physical and chemical properties. Practically in all branches of modern production, tungsten is used. Its formula is usually expressed as the designation of the metal oxide - WO 3 . Tungsten is considered the most refractory of the metals. It is assumed that only seaborgium can be even more refractory. But it is impossible to say for sure yet, since the seaborgium has a very short time of existence.
This metal has special physical and chemical properties. Tungsten has a density of 19300 kg / m 3, its melting point is 3410 ° C. According to this parameter, it ranks second after carbon - graphite or diamond. In nature, tungsten occurs in the form of five stable isotopes. Their mass numbers are in the range from 180 to 186. Tungsten has a 6th valence, and in compounds it can be 0, 2, 3, 4 and 5. The metal also has a fairly high level of thermal conductivity. For tungsten, this figure is 163 W/(m*deg). By this property, it exceeds even such compounds as aluminum alloys. The mass of tungsten is due to its density, which is 19kg/m 3 . The oxidation state of tungsten ranges from +2 to +6. IN higher degrees its oxidation, the metal has acidic properties, and in the lower - basic.
In this case, alloys of lower tungsten compounds are considered unstable. The most resistant are compounds with a degree of +6. They also exhibit the most characteristic chemical properties of a metal. Tungsten tends to easily form complexes. But metal tungsten is usually very resistant. It begins to interact with oxygen only at a temperature of +400 °C. The crystal lattice of tungsten belongs to the cubic body-centered type.
Interaction with other chemicals
If tungsten is mixed with dry fluorine, then a compound called "hexafluoride" can be obtained, which melts already at a temperature of 2.5 ° C, and boils at 19.5 ° C. A similar substance is obtained by combining tungsten with chlorine. But such a reaction requires a sufficiently high temperature - about 600 ° C. However, the substance easily resists the destructive action of water and practically does not undergo changes in the cold. Tungsten is a metal that, without oxygen, does not produce a dissolution reaction in alkalis. However, it readily dissolves in a mixture of HNO 3 and HF. The most important of the chemical compounds of tungsten are its trioxide WO 3, H 2 WO 4 - tungstic acid, as well as its derivatives - tungstate salts.
You can consider some of the chemical properties of tungsten with reaction equations. For example, the formula WO 3 + 3H 2 = W + 3H 2 O. In it, tungsten metal is reduced from oxide, its property of interaction with hydrogen is manifested. This equation reflects the process of obtaining tungsten from its trioxide. The following formula denotes such a property as the practical insolubility of tungsten in acids: W + 2HNO3 + 6HF = WF6 + 2NO + 4H2O. One of the most remarkable substances containing tungsten is carbonyl. From it, dense and ultra-thin coatings of pure tungsten are obtained.
Discovery history
Tungsten is a metal that gets its name from Latin. In translation, this word means "wolf foam." Such an unusual name appeared due to the behavior of the metal. Accompanying the mined tin ore, tungsten interfered with the release of tin. Because of it, only slags were formed during the smelting process. This metal was said to "eat tin like a wolf eats a sheep". For many, it is interesting who discovered the chemical element tungsten?
This scientific discovery was made simultaneously in two places by different scientists, independently of each other. In 1781, the Swedish chemist Scheele obtained the so-called "heavy stone" by experimenting with nitric acid and scheelite. In 1783, chemist brothers from Spain named Eluard also announced the discovery of a new element. More precisely, they discovered tungsten oxide, which was dissolved in ammonia.
Alloys with other metals
Currently, single-phase and multi-phase tungsten alloys are distinguished. They contain one or more extraneous elements. The most famous compound is an alloy of tungsten and molybdenum. The addition of molybdenum gives tungsten its tensile strength. Also, compounds of tungsten with titanium, hafnium, and zirconium belong to the category of single-phase alloys. Rhenium gives the greatest plasticity to tungsten. However, the practical application of such an alloy is a rather laborious process, since rhenium is very difficult to obtain.
Since tungsten is one of the most refractory materials, obtaining tungsten alloys is not an easy task. When this metal just begins to boil, others are already passing into a liquid or gas state. But modern scientists are able to obtain alloys using the electrolysis process. Alloys containing tungsten, nickel and cobalt are used to apply a protective layer on fragile materials.
The modern metallurgical industry also produces alloys using tungsten powder. Its creation requires special conditions, including the creation of a vacuum environment. Due to some features of the interaction of tungsten with other elements, metallurgists prefer to create alloys not with a two-phase characteristic, but with the use of 3, 4 or more components. These alloys are especially strong, but with strict adherence to the formulas. With the slightest deviations in the percentage components, the alloy can turn out to be brittle and unsuitable for use.
Tungsten - an element used in technology
The filaments of ordinary light bulbs are made from this metal. As well as tubes for X-ray machines, components of vacuum furnaces that must be used at extremely high temperatures. Steel, which includes tungsten, has a very high level of strength. These alloys are used to make tools in the most various fields: for drilling wells, in medicine, mechanical engineering.
The main advantage of joining steel and tungsten is wear resistance and low probability of damage. The most famous tungsten alloy in construction is called "win". Also, this element is widely used in the chemical industry. With its addition, paints and pigments are created. Tungsten oxide 6 is especially widely used in this area. It is used for the manufacture of carbides and tungsten halides. Another name for this substance is tungsten trioxide. 6 is used as a yellow pigment in paints for ceramics and glassware.
What are heavy alloys?
All tungsten-based alloys that have a high density index are called heavy. They are obtained only by powder metallurgy methods. Tungsten is always the basis of heavy alloys, where its content can be up to 98%. In addition to this metal, nickel, copper and iron are added to heavy alloys. However, they may also include chromium, silver, cobalt, molybdenum. The most popular alloys are VMZh (tungsten - nickel - iron) and VNM (tungsten - nickel - copper). The high level of density of such alloys allows them to absorb dangerous gamma radiation. Flywheels, electrical contacts, rotors for gyroscopes are made from them.
Wolfram carbide
About half of all tungsten is used to make durable metals, especially tungsten carbide, which has a melting point of 2770 C. Tungsten carbide is a chemical compound that contains an equal number of carbon and tungsten atoms. This alloy has special chemical properties. Tungsten gives it such strength that in this indicator it surpasses steel twice.
Tungsten carbide is widely used in industry. It is used to make cutting objects, which must be very resistant to high temperatures and abrasion. Also from this element are made:
- Aircraft parts, car engines.
- Parts for spaceships.
- Medical surgical instruments that are used in the field of abdominal surgery. Such instruments are more expensive than ordinary medical steel, but they are more productive.
- Jewelry, especially wedding rings. Such popularity of tungsten is associated with its strength, which for those who get married symbolizes the strength of relationships, as well as appearance. The characteristics of polished tungsten are such that it retains a mirror-like, shiny appearance for a very long time.
- Ballpoints for luxury ballpoint pens.
Win - tungsten alloy
Approximately in the second half of the 1920s, alloys for cutting tools began to be produced in many countries, which were obtained from tungsten carbides and metallic cobalt. In Germany, such an alloy was called vidia, in the States - carbola. In the Soviet Union, such an alloy was called "win". These alloys have proven to be excellent for machining cast iron products. Pobedit is a cermet alloy with extremely high level strength. It is made in the form of plates. various forms and sizes.
The manufacturing process of a Pobedit comes down to the following: Tungsten carbide powder, fine nickel or cobalt powder is taken, and everything is mixed and pressed into special forms. The plates pressed in this way are subjected to further heat treatment. This gives a very hard alloy. These inserts are not only used for cutting cast iron, but also for making drilling tools. Plates from Pobedit are soldered onto drilling equipment using copper.
The prevalence of tungsten in nature
This metal is very rare in environment. After all the elements, it ranks 57th and is contained in the form of tungsten clarke. The metal also forms minerals - scheelite and wolframite. Tungsten migrates into groundwater either as its own ion or as various compounds. But its highest concentration in groundwater is negligible. It is hundredths of mg/l and practically does not change their chemical properties. Tungsten can also get into natural water bodies from the effluents of plants and factories.
Impact on the human body
Tungsten practically does not enter the body with water or food. There may be a danger of inhaling tungsten particles with industrial air. However, despite belonging to the category of heavy metals, tungsten is not toxic. Tungsten poisoning occurs only in those associated with tungsten production. At the same time, the degree of influence of the metal on the body is different. For example, tungsten powder, tungsten carbide, and substances such as tungstic anhydrite can cause lung damage. Its main symptoms are general malaise, fever. More severe symptoms occur with poisoning with tungsten alloys. This occurs when inhaling the dust of alloys and leads to bronchitis, pneumosclerosis.
Metal tungsten, getting inside the human body, is not absorbed in the intestines and is gradually excreted. Tungsten compounds, which are soluble, can be of great danger. They are deposited in the spleen, bones and skin. With prolonged exposure to tungsten compounds, symptoms such as brittle nails, peeling of the skin, and various kinds of dermatitis may occur.
Tungsten reserves in various countries
The largest resources of tungsten are in Russia, Canada and China. According to scientists, about 943 thousand tons of this metal are located in domestic territories. According to these estimates, the vast majority of reserves are located in Southern Siberia and on Far East. The share of explored resources is very insignificant - it is only about 7%.
In terms of the number of explored deposits of tungsten, Russia is second only to China. Most of them are located in the regions of Kabardino-Balkaria and Buryatia. But in these deposits, not pure tungsten is mined, but its ores, which also contain molybdenum, gold, bismuth, tellurium, scandium and other substances. Two-thirds of the volumes of tungsten obtained from explored sources are contained in refractory ores, where the main tungsten-containing mineral is scheelite. The share of easily enriched ores accounts for only a third of all production. The characteristics of tungsten mined in Russia are lower than those abroad. The ores contain a high percentage of tungsten trioxide. There are very few alluvial metal deposits in Russia. Tungsten sands are also low quality, with big amount oxides.
Tungsten in Economics
Global production of tungsten began to grow around 2009, when the Asian industry began to recover. China remains the largest producer of tungsten. For example, in 2013, the production of this country accounted for 81% of the world supply. About 12% of demand for tungsten is related to the production of lighting products. According to experts, the use of tungsten in this area will be reduced against the background of the use of LED and fluorescent lamps both in domestic conditions and in production.
It is believed that the demand for tungsten in the electronics industry will grow. The high wear resistance of tungsten and its ability to withstand electricity make it the most suitable metal for the production of voltage regulators. However, in terms of volume, this demand is still quite small, and it is estimated that by 2018 it will grow by only 2%. However, according to the forecasts of scientists, in the near future there should be an increase in demand for cemented carbide. This is due to the growth of automotive production in the US, China, Europe, as well as an increase in the mining industry. It is believed that by 2018 the demand for tungsten will increase by 3.6%.
