Tungsten: properties and applications. Tungsten - what kind of metal? Properties and applications Structure of the tungsten atom

Tungsten is a chemical element of the Mendeleev periodic table, which belongs to group VI. In nature, tungsten occurs as a mixture of five isotopes. In its ordinary form and under ordinary conditions it is a hard metal of a silvery-gray color. It is also the most refractory of all metals.

Basic properties of tungsten

Tungsten is a metal with remarkable physical and chemical properties. Tungsten is used in almost all branches of modern production. Its formula is usually expressed in terms of the metal oxide symbol - WO 3. Tungsten is considered the most refractory of metals. It is assumed that only seaborgium may be even more refractory. But this cannot be stated for sure yet, since seaborgium has a very short lifetime.

This metal has special physical and chemical properties. Tungsten has a density of 19300 kg/m3, its melting point is 3410 °C. In terms of this parameter, it ranks second after carbon - graphite or diamond. In nature, tungsten occurs in the form of five stable isotopes. Their mass numbers range from 180 to 186. Tungsten has a valency of 6, 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). In terms of this property, it exceeds even such compounds as aluminum alloys. The mass of tungsten is determined by its density, which is 19 kg/m 3. The oxidation state of tungsten ranges from +2 to +6. In higher degrees of oxidation, the metal has acidic properties, and in lower states it has basic properties.

In this case, alloys of lower tungsten compounds are considered unstable. The most resistant are connections with degree +6. They also exhibit the most characteristic chemical properties of a metal. Tungsten has the property of easily forming complexes. But tungsten metal is usually very resistant. It begins to interact with oxygen only at a temperature of +400 °C. The tungsten crystal lattice is of the body-centered cubic type.

Interaction with other chemicals

If tungsten is mixed with dry fluorine, you can get a compound called hexafluoride, which melts 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 fairly high temperature - about 600 °C. However, the substance easily resists the destructive effects of water and is practically not subject to changes in the cold. Tungsten is a metal that, without oxygen, does not dissolve in alkalis. However, it dissolves easily in a mixture of HNO 3 and HF. The most important chemical compounds of tungsten are its trioxide WO 3, H 2 WO 4 - tungstic acid, as well as its derivatives - tungstate salts.

We can look at some of the chemical properties of tungsten with reaction equations. For example, the formula WO 3 + 3H 2 = W + 3H 2 O. In it, the metal tungsten is reduced from the oxide, and its ability to interact 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 notable substances containing tungsten is carbonyl. It produces dense and ultra-thin coatings of pure tungsten.

History of discovery

Tungsten is a metal that gets its name from the Latin language. Translated, this word means “wolf foam.” This 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 slag was formed during the smelting process. It was said about this metal that it “eats tin like a wolf eats a sheep.” Many people wonder 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 conducting experiments with nitric acid and scheelite. In 1783, chemist brothers from Spain named Eluard also reported the discovery of a new element. More precisely, they discovered tungsten oxide, which dissolved in ammonia.

Alloys with other metals

Currently, a distinction is made between single-phase and multiphase tungsten alloys. They contain one or more foreign elements. The most famous compound is an alloy of tungsten and molybdenum. The addition of molybdenum gives tungsten its tensile strength. Also included in the category of single-phase alloys are compounds of tungsten with titanium, hafnium, and zirconium. Rhenium gives tungsten the greatest ductility. However, practically using such an alloy is a rather labor-intensive process, since rhenium is very difficult to obtain.

Since tungsten is one of the most refractory materials, producing tungsten alloys is not an easy task. When this metal just begins to boil, others are already turning into a liquid or gas state. But modern scientists know how to produce alloys using the electrolysis process. Alloys containing tungsten, nickel and cobalt are used to apply a protective layer to fragile materials.

In the modern metallurgical industry, alloys are also produced using tungsten powder. To create it, special conditions are required, 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 two-phase characteristics, but with the use of 3, 4 or more components. These alloys are especially strong, but with strict adherence to the formulas. At the slightest deviations in the percentage components, the alloy can become brittle and unusable.

Tungsten is 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 contains tungsten, has a very high level of strength. Such alloys are used to make tools in a wide variety of fields: well drilling, medicine, and mechanical engineering.

The main advantage of joining steel and tungsten is wear resistance and the likelihood of damage. The most famous tungsten alloy in construction is called “win.” This element is also 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 production of tungsten carbides and halides. Another name for this substance is tungsten trioxide. 6 is used as a yellow pigment in ceramic and glass paints.

What are heavy alloys?

All tungsten-based alloys that have a high density are called heavy. They are obtained only using 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, and molybdenum. The most popular alloys are VMF (tungsten - nickel - iron) and VNM (tungsten - nickel - copper). The high level of density of such alloys allows them to absorb dangerous gamma radiation. Wheel flywheels, electrical contacts, and rotors for gyroscopes are made from them.

Wolfram carbide

About half of all tungsten is used to make strong metals, especially tungsten carbide, which has a melting point of 2770 C. Tungsten carbide is a chemical compound that contains equal numbers of carbon and tungsten atoms. This alloy has special chemical properties. Tungsten gives it such strength that it is twice as strong as steel.

Tungsten carbide is widely used in industry. Cutting objects are made from it, which must be very resistant to high temperatures and abrasion. Also made from this element:

• Aircraft parts, car engines.
• Parts for spaceships.
• Medical surgical instruments used in the field of abdominal surgery. Such instruments are more expensive than conventional medical steel, but they are more productive.
• Jewelry, especially wedding rings. The popularity of tungsten is associated with its durability, which for those getting married symbolizes the strength of the relationship, as well as its appearance. The characteristics of tungsten in polished form are such that it retains a mirror-like, shiny appearance for a very long time.
• Balls for luxury ballpoint pens.

Will win - tungsten alloy

Around the second half of the 1920s, many countries began to produce alloys for cutting tools, which were obtained from tungsten carbides and cobalt metal. 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 metal-ceramic alloy with an extremely high level of strength. It is made in the form of plates of various shapes and sizes.

The process of making a pobedit comes down to the following: tungsten carbide powder, fine nickel or cobalt powder are taken, and everything is mixed and pressed in special forms. The plates pressed in this way are subjected to further heat treatment. This produces a very hard alloy. These inserts are used not only for cutting cast iron, but also for making drilling tools. Pobedite plates are soldered onto drilling equipment using copper.

Prevalence of tungsten in nature

This metal is very rare in the environment. After all the elements, it ranks 57th and is found in the form of clarke tungsten. The metal also forms minerals - scheelite and wolframite. Tungsten migrates into groundwater either as its own ion or in the form of various compounds. But its highest concentration in groundwater is negligible. It amounts to hundredths of mg/l and practically does not change their chemical properties. Tungsten can also enter natural water bodies from wastewater from factories and factories.

Effect on the human body

Tungsten practically does not enter the body with water or food. There may be a risk of inhaling tungsten particles in the air at work. However, despite belonging to the category of heavy metals, tungsten is not toxic. Tungsten poisoning occurs only among those associated with tungsten production. At the same time, the degree of influence of the metal on the body varies. For example, tungsten powder, tungsten carbide, and a substance such as tungstic anhydrite can cause lung damage. Its main symptoms are general malaise and fever. More severe symptoms occur with poisoning from tungsten alloys. This occurs when inhaling alloy dust and leads to bronchitis and pneumosclerosis.

Metal tungsten, entering the human body, is not absorbed in the intestines and is gradually excreted. Tungsten compounds, which are classified as soluble, can pose a great danger. They are deposited in the spleen, bones and skin. With prolonged exposure to tungsten compounds, symptoms such as brittle nails, peeling skin, and various types of dermatitis may occur.

Tungsten reserves in various countries

The largest tungsten resources are found in Russia, Canada and China. According to scientists' forecasts, about 943 thousand tons of this metal are located in domestic territories. If we believe these estimates, the vast majority of reserves are located in Southern Siberia and the Far East. The share of explored resources is very small - it is only about 7%.

In terms of the number of explored tungsten deposits, Russia is second only to China. Most of them are located in the regions of Kabardino-Balkaria and Buryatia. But in these deposits it is not pure tungsten that 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 difficult-to-process ores, where the main tungsten-containing mineral is scheelite. The share of easily processed ores accounts for only a third of all production. The characteristics of tungsten mined in Russia are lower than abroad. The ores contain a large percentage of tungsten trioxide. There are very few placer metal deposits in Russia. Tungsten sands are also low quality, with a lot of oxides.

Tungsten in economics

Global tungsten production began to grow around 2009, when the Asian industry began to recover. China remains the largest tungsten producer. For example, in 2013, this country's production accounted for 81% of global supply. About 12% of tungsten demand comes from the lighting industry. According to experts, the use of tungsten in this area will decline against the backdrop 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 increase. Tungsten's high wear resistance and ability to withstand electricity make it the most suitable metal for producing voltage regulators. However, in terms of volume, this demand remains quite small, and it is believed that by 2018 it will grow by only 2%. However, according to scientists' forecasts, in the near future there should be an increase in demand for cemented carbide. This is due to the growth of automobile production in the USA, China, Europe, as well as the increase in the mining industry. It is believed that by 2018, demand for tungsten will increase by 3.6%.

Back in the 16th century, the mineral wolframite was known, which translated from German ( Wolf Rahm) means "wolf's cream". The mineral received this name due to its characteristics. The fact is that tungsten, which accompanied tin ores, during the smelting of tin turned it simply into foam of slag, which is why they said: “devours tin like a wolf devours a sheep.” Over time, it was from wolframite that the name tungsten was inherited by the 74th chemical element of the periodic system.

Tungsten Characteristics

Tungsten is a light gray transition metal. Has an external resemblance to steel. Due to its rather unique properties, this element is a very valuable and rare material, the pure form of which does not exist in nature. Tungsten has:

• a fairly high density, which equates to 19.3 g/cm 3 ;
• high melting point of 3422 0 C;
• sufficient electrical resistance - 5.5 μOhm*cm;
• normal indicator of the linear expansion parameter coefficient equal to 4.32;
• the highest boiling point among all metals, equal to 5555 0 C;
• low evaporation rate, even despite temperatures exceeding 200 0 C;
• relatively low electrical conductivity. However, this does not prevent tungsten from remaining a good conductor.

Table 1. Properties of tungsten

Characteristic	Meaning
Properties of the atom
Name, symbol, number	Tungsten / Wolframium (W), 74
Atomic mass (molar mass)	183.84(1) a. e.m. (g/mol)
Electronic configuration	4f14 5d4 6s2
Atomic radius	141 pm
Chemical properties
Covalent radius	170 pm
Ion radius	(+6e) 62 (+4e) 70 pm
Electronegativity	2.3 (Pauling scale)
Electrode potential	W ← W3+ 0.11 VW ← W6+ 0.68 V
Oxidation states	6, 5, 4, 3, 2, 0
Ionization energy (first electron)	769.7 (7.98) kJ/mol (eV)
Thermodynamic properties of a simple substance
Density (at normal conditions)	19.25 g/cm³
Melting temperature	3695 K (3422 °C, 6192 °F)
Boiling temperature	5828 K (5555 °C, 10031 °F)
Ud. heat of fusion	285.3 kJ/kg 52.31 kJ/mol
Ud. heat of vaporization	4482 kJ/kg 824 kJ/mol
Molar heat capacity	24.27 J/(K mol)
Molar volume	9.53 cm³/mol
Crystal lattice of a simple substance
Lattice structure	cubic body-centered
Lattice parameters	3.160 Å
Debye temperature	310K
Other characteristics
Thermal conductivity	(300 K) 162.8 W/(mK)
CAS number	7440-33-7

All this makes tungsten a very durable metal that is not susceptible to mechanical damage. But the presence of such unique properties does not exclude the presence of disadvantages that tungsten also has. These include:

• high fragility when exposed to very low temperatures;
• high density, which makes its processing difficult;
• low resistance to acids at low temperatures.

Production of tungsten

Tungsten, along with molybdenum, rubidium and a number of other substances, is part of a group of rare metals that are characterized by a very low distribution in nature. Due to this, it cannot be extracted in the traditional way, like many minerals. Thus, the industrial production of tungsten consists of the following stages:

• extraction of ore, which contains a certain proportion of tungsten;
• organizing appropriate conditions in which metal can be separated from the processed mass;
• concentration of a substance in the form of a solution or precipitate;
• purifying the resulting chemical compound from the previous step;
• isolation of pure tungsten.

Thus, the pure substance from the mined ore containing tungsten can be isolated in several ways.

1. As a result of beneficiation of tungsten ore by gravity, flotation, magnetic or electrical separation. In this process, a tungsten concentrate is formed, consisting of 55-65% tungsten anhydride (trioxide) WO 3. In concentrates of this metal, the content of impurities is monitored, which can include phosphorus, sulfur, arsenic, tin, copper, antimony and bismuth.
2. As is known, tungsten trioxide WO 3 is the main material for separating metal tungsten or tungsten carbide. The production of WO 3- occurs as a result of the decomposition of concentrates, leaching of an alloy or sinter, etc. In this case, the output is a material consisting of 99.9% WO 3.
3. From tungsten anhydride WO 3. It is by reducing this substance with hydrogen or carbon that tungsten powder is obtained. The use of the second component for the reduction reaction is used less frequently. This is due to the saturation of WO 3 with carbides during the reaction, as a result of which the metal loses its strength and becomes more difficult to process. Tungsten powder is produced by special methods, thanks to which it becomes possible to control its chemical composition, grain size and shape, as well as particle size distribution. Thus, the fraction of powder particles can be increased by rapidly increasing the temperature or by low hydrogen supply rate.
4. Production of compact tungsten, which has the form of bars or ingots and is a blank for the further production of semi-finished products - wire, rods, tape, etc.

The latter method, in turn, includes two possible options. One of them is associated with powder metallurgy methods, and the other is with smelting in electric arc furnaces with a consumable electrode.

Powder metallurgy method

Due to the fact that thanks to this method it is possible to more evenly distribute the additives that give tungsten its special properties, it is more popular.

It includes several stages:

1. Metal powder is pressed into bars;
2. The workpieces are sintered at low temperatures (so-called pre-sintering);
3. Welding of workpieces;
4. Obtaining semi-finished products by processing blanks. The implementation of this stage is carried out by forging or mechanical processing (grinding, polishing). It is worth noting that mechanical processing of tungsten becomes possible only under the influence of high temperatures, otherwise it is impossible to process it.

At the same time, the powder must be well purified with a maximum permissible percentage of impurities of up to 0.05%.

This method makes it possible to obtain tungsten rods with a square cross-section from 8x8 to 40x40 mm and a length of 280-650 mm. It is worth noting that at room temperatures they are quite strong, but have increased fragility.

Fuse

This method is used if it is necessary to obtain tungsten blanks of fairly large dimensions - from 200 kg to 3000 kg. Such blanks are usually needed for rolling, drawing pipes, and manufacturing products by casting. Melting requires the creation of special conditions - a vacuum or a rarefied atmosphere of hydrogen. The output is tungsten ingots, which have a coarse-crystalline structure and are also highly brittle due to the presence of a large amount of impurities. The impurity content can be reduced by pre-melting tungsten in an electron beam furnace. However, the structure remains unchanged. In this connection, to reduce the grain size, the ingots are further melted, but in an electric arc furnace. At the same time, during the smelting process, alloying substances are added to the ingots, giving tungsten special properties.

To obtain tungsten ingots with a fine-grained structure, arc skull melting is used with metal casting into a mold.

The method of obtaining the metal determines the presence of additives and impurities in it. Thus, several grades of tungsten are produced today.

Tungsten grades

1. HF - pure tungsten, which does not contain any additives;
2. VA is a metal containing aluminum and silica-alkali additives, which give it additional properties;
3. VM is a metal containing thorium and silica-alkali additives;
4. VT - tungsten, which contains thorium oxide as an additive, which significantly increases the emissive properties of the metal;
5. VI - metal containing yttrium oxide;
6. VL - tungsten with lanthanum oxide, which also increases emission properties;
7. VR - alloy of rhenium and tungsten;
8. VРН - there are no additives in the metal, however impurities may be present in large volumes;
9. MV is an alloy of tungsten with molybdenum, which significantly increases strength after annealing while maintaining ductility.

Where is tungsten used?

Thanks to its unique properties, chemical element 74 has become indispensable in many industrial sectors.

1. The main use of tungsten is as a basis for the production of refractory materials in metallurgy.
2. With the obligatory participation of tungsten, incandescent filaments are produced, which are the main element of lighting devices, picture tubes, and other vacuum tubes.
3. Also, this metal underlies the production of heavy alloys used as counterweights, armor-piercing cores of sub-caliber and swept-finned projectiles of artillery guns.
4. Tungsten is the electrode used in argon-arc welding;
5. Its alloys are highly resistant to various temperatures, acidic environments, as well as hardness and abrasion resistance, and are therefore used in the production of surgical instruments, tank armor, torpedo and projectile casings, aircraft and engine parts, as well as nuclear storage containers. waste;
6. Vacuum resistance furnaces, the temperature in which reaches extremely high values, are equipped with heating elements also made from tungsten;
7. The use of tungsten is popular to provide protection against ionizing radiation.
8. Tungsten compounds are used as alloying elements, high-temperature lubricants, catalysts, pigments, and also for converting thermal energy into electrical energy (tungsten ditelluride).

Tungsten is a chemical element of the 4th group, having atomic number 74 in the periodic table of Dmitri Ivanovich Mendeleev, designated W (Wolframium). The metal was discovered and isolated by two Spanish chemists, the d'Eluyard brothers, in 1783. The name “Wolframium” itself was transferred to the element from the previously known mineral wolframite, which was known back in the 16th century, it was then called “wolf foam”, or “Spuma lupi” in Latin, in German this phrase sounds like “Wolf Rahm” (Tungsten). The name was due to the fact that tungsten, when accompanying tin ores, significantly interfered with the smelting of tin, because converted tin into foam of slag (they began to say about this process: “The tin devours the tin like a wolf eats a sheep!”). Currently, in the USA, France, Great Britain and some other countries, the name “tungsten” (from the Swedish tung sten, which translates as “heavy stone”) is used to name tungsten.

Tungsten is a hard, gray transition metal. The main use of tungsten is as a base material in refractory materials in metallurgy. Tungsten is extremely refractory; under normal conditions, the metal is chemically resistant.

Tungsten differs from all other metals in its unusual hardness, heaviness and refractoriness. Since ancient times, people have used the expression “heavy as lead” or “heavier than lead”, “lead eyelids”, etc. But it would be more correct to use the word “tungsten” in these allegories. The density of this metal is almost twice that of lead, 1.7 times to be precise. With all this, the atomic mass of tungsten is lower and has a value of 184 versus 207 for lead.

Tungsten is a light gray metal; the melting and boiling points of this metal are the highest. Due to the ductility and refractoriness of tungsten, it can be used as filaments for lighting devices, in picture tubes, as well as in other vacuum tubes.

Twenty tungsten minerals are known. The most common: minerals of the scheelite-wolframite group, which are of industrial importance. Less commonly found is wolframite sulfide, i.e. tungstensite (WS2) and oxide-like compounds - ferro - and cuprotungstite, tungstite, hydrotungstite. Vadas, psilomelans with a high tungsten content, are widespread.

Depending on the conditions of occurrence, morphology and type of tungsten deposits, open-pit, underground, and combined methods are used in their development.

There are currently no methods for obtaining tungsten directly from concentrates. In this regard, first, intermediate compounds are isolated from the concentrate, and then metal tungsten is obtained from them. The isolation of tungsten includes: the decomposition of concentrates, then the transition of the metal into compounds, from which it is separated from the rest of the elements accompanying it. Release of tungstic acid, i.e. pure chemical compound tungsten, continues with the subsequent production of tungsten in metallic form.

Tungsten is used in the production of machinery and equipment for the metalworking, construction and mining industries, in the manufacture of lighting fixtures and lamps, in the transport and electronics industry, in the chemical industry and other areas.

Made from tungsten steel, the tool is capable of withstanding the enormous speeds of the most intense metalworking processes. Cutting speed using such a tool is usually measured in tens of meters per second.

Tungsten is quite rare in nature. The metal content in the earth's crust by mass is about 1.3·10−4%. The main tungsten-containing minerals are the naturally occurring tungstates: scheelite, originally called tungsten, and wolframite.

Biological properties

The biological role of tungsten is insignificant. Tungsten is very similar in properties to molybdenum, but, unlike the latter, tungsten is not an essential element. Despite this fact, tungsten is quite capable of replacing molybdenum in animals and plants, as part of bacteria, while it inhibits the activity of Mo-dependent enzymes, for example, xanthine oxidase. Due to the accumulation of tungsten salts in animals, uric acid levels decrease and hypoxanthine and xanthine levels increase. Tungsten dust, like other metal dusts, irritates the respiratory system.

On average, the human body receives approximately 0.001-0.015 milligrams of tungsten per day with food. The digestibility of the element itself, as well as tungsten salts, in the human gastrointestinal tract is 1-10%, of slightly soluble tungsten acids - up to 20%. Tungsten mainly accumulates in bone tissue and kidneys. Bones contain approximately 0.00025 mg/kg, and human blood contains approximately 0.001 mg/l of tungsten. The metal is usually excreted from the body naturally, through urine. But 75% of the radioactive tungsten isotope 185W is excreted in the feces.

Food sources of tungsten, as well as its daily requirement, have not yet been studied. A toxic dose for the human body has not yet been identified. Lethal outcome in rats occurs from a little more than 30 mg of the substance. In medicine, it is believed that tungsten does not have metabolic, carcinogenic or teratogenic effects on humans and animals.

Indicator of the elemental status of tungsten within the human body: urine, whole blood. There are no data on a decrease in the level of tungsten in the blood.

An increased content of tungsten in the body most often occurs in workers of metallurgical plants involved in the production of refractory and heat-resistant materials, alloy steels, as well as in people who have come into contact with tungsten carbide.

Clinical syndrome “heavy metal disease” or pneumoconiosis can result from chronic exposure to tungsten dust. Signs may include the appearance of a cough, breathing problems, the development of atopic asthma and changes inside the lungs. The above syndromes usually subside after a long rest, and simply in the absence of direct contact with vanadium. In the most severe cases, when the disease is diagnosed too late, the pathology “cor pulmonale”, emphysema and pulmonary fibrosis develops.

“Heavy metal diseases” and the prerequisites for its occurrence usually appear as a result of exposure to several types of metals and salts (for example, cobalt, tungsten, etc.). It has been established that the combined effect of tungsten and cobalt on the human body increases the detrimental effect on the pulmonary system. Combining tungsten and cobalt carbides can cause local inflammation and contact dermatitis.

At the present stage of medical development, there are no effective ways to accelerate metabolism or eliminate a group of metal compounds that can provoke the appearance of “heavy metal disease.” That is why it is so important to constantly carry out preventive measures and promptly identify people with high sensitivity to heavy metals and carry out diagnosis at the initial stage of the disease. All these factors determine the further chances of success in treating the pathology. But in some cases, if necessary, complexing agent therapy and symptomatic treatment are used.

More than half (58% to be exact) of all tungsten produced is used in the production of tungsten carbide, and almost a quarter (23% to be exact) is used in the production of various steels and alloys. The manufacture of tungsten “rolled” products (this includes filaments of incandescent lamps, electrical contacts, etc.) accounts for approximately 8% of the tungsten consumed in the world, and the remaining 9% is used to produce catalysts and pigments.

Tungsten wire, which has found use in electric lamps, has recently acquired a new profile: it has been proposed to use it as a cutting tool when processing brittle materials.

The high strength and good ductility of tungsten make it possible to make unique items from it. For example, from this metal you can draw such a thin wire that 100 km of this wire will have a mass of only 250 kg.

Molten liquid tungsten could remain in this state even near the surface of the Sun itself, because the boiling point of the metal is above 5500 °C.

Many people know that bronze consists of copper, zinc and tin. But the so-called tungsten bronze is not only not bronze by definition, because... does not contain any of the above metals; it is not an alloy at all, because there are no purely metallic compounds in it, and sodium and tungsten are oxidized.

Getting peach paint was very difficult and often completely impossible. This is neither red nor pink, but some kind of intermediate color, and even with a greenish tint. The legend says that it took more than 8,000 attempts to obtain this paint. In the 17th century, only the most expensive porcelain products were decorated with peach paint for the then Chinese emperor at a special factory in Shanxi province. But when, after some time, the secret of the rare paint was discovered, it turned out that it was based on nothing more than tungsten oxide.

This happened in 1911. A student came to Yunnan Province from Beijing, his name was Li. Day after day he disappeared in the mountains, trying to find some stone, as he explained, it was a tin stone. But nothing worked for him. The owner of the house in which student Li lived lived with a young daughter named Xiao-mi. The girl was very sorry for the unlucky student and in the evening, during dinner, she told him simple stories. One story told about an unusual stove that was built from some dark stones that were torn straight from the cliff and laid in the backyard of their house. This stove turned out to be quite successful, and most importantly durable; it served its owners well for many years. Young Xiao-mi even presented the student with even one such stone as a gift. It was a rolled, lead-heavy brown stone. Later it turned out that this stone was pure wolframite...

In 1900, at the opening of the World Metallurgical Exhibition in Paris, completely new examples of high-speed steel (an alloy of steel and tungsten) were demonstrated for the first time. Literally immediately after this, tungsten began to be widely used in the metallurgical industry of all highly developed countries. But there is a rather interesting fact: tungsten steel was first invented in Russia back in 1865 at the Motovilikha plant in the Urals.

At the beginning of 2010, an interesting artifact fell into the hands of Perm ufologists. It is believed to be a piece of spacecraft. An analysis of the fragment showed that the object consists almost entirely of pure tungsten. Only 0.1% of the composition is made up of rare impurities. According to scientists, rocket nozzles are made from pure tungsten. But one fact cannot yet be explained. In air, tungsten quickly oxidizes and rusts. But for some reason this fragment does not corrode.

Story

The word “tungsten” itself is of German origin. Previously, tungsten was not called the metal itself, but its main mineral, i.e. to wolframite. Some suggest that the word was then used almost as a swear word. From the early 16th century to the second half of the 17th century, tungsten was considered a tin mineral. Although it does quite often accompany tin ores. But from ores that included wolframite, much less tin was smelted. It was as if someone or something was “eating” the useful tin. This is where the name of the new element comes from. In German, Wolf means wolf, and Ram means ram in ancient German. Those. the expression “tin eats tin like a wolf eats a lamb” became the name of the metal.

The well-known chemical abstract journal of the USA or reference publications on all chemical elements by Mellor (England) and Pascal (France) do not even contain a mention of such an element as tungsten. The chemical element number 74 is called tungsten. The symbol W, which stands for tungsten, has only become widespread in the last few years. In France and Italy, until quite recently, the element was designated by the letters Tu, i.e. the first letters of the word tungstene.

The basis for such confusion lies in the history of the discovery of the element. In 1783, Spanish chemists the Eluard brothers reported that they had discovered a new chemical element. In the process of decomposition of the Saxon mineral “tungsten” with nitric acid, they managed to obtain “acid earth”, i.e. a yellow precipitate of oxide of an unknown metal; the precipitate turned out to be soluble in ammonia. In the source material, this oxide was present together with oxides of manganese and iron. The Eluard brothers named this element tungsten, and the mineral from which the metal was extracted wolframite.

But the Eluard brothers cannot be 100% called the discoverers of tungsten. Of course, they were the first to report their discovery in print, but... In 1781, two years before the brothers’ discovery, the famous Swedish chemist Carl Wilhelm Scheele found exactly the same “yellow earth” while treating another mineral with nitric acid. The scientist simply called it “tungsten” (translated from Swedish tung - heavy, sten - stone, i.e. “heavy stone”). Karl Wilhelm Scheele found that “yellow earth” differs in color, as well as in other properties, from similar molybdenum earth. The scientist also learned that in the mineral itself it was bound with calcium oxide. In honor of Scheele, the name of the mineral "tungsten" was changed to "scheelite". It is interesting that one of the Eluard brothers was a student of Scheele; in 1781 he worked in the teacher’s laboratory. Neither Scheele nor the Eluard brothers shared the discovery. Scheele simply did not lay claim to this discovery, and the Eluard brothers did not insist on the priority of their primacy.

Many people have heard about the so-called “tungsten bronzes”. These are very beautiful metals in appearance. Blue tungsten bronze has the following composition Na2O · WO2 ·, and golden – 4WO3Na2O · WO2 · WO3; violet and purple-red occupy an intermediate position, in them the ratio of WO3 to WO2 is less than four and more than one. As the formulas show, these substances contain neither tin, nor copper, nor zinc. These are not bronzes, and not alloys at all, because... they do not even contain metal compounds, and sodium and tungsten are oxidized here. Such “bronzes” resemble real bronze not only in appearance, but also in their properties: hardness, resistance to chemical reagents, and high electrical conductivity.

In ancient times, peach color was one of the rarest, it was said that 8,000 experiments had to be carried out to obtain it. In the 17th century, the most expensive porcelain of the Chinese emperor was painted peach. But after revealing the secret of this paint, it unexpectedly turned out that its basis was tungsten oxide.

Being in nature

Tungsten is poorly distributed in nature; the metal content in the earth's crust is 1.3·10 -4% by mass. Tungsten is mainly found in complex oxidized compounds, which are formed by tungsten trioxide WO3, as well as oxides of iron and calcium or manganese, sometimes copper, lead, thorium and various rare earth elements. The most common mineral wolframite is a solid solution of tungstates, i.e. salts of tungstic acid, manganese and iron (nMnWO 4 mFeWO 4). The solution appears as hard and heavy crystals of black or brown color, depending on the predominance of various compounds in the solution. If there are more manganese compounds (Hübnerite), the crystals will be black, but if iron compounds predominate (ferberite), the solution will be brown. Wolframite is an excellent conductor of electricity and is paramagnetic.

As for other tungsten minerals, scheelite is of industrial importance, i.e. calcium tungstate (formula CaWO 4). The mineral forms shiny crystals of light yellow and sometimes almost white colors. Scheelite is not magnetic at all, but it has another feature - the ability to luminesce. After ultraviolet illumination in the dark, it will fluoresce with a bright blue color. The presence of molybdenum impurities changes the color of the glow; it changes to pale blue, sometimes to cream. Thanks to this property, geological deposits of the mineral can be easily detected.

Typically, deposits of tungsten ore are associated with the area of ​​granite. Large crystals of scheelite or wolframite are very rare. Usually minerals are simply embedded in granite rocks. It is quite difficult to extract tungsten from granite, because... its concentration is usually no more than 2%. In total, no more than 20 tungsten minerals are known. Among them, we can distinguish stolzite and rasoite, which are two different crystalline modifications of lead tungstate PbWO 4. The remaining minerals are decomposition products or secondary forms of common minerals, for example, scheelite and wolframite (hydrotungstite, which is hydrated tungsten oxide, formed from wolframite; tungsten ochre), Rousselite, a mineral containing oxides of tungsten and bismuth. The only non-oxide tungsten mineral is tungstenite (WS 2), and its main reserves are located in the United States. Typically, the tungsten content is in the range of 0.3% to 1.0% WO 3 .

All tungsten deposits are of hydrothermal or magmatic origin. Scheelite and wolframite are quite often found in the form of veins, in places where magma has penetrated into cracks in the earth's crust. The bulk of tungsten deposits are concentrated in areas of young mountain ranges - the Alps, Himalayas and the Pacific belt. The largest deposits of wolframite and scheelite are located in China, Burma, the USA, Russia (Urals, Transbaikalia and the Caucasus), Portugal and Bolivia. The annual production of tungsten ores in the world is approximately 5.95 104 tons of metal, of which 49.5 104 tons (or 83%) are extracted in China. In Russia, about 3,400 tons are mined per year, in Canada - 3,000 tons per year.

China plays the role of the global leader in the development of tungsten raw materials (the Jianshi deposit accounts for 60 percent of Chinese production, Hunan - 20 percent, Yunnan - 8 percent, Guandong - 6 percent, Inner Mongolia and Guanzhi - 2% each, there are others). In Russia, the largest deposits of tungsten ore are located in 2 regions: in the North Caucasus (Tyrnyauz, Kabardino-Balkaria) and in the Far East. The Nalchik facility processes tungsten ore into ammonium paratungstate and tungsten oxide.

The largest consumer of tungsten is Western Europe (30%). USA and China - 25% each, 12%-13% - Japan. About 3000 tons of metal are consumed annually in the CIS.

Application

In total, the world produces approximately 30 thousand tons of tungsten per year. Tungsten steel and other alloys containing tungsten and its carbides are used in the manufacture of tank armor, shells and torpedoes, the most important parts of aircraft and internal combustion engines.

The best types of tool steels certainly contain tungsten. Metallurgy in general absorbs about 95% of all tungsten produced. What is typical for metallurgy, not only pure tungsten is used, mainly cheaper tungsten is used - ferrotungsten, i.e. an alloy containing about 80% tungsten and about 20% iron. It is produced in electric arc furnaces.

Tungsten alloys have a number of remarkable properties. An alloy of tungsten, copper and nickel, as it is also called a “heavy” metal, is a raw material in the manufacture of containers for storing radioactive substances. The protective effect of such an alloy is 40% greater than that of lead. This alloy is also used in radiotherapy, because the relatively small thickness of the screen provides sufficient protection.

An alloy of tungsten carbide and 16 percent cobalt has such hardness that it partially replaces diamond in drilling wells. Tungsten pseudo-alloys with silver and copper are an excellent material for switches and switches under high electrical voltage conditions. Such products last 6 times longer than conventional copper contacts.

The use of pure tungsten or alloys containing tungsten is based largely on their hardness, refractoriness and chemical resistance. Tungsten in its pure form is widely used in the production of filaments for electric incandescent lamps, as well as cathode ray tubes, used in the production of crucibles for the purpose of evaporating metals, used in contacts of automobile ignition distributors, used in targets for X-ray tubes; used as windings and heating elements of electric furnaces, as well as as a structural material for space and aircraft that operate at high temperatures.

Tungsten is part of the alloys of high-speed steels (tungsten content 17.5 - 18.5%), stellites (made from cobalt with additions of Cr, C, W), hastalloy (Ni-based stainless steels), as well as many other alloys. Tungsten is used as a base in the production of heat-resistant and tool alloys, namely ferrotungsten (W 68–86%, Mo and iron up to 7%), which is easily obtained by direct reduction of scheelite or wolframite concentrate. Tungsten is used in the production of pobedit. This is a super-hard alloy containing 80–85% tungsten, 7–14% cobalt, 5–6% carbon. Pobedit is simply irreplaceable in the metal processing process, as well as in the oil and mining industries.

Magnesium and calcium tungstates are widely used in fluorescent devices. Other tungsten salts are used in the tanning and chemical industries. Tungsten disulfide is a dry high-temperature lubricant, stable at temperatures up to 500 ° C. Tungsten bronzes, as well as other tungsten compounds, are used in the manufacture of paints. Quite a lot of tungsten compounds are excellent catalysts.

In the production of electric lamps, tungsten is indispensable because it is not only unusually refractory, but also quite ductile. 1 kg of tungsten serves as raw material for the manufacture of 3.5 km of wire. Those. From 1 kg of tungsten you can make incandescent filaments for 23 thousand 60-watt lamps. Thanks to this property alone, the electrical industry around the world consumes about one hundred tons of tungsten per year.

Production

The first stage in obtaining tungsten is ore enrichment, i.e. separation of valuable components from the main ore mass, gangue. The beneficiation methods used are the same as for other heavy metal ores: grinding and flotation, followed by magnetic separation (wolframite ores) and oxidative roasting. The concentrate obtained by this method is usually burned with an excess of soda, thereby bringing tungsten into a soluble state, i.e. in sodium wolframite.

Another method for obtaining this substance is leaching. Tungsten is extracted using a soda solution at elevated temperature and under pressure, followed by neutralization and precipitation of calcium tungstate, i.e. scheelitis. Scheelite is obtained because it is quite easy to extract purified tungsten oxide.

CaWO 4 → H 2 WO 4 or (NH 4) 2 WO 4 → WO 3

Tungsten oxide is also obtained through chlorides. The tungsten concentrate is treated with chlorine gas at elevated temperatures. In this case, tungsten chlorides are formed, which are easily separated from other chlorides by sublimation. The resulting chloride can be used to produce oxide or metal can be extracted from it directly.

In the next step, the oxides and chlorides are converted into tungsten metal. The best way to reduce tungsten oxide is to use hydrogen. With this reduction, the metal is the purest. The reduction of the oxide takes place in a special tubular furnace, where the “boat” of WO 3 moves through several temperature zones. Dry hydrogen flows towards the “boat”. Reduction of the oxide occurs in hot (450-600°C) and cold zones (750-1100°C). In cold zones, reduction occurs to WO 2, and then to metal. As time passes through the hot zone, grains of tungsten powder change their size.

Reduction can take place not only when hydrogen is supplied. Coal is often used. Due to the solid reducing agent, production is simplified, but the temperature in this case must reach 1300°C. Coal itself and the impurities that it always contains, reacting with tungsten, form carbides of other compounds. As a result, the metal becomes contaminated. But in the electrical industry only high-quality tungsten is used. Even 0.1% iron impurity makes tungsten for the production of the thinnest wire, because it becomes much more fragile.

The separation of tungsten from chlorides is based on pyrolysis. Tungsten and chlorine form some compounds. Excess chlorine allows all of them to be converted into WCl6, which in turn decomposes at a temperature of 1600°C into chlorine and tungsten. If hydrogen is present, the process begins at 1000°C.

This is how tungsten is obtained in powder form, which is then pressed at high temperature in a stream of hydrogen. The first stage of pressing (heating to approximately 1100-1300°C) produces a brittle, porous ingot. Then pressing continues, and the temperature begins to rise almost to the melting point of tungsten. In such an environment, the metal begins to become solid and gradually acquires its qualities and properties.

On average, 30% of tungsten produced in industry is tungsten from recycled materials. Tungsten scrap, sawdust, shavings and powder are oxidized and converted into ammonium paratungstate. As a rule, scrap cutting steels are disposed of at an enterprise that produces the same steels. Scrap from electrodes, incandescent lamps and chemical reagents is almost never recycled.

In the Russian Federation, tungsten products are produced at: Skopino Hydrometallurgical Plant "Metallurg", Vladikavkaz Plant "Pobedit", Nalchik Hydrometallurgical Plant, Kirovgrad Hard Alloy Plant, Elektrostal, Chelyabinsk Electrometallurgical Plant.

Physical properties

Tungsten is a light gray metal. It has the highest melting point of any known element except carbon. The value of this indicator ranges from approximately 3387 to 3422 degrees Celsius. Tungsten has excellent mechanical properties when reaching high temperatures; among all metals, tungsten has the lowest value of such an indicator as the expansion coefficient.

Tungsten is one of the heaviest metals, its density is 19250 kg/m3. The metal has a cubic body-centered lattice with parameter a = 0.31589 nm. At a temperature of 0 degrees Celsius, the electrical conductivity of tungsten is only 28% of the value of the same indicator for silver (silver conducts current better than any other metal). Pure tungsten is very easy to process, but it is rarely found in its pure form; more often it has impurities of carbon and oxygen, due to which it gets its well-known hardness. The electrical resistance of the metal at a temperature of 20 degrees Celsius is 5.5 * 10 -4, at a temperature of 2700 degrees Celsius - 90.4 * 10 -4.

Tungsten differs from all other metals in its special refractoriness, heaviness and hardness. The density of this metal is almost twice that of the same lead, or more precisely 1.7 times. But the atomic mass of the element, on the contrary, is lower and is 184 versus 207.

Tungsten has unusually high tensile and compressive modulus values, enormous resistance to temperature creep, and the metal has high electrical and thermal conductivity. Tungsten has a fairly high electron emission coefficient, which can be significantly improved by alloying the element with oxides of some other metals.

The color of the resulting tungsten largely depends on the method of its production. Fused tungsten is a shiny, gray metal that looks much like platinum. Tungsten powder can be gray, dark gray and even black: the smaller the grain of the powder, the darker it will be.

Tungsten is highly resistant: at room temperature it does not change in air; When the temperature reaches red heat, the metal begins to slowly oxidize, releasing tungstic anhydride. Tungsten is almost insoluble in sulfuric, hydrofluoric and hydrochloric acids. In aqua regia and nitric acid, the metal is oxidized from the surface. When in a mixture of hydrofluoric and nitric acid, tungsten dissolves, thereby forming tungstic acid. Of all tungsten compounds, the greatest practical benefits are: tungsten anhydride or tungsten trioxide, peroxides with the general formula ME2WOX, tungstates, compounds with carbon, sulfur and halogens.

Tungsten, found in nature, consists of 5 stable isotopes whose mass numbers are 186,184, 183, 182, 181. The most common isotope with mass number 184, its share is 30.64%. Of the relative variety of artificial radioactive isotopes of element number 74, only three are of practical importance: tungsten-181 (its half-life is 145 days), tungsten-185 (its half-life is 74.5 days), tungsten-187 (its half-life is half-life is 23.85 hours). All these isotopes are formed inside nuclear reactors in the process of bombarding tungsten isotopes with neutrons from a natural mixture.

The valency of tungsten is variable - from 2 to 6, the most stable is hexavalent tungsten; tri- and divalent compounds of the chemical element are unstable and have no practical significance. The radius of a tungsten atom is 0.141 nm.

The tungsten Clarke of the earth’s crust according to Vinogradov is 0.00013 g/t. Its average content in rocks, grams/ton: ultrabasic - 0.00001, basic - 0.00007, intermediate - 0.00012, acidic - 0.00019.

Chemical properties

Tungsten is not affected by: aqua regia, sulfuric, hydrochloric, hydrofluoric and nitric acids, an aqueous solution of sodium hydroxide, mercury, mercury vapor, ammonia (up to 700° C), air and oxygen (up to 400° C), hydrogen, water, hydrogen chloride (up to 600° C), carbon monoxide (up to 800° C), nitrogen.

After just a little heating, dry fluorine begins to combine with finely ground tungsten. As a result, hexafluoride is formed (formula WF 6) - this is a very interesting substance that has a melting point of 2.5 ° C and a boiling point of 19.5 ° C. After reaction with chlorine, a similar compound is formed, but the reaction is only possible at a temperature of 600 ° C. WC16, steel-blue crystals, begins to melt at a temperature of 275°C and boil when it reaches 347°C. Tungsten forms weakly stable compounds with iodine and bromine: tetra- and diiodide, penta- and dibromide.

At high temperatures, tungsten can combine with selenium, sulfur, nitrogen, boron, tellurium, silicon and carbon. Some of these compounds are characterized by amazing hardness, as well as other excellent qualities.

Of particular interest is carbonyl (formula W(CO) 6). Tungsten here combines with carbon monoxide and, therefore, has zero valence. Tungsten carbonyl is produced under special conditions, because he is extremely unstable. At a temperature of 0° it is released from a special solution in the form of colorless crystals; after reaching 50°C, carbonyl sublimes; at 100°C it completely decomposes. But it is precisely thanks to this connection that dense and hard tungsten coatings (from pure tungsten) can be obtained. Many tungsten compounds, like tungsten itself, are very active. For example, tungsten oxide tungsten oxide WO 3 has the ability to polymerize. In this case, so-called heteropolycompounds are formed (their molecules can contain more than 50 atoms) and isopolycompounds.

Tungsten oxide (VI)WO 3 is a crystalline substance with a light yellow color that turns orange when heated. The oxide has a melting point of 1473 °C and a boiling point of 1800 °C. Tungstic acid, corresponding to it, is not stable; in a water solution, the dihydrate precipitates, and it loses one molecule of water at temperatures from 70 to 100 ° C, and the second molecule at temperatures from 180 to 350 ° C.

Tungstic acid anions tend to form polycompounds. As a result of the reaction with concentrated acids, mixed anhydrides are formed:

12WO3 + H3PO4 = H3.

The reaction of tungsten oxide and sodium metal produces non-stoichiometric sodium tungstate, which is called "tungsten bronze":

WO 3 + xNa = Na x WO 3.

In the process of reduction of tungsten oxide with hydrogen, during separation, hydrated oxides are obtained that have a mixed oxidation state, they are called “tungsten blues”:

WO3–n(OH)n, n = 0.5–0.1.

WO 3 + Zn + HCl = (“blue”), W 2 O 5 (OH) (brown)

Tungsten (VI) oxide is an intermediate in the production process of tungsten, as well as its compounds. It is a component of selected ceramic pigments and industrially important hydrogenation catalysts.

WCl 6 – Higher tungsten chloride, formed as a result of the interaction of metal tungsten or tungsten oxide with chlorine, fluorine, or carbon tetrachloride. After reduction of tungsten chloride with aluminum, tungsten carbonyl is formed along with carbon monoxide:

WCl 6 + 2Al + 6CO = + 2AlCl 3 (in ether)

Having a light gray color. In Mendeleev's periodic system it has the 74th serial number. The chemical element is refractory. It contains 5 stable isotopes.

Chemical properties of tungsten

The chemical resistance of tungsten in air and water is quite high. When heated, it is susceptible to oxidation. The higher the temperature, the higher the rate of oxidation of the chemical element. At temperatures exceeding 1000°C, tungsten begins to evaporate. At room temperature, hydrochloric, sulfuric, hydrofluoric and nitric acids cannot have any effect on tungsten. A mixture of nitric and hydrofluoric acids dissolves tungsten. Neither in the liquid nor in the solid state does tungsten mix with gold, silver, sodium, or lithium. There is also no interaction with zinc, magnesium, calcium, or mercury. Tungsten is soluble in tantalum and niobium, and with chromium and molybdenum it can form solutions in both solid and liquid states.

Applications of tungsten

Tungsten is used in modern industry both in pure form and in alloys. Tungsten is a wear-resistant metal. Alloys containing tungsten are often used to make turbine blades and aircraft engine valves. Also, this chemical element has found its application for the manufacture of various parts in X-ray engineering and radio electronics. Tungsten is used for electric lamp filaments.

Tungsten chemical compounds have recently found their practical application. Phosphorus-tungstic heteropolyacid is used in the production of bright paints and varnishes that are stable in light. Tungstates of rare earth elements, alkaline earth metals and cadmium are used for the production of luminous paints and the production of lasers.

Today, traditional gold wedding rings have begun to be replaced with products made from other metals. Wedding rings made of tungsten carbide have become popular. Such products are highly durable. The mirror polishing of the ring does not fade over time. The product will retain its original condition for the entire period of use.

Tungsten is used as an alloying additive for steel. This gives the steel strength and hardness at high temperatures. Thus, tools made from tungsten steel have the ability to withstand very intensive metalworking processes.