The history of the discovery of tungsten. Chemical properties of tungsten

At room temperature, tungsten is resistant to atmospheric corrosion, but when heated already up to 750 K, it oxidizes to WO 3, reacts with halogens: with fluorine at room temperature, and with iodine at a temperature of about 900 K.

When heated to high temperatures, it reacts with carbon, silicon and boron, forming carbides, silicides, and borides, respectively. Sulfur and phosphorus do not act on tungsten under normal conditions. In air, it dissolves in hot aqueous solutions of alkalis, but is weakly amenable to the action of acids, except for hydrofluoric and nitric acids when heated.

Hydrogen and nitrogen do not give chemical compounds with tungsten, up to

3000 0 C, although some sources indicate the possibility of the formation of WH 2 hydride.

With oxygen, tungsten forms three stable oxides:

WO 2 - brown;

WO 3 - yellow;

W 2 O 5 - bluish color.

All these oxides are formed at a temperature of about 800 K in air or in oxygen, and all of them are very volatile and have a low melting point. For example, WO 3 melts at 1645 K.

In practice, in order to distinguish tungsten wire from molybdenum wire, a simple trick is used: the tip of the wire is set on fire with a match. If at the same time yellow or brown smoke is observed, then this is a tungsten wire, if white - molybdenum.

Carbon reduces oxides W:

At a temperature of 825 K;

At a temperature of 1325 K;

At a temperature of 1425 K.

With nitrogen, tungsten forms nitrides at temperatures above 1600 K, but above 2275 K they decompose.

When interacting with carbon and temperatures above 1800 K, tungsten forms W 2 C and WC carbides. Density W 2 C - 16000 kg / m 3, WC - 9000 kg / m 3, hardness about 9 Mohs units. At a temperature of 2875 K, WC carbide decomposes by the reaction

Figure 73 shows the W–C state diagram.

As can be seen from the diagram, tungsten carbides have a melting point well below that of the metal itself. So, WC melts at a temperature of about 2875 K, W 2 C - 3065 K. In addition, carbides can form eutectic alloys with tungsten with a melting point much lower than that of a metal that melts at 3683 K. Therefore, rocket scientists need to pay attention to the danger of a reaction formation of carbides at the graphite-tungsten interface, which occurs when heated above 2675 K. The warning is due to the fact that the design of the liner of the critical section of the nozzle of a solid propellant engine combines a tungsten inner lining with a graphite clip.

To avoid this reaction between the tungsten lining and the graphite of the casing, a so-called "barrier" layer of tantalum or titanium carbide (TaC, TiC) is applied.

Due to the high density of tungsten and its scarcity, designers and technologists seek to replace it with lighter and less scarce materials, which will be discussed below.

Rice. 73. Status diagram W-C

Rice. 74. Scheme of mass transfer in a lamp

incandescent: 1 - the wall of the flask, where WJ 2 is formed; 2 - helix, where WJ 2 decomposes into W and J

Although the reaction of tungsten with iodine is not related to rocket technology, I would still like to dwell on it briefly.

At temperatures above 850 K, tungsten with iodine vapor forms iodide, which is an easily sublimating salt of iodide acid:

At a temperature of 2475 K, iodide decomposes:

These two reactions are used to transfer tungsten, for example, in incandescent lamps: despite the low vapor pressure in them, tungsten still evaporates in a vacuum. Its vapors sit on the walls of the glass bulb of the lamp and its transparency decreases. If the flask is filled with iodine vapor, then the latter will react with tungsten on the hot wall of the lamp and form WJ 2, which, due to diffusion, enters the heated tungsten spiral and decomposes. Free iodine will again move to the wall, and tungsten will remain on the spiral, and so on without end. The end result is increased luminosity and durability of iodine-filled lamps.

The same reaction is used in technology to obtain pure refractory metals: tungsten, tantalum, molybdenum, hafnium, etc.

This reaction can also be used to obtain thin tungsten shells. In addition to the iodide method, carbonyl can be used for this purpose, i.e. decomposition of WCO 2 . In jet fuel engines, tungsten in its pure form, as a rule, is not used due to its low thermal stability, but is used in the form of so-called pseudo-alloys with copper. This will be discussed below.

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

Characteristics of tungsten

Tungsten is a light gray transition metal. It has an external resemblance to steel. In connection with the possession of rather unique properties, this element is a very valuable and rare material, the pure form of which is absent in nature. Wolfram has:

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

Table 1. Properties of tungsten

Characteristic	Meaning
Atom properties
Name, symbol, number	Tungsten / Wolframium (W), 74
Atomic mass (molar mass)	183.84(1) a. e.m. (g/mol)
Electronic configuration	4f14 5d4 6s2
Atom 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 n.a.)	19.25 g/cm³
Melting temperature	3695K (3422°C, 6192°F)
Boiling temperature	5828K (5555°C, 10031°F)
Oud. heat of fusion	285.3 kJ/kg 52.31 kJ/mol
Oud. heat of evaporation	4482 kJ/kg 824 kJ/mol
Molar heat capacity	24.27 J/(K mol)
Molar volume	9.53 cm³/mol
The crystal lattice of a simple substance
Lattice structure	cubic body-centered
Lattice parameters	3.160Å
Debye temperature	310K
Other characteristics
Thermal conductivity	(300 K) 162.8 W/(m K)
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 complicates the process of its processing;
• low resistance to acids at low temperatures.

Obtaining tungsten

Tungsten, along with molybdenum, rubidium and a number of other substances, is included in the group of rare metals, which are characterized by a very small distribution in nature. In this regard, it cannot be mined in the traditional way, like many minerals. Thus, the industrial production of tungsten consists of the following steps:

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

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

1. As a result of enrichment of tungsten ore by gravity, flotation, magnetic or electrical separation. In the process, a tungsten concentrate is formed, 55-65% consisting of tungsten anhydride (trioxide) WO 3 . In concentrates of this metal, the content of impurities is monitored, which can be phosphorus, sulfur, arsenic, tin, copper, antimony and bismuth.
2. As is known, tungsten trioxide WO 3 is the main material for separating tungsten metal or tungsten carbide. Obtaining WO 3-- occurs as a result of decomposition of concentrates, leaching of an alloy or sinter, etc. In this case, a material consisting of 99.9% of WO 3 is formed at the output.
3. From tungsten anhydride WO 3 . It is by reducing this substance with hydrogen or carbon that tungsten powder is obtained. Applications of the second component for the reduction reaction are 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 obtained 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 particle fraction of the powder can be increased by a rapid increase in temperature or a low hydrogen supply rate.
4. Production of compact tungsten, which has the form of rods or ingots and is a blank for further production of semi-finished products - wire, rods, strips, etc.

The last method, in turn, includes two possible options. One of them is related to powder metallurgy methods, and the other is related to melting 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. The metal powder is pressed into rods;
2. The blanks are sintered at low temperatures (so-called pre-sintering);
3. Welding workpieces;
4. Obtaining semi-finished products by processing blanks. The implementation of this stage is carried out by forging or machining (grinding, polishing). It should be noted that mechanical processing of tungsten becomes possible only under the influence of high temperatures, otherwise it cannot be processed.

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

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

Fuse

This method is used if it is necessary to obtain tungsten blanks of sufficiently large dimensions - from 200 kg to 3000 kg. Such blanks, as a rule, are necessary for rolling, pipe drawing, and the manufacture of products by casting. For melting, it is necessary to create special conditions - a vacuum or a rarefied atmosphere of hydrogen. At the output, tungsten ingots are formed, which have a coarse-grained structure, as well as high brittleness due to the presence of a large amount of impurities. The content of impurities can be reduced by premelting the tungsten in an electron beam furnace. However, the structure remains unchanged. In this connection, in order to reduce the grain size, the ingots are further melted, but already in an electric arc furnace. At the same time, alloying substances are added to the ingots during the melting process, endowing tungsten with special properties.

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

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

Tungsten grades

1. HF - pure tungsten, in which there are no additives;
2. VA - a metal containing aluminum and silicon alkali additives, which give it additional properties;
3. VM - a metal containing thorium and silicon-alkali additives;
4. VT - tungsten, which contains thorium oxide as an additive, which significantly increases the emission properties of the metal;
5. VI - metal containing yttrium oxide;
6. VL - tungsten with lanthanum oxide, which also increases the emission properties;
7. VR - an alloy of rhenium and tungsten;
8. BPH - there are no additives in the metal, however, impurities in large volumes may be present;
9. MW is an alloy of tungsten with molybdenum, which significantly increases the strength after annealing, while maintaining ductility.

Where is tungsten used?

Due to its unique properties, element 74 has become indispensable in many industries.

1. The main application 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, kinescopes, as well as other vacuum tubes.
3. Also, this metal is the basis for the production of heavy alloys used as counterweights, armor-piercing cores of sub-caliber and arrow-shaped feathered artillery shells.
4. Tungsten is an electrode in argon-arc welding;
5. Its alloys are highly resistant to various temperatures, acidic environments, as well as hardness and abrasion resistance, and therefore are used in the manufacture of surgical instruments, tank armor, torpedo and projectile shells, aircraft and engine parts, as well as containers for storing nuclear weapons. waste;
6. Vacuum resistance furnaces, in which the temperature reaches extremely high values, are equipped with heating elements also made of tungsten;
7. The use of tungsten is popular for providing 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).

Having a light gray color. In the periodic system of Mendeleev, he belongs to the 74th serial number. The chemical element is refractory. It contains 5 stable isotopes in its composition.

Chemical properties of tungsten

The chemical resistance of tungsten in air and in water is quite high. When heated, it oxidizes. The higher the temperature, the higher the rate of oxidation of the chemical element. At temperatures above 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, tungsten is mixed with gold, silver, sodium, lithium. Also, there is no interaction with zinc, magnesium, calcium, mercury. Tungsten is soluble in tantalum and niobium, and with chromium and molybdenum it can form solutions in both solid and liquid states.

Application of tungsten

Tungsten is used in modern industry both in pure form and in alloys. Tungsten is a wear-resistant metal. Often, alloys containing tungsten are 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 the filaments of electric lamps.

Chemical compounds of tungsten have recently found their practical application. Phosphotungstic heteropoly acid is used in the production of bright paints and varnishes that are stable in the light. For the manufacture of luminous paints and the manufacture of lasers, tungstates of rare earth elements, alkaline earth metals and cadmium are used.

Today, traditional gold wedding rings are being replaced by products made from other metals. Tungsten carbide wedding rings have gained popularity. Such products are highly durable. The mirror finish of the ring will 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 its strength and hardness at high temperatures. Thus, tools made from tungsten steel have the ability to withstand very intensive metalworking processes.

Tungsten is a chemical element of the 4th group, having atomic number 74 in the periodic system of Dmitry Ivanovich Mendeleev, designated W (Wolframium). The metal was discovered and isolated by two Spanish chemists, the d'Eluyar brothers, in 1783. The name “Wolframium” itself was transferred to an 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 associated with the fact that tungsten, while accompanying tin ores, significantly interfered with the smelting of tin, because. translated tin into slag foam (they began to say about this process: “Tin devours like a wolf 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 gray hard transition metal. The main application of tungsten is the role of the base 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 infusibility. Since ancient times, there has been an expression among the people “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, to be precise, 1.7 times. 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 plasticity and infusibility of tungsten, it is possible to use it as filaments in lighting devices, in kinescopes, and also in other vacuum tubes.

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

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

Currently, there are no methods for obtaining tungsten directly from concentrates. In this regard, intermediate compounds are first isolated from the concentrate, and then metallic 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 accompanying elements. Isolation of tungstic acid, i.e. pure chemical compound tungsten, continues with the subsequent production of tungsten in metallic form.

Tungsten is used in the manufacture of machinery and equipment in the metalworking, construction and mining industries, in the manufacture of lamps and lamps, in the transport and electronics industries, in the chemical industry and other fields.

Made of tungsten steel, the tool is able to withstand the enormous speeds of the most intensive processes in metalworking. The cutting speed using such a tool is usually measured in tens of meters per second.

Tungsten is rather poorly distributed in nature. The content of metal in the earth's crust by mass is about 1.3·10 −4%. The main minerals containing tungsten are natural tungstates: scheelite, originally called tungsten, and wolframite.

Biological properties

The biological role of tungsten is insignificant. Tungsten is very similar to molybdenum in its properties, but, unlike the latter, tungsten is not an essential element. Despite this fact, tungsten is quite capable of replacing molybdenum in animals and plants, in the composition 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 organs.

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

Food sources of tungsten, as well as its daily requirement, have not yet been studied. The 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 and teratogenic effects on humans and animals.

Indicator of the elemental status of tungsten inside the human body: urine, whole blood. There are no data on the 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 engaged in the production of refractory and heat-resistant materials, alloyed steels, as well as in people who have come into contact with tungsten carbide.

The clinical syndrome "heavy metal disease" or pneumoconiosis can be the result of chronic intake of tungsten dust into the body. Signs can include coughing, breathing problems, 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, with a belated diagnosis of the disease, the pathology "cor pulmonale", emphysema and pulmonary fibrosis develop.

"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 found that the combined effect of tungsten and cobalt on the human body enhances the detrimental effect on the pulmonary system. The combination of tungsten and cobalt carbides can cause local inflammation and contact dermatitis.

At the present stage of development of medicine, there are no effective ways to accelerate the metabolism or excretion of 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 timely identify people with high sensitivity to heavy metals, to diagnose at the initial stage of the disease. All these factors determine the further chances for the success of the treatment of pathology. But in some cases, if necessary, therapy with complexing agents and symptomatic treatment is used.

More than half (or rather 58%) of all tungsten produced is used in the manufacture of tungsten carbide, and almost a quarter (or rather, 23%) is used in the production of various steels and alloys. The production of tungsten “rolled products” (this includes incandescent lamp filaments, 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 application in electric lamps, has recently acquired a new profile: it has been proposed to use it as a cutting tool in the processing of brittle materials.

The high strength and good ductility of tungsten make it possible to produce unique items from it. For example, a wire so thin can be drawn from this metal 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 is composed 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. it lacks purely metallic compounds, 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, and even with a greenish tint. Giving says that more than 8,000 attempts had to be made to obtain this paint. In the 17th century, only the most expensive porcelain items for the then Chinese emperor were decorated with peach paint at a special factory in Shanxi province. But when, after some time, it was possible to reveal the secret of a rare paint, it turned out that it was based on nothing more than tungsten oxide.

This happened in 1911. A student named Li came to Yunnan Province from Beijing. Day after day he was lost in the mountains, trying to find some kind of stone, as he explained, it was a tin stone. But he didn't succeed. The owner of the house in which the student Li settled, lived with a young daughter named Xiao-mi. The girl was very sorry for the unfortunate student and in the evening, during dinner, she told him simple simple stories. One story told of an unusual stove that was built from some kind of dark stones that were torn off a cliff and laid in the backyard of their house. This stove turned out to be quite successful, and most importantly durable, for many years it regularly served the owners. Young Xiao-mi even gave the student even one such stone as a gift. It was a run-in, heavy, brown stone, like lead. Later it turned out that this stone was pure wolframite...

In 1900, at the opening of the world metallurgical exhibition in Paris, completely new specimens of high-speed steel (an alloy of steel with tungsten) were demonstrated for the first time. Literally immediately after that, tungsten began to be widely used in the metallurgical industry of all highly developed countries. But there is a rather interesting fact: for the first time, tungsten steel was invented in Russia as early as 1865 at the Motovilikha plant in the Urals.

In early 2010, an interesting artifact fell into the hands of Perm ufologists. It is assumed that this is a fragment of a spaceship. The analysis of the fragment showed that the object consists almost entirely of pure tungsten. Only 0.1% of the composition falls on rare impurities. According to scientists, rocket nozzles are made from pure tungsten. But so far one fact has not been explained. In air, tungsten quickly oxidizes and rusts. But for some reason this fragment does not lend itself to corrosion.

Story

The word "tungsten" itself is of German origin. Previously, not the metal itself was called tungsten, but its main mineral, i.e. to wolframite. Some suggest that then this word was used almost as a swear word. From the beginning of the 16th 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, which included wolframite, tin was smelted much less. As if someone or something "devoured" useful tin. Hence the name of the new element. In German, Wolf (Wolf) means wolf, and Ram (Ramm) translated from ancient German means ram. Those. the expression "eats tin like a wolf eats a lamb", and became the name of the metal.

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

The foundations of such confusion are laid in the history of the discovery of the element. In 1783, the 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 "acidic earth", i.e. yellow precipitate of the oxide of an unknown metal, the precipitate was soluble in ammonia. In the starting 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 mined 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 discovery of the brothers, the famous Swedish chemist Carl Wilhelm Scheele found exactly the same "yellow earth" in the process of treating another mineral with nitric acid. His scientist called it simply "tungsten" (translated from Swedish tung - heavy, sten - stone, i.e. "heavy stone"). Karl Wilhelm Scheele found that "yellow earth" differs in its color, as well as in other properties, from similar molybdenum. The scientist also learned that in the mineral itself, it was associated with calcium oxide. In honor of Scheele, the name of the mineral "tungsten" was changed to "scheelite". Interestingly, 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 began to share the discovery. Scheele simply did not claim this discovery, and the Eluard brothers did not insist on the priority of their superiority.

Many have heard of the so-called "tungsten bronzes". These are very beautiful looking metals. Blue tungsten bronze has the following composition Na2O WO2 , and golden bronze has the following composition 4WO3Na2O WO2 WO3; violet and purplish red are intermediate, with a WO3 to WO2 ratio of less than four and greater 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 have 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 chemicals, high electrical conductivity.

In ancient times, peach color was one of the rarest, it was said that 8000 experiments had to be carried out to obtain it. In the 17th century, the most expensive porcelain of the Chinese emperor was painted in peach color. But after revealing the secret of this paint, it suddenly turned out that it was based on 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 weight. Tungsten is mainly found as part of 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 is solid and heavy crystals of black or brown color, depending on the predominance of various compounds in the composition of the solution. If there are more manganese compounds (huebnerite), the crystals will be black, if iron compounds (ferberite) predominate, 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 brilliant crystals of light yellow and sometimes almost white colors. Sheelite is not at all magnetic, but it has another feature - the ability to luminesce. After UV illumination in the dark, it will fluoresce bright blue. The presence of an admixture of molybdenum changes the color of the glow, it changes to pale blue, sometimes to cream. Thanks to this property, it is possible to easily detect geological deposits of the mineral.

Typically, deposits of tungsten ore are associated with the area of ​​distribution of granite. Large crystals of scheelite or wolframite are very rare. Usually minerals are simply interspersed in granitic rocks. Extracting tungsten from granite is quite difficult, because. its concentration is usually not more than 2%. In total, no more than 20 tungsten minerals are known. Among them, stolzite and rasoite can be distinguished, which are two different crystalline modifications of lead tungstate PbWO 4 . The remaining minerals are decomposition products or secondary forms of ordinary minerals, for example, scheelite and wolframite (hydrotungstite, which is hydrated tungsten oxide, was formed from wolframite; tungsten ocher), russelite, a mineral containing oxides of tungsten and bismuth. Tungstenite (WS 2) is the only non-oxide mineral of tungsten, and its main reserves are located in the USA. As a rule, the content of tungsten is in the range from 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 main part of tungsten deposits is concentrated in areas of young mountain ranges - the Alps, the Himalayas and the Pacific belt. The largest deposits of wolframite and scheelite are located in China, Burma, the USA, Russia (the Urals, Transbaikalia and the Caucasus), Portugal and Bolivia. Annual extraction of tungsten ores in the world is approximately 5.95·104 tons of metal, of which 49.5·104 tons (or 83%) is extracted in China. About 3,400 tons per year are mined in Russia, and 3,000 tons per year in Canada.

The role of the global leader in the development of tungsten raw materials is played by China (the Jianshi field accounts for 60 percent of Chinese production, Hunan - 20 percent, Yunnan - 8 percent, Guangdong - 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 plant in Nalchik 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 3,000 tons of metal are consumed annually in the CIS.

Application

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

The best types of tool steels contain tungsten. Metallurgy absorbs in general about 95% of all tungsten produced. What is typical for metallurgy is that not only pure tungsten is used, but tungsten is mainly used, which is cheaper - 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 qualities. 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% higher than that of lead. Such an alloy is also used in radiotherapy, because with a relatively small thickness of the screen, quite sufficient protection is provided.

An alloy of tungsten carbide and 16% cobalt has such a hardness that it partially replaces diamond in well drilling. Pseudo-alloys of tungsten with silver and copper are an excellent material for switches and knife switches in high voltage environments. 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 as windings and heating elements of electric furnaces, as well 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 (from cobalt with Cr, C, W additives), hastalloys (stainless steels based on Ni), as well as many other alloys. Tungsten is used as a basis in the production of heat-resistant and tool alloys, namely, ferrotungsten is used (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 Pobeda. This is a superhard alloy, which contains 80–85% tungsten, 7–14% cobalt, 5–6% carbon. Pobedit is simply indispensable in the metalworking 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 that is stable at temperatures up to 500 ° C. Tungsten bronzes and 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 plastic. 1 kg of tungsten serves as a raw material for the manufacture of 3.5 km of wire. Those. 1 kg of tungsten can be used to make filaments for 23,000 60-watt lamps. Only thanks to this property, the electrical industry around the world consumes about a hundred tons of tungsten per year.

Production

The first stage in the production of tungsten is the enrichment of the ore, i.e. separation of valuable components from the main ore mass, waste rock. The same beneficiation methods are used 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. to sodium wolframite.

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

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 an elevated temperature. In this case, tungsten chlorides are formed, which are easily separated from other chlorides by sublimation. The resulting chloride can be used to obtain oxide or immediately extract metal from it.

In the next step, the oxides and chlorides are converted into metallic tungsten. To reduce tungsten oxide, it is best to use hydrogen. With this reduction, the metal is the purest. Oxide reduction takes place in a special tube furnace, where the "boat" with WO 3 moves through several temperature zones. Dry hydrogen enters towards the "boat". Oxide reduction occurs in hot (450-600°C) and cold zones (750-1100°C). In cold zones, reduction to WO 2 occurs, and then to metal. As time passes through the hot zone, the grains of powdered tungsten change their size.

Recovery can take place not only under the supply of hydrogen. Coal is often used. Due to the solid reducing agent production is simplified, but the temperature in this case should 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 is contaminated. But in the electrical industry, only high-quality tungsten is used. Even 0.1% iron impurities make tungsten for the manufacture of the thinnest wire, because. it becomes much more fragile.

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

This is how tungsten is obtained in the form of a powder, which is then pressed at high temperature in a stream of hydrogen. The first stage of pressing (heating to about 1100-1300°C) produces a brittle porous ingot. Then the 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 the industrially produced tungsten is recycled tungsten. Tungsten scrap, sawdust, shavings and powder are oxidized and converted into ammonium paratungstate. As a rule, scrap of cutting steels is disposed of at the enterprise that produces the same steels. Scrap from electrodes, incandescent lamps and chemicals is almost never recycled.

In the Russian Federation, tungsten products are produced at: Skopinsky 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 is approximately from 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 coefficient of expansion.

Tungsten is one of the heaviest metals, its density is 19250 kg/m3. The metal has a cubic body-centered lattice 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 rare 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 leaves 5.5 * 10 -4, at a temperature of 2700 degrees Celsius - 90.4 * 10 -4.

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

The values ​​of the tensile and compression moduli of tungsten are unusually high, the temperature creep resistance is enormous, the metal has high electrical and thermal conductivity. Tungsten has a rather 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 lustrous gray metal that looks a lot like platinum. Tungsten powder can be gray, dark gray and even black: the smaller the grains of the powder, the darker it will be.

Tungsten has a high resistance: at room temperature it does not change in air; when the red heat temperature is reached, 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. Being in a mixture of hydrofluoric and nitric acid, tungsten dissolves, forming tungstic acid. Of all the tungsten compounds, the most 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 a mass number of 184, its share is 30.64%. Of the entire relative set 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 during the bombardment of tungsten isotopes with neutrons from a natural mixture.

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

The clarke of tungsten in the earth's crust according to Vinogradov is 0.00013 g/t. Its average content in the composition of rocks, gram/ton: ultrabasic - 0.00001, basic - 0.00007, medium - 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.

Already after a slight heating, dry fluorine begins to combine with finely divided 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 the reaction with chlorine, a similar compound is formed, but the reaction is possible only at a temperature of 600 ° C. WC16, steel blue crystals, melts at 275°C and boils at 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 remarkably hard, as well as other excellent qualities.

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

Tungsten oxide (VI)WO 3 is a light yellow crystalline substance 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 solution of water the dihydrate precipitates, while it loses one molecule of water at a temperature of 70 to 100 ° C, and the second molecule at a temperature of 180 to 350 ° C.

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

12WO 3 + H 3 PO 4 \u003d H 3.

As a result of the reaction of tungsten oxide and metallic sodium, a non-stoichiometric sodium tungstate is obtained, which is called "tungsten bronze":

WO 3 + xNa = Na x WO 3.

In the process of reducing tungsten oxide with hydrogen, hydrated oxides are obtained during isolation, having a mixed oxidation state, they are called "tungsten blue":

WO 3–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 and its compounds. It is a component of certain ceramic pigments and industrially important hydrogenation catalysts.

WCl 6 - The highest tungsten chloride, is formed as a result of the interaction of metallic tungsten or tungsten oxide with chlorine, fluorine, or carbon tetrachloride. After the reduction of tungsten chloride with aluminum, tungsten carbonyl is formed together with carbon monoxide:

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

Tungsten (English Tungsten, French Tungstene, German Wolfram) was first obtained by the Spaniards brothers de Elguiar, students of Bergman in 1783. The name tungsten existed, however, long before the discovery of the element. Miners and metallurgists of the 14th-16th centuries, who were engaged in the extraction of tin, noticed that when one of the tin ores was calcined, a significant amount of tin was lost, going into slag. This ore was called wolf (Wolf, or Wolfert), which over time changed to tungsten; so they began to call the mineral contained in the ore. Agricola gives the Latin name for this mineral - Spuma Lupi, or Lupus spuma, which means wolf foam, i.e. foam in the mouth of an angry wolf. Miners of the 16th century they said about tungsten: "he steals tin and devours it, like a wolf a sheep." In 1781, Scheele obtained tungsten trioxide WO 3 from a mineral that was later named scheelite (CaWO 4) in his honor. Scheele's discovery was confirmed by Bergman, who called the mineral "heavy stone" (lat. Lapis ponderosus); translated into Swedish, it is tungsten (Tung Sten - a heavy stone). A little later, it was proposed to call the newly discovered metal Scheelium in honor of Scheele, but Berzelius, who at first supported this name, soon preferred the word tungsten to him. In Latin (Syuma lupi) and German (Wolf Rahm), tungsten means wolf saliva. The name tungsten is found in Lomonosov, then in Scherer; Solovyov and Hess (1824) call it wolframium, Dvigubsky (1824) - wolframium. There are also names of sheels, sheelev metal (tungsten beetle).