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Sergey Venezky
STORIES ON METALS

TUNGSTEN:

GIVING LIGHT

Need any comments? - "Wolf foam". - The opening of the great pharmacist. - Brothers comes luck. - "Samakal Muleta". - Not going to pass. - Peach color. - Experiments in St. Petersburg. -The success of German engineers. - Necessity is the mother of invention. - Tidbit. - Not a chance. - Agonizing silence. - "The plot" princes Vladimirovich. - To hell. - "Help" from the side. - In cold and heat. - Return "fugitives". - At the Sun's surface. - Billions of lightning. - Minutes and century. - "U-1" in Montreal. - Weight in society. - Precision. - "Whiskers" are in Vogue. - "Fluffy" tungsten. - Layered mirror. - The program "Soyuz - Apollo".

The names of many of the items speak for themselves: hydrogen - giving water" carbon "giving birth coal" Mendeley, einsteini, fermium, curium, kurchatovium named after prominent scientists; europium, americium, France, germanium, California is derived from the geographical concepts. But there are elements which, as they say, need comments. These elements include tungsten.

Even the translation of the word "tungsten" wolf foam is unlikely to explain the origin of this name. In fact, what could be more common element of group VI of the Periodic system D. I. Mendeleev forest predator?

...Back in the old days metallurgists came face to face with a strange phenomenon: from time to time, for no understandable reason smelting tin ore fell sharply. Because of the technical-economic indicators of melting could not fail to excite and our ancestors, they were to look closely to tin ore going into heat. They were soon able to notice a pattern: the trouble arose when the ore was met with heavy stones brown or yellowish-gray. The conclusion suggests itself: the stone devours tin, like the wolf the sheep". And if so, then let's called this evil stone "wolf foam" - wolframite. In some other countries, such as Sweden, met a similar mineral tungsten, which means "heavy stone".

The discovery of tungsten is associated with the name of the famous Swedish chemist Carl Wilhelm Scheele. A pharmacist by profession, he worked in pharmacies number of cities, where he spent his remarkable research, many enriched science. In 1781 Scheele found that tungsten (later called scheelite) is a salt of an unknown then acid, and extracted from it a white powder of the oxide of a new element. But beyond that he is not gone.

Tungsteno problem seriously interested in the Spanish chemical brothers Fausto and Juan Jose d Alwar started to experiment with wolframite and tungsten. Only two years later, they got lucky. Mix the white powder obtained from wolframite, with pounded charcoal, they are strongly heated the mixture in the crucible. When cooled after the experience of the crucible was opened, it was dark brown mass, scattered in the hands. Armed with a magnifying glass, the researchers noticed in the powder tiny metal balls - one, two, three. It was tungsten. Could think brothers d Alwar, looking for nuggets of new metal that he was destined to make a truly a revolution in the industry?

In 1864, the Englishman Robert Mushet first introduced the tungsten (approximately 5%) as an alloying additive in steel. Steel, known in the history of metallurgy called "samakal Muleta"could withstand a red heat, not only maintaining, but increasing its hardness, i.e. have the property of samostalni. Cutters are made of steel, has allowed one and a half times to increase the cutting speed metal ( 7.5 meters per minute instead of 5).

Four decades later appeared high speed steel containing up to 8% tungsten. Now the cutting speed metal has reached 18 meters per minute. It took another few years, and the processing speed metal increased to 35 meters per minute. So for about half a century tungsten managed to improve the performance of machine tools in seven times!

Well, how to hold higher cutting speed? Steel it was not under force, and even tungsten couldn nothing to help. Does the limit is reached? Is it really faster to cut the metal is impossible?

The answer gave the same tungsten. No, he had not exhausted its potentialities and does not intend to pass before the temperature in the battle of speed metal. In 1907, was created alloy consisting of tungsten, chromium and cobalt - Stellite, which became the ancestor of the now widely known hard alloys, which have helped to further increase the cutting speed. In our days it has already reached 2000 meters per minute.

From 5 to 2000! Such a huge road machinery Metalworking. And milestones on this path were all new tungsten materials.

 The hardness of relica so great that if the sample of this alloy to hold a file, the file remains furrow.Modern solid alloys are obtained by sintering a mixture of tungsten carbide and some other elements (titanium, niobium, tantalum). Grain carbides like are cemented with cobalt. Such materials do not lose their hardness even at 1000°C, allowing thus a lot of speed metal. The hardness of one of the alloys based on tungsten carbide - relica" is so great that if the sample of this alloy to hold the file, then it (the file!) remains furrow.

Metal has been the main but not the only direction in which tungsten was invaded technique. Even in the middle of the last century it was observed that fabric impregnated sodium salt of tungstic acid, acquired resistance. Widespread at the same time and paints containing tungsten, yellow, blue, white, purple, green, blue. These paints used in painting, ceramics and porcelain. By the way, is still preserved made in the XVII century in China by order of the Emperor amazing porcelain, painted in a very beautiful color - color "peach". According to legend, in order to achieve this, the ancient masters had to spend about eight thousand experiments with various minerals and compounds. As shown by the analysis carried out in our days, its delicate colouring porcelain obliged to tungsten oxide.

In 1860 by heating iron with tungsten acid was obtained alloy of iron and tungsten. The hardness of this alloy are interested in many chemists and metallurgists. Soon managed to develop an industrial production method of ferrosulfate - it has served as a powerful impetus to the use of tungsten in metallurgy.

It took another few years before had made the first attempts to introduce tungsten gun and gun steel. At the end of the last century such steel was melted at the Putilov plant in St. Petersburg, Professor V.N. Liping is one of the organizers of production of stainless steel in Russia (later a member-correspondent of the Academy of Sciences of the USSR). Even a small amount of tungsten added to steel, has greatly increased the resistance of rifle and gun barrels corrosion powder gases. Before the others managed to assess German engineers. During the first world war light of the German guns kept up to fifteen thousand shots, while the Russians and the French guns broke down after six to eight thousand shots.

Naturally, in these years the production of tungsten ore has increased dramatically. If in the 90-ies of the last century in the world each year were extracted only 200-300 tonnes of tungsten ore, in 1910, the production amounted to 8 thousand tons, and in 1918 had reached 35 thousand tons.

And yet, tungsten was not enough. Especially urgently needed in Germany it almost had its own sources of this metal. However, preparing for war, forward-thinking Germans were reserved for future use tungsten ore, but soon these reserves are exhausted, and military industry continues to demand tungsten steel.

Poverty forced the German metallurgists to smash his head. But as they say: necessity is the mother of invention. The solution to the problem was found, remembered that "wolf foam, eating tin, fascinated him in the slag, and in Germany, where several centuries smelted the metal accumulated mountains of tin slag. Soon metallurgists have already started to receive from them the tungsten. Of course, to fully satisfy tungsten hunger slag could not but be of the worm" with their help managed.

In tsarist Russia, even in a period of General growth tungsten mining of this precious metal was negligible. In 1915, with the TRANS-Baikal field on the Izhora plant near Petrograd has received only 1.4 tons of tungsten ore, and in 1916 Motovilikha plant in Perm was shipped 8.7 tons. Production ferrosulfate in Russia in these years amounted to only a few tens of pounds.

On the TRANS-Baikal field as a tasty morsel, glancing many foreign firms, mainly Swedish and Japanese. In the summer of 1916 geologists one Japanese company has spent in those places search exploration. Should be, the search results were encouraging as the company executives made more than one attempt to seize this underground treasure, but leased it to them was denied.

The largest local Deposit tungsten in those years was rented on shares industrialist Tolmachev and mining engineer Six. These traders have found it profitable to transfer the lease to the Swedish company, which surveyed the field, rather they are interested in. He already wanted to grab 30 thousand rubles in advance by agreement with the company, but this amount was not destined to end up in his pocket: suspecting that he deliberately understated the expected reserves of tungsten, geological Committee suggested that in view of the difficulties of wartime requisition Tolmachevsky mines and pass them to the jurisdiction of the Cabinet of the Royal court. Higher consent to this action was soon obtained.

In his memoirs of that period academician A.E. Fersman wrote: "Before the October revolution the work of the Commission of natural productive forces of the Academy of Sciences could not be deployed. In severe conditions, which was then the Russian science, the initiative of the scientists encountered countless obstacles. Even the development of such crucial issues as the development of tungsten deposits, within two years of the Academy of Sciences could not get the most insignificant loans".

Unfortunately, the scientists were not only financial, but also other, perhaps more complex problems. Indicative in this sense, the episode that recalls in one of his books outstanding scientist-naval academician A.N. Krylov. In January 1917, i.e. in the last weeks of the reign of Nicholas II, the Commission natural productive forces of the Academy of Sciences discussed the tungsten deposits, which was lacking then Russia. Speaker - influential Royal dignitary said that deposits of ores of this metal are in the territory of Turkestan and equipment there expedition requires 500 rubles. After his presentation there was silence. Almost everyone at the meeting knew that the tungsten rich and subsoil of the Altai, but to talk about it no one dared because all of the Altai Krai is one of the richest regions of the Russian land was owned by close relatives of the king of great princes Vladimirovich, and that their possessions to carry out exploration, it was a sin even to think.

Agonizing pause broke A.N. Krylov: "About Turkestan mines the matter is very simple - here's five hundred roubles, and took the piece of paper with a portrait of Peter the great, he gave her presiding at the meeting of the AU RAS. - More difficult to deal with Altai. The Rapporteur said that the mines are located on the lands of the Grand Dukes Vladimirovich. Tungsten is a high-speed steel, i.e. more than doubling the manufacture of shrapnel. If appropriate requisition or expropriation, it is here: no shrapnel means losing the war, and then not only Vladimirovich, but the dynasty the hell will fly".

Another obstacle that hindered the development of the tungsten industry in our country, was "help" foreign experts. In 1931, the Museum of Moscow University, going through old mineralogical collection, scientists came across the samples of scheelite from an unknown until that time deposits in Tajikistan. It turned out that these samples were found in 1912 and sent to Moscow to study. However involved as consultants German geologists rejected the Deposit as unprofitable, and the Imperial government put him on the cross. The Commission aimed to Tajikistan several months after the Museum's findings, found large deposits of tungsten.

Around the same years, the famous Soviet geologist, academician S. S. Smirnov, together with his disciples, he deployed on the territory of our country wide search tungsten deposits. More than one thousand kilometers in the cold and heat had to overcome geologists. On foot, on dogs, on the deer they traveled along and across many areas of the country. And where were the brave scouts subsoil in Transbaikalia, Yakutia, on the Okhotsk coast, there were new mines were built new factories were established Soviet tungsten industry.

Nowadays about 80% of the total produced in the world tungsten consumes metallurgy of high-quality steels, about 15% goes to the production of hard alloys, and the remaining 5% of the industry uses in the form of pure tungsten metal, which has remarkable properties.

To melt tungsten, it should be heated to a temperature at which most of the metals have already evaporated to 3410°C. the tungsten could remain in a liquid state even near the Sun: boiling point it almost 6000 °C. the Refractoriness of this element and provided him the use of one of the most important industries - electrical engineering.

Since the beginning of the XX century, the tungsten filament is replaced previously used for the manufacture of electric lamps coal, omiewise and tantalum filament, every night in our homes erupt tiny tungsten lightning. Every year the world produces several billion light bulbs. Billions of lights!.. And a lot of it? Judge for yourself: since the beginning of our chronology mankind lived only a little over one billion minutes (April 29, 1902 in 10 hours and 40 minutes time start to count down the second billion minutes of a new era).

Scientists and engineers are constantly improving the light bulb, trying to make her life continued as long as possible. Like melts burning wax candle, when you turn on the tungsten lamp starts to evaporate from the surface of the filament. To reduce evaporation and thereby extend the lamp life, it is under pressure usually impose various inert gases. And recently proposed to use for this purpose a pair of iodine, which, as it turns out, plays a curious role: he catches the evaporated molecules of tungsten, to join with him in a chemical bond, and then deposited on the filament, thereby returning to her "runaways". This lamp is much more durable.

The range of electric bulbs manufactured by the industry are very diverse: from tiny "beads"used in medicine, to the powerful searchlight "suns". In 1967, at the world exhibition in Montreal in the pavilion of the USSR was demonstrated to install radiation heating "U-1", one of the main elements of which lamp is an original design, equipped with water and air cooling. In a relatively small flask of heat-resistant quartz, filled with the inert gas xenon, there are two tungsten electrodes. When turning on the lamp between the electrodes breaks out of the gas plasma, heated to 8000 °C. Special mirror reflector, as compared to conventional mirrors seem dull cans, directs infrared rays of an artificial sun lamp recreates the solar spectrum) in the optical system of the installation, where they are focused into a single thread with a diameter of a little more than a centimeter. The temperature in the focus of the beam reaches 3000 °C. In this hot mode "U-1" can continuously work for hundreds of hours.

Wide application in technology are so-called cathode rays, which represent the flow of electrons escaping from the surface of the metal cathode in a vacuum (electron emission). As shown, one of the best materials for cathodes were tungsten.

One of the important features of tungsten - high density: it's as heavy as gold. In this respect, the tungsten is slightly inferior only to the OS, iridium and platinum, but it is much inferior to them in price. For aircraft or space launch weight of the material, usually an obvious drawback, however, in some other areas of technology, it is the quality, as they say, worth its weight in gold. But after all, why would the designers really apply in such cases, gold or platinum is too expensive. But tungsten appropriate here: based on it created the so-called heavy alloys, already found a variety of applications. Of them produce radiation screens (more reliable than lead), containers for radioactive isotopes, various balancers and balances in watches and other devices, the rotors of gyroscopes, cores for armor-piercing shells and other parts and products, which should have considerable weight in society."

Tungsten tremendously durablePure tungsten has enormous strength: tear resistance reaches. 40 tons per square centimeter, significantly exceeding the strength of the best steel. And such excellent strength characteristics of the metal manages to save even at 800°C!

High strength metal tungsten is combined with good ductility: it is possible to pull the thinnest wire, 100 kilometers which weigh only 250 grams!

Tungsten wire, which is widely used in light bulbs, has recently found another job: it is proposed to use as a cutting tool for machining brittle materials. Ultrasonic generator using the Converter gives a tungsten filament oscillatory motion, and she slowly but surely cut into the material being processed. New "cutter" is easy to cope with such a demanding materials, such as quartz, ruby, Sitall, glass, ceramics, cutting them with pinpoint accuracy on the part or leaving them in the grooves and cracks of any shape, any size. But no matter how great the strength of tungsten wire, it does not go to any comparison with the strength of the "whiskers" from this metal is very thin crystals, which are hundreds of times thinner than a human hair. Soviet physics managed to get tungsten moustache with a diameter of only two millionths of a centimeter. Their strength is 230 tons per square centimeter is almost equal to the absolute ceiling strength, i.e. the theoretical limit for terrestrial substances defined by calculation. But this miracle metal exists only inside laboratories.

Used the same technique in pure tungsten is produced by restoration of its oxide by hydrogen. The resulting smallest tungsten dust pressed and is sintered by heating the electric current up to 3000°C. From this pull tungsten filament light bulbs, punched parts radio and x-ray tubes produce contacts for switches, electrodes, switches.

Scientists developed a plasma-arc method of growing large single crystals of tungsten, molybdenum and other refractory metals. 8 the Institute of metallurgy of the Academy of Sciences of the USSR, this method has received a large single crystal of tungsten - he weighs 10 pounds . Due to the high purity of this metal is unusual mechanical properties even at very low temperatures, it retains plasticity, but with significant heat almost no loss of strength. The single crystals are used in many electrical devices.

Scientists have discovered the tungsten very curious ability to actively capture and store sunlight. It, however, is not about the metal, but his finest film obtained by deposition of tungsten from the gas phase. Metal with such a surface heated to 500 °C, can long maintain this temperature, if it will fall the Sun's rays. What accounts for such a thermal effect? If we consider the film in the microscope, it will show fluffy: its surface is a "thicket" of dendritic crystals-hairs, in which "confused" the sun's rays.

A huge panel with many almost invisible to the eye hairs tungsten coated with gold coating of physics are used to determine the trajectory of the protons.

As is well known, x-rays have high penetrating power. But every coin has another side: these rays do not want either reflected or refracted. And it is a pity because if he managed to focus, scientists could think about x-ray microscopes and lasers - science has opened new and interesting perspectives. Yet recently managed to create a so-called x-ray mirror that reflects some of the rays, including, and this is especially important, even falling perpendicular to the surface. The mirror consists of several tens of alternating layers of tungsten and carbon, deposited on a thin silicon substrate. The thickness of each layer of tungsten is less than 1 nanometer (i.e. one billionth of a fraction of a meter!), as each layer of carbon is twice as thick (if only here this term). Strict adherence to the dimensions of the layers is necessary in order to avoid possible interference of the rays, considerably weakening their reflection. The total thickness of unusual mirrors only 0.38 mm and a diameter of 76.2 mm .

An interesting experiment, which took an active part tungsten, was held during the joint flight of Soviet and American astronauts on the program "Soyuz - Apollo". In terrestrial conditions is difficult, and often impossible to obtain an alloy of metals that vary in density: melting and crystallization of the particles of the heavier component will gravitate to the bottom "floor" of the ingot, and at the top to "settle" particles of a lighter metal. Naturally, to use the alloy with such a mixed composition is almost impossible. Another thing - cosmic fusion. Here, in conditions of weightlessness, all metals are equal - and light, and heavy, so the alloy promises to be uniform in composition and structure. So it was decided to produce in space alloy lightweight and low-melting aluminum with a solid heavyweight tungsten, and have the record refractoriness.

This experiment is only the beginning of the development of space technology. "Take some time, " says one of the participants of the historic flight Valery Kubasov, and in space together, we can create whole plants. They will do a completely new metallurgy - receiving alloys and materials that cannot be obtained in the conditions of the Earth".

...Many centuries metals to serve the man, helping him to create amazing world of technology. And a respected place among them belongs to the tungsten metal, standing on the fire lines.

 

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