Tungsten — means «wolf's foam», the element of group VI of the table of Mendeleev, where indicated by the symbol W. the Atomic weight 183,92, specific weight at room temperature is 19.3 g/cm3. Is a rare metal, its content in the lithosphere is about 0,0055%; Tungsten metal in a light grey colour, in appearance similar to steel. Today you can buy it at the most affordable prices.
|The atomic number of W||Atomic (molar) mass, g/mol||The degree of oxidation||Density [g/cm3]||The melting temperature t°C||The boiling point of t°C||The heat of fusion kJ/kg|
|No. 74||Of 183.84||0, 2, 3, 4, 5, 6||19,25||3422°C||5500°C||191|
Tungsten has a melting point 3395 °C. Only carbon has a higher melting point. Due to the refractoriness of the metal became the basis of the most heat-resistant alloys. W boils at a temperature > 5500 °C, is characterized by minimum evaporation rate at t° 1500 — 2500 °C and a significant electrical resistance: almost 3 times higher than that of copper. Tungsten have excellent mechanical properties: wear resistance, hardness at high temperatures, the minimum thermal expansion coefficient, high hot hardness. This means that tungsten steel retains hardness and strength at high temperatures, unlike most steels, which after reaching the t° red heat and cooling in air lose their hardness. Instrumental tungsten steel is used for metal working at the speed of tens meters per second. Chemically pure W pretty plastic and only the admixture of carbon and oxygen is known to give it hardness. He has a very high resistance to temperature creep, high modulus of compression and tension, excellent thermal conductivity and high coefficient of electron emission, which is further enhanced in the alloy with oxides of other metals. Today, Wolfram took a firm place in everyday life. You can buy it at the most affordable prices.
Tungsten is chemically resistant in contact with moisture, concentrated solutions of alkalis and acids, Aqua Regia, hydrogen, 2 (up to 400°C), hydrogen chloride (up to 600°C), NH3 (up to 700°C), boiling mercury, N2, and CO (up to 800°C). W reacts with a mixture of NH3 + H2 O2, a mixture of hydrofluoric acid and nitric acid, with boiling sulfur and chlorine (over 250°C), with H2 S, at t° red heat, with hot HNO3 and hot Aqua Regia, molten chlorate, nitrite and potassium nitrate, sodium nitrate, lead dioxide, bromine, fluorine, iodine. Carbide WC receive in the interaction with carbon above 1400° C, the oxide in the interaction with water vapor and SO2 (at t° red heat), CO2 (above 1200°C), with oxides of Mg, Al, Th.
Disadvantages of tungsten
The difficulty of obtaining pure, brittle at normal temperature, big specific gravity, hardness, low plasticity. Forging, rolling, drawing tungsten amenable only by strong heating.
The production of rolled
Technological plasticity of the metal is insufficient, but with the increase of temperature improves. Therefore, tungsten hire, produce hot pressure treatment. The workpiece (for rods or wire) to the so-called Fort, formed by powder metallurgy methods. Then his warm and rusk on a rotary forging machine — to rods Ø 2 — 3 mm. They are supplied in straight lengths or rolled into the Bay. Of them after drawing in hot condition to get fine wire according to GOST 25 501−82. This wire comes wound on a spool.
· Wire and ribbon are in demand in electrical and electronics due to the low vapor pressure of tungsten at high temperatures up to 2500 °C. Refractoriness makes this metal essential in incandescent lamps, television tubes and other vacuum tubes, such as in the target x-ray tubes.
· Wire used in winding the heating elements and thermal insulation for high temperature furnaces operating in vacuum or hydrogen atmosphere or an inert gas at t° up to 3000 °C.
· Rods are used as fireproof electrodes.
· Produce tungsten crucibles for evaporation of metals.
· W is used in automotive distributors contact plugs.
· Due to the heaviness of the counterweights, and armor-piercing core and feathered arrow-piercing artillery shells, armor-piercing core bullets, the bullet (160 thousand rpm) the rotors of the gyros to stabilize ballistic missiles.
· Production tank armor, shells, torpedoes and shells, high-temperature parts of aircraft engines and space rockets, containers for storage of radioactive isotopes.
· From alloy amalloy make surgical instruments.
· Alloying of tool steels and heat-resistant. Ferrotungsten (70−86% W, up to 7% Mo and Fe) for these alloys is obtained by recovery of scheelite or wolframite concentrates. The best high-speed steel retain hardness at.800°C. They contain up to 18.5% W (or W+Mo), 7% Cr and a small amount of Co. Hastelloy — stainless Nickel alloy doped with tungsten. An even more solid «stellites» — based alloys of cobalt with the addition of W, Cr, P. The rigid — tungsten carbides. The alloy can be «seen» (WC + 15% co and a small admixture of titanium carbide) is 30% harder than normal steel, even tungsten при1100°C. the Cutters of this alloy is removed up to 2 kilometers of iron shavings for a minute, unable to process «capricious» ebonite, glass, porcelain themselves wears out slightly. «Win» — consists of crystals of WC carbide in a cobalt matrix is a very hard alloy, contains 80−87% W, 16% Co, 5−7% of carbon. Instead of tungsten carbide in the super hard alloy in the cermet can use titanium carbide as the filler.
· «Win» is indispensable in the processing of metals and non-metals turning, milling, drilling, slotting. He is represented by such Russian brands as: BK2, VK4, VK6, VK8, ВК15, ВК25, Т5К10, T15K6, Т30К4 and alloys WC, TiC, TaC (brand TT for especially difficult machining conditions: planing and chiselling of forgings of heat-resistant steels, hammer percussive-rotary drilling in the mining and oil industry).
· For the production of thermocouples used tungsten-rhenium wire with 5% rhenium wire with 20% rhenium (VR 5/20).
Wire marks BA, BM, BPH, BT-7, VT-10, VT-15 is used according to GOST 18903−73.
· Of wire brand of VA depending on the diameter and surface conditions produce filaments of incandescent lamps, spiral and respiratoorse cathodes, grids, springs and loop heaters electronic devices, springs of semiconductor devices.
· Wire make brand VRN inputs, and traverse those parts of the device that do not require the use of doped tungsten.
Salts of tungsten
· These salts are used in chemical and tanning industry, they are used as catalysts and pigments.
· Tungsten disulfide is used as a heat-resistant lubricant at t° to 500 °C.
· Tungsten bronze and other tungsten salts produce colors.
· A tungstate of magnesium and calcium fill fluorescence device.
· From WO3 produce heat-resistant solid electrolyte fuel cells.
· Single crystals of tungstates (tungstates of lead, cadmium, calcium) are used as scintillation detectors of ionizing radiation in nuclear energy and medical radiology.
· WTe2 ditelluride tungsten is used as the Converter of thermal energy into electrical energy (thermo-EMF of about 57 mV/K).
· Artificial isotope 185W is used as the radioactive tracer in the study of substances. With an alloy of uranium-235 is stable 184W is used in solid-state nuclear boilers because it has a narrow capture cross section for thermal neutrons (about 2 barn).
In the company «Electrocentury-steel» at a discount in Russia and Ukraine.
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In stock, LLC «Electrocentury-steel» a wide selection of tungsten products. Buy rare and refractory metals is possible through our representative offices in Russia or Ukraine. The timing of orders is minimal. When wholesale purchases are offered preferential discounts.