Mother Nature has enriched humanity with useful chemical elements. Some of them are hidden in its bowels and are contained in a relatively small amount, but their significance is very significant. One of these is tungsten. Its use is due to special properties.
Origin history
The XVIII century - the century of the opening of the periodic table - became fundamental in the history of this metal.
Previously, it was assumed that there was a certain substance that was part of the mineral rocks, which prevented the smelting of the necessary metals. For example, obtaining tin was difficult if such an element was contained in the ore. The difference in melting points and chemical reactions led to the formation of slag foam, which reduced the amount of tin output.
In the eighth century, metal was subsequently discovered by the Swedish scientist Scheele and the Spaniards the Eluard brothers. This happened as a result of chemical experiments on the oxidation of mineral rocks - scheelite and tungsten.
It is registered in the periodic system of elements in accordance with atomic number 74. A rare refractory metal with an atomic mass of 183.84 is tungsten. Its use is due to unusual properties discovered already during the 20th century.
Where to looking for?
According to the number in the bowels of the earth, it is “sparsely populated” and takes 28th place. It is a component of about 22 different minerals, but only 4 of them are essential for its extraction: scheelite (contains about 80% trioxide), tungsten, ferberite and guberite (each of them contains 75-77%). The ores most often contain impurities; in some cases, parallel extraction of metals such as molybdenum, tin, tantalum, etc. is carried out. The largest deposits are in China, Kazakhstan, Canada, the USA, and also are in Russia, Portugal, and Uzbekistan.
How to get it?
Due to its special properties, as well as its low content in rocks, the technology for producing pure tungsten is quite complicated.
- Magnetic separation, electrostatic separation or flotation in order to enrich the ore to 50-60% concentration of tungsten oxide.
- Isolation of 99% oxide by chemical reactions with alkaline or acid reagents and stepwise purification of the resulting precipitate.
- Metal reduction with carbon or hydrogen, yield of the corresponding metal powder.
- Production of ingots or powder sintered briquettes.
One of the important stages in the production of metallurgical products is powder metallurgy. It is based on the mixing of powdered refractory metals, their pressing and subsequent sintering. Thus, a large number of technologically important alloys are obtained, including tungsten carbide, the use of which is found mainly in the industrial production of cutting tools with increased power and durability.
Physical and chemical properties
Tungsten is a refractory and heavy silver-colored metal with a body-centered crystal lattice.
- Melting point - 3422 ˚.
- Boiling point - 5555 ˚.
- Density - 19.25 g / cm 3 .
It is a good conductor of electric current. It does not magnetize. Some minerals (e.g. scheelite) are luminescent.
Resistant to acids, aggressive substances in high temperatures, corrosion and aging. Tungsten also contributes to the deactivation of the influence of negative impurities in steels, the improvement of its heat resistance, corrosion resistance and reliability. The use of such iron-carbon alloys is justified by their manufacturability and wear resistance.
Mechanical and technological properties
Tungsten is a hard, tough metal. Its hardness is 488 HB, tensile strength - 1130-1375 MPa. In the cold state is not plastic. At a temperature of 1600 ° C, ductility increases to a state of absolute compliance with pressure processing: forging, rolling, drawing. It is known that 1 kg of this metal makes it possible to produce a thread with a total length of up to 3 km.
Cutting is difficult due to excessive hardness and brittleness. For drilling, turning, milling, carbide tungsten-cobalt materials made by powder metallurgy are used. Less often, at low speeds and special conditions, tools from high-speed alloyed tungsten-containing steel are used. Standard cutting principles are not applicable, as the equipment wears out extremely quickly and the tungsten being processed is cracked. The following technologies are applied:
- Chemical treatment and impregnation of the surface layer, including the use of silver for this purpose.
- The surface is heated with furnaces, a gas flame, an electric current of 0.2 A. The permissible temperature at which there is a slight increase in ductility and, accordingly, cutting improves, is 300-450 ° C.
- Tungsten cutting using fusible materials.
It is advisable to sharpen and grind using diamond and elbor tools, less often corundum ones.
Welding of this refractory metal is carried out mainly under the influence of an electric arc, tungsten or carbon electrodes in an inert gas environment or liquid shields. It is also possible to use contact welding.
This particular chemical element has characteristics that distinguish it in its total mass. So, for example, characterized by high heat resistance and wear resistance, it improves the quality and cutting properties of alloyed tungsten-containing steels, and a high melting point allows one to produce filament for bulbs and electrodes for welding.
Application
Rarity, unusualness and importance determine the widespread use in modern technology of metal called Tungsten - tungsten. Properties and applications justify high cost and demand. High indicators of melting temperature, hardness, strength, heat resistance and resistance to chemical influences and corrosion, wear resistance and cutting features - these are its main trump cards. Use cases:
- Filament.
- Alloying steels in order to obtain high-speed, wear-resistant, heat-resistant and heat-resistant iron-carbon alloys, which are used for the production of drills and other tools, punches, springs and springs, rail.
- Production of “powder” hard alloys, used mainly as especially wear-resistant cutting, drilling or pressing tools.
- Electrodes for argon-arc and resistance welding.
- Production of parts for x-ray and radio engineering, various technical lamps.
- Special luminous paints.
- Wire and parts for the chemical industry.
- Various practical small things, for example, mormyshki for fishing.
Various alloys, which include tungsten, are gaining popularity. The scope of such materials is sometimes surprising - from heavy machinery to light industry, where fabrics with special properties are made (for example, fireproof).
Universal materials do not exist. Each known element and created alloys are distinguished by their uniqueness and necessity for certain areas of life and industry. However, some of them have special properties that make previously impossible processes possible. One of these metals is tungsten. Its application is not wide enough, as in steel, but each of the options is extremely useful and necessary for humanity.