Tungsten: application, properties and chemical characteristics

Mother nature has enriched humanity with useful chemical elements. Some of them are hidden in its bowels and are contained in a relatively small number, but their significance is very significant. One such is tungsten. Its use is due to special properties.

History of origin

The eighteenth century, the century of the discovery of Mendeleyev's table, became fundamental in the history of this metal.

Earlier, the existence of a substance, which is a part of mineral rocks, was taken, which prevented the smelting of the necessary metals from them. For example, obtaining tin was difficult if the ore contained such an element. The difference in melting temperatures and chemical reactions led to the formation of slag foam, which reduced the amount of tin outlet.

In the VIII century the metal was consistently opened by the Swedish scientist Scheele and the Spaniards by the brothers Eluard. This happened due to chemical experiments on the oxidation of mineral rocks - scheelite and wolframite.

It is registered in the periodic table 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 that were discovered during the 20th century.

Where to look?

In terms of quantity in the bowels of the earth, it is "sparsely populated" and occupies the 28th place. It is a component of about 22 different minerals, but only 4 of them have a significant importance for its production: scheelite (contains about 80% trioxide), wolframite, ferberite and gubnerite (each 75-77% each). In the composition of ores most often contain impurities, in some cases, a parallel "recovery" of metals such as molybdenum, tin, tantalum and so on. The largest deposits are in China, Kazakhstan, Canada, the USA, also there are in Russia, Portugal, Uzbekistan.

How to get?

Due to its special properties, as well as its low content in the rocks, the technology of obtaining pure tungsten is rather complicated.

1. Magnetic separation, electrostatic separation or flotation to enrich the ore to 50-60% concentration of tungsten oxide.
2. Isolation of 99% oxide by chemical reactions with alkaline or acidic reagents and gradual purification of the resulting precipitate.
3. The reduction of the metal with carbon or hydrogen, the yield of the corresponding metal powder.
4. Manufacturing of ingots or powder sintered briquettes.

One of the important stages in obtaining 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 application of which is found mainly in the industrial production of cutting tools of increased power and durability.

Physical and chemical properties

Tungsten is a refractory and heavy metal of silver color with a volume-centered crystal lattice.

• The melting point is 3422 ° C.
• The boiling point is 5555 ° C.
• The density is 19.25 g / cm ³ .

It is a good conductor of electric current. It is not magnetized. Some minerals (for example, scheelite) are luminescent.

Resistant to the influence of acids, corrosive substances in the environment of high temperatures, corrosion and aging. Deactivation of the influence of negative impurities in steels, improvement of its heat resistance, corrosion resistance and reliability is also facilitated by tungsten. The use of such iron-carbon alloys is justified by their manufacturability and wear resistance.

Mechanical and technological properties

Tungsten is a hard, strong metal. Its hardness is 488 HB, the ultimate strength is 1130-1375 Mpa. In the cold state it is not plastic. At a temperature of 1600 ° C, plasticity is raised to the state of absolute compliance to pressure treatment: forging, rolling, and drawing. It is known that 1 kg of this metal makes it possible to produce a yarn 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 are used from high-speed alloyed tungsten-containing steel. The standard cutting principles are not applicable, since the equipment is extremely quickly worn out, and the tungsten being processed is cracked. The following technologies are applied:

1. Chemical treatment and impregnation of the surface layer, including the use of silver for this purpose.
2. Heating of the surface with the help of furnaces, gas flame, electric current of 0.2A. The permissible temperature at which there is a slight increase in ductility and, accordingly, improves cutting - 300-450 ° C.
3. Tungsten cutting with the use of low-melting substances.

Sharpening and grinding is expedient for carrying out with the help of diamond and elborovyh tools, less often - corundum tools.

Welding of this refractory metal is mainly carried out under the influence of an electric arc, tungsten or carbon electrodes in the environment of inert gases or liquid protectors. It is also possible to use contact welding.

This particular chemical element has characteristics that distinguish it in the 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 the high melting point makes it possible to produce filament for bulbs and welding electrodes.

Application

Rarity, unusualness and importance determine the wide use in modern technology of metal called Tungsten - tungsten. Properties and applications justify high cost and demand. High temperatures of melting, hardness, strength, heat resistance and resistance to chemical influences and corrosion, wear resistance and cutting characteristics are the main trump cards. Use cases:

1. Filament filament.
2. Doping of steels to obtain high-speed, wear-resistant, heat-resistant and heat-resistant iron-carbon alloys that are used for the production of drills and other tools, punches, springs and springs, rails.
3. Making "powder" hard alloys, used mainly as particularly wear-resistant cutting, drilling or pressing tools.
4. Electrodes for argon-arc and contact welding.
5. Manufacturing of parts for X-ray and radio engineering, various technical lamps.
6. Special luminous paints.
7. Wire and parts for the chemical industry.
8. 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 engineering to light industry, where fabrics with special properties (for example, fireproof ones) are made.

Universal materials do not exist. Every known element and created alloys are distinguished by their uniqueness and necessity for certain spheres of life and industry. However, some of them have special properties that make previously unrealizable processes possible. One such metal is tungsten. Its application is not widely enough, as in steel, but each of the options is extremely useful and necessary for mankind.