Tungsten — the most refractory metal, it is a little widespread in the nature and does not meet in a free look. Long time this metal did not find the broad application in the industry, only in the second half of the 19th century began to study influence of its additives on properties of steel.
Instruction
1. Tungsten represents heavy metal of light gray color, it was allocated in the form of anhydride in 1781 by the Swedish chemist K. Sheele. In 1783 the Spanish erudite brothers D'Elouiar for the first time received metal which was called tungsten. In France, Great Britain and the USA its initial name - "тангстен" is used that in translation from Swedish means "a heavy stone".
2. Tungsten differs from other metals in the hardness and weight, it melts at 3380 OS, and boils at 5900 OS that corresponds to temperature on the surface of the Sun. Mechanical properties of this metal depend on a way of its receiving, the previous mechanical and heat treatment and also purity.
3. At a normal temperature technical tungsten is fragile, but at +200-500os it becomes plastic. The compressibility coefficient at it is lower, than at all other metals. It considerably surpasses molybdenum, tantalum and niobium in duration of preservation of durability. Compact tungsten is steady on air, but begins to be oxidized at a temperature +400os.
4. As raw materials for receiving tungsten serve sheelitovy and volframitovy concentrates, from them melt ferro-tungsten — alloy of iron and tungsten which is used by production of steel. To emit pure metal, from sheelitovy concentrates receive tungsten anhydride, decomposing them in autoclaves solution of soda or hydrochloric acid. Volframitovy concentrates are cemented with soda, and then leached water.
5. At the moment tungsten is widely used in the equipment in the form of pure metal or alloys. The most important of them are alloyed steel. Along with other refractory metals, alloys on the basis of tungsten are applied in the aviation and rocket industry.
6. Low vapor pressure and refractoriness allow to use tungsten for production of spirals and filaments of electrolamps. This metal is also applied during creation of details of electrovacuum devices in X-ray engineering and radio electronics — cathodes, tubes, grids and rectifiers of high voltage.
7. Tungsten is a part of the durable alloys used for a covering of superficial details of cars and production of working parts of the cutting and boring tools. Its chemical compounds are applied in textile and paint and varnish industry and also are the catalyst in organic synthesis.