Natural mineral formations that contain tungsten in various compounds and industrial concentrations, when mining is technically possible and economically feasible - tungsten, molybdenum in ores, as well as beryllium, tin, copper, bismuth, occasionally mercury, antimony, silver, gold, arsenic, Tantalum, sulfur, scandium, niobium - the planet, judging by the name of their group, is not rich in such rare-earth metals. The associated component of tungsten ore - molybdenum, like most others, is extracted during enrichment and converted into selective or collective concentrates.
How tungsten appeared
The Swedish chemist Karl Scheele, a pharmacist by training, conducted experiments in his own laboratory. There he discovered mankind, barium, chlorine, even oxygen for humanity. All his life he only did what he made discoveries, for which he was admitted to the Stockholm Academy of Sciences. And even shortly before his death in 1781, he did not stop doing what he loved, thus making us another wonderful gift.
Carrying out the experiment, Karl Scheele discovered that tungsten (a mineral which was later named Scheelite in his honor) is a salt of some other unknown acid. This was a huge discovery, but only two years later, chemists from Spain and his students isolated a completely new element from this mineral, which turned all the postulates in the industry upside down. However, this revolution did not happen right away, a century passed before it became clear what exceptional properties tungsten has.
Separation
Depending on the deposit, all tungsten ores are divided into two types: exogenous and endogenous. Among the latter are skarn, pegmatite, vein-vein (hydrothermal), and graser types of genetic ores, which are combined into three main ore formations. This is tungsten - tin, tungsten - molybdenum, tungsten - polymetals.
Sometimes tungsten is found in pegmatites, from where it is extracted, and scheelite is extracted along the way, mining for beryl, cassiterite, tantalum, niobates or spodumene. Pegmatite deposits - the sources of the formation of alluvial placers - are developed most of all in Southeast Asia and Africa.
Stocks
Tungsten and molybdenum in ores are closely associated with granite intrusions, their apical parts, where near-bed deposits are observed, quite often accompanied by ore stockworks both intra- and supra-intrusive.
They are in the form of cloak-like deposits, isometric and oval, most often with a gentle bedding. Ore bodies of a pillar-like appearance and stockwork of irregular shape are also noted. The reserves of deposits containing molybdenum, tungsten and other rare earth minerals almost never have large reserves. Ore is estimated at only tens, very rarely hundreds of thousands of tons.
Production
Molybdenum, tungsten and other hydrothermal ores are located in the zones of exo and endocontact of granite massifs, which form quite long in depth - up to a kilometer - whole series of steep fall veins, the average fall of the vein is much less common. Stockworks are also found. Ore bodies are composed of quartz-tungsten-cassiterite, quartz-tungsten inclusions, often with molybdenum, beryl and bismuthine, interspersed with quartz-molybdenite-scheelite or quartz-scheelite ores.
Typically, such ores contain tungsten, molybdenum, another rare-earth metal in small amounts: tungsten from half percent to one and a half percent, more often less. And this is with ore reserves of several thousand or several tens of thousands of tons, which is also very, very small. Mining is usually done by underground or open pit mining.
Mining methods
Tungsten deposits suggest methods of mining either by collapse of the layers or by horizontal magnetization of the ore in layers in the spent blocks. The method of laying out the worked out space is also used, which is good when developing veins, skarn or greisen deposits.
An open method involves the presence of curtains, skarn or greisen deposits or placers. In quarries where tungsten and molybdenum ore is mined, the transport system and external dumping usually operate. In these cases, production is mechanized almost completely - by ninety-five percent. But the work does not end here. Ores require enrichment, since they contain rare earth metals - tungsten and molybdenum only at a maximum of one and a half percent.
Place of Birth
In the territory of the former USSR, the most significant deposits of tungsten ore are explored in Kazakhstan, Eastern Siberia and the Far East, the Caucasus and Central Asia. Not all of them are developed. Abroad, the processing of tungsten and molybdenum is carried out especially in South Korea and China. There are the most significant deposits in the world. In addition, tungsten is mined in Portugal, Australia, Canada, Bolivia, USA, France, Austria and Turkey.
It must be said here that Southeast Asia and its Pacific ore belt have more than sixty percent of all tungsten reserves on earth. In total, the total reserves of tungsten in the explored deposits of the planet are much less than one and a half million tons. For example, about 4,278,200 tons of gold are mined annually (not in reserves, namely, put into operation).
The properties
Being one of the most refractory metals , tungsten becomes literally indispensable in all areas that are associated with high temperatures. As a chemical element, Wolframium (W) is in the fourth group of the periodic system. Its atomic mass is 183.85, and number 74. It got its name due to its light gray color - Wolf and Rahm are translated from German as “wolf” and “cream”, if literally - “wolf foam”. Despite refractoriness, it is stable at ordinary temperature. The minerals supplying tungsten are scheelite and tungsten.
Tungsten is one of the most important components of superhard heat-resistant steels - high-speed and tool, as well as alloys with the same properties - stellite, win and so on. But we see pure tungsten every day, since it is widely used in electrical engineering. For example, in incandescent lamps, tungsten filaments. It is also indispensable in electronics. Electronic devices have cathodes and anodes of this metal.
Alloy grades
The processing of tungsten and molybdenum is complex, but extremely beneficial. The industry knows several brands, among which there are more common and less. Tungsten is pure, with additives and in alloys with other metals. Thus, the VR brands are distinguished - an alloy of tungsten and rhenium; VL - with lanthanum oxide as an additive; VI - with yttrium oxide; BT - thorium oxide as an additive; VM - with silica alkali and thorium additive; VA - with silica-alkali and aluminum additives; HF - pure tungsten.
Tungsten serves as the basis for hard alloys, and the alloy of tungsten and molybdenum is heat resistant, like some others. Also, with his participation, wear-resistant tool steel is being prepared. Such alloys make many parts of engines - aviation and space, in electric vacuum devices - various parts and filaments. Since the density of this metal is very high, it is used for counterweights, for bullets and artillery shells, for ballistic missiles (flight stabilization, tungsten withstands all one hundred eighty thousand revolutions per minute) for ultra-high-speed rotors, metals such as tungsten and molybdenum are also used. Their application, as we see, is very wide and even, one might say, exquisite.
Fields of application
Without these rare earth metals, such as chromium, molybdenum, tungsten, today neither medicine nor nuclear physics can do. Single crystals of all tungstates serve as scintillation detectors of x-ray radiation, as well as other ionizing radiation. Tungsten ditelluride (WTe 2 ) is used in the conversion of thermal energy into electrical energy. Even argon arc welding uses tungsten as an electrode.
Tungsten compounds are especially widely used. Composite materials and hard alloys based on tungsten carbide are needed for the machining of both metals and non-metallic structures. This is especially necessary in mechanical engineering: milling, turning, chiselling, planing. Hard alloys can not be dispensed with while drilling wells and in the mining industry, and for this, tungsten and molybdenum are needed - production masters new technologies with their help.
Types of products from rare earth metals
WS 2 (tungsten sulfide) is a high temperature grease that can withstand up to five hundred degrees Celsius. Where solid electrolyte is produced (high temperature fuel cells), tungsten trioxide is used. Textile, paint and varnish industries have significantly improved and complicated technologies using tungsten compounds as a catalyst and pigment in organic synthesis.
The industry produces a huge variety of products that contain tungsten, molybdenum and other rare earth metals. The most common are electrodes, wire, tungsten powder, sheet and bead. The electrodes never melt and therefore can be used for welding high alloy steels, non-ferrous metals and materials with different chemical compositions. No electrode can provide such a high strength weld.
Molybdenum
Alloys of molybdenum and he himself are refractory materials. In its pure form it is used in the form of wire or tape for heating appliances - electric furnaces, even operating in hydrogen with a temperature of 1600 ° C. Molybdenum sheet and wire are needed in the electronics industry, they are also used in X-ray technology, and various parts for x-ray tubes, electron tubes, and vacuum devices are made from molybdenum.
In addition, molybdenum, like tungsten, is widely used to improve steels. Molybdenum additive increases strength, hardenability, corrosion resistance, viscosity. Therefore, tungsten and molybdenum are used to create the most critical products and the most important parts. For hardness, stellites — chrome and cobalt — are introduced into such an alloy to fuse the edges of wear parts. Chrome, molybdenum, tungsten - such an alloy is almost impossible to erase. He was also given one of the first places in the series of acid-resistant and heat-resistant alloys.
Space
An alloy of tungsten and molybdenum as part of the sheathing of the head of any rocket and aircraft. In terms of strength, tungsten comes first, and molybdenum comes second. However, the specific strength at temperatures of about one and a half thousand degrees Celsius brings molybdenum alloys to the first place. If the temperatures are even higher, then tungsten and tantalum are invincible. Molybdenum is used to make honeycomb panels for all aircraft, capsule shells and rockets that return to Earth, heat exchangers, heat shields, wing-edge sheathing, and stabilizers.
Where working conditions are difficult, rare earth metals help. From such a material, one can expect high resistance to oxidation and gas erosion, high strength and ability to hold impact. Many parts of turbojet and rocket engines, tail skirts, turbine blades, nozzle flaps, control surfaces, rocket engine nozzles and so on - molybdenum copes with all these difficult jobs.
On the ground
Promising materials for equipment that work in the environment of phosphoric, sulfuric and hydrochloric acids are made from molybdenum and its alloys. It is resistant even in molten glass, and therefore the glass industry widely uses molybdenum as electrodes for melting.
The rods and molds for high-pressure casting of copper, zinc and aluminum alloys are made of its alloys. Steel is processed with molybdenum under pressure - stamps, dies, mandrels of piercing mills. Molybdenum steel itself also significantly improves.