Tungsten, molybdenum: application of the alloy

Natural mineral formations that contain tungsten in various compounds and industrial concentrations, when mining is technically possible and economically feasible, are tungsten, molybdenum in ores, and also beryllium, tin, copper, bismuth, occasionally mercury, antimony, silver, gold, arsenic, Tantalum, sulfur, scandium, niobium - such a rare earth metals planet, judging by the name of their group, is not rich. Associated component of tungsten ore - molybdenum, like most others, is extracted during enrichment and transferred to selective or collective concentrates.

How tungsten appeared

Swedish chemist Karl Scheele, an apothecary by training, conducted experiments in his own laboratory. There he discovered for mankind manganese, barium, chlorine, even oxygen. All his life he only did that 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 his favorite business, thus making us one more wonderful gift.

Carling Scheele discovered that tungsten (a mineral, later named in his honor for scheelite) is the salt of some unknown acid. It was a huge discovery, but only two years later chemists from Spain and his students isolated from this mineral a completely new element that turned all postulates in industry. However, this revolution did not happen immediately, a century passed before it became clear what exceptional properties tungsten possesses.

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), grayser types of genetic ores that combine into three main ore formations. This is tungsten - tin, tungsten - molybdenum, tungsten - polymetals.

Sometimes tungsten is found in pegmatites, from where both it and scheelite are extracted in passing, leading the extraction of beryl, cassiterite, tantalum, niobate or spodumene. Pegmatite deposits - the sources of alluvial placers formation - are developed most of all in Southeast Asia and Africa.

Inventory

Tungsten and molybdenum in ores are closely associated with granitic intrusions, their apical parts, where there are occluded deposits, often accompanied by ore stockworks, both intra- and nadtrusive.

They are in shape form cloak-shaped deposits, isometric and oval with the most common canopy. Also noted are the ore bodies of columnar form and stockwork of irregular shape. Reserves of deposits where molybdenum, tungsten and other rare earths are present, almost never have large reserves. Ore is estimated only in dozens, very rarely in hundreds of thousands of tons.

Extraction

Molybdenum, tungsten and other hydrothermal ores are located in the zones of exo-and endocontact of granite massifs, which form a whole length of a steep fall in depth - up to a kilometer -, the average fall in the vein is much less frequent. Also there are stockworks. Ore bodies are composed of quartz-wolframite-cassiterite, quartz-wolframite inclusions, often with molybdenum, beryl and bismuthin, alternating with quartz-molybdenite-scheelite or quartz-scheelite ores.

Typically, such ores contain tungsten, molybdenum, and metal from another rare earth in small quantities: tungsten from half 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 little. The extraction is usually carried out by underground or open methods.

Methods of extraction

Tungsten deposits suggest ways to mine or collapse the layers or horizontally oreganize the layers in the waste blocks. The method of laying the worked out space is also used, which is good for the development of veins, skarn or greisen deposits.

The open method assumes presence of shutters, skarn or greisen deposits or placers. In quarries, where tungsten or molybdenum ore is mined, the transport system and external dumping usually operate. In these cases, the extraction is mechanized almost completely - by ninety-five percent. But here the work does not end. The ores require enrichment, since only a maximum of one and a half percent they contain rare earth metals - tungsten, molybdenum.

Place of Birth

In the territory of the former USSR, the most significant deposits of tungsten ore have been explored in Kazakhstan, Eastern Siberia and the Far East, the Caucasus and Central Asia. Not all of them are being developed. Abroad, tungsten and molybdenum are processed 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.

Here it is necessary to say that Southeast Asia and its Pacific ore belt have more than sixty percent of all tungsten reserves on earth. In total in the reconnoitered deposits of the planet, the total reserves of tungsten are much less than one and a half million tons. For example, about 4,278,200 tons are produced annually (not in reserves, namely, put into operation).

Properties

Being one of the most refractory metals, tungsten becomes literally irreplaceable in all areas that are associated with high temperatures. As a chemical element, Wolframium (W) is in the fourth group of the periodic system. His atomic weight is 183.85, and number 74. He got the name because of his light gray color - from German Wolf and Rahm are translated as "wolf" and "cream", if literally - "wolf foam". Despite the high refractoriness, at normal temperatures it is stable. Minerals that supply tungsten are scheelite and wolframite.

Tungsten is one of the most important components of superhard high-temperature steels-high-speed and tool steels, as well as alloys with the same properties-stellite, win, and so on. But we see pure tungsten daily, as it is widely used in electrical engineering. For example, in filament lamps filaments of tungsten. He is also irreplaceable in radio electronics. Electronic devices have cathodes and anodes from this metal.

Grades of alloys

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 BP grades are distinguished: the alloy of tungsten and rhenium; VL - with lanthanum oxide as additives; VI - with yttrium oxide; BT - as an additive, thorium oxide; VM - with siliceous and thorium additives; VA - with siliceous and aluminum additives; HF - pure tungsten.

Tungsten is 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 prepared. Of these alloys, many parts of engines are made-aviation and space, in electrovacuum devices-various parts and filaments. Since the density of this metal is very high, it is used for counterbalances, for bullets and artillery shells, for ballistic missiles (stabilization of flight, tungsten stands all one hundred and eighty thousand rpm) for superfast rotors, metals such as tungsten and molybdenum are also used. Their application, as we see, is very wide and even, it can be said, exquisite.

Applications

Without these rare-earth metals, such as chromium, molybdenum, tungsten, today medicine, nuclear physics can not do. Single crystals of all tungstates serve as scintillation detectors for X-rays, as well as for 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 solid alloys, having a basis of tungsten carbide, are needed for machining both metals and nonmetallic structures. Especially it is necessary in mechanical engineering: milling, turning, chiselling, planing. Now we can do without hard alloys when drilling wells and in the mining industry, and for this we need tungsten, molybdenum - the production is mastering all new technologies with their help.

Types of products from rare earth metals

WS ₂ (tungsten sulphide) is a high-temperature grease that can withstand up to five hundred degrees Celsius. Wherever a solid electrolyte is produced (high-temperature fuel cells), tungsten trioxide is used. The textile, paint and varnish industry has significantly improved and complicated the technology, using tungsten compounds as a catalyst and a pigment in organic synthesis.

The industry produces a huge variety of products, which contain tungsten, molybdenum and other rare earth metals. The most common are electrodes, wire, tungsten powder, sheet and staff. Electrodes never melt and therefore can be used for welding high-alloy steels, non-ferrous metals and materials with different chemical composition. No electrode will provide such a high strength of the welded seam.

Molybdenum

Alloys of molybdenum and he himself refers to refractory materials. In its pure form is used in the form of wire or tape for heating appliances - electric furnaces, even working in hydrogen with a temperature of 1600 ° C. Molybdenum tin and wire are needed in the electronics industry, they are also used in radiotechnics, molybdenum is used to manufacture various parts for X-ray tubes, electronic tubes, vacuum devices.

In addition, molybdenum, like tungsten, is widely used to improve steels. Additive molybdenum increases strength, hardenability, corrosion resistance, viscosity. Therefore, tungsten and molybdenum are used in the creation of the most important products and the most important details. For stiffness in such an alloy stellite - chromium and cobalt are introduced to fuse the edges of the parts working on wear. Chromium, molybdenum, tungsten - such an alloy is almost impossible to erase. Also, he was given one of the first places in a row of acid-fast and heat-resistant alloys.

Space

Alloy of tungsten and molybdenum in the composition of the covering of the head part of any rocket and airplane. For strength, tungsten is in first place, molybdenum is on the second place. However, the specific strength at temperatures of about one and a half thousand degrees Centigrade deduces alloys with molybdenum in the first place. If the temperatures are even higher, then tungsten and tantalum are invincible. Molybdenum made honeycomb panels of all flying spacecrafts, capsule shells and rockets that return to Earth, heat exchangers, heat shields, wing edge lining, stabilizers.

Where the working conditions are heavy, rare earth metals help. From such material, one can expect high resistance to oxidation and gas erosion, high strength and ability to hold a blow. Many parts of turbojet and rocket engines, tail skirts, turbine blades, nozzle flaps, control surfaces, rocket engine nozzles, and so on - all these difficult jobs are handled by molybdenum.

On the ground

Promising materials for equipment that work in a medium of phosphoric, sulfuric and hydrochloric acids are made from molybdenum and its alloys. It is stable even in molten glass, and therefore the glass industry widely uses molybdenum as electrodes for melting.

From its alloys, rods and molds for high-pressure casting of copper, zinc and aluminum alloys are made. With molybdenum, steels are processed under pressure - press stamps, dies, mandrels of piercing mills. The molybdenum steel itself also improves significantly.