Tungsten, molybdenum: alloy application

2024 Author: Howard Calhoun | [email protected]. Last modified: 2024-01-02 13:48

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. An associated component of tungsten ore - molybdenum, like most others, is extracted during enrichment and converted into selective or collective concentrates.

How tungsten appeared

Swedish chemist Karl Scheele, a pharmacist by training, conducted experiments in his own laboratory. There he discovered manganese, barium, chlorine, even oxygen for mankind. All his life he did nothing but make discoveries, for which he was accepted into the Stockholm Academy of Sciences. And even shortly before his death in 1781, he did not do his favorite thing.stopped, thus giving us another wonderful gift.

While experimenting, Karl Scheele discovered that tungsten (a mineral later named scheelite in his honor) is a s alt of some still unknown acid. It 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 industry upside down. However, this revolution did not happen immediately, 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), grazer types of genetic ores, which are combined into three main ore formations. These are tungsten - tin, tungsten - molybdenum, tungsten - polymetals.

Sometimes tungsten is found in pegmatites, from where both it and scheelite are extracted along the way, mining beryl, cassiterite, tantalum, niobates or spodumene. Pegmatite deposits - sources of alluvial placer formation - are developed most of all in Southeast Asia and Africa.

Stocks

Tungsten, molybdenum in ores are closely related to granite intrusions, their apical parts, where roof deposits are observed, quite often accompanied by ore stockworks, both intra- and supra-intrusive.

They are cloak-like deposits in shape,isometric and oval with most often flat bedding. There are also columnar ore bodies and irregularly shaped stockworks. The reserves of deposits where molybdenum, tungsten and other rare earth minerals are present 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 extended in depth - up to a kilometer - whole series of veins of steep dip, much less often there is an average dip of the vein. There are also stockworks. Ore bodies are composed of quartz-wolframite-cassiterite, quartz-wolframite inclusions, often with molybdenum, beryl and bismuthine, interspersed with quartz-molybdenite-scheelite or quartz-scheelite ores.

Usually such ores contain tungsten, molybdenum, other rare earth metal in small quantities: tungsten from half a 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 carried out by underground or open pit methods.

Methods of mining

Tungsten deposits involve mining methods either by collapsing layers or by horizontally magnifying ore in layers in mined blocks. The goaf backfill method is also used, which is good when mining veins, skarn or greisen deposits.

Open waysuggests the presence of shutterworks, skarn or greisen deposits or placers. In quarries where tungsten, molybdenum ore is mined, a transport system and external dumping usually operate. In these cases, mining is almost completely mechanized - ninety-five percent. But the work doesn't end here. Ores require beneficiation, since only a maximum of one and a half percent they contain rare earth metals - tungsten, molybdenum.

Deposits

On 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, 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, in the explored 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 of gold is mined annually (not in reserves, but put into use)

Properties

Being one of the most refractory metals, tungsten is literally indispensable in all areas that are associated with high temperatures. How the chemical element Wolframium (W) is in the fourth groupperiodic system. Its atomic mass is 183, 85, and number 74. It got its name due to its light gray color - from the German Wolf and Rahm are translated as "wolf" and "cream", literally - "wolf foam". Despite its refractoriness, it is stable at ordinary temperatures. The minerals that supply tungsten are scheelite and wolframite.

Tungsten is one of the most important components of superhard heat-resistant steels - high-speed and tool steels, as well as alloys with the same properties - stellite, win and so on. But we see pure tungsten every day, because it is widely used in electrical engineering. For example, tungsten filaments in incandescent lamps. It is also indispensable in radio electronics. Electronic devices have cathodes and anodes made of this metal.

Alloy grades

Tungsten and molybdenum processing is difficult but extremely profitable. 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, BP grades differ - an alloy of tungsten and rhenium; VL - with lanthanum oxide as an additive; VI - with yttrium oxide; VT - thorium oxide as an additive; VM - with silica and thorium additive; VA - with silicon-alkali and aluminum additives; HF - pure tungsten.

Tungsten serves as the basis for hard alloys, and an alloy of tungsten and molybdenum is heat resistant, like some others. Also, with his participation, wear-resistant tool steel is prepared. From these alloysmany 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 counterweights, for bullets and artillery shells, for ballistic missiles (flight stabilization, tungsten can withstand all one hundred and eighty thousand revolutions per minute), for ultra-high-speed rotors, metals such as tungsten, molybdenum are also used. Their application, as we see, is very wide and even, one might say, elegant.

Application areas

Without these rare earth metals, which are chromium, molybdenum, tungsten, neither medicine nor nuclear physics can do today. Single crystals of all tungstates serve as scintillation detectors of X-rays, as well as other ionizing radiations. Tungsten ditelluride (WTe_{2) is used in the conversion of thermal energy into electrical energy. Even TIG welding uses tungsten as an electrode.}

Tungsten compounds are especially widely used. Composite materials and hard alloys based on tungsten carbide are needed for machining both metals and non-metallic structures. This is especially necessary in mechanical engineering: milling, turning, chiselling, planing. Hard alloys are now indispensable for drilling wells and in the mining industry, and for this we need tungsten, molybdenum - production is mastering new technologies with their help.

Types of rare earth metal products

WS_{2 (tungsten sulfide) is a high temperature grease that can withstand up to five hundred degrees Celsius. Where a 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.}

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

Molybdenum

Molybdenum alloys and molybdenum itself are refractory materials. In its pure form, it is used in the form of a wire or tape for heating devices - electric furnaces, even those operating in hydrogen at a temperature of 1600 ° C. Molybdenum tin and wire are needed in the radio-electronic industry, they are also used in X-ray engineering, molybdenum is used to make various parts for X-ray tubes, electronic lamps, and vacuum devices.

In addition, molybdenum, like tungsten, is widely used to improve steels. Molybdenum additive increases strength, hardenability, corrosion resistance, toughness. Therefore, tungsten and molybdenum are used to create the most critical products and the mostmain details. For hardness, stellites - chromium and cob alt - are introduced into such an alloy in order to weld the edges of wear parts. Chrome, molybdenum, tungsten - such an alloy is almost impossible to erase. Also, he was given one of the first places in a number of acid-resistant and heat-resistant alloys.

Space

An alloy of tungsten and molybdenum in the skin of the head of any rocket and aircraft. In terms of strength, tungsten is in first place, and molybdenum is in second place. However, specific strength at temperatures of about one and a half thousand degrees Celsius brings alloys with molybdenum to the first place. If the temperatures are even higher, then tungsten and tantalum are invincible. Molybdenum is used to make honeycomb panels of all flying spacecraft, shells of capsules and rockets that return to Earth, heat exchangers, heat shields, wing edge trim, stabilizers.

Where the 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 withstand impact. Many parts of turbojet and rocket engines, tail skirts, turbine blades, nozzle shutters, control surfaces, rocket engine nozzles and so on - molybdenum copes with all these difficult jobs.

On Earth

Promising materials for equipment that operate in 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 usesmolybdenum as electrodes for melting.

Rods and molds for high-pressure casting of copper, zinc and aluminum alloys are made from its alloys. With molybdenum, steels are processed under pressure - press dies, dies, mandrels of piercing mills. Molybdenum steel itself also greatly improves.