Tungsten price, occurrence, extraction and use

Tungsten [vɔlfram] is a chemical element with the element symbol W and the atomic number 74. It belongs to the transition metals, in the periodic table it is in the 6. Subgroup (group 6) or chromium group. Tungsten is a white-glossy, high-density heavy metal that is brittle in its pure state. It has the highest melting point and the second highest boiling point of all pure metals. His best known use is therefore the incandescent filament in incandescent lamps.

Already in 16. The mineralogist Georgius Agricola from Freiberger described the occurrence of a mineral in Saxon tin ores, which made the extraction of tin by slagging the tin fraction considerably more difficult. The name component "Wolf" stems from this property, as the mineral "gobbled" the tin ore like a wolf. Whether it was tungstenite is still controversial today, as it speaks of the "lightness" of the mineral. He called the mineral lupi spumumwhich translated from Latin means "wolf (s) foam". It was later called Wolfram, from mhd. R.A.M "Soot, dirt", as the black-gray mineral can be easily ground and then reminds you of soot. Its chemical symbol W comes from tungsten.

The common word in English, Italian and French Tungsten derives from Tung Sten (Swedish for "heavy stone"). This did not mean that Wolfram itself (Swedish Volfram), but calcium tungstate called. In this 1781 recognized the German-Swedish chemist Carl Wilhelm Scheele a hitherto unknown salt. Pure tungsten was first produced by 1783 from the Spanish brothers Fausto Juan José Elhuyar (who worked under Scheele's leadership) by reducing tungsten trioxide, which is obtained from wolframite.

 

occurrence 

The tungsten content of the earth's crust is around 0,0001 g / t or 0,0064 percent by weight (Clarke value). So far, the metal could not be proven in nature (in pure form). The "Doklady Akademii Nauk" in Russia published a report on solid tungsten in 1995 without this being examined by the IMA's "Commission on New Minerals, Nomenclature and Classification" (CNMNC). Some minerals, especially oxides and tungstates, are known. The most important tungsten ores are wolframite (Mn, Fe) WO₄ and Scheelite CaWO₄, There are also other tungsten minerals, such as Stolzit PbWO₄ and Tuneptit WO₃ · H₂O.

The largest deposits can be found in China, Peru, the USA, Korea, Bolivia, Kazakhstan, Russia, Austria and Portugal. Tungsten ores can also be found in the Ore Mountains. The safe and probable world deposits are currently 2,9 million tons of pure tungsten.

The most important known occurrence of tungsten in Europe is in the Felbertal in the Hohe Tauern (state of Salzburg in Austria).

 

Promotion worldwide 

In 2006 the world production of pure tungsten was 73.300 tons. By far the largest producer of tungsten is China. More than 80% of the tungsten produced in the world is made there. The states with the highest production of tungsten (2006):

Rank	Country	Delivery rates (in tons per year)
1	China	62.000
2	Russian Föd.	4.500
3	Canada	2.500
4	Austria	1.350
5	Portugal	900
6	North Korea	600
7	Bolivia	530
8	other countries	900

Promotion in Austria

In Austria, the tungsten ore scheelite was first discovered in 1815/16 on the Schellgaden gold deposit in the municipality of Muhr (state of Salzburg). As a result, beautiful scheelite crystals, sometimes several centimeters in size, were found in many crevices of the Hohe Tauern. All of these finds were of no practical use. The large deposit in the Felbertal remained undiscovered for the time being.

In 1950 it became known that large amounts of scheelite appeared in the magnesite deposit on the Wanglalm near Lanersbach / Tux (Tyrol) in the rear of the Zillertal, which had been being mined since 1927. It was coarse scheelite intergrown with magnesite and quartz. In the following years around 10.000 tons of ore with an average tungsten oxide content of 1,8% were extracted, which represented a high quality that is unique in the world. Because of the low market price, tungsten extraction was stopped at the end of the 1960s, but resumed in 1971 and continued until the magnesite mine was closed in 1976.

1967 was eventually discovered the largest Scheelitvorkommen Europe in the Felbertal. The ore pieces present in the streams were traced using UV light (Scheelite fluorescents). The difficult exploration work in the high alpine terrain (highest mining site on Brentling in 2100 at sea level) began 1971, the initially overground mining was recorded in Felbertal 1976 (from 1979 also underground mining, surface mining 1986 set). From the beginning of 1993 to the middle of 1995, mining was temporarily suspended due to the low market price of tungsten.

Wolframerz from the Felbertal is processed in the nearby Mittersill. From here, the scheelite concentrate reaches Sankt Martin in Sulmtal (Styria). A tungsten hut was built on the site of the 1976 underground brown coal mine in Pölfing-Bergla, where tungsten oxide, tungsten metal and tungsten carbide powder have been produced from concentrates from several countries since 1977.

The most important German processors are HC Starck and the Longyear GmbH.

 

Extraction and presentation

Tungsten can not be obtained by reduction with coal from the oxide ores, since this tungsten carbide is formed.

Adding an ammoniacal solution creates a complex called ammonium paratungstate (APW). This is filtered off and then converted into relatively pure tungsten trioxide at 600 ° C. Tungsten (VI) oxide (WO₃), which is reduced to steel-gray tungsten at 800 ° C under a hydrogen atmosphere:

This creates gray tungsten powder, which is usually compacted in molds and electrically sintered into bars. At temperatures above 3400 ° C, a compact tungsten metal can be melted in special electric furnaces with a reducing hydrogen atmosphere (zone melting process).

 

Features 

Physical Properties

Tungsten is a shiny white metal that can be stretched in its pure state and is of high hardness, density and strength. The density is almost the same as that of gold, the Brinell hardness is 250 HB, the tensile strength 550-620 N / mm² (soft) up to 1920 N / mm² (hard). The metal exists in a stable body-centered cubic α-modification with a lattice plane spacing (= lattice constant) of 316 pm at room temperature. This type of crystal structure is often called the tungsten type. With an as metastable β-modification of tungsten (distorted cubic-body-centered), on the other hand, it is the tungsten-rich oxide W₃O.

Tungsten has after the element carbon with 3422 ° C the second highest melting point of all chemical elements. The boiling point of 5555 ° C is surpassed only by the rare metal rhenium with 5596 ° C by 41 K.

The metal is a superconductor with a transition temperature of 15 mK.

 

Chemical properties

Tungsten is a chemically very resistant metal that is hardly attacked by hydrofluoric acid and aqua regia (at least at room temperature). It dissolves in mixtures of hydrofluoric and nitric acids and molten mixtures of alkali nitrates and carbonates.

 

isotope 

Tungsten is known as 33 isotopes and 5 core isomers. In nature, 5 isotopes occur ¹⁸⁰W, ¹⁸²W, ¹⁸³W, ¹⁸⁴W and ¹⁸⁶W. The tungsten isotope ¹⁸⁴W has the greatest frequency. All 5 natural isotopes were considered stable for a long time. It was not until 2004 that the CRESST experiment at the Laboratori nazionali del Gran Sasso succeeded in proving that the isotope was a secondary result of the search for dark matter ¹⁸⁰W is subject to alpha decay. The half-life is an extremely long 1,8 trillion years, so this decay cannot be detected in a normal laboratory environment. The radioactivity of this natural isotope is so low that it can be ignored for all practical purposes. In contrast, the artificial radioactive isotopes of tungsten have short half-lives between 0,9 ms ¹⁸⁵W and 121,2 days at ¹⁸¹W.

 

Usage

The most important application of tungsten is because of its high melting point in the lighting industry as a filament in incandescent lamps and as an electrode in gas discharge lamps and in electron tubes.

In light bulbs, use is made of the fact that the electrical conductivity of tungsten is significantly lower than that of the conductive metals copper and aluminum. As a result, the thin tungsten filament heats up until it glows, while the thicker leads made of the conductive metals hardly get warm.

Its second major importance as an alloying metal in iron metallurgy. It forms tungsten carbides in tool steels which increase the secondary hardness.

Due to its high density, it is used for balance weights and to shield radiation. Although its density, and thus the shielding effect, is much higher than that of lead, it is less commonly used as lead for this purpose because it is more expensive and harder to process. Also, because of the high density of tungsten in some armies, armor piercing ammunition is used with a tungsten carbide projectile core instead of the cheaper but radioactive and toxic depleted uranium. In the Second World War Wolfram was important for the construction of the German tank grenade 40, which had a tungsten core. In the future, ammunition with tungsten core from the new armored infantry vehicle Puma will be used to replace the marten.

Because of its high corrosion resistance, tungsten can also be used as a material for equipment in chemical plants. However, because of the poor machinability of tungsten (tungsten can only be welded by laser or electron beam), this embodiment is rarely used. The same applies to a conceivable application in the field of medical technology.

In physiology, especially neurophysiology, tungsten microelectrodes are used for extracellular recordings.

In addition, electrodes for welding processes are manufactured from tungsten. For example, in resistance welding, especially when welding materials such as copper, bronze or brass. Also in universal TIG (Tungsten Inert Gas) welding, an electrode is made of tungsten or an alloy thereof. These electrodes are not melted down during the welding process. The arc burns as plasma in a protective gas between the electrode and the component. The filler material is supplied separately in the form of rods.

In sports Wolfram is used for the production of high-quality barrels for the darts, in archery tips for special arrows are made of it, and the hammer throw hammerheads were temporarily made to reduce the air resistance and the radius of rotation also made of tungsten. In addition, tungsten plates are used as additional weights in the formula 1 to achieve the prescribed minimum weight of 1 Formula cars (including oil, brake and coolant, as well as drivers in racing overalls and with a helmet) of 620 kg (as of: 2010). Also in sailing it comes for some time in the keel bombs of large racers used. The water resistance is greatly reduced by the greater density compared to conventional materials such as lead or cast iron. Similarly, there are already thugs in tennis, in whose carbon fiber frame tungsten fibers were incorporated. In this way specific areas of the racket frame can be additionally stabilized to increase the game precision.

In fly fishing, nymphs and streamers (bait fished under water) are weighted down with tungsten beads that are pierced and pushed onto the shank of the hook, so that they dive faster and deeper.

Strings for musical instruments are sometimes wound with tungsten in order to increase their weight and thereby reduce the pitch.

Tungsten is also used in X-ray diagnostics as a target material in the anode. The - and Lines of characteristic X-ray radiation are 59 keV and 67 keV.

In scanning tunneling microscopy, tungsten is often used as the material for the probe tip.

Since the beginning of the 21. Tungsten carbide, falsely referred to as tungsten, is also used in jewelery (Tungsten jewelery), e.g. B. rings processed. This is very easily determined by the hardness and density. WC has the Mohs hardness 9,5, tungsten only 7,5. So far, all jewelry parts on the market made of tungsten carbide.

 

physiology 

Tungsten is considered a positive bioelement of anaerobic bacteria of the type Eubacterium acidaminophilum used and incorporated as a cofactor in some enzymes. E. acidaminophilum is an amino acid fermenting bacterium which uses tungsten in the enzymes formate dehydrogenase and aldehyde dehydrogenase. In these organisms, tungsten replaces molybdenum because it is much more common in their natural environment (volcanic vents on the sea floor).

 

toxicology 

According to current knowledge, tungsten and its compounds are physiologically harmless. Lung cancers in workers in cemented carbide producing or processing plants are attributed to the cobalt that is also present.

In the animal model it was found that the largest amount of orally ingested tungsten compounds is quickly excreted in the urine. A small part of the tungsten goes into the blood plasma and from there into the erythrocytes. It is then deposited in the kidneys and in the bone system. Three months after administration, most of the very small amounts of tungsten absorbed by the body are found in the bones.

2003 has been identified with 16 in 1997 with XNUMX in children suffering from leukemia and with nine children also with blood cancer in Sierra Vista / Arizona, two so-called cancer clusters - a local area with an above-average rate of cancer. In both places, the drinking water has unusually high concentrations of tungsten. Significantly increased tungsten concentrations were detected in the urine of the population. Both places are known for their occurrence of tungsten ores. However, no direct association between tungsten and leukemia diseases was found in the subsequent one-year investigations by the Center for Disease Control (CDC). Tungsten did not show any carcinogenic effects in any test procedure, and no other cancer clusters were found in other parts of Nevada with similar high levels of tungsten in the urine of the population.

 

safety instructions 

As a powder or dust, it is easily flammable, non-flammable in a compact form.

 

Connections 

Oxide 

Tungsten forms several oxides. Between the initial member:

• Tungsten (VI) oxide WO₃ - lemon yellow

and the final member:

• Tungsten (IV) oxide WO₂ - brown

Are there any other intermediate oxides?

• W₁₀O₂₉ blue-violet, homogeneity range WO_2,92-WHERE_2,88
• W₄O₁₁ red-violet, homogeneity range WO_2,76-WHERE_2,73
• W₁₈O₄₉, WHERE_2,72
• W₂₀O₅₀, WHERE_2,50

Other compounds

• Sodium Tungstate Na₂WO₄
• Zirconium tungstate ZrW₂O₈ shows an anomaly when heated.
• Tungsten bronzes M_xWO₃; M = alkali metal, alkaline earth metal, lanthanoid, approx. 0.3 <x <0.9 have electrical conductivity and are intense and differently colored depending on the metal content.
• Calcium tungstate CaWO₄ is known as a mineral under the name Scheelite.
• Tungsten Carbide WC is an extremely hard metal-like compound. There is also Diwungsten Carbide W₂C.
• Tungsten hexafluoride WF₆
• Lead tungstate PbWO₄
• Tungsten disulfide WS₂ Use as dry lubricant (Similar to MoS₂)

Use of the compounds

Tungsten carbide is used as a neutron reflector in nuclear weapons to reduce the critical mass. Tungsten carbides (hard metal) are used in material processing due to their high hardness.

Tungstates are used to impregnate fabrics to make them flame-retardant.

Tungsten colors are used in painting as well as in the ceramics and porcelain industry.

Lead tungstate is used as a modern scintillator in particle physics.

General
Name, symbol, atomic number	Tungsten, W, 74
Series	Transition metals
Group, period, block	6, 6, d
Appearance	greyish white, shiny
CAS number	7440-33-7
Mass fraction of the earth shell	64 ppm
Atomic
atomic mass	183,84 u
Atomic radius (calculated)	135 (193) pm
Covalent radius	162 pm
electron configuration	[Xe] 4f145d46s2
1. ionization	770 kJ / mol
2. ionization	1700 kJ / mol
Physically
Physical state	fixed
crystal structure	cubic body-centered
density	19,3 g / cm3 (20 ° C)
Mohs hardness	7,5
magnetism	paramagnetic ( = 7,8 10−5)
melting point	3695 K (3422 ° C)
boiling point	5828 K (5555 ° C)
Molar volume	9,47 · 10−6 m3/ mol
Heat of vaporization	824 kJ / mol
heat of fusion	35,4 kJ / mol
speed of sound	5174 m / s
Specific heat capacity	138 J / (kg · K)
Electric conductivity	18,52 · 106 A / (V · m)
thermal conductivity	170 W / (m K)
Chemical
oxidation states	6, 5, 4, 3, 2
normal potential	−0,119 V (WO2 + 4H+ + 4e- → W + 2H2O)
electronegativity	2,36 (Pauling scale)
isotope
isotope NH t1/2 ZA ZE (MeV) ZP 178W {Syn.} 21,6 d ε 0,091 178Ta 179W {Syn.} 37,05 min ε 1,060 179Ta 180W 0,13% 1,8 · 1018 a α 2,516 176Hf 181W {Syn.} 121,2 d ε 0,188 181Ta 182W 26,3% Sturdy 183W 14,3% Sturdy 184W 30,67 % Sturdy 185W {Syn.} 75,1 d β- 0,433 185Re 186W 28,6% Sturdy 187W {Syn.} 23,72 p.m. β- 1,311 187Re 188W {Syn.} 69,4 d β- 0,349 188Re
NMR properties
Spin γ in rad * T−1· s−1 Er(1H) fL consider W = 4,7 T in MHz 183W 1/2 1,128 · 107 1,07 · 10−5 4,166
safety instructions
GHS hazardous substances labeling powder

Hazard H and P phrases H: 228EUH: no EUH ratesP: 210-​240-​241-​280-​370+378 Gefahrstoffkennzeichnung

Light- flammable

(F)

Powder R- and S-phrases R: 11S: 43

 

Tungsten price

 

Tungsten Prices -> Strategic Metals Prices