This deals with the extraction of tungsten from tungsten(VI) oxide, WO3, produced from tungsten ores such as wolframite or scheelite.

Introduction

The production of the tungsten(VI) oxide from the ores is complicated, and not needed for any UK A level (or equivalent) syllabus. All we are interested in is the final reduction of the oxide to the metal.

Pure tungsten can't be obtained by reducing tungsten(VI) oxide using carbon, because it reacts with carbon to make tungsten carbide. Instead, the reducing agent is hydrogen.

The extraction process

Powdered tungsten(VI) oxide is heated to temperatures in the range 550 - 850°C in a stream of hydrogen.

An excess of hydrogen is used, and this carries away the steam produced during the reaction. The hydrogen is dried and recycled.

Great care obviously has to be taken to keep the whole system free of air to avoid explosion risks with the hydrogen at these high temperatures.

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Overall Industry Structure:  The tungsten industry may be considered to comprise three principal divisions:

    Primary Tungsten Producers – the mines which mine and carry out primary mineral processing to produce tungsten mineral concentrates

    Secondary Tungsten Processors – the processing plants which take the mineral concentrates and process them into a number of tungsten powders, including ammonium paratungstate (APT), suitable for use in downstream metal/alloy manufacturing.  These powders are often referred to as “intermediates”

    Tertiary Tungsten Product Manufacturers – the plants which produce finished tungsten metal, tungsten alloys, tungsten tools and other tungsten end products.

Traditionally there has been some degree of vertical integration within the industry, with some common ownership of secondary processing and tertiary manufacturing facilities, but this integration rarely extended upstream to the primary producers, the miners. However, the expansion of the Chinese economy and the demand for tungsten has, apparently, resulted in considerable vertical integration in the tungsten industry in China, whether through common ownership or contractual arrangements, with a move away from exports of concentrates and into downstream processing and manufacturing. This pressure towards vertical integration within China and an apparent desire to secure long term concentrate supply, has resulted in various large Chinese companies investing in Western tungsten projects. This activity in China has started to affect the industry outside China, with a number of strategic mergers, acquisitions and investment within the Western tungsten industry over the last two years.

Tungsten Products:  The usages of tungsten result in an industry structured to produce various categories of products:

    Approximately 50% of tungsten is used in the production of hardmetals, or cemented carbides; these are cutting, drilling and wear materials formed from tungsten carbides and cobalt, and occasionally other minor metals such as titanium, tantalum and niobium

    Some 17% of tungsten is used to produce specialist steel alloys, such as high speed steel, heat resistant steel and tool steels, all largely utilised in metal cutting applications and specialist engineering applications

    In the region of 15% of tungsten would be used to make “mill products”; the mill products would comprise tungsten rod, sheet and wire, electrical contacts, etc…

    The balancing 18% of tungsten is used by the chemical industry and in other specialist applications.

World Tungsten Metal Production:  The total yearly tonnage of mine tungsten metal production is very small relative to base metals, the more recent estimates being:

    83,000t  of primary tungsten metal (W) production – equivalent to 105,000t of tungsten trioxide, WO3 (79.3% W)

The breakdown of this production would be circa:

    70,000t/ year W from Chinese mines  -  of the order of 84% of World production

    7,000t /year W from Western orientated economies  -  circa 9%

    6,000t/year W from other communist or CIS countries  -  circa 7%

Tungsten Pricing:  Prices for tungsten concentrates produced by mines and the intermediate tungsten powers produced by the secondary processors are quoted in metric tonne units (mtu). An mtu consists of 10kg of WO3, as contained within the particular material in question, concentrates or APT (this relationship conveniently results in the fact that a 1% resource grade equates to 1 mtu). The two materials for which prices are quoted widely and reported in mtu of WO3 are:

    tungsten trioxide, WO3, (containing 79.3% tungsten metal), as the critical constituent in the minerals in mine concentrates

    ammonium paratungstate, APT, the main secondary downstream product made from concentrates.

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Tungsten Metal (W):  From a mining and metal industry perspective, tungsten falls into a loose grouping of around 20 metals termed the minor metals (the other metal groupings being; the precious metals, the base metals and the platinum group metals (PGMs)).  Tungsten is unique in having a combination of relatively extreme properties compared to other metals; its properties include:

    a very high melting point, 3422°C (5700°C, boiling)  -  highest melting point of all metals

    a very dense, heavy metal, 19.25 g/cm2

    an extremely strong, wear resistant metal; has a hardness close to that of diamonds - highest modulus of elasticity and highest tensile strength of all metals

    a thermally and chemically stable metal, with high thermal conductivity - lowest coefficient of expansion of the metals

    a high electrical conductivity

    a relatively inert metal which does not oxidise readily, is extremely corrosive resistant and relatively acid resistant and is deemed environmentally benign.

Tungsten Uses:  As a consequence of tungsten metal’s properties, tungsten alloys are used in various application areas:

    Tungsten, due to its hardness and ability to withstand heat, is very suitable as a critical component of cutting tools used to drill or cut other metals, concrete or rock (e.g. household drill bits, metal fabrication tools, dentists tools, etc..)

    These attributes also make tungsten alloys suitable for critical temperature sensitive and wear resistant machinery components (e.g. engine valves, ball-point pen tips, turbine blades, snow tyre studs)

    These wear and temperature resistant properties, in combination with tungsten’s electrical conductivity, also make tungsten ideal as a critical temperature resistant component in electronics and as a contact point in electrical circuits (e.g. LCD panels, TV tubes, laser printers, window heating wires, car horns, electrical switch gear)

    Tungsten’s high density properties also make it suitable as a weight or counterbalance in specific machinery applications (airplane flaps, mobile phone vibration systems, crankcase balancing weights, golf clubs and as an environmentally acceptable substitute for lead shot in cartridges).

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Tungsten Minerals: The only two tungsten minerals of any importance are two tungstates or oxides, their relative values being determined by the measure used to determine mine ore grades and mine concentrate grades, i.e. the tungsten trioxide or WO3, content:

Scheelite, a calcium tungsten oxide, CaWO4  -  contains 80.5% WO3

Wolframite, an iron-manganese tungsten oxide, (Fe, Mn)WO4  -  the iron rich variety, called Ferberite, contains 76.3% WO3; the manganese rich variety is termed Hubnerite and contains 76.6% WO3

Tungsten Deposits: Tungsten principally occurs in four main geological settings, as:

    Skarn deposits - where granites are intruded into limestones

    Vein deposits - in quartz veins adjacent to granites, as a series of larger separate veins

    Sheeted vein deposits - as multiple, narrow, closely spaced, quartz veins forming large sheeted vein systems within and adjacent to granites

    Pegmatites - very coarse segregations/concentrations of specific minerals at the margins of granites

Metals and Minerals Associated with Tungsten: Tungsten mineralisation is frequently associated with minor quantities of sulphides, usually iron sulphides, but occasionally with economic quantities of copper sulphides; it may also have specific associations with other potentially economic minerals:

    Tungsten and tin in vein and sheeted vein deposits

    Tungsten and gold in sheeted vein deposits

    Tungsten and magnetite in skarn deposits

    Tungsten and molybdenum in skarn deposits

    Tungsten and lithium, tantalum, niobium and tin in pegmatite deposits

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Tungsten is a metal with unique properties making it an essential component in many industrial applications. Critical properties include - very high melting point, very high density, hardness close to diamond, thermally and chemically stable, excellent conductor, and environmentally benign.

The most important use is as tungsten carbide in hardmetals, used mainly for industrial drilling and cutting tools. Secondary uses are in electronics and specialist steels.

China accounts for over 85% of world tungsten mine production; western world supply is very limited.

USA, Europe and Japan consume ~55% of world tungsten, but produce only ~5%.

Chinese domestic demand has increased, and China has moved from a net exporter to net importer of tungsten concentrates. This increase in Chinese demand, combined with increased controls by the Chinese Government on their domestic tungsten industry and tungsten exports.

Concerns over security of supply of tungsten concentrates to western processors and industry end-users. This along with other factors have resulted in the EU categorising tungsten as a "critical raw material".

Chinese domestic consumption of tungsten is forecasted to grow by 5-8% annually between 2012 and 2016.

Growth markets for tungsten are still being identified, such as nickel-tungsten alloys that could replace chrome plating and nickel-tungsten alloys that could replace gold-nickel plating.

Tungsten, with essential applications in industry, aerospace and military, is a strategic commodity.  Stockpiles exist in the US and Russia. China and Japan have also indicated that they intend to build stockpiles and there has been some discussion of the possible creation of a European stockpile.

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Mott Corp says that its porous metal components and filters are available in a range of refractory metal alloys including zirconium, titanium, tungsten, molybdenum, and niobium.

Mott Corp can design porous components or entire filter assemblies using refractory metals to meet various flow control or filtration requirements, to meet tolerances and to a sub-micron particulate removal. 

Porous components in refractory metals have melting points from 2400°C to over 3400°C and thus can meet demanding filtration or flow control requirements. They are also refractory metals are electrically conductive and chemically inert and can be a suitable material of construction for many where higher operating temperatures are critical.

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You may have heard that a tungsten carbide ring is unbreakable. This would have some good and bad effects. Having a wedding ring that would never bend, crack, scratch, or get marred would be a benefit.

Tungsten carbide rings are not indestructible. In case of emergency, you can remove them with relative ease. Just don't drop your wedding band on a hard surface - any Tungsten Carbide wedding ring (no matter who makes it) is brittle. It will crack, chip or even shatter upon impact with a hard surface or object. It is also not a metal or even solid, as Wikipedia confirms.

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You may know a few things about tungsten bands. Undoubtedly, you have heard that tungsten carbide rings have become the metal of choice for grooms throughout the nation. One of the main reasons this is so is due to its toughness. They resist scratching much better than any other metal out there. Few substances can scratch it. Diamonds are one of them. What some may find odd or shocking is that tungsten rings are not indestructible. Tungsten carbide rings can break! If a tungsten ring is dropped on a hard surface, it can break or crack.

Mens Tungsten Wedding Bands

JustMensRings.com has launched its annual Valentine’s Day Sale, featuring newly discounted prices and free shipping on over 600 styles of designer men’s rings, wedding bands and jewelry for men. With a variety of romantic gift options suitable for relationships at any stage, men’s love and sweetheart rings are already proving to be particularly popular with customers.

Jensen Beach, FL (PRWEB) January 08, 2013
Shoppers looking to save on the perfect Valentine’s Day gift are in luck: JustMensRings.com (JMR) has just commenced its annual Valentine’s Day Sale. With hundreds of deeply discounted styles now on offer, there is truly something for everyone: men’s wedding bands for the recently engaged, anniversary rings for husbands, men’s love and sweetheart rings for long-term couples and jewelry for men for newer romances.

Valentine’s Day is little more than a month away, and savvy shoppers are already stocking up on their favorite designs to avoid any last minute rush in February. Everyday low pricing is nothing new at JMR, but the Valentine’s Day Sale has further reduced pricing on over 600 styles of designer men’s rings, wedding bands and jewelry, for price tags that are well below wholesale. For the first time ever on the JustMensRings site, all sale items also enjoy free shipping across the United States.

One of the most popular items in the Valentine’s Sale section has proven to be men’s love and sweetheart rings. Often engraved with romantic words or phrases like “forever love,” “only love you” or “my one and only,” these decidedly romantic bands make for great pre-engagement rings and promise rings. Claddagh rings, a form of Celtic jewelry that feature an instantly recognizable motif of two hands clasping a crowned heart, are also a sought after sweetheart ring for new and old romances alike.

Of course, men’s wedding rings are also one of the primary picks for customers shopping the JMR Valentine’s Day Sale. For couples who became engaged over the holiday season, Valentine’s Day is often an ideal time for brides to present their husbands-to-be with their wedding bands. JustMensRings carries the U.S.-based designer brand Benchmark exclusively, and there are a significant number of Benchmark styles on sale to choose from, including men’s rings in precious metals like gold, platinum and palladium, diamond rings, and bands in affordable contemporary materials like titanium, tungsten, cobalt chrome, Argentium silver and ceramic (Seranite). For the more budget-conscious, there are plenty of affordable men’s rings and jewelry items to choose from as well, with many styles starting under $20.

“While the focus is generally on women on Valentine’s Day, men also love getting romantic gifts,” notes JustMensRings’ president and owner Roy Devine. “JMR’s Valentine’s Sale section is meant to take the guesswork out of finding the perfect Valentine’s gift for him.”

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There are many misconceptions and falsehoods about tungsten rings. Learn the truth about these durable, beautiful bands.

The truth of the matter is that there are a lot of falsehoods about tungsten carbide rings. Since they're newer to the market, many people are unfamiliar with tungsten carbide.

Many jewelers would like to dissuade you from considering a tungsten carbide ring, because they are not educated on them (or just don't sell them!). Here are a few of the myths we hear regularly and the truths about tungsten carbide rings that make them an excellent option.

Myth

Tungsten carbide rings cannot be removed in the event of an accident, and may cause your finger to be amputated.

Fact

Actually, if you're in an accident, a tungsten carbide ring is one of the safest rings to have on your hand! Because tungsten carbide rings are so dense, it is nearly impossible for them to deform or injure your finger in an accident. Wearing a tungsten carbide ring may even protect you. Rings made of silver, gold or even platinum may deform, becoming harder to get off or embedding in flesh. Hospitals have a number of ways to remove a tungsten carbide ring (depending on the accident) – none of which require amputation.

The durability and near-indestructability of tungsten carbide bands is why we say that if Superman were getting married, he'd want a Tungsten Pride wedding band.

Myth

Tungsten carbide rings should not contain nickel.

Fact

In truth, tungsten carbide wedding rings are not made from pure tungsten. Pure tungsten in its natural form is an ore, and does not polish up to the shine that people love about tungsten carbide rings. Makers of tungsten carbide rings need to combine tungsten ore in a powder form with various binders and sinter it all together at very high temperatures in order to achieve the desired result – a beautiful, polished and nearly indestructible tungsten carbide ring.

A nickel binder is the preferred formulation for tungsten carbide rings, as many other binders can cause your ring to discolor with wear. Many inexpensive rings use one of these lesser binders, and aren't pleasant to wear or look at!

Myth

Tungsten rings are only for men.

Fact

This couldn't be further from the truth! The same qualities that make tungsten carbide rings so great for men make them great for women as well. The strength and beauty of tungsten carbide matches well to a woman's own strength and beauty.

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