What is Tungsten?
Tungsten is an elementary metal which has found many uses in industry and our daily lives over the years. It's typically found in natural ores such as wolframite in mines all over the world. Tungsten is extremely heat resistant, having the highest melting point of all non-alloy metals in the world. This makes it perfect for jobs in high energy or high electricity environments. The filament in incandescent light bulbs are most commonly made from tungsten thanks to their ability to hold shape at such high temperatures. Though about as tough as steel when pure, when combined in a compound such as tungsten carbide, it's nearly indestructible. As a result it's used for drill heads in major mining and oil drilling as well as other high-stress work.

What are Tungsten Rings?
Tungsten rings are a decorative affectation which are becoming more popular with men throughout much of the world. Such rings are taking the place of class rings and wedding bands thanks to their durability. They should not be mistaken for being made from pure tungsten, as they're really tungsten carbide. This compound, once shined, will never dull, scratch, rust, or discolor. It's also completely hypo-allergenic. The reason for their popularity is as much an issue of symbolism as practicality. Gold wedding bands have a tendency to deform over time. One made from tungsten-carbide will not, giving the impression that the marriage union which the ring represents will endure as well.

How are Tungsten Rings Made?
Ground tungsten and carbon are poured into a metal die cube containing a ring mold. The mold is subjected to high pressure to push the powder together into a solid ring blank. The blank is then fired in an oxygen-powered furnace at temperatures exceeding 6,000 degrees Fahrenheit. Only at this obscenely high temperature will the blank's component elements intermingle and solidify as one. Once cooled, any burs or extra metal is removed with high-powered diamond edged saws. Diamond powdered files and sanders are then used to polish the ring until it shines. With this done the ring is ready to be worn. It should be noted that since such rings cannot be re-sized, each one must be constructed to order if it's to be a perfect fit.

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Nanoparticles of tungsten carbide and tungsten carbide cobalt can enter cultured mammalian cells. These are the findings of a study conducted by researchers from the University of Dresden, the Leipzig-based Helmholtz Centre for Environmental Research and the Fraunhofer Institute for Ceramic Technologies and Systems in Dresden.

The results further show that pure tungsten carbide nanoparticles do not have cytotoxic effects. Only when the nanoparticles are mixed with a toxic substance, metallic cobalt in this case, are cytotoxic effects observed. The in vitro study, which was published in the renowned journal Environmental Health Perspectives, examined the effect of tungsten carbide and tungsten carbide cobalt nanoparticles with an aggregate size of 150 nanometres on cell lines of human lung, skin and intestinal cells and of primary cultures of rat brain cells.

Tungsten carbide is used primarily in the heavy metal industry for the manufacture of tools. The addition of cobalt increases its toughness and strength. During the manufacture process workers may be exposured. But until now, no scientific findings on the effects of nano-sized particles of the material have been available. Before nano-grained materials are used on a large scale, the risks to humans and the environment need to be investigated and taken into account.

The chemical and physical studies confirmed that both tungsten carbide and tungsten carbide cobalt particles are stabilised by albumin or serum in nutrient solutions. Adding albumin to the nutrient solutions makes it possible to carry out research in conditions that are very close to those found in exposed organisms. Using electron microscope methods it was possible to detect uptake of the particles by the cells under investigation.

Subsequent biological tests showed that tungsten carbide nanoparticles alone are not acutely toxic, whereas combinations of these particles with cobalt did have toxic effects at high particle concentrations. The toxicity of the WC-Co mixture was higher than that of similar concentrations of cobalt ions. It is not yet entirely clear why the combination of tungsten carbide and cobalt is more toxic. It is possible that nanoparticles act as a Trojan horse, i.e. they increase the cell's uptake of toxic cobalt ions. Further research is needed to clarify the effect of particle size and combination effects in order to draw conclusions about possible consequences for health risk assessments.

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Background
Tungsten-filament bulbs, although the most widely used light source in the world, are inefficient, generating more heat than light. However, a new microscopic tungsten lattice developed at the Department of Energy’s Sandia National Laboratories has been shown to have the potential to redirect much of this wasted heat energy into visible light.

Increased Efficiency
This could raise the efficiency of an incandescent electric light bulb from 5% to greater than 60%. In doing so it would greatly reduce the world’s excess consumption of electrical power by inefficient lighting, and the accompanying environmental impact caused by CO2 emissions.

Fabrication of the New Lattices
The first step toward this goal, achieved at Sandia by Shawn Lin and Jim Fleming, was reported in Nature in May. The tungsten lattice device was built using an extension of well-known microelectro-mechanical systems technologies that themselves have been derived from mature semiconductor technologies. As a result, fabrication of such devices could be cheap and easy.

The tungsten structures, usually made out of silicon, consist of tiny bars fabricated to sit astride each other at regular pre-set distances and angles. Together, these form an artificial crystal. The spacing of the bars allows passage of only certain wavelengths of radiation they pass through but can also change direction as defects in the artificial crystal cause the light to follow the defect.

The Lattice’s Ability to Stop Other Frequencies
A further question considered by Lin and Fleming, with assistance from colleagues at Ames Laboratories in Iowa, was the tungsten lattice’s capability of ‘stopping’ other frequencies. If the crystals were built of tungsten, the metal could handle quite high temperatures and have a large and absolute photonic band gap in the visible range, where it is already known to emit light. But what would happen to the other, lower-wavelength radiation brought in by an electric current? Would the structure melt, or would the thermally excited tungsten atoms somehow prefer to reinforce emissions at higher wavelengths, such as in the visible frequency range?

Energy at the edge of the photonic band was observed to undergo an order-of-magnitude absorption increase energy was being preferentially absorbed into a selected frequency band. Meanwhile, periodic metal-air boundaries led to a large transmission enhancement. Experimental results show that a large photonic band gap for wavelengths from 8 to 20 microns proves ideally suited for suppressing broadband blackbody radiation in the infrared and has the potential to redirect thermal energy into the visible spectrum.

Results and Prospects
Lin and Fleming are delighted with the results, although the theory for the effect - re-partitioning energy between heat and visible light - remains unexplained. ‘It’s not theoretically predicted,’ says Fleming. ‘Possible explanations may involve variations in the speed of light as it propagates through such structures.’

Although the work was carried out with light in the mid-infrared range, no theoretical or practical difficulties are known to exist in downsizing the structure into the visible light range.

from www.azom.com

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The Democratic Republic of Congo (DRC) is a country rich in natural resources, including large deposits of tin, tantalum, and tungsten -- metals used to manufacture many of the electronics found in U.S. homes, such as laptops, cell phones, iPods and digital cameras.

U.S. and international electronics companies purchase significant quantities of these metals from the DRC, despite a ten-year civil war that has cost an estimated 5.4 million lives. Rebel groups perpetuating the country's conflict are funded by profits from mining activities, and by unwitting American consumers who purchase electronics using minerals sourced from mines in eastern DRC.

The Congo Conflict Minerals Act, recently introduced by Senators Sam Brownback (R-KS), Richard Durbin (D-IL) and Russ Feingold (D-WI), would require electronic companies such as Apple, Nokia and Nintendo, to report the exact location of mines in DRC from which they receive tin, tantalum and tungsten. This publicly available information would inform consumers whether the electronics they purchase originate from conflict zones in the DRC.

Passing the Congo Conflict Minerals Act, if accompanied by sufficient publicity, would likely have a significant impact on consumer (and eventually, corporate) behavior. As evident from the effective embargo on blood diamonds from Sierra Leone, many Americans and Europeans are conscientious consumers, sensitive to breaking the link between conflict and natural resources. U.S. and international companies also have reputational concerns. The SEC is a principal source of company information for potential investors.

Under this Act, all SEC-listed companies would be required to fully disclose the amount of money paid to foreign governments for oil, gas, and minerals in their required financial statements. Such transparency would allow companies to build solid reputations based on partnering with governments response to their citizens' needs and concerns. The Act would also mark an important step in ensuring sound revenue management, and fighting the corruption that hinders African countries from translating resource wealth into economic growth.

The pressing reality in eastern DRC, where on Monday Hillary Clinton met victims of one of the world's worst conflicts, underlines the urgency for precedent-setting U.S. action requiring companies to report on their financial flows into war-torn regions.

Despite a nine-year presence by the world's largest United Nations peacekeeping operation -- 18,422 personnel at an annual cost of $1.2 billion -- rebel forces in DRC continue to terrorize innocent citizens. Over one million women and children have become victims of sexual assault and rape in eastern DRC.

Lack of good governance in eastern DRC has played a significant role in allowing these atrocities to occur. Based on research by the World Resources Institute and our local partner organizations in Africa, we believe the Congo Conflict Minerals Act and the Extractive Industries Transparency Disclosure Act would provide a powerful platform for U.S. development assistance to work with governments to ensure revenues from natural resources contribute to economic growth and poverty reduction.

Ending the conflict in DRC is a long-standing and high-priority U.S. policy objective. In October 2006, then-President George Bush argued that the conflict constituted "an unusual and extraordinary threat" to our foreign policy. President Obama's administration has made its concern equally clear, hence the secretary of state's visit.

Strong Congressional support is needed now to prioritize and pass both the Congo Conflict Minerals Act and the Extractive Industries Transparency Disclosure Act. While iPods and cell phones are integral in our daily lives, our convenience should not be bought at great detriment to others.

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The sport of darts remains an incredibly popular game, very easy to play when out or at home. For the uninitiated, however, there are lots of options when it comes to selecting the right kind of equipment. Darts themselves are made with a variety of materials, weights and tips, each with their own advantages and disadvantages

Weight of the dart's barrel
In order to fly effectively, darts need a certain amount of weight behind them. The main part of the dart, the barrel, is usually made with metal alloy. Steel and tungsten are both used, as are brass and silver/nickel alloys. The advantage of tungsten over all other types is its density, meaning the dart can be quite weighty while still being slim. This is useful if you throw your darts in close groupings to one another on the board. Fatter shafts will tend to bounce off of other darts and may miss their intended target or even bounce off the board.

The tip of the dart
When it comes to selecting a tip for your darts, the board you play on is the critical factor. The tip of the dart is either made from steel or a soft tip. The steel is weighty enough to stay in the bed of the traditional bristle dartboard. Soft tips are essential for use on the electronic dartboards.

Costs
The cost of your darts may influence your choice. Brass and steel barrels tend to be cheaper, so if you are buying a set for the first time to see whether you enjoy the game, you might wish to try these before committing to the more expensive tungsten darts, which can sometimes be 2-3 times as expensive.

What professionals use
Although the original question asked whether steel darts were better than tungsten, the answer is probably that a combination is best. Professional darts players will typically use tungsten barrels and steel tips.

Personal preference
No matter what the professionals do, however, nothing is more important than how comfortable you are throwing the darts when choosing them. Go to a shop which stocks a variety and they will usually allow you to try them. Experiment with differently weighted darts, different alloys and pick a set which feel right in your hand.

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Protect and enhance the durability of your dart flights using flight protectors. Darts is a game of skill and is played by men and women of all ages. For serious players, a flight protector can help eliminate damage with a regular dart use as well as strengthening your flight so that is able to be used over and over again.

Instructions

1
Purchase flight protectors. Flight protectors can be purchased for a small price from retailers such as sporting good stores and online specialty stores. Typically, for a few dollars you can get several flight protectors in a package.

2
Attach the flight protector to the dart. Flight protectors are small clips that are usually made out of plastic or metal. Clip the flight protectors onto the dart by placing them on the top of each flight making sure to cover all four edges. The flight protectors will fit any shape of flight whether it is a soft tip or steel tip darts.

3
Test out your darts using your flight protectors. The flight protectors may alter the way the darts are thrown since they are also used to help with aerodynamics by keeping the dart flight in good shape. This translates into a more accurate hit when the dart is thrown at the target.

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Introduction
High-speed steels are tool steels that find applications in machine tools that have high rates of material removal. Tungsten high-speed steels (group T) and molybdenum high-speed steels (group M) are two types of high-speed steels. These two groups of high-speed steels have similar hardening abilities and other characteristics.

High-speed tool steels are capable of being hardened to 62 - 67 HRC and their hardness can be maintained at service temperatures up to 540°C (1004°F). This makes them suitable for use in high-speed machinery.

The tungsten series include the T1 to T15 class alloys. Tungsten is a good carbide former that prevents grain growth, enhances toughness and increases red hardness and high temperature strength. Tungsten is used in hot forming tool steels and high-speed steels.

Overview
White and Taylor developed the type T1 series of tungsten high-speed steels. In the early 1900s, they discovered that certain steels exhibited red hardness and such steels comprised more than 14% W, about 0.3% V and about 4% Cr. T1 in its earliest form contained about 18% W, 0.68% C, 0.3% V and 4% Cr. An increase in the quantity of vanadium was seen by 1920. The carbon content of most steels also increased to approximately 0.75% over the years.

The most significant alloying elements found in tungsten high-speed steels include carbon, tungsten, cobalt, chromium and vanadium. Tungsten high-speed steels contain 4% chromium. T4 and T15 are the cobalt-base tungsten varieties that contain different amounts of cobalt. The T1 type of tungsten high-speed steels is free of cobalt or molybdenum.

Classification
The American Iron and Steel Institute (AISI) has classified high-speed tool steels into about 40 individual categories. This classification system uses a T for referring to steels in which tungsten the primary alloying element. The letter T is followed by a number which distinguishes each of the tungsten tool steels ranging between T1 and T15.

Hardness
Tungsten high-speed steels have good wear resistance and high red hardness. The maximum hardness of group T steels differs according to the carbon content and also the alloy content. A minimum hardness of 64.5 HRC can be imparted to all types of high-speed steels. Types such as T15 can be hardened to 67 HRC as they have high carbide and carbon content (1.55%). Hence T15 is considered as the most wear-resistant steel of the tungsten high-speed steel series. Tungsten high-speed steels comprising more than 1.0% C and 1.5% V produce a high number of wear-resistant hard carbides in the microstructure due to the presence of high carbon and alloy content. Tungsten high-speed steels are deep hardening when they are quenched from their hardening temperature of 1205 to 1300°C (2200 to 2375°F). Solid tools such as cold extrusion punches and broaches with large diameters are made from tungsten high-speed steels. Full hardness is provided for tools with large diameters using an accelerated oil quench.

Applications
The major applications of tungsten high-speed steels are the following:

•Interrupted-cut applications and delicate tools
•Cutting tools including hobs, milling cutters, bits, reamers, drills, broaches and taps
•Production of dies and punches
•Making high-temperature and high load structural components, e.g., pump parts and aircraft bearings.

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When you buy an incandescent light bulb, you never know how long it will burn. Its service life is limited mainly by microscopic cracks in the tungsten filament. A simulation model for materials reveals crack formation before and after the drawing process.

Ideally, light bulbs last for 42 days in continuous operation – or so the manufacturers would have us believe. But the reality is not quite so lustrous: Some light bulbs do not burn out for years, but others last only a few days. Fine cracks in the tungsten filament, which eventually cause it to break, preclude a more uniform product quality. This is a problem also faced by Osram and Philips, the world’s biggest light bulb manufacturers. The industry has so far relied on trial and error to improve the drawing process for the filament. Production processes can be enhanced more strategically by simulating the material behavior. Supported by researchers from the Fraunhofer Institute for Mechanics of Materials IWM, the manufacturers are investigating the cracks and the resultant difficulties when spiraling the wire. Osram project manager Bernd Eberhard is confident that “Once we have more insight into the composition and behavior of the filament, we will be able to optimize and standardize our production processes.”

With an average diameter of 40 micrometers depending on the type of lamp, the tungsten filament is only about half as thick as a human hair. To reach this diameter, the wire has to be pulled repeatedly through a wire-drawing die that stretches it lengthwise and makes it progressively thinner. Depending how often the process is repeated, it may acquire a varying number of longitudinal cracks. Splits of this kind form primarily during the first stages of the drawing process, when the wire is thinned from almost four millimeters to only 0.3. The fine cracks grow longer when the wire is stretched further to a diameter of as little as five micrometers. This fact can be attributed to the tension that remains in the wire after drawing out, as IWM project manager Holger Brehm and his predecessor Sabine Weygand have discovered. “We have already succeeded in mathematically describing the behavior of the wire and the cracks that form during and after the drawing-out process. For the first time ever, the tungsten filament can be monitored on the screen during the entire thinning-out process.”

Crack formation is being further investigated and other decisive factors are integrated in the model. One such factor is the friction between the wire and the wire-drawing die. High friction makes the metal hotter. The researchers are therefore currently integrating the temperature change during and after drawing into their simulation. “The drawn wire cools faster on its surface than on the inside,” Brehm summarizes the latest experimental findings. “Unfortunately, splits can occur during this process as well.”

source from www.azom.com

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Introduction
Hot work tool steels are steels capable of withstanding high abrasion, heat and pressure conditions that prevail in manufacturing units that perform processes such as forming, shearing and punching of metals at high temperatures of 480 to 760°C (900 to 1400°F). These steels have wear resistance up to 540°C (1000°F).

Hot work tool steels are designated as group H steels and they have 0.35% to 0.45% carbon, 6% to 25% chromium, with vanadium, molybdenum, and tungsten as the other alloying elements. Tungsten is primarily used in hot forming tool steels due to its high temperature strength, toughness and resistance to grain growth.

Overview
Tungsten hot-work steels constitute the H21 to H26 types of hot work steels. These steels have similar characteristics as those of other of high-speed steels. The hot work steel type H26 has low carbon content when compared to that of T1 high speed steel. The primary alloying elements of tungsten hot-work steels include tungsten, carbon, chromium and vanadium.

Properties
Tungsten hot work steels have high alloy content, which enhances their heat resistance. The high alloy content also makes the tungsten steels brittle and unsuitable for the water-cooling process. Breakage of tungsten hot work steels can be reduced if they are preheated to operating temperatures prior to use. Tungsten steels have normal working hardness of 45 to 55 HRC. Thermal shock resistance and toughness of these steels can be improved by reducing the carbon content. In such cases, it is necessary to adjust the tungsten and vanadium content also as these two reduce the hardenability of steel by trapping large amount of carbon in the form of carbides.

Scaling can be reduced by quenching tungsten hot-work steels in oil or hot salt. Tungsten hot-work steels are resistant to distortion when they are air- hardened, and have higher hardening temperature when compared to chromium hot-work steels.

Applications
Tungsten hot work steels find applications in the following areas:

•Manufacturing mandrels and extrusion dies for high temperature applications, such as extrusion of brass, nickel alloys, and steel
•Hot-forging dies of rugged design.

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Background
Silver/Tungsten alloys containing between 25 and 50% silver are used for electrical contacts. These materials are produced via powder metallurgical techniques due to their widely different melting points.

Tungsten oxides and tungstates form on the surface of these metals. This can lead to increasing contact resistance over time.

If more arc resistance is required then these materials can withstand or if contact resistance becomes a problem, silver/tungsten carbide materials offer an alternative.
 
Key Properties
Silver/Tungsten metals combine the high thermal and electrical conductivities of silver with the arc resistance of tungsten.
 
Applications
As mentioned above, silver/tungsten materials are used for electrical contacts. Typically they are used in heavy duty devices subject to high currents. The presence of the refractory material tungsten, reduces the chances of welding and improves resistance to arc erosion. Optimal compositions are found by balancing conductivity and non-welding properties.

Devices that utilise silver/tungsten materials include:

•         Circuit breakers (often in the 50-100Amp range)

•         Relays that require good arc resistance
 

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