In addition to tungsten powder particle size by reducing temperature , humidity, hydrogen , hydrogen flow rate , the amount of loading the boat , push the boat speed and other factors , the dopants on the grain size is also affected. In general , doped tungsten oxide , to accelerate the reduction rate , the tungsten particles increases. In the tungsten oxide to tungsten powder by hydrogen reduction process, the reaction product should be doped with hydrogen , with the result that the potassium content of the tungsten powder decreased. Pickling tungsten powder is used in the 1960s began to produce , and its main purpose is to wash away excess tungsten powder dopant , ultrafine powder and some of the harmful impurities that can improve the processing performance , improve high temperature properties of tungsten . Production is generally pre-wash first with hydrochloric acid , and then washed with 5% hydrofluoric acid and then repeatedly washed to neutrality , and by low-temperature vacuum drying stage and two-stage reduction reduction reduction systems are different because the resulting tungsten powder particle size are different, the general particle size of the powder than D B fine powder . In actual production , after pickling , B and D pink powder mix to be reasonable , to ensure the match after producing tungsten powder particle size in the 3-4 m range. This is not only to control the average particle size , particle size optimization of composition, and, more importantly, to adjust the potassium content in the tungsten powder . Studies have shown that potassium tungsten particles mainly in the surface 100 within the tungsten powder with the particle size reduction therefore , surface area increases, the potassium content was increased.

However, if the potassium content of tungsten powder is too high, although the filament temperature performance is good, but the resulting processing performance deterioration . Must therefore be based on high temperature properties of tungsten required to determine the potassium content of the tungsten powder and the measured potassium content and particle size to match. Doped tungsten oxide , potassium powder only by the particle size distribution is adjusted , so the production process with powder a very important aspect . Doped tungsten powder pressing and sintering after pressing and sintering , you can get a dense doped tungsten billet . Is the use of force and the mold pressing the loose powder into a certain geometric shape, size , density and strength blanks . Compaction in many ways, the most common is steel cold forming and isostatic pressing ( see isostatic pressing ) . Since the powder between the former and the die and the powder and there is a large friction between the powder and thus the density compacts unevenly distributed within the parts . The latter compacts density distribution is uniform. Actual production , sometimes in order to reduce friction, reduce the pressing pressure , improving the quality of the green compacts . Kept suppressed to a small amount of tungsten powder forming agent or a lubricant ( such as glycerin and alcohol ) . The size of many compacts are generally square or circular cross-section , length 200-l000mm. The powder during the pressing behavior is very complex , which includes powders displacement, deformation or breaking, while it depends on the behavior of the powder particle shape , particle size , particle size and surface composition , these powders suppression characteristics of the tungsten powder process has a very important impact.


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Because blue tungsten oxide powder particles pores and cracks many large surface area , strong adsorption capacity , permeability , chemical activity is good, and in contact with an aqueous solution of a compound having an ion exchange capacity , so the use of blue tungsten oxide doped than doped tungsten oxide doped with better results. Production of tungsten oxide equipment are rotary tube furnace and two kinds. Doped tungsten oxide is tungsten or tungsten oxide doped blue trace hydroxide, alumina. Since the 1960s , many countries have adopted doping process instead of blue tungsten oxide doped tungsten trioxide , thereby increasing the doping effect . In order to make the dopant can be uniformly distributed in the tungsten oxide , the actual production are not used directly , potassium hydroxide, aluminum oxides such insoluble , but with which the decomposition of soluble salts and easy , usually formulated as a potassium silicate and aluminum nitrate ( or aluminum chloride ) was added. Dopant formulations typically within the following ranges ( based on tungsten ) : potassium : 0.3% -0.45 % ; alumina : 0.02% -0.03 % . Doping methods are wet method and the spray French. Wet method in the pot with a steam jacket for evaporation . First, the evaporation pot adding deionized water, was added under constant stirring yellow blue tungsten or tungsten , into a paste, and with stirring , adding potassium silicate solution side , stirred for a while , then add the aluminum nitrate solution , evaporated to dryness moved after drying oven , and finally mixed and sieved .

Spray method is potassium silicate solution was sprayed into the tungsten oxide fine mist ( 80 to 90C) , and continue stirring until basic evaporated to dryness , then a solution of aluminum nitrate was added to the same manner , the final drying , mixing, sieving . Studies have shown that the addition of silicon in the tungsten oxide , potassium aluminum nitrate solution , is not a simple mechanical mixing , but to partially react and generate a multi- tungsten oxide complex tungstate , which generates the same number of characteristics of the substrate , doped miscellaneous agents of the various components and the doping conditions. Tungsten powder and acid preparation is usually used in industrial production hydrogen reduction of tungsten oxide ( blue tungsten oxide or tungsten oxide ) tungsten powder preparation methods . Reduction process, the system depends on the particle size of tungsten powder , particle size composition and oxygen content , potassium content requirements. Often used in a production stage and two-stage reduction to restore two processes . A phase of tungsten oxide reduction is a direct reduction of tungsten powder (D powder ) . Two-stage reduction in two steps : first in the 550-800C will tungsten trioxide or tungsten dioxide reduction of blue tungsten ; Then make tungsten dioxide at 750-900 ℃ reduced to tungsten powder (B powder ) . Reduction is usually in a tubular furnace or rotary furnace . Practice has proved that the particle size of tungsten powder and tungsten trioxide or tungsten blue size is not a simple relationship , with the reduction of different specifications , either coarse or fine tungsten trioxide or blue tungsten powder, tungsten can get crude fine powder or tungsten powder, tungsten powder particle size depends largely on the particle size of tungsten dioxide .


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Until 1909 , the U.S. General Electric Company Coolidge (wDcoolidge) via powder metallurgy tungsten billet was then produced by machining ductile at room temperature with a tungsten filament , thereby laying the foundation tungsten processing industry , also laid the foundation powder metallurgy . However, this " ductility " tungsten filament in the light bulb lit showed significant brittleness. In 1913, Ping Qi (Pintseh) invented the thorium tungsten wire ( thorium oxide content of 1 % to 2% ) , so that the incandescent filament fragility greatly reduced. Initially, the filament sag ( see tungsten Hang sagging performance ) is not a problem , because the filament is straight wire , but after 1913 , Langmuir (Langmuir) will be replaced by straight wire spiral wire , so that when the light bulb when used , the high operating temperature and weight of the role of the filament sag, thus pure tungsten and tungsten are difficult to meet community requirements . In order to solve tungsten droop and short life and other issues, in 1917 , Perth (A.Pacz) invented the high temperatures , " no deformation " of the tungsten filament . At first, he used when in the preparation of pure tungsten Woe roasting fire tower tungsten trioxide , stumbled with this reduction of tungsten trioxide proceeds made ​​from tungsten powder tungsten spiral , after recrystallization exception mysteriously no longer droop.

Then, after 218 repeated experiments , he finally found that adding potassium tungstate and sodium silicate , after reduction , pressing, sintering and processing the obtained tungsten wire , a fairly coarse recrystallized grain structure neither soft and anti- sagging, this is the earliest non- sag tungsten wire . Perth discoveries laid the basis for the production of non- sag tungsten , until now, the United States does not sag tungsten wire is still called " 218 tungsten wire " to commemorate this major discovery in Perth . However, the first production does not sag tungsten filament brittle than male serious that some insist on using Vitex tungsten bulb factory for the filament. But with no sag tungsten production process of continuous development and improvement , people gradually realized by simultaneously adding the potassium tungsten oxide , silicon, aluminum compounds , can make the tungsten filament at high temperatures with a good anti- sag performance, but by then after crystallization has satisfactory ductility at room temperature . This is now commonly known as "AKS tungsten wire ," or " does not sag tungsten wire " or " doped tungsten wire ." It has many excellent properties , and become the electric light and electronic industries as an important base material . A brief history of the development of tungsten industry from the outset with the light bulb industry closely linked . In 1878 , Edison (TA Edison) invented the carbon filament light bulbs. But this lamp there is a serious disadvantage , primarily life is too short .


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Carolina (T.Millner) in 1931 will this improvement does not sag effect is known as "GK effect ." Then mixed tungsten -doped tungsten production process lengthy production processes , including tungsten smelting, processing of powder metallurgy and plastic preform several major phases . Preparation of tungsten billet billet production of tungsten used usually prepared by powder metallurgy , which includes the preparation of tungsten oxide , doped tungsten powder preparation , pickling, and pressure- sintering process . Preparation of tungsten oxide doped tungsten production is usually chosen by Jones Lang tungstate (APT) as raw materials . Preparation paratungstic from tungsten acid Holderness addition to traditional classical technique , but in the 1950s the international community to carry out extraction and ion exchange method of research, China in the 1970s also used these processes , thereby simplifying the process, improved recovery of tungsten . Industrial preparation of tungsten oxide in two ways :

(1) At a temperature of 500 to 800 ℃ calcined paratungstic acid obtained by the yellow tungsten trioxide ;

( 2 ) Temperature at 400 to 600C in a reducing gas atmosphere at reduced paratungstic acid blue tungsten oxide .

Blue tungsten oxide there is no fixed formula and uniform chemical composition , the main phases money tungsten bronze (ATB) and tungsten oxide . Followed tungsten trioxide , in a reducing atmosphere at a higher temperature will appear in the carbon filament yarn and buttons are spades replaced wire , but thallium low melting point, and thus the operating temperature and luminous efficiency is low . 1903 , according to Jay zafirlukast (A.Just) and Hannah door (F.Hannaman) patents, Hungary for the first time to create a tungsten filament. It is the carbon filament of hydrogen containing tungsten oxyhalide steam heated to high temperatures by the current , the carbon was completely replaced tungsten . Incandescent filament thus obtained contain more or less of carbon , not brittle quite serious , and in the use of the lamp , the filament continued densification , and thus the electrical parameters of the filament will change . In 1904, Jay zafirlukast and Hanna door recognizes the impact of carbon on the brittleness , using carbon- tungsten compound is mixed with a binder , and then extruded into filaments , and then heated in hydrogen reduced to metal . This method is very brittle tungsten obtained , but because of its much better light efficiency , or replacing the carbon filament , hungry for the production of filaments and filament lamps bear . These methods are not prepared thin tungsten wire. To solve this problem , in 1907 , a low nickel content of the tungsten alloy available, it is prepared by machining , but serious brittleness hindered its application .


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Detecting a high-quality fake tungsten gold bar would be extremely difficult. It would likely require significant and material alterations to the bar being tested and this would negatively affect the marketability if its hallmark veracity were vindicated.

This is likely a reason why page Page 11 of the GLD prospectus states “Neither the Trustee nor the Custodian independently confirms the fineness of the gold allocated to the Trust in connection with the creation of a Basket.”

Nevertheless, the truly determined and experienced can ferret out whether there is tungsten contained in their gold bars. In fact, some already have found tungsten in bars which purport to be gold and this is how.

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In theory, as its density is 19.1g/cm3, which is approximately 70% denser than lead, uranium could be used as material of making fake coin. However, it is weakly radioactive and not as dense as gold, so it does not appear to be a practical method. Then people have discovered that tungsten is environmental-friendly, durable and hardness, the most important is that its density of 19.25g/cm3 is just about the same density as gold (19.3g/cm3), which bears the similar specific gravity. These advantages make tungsten enjoys the superiority to be the best substitute for the costly metal of gold or platinum. It is necessary to tell that alloying gold with tungsten would not work for several reasons but a coin with a tungsten center and gold all around it could not be detected as counterfeit by density measurement alone.

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Tungsten heavy metal boring bars are manufactured in sintered or polished alloys of 90%-95% tungsten with a nickel-copper-iron-moly matrix. These alloys are very similar to tungsten-carbides but the chemical composition is developed differently to reduce embrittlement. The high density (twice as heavy as steel) and tensile strength (110 kpsi) of this alloy makes the ideal combination for chatter free tools and supper chatter free tools. Heavy metal boring bars greatly enhance boring application by absorbing vibration and drastically reduce chatter, enabling to machine deeper bores with greater precision and finish.

Tungsten heavy alloy bucking bars are denser than steel, resulting in a bucking bar of the same weight but half the size. Bucking bars are used in rivet setting to upset the shank of the rivet. Tungsten Heavy Alloy bucking bars reduce the recoil when reflecting the impact back to the rivet shank.

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A bucking bar is used to form the shop head of a rivet. It is held against the shank of a rivet and as the rivet gun bangs on the factory head the bar 'bucks' against the shop head causing the metal to deform. That deformation mushrooms the shank forming the shop head. There are many shapes, sizes, and weights of bucking bars. Many are shaped and sized for special-purpose (generally difficult) situations. Pictured is a typical set of bucking bars.

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The tungsten bucking bars are designed to significantly reduce vibration and provide greater comfort for the operator. These bars are up to twice as heavy as their ductile iron counterparts. Results have shown that using Tungsten bars is far superior to ductile iron and helps to reduce carpel tunnel syndrome. All edges are burr-free and all surfaces are polished to provide superb riveting results.

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SiC is a ceramic material with an outstanding hardness, only surpassed by diamond, cubic boron nitride and boron carbide. The material is highly wear resistant and chemically inert to all alkalies and acids. It is also highly heat resistant. These properties makes Silicon Carbide an outstanding abrasive and ceramic material to be used under extreme operating conditions.
 
• Density: 3.21 g/cm3
• Vickers hardness: 29 GPa
• Coefficient of Thermal expansion: 5·10-6/K
• Thermal conductivity: 50 to 100 W/m K
• Typical temperature resistance: 1500°C in air, 2400°C in inert atmosphere
• Specific heat: 750 J/kg K

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