Tungsten Carbide has only recently been used in the fashioning of jewelry due to its hypoallergenic nature and the fact that due to its extreme hardness it is not apt to lose its luster like other polished metals. In fact, a ring or bracelet made from Tungsten Carbide will never need polishing and it is virtually scratchproof...only another item with a diamond or diamond surface or a special sapphire in it can scratch tungsten jewelry. Carefree Tungsten Carbide is made without the use of any Cobalt additive and not just anyone can make a piece of Tungsten Carbide jewelry. In order to manufacture a perfectly crafted piece of jewelry, it takes skill that only a few companies have mastered. It cannot be made in someoneÕs garage with a lathe and a machinist.

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Tungsten has the highest melting point and boiling point of all the elements, melting at 3,420 degrees C or 6,700 degrees F, and boiling at 5,700 degrees C and 10,300 degrees F. What this means to the average person is that on the surface of the Sun, Tungsten would become liquid, but if you dropped a piece of Tungsten from outer space, it would enter the EarthÕs atmosphere, heat up and glow to red color, and still hit the Earth in a solid piece.

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Pure tungsten, that is, before alloying with any other material, is steel-gray to tin-white and is a very hard element. Tungsten can be cut with a hacksaw when it is very pure (it is brittle and hard to work when impure) and is otherwise worked by forging, drawing, or extruding. This element has the highest melting point (3422 ¡C) (6192 ¡F), lowest vapor pressure and the highest tensile strength at temperatures above 1650 ¡C (3000 ¡F) of all metals. Its corrosion resistance is excellent and any attack by a mineral acid is virtually imperceptible. Tungsten metal forms a protective oxide when exposed to air but can be oxidized at high temperature. When alloyed in small quantities with steel, it greatly increases its hardness.

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Like gold, silver and platinum, Tungsten is an element #74. It is naturally occurring and is one of the main elements responsible for the development of human civilization. Without tungsten, we would not have the incandescent light bulb as the filament inside the bulb is tungsten and has the toughness and resilience exceeding any other metal. In 1922 the Germans developed Tungsten Carbide as the material used in making better cutting tool bits for precision milling and cutting of steel. In World War II, tungsten played an enormous role in background political dealings. Portugal, as the main European source of the element, was put under pressure from both sides, because of its sources of wolframite ore. The resistance to high temperatures, as well as the extreme strength of its alloys, made the metal into a very important raw material for the weaponry industry.

Today tungsten carbide is in widespread use in the worldwide machinery of modern industry and is a darling super alloy that has made aerospace advances possible. And it is still the one little item that makes a light bulb work.

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Tungsten (Swedish and Danish tung sten meaning "heavy stone", even though the current name for the element in Swedish is Wolfram) was first suggested to exist by Peter Woulfe in 1779 who examined wolframite and concluded that it must contain a new substance. In 1781 Carl Wilhelm Scheele ascertained that a new acid could be made from tungstenite. Scheele and Torbern Bergman suggested that it could be possible to obtain a new metal by reducing tungstic acid. In 1783 JosŽ and Fausto Elhuyar found an acid in wolframite that was identical to tungstic acid. In Spain later that year the brothers succeeded in isolating tungsten through reduction of this acid with charcoal. They are credited with the discovery of the element.

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Radioactive element is the ability to spontaneously from the unstable nuclei emit particles or rays inside (such as α particles, β-rays, γ-rays, etc.), while the release of energy, and ultimately the formation of a stable nuclide class element, this process is called radioactive decay . Generally more than 84 atomic elements are radioactive, atomic number 83 some of the following elements such as technetium (Tc), promethium (Pm), also radioactive. Radioactive elements are divided into two types of natural radioactive elements and artificial radioactive elements. Including natural radioactive elements polonium (Po), radon (Rn), francium (Fr), radium (Ra), actinium (Ac), thorium (Th), protactinium (Pa) and uranium (U), etc.; synthetic radioactive element such as actinides elements after the plutonium. There are three main natural decay of nature, namely, uranium series, actinides and thorium series, the three lines of the "ancestor" nuclides are 238U, 235U and 232Th. As the "ancestor" of life and the earth nuclides similar age, so these nuclides decay has not completely lost. Department of radionuclides in each of the previous generation are made radionuclides decay via α or β, respectively, finally terminating in stable nuclide 206Pb, 207Pb and 208Pb.

As medical technology advances, more and more radiant life, has caused new problems, these rays are X-rays, gamma rays, α-rays, β-rays. Tungsten alloy is used to make the best of the shield material, whether medical or industrial equipment. Compared with conventional shielding materials, tungsten alloy shielding member reflects good value. High density alloy can be provided as the energy absorption, and the volume of lead less than 1/3 of people using the tungsten alloy can be a good and reliable shielding performance. Our common language tungsten alloy radiation shielding container shielded gamma shielding and industrial supplies. Shield member can also be used collimators, cancer treatment and radiation shielding syringe. In order to protect patients and health care workers, it is necessary to use shielded tungsten alloy equipment these harmful radiation.

The researchers found that radiation capacity and material density, the greater the density shielding performance is better. Has great density tungsten alloy, so it's shielding performance is high, and tungsten alloy product is environmentally friendly, than lead less hazardous products.

Tungsten alloy products are used to make the best shield materials, non-toxic and easy processing.


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Radioactive (or rather should radionuclide) is able to spontaneously emitted from the internal nucleus unstable particles or rays (such as α-rays, β-rays, γ-rays, etc.), while the release of energy, and ultimately the formation of stable elements decay stop radioactive elements. This property is called radiation, this process is called radioactive decay. Containing radioactive elements (such as U, Th, Ra, etc.) of minerals called radioactive minerals.

As medical technology advances, more and more radiant life, has caused new problems, these rays are X-rays, gamma rays, α-rays, β-rays. Tungsten alloy is used to make the best of the shield material, whether medical or industrial equipment. Compared with conventional shielding materials, tungsten alloy shielding member reflects good value. High density alloy can be provided as the energy absorption, and the volume of lead less than 1/3 of people using the tungsten alloy can be a good and reliable shielding performance. Our common language tungsten alloy radiation shielding container shielded gamma shielding and industrial supplies. Shield member can also be used collimators, cancer treatment and radiation shielding syringe. In order to protect patients and health care workers, it is necessary to use shielded tungsten alloy equipment these harmful radiation.

The researchers found that radiation capacity and material density, the greater the density shielding performance is better. Has great density tungsten alloy, so it's shielding performance is high, and tungsten alloy product is environmentally friendly, than lead less hazardous products.

Tungsten alloy products are used to make the best shield materials, non-toxic and easy processing.


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Tungsten-Rhenium Thermocouples Features

Tungsten-rhenium thermocouples is high temperature thermocouples. It has the potential of a linear relationship between temperature, thermal stability, reliable, cheap, etc.. And display instrument for direct measurement of liquids, steam and gases such as temperature. It can partially substitute platinum-rhodium thermocouple as high metallurgical industry, high-temperature electronic thermoelectric systems and space vehicle structural engineering, ultra-high temperature nuclear reactors measurement tools.

Tungsten-rhenium thermocouples for temperature dependence of thermopower meet ZBN05003-88 indexing table, equivalent ASTME696-84 standards. In a vacuum, reducing, inert atmosphere, at 0 ~ 2300 ℃ range. The use of special protective tube tungsten rhenium even can at 1600 ℃ under oxidizing atmosphere, long-term use, its price is lower than the platinum-rhodium thermocouple.
 
Tungsten-rhenium thermocouples production process

1: The Pre-alloyed Powders

Percentage by weight, said anode materials and cathode materials for each component were prepared anode materials and cathode materials, the use of high-energy dispersion method, reverse three speed 80-150r/min, dispersion time 15-20h

2: Forming

Mechanical pressing, pressure 150-450Mpa, time 15-20s

3: The Pre-Sintered

In a reducing atmosphere 1300-1500 ° * 3h

4: Vertical Melt

Separated into two parts, the first paragraph: 2000A * 20min, second :2800-3300A * 450min

5: Swaged:

Temperature of 1300-1600 °, pass compression rate is greater than 25%, processing size range 10% -20%

7: Cleaning

Electrolytic cleaning lye, lye concentration :15-20%, electrolysis voltage 30-100V, time 5s

8: Annealing

Finished wire annealing temperature 1200-1500 °, time 30-60min

9: Finished Packaging

Vacuum Packaging

 

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Tungsten Steel Sintering Process

1: Removal of forming agents burn stage, at this stage of the sintered body changes as follows: removal of forming agent, as the initial stage of sintering temperature, forming agent gradual decomposition or vaporization, excluded from the sintered body, at the same time , more or less to the sintered body forming agent by carbon, increasing the amount of carbon forming agent with the type, quantity and sintering process vary. The powder surface oxides are reduced, at the sintering temperature, the hydrogen can be reduced cobalt and tungsten oxides, if the vacuum-forming agent removal and sintering, the oxygen reaction is not strong. Contact stress between the powder particles gradual elimination, bonding metal powder begins to generate recovery and recrystallization, surface diffusion began, briquette strength increased.

2: solid-phase sintering stage (800 ℃ - eutectic temperature) appears before the temperature of the liquid phase, in addition to carry out the last stage of the process that occurs, the solid phase reaction and diffusion increase, reinforced plastic flow of the sintered body appear significant contraction.

3: The liquid phase sintering stage (eutectic temperature - sintering temperature) occurs when the liquid phase sintered body after contraction completed soon, and then produce crystalline transition, the formation of the basic organization and structure of the alloy.

4: cooling stage (sintering temperature - room temperature), at this stage, tungsten steel with the organization and phase composition of the different cooling conditions have some changes that can take advantage of this feature, tungsten steel, heat treated to improve its physical and mechanical performance.


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A plastic and metal powder produced by the method for processing a certain amount of the tungsten oxide of cerium (≤ 4%) of the electrode material . Cerium tungsten electrode material is a non-radioactive electrode material , it is since the 1950s to replace the radioactive thorium tungsten electrode material and gradually developed . This electrode material in an inert gas shielded arc welding and plasma welding , cutting, etc. has been widely applied .

Production began thorium tungsten electrode for the early 1950s , it was added to the tungsten ≤ 3% of thorium oxide . This material has a high electron emission capability , resistance to burning and arcing good performance ; However, because thorium is radioactive elements in the production, storage and use of the process prone to radioactive pollution, endangering human health , and thus from the mid-1950s , people have carried out research work on behalf of thorium materials . In 1956, the United States Lewis (A.Louis) conducted directly in the metal tungsten powder, 0.5 to 3.0% cerium oxide powder of testing, and then compacts melt down , rotary forging of welding electrodes . Two years later he cerium oxide content is reduced to 0.01% to 0.30% , so that the processing performance is improved. U.S. 1965 Herman (J.Hermann) using fine tungsten powder pressed into a pure green , green , or after this billet burn- soaked in a solution of rare earth salt , to achieve doping by imbibition , followed by sintering, according to the conventional method swaged to the desired diameter . 1967 ROMON Ivanov (V.N.Romonov) developed a 1% cerium oxide containing cerium tungsten material , the preparation process is: under 800 ~ 850 ℃ calcined ammonium paratungstate, tungsten trioxide , and the cerium nitrate an aqueous solution of a salt or oxide incorporated in the suspension of tungsten trioxide , tungsten trioxide and then doped with hydrogen good a reduced tungsten powder . Ethanol and glycerol mixture after a pressure of 600MPa into a 9mm × 9mm × 400mm billet bar , after burn-in and vertical melt , the billet of CeO2 content of 0.87% , when the swaging process , the heating temperature for the 1475 ~ 1500 ℃.

China started to develop in the 1970s, cerium tungsten electrode material , after nearly 10 years of production practice , the production process tends to be stable and mature , in the early 1980s , both domestically and internationally cerium tungsten electrode material for the production of patents. In the production process , how to make a tungsten doped ceria -based in vivo distribution and dispersion , the electrode is to improve the electron emission capability , improved arc performance , extend the life of one of the important factors . Therefore, the choice of raw materials , usually by blue tungsten oxide or doped tungsten oxide , and the doping agent is not used directly cerium oxide , instead of using the soluble salts such as cerium chloride or cerium nitrate . This aqueous solution as the mother liquor , add inwards blue tungsten trioxide or tungsten , during the addition , the heating and stirring continuously , and concentrated by evaporation to form a coating powder. Doping can also be an aqueous solution of cerium nitrate, cerium chloride or spray containing tungsten blue oxide powder, tungsten or a special container ( heat while rotating ) . The powder doped must be heated to a certain temperature , the salts decompose to form cerium oxide particles distributed in the tungsten trioxide powder, tungsten or blue on the surface of the particles , and then after hydrogen reduction , to obtain W-CeO2 powder. CeO2 content of 1% to 4%, selected according to requirements . Doped powder after molding, burn , vertical melt , get cerium tungsten billet , see doped tungsten its production process , but its swaged temperature slightly higher for 1500 ~ 1600 ℃.

Electrode performance as an electrode material , the level of electron work function is the amount of material raft electron emission performance is an important indicator of good or bad . Only a low electron work function , in order to meet the arc stability, focus , load current density process performance requirements.

Experiments show that cerium tungsten electrodes with thorium tungsten electrode is lower than the electron work function ( pure tungsten electron work function of 4.55eV, W-2% ThO2 is 2.7eV, W-2% CeO2 is 2.4eV ) , this electrode material than thoriated tungsten electrode has greater advantages . First , cerium tungsten electrodes electron emission capability , easy to get a slim arc , so that the heat is more concentrated , the allowable current density thoriated tungsten electrodes increased by 5 % to 8% . Secondly , cerium tungsten electrodes burning rate, long life , easy to arc initiation and stability are guaranteed . Again , cerium tungsten electrodes radioactive dose is very low, and only about one thousandth of thorium tungsten materials , the equivalent radiation dose earth soil . So instead of using cerium tungsten electrodes thorium tungsten electrode , not only can eliminate the production and use of human cumulative internal radiation hazards, and eliminating radioactive contamination of the environment , but also in technical performance and the results are also able to replace thoriated tungsten electrodes , Some properties even superior than thorium tungsten material .

Cerium tungsten electrode material in addition to the application in welding , plasma arc welding replacing thoriated tungsten electrode areas , but in plasma cutting , plasma spraying , plasma melting the application effect is satisfactory . In addition, as the pump laser light source to cerium tungsten electrodes after replacing thoriated tungsten electrodes , so that the light source efficiency by about 12% , life expectancy increased by 5 to 10 times. In the electric light , for small and medium power xenon lamp has been used cerium tungsten electrodes , the electric vacuum , cerium tungsten material as the sealing member having a good use of effects . Problems and trends Although cerium tungsten electrode material in a small tungsten electrodes for welding specifications had succeeded in replacing thoriated tungsten , but as AC welding electrodes and high-power xenon lamps and other aspects of the cathode gas discharge light source material , cerium tungsten electrodes performance and life compared with thorium tungsten , there are still fluctuated unstable situation . Further, since the cerium has a high vapor pressure , and thus as the cathode material , there are still fast decay , poor stability . Thus in these areas are still using thorium tungsten electrode material .

With the progress and development of modern industry , welding, cutting the base material of the species, size and shape of the increasingly numerous , but in the field of welding is the rise since the resumption shou automatic welding , a series of new high- precision welding technology, the electrode materials and arc features a higher and more demanding requirements. Thorium tungsten , cerium tungsten electrode material , whether in arc starting , stable arc burning resistance or in terms of performance are unable to meet the growing requirements of welding technology . To this end , national science and technology workers are working on a new type of electron-emitting material . Studies have shown that adding tungsten matrix lanthanum or yttrium and other rare earth oxides , can greatly improve the ability of tungsten electron emission , especially lanthanum tungsten electrode material , from small to large current current range , all with excellent arc, arc stability and resistance to burning performance. Japan in the late 1980s has been able to mass production of rare earth tungsten electrode material , shortly thereafter , China has successfully developed . It is anticipated that this new type of electron emission materials will be involved in many industrial fields , use more widely, promising .


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