Introduction of Non-sag Tungsten Wire
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- Category: Tungsten Information
- Published on Thursday, 04 June 2015 19:29
- Written by Yahong
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Non-sag tungsten wire, namely doped tungsten wire, which is widely used in electronic devices and hot wire, such as, high wire color temperature, thermal shock resistance wire and the cathode tube radiation. Its development could date back to 1920. Its large elongated grains are obtained by primary and secondary recrystallization, which are regarded as the desired microstructure to gain necessary creep resistance.
Non-sag tungsten wire of incandescent bulb is usually used at the temperature of 2600 ℃around, and the bulb requires the wire to ensure that it owns stable organization and unique high temperature resistance performance. The value of doped tungsten wire anti-sag resistance is an important parameter to evaluate high-temperature performance of tungsten wire. In recent years, studies have been continuing to report about the physical state of doped tungsten microstructure, and bubble reinforcement theory now is widely used to study high-temperature properties of tungsten wire. Long-term creep at high temperature conditions, required the gas atoms of strengthening effect must be insoluble, and has a sufficient vapor pressure, while the element content must be small, so as to ensure the formation of a dispersed state. In doped tungsten wire manufacturing process, aluminum and silicon in aluminum - silicon - potassium dopant, substantially soluble in the matrix, but there are large differences in potassium and tungsten atomic radius, potassium with greater atomic radius diffusion capacity in tungsten is bad. However, the tungsten in the processing and recovery temperature ranges, the vapor pressure of elements potassium is large, so can guarantee a solid solution in tungsten.
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Tungsten Trioxide and β-Tungsten Oxide comparison
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- Category: Tungsten Information
- Published on Thursday, 04 June 2015 19:29
- Written by xiaoshan
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From tungsten trioxide particle morphology we know tungsten trioxides partial are denser. And it is bad for hydrogen enter particles interior during reduction process, and the interior water is not easily discharged. Based on the oxidation-reduction deposition growth mechanism, which will help tungsten powder particle to growth, thus tungsten trioxide is suitable for produce coarse particles of tungsten powder, which is the actual situation of our industrial production.
With the reduction processing, the oxygen and vacancies of tungsten trioxide increase then a tungsten trioxide crystal partial gradually transformed into a β- tungsten oxide crystal partial. β-tungsten oxide particle morphology has some different with tungsten oxide particle shape which isβ-tungsten oxide particle more coarse and there has some cracks. The cracks depends on reduction temperature, reduction time, the speed of push the boat, boat mounted volume, hydrogen flow rate, and hydrogen-way. These cracks is good for water discharge and hydrogen into the interior of the particle so than it can make further depth reduction, and it also good for produce fine tungsten powder.
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Development Status of Using Sol-Gel Method Produces Tungsten Oxide Films
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- Category: Tungsten Information
- Published on Thursday, 04 June 2015 19:26
- Written by xiaoshan
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Sol-gel method for manufacture tungsten trioxide films has a lot of advantages, such as it can be produce different crystal structure material, different degrees of dense material, and easy to control the product's composition and particle size. The most important it can produce large area and uniform films. Thanks to these advantages, it is used by mostly researchers to study and continue to develop. In 1999, researchers use sodium tungstate as reaction precursor and in the different PH value to produce WO3 films. Then with the increasing of PH value, tungsten oxide hydrate gradually change to octahedral 12- tungstate, and this is conducive to the low valence W atoms formation and photochromic pheromone occurs. After that researchers who prepared the same way, produced several hybrid multi-metal oxide film in which phosphorus tungsten oxide film after exposure to UV light in the visible and near infrared region to have a strong absorptive capacity. The method for the sol - gel method large tungsten trioxide film has taken an important step. By 2002, using tungsten hexachloride and tungsten acid as raw materials, by changing the alcohol, water and the proportion of PH value polyethylene glycol to obtain a stable sol, and made into a film. The hybrid films which are using WCL6 as raw material to produced and it has fast response, strong absorption advantages.
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Non-sag tungsten Wire High Temperature Performance(2)
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- Category: Tungsten Information
- Published on Thursday, 04 June 2015 19:28
- Written by Yahong
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Non-sag tungsten wire working temperature is between 2300 ~ 2800 ℃, and the greater the average light bulb power, the higher the wire temperature.
According to a series of study and analysis conducted by Transmission Electron Microscopy (TEM) and Auger Spectrometer (AES) in 1970s, it shows that non-sag tungsten wire recrystallization structure, unique, with elongated strip whose coarse grains is overlapping each other, its formation is closely related to potassium content. Remaining trace potassium in doping tungsten bars form potassium bubble column which parallel to the axis of the filament during processing, and then hinder the process of lateral recrystallization grain growth, and thus generate long thick overlapping structure. Incandescent wire sagging is not only related to the additive element content and machining technology, but also the treatment process of wire production process. Tungsten retains a large number of internal stresses in finished products when we pulling it into wire, and will produce new internal stress of inhomogeneous deformation in the cross section of tungsten wire when we are winding the wire. The internal stress must eliminate thoroughly before tungsten wire is placing into the glass bulb, otherwise bulb will start twisting, distorting and sagging when it is lit. When the wire is sagging, it can severely reduce the luminous efficiency of the lamp.
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Tungsten Carbide Rod Hardness Test
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- Category: Tungsten Information
- Published on Thursday, 04 June 2015 19:22
- Written by Cristina
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Tungsten Carbide Rod Hardness Test
Tungsten carbide rod hardness test mainly adopts Rockwell hardness tester to test HRA hardness level. The portable Rockwell hardness tester weighs only 0.7kg which is really convenient both in usage and carry. Through the hardness test, we can figure out the different mechanical property of tungsten carbide rod under different chemical agents, organization structure and heat treatment processing. This is a kind of non-destructive test, and is relatively easy to operate. This kind of detection method has small testing force and little indentation, high measuring speed and high efficiency; therefore, it can be directly used to test finished products.
Hardness test has certain similarities with tensile test, both of which are used to test the resistance capability of metals to plastic deformation. Because tensile test is a kind of destructive test, so hardness test is adopted more frequently than tensile test.
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