Under a low temperature condition, the recrystallization will occur by adding some metals to the wire surface which is an important process when the wires act as reinforcement material in metal matrix composites because of its damage to the mechanical properties of non-sag tungsten wires.

The activated recrystallization was studied both for nickel plated and palladium plated 0.18 mm cold drawn doped tungsten wire. A recrystallized structure formed in both types of wires after annealing at 1100°C for 100 hours, but their structural features were different. Palladium presence will lead to recrystallizing behavior, which was very similar to that of un-doped tungsten wire, whereas the behavior of nickel plated wire was similar to the general recrystallization of doped wire, except for the much lower recrystallization temperature. This indicated that palladium was more effective as an activator than nickel was.

It was shown, using Atom Probe Field Ion Microscopy (APFIM) analysis, whose grain boundaries and lattice dislocations could act as fast paths for diffusion of activators in tungsten wire during annealing. The presence of the large potassium bubbles and the segregation of activators on potassium bubbles indicated that the effect of activators was to neutralize the impeding influence of potassium bubbles on dislocation movement and boundary migration.

Two types of nickel rich precipitates were found. One was a Ni (W) solid solution, which formed on the bubbles at grain boundaries, and another type, with Ni4W structure, was found on the potassium bubbles connected with dislocations. Palladium rich precipitates were present only in triple junctions. Their structure could not be established.

 

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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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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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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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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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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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Tungsten oxide is a good photochromic material, in 1973first reported amorphous tungsten oxide film photochromic phenomenon that has been widespread concern and research. In 1980 Gerard and others based on the previous first used vacuum deposition method, by changing the degree of vacuum to produce HXWO3-Y films. Then after that they switched to a sputtering method, in Ar-O2 (preparation pure sub-stoichiometric film), Ar-O2-H2 and Ar-O2-H2O (changing composition WO3 hydroxide) these three different atmospheres sputtering and prepared HXWO3-Y film. However, due to the vacuum deposition method and sputtering method equipment is expensive and technically complex, and the complex molecular structure of the film and ordered the film can not be prepared, besides it is difficult to control the film thickness and size, and more importantly, they are not easy to produce a large area so it is difficult to be widely used. With the development of technology there are many methods for the producing tungsten oxide, such as electron beam vapor deposition method, electrodeposition., spray pyrolysis, sol - gel method. Where the sol-gel method can produce different crystal structure, different degrees of dense material, easy to control the composition and particle size and easy production large area uniform films and other advantages, so now most researchers have been using and continue to develop.

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Tungsten Carbide Rod Tensile Strength Test

The hardness of tungsten carbide rod is related to other properties. Similar to tungsten carbide rod hardness test, tungsten carbide rod tensile strength test is also used to test the strength and resistance capability of metals to plastic deformation. Strength often refers to the capacity of tungsten carbide rod to resist elastic deformation, plastic deformation and breakage under the external force. Plasticity means the plastic deformation of tungsten carbide rod under certain loading action.

Tensile strength testing, also known as tension testing, is a fundamental materials science test in which a sample is subjected to a controlled tension until failure. The results from the test are commonly used to select a material for an application, for quality control, and to predict how a material will react under other types of forces. Properties that are directly measured via a tensile test are ultimate tensile strength, maximum elongation and reduction in area.
Tungsten carbide rod tensile test requires large testing equipment, the process is very complex, and test efficiency is lower than hardness test. Besides tensile strength test is a kind of destructive test, so hardness test is adopted more frequently than tensile test.

 
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Influence tungsten oxide photochromic has many factors, in addition to the structure and composition of itself, which the atmosphere the tungsten oxide exist will also impact on its chromogenic performance. Considered from the internal structure of tungsten oxide, there are different structures of tungsten oxide there. From relatively stable triclinic, monoclinic to cubic, tetragonal and very unstable hexagonal bronze, pyrochlore phase, but the most studied at the present is amorphous (a-WO₃) or polycrystalline (c-WO₃) film’s photochromic properties. After the study found that a-WO₃ compared with c-WO₃ has a good photochromic property, mainly because c-WO₃ has lattice defects or small surface area or others. The internal factors which mentioned above is the main reasons of determine the material properties, and external also has great impact on tungsten oxide photochromic which can not be underestimated, especially on different atmosphere. From colored aspects, some of the hydrogen or hydroxyl organic vapors is good for matachromatism reaction rate and improve absorption intensity of tungsten oxide. Respect for bleaching aspect，it will affected by the oxidizing gas largely, such as O₃, H₂O₂ and FE₂ (SO₄) ₃ and so on. These factors for improve the tungsten oxide photochromic performance have great help, but also conducive to the production of a more favorable performance photochromic material.

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Tungsten Carbide Rod Surface Roughness

Tungsten carbide rods have high hardness and abrasion resistance and thus its grinding process is quite complicated, which includes: coarse grinding, fine grinding, accurate grinding and polishing. There are two types of polishing: matte polishing and mirror polishing.

Grinding can help tungsten carbide rods get higher machining accuracy and lower surface roughness. Grinding precision usually reaches IT6 ~ IT7 tolerance grade, while surface roughness reaching Ra1.25 ~ 0.16μm. Surface roughness Ra of tungsten carbide rods before accurate grinding should be smaller than 6.3um. If tungsten carbide rods are polished, their surface roughness will be up to Ra0.1 μm, which makes its surface be smooth as that of a mirror. Its dimensional accuracy and shape accuracy can be within 1um, the error of which is equivalent to 1/70 thickness of human hair or even thinner. 


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