Suppression Method of Tungsten Tube Surface Transverse Cracks (2)
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- Category: Tungsten Information
- Published on Thursday, 18 June 2015 17:22
- Written by Yahong
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Controlling the deposition matrix removal process is one way of suppressing the generation of tungsten tube surface transverse cracks.
If adopting vacuum melting method to remove the deposition matrix, the temperature rising rate should be slow, especially when the temperature is over the deposition temperature to the melting point of copper. This method is preferred options, because this method can make the removal of the matrix and the deposited tungsten tube’s stress annealing process going on simultaneously. In one hand, the transverse cracks of tungsten tube surface can be suppressed; on the other hand, the deposited matrix material can be recycled directly.
Using nitric acid, then the concentration of nitric acid should be less than 35%. Because, if the corrosion rate of deposition matrix is excessive, then stress release rate of tungsten tube will be too fast, furthermore, it will also makes the corrosion deposit matrix uneven, resulting in t tungsten tube will generate cracks in deposit matrix removal process.
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Suppression Method of Tungsten Tube Surface Transverse Cracks (1)
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- Category: Tungsten Information
- Published on Thursday, 18 June 2015 16:45
- Written by Yahong
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Suppression method of tungsten tube surface transverse cracks:
Rate of temperature increase of annealing treatment should be carried out slowly instead of too fast; especially the temperature ranges below tungsten’s brittle transition temperature, in order to release deposition tungsten tube’s internal stress slowly.
Underspeed the cooling rate after the end of the deposition, especially the temperature ranges above tungsten’s brittle transition temperature. This is an important thing, particularly for the deposition preparation of products which has big size, thick wall, and complex shape and is easy to produce concentrated stress.
In the condition of meeting the strength requirements and processing conditions of the deposition matrix, the matrix thickness should be uniform and as thin as possible to reduce the deformation stress during cooling process.
Selecting the matrix material whose expansion coefficient is close to the base material, by this way, the residual stress within deposited products can be significantly reduced.
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Ammonium Metatungstate Introduction
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- Category: Tungsten Information
- Published on Thursday, 18 June 2015 16:34
- Written by Cristina
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Ammonium metatungstate, also known as AMT, is a tungsten chemical in the form of highly soluble hydrated crystals, solubility is 303.99/loogH:O when 20℃, aqueous fairly stable. It is white or slightly yellow crystals which has no harmful components and slightly acidic.
Component of ammonium metatungstate is listed as below:
|
Grade |
AMT-1A |
AMT-2A |
|
|
AMT-1B |
AMT-2B |
||
|
AMT-1C |
AMT-2C |
||
|
Purity Min.(%) |
99.95 |
99.9 |
|
|
Main content WO3 MIN.(%) |
83 |
83 |
|
|
Other |
Al |
0.001 |
0.001 |
|
As |
0.001 |
0.001 |
|
|
Bi |
0.0001 |
0.0001 |
|
|
Ca |
0.001 |
0.003 |
|
|
Cr |
0.001 |
0.001 |
|
|
Cu |
0.001 |
0.003 |
|
|
Fe |
0.002 |
0.003 |
|
|
K |
0.0015 |
0.002 |
|
|
Mg |
0.001 |
0.002 |
|
|
Mn |
0.001 |
0.001 |
|
|
Mo |
0.005 |
0.01 |
|
|
Na |
0.0015 |
0.002 |
|
|
Ni |
0.001 |
0.001 |
|
|
P |
0.001 |
0.003 |
|
|
Pb |
0.0001 |
0.0001 |
|
|
S |
0.0005 |
0.001 |
|
|
Sb |
0.001 |
0.002 |
|
|
Si |
0.001 |
0.002 |
|
|
Sn |
0.0001 |
0.0003 |
|
|
Ti |
0.001 |
0.002 |
|
|
V |
0.001 |
0.002 |
|
|
Insoluble Matter in |
0.5 |
0.5 |
|
|
PH Value |
3.0-4.5 |
3.0-4.5 |
|
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Ammonium Paratungstate Introduction
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- Category: Tungsten Information
- Published on Thursday, 18 June 2015 16:35
- Written by Cristina
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Ammonium paratungstate (or APT) is a white crystalline salt of ammonium and tungsten, with the chemical formula (NH4)10(H2W12O42)·4H2O.
Ammonium paratungstate is produced separating tungsten from its ore. Once the ammonium paratungstate is prepared, it is heated to its decomposition temperature, 600 °C. Left over is WO3, tungsten(VI) oxide. From there, the oxide is heated in an atmosphere of hydrogen, reducing the tungsten to elemental powder, leaving behind water vapor. From there, the tungsten powder can be fused into any number of things, from wire to bars to other shapes.
When concentrating an ammoniacal solution of tungstic acid (i.e. hydrous WO3), the product obtained is ammonium paratungstate. Below 50 °C, the hexahydrate is formed, whereas when the temperature of the solution is above 50 °C, the pentahydrate or heptahydrate is formed. The former crystallizes as triclinic plates or prisms, whereas the latter as pseudorhombic needles.
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Ammonium Metatungstate Usage
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- Category: Tungsten Information
- Published on Thursday, 18 June 2015 16:33
- Written by Cristina
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Ammonium metatungstate is a source of high purity, water soluble tungsten which is essentially free of alkali and other metallic impurities. Ammonium metatungstate is very versatile and can be used as catalysts, capacitors, nuclear shielding, flame retardants, corrosion inhibitors raw materials, but also excellent raw materials in the preparation of ultra fine tungsten powder, tungsten heavy alloy powder, phosphotungstic acid, arsenic acid, silicon tungstate.
It is also used as a raw material for the production of tungsten catalysts for a variety of reactions including oxidation, hydroxylation, hydrogenation, and polymerization. Suitable carriers can be impregnated with alkali-free solutions of tungsten and processed to remove the water and ammonia. Such catalysts are used by the petrochemical industry.
Other applications include: reagents for chemical analysis such as for chemical diagnosis; source material for the preparation of high purity tungsten trioxide used as a thin film substrate for certain semiconductor devices; high purity source material for research in tungsten chemistry; source material for DENOX catalysts industry; as a precursor to a variety of POM (polyoxometalates).
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