Metal powder pressing method includes single pressing process, double pressing process, floating pressing process, friction pressing process, etc. Tungsten carbide button produced by different pressing process has various density distribution law. Density is an important factor that would affect product quality. Besides from gradient and properties of metal powder, pressing mould surface roughness, tungsten carbide button density is also affected by powder movement after being pressed in the pressing mould. The friction between powder and side of pressing mould will affect density of tungsten carbide button.           

The conventional hydraulic pressing adopts single pressing process. Shape and thickness of powder layers are quite different. So the density is uneven. TPA pressing method adopts double pressing process. There is a neutral layer during the process, the powder in this layer almost stay still during the pressing process. Neutral layer is pressed from both up side and down, compared to single pressing process, the density is even. 



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Tungsten carbide button density is an important factor which affects tungsten carbide button quality. Apart from choosing proper pressing method, the size of material forming zone is very important.

If the forming zone is too low, the upper punch can not reach to the metal powder, and the lower punch can not reach the top layer which will cause the high pressure of the lower layer thus the density is uneven. And also the size of finished product will be too small.

If the forming zone is too high, both the upper punch and lower punch will not have enough power to press the middle layer. As a result the density in the neutral layer is lower than the other part. The punch needs to go deep inside the mould which will cause air block in the mould; the metal powder will stick to the punch and will cause damage. Also the mould will be overloaded; size of tungsten carbide button will be too large.

Only when the forming zone height is proper, the pressure on neutral layer from upper and lower punch is even, tungsten carbide button will be high density and quality. 


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Tungsten carbide button is used in the coal cutter drilling tools, mine machinery tools and road maintenance tools. It is also widely applied for rock tools, mining tools for use in quarrying, mining, tunneling, and civil constructions.

Requirement of tungsten carbide button in rock drill is super high. The hardness should be high enough to increase its wear resistance; also the tenacity should be able to resist cracking. Nano crystallization can enhance its hardness and wear resistance. Research shows that under the same amount of binder, if the tungsten carbide grain size is less than 1um, tungsten carbide button hardness and tenacity improve a lot.

As the tungsten carbide grain size getting smaller, the properties of tungsten carbide button arise. Some researchers applied nano materials to tungsten carbide button sintering process, and it shows the sintering temperature falls down. Tungsten carbide button hardness, wear resistance, tenacity also improve a lot. Thus its service life extended and cut the producing cost. 


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Tungsten carbide button bits applied in rock drills have different shapes: hemispherical button, conical button, parabolic button and wedge button.

As the long hole drilling being widely applied than before, the requirement for tungsten carbide button quality applied in related equipments also enhances. Hemispherical button and conical button are the most widely applied in industry. During the application process, it can be observed that regular tungsten carbide hemispherical button can be easily passivating. Tungsten carbide conical button due to its wiry bit, can be cracking under big crash and super hard rock. Thus button profile can affect its properties in a certain degree.

Researchers invented a kind of tungsten carbide button which can resist blunt. This kind of button combines the shape of hemispherical button and conical button. It turns out that this kind of tungsten carbide button is of higher hardness and wear resistance, also drill velocity is faster.


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It is known that a right tool coating has a large influence for the tungsten carbide end mill in terms of cutting speed, tool life and surface finish situation.



Polycrystalline diamond is an exceptionally hard coating used on cutters which must withstand high abrasive wear. A PCD coated tool may last up to 100 times longer than an uncoated tool. However the coating cannot be used at temperatures above 600 degrees C, or on ferrous metals. Tools for machining aluminium are sometimes given a coating of TiAlN. Aluminum is a relatively sticky metal, and can weld itself to the teeth of tools, causing them to appear blunt. However it tends not to stick to TiAlN, allowing the tool to be used for much longer in aluminum.


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There are several most commonly used workholding devices for tungsten carbide cutting tool in nowadays’ lathe boring processes. It comprises into three-jaw chuck, four-jaw chuck and collet, as well as faceplate.

Since the three-jaw chuck is automatically centered, it is an ideal choice for holding round or hex workpieces. On latest model, if the condition is great, the runout faces limitation can be quite low , while traditionally it is usually not less than 0.025-0.075 mm. For the four-jaw chuck, it is recommended to apply in irregular shapes holding or round or hex holding to extremely low runout in time spent indicating and clamping each piece, in both cases as its independent action on each jaw. The face plate is also used for irregular shapes. Although collets’ price are higher, it perfectly combine self-centering chucking with low runout.


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Tungsten tube is one of the tungsten products made by deep processing, which has excellent properties.

Tungsten tube owns the following properties:
High melting point;
High boiling point;
High temperature resistance;
Excellent corrosion resistance;
Productive technology: powder metallurgy;
High purity: its purity is over 99.95%;
Appearance: it appears silver grey metal luster;
Supply state: it supplied by state of sintering or processing;
With lower thermal expansion character at high temperature;
High density: if it is made by sintering, its density can reach 18.2g/cm3; if it processed by complete forging, its density can get 19.2g/cm3.While if the size is much bigger than its range, the density is only 18.8g/cm3 around. 

 

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Using WF6(high purity) and H2(high purity) as raw materials, by CVD (chemical vapor deposition) for tungsten tube preparation, its deposition temperature is controlled at 500-700 ℃.

Tungsten tube manufacturing process is as follows:

WF6 and H2 have a chemical reaction, and WF6 reduce to tungsten atoms, then a deposited tungsten layer is obtained on the deposition substrate profile.

After the end of aforementioned process, by melting the matrix in vacuum furnace or chemical etching to get deposited tungsten tube, its shape depends on the shape of deposited matrix, furthermore its size and precision is controllable.

Then, using a density meter to measure the density of the product;

Measuring micro-hardness by micro-hardness tester;

Measuring the tensile strength of the product with universal testing machine;

Observating the metallographic phase with a metalloscope and collecting metallographic phase picture with a digital camera;

Analyzing the deposition content and fluoride residue by using X-ray fluorescence spectroscopy and EDS (Energy Dispersive Spectroscopy);

Residual stress is measured with a diffractometer on tangential and axial product surface.


 

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The tungsten tube can be processed by CVD (chemical vapor deposition), in which WF6 and H2 are as raw material gases.

CVD is an important method for the preparation of pure tungsten products. At the end of 1970, there were related reports that foreign countries had adopted this technique for preparing high purity and high density tungsten products. In recent years, China has gradually carried out research in CVD technology on tungsten microstructure, properties, structure, coating process and other fields.

The tungsten tube processing by different deposition temperature (700 ℃, 600 ℃, 500 ℃)  is with different density, purity, residual stresses, micro-hardness and intensity.

Tungsten tube performances by chemical vapor deposition:
High purity :> 99.7%;
High density :> 19g / cm3;

Tensile strength range: 300-500Pa and it has considerable tensile strength with the conventional method of preparing tungsten rods in annealed state;

There is a larger residual stress along the radial and circumferential directions of tungsten tube;

Tungsten tube prepared by chemical vapor deposition with high purity and high density characteristics;

With the change of tungsten tube radius (4-21mm) and deposition temperature, the range of micro-hardness values is ​​between 500HB and 800HV.

 

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Riveting tungsten tube what is made of tungsten plate by riveting method is with high purity.

Riveting tungsten tube refers to convolute the tungsten plate into tungsten tubular piece, and then the rivet crack at the end of the tungsten titles is linked, so the two parts are connected.

Why tungsten tube is adopting riveting method mainly lies that its thickness is thin, the tungsten tube after sintering and polishing can not meet the thickness demand, thereby riveting method is employed. Thickness of the riveting tungsten tube is between 0.2 ~ 0.5mm, and its height can up to 850mm. Riveting tungsten tube used for sapphire crystal growth furnace will make tungsten tube with multiple different outer diameter simultaneously to fix a change of cut shape. Its main function is for insulation and thermal insulation. Riveting tungsten tube is representing polished surface and smooth metal silver.

Purity of riveting tungsten tube:
Its purity is not less than 99.95%.

Riveting tungsten tube surface:
Its surface is presenting silver gray metallic luster.

Riveting tungsten tube application:
It is mainly applied in the sapphire crystal furnace, thermocouple protection tube in high temperature furnace, high temperature sintering furnace’s support parts and other aspects.


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