Effect of Powder Property on Tungsten Copper Electrode Density (2 of 2)

Relevant foreign scholars have studied the densification process high-density tungsten alloy found W-Ni-Fe high density alloys, when the average particle size of the tungsten particles is 1μm, occurred at about 1200 ℃ rapid densification; when the tungsten particles have an average particle size of 5μm, at 1400 ℃ was undergoing rapid densification. It indicates that decreasing the granularity of powder and increasing the superficial area can remarkably decrease the sintering temperature of powder press.

In addition, the appearance of powder particles has an influence of densification processing. If the shape of the powder particles exhibit uneven shape it is easy to bypass the formation of voids between the particles and increases the friction powder and die wall, between the powder particles, which will not help to improve the sintered density after the bulk material. The higher the degree of spherical particles, the better mobility, it is easily to fill the cavity so that bulk density, but also conducive to pressing and sintering, to obtain a higher density. Nano tungsten powder and nano copper powder SEM image as follow:

tungsten copper

Viewed from the SEM image, we can find that micro Cu powder particle has more regular shape and high sphericity; compared with micro Cu powder, micro W powder particle is more irregular, it is polygonal and has low sphericity, which is not beneficial for tungsten copper electrode with high density manufacturing. Furthermore, micron tungsten powder and copper powder having a large surface area and the ratio of the excess surface energy, in a state of energy imbalance, has a high activity, favor the sintering process. Cu particles has good plasticity and soft texture, easily deformed during pressing and help to increase the contact area between the particles so that the tungsten copper electrode material density may be improved; however, W particles has high melting point, high hardness, low plasticity, it is not easily to be out of shape and fractured, which is not beneficial for the density improving.

 

Multi-Dimensional Network Structure Tungsten Trioxide Preparation

Multi-Dimensional Network Structure Tungsten TrioxideAt present, people have been able to prepare different pore sizes of porous tungsten oxide and have been prepared using a variety of methods and materials that containing a large hole, mesoporous and microporous, or only two of the pore size. These materials have important applications in catalysis, selective separation and sensors; however, the porous material with a foam shape is generally more fragile and friable. Tungsten trioxide is a transition metal oxide that is widely studied because of its unique properties. In addition, the doping tungsten trioxide complex also has a catalytic effect. It means that tungsten trioxide morphology and structure of the desired application function has a direct relationship.

Steps:
Preparing dimensional network structure WO3 containing mesopores by concentrating hydrogen peroxide (H2O2), methanol, over-acid and polyvinylpyrrolidone (PVP) solution. Preparing WO3 mesh structure by using optical microscopy, scanning electron microscopy (SEM), powder X- ray diffraction (XRD), thermal gravimetric analysis (TG), high-resolution transmission electron microscope (HRTEM) and N2 adsorption isotherms (BET) technology after firing.

Conclusions:
1. Optical microscopy and SEM photograph show this shape of the foam cube mesh structure regardless of WO3 is relatively stable before calcination or after calcination, supported by the nature of the performance.
2. Magnified SEM image shows that the wall mesh structure is assembled from nanoparticles made of WO3 after calcination.
3. XRD diffraction analysis shows that WO3 is amorphous foam before calcination, and is orthorhombic crystals after calcination. As PVP structure, it has the advantage of inducing inexpensive agents and stable solution.

 

Roughing in Wolframite Beneficiation Processing

In China, the main beneficiation of wolframite is combined beneficiation process based on gravity concentration, and its sorting operations segments are generally divided into roughing, gravity concentration, selection and slime treatment.
 
Mineral raw materials are selected preliminary as sorting job during beneficiation.
After roughing, mineral raw materials are namely sorted into rough concentrate, middlings, tailings or more products.
If roughing product is not qualified, it needs to continue sorting.
 
In roughing, based on the principles that "early retrieve and more, early lost and lost more", make wolframite retrieve as soon as possible after dissociation, which is an important measure to improve the recovery rates of tungsten. Some wolframite mines separately elected tungsten block and rich intergrowth in hand-selected operation, directly into the selection of operations, to avoid mud of job loss of the high-grade tungsten block and crushing, grinding, gravity concentration  and other aspects of the transport belt to achieve the "early retrieve and more" to improve the tungsten recovery. In Pangushan, Dajishan tungsten ore roughing process, it used a combination of these types of technology to improve the recovery of tungsten, reducing the loss of the rougher sections of tungsten.

Tungsten mine

 

New Types, Structure of Coated Cemented Carbide—Diamond Coating 2 of 3

Take YG6 tungsten carbide drawing die as an example, it deposits diamond coating (10-30pm crystalline diamond coating) on tungsten carbide drawing die matrix by chemical vapor deposition (CVD) and the finished products after polishing, finishing and some after processing. In general, the processes of tungsten carbide drawing die with diamond coating are tungsten carbide matrix milling → matrix washing → pre-processing → pretreatment → put in furnace → diamond coating deposited → film testing → finishing and polishing → finished product.

First of all, choose YG6 tungsten carbide die (the shape and size should be similar to the finished product). Then bore milling and finishing for proper shape, and reserve the size margin about 30μm to cooperate with the thickness of the coating layer. Afterwards, it adapts sand blast to eliminate the impurities and loose material of the surface, which can achieve good roughness. After sand blasting, it should be ultrasonic cleaning by distilled water and alcohol. Finally, the drawing die corroded by the acid or alkali prepared and ultrasonic cleaning by distilled water and alcohol again. When the preparation complete, put tungsten carbide drawing die into the equipment of CVD diamond coating deposited.

The most common equipment of coating deposited is hot wire furnace, which is equivalent to a reaction chamber. the gas containing other elements constituting the respective film gaseous reactant vapor or liquid reactants and reaction necessary introduced into the reaction chamber. That is, after the pre-pass hydrogen H2 and methane, CH4, hot filament heated to 2500 ℃, by adjusting the filament temperature, gas pressure, gas flow rate and relevant process parameters, so that the mold surface of diamond film deposition of a certain thickness. There are special requirements for accuracy or surface finish can be achieved by further optimizing the surface quality of the finishing and polishing process precision, to meet different working environment for the corresponding requirements of the mold.

coated cemented carbide

 

Wolframite Beneficiation Processing

In China, the main beneficiation of wolframite is combined beneficiation process based on gravity concentration, and its sorting operations segments are generally divided into roughing, gravity concentration, selection and slime treatment.
 
Principle process of wolframite beneficiation generally are: pre-accumulation and threw hand-selected waste; multi-level jigging multi-stage shaker, stage grinding, shaking throw the tail; rejoin fine mud treatment, a variety of process selections, useful minerals comprehensive recovery.
 
Some tungsten ore concentrators don’t have selection operation, so the raw products were taken into consigned processing, such as Piaotang Dajiang concentrator, Shilei tungsten ore, Xinzian tungsten ore and Dangping tungsten ore a concentrator of Zhangyuan Tungsten industry.
The main equipments of beneficiation : jaw crusher, cone crusher, roll crusher, rod mill, ball mill, jig, hydraulic classifier, shaker, flotation machines.
 
The dilution rate of wolframite mining is high. According to the surrounding rock and gangue of wolframite is recognizable and surface physical properties are different, roughing and throw waste need to be down before the gravity concentration.
 
At present, hand-selecting is still the main method for quartz-vein type wolframite roughing and throw waste, photoelectric sorting machine, heavy media beneficiation did not apply due to some reasons.

wolframite
 

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