Tungsten Electrodes Price

The Influencing Factors of Tungsten Copper Electrode Conductivity

Details: Category: Tungsten Information; Published on Thursday, 10 December 2015 16:06; Written by xiaobin; Hits: 323

Tungsten copper electrode is one of the most widely used in Electrical Discharge Machining (EDM). Due to EDM uses pulsed spark between tool and workpiece, which ablate the metal by partial high temperature of discharging. Therefore, it is necessary that the electrode of EDM requires ablation resistance and excellent conductivity. What’s more, its distribution should be uniform.

Some researchers find that the measured conductivity is generally lower than the theoretical value by theoretical model of thermal conductivity value (also applied in analyzing conductivity). The influencing factors of conductivity of tungsten copper electrode are impurities, porosity and micro structure. Among them, impurity is the main factor, which trace will remarkably decrease the thermal conductivity and electrical conductivity of tungsten copper.

The source of impurities in the following areas: 1. activator, for improving the densification of tungsten copper, will form the solid solution with Cu and has an effect on the electrical conductivity. 2. The purity of raw material is lower, probably lead in impurities from outside during the preparation.

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Ni-doped Effects on Tungsten Copper Electrode III

Details: Category: Tungsten Information; Published on Thursday, 10 December 2015 16:04; Written by xiaobin; Hits: 266

Except that the density and hardness of tungsten copper electrode, the effect of adding nickel (Ni) on the electrical conductivity of tungsten copper electrode is also can not be neglected. The effect of content of Ni on the electrical conductivity of tungsten copper electrode diagram as follow:

tungsten copper electrode

The diagram visually shows that the electrical conductivity of tungsten copper electrode dramatically decreases after adding nickel (Ni). (When the content of Ni is 0%, the electrical conductivity is 34.5%IACS, and the electrical conductivity decreases to 17.5%IACS after the content of Ni reaching 0.2 %.) Afterwards, with the increasing content of Ni, the electrical conductivity decreases constantly. The principle is similar to the adding cobalt (Co) that tungsten dissolved in nickel (Ni), which promoted the sintering densification. A large number of solid tungsten particles bonded contact with each other to form a continuous skeleton, limiting the role of liquid Cu infiltration, resulting in tissue tungsten copper alloy electrode uneven. In addition, external Ni atom enlarges the resistance through electrons of tungsten and copper scattering after adding active element Ni.

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Pure Ammonium Paratungstate from Tungsten Scraps

Details: Category: Tungsten Information; Published on Thursday, 10 December 2015 11:05; Written by xinyi; Hits: 275

Typical oxidation process of tungsten scraps was modified by the rotary kiln with oxygen burner to increase the oxidation rate of tungsten scraps. Also to accelerate the solubility of solid oxidized products, the hydrothermal reflux method was adapted. By heating tungsten scraps in rotary kiln with oxygen burner at around 900° for 2hrs, the scraps was oxidized completely. Then oxidized products (WO3 and CoWO4) was fully dissolved in the solution of NaOH by hydrothermal reflux method at 150° for 2hrs. The dissolution rate of oxidized products was increased with increasing the reaction temperature and concentration of NaOH. And then CaWO4 and H2WO4 could be generated from the aqueous sodium tungstate solution. Ammonium paratungstate (APT) also could be produced from tungstic acid using by aqueous ammonium solution. The morphologies (cubic and plate types) of APT was controlled by the stirring process of purified solution of ammonium paratungstate.

A Rotary kiln is a pyroprocessing device used to raise materials to a high temperature (calcination) in a continuous process. The kiln is a cylindrical vessel, inclined slightly to the horizontal, which is rotated slowly about its axis. The material to be processed is fed into the upper end of the cylinder. As the kiln rotates, material gradually moves down towards the lower end, and may undergo a certain amount of stirring and mixing. Hot gases pass along the kiln, sometimes in the same direction as the process material (co-current), but usually in the opposite direction (counter-current). The hot gases may be generated in an external furnace, or may be generated by a flame inside the kiln. Such a flame is projected from a burner-pipe (or "firing pipe") which acts like a large bunsen burner. The fuel for this may be gas, oil, pulverized petroleum coke or pulverized coal.

RotaryKiln

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Ammonium Paratungstate Tetrahydrate X-Ray Powder Diffraction Data and Unit Cells

Details: Category: Tungsten Information; Published on Thursday, 10 December 2015 11:34; Written by xinyi; Hits: 271

X-Ray powder diffraction data and unit cell parameters of industrially produced, as well as bench scale prepared, ammonium paratungstate tetrahydrate are reported and compared with current Powder Data File (1989) patterns. A least-squares refinement resulted in two slightly different unit cells. Both cells are monoclinic with S.G. = P21/n(14), Z = 2. The density, 4.639(2)kg/m3, calculated from one of these unit cells corresponds reasonably well with a measured value of 4.61 (2). It has, however, not been possible to determine at present why ammonium paratungstate tetrahydrate has two unit cells. No relation between the crystalline form and the method of preparation nor the exact water content could be established.

Powder diffraction is a scientific technique using X-ray, neutron, or electron diffraction on powder or microcrystalline samples for structural characterization of materials. Relative to other methods of analysis, powder diffraction allows for rapid, non-destructive analysis of multi-component mixtures without the need for extensive sample preparation. This gives laboratories around the world the ability to quickly analyze unknown materials and perform materials characterization in such fields as metallurgy, mineralogy, forensic science, archeology, condensed matter physics, and the biological and pharmaceutical sciences. Identification is performed by comparison of the diffraction pattern to a known standard or to a database such as the International Centre for Diffraction Data's Powder Diffraction File or the Cambridge Structural Database (CSD). Advances in hardware and software, particularly improved optics and fast detectors, have dramatically improved the analytical capability of the technique, especially relative to the speed of the analysis. The fundamental physics upon which the technique is based provides high precision and accuracy in the measurement of interplanar spacings, sometimes to fractions of an Ångström, resulting in authoritative identification frequently used in patents, criminal cases and other areas of law enforcement. The ability to analyze multiphase materials also allows analysis of how materials interact in a particular matrix such as a pharmaceutical tablet, a circuit board, a mechanical weld, a geologic core sampling, cement and concrete, or a pigment found in an historic painting. The method has been historically used for the identification and classification of minerals, but it can be used for any materials, even amorphous ones, so long as a suitable reference pattern is known or can be constructed.

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Ni-doped Effects on Tungsten Copper Electrode II

Details: Category: Tungsten Information; Published on Wednesday, 09 December 2015 16:03; Written by xiaobin; Hits: 244

Except cobalt (Co) element, Nickel (Ni) is also a kind of common additives, and the density, the hardness, the electrical conductivity and other comprehensive properties of tungsten copper electrode will be influenced by the content of Ni. According to the phase diagram of Cu-Ni and Ni-W as follow:

tungsten copper electrode

From the Cu-Ni and Ni-W phase diagram can visually see the nickel (Ni) and copper (Cu) is infinitely miscible, and tungsten W can be dissolved in Ni. Therefore, when tungsten copper composite powder mixed with Ni element, the porosity will decrease and the density and the hardness of tungsten copper electrode is improved. In addition, in the process of sintering, tungsten particles rearranged by the liquid Cu, which shortens the distance among the particles and further enhances the densification. Through SEM (Scanning Electron Microscope), we can find that the particle of skeleton is uniform and the granularity is finer. However, with the increasing content of Ni, the connectivity of tungsten skeleton will be better.

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