Carbide testing can be quick and easy if you follow the steps below

1.The first step to carbide testing is to see if your carbide is heavy? It does not take a lot of carbide for the weight to add up. Carbide is much heavier then steel is.  A coffee can full of carbide will weigh around 50 pounds while the same coffee can full of steel would weigh around 25 pounds.

2.Carbide testing with a magnet is very easy. First question is it magnetic? True tungsten carbide has very little attraction to a magnet. You should be able to easily pull the magnet away from the carbide. If your magnet is hard to pull away from the tool it is steel.

3.spark-test:How much does the material spark? If you place a piece of carbide on a grinding wheel the spark will be close together and the spark will be more orange in color. While a piece of steel will spark like a sparkler and the sparks will be whiter.

These three great ways of carbide testing while allow you to be confident in what you have is carbide.

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In recent years, people have pay more and more attention to metal injection molding of refractory metal, which is mainly used to produce parts of complex shape of small size, we call it MIM for short, and its full name is Metal Injection Molding. Under normal circumstances, this type of parts is functional unit under high temperature, and the requirement of high temperature strength and fatigue performance are relatively not so harsh, although this reduces the density requirements, but it achieves a nearly net shape, reducing the machine processing costs. Tungsten, owns the highest melting point at the refractory metals, which is the most widely used lighting electrode material.

The traditional preparation process of tungsten electrodes is showed as bellow: machining the tungsten rod which has been sintered and deformed to give pure tungsten / tungsten alloy electrodes. Because tungsten belongs to rare metal and its machining is difficult, therefore, net forming of tungsten electrodes are more and more paid attention in recent industry. Philips Advanced Metrology Systems Corporation is one of the earlier units to carry out a refractory metal injection molding research and development, the use of MIM to manufacture high-pressure gas discharge lamp with tungsten electrodes, in comparison with conventional tungsten electrode wounded with tungsten wire, MIM can achieve tungsten electrodes with different and complex shapes, which facilitate designers to design its shape according to the function of the electrode.



 

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Pure tungsten and doped tungsten are common anode material, and thorium tungsten, lanthanum tungsten are acting as cathode material. In order to improve the high temperature strength and the recrystallization temperature of tungsten, lanthanum oxide may be employed as the dispersed reinforcing phase. Therefore, lanthanum tungsten electrodes (W - La₂O₃ alloy) are often used as an electrode material. German KIT researchers had adopted tungsten powder with Fisher particle size (1-3 micron) to conduct MIM experiments of lanthanum tungsten electrodes, after sintering at 1600 ℃, then conducting the hot isostatic pressing to obtain basic fully dense parts. The density of lanthanum tungsten electrodes can be improved by increasing the sintering temperature and hot isostatic pressing treatment, but it is often limited by equipment and cost. On one hand, study more granular tungsten powder to do MIM experiment, on the other hand, use Ni as an activating element, studying its effect on the sintering density, and finally successful use of MIM technology to develop a kind of W - 1.5% La₂O₃ electrode with cuppy shape.

Remarks:

1. Fisher particle size: The average particle size of the powder measured by Fisher method. Fisher method is a relative measurement method; we can not accurately determine the true size of powder, it is only used to control the quality processes and products.

2. MIM, namely, Metal Injection Molding, which is a kind of forming method that injecting the plasticized mixture of metal powder and its binder in the model. 

 

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Tungsten has increasingly been applied in aerospace, chemical and nuclear and other fields, it is suitable for welding almost all of metal, especially active metals of refractory metals, nonferrous metals and alloys, titanium and its alloys, stainless steel and high temperature alloys.

Pure tungsten electrodes under high temperature will recrystallize to form equiaxial and coarse grain structure, what will result in the decrease of its mechanical properties. What is more, because the current capacity of pure tungsten is small, the work function (4.52eV) is high, so that the burning would be more serious under large currents. Therefore, the scientists discovered thorium tungsten electrodes material in 1913. Thorium tungsten electrode is the first used electrode in rare earth tungsten electrodes, its good performance and higher market share, what makes it one of the main hot electron emission materials currently, however, thorium element have a radioactive, its half-life grew 1.39 * 10¹⁰, In the production and use processes and its waste will have a great harm to the environment.

In view of this, in the 1970s, the former Soviet Union has started to develop a new type of electrode material, while China factories are almost successful trial-manufacture the cerium tungsten electrodes and make it popularization and application at this time. Thanks to cerium tungsten electrodes themselves own advantages, such as, no radiation pollution, good low-arc arcing performance, so it has become the preferred alternative between the small-diameter welding and low-current welding. However, there are still some limitations in the use of cerium tungsten electrodes, and therefore it can not fully replace the thorium tungsten electrodes.

 

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