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Tungsten Maintain Good Hardness
Oct 12, 2017

Tungsten and its alloys are widely used in electronics, electric light industry. For the manufacture of a variety of lighting bulbs, tube filament is used with anti-sagging properties of doped tungsten wire.

Doped tungsten wire is added rhenium. The thermocouple made of tungsten rhenium alloy wire with low rhenium content and tungsten rhenium alloy wire with high rhenium content has a wide temperature range (0 ~ 2500 ℃), the linear relationship between temperature and thermoelectromotive force is good. Temperature reaction speed (3 seconds), the price is relatively cheap, is measured in the hydrogen atmosphere of the ideal thermocouple.

Tungsten wire not only triggered a revolution in the lighting industry, but also because of its high melting point, without losing its mechanical integrity under the premise of becoming a kind of electronic thermionic emitters, such as scanning electrons (sub- Mirror and transmission electron (sub-microscopic) mirror of the electron source. Also used as a filament for an X-ray tube. In an X-ray tube, the electrons produced by the tungsten wire are accelerated to strike the tungsten and tungsten rhenium alloy anodes and emit X-rays from the anode. The energy of the electron beam produced by the tungsten filament is very high for the generation of X-rays, Tungsten so that the spots on the surface of the electron beam collide are very hot, so that the rotary anode is used in most X-ray tubes.

The tungsten has a density of 19.25 g / cm3, about 2.5 times that of iron (7.87 g / cm3), which is one of the heaviest metal elements in the cycle. A high-density tungsten alloy (i.e., high specific gravity tungsten alloy) made from this characteristic of tungsten has become an important application area for tungsten. The use of liquid phase sintering process, in the tungsten powder at the same time by adding nickel, iron, copper and a small amount of other elements, can be made of high-density tungsten alloy. According to the different components, high-density tungsten alloy can be divided into tungsten-nickel-iron and tungsten-nickel-copper alloy system. Through the liquid phase sintering, the density of up to 17 ~ 18.6 g / cm 3. The so-called liquid phase sintering is the mixed powder compact at the sintering temperature of a certain amount of liquid phase sintering process. The advantage is that the liquid phase moisturizes the solid particles and dissolves a small amount of solid matter, greatly accelerating the process of densification and grain growth and achieving a very high relative density. For example, in the case of nickel iron powder, which is usually used in the liquid phase sintering, Tungsten the nickel iron powder melts when sintering proceeds. Tungsten Although the solubility of liquid ferronium in the solid tungsten (95% of the body fraction) is minimal, the solid tungsten is easily dissolved in liquid nickel iron. Once the liquid nickel iron moistens the tungsten particles and dissolves a portion of the tungsten powder, the tungsten particles change the shape, and the internal pores disappear immediately when the stream enters. The process continues, the tungsten particles are coarsening and growing, resulting in a final product that is close to 100% dense and has the best microstructure.

Tungsten carbide at 1000 ℃ above the high temperature can still maintain good hardness, cutting, grinding the ideal tool. 1923 Germany Schroeer (Schroter) is the use of this feature of WC was invented WC-Co cemented carbide. As WC-Co cement as cutting tools and stretching, stamping die has brought great business opportunities, and soon in 1926 ~ 1927

Year will achieve the industrial production. Simply put, Tungsten the first tungsten powder (or W03) and carbon black mixture in hydrogen or vacuum in a certain temperature carbonization, that is made of tungsten carbide (WC), and then WC and metal binder cobalt according to a certain proportion of ingredients , After milling, molding, sintering and other processes, made of tools, molds, rolls, impact drill bit and other carbide products.

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