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Preparation Of Metal Powder By Atomization Method

wallpapers Resource 2020-11-25
Metal powder refers to a group of metal particles with a size of less than 1 mm. Including single metal powder, alloy powder and some refractory compound powder with metallic properties, it is the main raw material of powder metallurgy.
The simple substance of metal is generally silver-white. When the metal is under certain conditions, it is black powder. Most metal powders are black.
 
Atomization
 
The molten metal is atomized into fine droplets and solidified into powder in a cooling medium (Figure 3). Figure 4 The widely used two-stream (melt flow and high-speed fluid medium) atomization method uses high-pressure air, nitrogen, argon, etc. (gas atomization) and high-pressure water (water atomization) as the spray medium to break the metal liquid stream . There are also centrifugal atomization methods that use rotating disk pulverization and the rotation of the melt itself (consumable electrode and crucible), as well as other atomization methods such as hydrogen-dissolved vacuum atomization, ultrasonic atomization, etc.

 
Due to the small droplets and good heat exchange conditions, the condensation speed of the droplets can generally reach 100~10000K/s, which is several orders of magnitude higher than during ingot casting. Therefore, the composition of the alloy is uniform, the structure is fine, and the alloy material made with it has no macro-segregation and excellent performance. Gas atomized powder is generally nearly spherical, and water atomization can produce irregular shapes. The characteristics of the powder such as particle size, shape and crystalline structure mainly depend on the properties of the melt (viscosity, surface tension, superheat) and atomization process parameters (such as melt flow diameter, nozzle structure, spray medium pressure, flow rate, etc.) . Almost all metals that can be melted can be produced by atomization, especially suitable for producing alloy powder.
 
This method has high production efficiency and is easy to expand industrial scale. Not only used for mass production of industrial iron, copper, aluminum powder and various alloy powders, but also used to produce high-purity (O2<100ppm) high-temperature alloys, high-speed steel, stainless steel and titanium alloy powders. In addition, the use of chilling technology to produce fast-condensing powders (condensing speed>100,000K/s) has attracted increasing attention. It can be used to produce high-performance microcrystalline materials (see fast cooling microcrystalline alloy).

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