How to produce metal powders

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The first step of powder metallurgy is making metal powders. Powder production process mainly includes four steps: solid state reduction, atomization, electrolysis and chemical methods.

Solid state reduction

In the powder reduction process, the selected ore will be crushed firstly; afterwards, it will be mixed with the reducing material (such as carbon) and will be transferred to the continuous oven. The mixture will react in the furnace and will leave behind lanose metal; afterwards, smashing the mixture and separating it from all the non-metallic materials, screening and producing the powders. As there is no refining processing, the powder purity mainly depends on the raw materials. Irregular and lanose particles are soft and easy to compress, which will have good presintering strength.

Atomization

In this process, molten metal will be divided into droplet and will rapidly freeze before mutual contact or contacting with solid. Under general conditions, molten metal film flow will be resolved by the influence of high-energy jet of gas or liquid. In principle, this technology can apply to all molten metal and can be used in the commercial production of iron, copper, alloy steel, brass, bronze and low melting point metals, such as aluminum, tin, lead, zinc, cadmium as well as tungsten, titanium, rhenium and other high melting point materials under certain conditions.

metal powder productsElectrolysis

By choosing appropriate conditions, such as electrolyte composition, concentration and temperature as well as electric current density, many metals can be stored in the forms of lanose and powder. After further disposal, washing, drying, reduction, annealing and crushing, high purity and high density powder will be generated eventually. Copper is a kind of primary metal that is produced by electrolysis, but iron powder, cadmium powder and magnesium powder can also be produced by this method. Due to its high energy costs, electrolysis is usually limited to powders of high value, such as cooper powder that has high electrical conductivity.

Chemical methods

The most common chemical powder processing methods involve oxidation-reduction reaction, precipitation and thermal decomposition in the solution. The performances of powders that produced by these methods will vary a lot, but the powder particle size and shape are almost the same. Oxidation-reduction powders usually appear to be “sponge” shape as there are many pores in the particles. Solution precipitation powder often has narrow size distribution and high purity. Thermal decomposition is most commonly used in processing metal carbonyl compound. After grinding and anneal, the purity of the above mentioned powders will exceed 99.5 percents.