Metal powder injection molding technology is developed from ceramic powder injection molding technology, it is a new
type of powder metallurgy near net shape technology. Metal powder injection molding technology, production processes
are: metal powder mixed with binder – granulating – injection molding – degreasing – sintering – processing – the final
product. The technology is suitable for mass production of high performance and complex shape of powder metallurgy
parts of small size. Metal powder injection molding technology has extremely high requirement of raw material, it
requires the powder particle size below micron level, nearly spherical shape. In addition, it also has certain requirements
to the apparent density of the powder, rock density, powder length to diameter ratio, natural slope Angle, particle size
distribution.
The current main methods of producing powder are: water atomization method, gas atomization method, carbonyl
method. Water atomization method is the main pulverizing process, its efficiency is high, the mass production is
economy, can make the powder is fine, but the shape is irregular, it is advantageous to the conformal, but the binder
used more, which affects the precision. In addition, the oxide film formed by high temperature reaction of water and
metal interfering with sintering. Gas atomization method is the main method to produce metal powder of technology use,
its production of powder is spherical, oxidation degree is low, needs less adhesive, has good formability. But very fine
powder yield coefficient is low, the price is high, conformality is bad, and the C, N, H, O in binder have influence on
sinter. Carbonyl process produce powder with high purity, stable beginning, granularity superfine powder, it is the best
suited to MIM, but only for Fe and Ni powders, can not meet the requirements of varieties.
In order to meet the requirements of metal injection molding technology use powder, many pulverizing companies
improved the above methods, and developed the micro atomization and laminar atomized powder methods. Now the
often used powder is the mixture of atomized powder and water atomized powder, atomized powder increases the tap
density and water atomized powder maintains the conformalily.
