This requires powders with excellent flow properties to help spread the powder in thin layers before sinning or more precisely welding the shape of the part to be made. The oxygen content is interesting; Although some attempts have been made to use powders dipified with water, gas atomization dominates this field. A very important feature is that the particle size is closely limited to a range that is alternately set to nominal –53 + 20 μm or –45 + 15 μm.
There are several basic processes associated with all atomization methods, such as converting liquid to bulk into a jet or plate and growing disturbances that ultimately lead to the disintegration of the beam or plate into ligaments and then decrease. These processes determine the shape, structure, and penetration of the resulting spray, as well as the detailed characteristics of the drip rate and droplet size distribution. All these characteristics are strongly influenced by the size and geometry of the atomizer, the physical properties of the liquid and the properties of the gaseous medium in which the liquid flow is discharged. The liquid properties that are important in atomization are surface tension, viscosity, and density. Atomization takes place in principle as a result of competition between the stabilizing influences of surface tension and viscosity and the disruptive actions of various internal and external forces.
The drops are produced by the unstable growth of small waves on the surface of the beam caused by the interaction between the beam and the surrounding air. These waves separate from the surface of the beam to form ligaments that break down into boron nitride nozzle drops. The pressure ranges from 20 bar for thicker powders (say 0.3mm) to 200 bar for finer powders (say ~ 50 μm). Elements such as sulfur in the melt have a strong influence on the pressure required by reducing the melting surface tension.
If the pressure drop on the discharge opening is high enough, the jet or release fluid plate will drop in drops. Combustion applications for regular opening atomizers, as shown in Figure 2a, include diesel engines, rockets, and turbojets. In many mass transfer calculations, it is useful to work in terms of average diameters rather than the full drop size distribution.
On the other hand, the atomizing air is consumed during the combustion process. Assuming a stackable oxygen sensor is used to cut off the combustion air in the burner, the mass flow through the incinerator will be less when atomized with air. You may remember that reducing mass flow through the incinerator will increase residence time, which tends to improve waste destruction. It can also increase combustion capacity by increasing the amount of liquid waste that can be incinerated with the same residence time.
The most common chemical powder treatments are oxide reduction, solution precipitation, and thermal decomposition. The powders produced can have a wide variety of properties and still have a closely controlled particle size and shape. Powders reduced in oxide are often characterized as “spongy” due to the pores present in individual particles.
This intensive development has led to the technology being well used to produce powders for HIP, MIM and AM. Air atomization is where both atomization and fusion are performed in the air. Compressed air rays are used to break the molten metal, and cooling is often accomplished by sucking large amounts of cooling air through the equipment.
It is also widely used for Au, Ag, Zn and Cu alloys and for some types of Ni and Co alloys. The oxygen content is highly dependent on alloys, ranging from 500 ppm for some Ni-Cr-B-Si alloys and Cu alloys that automatically dissolve up to 1% for high manganese steel. The shape is generally somewhat irregular, but is strongly influenced by the composition of the alloy and atomization conditions, so apparent densities can vary from just 20% to ~ 50% of the solid. The particle size for steel ranges from ~ 30 μm to 1000 μm, because the rapid extinction of water jets allows larger particles to freeze rapidly.
In combination with the previous analysis, a hypothetical model was constructed to support gas atomized Cu coagulation (60.9 wt.%) / Sn powder. During gas atomization, when the melt was affected by the cold N2, the molten metal was divided into large numbers of unstable fusion films and turned into wavy films under the gas atmosphere . Figure 8a illustrates the phase transformation model based on the flight path .