Coating processes – Particles – flakes – or granules coated or encapsulated – Applying superposed diverse coatings or coating a coated base
Patent
1997-04-14
1999-03-02
Beck, Shrive
Coating processes
Particles, flakes, or granules coated or encapsulated
Applying superposed diverse coatings or coating a coated base
427215, 427216, 427217, 427426, 427427, B05D 700, B05D 106
Patent
active
058767940
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a process for atomizing a dispersible liquid material or a mixture of dispersible liquid materials.
At the present time, most metal powders are manufactured by various atomization processes. The principle underlying these processes is often the same: a liquid metal placed in a distributor is forced through a nozzle to obtain a thin jet which is dispersed in the form of particles by the rapid motion of a gas or of a stream of liquid.
Three classes of atomization processes can be distinguished. According to a first class, the liquid metal, in most cases, is atomized at the time of the casting. In a particular case of the process, the disintegration of the liquid into particles is produced by the mechanical action of a rotating disc, but, in general, the atomization is produced by air, gas, water and under vacuum by bursting of the liquid due to a great pressure difference. Spraying of solid particles has also been mentioned, but so far has been limited to the agglomeration of, or the introduction with, the dispersible liquid material.
Another class of process has been developed a little more recently. This is atomization by centrifugal force which is applied according to two variants: either the melting electrode forms the starting material for obtaining the particles, or the distributor containing the liquid is subjected to a rotation which causes the ejection of the liquid in the form of drops against the cooled walls of a plant, thus enabling a powder to be recovered.
Finally, a last class consists of processes employing ultrasonics, a vibrating electrode and cooled rolls which rotate.
Nevertheless, while the known atomization processes of the state of the art exhibit advantages which are not insignificant, such as, especially, obtaining very dense and homogeneous particles with a good purity and an efficient control of the composition, in most cases they require a number of parameters to be controlled at the same time, which makes the use of the processes difficult.
Thus, the atomization process is determined by the geometry of the system, namely: the diameter of the orifice (and therefore the diameter of the liquid jet), the geometry of the tuyere for injecting the atomizing agent (the stream velocity), the angle formed between the jet and the stream, the path length of the particles and the distance between the jet and the stream. All these constraints require sufficient knowledge of metallurgy in order to gain control and properly monitor the bath of liquid metal.
Furthermore, the atomization of metals presents the problem of transformations which can take place during the rapid cooling of a molten drop. Thus, in the case of some alloys--for example Cu/Pb--a more fusible phase may be situated owing to segregation in the core of the drop. A difference in composition may also appear between the particles of different sizes.
Furthermore, it is sometimes difficult to atomize a metal which is highly reactive to water (for example zirconium) in order to obtain a division in the range from 1 to 25 mm while retaining a solid particle form.
It is also very difficult for lightweight molten materials such as silicon, aluminium and their alloys to enter the water jet, and atomization with water is found to be inefficient. In both these cases it is necessary to resort to techniques of atomization with gas, which technique are sophisticated and costly.
In the case of an atomization using air or gas, the rapid cooling can also result in the occlusion of the gas in the particle. In the case of some alloys, even quenching structures are observed, resulting in the need to reheat the powders before they are shaped.
Finally, the particle size spectrum is generally quite wide, the production of a more uniform particle size requiring very strict control over the processes involved.
SUMMARY OF THE INVENTION
One objective of the present invention is therefore to provide a process for atomizing a dispersible liquid material, which overcomes the disadvantages or limitati
REFERENCES:
patent: 3991225 (1976-11-01), Blouin
patent: 4087572 (1978-05-01), Nimerick
patent: 4407450 (1983-10-01), Chegolya et al.
patent: 4969955 (1990-11-01), Rudin
patent: 5153030 (1992-10-01), Chatfield et al.
Beck Shrive
Chen Bret
LandOfFree
Process for atomizing a dispersible liquid material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for atomizing a dispersible liquid material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for atomizing a dispersible liquid material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-420282