Methods of metal powders production

Methods and Plant for Centrifugal - Hydraulic (CH) and Centrifugal - Pneumatic (CP) Atomizing. Amorphous Powders

The CHA and CPA methods are realized using a centrifugal nozzle which is shown schematically in Figure 1. Melt 1 is fed under the excess pressure of an inert gas to tangential channel 2 and then to swirling chamber 3 of the centrifugal nozzle. The melt is spinned in the channel and the swirling chamber and subsequently is directed to confuser 4, where the rotational component of the melt velocity further increases.

The melt comes to the atomizing coloumn through nozzle 5 in the form of a spinning hollow stream which widens under the action of centrifugal forces and transforms into thinning conical film 6. The film is unstable and desintegrates into fine droplets. Capacity of the CHA process is 100 to 1000 kg of powder or granules per hour. Gas consumption is on the average 0.005 nm per 1 kg of the product. The mean dimension of the powder particles is adjastable within 60 to 1000 mkm. The CHA method realized either in vacuum or in an inert gas medium.

If the melt and a gas under pressure are tangentially fed at a time to the swirling chamber, the so-called method of centrifugal-pneumatic atomizing (CPA) is realized. This method ensures production of powders with the mean dimension of particles from 10 to 60 mkm, capacity of 20...60 kg/h, and gas consumption no to exceed 0.05 nm/h.

The CHA method can be used efficiently for production of quick-hardened powders with amorphous or mycrocrystalline structure. Such powders provide fro production of materials featuring high service properties. The prduction scheme of these powders is given on the Figure 2. The melt 1 is force fed from the crucible to centrifugal nozzle 2 and is atomized to from droplets 3. The droplets get to rotating cooled crystallizer 4, where the droplets are hardened at a rate of 105 107 K/s and a powder with flaky shape particles is formed. The plant is capable of producing over 50 kg of quick-hardened powder per hour. The mean particel dimension is 0.75 to 2 mm.

Figure 1
Figure 2