Specialized metallurgical processes – compositions for use therei – Processes – Electrothermic processes
Patent
1988-05-16
1989-12-12
Rutledge, L. Dewayne
Specialized metallurgical processes, compositions for use therei
Processes
Electrothermic processes
425 6, 75 1023, B22F 300
Patent
active
048865478
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus for manufacturing a metal powder used in powder metallurgy or the like and a method for the same.
BACKGROUND ART
Powder metallurgy is a technique for manufacturing a metal product or ingot by charging a metal or alloy powder into a mold, pressure-molding the powder, and sintering the molded product. Powder metallurgy is advantageous in that segregation of components does not occur, a product can be obtained from a material difficult to work, a member having a very fine crystal structure can be obtained, secondary machining can be omitted, and the like. These advantages cannot be obtained using a technique for manufacturing a metal product or ingot by melting a metal.
Three typical methods of manufacturing a powder of a high alloy, a Ti alloy, and the like will be described.
A. R. Cox, J. B. Moore, E. C. Van Reuth; Int. Symp. Superalloys, 3rd discloses a technique in which a metal is melted in a container by an RF current, the molten metal is dropped onto a disk rotated at a high speed, the dropped molten metal is scattered by a centrifugal force, and the scattered metal particles are rapidly solidified with a cooling medium having a high thermal conductivity such as hydrogen gas and helium gas.
G. Friedman; AGARD Conf. Proc., (1976) SCI discloses a technique in which an arc is generated between a nonconsumable electrode and a consumable electrode rotated at a high speed, the metal droplets generated by the molten consumable electrode are scattered by a centrifugal force, and the scattered metal droplets are cooled, thereby obtaining a metal powder.
H. Schmit; Powder Metall. Int. 11(1976) 1, p17 discloses a technique in which an arc is generated between a water-cooled crucible and an electrode to thermally melt the distal end portion of the electrode by the heat of the arc, the molten droplets dripped into the crucible being rotated at a high speed to scatter and cool them, thereby manufacturing a powder.
In the method of A. R. Cox, since the molten metal is reserved in the container, impurities can be mixed in the molten metal from the container. Therefore, a high-purity powder cannot be manufactured.
In the method of G. Friedmean, since the droplets are scattered by the centrifugal force obtained by the rotating consumable electrode, when a powder having a small particle size is to be obtained, the consumable electrode must be rotated at a high speed. However, it is quite difficult to rotate the electrode at a high speed because of the electrode machining precision and an electrode rotating mechanism. When the diameter of the electrode is decreased, the electrode can be rotated at a high speed. In this case, however, the lot scale is decreased, and electrode manufacturing costs per unit volume become expensive
In the method of G. Schmit, since the rotating crucible also serves as the nonconsumable electrode, it must be rotated at a high speed while it is energized. This is quite difficult because of the crucible machining precision and the crucible rotating mechanism. This problem becomes conspicuous when a metal powder having a small particle size is to be obtained because in this case a higher speed of rotation is needed.
DISCLOSURE OF INVENTION
It is a first object of the present invention to provide a powder manufacturing apparatus which can manufacture a high-purity powder which is used in a product made of a high alloy, Ti, a Ti alloy, a superalloy, and the like with a high productivity, and a method for the same.
It is a second object of the present invention to manufacture the above powder at a low cost.
It is a third object of the present invention to provide a powder manufacturing apparatus for reliably manufacturing a powder having a desired particle size, and particularly a small particle size, and a method for the same.
It is a fourth object of the present invention to provide a powder manufacturing apparatus wherein metal droplets are stably formed and are constantly dropped at a predetermined position, and a method for the
REFERENCES:
patent: 2189387 (1940-02-01), Wissler
patent: 2310590 (1943-02-01), Marette
patent: 2897539 (1959-08-01), McMillan
patent: 3829538 (1974-08-01), Darmara et al.
patent: 3887667 (1975-06-01), Clark
patent: 4374075 (1983-02-01), Yolton et al.
patent: 4610718 (1986-09-01), Araya et al.
On the Rapid Solidificatiion of Superalloys, A.R. Cox, L. B. Moore, E. C. van Reuth.
Mathematical-Physical Considerations Regarding the Production of Metal Powders for Powder Metallurgy (Part I)-H. Schmitt.
G. Friedman, AGARD Conf. Proc. (1976) SCI pp. 1-2 to 1-5.
Fujioka Tadashi
Kawawa Takaho
Mizukami Hideaki
Mori Kentaro
Nakagawa Hirotaka
Nippon Kokan Kabushiki Kaisha
Rutledge L. Dewayne
Schumaker David
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