PRODUCTION OF PURE, SPHERICAL POWDERS

• US 3,802,816 A
• Filed: 06/22/1972
• Issued: 04/09/1974
• Est. Priority Date: 06/22/1972
• Status: Expired due to Term

• Current Assignee: Albert R. Kaufmann
• Original Assignee: Albert R. Kaufmann
• Inventors: Kaufmann, Albert R.
• Primary Examiner(s): Spicer, Jr., Robert L.
• Application Number:
  US05/265,360
• Time in Patent Office: 656 Days
• Field of Search: 425/6,8 264/8,27
• US Class Current: 425/8
• CPC Class Codes: B22F 2009/084 combination of methods
• CPC Class Codes: B22F 9/06 starting from liquid material
• CPC Class Codes: B22F 9/14 using electric discharge

Abstract

Generally spherical metallic powder of small size is produced in large quantities by extending a long bar of the material to be processed into a closed chamber through a sealed port, rapidly rotating the bar while striking an arc between it and a stationary electrode to melt portions of the bar and cast off these portions by centrifugal force to form the powder, and axially feeding the bar toward the electrode during consumption to maintain a fixed spark gap. When the bar is nearly fully consumed, it is replaced without opening the chamber simply by aligning a second bar with the unconsumed portion of the first bar and axially advancing this second bar into the chamber through the sealed port. A unique seal capable of withstanding high rotational speeds seals the chamber while a dynamic rest restrains the bar from '"'"''"'"''"'"''"'"'whipping.

Claims

1. Apparatus for producing relatively pure, generally spherical metallic powder comprising:

A. a chamber for maintaining a conrolled atmosphere therein, B. means introducing a first electrode into said chamber, C. a port communicating between the interior and exterior of said chamber and adapted to receive a second, rotating, consumable electrode extending therethrough, D. means external to said chamber for receiving one end of said second electrode therein and for rotating said electrode at a speed sufficient to cast off melted droplets therefrom, while simultaneously advancing said electrode into said chamber, and E. means for striking an electrical arc between said first electrode and the other end of said second electrode to thereby melt portions of said second electrode.

2. Apparatus according to claim 1 which includes means for restraining the eccentric rotation of said second electrode at a position adjacent said port whereby the load on said seal due to said rotation is minimized.

3. Apparatus according to claim 2 in which said second electrode is generally cylindrical in shape and is rotated along the major axis of said cylinder, and in which the means for restraining said eccentric rotation comprises a plurality of rotatable cylindrical plates circumferentially spaced apart from each other and in peripheral contact with said electrode adjacent said port.

4. Apparatus according to claim 1 in which said port includes a seal conformable to said second electrode for isolating the interior of said chamber from the exterior thereof.

5. Apparatus according to claim 4 in which said seal includes a first stationary collar, a rotatable collar mounted in said stationary collar and having an aperture for receiving said second electrode therethrough along a longitudinal axis thereof, the rotatable collar and the second electrode being rotatable with each other, a wearable low friction surface positioned in a plane normal to said longitudinal axis and abutting said rotary collar, and means for holding said low friction surface against said rotary collar to provide a seal therewith.

6. Apparatus according to claim 5 in which the aperture in rotatable collar is adapted to receive at least one resilient sealing element for sealing the clearance between the second electrode and the rotatable collar to thereby isolate the interior of the chamber from the exterior thereof.

7. Apparatus according to claim 1 which includes means to advance said second electrode toward said first electrode to thereby maintain said electrodes in arc supporting relation.

8. Apparatus according to claim 1 in which the means for receiving a second electrode therein comprises a chuck into which said electrode is releasably inserted and connected in driving relation with a motor for rotation thereby.

9. Apparatus according to claim 8 in which said chuck is mounted for translational motion toward said chamber at a controlled rate whereby said bar is simultaneously translated and rotated durig the powder-making operation.

10. Apparatus for producing powder from a bar of consumable material, comprising:

A. a chamber for maintaining a controlled atmosphere therein, B. means introducing a nonconsumable electrode into said chamber, C. a port in said chamber adapted to maintain a seal around a consumable electrode extending from the exterior of the chamber to the interior thereof along a longitudinal axis of said seal, D. means adjacent said seal for restraining a first end of the consumable electrode from eccentric rotation about said longitudinal axis, E. means external to said chamber for mounting a second end of the consumable electrode for rotation about said longitudinal axis at a speed sufficient to cast off melted droplets from the exterior of said electrode under the action of centrifugal force, the mounting means being positionable sufficiently far from the restraining means to accommodate therein an electrode having a length of the order of magnitude of the shortest critical length of the consumable electrode when rotated at the selected speed, F. means for translating the consumable electrode along the longitudinal axis of said seal and into said chamber at a controlled rate to thereby maintain the electrodes in arc-supporting relation.

11. Apparatus according to claim 10 in which the mounting means and the restraining means are positionable sufficiently far apart to accommodate a consumable electrode of at least 30 inches in length.

12. Apparatus according to claim 10 adapted to form powder of less than 500 microns in diameter from generally cylindrical bar stock at least 1.0 inches in diameter and 30 inches in length.

13. Apparatus for producing relatively pure, generally spherical metallic powder comprising:

A. a chamber for maintaining a controlled atmosphere therein;

B. means introducing a first energy source into said chamber;

C. a port communicating between the interior and exterior of said chamber and adapted to receive a rotating, consumable bar extending therethrough;

D. means external to said chamber for receiving one end of said bar therein and for rotating said bar at a speed sufficient to cast off melted droplets therefrom, and E. means for advancing said bar into said chamber at a controlled rate for maintaining said energy source and said bar in energy absorbing relation during rotation of said bar to thereby melt portions of said bar and cast them off in the form of spherical droplets by centrifugal force.

14. Apparatus according to claim 13 in which the bar is initially characterized by a length-to-diameter ratio such that the frequency at which the bar is rotated in producing powder is in excess of the frequency at which the bar, when supported only at one end thereof, would deviate from the longitudinal axis by an amount greater than the radius of the bar.