Process for manufacturing precious metal artifacts

• US 6,383,248 B1
• Filed: 03/23/2000
• Issued: 05/07/2002
• Est. Priority Date: 09/12/1997
• Status: Expired due to Term

• Current Assignee: Engelhard-Clal UK Limited
• Original Assignee: Engelhard-Clal UK Limited
• Inventors: Hurford, Stephen Paul, Taylor, Terence Ernest
• Primary Examiner(s): MAI, NGOCLAN THI
• Application Number:
  US09/486,270
• Time in Patent Office: 775 Days
• Field of Search: 419/28, 419/29, 419/38, 752/47, 753/31, 753/55
• US Class Current: 75/247
• CPC Class Codes: B22F 2009/0828 with water
• CPC Class Codes: B22F 5/10 of articles with cavities or holes, not otherwise provided for in the preceding subgroups
• CPC Class Codes: B22F 9/082 atomising using a fluid using centrifugal force B22F9/10

Abstract

A wedding ring is manufactured by a process comprising the production of a metal powder by the atomizing of a stream of molten precious metal, for example a gold alloy, the compaction of the metal powder into a hollow cylindrical body, the sintering of the compacted body, optionally the compression of the sintered body into a more toroidal shape, optionally the sintering of the toroidal body and the subjecting of the body to ring-rolling and annealing. The powder that is compacted any also comprise a minor proportion of precious-metal powder obtained by means other than atomization. The process may also be applied to the manufacture of artifacts other than rings by compacting the powder into an appropriate shape and modifying the compressing step, if employed, as appropriate to the intended product; in such embodiments, the ring-rolling step may be replaced by an appropriate step of further modifying the shape and/or dimension of the body. or may be omitted entirely.

Claims

1. A process for the manufacture of an artifact from a precious metal, which process comprises compacting a precious metal powder into a shaped body, wherein at least 80% by weight of the powder has been produced by water atomization of a stream of molten precious metal;

sintering the said body;

thereafter modifying the shape and/or dimensions of the body by a step selected from repressing, forging, and ring-rolling, and thereafter annealing the said body.

2. A process according to claim 1, in which the stream of molten metal is a stream falling from an orifice under gravity.

3. A process according to claim 1, in which the atomizing is effected by impinging at least one jet of water onto the stream of molten metal.

4. A process according to any of claim 1, in which the metal powder is dried before it is compacted.

5. A process according to claim 1, directed to the production of a ring, in which the modifying of the shape and/or dimensions of the body comprises a ring-rolling step.

6. A process according to claim 5, which comprises, between the said sintering step and the ring-rolling step, the further step of repressing the body.

7. A process according to claim 6, in which the repressing step is effected by pressing the body and thereby reducing its height or by compacting, compressing or squashing the body.

8. A process according to claim 6, which comprises, between the said repressing step and the said ring-rolling, the further step of sintering the body.

9. A process according to claim 8, in which the sintering of the shaped body is effected for from 0.25 hour to 2 hours and the step of further sintering is effected for 8 to 120 hours.

10. A process according to any of claim 1, directed to the production of a ring, which comprises compacting the metal powder to form a body of hollow, substantially cylindrical shape, sintering the shaped body, optionally compressing the sintered body in order to reduce its height, rolling the resultant sintered body into a ring, and subjecting the ring to annealing.

11. A process according to claim 10, in which the sintering of the shaped body is effected for from 8 to 120 hours.

12. A process according to claim 9 in which the shaped body is formed by compacting the powder in a die.

13. A process according to claim 9 in which the shaped body is formed by compacting the powder into the form of a tube and subdividing the tube to form a plurality of hollow, substantially cylindrical bodies.

14. A process according to claim 10 in which the shaped body shrinks in height during said sintering.

15. a process according to claim 1, in which the precious metal is gold, an alloy containing gold, silver, an alloy containing silver, platinum, an alloy containing platinum, palladium or an alloy containing palladium.

16. A process according to claim 15, in which the precious metal is an alloy comprising 30% by weight to 92% by weight of gold, or is platinum, or is an alloy containing at least 80% by weight of platinum.

17. A process according to any of claim 1, in which the metal forming the artefact has a porosity of less than 8% by volume.

18. A process according to any of claim 1, in which the metal forming the artefact has a content of oxide (measured as oxygen) of no more than 0.01% by weight of the metal.

19. An artefact whenever manufactured by a process according to any of claim 1.

20. A process according to any preceding claim in which the artefact is a wedding ring.

21. A process according to claim 1, in which the body obtained by the compaction of the powder is sintered and thereafter subjected to forging.

22. A process according to claim 21, in which the forging is effected using a punch of the required profile.

23. A process according to claim 1, in which the body obtained by compaction of the powder is sintered and thereafter subjected to repressing.

24. A process for the production of a ring from a precious metal, which comprises the steps of producing a powder from molten precious metal by water atomisation;

drying the powder under reduced pressure;

compacting the precious metal powder, from which particles coarser than 125 μ

m have been removed, to form a body of hollow, substantially cylindrical shape;

sintering the body under a reducing atmosphere;

rolling the body to form a ring; and

subjecting the ring to annealing.

25. A process according to claim 24 in which, prior to the rolling step, the sintered body is compressed to reduce its height.

26. A process according to claim 25 in which after the sintered body has been compressed to reduce its height and before the rolling step, the body is further sintered under a reducing atmosphere.

27. A process for the manufacture of an artefact from a precious metal, which process comprises producing at least 80% by weight of the precious metal powder by water atomization of a stream of molten precious metal;

compacting the powder into a shaped body, and sintering the said body;

thereafter modifying the shape and/or dimensions of the body by a step selected from repressing, forging or ring-rolling and thereafter annealing the said body.