MOLTEN SALT DE-OXYGENATION OF METAL POWDERS

• US 20170113273A1
• Filed: 12/02/2015
• Published: 04/27/2017
• Est. Priority Date: 12/02/2014
• Status: Active Grant

• Current Assignee: University of Utah Research Foundation (State of Utah)
• Original Assignee: University of Utah Research Foundation (State of Utah)
• Inventors: Fang, Zhigang Zak, Sun, Pei, Xia, Yang, Zhang, Ying
• Granted Patent: US 10,610,929 B2
• Time in Patent Office: Days
• CPC Class Codes: B22F 1/052 characterised by a mixture of particles of different sizes or by the particle size distribution
• CPC Class Codes: B22F 1/142 Thermal or thermo-mechanical treatment
• CPC Class Codes: B22F 1/145 Chemical treatment, e.g. passivation or decarburisation
• CPC Class Codes: B22F 2201/01 Reducing atmosphere
• CPC Class Codes: B22F 2201/013 Hydrogen
• CPC Class Codes: B22F 2201/11 Argon
• CPC Class Codes: B22F 2301/205 Titanium, zirconium or hafnium
• CPC Class Codes: B22F 2304/10 Micron size particles, i.e. above 1 micrometer up to 500 micrometer
• CPC Class Codes: B22F 2304/15 Millimeter size particles, i.e. above 500 micrometer
• CPC Class Codes: B22F 2998/10 Processes characterised by the sequence of their steps
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B22F 9/20 starting from solid metal compounds
• CPC Class Codes: C22B 1/005 Preliminary treatment of scrap C22B1/02 - C22B1/26 take precedence
• CPC Class Codes: C22B 34/1295 Refining, melting, remelting, working up of titanium
• CPC Class Codes: C22B 9/10 with refining or fluxing agents; Use of materials therefor, e.g. slagging or scorifying agentsC22B9/18 takes precedenceC22B9/006 takes precedence
• CPC Class Codes: C22C 1/04 by powder metallurgy C22C1/08 takes precedence
• CPC Class Codes: C22C 14/00 Alloys based on titanium
• CPC Class Codes: C22C 27/02 Alloys based on vanadium, niobium, or tantalum
• CPC Class Codes: Y02P 10/20 Recycling

Abstract

Methods of removing oxygen from a metal are described. In one example, a method (100) can include forming a mixture (110) including a metal, a calcium de-oxygenation agent, and a salt. The mixture can be heated (120) at a de-oxygenation temperature for a period of time to reduce an oxygen content of the metal, thus forming a de-oxygenated metal. The de-oxygenation temperature can be above a melting point of the salt and below a melting point of the calcium de-oxygenation agent. The de-oxygenated metal can then be cooled (130). The de-oxygenated metal can then be leached with water and acid to remove by-products and obtain a product (140).

Claims

1. A method of removing oxygen from a metal, comprising:

forming a mixture comprising a metal, a calcium de-oxygenation agent, and a salt;

heating the mixture at a de-oxygenation temperature for a period of time in a controlled atmosphere to reduce an oxygen content of the metal to form a de-oxygenated metal, wherein the de-oxygenation temperature is above a melting point of the salt and below a melting point of the calcium de-oxygenation agent; and

cooling the de-oxygenated metal.

2. The method of claim 1, wherein the metal is in a form of powders, milled articles, finished articles, scrap material, turning, cuttings, chips, chunks, or combinations thereof.

3. The method of claim 1, wherein the metal is in the form of a metal powder and has an average particle diameter from about 1 μ

m to 10 mm.

4. The method of claim 1, wherein the metal has an average diameter from about 1 μ

m to 10 cm.

5. The method of claim 1, wherein the metal comprises titanium, zirconium, hathium, thorium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, hydrides thereof, alloys thereof, or combinations thereof.

6. The method of claim 1, wherein the metal comprises titanium.

7. The method of claim 1, wherein the calcium de-oxygenation agent comprises calcium metal, CaH₂, or combinations thereof.

8. The method of claim 1, wherein the controlled atmosphere includes argon and the salt comprises a calcium halide-containing salt.

9. The method of claim 8, wherein the calcium-containing salt further comprises a secondary halide salt of a metal other than calcium.

10. The method of claim 8, wherein the calcium-containing salt is a eutectic mixture with a melting point from about 400°

C. to about 770°

C.

11. The method of claim 1, wherein the controlled atmosphere comprises hydrogen and the salt includes at least one of an alkali metal halide salt, an alkaline earth metal halide salt, a non-alkali halide salt, or combination thereof.

12. The method of claim 11, wherein the salt is non-calcium halide-containing salt including an alkali halide salt, or alkali halide-alkali halide eutectic salt.

13. The method of claim 12, wherein the non-calcium halide-containing salt is selected from the group consisting of potassium halide, lithium halide, magnesium halide, sodium halide, and combinations thereof.

14. The method of claim 1, wherein the calcium de-oxygenation agent is present in an amount such that a molar ratio of calcium atoms in the calcium de-oxygenation agent to oxygen atoms in the metal is from about 1 to 5.

15. The method of claim 1, wherein the de-oxygenation temperature is from about 400°

C. to about 850°

C.

16. The method of claim 1, wherein the controlled atmosphere comprises at least one of argon, hydrogen, and combinations thereof.

17. The method of claim 1, further comprising:

leaching the de-oxygenated metal with water then an acid; and

drying the de-oxygenated metal.

18. The method of claim 17, wherein the drying occurs in air or is freeze dried in vacuum.

19. The method of claim 1, wherein the oxygen content of the de-oxygenated metal is less than about 0.1 wt %.

20. A method of removing oxygen from a metal powder, comprising:

a) mixing a calcium de-oxygenation agent with a metal powder to be de-oxygenated according to a specific ratio depending on an amount of oxygen to be removed to form a powder mixture, wherein the calcium de-oxygenation agent includes at least one of solid calcium (Ca) and calcium hydride (CaH₂);

b) blending the powder mixture with a salt to form a blended mixture, wherein the salt has a melting point below a melting point of the calcium de-oxygenation agent;

c) heating the blended mixture to a high temperature for a period of time, in an inert or reducing atmosphere, sufficient to reduce oxygen content of the metal powder below a predetermined oxygen threshold to form a de-oxygenated metal powder, wherein the high temperature is above a melting point of the salt and below the melting point of the calcium de-oxygenation agent; and

d) cooling the de-oxygenated metal powder.

21. The method of claim 20, wherein the heating is in an inert atmosphere and the salt comprises at least one of calcium halide salt, calcium halide-alkali halide eutectic salt, calcium halide-calcium halide eutectic salt to form a blended mixture.

22. The method of claim 20, wherein the heating is in a reducing atmosphere and the salt comprises at least one of an alkali halide salt, and optionally a non-calcium alkali halide salt.