Metal powder, green compact and production method thereof

Abstract

A metal powder becoming a raw material for obtaining a green compact by compacting, the metal powder having a plurality of accessible surfaces allowing for surface contact of adjacent metal powders with each other when filled, and a method for producing a green compact by compacting the metal powder, the method comprising the steps of: a charging step of charging the metal powder into a predetermined die, a compacting step of filling the metal powder in the die, and a compacting step of compacting the metal powder to obtain the green compact.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view showing the metal powder in Example 1,

FIG. 2 is cross-sectional enlarged view showing the surface of the metal powder in Example 1,

FIG. 3 is a cross-sectional enlarged view showing the surface of the metal powder in Example 1,

FIG. 4 is an explanatory view showing the filled state of the metal powder in Example 1,

FIG. 5 is an explanatory view showing the green compact in Example 1,

FIG. 6 is an explanatory view showing the metal powder having other shape in Example 1,

FIG. 7 is an explanatory view showing the metal powder having other shape in Example 1,

FIG. 8 is an explanatory view showing the metal powder having other shape in Example 1,

FIG. 9 is an explanatory view showing the gear part (sprocket) in Example 2,

FIG. 10 is an explanatory view showing the pump part (rotor) in Example 2,

FIG. 11 is an explanatory view showing the powder for powder magnetic cores in Example 3,

FIG. 12 is a cross-sectional enlarged view showing the surface of the powder for powder magnetic cores in Example 3,

FIG. 13 is a cross-sectional enlarged view showing the surface of the powder for powder magnetic cores in Example 3,

FIG. 14 is an explanatory view showing the filled state of the powder for powder magnetic cores in Example 3, and

FIG. 15 is an explanatory view showing the powder magnetic core in Example 3.

Claims

1. A metal powder as a raw material for obtaining a green compact by compacting, said metal powder having a plurality of accessible surfaces allowing for surface contact of adjacent metal powders with each other when filled.

2. The metal powder as claimed in claim 1, wherein the total area of said accessible surfaces is 70% or more of the entire surface area of said metal powder.

3. The metal powder as claimed in claim 1, wherein said metal powder has any one shape of an approximate cube, an approximate rectangular parallelepiped, an approximate triangular pyramid and an approximate quadrangular pyramid and said accessible surface of said metal powder has any one shape of an approximate square, an approximate rectangle and an approximate triangle.

4. The metal powder as claimed in claim 3, wherein one side of said metal powder has a length of 10 to 500 μm.

5. The metal powder as claimed in claim 1, wherein assuming that the tap density of said metal powder is A and the density of said metal powder is B, the tapped filling rate represented by (A/B)×100(%) is 60% or more.

6. The metal powder as claimed in claim 1, wherein said metal powder has fine irregularities on the surface and the depth in the concave part of said irregularities is 10% or less of the outermost diameter of said metal powder.

7. The metal powder as claimed in claim 6, wherein the depth of said concave part is from 1 to 50 μm.

8. The metal powder as claimed in claim 1, wherein said metal powder is any one metal of Fe type, Fe—Al type, Fe—Si type, Fe—Al—Si type, Fe—Co type and Fe—Ni type.

9. The metal powder as claimed in claim 1, wherein said metal powder is a powder for powder magnetic cores, with the surface being coated with an insulating film.

10. The metal powder as claimed in claim 9, wherein said metal powder has an outermost diameter of 500 μm or less.

11. The metal powder as claimed in claim 9, wherein the thickness of said insulating film is from 10 to 1,000 nm.

12. The metal powder as claimed in claim 9, wherein said insulating film is a ceramic film, a resin film or a mixed film of ceramic and resin.

13. The metal powder as claimed in claim 12, wherein said ceramic film comprises at least one or more members selected from the group consisting of alumina, silica, magnesia, zirconia, titania, boron nitride and silicon nitride.

14. The metal powder as claimed in claim 12, wherein said resin film comprises at least one or more member(s) selected from the group consisting of a silicone resin, a polyimide resin, a polyphenylene sulfide resin, a phenol resin, a polyether ketone-based resin, a silicone resin and a silane coupling agent.

15. A method for producing a green compact by compacting the metal powder claimed in claim 1, said method comprising: a charging step of charging said metal powder into a predetermined die,a filling step of filling said metal powder in said die, anda compacting step of compacting said metal powder to obtain said green compact.

16. The method for producing a green compact as claimed in claim 15, wherein in said filling step, said metal powder is filled by vibrating said die.

17. The method for producing a green compact as claimed in claim 16, wherein in said filling step, said die is vibrated by using an ultrasonic generator.

18. The method for producing a green compact as claimed in claim 15, wherein said metal powder is a powder for powder magnetic cores, with the surface being coated with an insulating film, and assuming that the surface area of said metal powder before said compacting step is S1 and the surface area after said compacting step is S2, the value of (S1−S2)/S1 is 0.2 or less.

19. A green compact produced by the method claimed in claim 15.

20. The green compact as claimed in claim 19, wherein said green compact has a relative density of 95% or more.

21. The green compact as claimed in claim 19, wherein said green compact is a powder magnetic core obtained by compacting a powder for powder magnetic cores, which is said metal powder with the surface being coated with an insulating film and has a density of 7.4 Mg/m3 or more.

22. The green compact as claimed in claim 21, wherein said green compact has a saturation magnetic flux density of 1.6 T or more.