MAGNETIC FIELD MODLING DEVICE, DIE AND METHOD FOR MAGNETIC FIELD MOLDING

Abstract

The objects of the present invention are to provide a durable magnetic field molding device for producing molded bodies for ferrite magnets, which needs a controlled amount of releasing agent, reduces production cost and improves productivity, and die and magnetic field molding method. The lower die 12B of the die 12 is coated, on the surface which defines the cavity 11, with the coating film 30 with a high hardness and a low friction coefficient, which improves resistance of the lower die 12B surface to wear by the solid component (fine powder) in the slurry, thereby greatly improving durability of the coating film 30 itself and reducing lubricant usage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows one embodiment of the ferrite magnet production process flow scheme;

FIG. 2 illustrates a magnetic field molding device die structure with a plurality of cavities; and

FIG. 3 is a cross-sectional view illustrating part of a magnetic field molding device.

Claims

1. A magnetic field molding device for producing ferrite magnets, comprising: a die for compression molding of a slurry of a powder mainly composed of ferrite dispersed in a dispersion medium to form a molded body of a given shape, anda magnetic field generating source for applying a magnetic field of a given orientation to the slurry in the die,wherein a die cavity surface is coated, at least partly, with a coating film of a material harder than the powder and lower in friction coefficient than a die base material.

2. The magnetic field molding device according to claim 1, wherein the coating film is at least twice as hard as the powder.

3. The magnetic field molding device according to claim 1 or 2, wherein the coating film has a Vickers hardness Hv of 3,000 or more and a friction coefficient μ of 0.2 or less.

4. The magnetic field molding device according to claim 3, wherein the coating film is made of diamond-like carbon.

5. The magnetic field molding device according to claim 1, wherein the coating film is formed on a portion which forms an inner peripheral surface of the die cavity.

6. A die for producing ferrite magnets, in which a slurry of a powder mainly composed of ferrite dispersed in a dispersion medium is compression-molded to form a molded body of a given shape, comprising: a mortar-shaped die provided with a hole(s) having a cross-section of a given shape,a lower die fit into the mortar-shaped die hole from beneath, andan upper die provided to face the mortar-shaped die,wherein the lower die is coated, on the upper side, with a coating film of a material at least twice as hard as the powder and having a lower friction coefficient than a lower die base material.

7. The die according to claim 6, wherein the coating film has a Vickers hardness Hv of 3,000 or more.

8. The die according to claim 6, wherein the coating film has a friction coefficient μ of 0.2 or less.

9. The die according to claim 6, wherein the coating film is made of diamond-like carbon.

10. The die according to claim 6, wherein the mortar-shaped die is made of a superhard material.

11. The die according to claim 6, wherein the upper die is made of stainless steel.

12. The die according to claim 6, wherein the lower die is made of Stellite® steel.

13. A magnetic field molding method comprising the steps of: injecting a slurry of a powder mainly composed of ferrite dispersed in a dispersion medium into a die coated, at least partly, with a coating film of a material harder than the powder and lower in friction coefficient than a die base material,compressing the slurry in the die, while applying a magnetic field of a given orientation to the slurry, andopening the die to withdraw the resulting molded body, produced by compression-molding of the slurry, from the die.

14. The magnetic field molding method according to claim 13, wherein the coating film is made of diamond-like carbon.

15. The magnetic field molding method according to claim 13, wherein the powder is strontium ferrite and the coating film has a Vickers hardness Hv of 3,000 or more and a friction coefficient μ of 0.2 or less.