초록 ▼

A method of manufacturing magnetic powder is disclosed. This method can provide magnetic powder from which a bonded magnet having excellent magnetic properties and reliability can be manufactured. A melt spinning apparatus 1 is provided with a tube 2 having a nozzle 3 at the bottom thereof, a coil 4

A method of manufacturing magnetic powder is disclosed. This method can provide magnetic powder from which a bonded magnet having excellent magnetic properties and reliability can be manufactured. A melt spinning apparatus 1 is provided with a tube 2 having a nozzle 3 at the bottom thereof, a coil 4 for heating the tube and a cooling roll 5. The cooling roll 5 is constructed from a roll base 51 and a circumferential surface 53 in which gas flow passages 54 for expelling gas are formed. A melt spun ribbon 8 is formed by injecting the molten alloy 6 from the nozzle 3 so as to be collided with the circumferential surface 53 of the cooling roll 5, so that the molten alloy 6 is cooled and then solidified. In this process, gas is likely to enter between a puddle 7 of the molten alloy 6 and the circumferential surface 53, but such gas is expelled by means of the gas flow passages 54. The magnetic powder is obtained by milling thus formed melt spun ribbon 8. In this method, when the average pitch of these gas flow passages 54 is defined as Pμm and the average particle size of the magnetic powder is defined as Dμm, the relationship represented by the formula P<D is satisfied.

대표청구항 ▼

1. A magnetic powder which is manufactured by milling a ribbon-shaped magnetic material which has been obtained by colliding a molten alloy of a magnetic material to a circumferential surface of a rotating cooling roll so as to cool and then solidify it, comprising:a plurality of particles, each par

1. A magnetic powder which is manufactured by milling a ribbon-shaped magnetic material which has been obtained by colliding a molten alloy of a magnetic material to a circumferential surface of a rotating cooling roll so as to cool and then solidify it, comprising:a plurality of particles, each particle including: an average particle size Dμm in the range of 10-20 μm; a plurality of ridges and recesses, each ridge and recess having an average pitch in the range of 3-50 μm, a length of D/30 μm and an average depth or height in the range of 0.3-μm; and a composite structure composed of a hard magnetic phase and a soft magnetic phase, each of the hard and soft magnetic phases having an average crystal grain size in the range of 1-100 mn; wherein the cooling roll is formed with gas flow passages as gas expelling means defined by a plurality of grooves for expelling gas entered between the circumferential surface and a puddle of the molten alloy in the circumferential surface thereof, a width of the grooves preventing the molten alloy from fully entering the grooves; and when an average pitch of these gas flow passages is defined as Pμm and the average particle size of the magnetic powder is defined as Dμm, a relationship represented by a formula P<D is satisfied. 2. The magnetic powder which is manufactured according to the manufacturing method as defined in claim 1.3. The magnetic powder as claimed in claim 2, wherein a ratio of an area of a portion of the particle where the ridges or recesses are formed with respect to a total surface area of the particle is equal to or greater than 15%.4. The magnetic powder as claimed in claim 1, wherein the magnetic powder is subjected to at least one heat treatment during or after the manufacturing process thereof.5. A bonded magnet which is manufactured by binding the magnetic powder defined in claim 1 with a binding resin.6. A bonded magnet which is manufactured by binding the magnetic powder defined in claim 2, with a binding resin, wherein the binding resin enters between the ridges or into the recesses.7. The bonded magnet as claimed in claim 5, wherein the bonded magnet is manufactured by a warm molding.8. The bonded magnet as claimed in claim 5, wherein an intrinsic coercive force (HCJ) of the bonded magnet at room temperature lies within a range of 320-1200 kA/m.9. The bonded magnet as claimed in claim 5, wherein a maximum magnetic energy product (BH)max of the bonded magnet is equal to or greater than 40 kJ/m3.10. The bonded magnet as claimed in claim 5, wherein a content of the magnet powder contained in the bonded magnet is in a range of 75 to 99.5 wt %.11. The bonded magnet as claimed in claim 5, wherein a mechanical strength of the bonded magnet which is measured by the shear strength of the bonded magnet which is measured by the shear strength of a punching-out test is equal to or greater than 50 MPa.12. A magnetic powder comprising:a plurality of particles, each particle including: an average particle size Dμm in the range of 10-20 μm; a plurality of ridges and recesses, each ridge and recess having an average pitch in the range of 3-50 μm;, a length of D/30 μm, and an average depth or height in the range of 0.3-5 μm; and a composite structure composed of a hard magnetic phase and a soft magnetic phase, each of the hard and soft magnetic phases having an average crystal grain size in the range of 1-100 μm.