Method of producing atomized powder and method of manufacturing magnetic core

Patent metadata

Field	Value
Publication number	US-11097347-B2
Application number	US-201816497616-A
Country	US
Kind code	B2
Filing date	Mar 23, 2018
Priority date	Mar 27, 2017
Publication date	Aug 24, 2021
Grant date	Aug 24, 2021

Abstract

A method of producing an atomized powder includes: an atomizing step of forming magnetic alloy particles from a molten metal by an atomizing method, to obtain a slurry in which the magnetic alloy particles are dispersed in an aqueous dispersion medium; a slurry concentration step of causing magnetic separation means to separate the magnetic alloy particles from the slurry to form a concentrated slurry having the magnetic alloy particles of more than 80% by mass, the magnetic separation means using a rotary drum including a magnetic circuit part fixedly disposed at a position where at least a part of the magnetic circuit part is immersed in the slurry and an outer sleeve capable of rotating outside the magnetic circuit part; and a drying step of causing drying means using an air flow dryer to dry the concentrated slurry to form a magnetic alloy powder.

First claim

The invention claimed is:

1. A method of producing an atomized powder, the method comprising:
forming magnetic alloy particles from a molten metal by an atomization, to obtain a slurry in which the magnetic alloy particles are dispersed in an aqueous dispersion medium;
a slurry concentration step of causing magnetic separation means to separate the magnetic alloy particles from the slurry to form a concentrated slurry having the magnetic alloy particles of more than 80% by mass, the magnetic separation means using a rotary drum including a magnetic circuit part fixedly disposed at a position where at least a part of the magnetic circuit part is immersed in the slurry and an outer sleeve capable of rotating outside the magnetic circuit part;
a drying step of causing drying means using an air flow dryer to dry the concentrated slurry to form a magnetic alloy powder; and
a concentrated slurry storage step is provided between the slurry concentration step and the drying step, and the concentrated slurry is stirred.

2. The method of producing an atomized powder according to claim 1 , wherein:
a slurry storage stirring device that can cause bubbling to stir the concentrated slurry in the concentrated slurry storage step is used.

3. The method of producing an atomized powder according to claim 2 , wherein:
the slurry storage stirring device includes a container that stores the concentrated slurry;
the container includes an inner body surrounding the concentrated slurry and including a porous body; and
a gas is supplied as fine bubbles to the concentrated slurry through fine pores of the porous body.

4. The method of producing an atomized powder according to claim 1 , wherein a coarse powder removing step of sieving the slurry to form a slurry excluding a coarse powder of the magnetic alloy particles is provided between the forming and the slurry concentration step.

5. The method of producing an atomized powder according to claim 1 , wherein:
a slurry supply path between the forming and the concentration step includes a storage container for storing the slurry; and
the storage container includes stirring means for stirring the slurry.

6. The method of producing an atomized powder according to claim 1 , wherein:
a pump for pumping the slurry is provided in a path between the forming and the concentration step; and
the slurry is constantly supplied to the slurry concentration step by the pump.

7. The method of producing an atomized powder according to claim 1 , wherein the magnetic separation means includes:
a magnetic circuit part including a plurality of magnets fixedly disposed in an arc form;
a magnetic opening part where the magnet is not disposed;
a rotary drum including an outer sleeve capable of rotating outside the magnetic circuit part;
a flow path for causing the slurry to flow in a direction opposite to a rotation direction along an outer periphery of the outer sleeve;
a storage part for storing the slurry to be supplied to the flow path; and
a discharge part that causes a scraper provided in the magnetic opening part to scrape magnetic alloy particles adsorbed to the outer sleeve in the magnetic circuit part with a dispersion medium to obtain a concentrated slurry.

8. The method of producing an atomized powder according to claim 7 , wherein the slurry in the storage part is stirred by stirring means.

9. The method of producing an atomized powder according to claim 1 , wherein the separation means further includes a squeezing roller rotating in contact with the rotary drum.

10. The method of producing an atomized powder according to claim 1 , wherein the method includes classifying the atomized powder after the drying step into a predetermined particle size to perform particle size adjustment.

11. The method of producing an atomized powder according to claim 1 , wherein, in the drying step, the concentrated slurry is dried by drying means using an air flow dryer that causes an air flow to carry and dry the concentrated slurry.

12. The method of producing an atomized powder according to claim 1 , wherein the magnetic alloy contains Fe as a main component and an element M (M is at least one of Si, Cr, and Al) that is more easily oxidized than Fe.

13. A method of manufacturing a magnetic core, the method comprising pressing magnetic alloy particles prepared by the method of producing an atomized powder according to claim 1 as a compact having a predetermined shape.

14. The method of manufacturing a magnetic core according to claim 13 , further comprising annealing the compact at a temperature of 350° C. or higher.

15. The method of manufacturing a magnetic core according to claim 13 , wherein the method includes heat-treating the compact at 650° C. to 900° C. in an atmosphere containing steam or an atmosphere containing oxygen to oxidize the magnetic alloy particles, thereby forming an oxide layer on surfaces of the particles, and causing the oxide layer to form grain boundaries that bind the magnetic alloy particles.

Assignees

• Hitachi Metals Ltd

Inventors

• Nishimura Kazunori
• Noguchi Shin
• Yoshioka Nobuaki

Classifications

• C22C33/0278

  with at least one alloying element having a minimum content above 5% · CPC title

• B03C1/14

  with non-movable magnets · CPC title

• B03C1/247

  obtained by a rotating magnetic drum · CPC title

• C22C38/00

  Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00) · CPC title

• B22F2003/248

  Thermal after-treatment · CPC title