U.S. patent application number 11/718312 was filed with the patent office on 2009-03-05 for manufacture method of ndfeb isotropic and anisotropic permanent magnets.
Invention is credited to Ju Won Jeon, Hyoung Tae Kim, Yoon Bae Kim, Jang Seok Son.
Application Number | 20090060773 11/718312 |
Document ID | / |
Family ID | 36228049 |
Filed Date | 2009-03-05 |
United States Patent
Application |
20090060773 |
Kind Code |
A1 |
Kim; Hyoung Tae ; et
al. |
March 5, 2009 |
Manufacture Method of NDFEB Isotropic and Anisotropic Permanent
Magnets
Abstract
A fabrication method of isotropic and anisotropic NdFeB type
permanent magnets is disclosed. In the a fabrication method of
isotropic and anisotropic NdFeB type permanent magnets, the
isotropic and anisotropic NdFeB type permanent magnets can be
easily manufactured by means of Joule's heat using a self
resistance of a powder molded body by directly applying a DC
(Direct Current) to the upper and lower punches and the powder
molded body, without using external heating elements or high
frequency coils and so on, during press molding of the permanent
magnet powder using the punches, and it is simple in terms of
structure during the fabrication thereof, so that the manufacturing
cost is low.
Inventors: |
Kim; Hyoung Tae; (Daejeon,
KR) ; Kim; Yoon Bae; (Daejeon, KR) ; Son; Jang
Seok; (Gyeonggi-do, KR) ; Jeon; Ju Won;
(Jeonbuk, KR) |
Correspondence
Address: |
PARK LAW FIRM
3255 WILSHIRE BLVD, SUITE 1110
LOS ANGELES
CA
90010
US
|
Family ID: |
36228049 |
Appl. No.: |
11/718312 |
Filed: |
October 28, 2005 |
PCT Filed: |
October 28, 2005 |
PCT NO: |
PCT/KR05/03608 |
371 Date: |
June 11, 2007 |
Current U.S.
Class: |
419/52 |
Current CPC
Class: |
B22F 3/14 20130101; B22F
2999/00 20130101; B22F 2999/00 20130101; B22F 3/14 20130101; B22F
3/105 20130101; C22C 1/0441 20130101; H01F 1/0576 20130101; H01F
41/0266 20130101 |
Class at
Publication: |
419/52 |
International
Class: |
B22F 3/14 20060101
B22F003/14 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 28, 2004 |
KR |
10-2004-0086815 |
Oct 28, 2004 |
KR |
10-2004-0086816 |
Claims
1. A fabrication method of an isotropic NdFeB type permanent
magnet, comprising the steps of: putting a powder molded body of a
freeform type, in which a NdFeB type powder is compression molded
in normal temperature, into a graphite mold; adhering and fixing
the powder molded body to upper and lower punches located at upper
and lower parts thereof; applying a DC of 500-3,000 A/cm.sup.2 to
the upper and lower punches, whereby generating a resistance heat
of 700-800.degree. C. into the powder molded body; applying a
pressure of 10-150 Mpa to the upper and lower punches; and cooling
the isotropic permanent magnet, in which the powder molded body is
contracted in the pressure direction of the upper and lower
punches.
2. The method as claimed in claim 1, wherein the isotropic
permanent magnet, in which the powder molded body is contracted in
the pressure direction of the upper and lower punches, is cooled in
normal temperature.
3. The method as claimed in claim 1, wherein a material of the mold
for fixing the powder molded body is a metal or ceramic.
4. A fabrication method of an anisotropic NdFeB type permanent
magnet, comprising the steps of: adhering and fixing a molded body
of an isotropic permanent magnet between upper and lower punches;
applying a DC of 500-3,000 A/cm.sup.2 to the upper and lower
punches, whereby generating a resistance heat of 700-800.degree. C.
into the molded body; and applying a pressure of 50-200 Mpa to the
upper and lower punches, whereby contracting the molded body in the
pressure direction of the upper and lower punches and expanding the
molded body perpendicularly to the pressure direction of the upper
and lower punches.
Description
TECHNICAL FIELD
[0001] The present invention relates to a fabrication method of
isotropic and anisotropic NdFeB type permanent magnets, and more
particularly to a fabrication method of isotropic and anisotropic
NdFeB type permanent magnets in which the isotropic permanent
magnets is manufactured in such a manner that a powder molded body
of a freeform type, in which a NdFeB type powder based on
Nd.sub.2Fe.sub.14B ferromagnetic phase is compression molded in
normal temperature, is putted into a graphite mold, predetermined
pressure and electric current are applied to the powder molded body
through upper and lower punches, and the powder molded body is
contracted in the pressure direction, and the anisotropic permanent
magnet is manufactured in such a manner that an isotropic permanent
magnet molded body is adhered and fixed between upper and lower
punches, the isotropic permanent magnet molded body is heated by
applying a DC to the upper and lower punches, a predetermined
pressure is applied to the upper and lower punches, and the molded
body is contracted in the pressure direction of the upper and lower
punches and expanded perpendicularly to the pressure direction of
the upper and lower punches, whereby the isotropic and anisotropic
NdFeB type permanent magnets can be easily manufactured by means of
Joule's heat using a self resistance of a powder molded body by
directly applying a DC (Direct Current) to the upper and lower
punches and the powder molded body, without using external heating
elements or high frequency coils and so on, during press molding of
the permanent magnet powder using the punches, and it is simple in
terms of structure, during the fabrication thereof, so that the
manufacturing cost is low.
BACKGROUND ART
[0002] Generally, a manufacturing process of a permanent magnet
includes a hot process for manufacturing an isotropic magnet (see
FIG. 1) and a hot deformation process for manufacturing an
anisotropic magnet, in which the isotropic magnet manufactured by
the hot process is compressed and transformed in high temperature
and pressure as shown in FIG. 2.
[0003] However, since the hot process and hot deformation process
are performed in a high temperature of about 700.degree. C. and a
high pressure over 1 ton/cm.sup.2, it is necessary to raise the
temperature by winding heater coils 40 into a vessel containing a
powder 10, or to make a desired temperature circumstance and apply
a high pressure by placing high frequency coils 40 at the periphery
of a mold, so that it is extremely restricted to use a graphite
mold having a small strength. Also, because it is impossible to use
a molding aid of a special material, the material of the mold must
use a metal or ceramic. Moreover, in a case of damaging the mold,
an alternative cost is very high. Furthermore, in order to make
manufactured goods of a desired shape, there is a defect in that
the treatment process is essentially required, after the completion
of manufacture goods.
[0004] In the meantime, in order to improve the above problems, a
fabrication method of a permanent magnet by means of Joule's heat
using a powder and a self resistance of a mold proposed by the
present inventors had been registered as a patent in that a DC
(Direct Current) is directly applied to a permanent magnet powder
or a permanent magnet molded body through an electrical device,
without using external heating elements or high frequency coils,
during press molding of the permanent magnet powder.
[0005] That is, as shown in FIG. 3, Korean Patent No. 10-0424142
has been disclosed in that rare earth magnets are putted into the
mold, a pressure of 50-150 Mpa is applied to the upper and lower
punches 2 and 3, and a DC of 450-4,000 A/cm.sup.2 is applied to the
mold through the upper and lower punches 2 and 3 by means of the
electrical device 4, thereby obtaining a permanent magnet 5 of a
bulk status from the powder.
[0006] However, where predetermined pressure and electric current
are applied to the powder 1 putted into the mold through the upper
and lower punches 2 and 3 at the same time, since the pressure is
applied to the mold and the powder before the permanent magnet
powder expanded perpendicularly to the pressure direction is
plastic deformed, there is defects in that it is difficulty to
manufacture the permanent magnet and a permanent magnet 5 of a bulk
status having high purity and density.
DISCLOSURE OF INVENTION
Technical Problem
[0007] Accordingly, the present invention has been made to solve
the above-mentioned problems occurring in the prior art, and an
object of the present invention is to provide a fabrication method
of isotropic and anisotropic NdFeB type permanent magnets, in which
the isotropic and anisotropic NdFeB type permanent magnets can be
easily manufactured by means of Joule's heat using a self
resistance of a powder molded body by directly applying a DC
(Direct Current) to the powder molded body, without using external
heating elements or high frequency coils and so on, during the
fabrication thereof, and it is simple in terms of structure, during
the fabrication thereof, thereby the manufacturing cost is low.
Technical Solution
[0008] To accomplish the object, the present invention provides a
fabrication method of an isotropic NdFeB type permanent magnet,
comprising the steps of: putting a powder molded body of a freeform
type, in which a NdFeB type powder is compression molded in normal
temperature, into a graphite mold; adhering and fixing the powder
molded body to upper and lower punches located at upper and lower
parts thereof; applying a DC of 500-3,000 A/cm.sup.2 to the upper
and lower punches, whereby generating a resistance heat of
700-800.degree. C. into the powder molded body; applying a pressure
of 10-150 Mpa to the upper and lower punches; and cooling the
isotropic permanent magnet, in which the powder molded body is
contracted in the pressure direction of the upper and lower
punches.
[0009] Here, the isotropic permanent magnet, in which the powder
molded body is contracted in the pressure direction of the upper
and lower punches, is cooled in normal temperature.
[0010] Also, the material of the mold for fixing the powder molded
body is a metal or ceramic.
[0011] To accomplish the object, the present invention provides a
fabrication method of an anisotropic NdFeB type permanent magnet,
comprising the steps of: adhering and fixing a molded body of an
isotropic permanent magnet between upper and lower punches;
applying a DC of 500-3,000 A/cm.sup.2 to the upper and lower
punches, whereby generating a resistance heat of 700-800.degree. C.
into the molded body; and applying a pressure of 50-200 Mpa to the
upper and lower punches, whereby contracting the molded body in the
pressure direction of the upper and lower punches and expanding the
molded body perpendicularly to the pressure direction of the upper
and lower punches.
Advantageous Effects
[0012] As can be seen from the foregoing, in the fabrication method
of isotropic and anisotropic NdFeB type permanent magnet, there are
superior effects in that the isotropic and anisotropic NdFeB type
permanent magnets can be easily manufactured by means of Joule's
heat using a self resistance of a powder molded body by directly
applying a DC (Direct Current) to the powder molded body, without
using external heating elements or high frequency coils and so on,
during the fabrication thereof, and it is simple in terms of
structure, during the fabrication thereof, thereby the
manufacturing cost is low.
[0013] While this invention has been described in connection with
what are presently considered to be the most practical and
preferred embodiments, it is to be understood that the invention is
not limited to the disclosed embodiments and the drawings, but, on
the contrary, it is intended to cover various modifications and
variations within the spirit and scope of the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The above as well as the other objects, features and
advantages of the present invention will be more apparent from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0015] FIG. 1 is a schematic perspective view illustrating a
fabrication method of a permanent magnet according to a
conventional hot press process;
[0016] FIG. 2 is a schematic perspective view illustrating a
fabrication method of a permanent magnet according to a
conventional hot deformation process;
[0017] FIG. 3 is a schematic perspective view illustrating a
fabrication method of a permanent magnet according to a
conventional current applying;
[0018] FIG. 4 is a schematic perspective view illustrating a
fabrication method of an isotropic NdFeB type permanent magnet
according to the present invention; and
[0019] FIG. 5 is a schematic perspective view illustrating a
fabrication method of an anisotropic NdFeB type permanent magnet
according to another embodiment of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0020] A preferred embodiment of the invention will be described in
detail below with reference to the accompanying drawings.
[0021] FIG. 4 is a schematic perspective view illustrating a
fabrication method of an isotropic NdFeB type permanent magnet
according to the present invention. A NdFeB type permanent magnet
powder, which is manufactured by rapidly solidifying the NdFeB type
permanent magnet based on Nd.sub.2Fe.sub.14B ferromagnetic phase,
or a powder molded body 110 of a freeform type, in which the NdFeB
type permanent magnet powder is compression molded in normal
temperature, are putted into a graphite mold 120. In this case, the
powder molded body 110, which is putted into the graphite mold 120,
is adhered and fixed to upper and lower punches 130 and 140 located
at upper and lower parts thereof.
[0022] Here, instead of the graphite mold 110, a ceramic mold of
metal or nonmetal may be used.
[0023] As described above, the powder molded body 110 adhered and
fixed to the upper and lower punches 130 and 140 is plastic-worked
in such a manner that a DC (Direct Current) of 500-3,000 A/cm.sup.2
is applied to the upper and lower punches 130 and 140 through an
electrical device 150, so as to generate a resistance heat of
700-800.degree. C. into the powder molded body 110. Simultaneously
with this, a pressure of 10-150 Mpa is pressurized to the upper and
lower punches 130 and 140 to mold the isotropic NdFeB type
permanent magnet 160, in which the powder molded body 110 is
contracted in the pressure direction of the upper and lower punches
130 and 140.
[0024] Here, the reason for heating the resistance heat at
700-800.degree. C. is because that the plastic deformation of the
powder molded body 110 cannot be generated into the graphite mold
120 or can be degraded.
[0025] Also, it is preferred that the DC applied to the upper and
lower punches 130 and 140 through the electrical device 150 is
500-3,000 A/cm.sup.2. However, the present invention is not limited
to any intensity of the DC, it can be properly changed according to
the diameter size per unit area of the powder molded body 110 and
so on, which is located inside the graphite mold 120.
[0026] As described above, where the contraction of the isotropic
NdFeB type permanent magnet 160 is completed, the supply of the DC
is blocked and the contracted permanent magnet 160 is cooled at a
normal temperature, so that the molded boy of the isotropic
permanent magnet 160 is obtained.
[0027] FIG. 5 is a schematic perspective view illustrating a
fabrication method of an anisotropic NdFeB type permanent magnet
according to another embodiment of the present invention.
[0028] As shown in FIG. 5, a molded body 210 of an isotropic type
permanent magnet is adhere and fixed between upper and lower
punches 230 and 240 and then, the molded body 210 of an isotropic
type permanent magnet adhered and fixed between the upper and lower
punches 230 and 240 is plastic-worked in such a manner that a DC
(Direct Current) of 500-3,000 A/cm.sup.2 is applied to the upper
and lower punches 230 and 240 through an electrical device 250.
[0029] As described above, the DC applied to the upper and lower
punches 230 and 240 is flowed into the molded body 210 of an
isotropic type permanent magnet and a resistance heat of
700-800.degree. C. is generated into the molded body 210 of the
isotropic NdFeB type permanent. Thereafter, where the temperature
of the molded body 210 of the isotropic NdFeB type permanent magnet
reaches a predetermined firing temperature, a pressure of 50-200
Mpa is pressurized to the upper and lower punches 230 and 240 to
mold the anisotropic NdFeB type permanent magnet 220, in which the
molded body 210 is contracted in the pressure direction of the
upper and lower punches 230 and 240 and is expanded perpendicularly
to the pressure direction of the upper and lower punches 230 and
240.
[0030] Here, the reason for heating the resistance heat at
700-800.degree. C. is because that the plastic deformation of the
molded body 210 cannot be generated into the graphite mold 120 or
can be degraded.
[0031] Also, it is preferred that the DC applied to the upper and
lower punches 130 and 140 through the electrical device 150 is
500-3,000 A/cm.sup.2. However, the present invention is not limited
to any intensity of the DC, it can be properly changed according to
the diameter size per unit area of the molded body 210.
[0032] As described above, where the contraction of the anisotropic
NdFeB type permanent magnet 210 is completed, the supply of the DC
is blocked so that the molded body of the isotropic permanent
magnet 220 is obtained.
* * * * *