U.S. patent application number 16/769611 was filed with the patent office on 2020-10-08 for method for manufacturing atomized metal powder.
This patent application is currently assigned to JFE Steel Corporation. The applicant listed for this patent is JFE Steel Corporation. Invention is credited to Akio Kobayashi, Naomichi Nakamura, Makoto Nakaseko, Takuya Takashita.
Application Number | 20200316688 16/769611 |
Document ID | / |
Family ID | 1000004970330 |
Filed Date | 2020-10-08 |
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United States Patent
Application |
20200316688 |
Kind Code |
A1 |
Nakaseko; Makoto ; et
al. |
October 8, 2020 |
METHOD FOR MANUFACTURING ATOMIZED METAL POWDER
Abstract
[Object] Provided is a method for manufacturing atomized metal
powder having a high amorphous material fraction by using a water
atomizing method. [Solution] A method for manufacturing atomized
metal powder in which atomized metal powder having an amorphous
material fraction of 90% or more is obtained, the method including
ejecting high-pressure water so as to collide with a molten metal
stream flowing vertically downward, separating the molten metal
stream into metal powder, and cooling the metal powder, in which
the high-pressure water collides with the molten metal with a
collision pressure of 20 MPa or higher, and in which a temperature
of the molten metal and/or a temperature of the high-pressure water
are controlled so that the high-pressure water is in a subcritical
state or a supercritical state on a collision surface with the
molten metal.
Inventors: |
Nakaseko; Makoto;
(Chiyoda-ku, Tokyo, JP) ; Nakamura; Naomichi;
(Chiyoda-ku, Tokyo, JP) ; Kobayashi; Akio;
(Chiyoda-ku, Tokyo, JP) ; Takashita; Takuya;
(Chiyoda-ku, Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JFE Steel Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
JFE Steel Corporation
Tokyo
JP
|
Family ID: |
1000004970330 |
Appl. No.: |
16/769611 |
Filed: |
December 5, 2018 |
PCT Filed: |
December 5, 2018 |
PCT NO: |
PCT/JP2018/044727 |
371 Date: |
June 4, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 9/082 20130101;
B22F 2301/35 20130101; B22F 2301/15 20130101; B22F 2009/086
20130101; B22F 2009/0828 20130101 |
International
Class: |
B22F 9/08 20060101
B22F009/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 7, 2017 |
JP |
2017-234739 |
Claims
1. A method for manufacturing atomized metal powder in which
atomized metal powder having an amorphous material fraction of 90%
or more is obtained, the method comprising ejecting high-pressure
water so as to collide with a molten metal stream flowing
vertically downward, separating the molten metal stream into metal
powder, and cooling the metal powder, wherein the high-pressure
water collides with the molten metal with a collision pressure of
20 MPa or higher, and wherein a temperature of the molten metal
and/or a temperature of the high-pressure water are controlled so
that the high-pressure water is in a subcritical state or a
supercritical state on a collision surface with the molten
metal.
2. The method for manufacturing atomized metal powder according to
claim 1, wherein an average temperature of the molten metal and the
high-pressure water is 374.degree. C. or higher at a time of
collision between the high-pressure water and the molten metal.
3. The method for manufacturing atomized metal powder according to
claim 1, wherein, when a flow rate of the molten metal stream per
unit time is defined as Qm (kg/min) and an ejection rate of the
high-pressure water per unit time is defined as Qaq (kg/min), a
mass ratio (Qaq/Qm) is 35 or more.
4. The method for manufacturing atomized metal powder according to
claim 2 wherein, when a flow rate of the molten metal stream per
unit time is defined as Qm (kg/min) and an ejection rate of the
high-pressure water per unit time is defined as Qaq (kg/min), a
mass ratio (Qaq/Qm) is 35 or more.
5. The method for manufacturing atomized metal powder according to
claim 1, wherein the atomized metal powder contains iron-group
constituents (Fe, Ni, and Co) in a total amount of 76.0 at % or
more in terms of atomic fraction and Cu in an amount of 0.1 at % or
more and 2.0 at % or less in terms of atomic fraction.
6. The method for manufacturing atomized metal powder according to
claim 2, wherein the atomized metal powder contains iron-group
constituents (Fe, Ni, and Co) in a total amount of 76.0 at % or
more in terms of atomic fraction and Cu in an amount of 0.1 at % or
more and 2.0 at % or less in terms of atomic fraction.
7. The method for manufacturing atomized metal powder according to
claim 3, wherein the atomized metal powder contains iron-group
constituents (Fe, Ni, and Co) in a total amount of 76.0 at % or
more in terms of atomic fraction and Cu in an amount of 0.1 at % or
more and 2.0 at % or less in terms of atomic fraction.
8. The method for manufacturing atomized metal powder according to
claim 4, wherein the atomized metal powder contains iron-group
constituents (Fe, Ni, and Co) in a total amount of 76.0 at % or
more in terms of atomic fraction and Cu in an amount of 0.1 at % or
more and 2.0 at % or less in terms of atomic fraction.
9. The method for manufacturing atomized metal powder according to
claim 1, wherein the atomized metal powder contains iron-group
constituents (Fe, Ni, and Co) in a total amount of more than 82.5
at % and less than 86.0 at % in terms of atomic fraction, at least
two selected from Si, P, and B, and Cu and has an average particle
size of 5 .mu.m or more.
10. The method for manufacturing atomized metal powder according to
claim 2, wherein the atomized metal powder contains iron-group
constituents (Fe, Ni, and Co) in a total amount of more than 82.5
at % and less than 86.0 at % in terms of atomic fraction, at least
two selected from Si, P, and B, and Cu and has an average particle
size of 5 .mu.m or more.
11. The method for manufacturing atomized metal powder according to
claim 3, wherein the atomized metal powder contains iron-group
constituents (Fe, Ni, and Co) in a total amount of more than 82.5
at % and less than 86.0 at % in terms of atomic fraction, at least
two selected from Si, P, and B, and Cu and has an average particle
size of 5 .mu.m or more.
12. The method for manufacturing atomized metal powder according to
claim 4, wherein the atomized metal powder contains iron-group
constituents (Fe, Ni, and Co) in a total amount of more than 82.5
at % and less than 86.0 at % in terms of atomic fraction, at least
two selected from Si, P, and B, and Cu and has an average particle
size of 5 .mu.m or more.
13. The method for manufacturing atomized metal powder according to
claim 1, wherein the subcritical state is represented by a pressure
of 0.5 MPa to 22 MPa and a water temperature of higher than
150.degree. C. and lower than 374.degree. C., and wherein the
supercritical state is represented by a pressure of 22 MPa or
higher and a water temperature of 374.degree. C. or higher.
14. The method for manufacturing atomized metal powder according to
claim 2, wherein the subcritical state is represented by a pressure
of 0.5 MPa to 22 MPa and a water temperature of higher than
150.degree. C. and lower than 374.degree. C., and wherein the
supercritical state is represented by a pressure of 22 MPa or
higher and a water temperature of 374.degree. C. or higher.
15. The method for manufacturing atomized metal powder according to
claim 3, wherein the subcritical state is represented by a pressure
of 0.5 MPa to 22 MPa and a water temperature of higher than
150.degree. C. and lower than 374.degree. C., and wherein the
supercritical state is represented by a pressure of 22 MPa or
higher and a water temperature of 374.degree. C. or higher.
16. The method for manufacturing atomized metal powder according to
claim 4, wherein the subcritical state is represented by a pressure
of 0.5 MPa to 22 MPa and a water temperature of higher than
150.degree. C. and lower than 374.degree. C., and wherein the
supercritical state is represented by a pressure of 22 MPa or
higher and a water temperature of 374.degree. C. or higher.
17. The method for manufacturing atomized metal powder according to
claim 5, wherein the subcritical state is represented by a pressure
of 0.5 MPa to 22 MPa and a water temperature of higher than
150.degree. C. and lower than 374.degree. C., and wherein the
supercritical state is represented by a pressure of 22 MPa or
higher and a water temperature of 374.degree. C. or higher.
18. The method for manufacturing atomized metal powder according to
claim 6, wherein the subcritical state is represented by a pressure
of 0.5 MPa to 22 MPa and a water temperature of higher than
150.degree. C. and lower than 374.degree. C., and wherein the
supercritical state is represented by a pressure of 22 MPa or
higher and a water temperature of 374.degree. C. or higher.
19. The method for manufacturing atomized metal powder according to
claim 9, wherein the subcritical state is represented by a pressure
of 0.5 MPa to 22 MPa and a water temperature of higher than
150.degree. C. and lower than 374.degree. C., and wherein the
supercritical state is represented by a pressure of 22 MPa or
higher and a water temperature of 374.degree. C. or higher.
20. The method for manufacturing atomized metal powder according to
claim 10, wherein the subcritical state is represented by a
pressure of 0.5 MPa to 22 MPa and a water temperature of higher
than 150.degree. C. and lower than 374.degree. C., and wherein the
supercritical state is represented by a pressure of 22 MPa or
higher and a water temperature of 374.degree. C. or higher.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is the U.S. National Phase application of
PCT/JP2018/044727, filed Dec. 5, 2018, which claims priority to
Japanese Patent Application No. 2017-234739, filed Dec. 7, 2017,
the disclosures of these applications being incorporated herein by
reference in their entireties for all purposes.
FIELD OF THE INVENTION
[0002] The present invention relates to a method for manufacturing
atomized metal powder. In particular, the present invention can
preferably be used for manufacturing atomized metal powder
containing iron-group constituents (Fe, Ni, and Co) in a total
amount of 76 at % or more in terms of atomic fraction.
BACKGROUND OF THE INVENTION
[0003] Conventionally, examples of a method for manufacturing metal
powder include an atomizing method. Examples of such an atomizing
method include a water atomizing method in which high-pressure
water jets (high-pressure water) are ejected to a molten metal
stream to obtain metal powder and a gas atomizing method in which
an inert gas, instead of water jets, is ejected.
[0004] In a water atomizing method, atomized metal powder is
obtained not only by separating a molten metal stream into powdery
metal (metal powder) with water jets ejected from, for example,
nozzles, but also by cooling the powdery metal (metal powder) with
the water jets. On the other hand, in a gas atomizing method,
atomized metal powder is usually obtained by dropping powdery metal
(metal powder), which has been obtained by separating a molten
metal stream into powdery metal with an inert gas ejected through
nozzles, into a water tank or a flowing-water drum located under an
atomizing apparatus to cool the powdery metal.
[0005] As a method for manufacturing metal powder, a water
atomizing method is superior to a gas atomizing method from the
viewpoint of high production capability and low cost. In the case
of a gas atomizing method, it is necessary to use an inert gas when
performing atomizing, and such a method is inferior to a water
atomizing method from the viewpoint of atomizing energy. In
addition, while metal powder particles manufactured by using a gas
atomizing method have an almost spherical shape, metal powder
particles manufactured by using a water atomizing method have
irregular shapes. Therefore, a water atomizing method has an
advantage over a gas atomizing method in that, when metal powder is
formed into, for example, a motor core by performing compaction
forming, irregularly shaped metal powder particles manufactured by
using a water atomizing method are more likely than spherically
shaped metal powder particles manufactured by using a gas atomizing
method to be entangled with each other to increase strength after
compaction has been performed.
[0006] Nowadays, there is a demand for, for example, reducing the
iron loss and size of a motor core which is used for an electric
automobile or a hybrid automobile from the viewpoint of energy
saving. To date, such a motor core has been manufactured by placing
thin electrical steel sheets on top of one another. However,
nowadays, a motor core manufactured by using metal powder, which
has a high degree of freedom for shape design, is receiving much
attention. To reduce the iron loss of such a motor core, using
non-crystalline (amorphous) metal powder is considered effective.
To manufacture amorphous metal powder, it is necessary that
atomized metal powder be rapidly cooled by using a coolant to
prevent crystallization while atomizing high-temperature molten
metal. In addition, it is necessary to increase magnetic flux
density to realize a reduction in motor size and an increase in
motor power along with a reduction in iron loss. To increase
magnetic flux density, increasing iron-group constituent
concentration (including Ni and Co) is important, and there is a
demand for soft magnetic iron powder, which is an amorphous soft
magnetic metal powder for a motor core having an iron-group
constituent concentration of about 76 at % to 90 at %. In the case
where the iron-group constituent concentration is about 80 at %, it
is considered necessary to perform cooling at a cooling rate of
10.sup.6 K/s or more to obtain amorphous metal powder, and it is
very difficult to realize both a reduction in iron loss and an
increase in magnetic flux density of metal powder at the same
time.
[0007] In particular, one of the reasons why an increase in cooling
rate is suppressed is as follows. When high-temperature molten
metal is cooled with water, since water is instantly vaporized at
the time of contact between the water and the molten metal to form
vapor films around the molten metal, direct contact between a
surface to be cooled and water is suppressed (film boiling occurs),
which suppresses an increase in cooling rate.
[0008] To solve the problem of suppressed cooling due to vapor
films or film boiling when amorphous iron powder is manufactured,
investigations described in Patent Literature 1 through Patent
Literature 11 have been conducted.
[0009] For example, Patent Literature 1 describes a method for
manufacturing metal powder in which, when molten metal is cooled so
as to be solidified when being scattered to obtain metal powder,
the cooling rate until the molten metal is solidified is set to be
10.sup.3 K/s or more. It is indicated that, in the case of the
technique described in Patent Literature 1, it is possible to
achieve the cooling rate described above by bringing the scattered
molten metal into contact with a cooling liquid flow which is
formed by swirling a cooling liquid along the inner wall surface of
a cylinder. In addition, it is indicated that it is preferable that
the flow rate of the cooling liquid flow which is formed by
swirling the cooling liquid be 5 m/s to 100 m/s.
[0010] In addition, Patent Literature 2 describes a method for
manufacturing rapidly solidified metal powder. In the case of the
technique described in Patent Literature 2, molten metal is rapidly
solidified by feeding the molten metal onto the inner peripheral
surface of a swirling cooling liquid layer which is formed by
feeding the cooling liquid circumferentially from the outside of
the top end of the cylindrical part of a cooling container having a
cylindrical inner peripheral surface so that the cooling liquid
drops while swirling along the inner peripheral surface of the
cylindrical part in such a manner that the swirling cooling liquid
layer having a hollow space at the center thereof is centrifugally
formed due to swirling. It is indicated that, with this, it is
possible to obtain high-quality rapidly solidified powder with high
cooling efficiency.
[0011] In addition, Patent Literature 3 describes an apparatus for
manufacturing metal powder which uses a gas atomizing method and
which has gas jet nozzles for ejecting gas jets onto molten metal
flowing downward to separate the molten metal into droplets and a
cooling cylinder having an inner peripheral surface along which a
cooling liquid layer flows downward while swirling. It is indicated
that, in the case of the technique described in Patent Literature
3, it is possible to obtain rapidly solidified fine metal powder as
a result of molten metal being separated in two steps consisting of
one step utilizing gas-jet nozzles and the other step utilizing a
swirling cooling liquid layer.
[0012] In addition, Patent Literature 4 describes a method for
manufacturing fine amorphous metal particles in which fine
amorphous metal particles are obtained by feeding molten metal into
a liquid cooling medium to form vapor films covering the molten
metal in the cooling medium and to collapse the formed vapor films
so that boiling occurs due to spontaneous nucleation as a result of
the molten metal and the cooling medium being brought into direct
contact with each other and by utilizing a pressure wave due to
boiling to tear the molten metal into pieces so that the molten
metal is rapidly cooled to make amorphous metal. It is indicated
that it is possible to collapse the vapor films covering the molten
metal by controlling the temperature of the molten metal which is
fed into the cooling medium so that, when the molten metal and the
cooling medium being brought into direct contact with each other,
an interface temperature is equal to or lower than a minimum film
boiling temperature and equal to or higher than a spontaneous
nucleation temperature or by performing ultrasonic irradiation.
[0013] In addition, Patent Literature 5 describes a method for
manufacturing fine particles in which a molten material is made
into fine particles and cooled so as to be solidified by
controlling the temperature of the molten material so that the
material is molten at a temperature equal to or higher than the
spontaneous nucleation temperature of a cooling liquid medium when
the molten material is fed into the cooling liquid medium in the
form of droplets or jets and by controlling a relative velocity
between the molten material and the cooling liquid medium when the
molten material is fed into the cooling liquid medium to be 10 m/s
or more to forcibly collapse vapor films formed around the molten
material so that boiling occurs due to spontaneous nucleation. It
is indicated that, with this, it is possible to manufacture fine
particles or an amorphous material from a material which is
difficult to make into fine particles or an amorphous material by
using conventional methods.
[0014] In addition, Patent Literature 6 describes a method for
manufacturing a functional member which has a process of obtaining
homogeneous functional fine particles of polycrystalline or
amorphous material without segregation by dissolving a raw material
to which a functional additive is added in a base material and by
feeding the molten mixture into a cooling liquid medium so that the
molten mixture is made into fine particles due to vapor explosion
and cooled so as to be solidified while controlling the cooling
rate and a process of obtaining a functional member by compressing
the functional fine particles and fine particles of the base
material used as raw materials.
[0015] Patent Literature 7 and Patent Literature 8 state that it is
possible to collapse vapor films formed around powder particles,
which have been obtained by atomizing a molten material, by
suctioning the particles into a suction pipe disposed below a water
atomizing device.
[0016] Patent Literature 9 states that vapor films formed around
powder particles, which have been obtained by atomizing a molten
material, are collapsed by ejecting a liquid at a pressure of 80
kgf/cm.sup.2 or higher so that the particles collide with a cooling
block disposed below a water atomizing device.
[0017] Patent Literature 10 states that covering vapor films are
removed by ejecting a second liquid from a device for ejecting the
second liquid, which is disposed below an atomizing device, at an
ejection pressure of the liquid of 5 MPa to 20 MPa to forcibly
change the moving direction of a fluid dispersion containing molten
metal.
[0018] Patent Literature 11 discloses an invention regarding an
iron-boron-based ferromagnetic material (permanent magnet)
containing a rare-earth metal and states that, when performing
pulverizing and manufacturing of an amorphous material by using a
water atomizing method, it is preferable that a water pressure be
750 kgf/cm.sup.2 to 1200 kgf/cm.sup.2, that a water temperature be
20.degree. C. or lower, and that the amount (kg) of water for 1 kg
of iron be 25 [-] to 45 [-].
PATENT LITERATURE
[0019] PTL 1: Japanese Unexamined Patent Application Publication
No. 2010-150587 [0020] PTL 2: Japanese Examined Patent Application
Publication No. 7-107167 [0021] PTL 3: Japanese Patent No. 3932573
[0022] PTL 4: Japanese Patent No. 3461344 [0023] PTL 5: Japanese
Patent No. 4793872 [0024] PTL 6: Japanese Patent No. 4784990 [0025]
PTL 7: Japanese Unexamined Patent Application Publication No.
60-24302 [0026] PTL 8: Japanese Unexamined Patent Application
Publication No. 61-204305 [0027] PTL 9: Japanese Unexamined Patent
Application Publication No. 60-24303 [0028] PTL 10: Japanese
Unexamined Patent Application Publication No. 2007-291454 [0029]
PTL 11: Japanese Unexamined Patent Application Publication No.
2004-349364
SUMMARY OF THE INVENTION
[0030] In the case of the techniques described in Patent Literature
1 through Patent Literature 3, it is intended to remove vapor films
formed around separated metal particles by feeding molten metal
into a cooling liquid layer formed by swirling the cooling liquid.
However, in the case where the temperature of the separated metal
particles is high, since film boiling tends to occur in the cooling
liquid layer, and since the metal particles fed into the cooling
liquid layer move along with the cooling liquid layer, that is, a
relative velocity with respect to the cooling liquid layer is
small, there is a problem in that it is difficult to avoid film
boiling.
[0031] In addition, in the case of the techniques described in
Patent Literature 1 through Patent Literature 6, since a gas
atomizing method is used to manufacture metal powder, and since it
is necessary to use a large amount of inert gas for atomizing in a
gas atomizing method, there is a problem of an increase in
manufacturing costs.
[0032] The techniques described in Patent Literature 7 through
Patent Literature 10 relate to a water atomizing method. In the
case of the techniques described in Patent Literature 7 and Patent
Literature 8, it is indicated that it is possible to remove vapor
films by suctioning powder. However, when water exists around a
high-temperature object, since water is continuously vaporized to
form vapor films due to heat fed from the inside of the object, the
water and the molten metal are suctioned together with no change,
and it is difficult to remove the vapor films.
[0033] Patent Literature 9 states that it is possible to collapse
vapor films by allowing molten metal which is covered with vapor
films to collide with a cooling block disposed below an atomizing
device. However, in the case where a liquid is used for separation,
since there is an increase in the temperature of the liquid, vapor
films tend to be formed. In addition, since the ejection pressure
(pressure energy) of the liquid is utilized for separation, there
is insufficient energy for collapsing vapor films at the time of
collision with the cooling block. Even if vapor films are
collapsed, vapor films soon re-form as long as the molten metal
(powder) has a high temperature. Therefore, it is necessary to
always continue removing vapor films.
[0034] In addition, Patent Literature 10 states that, it is
possible to remove vapor films by changing the moving direction of
a liquid dispersion containing molten metal droplets, which have
been formed by performing atomizing, by using a liquid jet spray.
However, in the case where the temperature of the molten metal
covered with vapor films is excessively high when the moving
direction is changed, the molten metal may be covered with vapor
films again due to surrounding cooling water. On the contrary, in
the case where the temperature of the molten metal is excessively
low when the molten metal collides with a cooling block, there may
be a case where the molten metal solidifies and crystallization
progresses. In particular, in the case where the content of
iron-group elements (Fe+Co+Ni) is large, since there is an increase
in cooling start temperature due to an increase in melting point,
film boiling tends to occur at the beginning of cooling. Therefore,
it may be said that an ejection pressure of a liquid of about 5 MPa
to 20 MPa is not sufficient.
[0035] Patent Literature 11 relates to powder for a permanent
magnet and states that, to make powder pulverized and amorphous,
water pressure is set to be 750 kgf/cm.sup.2 to 1200 kgf/cm.sup.2,
water temperature is set to be 20.degree. C. or lower, and the
amount of water for 1 kg of iron is set to be 25 L (liters) to 45
L. Although it is not indicated that film boiling or a vapor film
is eliminated under these conditions, controlling an ejection
pressure to be 60 MPa or higher incurs costs for a high-pressure
pump and high-pressure pipework, which results in an increase in
product price. In addition, although the amount of water for 1 kg
of iron is set to be 25 L to 45 L, it may be said that this amount
is not sufficient for a soft magnetic material having a high
iron-group constituent content.
[0036] As described above in Background Art, a water atomizing
method is advantageous from the viewpoint of productivity and the
adhesiveness of particles. In addition, when rapid cooling is
performed to manufacture an amorphous material, performing rapid
cooling with water after having performed gas atomizing is
advantageous for the manufacture of an amorphous material as in the
case of Patent Literature 1 through Patent Literature 6. In the
case of a water atomizing method, since molten metal separated by
performing atomizing is covered with vapor films due to cooling
water that is used for atomizing, it is necessary to take further
measures exemplified by those described in Patent Literature 7
through Patent Literature 11. In particular, in the case of such
measures, there is an insufficient effect for manufacturing an
amorphous soft magnetic material containing iron-group elements in
a total amount of 76 at % or more.
[0037] Aspects of the present invention have been completed to
solve the problems described above, and an object according to
aspects of the present invention is to provide a method for
manufacturing atomized metal powder having a high amorphous
material fraction by using a water atomizing method.
[0038] The present inventors diligently conducted investigations to
solve the problems described above and, as a result, solved the
problems by focusing on collision pressure instead of ejection
pressure when atomized metal powder is obtained by ejecting
high-pressure water onto molten metal to separate and cool the
molten metal and by controlling the state of water on the collision
surface between the molten metal and the high-pressure water. More
specifically, aspects of the present invention provide the
following.
[0039] [1] A method for manufacturing atomized metal powder in
which atomized metal powder having an amorphous material fraction
of 90% or more is obtained, the method including ejecting
high-pressure water so as to collide with a molten metal stream
flowing vertically downward, separating the molten metal stream
into metal powder, and cooling the metal powder,
[0040] in which the high-pressure water collides with the molten
metal with a collision pressure of 20 MPa or higher, and
[0041] in which a temperature of the molten metal and/or a
temperature of the high-pressure water are controlled so that the
high-pressure water is in a subcritical state or a supercritical
state on a collision surface with the molten metal.
[0042] [2] The method for manufacturing atomized metal powder
according to item [1], in which an average temperature of the
molten metal and the high-pressure water is 374.degree. C. or
higher at a time of collision between the high-pressure water and
the molten metal.
[0043] [3] The method for manufacturing atomized metal powder
according to item [1] or [2], in which, when a flow rate of the
molten metal stream per unit time is defined as Qm (kg/min) and an
ejection rate of the high-pressure water per unit time is defined
as Qaq (kg/min), a mass ratio (Qaq/Qm) is 35 or more.
[0044] [4] The method for manufacturing atomized metal powder
according to any one of items [1] to [3], in which the atomized
metal powder contains iron-group constituents (Fe, Ni, and Co) in a
total amount of 76.0 at % or more in terms of atomic fraction and
Cu in an amount of 0.1 at % or more and 2.0 at % or less in terms
of atomic fraction.
[0045] [5] The method for manufacturing atomized metal powder
according to any one of items [1] to [3], in which the atomized
metal powder contains iron-group constituents (Fe, Ni, and Co) in a
total amount of more than 82.5 at % and less than 86 at % in terms
of atomic fraction, at least two selected from Si, P, and B, and Cu
and has an average particle size of 5 .mu.m or more.
[0046] [6] The method for manufacturing atomized metal powder
according to any one of items [1] to [5], in which the subcritical
state is represented by a pressure of 0.5 MPa to 22 MPa and a water
temperature of higher than 150.degree. C. and lower than
374.degree. C., and in which the supercritical state is represented
by a pressure of 22 MPa or higher and a water temperature of
374.degree. C. or higher.
[0047] According to aspects of the present invention, it is
possible to manufacture atomized metal powder having an amorphous
material fraction of 90% or more. With this, by performing an
appropriate heat treatment after having performed forming on the
atomized metal powder obtained in accordance with aspects of the
present invention, nanosized crystals are precipitated. In
particular, in the case where such powder is made of a soft
magnetic material having a high iron-group constituent content
(containing iron-group constituents (Fe, Ni, and Co) in a total
amount of 76 at % or more in terms of atomic fraction), by
performing an appropriate heat treatment after having performed
forming on such powder, it is possible to achieve both low iron
loss and high magnetic flux density. In such a manner, aspects of
the present invention can preferably be used for manufacturing any
conventionally known amorphous soft magnetic material.
[0048] Nowadays, in addition, as described in, for example, Materia
Japan, Vol. 41, No. 6, p. 392, the Journal of Applied Physics 105,
013922 (2009), Japanese Patent No. 4288687, Japanese Patent No.
4310480, Japanese Patent No. 4815014, International Publication No.
WO2010/084900, Japanese Unexamined Patent Application Publication
No. 2008-231534, Japanese Unexamined Patent Application Publication
No. 2008-231533, and Japanese Patent No. 2710938, hetero-amorphous
materials and nanocrystalline materials having a high magnetic flux
density have been developed. Aspects of the present invention can
very advantageously be used when such a soft magnetic material
having a high iron-group constituent concentration is manufactured
by using a water atomizing method. In particular, in the case where
the iron-group constituent concentration is more than 82.5 at %, or
further, more than 83.5 at %, it was difficult to increase an
amorphous material fraction by using conventional techniques.
However, by using the manufacturing method according to aspects of
the present invention, it is possible to increase the amorphous
material fraction to 90% or more after atomizing has been
performed. Moreover, it was very difficult to control the amorphous
material fraction to be 90% or more and an average particle size to
be 5 .mu.m or more by using conventional techniques. However, by
using the manufacturing method according to aspects of the present
invention, it is possible to control the amorphous material
fraction to be 90% or more, even in the case where the average
particle size is increased. Since it is possible to control the
amorphous material fraction to be 90% or more and the average
particle size to be 5 .mu.m or more, there is a significant
increase in saturated magnetic flux density (Bs) by performing an
appropriate heat treatment after having performed forming on
atomized metal powder.
[0049] In addition, although aspects of the present invention can
preferably be used to manufacturing atomized metal powder having a
high iron-group constituent concentration as described above, by
using aspects of the present invention as a method for
manufacturing atomized metal powder other than that having a high
iron-group constituent concentration, there is an advantage in that
it is possible to stably obtain amorphous powder having a high
particle size more easily than before.
[0050] Here, the term "amorphous material fraction" denotes a value
obtained by removing contaminants which are different from metal
powder from the obtained metal powder (soft magnetic iron powder),
by performing X-ray diffractometry to determine halo peaks from
amorphous materials (non-crystalline materials) and diffraction
peaks from crystals, and by performing a calculation by utilizing a
WPPD method. The term "WPPD method" here is an abbreviation of
"whole-powder-pattern decomposition method". The WPPD method is
described in detail in Hideo Toraya: Journal of the
Crystallographic Society of Japan, vol. 30 (1988), No. 4, pp. 253
to 258.
BRIEF DESCRIPTION OF THE DRAWINGS
[0051] FIG. 1 is a schematic diagram of an example of a
manufacturing apparatus which can be used in a method for
manufacturing atomized metal powder according to aspects of the
present invention.
[0052] FIG. 2 is a schematic diagram illustrating an example of
manufacturing equipment for implementing the manufacturing method
according to aspects of the present invention.
[0053] FIG. 3 is a diagram illustrating the relationship between
the pressure, temperature, and state of water.
[0054] FIG. 4 is a graph illustrating the relationship between an
amorphous material fraction and a collision pressure.
[0055] FIG. 5 is a schematic diagram illustrating a measurement
configuration for determining the collision pressure of molten
metal by using a collision pressure sensor.
[0056] FIG. 6 is a diagram illustrating a B-H diagram obtained by
using a VSM.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0057] Hereafter, an embodiment of the present invention will be
described. Here, the present invention is not limited to the
embodiment below.
[0058] FIG. 1 schematically illustrates an example of a
manufacturing apparatus which can be used in a method for
manufacturing atomized metal powder according to aspects of the
present invention. In FIG. 1, after molten metal 3 has been charged
into a tundish 2, the molten metal 3 flows downward through a
molten metal-injecting nozzle 4 due to the weight of the molten
metal 3. In addition, cooling water 20 (corresponding to
high-pressure water) fed into a nozzle header 5 is ejected through
cooling nozzles 6. The cooling water 20 collides with the molten
metal (molten metal stream flowing downward) and, as a result, the
molten metal is atomized, that is, separated into metal powder
8.
[0059] FIG. 2 schematically illustrates an example of manufacturing
equipment for implementing the manufacturing method according to
aspects of the present invention. In the manufacturing equipment
illustrated in FIG. 2, atomized metal powder is manufactured by
controlling the temperature of cooling water in a cooling water
tank 15 by using a cooling water-temperature controller 16, by
transporting the cooling water, whose temperature has been
controlled, to a high-pressure pump 17 for atomizing cooling water,
by transporting the cooling water from the high-pressure pump 17
for atomizing cooling water through pipework 18 for atomizing
cooling water to an atomizing apparatus 14 (corresponding to the
manufacturing apparatus in FIG. 1), and by ejecting the
high-pressure water, which collides with the molten metal stream
flowing vertically downward, from this atomizing apparatus 14 to
separate the molten metal stream into metal powder and to cool the
metal powder.
[0060] First, one aspect of the present invention is characterized
by controlling a collision pressure to be 20 MPa or higher when the
cooling water 20 collides with the molten metal and the state of
the water to be a subcritical state of water or a supercritical
state of water on a collision surface. The expression
"supercritical state of water" denotes a state which is represented
by a temperature of 374.degree. C. or higher and a pressure of 22
MPa or higher. The expression "subcritical state of water" denotes
a high-temperature and high-pressure state which is close to a
critical point and which is exemplified by, as illustrated in FIG.
3, a state which is represented by a temperature of higher than
150.degree. C. and lower than 374.degree. C. and a pressure of 0.1
MPa or higher and lower than 22 MPa, a state which is represented
by a temperature of 374.degree. C. or higher and a pressure of 2
MPa or higher and lower than 22 MPa, and a state which is
represented by a temperature of 250.degree. C. or higher and lower
than 374.degree. C. and a pressure of 22 MPa or higher.
[0061] In the manufacturing method according to aspects of the
present invention, the collision pressure of the cooling water 20
at the time of collision with the molten metal is set to be 20 MPa
or more. The collision pressure is determined by using a pressure
sensor having a collision surface sensor whose diameter is 2 mm
when atomizing is not performed. To control the collision pressure
to be 20 MPa or more, it is necessary that the ejection pressure of
the cooling water 20 be more than the collision pressure. To
control the collision pressure so that the maximum ejection
pressure is 98 MPa, it is preferable that the pressure control be
performed by using an inverter high-pressure pump. In addition,
since there is a decrease in ejection pressure in the case where
the cooling water 20 is spread out in a fan-like form, it is
preferable that solid stream-type nozzles be used. In addition,
since there is a decrease in ejection pressure in the case where
the distance between the cooling nozzles 6 and the molten metal is
increased, it is preferable that the linear distance between the
ejection ports of the cooling nozzles 6 for the cooling water 20
and the molten metal be 150 mm or less or more preferably 100 mm or
less.
[0062] In addition, in accordance with aspects of the present
invention, the temperature of the molten metal and/or the
temperature of the cooling water are controlled so that the cooling
water 20 is in a subcritical state or a supercritical state on a
collision surface with the molten metal. It is possible to control
the temperature of the molten metal by controlling the heating
temperature of a melting furnace through high-frequency output. In
addition, by holding the molten metal 3 in the melting furnace
after heating has been performed, it is possible to control the
temperature of the molten metal 3 which is fed into the tundish
2.
[0063] In the manufacturing method according to aspects of the
present invention, the temperature of the water on the collision
surface is defined as the average temperature of the molten metal
and the cooling water 20 (((molten metal temperature)+(cooling
water temperature))/2). It is possible to determine the molten
metal temperature by using a non-contact thermometer at an
atomizing point. It is possible to determine the temperature of the
cooling water by using a thermometer (not illustrated) for
determining the water temperature in the cooling water tank 15
illustrated in FIG. 2. In addition, in accordance with the
relationship between the pressure, the temperature, and the state
of water illustrated in FIG. 3, the collision pressure, the
temperature of the molten metal, and the temperature of the cooling
water 20 are controlled to achieve the average temperature and the
collision pressure with which the cooling water is in a subcritical
state or a supercritical state. Here, since the temperatures of the
molten metal and the cooling water tend to fluctuate, the molten
metal temperature may be determined within the margin of error of
plus or minus 50.degree. C., and the cooling water temperature may
be determined within the margin of error of plus or minus 5.degree.
C.
[0064] Hereafter, the effects according to aspects of the present
invention will be described.
[0065] FIG. 4 is a graph illustrating the relationship between an
amorphous material fraction and a collision pressure. The graph in
FIG. 4 relates to a case where atomized metal powder containing
iron-group constituents (Fe, Ni, and Co) in a total amount of 76.0
at % in terms of atomic fraction (water-molten metal ratio(mass
ratio: Qaq/Qm): 20) and Cu in an amount of 0.5 at % is manufactured
and a case where atomized metal powder containing iron-group
constituents (Fe, Ni, and Co) in a total amount of 85.8 at % in
terms of atomic fraction (water-molten metal ratio: 35) and Cu in
an amount of 0.5 at % is manufactured. In addition, in the graph in
FIG. 4, in the case of a collision pressure of 20 MPa, the state of
water was controlled to be a subcritical state on the collision
surface between the cooling water and the molten metal. In the case
of a collision pressure of 22 MPa or higher, that is, in the case
of a collision pressure of higher than 20 MPa, the state of water
was controlled to be a supercritical state on the collision surface
between the cooling water and the molten metal. In addition, in the
case of a collision pressure of lower than 20 MPa, the state of
water was controlled not to be either a subcritical state or a
supercritical state on the collision surface between the cooling
water and the molten metal.
[0066] As indicated in FIG. 4, in the case where the collision
pressure is 20 MPa or higher, it is possible to achieve an
amorphous material fraction of 90% or more regardless of a
variation in the chemical composition of obtained atomized metal
powder, a variation in water-molten metal ratio, or whether the
state of the water is a subcritical state or a supercritical state
on a collision surface.
[0067] In addition, when the manufacturing method according to
aspects of the present invention is implemented, it is preferable
that the average temperature of the molten metal and the cooling
water be 374.degree. C. or higher at the time of collision between
the cooling water (high-pressure water) and the molten metal. By
controlling the average temperature described above to be
374.degree. C. or higher, there is an advantage in that the state
of water is brought close to a critical state and that there is an
increase in vapor density.
[0068] When the flow rate of the molten metal stream per unit time
is defined as Qm (kg/min) and the ejection rate of the cooling
water (high-pressure water) per unit time is defined as Qaq
(kg/min), it is preferable that a mass ratio (Qaq/Qm) be 35 or
more. This is because, since there is a tendency for an amorphous
material fraction to increase in the case where such a mass ratio
is large, and since it is easy to control the mass ratio in the
case where the mass ratio is 35 or more, it is possible to achieve
a sufficiently high level of effect.
[0069] The manufacturing method according to aspects of the present
invention can preferably be used for manufacturing atomized metal
powder containing iron-group constituents (Fe, Ni, and Co) in a
total amount of 76 at % or more in terms of atomic fraction and Cu
in an amount of 0.1 at % or more and 2 at % or less in terms of
atomic fraction. In the case where the content of iron-group
elements (Fe+Co+Ni) is large, since there is an increase in cooling
start temperature due to an increase in melting point, film boiling
tends to occur at the beginning of cooling, which makes it
difficult to increase an amorphous material fraction to 90% or more
by using conventional methods. According to aspects of the present
invention, it is possible to increase an amorphous material
fraction, even in the case where the content of iron-group elements
(Fe+Co+Ni) is large. By using the manufacturing method according to
aspects of the present invention, since it is possible to increase
an amorphous material fraction while increasing the content of
iron-group elements (Fe+Co+Ni), it is possible to increase magnetic
flux density. As a result, the manufacturing method according to
aspects of the present invention contributes to reducing the size
of a motor and to increasing motor power.
[0070] Here, by controlling the chemical composition of the molten
metal to be within the range described above, the chemical
composition of the atomized metal powder is also within the range
described above.
[0071] The manufacturing method according to aspects of the present
invention can preferably be used for manufacturing atomized metal
powder containing iron-group constituents (Fe, Ni, and Co) in a
total amount of more than 82.5 at % and less than 86.0 at % in
terms of atomic fraction, at least two selected from Si, P, and B,
and Cu and having an average particle size of 5 .mu.m or more. In
the case where conventional techniques are used for manufacturing
atomized metal powder containing iron-group constituents in
significantly large amounts, specifically, containing iron-group
constituents (Fe, Ni, and Co) in a total amount of more than 82.5
at % and less than 86 at % in terms of atomic fraction, when an
average particle size is small, since it is easy to cool the
particles, it is possible to achieve an amorphous material fraction
larger than that achieved when the average particle size is large.
However, when the average particle size is 5 .mu.m or more, it is
very difficult to increase the amorphous material fraction to 90%
or more. According to aspects of the present invention, even when
the average particle size is 5 .mu.m or more, it is possible to
increase the amorphous material fraction to 90% or more. In
addition, the upper limit of the average grain diameter with which
it is possible to increase the amorphous material fraction to 90%
or more in accordance with aspects of the present invention is 75
.mu.m as a rough guide. Here, the particle size is determined by
performing classification utilizing a sieve method, and the average
particle size (D50) is calculated by using an integration method.
In addition, a laser diffraction/scattering particle size
distribution analyzer may also be used.
EXAMPLES
[0072] Examples and comparative examples were implemented by using
the manufacturing equipment illustrated in FIG. 2 in which the
apparatus for manufacturing water-atomized metal powder illustrated
in FIG. 1 was installed.
[0073] Molten metal 3, which has been prepared by melting a raw
material at a predetermined temperature by using a high-frequency
melting furnace or the like, is fed into a tundish 2. A molten
metal-injecting nozzle 4 having a predetermined molten
metal-injecting nozzle diameter has been set in the tundish 2 in
advance. When the molten metal 3 is fed into the tundish 2, the
molten metal is extruded through the molten metal-injecting nozzle
4 due to free drop or back pressure and flows downward. Cooling
water, which is ejected through cooling water nozzles 6 with a
predetermined water pressure by using a high-pressure pump 17 for
atomizing cooling water, collides with the molten metal, so that
the molten metal is separated, pulverized, and cooled. There may be
a case where the cooling water has been stored in a cooling water
tank 15 in advance to control the water temperature by using a
cooling water-temperature controller 16 as needed. As the cooling
water ejecting nozzles, solid stream-type nozzles were used. A
dozen cooling water nozzles were arranged around the molten metal
flowing downward so as to make an angle of 30.degree. with respect
to the vertical direction. Here, it is possible to realize the
effects according to aspects of the present invention, even in the
case where the nozzles are arranged so as to make an angle of
5.degree. to 60.degree. with respect to the vertical direction.
Before atomizing is started, the collision pressure of the molten
metal is determined by using a collision pressure sensor 51 (refer
to FIG. 5). The collision pressure sensor 51 is arranged in a
direction perpendicular to the nozzle ejection direction to confirm
whether a predetermined collision pressure is achieved. Here,
although FIG. 5 illustrates not only a configuration in which the
cooling water is ejected onto the molten metal but also a
configuration in which the cooling water is ejected onto the
collision pressure sensor 51, this is only for the purpose of
description, and the collision pressure is determined by using the
collision pressure sensor 51 before the molten metal is allowed to
flow down. Iron powder manufactured from the molten metal is
collected by using a hopper, dried, classified, and subjected to
evaluation regarding an amorphous material fraction. In the case of
an amorphous material fraction of 90% or more is judged as
satisfactory.
[0074] When the manufacturing methods of the examples and the
comparative examples were implemented, soft magnetic materials
having the following chemical compositions were prepared. "%" means
"at %". (i) through (v) are Fe-based soft magnetic row materials.
(vi) is an Fe--Co-based soft magnetic material. (vii) is an
Fe--Co--Ni-based soft magnetic material.
[0075] (i) Fe76%-Si9%-B10%-P5%
[0076] (ii) Fe78%-Si9%-B9%-P4%
[0077] (iii) Fe80%-Si8%-B8%-P4%
[0078] (iv) Fe82.8%-B11%-P5%-Cu1.2%
[0079] (v) Fe84.8%-Si4%-B10%-Cu1.2%
[0080] (vi) Fe69.8%-Co15%-B10%-P4%-Cu1.2%
[0081] (vii) Fe69.8%-Ni1.2%-Co15%-B9.4%-P3.4%-Cu1.2%
[0082] Although (i) through (vii) were prepared so that each of the
materials had a corresponding one of the target chemical
compositions, in actual chemical compositions, after having
performed melting and atomizing, there were errors within the
margin of about plus or minus 0.3 at % or impurities were contained
in some cases. In addition, in some cases, there was some variation
in chemical composition due to, for example, oxidation occurring in
a melting process or an atomizing process or after an atomizing
process.
[0083] Examples 1 through 4 and comparative examples 1 through 3
were implemented under the conditions given in Table 1. The average
particle size and the amorphous material fraction were evaluated by
using the method described above. From the results of the examples
and the comparative examples, it was clarified that an amorphous
material fraction of 90% or more was achieved in the case of all
the examples, which were within the range of the present invention.
In the case of the comparative examples, an amorphous material
fraction of 90% or more was not achieved.
[0084] The atomized metal powder of examples 1 through 4 were
subjected to an appropriate heat treatment after having been
subjected to forming. With this, nanosized crystals were
precipitated. In addition, it was clarified that both low iron loss
and high magnetic flux density were achieved. Specifically, such
results were clarified by using the following method.
[0085] The sizes of the nanosized crystals were derived by using
the Scherrer equation after having performed determination
utilizing an XRD (X-ray diffractometer). In the Scherrer equation,
K denotes a shape factor (usually assigned a value of 0.9), .beta.
denotes a full-width at half maximum (expressed in units of
radian), .theta. is expressed by the equation
2.theta.=52.505.degree. (Fe110-plane), and .tau. denotes a crystal
size.
.tau.=K.lamda./.beta. cos .theta. (Scherrer equation)
[0086] In addition, the magnetic properties of the obtained powder
were investigated by using a VSM (vibrating sample magnetometer),
and, from the B-H diagram (FIG. 6) obtained by using the VSM, the
saturated magnetic flux density was determined from point C (point
F), the retaining force was determined from point E, the magnetic
permeability was determined from the maximum slope of B, and the
iron loss was determined from the hysteresis area (C-D-F-G). Here,
the diagram in FIG. 6 is opened to the public by Japan Science and
Technology Agency (JST), which is one of the National Research and
Development Agencies, (URL:
https://www.jst.go.jp/pr/report/report27/grf2.html, as searched on
16 Nov. 2017)
TABLE-US-00001 TABLE 1 Temper- Ejection Molten Cooling Water- ature
Pressure of Atomizing Judgement Metal Flow Water Molten of High-
High- Start Average Iron-group Average Amorphous (A ratio Example/
(Downward) Flow Metal pressure pressure Collision Temper- Temper-
Constituent Particle Material of 90% Comparative Rate Rate Ratio
Water Water Pressure ature ature State of Chemical Composition Fe +
Ni + Co Size Fraction or more is Example [kg/min] [kg/min] [-]
[.degree. C.] [MPa] [MPa] [.degree. C.] [.degree. C.] Water [at %]
[at %] [.mu.m] [%] satisfactory.) Example 1 15 300 20 10 90 20 1200
605 Subcritical (i) Fe.sub.76Si.sub.9B.sub.10P.sub.5 76.0 32 93
Satisfactory Example 2 15 420 28 10 90 20 1200 605 Subcritical (i)
Fe.sub.76Si.sub.9B.sub.10P.sub.5 76.0 33 99 Satisfactory 10 90 605
Subcritical (ii) Fe.sub.78Si.sub.9B.sub.9P.sub.4 78.0 33 97
Satisfactory 10 90 605 Subcritical (iii)
Fe.sub.80Si.sub.8B.sub.8P.sub.4 80.0 35 94 Satisfactory Example 3
12 420 35 10 100 23 1200 605 Supercritical (i)
Fe.sub.76Si.sub.9B.sub.10P.sub.5 76.0 34 100 Satisfactory 10 100
605 Supercritical (ii) Fe.sub.78Si.sub.9B.sub.9P.sub.4 78.0 29 99
Satisfactory 10 100 605 Supercritical (iii)
Fe.sub.80Si.sub.8B.sub.8P.sub.4 80.0 29 97 Satisfactory 10 100 605
Supercritical (iv) Fe.sub.82.8B.sub.11P.sub.5Cu.sub.1.2 82.8 35 95
Satisfactory 10 100 605 Supercritical (v)
Fe.sub.84.8Si.sub.4B.sub.10Cu.sub.1.2 84.8 36 94 Satisfactory 10
100 605 Supercritical (vi)
Fe.sub.69.8Co.sub.15B.sub.10P.sub.4Cu.sub.1.2 84.8 32 93
Satisfactory 10 100 605 Supercritical (vii)
Fe.sub.69.8Ni.sub.1.2Co.sub.15B.sub.9.4P.sub.3.4Cu.sub.1.2 86.0 35
92 Satisfactory Comparative 12 120 8 10 55 12 1200 605 Vapor (i)
Fe.sub.76Si.sub.9B.sub.10P.sub.5 76.0 43 83 Unsatisfactory Example
1 10 55 605 Vapor (ii) Fe.sub.78Si.sub.9B.sub.9P.sub.4 78.0 44 62
Unsatisfactory 10 55 605 Vapor (iii)
Fe.sub.80Si.sub.8B.sub.8P.sub.4 80.0 43 45 Unsatisfactory 10 55 605
Vapor (iv) Fe.sub.82.8B.sub.11P.sub.5Cu.sub.1.2 82.8 44 40
Unsatisfactory 10 55 605 Vapor (v)
Fe.sub.84.8Si.sub.4B.sub.10Cu.sub.1.2 84.8 45 38 Unsatisfactory 10
55 605 Vapor (vi) Fe.sub.69.8Co.sub.15B.sub.10P.sub.4Cu.sub.1.2
84.8 42 35 Unsatisfactory 10 55 605 Vapor (vii)
Fe.sub.69.8Ni.sub.1.2Co.sub.15B.sub.9.4P.sub.3.4Cu.sub.1.2 86.0 39
32 Unsatisfactory Comparative 12 420 35 10 60 15 1200 605 Vapor (i)
Fe.sub.76Si.sub.9B.sub.10P.sub.5 76.0 44 88 Unsatisfactory Example
2 10 60 605 Vapor (ii) Fe.sub.78Si.sub.9B.sub.9P.sub.4 78.0 42 73
Unsatisfactory 10 60 605 Vapor (iii)
Fe.sub.80Si.sub.8B.sub.8P.sub.4 80.0 39 63 Unsatisfactory 10 60 605
Vapor (vi) Fe.sub.82.8B.sub.11P.sub.5Cu.sub.1.2 82.8 43 53
Unsatisfactory 10 60 605 Vapor (v)
Fe.sub.84.8Si.sub.4B.sub.10Cu.sub.1.2 84.8 46 52 Unsatisfactory 10
60 605 Vapor (vi) Fe.sub.69.8Co.sub.15B.sub.10P.sub.4Cu.sub.1.2
84.8 43 46 Unsatisfactory 10 60 605 Vapor (vii)
Fe.sub.69.8Ni.sub.1.2Co.sub.15B.sub.9.4P.sub.3.4Cu.sub.1.2 86.0 43
44 Unsatisfactory Comparative 10 350 35 10 15 5 1200 605 Vapor (i)
Fe.sub.76Si.sub.9B.sub.10P.sub.5 76.0 38 5 Unsatisfactory Example 3
Example 4 12 480 40 10 90 20 1200 605 Subcritical (i)
Fe.sub.76Si.sub.9B.sub.10P.sub.5 76.0 33 100 Satisfactory
[0087] In Table 1, the term "Atomizing Start Temperature" denotes
the temperature of the molten metal at the atomizing point. The
temperature of the molten metal at the atomizing point was
determined by using a non-contact thermometer.
[0088] In Table 1, the term "Average Temperature" denotes a value
obtained by using the formula ((molten metal temperature)+(cooling
water temperature))/2. The molten metal temperature at the
atomizing point was determined by using a non-contact thermometer
at an atomizing point, and the cooling water temperature was
defined as the temperature of water in the cooling water tank which
was determined by using a thermometer.
[0089] In Table 1, the term "Water-Molten Metal Ratio" denotes the
mass ratio Qaq/Qm.
REFERENCE SIGNS LIST
[0090] 2 tundish [0091] 3 molten metal [0092] 4 molten
metal-injecting nozzle [0093] 5 nozzle header [0094] 6 cooling
nozzle [0095] 8 metal powder [0096] 14 atomizing apparatus [0097]
15 cooling water tank [0098] 16 cooling water-temperature
controller [0099] 17 high-pressure pump for atomizing cooling water
[0100] 18 pipework for atomizing cooling water [0101] 20 cooling
water [0102] 51 collision pressure sensor
* * * * *
References