SE1551331A1 - Iron powder for dust core - Google Patents
Iron powder for dust core Download PDFInfo
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- SE1551331A1 SE1551331A1 SE1551331A SE1551331A SE1551331A1 SE 1551331 A1 SE1551331 A1 SE 1551331A1 SE 1551331 A SE1551331 A SE 1551331A SE 1551331 A SE1551331 A SE 1551331A SE 1551331 A1 SE1551331 A1 SE 1551331A1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/05—Metallic powder characterised by the size or surface area of the particles
- B22F1/052—Metallic powder characterised by the size or surface area of the particles characterised by a mixture of particles of different sizes or by the particle size distribution
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/05—Metallic powder characterised by the size or surface area of the particles
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
- H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
- H01F1/147—Alloys characterised by their composition
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
- H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
- H01F1/20—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
- H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
- H01F1/20—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder
- H01F1/22—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together
- H01F1/24—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together the particles being insulated
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F3/00—Cores, Yokes, or armatures
- H01F3/08—Cores, Yokes, or armatures made from powder
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C2202/00—Physical properties
- C22C2202/02—Magnetic
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Dispersion Chemistry (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Soft Magnetic Materials (AREA)
- Powder Metallurgy (AREA)
Description
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such powder metallurgy techniques, there is a demand for components to have
excellent iron loss properties after formation (low hysteresis loss and low
eddy current loss).
In response to this demand, JP 4630251 B2 (PTL 1) and WO08/032707
(PTL 2) disclose techniques for improving magnetic properties as follows.
Iron-based powder is adjusted so that upon sieve classification with a sieve
having an opening of 425 um, the iron-based powder that does not pass
through the sieve constitutes 10 mass% or less, and upon sieve classification
with a sieve having an opening of 75 um, the iron-based powder that does not
pass through the sieve constitutes 80 mass% or more, and so that upon
inspecting at least 50 iron-based powder cross-sections, measuring the grain
size of each iron-based powder, and calculating the grain size distribution
including at least the maximum grain size, crystal grains with a grain size of
50 um or more constitute 70 % or more of the measured crystal grains.
[0007] JP H08-921 B (PTL 3) discloses a technique related to pure iron
powder for powder metallurgy with excellent compressibility and magnetic
properties. The impurity content ofthe iron powder is C S 0.005 %, Si S 0.010
%, Mn S 0.050 %, P S 0.010 %, S S 0.010 %, O S 0.10 %, and N S 0.0020 %,
and the balance of the powder consists substantially of Fe and incidental
impurities. The particle size distribution is, on the basis of weight percent by
sieve classification using sieves prescribed in JIS Z 8801, constituted by 5 %
or less of particles of -60/+83 mesh, 4 % or more to 10 % or less of particles
of -83/+100 mesh, 10 % or more to 25 % or less of particles of -100/+140
mesh, and 10 % or more to 30 % or less of particles passing through a sieve of
330 mesh. Crystal grains included in particles of -60/+200 mesh are coarse
crystal grains with a mean grain size number (a smaller number indicating a
larger grain size) of 6.0 or less measured by a ferrite grain size measuring
method prescribed in JIS G 0052. When 0.75 % of zinc stearate is blended as a
lubricant for powder metallurgy and the result is compacted with a die at a
compacting pressure of 5 t/cmz, a green density of 7.05 g/cmg or more is
obtained.
[0008] Furthermore, JP 2005-187918 A (PTL 4) discloses a technique related
to insulation-coated iron powder for dust cores such that an insulating layer is
formed on the surface of iron powder particles having a micro Vickers
hardness Hv of 75 or less, and JP 2007-092162 A (PTL 5) discloses a
technique related to high compressibility iron powder that includes by mass%,
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as impurities, C: 0.005 % or less, Si: more than 0.01 % to 0.03 % or less, Mn:
0.03 % or more to 0.07 % or less, S: 0.01 % or less, O: 0.10 % or less, and N:
0.001 % or less, wherein particles of the iron powder have a mean crystal
grain number of 4 or less and a micro Vickers hardness Hv of 80 or less on
average.
CITATION LIST
Patent Literature
[0009] PTL 1: JP 4630251 B
PTL 2: WO08/032707
PTL 3: JP H08-921 B
PTL 4: JP 2005-187918 A
PTL 5: JP 2007-092162 A
[0010] While a reduction in iron loss is considered in the techniques
disclosed in PTL 1 and PTL 2, the value remains high at 40 W/kg for iron loss
at 1.5 T and 200 Hz.
A reduction in iron loss is not sufficiently considered in the techniques
disclosed in PTL 3 through PTL 5, and the reduction of iron loss has thus
remained a problem.
[0011] It could therefore be helpful to provide iron powder for dust cores in
order to manufacture a dust core that has low hysteresis loss even after the
iron powder is formed and subjected to strain relief annealing.
SUMMARY
[0012] In the case of an iron core used at a relatively low frequency (3 kHz or
less), such as a motor iron core, hysteresis loss accounts for the majority of
iron loss. Nevertheless, the hysteresis loss of a dust core is extremely high as
compared to a stacked steel sheet. In other words, in order to reduce iron loss
of a dust core, reduction of hysteresis loss becomes extremely important.
[0013] Upon carefully examining hysteresis loss in dust cores, we discovered
that hysteresis loss in dust cores has a particularly strong correlation with the
inverse of the grain size of the green compact, and that when the inverse of
the grain size is small, i.e. in the case of coarse crystal grains, low hysteresis
loss is obtained.
[0014] Furthermore, in order to obtain a dust core with coarse crystal grains,
POl40l32-PCT-ZZ (3/16)
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we discovered that the following factors are important:
(I) a coarse particle size and grain size in the original powder,
(II) no unnecessary strain in the powder,
(III) strain not accumulating easily upon formation, and
(IV) nothing to impede growth of crystal grains in the powder at the time of
strain relief annealing.
Our iron powder for dust cores is based on these discoveries.
[0015] We thus provide:
1. An iron powder for dust cores comprising iron as a principal component,
wherein the iron powder has an apparent density of 3.8 g/cm3 or more and a
mean particle size (D50) of 80 um or more, 60 % or more of powder with a
powder particle size of 100 um or more has a mean grain size of 80 um or
more inside the powder particle, an area ratio of an inclusion within an area of
a matrix phase of the powder is 0.4 % or less, and a micro Vickers hardness
(testing force: 0.245 N) of a powder cross-section is 90 HV or less.
[0016] 2. The iron powder for dust cores of 1., wherein 70 % or more of the
powder with the powder particle size of 100 um or more has the mean grain
size of 80 um or more inside the powder particle.
[0017] It is thus possible to obtain iron powder for dust cores in order to
manufacture a dust core that has a coarse grain size and low hysteresis loss
even after the iron powder is formed and subjected to strain relief annealing.
DETAILED DESCRIPTION
[0018] Our iron powder for dust cores will now be described in detail.
The reasons for the numerical limitations on our iron powder are
described. Iron is used as the principal component in our powder, and such a
powder with iron as the principal component refers to including 50 mass% or
more of iron. Other components may be included as per the chemical
composition and ratios used in conventional iron powder for dust cores.
[0019] (Apparent density)
Iron powder undergoes plastic deformation by press forming to
become a high-density green compact. We discovered that as the amount of
plastic deformation is smaller, the crystal grains after strain relief annealing
become coarser.
In other words, in order to reduce the amount of plastic deformation of
the powder at the time of forming, the filling rate of the powder into the die
PO140 1 32-PCT-ZZ (4/16)
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needs to be increased. We discovered that to do so, the apparent density ofthe
powder needs to be 3.8 g/cmg or more, preferably 4.0 g/cmg or more.
The reason is that if the apparent density falls below 3.8 g/cm3, a large
amount of strain is introduced into the powder at the time of formation, and
the crystal grains after formation and strain relief annealing end up being
refined. No upper limit is placed on the apparent density of the powder, yet in
industrial terms the upper limit is approximately 5.0 g/cmg.
The apparent density is an index indicating the degree of the filling
rate of the powder and can be measured with the experimental method
prescribed in JIS Z 2504.
[0020] (Mean particle size: D50)
The upper limit on the grain size of the green compact is the particle
size of the base power. The reason is that in the case of a dust core, the
particle surface is covered by an insulating layer, and the crystal grain cannot
grow coarser beyond the insulating layer. Therefore, the mean particle size of
the powder should be as large as possible, such as 80 um or more and
preferably 90 um or more. No upper limit is placed on the mean particle size
of the powder, yet the upper limit may be approximately 425 um.
In this disclosure, the mean particle size refers to the median size D50
of a weight cumulative distribution and is assessed by measuring the particle
size distribution using sieves prescribed in JIS Z 8801-1.
[0021] (Grain size within particles having a particle size of 100 um or more)
At the time of plastic deformation, high strain easily accumulates at
crystal grain boundaries, which easily become nuclei-generating sites of
recrystallized grains. In particular, powder with a large powder particle size
easily undergoes plastic deformation at the time of formation, and strain
easily accumulates. Therefore, in powder with a powder particle size of 100
um or more, there should be few crystal grain boundaries in the powder state.
Specifically, 60 % or more of powder with a powder particle size of 100 um or
more needs to have a mean grain size of 80 um or more inside the powder
particle when the mean grain size measured by powder cross-section
observation. The ratio of powder for which the mean grain size is 80 um or
more is preferably 70 % or more.
[0022] The grain size of our powder may be calculated with the following
method.
First, the iron powder to be measured is mixed into thermoplastic resin
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powder. The resulting mixed powder is then injected into an appropriate mold
and heated to melt the resin. The result is cooled and hardened to yield a resin
solid that contains iron powder.
An appropriate cross-section of this resin solid that contains iron
powder is cut, and the resulting face is polished and treated by corrosion.
Using an optical microscope or a scanning electron microscope (100x
magnification), the cross-sectional microstructure of the iron powder particles
is then observed and imaged. Image processing is then performed on the
captured image, and the area of the particles is calculated. Commercially
available image analysis software, such as Image J, may be used for image
analysis.
[0023] From the area of the particles, the particle sizes under spherical
approximation are calculated, and particles With a particle size of 100 um or
more are distinguished. Next, for particles with a particle size of 100 um or
more, the particle area is divided by the number of crystal grains in the
particle to calculate the crystal grain area. The size calculated by spherical
approximation from this crystal grain area is then taken as the grain size.
We performed this operation in at least four fields on 10 or more
particles with a particle size of 100 um or more to calculate the abundance
ratio (%) of particles with a grain size of 80 um or more in the powder. In
other words, calculating the abundance ratio (%) allows for calculation of the
ratio (%) of powder that, among powder with a particle size of 100 um or
more, has a mean grain size of 80 um or more inside the powder.
[0024] (Area ratio of inclusions)
When present in the powder, inclusions become a pinning site at the
time of recrystallization and thus are not preferable for suppressing grain
growth. Furthermore, inclusions themselves become nuclei-generating sites of
recrystallized grains and refine the crystal grain after formation and strain
relief annealing. Inclusions themselves also cause an increase in hysteresis
loss. Therefore, there are preferably few inclusions, and when observing a
powder cross-section, the area ratio of inclusions should be 0.4 % or less of
the area of the matrix phase of the powder, preferably 0.2 % or less. The lower
limit is not restricted and may be 0 %. The area of the matrix phase of the
powder refers to the phase occupying 50 % or more of the powder
cross-sectional area when observing a cross-section of a certain powder. For
example, in the case of pure iron powder, the matrix phase refers to the ferrite
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phase in the powder cross-section. In the case of pure iron powder, the matrix
phase is the result of subtracting the area of voids within the grain boundary
of the powder from the area surrounded by the grain boundary of the powder.
[0025] Oxides including one or more of Mg, Al, Si, Ca, Mn, Cr, Ti, Fe, and
the like are possible inclusions. The area ratio of inclusions may be calculated
with the following method.
[0026] First, the iron powder to be measured is mixed into thermoplastic resin
powder. The resulting mixed powder is then injected into an appropriate mold
and heated to melt the resin. The result is cooled and hardened to yield a resin
solid that contains iron powder. An appropriate cross-section of this resin
solid that contains iron powder is cut, and the resulting face is polished and
treated by corrosion. Using a scanning electron microscope (l000x to 5000x
magnification), the cross-sectional microstructure of the iron powder particles
is then observed and imaged as a backscattered electron image. In the
captured image, inclusions appear with dark contrast. Therefore, the area ratio
of inclusions can be calculated by applying image processing. We performed
this process in any five or more fields chosen from the entire amount of iron
powder that is being measured and then used the mean area ratio of inclusions
in each field.
[0027] (Micro Vickers hardness of powder cross-section)
If strain accumulates inside the powder from before formation, then
even if the above-described powder adjustment is performed, the crystal
grains end up being refined, after formation and strain relief annealing, to the
extent of the accumulated strain. Accordingly, the strain in the powder should
be reduced insofar as possible.
For manufacturing reasons, however, atomized iron powder is
subjected to reduction annealing in order to reduce the oxygen content, after
which the iron powder needs to be mechanically crushed. Therefore, strain
accumulates in the powder.
As described above, we discovered a correlation between strain in
powder and hardness of the powder. As the hardness is lower, there is less
strain.
Therefore, in our powder, the amount of strain is evaluated by micro
Vickers hardness. Specifically, the hardness of the iron powder cross-section
is set to be 90 Hv or less. The reason is that if the hardness of the powder
exceeds 90 HV, the crystal grains are refined after formation and strain relief
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annealing, thereby increasing hysteresis loss. The hardness is preferably 80
HV or less.
[0028] The micro Vickers hardness can be measured with the following
method.
First, the iron powder to be measured is mixed into thermoplastic resin
powder. The resulting mixed powder is then injected into an appropriate mold
and heated to melt the resin. The result is cooled and hardened to yield a resin
solid that contains iron powder. An appropriate cross-section of this resin
solid that contains iron powder is cut, and the resulting face is polished. After
removing this polished, treated layer by corrosion, the hardness is measured
using a micro Vickers hardness gauge (test force: 0.245 N (25 gf)) in
accordance with JIS Z 2244. With one measurement point per particle, the
hardness of at least ten particles of powder is measured, with the mean then
being taken.
[0029] Next, a representative method of manufacturing to obtain our product
is described. Of course, a method other than the one described below may be
used to obtain our product.
Our powder, which has iron as the principal component, is preferably
manufactured using an atomizing method. The reason is that powder obtained
by an oxide reduction method or electrolytic deposition has a low apparent
density, and a sufficient apparent density might not be obtained even if
processing such as additional crushing is performed to increase the apparent
density.
[0030] The atomizing method may be of any type, such as gas, water, gas and
water, centrifugation, or the like. ln practical terms, however, it is preferable
to use an inexpensive Water atomizing method or a gas atomizing method,
which is more expensive than a water atomizing method yet which allows for
relative mass production. As a representative example, the following
describes a method of manufacturing when using a water atomizing method.
[0031] It suffices for the chemical composition of molten steel being
atomized to have iron as the principal component. However, since a large
quantity of oxide-based inclusions might be generated at the time of atomizing,
the content of oxidizable metal elements (Al, Si, Mn, Cr, and the like) is
preferably low. The following contents are preferable: Al S 0.01 mass%, Si S
0.03 mass%, Mn S 0.1 mass%, and Cr S 0.05 mass%. Of course, the content of
oxidizable metal elements other than those listed above is also preferably
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reduced insofar as possible.
[0032] The atomized powder is then subjected to decarburization and
reduction annealing. The annealing is preferably high-load treatment
performed in a reductive atmosphere including hydrogen. For example, one or
multiple stages of heat treatment is preferably performed in a reductive
atmosphere including hydrogen, at a temperature of 700 °C or more to less
than 1200 °C, preferably 900 °C or more to less than 1100 °C, with a holding
time of 1 h to 7 h, preferably 2 h to 5 h. The grain size in the powder is thus
coarsened. The dew point in the atmosphere is not limited and may be set in
accordance with the C content included in the atomized powder.
[0033] After reduction annealing, the powder is subject to the first crushing.
The apparent density is thus set to 3.8 g/cmg or more. After the first crushing,
annealing is performed in hydrogen at 600 °C to 850 °C to remove strain in
the iron powder. The reason for performing the annealing at 600 °C to 850 °C
is in order to set the micro Vickers hardness of the powder cross-section to 90
Hv or less. After strain removal, the powder is crushed, avoiding the
application of strain insofar as possible. After crushing, the particle size
distribution is adjusted by sieve Classification using sieves prescribed in JIS Z
8801-1 so that the apparent density and mean particle size fall within the
ranges of our powder.
[0034] Furthermore, an insulation coating is applied to the above-described
iron powder, which is then formed into a dust core.
The insulation coating applied to the powder may be any coating
capable of maintaining insulation between particles. Examples of such an
insulation coating include silicone resin; a Vitreous insulating amorphous
layer with metal phosphate or metal borate as a base; a metal oxide such as
MgO, forsterite, talc, or AlgOg; or a crystalline insulating layer with SiOg as a
base.
[0035] After applying an insulation coating to the particle surface with such a
method, the resulting iron-based powder is injected in a die and pressure
formed to a shape with desired dimensions (dust core shape) to yield a dust
core. The pressure formation method may be any regular formation method,
such as cold molding, die lubrication molding, or the like. The compacting
pressure may be determined in accordance with use. If the compacting
pressure is increased, however, the green density increases. Hence, a
compacting pressure of 10 t/cmz (981 MN/mz) or more is preferable, with 15
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_]()_
t/cmz (1471 MN/mz) or more being more preferable.
[0036] At the time of the above-described pressure formation, as necessary, a
lubricant may be applied to the die walls or added to the powder. At the time
of pressure formation, the friction between the die and the powder can thus be
reduced, thereby suppressing a reduction in the green density. Furthermore,
the friction upon removal from the die can also be reduced, effectively
preventing cracks in the green compact (dust core) at the time of removal.
Preferable lubricants in this case include metallic soaps such as lithium
stearate, zinc stearate, and calcium stearate, and waxes such as fatty acid
amide.
[0037] The dust core thus formed is subjected, after pressure formation, to
heat treatment in order to reduce hysteresis loss via strain relief and to
increase the green compact strength. The heat treatment time of this heat
treatment is preferably approximately 5 min to 120 min. Any ofthe following
may be used Without any problem as the heating atmosphere: the regular
atmosphere, an inert atmosphere, a reductive atmosphere, or a vacuum. The
atmospheric dew point may be determined appropriately in accordance with
use. Furthermore, when raising or lowering the temperature during heat
treatment, a stage at which the temperature is maintained constant may be
provided.
EXAMPLES
(Example 1)
[0038] The iron powders used in this Example are 10 types of atomized pure
iron powder with different values for the apparent density, D50, grain size,
amount ofinclusions, and micro Vickers hardness.
The iron powders with an apparent density of 3.8 g/cms or more were
gas atomized iron powders, and the iron powder with an apparent density of
less than 3.8 g/cmg was water atomized iron powder. In either case, the
composition of each iron powder was C < 0.005 mass%, O < 0.10 mass%, N <
0.002 mass%, Si < 0.025 mass%, P < 0.02 mass%, and S < 0.002 mass%.
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[0039] [Tabie 1]
Table 1
Ratio of powder with a
ü Apparem grain size of 80 um or V 1\'/[icro
No. of iron . D50 more among powder Inclusions Vickers
ÖÛHSITY . . . Notes
powder 3 (um) with a particle size of (%) hardness
(g/Cm ) 100 um or more (Hv)
(%)
1 4.3 98.6 100 0.38 85 Example
2 4.2 102.4 86.2 0.24 80 Example
3 4.3 98.6 62.0 0.26 82 Example
4 4.2 102.2 65.0 0.21 83 Example
5 4.4 104.5 70.8 0.18 78 Example
6 4.4 106.4 95.0 0.39 100 Cmnparme
Example
7 4.1 09.0 45.0 0.37 37 Cmnparanve
Example
s 3.2 95.0 62.0 0.26 76 Cmnparanve
Example
9 3.8 75.5 60.1 0.37 35 Cmnparanve
Example
10 3.9 160.0 100 0.57 34 Cmnparanve
Example
[0040] An insulation coating was applied to these powders using Silicone
resin. The silicone resin was dissolved in toluene to produce a resin dilute
solution such that the resin component is 0.9 mass%. The powder and the resin
dilute solution were then mixed so that the rate of addition of the resin with
respect to the powder became 0.15 mass%. The result was then dried in the
atmosphere. After drying, a resin baking process Was performed in the
atmosphere at 200 °C for 120 min to yield coated iron-based soft magnetic
powders. These powders were then formed using die lubrication at a
compacting pressure of 15 t/cmz (1471 MN/mz) to produce ring-shaped test
pieces with an outer diameter of 38 mm, an inner diameter of 25 mm, and a
height of 6 rnrn.
The test pieces thus produced were subjected to heat treatment in
nitrogen at 650 °C for 45 min to yield samples. Winding was then performed
(primary Winding: 100 turns; secondary Winding: 40 turns), and hysteresis
loss measurement with a DC magnetizing device (l.5 T, DC magnetizing
measurement device produced by METRON, Inc.) and iron loss measurement
PO140 l 32-PCT-ZZ (1 l/l 6)
10
15
20
25
_12-
With an iron loss measurement device (l.5 T, 200 Hz, model 5060A produced
by Agilent Technologies) Were performed.
[0041] The samples after iron loss measurement Were dissected, and the grain
size Was measured. Since dissected samples maintain the grain size in a green
compact cross-section, the grain size in a green compact cross-section Was
measured With the following method.
First, the green compact (sample) to be measured Was cut into pieces
of an appropriate size (for example, l cm square), mixed With thermoplastic
resin, injected into an appropriate mold, and heated to melt the resin. The
result Was cooled and hardened to yield a resin solid containing green
compact.
Next, the resin solid containing green compact Was cut so that the
observation cross-section Was perpendicular to the circumferential direction
of the ring green compact, and the cut face Was polished and treated by
corrosion. Using an optical microscope or a scanning electron microscope
(200x magnification), the cross-sectional microstructure Was then imaged. In
the captured image, five vertical lines and five horizontal lines Were draWn,
and the number of crystal grains traversed by the lines Was counted. The grain
size Was calculated by dividing by the entire length of the five vertical and
five horizontal lines by the number of crystal grains traversed. In the case of a
line traversing a void, the traversed length of the void was subtracted from the
total length.
This measurement Was performed in four fields for each sample, and
the mean Was calculated and used.
Table 2 lists the results of measuring the crystal grains.
POl40l32-PCT-ZZ (12/16)
10
[0042] [Table 2]
Table 2
_13-
No. of green No. of iron Green compact Notes
compact sample powder used grain size (pm)
l l 27.0 Example
2 2 29.7 Example
3 3 28.7 Example
4 4 27.9 Example
5 5 33.6 Example
6 6 1 9. 9 Comparative
Example
Comparative
7 7 21.2
Example
8 8 12. 1 Comparative
Example
9 9 1 7. 7 Comparative
Example
10 10 19.0 Comparative
Example
[0043] Table 2 shows that the largest grain size in the Comparative Examples
Was 21.2 pm, Whereas in the Examples, the smallest grain size Was 27.0 pm,
and the largest Was 33.6 pm.
Table 3 lists the measurement results obtained by performing magnetic
measurements on the samples. The acceptance criterion for iron loss in the
Examples Was set to 30 W/kg or less, an even lower value than the acceptance
criterion for the Examples disclosed in PTL l (40 W/kg or less).
POl40l32-PCT-ZZ (13/16)
10
15
[0044] [Tabie 3]
_14-
Table 3
Sample No. of iron Hysteresis Eddy current
No. powder used loss (W/kg) loss (W/kg) Iron loss (W/kg) Notes
1 1 23. 1 3.7 26. 8 Example
2 2 20.6 3.8 24.4 Example
3 3 2 l. 1 3. 8 24. 9 Example
4 4 20.2 3.9 24. 1 Example
5 5 19. 6 4. 2 23. 8 Example
6 6 27.1 4.9 32.0 Comparatwe
Example
7 7 27.1 3.1 30.2 (hmparatwe
Example
8 8 3 1.2 unmeasurable unmeasurable Comparanve
Example
9 9 28.4 2.6 31.0 Cmnparatwe
Example
10 10 32.3 7.0 39.3 Comparatwe
Example
[0045] Table 3 shows that as compared to the Comparative Examples, the
hysteresis loss was kept lower in all of the Examples, thereby keeping the iron
loss low and satisfying the acceptance criterion for iron loss in all of the
above Examples.
[0046] It is also clear that for both the Examples and the Comparative
Examples, every sample with an apparent density of 3.8 g/cm3 or more had an
eddy current loss of less than 10 W/kg. This shows that by only covering with
Silicone resin, the insulation between particles was maintained even after
strain relief annealing at 650 °C, and that the increase in apparent density was
effective for reducing both hysteresis loss and eddy current loss.
POl40 l 32-PCT-ZZ (14/16)
Claims (2)
- l. An iron powder for dust cores comprising iron as a principal component, wherein the iron powder has an apparent density of 3.8 g/cmg or more and a mean particle size (D50) of 80 pm or more, 60 % or more of powder with a powder particle size of 100 pm or more has a mean grain size of 80 pm or more inside the powder particle, an area ratio of an inclusion to a matrix phase of the powder is 0.4 % or less, and a micro Vickers hardness (testing force: 0.245 N) of a powder cross-section is 90 HV or less.
- 2. The iron powder for dust cores of claim l, wherein 70 % or more of the powder with the powder particle size of 100 pm or more has the mean grain size of 80 pm or more inside the powder particle. POl40l32-PCT-ZZ (15/16)
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JP2013088720A JP5929819B2 (ja) | 2013-04-19 | 2013-04-19 | 圧粉磁芯用鉄粉 |
PCT/JP2014/001559 WO2014171065A1 (ja) | 2013-04-19 | 2014-03-18 | 圧粉磁芯用鉄粉 |
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JP (1) | JP5929819B2 (sv) |
KR (1) | KR101783255B1 (sv) |
CN (1) | CN105142823B (sv) |
CA (1) | CA2903392C (sv) |
SE (1) | SE540046C2 (sv) |
WO (1) | WO2014171065A1 (sv) |
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JPH08921B2 (ja) | 1992-06-19 | 1996-01-10 | 株式会社神戸製鋼所 | 圧縮性と磁気特性に優れた粉末冶金用純鉄粉 |
JP2005187918A (ja) * | 2003-12-26 | 2005-07-14 | Jfe Steel Kk | 圧粉磁心用絶縁被覆鉄粉 |
JP4457682B2 (ja) | 2004-01-30 | 2010-04-28 | 住友電気工業株式会社 | 圧粉磁心およびその製造方法 |
JP4305222B2 (ja) * | 2004-03-05 | 2009-07-29 | 住友電気工業株式会社 | 圧粉成形体の製造方法 |
SE0401042D0 (sv) | 2004-04-21 | 2004-04-21 | Hoeganaes Ab | Lubricants for metallurgical powder compositions |
JP2006024869A (ja) * | 2004-07-09 | 2006-01-26 | Toyota Central Res & Dev Lab Inc | 圧粉磁心およびその製造方法 |
JP2007092162A (ja) * | 2005-02-03 | 2007-04-12 | Jfe Steel Kk | 高圧縮性鉄粉、およびそれを用いた圧粉磁芯用鉄粉と圧粉磁芯 |
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JP4630251B2 (ja) | 2006-09-11 | 2011-02-09 | 株式会社神戸製鋼所 | 圧粉磁心および圧粉磁心用の鉄基粉末 |
CN101534979B (zh) * | 2007-01-30 | 2011-03-09 | 杰富意钢铁株式会社 | 高压缩性铁粉及使用该高压缩性铁粉的压粉磁芯用铁粉和压粉磁芯 |
JP5263653B2 (ja) * | 2007-04-04 | 2013-08-14 | 日立金属株式会社 | 圧粉磁心およびその製造方法 |
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JP4957859B2 (ja) | 2010-08-31 | 2012-06-20 | Jfeスチール株式会社 | 種子被覆用鉄粉及び種子 |
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- 2014-03-18 WO PCT/JP2014/001559 patent/WO2014171065A1/ja active Application Filing
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SE540046C2 (sv) | 2018-03-06 |
US10410780B2 (en) | 2019-09-10 |
JP2014210966A (ja) | 2014-11-13 |
US20150364236A1 (en) | 2015-12-17 |
CN105142823A (zh) | 2015-12-09 |
CA2903392A1 (en) | 2014-10-23 |
JP5929819B2 (ja) | 2016-06-08 |
CN105142823B (zh) | 2017-07-28 |
WO2014171065A1 (ja) | 2014-10-23 |
CA2903392C (en) | 2017-06-27 |
KR20150122180A (ko) | 2015-10-30 |
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