[Technical Field]
[0001]
The present invention relates to an electrical steel sheet, a laminated core, and a
laminated core manufacturing method.
Priority is claimed on Japanese Patent Application No. 2020-104245, filed June
10 17, 2020, the content of which is incorporated herein by reference.
[Background Art]
[0002]
A laminated core in which a plurality of electrical steel sheets are laminated is
used for a rotary electric machine. These electrical steel sheets are integrated in a
15 laminated state by a method such as fastening, welding, adhering, or the like. However,
when lamination is performed by fastening or welding, magnetic properties of each
electrical steel sheet may deteriorate due to a mechanical stress or a thermal stress
applied during processing, and furthermore interlayer short -circuiting, and performance
of the laminated core may not be fully exhibited. Lamination by adhesion is extremely
20 effective in solving this problem.
[0003]
For example, the non-grain-oriented electrical steel sheet product disclosed in
Patent Document 1 below employs a configuration in which it includes a plurality of
non-grain-oriented electrical steel sheets and an adhesive coating layer positioned
25 between the plurality of non-grain-oriented electrical steel sheets, the adhesive coating
1
layer contains a first component containing an organic/inorganic complex and a second
component containing a composite metal phosphate, the first component is contained in
an amount of 70 to 99% by weight and the second component is contained in an amount
of 1 to 30% by weight with respect to 100% by weight of a total amount of the adhesive
5 coating layer, the organic/inorganic complex is obtained by chemically substituting
inorganic nanoparticles with some functional groups in an organic resin, the organic resin
is one or more selected from an epoxy-based resin, an ester-based resin, an acrylic-based
resin, a styrene-based resin, a urethane-based resin, and an ethylene-based resin, and the
inorganic nanoparticles are one or more selected from Si02, Ah03, Ti02, MgO, ZnO, and
10 Zr02.
According to this configuration, it is explained that, even if a thickness of the
adhesive coating layer is formed thin, characteristics such as weldability, heat resistance,
adhesion before and after SRA, and a stacking factor can be improved while an excellent
adhesiveness and insulating properties are exhibited.
15 [0004]
Also, the electrical steel sheet disclosed in Patent Document 2 is an electrical
steel sheet with an insulation coating having a heat-resistant adhesive insulation coating
on one side or both sides thereof, and employs a configuration in which the heat-resistant
adhesive insulation coating contains 70% by mass or more of a polyether urethane resin
20 and 30 parts by mass or less of a silane compound with respect to 100 parts by mass of
the pol yether urethane resin.
According to this configuration, a high-temperature adhesiveness is required as
in automobile motors.
[Citation List]
25 [Patent Document]
2
[0005]
[Patent Document 1]
Published Japanese Translation No. 2019-508573 of the PCT International
Publication
5 [Patent Document 2]
10
Japanese Unexamined Patent Application, First Publication No. 2017-186542
[Summary of the Invention]
[Problems to be Solved by the Invention]
[0006]
An electrical steel sheet is required to combine both adhesiveness, and resistance
to slitting and scratch prevention ability. However, in the above-described Patent
Documents 1 and 2, while an adhesiveness after lamination is examined, a resistance to
slitting and a scratch prevention ability are not examined at all.
Here, the adhesiveness means that an insulation coating is melted and exhibits
15 adhesive properties when at least one of heating and pressurizing is applied. The
adhesiveness increases as the insulation coating becomes softer.
On the other hand, the resistance to slitting means difficulty in scratching and
peeling off of an insulation coating when front and back surfaces of an electrical steel
sheet are rubbed by a pad that presses the electrical steel sheet for performing slit
20 processing. Further, the "scratch prevention ability" means difficulty in being scratched
when a back surface of a base steel sheet is rubbed during transfer of the base steel sheet
between a plurality of molds. The resistance to slitting and the scratch prevention
ability become higher as the insulation coating becomes harder.
As described above, the adhesiveness, and the resistance to slitting and scratch
25 prevention ability are in a contradictory relationship with respect to the hardness of the
3
insulation coating by which they are realized. That is, the adhesiveness is sacrificed
when the hardness of the insulation coating is increased, and conversely, the resistance to
slitting and the scratch prevention ability are impaired when the hardness of the
insulation coating is decreased.
5 [0007]
The present invention has been made in view of the above circumstances and is
directed to providing an electrical steel sheet in which both high adhesiveness, and high
resistance to slitting and scratch prevention ability can be achieved, a laminated core
formed by laminating a plurality of these electrical steel sheets, and a laminated core
10 manufacturing method for manufacturing the laminated core.
[Means for Solving the Problem]
15
[0008]
In order to solve the above-described problems and achieve the objective, the
present invention employs the following aspects.
( 1) An electrical steel sheet according to one aspect of the present invention
includes a base steel sheet, a first insulation coating formed on a first surface of the base
steel sheet and having adhesiveness, and a second insulation coating formed on a second
surface of the base steel sheet which is a back surface to the first surface and having
adhesiveness, in which an average pencil hardness of the first insulation coating is HB or
20 higher and 3H or lower, and an average pencil hardness of the second insulation coating
is higher than the average pencil hardness of the first insulation coating.
According to the electrical steel sheet of the above-described (1 ), roles are
differently assigned to front and back surfaces of the base steel sheet by making a change
in hardness therebetween. Specifically, since the second surface side is covered with
25 the second insulation coating that is relatively hard, a high resistance to slitting and
4
scratch prevention ability can be exhibited. On the other hand, since the first surface
side is covered with the first insulation coating that is relatively soft and has an average
pencil hardness of HB or higher, a relatively high adhesive strength can be exhibited
while a necessary and sufficient resistance to slitting and scratch prevention ability are
5 secured.
Specifically, an adhesiveness of the first insulation coating and an adhesiveness
of the second insulation coating are exhibited when the first insulation coating and the
second insulation coating are melted by receiving at least one of heating and pressurizing
in a state in which a plurality of electrical steel sheets are laminated, and the first
10 insulation coating and the second insulation coating overlap each other. Here, since the
adhesiveness of the first insulation coating is higher than that of the second insulation
coating, an adhesive strength between the electrical steel sheets when the laminated core
is formed is mainly secured by the adhesiveness of the first insulation coating. Here, if
the adhesive strength described in a first example to be described later is used as an
15 example, the adhesiveness of the first insulation coating required for forming the
laminated core is 980 N or more.
As described above, according to the electrical steel sheet of the present aspect,
both adhesiveness for forming the laminated core, and high resistance to slitting and
scratch prevention ability can be achieved.
20 [0009]
(2) In the electrical steel sheet of the above-described (1), the average pencil
hardness of the second insulation coating may be 4H or higher and 9H or lower.
According to the electrical steel sheet of the above-described (2), both the
resistance to slitting and scratch prevention ability on the second surface, and the
25 adhesive strength on the first surface can be more reliably achieved.
5
[0010]
(3) In the electrical steel sheet of the above-described (1) or (2), the following
configuration may be employed. The first insulation coating and the second insulation
coating both contain the same main agent and the same curing agent, and, when an
5 equivalent ratio of the curing agent to the main agent in the first insulation coating is a
and an equivalent ratio of the curing agent to the main agent in the second insulation
coating is b, a relative ratio expressed by alb is 0.60 or more and 0.95 or less.
According to the electrical steel sheet of the above-described (3 ), both the
resistance to slitting and scratch prevention ability on the second surface, and the
10 adhesive strength on the first surface can be more reliably achieved.
15
20
[0011]
( 4) A laminated core according to one aspect of the present invention is formed
by laminating two or more electrical steel sheets according to any one of the abovedescribed
(1) to (3).
According to the laminated core of the above-described ( 4 ), since the laminated
core is manufactured by using the electrical steel sheet in which both necessary and
sufficient adhesive strength, and high resistance to slitting and scratch prevention ability
can be achieved, a rigidity is high and a yield is satisfactory.
[0012]
(5) A laminated core manufacturing method according to one aspect of the
present invention includes a punching step of obtaining a plurality of electrical steel
sheets according to any one of the above-described (1) to (3) by punching a material
while intermittently conveying the material in a conveying direction, and a laminating
step of laminating each of the electrical steel sheets, in which the material includes the
25 base steel sheet, the first insulation coating formed on an upper surface of the base steel
6
sheet, and the second insulation coating formed on a lower surface of the base steel sheet,
the material is conveyed with the second insulation coating facing downward in the
punching step, and each electrical steel sheet is laminated so that the second insulation
coating of the electrical steel sheet to be laminated later overlaps the first insulation
5 coating of the electrical steel sheet laminated previously in the laminating step.
According to the laminated core manufacturing method of the above-described
(5), in the punching step, the material is conveyed while the second insulation coating,
which has a relatively high average pencil hardness, faces downward. Therefore, since
scratches on the material during conveyance can be prevented, a robust laminated core
10 can be manufactured using the electrical steel sheet having less scratches and dusting.
[Effects of the Invention]
[0013]
According to the above-described aspects of the present invention, it is possible
to provide the electrical steel sheet in which both high adhesiveness, and high resistance
15 to slitting and scratch prevention ability can be achieved, the laminated core formed by
laminating a plurality of these electrical steel sheets, and the laminated core
manufacturing method for manufacturing the laminated core.
20
[Brief Description of Drawings]
[0014]
FIG. 1 is a cross-sectional view of a rotary electric machine including a
laminated core according to one embodiment of the present invention.
FIG. 2 is a side view of the laminated core.
FIG. 3 is a plan view of an electrical steel sheet constituting the laminated core.
FIG. 4 is a plan view of a strip-shaped steel sheet which is a material of the
25 electrical steel sheet.
7
5
FIG. 5 is a view illustrating the material and is a cross-sectional view along a
line A-A of a B portion in FIG. 4.
FIG. 6 is a side view illustrating an example of a manufacturing device which
obtains an electrical steel sheet from the material and manufactures the laminated core.
FIG. 7 is a flowchart showing an example of a laminated core manufacturing
method using the manufacturing device.
[Embodiments for implementing the Invention]
[0015]
Hereinafter, a laminated core according to one embodiment of the present
10 invention, a rotary electric machine including the laminated core, and a material
(electrical steel sheet) forming the laminated core will be described with reference to the
drawings. Further, in the present embodiment, an electric motor, specifically an AC
electric motor, more specifically a synchronous electric motor, and even more
specifically a permanent magnetic electric motor will be described as one example of the
15 rotary electric machine. An electric motor of this type is suitably employed for, for
example, electric automobiles.
[0016]
(Rotary electric machine 1 0)
As illustrated in FIG. 1, the rotary electric machine 10 includes a stator 20, a
20 rotor 30, a case 50, and a rotating shaft 60. The stator 20 and rotor 30 are housed in the
case 50. The stator 20 is fixed in the case 50.
In the present embodiment, an inner rotor type in which the rotor 30 is
positioned on a radially inner side of the stator 20 is employed as the rotary electric
machine 10. However, an outer rotor type in which the rotor 30 is positioned on an
25 outer side of the stator 20 may also be employed as the rotary electric machine 10.
8
Also, in the present embodiment, the rotary electric machine 10 is a 12-pole 18-slot
three-phase AC motor. However, the number of poles, the number of slots, the number
of phases, or the like can be changed as appropriate.
The rotary electric machine 10 can rotate at a rotation speed of 1000 rpm by
5 applying, for example, an excitation current having an effective value of 10 A and a
frequency of 100 Hz to each phase.
10
[0017]
The stator 20 includes a laminated core for a stator (hereinafter referred to as a
stator core) 21 and a winding (not illustrated).
A plurality of electrical steel sheets 40 constituting the stator core 21 each
include an annular core back part 22 and a plurality of tooth parts 23. Hereinafter, a
central axis 0 direction of the stator core 21 (or the core back part 22) is referred to as an
axial direction, a radial direction (a direction perpendicular to the central axis 0) of the
stator core 21 (or the core back part 22) is referred to as a radial direction, and a
15 circumferential direction (a direction revolving around the central axis 0) of the stator
20
core 21 (or the core back part 22) is referred to as a circumferential direction.
[0018]
The core back part 22 is formed in an annular shape in a plan view of the stator
20 from the axial direction.
The plurality of tooth parts 23 protrude inward in the radial direction (toward the
central axis 0 of the core back part 22 in the radial direction) from an inner
circumference of the core back part 22. The plurality of tooth parts 23 are disposed at
equiangular angle intervals in the circumferential direction. In the present embodiment,
18 tooth parts 23 are provided every 20 degrees in terms of the central angle with the
25 central axis 0 as a center. The plurality of tooth parts 23 are formed to have the same
9
shape and the same size as each other. Therefore, the plurality of tooth parts 23 have
the same thickness dimension as each other.
The winding is wound around each of the tooth parts 23. The winding may be
a concentrated winding or a distributed winding.
5 [0019]
The rotor 30 is disposed on a radially inner side with respect to the stator 20 (the
stator core 21). The rotor 30 includes a rotor core 31 and a plurality of permanent
magnets 32.
The rotor core 31 is formed in a ring shape (annular shape) disposed coaxially
10 with the stator 20. The rotating shaft 60 is disposed in the rotor core 31. The rotating
shaft 60 is fixed to the rotor core 31.
The plurality of permanent magnets 32 are fixed to the rotor core 31. In the
present embodiment, a set of two permanent magnets 32 forms one magnetic pole. The
plurality of sets of permanent magnets 32 are disposed at equiangular angle intervals in
15 the circumferential direction. In the present embodiment, 12 sets (24 in total) of the
permanent magnets 32 are provided every 30 degrees in terms of the central angle with
the central axis 0 as a center.
[0020]
In the present embodiment, an interior permanent magnet motor is employed as
20 the permanent magnetic electric motor. A plurality of through holes 33 penetrating the
rotor core 31 in the axial direction are formed in the rotor core 31. The plurality of
through holes 33 are provided to correspond to a disposition of the plurality of permanent
magnets 32. The permanent magnets 32 are each fixed to the rotor core 31 in a state of
being disposed in the corresponding through hole 33. Fixing of each permanent magnet
25 32 to the rotor core 31 can be realized, for example, by causing an outer surface of the
10
5
10
permanent magnet 32 and an inner surface of the through hole 33 to be adhered to each
other using an adhesive. Further, a surface permanent magnet motor may be employed
as the permanent magnetic electric motor instead of an interior permanent magnet motor.
[0021]
Both the stator core 21 and the rotor core 31 are laminated cores. As illustrated
in FIG. 2, the stator core 21 is formed by, for example, laminating the plurality of
electrical steel sheets 40 in a lamination direction. Further, the lamination direction is
the axial direction.
[0022]
Laminated thicknesses (entire length along the central axis 0) of the stator core
21 and the rotor core 31 are each, for example, 50.0 mm. An outer diameter of the
stator core 21 is, for example, 250.0 mm. An inner diameter of the stator core 21 is, for
example, 165.0 mm. An outer diameter of the rotor core 31 is, for example, 163.0 mm.
An inner diameter of the rotor core 31 is, for example, 30.0 mm. However, these values
15 are an example, and the laminated thickness, the outer diameter, and the inner diameter
of the stator core 21, and the laminated thickness, the outer diameter, and the inner
diameter of the rotor core 31 are not limited only to these values. Here, a distal end
portion of the tooth part 23 of the stator core 21 is used as a reference for the inner
diameter of the stator core 21. That is, the inner diameter of the stator core 21 is a
20 diameter of a virtual circle inscribed in the distal end portions of all the tooth parts 23.
[0023]
FIG. 3 illustrates one of the plurality of electrical steel sheets 40 constituting the
stator core 21. The electrical steel sheet 40 includes a base steel sheet 2, a first
insulation coating 3A formed on a first surface 2a which is a front surface of the base
25 steel sheet 2 and having adhesiveness, and a second insulation coating 3B formed on a
11
second surface 2b which is a back surface of the base steel sheet 2 and having
adhesiveness. Further, a disposition relationship between the first insulation coating
3A, the base steel sheet 2, and the second insulation coating 3B is the same as that of a
material 1 to be described later, and specifically has the same disposition configuration as
5 that of FIG. 5 to be described later.
10
15
Further, "having adhesiveness" described above means that the first insulation
coating 3A and the second insulation coating 3B are melted and exhibit adhesive
properties when at least one of pressurizing and heating is applied.
[0024]
An average pencil hardness of the second insulation coating 3B is higher than an
average pencil hardness of the first insulation coating 3A. The average pencil hardness
of the first insulation coating 3A is HB or higher and 3H or lower. The average pencil
hardness can be obtained by a scratch hardness (pencil method) described in JIS K5400
5-4.
The first insulation coating 3A is formed on an upper surface of the core back
part 22 and an upper surface of each tooth part 23. The second insulation coating 3B is
formed on a lower surface of the core back part 22 and a lower surface of each tooth part
23. At least a part of a side surface of the core back part 22 may be covered with at
least one of the first insulation coating 3A and the second insulation coating 3B.
20 Similarly, at least a part of a side surface of each tooth part 23 may be covered with at
least one of the first insulation coating 3A and the second insulation coating 3B. The
side surface referred to herein is a cut surface formed after punching when the electrical
steel sheet 40 is formed by punching from the material 1 to be described later, and
includes a side surface on an outer circumferential side forming an outer shape of the
25 core back part 22 and a side surface forming an outer shape of the tooth part 23 and an
12
inner shape of the core back part 22.
[0025]
Each electrical steel sheet 40 is formed by punching or the like of the material 1
illustrated in FIGS. 4 and 5. The material 1 is a steel sheet (electrical steel sheet)
5 serving as a base material of the electrical steel sheet 40. As the material 1, a stripshaped
steel sheet, a cut sheet, or the like can be used.
Although it is in the middle of description on the stator core 21, the material 1
will be described below. Further, in the present specification, a strip-shaped steel sheet
serving as the base material of the electrical steel sheet 40 may be referred to as the
10 material 1. A steel sheet obtained by punching the material 1 into a shape used for the
laminated core may be referred to as the electrical steel sheet 40.
[0026]
(Material 1)
When the material 1 is a strip-shaped steel sheet, the material 1 is handled, for
15 example, in a state of being wound around a coil IA (see FIG. 6). In the present
embodiment, a non-grain-oriented electrical steel sheet is employed as the material I. A
non-grain-oriented electrical steel strip of JIS C 2552:2014 can be employed as the nongrain-
oriented electrical steel sheet. However, a grain-oriented electrical steel sheet
may also be employed as the material I instead of a non-grain-oriented electrical steel
20 sheet. As the grain -oriented electrical steel sheet in this case, a grain -oriented electrical
steel strip of JIS C 2553:2019 can be employed. Also, as the material I, a non-grainoriented
thin electrical steel strip or a grain-oriented thin electrical steel strip of JIS C
2558:2015 can also be employed.
[0027]
25 Upper and lower limit values of an average sheet thickness tO of the material 1
13
are set, for example, as follows.
As a sheet thickness of the material 1 decreases, a manufacturing cost of the
material I increases. Therefore, a lower limit value of the average sheet thickness tO of
the material I is 0.10 mm, preferably 0.15 mm, and more preferably 0.18 mm when
5 considering the manufacturing cost.
On the other hand, if the material 1 is too thick, the manufacturing cost becomes
satisfactory, but when the material 1 is used as the electrical steel sheet 40, eddy current
loss increases and core iron loss deteriorates. Therefore, an upper limit value of the
average sheet thickness tO of the material 1 is 0.65 mm, preferably 0.35 mm, and more
10 preferably 0.30 mm when the core iron loss and the manufacturing cost are considered.
As the material 1 satisfying the above-described range of the average sheet
thickness tO, 0.20 mm can be exemplified.
[0028]
Further, the average sheet thickness tO of the material I includes not only a
15 thickness of the base steel sheet 2 to be described later but also thicknesses of the first
insulation coating 3A and the second insulation coating 3B. Also, a method of
measuring the average sheet thickness tO of the material 1 is performed by, for example,
the following measurement method. For example, when the material 1 is a strip-shaped
steel sheet wound in a shape of the coil IA (see FIG. 6), at least a part of the material 1 is
20 unwound into a flat sheet shape. In the material 1 unwound into a flat plate shape, a
predetermined position of the material 1 in a longitudinal direction (for example, a
position away from an end edge of the material 1 in the longitudinal direction by a length
of 10% of an entire length of the material 1) is selected. At the selected position, the
material I is divided into five regions in a width direction thereof. A sheet thickness of
25 the material 1 is measured at four positions that are boundaries of those five regions.
14
An average value of the sheet thicknesses at the four positions can be used as the average
sheet thickness tO of the material 1.
[0029]
The upper and lower limit values of the average sheet thickness tO of the
5 material 1 can also be employed as upper and lower limit values of the average sheet
thickness tO of the electrical steel sheet 40. Further, a method of measuring the average
sheet thickness tO of the electrical steel sheet 40 is performed by, for example, the
following measurement method. For example, a laminated thickness of the laminated
core is measured at four positions at equal intervals in the circumferential direction (that
10 is, every 90 degrees with the central axis 0 as a center). Each of the measured
laminated thicknesses at the four positions is divided by the number of laminated
electrical steel sheets 40 to calculate a sheet thickness per sheet. An average value of
the sheet thicknesses at the four positions can be used as the average sheet thickness tO of
the electrical steel sheet 40. The average sheet thickness tO measured in a state of the
15 electrical steel sheet 40 is equal to the average sheet thickness tO measured in a state of
the material 1.
[0030]
As illustrated in FIGS. 4 and 5, the material 1 includes the base steel sheet 2, the
first insulation coating 3A formed on the first surface 2a which is a front surface of the
20 base steel sheet 2 and having adhesiveness, and the second insulation coating 3B formed
on the second surface 2b which is a back surface of the base steel sheet 2 and having
adhesiveness. An average pencil hardness of the second insulation coating 3B is higher
than an average pencil hardness of the first insulation coating 3A. The average pencil
hardness of the first insulation coating 3A is HB or higher and 3H or lower. The
25 average pencil hardness of the first insulation coating 3A can also be obtained by the
15
scratch hardness (pencil method) described in JIS K5400 5-4 similarly to the second
insulation coating 3B.
[0031]
A chemical composition of the base steel sheet 2 contains 2.5% to 4.5% of Si in
5 units of % by mass as shown below. When the chemical composition is within this
range, a yield strength of the material 1 (electrical steel sheet 40) can be set to, for
example, 380 MPa or more and 540 MPa or less.
[0032]
10
[0033]
Si: 2.5% to 4.5%
Al: 0.001% to 3.0%
Mn: 0.05% to 5.0%
Remainder: Fe and impurities
When the material 1 is used as the electrical steel sheet 40, both the first
15 insulation coating 3A and the second insulation coating 3B exhibit insulation
performance between the electrical steel sheets 40 adjacent to each other in the
lamination direction. Also, both the first insulation coating 3A and the second
insulation coating 3B have adhesiveness (self-adhesion function) and adhere the
electrical steel sheets 40 adjacent to each other in the lamination direction. More
20 specifically, both the first insulation coating 3A and the second insulation coating 3B are
fused by being subjected to at least one of pressurizing and heating or the like.
25
[0034]
On the other hand, functions of the first insulation coating 3A and the second
insulation coating 3B are different from each other.
That is, an average pencil hardness of the second insulation coating 3B is set to
16
be high to secure resistance to slitting and scratch prevention ability. Further, the
"resistance to slitting" means difficulty in scratching and peeling off of the first
insulation coating 3A and the second insulation coating 3B when front and back surfaces
of the electrical steel sheet 40 are rubbed by a pad (not illustrated) that presses the
5 electrical steel sheet 40 for performing slit processing. Further, the "scratch prevention
ability" means difficulty in being scratched when the second insulation coating 3B
forming the back surface (lower surface) of the material 1 is rubbed during transfer of the
material I between molds. The resistance to slitting and the scratch prevention ability
become higher as the second insulation coating 3B is harder. A degree of damage to the
10 second insulation coating 3B can be evaluated by pressing the material I against a steel
sheet support roll of the factory line and rubbing them against each other, and visually
determining a degree of damage received by the second insulation coating 3B at that
time.
The resistance to slitting and the scratch prevention ability of the second
15 insulation coating 3B are characteristics already required from the time before the
electrical steel sheets 40 are laminated. On the other hand, softness required for the first
insulation coating 3A is a characteristic required when the electrical steel sheet 40 is
bonded by pressurizing and heating after the electrical steel sheets 40 are laminated.
20
[0035]
When the average pencil hardness is increased, an insufficient adhesive strength
occurs when the laminated core is manufactured by laminating the electrical steel sheets
40. Therefore, in order to make up for the insufficient adhesive strength, the average
pencil hardness is lowered in the first insulation coating 3A to make it softer.
Specifically, the average pencil hardness of the first insulation coating 3A is HB or higher
25 and 3H or lower. On the other hand, the average pencil hardness of the second
17
insulation coating 3B is 4H or higher and 9H or lower. At any combination in average
pencil hardness of the first insulation coating 3A and the second insulation coating 3B,
the second insulation coating 3B has a relatively higher average pencil hardness and is
harder than the first insulation coating 3A. Conversely, the first insulation coating 3A
5 has a relatively lower average pencil hardness and is softer than the second insulation
coating 3B.
[0036]
The first insulation coating 3A and the second insulation coating 3B may each
have a single-layer configuration or a multilayer configuration. More specifically, the
10 first insulation coating 3A and the second insulation coating 3B may each have a singlelayer
configuration having both insulation performance and adhesiveness.
Alternatively, the first insulation coating 3A and the second insulation coating 3B may
each have a multilayer configuration including an underlying insulation coating having
excellent insulation performance and an upper insulation coating having excellent
15 adhesive performance. In this case, the underlying insulation coating is formed to cover
a surface of the base steel sheet 2 without gaps, and the upper insulation coating is
formed to overlap a surface of the underlying insulation coating. In a case of this
multilayer configuration, an upper insulation coating formed on an outermost surface
(uppermost surface) of the electrical steel sheet 40 has an average pencil hardness
20 required for the first insulation coating 3A. Similarly, an upper insulation coating
formed on a most back side surface (lowermost surface) of the electrical steel sheet 40
has an average pencil hardness required for the second insulation coating 3B. That is,
the average pencil hardness of the upper insulation coating formed on the outermost
surface (uppermost surface) of the electrical steel sheet 40 is HB or higher and 3H or
25 lower. Also, the average pencil hardness of the upper insulation coating formed on the
18
5
most back side surface (lowermost surface) of the electrical steel sheet 40 is higher than
the average pencil hardness of the upper insulation coating formed on the outermost
surface (uppermost surface) of the electrical steel sheet 40.
[0037]
In a range in which insulation performance and adhesiveness are secured, the
underlying insulation coating may not cover both surfaces of the base steel sheet 2
without gaps. In other words, a part of the underlying insulation coating may be
intermittently provided on the surface of the base steel sheet 2. However, in order to
secure the insulation performance, both surfaces of the base steel sheet 2 are preferably
10 covered with the underlying insulation coating so that the entire surface thereof is not
exposed.
A coating composition for forming the underlying insulation coating is not
particular! y limited, and for example, a general treatment agent such as a chromic acidcontaining
treatment agent or a phosphate-containing treatment agent can be utilized.
15 [0038]
The first insulation coating 3A and the second insulation coating 3B are formed
by applying a coating composition for an electrical steel sheet onto the base steel sheet 2.
The first insulation coating 3A and the second insulation coating 3B are in an uncured or
semi -cured state (B stage) before pressurizing and heating during manufacture of the
20 laminated core, and exhibit an adhesiveness when a curing reaction proceeds due to
heating during the pressurizing and heating.
[0039]
The coating composition for an electrical steel sheet is not particular! y limited,
and, for example, a composition containing an epoxy resin and an epoxy resin curing
25 agent can be exemplified. That is, as an example of the insulation coating having
19
adhesiveness, a coating containing an epoxy resin and an epoxy resin curing agent can be
exemplified.
[0040]
As the epoxy resin, a general epoxy resin can be utilized, and specifically, any
5 epoxy resin having two or more epoxy groups in one molecule can be utilized without
particular limitation. As such epoxy resins, for example, a bisphenol A type epoxy
resin, a bisphenol F type epoxy resin, a phenol novolac type epoxy resin, a cresol novolac
type epoxy resin, an alicyclic epoxy resin, a glycidyl ester type epoxy resin, a glycidyl
amine type epoxy resin, a hydantoin type epoxy resin, an isocyanurate type epoxy resin,
10 an acrylic acid modified epoxy resin (epoxy acrylate), a phosphorus-containing epoxy
resin, halides (brominated epoxy resin and the like) or hydrogen additives thereof, and
the like can be exemplified. As the epoxy resin, one type may be used alone, or two or
more types may be used together.
15
[0041]
The coating composition for an electrical steel sheet may contain an acrylic
resin.
The acrylic resin is not particular! y limited. As monomers used for the acrylic
resin, for example, unsaturated carboxylic acids such as acrylic acid and methacrylic
acid, and (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl
20 (meth) acrylate, isobutyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth)
acrylate, 2-hydroxyethyl (meth) acrylate, and hydroxypropyl (meth) acrylate can be
exemplified. Further, the (meth) acrylate means acrylate or methacrylate. As the
acrylic resin, one type may be used alone, or two or more types may be used together.
[0042]
25 The acrylic resin may have structural units derived from other monomers other
20
5
than an acrylic monomer. As other monomers, for example, ethylene, propylene,
styrene, and the like can be exemplified. As other monomers, one type may be used
alone, or two or more types may be used together.
[0043]
When an acrylic resin is used, it may be used as an acrylic modified epoxy resin
in which the acrylic resin is grafted to an epoxy resin. In the coating composition for an
electrical steel sheet, it may be contained as monomers forming an acrylic resin.
[0044]
As the epoxy resin curing agent, a thermosetting type having potential can be
10 utilized, and for example, aromatic polyamine, acid anhydride, a phenol-based curing
agent, dicyandiamide, boron trifluoride-amine complex, organic acid hydrazide, and the
like can be exemplified. As the aromatic polyamine, for example, metaphenylenediamine,
diaminodiphenyl methane, diaminodiphenylsulfone, and the like can
be exemplified. As the phenol-based curing agent, for example, a phenol novolac resin,
15 a cresol novolak resin, a bisphenol novolak resin, a triazine-modified phenol novolak
resin, a phenol resol resin, and the like can be exemplified. Of these, as the epoxy resin
curing agent, a phenol-based curing agent is preferable, and a phenol resol resin is more
preferable. As the epoxy resin curing agent, one type may be used alone, or two or
more types may be used together.

[CLAIMS]
1. An electrical steel sheet comprising:
a base steel sheet;
a first insulation coating formed on a first surface of the base steel sheet and
having adhesiveness; and
a second insulation coating formed on a second surface of the base steel sheet
which is a back surface to the first surface and having adhesiveness, wherein
an average pencil hardness of the first insulation coating is HB or higher and 3H
10 or lower, and
an average pencil hardness of the second insulation coating is higher than the
average pencil hardness of the first insulation coating.
2. The electrical steel sheet according to claim 1, wherein the average pencil hardness
15 of the second insulation coating is 4 H or higher and 9H or lower.
20
3. The electrical steel sheet according to claim 1 or 2, wherein
the first insulation coating and the second insulation coating both contain the
same main agent and the same curing agent, and
when an equivalent ratio of the curing agent to the main agent in the first
insulation coating is a and an equivalent ratio of the curing agent to the main agent in the
second insulation coating is b, a relative ratio expressed by alb is 0.60 or more and 0.95
or less.
25 4. A laminated core formed by laminating two or more electrical steel sheets according
46
to any one of claims 1 to 3.
5. A laminated core manufacturing method comprising:
a punching step of obtaining a plurality of electrical steel sheets according to any
5 one of claims 1 to 3 by punching a material while intermittently conveying the material
10
15
in a conveying direction; and
and
a laminating step of laminating each of the electrical steel sheets, wherein
the material includes:
the base steel sheet;
the first insulation coating formed on an upper surface of the base steel sheet;
the second insulation coating formed on a lower surface of the base steel sheet,
the material is conveyed with the second insulation coating facing downward in
the punching step, and
each electrical steel sheet is laminated so that the second insulation coating of
the electrical steel sheet to be laminated later overlaps the first insulation coating of the
electrical steel sheet laminated previously in the laminating step.