DESCRIPTION
GRAIN-ORIENTED ELECTRICAL STEEL SHEET
5 Technical Field
[0001]
The present invention relates to a grain-oriented electrical steel sheet suitable for
the segment core of rotating machines such as motor or generator, the lamination core of
stationary apparatus such as transformer or reactor, or the like. In particular, the present
I 0 invention relates to a grain-oriented electrical steel sheet in which the high-frequency
magnetic properties along L-direction are almost the same as those of conventional one
and the high-frequency magnetic properties along C-direction are preferably improved.
15
Priority is claimed on Japanese Patent Application No. 2014-177136, filed
September 1, 2014, the content of which is incorporated herein by reference.
Background Art
[0002]
The grain-oriented electrical steel sheet has the excellent magnetic properties
along rolling direction, because the crystal orientation thereof highly aligns in the
20 {II 0} <00 I> orientation called Goss orientation. Thus, the grain-oriented electrical
steel sheet has been widely applied to the iron core materials such as transformer,
generator, or motor. In recent years, since power electronics have developed, the
high-frequency range over conventional commercial frequency range has been
increasingly utilized as the drive frequency for the rotating machines such as motor or
25 generator, the stationary apparatus such as transformer or reactor, or the like. Thus, it is
~-I
2
eagerly anticipated to further improve the core loss characteristics in high-frequency
range for the grain-oriented electrical steel sheet.
[0003]
In addition, in case of using the drive motor which employs the segment core for
5 hybrid vehicles (HEV), electric vehicles (EV), or the like, the excellent core loss
characteristics in high-frequency range are desired in both directions of teeth and back
yoke of the iron core. Thus, in addition to the core loss characteristics along the rolling
direction (L-direction) in high-frequency range, it is eagerly anticipated to further
improve the core loss characteristics along the transverse direction (C-direction)
10 perpendicular to the rolling direction in high-frequency range for the grain-oriented
electrical steel sheet. Specifically, in the grain-oriented electrical steel sheet, in addition
to the high-frequency core loss along L-direction (L-direction core loss), it is required to
be excellent in the average ofthe high-fi·equency core losses along L-direction and
C-direction (L&C average core loss).
15 [0004]
Herein, the segment core indicates the component included in the stator arranged
on the periphery of rotor of motor. The segment core is punched from the
grain-oriented electrical steel sheet so that the radial direction of motor rotational axis is
substantially parallel to the rolling direction (L-direction) of the electrical steel sheet, and
20 the circumferential direction of motor rotational axis is substantially parallel to the
direction (C-direction) perpendicular to the rolling direction of the electrical steel sheet.
Specifically, in the segment core, the teeth which is important for magnetic properties in
general is substantially parallel to the rolling direction of the electrical steel sheet, and
the back yoke is substantially parallel to the direction perpendicular to the rolling
25 direction. In case of the stator in which the back yoke is important for magnetic
------'-----~--'-- .......... • .. .
3
properties, the segment core may be punched so that the back yoke is substantially
parallel to the rolling direction of the electrical steel sheet.
[0005]
Also, the core loss indicates the energy loss caused by the interconversion of
5 electrical energy and magnetic energy. It is preferable that the value of core loss is low.
The core loss of the grain-oriented electrical steel sheet is able to be broken down into
two elements of hysteresis loss and eddy current loss. In particular, in order to reduce
the high-frequency core loss, it is effective to reduce the eddy current loss by controlling
the steel to be highly alloyed and by increasing the electrical resistance of steel.
10 Although it is possible to reduce the eddy current Joss by controlling the electrical steel
sheet to be thin, it is inevitable to increase the production cost in order to control the
electrical steel sheet to be thin due to a decrease in efficiency of cold rolling, annealing,
or the like.
[0006]
15 In conventional grain-oriented electrical steel sheets, the magnetic anisotropy is
obtained by the texture control, and thereby, the magnetic properties along the
L-direction are significantly excellent. However, the magnetic properties along the
C-direction thereof are markedly insufficient. Thus, it is unsuitable to apply the
conventional grain-oriented electrical steel sheet to the segment core in which it is
20 required to be balance the L&C average core loss with the L-direction core loss.
[0007]
In addition, as explained above, in order to reduce the high-frequency core loss,
it is effective to control the steel to be highly alloyed. However, when Si which is the
main alloying element of the electrical steel sheet is added in surplus as compared with
25 that of conventional one, the steel embrittles, and thereby, the cold rolling is hardly
5
-~~-.,~--~~------------
4
conducted. Also, AI is the alloying element which may not embrittle the steel as
compared with Si. However, when AI is added in surplus to the steel, it is difficult to
control the dispersion state of the inhibitor AlN which importantly functions for
controlling the crystal orientation in secondary recrystallization.
[0008]
Patent Document 1 discloses the method for producing the electrical steel sheet
excellent in the balance between the magnetic properties in L-direction and C-direction.
In the method thereof, the steel slab including 2.0 to 4.0% ofSi, 0.5% or less ofMn,
0.003 to 0.020% of sol. Al, or the like is subjected to hot-rolling, hot-band annealing,
10 cold-rolling twice with intermediate annealing, primary recrystallization annealing, and
secondary recrystallization annealing.
[0009]
Patent Document 2 discloses the method for producing the electrical steel sheet
excellent in the balance between the magnetic properties in L-direction and C-direction.
15 In the method thereof, the steel slab including 2.5 to 4.0% of Si, 2.0 to 4.0% ofMn,
0.003 to 0.030% of acid-soluble AI, or the like is subjected to hot-rolling, optionally
hot-band annealing, cold-rolling, primary recrystallization annealing, and secondary
recrystallization annealing.
20 Related Art Documents
Patent Documents
25
[0010]
[Patent Document 1] Japanese Unexamined Patent Applicatioi:J., First
Publication No. I-!11-350032
[Patent Document 2] Japanese Unexamined Patent Application, First
5
Publication No. H07-l8334
Summary oflnvention
Technical Problem to be Solved
5 [0011]
In the electrical steel sheet produced by the method disclosed in Patent
Document 1, the amount of alloying elements is insufficient, and therefore, the
high-frequency core Joss is not sufficiently reduced.
[0012]
10 In the electrical steel sheet according to Patent Document 2, Patent Document 2
only considers the core loss in commercial frequency range of 50 to 60Hz, and therefore,
the high-frequency core loss is not sufficiently reduced. Also, in the producing method
according to Patent Document 2, the secondary recrystallization tends to be unstable, and
therefore, the electrical steel sheet is not stably produced.
15 [0013]
The present invention has been made in consideration of the above mentioned
problems. An object of the present invention is to provide the grain-oriented electrical
steel sheet excellent in both the high-frequency magnetic properties in L-direction and
the average of high-frequency magnetic properties in L-direction and C-direction.
20
Solution to Problem
[0014]
Tne present inventors found that, by including a large amount of Mn which is
difficult to embrittle the steel in common withAl depending on Si content in the steel, by
25 controlling a total amount of Sn and Sb in the steel, and by optimally controlling the
II
'
II
II
'
5
6
production conditions, it is possible to obtain the electrical steel sheet in which the
high-frequency magnetic properties along L-direction are almost the same as those of
conventional one and the high-frequency magnetic properties along C-direction are
preferably improved.
[0015]
In the grain-oriented electrical steel sheet according to an aspect of the present
invention, the thickness of sheet is 0.1 to 0.40 mm, and the magnetic flux density B8
along the rolling direction is 1.60 to 1. 77T. When the magnetic flux density B8 along
the rolling direction is 1.60 to 1.77T, the balance between the L-direction core loss and
1 0 the L&C average core loss is preferably controlled. The present inventors found that,
when the magnetic flux density B8 along the rolling direction is less than 1.60T, the
L-direction core loss is insufficient. Also, the present inventors found that, when the
magnetic flux density BS along the rolling direction is more than 1. 77T, the L-direction
core loss is sufficient, however the C-direction core loss deteriorates, and as a result, the
15 L&C average core loss drastically deteriorates.
[0016]
An aspect of the present invention employs the following.
(1) A grain-oriented electrical steel sheet according to an aspect of the present
invention includes a steel layer and an insulation coating arranged on the steel layer,
20 wherein: the steel layer includes, as a chemical composition, by mass%, 0.0003 to
0.005% ofC, 2.9 to 4.0% ofSi, 2.0 to 4.0% ofMn, 0.003 to O.oJS% of sol. AI, 0.005%
or less ofS, 0 to 0.20% ofSn, 0 to 0.20% ofSb, and a balance consisting of Fe and
impUrities; a silicon content and a manganese content expressed in mass% in the
chemical composition of the steel layer satisfy 1.2% :S Si- 0.5 x Mn:S 2.0%; a tin content
25 and an antimony content expressed in mass% in the chemical composition of the steel
---- - ----·-------------------
7
layer satisfy 0.005% S Sn + Sb S 0.20%; and the insulation coating is arranged in directly
contact with the steel layer.
(2) In the grain-oriented electrical steel sheet according to (1), the steel layer
may include, as the chemical composition, by mass%, 0.004 to 0.20% of Sn, and 0.001 to
5 0.20% of Sb.
(3) A method of producing the grain-oriented electrical steel sheet according to
(l) or (2) includes a casting process, a hot-rolling process, a cold-rolling process, a
primary recrystallization annealing process, an annealing separator coating process, a
secondary recrystallization annealing process, and an insulation coating formation
10 process, wherein: in the casting process, a steel is cast so that the steel includes, as a
chemical composition, by mass%, 0.0003 to 0.005% ofC, 2.9 to 4.0% ofSi, 2.0 to 4.0%
ofMn, 0.003 to 0.018% of sol. Al, 0.001 to 0.01% ofN, 0.005% or less ofS, 0 to 0.20%
ofSn, 0 to 0.20% ofSb, and a balance consisting of Fe and impurities, a silicon content
and a manganese content expressed in mass% in the chemical composition satisfy 1.2% S
15 Si - 0.5 x Mn S 2.0%, and a tin content and an antimony content expressed in mass% in
the chemical composition satisfy 0.005% S Sn + Sb S 0.20%; in the primary
recrystallization annealing process, a primary recrystallization annealing is conducted for
the steel under conditions such that a heating rate in a temperature elevating stage is 100
°C/second to 5000 °C/second on average, an atmosphere in the temperature elevating
20 stage is 10 to 100 vol% ofH2 and H2 + N2 = 100 vol%, a temperature in a holding stage
is 800 to 1 000°C, a time in the holding stage is 5 seconds to 10 minutes, an atmosphere
in the holding stage is 10 to 100 vol% of Hz, Hz+ Nz = 100 vol%, and a dew point is
-1 0°C or lower; in the annealing separator coating pro bess, an annealing separator
including an alumina as a main component is only applied on the steel; and in the
25 secondary recrystallization annealing process, a secondary recrystallization annealing is
------ ---·-
8
conducted for the steel under conditions such that an atmosphere in a temperature
elevating stage is 0 to 80 vol% ofN2 and H2 + N2 = 100 vol%, a dew point in a
temperature range of 500°C or higher in the temperature elevating stage is 0°C or lower,
a temperature in a holding stage is 850 to l 000°C, a time in the holding stage is 4 to l 00
5 hours, an atmosphere in the holding stage is 0 to 80 vol% ofN2, H2 + N2 = 1 00 vol%, and
a dew point is ooc or lower.
10
(4) In the method of producing the grain-oriented electrical steel sheet
according to (3 ), in the casting process, the steel may include, as the chemical
composition, by mass%, 0.004 to 0.20% of Sn, and 0.00 l to 0.20% of Sb.
( 5) In the method of producing the grain-oriented electrical steel sheet
according to (3) or ( 4 ), in the secondary recrystallization annealing process, the steel is
heated to the temperature in the holding stage by a constant heating rate in the
temperature elevating stage.
15 Effects of Invention
[0017]
According to the above aspects of the present invention, it is possible to provide
the grain-oriented electrical steel sheet excellent in both the high-frequency magnetic
properties in L-direction and the average of high-frequency magnetic properties in
20 L-direction and C-direction.
Brief Description of Drawings
[0018]
Fig. 1 is a cross-sectional illustration of a grain-oriented electrical steel sheet
25 according to an embodiment of the present invention.
5
9
Fig. 2 is a cross-sectional illustration of a conventional grain-oriented electrical
steel sheet.
Detailed Description of Preferred Embodiments
[0019]
Hereinafter, a preferable embodiment of the present invention will be described
in detail. However, the present invention is not limited only to the configuration which
is disclosed in the embodiment, and various modifications are possible without departing
from the aspect of the present invention. In addition, the limitation range as described
I 0 below includes a lower limit and an upper limit thereof. However, the value expressed
by "more than" or "less than" is not include in the limitation range.
15
20
[0020]
Hereinafter, the grain-oriented electrical steel sheet according to the embodiment
will be described in detail.
[0021]
The present inventors thoroughly review the chemical composition of the steel
and the production conditions, and thereby, succeed in obtaining the grain-oriented
ele.ctrical steel sheet excellent in the balance between the high-frequency core losses in
L-direction and C-direction.
[0022]
The grain-oriented electrical steel sheet according to the embodiment includes a
steel layer (base steel) and an insulation coating arranged on the steel layer, wherein: the
steel layer includes, as a chemical composition, by mass%, 0.0003 to 0.005% of C, 2.9 to
4.0% ofSi, 2.0 to 4.0% ofMn, 0.003 to 0.018% of sol. AI, 0.005% or less ofS, 0 to
25 0.20% ofSn, 0 to 0.20% ofSb, and a balance consisting of Fe and impurities; a silicon
10
content and a manganese content expressed in mass% in the chemical composition of the
steel layer satisfy 1.2% <:: Si - 0.5 x Mn <:: 2.0%; a tin content and an antimony content
expressed in mass% in the chemical composition of the steel layer satisfy 0.005% <:: Sn +
Sb <:: 0.20%; and the insulation coating is arranged in directly contact with the steel layer.
5 In addition, it is preferable that the thickness of the grain-oriented electrical steel sheet is
0.1 to 0.40 mm and the magnetic flux density B8 along the rolling direction of the
grain-oriented electrical steel sheet is 1.60 to 1.77T.
[0023]
Fig. 1 shows the grain-oriented electrical steel sheet according to the
10 embodiment in case of viewing the cross section whose cutting direction is parallel to the
thickness direction. In the grain-oriented electrical steel sheet according to the
embodiment, the insulation coating 2 is arranged in directly contact with the steel layer 1
(base steel). Fig. 2 shows the conventional grain-oriented electrical steel sheet in case
of viewing the cross section whose cutting direction is parallel to the thickness direction.
15 In the conventional grain-oriented electrical steel sheet, the glass film 3 (forsterite film)
is arranged on the steel layer 1 (base steel), and the insulation coating 2 is arranged on
the glass film 3 (forsterite film).
20
25
[0024]
(1) Chemical composition of steel layer (base steel)
The chemical composition of steel layer of the grain-oriented electrical steel
sheet according to the embodiment will be described in detail. Hereinafter,"%" of the
amount of respective elements as described below expresses "mass%" unless otherwise
mentioned.
[0025]
In the chemical composition of steel layer of the grain-oriented electrical steel
11
sheet according to the embodiment, base elements are C, Si, Mn, and AI.
[0026]
C : 0.0003 to 0.005%
C (carbon) is the base element in the steel but the element which causes the
5 deterioration of core loss. Thus, it is preferable that C content is as small as possible.
In the grain-oriented electrical steel sheet according to the embodiment, the upper limit
ofC content is to be 0.005%. When the C content is more than 0.005%, the core loss of
the grain-oriented electrical steel sheet deteriorates, and thus, the excellent magnetic
properties are not obtained. The upper limit of C content is preferably 0.004% and
10 more preferably 0.003%. On the other hand, although the lower limit of C content is
not particularly limited, the lower limit is to be 0.0003%. Since the production cost for
steel making is excessive, it is industrially difficult to control the C content to be less
than 0.0003%.
15
[0027]
Si : 2.9 to 4.0%
Si (silicon) has the effect in increasing the electrical resistance of steel, reducing
the eddy current loss, and thereby, improving the high-frequency core loss. In order to
effectively obtain the effect, the lower limit of Si content is to be 2.9%. The lower limit
of Si content is preferably 3.0%. On the other hand, the upper limit of Si content is to
20 be 4.0%. When the Si content is more than 4.0%, the workability drastically
deteriorates, and thus, it is difficult to conduct the cold-rolling. The upper limit of Si
content is preferably 3 .8%.
[0028]
Mn: 2.0 to 4.0%
25 Mn (manganese) has the effect in increasing the electrical resistance of steel
12
without the deterioration of the workability of steel, reducing the eddy cunent loss, and
thereby, improving the high-frequency core loss. In order to effectively obtain the
effect, the lower limit ofMn content is to be 2.0%. When the Mn content is less than
2.0%, The effect in reducing the high-frequency core loss is insufficient. The lower
5 limit of Mn content is preferably 2.2% and more preferably 2.6%. On the other hand,
the upper limit ofMn content is to be 4.0%. When the Mn content is more than 4.0%,
the magnetic flux density drastically decreases. The upper limit ofMn content is
preferably 3.8% and more preferably 3.4%.
10
[0029]
Si - 0.5 x Mn : 1.2 to 2.0%
In addition, in the embodiment, the Si content and the Mn content are regulated
in connection with each other. In order to let the secondary recrystallization proceed
stably, it is necessary to control the microstructure of hot-rolled steel sheet to be uniform
and fine. Therefore, in the embodiment, the transformation between a ( fenite) and y
15 (austenite) is utilized. In the conventional grain-oriented electrical steel sheet, C which
is an austenite-forming element is contained at the stage of the hot-rolled steel sheet.
However, in the electrical steel sheet according to the embodiment, the C content is low
at the stage of the hot-rolled steel sheet. Thus, in the electrical steel sheet according to
the embodiment, the u-y transformation is mainly affected by the balance between the
20 amount ofSi which is a ferrite-forming element and the amount ofMn which is an
austenite-forming element. It is necessary to regulate the Si content and the Mn content
in connection with each other.
[0030]
Specifically, the upper limit of the value calculated by "(Si content)- 0.5 x (Mn
25 content)" is to be 2.0%. When the value is more than 2.0%, the u-y transformation does
--I
13
not occur sufficiently, the microstructure of hot-rolled steel sheet is not controlled to be
uniform and fine, and the secondary recrystallization becomes unstable. The upper
limit of"Si- 0.5 x Mn" is preferably 1.8% and more preferably 1.75%. On the other
hand, although the lower limit of "Si - 0.5 x Mn" is not particularly limited, the lower
5 limit is to be 1.2%. In order to let the secondary recrystallization proceed stably, the
lower limit of "Si - 0.5 x Mn" is preferably 1.6%. When the Si content and the Mn
content satisfy the above condition, it is possible to obtain the grain-oriented electrical
steel sheet excellent in the balance between the high-frequency core losses in L-direction
and C-direction.
10 [0031]
sol. AI : 0.003 to 0.018%
Sol. Al (acid-soluble aluminum) forms the inhibitor which importantly functions
for controlling the crystal orientation in secondary recrystallization. The inhibitor is the
nitrides as the precipitates, for example, the (AI, Si, Mn) composite nitrides. In the
15 embodiment, the lower limit of sol. AI content is to be 0.003%. When the sol. AI
content is less than 0.003%, the inhibitor's effect is not sufficiently obtained. On the
other hand, the upper limit of sol. Al content is to be 0.018%. When the sol. Al content
is more than 0.018%, the dispersion state of the nitrides is unfavorable, and thus, the
secondary recrystallization does not proceed stably. The upper limit of sol. Al content is
20 preferably 0.016%.
[0032]
The steel layer of the grain-oriented electrical steel sheet according to the
embodiment includes, as the chemical composition, the impurities. Herein, "impurities"
represent elements which are contaminated during industrial production of the steel from
25 ores and scrap that are used as a raw material of the steel, or from environment of a
5
14
production process. Among the impurities, it is preferable that S is limited as follows in
order to sufficiently obtain the effects of the embodiment. Moreover, since it is
preferable that the amount of respective impmities is low, a lower limit does not need to
be limited, and the lower limit of the respective impurities may be 0%.
[0033]
S : 0.005% or less
S (sulfur) is the impurity. S forms MnS by bonding to Mn in the steel, and
thus, the magnetic properties deteriorate. Therefore, the S content is limited to 0.005%
or less. The upper limit of S content is preferably 0.004% and more preferably 0.003%.
10 [0034]
The steel layer of the grain-oriented electrical steel sheet according to the
embodiment includes the above mentioned base elements and the balance contains Fe
and the above mentioned impurities. However, the steel layer of the grain-oriented
electrical steel sheet according to the embodiment includes at least one of Sn or Sb in
15 substitution for a part of Fe which is the balance.
20
[0035]
Sn : 0 to 0.20%
Sb : 0 to 0.20%
Sn + Sb : 0.005 to 0.20%
Sn (tin) and Sb (antimony) are the elements which let the secondary
recrystallization proceed stably and which let the high-frequency core loss be reduced by
refining the secondary recrystallized grains. In order to obtain the effect, the Sn content
is to be 0 to 0.20%, the Sb content is to be 0 to 0.20%, and the total amount of Sn and Sb
is to be 0.005 to 0.20%. When one of Sn or Sb is contained in the steel layer, the other
25 is not necessarily contained in the steel layer. Thus, the lower limit of each amount of
y,
15
Sn and Sb may be 0%. However, the lower limit of the total amount of Sn and Sb is to
be 0.005%. The lower limit of the total amount of Sn and Sb is preferably 0.01 %. On
the other hand, the upper limit of the total amount of Sn and Sb is to be 0.20%. When
the upper limit of the total amount of Sn and Sb is more than 0.20%, the above effect is
5 saturated.· The upper limit of the total amount of Sn and Sb is preferably 0.15% and
more preferably 0.13%.
[0036]
As described above, at least one of Sn or Sb may be included in the steel layer.
However, it is preferable that both Sn and Sb are simultaneously included in the steel
10 layer. For example, it is preferable that the lower limit ofSn content is 0.004% and the
lower limit ofSb content is 0.001%. Specifically, it is preferable that the steel layer of
the grain-oriented electrical steel sheet according to the embodiment includes Mn, Sn,
and Sb at the same time. When the condition is satisfied, the average of the
15
high-frequency core losses along L-direction and C-direction is preferably improved.
[0037]
In the grain-oriented electrical steel sheet according to the embodiment, the Mn
content and the Sn + Sb total content are simultaneously increased as the chemical
composition of the steel layer. By increasing the Mn content, it is possible to increase
the electrical resistance of steel, to reduce the eddy current loss, and as a result, to
20 improve the average of the high-frequency magnetic properties (core losses) along
L-direction and C-direction. Also, by increasing the Sn + Sb total content, it is possible
to refine the secondary recrystallized grains, to reduce the excess eddy current loss, and
as a result, to improve the average of the high-frequency magnetic properties (core
losses) along L-direction and C-direction.
25 [0038]
16
On the other hand, in the conventional grain-oriented electrical steel sheet, it is
not necessarily easy to increase the Mn content and the Sn + Sb total content at the same
time. In particular, when the Mn content is increased, it is not necessarily easy to
include Sn and Sb at the same time. In the conventional grain-oriented electrical steel
5 sheet, including Mn, Sn, and Sb at the same time causes the problem such that the
adhesion of insulation coating drastically deteriorates. The present inventors assume
that the above problem is derived from the excessive oxidation which occurs in the
vicinity of the surface of steel layer during the primary recrystallization annealing and
the secondary recrystallization annealing.
10 [0039]
In the conventional grain-oriented electrical steel sheet, in general, the steel slab
includes C whose content stabilizes the austenite at annealing temperature and hot rolling
temperature, the heating for primary recrystallization annealing is conducted by heating
rate of slower than 100 °C/second, the primary recrystallization annealing is conducted in
15 moist atmosphere (decarburizing atmosphere), the magnesia-based separator is used as an
annealing separator, and the secondary recrystallization annealing is conducted. In the
primary recrystallization annealing, since the atmosphere is moist ( decarburizing
atmosphere), the oxidation in addition to decarburization is promoted in the steel sheet
(steel layer). Also, since MgO in the annealing separator which is slurried for applying
20 to the steel sheet (steel layer) is changed to Mg(OH)z, the magnesia annealing separator
tends to oxidize the steel sheet (steel layer). Also, in the secondary recrystallization
annealing, the magnesia annealing separator and the oxide layer (silica) at the surface of
;steel sheet (steel layer) are chemically reacted, and thus, the glass film (forsterite film) is
formed.
25 [0040]
---- ---------------
17
In case of applying the above conventional producing method to the steel sheet
(steel layer) where the Mn content and the Sn + Sb total content are simultaneously
increased, the vicinity of the surface of steel layer may be excessively oxidized due to the
peculiar chemical composition of steel. As a result, the problem such that the adhesion
5 of insulation coating drastically deteriorates may occur. In the embodiment, by
optimally controlling the chemical composition of steel layer and the production
conditions, it is possible to increase the Mn content and the Sn + Sb total content at the
same time. In particular, in addition to increasing the Mn content, it is possible to
increase Sn and Sb at the same time. Although the detail of production conditions will
10 be described below, in the embodiment, the C content in steel slab is controlled to be low,
the rapid heating as compared with conventional heating is conducted in the temperature
elevating stage of primary recrystallization annealing, the primary recrystallization
annealing is conducted in dry atmosphere (non-decarburizing atmosphere), the
alumina-based separator is used as the annealing separator, and the secondary
15 recrystallization annealing is conducted in dry atmosphere.
[0041]
The grain-oriented electrical steel sheet produced by the specific production
conditions according to the embodiment does not include the glass film (forsterite film)
on the steel layer, because the primary recrystallization annealing is conducted in dry
20 atmosphere (non-decarburizing atmosphere), the alumina-based separator is used as the
annealing separator, and the secondary recrystallization annealing is conducted in dry
atmosphere. Specifically, in the grain-oriented electrical steel sheet according to the
embodiment, the insulation coating is arranged in directly contact with the steel layer.
[0042]
25 Even when the Mn content and the Sn + Sb total content are simultaneously
18
increased in the steel layer, in particular, even when Sn and Sb are included at the same
time in addition to increasing the Mn content, it is possible to suppress the excessive
oxidation in the vicinity of the surface of steel layer by applying the specific production
conditions according to the embodiment. Thus, it is possible to suppress the decrease in
5 the adhesion of insulation coating. As a result, it is possible to preferably improve the
average of the high-frequency magnetic properties (core losses) along L-direction and
C-direction as compared with those of conventional one.
[0043]
In addition, in the grain-oriented electrical steel sheet according to the
10 embodiment, even when the Sn + Sb total content is increased in addition to increasing
the Mn content, it is possible to preferably suppress the decrease in the punchability.
[0044]
Sn and Sb are the elements which tend to embrittle the steeL With respect to
the Si steel (steel layer) whose workability is essentially poor, when the Sn + Sb total
15 content is increased in addition to excessively increasing the Mn content although Mn is
difficult to embrittle the steel, the workability of steel may drastically deteriorate.
[0045]
Although the details are unclear, when the Si steel (steel layer) includes the large
amount ofMn, Mn oxides may be formed in addition to Si oxides in the vicinity of the
20 surface of steel layer, Sn and Sb may be segregated in the vicinity of the Si oxides and
the Mn oxides, and thereby, the punchability may deteriorate. Thus, in the conventional
grain-oriented electrical steel sheet, it is not necessarily easy to increase the Mn content
and the Sn + Sb total content at the same time. In particular, when the Mn content is
increased, it is not necessarily easy to include Sn and Sb at the same time.
25 [0046]
I . I
19
In the specific production conditions according to the embodiment, the oxidation
of Mn is suppressed in the vicinity of the surface of steel layer during the primary
recrystallization am1ealing, and the glass film is not formed during the secondary
recrystallization aMealing. Since the oxidation of Mn is suppressed and the glass film
5 is not formed, the oxides are not excessive in the vicinity of the surface of steel layer.
In particular, in addition to the specific production conditions according to the
embodiment, when the steel simultaneously includes Sn and Sb and when the
alumina-based separator is used as the aMealing separator, the oxide layer fmiher thins.
Also, the segregation of Sn and Sb is suppressed. Therefore, the deterioration of
10 punchability is preferably suppressed. The reason seems that the brittle fracture whose
origin is in the vicinity of the surface (whose origin is in the interface between the steel
layer and the insulation coating) is suppressed by thilll1ing the oxide layer in the vicinity
of the surface of the steel layer.
15
[0047]
Specifically, in the steel layer of the grain-oriented electrical steel sheet
according to the embodiment (the whole steel layer without the insulation coating), the
amo1.111t of 0 (oxygen) is preferably 0.03% (300 ppm) or less in mass%. Also, when the
surface area of steel layer is the area within 10 !!Ill in depth toward the steel layer from
the interface between the steel layer and the insulation coating, the 0 content is
20 preferably less than 0.01% (I 00 ppm) in mass% in the body area which is the area except
for the surface area in the steel layer. When the 0 content in the whole steel layer is
0.03% (300 ppm) or less, the deterioration of punchability is preferably suppressed.
The 0 content in the whole steel layer is preferably 0.02% (200 ppm) or less and more
preferably 0.01% (I 00 ppm) or less. In addition, although the lower limit of 0 content
25 in the whole steel layer is not particularly limited, the lower limit may be 0.001% (I 0
20
ppm). The 0 content in the steel layer may be measured by, for example, the
non-dispersive infrared absorption method after fusion in a current of inert gas.
[0048]
The steel layer of the grain-oriented electrical steel sheet according to the
5 embodiment may further include the optional element in addition to the above explained
elements. For example, the steel layer may further include, as the optional element, at
least one selected from the group consisting ofN, P, Ni, Cr, Cu, and Mo in substitution
for a part of Fe which is the balance. The optional elements may be included as
necessary. Thus, a lower limit of the respective optional elements does not need to be
l 0 limited, and the lower limit may be 0%. Moreover, even if the optional elements may
be included as impurities, the above mentioned effects are not affected.
[0049]
N: 0 to 0.01%
N (nitrogen) forms the nitrides which act as the inhibitor. Thus, the content in
15 the steel slab is preferably 0.0010% or more. However, when the large amount ofN
remains in the steel layer of the grain-oriented electrical steel sheet as final products, the
magnetic,properties may be negatively influenced. Thus, the upper limit ofN content is
preferably 0.0100% and more preferably 0.0050%.
20
25
[0050]
P: Oto 0.15%
P (phosphorus) has the effect in reducing the eddy current loss by increasing the
electrical resistance of steel. Thus, the P content may be 0 to 0.15%. The lower limit
of P content is preferably 0.000.1 %.
[0051]
Ni: 0 to 0.3%
5
10
15
20
21
Ni (nickel) has the effect in reducing the eddy current loss by increasing the
electrical resistance of steel and in improving the magnetic flux density. Thus, the Ni
content may be 0 to 0.3%. The lower limit ofNi content is preferably 0.0001%.
[0052]
Cr: 0 to 0.3%
Cr (chromium) has the effect in reducing the eddy current loss by increasing the
electrical resistance of steel. Thus, the Cr content may be 0 to 0.3%. The lower limit
of Cr content is preferably 0.0001%.
[0053]
Cu: Oto 0.3%
Cu (copper) has the effect in reducing the eddy current loss by increasing the
electrical resistance of steel. Thus, the Cu content may be 0 to 0.3%. The lower limit
of Cu content is preferably 0.0001%.
[0054]
Mo: Oto 0.3%
Mo (molybdenum) has the effect in reducing the eddy current loss by increasing
the.electrical resistance of steel. Thus, the Mo content may be 0 to 0.3%. The lower
limit ofMo content is preferably 0.0001%.
[0055]
The chemical composition of the steel layer as described above may be
measured by typical analytical methods for the steel. For example, the chemical
composition of the steel layer may be measured by using ICP-AES (Inductively Coupled
Plasma-Atomic Emission Spectrometer: inductively coupled plasma emission
spectroscopy spectrometry). Specifically, granular specimens are taken from center
25 position of the steel layer after removing the coating, chemical analysis is conducted
22
under the conditions based on the predetermined working curve, and thereby, the
chemical composition is identified. In addition, C and S may be measured by the
infrared absorption method after combustion, N may be measured by the thermal
conductometric method after fusion in a current of inert gas, and 0 may be measured by,
5 for example, the non-dispersive infrared absorption method after fusion in a current of
inert gas.
[0056]
(2) Thickness of grain-oriented electrical steel sheet
Next, a preferable thickness of the grain-oriented electrical steel sheet according
10 to the embodiment will be described.
In the grain-oriented electrical steel sheet according to the embodiment, the
upper limit of thickness may be 0.40 mm. When the thickness is thicker than 0.40 mm,
the eddy current loss may increase and the high-frequency core loss may deteriorate.
On the other hand, although the lower limit of thickness is not particularly limited, the
15 lower limit may be 0.1 mm. When the thickness is thinner than 0.1 mm, the
productivity is undesirably lowered.
[0057]
(3) Magnetic properties of grain-oriented electrical steel sheet
Next, preferable magnetic properties of the grain-oriented electrical steel sheet
20 according to the embodiment will be described.
In the grain-oriented electrical steel sheet according to the embodiment, the
lower limit of magnetic flnx density B8 along the rolling direction (L-direction) is
preferably 1.60T. :When the magnetic flux density B8 along the rolling direction is less
than 1.60T, both the L-direction core loss and the L&C average core loss may deteriorate.
25 The lower limit of magnetic flux density B8 along the rolling direction is preferably
23
1.62T. On the other hand, the upper limit of magnetic flux density B8 along the rolling
direction is preferably 1.77T. When the magnetic flux density B8 along the rolling
direction is more than 1. 77T, the L-direction core loss is sufficient, however the
C-direction core loss deteriorates, and as a result, the L&C average core loss drastically
5 deteriorates. The upper limit of magnetic flux density B8 along the rolling direction is
preferably I. 76T.
[0058]
In addition, in the grain-oriented electrical steel sheet according to the
embodiment, the core loss Wl0/400 along L-direction is preferably 13.0W /kg or less.
10 Also, the average of the core losses Wl0/400 along L-direction and C-direction is
preferably 14.5W/kg or less. In the core loss characteristics, since it is preferable that
the value thereof is low, the lower limit thereof is not particularly limited. Also, the
core loss WI 0/400 along C-direction is preferably 1.0 to 2.0 times as compared with the
core loss Wl 0/400 along L-direction. When the above conditions are satisfied, the
15 average of the high-frequency core losses along L-direction and C-direction is preferably
improved.
[0059]
Herein, the magnetic properties such as the magnetic flux density and the core
loss may be measured by a knoWn method, for example, the epstein test regulated by JIS
20 C2550, the single sheet tester (SST) method regulated by JIS C 2556, or the like. Also,
the magnetic flux density BS indicates the magnetic flux density under the magnetizing
field of SOOA/m, and the core loss Wl 0/400 indicates the core loss under conditions such
that the maximum magnetic flux density is LOT and the frequency is!400Hz.
[0060]
25 Next, a method of producing the grain-oriented electrical steel sheet according
24
to the embodiment will be described in detail.
[0061]
The method of producing the grain-oriented electrical steel sheet according to
the embodiment includes a casting process, a hot-rolling process, a cold-rolling process,
5 a primary recrystallization annealing process, an annealing separator coating process, a
secondary recrystallization annealing process, and an insulation coating formation
process. As necessary, a hot -band annealing process may be included after the
hot-rolling process and before the cold-rolling process. In the cold-rolling process, the
cold-rolling may be conducted once or twice or more with intermediate annealing.
10 [0062]
Casting process
In the casting process, a cast piece (slab) is cast so that the cast piece includes,
as a chemical composition, by mass%, 0.0003 to 0.005% ofC, 2.9 to 4.0% ofSi, 2.0 to
4.0% ofMn, 0.003 to 0.018% of sol. Al, 0.001 to 0.01% ofN, 0.005% or less of S, 0 to
15 0.20% ofSn, 0 to 0.20% ofSb, and a balance consisting of Fe and impurities, a silicon
content and a manganese content expressed in mass% in the chemical composition
satisfY 1.2% :<: Si - 0.5 x Mn :<: 2.0%, and a tin content and an antimony content
expressed in mass% in the chemical composition satisfY 0.005% :<: Sn + Sb :<: 0.20%.
For example, the slab may be cast by the cast method such as a continuous casting
20 method, an ingot making method, or a thin slab casting method in general. In the case
of the continuous casting, the steel may be subjected to the hot-rolling after the steel is
cooled once to a lower temperature (for example, room temperature) and is reheated, or
the steel (cast slab) may be continuously subjected to the hot-rollingjust after the steel is
cast.
25 [0063]
---- - ----------
25
At least one of Sn or Sb may be included in the above cast piece (slab).
However, it is preferable that both Sn and Sb are simultaneously included in the slab.
For example, it is preferable that the lower limit of Sn content is 0.004% and the lower
limit of Sb content is 0.00 I%. Specifically, it is preferable that the slab includes Mn,
5 Sn, and Sb at the same time in the casting process of the method of producing the
grain-oriented electrical steel sheet according to the embodiment.
[0064]
Hot-rolling process
In the hot-rolling process, the slab after the casting process is heated to 1050 to
I 0 1400°C, the hot-rolling is conducted for the above slab, and the hot-rolling is finished in
the range of 700 to 950°C. In the hot-rolling process, the hot-rolling may be conducted
so as to obtain the hot-rolled steel sheet with the thickness of 1.8 to 3.5 mm.
15
[0065]
Hot-band annealing process
After the hot-rolling process, the hot-band annealing may be conducted as
necessary. In the hot-band annealing process, for the hot-rolled steel sheet after the
hot-rolling process, the annealing may be conducted under conditions in 750 to 1200°C
for 10 seconds to 10 minutes for continuous-annealing, and the annealing may be
conducted under conditions in 650 to 950°C for 30 minutes to 24 hours for
20 box -annealing.
[0066]
Cold-rolling process
In the cold-rolling process, the cold-rolling is conducted for the hot-rolled steel
sheet after the hot-rolling process or the hot-band annealed sheet after the hot-band
25 annealing process. In the cold-rolling process, the cold-rolling may be conducted so as
26
to obtain the cold-rolled steel sheet with the thickness of 0.1 to 0.4 mm. In case that the
cold-rolling may be conducted twice or more with intermediate annealing, the reduction
of cold-rolling before the intermediate annealing may be 40 to 70%, and the reduction of
final cold-rolling after the intermediate annealing may be 40 to 90%. The intermediate
5 annealing may be conducted under the same mmealing conditions as those of the above
hot-band annealing.
[0067]
Primary recrystallization mmealing process
In the primary recrystallization annealing process, the primary recrystallization
10 annealing is conducted for the cold-rolled steel sheet after the cold-rolling process. In
the primary recrystallization annealing process, a rapid heating is conducted in a
temperature elevating stage. By conducting the rapid heating in the temperature
elevating stage of the primary recrystallization mmealing process, it is possible to shorten
the heating time, and as a result, to suppress the surface oxidation during the temperature
15 elevating stage. In addition, the holding is conducted in dry atmosphere
(non-decarburizing atmosphere). Specifically, in the temperature elevating stage, the
heating rate in the temperature elevating stage is 100 °C/second to 5000 °C/second on
average, the atmosphere in the temperature elevating stage is 10 to 100 vol% of H2 and
H2 + N2 = 100 vol%, and the dew point of the atmosphere in the temperature elevating
20 stage is preferably 0°C or lower. In a holding stage, the temperature in the holding
stage is 800 to 1 000°C, the time in the holding stage is 5 seconds to 10 minutes, the
atmosphere in the holding stage is 10 to 100 vol% ofH2, H2 + N2 = 100 vol%, and the
dew point is -1 0°C or lower. The heating rate in the temperature elevating stage is
preferably I 00 °C/second to 2000 °C/second.
25 [0068]
27
The atmosphere in the temperature elevating stage is preferably less than 50
vol% ofH2 and more preferably less than 25 vol% ofH2. Also, the atmosphere in the
holding stage is preferably less than 50 vol% of H2 and more preferably less than 25
vol% ofH2• When the above conditions are satisfied, the average of the high-frequency
5 core losses along L-direction aud C-direction is preferably improved.
[0069]
Annealing separator coating process
In the annealing separator coating process, an armealing separator including
alumina (Ah03) as main component is only applied on the primary-recrystallized steel
I 0 sheet after the primary recrystallization armealing process. The annealing separator
including magnesia (MgO) as main component does not use, the magnesia being changed
to hydroxide during coating aud thereby resulting in the large amormt of 0 brought in.
By using the alumina-based separator, it is possible to suppress the excessive oxidation in
the vicinity of the surface of steel layer in the secondary recrystallization armealing
15 process.
[0070]
Secondary recrystallization annealing process
In the secondary recrystallization annealing process, the secondary
recrystallization annealing is conducted for the separator-coated steel sheet after the
20 annealing separator coating process. In the secondary recrystallization armealing
process, au atmosphere in a temperature elevating stage is controlled and the holding is
conducted in dry atmosphere. Specifically, the atmosphere in the temperature elevating
stage is 0 to 80 vol% ofN2 and H2 + N2 = 100 vol%, the dew point in the temperature
range of 500°C or higher in the temperature elevating stage is 0°C or lower, the
25 temperature in the holding stage is 850 to 1 000°C, the time in the holding stage is 4 to
5
28
I 00 hours, the atmosphere in the holding stage is 0 to 80 vol% ofN2, H2 + N2 = 100
vol%, and the dew point is 0°C or lower. The atmosphere in the holding stage is
preferably Oto 50 vol% ofNz.
[0071]
In the temperature elevating stage, the steel sheet may be heated to the above
temperature of 850 to l 000°C in the holding stage by the constant heating rate in
substance (without the two stage annealing). The heating rate in the temperature of
800°C or higher is preferably 10 to 50 °C/hour on average. The atmosphere in the
temperature elevating stage is preferably less than 30 vol% ofNz and more preferably
10 less than 20 vol% ofN2. The atmosphere in the holding stage is preferably 100% of Hz.
15
When the above conditions are satisfied, the average of the high-frequency core losses
along L-direction and C-direction is preferably improved.
[0072]
Insulation coating formation process
In the insulation coating formation process, the insulation coating is formed for
the secondary recrystallized steel sheet after the secondary recrystallization annealing
process. For example, the mixture of resin such as acrylic and inorganic material such
as phosphate, the solution for insulation coating containing colloidal silica and
phosphate, or the like may be applied on the surface of steel sheet, and the heat treatment
20 may be conducted in the temperature range of 250 to 400°C in case that an organic is
contained and the temperature range of 840 to 920°C in case that an inorganic is only
contained.
[0073]
The grain-oriented electrical steel sheet produced as mentioned above includes a
25 steel layer (base steel) and an insulation coating arranged on the steel layer, wherein: the
II
··--·------------
29
steel layer includes, as a chemical composition, by mass%, 0.0003 to 0.005% ofC, 2.9 to
4.0% ofSi, 2.0 to 4.0% ofMn, 0.003 to 0.018% of sol. Al, 0.005% or less ofS, 0 to
0.20% of Sn, 0 to 0.20% of Sb, and a balance consisting of Fe and impurities; a silicon
content and a manganese content expressed in mass% in the chemical composition of the
5 steel layer satisfy 1.2% 'S Si - 0.5 x Mn 'S 2.0%; a tin content and an antimony content
expressed in mass% in the chemical composition of the steel layer satisfy 0.005% 'S Sn +
Sb 'S 0.20%; and the insulation coating is arranged in directly contact with the steel layer.
(0074]
In the grain-oriented electrical steel sheet produced by optimally and
10 comprehensively controlling the above production conditions, even when the Mn content
and the Sn + Sb total content are simultaneously increased in the steel layer, in particular,
even when Sn and Sb are included at the same time in addition to increasing the Mn
content, it is possible to suppress the excessive oxidation in the vicinity of the surface of
steel layer. Thus, it is possible to suppress the decrease in the adhesion of insulation
15 coating. Also, it is possible to preferably improve the average of the high-frequency
magnetic properties (core losses) along L-direction and C-direction.
20
Examples
(0075]
Hereinafter, the effects of an aspect of the present invention will be described in
detail with reference to the following examples. However, the condition in the
examples is an example condition employed to confirm the operability and the effects of
the present invention, so that the present invention is not limited to the example
condition. The present invention can employ various types of conditions as long as the
25 conditions do not depart from the scope of the present invention and can achieve the
object of the present invention.
[0076]
(Example 1)
30
The steel slabs whose chemical compositions were shown in Table 1 with the
5 balance consisting of Fe and impurities were heated to 1250°C and then were hot-rolled
so that the thickness was 2.6 mm. The cold-rolling was conducted so that the thickness
was 1.2 mrn, the intermediate annealing was conducted at 900°C for 30 seconds, the final
rolling was conducted so that the final thickness was 0.30 mrn, the primary
recrystallization annealing was conducted at 920°C for 15 seconds, the annealing
10 separator was applied, the secondary recrystallization annealing was conducted at the
maximum temperature of 940°C, and thereafter, the insulation coating was formed.
[0077]
In the primary recrystallization annealing process, the heating rate in the
temperature elevating stage was 400 °C/second, the atmosphere in the temperature
15 elevating stage was 20% ofH2 and 80% ofN2, the atmosphere in the holding stage was
20% ofH2 and 80% ofN2, and the dew point in the holding stage was -20°C. The
alumina-based separator was used for the annealing separator. In the secondary
recrystallization annealing process, the heating rate in the temperature elevating stage of
800°C or higher was 20 °C/hour, the temperature was elevated to 940°C by the constant
20 heating rate in substance, the atmosphere in the temperature elevating stage was 85% of
H2 and 15% ofN2, the dew point in the temperature range of 500°C or higher in the
temperature elevating stage was -1 0°C, the time in the holding stage was 10 hours, the
atmosphere in the holding• stage was 100% ofH2, and the dew point in the holding stage
was -30°C. In all steel sheets, the insulation coating was arranged in directly contact
25 with the steel layer, and the adhesion was sufficient.
STEEL CHEMICAL COMPOSITION OF STEEL SLAB (mass%)
TYPE c Si Mn s sol. AI N Sn Sb
NOTE
Si-0.5XMn
A ·- 0.002 3.00 2.63 0.002 0.002 0.0038 1.69. Tr. Tr. COMPARA Tl VE
EXAMPLE
~ ~ o;' g
rr .._,
~ 00
(1) ~
~
~
B 0.002 2.99 2.62 0.002 0.009 0.0031 1.68 0.03 Tr. EXAMPLE
c 0.002 3.00 2.63 0.002 0.021 0.0037 1.69 Tr. . Tr. COMPARATIVE
EXAMPLE
D 0.002 3.00 2.65 0.002 0.007 0.0044 1.68 0.05 Tr. EXAMPLE
E 0.002 3.12 3.23 0.002 0.016 0.0040 1.51 Tr. 0.06 EXAMPLE
F 0.003 3.20 3.30 0.002 0.014 0.0036 1.55 0.12 Tr. EXAMPLE
G 0.003 2.99 '. 2.62 . 0.002 0.020 0.0034 1.68 0.05 Tr. COMPARATIVE
- --·-······-··----~ ---- . ··-·······--- ---- .. ····---------- ............. --- ------ EX61\1PLE .I
~The under I ined value indicates out of the range of the present invention. itw
......
·-------------~~~~~-
[0079]
The specimens with a square 55 mm on a side were punched, the stress relief
mmealing was conducted at 750°C for 2 hours, and then, the magnetic properties
(magnetic flux density B8 and core loss WI 0/400) along L-direction and C-direction
5 were evaluated by the single sheet tester (SST) method. The steel sheet in which the
magnetic flux density B8 along L-direction was 1.60 to 1.77T was judged to be
acceptable, the steel sheet in which the core loss Wl 0/400 along L-direction was
13.0W/kg or less was judged to be acceptable, and the steel sheet in which the average of
the core losses WI0/400 along L-direction and C-direction was 14.5W/kg or less was
10 judged to be acceptable. Also, for the comparison with the conventional grain-oriented
electrical steel sheet, the magnetic properties of commercial steel sheet of JIS standard
30PI05 grade were evaluated as well. The results are shown in the Table 2.
[0080]
[Table 2]
I
No. STEEL
CHEMICAL COMPOSITION OF STEEL SLAB (mass%)
TYPE c Si Mn s sol. AI Si-0.5X Mn Sn Sb
1 A 0.001 3.00 2.63 0.002 0.001 1.69 Tr. Tr.
2 B 0.002 2.99 2.62 0.002 0.007 1.68 0.03 Tr.
3 c 0.002 3.00 2.63 0.002 0.020 1.69 Tr. Tr.
4 D 0.001 3.00 2.65 0.002 0.005 1.68 0.05 Tr.
5 E 0.001 3.12 3.23 0.002 0,016 1.51 Tr. 0.06
6 F 0.002 3.20 3.30 0.002 0.013 1.55 0.12 Tr.
7 G 0.002 299 2.62 0.002 0,019 1.68 0.05 Tr.
8 30P105 Tr. 3.00 Tr. Tr. Tr. !:;3.00 Tr. Tr.
---- -----L__ __
~The under! ined value indicates out of the range of the present invention.
BB(T) W10/400(W/kg)
L- L- c- L&C
DIRECTION DIRECTION DIRECTION AVERAGE
1.52 14.0 15.5 14.8
1.70 10.4 16.0 13.2
1.48 17.1 17.8 17.5
1.70 9.5 15.9 12.7
1.68 9.3 15.6 12.5
1.68 9.2 15.5 12.4
1.54 13.8 15.5 14.7
1.93 10.1 28.2 19.2
NOTE
COMPARATIVE
EXAMPLE
EXAMPLE
COMPARATIVE
EXAMPLE
EXAMPLE
EXAMPLE
EXAMPLE
COMPARATIVE
EXAMPLE
COMPARATIVE
EXAMPLE
'¥:
"."_",
- ----·---------- -----------------
(0081]
As shown in Table 2, in the examples of the steel types B, D, E, and F (No.2, 4,
5, and 6) which were the materials including sol. AI, since the secondary recrystallization
occurred in the entire surface of specimen, the L-direction core loss WI 0/400 and the
5 L&C average core loss Wl 0/400 were acceptable. On the other hand, in the steel type
A (No.I) where the sol. AI content was less than the lower limit and the steel types C and
G (No.3 and 7) where the sol. AI content was more than the upper limit, since the
secondary recrystallization did not occur sufficiently, the magnetic flux density B8 was
insufficient, and the L-direction core loss WI 0/400 and the L&C average core loss
I 0 WI 0/400 were insufficient.
(0082]
In addition, in comparison between the core loss W 10/400 of the examples of
the steel types B, D, E, and Fin (No.2, 4, 5, and 6) and the core loss Wl 0/400 of the
commercial steel sheet (No.8) of ITS standard 30P 105 grade, although the L-direction
15 core losses thereof were substantially the same, the L&C average core losses of the
examples were significantly improved.
[0083]
(Example 2)
The steel slabs whose chemical compositions were shown in Table 3 with the
20 balance consisting of Fe and impurities were heated to 1200°C and then were hot-rolled
so that the thickness was 2.1 mm. The hot-band annealing was conducted at 900°C for
30 seconds, the cold-rolling was conducted so that the final thickness was 0.35 rnrn, the
primary recrystallization annealing was conducted ~t 920°C for 15 seconds, the annealing
separator was applied, the secondary recrystallization annealing was conducted at the
25 maximum temperature of 940°C, and thereafter, the insulation coating was formed. In
5
addition, in order to evaluate the effect of the thickness of product, the steel sheet where
the cold-rolling was conducted so that the final thickness was 0.50 mm was produced,
wherein the production conditions except for the final thickness were the same.
[0084]
In the primary recrystallization annealing process, the heating rate in the
temperature elevating stage was 200 °C/second, the atmosphere in the temperature
elevating stage was 25% ofH2 and 75% ofN2, the atmosphere in the holding stage was
25% ofH2 and 75% ofN2, and the dew point in the holding stage was -20°C. The
alumina-based separator was used for the annealing separator. In the secondary
I 0 recrystallization annealing process, the heating rate in the temperature elevating stage of
800°C or higher was 15 °C/hour, the temperature was elevated to 940°C by the constant
heating rate in substance, the atmosphere in the temperature elevating stage was 90% of
H2 and 10% ofN2, the dew point in the temperature range of 500°C or higher in the
temperature elevating stage was -30°C, the time in the holding stage was 10 hours, the
15 atmosphere in the holding stage was 100% of H2, and the dew point in the holding stage
was -40°C. In all steel sheets, the insulation coating was arranged in directly contact
with the steel layer, and .the adhesion was sufficient.
[0085]
[Table 3]
STEEL
CHEMICAL COMPOSITION OF STEEL SLAB(mass%)
TYPE c Si Mn s sol. AI N Si-0.5XMn
H 0.003 3.03 2.80 0.003 0.013 0.0047 1.63
I 0.003 3.05 2.80 0.003 0.012 0.0045 1.65
J 0.003 3.10 2.82 0.002 . 0.011 0.0048 1.69
K .. 0.002 3.40 3.03 0.002 0.015 0.0050 1.89
L 0.002 3.38 2.58 0.002 0.015 0.0053 2.09
M 0.003 3.06 ill 0.003 0.011 0.0045 ~
~The under! ined value indicates out of the range of the present invention.
Sn Sb
0.05 Tr.
0.08 Tr.
Tr. 0.05
0.06 Tr.
0.05 Tr.
0.05 Tr.
NOTE
EXAMPLE
EXAMPLE
EXAMPLE
EXAMPLE
COMPARATIVE
EXAMPLE
COMPARATIVE
EXAMPLE
\;
""
"""
[0086)
The specimens with a square 55 mm on a side were punched, the stress relief
annealing was conducted at 750°C for 2 hours, and then, the magnetic properties
(magnetic flux density B8 and core loss WI 0/400) along L-direction and C-direction
5 were evaluated by the single sheet tester (SST) method. The steel sheet in which the
magnetic flux density B8 along L-direction was 1.60 to 1.77T was judged to be
acceptable, the steel sheet in which the core loss WI 0/400 along L-direction was
13.0W/kg or less was judged to be acceptable, and the steel sheet in which the average of
the core losses WI 0/400 along L-direction and C-direction was 14.5W /kg or less was
10 judged to be acceptable. The results are shown in the Table 4.
[0087]
[Table 4]
i_:'
:!
11
::I
,!
:!
1:!
q'
II
'•
No. STEEL
CHEMICAL COMPOSITION OF STEEL SLAB(mass%)
TYPE c Si Mn s sol. AI Si-O.oXMn Sn Sb
9 H 0.002 3.03 2.80 0.003 0,012 1.63 0.05 Tr.
10 l 0.002 3.05 2.80 0.003 0.011 1.65 0.08 Tr.
11 ! 0.002 3.05 2.80 0.003 0.011 1.65 0.08 Tr.
12 J 0.002 3.10 2.82 0.002 0.010 1.69 Tr. 0.05
13 K 0.002 3.40 3.03 0.002 O.o15 1.89 0.06 Tr.
14 L 0.002 3.38 2.58 0.002 0.015 2.09 0.05 Tr.
15 M 0.002 3.06 1.47 0.003 O.o10 m 0.05 Tr.
~The underlined value indicates out of the range of the present invention.
B8(T) W10/400(W/kg)
THICKNESS NOTE
(mm) L- L- c- L&C
DIRECTION DIRECTION DIRECTION AVERAGE
0.35 1.69 12.0 16.6 14.3 EXAMPLE
0.35 1.71 10.9 16.9 13.9 EXAMPLE
0.50 1.12 16.9 25.0 21.0 REFERENCE
EXAMPLE
0.35 1.10 11.0 16.9 14.0 EXAMPLE
~
0.35 1.69 10.5 16.5 13.5 EXAMPLE ~
""'
0.35 1.57 14.1 17.2 15.7 COMPARATIVE
EXAMPLE
0.35 1.59 13.9 17.4 15.7 COMPARATIVE
EXAMPLE
C'".==:;:-- -,,---_;c;:;- ~,- --~------
[0088]
As shown in Table 4, in the examples of the steel types H, I, J, and K (No.9, 10,
12, and 13) which were the materials with the thickness of0.35 mm, since the secondary
recrystallization occurred in the entire surface of specimen, the L-direction core loss
5 Wl0/400 and the L&C average core loss Wl0/400 were acceptable. On the other hand,
in the steel type I (No.ll) where the thickness was 0.5 mm and was thicker than the
upper limit, the L-direction core loss Wl 0/400 and the L&C average core loss WI 0/400
were significantly insufficient. Also, in the steel types Land M (No. 14 and 15) where
the value of "Si - 0.5 x Mn" was more than the upper limit, snice the linear defect of the
10 secondary recrystallization occurred in many areas, the magnetic flux density B8 was
insufficient, and the L-direction core loss WI 0/400 and the L&C average core loss
Wl 0/400 were insufficient.
15
[0089]
(Example 3)
The steel slabs whose chemical compositions were shown in Table 5 with the
balance consisting of Fe and impurities were heated to 1250°C and then were hot-rolled
so that the thickness was 2.8 mm. The first cold-rolling was conducted so that the
thickness was 1.4 mm, the intermediate annealing was conducted at 950°C for 30
seconds, the second cold-rolling was conducted so that the final thickness was 0.23 mm,
20 the primary recrystallization annealing was conducted at 920°C for 15 seconds, the
mmealing separator was applied, the secondary recrystallization annealing was conducted
at the maximum temperature of 940°C, and thereafter, the insulation coating was formed.
[0090]
In the primary recrystallization armealing process, the heating rate in the
25 temperature elevating stage was I 000 °C/second, the atmosphere in the temperature
--·-·------~~--~--------
_M" l(o
elevating stage was 15% ofH2 and 85% ofN2, the atmosphere in the holding stage was
15% ofH2 and 85% ofN2, and the dew point in the holding stage was -30°C. The
alumina-based separator was used for the annealing separator. In the secondary
recrystallization annealing process, the heating rate in the temperature elevating stage of
5 800°C or higher was 20 °C/hour, the temperature was elevated to 940°C by the constant
heating rate in substance, the atmosphere in the temperature elevating stage was 95% of
H2 and 5% ofN2, the dew point in the temperature range of 500°C or higher in the
temperature elevating stage was -20°C, the time in the holding stage was 15 hours, the
atmosphere in the holding stage was I 00% ofl-h, and the dew point in the holding stage
1 0 was -40°C. In all steel sheets, the insulation coating was arranged in directly contact
with the steel layer, and the adhesion was sufficient.
[0091]
[Table 5]
STEEL CHEMICAL COMPOSITION OF STEEL SLAB(mass%)
TYPE NOTE
c Si Mn s sol. AI N Si-0.5XMn Sn Sb I
N 0.002 2.99 2.72 0.001 0.014 0.0052 1.63 0.05 Tr. EXAMPLE
0 0.002 3.00 2.73 0.001 0.015 0.0051 1.64 0.10 Tr. EXAMPLE
p 0.003 3.05 2.68 0.001 0.013 0.0051 1.71 0.03 0.03 EXAMPLE
' ··- ...........
:::iHhe under I ined value indicates out of the range of the present invention.
~
c------~-----~-------------
- ----- ---
[0092]
The specimens with a square 55 mm on a side were punched, the stress relief
annealing was conducted at 750°C for 2 hours, and then, the magnetic properties
(magnetic flux density B8 and core loss Wl 0/400) along L-direction and C-direction
5 were evaluated by the single sheet tester (SST) method. The steel sheet in which the
magnetic flux density B8 along L-direction was 1.60 to 1. 77T was judged to be
acceptable, the steel sheet in which the core loss Wl 0/400 along L-direction was
13 .OW /kg or less was judged to be acceptable, and the steel sheet in which the average of
the core losses W!0/400 along L-direction and C-direction was 14.5W/kg or less was
1 0 judged to be acceptable. Also, for the comparison with the conventional grain-oriented
electrical steel sheet, the magnetic properties of commercial steel sheet of JIS standard
23P95 grade were evaluated as well. The results are shown in the Table 6.
[0093]
[Table 6]
No. STEEL CHEMICAL COMPOSITION OF STEEL SLAB(mass%) B8(T) W10/400(W/kg)
TYPE L- L- c- L&C NOTE c Si Mn s sol. AI Si-0.5 XMn Sn Sb DIRECTION DIRECTION DIRECTION AVERAGE
16 N 0.002 2.99 2.72 0.001 0.012 1.63 0.05 Tr. 1.63 8.7 13.0 10.9 EXAMPLE
17 0 0.002 3.00 2.73 0.001 0.013 1.64 0.10 Tr. 1.73 7.0 13.5 10.3 EXAMPLE
f-·
18 p 0.003 3.05 2.68 0.001 0.012 1.71 0.03 0.03 1.72 7.1 13.4 10.3 EXAMPLE
19 23P95 Tr. 3.00 Tr. Tr. Tr. =::3.00 Tr. Tr. 1.92 7.4 25.1 16.3 COMPARATIVE
EXAMPLE
~The under! ined value indicates out of the range of the present invention.
t
...c
w
(0094]
As shown in Table 6, in the examples of the steel types N, 0, and P (No.l6, 17,
and 18), since the secondary recrystallization occurred, the L-direction core loss
Wl0/400 and the L&C average core loss Wl0/400 were acceptable. Also. in
5 comparison between the core loss WJ0/400 ofthe examples of the steel types N, 0, and
10
P (No.l6, 17, and 18) and the core loss Wl0/400 ofthe commercial steel sheet (No.l9) of
JIS standard 23P95 grade, although the L-direction core losses thereof were substantially
the same, the L&C average core losses of the examples were significantly improved.
(0095]
(Example 4)
The steel slabs whose chemical compositions were shown in Table 7 with the
balance consisting of Fe and impurities were heated to 1230°C and then were hot-rolled
so that the thickness was 2.0 ll1l1L The hot-band annealing was conducted at 920°C for
30 seconds, the cold-rolling was conducted so that the final thickness was 0.30 mm, the
15 primary recrystallization annealing was conducted at 930°C for 15 seconds, the annealing
separator was applied, the secondary recrystallization annealing was conducted at the
maximum temperature of 940°C, and thereafter, the insulation coating was formed.
(0096]
In the primary recrystallization annealing process, the heating rate in the
20 temperature elevating stage was 120 °C/second, the atmosphere in the temperature
elevating stage was 20% ofH2 and 80% ofNz, the atmosphere in the holding stage was
20% ofH2 and 80% ofN2, and the dew points in the holding stage were under conditions
of -25°C, -l0°C, 0°C, and 30°C. The alumina-based separator was used for the
annealing separator. In the secondary recrystallization annealing process, the heating
25 rate in the temperature elevating stage of 800°C or higher was 20 °C/hour, the
j& Lr{
temperature was elevated to 940°C by the constant heating rate in substance, the
atmosphere in the temperature elevating stage was 85% ofH2 and 15% ofN2, the dew
point in the temperature range of 500°C or higher in the temperature elevating stage was
0°C, the time in the holding stage was 5 hours, the atmosphere in the holding stage was
5 100% of H2, and the dew point in the holding stage was -30°C. In the steel sheets of
test Nos. 20 and 21, the insulation coating was arranged in directly contact with the steel
layer, and the adhesion was sufficient. On the other hand, in the steel sheets of test Nos.
22 and 23, the oxide was formed between the insulation coating and the steel layer, and
the adhesion was insufficient.
10 [0097]
[Table 7]
STEEL CHEMICAL COMPOSITION OF STEEL SLAB(mass%)
TYPE NOTE
c Si Mn s sol. AI N Si-0.5XMn Sn Sb
Q 0.003 3.10 2.81 0.001 0.007 0.0042 1.70 0.030 Tr. EXAMPLE
R 0.003 3.00 2.84 0.003 0.015 0.0049 1.58 .0.003 0.0008 COMPARATIVE
EXAMPLE
s 0.003 2.98 • . 1.97 0.003 0.014 0.0049 2.00 0.050 0.050 COMPARATIVE
EXAMPLE
T 0.003 3.25 4.10 0.003 0.015 0.0049 1.20 0.050 0.050 COMPARATIVE
EXAMPLE :
~The under I ined value indicates out of the range of the present invention. ~
...:::
""
[0098]
The specimens with a square 55 mm on a side were punched, the stress relief
annealing was conducted at 750°C for 2 hours, and then, the magnetic properties
(magnetic flux density B8 and core loss Wl0/400) along L-direction and C-direction
5 were evaluated by the single sheet tester (SST) method. The steel sheet in which the
magnetic flux density B8 along L-direction was 1.60 to l.77T was judged to be
acceptable, the steel sheet in which the core loss Wl 0/400 along L-direction was
13.0W /kg or less was judged to be acceptable, and the steel sheet in which the average of
the core losses Wl0/400 along L-direction and C-direction was l4.5W/kg or less was
10 judged to be acceptable. The results are shown in the Table 8.
[0099]
[Table 8]
No. DEW POINT IN STEEL HOLDING CHEMICAL COMPOSITION OF STEEL SLAB(mass%) BB(T) W10/400(W/kg)
TYPE STAGE FOR PRIMARY L- L- c- L&C NOTE
RECRYSTALLIZATION c Si Mn s sol. AI Si-0.5 x Mn Sn Sb DIRECTION DIRECTION DIRECTION AVERAGE
20 Q -25t 0.002 3.10 2.81 0.001 0.006 1.70 0.03 Tr. 1.71 9.5 15.7 12.6 EXAMPLE
21 a -10°C 0.002 l10 ~81 0.001 0.005 1.70 0.03 Tr. 1.70 9.8 15.6 127 EXAMPLE
22 Q 0°C - - - - - - - - - - - - CEOXMAPAMRAPTLIVEE
23 Q 30°C COMPARATIVE - - - - - - - - - - - - EXAMPLE
24 R -25t 0.002 3.00 2.84 0.003 0.014 1.58 0.003 0.0008 1.69 13.1 16.0 14.6 COMPARATIVE
EXAMPLE,
25 s -25°C 0.003 2.98 1.97 0.003 0.013 2.00 0.050 0.050 1.68 13.2 15.9 14.6 COMPARATIVE!
EXAMPLE 1 r----
COMPARATIVE! 26 T -25°C 0.003 3.25 4.10 0.003 0.014 1.20 0.050 0.050 1.57 14.1 17.2 15.1 EXAMPLE
~
.!;:
""
--- ··-·--· --~--------------~
~The under! ined value indicates out of the range of the present invention.
--.----- -.-. -,.---,-~70~--- CC".::=-===7;:;:-~=-7 . ·--·
[0100]
As shown in Table 8, in the examples of test Nos.20 and 21, since the secondary
recrystallization occurred in the entire surface of specimen, the L-direction core loss
Wl0/400 and the L&C average core loss Wl0/400 were acceptable. Also, in the
5 examples of test Nos.20 and 21, the 0 content of the steel layer was 0.03% (300 ppm) or
less measured by the non-dispersive infrared absorption method after fusion in a current
of inert gas.
[0101]
On the other hand, in the comparative examples of test Nos.22 and 23, the 0
10 content of the steel layer was more than 0.03% (300 ppm), the thick oxide layer was
formed on the surface of steel layer, the adhesion of the insulation coating significantly
deteriorated, and thus, the magnetic properties could not be evaluated. Also, in the
comparative examples of the steel types R, S, and T (No.24 to 26), the magnetic flux
density B8 and the core loss Wl 0/400 were insufficient.
15
Industrial Applicability
[0102]
According to the above aspects of the present invention, it is possible to provide
the grain-oriented electrical steel sheet excellent in both the high-frequency magnetic
20 properties in L-direction and the average of high-frequency magnetic properties in
L-direction and C-direction. Accordingly, the present invention has significant
industrial applicability.
Reterence Signs List
25 [01 03]
-ro 8'1'--'
1: STEEL LAYER (BASE STEEL)
2: INSULATION COATING
3: GLASS FILM (FORSTERITE FILM)

CLAIMS
1. A grain-oriented electrical steel sheet comprising a steel layer and an insulation
coating arranged on the steel layer, characterized in that:
the steel layer includes, as a chemical composition, by mass%,
0.0003 to 0.005% of C,
2.9 to 4.0% of Si,
2.0 to 4.0% ofMn,
0.003 to 0.018% of sol. AI,
0.005% or less of S,
0 to 0.20% ofSn,
0 to 0.20% of Sb, and
a balance consisting of Fe and impurities;
a silicon content and a manganese content expressed in mass% in the chemical
15 composition of the steel layer satisfy 1.2% :S Si- 0.5 x Mn :S 2.0%;
a tin content and an antimony content expressed in mass% in the chemical
composition of the steel layer satisfy 0.005% :S Sn + Sb :S 0.20%; and
20 2.
25 3.
the insulation coating is arranged in directly contact with the steel layer.
The grain-oriented electrical steel sheet according to claim 1, wherein
the steel layer includes, as the chemical composition, by mass%,
0.004 to 0.20% of Sn, and
0.001 to 0.20% ofSb.
A method of producing the grain-oriented electrical steel sheet according to
claim 1 or 2,
the method comprising a casting process, a hot-rolling process, a cold-rolling
process, a primary recrystallization annealing process, an annealing separator coating
process, a secondary recrystallization annealing process, and an insulation coating
5 formation process, wherein:
10
15
in the casting process, a steel is cast so that the steel includes, as a chemical
composition, by mass%,
0.0003 to 0.005% of C,
2.9 to 4.0% ofSi,
2.0 to 4.0% ofMn,
0.003 to 0.018% of sol. AI,
0.001 to 0.01% ofN,
0.005% or less of S,
0 to 0.20% ofSn,
0 to 0.20% of Sb, and
a balance consisting of Fe and impurities,
a silicon content and a. manganese content expressed in mass% in the chemical
composition satisfY 1.2% ::S Si- 0.5 x Mn ::S 2.0%, and
a tin content and an antimony content expressed in mass% in the chemical
20 composition satisfY 0.005% ::S Sn + Sb ::S 0.20%;
in the primary recrystallization annealing process, a primary recrystallization
annealing is conducted for the steel under conditions such that a heating rate in a
temperature elevating stage is 100 °C/second to 5000 °C/second on average, an
atmosphere in the temperature elevating stage is 10 to 100 vol% ofH2 and H2 + N2 = 100
25 vol%, a temperature in a holding stage is 800 to 1 000°C, a time in the holding stage is 5
5
seconds to 10 minutes, an atmosphere in the holding stage is 10 to 100 vol% oflh H2 +
N2 = 100 vol%, and a d~w point is -1 ooc or lower;
in the annealing separator coating process, an annealing sepaxator including an
alumina as a main component is only applied on the steel; and
in the secondary recrystallization mmealing process, a secondm-y
recrystallization am1ealing is conducted for the steel under conditions such that 311
atmosphere in a temperature elevating stage is 0 to 80 vol% of,N2 a11d H2 + N2 = 100
vol%, a dew point in a temperature range of 500°C or higher in the temperature elevating
stage is 0°C or lower, a temperature in a holding stage is 85 0 to l 000°C, a time in the
10 holding stage is 4 to 100 hours, an atmosphere in the holding stage is 0 to 80 vol% ofN2,
H2 + Nz = 100 vol%, md a dew point is ooc or lower.
4. The method of producing the grain-oriented electrical steel sheet according to
claim 3, wherein,
15 in the casting process, the steel includes, as the chemical composition, by
1nasso/o,
0.004 to 0.20% of Sn, and
0.001 to 0.20% ofSb.
20 5. The method of producing the grain-oriented electrical steel. sheet according to .
claim 3 or 4, vvhereih,
in the secondary recrystallization annealing process, the steel is heated to the
temperature in the holding stage by a consta11t heating Iate in the temperature elevating
stage.