DESCRIPTION
TITLE.OF INVENTION: METHOD OF MANUFACTURING GRAINORIENTED
ELECTRICAL STEEL SHEET
TECHNICAL FIELD
[0001] The present invention relates to a method of
manufacturing a grain-oriented electrical steel sheet
in which the variation in magnetic property is
suppressed.
BACKGROUND ART
[0002] A grain-oriented electrical steel sheet is, a
steel sheet which contains Si and in which crystal
grains are highly integrated in a {110}<001>
orientation, and is used as a material of a wound
core of a stationary induction apparatus such as a
transformer. The control of the orientation of the
crystal grains is conducted with catastrophic grain
growth phenomenon called secondary recrystallization.
[0003] As a method of controlling the secondary
recrystallization, the following two methods can be
cited. In one method, heating is performed on a slab
at a temperature of 1280°C or higher to almost
completely solid-solve fine precipitates called
inhibitors, and thereafter hot rolling, cold rolling,
annealing and so on are performed to cause the fine
precipitates to precipitate during the hot rolling
and the annealing. In the other method, heating is
performed on a slab at a temperature of lower than
1280°C, and thereafter hot rolling, cold rolling,
decarburization annealing, nitridation, finish
annealing and so on are performed to cause AlN (Al,
Si)N and the like to precipitate as inhibitors during
the nitridation.
[0004] In recent years, it has been requested to
reduce a time taken for a decarburization annealing
in a manufacturing process of a grain-oriented
electrical steel sheet from a point of view of
reduction in CO2 emissions. Accordingly, it has been
studied to use a slab whose C content is low.
[0005] However, lowering the C content of the slab
causes a remarkable variation in magnetic property
(magnetic property deviation) depending on site,
after the finish annealing performed with the steel
being coiled.
CITATION LIST
PATENT LITERATURE
[0006] Patent Literature 1: Japanese Laid-open
Patent Publication No. 03-122227
Patent Literature 2: Japanese Laid-open Patent
Publication No. 11-323437
Patent Literature 3: Japanese Laid-open Patent
Publication No. 06-256847
Patent Literature 4: Japanese National
Publication of International Patent Application No.
2001-515540
Patent Literature 5: Japanese Laid-open Patent
Publication No. 2000-199015
2
Patent Literature 6: Japanese Laid-open Patent
Publication No. 2007-254829
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0007] An object of the present invention is to
provide a method of manufacturing a grain-oriented
electrical steel sheet, capable of suppressing the
variation in magnetic property.
SOLUTION TO PROBLEM
[0008] It turned out that the above-described
variation in magnetic properties after the finish
annealing is remarkable when the C content is 0.06
mass% or less, and further, it is particularly
noticeable when the C content is 0.048 mass% or less.
Although the cause of the variation in magnetic
property after the finish annealing,is not exactly
known, the variation is considered to occur because
the crystal grains sometimes do not uniformly grow
during the finish annealing even if the crystal
grains seem to be uniform before the finish
annealing. Further, it may be considered that the
reason why the crystal grains do not uniformly grow
is because, due to the low C content, a phase
transformation during the hot rolling is not
sufficiently performed, so that an amount of
austenite transformation is small, resulting in that
a hot-rolled texture becomes unstable. Specifically,
it may be considered that a sufficient secondary
3
recrystallization does not occur in a portion in
which the hot-rolled texture becomes nonuniform,
resulting in that sufficient magnetic properties are
not obtained.
[0009] The present inventors thought, based on such
knowledge, that it is possible to sufficiently cause
the secondary recrystallization throuth forming an
effective precipitate in order to make the crystal
grain growth uniform during the finish annealing.
Then, the present inventors repeatedly carried out an
experiment of measuring the magnetic properties of
the grain-oriented electrical steel sheets obtained
through adding various kinds of elements to slabs.
As a result, the present inventors found that
addition of Ti and Cu was effective to make the
secondary recrystallization uniform.
[0010] The present invention has been made based on
the above-described knowledge, and a summary thereof
is as follows.
[0011] (1) A method of manufacturing a grainoriented
electrical steel sheet, comprising:
performing hot rolling of a steel containing Si:
2.5 mass: to 4.0 mass:, C: 0.01 mass: to 0.060 mass:,
Mn: 0.05 mass: to 0.20 mass%, acid-soluble Al: 0.020
mass% to 0.040 mass%, N: 0.002 mass: to 0.012 mass-.,
S: 0.001 mass: to 0.010 mass%, and P: 0.01 mass% to
0.08 mass%, further containing at least one kind
selected from a group consisting of Ti: 0.0020 mass%
to 0.010 mass% and Cu: 0.010 mass% to 0.50 mass%, and
a balance composed of Fe and inevitable impurities,
to obtain a hot-rolled steel sheet;
performing annealing on the hot-rolled steel
sheet to obtain an annealed steel sheet;
performing cold rolling on the annealed steel
sheet to obtain a cold-rolled steel sheet;
performing decarburization annealing on the coldrolled
steel sheet at a temperature of 800°C to 950°C
to obtain a decarburization annealed steel sheet;
then, performing nitridation treatment on the
decarburization annealed steel sheet at 700°C to 850°C
to obtain a nitrided steel sheet; and
performing finish annealing on the nitrided steel
sheet.
[0012] (2) The method of manufacturing a grainoriented
electrical steel sheet according to (1),
wherein the hot rolling on the steel is performed
after heating the steel to a temperature of 1250°C or
lower.
[0013] (3) The method of manufacturing a grainoriented
electrical steel sheet according to (1) or
(2), wherein the steel further contains at least one
kind selected; from a group consisting of Cr: 0.010
mass% to 0.20 mass%, Sn: 0.010 mass% to 0.20 mass%,
Sb: 0.010 mass% to 0.20 mass%, Ni: 0.010 mass% to
0.20 mass%, Se: 0.005 mass% to 0.02 mass%, Bi: 0.005
mass% to 0.02 mass%, Pb: 0.005 masso to 0.02 mass%,
B: 0.005 mass% to 0.02 mass%, V: 0.005 mass% to 0.02
mass%, Mo: 0.005 mass% to 0.02 mass%, and As: 0.005
mass% to 0.02 masso.
[0014] (4) The method of manufacturing a grainoriented
electrical steel sheet according to any one
of (1) to (3), wherein
a Ti content in the steel is 0.0020 mass% to
0.0080 mass%,
a Cu content in the steel is 0.01 mass% to 0.10
mass%, and
a relation of "20x[Ti]+[Cu]-0.18" is established
where the Ti content (mass%) in the steel is
expressed as [Ti] and the Cu content (mass%) is
expressed as [Cu].
[0015] (5) The method of manufacturing a grainoriented
electrical steel sheet according to (4),
wherein a relation of "10x[Ti]+[Cu]c0.07" is
established.
ADVANTAGEOUS EFFECTS OF INVENTION
[0016] According to the present invention,
appropriate amounts of Ti and/or Cu are contained in
the steel, and decarburization annealing and
nitridation treatment are performed at appropriate
temperatures, thereby making it possible to suppress
the variation in magnetic property.
BRIEF DESCRIPTION OF DRAWINGS
[0017] [Fig. 1] Fig. 1 is a chart representing the
relation between a Ti content and a Cu content and
the magnetic flux density and the evaluation of its
variation.
[Fig. 2] Fig. 2 is a flowchart illustrating a
- 6 -
method of manufacturing a grain-oriented electrical
steel sheet according to an embodiment of the present
invention.
DESCRIPTION OF EMBODIMENTS
[0018] As described above, the present inventors
repeatedly conducted the experiments of measuring the
magnetic properties of the grain-oriented electrical
steel sheets obtained through adding various kinds of
elements to slabs and found out that addition of Ti
and Cu is effective to make the secondary
recrystallization uniform.
[0019] In the experiment, silicon steel with a
composition used for manufacturing a grain-oriented
electrical steel sheet based on a low-temperature
slab heating method in which a C content was 0.06
mass% or less was used, for example. Further, Ti and
Cu were contained at various ratios. into the carbon
steel to produce steel ingots with various
compositions. Further, the steel ingots were hAated
at a temperature of 1250°C or lower and subjected to
hot rolling, and then subjected to cold rolling.
Further' decarburization annealing was performed
after the cold rolling, and thereafter, nitridation
treatment and finish annealing were performed. Then,
the magnetic flux densities B8 of the obtained grainoriented
electrical steel sheets were measured and
the variations in the magnetic flux densities B8 in
coils after the finish annealing were checked. The
magnetic flux density B8 is the magnetic flux density
7
occurring in the grain-oriented electrical steel
sheet when a magnetic field of 800 A/m at 50 Hz is
applied thereto.
[0020] As a result of the experiment, it was found
out that the variation in the magnetic flux density
B8 in the coil after the finish annealing is
remarkably reduced when the steel ingot contains
0.0020 mass% to 0.010 mass% of Ti and/or 0.010 mass%
to 0.50 mass% of Cu.
[0021] An example of the results obtained through
the above-described experiments is illustrated in
Fig. 1. Though details of the experiments will be
described later, an open circle mark in Fig. 1
indicates that the average value of the magnetic flux
densities B8 of five single-plate samples was 1.90 T
or more and the difference between the maximum value
and the minimum value of the magnetic flux density B8
was 0.030 T or less. Further, a filled circle mark
in Fig. 1 indicates that at least the average value
of the magnetic flux densities B8 of the five singleplate
samples was less than 1.90 T or the difference
betweenthe maximum value and the minimum value of
the magnetic flux densities B8 was more than 0.030 T.
It is apparent from Fig. 1 that when the steel ingot
contains 0.0020 mass% to 0.010 mass% of Ti and/or
0.010 mass% to 0.50 mass% of Cu, the average value of
the magnetic flux densities B8 is high and the
variation in the magnetic flux densities B8 is small.
[0022] Next, a method of manufacturing a grainoriented
electrical steel sheet according to an
embodiment of the present invention will be
described. Fig. 2 is a flowchart illustrating the
method of manufacturing a grain-oriented electrical
steel sheet according to the embodiment of the
present invention.
[0023] In the present embodiment, first, a slab is
produced through casting of molten steel for a grainoriented
electrical steel sheet with a predetermined
composition (Step 1). The casting method therefor is
not particularly limited. The molten steel contains,
for example, Si: 2.5 mass% to 4.0 mass%, C: 0.01
mass% to 0.060 mass%, Mn: 0.05 mass% to 0.20 mass%,
acid-soluble Al: 0.020 mass% to 0.040 mass%, N: 0.002
mass% to 0.012 mass%, S: 0.001 mass% to 0.010 mass%,
and P: 0.01 mass% to 0.08 mass%. The molten steel
further contains at least one kind selected from a
group consisting of Ti: 0.0020 mass% to 0.010 mass%
and Cu: 0.010 mass% to 0.50 mass%. In short, the
molten steel contains one or both of Ti and Cu in
ranges of Ti: 0.010 mass% or less and Cu: 0.50 mass%
or less-to satisfy at least one of Ti: 0.0020 mass%
or more or Cu: 0.010 mass% or more. The balance of
the molten steel may be composed of Fe and inevitable
impurities. Note that the inevitable impurities may
include an element(s) forming an inhibitor in the
manufacturing process of the grain-oriented
electrical steel sheet and remaining in the grainoriented
electrical steel sheet after purification is
performed through a high-temperature annealing.
[0024] Here, reasons for numerical limitations of
the composition of the above-described molten steel
will be described.
[0025] Si is an element that is extremely effective
to enhance the electrical resistance of the grainoriented
electrical steel sheet to reduce the eddy
current loss constituting a part of the core loss.
When the Si content is less than 2.5 mass%, the eddy
current loss cannot be sufficiently suppressed. On
the other hand, when the Si content is more than 4.0
mass%, the processability is lowered. Accordingly,
the Si content is set to 2.5 mass% to 4.0 mass%.
[0026] C is an element that is effective to control
the structure (primary recrystallization structure)
obtained through primary recrystallization. When the
C content is less than 0.01 masso, the effect cannot
be sufficiently obtained. On the other hand, when
the C content is more than 0.06 mass, the time
required for decarburization annealing increases,
resulting in a larger exhaust amount of CO2. Note
that when the decarburization annealing is
insufficient,, the grain-oriented electrical steel
sheet with excellent magnetic properties is less
likely to be obtained. Accordingly, the C content is
set to 0.01 mass% to 0.06 mass%. Further, since the
variation in magnetic property after finish annealing
is particularly prominent when the C content is 0.048
mass% or less in the conventional technique as
- 10 -
described above, the embodiment is particularly
effective in the case where the C content is 0.048
mass% or less.
[0027] Mn increases the specific resistance of the
grain-oriented electrical steel sheet to reduce the
core loss. Mn also functions to prevent occurrence
of cracks in the hot rolling. When the Mn content is
less than 0.05 mass%, the effects cannot be
sufficiently obtained. On the other hand, when the
Mn content is more than 0.20 mass%, the magnetic flux
density of the grain-oriented electrical steel sheet
is lowered. Accordingly, the Mn content is set t
0.05 mass% to 0.20 masso.
[0028] Acid-soluble Al is an important element
forming AlN serving as an inhibitor. When the acidsoluble
Al content is less than 0.020 mass%, a
sufficient amount of AlN cannot be formed, resulting
in insufficient inhibitor strength. On the other
hand, when the acid-soluble Al content is more than
0.040 mass%, AlN becomes coarse, resulting in a
decrease in inhibitor strength. Accordingly, the
acid-soluble Al content is set to 0.020 mass% to
0.040 mass%.
[0029] N is an important element forming AlN through
reacting with the acid-soluble Al. Though a large
amount of N does not need to be contained in the
grain-oriented electrical steel sheet because
nitridation treatment is performed after the cold
rolling as will be described later, a great load may
- 11 -
be required in steelmaking in order to make the N
content less than 0.002 mass%. On the other hand,
when the N content is more than 0.012 mass%, a hole
called blister is generated in the steel sheet in the
cold rolling. Accordingly, the N content is set to
0.002 mass% to 0.012 mass%. The N content is
preferably 0.010% mass% or less in order to further
reduce the blister.
[0030] S is an important element forming a MnS
precipitate through reacting with Mn. The MnS
precipitate mainly affects the primary
recrystallization and functions to suppress the
variation depending on site in grain growth in the
primary recrystallization due to the hot rolling.
When the Mn content is less than 0.001 mass%, the
effect cannot be sufficiently obtained. On the other
hand, when the Mn content is more than 0.010 mass%,
the magnetic property is likely to decrease.
Accordingly, the Mn content is set to 0.001 mas,% to
0.010 mass%. The Mn content is preferably 0.009 mass%
or less in order to further improve the magnetic
property.
[0031] P increases the specific resistance of the
grain-oriented electrical steel sheet to reduce the
core loss. When the P content is less than 0.01
mass %, the effect cannot be sufficiently obtained.
On the other hand, when the P content is more than
0.08 mass%, the cold rolling may become difficult to
perform. Accordingly, the P content is set to 0.01
- 12 -
mass% to 0.08 masso.
[0032] Ti forms a TiN precipitate through reacting
with N. Further, Cu forms a CuS precipitate through
reacting with S. These precipitates function to make
the growth of the crystal grains in the finish
annealing uniform irrespective of the site of the
coil and suppress the variation in magnetic property
of the grain-oriented electrical steel sheet. In
particular, the TiN precipitate is considered to
suppress the variation in grain growth in a high
temperature region in the finish annealing to
decrease the deviation of the magnetic property of
the grain-oriented electrical steel sheet. Further,
the CuS precipitate is considered to suppress the
variation in grain growth in a low temperature region
in the decarburization annealing and the finish
annealing to decrease the deviation,of the magnetic
property of the grain-oriented electrical steel
sheet. When the Ti content is less than 0.0020 mass%
and the Cu content is less than 0.010 mass%, the
effects cannot be sufficiently obtained. On the
other hand, when the Ti content is more than 0.010
mass%, the TiN precipitate is excessively formed and
remains even after the finish annealing. Similarly,
when the Cu content is more than 0.50 mass%, the CuS
precipitate is excessively formed and remains even
after the finish annealing. If these precipitates
remain in the grain-oriented electrical steel sheet,
it is difficult to obtain a high magnetic property.
- 13 -
Accordingly, the molten steel contains one or both of
Ti and Cu in ranges of Ti: 0.010 mass% or less and
Cu: 0.50 mass% or less to satisfy at least one of Ti:
0.0020 mass% or more or Cu: 0.010 mass% or more. In
short, the molten steel contains at least one kind
selected from a group consisting of Ti: 0.0020 mass%
to 0.010 mass% and Cu: 0.010 mass% to 0.50 mass%.
[0033] Note that the lower limit of the Ti content
is preferably 0.0020 mass%, and the upper limit of
the Ti content is preferably 0.0080 mass%. Further,
the lower limit of the Cu content is preferably 0.01
mass%, and the upper limit of the Cu content is
preferably 0.10 mass%. Further, where the Ti content
(mass%) is expressed as [Ti] and the Cu content
(mass%) is expressed as [Cu], it is more preferable
that the relation of "20x[Ti]+[Cu]-,0.18" is
established and, preferably, the relation of
"l0x[Ti]+[Cu]-0.07" is established.
[0034] Note that. at least one kind of the following
various kinds of elements may be contained in the
molten steel.
[0035] Cr and Sn improve the quality of an oxide
layer to be formed in the decarburization annealing
and improve the quality of a glass film to be formed
of the oxide layer in the finish annealing. In other
words, Cr and Sn improve the magnetic property
through stabilization of the formation of the oxide
layer and the glass film to suppress the variation in
the magnetic property. However, when the Cr content
- 14 -
is more than 0.20 mass%, the formation of the glass
film may be unstable. Further, when the Sn content
is more than 0.20 mass%, the surface of the steel
sheet may be less likely to be oxidized to result in
insufficient formation of the glass film.
Accordingly, each of the Cr content and the Sn
content is preferably 0.20 mass% or less. Further,
in order to sufficiently obtain the above effects,
each of the Cr content and the Sn content is
preferably 0.01 mass% or more. Note that Sn is a
grain boundary segregation element and thus also has
an effect to stabilize secondary recrystallization.
[0036] Further, the molten steel may contain Sb:
0.010 mass% to 0.20 mass%, Ni: 0.010 mass% to 0.20
mass%, Se: 0.005 mass% to 0.02 mass%, Bi: 0.005 mass%
to 0.02 mass%, Pb: 0.005 mass% to 0.02 mass%, B:
0.005 mass% to 0.02 mass%, V: 0.005. mass% to 0.02
mass%, Mo: 0.005 mass% to 0.02 mass%, and/or As:
0.005 mass% to 0.02 mass%. These elements may he
inhibitor strengthening elements.
[0037] In the embodiment, after the slab is produced
from the molten steel with the composition, the slab
is heated (Step S2). The temperature of the heating
is preferably set to 1250°C or lower from the
viewpoint of energy saving.
[0038] Next, hot rolling is performed on the slab to
obtain a hot-rolled steel sheet (Step S3). The
thickness of the hot-rolled steel sheet is not
particularly limited, and may be set to 1.8 mm to 3.5
15 -
mm.
[0039] Thereafter, annealing is performed on the
hot-rolled steel sheet to obtain an annealed steel
sheet (Step S4). The condition of the annealing is
not particularly limited, and the annealing may be
performed, for example, at a temperature of 750°C to
1200°C for 30 seconds to 10 minutes. The annealing
improves the magnetic property.
[0040] Subsequently, cold rolling is performed on
the annealed steel sheet to obtain a cold-rolled
steel sheet (Step S5). The cold rolling may be
performed only once or a plurality of times while an
intermediate annealing is performed therebetween.
The intermediate annealing is preferably performed at
a temperature of 750°C to 1200°C for 30 seconds to 10
minutes.
[0041] Note that if the cold rolling is performed
without performing the above-described intermediate
annealing, it may be difficult to obtain uniform
properties. On the other hand, if the cold rolling
is performed a plurality of times while the
intermediate annealing is performed therebetween, the
uniform properties are easily obtained but the
magnetic flux density may decrease. Accordingly, it
is preferable to determine the number of times of the
cold rolling and the presence or absence of the
intermediate annealing according'to the property
required for and the cost of the finally obtained
grain-oriented electrical steel sheet.
- 16 -
[0042] Further, in any case, it is preferable to set
the rolling reduction at the final cold rolling to
80% to 95%.
[0043] The decarburization annealing is performed on
the cold-rolled steel sheet in a wet atmosphere
containing hydrogen and nitrogen at 800°C to 950°C
after the cold rolling to obtain a decarburization
annealed steel sheet (step S6). The decarburization
annealing removes carbon in the steel sheet and
causes primary recrystallization. When the
temperature of the decarburization annealing is lower
than 800°C, the crystal grain obtained through the,
primary recrystallization (primary recrystallization
grain) is small so that the subsequent secondary
recrystallization does not sufficiently appear. On
the other hand, when the temperature of the
decarburization annealing is higher. than 950°C, the
primary recrystallization grain is large so that the
subsequent secondary recrystallization does not
sufficiently appear.
[0044] Next, nitridation treatment is performed on
the decarburization annealed steel sheet in an
atmosphere containing hydrogen, nitrogen and a gas
having a nitriding capability such as ammonia at 700°C
to 850°C to obtain a nitrided steel sheet (step S7).
The nitridation treatment increases the nitrogen
content in the steel sheet. When the temperature of
the nitridation treatment is lower than 700°C or high
than 850°C, nitrogen is difficult to be diffused to
- 17
the inner part of the steel sheet so that the
subsequent secondary recrystallization does not
d
sufficiently appear.
[0045] After that, an annealing separating agent
containing MgO as a main component is applied, in a
water slurry, to the surface of the nitrided steel
sheet, and the nitrided steel sheet is coiled. Then,
batch-type finish annealing is performed on the
coiled nitrided steel sheet to obtain a coiled
finish-annealed steel sheet (Step S8). The finish
annealing causes secondary recrystallization.
[0046] Thereafter, the coiled finish-annealed steel
sheet is uncoiled, and the annealing separating agent
is removed. Subsequently, a coating solution
containing aluminum phosphate and colloidal silica as
main components is applied to the surface of the
finish-annealed steel sheet, and baking is performed
thereon to form an insulating film (step S9).
[0047] In the above manner, the grain-oriented
electrical steel sheet can be manufactured.
[0048] Note that the steel being an object for the
hot rolling is not limited to the slab obtained
through casting of the molten steel, but a so-called
thin slab may be used. Further, when using the thin
slab, it is not always necessary to perform the slab
heating at 1250°C or lower.
EXAMPLE
[0049] Next, experiments conducted by the present
inventors will be described. Conditions and so on in
- 18 -
these experiments are examples employed to verify
practicality and effects of the present invention,
and the present invention is not limited to these
examples.
[0050] (First Experiment)
First, 15 kinds of steel ingots each containing
Si: 3.2 mass% , C: 0.055 mass% , Mn: 0.10 mass%, acidsoluble
Al: 0.028 mass%, N: 0.003 mass %, S: 0.0060
mass% , and P: 0.030 mass%, further containing Ti and
Cu in amounts listed in Table 1, and the balance
composed of Fe and inevitable impurities were
produced using a vacuum melting furnace. Then,
annealing was performed on the steel ingots at 1150°C
for one hour, and then hot rolling was performed
thereon to obtain hot-rolled steel sheets with a
thickness of 2.3 mm.
[0051] Subsequently, annealing was, performed on the
hot-rolled steel sheets at 1100°C for 120 seconds to
obtain annealed steel sheets. Next, acid pick]:i_ng
was performed on the annealed steel sheets, and then
cold rolling was performed on the annealed steel
sheets to obtain cold-rolled steel sheets with a
thickness of 0.23 mm. Subsequently, decarburization
annealing was performed on the cold-rolled steel
sheets in an atmosphere containing water vapor,
hydrogen, and nitrogen at 860°C for 100 seconds to
obtain decarburization annealed steel sheets. Next,
nitridation treatment was performed on the
decarburization annealed steel sheets in an
- 19 -
atmosphere containing hydrogen, nitrogen, and ammonia
at 770°C for 20 seconds to obtain nitrided steel
4
sheets.
[0052] Thereafter, an annealing separating agent
containing MgO as a main component was applied, in a
water slurry, to the surfaces of the decarburized
nitrided steel sheets. Then, finish annealing was
performed on them at 1200°C for 20 hours to obtain
finish-annealed steel sheets. Subsequently, the
finish-annealed steel sheets were washed with water,
and then cutout into a single-plate magnetic
measurement size with a width of 60 mm and a length
of 300 mm. Subsequently, a coating solution
containing aluminum phosphate and colloidal silica as
main components was applied to the surfaces of the
finish-annealed steel sheets, and baking was
performed thereon to form an insula,t•ing film. In
this manner, samples of the grain-oriented electrical
steel sheets were obtained.
[0053] Then, the magnetic flux density B8 of each of
the grain-oriented electrical steel sheets was
measured. The magnetic flux density B8 is the
magnetic flux density occurring in the grain-oriented
electrical steel sheet when a magnetic field of 800
A/m at 50 Hz is applied thereto as described above.
Note that the magnetic flux densities B8 of five
single-plate samples for measurement were measured
for each of the samples. Then, ,for each sample, the
average value "average B8," the maximum value
- 20 -
"B8max," and the minimum value "B8min" were obtained.
The difference "IB8" between the maximum value
"B8max" and the minimum value "B8min" was also
obtained. The difference "AB8" is an index
indicating the fluctuation range of the magnetic
property. These results are listed in Table 1
together with the Ti contents and the Cu contents.
Further, the evaluation results based on the average
value "average B8" and the difference "IB8" are
indicated in Fig. 1. As described above, an open
circle mark in Fig. 1 indicates that the average
value "average B8" was 1.90 T or more and the
difference "AB8" was 0.030 T or less. Further, a
filled circle mark in Fig. 1 indicates that the
average value "average B8" was less than 1.90 T or
the difference "AB8" was more than 0.030 T.
[0054] [Table 1]
TABLE 1
SAMPLE
No.
Ti CONTENT .
(M.ASS% )
Cu CONTENT
( MASS )
20X [TI]+ CCul 10%C [Ti]+[Cu]
AVERAGE B8
(T)
BBmax
(T)
BBmin
(T)
A BB
(T)
NOTE
1 0.0011 0 .006 0.028 0.017 1.914 1 .931 1.890 0.041 COMPARATIVE EXAMPLE
2 0.0024 0.007 0.055 0.031 1.913 1.923 1.902 0.021 EMBODIMENT
3 0.0048 0:006 0.102 0.054 1.911 1.919 1.897 0.022 EMBODIMENT
4 0.0084 0.008 0.176 0 .092 1.902 1.915 1.889 0.026 EMBODIMENT
5 0.0109 0 .005 0 .223 0-114 1.877 1 .887 1 .866 1 0-021 COMPARATIVE EXAMPLE
6 0.0013 0.033 0.059 0.046 1.914 1.924 1.901 0.023 EMBODIMENT
7 0.0015 0.083 0.113 0.098 1 .913 1.922 1.895 0.027 EMBODIMENT
8 0.0014 0.182 0 .210 0.196 1.911 1.919 1.894 0.025 EMBODIMENT
9 0.0011 0.430 0.452 0.441 1.901 1.908 1 .884 0.024 EMBODIMENT
10 0.0013 0.576 0.602 0.589 1.876 1.884 1.861 0.023 COMPARATIVE EXAMPLE
11 0.0033 0 .079 0 .145 0.112 1.911 1.921 1.901 0.020 EMBODIMENT
12 0.0055 0-084 0.194 0.139 1.903 1.910 1.891 0.019 EMBODIMENT
13 0.0068 0.018 0.154 0.086 1.912 1.921 1.899 0.022 EMBODIMENT
14 0.0082 0.380 0.544 0.462 1`.902 1.908 1.893 0.015 EMBODIMENT
15 0.0028 0.022 0 .078 0.050 1.914 1.927 1.907 0.020 EMBODIMENT
[0055] As presented in Table 1 and Fig. 1, in the
samples No. 2 to No. 4, No. 6 to No. 9, and No. 11 to
No. 15,,in each of which the Ti content and the Cu
content were within the range of the present
invention, the average value "average B8" was large
to be 1.90 T or more, and the difference "/\B8" was
small to be 0.030 T or less. In short, high magnetic
property was obtained and the variation in magnetic
property was small.
[0056] In particular, the balance between the
average value "average B8" and the difference "hB8"
was excellent in the samples No. 11, No. 13, and No.
15, in which the relation of "20x[Ti]+[Cu]_0.18" was
established where the Ti content (mass%) was
expressed as [Ti] and the Cu content (mass%) was
expressed as [Cu]. Among them, the balance between
the average value "average B8" and the difference
"AB8" was extremely excellent in the sample No. 15,
in which the relation of "10x[Ti]+[Cu]:0.07" was
established.
[0057] On the other hand, in the sample No. 1, in
which the Ti content was less than 0.0020 mass% and
the Cu content was less than 0.010 mass%, the
difference "LB8" was large to be more than 0.030 T.
In short, the variation in magnetic property was
large. Further, in the sample No. 5, in which the Ti
content was more than 0.010 mass% and the sample No.
10, in which the Cu content was more than 0.50 mass%,
a large amount of precipitate was contained to affect
- 23 -
the finish annealing, with the result that the
average value "average B8" was small to be less than
1.90 T. In short, a sufficiently high magnetic
property could not be obtained.
[0058] (Second Experiment)
First, a steel ingot containing Si: 3.2 mass%, C:
0.051 mass%, Mn: 0.09 mass%, acid-soluble Al: 0.026
mass%, N: 0.004 mass%, S: 0.0053 mass%, P: 0.027
mass%, Ti: 0.0024 mass%, Cu: 0.029 mass%, and the
balance composed of Fe and inevitable impurities was
produced using a vacuum melting furnace. Then,
annealing was performed on the steel ingot at 1150°C
for one hour, and then hot rolling was performed
thereon to obtain a hot-rolled steel sheet with a
thickness of 2.4 mm.
[0059] Subsequently, annealing was performed on the
hot-rolled steel sheet at 1090°C for 120 seconds to
obtain an annealed steel sheet. Then, acid pickling
was performed on the annealed steel sheet, and then
cold rolling was performed on the annealed steel
sheet to obtain a cold-rolled steel sheet with a
thickness of 0.23 mm. Subsequently, eight pieces of
steel sheets for annealing were cutout from the coldrolled
steel sheet, and decarburization annealing was
performed on each of the steel sheets in an
atmosphere containing water vapor, hydrogen, and
nitrogen at a temperature T1 ranging from 790°C to
960°C listed in Table 2 for 80 seconds to obtain
decarburization annealed steel sheets. Next,
- 24 -
nitridation treatment was performed on each of the
decarburization annealed steel sheets in an
atmosphere containing water vapor, hydrogen,
nitrogen, and ammonia at a temperature T2 ranging
from 680°C to 880°C listed in Table 2 for 20 seconds
to obtain nitrided steel sheets.
[0060] Thereafter, an annealing separating agent
containing MgO as a main component was applied, in a
water slurry, to the surfaces of the nitrided steel
sheets. Then, finish annealing was performed on them
at 1200°C for 20 hours to obtain finish annealed steel
sheets. Subsequently, treatments from the water
washing to the formation of the insulating film were
performed similarly to the first experiment to obtain
samples of the grain-oriented electrical steel
sheets.
[0061] Then, for each of the samples, the average
value "average B8," the maximum value "B8max," the
minimum value "BBmin," and the difference "hB8" were
obtained similarly to the first experiment. These
results are listed in Table 2 together with the
temperatures Ti and the temperatures T2.
[0062] [Table 2]
CZ W 0 H 0 N)
Fl- 00 H-i N) F-h N O
h-h = O
F-h rt 0 Ft rt a
CD C ft C 0 W
r1 Di CD CD
CD co rt
C Cz 0
CD CD - ° >
CD Di (D 0 .. Cl)
ri Cl) CD Q) N
CD H- Ft 1-0
> CD CD ct hi
tai ct It G CD
co ct H- ri Di Cl)
0 H- C^ h'- CD CD
CD QJ N CZ CD
< ct Di ct
Di CD Cl) N- ct Z CD
Cn 0 H- 0 CZ
N rt CD 0
H- CD HDo
0 ct m CD
D C) CD Fl
F' ° CD C H
H H Di CD Qi
rt ct (D H- }
rr O 5 Ai CD H
O F-i (D (D EJ (D
CD HCD
0 C ^Q Hri
CD 0
O CD t-i- CD Di CL HDi
ri CD CD
o ^Q CD CL rt
W Di (D C' rt
O C Ft CD C'
CZ C H- C' CD
H rt CD ct
ct N CL (D Cl)
O C' C) H- Ft Di
ri (D CD CD CD
CD t
F-J = cm n N
CD Di C' CD Di CD
Cl) C (D hi rt Cn
Cn CD Di C)
Fi Fi Ft I-i
Q CD CD 0
^Q CD h
CD LQ CD H
CD N
TABLE 2
SAMPLE
No.
21
22
23
25
26
27
28
Tl T2
(°C) (°C )
790 780
820
870
930
960
860
860
860
780
780
780
760
670
750
860
AVERAGE B8
(T)
1.840
1.911
1.924
1.925
1.824
1.896
1.922
1.823
B8 max
(T)
1.859
1.918
LL 931
1.937
1.872
1.907
1.930
B8 min
(T)
1.832
1.895
1.908
1.908
1.770
1.880
1.906
1.872 1 1 .777
A B8
(T)
0.027
0.023
0.023
0.029
0.102
0.027
0.02 4
0.095
NOTE
COMPARATIVE EXAMPLE
EMBODIMENT
EMBODIMENT
EMBODIMENT
COMPARATIVE EXAMPLE
COMPARATIVE EXAMPLE
EMBODIMENT
COMPARATIVE EXAMPLE
short, a high magnetic property was obtained and the
variation in the magnetic property was small.
[0064] On the other hand, in the sample No. 21, in
which the temperature Ti of the decarburization
annealing was less than 800°C, the average value
"average B8" was small to be less than 1.90 T. In
the sample No. 25, in which the temperature Ti of the
decarburization annealing was higher than 950°C, the
difference "AB8" was large to be over 0.030 T, and
the average value "average B8" was small to be less
than 1.90 T. Further, in the sample No. 26, in which
the temperature T2 of the nitridation treatment was
less than 700°C, the average value "average B8" was
small to be less than 1.90 T. In the sample No. 28,
in which the temperature T2 of the nitridation
treatment is higher than 850°C, the difference "z^B8P'
was large to be high than 0.030 T, and the average
value "average B8" was small to be less than 1.90 T.
[0065] (Third Experiment)
First, 20 kinds of steel ingots each containing
Si: 3.2 mass%, Mn: 0.09 mass%, acid-soluble Al: 0.026
mass%, N-. 0.004 mass%, S: 0.0053 mass%, and P: 0.027
mass%, further containing C, Ti and Cu in amounts
listed in Table 3, and the balance composed of Fe and
inevitable impurities were produced using a vacuum
melting furnace. Then, annealing was performed on
the steel ingots at 1150°C for one hour, and then hot
rolling was performed to obtain hot-rolled steel
sheets with a thickness of 2.4 mm.
- 27 -
[0066] Subsequently, annealing was performed on the
hot-rolled steel sheets at 1090°C for 120 seconds to
obtain annealed steel sheets. Then, acid pickling
was performed on the annealed steel sheets, and then,
cold rolling was performed on the annealed steel
sheets to obtain cold-rolled steel sheets with a
thickness of 0.23 mm. Subsequently, steel sheets for
annealing were cutout from the cold-rolled steel
sheets, and decarburization annealing was performed
on the steel sheets in an atmosphere containing water
vapor, hydrogen, and nitrogen at 860°C for 80 seconds
to obtain decarburization annealed steel sheets.
Next, nitridation treatment was performed on the
decarburization annealed steel sheets in an
atmosphere containing water vapor, hydrogen,
nitrogen, and ammonia at 760°C for 20 seconds to
obtain nitrided steel sheets.
[0067] Thereafter, an annealing separating agent
containing MgO as a main component was applied, in a
water slurry, to the surfaces of the nitrided steel
sheets. Then, finish annealing was performed on them
at 1200°C for 20 hours to obtain finish annealed steel
sheets. Subsequently, treatments from the water
washing to the formation of insulating film were
performed similarly to the first experiment to obtain
samples of the grain-oriented electrical steel
sheets.
[0068] Then, for each of the samples, the average
value "average B8," the maximum value "B8max," the
- 28 -
minimum value "B8min," and the difference "/B8" were
obtained similarly to the first experiment. These
results are listed in Table 3 together with the C
contents, the Ti contents and the Cu contents.
[0069] [Table 3]
TABLE 3
SAMPLE C CONTENT
No. (MASS%)
31
32
Ti CONTENT Cu CONTENT
(MASS %) ( MASS%)
20X [T i]+[C u] 1 0 X [T i7+[C u] AVERAGE B8
(T)
A B8
(T)
0.028 0.001 4 0.006 0.034 0.020 1.868 0.051
0.028 0.0024 0.024 0.072 0.048 1.911 0.024
0.028 0.0042 0.051 0.135 0.093 1.906 0.021
0.028 0.0070 0.390 0.530 0.460 1.901 0.018
0.028 0.01 05 0.560 0.770 0.665 1.822 0.016
0.039 0.0015 0.005 0.035 0.020 1.892 0.046
0.039 0.0023 0.02" 0.068 0.045 1.913 0.022
0.039 0.0044 0.053 0.1 41 0.097 1.907 0.019
0.039 0.0075 0.350 0.500 0.425 1.902 0.017
0.039 0.0110 0.590 0.810 0.700 1.843 0.015
0.048 0.001 8 0.007 0.043 0.025 1.904 0.042
0.048 0.0026 0.025 0.077 0.051 1.914 0.021
0.048 0.0043 0.052 0.138 0.095 1.908 0.019
0.048 0.0072 0.370 0.51 4 0.442 1.903 0.017
0.048 0.01 22 0.550 0.794 0.672 1-852 0.01 4
0.057 0.0017 0.008 0.042 0.025 1.912 0.037
0.057 0.0024 0.026 0.074 0.050 1.915 0.020
0.057 0.0046 0.054 0.146 0.1 00 1.908 0.017
0.057 0.0074 0.380 0.528 0.454 1.907 0.015
0.057 0.0109 0.540 0.758 0.649 1.871 0.013 1
NOTE
COMPARATIVE EXAMPLE
EMBODIMENT
EMBODIMENT
EMBODIMENT
COMPARATIVE EXAMPLE
COMPARATIVE EXAMPLE
EMBODIMENT
EMBODIMENT
EMBODIMENT
COMPARATIVE EXAMPLE
COMPARATIVE EXAMPLE
EMBODIMENT
EMBODIMENT
EMBODIMENT
COMPARATIVE EXAMPLE
COMPARATIVE EXAMPLE
EMBODIMENT
EMBODIMENT
EMBODIMENT
COMPARATIVE EXAMPLE
[0070] As presented in Table 3, in the samples No.
32 to No. 34, No. 37 to No. 39, No. 42 to No. 44, and
No. 47 to No. 49, in each of which the C content, the
Ti content and the Cu content were within the range
of the present invention, the average value "average
B8" was large to be 1.90 T or more, and the
difference "LB8" was small to be 0.025 T or less. In
short, a highmagnetic property was obtained and the
variation in magnetic property was small.,
Particularly, when the C content was small, a good
result was obtained.
[0071] Further, the balance between the average
value "average B8" and the difference "AB8" was
excellent in the samples No. 32, No. 33, No. 37, No.
38, No. 42, No. 43, No. 47, and No. 48, in each of
which the Ti content was 0.0020 mass, to 0.080 mass%,
the Cu content was 0.010 mass to 0.10 mass%, and the
relation of "20x[Ti]+[Cu]c0.18" was established.
Among them, the balance between the average value
"average B8" and the difference "hB8" was extremely
excellent in the samples No. 32, No. 37, No. 42, and
No. 47, in each of which the relation of
"10x[Ti]+[Cu]c0.07" was established.
[0072] On the other hand, in the samples No. 31, No.
36, No. 41, and No. 46, in each of which the Ti
content was less than 0.010 mass%, and the Cu content
was less than 0.50 mass%, the difference "AB8" was
large to be higher than 0.030 T. Among them, in the
samples No. 31 and No. 36, in each of which the C
- 31 -
content was low, the average value "average B8" was
further small to be less than 1.90 T. Further, in
the samples No. 35, No. 40, No. 45, and No. 50, in
each of which the Ti content was higher than 0.010
mass%, and the Cu content was higher than 0.50 mass%,
the average value "average B8" was small to be less
than 1.90 T.
[0073] (Fourth Experiment)
First, 10 kinds of steel ingots each containing
Si: 3.2 mass%, C: 0.048 mass%, Mn: 0.08 mass%, acidsoluble
Al: 0.028 mass%, N: 0.004 mass%, S: 0.0061
mass%, P: 0.033 mass%, Ti: 0.0024 mass%, and Cu:
0.029 mass%, further containing Cr and Sn in amounts
listed in Table 4, and the balance composed of Fe and
inevitable impurities were produced using a vacuum
melting furnace. Then, annealing was performed on
the steel ingots at 1100°C for one hour, and then hot
rolling was performed thereon to obtain hot-rolled
steel sheets with a thickness of 2.3 mm.
[0074] Subsequently, annealing was performed on the
hot-rolled steel sheets at 1080°C for 120 seconds to
obtain annealed steel sheets. Then, acid pickling
was performed on the annealed steel sheets, and then
cold rolling was performed on the annealed steel
sheets to obtain cold-rolled steel sheets with a
thickness of 0.23 mm. Subsequently, decarburization
annealing was performed on the cold-rolled steel
sheets in an atmosphere containing water vapor,
hydrogen, and nitrogen at 870°C for 90 seconds to
- 32 -
obtain decarburization annealed steel sheets. Next,
nitridation treatment was performed on the
decarburization annealed steel sheets in an
atmosphere containing hydrogen, nitrogen, and ammonia
at 760°C for 20 seconds to obtain nitrided steel
sheets.
[0075] Thereafter, an annealing separating agent
containing MgO as a main component was applied, in a
water slurry, to the surfaces of the nitrided steel
sheets. Then, finish annealing was performed on them
at 1200°C for 20 hours to obtain finish annealed steel
sheets. Subsequently, treatments from the water
washing to the formation of the insulating film were
performed similarly to the first experiment to obtain
samples of the grain-oriented electrical steel
sheets.
[0076] Then, for each of the samples, the average
value "average B8," the maximum value "B8max," the
minimum value "B8min," and the difference "1B8" were
obtained similarly to the first experiment. These
results are listed in Table 4 together with the Cr
contents and the Sn contents.
[0077] [Table 4]
H C
H > Di Q1 0
UJ CD C
rt a 00 a J
co
(D Q, CD -
Di Di m CD Z" > LC CD o Cl)
Di rr co rt co
o '-0
Ft 0 Qi n
H- F- a Cl (D
0 10 H (D N cn
hi CD
't 0 c-I- t-' ct Di
0 0 Ft
o (D Qo (D
^0 n a o C a
(D rt (D o
Ft C Di
C 0 rr
Di O h a H
cn w (D Q)
O a
cn 0 0 Di H
a5' H ri C (D
cn Ft (D CD
Q) 0 Fi
QJ H- ri Di Sv
I- (D f- a (D H-
( D Di
CD rr Q
Q) U) ^D' Q1 Q1
> D (D H Di
0 ^. (D
rt F- H- 0
^4 a Di Ml = I-h
(D f h Qi
rr Cl) (D C ct
C a f-i (D a
(D Q) 0 (D t CD
E ri Fi Di Ai
H- rt 0
D CD (D
H- rt
0 Co
D
TABLE 4
SAMPLE
No.
51
52
53
54
55
56
57
58
59
60
Cr CONTENT
(MASS%)
0.007
0.068
0.141
0.214
0.003
S n CONTENT
(wt%)
0.008
0.003
0.008
0.006
0.042
0.006 0.087
0.005 0.264
0.070 0.124
0.150 0.035
0.170 0.154
AVERAGE B8 B8 max
(T) (T)
1.904 1218
1.91 5 1.928
1 .915 1 .927
1203 1217
1.917 1.928
1.918 1228
1.902 11.915
1.913
1.914
1.912
1-922
1.924
1.922
B$min
(T)
1.890
1.903
1.904
1.888
1.906
1.907
1.888
1.898
1.901
1.897
A B8
(T)
0.028
0.024
0.024
0.029
0.022
0.021
0.027
0.024
0.023
0.025
NOT E
EMBODIMENT
EMBODIMENT
EMBODIMENT
EMBODIMENT
EMBODIMENT
EMBODIMENT
EMBODIMENT
EMBODIMENT
EMBODIMENT
EMBODIMENT
the samples No. 52, No. 53, No. 55 , No. 56, and No.
58 to No. 60, each of which contains 0.010 mass% to
0.20 mass% of Cr and/or 0.010 mass% to 0.20 mass% of
Sn, the average value "average B8" was particularly
large to be 1.91 T or more, and the difference "OB8"
was particularly small to be 0.025 T or less.
INDUSTRIAL APPLICABILITY
[0079] The present invention is applicable, for
example, in electrical steel sheet manufacturing
industries and electrical steel sheet using
industries.
CLAIMS
[Claim 1] A method of manufacturing a grain-oriented
electrical steel sheet, comprising:
performing hot rolling of a steel containing Si:
2.5 mass: to 4.0 mass:, C: 0.01 mass: to 0.060 mass:,
Mn: 0.05 mass: to 0.20 mass:, acid-soluble Al: 0.020
mass: to 0.040 mass:, N: 0.002 mass: to 0.012 mass%,
S: 0.001 mass-'O to 0.010 mass%, and P: 0.01 mass% to
0.08 mass%, further containing at least one kind
selected from a group consisting of Ti: 0.0020 mass%
to 0.010 mass% and Cu: 0.010 mass: to 0.50 mass%, and
a balance composed of Fe and inevitable impurities,
to obtain a hot-rolled steel sheet;
performing annealing on the hot-rolled steel
sheet to obtain an annealed steel sheet;
performing cold rolling on the annealed steel
sheet to obtain a cold-rolled steel,sheet;
performing decarburization annealing on the coldrolled
steel sheet at a temperature of 800°C to 950°C
to obtain a decarburization annealed steel sheet;
then, performing nitridation treatment on the
decarburization annealed steel sheet at 700°C to 850°C
to obtain a nitrided steel sheet; and
performing finish annealing on the nitrided steel
sheet.
[Claim 2] The method of manufacturing a grainoriented
electrical steel sheet according to claim 1,
wherein the hot rolling on the steel is performed
after heating the steel to a temperature of 1250°C or
- 36 -
lower.
[Claim 3] The method of manufacturing a grainoriented
electrical steel sheet according to claim 1,
wherein the steel further contains at least one kind
selected from a group consisting of Cr: 0.010 mass%
to 0.20 mass%, Sn: 0.010 mass% to 0.20 mass%, Sb:
0.010 mass% to 0.20 mass%, Ni: 0.010 mass% to 0.20
mass%, Se: 0.005 mass% to 0.02 mass%, Bi: 0.005 mass%
to 0.02 mass%, Pb: 0.005 mass% to 0.02 mass%, B:
0.005 mass% to 0.02 mass%, V: 0.005 mass% to 0.02
mass%, Mo: 0.005 mass% to 0.02 mass%, and As: 0.005
mass% to 0.02 mass%.
[Claim 4] The method of, manufacturing a grainoriented
electrical steel sheet according to claim 2,
wherein the steel further contains at least one kind
selected from a group consisting of,Cr: 0.010 mass%
to 0.20 mass%, Sn: 0.010 mass% to 0.20 mass%, Sb:
0.010 mass% to.0.20 mass%, Ni: 0.010 mass% to 0.20
mass%, Se: 0.005 mass% to 0.02 mass%, Bi: 0.005 mass%
to 0.02 mass%, Pb: 0.005 mass% to 0.02 mass%, B:
0.005 mass% to 0.02 mass%, V: 0.005 mass% to 0.02
mass%, Mo: 0.005 mass% to 0.02 mass%, and As: 0.005
mass% to 0.02 masso.
[Claim 5] The method of manufacturing a grainoriented
electrical steel sheet according to claim 1,
wherein
a Ti content in the steel is'0.0020 mass% to
0.0080 mass%,
a Cu content in the steel is 0.01 mass% to 0.10
- 37 -
mass%, and
a relation of "20x[Ti]+[Cu]:_!S0.18" is established
where the Ti content (mass%) in the steel is
expressed as [Ti] and the Cu content (mass%) is
expressed as [Cu].
[Claim 6] The method of manufacturing a grainoriented
electrical steel sheet according to claim 2,
wherein
a Ti content in the steel is 0.0020 mass% to
0.0080 mass%,
a Cu content in the steel is 0.01 mass% to 0.10
mass%, and
a relation of "20x[Ti]+[Cu]:0.18" is established
where the Ti content (mass%) in the steel is
expressed as [Ti] and the Cu content (mass%) is
expressed as [Cu].
[Claim 7] The method of manufacturing a grainoriented
electrical steel sheet according to claim 3,
wherein
a Ti content in the steel is 0.0020 mass% to
0.0080 mass%,
a Cu content in the steel is 0.01 mass% to 0.10
mass%, and
a relation of "20x[Ti]+[Cu]_`^0.18" is established
where the Ti content (mass%) in the steel is
expressed as [Ti] and the Cu content (mass%) is
expressed as [Cu].
[Claim 8] The method of manufacturing a grainoriented
electrical steel sheet according to claim 4,
- 38
wherein
a Ti content in the steel is 0.0020 mass% to
fi
0.0080 mass%,
a Cu content in the steel is 0.01 mass% to 0.10
mass%, and
a relation of "20x [Ti] -^- [Cu] <0 e 18" is established
where the Ti content (mass%) in the steel is
expressed as [Ti] and the Cu content (mass%) ra
expressed as [Cu].
[Claim 9] The method of manufacturing a grainoriented
electrical steel sheet according wherein a
relation of "l0x[Ti]+[Cu] S0,07" is established. to
claim 5,
[Claim 10] The method of manufacturing a grainoriented
electrical steel sheet according to claim 6,
wherein a relation of "10x [Ti]+[Cu].c0.07" is
established.
[Claim 11] The method of manufacturing a grain--
oriented electrical steel sheet according to claim 7,
wherein a relation of "10x [Ti]+[Cu] c0.07" is
established.
-[Claim 12] The method of manufacturing a grainoriented
electrical steel sheet according to claim
wherein a relation of "10x [Ti]+[Cu] .0.07" is
established.