【Technical Field】
The present disclosure relates to a high silicon
steel sheet having excellent producibility and magnetic
properties, and a method for manufacturing the steel sheet.
【Background Art】
Steel sheets including silicon have good magnetic
properties and are thus widely used as electric steel
sheets. For example, silicon steel sheets are used as
materials for the cores of transformers, electric motors,
generators, and other electronic devices, and in this case,
silicon steel sheets are required to have good magnetic
properties. Particularly, silicon steel sheets are
required to be effective in reducing energy loss due to
current environmental and energy problems. Concern about
environmental and energy problems may be related to
magnetic flux density and core loss. That is, as the
density of magnetic flux is increased, the size of cores
can be reduced to make electric devices smaller, and as
core loss is reduced, energy loss is also reduced.
3
Core loss causing energy loss includes eddy current
loss and hysteresis loss. As the frequency of an
alternating current (AC) current increases, the amount of
eddy current loss increases. Eddy current loss occurs in
the form of heating when a magnetic field is applied to a
core, and silicon is added to a core to reduce eddy current
loss in the core. If the content of silicon in steel is
increased to 6.5%, magnetostriction causing noise does not
occur (0%), and the permeability of the steel is maximized.
In addition, in the case that the content of silicon in
steel is 6.5%, the magnetic properties of the steel may be
markedly improved. Therefore, high silicon steel having
good magnetic properties may be used in high-value
electrical devices such as inverters and reactors for new
renewable energy power stations, induction heaters for gas
turbine power generators, and reactors for uninterruptable
power supplies.
High silicon steel sheets including a silicon content
of 6.5% are excellent in terms of magnetic properties.
However, as the silicon content of steel sheets is
increased, the steel sheets are increased in brittleness
and markedly decreased in elongation properties. Thus, it
is known that silicon steel sheets having a silicon content
of 3.5% or greater are practically impossible to
4
manufacture using general cold-rolling methods. That is,
high silicon steel sheets known as having good magnetic
properties are not manufactured by cold-rolling methods due
to inherent limitations of cold-rolling technology. Thus,
research into new technology has long been conducted to
overcome limitations of cold-rolling methods.
Since it is difficult to manufacture high silicon
steel sheets having good magnetic properties through a
general hot-rolling process and a general cold-rolling (or
warm-rolling) process, there have been attempts to
manufacture high silicon steel sheets through other methods.
Methods currently known as techniques for
manufacturing high silicon steel sheets are casting methods
in which high silicon steel sheets having a final thickness
are directly manufactured through a casting process using a
single roll or a pair of rolls. An example of such a
method is disclosed in Patent Document 1. In such methods,
however, it is very difficult to control the shape of a
cast plate. Particularly, if molten steel is directly cast
as a plate having a final product thickness, the surface of
the plate may be very rough and easily cracked, and thus it
is difficult to obtain plates having improved magnetic
properties using such a direct casting method. In addition,
such a direct casting method is not suitable for commercial
5
mass production because of uneven thicknesses of cast
plates. Patent Document 2 discloses a so-called clad
method in which high silicon steel covered with low silicon
steel is rolled. However, the disclosed method has not yet
been commercialized.
In addition, Patent Document 3 discloses a powder
metallurgy technique for making a high silicon steel block
as a substitute for a high silicon steel sheet. Although
pure iron powder cores, high silicon steel powder cores,
and Sendust powder cores are used in combination, such
cores have soft magnetic properties inferior to those of
high silicon steel sheets because of characteristics of
powders they are produced from.
According to current mass-production technology for
manufacturing high silicon steel sheets having a silicon
content of 6.5%, a chemical vapor deposition (CVD) method
is used to diffuse SiCl4 into a steel sheet having a
silicon content of 3% during an (diffusion) annealing
process. Many examples of the technology such as that
disclosed in Patent Document 4 are known. According to the
technology, however, toxic SiCl4 is used, and it takes a
significant amount of time to perform a diffusion annealing
process.
In addition, there have been attempts to manufacture
6
thin high silicon steel sheets in laboratories by a socalled
warm-rolling method in which the temperature of a
rolling process is increased. If slabs are manufactured
through a general continuous casting process, the slabs are
heated to 1100°C or higher for several hours in a reheating
furnace before a hot-rolling process, and at this time the
slabs may crack due to differences in temperature between
the surfaces and centers thereof. In addition, when the
slabs are removed from the reheating furnace and hot-rolled,
the slabs may fracture. For example, FIG. 1 illustrates
6.5%-Si steel melted in a 50-kg vacuum induction melting
furnace, formed into a 200-mm slab by milling, heated to
1100°C for one and a half hours under an argon (Ar)
atmosphere, and immediately hot-rolled. The slab fractured
during hot-rolling. This technique of increasing rolling
temperature may improve rolling characteristics of steel
but causes many other problems during a hot-rolling process.
(Patent Document 1) Japanese Patent Application Laidopen
Publication No. S56-003625
(Patent Document 2) Japanese Patent Application Laidopen
Publication No. H5-171281
(Patent Document 3) Korean Patent No. 0374292
(Patent Document 4) Japanese Patent Application Laidopen
Publication No. S62-227078
7
【Disclosure】
【Technical Problem】
Aspects of the present disclosure may provide a high
silicon steel sheet having excellent producibility and
magnetic properties, and a method for manufacturing the
steel sheet.
【Technical Solution】
According to an aspect of the present disclosure, a
high silicon steel sheet having excellent producibility and
magnetic properties may include, by weight%, C: 0.05% or
less (excluding 0%), N: 0.05% or less (excluding 0%), Si:
4% to 7%, Al: 0.5% to 3%, Si+Al: 4.5% to 8%, and the
balance of Fe and inevitable impurities.
According to another aspect of the present disclosure,
a method for manufacturing a high silicon steel sheet
having excellent producibility and magnetic properties may
include: casting a molten metal as a strip having a
thickness of 5 mm or less, the molten metal including, by
weight%, C: 0.05% or less (excluding 0%), N: 0.05% or less
(excluding 0%), Si: 4% to 7%, Al: 0.5% to 3%, Si+Al: 4.5%
to 8%, and the balance of Fe and inevitable impurities;
hot-rolling the cast strip at a temperature of 800°C or
higher; annealing the hot-rolled strip at a temperature
within a range of 900°C to 1200°C; cooling the annealed
8
strip; warm-rolling the cooled strip at a temperature
within a range of 300°C to 700°C; and finally annealing the
warm-rolled strip at a temperature within a range of 800°C
to 1200°C.
The above-described aspects of the present disclosure
do not include all aspects or features of the present
disclosure. Other aspects or features, advantages, and
effects of the present disclosure will be clearly
understood from the following descriptions of embodiments.
【Advantageous Effects】
According to the present disclosure, a high silicon
steel sheet having good magnetic properties may be provided
by performing strip casting, hot-rolling, hot-rolled strip
annealing, cooling, warm-rolling, and annealing processes
in combination on steel having a silicon content of 5
weight% or higher. In addition, a high silicon steel sheet
having improved rolling properties and
may be provided by controlling the contents of silicon
(Si) and aluminum (Al) relative to each other.
【Description of Drawings】
FIG. 1 is an image of a hot-rolled plate fractured
during a hot-rolling process.
FIGS. 2A and 2B are a Si-Fe phase diagram and a view
showing atomic arrangements in a B2 ordered structure and a
9
DO3 ordered structure.
FIG. 3 is a graph showing the elongation of a high
silicon steel sheet with respect to temperature.
FIG. 4 is an image showing Si-segregation occurring
during a strip casting process.
【Best Mode】
The inventors have conducted research into techniques
for preventing fractures of steel sheets during hot-rolling
processes and improving brittleness of steel sheets for
cold-rolling processes. As a result, the inventors have
found that high silicon steel sheets free from fractures
during hot-rolling processes and improved in terms of
brittleness for cold-rolling processes can be mass-produced
by properly adjusting the composition of steel,
manufacturing a thin steel sheet directly through a strip
casting process, and then warm-rolling the thin steel sheet.
Hereinafter, a high silicon steel sheet will be
described in detail according to an embodiment of the
present disclosure.
An embodiment of the present disclosure provides a
high silicon steel sheet having excellent producibility and
magnetic properties. The high silicon steel sheet includes,
by weight%, C: 0.05% or less (excluding 0%), N: 0.05% or
less (excluding 0%), Si: 4% to 7%, Al: 0.5% to 3%, Si+Al:
10
4.5% to 8%, and the balance of Fe and inevitable impurities.
Carbon (C): 0.05 weight% or less (excluding 0%)
Since carbon (C) finely precipitates in steel and
hinders movement of dislocations during a rolling process,
if the content of carbon (C) in the steel sheet is high,
rolling properties of the steel sheet may be worsen. In
addition, if carbon (C) is not removed from a final product,
the remaining carbon (C) may hinder movement of magnetic
domains in an AC magnetic field and thus may worsen
magnetic properties of the final product. If the content
of carbon (C) in the steel sheet is greater than 0.05%, the
brittleness of the steel sheet may be increased, and thus
rolling properties of the steel sheet may deteriorate.
Nitrogen (N): 0.05 weight% or less (excluding 0%)
Nitrogen (N) is an interstitial element and hinders
the movement of dislocations during a rolling process like
carbon (C). Therefore, if a large amount of nitrogen is
added to the steel sheet, rolling properties of the steel
sheet may deteriorate. In addition, if a large amount of
nitrogen (N) is included in a final product, magnetic
domains may be hindered from moving in an AC magnetic field,
and thus magnetic properties of the final product may
11
deteriorate. Therefore, it may be preferable that the
upper limit of the content of nitrogen (N) be 0.05 weight%.
Silicon (Si): 4 weight% to 7 weight%
Silicon (Si) increases the specific resistance of the
steel sheet and thus reduces core loss. If the content of
silicon (Si) is less than 4 weight%, the magnetic
properties of the steel sheet intended in the embodiment of
the present disclosure may not be obtained. On the other
hand, if the content of silicon (Si) is greater than 7
weight%, it may be difficult to machine the steel sheet.
Therefore, it may be preferable that the content of silicon
(Si) be within the range of 4 weight% to 7 weight%.
Aluminum (Al): 0.5 weight% to 3 weight%
Aluminum (Al) is the most effective element next to
silicon (Si) in terms of increasing the specific resistance
of the steel sheet. If aluminum (Al) is substituted for
silicon (Si), the effect of increasing specific resistance
may be relatively low as compared with the case of using
silicon (Si). However, rolling properties of the steel
sheet may be improved. If the content of aluminum (Al) is
less then 0.5 weight%, the effect of improving rolling
properties may not be obtained, and if the content of
12
aluminum (Al) is greater than 3 weight%, the effect of
improving magnetic properties may not be obtained.
Therefore, it may be preferable that the content of
aluminum (Al) be within the range of 0.5 weight% to 3
weight%.
The contents of silicon (Si) and aluminum (Al) may be
controlled by adjusting the content of Si+Al for hotrolling
and cold-rolling processes according to an
embodiment of the present disclosure. That is, for example,
the specific resistance of the steel sheet may be increased
to lower core loss by controlling the contents of silicon
(Si) and aluminum (Al) relative to each other. If the
content of Si+Al in the steel sheet is less than 4.5
weight%, high-frequency characteristics of the steel sheet
may deteriorate, and if the content of Si+Al is greater
than 8 weight%, it may be difficult to machine the steel
sheet. Therefore, it may be preferable that the content of
Si+Al be within the range of 4.5 weight% to 8 weight%.
In the embodiment of the present disclosure, the
other component of the steel sheet is iron (Fe). However,
impurities from raw materials or manufacturing environments
may be inevitably included in the steel sheet, and thus,
such impurities may not be entirely removed from the steel
sheet. Such impurities are well-known to those of ordinary
13
skill in manufacturing industries, and thus, descriptions
thereof will not be given in the present disclosure.
Hereinafter, a method for manufacturing a high
silicon steel sheet will be described in detail according
to an embodiment of the present disclosure.
According to the embodiment of the present disclosure,
the method for manufacturing a high silicon steel sheet
includes: casting a molten metal as a strip having a
thickness of 5 mm or less, the molten metal including, by
weight%, C: 0.05% or less (excluding 0%), N: 0.05% or less
(excluding 0%), Si: 4% to 7%, Al: 0.5% to 3%, Si+Al: 4.5%
to 8%, and the balance of Fe and inevitable impurities;
hot-rolling the cast strip at a temperature of 800°C or
higher; annealing the hot-rolled strip at a temperature
within a range of 900°C to 1200°C; cooling the annealed
strip; warm-rolling the cooled strip at a temperature
within a range of 300°C to 700°C; and finally annealing the
warm-rolled strip at a temperature within a range of 800°C
to 1200°C.
Strip Casting
It is very difficult to manufacture high silicon
steel sheets using a general hot-rolling method. However,
the inventors have found that a hot-rolled strip (steel
14
sheet) can be simply manufactured by casting a molten metal
having the above-described composition into a strip (strip
casting). Thus, a strip casting method is used in the
embodiment of the present disclosure.
If high silicon steel sheets are manufactured using a
general hot-rolling method, slabs may crack due to a
temperature difference between inner and outer portions
thereof during cooling and heating processes. In addition,
if the surfaces of the slabs having a high silicon content
are heated to 1200°C or higher, fayalite (Fe2SiO4) having a
low melting point may be formed to cause erosion of the
surfaces (including lateral surfaces) of the slabs and to
thus cause cracks, and the slabs may be cracked while being
hot-rolled because of high brittleness.
However, if a molten metal having the above-described
composition is cast into a strip as proposed by the
inventors, a high silicon steel sheet having a thickness of
1 mm to 2 mm may be directly manufactured, and the high
silicon steel sheet may be free from cracks unlike a high
silicon steel sheet manufactured using a general hotrolling
method. In addition, if a strip casting machine is
connected to a hot-rolling mill, hot-rolling may be
continuously performed to further reduce the thickness of
the high silicon steel sheet. In addition, as shown in FIG.
15
4, silicon (Si) may segregate in a center region of the
high silicon steel sheet manufactured by the strip casting
process. The segregation of silicon (Si) may improve
rolling properties of the high silicon steel sheet.
In the embodiment of the present disclosure, an
initial casting thickness of the strip may be determined
depending on the thickness of a final product. For example,
it may be preferable that the initial casting thickness be
set to be 5.0 mm or less. More preferably, the initial
casting thickness may be set to be within the range of 1.0
mm to 5.0 mm. If the initial casting thickness is greater
than 5.0 mm, the load during a later warm-rolling process
may be increased, and thus productivity may deteriorate.
On the other hand, if the initial casting thickness is less
than 1.0 mm, the strip casting machine may be excessively
elongated, and there may be a limit to increasing the
surface quality of the strip by warm-rolling.
Furthermore, the strip casting process may be
performed under at least one of a nitrogen atmosphere and
an argon atmosphere.
Hot Rolling
The cast strip formed as described above may be
processed through a hot-rolling process. The hot-rolling
16
process may reduce the load of a later warm-rolling process
and break down a cast microstructure of the strip to form
fine grains in the strip. It may be preferable that the
process temperature of the hot-rolling process be set to be
800°C or higher. If the process temperature is lower than
800°C, a B2 ordered structure as shown in FIG. 2B may be
easily formed in the strip as shown in FIG. 2A, and thus
the ductility of the strip may be lowered to cause brittle
fractures. In view of ductility improvement and economical
aspects, it may be preferable that the upper limit of the
process temperature of the hot-rolling process be 900°C.
Annealing of Hot-Rolled Strip
The hot-rolled strip is annealed. The annealing of
the hot-rolled strip is performed to remove hot-rolling
stress from the strip. It may be preferable that the
annealing temperature be set to be within the range of
900°C to 1200°C. If the annealing temperature is lower
than 900°C, recrystallization of the strip may not
completed, and thus a desired degree of ductility may not
be obtained. On the other hand, if the annealing
temperature is greater than 1200°C, coarse grains may be
formed by recrystallization, and thus the strength of the
strip may be lowered. Therefore, it may be preferable that
17
the annealing temperature be within the range of 900°C to
1200°C.
The annealing process may be performed on the hotrolled
strip under a non-oxidizing atmosphere. The nonoxidizing
atmosphere may be at least one of a nitrogen
atmosphere, an argon atmosphere, and a hydrogen and
nitrogen mixture atmosphere.
In addition, the annealing process may be continued
until recrystallization is completed. Preferably, the
annealing process may be performed for 10 seconds to 5
minutes.
Cooling
The strip annealed as described above is cooled.
Preferably, the annealed strip may be cooled to a
temperature range of 100°C to room temperature within a
cooling time period of 5 seconds to 1 minute. In detail,
it may be preferable that the rate of cooling range from
13°C/sec to 160°C/sec. If the rate of cooling is lower
than 13°C/sec, cracks may be formed in an edge region of
the strip, and rolling properties of the strip may not be
improved by the cooling process due to the generation of
ordered phase. On the other hand, if the rate of cooling
is higher than 160°C, rolling properties and economical
18
efficiency intended in the embodiment of the present
disclosure may not be obtained together.
Warm-rolling
The cooled strip may be warm-rolled within the
temperature range of 300°C to 700°C. Referring to FIG. 3,
the cooling strip has a critical point at 300°C because the
content of Si+Al in the strip is properly determined. In
detail, the ductility of the strip is very low at
temperatures lower than 300°C. If the process temperature
of the warm-rolling process is greater than 700°C, problems
may occur in a later process such as a pickling process.
Therefore, it may be preferable that the process
temperature of the warm-rolling process be within the range
of 300°C to 700°C.
In addition, after the warm-rolling process, the
strip may have a final thickness of 0.5 mm or less.
Final Annealing
The warm-rolled strip (steel sheet) is annealed. It
may be preferable that the annealing temperature be set to
be within the range of 800°C to 1200°C. If the annealing
temperature is lower than 800°C, grains may be
insufficiently grown, and a desired degree of core loss may
19
not be obtained. On the other hand, if the annealing
temperature is greater than 1200°C, economic efficiency and
productivity may be lowered, and the formation of a surface
oxide layer may be facilitated even in the case that a nonoxidizing
atmosphere is used. Such a surface oxide layer
may hinder the movement of magnetic domains, and thus
magnetic properties of the strip may deteriorate.
Therefore, it may be preferable that the annealing
temperature be within the range of 800°C to 1200°C.
In addition, the annealing process may be continued
until recrystallization is completed. Preferably, the
annealing process may be performed for 10 seconds to 5
minutes.
【Mode for Invention】
High silicon steel alloys each including, by weight%,
a carbon content of 0.005%, a nitrogen content of 0.0033%,
and silicon and aluminum contents as shown in Table 1 were
cast as strips having a thickness of 2.0 mm by using a
vertical double roll strip caster. Thereafter, the cast
strips having a thickness of 2.0 mm were hot-rolled to form
high silicon steel sheets having a thickness of 1.0 mm by
using a hot-rolling mill connected to the strip caster.
The starting temperature of the hot-rolling process was
1050°C. The hot-rolled high silicon steel sheets were
20
heated under an atmosphere including 20% of hydrogen and
80% of nitrogen at a temperature of 1000°C for 5 minutes,
and were then quenched to room temperature at a cooling
rate of 200°C/sec. Thereafter, the high silicon steel
sheets were pickled with a hydrochloric acid solution to
remove surface oxide layers. The thickness of the heattreated
high silicon steel sheets was reduced to 0.1 mm at
a temperature of 400°C. Then, an annealing process was
performed on the high silicon steel sheets at 1000°C for 10
minutes under a dry atmosphere including 20% of hydrogen
and 80% of nitrogen and having a dew point of -10°C or
lower, so as to obtain final magnetic properties.
Thereafter, rolling and magnetic properties of the high
silicon steel sheets were measured.
In Table 1, B50 refers to magnetic flux density
values, and high silicon steel sheets having high magnetic
flux density values are evaluated as having good magnetic
properties. In addition, W10/400 and W10/1000 refer to
core loss values measured at commercial frequency, and high
silicon steel sheets having low core loss values are
evaluated as having poor magnetic properties.
[Table 1]
No. Si(wt%) Al(wt%) Rolling Magnetic properties
21
properties
B50 W10/400
(W/kg)
W10/1000
(W/kg)
*CS 1 7.0 Not
added
Bad 1.53 6.55 24.0
CS 2 6.5 0.3 Normal 1.61 6.04 23.2
**IS 1 6.1 0.7 Good 1.63 5.07 18.2
IS 2 5.6 1.5 Excellent 1.64 5.15 18.5
IS 3 4.8 2.0 Excellent 1.66 5.35 19.1
CS 3 3.8 3.0 Excellent 1.67 6.02 28.2
*CS: Comparative Samples, **IS: Inventive Samples
As shown in Table 1, Inventive Samples 1 to 3 have
excellent rolling properties because the contents of Si and
Al thereof are controlled according to the embodiments of
the present disclosure. In addition, the magnetic flux
density values B50 of Inventive Samples 1 to 3 are higher
than those of Comparative Samples 1 to 3, and the core loss
values W10/400 and W10/1000 of the Inventive Samples 1 to 3
are lower than those of Comparative Samples 1 to 3. That
is, the magnetic properties of the Inventive Samples 1 to 3
22
are good.
Comparative Sample 1 has bad rolling properties
because aluminum (Al) is not added thereto, and magnetic
properties of Comparative Sample 1 are not good.
Comparative Sample 2 has normal rolling properties
because the content of aluminum (Al) is low. In addition,
Comparative Sample 2 has a magnetic flux value B50 lower
than those of Inventive Samples 1 to 3 and core loss values
W10/400 and W10/1000 higher than those of Inventive Samples
1 to 3. That is, the magnetic properties of Comparative
Sample 2 are not good.
Comparative Sample 3 has excellent rolling properties
because of a high aluminum content of 3 weight%. However,
Comparative Sample 3 has core loss values W10/400 and
W10/1000 higher than those of Inventive Samples 1 to 3.
That is, the magnetic properties of Comparative Sample 3
are not good.
Those results show the effect of control of the
contents of silicon (Si) and aluminum (Al).
(Embodiment 2)
A silicon steel alloy including, by weight%, 6.3% of
Si, 0.3% of Al, 0.002% of C, and 0.003% of N was cast into
strips having a thickness of 2.0 mm by using a vertical
23
double roll strip caster. Thereafter, the cast strips
having a thickness of 2.0 mm were hot-rolled to form high
silicon steel sheets having a thickness of 1.0 mm by using
a hot-rolling mill connected to the strip caster. The
start temperature of the hot-rolling process was 1000°C.
An annealing process was performed by heating the hotrolled
high silicon steel sheets under an atmosphere
including 20% of hydrogen and 80% of nitrogen at a
temperature of 1000°C for 5 minutes, and then the high
silicon steel sheets were cooled at different cooling rates.
In detail, the high silicon steel sheets were cooled from
800°C to 100°C at cooling rates of 100°C/sec and 10°C/sec,
respectively. The heat-treated high silicon steel sheets
(samples) were pickled with a hydrochloric acid solution to
remove surface oxide layers, and then warm-rolled at 400°C.
Thereafter, the samples were inspected for cracks. The
thickness of samples cooled at a cooling rate of 100°C/sec
within the cooling range proposed in the embodiments of the
present disclosure could be reduced up to 0.1 mm, and
cracks were not observed. However, samples cooled at a
cooling rate of 10°C/sec outside of the cooling range
proposed in the embodiments of the present disclosure
started to crack at edge regions when the reduction ratio
thereof exceeded 50%. That is, if the rate of cooling is
24
low, although a steel sheet is heat-treated after being
rolled, ordered phases may not be removed from the steel
sheet, and thus the rolling properties of the steel sheet
may not be improved.
25
We Claim:
【Claim 1】
A method for manufacturing a high silicon steel sheet
having excellent producibility and magnetic properties, the
method comprising:
casting a molten metal as a strip having a thickness
of 5 mm or less, the molten metal comprising, by weight%,
C: 0.05% or less (excluding 0%), N: 0.05% or less
(excluding 0%), Si: 4% to 7%, Al: 0.5% to 3%, Si+Al: 4.5%
to 8%, and the balance of Fe and inevitable impurities;
hot-rolling the cast strip at a temperature of 800°C
or higher;
annealing the hot-rolled strip at a temperature
within a range of 900°C to 1200°C;
cooling the annealed strip;
warm-rolling the quenched strip at a temperature
within a range of 300°C to 700°C; and
finally annealing the warm-rolled strip at a
temperature within a range of 800°C to 1200°C.
【Claim 2】
The method of claim 1, wherein the casting of the
molten metal is performed under at least one of a nitrogen
26
atmosphere and an argon atmosphere.
【Claim 3】
The method of claim 1, wherein the annealing of the
hot-rolled strip is performed under a non-oxidizing
atmosphere.
【Claim 4】
The method of claim 3, wherein the non-oxidizing
atmosphere is at least one of a nitrogen atmosphere, an
argon atmosphere, and a hydrogen and nitrogen mixture
atmosphere.
【Claim 5】
The method of claim 1, wherein the cooling of the
annealed strip is performed at a rate of 13°C/sec to
160°C/sec until the strip is cooled to a temperature range
of 95°C to 105°C.
【Claim 6】
The method of claim 1, wherein the warm-rolling of
the strip is performed until the strip has a final
thickness of 0.5 mm or less.
27
【Claim 7】
A high silicon steel sheet having excellent
producibility and magnetic properties, the high silicon
steel sheet comprising, by weight%, C: 0.05% or less
(excluding 0%), N: 0.05% or less (excluding 0%), Si: 4% to
7%, Al: 0.5% to 3%, Si+Al: 4.5% to 8%, and the balance of
Fe and inevitable impurities.