yDESCRIPTIONz
yInvention Titlez
GRAIN-ORIENTED ELECTRICAL STEEL SHEET, AND METHOD FOR
MANUFACTURING SAME
5 yTechnical Fieldz
The present invention relates to an oriented electrical steel sheet and a
method of manufacturing the same. More particularly, the present invention
relates to an oriented electrical steel sheet and a method of manufacturing the
same that remove a surface pinning effect that causes magnetism deterioration
10 of a product by intentionally preventing an oxidation layer that is generated in a
decarburization annealing process and a base coating layer that is generated
through a chemical reaction of a MgO slurry that is used as a fusion-bonding
inhibitor of a coil.
yBackground Artz
15 An oriented electrical steel sheet contains 3.1 % of a Si component and has a
texture in which an orientation of grains is a {110}<001> direction, and because
the product has an excellent magnetic characteristic in a rolling direction, the
product is used as an iron core material of a transformer, a motor, a generator,
and other electrical devices using the characteristic.
20 Recently, while an oriented electrical steel sheet of a high magnetic flux density
is commercially available, a material having small iron loss has been requested.
In an electrical steel sheet, iron loss may be enhanced with four technical
methods including a first method of accurately orienting a {110}<001> grain
2
direction of a magnetic easy axis of an oriented electrical steel sheet in a rolling
direction, a second method of forming a material in a thin thickness, a third
method of minutely forming a magnetic domain through a chemical and physical
method, and a fourth method of enhancing a surface property or imparting
surface tension by a chemical method such as 5 surface processing.
Excellent insulating coating in an oriented electrical steel sheet should
generally have a uniform color that does not have a defect in an external
appearance, but by adding several technologies that impart a function,
technology that enhances an electrical insulating property and that reinforces a
10 close contacting property of a film is generally used.
However, currently, while a request for a low iron loss oriented electrical
steel sheet increases, it is requested that a final insulating film has high tension,
and it has been determined that an actual high tension insulating film largely
contributes to magnetic characteristic enhancement of a final product.
15 In order to improve a characteristic of a tension film, a control technique
of several process factors has been applied, and an oriented electrical steel
sheet presently available as a product obtains an iron loss reduction effect by
adding a tension stress to a steel sheet by using a difference of a thermal
expansion coefficient of an insulating film that is formed on a forsterite (Mg2SiO4,
20 hereinafter, base coating)-based base film and a steel sheet.
As a representative insulating film forming method, in Japanese
Unexamined Patent Application No. H11-71683, a method of improving film
tension using colloidal silica having a glass transition point of a high
temperature is disclosed, or in Japanese Patent No. 3098691 and Japanese
3
Patent No. 2688147, a technology that forms an oxide film with high tension in
an electrical steel sheet using alumina sol of an alumina subject and a boric
acid mixture liquid is suggested.
Further, by actively enhancing a property of an oriented electrical steel
sheet surface, magnetism of a material may be enhanced, 5 and by removing an
oxidation layer that is inevitably generated in a decarburization annealing
process among a process and a base coating layer that is generated through a
chemical reaction of a MgO slurry that is used as a fusion-bonding inhibitor of a
coil, an object thereof can be achieved.
10 Technology that removes the base coating includes a method of forcibly
removing a product in which base coating is already formed like a common
material with sulfuric acid or hydrochloric acid, and this is disclosed in Japanese
Patent No. 1985-076603.
However, in such a case, a complex process such as chemical polishing
15 or electrolytic polishing is required, and particularly, in order to remove a
surface with a constant thickness, there is a difficulty that an acid concentration
in a process should be constantly maintained and a processing cost offsets a
performance improvement effect of a product.
Further, when surface roughness of an obtained product is excessively
20 smooth, insulating coating cannot be performed on the product, and thus a
close contacting property may not be secured and an insulating property is very
poor without using a physical/chemical deposition method.
In order to overcome such a technical limitation, in a process of
generating a base coating, technology (hereinafter, glassless technology) that
4
removes or suppresses the base coating was suggested (U.S. Patent No.
4543134) and was performed in two directions of technology that adds a
chloride to MgO, which is an annealing separating agent, and that uses a
surface etching effect in a high temperature annealing process, and technology
that does not form a base coating in a high temperature 5 annealing process by
applying Al2O3 powder as an annealing separating agent.
First, in glassless technology, technology that does not form a base
coating using Al2O3 powder performs a process of (decarburization annealing) -
(acid pickling) - (Al2O3 application) - (high temperature annealing) - (forming of
10 oxide film by preliminary annealing) - (tension film coating), and is a method
using a property in which Al2O3 does not react with an oxide layer existing at a
material surface.
However, in the technology, Al2O3 that is used as an annealing
separating agent should be very small and uniform in a powder form, but when
15 producing an industrial use powder in a slurry for application having a grain size
of about 2-10 ƒÊm, it is difficult to maintain the powder in a distribution state.
As another glassless technology, a method of removing a base coating
includes a chloride addition method and performs a process of (decarburization
annealing) - (MgO+chloride powder application) - (high temperature annealing)
20 - (acid pickling) - (tension film coating), and has almost the same process as a
common production method.
As in U.S. Patent No. 4875947, a representative chloride addition
method is technology that uses a fusion-bonding inhibitor, i.e., an annealing
separating agent, between coil plates as a main component upon annealing
5
MgO at a high temperature, and that forms an FeCl2 film by enabling a chloride
to react with a material surface while high temperature annealing by adding the
chloride (hereinafter, conventional glassless additive) such as one based on Ca,
Li, K, Na, and Ba to the annealing separating agent and prevents a glass film
layer from being formed by removing the FeCl2 film by evaporation 5 at a surface.
However, according to the technology, an oxide film having excellent
application workability but still having a thin thickness exists, and obtained
surface roughness is higher than that of a specimen that is produced by
chemical polishing and thus only effects advantageous in workability, i.e.,
10 punching of a product due to a base coating member rather than an iron loss
enhancement effect, may be expected.
Therefore, technology that can compensate this was suggested, and as
described in Japanese Patent No. 1993-167164, a smoothed product having
excellent roughness compared to that of an existing annealing separating agent
15 using BiCl3 as the chloride and having no residual material, compared with a
general chloride, was obtained, and has excellent iron loss compared to that of
a common product that forms a base coating.
However, in order to use MgO and BiCl3 that are used in the technology
as an annealing separating agent, when MgO and BiCl3 are produced in a slurry
20 phase together with water, as suggested by a spinel (Al2O3EMgO) by a reaction
with active MgO and an Al component existing in steel, it is difficult to obtain a
product having very low roughness and Fe oxide generation that is caused by
dissociation of BiCl3, which is together used chloride is accelerated and thus
after high temperature annealing, a, Fe-based residual material remains at a
6
material surface.
Due to the problem, it is very difficult to obtain an excellent product in
terms of iron loss compared to that of an oriented electrical steel sheet general
material and in which the base coating is excluded.
5 yDISCLOSUREz
yTechnical Problemz
The present invention has been made in an effort to provide a base
coating free type of electrical steel sheet and a method of manufacturing the
same having advantages of very small iron loss by removing a pinning point,
10 which is a main element that limits magnetic domain movement within a
material by enabling a base coating layer that is limited to a smallest layer to be
voluntarily removed during a high temperature annealing process.
yTechnical Solutionz
An exemplary embodiment of the present invention provides an
15 annealing separating agent including MgO, an oxychloride material, and a
sulfate-based antioxidant.
The oxychloride material may be antimony oxychloride (SbOCl) or
bismuth oxychloride (BiOCl).
The sulfate-based antioxidant may be at least one that is selected from
20 an antimony-based (Sb2(SO4)3), strontium-based (SrSO4), or barium-based
(BaSO4) antioxidant.
The oxychloride material may be included at a ratio of 10-20 wt% to the
MgO at 100-200 wt%, and the sulfate-based antioxidant may be included at a
7
ratio of 1-5 wt% to the MgO at 100-200 wt%.
Another embodiment of the present invention provides a method of
manufacturing an oriented electrical steel sheet including: producing a hot rolled
steel sheet by hot rolling a steel slab; producing a cold rolled steel sheet by cold
rolling the hot rolled steel sheet; performing decarburization 5 annealing and
nitride annealing on the cold rolled steel sheet; and applying an annealing
separating agent including MgO, an oxychloride material, and a sulfate-based
antioxidant, and a glassless additive including water, and performing final high
temperature annealing on the electrical steel sheet of which the decarburization
10 annealing and nitride annealing is complete.
The oxychloride material may be antimony oxychloride (SbOCl) or
bismuth oxychloride (BiOCl).
The sulfate-based antioxidant may be at least one that is selected from
an antimony-based (Sb2(SO4)3), strontium-based (SrSO4), or barium-based
15 (BaSO4) antioxidant.
The oxychloride material may be included at a ratio of 10-20 wt% to the
MgO at 100-200 wt%, and the sulfate-based antioxidant may be included at a
ratio of 1-5 wt% to the MgO at 100-200 wt%.
An amount of SiO2 that is formed at a surface of the electrical steel
20 sheet of which the decarburization annealing and nitride annealing is complete
may be two times to five times greater than that of Fe2SiO4.
The decarburization and nitride annealing process may be performed in
a dew point range of 35-55 Ž.
An activation level of the MgO may be 400-3000 seconds.
8
Upon the final high temperature annealing, a temperature rising speed
may be 18-75 Ž/h in a temperature range of 700-950 Ž, and a temperature
rising speed may be 10-15 Ž/h in a temperature range of 950-1200 Ž.
Upon the decarburization and nitride annealing, a temperature may be
5 800-950 Ž.
The glassless additive may be applied at 5-8 g/m2.
The steel slab may include Sn at 0.03-0.07 wt%, Sb at 0.01-0.05 wt%,
and P at 0.01-0.05 wt%, the remaining portion may include Fe and other
inevitably added impurities, and the steel slab may satisfy P+0.5Sb at 0.0370-
10 0.0630 wt%.
Yet another embodiment of the present invention provides an oriented
electrical steel sheet that produces a hot rolled steel sheet by hot rolling a steel
slab including Sn at 0.03-0.07 wt%, Sb at 0.01-0.05 wt%, and P at 0.01-0.05
wt%, the remaining portion including Fe and other inevitably added impurities,
15 and the steel slab satisfies P+0.5Sb at 0.0370-0.0630 wt%, and that produces a
cold rolled steel sheet by cold rolling the hot rolled steel sheet and that performs
decarburization annealing and nitride annealing on the cold rolled steel sheet,
wherein an amount of SiO2 that is formed at a surface of the steel sheet of
which the decarburization annealing and nitride annealing is complete is two
20 times to five times greater than that of Fe2SiO4.
An oriented electrical steel sheet according to another embodiment of
the present invention is an oriented electrical steel sheet in which final high
temperature annealing is performed by applying an annealing separating agent
9
including MgO, an oxychloride material, and a sulfate-based antioxidant, and an
glassless additive including water, to the electrical steel sheet of which the
decarburization annealing and nitride annealing is complete.
The oxychloride material may be antimony oxychloride (SbOCl) or
bismuth oxychloride 5 (BiOCl).
The sulfate-based antioxidant may be at least one that is selected from
an antimony-based (Sb2(SO4)3), strontium-based (SrSO4), or barium-based
(BaSO4) antioxidant.
The oxychloride material may be included at a ratio of 10-20 wt% to the
10 MgO at 100-200 wt%, and the sulfate-based antioxidant may be included at a
ratio of 1-5 wt% to the MgO at 100-200 wt%.
An amount of SiO2 that is formed at a surface of the electrical steel
sheet of which the decarburization annealing and nitride annealing is complete
may be two times to five times greater than that of Fe2SiO4.
15 The decarburization and nitride annealing process may be performed in
a dew point range of 35-55 Ž.
An activation level of the MgO may be 400-3000 seconds.
Upon the final high temperature annealing, a temperature rising speed
may be 18-75 Ž/h in a temperature range of 700-950 Ž, and a temperature
20 rising speed may be 10-15 Ž/h in a temperature range of 950-1200 Ž.
Upon the decarburization and nitride annealing, a temperature may be
800-950 Ž.
The glassless additive may be applied at 5-8 g/m2.
10
yAdvantageous Effectsz
According to an exemplary embodiment of the present invention, an
oxidation layer that is inevitably generated in a decarburization annealing
process among a process of producing an oriented electrical steel sheet and a
base coating layer that is generated through a chemical 5 reaction of a MgO
slurry that is used as a fusion-bonding inhibitor of a coil can be minimized.
Further, because a pinning point, which is a main element that limits
magnetic domain movement by removing a base coating, may be excluded, iron
loss of an oriented electrical steel sheet can be improved.
10 Further, by appropriately adjusting an activation level of MgO, which is a
major component of an annealing separating agent and by introducing an
oxychloride-based material, which is an insoluble compound and a sulfatebased
antioxidant to an Fe-based oxide that is generated upon slurry
application and drying by introducing MgO in which an activation level is limited,
15 an oriented electrical steel sheet having excellent surface gloss and very
excellent roughness can be produced.
yMode for Inventionz
These and other objects of the present application and a method of
achieving them will become more readily apparent from the detailed description
20 given hereinafter. However, it should be understood that the detailed
description and specific examples while indicating preferred embodiments of the
invention are given by way of illustration only since various changes and
modifications within the spirit and scope of the invention will become apparent
to those skilled in the art from this detailed description.
11
In an exemplary embodiment according to the present invention, as a
means for achieving the object, entire control of a process of producing an
oriented electrical steel sheet is required. In this case, a use material
essentially includes Sn: 0.03-0.07 wt%, Sb: 0.01-0.05 wt%, and P: 0.01-0.05
wt%, and by hot rolling a steel slab essentially including Sn: 5 0.03-0.07 wt%, Sb:
0.01-0.05wt %, and P: 0.01-0.05 wt%, a hot rolled plate of a 2.0-2.8 mm
thickness is produced, and after annealing and acid pickling of the hot rolled
plate, a cold rolled plate having a final thickness of 0.23 mm is produced via
cold rolling.
10 In a process of performing a decarburization and nitriding treatment after
cold rolling, by controlling the temperature, atmosphere, and dew point of a
furnace, an amount of an oxidation layer that is generated at a material surface
is adjusted so that SiO2 becomes 2-5 times the Fe2SiO4. In this case, the dew
point is adjusted to 35-55 Ž.
15 By mixing an annealing separating agent that is formed with MgO: 100-
200 g, an oxychloride material: 10-20 g of an inorganic compound form having
an insoluble property in an aqueous solution, and a sulfate-based antioxidant:
1-5 g with water: 800-1500 g in a material that is produced with the above
method, by producing the mixture in a slurry, by drying, applying, and winding
20 the slurry at 300-700 Ž, by maintaining a temperature rising rate of 15 Ž/h or
more at a segment of 700-1200 Ž in a 10 % nitrogen-containing hydrogen
atmosphere, by performing final high temperature annealing that soaks for 20
hours or more at a temperature of 1200}10 Ž, and by finally applying an
12
insulating coating agent, an oriented electrical steel sheet is produced.
In an exemplary embodiment according to the present invention, an
activation level of activated MgO that is used in the annealing separating agent
is limited to 400-3000 seconds, and an oxychloride material of an inorganic
compound form that is insoluble in an aqueous solution may 5 be applied to an
antimony-based or bismuth-based material.
Further, in an exemplary embodiment according to the present invention,
as a sulfate-based material that is used as an anti-oxidizing agent, at least one
of an antimony-based, strontium-based, and barium-based material may be
10 used.
In an exemplary embodiment according to the present invention, when
producing an oriented electrical steel sheet not having a base coating, a base
coating free type of oriented electrical steel sheet in which a surface has very
good roughness and gloss and in which iron loss is thus remarkably enhanced
15 can be produced, compared with when producing a conventional glassless
oriented electrical steel sheet, through a complex process not having economic
efficiency such as acid pickling or chemical polishing or a process of
evaporating at a surface after enabling an FeCl2 film to form, as the chloride
reacts with a material surface while high temperature annealing by adding a
20 chloride to an annealing separating agent.
Hereinafter, a reason for limiting a component of an oriented electrical
steel sheet according to an exemplary embodiment of the present invention will
be described. This is because it is very appropriate in producing a base
coating free type of electrical steel sheet that is suggested in an exemplary
13
embodiment according to the present invention. Each element metallurgically
contributes to improve magnetism of an oriented electrical steel sheet by the
following operation.
In an exemplary embodiment according to the present invention, unless
particularly described, a component content is measured in 5 weight percent.
Sn: 0.03-0.07 wt%
When adding Sn, in order to reduce a size of a secondary grain, by
increasing the number of secondary nuclei of a {110}<001> orientation, iron loss
can be improved. Further, Sn performs an important function in suppressing
10 grain growth through segregation in a grain boundary, and prevents AlN
particles from coarsening and compensates weakening of an effect of
suppressing grain growth by increasing a Si content. Therefore, even with a
relatively high Si content, successful forming of the {110}<001> secondary
recrystallization texture can be resultantly guaranteed. That is, a Si content
15 can be increased and a final thickness can be reduced without weakening
completeness of a {110}<001> secondary recrystallization structure. As
described above, it is preferable that such a content of Sn is 0.03-0.07 wt%
within a range in which a content of other components is appropriately adjusted.
That is, as described above, when a content range of Sn is adjusted to 0.03-
20 0.07 wt%, a discontinuous and remarkable iron loss reduction effect that could
not be conventionally predicted may be determined, and thus a Sn content in an
exemplary embodiment according to the present invention is limited to the
range.
Further, when a Sn content excessively exists, there may be a problem
14
that brittleness increases, and thus when adjusting Sn to the above-described
range, it is effective in improving brittleness.
Sb: 0.01-0.05 wt%
Sb performs operation of suppressing excessive growth of a primary regrain
by segregating at a grain boundary. By removing 5 non-uniformity of a
primary recrystallized grain size according to a thickness direction of a sheet
and simultaneously stably forming secondary recrystallization by suppressing
grain growth at a primary recrystallization step by adding Sb, an oriented
electrical steel sheet having excellent magnetism may be formed. Particularly,
10 such an effect of Sb can be largely improved to a level that could not be
predicted in a conventional document when containing Sb at 0.01-0.05 wt%.
Sb suppresses excessive growth of a primary recrystallized grain by
segregating at a grain boundary, but when Sb at 0.01 wt% or less is contained,
it is difficult to appropriately exhibit suppression thereof, and when Sb at 0.05
15 wt% or more is contained, a primary recrystallized grain size excessively
decreases and thus a secondary recrystallization start temperature is lowered,
whereby a magnetic characteristic is deteriorated or a suppressing force of
grain growth excessively increases and thus secondary recrystallization may
not occur Therefore, in an exemplary embodiment according to the present
20 invention, a content of Sb is limited to the range.
P: 0.01-0.05 wt%
P promotes growth of a primary recrystallized grain in an oriented
electrical steel sheet of a low temperature heating method and thus enhances
integration of {110}<001> orientation in a final product by raising a secondary
15
recrystallization temperature. When a primary recrystallized grain is
excessively large, secondary recrystallization becomes unstable, but as long as
secondary recrystallization occurs, it is advantageous in magnetism that a
primary recrystallized grain is large to raise the secondary recrystallization
temperature. P lowers iron loss of a final product by increasing 5 the number of
grains having the {110}<001> orientation in a primarily recrystallized steel sheet
and improves {110}<001> integration of a final product by strongly developing a
{111}<112> texture in a primary recrystallization plate and thus a magnetic flux
density increases. Further, P reinforces a suppressing force by delaying
10 decomposition of deposition by segregating at a grain boundary to a high
temperature of about 1000 Ž upon secondary recrystallization annealing.
When such a content of P is limited to 0.01-0.05 wt%, a remarkable effect that
could not be predicted in a conventional art can be obtained. In order to
appropriately exhibit an effect of P, it is necessary to limit a content of P to 0.01
15 wt% or more, and when a content of P is 0.05 wt% or more, a size of a primary
recrystallized grain is reduced and thus secondary recrystallization becomes
unstable and brittleness is increased and thus cold rolling is impeded.
Therefore, in an exemplary embodiment according to the present invention, a
content of P is limited to the range.
20 P+0.5Sb: 0.0370-0.0630 %
Further, in an exemplary embodiment according to the present invention,
in addition to a case of adding the several elements, by adjusting a content of
the P+0.5Sb to the above-described range, iron loss was further improved.
This is because, by adding the elements together, a synergistic effect can be
16
obtained, and when a synergistic effect satisfies the equation range, the
synergistic effect is discontinuously maximized, compared with other numeral
ranges. Therefore, in an exemplary embodiment according to the present
invention, in addition to each component content, the P+0.5Sb is limited to the
5 range.
In addition to the above metallurgical merit, Sn and Sb that are used as
major elements are added to steel, and in an Fe-Si alloy like an oriented
electrical steel sheet, high temperature oxidation resistance is improved.
This is a very important precondition for producing a base coating free
10 product that is suggested in an exemplary embodiment according to the present
invention, and for base coating free production, only an appropriate amount of a
base coating layer should be generated through a selective reaction between a
SiO2 oxidation layer inevitably occurring during a decarburization annealing
process and a MgO slurry that is used as an annealing separating agent, and it
15 is very important to suppress an Fe-based oxidation layer that may produce
other by-products.
Therefore, in an exemplary embodiment according to the present
invention, in order to control quality of an oxidation layer that performs a most
important function in a base coating free process as well as a meaning as a
20 metallurgical element for improving magnetism of an oriented electrical steel
sheet, a slab including Sn and Sb in steel is used as a start material.
Hereinafter, a method of producing an oriented electrical steel sheet
according to an exemplary embodiment of the present invention will be
described.
17
A hot rolled plate of 2.0-2.8 mm is produced by hot rolling the abovedescribed
steel slab, and after annealing and acid pickling of the hot rolled plate,
cold rolling of the hot rolled plate is performed to a thickness of 0.23 mm, which
is a final thickness. Thereafter, the cold rolled steel sheet undergoes
decarburization annealing and recrystallization annealing, 5 and this will be
described in detail.
In order to generate an inhibitor that appropriately controls secondary
recrystallization growth upon high temperature annealing while removing carbon
that is included in steel, the cold rolled steel sheet undergoes decarburization
10 and nitride annealing in a mixed gas atmosphere of
ammonia+hydrogen+nitrogen. By setting a temperature within a furnace to
about 800-950 Ž under a humid atmosphere and at a temperature lower than
800 Ž, a sufficient decarburization annealing effect does not occur. As grains
are maintained in a micro-state, upon secondary recrystallization, crystals of an
15 undesirable orientation may grow, and when a temperature within a furnace is
higher than 950 Ž, primary recrystallized grains may excessively grow. Upon
decarburization and nitride annealing in an exemplary embodiment according to
the present invention, a temperature within a furnace is limited to 800-950 Ž.
Further, it is advantageous for management of an oxidation layer to set
20 about 50-70 Ž to have a lower temperature by about 2-4 Ž than that of a
component system that does not contain Sn, Sb, and P, and it is more
advantageous for grain orientation control or iron loss improvement of a final
product.
18
As described above, from a metallurgical viewpoint, in a decarburization
and nitride annealing process, an oxidation layer may be inevitably generated at
a surface in a conventional oriented electrical steel sheet production process,
and by applying a generated oxidation layer and a MgO slurry (aqueous
solution in which MgO is dispersed in water), in a high temperature 5 annealing
process, a base coating (Mg2SiO4) layer is formed. A forsterite layer, i.e., a
base coating that is generated in this way, generally prevents fusion-bonding
between a plates of an oriented electrical steel sheet coil and gives tension to
the plate, and thus it is known that iron loss is reduced and an insulating
10 property is imparted to a material.
However, currently, while demand for a low iron loss and high magnetic
flux density material increases, a thin thickness trend of a product is accelerated
and thus a magnetic property that is damaged at the material surface side
gradually becomes an important factor. From this viewpoint, a base coating
15 that is generated through a reaction with an oxidation layer that is generated in
a decarburization and nitride process and a MgO slurry that is used as an
annealing separating agent operate to generate a pinning point that disturbs
flow of magnetic domains moving through a material surface, and research for
removing this has been performed.
20 When a cold rolled plate passes through a heating furnace that is
controlled in a humid atmosphere for decarburization nitriding, Si having highest
oxygen affinity in steel reacts with oxygen that is supplied from a water vapor
within the furnace and thus SiO2 is first formed at a surface, and as oxygen
penetrates to the steel, an Fe-based oxide is generated. SiO2 that is
19
generated in this way forms the base coating through the following chemical
reaction equation.
2Mg (OH)2 + SiO2 --> Mg2SiO4 + 2H2O ----------------- (1)
As in the reaction equation 1, when SiO2 reacts with the MgO slurry in a
solid state, in order to perform a complete chemical reaction, 5 a material with a
catalyst function of connecting between two solids is required, and fayalite
(Fe2SiO4) performs the catalyst function. Therefore, conventionally,
appropriate fayalite forming as well as a SiO2 forming amount was important.
However, in an exemplary embodiment according to the present
10 invention, after minimally forming a base coating layer that disturbs magnetic
domain movement of a material in a front end portion of a high temperature
annealing process, the base coating layer is removed in a rear end portion, and
thus it is unnecessary to form a large amount of SiO2 and fayalite on a material
surface to enable the SiO2 and fayalite to react with MgO like a conventional
15 production method. In such a case, in a decarburization and nitriding
annealing process, it is advantageous to form a thin SiO2 layer at a material
surface through the control of a dew point, a soaking temperature, and an
atmosphere gas, and to generate a very small amount of fayalite. This is
because, in a conventional case, in order to perfectly induce a reaction between
20 SiO2 and MgO, fayalite, which is a relatively large amount of a catalyst material,
is required, and in order to generate fayalite, Fe-based oxides such as FeO and
Fe2SiO3 are essentially generated together. The generated FeO and Fe2SiO3
do not basically react with a glassless-based addition material and are attached
to a material surface to form an FeO system of an oxide mound (hereinafter, Fe
20
mound), and in such a case, a product having an enhanced surface in which
base coating is excluded and excellent gloss cannot be obtained.
Therefore, in an exemplary embodiment according to the present
invention, upon decarburization and nitride annealing, by imparting a change to
a dew point temperature within a furnace, a change of 5 an oxidation layer
composition was induced, and an amount of fayalite and SiO2 that is induced in
this way was quantified through FT-IR.
As a result, in an amount of an oxidation layer that is formed at a
surface, when SiO2 is adjusted to two times to five times that of fayalite,
10 roughness and glossiness of a surface were excellent, and when SiO2 is
adjusted to two times or less that of fayalite, an Fe mound defect occurs and
thus surface roughness is deteriorated, while when SiO2 is adjusted to five
times or more that of fayalite, forsterite forming is very weak and thus fostelite
forming is very poor, whereby at a material surface, much residual material
15 exists.
Therefore, in an exemplary embodiment according to the present
invention, SiO2 is formed at two times to five times that of fayalite.
As described above, on a specimen in which an oxidation layer of a
material is adjusted, a conventional glassless additive like BiCl3 was mixed with
20 MgO and water, applied, and finally annealed in a coil shape. Upon final
annealing, a primary soaking temperature was 700 Ž, a secondary soaking
temperature was 1200 Ž, and a temperature rising condition of a temperature
rising segment was 18-75 Ž/h at a temperature segment of 700-950 Ž and
21
was 10-15 Ž/h at a temperature segment of 950-1200 Ž. A soaking time at
1200 Ž was processed as 15 hours. An atmosphere upon final annealing
was a mixed atmosphere of 25 % nitrogen+75 % hydrogen up to 1200 Ž, and
after arriving at 1200 Ž, a 100 % hydrogen atmosphere was maintained and
the 5 furnace was cooled.
In a specimen that is processed in this way, roughness and glossiness
enhancement was excellent compared to that of a conventional glassless
process, but an enhanced surface property of an acid pickling and chemical
polishing level may not be obtained and a limitation exists in magnetism
10 enhancement.
Therefore, in an exemplary embodiment according to the present
invention, when components that are used for an annealing separating agent
are applied and dried at a surface of a material, a material remaining at a
surface after high temperature annealing and reaction mechanism on each
15 component basis was researched.
First, after high temperature annealing, when analyzing a residual
material of a specimen in which a base coating is not completely removed, the
residual material was determined as a spinel-based (MgO.Al2O3) compound
and an Fe-based oxide. Further, when such a residual material remains, a
20 magnetic characteristic that a low iron loss oriented electrical steel sheet
requires may not be satisfied. Therefore, in an exemplary embodiment
according to the present invention, in order to ultimately overcome a limitation of
a conventional glassless type and to remarkably enhance iron loss of an
22
oriented electrical steel sheet, research has been performed with an emphasis
on the above characteristic deterioration material forming mechanism.
When an activation level of MgO which a main component of an
annealing coating agent is high, a spinel-based oxide, which is a primary
characteristic deterioration cause of characteristic deterioration 5 causes that are
suggested in the foregoing description, reacts with SiO2 existing at a surface
like reaction equation 1 to form a base coating layer and reacts with a surface
oxidation layer and Al, which is a component among steel existing at a material
interface, and thus it is determined that the above spinel-based composite oxide
10 has occurred. In order to prove this, in an exemplary embodiment according to
the present invention, by artificially adjusting an activation level of MgO, MgO
having various activation levels was produced. An activation level of the MgO
is defined as an ability in which MgO powder may cause a chemical reaction
with other components, and is measured as a time that is taken for MgO to
15 completely neutralize a predetermined amount of citric acid solution.
In MgO that is generally used as an annealing separating agent for a
common oriented electrical steel sheet, high activation is used, with an
activation level of about 50-300 seconds, and in an exemplary embodiment
according to the present invention, in addition to MgO having a common
20 activation level, by applying an activation level of MgO to adjusted MgO through
a high temperature firing process, a spinel-based compound was suppressed
from remaining as a residual material.
Particularly, in an exemplary embodiment according to the present
invention, an activation level of MgO is limited to 400-3000 seconds, and when
23
an activation level is smaller than 400 seconds, after high temperature
annealing, spinel-based oxide remains at a surface like common MgO, while
when an activation level is larger than 3000 seconds, an activation level is
excessively weak and thus MgO does not react with an oxidation layer existing
at a surface and a base coating layer may thus not be formed. 5 Therefore, in
an exemplary embodiment according to the present invention, an activation
level of MgO is limited to 400-3000 seconds.
A second cause of magnetic characteristic deterioration is Fe-based
oxide. As described above, generation of the Fe-based oxide is limited
10 through introduction of Sn and Sb in steel as well as the control of a dew point
and an atmosphere within a furnace in a decarburization and nitriding process.
However, in spite of such a limitation, a generation cause of the Fe-based oxide
is related to a chemical reaction between chloride that is used as a glassless
additive and an aqueous solution that is used for distributing an annealing
15 separating agent. When BiCl3 that is well known as a chloride of a
conventional glassless system is generally applied on a specimen as an
aqueous solution together with MgO and a high temperature annealing process
is performed, the following chemical reaction occurs at a surface.
BiCl3 + H2O --> BiOCl (s) + 2HCl -------------------- (2)
20 As in the chemical reaction equation 2, 2HCl that is generated on an
aqueous solution causes the following chemical reaction together with Fe or
FeO existing at a material surface.
(Fe, FeO) + HCl --> FeCl2(s) + H2O --------------------- (3)
Therefore, in order to apply an annealing separating agent in which a
24
common glassless additive is introduced and to form the annealing separating
agent in a coil shape, when drying the annealing separating agent at 700 Ž or
less, an Fe-based oxidation layer is already generated, and a material that is
generated in this way forms a deep root at a material surface during a high
temperature 5 annealing process.
In order to suppress such a phenomenon, by using BiCl3 having strong
oxidation or an antimony oxychloride (SbOCl) additive that is not dissociated
within an aqueous solution other than chloride of a line similar to BiCl3 and that
originally suppresses Fe-based oxide and antimony sulfate (Sb2(SO4)3)) not
10 having a Cl group, an exemplary embodiment according to the present
invention is to solve such problem.
That is, in order to produce an oriented electrical steel sheet having
excellent gloss, roughness, and iron loss, MgO: 100-200 g in which activation is
adjusted by an annealing separating agent, antimony oxychloride (SbOCl): 10-
15 20 g having an insoluble property in an aqueous solution, antimony sulfate
(Sb2(SO4)3)): 1-5 g, and water 800-1500 g are mixed, are formed in a slurry
form, are applied in a thickness of 5-8 g/m2 at a surface of a material in which
decarburization and nitriding is terminated, and are dried at 300-700 Ž. After
a specimen that is produced in this way is produced in a coil shape, the
20 specimen undergoes high temperature annealing, and a temperature rising
speed of a fast temperature rising speed segment of an initial process of high
temperature annealing is determined to be 18-75 Ž/h, while a slow
temperature rising speed is determined to be 10-15 Ž/h in consideration of
25
secondary recrystallization. In this case, thermal decomposition of a glasslessbased
additive within an annealing separating agent at a first half of a high
temperature annealing process is performed at about 280 Ž as follows.
2SbOCl --> Sb2 (s) + O2 (g) + Cl2 (g) ------------------- (4)
As in the chemical reaction equation 4, unlike BiCl3 5 or SbCl3 in which a
Cl group may be dissociated in an aqueous solution, in a chloride of an
oxychloride form, a Cl group is generated only through thermal decomposition,
and after antimony oxychloride is produced in a slurry state on an aqueous
solution, in an application and drying process, an Fe-based oxide that may
10 ultimately impede roughness, glossiness, and iron loss reduction is not
generated.
A Cl gas that is separated in this way forms FeCl2 at an interface of a
material and an oxidation layer while being again diffused toward a material
surface rather than being discharged to the outside of a coil by a pressure
15 within a furnace operating in the coil.
Fe (material) + Cl2 --> FeCl2 (interface of material and oxidation layer) ---
-------- (5)
Thereafter, at about 900 Ž, by a MgO and SiO2 reaction, at an
outermost surface of a material, base coating is performed as in Equation 5.
20 Thereafter, at about 1025-1100 Ž, FeCl2 that has been formed at an interface
of a material and an oxidation layer starts to be decomposed, and while Cl2 gas
that is decomposed in this way is discharged to an outermost surface of the
material, the Cl2 gas separates the base coating that has been formed in an
26
upper portion from the material.
In an exemplary embodiment according to the present invention, after a
slurry is produced, when the slurry is dried, an amount of chloride of an
oxychloride form that does not impede iron loss reduction and that does not
generate the Fe-based oxide is limited and is used at 10-5 20 g to an injected
MgO amount of 100-200 g. When an amount of the chloride is injected to be
smaller than 10 g, Cl to form enough FeCl2 may not be supplied, and thus there
is a limitation in improving roughness and glossiness after high temperature
annealing, and when an amount of the chloride is injected to be larger than 20 g,
10 an excessively greater amount than that of MgO, which is a major component of
an annealing separating agent, disturbs the base coating from being formed
and may thus metallurgically have an influence on secondary recrystallization
as well as a surface, and thus in an exemplary embodiment according to the
present invention, for MgO of 100-200 g, the chloride is limited to 10-20 g.
15 Antimony sulfate (Sb2(SO4)3) together with antimony oxychloride
(SbOCl) is injected to thinly form a forsterite layer that is generated by a MgO
and SiO2 reaction, and is limited to 1-5 g for 100-200 g of MgO. When
antimony sulfate (Sb2(SO4)3)) together with antimony oxychloride (SbOCl) of an
amount smaller than 1 g is added, an effect as an additional auxiliary agent is
20 slight, and antimony sulfate (Sb2(SO4)3)) together with antimony oxychloride
(SbOCl) does not contribute to improvement of roughness and gloss, and when
with antimony sulfate (Sb2(SO4)3)) together with antimony oxychloride (SbOCl)
of an amount of more than 5 g is added, base coating forming may be disturbed
due to a much greater amount than that of MgO, which is a major component of
27
an annealing separating agent like antimony oxychloride (SbOCl), and thus in
an exemplary embodiment according to the present invention, an addition
amount of SbOCl and Sb2 (SO4)3 is limited to the range.
Hereinafter, an exemplary embodiment according to the present
invention will be described 5 in detail.
[Exemplary Embodiment 1]
In a component system that is suggested in the present invention and a
common oriented electrical steel sheet component system, after Si: 3.26 %, C:
0.055 %, Mn: 0.12 %, Sol. Al: 0.026 %, N: 0.0042 %, and S: 0.0045 %, and Sn,
10 Sb, and P contents were applied to a MgO annealing separating agent including
common chlorides, roughness and glossiness were measured, and it was
determined whether the base coating was formed. Here, the glossiness is
Gloss glossiness, and in a reflection angle of 60‹, an amount of light that is
reflected from a surface is measured, where mirror surface glossiness of 1000
15 is base glossiness.
(Table 1)
Specimen
number
Sn
content
(wt%)
P
content
(wt%)
Sb
content
(wt%)
Glassless
additive
Roughness
(Ra: ƒÊm)
Glossiness
(index)
1 0 0 0
MgCl2 0.65 54
CaCl2 0.58 67
2 0 0 0.015
MgCl2 0.55 72
CaCl2 0.67 48
28
3 0 0.02 0
MgCl2 0.74 66
CaCl2 0.62 59
4 0 0.035 0.015
MgCl2 0.59 62
CaCl2 0.60 57
5 0.01 0.035 0.025
MgCl2 0.57 82
CaCl2 0.61 48
6 0.03 0.035 0.025
MgCl2 0.48 103
CaCl2 0.45 107
7 0.04 0.035 0.025
MgCl2 0.49 95
CaCl2 0.50 89
8 0.05 0.02 0.035
MgCl2 0.46 106
CaCl2 0.47 109
9 0.05 0.035 0.045
MgCl2 0.54 97
CaCl2 0.51 98
10 0.06 0.35 0.025
MgCl2 0.43 115
CaCl2 0.42 121
As shown in Table 1, after mixing a material that is known as a
conventional glassless chloride annealing separating agent with MgO in Sn and
Sb addition materials that are suggested in the present invention, by applying a
slurry thereof, much better glossiness and roughness than 5 a common oriented
electrical steel sheet was obtained regardless of a kind of a chloride annealing
separating agent. It may be indirectly seen that Sn and Sb in steel are related
to improvement of high temperature oxidation resistance, and particularly have
29
an effect that disturbs Fe oxide existing as a residual material from being
formed upon performing a removal reaction of a forsterite layer of a chloride, i.e.,
a base coating in a high temperature annealing process by suppressing
external oxidation. In an exemplary embodiment according to the present
invention, Sn and Sb addition materials that are advantageous 5 in suppressing
external oxidation and removing a base coating were used as a testing material.
In Table 2, after cold rolling is performed to a thickness of 0.23 mm
using an Sn and Sb addition steel slab (specimen number 10 component
system) that is suggested in Table 1, when performing decarburization and
10 nitride annealing, a change of an oxidation layer composition according to a
dew point temperature within a furnace was induced, and base coating removal
ability was compared through a difference of roughness and glossiness
according to the induced change. In this case, a soaking temperature of a
furnace is 875 Ž, and by simultaneously injecting a mixed atmosphere of
15 hydrogen at 75 %, nitrogen at 25 %, and dry ammonia gas at 1 %, and
maintaining the state for 180 seconds, a simultaneous decarburization and
nitride processing was performed.
In a decarburization and nitride annealing process, a composition of an
oxidation layer and a total oxygen amount that is formed at a material surface is
20 largely affected by a change of a dew point temperature within a furnace. As
shown in Table 2, in an amount of an oxidation layer that is formed at a surface,
when SiO2 is adjusted to two times to five times that of Fe2SiO4, roughness and
glossiness of the surface is excellent, and when SiO2 is adjusted to two times or
less that of Fe2SiO4, a Fe mound defect occurs and thus surface roughness is
30
deteriorated, while when SiO2 is adjusted to five times or more that of Fe2SiO4,
Fe2SiO4 is very weakly formed and thus base coating forming is very poor,
whereby at a material surface, much residual material exists. This is because
excessively generated FeO and Fe2SiO3 do not basically react with a glasslessbased
additive and are attached to a material surface to 5 form the Fe mound
defect. In such a case, it can be seen that a product of an enhanced surface
and excellent gloss in which base coating is excluded cannot be obtained.
(Table 2)
Specime
n
number
Dew point
temperatur
e
Total
oxygen
amoun
t
(ppm)
SiO2
/
FeO
Glassles
s
additive
Roughnes
s
(Ra: ƒÊm)
Glossines
s
(index)
1
35 340 7.2
MgCl2 0.32 114
2 CaCl2 0.34 120
3 BiCl3 0.31 126
4 SbCl3 0.31 132
5
45 480 4.8
MgCl2 0.32 177
6 CaCl2 0.34 172
7 BiCl3 0.31 191
8 SbCl3 0.31 194
9
55 630 2.3
MgCl2 0.39 160
10 CaCl2 0.38 158
31
11 BiCl3 0.35 179
12 SbCl3 0.34 166
Therefore, in order to produce a base coating free type of oriented
electrical steel sheet having excellent roughness and glossiness and having
very good iron loss due to the excellent roughness and glossiness that is sought
in an exemplary embodiment according to the present invention, 5 a condition of
an amount and a composition of an oxidation layer and a slab component
system was derived from Tables 1 and 2. That is, in a cold rolled plate that is
produced with a component system of specimen number 5 of Table 1, a
specimen that is produced with an oxidation layer condition (SiO2/Fe2SiO4=4.8)
10 that is derived in Table 2 was used as a testing material, a new annealing
separating agent for new base coating free that is suggested in an exemplary
embodiment according to the present invention was produced and applied, as in
Table 3, and a material characteristic including a magnetic property was
compared.
15 When producing an annealing separating agent, the annealing
separating agent was produced based on MgO at 100 g and water at 1000 g.
As shown in Table 3, when using MgO having a high activation level and BiCl3
having strong oxidation, and MgO in which an activation level is appropriately
adjusted instead of a chloride of a line similar thereto, in a specimen that
20 applies an antimony oxychloride (SbOCl) additive that is not dissociated within
an aqueous solution and that thus originally suppresses Fe oxide and antimony
sulfate (Sb2(SO4)3) not having Cl group, an oriented electrical steel sheet
32
having excellent roughness and gloss and very low iron loss was obtained.
(Table 3)
MgO
Activ
ity
level
(S)
Comm
on
glassle
ss
(BiCl3)
Base coating free
annealing
separating agent
Rou
ghne
ss
(Ra:
ƒÊm)
Glossin
ess
(index)
Magn
etic
flux
Densit
y
B10
Iron loss
(W17/50
)
Remark
SbOC
l
Sb2 (SO4)3
50
- - - - - 1.91 0.87 Commo
n
material
5 - - 0.31 191 1.91 0.90
Compar
ative
material
10 - - 0.30 200 1.92 0.88
- 5 - 0.29 215 1.92 0.88
- 10 - 0.30 209 1.92 0.89
- 20 - 0.28 220 1.92 0.87
- 5 2.5 0.27 235 1.92 0.86
- 10 2.5 0.26 280 1.92 0.85
- 20 2.5 0.28 255 1.92 0.86
500
- 5 - 0.26 288 1.92 0.85 Compar
ative
material
- 10 - 0.25 301 1.92 0.83
- 10 0.5 0.25 299 1.93 0.83
- 10 3.5 0.24 316 1.93 0.81 Present
33
inventio
n
- 7.5 0.23 330 1.93 0.79 Present
inventio
n
- 20 2.5 0.25 287 1.93 0.82 Compar
ative
material
While the present invention has been particularly shown and described
with reference to exemplary embodiments thereof, it will be understood by those
skilled in the art that various changes in form and details may be made therein
without departing from the spirit and scope of the invention 5 as defined by the
appended claims.
Therefore, it should be understood that the foregoing exemplary
embodiments are not limited but are illustrated. The scope of the present
invention is represented by claims to be described later rather than the detailed
10 description, and it should be recognized that the meaning and scope of the
claims and an entire change or a changed form that is derived from an
equivalent concept thereof are included in the scope of the present invention.
While this invention has been described in connection with what is
presently considered to be practical exemplary embodiments, it is to be
15 understood that the invention is not limited to the disclosed embodiments, but,
on the contrary, is intended to cover various modifications and equivalent
34
arrangements included within the spirit and scope of the appended claims.

Claim
1. An annealing separating agent comprising MgO, an oxychloride material,
and a sulfate-based antioxidant.
Claim 2.
The annealing separating agent of claim 1, wherein the oxychloride
material is antimony oxychloride (SbOCl) or bismuth oxychloride (BiOCl).
10 yClaim 3z
The annealing separating agent of claim 2, wherein the sulfate-based
antioxidant is at least one that is selected from an antimony-based (Sb2(SO4)3),
strontium-based (SrSO4), or barium-based (BaSO4) antioxidant.
15 yClaim 4z
The annealing separating agent of any one of claims 1 to 3, wherein the
oxychloride material is included at a ratio of 10-20 wt% to the MgO at 100-200
wt%, and the sulfate-based antioxidant is included at a ratio of 1-5 wt% to the
MgO at 100-200 wt%.
20
yClaim 5z
A method of manufacturing an oriented electrical steel sheet, the
method comprising:
36
producing a hot rolled steel sheet by hot rolling a steel slab;
producing a cold rolled steel sheet by cold rolling the hot rolled steel
sheet;
performing decarburization annealing and nitride annealing on the cold
rolled 5 steel sheet; and
applying an annealing separating agent comprising MgO, an oxychloride
material, and a sulfate-based antioxidant, and a glassless additive comprising
water, and performing final high temperature annealing on the electrical steel
sheet of which the decarburization annealing and nitride annealing is complete.
10
yClaim 6z
The method of claim 5, wherein the oxychloride material is antimony
oxychloride (SbOCl) or bismuth oxychloride (BiOCl).
15 yClaim 7z
The method of claim 6, wherein the sulfate-based antioxidant is at least
one that is selected from an antimony-based (Sb2(SO4)3), strontium-based
(SrSO4), or barium-based (BaSO4) antioxidant.
20 yClaim 8z
The method of claim 7, wherein the oxychloride material is included at a
ratio of 10-20 wt% to the MgO at 100-200 wt%, and the sulfate-based
antioxidant is included at a ratio of 1-5 wt% to the MgO at 100-200 wt%.
37
yClaim 9z
The method of claim 8, wherein an amount of SiO2 that is formed at a
surface of the electrical steel sheet of which the decarburization annealing and
nitride annealing is complete is two times to five times greater 5 than that of
Fe2SiO4.
yClaim 10z
The method of claim 9, wherein the decarburization and nitride
10 annealing process is performed in a dew point range of 35-55 Ž.
yClaim 11z
The method of claim 10, wherein an activation level of the MgO is 400-
3000 seconds.
15
yClaim 12z
The method of claim 11, wherein upon the final high temperature
annealing, a temperature rising speed is 18-75 Ž/h in a temperature range of
700-950 Ž, and a temperature rising speed is 10-15 Ž/h in a temperature
20 range of 950-1200 Ž.
yClaim 13z
The method of claim 12, wherein in the decarburization and nitride
38
annealing, a temperature is 800-950 Ž.
yClaim 14z
The method of claim 13, wherein the glassless additive is applied at 5-8
5 g/m2.
yClaim 15z
The method of claim 14, wherein the steel slab comprises Sn at 0.03-
0.07 wt%, Sb at 0.01-0.05 wt%, and P at 0.01-0.05 wt%, the remaining portion
10 comprises Fe and other inevitably added impurities, and the steel slab satisfies
P+0.5Sb at 0.0370-0.0630 wt%.
yClaim 16z
An oriented electrical steel sheet that produces a hot rolled steel sheet
15 by hot rolling a steel slab comprising Sn at 0.03-0.07 wt%, Sb at 0.01-0.05 wt%,
and P at 0.01-0.05 wt%, the remaining portion comprises Fe and other
inevitably added impurities, and the steel slab satisfies P+0.5Sb at 0.0370-
0.0630 wt%, and that produces a cold rolled steel sheet by cold rolling the hot
rolled steel sheet and that performs decarburization annealing and nitride
20 annealing on the cold rolled steel sheet,
wherein an amount of SiO2 that is formed at a surface of the steel sheet
of which the decarburization annealing and nitride annealing is complete is two
times to five times greater than that of Fe2SiO4.
39
yClaim 17z
The oriented electrical steel sheet of claim 16, wherein final high
temperature annealing is performed by applying an annealing separating agent
comprising MgO, an oxychloride material, and a sulfate-based 5 antioxidant, and
a glassless additive comprising water, to the electrical steel sheet of which the
decarburization annealing and nitride annealing is complete.
yClaim 18z
10 The oriented electrical steel sheet of claim 17, wherein the oxychloride
material is antimony oxychloride (SbOCl) or bismuth oxychloride (BiOCl).
yClaim 19z
The oriented electrical steel sheet of claim 18, wherein the sulfate-based
15 antioxidant is at least one that is selected from an antimony-based (Sb2(SO4)3),
strontium-based (SrSO4), or barium-based (BaSO4) antioxidant.
yClaim 20z
The oriented electrical steel sheet of claim 19, wherein the oxychloride
20 material is included at a ratio of 10-20 wt% to the MgO at 100-200 wt%, and the
sulfate-based antioxidant is included at a ratio of 1-5 wt% to the MgO at 100-
200 wt%.
40
yClaim 21z
The oriented electrical steel sheet of claim 20, wherein the
decarburization and nitride annealing process is performed in a dew point range
of 35-55 Ž.
5
yClaim 22z
The oriented electrical steel sheet of claim 21, wherein an activation
level of the MgO is 400-3000 seconds.
10 yClaim 23z
The oriented electrical steel sheet of claim 22, wherein upon the final
high temperature annealing, a temperature rising speed is 18-75 Ž/h in a
temperature range of 700-950 Ž, and a temperature rising speed is 10-15 Ž/h
in a temperature range of 950-1200 Ž.
15
yClaim 24z
The oriented electrical steel sheet of claim 23, wherein upon the
decarburization and nitride annealing, a temperature is 800-950 Ž.
20 yClaim 25z
The oriented electrical steel sheet of claim 24, wherein the glassless
additive is applied at 5-8 g/m2.