[0001]The present invention relates to a method for producing a grain oriented
electrical steel sheet.
Priority is claimed on Japanese Patent Application No. 2019-005132, filed on
January 16, 2019, and the content of which is incorporated herein by reference.
Background Art
[0002]
A grain oriented electrical steel sheet is used mainly in a transformer. A
transformer is continuously excited over a long period of time from installation to disuse
15 such that energy loss continuously occurs. Therefore, energy loss occurring when the
transformer is magnetized by an alternating current, that is, iron loss is a main index that
determines the performance of the transformer.
[0003]
In order to reduce iron loss of a grain-oriented electrical steel sheet, various
20 methods have been developed. Examples of the methods include a method of highly
aligning grains in the { 110} <00 1 > orientation called Goss orientation in a crystal
structure, a method of increasing the content of a solid solution element such as Si that
increases electric resistance in a steel sheet, and a method of reducing the thickness of a
steel sheet.
25 [0004]
2
In addition, it is known that a method of applying tension to a steel sheet is
effective for reducing iron loss. Thus, in general, in order to reduce the iron loss, an
insulation coating is formed on a surface of the grain oriented electrical steel sheet. The
coating applies the tension to the grain oriented electrical steel sheet, and thereby,
5 reduces the iron loss as a single steel sheet. Moreover, the coating ensures interlaminar
electrical insulation when the grain oriented electrical steel sheets are utilized after being
laminated, and thereby, reduces the iron loss as an iron core.
[0005]
For instance, as the grain oriented electrical steel sheet with the coating, a
10 forsterite film which is an oxide film including Mg is formed on a surface of a base steel
sheet, and then, the insulation coating is formed on a surface of the forsterite film. In
the case, the coating on the base steel sheet includes the forsterite film and the insulation
coating. The forsterite film and the insulation coating respectively have a function of
increasing the electrical insulation and applying the tension to the base steel sheet.
15 [0006]
The forsterite film which is the oxide film including Mg is formed, during final
annealing which is a heat treatment at 900 to 1200°C for 30 hours or more to make the
steel sheet be secondary-recrystallized, by reacting an annealing separator mainly
including magnesia (MgO) with silicon dioxide (Si02) formed on the base steel sheet
20 during decarburization annealing.
[0007]
The insulation coating is formed by applying coating solution including, for
instance, phosphoric acid or phosphate, colloidal silica, and chromic anhydride or
chromate to the base steel sheet after final annealing, and by baking and drying it at 300
25 to 950°C for 10 seconds or more.
5
3
[0008]
In order that the coating ensures the function of increasing the insulation and
applying the tension to the base steel sheet, sufficient adhesion is required between the
coating and the base steel sheet.
[0009]
Conventionally, the above adhesion has been mainly ensured by the anchor
effect derived from the unevenness of an interface between the base steel sheet and the
forsterite film. However, in recent years, it has been found that the unevenness of the
interface becomes an obstacle of movement of a magnetic domain wall when the grain
10 oriented electrical steel sheet is magnetized, and thus, the unevenness is also a factor that
hinders the reduction of iron loss.
[0010]
For instance, Japanese Unexamined Patent Application, First Publication No.
S49-096920 (Patent Document 1) and PCT International Publication No.
15 W02002/088403 (Patent Document 2) disclose a technique to ensure the adhesion of the
insulation coating even in a state in which the forsterite film which is the oxide film
including Mg does not exist and the interface is smooth in order to further reduce the iron
loss.
20
[0011]
In the method for producing the grain oriented electrical steel sheet as disclosed
in the Patent Document 1, the forsterite film is removed by pickling or the like and then
the surface of the base steel sheet is smoothened by chemical polishing or electrolytic
polishing. In the method for producing the grain oriented electrical steel sheet as
disclosed in the Patent Document 2, the formation of the forsterite film itself is
25 suppressed by using an annealing separator containing alumina (Ah03) for the final
4
annealing and thereby the surface of the base steel sheet is smoothened.
[0012]
However, in the producing methods as disclosed in the Patent Document 1 and
the Patent Document 2, there is a problem that the insulation coating is difficult to adhere
5 to the surface of the base steel sheet (sufficient adhesion is not obtained) in a case where
the insulation coating is formed in contact with the surface of the base steel sheet
(directly on the surface of the base steel sheet).
Related Art Documents
10 Patent Documents
15
[0013]
[Patent Document 1] Japanese Unexamined Patent Application, First
Publication No. S49-096920
[Patent Document 2] PCT International Publication No. W02002/088403
Summary of Invention
Technical Problem to be Solved
[0014]
The present invention has been made in consideration of the above mentioned
20 situations. An object of the invention is to provide a method for producing a grain
oriented electrical steel sheet without the forsterite film and excellent in magnetic
characteristics (in particular, iron loss) and the coating adhesion.
Solution to Problem
25 [0015]
5
The present inventors have investigated a technique to improve the adhesion
(coating adhesion) between the steel sheet and the insulation coating even in a case
where the forsterite film is not formed for reducing the iron loss and the insulation
coating is formed on the surface of the grain oriented electrical steel sheet in which the
5 surface of the steel sheet is smoothened.
[0016]
As a result, it has been found that it is possible to produce the grain oriented
electrical steel sheet without the forsterite film and excellent in the magnetic
characteristics and the coating adhesion by appropriate! y combining predetermined
10 processes.
15
20
25
[0017]
An aspect of the present invention employs the following.
( 1) A method for producing a grain oriented electrical steel sheet according to
an aspect of the present invention includes:
a hot rolling process of hot-rolling a steel piece to obtain a hot rolled steel sheet,
the steel piece including, as a chemical composition, by mass%,
0.030 to 0.100% of C,
0.80 to 7.00% of Si,
0.01 to 1.00% of Mn,
0 to 0.060% in total of S and Se,
0.010 to 0.065% of acid soluble Al,
0.004 to 0.012% ofN,
0 to 0.30% of Cr,
0 to 0.40% of Cu,
0 to 0.50% of P,
5
10
15
0 to 0.30% of Sn,
0 to 0.30% of Sb,
0 to 1.00% ofNi,
0 to 0.008% ofB,
0 to 0.15% ofV,
0 to 0.20% of Nb,
0 to 0.10% ofMo,
0 to 0.015% of Ti,
0 to 0.010% ofBi, and
6
a balance consisting of Fe and impurities;
a cold rolling process of cold-rolling the hot rolled steel sheet to obtain a cold
rolled steel sheet;
a decarburization annealing process of decarburization -annealing the cold rolled
steel sheet to obtain a decarburization annealed sheet;
an annealing separator applying process of applying and drying an annealing
separator including Ah03 and MgO to the decarburization annealed sheet;
a final annealing process of final-annealing the decarburization annealed sheet
after applying the annealing separator to obtain a final annealed sheet;
an annealing separator removing process of removing a redundant annealing
20 separator from a surface of the final annealed sheet;
25
a smoothing process of smoothing the surface of the final annealed sheet after
removing the redundant annealing separator; and
an insulation coating forming process of forming an insulation coating on the
surface of the final annealed sheet after being smoothed,
wherein, in the decarburization annealing process,
7
PH20/PH2 which is an oxidation degree of an atmosphere is 0.18 to 0.80, an
annealing temperature is 750 to 900°C, and a holding is 10 to 600 seconds,
wherein, in the annealing separator applying process,
MgO I (MgO + Ah03) which is a mass ratio of MgO and Ah03 is 5 to 50%, and
5 a hydration water is 1.5 mass% or less in the annealing separator,
10
wherein, in the final annealing process,
the decarburization annealed sheet after applying the annealing separator is held
at 1100 to 1200°C for 10 hours or more in a mixed gas atmosphere including 50
volume% or more of a hydrogen,
wherein, in the annealing separator removing process,
the final annealed sheet is water-washed using a solution with an inhibitor which
is at least one of a triethanolamine, a rosinamine, or a mercaptan,
the final annealed sheet after water-washing is pickled using an acidic solution
whose volume concentration is less than 20%, and
15 an amount of an iron hydroxide and an iron oxide on the surface of the final
annealed sheet is controlled to 0.9 g/m2 or less per a side,
wherein, in the smoothing process,
the final annealed sheet after removing the redundant annealing separator is
annealed at 1 000°C or more in a mixed gas atmosphere including 50 volume% or more
20 of a hydrogen or a carbon monoxide, and
wherein, in the insulation coating forming process,
the insulation coating is formed on the surface of the final annealed sheet after
being smoothed by applying an insulation coating forming solution which mainly
includes a phosphate or a colloidal silica, by baking at 350 to 600°C, and then by
5
8
heat-treating at 800 to 1000°C.
(2) The method for producing the grain oriented electrical steel sheet
according to (1) may include,
between the hot rolling process and the cold rolling process,
at least one of a hot band annealing process of annealing the hot rolled steel
sheet or a hot band pickling process of pickling the hot rolled steel sheet.
(3) In the method for producing the grain oriented electrical steel sheet
according to (1) or (2),
in the decarburization annealing process, a nitriding treatment may be conducted
10 by annealing the cold rolled steel sheet in an atmosphere including ammonia.
( 4) The method for producing the grain oriented electrical steel sheet
according to any one of (1) to (3) may include,
between the cold rolling process and the decarburization annealing process,
between the decarburization annealing process and the annealing separator applying
15 process, between the smoothing process and the insulation coating forming process, or
after the insulation coating forming process,
a magnetic domain refining process of conducting a magnetic domain refining
treatment.
( 5) In the method for producing the grain oriented electrical steel sheet
20 according to any one of (1) to (4),
the steel piece may include, as the chemical composition, by mass%, at least one
selected from a group consisting of
0.02 to 0.30% of Cr,
0.05 to 0.40% of Cu,
25 0.005 to 0.50% of P,
5
10
9
0.02 to 0.30% of Sn,
0.01 to 0.30% of Sb,
0.01 to 1.00% of Ni,
0.0005 to 0.008% of B,
0.002 to 0.15% ofV,
0.005 to 0.20% of Nb,
0.005 to 0.10% ofMo,
0.002 to 0.015% ofTi, and
0.001 to 0.010% ofBi.
Effects of Invention
[0018]
According to the above aspects of the present invention, it is possible to provide
the method for producing the grain oriented electrical steel sheet without the forsterite
15 film and excellent in the magnetic characteristics and the coating adhesion.
Brief Description of Drawings
[0019]
Fig. 1 is a flow chart illustrating a method for producing a grain oriented
20 electrical steel sheet according to an embodiment of the present invention.
Detailed Description of Preferred Embodiments
[0020]
Hereinafter, a preferable embodiment of the present invention is described in
25 detail. However, the present invention is not limited only to the configuration which is
10
disclosed in the embodiment, and various modifications are possible without departing
from the aspect of the present invention. In addition, the limitation range as described
in the embodiment includes a lower limit and an upper limit thereof. However, the
value expressed by "more than" or "less than" does not include in the limitation range.
5 "%"of the amount of respective elements expresses "mass%".
[0021]
A method for producing a grain oriented electrical steel sheet according to an
embodiment of the present invention (hereinafter, referred to as "the method for
producing the grain oriented electrical steel sheet according to the embodiment") is the
10 method for producing the grain oriented electrical steel sheet without a forsterite film and
includes the following processes.
( i) Hot rolling process of hot-rolling a steel piece including predetermined
chemical composition to obtain a hot rolled steel sheet.
( ii) Cold rolling process of cold-rolling the hot rolled steel sheet by cold-rolling
15 once or by cold-rolling plural times with an intermediate annealing to obtain a cold rolled
steel sheet.
(iii) Decarburization annealing process of decarburization-annealing the cold
rolled steel sheet to obtain a decarburization annealed sheet.
( iv ) Annealing separator applying process of applying and drying an annealing
20 separator including Ah03 and MgO to the decarburization annealed sheet.
( v ) Final annealing process of final-annealing the decarburization annealed
sheet after applying the annealing separator to obtain a final annealed sheet.
( vi ) Annealing separator removing process of removing a redundant annealing
separator from a surface of the final annealed sheet by a method including water-washing
25 and pickling.
5
10
11
( vii ) Smoothing process of smoothing the surface of the final annealed sheet
after removing the redundant annealing separator.
( viii ) Insulation coating forming process of forming an insulation coating on
the surface of the final annealed sheet after being smoothed.
[0022]
In addition, the method for producing the grain oriented electrical steel sheet
according to the embodiment may further include the following processes.
( I ) Hot band annealing process of annealing the hot rolled steel sheet.
( II ) Hot band pickling process of pickling the hot rolled steel sheet.
( III ) Magnetic domain refining process of conducting a magnetic domain
refining treatment.
[0023]
In the method for producing the grain oriented electrical steel sheet according to
the embodiment, it is necessary to control not only one process in the above processes
15 but each of the above processes comprehensively and inseparably. Only when the
predetermined conditions in each of all processes as explained above are controlled, it is
possible to reduce the iron loss and improve the coating adhesion.
20
25
[0024]
Hereinafter, each process is described in detail.
[0025]
< Hot rolling process >
In the hot rolling process, the steel piece is hot-rolled to obtain the hot rolled
steel sheet, the steel piece including, as the chemical composition, by mass%,
0.030 to 0.100% of C,
0.80 to 7.00% of Si,
5
10
15
20
12
0.01 to 1.00% of Mn,
0 to 0.060% in total of S and Se,
0.010 to 0.065% of acid soluble Al,
0.004 to 0.012% ofN,
0 to 0.30% of Cr,
0 to 0.40% of Cu,
0 to 0.50% of P,
0 to 0.30% of Sn,
0 to 0.30% of Sb,
0 to 1.00% ofNi,
0 to 0.008% ofB,
0 to 0.15% ofV,
0 to 0.20% of Nb,
0 to 0.10% ofMo,
0 to 0.015% of Ti,
0 to 0.010% ofBi, and
a balance consisting of Fe and impurities. In the embodiment, the steel sheet
after the hot rolling process is referred to as the hot rolled steel sheet.
[0026]
The method for making the steel piece (slab) to be used in the hot rolling
process is not limited. For instance, molten steel with predetermined chemical
composition may be made, and the slab may be made by using the molten steel. The
slab may be made by continuous casting. An ingot may be made by using the molten
steel, and then, the slab may be made by blooming the ingot. Moreover, the slab may
25 be made by other methods.
13
[0027]
A thickness of the slab is not particular! y limited. The thickness of the slab
may be 150 to 350 mm for instance. The thickness of the slab is preferably 220 to 280
mm. The slab with the thickness of 10 to 70 mm which is a so-called thin slab may be
5 used.
[0028]
Limitation reasons of the chemical composition of the steel piece are explained.
Hereinafter,"%" of the chemical composition represents "mass%".
[0029]
10 ( 0.030 to 0.100% ofC)
C (carbon) is an element effective in controlling the primary recrystallized
structure, but negatively affective in the magnetic characteristics. Thus, Cis the
element to be removed by decarburization annealing before final annealing. When the
C content is more than 0.100%, a time for decarburization annealing needs to be
15 prolonged, and the productivity decreases. Thus, the C content is to be 0.100% or less.
The C content is preferably 0.085% or less, and more preferably 0.070% or less.
[0030]
It is favorable that the C content is lower. However, when considering the
productivity in industrial production and the magnetic characteristics of the product, the
20 lower limit of the C content is substantially 0.030%.
[0031]
( 0.80 to 7.00% of Si )
Si (silicon) increases the electric resistance of grain oriented electrical steel sheet,
and thereby, reduces the iron loss. When the Si content is less than 0.80%, y
25 transformation occurs during the final annealing and the crystal orientation of grain
14
oriented electrical steel sheet is impaired. Thus, the Si content is to be 0.80% or more.
The Si content is preferably 2.00% or more, and more preferably 2.50% or more.
On the other hand, when the Si content is more than 7.00%, the cold workability
deteriorates and the cracks tend to occur during cold rolling. Thus, the Si content is to
5 be 7.00% or less. The Si content is preferably 4.50% or less, and more preferably
4.00% or less.
[0032]
( 0.01 to 1.00% of Mn)
Mn (manganese) increases the electric resistance of grain oriented electrical
10 steel sheet, and thereby, reduces the iron loss. Moreover, Mn forms MnS and/or MnSe
which act as the inhibitor by bonding to Sand/or Se. When the Mn content is within
0.01 to 1.00%, the secondary recrystallization becomes stable. Thus, the Mn content is
to be 0.01 to 1.00%. The lower limit of the Mn content is preferably 0.08%, and more
preferably 0.09%. The upper limit of the Mn content is preferably 0.50%, and more
15 preferably 0.20%.
20
[0033]
( 0 to 0.060% in total of one or both of Sand Se)
S (sulfur) and Se (selenium) are elements to form MnS and/or MnSe which act
as the inhibitor by bonding to Mn.
When the total amount of one or both of Sand Se (S + Se) is more than 0.060%,
the dispersion state of precipitation of MnS and/or MnSe becomes uneven. In the case,
the desired secondary recrystallized structure cannot be obtained, and the magnetic flux
density may decrease. Moreover, MnS remains in the steel after purification annealing,
and the hysteresis loss may increase. Thus, the total amount of S and Se is to be
25 0.060% or less.
15
The lower limit of the total amount of S and Se is not particular! y limited, and
may be 0%. The lower limit thereof may be 0.003%. When the inhibitor thereof is
used, the lower limit is preferably 0.015%.
[0034]
5 ( 0.010 to 0.065% of acid soluble Al (Sol. Al))
The acid soluble Al (aluminum) is an element to form (Al, Si)N which acts as
the inhibitor by bonding toN. When the amount of acid soluble Al is less than 0.010%,
the effect of addition is not sufficiently obtained, and the secondary recrystallization does
not proceed sufficiently. Thus, the amount of acid soluble Al is to be 0.010% or more.
10 The amount of acid soluble Al is preferably 0.015% or more, and more preferably
0.020% or more.
[0035]
On the other hand, when the amount of acid soluble Al is more than 0.065%, the
dispersion state of precipitation of AlN and/or (Al, Si)N becomes uneven, the desired
15 secondary recrystallized structure cannot be obtained, and the magnetic flux density
decreases. Thus, the amount of acid soluble Al (Sol. Al) is to be 0.065% or less. The
amount of acid soluble Al is preferably 0.055% or less, and more preferably 0.050% or
less.
[0036]
20 ( 0.004 to 0.012% of N)
N (nitrogen) is an element to form AlN and/or (Al, Si)N which act as the
inhibitor by bonding to Al. When theN content is less than 0.004%, the formation of
AlN and/or (Al, Si)N becomes insufficient. Thus, theN content is to be 0.004% or
more. TheN content is preferably 0.006% or more, and more preferably 0.007% or
25 more.
16
On the other hand, when theN content is more than 0.012%, the blisters (voids)
may be formed in the steel sheet. Thus, theN content is to be 0.012% or less.
[0037]
The steel piece includes, as the chemical composition, the above elements, and
5 the balance consists of Fe and impurities. However, in consideration of the influence on
the magnetic characteristics and the improvement of the inhibitors functions by forming
compounds, the steel piece may include at least one of optional elements as substitution
for a part of Fe. For instance, the optional elements included as substitution for a part
of Fe may be Cr, Cu, P, Sn, Sb, Ni, B, V, Nb, Mo, Ti, and Bi. However, the optional
10 elements do not need to be included, the lower limits thereof may be 0% respectively.
15
Moreover, even if the optional elements may be included as impurities, the above
mentioned effects are not affected. Herein, the impurities correspond to elements which
are contaminated during industrial production of steel from ores and scrap that are used
as a raw material of steel, or from environment of a production process.
[0038]
( 0 to 0.30% ofCr)
Cr (chrome) is an element effective in increasing the electric resistance, and
thereby, reducing the iron loss, in common with Si. Thus, Cr may be included. In
order to obtain the above effects, the Cr content is preferably 0.02% or more, and more
20 preferably 0.05% or more.
On the other hand, when the Cr content is more than 0.30%, the magnetic flux
density may deteriorate. Thus, the upper limit of the Cr content is preferably 0.30%,
more preferably 0.20%, and further more preferably 0.12%.
[0039]
25 ( 0 to 0.40% ofCu)
5
17
Cu (copper) is also an element effective in increasing the electric resistance, and
thereby, reducing the iron loss. Thus, Cu may be included. In order to obtain the
above effects, the Cu content is preferably 0.05% or more, and more preferably 0.10% or
more.
On the other hand, when the Cu content is more than 0.40%, the improvement
effect of reducing the iron loss may be saturated, and surface defects called "copper scab"
may be incurred during hot rolling. Thus, the upper limit of the Cu content is preferably
0.40%, more preferably 0.30%, and further more preferably 0.20%.
[0040]
10 ( 0 to 0.50% ofP)
15
P (phosphorus) is also an element effective in increasing the electric resistance,
and thereby, reducing the iron loss. Thus, P may be included. In order to obtain the
above effects, the P content is preferably 0.005% or more, and more preferably 0.010%
or more.
On the other hand, when the P content is more than 0.50%, the rollability may
deteriorate. Thus, the upper limit of the P content is preferably 0.50%, more preferably
0.20%, and further more preferably 0.15%.
[0041]
( 0 to 0.30% of Sn )
20 ( 0 to 0.30% of Sb )
Sn (tin) and Sb (antimony) are elements effective in stabilizing the secondary
recrystallization, and thereby, developing the { 110} <00 1 > orientation. Thus, Sn and Sb
may be included. In order to obtain the above effects, the Sn content is preferably
0.02% or more, and more preferably 0.05% or more. Moreover, the Sb content is
25 preferably 0.01% or more, and more preferably 0.03% or more.
18
On the other hand, when the Sn content is more than 0.30% or when the Sb
content is more than 0.30%, the magnetic characteristics may deteriorate. Thus, the
upper limits of the Sn content and the Sb content are preferably 0.30% respectively.
The upper limit of the Sn content is preferably 0.15%, and more preferably 0.10%.
5 Moreover, the upper limit of the Sb content is preferably 0.15%, and more preferably
0.10%.
[0042]
( 0 to 1.00% ofNi)
Ni (nickel) is also an element effective in increasing the electric resistance, and
10 thereby, reducing the iron loss. Moreover, Ni is an element effective in controlling the
metallographic structure of the hot rolled steel sheet, and thereby, improving the
magnetic characteristics. Thus, Ni may be included. In order to obtain the above
effects, the Ni content is preferably 0.01% or more, and more preferably 0.02% or more.
On the other hand, when the Ni content is more than 1.00%, the secondary
15 recrystallization may be unstable. Thus, the Ni content is preferably 1.00% or less,
more preferably 0.20% or less, and further more preferably 0.10% or less.
[0043]
( 0 to 0.008% ofB)
B (boron) is an element effective in forming BN which acts as the inhibitor by
20 bonding toN. Thus, B may be included. In order to obtain the above effects, the B
content is preferably 0.0005% or more, and more preferably 0.0010% or more.
25
On the other hand, when the B content is more than 0.008%, the magnetic
characteristics may deteriorate. Thus, the upper limit of the B content is preferably
0.008%, more preferably 0.005%, and further more preferably 0.003%.
[0044]
( 0 to 0.15% ofV)
( 0 to 0.20% ofNb)
( 0 to 0.015% of Ti)
19
V (vanadium), Nb (niobium), and Ti (titanium) are elements which act as the
5 inhibitor by bonding to N, C, and the like. Thus, V, Nb, and Ti may be included. In
order to obtain the above effects, the V content is preferably 0.002% or more, and more
preferably 0.010% or more. The Nb content is preferably 0.005% or more, and more
preferably 0.020% or more. The Ti content is preferably 0.002% or more, and more
preferably 0.004% or more.
10 On the other hand, when the V content is more than 0.15%, when the Nb content
is more than 0.20%, or when the Ti content is more than 0.015% in the steel piece, there
elements may remain in the final product. In the case, as the final product, the V
content may be more than 0.15%, the Nb content may be more than 0.20%, or the Ti
content may be more than 0.015%. As a result, the magnetic characteristics of the final
15 product (grain oriented electrical steel sheet) may deteriorate.
Thus, the upper limit of the V content is preferably 0.15%, more preferably
0.10%, and further more preferably 0.05%. The upper limit of the Ti content is
preferably 0.015%, more preferably 0.010%, and further more preferably 0.008%. Thus,
the upper limit of the Nb content is preferably 0.20%, more preferably 0.10%, and further
20 more preferably 0.08%.
[0045]
( 0 to 0.10% ofMo)
Mo (molybdenum) is also an element effective in increasing the electric
resistance, and thereby, reducing the iron loss. Thus, Mo may be included. In order to
25 obtain the above effects, the Mo content is preferably 0.005% or more, and more
5
20
preferably 0.01% or more.
On the other hand, when the Mo content is more than 0.1 0%, the rollability of
the steel sheet may deteriorate. Thus, the upper limit of the Mo content is preferably
0.10%, more preferably 0.08%, and further more preferably 0.05%.
[0046]
( 0 to 0.010% ofBi)
Bi (bismuth) is an element effective in stabilizing precipitates such as sulfide,
and thereby, improving the inhibitors functions. Thus, Bi may be included. In order to
obtain the above effects, the Bi content is preferably 0.001% or more, and more
10 preferably 0.002% or more.
15
On the other hand, when the Bi content is more than 0.010%, the magnetic
characteristics may deteriorate. Thus, the upper limit of the Bi content is preferably
0.010%, more preferably 0.008%, and further more preferably 0.006%.
[0047]
The chemical composition as described above may be measured by typical
analytical methods for the steel. For instance, the chemical composition may be
measured by using ICP-AES (Inductively Coupled Plasma-Atomic Emission
Spectrometer: inductively coupled plasma emission spectroscopy spectrometry).
Herein, the acid soluble Al may be measured by ICP-AES using filtrate after heating and
20 dissolving the sample in acid. In addition, C and S may be measured by the infrared
25
absorption method after combustion, N may be measured by the thermal conductometric
method after fusion in a current of inert gas, and 0 may be measured by, for instance, the
non-dispersive infrared absorption method after fusion in a current of inert gas.
[0048]
Next, conditions for hot-rolling the above steel piece are explained.
21
The conditions of the hot rolling are not particularly limited. For instance, the
conditions are as follows.
The slab is heated before the hot rolling. The slab is put and heated in a known
heating furnace or a known soaking furnace. As one method, the slab is heated to
5 1280°C or less. By setting the heating temperature of the slab to 1280°C or less, for
instance, it is possible to avoid various problems when the heating temperature is more
than 1280°C (a dedicated high temperature heating furnace is required, the melt scale
amount rapidly increases, and the like). The lower limit of the heating temperature of
the slab is not particularly limited. However, when the heating temperature is
10 excessively low, the hot rolling may become difficult and the productivity may be
decreased. Thus, the heating temperature may be in the range of 1280°C or less in
consideration of the productivity. The lower limit of the heating temperature of the slab
is preferably 11 00°C. The upper limit of the heating temperature of the slab is
preferably 1250°C.
15
20
[0049]
In addition, as another method, the slab is heated to higher temperature of
1320°C or more. By heating the slab to higher temperature of 1320°C or more, it is
possible to stabilize the secondary recrystallization by solutionizing AlN and Mn(S, Se)
and by finely precipitating them in the subsequent processes.
The slab heating in itself may be omitted, and the hot rolling may be conducted
after casting and before decreasing the temperature of the slab.
[0050]
The heated slab is hot-rolled by a hot rolling mill, and thereby, the hot rolled
steel sheet is obtained. The hot rolling mill includes, for instance, a rough rolling mill
22
and a final rolling mill which is arranged downstream of the rough rolling mill. The
rough rolling mill includes rough rolling stands which are in a row. Each of the rough
rolling stands has plural rolls arranged one above the other. In the same way, the final
rolling mill includes final rolling stands which are in a row. Each of the final rolling
5 stands has plural rolls arranged one above the other. The heated steel piece is rolled by
the rough rolling mill and then by the final rolling mill, and thereby, the hot rolled steel
sheet is obtained.
A final temperature in the hot rolling process (the temperature of the steel sheet
at outlet side of the final rolling stand by which the steel sheet is finally rolled in the final
10 rolling mill) may be 700 to 1150°C. The hot rolled steel sheet is produced by the hot
rolling process explained above.
[0051]
< Hot band annealing process >
In the hot band annealing process, as necessary, the hot rolled steel sheet
15 obtained by the hot rolling process is annealed (hot band annealed) to obtain the hot band
annealed sheet. In the embodiment, the steel sheet after the hot band annealing process
is referred to as the hot band annealed sheet.
[0052]
The hot band annealing is conducted in order to homogenize the nonuniform
20 structure after hot rolling, to control the precipitation of AlN which is the inhibitor
(precipitate finely), and to control secondary phase, solid-soluted carbon, and the like.
As the annealing conditions, known conditions may be applied according to the purpose.
For instance, in order to homogenize the nonuniform structure after hot rolling, the hot
rolled steel sheet is hold at 750 to 1200°C of the heating temperature (furnace
25 temperature in a hot band annealing furnace) for 30 to 600 seconds.
23
The hot band annealing is not always necessary. The hot band annealing may
be conducted as a result of considering the characteristics and the producing cost required
for the grain oriented electrical steel sheet finally produced.
[0053]
5 < Hot band pickling process >
In the hot band pickling process, as necessary, the hot rolled steel sheet after the
hot rolling process or the hot band annealed sheet after the hot band annealing process in
a case where the hot band annealing has been conducted is pickled in order to remove
surface scale. The pickling conditions are not particularly limited, and known
10 conditions may be appropriate! y applied.
[0054]
< Cold rolling process >
In the cold rolling process, the hot rolled steel sheet or the hot band annealed
sheet after the hot rolling process, the hot band annealing process, or the hot band
15 pickling process is cold-rolled by once or by plural times with an intermediate annealing
to obtain the cold rolled steel sheet. In the embodiment, the steel sheet after the cold
rolling process is referred to as the cold rolled steel sheet.
[0055]
A cold rolling reduction rate in final cold rolling (cumulative cold rolling
20 reduction rate without intermediate annealing or cumulative cold rolling reduction rate
25
after intermediate annealing) is preferably 80% or more, and more preferably 90% or
more. The upper limit of the final cold rolling reduction rate is preferably 95%.
[0056]
Herein, the final cold rolling reduction rate(%) is defined as follows.
Final cold rolling reduction rate (%) = ( 1 - Sheet thickness of steel sheet after
24
final cold rolling I Sheet thickness of steel sheet before final cold rolling ) x 100
[0057]
< Decarburization annealing process >
In the decarburization annealing process, the cold rolled steel sheet after the cold
5 rolling process is subjected to the magnetic domain refining treatment as necessary, and
then, is decarburization -annealed to promote the primary recrystallization. Moreover, in
the decarburization annealing, C which negatively affective in the magnetic
characteristics is removed from the steel sheet. In the embodiment, the steel sheet after
the decarburization annealing process is referred to as the decarburization annealed sheet.
10 [0058]
For the above purposes, in the decarburization annealing, the oxidation degree
(PH20IPH2) in atmosphere is to be 0.18 to 0.80, an annealing temperature is to be 750 to
900°C, and a holding is to be 10 to 600 seconds. The oxidation degree PH20/PH2 is
defined as the ratio of water vapor partial pressure PH20 (atm) to hydrogen partial
15 pressure PH2 (atm) in the atmosphere.
[0059]
When the oxidation degree (PH20IPH2) is less than 0.18, dense silicon dioxide
(Si02) is quickly formed as an externally oxidized layer, it is suppressed to release C
outside the system, and thus, the decarburization does not occur properly. On the other
20 hand, when the oxidation degree is more than 0.80, the oxidized layer of the steel sheet
surface is thickened, and it is difficult to remove the oxidized layer.
When the annealing temperature is less than 750°C, it is difficult to sufficiently
conduct the decarburization. On the other hand, when the annealing temperature is
more than 900°C, the grain size after the primary recrystallization exceeds favorable size,
25 and thereby, the magnetic characteristics after the final annealing deteriorate.
5
25
When the holding time is less than 10 seconds, the decarburization does not
occur sufficiently. On the other hand, when the holding time is more than 600 seconds,
the grain size after the primary recrystallization exceeds favorable size, and thereby, the
magnetic characteristics after the final annealing deteriorate.
[0060]
Depending on the above oxidation degree (PH20/PH2), a heating rate in a
heating stage to the annealing temperature may be controlled. For instance, in a case
where the heating including an induction heating is conducted, an average heating rate
may be 5 to 1000 °C/second. Moreover, in a case where the heating including an
10 electric heating is conducted, an average heating rate may be 5 to 3000 °C/second.
[0061]
In addition, in the decarburization annealing process, the nitriding treatment may
be conducted. In the nitriding treatment, the cold rolled steel sheet may be annealed in
the atmosphere including ammonia in at least one stage before, during, or after the above
15 holding. In a case where the temperature for heating the slab is lower, it is preferable
that the nitriding treatment is conducted in the decarburization annealing process. By
additionally conducting the nitriding treatment in the decarburization annealing process,
the inhibitor such as AlN and (Al, Si)N is formed, and thus, it is possible to make the
secondary recrystallization occur stably.
20 [0062]
Although the conditions for the nitriding treatment are not particular! y limited, it
is preferable to conduct the nitriding treatment so that the nitrogen content increases by
0.003% or more, preferably 0.005% or more, and more preferably 0.007% or more.
When the nitrogen (N) content is more than 0.030%, the effects are saturated. Thus, the
25 nitriding treatment may be conducted so that the nitrogen content becomes 0.030% or
5
26
less.
[0063]
The conditions for the nitriding treatment are not particular! y limited, and
known conditions may be appropriate! y applied.
For instance, in a case where the nitriding treatment is conducted after the
holding at 7 50 to 900°C for 10 to 600 seconds in the oxidation degree (PH20IPH2) of
0.01 to 0.15, the nitriding treatment may be conducted such that the cold rolled steel
sheet is not cooled to the room temperature but held in the cooling stage in the
atmosphere including the ammonia. It is preferable that the oxidation degree
10 (PH20IPH2) in the cooling stage is within the range of 0.0001 to 0.01. Moreover, in a
case where the nitriding treatment is conducted during the holding at 750 to 900°C for 10
to 600 seconds in the oxidation degree (PH20IPH2) of 0. 01 to 0.15, the ammonia may be
included in the atmospheric gas with the above oxidation degree.
[0064]
15
In the annealing separator applying process, the decarburization annealed sheet
after the decarburization annealing process (or the decarburization annealed sheet after
the nitriding treatment) is subjected to the magnetic domain refining treatment as
necessary, and then, the annealing separator including Ah03 and MgO is applied to the
20 decarburization annealed sheet. Thereafter, the applied annealing separator is dried.
[0065]
In a case where the annealing separator includes MgO but does not include
Ah03, the forsterite film is formed on the steel sheet in the final annealing process. On
the other hand, in a case where the annealing separator includes Ah03 but does not
25 include MgO, mullite (3Ah03 · 2Si02) is formed on the steel sheet. The mullite
27
becomes the obstacle of movement of the magnetic domain wall, and thus, causes the
deterioration of the magnetic characteristics of the grain oriented electrical steel sheet.
[0066]
Thus, in the method for producing the grain oriented electrical steel sheet
5 according to the embodiment, as the annealing separator, the annealing separator
including Ah03 and MgO is utilized. By utilizing the annealing separator including
Ah03 and MgO, the forsterite film is not formed on the surface of the steel sheet, and it
is possible to smoothen the surface of the steel sheet after the final annealing.
10
15
20
[0067]
For the annealing separator, MgO I (MgO + Ah03) which is the mass ratio of
MgO and Ah03 is to be 5 to 50%, and the hydration water is to be 1.5 mass% or less.
When MgO I (MgO + Ah03) is less than 5%, the mullite is excessively formed,
and thus, the iron loss deteriorates. On the other hand, when MgO I (MgO + Ah03) is
more than 50%, the forsterite is formed, and thus, the iron loss deteriorates.
When the hydration water in the annealing separator is more than 1.5 mass%,
the secondary recrystallization may be unstable, and it may be difficult to smoothen the
surface of the steel sheet because the surface of the steel sheet is oxidized (Si02 is
formed) in the final annealing. The lower limit of the hydration water is not particularly
limited, but may be 0.1 mass% for instance.
[0068]
The annealing separator is applied by water slurry or by electrostatic spray. In
the annealing separator applying process, the annealing separator may further include
nitrides such as manganese nitride, iron nitride, and chromium nitride which are
decomposed before the secondary recrystallization in the final annealing process and
25 which nitride the decarburization annealed sheet or the decarburized and nitrided sheet.
28
[0069]
< Final annealing process >
The decarburization annealed sheet after applying the above annealing separator
is final-annealed to obtain the final annealed sheet. By conducting the final annealing
5 for the decarburization annealed sheet after applying the above annealing separator, the
secondary recrystallization proceeds, and the crystal orientation aligns in the { 110}<001>
orientation. In the embodiment, the steel sheet after the final annealing process is
referred to as the final annealed sheet.
10
[0070]
Specifically, in the final annealing process, the decarburization annealed sheet
after applying the annealing separator is held at 1100 to 1200°C for 10 hours or more in
the mixed gas atmosphere including 50 volume% or more of a hydrogen. The upper
limit of the annealing time is not particular! y limited, but may be 30 hours for instance.
By conducting the above final annealing, the secondary recrystallization proceeds, and
15 the crystal orientation aligns in the { 110} <00 1 > orientation.
[0071]
< Annealing separator removing process >
In the annealing separator removing process, the redundant annealing separator
is removed from the surface of the steel sheet after the final annealing (the final annealed
20 sheet) by methods including water-washing and pickling. Here, the redundant
annealing separator indicates, for instance, the unreacted annealing separator which has
not reacted with the steel sheet during the final annealing.
[0072]
Specifically, in order to prevent the iron after water-washing from corroding, the
25 final annealed sheet is water-washed using the solution including the inhibitor (corrosion
29
prevention agent) which is at least one of triethanolamine, rosinamine, or mercaptan.
[0073]
After water-washing the final annealed sheet, the pickling may be conducted
using the acidic solution whose volume concentration is less than 20%. For instance,
5 the final annealed sheet is pickled using the solution including less than 20 volume% in
total of at least one of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid,
chloric acid, chromium oxide in aqueous solution, chromate acid mixture, permanganic
acid, peroxosulfuric acid, and peroxophosphoric acid. The lower limit of the volume
concentration is not particularly limited, but may be 0.1 volume% for instance. Herein,
10 the above volume% may be the concentration based on the volume at room temperature.
15
20
[0074]
By conducting the above water-washing and pickling using the above solution, it
is possible to efficiently remove the redundant annealing separator from the surface of
the final annealed sheet.
[0075]
Moreover, the temperature of the solution is preferably 20 to 80°C. By
controlling the temperature of the solution to be within the above range, it is possible to
efficient! y remove the redundant annealing separator from the surface of the steel sheet.
[0076]
By water-washing and pickling explained above, the total amount of iron
hydroxide and iron oxide on the surface of the final annealed sheet is controlled to 0.9
g!m2 or less per a side.
When the removal of the redundant annealing separator on the steel sheet
surface is insufficient and when the total amount of the iron hydroxide and the iron oxide
25 on the steel sheet surface is more than 0.9 g/m2 per a side, the exposure of the base steel
5
30
sheet surface may be insufficient, and thus, the steel sheet surface may not be sufficiently
smoothed. The lower limit of the amount of the iron hydroxide and the iron oxide is not
particularly limited, but may be 0.01 g/m2 for instance.
[0077]
In order to remove the redundant annealing separator, a scrubber may be utilized
in addition to the above water-washing and pickling. By utilizing the scrubber, it is
possible to reliably remove the redundant annealing separator which deteriorates the
wettability in the insulation coating forming process.
[0078]
10 < Smoothing process >
The base steel sheet is exposed by conducting the above water-washing and
pickling, and thereafter, the annealing is conducted at 1 000°C or more in the mixed gas
atmosphere including 50 volume% or more of hydrogen or carbon monoxide, in order to
obtain the final annealed sheet whose surface (base steel sheet surface) is smoothed.
15 Hereinafter, the annealing for smoothing is referred to as the smoothing annealing.
[0079]
In the smoothing annealing, by heating the steel sheet whose surface is exposed
in the mixed gas atmosphere including reducing gas, atom evaporates and moves from
the base steel sheet surface, and the smooth surface which does not tend to interfere with
20 magnetization is revealed. The gas to be mixed with the reducing gas is preferably inert
gas such as nitrogen gas or argon gas. Although using the mixed gas of the hydrogen
and the nitrogen is industrially the lowest cost, the carbon monoxide may be substituted
for the hydrogen.
[0080]
25 When the hydrogen or the carbon monoxide included in the mixed gas
31
atmosphere for the smoothing annealing is less than 50 volume%, the base steel sheet
surface is oxidized, metallic luster decreases, and thus, the magnetic characteristics of the
final product deteriorate. When the volume fraction of the hydrogen or the carbon
monoxide increases, the effect in smoothing the base steel sheet surface increases.
5 When the mixed gas atmosphere includes 50 volume% or more of the hydrogen or the
carbon monoxide, the above effect is obtained. Thus, the lower limit of the volume
fraction of the hydrogen or the carbon monoxide is to be 50%. The upper limit of the
volume fraction of the hydrogen or the carbon monoxide is not particularly limited, but
may be 100% for instance.
10 [0081]
When the annealing temperature for the smoothing annealing is higher, the
smoothing effect is obtained in a shorter time. When the annealing temperature is
1000°C or more, it is possible to effectively promote that the atom evaporates and moves
from the base steel sheet surface. On the other hand, when the annealing temperature
15 for the smoothing annealing is less than 1000°C, the smoothing effect is insufficient, and
the magnetic characteristics deteriorate. Thus, the lower limit of the annealing
temperature for the smoothing annealing is to be 1 000°C. The upper limit of the
annealing temperature for the smoothing annealing is not particularly limited. However,
when the annealing temperature is more than 1200°C, the smoothing effect is saturated.
20 Thus, it is preferable that the annealing temperature is controlled to 1200°C or less.
[0082]
When the surface of the final annealed sheet is not smooth, the unevenness of
the surface becomes the obstacle of movement of the magnetic domain wall, and thus,
the iron loss deteriorates. However, by conducting the above smoothing annealing after
5
32
sufficient! y exposing the surface of the final annealed sheet, it is possible to obtain the
surface state such that the flatness is extremely high. Thus, in the case, the movement
of the magnetic domain wall becomes smooth, and thus, it is possible to sufficiently
obtain the effect of improving the iron loss.
[0083]
< Insulation coating forming process >
In the insulation coating forming process, the final annealed sheet after being
smoothed is subjected to the magnetic domain refining treatment as necessary, and then,
the insulation coating is formed on the surface of the final annealed sheet. In the
10 embodiment, the steel sheet after the insulation coating forming process is referred to as
the grain oriented electrical steel sheet.
[0084]
The coating applies the tension to the grain oriented electrical steel sheet, and
thereby, reduces the iron loss as the single steel sheet. Moreover, the coating ensures
15 interlaminar electrical insulation when the grain oriented electrical steel sheets are
utilized after being laminated, and thereby, reduces the iron loss as an iron core.
[0085]
The insulation coating is formed on the surface of the final annealed sheet by
applying the insulation coating forming solution which mainly includes at least one of
20 the phosphate or the colloidal silica, by baking at 350 to 600°C, and then by heat-treating
at 800 to 1 000°C.
[0086]
The above phosphate is favorably the phosphate of Ca, Al, Sr, and the like.
Among these, the aluminum phosphate is more preferable. The above colloidal silica is
25 not particularly limited to the colloidal silica having specific properties. Moreover, the
33
particle size thereof is not particular! y limited to specific particle size, but is preferably
200 nm or less (mean number diameter). For instance, the particle size may be 5 to 30
nm. When the particle size thereof is more than 200 nm, the particles may settle in the
solution. Moreover, the solution may further include the chromic anhydride or the
5 chromate.
[0087]
When the baking temperature for the insulation coating is less than 350°C, the
solution for the insulation coating drips during passing the steel sheet, poor appearance is
caused, and the insulation coating with sufficient adhesion is not obtained. When the
10 baking temperature for the insulation coating is more than 600°C, since the heating rate
is excessively fast, only the outermost surface of the insulation coating is solidified, and
the solidification of the inside is delayed, the formation of the coating becomes improper
and the coating adhesion becomes insufficient. When the temperature of the heat
treatment after baking is less than 800°C, the formation of the coating becomes improper
15 (insufficient solidification), and the coating adhesion becomes insufficient. When the
temperature of the heat treatment after baking is more than 1 000°C, the phosphate is
decomposed, the formation of the coating becomes improper, and the coating adhesion
becomes insufficient.
20
[0088]
In the insulation coating forming, when the oxidation degree (PH20IPH2) of the
atmosphere is 0.01 to 1.5, the phosphate is not excessively decomposed, and it is possible
to favorably form the insulation coating.
[0089]
The insulation coating forming solution may be applied to the surface of the
25 steel sheet, for instance, by the wet applying method such as roll coater.
34
[0090]
< Magnetic domain refining process >
The method for producing the grain oriented electrical steel sheet according to
the embodiment may include the magnetic domain refining process of conducting the
5 magnetic domain refining treatment at appropriate timing of (first) between the cold
rolling process and the decarburization annealing process, (second) between the
decarburization annealing process and the annealing separator applying process, (third)
between the smoothing process and the insulation coating forming process, or (fourth)
after the insulation coating forming process.
10 [0091]
By conducting the magnetic domain refining treatment, it is possible to reduce
the iron loss of the grain oriented electrical steel sheet. In a case where the magnetic
domain refining treatment is conducted between the cold rolling process and the
decarburization annealing process, between the decarburization annealing process and
15 the annealing separator applying process, or between the smoothing process and the
insulation coating forming process, the groove may be formed lineally or punctiformly so
as to extend in the direction intersecting the rolling direction and so as to have the
predetermined interval in the rolling direction. By forming the above groove, the width
of 180° domain may be narrowed (180° domain may be refined).
20 [0092]
In a case where the magnetic domain refining treatment is conducted after the
insulation coating forming process, the stress-strain or the groove may be applied or
formed lineally or punctiformly so as to extend in the direction intersecting the rolling
direction and so as to have the predetermined interval in the rolling direction. By
25 applying the above stress-strain or forming the above groove, the width of 180° domain
35
may be narrowed (180° domain may be refined).
[0093]
The above stress-strain may be applied by irradiating laser beam, electron beam,
and the like. The above groove may be formed by a mechanical groove forming
5 method such as toothed gear, by a chemical groove forming method such as electrolytic
etching, by a thermal groove forming method such as laser irradiation, and the like. In a
case where the insulation coating is damaged and the performance such as electrical
insulation deteriorates by applying the above stress-strain or forming the above groove,
the insulation coating may be formed again, and thereby, the damage may be repaired.
10
15
[0094]
Fig. 1 shows an instance of the method for producing the grain oriented
electrical steel sheet according to the embodiment. In the figure, the processed
surrounded by the solid line indicates the essential processed, and the processed
surrounded by the broken line indicates the optional processes.
[0095]
The grain oriented electrical steel sheet produced by the method according to the
embodiment does not include the forsterite film. Specifically, the grain oriented
electrical steel sheet includes a base steel sheet, an intermediate layer which is arranged
in contact with the base steel sheet, and the insulation coating which is arranged in
20 contact with the intermediate layer to be an outermost surface.
[0096]
Whether or not the grain oriented electrical steel sheet includes the forsterite
film may be confirmed by X-ray diffraction method. For instance, the X-ray diffraction
may be conducted for the surface after removing the insulation coating from the grain
25 oriented electrical steel sheet, and the obtained X-ray diffraction spectrum may be
5
36
collated with PDF (Powder Diffraction File). The forsterite (Mg2Si04) may be
identified by JCPDS No. 34-189. In the embodiment, when the primal constituent
phase in the above X-ray diffraction spectrum is not the forsterite, the grain oriented
electrical steel sheet is judged not to include the forsterite film.
[0097]
In order to only remove the insulation coating from the grain oriented electrical
steel sheet, the grain oriented electrical steel sheet with the coating may be immersed in
hot alkaline solution. Specifically, it is possible to remove the insulation coating from
the grain oriented electrical steel sheet by immersing the steel sheet in sodium hydroxide
10 aqueous solution which includes 30 mass% of NaOH and 70 mass% of H20 at 80°C for
20 minutes, washing it with water, and then, drying it. In general, only insulation
coating is removed by the alkaline solution, and the forsterite film is removed by the
acidic solution such as hydrochloric acid.
15
[0098]
In the grain oriented electrical steel sheet produced by the method according to
the embodiment, since the forsterite film is not included, the magnetic characteristics (the
iron loss characteristics) are improved. In addition, since each of the processes is
optimally controlled, the coating adhesion is improved.
20 Examples
[0099]
Hereinafter, the examples of the present invention are explained. However, the
condition in the examples is an example condition employed to confirm the operability
and the effects of the present invention, so that the present invention is not limited to the
25 example condition. The present invention can employ various types of conditions as
37
long as the conditions do not depart from the scope of the present invention and can
achieve the object of the present invention.
[0100]
In steel slabs having the chemical composition shown in Table 1, the steel slabs
5 of No. Al3 and No. all were heated to 1350°C, and then hot-rolled to obtain the hot
rolled steel sheets having the sheet thickness of 2.6 mm. The hot rolled steel sheets
were cold-rolled once or cold-rolled plural times with the intermediate annealing to
obtain the cold rolled steel sheets having the final sheet thickness of 0.22 mm. The cold
rolled steel sheets having the final sheet thickness of 0.22 mm were
10 decarburization-annealed in the decarburization annealing process under conditions
shown in Tables 2 to 4.
[0101]
Moreover, in the steel slabs having the chemical composition shown in Table 1,
the steel slabs except for No. Al3 and No. all were heated to 1150°C, and then
15 hot-rolled to obtain the hot rolled steel sheets having the sheet thickness of 2.6 mm.
The hot rolled steel sheets were cold-rolled once or cold-rolled plural times with the
intermediate annealing to obtain the cold rolled steel sheets having the final sheet
thickness of 0.22 mm. The cold rolled steel sheets having the final sheet thickness of
0.22 mm were decarburization-annealed in the decarburization annealing process under
20 conditions shown in Tables 2 to 4, and thereafter, the nitriding treatment was conducted
during cooling by being held in the atmosphere including the ammonia.
[0102]
In No. B5, the hot rolled steel sheet after the hot rolling was subjected to the hot
band annealing in which the annealing was conducted at 11 oooc and then at 900°C.
25 Thereafter, the pickling was conducted in order to remove the surface scale, and then, the
5
10
15
cold rolling was conducted.
[0103]
38
In the decarburization annealing, the average heating rate in the heating stage to
the annealing temperature was less than 15 °C/second.
[0104]
For the decarburization annealed sheets after the above decarburization
annealing, the annealing separator was applied and dried. The conditions of the ratio of
MgO and Ah03 (MgO I (MgO + Ah03)) and the hydration water are shown in Tables 2
to 4.
[0105]
The decarburization annealed sheets after applying the annealing separator were
final-annealed at 11 oooc or 1200°C. The conditions of the final annealing are shown in
Tables 5 to 7.
[0106]
After the final annealing, as shown in Tables 5 to 7, the redundant annealing
separator was removed by water-washing and pickling from the surface of the final
annealed sheet. For the water-washing, the solution including the inhibitor which was
at least one of triethanolamine, rosinamine, or mercaptan was used. For the pickling,
the sulfuric acid aqueous solution (volume concentration of sulfuric acid : 1 volume%)
20 was used. Herein, the comparative examples No. b15 to b17, the pickling was not
conducted.
[0107]
After removing the redundant annealing separator from the final annealed sheet,
the smoothing annealing for the final annealed sheet was conducted in the mixed gas
25 atmosphere at the baking temperature shown in Tables 8 to 10. By the smoothing
39
annealing, the surface of the final annealed sheet was smoothed.
[0108]
Thereafter, the insulation coating forming solution which mainly included the
phosphate or the colloidal silica and which included the chromic anhydride as necessary
5 was applied. In order to form the insulation coating, the above solution was baked at
the baking temperature shown in Tables 8 to 10, and then, was heat-treated at the
temperature shown in Tables 8 to 10.
[0109]
Moreover, in the examples, as shown in Tables 11 to 13, the magnetic domain
10 refining treatment was conducted at any timing of (first) between the cold rolling process
and the decarburization annealing process, (second) between the decarburization
annealing process and the annealing separator applying process, (third) between the
smoothing process and the insulation coating forming process, or (fourth) after the
insulation coating forming process. For the magnetic domain refinement, the groove
15 was formed mechanically or chemically, or the stress-strain or the groove was applied or
formed by the laser.
20
[0110]
For the obtained grain oriented electrical steel sheets Nos. B 1 to B46 and b 1 to
b33, the iron loss and the coating adhesion were evaluated.
[0111]

The samples were taken from the obtained grain oriented electrical steel sheets,
and the iron loss W17 /50 (W /kg) was measured under the conditions of 50 Hz of AC
frequency and 1. 7 T of excited magnetic flux density on the basis of the epstein test
25 regulated by JIS C2550-1: 2000. As for the grain oriented electrical steel sheets in
5
40
which the magnetic domain refinement was conducted, when the iron loss W17 /50 was
less than 0. 7 W /kg, it was judged to as acceptable. As for the grain oriented electrical
steel sheets in which the magnetic domain refinement was not conducted, when the iron
loss W17 /50 was less than 1.0 W /kg, it was judged to as acceptable.
[0112]
< Coating adhesion >
The samples were taken from the obtained grain oriented electrical steel sheets,
and the coating adhesion of the insulation coating was evaluated by rolling the sample
around the cylinder with 20 mm of diameter ( 180° bending) and by measuring the area
10 fraction of remained coating after bending back. In the evaluation of the coating
adhesion of the insulation coating, the presence or absence of delamination of the
insulation coating was visually evaluated. When the area fraction of remained coating
which was not delaminated from the steel sheet was 90% or more, it was regarded as @
(Very Good). When the area fraction was 85% or more and less than 90%, it was
15 regarded as o (Good). When the area fraction was 80% or more and less than 85%, it
was regarded as L. (Poor). When the area fraction was less than 80%, it was regarded
as x (NG). When the area fraction of remained coating was 85% or more (the above @
and o ), it was judged to as acceptable.
20
The results are shown in Tables 11 to 13.
[0113]
[Table 1]
41
STEEL CHEMICAL COMPOSITION (mass%) (BALANCE CONSISTING OF Fe AND IMPURITIES)
No. c Si Mn s Se S+Se AI N OTHER ELEMENTS
A1 0.030 3.45 0.10 0.006 0.006 0.022 0.008
A2 0.100 3.45 0.10 0.006 0.006 0.022 0.008
A3 0.060 0.80 0.10 0.006 0.006 0.022 0.008
A4 0.060 7.00 0.10 0.006 0.006 0.022 0.008
A5 0.060 3.45 0.01 0.006 0.006 0.022 0.008 Cu:0.15,. Ti:0.006
A6 0.060 3.45 1.00 0.006 0.020 0.026 0.022 0.008 B: 0.002,. Cr: 0.08,. V: 0.03
A7 0.060 3.45 0.10 0.004 0.002 0.006 0.022 0.008 P:0.10,. Nb:0.05
A8 0.060 3.45 0.10 0.050 0.010 0.060 0.022 0.008 Sn: 0.08,. Sb: 0.05,. Ni: 0.05
A9 0.060 3.45 0.10 0.006 0.006 0.010 0.008
A10 0.060 3.45 0.10 0.006 0.006 0.065 0.004
A11 0.060 3.45 0.10 0.006 0.006 0.022 0.012
A12 0.060 3.45 0.10 0.006 0.006 0.022 0.008
A13 0.080 3.25 0.08 0.025 0.001 0.026 0.022 0.007 Bi:0.004 .. Mo:0.03
a1 0.010 3.45 0.10 0.006 0.006 0.022 0.008
a2 0.400 3.45 0.10 0.006 0.006 0.022 0.008
a3 0.060 0.50 0.10 0.006 0.006 0.022 0.008
a4 0.060 9.00 0.10 0.006 0.006 0.022 0.008
a5 0.060 3.45 0.004 0.006 0.006 0.022 0.008 Cu:0.15,. Ti:0.006
a6 0.060 3.45 1.50 0.006 0.006 0.022 0.008 B :0.002 .. Cr:0.08 .. V:0.03
a7 0.060 3.45 0.10 0.070 0.070 0.022 0.008 P:0.10 .. Nb:0.05
a8 0.060 3.45 0.10 0.080 0.010 0.090 0.022 0.008 Sn: 0.08,. Sb: 0.05,. Ni: 0.05
a9 0.060 3.45 0.10 0.006 0.006 0.005 0.008
a10 0.060 3.45 0.10 0.006 0.006 0.080 0.001
a11 0.060 3.25 0.08 0.025 0.001 0.026 0.022 0.025 Bi: 0.004,. Mo: 0.03
[0114]
[Table 2]
42
DECARBURIZATION ANNEALING PROCESS ANNEALING SEPARATOR
APPLYING PROCESS
STEEL OXIDATION ANNEALING HOLDING MgO/ HYDRATION
No. No. DEGREE TEMPERATURE TIME (MgO+AI20 3) WATER
(-) (oC) (sec) (mass%) (mass%)
INVENTIVE 81 A 12 0.18 840 60 30 1.0
EXAMPLE 82 A12 0.80 840 60 30 1.0
83 A12 0.60 750 60 30 1.0
84 A12 0.60 900 60 30 1.0
85 A12 0.60 840 10 30 1.0
86 A12 0.60 840 600 30 1.0
87 A12 0.60 840 60 5 1.0
88 A12 0.60 840 60 50 1.0
89 A12 0.60 840 60 30 1.5
810 A 12 0.60 840 60 30 1.0
811 A12 0.60 840 60 30 1.0
812 A12 0.60 840 60 30 1.0
813 A12 0.60 840 60 30 1.0
814 A12 0.60 840 60 30 1.0
815 A12 0.60 840 60 30 1.0
816 A12 0.60 840 60 30 1.0
817 A 12 0.60 840 60 30 1.0
818 A 12 0.60 840 60 30 1.0
819 A 12 0.60 840 60 30 1.0
820 A12 0.60 840 60 30 1.0
821 A12 0.60 840 60 30 1.0
822 A12 0.60 840 60 30 1.0
823 A12 0.60 840 60 30 1.0
824 A12 0.60 840 60 30 1.0
825 A 12 0.60 840 60 30 1.0
826 A13 0.60 840 60 30 1.0
827 A 13 0.60 840 60 30 1.0
[0115]
[Table 3]
43
DECARBURIZATION ANNEALING PROCESS ANNEALING SEPARATOR
APPLYING PROCESS
STEEL OXIDATION ANNEALING HOLDING MgO/ HYDRATION
No. No. DEGREE TEMPERATURE TIME (MgO+AI20 3) WATER
(-) (oC) (sec) (mass%) (mass%)
INVENTIVE 828 A 13 0.60 840 60 30 1.0
EXAMPLE 829 A12 0.60 840 60 40 1.0
830 A12 0.60 840 60 30 1.0
831 A12 0.60 840 60 20 1.0
832 A13 0.60 840 60 40 1.0
833 A13 0.60 840 60 30 1.0
834 A 13 0.60 840 60 20 1.0
835 A1 0.60 840 60 30 1.0
836 A2 0.60 840 60 30 1.0
837 A3 0.60 840 60 30 1.0
838 A4 0.60 840 60 30 1.0
839 A5 0.60 840 60 30 1.0
840 A6 0.60 840 60 30 1.0
841 A7 0.60 840 60 30 1.0
842 AS 0.60 840 60 30 1.0
843 A9 0.60 840 60 30 1.0
844 A10 0.60 840 60 30 1.0
845 A 11 0.60 840 60 30 1.0
846 A 12 0.60 840 60 30 1.0
COMPARATIVE b1 A12 0.05 840 60 30 1.0
EXAMPLE b2 A12 0.98 840 60 30 1.0
b3 A12 0.60 600 60 30 1.0
b4 A12 0.60 1100 60 30 1.0
b5 A12 0.60 840 9. 30 1.0
b6 A12 0.60 840 800 30 1.0
b7 A12 0.60 840 60 ~ 1.0
b8 A12 0.60 840 60 60 1.0
[0116]
[Table 4]
44
DECARBURIZATION ANNEALING PROCESS ANNEALING SEPARATOR
APPLYING PROCESS
STEEL OXIDATION ANNEALING HOLDING MgO/ HYDRATION
No. No. DEGREE TEMPERATURE TIME (MgO+AI20 3) WATER
(-) (oC) (sec) (mass%) (mass%)
COMPARATIVE b9 A12 0.60 840 60 30 3.0
EXAMPLE b10 A12 0.60 840 60 30 1.0
b11 A12 0.60 840 60 30 1.0
b12 A12 0.60 840 60 30 1.0
b13 A12 0.60 840 60 30 1.0
b14 A12 0.60 840 60 30 1.0
b15 A 12 0.60 840 60 30 1.0
b16 A 12 0.60 840 60 30 1.0
b17 A 12 0.60 840 60 30 1.0
b18 A 12 0.60 840 60 30 1.0
b19 A 12 0.60 840 60 30 1.0
b20 A 12 0.60 840 60 30 1.0
b21 A12 0.60 840 60 30 1.0
b22 a1 0.60 840 60 30 1.0
b23 a2 0.60 840 60 30 1.0
b24 a3 0.60 840 60 30 1.0
b25 a4 - - - - -
b26 a5 0.60 840 60 30 1.0
b27 a6 0.60 840 60 30 1.0
b28 a7 0.60 840 60 30 1.0
b29 a8 0.60 840 60 30 1.0
b30 a9 0.60 840 60 30 1.0
b31 a10 0.60 840 60 30 1.0
b32 a11 0.60 840 60 30 1.0
b33 a10 0.60 840 60 30 1.0
[0117]
[Table 5]
45
FINAL ANNEALING PROCESS ANNEALING SEPARATOR REMOVING PROCESS
STEEL TEMPERATURE ATMOSPHERIC HOLDING TYPE OF PICKLING AMOUNT OF
No. No. GAS *1 TIME SOLUTION (YES HYDROXIDE *2 (oC) (vol%) (h) OR NO) (g/m2)
INVENTIVE 81 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
EXAMPLE 82 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
83 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
84 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
85 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
86 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
87 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
88 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
89 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
810 A12 1200 50 20 TRIETHANOLAMINE YES 0.2
811 A12 1200 75 10 TRIETHANOLAMINE YES 0.2
812 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
813 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
814 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
815 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
816 A12 1200 75 20 TRIETHANOLAMINE YES 0.9
817 A12 1200 75 20 ROSINAMINE YES 0.9
818 A12 1200 75 20 MERCAPTAN YES 0.9
819 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
820 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
821 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
822 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
823 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
824 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
825 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
826 A13 1200 75 20 TRIETHANOLAMINE YES 0.2
827 A13 1200 75 20 TRIETHANOLAMINE YES 0.2
~1 :MIXED GAS ATMOSPHERE OF HYDROGEN AND NITROGEN (SHOWN AS NITROGEN FRACTION)
~2:AMOUNT OF IRON HYDROXIDE AND IRON OXIDE (PER A SIDE)
[0118]
[Table 6]
46
FINAL ANNEALING PROCESS ANNEALING SEPARATOR REMOVING PROCESS
STEEL TEMPERATURE ATMOSPHERIC HOLDING TYPE OF PICKLING AMOUNT OF
No. No. GAS *1 TIME SOLUTION (YES HYDROXIDE
:>.<:2
(oC) (vol%) (h) OR NO) (g/m2)
INVENTIVE 828 A13 1200 75 20 TRIETHANOLAMINE YES 0.2
EXAMPLE 829 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
830 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
831 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
832 A13 1200 75 20 TRIETHANOLAMINE YES 0.2
833 A13 1200 75 20 TRIETHANOLAMINE YES 0.2
834 A13 1200 75 20 TRIETHANOLAMINE YES 0.2
835 A1 1200 75 20 TRIETHANOLAMINE YES 0.2
836 A2 1200 75 20 TRIETHANOLAMINE YES 0.2
837 A3 1100 75 20 TRIETHANOLAMINE YES 0.2
838 A4 1200 75 20 TRIETHANOLAMINE YES 0.2
839 A5 1200 75 20 TRIETHANOLAMINE YES 0.2
840 A6 1200 75 20 TRIETHANOLAMINE YES 0.2
841 A7 1200 75 20 TRIETHANOLAMINE YES 0.2
842 A8 1200 75 20 TRIETHANOLAMINE YES 0.2
843 A9 1200 75 20 TRIETHANOLAMINE YES 0.2
844 A10 1200 75 20 TRIETHANOLAMINE YES 0.2
845 A 11 1200 75 20 TRIETHANOLAMINE YES 0.2
846 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
COMPARATIVE b1 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
EXAMPLE
b2 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b3 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b4 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b5 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b6 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b7 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b8 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
~1 :MIXED GAS ATMOSPHERE OF HYDROGEN AND NITROGEN (SHOWN AS NITROGEN FRACTION)
~2:AMOUNT OF IRON HYDROXIDE AND IRON OXIDE (PER A SIDE)
[0119]
[Table 7]
47
FINAL ANNEALING PROCESS ANNEALING SEPARATOR REMOVING PROCESS
STEEL TEMPERATURE ATMOSPHERIC HOLDING TYPE OF PICKLING AMOUNT OF
No. No. GAS *1 TIME SOLUTION (YES HYDROXIDE *2 (oC) (vol%) (h) OR NO) (g/m2)
COMPARATIVE b9 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
EXAMPLE b10 A12 1200 30 20 TRIETHANOLAMINE YES 0.2
b11 A12 1200 75 .2 TRIETHANOLAMINE YES 0.2
b12 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b13 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b14 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b15 A12 1200 75 20 TRIETHANOLAMINE NO .1.2
b16 A12 1200 75 20 ROSINAMINE NO .1.2
b17 A12 1200 75 20 MERCAPTAN NO .1.2
b18 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b19 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b20 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b21 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b22 a1 1200 75 20 TRIETHANOLAMINE YES 0.2
b23 a2 1200 75 20 TRIETHANOLAMINE YES 0.2
b24 a3 1100 75 20 TRIETHANOLAMINE YES 0.2
b25 a4 - - - - - -
b26 a5 1200 75 20 TRIETHANOLAMINE YES 0.2
b27 a6 1200 75 20 TRIETHANOLAMINE YES 0.2
b28 a7 1200 75 20 TRIETHANOLAMINE YES 0.2
b29 aS 1200 75 20 TRIETHANOLAMINE YES 0.2
b30 a9 1200 75 20 TRIETHANOLAMINE YES 0.2
b31 a10 1200 75 20 TRIETHANOLAMINE YES 0.2
b32 a11 1200 75 20 TRIETHANOLAMINE YES 0.2
b33 a10 1200 75 20 TRIETHANOLAMINE YES 0.2
~1 :MIXED GAS ATMOSPHERE OF HYDROGEN AND NITROGEN (SHOWN AS NITROGEN FRACTION)
~2:AMOUNT OF IRON HYDROXIDE AND IRON OXIDE (PER A SIDE)
[0120]
[Table 8]
48
SMOOTHING PROCESS INSULATION COATING FORMING PROCESS
STEEL ATMOSPHERIC GAS ANNEALING BAKING HEAT
No. No. TYPE VOLUME TEMPERATURE TEMPERATURE TREATMENT
OF GAS FRACTION TEMPERATURE
(oC) (oC) (oC)
INVENTIVE 81 A12 H2 100 1200 400 850
EXAMPLE 82 A12 H2 100 1200 400 850
83 A12 H2 100 1200 400 850
84 A12 H2 100 1200 400 850
85 A12 H2 100 1200 400 850
86 A12 H2 100 1200 400 850
87 A12 H2 100 1200 400 850
88 A12 H2 100 1200 400 850
89 A12 H2 100 1200 400 850
810 A12 H2 100 1200 400 850
811 A12 H2 100 1200 400 870
812 A12 co 100 1200 400 870
813 A12 CO/N2 50/50 1200 400 870
814 A12 H2/N2 50/50 1200 400 870
815 A12 H2 100 1000 450 870
816 A12 H2 100 1200 450 870
817 A12 H2 100 1200 450 870
818 A12 H2 100 1200 450 870
819 A12 H2 100 1200 350 870
820 A12 H2 100 1200 600 870
821 A12 H2 100 1200 450 800
822 A12 H2 100 1200 450 1000
823 A12 H2 100 1200 450 850
824 A12 H2 100 1200 450 850
825 A12 H2 100 1200 450 850
826 A13 H2 100 1200 450 850
827 A13 H2 100 1200 450 850
[0121]
[Table 9]
49
SMOOTHING PROCESS INSULATION COATING FORMING PROCESS
STEEL ATMOSPHERIC GAS ANNEALING BAKING HEAT
No. No. TYPE VOLUME TEMPERATURE TEMPERATURE TREATMENT
OF GAS FRACTION TEMPERATURE
(oC) (oC) (oC)
INVENTIVE 828 A13 H2 100 1200 450 850
EXAMPLE 829 A12 H2 100 1200 450 870
830 A12 H2 100 1200 400 870
831 A12 H2 100 1200 400 850
832 A13 H2 100 1200 450 870
833 A13 H2 100 1200 400 850
834 A13 H2 100 1200 400 850
835 A1 H2 100 1200 400 870
836 A2 H2 100 1200 400 870
837 A3 H2 100 1200 400 870
838 A4 H2 100 1200 400 870
839 A5 H2 100 1200 400 870
840 A6 H2 100 1200 400 870
841 A7 H2 100 1200 400 870
842 AS H2 100 1200 400 870
843 A9 H2 100 1200 400 870
844 A10 H2 100 1200 400 870
845 A 11 H2 100 1200 400 870
846 A12 H2 100 1200 400 870
COM PARA Tl VE b1 A12 H2 100 1200 400 850
EXAMPLE b2 A12 H2 100 1200 400 850
b3 A12 H2 100 1200 400 850
b4 A12 H2 100 1200 400 850
b5 A12 H2 100 1200 400 850
b6 A12 H2 100 1200 400 850
b7 A12 H2 100 1200 400 850
b8 A12 H2 100 1200 400 850
[0122]
[Table 10]
50
SMOOTHING PROCESS INSULATION COATING FORMING PROCESS
STEEL ATMOSPHERIC GAS ANNEALING BAKING HEAT
No. No. TYPE VOLUME TEMPERATURE TEMPERATURE TREATMENT
OF GAS FRACTION TEMPERATURE
(oC) (oC) (oC)
COMPARATIVE b9 A12 H2 100 1200 400 850
EXAMPLE b10 A12 H2 100 1200 400 850
b11 A12 H2 100 1200 400 850
b12 A12 CO/N2 30/70 1200 400 850
b13 A12 H2/N2 30/70 1200 400 850
b14 A12 H2 100 800 400 850
b15 A12 H2 100 1200 400 850
b16 A12 H2 100 1200 400 850
b17 A12 H2 100 1200 400 850
b18 A12 H2 100 1200 300 850
b19 A12 H2 100 1200 800 850
b20 A12 H2 100 1200 400 700
b21 A12 H2 100 1200 400 1050
b22 a1 H2 100 1200 400 870
b23 a2 H2 100 1200 400 870
b24 a3 H2 100 1200 400 870
b25 a4 - - - - -
b26 a5 H2 100 1200 400 870
b27 a6 H2 100 1200 400 870
b28 a7 H2 100 1200 400 870
b29 a8 H2 100 1200 400 870
b30 a9 H2 100 1200 400 870
b31 a10 H2 100 1200 400 870
b32 a11 H2 100 1200 400 870
b33 a10 H2 100 1200 400 870
[0123]
[Table 11]
51
MAGNETIC DOMAIN REFINEMENT IRON LOSS COATING
STEEL TIMING FOR METHOD W17/50 ADHESION
No. No. CONTROLLING
(W/kg)
INVENTIVE 81 A12 FOURTH LASER I RRAD IA TI ON 0.68 0 EXAMPLE 82 A12 FOURTH I RRALDA SIAER T I ON 0.69 0
83 A12 FOURTH I RRALDA SIAERT ION 0.68 0
84 A12 FOURTH I RRALDA SIAER T I ON 0.69 0
85 A12 FOURTH I RRALDA SIAERT ION 0.69 0
86 A12 FOURTH I RRALDA SIAERT ION 0.68 0
87 A12 FOURTH I RRALDA SIAER T I ON 0.69 0
88 A12 FOURTH I RRALDA SIAERT ION 0.69 0
89 A12 FOURTH I RRALDA SIAER T I ON 0.69 0
810 A12 FOURTH I RRALDA SIAER T I ON 0.68 0
811 A12 FOURTH I RRALDA SIAERT ION 0.68 0
812 A12 FOURTH IRRk~t~~ION 0.67 0
813 A12 FOURTH I RRALDA SIAERT ION 0.69 0
814 A12 FOURTH I RRALDA SIAERT ION 0.67 0
815 A12 FOURTH I RRALDA SIAER T I ON 0.68 0
816 A12 FOURTH I RRALDA SIAERT ION 0.68 0
817 A12 FOURTH IRRk~Y~~ION 0.69 0
818 A12 FOURTH I RRALDA SIAER T I ON 0.68 0
819 A12 FOURTH I RRALDA SIAERT ION 0.68 0
820 A12 FOURTH I RRALDA SIAER T I ON 0.67 0
821 A12 FOURTH I RRALDA SIAERT ION 0.69 0
822 A12 FOURTH I RRALDA SIAER T I ON 0.69 0
823 A12 FIRST GROMOEVCEH AFNOICRAMLIN G 0.65 @
824 A12 SECOND GROMOEVCEH AFNOICRAMLIN G 0.64 @
825 A12 THIRD GROMOEVCEH AFNOICRAMLIN G 0.65 @
826 A13 FIRST GROOCHVEE MFICOARLM ING 0.67 @
827 A13 SECOND GROOCHVEE MFICOARLM ING 0.66 @
[0124]
[Table 12]
52
MAGNETIC DOMAIN REFINEMENT IRON LOSS COATING
STEEL TIMING FOR METHOD W17/50 ADHESION
No. No. CONTROLLING
(W/kg)
INVENTIVE 828 A13 THIRD GRo~O~M~~~~ING 0.64 @
EXAMPLE 829 A12 FOURTH IRR~Sy~~ION 0.63 @
830 A12 FOURTH IRR~Sy~~ION 0.65 @
831 A12 FOURTH IRRk~1~~ION 0.64 @
832 A13 FOURTH IRR~Sy~~ION 0.65 @
833 A13 FOURTH IRRk~Y~~ION 0.66 @
834 A13 FOURTH IRRk~1~~ION 0.64 @
835 A1 FOURTH IRR~Sy~~ION 0.68 0
836 A2 FOURTH LASER IR RAD IAT ION 0.69 0
837 A3 FOURTH IR RALDA SIAER T I ON 0.68 0
838 A4 FOURTH LASER
IRRADIATION 0.67 0
839 A5 FOURTH IRRk~1~~ION 0.66 0
840 A6 FOURTH LASER IR RAD IA TI ON 0.68 0
841 A7 FOURTH IR RALDA SIAERT ION 0.69 0
842 A8 FOURTH IR RALDA SIAER T I ON 0.68 0
843 A9 FOURTH IR RALDA SIAER T I ON 0.69 0
844 A10 FOURTH IRR~Sy~~ION 0.67 0
845 A 11 FOURTH IR RALDA SIAER T I ON 0.68 0
846 A12 NO - 0.95 @
COMPARATIVE b1 A12 FOURTH IR RALDA SIAER T I ON 1.16 !:::.. EXAMPLE b2 A12 FOURTH IR RALDA SIAER T I ON 1.08 !:::..
b3 A12 FOURTH IR RALDA SIAERT ION 1.45 !:::..
b4 A12 FOURTH LASER
IRRADIATION 1.27 !:::..
b5 A12 FOURTH IRRk~?~~ION 1.16 !:::..
b6 A12 FOURTH LASER
IRRADIATION 0.94 !:::..
b7 A12 FOURTH LASER
IRRADIATION 1.02 !:::..
b8 A12 FOURTH LASER
IRRADIATION 0.97 !:::..
[0125]
[Table 13]
53
MAGNETIC DOMAIN REFINEMENT IRON LOSS COATING
STEEL TIMING FOR METHOD W17/50 ADHESION
No. No. CONTROLLING
(W/kg)
COMPARATIVE b9 A12 FOURTH IRRkfl1~~ION 0.84 ~
EXAMPLE b10 A12 FOURTH IRRkS~~~ION 1.04 ~
b11 A12 FOURTH IRRkfly~~ION 1.08 ~
b12 A12 FOURTH IRRkfl1~~ION 1.10 ~
b13 A12 FOURTH IRRkfly~~ION 1.07 ~
b14 A12 FOURTH IRRkfly~~ION 1.06 ~
b15 A12 FOURTH IRRkfl1~~ION 1.12 ~
b16 A12 FOURTH IRRkfly~~ION 1.15 ~
b17 A12 FOURTH IRRkfly~~ION 1.13 ~
b18 A12 FOURTH IRRk~t~~ION 0.82 X
b19 A12 FOURTH IRRkfly~~ION 0.85 X
b20 A12 FOURTH LASER IR RAD IA TI ON 0.78 X
b21 A12 FOURTH LASER IR RAD IAT ION 0.81 X
b22 a1 FOURTH IR RALDA SIAER T I ON 0.79 0
b23 a2 FOURTH LASER IR RAD IAT ION 0.78 0
b24 a3 FOURTH IR RALDA SIAER T I ON 0.76 0
b25 a4 - - - -
b26 a5 FOURTH IR RALDA SIAER T I ON 0.95 0
b27 a6 FOURTH IR RALDA SIAER T I ON 1.12 0
b28 a7 FOURTH IR RALDA SIAERT ION 1.05 0
b29 a8 FOURTH IR RALDA SIAER T I ON 1.06 0
b30 a9 FOURTH IR RALDA SIAERT ION 0.97 0
b31 a10 FOURTH IRRk~t~~ION 1.08 0
b32 a11 FOURTH IR RALDA SIAERT ION 0.93 0
b33 a10 NO - 1.38 0
[0126]
As shown in Tables 1 to 13, in the inventive examples Nos. B1 to B46, all
process conditions satisfied the range of the present invention, and thus, the iron loss was
5 low. Moreover, the coating adhesion was excellent.
On the other hand, in the comparative examples Nos. b1 to b33, at least one of
the process conditions was out of the range of the present invention, and thus, the iron
loss and/or the coating adhesion was insufficient. Herein, in the comparative example
5
54
No. b25, the rolling could not be conducted, the evaluation thereafter was not conducted.
Industrial Applicability
[0127]
According to the above aspects of the present invention, it is possible to provide
the method for producing the grain oriented electrical steel sheet without the forsterite
film and excellent in the magnetic characteristics and the coating adhesion. The
obtained grain oriented electrical steel sheet is excellent in the magnetic characteristics
and the coating adhesion, and therefore, the present invention has significant industrial
10 applicability.

WE CLAIMS

1. A method for producing a grain oriented electrical steel sheet,
the method comprising:
a hot rolling process of hot-rolling a steel piece to obtain a hot rolled steel sheet,
the steel piece including, as a chemical composition, by mass%,
0.030 to 0.100% of C,
0.80 to 7.00% of Si,
0.01 to 1.00% of Mn,
0 to 0.060% in total of S and Se,
0.010 to 0.065% of acid soluble Al,
0.004 to 0.012% ofN,
0 to 0.30% of Cr,
0 to 0.40% of Cu,
0 to 0.50% of P,
0 to 0.30% of Sn,
0 to 0.30% of Sb,
0 to 1.00% ofNi,
0 to 0.008% ofB,
0 to 0.15% ofV,
0 to 0.20% of Nb,
0 to 0.10% ofMo,
0 to 0.015% of Ti,
0 to 0.010% ofBi, and
56
a balance consisting of Fe and impurities;
a cold rolling process of cold-rolling the hot rolled steel sheet to obtain a cold
rolled steel sheet;
a decarburization annealing process of decarburization -annealing the cold rolled
5 steel sheet to obtain a decarburization annealed sheet;
10
an annealing separator applying process of applying and drying an annealing
separator including Ah03 and MgO to the decarburization annealed sheet;
a final annealing process of final-annealing the decarburization annealed sheet
after applying the annealing separator to obtain a final annealed sheet;
an annealing separator removing process of removing a redundant annealing
separator from a surface of the final annealed sheet;
a smoothing process of smoothing the surface of the final annealed sheet after
removing the redundant annealing separator; and
an insulation coating forming process of forming an insulation coating on the
15 surface of the final annealed sheet after being smoothed,
20
wherein, in the decarburization annealing process,
PH20/PH2 which is an oxidation degree of an atmosphere is 0.18 to 0.80, an
annealing temperature is 750 to 900°C, and a holding is 10 to 600 seconds,
wherein, in the annealing separator applying process,
MgO I (MgO + Ah03) which is a mass ratio of MgO and Ah03 is 5 to 50%, and
a hydration water is 1.5 mass% or less in the annealing separator,
wherein, in the final annealing process,
the decarburization annealed sheet after applying the annealing separator is held
at 1100 to 1200°C for 10 hours or more in a mixed gas atmosphere including 50
25 volume% or more of a hydrogen,
57
wherein, in the annealing separator removing process,
the final annealed sheet is water-washed using a solution with an inhibitor which
is at least one of a triethanolamine, a rosinamine, or a mercaptan,
the final annealed sheet after water-washing is pickled using an acidic solution
5 whose volume concentration is less than 20%, and
an amount of an iron hydroxide and an iron oxide on the surface of the final
annealed sheet is controlled to 0.9 g/m2 or less per a side,
wherein, in the smoothing process,
the final annealed sheet after removing the redundant annealing separator is
10 annealed at 1 000°C or more in a mixed gas atmosphere including 50 volume% or more
of a hydrogen or a carbon monoxide, and
wherein, in the insulation coating forming process,
the insulation coating is formed on the surface of the final annealed sheet after
being smoothed by applying an insulation coating forming solution which mainly
15 includes a phosphate or a colloidal silica, by baking at 350 to 600°C, and then by
heat-treating at 800 to 1000°C.
20
25
2. The method for producing the grain oriented electrical steel sheet according to
claim 1,
the method including, between the hot rolling process and the cold rolling
process,
at least one of a hot band annealing process of annealing the hot rolled steel
sheet or a hot band pickling process of pickling the hot rolled steel sheet.
3. The method for producing the grain oriented electrical steel sheet according to
58
claim 1 or 2,
wherein, in the decarburization annealing process, a nitriding treatment is
conducted by annealing the cold rolled steel sheet in an atmosphere including ammonia.
5 4. The method for producing the grain oriented electrical steel sheet according to
any one of claims 1 to 3,
the method including, between the cold rolling process and the decarburization
annealing process, between the decarburization annealing process and the annealing
separator applying process, between the smoothing process and the insulation coating
10 forming process, or after the insulation coating forming process,
a magnetic domain refining process of conducting a magnetic domain refining
treatment.
5. The method for producing the grain oriented electrical steel sheet according to
15 any one of claims 1 to 4,
20
25
wherein, the steel piece includes, as the chemical composition, by mass%, at
least one selected from a group consisting of
0.02 to 0.30% of Cr,
0.05 to 0.40% of Cu,
0.005 to 0.50% of P,
0.02 to 0.30% of Sn,
0.01 to 0.30% of Sb,
0.01 to 1.00% of Ni,
0.0005 to 0.008% of B,
0.002 to 0.15% ofV,
5
0.005 to 0.20% of Nb,
0.005 to 0.10% ofMo,
0.002 to 0.015% ofTi, and
0.001 to 0.010% ofBi.