[0001]The present invention relates to a method for producing a grain oriented
electrical steel sheet.
Priority is claimed on Japanese Patent Application No. 2019-005085, 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 in order to remove the
redundant annealing separator from the surface thereof, and an amount of an iron
hydroxide and an iron oxide on the surface thereof is controlled to 0.9 g/m2 or less per a
15 side,
20
wherein, in the smoothing process,
the final annealed sheet after removing the redundant annealing separator is
chemical-polished, and an average roughness Ra of the surface thereof is controlled to
0.1 ~m or less, and
wherein, in the insulation coating forming process,
an insulation coating forming solution in which a phosphate, a colloidal silica,
and a crystalline phosphide are included is applied and is baked at 350 to 1150°C, and
after decreasing a temperature, an insulation coating forming solution in which the
phosphate and the colloidal silica are included and in which the crystalline phosphide is
25 not included is applied and is baked at 350 to 1150°C, in order to form the insulation
5
8
coating.
(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),
25
in the annealing separator removing process, a pickling may be conducted after
water-washing using an acidic solution whose volume concentration is less than 20%.
( 6) In the method for producing the grain oriented electrical steel sheet
according to any one of (1) to (5),
the steel piece may include, as the chemical composition, by mass%, at least one
9
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,
5 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,
10 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.
15 Effects of Invention
20
25
[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
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
electrical steel sheet according to an embodiment of the present invention.
10
Detailed Description of Preferred Embodiments
[0020]
Hereinafter, a preferable embodiment of the present invention is described in
detail. However, the present invention is not limited only to the configuration which is
5 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.
"%"of the amount of respective elements expresses "mass%".
10 [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
method for producing the grain oriented electrical steel sheet without a forsterite film and
15 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
once or by cold-rolling plural times with an intermediate annealing to obtain a cold rolled
20 steel sheet.
25
(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
separator including Ah03 and MgO to the decarburization annealed sheet.
( v ) Final annealing process of final-annealing the decarburization annealed
11
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.
( vii ) Smoothing process of smoothing the surface of the final annealed sheet
5 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
10 according to the embodiment may further include the following processes.
15
( 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
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
20 possible to reduce the iron loss and improve the coating adhesion.
[0024]
Hereinafter, each process is described in detail.
[0025]
< Hot rolling process >
25 In the hot rolling process, the steel piece is hot-rolled to obtain the hot rolled
5
10
15
20
12
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,
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
25 composition may be made, and the slab may be made by using the molten steel. The
5
10
13
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
be made by other methods.
[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
used.
[0028]
Limitation reasons of the chemical composition of the steel piece are explained.
Hereinafter,"%" of the chemical composition represents "mass%".
[0029]
( 0.030 to 0.100% ofC)
C (carbon) is an element effective in controlling the primary recrystallized
15 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
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.
20 [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
lower limit of the C content is substantially 0.030%.
[0031]
25 ( 0.80 to 7.00% of Si )
14
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
transformation occurs during the final annealing and the crystal orientation of grain
oriented electrical steel sheet is impaired. Thus, the Si content is to be 0.80% or more.
5 The Si content is preferably 2.00% or more, and more preferably 2.50% or more.
10
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
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
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
15 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
preferably 0.20%.
[0033]
20 ( 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,
25 the desired secondary recrystallized structure cannot be obtained, and the magnetic flux
15
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
0.060% or less.
The lower limit of the total amount of S and Se is not particular! y limited, and
5 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]
( 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
10 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.
The amount of acid soluble Al is preferably 0.015% or more, and more preferably
0.020% or more.
15 [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
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
20 amount of acid soluble Al is preferably 0.055% or less, and more preferably 0.050% or
less.
[0036]
( 0.004 to 0.012% of N)
N (nitrogen) is an element to form AlN and/or (Al, Si)N which act as the
25 inhibitor by bonding to Al. When theN content is less than 0.004%, the formation of
16
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
more.
On the other hand, when theN content is more than 0.012%, the blisters (voids)
5 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
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
10 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
elements do not need to be included, the lower limits thereof may be 0% respectively.
Moreover, even if the optional elements may be included as impurities, the above
15 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.
20
[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
preferably 0.05% or more.
On the other hand, when the Cr content is more than 0.30%, the magnetic flux
25 density may deteriorate. Thus, the upper limit of the Cr content is preferably 0.30%,
17
more preferably 0.20%, and further more preferably 0.12%.
[0039]
( 0 to 0.40% of Cu )
Cu (copper) is also an element effective in increasing the electric resistance, and
5 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"
10 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]
( 0 to 0.50% ofP)
P (phosphorus) is also an element effective in increasing the electric resistance,
15 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
20 0.20%, and further more preferably 0.15%.
[0041]
( 0 to 0.30% of Sn )
( 0 to 0.30% of Sb )
Sn (tin) and Sb (antimony) are elements effective in stabilizing the secondary
25 recrystallization, and thereby, developing the { 110}<001> orientation. Thus, Sn and Sb
18
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
preferably 0.01% or more, and more preferably 0.03% or more.
On the other hand, when the Sn content is more than 0.30% or when the Sb
5 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%.
Moreover, the upper limit of the Sb content is preferably 0.15%, and more preferably
0.10%.
10 [0042]
( 0 to 1.00% ofNi)
Ni (nickel) is also an element effective in increasing the electric resistance, and
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
15 magnetic characteristics. Thus, Ni may be included. In order to obtain the above
20
25
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
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
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.
On the other hand, when the B content is more than 0.008%, the magnetic
19
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)
5 ( 0 to 0.20% ofNb)
( 0 to 0.015% of Ti)
V (vanadium), Nb (niobium), and Ti (titanium) are elements which act as the
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
10 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.
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
15 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
product (grain oriented electrical steel sheet) may deteriorate.
Thus, the upper limit of the V content is preferably 0.15%, more preferably
20 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
more preferably 0.08%.
[0045]
25 ( 0 to 0.10% ofMo)
5
10
20
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
obtain the above effects, the Mo content is preferably 0.005% or more, and more
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
preferably 0.002% or more.
On the other hand, when the Bi content is more than 0.010%, the magnetic
15 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
20 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
dissolving the sample in acid. In addition, C and S may be measured by the infrared
absorption method after combustion, N may be measured by the thermal conductometric
25 method after fusion in a current of inert gas, and 0 may be measured by, for instance, the
21
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.
The conditions of the hot rolling are not particularly limited. For instance, the
5 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
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
10 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
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
15 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.
[0049]
In addition, as another method, the slab is heated to higher temperature of
20 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.
22
[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
and a final rolling mill which is arranged downstream of the rough rolling mill. The
5 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
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
10 sheet is obtained.
15
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
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
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
20 is referred to as the hot band annealed sheet.
[0052]
The hot band annealing is conducted in order to homogenize the nonuniform
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.
25 As the annealing conditions, known conditions may be applied according to the purpose.
23
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
temperature in a hot band annealing furnace) for 30 to 600 seconds.
The hot band annealing is not always necessary. The hot band annealing may
5 be conducted as a result of considering the characteristics and the producing cost required
for the grain oriented electrical steel sheet finally produced.
[0053]
< Hot band pickling process >
In the hot band pickling process, as necessary, the hot rolled steel sheet after the
10 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
conditions may be appropriate! y applied.
[0054]
15 < 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
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
20 rolling process is referred to as the cold rolled steel sheet.
[0055]
A cold rolling reduction rate in final cold rolling (cumulative cold rolling
reduction rate without intermediate annealing or cumulative cold rolling reduction rate
after intermediate annealing) is preferably 80% or more, and more preferably 90% or
25 more. The upper limit of the final cold rolling reduction rate is preferably 95%.
5
24
[0056]
Herein, the final cold rolling reduction rate(%) is defined as follows.
Final cold rolling reduction rate (%) = ( 1 - Sheet thickness of steel sheet after
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
rolling process is subjected to the magnetic domain refining treatment as necessary, and
then, is decarburization -annealed to promote the primary recrystallization. Moreover, in
10 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.
[0058]
For the above purposes, in the decarburization annealing, PH20/PH2 which is
15 the oxidation degree of 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
PH20IPH2 is defined as the ratio of water vapor partial pressure PH20 (atm) to hydrogen
partial pressure PH2 (atm) in the atmosphere.
20
25
[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
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, the decarburization does not
5
10
15
25
occur properly, and thereby, the magnetic characteristics after the final annealing
deteriorate. On the other hand, when the annealing temperature is more than 900°C, the
grain size after the primary recrystallization exceeds favorable size, and thereby, the
magnetic characteristics after the final annealing deteriorate.
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
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
holding. In a case where the temperature for heating the slab is lower, it is preferable
20 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 prior to the secondary recrystallization
in the final annealing process, and thus, it is possible to make the secondary
recrystallization occur stably.
25 [0062]
26
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
5 nitriding treatment may be conducted so that the nitrogen content becomes 0.030% or
less.
10
[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
15 (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]
20
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
25 decarburization annealed sheet. Thereafter, the applied annealing separator is dried.
27
[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
5 include MgO, mullite (3Ah03 · 2Si02) is formed on the steel sheet. The mullite
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
10 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.
15
20
25
[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]
28
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
5 which nitride the decarburization annealed sheet or the decarburized and nitrided sheet.
[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
10 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.
15
[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
20 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
25 sheet) by water-washing. Here, the redundant annealing separator indicates, for
29
instance, the unreacted annealing separator which has not reacted with the steel sheet
during the final annealing.
[0072]
In the case, in order to prevent the iron after water-washing from corroding, the
5 redundant annealing separator is removed by washing using the solution including the
inhibitor (corrosion prevention agent) which is at least one of triethanolamine,
rosinamine, or mercaptan. It is important to control the total amount of iron hydroxide
and iron oxide on the steel sheet surface to 0.9 g/m2 or less per a side, by conducting the
above washing.
10 [0073]
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
on the steel sheet surface is more than 0.9 g/m2 per a side, the exposure of the base steel
sheet surface may be insufficient, and thus, the steel sheet surface may not be controlled
15 to be a mirror like surface sufficient! y. 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.
[0074]
In order to remove the redundant annealing separator, a scrubber may be utilized
20 in addition to the washing using the solution including the above inhibitor. By utilizing
the scrubber, it is possible to reliably remove the redundant annealing separator which
deteriorates the wettability in the insulation coating forming process.
[0075]
Moreover, in a case where the redundant annealing separator is not sufficiently
25 removed even when the above washing is conducted, the pickling may be conducted after
30
water-washing. When the pickling is conducted, the pickling may be conducted using
the acidic solution whose volume concentration is less than 20%. In a case where the
pickling is conducted, it is preferable to utilize the solution including less than 20
volume% in total of at least one of sulfuric acid, nitric acid, hydrochloric acid,
5 phosphoric acid, chloric acid, chromium oxide in aqueous solution, chromate acid
mixture, permanganic acid, peroxosulfuric acid, and peroxophosphoric acid. It is more
preferable to utilize the solution including less than 10 volume% thereof. The lower
limit of the volume concentration is not particularly limited, but may be 0.1 volume% for
instance. By utilizing the above solution, it is possible to efficiently remove the
10 redundant annealing separator from the surface of the steel sheet. Herein, the above
volume% may be the concentration based on the volume at room temperature.
[0076]
Moreover, in a case where the pickling is conducted, the temperature of the
solution is preferably 20 to 80°C. By controlling the temperature of the solution to be
15 within the above range, it is possible to efficiently remove the redundant annealing
separator from the surface of the steel sheet.
[0077]
< Smoothing process >
The base steel sheet is exposed by conducting the above water-washing, and
20 thereafter, the average roughness Ra is controlled to 0.10 ~m or less by conducting the
chemical polishing, in order to obtain the final annealed sheet whose surface (base steel
sheet surface) is smoothed. The lower limit of the average roughness Ra is not
particularly limited, but may be 0.01 ~m for instance.
[0078]
25 One of the known chemical polishing to obtain the smoothed surface is
31
electrolytic polishing. As a method of the electrolytic polishing, for instance, the
polishing may be electrically conducted in the electrolytic solution of phosphoric acid
and chromic anhydride, in order to smooth the steel sheet surface. Moreover, the
solution obtained by adding a small amount of hydrofluoric acid to hydrogen peroxide
5 solution may be used.
[0079]
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
10 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.
[0080]
15 < 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
embodiment, the steel sheet after the insulation coating forming process is referred to as
20 the grain oriented electrical steel sheet.
[0081]
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
interlaminar electrical insulation when the grain oriented electrical steel sheets are
25 utilized after being laminated, and thereby, reduces the iron loss as an iron core.
32
[0082]
In order to form the insulation coating on the surface of the final annealed sheet,
the insulation coating forming solution (insulation coating forming solution 1) in which
phosphate, colloidal silica, and crystalline phosphide are included is applied and is baked
5 at 350 to 1150°C, and after decreasing a temperature, the insulation coating forming
solution (insulation coating forming solution 2) in which the phosphate and the colloidal
silica are included and in which the crystalline phosphide is not included is applied and is
baked at 350 to 1150°C.
10
[0083]
The crystalline phosphide may be the compound including, as a chemical
composition, 70 to 100 atomic% in total of Fe, Cr, P, and 0, and limited to 10 atomic%
or less of Si. The balance of the above chemical composition of the compound may be
impurities. For instance, the crystalline phosphide is preferably at least one selected
from Fe3P, Fe2P, FeP, FeP2, Fe2P207, (Fe,Cr)3P, (Fe,Cr)2P, (Fe,Cr)P, (Fe,Cr)P2, and
15 (Fe,Cr)2P207. The average diameter of the crystalline phosphide is preferably 10 to 300
nm. It is preferable that the insulation coating forming solution 1 includes 3 to 35
mass% of the crystalline phosphide.
[0084]
Except for controlling the crystalline phosphide as explained above, the
20 insulation coating forming solution 1 may be the same solution as the insulation coating
forming solution 2. For instance, the insulation coating forming solution 1 may mainly
include the phosphate and the colloidal silica.
[0085]
The baking temperature of the insulation coating forming solution 1 may be 350
25 to 1150°C. Moreover, the baking time is preferably 5 to 300 seconds, and the
33
atmosphere is preferably the mixed gas of water vapor, nitrogen, and hydrogen, in which
the oxidation degree PH20/PH2 is preferably 0.001 to 1.0. It is possible to form the
insulation coating which includes a crystalline phosphide-containing layer through the
above heat treatment. In order to obtain the adhesion of the insulation coating with
5 excellent repeatability, the above oxidation degree PH20/PH2 is more preferably 0.01 to
0.15, the baking temperature is more preferably 650 to 950°C, and the baking time is
more preferably 30 to 270 seconds. After the heat treatment, the steel sheet is cooled
with the oxidation degree of the atmosphere which is controlled to be lower, so that the
crystalline phosphide does not chemically change (the crystalline phosphide does not
10 degenerate by reacting with moisture during the cooling). The oxidation degree
PH20/PH2 of the atmosphere during the cooling is preferably 0.01 or less.
[0086]
After baking the insulation coating forming solution 1 and then decreasing the
temperature to the room temperature (approximately 25°C), the insulation coating
15 forming solution 2 in which the phosphate and the colloidal silica are mainly included
and in which the crystalline phosphide is not included is applied and is baked.
[0087]
The baking temperature of the insulation coating forming solution 2 may be 350
to 1150°C. Moreover, the baking time is preferably 5 to 300 seconds, and the
20 atmosphere is preferably the mixed gas of water vapor, nitrogen, and hydrogen, in which
the oxidation degree PH20/PH2 is preferably 0.001 to 1.0. It is possible to form the
insulation coating which does not include the crystalline phosphide-containing layer on
the insulation coating which includes the crystalline phosphide-containing layer through
the above heat treatment. In order to obtain the adhesion of the insulation coating with
25 excellent repeatability, the above oxidation degree PH20/PH2 is more preferably 0.01 to
34
0.15, the baking temperature is more preferably 650 to 950°C, and the baking time is
more preferably 30 to 270 seconds. After the heat treatment, the steel sheet is cooled
with the oxidation degree of the atmosphere which is controlled to be lower, so that the
crystalline phosphide does not chemically change (the crystalline phosphide does not
5 degenerate by reacting with moisture during the cooling). The oxidation degree
PH20/PH2 of the atmosphere during the cooling is preferably 0.01 or less.
[0088]
By the above two baking treatments, it is possible to form the crystalline
phosphide-containing layer and the insulation coating which does not include the
10 crystalline phosphide in contact with the crystalline phosphide-containing layer.
15
[0089]
The insulation coating forming solution 1 and the insulation coating forming
solution 2 may be applied to the surface of the steel sheet, for instance, by the wet
applying method such as roll coater.
[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
magnetic domain refining treatment at appropriate timing of (first) between the cold
20 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.
[0091]
25 By conducting the magnetic domain refining treatment, it is possible to reduce
35
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
the annealing separator applying process, or between the smoothing process and the
5 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).
10
[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
applying the above stress-strain or forming the above groove, the width of 180° domain
15 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
method such as toothed gear, by a chemical groove forming method such as electrolytic
20 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.
[0094]
25 Fig. 1 shows an instance of the method for producing the grain oriented
5
10
36
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
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
oriented electrical steel sheet, and the obtained X-ray diffraction spectrum may be
15 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.
20
[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
aqueous solution which includes 30 mass% of NaOH and 70 mass% of H20 at 80°C for
25 20 minutes, washing it with water, and then, drying it. In general, only insulation
37
coating is removed by the alkaline solution, and the forsterite film is removed by the
acidic solution such as hydrochloric acid.
[0098]
In the grain oriented electrical steel sheet produced by the method according to
5 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.
10
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
example condition. The present invention can employ various types of conditions as
15 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
of No. Al3 and No. all were heated to 1350°C, and then hot-rolled to obtain the hot
20 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 conditions
25 shown in Tables 2 to 4.
38
[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
hot-rolled to obtain the hot rolled steel sheets having the sheet thickness of 2.6 mm.
5 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
conditions shown in Tables 2 to 4, and thereafter, the nitriding treatment was conducted
10 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.
Thereafter, the pickling was conducted in order to remove the surface scale, and then, the
15 cold rolling was conducted.
20
25
[0103]
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
39
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
5 separator was removed by water-washing from the surface of the final annealed sheet
using the solution including the inhibitor which was at least one of triethanolamine,
rosinamine, or mercaptan.
[0107]
After the water-washing, the pickling was conducted as necessary. For
10 instance, in the examples of the pickling "Yes" shown in Tables, the redundant annealing
separator was removed by being pickled. In the pickling, the steel sheets were
immersed in the sulfuric acid aqueous solution (volume concentration of sulfuric acid : 1
volume%).
15
20
[0108]
After removing the redundant annealing separator from the final annealed sheet,
the chemical polishing (electrolytic polishing) was conducted in the electrolytic solution
of phosphoric acid and chromic anhydride, in order to control the surface of the final
annealed sheet to the average roughness Ra shown in Tables 8 to 10.
[0109]
Thereafter, the insulation coating forming solution (insulation coating forming
solution 1) was applied and was baked at the temperature shown in Tables 8 to 10, herein
the insulation coating forming solution 1 was the solution in which 10 parts by mass of
fine powder of crystalline phosphide was mixed by being stirred with 100 parts by mass
of the aqueous solution which mainly included magnesium phosphate and colloidal silica
25 and which included chromic anhydride as necessary. After decreasing the temperature,
40
the insulation coating forming solution (insulation coating forming solution 2) was
applied and was baked at the temperature shown in Tables 8 to 10, herein the insulation
coating forming solution 2 was the solution in which the crystalline phosphide was not
included, in which the phosphate and the colloidal silica were mainly included, and in
5 which the chromic anhydride was included as necessary. By conducting the above
baking, the insulation coating was formed.
[0110]
The crystalline phosphide mixed with the insulation coating forming solution 1
was at least one selected from Fe3P, Fe2P, FeP, FeP2, Fe2P207, (Fe,Cr)3P, (Fe,Cr)2P,
10 (Fe,Cr)P, (Fe,Cr)P2, and (Fe,Cr)2P207.
[0111]
Moreover, in the examples, as shown in Tables 11 to 13, the magnetic domain
refining treatment was conducted at any timing of (first) between the cold rolling process
and the decarburization annealing process, (second) between the decarburization
15 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
was formed mechanically or chemically, or the stress-strain or the groove was applied or
formed by the laser.
20
25
[0112]
For the obtained grain oriented electrical steel sheets Nos. B1 to B41 and b1 to
b31, the iron loss and the coating adhesion were evaluated.
[0113]

The samples were taken from the obtained grain oriented electrical steel sheets,
41
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
regulated by JIS C2550-1: 2000. As for the grain oriented electrical steel sheets in
which the magnetic domain refinement was conducted, when the iron loss W17 /50 was
5 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.
10
[0114]
< 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
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
15 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
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
20 as x (NG). When the area fraction of remained coating was 85% or more (the above @
and o ), it was judged to as acceptable.
The results are shown in Tables 11 to 13.
[0115]
[Table 1]
42
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 0.025 0.008
A2 0.100 3.45 0.10 0.006 0.006 0.025 0.008
A3 0.060 0.80 0.10 0.006 0.006 0.025 0.008
A4 0.060 7.00 0.10 0.006 0.006 0.025 0.008
A5 0.060 3.45 0.01 0.006 0.006 0.025 0.008 Cu:0.15,. Ti:0.006
A6 0.060 3.45 1.00 0.006 0.020 0.026 0.025 0.008 B: 0.002, Cr: 0.08, V: 0.03
A7 0.060 3.45 0.10 0.004 0.002 0.006 0.025 0.008 P:0.10, Nb:0.05
A8 0.060 3.45 0.10 0.050 0.010 0.060 0.025 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 0.025 0.012
A12 0.060 3.45 0.10 0.006 0.006 0.025 0.008
A13 0.080 3.25 0.08 0.025 0.001 0.026 0.025 0.007 Bi: 0.004, Mo: 0.03
a1 0.010 3.45 0.10 0.006 0.006 0.025 0.008
a2 0.400 3.45 0.10 0.006 0.006 0.025 0.008
a3 0.060 0.50 0.10 0.006 0.006 0.025 0.008
a4 0.060 9.00 0.10 0.006 0.006 0.025 0.008
a5 0.060 3.45 0.004 0.006 0.006 0.025 0.008 Cu:0.15, Ti:0.006
a6 0.060 3.45 1.50 0.006 0.006 0.025 0.008 8:0.002, Cr:0.08, V:0.03
a7 0.060 3.45 0.10 0.070 0.070 0.025 0.008 P:0.10 .. Nb:0.05
a8 0.060 3.45 0.10 0.080 0.010 0.090 0.025 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 0.025 0.025 Bi: 0.004, Mo: 0.03
[0116]
[Table 2]
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 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 A 12 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 A 12 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 A 12 0.60 840 60 30 1.0
814 A 12 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 A12 0.60 840 60 30 1.0
818 A 12 0.60 840 60 30 1.0
819 A12 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 A 12 0.60 840 60 30 1.0
824 A 12 0.60 840 60 30 1.0
[0117]
[Table 3]
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%)
INVENTIVE 825 A 13 0.60 840 60 30 1.0
EXAMPLE 826 A13 0.60 840 60 30 1.0
827 A13 0.60 840 60 30 1.0
828 A13 0.60 840 60 30 1.0
829 A1 0.60 840 60 30 1.0
830 A2 0.60 840 60 30 1.0
831 A3 0.60 840 60 30 1.0
832 A4 0.60 840 60 30 1.0
833 A5 0.60 840 60 30 1.0
834 A6 0.60 840 60 30 1.0
835 A7 0.60 840 60 30 1.0
836 AS 0.60 840 60 30 1.0
837 A9 0.60 840 60 30 1.0
838 A10 0.60 840 60 30 1.0
839 A 11 0.60 840 60 30 1.0
840 A12 0.60 840 60 30 1.0
841 A13 0.60 840 60 30 1.0
COMPARATIVE b1 A 12 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 .Q. 30 1.0
b6 A 12 0.60 840 800 30 1.0
b7 A 12 0.60 840 60 ~ 1.0
[0118]
[Table 4]
45
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 b8 A 12 0.60 840 60 60 1.0
EXAMPLE b9 A12 0.60 840 60 30 3.0
b10 A12 0.60 840 60 30 1.0
b11 A12 0.60 840 60 30 1.0
b12 A 12 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 A12 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 A12 0.60 840 60 30 1.0
b19 A12 0.60 840 60 30 1.0
b20 a1 0.60 840 60 30 1.0
b21 a2 0.60 840 60 30 1.0
b22 a3 0.60 840 60 30 1.0
b23 a4 - - - - -
b24 a5 0.60 840 60 30 1.0
b25 a6 0.60 840 60 30 1.0
b26 a7 0.60 840 60 30 1.0
b27 a8 0.60 840 60 30 1.0
b28 a9 0.60 840 60 30 1.0
b29 a10 0.60 840 60 30 1.0
b30 a11 0.60 840 60 30 1.0
b31 a10 0.60 840 60 30 1.0
[0119]
[Table 5]
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 (°C) (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 0.9
814 A12 1200 75 20 ROSINAMINE YES 0.9
815 A12 1200 75 20 MERCAPTAN YES 0.9
816 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
817 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
818 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
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
~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 6]
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 (°C) (vol%) (h) OR NO) (g/m2)
INVENTIVE 825 A13 1200 75 20 TRIETHANOLAMINE YES 0.2
EXAMPLE 826 A13 1200 75 20 TRIETHANOLAMINE YES 0.2
827 A13 1200 75 20 TRIETHANOLAMINE YES 0.2
828 A13 1200 75 20 TRIETHANOLAMINE YES 0.2
829 A1 1200 75 20 TRIETHANOLAMINE YES 0.2
830 A2 1200 75 20 TRIETHANOLAMINE YES 0.2
831 A3 1100 75 20 TRIETHANOLAMINE YES 0.2
832 A4 1200 75 20 TRIETHANOLAMINE YES 0.2
833 A5 1200 75 20 TRIETHANOLAMINE YES 0.2
834 A6 1200 75 20 TRIETHANOLAMINE YES 0.2
835 A7 1200 75 20 TRIETHANOLAMINE YES 0.2
836 A8 1200 75 20 TRIETHANOLAMINE YES 0.2
837 A9 1200 75 20 TRIETHANOLAMINE YES 0.2
838 A10 1200 75 20 TRIETHANOLAMINE YES 0.2
839 A11 1200 75 20 TRIETHANOLAMINE YES 0.2
840 A12 1200 75 20 TRIETHANOLAMINE NO 0.2
841 A13 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
~1 :MIXED GAS ATMOSPHERE OF HYDROGEN AND NITROGEN (SHOWN AS NITROGEN FRACTION)
~2:AMOUNT OF IRON HYDROXIDE AND IRON OXIDE (PER A SIDE)
[0121]
[Table 7]
48
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 (°C) (vol%) (h) OR NO) (g/m2)
COMPARATIVE b8 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
EXAMPLE b9 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b10 A12 1200 30 20 TRIETHANOLAMINE YES 0.2
b11 A12 1200 75 §. TRIETHANOLAMINE YES 0.2
b12 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b13 A12 1200 75 20 TRIETHANOLAMINE NO .L9.
b14 A12 1200 75 20 ROSINAMINE NO .L9.
b15 A12 1200 75 20 MERCAPTAN NO .L9.
b16 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b17 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b18 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b19 A12 1200 75 20 TRIETHANOLAMINE YES 0.2
b20 a1 1200 75 20 TRIETHANOLAMINE YES 0.2
b21 a2 1200 75 20 TRIETHANOLAMINE YES 0.2
b22 a3 1100 75 20 TRIETHANOLAMINE YES 0.2
b23 a4 - - - - - -
b24 a5 1200 75 20 TRIETHANOLAMINE YES 0.2
b25 a6 1200 75 20 TRIETHANOLAMINE YES 0.2
b26 a7 1200 75 20 TRIETHANOLAMINE YES 0.2
b27 a8 1200 75 20 TRIETHANOLAMINE YES 0.2
b28 a9 1200 75 20 TRIETHANOLAMINE YES 0.2
b29 a10 1200 75 20 TRIETHANOLAMINE YES 0.2
b30 a11 1200 75 20 TRIETHANOLAMINE YES 0.2
b31 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)
[0122]
[Table 8]
49
SMOOTHING PROCESS INSULATION COATING FORMING PROCESS
STEEL AVERAGE INSULATION COATING INSULATION COATING
No. No. ROUGHNESS Ra FORMING SOLUTION 1 FORMING SOLUTION 2
BAKING TEMPERATURE BAKING TEMPERATURE
( ,u m) CCC) (oC)
INVENTIVE 81 A12 0.05 840 840
EXAMPLE 82 A12 0.05 840 840
83 A12 0.05 840 840
84 A12 0.05 840 840
85 A12 0.05 840 840
86 A12 0.05 840 840
87 A12 0.05 840 840
88 A12 0.05 840 840
89 A12 0.05 840 840
810 A12 0.05 840 840
811 A12 0.05 840 840
812 A12 0.10 840 840
813 A12 0.05 840 840
814 A12 0.05 840 840
815 A12 0.05 840 840
816 A12 0.05 350 350
817 A12 0.05 1150 1150
818 A12 0.05 350 840
819 A12 0.05 1150 840
820 A12 0.05 840 350
821 A12 0.05 840 1150
822 A12 0.05 840 840
823 A12 0.05 840 840
824 A12 0.05 840 840
[0123]
[Table 9]
50
SMOOTHING PROCESS INSULATION COATING FORMING PROCESS
STEEL AVERAGE INSULATION COATING INSULATION COATING
No. No. ROUGHNESS Ra FORMING SOLUTION 1 FORMING SOLUTION 2
BAKING TEMPERATURE BAKING TEMPERATURE
( ,u m) (oC) CCC)
INVENTIVE 825 A13 0.05 840 840
EXAMPLE 826 A13 0.05 840 840
827 A13 0.05 840 840
828 A13 0.05 840 840
829 A1 0.05 840 840
830 A2 0.05 840 840
831 A3 0.05 840 840
832 A4 0.05 840 840
833 A5 0.05 840 840
834 A6 0.05 840 840
835 A7 0.05 840 840
836 A8 0.05 840 840
837 A9 0.05 840 840
838 A10 0.05 840 840
839 A 11 0.05 840 840
840 A12 0.05 840 840
841 A13 0.05 840 840
COMPARATIVE b1 A12 0.05 840 840
EXAMPLE b2 A12 0.05 840 840
b3 A12 0.05 840 840
b4 A12 0.05 840 840
b5 A12 0.05 840 840
b6 A12 0.05 840 840
A12 0.05 840 840
[0124]
[Table 10]
51
SMOOTHING PROCESS INSULATION COATING FORMING PROCESS
STEEL AVERAGE INSULATION COATING INSULATION COATING
No. No. ROUGHNESS Ra FORMING SOLUTION 1 FORMING SOLUTION 2
BAKING TEMPERATURE BAKING TEMPERATURE
( ,u m) (oC) CCC)
COMPARATIVE b8 A12 0.05 840 840
EXAMPLE b9 A12 0.05 840 840
b10 A12 0.05 840 840
b11 A12 0.05 840 840
b12 A12 0.50 840 840
b13 A12 0.05 840 840
b14 A12 0.05 840 840
b15 A12 0.05 840 840
b16 A12 0.05 300 840
b17 A12 0.05 1200 840
b18 A12 0.05 840 300
b19 A12 0.05 840 1200
b20 a1 0.05 840 840
b21 a2 0.05 840 840
b22 a3 0.05 840 840
b23 a4 - - -
b24 a5 0.05 840 840
b25 a6 0.05 840 840
b26 a7 0.05 840 840
b27 a8 0.05 840 840
b28 a9 0.05 840 840
b29 a10 0.05 840 840
b30 a11 0.05 840 840
b31 a10 0.05 840 840
[0125]
[Table 11]
52
MAGNETIC DOMAIN REFINEMENT IRON LOSS COATING
STEEL TIMING FOR METHOD W17/50 ADHESION
No. No. CONTROLLING
(W/kg)
INVENTIVE 81 A12 FOURTH LASER IRRADIATION 0.69 0 EXAMPLE 82 A12 FOURTH LASER IRRADIATION 0.67 0
83 A12 FOURTH LASER IRRADIATION 0.68 0
84 A12 FOURTH LASER IRRADIATION 0.68 0
85 A12 FOURTH LASER
IRRADIATION 0.69 0
86 A12 FOURTH IRR~Sy~~ION 0.68 0
87 A12 FOURTH LASER IRRADIATION 0.67 0
88 A12 FOURTH LASER IRRADIATION 0.65 0
89 A12 FOURTH IRR~Sy~~ION 0.69 0
810 A12 FOURTH LASER IRRADIATION 0.68 0
811 A12 FOURTH LASER IRRADIATION 0.67 0
812 A12 FOURTH LASER IRRADIATION 0.66 0
813 A12 FOURTH LASER IRRADIATION 0.68 0
814 A12 FOURTH LASER IRRADIATION 0.69 0
815 A12 FOURTH LASER IRRADIATION 0.68 0
816 A12 FOURTH LASER IRRADIATION 0.67 0
817 A12 FOURTH LASER IRRADIATION 0.66 0
818 A12 FOURTH LASER IRRADIATION 0.69 0
819 A12 FOURTH LASER IRRADIATION 0.68 0
820 A12 FOURTH LASER IRRADIATION 0.65 0
821 A12 FOURTH LASER IRRADIATION 0.68 0
822 A12 FIRST MECHANICAL GROOVE FORMING 0.64 @
823 A12 SECOND GR~B~~A~b~~TNG 0.64 @
824 A12 THIRD MECHANICAL GROOVE FORMING 0.63 @
[0126]
[Table 12]
53
MAGNETIC DOMAIN REFINEMENT IRON LOSS COATING
STEEL TIMING FOR METHOD W17/50 ADHESION
No. No. CONTROLLING
(W/kg)
INVENTIVE 825 A13 FIRST CHEMICAL GROOVE FORMING 0.63 @ EXAMPLE 826 A13 SECOND GROOCHVEE MFICOARLM ING 0.66 @
827 A13 THIRD GROOCHVEE MFICOARLM ING 0.65 @
828 A13 FOURTH IRRALADSIAERT ION 0.63 @
829 A1 FOURTH IRRALADSIAERT ION 0.68 0
830 A2 FOURTH IRRALADSIAERT ION 0.69 0
831 A3 FOURTH IRRALADSIAERT ION 0.67 0
832 A4 FOURTH IRRALADSIAERT ION 0.68 0
833 A5 FOURTH IRRALADSIAERT ION 0.65 0
834 A6 FOURTH IRRALADSIAERT ION 0.66 0
835 A7 FOURTH IRRALADSIAERT ION 0.69 0
836 A8 FOURTH IRRALADSIAERT ION 0.67 0
837 A9 FOURTH IRRALADSIAERT ION 0.68 0
838 A10 FOURTH IRRALADSIAERT ION 0.68 0
839 A 11 FOURTH IRRALADSIAERT ION 0.69 0
840 A12 FOURTH LASER
IRRADIATION 0.68 0
841 A13 NO - 0.93 @
COMPARATIVE b1 A12 FOURTH IRRALADSIAERT ION 1.16 ~ EXAMPLE b2 A12 FOURTH IRRALADSIAERT ION 0.84 ~
b3 A12 FOURTH IRRALADSIAERT ION 1.56 ~
b4 A12 FOURTH LASER
IRRADIATION 1.22 ~
b5 A12 FOURTH LASER
IRRADIATION 1.11 ~
b6 A12 FOURTH IRR~Sy~~ION 0.96 ~
b7 A12 FOURTH IRRALADSIAERT ION 1.04 ~
[0127]
[Table 13]
54
MAGNETIC DOMAIN REFINEMENT IRON LOSS COATING
STEEL TIMING FOR METHOD W17/50 ADHESION
No. No. CONTROLLING
(W/kg)
COMPARATIVE b8 A12 FOURTH lRRk~Y~~lON 0.97 ~
EXAMPLE b9 A12 FOURTH lRRk~Y~~lON 0.86 ~
b10 A12 FOURTH lRRk~Y~~lON 1.05 ~
b11 A12 FOURTH lRRk~Y~~lON 0.99 ~
b12 A12 FOURTH lRRk~Y~~lON 1.42 ~
b13 A12 FOURTH lRRk~Y~~lON 1.14 ~
b14 A12 FOURTH lRRk~Y~~lON 1.13 ~
b15 A12 FOURTH lRRk~Y~~lON 1.15 ~
b16 A12 FOURTH lRRk~Y~~lON 0.98 X
b17 A12 FOURTH lRRk~Y~~lON 0.97 X
b18 A12 FOURTH lRRk~Y~~lON 0.89 X
b19 A12 FOURTH lRRk~Y~~lON 0.95 X
b20 a1 FOURTH lRRk~Y~~lON 0.78 0
b21 a2 FOURTH lRRk~Y~~lON 0.76 0
b22 a3 FOURTH lRR~Sy~~lON 0.79 0
b23 a4 - - - -
b24 a5 FOURTH lRRk~Y~~lON 0.95 0
b25 a6 FOURTH lRR~Sy~~lON 1.12 0
b26 a7 FOURTH lRRk~Y~~lON 1.04 0
b27 a8 FOURTH lRRk~Y~~lON 1.06 0
b28 a9 FOURTH lRR~Sy~~lON 0.99 0
b29 a10 FOURTH lRRk~Y~~lON 1.13 0
b30 a11 FOURTH lRR~Sy~~lON 0.93 0
b31 a10 NO - 1.43 0
[0128]
As shown in Tables 1 to 13, in the inventive examples Nos. B1 to B41, 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 b31, 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
55
No. b23, the rolling could not be conducted, and thus, the evaluation thereafter was not
conducted.
Industrial Applicability
[0129]
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
10 and the coating adhesion, and therefore, the present invention has significant industrial
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
57
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,
58
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 in order to remove the
redundant annealing separator from the surface thereof, and an amount of an iron
5 hydroxide and an iron oxide on the surface thereof 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
chemical-polished, and an average roughness Ra of the surface thereof is controlled to
10 0.1 ~m or less, and
wherein, in the insulation coating forming process,
an insulation coating forming solution in which a phosphate, a colloidal silica,
and a crystalline phosphide are included is applied and is baked at 350 to 1150°C, and
after decreasing a temperature, an insulation coating forming solution in which the
15 phosphate and the colloidal silica are included and in which the crystalline phosphide is
not included is applied and is baked at 350 to 1150°C, in order to form the insulation
coating.
2. The method for producing the grain oriented electrical steel sheet according to
20 claim 1,
25
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.
5
59
3. The method for producing the grain oriented electrical steel sheet according to
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.
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
10 separator applying process, between the smoothing process and the insulation coating
forming process, or after the insulation coating forming process,
15
20
25
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
any one of claims 1 to 4,
wherein, in the annealing separator removing process, a pickling is conducted
after water-washing using an acidic solution whose volume concentration is less than
20%.
6. The method for producing the grain oriented electrical steel sheet according to
any one of claims 1 to 5,
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,
60
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,
5 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,
10 0.002 to 0.015% ofTi, and
0.001 to 0.010% ofBi.