In the grain oriented electrical steel sheet 10 according to the embodiment, the
25 oxide layer 15 is arranged between the base steel sheet 11 and the tension-insulation
25
coating 13, and thereby, the oxide layer 15, the tension-insulation coating 13, and the
base steel sheet 11 adhere tightly, even without the glass film (forsterite film).
[0059]
It is possible to judge whether or not the oxide layer 15 is included in the grain
5 oriented electrical steel sheet 10 by the analysis using the glow discharge spectroscopy.
10
Specifically, the glow discharge spectroscopy is conduced, and then, the GDS depth
profile may be confirmed. Hereinafter, the GDS depth profile is explained in detail with
reference to Figure 2 and Figure 3.
[0060]
Figure 2 is an instance of the GDS depth profile of the grain oriented electrical
steel sheet 10 according to the embodiment. Figure 2 is the GDS depth profile obtained
by conducting the glow discharge spectroscopy in the region from the surface of the
tension-insulation coating 13 to the inside of the base steel sheet 11. Figure 3 is an
instance of the GDS depth profile of the grain oriented electrical steel sheet which does
15 not include the forsterite film but is different from the grain oriented electrical steel sheet
20
according to the embodiment. Figure 3 is also the GDS depth profile obtained by
conducting the glow discharge spectroscopy in the region from the surface of the
tension-insulation coating to the inside of the base steel sheet.
[0061]
For both grain oriented electrical steel sheets of Figure 2 and Figure 3, the
tension-insulation coating which is based on phosphate-silica mixture which mainly
includes aluminum phosphate and colloidal silica and includes Cr has been formed. In
the GDS depth profiles shown as Figure 2 and Figure 3, the GDS analysis has been
conducted from the surface of the grain oriented electrical steel sheet to approximately 4
25 to 8 ~m in depth.
26
[0062]
GDS is a method of measuring an amount of target element at each position in
the thickness direction of the measured sample while sputtering the surface of the
measured sample. The horizontal axis of Figure 2 and Figure 3 corresponds to the
5 sputtering time (seconds) (in other words, elapsed time from starting the measurement),
and the position at which the sputtering time is 0 second corresponds to the surface
position of the grain oriented electrical steel sheet to be measured. The vertical axis of
Figure 2 and Figure 3 corresponds to the emission intensity (a. u.) of each element.
10
[0063]
First, in Figure 2 and Figure 3, attention is directed to a region from the
sputtering start until the emission intensity derived from Fe (hereinafter, referred to as Fe
emission intensity) starts to remarkably increase (in Figure 2 and Figure 3, the region
where the sputtering time is approximately 0 to 40 seconds). As clearly shown in
Figure 2, in the region, the emission peak derived from Al is noticeably detected.
15 Moreover, it seems that the emission intensities derived from Si and P decrease gradually,
and the emission peaks which are gently and broadly distributed are exist. It seems that
Al, Si, and P detected in the region are originated from the aluminum phosphate and the
colloidal silica which are used for the tension-insulation coating. Thus, the region until
the Fe emission intensity starts to remarkably increase (the region where the sputtering
20 time is 0 to 40 seconds in Figure 2) can be regarded as the tension-insulation coating in
the layering structure of the grain oriented electrical steel sheet. A region where the
sputtering time is longer than that of the above region can be regarded as the oxide layer
and the base steel sheet.
[0064]
25 Moreover, the Fe emission intensity shows a profile such that the Fe emission
27
intensity starts to gradually increase from the surface vicinity of the grain oriented
electrical steel sheet (the position at which the sputtering time is approximately 0 second
in Figure 2), starts to remarkably increase from a certain position (the position at which
the sputtering time is approximately 40 seconds in Figure 2), and thereafter, saturates to a
5 certain value. It seems that Fe detected in the profile is mainly originated from the base
steel sheet. Thus, a region where the Fe emission intensity is saturated can be regarded
as the base steel sheet in the layering structure of the grain oriented electrical steel sheet.
[0065]
In the embodiment, a position (sputtering time) at which the Fe emission
10 intensity becomes 0.05 times as compared with the Fe emission intensity of the base steel
sheet (i.e. the saturation value of the Fe emission intensity) on the depth profile is
regarded as a position at which the Fe content starts to increase in the tension-insulation
coating 13 and the oxide layer 15, and the sputtering time is expressed as "Feo.os" in unit
of seconds.
15 [0066]
Moreover, an interface between the oxide layer 15 and the base steel sheet 11 is
rarely horizontal. In the embodiment, a position (sputtering time) at which the Fe
emission intensity becomes 0.5 times as compared with the Fe emission intensity of the
base steel sheet (i.e. the saturation value of the Fe emission intensity) on the depth profile
20 is regarded as the interface between the oxide layer 15 and the base steel sheet 11, and
the sputtering time is expressed as "Feo.s" in unit of seconds.
[0067]
Moreover, the value "(Feo.s - Feo.os)" can be regarded as a region (thickness)
where the Fe content is high in the tension-insulation coating 13 and the oxide layer 15.
25 Thus, the value "(Feo.s - Feo.os) I Feo.s" corresponds to the ratio of the thickness where the
28
Fe content is high to the total thickness of the tension-insulation coating 13 and the oxide
layer 15.
[0068]
In the grain oriented electrical steel sheet 10 according to the embodiment, the
5 Feo.s and the Feo.os satisfy the following (formula 101).
[0069]
0.01 < (Feo.s - Feo.os) I Feo.s < 0.35
[0070]
---(formula 101)
In the grain oriented electrical steel sheet 10 according to the embodiment, by
10 including the oxide layer 15 satisfying the above (formula 101), the coating adhesion is
improved and the attained iron loss (the most favorable iron loss which is achieved) is
reduced. The reason why the above effect is obtained is not clear at present. However,
it seems that, when the oxides are excessively formed, the oxides remain excessively
inside the grain oriented electrical steel sheet after applying and baking the
15 tension-insulation coating, and thereby, the iron loss deteriorates. Thus, it seems that,
when the formation of the oxides is controlled, the oxide layer 15 satisfying the above
(formula 101) is formed, and thereby, the above effect is obtained. Herein, in the grain
oriented electrical steel sheet 10 according to the embodiment, the appearance becomes
light gray due to the above structure.
20 [0071]
On the other hand, Figure 3 is the GDS depth profile of the grain oriented
electrical steel sheet which does not include the forsterite film but is different from to the
embodiment. The GDS depth profile of Figure 3 is quite different from the GDS depth
profile of Figure 2. Moreover, in the GDS depth profile of Figure 3, the above (formula
25 101) is not satisfied. In the grain oriented electrical steel sheet in regard to Figure 3, the
29
appearance becomes dark brown.
[0072]
Herein, the value "(Feo.s - Feo.os) I Feo.s" is preferably 0.25 or less, more
preferably 0.24 or less, and further more preferably 0.23 or less. At this time, the
5 attained iron loss is improved. Moreover, the value "(Feo.s- Feo.os) I Feo.s" is preferably
0.02 or more.
[0073]
GDS is a method of analyzing an area of approximately 4 mm diameter with
sputtering. Thus, it seems that the GDS depth profile expresses average behavior of
10 each element in the area which is approximately 4 mm diameter in sample. Moreover,
the grain oriented electrical steel sheet may be coiled into a coil shape, and it is
considered that the GDS depth profiles are the substantial same at any points in width
direction in so far as the points are certain distance away from the head of the coil.
Moreover, when the substantial same GDS depth profiles are obtained at both the head
15 and tail of the coil, it is considered that the substantial same GDS depth profiles are
obtained in the whole coil.
[0074]
GDS is conducted in a region from a surface of the tension-insulation coating to
an inside of the base steel sheet. The conditions for GDS analysis may be as follows.
20 The measurement may be conducted under conditions such that output is 30W, Ar
pressure is 3 hPa, measurement area is 4 mm diameter, and measurement time is 100
seconds in high frequency mode using a typical glow discharge spectrum analyzer (for
instance, GDA 750 produced by Rigaku Corporation).
[0075]
25 Herein, it is preferable to judge the above (formula 101) after smoothing the
5
30
measured GDS depth profile. In order to smooth the GDS depth profile, for instance, a
simple moving average method may be used. Moreover, the sputtering time at which
the Fe emission intensity becomes the saturation value may be specified as 100 seconds
for instance.
[0076]
< Forsterite Film >
The grain oriented electrical steel sheet 10 according to the embodiment does
not include the forsterite film. In the embodiment, it may be judged by the following
procedure whether or not the grain oriented electrical steel sheet 10 includes the forsterite
10 film.
[0077]
Whether or not the grain oriented electrical steel sheet 10 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 tension-insulation coating 13 and
15 the like from the grain oriented electrical steel sheet 10, and the obtained X-ray
diffraction spectrum may be collated with PDF (Powder Diffraction File). The
forsterite (Mg2Si04) may be identified by JCPDS No. 34-189. In the embodiment,
when the main constituent phase in the above X-ray diffraction spectrum is not the
forsterite, the grain oriented electrical steel sheet 10 is judged not to include the forsterite
20 film.
[0078]
In order to only remove the tension-insulation coating 13 from the grain oriented
electrical steel sheet 10, the grain oriented electrical steel sheet 10 with the coating may
be immersed in hot alkaline solution. Specifically, it is possible to remove the
25 tension-insulation coating 13 and the like from the grain oriented electrical steel sheet 10
31
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 20 minutes, washing it with water,
and then by 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
5 acid. Thus, in a case where the forsterite film is included, by immersing in the above
alkaline solution, the tension-insulation coating 13 is removed, and the forsterite film is
exposed.
10
[0079]
< Magnetic Characteristics >
The magnetic characteristics of the grain oriented electrical steel sheet may be
measured on the basis of the epstein test regulated by JIS C2550: 2011, the single sheet
tester (SST) method regulated by JIS C 2556: 2015, and the like. In the grain oriented
electrical steel sheet 10 according to the embodiment, the magnetic characteristics may
be evaluated by adopting the single sheet tester method regulated by JIS C 2556: 2015
15 among the above methods.
[0080]
In the grain oriented electrical steel sheet 10 according to the embodiment, the
average magnetic flux density B8 in the rolling direction (the magnetic flux density
under the magnetizing field of 800A/m) may be 1.90 Tor more. The upper limit of the
20 magnetic flux density is not particularly limited, but may be 2.02 T for instance.
[0081]
When a steel ingot is formed in vacuum furnace and the like for the research and
development, it is difficult to take a test piece with the same size as that industrially
produced. In the case, for instance, the test piece with a width of 60 mm and a length of
25 300 mm may be taken, and the measurement may be conducted in accordance with the
5
32
single sheet tester method. Moreover, the measured value may be multiplied by the
correction factor in order to obtain the measured value equivalent to that based on the
epstein test. In the embodiment, the measurement is conducted in accordance with the
single sheet tester method.
[0082]
< Forming Method for Insulation Coating of Grain Oriented Electrical Steel Sheet >
Next, a forming method for the insulation coating of the grain oriented electrical
steel sheet according to a preferred embodiment of the present invention is described.
The forming method for the insulation coating of the grain oriented electrical steel sheet
10 according to the embodiment includes the insulation coating forming process. In the
insulation coating forming process, the solution for forming the tension-insulation
coating is applied to a steel substrate, and the solution is baked, in order to form the
tension-insulation coating.
15
[0083]
Figure 4 is a flow chart illustrating an instance of the forming method for the
insulation coating of the grain oriented electrical steel sheet according to the embodiment.
As shown in Figure 4, in the forming method for the insulation coating of the grain
oriented electrical steel sheet according to the embodiment, the steel substrate which
does not include the forsterite film is prepared (step S11), and the tension-insulation
20 coating is formed on a surface of the steel substrate (stepS 13). The stepS 13
corresponds to the insulation coating forming process.
[0084]
The above steel substrate includes the base steel sheet and the oxide layer
arranged in contact with the base steel sheet. The steel substrate does not include the
25 glass film (forsterite film).
5
10
15
33
[0085]
The base steel sheet of the steel substrate includes, as the chemical composition,
by mass%,
2.5 to 4.0% of Si,
0.05 to 1.0% of Mn,
0 to 0.01% of C,
0 to 0.005% of S+Se,
0 to 0.01% of sol.Al,
0 to 0.005% of N,
0 to 0.03% of Bi,
0 to 0.03% of Te,
0 to 0.03% of Pb,
0 to 0.50% of Sb,
0 to 0.50% of Sn,
0 to 0.50% of Cr,
0 to 1.0% of Cu, and
a balance consisting of Fe and impurities.
[0086]
The above chemical composition of the base steel sheet is identical to the
20 chemical composition of the base steel sheet 11 explained above, and thus, the detail
explanation is omitted.
25
[0087]
In addition, the base steel sheet and the oxide layer in the steel substrate include,
as a total chemical composition, by mass%, 0.008 to 0.025% of 0.
[0088]
5
10
34
The oxide layer of the steel substrate includes a layer including mainly iron
oxides and a Si included oxide layer. The oxide layer is not the forsterite film. The
details are explained below.
[0089]
The steel substrate which is utilized for the forming method for the insulation
coating of the grain oriented electrical steel sheet according to the embodiment satisfies
the following conditions (I) and (II). Herein, the steel substrate which includes the
forsterite film and typical steel substrate do not satisfy the conditions.
[0090]
(I) When a glow discharge spectroscopy is conducted in a region from a surface
of the oxide layer to an inside of the base steel sheet, when a sputtering time at which a
Fe emission intensity becomes a saturation value thereof on a depth profile is referred to
as Fesat in unit of seconds, a plateau region of a Fe emission intensity where a Fe
emission intensity stays for Fesat x 0.05 seconds or more in a range of 0.20 to 0.80 times
15 as compared with the saturation value is included between 0 second and the Fesat on the
depth profile.
(II) When a sputtering time at which a Si emission intensity becomes a maximal
value on the depth profile is referred to as Simax in unit of seconds, a maximal point of a
Si emission intensity at which a Si emission intensity at the Simax becomes 0.15 to 0.50
20 times as compared with a Fe emission intensity at the Simax is included between the
plateau region and the Fesat on the depth profile.
[0091]
Figure 5 is an instance of GDS depth profile of a steel substrate to be used in the
forming method for the insulation coating of the grain oriented electrical steel sheet
25 according to the embodiment. Figure 5 is the GDS depth profile obtained by
35
conducting the glow discharge spectroscopy in the region from the surface of the oxide
layer to the inside of the base steel sheet. In the GDS depth profile of Figure 5, 20
seconds of the sputtering time corresponds to approximately 1.0 to 2.0 J.lm in depth from
the surface of the grain oriented electrical steel sheet. In Figure 5, the horizontal axis
5 corresponds to the sputtering time (seconds), and the vertical axis corresponds to the
emission intensity (a. u.) of each element.
[0092]
In Figure 5, the Fe emission intensity shows a profile such that the Fe emission
intensity starts to remarkably increase with starting the sputtering, becomes substantially
10 horizontal (plateau) for a short time shown as a region surrounded by a broken line in the
figure, starts to increase again, and thereafter, saturates to a certain value. A region
where the Fe emission intensity is saturated can be regarded as the base steel sheet in the
layering structure of the steel substrate. Moreover, the region (plateau region)
surrounded by the broken line in Figure 5 can be regarded as a region including mainly
15 iron oxides in the oxide layer of the steel substrate, because the 0 (oxygen) emission
intensity is detected in the sputtering time which is identical to that of the above region.
[0093]
In a region where the sputtering time is longer than that of the above plateau
region, the Si emission intensity shows a maximal point (at near 3 seconds of the
20 sputtering time), and thereafter, gradually approaches a certain value. The asymptotic
value of Si can be regarded as the value corresponding to the Si content of the base steel
sheet.
[0094]
A region where the Si emission intensity shows the maximal point can be
25 regarded as the Si included oxide layer in the oxide layer of the steel substrate, because
36
Si and 0 are detected. The existence of the above maximal point of the Si emission
intensity indicates that the Si concentrated layer is included in the oxide layer.
[0095]
It is confirmed from the GDS depth profile of Figure 5 that the steel substrate to
5 be used in the forming method for the insulation coating according to the embodiment
includes, from the surface thereof, the layer including mainly iron oxides, the Si included
oxide layer, and the base steel sheet. In the embodiment, the layer including mainly
iron oxides and the Si included oxide layer are collectively regarded as the oxide layer.
10
15
20
[0096]
In the embodiment, the steel substrate which includes the above chemical
composition and satisfies the above conditions (I) and (II) is subjected to the insulation
coating forming process. As a result, the grain oriented electrical steel sheet 10 which
shows the GDS depth profile such as Figure 2 is produced.
[0097]
Moreover, with respect to the maximal point of the Si emission intensity which
is included between the plateau region and the Fesat on the depth profile, the Si emission
intensity is preferably 0.16 times or more and more preferably 0.17 times or more as
compared with the Fe emission intensity at the Simax. The value is preferably 0.48 times
or less and more preferably 0.45 times or less.
[0098]
On the other hand, Figure 6 is the GDS depth profile of the steel substrate which
does not include the forsterite film but is different from to the steel substrate to be used
for the embodiment. The GDS depth profile of Figure 6 is quite different from the GDS
depth profile of Figure 5. Moreover, in the GDS depth profile of Figure 6, the maximal
25 point of the Si emission intensity is not included, and the above conditions (I) and (II) are
5
37
not satisfied.
[0099]
Herein, the conditions for GDS analysis, the method for analyzing data, and the
method for judging the presence of the forsterite film are as described above.
[0100]
In addition, in the steel substrate to be used in the forming method for the
insulation coating according to the embodiment, the oxygen content in total of the base
steel sheet and the oxide layer is 0.008 to 0.025 mass%. When the oxygen content is
less than 0.008 mass%, it is difficult to obtain the grain oriented electrical steel sheet
10 satisfying the above (formula 101). The oxygen content is preferably 0.009 mass% or
more. On the other hand, when the oxygen content is more than 0.025 mass%, the
oxides are excessively formed, the oxides remain excessively inside the grain oriented
electrical steel sheet after applying and baking the tension-insulation coating, and thereby,
the attained iron loss (the most favorable iron loss which is achieved) deteriorates. The
15 oxygen content is preferably 0.023 mass% or less, and more preferably 0.020 mass% or
less.
[0101]
The above oxygen content may be measured by typical methods. For instance,
the oxygen content may be measured by the non-dispersive infrared absorption method
20 after fusion in a current of inert gas. In the method, test piece is put in a graphite
crucible, the test piece is heated and fused in an inert gas atmosphere, and then, the
carbon monoxide which is formed by reacting the oxygen in the test piece and the
crucible and the carbon dioxide are quantitatively measured by an infrared detector.
[0102]
25 In the forming method for the insulation coating according to the embodiment,
38
by using the steel substrate satisfying the above conditions, not only the coating adhesion
is improved, but also excellent attained iron loss is obtained stably. The reason why the
above effect is obtained is not clear at present. However, it seems that, when the steel
substrate satisfies the above conditions, the internally oxidized layer which is formed
5 during forming the tension-insulation coating is favorably controlled, and as a result,
domain wall motion becomes easy.
[0103]
The solution for forming the phosphate-silica mixed tension-insulation coating
is applied to the oxide layer of the steel substrate which includes the above chemical
10 composition and satisfies the above conditions (I) and (II) and the solution is baked so as
to form the tension-insulation coating with an average thickness of 1 to 3 ~m. The
solution may be applied to both sheet surfaces or one sheet surface of the steel substrate.
[0104]
The conditions in the insulation coating forming process are not particularly
15 limited. Known solution for forming the phosphate-silica mixed tension-insulation
coating may be used, and the solution may applied and baked by known method. For
instance, the solution is applied, and thereafter, is held at 850 to 950°C for 10 to 60
seconds. The tension-insulation coating is formed on the steel substrate, and thereby, it
is possible to further improve the magnetic characteristics of the grain oriented electrical
20 steel sheet.
[0105]
Herein, before applying the solution, the surface of the steel substrate to form
the insulation coating may be subjected to optional pretreatment such as degreasing
treatment with alkaline, pickling treatment with hydrochloric acid, sulfuric acid,
25 phosphoric acid, and the like. The pretreatment may not be conducted.
39
[0106]
The tension-insulation coating is not particular! y limited, and known coating
may be adopted. For instance, the tension-insulation coating may mainly include
inorganics and may further include organics. The tension-insulation coating may
5 mainly include metal phosphate and colloidal silica, and fine particles of organic resin
may be dispersed in the tension-insulation coating.
[0107]
Moreover, following the insulation coating forming process, the flattening
annealing may be conducted for straightening. By conducting the flattening annealing
10 for the grain oriented electrical steel sheet after the insulation coating forming process, it
is possible to favorably reduce the iron loss characteristics.
[0108]
Moreover, the magnetic domain refining treatment may be conducted for the
produced grain oriented electrical steel sheet. Herein, the magnetic domain refining
15 treatment is the treatment such that the laser beam which refines the magnetic domain is
irradiated to the surface of the grain oriented electrical steel sheet or the groove is formed
on the surface of the grain oriented electrical steel sheet. By conducting the magnetic
domain refining treatment, it is possible to favorably reduce the magnetic characteristics.
[0109]
20 < Producing Method for Grain Oriented Electrical Steel Sheet >
25
Next, a producing method for the grain oriented electrical steel sheet according
to a preferred embodiment of the present invention is described in detail with reference to
Figure 7. Figure 7 is a flow chart illustrating an instance of the producing method for
the grain oriented electrical steel sheet according to the embodiment.
[0110]
40
Herein, the producing method for the grain oriented electrical steel sheet 10 is
not limited to the following method. The following method is just an instance for
producing the grain oriented electrical steel sheet 10.
[0111]
5 < Overall Flow of Producing Method for Grain Oriented Electrical Steel Sheet >
10
The producing method for the grain oriented electrical steel sheet according to
the embodiment is for producing the grain oriented electrical steel sheet without the
forsterite film, and the overall flow thereof is as follows.
[0112]
The producing method for the grain oriented electrical steel sheet according to
the embodiment includes the following processes, which are shown in Figure 7.
(S 111) Hot rolling process of heating and thereafter hot-rolling a steel piece
(slab) including predetermined chemical composition to obtain a hot rolled steel sheet.
(S 113) Hot band annealing process of optionally annealing the hot rolled steel
15 sheet to obtain a hot band annealed steel sheet.
(S 115) Cold rolling process of cold-rolling the hot rolled steel sheet or the hot
band annealed steel sheet by cold-rolling once or by cold-rolling plural times with an
intermediate annealing to obtain a cold rolled steel sheet.
(S 117) Decarburization annealing process of decarburization-annealing the cold
20 rolled steel sheet to obtain a decarburization annealed steel sheet.
(S119) Final annealing process of applying an annealing separator to the
decarburization annealed steel sheet and thereafter final-annealing the decarburization
annealed steel sheet to obtain a final annealed steel sheet.
(S 121) Oxidizing process of conducting a washing treatment, a pickling
25 treatment, and a heat treatment in turn for the final annealed steel sheet to obtain an
5
41
oxidized steel sheet.
(S123) Insulation coating forming process of applying the solution for forming
the tension-insulation coating to a surface of the oxidized steel sheet and of baking the
solution.
[0113]
The above processes are respectively described in detail. In the following
description, when the conditions of each process are not described, known conditions
may be appropriate! y applied.
[0114]
10 < Hot Rolling Process >
The hot rolling process (step S 111) is the process of heating and thereafter
hot-rolling the steel piece (for instance, steel ingot such as slab) including predetermined
chemical composition to obtain the hot rolled steel sheet. In the hot rolling process, the
steel piece is heat-treated. The heating temperature of the steel piece is preferably in the
15 range of 1200 to 1400°C. The heating temperature of the steel piece is preferably
1250°C or more, and preferably 1380°C or more. Subsequently, the heated steel piece
is hot-rolled to obtain the hot rolled steel sheet. The average thickness of the hot rolled
steel sheet is preferably in the range of 2.0 to 3.0 mm for instance.
20
25
[0115]
In the producing method for the grain oriented electrical steel sheet according to
the embodiment, the steel piece includes, as the chemical composition, base elements,
optional elements as necessary, and a balance consisting of Fe and impurities.
Hereinafter,"%" of the amount of respective elements as described below expresses
"mass%" unless otherwise mentioned.
[0116]
42
In the producing method for the grain oriented electrical steel sheet according to
the embodiment, the steel piece (slab) includes Si, Mn, C, S+Se, sol. Al, and N as the
base elements (main alloying elements).
[0117]
5 ( 2.5 to 4.0% of Si )
Si is the element which increases the electric resistance of steel and which
reduces the eddy current loss. When the Si content of the steel piece is less than 2.5%,
the above effect to reduce the eddy current loss is not sufficiently obtained. On the
other hand, when the Si content of the steel piece is more than 4.0%, the cold workability
10 of steel deteriorates. Thus, in the embodiment, the Si content of the steel piece is to be
2.5 to 4.0%. The Si content of the steel piece is preferably 2.7% or more, and more
preferably 2.8% or more. Moreover, the Si content of the steel piece is preferably 3.9%
or less, and more preferably 3.8% or less.
[0118]
15 ( 0.05 to 1.00% of Mn )
Mn forms MnS and MnSe in the production processes by bonding to S and/or Se
explained later. These precipitates act as the inhibitor and induce the secondary
recrystallization in steel during final annealing. Moreover, Mn is an element which
improves the hot workability of steel. When the Mn content of the steel piece is less
20 than 0.05%, the above is not sufficiently obtained. On the other hand, when the Mn
content of the steel piece is more than 1.00%, the secondary recrystallization does not
occur and the magnetic characteristics of steel deteriorate. Thus, in the embodiment,
the Mn content of the steel piece is to be 0.05 to 1.00%. The Mn content of the steel
piece is preferably 0.06% or more. Moreover, the Mn content of the steel piece is
25 preferably 0.50% or less.
43
[0119]
( 0.02 to 0.10% of C)
Cis the element effective for microstructure control until the completion of the
decarburization annealing process in the production processes, and thereby, the magnetic
5 characteristics for the grain oriented electrical steel sheet are improved. When the C
content of the steel piece is less than 0.02%, or when the C content of the steel piece is
more than 0.10%, the above effect in improving the magnetic characteristics are not
sufficiently obtained. The C content of the steel piece is preferably 0.03% or more.
Moreover, the C content of the steel piece is preferably 0.09% or less.
10 [0120]
( 0.005 to 0.080% in total of S+Se )
S and Se form MnS and MnSe which act as the inhibitor by bonding to Mn in
the production processes. When the total amount of Sand Se of the steel piece is less
than 0.005%, it is difficult to obtain the effect for forming MnS and MnSe. On the other
15 hand, when the total amount of Sand Se is more than 0.080%, the magnetic
characteristics deteriorate, and the steel sheet may become brittle in the higher
temperature range. Thus, in the embodiment, the total amount of S and Se of the steel
piece is to be 0.005 to 0.080%. The total amount of Sand Se of the steel piece is
preferably 0.006% or more. Moreover, the total amount of S and Se of the steel piece is
20 preferably 0.070% or less.
[0121]
( 0.01 to 0.07% of sol.Al)
Sol. Al forms AlN which acts as the inhibitor by bonding to N in the production
processes. When the sol.Al content of the steel piece is less than 0.01 %, AlN does not
25 form sufficiently, and thus, the magnetic characteristics deteriorate. On the other hand,
44
when the sol.Al content of the steel piece is more than 0.07%, the magnetic
characteristics deteriorate, and the cracks tend to occur during cold rolling. Thus, in the
embodiment, the sol.Al content of the steel piece is to be 0.01 to 0.07%. The sol.Al
content of the steel piece is preferably 0.02% or more. Moreover, the sol.Al content of
5 the steel piece is preferably 0.05% or less.
[0122]
( 0.005 to 0.020% of N)
N forms AlN which acts as the inhibitor by bonding to Al in the production
processes. When theN content of the steel piece is less than 0.005%, AlN does not
10 form sufficiently, and thus, the magnetic characteristics deteriorate. On the other hand,
when the N content of the steel piece is more than 0.020%, AlN becomes difficult to act
as the inhibitor, and thus, the secondary recrystallization becomes difficult to occur. In
addition, the cracks tend to occur during cold rolling. Thus, in the embodiment, the N
content of the steel piece is to be 0.005 to 0.020%. TheN content of the steel piece is
15 preferably 0.012% or less, and more preferably 0.010% or less.
[0123]
In the producing method for the grain oriented electrical steel sheet according to
the embodiment, the steel piece (slab) may include the impurities. The impurities
correspond to elements which are contaminated during industrial production of steel
20 from ores and scrap that are used as a raw material of steel, or from environment of a
production process.
[0124]
Moreover, in the embodiment, the steel piece may include the optional elements
in addition to the base elements and the impurities. For example, as substitution for a
25 part of Fe which is the balance, the silicon steel sheet may include the optional elements
5
45
such as Bi, Te, Pb, Sb, Sn, Cr, and Cu. The optional elements may be included as
necessary. Thus, a lower limit of the respective optional elements does not need to be
limited, and the lower limit may be 0%. Moreover, even if the optional elements may
be included as impurities, the above mentioned effects are not affected.
[0125]
( 0 to 0.03% ofBi)
( 0 to 0.03% ofTe)
( 0 to 0.03% ofPb)
Bi, Te, and Pb are optional elements. When the amount of each of these
10 elements included in the steel piece is 0.03% or less, it is possible to favorably improve
the magnetic characteristics for the grain oriented electrical steel sheet. However, when
the amount of each of these elements is more than 0.03% respectively, the steel sheet
may become brittle in the higher temperature range. Thus, in the embodiment, the
amount of each of these elements included in the steel piece is to be 0.03% or less. The
15 lower limit of the amount of each of these elements included in the steel piece is not
particularly limited, but may be 0%. In order to favorably obtain the above effect, the
amount of each of these elements is preferably 0.0005% or more, and more preferably
0.001% or more.
20
[0126]
Herein, at least one of Bi, Te, and Pb may be included in the steel piece.
Specifically, the steel piece may be include at least one of 0.0005 to 0.03% of Bi, 0.0005
to 0.03% of Te, and 0.0005 to 0.03% of Pb.
[0127]
( 0 to 0.50% of Sb )
25 ( 0 to 0.50% of Sn )
( 0 to 0.50% of Cr )
( 0 to 1.0% ofCu)
46
Sb, Sn, Cr, and Cu are optional elements. When these elements are included in
the steel piece, it is possible to favorably improve the magnetic characteristics for the
5 grain oriented electrical steel sheet. Thus, in the embodiment, it is preferable to control
the amount of each of these elements included in the steel piece to 0.50% or less of Sb,
0.50% or less of Sn, 0.50% or less of Cr, and 1.0% or less of Cu. The lower limit of the
amount of each of these elements included in the steel piece is not particular! y limited,
but may be 0%. In order to favorably obtain the above effect, the amount of each of
10 these elements is preferably 0.0005% or more, and more preferably 0.001% or more.
15
[0128]
Herein, at least one of Sb, Sn, Cr, and Cu may be included in the steel piece.
Specifically, the steel piece may be include at least one of 0.0005 to 0.50% of Sb, 0.0005
to 0.50% of Sn, 0.0005 to 0.50% of Cr, and 0.0005 to 1.0% of Cu.
[0129]
The chemical composition of the steel piece may be measured by typical
analytical methods for the steel. For instance, the chemical composition may be
measured on the basis of the above analytical method.
[0130]
20 < Hot Band Annealing Process >
The hot band annealing process (step S 113) is the process of optionally
annealing the hot rolled steel sheet after the hot rolling process to obtain the hot band
annealed steel sheet. By conducting the annealing for the hot rolled steel sheet, the
recrystallization occurs in steel, and finally, the excellent magnetic characteristics can be
25 obtained.
47
[0131]
The heating method is not particular! y limited, and known heating method may
be adopted. Moreover, the annealing conditions are not particular! y limited. For
instance, the hot rolled steel sheet may be held in the temperature range of 900 to 1200°C
5 for 10 seconds to 5 minutes.
10
[0132]
The hot band annealing process may be omitted as necessary.
Moreover, after the hot band annealing process and before the cold rolling
process explained below, the surface of the hot rolled steel sheet may be pickled.
[0133]
< Cold Rolling Process >
The cold rolling process (step S 115) is the process of cold-rolling the hot rolled
steel sheet after the hot rolling process or the hot band annealed steel sheet after the hot
band annealing process by cold-rolling once or by cold-rolling plural times with the
15 intermediate annealing to obtain the cold rolled steel sheet. Since the sheet shape of the
20
hot band annealed steel sheet is excellent due to the hot band annealing, it is possible to
reduce the possibility such that the steel sheet is fractured in the first cold rolling. The
cold rolling may be conducted three or more times, but the producing cost increases.
Thus, it is preferable to conduct the cold rolling once or twice.
[0134]
In the cold rolling process, the cold rolling method for the steel sheet is not
particularly limited, and known method may be adopted. For instance, the cold rolling
reduction in final cold rolling (cumulative cold rolling reduction without intermediate
annealing or cumulative cold rolling reduction after intermediate annealing) may be in
25 the range of 80 to 95%.
5
10
15
48
[0135]
Herein, the final cold rolling reduction(%) is defined as follows.
Final cold rolling reduction(%)= ( 1 -Sheet thickness of steel sheet after final
cold rolling I Sheet thickness of steel sheet before final cold rolling ) x 100
[0136]
When the final cold rolling reduction is less than 80%, the Goss nuclei may not
be formed favorably. On the other hand, when the final cold rolling reduction is more
than 95%, the secondary recrystallization may be unstable in the final annealing process.
Thus, it is preferable that the cold rolling reduction in final cold rolling is 80 to 95%.
[0137]
When conducting the cold rolling plural times with the intermediate annealing,
the reduction in first cold rolling may be 5 to 50%, and the holding in the intermediate
annealing may be conducted in the temperature range of 950 to 1200°C for 30 seconds to
30 minutes.
[0138]
The average thickness of the cold rolled steel sheet (thickness after cold rolling)
is different from the thickness of the grain oriented electrical steel sheet which includes
the thickness of the tension-insulation coating. For instance, the average thickness of
the cold rolled steel sheet may be 0.10 to 0.50 mm. In the embodiment, even when the
20 cold rolled steel sheet is the thin sheet whose average thickness is less than 0.22 mm, the
adhesion of the tension-insulation coating is favorably improved. Thus, the average
thickness of the cold rolled steel sheet may be 0.17 mm or more and 0.20 mm or less.
[0139]
In the cold rolling process, the aging treatment may be conducted in order to
25 favorably improve the magnetic characteristics of the grain oriented electrical steel sheet.
49
For instance, since the thickness of the steel sheet is reduced by plural passes in the cold
rolling, the steel sheet may be held in the temperature range of 1 00°C or more for 1
minute or more at least once in the interval of plural passes. By the aging treatment, it
is possible to favorably control the primary recrystallized texture in the decarburization
5 annealing process, and as a result, it is possible to obtain the secondary recrystallized
texture where the { 110}<001> orientation is favorably developed in the final annealing
10
15
process.
[0140]
< Decarburization Annealing Process >
The decarburization annealing process (step S 117) is the process of
decarburization-annealing the cold rolled steel sheet after the cold rolling process to
obtain the decarburization annealed steel sheet. In the decarburization annealing
process, the cold rolled steel sheet is annealed under predetermined conditions in order to
control the primary recrystallized structure.
[0141]
In the producing method for the grain oriented electrical steel sheet according to
the embodiment, the annealing conditions in the decarburization annealing process are
not particularly limited, and known conditions may be adopted. For instance, the steel
sheet may be held in the temperature range of 750 to 950°C for 1 to 5 minutes.
20 Moreover, furnace atmosphere may be known moist atmosphere including hydrogen and
nitrogen.
[0142]
< Final Annealing Process >
The final annealing process (step S 119) is the process of applying the annealing
25 separator to the decarburization annealed steel sheet after the decarburization annealing
50
process and thereafter final-annealing the decarburization annealed steel sheet to obtain
the final annealed steel sheet. In the final annealing, the coiled steel sheet may be held
at a higher temperature for a long time in general. Thus, in order to suppress the seizure
between the inside and outside of the coiled steel sheet, the annealing separator is applied
5 to the decarburization annealed steel sheet and is dried before the final annealing.
[0143]
In the final annealing process, the annealing separator applied to the
decarburization annealed steel sheet is not particular! y limited, and known annealing
separator may be adopted. The producing method for the grain oriented electrical steel
10 sheet according to the embodiment is the method for producing the grain oriented
electrical steel sheet without the glass film (forsterite film), and thus, the annealing
separator which does not form the forsterite film may be adopted. In a case where the
annealing separator which forms the forsterite film is adopted, the forsterite film may be
removed by grinding or pickling after the final annealing.
15 [0144]
(Annealing Separator which does not form Forsterite Film)
As the annealing separator which does not form the glass film (forsterite film),
the annealing separator which mainly includes MgO and Ah03 and which includes
bismuth chloride may be utilized. For instance, it is preferable that the annealing
20 separator includes MgO and Ah03 of 85 mass% or more in total as percent solid, MgO :
Ah03 which is the mass ratio of MgO and Ah03 satisfies 3 : 7 to 7 : 3, and the annealing
separator includes the bismuth chloride of 0.5 to 15 mass% as compared with the total
amount of MgO and Ah03 as percent solid. The range of the above mass ratio of MgO
and Ah03 and the amount of the above bismuth chloride are determined from the
25 viewpoint of obtaining the base steel sheet excellent in the surface smoothness without
the glass film.
[0145]
51
In regard to the above mass ratio of MgO and Ah03, when the amount of MgO
exceeds the above range, the glass film may be formed and remained on the steel sheet
5 surface, and thus, the surface of the base steel sheet may not be smoothed. Moreover, in
regard to the above mass ratio of MgO and Ah03, when the amount of Ah03 exceeds the
above range, the seizure of Ah03 may occur, and thus, the surface of the base steel sheet
may not be smoothed. It is more preferable that MgO : Ah03 which is the mass ratio of
MgO and Ah03 satisfies 3.5 : 6.5 to 6.5 : 3.5.
10 [0146]
In a case where the bismuth chloride is included in the annealing separator, the
glass film is easily removed from the steel sheet surface even when the glass film is
formed in the final annealing. When the amount of the bismuth chloride is less than 0.5
mass% as compared with the total amount of MgO and Ah03, the glass film may be
15 remained. On the other hand, when the amount of the bismuth chloride is more than 15
mass% as compared with the total amount of MgO and Ah03, the effect to suppress the
seizure between the steel sheets may not be obtained as the annealing separator. The
amount of the bismuth chloride is more preferably 3 mass% or more, and more
preferably 7 mass% or less, as compared with the total amount ofMgO and Ah03.
20 [0147]
The type of the bismuth chloride is not particularly limited, and known bismuth
chloride may be adopted. For instance, bismuth oxychloride (BiOCl), bismuth
trichloride (BiCb), and the like may be used. Moreover, compounds which can form
the bismuth oxychloride by reaction in the annealing separator during the final annealing
25 process may be used. For instance, as the compounds which can form the bismuth
52
oxychloride during the final annealing, a mixture of bismuth compound and metal
chloride may be used. For instance, as the bismuth compound, bismuth oxide, bismuth
hydroxide, bismuth sulfide, bismuth sulfate, bismuth phosphate, bismuth carbonate,
bismuth nitrate, organobismuth compound, bismuth halide, and the like may be used.
5 For instance, as the metal chloride, iron chloride, cobalt chloride, nickel chloride, and the
like may be used.
[0148]
After applying the above annealing separator which does not form the forsterite
film to the surface of the decarburization annealed steel sheet and drying the annealing
10 separator, the final annealing is conducted. The annealing conditions in the final
annealing process are not particular! y limited, and known conditions may be adopted.
For instance, the steel sheet may be held in the temperature range of 1100 to 1300°C for
10 to 30 hours. Moreover, furnace atmosphere may be known nitrogen atmosphere or
mixed atmosphere of nitrogen and hydrogen. After the final annealing, it is preferable
15 that the redundant annealing separator is removed from the steel sheet surface by
water-washing or pickling.
[0149]
(Annealing Separator which forms Forsterite Film)
As the annealing separator which forms the glass film (forsterite film), the
20 annealing separator which mainly includes MgO may be utilized. For instance, it is
preferable that the annealing separator includes MgO of 60 mass% or more as percent
solid.
[0150]
After applying the annealing separator to the surface of the decarburization
25 annealed steel sheet and drying the annealing separator, the final annealing is conducted.
5
53
The annealing conditions in the final annealing process are not particular! y limited, and
known conditions may be adopted. For instance, the steel sheet may be held in the
temperature range of 1100 to 1300°C for 10 to 30 hours. Moreover, furnace atmosphere
may be known nitrogen atmosphere or mixed atmosphere of nitrogen and hydrogen.
[0151]
In a case where the annealing separator which forms the forsterite film is used,
MgO in the annealing separator reacts with Si02 of the steel sheet surface during the
final annealing, whereby the forsterite (Mg2Si04) is formed. Thus, it is preferable that
the forsterite film formed on the surface is removed by grinding or pickling the surface of
10 the final annealed steel sheet after the final annealing. The method for removing the
forsterite film from the surface of the final annealed steel sheet is not particularly limited,
and known grinding or known pickling may be adopted.
[0152]
For instance, in order to remove the forsterite film by pickling, the final
15 annealed steel sheet may be immersed in hydrochloric acid of 20 to 40 mass% at 50 to
90°C for 1 to 5 minutes, be water-washed, and then be dried. Moreover, the final
annealed steel sheet may be pickled in mixed solution of fluorinated ammonium and
sulfuric acid, be chemically polished in mixed solution of hydrofluoric acid and
hydrogen peroxide solution, be water-washed, and then be dried.
20 [0153]
< Oxidizing Process >
The oxidizing process (step S 121) is the process of conducting the washing
treatment, the pickling treatment, and the heat treatment in turn for the final annealed
steel sheet after the final annealing process (final annealed steel sheet without the
25 forsterite film) to obtain the oxidized steel sheet. Specifically, the surface of the final
54
annealed steel sheet is washed as the washing treatment, the final annealed steel sheet is
pickled using sulfuric acid of 2 to 20 mass% whose temperature is 70 to 90°C as the
pickling treatment, and the final annealed steel sheet is held in the temperature range of
700 to 900°C for 10 to 60 seconds in the atmosphere where the oxygen concentration is 5
5 to 21 volume% and the dew point is 10 to 30°C as the heat treatment.
[0154]
( Washing Treatment )
The surface of the final annealed steel sheet after the final annealing process is
washed. The method for washing the surface of the final annealed steel sheet is not
10 particularly limited, and known washing method may be adopted. For instance, the
surface of the final annealed steel sheet may be water-washed.
[0155]
( Pickling Treatment )
The final annealed steel sheet after the washing treatment is pickled using the
15 sulfuric acid whose concentration is 2 to 20 mass% and whose temperature is 70 to 90°C.
[0156]
When the sulfuric acid is less than 2 mass%, it is difficult to obtain the grain
oriented electrical steel sheet in which 0.01 < (Feo.s - Feo.os) I Feo.s < 0.35 is satisfied.
Also, when the sulfuric acid is more than 20 mass%, it is difficult to obtain the grain
20 oriented electrical steel sheet having the above features. The concentration of the
sulfuric acid is preferably 17 mass% or less, and more preferably 12 mass% or less.
[0157]
Moreover, when the temperature of the sulfuric acid is less than 70°C, the
sufficient adhesion is not obtained. On the other hand, when the temperature of the
55
sulfuric acid is more than 90°C, the effect in improving the adhesion is saturated, and the
tension which is applied to the steel sheet by the insulating coating is reduced. The
temperature of the sulfuric acid is preferably 75°C or more, and more preferably 80°C or
more. The temperature of the sulfuric acid is preferably 88°C or less, and more
5 preferably 85°C or less.
10
[0158]
The time for the pickling treatment is not particularly limited. For instance, the
final annealed steel sheet may be passed at general line speed in the pickling bath where
the above sulfuric acid is included.
[0159]
( Heat Treatment )
The final annealed steel sheet after the pickling treatment is held in the
temperature range of 700 to 900°C for 10 to 60 seconds in the atmosphere where the
oxygen concentration is 5 to 21 volume% and the dew point is 10 to 30°C. By the heat
15 treatment, the layer including mainly iron oxides and the Si included oxide layer are
formed on the surface of the final annealed steel sheet. The steel sheet after the heat
treatment becomes the steel substrate which satisfies the above conditions (I) and (II).
[0160]
When the oxygen concentration is less than 5 volume%, it is difficult to obtain
20 the grain oriented electrical steel sheet having the above features. When the oxygen
concentration is more than 21 volume%, the oxides are excessively formed, which is not
preferable. The oxygen concentration is preferably 15 volume% or more.
[0161]
When the dew point is less than 1 0°C, or when the holding temperature is less
5
10
56
than 700°C, it is difficult to obtain the grain oriented electrical steel sheet having the
above features. When the holding temperature is more than 900°C, the effect is
saturated, and the heating cost increases. When the dew point is more than 30°C, it is
difficult to obtain the grain oriented electrical steel sheet having the above features.
[0162]
When the holding time is less than 10 seconds, it is difficult to obtain the grain
oriented electrical steel sheet having the above features. Also, when the holding time is
more than 60 seconds, it is difficult to obtain the grain oriented electrical steel sheet
having the above features.
[0163]
The dew point is preferably 25°C or less, more preferably 20°C or less, and
further more preferably less than 20°C. The holding temperature is preferably 750°C or
more, and more preferably 800°C or more. The holding time is preferably 20 seconds
or more. The holding time is preferably 50 seconds or less, and more preferably 40
15 seconds or less.
[0164]
< Second Pickling Process >
In the forming method for the insulation coating according to the embodiment, a
second pickling treatment may be conducted, as necessary, after the oxidizing process
20 and before the insulation coating forming process. In the second pickling treatment, the
oxidized steel sheet after the oxidizing process may be pickled using a sulfuric acid of 1
to 5 mass% whose temperature is 70 to 90°C.
[0165]
By conducting the above second pickling treatment, it is possible to certainly
5
10
57
form the oxide layer including the layer including mainly iron oxides and the Si included
oxide layer on the surface of the oxidized steel sheet. Moreover, it is possible to
certainly obtain the grain oriented electrical steel sheet satisfying the above (formula
101).
[0166]
The concentration of the sulfuric acid is preferably 3 mass% or less. Moreover,
the temperature of the sulfuric acid is preferably 75°C or more, and more preferably
80°C or more. The temperature of the sulfuric acid is preferably 88°C or less, and more
preferably 85°C or less.
[0167]
< Insulation Coating Forming Process >
The insulation coating forming process (step S 123) is the process of applying
the solution for forming the tension-insulation coating to the surface of the oxidized steel
sheet after the oxidizing process or after the second pickling process, and of baking the
15 solution so as to form the tension-insulation coating with an average thickness of 1 to 3
~m. In the insulation coating forming process, the tension-insulation coating may be
formed on one sheet surface or both sheet surfaces of the oxidized steel sheet.
[0168]
Before applying the solution, the surface of the oxidized steel sheet to form the
20 insulation coating may be subjected to optional pretreatment such as de greasing
treatment with alkaline, pickling treatment with hydrochloric acid, sulfuric acid,
phosphoric acid, and the like. The pretreatment may not be conducted.
[0169]
The conditions for forming the tension-insulation coating are not particularly
25 limited, and known conditions may be adopted. Moreover, the tension-insulation
58
coating may mainly include inorganics and may further include organics. For instance,
the tension-insulation coating may mainly include at least one of metal chromate, metal
phosphate, colloidal silica, Zr compound, Ti compound, and the like as the inorganics,
and fine particles of organic resin may be dispersed in the tension-insulation coating.
5 From the viewpoint of reducing the environmental loading during producing, the
tension-insulation coating may be produced from starting material such as metal
phosphate, coupling agents of Zr or Ti, carbonates thereof, ammonium salts thereof.
[0170]
< Other Processes >
10 ( Flattening Annealing Process )
15
Following the insulation coating forming process, the flattening annealing may
be conducted for straightening. By conducting the flattening annealing for the grain
oriented electrical steel sheet after the insulation coating forming process, it is possible to
favorably reduce the iron loss characteristics.
[0171]
( Magnetic Domain Refining Process)
The magnetic domain refining treatment may be conducted for the produced
grain oriented electrical steel sheet. Herein, the magnetic domain refining treatment is
the treatment such that the laser beam which refines the magnetic domain is irradiated to
20 the surface of the grain oriented electrical steel sheet or the groove is formed on the
surface of the grain oriented electrical steel sheet. By conducting the magnetic domain
refining treatment, it is possible to favorably reduce the magnetic characteristics.
25
Examples
[0172]
59
Hereinafter, the effects of an aspect of the present invention are described in
detail with reference to the following examples. 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.
5 The present invention can employ various types of conditions as long as the conditions
do not depart from the scope of the present invention and can achieve the object of the
present invention.
10
15
20
[0173]
(Example 1)
A steel slab was heated to 1350°C, and then were hot-rolled to obtain the hot
rolled steel sheets having the average thickness of 2.3 mm, herein the steel slab including
0.081 mass% of C, 3.3 mass% of Si, 0.083 mass% of Mn, 0.022 mass% of S (0.022
mass% ofS+Se), 0.025 mass% ofsol.Al, 0.008 mass% ofN, 0.0025 mass% ofBi, and
the balance consisting of Fe and impurities.
[0174]
The obtained hot rolled steel sheets were annealed at 11 00°C for 120 seconds,
and then were pickled. The steel sheets after pickling were cold-rolled to obtain the
cold rolled steel sheets having the average thickness of 0.23 mm. The obtained cold
rolled steel sheets were decarburization-annealed.
[0175]
Subsequently, the annealing separator was applied and dried. In the annealing
separator, MgO and Ah03 of 95 mass% in total as percent solid were included, the
mixing ratio of MgO and Ah03 was 50% : 50% in mass%, and BiOCl of 5 mass% as
compared with the total amount of MgO and Ah03 was included. Thereafter, the final
25 annealing was conducted at 1200°C for 20 hours.
5
60
[0176]
The redundant annealing separator is removed by water-washing from the
obtained final annealed steel sheets. In the steel sheets, the glass film (forsterite film)
was not formed when confirmed by X-ray diffraction method.
[0177]
The steel sheets after removing the redundant annealing separator by
water-washing were subjected to the pickling treatment using the sulfuric acid whose
concentration was 5 mass% and whose temperature was 70°C. Thereafter, the heat
treatment was conducted at 850°C for 10 seconds in (A) 100% of N2 and 30°C of dew
10 point and (B) atmospheric air (specifically 21% of02 and 79% ofN2) and 10°C of dew
point.
[0178]
The aqueous solution which mainly included aluminum phosphate and colloidal
silica was applied to the steel sheets after the oxidizing process, the solution was baked at
15 850°C for 1 minute, and thereby, the tension-insulation coating whose coating weight
was 4.5 g/m2 per one side was formed on the surface of the steel sheets.
[0179]
The base steel sheets of the grain oriented electrical steel sheets were chemically
analyzed on the basis of the above method. The any steel sheets included, as the
20 chemical composition, by mass%, 0.002% or less of C, 3.3% of Si, 0.083% of Mn,
0.005% or less of S (0.005% or less of S+Se), 0.005% or less of sol.Al, 0.005% or less of
N, 0.0001% of Bi, and the balance consisting of Fe and impurities.
[0180]
For the obtained grain oriented electrical steel sheets of two types (A) and (B),
25 the GDS analysis, the oxygen content, the magnetic characteristics, and the coating
61
adhesion were evaluated.
[0181]
< GDS Analysis>
On the basis of the above method, for the surface of the oxidized steel sheet after
5 the oxidizing process and the surface of the grain oriented electrical steel sheet after
forming the tension-insulation coating, the glow discharge spectroscopy was conducted
using GDA750 produced by Rigaku Corporation. The measurement elements were 0,
Si, and Fe for the oxidized steel sheet and 0, Al, Si, P, and Fe for the grain oriented
electrical steel sheet. The obtained GDS depth profile was evaluated.
10
15
[0182]
(Analysis of Oxygen Content)
On the basis of the above method, the oxygen content in total of the base steel
sheet and the oxide layer was measured for the oxidized steel sheet after the oxidizing
process.
[0183]
< Magnetic Characteristics >
A test piece with a length of 300 mm parallel to the rolling direction and a width
of 60 mm was subjected to stress relief annealing at 800°C for 2 hours in nitrogen
atmosphere, and was subjected to the magnetic domain refining treatment by the laser
20 irradiation. Eight pieces of the test piece were prepared. The magnetic flux density
B8 in the rolling direction (unit : T) (magnetic flux density in 800A/m) and the iron loss
W17 /50 (unit : W /kg) (iron loss when excited to 1.7T at 50Hz) were evaluated on the
basis of the method regulated by JIS C 2556: 2015, using the test pieces. The average
of B8 was calculated using the results of the eight test pieces. Moreover, the most
25 favorable value ofW17/50 (specifically, the value of the attained iron loss) was obtained
from the results of the eight test pieces.
[0184]
< Adhesion of Insulation Coating >
62
The test piece whose longitudinal direction corresponded to the rolling direction
5 was taken from the obtained grain oriented electrical steel sheets, and the bend tests of
bending diameter
A test piece was taken from the obtained grain oriented electrical steel sheet, and
the average thickness of the tension-insulation coating was measured by the above
20 method.
[0187]
In regard to the adhesion of the insulation coating of the obtained grain oriented
electrical steel sheet, the adhesion of both steel sheets of the conditions (A) and (B) was
Grade A. The average thickness of the tension-insulation coating of both steel sheets of
25 the conditions (A) and (B) was 3.0 !-liD.
63
[0188]
Moreover, in regard to GDS depth profile, the oxidized steel sheets of the
condition (A) did not satisfy the above conditions (I) and (II). The grain oriented
electrical steel sheets of the condition (A) did not satisfy 0.01 < (Feo.s - Feo.os) I Feo.s <
5 0.35.
10
On the other hand, the oxidized steel sheets of the condition (B) satisfied the
above conditions (I) and (II). The grain oriented electrical steel sheets of the condition
(A) satisfied 0.01 < (Feo.s- Feo.os) I Feo.s < 0.35.
[0189]
Moreover, the oxygen content of the oxidized steel sheets of the condition (A)
did not satisfy 0.008 to 0.025%, and the oxygen content of the oxidized steel sheets of
the condition (B) satisfied 0.008 to 0.025%.
[0190]
Moreover, in regard to the magnetic characteristics, the grain oriented electrical
15 steel sheets of the condition (B) showed excellent attained iron loss as compared with the
grain oriented electrical steel sheets of the condition (A).
[0191]
(Example 2)
A steel slab A (steel piece A) and a steel slab B (steel piece B) were heated to
20 1350°C, and then were hot-rolled to obtain the hot rolled steel sheets having the average
thickness of 2.3 mm, herein the steel slab A including 0.082 mass% of C, 3.3 mass% of
Si, 0.082 mass% ofMn, 0.023 mass% of S (0.023 mass% of S+Se), 0.025 mass% of
sol.Al, 0.008 mass% of N, and the balance consisting of Fe and impurities, and the steel
slab B including. 0.081 mass% of C, 3.3 mass% of Si, 0.083 mass% of Mn, 0.022 mass%
25 of S (0.022 mass% of S+Se), 0.025 mass% of sol.Al, 0.008 mass% ofN, 0.0025 mass%
64
of Bi, and the balance consisting of Fe and impurities.
[0192]
The obtained hot rolled steel sheets were annealed at 11 00°C for 120 seconds,
and then were pickled. The steel sheets after pickling were cold-rolled to obtain the
5 cold rolled steel sheets having the average thickness of 0.23 mm. The obtained cold
rolled steel sheets were decarburization-annealed.
[0193]
Subsequently, the annealing separator was applied and dried. In the annealing
separator, MgO and Ah03 of 95 mass% in total as percent solid were included, the
10 mixing ratio of MgO and Ah03 was 50% : 50% in mass% ( 1 : 1 as mass ratio), and
BiOCl of 5 mass% as compared with the total amount of MgO and Ah03 was included.
Thereafter, the final annealing was conducted at 1200°C for 20 hours.
[0194]
The redundant annealing separator is removed by water-washing from the
15 obtained final annealed steel sheet. In any steel sheets, the glass film (forsterite film)
was not formed when confirmed by X-ray diffraction method.
[0195]
The steel sheets after removing the redundant annealing separator by
water-washing were subjected to the pickling treatment using the sulfuric acid whose
20 temperature was 70°C and whose concentration was shown in the following Table 1.
25
Thereafter, the heat treatment was conducted by changing atmosphere, dew point,
temperature, and time. Herein, in the test numbers 2-27, after the heat treatment, the
pickling treatment was conducted again using the sulfuric acid whose temperature was
85°C and whose concentration was 1%.
[0196]
65
[Table 1]
PRODUCTION CONDITIONS
OXIDIZING PROCESS
WASHING PICKLING HEAT TREATMENT
No. STEEL TYPE WASHING CONCENTRA Tl ON TEMPERATURE ATMOSPHERE TEMPERATURE TIME
METHOD OF OXYGEN NITROGEN HYDROGEN DEW POINT
SULFURIC ACID CONCENTRATION CONCENTRA Tl ON CONCENTRATION
mass% oc volume% volume% volume% oc oc seconds
2-1 A Water Washing 5 70 21 79 0 15 800 5
2-2 A Water Washing 5 70 21 79 0 15 850 15
2-3 A Water Washing 5 70 21 79 0 10 800 40
2-4 A Water Washing 15 70 21 79 0 20 680 20
2-5 A Water Washing 15 70 21 79 0 10 800 30
2-6 A Water Washing 15 70 21 79 0 10 840 20
2-7 A Water Washing 3 70 21 79 0 15 800 80
2-8 A Water Washing 15 70 21 79 0 10 800 30
2-9 A Water Washing 15 70 21 79 0 40 800 30
2-10 A Water Washing 15 70 0 96 4 40 850 30
2-11 A Water Washing 15 70 21 79 0 10 800 80
2-12 A Water Washing 5 70 0 100 0 40 800 40
2-13 A Water Washing 25 70 21 79 0 10 680 20
2-14 B Water Washing 5 70 21 79 0 15 800 5
2-15 B Water Washing 5 70 21 79 0 15 850 15
2-16 B Water Washing 5 70 21 79 0 10 800 40
2-17 B Water Washing 15 70 21 79 0 20 680 20
2-18 B Water Washing 15 70 21 79 0 10 800 30
2-19 B Water Washing 15 70 21 79 0 10 840 20
2-20 B Water Washing 3 70 21 79 0 15 800 80
2-21 B Water Washing 15 70 21 79 0 10 800 30
2-22 B Water Washing 15 70 21 79 0 40 800 30
2-23 B Water Washing 15 70 0 96 4 40 850 30
2-24 B Water Washing 15 70 21 79 0 10 800 80
2-25 B Water Washing 5 70 0 100 0 40 800 40
2-26 B Water Washing 25 70 21 79 0 10 680 20
2-27 B Water Washing 5 70 21 79 0 15 850 15
[0197]
The aqueous solution which mainly included aluminum phosphate and colloidal
5 silica was applied to the steel sheets after the oxidizing process, the solution was baked at
850°C for 1 minute, and thereby, the tension-insulation coating whose coating weight
was 4.5 g/m2 per one side was formed on the surface of the test piece.
[0198]
The base steel sheets of the grain oriented electrical steel sheets were chemically
10 analyzed on the basis of the above method. The steel sheets made from the steel slab A
included, as the chemical composition, by mass%, 0.002% or less of C, 3.3% of Si,
66
0.082% of Mn, 0.005% or less of S (0.005% or less of S + Se), 0.005% or less of sol.Al,
0.005% or less of N, and the balance consisting of Fe and impurities. The steel sheets
made from the steel slab B included, as the chemical composition, by mass%, 0.002% or
less of C, 3.3% of Si, 0.083% Mn, 0.005% or less of S (0.005% or less of S + Se),
5 0.005% or less of sol.Al, 0.005% or less of N, 0.0001 mass% of Bi, and the balance
consisting of Fe and impurities.
[0199]
< Evaluation >
The GDS analysis, the oxygen content, the magnetic characteristics, the coating
10 adhesion, and the like were evaluated. The evaluation methods were as follows.
[0200]
( Magnetic Characteristics )
A test piece with a length of 300 mm parallel to the rolling direction and a width
of 60 mm was subjected to stress relief annealing at 800°C for 2 hours in nitrogen
15 atmosphere, and was subjected to the magnetic domain refining treatment by the laser
irradiation. Ten pieces of the test piece were prepared. The magnetic flux density B8
in the rolling direction (unit : T) (magnetic flux density in 800A/m) and the iron loss
W17 /50 (unit : W /kg) (iron loss when excited to 1.7T at 50Hz) were evaluated on the
basis of the method regulated by JIS C 2556: 2015, using the test pieces. The average
20 of B8 was calculated using the results of the ten test pieces. Moreover, the most
favorable value ofW17/50 (specifically, the value of the attained iron loss) was obtained
from the results of the ten test pieces.
Herein, in regard to the steel type A, when the average of B8 was 1.90 Tor more
and the most favorable value ofW17/50 was 0.700 W/kg or less, it was judged to as
25 acceptable. In regard to the steel type B, when the average of B8 was 1.90 T or more
5
67
and the most favorable value of W17 /50 was 0.650 W /kg or less, it was judged to as
acceptable.
[0201]
( GDS Analysis)
On the basis of the above method, for the surface of the oxidized steel sheet after
the oxidizing process and the surface of the grain oriented electrical steel sheet after
forming the tension-insulation coating, the analysis was conducted under conditions such
that output was 30W, Ar pressure was 3 hPa, measurement area was 4 mm diameter, and
measurement time was 100 seconds in high frequency mode using GDA750 produced by
10 Rigaku Corporation. The measurement elements were 0, Si, and Fe for the oxidized
15
20
steel sheet and 0, Al, Si, P, and Fe for the grain oriented electrical steel sheet. By the
obtained GDS depth profile, it was confirmed whether or not the oxidized steel sheets
satisfied the above conditions (I) and (II), and whether or not the grain oriented electrical
steel sheets satisfied 0.01 < (Feo.s - Feo.os) I Feo.s < 0.35.
[0202]
(Analysis of Oxygen Content)
On the basis of the above method, the oxygen content in total of the base steel
sheet and the oxide layer was measured for the oxidized steel sheet after the oxidizing
process.
[0203]
( Adhesion of Tension-Insulation Coating )
The test piece whose longitudinal direction corresponded to the rolling direction
was taken from the obtained grain oriented electrical steel sheets, and the bend tests of
bending diameter
The GDS analysis, the oxygen content, the magnetic characteristics, the coating
5 adhesion, and the like were evaluated. The evaluation methods for the GDS analysis,
the oxygen content, the coating adhesion, and the average coating thickness were the
same as those in the Example 2. The magnetic characteristics were evaluated as
follows.
[0219]
10 ( Magnetic Characteristics )
Ten pieces of the test piece with a length of 300 mm parallel to the rolling
direction and a width of 60 mm were prepared. The test pieces were subjected to stress
relief annealing at 800°C for 2 hours in nitrogen atmosphere, and then, the magnetic
characteristics in the rolling direction was evaluated on the basis of the method regulated
75
by JIS C 2556: 2015. When the average of the magnetic flux density B8 (unit: T) was
1.90 Tor more, it was judged to as acceptable. For the steel sheets whose magnetic flux
density B8 was acceptable, the laser beam was irradiated in order to refine the magnetic
domain. For the steel sheets for which the laser beam was irradiated, the most favorable
5 value of the iron loss W17 /50 (unit : W /kg) (iron loss when excited to 1.7T at 50Hz) were
evaluated. Herein, when the average of B8 was 1.90 Tor more and the most favorable
value ofW17/50 was 0.700 W/kg or less, it was judged to as acceptable.
[0220]
The obtained results are summarized in the following Table 5.
10 [0221]
[Table 5]
PRODUCT I ON RESULTS EVALUATION RESULTS REMARKS
AFTER OXIDIZING PROCESS AFTER INSilATION COATING FORMIOO PROCESS MAGNETIC CHARACTERISTICS ADHESION
CONDITION CONDITION OXYGEN (Fe05-Fe005) AVERAGE 88 Wn;5o ¢20 ¢10
No. STEEL TYPE (I) (II) CONTENT /Feo.s THICKNESS MOST BENDING BENDING
PRESENCE RATIO OF AVERAGE FAVORABLE
OF OF INSULATION VALUE
PLATEAU Si EMISSION COATING
REGION INTENSITY mass% jlm T W/kg
3-1 A-1 Presence 0.385 0.019 0.13 2.0 1.944 0.699 A A INVENTIVE EXAMPLE
3-2 A-2 Presence 0.415 0.021 0.17 2.0 1.946 0.700 A A INVENTIVE EXAMPLE
3-3 A-3 Presence 0.431 0.022 0.18 2.0 1.985 0.618 A A INVENTIVE EXAMPLE
3-4 A-4 Presence 0.435 0.021 0.16 2.0 1.985 0.622 A A INVENTIVE EXAMPLE
3-5 A-5 Presence 0.425 0.019 0.17 2.0 1.985 0.622 A A INVENTIVE EXAMPLE
3-6 A-6 Presence 0.421 0.021 0.17 2.0 1.981 0.628 A A INVENTIVE EXAMPLE
3-7 A-7 Presence 0.463 0.022 0.15 2.0 1.982 0.629 A A INVENTIVE EXAMPLE
3-8 A-8 Presence 0.398 0.021 0.12 2.0 1.982 0.628 A A INVENTIVE EXAMPLE
3-9 A-9 Presence 0.425 0.019 0.13 2.0 1.986 0.615 A A INVENTIVE EXAMPLE
3-10 A-10 Presence 0.437 0.021 0.16 2.0 1.987 0.610 A A INVENTIVE EXAMPLE
3-11 A-11 Presence 0.411 0.022 0.14 2.0 1.988 0.608 A A INVENTIVE EXAMPLE
3-12 A-12 - - - - - - - - - COMPARATIVE EXAMPLE
3-13 A-13 Presence 0.425 0.021 0.13 2.0 1.681 - A A COMPARATIVE EXAMPLE
3-14 A-14 Presence 0.418 0.022 0.14 2.0 1.661 - A A COMPARATIVE EXAMPLE
3-15 A-15 Presence 0.421 O.D18 0.12 2.0 1.721 - A A COMPARATIVE EXAMPLE
3-16 A-16 Presence 0.435 0.019 0.13 2.0 1.691 - A A COMPARATIVE EXAMPLE
3-17 A-17 Presence 0.441 0.019 0.16 2.0 1.681 - A A COMPARATIVE EXAMPLE
3-18 A-18 Presence 0.465 O.D18 0.15 2.0 1.722 - A A COMPARATIVE EXAMPLE
3-19 A-19 Presence 0.397 0.019 0.18 2.0 1.701 - A A COMPARATIVE EXAMPLE
3-20 A-20 Presence 0.427 0.018 0.11 2.0 1.725 - A A COMPARATIVE EXAMPLE
3-21 A-21 - - - - - - - - - COMPARATIVE EXAMPLE
3-22 A-22 Presence 0.440 0.021 0.12 2.0 1.722 - A A COMPARATIVE EXAMPLE
3-23 A-23 Presence 0.420 0.021 0.13 2.0 1.741 - A A COMPARATIVE EXAMPLE
[0222]
As clearly shown in the Tables 3 to 5, since the chemical compositions of the
76
base steel sheets were satisfied in the test numbers 3-1 to 3-11, both magnetic
characteristics and adhesion of the insulation coating were excellent.
Moreover, since the chemical compositions of the steel slabs were favorable in
the test numbers 3-3 to 3-11 among the above test numbers, the magnetic characteristics
5 were further excellent.
10
[0223]
On the other hand,
since the Si content was excessive in the test number 3-12, the steel sheet was
fractured during cold rolling.
Since the Si content was insufficient in the test number 3-13, the magnetic
characteristics were inferior.
Since the C content was insufficient in the test number 3-14 and the C content
was excessive in the test number 3-15, the magnetic characteristics were inferior.
Since the sol.Al content was insufficient in the test number 3-16, the magnetic
15 characteristics were inferior.
20
Since the sol.Al content was excessive in the test number 3-17, the steel sheet
was fractured during cold rolling.
Since the Mn content was insufficient in the test number 3-18 and the Mn
content was excessive in the test number 3-19, the magnetic characteristics were inferior.
Since the total amount of Sand Se was insufficient in the test number 3-20, the
magnetic characteristics were inferior.
Since the total amount of Sand Se was excessive in the test number 3-21, the
steel sheet was fractured during hot rolling.
Since theN content was excessive in the test number 3-22, the magnetic
25 characteristics were inferior.
77
Since theN content was insufficient in the test number 3-23, the magnetic
characteristics were inferior.
[0224]
(Example 4)
5 Steel slabs (steel pieces) with chemical compositions shown in the following
Table 6 were heated to 1350°C, and then were hot-rolled to obtain the hot rolled steel
sheets having the average thickness of 2.3 mm.
[0225]
[Table 6]
PRODUCT! ON CONDIT! ONS
CHEMICAL COMPOSITION OF SLAB (STEEL PIECE) (UNIT: mass%, BALANCE CONSISTING OF Fe AND IMPURITIES)
c Si Mn s Se s soi.AI N Bi Sb Sn Cr Cu
STEEL TYPE +Se
B-1 0.081 3.35 0.081 0.022 - 0.022 0.025 0.008 0.0031 - - - -
B-2 0.083 3.25 0.082 0.023 - 0.022 0.025 0.008 0.0031 - - - -
B-3 0.082 3.30 0.082 0.023 - 0.022 0.025 0.008 0.0025 - - - -
B-4 0.081 3.30 0.083 0.022 - 0.022 0.025 0.008 0.0025 - - - -
B-5 0.082 3.30 0.082 0.023 - 0.023 0.025 0.008 - 0.021 - - -
B-6 0.081 3.30 0.083 0.022 - 0.022 0.025 0.008 - - 0.031 - -
B-7 0.082 3.30 0.082 0.023 - 0.023 0.025 0.008 - - - 0.052 -
B-8 0.081 3.30 0.083 0.022 - 0.022 0.025 0.008 - - - - 0.051
B-9 0.081 3.35 0.081 0.022 - 0.022 0.025 0.008 - - - - -
B-10 0.081 3.35 0.081 0.022 - 0.022 0.025 0.008 0.0025 - - - -
10
[0226]
The obtained hot rolled steel sheets were annealed at 11 00°C for 120 seconds,
and then were pickled. The steel sheets after pickling were cold-rolled to obtain the
cold rolled steel sheets having the average thickness of 0.23 mm. The obtained cold
78
rolled steel sheets were decarburization-annealed.
[0227]
Subsequently, the final annealing was conducted under conditions shown in the
following Table 7. In the Table 7, the amount of main materials in the annealing
5 separator is shown as percent solid. Moreover, the amount of the bismuth chloride is
shown as the amount compared with the total amount of MgO and Ah03.
[0228]
[Table 7]
PRODUCTION CONDITIONS
FINAL ANNEALING
ANNEALING SEPARATOR TEMPERATURE TIME REMOVING
No. STEEL TYPE MAIN MATERIALS BISMUTH CHLORIDE FILM
TYPE AMOUNT MgO TYPE AMOUNT
I or II (TOTAL) /AI20 3
mass% mass ratio mass% oc hour
4-1 B-1 I 95 1 : 1 BiCI3 5 1200 20 Not Conducted
4-2 B-2 I 95 1 : 1 BiCI3 5 1200 20 Not Conducted
4-3 B-3 II 100 1 :0 None - 1200 20 Conducted
4-4 B-4 II 100 1 :0 None - 1200 20 Conducted
4-5 B-5 I 93 1 : 1 BiOCI 7 1200 20 Not Conducted
4-6 B-6 I 93 1 : 1 BiOCI 7 1200 20 Not Conducted
4-7 B-7 I 93 1 : 1 BiOCI 7 1200 20 Not Conducted
4-8 B-8 I 93 1 : 1 BiOCI 7 1200 20 Not Conducted
4-9 B-9 I 93 1 : 1 BiOCI 7 1200 20 Not Conducted
4-10 B-9 I 93 1 : 1 BiOCI 7 1200 20 Not Conducted
4-12 B-9 I 93 1 : 1 BiOCI 7 1200 20 Not Conducted
4-13 B-9 I 93 1 : 1 BiOCI 7 1200 20 Not Conducted
4-14 B-9 I 93 1 : 1 BiOCI 7 1200 20 Not Conducted
4-15 B-9 I 93 1 : 1 BiOCI 7 1200 20 Not Conducted
4-16 B-10 I 93 6: 4 BiCI3 7 1200 20 Not Conducted
4-17 B-10 I 93 4:6 BiOCI 7 1200 20 Not Conducted
?.::: : "I" indicates "MgO+AI20 3" and "II" indicates "MgO" in the above table.
10 [0229]
The redundant annealing separator is removed by water-washing from the
79
obtained final annealed steel sheet. In any steel sheets except for the test numbers 4-3
and 4-4, the glass film (forsterite film) was not formed when confirmed by X-ray
diffraction method. In the steel sheets of the test numbers 4-3 and 4-4, the forsterite
film formed on the surface was removed by grinding or pickling the surface of the final
5 annealed steel sheet after the final annealing. Thereafter, in any steel sheets, the glass
film (forsterite film) was not formed when confirmed by X-ray diffraction method.
[0230]
The steel sheets after removing the redundant annealing separator by
water-washing (the steel sheets after removing the glass film in the test numbers 4-3 and
10 4-4) were subjected to the pickling treatment under conditions shown in the following
Table 8. Herein, in the test numbers 4-16 and 4-17 shown in the Table 8, the pickling
treatment in the oxidizing process was not conducted, and the oxygen concentration in
the atmosphere during the heat treatment was 0 volume% (25 volume% of nitrogen and
75 volume% of hydrogen).
15 [0231]
[Table 8]
80
PRODUCT! ON CONDITIONS
OXIDIZING PROCESS
WASHING PICKLING HEAT TREATMENT
No. STEEL TYPE WASHING CONCENTRATION TEMPERATURE ATMOSPHERE TEMPERATURE TIME
METHOD OF OXYGEN NITROGEN HYDROGEN DEW POINT
SULFURIC ACID CONCENTRATION CONCENTRA Tl ON CONCENTRATION
mass% oc volume% volume% volume% oc oc seconds
4-1 B-1 Water Washing 10 80 15 85 0 10 800 20
4-2 B-2 Water Washing 10 85 10 90 0 10 800 20
4-3 B-3 Water Washing 10 80 15 85 0 10 800 20
4-4 B-4 Water Washing 10 85 10 90 0 10 800 20
4-5 B-5 Water Washing 10 80 15 85 0 10 800 20
4-6 B-6 Water Washing 10 85 10 90 0 10 800 20
4-7 B-7 Water Washing 10 80 15 85 0 10 800 20
4-8 B-8 Water Washing 10 85 10 90 0 10 800 20
4-9 B-9 Water Washing 1 70 21 79 0 10 800 20
4-10 B-9 Water Washing 10 25 21 79 0 10 800 20
4-12 B-9 Water Washing 10 70 35 65 0 10 800 20
4-13 B-9 Water Washing 10 70 2 98 0 10 800 20
4-14 B-9 Water Washing 10 70 21 79 0 0 800 20
4-15 B-9 Water Washing 10 70 21 79 0 10 950 30
4-16 B-10 Water Washing Not Conducted Not Conducted - 25 75 -2 800 20
4-17 B-10 Water Washing Not Conducted Not Conducted - 25 75 0 800 10
[0232]
The aqueous solution which mainly included aluminum phosphate and colloidal
silica was applied to the steel sheets after the oxidizing process, the solution was baked at
5 850°C for 1 minute, and thereby, the tension-insulation coating whose coating weight
was 4.5 g/m2 was formed on the surface of the steel sheets. The laser beam was
irradiated on the test piece in order to refine the magnetic domain.
[0233]
The base steel sheets of the grain oriented electrical steel sheets were chemically
10 analyzed on the basis of the above method. The chemical compositions are shown in
Table 9. In regard to Table 6 and Table 9, the element which is expressed in blanc or"-"
in the tables indicates the element in which the purposeful control is not conducted for
the amount thereof during production.
81
[0234]
[Table 9]
PRODUCTION RESULTS
CHEMICAL COMPOSITION OF GRAIN ORIENTED ELECTRICAL STEEL SHEET (UNIT mass%, BALANCE CONSISTING OF Fe AND IMPURITIES)
c Si Mn s Se s soi.AI N Bi Sb Sn Cr Cu
No_ STEEL TYPE +Se
4-1 B-1 ;;;ao_oo2 3.35 0.081 0.005 0.001 ;;;ao_oo5 ;;;ao_oo5 0.005 0.0001 - - - -
4-2 B-2 ;;;ao_oo2 3.25 0.082 0.005 0.001 ;;;ao_oo5 ;;;ao_oo5 0.005 0.0001 - - - -
4-3 B-3 ;;;ao_oo2 3.30 0.082 0.005 0.001 ;;;ao_oo5 ;;;ao_oo5 0.005 0.0001 - - - -
4-4 B-4 ;;;ao_oo2 3.30 0.083 0.005 0.001 ;;;ao_oo5 ;;;ao_oo5 0.005 0.0001 - - - -
4-5 B-5 ;;;ao.oo2 3.30 0.082 0.005 0.001 ;;;ao.oo5 ;;;ao.oo5 0.005 - 0.021 - - -
4-6 B-6 ;;;;o.oo2 3.30 0.083 0.005 0.001 ;;;ao.oo5 ;;;ao.oo5 0.005 - - 0.031 - -
4-7 B-7 ;;;;o.oo2 3.30 0.082 0.005 0.001 ;;;ao.oo5 ;;;ao.oo5 0.005 - - - 0.052 -
4-8 B-8 ;;;;o.oo2 3.30 0.083 0.005 0.001 ;;;;o.oo5 ;;;;o.oo5 0.005 - - - - 0.051
4-9 B-9 ;;;;o.oo2 3.35 0.081 0.005 0.001 ;;;ao.oo5 ;;;ao.oo5 0.005 - - - - -
4-10 B-9 ;;;;o.oo2 3.35 0.081 0.005 0.001 ;;;ao.oo5 ;;;ao.oo5 0.005 - - - - -
4-12 B-9 ;;;;o.oo2 3.35 0.081 0.005 0.001 ;;;ao.oo5 ;;;ao.oo5 0.005 - - - - -
4-13 B-9 ;;;;o.oo2 3.35 0.081 0.005 0.001 ;;;ao.oo5 ;;;ao.oo5 0.005 - - - - -
4-14 B-9 ;;;ao.oo2 3.35 0.081 0.005 0.001 ;;;ao.oo5 ;;;ao.oo5 0.005 - - - - -
4-15 B-9 ;;;;o.oo2 3.35 0.081 0.005 0.001 ;;;ao.oo5 ;;;ao.oo5 0.005 - - - - -
4-16 B-10 ;;;;o.oo2 3.35 0.081 0.005 0.001 ;;;ao.oo5 ;;;ao.oo5 0.005 0.0001 - - - -
4-17 B-10 ;;;;o.oo2 3.35 0.081 0.005 0.001 ;;;;o.oo5 ;;;;o.oo5 0.005 0.0001 - - - -
[0235]
5 < Evaluation >
The GDS analysis, the oxygen content, the magnetic characteristics, the coating
adhesion, and the like were evaluated. The evaluation methods were the same as those
in the Example 2. Herein, when the average of B8 was 1.90 Tor more and the most
favorable value of W17 /50 was 0.650 W /kg or less, it was judged to as acceptable.
10 [0236]
The obtained results are summarized in the following Table 10.
[0237]
[Table 10]
82
PRODUCTION RESULTS EVALUATION RESULTS REMARKS
AFTER OXIDIZING PROCESS AFTER INSULATION COATING FORMING PROCESS MAGNETIC CHARACTERISTICS ADHESION
CONDITION CONDITION OXYGEN (Feo.5-Feo.o5) AVERAGE Ba W11;so ¢20 ¢10
No. STEEL TYPE (!) (II) CONTENT /Feo5 THICKNESS BENDING BENDING
PRESENCE RATIO OF MOST
OF OF INSULATION AVERAGE FAVORABLE
PLATEAU Si EMISSION COATING
VALUE
REGION INTENSITY mass% f..lm T W/kg
4-1 B-1 Presence 0.323 0.017 0.15 2.0 1.979 0.604 A A INVENTIVE EXAMPLE
4-2 B-2 Presence 0.435 0.014 0.21 2.0 1.981 0.601 A A INVENTIVE EXAMPLE
4-3 B-3 Presence 0.341 0.013 0.22 2.0 1.977 0.607 A A INVENTIVE EXAMPLE
4-4 B-4 Presence 0.336 0.021 0.28 2.0 1.978 0.603 A A INVENTIVE EXAMPLE
4-5 B-5 Presence 0.229 0.019 0.26 2.0 1.958 0.611 A A INVENTIVE EXAMPLE
4-6 B-6 Presence 0.287 0.009 0.19 2.0 1.954 0.613 A A INVENTIVE EXAMPLE
4-7 B-7 Presence 0.199 0.011 0.27 2.0 1.953 0.612 A A INVENTIVE EXAMPLE
4-8 B-8 Presence 0.188 0.012 0.31 2.0 1.956 0.613 A A INVENTIVE EXAMPLE
4-9 B-9 Presence 0.120 0.007 0.36 2.0 1.923 0.721 B B COMPARATIVE EXAMPLE
4-10 B-9 Presence 0.145 0.007 0.37 2.0 1.925 0.723 B B COMPARATIVE EXAMPLE
4-12 B-9 Presence 0.610 0.026 0.38 2.0 1.926 0.719 c c COMPARATIVE EXAMPLE
4-13 B-9 Presence 0.110 0.007 0.36 2.0 1.922 0.721 c c COMPARATIVE EXAMPLE
4-14 B-9 Presence 0.140 0.007 0.37 2.0 1.927 0.718 c c COMPARATIVE EXAMPLE
4-15 B-9 Presence 0.510 0.026 0.36 2.0 1.921 0.725 c c COMPARATIVE EXAMPLE
4-16 B-10 Absence 0.782 0.007 0.36 2.0 1.962 0.698 c c COMPARATIVE EXAMPLE
4-17 B-10 Absence 0.877 0.007 0.36 2.0 1.963 0.691 c c COMPARATIVE EXAMPLE
[0238]
As clearly shown in the Tables 6 to 10, since the chemical compositions of the
base steel sheets were satisfied and the production conditions were satisfied in the test
5 numbers 4-1 to 4-8, both magnetic characteristics and adhesion of the tension-insulation
coating were excellent. On the other hand, since the production conditions were not
favorable in the test numbers 4-9 and 4-17, the magnetic characteristics and the adhesion
of the tension-insulation coating were inferior.
10 Industrial Applicability
[0239]
According to the above aspects of the present invention, it is possible to provide
the grain oriented electrical steel sheet in which the adhesion of the tension-insulation
coating is excellent and the iron loss characteristics are also excellent (the iron loss is
5
10
83
low) even without the glass film (forsterite film). In addition, it is possible to provide
the method for forming the above insulation coating and for producing the above grain
oriented electrical steel sheet. Accordingly, the present invention has significant
industrial applicability.
Reference Signs List
[0240]
10 Grain oriented electrical steel sheet
11 Base steel sheet
13
15
Tension-insulation coating
Oxide layer
WE CLAIMS
1. A grain oriented electrical steel sheet without a forsterite film characterized in
that
the grain oriented electrical steel sheet comprises:
a base steel sheet;
an oxide layer arranged in contact with the base steel sheet; and
a tension-insulation coating arranged in contact with the oxide layer,
wherein the base steel sheet includes, as a chemical composition, by mass%,
2.5 to 4.0% of Si,
0.05 to 1.0% of Mn,
0 to 0.01% of C,
0 to 0.005% of S+Se,
0 to 0.01% of sol.Al,
0 to 0.005% of N,
0 to 0.03% of Bi,
0 to 0.03% of Te,
0 to 0.03% of Pb,
0 to 0.50% of Sb,
0 to 0.50% of Sn,
0 to 0.50% of Cr,
0 to 1.0% of Cu, and
a balance consisting of Fe and impurities,
the tension-insulation coating is a phosphate-silica mixed tension-insulation
25 coating with an average thickness of 1 to 3 ~m,
85
when a glow discharge spectroscopy is conducted in a region from a surface of
the tension-insulation coating to an inside of the base steel sheet, when a sputtering time
at which a Fe emission intensity becomes 0.5 times as compared with a saturation value
thereof on a depth profile is referred to as Feo.s in unit of seconds, and when a sputtering
5 time at which a Fe emission intensity becomes 0.05 times as compared with the
saturation value on the depth profile is referred to as Feo.os in unit of seconds, the Feo.s
and the Feo.os satisfy 0.01 < (Feo.s - Feo.os) I Feo.s < 0.35, and
10
15
a magnetic flux density B8 in a rolling direction of the grain oriented electrical
steel sheet is 1. 90 T or more.
2. A forming method for an insulation coating of a grain oriented electrical steel
sheet without a forsterite film characterized in that
the forming method for the insulation coating includes an insulation coating
forming process of forming a tension-insulation coating on a steel substrate,
wherein, in the insulation coating forming process,
a solution for forming a phosphate-silica mixed tension-insulation coating is
applied to an oxide layer of the steel substrate and the solution is baked so as to form the
tension-insulation coating with an average thickness of 1 to 3 ~m,
the steel substrate includes a base steel sheet and the oxide layer arranged in
20 contact with the base steel sheet,
25
the base steel sheet includes, as a chemical composition, by mass%,
2.5 to 4.0% of Si,
0.05 to 1.0% of Mn,
0 to 0.01% of C,
0 to 0.005% of S+Se,
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10
0 to 0.01% of sol.Al,
0 to 0.005% of N,
0 to 0.03% of Bi,
0 to 0.03% of Te,
0 to 0.03% of Pb,
0 to 0.50% of Sb,
0 to 0.50% of Sn,
0 to 0.50% of Cr,
0 to 1.0% of Cu, and
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a balance consisting of Fe and impurities,
the base steel sheet and the oxide layer include, as a total chemical composition,
by mass%,
0.008 to 0.025% of 0,
when a glow discharge spectroscopy is conducted in a region from a surface of
15 the oxide layer to an inside of the base steel sheet, when a sputtering time at which a Fe
emission intensity becomes a saturation value thereof on a depth profile is referred to as
Fesat in unit of seconds, a plateau region of a Fe emission intensity where a Fe emission
intensity stays for Fesat x 0.05 seconds or more in a range of 0.20 to 0.80 times as
compared with the saturation value is included between 0 second and the Fesat on the
20 depth profile, and
when a sputtering time at which a Si emission intensity becomes a maximal
value on the depth profile is referred to as Simax in unit of seconds, a maximal point of a
Si emission intensity at which a Si emission intensity at the Simax becomes 0.15 to 0.50
times as compared with a Fe emission intensity at the Simax is included between the
25 plateau region and the Fesat on the depth profile.
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3. A producing method for a grain oriented electrical steel sheet without a forsterite
film characterized in that
the producing method includes
a hot rolling process of heating and thereafter hot-rolling a steel piece to obtain a
hot rolled steel sheet,
a hot band annealing process of optionally annealing the hot rolled steel sheet to
obtain a hot band annealed steel sheet,
a cold rolling process of cold-rolling the hot rolled steel sheet or the hot band
10 annealed steel sheet by cold-rolling once or by cold-rolling plural times with an
intermediate annealing to obtain a cold rolled steel sheet,
a decarburization annealing process of decarburization -annealing the cold rolled
steel sheet to obtain a decarburization annealed steel sheet,
a final annealing process of applying an annealing separator to the
15 decarburization annealed steel sheet and thereafter final-annealing the decarburization
annealed steel sheet to obtain a final annealed steel sheet,
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25
an oxidizing process of conducting a washing treatment, a pickling treatment,
and a heat treatment in turn for the final annealed steel sheet to obtain an oxidized steel
sheet, and
an insulation coating forming process of applying a solution for forming a
phosphate-silica mixed tension-insulation coating to a surface of the oxidized steel sheet
and of baking the solution so as to form the tension-insulation coating with an average
thickness of 1 to 3 ~m,
wherein, in the hot rolling process,
the steel piece includes, as a chemical composition, by mass%,
5
10
15
2.5 to 4.0% of Si,
0.05 to 1.0% of Mn,
0.02 to 0.10% ofC,
0.005 to 0.080% of S+Se,
0.01 to 0.07% of sol.Al,
0.005 to 0.020% of N,
0 to 0.03% of Bi,
0 to 0.03% of Te,
0 to 0.03% of Pb,
0 to 0.50% of Sb,
0 to 0.50% of Sn,
0 to 0.50% of Cr,
0 to 1.0% of Cu, and
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a balance consisting of Fe and impurities, and
wherein, in the oxidizing process,
as the washing treatment, a surface of the final annealed steel sheet is washed,
as the pickling treatment, the final annealed steel sheet is pickled using a sulfuric
acid of 2 to 20 mass% whose temperature is 70 to 90°C, and
as the heat treatment, the final annealed steel sheet is held in a temperature range
20 of 700 to 900°C for 10 to 60 seconds in an atmosphere where an oxygen concentration is
5 to 21 volume% and a dew point is 10 to 30°C.
4. The producing method for the grain oriented electrical steel sheet according to
claim 3,
25 the producing method further including, after the oxidizing process and before
89
the insulation coating forming process,
a second pickling process of pickling the oxidized steel sheet using a sulfuric
acid of 1 to 5 mass% whose temperature is 70 to 90°C.
5 5. The producing method for the grain oriented electrical steel sheet according to
claim 3 or 4,
wherein, in the final annealing process,
the annealing separator includes MgO, Ah03, and a bismuth chloride.
10 6. The producing method for the grain oriented electrical steel sheet according to
15
20
any one of claims 3 to 5,
wherein, in the hot rolling process,
the steel piece includes, as the chemical composition, by mass%, at least one
selected from a group consisting of
0.0005 to 0.03% of Bi,
0.0005 to 0.03% of Te, and
0.0005 to 0.03% of Pb.
