U.S. patent application number 13/579684 was filed with the patent office on 2012-12-13 for method of manufacturing grain-oriented electrical steel sheet.
Invention is credited to Kenichi Murakami, Yoshiyuki Ushigami.
Application Number | 20120312423 13/579684 |
Document ID | / |
Family ID | 44483041 |
Filed Date | 2012-12-13 |
United States Patent
Application |
20120312423 |
Kind Code |
A1 |
Murakami; Kenichi ; et
al. |
December 13, 2012 |
METHOD OF MANUFACTURING GRAIN-ORIENTED ELECTRICAL STEEL SHEET
Abstract
Hot rolling is performed on a steel with a predetermined
composition containing Ti: 0.0020 mass % to 0.010 mass % and/or Cu:
0.010 mass % to 0.50 mass % to obtain a hot-rolled steel sheet.
Annealing is performed on the hot-rolled steel sheet to obtain an
annealed steel sheet. Cold rolling is performed on the annealed
steel sheet to obtain a cold-rolled steel sheet. Decarburization
annealing is performed on the cold-rolled steel sheet at a
temperature of 800.degree. C. to 950.degree. C. to obtain a
decarburization annealed steel sheet. Then, nitridation treatment
is performed on the decarburization annealed steel sheet at
700.degree. C. to 850.degree. C. to obtain a nitrided steel sheet.
Finish annealing is performed on the nitrided steel sheet.
Inventors: |
Murakami; Kenichi; (Tokyo,
JP) ; Ushigami; Yoshiyuki; (Tokyo, JP) |
Family ID: |
44483041 |
Appl. No.: |
13/579684 |
Filed: |
February 18, 2011 |
PCT Filed: |
February 18, 2011 |
PCT NO: |
PCT/JP2011/053491 |
371 Date: |
August 17, 2012 |
Current U.S.
Class: |
148/208 |
Current CPC
Class: |
C21D 3/04 20130101; C23C
8/02 20130101; H01F 1/16 20130101; C22C 38/04 20130101; C21D 8/1272
20130101; C22C 38/14 20130101; C21D 9/46 20130101; C22C 38/001
20130101; C23C 8/80 20130101; C22C 38/34 20130101; C21D 8/12
20130101; C22C 38/06 20130101; C22C 38/16 20130101; C21D 8/1255
20130101 |
Class at
Publication: |
148/208 |
International
Class: |
C23C 8/80 20060101
C23C008/80; C23C 8/02 20060101 C23C008/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 18, 2010 |
JP |
2010-033921 |
Claims
1. A method of manufacturing a grain-oriented electrical steel
sheet, comprising: performing hot rolling of a steel containing Si:
2.5 mass % to 4.0 mass %, C, 0.01 mass % to 0.060 mass %, Mn: 0.05
mass % to 0.20 mass %, acid-soluble Al: 0.020 mass % to 0.040 mass
%, N: 0.002 mass % to 0.012 mass %, S: 0.001 mass % to 0.010 mass
%, and P: 0.01 mass % to 0.08 mass %, further containing at least
one kind selected from a group consisting of Ti: 0.0020 mass % to
0.010 mass % and Cu: 0.010 mass % to 0.50 mass %, and a balance
composed of Fe and inevitable impurities, to obtain a hot-rolled
steel sheet; performing annealing on the hot-rolled steel sheet to
obtain an annealed steel sheet; performing cold rolling on the
annealed steel sheet to obtain a cold-rolled steel sheet;
performing decarburization annealing on the cold-rolled steel sheet
at a temperature of 800.degree. C. to 950.degree. C. to obtain a
decarburization annealed steel sheet; then, performing nitridation
treatment on the decarburization annealed steel sheet at
700.degree. C. to 850.degree. C. to obtain a nitrided steel sheet;
and performing finish annealing on the nitrided steel sheet.
2. The method of manufacturing a grain-oriented electrical steel
sheet according to claim 1, wherein the hot rolling on the steel is
performed after heating the steel to a temperature of 1250.degree.
C. or lower.
3. The method of manufacturing a grain-oriented electrical steel
sheet according to claim 1, wherein the steel further contains at
least one kind selected from a group consisting of Cr: 0.010 mass %
to 0.20 mass %, Sn: 0.010 mass % to 0.20 mass %, Sb: 0.010 mass %
to 0.20 mass %, Ni: 0.010 mass % to 0.20 mass %, Se: 0.005 mass %
to 0.02 mass %, Bi: 0.005 mass % to 0.02 mass %, Pb: 0.005 mass %
to 0.02 mass %, B: 0.005 mass % to 0.02 mass %, V: 0.005 mass % to
0.02 mass %, Mo: 0.005 mass % to 0.02 mass %, and As: 0.005 mass %
to 0.02 mass %.
4. The method of manufacturing a grain-oriented electrical steel
sheet according to claim 2, wherein the steel further contains at
least one kind selected from a group consisting of Cr: 0.010 mass %
to 0.20 mass %, Sn: 0.010 mass % to 0.20 mass %, Sb: 0.010 mass %
to 0.20 mass %, Ni: 0.010 mass % to 0.20 mass %, Se: 0.005 mass %
to 0.02 mass %, Bi: 0.005 mass % to 0.02 mass %, Pb: 0.005 mass %
to 0.02 mass %, B: 0.005 mass % to 0.02 mass %, V: 0.005 mass % to
0.02 mass %, Mo: 0.005 mass % to 0.02 mass %, and As: 0.005 mass %
to 0.02 mass %.
5. The method of manufacturing a grain-oriented electrical steel
sheet according to claim 1, wherein a Ti content in the steel is
0.0020 mass % to 0.0080 mass %, a Cu content in the steel is 0.01
mass % to 0.10 mass %, and a relation of
"20.times.[Ti]+[Cu].ltoreq.0.18" is established where the Ti
content (mass %) in the steel is expressed as [Ti] and the Cu
content (mass %) is expressed as [Cu].
6. The method of manufacturing a grain-oriented electrical steel
sheet according to claim 2, wherein a Ti content in the steel is
0.0020 mass % to 0.0080 mass %, a Cu content in the steel is 0.01
mass % to 0.10 mass %, and a relation of
"20.times.[Ti]+[Cu].ltoreq.0.18" is established where the Ti
content (mass %) in the steel is expressed as [Ti] and the Cu
content (mass %) is expressed as [Cu].
7. The method of manufacturing a grain-oriented electrical steel
sheet according to claim 3, wherein a Ti content in the steel is
0.0020 mass % to 0.0080 mass %, a Cu content in the steel is 0.01
mass % to 0.10 mass %, and a relation of
"20.times.[Ti]+[Cu].ltoreq.0.18" is established where the Ti
content (mass %) in the steel is expressed as [Ti] and the Cu
content (mass %) is expressed as [Cu].
8. The method of manufacturing a grain-oriented electrical steel
sheet according to claim 4, wherein a Ti content in the steel is
0.0020 mass % to 0.0080 mass %, a Cu content in the steel is 0.01
mass % to 0.10 mass %, and a relation of
"20.times.[Ti]+[Cu].ltoreq.0.18" is established where the Ti
content (mass %) in the steel is expressed as [Ti] and the Cu
content (mass %) is expressed as [Cu].
9. The method of manufacturing a grain-oriented electrical steel
sheet according wherein a relation of
"10.times.[Ti]+[Cu].ltoreq.0.07" is established to claim 5.
10. The method of manufacturing a grain-oriented electrical steel
sheet according to claim 6, wherein a relation of
"10.times.[Ti]+[Cu].ltoreq.0.07" is established.
11. The method of manufacturing a grain-oriented electrical steel
sheet according to claim 7, wherein a relation of
"10.times.[Ti]+[Cu].ltoreq.0.07" is established.
12. The method of manufacturing a grain-oriented electrical steel
sheet according to claim 8, wherein a relation of
"10.times.[Ti]+[Cu].ltoreq.0.07" is established.
Description
[0001] This application is a national stage application of
International Application No. PCT/JP2011/053491, filed Feb. 18,
2011, which claims priority to Japanese Application No.
2010-033921, filed Feb. 18, 2010, the content of which is
incorporated by reference herein in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to a method of manufacturing a
grain-oriented electrical steel sheet in which the variation in
magnetic property is suppressed.
BACKGROUND ART
[0003] A grain-oriented electrical steel sheet is a steel sheet
which contains Si and in which crystal grains are highly integrated
in a {110}<001> orientation, and is used as a material of a
wound core of a stationary induction apparatus such as a
transformer. The control of the orientation of the crystal grains
is conducted with catastrophic grain growth phenomenon called
secondary recrystallization.
[0004] As a method of controlling the secondary recrystallization,
the following two methods can be cited. In one method, heating is
performed on a slab at a temperature of 1280.degree. C. or higher
to almost completely solid-solve fine precipitates called
inhibitors, and thereafter hot rolling, cold rolling, annealing and
so on are performed to cause the fine precipitates to precipitate
during the hot rolling and the annealing. In the other method,
heating is performed on a slab at a temperature of lower than
1280.degree. C., and thereafter hot rolling, cold rolling,
decarburization annealing, nitridation, finish annealing and so on
are performed to cause AlN (Al, Si)N and the like to precipitate as
inhibitors during the nitridation.
[0005] In recent years, it has been requested to reduce a time
taken for a decarburization annealing in a manufacturing process of
a grain-oriented electrical steel sheet from a point of view of
reduction in CO.sub.2 emissions. Accordingly, it has been studied
to use a slab whose C content is low.
[0006] However, lowering the C content of the slab causes a
remarkable variation in magnetic property (magnetic property
deviation) depending on site, after the finish annealing performed
with the steel being coiled.
CITATION LIST
Patent Literature
[0007] Patent Literature 1: Japanese Laid-open Patent Publication
No. 03-122227 [0008] Patent Literature 2: Japanese Laid-open Patent
Publication No. 11-323437 [0009] Patent Literature 3: Japanese
Laid-open Patent Publication No. 06-256847 [0010] Patent Literature
4: Japanese National Publication of International Patent
Application No. 2001-515540 [0011] Patent Literature 5: Japanese
Laid-open Patent Publication No. 2000-199015 [0012] Patent
Literature 6: Japanese Laid-open Patent Publication No.
2007-254829
SUMMARY OF INVENTION
Technical Problem
[0013] An object of the present invention is to provide a method of
manufacturing a grain-oriented electrical steel sheet, capable of
suppressing the variation in magnetic property.
Solution to Problem
[0014] It turned out that the above-described variation in magnetic
properties after the finish annealing is remarkable when the C
content is 0.06 mass % or less, and further, it is particularly
noticeable when the C content is 0.048 mass % or less. Although the
cause of the variation in magnetic property after the finish
annealing is not exactly known, the variation is considered to
occur because the crystal grains sometimes do not uniformly grow
during the finish annealing even if the crystal grains seem to be
uniform before the finish annealing. Further, it may be considered
that the reason why the crystal grains do not uniformly grow is
because, due to the low C content, a phase transformation during
the hot rolling is not sufficiently performed, so that an amount of
austenite transformation is small, resulting in that a hot-rolled
texture becomes unstable. Specifically, it may be considered that a
sufficient secondary recrystallization does not occur in a portion
in which the hot-rolled texture becomes nonuniform, resulting in
that sufficient magnetic properties are not obtained.
[0015] The present inventors thought, based on such knowledge, that
it is possible to sufficiently cause the secondary
recrystallization through forming an effective precipitate in order
to make the crystal grain growth uniform during the finish
annealing. Then, the present inventors repeatedly carried out an
experiment of measuring the magnetic properties of the
grain-oriented electrical steel sheets obtained through adding
various kinds of elements to slabs. As a result, the present
inventors found that addition of Ti and Cu was effective to make
the secondary recrystallization uniform.
[0016] The present invention has been made based on the
above-described knowledge, and a summary thereof is as follows.
[0017] (1) A method of manufacturing a grain-oriented electrical
steel sheet, comprising:
[0018] performing hot rolling of a steel containing Si: 2.5 mass %
to 4.0 mass %, C, 0.01 mass % to 0.060 mass %, Mn: 0.05 mass % to
0.20 mass %, acid-soluble Al: 0.020 mass % to 0.040 mass %, N,
0.002 mass % to 0.012 mass %, S: 0.001 mass % to 0.010 mass %, and
P: 0.01 mass % to 0.08 mass %, further containing at least one kind
selected from a group consisting of Ti: 0.0020 mass % to 0.010 mass
% and Cu: 0.010 mass % to 0.50 mass %, and a balance composed of Fe
and inevitable impurities, to obtain a hot-rolled steel sheet;
[0019] performing annealing on the hot-rolled steel sheet to obtain
an annealed steel sheet;
[0020] performing cold rolling on the annealed steel sheet to
obtain a cold-rolled steel sheet;
[0021] performing decarburization annealing on the cold-rolled
steel sheet at a temperature of 800.degree. C. to 950.degree. C. to
obtain a decarburization annealed steel sheet;
[0022] then, performing nitridation treatment on the
decarburization annealed steel sheet at 700.degree. C. to
850.degree. C. to obtain a nitrided steel sheet; and
[0023] performing finish annealing on the nitrided steel sheet.
[0024] (2) The method of manufacturing a grain-oriented electrical
steel sheet according to (1), wherein the hot rolling on the steel
is performed after heating the steel to a temperature of
1250.degree. C. or lower.
[0025] (3) The method of manufacturing a grain-oriented electrical
steel sheet according to (1) or (2), wherein the steel further
contains at least one kind selected from a group consisting of Cr:
0.010 mass % to 0.20 mass %, Sn: 0.010 mass % to 0.20 mass %, Sb:
0.010 mass % to 0.20 mass %, Ni: 0.010 mass % to 0.20 mass %, Se:
0.005 mass % to 0.02 mass %, Bi: 0.005 mass % to 0.02 mass %, Pb:
0.005 mass % to 0.02 mass %, B: 0.005 mass % to 0.02 mass %, V:
0.005 mass % to 0.02 mass %, Mo: 0.005 mass % to 0.02 mass %, and
As: 0.005 mass % to 0.02 mass %.
[0026] (4) The method of manufacturing a grain-oriented electrical
steel sheet according to any one of (1) to (3), wherein
[0027] a Ti content in the steel is 0.0020 mass % to 0.0080 mass
%,
[0028] a Cu content in the steel is 0.01 mass % to 0.10 mass %,
and
[0029] a relation of "20.times.[Ti]+[Cu].ltoreq.0.18" is
established where the Ti content (mass %) in the steel is expressed
as [Ti] and the Cu content (mass %) is expressed as [Cu].
[0030] (5) The method of manufacturing a grain-oriented electrical
steel sheet according to (4), wherein a relation of
"10.times.[Ti]+[Cu].ltoreq.0.07" is established.
Advantageous Effects of Invention
[0031] According to the present invention, appropriate amounts of
Ti and/or Cu are contained in the steel, and decarburization
annealing and nitridation treatment are performed at appropriate
temperatures, thereby making it possible to suppress the variation
in magnetic property.
BRIEF DESCRIPTION OF DRAWINGS
[0032] FIG. 1 is a chart representing the relation between a Ti
content and a Cu content and the magnetic flux density and the
evaluation of its variation.
[0033] FIG. 2 is a flowchart illustrating a method of manufacturing
a grain-oriented electrical steel sheet according to an embodiment
of the present invention.
DESCRIPTION OF EMBODIMENTS
[0034] As described above, the present inventors repeatedly
conducted the experiments of measuring the magnetic properties of
the grain-oriented electrical steel sheets obtained through adding
various kinds of elements to slabs and found out that addition of
Ti and Cu is effective to make the secondary recrystallization
uniform.
[0035] In the experiment, silicon steel with a composition used for
manufacturing a grain-oriented electrical steel sheet based on a
low-temperature slab heating method in which a C content was
0.06-mass % or less was used, for example. Further, Ti and Cu were
contained at various ratios into the silicon steel to produce steel
ingots with various compositions. Further, the steel ingots were
heated at a temperature of 1250.degree. C. or lower and subjected
to hot rolling, and then subjected to cold rolling. Further,
decarburization annealing was performed after the cold rolling, and
thereafter, nitridation treatment and finish annealing were
performed. Then, the magnetic flux densities B8 of the obtained
grain-oriented electrical steel sheets were measured and the
variations in the magnetic flux densities B8 in coils after the
finish annealing were checked. The magnetic flux density B8 is the
magnetic flux density occurring in the grain-oriented electrical
steel sheet when a magnetic field of 800 A/m at 50 Hz is applied
thereto.
[0036] As a result of the experiment, it was found out that the
variation in the magnetic flux density B8 in the coil after the
finish annealing is remarkably reduced when the steel ingot
contains 0.0020 mass % to 0.010 mass % of Ti and/or 0.010 mass % to
0.50 mass % of Cu.
[0037] An example of the results obtained through the
above-described experiments is illustrated in FIG. 1. Though
details of the experiments will be described later, an open circle
mark in FIG. 1 indicates that the average value of the magnetic
flux densities B8 of five single-plate samples was 1.90 T or more
and the difference between the maximum value and the minimum value
of the magnetic flux density B8 was 0.030 T or less. Further, a
filled circle mark in FIG. 1 indicates that at least the average
value of the magnetic flux densities B8 of the five single-plate
samples was less than 1.90 T or the difference between the maximum
value and the minimum value of the magnetic flux densities B8 was
more than 0.030 T. It is apparent from FIG. 1 that when the steel
ingot contains 0.0020 mass % to 0.010 mass % of Ti and/or 0.010
mass % to 0.50 mass % of Cu, the average value of the magnetic flux
densities B8 is high and the variation in the magnetic flux
densities B8 is small.
[0038] Next, a method of manufacturing a grain-oriented electrical
steel sheet according to an embodiment of the present invention
will be described. FIG. 2 is a flowchart illustrating the method of
manufacturing a grain-oriented electrical steel sheet according to
the embodiment of the present invention.
[0039] In the present embodiment, first, a slab is produced through
casting of molten steel for a grain-oriented electrical steel sheet
with a predetermined composition (Step 1). The casting method
therefor is not particularly limited. The molten steel contains,
for example, Si: 2.5 mass % to 4.0 mass %, C, 0.01 mass % to 0.060
mass %, Mn: 0.05 mass % to 0.20 mass %, acid-soluble Al: 0.020 mass
% to 0.040 mass %, N: 0.002 mass % to 0.012 mass %, S: 0.001 mass %
to 0.010 mass %, and P: 0.01 mass % to 0.08 mass %. The molten
steel further contains at least one kind selected from a group
consisting of Ti: 0.0020 mass % to 0.010 mass % and Cu: 0.010 mass
% to 0.50 mass %. In short, the molten steel contains one or both
of Ti and Cu in ranges of Ti: 0.010 mass % or less and Cu: 0.50
mass % or less to satisfy at least one of Ti: 0.0020 mass % or more
or Cu: 0.010 mass % or more. The balance of the molten steel may be
composed of Fe and inevitable impurities. Note that the inevitable
impurities may include an element(s) forming an inhibitor in the
manufacturing process of the grain-oriented electrical steel sheet
and remaining in the grain-oriented electrical steel sheet after
purification is performed through a high-temperature annealing.
[0040] Here, reasons for numerical limitations of the composition
of the above-described molten steel will be described.
[0041] Si is an element that is extremely effective to enhance the
electrical resistance of the grain-oriented electrical steel sheet
to reduce the eddy current loss constituting a part of the core
loss. When the Si content is less than 2.5 mass %, the eddy current
loss cannot be sufficiently suppressed. On the other hand, when the
Si content is more than 4.0 mass %, the processability is lowered.
Accordingly, the Si content is set to 2.5 mass % to 4.0 mass %.
[0042] C is an element that is effective to control the structure
(primary recrystallization structure) obtained through primary
recrystallization. When the C content is less than 0.01 mass %, the
effect cannot be sufficiently obtained. On the other hand, when the
C content is more than 0.06 mass, the time required for
decarburization annealing increases, resulting in a larger exhaust
amount of CO.sub.2. Note that when the decarburization annealing is
insufficient, the grain-oriented electrical steel sheet with
excellent magnetic properties is less likely to be obtained.
Accordingly, the C content is set to 0.01 mass % to 0.06 mass %.
Further, since the variation in magnetic property after finish
annealing is particularly prominent when the C content is 0.048
mass % or less in the conventional technique as described above,
the embodiment is particularly effective in the case where the C
content is 0.048 mass % or less.
[0043] Mn increases the specific resistance of the grain-oriented
electrical steel sheet to reduce the core loss. Mn also functions
to prevent occurrence of cracks in the hot rolling. When the Mn
content is less than 0.05 mass %, the effects cannot be
sufficiently obtained. On the other hand, when the Mn content is
more than 0.20 mass %, the magnetic flux density of the
grain-oriented electrical steel sheet is lowered. Accordingly, the
Mn content is set to 0.05 mass % to 0.20 mass %.
[0044] Acid-soluble Al is an important element forming AlN serving
as an inhibitor. When the acid-soluble Al content is less than
0.020 mass %, a sufficient amount of AlN cannot be formed,
resulting in insufficient inhibitor strength. On the other hand,
when the acid-soluble Al content is more than 0.040 mass %, AlN
becomes coarse, resulting in a decrease in inhibitor strength.
Accordingly, the acid-soluble Al content is set to 0.020 mass % to
0.040 mass %.
[0045] N is an important element forming AlN through reacting with
the acid-soluble Al. Though a large amount of N does not need to be
contained in the grain-oriented electrical steel sheet because
nitridation treatment is performed after the cold rolling as will
be described later, a great load may be required in steelmaking in
order to make the N content less than 0.002 mass %. On the other
hand, when the N content is more than 0.012 mass %, a hole called
blister is generated in the steel sheet in the cold rolling.
Accordingly, the N content is set to 0.002 mass % to 0.012 mass %.
The N content is preferably 0.010% mass % or less in order to
further reduce the blister.
[0046] S is an important element forming a MnS precipitate through
reacting with Mn. The MnS precipitate mainly affects the primary
recrystallization and functions to suppress the variation depending
on site in grain growth in the primary recrystallization due to the
hot rolling. When the Mn content is less than 0.001 mass %, the
effect cannot be sufficiently obtained. On the other hand, when the
Mn content is more than 0.010 mass %, the magnetic property is
likely to decrease. Accordingly, the Mn content is set to 0.001
mass % to 0.010 mass %. The Mn content is preferably 0.009 mass %
or less in order to further improve the magnetic property.
[0047] P increases the specific resistance of the grain-oriented
electrical steel sheet to reduce the core loss. When the P content
is less than 0.01 mass %, the effect cannot be sufficiently
obtained. On the other hand, when the P content is more than 0.08
mass %, the cold rolling may become difficult to perform.
Accordingly, the P content is set to 0.01 mass % to 0.08 mass
%.
[0048] Ti forms a TiN precipitate through reacting with N. Further,
Cu forms a CuS precipitate through reacting with S. These
precipitates function to make the growth of the crystal grains in
the finish annealing uniform irrespective of the site of the coil
and suppress the variation in magnetic property of the
grain-oriented electrical steel sheet. In particular, the TiN
precipitate is considered to suppress the variation in grain growth
in a high temperature region in the finish annealing to decrease
the deviation of the magnetic property of the grain-oriented
electrical steel sheet. Further, the CuS precipitate is considered
to suppress the variation in grain growth in a low temperature
region in the decarburization annealing and the finish annealing to
decrease the deviation of the magnetic property of the
grain-oriented electrical steel sheet. When the Ti content is less
than 0.0020 mass % and the Cu content is less than 0.010 mass %,
the effects cannot be sufficiently obtained. On the other hand,
when the Ti content is more than 0.010 mass %, the TiN precipitate
is excessively formed and remains even after the finish annealing.
Similarly, when the Cu content is more than 0.50 mass %, the CuS
precipitate is excessively formed and remains even after the finish
annealing. If these precipitates remain in the grain-oriented
electrical steel sheet, it is difficult to obtain a high magnetic
property. Accordingly, the molten steel contains one or both of Ti
and Cu in ranges of Ti: 0.010 mass % or less and Cu: 0.50 mass % or
less to satisfy at least one of Ti: 0.0020 mass % or more or Cu:
0.010 mass % or more. In short, the molten steel contains at least
one kind selected from a group consisting of Ti: 0.0020 mass % to
0.010 mass % and Cu: 0.010 mass % to 0.50 mass %.
[0049] Note that the lower limit of the Ti content is preferably
0.0020 mass %, and the upper limit of the Ti content is preferably
0.0080 mass %. Further, the lower limit of the Cu content is
preferably 0.01 mass %, and the upper limit of the Cu content is
preferably 0.10 mass %. Further, where the Ti content (mass %) is
expressed as [Ti] and the Cu content (mass %) is expressed as [Cu],
it is more preferable that the relation of
"20.times.[Ti]+[Cu].ltoreq.0.18" is established and, preferably,
the relation of "10.times.[Ti]+[Cu].ltoreq.0.07" is
established.
[0050] Note that at least one kind of the following various kinds
of elements may be contained in the molten steel.
[0051] Cr and Sn improve the quality of an oxide layer to be formed
in the decarburization annealing and improve the quality of a glass
film to be formed of the oxide layer in the finish annealing. In
other words, Cr and Sn improve the magnetic property through
stabilization of the formation of the oxide layer and the glass
film to suppress the variation in the magnetic property. However,
when the Cr content is more than 0.20 mass %, the formation of the
glass film may be unstable. Further, when the Sn content is more
than 0.20 mass %, the surface of the steel sheet may be less likely
to be oxidized to result in insufficient formation of the glass
film. Accordingly, each of the Cr content and the Sn content is
preferably 0.20 mass % or less. Further, in order to sufficiently
obtain the above effects, each of the Cr content and the Sn content
is preferably 0.01 mass % or more. Note that Sn is a grain boundary
segregation element and thus also has an effect to stabilize
secondary recrystallization.
[0052] Further, the molten steel may contain Sb: 0.010 mass % to
0.20 mass %, Ni: 0.010 mass % to 0.20 mass %, Se: 0.005 mass % to
0.02 mass %, Bi: 0.005 mass % to 0.02 mass %, Pb: 0.005 mass % to
0.02 mass %, B: 0.005 mass % to 0.02 mass %, V: 0.005 mass % to
0.02 mass %, Mo: 0.005 mass % to 0.02 mass %, and/or As: 0.005 mass
% to 0.02 mass %. These elements may be inhibitor strengthening
elements.
[0053] In the embodiment, after the slab is produced from the
molten steel with the composition, the slab is heated (Step S2).
The temperature of the heating is preferably set to 1250.degree. C.
or lower from the viewpoint of energy saving.
[0054] Next, hot rolling is performed on the slab to obtain a
hot-rolled steel sheet (Step S3). The thickness of the hot-rolled
steel sheet is not particularly limited, and may be set to 1.8 mm
to 3.5 mm.
[0055] Thereafter, annealing is performed on the hot-rolled steel
sheet to obtain an annealed steel sheet (Step S4). The condition of
the annealing is not particularly limited, and the annealing may be
performed, for example, at a temperature of 750.degree. C. to
1200.degree. C. for 30 seconds to 10 minutes. The annealing
improves the magnetic property.
[0056] Subsequently, cold rolling is performed on the annealed
steel sheet to obtain a cold-rolled steel sheet (Step S5). The cold
rolling may be performed only once or a plurality of times while an
intermediate annealing is performed therebetween. The intermediate
annealing is preferably performed at a temperature of 750.degree.
C. to 1200.degree. C. for 30 seconds to 10 minutes.
[0057] Note that if the cold rolling is performed without
performing the above-described intermediate annealing, it may be
difficult to obtain uniform properties. On the other hand, if the
cold rolling is performed a plurality of times while the
intermediate annealing is performed therebetween, the uniform
properties are easily obtained but the magnetic flux density may
decrease. Accordingly, it is preferable to determine the number of
times of the cold rolling and the presence or absence of the
intermediate annealing according to the property required for and
the cost of the finally obtained grain-oriented electrical steel
sheet.
[0058] Further, in any case, it is preferable to set the rolling
reduction at the final cold rolling to 80% to 95%.
[0059] The decarburization annealing is performed on the
cold-rolled steel sheet in a wet atmosphere containing hydrogen and
nitrogen at 800.degree. C. to 950.degree. C. after the cold rolling
to obtain a decarburization annealed steel sheet (step S6). The
decarburization annealing removes carbon in the steel sheet and
causes primary recrystallization. When the temperature of the
decarburization annealing is lower than 800.degree. C., the crystal
grain obtained through the primary recrystallization (primary
recrystallization grain) is small so that the subsequent secondary
recrystallization does not sufficiently appear. On the other hand,
when the temperature of the decarburization annealing is higher
than 950.degree. C., the primary recrystallization grain is large
so that the subsequent secondary recrystallization does not
sufficiently appear.
[0060] Next, nitridation treatment is performed on the
decarburization annealed steel sheet in an atmosphere containing
hydrogen, nitrogen and a gas having a nitriding capability such as
ammonia at 700.degree. C. to 850.degree. C. to obtain a nitrided
steel sheet (step S7). The nitridation treatment increases the
nitrogen content in the steel sheet. When the temperature of the
nitridation treatment is lower than 700.degree. C. or high than
850.degree. C., nitrogen is difficult to be diffused to the inner
part of the steel sheet so that the subsequent secondary
recrystallization does not sufficiently appear.
[0061] After that, an annealing separating agent containing MgO as
a main component is applied, in a water slurry, to the surface of
the nitrided steel sheet, and the nitrided steel sheet is coiled.
Then, batch-type finish annealing is performed on the coiled
nitrided steel sheet to obtain a coiled finish-annealed steel sheet
(Step S8). The finish annealing causes secondary
recrystallization.
[0062] Thereafter, the coiled finish-annealed steel sheet is
uncoiled, and the annealing separating agent is removed.
Subsequently, a coating solution containing aluminum phosphate and
colloidal silica as main components is applied to the surface of
the finish-annealed steel sheet, and baking is performed thereon to
form an insulating film (step S9).
[0063] In the above manner, the grain-oriented electrical steel
sheet can be manufactured.
[0064] Note that the steel being an object for the hot rolling is
not limited to the slab obtained through casting of the molten
steel, but a so-called thin slab may be used. Further, when using
the thin slab, it is not always necessary to perform the slab
heating at 1250.degree. C. or lower.
Example
[0065] Next, experiments conducted by the present inventors will be
described. Conditions and so on in these experiments are examples
employed to verify practicality and effects of the present
invention, and the present invention is not limited to these
examples.
First Experiment
[0066] First, 15 kinds of steel ingots each containing Si: 3.2 mass
%, C, 0.055 mass %, Mn: 0.10 mass %, acid-soluble Al: 0.028 mass %,
N: 0.003 mass %, S: 0.0060 mass %, and P: 0.030 mass %, further
containing Ti and Cu in amounts listed in Table 1, and the balance
composed of Fe and inevitable impurities were produced using a
vacuum melting furnace. Then, annealing was performed on the steel
ingots at 1150.degree. C. for one hour, and then hot rolling was
performed thereon to obtain hot-rolled steel sheets with a
thickness of 2.3 mm.
[0067] Subsequently, annealing was performed on the hot-rolled
steel sheets at 1100.degree. C. for 120 seconds to obtain annealed
steel sheets. Next, acid pickling was performed on the annealed
steel sheets, and then cold rolling was performed on the annealed
steel sheets to obtain cold-rolled steel sheets with a thickness of
0.23 mm. Subsequently, decarburization annealing was performed on
the cold-rolled steel sheets in an atmosphere containing water
vapor, hydrogen, and nitrogen at 860.degree. C. for 100 seconds to
obtain decarburization annealed steel sheets. Next, nitridation
treatment was performed on the decarburization annealed steel
sheets in an atmosphere containing hydrogen, nitrogen, and ammonia
at 770.degree. C. for 20 seconds to obtain nitrided steel
sheets.
[0068] Thereafter, an annealing separating agent containing MgO as
a main component was applied, in a water slurry, to the surfaces of
the decarburized nitrided steel sheets. Then, finish annealing was
performed on them at 1200.degree. C. for 20 hours to obtain
finish-annealed steel sheets. Subsequently, the finish-annealed
steel sheets were washed with water, and then cutout into a
single-plate magnetic measurement size with a width of 60 mm and a
length of 300 mm. Subsequently, a coating solution containing
aluminum phosphate and colloidal silica as main components was
applied to the surfaces of the finish-annealed steel sheets, and
baking was performed thereon to form an insulating film. In this
manner, samples of the grain-oriented electrical steel sheets were
obtained.
[0069] Then, the magnetic flux density B8 of each of the
grain-oriented electrical steel sheets was measured. The magnetic
flux density B8 is the magnetic flux density occurring in the
grain-oriented electrical steel sheet when a magnetic field of 800
A/m at 50 Hz is applied thereto as described above. Note that the
magnetic flux densities B8 of five single-plate samples for
measurement were measured for each of the samples. Then, for each
sample, the average value "average B8," the maximum value "B8max,"
and the minimum value "B8 min" were obtained. The difference
".DELTA.B8" between the maximum value "B8max" and the minimum value
"B8 min" was also obtained. The difference "AB8" is an index
indicating the fluctuation range of the magnetic property. These
results are listed in Table 1 together with the Ti contents and the
Cu contents. Further, the evaluation results based on the average
value "average B8" and the difference ".DELTA.B8" are indicated in
FIG. 1. As described above, an open circle mark in FIG. 1 indicates
that the average value "average B8" was 1.90 T or more and the
difference ".DELTA.B8" was 0.030 T or less. Further, a filled
circle mark in FIG. 1 indicates that the average value "average B8"
was less than 1.90 T or the difference ".DELTA.B8" was more than
0.030 T.
TABLE-US-00001 TABLE 1 Ti Cu AVERAGE SAMPLE CONTENT CONTENT B8 B8
max B8 min .DELTA. B8 No. (MASS %) (MASS %) 20 .times. [Ti] + [Cu]
10 .times. [Ti] + [Cu] (T) (T) (T) (T) NOTE 1 0.0011 0.006 0.028
0.017 1.914 1.931 1.890 0.041 COMPARATIVE EXAMPLE 2 0.0024 0.007
0.055 0.031 1.913 1.923 1.902 0.021 EMBODIMENT 3 0.0048 0.006 0.102
0.054 1.911 1.919 1.897 0.022 EMBODIMENT 4 0.0084 0.008 0.176 0.092
1.902 1.915 1.889 0.026 EMBODIMENT 5 0.0109 0.005 0.223 0.114 1.877
1.887 1.866 0.021 COMPARATIVE EXAMPLE 6 0.0013 0.033 0.059 0.046
1.914 1.924 1.901 0.023 EMBODIMENT 7 0.0015 0.083 0.113 0.098 1.913
1.922 1.895 0.027 EMBODIMENT 8 0.0014 0.182 0.210 0.196 1.911 1.919
1.894 0.025 EMBODIMENT 9 0.0011 0.430 0.452 0.441 1.901 1.908 1.884
0.024 EMBODIMENT 10 0.0013 0.576 0.602 0.589 1.876 1.884 1.861
0.023 COMPARATIVE EXAMPLE 11 0.0033 0.079 0.145 0.112 1.911 1.921
1.901 0.020 EMBODIMENT 12 0.0055 0.084 0.194 0.139 1.903 1.910
1.891 0.019 EMBODIMENT 13 0.0068 0.018 0.154 0.086 1.912 1.921
1.899 0.022 EMBODIMENT 14 0.0082 0.380 0.544 0.462 1.902 1.908
1.893 0.015 EMBODIMENT 15 0.0028 0.022 0.078 0.050 1.914 1.927
1.907 0.020 EMBODIMENT
[0070] As presented in Table 1 and FIG. 1, in the samples No. 2 to
No. 4, No. 6 to No. 9, and No. 11 to No. 15, in each of which the
Ti content and the Cu content were within the range of the present
invention, the average value "average B8" was large to be 1.90 T or
more, and the difference ".DELTA.B8" was small to be 0.030 T or
less. In short, high magnetic property was obtained and the
variation in magnetic property was small.
[0071] In particular, the balance between the average value
"average B8" and the difference ".DELTA.B8" was excellent in the
samples No. 11, No. 13, and No. 15, in which the relation of
"20.times.[Ti]+[Cu].ltoreq.0.18" was established where the Ti
content (mass %) was expressed as [Ti] and the Cu content (mass %)
was expressed as [Cu]. Among them, the balance between the average
value "average B8" and the difference ".DELTA.B8" was extremely
excellent in the sample No. 15, in which the relation of
"10.times.[Ti]+[Cu].ltoreq.0.07" was established.
[0072] On the other hand, in the sample No. 1, in which the Ti
content was less than 0.0020 mass % and the Cu content was less
than 0.010 mass %, the difference ".DELTA.B8" was large to be more
than 0.030 T. In short, the variation in magnetic property was
large. Further, in the sample No. 5, in which the Ti content was
more than 0.010 mass % and the sample No. 10, in which the Cu
content was more than 0.50 mass %, a large amount of precipitate
was contained to affect the finish annealing, with the result that
the average value "average B8" was small to be less than 1.90 T. In
short, a sufficiently high magnetic property could not be
obtained.
Second Experiment
[0073] First, a steel ingot containing Si: 3.2 mass %, C, 0.051
mass %, Mn: 0.09 mass %, acid-soluble Al: 0.026 mass %, N: 0.004
mass %, S: 0.0053 mass %, P: 0.027 mass %, Ti: 0.0024 mass %, Cu:
0.029 mass %, and the balance composed of Fe and inevitable
impurities was produced using a vacuum melting furnace. Then,
annealing was performed on the steel ingot at 1150.degree. C. for
one hour, and then hot rolling was performed thereon to obtain a
hot-rolled steel sheet with a thickness of 2.4 mm.
[0074] Subsequently, annealing was performed on the hot-rolled
steel sheet at 1090.degree. C. for 120 seconds to obtain an
annealed steel sheet. Then, acid pickling was performed on the
annealed steel sheet, and then cold rolling was performed on the
annealed steel sheet to obtain a cold-rolled steel sheet with a
thickness of 0.23 mm. Subsequently, eight pieces of steel sheets
for annealing were cutout from the cold-rolled steel sheet, and
decarburization annealing was performed on each of the steel sheets
in an atmosphere containing water vapor, hydrogen, and nitrogen at
a temperature T1 ranging from 790.degree. C. to 960.degree. C.
listed in Table 2 for 80 seconds to obtain decarburization annealed
steel sheets. Next, nitridation treatment was performed on each of
the decarburization annealed steel sheets in an atmosphere
containing water vapor, hydrogen, nitrogen, and ammonia at a
temperature T2 ranging from 680.degree. C. to 880.degree. C. listed
in Table 2 for 20 seconds to obtain nitrided steel sheets.
[0075] Thereafter, an annealing separating agent containing MgO as
a main component was applied, in a water slurry, to the surfaces of
the nitrided steel sheets. Then, finish annealing was performed on
them at 1200.degree. C. for 20 hours to obtain finish annealed
steel sheets. Subsequently, treatments from the water washing to
the formation of the insulating film were performed similarly to
the first experiment to obtain samples of the grain-oriented
electrical steel sheets.
[0076] Then, for each of the samples, the average value "average
B8," the maximum value "B8max," the minimum value "B8 min," and the
difference ".DELTA.B8" were obtained similarly to the first
experiment. These results are listed in Table 2 together with the
temperatures T1 and the temperatures T2.
TABLE-US-00002 TABLE 2 SAMPLE T1 T2 AVERAGE B8 B8 max B8 min
.DELTA. B8 No. (.degree. C.) (.degree. C.) (T) (T) (T) (T) NOTE 21
790 780 1.840 1.859 1.832 0.027 COMPARATIVE EXAMPLE 22 820 780
1.911 1.918 1.895 0.023 EMBODIMENT 23 870 780 1.924 1.931 1.908
0.023 EMBODIMENT 24 930 780 1.925 1.937 1.908 0.029 EMBODIMENT 25
860 780 1.824 1.872 1.770 0.102 COMPARATIVE EXAMPLE 26 860 670
1.896 1.907 1.880 0.027 COMPARATIVE EXAMPLE 27 860 750 1.922 1.930
1.906 0.024 EMBODIMENT 28 860 860 1.823 1.872 1.777 0.095
COMPARATIVE EXAMPLE
[0077] As presented in Table 2, in the samples No. 22 to No. 24,
and No. 27, in which the temperature T1 of the decarburization
annealing and the temperature T2 of the nitridation treatment were
within the range of the present invention, the average value
"average B8" was large to be 1.90 T or more, and the difference
".DELTA.B8" was small to be 0.030 T or less. In short, a high
magnetic property was obtained and the variation in the magnetic
property was small.
[0078] On the other hand, in the sample No. 21, in which the
temperature T1 of the decarburization annealing was less than
800.degree. C., the average value "average B8" was small to be less
than 1.90 T. In the sample No. 25, in which the temperature T1 of
the decarburization annealing was higher than 950.degree. C., the
difference ".DELTA.B8" was large to be over 0.030 T, and the
average value "average B8" was small to be less than 1.90 T.
Further, in the sample No. 26, in which the temperature T2 of the
nitridation treatment was less than 700.degree. C., the average
value "average B8" was small to be less than 1.90 T. In the sample
No. 28, in which the temperature T2 of the nitridation treatment is
higher than 850.degree. C., the difference ".DELTA.B8" was large to
be high than 0.030 T, and the average value "average B8" was small
to be less than 1.90 T.
Third Experiment
[0079] First, 20 kinds of steel ingots each containing Si: 3.2 mass
%, Mn: 0.09 mass %, acid-soluble Al: 0.026 mass %, N: 0.004 mass %,
S: 0.0053 mass %, and P: 0.027 mass %, further containing C, Ti and
Cu in amounts listed in Table 3, and the balance composed of Fe and
inevitable impurities were produced using a vacuum melting furnace.
Then, annealing was performed on the steel ingots at 1150.degree.
C. for one hour, and then hot rolling was performed to obtain
hot-rolled steel sheets with a thickness of 2.4 mm.
[0080] Subsequently, annealing was performed on the hot-rolled
steel sheets at 1090.degree. C. for 120 seconds to obtain annealed
steel sheets. Then, acid pickling was performed on the annealed
steel sheets, and then, cold rolling was performed on the annealed
steel sheets to obtain cold-rolled steel sheets with a thickness of
0.23 mm. Subsequently, steel sheets for annealing were cutout from
the cold-rolled steel sheets, and decarburization annealing was
performed on the steel sheets in an atmosphere containing water
vapor, hydrogen, and nitrogen at 860.degree. C. for 80 seconds to
obtain decarburization annealed steel sheets. Next, nitridation
treatment was performed on the decarburization annealed steel
sheets in an atmosphere containing water vapor, hydrogen, nitrogen,
and ammonia at 760.degree. C. for 20 seconds to obtain nitrided
steel sheets.
[0081] Thereafter, an annealing separating agent containing MgO as
a main component was applied, in a water slurry, to the surfaces of
the nitrided steel sheets. Then, finish annealing was performed on
them at 1200.degree. C. for 20 hours to obtain finish annealed
steel sheets. Subsequently, treatments from the water washing to
the formation of insulating film were performed similarly to the
first experiment to obtain samples of the grain-oriented electrical
steel sheets.
[0082] Then, for each of the samples, the average value "average
B8," the maximum value "B8max," the minimum value "B8 min," and the
difference ".DELTA.B8" were obtained similarly to the first
experiment. These results are listed in Table 3 together with the C
contents, the Ti contents and the Cu contents.
TABLE-US-00003 TABLE 3 C Ti Cu SAMPLE CONTENT CONTENT CONTENT
AVERAGE B8 .DELTA. B8 No. (MASS %) (MASS %) (MASS %) 20 .times.
[Ti] + [Cu] 10 .times. [Ti] + [Cu] (T) (T) NOTE 31 0.028 0.0014
0.006 0.034 0.020 1.868 0.051 COMPARATIVE EXAMPLE 32 0.028 0.0024
0.024 0.072 0.048 1.911 0.024 EMBODIMENT 33 0.028 0.0042 0.051
0.135 0.093 1.906 0.021 EMBODIMENT 34 0.028 0.0070 0.390 0.530
0.460 1.901 0.018 EMBODIMENT 35 0.028 0.0105 0.560 0.770 0.665
1.822 0.016 COMPARATIVE EXAMPLE 36 0.039 0.0015 0.005 0.035 0.020
1.892 0.046 COMPARATIVE EXAMPLE 37 0.039 0.0023 0.022 0.068 0.045
1.913 0.022 EMBODIMENT 38 0.039 0.0044 0.053 0.141 0.097 1.907
0.019 EMBODIMENT 39 0.039 0.0075 0.350 0.500 0.425 1.902 0.017
EMBODIMENT 40 0.039 0.0110 0.590 0.810 0.700 1.843 0.015
COMPARATIVE EXAMPLE 41 0.048 0.0018 0.007 0.043 0.025 1.904 0.042
COMPARATIVE EXAMPLE 42 0.048 0.0026 0.025 0.077 0.051 1.914 0.021
EMBODIMENT 43 0.048 0.0043 0.052 0.138 0.095 1.908 0.019 EMBODIMENT
44 0.048 0.0072 0.370 0.514 0.442 1.903 0.017 EMBODIMENT 45 0.048
0.0122 0.550 0.794 0.672 1.852 0.014 COMPARATIVE EXAMPLE 46 0.057
0.0017 0.008 0.042 0.025 1.912 0.037 COMPARATIVE EXAMPLE 47 0.057
0.0024 0.026 0.074 0.050 1.915 0.020 EMBODIMENT 48 0.057 0.0046
0.054 0.146 0.100 1.908 0.017 EMBODIMENT 49 0.057 0.0074 0.380
0.528 0.454 1.907 0.015 EMBODIMENT 50 0.057 0.0109 0.540 0.758
0.649 1.871 0.013 COMPARATIVE EXAMPLE
[0083] As presented in Table 3, in the samples No. 32 to No. 34,
No. 37 to No. 39, No. 42 to No. 44, and No. 47 to No. 49, in each
of which the C content, the Ti content and the Cu content were
within the range of the present invention, the average value
"average B8" was large to be 1.90 T or more, and the difference
".DELTA.B8" was small to be 0.025 T or less. In short, a high
magnetic property was obtained and the variation in magnetic
property was small. Particularly, when the C content was small, a
good result was obtained.
[0084] Further, the balance between the average value "average B8"
and the difference ".DELTA.B8" was excellent in the samples No. 32,
No. 33, No. 37, No. 38, No. 42, No. 43, No. 47, and No. 48, in each
of which the Ti content was 0.0020 mass % to 0.080 mass %, the Cu
content was 0.010 mass % to 0.10 mass %, and the relation of
"20.times.[Ti]+[Cu].ltoreq.0.18" was established. Among them, the
balance between the average value "average B8" and the difference
".DELTA.B8" was extremely excellent in the samples No. 32, No. 37,
No. 42, and No. 47, in each of which the relation of
"10.times.[Ti]+[Cu].ltoreq.0.07" was established.
[0085] On the other hand, in the samples No. 31, No 36, No. 41, and
No. 46, in each of which the Ti content was less than 0.020 mass %,
and the Cu content was less than 0.010 mass %, the difference
".DELTA.B8" was large to be higher than 0.030 T. Among them, in the
samples No. 31 and No. 36, in each of which the C content was low,
the average value "average B8" was further small to be less than
1.90 T. Further, in the samples No. 35, No. 40, No. 45, and No. 50,
in each of which the Ti content was higher than 0.010 mass %, and
the Cu content was higher than 0.50 mass %, the average value
"average B8" was small to be less than 1.90 T.
Fourth Experiment
[0086] First, 10 kinds of steel ingots each containing Si: 3.2 mass
%, C, 0.048 mass %, Mn: 0.08 mass %, acid-soluble Al: 0.028 mass %,
N: 0.004 mass %, S: 0.0061 mass %, P: 0.033 mass %, Ti: 0.0024 mass
%, and Cu: 0.029 mass %, further containing Cr and Sn in amounts
listed in Table 4, and the balance composed of Fe and inevitable
impurities were produced using a vacuum melting furnace. Then,
annealing was performed on the steel ingots at 1100.degree. C. for
one hour, and then hot rolling was performed thereon to obtain
hot-rolled steel sheets with a thickness of 2.3 mm.
[0087] Subsequently, annealing was performed on the hot-rolled
steel sheets at 1080.degree. C. for 120 seconds to obtain annealed
steel sheets. Then, acid pickling was performed on the annealed
steel sheets, and then cold rolling was performed on the annealed
steel sheets to obtain cold-rolled steel sheets with a thickness of
0.23 mm. Subsequently, decarburization annealing was performed on
the cold-rolled steel sheets in an atmosphere containing water
vapor, hydrogen, and nitrogen at 870.degree. C. for 90 seconds to
obtain decarburization annealed steel sheets. Next, nitridation
treatment was performed on the decarburization annealed steel
sheets in an atmosphere containing hydrogen, nitrogen, and ammonia
at 760.degree. C. for 20 seconds to obtain nitrided steel
sheets.
[0088] Thereafter, an annealing separating agent containing MgO as
a main component was applied, in a water slurry, to the surfaces of
the nitrided steel sheets. Then, finish annealing was performed on
them at 1200.degree. C. for 20 hours to obtain finish annealed
steel sheets. Subsequently, treatments from the water washing to
the formation of the insulating film were performed similarly to
the first experiment to obtain samples of the grain-oriented
electrical steel sheets.
[0089] Then, for each of the samples, the average value "average
B8," the maximum value "B8max," the minimum value "B8 min," and the
difference ".DELTA.B8" were obtained similarly to the first
experiment. These results are listed in Table 4 together with the
Cr contents and the Sn contents.
TABLE-US-00004 TABLE 4 Cr Sn Content Content B8 B8 Sample (mass
(mass Average max min .DELTA.B8 No. %) %) B8 (T) (T) (T) (T) NOTE
51 0.007 0.008 1.904 1.918 1.890 0.028 Embodiment 52 0.068 0.003
1.915 1.927 1.903 0.024 Embodiment 53 0.141 0.008 1.915 1.928 1.904
0.024 Embodiment 54 0.214 0.006 1.903 1.917 1.888 0.029 Embodiment
55 0.003 0.042 1.917 1.928 1.906 0.022 Embodiment 56 0.006 0.087
1.918 1.928 1.907 0.021 Embodiment 57 0.005 0.264 1.902 1.915 1.888
0.027 Embodiment 58 0.070 0.124 1.913 1.922 1.898 0.024 Embodiment
59 0.150 0.035 1.914 1.924 1.901 0.023 Embodiment 60 0.170 0.154
1.912 1.922 1.897 0.025 Embodiment
[0090] As presented in Table 4, in any of the samples Nos. 51 to
60, the average value "average B8" was large to be 1.90 T or more
and the difference ".DELTA.B8" was small to be 0.030 T or less. In
short, a high magnetic property was obtained and the variation in
the magnetic property was small. Among them, in the samples No. 52,
No. 53, No. 55, No. 56, and No. 58 to No. 60, each of which
contains 0.010 mass % to 0.20 mass % of Cr and/or 0.010 mass % to
0.20 mass % of Sn, the average value "average B8" was particularly
large to be 1.91 T or more, and the difference ".DELTA.B8" was
particularly small to be 0.025 T or less.
INDUSTRIAL APPLICABILITY
[0091] The present invention is applicable, for example, in
electrical steel sheet manufacturing industries and electrical
steel sheet using industries.
* * * * *