DESCRIPTION
TITLE OF INVENTION: MANUFACTURING METHOD OF GRAIN-ORIENTED
MAGNETIC STEEL SHEET
TECHNICAL FIELD
[0001] The present invention relates to a manufacturing
method of a grain-oriented magnetic steel sheet suitable
for an iron core or the like of an electrical apparatus.
BACKGROUND ART
r 00021 A grain-oriented electrical steel <=heet is a soft
magnetic material, and is used for an iron core or the
like of an electrical apparatus such as a transformer
(trans.). In the grain-oriented electrical steel sheet, Si
of about 7 mass% or less is contained. Crystal grains of
the grain-oriented electrical steel sheet are highly
integrated in the {110}<001> orientation by Miller
indices. The orientation of the crystal grains is
controlled by utilizing a catastrophic grain growth
phenomenon called secondary recrystallization.
[0003] For controlling the secondary recrystallization,
it is important to adjust a structure (primary
recrystallization structure) obtained by primary
recrystallization before the secondary recrystallization
and to adjust a fine precipitate called an inhibitor or a
grain boundary segregation element. The inhibitor has a
function to preferentially grow, (in the primary
recrystallization structure, the crystal grains in the
{A10} <001> orientation and suppress growth of the other
crystal grains.
[0004] Then, conventionally, there have been made various
proposals aimed at precipitating an inhibitor effectively.
[0005] However, in conventional techniques, it has been
difficult to manufacture a grain-oriented electrical steel
sheet having a.high magnetic flux density industrially
stably.
CITATION LIST
PATENT LITERATURE
[0006] Parent Literature 1: Japanese Examined Patent
Application Publication No. 30-003651
Patent Literature 2: Japanese Examined Patent
Application Publication No. 33-004710
Patent Literature 3: Japanese Examined Patent
Application Publication No. 51-013469
Patent Literature 4: Japanese Examined Patent
Application Publication No. 62-045285
Patent Literature 5: Japanese Laid-open Patent
Publication No. 03-002324
. Patent Literature 6: U.S. Patent No. 3905842
Patent Literature 7: U.S. Patent No. 3905843
Patent Literature 8: Japanese Laid-open Patent
Publication No. 01-230721
Patent Literature 9: Japanese Laid-open Patent
Publication No. 01-283324
Patent Literature 10: Japanese Laid-open Patent
Publication No. 10-140243
- 2 -
Patent Literature 11: Japanese Laid-open Patent
Publication No. 2000-129352
Patent Literature 12: Japanese Laid-open Patent
Publication No. 11-050153
Patent Literature 13: Japanese Laid-open Patent
Publication No. 2001-152250
Patent•Literature 14: Japanese Laid-open Patent
Publication No. 2000-282142
Patent Literature 15: Japanese Laid-open Patent
Publication No. 11-335736
NON PATENT LITERATURE
[0007] Non Patent Literature 1: "Trans. Met. Soc. AIME",
212, pp. 769/781, 1958
Non Patent Literature 2: "J. Japan Inst. Metals",
27, p. 186, 19 63
Non Patent Literature 3: "Tetsu-to-Hagane (Iron
and Steel)", 53, pp. 1007/1023, 1967
Non Patent Literature 4: "J. Japan Inst. Metals",
43, pp. 175/181, 1979 and "J. Japan Inst. Metals", 44, pp.'
419/424, 1980
Non Patent Literature 5: "Materials Science
. Forum",. 204-206, pp. 593/598, 1996
Non Patent Literature 6: "IEEE Trans. Mag.", MAG-
13, p. 1427
SUMMARY OF THE INVENTION
TECHNICAL PROBLEM
[0008] The present invention has an object to provide a
manufacturing method of an grain-oriented magnetic steel
- 3 -
ifkeet, the method enabling industrially stable production
of an grain-oriented magnetic steel sheet having a high
magnetic flux density.
SOLUTION TO PROBLEM
[0009] A manufacturing method of a grain-oriented
electrical steel sheet according to a first aspect of the
present invention includes: hot rolling a silicon steel
material so as to obtain a hot-rolled steel strip, the
silicon steel material containing Si: 0.8 mass% to 7
mass%, acid-soluble Al: 0.01 mass% to 0.065 mass%, N:
0.004 mass% to 0.012 mass%, Mn: 0.05 mass% to 1 mass%, and
B: 0.0005 mass% to 0.0080 mass%, the silicon steel
material further containing at least one element selected
from a group consisting of S and Se being 0.003 mass% to
0.015 mass% in total amount, a C content being 0.085 mass%
or less, and a balance being composed of Fe and inevitable
impurities; annealing the hot-rolled steel strip so as to
obtain an annealed steel strip; cold roiling the annealed
steel strip one time or more so as to obtain a cold-rolled
steel strip; decarburization annealing the cold-roiled
steel strip so as to obtain a decarburization-annealed
steel strip in which primary recrystallization is caused;
coating an annealing separating agent containing MgO as
its main component on the decarburization-annealed steel
strip; and causing secondary recrystallization by finish
annealing the decarburization-anneaied steel strip,
wherein the method further includes performing a nitriding
treatment in which an N content of the decarburization-
- 4 -
^fnealed steel strip is increased between start of the
decarburization annealing and occurrence of the secondary
recrystallization in the finish annealing, the hot rolling
includes: holding the silicon steel material in a
temperature range between 1000°C and 800°C for 300 seconds
or longer; and then performing finish rolling.
[0010] A manufacturing method of a grain-oriented
electrical steel sheet according to a second aspect of the
present invention, in the method according to the first
aspect, further includes heating the silicon steel
material at a predetermined temperature which is a
temperature Tl (°C) cr lower before the hot rolling, in a
case when no 'Se is contained in the silicon steel
material, the temperature Tl being expressed by equation
(1) below.
Tl = 14855/(6.82 - log ( [Mn] x [S])) - 273 ...(1)
Here, [Mn] represents a Mn content (mass%) of the
silicon steel material, and [S] represents an S content
(mass%) of the silicon steel material.
[0011] A manufacturing method of a grain-oriented
electrical steel sheet according to a third aspect of the
present invention, in the method according to the first
aspect, further includes heating the silicon steel
material at a predetermined temperature which is a
temperature T2 (°C) or lower before the hot rolling, in a
case when no S is contained in the silicon steel material,
the temperature T2 being expressed by equation (2) below.
T2 = 10733/(4.08 - log ([Mn], * [Se])) - 273 ...(2)
- 5 -
Here, [Mn] represents a Mn content (mass%) of the
silicon steel material, and [Se] represents an Se content
(mass%) of the silicon steel material.
[0012] A manufacturing method of a grain-oriented
electrical steel sheet according to a fourth aspect of the
present invention, in the method according to the first
aspect, further includes heating the silicon steel
material at a predetermined temperature which is a
temperature Tl (°C) or lower and a temperature T2 (°C) or
lower before the hot rolling, in a case when S and Se are
contained in the silicon steel material, the temperature
Tl being expressed by equation (1), and the temperature T2
being expressed by equation (2).
[0013] In a manufacturing method of a grain-oriented
electrical steel sheet according to a fifth aspect of the
present invention, in the method according to any one of
the first to the fourth aspects, the nitriding treatment
is performed under a condition that an N content [N] of a
steel strip obtained after the nitriding treatment
satisfies inequation (3) below.
[N] ^ 14/27 [Al] + 14/11[B] + 14/47[Ti] ...(3)
Here, [N] represents the N content (mass%) of the
steel strip obtained after the nitriding treatment, [Al]
represents an acid-soluble Al content (mass%) of the steel
strip obtained after the nitriding treatment, [B]
represents a B content (mass%) of the steel strip obtained
after the nitriding treatment, and [Ti] represents a Ti
- 6 -
distent (mass%) of the steel strip obtained after the
nitriding treatment.
[0014] In a manufacturing method of a grain-oriented
electrical steel sheet according to a sixth aspect of the
present invention, in the method according to any one of
the first to the fourth aspects, the nitriding treatment
is performed under a condition that an N content [N] of a
steel strip obtained after the nitriding treatment
satisfies inequation (4) below.
[N] ^ 2/3[Al] + 14/11[B] + 14/47[Ti] ...(4)
Here, [N] represents the N content (mass%) of the
steel strip obtained after the nitriding treatment, [Al]
represents an acid-soluble Al content (mass%) of the steel
strip obtained after the nitriding treatment, [B]
represents a B content (mass%) of the steel strip obtained
after the nitriding treatment, and [Ti] represents a Ti
content-(mass%) of the steel strip obtained after the
nitriding treatment.
ADVANTAGEOUS EFFECTS OF INVENTION
[0015] According to the present invention, it is possible
to make BN precipitate compositely on MnS and/or MnSe
appropriately and to form appropriate inhibitors, so that
a.high magnetic flux density can be obtained. Further,
these processes can be executed industrially stably.
BRIEF DESCRIPTION OF DRAWINGS
[0016] Fig. 1 is a flow chart showing a manufacturing
- 7 -
nMfthod of a grain-oriented electrical steel sheet;
Fig. 2 is a view showing a result of a first
experiment (a relationship between precipitates in a hotrolled
steel strip and a magnetic property after finish
annealing);
Fig. 3 is a view showing the result of the first
experiment (a relationship between an amount of B that has
not precipitated as BN and the magnetic property after the
finish annealing);
Fig. 4 is a view showing the result of the first
experiment (a relationship between a condition of hot
rolling and the magnetic property after the finish
annealing);
Fig. 5 is a view showing a result of a second
experiment (a relationship between precipitates in a hotrolled
steel strip and a magnetic property after finish
annealing);
Fig. 6 is a view showing the result of the second
experiment (a relationship between an amount of B that has
not precipitated as BN and the magnetic property after the
finish annealing);
Fig. 7 is a view showing the result of the second
experiment (a relationship between a condition of hot
rolling and the magnetic property after the finish
annealing);
Fig. 8 is a view showing a result of a third
experiment (a relationship between precipitates in a hotrolled
steel strip and a magnetic; property after finish
annealing);
- 8 -
Fig. 9 is a view showing the result of the third
experiment (a relationship between an amount of B that has
not precipitated as BM and the magnetic property after the
finish annealing);
Fig. 10 is a view showing the result of the third
experiment (a relationship between a condition of hot
rolling and the magnetic property after the finish
annealing);
Fig. 11 is a view showing a relationship between a
precipitation amount of BN, a holding temperature and a
holding time.
DESCRIPTION OF EMBODIMENTS
[0017] The present inventors thought that in the case of
manufacturing a grain-oriented electrical steel sheet from
a silicon steel material having a predetermined
composition containing B, a precipitated form of B may
affect behavior of secondary recrystailization, and thus
conducted various experiments. Here, an outline of a
manufacturing method of a grain-oriented electrical steel
sheet will be explained. Fig. 1 is a flow chart showing
the manufacturing method of the grain-oriented electrical
steel sheet.
[0018] First, as illustrated in Fig. 1, in step SI, a
silicon steel material (slab) having a predetermined
composition containing B is subjected to hot rolling. By
the hot rolling, a hot-rolled steel strip is obtained.
Thereafter, in step S2, annealing, of the hot-rolled steel
strip is performed to normalize a structure in the hot-
- 9 -
jelled steel strip and to adjust precipitation of
inhibitors. By the annealing, an annealed steel strip is
obtained. Subsequently, in step S3, cold rolling of the
annealed steel strip is performed. The cold rolling may be
performed only one time, or may also be performed a
plurality of times with intermediate annealing being
performed ther.ebetween. By the cold rolling, a cold-rolled
steel strip is obtained. Incidentally, in the case of the
intermediate annealing being performed, it is also
possible to omit the annealing of the hot-rolled steel
strip before the cold rolling to perform the annealing
(step S2) in the intermediate annealing. That is, the
annealing (step S2) may be performed on the hot-rolled
steel strip, or may also be performed on a steel strip
obtained after being cold rolled one time and before being
cold rolled finally.
[0019] After the cold rolling, in step S4,
decarburization annealing of the cold-rolled steel strip
is performed. In the decarburization annealing, primary
recrystallization occurs. Further, by the decarburization
annealing, a decarburization-annealed steel strip is
obtained. Next, in step S5, an annealing separating agent
containing MgO (magnesia) as its main component is coated
on the surface of the decarburization- d"W*\. £0u(*A steel
strip and finish annealing is performed. In the finish
annealing, secondary recrystallization occurs, and a glass
film containing forsterite as its main component is formed
on the surface of the steel strip and is purified. As a
result of the secondary, recrystallization, a secondary
- 10 -
'^crystallization structure arranged in the Goss
orientation is obtained. By the finish annealing, a
finish-annealed steel strip is obtained. Further, between
start of the decarburization annealing and occurrence of
the secondary recrystallization in the finish annealing, a
nitriding treatment in which a nitrogen amount of the
steel strip is. increased is performed (step S6).
[0020] In this manner, the grain-oriented electrical
steel sheet can be obtained.
[0021] Further, details will be described later, but as
the silicon steel material, there is used one containing
Si: 0.8 mass% to 7 mass%, acid-soluble Al: 0.01 mass% to
0.065 mass%, N: 0.004 mass% to 0.012 mass%, and Mn: 0.05
mass% to 1 mass%, and further containing predetermined
amounts of S and/or Se, and B, a C content being 0.085
mass% or less, and a balance being composed of Fe and
inevitable impurities.
[0022] Then, as a result of the various experiments, the
present inventors found that it is important to adjust
conditions of the hot rolling (step SI) to thereby
generate precipitates in a form effective as inhibitors in
the hot-rolled steel strip. Concretely, the present
inventors found that when B in the silicon steel material
precipitates mainly as BN precipitates compositely on MnS
and/or MnSe by adjusting the conditions of the hot
rolling, the inhibitors are thermally stabilized and
grains of a grain structure of the primary
recrystallization are finely arranged. Then, the present
inventors obtained the knowledge capable of manufacturing
- 11 -
igfcp grain-oriented electrical steel sheet having a good
magnetic property stably, and completed the present
invention.
[0023] Here, the experiments conducted by the present
inventors will be explained.
[0024] (First Experiment)
In the first experiment, first, various silicon steel
slabs containing Si: 3.3 mass%, C: 0.06 mass%, acidsoluble
Al: 0.027 mass%, N: 0.008 mass%, Mn: 0.05 mass% to
0.19 mass%, S: 0.007 mass%, and B: 0.0010 mass% to 0.0035
mass%, and a balance being composed of Fe and inevitable
impurities were obtained. Next, the silicon steel slabs
were heated at a temperature of 1100°C to 1250°C and were
subjected to hot rolling. In the hot rolling, rough
rolling was performed at 1050°C and then finish rolling was
performed at 1000°C, and thereby hot-rolled steel strips'
each having a thickness of 2.3 mm were obtained. Then,
cooling water was jetted onto the hot-rolled steel strips
to then let the hot-rolled steel strips cool down to 550°C,
and thereafter the hot-rolled steel strips were cooled
down in the atmosphere. Subsequently, annealing of the
hot-rolled steel strips was performed. Next, cold rolling
was performed, and thereby cold-rolled steel strips each
having a thickness of 0.22 mm were obtained. Thereafter,
the cold-rolled steel strips were heated at a speed of
15°C/s, and were subjected to decarburization annealing at
a temperature of 840°C, and thereby decarburizationannealed
steel strips were obtained. Subsequently, the
decarburization-annealed steel strips were annealed in an
- 12 -
^timonia containing atmosphere to increase nitrogen in the
steel strips up to 0.022 mass%. Next, an annealing
separating agent containing MgO as its main component was
coated on the steel strips and finish annealing was
performed. In this manner, various samples were
manufactured.
[0025] Then, 'a relationship between precipitates in the
hot-rolled steel strip and a magnetic property after the
finish annealing was examined. A result of the examination
is illustrated in Fig. 2. In Fig. 2, the horizontal axis
indicates a value (mass%) obtained by converting a
precipitation amount of MnS into an amount of S, and the
vertical axis' indicates a value (mass%) obtained by
converting a precipitation amount of BN into B. The
horizontal axis corresponds to an amount of S that has
precipitated as MnS (mass%). Further, white circles each
indicate that a magnetic flux density B8was 1.88 T or
more, and black squares each indicate that the magnetic
flux density B8 was less than 1.88 T. As illustrated in
Fig. 2, in the samples each having the precipitation
amounts of MnS and BN each being less than a certain
value, the magnetic flux density B8 was low. This
indicates that secondary recrystallization was unstable.
[0026] Further, a relationship between an amount of B
that has not precipitated as BN and the magnetic property
after the finish annealing was examined. A result of the
examination is illustrated in Fig. 3. In Fig. 3, the
horizontal axis indicates a B content (mass%), and the
vertical axis indicates the value (mass%) obtained by
- 13 -
inverting the precipitation amount of BN into B. Further,
white circles each indicate that the magnetic flux density
B8 was 1.88 T or more, and black squares each indicate
that the magnetic flux density B8 was less than 1.88 T. As
illustrated in Fig. 3, in the samples each having the
amount of B that has not precipitated as BN being a
certain value or more, the magnetic flux density B8 was
low. This indicates that the secondary recrystallization
was unstable.
[0027] Further, as a result of examination of a form of
the precipitates in the samples each having the good
magnetic property, it turned out that MnS becomes a
nucleus and B'N precipitates compcsitely on MnS. Such
composite precipitates are effective as inhibitors that
stabilize the secondary recrystallization.
[0028] Further, a relationship between a condition of the
hot rolling and the magnetic property after the finish
annealing was examined. A result of the examination is
illustrated in Fig. 4. In Fig. 4, the horizontal axis
indicates a Mn content (mass%) and the vertical axis
indicates a temperature (°C) of slab heating at the time of
hot roiling. Further, white circles each indicate that the
magnetic flux density B8 was 1.88 T or more, and black
squares each indicate that the magnetic flux density B8
was less than 1.88 T. Further, a curve in Fig. 4 indicates
a solution temperature Tl (°C) of MnS expressed by equation
(1) below. As illustrated in Fig. A, it turned out- that in
the samples in which the slab heating is performed at a
temperature determined according to the Mn content or
- 14 -
jtower, the high magnetic flux density B8 is obtained.
Further, it also turned out that the temperature
approximately agrees with the solution temperature Tl of
MnS. That is, it turned out that it is effective to
perform the slab heating in a temperature zone where MnS
is not completely solid-dissolved.
Tl = 14855/(6.82 - log ( [Mn] * [S])) - 273 ...(1)
Here, [Mn] represents the Mn content (mass%), [S]
represents an S content (mass%).
[0029] Further, as a result of examination of
precipitation behavior of MnS and BN, it turned out that,
if MnS exists, BN compositely precipitated preferentially
with MnS serving as a nucleus, and a precipitation
temperature zone of BN is 800°C to 1000°C.
[0030] Further, the present inventors examined conditions
effective for the precipitation of BN. In the examination,
first, various silicon steel slabs containing Si: 3.3
mass%, C: 0.06 mass%, acid-soluble Al: 0.027 mass%, N:
0.006 mass%, Mn: 0.1 mass%, S: 0.007 mass%, and B: 0.0014
mass%, and a balance being composed of Fe and inevitable
impurities and having a thickness of 40 mm were obtained.
Next, the silicon steel slabs were heated at a temperature
of 1200°C and were subjected to rough roiling at 1100°C so
as to have a thickness of 15 mm. Then, the resultant
silicon steel slabs were held in a furnace at 1050°C to
800°C for a predetermined period of time. Thereafter,
finish rolling was performed and thereby hot-rolled steel
strips each having a thickness of 2.3 mm were obtained.
I
f
Then, the hot-rolled steel strips were cooled with water
- 15 -
djfcwn to a room temperature, and the precipitate was
examined. As a result, it turned out that, if the silicon
steel slab is held in a temperature range between 1000°C
and 800°C for 300 seconds or longer between the rough
rolling and the finish rolling, an excellent composite
precipitate is generated.
[0031] (Second Experiment)
In the second experiment, first, various silicon steel
slabs containing Si: 3.3 mass%, C: 0.06 mass%, acidsoluble
Al: 0.028 mass%, N: 0.0.07 mass%, Mn: 0.05 massl to
0.20 mass%, Se: 0.007 mass%, and B: 0.0010 mass% to 0.0035
mass%, and a balance being composed of Fe and inevitable
impurities were obtained. Next, the silicon steel slabs
were heated at a temperature of 1100°C to 1250°C and were
subjected to hot rolling. In the hot rolling, rough
rolling was performed at 1050°C and then finish rolling was
performed at 1000°C, and thereby hot-rolled steel strips
each having a thickness of 2.3 mm were obtained. Then,
cooling water was jetted onto the hot-rolled steel strips
to then let the hot-rolled steel strips cool down to 550°C,
and thereafter the hot-rolled steel strips were cooled
down in the atmosphere. Subsequently, annealing of the
hot-rolled steel strips was performed. Next, cold rolling
was performed, and thereby cold-rolled steel strips each
having a thickness' of 0.22 mm were obtained. Thereafter,
the cold-rolled steel strips were heated at a rate of
15°C/s, and were subjected to decarburization annealing at
a temperature of 840°C, and thereby decarburizationi
annealed steel strips were obtained. Subsequently, the
- 16 -
cjhcarburization-annealed steel strips were annealed in an
ammonia containing atmosphere to increase nitrogen in the
steel strips up to 0.022 mass%. Next, an annealing
separating agent containing MgO as its main component was
coated on the steel strips and finish annealing was
performed. In this manner, various samples were
manufactured.
[0032] Then, a relationship between precipitates in the
hot-rolled steel strip and a magnetic property after the
finish annealing was examined. A result of the examination
is illustrated in Fig. 5. In Fig. 5, the horizontal axis
indicates a value (mass%) obtained by converting a
precipitation'amount of MnSe into an amount of Se, and the
vertical axis indicates a value (mass%) obtained by
converting a precipitation amount of BN into B. The
horizontal axis corresponds to an amount of Se that has
precipitated as MnSe (mass%). Further, white circles each
indicate that the magnetic flux density B8 was 1.88 T or
more, and black squares each indicate that the magnetic
flux density B8 was less than 1.88 T. As illustrated in
Fig. 5, in the samples each having the precipitation
amounts of MnSe and BN each being less than a certain
value, the magnetic flux density B8 was low. This
indicates that secondary recrystallization was unstable.
[0033] Further, a relationship between an amount of B
that has not precipitated as BN and the magnetic property
after the finish annealing was examined. A result of the
examination is illustrated in Fig. 6. In Fig. 6, the
horizontal axis indicates a B content (mass%), and the
- 17 -
Mttrtical axis indicates the value (mass%) obtained by
converting the precipitation amount of BN into B. Further,
white circles each indicate that the magnetic flux density
B8 was 1.88 T or more, and black squares each indicate
that the magnetic flux density B8 was less than 1.88 T. As
illustrated in Fig. 6, in the samples each having the
amount of B that has not precipitated as BN being a
certain value or more, the magnetic flux density B8 was
low. This indicates that the secondary recrystallization
was unstable.
[0034] Further, as a result of examination of a form of
the precipitates in the samples each having the good
magnetic property, it turned out that MnSe becomes a
nucleus and BN precipitates compositely on MnSe. Such
composite precipitates are effective as inhibitors that
stabilize the secondary recrystallization.
[0035] Further, a relationship between a condition of the
hot rolling and the magnetic property after the finish
annealing was examined. A result of the examination is
illustrated in Fig. 7. In Fig. 7, the horizontal axis
indicates a Mn content (mass%) and the vertical axis
indicates a temperature (°C) of slab heating at the time of
hot rolling. Further, white circles each indicate that the
magnetic flux density B8 was 1.88 T or more, and black
squares each indicate that the magnetic flux density B8
was less than 1.88 T. Further, a curve in Fig. 7 indicates
a solution temperature T2 (°C) of MnSe expressed by
equation (2) below. As illustrated in Fig. 7, it turned
out that in the samples in which the slab heating is
- 18 -
performed at a temperature determined according to the Mn
content or lower, the high magnetic flux density B8 is
obtained. Further, it also turned out that the temperature
approximately agrees with the solution temperature T2 of
MnSe. That is, it turned out that it is effective to
perform the slab heating in a temperature zone where MnSe
is not completely solid-dissolved.
T2 = 10733/(4.08 - log.([Mn] x [Se])) - 273 ... (2 )
Here, [Se] represents a Se content (mass%).
[0036] Further, as a result of examination of
precipitation behavior of MnSe and BN, it turned out that,
if MnSe exists, BN compositely precipitated preferentially
with MnSe serving as a nucleus, and a precipitation
temperature zone of BN is 800°C to 1000°C.
[0037] Further, the present inventors examined conditions
effective for the precipitation of BN. In the examination,
first, various silicon steel slabs containing Si: 3.3
mass%, C: 0.06 mass%, acid-soluble Al : 0.028 mass%, N:
0.007 mass%, Mn: 0.1 mass%, Se: 0.007 mass%, and B: 0.0014
mass%, and a balance being composed of Fe and inevitable
impurities and having a thickness of 40 mm were obtained.
Next, the silicon steel slabs were heated at a temperature
of 1200°C and were subjected to rough rolling at 1100°C so
as to have a thickness of 15 mm. Then, the resultant
silicon steel slabs were held in a furnace at 1050°C to
800°C for a predetermined period of time. Thereafter,
finish roiling was performed and thereby hot-rolled steel
strips each having a thickness of 2.3 mm were obtained.
<
Then, the hot-rolled steel strips were cooled with water
- 19 -
jg^own to a room temperature, and the precipitate was
examined. As a result, it turned out that, if the silicon
steel slab is held in a temperature range between 1000°C
and 800°C for 30.0 seconds or longer between the rough
rolling and the finish rolling, an excellent composite
precipitate is generated.
[0038] (Third Experiment)
In the third experiment, first, various silicon steel
slabs containing Si: 3.3 mass%, C: 0.06 mass%, acidsoluble
Al: 0.026 mass%, N: 0.009 mass%, Mn: 0.05 mass% to
0.20 mass%, S: 0.005 mass%, Se: 0.007 mass%, and B: 0.0010
mass% to 0.0035 mass%, and a balance being composed of Fe
and inevitable impurities were obtained. Next, the silicon
steel slabs were heated at a temperature of 1100°C to
1250°C and were subjected to hot rolling. In the hot
rolling, rough rolling was performed at 1050°C and then
finish rolling was performed at 1000°C, and thereby hotrolled
steel strips each having a thickness of 2.3 mm were
obtained. Then, cooling water was jetted onto the hotrolled
steel strips to then let the hot-rolled steel
strips cool down to 550°C, and thereafter the hot-rolled
steel strips were cooled down in the atmosphere.
Subsequently, annealing of the hot-rolled steel strips was
performed. Next, cold rolling was performed, and thereby
cold-rolled steel strips each having a thickness of 0.22
mm were obtained. Thereafter, the cold-rolled steel strips
were heated at a rate of 15°C/s, and were subjected to
decarburization annealing at a temperature of 840°C, and
thereby decarburization-anneaied steel strips were
- 20 -
ciMcained. Subsequently, the decarburization-annealed steel
strips were annealed in an ammonia containing atmosphere
to increase nitrogen in the steel strips up to 0.022
mass%. Next, an annealing separating agent containing MgO
as its main component was coated on the steel strips and
finish annealing was performed. In this manner, various
samples were manufactured.
[0039] Then, a relationship between precipitates in the
hot-rolled steel strip and a magnetic property after the
finish annealing was examined. A result of the examination
is illustrated in Fig. 8. In Fig. 8, the horizontal axis
indicates the sum (mass%) of a value obtained by
converting a precipitation amount of MnS into an amount of
S and a value obtained by multiplying a value obtained by
converting a precipitation amount of MnSe into an amount
of Se by 0.5, and the vertical axis indicates a value
(mass%) obtained by converting a precipitation amount of
BN into B. Further, white circles each indicate that the
magnetic flux density B8 was 1.88 T or more, and black
squares each indicate that the magnetic flux density B8
was less than 1.88 T. As illustrated in Fig. 8, in the
samples each having the precipitation amounts of MnS,
MnSe, and BN each being less than a certain value, the
magnetic flux density B8 was low. This indicates that
secondary recrystallization was unstable.
[0040] Further, a relationship between an amount of B
that has not precipitated as BN and the magnetic property
after the finish annealing was examined. A result of the
examination is illustrated in Fig. 9. In Fig. 9, the
- 21 -
|kjrizontal axis indicates a B content (mass%), and the
vertical axis indicates the value (mass%) obtained by
converting the precipitation amount of BN into B. Further,
white circles each indicate that the magnetic flux density
B8 was 1.88 T or more, and black squares each indicate
that the magnetic flux density B8 was less than 1.88 T. As
illustrated in. Fig. 9, in the samples each having the
amount of B that has not precipitated as BN being a
certain value or more, the magnetic flux density B8 was
low. This indicates that the secondary recrystallization
was unstable.
[0041] Further, as a result of examination of a form of
the precipitates in the samples each having the good
magnetic property, it turned out that MnS or MnSe becomes
a nucleus and BN precipitates compositely on MnS or MnSe.
Such composite precipitates are effective as inhibitors
that stabilize the secondary recrystallization.
[0042] Further, a relationship between a condition of the
hot rolling and the magnetic property after the finish
annealing was examined. A result of the examination is
illustrated in Fig. 10. In Fig. 10, the horizontal axis
indicates a Mn content (mass%) and the vertical axis
indicates a temperature (°C) of slab heating at the time of
hot rolling. In Fig. 10, the horizontal axis indicates the
B content (mass%) and the vertical axis indicates the
temperature (°C) of the slab heating at the time of hot
rolling. Further, white circles each indicate that the
magnetic flux density B8 was 1.88 T or more, and black
i
squares each indicate that the magnetic flux density B8
- 22 -
wJte less than 1.88 T. Further, two curves in Fig. 10
indicate the solution temperature Tl (°C) of MnS expressed
by equation (1) and the solution temperature T2 (°C) of
MnSe expressed by equation (2) . As illustrated in Fig. 10,
it turned out that in the samples in which the slab
heating is performed at a temperature determined according
to the Mn content or lower, the high magnetic flux density
B8 is obtained. Further, it also turned out that the
temperature approximately agrees with the solution
temperature Tl of MnS and the solution temperature T2 of
MnSe. That is, it turned out that it is effective to
perform the slab heating in a temperature zone where MnS
and MnSe,, are 'not completely solid-dissolved.
[0043] Further, as a result of examination of
precipitation behavior of MnS, MnSe and BN, it turned out
that, if MnS and MnSe exist, BN compositely precipitated
preferentially with MnS and MnSe serving as a nucleus, and
a precipitation temperature zone of BN is 800°C to 1000°C.
[0044] Further, the present inventors examined conditions
effective for the precipitation of BN. In the examination,
first, various silicon steel slabs containing Si: 3.3
. massl, C: 0.06 mass%, acid-soluble Al : 0.027 mass%, N:
0.007 mass%, Mn: 0.1 mass%, S:0.006 mass%, Se: 0.008
mass%, and B: 0.0017 mass%, and a balance being composed
of Fe and inevitable impurities and having a thickness of
40 mm were obtained. Next, the silicon steel slabs were
heated at a temperature of 12C0°C and were subjected to
rough rolling at 1100°C so as to have a thickness of 15 mm.
)
I
Then, the resultant silicon steel slabs were held in a
- 23 -
fBrnace at 1050°C to 800°C for a predetermined period of
time. Thereafter, finish rolling was performed and thereby
hot-rolled steel strips each having a thickness of 2.3 mm
were obtained. Then, the hot-rolled steel strips were
cooled with water down to a room temperature, and the
precipitate was examined. As a result, it turned out that,
if_the silicon'steel slab is held in a temperature range
between 1000°C and 800°C for 300 seconds or longer between
the rough rolling and the finish rolling, an excellent
composite precipitate is generated.
[0045] According to these results of the first to third
experiments, it is found that controlling the crecipitated
form of BN makes it possible to stably improve the
magnetic property of the grain-oriented electrical steel
sheet. The reason why the secondary recrystallization
becomes unstable, thereby making it impossible to obtain
the good magnetic property in the case when B does not
precipitate compositely on MnS or MnSe as BN has not been
clarified yet so for, but is considered as follows.
[0046] Generally, B in a solid solution state is likely
to segregate in grain boundaries, and BN that has
precipitated independently after the hot rolling is often
fine. B in a solid solution state and fine BN suppress
grain growth at the time of primary recrystallization as
strong inhibitors in a low-temperature zone where the
decarburization annealing is performed, and in a hightemperature
zone where the finish annealing is performed,
B in a solid solution state and fine BN do not function as
inhibitors locally, thereby turning the grain structure
- 24 -
iKito a mixed grain structure. Thus, in the low-temperature
zone, primary recrystallized grains are small, so that the
magnetic flux density of the grain-oriented electrical
steel sheet is reduced. Further, in the high-temperature
zone, the grain structure is turned into the mixed grain
structure, so that the secondary recrystallization becomes
unstable.
[0047] Next, an embodiment of the present invention made
on the knowledge will be explained.
[0048] First, limitation reasons of the components of the
silicon steel material will be explained.
[0049] The silicon steel material used in this embodiment
contains Si: 0.8 mass% to 7 mass%, acid-soluble Al: 0.01
mass% to 0.065 mass%, N: 0.004 mass% to 0.012 mass%, Mn:
0.05 mass% to 1 mass%, S and Se: 0.003 mass% to 0.015
mass% in total amount, and B: 0.0005.mass% to 0.0080
mass%, and a C content being 0.085 mass% or less, and a
balance being composed of Fe and inevitable impurities.
[0050] Si increases electrical resistance to reduce a
core loss. However, when a Si content exceeds 7 mass%, the
cold rolling becomes difficult to be performed, and a
crack is likely to be caused at the time of cold rolling.
Thus, the Si content is set to 7 mass% or less, and is
preferably 4.5 mass% or less, and is more preferably 4
mass% or less. Further, when the Si content is less than
0.8 mass%, a y transformation is caused at the time of
finish annealing to thereby make a crystal orientation of
the grain-oriented electrical steel sheet deteriorate.
i
Thus, the Si content is set to 0.8 mass% or more, and is
- 25 -
preferably 2 mass% or more, and is more preferably 2.. 5
mass% or more.
[0051] C is an element effective for controlling the
primary recrystaliization structure, but adversely affects
the magnetic property. Thus, in this embodiment, before
the finish annealing (step S5), the decarburization
annealing is performed (step S4) . However, when the C
content exceeds 0.085 mass%, a time taken for the
decarburization annealing becomes long, and productivity
in industrial production is impaired. Thus, the C content
is set to 0.85 mass% or less, and is preferably 0.07 mass%
or less.
[0052] Acid-soluble Al bonds to N to precipitate as (Al,
Si) N and functions as an inhibitor. In the case when a
content of acid-soluble Al falls within a range of 0.01
mass% to 0.065 mass%, the secondary recrystallization is
stabilized. Thus, the content of acid-soluble Al is set to
be not less than 0.01 mass% nor more than 0.065 mass%.
Further, the content of acid-soluble Al is preferably 0.02
mass% or more, and is more preferably 0.025 mass% or more.
Further, the content of acid-soluble Al is preferably 0.04
mass% or less, and is more preferably 0.03 mass% or less.
[0053] B bonds to N to precipitate compositely on MnS or
MnSe as BN and functions as an inhibitor. In the case when
a B content falls within a range of 0.0005 mass% to 0.0080
mass%, the secondary recrystallization is stabilized.
Thus, the 3 content is set to be not less than 0.0005
mass% nor more than 0.0080 mass%. Further, the B content
•vwass'/o
is preferably 0.001 or more, and is more oreferablv
A
- 26 -
^.0015A% or more. Further, the B content is preferably
0.0040% or less, and is more preferably 0.0030% or less.
[0054] N bonds to B or Al to function as an inhibitor.
When an N content is less than 0.004 mass%, it is not
possible to obtain a sufficient amount of the inhibitor.
Thus, the N content is set to 0.004 mass% or more, and is
preferably 0.006 mass% or more, and is more preferably
0.007 mass% or more. On the other hand, when the -N content
exceeds 0.012 mass%, a hole called a blister occurs in the
steel strip at the time of cold rolling. Thus, the N
content is set to 0.012 mass% or less, and is preferably
0.010 mass% or less, and is more preferably 0.009 mass% or
less.
[0055] Mn, S and Se produce MnS and MnSe to be a nucleus
on which BN precipitates compositely, and composite
precipitates function as an inhibitor. In the case when a
Mn content falls within a range of 0.05 mass% to 1 mass%,
the secondary recrystallization is stabilized. Thus, the
Mn content is set to be not less than 0.05 mass% nor more
than 1 mass%. Further, the Mn content is preferably 0.08
mass% or more, and is more preferably 0.09 mass% or more.
Further, the Mn content is preferably 0.50 mass% or less,
and is more preferably 0.2 mass% or less.
[0056] Further, in the case when a content of S and Se
falls within a range of 0.003 mass% to 0.015 mass% in
total amount, the secondary recrystallization is
stabilized. Thus, the content of S and Se is set to be not
less than 0.003 mass% nor more than 0.015 mass% in total
amount. Further, in terms of preventing occurrence of a
- 27 -
^fcrack in the hot rolling, inequation (5) below is
preferably satisfied. Incidentally, only either S or Se
may be contained in the silicon steel material, or both S
and Se may also be contained in the silicon steel
material. In the case when both S and Se are contained, it
is possible to promote the precipitation of BN more stably
and to improve•the magnetic property stably.
[Mn]/( [S] + [Se] ) ^ 4 ...(5)
[0057] Ti forms coarse TiN to affect the precipitation
amounts of BN and (Al, Si)N functioning as an inhibitor.
When a Ti content exceeds 0.004 mass%, the good magnetic
property is not easily obtained. Thus, the Ti content is
preferably 0.004 mass% or less.
[0058] Further, one or more element(s) selected from a
group consisting of Cr, Cu, Ni, P, Mo, Sn, Sb, and Bi may
also be contained in the silicon steel material in ranges
below.
[0059] Cr improves an oxide layer formed at the time of
decarburization annealing, and is effective for forming
the glass film made by reaction of the oxide layer and MgO
being the main component of the annealing separating agent
at the time of finish annealing. However, when a Cr
content exceeds 0.3 mass%, decarburization is noticeably
prevented. Thus, the Cr content may be set to 0.3 mass% or
less .
[0060] Cu increases specific resistance to reduce a core
loss. However, when a Cu content exceeds 0.4 ma.-3s%, the
effect is saturated. Further, a .surface flaw called
"copper scab" is sometimes caused at the time of hot
- 28 -
lulling. Thus, the Cu content may be set to 0.4 mass% or
less .
[0061] Ni increases specific resistance to reduce a core
loss. Further, Ni controls a metallic structure of the
hot-rolled steel strip to improve the magnetic property.
However, when a Ni content exceeds 1 mass%, the secondary
recrystallization becomes unstable. Thus, the Ni content
may be set to 1 mass% or less.
[0062] P increases specific resistance to reduce a core
loss. However, when a P content exceeds 0.5 mass%, a
fracture occurs easily at the time of cold rolling due to
embrittlemen-1". . Thus, the P content may be set to 0.5 mass%
or less.
[0063] Mo improves a surface property at the time of hot
rolling. However, when a Mo content exceeds 0.1 mass%, the
effect is saturated. Thus, the Mo content may be set to
0.1 mass% or less.
[0064] Sn and Sb are grain boundary segregation elements.
The silicon steel material used in this embodiment
contains Al, so that there is sometimes a case that Al is
oxidized by moisture released from the annealing
separating agent depending on the condition of the finish
annealing. In this case, variations in inhibitor strength
occur depending on the position in the grain-oriented
electrical steel sheet, and the magnetic property also
sometimes varies. However, in the case when the grain
boundary segregation elements are contained, the oxidation
of Al can be suppressed. That is, Sn and Sb.suppress the
oxidation of Al to suppress the variations in the magnetic
- 29 -
Jfcroperty. However, when a content of Sn and Sb exceeds
0.30 mass% in total amount, the oxide layer is not easily
formed at the time of decarburization annealing, and
thereby the formation of the glass film made by the
reaction of the oxide layer and MgO being the main
component of the annealing separating agent at the time of
finish annealing becomes insufficient. Further, the
decarburization is noticeably prevented. Thus, the content
of Sn and Sb may be set to 0.3 mass% or less in total
amount.
[0065] Bi stabilizes precipitates such as sulfides to
strengthen the function as an inhibitor. However, when a
Bi content exceeds 0.01 mass%, the formation of the glass
film is adversely affected. Thus, the Bi content may be
set to 0.01 mass% or less.
[0066] Next, each treatment in this embodiment will be
explained.
[0067] The silicon steel material (slab) having the
above-described components may be manufactured in a manner
that, for example, steel is melted in a converter, an
electric furnace, or the like, and the molten- steel is
subjected to a vacuum degassing treatment according to
need, and next is subjected to continuous casting.
Further, the silicon steel material may also be
manufactured in a manner that in place of the continuous
casting, an ingot is made to then be bloomed. The
thickness of the silicon steel slab is set to, for
example, 150 mm to 350 mm, and is. preferably set to 220 mm
to 280 mm. Further, what is called a thin slab having a
- 30 -
Jgpickness of 30 mm to 70 mm may also be manufactured. In
the case when the thin slab is manufactured, the rough
rolling performed when obtaining the hot-rolled steel
strip may be omitted.
[0068] After the silicon steel slab is manufactured, the
slab heating is performed, and the hot rolling (step SI)
is performed. Then, in this embodiment, the conditions of
the slab heating and the hot rolling are set such that BN
is made to precipitate compositely on MnS and/or MnSe, and
that the precipitation amounts of BN, MnS, and MnSe in the
hot-rolled steel strip satisfy inequations (6) to (8)
below.
BasBN ^ 0.0005 ...(6)
[B] - Ba s B N ^ 0 . 0 0 1 ...(7)
SasMnS + 0 . 5 x SeasMnSe ^ 0 . 0 0 2 ... ( 8 )
Here, "BasBN" represents the amount of B that has
precipitated as BN (mass%), "SaSMns" represents the amount
of S that has precipitated as MnS (mass%), and "SeaSMnse"
represents the amount of Se that has precipitated as MnSe
(mass%).
[0069] As for B, a precipitation amount and a solid
solution amount of B are controlled such that inequation
(6) and inequation (7) are satisfied. A certain amount or
more of BN is made to precipitate in order to secure an
amount of the inhibitors. Further, in the case when the
amount of solid-dissolved B is large, there is sometimes a
case that unstable fine precipitates are formed in the
subsequent processes to adversely affect the primary
recrystallization structure.
- 31 -
^0070] MnS and MnSe each function as a nucleus on which
BN precipitates compositely. Thus, in order to make BN
precipitate sufficiently to thereby improve the magnetic
property, the precipitation amounts of MnS and MnSe are
controlled such that inequation (8) is satisfied.
[0071] The condition expressed in inequation (7) is
derived from Fig. 3, Fig. 6, and Fig. 9. It is found from
Fig. 3, Fig. 6, and Fig. 9 that in the case of [B] - BaSBN
being 0.001 mass% or less, the good magnetic flux density,
being the magnetic flux density B8 of 1.88 T or more, is
obtained.
[0072] The conditions expressed in inequation (6) and
inequation (8') are derived from Fig. 2, Fig. 5, and Fig.
8. It is found that in the case when BasBN is 0.0005 mass%
or more and SaSMns is 0.002 mass% or more, the good magnetic
flux density, being the magnetic flux density B8 of 1.88 T
or more, is obtained from Fig. 2. Similarly, it is found
that in the case when BaS3N is 0.0005 mass% or more and
SeaSMnse is 0.004 mass% or more, the good magnetic flux
density, being the magnetic flux density B8 of 1.88 T or
more, is obtained from Fig. 5. Similarly, it is found that
in the • case when BasBN is 0.0005 mass% or more and S..asMn3 +
0.5 x SeasMnSe is 0.002 mass% or more, the good magnetic
flux density, being the magnetic flux density B8 of 1.88 T
or more, is obtained from Fig. 8. Then, as long as SasMns
is 0.002 mass% or more, S r:asMnSf. + 0.5 * SeasMnSe becomes
0.002 mass% or more inevitably, and as long' as SeasHnSe is
0.OQ4 mass% or more, S asMns +0.5 x SeasMnse becomes 0.002
mass% or more inevitably. Thus, it is important'that
- 32 -
^asMns. + 0-5 x SeaSMnse is 0.002 mass% or more.
[0073] In addition, in the hot rolling, in order to
precipitate a sufficient amount of BN, it is necessary to
held the silicon steel material (slab) in a temperature
range between 1000°C and 800°C for 300 seconds or longer
during the hot rolling as illustrated in Figure 11. If the
holding temperature is lower than 800°C, the diffusion
speeds of B and N are small, and the period of time
required for the precipitation of BN is longer. Meanwhile,
if the holding temperature exceeds 1000°C, BN becomes more
scluble, the precipitation amount of BN is not sufficient,
and a hich magnetic flux density may not be obtained. In
addition, if the holding time is less than 300 seconds,
the diffusion distances of B and N are short, and the
precipitation amount of BN is insufficient.
[0074] The method of holding the silicon steel material
(slab) in the temperature range between 1000°C and 800°C is
not particularly limited. For example, the following
method is effective. First, rough rolling is performed,
and a steel strip is wound into a coil form. Then, the
steel strip is held or slowly cooled in an equipment such
as a coil box. After that, finish rolling is performed in
the temperature range between 1000°C and 800°C while the
steel strip is wound off.
[0075] The method of precipitating MnS and/or MnSe is not
particularly limited. For example, it is preferable that
the temperature of the slab heating is set so as to
satisfy the following conditions,
(i) in the case of S and Se being contained in the
- 33 -
^ilicon steel slab
the temperature Tl (°C) expressed by equation (1) or
lower, and the temperature T2 (°C) expressed by equation
(2) or lower
(ii) in the case of no Se being contained in the
silicon steel slab
the temperature Tl (°C) expressed by equation (1) or
lower
(iii) in the case of no S being contained in the
silicon steel slab
the temperature T2 (°C) expressed by equation (2) or
lower
Tl = 14855/(6.82 - log ( [Mn] * [S])) - 273 ...(1)
T2 = 10733/(4.08 - log ( [Mn] x [Se])) - 273 ...(2)
[0076] This is because when the slab heating is performed
at such temperatures, MnS and MnSe are not completely
solid-dissolved at the time of slab heating, and the
precipitations of MnS and MnSe are promoted during the hot
rolling. As is clear from Fig. 4, Fig. 7, and Fig. 10, the
solution temperatures Tl and T2 approximately agree with
the upper limit of the slab heating temperature capable of
obtaining the magnetic flux density B8 of 1.88 or more.
[0077] In addition, it is further preferable that the
temperature of the slab heating is set so as to also
satisfy the following conditions. This serves to
precipitate a preferable amount of MnS or MnSe during the
slab heating.
(i) in the case of no Se being contained in the
silicon steel slab
- 34 -
the temperature T3 (°C) expressed by equation ('9) or
lower
(ii) in the case of no S being contained in the
silicon steel slab
the temperature T4 (°C) expressed by equation (10) or
lower
T3 = 14855/(6.82 - log (([Mn] - 0.0034) * ([S] -
0.002))) - 273 ...(9)
T4 = 10733/(4.08 - log (([Mn] - 0.0028) * ([Se] -
0.004))) - 273 ...(10)
[0078] In the case when the temperature of the slab
heating ^s too high, MnS and /or E:S:.. are s^'"^0 1 , •_-.--!-•••-_
dissolved completely. In this case, it becomes difficult
to make MnS and/or MnSe precipitate at the time of hot
rolling. Thus, the slab heating is preferably performed at
the temperature Tl and/or the temperature T2 or lower.
Further, if the temperature of the slab heating is the.
temperature T3 or T4 or lower, a preferable amount of MnS
or MnSe precipitates during the slab heating, and thus it
becomes possible to make BN precipitate compositely on MnS
or MnSe to form effective inhibitors easily.
[0079] After, the hot rolling (step SI), the annealing ofthe
hot-rolled steel strip is performed (step S2). Next,
the cold rolling is performed (step S3). As described
above, the cold rolling may be performed only one time, or
may also be performed a plurality of times with the
intermediate annealing being performed therebetween. In
the cold rolling, the final cold'rolling rate is
- 35 -
jj^eferably set to 80% or more. This is to develop a good
primary recrystallization aggregate structure.
[0080] Thereafter, the decarburization annealing is
performed (step S4). As a result, C contained in the steel
strip is removed. The decarburization annealing is
performed in a moist atmosphere, for example. Further, the
decarburization annealing is preferably performed at a
time such that, for example, a grain diameter obtained by
the primary recrystallization becomes 15 urn or more in a
temperature zone of 770°C to 950°C. This is to obtain the
good magnetic property. Subsequently, the coating of the
anneali: g separating agent and the finish annealing are
performed (st'ep S5) . As a result, the grains oriented in
the {110}<001> orientation preferentially grow by the
secondary recrystallization.
[0081] Further, the nitriding treatment is performed
between start of the decarburization annealing and
occurrence of the secondary recrystallization in the
finish annealing (step S6). This is to form an inhibitor
of (Al, Si)N. The nitriding treatment may be performed
during the decarburization annealing (step S4), or may
also be performed during the finish annealing (step S5).
In the case when the nitriding treatment is performed
during the decarburization annealing, the annealing may be
performed in an atmosphere containing a gas having
nitriding capability such as ammonia, for example.
Further, the nitriding treatment may be performed during a
heating zone or a soaking zone in a continuous annealing
furnace, or the nitriding treatment may also be performed
- 36 -
£at a stage after the soaking zone. In the case when the
nitriding treatment is performed during the finish
annealing, a powder having nitriding capability such as
MnN, for example, may be added to the annealing separating
agent.
[0082] In order to perform the secondary
recrystallization more stably, it is desirable to adjust
the degree of nitriding in the nitriding treatment (step
S6) and to adjust the compositions of (Al, Si)N in the
steel strip after the nitriding treatment. For example,
according to the Al content, the B content, and the
content of Ti existing inevitably, the degree of nitriding
is preferably' controlled so as to satisfy inequation (3)
below, and the degree of nitriding is more preferably
controlled so as to satisfy inequation (4) below.
Inequation (3) and inequation (4) indicate an amount of N
that is preferable to fix B as BN effective as an
inhibitor and an amount of N that is preferable to fix Al
as A1N or (Al, Si)N effective as an inhibitor.
[N] ^ 14/27[A1] + 14/11[B] + 14/47[Ti] ...(3)
[N] ^ 2/3[Al] + 14/11[B] + 14/47[Ti] ...(4)
Here, [N] represents an N content (mass%) of a steel
strip obtained after the nitriding treatment, [Al]
represents an acid-soluble Al content (mass%) of the steel
strip obtained after the nitriding treatment, [3]
represents a B content (mass%) of the steel strip obtained
after the nitriding treatment, and [Ti] represents a Ti
content (mass%) of the steel strip obtained after the
nitriding treatment.
- 37 -
''PD0 8 3] The method of the finish annealing (step S5) is
also not limited in particular. It should be noted that,
in this embodiment, the inhibitors are strengthened by BN,
so that a heating rate in a temperature range of 1000°C to
1100°C is preferably set to 15°C/h or less in a heating
process of the finish annealing. Further, in place of
controlling the' heating rate, it is also effective to
perform isothermal annealing in which the steel strip is
maintained in the temperature range of 1000°C to 1100°C for
10 hours or longer.
[0084] According to this embodiment as above, it is
possible to stably manufacture the grain-oriented
electrical steel sheet excellent in the magnetic property.
EXAMPLE
[0085] Next, experiments conducted by the present
inventers will be explained. The conditions and so on in
the experiments are examples employed for confirming the
practicability and the effects of the present invention,
and the present invention is not limited to those
examples.
[0086] (Fourth Experiment)
In the fourth experiment, the effect of the B content
in the case of no Se being contained was confirmed.
[0087] In the fourth experiment, first, slabs containing
Si: 3.3 mass%, C: 0.06 mass%, acid-soluble Al: 0.028
mass%, N: 0.00 8 mass%, Mr.: 0.1 massl, S: 0.00 6 mass%, and
H
B having an amount listed in Table 1 (0 mass% to 0.005
A
- 38 -
^mass%), and a balance being composed of Fe and inevitable
impurities were manufactured. Next, the slabs were heated
at 1180°C, and were subjected to hot rolling. In the hot
rolling, rough rolling was performed at 1100°C, annealing
in which the slabs were held at 950°C for 300 seconds was
performed, and after that, finish rolling was performed at
900°C. In this manner, hot-rolled steel strips each having
a thickness of 2.3 mm were obtained. Subsequently,
annealing of the hot-rolled steel strips was performed at
1100°C. Next, cold rolling was performed, and thereby
cold-rolled steel strips each having a thickness of 0.22
mm were obtained. Thereafter, decarburization annealing
was performed'' in a moist atmosphere gas at 830°C for 100
seconds, and thereby decarburization-annealed steel strips
were obtained. Subsequently, the decarburization-annealed
steel strips were annealed in an ammonia containing
atmosphere to increase nitrogen in the steel strips up to
0.024 mass%. Next, an annealing separating agent
containing MgO as its main component was coated on the
steel strips, and the steel strips were heated up to 1200°C
at a rate of 15°C/h and were finish annealed. Then, a
magnetic property (the magnetic flux density B8) after the
finish annealing was measured. The magnetic property
(magnetic flux density B8) was measured based on JIS
C2556. A result of the measurement is listed in Table 1.
[0088]
[Table 1]
- 39 -
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CJ t rf - ^ -H rH rH M
3 CJ W O O C O O
M M Z
CC IX H
H
M
Z fH „
2 6P "3* *y
" M CJ CJ
EH J J
d) <* Q4 a,
Zi S. 2 s
X! CM x ;<
rrj S u cj
FH O
H cj
^ [0089] As listed in Table 1, in Comparative Example No.
1A having no B contained in the slab, the magnetic flux
density was low, but in Examples No. IB to No. IE each
having an appropriate amount of B contained in the slab,
the good magnetic flux density was obtained.
[0090] (Fifth Experiment)
In the fifth experiment, the effects of the Mn content
and the slab heating temperature in the case of no Se
being contained were confirmed.
[0091] In the fifth experiment, first, slabs containing
Si: 3.3 mass%, C: 0.06 mass%, acid-soluble Al: 0.028
mass%, N: 0.007 mass%, S: 0.006 mass%, B: 0.0015 mass%,
and Mn having- an amount listed in Table 2 (0.05 mass% to
0.2 mass%), and a balance being composed of Fe and
inevitable impurities were manufactured. Next, the slabs
were heated at 1200°C, and were .subjected to hot roiling.
In the hot rolling, for some of the samples (Examples No.
2A1 to No. 2A4), rough rolling was performed at 1100°C,
annealing in which the slabs were held at 1000°C for 500
seconds was performed, and after that, finish rolling was
performed. In this manner, hot-rolled steel strips each
having a thickness of 2.3 mm were obtained. On the other
hand, for the other samples (Examples No. 231 to No. 2B4),
rough rolling was performed at 1100°C, and after that,
finish rolling was performed at 1020°C without performing
an annealing. In this manner, hot-rolled steel strips each
having a thickness of 2.3 mm were obtained. Subsequently,
annealing of the hot-rolled steel strips was performed at
1100°C. Next, cold rolling was performed, and thereby
- 41 -
Ac old-rolled steel strips each having a thickness of 0.22
mm were obtained. Thereafter, decarburization annealing
was performed in a moist atmosphere gas at 830°C for 100
seconds, and thereby decarburization-annealed steel strips
were obtained. Subsequently, the decarburization-annealed
steel strips were annealed in an ammonia containing
atmosphere to .increase nitrogen in the steel strips up to
0.022 mass%. Next, an annealing separating agent
containing MgO as its main component was coated on the
steel strips, and the steel strips were heated up to 1200°C
at a rate of 15°C/h and were finish annealed. Then,
similarly to the fourth experiment, a magnetic property
(the magnetic/ flux density B8) was measured. A result of
the measurement is listed in Table 2.
[0092]
[Table 2]
- 42 -
u >- u >_
^ i - U ^ H - J h - y . .
2 fc 2 J
7T C M L O C O f O O C O ^ r u ")
S r n O O O O O O O O
S i: o o o o o o o o
co g
S. o o o o o o o o
CO
w
£H 2
. < C » ' ^ ' [ - - ^ > r - - r - C M . - t r - < rH
H .o rt: o o o O r H r d ^ i ^i
n ca "i o o o o o o o o
w ii; o o o o o o o o
H ~ a
<-> cQri o o o o o o o o
w —
Qj _ —I
"7^ cooc^rorn^r«T-vr
Z Jv, 0 " - H ^ H t - I O O OO
3 "^ O O O O O O O O
« ;* o o o o o o o o
CQ S
—. o o o o o o o o
M w UJ c*° c \j CM (\ , 0 c\ j cv ,: ^ \;
Q. 2 h M CM CM . -; CM CM. ' i ;M CM
H EH Z " i O O O O O O O O
05 sC O < • •
E H W U S O O O O O O O O
M O ; ~
2 EH Z
o $ <^
Q ** O O O O I I 1 I ^
,n J s vim m m in
z O S I
J
O
rr g ^ ^ o o o o
n S O O O O o . . . J U i~ ° ° ° °
O f t H H H H a: s
EH
z u
KC 5 S —• O O O O O O O O
W S 5 U O O O O O O O O
a S * n ° CMCMCMCMCMCMCMCM
I
EH
w ^
E H J ; L D C ^ r O u n O TO
'Z rr, O <—< i—I [N O H H CN
O UJ
C j S O O O O O O OO
s
^ CM ~ ^ f ^ CM r : ^r
Z CM CM CM CM CM CM CM CM
W >
M H U
CM J EH J
a. < en
H U ^
f^ S , , 5 H ^ \T> (M « (M ^r Ol If)
Z S Z J " ^ en en m t- r- c-
•~~ ^r co CM . - t r - rH co
£ ° „ CM CM CM CM ^-1 CM .H
£ " i O O O O O O O
3 ~J o o o o o o o
B ?
±. o o o o o o o
en ,
w
E-i aj fl ^ H O O O ^ H r H^
w CQ " ' O O O O O O O
QJ i "i o o o o o o o n — a
Q O i O O ' O O O O O
w —
• OJ .
"7? ro ID CN H v ^r n
z Sr o o , - t . H o oo
ISrn O O O O O O O
Jit,! o o o o o o o
5, o o o o o o o
O E-i E-<
2 2 12 • -
H C d C d d P i H r - H r H r H t - H T - H r H ,
' Q S E-l CO CM CM CM CM CM CM C\]
1-1 E« Z 0) O O O O O O O
OS < O <
— L-l C S7 O O O O O O O
M -*- r o o o o o o o
Q *s> o o o o o o o
O S o
M ^
O o" '
OS —-
EH U U
O -^ pi o o
a 2 £ ° O O o O o
Oi s
w
E-i
_. o o o o o o o
ro^_) en en en en en en en
E - * 0 .—] t-H r-H i—I (H t-J (—I
~" t-H rH ^H ^H >
M Cd a M Cd '
EH I-J KH E- K^ !
" < 5! < < rf
^ S a a s a
2 o o
•S u o
H 1 i I
[0097] As listed in Table 3, the good magnetic flux
density was obtained in Examples No. 3B to No. 3D in each
of which the slab was held at a predetermined temperature
for a predetermined period of time at an intermediate
stage of the hot rolling. But, the magnetic flux density
was low in Comparative Examples No. 3A and No. 3E to No.
3G in each of which the holding temperature or the holding
time was outside of the range of the present invention.
[0098] (Seventh Experiment)
In the eighth experiment, the effect of the N content
after the nitriding treatment in the case of no Se being
contained was confirmed.
[0099] In the seventh experiment, first, slabs containing
Si: 3.3 mass%, C: 0.06 mass%, acid-soluble Al: 0.028
mass%, N: 0.006 mass%, Mn: 0.15 mass%, S: 0.006 mass%, and
B: 0.002 mass%, a content of Ti that is an impurity being
0.0014 mass%, and a balance being composed of Fe and
inevitable impurities were manufactured. Next, the slabs
were heated at 1200°C, then annealing in which the slabs
were held at 950°C for 300 seconds was performed, and after
that, finish rolling was performed. In this manner, hotrolled
steel strips each having a thickness of 2.3 mm were
obtained. Subsequently, annealing of the hot-rolled steel
strips was performed at 1100°C. Next, cold rolling was
performed, and thereby cold-rolled steel strips each
having a thickness of 0.22 mm were obtained. Thereafter,
decarburization annealing was performed in a moist
atmosphere gas at 830°C for 100 s,econds, and thereby
decarburization-annealed steel strips were obtained.
- 47 -
Subsequently, the decarburization-annealed steel strips
were annealed in an ammonia containing atmosphere to
increase nitrogen in the steel strips up to 0.012 mass% to
0.022 mass%. Next, an annealing separating agent
containing MgO as its main component was coated on the
steel strips, and the steel strips were heated up to 1200°C
at a rate of 15°C/h and were finish annealed. Then,
similarly to the fourth experiment, a magnetic property
(the magnetic flux density B8) was measured. A result of
the measurement is listed in Table 4.
[0.100]
[Table 4]
- 48 -
£ os £ •><• ^ ~ CM <* o
z S § 3 « » <* <*
< os < " m ^ ^ M
2 a. 2 u
i n ^ ^ ^ • g * n n m
t , „ o o o
S ^ o o o
en 5) . . .
i o o o
CO
u
EH * " " O O O
H CQ " O O O
On I ^ O O O
O 03 £ O O O
os
0-,
~ r~ r- r-
Sg? o o o
a?< °. ° °
S. o o o
w z
Q O
£ £ CM CM CM •
k, S ~ ™ ^ ™
H O D 3 ° ° °
EH K a a" „• 0-
Z U W ° ° °
W M Z
2 OS M
EH | I
: M !
u. Q O
r n Cu
M y ?To ° ° °
Q s iriij ° ° °
U £ EH ^ ^ "> ^
3 _= ~_
3 ,,
° OS
-* U D
£ M < — o o o
ss a os i-1 LO m uo
•^ J a c_ en oi en
O 04
-c s
w
E-.
. _ LO U~> in
r o cj o o o
EH O CM CM CM
' " ' rH rH rH
!5 ^ ro n n
rf; ^ (J ro ro ro
7] EH O CM CM CM
% ~ * ^ -
rjj
~ W
w S S u o o o
Sw t ™ 2 ^
CC S
w
EH
0 < CQ CJ
-!
0! 0J
13 2!
« x
EH
W
[0101] As listed in Table 4, in Example No. 4C in which
• an N content after the nitriding treatment satisfied the
relation of inequation (3) and the relation of inequation
(4), the particularly good magnetic flux density was
obtained. On the other hand, in Example No. 4B in which an
N content after the nitriding treatment satisfied the
relation of inequation (3) but did not satisfy the
relation of inequation (4), the magnetic flux density was
slightly lower than those in Example No. 4C. Further, in
Example No. 4A in which an N content after the nitriding
treatment did not satisfy the relation of inequation (3)
and the relation of inequation (4) . fhe macrnetic flux
density was slightly lower than those in Example No. 4B.
[0102] (Eighth Experiment)
In the eighth experiment, the effect of the components
of the slab in the case of no Se being contained was
confirmed.
[0103] In the eighth experiment, first, slabs containing
components listed in Table 5 and a balance being composed
of Fe and inevitable impurities were manufactured. Next,
the slabs were heated at 1200°C, then annealing in which
the slabs were held at 950°C for 300 seconds was performed,
and after that, finish rolling was performed. In this
manner, hot-rolled steel strips each having a thickness of
2.3 mm were obtained. Subsequently, annealing of the hotrolled
steel strips was performed at 1100°C. Next, cold
rolling.was performed, and thereby cold-rolled steel
strips each having a thickness of 0.22 mm were obtained.
Thereafter, decarburization annealing was performed in a
- 50 -
fPoist atmosphere gas at 860°C for 100 seconds, and thereby
decarburization-annealed steel strips were obtained-
Subsequently, the decarburization-annealed steel strips
were annealed in an ammonia containing atmosphere to
increase nitrogen in the steel strips up to 0.023 mass%.
Next, an annealing separating agent containing MgO as its
main component'was coated on the steel strips, and the
steel strips were heated up to 1200°C at a rate of 15°C/h
and were finish annealed. Then, similarly to the fourth
experiment, a magnetic property (the magnetic flux density
B8) was measured. A result of the measurement is listed in
T L b 1 c 5 .
[0104]
• [Table 5]
- 51 -
£ ^ ^ E - < r r r - ~ - u " > U 5 r - - r ' i ( v ' > o o i c \ ] a D O C ^ ^ c ^ < j D ro
^ ! f^ =r* 25 i—c 5H r - . r - . c \ i C M C \ i c o < s ] r H c s i c N m c s i c \ i i - . n as cu a " | |
m —i
• o o
" i i i i i i i i i i o i i o i i
o o
^ I I I I I I I I I ° . I I I I I !
O
c ° i ' ° ° °. i '
o o o o
O • ° °
o b
cu i i i i i i ° . i i i i ° . ° . i i i
— o o o
co ,
co
i -H -1 ^ ° 2
s . " i i i • • • i i i i i i i i i
Z o o - . 0'
r-co^OkDr-r^^3r-^co'-Dr-«3«3 CM
o o o o o o o o o o o o o o o o
z co o o o o o o o o o o o o o o o o
jr1 o o o o o o o o o o o o o o o o
H ' •
co
O <-H <—< rH r—i rH —. —H t—i r—1 — . r H r H — • I — I — I ^
5 j s o o o o o o o o o o o o o o o o
CJ
c o r - c o c o r - c ^ r - c o c o c o c y i c o c o ^ c o ro
o o o o o o o o o o o o o o o
z o o o o o o o o o o o o o o o o
o o o o o o o o o o o o o o o o
cor~LOr--^r'r-cor--cO'-n^rOr^corvj in
, C \ J C \ ] C \ J C \ J C N C \ ] C \ J C N [ N C \ l C \ l c n C \ J C \ J C \ l m
• 2 o o o o o o o o o o o o o o o o
o o o o o o o o o o o o o o o o
U3 VD ^0 vD v£> ^ U2 ^) ^ ^ '*£ L-0 VQ ^D '*D ^D
J J O O O O O O O O O O O O O O O O
O O O O O O O O O O O O O O O O
-r_. r o c N ^ ' m m r o ^ r c M r o m m c N j c o m o D m
^ m m m c o r o r o o n r o m m r o r o c n c o c s ] ro
h I I I I—n M I—
^ L O i n L n L o m i n i o i O i n i n i n i n m LO u o LO
' w
! >
1-3 b J
Ul OJ < OJ
S, 05 2
0) < sC <
•-. X 1 X -a w aw
« C
E-. U
|[0105] As listed in Table 5, in Examples No. 5A to No. 50
each using the slab having the appropriate composition,
the good magnetic flux density was obtained, but in
Comparative Example No. 5P having a S content being less
than the lower limit of the present invention range, the
magnetic flux density was low.
[0106] (Ninth Experiment)
In the ninth experiment, the effect of the B content
in the case of no S being contained was confirmed.
[0107] In the ninth experiment, first, slabs containing
Si: 3.2 mass%, C: 0.06 mass%, acid-soluble. Al: 0.027
mass%, N: 0.008 mass%, Mn: 0.12 m?.^s%, ?P: 0.0 08 m=?s%.
and B having an amount listed in Table 6 (0 mass% to
0.0043 mass%), and a balance being composed of Fe and
inevitable impurities were manufactured. Next, the slabs
were heated at 1180°C, and were subjected to hot rolling.
In the hot rolling, rough rolling was performed at 1100°C,
annealing in which the slabs were held at 950°C for 300
seconds was performed, and after that, finish rolling was
performed at 900°C. In this manner, hot-rolled steel
strips each having a thickness of 2.3 mm were obtained.
Subsequently, annealing of the hot-rolled steel strips was
performed at 1100°C. • Next, cold rolling was performed, and
thereby cold-rolled steel strips each having a thickness
of 0.22 mm were obtained. Thereafter, decarburization
annealing was performed in a moist atmosphere gas at 830°C
for 100 seconds, and thereby decarburization-annealed
steel strips were obtained. Subs.eauently, the
decarburization-anneaied steel strips were annealed in an
- 53 -
lammonia containing atmosphere to increase nitrogen in the
steel strips up to 0.024 mass%. Next, an annealing
separating agent containing MgO as its main component was
coated on the steel strips, and the steel strips were
heated up to 1200°C at a rate of 15°C/h and were finish
annealed. Then, similarly to the fourth experiment, a
magnetic property (the magnetic flux density B8) was
measured. A result of the measurement is listed in Table
6.
[0108]
[Table 6]
- 54 -
I cj x CJ ._
^ ' ' > EH ^ ^ ["-• rH [~- ^
^ P ^ ^ 2 5 n ! l en H n w M
z S Z 3 " °° c" en en en
o o u i " i^ OD : J J J J
< Ci < W D ^ rH rH rH rH
s c- s u
a, " ^ n in U3 m
yi rj: -c ^r *rr ^r *r
| J5 o o o o o
» ii o 'O o o o
v tZ . . . . . w 5. o o o o o
CO
KI
r « C rH CN ^T 1"
£ *m O O O O
f 1 (0 ^ ^ o o o o
M i « ° ° ° °
H CQ £ o o o o
cu
~ m m m en
z ?? o .H CM n
S " 0 o o o o
« "J "-' o o o o
CQ < . . ..
£ o o o o
W 2
Q O
M M ,„ rH CN r^ LO
CO £H ~ CT\ O rH PO
fc<^T £, rt N N (N
E H H 0 0 3 - ° O O O
z ac a ' . . . .
Id (J W O O OO
5 n Z
EH Pi H
<
w w z
6 Q O
E H M H „ CO CO ^ C£3
T cj r~ r~ r- r- r-
EH 0 rH i—1 r—< rH t-H
^ rH rH rH rH rH
!~ „ oi [Ji oi fli cn
S CM u r o r - l p o nm
£ EHO CM CN CM CN CN
^ " rH r-i rH rH rH
-
3 z °
^ in ef — ° O O O O 1-3 S y U 00 CO CO CO CO
CO g P ^ O rH rH rH rH r—1
r i n_i r""~^ T" ^ T— ^""^ T—~^
X S
w
& r j en r- en m
H * O rn CN ^r « ^ o g g oo
j , i . O O OO
: ,——.—.—
n <; cq o Q w
^ m io » ID ID
w
> I
rH W W
H J rj
a) «c < 2
rn; CH X X
CD O
EH O
[0109] As listed in Table 6, in Comparative Example No.
6A having no B contained in the slab, the magnetic flux
density was low, but in Examples No. 6B to No. 6E each
having an appropriate amount of B contained in the slab,
the good magnetic flux density was obtained.
[0110] (Tenth Experiment)
In the tenth experiment, the effects of the Mn content
and the slab heating temperature in the case of no S being
contained were confirmed.
[0111] In the tenth experiment, first, slabs containing
Si: 3.3 mass%, C: 0.06 mass%, acid-soluble Al: 0.026
mass%, N: 0.007 mass^, Se: 0.009 mass%, B: 0.0015 rr.ass%,
and Mn having' an amount listed in Table 7 (0.1 mass% to
0.21 mass%), and a balance being composed of Fe and
inevitable impurities were manufactured. Next, the slabs
were heated at 1200°C, and were subjected to hot rolling.
In the hot rolling, for some of the samples (Examples No.
7A1 to No. 7A3), rough rolling was performed at 1100°C,
annealing in which the slabs were held at 1000°C for 500
seconds was performed, and after that, finish rolling was
performed. In this manner, hot-rolled steel strips each
having a thickness of 2.3 mm were obtained. On the other
hand, for the other samples (Examples No. 7B1 to No. 7B3),
rough rolling was performed at 1100°C, and after that,
finish roiling was performed at 1020°C without performing
an annealing. In this manner, hot-rolled steel strips each.
having a thickness of 2.3 mm were obtained. Subsequently,
annealing of the hot-rolled steel strips was performed at
1100°C. Next, cold rolling was performed, and thereby
- 56 -
cold-rolled steel strips each having a thickness of 0.22
mm were obtained. Thereafter, decarburization annealing
was performed in a moist atmosphere gas at 830°C for 100
seconds, and thereby decarburization-annealed steel strips
were obtained. Subsequently, the decarburization-annealed
steel strips were annealed in an ammonia containing
atmosphere to increase nitrogen in the steel strips up to
0.022 mass%. Next, an annealing separating agent
containing MgO as its main component was coated on the
steel strips, and the steel strips were heated up to 1200°C
at a rate of 15°C/h and were finish annealed. Then,
similarly to the fourth experiment, a magnetic Droperty
(the magnetic- flux density B8) was measured. A result of
the measurement is listed in Table 7.
[0112]
[Table 7]
- 57 -
\\% £ | u >, I I I I |
g S g 3 ^ c c c* r~ r- r~
vi °* CM m in .-H m T
I " 1 o o o o o o
m " i O O O O O O
nj ^
° ° 5 O O O O O O
CO
r. « f . O O O •-) rH ,H
£ na ^ o o o o o o
£ I ^ O O O O OO
6j £.5- O O O O O O
DC
cu
'T ^ n ^r ^ T
Z * !T ,-H rH O O O
£-• z z z —-
M U W <*> CM CM CM CM CM CM
Q 2 E-i W M M N N (N «
M E - i Z W O O O O O O
OS < O <
EH W O S O O O O O O
H PC I
Z EH Z
• CO
g r ~
H S rt-O o o o l
Q S i l ^ - o o o i i i
U ^ c- 2iv'in m in
J
O cd
CC CJ D
Z H
£ M < — O O O
y Q o; n
u o o o i i i
O Cu cc s
w
EH ,
W
CC
C Q 5 2 S — o o o o o o
< C £ 5 CJ o o o o o o
J J? 5> n ° CM CM CM CM CM CM
CC 33 2
E-<
z
E H * O u O t H O c r )^
Z r „ rH rH CM .H H CM O £
c j g o o o o oo
c "
S !
tH CM ro iH CM 00
I o <
H3 EH J
r- Cu < cu
cu < < <
-H X Cu X ,a a s w
c0 O
E H CJ
^|0113] As listed in Table 7, the good magnetic flux
density was obtained in Examples No. 7A1 to No. 7A3 in
each of which the slab was held at a predetermined
temperature at an intermediate stage of the- hot rolling,
but the magnetic flux density was low in Comparative
Examples No. 7B1 to No. 7B3 in each of which such holding
was not performed.
[0114] (Eleventh Experiment)
In the eleventh experiment, influences of the holding
temperature and the holding time in the hot rolling in the
case of no S being contained were confirmed.
[01151 In the eleventh exoeriment, first, slabs
containing Si': 3.2 mass%, C: 0.06 mass%, acid-soluble Ai:
0.027 mass%, N: 0.006 mass%, Mn: 0.12 mass%, Se: 0.008
mass%, and B: 0.0017 mass%, and a balance being composed
of Fe and inevitable impurities were manufactured. Next,
the slabs were heated at 1200°C, then, annealing in which
the slabs were held at 1050°C to 700CC for 100 seconds to
500 seconds was performed, and finish anncalin-g was
performed. In this manner, hot-rolled steel strips each
having a thickness of 2.3 mm- were obtained. Subsequently,
annealing of the hct-rolied steel strips was performed at
1100°C. Next, cold rolling was performed, and thereby
cold-rolled steel strips each having a thickness of 0.22
mm were obtained. Thereafter, decarburization annealing
was performed in a moist atmosphere gas at 830°C for 100
seconds, and thereby decarburization-annealed steel strips
were obtained. Subsequently, the decarburization-anneaied
steel strips were annealed in an ammonia containing
- 59 -
atmosphere to increase nitrogen in the steel strips up to
0.021 mass%. Next, an annealing separating agent
containing MgO as its main component was coated on the
steel strips, and the steel strips were heated up to 1200°C
at a rate of 15°C/h and were finish annealed. Then,
similarly to the fourth experiment, a magnetic property
(the magnetic flux density B8) was measured. A result of
the measurement is listed in Table 8.
[0116]
[Table 8]
- 60 -
U >H U ^
^ ^ r t ^ M t l <^ CM CN c\i r- ^r m
Z £ Z J °° ^ en en oi r- r~- ru
o u t w S o o • • ; • • • _ ;
< 05 < gcQ ^ ' H ' - i ' - i ^ ^ ' -i
S O. 2 J
,S ^ ^ (N » n !N i n »
£ "i o o o o o o o
S li o o o o o o o
a) 3
n s o o o o o o o
CO
W
< § „
* ! H " i ^ ^ CO ^r 15 ^r n ^r
' M ' ^ r ^ - l O O O r H r H r H
a. m ' o o o o o o o
M i "i o o o o o o o o ,-, 5
cd mi o o o o o o o
Pi =.
a,
OP
CO
„, co a^ n ,-i m -=r ro
if O O ^ H r H O O O
S o o o o o o o
„ o o o o o o o
I o o o o o o o
o !-' H I 1 I '
z z 2 -
MC£] W crtP rH <—t ^ r-1 r-l .—I i-l
O S H< CO CM CM CM CM CM CM CM
H fn SCO O O O O O O O
cC < O <
EH H O S O O O O O O O
M 05 —-
Z EH Z 3 ^ ' Z M § ^ ^ O O O O O O O r-H Q M oTf! O O O O O O O ^p
2 O H ^J
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EC U D
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cL. r~ r- P- r- r-- r- r~
r-t rH --H (—I ^ i—I rH
^p r-i ^ r^ rM rH r—I r-H
z —
n • O c?i en d ai c^ cii m
H ^ t L - c n r n r o r o r n c n c )
^ CM CM | CM CM CM CM CM
^ ^ 7 - H t - H r H r H r - i r H l H
" ^ tH
en I 1 L—i—\- 1
Hi 05
co op
2' E? -~ o o o o o o o
r ] | 5 r j o o o o o o o
> ~ 0 C\| CM C*l CM CM CM CM
2 g - rH r J r H r H . - i r H . -l
X 2
fa]
EH
^ < m •-_> c Ki r^ o
2 C O C O C O C O C O O D CO
. i Mil
> [>
HH fa] M M fa]
EH tH ^ EH J
CO < DJ OJ < OJ
05 2 2 05 2
CD < < < < <
•H OJ X X OJ X
X) 2 M W 2 M
(0 O O
EH O O
,[0117] As listed in Table 8, the good magnetic flux
density was obtained in Examples No. 8B to No. 8D in each
of which the slab was held at a predetermined temperature
for a predetermined period of time at an intermediate
stage of the hot rolling. But, the magnetic flux density
was low in Comparative Examples No. 8A and No. 8E to No.
8G^ in each of which the holding temperature or the holding
time was outside of the range of the present invention.
[0118] (Twelfth Experiment)
In the twelfth experiment, the effect of the N content
after the nitriding treatment in the case of no S being
contained was confirmed.
[0119] In the twelfth experiment, first, slabs containing
Si: 3.3 mass%, C: 0.06 mass%, acid-soluble Al: 0.027
mass%, N: 0.008 mass%, Mn: 0.12 mass%, Se: 0.007 mass%,
and B: 0.0016 mass%, a content of Ti that is an impurity
being 0.0013 mass%, and a balance being composed of Fe and
inevitable impurities were manufactured. Next, the slabs
were heated at 1180°C, then annealing in which the slabs
were held at 950°C for 300 seconds was performed, and after
that, finish rolling was performed. In this manner, hotrolled-
steel strips each having a thickness of 2.3 mm were
obtained. Subsequently, annealing of the hot-rolled steel
strips was performed at 1100°C. Next, cold rolling was
performed, and thereby cold-rolled steel strips each
having a thickness of 0.22 mm were obtained. Thereafter,
decarburization annealing was performed in a moist
atmosphere gas at 830°C for 100 seconds, and thereby
decarburization-annealed steel strips were obtained.
- 62 -
Jwbsequently, the decarburization-annealed steel strips
were annealed in an ammonia containing atmosphere to
increase nitrogen in the steel strips up to 0.015 mass% to
0.022 mass%. Next, an annealing separating agent
containing MgO as its main component was coated on the
steel strips, and the steel strips were heated up to 1200°C
at a rate of 15°C/h and were finish annealed. Then,
similarly to the fourth experiment, a magnetic property
(the magnetic flux density B8) was measured. A result of
the measurement is listed in Table 9.
[0120]
[Table 91
- 63 -
Z S z j B " " OT ^
< o : < g a ^ ^ ^
»* 2 2 2
s "x o o o
5 ii o o o
IT) 03 CN
£H CO H rH C\] I
2 CO O O O
U S O O O ^
z
I
2 u
M s r~r o o o
Q S n O O O
u J H I - c> m on
z O H
M cr:
9 £
Z fH
EH M .< — O O O
O a pi y <-n in in
O 0J
X S
H
EH
„ CM CM CNJ
^r (j in '~n in
EH o rH —I ^H
"-" rH ^H rH
U I
3 ~ - - -
p_ CM (J iM N N
5 EH O C\i C\] CM
2 ~ ^ ^ ^
s j i
CQ cd
< =S
• J O D « g g _. o c o
C 3 U CO CD CO
y ft o rH rH rH
< H ~_- rH rH rH
|H P-l rH rH c o r - r - i - o u 3 c\j M „, o o o o o o o o o o o o o o o o
r1 -o o o o o o o o o o o o o o o o o
M ^J
S2 o o o o o o o o o o o o o o o o
Oi 1 I _____
2 I
p L D C N C N i ^ t - H m O T — i r o o o r o o c v j o o
2
o o o o o o o o o o o o o o o o
c o r - - c o a > r - ^ r - c o c o c o a ^ c o o o ^ o r - en
o o o o o o o o o o o o o o o o
Z o o o o o o o o o o o o o o o o
o o o o o o o o o o o o o o o o
r - [ " - m a c [ ~ - ^ r c r \ r - o o c o o * T r - - ^ v H O
, c % ] C - j c N j c > j C N ] C N ! C N C N i C \ j c s j r o c N ] C N m c M n
jj. O O O O O O O O O O O O O O O O
O O O O O O O O O O O O O O O O
rj O O O O O O O O O O O O O O O O
O O O O O O O O O O O O O O O O
, r o c n ^ r c \ i ' = r r - f c O ' ^ ^ * r o m c ^ r ~ c \ i c o r-4
^ m r o r o r o r o c o r o r o o o r o c o c O f O r o c N ] en
< Q O 2 W L--: | O E M lo fcrf i-: I 2 — O CJ
o o o o l o o o o o o o o o o o o o
2 ; T - H r H ( — I t H i H r - f r H t H r H r H i — ) t - H t — f ^ f ' — I rH
u Ma!
O *-5 ^ ^
2 cc; 2
i) 3 < a;
i - 1 X Oi X
J 2 ! W 2 M
«3 j C
H 1 I"
[0125] As listed in Table 10, in Examples No. 10A to No.
10O each using the slab having the appropriate
composition, the good magnetic flux density was obtained,
but in Comparative Example No. 10P having a Se content
being less than the lower limit of the present invention
range, the magnetic flux density was low.
[0126] (Fourteenth Experiment)
In the fourteenth experiment, the effect of the B
content in the case of S and Se being contained was
confirmed.
[0127] In the fourteenth experiment, first, slabs
containing Si: 3.2 ir.;,8s%. C: 0.05 mass%, acid-soluble Al:
0.028 mass%, N: 0.008 mass%, Mn: 0.1 mass%, S: 0.006
mass%, Se: 0.006 mass%, and B having an amount listed in
Table 11 (0 mass% to 0.0045 mass%), and a balance being
composed of Fe and inevitable impurities were
manufactured. Next, the slabs were heated at 1180°C, and
were subjected to hot rolling. In the hot rolling, rough
rolling was performed at 1100°C, annealing in which the
slabs were held at 950°C for 300 seconds was performed, and
after that, finish rolling was performed at 900°C. In this
manner, hot-rolled steel strips each having a thickness of
2.3 mm were obtained. Subsequently, annealing of the hotrolled
steel strips was' performed at 1100°C. Next, cold
rolling was performed, and thereby cold-roiled steel
strips each having a thickness of 0.22 mm were obtained.
Thereafter, decarburization annealing was performed in a
moist atmosphere gas at 830°C for 100 seconds, and thereby
decarburization-annealed steel strips were obtained.
- 68 -
Subsequently, the decarburization-annealed steel strips
were annealed in an ammonia containing atmosphere to
increase nitrogen in the steel strips up to 0.024 mass%.
Next, an annealing separating agent containing MgO as its
main component was coated on the steel strips, and the
steel strips were heated up to 1200°C at a rate of 15°C/h
and were finish annealed. Then, similarly to the fourth
experiment, a magnetic property (the magnetic flux density
B8) was measured. A result of the measurement is listed in
Table 11.
[0128]
Liable 11]
- 69 -
U >< U ^
^ f c S y ^ h ^ co 10 m m
^ P ^ . ^ ^ H C O rH CM C\] C\]
CJ O O In 5 co ' " ' " '
< PS < HeQ ^ - H - I - H -H
S cu s u |
a)
c ^_^
+ j, o*P m LO i n LO LO
c „? CO O O O O O
£ ,™ co o . 0 0 0 0
£ ^ <
to £ 2 o 0 0 0 0
to al —
£ o
< C •
M S^ rn m m al
Oj « ^ O O OO
M CQ^ O O OO
O 1 ^ ° o o o o
QJ 23 £ O O OO
Oi ^ I
~ IC lO IT) O
z ?r o H « 7
?>£ 0 0 o o 0
.«rJ " 0 0 0 0
CQ < . . . .
S. 0 0 00
u 2;
Q O
£ £
r ;? —- ^ « M M M
H !H O § ^ ° ° ° ° ° .
g g g 0 0 0 00
s y z
§H OS M
< 1
U U 2
Oi Q O
6-1 K H in u> r~ ~ o
2 t - ;T o ~ i r
2 u a 0 . 0 0 0 0
H 1-1 2
a; a H
E- 1
M En —
3 2 cfP *a< ^r ^r- ^ j * ^
W CO CM CM CM CM IN
Z h 01 o 0 0 0 0
•z. < 1
O S o o o o o
CJ —
. O
CJ r^
M -V r~TO ° O O O O Q S £iviJ 0 0 0 0 0 I
CJ KJ " i l f j i ro ro co ro n
Z 2 Aj
rH CC ^^
J 1 ,
J W
O OS
PS CJ p
5H M < -~- o 0 0 0 0
O Q o; u m m m m m
m h-^tdv-- a> o> oi en m
O cu
3= 2
U
._. c— r- r— c— r—
C\] ;_) CTi
EH 0 rH rH rH rH rH
" ^-1 rH rH rH rH
2 _ 13 10 i£) vo 10
g rH (J O O O O O
C EHO CM C\J i\J C\] CM
S ^ rH r-^ j -H rH rH
OS
ffl 2 5
< 2 5 ,-. 0 o | o oo
" o 3 O 00 CO CO CC CO
CO S ^ ° 'i r- rH rH rH
2 S ~ -1 rH rH rH rH
x 2
co
i EH I I I
5 M 0 co 00 in
M co o rH CM ^r « I I ° § § § §
3 S 0 0 00
eC CQ U ' Q W
0 rH rH rH rH rH
Z rH r^ r- rH rH
j J i
> I
rH < Cu j CU
a) < < <
— Cu X X
£ S Cd W
ID O
EH 1 CJ
F0129] As listed in Table 11, in Comparative Example No.
11A having no B contained in the slab, the magnetic flux
density was low, but in Examples No. 11B to No. H E each
having an appropriate amount of B contained in the slab,
the good magnetic flux density was obtained.
[0130] (Fifteenth Experiment)
In the fifteenth experiment, the effects of the Mn
content and the slab heating temperature in the case of S
and Se being contained were confirmed.
[0131] In the fifteenth experiment, first, slabs
containing Si: 3.3 mass%, C: 0.06 mass%, acid-soluble Al:
0.027 irassl, N: 0.006 mass%, F: 0.006 mass!, Se: 0.004
mass%, B: 0.0015 mass%, and Mn having an amount listed in
Table 12 (0.05 mass% to 0.2 mass%), and a balance being
composed of Fe and inevitable impurities were
manufactured. Next, the slabs were heated at 1200°C, and
were subjected to hot rolling. In the hot rolling, for
some of the samples (Examples No. 12A1 to No. 12A4), rough
rolling was performed at 1100°C, annealing in which the
slabs were held at 1000°C for 500 seconds was performed,
and after that, finish rolling was performed. In this
manner, hot-rolled steel strips each having a thickness of
2.3 mm were obtained. On the other hand, for the other
samples (Examples No. 12B1 to No. 12B4), rough rolling was
performed at 1100°C, and after that, finish rolling was
performed at 1020°C without performing an annealing. In
this manner, hot-rolled steel strips each having a
thickness of 2.3 mm were obtained. Subsequently, annealing
of the hot-rolled steel strips was performed at 1100°C.
- 71 -
llext, cold rolling was performed, and thereby cold-rolled
steel strips each having a thickness of 0.22 mm were
obtained. Thereafter, decarburization annealing was
performed in a moist atmosphere gas at 830°C for 100
seconds, and thereby decarburization-annealed steel strips
were obtained. Subsequently, the decarburization-annealed
steel strips were annealed in an ammonia containing
atmosphere to increase nitrogen in the steel strips up to
0.022 mass%. Next, an annealing separating agent
containing MgO as its main component was coated on the
steel strips, and the steel strips were heated up. to 1200°C
at a rate of 1 r> ° ••": / h and were "M. n"~.r. annt.alei. Then,
similarly to the fourth experiment, a magnetic property
(the magnetic flux density B8) was measured. A result of
the measurement is listed in Table 12.
[0132]
[Table 12]
- 72 -
i n i i i i i i i
U >H U ^
£ ! v [ l ! v E - ' f I T f V ' , c x i a ^ ' - n r ' - a : i c n t x l
r p ; r ; c ; M C . c n o ^ H C N k O C T \ o o a i
S ^ S ^ c o c o c n c ^ c n v D c c r - r - -
Z ^ Z >~* *-?•
< o; «: W C Q ^ ^ - H ^ ^ ^ ^ ^
s a, s Q
c _^
£ CD r~ O O O O O O O O
» CO ^ O O O O . O O O
01 m 5 o o o o ° o o o
o
u
EH -^
Q S ^*VJ o o o o i i i i ru
;J ^ ?U^ in m ^ in
Z § v^ I
i-5 ,
O W
Pi OS
CJ p ^ S S - o o o o
" S S u o o o o ,
-1* J H ° o o o o ' ' '
E 2
u
a
(J !J D
ffl 5 2 ? — o o o o o o o o
< £j r 5 u o o o o o o o o
CO f^ ft ^ ~ ^ i ^ ^ ^ ^ ^ r - . ^
X = S
p) ~ m c o k O O L O C C J ' ^O
«Cp S;r*- n-J * O O ^ H C N O O r -! I CN
Q ^ O O O O O O O O
u - I
^ H C M r O ^ r r H C M C O ^
n" i
CM j c-, _q
r-H. 04 < Oj
S oi 2
CU e2 < <
•-I X OJ x
m o
E-< U
i0133] As listed in Table 12, the good magnetic flux
density was obtained in Examples No. 12A1 to No. 12A4 in
each of which the slab was held at a predetermined
temperature at an intermediate stage of the hot rolling,
but the magnetic flux density was low in Comparative
Examples No. 12B1 to No. 12B4 in each of which such
holding was not performed.
[0134] (Sixteenth Experiment)
In the sixteenth experiment, influences of the holding
temperature and the holding time in the hot rolling in the
case of S and Se being contained were confirmed.
[0135] In the sixteenth experiment, first, slabs
containing Si': 3.1 mass%, C: 0.06 mass%, acid-soluble Al:
0.026 mass%, N: 0.006 mass%, Mn: 0.12 mass%, S: 0.006
mass%, Se: 0.007 mass%, and B: 0.0015 mass% were
manufactured. Next, the slabs were heated at 1200°C, then,
annealing in which the slabs were held at 1050°C to 700°C
for 100 seconds to 500 seconds was performed, and finish
annoalin-f was performed. In this manner, hot-rolled steel
strips each having a thickness of 2.3 mm were obtained.
Subsequently, annealing of the hot-rolled steel strips was
performed at 1100°C. Next, cold rolling was performed, and
thereby cold-rolled steel strips each having a thickness
of 0.22 mm were obtained. Thereafter, decarburization
annealing was performed in a moist atmosphere gas at 830°C
for 100 seconds, and thereby decarburization-annealed
steel strips were obtained. Subsequently, the
decarburization-annealed steel scrips were annealed in an
t
ammonia containing atmosphere to increase nitrogen in the
- 74 -
i|teel strips up to 0.021 mass%. Next, an annealing
separating agent containing MgO as its main component was
coated on the steel strips, and the steel strips were
heated up to 1200°C at a rate of 15°C/h and were finish
annealed. Then, similarly to the fourth experiment, a
magnetic property (the magnetic flux density B8) was
measured. A result of the measurement is listed in Table
13.
[0136]
[Table 13]
- 75 -
u > u ^
^ h n H - O M CN CN r - CN r_ z! z: z! ^ z; Z; z!
. f i n ^H (—ii-Ht—• r-i —! ;—I
I f I I
d CQ o a w a CJ
O CO CO ^0 CO co co co
Z .-I r-( r-j ,-H ,-H ,-H ,-|
" a a ,
! > > '
-H a a Ma
CO ! EH _ i J EH J
t-u •-! CM
§S § 3 « » ^ ^
o o Ufa s co ; : :
i < a; < ^ m ^ ^ "
2 On 2 "
4- I "^ CM CM CM
X, S * ro ro co
| 0) $ O O O
M CO " i O O O
00 '-O 5 O O O
CO °
M
< CJ •>_,
^ & S v f H t ^ m H ^ q ' r ^ " ^ f O J ' i o - i r ^ . - i c M r o r - -H
^ l * f . ^ H ^ . H ( N ( M t M H co
o ° °
.g I : i I I O I I I I I O I I
o o
co ro CM
OJ I i i i i i ° i i i i ° . ° i i i
•— O O O
CJ . . 1 1 1
a 2 i i i - - i i i i i i *—' i i i
J I 1 l _ l — 1 1 1 1 1 1 1 —
! i I
^ 5 ! l
r _ ; ' 1 ' i i . . i . i i i
E-| •'• ° o
,_q M CM <—i ^-i ^-i
a ,, I • I I I I I I I I I • • • I I
a o o o o
E-i
W I
CM CM CM CM CM CM C M C M C M C M C M C M C M C M C M CM
2 o o o o o o o o o o o o o o oo
O CQ O O O O O O O O O O O O O O O O ^M
u oo
^ o o o o o o o o o o o o o o oo
I—I
M __ !
iv. „, O O O O O O O O O O O O O O O ii
O $ o o o o o o o o o o o o o o o Q
2 o o o o o o o o o o o o o o o^ o I °
M I I ' ' I
tn vOr-, ^ U 3 ^ D ^ O ^ D , ^ O ^ V D V £ ) ^ D L O ^ D ' q ' ! —I
1-1 O O O O O O O O O O O O O O OO
'-O CO O O O O O O o O O O O O O O O O O
ftj o o o o o o o o o o o o o o oo
O ' I
U CM CM CM CM CM CM C M C M C M C M C M C M C M C M C M CM
C M rH t—f rH .—I rH M r H M M M M r H - H —I .—I
s
o o o o o o o o o o o o o o o o
co c^ co co r- cr\ r - - c o c o c o c ^ c o c o a > c o ro
o o o o o o o o o o o o o o o
2 o o o o o o o o j o o o o o o o o
O O O O O O O O j O O O O O O O O
c o r - i n r - - < = r r - c o ; - - c o i n < 3 ' O r - - c o c M - n
, C M C M C M C M C M CM CM CM CM CM CM CO CM CM CM CO
^ O O O O O O O O O O O O O O O O
O O O O O O O O O O O O O O O O
1 i i i I 1 • ' 1 r-—
X! k£i kC U3 '-Xi ^3 vO '^D
^ j O O O O O O O O O O O O O O O O
O O O O O O O O O O O O O O O O
1 — . — i _ i — i i , ,
. (^ csj n? in n t-H ^r OJ en en en c\j co ro OD en
en en en en en en encnenencnenenencM en
< CQ o O K k- O X M f"D ^ ,_q S r^ O O-i
0 LO LO LT; u") LT) LO L0 LO Li") LT) LD LD Li, j LD LO LO
, i I I I I I I M i l
> - 'i
a Ma JV1 I i_, VI
^ i ^ e-i !-; j =-, - ;
- i a, si; a, cu < cu a) 3 < < 5! < <
M X 0J X X ^ X
-3 a 2 a a 2 a
H I O O
*l ! lif LH_
£0145] As listed in Table 15, in Examples No. 15A to No.
15E, and No. 15G to No. 150 each using the slab having the
appropriate composition, the good magnetic flux density
was obtained, but in Comparative Example No. 15F having a
Ni content being higher than the upper limit of the
present invention range, and in Comparative Example No.
15P having a S. content and a Se content being less than
the lower limit of the present invention range, the
magnetic flux density was low.
[0146] (Nineteenth Experiment)
In the nineteenth experiment, the effect of the
nitriding treatment in the case of S and Se being
contained was'confirmed.
[0147] In the nineteenth experiment, first, slabs
containing Si: 3.2 mass%, C: 0.06 mass%, acid-soluble Al:
0.027 mass%, N: 0.007 mass%, Mn: 0.14 mass%, S: 0.006
mass%, Se: 0.005 mass%, and B: 0.0015.%, and a balance
being composed of Fe and inevitable impurities were
manufactured. Next, the slabs were heated at 1200°C, and
were subjected to hot rolling. In the hot rolling, rough
rolling was performed, annealing in which the slabs were
held at 950°C for 300 seconds was performed, and after
that, finish rolling was performed. In this manner, hotrolled
steel strips each having a thickness of 2.3 mm were
obtained. Subsequently, annealing of the hot-rolled steel
strips was performed at 1100°C. Next, cold rolling was
performed, and thereby cold-rolled steel strips each
having a thickness of 0.22 mm were obtained.
[0148] Thereafter, as for a sample of Comparative Example
- 83 -
16A, decarburization annealing was performed in- a
moist atmosphere gas at 830°C for 100 seconds, and thereby
a decarburization-annealed steel strip was obtained.
Further, as for a sample of Example No. 163,
decarburization annealing was performed in a moist
atmosphere gas at 830°C for 100 seconds, and further
annealing was performed in an ammonia containing
atmosphere, and thereby a decarburization-annealed steel
strip having an N content of 0.022 mass% was obtained.
Further, as for a sample of Example No. 16C,
decarburization annealing was performed in a moist
atmosphere gas at 860°C f~r 1^0 seconds, and thereby a
decarburization-annealed steel strip having an N content
of 0.022 mass% was obtained. In this manner, three types
of the decarburization-annealed steel strips were
obtained.
[0149] Next, an annealing separating agent containing MgO
as its main component was coated on the steel strips, and
the steel strips were heated up to 1200°C at a rate of
15°C/h and were finish annealed. Then, similarly to the
fourth experiment, a magnetic property (the magnetic flux
density B8) was measured. A result of the measurement is
listed in Table 16.
[0150]
[Table 16]
- 84 -
U X U -,_
g £ g 3 « * <* <*
a o at- jco ' ; '
in
+ i/i o\o CD CO C£)
- J" CO O O O
z " a CM CM CM
i ' ^
Z 2 Q
O O 13 EH U
r-l M 2 Z l-l Q C
r - G EH H iii J U [ij
SC Z < , 3 S Cb W r-l
CJ CJ n .-1 H 3J J H3
n 2 H u a; <; <: a 4
iJ3 O ^ EH r£j Oi Oi
Oi O. M Pi E-i < <
CU Oj Z EH O
I
CO EH J J
rH ft, CU CM I
CS S 2 I
0) < < < I
<-< en x x I
ja 2 w w 1
« o
EH CJ I
I 1 1 1
10151] As listed in Table 16, in Example No. 16B in which
the nitriding treatment was performed after the
decarburization annealing, and Example No. 16C in which
the nitriding treatment was performed during the
decarburization annealing, the good magnetic flux density
was obtained. However, in Comparative Example No. 16A in
which no nitriding treatment was performed, the magnetic
flux density was low. Incidentally, the numerical value in
the section of "NITRIDING TREATMENT" of Comparative
Example No. 16A in Table 16 is a value obtained from the
composition of the decarburization-annealed steel strip.
INDUSTRIAL APPLICABILITY
[0152] The present invention can be utilized in, for
example, an industry of manufacturing electrical steel
sheets and an industry in which electrical steel sheets
are used.

CLAILMS
1 . A manufacturing method of a grain-oriented
electrical steel sheet, comprising:
hot roiling a silicon steel material so as to
obtain a hot-rolled steel strip, the silicon steel
material containing Si: 0.8 mass% to 7 mass%, acidsoluble
Al: 0.01 mass% to 0.065 mass%, N: 0.004 mass%
to 0.012 mass%, Mn: 0.05 mass% to 1 mass%, and B:
0.0005 mass% to 0.0080 mass%, the silicon steel
material further containing at least one element
selected from a group consisting of S and Se being
0.003 mass% to 0.015 mass% in total amount, a C
content being 0.085 mass% or less, and a balance
being composed of Fe and inevitable impurities;
annealing the hot-rolled steel strip so as to
obtain an annealed steel strip;
cold rolling the annealed steel strip one time or
more so as to obtain a cold-rolled steel strip;
decarburization annealing the cold-rolled steel
strip so as to obtain a decarburization-annealed
steel strip in which primary recrystal1ization is
caused;
coating an annealing separating agent containing
MgO as its main component on the decarburizationannealed
steel strip; and
causing secondary recrystallization by finish
annealing the decarburization-annealed steel strip,
where in
the method further comprises performing a
nitriding treatment in which an N content of the
decarburization-annealed steel strip is increased
between start of the decarburization annealing and
occurrence of the secondary recrystallization in the
finish annealing,
the hot rolling comprises:
holding the silicon steel material in a
temperature range between 1000°C and 800°C for 300
seconds or longer; and
then performing finish rolling.
2. The 'manufacturing method of the grainoriented
electrical steel sheet according to claim 1,
further comprising heating the silicon steel material
at a predetermined temperature which is a temperature
Tl (°C) or lower before the hot rolling, in a case
when no Se is contained in the silicon steel
material, the temperature Tl being expressed by
equation (1) below.
Tl = 14855/(6.82 - log ( [Mn] x [S])) - 273 ...(1)
Here, [Mn] represents a Mn content (mass%) of the
silicon steel material, and [S] represents an S
content (mass%) of the silicon steel material.
3. The manufacturing method of the grainoriented
electrical steel sheet according to claim 1,
further comprising heating the .silicon steel material
at a predetermined temperature which is a temperature
- 12--
12 (° C) or lower before the hot roiling, in a case
when no S is contained in the silicon steel material,
the temperature T2 being expressed by equation (2)
below .
T2 = 10733/(4.08 - log ([Mn] * [Se])) - 273 ...(2)
Here, [Mn] represents a Mn content (massi) of the
silicon stee1•materia1, and [Se] represents an Se
content (mass%) of the silicon steel material.
4. The manufacturing method of the grainoriented
electrical steel sheet according to claim 1,
further comprising heating the silicon steel material
at a predetermined temperature which is a temperature
Tl (°C) or lower and a temperature T2 (°C) or lower
before the hot rolling, in a case when S and Se are
contained in the silicon steel material, the
temperature Tl being expressed by equation (1) below,
and the temperature T2 being expressed by equation
(2) below.
Tl = 14855/(6.82 - log ([Mn] * [S])) - 273 ...(1)
T2 = 10733/(4.08 - log ([Mn] x [Se])) - 273 ...(2)
Here, [Mn] represents a Mn content (mass%) of the
silicon steel material, [S] represents an S content
(m a s s %) of the silicon steel material, and [Se]
represents an Se content (mass%) of the silicon steel
material .
5. The manufacturing method of the grainoriented
electrical steel sheet according to any one
%1
frf claims 1- 4, wherein the nitriding treatment is
performed under a condition that an N content [N] of
a steel strip obtained after the nitriding treatment
satisfies inequation (3) below.
[N] ^ 14/27 [Al] + 14/11 [B] + 14/47 [Ti] ...(3)
Here, [N] represents the N content (mass%) of the
steel strip obtained after the nitriding treatment,
[Al] represents an acid-soluble Al content (mass%) of
the steel strip obtained after the nitriding
treatment, [B] represents a B content (mass%) of the
steel strip obtained after the nitriding treatment,
and [Ti] re:res:; : a J. i content (mass :~. , o:: the .: - - •_ 1
strip obtained after the nitriding treatment.
6. The manufacturing method of the grainoriented
electrical steel sheet according to any one
of cla ims 1- 4, wherein the nitriding treatment is
performed under a condition that an N content [N] of
a steel strip obtained after the nitriding treatment
satisfies inequation (4) below.
[N] ^ 2/3 [Al] + 14/11 [B] + 14/47 [Ti] ...(4)
Here, [N] represents the N content (mass%) of the
steel strip obtained after the nitriding treatment,
[Al] represents an acid-soluble Al content (mass%) of
the steel strip obtained after the nitriding
treatment, [B] represents a B content (mass%) of the
steel strip obtained after the nitriding treatment,
and [Ti] represents a Ti content (mass%) of the steel
strip obtained after the nitriding treatment.

7. The manufacturing method of the grainoriented
electrical steel sheet according to any one
one of claim 1-6, wherein the silicon steel material
farther ccr.iains at least one element selected from a
crouo consisting of Cr: 0.3 mass% or less, Cu: 0.4
mass% or less., Ni: 1 mass% or less, P: 0.5 mass!', cr
less, Mo: 0.1 mass% or less, Sn: 0.3 mass% or less,
S b: 0.3 m a s s % or less, and 3 i: 0.01 m a s s % or less.