DESCRIPTION
TITLE OF INVENTION: MANUFACTURING METHOD OF
GRAIN-ORIENTED ELECTRICAL STEEL SHEET
TECHNICAL FIELD
[0001] The present invention relates to a
manufacturing method of a grain-oriented electrical
steel sheet suitable for an iron core or the like of
an electrical apparatus.
BACKGROUND ART
[0002] A grain-oriented electrical steel sheet is a
soft magnetic material, and is used for an iron core
or the like of an electrical apparatus such as a
transformer. 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 {I10}<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
- 1 -
precipitate called an inhibitor or a grain boundary
segregation element. The inhibitor has a function to
preferentially grow, in the primary recrystal1ization
structure, the crystal grains in the {110)<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] Patent 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
- 2 -
Publication No. 01-230721
Patent Literature 9: Japanese Laid-open Patent
Publication No. 01-283324
Patent Literature 10: Japanese Laid-open Patent
Publication No. 10-14 024 3
Patent Literature 11: Japanese Laid-open Patent
Publication No. 2001-152250
Patent Literature 12: Japanese Laid-open Patent
Publication No. 2-258929
NON-PATENT LITERATURE
[0007] Non-Patent Literature 1: Trans. Met. Soc.
AIME, 212 ( 1958) p 759/781
Non-Patent Literature 2 : Journal of The Japan
Institute of Metals 27 (1963} p 186
Non-Patent Literature 3: Testu-to-Hagane 53
(1967) p 1007/102 3
Non-Patent Literature 4: Journal of The Japan
Institute of Metals 43 (1979) p 175/181, Journal of
The Japan Institute of Metals 44 (1980) p 419/424
Non-Patent Literature 5: Materials Science Forum
204-206 (1996) p 593/598
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 a grain-oriented
electrical steel sheet capable of manufacturing a
- 3 -
grain-oriented olectrical stee.l sheet havinq a high
magnetic flux density industrially stably.
SOLUTION TO PROBLEM
[0009] A manufacturing method of a grain-oriented
electrical steel sheet according to a first aspect of
the present invention includes: at a predetermined
temperature, heating a 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 raass% to 1 mass-d, 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; hot rolling the heated silicon
steel material so as to obtain a hot-rolled steel
strip; 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
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-annealed steel strip,
- 4 -
wherein 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 decarburiz ation annealing and
occurrence of the secondary recrysta 11ization in the
finish annealing, the predetermined temperature is,
in a case when S and Se are contained in the silicon
steel material, a temperature Tl {°C) or lower, a
temperature T2 (°C) or lower, and a temperature T3
(°C) or lower, the temperature Tl being expressed by
equation (1) below, the temperature T2 being
expressed by equation (2) below, and the temperature
T3 being expressed by equation (3) below, in a case
when no Se is contained in the silicon steel
material, the temperature Tl (°C) or lower, and the
temperature T3 (°C) or lower, in a case when no S is
contained in the silicon steel material, the
temperature T2 {°C) or lower, and the temperature T3
(°C) or lower, a finish temperature Tf of finish
rolling in the hot rolling satisfies inequation (4)
belo.w, and amounts of BN, MnS, and MnSe in the hotrolled
steel strip satisfy inequations (5), (6), and
(7) below.
Tl = 14855/(6.82 - log ([Mn] ^ [S])) - 273 ...(1)
T2 = 10733/(4.08 - log ([Mn] x [Se])> - 273 ...(2)
T3 = 16000/(5.92 - log ([B] x [N])) - 273 ...(3)
Tf ^ 1000 - 10000 X [B] ... (4)
BasBN ^ 0.0005 ...(5)
[B] - BasBN ^ 0 . 0 0 1 ...(6)
- 5 -
S . s M n S + 0 . 5 X S e a s M n S c ^ 0 . 0 0 2 . . . ( 7)
Here, [Mn] represents a Mn content {mass^) of the
silicon steel material, [S] represents an S content
(mass%) of the silicon steel material, [Se]
represents a Se content {mass!} of the silicon steel
material, [B] represents a B content (mass%) of the
silicon steel material, [N] represents an N content
(mass%} of the silicon steel material, BasBN represents
an amount of B [mass%) that has precipitated as BN in
the hot-rolled steel strip, SasMns represents an amount
of S {mass%) that has precipitated as MnS in the hotrolled
steel strip, and SeasMnse represents an amount
of Se (mass%} that has precipitated as MnSe in the
hot-rolled steel strip.
[0010] In a manufacturing method of a grainoriented
electrical steel sheet according to a second
aspect of the present invention, in the method
according to the first aspect, the nitriding
treatment is performed under a condition that an N
content [N] of a steel strip obtained after the
nitriding treatment satisfies inequation (8) below.
[N] S 14/27[A1] + 14/11[B] + 14/47[Ti] ...(8)
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, and [Ti] represents a Ti content (mass%>
of the steel strip obtained after the nitriding
treatment.
- 6 -
[0011] In a manufacturing method of a grainoriented
electrical steel sheet according to a third
aspect of the present invention, in the method
according to the first aspect, the nitriding
treatment is performed under a condition that an N
content [N] of a steel strip obtained after the
nitriding treatment satisfies inequation (9) below.
[N] ^ 2/3[Al] + 14/11[B] + 14/47[Ti] ...(9)
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, and [Ti] represents a Ti content {mass%)
of the steel strip obtained after the nitriding
treatment.
ADVANTAGEOUS EFFECTS OF INVENTION
[0012] According to the present invention, it is
possible to make BN precipitate compositely on MnS
and/or MnSe approprlately 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
[0013] [Fig. 1] Fig. 1 is a flow chart showing a
manufacturing method of a grain-oriented electrical
steel sheet;
[Fig. 2] Fig. 2 is a view showing a result of a
- 7 -
first experiment (a relationship between precipitates
in a hot-rolled steel strip and a magnetic property
after finish annealing);
[Fig. 3] 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] Fig. 4 is a view showing the result of
the first experiment (a relationship between a Mn
content, a condition of hot rolling, and the magnetic
property after the finish annealing);
[Fig. 5] Fig. 5 is a view showing the result of
the first experiment (a relationship between a B
content, the condition of the hot rolling, and the
magnetic property after the finish annealing);
[Fig. 6] Fig. 6 is a view showing the result of
the first experiment (a relationship between a
condition of finish rolling and the magnetic property
after the finish annealing);
[Fig. 7] Fig. 7 is a view showing a result of a
second experiment (a relationship between
precipitates in a hot-rolled steel strip and a
magnetic property after finish annealing);
[Fig. 8] Fig. 8 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. 9] Fig. 9 is a view showing the result of
the second experiment (a relationship between a Mn
- 8 -
content, a condition of hot rolling, and the magnetic
property after the finish annealing} ;
[Fig. 10] Fig. 10 is a view showing the result of
the second experiment (a relationship between a B
content, the condition of the hot rolling, and the
magnetic property after the finish annealing);
[Fig. 11] Fig. 11 is a view showing the result of
the second experiment (a relationship between a
condition of finish rolling and the magnetic property
after the finish annealing);
[Fig. 12] Fig. 12 is a view showing a result of a
third experiment (a relationship between precipitates
in a hot-rolled steel strip and a magnetic property
after finish annealing);
[Fig. 13] Fig. 13 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. 14] Fig. 14 is a view showing the result of
the third experiment (a relationship between a Mn
content, a condition of hot rolling, and the magnetic
property after the finish annealing);
[Fig. 15] Fig. 15 is a view showing the result of
the third experiment (a relationship between a B
content, the condition of the hot rolling, and the
magnetic property after the finish annealing); and
[Fig. 16] Fig. 16 is a view showing the result of
the third experiment (a relationship between a
condition of finish rolling and the magnetic property
- 9 -
after the finish annealing) .
DESCRIPTION OF EMBODIMENTS
[0014] The present inventors thought that in the
case of manufacturing a grain-oriented electrical
steel sheet from a silicon steel material having a
predetermined compos ition containing B, a
precipitated form of B may affect behavior of
secondary recrystallization, and thus conducted
various experiments. Here, an outline of a
manufacturing method of a grain-oriented electrical
steel sheet will be explained. Eig. 1 is a flow
chart showing the manufacturing method of the grainoriented
electrical steel sheet.
[0015] First, as illustrated in Fig. 1, in step SI,
a silicon steel material (slab) having a
predetermined compos ition containing B is heated to a
predetermined temperature, and in step S2, hot
rolling of the heated silicon steel material is
performed. By the hot rolling, a hot-rolled steel
strip is obtained. Thereafter, in step S3, annealing
of the hot-rolled steel strip is performed to
normalize a structure in the hot-rolled steel strip
and to adjust precipitation of inhibitors. By the
annealing, an annealed steel strip is obtained.
Subsequently, in step S4, 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
- 10 -
annealing being performed therebetween. 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 S3) in the intermediate annealing. That is,
the annealing (step S3) may be performed on the hotrolled
steel strip, or may also be performed on a
steel strip obtained after being cold rolled one time
and before being cold rolled finally.
[0016] After the cold rolling, in step S5,
decarburization annealing of the cold-rolled steel
strip is performed. In the decarburization
annealing, primary rearysta 11ization occurs.
Further, by the decarburization annealing, a
decarburization-annealed steel strip is obtained.
Next, in step 86, an annealing separating agent
containing MgO (magnesia) as its main component is
coated on the surface of the decarburization-annealed
steel strip and finish annealing is performed. In
the finish annealing, secondary recrysta 11ization
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 recrystallization
structure arranged in the Goss orientation is
obtained. By the finish annealing, a finish-annealed
steel strip is obtained. Further, between start of
- 11 -
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 S7).
[0017] In this manner, the grain-oriented
electrical steel sheet can be obtained.
[0018J Further, details will be described later,
but as the silicon steel material, there is used one
containing Si: 0.8 mass% to 7 massfi, acid-soluble Al:
0.01 mass'i 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.
[0019] Then, as a result of the various
experiments, the present inventors found that it is
important to adjust conditions of slab heating (step
SI) and the hot rolling (step 82) to then 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 slab heating and the hot rolling,
the inhibitors are thermally stabilized and grains of
a grain structure of the primary recrystallization
are homogeneously arranged. Then, the present
inventors obtained the knowledge capable of
- 12 -
manufacturing the grain-oriented electrical steel
sheet having a good magnetic property stably, and
completed the present invention.
[0020] Here, the experiments conducted by the
present inventors will be explained.
[0021] (First Experiment)
In the first experiment, first, various silicon
steel slabs containing Si: 3.3 mass;;, C: 0.06 mass%,
acid-soluble 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 hotrolled
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 hotrolled
steel strips cool down to 550°C, and thereafter
the hot-rolled steel strips were cooled down in the
atmosphere. Subsequently, annealing of the hotrolled
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
- 13 -
8 4 0°C, 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
finish annealing was performed. In this manner,
various samples were manufactured.
[0022J 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 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. 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,
[0023] Further, a relationship between an amount of
- 14 -
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 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. 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.
[0024] 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 BN precipitates compositely on
MnS. Such composite precipitates are effective as
inhibitors that stabilize the secondary
recrystallization.
[0025] 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 and Fig, 5. 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 rolling. In
- 15 -
Fig. 5, 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 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, and a
curve in Fig. 5 indicates a solution temperature T3
C O of BN expressed by equation (3) below. As
illustrated in Fig. 4, 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. Further, as illustrated in Fig. 5, it also
turned out that in the s amples in which the slab
heating is performed at a temperature determined
according to the B 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 T3 of BN. That
is, it turned out that it is effective to perform the
slab heating in a temperature zone where MnS and BN
are not completely solid-dissolved.
Tl = 1^855/(6.82 - log ([Mn] x [S])) - 273 ...(1)
T3 = 16000/(5.92 - log ([B] x [N])) - 273 ...{3)
- 16 ~
Here, [Mn] represents the Mn content (mass%), [S]
represents an S content {mass%), [B] represents the B
content (mass%), and [N] represents an N content
(ma s s %) .
[0026] Further, as a result of examination of
precipitation behavior of BN, it turned out that a
precipitation temperature zone of BN is 800°C to
1000°C.
[0027] Further, the present inventors examined a
finish temperature of the finish rolling in the hot
rolling. Generally, in the finish rolling of the hot
rolling, the rolling is performed a plurality of
times and thereby a hot-rolled steel strip having a
predetermined thickness is obtained. Here, the
finish temperature of the finish rolling means the
temperature of the hot-rolled steel strip after the
final rolling among a plurality of times of rolling.
In the examination, first, various silicon steel
slabs containing Si: 3.3 mass%, C: 0.06 massi, acidsoluble
Al: 0.027 mass%, N: 0.008 mass%, Mn : 0.1
mass%, S: 0.007 mass%, and B: 0.001 mass% to 0.004
mass%, and a balance being composed of Fe and
inevitable impurities were obtained. Next, the
silicon steel slabs were heated at a temperature o f
1150°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 1020°C to 900°C,
and thereby hot-rolled steel strips each having a
thickness of 2.3 mm were obtained. Then, cooling
- 17 -
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
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 finish annealing was
performed. In this manner, various samples were
manufactured.
[0028] Then, a relationship between the finish
temperature of the finish rolling in the hot rolling
and a 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 vertical
axis indicates a finish temperature Tf of the finish
rolling. Further, white circles each indicate that
the magnetic flux density B8 was 1.91 T or more, and
- 18 -
black squares each indicate that the magnetic flux
density B8 was less than 1.91 T. As illustrated in
Fig. 6, it turned out that when the finish
temperature Tf of the finish rolling satisfies
inequation (4) below, the high magnetic flux density
B8 is obtained. This is conceivably because by
controlling the finish temperature Tf of the finish
rolling, the precipitation of BN was further
promoted.
Tf ^ 1000 - 10000 X [B] ...(4)
[0029] [Second Experiment)
In the second experiment, 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:
0.05 mass^ to 0.20 raass%, 3e: 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 llOCC 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 hot-rolled steel strips to then let the hotrolled
steel strips cool down to 550°C, and thereafter
the hot-rolled steel strips were cooled down in the
atmosphere. Subsequently, annealing of the hotrolled
steel strips was performed. Next, cold
- 19 -
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 850°C,
and thereby decarburization-annealed steel strips
were obtained. Subsequently, the decarburizationannealed
steel strips were annealed in an ammonia
containing atmosphere to increase nitrogen in the
steel strips up to 0.023 mass°s. 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 sample s were
manufactured.
[0030] 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. 7, In Fig. 7,
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. 7, in the samples each having
- 20 -
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.
[0031] 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. 8.
In Fig. 8, the horizontal 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. 8, 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.
[0032] 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.
[0033] Further, a relationship between a condition
of the hot rolling and the magnetic property after
- 21 -
the finish annealing was examined. A result of the
examination is illustrated in Fig. 9 and Fig. 10. In
Fig. 9, 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 sguares each indicate that the magnetic
flux density B8 was less than 1.88 T. Further, a
curve in Fig. 9 indicates a solution temperature T2
[°C> of MnSe expressed by equation (2) below, and a
curve in Fig. 10 indicates the solution temperature
T3 (°C) of BN expressed by equation (3). As
illustrated in Fig. 9, 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 88 is obtained.
Further, it also turned out that the temperature
approximately agrees with the solution temperature T2
of MnSe. Further, as illustrated in Fig. 10, it also
turned out that in the samples in which the slab
heating is performed at a temperature determined
according to the B 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 T3 of BN. That
- 22 -
is, it turned out that it is effective to perforin the
slab heating in a temperature zone where MnSe and BN
are not completely solid-dissolved.
T2 = 10733/(4.08 - log ([Mn] " [Se])) - 273 ...(2)
Here, [Se] represents a Se content (mass^).
[0034] Further, as a result of examination of
precipitation behavior of BN, it turned out that a
precipitation temperature zone of BN is 800°C to
1000°C.
[0035] Further, the present inventors examined a
finish temperature of the finish rolling in the hot
rolling. 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: 0.001 mass! to 0.004
mass%, and a balance being composed of Fe and
inevitable impurities were obtained. Next, the
silicon steel slabs were heated at a t empe rature of
1150°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 1020°C to 900°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
- 23 -
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 dcca rbu r i z at ion
annealing at a temperature of SSCC, and thereby
decarburization-annea1ed 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 componen t was coated
on the steel strips and finish annealing was
performed. In this manner, various samples were
manufactured.
[0036] Then, a relationship between the finish
t empe rature of the finish rolling in the hot rolling
and a magnetic property after the finish annealing
was examined. A result of the examination is
illustrated in Fig. 11. In Fiq. 11, the horizontal
axis indicates a B content (mass%), and the vertical
axis indicates the finish temperature Tf of the
finish rolling. Further, white circles each indicate
that the magnetic flux density B8 was 1.91 T or more,
and black squares each indicate that the magnetic
flux density B8 was less than 1.91 T. As illustrated
in Fig. 11, it turned out that when the finish
temperature Tf of the finish rolling satisfies
ineqation (4), the high magnetic flux density B8 is
obtained. This is conceivably because by controlling
- 24 -
the finish temperature Tf of the finish rolling, the
precipitation of BN was further promoted.
[0037] (Third Experiment)
In the third experiment, first, various silicon
steel slabs containing Si: 3.3 mass%, C: 0.06 mass%,
acid-soluble Al : 0.026 masses, N: 0.009 mass"o, 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
impuri ties 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 lOSO^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
SSCC, 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 decarbur1zation
annealing at a temperature of 850''C, and thereby
decarburization-annealed steel strips were obtained.
Subsequently, the decarburization-annealed steel
- 25 -
strips were annealed in an ammonia containing
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 finish annealing was
performed. In this manner, various samples were
manufactured.
[0038] 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. 12. In Fig.
12, the horizontal axis indicates the sum (mass%> of
a value obtained by converting a precipitation amount
of MnS into an amount of 3 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. 12, 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.
[0039] Further, a relationship between an amount of
B that has not precipitated as BN and the magnetic
- 26 -
property after the finish annealing was examined. A
result of the examination is illustrated in Fig. 13.
In Fig. 13, the horizontal 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. 13, 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.
[0040] 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.
[0041] 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. 14 and Fig. 15.
In Fig. 14, 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. 15, the horizontal axis indicates
- 27 -
the B content (mass%) and the vertical axis jndi. cates
the temperature CC) of the slab heating at the time
of hot rolling. b'urther, vjhite circles each indicate
that the maq[ietic flux density BS was 1.88 T or more,
and black squares each indicate that the magnetic
flux density B8 was less than 1.88 T. Further, two
curves in Fig. 14 indicate the solution temperature
Tl (°C) of MnS expressed by equation (1) and the
solution temperature T2 (°C) of MnSe expressed by
equation (2), and a curve in Fig. 15 indicates the
solution temperature T3 (°C) of BN expressed by
equation (3). As illustrated in Fig-l^ 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 88 is obtained. Further, it also turned out
that the temperature approximately agrees with the
solution temperature Tl of MnS and the solution
temperature V2 of MnSe. Further, as illustrated in
Fig. 15, it also turned out that in the samples in
which the slab heating is performed at a temperature
determined according to the B 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 T3 of BN. That
is, it turned out that it is effective to perform ttie
slab heating in a temperature zone vjhere MnS, MnSe,
and BN are not complet ely solid-dissolved.
[0 0 421 Further, as a result of examination of
- 28 -
precipitation behavior of BN, it turned out that a
precipitation temperature zone of BN is 800°C to
1000°C.
[0043] Further, the present inventors examined a
finish temperature of the finish rolling in the hot
rolling. In the examination, first, various silicon
steel slabs containing Si: 3.3 mass%, C: 0.06 mass%,
acid-soluble Al: 0.026 mass%, N: 0.009 mass%, Mn: 0.1
mass%, S: 0.005 mass%, Se: 0.007 mass%, and B: 0.001
inass% to 0.004 mass%, and a balance being composed of
Fe and inevitable impurities were obtained. Next,
the silicon steel slabs were heated at a temperature
of 1150°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 1020°C to 900°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 850°C, and thereby
decarburization-annealed steel strips were obtained.
- 29 -
Subsequently, the decarburization-annealed steel
strips were annealed in an ammon ia containing
atmosphere to increase nitrogen in the steel strips
up to 0.021 mass'o. Next, an annealing separating
agent containing MgO as its main componen t was coated
on the steel strips and finish annealing was
performed. In this manner, various sample s were
manu factured,
[004*3] Then, a relationship between the finish
tempera ture of the finish rolling in the hot rolling
and a magnetic property after the finish annealing
was examined. A result of the examination is
illustrated in Fig. 16. In Fig. 16, the horizontal
axis indicates a B content (massif), and the vertical
axis indicates the finish temperature Tf of the
finish rolling. Further, white circles each indicate
that the magnetic flux density B8 was 1.91 T or more,
and black squares each indicate that the magnetic
flux density B8 was less than 1.91 T. As illustrated
in Fig. 16, it turned out that when the finish
temperature Tf of the finish rolling satisfies
inequation {4), the high magnetic flux density B8 is
obtained. This is conceivably because by controlling
the finish temperature Tf of the finish rolling, the
precipitation of BN was further promoted.
[0045] According to these results of the first to
third experiments, it is found that controlling the
precipitated form of BN makes it possible to stably
improve the magnetic property of the grain-oriented
- 30 -
electrical steel sheet. The reason why the secondary
recrystaliization becomes unstable, thereby making it
impOS sible to obtain the good magnetic property in
the case when B does not preci. pitate compositely on
MnS or MnSe as BN has not been clari. fled 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 lowtemperature
zone where the decarburization annealing
is performed, and in a hi gh-1empe rature 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 into a mixed grain structure with coarse
grains. 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 with coarse grains, 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.
- 31 -
[0049] The silicon steel material used in this
embodiment contains 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%, S and Se:
0.003 rriass% to 0.015 rnass^ 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 o f
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. Thus, the Si content is set to 0.8
ma5S% or more, and is preferably 2 mass% or more, and
is more preferably 2.5 massi or more.
[0051] C is an element effective for controlling
the primary recrystal1ization structure, but
adversely affects the magnetic property. Thus, in
this embodiment, before the finish annealing (step
S6), the decarburization annealing is performed (step
S5). However, when the C content exceeds 0.085
- 32 -
Tnass%, a time taken for the deca rbur i z a t i on 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 massi
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.O08O mass%, the secondary
recrystallization is stabilized. Thus, the B content
is set to be not less than 0.0005 mass% nor more than
0.0080 mass%. Further, the B content is preferably
0.001% or more, and is more preferably 0.0015% or
more. Further, the B content is preferably 0.0040%
or less, and is more preferably 0.0030% or less.
- 33 -
[0054] N bonds to B or Al to function as an
inhibitor. When an N content is less than 0.004
mass°G, it is not possible to obtain a sufficient
amount of the inhibitor. Thus, the N content is set
to 0.004 Tuassl 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?i, 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 raass% or less, and is more
preferably 0.009 mass% or less.
[0055] Mn, S and 3e 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 mas5% 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
- 34 '
be not less than 0.003 mass% nor more than 0.015
mass% in total amount. Further, in terms of
preventing occurrence of a crack in the hot rolling,
inequation (10) 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] } Z 4 ... (10)
[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
- 35 -
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
rnass^, the effect is saturated. Further, a surface
flaw called "copper scab" is sometimes caused at the
time of hot rolling. Thus, the Cu content may be set
to 0.4 raass% 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
raass^, the secondary recrysta 11ization 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 embrittlement. 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] 3n 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
~ 36 -
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 some t ime s
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 property. 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 t reatment in this embodiment will
be explained.
- 37 -
[0067] The silicon steel material (slab) having the
above-described componen ts 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 thickness of 30 mm to 7 0
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 (step
SI), and the hot rolling (step S2) 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 (5) to (7) below.
B^.BN S 0.000 5 ...(5)
[B] - B,,BN ^ 0.001 ...(6)
- 38 -
S.sMnS + 0.5 X Se,s«nSo ^ 0.002 .,.(7)
Here, "BasBtj" represents the amount of B that has
precipitated as BN (mass%), "Sas^^s" represents the
amount of S that has precipitated as MnS {mass%}, and
"Se^sMnse" 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 {5) and inequation (6) 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 soliddissolved
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.
[0070] MnS and MnSe each function as a nucleus on
which BN precipitates compositely. Thus, in order to
ma] in the case of no Se being contained in the
silicon steel slab
the temperature Tl (°C) expressed by equation (1)
or lower and the temperature T3 (°C) expressed by
equation (3> 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 and the temperature T3 (°C) expressed by
equation (3) or lower
Tl - 1^855/(6.82 - log ( [ Mn ) x [S])) - 273 ...(1)
T2 - 10733/(4.08 - log ([Mn] x [Se])} - 273 ...(2)
T3 = 16000/(5.92 - log ([B] x [N])) - 273 ...(3)
[0074] This is because when the slab heating is
performed at such temperatures, BN, MnS, and MnSe are
not completely sol id-dissolved at the time of slab
heating, and the precipitations of BN, MnS, and MnSe
are promoted during the hot rolling. As is clear
from Fig. 4, Fig. 9, and Fig. 14, 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. Further, as is clear from Fig. 5, Fig. 10, and
Fig. 15, the solution temperature T3 approximately
- 41 -
agrees with the upper limit of the slab heating
temperature capable of obtaining the magnetic flux
density B8 of 1.88 or more.
[0075] Further, the temperature of the slab heating
is more preferably set so as to satisfy the following
conditions as well. This is to make a preferable
amount of MnS or MnSe precipitate during the slab
heating.
(i> in the case of no Se being contained in the
silicon steel slab
a temperature T4 (°C) expressed by equation (11)
below or lowe r
(ii) in the case of no S being contained in the
silicon steel slab
a temperature T5 [ °C) expressed by equation (12)
below or lower
T4 = 14855/(6.82 - log [([Mn] - 0.0034) " ([S] -
0.002))) - 273 ...(11)
T5 = 10733/(4.08 - log (([Mn] - 0.0028) x ([Se] -
0.004))) - 273 ... (12)
[0076] In the case when the temperature of Che slab
heating is too high, BN, MnS, and/or MnSe are
sometimes solid-dissolved completely. In this case,
it becomes difficult to make BN, 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,
and at the temperature T3 or lower. Further, if the
- 42 -
temperature of the slab heating is the temperature T4
or T5 or lower, a preferable amount of MnS or MnSe
precipitates during the slab heating, and thus it
becomes possible to make BM precipitate compositely
on MnS or MnSe to form effective inhibitors easily.
[0077] Further, as for B, the finish temperature Tf
of the finish rolling in the hot rolling is set such
that inequation (4) below is satisfied. This is to
promote the precipitation of BN.
Tf S 1000 - 10000 X [Bj ...{4)
[0078] As is clear from Fig. 6, Fig. 11, and Fig.
16, the condition expressed in inequation (4)
approximately agrees with the condition capable of
obtaining the magnetic flux density B8 of 1.91 T or
more. Further, the finish temperature Tf of the
finish rolling is preferably set to 800°C or higher in
terms of the precipitation of BN,
[0079] After the hot rolling (step S2>, the
annealing of the hot-rolled steel strip is performed
{step S3). Next, the cold rolling is performed (step
34). 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 preferably set to 80%
or more. This is to develop a good primary
recrystallization aggregate structure.
- 43 -
[008 0] Thereafter, the decarburizaticn annealing is
performed (step S5). As a result, C contained in the
steel strip is removed. The decarburizaticn
annealing is performed in a moist atmosphere, for
example. Further, the decarburizaticn annealing is
preferably performed at a time such that, for
example, a grain diameter obtained by the primary
recrystaliization becomes 15 pm 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 annealing separating agent and the
finish annealing are performed {step S6). 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 decarburizaticn
annealing and occurrence of the secondary
recrystallization in the finish annealing {step S7) .
This is to form an inhibitor of (Al, Si)N. The
nitriding treatment may be performed during the
decarburization annealing (step S5), or may also be
performed during the finish annealing (step 36). In
the case when the nitriding treatment is performed
during the decarburizaticn annealing, the annealing
may be performed in an atmosphere containing a gas
having nitriding capability such as ammoni a, for
example. Further, the nitriding treatment may be
- 44 -
performed during a heating zone or a soaking zone in
a continuous annealing furnace, or the nit riding
treatment may also be performed at a stage after the
soaking zone. In the case when the nitriding
treatment is performed during tho 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 37) 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 (8) below, and
the degree of nitriding is more preferably controlled
so as to satisfy inequation (9) below. Inequation
(8) and inequation {9) 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 AIN or {Al, Si)N effective as an inhibitor.
[Nj ^ 14/27[A1] + 14/11[B] + 14/47[Ti] ...(8)
[N] ^ 2/3[Alj + 14/11[B] + 14/47[Ti] ...(9)
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
- 45 -
the steel strip obtained after the nitriding
treatment, [B] represents a B content (mass%) ol the
steel strip obtained after the nitriding treatment,
and [Ti] represents a Ti content (mass%) of the steel
strip obtained after the nitriding treatment.
[0083] The method of the finish annealing (step S6)
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 llOCC 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 tempe rature range of lOOO^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 examp1es employed for
confirming the practicability and the effects of the
present invention, and the present invention is not
limited to those examples.
- 46 -
[0086] {Fourth Experiment)
In the fourth experiment, the effect of the B
content in the case of no Se being contained was
conf irmed.
[0087] In the fourth experiment, first, slabs
containing Si: 3.3 mass%, C: 0.06 mass%, acid-soluble
Al: 0.028 mass%, N: 0.008 mass%, Mn: 0.1 ma3S%, S:
0.006 mass%, and B having an amount listed in Table 1
[0 ma3S°5 to 0.0045 mass%), and a balance being
composed of Fe and inevitable impurities were
manufactured. Next, the slabs were heated at 1100°C,
and thereafter were subjected to finish rolling 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 decarburizationannealed
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 IS^C/h and were
- 47 -
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]
- 48 -
;_) i-H u m
e E f r l r f E i - ( - H . - l i - l r -(
a
.T LO O O O O O
V in o o o o o
"^ >l o o o o o
H ;.;
n , ,-: f, „ r- o "
a- l b " ° '^^ o o
n a - .
a:
a,
a> CD o m
^ ?n O i-H n ^
'"•: Lo . - , 0 0 0 0
of 3 °. ° ° °
C 0 0 00
Q S E • W C J ( ^ l ( ^ J ^ N r ^ ) CTi
H r ^ i U E o 0 0 0 0
i-i rv; -- I
s [< B
— r-- r-- [— r-H
m U 1 ixi ^ ^ r---
[ 1 0 ' I-I CM (N CM
—" r-l rH 1-H 1—I
t5 ^ 'j; '.E ^C 'J3 'ii
p; ' ' (J o 0 0 0 0
I-I E ' o IN !NJ !N1 (M |->J
E-H "-" T—I T—I r—I r H T—I a
i-j 3 & — o 0 0 0 0
t.' pZ^r?!-! O 0 0 0 0
g w - , r ^ ^ ^ ^
a; s
£-
S rto~ CO O^ -H Ul
S fn O ^ ro -T
O S " 0 0 0 0
' - ' £ . 0 0 00
n sK m CJ Q W
1 ^ T—I T—I r-H .—f ,—I
>
M b ] DJ
^ Oi Qj
,-t Cii X X
nj (J
H I II
[0089] As listed in Table 1, in Comparative Example
No. lA 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 B
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: 0.008 mass%, Mn: 0.1 mass%, S:
0.006 raass%, Cr: 0.1 mass%, P: 0.03 mass*, Sn: 0.06
mass%, and B having an amount listed in Table 2 (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 thereafter
were subjected to finish rolling at 950°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
- 50 -
were obtained. Subsequently, the decarburizationannealed
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 Table 2.
[0092]
[Table 2]
- 51 -
03
( J >-l w (fl
u o n ui (.0 J J ; i J
a
,, V" Lo Lo Ln wi u>
>; 1,1 (X (xj IN] CM o]
j ; oT c o o o o
'•'~' S o o o o o
LO " ""
t J ^
f - ?^
cC ^ • so r-- r- iTi
E- tn •„ o o o o
OJ I y ^ o o o o
O "• S. o o o o
w CO
nj
" CM !M =J' ".D
•^ 'Pn O ,-1 fM m
-S ^ _ O O O C
«i i l i " o o o o
ma . . ..
£; o o o o
O H H I
M W Mo'^ c n c o f o n r^
Q S t H W C M C M f N j r j r s ) C>I
H H S to O O o o o ,n cc < o rf
H U U S o o o o o
[--- r- r- ^
CO (1 I ko rH ^ r-
H o rH (Nl M CM
• - ' ^ .-I ^ ^
(5 .—. I.D lo yj VD 'ii
E "-lO O o o o o
M EHO C M C M l N f ^ J CM
E-i ^-^ T—I r—1 i-H T—I T—I
<
W
J S ^ - - . o o o o o
"5 t j r ? U o a r o o n i D co
E - p i gg-o - ^^ .^- H^i -.i.i - i^^
a: S
id
E-
^ "^ CO CTi r-1 in
g S^ „ o o o o
g 3 " o o o o
^ ^ o o o o
CD
-; <: CO u a u
^ r\j CN) r\j (NJ CN
>
M b ] [J
t^ ^ 0^ a.
[0093] As listed in Table 2, in Comparative Example
No. 2A having no B contained in the slab and
Comparative Example No. 2B having the slab heating
temperature higher than the temperature T3, the
magnetic flux density was low. On the other hand, in
Examples No. 2C to No. 2E each having an appropriate
amount of B contained in the slab and having the slab
heating temperature being the t empe rature Tl or lower
and the tempe rature T3 or lower, the good magnetic
flux density was obtained.
[0094] (Sixth Experiment)
In the sixth experiment, the effects of the Mn
content and the slab heating temperature in the case
of no Se being contained were confirmed.
[0095] In the sixth experiment, first, slabs
containing Si; 3.3 mass%, C: 0.06 mass%, acid-soluble
Al: 0.028 mass%, N: 0.009 mass%, S: 0.007 mass%, B:
0.002 mass%, and Mn having an amount listed in Table
3 [0.05 mass% to 0.20 mass%), and a balance being
composed of Fe and inevitable impurities were
manufactured. Next, the slabs were heated at 1200''C,
and thereafter were subjected to finish rolling at
950''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 per formed at llOO^C. Next, cold rolling
was performed, and thereby cold-rolled steel strips
each having a thickness of 0.22 ram were obtained.
- 53 -
Thereafter, decarburization annealing was performed
in a moist atmosphere gas at 830°C for 100 seconds,
and thereby decarburization-annea1ed steel strips
were obtained. Subsequently, the decarburizationannealed
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 3.
t0096]
[Table 3]
- 54 -
U >H U CI
^ ^ r"! V •>H -^ .n ,-^ in
^ s ^ •" s -• -• ^ ^^
Q
;- 0"> M (M =!• LD
B Ul O O C O
K W O O O O
^ E o o C o
w ^ ^—-
i-l ^
£-1 CO fn o o o O
a. I ^ o o o o
u ^ S o o o o
a.
— d ^ un >i>
^ " O O O O
» ^ o o o o
5. o o o o
O E- [< I
Z. Z ^ — I
M [,1 b] o'f CM CJ m
E •-"' U r-- I—I c! lo
M E-H o M (M !N1 (NJ
ir< "~ i-H i-H r-H r-l <; .
Id
J F i d - — o o o o
[/) c J f i ' U O o o o
g g - ^ ^ M M
a: S
E-t s ; LH o -=1' o
U ^ o o oo
a]
>
•9 o
[0097] As listed in Table 3, in Comparative Example
No. 3A having tl'ie slab heatinq tempeiatuie higher
t h an the t e mp crature 'i'l, the magnetic 11 ux density
was low. On the other hand, in Examples No. 3B to
No. 3D each having the slab heating temperature being
the temperature Tl or lower and the temperature T3 or
lower, the good magnetic flux density was obtained.
[0098] (Seventh Experiment}
In the seventh experimen t, the effect of the
finish temperature Tf of the finish rolling in the
hot rolling 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: 0.008 mass%, Mn: 0.1 mass%, S;
0.006 mass%, and B: 0.002 mass%, and a balance being
composed of Fe and inevitable impurities were
manufactured. Next, the slabs were heated at 11S0°C,
and thereafter were subjected to finish rolling at
the finish temperature Tf listed in Table 4 (800°C to
1000°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 I100°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 perfo rm e d
in a moist atmosphere gas at 830°C for 100 seconds,
- 56 -
and thereby decarburization - annealed steel strips
were obtained. Subsequently, the decarburizationannealed
steel strips were annealed in an ammoni a
containing atmosphere to increase nitrogen in the
steel strips up to 0.020 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.
[0100]
[Table 4]
- 37 "
El g H X >H _ ^ ^ ^
O O t'j t ' c; _J -] ! _,'
S Q; rt- 7t ^ rH , I ^
Q
. •-' n-, i'^ r\. rj f :n o o o o
';; W o o o c
'^•' S o o c o
[J ;-.
< rrJ ^: LI r- >^ Ci
fH CQ 7, O O C O
n ^ . . . .
O ^^ £1 o O o o
Ui CD
n: ^
n.
" ^ i-M m rj r—I
V, ^^ C O O O
m< ^ ^. ° °
£ o o o o
Z z s —
M H KW O O O O
a: cC o < . . .
H t ] U S O O O o
M O ; —
S El ^
Q O
l-H l-H
« f., ^ .- O O O O I
M y a; u^
^ >H >;
J rt i.l I
cc
a: tJ
S g
g I S ? o o o g
[i, 5 :£ — o I.-! o S^
M Gj H-l •"'
w
E-
--. O O O O
( ^ O rj (N fN iM
E-i o ? O m c o o i cc
S- S ° ^ ^ ^ .--I
a s; - - -H -• "
tJ
,; .< CD (J D
^ ^ ^ -T •J'
>
Ui H CJ
•S o
(0 U
[0101] In the case of the B content being 0.002
mass% (20 ppm), the finish temperature Tf is
necessary to be 980°C or lower based on inequation
[A). Then, as listed in Table 4, in Examples No. 4A
to 4C each satisfying the condition, the good
magnetic flux density was obtained, but in
Comparative Example No. 4D not satisfying the
condition, the magnetic flux density was low.
[0102] (Eighth 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,
[0103] In the eighth experiment, first, slabs
containing Si; 3.3 mass%, C: 0.06 mass%, acid-soluble
Al; 0.028 ma5s%, N: 0.008 mass%, Mn: 0.1 mass%, S:
0.006 massi, 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 IISCC,
and thereafter were subjected to finish rolling 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 llOO^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,
- 59 -
and thereby decarburization-annealed steel strips
were obtained. Subsequently, the decarburizationannealed
steel strips were annealed in an ammonia
containing atmosphere to increase nitrogen in the
steel strips up to an amount listed in Table 5 {0.012
mass% to 0.028 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 5.
[0104 ]
[Table 5]
- 60 -
CO
rtStf'^g ^ ^ ^^
•
, " ' in L"^ LTI L^;
J IJI O C O C
^r- CT O O O C:
<^' I 6 6 6 cl
a ?
K , " o o o o
E lb o o o o
!j ;;r i u u o o
a:
~ r- [-- T- r-
?"' S S S S
oi^ ° ° ° °.
^ . o o n CD
p r:^ ^^J IN r j ^^]
i-* YA ^ rj oj CN rj
m ^ oi o o o o
H ? o o o o a: S
g ^I^
s ^?^
E-H '^ m CTf IC/ CD CD
i:i U 3 | ^ C D O O O O
I^d |V ""^ . . . ,
H (-1 g ; o o c? o
s "J S
CC --I
H it I
M
i-- (/} r-H •—I rj rj
E (/I o o o o
O < • ' • ' I
L.' ^ O O O O
I.-
g2
n 5^ — O O O D
LO , : ' T aj HE OD CO
^ g — oi 01 cn 01
s ^^
G S g O „ „ ^ ^
i2 It. ^-- O O O O
1 ^ [ J (Ti O' Ol O^
h ' fli ^
' " E H
- - - O O O C:^
: ^ (J rj cj r j CJ
EH D (^J IM <>J d
" TH —• TH .-•
,r, --- lil Li> \D ^if
^ '-I O O O O O
S EH 0 iN OJ CJ c^i
H - ^ ^ ^ _
S (J
3 5!?— c o c j o c ji
w f i a u i n u ; > ; 2 :2
U Q, -I - . -H -H
a: E
^ < CO u Q
L1-) ^ I I I
'^ B
[0105] As listed in Table 5, in Examples No. 5C and
No. 5D in which an N content after the nitriding
treatment satisfied the relation of inequation (8)
and the relation of inequation (9), the particularly
good magnetic flux density was obtained. On the
other hand, in Examples No. 5A and No. 5B in which an
N content after the nitriding treatment did not
satisfy the relation of inequation (8) and the
relation of inequation (9), the magnetic flux density
was slightly lower than those in Examples No. 5C and
No. 5D.
[0106] . (Ninth Experiment)
In the ninth experiment, the effect of the
condition of the finish annealing in the case of no
Se being contained was confirmed.
[0107] In the ninth experiment, first, slabs
containing Si: 3.3 ma ss%, C: 0.06 mass%, acid-soluble
Al: 0.028 mass%, N: 0.008 mass%, Mn: 0.1 mass%, S:
0.006 massi, and B: 0.002 mass%, and a balance being
composed of Fe and inevitable impurities were
manufactured. Next, the slabs were heated at 1150°C,
and thereafter were subjected to finish rolling 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.
- 62 -
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 decarburizat ionannealed
steel strips were annealed in an ammonia
containing atmosphere to increase nitrogen in the
steel strips up to 0.024 masses. 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 1000°C at a rate of 15°C/h, and
further were heated up to 1200°C at a rate listed in
Table 6 {5°C/h to 30°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]
- 63 -
LI >• U CQ
L i S u ' l f ^— "^ " t^ "^
gs i'^g ^ ^ - -
Q
•i o^ CJ o o o
i: 'jn O O O O
'-^ E o o o o
t - ^'1 :' (T^ cj C3 cj
M J^ O O O O
a- I ^ o o o o
y m- o d o d
• ^ I- f- r- r-
?JS 3 S 3 S
afa ° ° ° °
^ O O O (^
a o
Ho3e=. ° ° °
H g S O O O Q
13 M X
w ft i3
t -
" W E g a o
""I !"• r- r^ r- r-
C^ r |- r-l --H T-H T-H
I—I -[- fV' . . . .
Q g j^ O O O O
S M >: g a u
M
^ —-
^ Ul. -^ T -^ T
Ui iJ} rj ^N cj :
g
tn ft
[i. L' Pi ^-- o o o o
^ Q] (Ti en m Hji
p* a , MH
u
H
^ O (3) O O
E-H o rN CJ CJ CJ
- - - ,-< .—I ,—I ,—I
f n „ ••O -ij \0 \D
^ '-I O O O O O
S E-H a r-l 'N yj ko kO
I—I d.
[0109] As listed in Table 6, in Examples No. 6A to
No. 6C, the heating rate in a temperature range of
1000°C to llOCC was set to IS^C/h or less, so that
the particularly good magnetic flux density was
obtained. On the other hand, in Example No. 6D, the
heating rate in the temperature range exceeded 15°C/h,
so that the magnetic flux density was slightly lower
than those in Examples No. 6A to No. 6C.
[0110] (Tenth Experiment)
In the tenth experiment, the effect of the
condition of the finish annealing in the case of no
Se being contained was confirmed.
[0111] In the tenth experiment, first, slabs
containing Si: 3.3 mass%, C: 0.06 mass%, acid-soluble
Al: 0.028 mass%, N: 0.008 mass%, Mn: 0.1 mass%, S:
0.006 mass%, and B: 0.002 mass%, and a balance being
composed of Fe and inevitable impurities were
manufactured. Next, the slabs were heated at 1150°C,
and thereafter were subjected to finish rolling at
900°C. In this manner, hot-rolled steel strips each
having a thiclcness 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-annea1ed steel strips
- 65 -
were obtained. Subsequently, the decarburizationannealed
steel strips were annealed in an ammonia
containing atmosphere to increase nitrogen in the
steel strips up to 0.02A mass%. Next, an annealing
separating aqenL containing MgO as its main component
was coated on the steel strips. Then, in Example No.
7A, the steel strip was heated up to 1200°C at a rate
of 15°C/h and was finish annealed. Further, in
Examples No. 7B to No. 7E, the steel strips were
heated up to a temperature listed in Table 7 (lOOCC
to 1150°C) at a rate of 30°C/h and were kept for 10
hours at the temperature, and thereafter were heated
up to 1200''C at a rate of 30°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 7.
[0112]
[Table 7]
- 66 -
CD
L ^ f c l l l - ^ s . c o c o - i r - ' -i
M M K l ^ L . ' - ' ^ '^ '^ '^ ™
[') o <.'^ C Lo "•" _; J ; ; ;
. -,^ LTI []-| J^ L'; LTJ
i- m o o o c o
V I/} (-) ID C> CJ O
^'' S o o o o o
E- '. _
F-i; - ", m r" r^ r^ f^
EH '^ 'rr. O C O O O
HH J^ O O O O O
aj I ''J o o o o o
•-H i'l , . . . .
u ~t:^ o o o o o
[ J CQ
C-i
[•- r- f-- I- r-
•? f ^ o o o o c
' ^J c:> cj u iu o
ci S
rj. o o o o c
C O
i-i i-i ^ ^ ^ —I —J
r'l rr rH r-H --I i-H -H
r r^ - - f^] rj rJ rJ rj
t - o i i s ; = : ^ ^ =^ ^
B- g ^ o n ci C3 c;
I i:LJ
y '^ s
Q 5 £ n o o n c T
H M X
cc B: (J
U -• • •J •]> -ji i;!! ^
E-i LO fN ^j cj rj CI
E LO G O O O O
O "T . . . . .
[ J E C O O O O I
s
Q O kO
^' , ^ -- c o o o o
s -•• ^
H O O.
J H X
J CS N
D
« ^
5 t : : g - O O O O O
k. i ^ V i ^ - ^ o o o o o
M S -- ""• "-"^ o^ "
H I '•'
[0113] As listed in Table 7, in Example No. '?A, the
heating rate in a temperature range of 1000°C to
1100°C was set to 15°C/h or less, so that the
particularly good magnetic flux density was obtained.
Further, in Examples No. 7B to 7D, the steel strips
were kept in the temperature range of lOOCC to 1100°C
for 10 hours, so that the particularly good magnetic
flux density was obtained. On the other hand, in
Example No. 7E, the temperature at which the steel
strip was kept for 10 hours exceeded 1100°C, so that
the magnetic flux density was slightly lower than
those in Examples No. 7A to No. 7D.
[Oll'^] (Eleventh Experiment)
In the eleventh experiment, the effect of the
slab heating tempe rature in the case of no Se being
contained was confirmed.
[0115] In the eleventh experiment, first, slabs
containing Si: 3.3 mass%, C: 0.06 mass%, acid-soluble
Al: 0.028 mass%, N: 0.008 mass%, Mn: 0.1 mass%, S:
0.006 mass%, and B: 0.0017 mass%, and a balance being
composed of Fe and inevitable impur ities were
manufactured. Next, the slabs were heated at a
temperature listed in Table 8 (1100°C to 1300°C), and
thereafter were subjected to finish rolling at 950°C.
In this manner, hot-rolled steel strips each having a
thickness of 2.3 ram were obtained. Subsequently,
annealing of the hot-rolled steel strips was
performed at 1100°C. Next, cold rolling was
- 68 -
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 decaiburizationannealed
steel strips were annealed in an ammonia
containing 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)
- 69 -
r\ !-[ f 1 K S ^ - - < M r^ o r- (M z [ ^ g 3 ^ ^ , ^ ' ^ ° ^ ^ ' ^
t ^ Q i S E . • • - ( • - i i - ' ' -i
E CM S W
Q
,, 0,0 lO LJl t\J ^ i-l
i: tn 0 0 0 0 c
^, u} 0 0 0 0 0
- " (4
"^ S 0 0 0 0 0
u: "^^ ~~
H "^
F- CQ''^ 0 0 0 - H - (
I-" ,' 0 0 0 0 0
o- I "^J 0 0 0 0 0
n ^
( J 1-^ - : 0 0 0 0 0
ui m
'^ - t
~ 10 ro ^ I!") IN C>
^ i J n - H ^ i - H O O X
" , , ^ 0 0 0 0 0 ^
' ' i ! 0 0 0 0 0
ma I
s . 0 0 0 0 0
•^ -^ S —
M W W OC ^H . I , I ^H ^
OS. H W C N r J ( N ( M H rH
O ,-- liJ US kD 'X) ".C
2 '-lO 0 0 0 0 0
H •-" . I . -F . I .-I M <
^ 1,1
' • ' ' •-•• r I
. J S S - 0 0 0 0 0
" ^ t j f ? U o i i i O L Oo
1.3
n cC m U Q H
lg CO (D CD o) ro
U M U
H L—_
[0117] As listed in Table 8, in Examples No. 8A to
No. 8C each having the slab heating temperature being
the temperature Tl or lower and the temperature T3 or
lower, the good magnetic flux density was obtained.
On the other hand, in Comparative Examples No. 8D and
No. 8E each having the slab heating temperature
higher than the temperature Tl and the temperature
T 3 , the magnetic flux density was low.
[0118] (Twelfth Experiment)
In the twelfth experiment, the effect of the
components of the slab in the case of no Se being
contained was confirmed.
[0119] In the twelfth experiment, first, slabs
containing components listed in Table 9 and a balance
being composed of Fe and inevitable impurities were
manufactured. Next, the slabs were heated at 1100°C,
and thereafter were subjected to finish rolling at
9G0''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 BSCC for 100 seconds,
and thereby decarburization-annealed steel strips
were obtained. Subsequently, the decarburizationannealed
steel strips were annealed in an ammonia
- 71 -
containing atmosphere to increase nitrogen in the
steel strips up to 0.022 niass%. 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 10.
[0120]
[Table 9]
- 72 -
-I O O
g I I I I I ( I I I I o I I o I I
o o
^^
^ " I I I 1 1 I
o
^ ' ^ ^r LTJ
c I I I I , I I , c , I ^ ^ ^ I I
o o o o
LI") --r-l
n o o
^ I I I I I I I O I I I I I O I I
o o
^^ cj ro CM
!.•; tij I I I I I I ^ t I I I ^ ' ^ I I I
1-4 , i-i vr o ~i
FX .? I I I I I I ' I I I
M *=- O O ^ O cc
w
u . ___—_
H LD O LTJ ra
'••"^ (^ I -^ 1 1 I I . I I I I - ; o o I I
2 o o o o
o
u _—_ ^
r i o o o o o o o o o o o o o o o o ,_„
* ; : c Q o o o o o o o o o o o o o o o o ''
i^^ o o o o o o o o o o o o o o o o
O I
•z, or--miDU)r-r-^or--'iJ(DiO[~-'ijy3 INJ
O o o o o o o o o o o o o o o o o
n m o o o o o o o o o o o o o o o o
^
H o o o o o o o o o o o o o o o o
M o "
!2j _ , T — 1 - — I T — I r H T — I ^ T — l i — 1 ( — I T — I r — I F - H T — I T — [ T — I rH
O ' ^ o o o o o o o o o o o o o o o o
t o r - m o j r - i J i r - m t o r a i T i a i O T ' i J c o r--
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
o o o o o o o o o o o o o o o o
cor-Lnr~-"ii'r~-OTr-(nun-jto[~-i»(X) in
^ 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
( . 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
^ OTa^^J^a^OTa^TT^o^ - ' ' - * ' - ' ' - ' — * ^ LD
^ Q
^r, o \ O L n v c r ~ - L n L n i x > > x i i r > r ~ - t r ) r ~ - u i > x > L n L n ^
^ i t / i o o o o o o o o o o o o o o o o
' - t / ) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 O
' ^ E O O O O O O O O O O O O C D O O O
< •J'Tr^^r-HCNf^r^OJi-fCNIi-'^CNJi-ICMCNJ CM
fr> 0 J ? ; o o o o o o o o o o o o o o o o
M y ^ o o o o o o o o o o o o o o o o
Cij i ^ 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 o
a; ^
" C 0 1 T l < T l C O C T l < J l O D ( J l C O C V l C h C O C r i C O C O CO
? 3 , n O O O O O O O O O O O O O C 3 0 O ^ ^ o o o o o o o o o o o o o o o o
cQ a
£ , O O O O O O O O O O O O O O C 3 O
n rf;cQUQWU.t53:n'-5^i-4S30 Cu
lg a i o i c T i C T i c r i c r i o i c r i c r i o i c r i a i c r i c r i e r i ai
>
•9 o
H I I I
[0122] As listed in Table 10, in Examples No. 9A to
No. 90 each using the slab having the appropriate
composition, the good magnetic flux density was
obtained, but in Comparative Example No. 9P having an
S content being less than the lower limit of the
present invention range, the magnetic flux density
was low.
[0123] (Thirteenth Experiment)
In the thirteenth experiment, the effect of the
nitriding treatment in the case of no Se being
contained was confirmed.
[0124] In the thirteenth experiment, first, slabs
containing Si: 3.3 mass%, C: 0.06 mass%, acid-soluble
Al: 0.027 mass%, N: 0.007 mass%, Mn: 0.14 mass%, S:
0.006 mass^, and B: 0.0015 mass?;, and a balance being
composed of Fe and inevitable impur ities were
manufactured. Next, the slabs were heated at IISO^C,
and thereafter were subjected to finish rolling 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.
[0125] Thereafter, as for a sample of Comparative
Example No. lOA, decarburization annealing was
performed in a moist atmosphere gas at 830°C for 100
seconds, and thereby a decarburization-annealed steel
- 76 -
strip was obtained. Further, as for a sample of
Example No. lOB, 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 0.021 mass% was obtained. Further, as for
a sample of Example No. IOC, decarburization
annealing was performed in a moist atmosphere gas at
860°C for 100 seconds, and thereby a decarburizationannealed
steel strip having an N content of 0.021
mass% was obtained. In this manner, three types of
the decarburization-annealed steel strips were
obtained.
[0126] 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 IS^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.
[0127]
[Table 11]
- 77 -
M tH H _ ~-. ,,1
i S ^ '^ g " '•' - - a n. ^ w
D
, . • 1-1 U^ Ul
^ a: o '_J o
•• oq o o o
"i' § o o o
m
^ C " o o o
H " O O O
CJ I '•5 o o o
H a . . .
LI '—' -^ o n cii
-. S o o o
ma . . .
a o
B o 3 2: ° '^ °
t ' S S O O O
y cc !d
H .
<
H u. S
^ Q O
'J ^. 'lo - ^ ^ ^
g HOw2 ° ° °
D g ^ o = O I
g W tJ CO
H
H — I
pj u: CO c^ CM
3 EH W O 0 0
2 < - . .
O T. 0 0 0
U ---
^-. in in in
EH 3 ^ .H TH
•-- ,1 . H . H
r^ri ._ ai CO CD
• ^ •-! U CM r-l CM
H EH 3 CM i"N CM
EH •-" --I H iH
CC • • ••
l a
a : tj
"A S S — l^ O Q
O O U n
-1 3 (^ H
5 ^ g EH CU -J J
a. o o ^
o 0 00
go. O.
ra 8
H I I I
[0128] As listed in Table 11, in Example No. lOB in
which the nitriding treatment was performed after the
decarburization annealing, and Example No. IOC in
which the nitriding treatment was performed during
the decarburization annealing, the good magnetic flux
density was obtained. However, in Comparative
Example No. 1OA 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. 1OA
in Table 11 is a value obtained from the compos it i on
of the decarburization-annealed steel strip.
[0129] (Fourteenth Experiment)
In the fourteenth experiment, the effect of the B
content in the case of no S being contained was
confi rmed.
[0130] In the fourteenth exper iment, first, slabs
containing Si: 3.2 mass%, C: 0.06 mass%, acid-soluble
Al: 0.027 massi, N: 0.008 mass%, Mn: 0.12 mass%, Se:
0.008 mass%, and B having an amount listed in Table
12 (0 mass% to 0.0043 mass%), and a balance being
composed of Fe and inevitable impuri ties were
manufactured. Next, the slabs were heated at 1100°C,
and thereafter were subjected to finish rolling 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
- 79 -
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 decarburizationannealed
steel strips were annealed in an ammonia
containing atmosphere to increase nitrogen in the
steel strips up to 0.024 raassl. 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 12.
[0131]
[Table 12]
- 80 -
0 >• U CD
T " ^ o'l oil o tr^ •—I
';! ; ' " i^ i^ r- ifi r-
-J , ' O O O O O
1 0 ^ O O O O O
4) S
w ^ o o o o o
f ^ rvl" r f l CM fSJ n Ul
f 03 f n O O O O
M '/^ ^ O O O O a. I ^ " o o o o
[J '• ' S u m o o o o
c i : • '
OJ ^__
•"J r^ in ^c cG
^- r n O .-( (N j l\l (M ,-H
m < o rt °^
F-< f"! U S O O C O O
1 I m — I
2 [' 2
_ r^ c f) CO
r o (J , r- i-H ^ U3
E-i o ^ CNj cj f\|
"—" .—I T—I r-H iH
O ^-, ty^, ij', iTi cy, tTi
M [-IO (M ( M t M f M t Nl
E-i "—" i-H •-( 1 I . ^ r-l
rf! _ _ _ ^
[d
J 5 = ? — "^ o o o o
'^'^ F H C S < - ' •—' o o o o
< ^ °- •-! -^^ ';^ '•' '•]
[ J OJ •-! .-I i-H .H . I
a: E
Eg
f^ o o o o o
~ o o oo
CD
O .H 1-1 iH rH .-I
2 .-I .H .-I .H ,-1
W >
rsj i-H W Ci]
(D F=J: S a
7^ S H Id
H I I I
[0132] As listed in Table 12, in Comparative
Example No. IIA having no B contained in the slab,
the magnetic flux density was low, but in Examples
No. IIB to No. IIE each having an appropriate amount
of B contained in the slab, the good magnetic flux
density was obtained.
[0133] (Fifteenth Experiment)
In the fifteenth experiment, the effects of the B
content and the slab heating temperature in the case
of no S being contained were confirmed.
[0134] In the fifteenth 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 mass%, Se:
0.008 massi, and B having an amount listed in Table
13 (0 raass% to 0.0043 mass%), and a balance being
composed of Ee and inevitable impurities were
manufactured. Next, the slabs were heated at 1180°C,
and thereafter were subjected to finish rolling at
950°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-
- 82 -
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 Table 13,
[0135]
[Table 13]
- 83 -
r ^ r l r l f ^ L ^ - — en r^ r j o CM
O O O [^ « ^ ^' ^ _, ^
Q
(. " osj ^^ ^^ LT: f^
=S . J o o o o o
fi " J o o o o o
0) a
w S o c o o o
cT •-,•-—- !£ M' a; ui
EH m f' o o o o
M J*' „ O O O O
Ch I S ^ G O O O
r J •—^ E o o o o
PC "
OJ
' ^ ro ro T—I rr
^ ^' O •-( CN 1^
? ^ o o o o
-.'ff " o o o o
^ o o o o
U ^ EM
b ] [J-K m r n m r n ro
i - i E - ' ? ; w o n n o o -v.
CC a: o i=C ^
^ M U E O O O O O
n o ; — I
._. 01 o ro CO
n o r- i-i •=)• ID
E-i O ' ,-1 CN) (TNI CN
,-( ,-1 ,-1 M
to ,^ O^ 0> c^ a> o^
f-> "-- ,—I T—' T—' T—f . -I
g _
J S S — O O O O O
f l PHrPU c o r a r a r am
a S ^•' M ^ rH M M
a; E
M ^ di r- oi n
^ rn _ o o o O
g ^ ^ O O O O
'-' 5- o o o o
m
sC CQ O Q Cd
O IN (XI (N (M CM
2 M M M i—I TH
['1
LJ E- ^ J
• ^ F£ OJ Oi
:-! Ol S X
O S I-] td
H L I I
[0136] As listed in Table 13, in Comparative
Example No. 12A having no B contained in the slab and
Comparative Example No. 12B having the slab heating
temperature higher than the temperature T3, the
magnetic flux density was low. On the other hand, in
Examples No. 12C to No. 12E each having an
appropriate amount of B contained in the slab and
having the slab heating temperature being the
temperature T2 or lower and the temperature T3 or
lower, the good magnetic flux density was obtained.
[0137] {Sixteenth Experiment)
In the sixteenth experiment, the effects of the
Mn content and the slab heating temperature in the
case of no S being contained were confirmed.
[0138] In the sixteenth experiment, first, slabs
containing Si: 3.3 mass-d, C; 0.06 mass%, acid-soluble
Al: 0.028 raass%, N: 0.008 mass%, Se: 0.007 raass%, B:
0.0018 mass%, and Mn having an amount listed in Table
14 (0.04 mass% to 0.2 mass%), and a balance being
composed of Fe and inevitable impurities were
manufactured. Next, the slabs were heated at 1150°C,
and thereafter were subjected to finish rolling at
950°C. In this manner, hot-rolled steel strips each
having a thickness of 2.3 ram 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.
- 85 -
Thereafter, decarburization annealing was performed
in a moist atmosphere gas at 830°C for 100 seconds,
and 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 14 .
[0139]
[Table 1^]
- 86 -
CO
L> >^ O CQ
^ g S 3 E ; H -^ S S S^
'i^ i'^'s ' •' - - -•
Q
I
—I Cij S S
^ I I I
[0140] As listed in Table 14, in Comparative
Example No. 13A having a Mn content being less than
the lower limit of the present invention range, the
magnetic flux density was low, but in Examples No.
13B to No. 13D each having an appropriate amount of
Mn contained in the slab, the good magnetic flux
density was obtained.
[0141] (Seventeenth Experiment)
In the seventeenth experiment, the effect of the
finish temperature Tf of the finish rolling in the
hot rolling in the case of no S being contained was
conf irmed.
[0142] In the seventeenth experiment, first, slabs
containing Si: 3.3 mass%, C: 0.06 massi, acid-soluble
Al: 0.026 masS'o, N: 0.008 mass"ti, Mn : 0.15 mass%, Se :
0.006 mass%, and B: 0.002 raass^, and a balance being
composed of Fe and inevitable impurities were
manufactured. Next, the slabs were heated at 1150°C,
and thereafter were subjected to finish rolling at
the finish temperature Tf listed in Table 15 (800°C to
1000°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 llOCC. 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,
- 88 -
and thereby decarburization-annea1ed steel strips
were obtained. Subsequently, the decarburizationannealed
steel strips were annealed in an ammonia
containing atmosphere to increase nitroqen in the
steel strips up to 0.020 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 15.
[01^3]
[Table 15]
- 89 -
u >' u m
e l Q l f l S i - ( , - i i - .M
^1: " Lj"> -^ ^r (N
.'i'm T T M' er
« m o o o iij
" ^ ' O O O O
<^ S o o o o
tC J; I cj r'j m ic
• I , ,,; o o o O
CJ I ^1 O O O O
H & . . . .
( J — £L O O O O
Oi ^ _ _ _ _ ^ ^
" CO r- c- T
m § o o o o
i , o o o o
O H E-i
•Z Z 3 —
M t i ] DJfio O C O O
C I S Fnt/J C l f N l N (N
M H ?•. W O C O O
Q; =1 O < . . .
H D J O E O O C U
u p ;
I,] 2
Q O
IH M
H [J CI. en
>i H >s
^ Qi W I
n^
g ^ < o ^ o o o g
r,, 5 i^ — o in o y
5 W CO CO OI H
f " S H
Id
H
, - , o o o c2
rt (J CM CNJ (N (M
E-i 0 (N CN (N r-J
- - ' i-H H t-H ^
2 oJ u n m (-1 fi
M MO r>l (M r\l f-i
H ~ 1-1 rH rH ,-H
SC ^
Ld
a: t.i
3 5 S — O O O O
< S °_ ^ :^ ^ ::^
[ J OJ ,-H .-H ,-H ,-1
rd
EH
>< P3
i n [d M cj
, J HI ^J
0) a d: a
^ |_ J I
[0144] In the case of the B content being 0.002
mass% {20 ppm), the finish temperature Tf is
necessary to be 980°C or lower based on inequation
(4>. Then, as listed in Table 15, In Examples No.
14A to 14C each satisfying the condition, the good
magnetic flux density was obtained, but in
Comparative Example No. 1'^ D not satisfying the
condition, the magnetic flux density was low.
[0145] (Eighteenth Experiment)
In the eighteenth experiment, the effect of the N
content after the nitriding treatment in the case of
no S being contained was confirmed.
[0146] In the eighteenth experiment, first, slabs
containing Si: 3.3 raass%, 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 1100°C,
and thereafter were subjected to finish rolling 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 llOO^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 SSO^C for 100 seconds,
- 91 ~
and thereby decarburization-annea1ed steel strips
were obtained. Subsequently, the decarburizationannealed
steel strips were annealed in an ammonia
containing atmosphere to increase nitrogen in the
steel strips up to an amount listed in Table 16
(0.011 mass% to 0.029 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 16.
[0147]
[Table 16]
- 92 -
It
u H E S C — '^ •"' " t^
3 Q: rt 3 ,, ^ ^ rt
Q
J ^ Ol Ol Ql (Tl
f,,: o o o o
«.'£ ° ° ° °
f'J ^ o (J (r> o
^ —
ill
S °f^ S S 3 3
^ , J5 o o o o
E^ '3 • Q Q II
y -E d d o o
CM
'^^ in in Ln i-n
" ,n CO o O O
mS ° ° ° °
?^ o o o o
_~ .
1-1 2
Q Tn O O O O
n ,n -^ rj c^J ^N OJ
^ [J ^ O O O O
^ £ o o o o
S _a
^ or; uj ji vo lo
!"• iii — I"! <-* '•"•' ---^
[J 1/)^1D O O O O
M t" ? O O OO
a a S
M —' I
U (,r 1-1 U- r^ C-\ rr-.
fH l/i , I ,-i r j OJ ^'
'^ Ui O O OO
U S o o o o '
in
L5 "!? — (7^ iJ\ CT^ O'
o «
(C
a: H
u>
Ms a: Wa
S S ' - ' O O O O
g 2 i, ai oi oi 01
h- (J
t-
— r- r- r- r^
rn (J o o HID o
B- o rj ^ IX] (N
^^ H r-H r-H r 1
, n — r- r- r- [--
y IN u fS rj (N nj
^ e-i Q 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 17.
[0151]
[Table 17]
- 95 -
CO
IJ >• U! CQ
S S u B f ^— 1^ fJ f^ ™
UJOtsU-ui J J _ ; _!
Q
,^ T £-- r- r^ r-
^ ^ 0 0 0 0
C/l ^ C O O CJi
< ^ "^^ f'J '•J ^> '•J tJ " ,; o ci c o
i-< , rA o O C o
0- I ' i ; o o c o
M S . . . .
u — e o o o (3
[£| CO
Qi
"T r: o o o
" . • " 0 0 0 0
CQ S 0 0 0 0
s 0 0 0 0
• o
r;! !;;J rj r>i <%] cj
- r, .-i — IN 'N iN <^J
g S o o o d
I s a
i f^ g
S T fi'
S 3 cS o o n o
S n X
E « "
h .
a H _
[b] •: 1^ 11 ^3" ^3"
E LO O O O O I
U E ID O O O
• - ^
^ 0
Q O
H U B .
. l u x
d ft tJ
i t .—
t i (i;
•^ i: 3 — s t : ! S . " o o oc
r\ iif (j^ (T d (TL
Er
o [J rj oJ CN IN
E-' o (N tJ £N fN
—- ,_H ^ ,-1 ,-•
n ^ f^ r- r-- r-
^ ^ tJ a^ i ^ at a rate of 30°C/h and were kept for 10
hours at the temperature, and thereafter were heated
up to 1200''C at a rate of 30°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 18.
[0155]
[Table 18]
- 98 -
{_> >- U ai
E P S V - V r j o r - i r -o
Q
I 'T r- r r- r- r-
6 m ^ «• =r =r T 5 , „ o o c o o
1 ^ O O O O o
oj a . . ^ , .
^ S o o o o o
^ I
H , i^; o o o o o
Cu I ^ f:3 O o o o
M & . . . . .
U TTC O O O O O
[ J ffi K —
CL. ^
" ^ O Ci O C CJ
5 :;: IN d CJ CM rj
^ S O O Q O O
l^-" g O C O O Q
?. 0 0 0 0 ( 13
a o
. ^ ,^! CM OJ IN r j (>i
[,. Si --• iXf ^ lO •£•
: ^ t> r'l ] „ r ;^ O O O O O
T "-; o o o o o
a> &
(/) ^ O O O O O
OT " • ""
III' :•,
^ "i
< ^' r^ -H ! ^ CO ij-l rl-
H ,n O C O O O
ftj I y o o o o o
I—I ^ . . . . ,
U ' " ' ^ O O O O O
DJ ^ I
" CO ixi ^ ^ (sj IN
^^ J „ ^ ^ ^ o o O
i> i , : [J O O O O
ma
^ , 0 0 0 0 0 I
1-1 H t] o." CJ (M 0 CJ CM
Q E [ H M 0 > ) t M f M t N J (N
1 - 1 ^ 1 KCQ O O O O O
n: a: o <
[ i t a O S O O O O O
M B^
, - - r-- [---[--- r-- r-
1 1 f j ^ ^ ^ i-H .H
^ o tNJ (M IN (NJ CM
— ^ i-H ^ i-H ^
O --- OT a% o^ J
LJ O O O O O O O O O O O O O O O O LO
J ^ m o o o o o o o o o o o o o o o o O
^ O O O O O O C O O G O O O O O O ^
-J-l
O ^ — I
3: i o r - - r - - c o ' i i r - - - a ; ^ r - i o a ) r - ~ - ' i ) i i i i\j
0 » i ' 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 O
H ( J ^ O O O O O O O O O O O O O O O O
l-H O O O O O O O O O O O O O O O O
M o - — '
Cu i n c N j r \ j ^ r — i r o o ' — ' f ' l o o r n o o j o O
S L ; - - H - - H ' — I T — i T — f r - H . — 1 < — f T H r H T H . — l i — r ^ ^ ^
O S
( J O O O O O O U O O O O O O O O O
c o r - a > c o r - - ^ r - c c i c o c o ( T i c c c c ^ r ^ c^
o o o o o o o o o o o o o o o o
E i 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 - L n < o [ - - - ^ ( r i r - - t o i i i O M ' r - - - j ' , - i 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 O
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 H T - H r - H W r - l . — I T — I ' — ' r - H r H r H , 1 ^ H ^ n - l T—I
•5^ o
to u
H I I „.^ I
[ 0 1 6 4 ]
( T a b l e 21]
- 106 -
y y t J ^ ^ r H r - H ^ i — l i - H i — l i — ! • — l i - H ' — l i — I ' - H i — ! • — ! • — I CT
g &. g g ^
S Q I
• " ' • ^ o o o o o o o o o o o o o o o o
0) a
V l t L O O O O O O O O O O O C - O O O O
E-i '^
f l • l 3 ' ? c ^ t ^ ^ r ^ c ^ J ^ H T - l c ^ J 1 H 0 ^ , ^ • - l c ^ J ^ ^ . J C M eg
£-1 w ™ ; o o o o o o o o o o c > o o o o o
M f J o o o o o o o o o o o o o o o o
(u l i i o o o o o o o o o o o o o o o o
M a
D " S . O O O O O O O O O O O O O O O o
W a: cc ^
^ S . ! — I r H t — < • — l i — I T - I I — I ^ ^ ^ H ^ ^ ' — l i — ! • — I i — l i — I r—I
S r n O O C a O O O O O O C D O O O O O O
^ • ^ o o o o o o o o o o o o o o o o
£ . O C I O O O C ) 0 0 0 0 0 0 0 0 0 O
2 ^ r H i H ' — I t - H r - l ' — I r H . - H ^ i — 1 . ^ . - ^ ^ ^ . — I !—I
>
CNi Cl< ^ ' ^
•2 o
iC (J
H I 1 _^ I
[0165] As listed in Table 21, in Examples No. 19A
to No. 190 each using the slab having the appropriate
composition, the good magnetic flux density was
obtained, but in Comparative Example No. 19P having a
Se content being less than the lower limit of the
present invention range, the magnetic flux density
was low.
[0166] (Twenty-third Experiment)
In the twenty-third experiment, the effect of the
nitriding treatment in the case of no S being
contained was confirmed.
[0167] In the twenty-third experiment, first, slabs
containing Si: 3.3 massi, C: 0.06 mass%, acid-soluble
Al: 0.027 raass%, N: 0.007 mass%, Mn: 0.12 mass%, Se:
0.007 mass%, and B: 0.0015 mass;?, and a balance being
composed of Fe and inevitable impurities were
manufactured. Next, the slabs were heated at 1100°C,
and thereafter were subjected to finish rolling 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 ram were obtained.
[0168] Thereafter, as for a sample of Comparative
Example No. 20A, decarburization annealing was
performed in a moist atmosphere gas at 830°C for 100
seconds, and thereby a decarburization-annealed steel
- 108 -
strip was obtained. Further, as for a sample of
Example No. 20B, 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 0.023 mas3% was obtained. Further, as for
a sample of Example No. 20C, decarburization
annealing was performed in a moist atmosphere gas at
850°C for 100 seconds, and thereby a decarburizationannealed
steel strip having an N content of 0.023
mass% was obtained. In this manner, three types of
the decarburization-annealed steel strips were
obtained.
[0169] Next, an annealing separating agent
containing MgO as its main component was coated on
the steel strips, and the steol 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 22.
[0170]
[Table 22]
- 109 -
CO
I"" t - I"! . CO o r-
E-* | i , E~' ^ F^ ,^ r—. ff-, r--i
Q
'• " ^ 'H .H . '
,' y^ ^ '^ IE
<••)
t - ?-
f l " .• " . ' T-l ,H -H
EH 03 !)- <-: >"' "
I I , ' O O o
OJ ( - ! c ei o
H a . . .
( J ^^ £• c e o
U] ffi
W ' '
S ^ o o o
ma . . .
£ i O O O
^ g g " o o
S H X
I J Ct U
s
a.
y w ?^
iS " o
'' 'J. 'J) '^ l^
^ g g o o o '
g a s o
M ^
H --
IP^ f.o r-- ro r^ I
la CO o (M oj
E EH M O o n
2 < - . . O S o o o
(J —
i n in in
EH O .-H r-H r-H
( 5 ,-. r- r- rn
FH c IN r>l CM
u: ^
W
rn ij U
g 5 ^ ^^ o o o
to K 2 t-> o o o
a: E
H
FH
a; E
O O (J Q
fli O O •^
o o o o
CM >
'—' ^ X X
O 3 [J !4
m 8
H I I I
[0171] As listed in Table 22, in Example No. 20B in
which the nitriding treatment was performed after the
decarburization annealing, and Example No, 2 0C in
which the nitriding treatment was performed during
the decarburization annealing, the good magnetic flux
density was obtained. However, in Comparative
Example No. 20A 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. 20A
in Table 22 is a value obtained from the composition
of the decarburization-annealed steel strip.
[0172] (Twenty-fourth Experiment)
In the twenty-fourth experiment, the effect of
the B content in the case of S and Se being contained
was confirmed.
[0173] In the twenty-fourth experiment, first,
slabs containing Si: 3.2 mass%, C: 0.05 mass%, acidsoluble
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 23 (0 mass% to 0.0045
mass'd), and a balance being composed of Fe and
inevitable impurities were manufactured. Next, the
slabs were heated at llOCC, and thereafter were
subjected to finish rolling 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.
- Ill -
Next, cold rolling was performed, and thereby coldrolled
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 decarburizationannealed
steel strips were obtained. Subsequently,
the decarburization-annealed steel strips were
annealed in an ammoni a containing a tmosphe re to
increase nitrogen in the steel strips up to 0.023
raass%. 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 23.
[0174]
[Table 23]
- 112 -
(J >< (J m
F i r l i i ^ L ] — ™ . i t - i i s i i T Ni
n
J
(U"
[^
« -^^ '-- r^ T^ r- r- co o o o o o
iJ^ <^': ::i o o CD O
o g o o o o o
4-
H
hi " -—
u
a; " _
K nj - ' ^ ^ ^
ffi g; o • o
1 « ° ° S S S
m-- d o o
7- |J^ r- r- ^
•S m Q O O O O
t g ^ O O O O
5. o c o o
_ __ . ^
S ^ ^ '—-
H w iJ cBJ n fi (-1 f i r-i ro
^ E t - • ! ' J C N C ^ I ^ ^ J ^ ^ J C ^ J i—j
H F a t O Q O C O O I
ct cc o rt ^
E-i[tl J?S ^ C J C OO
M O ; - - - I
.— :'i ^ TH .H
ro Q I r- ^ ^ r-
H o .-H rj cj iNJ
— r-- r- r- r^ t^
CM [J 0\ O^ CTl C^ 0^
\r- o r-H ^ TH .H ^-l
( ^ "^ r-H TH TH H -H
S —^
^ — ^ CD >• VD UJ
t l '-^U O O O O O
PI H O o j c M r s j c N CM
U •-• ^ ^ ,j ^ ^
to U 3
ay""" -^ ^ - ^ ^^
g — cr. CO CD in
S ^ O ^ CJ T E i2 „ o o o o
^ 5 o o oo
m
f t m u Q w
O T-H ^ TH TH ^
E CNJ OJ CM (Nl CJ
H Si s ^
(0 U
H I I I
[0175] As listed in Table 23, in Comparative
Example No. 21A having no B contained in the slab,
the magnetic flux density was low, but in Examples
No. 21B to No. 21E each having an appropriate amount
of B contained in the slab, the good magnetic flux
density was obtained.
[0176] (Twenty-fifth Experiment)
In the twenty-fifth experiment, the effects of
the B content and the slab heating temperature in the
case of S and Se being contained were confirmed.
[0177] In the twenty-fifth experiment, first, slabs
containing Si: 3.2 mass-c, C: 0.05 mass%, acid-soluble
Al: 0.028 mass%, N: 0.008 mass%, Mn: 0.1 raass%, S:
0.006 mass%, Se: 0.006 mass%, and B having an amount
listed in Table 24 (0 mass-s to 0.0045 mass%), and a
balance being composed of Fe and inevitable
impu rities were manufactured. Next, the slabs were
heated at 1180°C, and thereafter were subjected to
finish rolling at 950°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 thiclcness 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
- 114 -
decarburization-annealed steel strips were annealed
in an ammon ia 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 Table 24.
[0178]
[Table 24]
- 115 -
y. 'S. y. ^:i ^< [:. "^ "^ '^' •^' ""
U O O [•! TO ! ; ! ! , "
n
;!
<[:•
>^ •- r"j j'H f l :'^ n
'•r. o o o r^ o
1^ CO O O O O O - <:
C3 2! 0 0 0 0 0
to
£' i
i_i
u
n. i^' „ ^ iTi ifi r--
W ' 0 0 00
r i 0 0 00
1 ^ ° o o o o
^ .^' c o o o
m -
'.~ c, f i n CO
;'.;,-, o .-I CM rn
•„1 . ' _ o o o D
•i-' i i ^ 0 0 0 0
m a . . . .
•S; c o o o
___ ^
WE- H
^ iz^ ;^ - -
n E E-H r'^ IN '•] IM 'NJ 1"^ 1—I
K ft O < >—I
E H U ( > S 0 0 0 0 0
S E' 3 I
,—. r: 'J' TH .-I
."^ f j I r^ .-I ^ r^
H o ' T-i CNj r-j c^
" ^ .-' .-I .H .-I
c- r-- r- [•- r-
.-sj fj tTi tr O' O^ O^
H o TH .-< .H TH .-I
O ~ rt .- ^ .H ^1
3 —^—
^ ,-. VO 1.|;^ VO kO VC
y •' c 0 0 0 0 0
^ —" TH .-• .-I ^ .-I
S ^ - - - 0 0 0 0 0
r a u c D t c t c r o co
X S
M
H
t '
S " ^ 01 CO CO lO
g [^ 0 0 00
5 S ° o o o o
' - ' S. 0 0 00
ID
fC ffl U Q W
O i~j (sj r i iM oj
E IN oj rj oj tN
^ >
CM H J J
^ ft- X S
H I I I
[0179] As Listed in Table 24, in Comparative
ir.' X a m p ]. e I\i o . '/.[' i\ having no B contained in the slab and
Comparative F.xample No. 22B having the slab heating
t eirpera t ur e higher than the temperature T3, the
niagnetic flux density was low. On the other hand, in
Examples No. 22C to No. 22E each having an
appropriate amount of B contained in the slab and
having the slab heating temperature being the
temperature Tl or lower, the temperature T2 or lower,
and the temperature T3 or lower, the good magnetic
flux density was obtained.
[0180] (Twenty-sixth Experiment)
In the twenty-sixth experiment, the effects of
the Mn content and the slab heating temperature in
the case of S and Se being contained were confirmed,
[0181] In the twenty-sixth experiment, first, slabs
containing Si: 3.3 mass%, C: 0.06 mass%, acid-soluble
Al: 0.028 mass%, N: 0.009 mass%, S: 0.006 mass%, Se:
0.004 mass%, B: 0.002 mass%, and Mn having an amount
listed in Table 25 (0,05'mass% to 0.20 mass%), and a
balance being composed of Fe and inevitable
impu rities were manufactured. Next, the slabs were
heated at 1200''C, and thereafter were subjected to
finish rolling at 950°C. In this manner, hot-rolled
.steel strips each having a thickness of 2.3 mm we re
obtained. Subsequently, annealing of the hot-rolled
.steel strips was performed at llOO^C. Next, cold
rolli. ng was performed, and thereby cold-rolled steel
- 117 -
strips each having a thickness of 0.22 mm were
obtained. Thereafter, decarburizatjon 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-o.
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 25.
[0182]
[Table 25]
- 118 -
'^ \Y t\ V -M • s r i . - l i H u -,
S i^ X Id
Q
a?
X ij^ --I . 1 ^^ 111
(/: o o o o
L'l J CM
h 1 [ H ^, CT O O O O ,
K Ft O f t • • • • •"*
H U I O E O - T C O ,—(
,--. r- r- r-- r--
r o {J o4 rN rM oj
H e C^f CNJ CNJ CJ
-^ '-\ , K ' K <-r- ^ f l (NJ
(Nj f j o -a- o oj
f - O —I TH CNJ CJ
t j - -H ^ ^-^ . I
T- "" "
H ,-, ro (N r- ^.J
El ' ' O ^o iTi n i/j
f i F-" O 1-H 1—I CJ C^i
[ J "^ 1-H 1—I T 1 , -I
I g
g fe „ o o o o
r ] 5 O Q a o o
H fc ~ ^ ., ,, .H
a: S
u
f -
:2 „ w ^
EH n, in CO LO O
g s '='.'='.-'.".
U S D O O O
cd CQ O Q
O f^ r^ r*i n
^ ' H w Id
CM H -J J
iH OJ S H
H I I I
[0183] As listed in Table 25, in Comparative
Examples No. 23A and No. 23B each having the slab
heating temperature higher than the temperature Tl
and the temperature T2, the magnetic flux density was
low. On the other hand, in Examples No. 23C and No.
23D each having the slab heating temperature being
the temperature Tl or lower, the temperature T2 or
lower, and the temperature T3 or lower, the good
magnetic flux density was obtained.
[0184] (Twenty-seventh Experiment)
In the twenty-seventh experiment, the effect of
the finish temperature Tf of the finish rolling in
the hot rolling in the case of S and Se being
contained was confirmed.
[0185] In the twenty-seventh experiment, first,
slabs containing Si: 3.3 mass-o, C: 0.06 raass%, acidsoluble
Al: 0.027 mass%, N: 0.008 mass%, Mn: 0.12
mass%, S: 0.005 mass%, Se: 0.005 mass%, and B: 0.002
mass%, and a balance being composed of Fe and
inevitable impurities were manufactured. Next, the
slabs were heated at 1180°C, and thereafter were
subjected to finish rolling at the finish temperature
Tf listed in Table 26 (800°C to 1000°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 llOO^C. Next, cold rolling was
performed, and thereby cold-rolled steel strips each
- 120 -
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 decarburizationannealed
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 26.
[0186]
[Table 26]
- 121 -
i l f c ^ t l v v ,
H I I I
[0187] In the case of the B content being 0.002
inass% (20 ppm}, the finish temperature Tf is
necessary to be 980°C or lower based on inequation
(4). Then, as listed in Table 26, in Examples No.
24A to 24C each satisfying the condition, the good
magnetic flux density was obtained, but in
Comparative Example No. 24D not satisfying the
condition, the magnetic flux density was low,
[0188] (Twenty-eighth Experiment)
In the twenty-eighth experiment, the effect of
the N content after the nitriding treatment in the
case of S and Se being contained was confirmed,
[0189] In the twenty-eighth experiment, first,
slabs containing Si: 3.3 mass%, C: 0.06 mass%, acidsoluble
Al: 0.028 mass%, N: 0,008 mass%, Mn: 0.14
mass%, S: 0.005 mass%, Se: 0,005 mass%, and B: 0,002
mass%, a content of Ti that is an impurity being
0.0018 mass%, and a balance being composed of Fe and
inevitable impurities were manufactured. Next, the
slabs were heated at IISO^C, and thereafter were
subjected to finish rolling at 900°C, In this manner,
hot-rolled steel strips each having a thickness of
2.3 ram were obtained. Subsequently, annealing of the
hot-rolled steel strips was performed at 1100°C.
Next, cold rolling was performed, and thereby coldrolled
steel strips each having a thickness of 0.22
mm were obtained. Thereafter, decarburization
annealing was performed in a moist atmosphere gas at
- 123 -
830°C for 100 seconds, and thereby decarburizationannealed
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 an amount
listed in Table 27 [0.012 mass% to 0.028 raass%).
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 27.
[0190]
[Table 27]
- 124 -
m
f jS fcSgS'-S :1 S S
U
' - ' ^ ,v -^ -^ --J- --1'
, "^ Lfi O O C O
"^ i 2 j d t ) 1J O O
,. " g o o c o
; M
^r:
U
E^ J •" I-.; r-.r cj oj
' ™ ;. c o o o
n r-; O C O O
u, m ---
fX
Pffi
O) (O OJ
: ^ ; . —I ^ ^ ^
•;^ , ^ o o o o
mS o o o o
^ o o o o
• o
!n ^ OJ IM <-J r>l
H S S O C d O
^ i-l X
^ Ll^ [J
B- _
^ •••3 S
n- • o
M —- JV
O ^ £ o o o cj
S [^ S
S I
H —
^ .^ r^ r - r J 03 , *
LJ t.1 TH T-H r j r j " '
O S n <) c j cj T—4
U - -
i
c; o
H "^^ & d s i^
o
K • •• — •
X U
11} H,
M ^ n _
!-i 2. <, ^ O O O O u. 5 [£ — o o o o
^ !£l CTi en sJi tn
M c u-i
'^ S t-
(J
—. o o o o
n ;j cj r-i f\] rj
Ho rj rj cj IN
—• r-H i-l i-l --i
^ - , .-I .-I T-l .-I
r j rj r-l r-H r-H i-f
H o cj rj cj IN
I " •— H r—I r—I r-»
Z
t;: H y r-i ^ H ^
f^ E-i n ;
^ tt (J
C-H
I g g
u t^ m 2 2 2 2
D g g 0 0 0 0
0; n >^
H CL U
E
S o ' 0-1 m r^ m
U^ If! r^] £\] i-j (\]
S i H L O czi cj C3 was measured. A result of
the measurement is listed in Table 29.
[0198]
[Table 29]
- 130 -
u o u u. (fi _1 _,• _" J _,"
Q
£ [ i - h ^ C / 1 0 0 0 0 0
t^^ o S £ o o o cj o
'C ^ '^T fN i1 Csj I'J ;•]
EH * irt O O O O CJ M y/ (^ o o o o
Cu ' ^ ' O O O O O
U :^ .-- O C3 O O O
[ J to
a; • •
"]7 oj a: CD CG ai
^ ;" .H . I -•• ^ -I
ir 5*^ o c o o o
m ^ o c o o o
^ O C O i_f (J
I d B
Q O
" 1: rN i-ij <>J OJ i-J
lr^ O U ?1 '^. °. °. '='. °.
H S £ o o d c J o
S H X
g CE (J
i s s
g o o
" " CD CO CO CO CO
Q g g O O O O O
s s s
H ^
t d i-'^ T ^r ^ -a- ^
t ~ CO rj C\l oj CJ CJ
S t/J C^ C3 o a o O O
t j ?; (J CJ CO cu o
B
W B I
o a
' ^ , ^ 3 — 0 0 0 0 0 >-H
y g ' - ' g - . - c n a i C T ! t n c n ''
H [^ rn ^
• J M >:
^ C M ,
Cd —
S ^ ^ "
M ! ^ < y o o o o o
t ^ J J o : - - - o o o o o
1 ^ [in ij» a^ Ti oi dh
I ^
,-. O O CD O O
n J) CJ f v r j CJ i-j
EH o rj CJ OJ OJ <\J
'— •—I rH ,—I rH H
. ^ T-* <-\ <-* -^-1 ,-*
r-i (J ^H 1—I 1—I .-H ,H
EH D fNJ CJ J C J C J C N C 'I
-J- —• rH ^H .—I I—I 1—I
in [J) u
S y _ Q o c j oo
Hi- ^ ^ :^ ^ ^
Et
j CJ
S US
S H
O ^ ' < m [J D [J
rti o r- r- r^ [-- r-
^ ^ B CJ CJ CJ CN rj
0) u
I J
I—I a,
-Q I
[0199] As listed in Table 29, in Example No. 27A,
the heating rate in a temperature range of 1000°C to
1100°C was set to 15°C/h or less, so that the
particularly good magnetic flux density was obtained.
Further, in Examples No. 27B to 27D, the stee] strips
were kept in the temperature range of 1000''C to 1100°C
for 10 hours, so that the particularly good magnetic
flux density was obtained. On the other hand, in
Example No. 27E, the temperature at which the steel
strip was kept for 10 hours exceeded llOO^C, so that
the magnetic flux density was slightly lower than
those in Examples No. 27A to No. 27D.
[0200] (Thirty-first Experiment}
In the thirty-first experiment, the effect of the
slab heating temperature in the case of S and Se
being contained was confirmed.
[0201] In the thirty-first experiment, first, slabs
containing Si: 3.1 mass%, C: 0.05 mass%, acid-soluble
Al: 0.027 mass%, N: 0.008 mass%, Mn: 0.11 mass%, S:
0.006 mas3%, Se: 0.007 mass%, and B: 0.0025 raass%,
and a balance being composed of Fe and inevitable
impurities were manufactured. Next, the slabs were
heated at a temperature listed in Table 30 (1100°C to
ISOO^C), and thereafter were subjected to finish
rolling at SSCC. 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 llOO^C. Next, cold
- 132 -
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-annea1ed steel
strips were obtained. Subsequently, the
decarburi2ation-annealed steel strips were annealed
in an ammonia containing 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 30.
[0202]
[Table 30]
- 133 -
a;
U >- U tC
£• S u LJ ^^ - ^> ^ ^ '~- "^
e; c u In 'J-. ', ', J ', _j'
u
0)
V)
•• ^•" oil ko r-j r—I ^
W 0 0 0 0 0
~~' Ll 0 0 0 0 0
• <
f- E 0 0 0 0 0
I
1.1
CJ
IH
DJ
I I
U i
'^ J:-^" iM ^ r- -H m
£ ™rn O O O I \ J iM
, " " O O O O "Tl
I ^ 0 0 0 0 0
'—' ^ c:- c-> ir^ ITS' d
" i-i ^ ra -~- 01
1: ,„ IM IN ^ O O I
•^ ^ 0 0 0 0 0
•: y O O O O D ^
51 fv,
;:, o o o o o
1—1
M E - j SOT 0 0 0 0 0
K <: 03
[-ICJ us 0 0 0 00
^ - . ^j. -a- ^r ^j- -^
r^ ij C) r~i m m n-t
t n o fNJ r>j OJ (N tN)
.—. CTi 3^ o^ (T^ c^
CsJ^^J 7 — I ^ H T - H T — I nH
y "-^ ^H T—I T—I TH n^
l-H '~~
^ „ r-j r\j CM r\i i>i
cC ' " ' O ^ ^ ^ ^ ^
UJ ^ o r j ( N t N f M (M
a ; •-" l-H ^ ^ r H r I
CD
2 t l „ 0 0 0 0 0
t J ^ C J o u i o u - i o
[ J CU ' NH T-H T—' .—I T—I
a: ^
w
cC CD (J Q Cd
O ro CO CO a ; CO
E CM (NJ CM (M CM
W
O W H U]
' ' rii g a.
H
[0203] As listed in Table 30, in Examples No. 28A
to No. 28C each having the slab heating temperature
being the temperature Tl or lower, the temperature T2
or lower, and the temperature T3 or lower, the good
magnetic flux density was obtained. On the other
hand, in Comparative Examples No. 28D and No. 28E
each having the slab heating temperature higher than
the temperature Tl, the temperature T2, and the
temperature T3, the magnetic flux density was low.
[0204] (Thirty-second Experiment)
In the thirty-second experiment, the effect of
the components of the slab in the case of S and Se
being contained was confirmed.
[0205] In the thirty-second experiment, first,
slabs containing components listed in Table 31 and a
balance being composed of Fe and inevitable
impurities were manufactured. Next, the slabs were
heated at llOO^C, and thereafter were subjected to
finish rolling 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
- 135 -
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 ma i n 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 32.
[0206]
[Table 31]
- 136 -
n I I
. o o
p F I I F 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 1
o
^ ^ I l ^ ' ^ ' - ^ l I
o c; c o
1 1 1 -'•I
fe I I I I I I 1 c I I I I I o I I
c ri
o o o
cC , i I I . I r I 1 1 ( 1 1 ( ^ 1 1 I
« '^
i j ] __ _ „_
g in o in CO
^ ^ 1 ^ '~!°'^i I
hj O O O O
u _
O O O O O O O O O O C O O O O O
E C f l o o o o o o o o o o o o o o o c
o
O O O O O O O O O O O O O O O O C5
M _ ,
—I m
r n r - i - n r ^ r ^ r ^ r ^ r ^ f ^ r ^ r - r - - ^ L n - ^ r - ' r-^
-I, o o o o o o o o o o o o o c o ^ L.
'_Li ^ O <3 O O O O O O (_) CJ' O O O C O (13 I J
-^ O O C ^ O C J O O O O O O O O O O '
g ,^ ,
M O O O O O O 0 0 0 C 3 O O 0 0 O O
C 0 < / ) i O O O O O O 0 0 0 0 O O C 3 0 0 O
o
CLi O O O O O O < 3 0 0 0 0 0 0 0 0 O
o ^ — — ——
' > ] t N i ^ f \ J f N J 1^ ^ ^ J C ^ i ^ ^ ] ^ • J ^ s J O J C M C ^ J t ^ J {\i
l l n l ' - H — 1 i — l i — < 'T-i r — l i — J r — I . H r - H ' H i H ' — l i — I •—I g
O O O O O O O O O O O O O O O O
CD o^ CO CO r- j ( N c s j r ^ w r s | O j ro
^ O 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
[ j O O O O O O O O O O O O O O O O
O C D O O O O O O O O O O O O O O
.^ <^ 'T^ -^ f^y 'T^ 1—1 - ^ C s J r o ^ ^ r i t N j c o r o i X ) CO
O C F i i ^ ^ T i O ^ o ^ iTi o ^ i T k c r ' a ^ c r i O > a i < r i i T i cr,
2 ( N J c - i o j c j C N j CN f • } C s J ^ ^ J ^ J t ^ J O J C J O ^ J t ^ J CM
,—1 S ci. ^ 3 cu S
(0 U '.)
H I I [ I I
[ 0 2 0 7 ]
[ T a b l e 32]
- 138 -
D L
n f i U ' ^ ^ ' ^ M r ^ i M r j ^ n o j c j r x j C ' i r n i - i t M f O r--
' ^ ^ ^ f — i ' ^ . . . . . . . . . . . . . . .
^ J ^ y i i l ^ r — . — I T — I T — I T — I T—I r — I : — I f — I f — 1 - — I f — 1 | — l l H h H rH
M [i^ h^ I—I
•?• g
I
oi
"- 1—1
0)
« _ I
> ' s r ' - - 0 3 c a ( x i a i o) c o ( K < D a ; c D ' - - ' J J r - - y 3 i—i
m o o o o o o o o o o o o o o o o
L O t / i o o o o o o o o o o o o o o o o
o s o o o o o o o o o o o o o o o o
+
U. i;
^ ;:
^ ui
h-»
iX
I—I
(J . ___ __
a; ^,
" ' ' T r t M i - I O ' J ' M O - I T-l C N j T - l ( ~ j T - l T - i r M i - ' i - l l M CM
< o ° ^ o o o o o o o o o o o o o o o o
, ^ 0 0 0 0 0 o o o o o o o o o o o
1 ^ 0 0 0 0 0 o o o o o o o o o o o
^ - ' ' ' ' 0 0 0 0 0 o o o o o o o o o o o
s f X i - H T H T - t T H T H TH I — l . - l , - l , - l r H r H i H , H i - ( .H
¥ , n 0 0 0 0 0 O o o o o o o o o o O ^"i 0 0 0 0 0 o o o o o o o o o o o
ma
£ ^ 0 0 0 0 0 o o o o o o o o o o o
c C c Q U Q i a ti O a : H > - : i M i 7 S ^ O Oi
Z ; ( N ( N 1 C M ( N | I S ) CS| C J C M t N ( N J ( M < N ( M ( \ J ( N t (NJ
CM w 1-1 [.] la M tj
' ' ft- g Oi (1. ^ "^
,—1 X CU >3 S PI X
O DJ E H Dut S W •r o o
fO U O
[0208] As listed in Table 32, in Examples No. 29A
to No. 29E and No. 29G to No. 290 each using the slab
having the appropriate composition, the good magnetic
flux density was obtained, but in Comparative Example
No. 29F having a Ni content higher than the upper
limit of the present invention range and Comparative
Example No. 29P having a total amount of a content of
S and Se being less than the lower limit of the
present invention range, the magnetic flux density
was low,
[0209] [Thirty-third Experiment)
In the thirty-third experiment, the effect of the
nitriding treatment in the case of S and Se being
contained was confi rmed.
[0210] In the thirty-third 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 raass%, S:
0.006 mass%, Se: 0.005 mass%, and B: 0.0015 mass%,
and a balance being composed of Fe and inevitable
impurities were manufactured. Next, the slabs were
heated at 1150''C, and thereafter were subjected to
finish rolling 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.
- 140 -
[Q211] Thereafter, as for a sample of ComparaLive
Example No. 30A, decarfturization annealing was
performed in a moist atmosphere qas at &30°C for 100
seconds, and thereby a decarburization-annealed steel
strip was obtained. Further, as for a sample of
Example No. 308, 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 0.0/t' mass% was obtained. Further, as for
a sample of Example No. 30C, decarburization
annealing was performed in a moist atmosphere gas at
860°C for 100 seconds, and thereby a decarburizationannealed
steel strip having an N content of 0.02|
mass% was obtained. In this manner, three types of
the decarburization-annealed steel strips were
obtained.
[0212] 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 33.
[0213]
[Table 33]
- 141 -
U > U ID
P I I S t - - -
p i a: < E T-i H '-I
i n
? m o o o
•- 1/1 E " n o
I
! • ] —^
H « ~ rf .-I . I
L) I S O O Q
u a . . .
••i ir, --I ^ rH
• m O O O
^ o o o
iZ
i-H Xi — CJ rj i-J
tn M 'J' >= o o
H S I ~ -• O O
f: -^
I °g
O M " —. --I ,-1 r-l I
S CO [ J ro o o O '
E-, ,-, ,
S .v' r-- iH TH '
[.1 O O CJ OJ
^ £H en O O O
O S o o C^
u —
^^ Q *^ iTk (1^
- - H M ^
1-1 1—1 rH
OJ (J 1-J r-l rH
^n "-^ 1—' 1—I r-l
^ — to 11 03
^ —' U c-j rj iM
a. g
i j n;
ui p 3
S ^ " O O O
I i - - ^ s
l;' H S t^ S
d '^ u.^ g
c O O ^
"3 8
[0214] As listed in Table 33, in Example No. 3 OB in
which the nitriding treatment was performed after the
decarburization annealing, and Example No. 30C in
which the nitriding treatment was performed during
the decarburization annealing, the good magnetic flux
density was obtained. However, in Comparative
Example No. 30A 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. 30A
in Table 33 is a value obtained from the composition
of the decarburization-annealed steel strip.
INDUSTRIAL APPLICABILITY
[0215] 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.

CLAIMS
CLAIMS
1. A manufacturing method of a grain-oriented
electrical steel sheet, comprising:
at a predetermined temperature, heating a 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;
hot rolling the heated silicon steel material so
as to obtain a hot-rolled steel strip;
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 recrysta 11ization by finish
annealing the decarburization-annealed steel strip,
wherein
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 recrysta 11ization in the
finish annealing,
the predetermined temperature is,
in a case when S and Se are contained in the
silicon steel material, a temperature Tl (°C) or
lower, a temperature T2 (°C) or lower, and a
temperature T3 (°C) or lower, the temperature Tl being
expressed by equation (1) below, the temperature T2
being expressed by equation (2) below, and the
temperature T3 being expressed by equation (3) below,
in a case when no Se is contained in the
silicon steel material, the temperature Tl (°C) or
lower, and the temperature T3 (°C) or lower,
in a case when no S is contained in the
silicon steel material, the temperature T2 (°C) or
lower, and the temperature T3 (°C) or lower,
a finish temperature Tf of finish rolling in the
hot rolling satisfies inequation (4) below, and
amounts of BN, MnS, and MnSe in the hot-rolled
steel strip satisfy inequations (5), (6), and (7)
below.
Tl = 14855/(6.82 - log ([Mn] x [S])) - 273 ...(1)
T2 = 10733/(4.08 - log ([Mn] x [Se])) - 273 ...(2)
T3 = 16000/(5.92 - log ([B] x [N])) - 273 ...(3)
Tf ^ 1000 - 10000 X [B] ...(4)
BasBN ^ 0 . 0 0 0 5 . . . ( 5)
[ B ] - BasBN ^ 0 . 0 0 1 ...(6)
SasMnS + 0 . 5 X SeasHnSe ^ 0 . 0 0 2 ...(7)
Here, [Mn] represents a Mn content (mass%) of the
silicon steel material, [S] represents an S content
(mass%) of the silicon steel material, [Se]
represents a Se content (mass%) of the silicon steel
material, [B] represents a B content (mass%) of the
silicon steel material, [N] represents an N content
(mass%) of the silicon steel material, BasBN represents
an amount of B (mass%) that has precipitated as BN in
the hot-rolled steel strip, SasMns represents an amount
of S (mass%) that has precipitated as MnS in the hotrolled
steel strip, and SeasMnse represents an amount
of Se (mass%) that has precipitated as MnSe in the
hot-rolled steel strip.
2. The manufacturing method of the grainoriented
electrical steel sheet according to claim 1,
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 (8) below.
[N] ^ 14/27[A1] + 14/11[B] + 14/47[Ti] ...(8)
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
- 9 -
treatment, and [Ti] represents a Ti content (mass%)
of the steel strip obtained after the nitriding
treatment.
3. The manufacturing method of the grainoriented
electrical steel sheet according to claim 1,
wherein the nitriding treatment is performed under a
condition that an N content [N] of a steel strip
obtained after the nitriding treatment satisfies
ineguation (9) below.
[N] ^ 2/3[Al] + 14/11[B] + 14/47[Ti] ...(9)
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, and [Ti] represents a Ti content (mass%)
of the steel strip obtained after the nitriding
t reatment.
4. The manufacturing method of the grainoriented
electrical steel sheet according to any one
of claims 1- 3, wherein the causing the secondary
recrystallization includes heating the
decarburization-annealed steel strip at a rate of
15°C/h or less in a temperature range of 1000°C to
1100°C in the finish annealing.
5. The manufacturing method of the grainoriented
electrical steel sheet according to any one
o f claims 1- 4, wherein the causing the secondary
recrystallization includes keeping the
decarburization-annealed steel strip in a temperature
- 1£L-
1M>
range of 1000°C to 1100°C for 10 hours or longer in
the finish annealing.
6. The manufacturing method of the grainoriented
electrical steel sheet according to any one
of claims 1- 5, wherein the silicon steel material
further contains at least one element selected from a
group consisting of Cr: 0.3 mass! or less, Cu: 0.4
mass% or less, Ni: 1 mass% or less, P: 0.5 mass% or
less. Mo: 0.1 mass% or less, Sn: 0.3 mass% or less,
Sb: 0.3 mass% or less, and Bi: 0.01 mass% or less.
Dated this 02/01/2012