U.S. patent application number 15/549578 was filed with the patent office on 2018-02-08 for grain-oriented electrical steel sheet and method for producing same.
This patent application is currently assigned to JFE STEEL CORPORATION. The applicant listed for this patent is JFE STEEL CORPORATION. Invention is credited to Yasuyuki HAYAKAWA, Kunihiro SENDA, Takashi TERASHIMA.
Application Number | 20180037966 15/549578 |
Document ID | / |
Family ID | 56614355 |
Filed Date | 2018-02-08 |
United States Patent
Application |
20180037966 |
Kind Code |
A1 |
HAYAKAWA; Yasuyuki ; et
al. |
February 8, 2018 |
GRAIN-ORIENTED ELECTRICAL STEEL SHEET AND METHOD FOR PRODUCING
SAME
Abstract
A grain-oriented electrical steel sheet having a composition
containing, in mass %, C: 0.005% or less, Si: 2.0% to 4.5%, and Mn:
0.5% or less, and also containing Sb and P in respective ranges
satisfying 0.01%.ltoreq.[% Sb].ltoreq.0.20% and 0.02%.ltoreq.[%
P].ltoreq.2.0.times.[% Sb], with a balance being Fe and incidental
impurities, wherein when the steel sheet is excited to 1.0 T at 50
Hz in a rolling transverse direction, a magnetizing force
(TD-H.sub.10) and an iron loss (TD-W.sub.10) are respectively
(TD-H.sub.10).gtoreq.200 A/m and (TD-W.sub.10).gtoreq.1.60 W/kg.
Thus, a grain-oriented electrical steel sheet having excellent
transformer core loss can be obtained industrially stably at low
cost.
Inventors: |
HAYAKAWA; Yasuyuki;
(Chiyoda-ku, Tokyo, JP) ; SENDA; Kunihiro;
(Chiyoda-ku, Tokyo, JP) ; TERASHIMA; Takashi;
(Chiyoda-ku, Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JFE STEEL CORPORATION |
Chiyoda-ku, Tokyo |
|
JP |
|
|
Assignee: |
JFE STEEL CORPORATION
Chiyoda-ku, Tokyo
JP
|
Family ID: |
56614355 |
Appl. No.: |
15/549578 |
Filed: |
February 13, 2015 |
PCT Filed: |
February 13, 2015 |
PCT NO: |
PCT/JP2015/000685 |
371 Date: |
August 8, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22C 38/60 20130101;
C21D 8/1283 20130101; C22C 38/02 20130101; C22C 38/08 20130101;
C22C 38/06 20130101; C22C 38/12 20130101; C21D 8/1266 20130101;
C22C 38/00 20130101; H01F 1/16 20130101; C21D 6/008 20130101; C21D
9/46 20130101; C22C 38/004 20130101; C22C 38/001 20130101; C22C
38/002 20130101; C22C 38/34 20130101; C21D 6/005 20130101; C21D
8/1233 20130101; C21D 8/1222 20130101; C21D 8/1272 20130101; C22C
38/008 20130101; C22C 38/04 20130101; C22C 38/16 20130101; C21D
8/1238 20130101 |
International
Class: |
C21D 9/46 20060101
C21D009/46; C21D 6/00 20060101 C21D006/00; C22C 38/00 20060101
C22C038/00; C22C 38/04 20060101 C22C038/04; C22C 38/06 20060101
C22C038/06; C22C 38/02 20060101 C22C038/02; C21D 8/12 20060101
C21D008/12; C22C 38/60 20060101 C22C038/60 |
Claims
1. A grain-oriented electrical steel sheet having a composition
containing, in mass %, C: 0.005% or less, Si: 2.0% to 4.5%, and Mn:
0.5% or less, and also containing Sb and P in respective ranges
satisfying 0.01%.ltoreq.[% Sb].ltoreq.0.20% and 0.02%.ltoreq.[%
P].ltoreq.2.0.times.[% Sb], with a balance being Fe and incidental
impurities, wherein when the steel sheet is excited to 1.0 T at 50
Hz in a rolling transverse direction, a magnetizing force
(TD-H.sub.10) and an iron loss (TD-W.sub.10) are respectively
(TD-H.sub.10).gtoreq.200 A/m and (TD-W.sub.10).gtoreq.1.60
W/kg.
2. The grain-oriented electrical steel sheet according to claim 1,
wherein the composition further contains, in mass %, one or more
selected from Ni: 0.005% to 1.50%, Sn: 0.03% to 0.20%, Cu: 0.02% to
0.50%, Cr: 0.02% to 0.50%, Mo: 0.01% to 0.50%, and Nb: 0.002% to
0.01%.
3. A method for producing a grain-oriented electrical steel sheet,
comprising: providing a steel slab having a composition containing,
in mass %, C: 0.08% or less, Si: 2.0% to 4.5%, and Mn: 0.5% or
less, containing each of S, Se, and O: less than 50 ppm, N: less
than 60 ppm, and sol.Al: less than 100 ppm, and also containing Sb
and P in respective ranges satisfying 0.01%.ltoreq.[%
Sb].ltoreq.0.20% and 0.02%.ltoreq.[% P].ltoreq.2.0.times.[% Sb],
with a balance being Fe and incidental impurities; optionally
reheating the steel slab; thereafter hot rolling the steel slab to
obtain a hot rolled sheet; optionally hot band annealing the hot
rolled sheet; thereafter cold rolling the hot rolled sheet either
once, or twice or more with intermediate annealing performed
therebetween, to obtain a cold rolled sheet having a final sheet
thickness; thereafter performing decarburization and primary
recrystallization annealing on the cold rolled sheet, to obtain a
decarburization and primary recrystallization annealed sheet;
thereafter applying an annealing separator mainly composed of MgO
to the decarburization and primary recrystallization annealed
sheet; thereafter performing secondary recrystallization annealing
on the decarburization and primary recrystallization annealed
sheet, to obtain a secondary recrystallization annealed sheet; and
further performing flattening annealing on the secondary
recrystallization annealed sheet, wherein 2.0 mass % to 15.0 mass %
magnesium sulfate is contained in the annealing separator, the
flattening annealing is performed at a temperature of 830.degree.
C. or more in an atmosphere having a H.sub.2 partial pressure of
0.3% or more, and when the steel sheet is excited to 1.0 T at 50 Hz
in a rolling transverse direction, a magnetizing force
(TD-H.sub.10) and an iron loss (TD-W.sub.10) are respectively
(TD-H.sub.10).gtoreq.200 A/m and (TD-W.sub.10).gtoreq.1.60 W/kg.
Description
TECHNICAL FIELD
[0001] The disclosure relates to a grain-oriented electrical steel
sheet having excellent iron loss property and a method for
producing the grain-oriented electrical steel sheet, and is
particularly intended to obtain a grain-oriented electrical steel
sheet having excellent magnetic property at low cost.
BACKGROUND
[0002] A grain-oriented electrical steel sheet is a soft magnetic
material used as an iron core material of a transformer or
generator, and has crystal texture in which <001> orientation
which is the easy magnetization axis of iron is highly accumulated
into the rolling direction of the steel sheet. Such texture is
formed through secondary recrystallization of preferentially
causing the growth of giant crystal grains in (110)[001]
orientation which is called Goss orientation, when secondary
recrystallization annealing is performed in the process of
producing the grain-oriented electrical steel sheet.
[0003] A conventional process of producing such a grain-oriented
electrical steel sheet is as follows.
[0004] A slab containing about 4.5 mass % or less Si and an
inhibitor component such as MnS, MnSe, and AlN is heated to
1300.degree. C. or more to dissolve the inhibitor component. The
slab is then hot rolled, and optionally hot band annealed. The hot
rolled sheet is then cold rolled once, or twice or more with
intermediate annealing therebetween, to final sheet thickness. The
cold rolled sheet is then subjected to primary recrystallization
annealing in a wet hydrogen atmosphere, to perform primary
recrystallization and decarburization. After this, an annealing
separator having magnesia (MgO) as a main ingredient is applied to
the primary recrystallization annealed sheet, and then final
annealing is performed at 1200.degree. C. for about 5 h to develop
secondary recrystallization and purify the inhibitor component (for
example, the specification of U.S. Pat. No. 1,965,559 A (PTL 1), JP
S40-15644 B2 (PTL 2), and JP S51-13469 B2 (PTL 3)).
CITATION LIST
Patent Literatures
[0005] PTL 1: U.S. Pat. No. 1,965,559 A
[0006] PTL 2: JP S40-15644 B2
[0007] PTL 3: JP S51-13469 B2
[0008] PTL 4: JP 2000-129356 A
[0009] PTL 5: JP 2004-353036 A
SUMMARY
Technical Problem
[0010] As described above, the grain-oriented electrical steel
sheet is conventionally manufactured by the process of containing a
precipitate (inhibitor component) such as MnS, MnSe, and AlN in the
slab stage, heating the slab at a high temperature exceeding
1300.degree. C. to dissolve the inhibitor component, and causing
fine precipitation in the subsequent step to develop secondary
recrystallization. Thus, high-temperature slab heating exceeding
1300.degree. C. is necessary in the conventional grain-oriented
electrical steel sheet manufacturing process, which requires very
high manufacturing cost. The conventional process therefore has a
problem of being unable to meet the recent demands to reduce
manufacturing costs.
[0011] To solve this problem, a technique (inhibitorless method)
for enabling secondary recrystallization without containing any
inhibitor component was developed in JP 2000-129356 A (PTL 4). This
method involves a completely different technical idea from that of
the conventional grain-oriented electrical steel sheet producing
method.
[0012] In detail, while the conventional grain-oriented electrical
steel sheet producing method develops secondary recrystallization
using a precipitate (inhibitor) such as MnS, AlN, and MnSe, the
inhibitorless method develops secondary recrystallization by
texture (texture control) through high purification without using
such an inhibitor. The inhibitorless method does not require
high-temperature slab heating and high-temperature and
long-duration secondary recrystallization annealing, and so enables
the manufacture of the grain-oriented electrical steel sheet at low
cost.
[0013] However, the inhibitorless method cannot necessarily achieve
sufficient magnetic property and stability, although it is
advantageous in that the grain-oriented electrical steel sheet can
be manufactured at low cost.
[0014] To solve this problem, we further studied the technique of
developing secondary recrystallization without containing any
inhibitor component in the slab. As a result, we developed and
proposed a technique (sulfurization method) that can stably develop
secondary recrystallization by increasing the amount of S in the
steel substrate after the primary recrystallization annealing and
before the completion of secondary recrystallization, even in the
case where no inhibitor component is contained in the slab (JP
2004-353036 A (PTL 5)).
[0015] By increasing the amount of S in the steel substrate using
the sulfurization method, the amount of S segregating to grain
boundaries increases, as a result of which the movement of grain
boundaries surrounding orientations other than the Goss orientation
is further suppressed. This stabilizes secondary recrystallization,
and enhances the sharpness of secondary grains to the Goss
orientation, with it being possible to improve magnetic
property.
[0016] However, there is a problem in that the addition of a large
amount of sulfurization agent causes excessive oxidation reaction
during the secondary recrystallization annealing, and leads to the
formation of a base film defective part called sparkle or
frost.
[0017] As is well known, grain-oriented electrical steel sheets are
mainly used as transformer iron cores. Transformers are broadly
classified into stacked iron core transformers and wound iron core
transformers, depending on their iron core structures.
[0018] A stacked iron core transformer has an iron core formed by
stacking steel sheets cut to a desired shape. A wound iron core
transformer has an iron core formed by winding a steel strip slit
to a desired width. As large-capacity transformers, stacked iron
core transformers are used exclusively.
[0019] An important property required of transformers is
transformer core loss. Transformer core loss is energy loss when a
transformer iron core is excited. Higher transformer core loss
leads to higher power loss, and so transformer core loss needs to
be as low as possible.
[0020] However, iron loss can degrade as a result of processing a
steel sheet into a transformer.
[0021] For example, there are instances where low iron loss cannot
be maintained when pinch rolls for conveying the steel sheet or
measuring rolls for measuring the length of the steel sheet are
pressed against the steel sheet.
[0022] In such instances, even when a transformer is formed using a
steel sheet whose iron loss is lowered by a magnetic domain
refining effect such as a linear flaw, its iron loss value may not
be as low as expected. Particularly in the case of using the steel
sheet for a stacked iron core transformer, stress relief annealing
is not performed after processing the steel sheet into the iron
core, and so problems such as degraded iron loss and increased
noise can arise.
[0023] The conventional technique of adding a sulfurization agent
has difficulty in forming the base film, and therefore has a
problem in that the influence of strain associated with processing
into a transformer is significant and transformer core loss
degrades.
[0024] It could be helpful to propose a grain-oriented electrical
steel sheet that has excellent magnetic property and can be
produced at low cost with no need for high-temperature slab heating
and whose transformer core loss is effectively improved by reducing
the influence of strain associated with processing into a
transformer, and an advantageous method for producing the
grain-oriented electrical steel sheet.
Solution to Problem
[0025] We closely examined the technique of developing secondary
recrystallization without containing any inhibitor component in a
slab and improving magnetic property by sulfurization
treatment.
[0026] As a result, we developed a technique that can stably
realize favorable base film formation by optimizing material
components even in the case where sulfurization treatment is
performed.
[0027] The following describes the experimental results that led to
the disclosure. In the following description, "%" with regard to
components denotes mass % unless otherwise stated.
Experiment 1
[0028] A silicon steel slab containing, in mass %, Si: 3.3%, C:
0.03%, Mn: 0.07%, S: 0.002%, Al: 0.006%, and N: 0.003% and further
containing P and Sb in the ranges of P: 0% to 0.2% and Sb: 0% to
0.2% was heated at 1220.degree. C. for 30 minutes, and then hot
rolled to obtain a hot rolled sheet of 2.5 mm in thickness. The hot
rolled sheet was hot band annealed at 1025.degree. C. for 1 minute,
and then cold rolled to final sheet thickness.
[0029] Following this, the cold rolled sheet was primary
recrystallization annealed, and then an annealing separator having
MgO as a main ingredient and containing 10% magnesium sulfate was
applied at 12.5 g/m.sup.2 to the primary recrystallized sheet and
dried. The primary recrystallized sheet was then secondary
recrystallization annealed under the following condition: heating
rate: 15.degree. C./h, atmosphere gas: N.sub.2 gas up to
900.degree. C., and H.sub.2 gas at 900.degree. C. or more, and
soaking treatment: 1160.degree. C. for 5 h.
[0030] FIG. 1 illustrates the result of studying the relationship
between the additive amount of P, the additive amount of Sb, and
the magnetic flux density.
[0031] As illustrated in FIG. 1, in the case of adding P singly,
the magnetic flux density improving effect was poor, and rather the
magnetic flux density tended to degrade by the addition of P. In
the case of adding Sb, the magnetic flux density increased with the
addition of P until the additive amount of P reached the additive
amount of Sb, and gradually decreased once the additive amount of P
exceeded the additive amount of Sb. This demonstrates that the
magnetic flux density improving effect by the addition of P is
achieved by adding Sb up to about the same amount as P.
[0032] Although the effect of adding P and Sb in combination is not
clear, we assume the following:
[0033] P is a grain boundary segregation element, and has a
function of suppressing recrystallization nucleation from the grain
boundaries and facilitating recrystallization nucleation from
inside the grains to increase the Goss orientation in the primary
recrystallized texture. P thus has an effect of stabilizing
secondary recrystallization nucleation and improving magnetic
property. However, the addition of P has an adverse effect of
facilitating surface oxidation during the secondary
recrystallization annealing and hindering the sulfurization effect
and also hindering normal base film formation.
[0034] Sb is a surface segregation element, and has a function of
suppressing oxidation during the secondary recrystallization
annealing to optimize the oxidation quantity and stabilize
secondary recrystallization and base film formation. Sb thus has an
effect of lessening the adverse effect of the addition of P.
[0035] Accordingly, adding Sb and P in combination is very
effective in achieving the aforementioned texture improving effect
by the addition of P.
[0036] The phenomenon of improving magnetic property by
sulfurization is specific to the case where the steel slab contains
no inhibitor component. In the case where there is no inhibitor
(precipitate) such as AlN and MnS in the steel, the grain
boundaries surrounding the Goss-oriented grains in the primary
recrystallized texture have higher mobility than the grain
boundaries surrounding the grains in the other orientations, as a
result of which the Goss orientation undergoes preferential growth
(secondary recrystallization).
[0037] Although the reason why magnetic property is improved by
increasing the amount of S in the steel substrate after primary
recrystallization is not clear, we assume the following:
[0038] When the amount of S in the steel substrate is increased,
the amount of S segregating to grain boundaries increases, as a
result of which the movement of the grain boundaries surrounding
the orientations other than the Goss orientation is further
suppressed. This stabilizes secondary recrystallization, and
enhances the sharpness of secondary grains to the Goss orientation.
The coexistence of P and S which are elements having a strong
tendency to segregate to grain boundaries further enhances the
magnetic property improving effect.
[0039] Moreover, regarding the method of reducing the influence of
strain associated with processing into a transformer, we studied
the condition of the flattening annealing atmosphere, and
discovered that the magnetic property in the rolling transverse
direction (the direction orthogonal to the rolling direction)
changes, and there is a very high correlation between the magnetic
property in the transverse direction and the influence of strain
associated with processing into a transformer.
[0040] We then discovered a preferable range of the magnetic
property in the transverse direction effective in reducing the
influence of strain, as described below.
Experiment 2
[0041] A silicon steel slab containing, in mass %, Si: 3.3%, C:
0.03%, Mn: 0.07%, S: 0.002%, Al: 0.006%, N: 0.003%, P: 0.05%, and
Sb: 0.05% was heated at 1220.degree. C. for 30 minutes, and then
hot rolled to obtain a hot rolled sheet of 2.5 mm in thickness. The
hot rolled sheet was hot band annealed at 1025.degree. C. for 1
minute, and then cold rolled to final sheet thickness.
[0042] Following this, the cold rolled sheet was primary
recrystallization annealed, and then an annealing separator having
MgO as a main ingredient and containing 10% magnesium sulfate was
applied at 12.5 g/m.sup.2 to the primary recrystallized sheet and
dried. The primary recrystallized sheet was then secondary
recrystallization annealed under the following condition: heating
rate: 15.degree. C./h, atmosphere gas: N.sub.2 gas up to
900.degree. C., and H.sub.2 gas at 900.degree. C. or more, and
soaking treatment: 1160.degree. C. for 5 h.
[0043] Further, an insulating coating mainly composed of colloidal
silica and magnesium phosphate was applied. An experiment of
changing the soaking temperature (soaking time of 10 s) and the
H.sub.2 partial pressure (the rest being N.sub.2 atmosphere) in the
annealing atmosphere in flattening annealing was then conducted
under the conditions shown in Table 1.
[0044] The magnetic property of the obtained product in each of the
rolling direction and the transverse direction was measured. In the
rolling direction, the iron loss (W.sub.17/50) when exciting the
product to 1.7 T at 50 Hz was measured. In the transverse
direction, the magnetizing force (TD-H.sub.10) and iron loss
(TD-W.sub.10) when exciting the product to 1.0 T at 50 Hz were
measured. Strain sensitivity was evaluated based on the change
(.DELTA.W) in iron loss W.sub.17/50 value when passing the sheet
while pressing it by measuring rolls, which were made up of steel
rolls of 100 mm in diameter and 50 mm in width, with a rolling
reduction force of 1.5 MPa (15 kgf/cm).
[0045] Table 1 shows the obtained results.
TABLE-US-00001 TABLE 1 Annealing H.sub.2 partial temperature
pressure TD-H.sub.10 TD-W.sub.10 W.sub.17/50 .DELTA.W No. (.degree.
C.) (%) (A/m) (W/kg) (W/kg) (W/kg) 1 780 0.5 172 1.01 0.945 0.055 2
790 0.5 180 1.05 0.935 0.035 3 800 0.5 192 1.11 0.912 0.018 4 810
0.5 202 1.17 0.900 0.006 5 820 0.5 240 1.33 0.892 0.003 6 830 0.5
253 1.63 0.882 0.003 7 840 0.5 255 1.72 0.874 0.004 8 850 0.5 260
1.95 0.871 0.003 9 860 0.5 258 1.98 0.875 0.002 10 850 0 156 1.94
0.883 0.102 11 850 0.1 191 1.93 0.880 0.020 12 850 0.2 222 1.96
0.873 0.005 13 850 0.5 260 1.95 0.871 0.001 14 850 1 258 1.93 0.874
0.003 15 850 3 256 1.95 0.871 0.002 16 850 5 265 1.94 0.868 0.001
17 850 10 260 1.94 0.873 0.003
[0046] FIGS. 2A and 2B summarize the influence of the flattening
annealing temperature on the iron loss (W.sub.17/50) in the rolling
direction and the influence of the H.sub.2 partial pressure in the
annealing atmosphere on the iron loss (W.sub.17/50) in the rolling
direction.
[0047] As illustrated in FIGS. 2A and 2B, the flattening annealing
temperature significantly influences the iron loss (W.sub.17/50) in
the rolling direction, and needs to be 830.degree. C. or more to
improve the iron loss. Meanwhile, the H.sub.2 partial pressure in
the flattening annealing atmosphere hardly influences the iron loss
(W.sub.17/50).
[0048] FIGS. 3A and 3B summarize the influence of the flattening
annealing temperature on the iron loss degradation (.DELTA.W) upon
measuring roll rolling reduction and the influence of the H.sub.2
partial pressure in the annealing atmosphere on the iron loss
degradation (.DELTA.W) upon measuring roll rolling reduction.
[0049] As illustrated in FIGS. 3A and 3B, the flattening annealing
temperature significantly influences the iron loss degradation
(.DELTA.W) upon measuring roll rolling reduction, and needs to be
820.degree. C. or more to reduce the iron loss degradation. The
H.sub.2 partial pressure in the flattening annealing atmosphere
also significantly influences the iron loss degradation (.DELTA.W),
and the iron loss degradation (.DELTA.W) upon measuring roll
rolling reduction is very high in the case where the hydrogen
atmosphere is not introduced.
[0050] FIGS. 4A and 4B summarize the influence of the flattening
annealing temperature on the iron loss (TD-W.sub.10) in the
transverse direction and the influence of the H.sub.2 partial
pressure in the annealing atmosphere on the iron loss (TD-W.sub.10)
in the transverse direction.
[0051] As illustrated in FIGS. 4A and 4B, the flattening annealing
temperature significantly influences the iron loss (TD-W.sub.10) in
the transverse direction, and a higher flattening annealing
temperature increases the iron loss (TD-W.sub.10) in the transverse
direction. Meanwhile, the H.sub.2 partial pressure in the
flattening annealing atmosphere hardly influences the iron loss
(TD-W.sub.10) in the transverse direction.
[0052] FIGS. 5A and 5B summarize the influence of the flattening
annealing temperature on the magnetizing force (TD-H.sub.10) in the
transverse direction and the influence of the H.sub.2 partial
pressure in the annealing atmosphere on the magnetizing force
(TD-H.sub.10) in the transverse direction.
[0053] As illustrated in FIGS. 5A and 5B, the flattening annealing
temperature significantly influences the magnetizing force
(TD-H.sub.10) in the transverse direction, and a higher flattening
annealing temperature increases the magnetizing force (TD-H.sub.10)
in the transverse direction. The hydrogen atmosphere also
significantly influences the magnetizing force (TD-H.sub.10) in the
transverse direction, and the magnetizing force (TD-H.sub.10) in
the transverse direction decreases in the case where the hydrogen
atmosphere is not introduced.
[0054] The aforementioned experiment revealed that the flattening
annealing temperature and the hydrogen partial pressure in the
flattening annealing atmosphere influenced the iron loss
(W.sub.17/50) in the rolling direction, the iron loss degradation
(.DELTA.W) upon measuring roll rolling reduction, the iron loss
(TD-W.sub.10) in the transverse direction, and the magnetizing
force (TD-H.sub.10) in the transverse direction. We then studied
their correlations.
[0055] FIG. 6 illustrates the result of studying the relationship
between the iron loss (TD-W.sub.10) in the transverse direction and
the iron loss (W.sub.17/50) in the rolling direction.
[0056] As illustrated in FIG. 6, when the iron loss in the
transverse direction increases, the iron loss in the rolling
direction decreases. Setting the iron loss (TD-W.sub.10) in the
transverse direction to 1.6 W/kg or more is effective in improving
the iron loss (W.sub.17/50) in the rolling direction. As
illustrated in FIG. 4A, the iron loss in the transverse direction
increases with an increase in flattening annealing temperature. In
the case where there is residual strain by shape adjustment, the
stability of the 180.degree. magnetic domain structure decreases,
which is likely to cause an increase in iron loss in the transverse
direction.
[0057] In other words, the iron loss in the transverse direction
serves as an index of residual strain.
[0058] The results in FIGS. 6 and 4A indicate that, to improve the
iron loss in the rolling direction, the flattening annealing
temperature needs to be 830.degree. C. or more so that the iron
loss in the transverse direction is 1.6 W/kg or more.
[0059] FIG. 7 illustrates the relationship between the magnetizing
force (TD-H.sub.10) in the transverse direction and the iron loss
degradation (.DELTA.W) in the rolling direction.
[0060] As illustrated in FIG. 7, when the magnetizing force in the
transverse direction increases, the iron loss degradation
(.DELTA.W) upon measuring roll rolling reduction decreases. The
magnetizing force in the transverse direction increases by
increasing the flattening annealing temperature and introducing the
hydrogen atmosphere, as illustrated in FIGS. 5A and 5B.
[0061] In other words, the magnetizing force in the transverse
direction serves as an index of film tension.
[0062] The results in FIGS. 7 and 5A and 5B indicate that, to limit
the iron loss degradation (.DELTA.W) upon measuring roll rolling
reduction to a low level of 0.01 W/kg or less, the flattening
annealing temperature needs to be 810.degree. C. or more and
preferably 830.degree. C. or more and 0.30% or more hydrogen needs
to be introduced into the flattening annealing atmosphere so that
the magnetizing force (TD-H.sub.10) in the transverse direction is
200 A/m or more.
[0063] It is assumed that, by increasing the flattening annealing
temperature and introducing the hydrogen atmosphere, the water
content in the coating mainly composed of phosphate is reduced to
strengthen the coating film tension.
[0064] The disclosure is based on the results of the two
experiments described above and further studies.
[0065] In detail, we provide the following:
[0066] 1. A grain-oriented electrical steel sheet having a
composition containing (consisting of), in mass %, C: 0.005% or
less, Si: 2.0% to 4.5%, and Mn: 0.5% or less, and also containing
Sb and P in respective ranges satisfying 0.01%.ltoreq.[%
Sb].ltoreq.0.20% and 0.02%.ltoreq.[% P].ltoreq.2.0.times.[% Sb],
with a balance being Fe and incidental impurities,
[0067] wherein when the steel sheet is excited to 1.0 T at 50 Hz in
a rolling transverse direction, a magnetizing force (TD-H.sub.10)
and an iron loss (TD-W.sub.10) are respectively
(TD-H.sub.10).gtoreq.200 A/m and (TD-W.sub.10).gtoreq.1.60
W/kg.
[0068] 2. The grain-oriented electrical steel sheet according to 1,
wherein the composition further contains, in mass %, one or more
selected from Ni: 0.005% to 1.50%, Sn: 0.03% to 0.20%, Cu: 0.02% to
0.50%, Cr: 0.02% to 0.50%, Mo: 0.01% to 0.50%, and Nb: 0.002% to
0.01%.
[0069] 3. A method for producing a grain-oriented electrical steel
sheet, comprising:
[0070] providing a steel slab having a composition containing, in
mass %, C: 0.08% or less, Si: 2.0% to 4.5%, and Mn: 0.5% or less,
containing each of S, Se, and O: less than 50 ppm, N: less than 60
ppm, and sol.Al: less than 100 ppm, and also containing Sb and P in
respective ranges satisfying 0.01%.ltoreq.[% Sb].ltoreq.0.20% and
0.02%.ltoreq.[% P].ltoreq.2.0.times.[% Sb], with a balance being Fe
and incidental impurities;
[0071] optionally reheating the steel slab;
[0072] thereafter hot rolling the steel slab to obtain a hot rolled
sheet;
[0073] optionally hot band annealing the hot rolled sheet;
[0074] thereafter cold rolling the hot rolled sheet either once, or
twice or more with intermediate annealing performed therebetween,
to obtain a cold rolled sheet having a final sheet thickness;
[0075] thereafter performing decarburization and primary
recrystallization annealing on the cold rolled sheet, to obtain a
decarburization and primary recrystallization annealed sheet;
[0076] thereafter applying an annealing separator mainly composed
of MgO to the decarburization and primary recrystallization
annealed sheet;
[0077] thereafter performing secondary recrystallization annealing
on the decarburization and primary recrystallization annealed
sheet, to obtain a secondary recrystallization annealed sheet;
and
[0078] further performing flattening annealing on the secondary
recrystallization annealed sheet,
[0079] wherein 2.0 mass % to 15.0 mass % magnesium sulfate is
contained in the annealing separator,
[0080] the flattening annealing is performed at a temperature of
830.degree. C. or more in an atmosphere having a H.sub.2 partial
pressure of 0.3% or more, and
[0081] when the steel sheet is excited to 1.0 T at 50 Hz in a
rolling transverse direction, a magnetizing force (TD-H.sub.10) and
an iron loss (TD-W.sub.10) are respectively
(TD-H.sub.10).gtoreq.200 A/m and (TD-W.sub.10).gtoreq.1.60
W/kg.
Advantageous Effect
[0082] It is thus possible to produce a grain-oriented electrical
steel sheet having excellent transformer core loss industrially
stably at low cost, which is of great industrial value.
BRIEF DESCRIPTION OF THE DRAWINGS
[0083] In the accompanying drawings:
[0084] FIG. 1 is a graph illustrating the relationship between the
additive amount of P, the additive amount of Sb, and the magnetic
flux density;
[0085] FIG. 2A is a graph illustrating the influence of the
flattening annealing temperature on the iron loss (W.sub.17/50) in
the rolling direction;
[0086] FIG. 2B is a graph illustrating the influence of the H.sub.2
partial pressure in the annealing atmosphere on the iron loss
(W.sub.17/50) in the rolling direction;
[0087] FIG. 3A is a graph illustrating the influence of the
flattening annealing temperature on the iron loss degradation
(.DELTA.W) upon measuring roll rolling reduction;
[0088] FIG. 3B is a graph illustrating the influence of the H.sub.2
partial pressure in the annealing atmosphere on the iron loss
degradation (.DELTA.W) upon measuring roll rolling reduction;
[0089] FIG. 4A is a graph illustrating the influence of the
flattening annealing temperature on the iron loss (TD-W.sub.10) in
the transverse direction;
[0090] FIG. 4B is a graph illustrating the influence of the H.sub.2
partial pressure in the annealing atmosphere on the iron loss
(TD-W.sub.10) in the transverse direction;
[0091] FIG. 5A is a graph illustrating the influence of the
flattening annealing temperature on the magnetizing force
(TD-H.sub.10) in the transverse direction;
[0092] FIG. 5B is a graph illustrating the influence of the H.sub.2
partial pressure in the annealing atmosphere on the magnetizing
force (TD-H.sub.10) in the transverse direction;
[0093] FIG. 6 is a graph illustrating the relationship between the
iron loss (TD-W.sub.10) in the transverse direction and the iron
loss (W.sub.17/50) in the rolling direction; and
[0094] FIG. 7 is a graph illustrating the relationship between the
magnetizing force (TD-H.sub.10) in the transverse direction and the
iron loss degradation (.DELTA.W) in the rolling direction.
DETAILED DESCRIPTION
[0095] One of the disclosed embodiments is described in detail
below.
[0096] The reasons for limiting the chemical composition of a steel
slab to the aforementioned range in this embodiment are described
first.
C: 0.08% or less
[0097] C is an element useful in improving primary recrystallized
texture. If the C content is more than 0.08%, however, the primary
recrystallized texture degrades. The C content is therefore limited
to 0.08% or less. The C content is desirably in the range of 0.01%
to 0.06%, in terms of magnetic property. In the case where the
required level of magnetic property is not so high, the C content
may be 0.01% or less in order to omit or simplify decarburization
in primary recrystallization annealing.
[0098] Moreover, it is essential to reduce the C content to 0.005%
or less in the steel sheet after final annealing, in order to
prevent magnetic aging.
[0099] Si: 2.0% to 4.5%
[0100] Si is an element useful in improving iron loss by increasing
electrical resistance, and so the Si content is 2.0% or more. If
the Si content is more than 4.5%, however, cold rolling
manufacturability decreases significantly. The upper limit of the
Si content is therefore 4.5%. The addition of Si may be omitted
depending on the required iron loss level.
[0101] Mn: 0.5% or less
[0102] Mn has an effect of improving hot workability during
manufacture.
[0103] If the Mn content is more than 0.5%, however, the primary
recrystallized texture deteriorates and leads to lower magnetic
property. The Mn content is therefore limited to 0.5% or less. The
lower limit of the Mn content is preferably 0.05%.
[0104] S, Se, and O: less than 50 ppm each
[0105] If the content of each of S, Se, and O is 50 ppm or more,
secondary recrystallization is difficult. This is because a coarse
oxide or MnS or MnSe coarsened due to slab heating makes the
primary recrystallized texture non-uniform. The content of each of
S, Se, and O is therefore limited to less than 50 ppm.
[0106] N: less than 60 ppm
[0107] Excessive N also makes secondary recrystallization
difficult, as with S, Se, and O. Particularly if the N content is
60 ppm or more, secondary recrystallization is unlikely to occur,
and the magnetic property degrades. The N content is therefore
limited to less than 60 ppm.
[0108] sol.Al: less than 100 ppm
[0109] Excessive Al also makes secondary recrystallization
difficult. Particularly if the sol.Al content is 100 ppm or more,
secondary recrystallization is unlikely to occur under the
low-temperature slab heating condition, and the magnetic property
degrades. Al is therefore limited to less than 100 ppm in sol.Al
content.
[0110] Sb and P: 0.01%.ltoreq.[% Sb].ltoreq.0.20% and
0.02%.ltoreq.[% P].ltoreq.2.0.times.[% Sb] respectively
[0111] In this embodiment, it is important to contain Sb and P in
combination in these respective ranges. By adding Sb and P in
combination in these ranges, the desired sulfurization effect in
this embodiment is effectively achieved, and magnetic property
degradation due to surface oxidation is suppressed. As a result,
favorable magnetic property and base film property can be obtained
throughout the coil length. If the Sb content or the P content is
less than the aforementioned range, the effect cannot be achieved.
If the Sb content or the P content is more than the aforementioned
range, not only the magnetic property degrades, but also the
formation of the base film is difficult.
[0112] While the essential components have been described above,
the following elements may be contained as appropriate as
components for improving the magnetic property industrially more
stably in this embodiment.
Ni: 0.005% to 1.50%
[0113] Ni has a function of improving the magnetic property by
enhancing the uniformity of the hot rolled sheet texture. To do so,
the Ni content is preferably 0.005% or more. If the Ni content is
more than 1.50%, secondary recrystallization is difficult, and the
magnetic property degrades. Accordingly, the Ni content is
desirably in the range of 0.005% to 1.50%.
[0114] Sn: 0.03% to 0.20%
[0115] Sn has a function of suppressing the nitriding or oxidation
of the steel sheet during secondary recrystallization annealing and
promoting the secondary recrystallization of crystal grains having
favorable crystal orientation to effectively improve the magnetic
property, in particular the iron loss property. To do so, the Sn
content is preferably 0.03% or more. If the Sn content is more than
0.20%, cold rolling manufacturability decreases. Accordingly, the
Sn content is desirably in the range of 0.03% to 0.20%.
[0116] Cu: 0.02% to 0.50%
[0117] Cu is a useful element that suppresses the nitriding or
oxidation of the steel sheet during secondary recrystallization
annealing and promotes the secondary recrystallization of crystal
grains having favorable crystal orientation to effectively improve
the magnetic property. To do so, the Cu content is preferably 0.02%
or more. If the Cu content is more than 0.50%, cold rolling
manufacturability decreases. Accordingly, the Cu content is
desirably in the range of 0.02% to 0.50%.
[0118] Cr: 0.02% to 0.50%
[0119] Cr has a function of stabilizing the formation of the
forsterite base film. To do so, the Cr content is preferably 0.02%
or more. If the Cr content is more than 0.50%, secondary
recrystallization is difficult, and the magnetic property degrades.
Accordingly, the Cr content is desirably in the range of 0.02% to
0.50%.
[0120] Mo: 0.01% to 0.50%
[0121] Mo has a function of suppressing high-temperature oxidation
and reducing surface defects called scab. To do so, the Mo content
is preferably 0.01% or more. If the Mo content is more than 0.50%,
cold rolling manufacturability decreases. Accordingly, the Mo
content is desirably in the range of 0.01% to 0.50%.
[0122] Nb: 0.002% to 0.01%
[0123] Nb is a useful element that inhibits the growth of primary
recrystallized grains and promotes the secondary recrystallization
of crystal grains having favorable crystal orientation to improve
the magnetic property. To do so, the Nb content is desirably 0.002%
or more. If the Nb content is more than 0.01%, Nb remains in the
steel substrate and degrades the iron loss. Accordingly, the Nb
content is desirably in the range of 0.002% to 0.01%.
[0124] The following describes a production method in this
embodiment.
[0125] A steel slab adjusted to the aforementioned chemical
composition range is, after or without being reheated, hot rolled.
In the case of reheating the slab, the reheating temperature is
desirably about 1000.degree. C. or more and 1300.degree. C. or
less. Slab heating exceeding 1300.degree. C. is meaningless in this
embodiment in which the slab contains no inhibitor, and not only
causes an increase in cost but also significantly degrades the
magnetic property due to the growth of giant crystal grains. If the
reheating temperature is less than 1000.degree. C., the rolling
load increases, making the rolling difficult.
[0126] Following this, the hot rolled sheet is optionally hot band
annealed. The hot rolled sheet is then cold rolled once, or twice
or more with intermediate annealing therebetween, to obtain a final
cold rolled sheet. The cold rolling may be performed at normal
temperature. Alternatively, the cold rolling may be warm rolling
with the steel sheet temperature being higher than normal
temperature, e.g. about 250.degree. C.
[0127] The final cold rolled sheet is then subjected to
decarburization/primary recrystallization annealing. A first
objective of the decarburization/primary recrystallization
annealing is to cause the primary recrystallization of the cold
rolled sheet having rolled microstructure to adjust it to an
optimal primary recrystallized texture for secondary
recrystallization. For this objective, the annealing temperature in
the primary recrystallization annealing is desirably about
800.degree. C. or more and less than about 950.degree. C. The
annealing atmosphere is desirably a wet hydrogen nitrogen
atmosphere or a wet hydrogen argon atmosphere.
[0128] A second objective is decarburization. If more than 0.005%
carbon is contained in the product sheet, the iron loss degrades.
The carbon content is therefore desirably reduced to 0.005% or
less.
[0129] A third objective is to form a subscale made up of an
internal oxidation layer of SiO.sub.2 which is the raw material of
the base film mainly composed of forsterite. If the upstream-stage
temperature of decarburization annealing is less than 800.degree.
C., oxidation reaction and decarburization reaction do not progress
sufficiently, and necessary oxidation and decarburization cannot be
completed.
[0130] After the decarburization/primary recrystallization
annealing, an annealing separator mainly composed of magnesia (MgO)
is applied to the surface of the steel sheet. Here, magnesium
sulfate is added to the annealing separator mainly composed of MgO,
in order to improve the magnetic property by the sulfurization
treatment of increasing the amount of S in the steel substrate
after the primary recrystallization annealing and before the
completion of secondary recrystallization.
[0131] If the additive amount of magnesium sulfate is less than
2.0%, the magnetic property improving effect is insufficient. If
the additive amount of magnesium sulfate is more than 15.0%, the
grain growth is suppressed excessively, and the magnetic property
improving effect is insufficient and also the formation of the base
film is adversely affected.
[0132] The expression "mainly composed of magnesia" in this
embodiment means that 50% or more magnesia is contained in the
annealing separator. Sub-components such as Na.sub.2S.sub.2O.sub.3
and TiO.sub.2 may be added to the annealing separator in small
amounts, according to conventional methods.
[0133] After this, secondary recrystallization annealing is
performed. During the secondary recrystallization annealing,
magnesium sulfate decomposes and exerts the sulfurization effect,
thus realizing crystal texture highly aligned with the Goss
orientation. Favorable magnetic property can be obtained in this
way.
[0134] The secondary recrystallization annealing is effectively
performed by diffusing S into the steel substrate with a heating
rate of 30.degree. C./H or less, as disclosed in JP 4321120 B. The
annealing atmosphere may be any of N.sub.2, Ar, and mixed gas
thereof. Here, H.sub.2 is not used as atmosphere gas until the
completion of secondary recrystallization. This is because S in the
annealing separator goes out of the system as H.sub.2S (gas),
causing lower sulfurization effect especially in the coil
edges.
[0135] After the secondary recrystallization annealing, an
insulating coating is further applied to the surface of the steel
sheet and baked. The type of the insulating coating is not
particularly limited, and may be any conventionally well-known
insulating coating. For example, a method of applying an
application liquid containing phosphate-chromate-colloidal silica
described in JP S50-79442 A and JP S48-39338 A to the steel sheet
and baking it to also perform flattening annealing is
preferable.
[0136] Flattening annealing is then performed. This flattening
annealing is important in this embodiment.
[0137] The flattening annealing temperature needs to be 830.degree.
C. or more. If the flattening annealing temperature is less than
830.degree. C., strain for shape adjustment remains, which
decreases the iron loss in the TD direction and simultaneously
degrades the iron loss in the RD direction. The iron loss in the TD
direction for preventing degradation in the iron loss in the RD
direction in the product sheet is 1.60 W/kg or more.
[0138] Moreover, 0.30% or more hydrogen needs to be introduced into
the flattening annealing atmosphere. If the hydrogen partial
pressure in the atmosphere is less than 0.30%, the coating film
tension decreases, and the magnetizing force in the TD direction
decreases. This results in higher degradation of transformer core
loss due to the application of strain associated with processing
into a transformer. To reduce the iron loss degradation caused by
the application of strain associated with processing into a
transformer and improve the transformer core loss, the magnetizing
force when exciting the product sheet to 1.0 T in the TD direction
needs to be 200 A/m or more.
EXAMPLES
Example 1
[0139] A continuously cast slab having a composition containing C:
0.03%, Si: 3.5%, Mn: 0.08%, sol.Al: 75 ppm, N: 45 ppm, S: 30 ppm,
Se: 1 ppm, O: 9 ppm, P: 0.06%, and Sb: 0.10% with the balance being
Fe and incidental impurities was reheated to 1230.degree. C., and
then hot rolled to obtain a hot rolled sheet of 2.5 mm in sheet
thickness. The hot rolled sheet was then hot band annealed at
1050.degree. C. for 10 s, and subsequently cold rolled at
200.degree. C. to a sheet thickness of 0.27 mm. The cold rolled
sheet was then subjected to primary recrystallization annealing
also serving as decarburization at 850.degree. C. for 120 s in an
atmosphere of H.sub.2: 55%, N.sub.2: 45%, and dew point: 55.degree.
C., with the heating rate from 500.degree. C. to 700.degree. C.
being 20.degree. C./s. The C content after this annealing was 30
ppm.
[0140] A sample was collected from the obtained primary
recrystallization annealed sheet, and an annealing separator having
MgO as a main ingredient and containing magnesium sulfate in the
proportion shown in Table 2 was applied at 12.5 g/m.sup.2 to the
sheet surface and dried. The sample was then subjected to secondary
recrystallization annealing under the condition of heating to
800.degree. C. at a heating rate of 15.degree. C./h, heating from
800.degree. C. to 850.degree. C. at a heating rate of 2.0.degree.
C./h, retaining at 850.degree. C. for 50 h, and then heating to
1160.degree. C. at a heating rate of 5.0.degree. C./h and soaking
for 5 h. As the atmosphere gas, N.sub.2 gas was used up to
850.degree. C., and H.sub.2 gas was used at 850.degree. C. or
more.
[0141] A treatment liquid containing phosphate-chromate-colloidal
silica at a mass ratio of 3:1:3 was applied to the surface of the
secondary recrystallization annealed sheet obtained under the
aforementioned condition, and subsequently flattening annealing was
performed under the condition shown in Table 2.
[0142] The magnetic property of the obtained product sheet was then
examined. The magnetic property was evaluated based on the magnetic
flux density B.sub.8 when exciting the sheet at 800 A/m in the
rolling direction and the iron loss W.sub.17/50 when exciting the
sheet to 1.7 T at 50 Hz in an alternating magnetic field in the
rolling direction, the magnetizing force (TD-H.sub.10) and iron
loss (TD-W.sub.10) when exciting the sheet to 1.0 T at 50 Hz in the
transverse direction, and the strain sensitivity.
[0143] The strain sensitivity was evaluated based on the change
(.DELTA.W) in iron loss W.sub.17/50 value when passing the sheet
while pressing it by measuring rolls, which were made up of steel
rolls of 100 mm in diameter and 50 mm in width, with a rolling
reduction force of 1.5 MPa (15 kgf/cm).
[0144] Table 2 shows the obtained results. Magnetic flux density
B.sub.8 of 1.94 T or more, iron loss W.sub.17/50 of 0.82 W/kg or
less, and .DELTA.W of 0.005 W/kg or less are regarded as excellent
properties.
TABLE-US-00002 TABLE 2 Flattening annealing condition Additive
amount of Soaking H.sub.2 partial pressure in Magnetic property of
product sheet magnesium sulfate temperature atmosphere B.sub.8
W.sub.17/50 TD-H.sub.10 TD-W.sub.10 .DELTA.W No. (%) (.degree. C.)
(%) (T) (W/kg) (A/m) (W/kg) (W/kg) Remarks 1 2.5 850 3.0 1.943
0.812 271 1.903 0.005 Example 2 5.0 850 3.0 1.955 0.784 280 1.993
0.004 Example 3 10.0 850 3.0 1.960 0.775 290 2.011 0.003 Example 4
10.0 880 3.0 1.957 0.763 272 2.028 0.004 Example 5 0 850 3.0 1.911
0.880 188 1.774 0.023 Comparative Example 6 20.0 850 3.0 1.868
1.050 292 2.044 0.003 Comparative Example 7 5.0 800 3.0 1.953 0.883
280 1.503 0.004 Comparative Example 8 5.0 850 0 1.956 0.788 180
1.983 0.028 Comparative Example
[0145] As is clear from Table 2, by using the material containing P
and Sb in combination, applying the annealing separator mainly
composed of MgO and containing 2.0% or more magnesium sulfate, and
performing secondary recrystallization annealing according to the
disclosure, favorable magnetic flux density was obtained. Moreover,
by setting the flattening annealing temperature to 830.degree. C.
or more, the iron loss in the TD direction was 1.60 W/kg or more,
resulting in favorable iron loss in the rolling direction. Further,
by introducing 0.30% or more a hydrogen atmosphere into the
flattening annealing atmosphere, the magnetizing force when
exciting the sheet to 1.0 T in the transverse direction was ensured
to be 200 A/m or more, as a result of which the iron loss
degradation caused by the application of strain associated with
processing into a transformer was reduced.
Example 2
[0146] A continuously cast slab composed of various components
shown in Table 3 was reheated to 1230.degree. C., and then hot
rolled to obtain a hot rolled sheet of 2.2 mm in sheet thickness.
The hot rolled sheet was then hot band annealed at 1050.degree. C.
for 10 s, and subsequently cold rolled at 200.degree. C. to a sheet
thickness of 0.23 mm. The cold rolled sheet was then subjected to
decarburization annealing at 850.degree. C. for 120 s in an
atmosphere of H.sub.2: 55%, N.sub.2: 45%, and dew point: 55.degree.
C., with the heating rate from 500.degree. C. to 700.degree. C.
being 20.degree. C./s. The C content after the decarburization
annealing was 30 ppm.
[0147] A sample was collected from the decarburization annealed
sheet, and an annealing separator having MgO as a main ingredient
and containing magnesium sulfate in the proportion shown in Table 4
was applied at 12.5 g/m.sup.2 to the sheet surface and dried. The
sample was then subjected to secondary recrystallization annealing
under the condition of heating to 800.degree. C. at a heating rate
of 15.degree. C./h, heating from 800.degree. C. to 850.degree. C.
at a heating rate of 2.0.degree. C./h, retaining at 850.degree. C.
for 50 h, and then heating to 1160.degree. C. at a heating rate of
5.0.degree. C./h and soaking for 5 h. As the atmosphere gas,
N.sub.2 gas was used up to 850.degree. C., and H.sub.2 gas was used
at 850.degree. C. or more.
[0148] A treatment liquid containing phosphate-chromate-colloidal
silica at a mass ratio of 3:1:3 was applied to the surface of the
secondary recrystallization annealed sheet obtained under the
aforementioned condition, and subsequently flattening annealing was
performed under the condition shown in Table 4.
[0149] The magnetic property of the obtained product sheet was then
examined. The method of evaluating the magnetic property is the
same as that in Example 1.
[0150] Table 4 shows the obtained results.
TABLE-US-00003 TABLE 3 Chemical composition (mass %) No. C Si Mn Sb
P S Se O Al N Others Remarks 1 0.03 3.3 0.07 0.052 0.055 0.001
0.001 0.001 0.003 0.003 -- Conforming steel 2 0.04 3.2 0.08 0.066
0.075 0.002 0.001 0.001 0.004 0.002 Ni: 0.30 Conforming steel 3
0.02 3.2 0.08 0.036 0.055 0.002 0.001 0.001 0.004 0.002 Sn: 0.10
Conforming steel 4 0.03 3.4 0.11 0.044 0.045 0.001 0.001 0.001
0.005 0.003 Cu: 0.10 Conforming steel 5 0.04 3.3 0.06 0.078 0.077
0.002 0.001 0.001 0.006 0.001 Cr: 0.08 Conforming steel 6 0.03 3.1
0.07 0.055 0.058 0.001 0.001 0.001 0.004 0.003 Mo: 0.1 Conforming
steel 7 0.02 3.2 0.08 0.060 0.050 0.002 0.001 0.001 0.004 0.002 Nb:
0.004 Conforming steel 8 0.03 3.5 0.05 0.001 0.001 0.002 0.001
0.001 0.007 0.003 -- Comparative steel 9 0.04 3.3 0.06 0.001 0.050
0.002 0.001 0.001 0.006 0.001 -- Comparative steel 10 0.04 3.3 0.06
0.053 0.001 0.002 0.001 0.001 0.006 0.001 -- Comparative steel 11
0.04 3.3 0.07 0.064 0.041 0.001 0.024 0.001 0.003 0.003 --
Comparative steel 12 0.03 3.4 0.06 0.045 0.068 0.021 0.001 0.011
0.003 0.003 -- Comparative steel 13 0.02 3.2 0.07 0.035 0.050 0.001
0.001 0.001 0.023 0.003 -- Comparative steel 14 0.03 3.3 0.09 0.045
0.049 0.002 0.001 0.001 0.003 0.008 -- Comparative steel
TABLE-US-00004 TABLE 4 Additive amount of Magnetic property of
product sheet magnesium sulfate B.sub.8 W.sub.17/50 TD-H.sub.10
TD-W.sub.10 .DELTA.W No. (%) (T) (W/kg) (A/m) (W/kg) (W/kg) Remarks
1 3 1.949 0.81 282 2.003 0.004 Example 2 10 1.960 0.80 278 1.922
0.005 Example 3 5 1.950 0.77 285 2.022 0.003 Example 4 5 1.954 0.78
288 2.101 0.002 Example 5 3 1.950 0.79 286 2.076 0.003 Example 6 3
1.950 0.78 278 1.983 0.005 Example 7 10 1.960 0.78 281 2.000 0.004
Example 8 0 1.909 0.90 220 1.703 0.008 Comparative Example 9 0
1.951 0.89 188 1.783 0.030 Comparative Example 10 0 1.905 0.93 238
1.803 0.010 Comparative Example 11 0 1.830 1.45 160 1.432 0.045
Comparative Example 12 0 1.802 1.77 145 1.382 0.059 Comparative
Example 13 0 1.804 1.72 138 1.432 0.055 Comparative Example 14 0
1.811 1.62 165 1.543 0.044 Comparative Example
[0151] As is clear from Table 4, by using the material containing
appropriate amounts of P and Sb in combination, applying the
annealing separator having MgO as a main ingredient and containing
2.0% or more magnesium sulfate, performing secondary
recrystallization annealing, and further applying an appropriate
flattening annealing condition according to the disclosure, not
only favorable magnetic flux density was obtained, but also iron
loss degradation caused by the application of strain associated
with processing into a transformer was reduced.
* * * * *