TECHNICAL FIELD
[0001] The present invention relates to a nonoriented
magnetic steel sheet, and a method of
manufacturing the same.
BACKGROUND ART
[0002] Non-oriented magnetic steel sheets are used
for various motors. For example, the non-oriented
magnetic steel sheets are used for compressor motors
of an air-conditioner and a refrigerator, and driving
motors of an electric vehicle and a hybrid vehicle.
The compressor motors of the air-conditioner and the
refrigerator are mainly driven in an inverter mode,
and therefore, reduction in core loss at a commercial
frequency (50 Hz and 60 Hz) and reduction in core
loss at a high frequency (100 Hz to 1000 Hz) are
important to improve efficiency. A driving motor of
an automobile changes a rotation speed in accordance
with a traveling speed of the automobile. Besides,
high motor torque is required when the automobile
starts.
[0003] In consideration of the above, high magnetic
flux density, low core loss at the commercial
frequency, and low core loss at the high frequency
(hereinafter, it is sometimes called a "highfrequency
core loss") are demanded for the nonoriented
magnetic steel sheet. Further, a motor core
is roughly classified into an integral type and a
separate type, and the integral-type motor core is
mainly used, and therefore, isotropic magnetic
properties are demanded. However, a conventional
non-oriented magnetic steel sheet cannot satisfy
these requirements.
CITATION LIST
PATENT LITERATURES
[0004] Patent Literature 1: Japanese Laid-open
Patent Publication No. 2010-185119
Patent Literature 2: Japanese Laid-open Patent
Publication No. 2003-213385
Patent Literature 3: Japanese Laid-open Patent
Publication No. 2013-91837
Patent Literature 4: Japanese Laid-open PaLent
Publication No. 2007-162096
Patent Literature 5: Japanese Laid-open Patent
Publication No. H7-188752
Patent Literature 6: Japanese Laid-open Patent
I Publication No. 2013-44010
SUMMARY OF INVENTION
TECHNICAL PROBIsEM
[0005] An object of the present invention is to
- 2 -
i
I!
provide a non-oriented magnetic steel sheet capable
of accomplishing high magnetic flux density, low core
loss at a commercial frequency, low high-frequency
core loss and isotropic rnagnetlc properties, and a
method of manufacturing the same.
SOLUTION TO PROBLEM
[0006] The present inventors studied hard to solve
the above-stated problems. As a result, it turned
out that Sb or Sn, or both of them are contained for
proper amounts, and P, Ni, and C are contained for
proper amounts, a sheet thickness is small, and so on
are important to accomplish the high magnetic flux
density, the low core loss at the commercial
frequency, and the low high-frequency core loss
[0007] The present inventors came up to various
modes of the invention described below by further
hard studies based on the above-stated knowledges.
[00081 (1)
A non-oriented magnetic steel sheet, including:
a chemical composition represented by, in mass%:
Si: 3.0% to 3.6%;
Al: 0.50% to 1.25%;
Mn: 0.5% to 1.5%;
Sb or Sn or both of them: [Sb] + [Sn] / 2 is
0.0025% to 0.05% where [Sb] denotes an Sb content and
[Sn] denotes an Sn content;
P: 0.010% to 0.150%;
Ni: 0.010% to 0.200%;
C: 0.0010% to 0.0040%;
N: 0.0030% or less;
S: 0.0020% o~ less;
Ti: 0.0030% or less;
Cu: 0.0500% or less;
Cr: 0.0500% or less;
Mo: 0.0500% or less;
Bi: 0.0050% or less;
~ b :0. 0050% or less;
V: 0.0050% or less;
B: 0.0050% or less; and
balance: Fe and impurities, and
magnetic properties represented by, where t
denotes a thickness (mm) of the non-oriented magnetic
steel sheet:
a magnetic flux density B50: "0.2 x t + 1.52" T
or more;
a magnetic flux density difference AB50: 0.08 T
or less;
core loss W10/50: 0.95 W/kg or less; and
core loss W10/400: "20 x t + 7.5" W/kg or less,
wherein
i
I the thickness is 0.15 mm to 0.30 mm, and
a ratio of a number of intergranular carbides
precipitated in grains relative to a sum of the '
number of the intergranular carbides and a number of
grain boundary carbides precipitated on grain
boundaries is 0.50 or less.
[00091 (2)
The non-oriented magnetic steel sheet according
to (1), wherein in the chemical composition,
P: 0.015% to 0.100%,
Ni: 0.020% to 0.100%, or
C: 0.0020% to 0.0030%, or
any combination thereof is satisfied.
[00101 ( 3 )
A method of manufacturing a non-oriented magnetic
steel sheet, including:
hot-rolling of a steel material to obtain a hotrolled
steel sheet;
cold-rolling of the hot-rolled steel sheet to
obtain a cold-rolled steel sheet;
first annealing of the hot-rolled steel sheet
before the cold-rolling is completed; and
second annealing of the cold-rolled steel sheet,
wherein the first annealing includes:
retaining the hot-rolled steel sheet in a
first temperature range from 850°C to 110O0C for
10 seconds to 120 seconds, and
after the retaining, cooling the hot-rolled
steel sheet at a rate of S°C/s to 50°C/s in a
temperature zone from 850°C to 600°C,
wherein the second annealing includes:
retaining the cold-rolled steel sheet in a
second temperature range from 900°C to llOO°C for
10 seconds to 240 seconds, and
after the retaining, cooling the cold-rolled
steel sheet at a rate of 1O0C/s to 40°C/s in a
temperature zone from 900°C to 300°C, and
wherein the steel material includes a chemical
composition represented by, in mass%,
Si: 3.0% to 3.6%;
Al: 0.50% to 1.25%;
Mn: 0.5% to 1.5%;
~b or Sn or both of them: [Sb] + [Sn] / 2 is
0.0025% to 0.05% where [ S b ] denotes an Sb content and
[Sn] denotes an Sn content;
P: 0.010% to 0.150%;
Ni: 0.010% to 0.200%;
C : 0.0010% to 0.0040%;
N: 0.0030% or less;
S: 0.0020% or less;
Ti: 0.0030% or less;
Cu: 0.0500% or less;
C r : 0.0500% or less;
Mo: 0.0500% or less;
Bi: 0.0050% or less;
Pb: 0.0050% or less;
V: 0.0050% or less;
B: 0.0050% or less; and
balance: Fe and impurities.
[OOlll (4)
The method of manufacturing the non-oriented
magnetic steel sheet according to (3), wherein hotrolled
sheet annealing is performed as the first
annealing before the cold-rolling.
[00121 ( 5 )
The method of manufacturing the non-oriented
magnetic steel sheet according to (3), further
including hot-rolled sheet annealing before the coldrolling,
wherein an intermediate annealing is
performed as the first annealing during the coldrolling.
[00131 (6)
The method of manufacturing the non-oriented
magnetic steel sheet according to any one of (3) to
(5), wherein in the chemical composition,
P: 0.015% to 0.100%,
Ni: 0.020% to 0.100%, or
C: 0.0020% to 0.0030%, or
any combination thereof is satisfied.
[00141 (7)
The method of manufacturing the non-oriented
magnetic steel sheet according to any one of (3) to , (6), wherein a thickness of the cold-rolled steel
sheet is 0.15 mm to 0.30 mm.
j
j
ADVANTAGEOUS EFFECTS OF INVENTION
[0015] According to the present invention, it is
possible to obtain excellent magnetic properties
;:
because a chemical composition, a ratio of a number
of intergranular carbides precipitated in grains
relative to a sum of the number of the intergranular
carbides and a number of grain boundary carbides
precipitated on grain boundaries, and so on are
appropriate.
DESCRIPTION OF EMBODIMENTS
[0016] Hereinafter, embodiments of the present
invention are described.
[0017] First, a chemical composition of a nonoriented
magnetic steel sheet according to an
embodiment of the present invention and a steel
material used for manufacturing the same is
described. The non-oriented magnetic steel sheet
according to the embodiment of the present invention
is manufactured through hot-rolling of a steel
material, hot-rolled sheet annealing, cold-rolling,
finish annealing, and so on, though details will be
described later. Accordingly, the chemical
compositions of the non-oriented magnetic steel sheet
and the steel material are appropriate for the abovestated
processes in addition to properties of the
non-oriented magnetic steel sheet. In the following
! description, a sign " % " being a unit of a content of
:
>
each element contained in the non-oriented magnetic
steel sheet or the steel material .means "mass%"
,: : unless otherwise specified. The non-oriented
magnetic steel sheet according to the embodiment
includes a chemical composition represented by: Si:
3.0% to 3.6%; Al: 0.50% to 1.25%; Mn: 0.5% to 1.5%;
Sb or Sn or both of them: [Sb] + [Sn] / 2 is 0.0025%
to 0.05% where [Sb] denotes an Sb content and [Sn]
denotes an Sn content; P: 0.010% to 0.150%; Ni:
0.010% to 0.200%; C: 0.0010% to 0.0040%; N: 0.0030%
or less; S: 0.0020% or less; Ti: 0.0030% or less; Cu:
0.0500% or less; Cr: 0.0500% or less; Mo: 0.0500% or
less; Bi: 0.0050% or less; Pb: 0.0050% or less; V:
0.0050% or less; B: 0.0050% or less; and balance: Fe
and impurities. As the impurities, ones contained in
raw materials such as ore and scrap, and ones
contained during a manufacturing process are
exemplified.
[0018] (Si: 3.0% to 3.6%)
Si increases a specific resistance and reduces
core loss. When a Si content is less than 3.0%, the
core loss cannot be sufficiently reduced. Thus, the
Si content is 3.0% or more, and preferably 3.28 or
more. On the other hand, when the Si content is over
3.6%, toughness deteriorates and cold-rolling becomes
difficult. Thus, the Si content is 3.6% or less.
[0019] (Al: 0.50% to 1.25%)
A1 increases the specific resistance and reduces
the core loss, particularly a 1 high-frequency core - loss. When an A1 content is less than 0.50%, the
high-frequency core loss cannot be sufficiently
reduced. Thus, the Al content is 0.50% or more. On
the other hand, when the A1 content is over 1.25%,
hysteresis loss increases, and core loss at a
commercial frequency increases. Thus, the Al content
is 1.25% or less.
[0020] (Mn: 0.5% to 1.5%)
Mn reduces the core loss. When a Mn content is
less than 0.5%, the core loss cannot be sufficiently
reduced. Fine precipitates are sometimes formed so
as to increase the core loss. Thus, the Mn content
is 0.5% or more, and preferably 0.7% or more. On the
other hand, when the Mn content is over 1.5%, many Mn
carbides are formed, and the core loss increases.
Thus, the Mn content is 1.5% or less.
[00211 (Sb or Sn or both of them: [Sbl + [Sn] / 2 is
0.0025% to 0.05%)
Sb and Sn improve magnetic flux density. Sb are
effective twice as much as Sn. When Sb] + [Sn] / 2
is less than 0.0025% where [Sb] denotes an Sb content
and [Sn] denotes an Sn content, sufficient magnetic
flux density cannot be obtained. Thus, [Sb] + [Snl /
2 is 0.0025% or more. On the other hand, when [Sb] +
[Sn] / 2 is over 0.05%, an improvement effect of the
magnetic flux density is saturated, and cost
increases in vain. Thus, [Sb] + [Sn] / 2 is 0.05% or
less.
[0022] (P: 0.010% to 0.150%)
It was made clear by the present inventors that P
conllributes to improvement in the magnetic flux
density. When a P content is less than 0.010%, the
sufficient magnetic flux density cannot be obtained.
Thus, the P content is 0.010% or more, and preferably
0.011% or more. On the other hand, when the P
content is over 0.150%, the core loss increases.
Thus, the P content is 0.150% or less, and preferably
0.100% or less.
[0023] (Ni: 0.010% to 0.200%)
It was made clear by the present inventors that
Ni contributes to improvement in the magnetic flux
density. When a Ni content is less than 0.010%, the
sufficient magnetic flux density cannot be obtained.
Thus, the Ni content is 0.010% or more, and
preferably 0.020% or more. On the other hand, when
the Ni content is over 0.200%, the core loss
increases. Thus, the Ni content is 0.200% or less,
and preferably 0.100% or less.
[0024] (C: 0.0010% to 0.0040%)
It was made clear by the present inventors that C
contributes to improvement in the magnetic flux
density. When a C content is less than 0.0010%, the
I sufficient magnetic flux density cannot be obtained.
Thus, the C content is 0.0010% or more, and
preferably 0.0020% or more. When the C content is
over 0.0040% and the Mn content is 0.5% or more, many
Mn carbides are formed, and the core loss increases
Thus, the C content is 0.0040% or less, and
prererably 0.0030% or less.
[0025] (N: 0.0030"sr less)
N is not an essential element, and is contained
as an impurity in the steel, for example. N causes
magnetic aging so as to increase the core loss.
Accordingly, the lower an N content is, the better.
The increase in the core loss is remarkable when the
N content is over 0.0030%. Thus, the N content is
0.0030% or less. It requires considerable cost to
lower the N content to less than 0.0001%. Therefore,
it is not necessary to lower the N content to less
than 0.0001%.
[0026] (S: 0.0020% or less)
S is not an essential element, and is contained
as an impurity in the steel, for example. S forms
fine precipitates so as to increase the core loss.
Accordingly, the lower an S content is, the better.
The increase in the core loss is remarkable when the
S content is over 0.0020%. Thus, the S content is
0.0020% or less. It requires considerable cost to
lower the S content to less than 0.0001%. Therefore,
1 it is not necessary to lower the S content to less
1 than 0.0001%.
j
l 100271 (Ti: 0.0030% or less)
Ti is not an essential element, and is contained 'I i as an impurity in the steel, for example. Ti forms
flne precipitates so as to increase the core loss.
Accordingly, the lower a Ti content is, the better.
The increase in the core loss is remarkable when the
Ti content is over 0.0030%. Thus, the Ti content is
0.0030% or less. It requires considerable cost to
lower the Ti content to less than 0.0001%.
Therefore, it is noL necessary to lower the Ti
content to less than 0.0001%.
[0028] (Cu: 0.0500% or less)
Cu is not an essential element, and is contained
as an impurity in the steel, for example. There is a
possibility that Cu forms fine sulfides so as to
deteriorate the magnetic properties. Accordingly,
the lower a Cu content is, the better. The formation
of Cu sulfides is remarkable when the Cu content is
over 0.0500%. Thus, the Cu content is 0.0500% or
less. It requires considerable cost to lower the Cu
content to less than 0.0001%. Therefore, it is not
necessary to lower the Cu content to less than
0.0001%.
[0029] (Cr: 0.0500% or less)
Cr is not an essential element, and is contained
as an impurity in the steel, for example. There is a
possibility that Cr forms carbides so as to
deteriorate the magnetic properties. Accordingly,
the lower a Cr content is, the better. The formation
of Cr carbides is remarkable when the Cr content is
over 0.0500%. Thus, the Cr content is 0.0500% or
less. It requires considerable cost to lower the Cr
content to less than 0.0001%. Therefore, it is not
necessary to lower the Cr content to less than
0.0001%.
[0030] (Mo: 0.0500% or less)
Mo is not an essential element, and is contained
as an impurity in tile steel, for example. There is a
possibility that Mo forms carbides so as to
deteriorate the magnetic properties. Accordingly,
the lower an Mo conLent is, the better. The
formation of Mo carbides is remarkable when the Mo
content is over 0.0500%. Thus, the Mo content i.s
0.0500% or less. It requires considerable cost to
lower the Mo content to less than 0.0001%.
Therefore, it is not necessary to lower the Mo
content to less than 0.0001%.
[0031] (Bi: 0.0050% or less)
Bi is not an essential element, and is contained
as an impurity in the steel, for example. There is a
possibility that Bi facilitates formation of fine Mn
sulfides so as to deteriorate the magnetic
properties. Accordingly, the lower a Bi content is,
the better. The facilitation of the fine Mn sulfides
I
I
is remarkable when the Bi content is over 0.0050%.
Thus, the Bi content is 0.0050% or less. It requires
( considerable cost to lower the Bi content to less
? than 0.0001%. Therefore, it is not necessary to
:I
lower the Bi content to less than 0.0001%.
[0032] (Pb: 0.0050% or less)
Pb is not an essential element, and is contained
as an impurity in the steel, for example. There is a
possibility that Pb facilitates formation of fine Mn
sulfides so as to deteriorate the magnetic
properties. Accordingly, the lower a Pb content is,
the better. The facilitation of the fine Mn sulfides
is remarkable when the Pb content is over 0.0050%.
Thus, the Pb content is 0.0050% or less. It requires
considerable cost to lower the Pb content to less
than 0.0001%. Therefore, it is not necessary to
lower the Pb content to less than 0.0001%.
[0033] (V: 0.0050% or less)
V is not an essential element, and is contained
as an impurity in the steel, for example. There is a
possibility that V forms carbides or nitrides so as
to deteriorate the magnetic properties. Accordingly,
the lower a V content is, the better. The formation
of the V carbides or the V nitrides is remarkable
when the V content is over 0.0050%. Thus, the V
content is 0.0050% or less. It requires considerable
cost to lower the V content to less than 0.0001%
Therefore, it is not necessary to lower the V content
to less than 0.0001%.
[0034] (B: 0.0050% or less)
I
B is not an essential element, and is contained
I
as an impurity in the steel, for example. There is a
possibility that B forms nitrides or precipitates
containing Fe so as to deteriorate the magnetic
properties. Accordingly, the lower a B content is,
the better. The formation of the nitrides or the
precipitates is remarkable when the B content is over
0.0050%. Thus, the B content is 0.0050% or less. It
requires considerable cost to lower the B content to
less than 0.0001%. Therefore, it is not necessdry to
lower the B content to less than 0.0001%.
[0035] Next, a thickness of the non-oriented
magnetic steel sheet according to the embodiment of
the present invention is described. The thickness of
the non-oriented magnetic steel sheet according to
the embodiment is 0.15 mm or more and 0.30 mm or
less. When the thickness is over 0.30 mm, excellent
high-frequency core loss cannot be obtained. Thus,
the thickness is 0.30 mm or less. When the thickness
is less than 0.15 mm, sheet passing through an
annealing line in the finish annealing is difficult.
Thus, the thickness is 0.15 mm or more.
[0036] Next, the magnetic properties of the nonoriented
magnetic steel sheet according to the
embodiment of the present invention are described
The non-oriented magnetic steel sheet according to
the embodiment includes magnetic properties
represented by, where the thickness is represented by
t (mm) , a magnetic flux density B50: "0.2 x t + 1.52"
1 T or more; a magnetic flux density difference AB50:
I
0.08 T or less; core loss W10/50: 0.95 W/kg or less
and core loss W10/400: "20 x t + 7.5" W/kg or less.
[0037] (Magnetic Flux Density B50: "0.2 x t + 1.52"
T or more)
The magnetic flux densi.ty 850 is a magnetic flux
density at a magnetic field of 5000 A/m. An average
value between a magnetic flux density B50 in a
rolling direction (hereinafter, it is sometimes
called an "L direction") and a magnetic flux density
B50 in a direction perpendicular to the rolling
direction and a sheet thickness direction
(hereinafter, it is sometimes called a " C direction")
is used as the magnetic flux density B50 of a nonoriented
magnetic steel sheet. When the magnetic
flux density B50 is less than "0.2 x t + 1.52" T, a
motor manufactured by using this non-oriented
magnetic steel sheet cannot secure sufficient motor
torque. Automobiles mounting such motor, for
example, a hybrid vehicle and an electric vehicle,
have disadvantages at starting. Thus, the magnetic
flux density B50 is "0.2 x t + 1.52" T or more. The
larger the magnetic flux density B50 is, the more
preferable.
[0038] (Magnetic Flux Density Difference AB50: 0.08
T or less)
i
i
j
When the difference AB50 of the magnetic flux
I
1!, densities B50 in the L direction and the C direction
I, :I is over 0.08 T, anisotropy is excessive, and
'i j excellent properties cannot be obtained in an
, I
t i integral type motor core. Thus, Vhe magnetic flux
density difference AB50 is 0.08 T or less.
[00391 (Core Loss W10/50: 0.95 W/kg or less)
The core loss W10/50 is core loss at a magnetic
flux density of 1.0 T and a frequency of 50 Hz. An
average value between a core loss W10/50 in the L
direction and a core loss WlO/SO in the C direciion
is used as the core loss Wl0/50 of a non-oriented
magnetic steel sheet. When the core loss W10/50 is
over 0.95 W/kg, energy loss of a motor core
manufactured by using this non-oriented magnetic
steel sheet becomes excessively large, and a heating
value and a power generator size increase. Thus, the
core loss W10/50 is 0.95 W/kg or less. The smaller
the core loss W10/50 is, the more preferable.
[0040] (Core Loss W10/400: '20 x t + 7.5" W/kg or
less)
The core loss W10/400 is core loss at the
magnetic flux density of 1.0 T and a frequency of 400
Hz. An average value between a core loss W10/400 in
the L direction and a core loss W10/400 in the C
direction is used as the core loss W10/400 of d nonoriented
magnetic steel sheet. When the core loss
W10/400 is over '20 x t + 7.5" W/kg, energy loss of a
motor core manufactured by using this non-oriented
magnetic steel sheet becomes excessively large, and a
heating value and a power generator size increase.
Thus, the core loss W10/400 is '20 x t + 7.5" W/kg or
less. The smaller the core loss W10/400 is, the more
preferable.
[0041] The magnetic flux density B50, the core loss
W10/50, and the core loss W10/400 may be measured by
an Epstein tester defined in JIS C 2550 or a single
sheet tester (SST) defined in JIS C 2556, for
example.
[0042] Next, carbides contained in the non-oriented
magnetic steel sheet according to the embodiment of
the present invention are described. In the nonoriented
magnetic steel sheet according to the
embodiment, a ratio of a number of intergranular
carbides precipitated in grains relative to a sum of
the number of the intergranular carbides and a number
of grain boundary carbides precipitated on grain
boundaries is 0.50 or less. When the ratio is over
0.50, the intergranular carbides are excessive, and
the core loss increases. Thus, the ratio is 0.50 or
less. The number of intergranular carbides and the
number of grain boundary carbides may be specified by
a scanning microscopic observation.
[0043] Next, a method of manufacturing the nonoriented
magnetic steel sheet according to the
embodiment is described. In the manufacturing
method, hot-rolling, hot-rolled sheet annealing,
cold-rolling, finish annealing, and so on are
performed.
(00441 In the hot-rolling, heatlng of a steel
material such as a slab having the above-stated
chemical composition (slab heating) is performed,
then rough rolling and finish rol~ling are performed,
for example. A temperature of the slab heating is
preferably 1000°C or more and 1250°C or less. A
thickness of a hot-rolled steel sheet obtained by the
hot-roiling is preferably 1.6 mrn or more and 2.6 mm
or less. After the hot-rolling, annealing of the
hot-rolled steel sheet (hot-rolled sheet annealing)
is performed. After the hot-rolled sheet annealing,
the cold-rolling of the hot-rolled steel sheet is
performed to obtain a cold-rolled steel sheet. The
cold-rolling may be performed once, or twice or more
being intervened by intermediate annealing.
[0045] The hot-rolled steel sheet is retained in a
first temperature range from 850°C to llOO°C for 10
seconds to 120 seconds, and thereafter, cooled at a
rate of 5'C/s to 50°C/s in a temperature zone from
850°C to 600°C, in the intermediate annealing if the
intermediate annealing is performed, or in the hotrolled
sheet annealing if the intermediate annealing
is not performed. If the intermediate annealing is
not performed, the hot-rolled sheet annealing is an
I example of first annealing, and if the intermediate
annealing is performed, the intermediate annealing is
an example of the first annealing. When the
retaining temperature (first retention temperature)
is less than 850°C, crystal grains are not
i sufficiently coarsened, and the sufficient maynetic
flux density B50 cannot be obtained. Thus, the first
retention temperature is 850°C or more, and preferably
950°C or more. When the first retention temperature
is over llOO°C, the toughness is lowered, and
fractures occur easily in the subsequent coldrolling.
Thus, the first retention temperature is
llOO°C or less. When the retaining time (first
retention time) is less than 10 seconds, the crystal
grains are not sufficiently coarsened, and the
sufficient magnetic flux density 850 cannot be
obtained. Thus, the first retention time is 10
seconds or more. When the first retention time is
over 120 seconds, the toughness is lowered, and the
fractures occur easily in the subsequent coldrolling.
Thus, the first retention time is 120
seconds or less. When the cooling rate (first
cooling rate) after the retention is less than 5'C/s,
the sufficient magnetic flux density B50 cannot be
obtained, and the core loss Wl0/50 and the core loss
W10/400 increase. Thus, the first cooling rate is
5'C/s or more, and preferably 20°C/s or more. When
the first cooling rate is over 50°C/s, the steel sheet
largely deforms, and the fractures occur easily in
1 the subsequent cold-rolling. Thus, the first cooling
j
j rate is 50°C/s or less.
:; I [00461 After the cold-rolling, the finish annealing
9
of the cold-rolled steel sheet is performed. The
finish annealing is an example of second annealing.
In the finish annealing, the cold-rolled steel sheet
is retained in a second temperature range from 900°C
to 1100°C for 10 seconds to 240 seconds, and
thereafter, cooled at a rate of 1O0C/s to 40°C/s in a
temperature zone from 900°C to 300°C. When the
retaining temperature (second retention temperature)
is less than 900°C, the crystal grains are not
sufficiently coarsened, and the excellent magnetic
properties cannot be obtained. Thus, the second
retention temperature is 900°C or more, and preferably
950°C or more. When the second retention temperature
is over llOO°C, the crystal grains are excessively
coarsened, and the high-frequency core loss
increases. Thus, the second retention temperature is
l10O0C or less, and preferably 1050°C or less. When
the retaining time (second retention time) is less
than 10 seconds, the crystal grains are not
sufficiently coarsened, and the excellent magnetic
properties cannot be obtained. Thus, the second
retention time is 10 seconds or more, and preferably
15 seconds or more. When the second retention time
is over 240 seconds, the crystal grains are
excessively coarsened, and the high-frequency core
loss increases. Thus, the second retention time is
240 seconds or less, and preferably 200 seconds or
less. When the cooling rate (second cooling rate)
after the retention is over 40°C/s, the ratio of the
number of intergranular carbides relative to the
total number of intergranular carbides and grain
boundary carbides becomes over 0.50, and the core
loss increases. Thus, the second cooling rate is
40°C/s or less, and preferably 30°C/s or less. When
the second cooling rate is less than 10°C/s, an effect
of lowering the core loss is saturated, and
productivity is lowered. Thus, the second cooling
rate is 10°C/s or less.
[0047] The non-oriented magnetic steel sheet
according to the embodiment may be thereby
manufactured. After the finish annealing, an
insulating coating film may be formed by coating and
baking.
[00481 The non-oriented magnetic steel sheet
according to the embodiment as stated above is used
for, for example, an iron core of a motor, and it is
possible to largely contribute to reduction in energy
consumption of an air-conditioner, a refrigerator, an
electric vehicle, a hybrid vehicle, and so on.
[0049] Hereinabove, preferred embodiments of the
present invention are described in detail, but the
I
present invention is not limited to these examples.
I
! It is apparent to a person skilled in the art to
! which the present invention belongs that various
I
!
I modification examples or revised examples can be 1
I devised within the scope of technical ideas described
in claims, and it is understood that these also fall
into the technical scope of the present invention as
a matter of course.
EXAMPLES
[0050] Next, the non-oriented magnetic steel sheet
according to the embodiment of the present invention
is concretely described while illustrating examples.
The examples illustrated in the following are only
examples of the non-oriented magnetic steel sheet
according to the embodiment of the present invention,
and the non-oriented magnetic steel sheet according
to the present invention is not limited to the
following examples.
[00511 (First Experiment)
In a first experiment, a steel ingot containing:
in mass%, C: 0.0022%, S: 0.0012%, Ti: 0.0015%, N:
0.0018%, Sn: 0.022%, P: 0.016%, Ni: 0.031%, Cu:
0.024%, and the balance of Si, Al, Mn, Fe and
impurities was manufactured by using a vacuum melting
furnace. Contents of Si, Al, and Mn in each steel
ingot are listed in Table 1.
[0052] Then, the steel ingot was heated at 1150°C for
one hour in a heating furnace, taken out of the
heating furnace, then six passes of hot-rolling in
total were performed to obtain a hot-rolled steel
i
I sheet with a thickness of 2.0 mm. Thereafter, the
I hot-rolled steel sheet was retained at 1000°C for 60 !,
seconds in hot-rolled sheet annealing. The cooling
rate in 'cooling after the retention from'850°C to
600°C was 25'C/s. Subsequently, cold-rolling of the
hot-rol~led steel sheet was performed to obtain a
cold-rolled steel sheet with a thickness of 0 . 3 0 mm.
Then, the cold-rolled steel sheet was retained at
1 0 0 0 ° C for 2 0 seconds in finish annealing. The
cooling rate in cooling after the retention from 9 0 0 ° C
to 3 0 0 ° C was 1 5 ' C / s . Thereafter, an insulating
coating film was formed by coating and baking. A
non-oriented magnetic steel sheet was thereby
manufactured.
[ 0 0 5 3 ] Six pieces of 5 5 mm square samples were made
of each non-oriented magnetic steel sheet, then the
core losses W 1 0 / 4 0 0 , the core losses 1 0 / 5 0 , and the
magnetic flux densities B 5 0 in the L direction and
the C direction of each sample were measured by the
SST method. An average value between the core loss
W 1 0 / 4 0 0 in the L direction and the core loss W 1 0 / 4 0 0
in the C direction, an average value between the core
loss W 1 0 / 5 0 in the L direction and the core loss
W 1 0 / 5 0 in the C direction, an average value between
the magnetic flux density B 5 0 in the L direction and
the magnetic flux density B 5 0 in the C direction, and
a difference AB50 between the magnetic flux density
i
I
! B 5 0 in the L direction and the magnetic flux density
I
j B 5 0 in the C direction were calculated by each
I
!
'1 ' sample. An average value among the core losses
1: W 1 0 / 4 0 0 of the six pieces of samples, an average
i :
value among the core losses W 1 0 / 5 0 of the six pieces
of samples, and an average value among the core
losses B 5 0 of the slr pieces of samples were
calculated by each of the non-oriented magnetic steel
sheets by using the above-stated average values. An
average value among the magnetic flux densities I350
in the L direction of the six pieces of samples, an
average value among the magnetic flux densities B50
in the C direction of the six pieces of samples, and
an average value among the magnetic flux density
differences AB50 of the six pieces of samples were
calculated by each of the non-oriented magnetic steel
sheets. These results are also listed in Table 1.
Underlines in Table 1 indicate that the numerical
values are out of the range of the present invention.
[0054] Scanning microscopic observation was
performed within a visual field with an area of 0.25
mmz by each non-oriented magnetic steel sheet, and it
was found that a ratio of a number of intergranular
carbides precipitated in grains relative to a sum of
the number of the intergranular carbides and a number
of grain boundary carbides precipitated on grain
boundaries was 0.50 or less in any non-oriented
magnetic steel sheet.
LO0551 [Table 11
1-16 31 1 0.80 0.7 UNMEASURABLE COMPARATIVE EXAMPLE
[0056] As listed in Table 1, in each of samples No.
1-2, No. 1-4, No. 1-6 to No. 1-9, No. 1-11, No. 1-12,
No. 1-14 and No. 1-15, the chemical composition was
within the range of the present invention, and
excellent magnetic properties could be obtained. In
each of the samples No. 1-7 to No. 1-9, No. 1-11, No.
1-14 and No. 1-15, the Si content and the Mn content
were within the preferable range, and particularly
excellent magnetic properties could be obtained.
[0057] In a sample No. 1-1, the Si content was less
than the lower limit of the range of the present
invention, and therefore, the core loss was high. In
a sample No. 1-3, the A1 content was less than the
lower limit of the range of the present invention,
and therefore, the core loss was high. In a sample
No. 1-5, the Mn content was less than the lower limit
of the range of the present invention, and therefore,
the core loss was high. In a sample No. 1-10, the Mn
content was over the upper limit of the range of the
. ~
present invention, and therefore, 'the core loss was
high. In a sample No. 1-13, the A1 content was over
the upper limit of the range of the present
invention, and therefore, the core loss at the
commercial frequency was high, and the magnetic flux
density difference was large. In a sample No. 1-16,
the Si content was over the upper limit of the range
of the present invention, and therefore, fractures
occurred during the cold-rolling, and the magnetic
properties could not be measured.
[0058] (Second Experiment)
In a second experiment, a steel ingot containing:
in mass%, Si: 3.2%, Al: 0.80%, Mn: 0.9%, C: 0.0029%,
S: 0.0019%, Ti: 0.0012%, N: 0.0024%, Sb: 0.010%, Sn:
0.042%, P: 0.025%, Ni: 0.024%, Cr: 0.02%, and the
balance of Fe and impurities was manufactured by
using a vacuum melting furnace.
I [0059] Then, the steel ingot was heated at llOO°C for
one hour in a heating furnace, taken out of the
heating furnace, then six passes of hot-rolling in
I I total were performed to obtain a hot-rolled steel
i sheet with a thickness of 2.0 mm. Thereafter, the
hot-rolled sheet annealing was performed. A first
retention temperature TI, a first retention time tl,
and a first cooling rate R1 in the hot-rolled sheet
annealing were listed in Table 2. Subsequently,
cold-rolling of the hot-rolled steel sheet was
performed to obtain a cold-rolled steel sheet with a
thickness of 0.25 mm. Then, the cold-rolled steel
sheet was retained at 980°C for 25 secoinds in finish
annealing. The cooling rate in cooling after the
retention from 9OO0C to 300°C was 20°C/s. Thereafter,
an insulating coating film was formed by coating and
baking. A non-oriented magnetic steel sheet was
thereby manufactured.
[0060] Measurements of the magnetic properties were
performed similarly to the first experiment. These
results are also listed in Table 2. Underlines in
Table 2 indicate that the numerical values are out of
the range of the present invention. It was found
that a ratio of a number of intergranular carbides
precipitated in grains relative to a sum of the
number of the intergranular carbides and a number of
grain boundary carbides precipitated on grain
boundaries was 0.50 or less in any non-oriented
magnetic steel sheet similarly to the firs
experiment.
[0061] [Table 21
[0062] As listed in Table 2, in each of samples No.
2-3, No. 2-5 to No. 2-9 and No. 2-11, the conditions
of the first annealing were within the range of the
present invention, and the excellent magnetic
properties were obtained. In each of the samples No.
2-7 to No. 2-9 and No. 2-11, the first retention
temperature and the first cooling rate were each
within the preferable range, and particularly
excellent magnetic properties could be obtained.
[0063] In a sample No. 2-1, the first retention
temperature T1 was less than the lower limit of the
range of the present invention, and therefore, the
core loss was high, and the magnetic flux density was
low. In a sample No. 2-2, the first retention time
tl was less than the lower limit of the range of the
present invention, and therefore, t.he core loss was
high, and the magnetic flux density was low. In a
sample No. 2-4, the first cooling rate R1 was less
than the lower limit of the range of the present
invention, and therefore, the core loss was high, and
the magnetic flux denslty was low. In a sample No.
2-10, the fist cooling rate R1 was over the upper
limit of the range of the present invention, and
therefore, the steel sheet largely deformed,
fractures occurred during the cold-rolling, and the
magnetic properties could not be measured. In a
sample No. 2-12, the first retention time tl was over
the upper limit of the range of the present
invention, and therefore, the toughness was lowered,
the fractures occurred during the cold-rolling, and
the magnetic properties could not be measured. In a
sample No. 2-13, the first retention temperature TI
was over the upper limit of the range of the present
invention, and therefore, the toughness was lowered,
the fractures occurred during the cold-rolling, and
the magnetic properties could not be measured.
[0064] (Third Experiment)
In a third experiment, a steel ingot containing:
in mass%, Si: 3.4%, Al: 0.80%, Mn: 0.9%, C: 0.0010%,
S: 0.0014%, Ti: 0.0018%, N: 0.0022%, Sb: 0.022%, Sn:
0.051%, P: 0.018%, Ni: 0.034%, Cr: 0.03%, Cu: 0.04%,
Mo: 0.01%, B: 0.0009%, and the balance of Fe and
impurities was manufactured by using a vacuum melting
furnace.
[0065] Then, the steel ingot was heated at 1170°C for
one hour in a heating furnace, taken out of the
heating furnace, then six passes of hot-rolling in
total were performed to obtain a hot-rolled steel
sheet with a thickness of 2.1 mm. Thereafter, the
hot-rolled steel sheet was retained at 980°C for 50
seconds in hot-rolled sheet annealing. The cooling
rate in cooling after the retention from 850°C to
600°C was 2g°C/s. Subsequently, cold-rolling of the
hot-rolled steel sheet was performed to obtain a
cold-rolled steel sheet with a thickness of 0.25 mm.
Then, finish annealing was performed. A second
retention temperature T2, a second retention time t2
and a second cooling rate R2 in the finish annealing
are listed in Table 3. Thereafter, an insulating
coating film was formed by coating and baking. A
non-oriented magnetic steel sheet was thereby
manufactured.
[0066] Measurements of the magnetic properties were
performed, and a ratio of a number of intergrariular
carbides precipitated in grains relative to a sum of
the number of the intergranular carbides and a number
of grain boundary carbides precipitated on grain
boundaries was measured, similarly to the first
experiment. These results are also listed in Table
i 3. Underlines in Table 3 indicate that the numerical
values are out of the range of the present invention.
[0067] [Table 31
LO0681 As listed in Table 3, in each of samples No.
3-2, No. 3-4 to No. 3-7 and No. 3-10 to No. 3-16, the
conditions of the second annealing were within the
range of the present invention, and the excellent
magnetic properties were obtained. In each of the
samples No. 3-5 to No. 3-7 and No. 3-11 to No. 3-13,
the second retention temperature, the second
retention time, and the second cooling rate were
within the preferable range, and particularly
excellent magnetic properties were obtained.
[0069] In a sample No. 3-1, the second retention
temperature T2 was less than the lower limit of the
range of the present invention, and therefore, the
core loss was high. In a sample No. 3-3, the second
retention time t2 was less than the lower limit of
the range of the present invention, and therefore,
the core loss was high. In a sample No. 3-8, the
second retention time t2 was over the upper limit of
the range of the present invention, and therefore,
the high-frequency core loss was high. In d sample
No. 3-9, the second cooling rate R2 was over the
upper limit of the range of the present invention,
and therefore, the ratio of the intergranular
carbides was high, and the core loss was high. In a
sample No. 3-17, the second retention temperature T2
was over the upper limit of the range of the present
invention, and therefore, the high-frequency core
loss was high.
[OOIO] (Fourth Experiment)
In a first experiment, a steel ingot containing:
in mass%, Si: 3 . 2 % , Al: 0.80%, Mn: 1.0%, S: 0.0010%,
Ti: 0.0012%, N: 0.0020%, Sn: 0.041%, Cu: 0.022%, and
the balance of P, Ni, C, Fe and impurities was
manufactured by using a vacuum melting furnace
Contents of P, Ni, and C in each steel ingot are
listed in Table 4.
[0071] Then, the steel ingot was heated at 1140°C for
one hour in a heating furnace, taken out of the
heating furnace, then six passes of hot-rolling in
I total were performed to obtain a hot-rolled steel
I
sheet with a thickness of 2.0 mm. Thereafter, the
hot-rolled steel sheet was retalned at 880°C for 40
seconds in hot-rolled sheet annealing. The cooling
rate in cooling after the retention from 850°C to
600°C was 2g°C/s. Subsequently, cold-rolling of the
hot-rolled steel sheet was performed to obtain a
cold-rolled steel sheet with a thickness of 0 . 3 0 mm
Then, the cold-rolled steel sheet was retained at
1 0 0 0 ° C for 12 seconds in finish annealing. The
cooling rate in cooling after the retention from 900°C
to 300°C was 25'C/s. Thereafter, an insulating
coating film was formed by coating and baking. A
non-oriented magnetic steel sheet was thereby
manufactured.
[ 0 0 7 2 ] Measurements of the magnetic properties were
performed similarly to the first experiment. These
results are also listed in Table 4 . Underlines in
Table 4 indicate that the numerical values are out of
the range of the present invention. It was found
that a ratio of a number of intergranular carbides
precipitated in grains relative to a sum of the
number of the intergranular carbides and a number of
grain boundary carbides precipitated on grain
boundaries was 0 . 5 0 or less in any non-oriented
magnetic steel sheet similarly to the first
experiment.
[ 0 0 7 3 ] [Table 41
[0074] As illustrated in Table 4, in each of samples
No. 4-2 to No. 4-9, the chemical composition was
within the range of the present invention, and the
excellent magnetic properties could be obtained. In
each of samples No. 4-6 to No. 4-8, the P content,
the Ni content and the C content were within the
preferable range, and particularly excellent magnetic
properties could be obtained.
[0075] In a sample No. 4-1, the P content, the Ni
content and the C content were each less than the
lower limit of the range of the present invention,
and therefore, the magnetic flux density was low. In
each of samples No, 4-10 and No. 4-11, the P content,
the Ni content and the C content were each over the
upper limit of the range of the present invention,
and therefore, the core loss was high.
[0076] (Fifth Experiment)
In a fifth experiment, a steel ingot containjng:
in mass%, Si: 3 . 3 % , Al: 0.80%, Mn: 1.1%, C: 0.0012%,
S: 0.0018%, Ti: 0.0015%, N: 0.0024%, Sb: 0.004%, Sn:
0.058%, P: 0.015%, Ni: 0.018%, Cr: 0.005%, Cu:
0.010%, and the balance of Fe and impurities was
manufactured by using a vacuum nieltiny furnace.
[00771 Then, the steel ingot was heated at 1160°C for
one hour in a heating furnace, taken out of the
heating furnace, then six passes of hot-rolling in
total were performed to obtain a hot-rolled steel
sheet with a thickness of 2.0 mm. Thereafter, the
hot-rolled steel sheet was retained at 1000°C for 60
seconds in hot-rolled sheet annealing. The cooling
rate in cooling after the retention from 850°C to
600°C was 2E0C/s. Subsequently, cold-rolling of the
hot-rolled steel sheet was performed to obtain a
cold-rolled steel sheet with a thickness of 0.15 mm.
Then, finish annealing was performed. A second
retention temperature T2, a second retention time t2
and a second cooling rate R2 in the finish annealing
are listed in Table 5. Thereafter, an insulating
coating film was formed by coating and baking. A
non-oriented magnetic steel sheet was thereby
I
I manufactured.
j
j [0078] Measurements of the magnetic properties were
i
I 1 8 performed similarly to the first experiment. These
1 results are also listed in Table 5. Underlines in
Table 5 indicate that the numerical values are out of
the range of the present invention. It was found
that a ratio of a number of intergranular carbides
precipitated in grains relative to a sum of the
number of the intergranular carbides and a number of
grain boundary carbides precipitated on grain
boundaries was 0.50 or less in any non-oriented
magnetic steel sheet similarly to the firs
experiment
[0079] [Table 51
SAMPLE T2 t2 R2 Wt0/400 Wt0/50 850 hB50 REMARKS
[0080] As listed in Table 5, in each of samples No
5-2, No. 5-4 to No. 5-7, and No. 5-9 to No. 5-11, the
conditions of the second annealing were within the
range of the present invention, and the excellent
magnetic properties could be obtained. In each of
the samples No. 5-4 to No. 5-7, No. 5-9 and No. 5-10,
the second retention temperature, the second
retention time, and the second cooling rate were
within the preferable range, and particularly
excellent magnetic properties could be obtained.
[0081] In a sample No. 5-1, the second retention
temperature T2 was less than the lower limit of the
range of the present invention, and therefore, the
core loss was hlgh, and the magnetic ilux density was
low. In a sample No. 5-3, the second retention time
t2 was less than the lower limit of the range of the
present invention, and therefore, the core loss was
high. In a sample No. 5-8, the second retention time
t2 was over the upper limit of the range of the
present invention, and therefore, the core loss was
high, and the magnetic flux density was high. In a
sample No. 5-12, the second retention temperature T2
was over the upper limit of the range of the present
invention, and therefore, the core loss was high, and
the magnetic flux density was high.
INDUSTRIAL APPLICABILITY
[0082] The present invention may be used for, for
example, manufacturing industries of a non-oriented
magnetic steel sheet and utilizing industries of the
non-oriented magnetic steel sheet.

CLAIMS
[Clam 11 A non-oriented magnetic steel sheet,
comprising:
a che~i~icaclo mposition represented by, in mass%:
Si: 3.0% to 3.6%;
Al: 0.50% to 1.25%;
Mn: 0.5% to 1.5%;
Sb or Sn or both of them: [Sb] + [Sn] / 2 is
0.0025% to 0.05% where [Sb] denotes an Sb content and
[Sn] denotes an Sn content;
P: 0.010% to 0.150%;
Ni: 0.070% to 0.200%;
C: 0.0010% to 0.0040%;
N: 0.0030% or less;
S: 0.0020% or less;
Ti: 0.0030% or less;
Cu: 0.0500% or less;
Cr: 0.0500% or less;
Mo: 0.0500'k or less;
Bi: 0.0050% or less;
Pb: 0.0050% or less;
V: 0.0050% or less;
B: 0.0050% or less; and
balance: Fe and impurities, and
magnetic properties represented by, where t
denotes a thickness (mm) of the non-oriented magnetic
steel sheet:
a magnetic flux density B50: "0.2 x t + 1.52" T
or more;
a magnetic flux density difference AB50: 0.08 T
or less;
core loss W10/50: 0.95 Wjkg or less; and
core loss W10/400: "20 x t t 7 . 5 " W/kg or less,
wherein
the thickness is 0.15 mm to 0.30 mm, and
a ratio of a number of intergranular carbides
precipitated in grains relative to a sum of the
number of the intergranular carbides and a number of
grain boundary carbides precipitated on grain
boundaries is 0.50 or less.
[Claim 21 The non-oriented magnetic steel sheet
according to claim 1, wherein in the chemical
composition,
P: 0.015% to 0.100%,
Ni: 0.020% to 0.100%, or
C: 0.0020% to 0.0030%, or
any combination thereof is satisfied.
[Claim 31 A method of manufacturing a non-oriented
magnetic steel sheet, comprising:
I
hot-rolling of a steel material to obtain a hotrolled
steel sheet;
cold-rolling of the hot-rolled steel sheet to
obtain a cold-rolled steel sheet;
first annealing of the hot-rolled steel sheet
before the cold-rolling is completed; and
second annealing of the cold-rolled steel sheet,
wherein the first annealing includes:
retaining the hot-rolled steel sheet in a
first temperature range from 850°C to 1100°C for
10 seconds to 120 seconds, and
after the retaining, cooling the hot-rolled
steel sheet at a rate of 5'C/s to 50°C/s in a
temperature zone from 850°C to 600°C,
wherein the second annealing includes:
retaining the cold-rolled steel sheet in a
second temperature range from 900°C to llOO°C for
10 seconds to 240 seconds, and
after the retaining, cooling the cold-rolled
steel sheet at a rate of 1O0C/s to 40°C/s in a
temperature zone from 900°C to 300°C, and
wherein the steel material comprises a chemical
composition represented by, in mass%,
Si: 3.0% to 3 . 6 % ;
Al: 0.50% to 1.25%;
Mn: 0.5% to 1.5%;
Sb or Sn or both of them: [Sb] + [Sn] / 2 is
0.0025% to 0.05% where [Sb] denotes an Sb content and
[Sn] denotes an Sn content;
P: 0.010% to 0.150%;
Ni: 0.010% to 0.200%;
C: 0.0010% to 0.0040%;
N: 0.0030% or less;
S: 0.0020% or less;
Ti: 0.0030% or less;
Cu: 0.0500% or less;
Cr: 0.0500% or less;
Mo: 0.0500% or less;
Bi: 0.0050% or less;
Pb: 0.0050% or less;
V: 0.0050% or less;
B: 0.0050% or less; and
balance: Fe and impurities.
[Claim 41 The method of manufacturing the nonoriented
magnetic steel sheet according to claim 3,
wherein hot-rolled sheet annealing is performed as
the first annealing before the cold-rolling.
[Claim 51 The method of manufacturing the nonoriented
magnetic steel sheet according to claim 3,
further comprising hot-rolled sheet annealing before
the cold-rolling, wherein an intermediate annealing
is performed as the first annealing during the coldrolling.
[Claim 61 The iilethod of manufacturing the nonoriented
magnetic steel sheet according to any one of
claims 3 to 5, wherein in the chemical composition,
P: 0.015% to 0.100%,
Ni: 0.020% to 0.100%, or
C: 0.0020% to 0.0030%, or
any combination thereof is satisfied
[Claim 71 The method of manufacturing the nonoriented
magnetic steel sheet according to any one of
claims 3 to 6, wherein a thickness of the cold-rol!~ed
steel sheet is 0.15 mm to 0.30 mm