The present description relates to an induction heating device for a metal strip.
Background Art
[0002] Heating of a metal strip in a heat-treating furnace has been performed mainly by
indirect heating using a radiant tube. The indirect heating restricts productivity because, in
addition to large thermal inertia, valid heat input into a metal strip becomes difficult as the
difference between the temperature of metal strip and furnace temperatnre becomes small.
Furthermore, in the indirect heating using a radiant tube, for example, for a steel sheet such as
a carbon steel, it is difficult to perform rapid heating near the transformation point at which
endothermic reaction occurs, and to perform high-temperature annealing because of
restriction by heat resistance of the radiant tube, restricting choice of degrees of freedom of
heat treatment conditions for metal strip.
(0003] In contrast, induction heating in which a metal strip is heated with high-frequency
current is capable of freely controlling heating speed and heating temperature, so that the
induction heating has large degrees of freedom at the points of heat treatment operation and
development of metal strip products and is a heating method that has been paid attention
recently.
[0004] The induction heating is largely categorized into two methods. One is an LF
(longitudinal flux heating) system for heating a metal strip by flowing high-frequency current
in an induction coil surrounding the circumference of a metal strip to make magnetic flux pass
through a cross section in the longitudinal direction (traveling direction) of the metal strip to
generate induction current circulating in a cross section in the width direction of the metal
strip perpendicular to the magnetic flux.
(0005] The other method is a TF (transverse flux heating) system for heating a metal strip by
arranging inductors (sufficient magnetic bodies) around which respective primary coils are
wound to sandwich the metal strip and flowing currents in the primary coils to make the
magnetic fluxes generated by the currents pass through sheet surfaces of the metal strip via
the inductors to generate induction currents in the sheet surfaces of the metal strip.
(0006] In the induction heating by the LF system for making induction current circulate in a
sheet cross section, on the basis of the relationship between current penetration depth o and
cunent frequency f (8 (mm) = 5.03 x 1 o\l(p/f.tr·f), p(Qm): specific resistance, f-IT: relative
1
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magnetic permeability, f: frequency (Hz)), when the current penetration depth of the induction
current generated on the front and back of the metal strip is deeper than the thickness of the
steel sheet, the generated currents interfere with each other, generating no induction current in
a cross section of the metal strip.
[0007] For example, in the case of a non-magnetic metal strip or a steel sheet that loses
magnetic properties over its Curie temperature, current penetration depth 8 becomes deep,
generating no induction current when the sheet thickness of the metal strip is thin.
Furthermore, even in the case of magnetic material, no induction current generates in a cross
section of steel sheet in the LF system when the sheet thickness is too thin as compared with
penetration depth.
[0008] On the other hand, in the induction heating by the TF system, magnetic flux passes
through a sheet surface of the metal strip, enabling the metal strip to be heated regardless of
sheet thickness and difference of magnetism and non-magnetism, but heating efficiency is
lowered or heating is entirely impossible in some cases when opposite inductors are not
adjacent. Furthermore, overheating readily occurs at ends of the metal strip
disadvantageously (for example, see Japanese Patent Application Laid-Open (JP-A) No.
862-281291).
[0009] Furthermore, when a magnetic metal strip is not located at the center of opposing
inductors, the magnetic metal strip may be pulled to one of the inductors to make magnetic
flux be concentrated regionally to increase temperature variation of the metal strip.
Furthermore, in the induction heating by normal TF system, the inductor is difficult to be
easily changed in its shape, disadvantageously making it difficult to cope with change in sheet
width of the metal strip.
[0010] For that reason, for example, an electromagnetic induction heating device has been
disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2008-186589 that includes a
magnetic pole segments arranged in parallel with a sheet width direction of a sheet to oppose
v the sheet and independently movable in the thick direction of the sheet and a movable
masking shield made of a non-magnetic metal capable of appearing and retreating in the sheet
width direction of the sheet for adjusting magnetic field generated by the magnetic pole
segments.
[0011] The electromagnetic induction heating device ofJP-A No. 2008-186589 is capable of
adjusting magnetic flux in response to change in sheet width of the sheet, but is difficult to
rapidly adjust magnetic flux in sheet width direction when sheet width of the sheet is largely
changed.
[0012] Japanese Patent Application Laid-Open (JP-A) No. 2009-259588 discloses an
2
induction heating device having a plurality of independent magnetic bars and equipped with a
magnetic circuit with a variable width adaptable to the width of a metal strip. However, in
the induction heating device of JP-A No. JP 2009-259588, an example is illustrated in which
magnetic cores movable in a width direction is provided near respective induction coils placed
apmi from front and back sides.
SUMMARY OF INVENTION
[00 13] Embodiments of the description aims mainly to provide an induction heating device
for a metal strip capable of controlling temperature distribution at ends in the sheet width
direction of a metal strip by adjusting current density of and heating period by induction
currents flowing at the ends in the sheet width direction of the metal strip.
[0014] According to an aspect of the present description, there is provided an induction
heating device for a metal strip including: an induction coil including a first induction coil
member and a second induction coil member that are provided in parallel with a metal strip
across the metal strip that travels in a longitudinal direction thereof, that are provided such
that both ends of each of the first induction coil member and the second induction coil
member protrude from the traveling metal strip in a sheet width direction of the traveling
metal strip, and that are arranged such that vertical projection images thereof onto the
traveling metal strip do not overlap each other in a traveling direction in which the metal strip
travels, first electrical connection means for electrically connecting one of both ends of the
first induction coil member and one of both ends of the second induction coil member, and
second electrical connection means for electrically connecting another one of the both ends of
the first induction coil member and another one of the both ends of the second induction coil
member; a first magnetic core including a first magnetic core member provided between the
first induction coil member and the second induction coil member in the traveling direction,
the first magnetic core member being provided on one of surface sides of the traveling metal
strip and covering a large area of one end portion in the sheet width direction of the traveling
metal strip, the large area being on a side of each of the first induction coil member and the
second induction coil member, and covering a small area ofthe one end portion at a center
portion between the first induction coil member and the second induction coil member, and a
second magnetic core member provided between the first induction coil member and the
second induction coil member in the traveling direction, the second magnetic core member
being provided on another one of the surface sides opposite from the one of the surface sides
of the traveling metal strip and covering a large area of the one end portion in the sheet width
direction of the traveling metal strip, the large area being on the side of each of the first
3
induction coil member and the second induction coil member, and covering a small area of the
one end portion at the center portion betwe.en the first induction coil member and the second
induction coil member; and a second magnetic core including a third magnetic core member
provided between the first induction coil member and the second induction coil member in the
traveling direction, the third magnetic core member being provided on the one of the surface
sides of the traveling metal strip and covering a large area of another end portion opposite
from the one end portion in the sheet width direction of the traveling metal strip, the large
area being on the side of each of the first induction coil member and the second induction coil
member, and covering a small area of the another end portion at the center portion between
the first induction coil member and the second induction coil member, and a fourth magnetic
core member provided between the first induction coil member and the second induction coil
member in the traveling direction, the fourth magnetic core member being provided on
another one of the surface sides of the traveling metal strip and covering a large area of the
another end portion in the sheet width direction of the traveling metal strip, the large area
being on the side of each of the first induction coil member and the second induction coil
member, and covering a small area of the another end portion at the center portion between
the first induction coil member and the second induction coil member.
BRIEF DESCRIPTION OF DRAWINGS
[0015] Fig. 1 is a diagram illustrating a mode of an induction heating device in which an
induction coil member on a front surface side of a metal strip and an induction coil member
on a back surface side of the metal strip are arranged such that a vertical projection image of
the induction coil member on the front surface side ofthe metal strip and a vertical projection
image of the induction coil member on the back surface side of the metal strip do not overlap
in a longitudinal direction of the metal strip.
Fig. 2A is a diagram illustrating a plane aspect of an induction current generated in
the whole metal strip.
Fig. 2B is A -A cross section of Fig. 2A, and is a diagram illustrating a mode of the
induction current at the end cross section of the metal strip of the induction current generated
in the whole metal strip.
Fig. 3A is a diagram illustrating a cross sectional structure of a magnetic core for
comparison.
Fig. 3B is a diagram schematically illustrating a cross sectional structure of a
magnetic core used in embodiments of the description.
Fig. 3C is a diagram schematically illustrating a cross sectional structure of another
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magnetic core used in the embodiments of the description.
Fig. 3D is a diagram schematically illustrating a cross sectional structure of still
another magnetic core used in the embodiments of the description.
Fig. 4 is a diagram illustrating an arrangement mode of the magnetic core in the
embodiments of the description, and is a diagram illustrating a case where the magnetic core
is not divided into a plurality of magnetic cores and the induction coil members are arranged
in parallel with a sheet width direction of the metal strip.
Fig. SA is a diagram illustrating an arrangement mode of the magnetic core in the
embodiments of the description, and is a diagram illustrating a case where the magnetic core
is divided into a plurality of magnetic cores and the induction coil members are arranged in
parallel with the sheet width direction of the metal strip. ·
Fig. SB is a diagram illustrating an arrangement mode of the magnetic core in the
embodiments of the description, and is a diagram illustrating a case where the magnetic core
is divided into a plurality of magnetic cores and the induction coil members are arranged so as
to incline toward ends in the sheet width direction.
Fig. 6 is a diagram illustrating a circulation mode of induction current circulating in
the metal strip.
Fig. 7 is a diagram illustrating an arrangement mode of magnetic cores in the case
where two pairs of induction coils are adjacently placed in parallel.
Fig. 8 is a diagram illustrating an arrangement mode of magnetic cores in the case
where two pairs of induction coils are coupled by series connection.
Fig. 9 A is a diagram illustrating an arrangement mode of the magnetic core in the
embodiments of the description, and is a diagram illustrating a case where the induction coil
is of a TF system.
Fig. 9B is a diagram illustrating a circulation mode of induction current circulating in
the metal strip in the case of Fig. 9A.
Fig. 9C is a diagram illustrating a circulation mode of induction current circulating in
the metal strip in the case where the plurality of magnetic cores is not provided in Fig. 9 A
Fig. 10 is a diagram schematically illustrating a configuration of analysis model in an
example.
Fig. 11 is a diagram schematically illustrating a configuration of analysis model in
Comparative Example 2.
Fig. 12 is a diagram schematically illustrating a configuration of analysis model in
Comparative Example 3.
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DESCRIPTION OF EMBODIMENTS
[00 16] In an induction heating device, a magnetic core arranged on the side of an end in the
sheet width direction of a metal strip that travels in a longitudinal direction to cover the end
pushes, at the end of the metal strip, the induction current generated by induction coils
arranged on the front and the back sides of the metal strip outside the magnetic core (center
direction of the metal strip) to suppress the induction current from being concentrated at the
end of the metal strip.
[0017] However, it is difficult to adequately control current density of and heating period by
induction current flowing at the end in the sheet width direction of the metal strip to
appropriately control temperature distribution at the end in the sheet width direction of the
metal strip by only partially arranging the magnetic core at the end in the sheet width
direction of the metal strip.
[00 18] The present inventors have intensively studied about a method of adequately
controlling current density of and heating period by induction current flowing at the end in the
sheet width direction of the metal strip to appropriately control temperature distribution at the
end in the sheet width direction of the metal strip. As a result, the inventors have found that
arrangement of a magnetic core having a predetermined profile on the side of an end in the
sheet width direction at the end in the sheet width direction of the metal strip at which
induction current flows instead of partially arranging a magnetic core at the end in the sheet
width direction of the metal strip makes it possible to adequately control current density of
and heating period by induction current flowing at the end in the sheet width direction of the
metal strip and to appropriately control temperature distribution at the end in the sheet width
direction of the metal strip. It is preferable that the predetermined profile is a shape covering
a large area of the end in the sheet width direction of the metal strip on each of both end sides
in the traveling direction of the metal strip and near corresponding one of induction coils, and
covering a small area of the end at a center portion as compared with the both end sides.
[0019] Furthermore, the inventors have found that the magnetic core may be divided into a
plurality of members in a traveling direction of a metal strip, and that temperature distribution
of an end in the sheet width direction of a metal strip can be freely controlled as long as
including moving means for moving each of the divided plurality of members in the sheet
width direction of the metal strip.
[0020] Embodiments of the description are made on the basis of the above knowledge.
Hereinafter, induction heating devices of the embodiments of the description will be described
with reference to the drawings.
[0021] First, the induction heating device that is the premise of the embodiments of the
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II
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Li
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description and a mode of induction current generated in a metal strip by the induction heating
device will he described.
[0022] Fig. I illustrates a mode of the induction heating device in which an induction coil
member 2a on the front surface side of the metal strip I and an induction coil member 2b on
the back surface side of the metal strip 1 are arranged such that a vertical projection image of
the induction coil member 2a on the front surface side of the metal strip I onto the metal strip
1 and a vertical projection image of the induction coil member 2b on the back surface side of
the metal strip 1 onto the metal strip I are not overlapped in a longitudinal direction (traveling
direction) of the metal strip 1.
[0023] The induction coil member 2a and the induction coil member 2b are arranged in
parallel with the metal strip 1. Both ends of the induction coil member 2a and both ends of
the induction coil member 2b are protruded from the metal strip 1 in the sheet width direction
of the metal strip 1.
[0024] In the induction heating device illustrated in Fig. 1, an end of the induction coil
member 2a on the front surface side of the metal strip 1 passing through the inside of an
induction coil 2 and an end of the induction coil member 2b on the back surface side of the
metal strip 1 are coupled with a conductor 2c, and the other end of the induction coil member
2b is connected to a power source 3 via a conductor 2d and a conductive wire 2e, and the
other end of the induction coil member 2a is connected to the power source 3 via a conductor
2h, a coupler 2g, and a conductive wire 2f. Current flows in the directions of the arrows in
the drawing. The conductor 2c is an example of electrical connection means, and the
conductor 2d, the conductive wire 2e, the conductive wire 2f, and the conductor 2h are also
examples of electrical connection means. The induction coil 2 includes the induction coil
rnember 2a, the induction coil member 2b, the conductor 2c, the conductor 2d, the conductive
wire 2e, the conductive wire 2f, and the conductor 2h.
[0025] The induction coil member 2a and the induction coil member 2b are arranged such
that the vertical projection image that is the vertical projection of the induction coil member
2a onto the metal strip 1 and the vertical projection image that is the vertical projection of the
induction coil member 2b onto the metal strip 1 are not overlapped in the longitudinal
direction (traveling direction) of the metal strip 1.
[0026] In the case of the above LF method, induction currents having the same magnitude
flow on the respective front and back surfaces of the metal strip in reverse directions, so that
when current penetration depth o is deep, the induction currents interfere to each other,
making no induction current flow. However, in the case of Fig. 1, the induction coil
members 2a and 2b are arranged such that the vertical projection images that are vertical
7
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I
I
projections thereof onto the metal strip 1 are not overlapped in the longitudinal direction
(traveling direction) of the metal strip l, so that each of the induction current flowing in the
metal strip 1 just below the induction coil member 2a and the induction current flowing in the
metal strip 1 just below the induction coil member 2b becomes a current that flows in only
one direction, allowing the currents to flow without interfering to each other even when
current penetration depth o is deep.
[0027] Figs. 2A and 2B illustrate a mode of an induction current 5 generated in the whole
metal strip 1. Fig. 2A illustrates a planer mode of the induction current, and Fig. 2B
illustrates a mode of the induction current 5 at an end cross section (A-A cross section of Fig.
2A) of the metal strip 1.
[0028] In the metal strip 1 just below the induction coil members 2a, 2b (not shown), an
annular induction current 5 (Sa, 5b) generates that flows in the directions of the arrows
(inverse directions of the current flowing in the induction coil members 2a, 2b) as illustrated
in Fig. 2A. The induction coil member 2a is arranged on the front surface side of the metal
strip 1, and the induction coil member 2b is arranged on the back surface side of the metal
strip 1, so that the induction current 5 flows to obliquely cross the end cross section of the
metal strip 1 as illustrated in Fig. 2B. Even when the metal strip 1 is non-magnetic material,
the induction currents 5 generates and circulates, enabling the metal strip 1 to be heated. Fig.
2B illustrates a state of current flow when the sheet thickness of the metal strip l is thick, but
when the sheet thickness of the metal strip 1 is thin, current does not obliquely cross and
flows in the whole sheet thickness of the metal strip 1.
[0029] However, overheating readily occurs at the ends in the sheet width direction of the
metal strip l, because, for example, (a) the induction current flowing at the ends in the sheet
width direction of the metal strip l tries to make the reactance between with the primary
current flowing in the conductor 2c (see Fig. l) coupling the induction coil member 2a on the
front surface side with the induction coil member 2b on the back surface side of the metal
strip 1 (see Fig. 1 ), or flowing in the conductor 2d, the conductive wire 2e, the conductive
wire 2f, and the conductor 2h (see Fig. 1) coupling the induction coil on the front surface side
and the induction coil on the back surface side of the metal strip with the power source small
to be unfortunately shifted to the ends in the sheet width direction of the metal strip l,
unfortunately narrowing the width d2 of the current path, (b) the magnetic flux generated by
the primary current flowing in the conductor 2c, the conductor 2d, the conductive wire 2e, the
conductive wire 2f, and the conductor 2h concentrically passing through the ends in the sheet
width direction of the adjacent metal strip 1, and (c) at the ends in the sheet width direction of
the metal strip 1, as compared with the center of the metal strip 1, heating is performed for a
8
long period by the distance d3 in the longitudinal direction (traveling direction) of the metal
strip I (heating distance for the center is dl x 2, heating distance for the ends in the sheet
width direction is dl x 2 + d3).
[0030] Furthennore, when the induction coil2 is a pair of coil members, magnetic flux
spreads outside the induction coil2, which lowers the current density of the induction current
5 at the center of the metal strip I, making it difficult to increase the temperature at the center
to make the thermal difference between the center and the ends in the sheet width direction of
the metal strip I readily increase.
[0031] So, in the induction heating device of the embodiments of the description, to control
the induction current 5 flowing at the ends in the sheet width direction of the metal strip I
across the whole width of the ends where the induction current 5 flows and to freely control
the temperature distribution in the sheet width direction of the metal strip I, a plurality of
magnetic cores capable of covering the ends in the sheet width direction of the metal strip 1
and the metal strip 1 beyond the ends is arranged across the whole width between the vertical
projection image ofthe induction coil member 2a on the front surface side of the metal strip 1
onto the metal strip 1 and the vertical projection image of the induction coil member 2b on the
back surface side of the metal strip 1 onto the metal strip I so as to be movable forwardly and
backwardly in the sheet width direction of the metal strip 1.
[0032] The induction coil members 2a, 2b may be one conductor or may be a plurality of
conductors. Furthermore, a magnetic core for a back surface may be mounted at the back
surface of the induction coil members 2a, 2b to enforce magnetic flux.
[0033] Figs. 3A to 3D each illustrate a cross sectional structure of a magnetic core 6. Fig.
3Aillustrates a cross sectional structure of the magnetic core 6 for comparison, Fig. 3B
illustrates a cross sectional structure of the magnetic core 6 used in the embodiments, and Fig.
3C illustrates a cross sectional structure of another magnetic core 6 used in the embodiments.
Fig. 3D schematically illustrates a cross sectional structure of a still another magnetic core 6
used in the embodiments.
[0034] The size of the magnetic core 6 is not limited to a specific range and may be
appropriately set on the basis of the distance between the induction coil members 2a, 2b on
the front surface side and back surface side of the metal strip 1, the sheet width of the metal
strip I, and the number of the magnetic cores 6 to be arranged.
[0035] Although the magnetic core 6 is formed of a ferromagnetic substance, the
ferromagnetic substance is not limited to a ferromagnetic substance of a specific material.
The ferromagnetic substance includes, for example, ferrite, laminated magnetic steel sheet,
and amorphous alloy, and may be appropriately selected depending on heating capability,
9
frequency, etc. applied to the induction heating device.
[0036] As illustrated in Fig. 3A, the magnetic core 6 for comparison covering the end in the
sheet width direction of the metal strip 1 absorbs magnetic flux 4' excited by the induction
coil (not shown) (see the a1rows passing through the magnetic core 6') to prevent magnetic
flux concentration to the end in the sheet width direction of the metal strip 1, and suppresses
excessive temperature increase at the end in the sheet width direction of the metal strip 1.
However, when the magnetic core 6' is partially and individually arranged, the suppress effect
of end current is limited, so that the effect is small.
[003 7] In the magnetic core 6 used in the embodiments illustrated in Fig. 3B, the distance d
with the metal strip 1 is set narrow to suppress passage of current effectively at the end in the
sheet width direction ofthe metal strip I, the length L of the magnetic core in the sheet width
direction of the metal strip 1 is set long such that the magnetic core 6 covers the metal strip
beyond the end in the sheet width direction of the metal strip 1 to be able to appropriately
control distribution of the induction current, and the depth of the portion covering the metal
strip 1 is set deep such that the magnetic core 6 is capable of immediately cope with change
W in the sheet width of the metal strip 1.
[003 8] The magnetic core 6 includes a magnetic core member 6a on the front surface side of
the metal strip 1, a magnetic core member 6b on the back surface side thereof, and a magnetic
core member 6e for coupling ends (right side ends in the drawings) of the magnetic core
member 6a and the magnetic core member 6b, which are on the side opposite from the
portions of the magnetic core member 6a and the magnetic core member 6b covering the
metal strip 1.
[0039] A surface portion readily accepting heat of the magnetic core 6 may be covered with
a non-magnetic heat insulating material 6c as illustrated in Fig. 3C to suppress temperature
increase due to radiation heat from the heated metal strip 1 to stably use the magnetic core 6.
Note that when temperature increase of the magnetic core 6 cannot be suppressed only by
coating of the heat insulating material 6c, the magnetic core 6 may be cooled by, for example,
attaching a water-cooling plate (not shown) to the magnetic core 6 or by providing a gas
cooling device (not shown) near the magnetic core 6.
[0040] The induction heating device of the embodiments is provided with a moving member
9 for moving the magnetic core 6 illustrated in Fig. 3B or 3C forward and backward in the
sheet width direction of the metal strip 1. Moving the magnetic core 6 in the sheet width
direction of the metal strip 1 by the moving member 9 is performed by, for example, moving a
carriage for holding the magnetic core with a driving device such as an electric cylinder, an
air cylinder, or a motor in an orbit. However, the magnetic core 6 may only to be moved
10
quickly and smoothly in the sheet width direction of the metal strip I, and the moving
member for the magnetic core 6 is not specifically specified as long as the conditions are
satisfied.
[0041] Fig. 3D schematically illustrates a cross sectional structure of a still another magnetic
core 6 used in the embodiments. In the magnetic core 6 illustrated in Fig. 3D, an end (a right
end in the drawing) of the magnetic core 6 are not coupled by a magnetic body. The
magnetic core 6 includes a magnetic core member 6a on the front surface side and a magnetic
core member 6b on the back surface side of the metal strip 1. To keep the distance between
the magnetic core member 6a and the magnetic core member 6b, the ends on the side opposite
to the portions covering the metal strip 1 (in the drawing, right side ends) are coupled by a
coupling member 6d that is non-magnetic and has heat resistance.
[0042] In the magnetic core 6 illustrated in Fig. 3D, although the magnetic core member 6a
and the magnetic core member 6b are arranged on the front surface side and the back surface
side of the metal strip 1, respectively, and the magnetic core member 6a and the magnetic core
member 6b are coupled by the coupling member 6d, the magnetic core 6 illustrated in Fig. 3D
has the current suppressing effect similar to that by the magnetic core 6 illustrated in Fig. 3B
in which the magnetic core member 6a and the magnetic core member 6b are coupled by the
magnetic core member 6e. The magnetic core 6 is capable of immediately following change
in sheet width by forward/backward movement in the sheet width direction of the metal strip
1 by the moving member 9 even when the sheet width of the metal strip 1 is changed, and
makes it possible to immediately follow positional deviation even when the metal strip 1
continuously snakes and the position of the end in the sheet width direction is largely
deviated.
[0043] Fig. 4 illustrates an arrangement mode of the magnetic cores 6 in the embodiments.
The induction coil members 2a, 2b are arranged in parallel with the sheet width direction of
the metal strip 1. The magnetic cores 6 capable of covering the respective ends in the sheet
width direction of the metal strip 1 and the metal strip 1 beyond the ends are arranged on the
both sides in the sheet width direction of the metal strip 1. The magnetic cores 6 are
arranged across the whole width between the vertical projection image of the induction coil
member 2a on the front surface side of the metal strip 1 onto the metal strip 1 and the vertical
projection image of the induction coil member 2b on the back surface side of the metal strip 1
onto the metal strip 1.
[0044] As illustrated in Fig. 3B, the magnetic core 6 includes the magnetic core member 6a
on the front surface side and the magnetic core member 6b on the back surface side of the
metal strip 1, and the magnetic core member 6e coupling the ends (in the drawing, right side
11
ends) on the side opposite from the portions covering the metal strip 1 of the magnetic core
member 6a and the magnetic core member6b. Note that the non-magnetic coupling member
6d may be provided instead of the magnetic core member 6e as illustrated in Fig. 3D.
Alternatively, as illustrated in Fig. 3C, the magnetic core 6 may be covered with the
non-magnetic heat insulating material 6c.
[0045] The magnetic core member 6a and the magnetic core member 6b cover a large area
of the end in the sheet width direction of the metal strip 1 on the side of each of the induction
coil member 2a and the induction coil member 2b, and cover a small area of the ends at the
center portion between the induction coil member 2a and the induction coil member 2b. The
side of each of the magnetic core member 6a and the magnetic core member 6b covering the
end in the sheet width direction of the metal strip 1 is bent.
[0046] The magnetic core member 6a and the magnetic core member 6b are movable
forwardly and backwardly in the sheet width direction of the metal strip 1 by the moving
member 9 to follow change in the sheet wi!ith, and capable of following positional deviation
due to snaking or the like of the metal strip 1.
[0047] Figs. SA and SB each illustrate an arrangement mode of the magnetic cores 6 of the
embodiment. Fig. 5Aillnstrates a case where the induction coil members 2a, 2b are
arranged in parallel with the sheet width direction of the metal strip 1, and Fig. SB illustrates a
case where the induction coil members 2a, 2b are arranged to incline toward the ends in the
sheet width direction of the metal strip 1. The case is illustrated in which the induction coil
member 2a is arranged to incline on the side of the induction coil member 2b toward the ends
in the sheet width direction of the metal strip 1, and the induction coil member 2b is arranged
to incline on the side of the induction coil member 2a toward the ends in the sheet width
direction of the metal strip 1.
[0048] As illustrated in Figs. SA, SB, the magnetic cores 6 capable of covering the ends in
the sheet width direction ofthe metal strip 1 and the metal strip 1 beyond the ends in the sheet
width direction are arranged on the respective both sides in the sheet width direction of the
metal strip 1. The magnetic cores 6 are arranged across the whole width between the vertical
projection image of the induction coil member 2a on the front surface side of the metal strip 1
onto the metal strip 1 and the vertical projection image of the induction coil member 2b on the
back surface side of the metal strip 1 onto the metal strip 1.
[0049] The magnetic core 6 is divided into a plurality of magnetic cores 60 in the
longitudinal direction (traveling direction) of the metal strip 1. The magnetic core member
6a on the front surface side of the metal strip 1 is divided into a plurality of magnetic core
members 60a. The magnetic core member 6b on the back surface side of the metal strip 1 is
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divided into a plurality of magnetic core members 60b. The magnetic core member 6e
coupling the ends on the side opposite from the portions covering the metal strip 1 (in the
drawing, right side ends) of the magnetic core member 6a and the magnetic core member 6b
is divided into a plurality of magnetic core members 60e. The number of the plurality of
magnetic core members 60a equals to the number of the plurality of magnetic core members
60b, and the plurality of magnetic core members 60a and the plurality of magnetic core
members 60b are arranged such that the vertical projection image of the plurality of magnetic
core members 60a and the vertical projection image of the plurality of magnetic core
members 60b onto the metal strip 1 are overlapped each other in the traveling direction ofthe
metal strip I.
[0050] The divided magnetic core 60 includes the magnetic core member 60a on the front
surface side and the magnetic core member 60b on the back surface side of the metal strip 1,
and the magnetic core member 60e coupling the ends on the side opposite from the portions
covering the metal strip 1 (in the drawing, right side ends) of the magnetic core member 6a
and the magnetic core member 6b as illustrated in Fig. 3B. Note that the non-magnetic
coupling member 60d may be provided instead of the magnetic core member 60e as
illustrated in Fig. 3D. Alternatively, as illustrated in Fig. 3C, the magnetic core 60 may be
covered with the non-magnetic heat insulating material 60c.
[0051] The plurality of magnetic core members 60a and the plurality of magnetic core
members 60b are movable forwardly and backwardly in the sheet width direction of the metal
strip 1 by the moving member 9 to follow change in the sheet width, and capable of following
positional deviation due to snaking or the like of the metal strip 1. Furthermore, the moving
member 9 enables a line connecting the side of the magnetic core members 60a mid magnetic
core members 60b covering the end in the sheet width direction of the metal strip 1 to be a
predetermined profile.
[0052] The plurality of magnetic cores 60 is not necessary to be arranged with no gap in the
whole width between the vertical projection image of the induction coil member 2a on the
front surface side of the metal strip 1 onto the metal strip 1 and the vertical projection image
of the induction coil member 2b on the back surface side of the metal strip 1 onto the metal
strip 1, and an appropriate number of magnetic cores 60 may be arranged at predetermined
intervals to provide a desired heating temperature distribution.
[0053] The line connecting the side of the magnetic core members 60a and magnetic core
members 60b covering the end in the sheet width direction of the metal strip 1 is bent. The
plurality of magnetic cores 60 is arranged to cover the end in the sheet width direction of the
metal strip 1 in the center area between the induction coil member 2a and the induction coil
13
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member 2b, and is arranged to cover an inside of the metal strip 1 beyond the end in the sheet
width direction of the metal strip 1 in the area near the induction coil member 2a and the area
near the induction coil member 2b. The magnetic core members 60a and the magnetic core
members 6b cover a large area of the end in the sheet width direction of the metal strip 1 on
the side of each of the induction coil member 2a and the induction coil member 2b, and cover
a small area of the end at the center portion between the induction coil member 2a and the
induction coil member 2b.
[OOS4] Advance/retreat control of the magnetic core members 60a and the magnetic core
members 60b in the sheet width direction gradually suppresses flowing direction of the
induction current concentrated at the ends in the sheet width direction of the metal strip 1 to
adjust current density and heating period of the cunent flowing at the ends ofthe metal strip
to prevent overheating at the ends in the sheet width direction of the metal strip 1.
[OOSS] Furthermore, heat generation distribution in the sheet width direction of the metal
strip 1 is accurately controlled by freely adjusting the current distribution of the induction
current circulating on the sheet surface of the metal strip 1.
[OOS6] For example, when the metal strip 1 is heated by a radiant tube in the stage before
using the induction heating device to make the ends of the metal strip be in a high temperature
state, making temperature distribution in the sheet width direction of the metal strip even is
possible at the exit side of the induction heating device by suppressing calorific value at the
ends so as to be smaller than calorific value at the center of the metal strip by suppressing the
current flowing at the ends of the metal strip.
[OOS7] In the case of the arrangement of the magnetic cores 60 illustrated in Fig. SB, the
current flowing at the ends in the sheet width direction of the metal strip 1 can be adjusted to
some extent by the induction coil members 2a, 2b themselves, so that the number of the
magnetic cores 60 arranged between the induction coil members 2a, 2b may be smaller as
compared with the case of Fig. SA.
[OOS8] Fig. 6 illustrates a circulation mode of an induction current 7 generated in the metal
strip 1 in the case where the induction coil member 2a, the induction coil member 2b, and the
plurality of magnetic cores 60, which are described with reference to Fig. SA, are arranged.
The induction current 7 generated by the induction coil member 2a on the front surface side of
the metal strip 1 and the induction coil member 2b on the back surface side of the metal strip
1 and suppressed in its concentration to the ends ofthe metal strip 1 by the plurality of
magnetic cores 60 arranged on the both sides of the ends in the sheet width direction of the
metal strip 1 elliptically circulates clockwise in the. sheet surface of the metal strip 1. In this
marmer, the plurality of magnetic cores 60 gradually suppresses flowing direction ofthe
14
induction current concentrated at the ends in the sheet width direction of the metal strip 1 to
adjust current density and heating period of the current flowing at the ends of the metal strip 1
to prevent overheating at the ends in the sheet width direction of the metal strip 1.
(0059] Note that also in the case where the induction coil member 2a, the induction coil
member 2b, and the plurality of magnetic cores 60 described with reference to Fig. 5B are
arranged, the induction current 7 generated by the induction coil member 2a on the front
surface side of the metal strip 1 and the induction coil member 2b on the back surface side of
the metal strip I and suppressed in its concentration to the ends of the metal strip I by the
plurality of magnetic cores 60 arranged on the both sides of the ends in the sheet width
direction of the metal strip 1 elliptically circulates clockwise in the sheet swface of the metal
strip 1. Further, also in the case where the induction coil member 2a, the induction coil
member 2b, and the magnetic cores 6 described with reference to Fig. 4 are arranged, the
induction current 7 generated by the induction coil member 2a on the front surface side of the
metal strip 1 and the induction coil member 2b on the back surface side of the metal strip 1
and suppressed in its concentration to the ends of the metal strip 1 by the magnetic cores 6
arranged on the both sides of the ends in the sheet width direction of the metal strip 1
elliptically circulates clockwise in the sheet surface of the metal strip 1.
[0060] The arrangement of the plurality of magnetic cores 60 and advance/retreat control of
the plurality of magnetic cores 60 do not necessarily need to be symmetric on the both sides in
the sheet width direction of the metal strip 1. In the case where temperature distribution is
already asymmetric in the sheet width direction of the metal strip 1 at the entrance side of the
induction heating device, or in the case where distribution of magnetic field is asymmetric due
to snaking, etc., the plurality of magnetic cores 60 does not need to be arranged symmetrically
in the sheet width direction of the metal strip 1, and the arrangement thereof may be
appropriately changed depending on purpose.
(0061] Furthermore, circulation mode of the induction current 7 is not limited to be
ellipsoidal, and can be any mode by appropriately changing the entering distances and/or the
number of the magnetic cores 60 to be arranged.
(0062] So far, the case of one pair of induction coils is described in which the induction coil
member 2a on the front surface side and the induction coil member 2b on the back surface
side of the metal strip 1 are coupled, but the inventor confirmed that the above magnetic cores
6 and plurality of magnetic cores 60 effectively function also in the induction heating device
in which a plurality of pairs of induction coils is successively arranged.
[0063] Fig. 7 illustrates an arrangement mode of the magnetic cores 60 when two pairs of
induction coils 2 are arranged in parallel adjacently.
15
In this case, currents having same phase
need to flow in respective the induction coil member 2b and the induction coil member 2a
located at the center. Making the induction coils 2 be placed to align in the traveling
direction of the metal strip I and making currents having same phase flow in respective the
adjacent induction coils 2 increases magnetic flux density at a center pmiion to relatively
increase the ratio of heat generation at the center in the sheet width direction, which makes it .
possible to reduce degree of overheating at the ends in the sheet width direction, enabling
more even heating.
[0064] Furthermore, changing outputs of the induction coils 2 of the first stage and second
stage allows heating speed to be freely controlled, wbich makes it possible to heat different
temperature areas at different heating speeds, and making it possible to adequately cope with
various heating conditions metallurgically required.
[0065] Fig. 8 illustrates an arrangement mode of the magnetic cores 60 when two pairs of
induction coils 2 are coupled by series connection and arranged. Arranging the induction
coils 2 by series connection makes the currents flowing respective the induction coils 2 of the
first stage and the second stage become same, making it possible to make the calorific values
at respective the induction coils 2 of the first stage and the second stage same.
[0066] Fig. 9A illustrates an arrangement mode of an induction coil 20 and the magnetic
cores 60 in the case of an induction heating device of a TF system.
[0067] The induction coil 20 is arranged on the both sides of the front surface side and back
surface side of the metal strip 1. The direction of the current flowing in the induction coil 20
on the front surface side of the metal strip I is same as the direction of the current flowing in
the induction coil 20 on the back surface side of the metal strip 1. The current flows in the
directions shown by the arrows in the drawing.
[0068] The induction coil 20 on the front surface side of the metal strip 1 and the induction
coil20 on the back surface side of the metal strip I each include an induction coil member
20a, an induction coil member 20b, an induction coil member 20c, and an induction coil
member 20d. The induction coil member 20a and the induction coil member 20b are
arranged in parallel with the metal strip 1. The both ends of the induction coil member 20a
and the both ends ofthe induction coil member 20b are protruded from the metal strip 1 in the
sheet width direction of the metal strip 1. One end of the induction coil member 20a and one
end of the induction coil member 20b are coupled by the induction coil member 20c, and the
other end of the induction coil member 20a and the other end ofthe induction coil member
20b are coupled by the induction coil member 20d. The induction coil member 20c is an
example of electrical connection means, and the induction coil member 20d is also an
example of electrical connection means.
16
[0069] The induction coil member 20a and the induction coil member 20b are arranged such
that the vertical projection image that is the vertical projection of the induction coil member
20a onto the metal strip I, and the vertical projection image that is the vertical projection of
the induction coil member 20b onto the metal strip I are not overlapped in the longitudinal
direction (traveling direction) of the metal strip I.
[0070] The vertical projection image of the induction coil member 20a of the induction coil
20 on the front surface side of the metal strip I onto the metal strip I, and the vertical
projection image of the induction coil member 20a of the induction coil 20 on the back
surface side of the metal strip I onto the metal strip 1 are arranged to overlap in the
longitudinal direction (traveling direction) of the metal strip I.
[0071] The vertical projection image of the induction coil member 20b of the induction coil
20 on the front surface side of the metal strip 1 onto the metal strip 1, and the vertical
projection image of the induction coil member 20b of the induction coil20 on the back
surface side of the metal strip 1 onto the metal strip 1 are arranged to overlap in the
longitudinal direction (traveling direction) of the metal strip I.
[0072] The magnetic core 6 including a plurality of magnetic cores 60 (a plurality of
magnetic core members 60a and a plurality of magnetic core members 60b) has the same
configuration as that of the magnetic core 6 including the plurality of magnetic cores 60 (the
plurality of magnetic core member 60a and the plurality of magnetic core member 60b)
described with reference to Fig. SA, and a moving member 9 that makes each of the plurality
of magnetic core members 60a and the plurality of magnetic core members 60b move
forwardly and backwardly in the sheet width direction of the metal strip 1 is also identical to
the moving member 9 described with reference to Fig. SA.
[0073] Fig. 9B illustrates a plane mode of an induction current 70 generated in the metal
strip 1 when the magnetic cores 6 as illustrated in Fig. 9A are provided. Fig. 9C illustrates a
plane aspect of an induction current 70a generated in the metal strip 1 when the magnetic
cores 6 illustrated in Fig. 9 A are not provided.
[007 4] Referencing to Fig. 9C, in the metal strip I just below the induction coil members
20a, 20b, the armular induction current 70a flowing in the directions of the arrows generates.
Overheating readily occurs at the ends in the sheet width direction of the metal strip 1,
because, for example, the induction current 70a flowing at the ends in the sheet width
direction of the inetal strip l (a) tries to make the reactance between with the primary current
flowing in the induction coil member 20c or the induction coil member 20d coupling the
induction coil member 20a and the induction coil member 20b small to be unfortunately
shifted to the ends in the sheet width direction of the metal strip 1, unfortunately narrowing
17
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the width d2 of the current path, (b) the magnetic flux generated by the primary current
flowing in the induction coil member 20c or the induction coil member 20d concentrically
passing through the ends in the sheet width direction of the adjacent metal strip I, and (c) at
the ends in the sheet width direction of the metal strip I, as compared with the center of the
metal strip 1, heating is performed for a long period by the distance in the longitudinal
direction (traveling direction) of the metal strip 1.
[0075] In contrast, referencing to Fig. 9B, the plurality of magnetic cores 60 is provided, so
that the induction current 70 generated by the induction coil member 20a and the induction
coil member 20b and suppressed in its concentration to the ends of the metal strip 1 by the
plurality of magnetic cores 60 arranged at the both sides of the ends in the sheet width
direction of the metal strip 1 elliptically circulates in thesheet surface of the metal strip 1. In
this manner, the plurality of magnetic cores 60 gradually suppresses flowing direction of the
induction current concentrated at the ends in the sheet width direction of the metal strip 1 to
adjust the current density and heating period of the current flowing at the ends of the metal
strip 1 to prevent overheating at the ends in the sheet width direction of the metal strip 1.
Example
[0076] Next, an example will be described, but the condition of the example is a conditional
example employed to confirm operability and effects of the invention, and the invention is not
limited to the conditional example.
[0077] (Example 1)
Electromagnetic field analysis was performed under the following conditions to
confirm effects.
Target Material: 0.06% C steel sheet (sheet width 1 m, sheet thickness 1 mm).
Induction Coils: copper sheets having a width of 150 mm were placed to sandwich
the steel sheet and such that the copper sheets onthe front and back side become in parallel to
each other, and vertical projection images thereof onto the steel sheet are separated by 300
mm in inside dimension. The distance between the steel sheet and the induction coils is I 0
mm.
Magnetic core A: A magnetic core (made of ferrite) disposed between the induction
coil and the induction coil. Width 30 mm, thickness 20 mm, depth 200 mm, inside height
100 mm, and depth 180 mm; Seven cores (one side of steel sheet ends) are arranged at
intervals 6f 10 mm so as to be separated by 15 mm from the induction coils. Relative
magnetic permeability is 2000.
Magnetic core B; A magnetic core (made of ferrite) for concentrating magnetic flux
mounted on the back surface of the induction coil. Physical properties are same as those of
18
····---··-·--·~-~----------------
the magnetic core A.
Heating: Heating at 800°C in non-magnetic area.
Property Values
Steel Sheet: relative magnetic permeability l [-], electric conductivity 106
[S/m]
Induction Coils: relative magnetic permeability 1 [-],electric conductivity 0
[S/m]
Magnetic Cores: relative magnetic permeability 2000 [-], electric
conductivity 0 [S/m]
Boundary Condition
Periphery Portion: symmetrical boundary
Current: I 0 kHz constant current
[0078] Analytical Model
Example: The induction coils 2a, 2b laid in the whole sheet width with a gap of 300
mrn are placed in parallel on the front surface side and back surface side of the steel sheet 1
and magnetic cores A 1 to A 7 are arranged on both sides of the ends of the steel sheet and
between the two induction coils 2a, 2b. Fig. 10 schematically illustrates a configuration of
the analytical model of the example.
[0079] A circulation mode of the induction current 7 generated by the induction coil 2a
(front surface side) and the induction coil 2b (back surface side) was changed by changing
'
entering distances (mrn) of the magnetic cores AI to A 7 from steel sheet end, the temperature
at the steel sheet end and the temperature at the steel sheet center were calculated, and the
temperature ratio = temperature of steel sheet end/temperature of steel sheet center was
calculated. Table 1 shows the results.
[0080] Comparative Examples 1 to 3: The induction coils 2a, 2b laid in the whole sheet
width with a gap of 300 mrn ware placed in parallel on the front surface side and back surface
side of the steel sheet 1, and in each of the cases where no magnetic core was arranged on
both sides of the ends of the steel sheet and between the two induction coils 2a, 2b
(Comparative Example 1), where the magnetic coreA! was arranged at one end of the steel
sheet 1 and near the induction coil2a, and the magnetic core A7 was arranged at the other end
of the steel sheet 1 and near the induction coil2b (Comparative Example 2), and where the
magnetic cores Al, A7 are arranged at each of the both ends of the steel sheet and near the
induction coils 2a, 2b, respectively (Comparative Example 3), the temperature at the steel
sheet end and the temperature at the steel sheet center were calculated, and the temperature
ratio = temperature of the steel sheet end/the temperature of steel sheet center was calculated.
19
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Table I illustrates the results. Fig. 11 and Fig. 12 each schematically illustrate a
configuration of the analytical model of Comparative Example 2 and Comparative example 3,
respectively.
[0081] [Table I]
Temperature ratio (- end temperature/center temperature)
Example of the invention 1.08
Comparative Example I 7.3
Comparative Example 2 5.2
Comparative Example 3 3.0
[0082] The temperature rat1os illustrated m Table I show that temperature d1stnbut10n m the
sheet width direction of the steel sheet was largely improyed to be homogenized.
[0083] According to the embodiments of the above description, it is possible to control the
induction cunent flowing on end sides in the sheet width direction of the metal strip and to
freely control temperature distribution of the metal strip in the sheet width direction regardless
of magnetic or non-magnetic also when the sheet thickness is thin.
[0084] Furthermore, according to the embodiments of the description, it is possible to freely
correct temperature distribution so as to be desired temperature distribution during heating the
metal strip also in the case where the metal strip is heated before entering in the induction
heating device and a large deviation exists in temperature distribution of the metal strip,
thereby making it possible to improve heat processing quality of the metal strip.
[0085] Furthermore, according to the embodiments of the description, heating is possible
without lowering heating rate also in the temperature area where temperature exceeds Curie
point at which heat transfer becomes difficult as a heated material becomes high temperature
by radiation heating, thereby making it possible to improve productivity to dramatically
improve flexibility of schedule of production.
[0086] The disclosure of Japanese Patent Application No. 2014-181710 filed on September
5, 2014 in its entirety is hereby incorporated by reference.
All the documents, patent applications, and technical standards described in the
present description are hereby incorporated by reference to the same extent as in cases where
each document, patent application, or technical standard is specifically and individually
described as being incorporated by reference.
[0087] Although various typical embodiments are described above, the present invention is
not limited to the embodiments. The scope of the present invention is limited only by the
following claims.

CLAIMS
1. An induction heating device for a metal strip, comprising:
an induction coil including:
a first induction coil member and a second induction coil member that are
provided in parallel with a metal strip across the metal strip that travels in a longitudinal
direction thereof, that are provided such that both ends of each of the first induction coil
member and the second induction coil member protrude from the traveling metal strip in a
sheet width direction of the traveling metal strip, and that are arranged such that vertical
projection images thereof onto the traveling metal strip do not overlap each other in a
traveling direction in which the metal strip travels;
first electrical connection means for electrically connecting one of both ends
of the first induction coil member and one of both ends of the second induction coil member;
and
second electrical connection means for electrically connecting another one
of the both ends of the first induction coil member and another one of the both ends of the
second induction coil member;
a first magnetic core including:
a first magnetic core member provided between the first induction coil
member and the second induction coil member in the traveling direction, the first magnetic
core member being provided on one of surface sides of the traveling metal strip and covering
a large area of one end portion in the sheet width direction of the traveling metal strip, the
large area being on a side of each of the first induction coil member and the second induction
coil member, and covering a small area of the one end portion at a center portion between the
first induction coil member and the second induction coil member; and
a second magnetic core member provided between the first induction coil
member and the second induction coil member in the traveling direction, the second magnetic
core member being provided on another one of the surface sides opposite from the one ofthe
surface sides of the traveling metal strip and covering a large area of the one end portion in
the sheet width direction of the traveling metal strip, the large area being on the side of each
of the first induction coil member and the second induction coil member, and covering a small
area of the one end portion at the center portion between the first induction coil member and
the second induction coil member; and
a second magnetic core including:
a third magnetic core member provided between the first induction coil
21
-- ---~----------- ---~------
member and the second induction coil member in the traveling direction, the third magnetic
core member being provided on the one ofthe surface sides of the traveling metal strip and
covering a large area of another end portion opposite from the one end portion in the sheet
width direction of the traveling metal strip, the large area being on the side of each of the first
induction coil member and the second induction coil member, and covering a small area of the
another end portion at the center portion between the first induction coil member and the
second induction coil member; and
a fourth magnetic core member provided between the first induction coil
member and the second induction coil member in the traveling direction, the fourth magnetic
core member being provided on the another one of the surface sides of the traveling metal
strip and covering a large area of the another end portion' in the sheet width direction of the
traveling metal strip, the large area being on the side of each of the first induction coil
member and the second induction coil member, and covering a small area of the another end
portion at the center portion between the first induction coil member and the second induction
coil member.
2. The induction heating device for a metal strip according to claim 1, wherein
the first induction coil member is provided on the one of the surface sides of the
traveling metal strip, and the second induction coil member is provided on the another one of
the surface sides of the traveling metal strip.
3. The induction heating device for a metal strip according to claim 1, further
comprising a second induction coil including:
a third induction coil member and a fourth induction coil member that are
provided in parallel with the metal strip across the metal strip that travels in the longitudinal
direction thereof, that are provided such that both ends of each of the third induction coil
member and the fourth induction coil member protrude from the traveling metal strip in the
sheet width direction of the traveling metal strip, and that are arranged such that vertical
projection images thereof onto the traveling metal strip do not overlap each other in the
traveling direction in which the metal strip travels;
third electrical connection means for electrically connecting one of both
ends ofthe third induction coil member and one of both ends of the fourth induction coil
member; and
fourth electrical connection means for .electrically connecting another one of
the both ends of the third induction coil member and another one of the both ends of the
22
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foutih induction coil member,
wherein vertical projection images of the first induction coil member and the third
induction coil member onto the traveling metal strip overlap each other in the traveling
direction in which the metal strip travels, and vertical projection images of the second
induction coil member and the fourth induction coil member onto the traveling metal strip
overlap each other in the traveling direction in which the metal strip travels, and
wherein the first induction coil member and the second induction coil member m-e
provided on the one of the surface sides of the traveling metal strip, and the third induction
coil member and the fourth induction coil member are provided on the another one of the
surface sides of the traveling metal strip.
4. The induction heating device for a metal strip according to any one of claim 1 to
claim 3, wherein
the first magnetic core member ar:td the second magnetic core member each m-e
divided into a same number of a plurality of members in the traveling direction, and the
plurality of divided first magnetic core members and the plurality of divided second magnetic
core members m-e m-ranged such that vertical projection images of the divided first magnetic
core members and vertical projection images of the divided second magnetic core members
onto the traveling metal strip respectively overlap each other in the traveling direction in
which the metal strip travels, and
the third magnetic core member and the fourth magnetic core member each m-e
divided into a same number of a plurality of members in the traveling direction, and the
plurality of divided third magnetic core members and the plurality of divided fourth magnetic
core members m-e arranged such that vertical projection images of the divided third magnetic
core members and vertical projection images of the divided fourth magnetic core members
onto the traveling metal strip respectively overlap each other in the traveling direction in
which the metal strip travels.
5. The induction heating device for a metal strip according to claim 4, further
comprising: moving means configured to move each of the divided plurality of members of
the first magnetic core member and the second magnetic core member, and each of the
divided plurality of members of the third magnetic core member and the fourth magnetic core
member in the sheet width direction of the traveling metal strip.
6. The induction heating device for a metal strip according to claim 2, further
23
compnsmg:
a second induction coil having a structure identical to a structure of the induction
coil;
a third magnetic core having a structure identical to a structure of the first magnetic
core; and
a fourth magnetic core having a structure identical to a structure of the second
magnetic core,
wherein the induction coil and the second induction coil are arranged in parallel in
the traveling direction.