JP2010182594A - Induction heating apparatus of metal plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating apparatus capable of heating a metal plate at a stable frequency. <P>SOLUTION: In the induction heating apparatus for heating the metal plate, a specific space is maintained against a surface and a backside of the metal plate, a conductor is arranged to encircle the metal plate in its width direction, and an AC current generated at a high frequency power source is passed to an induction coil composed of a conductor on a surface side of the metal plate connected with a conductor on a backside and is transmitted through an inner side of the induction coil encircling the metal plate in the width direction. (a) The conductor on the surface side and the conductor on the backside are arranged at intervals so that perpendicular projection images of the conductor to the metal plate may not be superimposed in a length direction of the metal plate at a central part of the metal plate in the width direction, (b) a slanted part in the width direction toward both ends of the metal plate in the width direction is formed at either or both of ends of the surface side conductor and the backside conductor, and (c) electrodes which are pinched between the surface side conductor and the backside conductor and conducts both conductors are arranged so that they are located outside of both ends of the metal plate in the width direction, thereby the induction coil is formed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an induction heating apparatus and induction heating method for iron and non-ferrous metal plates such as iron and aluminum. In particular, the present invention relates to an induction heating apparatus having a mechanism in which an induction coil follows a change in the plate width of a metal plate, suppressing impedance fluctuations while efficiently reducing impedance, and efficiently stabilizing and electrically heating.

  Induction heating by high frequency current of metals is widely used for heat treatment including quenching. Induction heating is also used to control the quality of steel and non-ferrous thin plates such as steel plates and aluminum plates during the manufacturing process, increase the heating rate to improve productivity, and adjust the production volume freely. For example, it has been used as a heating method instead of indirect heating by conventional gas heating or electric heating.

  There are two main methods for induction heating a metal plate. One is an LF in which a magnetic flux generated by passing a high-frequency current through an induction coil surrounding the metal plate is penetrated in the longitudinal direction of the metal plate, and an induction current is generated and induced in the cross section of the metal plate. (Longitudinal magnetic flux heating) method.

  The other is that a metal plate is placed between a good magnetic body called an inductor wound with a primary coil, and a magnetic flux generated by passing a current through the primary coil is passed through the inductor. This is a TF (transverse heating system) system that passes through the steel plate and generates induction current in the plane of the metal plate for induction heating.

  In the LF type induction heating, the generated induced current circulates in the cross section of the plate, and the temperature distribution is uniform. However, due to the current penetration depth, when the plate thickness is thin, an induced current is not generated unless the frequency of the power source is increased. Furthermore, when the plate thickness is thin, even a non-magnetic material or a magnetic material has a problem that when the temperature rises and exceeds the Curie point, the current penetration depth becomes deep and heating is impossible. The reason will be explained.

  FIG. 1 shows a conventional LF type induction heating mode. A metal plate 1 that is a material to be heated is surrounded by an induction coil 2 connected to a high-frequency power source 3, and a primary current 5 is passed through the induction coil 2 to generate a magnetic flux 4 that penetrates the inside of the metal plate 1. An induced current is generated around the magnetic flux 4, and the metal plate 1 is heated by the generated induced current. FIG. 2 shows a mode in which the induced current is generated in the cross section of the metal plate 1.

Due to the magnetic flux 4 penetrating the metal plate 1, induced currents 6 a and 6 b in the opposite direction to the primary current 5 flowing in the induction coil 2 flow in the cross section of the metal plate 1. The induced currents 6 a and 6 b flow from the surface of the metal plate 1 in a concentrated manner within the range of the current penetration depth δ represented by the following formula (1).
δ [mm] = 5.03 × 10 ⁺⁵ (ρ / μrf) ^0.5 (1)
Here, ρ is a specific resistance [Ωm], μr is a relative permeability [−], and f is a heating frequency [Hz].

  As shown in FIG. 2, the generated induced current 6 flows in opposite directions on the front and back of the cross section of the metal plate. Therefore, when the current penetration depth δ increases, the induced currents 6a and 6b on the front and back of the metal plate cancel each other. , No current flows inside the metal plate 1.

  Since ρ increases with increasing temperature, δ increases with increasing temperature. In the case of a ferromagnetic or paramagnetic magnetic material, μr begins to decrease as the temperature rises and approaches the Curie point, and becomes 1 when the Curie point is exceeded.

  The non-magnetic material also has a μr of 1. When μr becomes small, from equation (1), in the case of a non-magnetic material or a magnetic material, the current penetration depth δ becomes deep in the temperature range exceeding the Curie point immediately before the Curie point. It becomes impossible to heat.

  For example, when the heating frequency is 10 KHz, the current penetration depth δ is about 1 mm for nonmagnetic aluminum and about 4.4 mm for SUS304 at room temperature. The current penetration depth δ of the magnetic steel is about 0.2 mm, but when the temperature rises and reaches 750 ° C. exceeding the Curie point, the current penetration depth δ becomes about 5 mm.

  In order to prevent the currents generated on the front and back of the metal plate from canceling each other, the thickness of the plate needs to be at least 10 mm or more, and about 15 mm is necessary to efficiently apply power.

  In general, the heat treatment is intended for metal plates having various thicknesses, from a thin plate such as a foil of several tens of μm to a thick plate exceeding 100 mm.

  For example, steel sheets for automobiles and home appliances, which are used in large quantities and are typical materials, usually have a sheet thickness of less than about 3 mm after cold rolling, and particularly those with a thickness of 2 mm or less. In order to inductively heat these metal plates by the LF method, it is necessary to raise the heating frequency to several hundreds KHz or more, but there is a limit in producing a large capacity and high frequency power source, which is realized on an industrial scale. It is difficult.

  On the other hand, in TF type induction heating, the magnetic flux penetrates the plane of the metal plate, so that it can be heated without distinction between plate thickness, magnetic and non-magnetic, and the use of an inductor with low magnetic resistance reduces the leakage flux. In addition, since the magnetic flux can be concentrated between the inductors facing the front and back of the metal plate, the heating efficiency is high.

  On the other hand, the problem of uneven temperature distribution is likely to occur, and if the metal plate is not at the center of the opposing inductor, if the metal plate is a magnetic material, it will be attracted by either inductor, resulting in temperature deviation. There is a problem of becoming larger.

  Furthermore, in the case of induction heating using the TF method, there is a drawback that it is difficult to cope with changes in the plate width of a metal plate or meandering with a continuous plate line.

  In order to solve these problems, the inventors of the present invention disclosed in Patent Document 1 that the induction coils are shifted on the front and back surfaces in the traveling direction of the metal plate, and in the temperature range exceeding the Curie point, We proposed a method that can heat even thin metal plates while controlling the temperature distribution.

  In this method, as shown in FIG. 3, the induction coils on the front and back of the metal plate are shifted in the traveling direction of the metal plate, and an induced current is generated in the metal plate as shown in FIG. Even if the thickness is thinner than the penetration depth of the current, this is a method capable of induction heating. FIG. 4 shows the magnetic flux of the AA cross section of FIG. 3 and the induced current flowing through the cross section.

  However, if the induction coil is simply shifted in the traveling direction of the metal plate, the current density of the current flowing through the end of the metal plate is high, and the heating time is also increased. As a result, the temperature of the end of the metal plate is increased. There is a problem that it is higher than the central part of the plate.

  As a solution to this problem, the inventors of the present invention disclosed in Patent Document 2 that the front and back induction coils heading toward the end of the metal plate are made smaller and inclined than the shift amount of the front and back induction coils on the center side. Proposed to resolve.

  Furthermore, the present inventors have disclosed in Patent Document 2 that when the plate width is changed, the induction coils on the front and back sides are arranged in the traveling direction of the metal plate according to the width of the metal plate so that the change of the plate width can be dealt with. A method of heating by shifting was proposed.

  Further, regarding the plate width change of the metal plate, the present inventors provide a mechanism for moving the induction coil in the traveling direction of the metal plate, and toward the end side of the metal plate in accordance with the change of the plate width of the metal plate. Patent Document 2 also proposed a method that can control the overlapping position of the inclined front and back induction coils to cope with the change in the plate width.

JP 2002-151245 A JP 2007-95651 A JP 2008-288200 A

  However, a mechanism is provided to control the overlapping position of the front and back induction coils inclined toward the end side of the metal plate according to the change of the plate width of the metal plate by providing a mechanism for moving the induction coil in the traveling direction of the metal plate (patent) The method in Document 2 is effective when the metal plate does not meander and travels straight, but when the metal plate meanders, there is a problem that temperature deviation tends to occur at both ends of the metal plate. I understand.

  Accordingly, the inventors of the present invention disclosed in Patent Document 3 that the temperature deviation is eliminated even when meandering or when changing the width by moving an induction coil having an inclination in the width direction of the metal plate in the plate width direction. An induction heating device that can do is proposed.

  The method of Patent Document 2 has no problem when the change in the width of the metal plate is small, but when the width of the metal plate changes greatly, it is generated by the front and back induction coils that affect the inductance. The volume of the space surrounded by the magnetic flux changes greatly, and the inductance also changes greatly.

  Since the resonance frequency is inversely proportional to the 1/2 power of the product of the inductance and the capacitance, if the inductance greatly changes, the resonance frequency is greatly shifted. Therefore, matching must be performed again according to the plate width. It has been found that the method 2 is disadvantageous when continuous heating is performed.

  In order to re-match, it is necessary to temporarily turn off the power. In high-production facilities, the quality of the stopped part becomes poor, yield decreases, and a device for switching capacitors and transformer taps for switching matching is required, resulting in high facility costs. .

  Further, in the method of Patent Document 3, in order to move the front and back induction coils in the plate width direction, a water-cooled cable that can follow the movement must be used, but the water-cooled cable moves the induction coil at both ends of the induction coil. Since a length of about twice the amount is required and the bending radius cannot be reduced, a loop corresponding to the bending radius must be formed.

  If the water-cooled cable is formed in a loop according to the bending radius, not only the inductance but also the resistance including the induction coil and the water-cooled cable is increased. As a result, the impedance is increased and the voltage applied to the induction coil is increased. It has also been found that there is a problem that the power consumed by the water-cooled cable and the like is increased and the efficiency as the induction heating device is lowered.

  Therefore, the present invention uses an induction coil in order to solve the problem related to induction heating of a metal plate held by a conventional LF method or TF method when heating a non-magnetic material or a metal thin plate in a non-magnetic region, It is an object of the present invention to provide an induction heating device that is excellent in temperature controllability and can be heated more efficiently, not only in a magnetic metal plate, but also in a nonmagnetic metal plate and a nonmagnetic region of the metal plate.

  In addition, the present invention can effectively cope with a change in width or meandering of the metal plate, and even if the plate width of the metal plate changes, without changing the frequency, It is an object of the present invention to provide an induction heating apparatus that can heat more efficiently.

  The gist of the present invention is as follows.

(1) A conductor is arranged so as to circulate in the width direction of the metal plate while maintaining a necessary gap between the surface and the back surface of the metal plate, and the conductor on the front side and the back side of the metal plate are made of conductive members. In the apparatus for inductively heating the metal plate that passes through the inside of the induction coil that circulates in the width direction of the metal plate by passing an alternating current generated from a high-frequency power source to the induction coil that is connected and configured,
(A) The conductor on the front surface side and the conductor on the back surface side of the metal plate are spaced apart so that the vertical projection image of the conductor on the metal plate does not overlap in the longitudinal direction of the metal plate at the center in the width direction of the metal plate. Place and
(B) at one or both ends of the conductor on the front surface side and the conductor on the back surface side, forming a portion inclined with respect to the width direction of the metal plate toward both ends in the width direction of the metal plate; and
(C) An electrode that is sandwiched between a conductor on the front surface side and a conductor on the back surface side to conduct both conductors is disposed so as to be located outside both ends in the width direction of the metal plate,
An induction heating apparatus for a metal plate, wherein an induction coil of 1T (turns) or more is formed around the metal plate.

  (2) Of the electrodes arranged so as to be located outside both ends of the metal plate in the width direction, (c1) the electrode on the high frequency power source side is separated into two with an electrically insulated electrode base in between (C2) One of the separated electrodes is in contact with the conductor on the front side, the other is in contact with the conductor on the back side, and (c3) Each of the separated electrodes is a conductive member and is a high-frequency power source. The metal plate induction heating device according to (1), wherein the metal plate induction heating device is connected to the metal plate.

  (3) The induction heating apparatus for a metal plate according to (1) or (2), wherein the conductor on the front surface side and the conductor on the back surface side include means for moving in the width direction of the metal plate.

(4) The induction coil is a 2T (turn) induction coil,
(I) The vertical projection image onto the metal plate of the conductor on the front surface side and the conductor on the back surface side of the metal plate is at a central portion in the width direction of the metal plate, with a distance that does not overlap in the longitudinal direction of the metal plate,
(I-1) The conductors on the front surface side are arranged close to each other in the longitudinal direction of the metal plate, and the conductors on the back surface side are arranged at intervals larger than the proximity interval between the conductors on the front surface side. Place in the direction, or
(I-2) The conductors on the back surface side are arranged close to each other in the longitudinal direction of the metal plate, and the conductors on the front surface side are arranged at intervals longer than the proximity interval between the conductors on the back surface side. Two sets of conductor-side conductors and back-side conductor units,
(Ii) In each of the above two sets of units, the electrodes are arranged so as to be outside the both ends in the width direction of the metal plate,
(C1) Among the above electrodes, the electrode opposite to the high frequency power source is separated into two with an electrically insulated electrode base in between,
(C2) One of the separated electrodes is in contact with the conductor on the front side, the other is in contact with the conductor on the back side, and
(C3) Each separated electrode is a conductive member and contacts the above-mentioned separated electrode in the two sets of one unit and the back-side conductor in the other set of two units. The induction heating apparatus for a metal plate according to any one of (1) to (3), wherein the induction heating apparatus is connected to the separated electrode.

  (5) The metal according to any one of (1) to (4), wherein a hardness of a portion in contact with the electrode is higher than a hardness of the electrode in the conductor on the front surface side and the conductor on the back surface side. Induction heating device for plates.

  The “longitudinal direction of the metal plate” as used in the present invention is the direction in which the metal plate passes (the same direction as the transport line). Moreover, the “width direction of the metal plate” as used in the present invention is the plate width direction of the metal plate (perpendicular to the passing direction of the metal plate).

  According to the present invention, not only can a thick metal plate and a magnetic thin plate be heated, but also a non-magnetic aluminum or copper having a small specific resistance, which is impossible with the conventional induction heating method. It is possible to heat a non-ferrous metal plate such as the above, and it is possible to perform heating more efficiently than in the prior art even in a non-magnetic region above the Curie point of a magnetic material.

  According to the present invention, since the induction coil can be moved according to the plate width and meandering of the metal plate, temperature control can be performed more precisely. Moreover, even when the induction coil moves, changes in inductance and impedance can be kept small, so that changes in the resonance frequency for heating can be reduced, and stable heating can be performed.

  According to the present invention, since the transmission frequency does not change, it is not necessary to provide an additional matching capacitor or transformer, and no device for switching the capacitor capacity is required, so that the equipment cost can be suppressed. . Furthermore, since the change in impedance according to the plate width of the metal plate is small, the change in heating efficiency is also small, and stable and efficient heating can be performed.

  In addition, according to the present invention, it is possible to heat the metal plate by forming a desired temperature distribution in consideration of the temperature deviation brought in from the previous process of the induction heating device and the temperature characteristics in the subsequent process. In accordance with the required metallurgical characteristics, the heating rate and temperature distribution can be adjusted to stably produce a high-quality product, and the influence on quality due to operational fluctuations can be eliminated.

  Furthermore, according to the present invention, since there is no influence of thermal inertia, which is a problem in a gas heating furnace, the heating temperature must be changed by changing the thickness, width, and / or type of the metal plate. Even at times, it is not necessary to freely control the heating rate and change the plate passing speed.

  In a gas-heated furnace, a connecting material is usually required until the furnace stabilizes when the furnace temperature is changed. According to the present invention, the connecting material is not necessary, and the plate passing speed is reduced. Since production can be continued without any problems, it is possible to avoid a decrease in productivity and greatly improve the degree of freedom in operation planning.

  According to the present invention, not only can the plate thickness and / or plate width of the metal plate be changed, but also a desired temperature distribution can be obtained by flexibly responding to fluctuation factors such as meandering of the metal plate. Instead, it is not necessary to have a plurality of induction coils according to the width of the metal plate, so that the equipment cost can be reduced.

It is a figure which shows the aspect of the conventional LF type induction heating. It is a figure which shows the aspect of the induced current which flows into the cross section of a metal thin plate by the conventional LF type induction heating. It is a figure which shows the one aspect | mode of the induction heating performed by shifting and arrange | positioning the front and back induction coils. It is a figure which shows the generation | occurrence | production aspect of the electric current in the AA cross section of FIG. It is a figure which shows the aspect of the induced electric current which generate | occur | produces in a metal plate by the induction heating shown in FIG. It is a figure which shows the system which shifts the conductor of a front and back in the center, inclines the conductor of a front and back in the vicinity of the edge part side of a metal plate, energizes and inductively heats while sliding with an electrode. It is a figure which shows the aspect of the electrode which contacts a power supply and an induction coil. (A) shows the electrode of the power supply side of the AA cross section of FIG. 6, (b) shows the electrode on the opposite side to the power supply of the BB cross section of FIG. It is a figure which shows the aspect of the induced electric current which generate | occur | produces in a metal plate by the coil arrangement | positioning shown in FIG. It is a figure which shows the positional relationship of a metal plate end surface and an induction coil. It is a figure which shows distribution of the induced current which generate | occur | produces when a metal plate end surface cross | intersects an induction coil in the position A. It is a figure which shows distribution of the induced current which generate | occur | produces when a metal plate end surface cross | intersects an induction coil in the position B. It is a figure which shows distribution of the induced current which generate | occur | produces when a metal plate end surface cross | intersects an induction coil in the position C. FIG. It is a figure explaining the conventional method of moving an induction coil using a water cooling cable. It is a figure which shows the relationship between the conductor of a front and back, and an electrode when the board width of a metal plate changes. It is a figure which shows the relationship between the conductor of a front and back, and an electrode when the board width of a metal plate changes. It is a figure which shows the mechanism which adheres an electrode and the conductor of front and back. It is a figure which shows the structural example of an electrode. (A) is a figure which shows the front of the structural example of an electrode. (B) is a figure which shows the side of the structural example of an electrode. It is a figure which shows the aspect of the 2T induction coil which has arrange | positioned and comprised 2 sets of 1T induction coils in parallel. It is a figure which shows the aspect of another 2T induction coil comprised by arrange | positioning 2 sets of 1T induction coils in parallel. It is a figure which shows the aspect of another induction coil (4 units) arrange | positioned in parallel with one set of induction coils. It is a figure which shows the electrode structure of this invention. (A) shows the electrode structure on the power supply side. (B) shows an electrode structure in the case where a conductive member is disposed between adjacent induction coil units. (C) shows the electrode structure in the case of conducting between the front and back conductors forming the 1T induction coil. (D) shows another electrode structure on the power source side. It is a figure which shows the aspect of the conductor of the front and back used in the Example.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 6 shows an example of the induction heating apparatus of the present invention. FIG. 7 shows the positional relationship between the power source and the electrode. 7A shows the electrode on the power source side of the AA cross section of FIG. 6, and FIG. 7B shows the electrode on the opposite side of the power source side of the BB cross section of FIG. FIG. 8 shows an aspect of the induced current generated in the metal plate 1 in the coil arrangement shown in FIG.

  In the following description, the “induction coil” is a general term for coils that circulate a material to be heated one or more times with pipes, wires, plates, and the like made of a good electric conductor. The shape of the good electric conductor surrounding the material to be heated may be rectangular or circular, and is not particularly defined. The material of the electrical good conductor forming the coil is preferably a material having good electrical conduction such as copper or aluminum.

  As shown in FIG. 6, the induction heating device of the present invention (hereinafter sometimes referred to as “the device of the present invention”) maintains a gap between the surface of the metal plate 1 and the width direction of the metal plate 1 (in the drawing). AC current generated from the high-frequency power source 3 having an induction coil formed by connecting the conductor 2a on the front surface side and the conductor 2b on the back surface side of the metal plate 1 with conductive members 7a and 7b so as to circulate in the left-right direction) An electric current is passed through the induction coil to induction-heat the metal plate 1 that passes inside the circulating induction coil.

  At that time, in the device of the present invention, (i) the width of the metal plate 1 in the vertical projection image when the conductor 2a on the front surface side and the conductor 2b on the back surface side of the metal plate 1 are vertically projected onto the metal plate 1, respectively. In the central part of the direction, the conductor 2a on the front surface side and the conductor 2b on the back surface side are arranged at an interval so as not to overlap each other in the longitudinal direction of the metal plate 1 (vertical direction in the figure) ii) toward both ends of the metal plate 1 in the width direction, at least one of the conductor 2a on the front surface side and the conductor 2b on the back surface side includes a portion inclined with respect to the width direction of the metal plate 1, and The electrodes 8 and 8 'are arranged outside the both ends in the width direction of the metal plate 1 so that both conductors are conducted between the conductor 2a on the front surface side and the conductor 2b on the back surface side. A circuit of 1T (turn) or more (1T in FIG. 6) is formed around the plate 1 It has been.

  In the device of the present invention, it is preferable that the conductor 2a on the front surface side and the conductor 2b on the back surface side have means for moving by driving the motor or the like. As the conductive members 7a and 7b, water-cooled cables may be used. However, when the water-cooled copper plate is in close contact with an insulating plate interposed therebetween, or a water-cooled coaxial cable is used, the reactance can be reduced. It is desirable in terms of efficiency.

  Next, the function and effect of the device of the present invention will be described. In the device of the present invention, first, as shown in FIG. 3, conductors 2a and 2b (hereinafter referred to as "front and back conductors 2a2b") that constitute the induction coils on the front side and the back side of the metal plate 1 that pass through the inside of the induction coil. When the vertical projection is performed on the metal plate 1, the front and back conductors 2 a 2 b are arranged so that the vertical projection images on the front side and the back side are shifted from each other in the longitudinal direction of the metal plate 1.

  Then, as shown in FIG. 4 (AA cross section in FIG. 3) (for simplicity, only the case of the conductor 2a is shown), the magnetic flux 4 penetrates the metal plate 1 diagonally, and the magnetic flux An induced current 6a is generated. Therefore, the induced current flows even if the penetration depth δ of the induced current 6a generated by the oblique expansion of the current path is larger than the plate thickness t.

  Since the front and back conductors 2a2b constituting the induction coil are shifted in the traveling direction of the metal plate, the induction currents 6a and 6b generated in the front and back conductors 2a2b do not interfere with each other in the entire metal plate 1. The annular current as shown in FIG. 5 is formed. As a result, even if the metal plate 1 is a nonmagnetic material, it can be heated.

  However, the current flowing through the end of the metal plate 1 should reduce the reactance between the connecting conductor 7 'connecting the front and back conductors 2a2b or the primary current flowing through the conductive member 7 connecting the front and back conductors 2a2b and the power source. As a result, the current path is narrowed toward the end of the metal plate 1 and the current path becomes narrow.

  This means that the magnetic flux generated by the primary current flowing through the conductive member 7 and the connecting conductor 7 ′ intensively penetrates the end portion of the metal plate having the shortest distance, and the end portion of the metal plate is the central portion. Compared to the above, the end of the metal plate 1 is likely to be overheated because the heating time is increased by the distance d3 (see FIG. 5). The connection conductors 7 and 7 'are usually made of a water-cooled copper plate or a water-cooled cable.

  Therefore, in the device of the present invention, as shown in FIG. 6, at least one of the front and back conductors 2 a 2 b toward the metal plate end is inclined and crossed toward the end of the metal plate 1. In FIG. 6, the aspect in which a conductor inclines in the both ends of the metal plate 1 of the conductor 2a2b of front and back is shown. With such a conductor shape, an annular current as shown in FIG.

  As a result, compared to the case of FIG. 5 described above, the current path is less likely to be narrow at the end of the metal plate, so the current density is less likely to increase, and the conductors on the front and back intersect near the end of the metal plate. Therefore, since the heating time by the induced current flowing through the end portion of the metal plate can be shortened, as shown in FIG. 3, avoid overheating of the end portion of the metal plate rather than just shifting the conductors on the front and back sides in parallel. Can do.

  In order to control this overheating, it is important where the conductor portion from the inclined portion to the horizontal portion intersects the end portion of the metal plate. FIG. 9A is a diagram showing the positional relationship between the end face of the metal plate and the induction coil (front and back conductors 2a2b).

  As shown in FIG. 9B, when the end face of the metal plate crosses the middle of the conductor 2b (position A), the induced current flowing through the end of the metal plate has a high current density and flows through the end of the metal plate. Since the time becomes longer, the temperature at the end of the metal plate tends to be higher than that at the center of the metal plate.

  Conversely, as shown in FIG. 9D, when the metal plate end faces intersect at the horizontal portion (position C) of the induction coil, the conductors 2a2b on the front and back overlap in the vicinity of the metal plate end. This is the same as conventional LF heating, and in the case of a non-magnetic thin plate, no induced current is generated in this portion, and as shown in FIG. 9 (D), it turns to the center side of the metal plate. The temperature at the end of the metal plate decreases.

  In the case of FIG. 9C, the temperature distribution is intermediate between the temperature distribution of FIG. 9B and the temperature distribution of FIG. 9D. Thus, the temperature distribution of the metal plate can be controlled by controlling the position where the conductor that changes from the inclined portion to the horizontal portion intersects the end surface of the metal plate.

  Therefore, in the induction coil of the present invention, it is preferable that the positions of the front and back conductors can be moved in the width direction of the metal plate in accordance with the position of the end portion of the metal plate. In order to move the front and back conductors, the front and back conductors may be fixed to a support base and moved by a driving device such as a motor, an air cylinder, or a hydraulic cylinder. A sensor for detecting the position of the metal plate may be arranged in front of or behind the induction coil, and the conductors on the front and back sides may be moved according to the position information from the sensor.

  When changing the plate width of the metal plate, the induction coil may be moved in the same manner based on information from a process control computer that controls the entire production. In addition, the induction coil driving device receives the plate width change information of the metal plate from the computer that controls the passing position of the welded portion, and immediately before the metal plate whose plate width has been changed passes through the induction coil device. If the front and back conductors are moved in the width direction of the metal plate and a control means for adjusting the electric power is incorporated, heating without excess or deficiency becomes possible.

  The amount of movement of the conductors on the front and back sides is about several tens of millimeters in the case of meandering, but for example, in the case of a steel plate, the change in plate width changes greatly from about 600 mm to about 1800 mm, about three times. It is necessary to move the front and back conductors and the conductive member connecting the front and back conductors in accordance with the change width of the plate width. Usually, a water-cooled cable is used for moving the front and back conductors and the conductive member connecting the front and back conductors.

  The water-cooled cable allows a relatively large current to flow while cooling water flows in or out of the conductor and cools the conductor. However, since the bending radius is large, as shown in FIG. 10, between the conductors 2a2b on the front and back sides It is necessary to form a loop with a radius larger than the distance.

  The loop formed creates a large inductance, and a long water-cooled cable must be used for movement, and the resistance increases. As a result, although the overall impedance depends on the amount of movement of the induction coil, it increases more than twice as compared with the case of a fixed induction coil alone, and the heating efficiency is greatly reduced.

  In particular, when the frequency is high, the impedance increases, and the influence on the heating efficiency is large. Further, when the impedance increases, the voltage of the power source must be increased, and a high voltage power source is required. For this reason, there arises a problem that the equipment cost is increased, or that only a small amount of electric power can be heated within the range allowed by the power supply voltage.

  Therefore, in the present invention, as shown in FIG. 6, electrodes 8 and 8 ′ are provided between the moving front-side conductor 2 a and the moving back-side conductor 2 b, and the front and back conductors 2 a 2 b are provided on this electrode. Are energized.

  FIG. 7 shows an aspect of electrodes for connecting the power source and the induction coil. In the positional relationship between the power source and the electrode shown in FIG. 7A, the conductive members 7a and 7b from the power source are connected to the electrodes 8 and 8 ′ with an insulator 9 that is electrically insulated therebetween. . For the conductive members 7a and 7b, a water-cooled copper plate is usually used, and in order to reduce the inductance, the insulator 9 is in close contact with each other to extend to the electrodes 8 and 8 'and slide on the surface-side conductor 2a. And it is made to contact with the conductor 2b of the back surface side which slides, and it supplies with electricity.

  As shown in FIG. 7 (b), the electrode 8 'and the induction coils 2a and 2b are similarly brought into contact with each other at the other end to energize. However, the other end shown in FIG. 7B needs to make the induction coil 2a and the induction coil 2b conductive. Therefore, FIG. 7B shows an electrode without the insulator 10, but as shown in FIG. 13A, the sliding electrode is divided into upper and lower parts with an electrical insulator in between. A structure in which the sliding electrodes are short-circuited with a conductive member such as a water-cooled copper pipe may be used.

  In addition, what is necessary is just to use what has a small resistance value, such as copper, an alloy of copper, metal impregnation carbon, and an intensity | strength normally. When oxidation or the like is concerned, the electrode may be subjected to surface treatment such as thermal spraying of an oxidation resistant material or plating. When the current flowing through the electrode is large, stable energization is possible if the electrode has a water cooling structure.

  As in the present invention, when an electrode fixed in place of the water-cooled cable is used between the sliding front and back conductors, changes in inductance and impedance can be reduced. FIG. 11A and FIG. 11B show the relationship between the front and back conductors and electrodes when the plate width of the metal plate changes.

  The electrodes 8 and 8 'are fixed with bolts or the like to a moving mechanism such as the conductor 2a on the front surface side and the conductor 2b on the back surface side or a beam 12 of a structure for attaching a support base to which the induction coil body is attached. And keep the position unchanged. Although not shown, the conductors 2a2b on the front and back sides are fixed to a support base connected to a moving mechanism such as an air cylinder, and move in the plate width direction of the metal plate by the movement of the cylinder to control the heating temperature distribution of the material to be heated. To do.

  Even if the conductors on the front and back sides move, the conductor lengths of the induction coil are almost the same, the conductors on the front and back sides are shifted in parallel to the plate width direction of the metal plate, and the range affected by the magnetic flux generated by each conductor is almost the same. Since the range of the central portion of the metal plate only increases or decreases, the inductance does not change greatly in the space (hatched portion in the figure) surrounded by the conductors and electrodes on the front and back sides.

  The resonance frequency in induction heating is inversely proportional to the 0.5th power of the inductance, but as described above, since the change in inductance is small, there is almost no influence on the resonance frequency due to the change in inductance, without changing the frequency, Stable heating is possible.

  Here, when a water-cooled cable as shown in FIG. 10 is used without using an electrode, the bending radius of the water-cooled cable is large, so that a large loop must be formed. An extra current path that is several times longer must be made. As a result, the resistance of the cable increases, the copper loss increases, and the heating efficiency decreases.

  According to the present invention, it is not necessary to provide a current path having an extra length, and the resistance of the circuit formed by the front and back conductors and electrodes is substantially constant, so that an increase in impedance can be avoided. If the current that must be passed through the induction coil is constant, it is inevitable to increase the power supply voltage as the impedance increases. However, in the present invention, the problem of increasing the power supply voltage can be avoided.

  In the case of the present invention, the electrode and the conductors on the front and back sides are brought into contact with each other and energized, and an induction coil of 1T (turns) or more can be formed around the metal plate. The structure for connecting the conductor is not limited, but it is particularly preferable to employ a structure that can stably adhere the electrode and the front and back conductors.

  Therefore, it is preferable to provide a mechanism for applying pressure to the outside of the front and back conductors in the vertical direction. FIG. 12 shows an example of the mechanism. In the mechanism shown in FIG. 12, a roll 13 is provided on the outer side in the vertical direction of the conductors 2a2b on the front and back sides, and the roll 13 itself is reduced by a reduction mechanism such as an air cylinder, a hydraulic cylinder, or an electric cylinder.

  The electrode 8 'is sandwiched between the front and back conductors 2a2b stably and tightly by the roll 13 being pressed. As the roll 13, a rubber roll or the like may be used so that the rolling force is applied as evenly as possible, and it is desirable to use a non-conductive material such as resin or ceramic that does not receive induction for the shaft of the roll.

  At this time, if the conductor 2a2b on the front and back sides is made of a soft and thin tube such as a copper tube, the induction coil is damaged. Therefore, the conductor 2a2b on the front and back sides is molded with resin or the like, and further baked. It is desirable to provide a non-magnetic insulating insulating plate 14 such as a resin such as a plate or ceramic on a support base (not shown) of the induction coil so that a local force is not applied to the induction coil.

  The mechanism for rolling down the conductors on the front and back sides may not be a roll but may be a rack and pinion mechanism, for example, and is not particularly defined.

  On the other hand, it is preferable to provide an electrode push-up structure on the electrode side as shown in FIG. 13 in order to uniformly contact the conductors on the front and back sides. FIG. 13A shows the front of a structural example provided with an electrode push-up structure, and FIG. In the structure shown in FIG. 13, an electrode 15 is provided on an electrode base 18 such as engineering plastic via a flexible structure 17 such as rubber, felt, or spring.

  When the conductor 2a is not in contact, the electrode 15 protrudes up to the position indicated by a solid line, but when the conductor 2a is pressed against the conductor 2a, the flexible structure 17 contracts and is indicated by a dotted line. Go down to position a.

  By doing so, the induction coil and the electrode are in uniform contact and stable energization is possible. The electrode 15 is preferably provided with a water-cooled copper pipe 16. What is necessary is just to fix this electrode to the beam 12 etc. of the structure which supports a furnace shell or an induction coil with the volt | bolt 20 and the nut 21 via the attachment plate 19. FIG.

  In addition, the contact part between the electrode and the front and back conductors wears out during use, but the front and back conductors are difficult to manufacture, installation and removal takes time, and the front and back conductors are copper pipes, etc. In the case of manufacturing with a thin material, it is preferable that the conductors on the front and back sides are not worn as much as possible and the electrodes are worn because the cooling water is likely to leak and cause equipment troubles.

  For this reason, it is preferable to make a difference in hardness that greatly affects the wear of the induction coil and the electrode. That is, it is preferable to increase the hardness of the surface (contact surface) of the front and back conductors compared to the hardness of the electrode surface (contact surface). Specifically, it is preferable to form a conductive high-hardness ceramic film on the front and back conductor surfaces by thermal spraying or vapor deposition. As the conductive ceramic, a material having high hardness and high melting point such as WC, TiC, TiN, and Mo is preferable.

  The front and back conductors are usually manufactured with a single plate-like conductor, but need not be a single plate-like conductor, and a plurality of conductors may be arranged, or rod-shaped conductors may be arranged. Good. The front and back conductors do not need to be exactly parallel to the width direction of the metal plate, and the entire front and back conductors may be arranged obliquely with respect to the metal plate.

  Further, the induction coil circuit need not be 1T (turn), and may be 2T (turn) as shown in FIG. 14, for example.

  FIG. 14A shows an aspect of a 2T (turn) induction coil in which two sets of the induction coil shown in FIG. 6 are arranged in parallel.

  In the induction coil shown in FIG. 14A, the vertical projection images of the conductor 2b and the conductor 22b on the back surface side are arranged at close intervals in the longitudinal direction of the metal plate, and the vertical projection of the conductor 2a and the conductor 22a on the front surface side. The images are arranged at intervals larger than the proximity interval between the conductors 2b and 22b on the back surface side in the longitudinal direction of the metal plate.

  On the contrary, the vertical projection images of the conductor 2b and the conductor 22b on the back surface are made of metal so that the vertical projection images of the conductor 2a and the conductor 22a on the front surface are close to each other in the longitudinal direction of the metal plate. You may arrange | position so that it may become a space | interval larger than the adjacent space | interval of the conductors 2a and 22a of the surface side in the longitudinal direction of a board.

  In the longitudinal direction of the metal plate 1, a unit of a conductor 2a on the front side and a conductor 2b on the back side, and a unit of a conductor 22a on the front side and a conductor 22b on the back side are formed. In each of the two sets of units, the electrodes 25 and 25 ′ and the electrodes 26 and 26 ′ are disposed outside the both ends in the width direction of the metal plate 1.

  Among these electrodes, the electrodes 25 ′ and 26 ′ arranged on the opposite side of the high frequency power source 3 are separated into two with an electrically insulated electrode base interposed therebetween, and one of the separated electrodes is a surface. The other side is in contact with the conductors 2a and 22a on the side, and the other side is in contact with the conductors 2b and 22b on the back side.

  Conductive members 7c and 7c 'are connected to the separated electrodes. The conductive members 7c and 7c 'connect the electrode in contact with the conductor on the front surface side of one unit and the electrode in contact with the conductor on the back surface side of the other unit.

  FIG. 16 shows an electrode structure. For example, as shown in FIG. 16 (b), the copper plates 7c and 7c ′ connected to the electrode materials 15a and 15c that are in contact with the upper conductors 2a and 22a intersect to make contact with the conductors 2b and 22b on the back surface side. Are connected to the electrode materials 15d and 15b.

  For example, as shown in FIG. 16A, the electrode 26 connected to the power source 3 extends to the vicinity of the electrode by bringing the conductors 7a and 7b connected to the power source 3 into close contact with the insulating material 28 interposed therebetween. The electrode material 15a that contacts the conductor 22a and the electrode material 15b that contacts the conductor 24b on the back surface side are connected to each other.

  As shown in FIG. 16C, the electrode 25 that short-circuits between the sliding front and back conductors has a structure in which the upper electrode material 15a and the lower electrode material 15b are connected by the conductor 7. That's fine.

  In these electrodes, the electrode materials on the front and back are connected by a fixed conductor at the shortest distance, and it is not necessary to form a useless loop as in a water-cooled cable, so that an increase in inductance can be prevented. it can.

  According to this arrangement method of the coil conductor, since the current of the same phase can be passed through the adjacent induction coils to increase the magnetic flux density, the heating efficiency is improved, and each induction coil is moved independently. Therefore, the temperature distribution can be precisely controlled as compared with the 1T induction coil shown in FIG.

  In this case, the current from the power source 3 is as follows: the conductive member 7a → the upper side of the electrode 26 → the conductor 22a on the front side → the electrode 26 ′ upper side → the conductive member 7c → the lower side of the electrode 25 ′ → the back side conductor 2b → the lower side of the electrode 25. Side → upper side of electrode 25 → surface side conductor 2a → upper side of electrode 25 ′ → conductive member 7c ′ → lower side of electrode 26 ′ → back side conductor 22b → lower side of electrode 26 → conductive member 7b → power supply 3 A 2T induction coil is formed.

  FIG. 14B shows another connection example constituting a 2T induction coil. The current from the power source 3 is: the conductive member 7a → the upper side of the electrode 26 → the conductor 22a on the front side → the upper side of the electrode 26 ′ → the lower side of the electrode 26 ′ → the conductor 22b on the back side → the lower side of the electrode 26 → the conductive member 7c → upper side of electrode 25 → surface conductor 2a → upper side of electrode 25 ′ → lower side of electrode 25 ′ → backside conductor 2b → lower side of electrode 25 → conductive member 7b → power supply 3 An induction coil is formed.

  In this case, the connection between the electrode 25 and the electrode 26 may be the structure shown in FIG. 16D, and the connection between the electrode 25 'and the electrode 26' may be the structure shown in FIG.

  FIG. 15 shows a mode of induction coils (4 units) arranged in parallel with another set of induction coils shown in FIG.

  In the induction coil shown in FIG. 15, the current from the power source 3 is applied to the lower set of induction coils from the conductive member 7 a → the upper side of the electrode 27 → the conductor 24 a on the surface side → the upper side of the electrode 27 ′ → the conductive member 7 c → Electrode 26 'lower side → back side conductor 23b → electrode 26 lower side → electrode 26 upper side → surface side conductor 23a → electrode 26' upper side → conductive member 7c '→ electrode 27' lower side → back side conductor 24b → Flowing from the lower side of the electrode 27 → the conductive member 7b ′ → the power source 3, a 2T induction coil is formed.

  Similarly, the current from the power source 3 is applied to the other upper set of induction coils from the conductive member 7a ′ → the upper side of the electrode 25 → the conductor 22a on the front side → the upper side of the electrode 25 ′ → the conductive member 7d → the electrode 8 ′. Lower side → back side conductor 2b → electrode 8 lower side → electrode 8 upper side → surface side conductor 2a → electrode 8 'upper side → conductive member 7d' → lower side of electrode 25 '→ back side conductor 22b → lower side of electrode 25 The flow then flows through the conductive member 7b ′ → the power source 3 to form a 2T induction coil. The 2T induction coil is connected in parallel with the previous 2T induction coil.

  Thus, even if a plurality of induction coils are used, the conductors (2a, 2b), (22a, 22b), (23a, 23b), (24a, 24b) on the front and back sides are in the plate width direction of the metal plate 1, Although each can move freely, electrodes 8, 8 ', 25, 25', 26, 26 ', 27, 27' and conductive members 7a, 7a ', 7b, 7b', 7c, 7c ', 7d 7d 'can be fixed.

  In particular, the conductive members 7a and 7a ', 7b and 7b', 7c and 7c ', and 7d and 7d' are laid and fixed to the electrodes in close contact with an insulator therebetween so that no inductance is generated.

  As described above, the induction heating device of the present invention can be effectively heated regardless of the width of the metal plate to be heated, regardless of whether it is magnetic or non-magnetic. In addition, the induction heating device of the present invention can freely control the temperature because the conductors on the front and back sides can move according to the plate width and meandering.

  Further, in the induction heating device of the present invention, since the change in the length and shape of the conductor between the electrodes is small, the change in inductance and impedance of the conductor including the conductors on the front and back sides can be minimized, and the frequency Without changing the temperature, stable and highly efficient heating becomes possible.

  Further, in the induction heating device of the present invention, since the impedance of the induction coil can be kept low, it is inexpensive without using a special power source corresponding to a high voltage even when heating with a relatively large power capacity. It is possible to use a normal power supply and eliminate the need for high voltage countermeasures, so that the equipment cost can be kept low and the equipment can be made safe from the viewpoint of safety.

  The induction heating apparatus of the present invention can be used in a wide range with a single unit regardless of the type and size of the metal plate. The heating temperature distribution can also be controlled to prevent overheating of the plate edge, which has been a problem with conventional induction heating devices, and the temperature distribution can be precisely controlled to the target temperature distribution. Is possible.

  Even if the plate width of the metal plate is changed, when the plate width change portion of the metal plate passes through the induction heating device according to a command from the computer that controls the passing position of the welded portion, induction is performed. The coil can be moved instantaneously in the width direction of the metal plate and the electric power can be controlled to allow heating without excess or deficiency and to prevent useless electric power from being input.

Example 1
In order to confirm the effect of the present invention, in the case of the 1 unit induction heating device shown in FIG. 6 and the 4 unit induction heating device shown in FIG. ) To measure the change in inductance.

  The front and back conductors used were each one set of 10 copper pipes with an outer diameter of 10 mm and a thickness of 1 mm bent to 15 ° (see “α” in FIG. 15) and arranged at 5 mm intervals to a width of 145 mm. (Refer to FIG. 17) One unit was used, and the length in the width direction of the metal plate was set to L = 3 m in the arrangement shown in FIG. 6 and FIG.

  The deviation S between the front and back conductors in each unit is 250 mm, and the gap between the lower surface of the conductor on the front surface side and the upper surface of the SUS plate and the gap between the upper surface of the conductor on the back surface side and the lower surface of the SUS plate are both 150 mm. did. In the arrangement shown in FIG. 6, the induction coil constituted 1T (turn). In the arrangement shown in FIG. 15, two sets (4 units) of 2T (turn) induction coils are arranged in the longitudinal direction of the metal plate and connected in parallel.

  Example 1 is a case where carbon electrodes having a contact length w (= 150 mm) as shown in FIG. 13 are fixedly arranged with Le (= 2.1 m) apart as shown in FIG. Example 2 is a case in which the carbon electrodes as shown in FIG. 13 are fixedly arranged with Le (= 2.1 m) apart in each unit in the arrangement shown in FIG.

  In the arrangement shown in FIG. 12, the bake plate as the contact plate 14 is sandwiched between 10 copper tubes constituting the front and back conductors and the electrode 8 'in the arrangement shown in FIG. Added load.

Comparative Example 1 is an arrangement shown in FIG. 6 in which an electrode between the front and back conductors is removed, and the front and back conductors are short-circuited with a cable having a cross-sectional area of 14 mm ² (when the plate width is 800 mm, the induction coil width L = This is a case of using an induction coil width L = 2200 mm when the plate width is 1200 mm and the plate width is 1800 mm.

Comparative Example 2 is an arrangement shown in FIG. 15, in which an electrode between front and back conductors is removed, and the front and back conductors are short-circuited with a cable having a cross-sectional area of 14 mm ² (when the plate width is 800 mm, the induction coil width L = This is a case of using an induction coil width L = 2200 mm when the plate width is 1200 mm and the plate width is 1800 mm.

Comparative Example 3 is the same as Example 2 except that instead of the electrodes, a commercially available water-cooled cable (cross-sectional area of 125 mm ² , ^two per induction coil unit) was used, and between the front and back conductors, 3.5 m on one side, This is a case where a total of 7 m per induction coil is connected by a cable and a loop having a radius of 500 mm is provided in the middle.

  In Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3, the inductances when SUS304 plates having a plate width of 800 mm and a plate width of 1800 mm were placed in the induction coil were compared. Note that the cable length of 3.5 m is 0.5 m on one side plate width + margin of meander ± 0.1 m (total 0.2 m) + the total of the upper and lower parts of the straight line 0.3 m is 2 m, and the loop part is about 1.5 m. Inductance was measured with an impedance meter while changing the frequency and at rest.

  The results are shown in Table 1. In Comparative Example 1 and Comparative Example 2 in which the induction coil width was adjusted to the plate width, the inductance increased by about 70% because the plate width was changed from 800 mm to 1800 mm. This means that the capacitor capacity must be reduced by 70% in order to oscillate at the same frequency, and eventually the resonance state cannot be maintained.

  On the other hand, in Example 1 and Example 2, it was found that the change in inductance was only about 3%, and was within a range in which the resonance state of the power supply could be maintained.

  In Comparative Example 3, even when the plate width of the metal plate changes, the volume of the space surrounded by the cable and the conductors on the front and back sides hardly changes, so the change in inductance is small, but the absolute value is about four times that of the present invention, When the same current is applied, a voltage more than four times must be applied. Therefore, when a large amount of power is input, the power supply voltage must be increased, an expensive high voltage power supply is required, and other problems such as measures against insulation occur.

  On the other hand, in the case of the present invention, the inductance value is low at the same level as in Comparative Example 1, and the change in inductance due to the change in the plate width of the metal plate is small, so the frequency is changed without increasing the power supply voltage. And can continue heating stably.

  Actually, in the arrangement shown in FIG. 15, even when the SUS304 plate with a plate width of 1000 mm and a plate thickness of 0.6 mm is inserted, the front and back conductors are energized while moving ± 500 mm in the plate width direction with an air cylinder. It was confirmed that energization could be continued stably at a resonance frequency of 9.8 kHz ± 0.2 kHz without powering down.

  As described above, according to the present invention, a thick metal plate, a thin magnetic region plate, a non-ferrous metal plate such as non-magnetic aluminum or copper having a small specific resistance can be heated, and the magnetic material Heating can be performed efficiently even in a nonmagnetic region above the Curie point. In addition, according to the present invention, the temperature control can be performed more precisely by moving the induction coil in response to the change in the thickness and / or width of the metal plate and the meandering of the metal plate. . Thus, the present invention has high applicability in the metal industry.

DESCRIPTION OF SYMBOLS 1 Metal plate 2 Inductive coil 2a Front side conductor 2b Back side conductor 3 High frequency power supply 4 Magnetic flux 5 Primary current 6 Inductive current 6a Inductive current 6b Inductive current 7 Conductive member 7a, 7a 'Conductive member 7b, 7b' Conductive member 7c, 7c 'Conductive member 7d, 7d' Conductive member 8, 8 'Electrode 9 Insulator 10 Insulator 11 Water-cooled cable 12 Beam of structure 13 Roll 14 Address plate 15 Electrode material 15a, 15b Electrode material 15c, 15d Electrode material 16 Water-cooled copper Pipe 17 Flexible structure 18 Electrode base 19 Mounting plate 20 Bolt 21 Nut 22a, 23a, 24a Front side conductor 22b, 23b, 24b Back side conductor 25, 25 'Electrode 26, 26' Electrode 27, 27 'Electrode 28 Insulation Material

Claims (5)

Maintain the required gap between the front and back surfaces of the metal plate, place the conductor around the width of the metal plate, connect the conductor on the front side and the back side of the metal plate with a conductive member In the apparatus for inductively heating the metal plate that passes through the inside of the induction coil that circulates in the width direction of the metal plate by passing an alternating current generated from a high-frequency power source to the configured induction coil,
(A) The conductor on the front surface side and the conductor on the back surface side of the metal plate are spaced apart so that the vertical projection image of the conductor on the metal plate does not overlap in the longitudinal direction of the metal plate at the center in the width direction of the metal plate. Place and
(B) at one or both ends of the conductor on the front surface side and the conductor on the back surface side, forming a portion inclined with respect to the width direction of the metal plate toward both ends in the width direction of the metal plate; and
(C) An electrode that is sandwiched between a conductor on the front surface side and a conductor on the back surface side to conduct both conductors is disposed so as to be located outside both ends in the width direction of the metal plate,
An induction heating apparatus for a metal plate, wherein an induction coil of 1T (turns) or more is formed around the metal plate.   Of the electrodes arranged so as to be located outside both ends in the width direction of the metal plate, (c1) the electrode on the high frequency power source side is separated into two with an electrically insulated electrode base in between, c2) One of the separated electrodes is in contact with the conductor on the front side, the other is in contact with the conductor on the back side, and (c3) each separated electrode is connected to a high-frequency power source with a conductive member The induction heating apparatus for a metal plate according to claim 1, wherein the induction heating apparatus is a metal plate.   The induction heating apparatus for a metal plate according to claim 1 or 2, wherein the conductor on the front surface side and the conductor on the back surface side include means for moving in the width direction of the metal plate. The induction coil is a 2T (turn) induction coil,
(I) The vertical projection image onto the metal plate of the conductor on the front surface side and the conductor on the back surface side of the metal plate is at a central portion in the width direction of the metal plate, with a distance that does not overlap in the longitudinal direction of the metal plate,
(I-1) The conductors on the front surface side are arranged close to each other in the longitudinal direction of the metal plate, and the conductors on the back surface side are arranged at intervals larger than the proximity interval between the conductors on the front surface side. Place in the direction, or
(I-2) The conductors on the back surface side are arranged close to each other in the longitudinal direction of the metal plate, and the conductors on the front surface side are arranged at intervals longer than the proximity interval between the conductors on the back surface side. Two sets of conductor-side conductors and back-side conductor units,
(Ii) In each of the above two sets of units, the electrodes are arranged so as to be outside the both ends in the width direction of the metal plate,
(C1) Among the above electrodes, the electrode opposite to the high frequency power source is separated into two with an electrically insulated electrode base in between,
(C2) One of the separated electrodes is in contact with the conductor on the front side, the other is in contact with the conductor on the back side, and
(C3) Each separated electrode is a conductive member and contacts the above-mentioned separated electrode in the two sets of one unit and the back-side conductor in the other set of two units. The induction heating apparatus for a metal plate according to claim 1, wherein the induction heating apparatus is connected to the separated electrode.   The induction heating of the metal plate according to any one of claims 1 to 4, wherein a hardness of a portion in contact with the electrode is higher than a hardness of the electrode in the conductor on the front surface side and the conductor on the back surface side. apparatus.