JP6331900B2 - Induction heating device for metal strip - Google Patents

Description

  The present invention uniformly heats a metal strip that runs in the longitudinal direction while suppressing overheating at the end in the plate width direction, and responds quickly to changes in the position of the plate end due to changes in the plate width, meandering, etc. It is related with the induction heating apparatus which can be performed.

  Heating of a metal strip such as a steel plate in a heat treatment furnace is mainly performed by indirect heating using a radiant tube, but in addition to the large thermal inertia, this indirect heating reduces the difference between the plate temperature and the furnace temperature, Since the radiation heat capacity is reduced, effective heat input to the metal strip is difficult, and productivity is restricted. Further, in indirect heating using a radiant tube, the heating rate is slow and it is difficult to realize annealing at a high temperature, so the degree of freedom in selecting heat treatment conditions and operation conditions is limited.

  In contrast, induction heating, in which a metal strip is heated with a high-frequency current, can freely control the heating rate and heating temperature, and thus has a large degree of freedom in terms of heat treatment conditions and operation conditions. It is a heating method.

  There are two main types of induction heating. One is to generate a magnetic flux through the longitudinal section of the metal strip by passing a high-frequency current through an induction coil that surrounds the circumference of the metal strip. This is an LF (longitudinal magnetic flux heating) method in which an inductive current is generated to heat a metal strip.

  The other is that a metal strip is placed between the induction coil (good conductor) wound with the primary coil, and the magnetic flux generated by passing a current through the primary coil is made to penetrate the plate surface of the metal strip. This is a TF (transverse magnetic flux heating) system in which an induction current is generated on the surface of the metal strip to heat the metal strip.

In the LF type induction heating in which the induced current circulates in the cross section of the plate, the relationship between the current penetration depth δ and the current frequency f (δ (mm) = 5.03 × 10 ⁵ √ (ρ / μr · f), ρ ( Ωm): specific resistance, μr: relative permeability, f: frequency (Hz)), when the thickness of the metal strip is thin, no induced current is generated unless the current frequency f is increased. Furthermore, in the case of a non-magnetic metal strip or a metal strip that is magnetic at room temperature exceeding the Curie temperature, the current penetration depth δ becomes deep, so that no induced current is generated if the thickness of the metal strip is thin.

  On the other hand, in the TF method induction heating in which the magnetic flux penetrates the plate surface of the metal strip, the metal strip can be heated regardless of the plate thickness, regardless of whether it is magnetic or non-magnetic. Otherwise, the heating efficiency is low, and overheating occurs at the end of the metal strip, making uniform heating in the plate width direction difficult.

  In TF induction heating, overheating at the end of the metal strip is a major issue, and several techniques for suppressing overheating at the end of the metal strip have been disclosed.

  For example, in Patent Document 1, in an induction heating apparatus that heats a band-shaped metal material by running in the longitudinal direction, the opposite sides of the induction heating coil wound in a substantially quadrilateral shape and the other side are the length of the band-shaped metal material. An induction heating apparatus is disclosed that includes a magnetic flux concentrating member that is displaced in the direction and covers both ends of the band-shaped metal material in the width direction inside the induction heating coil.

  In Patent Document 2, in an electromagnetic induction heating apparatus that heats a traveling thin plate by electromagnetic induction, a plurality of magnetic pole segments arranged in parallel to each other and opposed to the thin plate in the plate width direction of the thin plate, and each magnetic pole A drive mechanism that moves the segments independently in the thickness direction of the thin plate, a coil common to the plurality of magnetic pole segments, and a movable shielding plate made of nonmagnetic metal that can be moved in and out in the width direction of the thin plate and adjust the magnetic field from the magnetic pole segments An electromagnetic induction heating device is disclosed.

  U.S. Patent No. 6,053,049 includes an adjustable cross-flow flux induction heating system for heating a metal strip, comprising a fixed pole assembly and at least one auxiliary pole piece and / or provided on each side of the strip travel path. Or a cross flux induction heating system, characterized in that it comprises an assembly having a shielding plate.

  Patent Document 4 discloses an induction heating device that heats a metal strip that passes inside a circulating induction coil. The induction coils on the front and back sides of the metal strip are vertically projected onto the metal strip. Inductive heating devices are disclosed that are arranged so as not to overlap with each other in the longitudinal direction of the metal strip, and in which a magnetic core is provided between both end portions of the metal strip and coil conductors on both sides thereof.

  Patent Document 5 discloses an induction heating device that heats a metal strip that passes through the inside of an induction coil that circulates in the width direction of the metal strip, and includes two or more induction coils in the longitudinal direction of the metal strip. However, the center part of the vertical projection image onto the metal band plate of the induction coil on the front side and the back side of the metal band plate is arranged so as not to overlap in the longitudinal direction of the metal band plate. In the induction coil, the induction coil on the front surface side is close and the induction coil on the back surface side is arranged at a larger interval than the proximity interval on the front surface side, or the induction coil on the back surface side is close and the induction coil on the front surface side Are disposed at intervals larger than the proximity interval on the back surface side, and the magnetic core is disposed between the front surface side and the back surface side in the longitudinal direction of the metal strip so as to cover the end of the metal strip. An induction heating device for a metal strip is disclosed.

JP-A-62-281291 JP 63-027836 A Japanese National Patent Publication No. 11-500026 JP 2008-186589 A JP 2009-259588 A

  In the induction heating of the thin metal strip, the shielding plates (Patent Documents 2 and 3) that shield the magnetic flux are heated by the shielding plate itself, so that the heating efficiency is lowered and the cooling is sufficiently performed. Otherwise, it may burn out.

  The magnetic core (Patent Documents 4 and 5) and the magnetic flux concentrating member (Patent Document 1) are slanted from the front surface side to the back surface side or from the back surface side to the front surface side at the end in the plate width direction of the metal strip. However, in the case of heating with a large output, a sufficient cross-sectional area and a countermeasure against heat generation of the core itself are required so as not to saturate the magnetic flux.

  Therefore, the present invention suppresses overheating at the end of the metal strip in the plate width direction, equalizes the temperature distribution in the plate width direction of the metal strip, and further changes the plate width of the metal strip, An object of the present invention is to provide a induction heating apparatus that can quickly cope with the meandering of the strip and improve the heating efficiency and solve the problem.

  The inventor has intensively studied a method for solving the above problems. As a result, the inventor has a current path in which the current flows in the direction opposite to the direction of the current flowing in the induction coil located at the end of the metal strip in the width direction of the metal strip, It has been found that if it is formed opposite to the plate surface opposite to the induction coil, overheating in the width direction portion of the metal strip can be suppressed.

  In addition, even if the width of the metal strip changes, the inventor does not change the shape / positional relationship on the end side of the induction coil, and the induction coil other than the end side is made of a flexible conductor. For example, the width of the induction coil in the plate width direction of the metal strip can be expanded and contracted according to the change in the width of the metal strip, and even if the metal strip is meandering and the position of the end of the plate is moved, the metal strip We found that it was possible to respond quickly to changes in the plate edge.

  This invention was made | formed based on the said knowledge, and the summary is as follows.

  (1) Connect at least one end of two rows of conductors in the same plane along the plate width direction of the metal strip and close to each other toward the end in the plate width direction with the conductor in the longitudinal direction. In the induction heating apparatus in which the coil surface facing the same plate surface of the traveling metal strip is formed away from the traveling direction of the metal strip, the conductor connecting at least one end of the two rows of conductors is the metal strip The current path on the primary side is circulated around the end in the plate width direction of the metal plate so that the induced current flows in the direction opposite to the current flowing in the plate end of the induced current generated by the two rows of conductors. An induction heating apparatus for a metal strip, characterized by being formed along an end portion in the plate width direction and facing the plate surface of the end portion.

  (2) The magnetic core according to (1), wherein a plurality of magnetic cores movable in the plate width direction along the induction coil are disposed on the back surface of the two rows of conductors independently of the induction coil. Induction heating device for metal strip.

  (3) A portion other than the end portions of the two rows of conductors is a flexible conductor, the magnetic core is movable in accordance with the expansion and contraction of the flexible conductor, and the induction coil changes the plate width of the metal strip. The induction heating device for a metal strip according to the above (1) or (2), which can respond to meandering immediately.

  (4) The metal strip according to any one of (1) to (3), wherein a magnetic core that covers a plate width direction end of the metal strip is disposed before and after the current path. Induction heating device.

  According to the present invention, overheating at the end of the metal strip in the plate width direction can be suppressed, the temperature distribution in the plate width direction of the metal strip can be made uniform, and the metal strip can be quickly changed or meandered. Therefore, productivity is greatly improved and stable and highly accurate heating is possible.

It is a figure which shows the plane aspect of the induction heating apparatus of this invention. It is a figure which shows the cross-sectional aspect of another induction heating apparatus of this invention. It is a figure which shows the cross-sectional aspect of another induction heating apparatus of this invention. It is a figure which shows typically the cross-sectional aspect of another induction heating apparatus of this invention. (A) shows the cross-sectional aspect in case the plate | board width of a metal strip is narrow, (b) shows the cross-sectional aspect in case the plate | board width of a metal strip is wide. The cross-sectional aspect of another induction heating apparatus of this invention is shown. (A) shows the cross-sectional aspect in case the plate | board width of a metal strip is narrow, (b) shows the cross-sectional aspect in case the plate | board width of a metal strip is wide.

The metal strip induction heating device of the present invention (hereinafter sometimes referred to as the “device of the present invention”) is in the same plane along the plate width direction of the metal strip and close to each other toward the end in the plate width direction. At least one end of the two rows of conductors is connected by a conductor to form a coil conductor surface facing the plate surface of the metal strip that runs in the longitudinal direction, the coil conductor being in the direction of travel of the metal strip In an induction heating apparatus provided with an induction coil that is installed apart from each other and through which primary currents flow in opposite directions,
A conductor connecting at least one end of the two rows of coil conductors circulates outward in the plate width direction end of the metal strip, and is in a direction opposite to the current flowing through the ends of the two rows of conductors. A current path through which the current flows is formed along the end portion in the plate width direction of the metal strip and facing the plate surface of the end portion.

  The apparatus of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a plan view of the device of the present invention.

  While the metal strip 1 travels under the induction coil 2 in the longitudinal direction (arrow direction in the figure), the induction coil 2 in the plate width direction of the metal strip 1 (current flows in the arrow direction). An induced current in the direction opposite to that of the induction coil 2 is generated on the plate surface of the metal strip 1 and the metal strip 1 is heated.

  The induction coil 2 composed of two rows of conductors in the same plane includes two rows of straight portions 2a and 2d, approach portions 2b and 2c approaching each other toward the end in the plate width direction, and the approach portions 2b and 2c. It is composed of conductors 3 to be connected. Although not shown, for example, a conductor extends in the direction perpendicular to the paper surface near the center of the metal strip and is connected to a power source.

  In the configuration of the induction coil 2, the coil length in the plate width direction and the longitudinal direction of the metal strip and the number of turns of the conductor (the number of conductors constituting one line of the linear portion) are not limited to a specific range. Further, the form of the approaching part following the straight part is preferably a form of approaching each other toward the end in the plate width direction in order to adjust the time during which the plate end side is heated by the induced current flowing on the plate end side. It is not limited to a specific form, such as a triangle, a semicircle, or a curve.

  In other words, the induction coil may be appropriately designed according to the width, thickness, traveling speed, temperature distribution, etc. of the metal strip to be subjected to induction heating. The conductor forming the induction coil is preferably a good conductor such as copper.

  As shown in FIG. 1, in the induction coil 2, the conductor 3 connecting the approaching part 2b and the approaching part 2c approaching each other toward the end in the plate width direction of the metal band plate continues to the one approaching part 2b. A current path 3a extending vertically from the end of the plate 1, a current path 3b extending from the current path 3a below the end of the metal strip 1, and extending parallel to the end face of the end, and from the current path 3b to the metal strip 1 A current path 3c extending perpendicularly to the end portion and below the plate surface of the end portion, and a current path 3d extending along the end portion from the current path 3c under the plate surface of the end portion of the metal strip 1; A current path 3e extending from the current path 3d above the end of the metal strip 1, a current path 3f extending from the current path 3e above the end of the metal strip 1 and parallel to the end face of the end, and The current path 3g extends from the current path 3f to the other approaching portion 2c.

  In the configuration of the current path, the current path 3a following the approaching portion 2b and the current path 3g following the approaching portion 2c may be located in the same plane perpendicular to the metal strip 1 in the plate width direction. In addition, the current path 3b that connects the current path 3a and the current path 3c and the current path 3f that connects the current path 3e and the current path 3g may be located in the same plane perpendicular to the metal strip 1 in the longitudinal direction. .

  What is important in constructing a current path with conductors connecting two rows of approaching portions that are close to each other toward the end in the width direction of the metal strip is the direction opposite to the current flowing through the two rows of approaching portions. The current path (current path 3d in FIG. 1) through which the current flows is formed along the plate width direction end of the metal strip and facing the plate surface of the end.

  In the device of the present invention, the end portions of the two rows of induction coils are brought close to each other toward the end portion in the plate width direction of the metal strip (refer to the approach portions 2b and 2c in FIG. 1), and the current density of the induced current is reached. And the heating time is controlled to suppress overheating at the end of the metal strip in the plate width direction, but at the end of the metal strip in the plate width direction, the induced current approaches the end due to the skin effect. Overheating compared to the center.

  Therefore, in order to suppress the current flowing in the end portion in the width direction of the metal strip, the induced current in the direction opposite to the direction of the induced current generated in the end portion in the width direction of the metal strip on the induction coil side is A conductor that connects two rows of approaching portions approaching each other toward the plate width direction end of the metal band so as to occur on the plate surface opposite to the induction coil side of the plate width direction end of the band plate is made of metal. A current path in which the current flows in the direction opposite to the current flowing in the end portions of the two rows of conductors around the end portion in the plate width direction of the strip is formed along the end portion in the plate width direction of the metal strip. It is formed opposite to the plate surface at the end.

  In FIG. 2, the cross-sectional aspect of another this invention apparatus is shown. In the device of the present invention shown in FIG. 2, in the configuration of the induction coil, two rows of rails 5 are arranged symmetrically, and the two strips of straight portions 2a and 2d of the induction coil 2 are made of metal strip plates. The same number of rectangular parallelepiped magnetic cores 4 are arranged on both sides in the width direction.

  Since the magnetic core 4 has a high magnetic permeability, it acts to collect the magnetic flux generated by the induction coil, the temperature distribution can be controlled by controlling the magnetic flux distribution, and the heating efficiency can be improved by concentrating the magnetic flux. The induction coil and the metal strip can be spaced apart from each other without reducing efficiency, and the induction coil and the insulation that protects the induction coil can be used when heating a defective metal strip. It has important functions such as avoiding contact with the device.

  The shape of the magnetic core 4 is basically a rectangular parallelepiped shape, but is not limited to the rectangular parallelepiped shape. When the magnetic core has a rectangular parallelepiped shape, the long side width (the length of the metal strip in the plate thickness direction), the short side width (the length in the running direction of the metal strip), and the thickness (the plate of the metal strip) The length in the direction perpendicular to the surface is not limited to a specific range. What is necessary is just to set suitably based on the shape and length of an induction coil.

  The ferromagnetic material constituting the magnetic core 4 is not limited to a ferromagnetic material of a specific material. Ferromagnetic materials include, for example, ferrite, laminated electrical steel sheets, amorphous alloys, and the like, and may be appropriately selected and designed so as not to saturate the magnetic flux according to the heating capability applied to the induction heating device. When there is a concern about heat generation, it is desirable to cool the magnetic core with a cooling device such as a water-cooled copper plate.

  The arrangement mode of the magnetic core 4 is determined in advance so that the position, the cross-sectional area, etc. are determined in advance by electromagnetic field analysis or the like and can be optimally heated by actual heating. Need not be the same number. What is necessary is just to increase / decrease suitably according to an overheating condition and desired temperature distribution. Further, the number of the magnetic cores 4 may be appropriately changed during the traveling of the metal strip.

  The number of magnetic cores 4 (or the interval between the magnetic cores) depends on the length of the induction coil (see FIG. 1) where the magnetic cores are disposed, the shape of the magnetic cores, and the temperature of the metal strip. Based on distribution, it sets so that required heating efficiency can be ensured.

  FIG. 3 shows still another cross-sectional aspect of the device of the present invention. The induction coil 6 shown in FIG. 3 separates the straight portions 2a (2d) of the two rows of the induction coils 2 shown in FIG. 1 at the center, and each of them (the straight portion 6a in the figure) is a movable conductor 6d that rises at the center. And connected to the approaching part 6b via the connecting part 6c. And the flexible rail 7 which expands / contracts according to expansion / contraction of the flexible conductor 6d is arrange | positioned on the back surface of the flexible conductor 6d which comprises the linear part 6a of 2 rows.

  The approaching portion 6b is positioned along the current path 6e and the current path 6f that circulate around the end portion of the metal strip 1 and the end portion in the plate width direction of the metal strip 1 so as to face the plate surface of the end portion. In addition, a current path 6g through which a current flows in a direction opposite to the current flowing through the end portion of the approaching portion 6b is connected.

  In the arrangement mode of the induction coil and the magnetic core shown in FIG. 3, in addition to being able to suppress overheating at the end in the width direction of the metal strip 1, the induction coil While changing the width | variety of a board width direction, the arrangement | positioning of a magnetic body core can also be changed suitably, and a desired heating aspect can be ensured.

  Further, even when the metal strip is meandering, it is possible to always maintain the optimum positional relationship between the end portion of the metal strip, the induction coil, and the magnetic core. The induction coil or magnetic core may be driven by moving the induction coil or magnetic core on the rail with a motor or the like, and the method is not particularly limited.

  The number of magnetic cores disposed on the left and right sides in the plate width direction of the metal strip does not necessarily have to be the same number at the beginning and / or during travel of the metal strip. The number of magnetic cores arranged (or the interval between magnetic cores) depends on the length of the induction coil in which the magnetic cores are arranged, the shape of the magnetic cores, and the temperature distribution of the metal strip. Set to ensure efficiency.

  In the arrangement example of the magnetic core shown in FIG. 3, the magnetic flux density at the center of the metal strip is reduced, but eddy current is generated on the surface of the metal strip and forms a closed circuit. There is no problem.

  In FIG. 4, the example of the cross-sectional aspect of another this invention apparatus is shown typically. FIG. 5 (a) shows a cross-sectional aspect when the plate width of the metal strip is narrow, and FIG. 5 (b) shows a cross-sectional aspect when the plate width of the metal strip is wide.

  In the apparatus of the present invention shown in FIG. 4, the induction coil 6 has two rows of linear portions 6a formed of flexible conductors 6d, and the end portions of the metal strip 1 via the connecting portions 6c connected to the two rows of linear portions 6a. The approach part 6b approaching toward is connected.

  The approaching portion 6b is positioned along the current path 6e and the current path 6f that circulate around the end portion of the metal strip 1 and the end portion in the plate width direction of the metal strip 1 so as to face the plate surface of the end portion. In addition, a current path 6g through which a current flows in a direction opposite to the current flowing through the end portion of the approaching portion 6b is connected.

  Usually, in induction heating, magnetic flux concentrates on the end of the metal strip and is overheated, so in the device of the present invention shown in FIG. 4, facing one plate surface of the end of the metal strip, In order to reduce the induced current of the main current that goes around the end of the metal strip, the metal strip opposite to the induction coil surface side that generates the main induced current so as to suppress the induced current of the main current. A coil surface is formed on the end side so as to generate a current in the direction opposite to the main induced current, thereby suppressing overheating at the end of the metal strip.

  The coil that generates the reverse current may be adjusted so that the area and length covering the end of the metal strip and the range covered from the end have a desired temperature distribution, but the induction coil can be freely adjusted in the width direction. Therefore, if the position is adjusted so as to control the temperature distribution, the temperature distribution can be controlled more effectively.

  Even if the plate width is changed or meandering while the metal strip is running, the width of the induction coil in the plate width direction can be expanded and contracted immediately in response to the change in the plate width of the metal strip. Can be maintained.

  In FIG. 5, the cross-sectional aspect of another this invention apparatus is shown. Fig.5 (a) shows the cross-sectional aspect in case the plate | board width of a metal strip is narrow, FIG.5 (b) shows the cross-sectional aspect in case the plate | board width of a metal strip is wide.

  The device of the present invention shown in FIG. 6 is the device of the present invention shown in FIG. 5 in which a rail 7 for transferring the magnetic core 4 is disposed on the back surface of the induction coil 6.

  If the plate width is changed during the running of the metal strip, the width of the induction coil in the plate width direction is expanded and contracted in response to the change in the width of the metal strip, and the flexible rail is expanded and contracted. By changing the number of magnetic cores arranged on the back surface, the required heating mode can be maintained.

  The number of the magnetic cores arranged on the upper and lower portions of the metal strip does not necessarily have to be the same number at the beginning and / or during the travel of the metal strip. The number of magnetic cores arranged (or the interval between magnetic cores) depends on the length of the induction coil in which the magnetic cores are arranged, the shape of the magnetic cores, and the temperature distribution of the metal strip. Set to ensure efficiency.

  In the device of the present invention, the conductor connecting at least one end of the two rows of conductors of the induction coil circulates around the end in the plate width direction of the metal strip (before and after the current path of the metal strip). You may arrange | position an appropriate number of the magnetic body cores which cover the board width direction edge part of a metal strip in front and back of a longitudinal direction. With this arrangement, overheating at the end of the metal strip in the plate width direction can be more effectively suppressed.

DESCRIPTION OF SYMBOLS 1 Metal strip 2 Induction coil 2a, 2d Linear part 2b, 2c Approach part 3 Conductor 3a, 3a ', 3b Current path 3c, 3c', 3d Current path 3e, 3f, 3g Current path 4 Magnetic body core 5 Rail 5a Transfer Means 6 Inductive coil 6a Linear part 6b Approach part 6c Connection part 6d Flexible conductor 6e, 6f, 6g Current path 7 Flexible rail 7a Transfer means t Thickness of magnetic core l Long side width of magnetic core d Magnetic core Interval

Claims (4)

A metal that runs in the longitudinal direction by connecting at least one end of two rows of conductors in the same plane that are along the plate width direction of the metal strip and close to each other toward the end in the plate width direction. In the induction heating device formed by separating the coil surface facing the same plate surface of the strip in the metal strip travel direction,
Direction of current flowing in the plate end of the induced current generated in the two rows of conductors, the conductor connecting at least one end of the two rows of conductors goes around the plate width direction end of the metal strip The primary current path is formed so as to face the plate surface of the end along the plate width direction end of the metal strip so that the induced current flows in the direction opposite to that of the metal strip. Induction heating device for metal strip.   2. The metal strip according to claim 1, wherein a plurality of magnetic cores movable in the plate width direction along the induction coil are disposed on the back surface of the two rows of conductors independently of the induction coil. Induction heating device.   The conductors other than the end portions of the two rows of conductors are flexible conductors, and the magnetic core is movable according to the expansion and contraction of the flexible conductors. 3. The induction heating device for a metal strip according to claim 1 or 2, characterized in that it can respond immediately.   The induction heating apparatus for a metal strip according to any one of claims 1 to 3, wherein a magnetic core that covers end portions in the plate width direction of the metal strip is disposed before and after the current path.

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