JP4318219B2 - Induction heating device - Google Patents

Description

  The present invention relates to an induction heating device with a countermeasure against leakage magnetic flux, and more particularly to an induction heating device capable of reducing leakage magnetic flux even if a material to be heated is a ferromagnetic material.

  In general, in a hot rolling line, a material to be heated (rolled material) is heated to a temperature at which rolling is possible in a heating furnace, and is roughly rolled by a roughing mill and formed into a state called a rough bar. Furthermore, the product which has a desired board thickness and board width is obtained by applying a rough bar to a finishing mill. As a heating means in such a hot rolling line, an induction heating apparatus having a high heating density is usually used. The induction heating device re-heats the coarse bar to prevent the coarse bar temperature from being lowered and to equalize the temperature of each part, and can stabilize the product quality at a high level.

  The induction heating device includes an induction heating coil that sandwiches a material to be heated from above and below, and includes a conveying unit that conveys the material to be heated to the induction heating coil. A high-frequency current is passed through the induction heating coil to generate an alternating magnetic flux along the direction of conveyance of the heated material, and an eddy current is generated inside the heated material to heat the heated material by Joule heat. ing. Known types of such devices include a bar heater that heats the full width of the coarse bar and an edge heater that heats only the end of the coarse bar. FIG. 8 shows an example of an edge heater. In this apparatus, induction heating coils 52 and 53 are provided so as to sandwich a heated plate 1 to be heated from above and below, and a lower roll 50 that conveys the heated plate 1 before and after these induction heating coils 52 and 53 is provided. It is arranged. In this edge heater, both ends of the heated thick plate 1 can be heated by supplying an alternating current to the induction heating coils 52 and 53.

  By the way, in the edge heater, when an alternating current is applied to the induction heating coils 52 and 53, not only the main magnetic flux 54 directed to the induction heating coils 52 and 53 but also a leakage magnetic flux 55 curved around is generated. At this time, since the lower roll 50 for conveying the heated thick plate 1 exists in the vicinity of the induction heating coils 52 and 53, a part of the leakage magnetic flux 55 does not pass through the thick plate 1 but passes through the lower roll 50. Will do. As a result, an induced current flows there to heat the lower roll 50. Further, if the thick plate 1 has a shape defect such as an ear wave, when the end of the thick plate 1 leaves the lower roll 50, a current flows between the lower roll 50 and the thick plate 1, and sparks occur. Thereby, there existed a possibility of giving an arc trace to the thick board 1 and the lower roll 50 used as a product. If an arc mark is generated on the thick plate 1 or the lower roll 50, the quality of the product is deteriorated and the productivity is lowered, which is a problem.

Therefore, conventionally, as in Patent Document 1 and Patent Document 2, an induction heating apparatus that suppresses the leakage magnetic flux from the induction heating coil and prevents arc marks on the heated material and the conveying means has been proposed.
JP 2000-15319 A JP-A-8-115787

  Here, a conventional example of an induction heating apparatus that takes measures against leakage magnetic flux will be specifically described with reference to FIG. In the induction heating apparatus of FIG. 9, the induction heating coil 2 is arranged so as to sandwich the heated plate 1 from above and below, and the heated plate 1 is adjacent to the opening 3 through which the heated plate 1 can pass. A lower roll 4 for continuously conveying the thick plate 1 in contact with the lower surface is rotatably provided. Moreover, the upper roll 8 which opposes the lower roll 4 and touches the upper surface of the to-be-heated thick board 1 and presses the thick board 1 from upper direction is provided. Furthermore, a strip block-shaped iron core 5 is installed on the outer periphery of the induction heating coil 2. An inductor 6 is constituted by the iron core 5 and the induction heating coil 2.

  The iron core 5 is made of a high relative permeability material having a relative permeability μs of about several hundred to 1000, and surrounds the end of the induction heating coil 2 by overhanging. The iron core 5 plays a role of reducing leakage magnetic flux. Further, a shield plate 7 is disposed as a member having the same function. The shield plate 7 is made of a nonmagnetic material having a high conductivity such as copper in order to prevent heating, and covers the outer periphery of the inductor 6. More specifically, the shield plate 7 extends not only in the opening 3 but also in the vertical direction to reach the outer dimensions of the inductor 6, and shields the entire end face of the inductor 6 including the opening 3.

  According to the induction heating apparatus having such a configuration, the iron core 5 forms a magnetic path through which most of the magnetic flux generated by the induction heating coil 2 passes, so that leakage magnetic flux can be reduced. Therefore, there is an effect of suppressing the leakage magnetic flux from the opening 3 of the induction heating coil 2 to the outside as much as possible, and the magnetic flux can be efficiently guided to the magnetic path that penetrates the heated thick plate 1. In this way, most of the magnetic flux can be contained in the iron core 5.

  By the way, since the iron core 5 has a strip block shape and the opening 3 exists, a part of the magnetic flux may leak to the outside of the opening 3. A member for containing leakage magnetic flux from the opening 3 is a shield plate 7. That is, a current that generates a reverse magnetic flux flows in the shield plate 7 with respect to the magnetic flux that attempts to penetrate the shield plate 7, and the leakage magnetic flux to the outside can be reduced. In addition, as a material of the to-be-heated thick plate 1, nonmagnetic materials, such as austenitic SUS and a high temperature steel material more than a Curie point, are used. When such a material is heated, most of the magnetic flux can be contained by the iron core 5 and the shield plate 7.

  However, depending on the material of the to-be-heated thick plate 1, the above-described iron core 5 and shield plate 7 alone may not provide a sufficient magnetic shielding effect, and leakage flux may be generated. When the thick plate 1 material is a ferromagnetic material such as a steel material having a Curie point or less, it is difficult to reduce the leakage magnetic flux. Passing the ferromagnetic material between the induction heating coils places a material having a high relative magnetic permeability μs in the center of the induction heating coil 2, so that the thick plate 1 itself corresponds to the magnetic core material. . Therefore, when carrying out the thick plate 1 from the inductor 6, the strong magnetic flux inside the thick plate 1 leaks to the outside of the inductor 6. As a result, as described above, there is a possibility that a spark may occur between the thick plate 1 and the lower roll 4, and there is an adverse effect that an arc mark is generated on both. In recent years, the capacity of induction heating devices has been increasing, and even devices of a scale of over 10 MW have been put to practical use. Therefore, the deterioration of product quality and yield due to arc marks has become more serious, and countermeasures against leakage magnetic flux have been fully implemented. There was a strong demand for it.

  The present invention has been proposed in order to solve such problems of the prior art, and even if the material to be heated itself becomes a magnetic core material and magnetic flux easily leaks to the outside, the leakage magnetic flux can be reliably ensured. Can reduce the occurrence of sparks between the material to be heated and the conveying means to prevent arc marks, and can obtain high quality products and contribute to productivity improvement. An object is to provide a heating device.

In order to achieve the above-mentioned object, the invention of claim 1 includes an induction heating coil that heats a material to be heated sandwiched from above and below, and a conveying means that conveys the material to be heated to the induction heating coil. In the induction heating apparatus provided, a one-turn short-circuit ring coil made of a conductive member is provided so as to surround the material to be heated, and the short-circuit ring coil extends in a direction parallel to the conveying direction of the material to be heated. A horizontal portion is formed, and as the conveying means, an upper roll in contact with the upper surface of the material to be heated and a lower roll in contact with the lower surface of the material to be heated are provided, and as the horizontal portion in the short-circuit ring coil, close to the upper roll An upper edge portion and a lower edge portion close to the lower roll, and the upper edge portion of the edges is parallel to the conveying direction of the heated material. long Characterized in that the field.
In this invention of Claim 1, a short circuit ring coil produces a counter magnetomotive force with respect to the penetration magnetic flux in the inside. For this reason, the magnetic flux which penetrates a to-be-heated material can be decreased because a short circuit ring coil surrounds a to-be-heated material. Therefore, even if the material to be heated is a ferromagnetic material such as a steel material having a Curie point or less, the material to be heated itself does not become a magnetic core material, and magnetic flux leaks to the outside due to the movement of the material to be heated. Can be sufficiently suppressed.
In addition, the short circuit ring coil formed with the horizontal portion has a higher leakage flux from the heated material to the outside than the short circuit ring coil formed with the vertical portion extending perpendicular to the conveying direction of the heated material. It can be suppressed efficiently.
Furthermore, when an upper roll and a lower roll in contact with the upper and lower surfaces of the material to be heated are provided as the conveying means, an analysis result has been obtained that the magnetic flux density near the upper roll appears larger than that near the lower roll. Therefore, by extending the upper edge of the edge of the short-circuit ring coil in a direction parallel to the conveying direction of the material to be heated rather than the lower edge, it is ensured even if strong magnetic flux exists near the upper roll. Can be suppressed.

According to a second aspect of the invention, in the induction heating apparatus according to claim 1, wherein the short-circuit ring coil expands and contracts the width direction of the plate thickness adjuster and the material to be heated to stretch in the thickness direction of the material to be heated plate At least one of the width adjusters is provided.
In the invention of claim 2, even when the thickness dimension and the width dimension of the heated material are changed, the dimension of the short-circuit ring coil can be adjusted by the adjuster according to the dimension change. Therefore, it is possible to always keep a constant distance between the short-circuit ring coil and the material to be heated. Thereby, the short circuit ring coil can exhibit the magnetic shielding effect stably, and can reduce the leakage magnetic flux through a to-be-heated material reliably.

A third aspect of the present invention, in the induction heating apparatus according to claim 1 or 2, wherein the shorting ring coil, characterized by being disposed between the induction heating coil and which in the immediate vicinity of the conveying means.
In the invention of the third aspect described above, since the short-circuit ring coil is disposed between the induction heating coil and the conveying means nearest to the induction heating coil, it is possible to prevent a spark generated when the material to be heated leaves the conveying means. Yes, it is possible to avoid arc marks on the heated material and the conveying means.

  As described above, according to the induction heating device of the present invention, the magnetic shielding effect can be enhanced by a very simple configuration including a short-circuit ring coil, and the material to be heated itself can be a magnetic core. Even if it is a magnetic material, it is possible to suppress the spark induced between a to-be-heated material and a conveyance means, and to prevent generation | occurrence | production of an arc mark, and the quality and yield of a product improve.

  Hereinafter, an example of the best mode (hereinafter referred to as an embodiment) for carrying out the present invention will be specifically described with reference to FIGS. The induction heating device of this embodiment is an improvement of the conventional example shown in FIG. 9, and the configuration of this embodiment shown in FIG. 1 is basically the same as that of FIG. For this reason, the same reference numerals are assigned to the same members, and descriptions thereof are omitted.

[1] Configuration As shown in FIG. 1 and FIG. 2, the structural feature of this embodiment is that a one-turn short-circuit ring coil 9 is installed in the opening 3 of the inductor 6 so as to surround the heated thick plate 1. In the point. The short-circuit ring coil 9 is made of a conductive member such as copper, and has an upper edge portion 10 and a lower edge portion 11 extending in parallel with the conveying direction of the heated thick plate 1. Among these, the upper edge portion 10 close to the upper roll 8 extends longer in the horizontal direction (left-right direction in FIG. 1) than the lower edge portion 11 close to the lower roll 4. The upper roll 8 of the present embodiment is made of a nonmagnetic material.

  FIG. 3 is a front view of the short-circuit ring coil 9. As shown in this figure, the short-circuit ring coil 9 is a frame-like member, and includes an upper edge portion 10, a lower edge portion 11, and left and right edge portions 12. At the center of the upper edge portion 10 and the lower edge portion 11, a groove portion extending in parallel with the transport direction of the heated thick plate 1 is formed. A plate width adjuster 13 is attached so as to cover the groove. The plate width adjuster 13 is made of a flexible copper strip that can expand and contract in the width direction of the short-circuit ring coil 9 (left-right direction in FIG. 3). Further, actuators 14 such as air cylinders are provided at the left and right edge portions 12 of the short-circuit ring coil 9, and the plate width adjuster 13 expands and contracts in the width direction of the short-circuit ring coil 9 by operating this actuator 14. It has become.

[2] Operational Effects The operational effects of the present embodiment having the above-described configuration are as follows. That is, the short-circuit ring coil 9 generates a counter electromotive force with respect to the internal penetrating magnetic flux, and the magnetic flux penetrating the heated thick plate 1 is greatly reduced. Thereby, even if the heated thick plate 1 is a ferromagnetic material that can be a magnetic core, when the thick plate 1 is carried out of the inductor 6, there is a concern that strong magnetic flux leaks to the outside of the inductor 6 through the thick plate 1. Absent. In addition, since the upper edge portion 10 and the lower edge portion 11 of the short-circuit ring coil 9 extend in parallel with the transport direction of the thick plate 1, the upper and lower edges of the short-circuit ring coil 9 are perpendicular to the transport direction of the thick plate 1. Compared with the case of extending in the vertical direction (according to FIG. 1), magnetic flux leakage from the thick plate 1 to the outside can be efficiently suppressed. And by arrange | positioning such a short circuit ring coil 9 between the induction heating coil 2 and the roller 4 and 8 nearest to this, the leakage magnetic flux of the to-be-heated thick board 1 can be decreased rapidly. As a result, the occurrence of sparks induced between the end of the thick plate 1 and the rollers 4 and 8 can be prevented, and arc marks on the heated thick plate 1 and the rollers 4 and 8 can be avoided.

  Moreover, in this embodiment, although the upper roll 8 and the lower roll 4 are provided as a conveyance means of the to-be-heated thick board 1, the voltage induced by the thick board 1 in the roll vicinity has a big difference. That is, the voltage induced in the thick plate 1 in the vicinity of the lower roll 4 is only slightly affected. On the other hand, the voltage induced in the thick plate 1 in the vicinity of the upper roll 8 remains as a relatively large voltage value.

  As shown in the graph of FIG. 4, when the opening height of the short-circuit ring coil 9 is about 180 mm, the voltage near the lower roll 4 is slightly over 0.2 PU, whereas the voltage near the upper roll 8 is 0. 7PU, which is about three times the voltage value (here, the voltage when there is no short-circuit ring coil 9 is 1PU). Thus, the magnetic flux density near the upper roll 8 appears larger than that near the lower roll 4. Therefore, in the present embodiment, the upper edge portion 10 of the short-circuit ring coil 9 is extended in the horizontal direction so as to be larger than the lower edge portion 11, so that even if the magnetic flux from the short-circuit ring coil 9 is strong, this can be reliably reduced. it can. In addition, since the magnetic flux density in the vicinity of the upper roll 8 is large, it is more preferable that the upper roll 8 is made of a nonmagnetic material.

  Further, in the present embodiment, even if the width dimension of the heated thick plate 1 changes, the actuator 14 is operated to expand and contract the sheet width adjuster 13 in the width direction in accordance with the dimension change, and the short-circuit ring coil 9 The width dimension can be increased or decreased. For this reason, the distance between the short-circuit ring coil 9 and the heated thick plate 1 can always be maintained at a desired length. Therefore, the short-circuit ring coil 9 is not greatly separated from the heated thick plate 1, and there is no fear that the magnetic shielding effect of the short-circuit ring coil 9 is impaired. Moreover, since the short circuit ring coil 9 does not approach the to-be-heated thick plate 1 too much, the conveyance operation of the thick plate 1 can be ensured stably.

[3] Other Embodiments The present invention is not limited to the above embodiment. For example, in the short-circuit ring coil 15 shown in FIG. 5, the upper edge portion 16 and the lower edge portion 17 are divided. A plate thickness adjuster 19 is attached to the center of the left and right edges 18 to connect the upper and lower edges 16, 17. The plate thickness adjuster 19 is made of a flexible copper strip that can expand and contract in the thickness direction of the short-circuit ring coil 9 (vertical direction in FIG. 5). Further, an actuator 20 such as an air cylinder is attached to the upper and lower edges 16 and 17 of the short-circuit ring coil 9 so that the plate thickness adjuster 19 expands and contracts in the thickness direction of the short-circuit ring coil 9 by operating this actuator 20. It has become.

  According to such a short-circuit ring coil 15, it is possible to cope with a case where the thickness dimension of the heated thick plate 1 changes. That is, according to the change of the thickness dimension, the plate thickness adjuster 19 can be expanded and contracted in the thickness direction by the actuator 20 to increase or decrease the thickness dimension of the short-circuit ring coil 15. Further, by combining such a plate thickness adjuster 19 and the plate width adjuster 13, both the thickness dimension and the width dimension of the short-circuit ring coil may be adjustable. Further, the member constituting the adjuster is not limited to the flexible copper strip, but may be a short-circuit ring coil having a structure that can slide in the thickness direction or the width direction of the coil.

  Further, the shape and dimensions of each member can be changed as appropriate, and the shape of the short-circuit ring coil includes an angle-shaped short-circuit ring coil 21 and a laminated short-circuit ring coil 22 as shown in FIG. The horizontal short-circuit ring coil shown in FIG. 6 is the short-circuit ring coil 9 in the above embodiment. When these short-circuit ring coils 21 and 22 are provided, as shown in the graph of FIG. 7, when the opening size of the coil is about 200 mm, the laminated coil 22 (two layers in FIG. 7) is the above embodiment. The short-circuit ring coil 9 (parallel in FIG. 7) can have the same current value characteristic. This indicates a value superior to that of the vertical short-circuit ring coil 23. In addition, the angle-shaped short-circuit ring coil 21 (L-shaped in FIG. 7) can have a higher current value characteristic than the short-circuit ring coil 9, and can exhibit an excellent magnetic shielding effect. In addition, if the number of installation of a short ring coil and an installation location are also a conveyance line of a to-be-heated material, it can be selected freely.

The side view which shows the structure of the induction heating apparatus in embodiment of this invention. The expanded side view of the short circuit ring coil periphery in this embodiment. The front view of the short circuit ring coil in this embodiment. The graph which shows the difference in the voltage induced by the to-be-heated thick board in the upper roll and lower roll vicinity in this embodiment. The front view of the short circuit ring coil which concerns on other embodiment of this invention. The side view of the short circuit ring coil which concerns on other embodiment of this invention. The graph which compared the electric current value characteristic of the short circuit ring coil shown in FIG. 6, and the short circuit ring coil shown in FIGS. The side view of the edge heater which is the conventional induction heating apparatus. The side view which shows the structure of the induction heating apparatus which took the magnetic flux leakage countermeasure in the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Thick board 2,52,53 ... Induction heating coil 3 ... Opening part 4, 50 ... Lower roll 5 ... Iron core 6 ... Inductor 7 ... Shield board 8 ... Upper roll 9, 15, 21, 22, 23 ... Short circuit Ring coils 10 and 16 ... upper edge parts 11 and 17 ... lower edge parts 12 and 18 ... left and right edge parts 13 ... plate width adjusters 14 and 20 ... actuator 19 ... plate thickness adjuster

Claims (3)

In an induction heating apparatus comprising an induction heating coil that sandwiches a material to be heated from above and below and heats the material, and a conveying means that conveys the material to be heated to the induction heating coil.
A one-turn short-circuit ring coil made of a conductive member is provided so as to surround the heated material ,
As the conveying means, an upper roll in contact with the upper surface of the heated material, and a lower roll in contact with the lower surface of the heated material,
As a horizontal portion in the short-circuit ring coil, comprising an upper edge portion close to the upper roll, and a lower edge portion close to the lower roll,
The induction heating apparatus characterized in that the upper edge portion of these edges extends longer in the direction parallel to the conveying direction of the heated material than the lower edge . The short ring coil is in the plate width adjuster for stretching the width direction of the plate thickness adjuster and the material to be heated to stretch in the thickness direction of the material to be heated, wherein characterized by comprising the at least one Item 2. The induction heating device according to Item 1. The short ring coil, the induction heating apparatus according to claim 1 or 2, characterized in that disposed between the induction heating coil and which in the immediate vicinity of the conveying means.

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