JP2019179733A - Induction heating device of metal band, method for manufacturing metal band, and method for manufacturing hot-dip galvanized steel sheet - Google Patents

Abstract

An object of the present invention is to provide a metal strip induction heating apparatus capable of uniformly heating a metal strip in a width direction with a simple apparatus configuration. A first coil (10) and a second coil (20) are arranged close to one side of a metal band (S), and high-frequency currents in opposite directions flow. Edge masks 80 and 90 as a pair of magnetic flux attenuating members are arranged between the first coil 10 and the second coil 20 and both ends EP1 and EP2 in the width direction of the metal band S. One edge mask 80 includes a first plate-shaped portion 81, and a first protrusion 84 protruding in a direction toward the metal band is provided at an end of the first plate-shaped portion on the center side in the width direction of the metal band. Is provided. The same applies to the other edge mask 90. [Selection diagram] FIG.

Description

  The present invention relates to an induction heating apparatus for a metal band that induction-heats a continuously conveyed metal band with a high-frequency current, a method for manufacturing a metal band using the induction heating apparatus, and a method for manufacturing a galvannealed steel sheet.

  When heating while passing a non-magnetic metal band such as stainless steel, steel with a high austenite fraction, aluminum, etc., it has a structure in which induction coils are arranged on the front and back of the metal band, and the magnetic flux is the thickness of the metal band A so-called transverse type (TF type) induction heating device that passes in the direction is used.

  FIG. 7 of Patent Document 1 shows a main coil 1 that generates magnetic flux, a high-frequency power supply device that allows a high-frequency current to flow through the main coil 1, a main iron core 2 around which the main coil 1 is wound, and a strip 9. Describes a transverse induction heating apparatus composed of a magnetic shielding material (F / M) 10 that adjusts the magnetic flux density of the edge portion of the substrate. In this induction heating apparatus, a main inductor is configured by a combination of the main coil 1 and the main iron core 2. The main iron core 2 is composed of a pair arranged opposite to each other with the strip 9 in between. The main iron core 2 is for increasing the magnetic flux density generated by the main coil 1, suppressing the leakage magnetic flux, and increasing the heating efficiency of the strip 9. In FIG. 7, the strip 9 is supplied to the induction heating device while continuously moving from the upper side to the lower side, for example. When an alternating magnetic flux having a vertical direction component is applied to the thin plate-like conductive strip 9, an induced current (eddy current) is generated in the strip 9 so as to cancel it, and due to the Joule heat generated thereby, the strip 9 is heated.

  In the induction heating device of Patent Document 1, the main coil 1 is formed by arranging two coils in close proximity to each other such that the longitudinal direction thereof coincides with the width direction of the strip. Therefore, as shown in FIG. 8 of Patent Document 1, uniform heating is possible in the central portion a in the width direction of the strip where two coils are adjacent.

  However, the generated eddy current has a property of being concentrated at both ends in the width direction of the strip according to the boundary condition of the electromagnetic field, so that both ends in the width direction of the strip are heated to a higher temperature than the uniformly heated central portion. It is known to be. In the induction heating device of Patent Document 1, the magnetic shielding material 10 serves as a so-called edge mask, and shields and attenuates the magnetic flux passing through both ends of the strip, thereby preventing overheating of both ends. . By adjusting the amount of edge mask insertion from the edge of the strip, the temperature distribution at both ends of the strip can be adjusted.

  However, in this case, as shown in FIG. 8 of Patent Document 1, if the insertion amount of the edge mask is adjusted so that the temperature at both ends c of the strip becomes equal to the temperature at the central portion a of the strip, a little at both ends. A low temperature region b is generated inside. This is because the eddy current flowing in the strip width direction in the central portion changes its direction in the strip longitudinal direction in a region slightly inward of both ends, and as a result, the density of the eddy current is diluted in this region.

  As described above, the conventional edge mask cannot sufficiently adjust the eddy current distribution at both ends of the strip and a region slightly inside thereof. Therefore, Patent Document 1 discloses a transverse induction heating apparatus in which an auxiliary inductor including the auxiliary iron core 4 and the auxiliary coils 31 and 32 is provided at a position corresponding to a low temperature region in FIG. In this apparatus, it is described that uniform heating can be performed in the width direction of the strip by heating a region slightly inside the both ends of the strip with the auxiliary inductor.

JP-A-7-169561

  However, in the induction heating apparatus shown in FIG. 1 of Patent Document 1, since an auxiliary inductor is disposed in addition to the main inductor, a large number of control apparatuses for controlling these inductors are required, and the apparatus configuration is complicated and expensive. There was a problem of becoming.

  Therefore, in view of the above problems, the present invention provides a metal band induction heating device capable of uniformly heating a metal band in the width direction with a simple apparatus configuration, a metal band manufacturing method using the induction heating device, and It aims at providing the manufacturing method of a galvannealed steel plate.

  In order to solve the above-mentioned problems, the inventors have overheated both ends of the metal band by devising the shape of a magnetic flux attenuating material (edge mask) that shields the magnetic flux passing through both ends in the width direction of the metal band. The idea was that it would be possible to prevent the occurrence of a low temperature region slightly inside. As a result of intensive studies, a protrusion that protrudes in the direction toward the metal band is provided on the plate-like member with respect to the conventional edge mask that is composed of a pair of plate-like members that respectively face at least one side of the metal band. It has been found that the above-mentioned problems can be solved by disposing the portion at the position of the low temperature region.

The gist configuration of the present invention completed based on the above findings is as follows.
(1) A metal strip induction heating device that induction-heats a metal strip that is continuously transported in a transport direction orthogonal to the width direction by high-frequency current,
A first coil having a straight portion extending wider than the metal band along the width direction of the metal band, and disposed at least on one side of the metal band;
It has a straight part extending wider than the metal band along the width direction of the metal band, and is disposed so as to face at least one side of the metal band and the first coil and the straight part are adjacent to each other. A second coil,
An alternating current power source for flowing high-frequency currents in opposite directions to the first coil and the second coil;
A pair of magnetic flux attenuating members disposed between the first coil and the second coil and both ends of the metal strip in the width direction;
Have
The pair of magnetic flux attenuating members includes a first plate-like portion facing one side of the metal band, and an end of the first plate-like portion on the center side in the width direction of the metal band is attached to the metal band. An induction heating device for a metal strip, characterized in that a first projecting portion projecting in a direction is provided.

(2) A straight portion extending wider than the metal band along the width direction of the metal band, facing at least the other surface of the metal band and overlapping the first coil in the transport direction. A third coil arranged at a position;
It has a straight part that extends wider than the metal band along the width direction of the metal band, faces at least the other surface of the metal band, and the third coil and the straight part are adjacent to each other. A fourth coil disposed at a position overlapping the second coil in the transport direction;
An alternating current power source for flowing high-frequency currents in opposite directions to the third coil and the fourth coil;
A first portion around which the first coil is wound, a second portion around which the second coil is wound, and a first connecting portion that connects the first portion and the second portion, The first part, the second part, and the first connecting part are wider than the metal band so as to face one side of the metal band so as to surround adjacent straight parts of the first coil and the second coil. A first iron core disposed in
A third portion around which the third coil is wound, a fourth portion around which the fourth coil is wound, and a second connecting portion that connects the third portion and the fourth portion, The third part, the fourth part, and the second connecting part are opposed to the other surface of the metal band so as to surround adjacent straight parts of the third coil and the fourth coil, and more than the metal band. A second iron core arranged wide,
Further comprising
The pair of magnetic flux attenuating members further includes a second plate-like portion facing the other surface of the metal band, and a connecting portion for connecting the first plate-like portion and the second plate-like portion, The plate-shaped portion, the second plate-shaped portion, and the connecting portion surround the end portion in the width direction of the metal band, and the end portion of the second plate-shaped portion on the center side in the width direction of the metal band is The induction heating apparatus for a metal strip according to (1), wherein a second projecting portion that protrudes in a direction toward the metal strip is provided.

  (3) The said 1st thru | or 4th coil has a pair of straight part extended wider than the said metal strip along the width direction of the said metal strip, The induction heating of the metal strip as described in said (2) apparatus.

  (4) In the first to fourth coils, the metal band induction heating device according to (3), wherein a distance in the conveyance direction between the pair of straight portions is 40% or less of a width of the metal band.

  (5) In the pair of magnetic flux attenuating materials, the end of the first plate-like portion and the second plate-like portion on the center side in the width direction of the metal strip is the first of the first iron core in the transport direction. The induction heating apparatus for a metal strip according to any one of (2) to (4), wherein the connection portion and a portion corresponding to the second connection portion of the second iron core have a first notch.

  (6) In the pair of magnetic flux attenuating materials, the first plate-like portion and the second plate-like portion have an end portion on the center side in the width direction of the metal band that is notched at both ends in the transport direction. The induction heating apparatus for a metal strip according to any one of (2) to (5), which includes a portion.

(7) a sensor that detects the positions of both edges of the metal strip;
A movable device that advances and retracts the pair of magnetic flux attenuating materials in the width direction of the metal strip;
A control unit that receives input from the sensor and controls the movable device such that each first protrusion of the pair of magnetic flux attenuating members maintains a certain distance from the edge of the metal strip in the width direction of the metal strip. When,
The induction heating device for a metal strip according to any one of (1) to (6), further including:

  (8) In the metal band manufacturing process, the induction heating device according to any one of (1) to (7) is used, and the metal band continuously conveyed in the conveyance direction orthogonal to the width direction is used as a high frequency wave. A method for producing a metal strip, comprising a step of induction heating with an electric current.

(9) A step of hot dip galvanizing the steel strip continuously conveyed in the direction orthogonal to the width direction;
Using the induction heating apparatus according to any one of (1) to (7), the steel strip that is continuously conveyed in a conveyance direction orthogonal to the width direction is induction-heated by a high-frequency current, and the steel strip A step of heat-alloying the galvanizing applied to
A method for producing an alloyed hot-dip galvanized steel sheet.

  According to the metal band induction heating apparatus and the metal band manufacturing method of the present invention, the metal band can be uniformly heated in the width direction with a simple apparatus configuration. According to the method for producing an alloyed hot-dip galvanized steel sheet of the present invention, the steel strip can be heated uniformly in the width direction with a simple apparatus configuration, and the galvanizing can be heated and alloyed.

It is a figure which shows typically the induction heating apparatus of the metal strip by the comparative example 1, (A) is a top view, (B) is a sectional side view. It is a figure which shows steel strip temperature distribution of the plate width direction by the induction heating in the comparative example 1. It is a conceptual diagram which shows distribution of the induced current which flows in a steel strip in the comparative example 1, (A) is a case where a board width is large, (B) is a case where a board width is small. It is a figure which shows typically the induction heating apparatus 100 of the metal strip by one Embodiment of this invention, (A) is a top view, (B) is sectional drawing perpendicular | vertical to a conveyance direction. It is sectional drawing perpendicular | vertical to a conveyance direction which shows typically the induction heating apparatus of the metal strip by the comparative example 2. It is a figure which shows the steel strip temperature distribution of the plate width direction by induction heating, (A) is the comparative example 2 when (B) and (C) use the induction heating apparatus 100 by one Embodiment of this invention. This is the case of using the induction heating apparatus. It is a figure which shows magnetic flux distribution typically, (A) is the case where the induction heating apparatus 100 by one Embodiment of this invention is used, (B) is the case where the induction heating apparatus by the comparative example 2 is used. . (A) is a typical perspective view of the edge mask 80 used with the induction heating apparatus 100 by one Embodiment of this invention, (B) is a typical perspective view of the edge mask 80C by a 1st modification. It is a conceptual diagram which shows the distribution of the induced current which flows through a steel strip, (A) is the case of the comparative example 1 without an edge mask, (B) is the case of one embodiment of this invention using the edge mask 80, (C ) Is a case where an edge mask 80C according to a modification is used. It is a typical perspective view of edge mask 80D by the 2nd modification.

(Induction heating device for metal strip)
Hereinafter, an induction heating apparatus 100 for a metal strip according to an embodiment of the present invention will be described. 4 (A) and 4 (B), an induction heating apparatus 100 according to this embodiment is a so-called transformer that induction-heats a steel strip S continuously conveyed in a conveyance direction T orthogonal to the width direction by a high-frequency current. It is a berth type induction heating device. In the present embodiment, the transport direction T is the vertical direction, but the present invention is not limited to this. Hereinafter, the width direction of the steel strip S is referred to as “plate width direction”, and the width of the steel strip S is referred to as “plate width”.

(Basic equipment configuration)
The induction heating apparatus 100 of this embodiment has the same configuration as that of the induction heating apparatus according to the comparative example 1 shown in FIGS. 1A and 1B except for the edge masks 80 and 90 as magnetic flux attenuation materials. First, the configuration of the induction heating apparatus according to Comparative Example 1 will be described with reference to FIGS. 1 (A) and 1 (B).

  The induction heating apparatus shown in FIG. 1 includes a first coil 10 and a second coil 20 that are disposed close to each other, and a third coil 30 and a fourth coil 40 that are disposed close to each other. The first coil 10 is a coil having a pair of straight portions 12A and 12B extending along the plate width direction (preferably parallel to the plate width direction as shown in FIG. 1A). It arrange | positions facing one side S1. The second coil 20 is a coil having a pair of straight portions 22A and 22B extending along the plate width direction (preferably parallel to the plate width direction as shown in FIG. 1A). Opposing to one side S <b> 1 and close to the first coil 10. More specifically, the first coil 10 and the second coil 20 are arranged so that the inner straight portions 12B and 22A are adjacent to each other. The third coil 30 is a coil having a pair of straight portions 32A and 32B extending along the plate width direction (preferably parallel to the plate width direction), facing the other surface S2 of the steel strip, and being conveyed. In the direction T, the first coil 10 is disposed at a position (preferably the same position as the first coil 10 as shown in FIG. 1B). The fourth coil 40 is a coil having a pair of straight portions 42A and 42B extending along the plate width direction (preferably in parallel with the plate width direction), facing the other surface S2 of the steel strip, and being conveyed. A position overlapping the second coil 20 in the direction T (preferably at the same position as the second coil 20 as shown in FIG. 1B). More specifically, the third coil 30 and the fourth coil 40 are arranged such that the inner straight portions 32B and 42A are adjacent to each other.

  As shown in FIG. 1, the induction heating device has a first iron core 60 and a second iron core 70 disposed to face both surfaces S1 and S2 of the steel strip S in order to focus and amplify the magnetic flux. Is preferred. The first iron core 60 connects the first portion 62 around which the first coil 10 is wound, the second portion 64 around which the second coil 20 is wound, and the first portion 62 and the second portion 64. As shown in FIG. 1B, the cross-sectional shape perpendicular to the plate width direction has a substantially U shape. The first portion 62, the second portion 64, and the first connecting portion 66 constituting the substantially U shape are disposed so as to surround the adjacent straight portions 12B and 22A of the first coil 10 and the second coil 20. . The second iron core 70 connects the third portion 72 around which the third coil 30 is wound, the fourth portion 74 around which the fourth coil 40 is wound, and the third portion 72 and the fourth portion 74. As shown in FIG. 1B, the cross-sectional shape perpendicular to the plate width direction has a substantially U shape. The third portion 72, the fourth portion 74, and the second connecting portion 76 constituting the substantially U shape are arranged so as to surround the adjacent straight portions 32B, 42A of the third coil 30 and the fourth coil 40. . The first iron core 60 and the second iron core 70 may be made by laminating electromagnetic steel plates, or a ferrite core that is a magnetic material.

  As shown in FIG. 1A, an AC power source 50 is connected to the first coil 10 and the second coil 20, and the AC coil 50 causes the first coil 10 and the second coil 20 to be in opposite directions. Preferably, a high-frequency current having the same phase can be passed. Similarly, a separate AC power source (not shown) is also connected to the third coil 30 and the fourth coil 40, and the AC coil power source causes the third coil 30 and the fourth coil 40 to move in the opposite directions. Preferably, a high-frequency current having the same phase can be passed. An alternating magnetic field is formed by passing an alternating current through these first to fourth coils 10, 20, 30, 40, and a magnetic flux M perpendicular to the steel strip S causes the steel strip S to pass through as shown in FIG. pass. The first iron core 60 and the second iron core 70 amplify the magnetic flux M and prevent leakage to the outside. The first portion 62, the third portion 72, and the second portion facing each other with the steel strip S interposed therebetween. 64 and the fourth portion 74 form a magnetically applied region for substantial induction heating. However, the present invention is not limited to the basic apparatus configuration shown in FIGS. 1 (A) and 1 (B). As long as the first coil 10 and the second coil 20 are provided, the present invention can be used in the thickness direction of the steel strip S. A passing magnetic flux can be formed.

  As shown in FIG. 1A, the straight portions of the first to fourth coils 10, 20, 30, 40 are all arranged wider than the steel strip S, and the first iron core 60 and the second core The iron core 70 is also arranged wider than the steel strip S. Thereby, the range which applies a uniform magnetic field can be made wider than plate | board width. In addition, this induction heating apparatus can respond to various plate widths. The range of plate width that can be handled is determined by the specifications. As shown in FIG. 1A, the width Wo of each coil and the width W of each iron core are set larger than the maximum plate width Ws (for example, 1500 mm) determined by the specifications.

  From the viewpoint of surely applying a uniform magnetic field to the entire width direction of the steel strip, the coil width Wo is preferably 20% or more larger than the specified maximum plate width Ws. Further, the width W of the iron core is preferably 10% or more larger than the maximum specification plate width Ws. Further, from the viewpoint of preventing the apparatus from becoming large, the coil width Wo is preferably 50% or less larger than the specification maximum plate width Ws. The width W of the iron core is preferably 25% or less larger than the maximum specification plate width Ws.

  The first to fourth coils 10, 20, 30, 40, the first iron core 60, and the second iron core 70 are appropriately fixed with a structure. The conventional transverse induction heating apparatus has a configuration in which the coil is moved. In such a case, the current-carrying cable is bent, which may increase the electrical resistance loss or cause the cable to burn out. However, this is not the case with the induction heating apparatus shown in FIG.

  The steel strip temperature distribution in the plate width direction and the distribution of the induction current flowing through the steel strip when the steel strip S is heated by the induction heating device having the above-described configuration are shown in FIGS. 2 and 3A and 3B, respectively. The description will be given with reference. FIG. 3 (A) shows a case where a steel strip having a specified maximum sheet width Ws is heated. As shown in this figure, since the two coils 10 and 20 that flow currents in opposite directions are arranged next to each other, in the portion of the steel strip S positioned between the two coils 10 and 20, each coil The current caused by the current flows and regulates the flow of each other, and a section in which the current C1 having a linear shape and a large current density flows is formed. In this section, since the current density is uniform, the temperature change due to heating is also uniform. Therefore, as shown in FIG. 2, the steady portion Wg in the central portion of the steel strip S can be heated to a uniform temperature.

  The current C1 flowing through the steady portion Wg branches in the vertical direction in FIG. 3A at both ends EP1 and EP2 in the width direction of the steel strip, and circulates in different directions. The problem with this induction heating device is that the current C2 that has changed direction flows in the longitudinal direction along both ends of the steel strip, so that heat is generated at both ends of the steel strip in a region that is long in the transport direction. Both ends are at a high temperature. In addition, the current distribution in the vicinity of the start of direction change (slightly inside the high temperature region at both ends of the steel strip) is complex, and the temperature after heating tends to be lower than that in other parts in the width direction. As a result, as shown in FIG. 2, unsteady portions Wx having a non-uniform temperature distribution are formed on both sides of the steady portion Wg. The unsteady portions Wx are once cooled toward the edge in the width direction of the steel strip. It becomes high temperature after becoming.

  In this induction heating apparatus, since the coil width Wo and the iron core width W are both larger than the specified maximum plate width Ws, the unsteady portion Wx can be minimized with respect to the plate width. Even if it changes, the width of the unsteady part can be made constant. That is, as shown in FIG. 3 (B), for example, when heating a steel strip having a half plate width Ws, the temperature distribution shown by the two-dot chain line in FIG. Wg ′ is formed, the direction of the current C1 ′ is changed, and unsteady portions Wx ′ are formed at both ends where the current C2 ′ flows. At that time, the width of the unsteady portion Wx ′ is equal to the width of the unsteady portion Wx. Further, the distance from the steel strip edge in the low temperature portion is also constant regardless of the plate width.

  As shown in FIGS. 3 (A) and 3 (B), the currents C3 and C3 'after turning at both ends of the steel strip circulate greatly and spread over a wide area. The total amount of current in this region is the same as the currents C1 and C1 'flowing between the coils, but the current density flowing through the unit cross-sectional area is small because the flowing region is wide. Since the heat generated by the induced current is proportional to the square of the current density, it can be ignored as compared to the heat generated by the linear currents C1 and C1 ', and the temperature uniformity is hardly affected.

  In addition, with reference to FIG. 1 (A), from a viewpoint of applying a uniform magnetic field to the whole width direction of a steel strip reliably, in 1st thru | or 4th coil 10,20,30,40, a pair of straight part of The conveyance direction interval L is preferably 40% or less of the maximum plate width Ws. In order to secure a sufficient amount of magnetic flux generated by the coil, the L is preferably 5% or more of the maximum plate width Ws.

  Referring to FIG. 1A, the distance D between adjacent coils is preferably 10 mm or more from the viewpoint of preventing the coils from heating each other. The distance D is preferably 100 mm or less from the viewpoint of generating a uniform current in the steel strip and performing uniform heating.

  1B, the distance G between the coil and the steel strip is preferably 10 mm or more from the viewpoint of preventing the steel strip and the induction heating device from contacting each other due to vibration of the steel strip. The distance G is preferably set to 100 mm or less from the viewpoint of making the magnetic flux in the space sandwiched between the induction heating devices uniform.

(Edge mask)
Next, the induction heating device 100 of the present embodiment shown in FIGS. 4 (A) and (B) has the same configuration as the induction heating device shown in FIGS. 1 (A) and (B), and further, a steel strip. Edge masks 80 and 90 as a pair of magnetic flux attenuating materials arranged so as to surround both end portions EP1 and EP2. The pair of edge masks 80 and 90 are members for suppressing temperature nonuniformity at both ends (unsteady portions) of the steel strip shown in FIG. The edge masks 80 and 90 may be formed by laminating electromagnetic steel plates, like a core, or a ferrite core that is a magnetic material.

  In the present embodiment, the edge masks 80 and 90 have a width of the steel strip between the first coil 10, the second coil 20 and the first iron core 60, and the third coil 30, the fourth coil 40 and the second iron core 70. It arrange | positions so that the direction both ends EP1, EP2 may be enclosed, respectively. The edge masks 80 and 90 surround both end portions EP1 and EP2 of the steel strip with the first plate-like portions 81 and 91, the second plate-like portions 82 and 92, and the connecting portions 83 and 93. The first plate-like portions 81 and 91 are rectangular plate-like portions that face one side S1 of the steel strip and whose longitudinal direction coincides with the transport direction T. The second plate-like portions 82 and 92 are rectangular plate-like portions that face the other surface S2 of the steel strip and whose longitudinal direction coincides with the transport direction T. The connecting portions 83 and 93 connect the first plate-like portion and the second plate-like portion, are rectangular plates whose orthogonal directions are perpendicular to the first plate-like portion and the second plate-like portion, and whose longitudinal direction coincides with the transport direction T. It is a shape part. In the present embodiment, as shown in FIG. 4B, the connecting portion 83 connects the outer ends in the plate width direction of the first plate-like portion 81 and the second plate-like portion 82. However, this invention is not limited to this, You may connect the parts of the plate width direction center side rather than the said edge part. Then, the first plate portions 81 and 91 and the second plate portions 82 and 92 shield and attenuate the magnetic flux passing through both end portions EP1 and EP2 of the steel strip of the steel strip, and the high temperature portion of the unsteady portion. It works to eliminate.

  Further, the edge mask 80 is provided with a first projecting portion 84 projecting in the direction toward the steel strip S along the transport direction T at the end of the first plate-shaped portion 81 on the center side in the plate width direction. Moreover, the 2nd protrusion part 85 protruded in the direction which goes to the steel strip S along the conveyance direction T also in the edge part of the plate width direction center side of the 2nd plate-shaped part 82 is provided. Similarly, the edge mask 90 is provided with a first projecting portion 94 projecting in the direction toward the steel strip S along the transport direction T at the end of the first plate-shaped portion 91 on the center side in the plate width direction. A second projecting portion 95 projecting in the direction toward the steel strip S along the transport direction T is also provided at the end of the two plate-shaped portions 92 on the center side in the plate width direction. By disposing these protrusions 84, 85, 94, and 95 at the position of the low temperature portion of the unsteady portion, the magnetic flux at this position is strengthened, and the low temperature portion is further heated. In addition, when it has only the 1st coil 10 and the 2nd coil 20 as a basic apparatus structure, the edge masks 80 and 90 are the 1st plate-shaped parts 81 and 91 and the 1st protrusion part provided in the edge part. Only 84 and 94 need be provided.

  The mechanism for obtaining such an effect will be described in comparison with the edge masks 80B and 90B in the induction heating apparatus according to Comparative Example 2 shown in FIG. The edge masks 80B and 90B shown in FIG. 5 include the first mask portions 81 and 91, the second plate portions 82 and 92, and the connection portions 83 and 93. Although it is common with 90, it does not have a 1st protrusion part and a 2nd protrusion part.

  When the edge masks 80B and 90B are used, the temperature distribution at both ends (unsteady portions) of the steel strip is as shown in FIG. 6 (B) or FIG. 6 (C). That is, when the edge masks 80B and 90B are inserted at a sufficient depth from both ends of the steel strip so that the temperature at both edges of the steel strip is equal to the temperature at the central portion (steady portion) of the steel strip, FIG. As shown in FIG. 2, a large low temperature part is formed in the unsteady part. At this time, the magnetic flux distribution at the end of the steel strip is as shown in FIG. That is, in the space between the first plate-like portion 81 and the second plate-like portion 82, the magnetic flux density decreases, the temperature at the end of the steel strip decreases as a whole, and the steel strip edge temperature becomes equal to the central portion. However, the magnetic flux density is too low in the space near the center of the plate width in the space, and as a result, a large low temperature portion is formed. On the other hand, if the insertion amount from both ends of the steel strips of the edge masks 80B and 90B is reduced in order to eliminate this low temperature portion, the temperature drop at the low temperature portion can be suppressed as shown in FIG. Therefore, the original purpose of shielding the magnetic flux and eliminating the high temperature part cannot be sufficiently achieved, and the temperature rise in the high temperature part must be increased. As described above, in either case of FIGS. 6B and 6C, the temperature difference at both ends (unsteady portion) of the steel strip cannot be sufficiently reduced.

  On the other hand, when the edge masks 80 and 90 in the present embodiment are used, the temperature distribution at both ends of the steel strip (unsteady portion) is as shown in FIG. 6A, and the magnetic flux distribution at the end of the steel strip. Is as shown in FIG. That is, in the space sandwiched between the first plate-like portion 81 and the second plate-like portion 82, the magnetic flux density decreases, the temperature at the end of the steel strip decreases as a whole, and the steel strip edge temperature can be made equal to the central portion. it can. Moreover, in the space near the center of the plate width in the space, the magnetic flux is concentrated by the first protrusion 84 and the second protrusion 85, and the magnetic flux density is increased. Therefore, the density of the induced current is also increased at the position, and the temperature drop at the low temperature part can be suppressed. As a result, as shown in FIG. 6 (A), the temperature difference at both ends (unsteady part) of the steel strip can be made sufficiently small.

  As described above, in the present embodiment, the distance from the steel strip edge in the low temperature portion is constant regardless of the plate width. The distance is unique to the induction heating device and can be grasped in advance. Therefore, the positions of the protrusions 84, 85, 94, and 95 may correspond to the positions of the low temperature parts. That is, referring to FIG. 4A, the distance Le from the steel strip edge to the inner edge of the edge mask may be appropriately set according to the position of the low temperature portion. The position may be a half of L.

  In the present embodiment, it is preferable to include a movable device (not shown) that moves the pair of edge masks 80 and 90 back and forth in the plate width direction in order to cope with various plate widths. Further, even when a steel strip having a constant plate width is passed, the distance Le from the steel strip edge to the inner edge of the edge mask varies by about ± 5 to 10 mm due to meandering when the steel strip is passed. At that time, it is preferable that the pair of edge masks 80 and 90 is advanced and retracted in the plate width direction by the movable device so as to reduce the fluctuation of Le as much as possible. Specifically, a sensor (not shown) for detecting the positions of both edges of the steel strip is arranged, and a control unit (not shown) receives an input from the sensor and receives each first protrusion of the pair of edge masks. The part controls the movable device so as to maintain a certain distance from the steel strip edge in the plate width direction.

  Referring to FIG. 4A, the length Lm in the conveyance direction of the edge masks 80 and 90 should be at least three times the length L in the conveyance direction of the coil from the viewpoint of effectively covering a region where a large amount of magnetic flux is distributed. Is preferred. In addition, the length Lm is preferably 4 times or less than L from the viewpoint that the equipment becomes excessive and does not interfere with the incidental equipment.

  With reference to FIG. 4 (B), the width Wm of the protrusion is preferably 0.05 times or more of the length L in the conveying direction of the coil from the viewpoint of effectively collecting the magnetic flux. In addition, the length L is preferably 0.5 times or less of L from the viewpoint that the temperature rise effect does not become excessive.

  With reference to FIG. 4 (B), it is preferable that the protrusion length Hm of a protrusion part shall be 0.1 times or more of the distance G of a coil and a steel strip from a viewpoint of collecting magnetic flux effectively. Moreover, it is preferable that the said length Hm shall be 0.5 times or less of G from a viewpoint of contact prevention with a steel strip.

  With reference to FIG. 4 (B), it is preferable that the plate width direction depth Dm of the edge mask is not less than the length L in the conveying direction of the coil from the viewpoint of preventing contact with the steel strip edge. Further, from the viewpoint of securing the effect of the mask, it is preferable to set it to 2 times L or less.

(Modification of edge mask)
A modification of the edge mask 80 shown in FIG. 8A is shown in FIG. The edge mask 80C shown in FIG. 8B is the same as the edge mask 80 except that the first notch 86 is provided. The first notch 86 is a central portion in the transport direction (specifically, the first core of the first iron core in the transport direction) at the end of the first plate-shaped portion 81 and the second plate-shaped portion 82 on the center side of the plate width. And a portion corresponding to the second connecting portion 76 of the connecting portion 66 and the second iron core). Thereby, even if the fluctuation | variation of Le by the meandering of a steel strip becomes somewhat large, it can suppress that the temperature difference in an unsteady part becomes large, and can improve the stability of operation. Note that the first notch 86 has no protrusion.

  A mechanism for obtaining such an effect will be described with reference to FIGS. As shown in FIG. 9A, when the edge mask is not provided, the current is changed in direction in a narrow range of the steel strip end portion, and is overheated at the end portion. As shown in FIG. 9 (B), when the edge mask 80 is provided, the heating value distribution at the edge is made gentle by distant the position where the current changes direction from the steel strip edge, and the steel strip end is overheated. On the other hand, the region through which the linear current flows becomes narrower. Further, in the edge mask 80, the protrusion has an effect of increasing the magnetic flux density, and the induced current is not shunted to the vicinity of the edge, so that the heat generation amount distribution at the edge becomes local. Therefore, in order to make the temperature distribution constant, the edge mask must be arranged at an appropriate position for suppressing the local heat generation amount, and position control tends to be difficult. On the other hand, as shown in FIG. 9C, when the edge mask 80C provided with the first notch portion 86 is provided, the current after the direction is changed at the same time as increasing the region where the linear current flows. Has the effect of spreading the heat generation, so the calorific value distribution becomes gentle. Therefore, the necessity for precise control of the edge mask position can be reduced.

  As shown in FIG. 8B, the shape of the first notch 86 is preferably rectangular in the top view of the edge mask. And it is preferable that the notch depth (length in the plate width direction) of the first notch part 86 is Wm or more from the viewpoint of suppressing the edge mask inhibiting effect of the protruding part. Moreover, it is preferable that the said notch depth shall be 2 times or less of Wm from a viewpoint which does not impair the effect of an edge mask. Moreover, it is preferable that the width | variety (length of a conveyance direction) of the 1st notch part 86 shall be D or more from a viewpoint that the temperature rise by a protrusion part does not become excessive. Moreover, it is preferable that the said width | variety shall be 2 times or less of D from a viewpoint that the influence of the temperature rise by a protrusion part does not spread too much.

  A further modification of the edge mask 80 shown in FIG. 8A is shown in FIG. The edge mask 80D shown in FIG. 10 is the same as the edge mask 80 except that the second cutout portions 87A and 87B are provided in addition to the first cutout portion 86. The second notches 87A and 87B are provided at both ends of the first plate-like portion 81 and the second plate-like portion 82 on the center side in the sheet width direction, respectively. As a result, the current C1 shown in FIG. 3A can flow linearly to the vicinity of the edge, and the current from the current C2 to the current C3 can be widely dispersed. As a result, the temperature difference in the plate width direction of the steel strip can be further reduced.

  As shown in FIG. 10, the shape of the second notches 87A and 87B is preferably rectangular in the top view of the edge mask. And it is preferable that the notch depth (length in the plate width direction) of the second notch portions 87A and 87B is Wm or more from the viewpoint of suppressing the edge mask inhibiting effect of the protruding portion. Moreover, it is preferable that the said notch depth shall be 2 times or less of Wm from a viewpoint which does not impair the effect of an edge mask. Moreover, it is preferable that the 2nd notch part 87A, 87B starts from the outer side of both coils from a viewpoint which does not impair the heating effect of a protrusion part.

(Metallic band manufacturing method)
In the metal strip manufacturing method according to the present embodiment, in the metal strip manufacturing process, the induction heating apparatus 100 according to the present embodiment as described above is used, and the metal strip that is continuously transported in the transport direction orthogonal to the width direction is subjected to high frequency. The method includes a step of induction heating with an electric current. According to this method, the metal strip can be heated uniformly in the width direction.

  Moreover, when predetermined heating cannot be performed by one transverse induction heating apparatus of the present embodiment, a plurality of units may be arranged and heated along the conveyance direction. However, it is preferable to install them with an interval of 2L or more so that the currents C circulating around the outside of the coil do not interfere with each other.

(Metal band)
Although the case where the metal strip is a steel strip has been described in the above embodiment, the present invention is not limited to this, and a non-magnetic metal strip such as copper, austenitic stainless steel, or aluminum can also be applied.

(Method for producing alloyed hot-dip galvanized steel sheet)
The induction heating apparatus 100 according to the present embodiment can be suitably applied to alloying treatment of a hot dip galvanized steel sheet. That is, the manufacturing method of the galvannealed steel sheet according to the present embodiment includes a step of hot dip galvanizing a steel strip continuously conveyed in a direction orthogonal to the width direction, and the induction heating apparatus according to the present embodiment as described above. And 100, heat-alloying the galvanizing applied to the steel strip by induction heating the steel strip that is continuously transported in the transport direction orthogonal to the width direction by a high-frequency current. According to this method, the steel strip can be heated uniformly in the width direction, and galvanization can be made into a heat alloy.

(Comparative Example 1)
Using the induction heating apparatus shown in FIGS. 1 (A) and 1 (B), induction heating was performed while passing a SUS304 steel strip having a thickness of 1.0 mm at a passing speed of 60 mpm. The first iron core 60 and the second iron core 70 were formed by laminating electromagnetic steel sheets having a thickness of 0.3 mm. Circulation directions of currents flowing in adjacent coils are opposite to each other and have the same phase, and an alternating current is set to 1000 Hz. Various dimensions were as follows.
Maximum plate width Ws: 1500mm
Coil conveyance length L: 300mm
Iron core width W: 1800mm
Coil width Wo: 2100 mm
Distance D between adjacent coils: 50 mm
Distance G between coil and steel strip: 100 mm

  After heating a steel strip with a plate width of 1500 mm from a uniform initial temperature Ti at 26 ° C., the temperature distribution in the plate width direction was measured with a radiation thermometer. As shown by the solid line in FIG. The region where Wg = about 1200 mm inside the region where Wx = about 150 mm could be heated to a constant temperature of 145 ° C. However, in the unsteady part Wx, the temperature difference was as large as 92 ° C. In this example, induction heating was performed with an output of 1 MW.

  Next, when a steel strip having a plate width of 750 mm was heated in the same manner, as shown by the two-dot chain line in FIG. 2, the unsteady portion Wx ′ at both ends was about 150 mm, which was not different from the case of a plate width of 1500 mm. The steady portion Wg ′ was 450 mm, and this region could be heated to a constant temperature. In this example, in order to heat to the same temperature as in the case of a plate width of 1500 mm, the output of induction heating was set to 500 kW.

(Invention Example 1)
Using the induction heating apparatus shown in FIGS. 4 (A) and 4 (B), SUS304 steel strip having a plate width of 1500 mm and a plate thickness of 1.0 mm was subjected to induction heating under the same conditions as in Comparative Example 1. Various dimensions were as follows.
Distance Le from the steel strip edge to the inner edge of the edge mask: 150mm
Edge mask conveyance direction length Lm: 900 mm
Width of protrusion Wm: 60mm
Protrusion length Hm: 25mm
Edge mask depth Dm: 450mm

  After the steel strip was heated, the temperature distribution in the plate width direction was measured with a radiation thermometer. As shown in FIG. 6 (A), the steady portion was heated to 145 ° C., and in the unsteady portion, the steel strip edge temperature was While maintaining the same 145 ° C. as the steady portion, the temperature difference of the unsteady portion could be suppressed to 2 ° C.

  In addition, the structure includes a sensor that detects the positions of both edges of the steel strip described above, a movable mechanism that moves the edge mask back and forth in the plate width direction, and a control unit of the movable mechanism. Le fluctuation due to meandering was suppressed. However, when the meandering of the steel strip is steep, follow-up is delayed. At that time, in Example 1 of the present invention, the temperature difference of the unsteady part was 1.5 times when the variation of Le was ± 10 mm, compared with the case where the variation of Le was not.

(Comparative Example 2)
A SUS304 steel strip having a plate width of 1500 mm and a plate thickness of 1.0 mm under the same conditions as in Comparative Example 1 using the same induction heating apparatus as in Comparative Example 1 except that the edge masks 80B and 90B shown in FIG. 5 were provided. Induction heating was performed. The dimensions of the edge mask were the same as those shown in Example 1 of the present invention except that there were no protrusions.

  After heating the steel strip with a distance Le from the steel strip edge to the inner edge of the edge mask being 200 mm, the temperature distribution in the plate width direction was measured with a radiation thermometer. As shown in FIG. Although it was heated to 145 ° C. and the steel strip edge temperature could be 145 ° C., which was the same as that in the steady portion, the temperature drop in the low temperature portion was large and the temperature difference in the unsteady portion became 10 ° C. .

  After heating the steel strip with a distance Le from the steel strip edge to the inner edge of the edge mask of 150 mm, the temperature distribution in the plate width direction was measured with a radiation thermometer. As shown in FIG. In the unsteady part, the temperature drop in the low temperature part was suppressed to 2 ° C, but the steel strip edge temperature was 8 ° C higher than the steady part, and the temperature difference in the unsteady part was still 10 ° C. became.

  Further, in the present comparative example 2, when the fluctuation of Le becomes larger than ± 3 mm during the sudden meandering of the steel strip, the temperature difference of the unsteady portion is abruptly increased 1.5 times compared to the case where the fluctuation of Le is not present. Became bigger.

(Invention Example 2)
An SUS304 steel strip having a plate width of 1500 mm and a plate thickness of 1.0 mm was subjected to induction heating under the same conditions as Example 1 except that the edge mask 80C of the modified example shown in FIG. 8B was used. The dimensions of the first notch were 60 mm in the plate width direction and 50 mm in the conveyance direction.

  In Example 2 of the present invention, when the fluctuation of Le is ± 20 mm or less when the steel strip is suddenly meandering, the temperature difference of the unsteady part is 1.5 times or less compared to the case where there is no fluctuation of Le. The stability of the operation was further enhanced.

(Invention Example 3)
An SUS304 steel strip having a plate width of 1500 mm and a plate thickness of 1.0 mm was subjected to induction heating under the same conditions as Example 1 except that the edge mask 80D of the modification shown in FIG. 10 was used. The dimension of the first notch is the same as that of Example 2 of the present invention. The dimensions of the second notch were 60 mm in the plate width direction and 125 mm in the conveyance direction.

  In Invention Example 3, the steady portion was heated to 145 ° C., and in the unsteady portion, the temperature difference of the unsteady portion could be suppressed to 1 ° C. while keeping the steel strip edge temperature at 145 ° C., the same as the steady portion.

  According to the metal band induction heating apparatus and the metal band induction heating method of the present invention, the metal band can be uniformly heated in the width direction with a simple apparatus configuration.

DESCRIPTION OF SYMBOLS 100 Induction heating apparatus of metal strip 10 1st coil 12A, 12B Straight part 20 2nd coil 22A, 22B Straight part 30 3rd coil 32A, 32B Straight part 40 4th coil 42A, 42B Straight part 50 AC power supply 60 1st iron core 62 1st part 64 2nd part 66 1st connection part 70 2nd iron core 72 3rd part 74 4th part 76 2nd connection part 80,90 Edge mask (magnetic flux attenuation material)
81, 91 First plate-like portion 82, 92 Second plate-like portion 83, 93 Connection portion 84, 94 First protrusion 85, 95 Second protrusion 86 First notch 87A Second notch 87B Second Notch S Steel strip S1 One side of the steel strip S2 Other side of the steel strip T Transport direction of the steel strip EP1, EP2 Both ends in the width direction of the steel strip E1, E2 Both edges in the width direction of the steel strip Ws Maximum specification of the steel strip Width L Distance between the pair of straight sections in the conveyance direction (coil conveyance direction length)
W Width of iron core Wo Width of coil D Distance between adjacent coils G Distance between coil and steel strip Le Distance from steel strip edge to edge mask inner edge Lm Edge mask transport direction length Wm Protrusion width Hm Protrusion Projection length Dm Edge mask depth in the plate width direction M Magnetic flux C1 Current vector between adjacent coils C2 Current vector at the end of the steel strip width direction C3 Current vector around the coil Ti Initial temperature Wg Steady part Wx Unsteady part

Claims (9)

An induction heating device for a metal strip that induction-heats a metal strip that is continuously transported in a transport direction orthogonal to the width direction by high-frequency current,
A first coil having a straight portion extending wider than the metal band along the width direction of the metal band, and disposed at least on one side of the metal band;
It has a straight part extending wider than the metal band along the width direction of the metal band, and is disposed so as to face at least one side of the metal band and the first coil and the straight part are adjacent to each other. A second coil,
An alternating current power source for flowing high-frequency currents in opposite directions to the first coil and the second coil;
A pair of magnetic flux attenuating members disposed between the first coil and the second coil and both ends of the metal strip in the width direction;
Have
The pair of magnetic flux attenuating members includes a first plate-like portion facing one side of the metal band, and an end of the first plate-like portion on the center side in the width direction of the metal band is attached to the metal band. An induction heating device for a metal strip, characterized in that a first projecting portion projecting in a direction is provided. It has a straight part extending wider than the metal band along the width direction of the metal band, and is disposed at a position facing at least the other surface of the metal band and overlapping the first coil in the transport direction. A third coil,
It has a straight part that extends wider than the metal band along the width direction of the metal band, faces at least the other surface of the metal band, and the third coil and the straight part are adjacent to each other. A fourth coil disposed at a position overlapping the second coil in the transport direction;
An alternating current power source for flowing high-frequency currents in opposite directions to the third coil and the fourth coil;
A first portion around which the first coil is wound, a second portion around which the second coil is wound, and a first connecting portion that connects the first portion and the second portion, The first part, the second part, and the first connecting part are wider than the metal band so as to face one side of the metal band so as to surround adjacent straight parts of the first coil and the second coil. A first iron core disposed in
A third portion around which the third coil is wound, a fourth portion around which the fourth coil is wound, and a second connecting portion that connects the third portion and the fourth portion, The third part, the fourth part, and the second connecting part are opposed to the other surface of the metal band so as to surround adjacent straight parts of the third coil and the fourth coil, and more than the metal band. A second iron core arranged wide,
Further comprising
The pair of magnetic flux attenuating members further includes a second plate-like portion facing the other surface of the metal band, and a connecting portion for connecting the first plate-like portion and the second plate-like portion, The plate-shaped portion, the second plate-shaped portion, and the connecting portion surround the end portion in the width direction of the metal band, and the end portion of the second plate-shaped portion on the center side in the width direction of the metal band is The metal band induction heating device according to claim 1, wherein a second projecting portion that projects in a direction toward the metal band is provided.   The induction heating apparatus for a metal strip according to claim 2, wherein the first to fourth coils have a pair of straight portions extending wider than the metal strip along the width direction of the metal strip.   4. The metal band induction heating device according to claim 3, wherein, in the first to fourth coils, a conveyance direction interval between the pair of straight portions is 40% or less of a width of the metal band.   In the pair of magnetic flux attenuating materials, the first plate-like portion and the second plate-like portion have an end portion on the center side in the width direction of the metal strip, and the first connecting portion of the first iron core in the transport direction and The induction heating apparatus for a metal strip according to any one of claims 2 to 4, further comprising a first notch at a portion corresponding to the second connecting portion of the second iron core.   In the pair of magnetic flux attenuating materials, the ends of the first plate portion and the second plate portion on the center side in the width direction of the metal strip have second notches at both ends in the transport direction. The induction heating apparatus of the metal strip as described in any one of Claims 2-5. A sensor for detecting the positions of both edges of the metal strip;
A movable device that advances and retracts the pair of magnetic flux attenuating materials in the width direction of the metal strip;
A control unit that receives input from the sensor and controls the movable device such that each first protrusion of the pair of magnetic flux attenuating members maintains a certain distance from the edge of the metal strip in the width direction of the metal strip. When,
The metal strip induction heating device according to any one of claims 1 to 6, further comprising:   In the process of manufacturing a metal strip, using the induction heating device according to any one of claims 1 to 7, the step of induction heating the metal strip that is continuously transported in a transport direction orthogonal to the width direction by a high-frequency current. The manufacturing method of the metal strip characterized by including. A step of hot-dip galvanizing the steel strip continuously conveyed in the direction orthogonal to the width direction;
Using the induction heating device according to any one of claims 1 to 7, the steel strip that is continuously conveyed in the conveyance direction orthogonal to the width direction is induction-heated by a high-frequency current and applied to the steel strip. Galvanizing by heating alloying,
A method for producing an alloyed hot-dip galvanized steel sheet.

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