JPH0938712A - Method for induction-heating metallic plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an induced current from being transmitted to a carrying roll and to prevent the occurrence of spark by bringing a side roll electrically grounded into contact with the side end of a metallic plate between an induction heating coil and a carrying roll. SOLUTION: The metallic plate 3 is placed on carrying rolls 2a, 2b and carried and the induction heating coils 4 for heating the side end parts of the metallic plate are arranged at two positions. The side rolls 1a, 1b grounded with lead wire 12 are brought into contact with the side end parts of the metallic plate 3 between the induction heating coils 4 and the carrying rolls 2a or 2b, respectively. Therefore, the current intended to flow from the metallic plate 3 to the carrying rolls 2a, 2b is allowed to flow to the grounded side rolls 1a, 1b and the the induced current can be prevented from being transmitted to the carrying rolls 2a, 2b for metallic plate and the generation of the induced current loop causing the occurrence of spark can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to suppress a spark generated between a metal plate and a transfer roll when a side end portion of the metal plate such as a hot rolled steel plate is conveyed while being partially heated. The present invention relates to a possible induction heating method.

[0002]

2. Description of the Related Art High-pressure water is sprayed on the surface of a hot-rolled steel sheet after rough rolling for descaling, but at this time, the side edges of the steel sheet tend to be overcooled compared to the central portion. For this reason, a difference occurs in the deformation resistance in the width direction of the steel sheet, which hinders subsequent finish rolling or hot straightening. As a countermeasure, there is a method in which the end portion on the metal plate side is rapidly heated by induction heating during hot rolling to make the temperature distribution in the width direction of the steel sheet uniform.

Further, in a thick steel plate used as a building material such as a long material for shipbuilding or a bridge or a steel frame, the end portion on the steel plate side is similarly supercooled by water cooling or accelerated cooling during controlled rolling. Therefore, there is a problem that not only the finish rolling is hindered, but also the residual stress of the product is generated, and the stripping camber (lateral bending) of the stripping and cutting material of the thick steel plate becomes large. As a countermeasure against this, Japanese Patent Laid-Open No. 4-662
No. 71 discloses that the supercooled region of the steel sheet side end portion is reheated by induction heating immediately before hot leveling after water cooling and / or during hot leveling, and the temperature difference between the central portion and the side end portion of the steel sheet is, for example, A method of making the temperature uniform in the plate width direction so as to be within 50 ° C is disclosed.

FIG. 4 is a diagram showing a schematic configuration of an apparatus for inductively heating the end portion on the metal plate side. When heating the side end of the metal plate 3 in the hot rolling line, the induction heating coil 4 capable of rapid heating is used, and the metal plate side end is heated between the induction heating coils 4. It However, in order to convey the hot-rolled steel plate or the thick steel plate, a metal-made conveyance roll such as steel is used from the viewpoint of strength and durability.
Induced electromotive current is secondarily generated between the metal plate and the transport roll due to the induction heating of the side end portion by.

FIG. 5 is a diagram showing the state of generation of induced electromotive current due to induction heating. As shown in the drawing, when the side end of the metal plate 3 is induction-heated, most of the magnetic flux generated from the induction heating coil 4 concentrates on the side end of the metal plate 3 with the induction heating coil 4 at the center. , Partly spreads to the periphery and generates an induced electromotive current 5.

FIG. 6 is a diagram for explaining the induced electromotive current loop. As shown in FIG. 5, if the induced electromotive force 5 spreads over the metal plate transport roll 2, a part of the induced electromotive current 5 is generated between the metal plate and the metal plate transport roll 6 and the induced electromotive current loop 6 shown in FIG. make. Therefore, when the metal plate comes into contact with the roll intermittently or momentarily at the end of the metal plate during transportation of the metal plate, a spark is generated between the metal plate and the roll.

FIG. 7 shows a plate width 25 explained in the embodiment described later.
It is a diagram showing the situation of the spark traces generated on the back surface of the hot rolled steel sheet of 00 mm, but the side edge of the steel sheet, for example, from the steel sheet end surface
Continuous spark marks are generated on the 100 mm part. When such spark marks are generated, the value of the product is remarkably reduced. Therefore, suppressing the spark generation is an indispensable condition for induction heating the side edges of a metal plate such as a hot rolled steel plate.

As means for suppressing the generation of sparks, Japanese Utility Model Laid-Open No. 4-134203 discloses a side end heating device for rolled material provided with a carrier roll having an insulating layer such as ceramics sprayed on the surface thereof, and both sides of the rolled steel sheet. There is disclosed a side end heating device for a rolled material and the like, which is provided with a stepped conveying roll having a small diameter at a portion through which the end passes.

FIG. 8 is a sectional view of a roll whose surface is sprayed with an insulative ceramic. This insulating roll 2 suppresses the generation of sparks by providing the insulating layer 9 on the roll surface by thermal spraying.

FIG. 9 is a sectional view of a stepped roll. The stepped conveying roll 2 is provided with a step portion 10 with both ends of the roll having a smaller diameter than the central portion, and is supported only by the steel plate supporting portion 11 of the roll, and the steel plate side end portion where the induced electromotive current flows and the steel plate conveying roll 2
Avoid contact with.

Although the above-mentioned side end heating devices proposed so far have a desired effect in suppressing the occurrence of sparks, when they are arranged in a rolling line, they have the following operational problems. There is.

1) The roll having a ceramic insulating layer on the surface shown in FIG. 8 has a short insulating layer life. The shape of the hot-rolled steel sheet changes depending on the rolling conditions, and the shape of the tip of the steel sheet is particularly susceptible to the influence. Therefore, the tip portion warps downward depending on the rolling conditions. In this case, since the front end portion of the steel sheet collides with the steel sheet conveying rolls one after another during the conveyance, the insulating layer formed by the ceramic spraying on the roll surface is easily broken by the impact, and the life of the insulating layer of the conveying roll is extremely shortened.

2) The stepped transport roll shown in FIG. 9 has a problem when the heating region is limited to a narrow range of the side end of the steel sheet, that is, when the induced electromotive current flows only to the side end. Not, but if you need to increase the heating area,
That is, when the range of the induced electromotive force extends to the vicinity of the central portion of the plate width, the width of the steel plate supporting portion 11 shown in the figure is limited, and the conveyance of the steel plate becomes unstable.

[0014]

DISCLOSURE OF THE INVENTION The present invention is not limited to the above-mentioned insulating layer spraying roll or stepping roll for partial induction heating of a metal plate side end portion of a hot-rolled steel plate or the like, An object of the present invention is to provide an induction heating method capable of suppressing the occurrence of sparks between a metal plate and a metal plate transport roll by using a metal transport roll.

[0015]

[Means for Solving the Problems] The inventors of the present invention have diligently conducted experiments on a method for suppressing the generation of sparks between a metal plate and a metal plate transport roll when performing induction heating of a metal side end during transport of the metal plate. Study was carried out. As a result, the steel plate side end portion between the induction heating device and the transport roll can be prevented from spreading the induced electromotive current onto the transport roll by contacting the electrically grounded side roll with each other. I came to know that to prevent the occurrence.

[0016] The gist of the present invention is that "when the metal plate is placed on a transport roll and is transported while the end of the metal plate is induction heated, the end of the metal plate between the induction heating coil and the transport roll is grounded. The method of induction heating is characterized in that the rolls are brought into contact with each other to suppress sparks generated between the metal plate and the transport rolls. "

As described above, the cause of the sparks during the induction heating of the metal plate is that the induced electromotive current spreads to the metal plate on the metal plate transport roll, and the induction shown in FIG. 6 between the metal plate and the transport roll. This is because the electromotive current loop 6 is generated. The present invention prevents the occurrence of sparks by preventing the occurrence of the induced electromotive current loop 6.

By bringing a grounded side roll into contact with the side end of the metal plate between the induction heating coil and the transport roll, the current flowing from the metal plate to the transport roll flows to the grounded side roll. Therefore, it is possible to suppress the spread of the induced electromotive current onto the metal plate transport roll, and it is possible to prevent the occurrence of the induced electromotive current loop that causes the spark generation. Therefore, the position where the side roll contacts the metal plate needs to be between the induction heating coil and the transport roll. Further, in order to secure a wide heating area by the induced electromotive current, it is preferable to locate the position as close to the transport roll as possible.

As the material to be heated, steel plate, aluminum,
Any metal plate such as stainless steel that can be induction-heated may be used without particular limitation.

Usually, when a metal plate is heated using an induction heating device, its heating capacity is affected by the position of the induction heating coil in the plate width direction. Therefore, when a camber (horizontal bending) occurs in the metal plate or when the metal plate meanders or skews during transportation, it may not be possible to uniformly heat the metal plate in the longitudinal direction. However, in the spark suppressing method of the present invention, since the side rolls also function as the centering guides for the metal plate, the position of the induction heating coil in the plate width direction can be made constant over the entire length of the plate, and uniform heating can be performed in the plate longitudinal direction. Can be done.

[0021]

FIG. 1 is a diagram showing an embodiment of the method of the present invention in which induction heating is performed using a grounding roll. The metal plate 3 is placed and transported on the transport rolls 2a and 2b, and the induction heating coil 4 for heating the end portion on the metal plate side.
Are provided in two places. A side roll 1a grounded by a lead wire 12 at the side end of the metal plate 3 between the induction heating coil 4 and the transport roll 2a or 2b,
Contact 1b. This side roll is rotatable and rotates with the movement of the metal plate. In the example shown in the figure, four side rolls are provided at four positions between the induction coil and the transport roll, but for example, the induction heating coil 4 and the transport roll 2b are spaced apart from each other so that the induced electromotive current is increased. Side roll 1 if you don't worry about spreading to the top
b is omitted and only 1a is required.

FIG. 3 is a view showing another embodiment of the method of the present invention using eight side rolls 1c. Induced electromotive current 5
A side roll 1c may be additionally installed as shown in FIG.

The induction heating coil may be of any type. For heating the steel plate, a coil having a front surface and a back surface of a metal plate as shown in FIG. 4 is usually used.

The material of the side roll 1 may be an alloy excellent in corrosion resistance, heat resistance and wear resistance, for example, high chrome steel, stainless steel, etc., since it constantly contacts with a hot rolled material at a high temperature in a hot rolling line. .

[0025]

EXAMPLES The effects of the present invention will be described based on examples.

As shown in FIG. 1, side rolls are installed at four positions between the induction heating coil and the transfer roll, and the steel plate after heating is examined in order to check the state of spark generation between the steel plate and the transfer roll during induction heating. The surface was observed. In addition, for comparison, induction heating was performed with the apparatus of FIG. 1 without contacting the side rolls with the steel sheet.

The side rolls were made of stainless steel and had a roll outer diameter of 100 mm and a roll barrel length of 100 mm.

FIG. 2 is an enlarged view of the portion A of FIG. 1 and is a plan view showing the installation position of the side rolls with respect to the transport rolls. The metal plate 3 is placed on the transport roll 2, the induction heating coil 4 is provided so as to face the upper and lower surfaces of the metal plate, and the side roll 1 is in contact with the side surface of the metal plate 3. . In this embodiment, between the side roll 1 and the transport roll 2
It was set to 50 mm.

As the material to be heated, a plate thickness of 30 mm, a plate width of 2500 mm,
A carbon steel strip with a plate length of 10000 mm was used. The transport conditions are a transport speed of 50 m / min and a distance between transport rolls of 1000 mm. The central temperature of the heated material before induction heating was about 500 ° C, and the temperature of the end of the heated material during conveyance was increased by 100 ° C by induction heating.

The electric power input to the induction heating was 4000 kW.

Induction heating of the steel sheet side end portion was carried out under the above-mentioned conditions, and the state of spark generation was compared between the case of using the spark suppression method using the side rolls of the present invention and the case of not using the side rolls.

Further, in order to examine the temperature rising condition of the steel sheet due to induction heating, the temperature of the steel sheet surface was measured by a thermometer provided 50 cm downstream from the induction heating coil.

The results were as follows:

(Invention method) Use of four side rolls: No spark marks at all (Comparison method) No side rolls: Spark marks having a diameter of about 2 mm and a depth of about 0.5 mm Countless generation (Fig. 7) As described above, when the side roll is not used in the usual induction heating method, the spark generation near the side edge of the steel plate can be visually confirmed, and as shown in Fig. 7, the countless sparks are generated. There were marks. On the other hand, in the case of the spark suppression method using the side rolls of the present invention, no spark generation was observed.

FIG. 10 is a diagram showing the results of measuring the temperature at one end of the steel plate over the entire length of 10 m.

In the case of the method of the present invention using the side rolls, it can be seen that the temperature rise amount is substantially uniform over the entire plate length. On the other hand, in the case of the comparative example in which the side roll was not used, the temperature rise amount was not stable in the plate longitudinal direction. It was found that the steel sheet being conveyed was skewed.

[0037]

According to the spark suppression method of the present invention, it is possible to suppress the generation of sparks between the metal plate and the metal plate transport roll during induction heating, and to perform stable and uniform heating in the plate longitudinal direction. It is possible to manufacture high quality products.

[Brief description of drawings]

FIG. 1 is a diagram showing a spark suppressing method of the present invention using four ground rolls.

FIG. 2 is a diagram showing an installation position of a side roll of the embodiment of the present invention.

FIG. 3 is a diagram showing a spark suppression method of the present invention using eight ground rolls.

FIG. 4 is a diagram showing a schematic configuration of an induction heating device for a steel plate side end portion.

FIG. 5 is a diagram showing a state of occurrence of an induced electromotive current due to induction heating.

FIG. 6 is a diagram illustrating an induced electromotive current loop.

FIG. 7 is a view showing a situation of spark marks generated on the back surface of a steel plate.

FIG. 8 is a longitudinal cross-sectional view in the axial direction of a conventional steel plate transport roll having an insulating layer on the surface.

FIG. 9 is a longitudinal sectional view in the axial direction of a conventional stepped steel plate transport roll.

FIG. 10 is a diagram showing a temperature rise distribution in the steel sheet longitudinal direction in the example.

[Explanation of symbols]

1a, 1b, 1c Side roll 6 Induced electromotive current loop 2a, 2b Metal plate transport roll 9 Insulating layer 3 Metal plate 10 Step 4 Induction heating coil 11 Steel plate support 5 Induced electromotive force

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication H05B 6/10 381 H05B 6/10 381

Claims (1)

[Claims] 1. A method of performing induction heating of an end portion of a metal plate side while a metal plate is placed on a conveyance roll and conveyed, in which a metal plate side end between an induction heating coil and a conveyance roll is brought into contact with a grounded roll. , An induction heating method characterized by suppressing sparks generated between a metal plate and a transport roll.