JP2005264218A - Heat treatment apparatus for thick steel plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat treatment apparatus for a thick steel plate, which prevents a spark from occurring due to an induced current formed between the steel plate and a transport roll by a magnetic leakage flux, and also corrects a shape of the steel plate. <P>SOLUTION: This heat treatment apparatus comprises: a transport line for moving the thick steel plate; an induction heating device for heat-treating the thick steel plate on the transport line by high-frequency induction heating; and a pinch roll which has a predetermined rolling force, is installed so as to face a transport roll placed in an appearance side of the induction heating device and is electrically connected with the transport roll to form a closed loop. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat treatment apparatus for a thick steel plate provided with an induction heating device that surrounds a periphery of a heated object moving on a conveying line with an induction heating coil and performs high-frequency induction heating, and relates to the heated object and the conveying roller during moving heating. It is related with the thing which is excellent in prevention of the spark which generate | occur | produces between.

  The heating device for induction heating (moving heating) of the object to be heated by the induction heating coil includes a device for partially heating the side end portion of the hot rolled steel material, and surrounding the object to be heated by the induction heating coil. There are devices that heat the entire object to be heated by high frequency induction.

In the production of thick plates, if a hot rolling mill, a cooling device, and a heat treatment device are arranged on the same line, the production capacity is remarkably increased. Therefore, a small plate that uses a high-frequency induction heating device that can be arranged on the line as a heat treatment device Manufacturing equipment has been developed and put into practical use.
Patent Document 1 relates to a heat treatment method and apparatus for a thick steel plate, which describes a production line in which a hot-rolled thick steel plate is accelerated and cooled by a cooling device provided on the exit side of the rolling mill and then heat-treated by an induction heating device. It has been shown that a solenoid type induction heating device or a transverse type induction heating device is used as the device.

  In a heating device that performs high-frequency induction heating (moving heating), a spark may occur between the heated body and the transport roller, the side edge portion of the back surface of the heated body may be damaged, and a spark mark may be generated on the surface of the transport roller. Various techniques have been proposed to prevent this.

  Patent Document 2 relates to a technique for preventing a spark generated between a metal plate and a transport roll due to an induced electromotive current when a side end portion of a metal plate such as a hot-rolled steel plate is partially induction-heated. By bringing an electrically grounded side roll into contact with the steel plate side end between the induction heating device and the transport roll. Suppresses the spread of the induced electromotive current on the transport roll and prevents sparks.

Patent Document 3 relates to a device for high-frequency induction heating by surrounding a continuously cast hot rolled steel material such as a thin slab with a solenoid induction heating coil, and a circulating current caused by an eccentric magnetic flux by winding it with a lead angle in a spiral shape It is described that a spark is generated between the steel sheet and the surface of the transport roll due to the circulating current.
JP 2003-13133 A JP-A-9-38712 Japanese Patent Laid-Open No. 11-233247

  In the method described in Patent Document 1, the thick steel plate moving on the conveying line is surrounded by an induction heating coil, and the method of high frequency induction heating is that the steel plate is not uniformly heated as in the atmosphere heating of the heat treatment furnace. It is easy to produce distortion.

  The distortion of the steel sheet causes troubles in conveyance, and further makes it difficult to uniformly heat the steel sheet when induction heating is performed, so it must be corrected on the exit side of the induction heating apparatus.

  Moreover, when heating a steel plate with an induction heating apparatus, a part of magnetic flux is also withdrawn with a steel plate, and becomes a leakage magnetic flux, as the heated steel plate is carried out of the induction heating apparatus.

  Leakage magnetic flux generates an induced current that flows in a closed circuit from the steel plate to the transport roll. When a gap is generated between the steel plate and the transport roll, sparks are generated by the induced current, and spark marks are formed at the end of the steel plate and the surface of the transport roll. Occur.

  4 and 5 are diagrams for explaining how a spark is generated between the steel sheet and the transport roll due to the induction current of the steel sheet. The induction heating device 3 is provided with a shield plate 31 for preventing magnetic flux leakage. The magnetic flux A is drawn by carrying out the steel plate 5, and an induced current loop B is formed between the steel plate 5 and the transport roll 6.

  Since the steel plate 5 often has distortion due to induction heating, a gap d occurs at the contact point C between the steel plate 5 and the transport roll 6 and spark is generated (FIG. 5).

  When the steel plate 5 is a thick steel plate, since the distortion of the steel plate due to induction heating is large, it is difficult to make the grounded side roll described in Patent Document 2 contact the end of the steel plate and eliminate the induced current. The described method is also not applicable to existing equipment.

  An object of this invention is to provide the heat processing apparatus of the thick steel plate which can prevent generation | occurrence | production of the spark by the induced current formed in the conveyance roll from the steel plate with the leakage magnetic flux, and can also correct the steel plate shape.

The problems of the present invention are solved by the following means.
1 A heat treatment apparatus for a thick steel plate, comprising a transport line for moving a thick steel plate, and an induction heating device for heat-treating the thick steel plate by high-frequency induction heating on the transport line, the transport roll on the outlet side of the induction heating device A thick steel plate heat treatment apparatus provided with a pinch roll having a predetermined rolling force opposite to each other, wherein the pinch roll and the transport roll are connected to form a closed circuit.

  According to the present invention, since the space between the pinch roll and the transport roll is a closed circuit, the induced current generated by the leakage magnetic flux during induction heating flows from the steel plate to the transport roll via the pinch roll, and between the steel plate and the transport roll. The occurrence of sparks is suppressed.

  In addition, since the distortion of the steel material after induction heating is eliminated, when a plurality of induction heating devices are arranged, uniform heating can be performed in the second and subsequent induction heating devices, and a thick steel plate with excellent characteristics can be produced with high productivity. It can be manufactured and is extremely useful industrially.

  The present invention is applied to a heat treatment apparatus for a thick steel plate provided with a conveyance line for moving the thick steel plate and an induction heating device for heat treating the thick steel plate by high-frequency induction heating on the conveyance line.

  FIG. 1 shows an example of equipment layout of a thick steel plate heat treatment apparatus to which the present invention is applied. The thick steel plate 5 hot-rolled by the rolling mill 1 is cooled to a predetermined cooling stop temperature by the cooling device 2 at a predetermined cooling rate. After that, it is heated to a predetermined temperature by the induction heating device 3, and distortion caused by heating is removed by the hot leveler 4.

  FIG. 2 is a diagram for explaining the configuration around the induction heating apparatus according to an embodiment of the present invention. 3 is an induction heating apparatus body, 31 is a shield plate for preventing leakage of magnetic flux, 6 is a transport roll, and 7 is a predetermined one. A pinch roll provided to oppose the transport roll 6, which presses down the thick steel plate 5 with a rolling force, D is a connection for electrically joining the transport roll 6 and the pinch roll 7, and electrically joins both end portions thereof. Show things.

  When there is no connection D that electrically joins the transport roll 6 and the pinch roll 7, when the leakage magnetic flux A is pulled out together with the carrying out of the thick steel plate 5, it goes from the thick steel plate 5 to the transport roll 6 and again passes through the thick steel plate 5 to pinch. An induced current loop B toward the roll 7 is formed.

  When an air gap is generated between the thick steel plate 5 and the transport roll 6 or the pinch roll 7 due to distortion generated in the thick steel plate 5 or vibration during transport, an induced current loop is cut, and a spark is generated at the corresponding location. .

FIG. 3 is a diagram for explaining the principle of the present invention. FIG. 3 shows a case where the induction heating apparatus of FIG. 2 is observed from the direction of carrying out the steel sheet. When the transport roll 6 and the pinch roll 7 are electrically joined by the connection D, The current loop B is formed on an abcd circuit (virtual electric circuit explaining a circuit composed of the transport roll 6, the pinch roll 7, and the connection D), and the induced current is generated between the transport roll 6 and the pinch. It flows in the circuit constituted by the roll 7 and the connection D, but does not flow in the thick steel plate 5. Therefore, even if a gap is formed between the thick steel plate 5 and the transport roll 6 or the pinch roll 7, no spark is generated.

  The effects of the present invention will be described with reference to examples. After being heated by the induction heating device, the front and back surfaces of the thick steel plate conveyed while being reduced with a pinch roll on the conveyance roll were observed off-line, and the occurrence of spark marks was observed. The steel plate was a welded structural steel having a plate thickness of 30 mm, a width of 3000 mm, and a length of 3000 mm.

  In the inventive example, the transport roll and the pinch roll were connected to form a closed circuit, and in Comparative Example 1, the connection was not performed. Further, as Comparative Example 2, the same observation was performed when no pinch roll was used. In addition, the presence or absence of the generation | occurrence | production of a spark trace was observed about the three thick steel plates induction-heated by changing the electric power input amount.

  Table 1 shows the observation results. In the example of the present invention, no spark trace was observed, but in Comparative Examples 1 and 2, the occurrence was observed.

The equipment arrangement | positioning figure explaining the thick board production line to which this invention is applied. The figure which shows the example of this invention. The figure explaining the principle of this invention. Conventional example. Conventional example (a diagram for explaining the cause of occurrence of sparks).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rolling machine 2 Cooling device 3 Induction heating device 31 Shield plate 4 Hot leveler 5 Thick steel plate (material to be heated)
6 Transport roll
7 Pinch roll
A Leakage magnetic flux B Inductive current loop C Contact point D Connection

Claims (1)

A heat treatment apparatus for a thick steel plate having a conveyance line for moving the thick steel plate, and an induction heating device for heat-treating the thick steel plate by high-frequency induction heating on the conveyance line, and on a conveyance roll on the outlet side of the induction heating device A heat treatment apparatus for thick steel plates provided with pinch rolls having a predetermined rolling force facing each other, wherein the pinch roll and the transport roll are connected to form a closed circuit.

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