JP2000150128A - Induction heating device for metal plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress sparks without using a complicated device by insulatingly supporting conveying rollers provided in the neighborhood of induction heating coils and grounding them via resistors. SOLUTION: While a metal plate 10 is conveyed on conveying rollers 12a, 12b, 12c, its side end parts are induction-heated by induction heating coils 11. When part of current induced in the metal plate 10 flows through the conveying rollers 12a, the induced current flowing there is small because the conveying rollers 12a are insulation supported and there is hardly any possibility that sparks occur. Because the conveying rollers 12b are electrically grounded via resistors 13, when the current induced in the metal plate 10 flows through the conveying rollers 12b and the resistors 13, the current flowing from the metal plate 10 to the conveying rollers 12b is suppressed and therefore there is hardly any possibility that sparks occur. Because the conveying rollers 12c are grounded, voltage induced there is small and there is hardly any possibility that sparks occur.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating apparatus for inductively heating a metal sheet such as a hot-rolled steel sheet being conveyed, and more particularly to suppressing sparks generated between the metal sheet and a conveying roller.

[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. At this time, the side edges of the steel sheet are supercooled as compared with the central part. Further, in the case of a thick steel plate, the side end of the steel plate is similarly supercooled by water cooling or accelerated cooling during controlled rolling.

[0003] In order to overcool the side end of such a steel plate, a method of induction heating the side end of the metal plate being conveyed by an induction coil has been adopted. However, since the metal transport roller is used to transport the metal plate, an induced electromotive current is generated in the metal plate with the induction heating of the side end by the induction heating coil. A part of the induced electromotive current flows as a ground current via a transport roller (ground roller). Therefore, when the metal plate and the transport roller are separated, a spark is generated between the metal plate and the transport roller. When this spark is generated, a spark mark is generated on the metal plate, and the product value is significantly reduced. As a technique for suppressing the generation of the spark, for example, there is an induction heating device disclosed in Japanese Patent Application Laid-Open No. 9-38712.

FIG. 4 is a diagram showing a configuration of an induction heating apparatus disclosed in Japanese Patent Application Laid-Open No. 9-38712. In this induction heating device, the metal plate 3 is transported by the transport rollers 2a,
2b, two induction heating coils 4 for heating the metal plate side end are provided.
Side rollers 1a and 1b grounded by a lead wire 12 are installed at the side ends of the metal plate 3 between the induction heating coil 4 and the transport rollers 2a or 2b.

In the induction heating apparatus shown in FIG. 4, the side plates 1a and 1b, which are grounded, are brought into contact with the side ends of the metal plate between the induction heating coil 4 and the conveying rollers 2a and 2b, so that the metal plate 3 The current that is about to flow to the transport rollers 2a, 2b from the side rollers 1a,
1b, the induced electromotive current is suppressed from spreading to the portion of the metal plate 3 above the transport rollers 2a, 2b, and the earth current flowing through the transport rollers 2a, 2b is reduced. .

[0006]

FIG. 5 is a characteristic diagram showing an example of the spread of the induced electromotive current with respect to the position of the induction coil in FIG. As is clear from the characteristics of FIG. 5, when the metal plate is induction-heated by the induction heating coil, the distribution of the induced electromotive current is highest near the induction coil and becomes smaller as the distance increases.

In the induction heating apparatus of FIG. 4, as described above, a side roller (earth roller) is provided between the induction heating coil and the nearest conveying roller, and the induced electromotive current is grounded from the side roller (earth roller). For this reason, grounding occurs in the region where the induced electromotive current is maximum, and there is a high possibility of spark generation on the side end surface of the metal plate. In particular, after detecting the front end of the metal plate, the metal side roller (earth roller) is brought close to the side end surface of the metal plate and pressed, and the rear end of the metal plate is detected and retracted. Sparks are inevitable when the rollers approach or retreat,
The quality of the product surface quality may be significantly deteriorated.
Further, as described above, since it is necessary to detect the leading and trailing end of the product and move the ground roller, it is necessary to detect the leading and trailing end of the product and to accurately operate the product. Further, since the apparatus is installed in a high temperature part, it is difficult to secure reliability.

The present invention has been made in order to solve the above-described problems, and provides an induction heating apparatus capable of suppressing generation of sparks without using the above-described complicated mechanism. The purpose is to do.

[0009]

An induction heating apparatus for a metal plate according to the present invention is an apparatus for induction heating an end of a metal plate by an induction heating coil while placing and transporting the metal plate on a transport roller. In addition, a transfer roller provided around the induction heating coil is insulated and supported, and then grounded via a resistor.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. FIG. 1 is a conceptual diagram of a metal plate induction heating apparatus according to one embodiment of the present invention. In this induction heating device, the induction heating coils 11 are provided on both side ends of the metal plate 10 so as to face up and down, and are arranged so as to perform induction heating on both side ends of the metal plate 10 from both directions. ing. The transport rollers 12a and 12b around the induction coil 11 are insulated and supported below the bearing.
Among them, the transport roller 12b at a position distant from the induction coil 11 is electrically grounded via the resistor 13. The transport roller 12c disposed outside (the entrance side and the exit side) of the transport roller 12b is not insulated.

FIG. 2 is a side view showing a specific configuration of the transport roller 12b. In FIG.
1 (corresponding to the transport roller 12b in FIG. 1) are supported at both ends by bearings 23 in a bearing box 22, and one end of the transport roller 21 is connected to a rotating shaft of a motor 25 via an insulating coupling 24. Have been. The bearing box 22 is fixed by bearing fixing bolts 26, at which time the insulator 2
7, and is fixed to the transport roller base 30 in an electrically insulated state. A current collector 28 is attached to the other end of the transport roller 21 and a resistor 29
One end of (corresponding to the resistor 13 in FIG. 1) is electrically connected to the current collector 28, and the other end of the resistor 29 is grounded. Thus, the transport roller 21 (12b) is insulated and supported,
In addition, it is electrically grounded via the resistor 29 (13).

In the induction heating apparatus configured as described above, the metal plate 10 is transported by the transport rollers 12a, 12b, 12
c while being conveyed over the induction heating coil 1
1 is induction heated. At the time of the induction heating, an induced electromotive current flows through the metal plate 10, and the operation of the transport rollers 12a, 12b, and 12c at that time will be described below.

(A) Conveying Roller 12a When the lower surface of the metal plate 10 is in contact with the conveying roller 12a, a part of the induced electromotive current of the metal plate 10 flows to the conveying roller 12a. For this reason, when the lower surface of the metal plate 10 is separated from the transport roller 12a (when the metal plate is lifted up), a spark may be generated. Since the induced electromotive current is small, there is practically no possibility of spark generation.

(B) Transport Roller 12b The transport roller 12b is electrically grounded via a resistor 13. Therefore, the induced electromotive current of the metal plate 10 flows from the end of the metal plate 10 to the vertical roller 12b and the resistor 13, and when the metal plate 10 is separated from the metal plate 10, a spark may be generated. Roller 12b
Is arranged at a position relatively separated from the induction heating coil 11, and as is clear from the characteristic diagram of FIG. 5, its induced voltage is relatively small, and is grounded via the resistor 13. Therefore, the metal plate 10 and the transport roller 12b
The current flowing between them is suppressed, and there is practically no possibility of sparks. Even if a spark is generated, the current is small and the spark mark is also small.

(C) Conveying roller 12c This conveying roller 12c is grounded. For this reason,
The induced electromotive current of the metal plate 10 flows from the lower surface of the metal plate 10 to the transport roller 12c, and when the lower surface of the metal plate 10 is separated from the transport roller 12c,
Although a spark may occur, the transport rollers 12
c is arranged at a position sufficiently distant from the induction heating coil 11 and, as is clear from the characteristic diagram of FIG. 5, its induced voltage is small, and the current flowing through the transport roller 12c is extremely small. Since the transport roller 12b is grounded via the resistor 13, the induced electromotive current generated in the vicinity of the induction coil 11 does not flow into the transport roller 12c.
The current flowing through c becomes extremely small. Therefore, there is practically no possibility that a spark will occur.

In the embodiment of FIG. 1, as described above, the occurrence of spark marks can be suppressed or reduced, but the following effects are also obtained. In the present embodiment, the equipment arrangement is easy. That is, as in the related art (FIG. 4), the space between the nearest transport rollers provided with the induction heating coil is limited by the provision of the induction heating coil. In addition, since the earthing device has a moving mechanism (cylinder) for moving the vertical roller in a direction orthogonal to the transport direction, it is difficult to arrange the equipment from this point as well. However, in this embodiment, since only the transport roller 12b grounded via the resistor 13 is provided, the facility arrangement is easy. In the present embodiment, the heating efficiency is not hindered. That is, when a grounding device is provided near the induction heating coil as in the related art (FIG. 4), a large induced electromotive current flows through the side roller, and the heating efficiency of the metal plate is reduced. However, since such a configuration is not employed in the present embodiment, such adverse effects can be avoided.

Embodiment 2 FIG. In the above-described embodiment, an example in which a fixed resistor is used as the resistor 13 has been described. However, the value may be adjusted after installation using a variable resistor. In addition, the number, interval, and arrangement of the transport rollers 12a and 12b and the value of the resistor 13 are determined so that no spark is generated between the transport rollers 12b and 12c and the metal plate 10. The transport roller 12a may not be provided if unnecessary. The distribution and size of the current flowing through the metal plate vary depending on the scale, number, installation, power supply frequency and phase difference of the induction heating coils.
It is necessary to determine the number, spacing and arrangement of the resistors and the value of the resistor 13. In addition, as shown in FIG. 5, since the distribution of the magnitude of the current may occur even in the line, the value of the resistor 13 may be different depending on the distribution. In addition, the transport roller 12a needs to be arranged at the place where the current is the largest for the same reason, and need not always be arranged immediately near the induction heating coil 11.

[0018]

FIG. 3 is a conceptual diagram of an induction heating apparatus according to an embodiment of the present invention. Conveying roller 1 around induction heating coil 11
For 2a and 12b, the number of the transport rollers 12a is three, and the number of the transport rollers 12b is seven on each of the entrance side and the exit side. The pitch between these transport rollers 12a and 12b was 800 to 1100 mm. Metal plate 10
Is a carbon steel strip having a thickness of 30 mm, a width of 1200 mm, and a length of 50 m, and the electric power supplied to the induction heating coil 11 is 1000 K
W. The resistance value of the resistor 13 is
2b and the resistance value between the roller base 10 (see FIG. 2) is 5
Adjusted to be Ω.

When induction heating is performed under the above conditions, sparks do not occur and there is no problem with the surface properties of the product. On the other hand, when no countermeasures were taken (under similar conditions), sparks were generated, and countless sparks having a diameter of about 2 mm were generated on the product surface.

[0020]

As described above, according to the present invention, the transfer roller provided around the induction heating coil is insulated and supported, and then grounded via the resistor. It is possible to prevent sparks generated between the metal plate and the transport roller without using a metal plate, and to manufacture a metal plate having excellent product surface properties.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an induction heating apparatus for a metal plate according to an embodiment of the present invention.

FIG. 2 is a side view showing a specific configuration of a transport roller 12b of FIG.

FIG. 3 is a conceptual diagram of an induction heating device according to an embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of an induction heating device disclosed in Japanese Patent Application Laid-Open No. 9-38712.

FIG. 5 is a characteristic diagram showing an example of the spread of induced electromotive current with respect to the position of the induction coil in FIG. 4;

[Explanation of symbols]

 11 Induction heating coil 12a, 12b, 12c Transport roller 13 Resistance

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Sei Nakano 1-2-1 Marunouchi, Chiyoda-ku, Tokyo F-term in Nihon Kokan Co., Ltd. (Reference) 3K059 AA08 AB19 AB26 AB28 AC54 AC62 AD07 AD27 AD28 AD34 CD47 CD75

Claims (1)

[Claims] 1. An apparatus for inductively heating an end of a metal plate by an induction heating coil while placing and transporting the metal plate on a transport roller, wherein a transport roller provided around the induction heating coil is insulated and supported. An induction heating apparatus for a metal plate, which is grounded via a resistor after the heating.