JPH0788426A - Method of heating steel sheet by induction heating device - Google Patents

Abstract

(57) [Abstract] [Purpose] Suppression of electrolytic corrosion on bearings of cutting machines installed on the line exit side in the method of heating a steel sheet coated or coated with an insulating coating in an induction heating device having a solenoid type heating coil. , Furthermore, prevention of electric shock accidents. [Constitution] In a method of heating a steel sheet coated or coated with an insulating film in an induction heating device having a solenoid type heating coil, when the induction heating device is composed of one AC power source and a plurality of heating coils, If the polarity of the heating coil power supply is reversed and the heating coil consists of multiple coils,
Reverse the winding direction of half the coils, and reverse the polarity of the power supply.Furthermore, depending on the configuration of the power supply and the heating coil,
By combining them, the stray current in the longitudinal direction of the steel plate is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for heating a steel sheet coated or coated with an insulating coating by an induction heating device having a solenoid type heating coil.

[0002]

2. Description of the Related Art An induction heating coil is typically a solenoid type coil in the longitudinal magnetic flux system and a transverse type coil in the transverse magnetic flux type. There are problems of uneven heat generation in the direction and suction of thin plate by coil,
Generally, a solenoid coil is used for heating the thin plate.

FIG. 1 shows the structure of a solenoid type heating coil. 1A is a perspective view showing an outline of the appearance, and FIG. 1B is an enlarged sectional view taken along the longitudinal direction of the steel plate. A current Ic flowing through the coil 1 by the AC power supply 2 generates an alternating magnetic flux φ in the traveling direction of the steel plate 3. Alternating magnetic flux φ
As a result, an induced current Iw is generated in the steel plate 3 in the direction of canceling the magnetic flux. This current Iw is called an eddy current.
The steel plate 3 generates heat due to the Joule heat accompanying the eddy current Iw.

Since the induction heating device has eddy current heat generation of the steel plate as compared with the atmosphere heating furnace, it has advantages that the heating temperature can be easily set and controlled, and that the thermal efficiency is good. The application of induction heating devices has become widespread.

FIG. 2 shows an example of an induction heating apparatus for drying and baking paint in a painting facility. The steel sheet 3 is coated or painted with a coater 4 and heated with induction heating devices 1a to 1g to dry and bake the paint.
In this case, in order to secure a heat pattern for drying and baking the paint, a furnace length of about 30 to 50 m is required, and a plurality of heating coils 1a to 1g are installed between them. In the furnace, the steel sheet is passed through in a catenary state. In this case, in order to increase the heating efficiency, it is desirable to make the height of the heating coil cross section as small as possible. Therefore, if the heating coil is divided into multiple parts according to the shape of the catenary and a plurality of heating coils are provided and a power source is prepared for each heating coil, the equipment cost will be extremely high. It is common to connect a plurality of heating coils.

In the conventional induction heating device, the alternating magnetic flux ideally exists only in the longitudinal direction of the steel sheet, but actually contains a component in the width direction of the steel sheet. As a cause of this,
The heating coil does not have an ideal shape, that is, the winding of the coil is wound in a spiral shape, the magnetic flux is disturbed due to the shape of the coil feeding part, etc. The position variation of the steel plate of No. 1 is included. A stray current in the longitudinal direction of the steel sheet is generated due to the component of the alternating magnetic flux in the width direction of the steel sheet caused by these factors, but in a normal line, the steel sheet directly contacts the grounded metal rolls before and after the induction heating device. Therefore, this stray current is grounded and is not a particular problem. However, as seen in coating equipment, in equipment where the front and back surfaces of the steel sheet are coated with paint or the like, stray current generated in the longitudinal direction of the steel sheet on the outlet side of the induction heating device cannot be grounded. Therefore, at the moment the steel plate is cut by the cutting machine installed on the line output side, the blade of the cutting machine and the steel plate come into direct contact, and a stray current flows through the grounded metal roll on the input side of the induction heating device. Since the current flows through the blade holder, the current flowing in the bearing is suppressed by grounding the blade holder. However, the bearing may be electrolytically corroded during long-term use. Further, in the verification work on the outgoing side, if the worker directly touches an unpainted part of the steel sheet that is not coated with an insulating film, a stray current similarly flows, which may cause an electric shock accident. The electrolytic corrosion of the bearing of the cutting machine can be solved by insulating the entire cutting machine from the ground, but the cost for that is very high and not practical. In addition, the prevention of electric shock is left to the attention of the operator, and the fact is that there is no special means for eliminating stray current generated in the longitudinal direction of the steel sheet.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is a method for heating a steel sheet coated or coated with an insulating coating in an induction heating device having a solenoid type heating coil. In the above, it is an object of the present invention to provide a method for heating a steel plate in an induction heating device, which can suppress electrolytic corrosion of a bearing of a cutting machine installed on the line outlet side, and further can prevent an electric shock accident.

[0008]

The gist of the present invention is as follows. (1) In a method for heating a steel sheet coated or coated with an insulating film in an induction heating device having a solenoid type heating coil, A stray current generated in the longitudinal direction of the steel sheet is reduced by reducing the magnetic flux. A method for heating a steel sheet in an induction heating device; (2) One AC power source has N heating coils (N ≧
In the induction heating device composed of 2), it is possible to invert the polarity of the power source for energizing N / 2 pieces when N is an even number and (N ± 1) / 2 pieces when N is an odd number. A method of heating a steel sheet in the induction heating device according to (1) above, characterized in that (3) one heating coil is composed of n (n ≧ 2) coils, and n is an even number. Is n
/ 2, when n is an odd number, the winding directions of (n ± 1) / 2 coils are reversed, and the polarity of a power source to be energized is reversed. Method of heating steel plate in apparatus; and (4) N heating coils (N ≧) for one AC power source.
2) and one heating coil is n (n
In an induction heating device composed of coils of ≧ 2),
When N is an even number, N / 2 pieces, and when N is an odd number, (N ±
1) Reversing the polarity of the power source that energizes the two heating coils, and when n is an even number, n / 2 coils, and when n is an odd number, (n ± 1) / 2 coil winding directions. And reversing the polarity of the power supply to be energized.

[0009]

The operation and embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a configuration diagram showing a conventional method, and FIG. 4 is a configuration diagram showing an example of two heating coils / power source in the method (2) of the present invention. The stray current in the longitudinal direction of the steel sheet is generated by the component of the alternating magnetic field in the steel sheet width direction. In the conventional method shown in FIG. 3, since the magnetic fluxes φ generated by the two heating coils are in the same direction, the currents induced in the steel sheet by these magnetic fluxes φ are in the same direction. The stray currents generated are in the same direction. That is, a stray current flows in the longitudinal direction of the steel sheet. However, in the method of the present invention shown in FIG. 4, since the polarity of the power supply supplied to one of the two heating coils is reversed, the magnetic flux φ generated by the two heating coils is in the opposite direction. The component of the alternating magnetic field in the steel plate width direction that is generated by the spiral winding is canceled out, and the stray current in the steel plate longitudinal direction is reduced.

FIG. 5 shows the method 2 of the method (3) of the present invention.
It is a block diagram of a coil / heating coil. Reversing the winding of each coil, and by reversing the polarity of the power supply, cancels only the component in the steel plate width direction without affecting the component in the steel plate longitudinal direction of the alternating magnetic field generated in the heating coil, Reduces stray current in the steel sheet longitudinal direction. Since the winding of each coil is in the opposite direction, the deviation of the magnetic flux induced in the steel sheet by each coil in the lateral direction (width direction of the steel sheet) becomes the opposite direction, and the transverse component is canceled out, so stray in the longitudinal direction of the steel sheet. The current is reduced. Since the polarity of the power supply is reversed, the magnetic flux induced in the steel sheet by each coil is in the same direction (the same polarity), so the components of the alternating magnetic field in the steel sheet longitudinal direction do not cancel each other out, so heating efficiency is improved. high.

FIG. 6 is a block diagram of (2 coils / heating coil) × 2 in the method (4) of the present invention. In this example, the heating coils 1a and 1b each have the configuration shown in FIG. 5, and the space between the heating coils 1a and 1b has the configuration shown in FIG.
Inside each of a and 1b, the stray current in the longitudinal direction of the steel plate is reduced, and in addition, the stray current in the longitudinal direction of the steel plate is also reduced between the heating coils 1a and 1b.

[0013]

EXAMPLE In a coating facility having an induction heating device consisting of four sets of two heating coils / power sources, each set of two heating coils / power sources was processed by the conventional method (FIG. 3) and the method (2) of the present invention (FIG. 4). As a result of measuring the electric potential of the steel plate near the cutting machine and the bearing portion of the cutting machine at the time of energization at 500 KW which is the maximum power of each power source, the conventional method shows that the steel plate has 30 V or more and the bearing portion has Although a potential of 1.5 V or more was generated, the steel plate potential can be reduced to about 9 V and the bearing portion potential to about 0.1 V by the method of the present invention. Within the allowable contact voltage of
Furthermore, it became possible to reduce the bearing of the cutting machine to a potential that is not affected by electrolytic corrosion. The embodiment described above is an example of an induction heating device that is composed of a plurality of heating coils for one power source in a coating facility, but an induction heating device is used in a facility for coating or coating an insulating film on a steel plate. Is composed of one AC power supply and a plurality of heating coils, the polarity of the power supply of half the heating coils is reversed, and when the heating coil is composed of a plurality of coils, the winding direction of the half of the coils is reversed, and The present invention can be similarly applied by reversing the polarity of the power supply and combining them depending on the configurations of the power supply and the heating coil.

[0014]

As described above, according to the present invention,
When the induction heating device was energized, it was possible to suppress electrolytic corrosion of the bearings of the cutting machine installed on the line outlet side, and to prevent electric shock accidents, and great results were obtained.

[Brief description of drawings]

1A and 1B are drawings showing a heating mode of a steel sheet using a solenoid type heating coil, in which FIG. 1A is a perspective view showing an outline of appearance, and FIG. 1B is an enlarged sectional view taken along line AA of FIG.

FIG. 2 is a side view showing a heating coil array of an induction heating device for drying and baking paint in a painting facility.

FIG. 3 is a block diagram showing the configuration of a conventional induction heating device of two heating coils / power source, in which a steel plate 3 shows a cross section.

FIG. 4 is a block diagram showing a configuration of an induction heating device of two heating coils / power source used in the present invention, and a steel plate 3 shows a cross section.

FIG. 5 is a block diagram showing a configuration of an induction heating device of two heating coils / power source used in the present invention, in which a steel plate 3 shows a cross section.

FIG. 6 is a block diagram showing a configuration of a two heating coil / power source and a two coil / heating coil induction heating device used in the present invention, and a steel plate 3 shows a cross section.

[Explanation of symbols]

1,1a-1g: Induction heating coil 2,2a-2d:
AC power supply 3: Steel plate 4: Coater equipment 5: Cooling equipment

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[Procedure amendment]

[Submission date] October 22, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

FIG. 3 is a block diagram showing a configuration of a conventional induction heating device having two heating coils / power source .

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

FIG. 4 is a block diagram showing the configuration of a two heating coil / power source induction heating device used in the present invention .

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

FIG. 5 is a block diagram showing a configuration of a two-coil / heating-coil induction heating device used in the present invention.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

[6] used in the present invention, showing the configuration of the induction heating apparatus of the second heating coil / power supply and second coil / heating coil Bro
FIG .

[Procedure Amendment 5]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Saito 1 Kimitsu, Kimitsu-shi Kimitsu Works, Nippon Steel Corporation

Claims (4)

[Claims] 1. A method for heating a steel sheet coated or coated with an insulating coating by an induction heating device having a solenoid type heating coil, wherein stray current generated in the steel sheet longitudinal direction is reduced by reducing magnetic flux in the steel sheet width direction. A method for heating a steel sheet by an induction heating device, which is characterized by reducing the amount. 2. The heating coil is N for one AC power source.
In a method of heating a steel sheet coated or coated with an insulating film by an induction heating device composed of N pieces of ≧ 2, N / 2 pieces when N is an even number, and (N ± 1) / when N is an odd number.
The method for heating a steel sheet by an induction heating device according to claim 1, wherein the polarities of the power supplies for energizing the two heating coils are reversed. 3. A method for heating a steel sheet coated or coated with an insulating coating by an induction heating device, wherein one heating coil is composed of n coils with n ≧ 2, and n / 2 is an even number when n is an even number. 2. The steel sheet according to claim 1, wherein the winding directions of (n ± 1) / 2 coils are reversed and the polarity of a power source to be energized is reversed when n is an odd number. Heating method. 4. The heating coil is N for one AC power source.
≧ 2, and one heating coil is n
In a method of heating a steel sheet coated or coated with an insulating coating by an induction heating device composed of n coils of ≧ 2, N / 2 is obtained when N is an even number, and (N ± 1 when N is an odd number). ) / 2 reverse the polarity of the power supply that energizes the heating coils, and when n is an even number, n / 2 coils, and when n is an odd number, the winding direction of (n ± 1) / 2 coils is changed. The method for heating a steel sheet by the induction heating device according to claim 1, wherein the polarities of a power source for energization are reversed.