JPH07316670A - Electric heating device - Google Patents

Abstract

PURPOSE:To provide an electric heating device by which the defective shape and the generation of spark at the time of heating are prevented and stable electric heating can be executed even in the case of electrical heating, by winding a thin metal strip around an electric conducting roll. CONSTITUTION:A roll 3 is arranged adjacently to the metal strip 1 wound around the electric conducting roll 2. The gap between the roll 3 and the metal strip 1 is made freely changeable and the surface of the roll 3 has electric insulating property.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric heating device in a continuous annealing line for metal strips of steel, aluminum, copper, etc., and particularly to an electric heating device capable of preventing a defective shape that occurs when a thin material is heated. Regarding

[0002]

2. Description of the Related Art Heretofore, in the case of continuously annealing a metal strip, it has been almost common to use radiation by gas heating or indirect heating by an electric heater for heating and heat retention. But,
Since these heating methods indirectly heat the material to be heated,
There is a problem that rapid heating cannot be performed, which greatly limits productivity when the plate thickness or plate width changes.

In order to solve this problem, it has been proposed to adopt electric heating, for example, Japanese Patent Laid-Open No. 61-829.
In Japanese Patent No. 54, a steel plate is directly energized via an energizing roll,
The steel plate itself is used as a heating element to raise the temperature, and Japanese Patent Laid-Open Nos. 1-142032 and 1-187789 disclose that metal rolls are provided before and after a metal strip passage passing through an annular transformer. Heating the strip is described.

In the case where an electric current is directly applied to the metal strip and heating is performed by Joule heat as described above, the heating capacity per unit time is high as compared with the indirect heating of gas or electricity, and the productivity accompanying the change of the plate thickness or the plate width. It is excellent in that the problem of deterioration can be solved and the equipment can be made compact.

[0005]

However, there are two major problems when the metal strip is heated by the energizing roll.
One is the problem of sparks that occur in the energizing roll, and the other is the problem of defective shape that occurs when contacting the energizing roll.

In order to suppress the spark, it is effective to use a current-carrying roll whose shape does not easily change even when it comes into contact with the heated metal strip, and press down the metal strip with the restraining roll, so that a large current can flow. Becomes However, when the thickness of the metal strip is thin, the temperature of the heated metal strip drops when the metal strip is restrained by the energizing roll and the restraining roll,
There is a problem that the thermal stress easily causes the metal strip to be narrowed.

If the metal strip does not come into stable contact with the current-carrying roll, sparks are likely to occur. Therefore, Japanese Patent Application Laid-Open No. 61-82954 discloses that a restraining roll for preventing the deflection of the strip is provided near the energizing roll. Generally, the winding energization heating is performed in the form as shown in FIG. 7. However, when the winding energization is performed, the restriction by the restraining rolls is removed, and the metal strip plate 1 as a whole goes in a direction in which the restriction is eliminated. Compared with the method of energizing while pressing down, the heated metal strip 1 has a larger contact area with the energizing rolls 21 and 22, so that the temperature drop is large and buckling is likely to occur near the center of the metal strip 1. Buckling is also likely to occur due to the distribution of tension applied to the metal strip 1 and the like. When the buckling occurs, the shape of the metal strip 1 changes variously when the metal strip 1 comes into contact with the energizing rolls 21 and 22, so that the metal strip 1 cannot come into close contact with the energizing rolls 21 and 22 and a spark is likely to occur. There is a problem of becoming.

Therefore, the present invention provides an electric heating device which does not cause a shape defect and is less likely to cause a spark in the electric heating of a thin metal strip which is apt to cause a shape defect.

[0009]

DISCLOSURE OF THE INVENTION The present invention relates to an electric heating apparatus for winding a metal strip on an energizing roll and heating the metal strip by passing an electric current, wherein the roll is arranged close to the metal strip wrapped around the energizing roll. It is an electric heating device characterized in that, preferably, the roll arranged in proximity to the metal strip wound around the energizing roll can freely adjust the gap with the metal strip, more preferably, This is an electric heating device in which the surface of the roll has electrical insulation.

[0010]

The present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an electric heating device using an annular transformer 10 as a primary power source. The metal strip 1 passes through an annular transformer 10 around which a coil is wound,
A secondary voltage is induced by the primary voltage applied to the 0 from the primary power supply 8. An induced current flows through the metal strip 1 by the induced secondary voltage, and a circuit including the energizing roll 2, the metal strip 1, the energizing roll 6, the conductive material 9, and the energizing roll 2 is completed, and the metal strip is heated by Joule heat. 1 heating is performed.

At this time, as shown in FIG. 2, the metal strip 1 heated without the roll 3 is cooled by coming into contact with the energizing roll 2, and a compressive force acts in the central direction. This compressive force causes wrinkles on the metal strip 1 to cause swelling on the contact surface with the current-carrying roll 2 as shown in FIG. 4, resulting in a defective shape such as a buckling. Then, a portion of the metal strip 1 that may or may not come into contact with the energizing roll 2 is generated, resulting in unstable energization and sparking. This is because the compressed metal strip 1 escapes upward with less restraint. In order to regulate this escape, the roll 3 is placed close to the metal strip 1 on the energizing roll 2 as shown in FIG. Place it. When the rolls 3 are arranged in this way, the force of compressing and deforming escapes in the width direction of the metal strip 1, so that the deformation of the metal strip 1 can be prevented. Therefore, the contact between the metal strip 1 and the energizing roll 2 is improved, and the occurrence of sparks can be prevented.

The gap between the roll 3 and the metal strip 1 arranged in close proximity is determined by the heating temperature of the metal strip 1 to be energized, the material,
It is necessary to be able to freely adjust according to the thickness.
When the roll 3 is brought into close contact with the metal strip 1 and a reduction force is generated between the roll 3 and the energizing roll 2, the force acting on the metal strip 1 that tries to escape in the plate width direction is restricted, so that the metal strip 1 Deformation such as drawing may occur, which is not preferable.

FIG. 5 shows an example of a mechanism for adjusting the gap. The energizing roll shaft 16 is fixed to the stand 11 via the roll chock 14. The roll 3 moves up and down together with the roll chock 13 directly connected to the cylinder 12 as the cylinder 12 moves up and down. If the roll chock 13 is moved up and down along the precisely finished linear guide 17, the roll 3 does not move back and forth, but always moves up and down at the same position.

FIG. 6 is a front view for explaining this rolling-down mechanism. In FIG. 6, the roll 3 is still above the metal strip 1, but when the cylinder 12 extends and pushes the roll chock 13 downward, the roll 3 approaches the metal strip 1. If the gap between the roll 3 and the energizing roll 2 is calculated based on the value measured by the gap sensor 18 provided on the roll chock 14 or the displacement sensor, the limit switch, etc., and the cylinder 12 is stopped at a predetermined position, the metal strip plate 1
A certain gap can be provided between the roll and the roll 3. A hydraulic cylinder, an air cylinder, or the like may be used as the cylinder 12. The gap varies depending on the surface condition of the roll 3, the type of the metal strip 1 and the heating temperature. However, if the gap is too narrow, restraint in the width direction starts to work.
It is preferable to set it to mm or more.

Further, the roll 3 and the metal strip 1 are not always in stable contact with each other over the entire width, and when the surface of the roll 3 is made of a conductive material, a spark is generated between the roll 3 and the metal strip 1. Therefore, the surface of the roll 3 needs to be non-conductive.

[0017]

[Embodiment 1] FIG. 1 is a side view of an embodiment of an electric heating apparatus of the present invention.

The energizing roll 6 on the low temperature side has a body length of 1300 m.
m, a diameter of 300 mm made of S45C, a roll 7 made of a urethane rubber roll having a body length of 1300 mm and a diameter of 300 mm, and a high temperature side energizing roll 2 and a roll 3 made of a body length 13
A carbon roll having a diameter of 00 mm and a diameter of 300 mm was used.

On the surface of the roll 3, an insulating Al ₂
O ₃ -Cr and the sprayed coating was 200 microns formed of ₂ O ₃ (50:50). The distance between the energizing roll 1 and the energizing roll 6 was 200 mm. The roll 3 can be moved up and down by hydraulic pressure, and the gap sensor measures the distance between the roll chock of the energizing roll 2 and the roll chock of the roll 3, and the gap between the metal strip 1 and the roll 3 is calculated and converted by the controller of the hydraulic cylinder. The mechanism is such that it can be stopped at any roll gap.

The power source used for energization is 50 Hz on the primary side,
The voltage is 600V, and the annular transformer 10 has a winding of 7 turns and forms a 7: 1 transformer with the metal strip 1. The electrically conductive roll 1 and the electrically conductive roll 6 were short-circuited with a conductive material 9 made of copper to form a closed circuit. On the exit side of the energizing roll 2, a body length of 1300 mm, so that the wrapping angle can be adjusted,
A carbon roll 5 and a carbon roll 4 having a diameter of 300 mm were arranged. The rolls 5 and 4 were insulated from the installation floor to prevent the bearing from burning due to stray current.

Using this electric heating device, a plate thickness of 0.19 m
50 mm cold rolled steel sheet (0.04% C) with a width of 900 mm
The plate was passed at mpm, and a current of 12100 A was passed to heat it to 750 ° C. The tension was 180 kg.

When the roll 3 is not used, the steel plate is 4
Buckling of a dozen millimeters of the book occurred, and sparks were generated between the buckling portion and the energizing roll portion. On the other hand, when the gap between the steel sheet and the roll 3 was adjusted to 0.2 mm and electricity was applied, no buckling or sparking was observed on the steel sheet.

[0023]

Example 2 A heating experiment was conducted in the same manner as in Example 1 except that the conductive carbon surface was exposed without forming a film of Al ₂ O ₃ —Cr ₂ O _{3 on} the roll 3 and the gap was changed variously. .

When the gap between the steel plate and the roll was 2 mm, there were two buckling streaks, but sparks occurred on both the buckling portion and the current-carrying rolls and rolls. When the gap between the steel plate and the roll was set to 0.5 mm, the buckling became extremely small, but sparks occasionally occurred between the roll and the roll.

[0025]

With the electric heating apparatus of the present invention, it is possible to prevent the occurrence of shape defects even by the electric heating of a metal strip which is apt to cause shape defects, and to prevent the occurrence of sparks.
It enables stable and high quality electric heating.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of an electric heating device of the present invention.

FIG. 2 is a diagram schematically showing the deformation of a metal strip and the generation of a compressive force during energization.

FIG. 3 is a front view showing a relationship between an energizing roll and a metal strip in the case where energization heating is performed using a roll by the energization heating device of the present invention.

FIG. 4 is a diagram showing a deformation of the metal strip on the energizing roll when the energizing heating is performed without using the roll.

FIG. 5 is a side view showing a roll elevating mechanism.

FIG. 6 is a front view showing a roll elevating mechanism.

FIG. 7 is a diagram showing an example of a conventional electric heating device.

[Explanation of symbols]

 1 Metal Strip 2 Electric Roll 3 Roll 4 Carbon Roll 5 Carbon Roll 6 Electric Roll 7 Roll 8 Primary Power 9 Conductive Material 10 Annular Transformer 11 Stand 12 Cylinder 13 Roll Chock 14 Roll Chock 15 Roll Shaft 16 Electric Roll Shaft 17 Linear Guide 18 Gap Sensor 19 Receiving metal fitting 20 Hearth roll 21 Conductive roll 22 Conductive roll 23 Conductive material 24 Power supply

Claims (3)

[Claims] 1. An energization heating device for winding a metal strip plate around an energization roll and heating the metal strip plate by passing an electric current, wherein the roll is arranged close to the metal strip plate wrapped around the energization roll. apparatus. 2. The electric heating device according to claim 1,
An electric heating device characterized in that a roll arranged near a metal strip wrapped around an electric roll can freely adjust a gap between the roll and the metal strip. 3. The electric heating apparatus according to claim 1 or 2, wherein the surface of the roll arranged close to the metal strip wrapped around the electric roll has electrical insulation.