JPH08176683A - Resistance heater - Google Patents

Abstract

PURPOSE: To perform heating capable of keeping the shape of a metallic band plate good by suppressing generation of waves in the metallic band plate generating at the time of heating and to run a stabilized operation by preventing a spark accompanied with generation of waves in a device for heating the metallic bend plate. CONSTITUTION: In a resistance heater heating the traveling metallic band plate by energizing between a first conductive roll and a second conductive roll, at least one couple among a pairs of rolls 10-15 which are arranged between the first conductive roll and the second conductive roll and are disposed to face each other with spaces of above the width of the metallic band plate and <=3mm is arranged while insulating from the earth.

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 such as steel, aluminum and copper.

[0002]

2. Description of the Related Art Conventionally, when a metal strip is continuously annealed, most of the heating and heat retention are radiation by gas heating and indirect heating by an electric heater. However, since these heating methods indirectly heat the material to be heated, there is a problem that rapid heating cannot be performed, and when the plate thickness or the plate width is changed, the production is largely restricted.

To solve this problem, it has been proposed to employ electric heating. For example, JP-A-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 strips are provided before and after a metal strip passage passing through an annular transformer. A method of heating the is described. As a heating method, Japanese Patent Application Laid-Open No. 61-82954 discloses a method of winding a metal strip around an energizing roll, and Japanese Patent Application Laid-Open No. 1-142032 discloses a method of sandwiching the metal strip between rolls.

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. The advantage is that the problem of deterioration can be eliminated and the equipment can be made compact.

[0005]

However, there are two major problems in heating a metal strip with an 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 the energizing roll contacts.

As for the spark, the thicker the strip material is and the faster the strip passing speed is, the larger current is required, and the spark is apt to occur. In order to suppress the spark, it is possible to use a roll whose shape does not easily change even when it comes into contact with the heated steel plate and apply a reduction to allow a large current to flow. However, in this case, when the thickness of the strip is thin, the roll restrains the strip, which causes a temperature drop of the heated strip due to the roll, resulting in a defective shape such as drawing of the strip. The generated throttle remains even after the energizing roll, and a wave is generated in the strip material from before the energizing roll. When the wave comes into contact with the energizing roll, unstable contact and unstable energization occur, which causes sparks.

Therefore, the present invention is capable of suppressing electric current heating of metal strips, particularly shape defects occurring in thin materials,
An object of the present invention is to provide an electric heating device capable of performing stable operation.

[0008]

The gist of the present invention is as follows. In an energization heating device that heats a metal strip traveling through an electric current between a first energizing roll and a second energizing roll, a gap larger than the thickness of the traveling metal strip is between the first energizing roll and the second energizing roll. Is a pair of rolls provided to face each other, at least one set is a conductive heating device, characterized in that in the conductive heating device, a gap to be arranged between the first conductive roll and the second conductive roll The surface of the roll provided is an electrically conductive heating device, characterized in that it is made of an insulator, in the above electrically conductive heating device, a roll provided with a gap arranged between the first electrically conductive roll and the second electrically conductive roll, One energizing roll, a second energizing roll, an energizing heating device characterized by being insulated from a circuit composed of a metal strip, in the above energizing heating device, a first energizing roll Two roll barrel portion having a gap disposed between the conductive rolls is a resistance heating apparatus, characterized by comprising a non-magnetic material.

[0009]

The operation of the present invention will be described below with reference to the drawings. FIG. 1 is a side view for explaining the structure of an electric heating device according to the present invention. The running metal strip 9 is supplied with current from the energizing roll 1 and the energizing roll 3 through the power source 5 and the conductive material 6.
Joule heating is performed between the energizing roll 1 and the energizing roll 3. Brushes (not shown) for passing an electric current through the rolls are connected to the roll shafts 7 and 8 in the figure. The pressing roll 2 and the pressing roll 4 are
It is used to surely bring the running metal strip 9 into contact with the energizing roll. In this example, the running metal strip 9 is supplied with an electric current while being subjected to a reduction by the energizing roll 1 and the pressing roll 2 at room temperature, and reaches the maximum temperature by the energizing roll 3.

In this case, when the metal strip 9 is not heated as shown in FIG. 2, the metal strip 9 passes through the energizing roll 3 without changing its width as shown by 16, but when a current flows and heating is started. Due to the thermal expansion, the width widens like 17, and if there is no temperature drop, the energizing roll 3 exits while expanding as at 18. However, when the temperature of the energizing roll 3 and the pressing roll 4 is lower than that of the heated metal strip 9, the width is reduced as in 19 due to rapid cooling due to contact heat transfer. Due to this rapid width reduction, the metal strip is easily deformed, and as shown in FIG. 3, a wave is generated in front of the current-carrying roll 3 on the high temperature side, in the AA cross section of FIG. When it exits the energizing roll 3, it becomes a squeezed shape.

This diaphragm has a larger one as the wave height in front of the energizing roll 3 on the high temperature side is higher. Therefore, if it is dispersed in a wave as small as possible, it becomes extremely small even if the diaphragm remains. If it passes, it will disappear and no real harm will remain. In order to disperse the waves small, it is sufficient to suppress the growth of the waves. As shown in FIG. 1, rolls 10 and 11, rolls 12 and 13, and rolls 14 are provided between the energizing roll 1 and the energizing roll 3. If the rolls are arranged close to each other so as not to roll down the traveling metal strip 9 as shown by Nos. 15 and 15, the wave to be generated does not grow beyond the gap between these rolls, and the wave is generated in the width direction of these rolls. Is dispersed into FIG. 4 schematically shows this, but the closer the rolls are, the smaller the wave height becomes, which is effective. However, if the roll interval is too narrow, the waves may be restricted and throttling may occur. Therefore, as shown in FIG. 1, a plurality of wave regulation rolls may be provided to divide the wave into several stages to reduce the waves. , If you can do it, you can do it.

Further, since these wave regulating rolls come into contact with the metal strip 9 through which the current flows, unless the current flows through the roll bearings, the bearing is burnt or sparks are generated, and the heating efficiency is increased. Insulation is necessary to cause deterioration of the battery. Insulation may be applied to the ground or to a closed circuit including the metal strip 9, the energizing roll 1, the conductive member 6, the power source, and the energizing roll 3. As an insulating method, a layer of an insulating material may be provided on the surface layer of the roll, or the roll chock may be insulated by using a baking plate or an insulating bolt.

These wave regulating rolls, for example, the rolls 10, 12, and 14 in FIG. 1 are large because they are in a closed circuit consisting of the metal strip 9, the energizing roll 1, the conductive member 6, the power source, and the energizing roll 3. When an electric current is applied, it is heated by electromagnetic induction, resulting in a loss of heating efficiency. In order to prevent this, a roll made of a non-magnetic material may be used as the roll that enters the circuit surrounded by the energizing roll and the metal strip so as not to receive electromagnetic induction.

Further, rolls which are likely to come into contact with the metal strip 9 having a high temperature, rolls 10, 11 and 1 in FIG.
Regarding Nos. 2 and 13, it is necessary to cool the inside of the roll with water, and it is desirable to perform heat insulation so that heat is not taken from the metal strip 9 as much as possible when it comes into contact with the metal strip 9.

[0015]

EXAMPLES The present invention will be described below based on examples. In the experiment, an S45C roll (diameter 300 mm, length 1300 m) with Cr plating on the surface layer was used as the low temperature side energizing roll.
m) and a rubber roll (diameter 30
0 mm, length 1300 mm), a high temperature side energizing roll and a carbon roll (each having a diameter of 300 mm and a length of 1300 mm) as a pressing roll, an AC power source (50 Hz) was controlled by thyristor control to control the input power, and a cold rolled steel sheet (0. 2 mm thick × 900 mm wide) was heated from room temperature to 700 ° C.
The heating distance is 2 m and the line speed is 10 to 50 mpm.

The wave regulating roll has a diameter of 100 mm and a length of 1300 mm and is internally water-cooled, and ZrO is formed on the surface layer.
Insulation sprayed layer of ₂ -8% Y ₂ O ₃ and (400 [mu] m) provided,
By changing the gap between the rolls, the effect of reducing the generated wave height and the shape of the steel sheet after heating were observed. The position of the wave regulating roll is 300 mm before the high temperature side energizing roll.

Table 1 shows the spacing between the wave regulating rolls, the height of the waves entering the high temperature side energizing roll, and the shape of the steel sheet after heating. In the example of the present invention in which the gap of the wave regulating roll was 3 mm or less, there was no drawing remaining in the steel sheet after heating, or it was small enough to be easily erased by applying a skin pass, but the roll gap is increased to 5 mm or more. By
The waves on the high temperature roll side gradually increased, and the drawing of the steel sheet after heating also gradually increased. Further, since the wave regulation roll is sprayed with an insulating material, there is no problem such as bearing burnout and stable operation is possible.

[0018]

[Table 1]

[0019]

With the electric heating apparatus according to the present invention, it is possible to heat without deteriorating the shape of the metal strip that greatly affects the quality of the product, and to generate sparks due to the defective shape of the heated metal strip. Since the electric current can be supplied without causing any damage, the electric current can be stably operated without damaging the electric roll and the metal strip, and the life of the roll can be extended.

[Brief description of drawings]

FIG. 1 is a side view showing an arrangement of devices for electrically heating a metal strip according to the present invention by applying a reduction with an electric roll and a pressing roll.

FIG. 2 is a schematic view from above showing a change in width of the metal strip during heating from the low temperature energizing roll to the high temperature energizing roll.

3 is a front sectional view showing the shape of a metal strip plate taken along the line AA in FIG.

FIG. 4 is a schematic diagram for explaining a state in which the metal band plate in which waves are generated according to the present invention suppresses the growth of waves by a wave regulation roll.

[Explanation of symbols]

1 Low-temperature side energizing roll 2 Low-temperature side holding roll 3 High-temperature side energizing roll 4 High-temperature side holding roll 5 Power source 6 Conductive member 7, 8 Roll shaft 9 Metal strip 10-15 Wave regulation roll 16 Passing line of metal strip before heating 17 Passage line for metal strips expanded by heating 18 Passage line for metal strips expanded by heating when no heat is applied to the energizing roll 19 Metal strip expanded by heating when being cooled by energizing rolls Passage line

Claims (4)

[Claims] 1. A current-carrying heating device for heating a traveling metal strip by passing an electric current between the first current-carrying roll and the second current-carrying roll, wherein the metal strip is located between the first current-carrying roll and the second current-carrying roll. An electric heating device, characterized in that at least one set of a pair of rolls facing each other is arranged with a gap of 3 mm or more in thickness being provided. 2. The electric heating device according to claim 1, wherein the surface of the roll provided with a gap arranged between the first energizing roll and the second energizing roll is made of an insulating material. 3. A roll having a gap arranged between the first energizing roll and the second energizing roll is insulated from a circuit composed of the first energizing roll, the second energizing roll and the metal strip. The electric heating device according to claim 1. 4. The electric heating device according to claim 1, wherein the body of the roll provided with a gap between the first energizing roll and the second energizing roll is made of a non-magnetic material.