JPH07316671A - Electric heating device and method therefor - Google Patents

Abstract

PURPOSE:To prevent the generation of spark and the defective shape of a heated metal strip and to stabilize the electric heating by quickly changing pass-line in accordance with an operational condition. CONSTITUTION:A support roll 4 is arranged so as to come it into contact with the surface of the metal strip 1 in contact with an electric conducting roll 2 in the advancing direction of the metal strip 1. An intermediate roll 5 for winding the metal strip 1 around the electric conducting roll 2 by pushing the metal strip 1 is arranged at the side opposite to the surface of the metal strip 1 in contact with the electric conducting roll 2 between the support roll 4 and the electric conducting roll 2. A pressing roll 3 is provided with a rolling reduction mechanism capable of reducing the metal strip 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric heating apparatus and an electric heating method in a continuous annealing line for metal strips such as steel, aluminum and copper.

[0002]

2. Description of the Related Art Conventionally, in the case of continuously annealing a metal strip, in most cases, radiation by gas heating or indirect heating by an electric heater is used 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 in Japanese Patent Laid-Open Nos. 1-142032 and 1-187789, the front and rear of a metal strip passage that penetrates the annular transformer 10 as shown in FIG. The method for heating the metal strip 1 by providing the energizing rolls 2 and 6 in the above is described.

Further, Japanese Unexamined Patent Publication No. 61-82954 discloses a method of winding a metal strip around an energizing roll, and Japanese Unexamined Patent Publication No. 1-142032 discloses a method of sandwiching the metallic strip between rolls. Generally, as shown in FIGS. 7 and 8, the metal strip 1 is sandwiched between energizing rolls 2 and 6 to energize, and as shown in FIG. 9, the metal strip 1 is wound around energizing rolls 2 and 6 to energize. How to do it.

In this way, when the electric current is directly applied to the metal strip and the surreal heat is used for heating, the heating capacity per unit time is higher than that of the indirect heating of gas or electricity, and the productivity due to 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.

[0006]

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.

As the thickness of the metal strip becomes thicker and the stripping speed becomes faster, a larger current is required.
Sparks are more likely to occur. In order to suppress sparks, it is effective to use a current-carrying roll whose shape does not easily change even when it comes into contact with a heated metal strip, and to apply a reduction by a restraining roll from above to the metal strip on the current-carrying roll. It becomes possible to flow a large current. However, when the thickness of the metal strip is thin, the metal strip is constrained by the restraining roll, so that the temperature drop of the heated metal strip due to the current-carrying roll and the restraining roll occurs, and the restriction tends to occur. There is.

In order to eliminate the restriction, it is sufficient to remove the restraint of the metal strip plate by the metal roll and the pressing roll, and the energization method by winding is advantageous. In particular, when the thickness is thin, the amount of current required is small, and when the pressure is reduced, a defective shape is likely to occur. Therefore, energization by winding is preferable. However, it is very poor in workability to apply the pressure reduction or switch the path with one electric heating device. Especially, when the atmosphere of the heating device is a non-oxidizing atmosphere, it takes time to exchange the atmosphere. However, there is a problem that productivity is greatly hindered by roll installation adjustment and plate threading.

In view of the above, the present invention provides an apparatus and a method capable of freely and quickly selecting a heating method in the energization heating of a metal strip according to the change of the sheet thickness, the shape defect, and the required current amount without impairing the productivity. I will provide a.

[0010]

The electric heating apparatus of the present invention is an electric heating apparatus for heating a metal strip by applying an electric current to the metal strip by using an electric roll. The metal strip is in contact with the electric roll in the traveling direction of the metal strip. Arrange the support roll so that the surface of the plate is in contact, between the support roll and the energizing roll,
It is an electric heating device characterized by arranging an intermediate roll on the side opposite to the surface of the metal strip in contact with the current-carrying roll, the metal roll being able to be pushed in, preferably a roll capable of rolling down the metal strip. A pressing roll having a reduction mechanism is provided so as to face the energizing roll. Further, the energization heating method of the present invention, using the energization heating device, energization performed by winding around the energizing roll without applying reduction with the restraining roll, and energization performed while applying reduction with the restraining roll without winding around the energizing roll, and energizing It is an energization heating method characterized in that three kinds of energization, that is, energization while being wound around a roll and being pressed by a restraining roll, are selected and heated according to the plate thickness of the metal strip.

[0011]

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

1 to 3 are views showing an example of an electric heating apparatus of the present invention. The electric heating device of the present invention is a metal strip 1
Has two pairs of rolls consisting of an energizing roll 2 and a restraining roll 3, and a conducting roll 6 and a restraining roll 7 in the traveling direction of
Conducting material 9 from the power source 8 to the energizing rolls 2 and 6
An electric current is supplied to the battery through a current collecting brush or the like. Restraining roll 3
The restraining roll 7 may be conductive or non-conductive. When the holding roll 3 and the holding roll 7 are conductive, a current collecting brush may be attached to allow the current to flow from the conductive material. The metal strip 1 is energized while being pressed down by the pressing roll 7 and the energizing roll 6, and is joule-heated up to the energizing roll 2 by an energizing current.

When the heated metal strip 1 goes straight without being wound around the energizing roll 2, as shown in FIG. 1, it is sandwiched between the restraining rolls 3 and 7 and the energizing rolls 2 and 6 to energize,
The intermediate roll 5 does not come into contact with the metal strip 1 and is in a standby state. Further, although the support roll 4 is arranged on the pass line and in contact with the metal strip 1 in FIG. 1,
It is not always necessary to contact the metal strip 1.

The pressing roll 3 and the pressing roll 7 are provided with a pressing mechanism. FIG. 4 is a side view showing an example of a current-carrying roll having a rolling-down mechanism and a stand. Electric power roll shaft 18
Is fixed to the stand 15 via the roll chock 14. FIG. 4 shows an example in which the load cell 19 and the receiving metal fitting 20 for measuring the rolling force are connected to the stand 15, but this is not necessary when the rolling force is measured by another method.

The pressing roll 3 or the pressing roll 7 can be moved up and down by a roll chock 13 directly connected to the cylinder 12. If the roll chock 13 is moved up and down along the precisely finished linear guide 16, the restraining rolls 3 and 7 do not move back and forth, but always move up and down at an accurate position.

FIG. 5 is a front view for explaining this rolling-down mechanism. In FIG. 5, the pressing roll 3 is not in contact with the metal strip 1 yet, but the pressing roll 3 comes into contact with the metal strip 1 when the cylinder 12 extends and the roll chock 13 is pushed in. Since the energizing roll 2 is fixed to the stand 15, when pressure is applied to the cylinder 12, pressure is applied to the restraining roll 3 and the metal strip 1 is pressed down. A hydraulic cylinder, an air cylinder, or the like is used as the cylinder 12 for transmitting the pressure.

FIG. 2 is an explanatory diagram of the case where the winding energization is performed. When the metal strip 1 heated as shown in FIG. 1 is held between the roll 3 and the energizing roll 2 to energize, the metal strip 1
When the thickness is thin, the metal strip 1 is likely to be narrowed. This squeezing occurs when the heated metal strip 1 contacts the energizing roll 2 and the restraining roll 3 because both rolls restrain the shrinking due to cooling. Therefore, in order to eliminate the restraint by the roll, the restraining roll 3 is made to stand by above the metal strip 1 so as not to apply the rolling. When the metal strip 1 is not heated and is in contact with both rolls without much temperature difference, the pressing roll 7 and the energizing roll 6 are sandwiched and rolled down for stable contact to prevent sparking. Better to add.

The heated metal strip 1 makes unstable contact with the current-carrying roll 2 if it is left in a horizontal path, so that sparks are generated and the current-carrying roll 2 and the metal strip 1 are damaged.
In order to prevent sparks, it is necessary to bring the metal strip 1 into stable contact with the energizing roll 2. In order to make the metal strip 1 almost unconstrained and to make a stable contact, the metal strip 1 is wound around the energizing roll 2 as shown in FIG.
The method of pressing with the tension applied to the metal strip 1 is used.
In order to wind the metal strip 1 around the energizing roll 2, it is necessary to change the path of the metal strip 1 and therefore the intermediate roll 5
And the support roll 4 is used. That is, by pushing the intermediate roll 5 above the metal strip 1 shown in FIG. 1 downward, the metal strip 1 is wound around the energizing roll 2 and the support roll 4 as shown in FIG.

An example of the lifting mechanism for the intermediate roll 5 is shown in FIG. Intermediate roll 5 attached to roll chock 21
Moves up and down along with the roll chock 21 along the linear guide 24 when the cylinder 23 is moved up and down. The roll chock 21 descends and lowers the metal strip 1 from the horizontal pass line to move the metal strip 1 to the energizing roll 2
And wrap around the support roll 4.

The roll chock 21 is used for the cylinder 2 while confirming the height with a limit switch or displacement sensor.
It can be set to any position by deciding the movement amount of 3 and can be positioned easily and in a short time because it moves up and down on the linear guide 24. From horizontal pass to winding pass, winding pass to horizontal pass. The time required to change the path line to the path is extremely short, and in some cases, the path can be switched continuously without interrupting the operation.

In this way, the intermediate roll 5 can freely push the metal strip 1 by means of the lifting device, whereby the metal strip 1 can be wound around the energizing roll 2.
In the case where the generation of the diaphragm becomes a problem when sandwiched and energized, if the metal strip 1 is wound around the energizing roll 2 and energized, the heating without the occurrence of the diaphragm and the spark becomes possible. In addition, when the metal strip 1 is neither thick nor thin, and when the energization is performed by applying a reduction, the diaphragm is slightly visible and the amount of energizing current is required, the metal strip 1 is formed as shown in FIG. It is advisable to wind the strip 1 around the energizing roll 2 and energize while pressing it down by the holding roll 3. The amount of reduction may be adjusted according to the diaphragm generated in the metal strip 1.

As shown in FIGS. 1 to 3, the electric heating apparatus of the present invention can freely select three kinds of heating methods in a short time. In the above description, the thickness of the metal strip was explained, but the easiness of occurrence of throttling and sparking depends on the material and strength of the metal strip to be heated, stripping speed, heating temperature, operating conditions such as roll temperature. Since it changes, it may be appropriately selected by the heating device of the present invention and heated by the most effective method. Since the pass line of the metal strip can be easily changed and the heating method can be switched only by the presence or absence of the pressing of the intermediate roll, the heating method can be changed quickly without hindering the production.

The above description is an example of a horizontal path, but the device configuration does not change whether the path is a vertical path or another path is oblique. In addition, the annular transformer 10 as shown in FIG.
Even when a current is directly induced in the metal strip 1 by using, and the metal strip 1 is heated by short-circuiting between the energization rolls 2 and 6, as shown in FIGS. It does not matter whether the metal strip 1 is heated by supplying an electric current.

[0024]

Example 1 FIG. 1 shows an example of a horizontal pass in which the intermediate roll 5 of the electric heating apparatus of the present invention is not used. With the structure shown in FIG. 1, the low-temperature side energizing roll 6 has a body length of 1300 mm and a diameter of 30.
A 0 mm S45C roll was used, a urethane rubber roll having a body length of 1300 mm and a diameter of 300 mm was used as the pressing roll 7, and a carbon roll having a body length of 1300 mm and a diameter of 300 mm was used as the energizing roll 2 and the pressing roll 3 on the high temperature side. The distance between the energizing roll 2 and the energizing roll 6 is 2000 mm
And Further, the pressing rolls 3 and 7 can be moved up and down by hydraulic pressure, and a reduction of up to 10 t can be applied.

When a cold-rolled steel sheet having a sheet thickness of 0.6 mm and a sheet width of 600 mm is passed at 40 mpm and a rolling force of 1800 kg is suppressed and the rolls 3 and 7 are energized, the current required for heating to 750 ° C. 1500A (Line current density 25A /
mm: current amount per plate width), neither spark nor defective shape occurred.

On the other hand, the plate thickness is 0.18 mm and the plate width is 810 mm.
When a cold-rolled steel sheet of the same material is used at 40 mpm and a rolling force of 2430 kg is suppressed and the rolls 3 and 7 are energized to heat to 750 ° C., a current of 8900 A (line current density of 11 A / mm: Spark did not occur in the amount of current per plate width), but vertical streaks were introduced into the steel plate after passing through the energizing roll 2 to cause defective shape.

[0027]

Embodiment 2 FIG. 2 shows an example in which the intermediate roll 5 of the electric heating apparatus of the present invention is used and the restraining roll 3 is not used. As the energizing rolls 2 and 6 and the restraining rolls 3 and 7, the same ones as in Example 1 were used, and a roll chock was placed at a position 1 m behind the energizing roll 2 with a hydraulic cylinder on the linear guide ± 700.
A support roll 4 of the same size as a carbon roll having a body length of 1300 mm and a diameter of 300 mm attached so as to be able to move up and down by mm was placed 1 m behind the intermediate roll 5 and the cold-rolled steel sheet was electrically heated.

The experiment was conducted after finishing Example 1 by lowering the intermediate roll 5 as it is and then raising the restraining roll 3. It took less than a minute to change the pass line from the horizontal pass to the winding pass.

As in Example 1, a plate thickness of 0.6 mm and a plate width of 6
A cold rolled steel plate of 00 mm was passed at 40 mpm and heated at 750 ° C., but the current was 6000 A (line current density 10 A
/ Mm: the amount of current per plate width) caused sparks.

On the other hand, the plate thickness is 0.18 mm and the plate width is 810 mm.
Of cold-rolled steel sheet of the same material as above, passed at 40 mpm and pressed down at a roll-down force of 2430 kg and applied to the roll 750.
When heated to ℃, the current is 8900A (Line current density 11
A / mm: amount of current per plate width), sparks did not occur, and the steel sheet after passing through the energizing roll 2 also had a good shape.

[0031]

Third Embodiment FIG. 3 shows an example of using the intermediate roll 5 and the pressing roll 3 of the electric heating apparatus of the present invention. In the state of Example 2, the pressing roll 3 was lowered.

As in Examples 1 and 2, a cold-rolled steel plate having a plate thickness of 0.4 mm and a plate width of 600 mm and having a 20-micron edge drop and a corrugated shape was passed at 40 mpm and heated at 750 ° C. When no reduction was applied by the pressing rolls 3 and 7, sparks were generated at the steel plate edges even at 5000 A (linear current density 8.3 A / mm: current amount per plate width), and the shape was good. Next, when energization was performed while applying a reduction of 1500 kg and winding, sparks were not generated at the same current, but several vertical wrinkles were generated. When energizing the rolling force with 400 kg of roll weight, 1
At 3500 A (line current density 22.5 A / mm: amount of current per plate width), neither spark nor defective shape occurred.

[0033]

According to the present invention, the pass line can be quickly and freely changed without stopping the line depending on the thickness, shape, material and operating conditions of the metal strip to be heated, thus impairing the productivity. Stable operation is possible.

[Brief description of drawings]

FIG. 1 is a side view showing a case where an electric heating apparatus of the present invention applies electric current to a metal strip by applying a reduction to the metal strip with an electric roll and a holding roll.

FIG. 2 is a side view showing a case where a metal strip is wound around a current-carrying roll by the current-carrying heating device of the present invention and heated by current-carrying without rolling.

FIG. 3 is a side view showing a case where a metal strip is wound around an electrically conductive roll and electrically heated by applying a reduction by the electrically conductive heating apparatus of the present invention.

FIG. 4 is a side view of a lifting roll lifting device.

FIG. 5 is a front view of a lifting roll lifting device.

FIG. 6 is a side view of an intermediate roll lifting device.

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

FIG. 8 is a diagram showing an example of a conventional electric heating device by sandwiching.

FIG. 9 is a diagram showing an example of a conventional energization heating device using energization for winding.

[Explanation of symbols]

 1 metal strip 2 energizing roll 3 restraining roll 4 support roll 5 intermediate roll 6 energizing roll 7 restraining roll 8 power supply 9 conductive material 10 annular transformer 11 hearth roll 12 cylinder 13 roll chock 14 roll chock 15 stand 16 linear guide 17 restraining roll shaft 18 Energizing roll shaft 19 Load cell 20 Receiving metal fitting 21 Roll chock 22 Intermediate roll shaft 23 Cylinder 24 Linear guide 25 Stand

Claims (3)

[Claims] 1. In an electric heating device for heating a metal strip by applying an electric current to the metal strip by using an electric roll, a support roll is arranged so that the surface of the metal strip contacting the current roll is in contact with the traveling direction of the metal strip. An electric heating device is provided between the support roll and the energizing roll, and an intermediate roll is disposed on the opposite side of the surface of the metal strip that contacts the energizing roll and into which the metal strip can be pushed. 2. The electric heating device according to claim 1,
An electric heating device comprising a pressing roll having a roll pressing mechanism capable of pressing a metal strip and facing the current applying roll. 3. An energizing roll using the energization heating device according to claim 2, wherein energization is performed by winding the energizing roll around the restraining roll without applying reduction, and energization performed by applying a reduction with the restraining roll without winding around the energizing roll. An energization heating method, characterized in that three kinds of energization, that is, energization performed by applying a reduction with a restraining roll by winding the wire around the sheet are selected and heated according to the plate thickness of the metal strip.