JPH0773074B2 - Electric heating device - Google Patents

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 for electrically heating a mass-produced electrically conductive material to be continuously fed at a high speed, for example, as a preheat treatment for galvanizing a steel material. The present invention relates to an electric heating device for heating.

[0002]

2. Description of the Related Art A material to be heated having electrical conductivity, for example, a steel material, is continuously fed at high speed for various purposes such as preheating for plating, annealing, and quenching, and an alternating current is applied to the material to be heated. An apparatus for heating a material to be heated by resistance heating is known. As such a device, for example, two sets of electrically conductive roll electrodes facing each other with the material to be heated sandwiched are provided at predetermined intervals in the feed passage of the material to be continuously fed, and between the two sets of roll electrodes. There is one that heats a material to be heated by applying an AC voltage to the material. That is, the material to be heated to be fed is heated by applying a predetermined AC voltage in the feeding passage between the two sets of roll electrodes.

Further, two sets of electrically conductive roll electrodes sandwiching the material to be heated are provided at predetermined intervals in the feed passage for the material to be heated, and an annular transformer is provided around the material to be heated between the two sets of roll electrodes. It is known that this is arranged. In such a device, the inside of the annular transformer is formed so as to serve as a feed passage for the material to be heated, and a secondary voltage is induced in the material to be heated by applying a primary voltage from the power source to the annular transformer. The material to be heated is electrically heated.

[0004]

In the electric heating device as described above, the current, voltage, or electric power supplied to the device is controlled in order to heat the material to be heated to a predetermined temperature.

The method of controlling the current has the advantage that the set current has a predetermined value, but the temperature of the heated material obtained by heating is the power factor of the current, the specific heat of the heated material, the specific resistance and It is affected by the cross-sectional area. Generally, the specific resistance value of the material to be heated largely depends on the temperature of the material to be heated. For example, the specific resistance of medium carbon steel is 14.40 μΩcm at 20 ° C.,
At 400 ° C., it changes to 46.15 μΩcm. In this way, the physical property values such as the specific resistance fluctuate, and the method of controlling the current has a drawback in that stable temperature cannot be controlled because the temperature of the obtained material to be heated is affected by these physical property values.

On the other hand, in the case of the method of controlling the voltage, the temperature of the obtained heated material is not influenced by the cross-sectional area of the heated material. Further, in the case of the method of controlling the electric power, the obtained temperature of the material to be heated is not affected by the specific resistance of the material to be heated, and the influence of the cross-sectional area can be reduced.

Therefore, according to the method of controlling electric power or voltage, the influence of the state of the material to be heated can be reduced,
It is possible to perform stable temperature control that is resistant to disturbance. However, in an unsteady state in which the temperature distribution of the heated material is not stable, such as immediately after starting the device or when passing the joint between heated materials of different sizes, the power required to obtain the desired temperature is obtained. Alternatively, since it is impossible to determine the voltage, there is a problem that the temperature control cannot be performed by controlling the power or the voltage.

The present invention solves the above problems,
An object of the present invention is to provide an electric heating device capable of appropriately controlling the temperature of a material to be heated even in an unsteady state such as immediately after starting the apparatus or when passing a joint between materials to be heated of different sizes.

[0009]

According to the present invention, there is provided an electric heating apparatus in which a material to be continuously fed is brought into contact with a roll electrode arranged on the inlet side of a feed passage of the material to be heated,
Electrical heating is performed by bringing the material into contact with a roll electrode or a metal bath provided on the outlet side of the material to be heated.

The electric heating apparatus includes a current control means for controlling a heating temperature of a material to be heated by controlling an electric current supplied to the material to be heated, and an electric power supplied to the material to be heated. It has a power control means for controlling the heating temperature of the material and a voltage control means for controlling the heating temperature of the material to be heated by controlling the voltage supplied to the material to be heated, and the current control means in the unsteady state. Control the heating temperature of the material to be heated, and in the steady state, the heating temperature of the material to be heated is controlled by either the power control means or the voltage control means.

[0011]

According to the present invention, an AC voltage is applied between the roll electrode on the entrance side and the roll electrode on the exit side or the metal bath,
The material to be heated is electrically heated. When the annular transformer is provided, a voltage is applied to the annular transformer to induce a secondary voltage in the material to be heated, and the material to be heated is electrically heated.

The heating temperature of the material to be heated is controlled by the current control means in the unsteady state and controlled by the power control means or the voltage control means in the steady state. Therefore, even when the power or voltage cannot be determined during an unsteady state, such as immediately after the device is started up or when the joints of materials of different sizes are being passed, it is possible to control the temperature of the material to be heated by controlling the current. Temperature control can be performed. Further, in the steady state, stable control that is strong against disturbance can be performed by controlling the power or voltage.

[0013]

EXAMPLE FIG. 3 is a view showing a first example of the electric heating mechanism of the electric heating apparatus of the present invention. An auxiliary roll R1 lined with a rubber material or the like and an electrically conductive roll electrode R2 are arranged on the inlet side of the feed path L for the heated material W so as to face each other with the heated material W interposed therebetween. Similarly, an auxiliary roll R3 and a roll electrode R4 are provided on the exit side so as to face each other. The heated material W is a conductive metal plate such as a steel plate. A slider S is provided between the roll electrodes R2 and R4.
The conductive member 14 is connected via 1 and S2.

The conductive member 14 connected to one end of the transformer 12 is a conductive member 14a disposed above and below the material W to be heated.
1 and 14a2. Further, the conductive member 14 connected to the other end of the transformer 12 is connected to the conductive members 14b1 and 14b2. Conductive members 14a1 and 14b
1 is a conductive member 14 near the energizing rolls R2 and R4, respectively.
It is connected to a2 and 14b2. The conductive member 14a2 is a slider S1 of the energizing roll R2, and 14b2 is a slider S of R4.
Connected to 2. The transformer 12 is connected to the AC power source 10, the voltage supplied from the AC power source 10 is transformed by the transformer 12, and the roll electrode R2 is passed through the conductive member 14.
And R4.

An AC voltage supplied from the roll electrodes R2 and R4 is applied to the material to be heated W in the feed passage sandwiched by the auxiliary roll R1, the roll electrode R2, the auxiliary roll R3, and the roll electrode R4, and the material to be heated W is heated. W is electrically heated.

In the present apparatus, since the conductive members 14 are provided on both sides of the material W to be heated, vibration of the material W to be heated can be prevented. Further, a choke CH is provided on the inlet side of the feed passage to prevent voltage from leaking from the heating zone to the inlet side. Furthermore, immediately before the choke CH, the ground roll R0
1, R02 are provided, and the entrance side is grounded to keep safety.

Roll electrodes R2, R4 and auxiliary roll R
1, R3 have an axial length that is equal to or greater than the width of the material W to be heated
The respective peripheral surfaces are arranged to face each other with a predetermined gap through which the heated material W can pass while being in contact with the respective peripheral surfaces across the feed passage L. The conductive member 14 is formed of a good conductive material such as a copper material having a predetermined width and thickness.

The sliders S1 and S2 are connected to both ends of the conductive member 14 and are slidably contactable with the power receiving portions provided on the rotating shafts of the rolls forming the roll electrodes R2 and R4. There is.

Although not shown, a support roll such as a metal roll, a ceramic coating roll, or a ceramic roll may be provided in the feed passage of the heated material W.

In this apparatus, an AC voltage is supplied from a power source 10, converted into a predetermined voltage by a transformer 12, and supplied to the roll electrodes R2 and R4 through a conductive member 14. As a result, an AC voltage is applied to the heated material W passing through the feed passage between the roll electrodes R2 and R4, and the heated material W is electrically heated.

Next, the temperature control for the material W to be heated, which is performed in the apparatus having such a mechanism, will be described.
The temperature control for the heated material W is performed by the size of the heated material W,
A preset method in which the input to the transformer 12 is set in advance so as to give the heated material W any one of the required power, the required current, and the required voltage which are obtained in advance from the feed rate, the specific heat, the desired temperature rise, etc., And the material to be heated W on the output side of the device
Is measured, and if there is a difference between the measured value and the planned temperature, the feedback method is used to adjust the power corresponding to the difference.

FIG. 1 shows a material W to be heated in the apparatus shown in FIG.
A block diagram of a current setting circuit for temperature control is shown. The expected voltage value V and the actual voltage value Va are input to the comparison section 40. The expected voltage value V is set in advance to a predetermined value based on the desired temperature of the material W to be heated. The actual voltage value Va is the voltage value actually supplied to the device. The comparison unit 40 compares these two voltage values and outputs the difference to the voltage-current conversion unit 42 as an operation amount.

The voltage-current converter 42 divides the input voltage value by the resistance expected value R to convert it into a current value, and PI
It is output to the D calculation unit 44. The PID calculation unit 44 is an adjustment unit that performs PID calculation on the input current value. That is, a predetermined operation is selected from a P (proportional) operation for obtaining an output proportional to the input, an I (integral) operation for obtaining an integrated value of the input as an output, and a D (derivative) operation for obtaining a differential value of the input as an output. Perform calculations by selecting or combining.

The output from the PID calculator 44 is the switch 4
6a. The switch 46a is a switch 4 described later.
6b constitutes a switch, and one of the switch 46a and the switch 46b is closed by the operation of the operator. The output of the switch 46a is sent to the adder 48. The adder 48 adds the outputs of the switches 46a and 46b. However, since one of the switches 46a and 46b is closed and the other is open, the input from either one is output as the output from the adder 48.

The expected power value P and the actual power value Pa are input to the comparison section 50. The expected power value P is set in advance to a predetermined value based on the desired temperature of the material W to be heated. The actual power value Pa is the power value actually supplied to the device. Comparison unit 5
0 compares these two power values and outputs the difference to the power-current converter 52 as an operation amount.

The power-current converter 52 divides the input power value by the product R · cos φ of the resistance expected value R and the power factor expected value cos φ, and converts it into an amount corresponding to the square of the current value. Output to the square root calculator 54. The square root calculator 54 calculates the square root of the input value and calculates the amount corresponding to the current value. It is output to the PID calculator 56. PID calculator 56
Is an adjusting unit that performs PID calculation on the input current value similarly to the PID calculating unit 44.

The output from the PID calculator 56 is the switch 4
Sent to 6b. One of the switches 46b is selected and closed together with the switch 46a as described above.
Therefore, the output from the adder 48 becomes the value sent from either the switch 46a or 46b. Adder 4
The output from 8 is sent to switch 60. Switch 60
Is opened and closed automatically. That is, it is closed in the steady state and opened in the non-steady state.

The output of the switch 60 is sent to one input of the adder 62. The expected current value I is input to the other input of the adder 62. As will be described later, since only one of the input from the switch 60 and the expected current value I is input to the addition unit 62, the one input value is sent to the speed correction unit 64 as it is.

The speed correction unit 64 is a correction unit that corrects the current value input from the addition unit 62 according to the line speed of the material W to be heated. Assuming that the current value required at the predetermined line speed U0 is I0, the current value I in the case of the actual line speed set value U is obtained by the following formula.

[0030]

[Equation 2]

Here, K is a constant, and K = 0.95-
It is 1.05. The speed correction unit 64 corrects the current value according to the line speed in this way, and outputs it to the transformer 12.

In the control circuit as described above, the switch 60 is automatically opened when the material W to be heated is in an unsteady state. As a result, only the expected current value I is input to the adder 62. Therefore, the expected current value I is corrected by the speed correction unit 64 and becomes a current command. Therefore, in this case, the current supplied to the transformer 12 is controlled based on the expected current value I in the steady state.

In the steady state, switch 60 is closed and either switch 46a or 46b is closed. Switch 4 when voltage control is performed
6a is closed, and the data based on the voltage value, which has been PID-calculated by the PID calculator 44, is sent to the adder 62 through the switch 46a, the adder 48, and the switch 60. After being added to the expected current value I input by the adding unit 62, the value is sent to the speed correcting unit 64, and the value on which the above speed correction is performed becomes the current command. Therefore, in this case, the current value supplied to the transformer 12 is set by voltage control based on the expected voltage value V and the actual voltage value Va input to the comparison unit 40.

The switch 46 is used when power control is performed.
b is closed, and data based on the power value, which has been PID-calculated by the PID calculator 56, is sent to the adder 62 through the switch 46b, the adder 48, and the switch 60, and new data is generated as in the case of the voltage control described above. A current command is calculated at. Therefore, in this case, the current value supplied to the transformer 12 is set by the power control based on the expected power value P and the actual power value Pa input to the comparison unit 50.

FIG. 2 shows a material W to be heated in the apparatus shown in FIG.
A block diagram of another embodiment of a current setting circuit for temperature control is shown. In this circuit, a comparator 70, a temperature power converter 72, a PID calculator 74, a switch 76, an adder 8 are provided before the comparator 50 of the circuit of FIG.
0 is added.

The target value T of the temperature and the sampled actual temperature value Ta are input to the comparison unit 70. Comparison unit 70
Compares these values and outputs the difference to the temperature power converter 72 as an operation amount. The temperature-power converter 72 converts the temperature difference input from the comparator 70 into a power difference according to a physical property value such as a specific heat expected value CP, an expected density value m, an expected thickness value H, an expected width value W or a size value. To do. Temperature power converter 7
The output from 2 is sent to the PID calculator 74, and the above-mentioned PI
D operation is performed. The output from the PID calculator 74 is sent to the switch 76.

When sampling control is performed, the switch 76 is closed and the output from the PID calculation unit 74 is sent to the addition unit 80. Therefore, in this case, the sampling control is performed based on the average temperature of the material to be heated W measured at the outlet of the heating zone.

According to each of the above devices, the current value supplied to the transformer 12 is set by current control in the unsteady state, and set by voltage control or power control in the steady state. Therefore, stable and highly accurate temperature control can be performed by voltage control or power control in the steady state, and temperature control can be performed by current control in the unsteady state in which voltage or power cannot be set. Furthermore, extremely stable temperature control can be realized by controlling the temperature of the material to be heated in a steady state by sampling control over the length of the heating zone.

In the heating zone of the material W to be heated having the length L sandwiched between the energizing rolls R2 and R4 in FIG. 3, the specific heat CP of the material W to be heated, the density m, the specific resistance ρ, the thickness H, and the width w. ,
Assuming the resistance R, the supplied voltage V, the current I, the power factor cos φ, and the power P, the rate of change of the temperature T at any point between the energizing rolls R2 and R4 is expressed as follows. dT / dt = V · I cosφ / Cp · m · H · w (1) = (V ² / R) × cosφ / Cp · m · H · w = [V ² / (ρ × L / H × w)] × cosφ / Cp · m · H · w = V ² · cosφ / ρ · L · Cp · m (2) = RI ² cosφ / Cp · m · H · w = (ρ · L / H × w) ・ I ² cosφ / Cp ・ m ・ H ・ w ＝ I ² cosφ ・ ρ ・ L / Cp ・ m ・ H ²・ w ² (3) = P / Cp ・ m ・ H ・ w ...... (4)

Therefore, from the above equation (2), it is understood that in the case of voltage control with constant V, it is affected by the specific resistance ρ, the specific heat CP and the power factor cos φ, but not by the cross-sectional area Hw. . Further, from the equation (3), in the case of current control with constant I, the specific resistance ρ, the specific heat CP, the cross-sectional area Hw
It can be seen that and is affected by the power factor cosφ. Also,
From the equation (4), it can be seen that in the case of power control with P constant, the influence of the specific resistance ρ is not exerted, and the influence of the sectional area Hw is smaller than that in the case of current control.

Therefore, according to the above-mentioned device of the present invention, in the steady state, stable control is performed by the voltage control or the power control which is less influenced by these physical property values.
In the unsteady state, the current value can be set by current control.

In the present apparatus, the non-steady state in which temperature control is performed by current control means, for example, when the equipment W is started, the portion existing in the heating zone while the material W to be heated is stopped is discharged from the heating zone. Until As a specific example, when the heating length is L, the material W to be heated is 1 to
The temperature control is performed by current control in an unsteady state until the length of 1.5 L is fed. Further, when a connecting portion of different materials to be heated W passes through the heating zone, a non-steady state is set while the connecting portion exists in the heating zone.

FIGS. 4 and 7 are views showing a second embodiment of the electric heating mechanism of the electric heating apparatus of the present invention. In this apparatus, an annular transformer 20 is provided as a means for energizing the material W to be heated. The annular transformer 20 is formed by stacking, for example, a silicon steel plate having a property suitable as a magnetic path as a square-shaped member 22 as shown in FIG. The primary coil 24 and the primary coil 24 form a feed passage L for the material W to be heated. That is, the size of the cross-sectional space in the annulus depends on the distance in which the heated material W moves in the width direction, that is, the lateral wobbling, the undulation in the vertical direction, for example, the wave and flap of the plate generated in the case of a thin steel plate, and catenary. In consideration of the bending of the material to be heated W and the like, the material W is allowed to pass in a non-contact state.

The annular transformer 20 may have the structure shown in FIG. That is, the inner space of the iron core 22 is made slightly larger, and a protective partition wall 26 is provided inside the annulus so as to surround the feed passage L for the material W to be heated and which has an annular shape concentric with the iron core 22. The protective partition 26 has one layer or two layers as shown. The protective partition 26 in the case of one layer is made of a non-magnetic material, for example, a metal material such as stainless steel,
This prevents the material W to be heated from coming into contact with the primary coil 24 and being damaged by swaying when passing through the transformer 20 or splashing in an accident such as breakage. In the case of the two-layer protective barrier 26, the non-magnetic metal material is used as the inner layer 26a and the heat insulating material such as heat insulating fiber is used as the outer layer 26b. The primary coil 24 is prevented from burning due to heat. If the material W to be heated is not likely to damage the primary coil 24, one layer may be formed of only a heat insulating material to prevent the primary coil 24 from being burned. Note that the primary coil 24 may be a pipe material, and cooling water for cooling the primary coil 24 may pass through the pipe.

The annular transformer 20 is connected to the power source 10,
When a predetermined voltage is applied from the power source 10 to the annular transformer 20, a secondary voltage is induced in the heated material W corresponding to the secondary side of the transformer, and the heated material W is electrically heated. The number of turns of the annular transformer 20 can be arbitrarily changed by a tap changer (not shown), and the voltage induced in the heated material W can be adjusted. Further, the annular transformer 20 is supplied with power from the power source 10 having a power control switch.

In this apparatus, when power is supplied from the power source 10 to the annular transformer 20, a secondary voltage is induced in the material W to be heated, and the secondary current generated in the material W to be heated passes through the sliders S1 and S2. It will flow as a return line through the conductive member 14 connected through. In this case, the resistance of the conductive member 14 is
Since the resistance is set to be significantly smaller than the resistance of the heated material W, most of the current is consumed for heating the heated material W, and the loss in the conductive member 14 is small. Therefore, the material W to be heated is efficiently energized and heated, and most of the voltage generated in the material W to be heated is consumed inside the material W to be heated, and the voltage applied to the energizing rolls R2, R4 and the conductive member 14 is It is very low and can prevent damage to the equipment arranged around the heating device, while keeping the operator safe.

FIG. 5 is a view showing a third embodiment of the electric heating mechanism of the electric heating apparatus of the present invention. In this device, an annular transformer 20 is provided in a part of the feed passage of the material to be heated W. Therefore, the conductive members 14 are arranged on both the upper and lower sides of the annular transformer 20, and the parts where the annular transformer 20 is not arranged around the heated material W are disposed close to the upper and lower sides of the heated material W. There is.

FIG. 6 is a diagram showing a fourth embodiment of the electric heating apparatus of the present invention. In this apparatus, a metal bath 30 is provided instead of the roll electrode R4 of the apparatus shown in FIG.
The metal bath 30 is configured by filling a bath 31 with molten metal 32, and the end of the conductive member 14 is immersed in the molten metal 32. The material W to be heated which is heated by electric current is changed in direction by the direction changing roll R5, is immersed in the molten metal 32, is changed in direction by the direction changing roll R6, and is discharged. In addition, the conductive member 14 is a roll electrode R1,
Immediately after R2, it is divided into an upper part 14a and a lower part 14b, and is combined into one immediately before the direction changing roll R5, and immediately after the direction changing roll R5, it is again divided into an upper part 14c and a lower part 14d, and an upper part. 14c, lower part 14d
Are respectively immersed in the molten metal 32.

Therefore, the metal bath 30 has the same action as that of the roll electrode R4 of FIG. 5, and the voltage induced in the material W to be heated by the annular transformer 20 is passed through the roll electrode R2 and the metal bath 30 to the conductive member 14. And the heated material W is heated.

Although not shown, the metal bath 30 may be used instead of the roll electrode R4 in the apparatus shown in FIG. 3 or FIG.

In the case where the outlet side is constituted by the metal bath 30 as described above, when the connecting portion of the materials W to be heated made of different materials has a heating length of L before the inlet side energizing roll, (0.8 to
From the time of reaching 1.2) L to the time of moving by (2.4 to 3.6) L, the current setting value is temporarily set to 1.0 to
It is preferably 1.05 times.

In each of the above embodiments, the roll electrode R
At 2 and R4, the dust in the atmosphere and the dust brought in by the heated material W may be gradually accumulated. When making poor contact with the heated material W, a roll cleaner may be arranged. is there.

Further, the auxiliary rolls R1 and R3 may be replaced with roll electrodes R1 and R3 made of a conductive material. In this case, the roll electrodes R1 and R3
The conductive member 14 may be connected between the two.

As an additional note, the device of the present invention can be arranged not only horizontally or vertically but also at any angle.

[0055]

According to the present invention, the heating temperature of the material to be heated is controlled by the current control means in the unsteady state and is controlled by the power control means or the voltage control means in the steady state. Be seen. Therefore, even when the power or voltage cannot be determined during an unsteady state, such as immediately after the device is started up or when the joints of materials of different sizes are being passed, it is possible to control the temperature of the material to be heated by controlling the current. Temperature control can be performed. Further, in the steady state, stable control that is strong against disturbance can be performed by controlling the power or voltage.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a current setting circuit for controlling the temperature of a material W to be heated of an electric heating apparatus according to the present invention.

FIG. 2 is a block diagram of another embodiment of a current setting circuit for controlling the temperature of the material to be heated W of the electric heating apparatus of the present invention.

FIG. 3 is a schematic configuration diagram showing a first embodiment of an energization mechanism of the energization heating device.

FIG. 4 is a schematic configuration diagram showing a second embodiment of the energization mechanism of the energization heating device.

FIG. 5 is a schematic configuration diagram showing a third embodiment of the energization mechanism of the energization heating device.

FIG. 6 is a schematic configuration diagram showing a fourth embodiment of the energization mechanism of the energization heating device.

FIG. 7 is a cross-sectional view showing an annular transformer used in an electric heating device.

FIG. 8 is a cross-sectional view showing an annular transformer used in an electric heating device.

[Explanation of symbols]

 10 power supply 12 transformer 14 conductive member 20 annular transformer 30 metal bath 40 comparison unit 42 voltage / current conversion unit 44 PID calculation unit 48 addition unit 50 comparison unit 52 power / current conversion unit 54 square root calculation unit 56 PID calculation unit 62 addition unit 64 speed correction Part 70 Comparison part 72 Temperature power conversion part 74 PID calculation part 80 Addition part R1, R3 Auxiliary rolls R2, R4 Roll electrodes S1, S2 Sliding element W Heated material L Feed path

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-3-8286 (JP, A) JP-A-63-128125 (JP, A) JP-A-59-198684 (JP, A) JP-A-56- 152919 (JP, A)

Claims (11)

[Claims] 1. A continuously fed material to be heated is brought into contact with a roll electrode arranged on the inlet side of a feed passage of the material to be heated, and a conductive mechanism is provided on the outlet side of the material to be heated. In an apparatus for electrically heating the material to be heated by bringing them into contact, the apparatus comprises a current control unit that controls a heating temperature of the material to be heated by controlling an electric current supplied to the material to be heated, A power control unit that controls the heating temperature of the heated material by controlling the power supplied to the heated material, and the heating temperature of the heated material by controlling the voltage supplied to the heated material. And a voltage control means for controlling the heating temperature of the material to be heated by control by the current control means in a non-steady state, and in the steady state, the power control means and the voltage control hand. Resistance heating apparatus, characterized by controlling the heating temperature of the material to be heated by the control of either. 2. The current control means at the start of facility operation of the electric heating device until a portion of the heated material existing in the heating zone is discharged from the heating zone while the heated material is stopped. 2. The heating temperature of the material to be heated is controlled by the control according to, and thereafter, the heating temperature of the material to be heated is controlled by the control by either the power control means or the voltage control means. The electric heating device described. 3. The material to be heated is controlled by the current control means while the connecting portion is present in the heating zone of the material to be heated when passing through the connection portion connecting different materials of the material to be heated. 2. The electric heating apparatus according to claim 1, wherein the heating temperature of the heated material is controlled, and then the heating temperature of the material to be heated is controlled by the control of either the power control means or the voltage control means. 4. The current-carrying heating device further comprises temperature measuring means for measuring the temperature of the material to be heated on the outlet side of the heating zone of the material to be heated, and the material to be heated measured by the temperature measuring means. 4. The sampling control means for correcting the control by the electric power control means by performing sampling control with a corresponding length of the heating zone of the material to be heated based on the temperature. The electric heating device described. 5. When the facility operation of the electric heating device is started, the length of the electric heating device is L, and the material to be heated is fed by a length of (1 to 1.5) L. The heating temperature of the material to be heated is controlled by the control of the current control means, and then the heating temperature of the material to be heated is controlled by either the power control means or the voltage control means. The electric heating device according to claim 2. 6. The electric heating device further comprises temperature measuring means for measuring the temperature of the material to be heated on the outlet side of the heating zone of the material to be heated, wherein the temperature of the material to be heated is used as a feedback value. The electric heating device according to any one of claims 1 to 3, which is controlled by a voltage control means. 7. The current control means sets a current I in the case of an actual line speed U to a voltage V0 required in the case of a predetermined line speed U0 as K = 0.95 to 1. As 05, The electric heating device according to any one of claims 1 to 6, wherein: 8. The heating device further comprises a power supply means for supplying an AC voltage between the roll electrode and the conductive mechanism, and the heated source is supplied from the power supply means through the roll electrode and the conductive mechanism. The electric heating device according to claim 1, wherein the material to be heated is heated by supplying electric current to the material. 9. The electric heating device further includes an annular transformer disposed between the roll electrode and the conductive mechanism, the annular transformer being connected to a power source and the inside of the ring feeding the material to be heated. The heating member is heated by a voltage induced in the heating target material by the annular transformer, and the conductive member is provided in the feeding path of the heating target member in which the annular transformer is disposed. Is arranged close to the outer circumference of the annular transformer.
The electric heating device according to any one of 1. 10. The electric heating device according to claim 1, wherein the conductive mechanism is a roll electrode arranged on an outlet side of a feed passage of the material to be heated. 11. The conductive mechanism is a metal bath arranged on an outlet side of a feed passage of the heated material, the heated material is fed through the metal bath, and the conductive member has an end portion. The electric heating device according to any one of claims 1 to 9, wherein the electric heating device is immersed in a metal bath.