JPH0864343A - Power feeding device for electric heating and power feeding method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a power feeding device and a power feeding method for current heating capable of performing stable power feeding and uniform heating to a metal material such as a metal plate by heating the material to be heated. [Composition] An energization heating power supply device for heating by heating an electrode by bringing the electrode into contact with the material to be heated, in which a metal having a melting point lower than that of the material to be heated is provided on an electrode surface facing the material to be heated. It is a power supply device for heating, and it is preferable to further provide a temperature control mechanism for the low melting point metal. Further, in the energization heating, the metal having a lower melting point than the material to be heated is energized in a state of being in contact with both the electrode and the material to be heated, and the low melting point is softened or melted by resistance heating during energization and / or external heating. This is a method of feeding power to a metal plate in direct energization in which power is fed through a metal. Further, it is preferable to soften, melt or solidify the low melting point metal by controlling the temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power feeding device and a power feeding method used for energizing and heating when a material such as a metal plate is brought into contact with an electrode to be energized to heat or heat the material.

[0002]

2. Description of the Related Art Conventionally, induction heating or direct current heating has been adopted as a method for heating a metal material such as a metal plate. However, since induction heating uses high frequency, the equipment is complicated and expensive.
Further, since the heating efficiency is low, the adoption of direct electric heating has recently been considered.

As a method for electrically heating a metal plate, as shown in FIG. 7, a pair of current-carrying pinch rolls 21, one of which is one of the upper and lower two or two of which are current-carrying electrode rolls, is used as the metal plate. The power feeding roller 22 is sandwiched between two points 23 in the longitudinal direction.
Has been proposed to continuously heat the running metal plate 23 by supplying power to the current-carrying electrode roll 21 from the two and supplying current to the metal plate 23 between the two sets of the current-carrying pinch rolls 21 (Japanese Patent Application Laid-Open No. Hei 3 (1999)). -8286).

When power is supplied by using such an energizing pinch roll, the contact arc length between the energizing pinch roll and the metal plate is usually 1 mm or less, although it depends on the pressing pressure and the roll diameter. Therefore, especially when the thickness of the metal plate to be heated is large, the contact area between the energizing pinch roll and the metal plate is very small compared to the cross-sectional area (width x thickness) of the metal plate, so the current flows at the contact part. Current density increases. Further, since the contact resistance becomes larger than the resistance of the metal plate itself, local heating occurs at the contact portion of the energizing pinch roll, and the heating temperature becomes nonuniform.

Further, since the thick metal plate has a high rigidity, if there is a slight unevenness of the plate surface or a warp in the plate width direction, the contact with the energizing pinch roll becomes uneven in the width direction, and the current density in the plate width direction is reduced. A difference occurs, resulting in uneven heating in the plate width direction. Also,
The current locally concentrates in the width direction at the contact part with the energizing pinch rolls, resulting in extremely high temperature. Further, a local current concentration causes a spark, which causes a problem such as a surface flaw called a spark mark on the surface of the metal plate.

Further, the thick metal plate has a larger heat capacity than the thin metal plate, and the cut plate material has a limited plate length, so that there is a problem that the distance between two sets of energizing pinch rolls cannot be long. When the plate is heated while traveling, it requires a huge amount of current because it is heated within a limited time until it passes between the energizing pinch rolls, and the equipment becomes large-scale.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, which have been a problem in the prior art, when heating a material to be heated such as a metal plate by directly energizing, and to generate uniform heating and sparks. An object of the present invention is to provide a power supply method and a power supply device that suppress the above-mentioned problem and enable stable electric heating.

[0008]

As a result of examining the above problems, it is important for the present inventors to stabilize the contact condition between the electrode and the material to be heated in order to uniformly heat and suppress the generation of sparks. From this point of view, the present invention has been completed.

The present invention is a power supply device for electric heating for heating an electrode by bringing the electrode into contact with a material to be heated and applying current thereto, wherein a metal having a melting point lower than that of the material to be heated is opposed to the material to be heated. It is preferable that the temperature control mechanism for the low melting point metal is further provided.

As another aspect, in the energization heating, energization is performed in a state where a metal having a melting point lower than that of the material to be heated is in contact with both the electrode and the material to be heated, and resistance heating and / or external This is a method of feeding power to a metal plate in direct energization in which power is fed through the low melting point metal that is softened or melted by heating. Further, it is preferable to soften, melt or solidify the low melting point metal by controlling the temperature.

[0011]

The details of the present invention will be described below.

The material to be heated according to the present invention may be any metal material which is heated by generating Joule heat by energization, and generally, carbon steel, low alloy steel, stainless steel and the like can be mentioned.

Further, the shape of the material to be heated is not limited to the plate-shaped material (strip plate, cut plate), but the material to be heated of the power feeding device can be used for various shapes of metal materials such as tubular materials and rod-shaped materials. The present invention can be applied by changing the shape of the contact portion, but in the following description, a metal plate will be described as an example.

FIG. 1 (a) is a longitudinal sectional view of a metal plate of an example of the power feeding device 10 of the present invention, and FIG. 1 (b) is a sectional view in the width direction thereof. The low melting point metal 4 is provided on the surface of the electrode 1 that faces the metal plate 5 that is the material to be heated. Further, in order to prevent the low melting point metal 4 from flowing out from the surface of the electrode 1 facing the material to be heated when it is heated, it is surrounded by a frame 3 fixed to the electrode 1 around the electrode 1 in FIG. The low melting point metal 4 is provided between the frame 1, the frame 3 and the metal plate 5.

A cushion member 6 is attached to a portion of the frame 3 that comes into contact with the metal plate 5, and the cushion member 6 presses the power supply device 10 against the metal plate 5 with an appropriate pressing force to soften or melt the low-temperature material. The melting point metal 4 is prevented from flowing out of the frame 3.

Copper or the like having good conductivity is generally used for the electrode 1. Further, since the frame 3 is exposed to a high temperature atmosphere and comes into direct contact with the low melting point metal, a material such as ceramics having excellent heat resistance and wear resistance is suitable, and the cushion material 6 is used when the low melting point metal 4 is melted. However, it is used to prevent the metal from leaking to the outside, but since it is in direct contact with the metal plate 5 and the low melting point metal 4 which are the materials to be heated, it is preferable to use a material such as an alumina-silica material having excellent heat resistance and a low bulk density. Is preferred.

The low melting point metal 4 may be any metal having a melting point lower than that of the metal plate, and for example, lead having a melting point of about 330 ° C. or tin having a melting point of about 230 ° C. is preferably used.

The low melting point metal 4 is the low melting point metal 4 at the time of electric heating.
Although it may be softened and melted by using the heat generated by the resistance heat of itself and the heat generated by the resistance heat of the metal plate 5, in order to improve the heating efficiency and more accurate temperature control, the heater 7 provided on the outer periphery of the electrode 1 may be used. The low melting point metal 4 may be softened and melted.

Further, the temperature control of the low melting point metal 4 and the electrode 1
In order to prevent wear and damage due to abnormal heating of the
The cooling water channel 2 may be provided inside. This allows the electrode 1
It is possible to prevent abnormal temperature rise. Furthermore, electrode 1
The low-melting-point metal 4 is cooled by way of the metal and the low-melting-point metal 4 is immediately solidified at the time point when the electric heating is completed.
Even when the metal is separated from the metal plate 5, the low melting point metal can be prevented from flowing out.

Furthermore, by adjusting the flow rate of the cooling water flowing in the cooling water passage 2, the temperature of the low melting point metal 4 can be controlled and the low melting point metal 4 can be maintained under appropriate conditions of softening, melting and solidification. In addition to water, oil or the like may be used as the fluid flowing in the cooling water passage 2, and the fluid may be heated and cooled in advance in order to ensure temperature control.

FIG. 2 shows an example of a power feeding method using the power feeding device 10 of the present invention. The power supply device 10 shown in FIG. 1 is arranged on the upper surfaces of both ends of the region where the metal plate 5 needs to be heated,
The heating power source 8 and the short-circuit member 9 energize the metal plate 5 between the power supply devices 10 to heat it.

At room temperature, the low melting point metal 4 is solid, but when the energization is started, the temperature rises due to resistance heating like the metal plate 5, and the metal 4 melts when it softens or reaches the melting point. If the softening or melting is insufficient, the electrode 10 for electric heating is heated.
The low melting point metal 4 may be heated by the heater 7 incorporated therein to be softened and melted.

Since the melted or softened low melting point metal 4 fills the space between the metal plate 5 and the electrode 1 without a gap, the low melting point metal 4
The contact between the metal plate 5 and the metal plate 5 is uniform, and stable power supply can be performed. On the other hand, when the heating is completed, water or the like is sent to the cooling water passage 2 to cool the power feeding device 10 and solidify the low melting point metal 4, so that the low melting point metal 4 is separated even when the power feeding device 10 is separated from the metal plate 5. Can be removed integrally with the power supply device 10 without flowing out, and the low melting point metal 4 does not remain on the metal plate 5.

Furthermore, since the temperature of the power feeding device 10 can be prevented from being raised by cooling from the cooling water passage 2, the heat resistance limit of the cushion material 6 and the frame 3 which are in direct contact with the heated metal plate 5 or exposed to a high temperature atmosphere. It is possible to heat the metal plate 5 to the temperature of.

It is desirable that the width of the power feeding device 10 is approximately the same as the width of the metal plate 5. However, since there are various widths of the metal plate in the actual operation, as shown in FIG. It is also possible to arrange a plurality of the power supply devices 10 in the width direction and select the number of power supply devices 10 to be used according to the width of the metal plate to supply power.

Further, although it is desirable to carry out the direct energization of the present invention to a material to be heated in a stationary state, for example, by sliding the energization heating electrode 10 on the metal plate 5 relatively, It can also be used for the plate 5.

[0027]

EXAMPLES The effects of the present invention will be described with reference to examples.

FIG. 4 is a diagram showing the dimensions of the power feeding device used in the present test of the structure shown in FIG. (The unit of the numbers in the table is mm.) The effect of electric heating of the present invention was examined using the power supply device.

The electrode 1 is made of copper, the frame 3 is made of alumina, and the cushion material 6 is made of an alumina-silica composite material (80% Al ₂ O ₃ + 20% SiO ₂ ) having a bulk density of 0.12 g / cm ³ , Lead was used as the melting point metal. The thickness of the cushion material is 5 mm in Fig. 4, but it is 2.5 mm when the electrode for electric heating is pressed against the steel plate.
Compressed up. The heater for heating low-melting-point metal is a nichrome wire with a diameter of 1 mm whose surface is covered with a heat-resistant insulator.
The surface was wound on the electrode at a pitch of 5 mm.

Further, as a comparison this time, a test was performed by the conventional power feeding method shown in FIG. The power supply pinch roll used had a diameter of 200 mm and a roll barrel width of 400 mm.

The material to be heated (metal plate) to be tested is 3
A 40 kg carbon steel plate having a thickness of 0 mm, a width of 250 mm and a length of 600 mm was used.

Table 1 shows the heating condition when the steel sheet temperature is electrically heated to about 600 ° C. The maximum current during energization heating is 80000A, and the temperature difference in the steel sheet width direction is a value excluding the supercooled region at the steel sheet end. In addition, the contact area between the steel plate and the power feeding part of the conventional power feeding method is the value obtained by calculating the contact arc length from the roll pressing load and the roll diameter, and the maximum current density is the value obtained by dividing the maximum current by the contact area. is there.

According to Table 1, the current density in the power feeding section exceeds 1000 A / mm ² in the conventional power feeding method, whereas the current density in the conventional power feeding method of the present invention is 10 A / 100 which is 1/100 of the conventional current density. I was able to hold down to about ² mm ² . Also, FIG.
FIG. 4 is a diagram showing a temperature distribution in the width direction at the center of the steel sheet in the longitudinal direction. In the power feeding method of the present invention, a temperature distribution in the steel sheet width direction hardly occurs, whereas in the conventional power feeding method, about 7
There is a temperature variation of 0 ° C.

[0034]

[Table 1]

Further, in the conventional power feeding method, the current locally concentrates at the power feeding point and seizure of the roll and the steel plate occurs, so that FIG.
Although a seizure trace as shown in Fig. 3 remained on the surface of the steel sheet, seizure did not occur in the power feeding method of the present invention.

After the energization is completed, liquid lead is solidified by flowing water through the cooling water passage inside the electrode to cool it, and it can be integrated with the power feeding device and removed. Lead pieces remain on the steel plate surface. I didn't do it.

Next, Table 2 shows the results of an investigation of the temperature distribution in the width direction of the steel sheet when electrically heated to various temperatures by the power feeding method of the present invention, in comparison with the current heating method by the same conventional method as above. Show. According to the power feeding method of the present invention, the difference in the temperature distribution in the width direction is reduced in a wider heating temperature range as compared with the conventional power feeding method, and the temperature of the metal plate is accurately controlled in heating or heat treatment of the metal plate. It is possible.

[0038]

[Table 2]

[0039]

By using the power feeding device and the power feeding method of the present invention, stable power feeding to a metal material such as a metal plate can be achieved.
The metal plate can be heated uniformly and accurately.

[Brief description of drawings]

1A is a longitudinal sectional view of a metal plate of an example of a power feeding device of the present invention, and FIG. 1B is a sectional view in the width direction thereof.

FIG. 2 is a diagram showing an example of a power feeding method of the present invention.

FIG. 3 is a diagram showing a power feeding method when a plurality of power feeding devices shown in FIG. 1 are installed in a metal plate width direction.

4A and 4B are diagrams showing the dimensions of the power feeding device used in the present test of the structure shown in FIG. 1, in which FIG. 4A is a longitudinal sectional view of the metal plate, and FIG. 4B is a sectional view in the width direction thereof.

FIG. 5 is a diagram showing a width-direction surface temperature distribution at the center of the steel sheet in the longitudinal direction when the steel sheet is heated to about 600 ° C.

FIG. 6 is a diagram showing traces of seizure between a current-carrying roll and a steel plate by a conventional power feeding method.

FIG. 7 is a diagram showing a conventional power feeding method.

[Explanation of symbols]

 1: Electrode 2: Cooling water channel 3: Frame 4: Low melting point metal 5: Metal plate 6: Cushion material 7: Heater 8: Power supply 9: Short-circuit member 10: Power supply device

Claims (4)

[Claims] 1. A power supply device for energization heating, wherein an electrode is heated by bringing an electrode into contact with a material to be heated and conducting electricity, wherein a metal having a melting point lower than that of the material to be heated faces the material to be heated. A power supply device for electric heating, which is provided in the. 2. The power supply device for electric heating according to claim 1, further comprising a temperature control mechanism for the low melting point metal. 3. A power feeding method of energization heating, wherein heating is performed by bringing an electrode into contact with a material to be heated and conducting electricity, wherein a metal having a melting point lower than that of the material to be heated is brought into contact with both the electrode and the material to be heated. A method for supplying power to a metal plate in direct energization, which is characterized in that energization is performed in this state, and power is supplied through the low melting point metal softened or melted by resistance heating and / or external heating during energization. 4. The low melting point metal is softened by temperature control,
The method for supplying power to a metal plate in direct energization according to claim 3, wherein the method is to melt or solidify.