JPH06179925A - Energizing method to band metal in energizing heating for band metal - Google Patents

Abstract

PURPOSE:To solve a problem generating the spark between an energizied roll and a band metal, at the time of energize-heating the band metal by conducting the current on the band metal to heat the band metal by Joule's heat CONSTITUTION:Electrolyts solution vessels 2 are arranged at the starting end and the finishing end in the range of heating the metal strip 1, and an energizing electrodes 3 are arranged in the electrolytic solution vessels 2. Both energizing electrodes 3 arranged in the electrolytic solution vessels 2 at the starting end and the finishing end are connected with an electric conductive member 5 to constitute a closed circuit containing the band metal 1, electrolytic solution 4, energizing electrodes 3 and the electric conductive member 5. The band metal 1 is passed through the electrolytic solution vessels 2 so as to face to the energizing electrodes 3 in the non-contact condition and the energization is executed to the band metal 1 from the energizing electrodes 3 through the electrolytic solution 4 in the non-contact condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for energizing a metal strip when the metal strip is heated by energization for continuous heat treatment.

[0002]

2. Description of the Related Art As a heating method for continuously heat treating a metal strip such as a cold-rolled steel sheet, as described in Japanese Patent Publication No. 60-26818, the metal strip is directly energized via an energizing roll, There is a method of heating by the Joule heat of the metal band itself. Further, as described in Japanese Patent Application Laid-Open Nos. 1-142032 and 1-187789, current-carrying rolls are provided in front of and behind a metal band passage that penetrates an annular transformer, and both current-carrying rolls are connected by a conductive member. Then, a closed circuit is constituted by the metal band, the current-carrying roll and the conductive member, and an induction current is generated by using the closed circuit as a secondary coil by supplying an alternating current from an external power source to the annular transformer. There is a method of heating the metal strip with heat.

A method of directly applying an electric current to these metal strips and heating them with Joule heat is as follows: direct fire type non-oxidizing heating, radiation tube heating,
Compared with heating by heat transfer such as indirect electric heating, the heating capacity per unit time is higher, the equipment can be made compact, and the atmosphere in the heating zone can be easily maintained, which is excellent. However, in both cases, since the metal strip is energized via the energizing roll, the contact between the surface of the energizing roll and the surface of the metal strip is not sufficient, and there is a problem that sparking occurs when the current density is increased to increase the heating rate. That is, since a metal strip such as a cold-rolled steel sheet has a wide strip width and the flatness in the width direction is not always perfect, the surface of the current-carrying roll and the surface of the metal strip are partially separated from each other during striping, and sparks are generated here. As a result, melting damage flaws are generated on the surfaces of both the current-carrying roll and the metal strip, which causes quality deterioration.

As a means for solving this problem, in Japanese Utility Model Laid-Open No. 61-82954, a pressing roll is provided in the vicinity of the energizing roll to prevent the metal band from swinging, thereby contacting the energizing roll with the metal band. A device that prevents the occurrence of sparks by preventing fluctuations in the starting point, and by providing an enclosure that surrounds the metal band that is being electrically heated by a non-oxidizing atmosphere to prevent the formation of an oxide film on the surface of the metal band. Have been described.

Further, in Japanese Patent Application Laid-Open No. 61-242768, when current is applied from a current-carrying roll to a rolled material such as a sheet bar in order to heat and join the ends of the sheet bar, a description will be given of the relationship between the current-carrying roll and the rolled material. As a means for reducing the contact resistance between the rolled materials, a method is described in which the rolled material is energized while being rolled at a rolling reduction of 1% or more. Similarly, the actual development 61
In JP-A-206668, by sandwiching a metal strip with an energizing roll, it is possible to prevent contact failure between the energizing roll and the metal strip even if the metal strip has a defective shape.
A device for preventing the occurrence of sparks is described.

Further, British Patent No. 718835 uses a bath of a conductive liquid such as mercury or molten lead as an airtight valve when performing continuous heat treatment by passing a metal strip through a furnace in a controlled atmosphere. Is described.
This is a closed circuit composed of a metal strip, a conductive liquid in a bath that is an airtight valve, and a conductive member that connects the inlet and outlet baths, and an annular transformer that surrounds the furnace is used in this closed circuit. An induction current is generated and Joule heat is used to heat the metal strip.

[0007]

However, these means are not sufficient as means for preventing the occurrence of sparks between the surface of the current-carrying roll and the surface of the metal strip.

That is, in the apparatus disclosed in Japanese Utility Model Laid-Open No. 61-82954, sparks are often generated in the vicinity of the contact start portion between the energizing roll and the metal strip, which causes a slight variation in the contact start point due to the swing of the metal strip. It is thought that sparks are likely to occur because it occurs, and the press roll prevents the metal strip from swinging.However, even if the metal strip can be prevented from swinging, the metal strip still has a defective shape. Since there is a slight variation in the contact start point, the spark is not completely prevented even if there is no shake.

Further, the device disclosed in Japanese Utility Model Laid-Open No. 61-206668 prevents contact failure by sandwiching the metal strip with a current-carrying roll, that is, by pressing it down and pressing it, even if the metal strip has a defective shape. However, if the metal strip with a bad shape cannot be pressed with high-pressure lower force to hold down the bad spot, the contact area cannot be increased. In this case, the prevention of contact failure becomes insufficient, and there is a possibility that vibration or meandering may occur and stable plate passing may not be possible. The method described in JP-A-61-2242768 is intended to reduce the contact resistance at the time of energizing a rolled material such as a sheet bar so as to secure an energization amount necessary for heating. It is not intended to prevent the occurrence of sparks during energization, so it is not clear whether it can be used for metal strips as it is, and even if it is adopted, it is intended to increase the contact area by applying reduction. Has the same drawbacks as the device described in Japanese Utility Model Laid-Open No. 61-206668.

Further, as described in British Patent No. 718835, a bath of a conductive liquid such as mercury or molten lead is used as an airtight valve, and this can be energized as an electrode to a metal strip. Anyway as an experiment,
It is industrially difficult to implement due to problems such as cost, environmental pollution, and carrying out of conductive liquid due to metal bands.

The present invention further aims to provide a method of energizing a metal strip without generating sparks, in order to further utilize the advantages of the above-described energization heating method.

[0012]

Means for Solving the Problems The gist of the present invention is to pass an electric current through a metal strip and heat the metal strip by Joule heat. A non-contact metal foil in the electrolysis heating of the metal strip, characterized in that it is passed in the electrolyte solution tank while facing the current-carrying electrode in a non-contact manner and energizing the metal strip in a non-contact manner from the current-carrying electrode through the electrolyte solution. Is a method of energizing. As a specific embodiment, the electrolyte solution tank is provided at the beginning and the end of the region for heating the metal strip, and both conducting electrodes installed in the electrolyte solution bath at the beginning and the end are connected by a conductive member to form the metal strip and the electrolyte. A solution, a current-carrying electrode, and a closed circuit that includes a conductive member, and a mode in which current is applied to the metal strip in a non-contact manner from the current-carrying electrode through the electrolyte solution, the starting end of a region for heating the metal strip in the electrolyte solution tank or Provided on either one of the terminal ends, provided with an energizing roll at the other end, and connecting the energizing electrode and the energizing roll installed in the electrolyte solution tank with a conductive member, a metal strip, an electrolyte solution, an energizing electrode, and a conductive member. It is possible to adopt a mode in which a closed circuit including a conductive member and an energizing roll is configured to energize the energizing electrode from the energizing electrode to the metal strip in a non-contact manner via the electrolyte solution. The electrolyte solution is, for example, NH ₄ N having a high conductivity.
O ₃ , NaNO ₃ , (NH ₄ ) ₂ SO ₄ , HCl or the like can be used.

[0013]

In the present invention, the metal strip is energized from the current-carrying electrode through the electrolyte solution without contact. for that reason,
Even if the metal strip has a runout or a defective shape, the problem of contact failure as in the case of the energizing roll does not occur, and the occurrence of spark can be completely prevented. Therefore,
It is possible to solve the problem of melting damage flaws on the surfaces of both the current-carrying roll and the metal strip due to the spark, and eliminate the cause of the quality deterioration.

Further, as compared with the case of using mercury or molten lead, there is no problem of environmental pollution, and the problem of carrying out the electrolyte solution by the metal strip can be easily solved by washing the metal strip with water.

When a current is passed through the electrolyte solution, bubbles may be generated and adhere to the electrodes due to electrolysis, which may reduce the contact area between the electrodes and the electrolyte solution. This can be easily solved by preventing bubbles from adhering to the electrode.

An embodiment of the present invention is shown in FIGS.

FIG. 1 shows a mode in which the heating region is energized in a non-contact manner at both ends of the start end and the end. In this case, the electrolytic solution tank 2 is provided at the starting end and the terminating end of the heating area to form a closed circuit including the metal strip 1, the electrolytic solution 4, the current-carrying electrode 3, and the conductive member 5. Then, when an alternating current is passed from the outside through the annular transformer 7 that surrounds the metal band passage, an induced current is generated in the closed circuit, and the metal band 1 and the current-carrying electrode 3 are energized without contact via the electrolyte solution 4. To be done.

The present invention can also adopt a mode in which current is applied to only one of the beginning and the end of the heating region of the metal strip through the electrolytic solution. FIG. 2 shows that the inner end is energized through an electrolytic solution and the start end is energized by a conventional energizing roll 6. For example, in the case where there is a problem that a spark occurs due to a high temperature only in the current-carrying roll at the end of the heating region, the problem can be solved by the mode shown in FIG.

The above embodiment is a case where the present invention is applied to an electric heating method in which an electric current is applied to a metal strip by using an annular transformer. However, the external power source method described in Japanese Patent Publication No. 60-26818 is used. The present invention can be applied to an electric heating method. In this case, the annular transformer 7 shown in FIGS. 1 and 2 may be removed and the conductive member 5 may be connected to an external power source.

[0020]

EXAMPLES The present invention was carried out in the mode shown in FIG. 1 at a line speed of 300 mpm using a steel plate having a thickness of 0.2 mm and a width of 1000 mm as a metal strip. 40 ℃ as electrolyte solution
(NH ₄ ) ₂ SO ₄ 30 wt% solution (conductivity 270
mS / cm), a 2 m × 1 m Pt electrode was used as a current-carrying electrode, the distance between the metal strip and the current-carrying electrode was 20 mm, and a current of 36000 A was applied at a voltage of 100 V.

As a result, the steel sheet could be heated up to 800 ° C., but no spark was generated from the current-carrying electrode to the steel sheet. Also, the electric resistance of the metal strip R ₁ = 2.87
The electrical resistance R ₂ = 0.
37mΩ, heating efficiency = R ₁ / (R ₁ + R ₂ ) =
It was 0.88, and there was no problem in heating efficiency.

[0022]

According to the present invention, the current density applied to the metal strip can be increased without generating sparks.
As a result, it is possible to further utilize the advantages of the electric heating method for the metal strip.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention.

[Explanation of symbols]

 1 Metal Band 2 Electrolyte Solution Tank 3 Energizing Electrode 4 Electrolyte Solution 5 Conductive Member 6 Energizing Roll 7 Annular Transformer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Susumu Yamaguchi 20-1 Shintomi, Futtsu City, Chiba Shin Nippon Steel Co., Ltd. Technology Development Division

Claims (3)

[Claims] 1. A current-carrying electrode is provided in an electrolyte solution tank, wherein a current-carrying electrode is installed in an electrolyte solution tank when the metal band is heated by applying an electric current to the metal band by Joule heat. A non-contacting electric current is applied to the metal strip through the electrolysis electrode through the electrolytic solution to the metal strip in a non-contact manner. 2. The metal strip and the electrolyte solution are provided by providing the electrolyte solution bath at the beginning and the end of a region for heating the metal strip, and connecting both conducting electrodes installed in the electrolyte bath at the beginning and the end by a conductive member. 2. A metal for electric heating of a metal strip according to claim 1, wherein a closed circuit including a conductive electrode, a conductive electrode, and a conductive member is formed, and electric current is applied to the metal strip from the current-carrying electrode through an electrolyte solution in a non-contact manner. How to energize the belt. 3. The electrolyte solution tank is provided at either the beginning or the end of a region for heating a metal strip, and the other end is provided with an energizing roll, and the energizing electrode and the energizing roll installed in the electrolyte solution tank. To form a closed circuit including a metal band, an electrolyte solution, a current-carrying electrode, a conductive member, and a current-carrying roll by connecting a conductive member, and the current-carrying current is applied to the metal band through the electrolyte solution in a non-contact manner. The method for energizing a metal strip according to claim 1, wherein the metal strip is electrically heated.