JP2001192899A - Electrolytic cleaning method and device for steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic cleaning method and device which can inexpensively prevent stains generated on the surface of a steel strip existing in an electrolytic cell during the stoppage of traveling of the steel strip. SOLUTION: The residual voltage occurring in the residual charges within the electrolytic cell when the steel strip stops traveling in cleaning the electrolytic cleaning of the steel strip by allowing the steel strip to travel in the electrolytic cell is specified to <=3 V.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for electrolytically cleaning a steel strip, and more particularly, to an electrolytic cleaning method capable of preventing stains generated on the surface of a steel strip in an electrolytic cell when the running of the steel strip is stopped. And an apparatus.

[0002]

2. Description of the Related Art In a process of manufacturing a steel strip such as a thin steel strip, after cold rolling, and before performing annealing and temper rolling, deposits on the steel strip surface are removed to clean the steel strip surface. For this reason, electrolytic cleaning of a steel strip is performed using an electrolytic cleaning apparatus.

FIG. 1 shows an example of the arrangement of the main equipment of a steel strip electrolytic cleaning line provided with an electrolytic cleaning apparatus. In FIG. 1, S
Is a steel strip, 1 is a rewinding device, 2 is an inlet side treatment section, 3 is a dipping tank (dunk tank), 4 and 6 are scrubber brushes, 5 is an electrolytic tank containing an electrolytic solution (alkaline cleaning liquid), and 7 is an electrolytic tank. A washing tank (rinse tank), 8 is a dryer, 9 is an outlet processing unit, and 10 is a winding device.

FIG. 10 shows a schematic configuration diagram of an electrolytic cell (electrolytic cleaning device) 5. FIG. 10 shows only two pairs of electrodes provided with the steel strip S interposed therebetween, 11a and 11b are electrodes, 12 is an electrolytic solution (alkaline cleaning solution), 13 is a power supply device (rectifier), 14 is an electrode polarity switch, 1
5 is a control device.

[0005] In the above equipment, the steel strip S is unwound from the rewinding device 1 and subjected to off-gauge processing of the coil and welding processing of the preceding coil and the succeeding coil in the entry-side processing section 2. After passing through the scrubber brush 4, a predetermined electrolytic current is passed between the steel strip S and the electrodes 11 a and 11 b from the power supply 13 in the electrolytic cell 5 and electrolysis is performed to remove deposits on the surface of the steel strip S, and then the scrubber brush 6 is washed with water. Through the tank 7 and the dryer 8, the electrolytic solution, the electrolytic solution residue and the like are removed,
The coil is dried, divided at the welding part by the outlet side processing unit 9, wound by the winding device 10, and the wound coil is discharged out of the line.

When the electrolytic cleaning operation is performed, the electrodes 11a, 11b
Since foreign matter and gas adhere to the surface and the resistance increases, the polarity switching switch 14 is operated by the controller 15 every several hours,
The polarity of the electrodes 11a and 11b is switched and reversed.

In the above equipment, the line stops during coil handling in the rewinding device 1 and welding work in the entry-side processing section 2. When welding is completed, perform line operation,
When the welded part arrives at the outlet processing part 9, the line is stopped again for cutting work of the welded part and coil handling in the winding device 10. When the coil handling is completed in the winding device 10, the line operation is restarted. That is, in the above facility, the line is stopped twice by one coil (the steel strip S stops running).

While the line is stopped, the supply of the electrolytic current from the power supply unit 13 is stopped. When the running of the steel strip S is stopped, the surface of the steel strip S in the electrolytic cell 5 is oxidized by the electrolytic solution to generate stain (so-called electrolytic stain). Various proposals have been made to prevent stain.

For example, in Japanese Patent Publication No. Hei 6-33518, buffer portions for storing strips are formed on the inlet side and the outlet side of the cleaning device, and the strip is stopped at one of the inlet side and the outlet side. In this case, it has been proposed that the feeding of the strip to the inlet buffer and the feeding of the strip from the outlet buffer are stopped, the strip is reciprocated between both buffers, and the strip is not stopped in the cleaning device. .

Japanese Unexamined Patent Publication (Kokai) No. 2-159323 discloses that a welding machine, an electrolytic cleaning device, a plating device, and an entrance looper are sequentially installed in a continuous annealing furnace on an entrance side of a welding machine. It has been proposed that a mini looper is interposed between the steel strip and the strip stored in the mini looper is dispensed during welding of the steel strip so that the steel strip is not stopped by the cleaning device.

Further, in Japanese Patent Application Laid-Open No. 4-107300, a cleaning liquid discharging device is installed near an electrode of a metal strip passage in an electrolytic cell, and when the metal strip is stopped, the cleaning liquid discharging device is directed toward the surface of the metal strip. It has been proposed to prevent the stain by discharging the cleaning liquid.

[0012]

However, Japanese Patent Publication No. Hei 6-3
In the proposals of Japanese Patent No. 3518 and Japanese Patent Application Laid-Open No. 2-159323, there is a problem that the equipment cost becomes excessively large because the buffer unit and the like are large-scale equipment. Further, since a large space for installing a large-scale facility is required in addition to an excessive facility cost, it is difficult to modify the existing facility and implement the proposal. Further, according to the proposal of Japanese Patent Application Laid-Open No. 4-107300, the present invention in which stain cannot be reliably prevented,
In view of the above circumstances, an object of the present invention is to provide an electrolytic cleaning method and apparatus capable of inexpensively preventing stains generated on the surface of a steel strip in an electrolytic cell when running of the steel strip is stopped.

[0013]

The gist of the present invention for solving the above problems is as follows. (1) When the steel strip is run in the electrolytic bath to perform electrolytic cleaning of the steel strip, the residual voltage caused by the residual charge in the electrolytic bath when the running of the steel strip is stopped is set to 3 V or less. Method for electrolytic cleaning of steel strip. (2) When the steel strip is run in the electrolytic bath to perform electrolytic cleaning of the steel strip, the product of the residual voltage and the residual current caused by the residual charge in the electrolytic bath when the running of the steel strip is stopped is 1000 V.
A method for electrolytically cleaning a steel strip, wherein the method is A or less. (3) A method for electrolytically cleaning a steel strip, comprising: removing a residual charge in the electrolytic tank when the steel strip stops running when performing the electrolytic cleaning of the steel strip by running the steel strip in the electrolytic tank. . (4) The method for electrolytic cleaning of a steel strip according to the above (3), wherein the polarity of the electrode of the electrolytic cell is switched to remove residual charges in the electrolytic cell. (5) The electrolytic cleaning method for a steel strip according to the above (4), wherein the number of times of switching the polarity of the electrode in one coil is an odd number of three or more. (6) In an apparatus for performing electrolytic cleaning of a steel strip by running the steel strip in the electrolytic cell, it is provided that the electrode polarity of the electrolytic cell is automatically switchable when the steel strip stops running. Characteristic electrolytic cleaning equipment for steel strip. (7) The number of times that the electrode polarity in one coil is automatically switched is 3
The steel strip electrolytic cleaning apparatus according to the above (6), wherein the steel strip is disposed so as to be an odd number of times or more.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. When the steel strip stops running in the electrolytic cell, a stain as shown in FIG. 2 is generated on the surface of a steel strip in the electrolytic cell. The present inventors have found that even when the supply of the electrolytic current is stopped from the power supply device when the line is stopped, the electrolytic action is continued by the residual charge due to the capacitor action of the electrolytic cell, and this is the cause of the occurrence of stain. I thought it might be. Therefore, the residual charge in the electrolytic cell when the line is stopped, that is, the residual voltage between the electrode and the steel strip when the line is stopped,
And the residual current flowing between the electrode and the steel strip according to the residual voltage was investigated. FIG. 3 is a schematic diagram illustrating the state of voltage and current changes before and after the line stop obtained based on the result of the investigation.

During the line operation (during the cleaning operation), the electrolytic current of the electrolytic cell is set at 4.6 kA, and the electrolytic voltage at this time is 2 kA.
It was 7.5V. The line was stopped, and the supply of the electrolytic current was stopped, that is, the voltage applied to the power supply device was set to 0V. In this state, a current of 290 A and a voltage of 5.5 V were measured between the steel strip and the electrode. The voltage and current measured after the stop of the electrolytic current are regarded as residual voltage and residual current due to residual charge due to the capacitor action of the electrolytic cell, thereby oxidizing the steel strip surface and generating stain. Was speculated.

The occurrence of stain is considered to be correlated with the magnitude of the residual charge, that is, the magnitude of the residual voltage and the magnitude of the residual current. Therefore, the residual voltage and the residual current between the electrode and the steel strip when the line is stopped are considered. Was measured and the occurrence of stain was investigated. The survey results are shown in FIGS.

In FIG. 4, the residual voltage V exceeds 3 V, and in FIG. 5, the product of the residual voltage × the residual current exceeds 1000 V · A, and stains are generated. Therefore, the residual voltage due to the residual charge in the electrolytic cell when the running of the steel strip is stopped is 3 V or less, or the residual voltage and the residual current due to the residual charge in the electrolytic cell when the running of the steel strip is stopped. Multiply by 100
When the voltage is set to 0 V · A or less, it is possible to prevent stains generated in the steel strip in the electrolytic cell when the line is stopped.

Next, when the line is stopped, the polarity of the electrode is switched from the state shown in FIG. 6A to the state shown in FIG. 6B to discharge the residual charge. The changes of residual voltage and residual current were investigated.
FIG. 7 shows the results of the investigation. As shown in FIG. 7, the residual voltage of 5 V measured before switching the polarity of the electrodes, approximately 300
Residual current of A (residual voltage × residual current = 1500 V · A)
Are -1 after 8.4 seconds of electrode polarity switching.
V, reduced to 108A (residual voltage x residual current = 108V
A), the residual charge is at a level at which no stain occurs due to the switching of the electrode polarity, that is, the residual voltage is 3 V
Hereinafter, it can be seen that the residual voltage × the residual current is reduced to 1000 V · A or less.

As described in the section of the prior art, when the steel strip is washed with the equipment shown in FIG. 1, the line is stopped twice with one coil. FIG. 8A is a schematic diagram illustrating this state. In (a), the line stop is a line stop associated with coil handling and welding work on the entry side,
The line stop is a line stop associated with the cutting operation of the entry side welded portion on the output side and the coil handling.

In order to prevent stains generated in the steel strip in the electrolytic cell when the line is stopped, it is necessary to stop the line each time the line is stopped.
Preferably, the polarity of the electrodes is switched to reduce the residual charge in the electrolytic cell. From the viewpoint of preventing stains, it is sufficient to switch the polarity of the electrode once every line stop. However, when the polarity of the electrode is switched once each time each line is stopped, switching is performed twice in total with one coil. As a result, during the cleaning operation, the polarity of the electrode continues to be fixed to either the anode or the cathode, and the amount of electrode wear between the electrode fixed to the anode and the electrode fixed to the cathode is remarkable. Due to the difference, the electrode life becomes unbalanced, the distance between the steel strip and the electrode becomes non-uniform, and the contamination on the electrode surface increases, so that the problem of cleaning property easily occurs.

In order to prevent the above problem, it is preferable that the number of switching of the polarity of the electrode in one coil is an odd number, that is, the switching of the electrode is performed twice when one of the lines is stopped. The polarity of the electrode may be switched a plurality of times each time each line is stopped. However, also in this case, from the viewpoint of preventing the polarity of the electrode from being fixed to one of the lines, the total number of electrodes in one coil may be reduced. The number of switching is preferably set to an odd number. Further, it is preferable that the polarity switching of the electrodes when the line is stopped be performed as soon as possible after the line is stopped. In the case where the polarity of the electrode is switched twice or more at the time of one line stop, it is preferable to perform the second switching after the discharge of the residual charge is almost finished in the first switching.

Hereinafter, the present invention will be further described with reference to FIG. 1, FIG. 8 and FIG. FIG. 9 is a diagram showing a schematic configuration of an electrolytic cell (electrolytic cleaning device) 5 according to the embodiment of the present invention, which is provided in the facility of FIG. For the control device 15 of the electrolytic cell 5,
Further, a function of automatically switching the electrode polarity when the line is stopped is added, and the other configuration is the same as the configuration of the apparatus shown in FIG.

In the equipment shown in FIG. 1, when the coiling is completed by the rewinding device 1 during the cleaning operation of the steel strip S, the line is stopped and the supply of the electrolytic current from the power supply device 13 is stopped. Next, the next coil is prepared by the rewinding device 1, and the leading side coil and the succeeding coil are welded by the entry-side processing section 2 (the line stop section in FIG. 8A). In addition, a signal indicating that the coil has been discharged from the rewinding device 1 is sent from the entrance control device (not shown) to the control device 15a. The control device 15a operates the polarity switch 14 based on the signal,
The first polarity switching of the electrodes 11a and 11b is performed, and the elapsed time after receiving the signal is further measured by a timer built in the control device 15a, and the predetermined time is set within a time not exceeding the stop time of the line stop unit. After a lapse of time, the polarities of the electrodes 11a and 11b are switched again, and the second switching is performed. The predetermined time set in the timer is a stop time of the line stop unit, and a residual voltage caused by residual charge after the first electrode polarity switching is 3 V or less, or a product of the residual voltage and the residual current is 1000 V · A or less. The required discharge time is determined in advance, and is set to a range not less than the required discharge time determined above and not exceeding the stop time.

When the welding of the preceding coil and the succeeding coil is completed in the entrance processing unit 2, a line operation is performed to send the welded portion to the exit side, and at the same time, an electrolytic current is supplied from the power supply unit 13.

When the welded part arrives at the outlet processing part 9, the line is stopped again, the welded part is cut by the shearing device of the outlet processing part 9, and the leading coil is discharged from the winding device 10 (FIG. 8).
(A) Line stop part). During this time, the outlet processing facility 9
Is transmitted from the output side control device (not shown) to the control device 15a, and the control device 1
5a operates the changeover switch 14, and the electrode 11a
And 11b are switched.

When the winding device 10 is ready to wind the subsequent coil, the line operation is resumed, and
To supply the electrolytic current.

In FIG. 8, crosses in (a) indicate the polarity switching points of the electrodes, and x and x indicate the first and second polarity switching points of the line stop, respectively.
X is the polarity switching point of the line stop. Also,
(B) is an example showing the polarity of the electrode corresponding to the polarity switching. Also, (a) shows the relationship between each line stop and the position in the coil longitudinal direction. The line stop is located on the coil tip (T portion) side, and the line stop is located at the coil tail ( B)) side.

When the polarity of the electrode is switched as shown in FIG. 8, the electrode polarity is switched every time the line is stopped, and the residual charge in the electrolytic cell is removed. Stain no longer occurs on certain steel strips. In addition, since the polarity of the electrode is switched three times in one coil, the polarity of the electrode at the time of washing the preceding coil and the succeeding coil is reversed. There is no occurrence of the problem of the electrode life and the problem of cleanability that occur.

According to the present invention, the stain (so-called electrolytic stain) generated in the steel strip in the electrolytic cell when the line is stopped can be reliably prevented. In addition, installation of the above-described device for automatically switching the electrode polarity when the line is stopped is inexpensive, and it is easy to modify the existing equipment and implement the present invention.

[0030]

EXAMPLE In the equipment of FIG. 1, when the electrode polarity was switched when the line was stopped and when the electrode polarity was not switched, the residual voltage and the residual current were investigated, and the presence or absence of stain on the steel plate stopped in the electrolytic cell was investigated. did. When switching the electrode polarity, the first switching is performed immediately after the line is stopped, and the second switching is performed after the first switching.
Performed after 0 seconds. The measurement of the residual voltage and the residual potential was performed immediately after the line was stopped when the electrode polarity was not switched, and immediately after the first polarity switching when the electrode polarity was switched. Table 1 shows the survey results.

[0031]

[Table 1]

When the electrode polarity is not switched when the line is stopped, stain occurs. When the electrode polarity is switched when the line is stopped, the residual voltage is 3 V or less, and the residual voltage × residual current is 1000 V · A or less,
No stain has occurred.

In the coils B and C, switching of the electrode polarity is performed three times with one coil. Such switching of the electrode polarity not only prevents the occurrence of stain, but also makes the electrode polarity of the subsequent coil of the coils B and C reverse to that of the coils B and C. This is a more preferable electrolytic cleaning method because it is possible to prevent the problem of electrode life and the problem of cleaning property caused by the problem.

[0034]

According to the present invention, stains generated on the surface of the steel strip in the electrolytic cell when the running of the steel strip is stopped can be reliably prevented by a simple method and with inexpensive equipment.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main part of a steel strip electrolytic cleaning apparatus.

FIG. 2 is a diagram showing the appearance of stains generated in a steel strip in an electrolytic cell when traveling of the steel strip is stopped.

FIG. 3 is a schematic diagram illustrating a state of a change in voltage and current between a steel strip and an electrode before and after the line is stopped.

FIG. 4 is a diagram showing a relationship between a residual voltage and a stain generation state when a line is stopped.

FIG. 5 is a diagram showing a relationship between a product of a residual voltage and a residual current when a line is stopped and a stain generation state.

FIG. 6 is a diagram illustrating switching of electrode polarity when a line is stopped.

FIG. 7 is a diagram showing an example of changes in residual voltage and residual current when the electrode polarity is switched when the line is stopped.

8A and 8B are diagrams illustrating a change in line speed, a switching timing of electrode polarity, and an electrode polarity in an electrolytic cleaning apparatus for a steel strip, and FIG. 8A is a schematic diagram illustrating a change in line speed and switching timing of electrode polarity; ) Indicates the electrode polarity.

FIG. 9 is a diagram showing a schematic configuration of an electrolytic cleaning apparatus according to an embodiment of the present invention, in which electrode polarities are automatically switched.

FIG. 10 is a diagram showing a schematic configuration of a conventional electrolytic cleaning apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Unwinding apparatus 2 Inlet-side processing part 3 Immersion tank (dunk tank) 4, 6 Scrubber brush 5 Electrolytic tank (electrolytic washing apparatus) 7 Rinse tank (rinse tank) 8 Dryer 9 Outlet-side processing part 10 Winding apparatus 11a, 11b Electrode 12 Electrolyte solution (alkaline cleaning solution) 13 Power supply device (rectifier) 14 Polarity changeover switch 15, 15a Control device S Steel strip

Claims (7)

[Claims] When a steel strip is run in an electrolytic cell to perform electrolytic cleaning of the steel strip, a residual voltage caused by residual charges in the electrolytic tank when the running of the steel strip is stopped is set to 3 V or less. A method for electrolytically cleaning steel strips. 2. When the steel strip is run in the electrolytic cell to perform electrolytic cleaning of the steel strip, the product of the residual voltage and the residual current caused by the residual charge in the electrolytic cell when the running of the steel strip is stopped. 1
A method for electrolytically cleaning steel strips, wherein the method is to make the voltage of 000 V · A or less. 3. An electrolytic cleaning of a steel strip, wherein when the steel strip is run in the electrolytic bath to perform electrolytic cleaning of the steel strip, residual electric charges in the electrolytic bath are removed when the running of the steel strip is stopped. Cleaning method. 4. The method for electrolytically cleaning steel strip according to claim 3, wherein the polarity of the electrodes in the electrolytic cell is switched to remove residual charges in the electrolytic cell. 5. The method for electrolytically cleaning steel strip according to claim 4, wherein the number of times of switching the polarity of the electrode in one coil is an odd number of three or more. 6. An apparatus for performing electrolytic cleaning of a steel strip by running a steel strip in an electrolytic cell, wherein the electrode polarity of the electrolytic cell is automatically switchable when the steel strip stops running. An electrolytic cleaning apparatus for a steel strip, comprising: 7. The electrolytic cleaning apparatus for a steel strip according to claim 6, wherein the number of times of automatic switching of the electrode polarity in one coil is set to an odd number of three or more.