JPS63255396A - Method and device for preventing overplating - Google Patents

Abstract

PURPOSE:To control the end effect by arranging insulating material-coated metallic sheets in parallel at a specified distance from the end of a traveling steel sheet, and keeping the polarity and electric potential of the metallic sheet same as those of the steel sheet to correct the electric field at the end of the steel sheet. CONSTITUTION:The steel sheet 1 to be plated is led by a current collecting roll 6, and traveled in opposition to an anode 2 in a plating soln. and at a specified distance from the anode 2. The anode 2 and the roll 6 are respectively connected to the plus output and minus output of a plating power source 7, and electroplating is continuously applied on the traveling steel sheet 1. At this time, a bakelite-coated guard electrode 5 with both ends extended is set at a specified distance from the steel sheet 1 and in parallel with the sheet 1, and connected to the minus output of the power source 7. The direction signal of an end position detecting sensor 8 is processed by a computing element 9 to calculate the variations in the end position of the steel sheet 1, a cylinder 4 is driven by a controller 10 in accordance with the output of the computing element 9, and the guard electrode 5 is kept at a specified distance in follow-up to the movement of the end of the steel sheet 1. By this method, the overplating of the end of the steel sheet 1 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method and apparatus for preventing over-plating at the end of a moving metal strip (for example, a steel plate) in continuous plating equipment.

(Prior art) Equipment for continuously electroplating tin, zinc, iron-zinc, etc. onto steel plates is constructed as follows: A steel plate running in an electrolytic solution serves as a cathode, and anodes are connected to it at predetermined intervals. facing each other and plating continuously. In the case of double-sided plating, anodes are placed opposite both sides of the steel plate.

In this case, if the ends of the steel plate are left as they are, the electric field will concentrate on the ends of the steel plate, resulting in overplating. FIG. 4 is a partial cross-sectional view of the vicinity of the end of the steel plate, showing a cross section perpendicular to the running direction of the steel plate, and the electric field generated between the steel plate 1 and the anode 2 facing it is illustrated by broken lines. As in the case of parallel plate capacitors, the electric field is distorted at the edges of the plates, which have a finite expanse, causing the electric lines of force to concentrate and wrap around to the back side. If this is left untreated, metal ions will concentrate at the edges. Causes overplating. This lowers the basic unit of plated metal, and when wound into a coil, it causes edge build-up, resulting in a decrease in product quality and poor shape.

The conventional means to prevent overplating is an L-shaped or U-shaped shielding plate (masking device) made of insulating material.
This covers the edges of the steel plate to correct disturbances in the electric field and prevent metal ions from concentrating and circulating around.

FIG. 5 shows the electric field when such a masking device 3 is provided at the end of the steel plate 1 in FIG. 4 with broken lines. When an insulator is inserted as a shielding plate, the dielectric constant (ε, ) of the electrolyte increases.
Since the dielectric constant (ε2) of the insulator and the insulator are different, the electric lines of force are bent, and the concentration and distortion of the lines of force at the edge of the steel plate are corrected. The masking device 3 is driven by a cylinder 4 and follows the movement of the end of the steel plate 1.

However, this conventional method has the following problems.

■If the masking device is not able to follow the meandering or passing of the welding point of the steel plate, the masking device that overlaps the steel plate at the edge will collide with the steel plate, causing the L-shaped or U-shaped masking device to overlap. A collision occurs between them. This causes damage to the edge of the steel plate and damage to the masking insulator, resulting in a large loss.

■If the steel plate and the masking insulator do not always overlap properly, there will be no masking effect, so very expensive follow-up devices and overlap detection devices are required, increasing equipment costs.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide an end plate that does not require a sophisticated follow-up device and that does not cause any danger of accidents such as bumps between the plated metal strip and the plated metal strip. An object of the present invention is to provide a method and device for preventing overplating.

(Means for Solving the Problems) The gist of the method of the present invention is that in continuous electroplating equipment for a traveling metal strip, the metal strip is A metal plate covered with an insulator is placed parallel to the body, and the metal plate is held at the same polarity and potential as the metal strip to be plated, thereby correcting the electric field at the end of the metal strip. This is a method for preventing over-plating at the end of a metal strip, which is characterized by suppressing the end effect.

The gist of the apparatus of the present invention is to provide an apparatus for preventing over-plating of the end of a metal strip in continuous electroplating equipment for a moving metal strip, which is capable of separating the end of the metal strip to be plated at a predetermined distance from the end of the metal strip to be coated. a metal plate covered with an insulator and arranged parallel to the plated metal strip; means for holding the metal plate at the same polarity and potential as the metal strip to be plated; An overplating prevention device for an end of a metal strip, comprising means for keeping the end of the metal strip to be plated and the ruI corner of the metal plate substantially constant by following changes in the end position of the plated metal strip. be.

The metal strip to be plated is, for example, a steel plate, and in this case,
Continuous electroplating equipment is equipment for plating steel plates with tin, zinc, iron-zinc, etc. The insulating coated metal plate can also be constructed from steel plate. For example, ceramics, Bakelite, etc. are used as the covering insulator.

(Function) FIG. 1 is a diagram corresponding to FIG. 4, in which the guard electrode (insulator-coated metal plate) 5 is placed at the end of the steel plate (metal strip to be plated) 1, and the anode 2 and The electric field generated between the two is shown by the dashed line.

The metal plate 5a of the guard electrode 5, which is arranged to extend the steel plate 1 at a predetermined distance g from the steel plate 1, is held at the same potential (negative) as the steel plate 1, so that the electric field is concentrated at the end of the steel plate l. , the wraparound of electric lines of force is effectively prevented. Figure 2 explains the principle. In a parallel plate capacitor having a main electrode 1" and a counter electrode 2", a guard electrode 5
′ is shown. By arranging the guard electrode 5° having the same polarity and potential as the main electrode 1, the end effect (electric field concentration) at the end of the main electrode 1' is suppressed, and an equal electric field is realized at that part. The guard electrode 5 (FIG. 1) of the present invention has the same function as the guard electrode 5 of a parallel plate capacitor in principle, and the present invention is an application of the idea of Kelvin protection ring.

The guard electrode 5 is driven by the cylinder 4 and follows the end of the steel plate 1, and the distance g between the steel plate 1 and the anode is maintained at a predetermined value (Fig. 1). The end effect can be sufficiently suppressed with a size approximately equal to the distance d between the two.

Since the guard electrode 5 is covered with the insulator 5b, this electrode itself will not be damaged.

In addition, in double-sided plating equipment, anodes are arranged opposite both sides of the steel plate 1, but in this case, the guard electrode 5 similarly suppresses the end effect.

(Example) Next, an example of the present invention will be described in detail with reference to FIG.

The steel plate 1 to be plated is guided by a current collector roll 6 and runs facing an anode 2 in the plating solution at a predetermined interval. The anode 2 and the roll 6 are connected to a plus output and a minus output of a plating power source 7, respectively, and electroplating is continuously performed on the traveling steel plate 1.

The guard electrode 5 is arranged parallel to the steel plate 1 with a predetermined distance therebetween, with both ends thereof extending.
Connected to the negative output of 7. The guard electrode 5 is constructed by covering a steel plate with Bakelite.

The follow-up drive means for the guard electrode 5 is constructed as follows.

The end position detection sensor 8 is composed of an optical sensor such as a commonly used phototube type sensor, and outputs a detection signal to the end position detection signal processing calculator 9. The computing unit 9 calculates the steel plate 1 from the detection signal.
Calculate the variation in the end position of.

The guard electrode drive controller 10 drives the guard electrode drive cylinder 4 according to the output of the calculator 9, causes the guard electrode 5 to follow the movement of the end of the steel plate 1, and adjusts the distance between the guard electrode 5 and the steel plate 1. is maintained approximately equal to the distance between the anode 2 and the steel plate l.

(Effects of the Invention) As described above, in the present invention, since the guard electrode (insulator-coated metal plate) has a thickness substantially equal to that of the steel plate, breakage due to bumping and damage to the device do not occur in principle.

Furthermore, since the distance between the guard electrode and the steel plate to be plated can be larger than in the conventional device, a plain tracking device is sufficient.

Therefore, it has a great effect on improving the quality of the steel plate edges, the reliability of the plating equipment, and the maintainability.

[Brief explanation of the drawing]

Fig. 1 is a partial cross-sectional view along the direction perpendicular to the steel plate traveling method, showing the electric field near the end of the steel plate to be plated when the guard electrode (insulator-coated metal plate) according to the present invention is arranged; is a cross-sectional view of a parallel plate capacitor having guard electrodes, showing the principle of the present invention; FIG. 3 is an explanatory diagram showing the configuration of an embodiment of the device of the present invention; FIG. 4 is a diagram showing an end over-plating prevention device. FIG. 5 is a partial cross-sectional view showing an electric field near the end of a steel plate when a conventional masking device is not used; and FIG. 5 is a partial cross-sectional view showing an electric field near the end of a steel plate when a conventional masking device is used.

Claims (2)

[Claims] (1) In continuous electroplating equipment for moving metal strips, a metal plate coated with an insulator is placed parallel to the metal strip at a predetermined distance from the end of the metal strip to be plated, and Overplating of the end of a metal strip, characterized in that the metal plate is held at the same polarity and potential as the metal strip to be plated, thereby correcting the electric field at the end of the metal strip and suppressing the edge effect. How to prevent it. (2) A device for preventing over-plating of the end of a moving metal strip in continuous electroplating equipment, which is arranged parallel to the end of the metal strip to be plated, with a predetermined distance from the end of the strip. means for holding the metal plate at the same polarity and potential as the metal strip to be plated; and a means for holding the metal plate at the end position of the traveling metal strip to be plated. An over-plating prevention device for an end of a metal strip, comprising means for keeping the distance between the end of the metal body to be plated and the metal plate substantially constant by following fluctuations in the metal plate.