JPH02149696A - Method for controlling plating amount at plate edge in electroplating - Google Patents

Abstract

PURPOSE:To control the plating amt. at the plate edge and to prevent overplating by generating a controllable magnetic field with a plating current at the end of a metallic strip in its cross direction, and exerting force on the outside of the end. CONSTITUTION:A metallic strip 3 is brought into contact with the periphery of a conductor roll 1 with almost the lower half dipped in a plating soln. in a plating tank 2, and synchronously traveled. A plating current is applied through the roll 1 between the strip 3 and the plural anodes 4 arranged away from the strip 3 with a conduction gap in between, and one surface of the strip 3 is plated. In this radial cell-type plating tank 2, an electromagnet 5 is provided to impress a magnetic field vertically to the plating current and in the opposite direction to the plating current. The intensity of the magnetic field is controlled through a coil 6. As a result, an electromagnetic force is exerted on the edge of the strip 3 in its cross direction to prevent the concentration of the current on the edge, and the overplating of the edge is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for controlling the amount of plating deposited at the edge of a plate in electroplating.

<Prior art> Conventionally, the countermeasure for preventing over-plating on the edge of a metal strip (hereinafter simply referred to as a strip) during electroplating is to cover the edge of the plate with an insulating plate called an edge mask, which prevents the current from concentrating on the edge of the plate. The main method is to limit

For example, in a radial cell type plating bath, abnormal adhesion is likely to occur due to metal wrapping around both edges of the strip, especially during high-speed plating using a large current. 5
It is disclosed in Japanese Patent No. 5598.

That is, in general, in a radial cell type plating apparatus, a large-diameter rotating drum for conducting electricity is immersed in about 1/2 of a plating solution, and while the strip is brought into contact with the outer periphery of the rotating drum and runs in synchronization with the rotation of the drum, An electroplating apparatus that conducts current through the plating solution between the strip and an anode installed across a radial current-carrying gap, and is suitable for plating only one side. Since the distance between the threading strip and the anode surface can be reduced, wasteful consumption of plating power is reduced, and high-speed plating with large current is possible, but especially in such cases, the occurrence of edge overcoat can be prevented. In order to do this, an edge mask is provided that can move forward and backward in parallel to the generatrix direction of the current-carrying rotating drum to avoid concentration of plating current at both edges of the strip.

<Problems to be Solved by the Invention> By the way, in the above-mentioned over-plating prevention method, the current control of the edge portion is determined by how much the edge mask is covered from the edge of the plate, and its movement is controlled by a hydraulic servo or a servo motor. However, because it involves mechanical operation in the harsh environment of plating solution, there are problems with its reliability, lifespan, etc.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a method for controlling the amount of plating deposited at the edge of a plate in electroplating, which prevents over-plating using electromagnetic force.

Means for Solving the Problems> In order to achieve the above object, according to the present invention, in a radial cell type plating tank, the plating current is applied to the widthwise end of the metal strip, and the outside of the widthwise end is Provided is a method for controlling the amount of plating deposited on a plate edge portion in electroplating, the method comprising generating a magnetic field to generate a force acting in the direction of the plate, and controlling the strength of the magnetic field to perform electroplating. .

The present invention will be explained in more detail below.

FIG. 1 is an explanatory diagram of main parts showing an embodiment of the present invention.

In FIG. 1, the current-carrying roll 1 is immersed in about 1/2 of the plating solution in the plating bath 2, and while the strip 3 is brought into contact with the outer periphery of the roll 1 and is run in synchronization with its rotation, the strip 3, a plurality of anodes 4 are installed at both ends of the plate, with a radial conduction gap in between, in preparation for variations in the plate width. Since it would be confusing to explain both ends of the board at the same time, only one end of the board, that is, the end nearer in FIG. 1 will be described.

In such a radial cell type plating apparatus, if a force is applied to the edge part of the strip 3 in the direction away from the edge part, current concentration due to unnecessary current flowing around the edge part can be prevented. will no longer occur. In order to do this, an electromagnet 5 is provided on the side opposite to the strip of the anode 4 so as to generate a magnetic field in the direction opposite to the direction of the strip. In other words, if the magnetic field is set perpendicular to the direction of the plating current, which is opposite to the flow direction of the plating solution, Fleming's left-hand rule will cause the plating solution to flow in the direction of the edge of the plate width, i.e., as shown in Figure 1. An electromagnetic force acts in the direction toward the front when viewed from , changing the route of the plating current on the edge side toward the front. Therefore, current concentration on the front edge portion does not occur, and overcoating is prevented.

Since this electromagnetic force is proportional to the strength of the magnetic field, for example, when a static magnetic field is generated by an electromagnet, the electromagnetic force can be easily controlled by changing the current flowing through the electromagnet.

Next, a method for controlling the amount of glue deposited on the edge portion of the plate based on the principle of the present invention will be explained.

FIG. 2 is a control block diagram illustrating one embodiment of the present invention for preventing edge overcoat on one end of a strip. In order to cope with the change in the width of the strip 3 to be passed, a plurality of electromagnets 5 are arranged at the one end of the roll 1 in the longitudinal direction of the roll 1 so as to be able to cope with the change in the width of the strip. 6 indicates a coil of each electromagnet 5.

A reference value for the amount of plating deposited is set in the coil current calculation device 7 in advance, and the amount of plating deposited on one of the plate edges measured by the plating amount meter 8 is set to match the reference value. The coil current is calculated and a current command is given to the DC power supply device 9. The DC power supply device 9 outputs a DC current according to the current command from the coil current calculation device 7 to the coil switching device 10 . The coil switching device 10 selects the coil 6 through which the current is to be applied by the coil switching control device 12 so that the current is applied to the coil 6 closest to the sheet end based on the signal from the sheet end position detection device 11, and causes the DC current to flow therethrough.

In this way, the amount of plating deposited is controlled to be appropriate depending on the change in the width of the strip 3 and the amount of plating deposited on the edge portion.

In addition, the inside of the magnetic field, the D structural material, the roll 1, the nozzle, the accessory parts (4 not shown), etc. are all made of non-magnetic materials.

<Example> The present invention will be specifically explained below based on Examples.

(Example 1) Using the plating equipment shown in Fig. 1, a plating film with a thickness of 1.6 mm and a width of 1
A 200 mm steel strip was plated using a zinc sulfate-based plating solution at a plating solution flow rate of 1000 mm/sec and a current density of 200 A.
/dm2 Zn plated. At this time, control was performed to prevent edge overcoat according to the control block shown in FIG. The amount of plating on the edge portion was measured every 10 seconds using a plating amount meter 5, and a current of 18 OA was passed through the electromagnetic coil.

The obtained galvanized steel sheet was able to maintain the plating thickness set as a standard without substantially generating an overcoat at the edge portion.

On the other hand, when the control current to the electromagnet coil was stopped,
A 35% overcoat occurred on the edges.

<Effects of the Invention> Since the present invention is configured as described above, over-plating of the edge portion can be prevented by electromagnetic force.

In addition, the amount of plating deposited on the edges can be easily controlled by controlling the current of the electric fin force that generates the static magnetic field, and since no mechanical movement is involved, reliability and service life can be improved. This has the effect of significantly extending the length of time.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional view of essential parts showing an embodiment of the present invention in a radial cell type plating tank. FIG. 2 is a control block diagram illustrating one embodiment of the present invention for preventing edge overcoating on one end of a strip. Explanation of symbols 1...Roll, 2...Melt tank, 3...Strip, 4...Anode, 5...Electromagnet, 6...Coil, 7...Coil current calculation Apparatus, 8... Plating coating weight meter, 9... DC power supply device, 10... Coil switching device, 11... Board edge position detection device, 12... Coil switching control device

Claims (1)

[Claims] (1) In a radial cell type plating bath, a magnetic field is generated at the widthwise ends of the metal strip so as to generate a force acting outward from the widthwise ends with respect to the plating current,
A method for controlling the amount of plating deposited on a plate edge portion in electroplating, characterized in that electroplating is performed by controlling the strength of a magnetic field.