JPS62103393A - Continuous electroplating method for metallic strip - Google Patents

Abstract

PURPOSE:To prevent the generation of an over-coat and under-coat at the ends of a metallic strip in the stage of subjecting the surface of the strip to continuous plating by disposing plural auxiliary cathodes in proximity to both ends of the strip in the moving direction thereof and discretely adjusting the potentials or currents of the respective auxiliary cathodes. CONSTITUTION:Electricity is conducted between the metallic strip 4 and anodes 9, 9 disposed on both sides of the strop 4 by a cathode conductor roll 2 to plate the surface of the strip. The plural auxiliary cathodes 10a, 10a'-10c, 10c' are disposed in proximity to both ends of the metallic strip along the progressing direction of the strip 4. Voltage regulators 13a-13c are respectively connected to the auxiliary cathodes and the potentials of the respective auxiliary cathodes are made coincident with the potentials of the strip 4 in the position facing the respective auxiliary cathodes by the voltage regulators so that the current densities at both ends of the strip are made uniform in the auxiliary cathodes parts. The generation of the over-coat and under-coat at the ends of the strip is thus prevented.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to over-plating, in which the amount of plating at the edges of the metal strip is greater than that at the center, when continuously electroplating a metal strip such as steel or aluminum. The present invention relates to a continuous electroplating method for metal strips that does not cause coating and can be plated with uniform surface properties.

[Prior art and its problems]

For example, in order to continuously electroplate steel (IJ) tubes, there are two methods: a vertical electroplating device as shown in Figure 4, and a horizontal electroplating device as shown in Figure 5. There is a method of plating using As shown in FIG. 4, the vertical electroplating apparatus includes conductor rolls 2 and 2' provided above the steel strip inlet and outlet sides of the vertical electroplating tank 1, and conductor rolls 2 and 2' provided above the steel strip inlet and outlet sides of the vertical electroplating tank 1, and conductor rolls 2 and 2' installed at the lower part of the electroplating tank Is it set up? 1. Between the zinc roll 3, each of the conductor rolls 2゜2', and the zinc roll 3, a pair of steel strips 4 are arranged parallel to each other, with the steel strip 4 moving in the electroplating tank 1 in between. It consists of vertical electrode plates 5, 5' and 6.6'. The steel strip 4 moves downwardly and then upwardly in the electroplating bath 1 in which the plating bath is contained and flowing, continuously passing through a pair of electrode plates 5, 5' and 6, 6'. electroplated.

As shown in FIG. 5, the horizontal electroplating apparatus includes conductor rolls 2 and 2' provided outside the steel strip inlet and outlet sides of the horizontal electroplating tank 7, and Upper and lower 1 installed on the steel strip entry and exit sides
Pairs of dumb rolls 8a, 8a' and 8b, 8
b' and dam o-/l/8 a, 3 a' and B
b, B b', a pair of horizontal galvanic plates 5° 5' and 6 arranged parallel to the steel strip 4, with the steel strip 4 moving in the electroplating tank 1 in between. ,6
It consists of '. The steel strip is moved through an electroplating bath 7 in which a plating bath is contained and flowing.
Electroplating is carried out continuously while passing through pairs of electrode plates 5, 5' and 6, 6'.

The problem when electroplating both sides of the steel plate 764 using this method is as shown in Figure 6.
The plating current concentrates on the edge portions of the steel strip 4, resulting in overcoat in which the amount of plating on the edge portions is greater than on other portions.

When electroplating one side of the steel strip 4, as shown in Figure 7, in addition to overcoating the edges as described above, the problem arises that the current flows around to the non-plated side as well, resulting in plating. do.

In this way, when an overcoat occurs on the edges of a steel strip, when the steel strip is wound into a coil,
A build-up phenomenon occurs in which the edges swell, causing the plating films on the overcoat parts to rub against each other, causing scratches, poor welding strength of the overcoat part during welding, and poor appearance due to discoloration of the overcoat part. The problem arises.

Therefore, in order to prevent the above-mentioned problems, the 8th
As shown in FIG. 9 and FIG. 9, the main electrode plates 9, 9'
A narrow auxiliary electrode plate 10, 1 with a length similar to that of
0', the main electrode plate 9°9' and the auxiliary electrode plate 10,
By passing a current between the steel strip 4 and the auxiliary electrode plate 1, the current concentrated in both esso parts of the steel strip 4 is
0,10', thus preventing overcoating on the edges of the steel strip f4 and, in the case of single-sided plating, preventing plating on the unplated side. According to the method described above, it has become possible to prevent overcoating from occurring on the edges of the steel strip.

On the other hand, when continuous electroplating is performed on steel IJ tubes using an electroplating apparatus as shown in FIGS. 4 and 5, the following problems occur. That is, for example, when continuous electroplating is performed on a steel strip using the vertical electroplating apparatus shown in FIG. steel strip 4
A plating current flows therein in the direction of movement of the steel strip 4 as shown by the arrow towards the conductor roll 2 located above. As a result, the conductor roll 2 of the steel strip 4
A potential difference occurs between the upper part near the conductor roll 2 and the lower part far away from the conductor roll 2, and the potential of the upper part becomes lower than that of the lower part.

This phenomenon does not change even if the auxiliary electrode plate is arranged as described above. In Fig. 11, an auxiliary electrode plate is arranged in a vertical electroplating apparatus, a potential of 7μ is applied to the auxiliary electrode plate with reference to the conductor roll, and a potential of 15μ is applied to the main electrode plate.
This is the potential in the depth direction in the plating bath of the steel strip when tin plating is applied to the potential of V.

As can be seen from Fig. 11, the potential of the steel strip 0 is
At the top of the electroplating bath, the potential is 3.9 higher than that of the auxiliary electrode plate.
On the other hand, the potential at the bottom of the electroplating bath is 2V higher than the potential of the auxiliary electrode plate, and the potential at the top and bottom is 2V.
A potential difference of 5.9V results.

As a result, the current density at the edge of the IJ tube is
It is high at the top and low at the bottom.

FIG. 12 shows the results of examining the current density of the steel strip edge in the above case at the upper end of the main electrode plate near the conductor roll, at the center, and at the lower end far from the conductor roll. As can be seen from FIG. 12, the current density at the edge portion at the top end is extremely high near the edge, while the current density at the edge portion at the bottom end is conversely low near the edge. This problem also occurs when spot plating is performed using horizontal electroplating.

Generally, the voltage of an auxiliary electrode plate placed near the edge of a steel strip moving in an electroplating tank is set so that the time product (amount of coulombs) of the plating current flowing across the surface of the steel strip is uniform in the width direction. Therefore, as mentioned above, an excessive current flows through the edges near the conductor roll, and an undercurrent flows through the edges far from the conductor roll.

When the above-mentioned phenomenon occurs, for example, when the surface quality of the plating is affected by the current density, such as in iron-zinc alloy electroplating, a plating film with a uniform surface quality cannot be obtained. Otherwise, a problem arises in which the quality is impaired.

[Purpose of the invention]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to prevent overcoating of the edges of the metal strip during continuous electroplating of the metal strip, and to make the current density at the edges of the metal strip uniform in the direction of movement thereof.
An object of the present invention is to provide a continuous electroplating method for metal strips that can form a plating film of excellent quality.

[Summary of the invention]

The present invention continuously introduces a metal strip into an electroplating tank containing a plating bath, in which at least one electrode plate is arranged, and the surface of the metal strip as it passes through the electrode plate. In a continuous electroplating method for metal strips in which plating is continuously applied to a metal strip, the electrode plate is placed in the plating bath at a position where the electrode plate is placed,
A plurality of auxiliary electrode plates are disposed in the moving direction of the metal strip close to both sides of the metal strip passing through the plating tank, and a plurality of auxiliary electrode plates are arranged between each of the plurality of auxiliary electrode plates and the electrode plate. While applying a current, the potential or current of each of the plurality of auxiliary electrode plates is adjusted individually to prevent overcoat from occurring at the edges of the metal strip and to uniformize the current density at the edges. It is characterized by its ability to become

[Structure of the invention]

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is an explanatory view showing one embodiment of continuous electroplating of a steel strip using a vertical electroplating apparatus according to the method of the present invention.

As shown in the drawing, a pair of vertical main electrode plates 9 are placed parallel to the IJ tube 4 with the steel tube 11 moving in the electroplating tank guided by the conductor roll 2 with the steel tube 4 in between. (only one of which is shown in the drawing) are arranged.

Along the main electrode plate 9, on the same plane as the steel strip 4 and close to both of its edges, a plurality of auxiliary electrode plates 10a, L Oa' are arranged in the direction of movement of the IJ tag.

LOb, 10b', loc, and LOc' are arranged. The main electrode plate 9 is connected to the anode side of a power source (not shown),
A conductor roll 2 is connected to its cathode side and the steel strip 4 is energized by the conductor roll 2.

Auxiliary electrode plates 10a, LOa', 10b, 10b'.

10 c , l Oc' are each differentially connected to the conductor roll 2 via an individual voltage regulator 13a, 13b, 13c. 11 and 11' are current collectors attached to the shaft of the conductor roll 2.

The auxiliary electrode plates 10a, 10a' are the current collectors 11.
The auxiliary electrode plates 10b, lOb' are connected to the conductor 12 from the conductor 11' via the voltage regulator 13a.
2 via a voltage regulator 13b, and the auxiliary electrode plates 10c, lOc' are connected to the conducting wire 12 via a voltage regulator 13C. Auxiliary electrode plate 10a.

10a' and 10b, 10b' and to
c, LOC' are voltage regulators 13a,
The potential is individually adjusted by each of 13b and 13c.

FIG. 2 is a graph showing the potential of the auxiliary electrode plate adjusted in this manner. In FIG. 2, the vertical axis is the distance from the conductor roll, the horizontal axis is the potential with respect to the conductor roll, curve A is the potential of the steel strip, and straight line a is the auxiliary electrode plate LOa.

10 a' potential, direct Isb is the auxiliary electrode plate 10b, 10
The potential of b', the straight line C is the auxiliary electrode plate i o c + i
It is the potential of oc'. As shown in the drawings, the auxiliary electrode plate LOa.

The potentials of 10a', LOb, job', LOc, and LOc' are made to match the potentials of the steel IJ tube at positions corresponding to the respective auxiliary electrode plates.

As described above, the auxiliary electrode plate is divided into a plurality of pieces in the direction of movement of the steel strip, and the potential of each plate is made to match the potential of the position corresponding to the auxiliary electrode plate on the steel strip. The current density of is made uniform throughout.

FIG. 3 is an explanatory diagram showing another embodiment of the present invention. This embodiment uses a resistance regulator 14a instead of the voltage regulator in the embodiment shown in FIG.

14b and 14C are provided 9, which are the same as the embodiment described above, except that the current flowing through each auxiliary electrode plate is individually adjusted.

Note that the potential adjustment of multiple auxiliary electrode plates using a voltage regulator or resistance regulator does not necessarily match the potential at the position corresponding to each of the auxiliary electrode plates on the IJ tube as shown in Figure 2. It is not necessary, and the potential may be a certain difference from each potential of the steel strip.

〔Effect of the invention〕

As mentioned above, according to the present invention, when a metal strip is continuously electroplated using a vertical electroplating device or a horizontal electroplating device, no overcoat is generated on the edge portion of the metal strip. Moreover, the current density in the edge portion of the metal strip is made uniform in the direction of movement thereof, and a superior industrial effect is brought about in that a plating film of excellent quality can be formed.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an embodiment of continuous electroplating using a vertical electroplating apparatus according to the method of the present invention, Fig. 2 is a graph showing the potential of the auxiliary electrode plate, and Fig. 3 is an explanatory diagram showing another embodiment, FIG. 4 is a schematic vertical cross-sectional view of a vertical electroplating device, FIG. 5 is a schematic vertical cross-sectional view of a horizontal electroplating device, and FIG. 6 is a schematic vertical cross-sectional view of a horizontal electroplating device. Figure 7 is an explanatory diagram showing the state in which the plating current is concentrated on the non-plated surface in the case of single-sided plating. Figures 8 and 9 are diagrams showing the state in which the plating current is concentrated on the non-plated surface. An explanatory diagram showing the distribution of plating current in the case of steel (Fig. 10)
l) An explanatory diagram showing the state of the plating current flowing through the lug. Figure 11 is a graph showing the potentials of the main electrode plate, auxiliary electrode plate and steel strip. Figure 12 is a graph showing the electric potential of the steel strip.) Current density at the edge of the IJ tube. This is a graph showing. In the drawings, ■...Vertical electroplating tank, 2I2'...Conductor roll, 3...Zin roll, 4...Yui strip, 5
．． 5', 6.6'...electrode plate, 7...horizontal electroplating f~, 8a, 8a', 8b, 8
b'-=gum roll, 9.9'...main electrode plate, 10a+10a', 10b, 10b', 10c, 10c
'-jH Sukego・l! Me board, 11, 11'... Electron collector, 12... Chrysanthemum, 13a, 13b, 13c -"
hi pressure adjuster, 14a, 14b, 14c ---resistance adjuster.

Claims (1)

Claims: A metal strip is successively guided into an electroplating tank containing a plating bath in which at least one electrode plate is arranged, while the metal strip passes through the electrode plate. In a continuous electroplating method for a metal strip in which the surface of the metal strip is continuously plated, at a position in the plating bath where the electrode plate is arranged,
A plurality of auxiliary electrode plates are disposed in the direction of movement of the metal strip close to both edges of the metal strip passing through the plating bath, and a current is applied between each of the plurality of auxiliary electrode plates and the electrode plate. and individually adjusting the potential or current of each of the plurality of auxiliary electrode plates, thus preventing overcoat from occurring at the edges of the metal strip and equalizing the current density at the edges. A continuous electroplating method for metal strips characterized by: