JPH0225440B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] This invention prevents the formation of an overcoat in which the amount of plating is greater at both ends of the metal strip than at the center when continuously electroplating a metal strip such as steel or aluminum. The present invention relates to a method for continuous electroplating of metal strips, which allows plating with uniform surface properties. [Prior art and its problems] For example, when a steel strip is electroplated by passing it continuously through an electroplating tank in which electrode plates are arranged, a current for plating is applied to both widthwise ends of the steel strip. A so-called overcoat occurs in which the amount of plating on both ends is larger than on other parts. When an overcoat occurs on both ends of the steel strip, the following problems occur. (1) Pill-up defect Since the amount of plating on both ends is larger than on other parts, when such a steel strip is wound into a coil, or when steel plates cut to a specified size are stacked, both ends will be damaged. A build-up phenomenon occurs, and the plating films on the overcoat portion rub against each other, causing scratches. (2) Poor welding When electrical resistance welding is performed on galvanized steel plates that have an overcoat on both ends, if the welding conditions are constant, the resistance of the overcoat area will be lower and the amount of heat generated will be lower, resulting in welding to the overcoat area. Strength defects occur. (3) Defects due to metal powder adhesion A dendrite-like film tends to grow on both ends where the overcoat occurs. Such a dendrite-like film easily peels off even with a small impact, so the powder of the peeled off dendrite-like film adheres to the steel strip or roll, causing flaws on the steel strip and causing damage to the peeled part. This will lead to paint defects. (4) Poor paint film adhesion Plated steel strips are subjected to chemical conversion treatment to increase the adhesion of the paint film. An overcoat is formed in which excessive chemical conversion coating is deposited on both ends. This results in poor adhesion of the coating film in the overcoat area. (5) Poor appearance The overcoat parts on both ends of the steel strip become discolored, impairing the appearance and reducing the product value. The causes of overcoating as described above are as follows. That is, for example, an equipotential line is generated between a pair of upper and lower electrode plates and a steel strip that passes between the electrode plates, but since this potential wraps around to both ends of the steel strip, there is a difference with respect to this equipotential line. The current flowing at right angles to each other is concentrated at both ends. When the current is concentrated at both ends in this way, the current density at both ends becomes higher than that at the other ends, resulting in overcoating at both ends. The following method is known as a means to prevent overcoating of both ends of a steel strip. (1) Adjustment of the width of the electrode plate The overcoating ratio at both ends is different depending on whether the width of the electrode plate is longer or shorter than the width of the steel strip. That is, when the width of the electrode plate is longer than the width of the steel strip, the amount of plating on both ends increases, while when the width of the electrode plate is shorter than the width of the steel strip, the amount of plating on both ends increases. Since the amount of adhesion decreases, the number of electrode plates that are divided into multiple pieces in the width direction of the steel strip is adjusted, and the electrode plate is divided into parts whose width is longer and shorter than the width of the steel strip. and then compose,
Plating the steel strip. (2) Interrupting the plating current at both ends of the steel strip An electrical insulator, commonly called an edge mask, is placed between the electrode plate and both ends of the steel strip to physically block the current flow to both ends. Cut off. However, with method (1) above, even if the width of the electrode plate is made shorter than the width of the steel strip,
The amount of plating on both end faces of the steel strip does not decrease much. Furthermore, there is a problem in that a lot of effort is required to adjust the number of electrode plates that are divided into a plurality of pieces in order to adjust the width of the electrode plates. In addition, with method (2) above, it is difficult to prevent overcoating properly, and furthermore, if the steel strip meanderes, the steel strip may come into contact with the edge mask and cause damage to the steel strip. This may cause problems such as damage to the edge mask or damage to the edge mask. [Object of the Invention] Therefore, the object of the present invention is to form a high-quality plating film having a uniform surface texture without causing an overcoat at both ends of the metal strip during continuous electroplating of the metal strip. The object of the present invention is to provide a method for continuous electroplating of metal strips. [Summary of the Invention] The present inventors have conducted extensive research to solve the above-mentioned problems. As a result, the overcoat that occurs on the metal strip is caused by the potential flowing around to both ends of the metal strip, so electric conductors as auxiliary electrode plates are placed near both ends of the metal strip, and If the electric conductor is connected to a power source with the same polarity as the metal strip, and the electric conductor is also plated at the same time as the metal strip, current concentration at both ends of the metal strip is prevented, and the current concentration at both ends is prevented. The plating film formed on the surface of the electrical conductor can be prevented from overcoating, and the plating film formed on the surface of the electrical conductor can be continuously or intermittently
It has been found that removing the powder outside the electroplating tank can prevent the occurrence of product defects caused by the dendrite-like powder of the plating film, which is formed on the electrical conductor and peeled off due to plating, adhering to the metal strip or roll. . The present invention has been made based on the above findings, and consists of continuously introducing a metal strip into an electroplating tank in which at least one electrode plate is arranged, and moving the metal strip along the electrode plate. In a method for continuous electroplating of a metal strip, in which the surface of the metal strip is continuously electroplated, the metal strip is moved along the at least one electrode plate in the electroplating bath at both widthwise ends of the metal strip. By arranging adjacent, endless electrically conductive strips in a circularly movable manner, and passing a current between the electrically conductive strips and the at least one electrode plate, the electrical conductors along with the metallic strips are connected to each other. The conductor is also plated to prevent an overcoat from forming on both ends of the metal strip, and the plating film formed on the band-shaped electrical conductor is transferred to the metal strip by circulating the strip-shaped electrical conductor. It is characterized by being removed outside the electroplating bath. [Structure of the Invention] Next, the present invention will be explained with reference to the drawings. FIG. 1 shows a first embodiment of the invention,
FIG. 2 is a schematic longitudinal sectional view of the vertical electroplating apparatus, and FIG. 2 is a schematic plan view thereof, in the case of continuous electroplating of steel strips using the vertical electroplating apparatus. As shown in FIG. 1, the vertical electroplating device includes conductor rolls 2, 2 provided above the steel strip inlet and outlet sides of the vertical electroplating tank 1, and conductor rolls 2, 2 provided at the bottom of the electroplating tank 1. The provided sink roll 3 and conductor rolls 2, 2
and the sink roll 3, a pair of vertical electrode plates 5, 5 and 6, arranged parallel to the steel strip 4, with the steel strip 4 moving in the electroplating bath 1 in between. It consists of 6. Each of the pair of vertical electrode plates 5,5 and 6,6 is connected to the anode side of the power source 7, and the conductor rolls 2,2 are connected to the cathode side of the power source 7. The steel strip 4 moves downwardly and then upwardly in the electroplating bath 1 in which the plating bath is contained and flowing, continuously while passing a pair of electrode plates 5,5 and 6,6. It is electroplated. In this invention, in the electroplating tank 1, one
Close to both ends in the width direction of the steel strip 4 moving between each of the pairs of vertical electrode plates 5, 5 and 6, 6, on the same plane as the surface of the steel strip 4 and parallel to the steel strip 4, Short, endless band-shaped electrical conductors 8, 8 made of thin steel plates are arranged so as to be able to circulate. Each of the band-shaped electrical conductors 8, 8 is connected to a conductor roll 9 disposed above the electroplating tank 1 and a drive roll 1 rotated by a drive mechanism (not shown).
0 and 2 for reversing the moving direction of the band-shaped electrical conductor 8 upward, which is arranged near the lower ends of the electrode plates 5, 5 and 6, 6 in the electroplating bath 1.
The two sink rolls 11, 11 are routed around each other. The conductor roll 9 is connected to the cathode side of the power source 7, so that a plating current also flows between the electrode plates 5, 5 and 6, 6 and the strip-shaped electrical conductor 8. Between the conductor roll 9 and the drive roll 10 arranged above the electroplating tank 1, a plating layer formed on the surface of the strip-shaped electrical conductor 8 moving between the conductor roll 9 and the drive roll 10 is peeled off. A pair of upper and lower knife edges 1 for removing
A plating film removal mechanism 13 consisting of two parts is provided. The strip-shaped electrical conductor 8 is movable by means of a position adjuster 14 towards the ends of the steel strip 4 so that the distance therebetween can be controlled. Endless strip-shaped electrical conductors 8, 8 are each wound around a conductor roll 9 and a drive roll 10 arranged above the electroplating tank 1, and sink rolls 11, 11 arranged inside the electroplating tank 1. , by the rotation of the drive roll 10, it circulates continuously or intermittently at a predetermined speed. The steel strip 4, moving downwards and then upwards in the electroplating bath 1 in which the electroplating bath is contained and flowing, receives electricity while passing between a pair of electrode plates 5,5 and 6,6. It will be marked. At this time, a band-shaped electrical conductor 8 and an electrode plate 5, which are disposed close to each of both widthwise ends of the steel strip 4,
5 and 6, 6, the current from the power supply 7 also flows between them. Therefore, as before, the steel strip 4
The current concentrated at the ends of the steel strip 4 is concentrated in the strip electrical conductor 8, thus preventing overcoating of the ends of the steel strip 4. The plating film formed on the strip-shaped electrical conductor 8 is removed by the plating film removal mechanism 13 provided above the electroplating tank 1 by circulating the strip-shaped electrical conductor 8. Moreover, the band-shaped electrical conductor 8 is
The position adjustment mechanism 14 allows movement in the width direction of the steel strip 4 so as to follow the meandering of the steel strip 4 and to maintain a constant position from both end faces thereof. FIG. 3 is a schematic longitudinal cross-sectional view of a vertical electroplating device according to a second embodiment of the present invention, in the case where a steel strip is continuously electroplated, and FIG. FIG. The second embodiment of the method shown in FIGS. 3 and 4 is similar to that shown in FIG. and the first one shown in Figure 2.
The method is the same as that of the embodiment. FIG. 5 is a schematic vertical cross-sectional view of a horizontal plating device according to a third embodiment of the present invention, in the case where a steel strip is continuously electroplated using the horizontal plating device, and FIG. FIG. The horizontal electroplating device is connected to the cathode side of a power source 7 provided at each of the steel strip inlet and outlet sides of the horizontal electroplating bath 15, as shown in FIGS. 5 and 6. It consists of conductor rolls 16, 16 and a horizontal electrode plate 17 arranged below and parallel to the steel strip 4 while it is moving in the electroplating bath 15. The steel strip 4 moves horizontally in an electroplating bath 15 in which a plating bath is contained and flowing;
While passing over the electrode plate 17, one side thereof is continuously electroplated. In the method of the third embodiment, in the electroplating bath 15, there is provided a plate that is close to both ends in the width direction of the steel strip 4 that is moving above the electrode plate 17, and that is on the same plane as the surface of the steel strip 4. Parallel to the strip 4, a short endless band-shaped electrical conductor 8 made of a thin steel plate is arranged so as to be able to circulate. The strip-shaped electrical conductor 8 is wound around a conductor roll 9 and a drive roll 10 arranged above the electroplating tank 15 and two sink rolls 11, 11 arranged inside the electroplating tank 1.
The conductor roll 9 is connected to the cathode side of the power source 7. Between the conductor roll 9 and the drive roll 10 arranged above the electroplating tank 15, there is a plating made of a knife edge 12 or the like for peeling off and removing the plating film formed on the surface of the strip-shaped electrical conductor 8. A film removal mechanism 13 is provided. The band-shaped electrical conductor 8 is made movable in the width direction of the steel strip 4 by a position adjustment mechanism 14 so as to follow the meandering of the steel strip 4 and to be maintained at a constant position from both end faces thereof. The operation of the method of the third embodiment is the same as the method of the first embodiment. FIG. 7 is a schematic plan view showing an example of a strip-shaped electrical conductor for single-sided electroplating, and FIG. 8 is a schematic cross-sectional view thereof. The band-shaped electrical conductor 18 shown in FIGS. 7 and 8 consists of a stainless steel mesh plate 18a and a fluororesin layer 18b coated on one surface of the mesh plate 18a.
It is made up of. According to this band-shaped electrical conductor 18, the fluororesin layer 18b is not plated. Therefore, the knife edge 12 in the plating film removal mechanism 13 need only be provided on the mesh plate 18a side of the strip-shaped electrical conductor 18. Note that the plating film removal mechanism 13 removes the plating film using the knife edge 1.
The removal is not limited to 2, and may be performed by, for example, chemical removal such as hydrochloric acid, or electrochemical removal. [Examples of the Invention] Next, examples of the invention will be explained together with comparative examples. Example 1 A degreased and pickled steel strip 4 with a width of 500 mm was
According to the method of the first embodiment shown in FIGS. 1 and 2, an electro-tinning bath is moved at a speed of 180 mpm in a vertical electro-plating tank 1 containing an electro-tinning bath;
Both surfaces were continuously electroplated with tin so that the amount of tin deposited was 10 g/m ² . The strip-shaped electrical conductor 8 uses a steel strip with a width of 20 mm,
The steel strip 4 was spaced 10 mm from each end. The strip-shaped electrical conductor 8 was circulated at a speed of 60 mpm, and the tin plating film formed on its surface was removed by a plating film removal mechanism 13 disposed above the plating tank 1. Example 2 One side of a steel strip 4 is electroplated with tin, and a band-shaped electrical conductor is made of a stainless steel mesh plate 18a and a fluororesin layer 18b coated on one side, as shown in FIGS. 7 and 8. Continuous electrolytic tin plating was carried out in the same manner as in Example 1, except that the strip-shaped electrical conductor 18 was used. Example 3 A degreased and pickled steel strip 4 with a width of 500 mm was
According to the method of the second embodiment shown in FIGS. 3 and 4, the vertical electroplating bath 1 containing the electrolytic tinning bath was moved, and both surfaces thereof were continuously electroplated. The band-shaped electrical conductor 8 has a width of 20
mm steel strip was used and placed perpendicular to the steel strip 4 with a spacing of 20 mm from each of its ends. The moving speed of the steel strip 4 and the band-shaped electrical conductor 8, the amount of tin deposited on the steel strip 4, etc. are as follows.
Same as Example 1. Example 4 A degreased and pickled steel strip 4 with a width of 500 mm was
According to the method of the third embodiment shown in FIGS. 5 and 6, the horizontal electroplating tank 15 containing the electrogalvanizing bath is moved at a speed of 100 mpm, and the amount of zinc deposited on one side is 20 g. Continuous electrogalvanizing was carried out so that the ^{area of} Width 20 for single-sided plating shown in Figures 7 and 8
mm electrical conductors 18 were used and spaced 10 mm from each end of the steel strip 4. The strip-shaped electrical conductor 18 was circulated at a speed of 50 mpm, and the galvanized film formed on its surface was removed by the plating film removing mechanism 13 disposed above the plating tank 1. Comparative Example 1 Example 1 except that the band-shaped electrical conductor 8 is not provided.
The steel strip 4 was electroplated continuously under the same conditions. Comparative Example 2 When continuously electrolytically tin-plating the steel strip 4 under the conditions of Example 1, a thin steel plate of 20 mm width and 1 mm thickness was placed near the electrode plate at a distance of 20 mm from both ends of the steel strip 4. An electrical conductor was fixedly placed flush with and parallel to the surface of the steel strip 4. Comparative Example 3 A steel strip 4 was continuously electrogalvanized under the same conditions as in Example 4, except that the strip electrical conductor 18 was not provided. Table 1 shows the above-mentioned Examples 1 to 4 and comparative examples.
Table showing the amount of plating in the width direction of the steel strip electroplated with 193, the degree of prevention of overcoat generation, and the presence or absence of dendrites.

〔Effect of the invention〕

As described above, according to the present invention, during continuous electroplating of a metal strip, an overcoat does not occur at both ends of the metal strip, and a high-quality plating film with uniform surface properties can be formed. Excellent industrial effects are brought about.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view of the electroplating device in the case of continuously electroplating a steel strip using a vertical electroplating device, showing a first embodiment of the present invention, and FIG. 2 is a schematic plan view thereof. , 3rd
The figures show a second embodiment of the present invention, in which a vertical electroplating apparatus is used to electroplat a steel strip; FIG. 4 is a schematic longitudinal sectional view of the electroplating apparatus; FIG. The figure shows a third embodiment of the present invention, a schematic vertical sectional view of a horizontal electroplating device in the case of continuous electroplating on a steel strip;
FIG. 6 is a schematic plan view thereof, FIG. 7 is a schematic plan view showing an example of a strip-shaped electrical conductor for single-sided electroplating used in the present invention, and FIG. 8 is a schematic cross-sectional view thereof.
FIG. 9 is a graph showing the distribution of the amount of plating in the width direction of the steel strip in the example of the present invention and the comparative example. In the drawings, 1...Vertical electroplating tank, 2...Conductor roll, 3...Sink roll, 4...Steel strip, 5, 6...Electrode plate, 7...Power supply, 8...Strip-shaped electrical conductor , 9... Conductor roll, 10...
Drive roll, 11... sink roll, 12... knife edge, 13... plating film removal mechanism, 14
... Position adjustment mechanism, 15 ... Horizontal electroplating tank, 16 ... Conductor roll, 17 ... Electrode plate.

Claims (1)

[Scope of Claims] 1. A metal strip is continuously introduced into an electroplating bath in which at least one electrode plate is disposed, and while the metal strip moves along the electrode plate, a continuous electroplating layer is applied to the surface of the metal strip. In a continuous electroplating method of a metal strip, an endless band-shaped electrical conductor is disposed adjacent to both widthwise ends of the metal strip moving along the at least one electrode plate in the electroplating bath. are disposed so as to be cyclically movable, and the strip-shaped electrical conductor is plated together with the metal strip by passing a current between the strip-shaped electrical conductor and the at least one electrode plate, Preventing an overcoat from occurring on both ends of the metal strip, and removing a plating film formed on the strip-shaped electrical conductor outside the electroplating bath by circulating the strip-shaped electrical conductor. A continuous electroplating method for metal strips characterized by: