JPS6122040B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for electrolytic treatment of metal strips such as electroplating and surface cleaning treatment, and more particularly to a method and apparatus for electrolytic treatment of metal strips while fluidly supporting the strip in a horizontal position. .

For example, in recent years, a method for continuous electroplating of steel sheets has been developed in which a strip is run horizontally through a horizontal plating cell, and electrolyte is flowed between the electrodes in the cell and the strip. has been adopted. Generally, in order to operate efficiently and obtain products of excellent quality in an electroplating method, a configuration is required that allows metal to be deposited at a high current density and that enables low voltage operation. The policy for increasing current density is as shown in equation (1), which is the critical current density i
The goal is to increase _d .

i _d = nFDC/δ ...(1) i _d = critical current density (A/cm ² ) n = number of charges of metal ion F = Faraday constant D = diffusion coefficient of metal ion (cm ² /sec) C = metal Ion concentration δ=thickness of the diffusion layer To this end, increasing the concentration of metal ions, increasing the bath temperature, etc. can be proposed as measures to improve the solution surface.
On the other hand, it is known that the diffusion layer δ becomes smaller due to the moving speed of the plating solution on the electrolytic surface, i.e., due to stirring or an increase in the flow rate. desirable.
Furthermore, for low voltage operation, it is necessary to take into account the voltage increase due to strip resistance, liquid resistance, and gas accumulation, as expressed by equation (2).

V _T = Vd + Vs + Vl + Vg ... (2) V _T = Voltage between electrodes Vd = Decomposition voltage Vs = Voltage due to strip resistor Rs. Proportional to the effective length L from the conductor roll to the anode.

=I・Rs・L Vl=Voltage due to liquid resistance Re. Proportional to distance H between poles.

=I・Re・H Vg = voltage due to gas accumulation.

As is clear from equation (2) above, the key points of the Metsuki cell design to achieve low voltage operation are to shorten the distance between the electrodes as much as possible and to remove the oxygen gas generated at the anode from between the electrodes as quickly as possible. must be placed.

Various electroplating techniques that satisfy the above conditions have been proposed in the past, but no plating method or apparatus has been found that can perform more efficient and reliable plating. For example, in Japanese Patent Publication No. 50-8020, an electrolytic solution is jetted countercurrently to the traveling direction of the strip in a cylindrical plating tank with a rectangular cross section, the sides of which are opposite to the upper and lower surfaces of the strip are made up of insoluble anodes. However, a method for removing air bubbles generated from the anode is disclosed. However, with this method, there is no suitable means for holding the strip running horizontally, so the strip may have catenary, C-curvature (curvature in the width direction), or twist (tilt in the width direction).
It is easy to cause these problems, and it does not have a corrective function.

On the other hand, as a means of obtaining the supporting force of the strip by the collision pressure of the electrolyte jet (dynamic pressure support),
Publication No. 3604 is mentioned, but with this method, the pressure attenuation due to the distance between the strip and the spout is small;
It does not cause C-curvature of the strip, corrective force of twist, or restoring force of the center ring of the catenary.

In order to prevent such unstable behavior that occurs when threading a strip catenary, etc., and to maintain a stable threading state, an attempt has been made to support the strip with the static pressure of an electrolytic solution, and this method has been shown to have good effects. It has been found that the following can be obtained (Japanese Patent Application No. 57-18836 (Japanese Unexamined Patent Publication No. 58-136796)). This patent application No. 18836/1983 relates to a horizontal fluid-supported electrolytic cell with a strip, in which a slit nozzle is installed on a part of the electrode surface facing the strip for spraying the electrolyte and for generating static pressure on the strip surface. It is characterized in that the hydrostatic fluid support pads having the following characteristics are vertically symmetrically provided.

However, when the above-mentioned static pressure support pad is actually applied to a horizontal electrolytic treatment method for strips, the arrangement and shape of the spout of the support pad pose problems. In other words, the placement of the hydrostatic fluid support pad uses its static pressure to reduce the catenary of the strip and maintain the strip stably, and also improves the flow of electrolyte between the electrodes compared to conventional methods, thereby stabilizing the ions. Although it is clear that it is effective in supplying and removing gas, the recent increase in line speed aimed at improving productivity requires that the function of the static pressure support pad be demonstrated to an even higher level. ing. In particular, the flow of electrolyte is affected by the increase in line speed, and with the static pressure pad of the slit nozzle arrangement and shape used up until now, the liquid does not flow uniformly over the entire electrode installation range.
This causes variations in ion concentration, making it difficult to remove gas.

An object of the present invention is to provide an electrolytic treatment method that allows the electrolytic solution to flow as a uniformly distributed flow throughout the strip and between the electrodes when passing through the plate, eliminates gas accumulation, and performs a good electrolytic treatment.

On the other hand, the present invention provides an electrolytic treatment apparatus which can effectively carry out the above method, can reduce the distance between the poles as much as possible, can stably hold the strip, and can exert the ability to correct C warpage, twist, etc. Another purpose is to do something.

The details of the present invention will be explained below based on the drawings.

FIG. 1 shows the basic configuration of electroplating equipment as an example. As shown in FIG. 1A, a box-shaped tank 2 containing an anode 1 facing the upper and lower surfaces of a strip 3 running horizontally in the direction of the arrow is arranged along the direction in which the strip travels. Opposed fluid pads 12 are incorporated in the longitudinal center of the box-shaped tank 2, and the plating liquid is supplied into the pads from a header 10 connected to the back of the fluid pads 12, and the strips of the pads 12 are Slit 16 provided on the opposing surface
It is ejected towards the strip surface. The plating liquid is divided into the advancing direction of the strip 3 (parallel flow) and the direction opposite to the strip (counterflow), and is then passed through the discharge ports 8 and 9.
More leakage. There are fitting liquid outflow rate control plates 11 at the discharge ports 8 and 9, and the flow rate is controlled by moving the control plate 11 up and down to control the gap with the strip. The plating liquid flowing out from the outflow ports 8 and 9 is stopped by the conductor roll 6 and the back-up roll 7, is received in the receiving tank 4, enters the circulation tank (not shown) from the plating liquid outlet 5, and is pumped by the pump. Then, it is forced to circulate to the header 10. Power is supplied from the conductor roll 6 to the strip and to the anode via the bus bar. The flow of liquid between the electrodes is illustrated using arrow symbols.

The part of the fluid pad 12 facing the strip in which the slit 16 is provided may be made of the same material as the electrode 1 and energized, or may be made of a different material from the electrode and not energized.

Figures 1B and 1C are cross-sectional views of the above-mentioned device (A-
A, B--B), and as shown in the drawings, the ends of the strips 3 can optionally be provided with a sealing mechanism, for example an edge mask 17 connected to a horizontally movable support 18. Furthermore, when the edge mask 17 is not used or when the support 18 is accommodated within the tank, the side walls may be integrated.

Hydrostatic fluid support pad 1 used in the present invention
As shown in Fig. 2A, the jet nozzle in No. 2 is surrounded by slits 16 at least in both the width direction and the traveling direction of the strip. The shape is not limited to this, and it is sufficient that a substantially closed loop shape is formed by, for example, a plurality of slits. In addition, as shown in Figure 2B, the spout opening of the pad is not a slit, but a number of holes (square holes or circular holes may also be used) arranged close together so that the jetted liquid forms a substantially closed curtain. It is also possible to configure an outlet 16A. The point is that a substantially closed loop can be formed by the slit or hole and the ejected liquid can be kept in a continuous state. More preferably, two or more pairs of ejection ports extending in the direction of travel of the strip are provided within the one closed loop.

Next, the present invention is characterized by the direction in which the electrolyte is sprayed from the static pressure pad 12 onto the three surfaces of the strip. That is, among the slits 16 or jet ports 16A of the static pressure pad 12, the slits or jet ports (hereinafter referred to as slits, etc.) along the width direction of the strip 3 are inclined in a direction opposite to the direction in which the strip 3 moves. In particular, among the slits, etc. extending in the width direction of the strip in the static pressure pad 12, at least the exit side slits, etc. are always inclined in the opposite direction to the strip advancing direction, and the slits, etc. other than the exit side slits, etc. are on the strip surface. or inclined in a direction opposite to the direction of strip movement.

In conventional hydrostatic pads, the slits extending in the width direction of the strip are all oriented approximately perpendicular to the strip plane or inclined inwardly at symmetrical angles, but with this slit arrangement, the strip advances in one direction. Therefore, the flow of the electrolyte is biased by the strip, and a difference in the distribution flow rate of the electrolyte occurs before and after the pad. In other words, even if the electrolytic solution is ejected evenly in the front-rear direction at the pad position, the strip carries out the solution in the advancing direction, causing the above-mentioned flow rate difference and hindering uniform electrolytic action. In particular, this tendency increases as the stripping speed increases.
Moreover, the smaller the distance between the strip and the electrode (the closer the strip is), the more conspicuous it becomes.

Therefore, in the present invention, as described above, a large amount of electrolyte is caused to flow in the direction opposite to the direction in which the strip travels. For example, in the example shown in FIG. 3A, of the pair of slits extending in the width direction of the strip 3 of the pad 12, the exit side slit 16B is inclined in a direction opposite to the direction of movement of the strip 3, and the entrance side slit 16C is is formed perpendicularly to the surface of the strip 3, and generates static pressure in the space 20 between the pad surface and the strip 3 sandwiched between the slits 16B and 16C.

The pad shown in Figure 3B is effective when the stripping speed is faster and/or the distance between the electrode and the pad is short.
Both 6D and 16E are inclined in a direction opposite to the direction in which the strip 3 moves. Furthermore, if the stripping speed becomes extremely high and/or the distance between the electrodes and the pads becomes extremely small, the inclined slits 16F, 16G, 16H in the opposite direction to the advancement of the strip 3, as shown in FIG. All you have to do is increase the number of . In this way, the flow rate of the electrolytic solution is made uniform over the entire electrode area, and a good electrolytic treatment is achieved.

As mentioned above, at least the strip outlet slit is inclined in the opposite direction to the strip advancement, and the other slits are inclined in the same direction as the outlet side slit or are made almost vertically, so that uniform distribution of the electrolyte can be ensured. Since the effective area on which the static pressure acts is not narrowed that much, there is no problem in maintaining the stability of the strip.

Next, the restoring force of the static pressure support pad used in the present invention will be explained. When electrolyte is injected onto the strip surface using a pad with a slit shown in Figure 3, static pressure is generated between the pad and the strip, holding the strip in a fixed position and causing the strip to warp or curve. It is known that there is an effect to correct the twisting phenomenon when it occurs. FIG. 4 shows an example of a static pressure pad with a strong restoring force that can more reliably and quickly correct C-curves and twists in the strip.

That is, in all of FIGS. 4A to 4C, the strip longitudinal slit etc. in the peripheral slit etc. formed in the pad body is divided into two or more in the width direction. First, the example in Figure 4A is for strip 3.
The example in Figure 4B has two pairs of slits 26 arranged symmetrically in the width direction of the strip, the example in Figure 4B has a center slit added to A, and the example in Figure 4C has slits closer to the ends in the width direction of the strip. It is divided into four pairs of slits 36.

Next, embodiments of the present invention will be described.

FIG. 5 shows the relationship between line speed and flow distribution ratio when electrolyte is injected using a static pressure pad 12 having an ejection angle perpendicular to the strip 3. C indicates counterflow, P indicates parallel flow. As the line speed increases, the flow velocity of the countercurrent decreases, the flow rate distribution ratio decreases, and the gas retention within the electrolytic cell 1 increases significantly. As a result, as shown in FIG. 6, a voltage rise occurs, making it impossible to attach. Note that, as shown in FIG. 5, as the distance H between poles increases, the distribution ratio tends to decrease as the line speed increases.

Therefore, as shown in FIG. 7, a static pressure pad was created in which the angle of the nozzle extending in the width direction of the strip with respect to the strip surface was changed, and the liquid distribution ratio to the opposing flow was investigated. The results are shown in FIG. In Fig. 7, θ ₁ is the nozzle angle on the inlet side in the strip advancing direction, θ ₂ is the nozzle angle on the outlet side, and A is θ ₁ =
90°, θ ₂ = 45°, b is θ ₁ = 90°, θ ₂ = 30
°, C is θ ₁ = 60 °, θ ₂ = 45 °, D is θ ₁ =
135°, θ ₂ = 45°, E is θ ₁ = 90°, θ ₂ = 90
(a) to (c) are examples of the present invention, and (d) and (e) are comparative examples.

As can be seen from FIG. 8, at least the nozzle angle _θ2 on the strip exit side is inclined in the direction opposite to the direction of strip movement, and the other nozzle angles are inclined perpendicular to the strip plane or in the direction opposite to the direction of movement of the strip. It was found that almost equal liquid distribution was possible even at a line speed of 200 m/min. On the other hand, with the combination of nozzle angles as in the comparative example, uniform liquid distribution is impossible.

Therefore, when manufacturing an actual electrolyzer, by selecting an appropriate angle θ in accordance with the set line speed, rapid gas removal is possible without reducing the flow velocity of the counterflow.

As described above, according to the electrolytic treatment method of the present invention, the electrolytic solution is distributed almost equally to both sides of the pad and the holding force of the strip is large, so the distance between the electrodes can be shortened, resulting in extremely high efficiency. It becomes possible to perform good electrolytic treatment. In addition, it can be expected to have the ability to correct C warpage and twist of the strip.
Contributes to stable running of the strip and good processing operation. On the other hand, according to the electrolytic treatment apparatus of the present invention, the above-mentioned method can be carried out effectively, and there are great advantages in terms of equipment.

[Brief explanation of the drawing]

FIG. 1A is a schematic sectional view showing the overall structure of the electroplating equipment, B is a sectional view taken along line AA in FIG. 1, and C is a sectional view taken along line BB in FIG. FIGS. 2A and 2B are plan views showing the configuration of fluid jet ports provided in the hydrostatic fluid support pad. 3A, 3B, and 3C are cross-sectional views showing various aspects of the ejection direction of the electrolytic solution, and 4A, 4B, and 3C are plan explanatory views showing examples of nozzle (slit) patterns formed on the pad body. . Figure 5 is a graph showing the relationship between line speed and liquid distribution ratio when using a pad with a vertical nozzle, Figure 6 is a graph showing the relationship between line speed and electrolytic voltage in Figure 5, and Figure 7 is a graph showing the relationship between line speed and electrolysis voltage in Figure 5. -E are sectional views showing various examples of nozzle angles used in the examples, and FIG. 8 is a graph showing the results of the study in FIG. 7 in terms of the relationship between line speed and liquid volume distribution ratio. 1... Anode, 2... Electrolytic cell, 3... Strip, 12... Fluid pad, 16, 26... Slit.

Claims (1)

[Claims] 1. When performing electrolytic treatment by arranging electrodes facing each other on the upper and lower surfaces of a horizontally passing metal strip and flowing an electrolytic solution between the electrodes and the strip,
The electrolytic solution is ejected toward the strip surface from a hydrostatic fluid support pad provided at the center of the electrode in the direction in which the strip travels, and a slit or spout opening on the strip exit side extends in the strip width direction of the hydrostatic pad. Alternatively, the electrolytic solution is injected diagonally in the direction opposite to the direction in which the strip travels from the spout, and the electrolyte is injected perpendicularly to the strip surface or diagonally in the opposite direction to the direction in which the strip travels from other slits or jet ports. 1. A horizontal fluid-supported electrolytic treatment method for a metal strip, characterized in that: 2. Electrodes are disposed opposite the upper and lower surfaces of a metal strip that passes horizontally, and the electrode has a slit or a substantially continuous ejection port in the center of the electrode in the direction of strip movement for ejecting the electrolyte toward the strip surface. a hydrostatic fluid support pad is provided, of the slits or spout openings extending in the strip width direction of the static pressure pad, the strip width direction slits or spout openings on the strip exit side are inclined in a direction opposite to the traveling direction of the strip; A horizontal type fluid-supported electrolytic treatment apparatus for a metal strip, characterized in that the other slits or jet ports are arranged perpendicular to the strip surface or inclined in a direction opposite to the direction in which the strip travels.