JPH0459399B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an insoluble electrode used as an anode of an apparatus for continuously electroplating metal strips such as steel strips, and a method for manufacturing the same.

(Prior Art) As shown in FIG. 3, a normal electric plating line is arranged above and below a steel strip through which the anode electrode 8 is passed, and a plating liquid is supplied from a nozzle 19.
17 in the figure is an energized roll that comes into contact with the steel strip,
Reference numeral 18 denotes an auxiliary roll that supports the energizing roll 17. As shown in FIG. 4, the structure of this anode electrode 8 is as shown in FIG.
21 are connected by welding 7, and the entire current-carrying plate 21 is covered with a lead alloy 22. In order to cover the current-carrying plate 21 with the lead alloy 22, the cast base material of the lead alloy is heated using an acetylene gas or other burner. The method used was to melt the material while directly heating it using a molten metal and then apply it one by one.

Note that 5 in the figure is a separator for the purpose of preventing contact between the strip and the electrode.

When an insoluble electrode manufactured by this method is used as an anode for electrogalvanizing in a sulfuric acid plating solution, the surface layer of the lead alloy coated on the insoluble electrode surface is gradually worn away by electrolytic corrosion, and the electrode surface The distance between the steel strip and the steel strip increases, and the electrical resistance between the electrode and the steel strip during electroplating increases due to the increase in the current conduction distance during plating. Therefore, the voltage drop during energization increases and the plating power increases. In addition, since the wear and tear caused by electrolytic corrosion is different for each part of the surface, unevenness occurs on the surface. In this case, the smooth flow of the plating liquid on the electrode surface is obstructed, and the gas generated by electrolysis on the electrode surface cannot be smoothly discharged, resulting in local gas accumulation at the boundary between the electrode surface and the plating liquid. , the electrical resistance increases, and the voltage drop during energization increases in the same way as the distance between the electrode and the steel strip increases.

Moreover, the unevenness of the electrode surface further increases the pressure loss when the plating liquid passes between the electrode and the steel strip, reduces the flow rate of the plating liquid due to the pump characteristics, and also impedes smooth gas discharge.

Furthermore, if leached lead gets mixed into the plating layer of the steel sheet, it will impair the heat resistance of the plating surface, causing quality problems.

In order to solve these problems, the present applicant previously proposed in Japanese Utility Model Application Publication No. 62-180077 to cover the discharge side surface of a current-carrying plate for electroplating with a layer made of a rolled lead alloy plate or drawn material. is suggesting.

(Problems to be Solved by the Invention) The present inventor has confirmed that the technology presented in the previously filed Utility Model Publication No. 180077/1983 can be fully utilized as an insoluble electrode, but in addition, the corrosion resistance in a bath is We devised ways to improve electrical conductivity. When the lead alloy 2 is built up on the current-carrying plate 21 of the insoluble electrode shown in FIG. 4 by homogenization or casting, the structure is coarse and has many pores and the like, resulting in a coarse density.

Furthermore, since there are many internal defects such as cavities peculiar to homogeneous processing and casting, such as segregation of tin, the plating solution easily penetrates and diffuses from the surface of the lead alloy into the interior. Furthermore, if there is segregation within the lead alloy structure, a local battery will be formed in the presence of the plating liquid, and tin at the interface in contact with the liquid will be eluted, making the skin of that area rough, and further caused by erosion wear due to the plating liquid passing between the electrodes. It wears out. In the case of non-dissolving electrodes for galvanizing, further penetration and
Corrosion progresses in a chain due to diffusion, leading to early wear.

Recently, expensive lead alloys to which high-grade elements such as silver (Ag) or indium (In) are added have been developed as lead alloy materials for coating the current-carrying surfaces of electrodes. It is known from Japanese Patent Publication No. 60-24197 that if these materials are applied to the current-carrying surface, the life of the electrode will be greatly improved. However, when coating a current-carrying surface with a lead alloy, if the thickness is too thin, the current-carrying plate will be exposed even if the lead alloy wears down slightly, and if the strip comes into contact with the exposed part, the heat from the shot will be absorbed by the melting heat of the lead. It becomes a source of ignition because it is not consumed as
Hydrogen generated on the electrode surface ignites, causing a small explosion.

To prevent this problem, the thickness of the lead alloy is generally
Although the thickness is 10 mm or more, if the lead alloy added with high-grade elements such as silver and indium is used as a single material throughout the thickness, the price will be extremely high.

(Means for Solving the Problems) Therefore, the inventors of the present invention have developed an electrode that does not impair current efficiency and has superior strength and corrosion resistance in plating baths compared to conventional insoluble electrodes. do.

The gist of the present invention is that lead or tin 2 is formed on the discharge side surface of a current-carrying plate for electroplating by being cast into a mold or overlaid by homogenization.
A first metal layer of lead or lead-tin alloy consisting of ~8% balance lead and unavoidable impurities, and either 0.2~1.0% silver or 1~5% indium consisting of a rolled plate or drawn material on the first metal layer. Or, a second metal layer of lead or lead-tin alloy containing both and the balance consisting of lead and unavoidable impurities is overlaid, and the second metal layer of lead alloy and the first metal layer of lead or lead-tin alloy are stacked. An insoluble electrode for continuous electrogalvanizing of metal strips, characterized in that the adhesive surfaces are bonded by diffusion, and an electrode formed by casting in a mold on the discharge side surface of a current-carrying plate for electroplating. Alternatively, a first metal layer of lead or a lead-tin alloy made of lead or tin with a balance of 2 to 8% lead and unavoidable impurities and a first metal layer of lead or a lead-tin alloy overlaid by homogen processing. A second metal layer of a lead alloy made of rolled plate or drawn material containing either 0.2 to 1.0% silver, 1 to 5% indium, or both, and the balance consisting of lead and unavoidable impurities is overlaid, and this is processed. After inserting it into a pressure vessel and filling it with inert gas, pressurize it until the internal pressure reaches 600~
An insoluble electrode for continuous electrogalvanizing of metal strips, which is characterized by bonding a current-carrying plate to each of the first and second metal layers by holding the electrode at a heating temperature of 100 to 300°C for a while at 2000Kg/ ^cm 2 This is a manufacturing method.

(Function) As shown in Fig. 1, the insoluble electrode of the present invention has a structure in which lead (Pb) is placed on the discharge side surface of the current-carrying plate A1 for electroplating.
or a first metal layer 2 of lead or lead-tin alloy containing 2 to 8% of tin (Sn) and 0.2 to 1.0 of silver (Ag).
%, indium (In) 1 to 5%, or both, the second metal layer 3 is stacked to form a three-layer structure.

In the present invention, an expensive material with high corrosion resistance and electrical conductivity is used for the upper second metal layer 3 of lead alloy. In addition, relatively low-cost lead or lead-tin alloy with high electrical conductivity is used for the second metal layer 2 of lead or lead-tin alloy in the lower layer, and the first metal layer 2 of lead or lead-tin alloy is used. In order to improve the adhesion between the layer 2 and the second metal layer 3 made of lead alloy, the adhesive surfaces are bonded by diffusion. Lower lead or lead-tin alloy first metal layer 2
The reason why we limited the composition to a lead alloy containing 2 to 8% tin (Sn) is that tin is a lead oxide (BbO ₂ ) formed on the lead surface, which originally does not have very good electrical conductivity.It makes the surface porous and conducts electricity. However, if the tin content exceeds 8%, the elution of tin becomes intense and the surface of the electrode becomes rough. Also%
Below, PbO ₂ increases the current carrying resistance and increases the electric power consumption when the electroplating exceeds 8%.

In addition, the composition of the second metal layer 3 of the upper lead alloy is 0.2 to 1.0% silver (Ag) and 1 to 5% indium (In).
The reason for adding silver and indium to lead is to intentionally make the surface of the PbO ₂ coating non-uniform with these elements, thereby reducing current carrying resistance, and at the same time reducing PbO ₂ , which has low mechanical strength. Although it is for reinforcement, the lower limit of silver/indium is 0.2 for silver.
This is because if the amount of indium is less than 1.0%, the effect becomes significantly smaller.

The reason why the upper limits are set to 1.0% silver and 5.0% indium is that if the content exceeds these limits, these additive metals are expensive, so the manufacturing cost of the electrode becomes extremely high.

Furthermore, as shown in FIG. 2, the method for producing an insoluble electrode of the present invention is to place a dissolving electrode 8 in which a first metal layer 2 of lead or a lead-tin alloy and a second metal layer 3 of a lead alloy are stacked in a pressurized container. 9, and after filling with inert gas, pressurize until the internal pressure is 600~2000Kg/cm ² and the heating temperature is 100~2000Kg/cm2.
Hold the temperature in the range of 300℃ for a while, then connect the current-carrying plate and each
The metal layer and the second metal layer are bonded together.

By the method of the present invention, the lead alloy part contracts under high temperature and high pressure, and the structure becomes dense, which suppresses the penetration and diffusion of liquid and prevents chain corrosion. Since the part is reconstituted into a solid solution, segregation is significantly improved, and corrosion due to local battery formation inside the electrode can be greatly suppressed.

The pressure inside the pressurized container in the present invention is 600 to 2000.
The reason why we set the upper limit to Kg/cm ² is that if it is less than 600 Kg/cm ² , the effect of densifying the structure and improving segregation is extremely small, and we set the upper limit to 2000 Kg/cm ² because if it is higher than this, the equipment price will increase. This is because it becomes expensive and uneconomical, and the reforming effect commensurate with the cost cannot be expected to be that large.

In addition, the heating temperature was limited to 100 to 300℃ because
This is because, like the pressure, the reforming effect is small at temperatures below 100°C, and the upper limit of 300°C is a value naturally determined from the melting point of the lead alloy.

(Example) FIG. 1 is a schematic diagram showing the entire insoluble electrode for electrogalvanizing of the present invention. Moreover, FIG. 2 is a schematic diagram showing the method for manufacturing the above-mentioned insoluble electrode.

As shown in Figure 1, a rolled or drawn plate of a lead alloy containing 95% lead and 5% tin is used as the intermediate plate 2 on the discharge side surface of the titanium current-carrying plate A1, and the periphery of the mating end surface is exposed to electron beams. It is installed by seal welding, etc., and then tin is applied to the surface opposite to the joint surface.
A rolled plate or drawn plate 3 made of 0.5% indium, 3% indium, and the remaining lead is attached by seal welding in the same way as the intermediate plate 2, so that it has a three-layer structure of the current-carrying plate and the middle and upper layer lead alloy plates. After laminating the
The laminate is placed in a pressurized container 9 shown in FIG. 2, and after filling the inside with an inert gas such as nitrogen or argon, the internal pressure is increased to 1200 Kg/cm ² using a compressor 10.
An insoluble electrode for electrogalvanizing was fabricated by increasing the pressure to 300°C and holding the heating temperature for about 1 hour, and used it in electrogalvanizing equipment.

At that time, the current-carrying plate 1 in FIG. 1 was 10 mm thick, the intermediate plate 2 was 15 mm thick, and the upper layer lead alloy 3 was 5 mm thick. Further, 4 indicates each joint surface. Furthermore, the second
In the figure, 11 is a heater for heating, 12 is a lid for the charging section, 13 is a heat insulating material, 14 is a support stand, and 15 is a high pressure gas introduction pipe.

In addition, this time, we created a three-layer structure by joining a rolled plate or a drawn plate to the current-carrying plate 1, but instead of using a rolled or drawn plate, the intermediate layer 2 was made in advance using a build-up called homogen processing or a casting method. The treatment of the present invention may be carried out after coating.

In Figure 1, the first metal layer 2 of lead or lead-tin alloy and the second metal layer 3 of lead metal are heated under high pressure to near their melting points, which further promotes the diffusion of titanium at the interface of the current-carrying plate and causes discharge. The bonding strength of each bonding surface 4 of the plate 1, intermediate plate 2, and upper layer 3 was 2 to 3 Kg/mm ² in the conventional homogen processing, but it was greatly improved to 4 to 6 Kg/mm ² in the present manufacturing method. .

(Effect of the invention) By applying the electrode for electrogalvanizing according to the present invention, the corrosion resistance and adhesion to the current-carrying plate can be improved without changing the conventional chemical composition of the electrode coated by homogenization and casting. It can be increased very easily. Therefore, the above-mentioned problems such as the increase in the distance between the electrodes and the obstruction of the flow of the plating solution can be considerably improved.

In addition, by increasing the adhesion between the current-carrying plate and the lead alloy, the electrical resistance value between them is reduced, and as with the improvement of the gap between electrodes and the plating liquid described above, it is possible to reduce the plating power by suppressing the plating voltage. In addition, since the amount of lead eluted into the plating solution is reduced, quality problems caused by lead being mixed into the plating metal can be greatly improved.

[Brief explanation of the drawing]

Fig. 1 is an explanatory cross-sectional view of an insoluble electrode for electrogalvanizing of the present invention, Fig. 2 is an explanatory cross-sectional view of an apparatus showing a method for manufacturing an insoluble electrode of the present invention, and Fig. 3 is an explanatory cross-sectional view of an electrolytic galvanizing electrode using an insoluble electrode. A schematic diagram of the plating device, and FIG. 4 is a cross-sectional explanatory diagram of a conventional insoluble electrode. 1... Current-carrying plate A, 2... First metal layer of lead or lead-tin alloy lined in the lower layer, 3... Second metal layer of lead alloy lined in the upper layer, 4... Joint interface of solid-phase bonded dissimilar lead alloys. , 5... Separator for the purpose of preventing contact between the strip and the electrode, 6... Booth bar for supplying electricity to the undissolved electrode, 7... Welding for joining the booth bar to the current carrying plate, 8... Undissolved electrode plate, 9... Pressurized container, 10... Compressor, 11...
Heater, 12... Lid, 13... Heat insulating material, 14... Support stand, 15... High pressure gas introduction pipe, 16... Electrode mounting frame, 17... Current supply roll, 18... Auxiliary roll,
19...Plating liquid nozzle, 20...Plating tank, 21...
Current-carrying plate B, 22...Lead alloy.

Claims (1)

[Scope of Claims] 1. Lead or tin 2 to 8% balance lead and unavoidable lead molded on the discharge side surface of the current-carrying plate for electroplating or built up by homogenization. The first of lead or lead-tin alloys consisting of impurities.
A second metal of a lead alloy made of rolled plate or drawn material on the metal layer and the first metal layer, containing either 0.2 to 1.0% silver, 1 to 5% indium, or both, and the balance consisting of lead and inevitable impurities. For continuous electrogalvanizing of metal strips, the adhesive surfaces of the first metal layer of lead or lead-tin alloy and the second metal layer of lead alloy are bonded by diffusion in stacked layers. Insoluble electrode. 2. Lead that has been cast into a mold on the discharge side surface of the current-carrying plate for electroplating, or has been overlaid by homogen processing, or lead that is made of 2 to 8% tin, the balance being lead and unavoidable pure substances. On the first metal layer of lead-tin alloy and the first metal layer of lead or lead-tin alloy, either 0.2 to 1.0% of silver, 1 to 5% of indium, or both, made of rolled plate or drawn material is applied. A second metal layer of lead alloy consisting of residual lead and unavoidable impurities is layered, placed in a pressurized container, filled with active gas, and pressurized until the internal pressure reaches 600 -
2000Kg/cm ² , heating temperature range of 100 to 300℃ for a while to join the current-carrying plate and each of the first and second metal layers. Production method.