JPH10273800A - Production of one-side copper plated steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably produce a one-side copper plated steel sheet by executing electrolysis at a specified current density so as to make the width of a counter electrode narrower than the width of a steel strip by using an electrolyte in which the concn. of ammonium ions and pH are specified. SOLUTION: A copper plating layer on the face free from plating is melted away by electrolysis. As an electrolyte therefor, the one in which the electrolyte essentially contains ammonium ion and sulfate ions, the concn. of the ammonium ions is regulated to 13.5 to 80 g/l, and pH is regulated to 5 to 9 is used. Then, a counter electrode having a width narrower than that of the steel strip by >=50 mm is arranged on the side of the face free from the need of plating as a cathode, and the copper plating layer on the face free from plating is electrolyzed away under the condition of 1 to 30 A/dm<2> anodic current density. For the regulation of the concn. of the ammonium ions and pH at the time of initial make-up of electrolytic bath and after the electrolysis in the electrolyte, mainly, ammonium sulfate, sulfuric acid and aq. ammonia or their aq. solns. are used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a single-sided copper-plated steel strip by an electroplating method, and more particularly to a single-sided copper-plated steel strip which electrolytically removes a plating layer on a surface which does not require plating after both sides are subjected to electrolytic copper plating. The present invention relates to a method of manufacturing a belt.

[0002]

2. Description of the Related Art Various types of electroplated steel strips manufactured in a continuous line using coiled steel strips as original plates are used in a wide range of fields because of their excellent manufacturability and low cost. For example, as a use of the electrolytic copper-plated steel strip, there is a bearing sintered metal used for a bearing of a connecting rod of an automobile. This sintered metal is manufactured by placing a copper-based alloy powder on a copper-plated steel sheet and then performing a heat treatment to sinter the copper-based alloy powder. In this case, if a copper plating layer is present on the surface on which the copper powder is not placed, seizure with the connecting rod will occur, so it is necessary to use single-side plating, or in the case of double-side plating, it is necessary to remove the copper plating layer on the plating unnecessary surface. is there.

In the case of batch-type electroplating using a cut plate or the like as an original plate, it is relatively easy to apply one-side plating, and usually, the non-plated surface is mechanically sealed or placed outside the plating bath. This is performed by the following means. Even in the case of continuous electroplating, the technology to seal one side and perform electroplating,
For example, JP-A-49-28534 and JP-A-63-9
Although disclosed in Japanese Patent No. 6291, in this case, it is difficult to effectively seal the non-plated surface because the steel strip as the object to be plated continuously runs and moves. For this reason, in the production of a continuous single-sided electroplated steel strip, it is common to apply desired plating to both sides and then remove the plating layer on the plating-free side.

As means for removing unnecessary plating layers,
Examples include a mechanical grinding method, a chemical dissolution method, and an electrochemical dissolution (electrolysis) method. Here, the mechanical grinding method is
Although this method is suitable for selectively removing only one side of the plating layer, it is difficult to perform in-line processing in a continuous line in terms of time, and there is also a problem in working environment such as generation of dust. Further, in the case of the chemical dissolution method, similarly to the case of single-sided plating, it is difficult to continuously seal the non-treated surface, and it is difficult to selectively remove only the plating layer on one side. . In the case of the electrolytic method, it is possible to selectively dissolve and remove the plating layer on one side by disposing the counter electrode only on the side where plating is unnecessary and performing anodic electrolysis.

[0005]

A technique for selectively removing only one side of a steel strip having zinc-based electroplating on both sides by electrolysis is disclosed in, for example, JP-A-59-126786. I have. In this case, the reason why the electroplating is performed also on the surface not requiring plating is to prevent acid burning of the non-plated surface when performing single-sided electroplating, and the electrolytic solution used in the electrolytic method is not particularly limited in its type. Absent.

On the other hand, in the case of a copper-plated steel strip, when the copper plating layer is dissolved in an ordinary aqueous solution of an acid or alkali, the copper ions dissolved in the electrolytic solution are displaced to the exposed steel substrate by a substitution reaction. Because of the re-precipitation, it has been more difficult to produce a single-sided copper-plated steel strip by the electrolytic method.

An object of the present invention is to solve the above problems and to provide a method for stably producing a single-sided copper-plated steel strip.

[0008]

In order to achieve the above object, in the present invention, after electrolytic copper plating is performed on both surfaces of a steel strip, a copper plating layer on a surface not requiring plating is dissolved and removed by an electrolytic method. In the method for producing a single-sided copper-plated steel strip, as an electrolytic solution for dissolving and removing the plating layer, the electrolyte is mainly composed of ammonium ions and sulfate ions, the ammonium ion concentration of which is 13.5 to 80 g / l, and the pH of which is 13.5 to 80 g / l. Using an aqueous solution of 5 to 9, 50 mm from the width of the steel strip
Alternatively, a counter electrode having a width narrower than that is disposed on the side where plating is not required to serve as a cathode, and the anode current density is 1 to 30 A / dm.
^A method for producing a single-sided copper-plated steel strip is provided, wherein the copper-plated layer is electrolytically removed under the condition ( ² ).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In order to suppress the reprecipitation of substituted copper on a steel substrate exposed by electrolytically removing a copper plating layer, copper ions present in an electrolytic solution are complex-ionized.
It is necessary to lower the deposition potential of copper. Complexing agents exhibiting such an action include inorganic ions such as ammonium ion, cyanide ion and pyrophosphate ion, and organic chelate compounds such as EDTA. Among them, cyanide is toxic, and it is difficult to use it industrially in terms of working environment and waste liquid treatment. Further, pyrophosphate and various organic chelating agents are expensive and increase the cost, so that it is still difficult to use them for industrial electrolytic removal.

[0010] Among the above complexing agents, ammonium salts are inexpensive and easily available, and are suitable for use in electrolytic removal. The concentration of ammonium ion in the electrolyte is preferably 13.5 to 80 g / l. Concentration 1
If it is less than 3.5 g / l, the complexing ability is insufficient, and the replacement copper is reprecipitated after electrolytic removal of the copper plating layer. When the concentration exceeds 80 g / l, there is no problem in terms of complexing ability, but the amount of the electrolyte attached to the running steel strip and taken out of the electrolytic cell increases, and the concentration of the electrolyte is adjusted. This is not preferred because the cost required for

As the anion species paired with the ammonium ion, any anion species can be used, including commonly used inorganic acid ions such as sulfate ion, nitrate ion and chloride ion. In the case of the process, for the main plating after the strike plating, usually, a copper sulfate bath capable of electrolysis at a large current density is often used. Therefore, the use of sulfate ions is preferable in consideration of the carry-in and mixing of the electrolyte. . In addition, when monobasic acid ions such as nitrate ions and chloride ions are used, when the steel substrate is exposed by electrolytic removal, the surface of the steel substrate is likely to be roughened. Is preferred.

The pH of the electrolyte is preferably from 5 to 9. When the pH is 4 or less, even if the ammonium ion concentration is adjusted to the above-mentioned range, re-deposition of the substituted copper occurs, which is inappropriate. On the other hand, if the pH is 10 or more, the current efficiency at the time of electrolytic removal is reduced, and the cost is increased, which is not preferable. In addition, ammonium sulfate, sulfuric acid, aqueous ammonia, or an aqueous solution thereof is mainly used for adjusting the ammonium ion concentration and the pH at the time of building the electrolytic bath or after the electrolysis. The electrolytic solution for electrolytic removal mainly contains ammonium ions and sulfate ions as electrolytes.In addition to these, other supporting electrolytes, inhibitors for suppressing corrosion of the steel base, and iron dissolved from the steel base. It is also possible to add a complexing agent for complexing ions, a pH adjuster, and the like.

In order to electrolytically remove only the plating layer on one side, a counter electrode is provided only on the side of the electrolytic cell that does not require plating to serve as a cathode, and electrolysis is performed using a copper-plated steel strip as an untreated material as an anode. Then, the copper plating layer is dissolved electrochemically. that time,
Since the electrolytic solution of the present invention contains a large amount of electrolyte and has high conductivity, current spills to a non-electrolytic surface (a surface requiring a plating layer), and the plating layer at the edge portion of this surface is partially dissolved. In the practice of the present invention, since the plating layer on the surface that does not require plating is ultimately electrolytically removed, it is economical to make the copper plating thickness on this surface thinner than that of the surface requiring plating. It is.

As means for preventing the current from sneaking,
Between the counter electrode and the copper-plated steel strip, there are a method in which insulating current shielding plates are provided at both edges of the steel strip, and a method in which the width of the counter electrode is narrower than that of the non-processed material. In the former method, it is necessary to change the arrangement of the electrolytic cell in accordance with the width of the copper-plated steel strip to be treated, which is practically difficult. In the latter case, the width of the counter electrode required for electrolysis has an allowance, and a copper-plated steel strip having a plurality of widths with the same counter electrode width can be processed, which is suitable for industrial production. In the present invention, the counter electrode used for electrolytic removal needs to have a width 50 mm or more narrower than that of the copper-plated steel strip to be processed.

The current density for electrolytic removal is 1 to 30 A
/ Dm ² is preferred. If the current density is less than 1 A / dm ² , the processing speed is low, and the manufacturing cost is undesirably increased. If the current density exceeds 30 A / dm ² , the electrolytic voltage rises, and even if the width of the counter electrode is set in the above range, the current wraps around and the edge portion of the non-electrolytic surface dissolves, which is inappropriate. .

Table 1 shows the results of a preliminary investigation for setting suitable electrolysis conditions. Board thickness 2mm (area 1dm ² )
Oxygen-free copper plate as an anode, ammonium sulfate 50 to 30
0 g / l (ammonium ion concentration 13.5 to 80 g /
1), electrolysis was performed at a current density of 20 A / dm ² for 10 minutes in an electrolytic solution having a pH of ⁴ to 10 and a bath temperature of 45 ° C., and the weight loss of the copper plate was measured to calculate the current efficiency. In addition, the cold-rolled steel sheet subjected to electrolytic degreasing and pickling according to a conventional method was immersed in the electrolytic solution after the above-described electrolysis for 1 minute, and the presence or absence of substitution copper on the surface of the cold-rolled steel sheet was visually observed. Was evaluated.

[0017]

[Table 1]

In each of the samples Nos. 1 to 6 corresponding to the electrolysis conditions of the present invention, the current efficiency was 100%, and the substitution copper did not precipitate on the surface of the cold-rolled steel sheet. Sample No. 7 with low electrolyte concentration and Sample Nos. 8 and 9 with low pH
Then, precipitation of substituted copper occurred on the surface of the cold-rolled steel sheet. In Sample Nos. 10 and 11 having a high electrolyte pH, the deposition of substituted copper did not occur, but the current efficiency was reduced.

[0019]

EXAMPLE 1 A cold-rolled steel strip having a thickness of 0.5 mm and a width of 300 mm was subjected to electrolytic degreasing and pickling in a conventional manner, followed by copper pyrophosphate plating bath (strike plating) and copper sulfate plating bath. (Main plating)
After applying 4 μm of copper plating of 8 μm to the surface requiring plating, using an oxygen-free copper plate having a different width as a cathode, ammonium sulfate 200 g / l, pH 7, bath temperature of 45 ° C. in an electrolytic solution,
Electrolysis was performed at a current density of 20 A / dm ² until the entire copper plating layer on the plating-unnecessary surface was dissolved, and the amount of the copper plating layer on the plating-necessary surface was dissolved.

After electrolytically removing the entire amount of the copper plating layer on the plating-free surface, the thickness of the copper plating layer on the plating-requiring surface at a position 5 mm from the edge of the steel strip was measured by an X-ray fluorescent film thickness meter at an average value of 5 points. The difference between the film thickness before and after the electrolysis was defined as the dissolved film thickness. A film having a value equal to or less than the edge overcoat amount (2 μm) normally generated during the production of a copper-plated steel strip was determined to be good, and a film exceeding this amount was determined to be defective. Table 2 shows the measurement results. When the difference between the width of the steel strip and the width of the counter electrode is set to 50 mm or more, the dissolved film thickness becomes 2 μm.
m or less, and there is no problem in producing a single-sided copper-plated steel strip.

[0021]

[Table 2]

[0022]

Example 2 A steel strip having copper plating of different thicknesses on both sides under the same conditions as in Example 1 was made to have a counter electrode width 50 mm narrower than that of the steel strip in an electrolytic solution under the same conditions, and a current density of 1 mm. ~ 50
Electrolysis was performed at A / dm ² until the entire copper plating layer on the plating-unnecessary surface was dissolved, and the amount of dissolution of the copper plating layer on the plating-necessary surface was investigated. Table 3 shows the survey results. Current density 1 to 30 A / d
In the range of m ^2, the thickness of the dissolved film becomes 2 μm or less, and there is no problem in producing a single-sided copper-plated steel strip.

[0023]

[Table 3]

[0024]

As described above, a steel strip having copper plating on both sides is electrolyzed in an electrolytic solution containing ammonium ions with a counter electrode width narrower than the steel strip width by 50 mm or more, thereby obtaining a copper foil on one side. It has become possible to easily manufacture a plated steel strip.

Claims (1)

[Claims] An electrolytic solution for dissolving and removing a plating layer in a method for producing a single-sided copper-plated steel strip in which an electrolytic copper plating is applied to both sides of a steel strip and then a copper plating layer on a plating unnecessary surface is dissolved and removed by an electrolytic method. The electrolyte is mainly composed of ammonium ions and sulfate ions, the ammonium ion concentration of which is 13.5 to 80 g / l, and the pH of which is 5 to 80 g / l.
Using the aqueous solution of No. 9, a counter electrode having a width narrower than 50 mm or more than the width of the steel strip is disposed on the side where plating is not required to serve as a cathode, and the copper plating layer is formed under the conditions of an anode current density of 1 to 30 A / dm ^2. A method for producing a single-sided copper-plated steel strip, wherein the strip is electrolytically removed.