JP4844021B2 - Method for producing tin-plated steel strip - Google Patents

Description

  The present invention relates to a method for producing an electroplated metal strip using a horizontal electroplating line having a plurality of plating cells, and a method for producing a tin-plated steel strip.

  As a metal band electroplating line in which a metal band is immersed in an aqueous electrolyte solution (plating bath) to form a plating film by electrolysis, the metal band moves horizontally in multiple plating cells and plating is performed on each side of the metal band. There is a horizontal electroplating line done. Since this electroplating line has a relatively simple structure, there is an advantage that the plating process can be performed while moving the metal strip at a high speed. A typical example is a halogen tin plating line in which a halogen bath is used as a plating bath and a steel strip is subjected to tin plating. In particular, in the halogen tin plating line, tin in the plating bath is oxidized from divalent to tetravalent by oxygen in the air to form a low-solubility halide, and a large amount of sludge is generated. A horizontal type plating cell that can precipitate and remove at the cell bottom is suitable.

  On the other hand, in recent years, as environmental problems have been closed up, it has become difficult to treat sludge containing halogen ions. It is being switched to an acidic plating bath such as a bath. However, because the pH of such acidic plating baths is low, the elution rate of iron from the steel strip into the plating bath is increased, and the iron ion concentration in the plating bath is increased, enabling high current density that enables high productivity. If electrotin plating is performed under the conditions, the plating uniformity deteriorates (for example, see Non-Patent Document 1). Moreover, the increase of the iron ion in a plating bath accelerates | stimulates the oxidation of a tin ion, and causes sludge generation. In particular, as described above, when using a horizontal type plating cell in which the steel strip is plated one side at a time, the elution of iron from the surface of the unplated steel strip is remarkable, and the unevenness of plating is promoted. Or a large amount of sludge is generated. That is, as schematically shown in FIG. 3, in the horizontal electroplating line, the metal strip 1 transported by the transport roll 4 is formed with a plating film from the surface facing the anode 3 in the plating cell 2. Therefore, the surface opposite to the surface of the metal strip 1 (referred to as “A surface”) on which the plating film is first formed (referred to as “B surface”) is plated until the plating film is formed on the A surface. Since the metal strip 1 is still immersed in the plating bath 2, a large amount of iron is eluted from the B surface into the plating bath when the metal strip 1 is a steel strip.

As a method of preventing the elution of iron into the plating bath, an acidic tin plating bath is used, and the steel strip is immersed in a plating solution before the start of tin electrodeposition. A method of preventing the elution of iron into the plating bath by allowing a current of 0.03 to 1 A / dm ² to flow between them to cause slight electrodeposition of tin is disclosed (see Patent Document 1). . In addition, when a steel strip is subjected to zinc or zinc alloy plating or fine particle dispersion plating based on zinc or zinc alloy using a continuous electroplating facility, a conductive coating is previously applied to the steel strip using a conductive material other than iron. There is also disclosed a method for preventing the elution of iron in the subsequent zinc or zinc alloy plating step (see Patent Document 2).
Japanese Patent Laid-Open No. 10-237685 Japanese Patent Laid-Open No. 5-106085 George A. Federman et al: “5th International Tinplate Conference” (Industrial Tin Research Institute), 1992, P.88-98

  However, even if the method described in Patent Document 1 is applied to a horizontal electroplating line and tin electrodeposition occurs slightly on the surface of the steel strip in the first plating cell, the electrodeposition is Since it only occurs on the steel strip surface facing the anode, iron elution from the steel strip surface on the opposite side is inevitable. In addition, in the method described in Patent Document 2, it is necessary to install a pre-plating apparatus before the electroplating line to form a conductive film, resulting in an increase in manufacturing cost and a decrease in productivity.

  The present invention is a method for producing an electroplated metal strip that uses a horizontal electroplating line and can prevent elution of the metal constituting the metal strip into the plating bath without causing an increase in production cost or a decrease in productivity, And it aims at providing the manufacturing method of a tin plating steel strip.

  The above object is to produce an electroplated metal strip by subjecting a metal strip to electroplating using a horizontal electroplating line having a plurality of plating cells, and at least the first plating of the plurality of plating cells. This is achieved by a method for producing an electroplated metal strip, characterized in that electroplating is performed on both sides of the metal strip in a cell.

When manufacturing an electrotin-plated steel strip by subjecting the steel strip to electrotin plating using a horizontal electrotin plating line having a plurality of plating cells using a tin methane sulfonate plating bath or a phenol sulfonate tin plating bath Requires at least the first plating cell of a plurality of plating cells to be subjected to electrotin plating treatment on both surfaces of the steel strip so that the amount of tin adhered is 0.02 to 0.3 g / m ² per one surface of the steel strip. It is.

  According to the present invention, in producing an electroplated metal strip using a horizontal electroplating line, the metal constituting the metal strip can be eluted into the plating bath without causing an increase in production cost or a decrease in productivity. It became possible to prevent. The present invention is particularly suitable for the production of an electrotin-plated steel strip.

  The method for producing an electroplated metal strip according to the present invention can be realized by a horizontal electroplating line schematically shown as an example in FIG. In the existing first plating cell 2, an anode 3 is newly installed so that a plating film can also be formed on the B surface opposite to the A surface of the metal band 1 where the plating film is formed first. If a plating film is also formed on the B surface in the first plating cell 2, the metal band 1 does not come into direct contact with the plating bath in the subsequent plating cell 2, so the metal constituting the metal band 1, that is, the metal When band 1 is a steel band, elution of iron into the plating bath is prevented. In addition, since the anode 3 is simply installed in the existing plating cell 2, there is no increase in manufacturing cost or productivity. In order to achieve the object of the present invention, it is essential to form plating films on both surfaces of the metal strip 1 in the first plating cell 2, but the anode 3 is newly added to the second and subsequent plating cells 2. There is no problem even if a plating film can be formed on both sides. Since the number of plating cells 2 that can form plating films on both sides of the metal strip 1 at the same time increases, the total number of plating cells 2 can be reduced and the equipment can be made more compact and the cost can be reduced.

  FIG. 2 schematically shows another example of a horizontal electroplating line for carrying out the method of the present invention. In this line, a vertical plating cell 2 capable of forming a plating film on both sides of the metal strip 1 is newly provided before the first plating cell 2 of the conventional horizontal electroplating line. In particular, since two sets of anodes 3 can form plating films on both sides of the metal strip 1, not only can the plating efficiency be improved, but the amount of plating can be increased, so the metal constituting the metal strip 1 Can be more reliably prevented. Although it is necessary to add one plating cell 2, it is possible to reduce the number of plating cells 2 for forming a plating film on the B surface, so that there is no increase in manufacturing cost or productivity.

  When producing a tin-plated steel strip in such a horizontal electroplating line, the method of the present invention is effective in the pH of a methanesulfonic acid bath, sulfuric acid bath, phenolsulfonic acid bath, etc., in which iron elution into the plating bath is significant. This is particularly effective when an acidic plating bath having a low resistance is used. Needless to say, the present invention is also effective for a halogen bath with high pH and low elution of iron.

In addition, it is effective for preventing the elution of iron that the tin adhesion amount in the first plating cell is 0.02 to 0.3 g / m ² per one surface of the steel strip. The amount of iron eluted from the steel strip into the plating bath is preferably 10 g / l or less, and more preferably 5 g / l or less. When using a tin methane sulfonate plating bath, the amount of iron leaching is 10 g / l or less if both sides are plated in the first plating cell so that the amount of tin attached is 0.02 g / m ² or more per side of the steel strip. If the amount of tin adhered is 0.2 g / m ² or more per side of the steel strip, the elution amount of iron can be reduced to 5 g / l or less. If the amount of tin deposited exceeds 0.3 g / m ² per side of the steel strip, the equipment cost may increase.

  As a metal strip, a steel strip or a zinc strip is used. The steel strip is subjected to pretreatment consisting of alkaline electrolytic degreasing and subsequent sulfuric acid pickling, and the zinc strip is pretreated only with alkaline electrolytic degreasing. Tests 1 to 9 were performed in which the plating metals shown in Table 1 were continuously plated in the plating bath shown in Table 1 using the horizontal electroplating line shown in FIGS. At this time, in Tests 1 to 7 in which plating films were formed on both surfaces of the metal strip in the first plating cell with reference to FIGS. 1 and 2, the plating adhesion amount per one surface was changed as shown in Table 1. And the density | concentration of the metal which comprises the metal band in the plating bath in the 2nd plating cell after 30-day continuous plating, ie, the iron in the case of a steel strip, and the zinc in the case of a zinc strip was measured.

The results are shown in Table 1. In Tests 2 , 3 , 5 , 6 , and 7 , which are examples of the present invention, the concentration of iron in the plating bath after continuous plating for 30 days is as low as 15 g / l or less, and elution of iron into the plating bath is prevented. Yes. In particular, by making the coating weight per piece surface to 0.02 g / m ² or more, the concentration of iron in the plating bath may be less remarkably low 10 g / l.

  On the other hand, in tests 8 and 9 of comparative examples in which plating treatment was performed by the conventional method, the concentration of iron or zinc in the plating bath was as high as 30 g / l or more, and the elution of iron or zinc into the plating bath was remarkable.

It is a figure which shows typically an example of the horizontal type electroplating line for implementing this invention. It is a figure which shows typically another example of the horizontal type electroplating line for implementing this invention. It is a figure which shows typically an example of the conventional horizontal type electroplating line.

Explanation of symbols

1 Metal strip
2 Plating cell
3 Anode
4 Transport roll

Claims (1)

In producing an electrotin-plated steel strip by subjecting the steel strip to electrotin plating using a horizontal electrotin plating line having a plurality of plating cells using a tin methane sulfonate plating bath or a phenol sulfonate tin plating bath. The tin plating amount is 0.02 to 0.3 g / m ² per one side of the steel strip on both surfaces of the steel strip in at least the first plating cell among the plurality of plating cells, A method for producing a tin-plated steel strip.

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