KR19990018151A - Manufacturing method of galvanized steel sheet with excellent surface appearance - Google Patents

Abstract

The present invention relates to a method for plating zinc in a carousel (CAROSEL) type electroplating bath, and to provide a method for producing an electrogalvanized steel sheet having a plating film having excellent surface appearance and improved glossiness. have.

In the carousel type electroplating bath, since the surface of the plated steel sheet is low in hardness of the plating layer, it is necessary to remove these defects in continuous contact with the edges of the conductive roll bands to form pressed marks called band marks. In order to solve the above problems, the present invention provides a method for producing an electrogalvanized steel sheet having excellent surface appearance and improved surface glossiness, in which a sulfuric acid bath is horizontal or vertical on a zinc plated layer of a plated steel sheet obtained from a carousel type continuous electroplating bath. The technical gist of the replating of zinc at a deposition rate of 3 to 10 g / m ² using a plating bath is considered.

Description

Manufacturing method of galvanized steel sheet with excellent surface appearance

The present invention relates to a method for coating zinc coating film in a carousel (CAROSEL) type electroplating bath, and more specifically, a zinc plated film plated in a carousel plating bath is a pressed mark formed by a band edge of a conductive roll. In order to remove the mark, in a horizontal electrolytic bath, a sulfuric acid bath is selected and zinc is replated at an adhesion amount of 3 to 10 g / m ² to provide a good surface appearance and a method for producing an electro-zinc plated steel sheet for improving surface glossiness. It is about.

In the carousel type electroplating bath, a conductive roll 2 having a length of 2060 mm and a diameter of 2440 mm is half immersed in the plating solution, as shown in Fig. 1 (a), and the steel sheet 1 winds and turns the conductive roll. In this case, plating is performed on the part of the steel plate immersed in the solution. The conductive roll is made of a metal conductor (band) so that only 700 mm of the current is conducted, and the remaining part is made of synthetic rubber. Since the temperature of the plating solution is usually 60 ° C, the surface of the conductive roll is raised to this temperature, and as the work proceeds, heat is generated by the flow of current, causing the synthetic rubber to swell. If the rubber is too swelling, the band, which is the conduction part of the conducting roll, becomes lower than the height of the rubber, resulting in uneven contact between the steel plate and the band at the edge of the band. Results in being damaged. Therefore, during energization, the band is configured to be as high as or slightly higher than the rubber as possible. However, the carousel type electroplating bath is divided into two plating units. In the previous plating unit, only one side of the steel plate is plated and the other side is plated in the next plating unit. The plating is made on the opposite side. Since the galvanized layer has a low hardness, a band mark is formed on the surface in contact with the conductive roll in the second plating unit. The band mark thus formed damages the appearance of the plated steel sheet, and if it is severely transferred even after painting, it has been a long time a complaint from the customers, but it has been regarded as a problem of the facility of the carousel plating tank.

In addition, the hydrochloric acid bath has a three times greater electrical conductivity than the sulfuric acid bath, so that the overvoltage of the solution is small, so that a surface with a high gloss of 10 or more cannot be obtained. However, since the overvoltage of the sulfuric acid bath solution is large, there is an advantage that the crystal grains are small to easily secure glossiness of 20 or more.

Accordingly, the present invention has been made to solve the problems of the prior art described above, 3 to 10 g / m of zinc in the sulfate bath of the horizontal plating bath to remove the band mark formed on the zinc plating layer in the carousel electroplating bath. ^It is an object of the present invention to provide a method for producing an electrogalvanized steel sheet having excellent surface appearance by replating with an amount of adhesion.

In order to achieve the above object, in the present invention, using a horizontal electrolytic bath of sulfuric acid bath on the zinc plated layer of the plated steel sheet obtained in the carousel-type continuous electroplating bath characterized in that the zinc is replated in an amount of 3 to 10 g / m ² It provides a method for producing an electro-galvanized steel sheet having an excellent surface appearance and improved surface gloss.

Figure 1 (a) is a schematic diagram showing a plating process performed in a conventional carousel electrolytic cell,

Figure 1 (b) is a diagram schematically showing a plating process of the present invention.

Explanation of symbols for the main parts of the drawings

1: steel sheet 2: conductive roll 3: carousel type electrolyzer

4: horizontal electrolytic cell 5: anode 6: support roll

Hereinafter, with reference to the accompanying drawings will be described in detail a method for producing an electrogalvanized steel sheet of the present invention.

The method for producing an electrogalvanized steel sheet having excellent surface appearance and improved surface glossiness is primarily plated to remove band marks, which are surface defects formed in a carousel type continuous electroplating bath, and to improve surface glossiness. 3 to 10 g / m ² of zinc is further attached to the zinc plating layer in a sulfuric acid bath.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, a radial type, in particular a carousel type electroplating installation is an apparatus designed to be advantageous for plating only one side of a steel sheet. Therefore, the plating unit is divided into two. In the previous plating unit, only one side of the steel plate can be plated and the other side can be plated in the next plating unit. When plated in the unit, a band mark is formed while contacting the band of the conductive roll. This band mark has been a big complaint from consumers because it is still transferred after painting for home appliances. However Caro gel plating bath major surface by coating material because it is not possible to prevent the formation of the band mark facility nature plating of zinc in a plating bath gel Caro horizontal plating bath of sulfuric acid on the zinc plating layer in the plating 3~10 g / m ² There are two effects that eliminate band marks and improve surface glossiness.

Fig. 1 (a) shows a conventional example composed of only a carousel electrolytic cell, in which the leading surface is in contact with the conducting roll 2 as the steel plate 1 is plated on one side in the first plating unit and the other side is plated in the second plating unit. Therefore, a band mark is formed.

However, in the plating process proposed in the present invention of FIG. 1 (b), even when the steel sheet 1 is plated in the carousel plating bath 3 and forms a band mark, zinc is plated on the band mark again. The band mark disappears. In other words, in the horizontal electrolytic cell 4 of the sulfuric acid bath, the steel sheet is charged to the cathode by the conductive roll 2, and the band mark is removed by replating between the anodes 5 positioned up and down. In addition, the horizontal electrolytic cell can obtain a uniform and beautiful plating film because the steel roll does not turn around the conductive roll and the conductive roll is positioned horizontally on the steel sheet and the entire conductive roll is a conductor.

In the present invention, the zinc adhesion in the horizontal electrolytic bath of the sulfuric acid bath is limited to 3 g / m ² or more because the band mark is not removed thereafter and the reason for limiting the adhesion amount to 10 g / m ² or less is It is because plating adhesiveness deteriorates more than that.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.

Example 1

After plating 20 g / m ² of the coating weight with a current density of 60 A / dm ² in the carousel plating bath, the coating weight was adjusted while varying the amount of current using a sulfuric acid bath in a horizontal electrolytic cell. The degree of removal of the band mark was measured. In addition, the glossiness of the surface was used with a gloss meter, and the adhesion of the plate was cut to 25 × 100 mm, a transparent tape was attached to the plated layer, and the specimen was bent at 180 °, depending on the amount of plated layer buried on the transparent tape. The case where there was no peeling of the plating layer was made into grade 0, and the case with the most peeling was determined as grade 3.

1) Plating condition of carousel plating bath

(1) solution composition

Zinc Chloride: 130 ㎖ / ℓ

Potassium chloride: 320 g / ℓ

Polishing agent: 0.1 ml / l

(2) plating condition

Temperature: 55 ℃

Current density: 60 A / dm ²

Flow rate: 2 m / s

PH: 4.5

Coating Weight: 20 g / m ²

2) Horizontal Electrolyzer

(1) Solution composition

Zinc ion: 63 g / ℓ

Sodium sulfate: 100 g / ℓ

(2) plating condition

Temperature: 60 ℃

Current density: 50 A / dm ²

Flow rate: 3 m / s

PH: 1.2

Coating weight: 1-15 g / m ²

division Zinc deposition in sulfuric acid bath (g / m ² ) Band mark * removal degree Glossiness (60。) Plating adhesion turn Conventional example - × 4 0 One Comparative example One ◇ 5.3 0 2 2 ○ 6.1 0 3 12 ◎ 23.5 2 4 15 ◎ 28.0 3 5 Inventive Example 3 ◎ 10.5 0 6 5 ◎ 12.0 0 7 7 ◎ 15.9 0 8 9 ◎ 17.5 0 9 10 ◎ 21.7 0 10

Band mark removal degree: not removed ← × ◇ ○ ◎ → completely removed

As can be seen in Table 1, in the case of the conventional example (1), the band mark is clear and has a dark surface with glossiness of 4, and 2 g / m ² of zinc in the sulfate bath of the horizontal electrolytic cell (3) If only plating is applied, the glossiness is slightly increased, but the band mark remains without being removed. However, when 3 to 10 g / m ² (6 to 10) of zinc is deposited on the zinc plated layer on which the band mark is formed, as shown in the present invention, the glossiness rises to 10 to 20, no peeling off of the plating layer, and the band mark is removed. It is possible to produce a galvanized steel sheet having an excellent appearance. However, in the comparative example (4) which made zinc adhesion amount 12, although a band mark is removed and glossiness improves, it is not applicable because peeling of a plating layer occurs.

Therefore, according to the method for producing an electrogalvanized steel sheet of the present invention as described above, by attaching zinc 3 to 10 g / m ² in a horizontal electrolytic bath of sulfuric acid bath on the zinc plating layer plated in the carousel plating bath By removing the band mark formed on the plating layer generated in the electroplating bath of the to improve the surface glossiness, the effect of obtaining an electro-galvanized steel sheet with excellent surface appearance and improved glossiness is achieved.

Claims (1)

The surface appearance is excellent and the surface glossiness is characterized by replating zinc at a coating amount of 3 to 10 g / m ² using a horizontal electrolytic bath in a sulfuric acid bath on a zinc plating layer of a plated steel sheet obtained from a carousel type continuous electroplating bath. Improved manufacturing method of electro galvanized steel sheet.