KR20000026560A - Process for producing continuous zinc electroplating steel plate without black pattern defect - Google Patents

Abstract

PURPOSE: Provided is a zinc electroplating steel plate which is improved surface quality without black pattern defect on the plate. CONSTITUTION: The process comprises the steps of: rinsing a zinc electroplating plate by acid and water to be plated in the cell; rinsing it with water and treating it with phosphorus acid salt, wherein the plating cell in the plating step is divided to plating cell of a front portion and a rear portion; and then respectively, supplying a plating solution in the its divided plating cell. Low amount of carbon is used to electroplating steel plate. When the adhesion amount of plating layer formed in the front portion is 1g/m¬2 black pattern defect was not caused. When the adhesion amount of plating layer formed in the rear portion is 2g/m¬2 black pattern defect was not caused. Thereby it is possible to prevent black pattern defect on the surface of the zinc electroplating steel plate, and it is possible to improve productivity due to the operation of high current density.

Description

Manufacturing method of continuous galvanized steel sheet without black pattern defects

The present invention relates to a method of manufacturing an electrogalvanized steel sheet free from black pattern defects. In particular, it is possible to prevent the occurrence of black pattern defects after a phosphate treatment to improve surface quality and to avoid black patterning, The present invention relates to a method of manufacturing an electrogalvanized steel sheet free from black pattern defects that can greatly improve the strength of the steel sheet.

Generally, electro-galvanized products are widely used in automobiles, building materials, and household appliances. In particular, home appliances have not only corrosion resistance, which is a unique function of galvanized steel sheet, but also function as ornaments. That is, whether or not the appearance of the surface appearance affects the success as a product.

On the other hand, in the case of an inner panel, an electro-galvanized steel sheet, which is a material for home appliances, is generally subjected to post-treatment such as chromate treatment. Therefore, the surface appearance of the galvanized steel sheet directly affects the surface appearance quality of the final product. Methods for improving the surface appearance of an electrogalvanized steel sheet have been well known in the past. In particular, a method for selectively removing iron ions using an ion exchange resin or a method for preventing iron ion leaching from a steel sheet by applying a corrosion inhibitor is used to prevent the decrease in whiteness and black pattern due to iron ions, which are impurities of an electrodeless zinc plating solution It is known. However, the increase in production cost and other deterioration in the quality of plating have been a problem, and thus, they have not been actually applied.

The present invention solves the above-mentioned problems, and it is an object of the present invention to provide a plating apparatus which separately supplies a plating solution supplied to plating cells before and after plating, The purpose of the supplied plating solution is to produce an electro galvanized steel sheet having excellent surface appearance because it prevents contamination.

In order to accomplish the above object, the present invention provides a method of manufacturing a continuous galvanized steel sheet comprising degreasing, pickling and washing, plating in a plating cell, and washing and phosphating in a plating step, The cell is divided into the plating cell at the front end portion and the plating cell at the rear end portion, and then the plating liquid is separately supplied to the divided plating cells to perform plating, thereby preventing black pattern defects.

The method of separating the plating cells includes a method in which the plating amount of the plating layer formed in the front end plating cell is set to 1 g / m 2 or more and the remaining plating layer is adhered at the rear end portion, and a method in which the plating amount of the plating layer formed in the rear end plating cell 2 g / m < 2 > or more, and the remaining plating layer is controlled to be plated at the front end. Both methods can achieve the object of the present invention.

1 (a) and 1 (b) are cross-sectional schematic views of an electrogalvanized steel sheet according to the present invention.

Fig. 2 is a manufacturing process diagram of a continuous galvanized steel sheet according to a conventional technique; Fig.

3 is a view showing a manufacturing process of a continuous galvanized steel sheet according to the present invention.

Description of the Related Art

1: a device for uncoiling a cold rolled steel sheet 2: degreasing

3: Pickle 4: Wash

5: Plating cell 5-1: Plating cell at the front end

5-2: back end plating cell 6:

7: Phosphate treatment 8: Plating steel sheet winding device

9: plating solution storage tank 9-1: plating solution storage tank of the plating cell at the front end

9-2: Plating solution storage tank of the rear end plating cell

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 is a schematic view showing a manufacturing process of a continuous galvanized steel sheet according to the present invention. As shown in FIG. 3, the inventor of the present invention has found various problems in the practical application of the method of blocking iron elution from a steel sheet to a plating solution, The inventors have studied a method for preventing deterioration of the quality of the galvanized steel sheet due to the iron ion of the plating solution. The elution of iron ions is concentrated at the beginning of the plating, the black pattern is caused by the difference in phosphate deposition amount, and the phosphate reaction occurs only on the surface of the plating layer. Thus, the plating cell of the front end where the initial plating layer is formed is supplied The zinc plating solution is separated from the plating solution supplied to the plating cell at the rear end to prevent the plating solution supplied to the rear end cell from being contaminated with iron ions, thereby preventing black pattern defects appearing after the phosphate treatment due to iron ion contamination It is possible to produce an electric galvanized steel sheet.

The present invention relates to a continuous electroplating facility in which a plating layer is formed by passing a plurality of plating cells through a plurality of plating cells to prevent black pattern defects appearing after a phosphate treatment by an iron ion which is an impurity of a plating liquid in a process of producing a continuous galvanized steel sheet The plating liquid supplied to the plating cell of the front end portion and the plating liquid supplied to the plating cell of the rear end portion are separately supplied and the plating amount of the plated layer to be plated at the front end portion 1g / ㎡ or more, or by controlling the amount of plating to be 2mg / ㎡ or more at the rear end, a coated steel sheet which does not cause defective black pattern after phosphate treatment is produced.

The following is the principle of occurrence of black pattern defects. The black pattern appears when the electroplated galvanized steel sheet is treated with phosphate, because the iron ion introduced into the galvanized steel sheet from the steel sheet used as the plating substrate is galvanized with zinc during electroplating. At this time, the amount of iron deposited on the surface of the steel sheet due to unevenness of the plating solution flow rate becomes uneven in the width and length direction of the steel sheet, so that black pattern defects in the form of a flow pattern of the plating solution appear. Also, the reason why the black pattern defects appear only when the galvanized steel sheet is treated with phosphate is because the amount of phosphate deposited on the surface of the galvanized steel sheet by the unevenly deposited iron is different. Generally, since the color difference is caused by the difference in the amount of phosphate deposition, black pattern defects can be seen only when the galvanized steel sheet is treated with phosphate.

The plating solution supplied to the plating cell at the front end portion and the plating solution supplied at the rear end portion of the continuous electroplating apparatus in which the plating layer is formed by passing through several plating cells which are the contents of the present invention are separated and supplied. The black pattern defects after the phosphate treatment can be prevented by the two methods of making the coating amount of the plating layer 1 g / m 2 or more or secondly managing the plating amount to be 2 mg / m 2 or more at the rear end portion, It is because of reason.

In the first method, when the amount of the zinc plating layer formed from the plating cell at the front end is set to 1 g / m 2 or more, the reason for regulation of the adhesion amount is that when the zinc plating layer formed in the front end plating cell is 1 g / Since the plating layer does not completely cover the steel sheet, the plating solution supplied to the plating cell at the rear end portion can not sufficiently prevent contamination due to iron leaching from the steel sheet. (See Fig. 1 (a)).

In the second method, the adhesion amount of the plating layer formed in the cell at the rear end portion is regulated to 2 g / m 2 or more.

The black pattern is due to the difference in color due to differences in adhesion amount of the phosphate coating formed on the surface of the zinc plated layer, and the difference in phosphate deposition amount is due to differences in the iron content of the zinc plating layer, If the zinc plating layer is not formed on the surface of at least 2 g / m < 2 > or more of the surface of the plating layer participating in the phosphate reaction, the difference in phosphate deposition will not be caused and the black pattern will not be generated. (See Fig. 1 (b)).

Hereinafter, embodiments will be described in detail.

Example

Cold-rolled cold-rolled steel sheets were used as plating materials and tested in the following manner.

end. Electro galvanizing

The electroplating was carried out under the conditions of electro-galvanizing generally performed in a continuous electroplating line, and the plating adhesion amount was 20 g / m 2.

≪ Plating condition >

Zn ²⁺ : 50 to 80 g / l

SO ₄ ^2- : 100-200 g / l

pH: 1.2 ± 0.2

Plating solution temperature: 80 ± 5 ℃

I. The whiteness measurement was performed using a Multispectro Color Meter manufactured by SUGA.

All. The iron ion concentration of the plating solution was analyzed using Atomic Absorption Spectroscopy (AA).

la. Phosphate treatment

1) Surface adjustment

Solution: PREPALENE-ZJ (Nippon Parkerizing Co., Ltd.)

Method: Immersed in a 40 ° C solution for 2 seconds

2) Phosphate treatment

Solution: PALBOND 3312J (manufactured by Nippon Parkerizing Co., Ltd.)

Method: Immersion for 8 seconds in 60 ° C solution

3) Washing: Spraying for 5 seconds at room temperature tap water

The following is a description of the main results and effects evaluated from the above examples.

Table 1 below shows the degree of occurrence of black pattern after phosphating treatment of the galvanized steel sheet according to the plating solution iron ion concentration and the plating current density. As the plating current density and the iron ion concentration of the zinc plating solution increase, the black pattern after the phosphate treatment It can be seen that the degree of defect occurrence increases.

Table 2 below shows that when the plating solution supplied to the front end plating cell and the rear end plating cell is separated, a plating solution is newly prepared to change the amount of zinc plating in the front end plating cell in the absence of iron ion contamination. The results show that the black patterning of the zinc plating solution supplied to the back end plating cell after plating and phosphoric treatment of iron ion concentration and current density of 140 A / dm 2 after the operation for one month was 1 g / ㎡ It can be seen that the plating solution of the rear end plating cell does not involve iron ions and does not cause black pattern defects.

When the plating solution supplied to the front end plating cell and the rear end plating cell was separated, the following Table 3 shows that the front end plating cell was plated for at least 1 g / The black pattern was evaluated after the phosphating treatment according to the amount of the zinc plating layer formed in the rear end plating cell. The black pattern was not generated when the adhesion amount of the plating layer formed at the rear end was 2 g / m 2 or more have.

FIG. 1 is a schematic view showing a method of operating a plating solution according to a conventional method and a method of operating a plating solution improved by the present method in a continuous electro-galvanizing system. In the past, since the system was supplied from one plating solution storage tank to the entire plating cell, The plating solution of the rear end plating cell, which forms the surface plating layer, can prevent the contamination of the iron ions. Therefore, it is possible to prevent the occurrence of the black pattern defects even after the phosphating treatment .

(Total plating coverage 20g / m ² constant) Iron ion concentration in plating solution (mg / l) Plating current density (A / dm ² ) 80 100 120 140 0 One* One One One 200 One One 2 2 400 One 2 2 3 600 2 2 3 3 800 2 2 3 5 1000 2 4 4 5 1200 2 3 5 6 1400 3 4 6 6 1600 3 5 6 6 1800 3 5 6 6 2000 3 6 6 6

* Black pattern defect occurrence degree: No occurrence ← 1 ~ 6 → Generation lot

Table 1 shows the occurrence of black pattern defects in the zinc-coated steel sheet treated with phosphate depending on the iron concentration of the plating solution.

(Total plating coverage 20 g / m ² , current density 140 A / dm ² ) (G / m < ² >) of zinc plating formed from the front end plating cell The iron ion concentration (mg / l) of the zinc plating solution supplied to the rear end plating cell Degree of occurrence of black pattern after phosphate treatment * Comparative Example 0 1562 6 0.2 1254 6 0.4 825 5 0.6 485 3 0.8 151 2 Honor 1.0 32 One 1.2 22 One 1.4 15 One 1.6 20 One 2 18 One 4 23 One

* Black pattern defect occurrence degree: No occurrence ← 1 ~ 6 → Generation lot

Table 2 shows the change in iron content and the occurrence of black pattern in the zinc plating solution supplied to the rear end plating cell after 3 months of operation, depending on the amount of plating deposited from the plating cell at the front end plating.

(Total plating coverage 20 g / m ² , current density 140 A / dm ² ) (G / m < ² >) formed from the back end plating cell, Degree of occurrence of black pattern after phosphate treatment * Comparative Example 0 6 0.2 6 0.4 6 0.6 5 0.8 5 1.0 4 1.2 4 1.4 3 1.6 3 1.8 2 Honor 2.0 One 2.2 One 2.4 One 3.0 One 5.0 One

* Black pattern defect occurrence degree: No occurrence ← 1 ~ 6 → Generation lot

* Iron ion concentration of the plating solution supplied to the front end plating cell after 3 months operation is 1562 mg / L, iron ion concentration of the plating solution supplied to the rear end plating cell is 22 mg / L

Table 3 shows the occurrence of black pattern according to the amount of deposition of the rear end plating cell after 3 months of operation after the initial preparation of the plating solution while maintaining the deposition amount of zinc plating from the front end plating cell at 1 g / m ² or more.

By applying the present invention, it is possible not only to improve the surface quality by preventing occurrence of black pattern defects after the phosphate treatment, but also to work with a high current density because black pattern does not occur, and productivity can be greatly improved. In addition, when the plating solution is prevented from being contaminated with iron, the whiteness of the coated steel sheet can be improved.

Claims (3)

A method for producing a continuous electrogalvanized steel sheet comprising degreasing, pickling and washing, plating in a plating cell, and washing and phosphating, characterized in that the plating cell in the plating step is a plating cell in the plating step, Wherein the plating solution is separately supplied to each of the divided plating cells to deposit the plating solution. The method of manufacturing a continuous galvanized steel sheet free of black pattern defect. The method according to claim 1, Wherein the deposition amount of the plating layer formed in the front end plating cell is adjusted to 1 g / m < 2 > or more. 3. The method according to claim 1 or 2, Wherein an amount of the plating layer formed on the rear end plating cell is adjusted to 2 g / m < 2 > or more, so as to produce a continuous galvanized steel sheet without black defects.