KR20190035419A - Electro galvanized steel sheet and manufacturing method thereof - Google Patents

Abstract

An electric galvanized steel sheet according to an embodiment of the present invention comprises: a base steel sheet; a galvanized layer formed on the surface of the base steel sheet; and a phosphate coated layer formed upon the galvanized layer. The attached amount of phosphate of the phosphate coated layer is between 1.53 and 1.73 g/m^(2). The length of an average major axis of the phosphate is between 1.3 and 3.5 μm, and the ratio between an average minor axis and the average major axis (the minor axis : the major axis) is between 1 : 3 and 1 : 7. The phosphate coated layer comprises 5,000 to 8,000 ppm of manganese (Mn), 32,000 to 52,000 ppm of zinc (Zn), and 700 to 1,300 ppm of nickel (Ni).

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electro-galvanized steel sheet,

The present invention relates to an electro-galvanized steel sheet and a method of manufacturing the same. More specifically, the present invention relates to an electrolytically treated zinc electroplated steel sheet excellent in alkali resistance, chipping resistance, internal bending resistance and the like, and a method for manufacturing the same.

The vehicle hood has a structure in which a hood inner panel is coupled to a hood outer panel. Generally, a galvanized steel sheet excellent in corrosion resistance is used as a steel plate for a hood outer panel. Examples of such galvanized steel sheets include galvannealed steel sheets (GA), electro galvanized steel sheets (EG), and the like.

The electrogalvanized steel sheet (EG) is a zinc sheet formed on the steel sheet surface by the electrolytic method. The electro-galvanized steel sheet is capable of forming a uniform galvanized layer over the entire steel sheet and is excellent in chipping resistance and is applied to an automobile hood outer panel and the like, A post-treatment step of forming a film on the surface of the steel sheet is carried out after zinc plating is performed. The post-treatment process is performed by a method such as a phosphate treatment and a chromate treatment. Further, in consideration of the human body or environmental influences, the phosphate treatment is mainly used in a post-treatment process.

Background Art related to the present invention is disclosed in Korean Patent Laid-Open Publication No. 2014-0084630 (filed on Jul. 07, 2007, titled "Phosphate solution for zinc or zinc-plated gold-plated steel sheet and zinc or zinc-plated gold-plated steel sheet using the same).

According to one embodiment of the present invention, there is provided an electrolytically zincated electroplated galvanized steel sheet excellent in alkali resistance, chipping resistance, internal bending ability and the like.

According to an embodiment of the present invention, there is provided a method of manufacturing the above-mentioned electro-galvanized steel sheet.

One aspect of the present invention relates to an electrogalvanized steel sheet. In one embodiment, the electrogalvanized steel sheet comprises a base steel sheet; A zinc plated layer formed on the surface of the base steel sheet; And a phosphate coating layer formed on the zinc plating layer, wherein the phosphate coating amount of the phosphate coating layer is 1.53 to 1.73 g / m ² , the average long diameter of the phosphate is 1.3 to 3.5 μm, the average short diameter and the average long diameter Wherein the phosphate coating layer comprises 5,000 to 8,000 ppm of manganese (Mn), 32,000 to 52,000 ppm of zinc (Zn), and 700 to 1,300 ppm of nickel (Ni) in a ratio of 1: 3 to 1: .

In embodiments, the weight ratio of manganese and zinc (Mn / Zn) in the phosphate coating layer may be between 0.12 and 0.25.

Another aspect of the present invention relates to a method of manufacturing the above-described electro-galvanized steel sheet. In one embodiment, the method of manufacturing an electro-galvanized steel sheet includes: forming a zinc-plated layer on a surface of a base steel sheet by electroplating; Treating the zinc plated layer with a surface conditioning agent; And coating the zinc plating layer treated with the surface modifier with an aqueous phosphate solution for treatment at a temperature of 50 ° C to 60 ° C at a coverage of 1.4 to 1.6 g / m ² , followed by drying to form a phosphate coating layer, The aqueous solution for phosphate treatment is characterized by comprising 2,000 to 3,000 ppm of manganese (Mn), 1,500 to 2,000 ppm of zinc (Zn), and 1,500 to 1,800 ppm of nickel (Ni).

In an embodiment, the phosphate coating amount of the phosphate coating layer is 1.53 to 1.73 g / m ² , the average long diameter of the phosphate is 1.3 to 3.5 μm, and the ratio of the average short diameter and the average long diameter is 1: 3 To 1: 7, and the phosphate coating layer may contain 5,000 to 8,000 ppm of manganese (Mn), 32,000 to 52,000 ppm of zinc (Zn), and 700 to 1,300 ppm of nickel (Ni).

In an embodiment, the surface modifier is in the form of a solution in which the surface modifier is diluted with water, and the concentration of the surface modifier in 100 wt% of the solution may be 0.1 to 0.2 wt%.

In a specific example, in the step of forming the phosphate coating layer, the total acid of the aqueous phosphate solution may be 19 to 29 and the free acid may be 1.2 to 2.2.

The present invention provides a phosphate-treated electrogalvanized steel sheet improved in alkali resistance, chipping resistance, intact bending resistance and the like by controlling the phosphate deposition amount, the phosphate scale and the manganese content in the phosphate coating layer to a specific range and a method for producing the same .

1 shows a method of manufacturing an electro galvanized steel sheet according to one embodiment of the present invention.
2 is a scanning electron microscope (SEM) photograph of the surface (phosphate coating layer) of an electrogalvanized steel sheet produced according to Example 1 of the present invention.
3 is a scanning electron microscope (SEM) photograph of the surface (phosphate coating layer) of an electrogalvanized steel sheet produced according to Comparative Example 1 of the present invention.
4 is a scanning electron microscope (SEM) photograph of the surface (phosphate coating layer) of an electrogalvanized steel sheet produced according to Comparative Example 2 of the present invention.
5 is a scanning electron microscope (SEM) photograph of the surface (phosphate coating layer) of the galvanized steel sheet produced in Example 1 of the present invention after alkali treatment.
6 is a scanning electron microscope (SEM) photograph of the surface of an electrogalvanized steel sheet produced according to Comparative Example 1 of the present invention (phosphate coating layer) after alkali treatment.

Hereinafter, the present invention will be described in detail. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to be exemplary, self-explanatory, allowing for equivalent explanations of the present invention.

Galvanized steel sheet

One aspect of the present invention relates to an electrogalvanized steel sheet. In one embodiment, the electrogalvanized steel sheet comprises a base steel sheet; A zinc plated layer formed on the surface of the base steel sheet; And a phosphate coating layer formed on the zinc plating layer.

In a specific example, the base steel sheet can be used without limitation, and a steel sheet for a hood outer panel is preferably used from the viewpoint of improving the chipping resistance, the inner ring lining and the like.

In an embodiment, the zinc plated layer may be formed by a conventional electroplating method, and the thickness of the formed zinc plated layer may be 2 to 3 占 퐉, and the deposition amount of the zinc plated layer may be 10 to 30 g / m < ² >. Within the above range, the chipping resistance, adhesion, surface uniformity of the zinc plated layer and the like can be excellent.

In embodiments, the amount of phosphate adhered to the phosphate coating layer may be from 1.53 to 1.73 g / m < ² >. If the amount of phosphate adhered is less than 1.53 g / m ² , the alkali resistance of the electro-galvanized steel sheet may deteriorate. When the amount of phosphate is more than 1.73 g / m ² , phosphate peeling (powder ring) There is a possibility of occurrence.

In a specific example, the average long diameter of the phosphate may be 1.3 to 3.5 mu m and the ratio of the average short diameter and the average long diameter may be 1: 3 to 1: 7, for example, 1: 3.3 to 1: 6.4. If it is out of the above range, the alkalinity of the electro-galvanized steel sheet may be lowered.

In embodiments, the phosphate coating layer may comprise 5,000 to 8,000 ppm of manganese (Mn), 32,000 to 52,000 ppm of zinc (Zn), and 700 to 1,300 ppm of nickel (Ni). If it is out of the above range, the alkalinity of the electro-galvanized steel sheet may be lowered.

Specifically, the manganese (Mn) can improve the durability of the coating (phosphate coating layer). In the present invention, the manganese (Mn) is contained in an excessive amount in comparison with the conventional phosphate coating layer, thereby improving the alkali resistance of the electrogalvanized steel sheet have.

Specifically, the zinc (Zn) serves to improve mechanical properties by improving the corrosion resistance and durability of the coating. In addition, zinc (Zn) can play a role in making the phosphate coating layer have better adhesion with the zinc plating layer.

Specifically, the nickel (Ni) can promote a film forming reaction and form a dense phosphate coating layer. Nickel (Ni) can also improve the adhesion of the phosphate coating layer and the paint (coating layer).

In embodiments, the weight ratio of manganese and zinc (Mn / Zn) in the phosphate coating layer may be between 0.12 and 0.25. Within the above range, the alkali resistance of the galvanized steel sheet may be more excellent.

Manufacturing method of galvanized steel sheet

Another aspect of the present invention relates to a method of manufacturing the above-described electro-galvanized steel sheet. 1 shows a method of manufacturing an electro galvanized steel sheet according to one embodiment of the present invention. Referring to FIG. 1, the method for manufacturing an electro-galvanized steel sheet includes the steps of: (S10) forming a zinc-plated layer; (S20) a surface modifier treatment step; And (S30) forming a phosphate coating layer.

More specifically, the method for manufacturing an electro-galvanized steel sheet comprises the steps of: (S10) forming a zinc-plated layer on the surface of a base steel sheet by electroplating; (S20) treating the zinc plated layer with a surface conditioning agent; And (S30) coating the zinc plating layer treated with the surface-modifying agent at a coating amount of 1.4 to 1.6 g / m < ² > at 50 DEG C to 60 DEG C and drying to form a phosphate coating layer do.

Hereinafter, a method of manufacturing an electro-galvanized steel sheet according to the present invention will be described in detail. The constituents, properties and contents of the electro-galvanized steel sheet are the same as those contained in the above-mentioned electro-galvanized steel sheet, and a detailed description thereof will be omitted.

(S10) Zinc plating layer formation step

The above step is a step of forming a zinc plating layer on the surface of the base steel sheet by electroplating. The electroplating method is used in a conventional electrogalvanizing (EG) method, and can be easily carried out by those skilled in the art.

In a specific example, the base steel sheet may be used after degreasing and rinsing the surface. In this case, the surface uniformity of the zinc plated layer formed on the base steel sheet can be further improved.

(S20) Surface conditioning agent treatment step

The step is a step of treating the zinc plated layer with a surface modifier. The surface control agent is capable of forming a reaction site (phosphate crystal nucleus) at the time of forming a phosphate coating layer (at the time of precipitation of phosphate (crystal)), and is a conventional surface conditioner containing a titanium dioxide (TiO ₂ ) Can be used. Such a surface modifier treatment process can be easily carried out by those skilled in the art according to a conventional method of producing an electro galvanized steel sheet.

In an embodiment, the surface modifier is in the form of a solution in which the surface modifier is diluted with water, and the concentration of the surface modifier in 100 wt% of the solution may be 0.1 to 0.2 wt%. In the concentration range, a phosphate coating layer having the phosphate adherence amount and the phosphate size (the average long diameter, the average short diameter and the long diameter ratio) of the above range can be formed.

In an embodiment, the surface conditioner treatment may be treated with a total alkalinity of 1.4 to 2.4 pt under the concentration conditions and the temperature conditions of 30 to 40 占 폚. In this case, the uniformity of the zinc plating layer formed on the base steel sheet and the surface uniformity of the entire galvanized steel sheet can be further improved.

(S30) Phosphate coating layer forming step

This step is to form a phosphate coating layer on the zinc plated layer treated with the surface conditioner. In one embodiment, the phosphate coating layer may be formed by coating (spray) an aqueous phosphate solution at a coating amount of 1.4 to 1.6 g / m ² at 50 ° C to 60 ° C, followed by drying. If the coating temperature of the aqueous solution for phosphate treatment is less than 50 캜, the crystal growth to be formed in the phosphate coating layer may be insufficient and surface properties may be deteriorated. If the coating temperature is higher than 60 캜, . Further, when the amount of the phosphate coating layer is out of the above range, the amount of the phosphate coating on the phosphate coating layer is out of the range of the present invention, and the alkali resistance of the electroplated galvanized steel sheet is lowered or phosphate peeling (powdering) .

In an embodiment, the aqueous solution for treating phosphates may include 2,000 to 3,000 ppm of manganese (Mn), 1,500 to 2,000 ppm of zinc (Zn), and 1,500 to 1,800 ppm of nickel (Ni). The content range of manganese, zinc and nickel in the phosphate coating layer can be controlled within the range of the present invention by controlling the content range of manganese, zinc and nickel in the aqueous phosphate solution for treatment. And nickel content falls outside the above range, there is a possibility that the alkali resistance and the like of the electro-galvanized steel sheet are lowered.

In a specific example, in the step of forming the phosphate coating layer, the total acid of the aqueous phosphate solution may be 19 to 29 and the free acid may be 1.2 to 2.2. The surface uniformity of the galvanized steel sheet in the above range can be excellent.

The electrodeless galvanized steel sheet according to one embodiment of the present invention is characterized in that even when immersed in a degreasing solution (an aqueous solution such as sodium hydroxide and potassium hydroxide) having a pH of 8 to 13 for 60 minutes at a temperature of 40 DEG C (alkali treatment) It is not lost, and a small amount of zinc oxide is formed on the surface, which shows that the alkali resistance is excellent. This can be confirmed from the SEM photograph of the surface (phosphate coating layer) of the galvanized steel sheet after the alkali treatment.

The zinc electroplated steel sheet of the present invention is improved in alkali resistance, chipping resistance and in-bore lining by controlling the amount of phosphate coating, phosphate size and manganese content in the phosphate coating layer to a specific range. For example, It is possible to improve the surface smearing phenomenon and the like and to stabilize the production quality.

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

Example

Example 1

A base steel sheet having a thickness of 0.8 mm was degreased and washed with water and subjected to electro-galvanizing at an adhesion amount of 20 g / m < ² > to prepare a base steel sheet having a zinc-plated layer. The prepared galvanized steel sheet was treated with water after surface treatment with a surface conditioner (manufacturer: Gardolene 6513 / M1 manufactured by Samyang Chemical Co., Ltd., concentration of surface control agent: 0.15 wt% in 100 wt% solution). Thereafter, an electrolytic galvanized steel sheet was prepared by spray-coating the surface of the galvanized steel sheet with an aqueous solution for treating phosphates having the conditions shown in Table 1 below, followed by drying to form a phosphate coating layer. (A ratio of the average long diameter and the average short diameter and the average long diameter (short diameter: long diameter)) of the phosphate coating layer, the phosphate deposit size (the average long diameter and the average long diameter) of the phosphate coating layer, The contents of manganese, zinc and nickel were measured, and the results are shown in Table 1.

Comparative Examples 1 and 2

An electrolytic galvanized steel sheet was prepared in the same manner as in Example 1, except that the phosphate aqueous solution was spray-coated under the conditions shown in Table 1 below. (A ratio of the average long diameter and the average short diameter and the average long diameter (short diameter: long diameter)) of the phosphate coating layer, the phosphate deposit size (the average long diameter and the average long diameter) of the phosphate coating layer, The contents of manganese, zinc and nickel were measured, and the results are shown in Table 1.

Property evaluation method

(1) Amount of phosphate adhered (unit: g / m ² ): An amount of phosphate adhered was calculated using an electronic balance according to the following formula 1.

[Formula 1]

Phosphate adhesion amount = (W2 - W1) / a

In the formula (1), W1 is the weight of the specimen before the formation of the phosphate coating layer, W2 is the weight of the specimen after the formation of the phosphate coating layer, and a is the area of the specimen (m ² ).

(2) Evaluation of Alkali Resistance: The electrodeposited steel sheet specimens prepared according to Example 1 and Comparative Examples 1 and 2 were immersed in a degreasing solution having a pH of 8 to 13 at a temperature of 40 DEG C for 60 minutes (after alkali treatment ) And scanning electron microscope (SEM) photographs of the specimen surface (phosphate coating layer) were taken to confirm phosphate loss and zinc oxide. SEM photographs taken are shown in Figs. 5 and 6. Fig.

Example 1 Comparative Example 1 Comparative Example 2 Aqueous solution for treating phosphates Mn content (ppm) 2500 2500 2500 Zn content (ppm) 1750 1750 1750 Ni content (ppm) 1650 1650 1650 Application temperature (℃) 55 55 55 Application (g / m ² ) 1.5 1.25 1.8 Phosphate coating layer Phosphate Adhesion (g / m ² ) 0.94 1.63 2.44 Phosphate average long diameter length (탆) 0.95 2.8 3.0 Average Short Diameter: Average Long Diameter 1: 6 1: 6 1: 5.5 Mn content (ppm) 6,800 4,400 4,600 Zn content (ppm) 50,000 53,000 51,000 Ni content (ppm) 800 500 600 Mn / Zn 0.14 0.08 0.09

From the results shown in Table 1, it can be seen that the electro-galvanized steel sheet of the present invention (Example 1) is excellent in alkali resistance, chipping resistance, and intact bending resistance. In particular, from FIG. 5, it was confirmed that even after the alkali treatment, almost no phosphate dissolution and zinc oxide adhesion (surface damage (stain)) occurred and the alkali resistance was excellent.

On the other hand, in Comparative Example 1 in which the amount of phosphate adhered was less than 1.53 g / m ² (0.94 g / m ² ) and the average long diameter length of the phosphate was less than 1.3 μm (0.95 μm), the ratio of manganese and zinc in the phosphate coating layer Zn) was decreased as compared with the examples. From the SEM photograph (FIG. 6), it was confirmed that phosphate dissolution and zinc oxide (surface damage (stain)) occurred after the alkali treatment (lower alkaline resistance) there was.

In addition, in the case of Comparative Example 2 in which the amount of phosphate adhered exceeds 1.73 g / m ² (2.44 g / m ² ), it can be seen that phosphate peeling (powdering) can occur during molding, and manganese and zinc (Mn / Zn) was decreased as compared with the examples.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (6)

Base steel plate;
A zinc plated layer formed on the surface of the base steel sheet; And
And a phosphate coating layer formed on the zinc plating layer,
The phosphate coating amount of the phosphate coating layer is 1.53 to 1.73 g / m ² ,
The average long diameter of the phosphate is 1.3 to 3.5 占 퐉, the ratio of the average short diameter and the average long diameter is 1: 3 to 1: 7,
Wherein the phosphate coating layer comprises 5,000 to 8,000 ppm of manganese (Mn), 32,000 to 52,000 ppm of zinc (Zn), and 700 to 1,300 ppm of nickel (Ni).
The electrogalvanized steel sheet according to claim 1, wherein a weight ratio (Mn / Zn) of manganese and zinc in the phosphate coating layer is 0.12 to 0.25.
Forming a zinc plated layer on the surface of the base steel sheet by electroplating;
Treating the zinc plated layer with a surface conditioning agent; And
Coating the zinc plating layer treated with the surface modifier with an aqueous phosphate solution for treatment at a temperature of 50 ° C to 60 ° C at a coverage of 1.4 to 1.6 g / m ² and then drying to form a phosphate coating layer,
Wherein the aqueous solution for phosphate treatment comprises 2,000 to 3,000 ppm of manganese (Mn), 1,500 to 2,000 ppm of zinc (Zn), and 1,500 to 1,800 ppm of nickel (Ni).
[4] The method according to claim 3, wherein the phosphate coating layer has a phosphate deposition amount of 1.53 to 1.73 g / m < ² >, an average long diameter of the phosphate is 1.3 to 3.5 mu m and an average short diameter and an average long diameter : 3 to 1: 7, and the phosphate coating layer comprises 5,000 to 8,000 ppm of manganese (Mn), 32,000 to 52,000 ppm of zinc (Zn), and 700 to 1,300 ppm of nickel (Ni) Way.
4. The method of claim 3, wherein the surface modifier is in the form of a solution in which the surface modifier is diluted with water, and the concentration of the surface modifier in 100% by weight of the solution is 0.1 to 0.2% by weight.
4. The method of claim 3, wherein in the step of forming the phosphate coating layer, the total acid of the aqueous solution for phosphate treatment is 19 to 29 and the free acid is 1.2 to 2.2. Gt;

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