KR101819381B1 - Zn ALLOY PLATED STEEL SHEET HAVING EXCELLENT BENDABILITY AND METHOD FOR MANUFACTURING SAME - Google Patents

Abstract

A zinc-plated steel sheet comprising a base steel sheet and a zinc alloy plating layer, wherein the zinc alloy plating layer contains a Zn single-phase structure and a Zn-Al-Mg based intermetallic compound in a microstructure, (0001) preferred orientation degree (f) is 50% or more, and a method for producing the same.
[Relation 1]
f (%) = (I _basal / I _total ) x 100
(Where I _total means the value obtained by integrating the diffraction peaks of all Zn single phase when the X-ray diffraction pattern is measured from 2 ° to 10 ° to 100 ° using a Cu-Kα source, and I _basal means a value obtained by integrating the _basal plane Means a value obtained by integrating the diffraction peak of the related Zn single phase)

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alloyed gold-plated steel sheet having excellent bending workability,

The present invention relates to an alloyed gold-plated steel sheet excellent in bending workability and a method of manufacturing the same.

The zinc plating method which suppresses the corrosion of iron through the cathode method is widely used for manufacturing a steel material having excellent corrosion resistance and performance and excellent corrosion resistance. Particularly, the hot-dip galvanized steel sheet which forms the coating layer by immersing the steel into the molten zinc has a simpler manufacturing process than that of the electro-galvanized steel sheet and has a low product price, The demand is increasing.

The zinc-plated hot-dip galvanized steel sheet has a characteristic of sacrificial corrosion protection in which corrosion of the steel sheet is firstly inhibited by zinc which is lower in oxidation-reduction potential than iron when exposed to a corrosive environment, Thereby forming a dense corrosion product on the surface of the steel sheet and blocking the steel from the oxidizing atmosphere, thereby improving the corrosion resistance of the steel sheet.

However, the increase in the air pollution and deterioration of the corrosive environment due to the industrial advancement are increasing, and due to the strict regulations on the resource and energy saving, there is a growing need for the development of steels having better corrosion resistance than the conventional zinc plated steel sheets.

As a part of this research, various researches have been made on a technique of manufacturing a steel sheet with a zinc alloy plating which improves the corrosion resistance of a steel material by adding an element such as aluminum (Al) and magnesium (Mg) to the zinc plating bath. Studies on the fabrication technology of Zn-Al-Mg alloyed gold-plated steel sheet in which Mg is additionally added to a Zn-Al plating composition system as a representative Au-based gold plating material are actively studied.

However, such a Zn-Al-Mg-based alloy gold-plated steel sheet is disadvantageous in that bending workability is heated. That is, the zinc-coated gold-plated steel sheet contains a large amount of Zn-Al-Mg intermetallic compounds formed by thermodynamic interactions of Zn, Al and Mg in the plating layer. Since such intermetallic compounds have high hardness, Cracks are caused, and the bending workability is deteriorated.

One of the objects of the present invention is to provide an alloyed gold-plated steel sheet excellent in bending workability and a method of manufacturing the same.

The object of the present invention is not limited to the above description. Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.

One aspect of the present invention resides in a zinc alloy plating layer comprising a base steel sheet and a zinc alloy plating layer, wherein the zinc alloy plating layer contains a Zn single phase structure and a Zn-Al-Mg based intermetallic compound as a microstructure, (0001) preferred orientation degree (f) of the single phase structure expressed by the following relational expression 1 is 50% or more (including 100%).

[Relation 1]

f (%) = (I _basal / I _total ) x 100

(Where I _total means the value obtained by integrating the diffraction peaks of all Zn single phase when the X-ray diffraction pattern is measured from 2 ° to 10 ° to 100 ° using a Cu-Kα source, and I _basal means a value obtained by integrating the _basal plane Means a value obtained by integrating the diffraction peak of the related Zn single phase)

According to another aspect of the present invention, there is provided a method of manufacturing a galvanized steel sheet, comprising the steps of: preparing a zinc alloy plating bath containing Mg and Al; immersing the steel sheet in the zinc alloy plating bath and performing plating to obtain a galvanized steel sheet; A step of adjusting the plating amount by gas wiping the steel sheet, a step of spraying a droplet of water or an aqueous solution on the galvanized steel sheet having the adjusted plating amount and cooling the same, followed by air cooling, Wherein the starting temperature is 405 to 425 ° C and the droplet jetting end temperature is 380 to 400 ° C.

As one of various effects of the present invention, the steel sheet according to one embodiment of the present invention is not only excellent in corrosion resistance but also excellent in bending workability.

Also, as one of various effects of the present invention, the steel sheet according to one embodiment of the present invention has an advantage of excellent surface appearance.

Also, as one of various effects of the present invention, the steel sheet according to one embodiment of the present invention has an advantage of excellent scratch resistance.

Fig. 1 shows the results of observation of surface microstructure of (a) Inventive Example 1 and (b) Comparative Example 5 of the present invention.
Fig. 2 shows the results of observing the microstructure of the cross section of Inventive Example 1 (a) and Comparative Example 5 (b) of the present invention.
3 is an X-ray diffractometer (XRD) analysis result of Inventive Example 1 of the present invention.

Hereinafter, the gold alloy steel sheet excellent in bending workability which is one aspect of the present invention will be described in detail.

An alloy gold-plated steel sheet which is one aspect of the present invention includes a base steel sheet and a zinc alloy plating layer. In the present invention, the kind of the base steel sheet is not particularly limited, and it may be, for example, a hot-rolled steel sheet or a cold-rolled steel sheet used as a base of an ordinary zinc alloy-coated steel sheet. However, in the case of a hot-rolled steel sheet, a large amount of oxide scale is present on the surface of the hot-rolled steel sheet. Such an oxide scale has a problem of deteriorating the plating adhesion and deteriorating the plating quality. Therefore, More preferable. On the other hand, the zinc alloy plating layer may be formed on one side or both sides of the base steel sheet.

The zinc alloy plating layer may contain 0.5 to 3% of Al, 0.5 to 3% of Mg, and the remainder Zn and unavoidable impurities in weight%.

Mg reacts with Zn and Al in the zinc alloy plating layer to form a Zn-Al-Mg intermetallic compound and thus plays a very important role in improving the corrosion resistance of the coated steel sheet. If the content is excessively low, the microstructure of the plating layer The sufficient amount of Zn-Al-Mg intermetallic compound can not be secured and the corrosion resistance improving effect may not be sufficient. Therefore, the Mg in the zinc alloy plating layer may be contained in an amount of 0.5 wt% or more, and preferably 1.0 wt% or more. However, when the content is excessive, not only the effect of improving the corrosion resistance is saturated but also the Mg oxide-related dross is formed in the plating bath, thereby deteriorating the plating ability. Further, there is a fear that the Zn-Al-Mg based intermetallic compound having a high hardness in the microstructure of the plated layer is excessively formed and the bending workability is lowered. Therefore, the content of Mg in the zinc alloy plating layer may be 3 wt% or less, preferably 2.9 wt% or less.

The above-mentioned Al suppresses formation of Mg oxide dross and reacts with Zn and Mg in the plating layer to form a Zn-Al-Mg intermetallic compound, and plays an important role in improving the corrosion resistance of the coated steel sheet. Is too low, the ability to inhibit Mg dross formation is insufficient and a sufficient amount of Zn-Al-Mg based intermetallic compound can not be secured in the microstructure of the plating layer, so that there is a possibility that the effect of improving the corrosion resistance may not be sufficient. Al may be contained in an amount of 0.5 wt% or more, and preferably 0.6 wt% or more. However, if the content is excessive, not only the effect of improving the corrosion resistance is saturated but also the plating bath temperature is increased, which may adversely affect the durability of the plating apparatus. Furthermore, there is a fear that the Zn-Al-Mg based intermetallic compound having a high hardness in the microstructure of the plated layer is excessively formed and the bending workability is lowered. Therefore, the content of Al in the zinc alloy plating layer may be 3 wt% or less, preferably 2.6 wt% or less.

According to one example, the content of Mg and Al contained in the zinc alloy plating layer may satisfy the following relational expression (1). When [Mg] / [Al] is less than 1.0, the scratch resistance may deteriorate. On the other hand, when [Mg] / [Al] exceeds 4.0, Mg system dross in the hot- There is a possibility that the sex will deteriorate.

[Relation 1]

1.0 <[Mg] / [Al]? 4.0

(Where each of [Mg] and [Al] represents the weight% of the element)

The zinc alloy plating layer may contain a Zn single phase structure and a Zn-Al-Mg based intermetallic compound in its microstructure. In the present invention, the kind of the Zn-Al-Mg intermetallic compound is not particularly limited. For example, a Zn / Al / MgZn ₂ three-element process structure, a Zn / MgZn ₂ two- A primary process structure and a MgZn ₂ single phase structure.

The inventors of the present invention have studied in depth to improve the bending workability of the zinc alloy-plated steel sheet. As a result, the zinc single phase structure having hexagonal close packing (HCP) among the microstructure of the zinc alloy plating layer is oriented in the (0001) orientation It was found that the slip is easy to grow and the ductility is increased, so that the occurrence of cracks during bending can be remarkably reduced.

In order to obtain such an effect in the present invention, it is preferable to control the (0001) preferential orientation degree f of the Zn single phase structure represented by the following relational expression 1 to 50% or more (inclusive) It is more preferable to control it.

[Relation 1]

f (%) = (I _basal / I _total ) x 100

(Where I _total means the value obtained by integrating the diffraction peaks of all Zn single phase when the X-ray diffraction pattern is measured from 2 ° to 10 ° to 100 ° using a Cu-Kα source, and I _basal means a value obtained by integrating the _basal plane Means a value obtained by integrating the diffraction peak of the related Zn single phase)

Further, the inventors of the present invention have found that miniaturizing the size of the Zn single phase structure formed in the zinc alloy plating layer coarsely helps to reduce the occurrence of cracks during the bending process.

In order to obtain the desired effect in the present invention, it is preferable to control the average particle size of the Zn single phase structure to 15 mu m or less, more preferably to 12 mu m or less, and further preferably to 10 mu m or less. Here, the average particle diameter of the Zn single phase structure means the equivalent circular diameter of the Zn single phase structure detected by observing the plate thickness direction section of the plating layer.

The gold-plated steel sheet according to the present invention has not only excellent corrosion resistance but also excellent bending workability.

According to one example, the steel sheet according to the present invention may have a very good surface appearance. More specifically, the number of black spots on the surface of the steel sheet is 0.1 / cm ² &Lt; / RTI &gt;

In order to obtain this effect in the present invention, it is preferable that the area fraction of the Zn single phase structure observed on the surface of the zinc alloy plating layer is 40% or less (excluding 0%). That is, by maximizing the fraction of the Zn-Al-Mg intermetallic compound observed on the surface of the zinc alloy plating layer, the surface appearance can be maximized.

According to one example, the steel sheet according to the present invention may have excellent scratch resistance.

If maximizing the findings of the inventors, the area fraction of the layered structure Zn / MgZn _{2 2} won process organization and Zn / Al / MgZn ₂ 3 won step tissues are observed in the surface of the zinc alloy coating layer, improving the scratch resistance remarkably .

In order to obtain the desired effect in the present invention, the sum of the area fraction of Zn / MgZn _{2 2} won process organization and Zn / Al / MgZn ₂ 3 won process tissue that is observed at the surface of the zinc alloy plating layer (100% to 50% And the area fraction of the MgZn ₂ single phase structure is preferably 10% or less (including 0%). The MgZn ₂ single phase structure has a high hardness, which causes cracking during processing, and therefore, it is preferable to reduce the area fraction to the maximum.

The gold-plated steel sheet of the present invention can be produced by various methods, and the production method thereof is not particularly limited. However, as a preferred example, when the zinc alloy plated layer in the molten state is coagulated, it is possible to obtain the preferred orientation degree and the average particle size as described above when the droplets are sprayed on the surface thereof and then cooled.

At this time, the droplet jetting may be such that the droplet is jetted so as to be adhered by the electrostatic attraction force with the galvanized steel sheet. Such a jet is not only helpful for finely and uniformly forming a droplet, but also reduces the amount of repulsion after the jetted droplet impinges on the surface of the associated gold-plated steel sheet, thereby rapidly cooling the molten zinc alloy plating layer , Which is more effective for growth and miniaturization of (0001) orientation of Zn single phase texture.

The droplet may be an aqueous solution of phosphate, and the aqueous phosphate solution is effective for rapidly growing the Zn single phase structure in a (0001) orientation by microwaving the zinc alloy plating layer in a molten state by an endothermic reaction, and refining the microstructure. For example, an aqueous solution of ammonium hydrogenphosphate ((NH ₄ ) ₂ HPO ₄ ), an aqueous solution of sodium hydrogenphosphate (NaNH ₄ HPO ₄ ), an aqueous solution of zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ) ₃ (PO ₄ ) ₂ ) aqueous solution.

The concentration of the phosphate aqueous solution may be 1 to 3% by weight. If the concentration of the phosphate aqueous solution is less than 1% by weight, the effect may not be sufficient. If the concentration exceeds 3% by weight, the effect is saturated, and when continuous production is performed, nozzle clogging occurs, .

The droplet jetting start temperature may be 405 to 425 deg. C, and more preferably 410 to 420 deg. C at the droplet jetting. At this time, the droplet jetting start temperature means the surface temperature of the sub-gold-plated steel sheet at the point of time when the droplet jetting starts. If the droplet jetting initiation temperature is lower than 405 ° C, solidification of the Zn single phase is already initiated and black spots may be generated on the surface of the alloyed gold-plated steel sheet. On the other hand, when the temperature exceeds 425 ° C, endothermic reaction by droplet jetting is effective There is a possibility that it is difficult to obtain a desired tissue.

The droplet jetting end temperature at the droplet jetting may be 380 to 400 占 폚, and more preferably 390 to 400 占 폚. At this time, the droplet jet finishing end temperature means the surface temperature of the gold plated steel sheet at the time when the droplet jetting is finished. If the droplet jetting end temperature is higher than 400 ° C, the endothermic reaction due to droplet jetting is not effective and it may be difficult to secure the target structure. On the other hand, when the temperature is lower than 380 ° C, the Zn / MgZn ₂ two- There is a fear that Mg ₂ Zn ₁₁ phase is induced by subcooling during the initiation of solidification in the Al / MgZn ₂ ternary process and a large amount of black spots are generated, thereby lowering the preferential orientation degree of the (0001) Zn single phase structure.

The difference between the droplet jetting start temperature and the droplet jetting ending temperature at the droplet jetting may be 15 ° C or higher. If the temperature difference is less than 15 ° C, the endothermic reaction by droplet jetting is not effective and it may be difficult to secure the desired structure.

In addition, the droplet injection amount may be 50 to 100 g / m &lt; ² &gt; If, when the injection amount is 50 g / m ² is less than, and is a fear that the effect is insufficient, while if it exceeds 100g / m ² is not preferable because the effect is saturated.

Hereinafter, the present invention will be described more specifically by way of examples. It should be noted, however, that the following examples are intended to illustrate and specify the present invention and not to limit the scope of the present invention. And the scope of the present invention is determined by the matters described in the claims and the matters reasonably deduced therefrom.

( Example  One)

A low carbon cold-rolled steel sheet having a thickness of 0.8 mm, a width of 100 mm and a length of 200 mm was prepared as a test piece for plating, and the above-ground steel sheet was immersed in acetone and ultrasonically cleaned to remove foreign substances such as rolling oil present on the surface. Thereafter, the steel sheet was subjected to a heat treatment in a reducing atmosphere at 750 ° C for securing the mechanical properties of the steel sheet at the general hot-dip plating site, and then immersed in a plating bath (bath temperature: 460 ° C) . Thereafter, each of the manufactured gold-plated steel sheets was gas-wiped to adjust the amount of plating adhered to 70 g / m ² per one side, and then cooled under the conditions shown in Table 1 and then air-cooled. On the other hand, although not shown in the following Table 1, in Comparative Example 5, after the gold-plated steel sheet produced using the same plating bath as in Inventive Example 1 was gas-wiped to adjust the amount of plating adhering to 70 g / m ² per one side, And cooled to a point of time when the plating layer completely solidified (about 300 DEG C or less) at an average cooling rate of 12 DEG C / sec by a cooling device.

Thereafter, the microstructure of the zinc alloy-coated steel sheet produced by FE-SEM (SUPRA-55VP, ZEISS) was observed and shown in FIGS. 1 and 2, and the average grain size of the Zn single phase structure was measured and shown in Table 2 .

Then, the (0001) preferred orientation degree (f) of the Zn single phase structure was measured according to the following relational expression 1, and the results are shown in Table 2 below.

[Relation 1]

f (%) = (I _basal / I _total ) x 100

(Where I _total means the value obtained by integrating the diffraction peaks of all Zn single phase when the X-ray diffraction pattern is measured from 2 ° to 10 ° to 100 ° using a Cu-Kα source, and I _basal means a value obtained by integrating the _basal plane Means a value obtained by integrating the diffraction peak of the related Zn single phase)

After that, the bending workability of the manufactured gold alloy steel sheet was evaluated, and the results are shown in Table 2 below.

The corrosion resistance was evaluated by the following method.

Each alloyed gold-plated steel sheet was subjected to a corrosion promotion test using a salt spray test (salt spray test according to KS-C-0223), and the elapsed time until the red area of the plating layer surface reached 5% was measured Respectively.

The bending workability was evaluated by the following method.

After each 3-inch gold-plated steel sheet was observed by SEM with a length of 1 mm at the top of the bending process, the area ratio of the bending cracks was measured using an image analysis system.

No. Plating bath composition
(weight%) Droplet injection start temperature
(° C) Drop ejection end temperature
(° C) Droplet type Injection quantity
(g / m ² ) Remarks Al Mg One 1.6 1.6 410 390 Aqueous ammonium hydrogen phosphate solution,
2 wt% 70 Inventory 1 2 1.6 1.6 420 400 Aqueous ammonium hydrogen phosphate solution,
2 wt% 70 Inventory 2 3 1.6 1.6 430 400 Aqueous ammonium hydrogen phosphate solution,
2 wt% 70 Comparative Example 1 4 1.6 1.6 400 390 Aqueous ammonium hydrogen phosphate solution,
2 wt% 70 Comparative Example 2 5 1.6 1.6 420 405 Aqueous ammonium hydrogen phosphate solution,
2 wt% 70 Comparative Example 3 6 1.6 1.6 410 375 Aqueous ammonium hydrogen phosphate solution,
2 wt% 70 Comparative Example 4

No. Average particle size of Zn single phase structure (μm) f (%) Red rush hour
(h) Bending crack
Area ratio (%) Remarks One 8 63 650 8 Inventory 1 2 10 62 645 9 Inventory 2 3 12 49 640 25 Comparative Example 1 4 14 47 630 38 Comparative Example 2 5 15 46 620 40 Comparative Example 3 6 16 44 610 42 Comparative Example 4 7 18 42 600 45 Comparative Example 5

Table 2 shows that Examples 1 and 2 satisfying the conditions proposed by the present invention exhibit excellent bending workability.

On the other hand, Comparative Examples 1 to 5 exhibited excellent corrosion resistance, but the f value was less than 50% and the bending workability was poor.

Fig. 1 shows the result of observing the surface microstructure of (a) inventive example 1 and (b) comparative example 5 of the present invention. Fig. 2 (a) And the microstructure of the cross section was observed.

3 is an X-ray diffractometer (XRD) analysis result of Inventive Example 1 of the present invention. In Fig. 1, the peaks corresponding to &quot;?"And"?&Quot; correspond to the diffraction peaks of all Zn single phases, and the peaks corresponding to "? &Quot; correspond to the diffraction peaks of Zn single phase related to the basal plane.

( Example  2)

A low carbon cold-rolled steel sheet having a thickness of 0.8 mm, a width of 100 mm and a length of 200 mm was prepared as a test piece for plating, and the above-ground steel sheet was immersed in acetone and ultrasonically cleaned to remove foreign substances such as rolling oil present on the surface. Thereafter, the steel sheet was subjected to a heat treatment in a reducing atmosphere at 750 캜 for securing the mechanical properties of the steel sheet at the general hot-dip coating site, and then immersed in a plating bath having the composition shown in the following Table 3 to prepare an alloyed gold-plated steel sheet. Thereafter, each of the manufactured gold-plated steel sheets was gas-wiped to adjust the plating adhesion amount to 70 g / m ² per one side, and cooling was performed under the same conditions as that of Inventive Example 1 in Example 1.

Thereafter, the phase fraction of the microstructure observed on the surface of each of the gold-plated steel sheets was measured and the number of black spots was measured. The results are shown in Tables 3 and 4, respectively.

Then, for a linear friction test, friction was applied to the surface of each alloyed gold-plated steel sheet manufactured with a tool head for 20 times while applying a constant pressure. At this time, the target load was 333.3 kgf, the pressure was 3.736 MPa, the movement distance of the tool head was 200 mm and the movement speed of the tool head was 20 mm / s.

After the rubbing, the peel test was performed on each of the subassembled gold-plated steel sheets. More specifically, a cellophane adhesive tape (Ichiban Corp. NB-1) was closely adhered to the bending portion of each alloyed gold-plated steel sheet bended at 10R, and then instantaneously peeled off. Using an optical microscope (50 magnification) The number of plating layer defects was measured. If the measurement result, the plating layer number is 5 / m ² or less defects, "○", the coating layer Number of defects were evaluated as "X", if it exceeds 5 / m ^2, it is shown with the results in Table 4 below.

Further, after the rubbing, each of the alloyed gold-plated steel sheets was charged into a salt spray tester and the time of occurrence of red rust was measured by an international standard (ASTM B117-11). At this time, 5% brine (temperature 35 ° C, pH 6.8) was used, and 2 ml / 80 cm ² of brine was sprayed per hour. "○" when the red rusting time was 500 hours or more, and "X" when the red rusting time was less than 500 hours, and the results are shown in Table 4 below.

No. Alloy composition (% by weight) Surface texture area fraction (area%) Remarks Al Mg Mg / Al Zn Zn / MgZn ₂ Zn / Al / MgZn ₂ MgZn ₂ Zn / Al _{Zn / Al / MgZn 2 + Zn} / MgZn 2 One 0.6 2.3 3.83 28 41 31 0 0 72 Inventory A 2 1.5 2.8 1.87 20 57 21 One One 78 Inventory B 3 2 2.9 1.45 8 63 28 One 0 91 Honor C 4 2.2 2.7 1.23 4 58 34 2 2 92 Inventory D 5 2.6 2.9 1.12 4 39 51 3 3 90 E 6 0 0 - 100 0 0 0 0 0 Comparative Example A 7 1.4 One 0.71 82 7 11 0 0 18 Comparative Example B 8 2.5 1.2 0.48 6 21 26 46 One 47 Comparative Example C 9 5 0 0.00 76 0 0 0 24 0 Comparative Example D 10 5 One 0.20 59 9 11 0 21 20 Comparative Example E 11 8 3 0.38 13 7 13 18 49 20 Comparative Example F 12 55 0 0.00 14 0 0 0 86 0 Comparative Example G Here, surface texture refers to the microstructure observed on the surface of the zinc alloy plating layer.

No. Number of sunspots
(Pieces / cm ² ) After rubbing, peeling test result After rubbing, salt water spray test results Remarks Number of defects (pieces / m ² ) Evaluation results Dropout area (%) Evaluation results One 0.05 3 ○ 520 ○ Inventory A 2 0.08 2 ○ 550 ○ Inventory B 3 0.04 4 ○ 600 ○ Honor C 4 0.08 3 ○ 650 ○ Inventory D 5 0.04 2 ○ 580 ○ E 6 1.2 2 ○ 120 X Comparative Example A 7 0.8 3 ○ 230 X Comparative Example B 8 0.05 23 X 620 ○ Comparative Example C 9 1.1 3 ○ 350 X Comparative Example D 10 0.6 2 ○ 420 X Comparative Example E 11 0.06 15 X 650 ○ Comparative Example F 12 0.05 11 X 200 X Comparative Example G

Referring to Table 4, it can be confirmed that both of the surface appearance and the scratch resistance are excellent in Inventive Examples A to E satisfying the conditions proposed by the present invention.

On the other hand, Comparative Example A, Comparative Example B, Comparative Example D, and Comparative Example E exhibited poor surface appearance due to excessive Zn single-phase structure in the surface of the plating layer, The scratch resistance of the Zn / MgZn ₂ binary structure and the Zn / Al / MgZn ₂ three-element structure were inferior due to the low area fraction.

Claims (18)

In an alloyed gold-plated steel sheet comprising a base steel sheet and a zinc alloy plating layer,
The zinc alloy plating layer is a microstructure comprising Zn single phase structure and Zn-Al-Mg intermetallic compound,
(0001) preferred orientation degree (f) expressed by the following relational expression 1 of the Zn single phase structure is 50% or more (including 100%).
[Relation 1]
f (%) = (I _basal / I _total ) x 100
(Where I _total means the value obtained by integrating the diffraction peaks of all Zn single phase when the X-ray diffraction pattern is measured from 2 ° to 10 ° to 100 ° using a Cu-Kα source, and I _basal means a value obtained by integrating the _basal plane Means a value obtained by integrating the diffraction peak of the related Zn single phase)
The method according to claim 1,
Wherein the (0001) preferred orientation degree (f) of the Zn single phase structure expressed by the following relational expression 1 is 60% or more (including 100%).
[Relation 1]
f (%) = (I _basal / I _total ) x 100
(Where I _total means the value obtained by integrating the diffraction peaks of all Zn single phase when the X-ray diffraction pattern is measured from 2 ° to 10 ° to 100 ° using a Cu-Kα source, and I _basal means a value obtained by integrating the _basal plane Means a value obtained by integrating the diffraction peak of the related Zn single phase)
The method according to claim 1,
The Zn-Al-Mg intermetallic compound is one selected from the group consisting of a Zn / MgZn ₂ binary process structure, a Zn / Al binary process structure, a MgZn ₂ single phase structure, and a Zn / Al / MgZn ₂ three- Au alloy gold plated steel plate.
The method according to claim 1,
Wherein the area fraction of the Zn single phase structure observed on the surface of the zinc alloy plating layer is 40% or less (excluding 0%).
The method according to claim 1,
Wherein the sum of the area percentages of the Zn / MgZn ₂ original structure and the Zn / Al / MgZn ₂ original structure observed on the surface of the zinc alloy plating layer is 50% or more (excluding 100%).
The method according to claim 1,
Wherein the area fraction of the MgZn ₂ single phase structure observed on the surface of the zinc alloy plating layer is 10% or less (including 0%).
The method according to claim 1,
Wherein the average grain size of the Zn single phase structure observed in the plate thickness direction cross section of the zinc alloy plating layer is 15 占 퐉 or less (excluding 0 占 퐉).
The method according to claim 1,
Wherein the zinc alloy plating layer contains 0.5 to 3% of Al, 0.5 to 3% of Mg, and the balance of Zn and unavoidable impurities in terms of% by weight.
The method according to claim 1,
Wherein the zinc alloy plating layer satisfies the following relational expression (1).
[Relation 1]
1.0 <[Mg] / [Al]? 4.0
(Where each of [Mg] and [Al] represents the weight% of the element)
The method according to claim 1,
Wherein the number of black spots on the surface of the alloy gold-plated steel sheet is 0.1 per cm ² or less per unit area.
Preparing a zinc alloy plating bath containing Mg and Al;
Immersing the base steel sheet in the zinc alloy plating bath and performing plating to obtain a galvanized steel sheet;
Adjusting the plating adhesion amount by gas wiping the zinc-coated gold-plated steel sheet;
A step of spraying a droplet of water or an aqueous solution onto the galvanized gold-plated steel sheet whose plating amount is adjusted, cooling the steel sheet,
Wherein the droplet jetting start temperature and the droplet jetting end temperature are in the range of 405 to 425 캜 and 380 to 400 캜, respectively.
12. The method of claim 11,
Wherein the difference between the droplet jetting start temperature and the droplet jetting end temperature at the droplet jetting is 15 to 45 ° C.
12. The method of claim 11,
Wherein the droplet is jetted so that the droplet is adhered to the steel sheet by electrostatic attraction with the gold plated steel sheet when the droplet is sprayed.
12. The method of claim 11,
Wherein the spray amount of the droplet is 50 to 100 g / m ² when the droplet is sprayed.
12. The method of claim 11,
Wherein the aqueous solution is a phosphate aqueous solution.
16. The method of claim 15,
The aqueous phosphate solution is prepared by adding an aqueous solution of ammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ), an aqueous solution of sodium hydrogenphosphate (NaNH ₄ HPO ₄ ), an aqueous solution of zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ) Ca ₃ (PO ₄ ) ₂ ) aqueous solution.
16. The method of claim 15,
Wherein the concentration of the phosphate aqueous solution is 0.5 to 5 wt%.
12. The method of claim 11,
Wherein the zinc alloy plating bath comprises 0.5 to 3% of Al, 0.5 to 3% of Mg, and the balance of Zn and unavoidable impurities, in weight percent.

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