KR101665883B1

KR101665883B1 - Zn ALLOY PLATED STEEL SHEET HAVING EXCELLENT CORROSION RESISTANCE AND BENDABILITY AND METHOD FOR MANUFACTURING SAME

Info

Publication number: KR101665883B1
Application number: KR1020150118847A
Authority: KR
Inventors: 오민석; 김종상; 유봉환; 안호수
Original assignee: 주식회사 포스코
Priority date: 2015-08-24
Filing date: 2015-08-24
Publication date: 2016-10-13

Abstract

Steel wire; And a Zn-Mg-Al-based alloy plating layer containing 0.5 to 4 wt% of Al (excluding 4 wt%), Mg: 0.8 to 3.5 wt%, the remainder of Zn and unavoidable impurities, Zn-based alloy layer formed on the interface of a Zn-Mg-Al-based alloy plating layer and a method for manufacturing the same.

Description

TECHNICAL FIELD [0001] The present invention relates to a galvanized steel wire having excellent corrosion resistance and workability and a method of manufacturing the same. [0002] The present invention relates to a galvanized steel wire,

The present invention relates to a plated steel wire excellent in corrosion resistance and workability and a method of manufacturing the same, and more particularly to a plated steel wire excellent in corrosion resistance and workability which can be preferably applied to bridges such as suspension bridges and cable- .

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 galvanizing method in which a steel material is immersed in molten zinc to form a plated layer is simpler in manufacturing process than an electro-galvanizing method, and its product price is low, so that the demand for the entire industry such as automobiles, household appliances, Is increasing.

Zinc-plated galvanized steel has the characteristic of Sacrificial Corrosion Protection in which corrosion of steel is firstly prevented by zinc which is lower in oxidation-reduction potential than iron when exposed to a corrosive environment, and zinc The steel is oxidized to form a dense corrosion product on the surface of the steel sheet to block the steel from the oxidizing atmosphere, thereby improving the corrosion resistance of the steel.

However, the increase of the air pollution and the 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 steels.

As a part of this, in the related art, there have been various studies on a plating steel wire manufacturing technology for improving corrosion resistance by adding an element such as aluminum (Al) or manganese (Mn) to a zinc plating bath (see Patent Documents 1 and 2 ).

However, in the case of Patent Document 1, there is a disadvantage in that the Al addition alone is not sufficient in improving the corrosion resistance and is disadvantageous in terms of workability due to an increase in hardness of the plating layer, and Patent Literature 2 has a disadvantage in that workability is very low due to a large amount of dross etc. .

Japanese Laid-Open Patent Publication No. 2015-030857 Korean Patent Publication No. 2006-0076173

One of the objects of the present invention is to provide a coated steel wire excellent in corrosion resistance and workability and a method of manufacturing the same.

According to an aspect of the present invention, And a Zn-Mg-Al-based alloy plating layer containing 0.5 to 4 wt% of Al (excluding 4 wt%), Mg: 0.8 to 3.5 wt%, the remainder of Zn and unavoidable impurities, Zn-based alloy layer formed on the interface of the Zn-Mg-Al-based alloy plating layer.

According to another aspect of the present invention, Immersing the steel wire in a Zn plating bath containing not more than 0.01% by weight of Al and performing plating to obtain a Zn-plated steel wire; Cooling the Zn-plated steel wire to a temperature lower than the melting point of the Zn plating layer; And the cooled Zn-plated steel wire is immersed in a Zn-Mg-Al alloy plating bath containing 0.5 to 4% by weight of Al (excluding 4%), 0.8 to 3.5% of Mg and the remainder Zn and unavoidable impurities Thereby forming a Zn-Mg-Al based alloy plating layer.

It is possible to provide a plated steel wire excellent in corrosion resistance and workability as one of the effects of the present invention.

1 is a photograph of a section of a plated steel wire according to an embodiment of the present invention cut in a direction perpendicular to the longitudinal direction and then enlarging the cross section by 2000 times using a field-emission scanning electron microscope (FE-SEM) .
2 is a photograph of a section of a plated steel wire according to an embodiment of the present invention cut in a direction perpendicular to the longitudinal direction and then enlarging the cross section by 5000 times with a scanning electron microscope (FE-SEM, Field Emission Scanning Electron Microscope) .
3 (a) to 3 (d) are photographs taken after 800 hours after charging the coated steel wire according to Comparative Example 5, Inventive Example 6, Inventive Example 9 and Comparative Example 7 into a salt water spray tester.

Hereinafter, a plated steel wire excellent in corrosion resistance and workability, which is one aspect of the present invention, will be described in detail.

1 is a photograph of a section of a plated steel wire according to an embodiment of the present invention cut in a direction perpendicular to the longitudinal direction and then enlarging the cross section by 2000 times using a field-emission scanning electron microscope (FE-SEM) .

1, a plated steel wire according to an exemplary embodiment of the present invention includes a steel wire 100, an Fe-Zn alloy layer 200, and a Zn-Mg-Al alloy coating layer 300 sequentially from the inside thereof do.

The steel wire 100 is obtained by heat treating and drawing the wire material obtained by rolling the billet. In the present invention, the wire diameter, alloy composition, microstructure and the like of the steel wire are not particularly limited.

On the other hand, in general, the steel wire 100 has a large amount of oxide scale on its surface. Such an oxide scale has a problem of deteriorating the plating adhesion and deteriorating the plating quality. Therefore, the steel wire with the oxide scale removed by degreasing and flux treatment And it is more preferable to have it.

The Fe-Zn alloy layer 200 is interposed between the steel wire and the alloy plating layer, and plays a role of imparting adhesion between the steel wire and the alloy plating layer. In particular, the Fe-Zn alloy layer 200 absorbs the strain difference due to the difference in strain coefficient between the steel wire and the alloy plating layer during bending of the coated steel wire, thereby preventing peeling of the alloy plating layer in the machined portion, .

FeZn based alloy layer 200 comprises a FeZn-based alloy, for the _{example, FeZn 13, FeZn 7, Fe} 5 Zn 21 and Fe ₃ Zn ₁₀ 1 alone or in combination of two or more selected from the group consisting of . On the other hand, the fact that the Fe-Zn based alloy layer contains an Fe-Zn based alloy means that the main component (about 60% by weight or more) contains an Fe-Zn based alloy and other effective components and unavoidable impurities It is not excluded.

According to one example, the Fe-Zn alloy layer 200 may have an average thickness of 3 to 14 占 퐉. If the thickness of the Fe-Zn alloy layer is too thin, it may be difficult to ensure sufficient adhesion between the steel wire and the alloy plating layer. Therefore, the lower limit of the average thickness can be limited to 3 占 퐉 in view of ensuring sufficient adhesion between the steel wire and the alloy plating layer. On the other hand, if the average thickness of the Fe-Zn alloy layer is excessively large, unalloyed regions are formed when the Fe-Zn alloy layer is formed by alloying the Zn plating layer, so that the adhesion between the steel wire and the alloy plating layer may be deteriorated. The Fe-Zn alloy layer has brittleness and cracking may occur during processing. Therefore, in order to prevent this, the upper limit of the average thickness can be limited to 14 占 퐉. At this time, the average thickness was measured by cutting the plated steel wire in the direction perpendicular to the longitudinal direction, photographing the cross-section thereof with a scanning electron microscope (FE-SEM), measuring the maximum thickness and the minimum thickness These can be defined as averaged values.

As described above, when the unalloyed region exists in the Fe-Zn alloy layer 200, adhesion between the steel wire and the alloy plating layer may be deteriorated. Therefore, it is preferable that the Fe-Zn alloy layer does not have substantially unalloyed regions. According to one example, at a position apart from the interface of the steel wire and the Fe-Zn alloy layer in the thickness direction of the Fe-Zn alloy layer at a distance of 7 / 8t (where t is the thickness of the Fe-Zn alloy layer) When the concentration is measured, the Fe concentration may be 3 wt% or more.

FIG. 2 is a cross-sectional view of a plated steel wire according to an exemplary embodiment of the present invention cut in a direction perpendicular to the longitudinal direction, and then its cross section is magnified 5000 times by a scanning electron microscope (FE-SEM, Field Emission Scanning Electron Microscope) It is a photograph.

Referring to FIG. 2, the Fe-Zn alloy layer 200 of the plated steel wire according to an embodiment of the present invention may include an Fe-Al-Zn alloy phase 210. The Fe-Al-Zn alloy phase 210 can improve the corrosion resistance of the plated steel wire at the machining portion by buffering during processing.

According to one example, the Fe-Al-Zn alloy phase 210 may include up to 35 weight percent of Al. If the content of Al contained in the Fe-Al-Zn alloy phase 210 exceeds 35% by weight, the plating layer may be detached during the bending process and the corrosion resistance of the processed steel wire may be deteriorated.

Here, the method of measuring the Fe and Al concentrations is not particularly limited, but the following method can be used, for example. That is, after cutting the plated steel wire in the direction perpendicular to the longitudinal direction, the cross-sectional photograph was taken at 5,000 times using a FE-SEM (Field Emission Scanning Electron Microscope), and an EDS (Energy Dispersive Spectroscopy) The concentration of Fe and Al can be measured by analyzing.

The Zn-Al-Mg based alloy plating layer 300 contains, by weight%, Al: 0.5 to 4% (excluding 4%), Mg: 0.8 to 3.5%, the remainder Zn and unavoidable impurities.

Mg reacts with Zn and Al in the Zn-Al-Mg alloy plating layer to form a Zn-Al-Mg intermetallic compound and plays an important role in improving the corrosion resistance of the coated steel wire. If the content is too low A sufficient amount of Zn-Al-Mg based intermetallic compound in the microstructure of the plated layer can not be secured and the corrosion resistance improving effect may not be sufficient. Therefore, the content of Mg in the zinc alloy plating layer may be 0.8 wt% or more, preferably 1.0 wt% or more, and more preferably 1.5 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 3.5 wt% or less, preferably 3.2 wt% or less.

Al suppresses the Mg oxide dross formation 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 wire. The Zn-Al-Mg based intermetallic compound can not be obtained in a sufficient amount in the microstructure of the plated layer, so that the effect of improving the corrosion resistance may not be sufficient. Therefore, the Zn-Al-Mg based The amount of Al in the alloy plating layer may be 0.5 wt% or more, preferably 0.7 wt% or more, and more preferably 1.0 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 rises, causing erosion of the plating bath and the peripheral plating apparatus, which may adversely affect durability. In addition, the content of Al contained in the Fe-Al-Zn alloy phase in the Fe-Zn alloy layer is excessive, and the corrosion resistance of the processed portion may be deteriorated. Therefore, the content of Al in the Zn-Al-Mg based alloy plating layer may be less than 4.0 wt%, and preferably not more than 3.8 wt%.

According to an example, the Zn-Mg-Al based alloy plating layer 300 may include at least one selected from the group consisting of 0.01 to 0.5% by weight of Ca, 0.01 to 0.2% by weight of Si and 0.01 to 0.2% . When these elements are added, a thin passive film is formed on the surface of the alloy plating layer. This passive film suppresses the surface reaction and inhibits the alloy plating layer from reacting with the surrounding corrosion-inducing electrolytic material, thereby improving the corrosion resistance of the plating steel wire do. However, if the content is excessive, it is advantageous from the viewpoint of corrosion resistance, but a large amount of dross may be generated in the plating bath at the time of alloy plating, resulting in plating defects.

The unavoidable impurities included in the Zn-Mg-Al based alloy plating layer 300 may include at least one selected from the group consisting of Pb, Sb, Sn, La, Ce, Ni, Zr and Bi , And in this case, the sum of these contents is preferably 0.1 wt% or less. These elements cause segregation in the alloy plating layer, causing local corrosion and deteriorate the overall corrosion resistance of the coated steel wire. In order to prevent this, the sum of the contents of the elements is preferably limited to 0.1 wt% or less.

The average thickness of the Zn-Mg-Al-based alloy plating layer 300 is not particularly limited, but may be 10 to 50 占 퐉 according to one example. If the average thickness is less than 10 탆, the corrosion resistance improvement effect may be insufficient. On the other hand, when the average thickness exceeds 50 탆, the corrosion resistance improving effect may be saturated and the economical efficiency may deteriorate.

The above-described plated steel wire of the present invention can be manufactured by various methods, and the production method thereof is not particularly limited. However, as one embodiment thereof, it can be produced by the following method.

Hereinafter, a method of manufacturing a coated steel wire having corrosion resistance and workability, which is another aspect of the present invention, will be described in detail.

First, prepare a steel wire. In the present invention, the method for preparing the steel wire is not particularly limited. For example, a wire material obtained by rolling a billet can be prepared by heat treatment and drawing.

On the other hand, as described above, generally, in the case of a steel wire, a large amount of oxide scale is present on the surface thereof, and such an oxide scale may lower the plating adhesion and lower the plating quality. Therefore, if necessary, the steel strip can be degreased and pickled before the Zn plating, which will be described later, and then pretreated by an appropriate method to remove the oxide scale and clean the surface. In this case, the pretreatment can be carried out by a known method such as flux treatment using a flux mainly composed of zinc chloride (ZnCl ₂ ) and ammonium chloride (NH ₄ Cl) or heat treatment in a non-oxidizing atmosphere.

Next, the steel wire is immersed in a Zn plating bath to obtain a Zn-plated steel wire. The Zn-plated layer of the Zn-plated steel wire is alloyed with Fe to form an Fe-Zn alloy layer when plating a Zn-Mg-Al based alloy to be described later.

The Zn plating bath contains Zn and unavoidable impurities, and the unavoidable impurities may include Al. In this case, the content of Al is preferably suppressed to 0.01% by weight or less. If the content of Al in the Zn plating bath is more than 0.01% by weight, alloying between Fe and Zn is suppressed, and it may be difficult to form a desired alloy layer.

According to one example, the temperature of the Zn plating bath may be 420 to 480 캜. If the Zn plating bath temperature is lower than 420 ° C, the viscosity of the plating bath may excessively increase and the plating workability may be deteriorated. On the other hand, if it exceeds 480 ° C, corrosion of the plating bath and peripheral devices may occur.

The Zn plating bath immersion time of the steel wire can be from 3 to 30 seconds, preferably from 5 to 25 seconds, and even more preferably from 8 to 20 seconds. If the deposition time of the Zn plating bath is less than 3 seconds, there is a possibility of unplating. On the other hand, if the deposition time is more than 30 seconds, the Fe-Zn alloy layer becomes excessively developed and the plating layer of the Zn- There is concern that it will grow abnormally. At this time, the Zn plating bath deposition time means the time taken from the time when one point of the steel wire is drawn into the Zn plating bath to when it is drawn out.

Next, the Zn-plated steel wire is cooled to a temperature below the melting point of the Zn plating layer. This is because it is difficult to obtain a desired multi-layered plated steel wire if the subsequent Zn-Mg-Al alloy plating is performed without completely solidifying the Zn plating layer.

According to an example, the method may further include adjusting an average thickness of the Zn-plated layer of the Zn-plated steel wire to 3 to 14 m before cooling the Zn-coated steel wire. When the average thickness of the Zn plating layer is controlled within the above range, the workability can be maximized. At this time, the method of controlling the average thickness of the Zn plating layer is not particularly limited, and it can be a known method such as gas wiping.

Next, the steel wire having the Zn plating layer formed thereon is immersed in a Zn-Mg-Al based alloy plating bath having the above composition to form a Zn-Mg-Al based alloy plating layer.

The temperature of the Zn-Mg-Al alloy plating bath may be 380 to 480 캜, preferably 400 to 460 캜, and more preferably 420 to 440 캜. When the Zn-Mg-Al based alloy plating bath temperature is lower than 380 ° C, there is a fear that the plating bath viscosity increases and the plating workability is lowered. On the other hand, when the temperature is higher than 480 ° C, the plating bath and peripheral devices may be eroded .

The Zn-Mg-Al based alloy plating bath time of the steel wire may be 5 to 25 seconds, preferably 7 to 22 seconds, and more preferably 10 to 20 seconds. Zn-Mg-Al based alloy plating When the bath immersion time is less than 5 seconds, there is an unalloyed region in the Fe-Zn based alloy layer, and adhesion between the steel wire and the alloy plating layer may be lowered. On the other hand, if it exceeds 25 seconds, the content of Al contained in the Fe-Al-Zn alloy phase in the Fe-Zn-based alloy layer is excessive, and the corrosion resistance of the processed portion may be deteriorated. In this case, the Zn-Mg-Al based alloy plating bath immersion time means the time taken from the time when one point of the steel wire is drawn into the Zn-Mg-Al alloy plating bath to when it is drawn out.

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: Zn - Mg - Al Alloy Plated Evaluation of processability according to composition

First, a steel wire having a wire diameter of 2 mm, which contains 0.82% of C, 0.2% of Si, 0.5% of Mn and 0.003% of P and the balance of Fe and inevitable impurities, was prepared as a test piece for plating, And pickled, and subjected to flux treatment using a flux mainly composed of zinc chloride (ZnCl ₂ ) and ammonium chloride (NH ₄ Cl). Thereafter, the steel wire was immersed in a Zn plating bath (Al content: 0.01 wt% or less) at 450 캜 for 10 seconds to adjust the average thickness of the Zn plating layer to 10 탆 and then cooled to a temperature below the melting point of the Zn plating layer. Thereafter, the steel wire with the Zn plating layer formed was immersed in a Zn-Mg-Al alloy plating bath having a composition shown in Table 1 below at 440 캜 for 15 seconds to prepare a plated steel wire.

Then, each of the prepared coated steel wires was cut in a direction perpendicular to the longitudinal direction, and a cross-sectional photograph was taken at 5,000 times using a field-emission scanning electron microscope (FE-SEM) The presence of Fe-Al-Zn alloy phase was observed and the concentration of Al in the Fe-Al-Zn alloy phase was measured using EDS (Energy Dispersive Spectroscopy).

Thereafter, for the evaluation of workability, each of the produced coated steel wires was bended at 10R, and then each of the coated steel wires subjected to bending was subjected to a peeling test and a salt water spray test.

(1) peeling test

A cellophane adhesive tape (Ichiban NB-1) was closely adhered to the bending portion of each of the bended plated steel wires and then peeled off instantly. The area of the plated layer was measured using an optical microscope (50 magnification).

(2) Salt spray test

Each of the bended plated steel wires was charged into a salt spray tester, and the occurrence time 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. ? "For 500 hours or more and less than 1000 hours,"? "For less than 500 hours and 300 hours or less, and"? "For less than 300 hours.

Pseudo-No. Zn-Mg-Al alloy
Plating layer composition (% by weight) Fe-Al-Zn alloy phase Peel test result Salt water spray test result Remarks Al Mg Presence or absence Al content
(weight%) Plated layer removal area ratio (%) Time (h) evaluation One 0.2 1.2 X - 22.1 220 X Comparative Example 1 2 0.5 0.8 O 1.5 6 720 O Inventory 1 3 One 2.3 O 12.6 7.1 1200 ◎ Inventory 2 4 2.1 2.5 O 19.2 7.5 1500 ◎ Inventory 3 5 2.6 1.5 O 26.3 6.2 1100 ◎ Honorable 4 6 3.8 3.2 O 34.1 8.3 1500 ◎ Inventory 5 7 4 2.5 O 36.8 15.8 450 △ Comparative Example 2 8 4.3 3.6 O 42.1 22.3 400 △ Comparative Example 3 9 5 4 O 50.7 31.2 420 △ Comparative Example 4

Referring to Table 1, Examples 1 to 5, which satisfy the composition of the alloy plating layer proposed in the present invention, can be confirmed to have excellent corrosion resistance at the machined portion.

Example 2: Fe - Zn system Alloy layer Evaluation of workability by thickness

First, a steel wire having a wire diameter of 2 mm, which contains 0.82% of C, 0.2% of Si, 0.5% of Mn and 0.003% of P and the balance of Fe and inevitable impurities, was prepared as a test piece for plating, And pickled, and subjected to flux treatment using a flux mainly composed of zinc chloride (ZnCl ₂ ) and ammonium chloride (NH ₄ Cl). Thereafter, the steel wire was immersed in a Zn plating bath (Al content: 0.01 wt% or less) at 450 캜 for 10 seconds to adjust the average thickness of the Zn plating layer under the conditions shown in Table 2 and then cooled to a temperature below the melting point of the Zn plating layer Respectively. Thereafter, a steel wire with a Zn plating layer formed was immersed in a Zn-Mg-Al alloy plating bath (Al content: 2 wt%, Mg content: 3 wt%) at 440 DEG C for 15 seconds to prepare a plated steel wire.

Then, in order to measure the Fe content in the alloy layer, the plated steel wire was cut in a direction perpendicular to the longitudinal direction, and then cross-sectional photographs were taken at a magnification of 5000 times with a scanning electron microscope (FE-SEM, Field Emission Scanning Electron Microscope) And the Fe concentration at a position of 7 / 8t (here, t means the thickness of the Fe-Zn alloy layer) in the thickness direction of the Fe-Zn alloy layer was measured using EDS (Energy Dispersive Spectroscopy) , And the results are shown together in Table 2 below.

Then, each of the manufactured steel wires was bended at 10R for evaluation of the corrosion resistance of the processed portion, and the processed portion was observed at a magnification of 500 times using a FE-SEM (Field Emission Scanning Electron Microscope) , And the number of generated cracks was measured. The cases where the number of cracks was less than 10 were evaluated as "acceptable ", and those with 10 or more cracks were evaluated as" fail ", and the results are shown in Table 2 below.

Pseudo-No. Fe-Zn alloy layer thickness
(μm) At the 7 / 8t position
Fe content (% by weight) Processability Remarks Cracks () Passed? One 0.5 13 16 fail Comparative Example 5 2 2.8 11.5 11 fail Comparative Example 6 3 3.7 9.2 5 pass Inventory 6 4 7.0 5.7 5 pass Honorable 7 5 9.0 5.5 4 pass Honors 8 6 12.6 4.2 5 pass Proposition 9 7 14.0 3.5 6 pass Inventory 10 8 15.0 2.1 11 fail Comparative Example 7 9 21.0 1.3 16 fail Comparative Example 8 10 23.0 0.8 13 fail Comparative Example 9 11 25.0 0.5 16 fail Comparative Example 10 12 27.0 0.2 15 fail Comparative Example 11

It can be seen from Table 2 that Examples 6 to 10 satisfying the average thickness of the Fe-Zn based alloy layer proposed in the present invention have a small number of cracks in the bending portion and excellent corrosion resistance in the processed portion.

3 (a) to 3 (d) are photographs taken after 800 hours after charging the coated steel wire according to Comparative Example 5, Inventive Example 6, Inventive Example 9 and Comparative Example 7 into a salt water spray tester. 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. 3 (a) to 3 (d), Inventive Example 6 and Inventive Example 9, which satisfy the average thickness of the Fe-Zn alloy layer proposed in the present invention, show that even after 800 hours of the salt water spray test It can be confirmed that the corrosion resistance of the machined portion is very excellent.

Claims

Steel wire; And
A Zn-Mg-Al based alloy plating layer containing 0.5 to 4 wt% of Al (excluding 4 wt%), Mg: 0.8 to 3.5 wt%, the remainder of Zn and unavoidable impurities,
And a Fe-Zn alloy layer formed on the interface between the steel wire and the Zn-Mg-Al based alloy plating layer.

The method according to claim 1,
Wherein the Fe-Zn alloy layer has an average thickness of 3 to 14 占 퐉.

The method according to claim 1,
The Fe concentration was measured at the position of 7 / 8t (where t is the thickness of the Fe-Zn alloy layer) in the thickness direction of the Fe-Zn alloy layer from the interface between the steel wire and the Fe-Zn alloy layer , The Fe concentration being not less than 3% by weight (excluding 100% by weight).

The method according to claim 1,
Wherein the Fe-Zn alloy layer comprises a Fe-Al-Zn alloy phase.

5. The method of claim 4,
The Fe-Al-Zn alloy phase contains 35 wt% or less (excluding 0 wt%) of Al.

The method according to claim 1,
Wherein the Zn-Mg-Al based alloy plating layer further comprises at least one selected from the group consisting of Ca: 0.01 to 0.5 wt%, Si: 0.01 to 0.2 wt%, and Cr: 0.01 to 0.2 wt%.

The method according to claim 1,
The inevitable impurities contained in the Zn-Mg-Al based alloy plating layer are at least one selected from the group consisting of Pb, Sb, Sn, La, Ce, Ni, Zr and Bi, Plated steel wire.

The method according to claim 1,
Wherein the Zn-Mg-Al based alloy plating layer has an average thickness of 10 to 50 占 퐉.

Preparing a steel wire;
Immersing the steel wire in a Zn plating bath containing not more than 0.01% by weight of Al and performing plating to obtain a Zn-plated steel wire;
Cooling the Zn-plated steel wire to a temperature lower than the melting point of the Zn plating layer; And
The cooled Zn-plated steel wire was immersed in a Zn-Mg-Al based alloy plating bath containing 0.5 to 4% by weight of Al (excluding 4%), Mg: 0.8 to 3.5%, the remainder Zn and unavoidable impurities Forming a Zn-Mg-Al based alloy plating layer;
Wherein the plating wire is made of a metal.

10. The method of claim 9,
Further comprising the step of adjusting an average thickness of the Zn plating layer to 3 to 14 占 퐉 before cooling the Zn-plated steel wire.

10. The method of claim 9,
Further comprising the step of performing a flux treatment after degreasing and pickling the steel wire before forming the Zn plating layer.

10. The method of claim 9,
Wherein the Zn plating bath has a temperature of 420 to 480 [deg.] C.

10. The method of claim 9,
Wherein the Zn plating bath immersion time of the steel wire is 3 to 30 seconds.

10. The method of claim 9,
Wherein the temperature of the Zn-Mg-Al-based alloy plating bath is 380 to 480 캜.

10. The method of claim 9,
Wherein the Zn-Mg-Al based alloy plating bath immersing time of the steel wire is 5 to 25 seconds.