KR101657843B1 - Zn ALLOY PLATED STEEL SHEET HAVING EXCELLENT WELDABILITY AND PROCESSED PART CORROSION RESISTANCE AND METHOD FOR MANUFACTURING THE SAME - Google Patents

Abstract

A galvanized gold-plated steel sheet excellent in weldability and machined portion corrosion resistance and a method of manufacturing the same. In one aspect of the present invention, there is provided an alloyed galvanized steel sheet comprising a base steel sheet and a zinc alloy plating layer, wherein the base steel sheet comprises 0.1% or more by weight of at least one member selected from the group consisting of Si, Wherein the zinc alloy plating layer contains 0.1 to 5.0% of Al, 0.1 to 5.0% of Mg, and the balance of Zn and unavoidable impurities, the zinc alloy plating layer containing, in terms of% by weight, A lower interface layer formed on the base steel sheet and having a dense structure; And an upper interface layer formed on the lower interface layer and having a network-type or island-like structure. The present invention also provides an alloyed gold-plated steel sheet excellent in weldability and processing corrosion resistance.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Zn alloyed steel sheet having excellent weldability and corrosion resistance at a machining part,

The present invention relates to an alloyed gold-plated steel sheet excellent in weldability and processed portion corrosion resistance, and a method for producing 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 alloy gold-plated steel sheet has the following disadvantages.

First, the Zn-Al-Mg alloyed gold-plated steel sheet has a disadvantage that cracking of LME (Liquid Metal Embrittlement) occurs easily during welding, which leads to weldability. That is, when the zinc-plated steel sheet as described above is welded, the Zn-Al-Mg intermetallic compound having a low melting point dissolves and penetrates along the grain boundaries of the base steel sheet, thereby causing liquid metal embrittlement.

Second, the Zn-Al-Mg alloyed gold-plated steel sheet has a disadvantage in that the corrosion resistance of the processed portion is increased. 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, Thereby causing the surface of the base steel sheet to be exposed to the outside, thereby lowering the corrosion resistance of the processed portion.

One aspect of the present invention is to provide an alloyed gold-plated steel sheet excellent in weldability and corrosion resistance at a machining portion.

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.

In one aspect of the present invention, there is provided an alloyed galvanized steel sheet comprising a base steel sheet and a zinc alloy plating layer, wherein the base steel sheet comprises 0.1% or more by weight of at least one member selected from the group consisting of Si, Wherein the zinc alloy plating layer contains 0.1 to 5.0% of Al, 0.1 to 5.0% of Mg, and the balance of Zn and unavoidable impurities, the zinc alloy plating layer containing, in terms of% by weight, A lower interface layer formed on the base steel sheet and having a dense structure; And an upper interface layer formed on the lower interface layer and having a network-type or island-like structure. The present invention also provides an alloyed gold-plated steel sheet excellent in weldability and processing corrosion resistance.

According to another aspect of the present invention, there is provided a method for producing a steel sheet, comprising the steps of: preparing a base steel sheet containing 0.1% or more of a total of at least one selected from the group consisting of Si, Mn and Ni in terms of% by weight; Heat treating the base steel sheet to form a surface oxide layer; Surface-activating a base steel sheet on which the surface oxide layer is formed; The surface-activated ground steel sheet is immersed in a zinc alloy plating bath containing 0.1 to 5.0% of Al, 0.1 to 5.0% of Mg, and the remainder of Zn and unavoidable impurities in terms of% by weight to obtain an alloyed gold- step; And a step of cooling the waxed gold-plated steel sheet after gas wiping and cooling the waxed gold-plated steel sheet.

Another embodiment of another aspect of the present invention is a method for manufacturing a steel sheet, comprising the steps of: preparing a base steel sheet containing 0.1% or more of a total of at least one selected from the group consisting of Si, Mn and Ni in terms of% by weight; Surface-activating the underlying steel sheet; Heat-treating the surface-activated ground steel sheet to form a surface oxide layer; The base steel sheet on which the surface oxide layer is formed is immersed in a zinc alloy plating bath containing 0.1 to 5.0% of Al, 0.1 to 5.0% of Mg and the remainder of Zn and unavoidable impurities in terms of% by weight, ; And a step of cooling the waxed gold-plated steel sheet after gas wiping and cooling the waxed gold-plated steel sheet.

The gold-plated steel sheet according to the present invention is not only excellent in weldability, but also has excellent corrosion resistance at the machined portion.

1 is an SEM image of an interface layer of an alloyed gold-plated steel sheet according to Inventive Example 1. FIG.
FIG. 2 is an SEM image of the interface layer of the gold-plated steel sheet according to Comparative Example 1. FIG.

Hereinafter, a gold alloy steel sheet excellent in weldability and corrosion resistance at the processing part, 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. The base steel sheet may contain 0.1% or more (preferably 0.5% or more, more preferably 1.0% or more) of the total of one or more species selected from the group consisting of Si, Mn and Ni. However, the present invention can be applied even when the sum of the contents of Si, Mn and Ni is lower than the above range. These elements are surface-enriched elements, and are partially employed in the interface layer formed between the base steel sheet and the plating layer, This is because we can set the lower limit to maximize the effect. In addition, the higher the content of the above elements, the better the weldability and the corrosion resistance of the processed portion, so the upper limit is not particularly limited.

The zinc alloy plating layer preferably contains 0.1 to 5.0% of Al, 0.1 to 5.0% of Al, and the balance of Zn and unavoidable impurities, in weight%.

Mg in the zinc alloy plating layer is an element that plays a role in improving the corrosion resistance of the coated steel sheet. If the content is too low, there is a problem that the effect of improving the corrosion resistance is insignificant. Therefore, the lower limit of the Mg content in the zinc alloy plating layer is preferably 0.1 wt%, more preferably 0.5 wt%, and even more preferably 0.8 wt%. However, if the content is excessive, there is a problem of occurrence of plating bath loss due to Mg oxidation in the plating bath. Therefore, the upper limit of the Mg content in the zinc alloy plating layer is preferably 5.0 wt%, more preferably 3.0 wt%, and even more preferably 2.0 wt%.

Al in the zinc alloy plating layer is an element that plays a role of suppressing Mg oxide dross. If the content is too low, the effect of Mg oxidation prevention is small in the plating bath. Therefore, the lower limit of the Al content in the zinc alloy plating layer is preferably 0.1 wt%, more preferably 0.5 wt%, and even more preferably 0.8 wt%. However, when the content is excessive, there is a problem that the plating bath temperature must be increased. If the plating bath temperature is high, the plating facility may be eroded. Therefore, the upper limit of the Al content in the zinc alloy plating layer is preferably 5.0 wt%, more preferably 3.0 wt%, and even more preferably 2.0 wt%.

A lower interface layer formed on the base steel sheet and having a dense structure between the base steel sheet and the zinc alloy plating layer; And an upper interface layer formed on the lower interface layer and having a network or island-like structure.

As described above, since the double-layered interfacial layer is formed, it is possible to effectively suppress the occurrence of LME (Liquid Metal Embrittlement) cracks, which is a main problem in welding of the zinc alloy-plated steel sheet, It is possible to effectively prevent external exposure of the base steel sheet itself, thereby improving the corrosion resistance of the processed portion.

Here, whether or not the double layered interfacial layer is formed can be confirmed by the following method. That is, since the above-described double-layered interfacial layer exists at the interface between the base steel sheet and the zinc alloy plating layer as described above, it is difficult to confirm the structure or the like unless the zinc alloy plating layer is removed. Therefore, the zinc alloy plating layer is completely dissolved by immersing the alloyed gold-plated steel sheet in the chromic acid solution capable of chemically dissolving only the gold alloy gold layer on the upper part thereof without damaging the interface layer of the double structure for 30 seconds, Scanning Electron Microscope (SEM) photographs were taken of the interfacial layer, and the formation of the interfacial layer of the double structure was confirmed by photo analysis and the thickness of each interfacial layer was measured. As an example of preparing the chromic acid solution, 200 g of CrO 3, 80 g of ZnSO 4 and 50 g of HNO 3 may be mixed with 1 liter of distilled water. Meanwhile, the composition of each interfacial layer described below can be analyzed using EDS (Energy Dispersive Spectroscopy), and the area occupancy of the upper interface layer can be measured through an image analyzer.

According to an embodiment of the present invention, the upper and lower interface layers include a Fe-Al-based alloy, and the Fe-Al-based alloy is one or two selected from the group consisting of Fe ₂ Al ₅ , FeAl ₃ , It can be more than a species. Here, the meaning that the upper and lower interface layers include an Fe-Al-based alloy means that the main component (about 80% by weight or more) includes an Fe-Al-based alloy and other effective components and inevitable impurities It is not excluded.

According to an embodiment of the present invention, the upper and lower interfacial layers may include 0.001 wt% or more of one or more species selected from the group consisting of Si, Mn and Ni. When the surface enrichment elements (Si, Mn and Ni) are suitably employed in the interface layer, it is possible to increase the melting point of the interface layer to more effectively suppress the occurrence of LME (Liquid Metal Embrittlement) cracks, External exposure can be prevented more effectively. In order to exhibit such effects in the present invention, the lower limit of the sum of the contents of the surface thickening elements is preferably 0.001 wt% or more, more preferably 0.005 wt% or more, and even more preferably 0.01 wt% or more. On the other hand, the larger the sum of these contents is, the more advantageous to inhibit the LME cracking and the external exposure of the base steel sheet itself in the bending process, and the upper limit is not particularly limited.

According to an embodiment of the present invention, the occupancy ratio of the upper interface layer to the lower interface layer may be 10 to 90%, preferably 15 to 85%, more preferably 20 to 80% . The area occupancy means the ratio of the area of the upper interfacial layer to the area of the lower interfacial layer when assuming a plane without considering three-dimensional bending or the like when projected in the thickness direction of the steel sheet from the top of the steel plate do. If the area occupancy of the upper interface layer is less than 10%, the area of the upper interface layer is excessively low, and there is a possibility that the weldability and the processed portion corrosion resistance of the alloyed gold-plated steel sheet are lowered. On the other hand, if it exceeds 90%, cracking may occur during processing due to brittleness.

According to an embodiment of the present invention, the upper interface layer may contain 15 to 80% of Al, 20 to 85% of Fe, 10% or less of Zn (including 0%), more preferably Al The alloy may contain 15 to 60% of Al, 40 to 80% of Fe and 10% or less of Zn (inclusive of 0%), more preferably 20 to 40% of Al, 60 to 80% of Fe, And Zn: 10% or less (including 0%).

Generally, the content of Al in the interfacial layer formed at the interface between the zinc-based plated layer and the base steel sheet is about 10% by weight or less. However, in the steel sheet according to the present invention, the content of Al contained in the upper interface layer is And is somewhat higher. If the content of Al in the upper interface layer is less than 15%, the effect of reducing the LME crack may be insufficient. On the other hand, when the content of Al exceeds 80%, cracking may occur during processing due to brittleness.

According to an embodiment of the present invention, the thickness of the upper interface layer may be 0.1 to 2 탆, more preferably 0.5 to 1.5 탆, and even more preferably 0.8 to 1.2 탆. If the thickness of the upper interface layer is less than 0.1 占 퐉, the LME crack reduction effect may be insufficient. On the other hand, when the thickness is more than 2 占 퐉, the crack area may be widened during processing.

According to an embodiment of the present invention, the thickness of the lower interface layer may be 0.5 占 퐉 or less (excluding 0 占 퐉), more preferably 0.3 占 퐉 or less (excluding 0 占 퐉) May be 0.1 占 퐉 or less (excluding 0 占 퐉). Unlike the upper interfacial layer, the lower interfacial layer must uniformly cover the surface of the front surface of the base steel sheet. When the thickness of the lower interfacial layer exceeds 0.5 mu m, the lower interface layer uniformly covers the surface of the base steel sheet It is unlikely. On the other hand, as the lower interface layer uniformly covers the surface of the base steel sheet, the thinner the thickness, the more uniformity usually increases. The lower limit is not particularly limited.

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, it can be produced by the following method as one embodiment thereof.

Hereinafter, a method of manufacturing an aluminum alloy-plated steel sheet excellent in weldability and corrosion resistance at a processing part, which is another aspect of the present invention, will be described in detail.

Surface activation step

After the base steel sheet is prepared, the surface activation of the base steel sheet is performed. This step is carried out to form a double-layered interface layer between the base steel sheet and the zinc alloy plating layer.

According to an embodiment of the present invention, the centerline average roughness Ra of the surface activated ground steel sheet may be 0.8 to 1.2 탆, more preferably 0.9 to 1.15 탆, Lt; / RTI > Here, the arithmetical average roughness (Ra) means an average height from the centerline (arithmetical mean line of profile) to the section curve.

Also, according to an embodiment of the present invention, the ten-point average roughness (Rz) of the surface activated base steel sheet may be 7.5 to 15.5 mu m. Here, the ten point median height (Rz) is a value obtained by subtracting the third peak from the highest point in the roughness profile within the reference cut-off of the harvesting portion, It means the distance between two parallel lines passing through each bone and parallel to the center line.

Also, according to an embodiment of the present invention, the maximum height roughness Rmax of the surface activated ground steel sheet may be 8 to 16.5 mu m. Here, the maximum height roughness (Rmax) refers to a distance from a centerline (arithmetical mean line of profile) parallel to a roughness profile in a cut-off of the harvesting portion, And the distance between the two parallel lines passing through the lowest point.

When the surface roughness (Ra, Rz, Rmax) of the base steel sheet is controlled in the above-described range, the reaction between the base steel sheet and the plating layer becomes more active, so that the interface layer of the double structure can be formed more easily.

The method of activating the surface of the base steel sheet is not particularly limited. For example, surface activation of the base steel sheet can be achieved by plasma treatment or an absorption polymer laser treatment. The specific process conditions for the plasma treatment or the liquid crystal laser treatment are not particularly limited, and any apparatus and / or conditions can be applied as long as the surface of the plating layer can be uniformly activated.

Surface oxide layer formation step

The base steel sheet is heat-treated to form a surface oxide layer on its surface. This step is a step for inducing surface enrichment of Si, Mn and Ni so that the Si, Mn and Ni can be sufficiently contained in the interfacial layer formed by a post-process.

On the other hand, if this step is carried out before the step of obtaining the coated steel sheet, the process order is not particularly limited. For example, after the surface activation of the base steel sheet, a surface oxide layer may be formed on the surface activated base steel sheet, or a surface oxide layer may be formed, followed by surface activation of the base steel sheet on which the surface oxide layer is formed.

According to an embodiment of the present invention, the heat treatment temperature during the heat treatment may be 700 to 900 ° C, more preferably 750 to 850 ° C. If the heat treatment temperature is lower than 700 ° C, the effect may not be sufficient. On the other hand, when the heat treatment temperature is higher than 900 ° C, there is a fear of lowering the process efficiency.

Au alloy gold-plated steel  Steps to Obtain

After the surface activation step and the surface oxide layer formation step, the base steel sheet is immersed in a zinc alloy plating bath containing 0.1 to 5.0% of Al, 0.1 to 5.0% of Al, and the remainder of Zn and unavoidable impurities in terms of% by weight, To obtain the alloy gold-plated steel sheet.

At this time, a normal plating bath temperature can be applied to the temperature of the plating bath. Generally, if the content of Al in the plating bath is increased, the melting point of the plating bath becomes higher, so that the inside of the plating bath is eroded to shorten the service life of the equipment, and the Fe alloy dross in the plating bath is increased, have. However, in the present invention, since the content of Al is controlled to be relatively low as 0.5 to 3.0 wt%, it is not necessary to set the temperature of the plating bath to be high, and it is preferable to apply the ordinary plating bath temperature. For example, it may be 430 to 480 캜.

gas Wiping  After cooling,

Thereafter, the zinc alloy-coated steel sheet is subjected to gas wiping treatment to adjust the plating adhesion amount. The gas wiping treatment is for adjusting the plating adhesion amount, and the method is not particularly limited. At this time, air or nitrogen may be used as the gas to be used, and nitrogen is more preferably used. This is because, when air is used, Mg oxidation is preferentially generated on the surface of the plating layer, which may cause surface defects of the plating layer.

Thereafter, the galvanized steel sheet having the coated amount of plating is cooled. In the present invention, the cooling rate, the cooling rate and the cooling termination temperature at the time of cooling are not particularly limited, and can be set under ordinary cooling conditions. On the other hand, the cooling method at the time of cooling is not particularly limited, and cooling can be performed by, for example, using an air jet cooler or spraying N ₂ wiping or water fog.

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 )

A high strength steel plate (0.8 mm in thickness, 100 mm in width, and 200 mm in length) having the composition and physical properties shown in the following Table 1 was prepared as a test piece for plating, and the surface of the test piece for plating was subjected to plasma treatment for surface activation. Here, Ra, Rz, and Rmax of the test piece for surface activated plating are shown in Table 2 below. Thereafter, the surface-activated plating test piece was heat-treated at a heat treatment temperature of 800 ° C. Thereafter, the heat-treated test piece for plating was immersed in a zinc alloy plating bath having the composition shown in Table 2 below to prepare an alloyed gold-plated steel sheet. Thereafter, the zinc alloy-coated steel sheet was gas-wiped to adjust the amount of plating adhered to 70 g / m ² per side and cooled to room temperature (about 25 ° C) at an average cooling rate of 10 ° C / sec.

Then, the composition, thickness, area occupancy, etc. of the interfacial layers of each of the manufactured gold-plated steel sheets were measured, and the results are shown in Table 1 below. The measurement method is as described above. FIG. 1 is an SEM image of an interface layer of an alloyed gold-plated steel sheet according to Inventive Example 1, and FIG. 2 is an SEM image of an interface layer of an alloyed gold-plated steel sheet according to Comparative Example 1. FIG.

Then, the weldability and the corrosion resistance of the machined portion of each of the manufactured gold-plated steel sheets were evaluated. The results are shown in Table 3 below.

Weldability was evaluated by the following method.

A welding current of 7 kA was flowed using a Cu-Cr electrode having a tip radius of 6 mm and a welding time of 11 Cycles at a pressing force of 2.1 kN (here, 1 cycle means 1/60 second, hereinafter the same) Welding was performed. A total of five specimens were fabricated in each example and the lengths of all LME cracks generated in the five specimens were measured and the average LME crack length and maximum LME crack length were derived. As a result, it was evaluated as "Pass" when the average LME crack length was 20 μm or less, "Fail" when the average LME crack length was 20 μm or more, "Pass" when the maximum LME crack length was 100 μm or less, "Failed".

The corrosion resistance of the machined part was evaluated by the following method.

Each of the coated steel sheets was subjected to 180 ° bending (0T bending), and each of the coated steel sheets subjected to bending 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. "Pass" if the redness time was 500 hours or more, and "Failed" if it was less than 500 hours.

Composition (% by weight) The tensile strength
(MPa) C Si Mn P S 0.25 1.5 0.003 0.001 590

Remarks Surface roughness Plating bath composition (% by weight) The upper interface layer Lower interface layer Al Mg Furtherance
(weight%) thickness
(탆) Share
(area%) Furtherance
(weight%) thickness
(탆) Inventory 1 Ra: 1.04
Rz: 8.57
Rmax: 10.5 One One Al: 20.10
Fe: 77.63
Zn: 1.11
Si: 0.001
Mn: 0.005 0.83 25 Al: 9.8
Fe: 88.8
Zn: 1.35
Si: 0.001
Mn: 0.005 0.08 Inventory 2 Ra: 1.07
Rz: 14.3
Rmax: 15.2 1.6 1.6 Al: 55.45
Fe: 43.4
Zn: 1.11
Si: 0.001
Mn: 0.005 1.01 56 Al: 10.5
Fe: 88.4
Zn: 1.04
Si: 0.001
Mn: 0.005 0.09 Comparative Example 1 Ra: 0.56
Rz: 9.26
Rmax: 13.7 One One - - - Al: 10.3
Fe: 88.65
Zn: 1.01
Si: 0.001
Mn: 0.005 0.05 Comparative Example 2 Ra: 1.57
Rz: 15.2
Rmax: 12.8 1.6 1.6 - - - Al: 12.5
Fe: 86.34
Zn: 1.15
Si: 0.001
Mn: 0.005 0.06

Remarks Weldability Corrosion resistance Average LME crack length Maximum LME crack length Red rush hour Inventory 1 18 94 550 Inventory 2 12 72 650 Comparative Example 1 30 179 300 Comparative Example 2 34 125 250

With reference to Tables 1 and 2, in Examples 1 and 2 which satisfy all the conditions of the present invention, not only the average LME crack length is 20 탆 or less, the maximum LME crack length is 100 탆 or less, , And the occurrence time of the red rust was 500 hours or more, and it was confirmed that the corrosion resistance of the processed portion was excellent. On the other hand, in Comparative Examples 1 and 2, weldability and machined portion corrosion resistance were poor due to the non-formation of the double structure interface layer.

Claims (12)

In an alloyed gold-plated steel sheet comprising a base steel sheet and a zinc alloy plating layer,
The base steel sheet according to claim 1, wherein the base steel sheet contains 0.1% or more by total of at least one member selected from the group consisting of Si, Mn and Ni,
Wherein the zinc alloy plating layer contains 0.1 to 5.0% of Al, 0.1 to 5.0% of Al, and the balance of Zn and unavoidable impurities,
A lower interface layer formed on the base steel sheet and having a dense structure between the base steel sheet and the zinc alloy plating layer; And an upper interface layer formed on the lower interface layer and having a network or island-like structure.
The method according to claim 1,
Wherein the upper and lower interface layers include a Fe-Al alloy, and the Fe-Al alloy is at least one selected from the group consisting of Fe ₂ Al ₅ , FeAl _3, and FeAl, Allied gold-plated steel plate.
The method according to claim 1,
Wherein the upper and lower interface layers contain at least 0.001% of a total of at least one selected from the group consisting of Si, Mn and Ni, in terms of% by weight, and excellent corrosion resistance at the processed portion.
The method according to claim 1,
Wherein the area occupancy of the upper interfacial layer is 10 to 90% of the lower interfacial layer area.
The method according to claim 1,
Wherein the upper interface layer comprises 15 to 80% of Al, 20 to 85% of Fe, and 10% or less of Zn (including 0%) in terms of% by weight.
The method according to claim 1,
Wherein the upper interfacial layer has a thickness of 100 nm to 2 탆 and is excellent in weldability and corrosion resistance at the processed portion.
The method according to claim 1,
Wherein the lower interfacial layer has a thickness of 500 nm or less (excluding 0 nm) and is excellent in weldability and corrosion resistance in the processed portion.
Preparing a base steel sheet containing 0.1% or more of a total of at least one member selected from the group consisting of Si, Mn and Ni in terms of% by weight;
Heat treating the base steel sheet to form a surface oxide layer;
Surface-activating a base steel sheet on which the surface oxide layer is formed;
The surface-activated ground steel sheet is immersed in a zinc alloy plating bath containing 0.1 to 5.0% of Al, 0.1 to 5.0% of Mg, and the remainder of Zn and unavoidable impurities in terms of% by weight to obtain an alloyed gold- step; And
And after cooling the waxed gold-plated steel sheet after gas wiping,
The surface activated steel sheet has a center line average roughness (Ra) of 0.8 to 1.2 탆, a 10-point average roughness (Rz) of 7.5 to 15.5 탆, a maximum height roughness (Rmax) of 8 to 16.5 탆, A method of manufacturing a galvanized steel sheet excellent in corrosion resistance.
Preparing a base steel sheet containing 0.1% or more of a total of at least one member selected from the group consisting of Si, Mn and Ni in terms of% by weight;
Surface-activating the underlying steel sheet;
Heat-treating the surface-activated ground steel sheet to form a surface oxide layer;
The base steel sheet on which the surface oxide layer is formed is immersed in a zinc alloy plating bath containing 0.1 to 5.0% of Al, 0.1 to 5.0% of Mg and the remainder of Zn and unavoidable impurities in terms of% by weight, ; And
And after cooling the waxed gold-plated steel sheet after gas wiping,
The surface activated steel sheet has a center line average roughness (Ra) of 0.8 to 1.2 탆, a 10-point average roughness (Rz) of 7.5 to 15.5 탆, a maximum height roughness (Rmax) of 8 to 16.5 탆, A method of manufacturing a galvanized steel sheet excellent in corrosion resistance.
10. The method according to claim 8 or 9,
Wherein the heat treatment temperature is 700 to 900 DEG C during the heat treatment, and the corrosion resistance of the processed part is excellent.
delete 10. The method according to claim 8 or 9,
Wherein the surface activation of the base steel sheet is excellent in the weldability and the process corrosion resistance which are achieved by the plasma treatment or the liquid crystal laser treatment.

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