Detailed description of the invention
Technical challenge
[13]
An aspect of the present invention is to provide a zinc alloy plated steel material having excellent surface quality, excellent corrosion resistance in the cross-section, as well as excellent corrosion resistance in the processed portion, and a manufacturing method thereof.
[14]
The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems that are not mentioned will be clearly understood by those skilled in the art from the following description.
[15]
Means of solving the task
[16]
One aspect of the present invention is Ji-cheol So;
[17]
A zinc alloy plating layer formed on the base iron; And
[18]
It includes a suppression layer formed between the base iron and zinc alloy plating layer,
[19]
The Zn phase on the surface of the zinc alloy plating layer contains 15 to 90% by area fraction,
[20]
And a ternary alloy layer of Zn/MgZn 2 /Al formed on the suppression layer to a thickness of 2 μm or less , wherein the ternary alloy layer is formed in a ratio of 30 to 90% of the total area, and It relates to a zinc alloy plated steel with excellent corrosion resistance.
[21]
[22]
Another aspect of the present invention is to prepare a base iron;
[23]
Plating the base iron by immersing it in a plating bath;
[24]
Wiping and cooling the plated base iron,
[25]
The cooling relates to a method of manufacturing a zinc alloy plated steel material having excellent surface quality and corrosion resistance satisfying the following relational equation 1.
[26]
[Relationship 1]
[27]
0.7Vc ≤ Vc' ≤ 1.5Vc
[28]
However, Vc is the cooling rate until the solidification of the plating layer is completed immediately after wiping, and Vc' is the cooling rate until the start of solidification of the plating layer immediately after wiping.
[29]
Effects of the Invention
[30]
Advantageous Effects of Invention According to the present invention, it is possible to provide a zinc alloy plated steel material and a method of manufacturing the same, which secures excellent surface characteristics by preventing discoloration of the surface of the plating layer, and has excellent corrosion resistance not only in the end face but also in the processed portion. Through this, there is an advantage in that the use area can be extended to an area where conventional use is limited.
[31]
Brief description of the drawing
[32]
1 is a photograph illustrating a cross section of a plating layer of Inventive Example 3 of the embodiments of the present invention.
[33]
2 is a photograph illustrating a cross section of a plating layer of Comparative Example 2 of the Examples of the present invention.
[34]
3 is a photograph of observation of a ternary alloy phase layer of Zn/MgZn 2 /Al formed on the suppression layer in the photograph of FIG. 1 .
[35]
4 is a schematic view showing a plated steel and a wiping knife.
[36]
Best mode for carrying out the invention
[37]
While conventional zinc plating solidifies into a single Zn phase, Zn-Al-Mg-based zinc alloy plating coexists with a Zn phase, an alloy phase of Mg and Zn, an Al phase, and the like. This plating structure forms a very complex plating structure according to the physical and chemical state of the surface of the base iron according to the trace elements in the plating bath and the manufacturing process.
[38]
[39]
In the plating structure of the Zn-Al-Mg-based zinc alloy plating layer (hereinafter, the zinc alloy plating layer or the plating layer), the alloy phase of Zn and Mg may be made of various intermetallic compounds such as MgZn 2 , Mg 2 Zn 11 , and the hardness thereof is Hv It reaches 250-300. In addition, an inhibition layer made of an intermetallic compound of Fe and Al may be formed at the interface between the plating layer and the base iron. The intermetallic compounds of Fe and Al include Fe 4 Al 13 and Fe 2 Al 5 . Since these intermetallic compounds also have high brittleness, cracks in the plating layer are likely to occur during physical deformation.
[40]
[41]
The zinc alloy-plated steel of the present invention includes a base iron, a zinc alloy plating layer formed on the base iron, and an inhibition layer formed between the base iron and the zinc alloy plating layer.
[42]
[43]
The composition of the zinc alloy plating layer is not particularly limited, but as a preferred example, Mg: 0.5 to 3.5%, Al: 0.5 to 20.0%, and the rest include Zn and unavoidable impurities.
[44]
The magnesium (Mg) plays a very important role in improving the corrosion resistance of the zinc-based plated steel, and effectively prevents corrosion of the zinc-based plated steel by forming a dense zinc hydroxide-based corrosion product on the surface of the plated layer in a corrosive environment. In order to obtain the above effect, it is preferable to include 0.5% by weight or more, more preferably 0.8% by weight or more. However, if the content is excessive, there is a problem that Mg oxidizing dross on the surface of the plating bath increases rapidly on the bath surface of the plating bath. In terms of preventing this, the Mg is preferably 3.5% by weight or less, and more preferably 2.0% by weight or less.
[45]
The aluminum (Al) suppresses the formation of Mg oxide dross in the plating bath, and improves the corrosion resistance of the plated steel by reacting with Zn and Mg in the plating bath to form a Zn-Al-Mg-based intermetallic compound. In order to obtain the above effect, it is preferable to include 0.5% by weight or more, more preferably 0.8% by weight or more. However, if the content is excessive, the weldability and phosphate treatment of the plated steel may be deteriorated, so in terms of preventing this, the Al is preferably 20.0% by weight or less, more preferably 6.0% by weight or less, and plating In order to accelerate the coagulation behavior of the bath, it is more preferably 3.0% by weight or less.
[46]
The rest contains zinc (Zn) and unavoidable impurities.
[47]
[48]
In the zinc alloy plated steel sheet, an inhibition layer, a so-called inhibition layer, is formed between the zinc alloy plated layer and the base iron. The suppression layer is composed of an intermetallic compound of Fe and Al (ex. Fe 4 Al 13 , Fe 2 Al 5, etc.). The suppression layer is composed of fine grains, and when the size of the grains is coarse, it becomes brittle. Therefore, when external stress is applied to the steel sheet, the suppression layer is destroyed, and there is a concern that corrosion resistance may decrease due to peeling of the plating layer or processing crack. Therefore, the suppression layer preferably has a grain size of 300 nm or less, and an average grain size of 100 nm or less.
[49]
[50]
It is preferable that a ternary alloy layer of Zn, MgZn 2 and Al is formed on the suppression layer to a thickness of 2 μm or less . At the interface between the base iron and the zinc alloy plating layer, the sacrificial cathode reaction begins primarily in a corrosive environment. When such a ternary alloy phase is formed at the interface between the base iron and the zinc alloy plating layer, the effect of the sacrificial method increases from the interface when the cross-section of the product is exposed to a corrosive environment, and the effect of the sacrificial method continues to appear. This is because Zn, Mg, which mainly participates in the sacrificial method, and Al, which is advantageous for the formation of a passivation film, are concentrated in the plating layer and the base iron interface. The ternary alloy phase layer is preferably formed on the suppression layer, and is preferably formed at least 30% of the total area. However, in the case of excessive formation, since there is a concern that the upper hardness of the plating layer is reduced and the friction characteristics of the plating layer are deteriorated, it is preferable not to exceed 90%. An example of a method of confirming the ternary alloy layer is a method of enlarging the cross-sectional magnification and confirming it with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Another method is a method of dissolving the plating layer with an aqueous hydrochloric acid (HCl) solution and observing the surface to observe the ternary alloy layer remaining on the suppression layer. On the other hand, in the case of observing the cross-section, along the cross-sectional boundary, it can also be measured as the length at which the three circles are formed on the suppression layer in the entire length of the suppression layer.
[51]
When the thickness of the ternary alloy layer of Zn, MgZn 2 and Al is formed exceeding 2㎛ on the suppression layer, the effect of the sacrificial method at the interface between the base iron and the zinc alloy plating layer decreases, and The effect of improving corrosion resistance is also reduced. Therefore, it is important to control the material state or cooling conditions so that the thickness of the ternary alloy layer does not exceed 2 μm.
[52]
[53]
The zinc alloy plating layer includes a Zn phase, an alloy phase of Mg and Zn (ex. MgZn 2 , Mg 2 Zn 11, etc.), an Al phase, and the like. The microstructure observed on the surface of the zinc alloy plating layer of the present invention preferably contains 15 to 90% of the Zn phase as an area fraction. The microstructure appearing on the surface of the plating layer has a very close relationship with the surface characteristics of the plating layer. If the ratio of the Zn phase on the surface of the plating layer is small, the color of the plating surface becomes dark due to the influence of Mg oxidation during long-term storage of the plated steel sheet. Therefore, the Zn phase on the surface is preferably 15% or more. On the other hand, when the ratio of the Zn phase exceeds 90%, excessive cooling is required and productivity is degraded, which is not preferable.
[54]
[55]
The zinc alloy plating layer includes various phases as described above, and of which the Zn phase and the MgZn 2 phase may include a binary phase having a lamella structure. The zinc alloy plating layer of the present invention preferably has an average thickness of 1.5 μm or less in the width direction of the Zn phase and the MgZn 2 phase in the lamellar structure of the Zn and MgZn 2 phases included in the zinc alloy plating layer . Compared to the Zn phase, the MgZn 2 phase is brittle, so when the lamellar structure is coarse, the possibility of destruction due to external stress is high. Therefore, in the lamellar structure of the Zn and MgZn 2 phases formed inside from the surface of the plating layer , it is preferable that the average thickness of each of the Zn and MgZn 2 phases in the width direction is 1.5 μm or less (excluding 0). The lamellar structure of the Zn phase and MgZn 2 phase contained in the zinc alloy plating layer is preferably a lamellar structure in which up to 70% of the plating layer exists on the surface of the zinc alloy plating layer. The width direction thickness may be determined as an average value by measuring at least 10 locations of the lamellar structure present in the plating layer.
[56]
[57]
Hereinafter, an embodiment of a method for manufacturing a zinc alloy plated steel of the present invention will be described in detail. The method of manufacturing a zinc alloy plated steel of the present invention includes preparing a base iron, and then immersing the prepared base iron in a plating bath to plate, and then wiping to adjust the thickness of the plating layer and cooling.
[58]
[59]
In preparing the base iron, it is preferable to uniformize the metal structure of the hot-rolled steel first. Accordingly, it is preferable that the average grain size of the hot-rolled steel is 1 to 100 μm. The crystal grains of the hot-rolled steel are preferably in the surface layer (within 1/8 of the total thickness from the surface). When the structure of the hot-rolled steel, in particular, the non-uniformity of the surface structure occurs, uniform formation of the suppression layer becomes difficult due to the non-uniformity of the surface shape during cold rolling and the non-uniform diffusion of Fe from the base iron required for the formation of the suppression layer. The formation of the ternary phase to be formed is also non-uniformly, so that the corrosion resistance of the cross section is deteriorated. For this purpose, it is preferable that the average grain size of the hot-rolled steel is 1 to 100 μm. More preferably, the size of the crystal grains is 1 ~ 50㎛, or even more preferably 5 ~ 30㎛.
[60]
When the crystal grains of the hot-rolled steel are less than 1㎛, it is advantageous to secure strength, but surface roughness due to the crystal grains may increase during cold rolling. In addition, when it exceeds 100㎛, it is advantageous in terms of homogenization of the shape, but there is concern about scale defects due to an excessive increase in hot rolling temperature, and product manufacturing cost increases. As an example of a method for obtaining the crystal grain size of the hot-rolled steel, there is a method of maintaining the hot rolling temperature to be at least 800°C or higher, or increasing the coiling temperature after hot rolling by 550°C or more.
[61]
[62]
In manufacturing a cold-rolled steel by cold rolling the hot-rolled steel, it is preferable that the surface roughness (Ra) of the cold-rolled steel is 0.2 to 1.0 μm and the steepness is 0.2 to 1.2.
[63]
The surface roughness is determined according to the pressure of the roll and the surface shape of the roll when the roll rolls the material. When the surface roughness exceeds 1.0 μm, the roughness increases, so that a non-uniform suppression layer may be formed when the plating layer is formed, and the non-uniformity may increase in formation between phases in the plating layer. On the other hand, if the thickness is less than 0.2 μm, the surface friction coefficient decreases, so that the steel material may slip on the roll.
[64]
The measurement of the steepness is a method of measuring the degree of curvature of the steel after placing a steel material of 1 m or more in the width direction and 2 m or more in the length direction on a flat surface so that the surface can be closely adhered to it. It is expressed as the value multiplied by 100 after dividing the height (H) of the bend by the wavelength (P). That is, it is expressed by the expression of height (H)/wavelength (P) x 100. The smaller the steepness, the better the flatness of the steel. When the steepness exceeds 1.2, the curvature of the steel material is large, causing deviation in the surface flow when the steel material passes through the plating bath, which adversely affects the formation of the suppression layer and homogenization of the plating layer. The lower the steepness is, the more advantageous it is, but in order to manage it to less than 0.2, as an example, there is a method of slowing the speed of cold rolling, but this is not preferable because it requires excessive process cost.
[65]
The method for controlling the illuminance and steepness to an appropriate range is not limited to any one. In the final stage of cold rolling, the rolling reduction is preferably in the range of 2 to 5%. It is necessary to apply an appropriate tension to the steel sheet during rolling. In addition, as an example for imparting surface roughness, plasma treatment may be performed on the steel surface. That is, during the cold rolling, since the final shape is determined by the last rolling roll, the rolling rate is preferably 5% or less. However, in the case of a thin plate with a thickness of 0.5 mm, it is preferable to set it to 2% or more in order to reduce the overload of shear rolling.
[66]
[67]
On the other hand, the cold-rolled material as described above may be annealed and heat treated at a temperature of 600 to 850°C as necessary. It is preferable to use a gas containing 1 to 10% by volume of hydrogen (H 2 ) in nitrogen (N 2 ) during the annealing . When the hydrogen concentration is less than 1% by volume, it is difficult to reduce the oxide on the steel surface, and when it exceeds 10% by volume, the manufacturing cost increases.
[68]
As the dew point temperature in the atmosphere during the annealing is different, not only the ratio of components constituting the oxide film formed on the surface of the base iron is different, but also the internal oxidation rate is different, so the dew point temperature is -60 to -10 It is preferable to manage at ℃. If the dew point temperature is less than -60°C, it is not preferable because it may incur excessive cost in managing the purity of the raw material gas. On the other hand, when the dew point temperature exceeds -10°C, the reduction of contaminants on the surface of the base iron may not be performed well, and oxide films such as B and Mn, which are trace elements or impurities contained in steel, are formed to improve plating wettability. There is a risk of hindering.
[69]
[70]
A zinc alloy-plated steel is manufactured through a plating process of immersing and withdrawing the base iron prepared as described above in a plating bath. The plating bath is in weight %, Al: 0.5-20.0%, Mg: 0.5-3.5%, the rest contains Fe and inevitable impurities. Each of the above components is not different from the contents described in the above-described zinc alloy plating layer.
[71]
A suppression layer of Fe and Al is formed on the surface of the base iron immersed in the plating bath, and a plating layer similar to the components of the plating bath is formed on the suppression layer, so that the steel sheet is extracted from the plating bath. At this time, the temperature of the plating bath is preferably 430 ~ 500 ℃. When the plating bath temperature is less than 430° C., even if the base iron is immersed in the plating bath, the surface oxide decomposition of the base iron is not smoothly performed, which is disadvantageous to the formation of the suppression layer. On the other hand, if the temperature of the plating bath exceeds 500°C, it is not preferable because dross and Mg oxidation occur remarkably on the surface of the plating bath.
[72]
[73]
In the plating process, a method of individually immersing parts in a plating bath and a continuous hot dip plating method of forming a plating layer by continuously passing a steel material (especially a steel sheet) through a plating bath may be used. In the case of the continuous hot-dip plating, the plate speed of the steel is preferably 60 to 200 MPM (passing distance per minute, meter per min.). If the plate speed is less than 60 MPM, product productivity is lowered, and if it exceeds 200 MPM, the suppression layer and the plating layer may be uneven.
[74]
[75]
The zinc alloy plated steel material drawn into the plating bath is cooled by adjusting the thickness of the plating layer by a wiping nozzle called an air knife above the plating bath. The wiping nozzle adjusts the thickness of the plating layer by spraying air or an inert gas. The temperature of the plating layer and the steel material when passing through the wiping nozzle, and the bone grain of the wiping nozzle affect the formation of the structure of the plating layer.
[76]
4 is a schematic diagram schematically showing a plated steel material and a wiping nozzle. 4, the present invention relates to the gas injection pressure (P) in the wiping nozzle, the distance between the wiping nozzle and the steel plate (D), the slot thickness of the wiping nozzle (t), and the plate speed of the steel material ( S) and the plating bath temperature (T) is preferably a working factor (working index) calculated by the following relationship 3 satisfies the range of 0.5 to 40.
[77]
[Relationship 2]
[78]

[79]
However, P: Wiping gas pressure (KPa), D: Wiping nozzle and plating steel distance (mm), t: Wiping nozzle slot thickness (mm), S: plate speed (MPM), T: plating bath temperature ( ℃)
[80]
[81]
The work factor is a shape factor of the base iron before plating, and is suitable for forming a plating structure that is preferable when the plating layer is formed in a state where the surface roughness (Ra) is 0.2 to 1.0 μm and the steepness is 0.2 to 1.2. That is, it is possible to make the lamellar structure in the plating layer fine, and at the same time facilitate the generation of a ternary eutectic alloy directly on the inhibition layer at the interface between the plated iron and the base iron. When the working index is less than 0.5, the Zn phase fraction of the plating surface layer decreases, so that the plating surface is easily discolored, and the lamellar structure is coarse, so that plating cracks are likely to occur during processing. On the other hand, when the work factor exceeds 40, defects such as flow patterns tend to occur on the surface of the plating layer. Therefore, it is preferable that the working index defined by the relational expression 2 is 0.5 to 40.
[82]
[83]
After the wiping process, the plated steel is cooled, and the cooling preferably satisfies the following relationship.
[84]
[Relationship 1]
[85]
0.7Vc ≤ Vc' ≤ 1.5Vc
[86]
However, Vc is the average cooling rate immediately after wiping until the solidification of the plating layer is completed, and Vc' is the average cooling rate immediately after wiping until the solidification of the plating layer begins.
[87]
As a factor affecting the structure and growth of the plating layer, in order to obtain a desirable structure, the solidification rate after adjusting the plating layer thickness in the liquid state relative to the average cooling rate (Vc) at the point where solidification is completed after the plating layer thickness is adjusted in the liquid state. The average cooling rate (Vc') ratio (Vc'/Vc) at the start point is preferably 0.7 to 1.5.
[88]
Mode for carrying out the invention
[89]
Hereinafter, embodiments of the present invention will be described in detail. The following examples are only for understanding the present invention, and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by matters described in the claims and matters reasonably inferred therefrom.
[90]
[91]
(Example)
[92]
As a base iron, a cold-rolled steel sheet with a thickness of 0.8 mm and a base steel sheet for automobile outer plates containing 0.03%C-0.2%si-0.15%Mn-0.01%P-0.01%S was prepared, and at this time, the surface roughness (Ra) of the base steel sheet And the steepness are as shown in Table 1. The cold rolled steel coil was continuously immersed in a Zn-Al-Mg alloy plating bath and withdrawn, followed by a wiping process and cooling to prepare a zinc alloy plated steel sheet. Specific conditions are as shown in Table 1.
[93]
The plating layer component of the prepared zinc alloy plated steel sheet and the spraying pressure of the wiping nozzle (P), the distance between the wiping nozzle and the steel sheet (D), the thickness of the slot of the wiping nozzle (t), the plate speed of the steel material ( S) and the plating bath temperature (T) under the conditions of Table 1 below, the Working Index of the relational formula 2 was calculated and shown together in Table 1.
[94]
[95]
The area fraction of the Zn phase observed on the surface of the zinc alloy-plated steel sheet prepared as described above, the widthwise spacing of the lamella structure of the Zn phase and the MgZn 2 phase present up to 70% of the thickness of the plating layer on the surface, and the Zn contained within 2㎛ on the suppression layer The area fraction of the ternary alloy layer of /MgZn 2 /Al was measured and shown in Table 2.
[96]
In addition, in order to confirm the characteristics of each zinc alloy plated steel sheet, the surface characteristics, the corrosion resistance of the end face and the processed portion were evaluated, and the results are shown in Table 3. For the surface characteristics, the flow pattern and the degree of surface discoloration were measured, and the degree of surface discoloration was determined by measuring the color difference of the surface of each specimen, and then leaving the specimen at a temperature of 50°C and humidity (95%) for 24 hours, and then again, the color difference of the specimen. By measuring the value (dE) the brightness value was reduced. Corrosion resistance of the cross-sectional and processed portions was subjected to a cyclic corrosion test specified in ISO TC 156 for each sample. The number of repeated corrosion tests (number of cycles) in which red rust occurs on the cut surface of the specimen and the number of repeated corrosion tests in which red rust occurs in the bent area were recorded by performing a corrosion test after bending the specimen at 180°.
[97]
[98]
[Table 1]
division Plating layer component (% by weight) Steel plate Ra(㎛) Steel plate steepness Mail Order Speed ​​(MPM) Plating bath temperature (℃) Air knife pressure (Kpa) Air knife steel plate distance (㎜) Nozzle slot thickness (mm) Work factor value Average cooling rate (Vc'/Vc)
Mg Al
Invention Example 1 1.2 One 0.4 0.2 170 455 35 15 2 1.5 0.7
Invention Example 2 1.6 2.5 0.3 0.7 120 455 65 10 1.5 4.5 1.1
Invention Example 3 1.5 1.5 0.5 0.8 80 430 75 7 2 8.0 1.3
Invention Example 4 3 2.5 0.8 1.0 65 470 70 5 2.5 37.7 1.0
Invention Example 5 3 6 0.6 1.2 65 425 65 12 1.5 3.1 1.2
Inventive Example 6 3 20 0.3 0.4 80 490 55 12 2 10.3 1.5
Comparative Example 1 1.6 1.6 0.4 1.3 55 470 90 4 1.5 43.0 0.8
Comparative Example 2 1.3 1.6 1.3 1.5 180 450 20 20 0.8 0.2 0.5
Comparative Example 3 3 3 0.8 1.3 160 410 40 17 1.5 0.2 0.4
Comparative Example 4 3 6 1.1 1.4 75 460 90 6 3 36.0 1.8
[99]
[Table 2]
division No flow pattern defects (○,×) Plating layer structure Characteristic evaluation
Surface Zn phase area fraction (%) Zn phase and MgZn 2 phase spacing in the width direction (㎛) Area fraction of the ternary alloy phase layer of Zn/MgZn 2 /Al (%) Color difference (dE) Red rust occurrence time in cross section (number of cycles) Red rust occurrence time in processing part (number of cycles)
Invention Example 1 × 75 0.5 65 3 55 35
Invention Example 2 × 56 0.7 30 3 60 35
Invention Example 3 × 15 1.4 45 2 65 45
Invention Example 4 × 30 1.0 55 2 50 40
Invention Example 5 × 45 0.8 35 2 65 35
Inventive Example 6 × 60 0.4 38 2 50 45
Comparative Example 1 ○ 13 1.8 25 5 45 20
Comparative Example 2 × 7 1.7 30 6 35 25
Comparative Example 3 × 10 2.0 15 5 45 25
Comparative Example 4 ○ 12 2.2 5 5 30 25
[100]
[101]
Meanwhile, FIG. 1 is a photograph illustrating a cross section of the plating layer of Inventive Example 3. As shown in Figure 1, there is a plating layer on the holding steel sheet 11, the plating layer has a single Zn phase 12 and a lamellar structure 13, and the lamellar structure 13 is formed finely and cracks during processing. It can be seen that the occurrence can be reduced. 3 is an observation of the interface between the holding steel sheet 11 and the Zn single phase 12 in FIG. 1, and it can be seen that the suppression layer 14 and the ternary alloy phase of Zn/MgZn 2 /Al are formed. Specifically, it can be seen that the MgZn 2 phase (15), the Al phase (16), and the Zn phase (17) were formed. On the other hand, FIG. 2 is a photograph of a cross section of the plating layer of Comparative Example 2, and it can be seen that the lamellar structure 23 is coarse. Therefore, it can be seen that cracks can be easily generated during processing.
[102]
[103]
From the results of Table 2 and FIGS. 1 to 3, in the example of the invention that satisfies the conditions of the present invention, excellent surface properties were secured, and excellent corrosion resistance was also secured in the end face and the processed portion.
Claims
[Claim 1]
So Ji-cheol; A zinc alloy plating layer formed on the base iron; And a suppression layer formed between the base iron and the zinc alloy plating layer, wherein the Zn phase on the surface of the zinc alloy plating layer includes 15 to 90% by area fraction, and Zn/MgZn formed on the suppression layer to a thickness of 2 μm or less. It includes a ternary alloy phase layer of 2 /Al, and the ternary alloy phase layer covers the surface of the suppression layer in an area ratio of 30 to 90%, and has excellent surface quality and corrosion resistance.
[Claim 2]
The method according to claim 1, wherein the zinc alloy plating layer is a Zn and MgZn 2 comprises a lamellar structure on, and the Zn phase and MgZn 2 the average thickness is not more than each of the width direction on the surface quality and the excellent corrosion resistance 1.5㎛ Oh alloy coated steel.
[Claim 3]
The zinc alloy plated steel according to claim 1, wherein the grain size of the Fe-Al-based intermetallic compound of the suppression layer is 300 nm or less, and has excellent surface quality and corrosion resistance.
[Claim 4]
The zinc alloy plated steel according to claim 1, wherein the zinc alloy plated layer is a weight%, Mg: 0.5 to 3.5%, Al: 0.5 to 20.0%, and the remainder comprises Zn and inevitable impurities.
[Claim 5]
Preparing a base material; Plating the base iron by immersing it in a zinc alloy plating bath containing Mg and Al; Wiping and cooling the plated base iron, wherein the cooling is a method of manufacturing a zinc alloy plated steel material having excellent surface quality and corrosion resistance satisfying the following relational formula 1. [Relational Equation 1] 0.7Vc ≤ Vc' ≤ 1.5Vc However, Vc is the average cooling rate right after wiping until the solidification of the plating layer is completed, and Vc' is the average cooling rate until the start of solidification of the plating layer immediately after wiping.
[Claim 6]
The method according to claim 5, wherein the preparing of the base iron is to prepare a hot-rolled steel material having a grain size of 1 to 100 μm in the surface layer, and cold-rolling the hot-rolled steel material to have a surface roughness of 0.2 to 1.0 μm and a steepness of 0.2 to 1.2 μm. A method of manufacturing a zinc alloy plated steel material having excellent surface quality and corrosion resistance, comprising manufacturing a cold rolled steel material having a.
[Claim 7]
The method according to claim 5, wherein the plating bath composition is in wt%, Mg: 0.5 to 3.5%, Al: 0.5 to 20.0%, the remainder is Zn and unavoidable impurities, including excellent surface quality and corrosion resistance. .
[Claim 8]
The method of claim 5, wherein in the plating and wiping process, the working index of the following relational formula 2 satisfies 0.5 to 40, and has excellent surface quality and corrosion resistance. [Relationship 2] However, P: Wiping knife pressure (KPa), D: Wiping knife and plated steel distance (mm), t: Wiping slot thickness (mm), S: Plate speed (MPM), T: Plating It is bath temperature (℃)
[Claim 9]
The method according to claim 5, wherein the plating bath temperature is 430 to 500°C, which is excellent in surface quality and corrosion resistance.
[Claim 10]
The method of claim 5, wherein the plate speed during plating is 60 to 200 MPM (meter per min.), which is excellent in surface quality and corrosion resistance.