KR20190076129A - Hot dip aluminium alloy plated steel sheet having excellent corrosion resistance and weldability, method for manufacturing the same - Google Patents

Abstract

The present invention relates to a fused aluminum alloy plated steel sheet having excellent corrosion resistance and weldability and a manufacturing method thereof. According to an embodiment of the present invention, the plated steel sheet comprises a fused aluminum alloy plated film formed on the surface of the sheet. The plated film includes an interface alloy layer existing on an interface with the steel sheet; and a plated upper layer existing on the interface alloy layer. Among phases existing on positions within a range of 1μm in a direction from the border between the interface alloy layer and the steel sheet to the interface allow layer, the ratio of phases having an Fe-Al atom ratio of 1 : 2.8-1 : 3.3 is no less than 70% based on area.

Description

TECHNICAL FIELD [0001] The present invention relates to a hot-dip aluminum alloy plated steel sheet having excellent corrosion resistance and weldability, and a method of manufacturing the same.

The present invention relates to a molten aluminum alloy plated steel sheet excellent in corrosion resistance and weldability and a method for producing the same.

The molten Al-Zn-based coated steel sheet exhibits excellent corrosion resistance compared to other hot-dip galvanized steel sheets because both the sacrificial manner of Zn and the high corrosion resistance of Al are compatible.

Patent Document 1 discloses an alloy plating comprising 25 to 75% by weight of Al, 0.1 to 10% by weight of Mg, 1 to 7.5% by weight of Si, 0.05 to 5% by weight of Cr and the balance of Zn and unavoidable impurities Thereby improving the corrosion resistance.

However, the above-mentioned plating component has problems of generation of dross in the plating bath and deterioration of material when applied to automotive grade steel due to increase of melting point of plating bath due to addition of high melting point metal such as Cr, There is a problem that liquid metal embrittlement occurs during welding due to formation of phase.

In addition, there is a possibility that the adhesion between the base steel sheet and the plating layer is insufficient depending on the plating bath, resulting in detachment of the plating layer and poor plating adhesion.

Korean Patent Publication No. 10-2011-0088573

One of the objects of the present invention is to provide a molten aluminum alloy plated steel sheet excellent in weldability and corrosion resistance.

Another object of the present invention is to provide a molten aluminum alloy plated steel sheet excellent in plating adhesion.

The object of the present invention is not limited to the above-mentioned matters. Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

A plated steel sheet according to one aspect of the present invention comprises a molten aluminum alloy plated coating formed on a surface of a steel sheet, the plated coating comprising an interfacial alloy layer present at an interface with a steel sheet and a plated upper layer present on the interfacial alloy layer , And the proportion of the phase having the atomic ratio of Fe and Al in the range of 1: 2.8 to 1: 3.3 in the phase existing within 1 占 퐉 in the direction of the interface alloy layer from the interface between the interface alloy layer and the base steel sheet is It may be a molten aluminum alloy plated steel sheet excellent in corrosion resistance and weldability of 70% or more.

According to another aspect of the present invention, there is provided a hot-dip galvanized steel sheet comprising a hot-rolled aluminum alloy plated coating formed on a surface of a steel sheet, the plated coating comprising an interfacial alloy layer present at an interface with a steel sheet and a plated upper layer present on the interfacial alloy layer , A molten aluminum-plated steel sheet excellent in corrosion resistance and weldability can be provided, wherein the ratio of phases having an atomic ratio of Fe to Al in the interface alloy layer of 1: 2.2 to 1: 2.7 is 10% or less on an area basis.

According to another aspect of the present invention, there is provided a method of manufacturing a steel plate, which comprises a molten aluminum alloy plating film formed on a surface of a steel sheet, the plating film including an interfacial alloy layer existing at an interface with a steel sheet and a plating upper layer present on the interfacial alloy layer Wherein the interfacial alloy layer has a single-layer structure, and when a component in the thickness direction central portion of the interfacial alloy layer is analyzed, it is preferable that the atomic ratio of Fe and Al is 1: 2.8 to 1: 3.3, A plated steel sheet may be provided.

According to another aspect of the present invention, there is provided a method of manufacturing a steel sheet, Immersing the prepared base steel sheet in a molten aluminum alloy plating bath to perform plating; And cooling after the plating, wherein the temperature of the plating bath is 30 DEG C or lower relative to the melting point of the plating bath, and the surface temperature of the base steel sheet discharged from the plating bath is lower than the plating bath melting point temperature within 2 seconds And a method of manufacturing a molten aluminum alloy plated steel sheet excellent in weldability.

As one of various effects of the present invention, the molten aluminum alloy plated steel sheet according to an embodiment of the present invention is advantageous in that the plated steel material has excellent weldability and corrosion resistance.

1 is a photograph of a cross section of a plated film of Comparative Example 1. Fig.
Fig. 2 is a photograph of a plating film section of Inventive Example 2 observed. Fig.
Fig. 3 is a photograph of a cross section after welding of the inventive example 4; Fig.
4 is a photograph of a cross-section after welding of Comparative Example 7. Fig.

Hereinafter, the present invention will be described in detail. First, a molten aluminum alloy plated steel sheet excellent in corrosion resistance and weldability which is one aspect of the present invention will be described in detail.

The molten aluminum alloy plated steel sheet as one aspect of the present invention includes a base steel sheet and a molten aluminum alloy plated coating (hereinafter referred to as a plated coating). The plated coating may be formed on one side or both sides of the base steel sheet.

The plating film is composed of an interfacial alloy layer present at the interface with the steel sheet and a plating upper layer present on the interfacial alloy layer. Generally, in the interface alloy layer, Fe ₂ Al ₅ phase having a high Fe content is formed in a layer shape at a position close to the base steel sheet. In one embodiment of the present invention, an FeAl ₃ phase is formed at a position close to the base steel sheet in the interface alloy layer.

FIG. 1 shows a simulation of an interfacial alloy layer of a conventional aluminum alloy-plated steel sheet. The interfacial alloy layer of Comparative Example 1, which will be described later, was observed with a scanning electron microscope (SEM). On the other hand, FIG. 2 is a scanning electron microscope (SEM) photograph of the interfacial alloy layer of the aluminum alloy plated steel sheet of Inventive Example 2 in the following Examples.

In the case of the interfacial alloy layer of the conventional aluminum alloy plated steel sheet shown in Fig. 1, it can be seen that the interfacial alloy layer is composed of multiple layers. The lower interfacial alloy layer is composed of Fe ₂ Al ₅ , which is a hard Fe-Al alloy phase, and the hard Fe-Al alloy phase is a liquid metal embrittlement , LME) or induce peeling of the plating layer.

However, in the case of the aluminum alloy-plated steel sheet according to the embodiment of the present invention shown in FIG. 2, it can be seen that the interfacial alloy layer has a single-layer structure, and the single-layer interfacial alloy layer is composed mainly of FeAl ₃ . Therefore, since hard Fe-Al alloy phase such as Fe ₂ Al ₅ does not substantially exist at a position close to the base steel sheet among the interface alloy layers, the generation of Liquid Metal Embrittlement (LME) .

Being in the position close to hold the steel sheet of the surface alloy layer FeAl ₃ image is formed in the first implementation example of the invention on the in-phase FeAl ₃ present in position within the alloy layer 1㎛ direction from the boundary of the surface alloy layer and the steel sheet possessing Means that the ratio is 70% or more based on the area basis.

At this time, the interfacial alloy layer may have a single-layer structure, and in some cases, the interfacial alloy layer may have two or more layers, but an FeAl ₃ phase is formed at a position close to the base steel sheet in the interfacial alloy layer. When the interfacial alloy layer has a structure of two or more layers, the Al content in all of the layers formed may be higher than the Al content of the FeAl ₃ phase.

Referred to as FeAl ₃ phase in the present invention, Fe and Al in an atomic ratio (based on weight of the Fe content / Fe atomic weight of: atomic weight of Al content / Al in weight) is 1: 2.8 to 1: phase having a ratio of between 3.3 . Also referred to as FeAl ₃ phase in the present invention is to define the ratio between Fe and Al, should be noted that the additional components derived etc. plating bath and carry the steel sheet it is not preclude contained on the FeAl ₃ . Non-limiting examples of the components that can be additionally contained in addition to the FeAl ₃ phase include Si and Mn.

According to the second embodiment of the present invention, the ratio of the content of the Fe ₂ Al ₅ phase in the interface alloy layer is limited to 10% or less on the area basis, preferably to 5% or less.

In the present invention, the term Fe ₂ Al ₅ phase means an Fe / Al atom ratio of 1: 2.2 to 1: 2.7.

At this time, the interfacial alloy layer may have a single-layer structure, and in some cases, the interfacial alloy layer may have two or more layers, but an FeAl ₃ phase is formed at a position close to the base steel sheet in the interfacial alloy layer. When the interfacial alloy layer has a structure of two or more layers, the Al content in all the layers formed may be higher than the Al content of the FeAl ₃ phase (that is, Al is included so that the atomic ratio of Fe and Al is more than 1: 2.8) .

According to a third embodiment of the present invention, the interface alloy layer may be formed as a substantially single layer. When the component in the thickness direction center portion of the interface alloy layer is analyzed, the Al content may correspond to the FeAl ₃ phase content . According to one embodiment of the present invention, the component in the thickness direction center portion can be obtained by selecting five arbitrary points in the center in the thickness direction, analyzing the points by EDS, and calculating the average value of the components.

The above-described embodiments of the present invention do not exclude different embodiments. It should be noted that although each implementation may overlap in scope, it should be noted that the conditions of all implementations need not be simultaneously satisfied in order to obtain the advantageous effect of the present invention.

According to one example, the interfacial alloy layer having a single-layer structure can be obtained by cutting the molten aluminum alloy plated steel sheet in the thickness direction and then subjecting it to a cross-sectional view at a magnification of 3000 at a scanning electron microscope (FE-SEM, Field Emission Scanning Electron Microscope) It may mean that layer separation in the interfacial alloy layer is not observed.

According to an example, the plated film may include 50 to 90% of Al, 2 to 35% of Zn, 3 to 15% of Si, and 0.1 to 5% of Fe in weight percent. The plating film of the present invention can be obtained by dissolving both the plating upper layer and the interfacial alloy layer in hydrochloric acid, and then analyzing the obtained solution by ICP (Inductively Coupled Plasma) method, but the analysis method is not necessarily limited to this method.

Al is added to form a high melting point alloy phase with iron. If the content is too low, formation of a high-melting-point alloy phase is insufficient, and there is a fear that a weld metal-brittle brittleness may occur. Therefore, the Al content may be 50 wt% or more, 55 wt% or more, or 60 wt% or more. However, if the content is excessive, there is a fear that the corrosion resistance on one side may be deteriorated. Therefore, the Al content may be 90 wt% or less, 80 wt% or less, or 75 wt% or less.

Zn is added for cross-sectional sacrificial durability. If the content is too low, it may be difficult to ensure sufficient cross-sectional corrosion resistance. Therefore, the Zn content is preferably 2% by weight or more, and may be 10% by weight or more and 20% by weight or more. However, if the content is excessive, there is a possibility that a phenomenon of liquefied embrittlement occurs at the time of welding. Therefore, the Zn content may be 35 wt%, 30 wt% or less, or 25 wt% or less.

Si is added to lower the melting point of the plating bath and to improve the plating adhesion. If the content is excessively low, the Al-Fe alloy phase may be excessively formed and the plating adhesion may be deteriorated. Thus, the Si content can be at least 3 wt%, at least 5 wt%, or at least 6 wt%. However, if the content thereof is excessively excessive, the melting point of the plating bath may rise and the formation of the Al-Fe alloy phase may be excessively suppressed. Accordingly, the Si content can be 15 wt% or less, 12 wt% or less, or 10 wt% or less.

Fe reacts with Al to form an Fe-Al intermetallic compound having a high melting point, thereby inhibiting LME. If the content is excessively low, an Al-Fe alloy phase is hardly formed and LME may be generated. Therefore, the Fe content may be 0.1 wt% or more, 1 wt% or more, or 3 wt% or more. However, when the content is excessively excessive, there is a fear that the Al-Fe alloy phase is excessively formed and the plating adhesion is deteriorated. Accordingly, the Si content may be 5 wt% or less, 4.5 wt% or less, or 4 wt% or less.

The remainder of the composition is inevitable impurities. Impurities that are not intended from the raw material or the surrounding environment may be inevitably incorporated in a conventional process for producing a coated steel sheet, so that it can not be excluded. These impurities are not specifically referred to in this specification, as they are known to one of ordinary skill in the art.

On the other hand, addition of an effective component other than the above-mentioned composition is not excluded. For example, the plating film may further contain 0.5 to 5% by weight of Mg.

Mg is added to improve surface and cross-section corrosion resistance. In order to sufficiently obtain such an effect, 0.5% by weight or more, 1% by weight or more, or 2% by weight or more can be added. However, if the content is excessive, liquid metal embrittlement may occur during welding. Therefore, the Mg content may be 5 wt% or less, 4 wt% or less, or 3 wt% or less.

According to one example, the Fe alloy contained in the interfacial alloy layer is preferably 45 wt% or less. As an example of a method of measuring the Fe content of the interfacial alloy layer, it can be measured by point analysis using EDS (Energy Dispersive Spectroscopy). The Fe alloy contained in the interfacial alloy layer has a value exceeding 45% by weight, which means that a hard Fe-Al alloy phase exists in the interfacial alloy layer. As described above, the hard Fe- The alloy phase has a problem of deteriorating the spot weldability and the plating adhesion at the time of processing, and it is preferable to manage such an area so as not to exist.

According to one example, the average content of Si contained in the interfacial alloy layer may be at least two times, preferably at least three times, and more preferably at least seven times the average content of Si contained in the plating upper layer , And most preferably 10 times or more. If the average content of Si contained in the interfacial alloy layer is less than twice the average content of Si contained in the plating upper layer, there is a fear that the alloy phase is excessively formed.

On the other hand, a specific method for measuring the average content of Si contained in the plating upper layer and the interfacial alloy layer is not particularly limited. For example, the average content of Si contained in the plating upper layer is determined by dissolving the upper plating layer with chromic acid, (ICP). The average content of Si contained in the interfacial alloy layer can be measured by dissolving in hydrochloric acid and performing wet analysis (ICP).

For example, the Si content in the upper plating layer is 0.7 to 1 wt%, and the Si content in the interfacial alloy layer is preferably 7 to 12 wt%.

According to one example, the interfacial alloy layer may have an average thickness of 7 占 퐉 or less (excluding 0 占 퐉), and preferably an average thickness of 5 占 퐉 or less (excluding 0 占 퐉). If the average thickness of the interfacial alloy layer is more than 7 mu m, the plating adhesion may be deteriorated during processing. On the other hand, in the present invention, the lower limit of the average thickness of the interfacial alloy layer is not particularly limited, but if the thickness is too thin, the LME resistance may not be suppressed during welding. There is a number.

Next, an example of a method for manufacturing the molten aluminum alloy plated steel sheet of the present invention will be described in detail. The molten aluminum alloy plated steel sheet of the present invention can be produced by various methods, and the production method thereof is not particularly limited. However, as a preferable example, it can be produced by the following method.

Prepare steel plate. The kind of the above-mentioned base steel sheet is not particularly limited and is not limited, and it is sufficient that the base steel sheet is recognized as being applicable in the technical field to which the present invention belongs.

The base steel sheet is immersed in a molten aluminum plating bath (hereinafter referred to as a plating bath) to perform plating. The composition of the plating bath may be, for example, 50 to 90% Al, 2 to 35% Zn, 3 to 15% Si, and 0.1 to 5% Fe.

On the other hand, the temperature of the plating bath affects not only the physical properties of the base steel sheet but also the interfacial alloy layer structure, and more specifically, the plating bath temperature is higher than 30 占 폚 of the plating bath melting point There is a possibility that the material such as retained austenite or martensite may be decomposed to deteriorate the material of the base steel sheet and the surface of the base steel sheet introduced into the plating bath may contain Fe ₂ The formation of Al ₅ is promoted and a multi-layered interfacial alloy layer may be obtained. Therefore, the plating bath temperature may be set to 30 ° C or lower relative to the melting point of the plating bath, and may be controlled to 25 ° C or lower or 20 ° C.

After the plating is performed, the plating layer is cooled. After plating, cooling also greatly affects the structure of the interfacial alloy layer. The cooling is preferably performed such that the surface temperature of the steel sheet discharged from the plating bath is within 5 seconds, within 4 seconds, or within 3 seconds. If the plated layer is not solidified in a short time, a multi-layered interfacial alloy layer may be obtained or the Fe-Al alloy phase may be continuously grown to deteriorate the plating adhesion.

On the other hand, the cooling rate at a temperature not higher than the plating bath melting point temperature is not particularly limited, but can be cooled at a rate of 5 to 20 占 폚 / sec until the upper layer of the plating is completely cooled, for example. If it is less than 5 ° C / sec, the plated layer may be adsorbed to the top roll or the like, and if it is more than 20 ° C / sec, there is a fear that a wave pattern in the form of a waveform may occur on the surface.

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 steel material having a strength of 1 GPa or more) having a thickness of 1.4 mm and containing 0.15% of C, 1.5% of Si, 2.5% of Mn, 0.4% of Cr and the balance of Fe and unavoidable impurities The strength of the steel used in this example was 1.18 GPa) was prepared as the base steel, the base steel was immersed and ultrasonically cleaned to remove foreign substances such as rolling oil present on the surface. Thereafter, the steel sheet was dipped in a plating bath having the composition and temperature as shown in Table 1 below to prepare a hot-dip aluminum alloy plated steel sheet.

Thereafter, each of the produced hot-dip coated aluminum alloy sheets was cooled to a temperature not higher than the melting point of the plating bath, and was wiped with gas to adjust the amount of the deposited coating to 70 g / m 2 per one side. Cooling was carried out. On the other hand, in each example, the time (t _m ) taken for the temperature of the molten aluminum alloy plated steel sheet discharged into the plating bath to become lower than the melting point of the plating bath is shown together in Table 1 below.

Thereafter, each of the produced hot-dip coated aluminum alloy sheets was cut in the plate thickness direction, and a cross-sectional photograph was taken at a magnification of 3,000 by a scanning electron microscope (FE-SEM) to observe whether layer separation in the interfacial alloy layer was observed , And the thickness thereof was measured. The Fe content in the interfacial alloy layer was analyzed by EDS (Energy Dispersive Spectroscopy) to determine the maximum value of the Fe content. The maximum value of the Fe content was measured by the above-described wet analysis (ICP) The average content of Si contained in each of the alloy layers was measured. The results are shown in Table 2 below.

Then, the material of each of the molten aluminum alloy plated steel sheets was measured, and the corrosion resistance, the weldability and the plating adhesion were evaluated. The results are shown in Table 3 below.

The corrosion resistance evaluation was carried out by charging each of the molten aluminum alloy plated steel sheets into a salt water spray tester and spraying 2% by volume of a 5% saline solution (temperature 35 ° C, pH 6.8) per hour, removing the corrosion products after 1200 hours of charging, Was measured. The results were evaluated as "excellent" in the case of 300 mu m or less, as "normal" in the case of 300 to 600 mu m and as "defective"

Weldability was measured using a Cu-Cr electrode with a tip radius of 6 mm and a welding current of 0.5 kA was flowed through the specimen under the conditions of a pressing force of 4.0 kN. After welding, the length of the LME cracks formed on the cross section was measured by a scanning electron microscope (FE-SEM). The results were evaluated as "good" when the LME crack length was 150 μm or less, "normal" when the LME crack length was 150 μm or more and 500 μm or less, and "poor" when the LME crack length was more than 500 μm.

On the other hand, the evaluation of the coating adhesion was made by keeping the automotive structural sealer type D at 175 ° C for 25 minutes and then bending at 90 °. The specimen size was 30 * 75 mm, the sealer application area was 10 * 40 mm, and the thickness was 10 mm or less. When the shear bond strength was higher than 24.5 Mpa, the result was rated as 'excellent', and when the shear bond strength was less than 24.5 Mpa, 'poor'.

No. Plating bath composition (%) Plating bath melting point
(° C) Plating bath temperature
(° C) t _m
(sec) Plating layer composition (%) Remarks Al Zn Si Fe Other Al Zn Si Fe Other One 72 15 10 3 - 530 550 4 71 14 10 5 - Inventory 1 2 84 One 10 5 - 620 650 7 81 2 10 7 - Comparative Example 1 3 58 20 20 2 - 550 590 6 39 38 20 3 - Comparative Example 2 4 64 25 7 4 - 535 550 2 65 24 7 4 - Inventory 2 5 64 25 7 4 - 535 550 6 41 48 7 4 - Comparative Example 3 6 56 30 10 4 - 535 550 4 58 29 10 3 - Inventory 3 7 51 40 2 7 - 570 610 6 51 40 2 7 - Comparative Example 4 8 71 20 5 4 - 540 600 6 71 20 5 4 - Comparative Example 5 9 71 20 5 4 - 540 560 3 73 18 5 4 - Honorable 4 10 71 20 5 4 - 540 560 7 71 20 5 4 - Comparative Example 6 11 69 15 10 4 Mg 2 540 560 4 69 14 10 5 Mg 2 Inventory 5 12 63 15 10 2 Mg 10 530 570 7 61 15 10 4 Mg 10 Comparative Example 7 13 62 25 7 4 Mg 2 530 545 3 65 23 7 3 Mg 2 Inventory 6 14 62 25 7 4 Cr 2 580 620 5 63 24 7 4 Cr 2 Comparative Example 8

No. Interfacial alloy layer Plating upper layer Remarks Total interfacial alloy layer A point within 1 탆 from the boundary with the steel sheet rescue thickness
(탆) Fe content
(weight%) Si content
(weight%) The ratio of Fe ₂ Al ₅ (area%) The ratio of FeAl ₃ (area%) Si content
(weight%) One fault 4 32 11 One 99 One Inventory 1 2 Duplex 5 48 11 20 80 One Comparative Example 1 3 Duplex 2 40 25 12 88 2 Comparative Example 2 4 fault 4 38 9 2 98 0.7 Inventory 2 5 Duplex 5 46 9 17 83 0.7 Comparative Example 3 6 fault 3 36 12 9 91 One Inventory 3 7 Duplex 8 55 4 30 70 0.1 Comparative Example 4 8 Duplex 7 48 7 15 85 0.8 Comparative Example 5 9 fault 5 40 7 3 97 0.8 Honorable 4 10 Duplex 7 50 7 13 87 0.8 Comparative Example 6 11 fault 3 30 10 One 99 One Inventory 5 12 Duplex 2 45 9 14 86 One Comparative Example 7 13 fault 4 31 9 2 98 0.7 Inventory 6 14 Duplex 5 45 8 22 78 0.7 Comparative Example 8

No. Corrosion resistance Weldability Plating adhesion Remarks One Great Great Great Inventory 1 2 Bad Great Bad Comparative Example 1 3 Great Great Bad Comparative Example 2 4 Great Great Great Inventory 2 5 Great Great Bad Comparative Example 3 6 Great Great Great Inventory 3 7 Great Bad Bad Comparative Example 4 8 Great Bad Bad Comparative Example 5 9 Great Great Great Honorable 4 10 Great Great Bad Comparative Example 6 11 Great Great Great Inventory 5 12 Great Bad Bad Comparative Example 7 13 Great Great Great Inventory 6 14 Great Great Bad Comparative Example 8

1 and 2 are photographs of cross sections of Comparative Example 1 and Inventive Example 2 respectively observed by a scanning electron microscope (FE-SEM, Field Emission Scanning Electron Microscope). As shown in Figs. 1 and 2, the comparative example 1 has a multi-layer structure, whereas the inventive example 2 has a single layer structure.

FIG. 3 is a photograph of a cross section observed by a scanning electron microscope (FE-SEM) after welding of the inventive example 4, FIG. 4 is a photograph of the cross section after welding of the comparative example 7 by a scanning electron microscope (FE-SEM) And the cross section is observed. 3 and 4, weldability is effectively improved in the inventive example satisfying all the conditions proposed in the present invention, but LME is generated in the comparative example.

As can be seen from the results of Table 3, all of the inventions satisfying the conditions of the present invention were able to secure excellent corrosion resistance, weldability, and adhesion to the plating, but it is not true in the comparative example outside the scope of the present invention.

Claims (16)

And a molten aluminum alloy plating film formed on the surface of the base steel sheet,
Wherein the plated coating comprises an interfacial alloy layer present at the interface with the steel sheet and a plated upper layer present on the interfacial alloy layer,
The ratio of the phase having the atomic ratio of Fe: Al of 1: 2.8 to 1: 3.3 in the phase existing within 1 占 퐉 in the direction of the interface alloy layer from the interface between the interface alloy layer and the base steel sheet is 70% Aluminum alloy coated steel sheet excellent in corrosion resistance and weldability.
And a molten aluminum alloy plating film formed on the surface of the base steel sheet,
Wherein the plated coating comprises an interfacial alloy layer present at the interface with the steel sheet and a plated upper layer present on the interfacial alloy layer,
A molten aluminum-plated steel sheet excellent in corrosion resistance and weldability, wherein the proportion of phases having an atomic ratio of Fe to Al in the interfacial alloy layer of 1: 2.2 to 1: 2.7 is 10% or less on an area basis.
The hot-dip coated aluminum alloy plate according to claim 1 or 2, wherein the interfacial alloy layer has a single-layer structure and is excellent in corrosion resistance and weldability.
The method of claim 3,
When the hot-dip coated aluminum alloy sheet was cut in the thickness direction and its sectional photograph was taken at a magnification of 3,000 by a scanning electron microscope (FE-SEM, Field Emission Scanning Electron Microscope), layer separation in the interfacial alloy layer was not observed Aluminum alloy coated steel sheet with excellent corrosion resistance and weldability.
The alloy according to claim 1 or 2, wherein the interfacial alloy layer is composed of two or more layers, and in all of the layers formed, a molten aluminum alloy containing Al in an atomic ratio of more than 1: Plated steel plate.
And a molten aluminum alloy plating film formed on the surface of the base steel sheet,
Wherein the plated coating comprises an interfacial alloy layer present at the interface with the steel sheet and a plated upper layer present on the interfacial alloy layer,
Wherein the interfacial alloy layer has a single layer structure and the composition of the central portion in the thickness direction of the interfacial alloy layer is analyzed to find that a molten aluminum alloy plating having a ratio of Fe to Al of 1: 2.8 to 1: 3.3 and excellent corrosion resistance and weldability Steel plate.
The method according to claim 6,
When the hot-dip coated aluminum alloy sheet was cut in the thickness direction and its sectional photograph was taken at a magnification of 3,000 by a scanning electron microscope (FE-SEM, Field Emission Scanning Electron Microscope), layer separation in the interfacial alloy layer was not observed Aluminum alloy coated steel sheet with excellent corrosion resistance and weldability.
7. The method according to any one of claims 1, 2, and 6,
Wherein the plating film contains, by weight%, Al: 50 to 90%, Zn: 2 to 35%, Si: 3 to 15%, and Fe: 0.1 to 5%.
9. The method of claim 8,
Wherein the plating film further comprises 0.5-5% of Mg, and has excellent corrosion resistance and weldability.
7. The method according to any one of claims 1, 2, and 6,
Wherein the interfacial alloy layer has an Fe content of 45 wt% or less and is excellent in corrosion resistance and weldability.
7. The method according to any one of claims 1, 2, and 6,
Wherein the Si content of the interfacial alloy layer is at least twice the Si content of the upper layer of the plating, and is excellent in corrosion resistance and weldability.
7. The method according to any one of claims 1, 2, and 6,
Wherein the average thickness of the interfacial alloy layer is 7 占 퐉 or less (excluding 0), which is excellent in corrosion resistance and weldability.
Preparing a base steel sheet;
Immersing the prepared base steel sheet in a molten aluminum alloy plating bath to perform plating; And
And cooling after the plating,
Wherein the temperature of the plating bath is 30 ° C or lower relative to the melting point of the plating bath and the surface temperature of the base steel sheet discharged from the plating bath is lowered to the plating bath melting point temperature or lower within 5 seconds to manufacture a molten aluminum alloy plated steel sheet excellent in corrosion resistance and weldability Way.
14. The method of claim 13,
And a cooling rate at a plating bath melting point temperature or lower of 5 to 20 占 폚 / sec.
14. The method of claim 13,
Wherein the plating bath comprises, in terms of% by weight, a molten aluminum alloy plated steel sheet excellent in corrosion resistance and weldability including 50 to 90% of Al, 2 to 35% of Zn, 3 to 15% of Si and 0.1 to 5% Way.
16. The method of claim 15,
Wherein the plating bath further comprises 0.5 to 5% of Mg, and has excellent corrosion resistance and weldability.

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