Specification
Title of invention: Zn-Al-Mg system hot-dip plated steel sheet
Technical field
[0001]
The present invention relates to a Zn-Al-Mg hot-dip plated steel sheet.
This application claims priority based on Japanese Patent Application Nos. 2019-216685 and 2019-216686 filed in Japan on November 29, 2019, the contents of which are incorporated herein.
Background technology
[0002]
Zn-Al-Mg-based hot-dip steel sheets, which have higher corrosion resistance than hot-dip galvanized steel sheets, are widely used in various manufacturing industries such as building materials, home appliances, and automobile fields, and their usage has been increasing in recent years. .
[0003]
By the way, for the purpose of showing letters, patterns, design drawings, etc. on the surface of the hot-dip plated steel sheet, letters, patterns, designs, etc. It may appear on the surface of the hot-dip plating layer.
[0004]
However, when processes such as printing and painting are performed on the hot-dip plating layer, there is a problem that the cost and time for applying characters and designs will increase. Furthermore, when printing or painting characters or designs on the surface of the plating layer, not only does the metallic luster appearance that is highly popular with consumers be lost, but the coating itself deteriorates over time and the adhesion of the coating film deteriorates. Due to the problem of deterioration over time, the durability is poor, and characters and designs may disappear over time. In the case of stamping ink to reveal characters, designs, etc. on the surface of the plated layer, the cost and time can be kept relatively low, but there is a concern that the corrosion resistance of the hot-dip plated layer is lowered by the ink. Furthermore, when the design is created by grinding the hot-dip plating layer, the durability of the design is excellent, but the thickness of the hot-dip plating layer at the grinding point is greatly reduced, which inevitably leads to a decrease in corrosion resistance and plating characteristics. is concerned.
[0005]
As shown in the following patent documents, various technical developments have been made for Zn-Al-Mg hot-dip plated steel sheets. Techniques for improving the durability of letters, designs, etc. on the surface of the plating layer. is not known.
[0006]
Regarding the Zn-Al-Mg hot-dip plated steel sheet, there are conventional technologies that aim to make the satin-like plating appearance seen in the Zn-Al-Mg hot-dip plated steel sheet more beautiful.
For example, Patent Document 1 discloses a Zn-Al-Mg hot dip plated steel sheet having a fine texture and a satin-like appearance with many smooth glossy parts, that is, a large number of white parts per unit area, and a glossy A Zn-Al-Mg hot-dip plated steel sheet having a good satin-like appearance in which the ratio of the area of ​​the part is large is described. In addition, Patent Document 1 describes that the unfavorable pear-skin state is a state in which irregular white portions and circular glossy portions are intermingled and scattered on the surface, presenting a surface appearance. there is
In addition, in Patent Document 2, in the thickness direction cross section of the plating layer, the portion where Al crystals are absent between the interface between the plating layer and the base iron and the plating surface layer is 10% of the width direction length of the cross section. A Zn-Al-Mg-based plated steel sheet with an improved plating appearance is described.
Furthermore, in Patent Document 3, the center line average roughness Ra of the surface of the plated steel sheet is 0.5 to 1.5 μm, and the PPI (1.27 μm or more included per inch (2.54 cm)) number of peaks) is 150 to 300, and Pc (the number of peaks having a size of 0.5 μm or more contained per 1 cm) is Pc≧PPI/2.54+10 and has excellent formability. Have been described.
Furthermore, in Patent Document 4, by refining the ternary eutectic structure of Al/MgZn2/Zn, the glossiness of the coating layer is increased as a whole, and the appearance uniformity is improved. High corrosion resistance hot-dip galvanized steel sheet is described.
However, no technology has been known in the past to improve durability and prevent deterioration in corrosion resistance when letters and the like are displayed on the surface of the plating layer.
prior art documents
patent literature
[0007]
Patent Document 1: Japanese Patent No. 5043234
Patent Document 2: Japanese Patent No. 5141899
Patent Document 3: Japanese Patent No. 3600804
Patent Document 4: International Publication No. 2013/002358
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0008]
The present invention has been made in view of the above circumstances, and provides a hot-dip plated steel sheet that can display letters, designs, etc. on the surface of the plating layer, has excellent durability, and is also excellent in corrosion resistance. The challenge is to
Means to solve problems
[0009]
The gist of the present invention is as follows.
[1] A steel plate and a hot-dip coating layer formed on the surface of the steel plate,
The hot-dip plating layer is
The average composition contains Al: 4% by mass or more and less than 25% by mass, Mg: 0% by mass or more and less than 10% by mass, and the balance contains Zn and impurities,
The metal structure includes [Al phase] and [Al/Zn/MgZn2 ternary eutectic structure],
The hot-dip plating layer includes a first region and a second region,
the first region and the second region satisfy either (a) or (b) below,
A Zn-Al-Mg hot-dip plated steel sheet characterized in that the first region or the second region is arranged to have a predetermined shape.
(a) The first region is a region in which the average length of the [Al phase] on the surface of the hot dip plated layer is 200 μm or more, and the second region is the [Al phase] on the surface of the hot dip plated layer ] has an average length of less than 200 μm.
(b) In the first region, the length Le at which the [Al/Zn/MgZn2 ternary eutectic structure] faces the steel plate at the boundary between the steel plate and the hot-dip coating layer is the length of the boundary The second region is a region where the [Al / Zn / MgZn ternary eutectic structure] is the steel plate at the boundary between the steel plate and the hot-dip coating layer. The opposing length Le is a region of 0.3 or less with respect to the length L of the boundary.
[2] When the first region and the second region are the above (b), the X-ray diffraction intensity I (200) of the (200) plane of the [Al phase] on the surface of the hot dip plated layer and (111) plane X-ray diffraction intensity I(111) ratio I(200)/I(111) is 0.8 or more.
[3] So that the first region or the second region has a shape that is a combination of any one of straight line portions, curved portions, figures, numbers, symbols, patterns, or characters, or two or more of these. The Zn-Al-Mg-based hot-dip plated steel sheet according to [1] or [2], which is arranged.
[4] The Zn-Al-Mg hot-dip plated steel sheet according to any one of [1] to [3], wherein the first region or the second region is intentionally formed.
[5] The Zn-Al-Mg-based melt according to any one of [1] to [4], wherein the hot-dip plating layer further contains Si: 0.0001 to 2% by mass in average composition. Galvanized steel sheet.
[6] The hot-dip plated layer further contains one or more of Ni, Ti, Zr, and Sr in an average composition of 0.0001 to 2% by mass in total, [1] to [ 5], the Zn-Al-Mg hot-dip plated steel sheet according to any one of items.
[7] The hot-dip plated layer further has an average composition of any one of Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM, Hf, C or The Zn-Al-Mg hot-dip plated steel sheet according to any one of [1] to [6], containing 0.0001 to 2% by mass of two or more kinds in total.
[8] The Zn-Al-Mg hot-dip plated steel sheet according to any one of [1] to [7], wherein the total adhesion amount of the hot-dip plating layer on both sides of the steel sheet is 30 to 600 g/m 2 .
Effect of the invention
[0010]
According to the present invention, it is possible to provide a hot-dip plated steel sheet that is excellent in durability and corrosion resistance when characters, designs, etc. are displayed on the surface of the hot-dip plated layer.
Brief description of the drawing
[0011]
1 is a diagram illustrating a method for measuring the size of an Al phase of a Zn—Al—Mg hot-dip plated steel sheet that is an example of the present embodiment; FIG.
[Figure 2] No. 1 is a photograph showing observation results of the first region of 1-4 with a scanning electron microscope.
[Figure 3] No. 1 is a photograph showing observation results of the second region of 1-4 with a scanning electron microscope.
4 is a photograph showing an example of the Zn—Al—Mg hot-dip plated steel sheet of Example 1. FIG.
[Fig. 5] No. 2 is a cross-sectional photograph taken by a scanning electron microscope in the first region of 2-1.
[Fig. 6] No. 2 is a cross-sectional photograph taken by a scanning electron microscope in the second region of 2-1.
7 is a photograph showing an example of the surface of the hot-dip plated layer of the Zn--Al--Mg hot-dip plated steel sheet of Example 2, showing a state in which the second region reveals a predetermined pattern. FIG.
MODE FOR CARRYING OUT THE INVENTION
[0012]
Embodiments of the present invention will be described below.
In this specification, a numerical range represented by "-" means a range including the numerical values ​​before and after "-" as lower and upper limits.
[0013]
The Zn-Al-Mg-based hot-dip plated steel sheet of the present embodiment includes a steel plate and a hot-dip plated layer formed on the surface of the steel plate, and the hot-dip plated layer has an average composition of Al: 4% by mass or more and 25% by mass. Mg: 0% by mass or more and less than 10% by mass, the balance containing Zn and impurities, and as the metal structure, [Al phase] and [Al / Zn / MgZn 2 ternary eutectic structure] include. The hot-dip plated layer includes a first region and a second region, the first region and the second region satisfy either one of (a) or (b) below, and the first region or the second region is They are arranged in a predetermined shape.
(a) The first region is a region where the average length of [Al phase] on the surface of the hot dip plated layer is 200 μm or more, and the second region is the average length of [Al phase] on the surface of the hot dip plated layer It is a region of less than 200 μm.
(b) In the first region, the length Le at which the [ternary eutectic structure of Al/Zn/MgZn2] faces the steel sheet at the boundary between the steel sheet and the hot-dip coating layer is 0 with respect to the boundary length L. The second region is the region where the [ternary eutectic structure of Al / Zn / MgZn 2] faces the steel plate at the boundary between the steel plate and the hot-dip coating layer Le is the length of the boundary It is a region of 0.3 or less with respect to L.
[0014]
In the Zn-Al-Mg hot-dip plated steel sheet of the present embodiment, preferably, the first region or the second region is any one of linear portions, curved portions, figures, numbers, symbols, patterns or characters, or any one of these It is arranged so as to have a shape in which two or more of them are combined. The first region or the second region is intentionally formed.
[0015]
Here, [Al phase] is a phase that looks like an island with a clear boundary in the [Al/Zn/MgZn2 ternary eutectic structure] matrix. It corresponds to the "Al" phase" (a solid solution of Al that dissolves Zn and contains a small amount of Mg) at high temperatures in the elemental equilibrium diagram, and is distinguished from Al in the ternary eutectic structure. Hereinafter, in this embodiment, it is described as [Al phase].
[0016]

The material of the steel sheet used as the base of the hot-dip plating layer is not particularly limited. Although the details will be described later, as the steel plate, general steel or the like can be used, and it is also possible to use Al-killed steel or some high-alloy steel. Also, the shape of the steel plate is not particularly limited. The hot-dip plating layer according to the present embodiment is formed by applying the hot-dip plating method, which will be described later, to the steel sheet.
[0017]

(Chemical composition)
Next, the chemical composition of the hot-dip plating layer will be explained.
The average composition of the hot-dip plated layer is Al: 4% by mass or more and less than 25% by mass, Mg: 0% by mass or more and less than 10% by mass, and the balance is Zn and impurities. The hot-dip plated layer preferably contains, in average composition, 4 to 22% by mass of Al, 1 to 10% by mass of Mg, and the balance of Zn and impurities.
The hot-dip plated layer may contain Si: 0.0001 to 2% by mass in average composition. The hot dip plated layer has an average composition of any one of Ni, Ti, Zr, and SrAlternatively, two or more may be contained in a total of 0.0001 to 2% by mass. The hot-dip plated layer has an average composition of one or more of Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM, and Hf, in total, 0 .0001 to 2% by mass.
[0018]
[Al: 4% by mass or more and less than 25% by mass]
The content of Al in the hot-dip plated layer is 4% by mass or more and less than 25% by mass, preferably 4.0% by mass or more and less than 25.0% by mass in terms of average composition. Al is an element necessary for ensuring corrosion resistance. If the content of Al in the hot-dip plating layer is less than 4% by mass, the effect of improving the corrosion resistance is insufficient, and the [Al phase] is not sufficiently formed, which is not preferable for ensuring designability. If the content is 25% by mass or more, [Al phase] is excessively formed, which is not preferable for ensuring designability. From the viewpoint of corrosion resistance, the content of Al in the hot dip plated layer may be 5 to 22% by mass, 5.0 to 22.0% by mass, or 5 to 18% by mass. It may be 5.0 to 18.0% by mass, or 6 to 16% by mass. It may be 6.0 to 16.0% by mass.
[0019]
[Mg: 0% by mass or more and less than 10% by mass]
The content of Mg in the hot-dip plated layer is 0% by mass or more and less than 10% by mass in average composition, and may be 0% by mass or more and less than 10.0% by mass in average composition. It is preferably 1% by mass or more and less than 10% by mass, and preferably 1% by mass or more and less than 10.0% by mass. Mg may be added to improve corrosion resistance. When the content of Mg in the hot-dip plating layer is 1% by mass or more, the effect of improving the corrosion resistance becomes more sufficient, which is preferable. In addition, if the Mg content is 10% by mass or more, the Mg compound crystallizes, which is not preferable for ensuring designability. It is not preferable because From the viewpoint of the balance between corrosion resistance and suppression of dross generation, the content of Mg in the hot-dip plating layer may be 1.5 to 6% by mass, 1.5 to 6.0% by mass, or 2 to 5% by mass. % by mass, or 2.0 to 5.0% by mass.
[0020]
The hot dip plated layer may contain Si in the range of 0.0001 to 2% by mass, preferably 0.0001 to 2.000% by mass. Si is an effective element for improving the adhesion of the hot-dip plating layer.
By containing 0.0001% by mass or more of Si in the hot-dip plating layer, the effect of improving adhesion is exhibited, so it is preferable to contain 0.0001% by mass or more of Si.
On the other hand, even if the Si content exceeds 2% by mass, the effect of improving the plating adhesion is saturated.
From the viewpoint of plating adhesion, the content of Si in the hot-dip plating layer may be 0.0010 to 1% by mass, 0.0010 to 1.000% by mass, or 0.0100 to 0.8% by mass. , or 0.0100 to 0.800% by mass.
[0021]
The hot-dip plated layer may contain one or more of Ni, Ti, Zr, and Sr in an average composition of 0.0001 to 2% by mass, preferably 0.0001 to 2% by mass. You may contain 2.00 mass %. The intermetallic compounds containing these elements act as crystallization nuclei for the [Al phase], making the [ternary eutectic structure of Al/MgZn2/Zn] finer and more uniform, and improving the appearance of the hot-dip coating layer. Improve smoothness. If the content of these elements in the hot-dip plating layer is less than 0.0001% by mass, the effect of making the solidified structure fine and uniform becomes insufficient, which is not preferable. In addition, when the content of these elements in the hot-dip plated layer exceeds 2% by mass, the effect of refining the [Al/MgZn 2/Zn ternary eutectic structure] is saturated, and the surface of the hot-dip plated layer This is not preferable because it increases the roughness and deteriorates the appearance.
In particular, when the above elements are added for the purpose of improving the appearance of the hot-dip plating layer, the content of the above elements is preferably 0.001 to 0.5% by mass, preferably 0.001 to 0.50% by mass, and 0 0.001 to 0.05 mass % is more preferred, and 0.002 to 0.01 mass % is even more preferred.
[0022]
In the hot-dip plating layer, one or more of Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM, and Hf are contained in an average composition of 0.5 in total. 0001 to 2% by mass, preferably 0.0001 to 2.00% by mass. Corrosion resistance can be further improved by including these elements in the hot-dip plated layer.
Note that REM refers to one or more rare earth elements with atomic numbers 57 to 71 in the periodic table.
[0023]
The rest of the chemical composition of the hot-dip plating layer is zinc and impurities. Impurities include those that are unavoidably contained in base metals such as zinc, and those that are contained by dissolving steel in the plating bath. In addition, Fe derived from an alloy layer that is generated at the interface between the plating layer and steel when dissolving the plating is sometimes measured.
[0024]
The average composition of the hot dip plated layer can be measured by the following method. First, after removing the surface coating film with a coating remover that does not corrode the plating (for example, Neoriver SP-751 manufactured by Sansai Kako Co., Ltd.), the hot-dipped plating layer with hydrochloric acid containing an inhibitor (for example, Hibilon manufactured by Sugimura Chemical Industry Co., Ltd.) can be determined by dissolving and subjecting the resulting solution to inductively coupled plasma (ICP) emission spectrometry. The concentration of hydrochloric acid may be, for example, 10% by weight. Moreover, when the surface layer coating film is not provided, the operation for removing the surface layer coating film can be omitted.
[0025]
(Metal structure)
Next, the metal structure of the hot-dip plating layer will be explained. The hot-dip plated layer according to the present embodiment contains [Al phase] and [Al/Zn/MgZn2 ternary eutectic structure] as metal structures.
Specifically, the hot-dip plated layer according to the present embodiment has a form in which [Al phase] is included in the base of [Al/Zn/MgZn2 ternary eutectic structure].
Further, the [Al/Zn/MgZn2 ternary eutectic structure] matrix may contain [MgZn2 phase] or [Zn phase].
Further, when Si is added, [Mg 2 Si phase] may be included in the [Al/Zn/MgZn 2 ternary eutectic structure] matrix.
[0026]
[Al/Zn/MgZn2 ternary eutectic structure]
Here, the [Al/Zn/MgZn2 ternary eutectic structure] is a ternary eutectic structure of the Al phase, the Zn phase, and the intermetallic compound MgZn2 phase, [Al/Zn/MgZn2 The Al phase forming the ternary eutectic structure] is, for example, the "Al" phase at high temperatures in the Al-Zn-Mg ternary equilibrium diagram (Al solid solution that dissolves Zn, and a small amount of including Mg).
This Al″ phase at high temperature usually appears separated into a fine Al phase and a fine Zn phase at room temperature. It is a Zn solid solution in which Al is solid-dissolved, and in some cases, a small amount of Mg is also solid-dissolved in. The MgZn 2 phase in [a ternary eutectic structure of Al/Zn/MgZn 2] is a binary system of Zn—Mg. Zn in the equilibrium diagram: This is an intermetallic compound phase present in the vicinity of about 84% by mass.
As far as the phase diagram is concerned, it is thought that each phase does not dissolve other additive elements, or even if they do, the amount is extremely small. However, since the amount cannot be clearly distinguished by ordinary analysis, the ternary eutectic structure consisting of these three phases is referred to herein as [a ternary eutectic structure of Al/Zn/MgZn2].
[0027]
In the present embodiment, as will be described later, at the boundary between the steel sheet and the hot-dip coating layer, the [ternary eutectic structure of Al/Zn/MgZn2] faces the steel sheet. The second region may have a region where the length L is more than 0.3, and the second region may be a region where the length L of the boundary is 0.3 or less.
[0028]
[Al phase]
[Al phase] is a phase that looks like an island with a clear boundary in the [Al/Zn/MgZn2 ternary eutectic structure] matrix. Corresponds to the "Al" phase" (Al solid solution that dissolves Zn and contains a small amount of Mg) at high temperatures in the phase diagram. The Al″ phase at high temperature differs in the amount of solid solution Zn and Mg depending on the concentration of Al and Mg in the plating bath. It separates into fine Zn phases, and the island-like shape seen at room temperature is considered to be due to the shape of the Al″ phase at high temperatures.
As far as the phase diagram is concerned, it is thought that this phase does not dissolve other additive elements, or that even if they do, the amount is extremely small. However, since it cannot be clearly distinguished by ordinary analysis, the phase derived from the Al″ phase at high temperature and morphologically attributed to the shape of the Al″ phase is referred to as [Al phase] in this specification.
The [Al phase] can be clearly distinguished from the Al phase forming the [Al/Zn/MgZn2 ternary eutectic structure] by microscopic observation.
In the present embodiment, as will be described later, when the first region and the second region satisfy (a) above, the average length of the [Al phase] is 200 μm or more in the first region, and 200 μm or more in the second region. However, it may be less than 200 μm.
[0029]
[Zn phase]
[Zn phase] is a phase that looks like islands with clear boundaries in the [Al/Zn/MgZn2 ternary eutectic structure] matrix. I have been As far as the phase diagram is concerned, it is considered that this phase does not contain other additive elements in solid solution, or even if it does, the amount is extremely small.
The [Zn phase] can be clearly distinguished from the Zn phase forming the [ternary eutectic structure of Al/Zn/MgZn2] by microscopic observation. Although the hot-dip plated layer according to the present embodiment may contain [Zn phase] depending on the manufacturing conditions, almost no influence of the [Zn phase] on the corrosion resistance was observed. Therefore, even if the hot-dip plating layer contains [Zn phase], there is no particular problem.
[0030]
[MgZn 2-phase]
[MgZn 2 phase] is a phase that looks like islands with clear boundaries in the [Al/Zn/MgZn 2 ternary eutectic structure] matrix, and actually contains a small amount of Al as a solid solution. Sometimes. As far as the phase diagram is concerned, it is considered that this phase does not contain other additive elements in solid solution, or even if it does, the amount is extremely small.
The [MgZn 2 phase] and the MgZn 2 phase forming the [Al/Zn/MgZn 2 ternary eutectic structure] can be clearly distinguished by microscopic observation. The hot-dip plated layer according to the present embodiment may not contain [MgZn 2 phase] depending on the manufacturing conditions, but it is included in the hot-dip plated layer under most manufacturing conditions.
[0031]
[Mg 2Si phase]
The [Mg2Si phase] is a phase that looks like an island with clear boundaries in the solidified structure of the plating layer to which Si is added. As far as the phase diagram is concerned, it is considered that Zn, Al and other additive elements are not solid-dissolved in the [Mg 2 Si phase] or, if they are solid-dissolved, the amount is extremely small. [Mg 2 Si phase] can be clearly distinguished from other phases in the hot-dip plated layer by microscopic observation.
[0032]
The hot-dip plated layer of the present embodiment is formed by immersing the steel sheet in a plating bath and then pulling it up, and then solidifying the molten metal adhering to the surface of the steel sheet. At this time, [Al phase] is first formed, and then [ternary eutectic structure of Al/Zn/MgZn2] is formed as the temperature of the molten metal decreases.
Depending on the chemical composition of the hot-dip plating layer (that is, the chemical composition of the plating bath), [Mg 2 Si phase], [MgZn 2 phase] or [ Zn phase] may be formed.
[0033]
(first area and second area)
Next, the first region and the second region of the hot dip plated layer will be described. A first region and a second region exist in the hot-dip plated layer (surface of the hot-dip plated layer) according to the present embodiment. As will be described later, the first area and the second area are distinguishable with the naked eye, under a magnifying glass, or under a microscope.
[0034]
The first area may represent a straight portion, curved portion, etc., and the second area may represent a straight portion, curved portion, etc. When the first area represents a straight line portion, a curved portion, or the like, the first area is arranged to have a predetermined shape, and the other area can be used as the second area. Further, when the second area represents a linear portion, a curved portion, or the like, the second area is arranged to have a predetermined shape, and the other area can be the first area.
The boundary between the first region and the second region can be grasped with the naked eye, under a magnifying glass, or under a microscope.
[0035]
When the first area is arranged to have a predetermined shape, the first area is preferably formed to a size that allows the presence of the first area to be determined with the naked eye, under a magnifying glass, or under a microscope. The second region in this case is a region that occupies a portion other than the first region in the hot-dip plated layer (surface of the hot-dip plated layer), and may occupy most of the hot-dip plated layer. Also, the first area may be arranged within the second area. Specifically, in the second region, the first region has a shape that is a combination of any one of linear portions, curved portions, figures, numerals, symbols, patterns, and characters, or two or more of these. may be arranged so as to be By adjusting the shape of the first region, the surface of the hot-dip plating layer can be formed into any one of linear portions, curved portions, figures, numerals, symbols, patterns and letters, or a combination of two or more of these. appears. This shape is an artificially formed shape, not a naturally formed one.
[0036]
On the other hand, when the second region is arranged to have a predetermined shape, the second region is formed to have a size that allows the presence of the second region to be determined with the naked eye, under a magnifying glass, or under a microscope. good. In this case, the first region is a region that occupies a portion other than the second region in the hot-dip plated layer (surface of the hot-dip plated layer), and may occupy most of the hot-dip plated layer. Also, the second area may be arranged within the first area. Specifically, the second region has a shape in which any one of linear portions, curved portions, figures, numerals, symbols, patterns, and characters, or a combination of two or more of these, is used in the first region. may be arranged so as to be By adjusting the shape of the second region, the surface of the hot-dip plating layer can be formed into any one of linear portions, curved portions, figures, numerals, symbols, patterns and letters, or a combination of two or more of these. appears. This shape is an artificially formed shape, not a naturally formed one.
[0037]
The first area and the second area may be identifiable not only with the naked eye but also under a magnifying glass or a microscope. Specifically, the shape of the linear portion or the like formed by the first region or the second region should be identifiable in a field of view of 50 times or less. With a field of view of 50 times or less, the predetermined shape formed by the first region or the second region can be identified by the difference in surface state.
The first region or the second region is preferably 20-fold or less, more preferably 10-fold or less, and more preferably 5-fold or less.
[0038]
The first and second areas satisfy either (a) or (b) below.
(a) The first region is a region where the average length of [Al phase] on the surface of the hot dip plated layer is 200 μm or more, and the second region is the average length of [Al phase] on the surface of the hot dip plated layer It is a region of less than 200 μm.
(b) In the first region, the length Le at which the [ternary eutectic structure of Al/Zn/MgZn2] faces the steel sheet at the boundary between the steel sheet and the hot-dip coating layer is 0 with respect to the boundary length L. The second region is the region where the [ternary eutectic structure of Al / Zn / MgZn 2] faces the steel plate at the boundary between the steel plate and the hot-dip coating layer Le is the length of the boundary It is a region of 0.3 or less with respect to L.
Below, the above cases (a) and (b) will be described in order.
[0039]
(When the first region and the second region satisfy the above (a))
In the first region where the above (a) is satisfied, metallic luster due to the Al phase having a long average length is observed. Therefore, compared to the second area, the gloss can be recognized linearly. On the other hand, in the second region, due to the Al phase having a short average length, the metallic luster is perceived as dots compared to the first region. Thus, the first area and the second area are distinguishable to the naked eye, under a magnifying glass, or under a microscope.
[0040]
At least [Al phase] and [Al/Zn/MgZn2 ternary eutectic structure] are present in the hot-dip plated layer. The hot-dip plated layer has a form in which the [Al phase] is included in the [ternary eutectic structure of Al/Zn/MgZn2]. The [Al phase] precipitates at a relatively early stage during the solidification of the hot-dip plated layer, and the [Al phase] at that time takes the form of a dendrite.
[0041]
When the above (a) is satisfied, the average length of the [Al phase] present in the first region is 200 μm or more.
When the average length of [Al phase] is 200 μm or more, relatively large dendrites of [Al phase] are exposed on the surface of the hot-dip plating layer, and the surrounding [Al/Zn/MgZn ternary The [Al phase], which has a metallic luster, is longer than the eutectic structure], etc., and the irregularities are clearly defined, so that the whole can be visually recognized as a linear shape.
[0042]
On the other hand, the average length of the [Al phase] present in the second region is less than 200 μm. When the average length of [Al phase] is less than 200 μm, relatively small dendrites of [Al phase] are exposed on the surface of the hot-dip plating layer, and the surrounding [Al/Zn/MgZn ternary The [Al phase], which has a metallic luster, is shorter than that of the eutectic structure], and the unevenness becomes unclear, so that the whole can be visually recognized as dots. The second region is preferably a region in which the [Al phase] has an average length of 180 μm or less, more preferably a region in which the [Al phase] has an average length of less than 150 μm. The larger the difference between the average length of [Al phase] in the first region and the average length of [Al phase] in the second region, the easier it is to distinguish between the first region and the second region, which is preferable.
[0043]
It is presumed that the first region is formed when the [Al phase] is generated at a relatively low number density in the early stage of solidification of the hot-dip plated layer and the [Al phase] itself is coarsened. In addition, the second region is formed by the [Al phase] being generated at a relatively high number density in the early stage of solidification of the hot-dip plated layer, and the [Al phase] itself remaining fine without being coarsened. presumed to be
[0044]
In order to control the size of the [Al phase], the cooling rate of the molten metal should be controlled during solidification of the hot-dip plating layer. Specifically, when the [Al phase] is coarsened, the cooling rate during solidification is decreased, and when the [Al phase] is refined, the cooling rate during solidification is increased. When the steel sheet is immersed in the hot dipping bath and then pulled out, the cooling rate of the molten metal on the surface of the steel sheet is partially increased or decreased so that straight portions, curved portions, figures, numbers, symbols, patterns and Any one type of character or a shape obtained by combining two or more of these types can be intentionally or artificially created by the manufacturing method described below.
[0045]
The average length of [Al phase] is measured by the following method. First, in each of the first region and the second region on the surface of the hot-dip plated layer, arbitrary three fields of view are photographed as backscattered electron images with a scanning electron microscope. The size of each area is a rectangular area of ​​500 μm×360 μm. A dendritic Al phase is confirmed in the photograph taken. The dendritic Al phase generally has a shape having a main shaft portion and secondary arm portions extending from the main shaft portion, as shown in FIG. The length A of the Al phase in the photograph is measured in the longitudinal direction. The lengths A of all the Al phases are obtained in the three fields of view, and the average value thereof is taken as the average length of the Al phases in the first region or the second region. Although the dendritic Al phase often grows radially from the solidification nucleus, it is not always arranged on the same plane, and when observed from the surface, only a part of it, for example, the tip of the secondary arm, is observed. or only the main shaft may be observed. Such an Al phase is excluded from measurement targets. On the other hand, if another phase is covered between the main shaft and the secondary arm and it can be observed as if they are not connected, it will be considered.
[0046]
(When the first region and the second region satisfy the above (b))
The first region when satisfying the above (b) is a region that has a low metallic luster on the surface and is relatively white or gray compared to the second region. On the other hand, the second region is a region having a relatively higher surface metallic luster than the first region. Thus, the first area and the second area are distinguishable to the naked eye, under a magnifying glass, or under a microscope.
[0047]
At least [Al phase] and [Al/Zn/MgZn2 ternary eutectic structure] are present in the hot-dip plated layer. The hot-dip plated layer has a form in which the [Al phase] is included in the [ternary eutectic structure of Al/Zn/MgZn2]. The [Al phase] precipitates at a relatively early stage during the solidification of the hot-dip plated layer, and the [Al phase] at that time takes the form of a dendrite.
[0048]
When the above (b) is satisfied, the first region has a length Le in which the [ternary eutectic structure of Al/Zn/MgZn2] faces the steel plate at the boundary between the steel plate and the hot-dip coating layer. It is in the range of more than 0.3, preferably more than 0.30 with respect to the height L. As a result, on the steel sheet side in the thickness direction of the hot-dip coating layer in the first region, there is a relatively large amount of [Al/Zn/MgZn2 ternary eutectic structure], and [Al phase] and other phases or structures relatively less. As a result, a relatively large amount of dendrite [Al phase] is present on the surface side in the thickness direction of the hot-dip plated layer. For this reason, the surface of the first region has a relatively large surface roughness Ra, and the light incident on the first region is diffusely reflected, and it is presumed that it becomes relatively white or gray compared to the second region. be done.
[0049]
In the first region, the length Le at which the [ternary eutectic structure of Al/Zn/MgZn2] faces the steel plate at the boundary between the steel plate and the hot-dip coating layer is preferably 0.30 with respect to the boundary length L. Super. That is, Le/L in the first region is preferably greater than 0.30.
[0050]
On the other hand, in the second region, the length Le at which the [ternary eutectic structure of Al/Zn/MgZn2] faces the steel plate at the boundary between the steel plate and the hot-dip coating layer is 0.0 to the length L of the boundary. 3 or less, more preferably 0.30 or less. As a result, on the steel sheet side in the thickness direction of the hot-dip coating layer in the second region, there is a relatively small amount of [Al/Zn/MgZn2 ternary eutectic structure], and [Al phase] and other phases or structures are present. relatively more. As a result, a relatively small amount of dendrite-like [Al phase] is present on the surface side in the thickness direction of the hot-dip plated layer. Therefore, it is presumed that the surface of the second region has a relatively small surface roughness Ra, and the second region exhibits a relatively metallic luster compared to the first region.
[0051]
In the second region, the length Le at which the [ternary eutectic structure of Al/Zn/MgZn2] faces the steel plate at the boundary between the steel plate and the hot-dip coating layer is preferably 0.30 with respect to the boundary length L. below, more preferably 0.15 or less, still more preferably 0.1 or less, and particularly preferably 0.10 or less. As the difference between Le/L in the first region and Le/L in the second region increases, the first region and the second region become relatively easier to distinguish, which is preferable.
[0052]
The [Al phase] generated during the solidification of the hot-dip plated layer usually precipitates in the entire thickness direction of the hot-dip plated layer. However, by intentionally or artificially controlling the length Le at which the [ternary eutectic structure of Al/Zn/MgZn2] faces the steel sheet at the boundary between the steel sheet and the hot-dip coating layer, the surface of the hot-dip coating layer The existence ratio of [Al phase] in can be controlled. Since the [Al phase] has a dendrite form, the surface roughness of the hot-dip plated layer increases as the proportion of [Al phase] on the surface of the hot-dip plated layer increases. When the proportion of the [Al phase] on the surface decreases, the surface roughness of the hot-dip plated layer decreases. In this way, at the boundary between the steel sheet and the hot-dip coating layer,By controlling the length Le in which the [ternary eutectic structure of Al/Zn/MgZn2] faces the steel sheet, the first region and the second region can be formed on the surface of the hot-dip plated layer.
[0053]
When an interfacial alloy layer containing Fe and Zn is formed at the boundary between the steel sheet and the hot-dip coating layer, the [ternary eutectic structure of Al/Zn/MgZn2] faces the steel sheet through the interfacial alloy layer. It suffices to set the length Le to be within the above range. However, since the interfacial alloy layer is very thin compared to the thickness of the hot-dip plated layer, as described below, when measuring the length Le with a microscope, the interfacial alloy layer In some cases, the alloy layer cannot be confirmed, but the interface between the steel sheet and the hot-dip coating layer can be confirmed.
In the first region in this case, the length Le at which the [ternary eutectic structure of Al/Zn/MgZn2] faces the steel plate at the interface between the steel plate and the hot-dip coating layer is 0 with respect to the length L of the interface. .3 or more. In the second region, the length Le at which the [ternary eutectic structure of Al/Zn/MgZn2] faces the steel plate at the interface between the steel plate and the hot-dip coating layer is 0.00 to the length L of the interface. A region of 3 or less may be used.
[0054]
At the boundary (interface) between the steel sheet and the hot-dip coating layer, the ratio of the length Le at which the [ternary eutectic structure of Al/Zn/MgZn2] faces the steel sheet with respect to the length L of the boundary (interface) is as follows. It can be measured by such a method. First, the section of the Zn-Al-Mg hot-dip plated steel sheet in the plate thickness direction is exposed. Five cross sections are provided for each of the first region and the second region. Each section is photographed with a scanning electron microscope. In each cross section, a region with a length of 150 μm is arbitrarily selected from the boundary (interface) between the steel sheet and the hot-dip plating layer. Let this length be boundary length L (interface length L). Then, the [Al/Zn/MgZn ternary eutectic structure] is confirmed in the selected boundary (interface) length range, and all [Al/Zn/ The total length Le of the ternary eutectic structure of MgZn2] is measured to obtain Le/L. Le / L is obtained in cross sections at five locations in each of the first region and the second region, and the average is calculated as the boundary (interface) between the steel sheet and the hot-dip coating layer [Al / Zn /MgZn2 ternary eutectic structure] is the ratio of the length Le facing the steel plate.
[0055]
The [Al phase] generated during the solidification of the hot-dip plated layer usually precipitates in the entire thickness direction of the hot-dip plated layer. However, if a substance that serves as solidification nuclei is arranged on the surface of the steel sheet in advance, when the molten metal adhering to the surface of the steel sheet solidifies in the area where the solidification nuclei are arranged, many [ Al phase] precipitates. The generated [Al phase] segregates on the side relatively close to the steel sheet.
In addition, in the region where the solidification nuclei are arranged, the [Al phase] is generated at a relatively high density, so the [Al phase] itself does not coarsen and remains fine. Therefore, in the region where the solidification nuclei are arranged, [Al phase] does not grow to the surface side of the hot-dip coating layer, and a large amount of [Al phase] precipitates near the boundary (interface) between the steel sheet and the hot-dip coating layer. As a result, the [ternary eutectic structure of Al/Zn/MgZn 2] in the region where the solidification nuclei are arranged has a reduced amount of precipitation, and the [Al/Zn/MgZn 2 The proportion of the length Le in which the ternary eutectic structure] faces the steel sheet is reduced.
[0056]
In the case of (b) above, the area where the solidification nuclei exist on the steel sheet surface becomes the second area of ​​the hot-dip plating layer, and the area where the solidification nuclei do not exist becomes the first area of ​​the hot-dip plating layer. Further, since the second region is formed by the mechanism described above, solidification nuclei may exist at the boundary (interface) between the steel sheet and the hot-dip coating layer in the second region. More specifically, carbon (C), nickel (Ni), calcium (Ca), boron (B), phosphorus (P), titanium ( Ti), manganese (Mn), iron (Fe), cobalt (Co), zirconium (Zr), molybdenum (Mo), tungsten (W), any one or more elements selected from the group consisting of Alternatively, there may be compounds containing any one or more of the above elements.
[0057]
In order to confirm the presence of the above-mentioned elements or compounds at the boundary (interface) between the steel sheet and the hot-dip coating layer, a glow discharge optical emission spectrometer (GDS) is used to excavate the sample by sputtering while digging the steel sheet in the second region. It can be confirmed by performing an elemental analysis at the boundary between and the hot-dip plating layer.
[0058]
As described above, before the steel sheet is immersed in the hot-dip plating bath, any one of linear portions, curved portions, figures, numbers, symbols and characters, or a shape obtained by combining two or more of these, is applied to the surface of the steel plate. By arranging the solidification nuclei at , it is possible to form the second regions having these shapes in the hot-dip plating layer.
[0059]
In addition, before immersing the steel sheet in the hot-dip plating bath, the surface of the steel sheet is treated with any one of linear portions, curved portions, figures, numbers, symbols and characters, or a region excluding a shape in which two or more of these are combined. In addition, by arranging solidification nuclei, it is possible to form the first regions having these shapes in the hot-dip plating layer.
[0060]
Further, in the case of (b) above, the ratio of the X-ray diffraction intensity I (200) of the (200) plane of the Al phase on the surface of the hot-dip plated layer to the X-ray diffraction intensity I (111) of the (111) plane I(200)/I(111) is preferably 0.8 or more, more preferably 0.80 or more. Regardless of the first region or the second region, the ratio I(200)/I(111) is preferably 0.8 or more, more preferably 0.80 or more.
[0061]
When the ratio I(200)/I(111) increases, the [Al phase] in which the (200) plane is parallel to the surface of the hot-dip plated layer increases, and the (111) plane is hot-dip plated. Less [Al phase] becomes parallel to the surface of the layer. As a result, when viewed from the surface of the hot-dip plated layer, there are many cross-shaped dendrites and fewer hexagonal dendrites. In the process of solidifying the hot-dip plated layer from a molten state, when the [Al phase] precipitated as primary crystals grows in a cross shape from the crystal nucleus when viewed from the plating surface side, the angle between the branches As a result, the flow path of the melt becomes easy to form in the direction perpendicular to the plating surface, and the [Al phase] on the plating surface is covered with the [ternary eutectic structure of Al/Zn/MgZn2] that finally solidifies. become fragile. As a result, the higher the ratio I(200)/I(111), the more the surface appears to have metallic luster. This can improve the overall appearance of the hot-dip plated layer. In addition, in the first region, a large amount of [Al/Zn/MgZn2 ternary eutectic structure] exists near the boundary (interface) in the plate thickness direction, and therefore a large amount of [Al phase] exists near the surface. There is a tendency. On the other hand, the second area is vice versa. For the reason described above, metallic luster is further emphasized at locations where a large amount of [Al phase] exists on the surface, so that the first region and the second region can be distinguished more clearly.
[0062]
The ratio I(200)/I(111) on the surface of the hot-dip plating layer can be controlled by adjusting the cooling rate after forming the plating layer.
[0063]

The Zn-Al-Mg-based hot-dip plated steel sheet according to the present embodiment may have a chemical conversion treatment film layer or a coating film layer on the surface of the hot-dip plated layer. Here, the types of the chemical conversion treatment film layer and the coating film layer are not particularly limited, and known chemical conversion treatment film layers and coating film layers can be used.
[0064]
[Manufacturing method of Zn-Al-Mg hot dip plated steel sheet]
A method for manufacturing the Zn-Al-Mg hot-dip plated steel sheet according to the present embodiment will be described below. In the following description, the case where the first region and the second region satisfy the above (a) or (b) will be sequentially described.
[0065]
(Manufacturing method when the first region and the second region satisfy the above (a))
In the manufacturing method in which the first region and the second region satisfy (a) above, first, hot-rolled steel sheets are manufactured, and if necessary, hot-rolled steel sheets are annealed. After pickling, cold rolling is performed to obtain a cold-rolled sheet. After the cold-rolled sheet is degreased and washed with water, it is annealed (cold-rolled sheet annealing), and the annealed cold-rolled sheet is immersed in a hot-dip plating bath to form a hot-dip plating layer. Hot-dip plating may be a continuous hot-dip plating method in which a steel sheet is continuously passed through a hot-dip plating bath, or a hot-dip plating method in which a steel material processed into a predetermined shape or the steel plate itself is immersed in a hot-dip plating bath and then pulled out. It's okay.
[0066]
The hot-dip plating bath preferably contains Al: 4% by mass or more and less than 25% by mass, Mg: 0% by mass or more and less than 10% by mass, with the balance being Zn and impurities. The hot-dip plating bath may contain 4 to 22% by mass of Al, 1 to 10% by mass of Mg, and the balance may be Zn and impurities. Furthermore, the hot dip plating bath may contain Si: 0.0001 to 2% by mass. Furthermore, the hot dip plating bath is any one or two of Ni, Ti, Zr, Sr, Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM and Hf. A total of 0.001 to 2% by weight of seeds or more may be contained. The average composition of the hot-dip plating layer of this embodiment is substantially the same as the composition of the hot-dip plating bath.
[0067]
The temperature of the hot-dip plating bath varies depending on the composition, but is preferably in the range of 400-500°C, for example. This is because a desired hot-dip plating layer can be formed if the temperature of the hot-dip plating bath is within this range.
Also, the adhesion amount of the hot-dip plating layer may be adjusted by gas wiping or the like on the steel sheet pulled up from the hot-dip plating bath. It is preferable to adjust the coating weight of the hot-dip plating layer so that the total coating weight on both sides of the steel sheet is in the range of 30 to 600 g/m 2 . If the adhesion amount is less than 30 g/m 2 , the corrosion resistance of the hot-dip plated steel sheet is lowered, which is not preferable. If the coating amount exceeds 600 g/m 2 , the molten metal that adheres to the steel sheet will drip, making it impossible to smoothen the surface of the hot-dip plated layer, which is not preferable.
[0068]
In order to form the first region and the second region that satisfy the above (a), after adjusting the adhesion amount of the hot-dip coating layer, while cooling the entire steel sheet, non-oxidizing gas is applied to the molten metal is locally sprayed by a gas nozzle. A non-oxidizing gas such as nitrogen or argon may be used as the non-oxidizing gas.
[0069]
In order to make the first region have a predetermined shape, the average cooling rate from the bath temperature to 345 ° C. is 10 ° C./sec for almost the entire hot-dip plating layer for the formation of the second region. Cool above. In addition, for the formation of the first region, the average cooling rate from the bath temperature to 345 ° C. for part of the hot dip layer is cooled at less than 8 ° C./sec, which is a slower speed than the second region. .
[0070]
More preferably, the average cooling rate from the bath temperature to 345 ° C. is 15 ° C./sec or more by blowing air cooling or mist cooling to almost the entire hot-dip plating layer for forming the second region, For the formation of the first region, a part of the hot-dip plating layer is left to cool (left) without being cooled, or a relatively high temperature non-oxidizing gas is blown, so that the bath temperature is reduced to 345 ° C. The average cooling rate during the period shall be 5°C/sec or less. The temperature of the non-oxidizing gas in this case is preferably in the range of 100 to 300° C., for example. However, the temperature of the non-oxidizing gas need not be limited as long as the above average cooling rate can be satisfied.
[0071]
In addition, in order to form the second region into a predetermined shape, the average cooling rate from the bath temperature to 345 ° C. for almost the entire hot-dip plating layer for the formation of the first region is 8 ° C. / seconds or less. In addition, for the formation of the second region, part of the hot-dip plated layer is cooled at an average cooling rate of 10 ° C./sec or more, which is a faster rate than the first region, from the bath temperature to 345 ° C. .
[0072]
More preferably, almost the entire hot-dip plated layer is allowed to cool for the formation of the first region, and the average cooling rate from the bath temperature to 345 ° C. is 5 ° C./sec or less, while forming the second region. Therefore, by blowing a relatively low-temperature non-oxidizing gas against a part of the hot-dip plating layer, the average cooling rate from the bath temperature to 345 ° C. is 15 ° C./sec or more.do. Cooling of the first zone may be performed in an atmosphere of 50 to 150° C. in order to reduce the cooling rate. Also, the temperature of the non-oxidizing gas when cooling the second region may be, for example, in the range of 10 to 30° C., or may be a mist gas containing water droplets. However, if the above average cooling rate can be satisfied, the ambient temperature and the temperature of the non-oxidizing gas during cooling of the first region need not be limited.
[0073]
(Manufacturing method when the first region and the second region satisfy the above (b))
In the manufacturing method in which the first region and the second region satisfy the above (b), the solidification nuclei are arranged in a predetermined pattern on the steel sheet, then the steel sheet is immersed in a hot dip plating bath and then pulled up, and then A Zn-Al-Mg system hot-dip plated steel sheet is manufactured by cooling and solidifying the hot-dip plated layer.
[0074]
First, hot-rolled steel sheets are manufactured, and if necessary, hot-rolled steel sheets are annealed. After pickling, cold rolling is performed to obtain a cold-rolled sheet. After the cold-rolled sheet is degreased and washed with water, it is annealed (cold-rolled sheet annealing), and the annealed cold-rolled sheet is immersed in a hot-dip plating bath to form a hot-dip plating layer.
[0075]
Here, during the period from cold rolling to immersion in the hot-dip plating bath, solidification nuclei are attached to the surface of the steel sheet, and any one of straight parts, curved parts, figures, numbers, symbols and letters or these A pattern portion having a shape obtained by combining two or more of the above is formed. Adhesion of solidification nuclei occurs between cold rolling and cold-rolled sheet annealing, between cold-rolled sheet annealing and immersion in a hot-dip plating bath, or immediately before the final annealing of cold-rolled sheet annealing. should be implemented.
[0076]
The component that forms solidification nuclei (hereinafter sometimes referred to as a solidification nucleus-forming component) is not particularly limited as long as it is a component that forms solidification nuclei in the process of solidifying the plating layer. Solidification nucleus forming components include, for example, carbon (C), nickel (Ni), calcium (Ca), boron (B), phosphorus (P), titanium (Ti), manganese (Mn), iron (Fe), cobalt (Co), zirconium (Zr), molybdenum (Mo), tungsten (W), any one or two or more elements selected from the group consisting of, or any one or two or more of the above elements compounds containing You may use the said component in combination of 1 or 2 or more. Examples of methods for attaching solidification nuclei to the steel sheet surface include, in addition to solidification nucleus-forming ingredients themselves, a method of adding solidification nucleus-forming ingredients to an alloy foil, resin, surfactant, ink, oil, etc. and attaching them to the steel sheet surface. is mentioned. These solidification nucleus-forming components may be solids themselves, or may be dissolved or dispersed in water or an organic solvent. Alternatively, it may be contained in the ink as a pigment or dye.
[0077]
Examples of the method of attaching solidification nuclei to the surface of the steel sheet include transferring, coating, or spraying a material containing solidification nucleus-forming components onto the surface of the steel sheet. For example, foil transfer method using hot stamping, cold stamping, etc., printing method using various plates (gravure printing, flexo printing, offset printing, silk printing, etc.), inkjet method, thermal transfer method using ink ribbon, etc. , general printing methods can be used.
[0078]
As an example of the transfer method using alloy foil, there is a method in which an alloy foil containing a solidification nucleus-forming component is adhered to the surface of a steel sheet, and a heated silicon roll is pressed against the alloy foil to transfer it to the surface of the steel sheet.
[0079]
As an example of a printing method using a plate, a rubber roll or rubber stamp having a printing pattern formed on its peripheral surface is coated with ink or a surfactant containing a component that serves as a coagulation nucleus while the rubber roll or rubber stamp is applied to the surface of a steel plate. A method of pressing to transfer ink or a surfactant may be used. With this method, the solidification nucleus-forming components can be efficiently adhered to the surface of the steel sheet that is continuously passed through.
[0080]
The adhered amount of coagulation nuclei is preferably in the range of, for example, 50 mg/m 2 or more and 5000 mg/m 2 or less. If the adhesion amount is less than 50 mg/m 2 , the first region may not be formed to the extent that it can be identified with the naked eye, under a magnifying glass, or under a microscope, which is not preferable. On the other hand, if the coating amount exceeds 5000 mg/m 2 , the adhesiveness of the hot-dip plating layer may deteriorate, which is not preferable.
[0081]
Next, the steel sheet on which the patterned portion composed of solidification nuclei is formed is immersed in a hot-dip plating bath. Hot-dip plating may be a continuous hot-dip plating method in which a steel sheet is continuously passed through a hot-dip plating bath, or a hot-dip plating method in which a steel material processed into a predetermined shape or the steel plate itself is immersed in a hot-dip plating bath and then pulled out. It's okay.
[0082]
The composition of the hot-dip plating bath, the temperature of the hot-dip plating bath, the adhesion amount of the hot-dip plating layer, and the method for controlling the adhesion amount may be the same as the manufacturing method when the first region and the second region satisfy the above (a).

The scope of the claims

[Claim 1]
A steel plate and a hot-dip coating layer formed on the surface of the steel plate,
The hot-dip plating layer is
The average composition contains Al: 4% by mass or more and less than 25% by mass, Mg: 0% by mass or more and less than 10% by mass, and the balance contains Zn and impurities,
The metal structure includes [Al phase] and [Al/Zn/MgZn2 ternary eutectic structure],
The hot-dip plating layer includes a first region and a second region,
the first region and the second region satisfy either (a) or (b) below,
A Zn-Al-Mg hot-dip plated steel sheet characterized in that the first region or the second region is arranged to have a predetermined shape.
(a) The first region is a region in which the average length of the [Al phase] on the surface of the hot dip plated layer is 200 μm or more, and the second region is the [Al phase] on the surface of the hot dip plated layer ] has an average length of less than 200 μm.
(b) In the first region, the length Le at which the [Al/Zn/MgZn2 ternary eutectic structure] faces the steel plate at the boundary between the steel plate and the hot-dip coating layer is the length of the boundary The second region is a region where the [Al / Zn / MgZn ternary eutectic structure] is the steel plate at the boundary between the steel plate and the hot-dip coating layer. The opposing length Le is a region of 0.3 or less with respect to the length L of the boundary.
[Claim 2]
When the first region and the second region are the above (b), the X-ray diffraction intensity I of the (200) plane of the [Al phase] on the surface of the hot dip plated layer I (200) and (111 2. The Zn-Al-Mg hot-dip plated steel sheet according to claim 1, wherein the ratio I(200)/I(111) of the X-ray diffraction intensity I(111) of the ) plane is 0.8 or more.
[Claim 3]
The first region or the second region is arranged to have a shape that is a combination of any one of linear portions, curved portions, figures, numerals, symbols, patterns, characters, or two or more of these. The Zn-Al-Mg system hot-dip plated steel sheet according to claim 1 or claim 2.
[Claim 4]
The Zn-Al-Mg hot-dip plated steel sheet according to any one of claims 1 to 3, wherein the first region or the second region is intentionally formed.
[Claim 5]
The Zn-Al-Mg hot-dip plated steel sheet according to any one of claims 1 to 4, wherein the hot-dip plated layer further contains Si: 0.0001 to 2 mass% in average composition.
[Claim 6]
The hot-dip plated layer further contains, in average composition, any one or more of Ni, Ti, Zr, and Sr in a total of 0.0001 to 2% by mass. The Zn-Al-Mg hot-dip plated steel sheet according to any one of items.
[Claim 7]
The hot-dip plated layer further has an average composition of any one or more of Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM, Hf, and C The Zn-Al-Mg hot-dip plated steel sheet according to any one of claims 1 to 6, containing 0.0001 to 2 mass% in total.
[Claim 8]
The Zn-Al-Mg hot-dip plated steel sheet according to any one of claims 1 to 7, wherein the total adhesion amount of the hot-dip plating layer on both sides of the steel sheet is 30 to 600 g/m 2 .