Title of the invention: Zn-Al-Mg-based hot-dip galvanized steel sheet and its manufacturing method
Technical field
[0001]
　The present invention relates to a Zn—Al—Mg-based hot-dip galvanized steel sheet and a method for producing the same.
　The present application claims priority based on Japanese Patent Application No. 2018-104000 filed in Japan on May 30, 2018, the contents of which are incorporated herein by reference.
Background technology
[0002]
　Zn-Al-Mg-based hot-dip galvanized 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 enhancing the distinctiveness and design of products, there is a demand for designing a plated steel sheet such as a character string, a pattern, and a design drawing. Conventionally, character strings, patterns, design drawings, etc. are expressed by applying processes such as painting and grinding to the plating layer of a plated steel sheet.
[0004]
　However, when a process such as painting or grinding is performed, there is a problem that the cost and time for applying the design increase. Further, when the design is applied by painting, the durability is inferior due to the problem of the deterioration of the coating film itself with time and the deterioration of the adhesion of the coating film with time, and the design may disappear with time. Further, when the design is applied by grinding the plating layer, although the durability of the design is excellent, the corrosion resistance is lowered at the place where the thickness of the plating layer is reduced, and there is a concern that the plating characteristics are deteriorated.
[0005]
　As shown in the following patent documents, various techniques for Zn—Al—Mg-based hot-dip galvanized steel sheets have been developed, but a technique for applying a design having excellent durability to a plated layer is not known.
Prior art literature
Patent documents
[0006]
Patent Document 1: Japanese Patent No. 5043234
Patent Document 2: Japanese Patent No. 5141899
Patent Document 3: Japanese Patent No. 360804
Patent Document 4: International Publication WO2013 / 002358
Outline of the invention
Problems to be solved by the invention
[0007]
　Regarding Zn-Al-Mg-based hot-dip galvanized steel sheets, there is a conventional technique for making the satin-skin-like plating appearance seen in Zn-Al-Mg-based hot-dip galvanized steel sheets more beautiful.
　For example, Patent Document 1 describes a Zn—Al—Mg-based hot-dip galvanized steel sheet having a satin surface with fine texture and many smooth glossy portions, that is, a large number of white portions per unit area and a glossy portion. A Zn—Al—Mg hot-dip galvanized steel sheet having a good satin finish with a large area ratio is disclosed. Further, Patent Document 1 discloses that an unfavorable pear-skinned state is a state in which irregular white portions and circular glossy portions are mixed to exhibit a surface appearance scattered on the surface. There is.
Further, Patent Document 4 describes a highly corrosion-resistant hot-dip galvanized steel sheet in which the glossiness of the plating layer is increased as a whole and the appearance uniformity is improved by refining the ternary eutectic phase of Al / MgZn 2 / Zn. It is disclosed.
　However, a technique for applying a design having excellent durability to a hot-dip galvanized layer has not been known. An object of the present invention is to provide a Zn—Al—Mg-based hot-dip galvanized steel sheet and a method for producing the same, which are positively imparted with a design having high durability and suitable corrosion resistance.
Means to solve problems
[0008]
　The gist of the present invention is as follows.
[1] A steel plate and
　a hot-dip galvanized layer formed on the surface of the steel plate are provided, and the
　hot-dip galvanized layer contains Al: 4 to 22% by mass and Mg: 1 to 10% by mass in average composition. The balance contains Zn and impurities, and the
　hot-dip galvanized layer contains an Al phase and a ternary eutectic structure (ternary eutectic phase) of Al / Zn / MgZn 2 , and
　further, the hot-dip galvanized layer. There is a first region in which the exposure ratio of the Al phase on the surface is less than 30 area% and a second region in which the exposure ratio of the Al phase on the surface is 30 area% or more
　. A Zn—Al—Mg-based hot-dip galvanized steel sheet, characterized in that one region is arranged so as to have a predetermined shape.
[2]
　The Zn according to [1], wherein the first region has a surface roughness Ra of 1 nm or more and less than 10 nm, and the second region has a surface roughness Ra of 10 nm or more and less than 200 nm. -Al-Mg hot-dip galvanized steel sheet.
[3] A steel sheet and
　a hot-dip galvanized layer formed on the surface of the steel sheet are provided, and the
　hot-dip galvanized layer contains Al: 4 to 22% by mass and Mg: 1 to 10% by mass in average composition. The balance contains Zn and impurities, and the
　hot-dip galvanized layer has an Al phase and Al / Zn / MgZn 2The
　hot-dip galvanized layer contains a first region having a surface roughness Ra of 1 nm or more and less than 10 nm, and a surface roughness Ra of 10 nm or more and less than 200 nm. A
　Zn—Al—Mg-based hot-dip galvanized steel sheet, characterized in that the second region of the above is present and the first region is arranged so as to have a predetermined shape.
[4] The first region is arranged so as to have a shape obtained by any one of a straight line portion, a curved portion, a figure, a number, a symbol or a character, or a combination of two or more of these. The Zn—Al—Mg-based hot-dip galvanized steel sheet according to any one of [1] to [3].
[5] The Zn—Al according to any one of [1] to [4], wherein the hot-dip galvanized layer further contains Si: 0.0001 to 2% by mass in an average composition. -Mg-based hot-dip galvanized steel sheet.
[6] The hot-dip galvanized layer further contains, in average composition, any one or more of Ni, Ti, Zr, and Sr in an amount of 0.001 to 2% by mass [6]. The Zn—Al—Mg-based hot-dip galvanized steel sheet according to any one of 1] to [5].
[7] The hot-dip galvanized layer further has an average composition of any one of Fe, Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM, and Hf. The Zn—Al—Mg-based hot-dip galvanized steel sheet according to any one of [1] to [6], which contains two or more types in a total amount of 0.001 to 2% by mass.
[8] The total amount of the hot-dip galvanized layer adhered to both sides of the steel sheet is 40 to 600 g / m 2.The Zn—Al—Mg-based hot-dip galvanized steel sheet according to any one of [1] to [7].
[9] A step of forming an arbitrary-shaped pattern portion
　made of a material containing solidified nuclei on the surface of a steel sheet and the steel sheet to which a material containing solidified nuclei is adhered have an average composition of Al: 4 to 22% by mass. A method for producing a Zn—Al—Mg-based hot-dip galvanized steel sheet, which comprises a step of immersing the steel sheet in a plating bath containing Mg: 1 to 10% by mass and the balance containing Zn and impurities.
[10] The solidified nucleus is characterized in that it is carbon, nickel, calcium, boron, phosphorus, titanium, manganese, iron, cobalt, zirconium, molybdenum, tungsten, or any of these compounds [9]. The method for producing a Zn—Al—Mg-based hot-dip galvanized steel sheet according to the above method.
[11] The pattern portion has a shape obtained by any one of a straight portion, a curved portion, a figure, a number, and a character, or a combination of two or more of these [9] or [10]. The method for producing a Zn—Al—Mg-based hot-dip galvanized steel sheet according to.
[0009]
[12] A steel plate and
　a hot-dip galvanized layer formed on the surface of the steel sheet
are provided, and the
　hot-dip galvanized layer contains
　　Al: 4 to 22% by mass and Mg: 1 to 10% by mass in average composition. The balance contains Zn and impurities, and the
　　metal structure includes an Al phase and a ternary eutectic structure (ternary eutectic phase) of Al / Zn / MgZn 2.
　The surface of the hot-dip galvanized layer is first.
　The first region is composed of a region and a second region, and the first region is arranged so as to have a shape obtained by any one of a straight portion, a curved portion, a figure, a number, a symbol and a character, or a combination of two or more of them. The Zn—Al—Mg-based hot-dip galvanized steel sheet is characterized in that
　the first region and the second region satisfy at least one of the following (a) and (b)
.
　(A) The first region is a region where the exposure ratio of the Al phase on the surface is less than 30 area%, and the second region is a region where the exposure ratio of the Al phase on the surface is 30 area% or more. Is.
　(B) The first region is a region having a surface roughness Ra of 1 nm or more and less than 10 nm, and the second region is a region having a surface roughness Ra of 10 nm or more and less than 200 nm.
[13] The interface between the steel sheet and the hot-dip galvanized layer in the first region is selected from the group consisting of C, Ni, Ca, B, P, Ti, Mn, Fe, Co, Zr, Mo, and W. The Zn—Al—Mg-based hot-dip galvanized steel sheet according to [12], wherein a compound containing any one or more of the elements, or any one or more of the elements is present.
[14] The Zn—Al—Mg-based hot-dip galvanized product according to [12] or [13], wherein the hot-dip galvanized layer further contains Si: 0.0001 to 2% by mass in an average composition. Steel plate.
[15] The hot-dip galvanized layer further contains 0.0001 to 2% by mass of any one or more of Ni, Ti, Zr, and Sr in an average composition [15]. The Zn—Al—Mg-based hot-dip galvanized steel sheet according to any one of [12] to [14].
[16] The hot-dip galvanized layer further has an average composition of Fe, Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM, Hf, C, Mo, W. The Zn—Al—Mg-based hot-dip galvanized product according to any one of [12] to [15], which contains 0.0001 to 2% by mass in total of any one or more of the above. Steel plate.
[17] The Zn—Al—Mg system according to any one of [12] to [16], wherein the amount of adhesion of the hot-dip galvanized layer is 30 to 600 g / m 2 in total on both sides of the steel sheet. Hot-dip galvanized steel sheet.
[18] The steel plate is formed by adhering solidified nuclei to the surface of the steel plate and forming a pattern portion having a shape in which any one of a straight portion, a curved portion, a figure, a number, a symbol and a character, or two or more of these are combined. And the process of forming on the surface of
　A step of immersing the steel sheet having the pattern portion formed on the surface in a hot-dip galvanizing bath containing Al: 4 to 22% by mass and Mg: 1 to 10% by mass in average composition, and the balance containing Zn and impurities. A
method for producing a Zn—Al—Mg-based hot-dip galvanized steel sheet, which comprises.
[19] One or more of the elements selected from the group consisting of C, Ni, Ca, B, P, Ti, Mn, Fe, Co, Zr, Mo, and W, or the solidified nuclei. The method for producing a Zn—Al—Mg-based hot-dip galvanized steel sheet according to [18], wherein the compound contains any one or more of the above elements.
[20] The Zn—Al—Mg-based hot-dip galvanizing according to [18] or [19], wherein the hot-dip galvanizing bath further contains Si: 0.0001 to 2% by mass in an average composition. Steel plate manufacturing method.
[21] The hot-dip galvanizing bath further contains, in average composition, any one or more of Ni, Ti, Zr, and Sr in an amount of 0.0001 to 2% by mass [21]. 18] The method for producing a Zn—Al—Mg-based hot-dip galvanized steel sheet according to any one of [20].
The invention's effect
[0010]
　According to the present invention, it is possible to provide a Zn—Al—Mg-based hot-dip galvanized steel sheet having high design durability and suitable plating characteristics such as corrosion resistance, and a method for producing the same.
A brief description of the drawing
[0011]
FIG. 1 is a diagram illustrating a solidification process of a hot-dip galvanized layer at the time of manufacturing the Zn—Al—Mg-based hot-dip galvanized steel sheet of the present embodiment.
[Fig. 2A] No. It is a micrograph which shows the result of having observed the 1st region of the hot dip galvanizing layer of 1 with a scanning electron microscope.
FIG. 2B is an enlarged photograph of FIG. 2A.
[Fig. 3A] No. It is a micrograph which shows the result of having observed the 2nd region of the hot dip galvanizing layer of 1 with a scanning electron microscope.
FIG. 3B is an enlarged photograph of FIG. 3A.
FIG. 3C is an enlarged photograph of the vicinity of [Al phase] in FIG. 3B.
[Fig. 4] No. It is a figure which shows the appearance of the hot dip galvanizing layer of 1 and the measurement result of the surface roughness by the AFM measurement of the 1st region, and the surface roughness by the AFM measurement of a 2nd region.
FIG. 5 is a plan view showing a hot-dip galvanized steel sheet which is an example of the present embodiment.
FIG. 6 is a plan view showing a hot-dip galvanized steel sheet which is an example of the present embodiment.
FIG. 7 is a plan view showing a hot-dip galvanized steel sheet which is an example of the present embodiment.
Mode for carrying out the invention
[0012]
　Hereinafter, embodiments of the present invention will be described.
　[Zn-Al-Mg-based hot-dip galvanized steel sheet]
　The Zn-Al-Mg-based hot-dip galvanized steel sheet of the present embodiment includes a steel sheet and a hot-dip galvanized layer formed on the surface of the steel sheet.
　The hot-dip galvanized layer contains 4 to 22% by mass of Al and 1 to 10% by mass of Mg in an average composition, and the balance contains Zn and impurities.
　Further, the hot-dip galvanized layer contains [Al phase] and [ ternary eutectic structure of Al / Zn / MgZn 2 (ternary eutectic phase)].
　Further, the hot-dip galvanized layer has a first region and a second region, and the first region is one of a straight part, a curved part, a figure, a number, a symbol and a character, or two of them. It is arranged so as to have a shape that combines the above.
[0013]
　
　The material of the steel plate used as the base of the hot-dip plating layer is not particularly limited. Although the details will be described later, as the steel sheet, general steel or the like can be used, and Al killed steel or some high alloy steel can also be used. Further, the shape of the steel plate is not particularly limited. By applying the hot-dip galvanizing method described later to the steel sheet, the hot-dip galvanizing layer according to the present embodiment is formed.
[0014]
　
　(Chemical composition)
　Next, the chemical composition of the hot-dip plating layer will be described.
　The hot-dip galvanized layer contains Al: 4 to 22% by mass and Mg: 1 to 10% by mass in average composition, and contains Zn and impurities as the balance. The hot-dip galvanized layer preferably contains 4 to 22% by mass of Al and 1 to 10% by mass of Mg in an average composition, and is composed of Zn and impurities as the balance.
　The hot-dip galvanized layer may contain Si: 0.0001 to 2% by mass in average composition. The hot-dip galvanized layer may contain 0.0001 to 2% by mass in total of any one or more of Ni, Ti, Zr, and Sr in an average composition. The hot-dip galvanized layer has an average composition of any one of Fe, Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM, Hf, C, Mo, and W. A total of two or more types may contain 0.0001 to 2% by mass.
[0015]
　[Al: 4 to 22% by mass]
　The content of Al in the hot-dip galvanized layer is 4 to 22% by mass on average. Al is an element necessary for ensuring corrosion resistance. If the Al content in the hot-dip galvanized layer is less than 4% by mass, the effect of improving the corrosion resistance is insufficient, and the exposure ratio of the [Al phase] is reduced as a whole, thus ensuring the design. It is not preferable, and if it exceeds 22% by mass, the exposure ratio of [Al phase] increases as a whole, which is not preferable for ensuring the design. The content of Al in the hot-dip galvanized layer is preferably 5 to 18% by mass, more preferably 6 to 16% by mass, from the viewpoint of corrosion resistance.
[0016]
　[Mg: 1 to 10% by mass]
　The content of Mg in the hot-dip galvanized layer is 1 to 10% by mass on average. Mg is an element necessary for improving corrosion resistance. If the content of Mg in the hot-dip galvanized layer is less than 1% by mass, the effect of improving corrosion resistance is insufficient, which is not preferable. If it exceeds 10% by mass, the Mg compound crystallizes, which is not preferable for ensuring designability. In addition, dross is significantly generated in the plating bath, which makes it difficult to stably produce a hot-dip galvanized steel sheet, which is not preferable. From the viewpoint of the balance between corrosion resistance and suppression of dross generation, the content of Mg in the hot-dip galvanized layer is preferably 1.5 to 6% by mass, more preferably 2 to 5% by mass.
[0017]
　The hot-dip galvanized layer may contain Si in the range of 0.0001 to 2% by mass. Si is an element effective for improving the adhesion of the hot-dip galvanized layer.
　Since the effect of improving the adhesion is exhibited by containing 0.0001% by mass or more of Si in the hot-dip plating layer, it is preferable to contain 0.0001% by mass or more of Si.
　On the other hand, even if the content exceeds 2% by mass, the effect of improving the plating adhesion is saturated. Therefore, even when the hot-dip galvanizing layer contains Si, the Si content is 2% by mass or less.
　From the viewpoint of plating adhesion, the Si content in the hot-dip galvanized layer is more preferably 0.0010 to 1% by mass, and even more preferably 0.0100 to 0.8% by mass.
[0018]
　The hot-dip galvanized layer may contain 0.0001 to 2% by mass in total of any one or more of Ni, Ti, Zr, and Sr in an average composition. The intermetallic compound containing these elements acts as a crystallizing nucleus of the primary Al phase to make [Al / MgZn 2 / Zn ternary eutectic structure (ternary eutectic phase)] finer and more uniform. , Improves the appearance and smoothness of the hot-dip plating layer. If the content of these elements in the hot-dip galvanized layer is less than 0.0001% by mass, the effect of making the solidified structure finely uniform becomes insufficient, which is not preferable. Further, when the content of these elements in the hot-dip galvanized layer exceeds 2% by mass, the effect of refining [Al / MgZn 2 / Zn ternary eutectic structure (ternary eutectic phase)] is saturated. In addition, the surface roughness of the hot-dip galvanized layer becomes large and the appearance deteriorates, which is not preferable.
　In particular, when the above-mentioned elements are added for the purpose of improving the appearance of the hot-dip galvanized layer, the content of the above-mentioned elements is preferably 0.001 to 0.5% by mass, more preferably 0.001 to 0.05% by mass. More preferably, it is 0.002 to 0.01% by mass.
[0019]
　In the hot-dip galvanized layer, one or more of Fe, Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM, and Hf are added in total in average composition. It may contain 0.0001 to 2% by mass. When the hot-dip galvanized layer contains these elements, the corrosion resistance can be further improved.
　REM refers to one or more rare earth elements having atomic numbers 57 to 71 in the periodic table.
　Further, as will be described later, the method for producing a Zn—Al—Mg-based hot-dip galvanized steel sheet according to the present embodiment is a step of adhering solidified nuclei to the surface of the steel sheet between cold rolling and immersion in a hot-dip galvanized bath. Has. Therefore, a component used as a solidified nuclei (hereinafter, may be referred to as a solidified nucleation component) may be contained in the hot-dip galvanized layer. Elements derived from solidified nucleation components that may be contained in the hot-dip galvanized layer include one of C, Ni, Ca, B, P, Ti, Mn, Fe, Co, Zr, Mo, and W. Two or more types can be mentioned. When these elements are contained in the hot-dip galvanized layer, the total content in the hot-dip galvanized layer is 0.0001 to 2% by mass.
[0020]
　The rest of the chemical components of the hot-dip galvanized layer are zinc and impurities.
[0021]
　(Metal structure)
　Next, the metal structure of the hot-dip galvanized layer will be described. The hot-dip plating layer according to the present embodiment contains [Al phase] and [ ternary eutectic structure of Al / Zn / MgZn 2 (ternary eutectic phase)] as a metal structure .
　Specifically, the hot-dip galvanized layer according to the present embodiment has a form in which [Al phase] is included in the base material of [ternary eutectic structure of Al / Zn / MgZn 2 (ternary eutectic phase)]. have.
　[ Mg 2 Si phase] may be contained in the substrate of [Al / Zn / MgZn 2 ternary eutectic structure (ternary eutectic phase)]. Further , [MgZn 2 phase] and [Zn phase] may be contained in the base material of [Al / Zn / MgZn 2 ternary eutectic structure (ternary eutectic phase)].
[0022]
　[Al / Zn / MgZn 2 ternary eutectic structure (ternary eutectic phase)]
　Here, [Al / Zn / MgZn 2 ternary eutectic structure (ternary eutectic phase)] is the Al phase. And the Zn phase and the metal compound MgZn 2 phase are ternary eutectic structures (ternary eutectic phases), and the Al phase forming this ternary eutectic structure (ternary eutectic phase) is, for example. Corresponds to the "Al" phase "at high temperature in the ternary equilibrium diagram of Al-Zn-Mg (an Al solid solution that solid-dissolves the Zn phase and contains a small amount of Mg).
　The Al ″ phase at high temperature usually appears as a fine Al phase and a fine Zn phase at room temperature. The Zn phase in the ternary eutectic structure (ternary eutectic phase) is a small amount of Al. Is a Zn solid solution in which a small amount of Mg is dissolved in a solid solution. The MgZn two phase in the ternary eutectic structure (ternary eutectic phase ) is in a binary system equilibrium state of Zn—Mg. Zn in the figure is an intermetallic compound phase existing in the vicinity of about 84% by mass. As
　far as the state diagram is seen, Si and other additive elements are not solid-solved in each phase, or even if they are solid-solved, they are extremely polar. However, since the amount is not clearly distinguishable by ordinary analysis, the ternary eutectic structure (ternary eutectic phase) consisting of these three phases is referred to as [Al / Zn /] in the present specification. MgZn 2 ternary eutectic structure (ternary eutectic phase)].
[0023]
　[Al phase]
　[Al phase] is a phase that looks like an island with a clear boundary in the base material of the ternary eutectic structure (ternary eutectic phase), and this is, for example, Al-Zn-Mg. It corresponds to the "Al" phase "at high temperature in the ternary equilibrium diagram (an Al solid solution that dissolves the Zn phase and contains a small amount of Mg). The amount of Zn or Mg that dissolves in the Al "phase at high temperature differs depending on the concentration of Al or Mg in the plating bath. The Al" phase at high temperature is usually a fine Al phase at room temperature. Although it separates into a fine Zn phase, the island-like shape seen at room temperature is thought to be due to the shape of the Al ″ phase at high temperature. As
　far as the state diagram is concerned, Si and other additive elements are dissolved in this phase. However, it is considered that the amount is extremely small even if it is dissolved in solid solution. However, since it cannot be clearly distinguished by ordinary analysis, it is derived from the Al ″ phase at this high temperature and is formed in the form of the Al ″ phase. The phase due to the shape is referred to as [Al phase] in the present specification.
　[Al phase] is clearly different from the Al phase forming the ternary eutectic structure (ternary eutectic phase) by microscopic observation. Can be distinguished.
[0024]
　[Zn phase]
　[Zn phase] is a phase that looks like an island with a clear boundary in the base material of the ternary eutectic structure (ternary eutectic phase), and is actually a small amount of Al or a small amount of Al. Mg may be dissolved as a solid solution. As far as the phase diagram is concerned, it is considered that Si and other additive elements are not solid-solved in this phase, or even if they are solid-solved, the amount is extremely small.
　The [Zn phase] can be clearly distinguished from the Zn phase forming the ternary eutectic structure (ternary eutectic phase) by microscopic observation. The hot-dip galvanized layer according to the present embodiment may contain a [Zn phase] depending on the production conditions, but almost no effect on the corrosion resistance due to the [Zn phase] was observed. Therefore, even if the hot-dip galvanized layer contains [Zn phase], there is no particular problem.
[0025]
　[MgZn 2- phase]
　[MgZn 2- phase] is a phase that looks like an island with a clear boundary in the substrate of the ternary eutectic structure (ternary eutectic phase), and actually contains a small amount of Al. It may be in solid solution. As far as the phase diagram is concerned, it is considered that Si and other additive elements are not solid-solved in this phase, or even if they are solid-solved, the amount is extremely small.
　[MgZn 2 phase] and the ternary eutectic structure (ternary eutectic phase) was formed and MgZn 2 The phase can be clearly distinguished in microscopic observation. The hot-dip galvanized layer according to the present embodiment may not contain [MgZn 2- phase] depending on the manufacturing conditions, but is contained in the hot-dip galvanized layer under most manufacturing conditions.
[0026]
　[Mg 2 Si phase]
　[Mg 2 Si phase] is a phase that looks like an island with a clear boundary in the solidified structure of the Si-added plating layer. As far as the phase diagram is concerned, it is considered that Zn, Al, and other additive elements are not solid-solved in [Mg 2 Si phase], or even if they are solid-solved, the amount is extremely small. [Mg 2 Si phase] can be clearly distinguished from other phases in the hot-dip galvanized layer by microscopic observation.
[0027]
　The hot-dip galvanized layer of the present embodiment is formed by immersing the steel sheet in a plating bath, pulling it up, and then solidifying the molten metal adhering to the surface of the steel sheet. At this time, the [Al phase] is first formed, and then [Al / Zn / MgZn 2 ternary eutectic structure (ternary eutectic phase)] is formed as the temperature of the molten metal decreases .
　Depending on the chemical composition of the hot-dip galvanizing layer (that is, the chemical composition of the plating bath ), [Mg 2 Si phase] may be contained in the base material of [Al / Zn / MgZn 2 ternary eutectic structure (ternary eutectic phase)]. , [MgZn 2 phase] or [Zn phase] may be formed.
[0028]
　(First region and second region)
　Next, the first region and the second region of the hot-dip plating layer will be described. The hot-dip galvanized layer (surface of the hot-dip galvanized layer) according to the present embodiment has a first region and a second region. The first region is a region having a high metallic luster on its surface. The second region is a region whose surface has a low metallic luster and is white or gray. Therefore, the first region and the second region can be distinguished with the naked eye.
　In particular, the first region may be formed in a size that allows the presence of the first region to be discerned with the naked eye. Further, the second region is a region that occupies most of the hot-dip plating layer (the surface of the hot-dip plating layer), and the first region may be arranged in the second region. The first region is arranged in a predetermined shape in the second region. Specifically, the first region has a shape in the second region, which is one of straight lines, curved lines, figures, numbers, symbols and letters, or a combination of two or more of them. It is located in. By adjusting the shape of the first region, the surface of the hot-dip galvanized layer has a shape in which any one of a straight part, a curved part, a figure, a number, a symbol and a character, or two or more of these are combined. Will be done. For example, on the surface of the hot-dip galvanized layer, a character string, a number string, a symbol, a mark, a diagram, a design drawing, or a combination thereof, which are composed of the first region, is displayed. This shape is an artificially formed shape, not a naturally formed one.
　The second region occupies most of the surface of the hot-dip galvanized layer, and is a region showing a pear-skin appearance seen in Zn—Al—Mg-based hot-dip galvanized steel sheets.
[0029]
　Furthermore, the first region and the second region may be distinguishable under a microscope. Specifically, the shape composed of the first region may be identifiable in a field of view of 50 times or less. If the field of view is 50 times or less, the first region and the second region can be identified by the difference in the surface state.
　The first region and the second region can be distinguished by preferably 20 times or less, more preferably 10 times or less, and more preferably 5 times or less.
[0030]
　The first region and the second region satisfy at least one of the following (a) and (b).
　(A) The first region is a region where the exposure ratio of [Al phase] on the surface of the hot-dip plating layer is less than 30 area%, and the second region is a region where the exposure ratio of [Al phase] on the surface of the hot-dip plating layer is less than 30 area%. It is an area of ​​30 area% or more.
　(B) The first region is a region having a surface roughness Ra of 1 nm or more and less than 10 nm, and the second region is a region having a surface roughness Ra of 10 nm or more and less than 200 nm.
　The hot-dip plating layer has at least [Al phase] and [Al / Zn / MgZn 2 ternary eutectic structure (ternary eutectic phase)], but in the first region, [Al phase] is the hot-dip plating layer. On the surface side in the thickness direction, the [Al phase] is relatively small, and there are many structures or phases other than the [Al phase]. Therefore, in the first region, the exposure ratio of the [Al phase] on the surface of the hot-dip galvanized phase is less than 30 area%.
　The surface of the first region, [Al / Zn / MgZn 2 ternary eutectic structure (ternary eutectic)] but there relatively often, [Al / Zn / MgZn 2 ternary of Since the crystal structure (ternary eutectic phase)] forms a relatively flat surface when the hot-dip plating layer is solidified, the surface roughness Ra of the first region is in the range of 1 nm or more and less than 10 nm.
　As described above, in the first region, the exposure ratio of the [Al phase] is less than 30 area%, or the surface roughness Ra is relatively small, so that it is presumed to exhibit a metallic luster.
[0031]
　On the other hand, at least [Al phase] and [Al / Zn / MgZn 2 ternary eutectic structure (ternary eutectic phase)] are present in the hot-dip galvanized layer, but [Al phase] is melted in the second region. It is distributed relatively widely in the entire thickness direction without being unevenly distributed on the steel plate side in the thickness direction of the plating layer. Therefore, in the second region, the exposure ratio of the [Al phase] on the surface of the hot-dip galvanized phase is 30 area% or more.
　Further, as described above, in the second region, the exposed area of ​​the [Al phase] is larger than that in the first region. The [Al phase] is a phase formed at the initial stage of solidification of the hot-dip plating layer, and precipitates in a dendrite shape. Since a relatively large amount of [Al phase] precipitated in the form of dendrite is present on the surface of the hot-dip galvanized layer, the surface roughness Ra of the second region is in the range of 10 nm or more and 200 nm or less.
　As described above, in the second region, the exposure ratio of the [Al phase] is 30 area% or more, or the surface roughness Ra is relatively large, so that the light incident on the second region is diffusely reflected and white. It is presumed that it will become gray.
[0032]
　The [Al phase] generated when the hot-dip galvanized layer solidifies is usually deposited in the entire thickness direction of the hot-dip galvanized layer. However, if a substance that becomes a solidified nucleus is arranged in advance on the surface of the steel sheet, in the region where the solidified nucleus is arranged, when the molten metal adhering to the surface of the steel sheet solidifies, a large number of solidified nuclei on the surface of the steel sheet become nuclei. Al phase] precipitates. The generated [Al phase] segregates on the side relatively close to the steel sheet. Further, in the region where the solidified nuclei exist, the [Al phase] is generated at a relatively high density, so that the [Al phase] itself does not become coarse and remains fine. Therefore, in the region where the solidified nuclei are arranged, the [Al phase] does not grow to the surface side of the hot-dip galvanized layer, and the exposure ratio of the [Al phase] becomes small.
　As described above, the region where the solidified nuclei exist on the surface of the steel sheet becomes the first region of the hot-dip plating layer, and the region where the solidified nuclei do not exist becomes the second region of the hot-dip plating layer. Further, since the first region is formed by the mechanism as described above, solidified nuclei are present at the interface between the steel plate and the hot-dip galvanized layer in the first region. More specifically, at the interface between the steel plate in the first region and the hot-dip plating layer, carbon (C), nickel (Ni), calcium (Ca), boron (B), phosphorus (P), titanium (Ti), Any one or more of the elements selected from the group consisting of manganese (Mn), iron (Fe), cobalt (Co), zirconium (Zr), molybdenum (Mo), and tungsten (W), or the above-mentioned There are compounds containing any one or more of the elements.
　To confirm the presence of the above-mentioned elements or compounds at the interface between the steel sheet in the first region and the hot-dip plating layer, a glow discharge emission spectrophotometer (GDS) is used to dig a sample by sputtering in the first region. It can be confirmed by performing elemental analysis at the interface between the steel sheet and the hot-dip plating layer.
[0033]
　Therefore, before immersing the steel sheet in the hot-dip galvanizing bath, the solidified nuclei are formed on the surface of the steel sheet in the form of any one of straight parts, curved parts, figures, numbers, symbols and letters, or a combination of two or more of them. By arranging, the first region having these shapes can be formed in the hot-dip galvanized layer.
[0034]
　The surface roughness Ra usually differs depending on the measuring method, but the arithmetic mean roughness (Ra) of the present embodiment is measured by the following method. First, the surface of the hot-dip galvanized layer is imaged with an atomic force microscope (AFM), and five 25 μm 2 field-of-view images are prepared in each of a region and a second region.
The arithmetic mean roughness (Ra) of these images is obtained, and the average value of the arithmetic mean roughness (Ra) of the five images is obtained in each of the first region and the second region, respectively. The average value of the arithmetic mean roughness (Ra) obtained in this way is defined as the arithmetic average roughness Ra of the first region and the second region.
[0035]
　The exposure ratio of [Al phase] is measured by the following method. First, the surface of the hot-dip galvanized layer is photographed with a 100x scanning electron microscope. Prepare five 1 mm 2- field images of the first region and five 1 mm 2- field images of the second region . For each image, the area of ​​the [Al phase] exposed on the surface of the hot-dip galvanized layer is measured using commercially available image analysis software. In each of the first region and the second region, the average value of the exposed areas of [Al phase] in the five images is calculated. Then, by dividing the average value of the exposed area of ​​the [Al phase] by the total area of ​​the observation field of view, the average exposed area ratio (%) of the [Al phase] in the observation field of view is calculated in the first region and the second region, respectively. Ask for. The average exposed area ratio (%) of the [Al phase] obtained in this way is defined as the exposure ratio of the [Al phase].
[0036]
　
　The Zn-Al-Mg-based hot-dip galvanized steel sheet according to the present embodiment has a chemical conversion-treated film layer or coating film on the surface of the hot-dip galvanized layer for the purpose of improving designability and corrosion resistance. It may have a layer. Here, the type of the chemical conversion treatment film layer or the coating film layer is not particularly limited, and a known chemical conversion treatment film layer or coating film layer can be used.
[0037]
　[Method for Manufacturing Zn-Al-Mg Hot-Dip Galvanized Steel Sheet]
　Hereinafter, the method for manufacturing the Zn-Al-Mg-based hot-dip galvanized steel sheet of the present embodiment will be described.
　First, a hot-rolled steel sheet is manufactured, and if necessary, hot-rolled sheet is annealed. After pickling, cold rolling is performed to obtain a cold rolled plate. After degreasing and washing the cold-rolled plate with water, it is annealed (annealed by cold-rolled plate), and the cold-rolled plate after annealing is immersed in a hot-dip galvanizing bath to form a hot-dip plating layer.
[0038]
　Here, between cold rolling and immersion in a hot-dip galvanizing bath, solidified nuclei are attached to the surface of the steel sheet, and any one of straight parts, curved parts, figures, numbers, symbols and letters, or any of these, is attached. A pattern portion having a shape in which two or more of the above are combined is formed. Adhesion of solidified nuclei occurs either between cold rolling and cold-rolled sheet annealing, between cold-rolled sheet annealing and immersion in a hot-dip galvanizing bath, or just prior to the final annealing of cold-rolled sheet annealing. carry out.
[0039]
　The component that forms solidified nuclei (hereinafter, may be referred to as a solidified nucleation component) is not particularly limited as long as it is a component that forms solidified nuclei in the process of solidifying the plating layer. Examples of the solidification nucleating component include carbon (C), nickel (Ni), calcium (Ca), boron (B), phosphorus (P), titanium (Ti), manganese (Mn), iron (Fe), and cobalt. Any one or more of the elements selected from the group consisting of (Co), zirconium (Zr), molybdenum (Mo), and tungsten (W), or any one or more of the above-mentioned elements. Examples include compounds containing. The above components may be used in combination of 1 or 2 or more. As an example of the method of adhering the solidified nuclei to the surface of the steel sheet, in addition to the solidified nucleation component itself, a method of containing the solidified nucleation component in an alloy foil, resin, surfactant, ink, oil, etc. and adhering to the surface of the steel sheet. Can be mentioned. These solidified nucleation 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.
[0040]
　As a method of adhering the solidified nuclei to the surface of the steel sheet, for example, a method of transferring, applying, or spraying a material containing a solidified nucleation component to the surface of the steel sheet can be exemplified. For example, a foil transfer method using hot stamps and cold stamps, a printing method using various plates (gravure printing, flexographic printing, offset printing, silk printing, etc.), an inkjet method, a thermal transfer method using an ink ribbon, etc. , A general printing method can be used.
[0041]
　As an example of the transfer method using the alloy foil, there is a method in which a heated silicon roll is pressed against the alloy foil to transfer it to the surface of the steel sheet while adhering the alloy foil containing the solidified nucleation component to the surface of the steel sheet.
[0042]
　As an example of a printing method using a plate, a rubber roll or a rubber stamp is attached to a steel plate surface while an ink or a surfactant containing a component that becomes a solidification nucleus is attached to a rubber roll or a rubber stamp having a printing pattern formed on the peripheral surface. A method of pressing to transfer the ink or the surfactant can be mentioned. With this method, the solidified nucleation-forming component can be efficiently adhered to the surface of the steel sheet that is continuously passed through.
[0043]
　The amount of coagulated nuclei attached is preferably in the range of, for example, 50 mg / m 2 or more and 5000 mg / m 2 or less. If the amount of adhesion is less than 50 mg / m 2 , the first region may not be formed to the extent that it can be discerned with the naked eye, which is not preferable. On the other hand, when the adhesion amount exceeds 5000 mg / m 2 , the adhesion of the hot-dip plating layer may decrease, which is not preferable.
[0044]
　Next, the steel plate having the pattern portion formed on the surface is immersed in a hot-dip galvanizing bath. The hot-dip galvanizing bath preferably contains Al: 4 to 22% by mass and Mg: 1 to 10% by mass, and contains Zn and impurities as the balance. Further, the hot-dip galvanizing bath may contain Si: 0.0001 to 2% by mass. Further, the hot-dip galvanizing bath may contain 0.0001 to 2% by mass in total of any one or more of Ni, Ti, Zr, and Sr. Further, in the hot-dip galvanizing bath, any one or more of Fe, Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM, and Hf are 0 in total. It may contain .0001 to 2% by mass.
　The average composition of the hot-dip galvanized layer of this embodiment is almost the same as the composition of the hot-dip galvanized bath.
　The composition of the hot-dip galvanized layer can be measured by the following method. First, the surface coating film is removed with a coating film remover that does not erode the plating (for example, Neo River SP-751 manufactured by Sansai Kako Co., Ltd.), and then a hot-dip plating layer is used with hydrochloric acid containing an inhibitor (for example, Hiviron manufactured by Sugimura Chemical Industrial Co., Ltd.). Can be obtained by dissolving the solution and subjecting the obtained solution to inductively coupled plasma (ICP) emission spectroscopy.
[0045]
　The temperature of the hot-dip galvanizing bath is preferably in the range of 400 to 500 ° C. This is because if the temperature of the hot-dip galvanizing bath is within this range, a desired hot-dip galvanizing layer can be formed.
　Further, the amount of adhesion of the hot-dip galvanized layer may be adjusted by means such as gas wiping with respect to the steel sheet pulled up from the hot-dip galvanized bath. The amount of adhesion of the hot-dip plating layer is preferably adjusted so that the total amount of adhesion 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 Zn—Al—Mg hot-dip galvanized steel sheet is lowered, which is not preferable. If the amount of adhesion exceeds 600 g / m 2, the molten metal adhering to the steel sheet will hang down and the surface of the hot-dip plating layer cannot be smoothed, which is not preferable.
[0046]
　After adjusting the amount of adhesion of the hot-dip galvanized layer, the steel sheet is cooled. The cooling conditions may be, for example, cooling at a cooling rate of 3 to 25 ° C./sec until the temperature falls within the range of 300 to 340 ° C.
[0047]
　Cooling of the molten metal adhering to the steel sheet is started after the steel sheet is pulled out of the hot dip galvanizing bath. Although it depends on the composition of the hot-dip galvanizing bath, [Al phase] begins to precipitate from around 430 ° C. Next, [MgZn 2 ] began to precipitate from around 370 ° C., and [Al / Zn / MgZn 2 ternary eutectic structure (ternary eutectic phase)] began to precipitate from around 340 ° C. at about 300 ° C. or lower. Solidification of [ ternary eutectic structure of Al / Zn / MgZn 2 (ternary eutectic phase)] is almost completed.
[0048]
　At this time, in the region where the solidified nuclei are attached to the surface of the steel plate, as shown in FIG. 1, the [Al phase] 40 begins to precipitate with the solidified nuclei 30 as the nuclei (Step 1 in FIG. 1), and the [Al phase] 40 is the steel plate. A large amount is deposited near the interface between 10 and the molten metal (not shown). Since the [Al phase] 40 is generated at a relatively high density by the solidified nuclei 30, the [Al phase] 40 itself does not become coarse and remains fine. Therefore, the [Al phase] 40 does not grow to the surface side of the hot-dip plating layer 20, and the exposure ratio of the [Al phase] 40 becomes relatively small. On the surface of the molten metal (not shown), the surface becomes uneven as the [Al phase] 40 solidifies and shrinks (Step 2 in FIG. 1). After that, solidification of [Al / Zn / MgZn 2 ternary eutectic structure (ternary eutectic phase)] 50 begins, and the uneven surface in Step 2 gradually becomes gentle, and [Al phase] 40 A part of the surface is exposed to the surface (Step 3 in FIG. 1). In this way, it is presumed that the region where the solidified nuclei 30 exist on the surface of the steel sheet 10 becomes the first region of the hot-dip galvanized layer 20.
[0049]
　On the other hand, in the region where the solidified nuclei 30 are not attached to the surface of the steel sheet 10, the [Al phase] 40 is deposited in the entire thickness direction of the molten metal (not shown). That is, since the precipitation density of [Al phase] 40 is relatively low, the precipitation of [Al phase] 40 is not inhibited. As a result, the [Al phase] 40 becomes coarse. Therefore, since the [Al phase] 40 grows up to the surface side of the hot-dip galvanized layer 20, the exposure ratio of the [Al phase] 40 on the surface of the hot-dip galvanized layer 20 becomes relatively large.
　By such a mechanism, it is presumed that the region where the solidified nuclei 30 do not exist on the surface of the steel sheet 10 becomes the second region of the hot-dip galvanized layer 20.
[0050]
　When a chemical conversion treatment layer is formed on the surface of the hot-dip galvanized layer, the Zn—Al—Mg-based hot-dip galvanized steel sheet after the hot-dip galvanized layer is formed is subjected to chemical conversion treatment. The type of chemical conversion treatment is not particularly limited, and a known chemical conversion treatment can be used.
　When a coating layer is formed on the surface of the hot-dip plating layer or the surface of the chemical conversion treatment layer, Zn-Al-Mg-based hot-dip plating is performed after the hot-dip plating layer is formed or after the chemical conversion treatment layer is formed. The steel plate is coated. The type of coating treatment is not particularly limited, and a known coating treatment can be used.
[0051]
　According to the present embodiment, it is possible to provide a Zn—Al—Mg-based hot-dip galvanized steel sheet having high durability of the design and suitable plating characteristics such as corrosion resistance, and a method for producing the same. In particular, in the present embodiment, the range of the first region can be intentionally determined by adhering the solidified nuclei to the surface of the steel sheet in an arbitrary pattern, and the range of the first region can be determined intentionally, and a straight portion, a curved portion, a figure, a number, and a symbol can be determined. The first region can be arranged so as to form a shape in which any one of the characters and two or more of them are combined. As a result, various designs can be applied to the surface of the hot-dip galvanized layer without painting or grinding, and the distinctiveness and design of the steel sheet can be improved.
Example
[0052]
　Next, examples of the present invention will be described.
　(No. 1-11, 16-19)
　First, the steel sheet after cold rolling was degreased and washed with water. An ink containing the solidified nucleation component shown in Table 1 was adhered to a rubber plate having a shape in which a grid pattern at 50 mm intervals was transferred. By pressing this rubber plate against the steel sheet after washing with water, the ink adhered to the surface of the steel sheet. Then, the steel sheet was annealed by cold rolling. The steel sheet after annealing the cold-rolled sheet was immersed in a hot-dip galvanizing bath to form a hot-dip plating layer on the surface of the steel sheet. After that, the amount of adhesion was controlled by the wiping nozzle, and further cooling was performed. As a result, the No. 1 shown in Table 2 Zn—Al—Mg-based hot-dip galvanized steel sheets of 1 to 11 and 16 to 19 were produced.
[0053]
　(No. 12) A
　Zn—Al—Mg-based hot-dip galvanized steel sheet was produced in the same manner as above except that the ink was not transferred by the rubber plate. Then, a grid pattern at intervals of 50 mm was printed on the surface of the hot-dip galvanized layer by an inkjet method. This result is described as No. It is shown in Table 2 as 12.
[0054]
　(No. 13) A
　Zn—Al—Mg-based hot-dip galvanized steel sheet was produced in the same manner as above except that the ink was not transferred by the rubber plate. Then, the surface of the hot-dip galvanized layer was ground to form a grid pattern at intervals of 50 mm. This result is described as No. It is shown in Table 2 as 13.
[0055]
　(No. 14) In the same
　manner as above, Zn is used in the same manner as above, except that instead of adopting the method of pressing the rubber plate against the steel sheet after washing with water, the method of spraying the aqueous calcium carbonate solution on the steel sheet after washing with water in a grid pattern is adopted. -Al-Mg-based hot-dip galvanized steel sheet was manufactured. This result is described as No. It is shown in Table 2 as 14.
[0056]
　(No. 15) In
　the same manner as above, except that instead of adopting the method of pressing the rubber plate against the steel plate after washing with water, the method of transferring the nickel alloy foil to the steel plate after washing with water in a grid pattern was adopted. , Zn-Al-Mg-based hot-dip galvanized steel sheet was manufactured. This result is described as No. It is shown in Table 2 as 15.
[0057]
[Method for measuring surface roughness Ra]
　The surface of the hot-dip galvanized layer was imaged with an atomic force microscope (AFM), and five 25 μm 2 visual field images were prepared for each of the first region and the second region. The roughness curves of these images were obtained respectively, and the average value of the arithmetic mean roughness (Ra) of the five images was obtained in the first region and the second region, respectively. The average value of the arithmetic mean roughness (Ra) thus obtained was defined as the surface roughness Ra of the first region and the second region.
　In particular, for the second region, the number of images for obtaining the arithmetic mean roughness (Ra) may be increased in order to obtain the average value of the arithmetic mean roughness (Ra) more accurately.
[0058]
[Evaluation method of exposure ratio of [Al phase]] The
　surface of the hot-dip galvanized layer was photographed with a 100x scanning electron microscope. 1mm taken the first region 2 five images of the field of view, 1mm were taken second region 2 and the image of the field of view five pieces each. For each image, the area of ​​the [Al phase] exposed on the surface of the hot-dip galvanized layer was measured using commercially available image analysis software. In each of the first region and the second region, the average value of the exposed areas of [Al phase] in the five images was calculated. Then, by dividing the average value of the exposed area of ​​the [Al phase] by the total area of ​​the observation field of view, the average exposed area ratio (%) of the [Al phase] in the observation field of view is calculated in the first region and the second region, respectively. I asked for it. The average exposed area ratio (%) of the [Al phase] obtained in this way was taken as the exposure ratio of the [Al phase].
　For the second region, in order to improve the measurement accuracy of the exposure ratio of [Al phase], the number of images used for the measurement is increased, and the same measurement is performed with a 10x scanning electron microscope. You may.
[0059]
[Design]
　Whether or not the grid pattern was visible with respect to the test plates according to the examples and comparative examples was evaluated based on the following criteria. The evaluation was performed immediately after the test plate was manufactured and on the ones exposed to the outdoors for 6 months over time. A was passed in both the initial state and the time-lapse state.
[0060]
　A: You can see the grid even from 5m away.
　B: The grid cannot be seen from 5 m ahead, but the visibility is high from 2 m ahead.
　C: I can't see the grid from 2m away.
[0061]
　[Corrosion resistance]
　A corrosion acceleration test CCT conforming to JASO-M609 was carried out for 30 cycles on a test plate cut to 150 × 70 mm. Then, the corrosion resistance was evaluated as follows based on the occurrence of rust. A was accepted.
[0062]
　A: No rust is generated, and a beautiful design appearance is maintained.
　B: The appearance of the design is impaired due to the generation of rust.
　C: The appearance quality is significantly deteriorated due to the occurrence of rust.
[0063]
　As shown in Table 3, No. 1 to No. 11, No. 14 and No. The Zn—Al—Mg-based hot-dip galvanized steel sheet of the 15 examples of the present invention was excellent in both designability and corrosion resistance.
　In addition, No. 1 to No. 11, No. 14 and No. Elemental analysis was performed by a glow discharge emission spectroscopic analyzer (GDS) using 15 Zn—Al—Mg-based hot-dip plated steel sheets of the present invention as a sample, and they were used in all of the invention examples. The solidified nucleating component was detected at the interface between the steel sheet in the first region and the hot-dip plating layer.
[0064]
　2A and 2B show No. It is the observation result by the scanning electron microscope of the first region of 1. 3A to 3C show No. It is the observation result by the scanning electron microscope of the second region of 1.
　As can be seen from these figures, the second region had more white regions than the first region. This white region corresponds to the exposed portion of the [Al phase].
[0065]
　FIG. 4 shows No. It is a figure which shows the appearance of the hot dip galvanizing layer of 1 and the measurement result of the surface roughness by the AFM measurement of the 1st region, and the surface roughness by the AFM measurement of a 2nd region.
　As shown in FIG. 4, the surface roughness Ra of the first region 22 of the hot-dip galvanized layer of the example was 6.5 nm, and the surface roughness Ra of the second region 24 was 80.4 nm. From this result, it can be seen that the surface roughness Ra is significantly different between the first region and the second region.
[0066]
　On the other hand, although not shown, No. 1 in which a grid-like pattern is printed by an inkjet method. In No. 12, the grid-like pattern became thin and the design was deteriorated by outdoor exposure for 6 months.
　Similarly, although not shown, No. 2 in which a grid-like pattern was formed by grinding. In No. 13, the thickness of the plating layer at the ground portion was reduced, and the corrosion resistance at the ground portion was reduced.
　Further, although not shown in the same manner, No. No. 1 was produced by the same production method as 1 to 11, but the composition of the hot-dip galvanized layer was outside the scope of the present invention. In No. 16, the exposure ratio of the [Al phase] was lowered as a whole, and a suitable metal structure could not be obtained due to the crystallization of Zn as primary crystals, so that both the design property and the corrosion resistance were lowered. Similarly, No. In No. 17, the exposure ratio of the [Al phase] increased as a whole, resulting in a decrease in designability. In No. 18, since the amount of Mg is small, the corrosion resistance is lowered. In No. 19, the designability was deteriorated due to the crystallization of the Mg compound.
　In addition, No. In the hot-dip galvanized layers 12, 13 and 16 to 19, patterns such as straight portions formed by the first region were not formed.
　In addition, No. 1 to No. 11, No. 14 and No. All the hot-dip galvanized layers 15 contained [Al phase] and [ ternary eutectic structure of Al / Zn / MgZn 2 (ternary eutectic phase)].
[0067]
　FIG. 5 shows the surface of a hot-dip galvanized steel sheet in which a character string (Kanji and alphabet) and a mark are represented in the first region by applying an ink containing carbon and then hot-dip galvanizing.
　In FIG. 6, the above-mentioned No. In the same manner as in No. 14, the surface of the hot-dip galvanized steel sheet whose curve is represented by the first region is shown by spraying an aqueous solution of calcium carbonate and then hot-dip galvanizing.
　In FIG. 7, the above-mentioned No. In the same manner as in No. 15, the surface of the hot-dip galvanized steel sheet whose alphabets and numbers are represented by the first region is shown by hot-dip galvanizing after transferring the nickel alloy foil to the foil.
　According to the present invention, characters and marks can be arbitrarily represented by the first region on the surface of the hot-dip galvanized steel sheet.
[0068]
[table 1]

[0069]
[Table 2]

[0070]
[Table 3]

Description of the sign
[0071]
　1 Zn-Al-Mg hot-dip galvanized steel sheet
　10 Steel sheet
　20 Hot-dip galvanized layer
　22 First region
　24 Second region
　30 Solidification nuclei
　40 [Al phase]
　50 [Al / Zn / MgZn 2 ternary eutectic structure (ternary) Crystal phase)]
The scope of the claims
[Claim 1]
　; Steel plate and
　a hot dip plated layer formed on the surface of the steel sheet;
equipped with,
　the molten plating layer:
　　the average composition, Al: 4 - 22 wt%, Mg: 1 containing ~ 10 wt%, the balance being ; wherein Zn and impurities
　　as a metallographic structure, and Al phase, Al / Zn / MgZn 2 and a ternary eutectic phase of;
　made from the surface of the molten plating layer, a first region and a second region,
　wherein The first region is arranged so as to form a shape in which any one of a straight portion, a curved portion, a figure, a number, a symbol and a character, or two or more of these are combined, and
　the first region and the second region are combined.
A Zn—Al—Mg-based hot-dip galvanized steel sheet, characterized in that the region satisfies at least one of the following (a) and (b) .
　(A) The first region is a region where the exposure ratio of the Al phase on the surface is less than 30 area%, and the second region is a region where the exposure ratio of the Al phase on the surface is 30 area% or more. Is.
　(B) The first region is a region having a surface roughness Ra of 1 nm or more and less than 10 nm, and the second region is a region having a surface roughness Ra of 10 nm or more and less than 200 nm.
[Claim 2]
　Any of the elements selected from the group consisting of C, Ni, Ca, B, P, Ti, Mn, Fe, Co, Zr, Mo, and W at the interface between the steel sheet and the hot-dip galvanized layer in the first region. The Zn—Al—Mg-based hot-dip galvanized steel sheet according to claim 1, wherein a compound containing one or more, or one or more of the above elements is present.
[Claim 3]
　The Zn—Al—Mg-based hot-dip galvanized steel sheet according to claim 1 or 2, wherein the hot-dip galvanized layer further contains Si: 0.0001 to 2% by mass in an average composition.
[Claim 4]
　The hot-dip galvanized layer further contains 0.0001 to 2% by mass in total of any one or more of Ni, Ti, Zr, and Sr in an average composition. The Zn—Al—Mg-based hot-dip galvanized steel sheet according to any one of 3.
[Claim 5]
　The hot-dip galvanized layer further has an average composition of any of Fe, Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM, Hf, C, Mo, and W. The Zn—Al—Mg-based hot-dip galvanized steel sheet according to any one of claims 1 to 4, wherein one or more of them are contained in a total amount of 0.0001 to 2% by mass.
[Claim 6]
The Zn—Al—Mg-based hot-dip galvanized steel sheet according to any one of claims 1 to 5, 　wherein the amount of adhesion of the hot-dip galvanized layer is 30 to 600 g / m 2 in total on both sides of the steel sheet.
[Claim 7]
　A solidified nucleus is attached to the surface of the steel sheet, and a pattern portion having a shape in which any one of a straight portion, a curved portion, a figure, a number, a symbol and a character, or two or more of these is combined is formed on the surface of the steel plate. The
　steel sheet having the pattern portion formed on the surface thereof is hot-dip galvanized with an average composition of Al: 4 to 22% by mass and Mg: 1 to 10% by mass, and the balance containing Zn and impurities. A
method for producing a Zn—Al—Mg-based hot-dip galvanized steel sheet, which comprises a step of immersing in a bath and;
[Claim 8]
　One or more of the elements selected from the group consisting of C, Ni, Ca, B, P, Ti, Mn, Fe, Co, Zr, Mo, and W, or the solidified nuclei of the element. The method for producing a Zn—Al—Mg-based hot-dip galvanized steel sheet according to claim 7, wherein the compound contains any one or more of them.
[Claim 9]
　The method for producing a Zn—Al—Mg-based hot-dip galvanized steel sheet according to claim 7 or 8, wherein the hot-dip galvanized bath further contains Si: 0.0001 to 2% by mass in an average composition.
[Claim 10]
　7. To claim 7, the hot-dip galvanizing bath further contains 0.0001 to 2% by mass of any one or more of Ni, Ti, Zr, and Sr in an average composition. 9. The method for producing a Zn—Al—Mg-based hot-dip galvanized steel sheet according to any one of 9.