TWI552864B - Preparation method of quasi - crystalline plated steel sheet and quasi - crystalline plated steel sheet - Google Patents

Description

Method for producing quasi-crystallized plated steel sheet and quasi-crystallized plated steel sheet Field of invention

The present invention relates to a method for producing a quasi-crystalline plated steel sheet and a quasi-crystalline plated steel sheet.

Background of the invention

Generally, from the viewpoint of rust prevention, the outer panel of an automobile uses a plated steel sheet and mainly a plated zinc-plated steel sheet is used. The alloyed zinc-plated steel sheet is alloyed after the galvanization of the steel sheet, and the Fe is improved from the base material, that is, the steel sheet (the mother steel sheet) in the plating layer, thereby improving the weldability and the corrosion resistance after coating. Plated steel. On the other hand, in the case of alloying a zinc-plated steel sheet, since the Fe is diffused from the mother steel sheet to make the plating layer hard, the plating layer is easily peeled off, and there is also a soft melt plating called pulping and flaking. A problem unique to zinc steel sheets.

A plated steel sheet having a hard plating layer is likely to cause cracks in the plating layer due to external pressure, and when a crack occurs, the crack propagates to the interface with the mother steel sheet and the plating layer peels off from the interface and falls off. For example, when a plated zinc-plated steel sheet is used in an outer panel of a car, the traveling vehicle is peeled off due to the stone beating and the coating is peeled off simultaneously with the plating layer, and the mother steel sheet becomes easily exposed and corroded than the unalloyed soft plating. The plate is more intense (low peeling resistance) drop).

Here, in order to improve the peeling resistance of the outer panel of the automobile, the charging is used. A plated steel sheet having a plating layer having a high corrosion resistance which is sufficiently resistant to corrosion from the peeling portion is preferably provided as an outer sheet. In order to improve the peeling characteristics, it is easy to use a soft plating layer, a hot-dip Zn steel plate, or a Zn-plated steel plate. However, when the plated steel sheet is peeled off due to peeling or the like, the corrosion system is rapidly performed. Therefore, the peeling-off part is not completely solved. When the plated steel sheet is subjected to corrosion, the pitting corrosion portion becomes too large and red rust is generated from the center portion.

For example, Patent Document 1 discloses a Zn-Al-Mg-Si plating. In the steel plate, Patent Document 2 discloses a molten Zn-Mg-based alloy plated steel sheet as a plated steel sheet having excellent corrosion resistance. In the plating layer described in Patent Document 1, a plated steel sheet-based Zn-based plated steel sheet in which various alloying elements such as Al, Mg, and Si are added to improve corrosion resistance is used, and a relatively soft plating layer is used. Further, the peeling portion was small, but when the peeling portion and the peeling portion of the coating film were generated, pitting corrosion was still performed early. Since the red rust is still generated from the center portion as the progress of the corrosion progresses, there is no sufficient corrosion resistance. Therefore, the peeling resistance of the plated steel sheet which improved the corrosion resistance based on the patent document 1 cannot be said to be sufficient.

Patent Document 2 describes a Zn-Mg-based alloy plated steel sheet as a means for solving the above problems. Since the plating layer contains a large amount of Mg, it is sufficiently provided with an anti-corrosion ability, and is an effective plated steel sheet which does not cause red rust for a long period of time even if the pitting progresses. However, in the plated steel sheet described in Patent Document 2, Zn ₃ Mg ₇ is formed in the plating layer, and the hardness rise becomes intense and the occurrence of pitting corrosion becomes too large, so that the peeling resistance is remarkably lowered.

Here, in order to have both corrosion resistance and peeling resistance, a means for forming a plating layer from a plurality of layers and combining the plurality of layers is conceivable. For example, Patent Document 3 discloses a method of forming a hard Mg having high corrosion resistance by ion plating on the surface of a soft low alloy plating layer (a zinc alloy plating layer) formed on a steel sheet. Al alloy plating layer. When the plating layer is stratified by laminating a soft low alloy plating layer and a hard and highly corrosion-resistant Mg-Al alloy plating layer, it is possible to have both corrosion resistance and peeling resistance. However, in practice, since the mother layer of the plating layer, that is, the low alloy plating layer is simply alloyed zinc, the corrosion resistance system is compared with the alloy plated steel sheets disclosed in Patent Document 1 and Patent Document 2. Poor. In addition, in order to obtain the corrosion resistance equivalent to the corrosion resistance disclosed in Patent Documents 1 and 2, the plated steel sheet obtained by laminating the plating layer disclosed in Patent Document 3 must be ion-plated by ion plating. The film thickness of the formed upper Mg-Al alloy plating layer is relatively thick. However, the method of thickening the film thickness by the ion spray method is difficult to produce a plated steel sheet having excellent high corrosion resistance and peeling resistance. Moreover, since it is necessary to perform the two-step process of alloying zinc and ion plating, there is also a problem that the cost rises.

As described above, in the prior art, an alloy-based plated steel sheet to which a relatively large amount of alloy is added in order to improve corrosion resistance has not been disclosed as having a peeling resistance.

The quasicrystal is a crystal structure first discovered by Daniel Shechtman in 1982, which has an atomic arrangement of the icosahedron. It is known that the crystal structure is not available in usual metals and alloys. The aperiodic crystal structure of specific rotational symmetry (for example, 5 symmetry) is designed as a non-periodic structure represented by a three-dimensional Penrose pattern and an equivalent crystal structure.

Discover the configuration of the novel metal atom (ie, the novel crystal knot After the structure, a quasi-crystal structure having a quasi-periodic structure and having a specific rotational symmetry is attracting attention. In recent years, it has been clearly understood that quasicrystals can also be obtained by crystal growth. However, conventionally, the quasi-crystal production method is usually a liquid quenching method. Therefore, the shape of the quasi-crystal is limited to a powder, a foil, and a small piece, and therefore, a practical example using a quasi-crystalline product is very small.

Patent Document 4 and Patent Document 5 disclose a high strength Mg-based alloy and its method of manufacture. These Mg-based alloys are alloys having excellent strength and elongation by dispersing and depositing a hard quasi-crystalline phase having a particle diameter of about several tens of nanometers to several hundreds of nanometers in a metal structure. In Patent Document 4 and Patent Document 5, the quasi-crystal is used as a hard property.

Further, Patent Document 6 discloses a method of crystallizing using Al standard. Thermoelectric material. Patent Document 6 utilizes characteristics in which quasi-crystallization has excellent thermoelectric characteristics. Patent Document 7 discloses a heat-resistant catalyst using a quasi-crystalline Al alloy (Al-based crystal) as a precursor and a method for producing the same. In Patent Document 7, a quasi-crystal having a periodic crystal structure is brittle and easily broken. As described above, in the conventional invention, the quasicrystal is dispersed as fine particles or the quasicrystals of fine particles are solidified and molded.

As a form of utilization with these inventions, it is a patent Document 8, discloses that a conditioning device containing quasi-crystals is coated with a metal. in According to Patent Document 8, the alloy of the quasi-crystalline alloy powder having excellent corrosion resistance, which is composed of Al, Fe, and Cr, is sprayed, thereby imparting excellent wear resistance and corrosion resistance to salt to the conditioning tool. Coated.

As described above, the Mg reference crystal system is utilized as having excellent The material of the strength, the Al reference crystal system is used as a member having excellent strength, a thermoelectric material, a conditioning tool, and the like. However, such quasi-crystalline systems are not necessarily used in many fields.

The quasi-crystalline system has excellent properties derived from a unique crystal structure. can. However, its characteristics are only partially explained clearly, and at present, it cannot be said that it is a material that has been widely used in industry. The present inventors attempted to apply a quasi-crystal which has not been utilized in the industry to a plating layer of a plated steel sheet, and at the same time, to improve corrosion resistance and peeling resistance.

Prior technical literature Patent literature

Patent Document 1: Japanese Laid-Open Patent Publication No. 2001-355055

Patent Document 2: Japanese Laid-Open Patent Publication No. 2008-255464

Patent Document 3: Japanese Patent Laid-Open No. 4-52284

Patent Document 4: Japanese Laid-Open Patent Publication No. 2005-113235

Patent Document 5: Japanese Laid-Open Patent Publication No. 2008-69438

Patent Document 6: Japanese Patent Laid-Open No. Hei 8-176762

Patent Document 7: Japanese Laid-Open Patent Publication No. 2004-267878

Patent Document 8: Japanese Patent Publication No. 2007-525596

Summary of invention

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a quasi-crystalline plated steel sheet and a quasi-crystalline plated steel sheet having both corrosion resistance and peeling resistance.

The inventors of the present invention have studied a Zn-Mg-based alloy-plated steel sheet, and have studied a structure in which a plating layer is formed by laminating a plurality of layers of different properties as a means for obtaining good peeling resistance. As a result, it was found that in the plating layer composed of the laminated structure, the properties of the layer on the surface layer side and the layer inside the plating layer are greatly different, and the surface layer of the plating layer is generated from the external pressure of the surface layer of the plating layer. The crack system does not easily progress to the inside, and the peeling resistance can be greatly improved.

In addition, it has been found that by increasing the quasi-crystalline phase while containing Al in the plating layer, the corrosion resistance is improved, and an alloy layer is formed on the interface between the plating layer and the base material steel sheet in addition to the plurality of layers. A quasi-crystalline plated steel sheet having corrosion resistance and peeling resistance which can be further advanced.

Further, as a method for producing a quasi-crystalline plated steel sheet, it was found that a plating layer was formed by plating with a Zn-Mg-based alloy in a molten state, and then heated to a predetermined temperature region for a predetermined period of time. According to such a manufacturing method, the plating layer can be separated into two layers: a relatively soft layer composed of fine crystal grains; and a dendritic hard layer located inside the plating layer; and can be manufactured at low cost. The characteristic features a quasi-crystalline plated steel sheet.

The present invention is based on the above knowledge, and the gist thereof is under.

(1) A quasi-crystalline plated steel sheet comprising: a plating layer on at least one surface of the steel sheet; and an alloy layer located at an interface between the plating layer and the steel sheet and interposed by Al-Fe metal The chemical composition of the plating layer in terms of atomic % includes: Zn: 28.5% to 50%, Al: 0.3% to 12%, La: 0% to 3.5%, Ce: 0% to 3.5%, Y: 0%~3.5%, Ca: 0%~3.5%, Sr: 0%~0.5%, Si: 0%~0.5%, Ti: 0%~0.5%, Cr: 0%~0.5%, Fe: 0%~2%, Co: 0%~0.5%, Ni: 0%~0.5%, V: 0%~0.5%, Nb: 0%~0.5%, Cu: 0%~0.5%, Sn: 0% ~0.5%, Mn: 0%~0.2%, Sb: 0%~0.5%, Pb: 0%~0.5%, and the remaining part is composed of Mg and impurities; the plating layer has the order from the side of the steel plate a first plating layer comprising a structure containing a MgZn phase, a Mg phase, and a quasi-crystalline phase; and a second plating layer on the first plating layer and containing a Mg ₅₁ Zn ₂₀ phase The structure of the Zn phase and the quasi-crystalline phase.

(2) The quasi-crystalline plated steel sheet according to (1), wherein the chemical composition of the plating layer is in atom%, and contains: Zn: 32% to 40%, Al: 2% to 5%, Ca: 1% ~ 2.5%, and the remainder is composed of Mg and impurities; and the aforementioned chemical composition satisfies: Zn / Al = 7.5 ~ 18, Ca / Al = 0.4 ~ 1.1; in addition, the largest crystal grain of the second plating layer The diameter is 1 μm or less in terms of the circle equivalent diameter.

(3) The quasi-crystalline plated steel sheet according to (1) or (2), wherein the MgZn phase of the first plating layer is observed when the plating layer is viewed in a cross section parallel to the cutting direction in the thickness direction It is composed of crystal grains having a circle equivalent diameter of 1 μm or more, and the quasi-crystalline phase of the first plating layer is composed of a structure growing in the thickness direction.

(4) The quasi-crystalline plated steel sheet according to any one of (1) to (3), wherein, when the plating layer is viewed in a cross section parallel to the cutting direction in the thickness direction, the second plating layer is The cross-sectional area of the entire plating layer is 90% or more of the area of the first crystal layer having a maximum crystal grain size of 1 μm or less in terms of a circle equivalent diameter.

(5) The quasi-crystalline plated steel sheet according to any one of (1) to (4), wherein the first plating layer is viewed in a cross section parallel to the cutting direction in the thickness direction, relative to the first The cross-sectional area of the entire plating layer is 10% to 70% of the area of the MgZn phase in the first plating layer.

The quasi-crystalline plated steel sheet according to any one of (1) to (5), wherein the second plating layer does not contain a Mg phase.

The quasi-crystalline plated steel sheet according to any one of (1) to (6), wherein the second plating layer has an average Vickers hardness of 250 to 350 Hv.

The quasi-crystalline plated steel sheet according to any one of (1) to (7), wherein the alloy layer contains at least one of Fe ₅ Al ₂ or Al _3.2 Fe as the aforementioned Al-Fe intermetallic layer a compound, and the alloy layer has a thickness of 10 nm to 200 nm.

(9) A method for producing a quasi-crystalline plated steel sheet, comprising the steps of: a plating step of disposing a molten alloy in a molten state on at least one of the surfaces of the steel sheet, the chemical composition of the plating alloy being atomic % Calculated, containing: Zn: 28.5%~50%, Al: 0.3%~12%, La: 0%~3.5%, Ce: 0%~3.5%, Y: 0%~3.5%, Ca: 0%~3.5 %, Sr: 0%~0.5%, Si: 0%~0.5%, Ti: 0%~0.5%, Cr: 0%~0.5%, Fe: 0%~2%, Co: 0%~0.5%, Ni: 0% to 0.5%, V: 0% to 0.5%, Nb: 0% to 0.5%, Cu: 0% to 0.5%, Sn: 0% to 0.5%, Mn: 0% to 0.2%, Sb: 0%~0.5%, Pb: 0%~0.5%, And the remaining portion is composed of Mg and an impurity; and the first cooling step is performed by cooling the plating alloy in the molten state at an average cooling rate of 10° C./sec or less to a temperature range of 330° C. or less to form a surface of the steel sheet. Forming a plating layer; and maintaining a temperature increase step of heating the plated layer to a temperature range of 350° C. to 400° C. at a temperature increase rate of 10 to 50° C./second after the first cooling step, and simultaneously Holding for 5 to 30 seconds; and a second cooling step of cooling the plating layer at a cooling rate of 20 ° C /sec or more after the temperature rising and holding step.

(10) The method for producing a quasi-crystalline plated steel sheet according to (9), wherein the plating step is performed by a hot-dip plating method, and after the steel sheet is taken out from the molten plating bath, the first step is performed 1 cooling step.

(11) The method for producing a quasi-crystalline plated steel sheet according to any one of (8) to (10), wherein the chemical composition of the molten alloy in the molten state is in atom%, and contains: Zn: 32%~ 40%, Al: 2% to 5%, Ca: 1% to 2.5%, and the remainder is composed of Mg and impurities; and the aforementioned chemical composition satisfies Zn/Al = 7.5 to 18, Ca / Al = 0.4 to 1.1 .

As described above, according to the present invention, it is possible to provide a quasi-crystalline plated steel sheet which is superior in both corrosion resistance and peeling resistance as compared with the conventional molten Zn-Mg-based alloy plated steel sheet.

In addition, the quasi-crystalline plated steel sheet according to the present invention can be suitably used for components related to building materials, home electric appliances, and energy, in addition to automotive members that are required to have excellent peeling resistance, and are based on the height of such members. Life expectancy, reduction of maintenance labor, cost reduction, etc. The development has contributed.

1‧‧‧2nd plating layer (micro layer)

2‧‧‧1st plating layer (compound layer)

3‧‧‧ alloy layer (interface alloy layer)

4‧‧‧Cracks (exfoliation cracks)

Fig. 1 is an example of a cross-sectional structure photograph (TEM image) of a plating layer according to an embodiment of the present invention.

2A is an example of an electron beam diffraction image of a Mg ₅₁ Z ₂₀ phase contained in a second plating layer in a plating layer according to an embodiment of the present invention.

2B is an example of an electron beam diffraction image of a quasi-crystalline phase contained in the second plating layer in the plating layer according to the embodiment of the present invention.

3A is an example of an electron beam diffraction image of a MgZn phase contained in a first plating layer in a plating layer according to an embodiment of the present invention.

3B is an example of an electron beam diffraction image of a quasi-crystalline phase contained in the first plating layer in the plating layer according to the embodiment of the present invention.

4 is a cross-sectional TEM image of the plating layer as shown in FIG. 1, and shows a TEM in which cracks (peel cracks) 4 of the plating layer after the peeling test progress along the interface between the fine layer 1 and the compound layer 2. image.

Form for implementing the invention

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, constituent elements that have substantially the same functional configuration are denoted by the same reference numerals, and the repeated description is omitted.

(for quasi-crystalline plated steel sheets)

One of the features of the quasi-crystalline plated steel sheet of the present invention is that a plating layer having a specific chemical composition is set as a specific structure and the plating is performed. The coating layer is formed on the surface of a mother steel sheet (hereinafter, also simply referred to as "steel sheet").

Hereinafter, first, the chemical composition and the structure of the plating layer will be described in detail with respect to the quasi-crystalline plated steel sheet according to the embodiment of the present invention.

The quasi-crystalline plated steel sheet according to the embodiment includes: a plating layer on at least one surface of the steel sheet; and an alloy layer located at an interface between the plating layer and the steel sheet and made of Al-Fe metal The composition of the inter-compound. Here, the chemical composition of the plating layer is, in atom%, containing: Zn: 28.5% to 50%, Al: 0.3% to 12%, La: 0% to 3.5%, Ce: 0% to 3.5%, Y: 0%~3.5%, Ca: 0%~3.5%, Sr: 0%~0.5%, Si: 0%~0.5%, Ti: 0%~0.5%, Cr: 0%~0.5%, Fe: 0% ~2%, Co: 0%~0.5%, Ni: 0%~0.5%, V: 0%~0.5%, Nb: 0%~0.5%, Cu: 0%~0.5%, Sn: 0%~0.5 %, Mn: 0% to 0.2%, Sb: 0% to 0.5%, Pb: 0% to 0.5%, and the remainder is composed of Mg and impurities.

Further, the plating layer containing the quasi-crystalline plated steel sheet of the present embodiment has, in order from the steel sheet side, a first plating layer composed of a structure containing a MgZn phase, a Mg phase, and a quasi-crystalline phase; A plating layer on the first plating layer and containing a Mg ₅₁ Zn ₂₀ phase, a Zn phase, and a quasi-crystalline phase.

Further, the steel sheet which is the base material of the quasi-crystalline plated steel sheet according to the present embodiment is not particularly limited. Examples of such a steel sheet include various steel sheets such as Al killed steel, extremely low carbon steel, high carbon steel, various high tensile steels, and Ni and Cr containing steel. Further, the production conditions of the steel sheet such as the steel forming method of the base material steel sheet, the strength of the steel, the hot rolling method, the pickling method, and the cold rolling method are not particularly limited. That is, the manufacturing conditions and materials for the steel sheet provided as the base material of the quasi-crystalline plated steel sheet The quality system is not particularly limited.

<Chemical composition for the plating layer>

First, the chemical composition of the plating layer will be described below.

Further, the plating layer of the present embodiment has a characteristic structure in which various phases of different forms, crystal structures, and compositions are layered, as will be described later. The morphology and crystal structure of the plating layer can be observed. However, since it is difficult to define the component composition of each layer constituting the plating layer, the chemical composition of the plating layer of the present invention is set as a predetermined plating. The chemical composition of the layer as a whole. Further, in the following description, the % of the chemical component is shown to mean the atomic % unless otherwise notified. Since the structural formula of the metal phase and the intermetallic compound is usually expressed, the atomic ratio is used instead of the mass ratio.

[Zn (zinc): 28.5%~50%]

Basically, the wettability and reactivity of the Mg-based steel sheet and the steel sheet are poor, and only the Mg plating layer is very difficult to form on the steel sheet. This is because Fe in the steel sheet does not diffuse into the plating layer, so that the plating layer is not adhered to the steel sheet. Therefore, by containing a certain concentration or more of Zn in the plating layer, the reactivity (adhesion) with the mother steel sheet can be improved, and the plating layer containing Mg as a main component can be stably formed on the steel sheet.

Further, the Zn-based atom has a radius close to that of the chemical component described later. Generally, when Al is added to the plating layer, the Al system can be more displaced from the Zn position than the Mg and Ca positions. In the present embodiment, it is disclosed that by forming a composition of Mg-Zn in the plating layer as described above, formation of a fragile intermetallic compound can be avoided, and a multilayer structure having excellent peeling resistance can be formed. because As described above, in the case where Al is added as a chemical component, the substitution behavior with the Zn position also changes. Therefore, it is necessary to define the chemical composition of Zn in accordance with the amount of addition of Al. The appropriate Zn content of the plating layer that satisfies this condition is 28.5% to 50%.

Quasi-crystallization can be obtained by setting the Zn content to 28.5% to 60%. The phase serves as the metal structure of the plating layer. When the Zn content is less than 28.5%, a quasi-crystalline phase cannot be formed in the plating layer. Further, when the Zn content is more than 50%, in the production method disclosed in the present invention, the quasi-crystalline phase cannot be favorably formed and dispersed in the plating layer. In order to well control the formation of the quasi-crystalline phase, the Zn content can be set to 30% to 50%. The Zn content is preferably from 35% to 45%. Further, the Zn content is more preferably 36% to 40%. By setting the Zn content to 36% to 40%, the quasi-crystalline phase can be favorably formed at a predetermined position of the plating layer, and the corrosion resistance can be further improved.

[Al (aluminum): 0.3% to 12%]

Al is an element that enhances the performance of the plating layer. Specifically, the planar corrosion resistance of the plating layer can be improved by including Al in the plating layer. Further, by containing Al, a phase in the plating layer and a part of Zn existing in the intermetallic compound are substituted with Al to form a substitutional solid solution. As a result, the insulating property of the plating layer is increased, and the corrosion resistance is increased, and the ion reaction at the time of plating dissolution can be suppressed to reduce the corrosion loss.

In particular, the displacement effect, based for the Zn Mg ₅₁ Zn ₂₀ contained is likely to occur, and the composition ratio of Zn becomes constant when, Mg crystal grains line ₅₁ Zn ₂₀ is more easily reduced, so that the plane of the corrosion resistance further enhance The tendency. The inventors of the present invention have estimated that the composition range of the Zn and Al is important to satisfy the Zn/Al=7.5 to 18 system. Further, in order to further improve the planar corrosion resistance, it is also important to satisfy the composition ratio with Ca, and it is estimated that the composition range of Ca and Al satisfies Ca/Al = 0.4 to 1.1.

That is, it usually contains only a quasi-crystalline phase and can expect a certain resistance. Though the etching property is improved, the effect of further improving the corrosion resistance of the flat portion can be expected by further limiting the component composition and producing the plated steel sheet by the production method of the present invention.

Further, Al is also an element which imparts a certain effect to the formation and growth of quasi-crystals, and as will be described later, the interface between the plating layer and the mother steel sheet is formed by appropriately controlling the heat history during the production of the plating layer. The Al-Fe intermetallic compound layer such as Al3Fe (in more detail, Al _3.2 Fe) or Fe ₅ Al ₂ can further improve the adhesion of the plating layer and further improve the peeling resistance.

In order to obtain the effect as described above more reliably, the Al content is set. It is 0.3%~12%. When the Al content is less than 0.3%, the effect of increasing the insulating property obtained by substituting Zn cannot be sufficiently enjoyed, and the formation of the intermetallic compound layer may be insufficient. Also, the multi-layer structure was not observed and almost no quasi-crystalline phase was formed.

On the other hand, when the Al content is more than 12%, the details are as follows. (2) The change in the fine structure of the plating layer is a result of the coarse primary crystal Al phase dispersed in the structure of the microstructure, and the result of the formation of the multi-layer structure, and the peeling resistance is likely to be low. Further, since the Al phase grows, the quasi-crystalline phase is hardly observed.

From the viewpoint of quasi-crystallization and formation of Al-Fe intermetallic compounds, The Al content is preferably from 2% to 5%. By setting the Al content to 2% to 5%, the quasi-crystal system can obtain a dendritic form in the first layer, and the first layer can maintain an appropriate hardness. As a result, it is possible to produce a plated steel sheet which is excellent in corrosion resistance and adhesion, and for example, it can be confirmed that impact resistance characteristics such as a ball impact test can be improved.

[Mg (magnesium)]

Similarly to Zn and Al, Mg (magnesium) is a main element constituting a plating layer, and is an element which enhances corrosion resistance. Further, Mg is an important element that promotes the formation of a quasi-crystalline phase. In the present embodiment, the Mg content of the plating layer is not particularly limited, and may be a content obtained by removing the content of the impurities in the remaining portion described above.

Here, in the case where the Mg content is less than 45%, Zn in the plating layer The balance with the ratio of Mg collapses, resulting in the formation of fragile intermetallic compounds in the plating layer. When such an intermetallic compound is formed, the adhesion of the plating layer is extremely poor, and it is difficult to form a plating layer on the steel sheet. Therefore, the lower limit of the Mg content in the plating layer is set to 45%. Further, the Mg content is preferably 50% or more, more preferably 55% or more.

On the other hand, when the Mg content is more than 67%, the second item detailed below The Zn content in the fine structure of the plating layer becomes low, and the amount of formation of the Mg phase is increased and the corrosion resistance is lowered. Therefore, the upper limit of the Mg content in the plating layer is set to 67%. Further, the Mg content is preferably 62% or less, more preferably 57% or less.

In addition to the basic components described above, the quasi-junction of this embodiment The plating layer containing the plated copper plate contains impurities. Here, the term "impurity system" means industrially producing the quasi-crystalline plated steel sheet of the present embodiment. In the case of materials such as C (carbon), N (nitrogen), O (oxygen), P (phosphorus), S (sulfur), Cd (cadmium), etc., which are mixed with raw materials of steel and plating alloy or manufacturing environment. . These elements are not pure and each of them contains about 0.1%, and the above effects are not impaired.

The metal coating layer of the plated steel sheet according to the embodiment may be further The step contains at least one selected from the group consisting of Ca, Y, La, Ce, Si, Ti, Cr, Fe, Co, Ni, V, Nb, Cu, Sn, Mn, Sr, Sb, and Pb. Replace the remaining part of the above Mg. Which component is contained in the selected components may be appropriately determined depending on the purpose thereof. Therefore, it is not necessary to limit the lower limit of the selected components, and the lower limit may be 0%. Further, even if the selected components are contained as an impurity, the above effects are not impaired.

[Ca (calcium): 0%~3.5%]

When a plating layer is formed by a melt plating method, in order to improve the smelting-plating workability, Ca may be contained as necessary. When the quasi-crystalline plated steel sheet is produced in the present embodiment, a molten Mg alloy having high oxidizing property is maintained in the atmosphere as a plating bath. Therefore, it is preferred to use some of the antioxidant means of Mg. The Ca system is more oxidized than Mg, and a stable oxide film is formed on the plating bath surface in a molten state to prevent oxidation of Mg in the bath. Therefore, the Ca content of the plating layer can be set to 0% to 3.5%.

In addition, when Ca is contained in the plating bath, it is possible to suppress formation of a Mg-Zn-based intermetallic compound which is contained in the plating layer, and as a result, it is preferable from the viewpoint of adhesion of the plating layer. Plating layer structure. Moreover, by containing Ca in the plating bath, it is possible to suppress the amount of scum generated and plating The viscosity of the bath is small, and the operability of the high Mg-containing plating bath can also be improved. When the Ca content is 0.3% or more, the effect of the Ca can be confirmed, and it can be more reliably exhibited by setting it as 1.0% or more. Therefore, when Ca is contained in the plating bath, the Ca content is preferably 1.0% or more. On the other hand, when the Ca content is more than 2.5%, the balance of the ratio of Zn to Mg collapses, resulting in the formation of a weak intermetallic compound in the plating layer or the formation of an intermetallic compound containing Ca to lower the corrosion resistance. Becomes high. Therefore, the Ca content is preferably 2.5% or less. When the Ca concentration is high, the test for evaluating the adhesion of a ball impact or the like tends to be easily peeled off in the concave flange portion, the top portion, and the like.

Further, from the viewpoint of controlling the crystal grains of Mg ₅₁ Zn ₂₀ , the Ca content is preferably 1-2%. Further, as described above, the composition ratio with Al is preferably such that Ca/Al = 0.4 to 1.1 is satisfied. At this time, the substitution effect of Mg and Ca in Mg ₅₁ Zn ₂₀ is generated, so that the crystal grains of Mg ₅₁ Zn ₂₀ tend to become small.

[Y(钇): 0%~3.5%]

[La(镧): 0%~3.5%]

[Ce(铈): 0%~3.5%]

In the same manner as Ca, when Y, La, and Ce are used to form a plating layer by a hot-dip plating method, in order to improve the smelting-plating workability, it may be contained as necessary. Y, La, and Ce are more oxidized than Mg, and are more susceptible to oxidation. By forming a stable oxide film on the plating bath surface in a molten state, oxidation of Mg in the bath is prevented. Therefore, the Y content of the plating layer can be set to 0% to 3.5%, the La content can be set to 0% to 3.5%, and the Ce content can be set to 0% to 3.5%. Regarding the more preferable Y content, La content, and Ce content, the lower limit of each may be set to 0.3%, and the upper limit may be set to 2.0%.

Further, a total of 0.3% or more is selected from Ca, Y, La, and Ce. When at least one of the elements is contained, it is preferable because the plating bath having a high Mg content is not oxidized in the atmosphere and can be held. On the other hand, since Ca, Y, La, and Ce are easily oxidized and have an adverse effect on corrosion resistance, it is preferable to set the upper limit of the contents of Ca, Y, La, and Ce to 3.5%. That is, the Ca content, the Y content, the La content, and the Ce content in the chemical composition of the plating layer are preferably 0.3% ≦Ca+Y+La+Ce≦3.5% in terms of atomic %.

In addition, in order to form a quasi-crystalline phase more accurately in the plating layer, the total content of Ca, Y, La, and Ce is preferably 0.3% or more and 2.0% or less. It is considered that these elements are substituted with Mg constituting the quasi-crystalline phase, but it is considered that when a large amount of these elements are contained, the formation of the quasi-crystalline phase is inhibited. When these elements are contained in an appropriate amount, the effect of suppressing red rust in the quasi-crystalline phase and other phases is enhanced. It is presumed that this effect is caused by the elution timing of the quasi-crystalline phase affecting the retention of white rust. In other words, after the quasi-crystalline phase in the plating layer is dissolved, the elements are contained in the formed white rust, so that the rust prevention force of the white rust is increased and the red rust is caused by the corrosion of the ferrite iron. The period becomes longer.

Further, among these elements, by containing Ca, La, and Ce, it is possible to obtain a larger effect (antioxidation, generation of a quasi-crystalline phase). On the other hand, it is clear that the above effects obtained by containing Y are small compared to Ca, La, and Ce. Compared with Y, Ca, La, and Ce are more susceptible to oxidation, and it is speculated that they are associated with elements that are reactive. Since the chemical composition of the quasi-crystalline phase is analyzed by EDX (Energy Dispersive X-ray Spectroscopy), most of the cases cannot detect Y, so It is estimated that the Y system is not easily accommodated in the quasicrystal. On the other hand, Ca, La, and Ce have a tendency to detect quasi-crystals having a content of more than or equal to the content thereof. Therefore, it is not necessary to contain Y in the plating layer. When the plating layer does not contain Y, it may be 0.3% ≦Ca+La+Ce≦3.5%, or may be 0.3% ≦Ca+La+Ce≦2.0%.

[Si(矽): 0%~0.5%]

[Ti (titanium): 0% to 0.5%]

[Cr (chromium): 0%~0.5%]

In order to form a quasi-crystalline phase more well in the plating layer, Si, Ti, and Cr may be contained as necessary. When a small amount of Si, Ti, or Cr is contained in the plating layer, the quasi-crystalline phase is easily formed and the structure of the quasi-crystalline phase is stabilized. It is considered that fine Mg ₂ Si is formed by bonding of Si and Mg to form a starting point (core) for generating a quasi-crystalline phase. Further, it is considered that Ti and Cr which are deficient in Mg become a starting point (core) which forms a quasi-crystalline phase by forming a fine metal phase. The formation of the quasi-crystalline phase is generally affected by the cooling rate at the time of manufacture. However, when Si, Ti, and Cr are contained, the dependence of the cooling rate on the formation of the crystal phase tends to be small. Therefore, the Si content of the plating layer can be set to 0% to 0.5%, the Ti content can be set to 0% to 0.5%, and the Cr content can be set to 0% to 0.5%. With respect to the Si content, the Ti content, and the Cr content, it is more preferable to set each lower limit to 0.005% and the upper limit to 0.1%.

Further, the total content of 0.005% to 0.5% is selected from the group consisting of Si, Ti, and Cr. In the case of at least one element, it is preferred because the quasi-crystalline structure is further stabilized. That is, the total of the Si content, the Ti content, and the Cr content in the chemical composition of the plating layer is 0.005% ≦Si+Ti+Cr≦ in atom%. 0.5% is preferred. Further, since the quasi-crystalline system is formed in a large amount by a good amount by containing these elements in an appropriate amount, the corrosion resistance of the surface of the plating layer is improved. As a result, the corrosion resistance in the wet environment is further improved and white rust generation can be suppressed.

[Co (cobalt): 0% to 0.5%]

[Ni (nickel): 0% to 0.5%]

[V (vanadium): 0%~0.5%]

[Nb(铌): 0%~0.5%]

Co, Ni, V, and Nb have elements having the same effects as those of Si, Ti, and Cr described above. In order to obtain the above effects, the Co content may be set to 0% to 0.5%, the Ni content may be set to 0% to 0.5%, the V content may be set to 0% to 0.5%, and the Nb content may be set to 0% to 0.5%. With respect to the Co content, the Ni content, the V content, and the Nb content, it is more preferable to set the lower limit to 0.05% and the upper limit to 0.1%. However, compared with Si, Ti, and Cr, these elements have a small effect of improving corrosion resistance.

[Fe (iron): 0%~2%]

The plating layer is a case where an element constituting the steel sheet is mixed from a base material, that is, a steel sheet. In particular, in the hot-dip plating method, adhesion between elements is promoted by a solid-liquid reaction between the steel sheet and the plating layer, so that the adhesion is improved. Therefore, in the plating layer, there is a case where a certain amount of Fe is contained. For example, in the case of the chemical composition of the entire plating layer, there is a case where about 2% of Fe is contained. However, most of the Fe diffused into the plating layer reacts with Al and Zn in the vicinity of the interface between the steel sheet and the plating layer to form an intermetallic compound. Therefore, the Fe system contained is less likely to affect the corrosion resistance and the peeling resistance of the plating layer. Therefore, the Fe content of the plating layer can be set to 0% to 2%. Similarly, to plating The element constituting the steel sheet from which the layer is diffused (in addition to the element described in the present embodiment, the element diffused from the steel sheet to the plating layer) is less likely to affect the corrosion resistance of the plating layer.

[Cu (copper): 0% to 0.5%]

[Sn (tin): 0%~0.5%]

In order to improve the adhesion between the steel sheet and the plating layer, there is a case where pre-plating of Ni, Cu, Sn, or the like is performed on the steel sheet. When a quasi-crystalline plated steel sheet is produced by using a pre-plated steel sheet, the elements may be contained in the plating layer to about 0.5%. Among the Ni, Cu, and Sn of the pre-plating component, Cu and Sn do not have the above-described effects of Ni. However, even if the plating layer contains about 0.5% of Cu or Sn, Cu and Sn are less likely to affect the formation of quasicrystals and the corrosion resistance and peeling resistance of the plating layer. Therefore, the Cu content of the plating layer can be set to 0% to 0.5%, and the Sn content can be set to 0% to 0.5%. It is more preferable that the lower limit of each of the Cu content and the Sn content be 0.005% and the upper limit be 0.4%.

[Mn (manganese): 0% to 0.2%]

As a base material which is a base material containing a quasi-crystalline plated steel sheet, in recent years, high-tensile steel (high-strength steel) has been gradually used. When a quasi-crystalline plated steel sheet is produced by using high-tensile steel, elements such as Si and Mn contained in the high-tensile steel may be diffused into the plating layer. Among Si and Mn, Mn does not have the above-described effects of Si. However, even if the plating layer contains about 0.2% of Mn, Mn is less likely to affect the formation of quasicrystals and the corrosion resistance and peeling resistance of the plating layer. Therefore, the Mn content of the plating layer can be set to 0% to 0.2%. Regarding the Mn content, it is more preferable to set the lower limit to 0.005%. Set the upper limit to 0.1%.

[Sr(锶): 0%~0.5%]

[Sb(锑): 0%~0.5%]

[Pb (lead): 0%~0.5%]

Sr, Sb, and Pb are elements that enhance the appearance of plating and have an effect of improving anti-glare. In order to obtain this effect, the Sr content of the plating layer may be set to 0% to 0.5%, the Sb content may be set to 0% to 0.5%, and the Pb content may be set to 0% to 0.5%. When the Sr content, the Sb content, and the Pb content are in the above ranges, there is almost no influence on the corrosion resistance and the peeling resistance. More preferably, the lower limit of each of the Sr content, the Sb content, and the Pb content is 0.005%, and the upper limit is made 0.4%.

Sr, Sb, and Pb have little effect on the plating properties such as workability and corrosion resistance, but have an influence on the appearance of plating. In the plating layer disclosed in the present invention, metallic luster is present on the surface, and by containing these elements in the above composition range, the metallic luster disappears and an antiglare effect can be obtained.

[Measuring method of chemical composition]

The chemical composition of the above plating layer can be ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry) or ICP-MS (Inductively Coupled Plasma Mass Spectrometry) It is measured by well-known analytical techniques. The quasi-crystalline plated steel sheet was immersed in 10% hydrochloric acid to which an inhibitor was added for about 1 minute to partially peel off the plating layer, and a solution in which the plating layer was dissolved was prepared. By analyzing the obtained solution by ICP-AES, ICP-MS or the like, the chemical composition can be obtained as a whole of the plating layer.

Moreover, in the hot-dip plating method, it is formed to have a bath with a molten plating bath. A plating layer of chemical components having substantially the same chemical composition. Therefore, the element which can neglect the mutual diffusion between the steel sheet and the plating layer can measure the chemical composition of the plating bath to be used, and substitute the obtained measured value as the chemical component of the plating layer. A small ingot is taken from the plating bath and a drilled powder is taken to prepare a solution in which the drilled powder is acid-dissolved. The obtained solution is analyzed by ICP or the like to obtain a chemical composition of the plating bath. The measured value of the chemical composition of the obtained plating bath can be used as the chemical component of the plating layer.

The quasi-crystalline plating of the present embodiment has been described in detail above. The chemical composition of the steel plate.

<Organization structure for plating layer>

Next, the plating structure of the quasi-crystalline plated steel sheet according to the present embodiment will be described in detail.

The plating layer of the quasi-crystalline plated steel sheet of the present invention is composed of a composite layer of a multilayer structure in which the composite layer of the multilayer structure is laminated in the thickness direction of the plating layer by mutually different tissues. It is made up of multiple layers. Specifically, the plating layer of the present embodiment has, in order from the steel sheet side, a first plating layer composed of a structure containing a MgZn phase, a Mg phase, and a quasi-crystalline phase, and a second plating layer. It is located on the first plating layer and is composed of a structure containing a Mg ₅₁ Zn ₂₀ phase, a Zn phase, and a quasi-crystalline phase. Further, such a second plating layer is preferably composed of a structure having a maximum crystal grain size of 1 μm or less.

The quasi-crystalline plated steel sheet according to the embodiment is as described in detail below. The plating layer contains a quasi-crystalline phase as a metal structure, and is one of the features. Therefore, the following quasi-crystalline phase will be described first.

The quasi-crystalline phase can define the Mg content, the Zn content, and the Al content contained in the particles in the quasi-crystalline phase, and the quasi-crystalline phase satisfying 0.5 ≦Mg/(Zn+Al)≦0.83 in terms of atomic %. That is, it is possible to define a quasi-crystalline phase in which Mg:(Zn+Al) is a ratio of 3:6 to 5:6 as a total ratio of Mg atoms to Zn atoms and Al atoms. The theoretical ratio of the quasi-crystalline phase is considered to be Mg:(Zn+Al)=4:6. The chemical composition of the quasi-crystalline phase is quantified by using TEM-EDX (Transmission Electron Microscope-Energy Dispersive X-ray Spectroscopy), using EPMA (electron probe micro The analyzer; Electron Probe Micro-Analyzer) is preferably calculated by quantitative analysis of the survey. Also, it is not easy to define quasicrystals such as intermetallic compounds in the correct chemical formula. Since the quasi-crystalline phase cannot define a repeating lattice unit as in the unit crystal of the crystal, the atomic positions of the specific Zn and Mg are also difficult. When the quasi-crystalline layer was measured by TEM-EDX as a reference, the quasi-crystalline phase system was able to detect a state in which the Zn ratio was high and the Mg ratio was low as compared with the Mg ₅₁ Zn ₂₀ phase. Further, in the case where Al is contained, the element such as Ca tends to have a higher ratio in the quasi-crystalline phase than the Mg ₅₁ Zn ₂₀ phase. Further, the chemical composition of the metal phase other than the quasi-crystalline phase contained in the plating layer can also be identified by quantitative analysis using TEM-EDX, quantitative analysis using EPMA mapping, or the like.

Further, in order to recognize the metallic phase and the quasi-crystalline phase, it is necessary to photograph the electron ray diffraction image by TEM to confirm whether or not the symmetrical crystal structure can be observed five times in the electron beam diffraction image. The 5th symmetric crystal structure can be identified by obtaining an electron ray diffraction image called a Penrose pattern. It is difficult to observe a range of 10 μm or more by using TEM. Therefore, as described in detail below, the phase of the contained structure is estimated from a representative field of view of the plating layer, and when the same structure is obtained, From the measurement results of EPMA and EDX, the metal phase and the quasi-crystalline phase are identified.

The presence or absence of a quasi-crystalline system has an effect on the basic properties of the plated steel sheet and the effect of suppressing red rust. When the quasi-crystal phase is present, enough to ensure that the apparent based red rust occurred with respect to the plating line thickness (μ m), usually to the plating surface of red rust generation is far × 150 hours or more.

Hereinafter, the structure of the plating layer of the present embodiment will be described in detail.

Fig. 1 is an electron micrograph of a plating layer containing a quasi-crystalline plated steel sheet according to the present embodiment, and is obtained by observing a cut surface in which the cutting direction is parallel to the thickness direction of the quasi-crystalline plated steel sheet. The cross-sectional tissue photograph is a bright-field image obtained by observing the cut surface using a TEM. The more specific structure of the plating layer is as shown in Fig. 1, and is composed of the second plating layer 1 which is composed of fine structure on the surface side of the plating layer (opposite side of the steel sheet). And the first plating layer 2 is located inside the second plating layer (that is, on the steel plate side of the plating layer) and contains a structure grown in the thickness direction of the plating layer. Further, an alloy layer (interface alloy layer) 3 composed of an Al-Fe metal compound is formed at the interface between the plating layer of the multilayer structure and the mother steel sheet.

In the future, it will also be located on the surface side of the plating layer by the microstructure organization. The first plating layer of the structure is simply referred to as a "microlayer", and the first plating layer which is located on the steel sheet side of the plating layer and which has a structure in which the thickness of the plating layer is grown is simply referred to as a "compound layer". Further, the Fe-Al intermetallic compound layer located at the interface of the mother steel sheet is also simply referred to as "interface alloy layer".

○ second plating layer (micro layer)

Among the plurality of layers constituting the plating layer, the fine layer (second plating layer) 1 located at the outermost layer of the plating layer is a structure having a maximum crystal grain size of 1 μm or less in terms of an equivalent circle diameter. By using such a fine structure to constitute the fine layer 1, one of the features of the present invention, which will control the effect of crack propagation in the plating layer (that is, the peeling resistance), will not appear. In other words, by making the crystal grain size of the structure constituting the fine layer 1 fine, it is possible to suppress the propagation of cracks inside the plating layer.

Here, the circle of the maximum crystal grain size contained in the fine layer 1 or the like The effective diameter is preferably 500 nm or less, more preferably 200 nm or less. Further, in the example shown in Fig. 1, the crystal grain size of the phase constituting the fine layer 1 is almost 100 nm or less in terms of a circle equivalent diameter (a crystal phase of 1 μm or more cannot be observed). Moreover, the lower limit of the circle equivalent diameter of the maximum crystal grain size contained in the fine layer 1 is not particularly limited. However, the lower limit may be set to 10 nm as necessary.

In the fine layer 1, the area of the structure in which the maximum crystal grain size is 1 μm or less in terms of the circle equivalent diameter is 90% or more in the cross-sectional area of the entire cut surface of the arbitrary plating layer with respect to the entire fine layer 1. good. In other words, the area ratio of the structure in which the maximum crystal grain size of the fine layer 1 is 1 μm or less in terms of the circle equivalent diameter is preferably 90% or more. When the area ratio of the structure having a maximum crystal grain diameter of 1 μm or less in a circle equivalent diameter is 90% or more, the effect of suppressing crack propagation in the plating layer can be surely exhibited, and corrosion resistance can be further improved. Sex. The area ratio of the structure having a maximum crystal grain size of 1 μm or less in terms of a circle equivalent diameter is preferably 95% or more, more preferably 100%.

In the fine phase 1, when a large crystalline phase (or quasi-crystalline phase) is present, During the Gravelotest test, the frequency of plating peeling tends to increase. In addition, when the crystal grains of the fine layer 1 are fine, the corrosion resistance tends to be improved and the plating hardness tends to be high.

The metal phase of the structure constituting the fine layer 1 is at least a Zn phase, a quasi-crystalline phase, and a Mg ₅₁ Zn ₂₀ phase, and a phase containing both Zn and Mg having an unclear crystal structure may be present. Further, among the Zn phase, the quasi-crystalline phase, and the Mg ₅₁ Zn ₂₀ phase mainly constituting the fine layer 1, the main metal phase Mg ₅₁ Zn ₂₀ phase. Further, in the fine layer 1 of the present embodiment, the Mg phase is hardly present in the fine layer 1.

It is blackened when there is Mg in the surface of the plating in a humid environment. In order to impair the appearance, it is preferable that the fine layer 1 does not contain Mg.

2A is an electron ray diffraction image obtained from a majority of the black portion of the fine layer 1 shown in FIG. 1, and FIG. 2B is obtained from the white portion of the fine layer 1 shown in FIG. Electron rays circulate images. The electron ray diffraction image shown in Fig. 2A, which occupies most of the fine layer 1, is derived from an electron ray diffraction image of the Mg ₅₁ Zn ₂₀ phase. According to the electron beam diffraction image shown in FIG. 2A, it was confirmed that the fine layer 1 contained the Mg ₅₁ Zn ₂₀ phase. Further, in FIG. 2B, although the intensity is weak, it is possible to confirm the electron ray diffraction image derived from the radial regular pentagon of the regular icosahedral structure. The electron beam diffraction image shown in FIG. 2B is an image obtained from a fine quasi-crystalline phase contained in the fine layer 1. It was confirmed by the electron beam diffraction image shown in FIG. 2B that the fine layer 1 contains a fine quasi-crystalline phase.

Further, although not shown, it was confirmed that the Zn phase was contained in the fine layer 1 by analyzing the electron ray diffraction image obtained from the gray portion in the fine layer 1. Further, the presence of an intermetallic compound of Mg ₅₁ Zn ₂₀ and a metal phase equivalent to Zn contained in the fine layer 1 can also be confirmed by using an electron beam diffraction image as described above for TEM, and XRD can also be used ( X-Ray Diffractometer) to confirm.

The Mg ₅₁ Zn ₂₀ phase system is defined as a JCPDS card (PDF): PDF #00-008-0269, or #00-065-4290, or a non-patent document of the Journal of Solid State chemistry (Journal of solid state chemistry ( Journal of Solid State Chemistry, 36, 225-233 (1981)) identified structural phase.

Further, according to the non-patent literature of Dong et al., it is reported that the Mg ₅₁ Zn ₂₀ phase system has a unit lattice close to a cubic crystal and has an atomic structure forming a regular icosahedron in a unit lattice. Since the lattice system units and Mg ₅₁ Zn _20, different icosahedral quasi-crystal structure, so strictly speaking, Mg _{20 and} quasi-crystalline phase with ₅₁ Zn. However, since the crystal structure of Mg ₅₁ Zn ₂₀ and quasicrystal is similar, it is considered that the formation of the Mg ₅₁ Zn ₂₀ phase is affected by the formation of the crystal phase.

The Zn phase contained in the fine layer 1 is chemically formed with the quasi-crystalline phase The fraction and the crystal structure are very different. When manufacturing a quasi-crystalline plated steel sheet, The Zn phase sufficiently produces a diffusion of elements at a high temperature, and it can be judged that a stable phase has been generated.

Further, it is determined whether or not the Mg phase is present, and it can be confirmed by TEM-EDX or SEM-EDX, or can be confirmed by XRD. For example, in the XRD diffraction pattern in which the fine layer 1 is measured, the diffraction intensity from the (110) plane of the Mg phase with respect to the diffraction angle at the Mg ₅₁ Zn ₂₀ phase: 2 θ = 36.496° When it is 1% or less, the metal structure of the fine layer 1 can be said to contain no Mg phase. Similarly, when the TEM diffraction image of the fine layer 1 is sampled by sampling 100 or more crystal grains, the even number of crystal grains of the Mg phase is 3% or less, and the metal structure of the fine layer 1 can be said to be no. Contains Mg phase. The crystal fraction of the Mg phase is more preferably less than 2%, and more preferably less than 1%.

Here, the existence ratio of the aforementioned phases in the fine layer 1 is not Special regulations. The existence ratio of each phase varies depending on the composition of the component, and the main factor affecting the peeling resistance is more dependent on the fineness of the crystal grain size than the ratio of the existence of each phase.

In the composition range of the present plating, the existence of the aforementioned phases in the fine layer 1 Even if the ratio changes, the influence on the planar corrosion resistance is small, and the corrosion resistance which is a problem does not deteriorate.

In addition, the thickness of the fine layer 1 is not particularly limited, and the thickness of a normal plating layer of a molten plated steel sheet having a large basis weight tends to be about 3 μm to 30 μm , which is fine in the present embodiment. Since most of the layers 1 occupy 1/4 to 2/3 of the entire plating layer, the thickness of the fine layer 1 can be set to 0.75 to 20 μm .

Compared with the compound layer (first plating layer) 2 described later, as described above The fine layer (second plating layer) 1 composed of the structure is a relatively hard plating layer. Specifically, the Vickers hardness of the fine layer 1 measured in accordance with JIS Z2244 is 250 to 350 Hv in terms of an average value of 30 points of any fine layer 1. The fine layer 1 is composed of a fine structure having a maximum crystal grain size of 1 μm or less in terms of a circular equivalent diameter, and is formed into a harder layer than the first plating layer, and can be formed inside a plating layer to be described later. The inhibitory effect of crack propagation (ie, peeling resistance). The hardness distribution of the fine layer 1 depends on the cooling rate at the time of plating production. When the plating hardness is increased, it also has an effect of improving the peeling resistance, the scratch resistance, the abrasion resistance, and the like.

○1st plating layer (compound layer)

Among the plurality of layers constituting the plating layer, the inside of the plating layer (the side of the steel sheet), in other words, the compound which is formed between the fine layer 1 and the steel sheet which is the second plating layer and which grows in the thickness direction of the plating layer The layer (first plating layer) 2 is composed of a structure containing a MgZn phase, a Mg phase, and a quasi-crystalline phase. Hereinafter, the form of a representative compound layer will be described in detail.

The structure of the compound layer 2 first contains the structure of the gray portion at the bottom of the compound layer 2 of Fig. 1, that is, the MgZn phase. It can also be clearly seen from Fig. 1 that the MgZn phase is a hard structure having an equivalent diameter of 1 μm or more and a relatively large crystal grain size. Further, the compound layer 2 is on the upper side of the hard MgZn phase (on the surface side of the plating layer), and contains a structure which is smaller than the hard MgZn phase and which grows in the thickness direction of the plating layer. The structure grown in the thickness direction of the plating layer is composed of a minute MgZn phase and a quasi-crystalline phase, and the soft Mg phase exists in such a manner as to fill the gap between the MgZn phase and the quasi-crystalline phase. .

Here, the crystallization of the hard MgZn phase contained in the compound layer 2 The particle diameter is preferably 500 nm or more in terms of a circle equivalent diameter, more preferably 1 μm or more. In addition, the upper limit of the circle equivalent diameter of the crystal grain of the hard MgZn phase contained in the compound layer 2 is not particularly limited. However, the upper limit can be set to 5 μm as necessary. The size of the MgZn phase is related to the thickness of the compound layer 2. When it is small, the compound layer 2 is also small, and when it is large, the compound layer 2 is also large. From the judgment of the appropriate thickness of the compound layer, 500 nm to 5 μm can be said to be an appropriate thickness of MgZn. When the equivalent circular diameter of the MgZn layer is large and is 1 μm, the thickness of the compound layer 2 is also increased. For example, the portion of the ferrite iron exposed at the time of peeling is reduced. That is, since the plating layer of the compound layer 2 remains after the peeling, the red rust does not occur and is covered with white rust.

Also, a minute MgZn phase and a slight quasicrystal in the MgZn phase In many cases, as described above, it grows into a dendritic shape in the thickness direction and the cooling direction of the plating layer. Therefore, when observed using an SEM, an optical microscope, or the like, the compound layer 2 is as shown in Fig. 1, and can be seen as an open fan. Further, a part of the branches which grow into a dendritic structure is mostly a quasi-crystalline phase as compared with the MgZn phase. That is, among the dendritic tissues, a part of the branches is mainly composed of a quasi-crystalline phase and a minute MgZn phase exists at the same time, so that the portion corresponding to the leaves of the branches can be compared to the presence of a Mg phase. The dendritic structure refers to a structure in which a structure which does not have a clear division in an arbitrary cross section and which can be replaced in a state of being relatively round or the like, and which is agglomerated into a specific area such as a ball, a flat circle, or a polygonal shape. The organizational form is different. Regarding the peeling resistance, the dispersion of the spherical or polygonal structure cannot be suppressed from cracking. The effect of the sowing can be obtained by the presence of a dendritic structure.

Figure 3A is a composite layer 2 as shown in Figure 1, from coarse The electron ray diffraction image obtained by the MgZn phase is shown in Fig. 3B as an electron beam diffraction image obtained from a structure which grows into a dendritic structure in the compound layer 2 shown in Fig. 1. The electron ray diffraction image shown in Fig. 3A is derived from an electron ray diffraction image of a coarse MgZn phase. According to the electron beam diffraction image shown in FIG. 3A, it was confirmed that the compound layer 2 does not contain the MgZn phase. Moreover, in FIG. 3B, the electron beam diffraction image derived from the radial regular pentagon of the icosahedral structure can be confirmed. The electron beam diffraction image shown in FIG. 3B is an image obtained from the quasi-crystalline phase contained in the compound layer 2. It can be confirmed that the compound layer 2 contains a quasi-crystalline phase by the electron beam diffraction image shown in FIG. 3B. Further, although not shown, it is confirmed that the compound layer 2 contains Mg in the dendritic structure in the compound layer 2 by analyzing the electron beam diffraction image obtained from the portion corresponding to the leaf of the branch. phase. Further, the presence of an intermetallic compound of MgZn and a metal phase equivalent to Mg contained in the compound layer 2 can be confirmed by using an electron beam diffraction image as described above and can also be confirmed by XRD.

On the cut surface of any plating layer of compound layer 2, relative to The cross-sectional area of the entire composite layer 2 is preferably 10% to 70% of the area of the bulk MgZn phase. In other words, the area ratio of the MgZn phase in the compound layer 2 is preferably 10% to 70%. By the area ratio of the bulk MgZn phase being 10% to 70%, the peeling resistance can be surely exhibited, and the corrosion resistance can be further improved. The area ratio of the bulk MgZn phase is preferably from 20% to 40%.

Here, the existence ratio and shape of the aforementioned respective phases in the compound layer 2 State, can consider a variety of conditions. However, the existence ratio and morphology of the above respective layers in the compound layer 2 are not particularly limited. In the present plating composition range, even if the ratio and form of the respective phases in the compound layer 2 are changed, the influence on the planar corrosion resistance is small and the corrosion resistance which is a problem does not deteriorate.

Further, the thickness of the compound layer 2 is not particularly limited, and the molten plated steel sheet tends to have a large basis weight. Generally, the thickness of the plating layer is generally about 3 μm to 30 μm because of the compound of the present embodiment. In the case where most of the layer 2 is 1/3 to 3/4 of the entire plating layer, the thickness of the compound layer 2 can be set to 1 μm to 23 μm .

Further, in the compound layer 2, an oxide such as MgO, Fe oxide or Zn oxide is used in the process of manufacturing the plating layer, and it may be mixed as an unavoidable impurity. However, as long as the impurities are in a small amount, there is no problem, and when the compound layer 2 is composed of the above-mentioned phases, it is possible to sufficiently enjoy the excellent peeling resistance and corrosion resistance of the effects of the present invention. Further, in the compound layer 2, in addition to the MgZn phase, the Mg phase, and the quasi-crystalline phase, a very small amount of "Mg ₅₁ Zn ₂₀ " can be observed. In this case, the "Mg ₅₁ Zn ₂₀ " is a trace amount. There is no problem, and when the compound layer 2 is composed of the above phases, the peeling resistance and the corrosion resistance which are excellent in the effects of the present invention can be sufficiently enjoyed.

Compared to the aforementioned fine layer (second plating layer) 1, as described above The compound layer (first plating layer) composed of the structure is relatively soft. Plating layer. Specifically, the Vickers hardness of the compound layer 2 measured in accordance with JIS Z2244 is 80 to 200 Hv on the average. When the compound layer 2 is composed of a structure containing the MgZn phase, the quasi-crystalline phase, and the Mg phase described above and is softer than the second plating layer, crack propagation can be suppressed in the plating layer to be described later. The effect (ie, peeling resistance).

In the present invention, heat treatment after formation of a plating alloy to be described later The method has a feature that a plating layer composed of the fine layer 1 and the compound layer 2 can be formed according to such a heat treatment method.

The quasi-crystalline plating of the present embodiment has been described in detail above. The plating layer provided on the steel plate.

<For interface alloy layer>

Next, the interface alloy layer which is an alloy layer provided in the quasi-crystalline plated steel sheet according to the present embodiment will be described in detail.

In the present embodiment, as shown in Fig. 1, an interface alloy layer 3 composed of an Al-Fe intermetallic compound is formed at the interface between the plating layer having the fine layer 1 and the compound layer 2 and the mother steel sheet.

In the plating alloy, Al is contained in an appropriate concentration range as described above, and by performing appropriate heat treatment after the formation of the plating alloy, it is possible to be closer to the steel sheet side of the compound layer 2 (that is, in plating). The interface between the layer and the mother steel sheet) forms an interface alloy layer 3 composed of an Al-Fe intermetallic compound. The interface alloy layer 3 preferably contains at least one of Al3Fe (more specifically, Al _3.2 Fe) or Fe ₅ Al ₂ as the intermetallic compound. Since the Al-Fe intermetallic compound containing the above intermetallic compound has a needle-like complex form, the adhesion between the upper compound layer 2 and the mother steel sheet is increased by the anchoring effect, whereby the adhesion is improved, and further Improve peeling resistance. Further, it is clear that the Al-Fe intermetallic compound layer has an influence on the adhesion of the plating layer in addition to the peeling resistance.

Here, the thickness of the interface alloy layer 3 is not particularly limited, and is preferably 10 to 200 nm. Further, since the thickness of the interface alloy layer 3 is less than 1 μm as described above, the presence or absence of the interface alloy layer 3 is preferably confirmed by TEM observation or the like.

Moreover, in the outermost layer of the plating layer, a thickness of less than 200 nm is formed. The case of the left and right oxide film. Since such an oxide film does not affect the peeling resistance of the quasi-crystalline plated steel sheet of the present embodiment, it is not particularly limited in the present invention.

<Method for confirming metal structure>

Next, a method of confirming various metal structures of the plating layer included in the quasi-crystalline plated steel sheet according to the present embodiment will be described.

The microstructure of the plating layer can be observed by optical microscopy, SEM, TEM, etc., polishing test piece, CP (Cross Section Polisher) processing, FIB (Focused Ion Beam) processing, and ion etching. (ion milling) The structure of the obtained plating layer cross section was subjected to various analysis treatments for confirmation. Further, the crystal grain size of the metal structure is as long as 1 μm or more, and can be measured by SEM observation. The microstructure and the quasi-crystalline phase system which are finer than 1 μm can be measured by TEM observation or the like as described above. .

Moreover, the type of the phase of the fine layer 1 and the compound layer 2 is capable of Known methods such as EPMA and TEM electron ray diffraction patterns confirm.

Moreover, in order to define each of the above in the tissue constituting the plating layer The ratio of the phase must be calculated based on the observation of a plurality of fields of view to calculate the area ratio of the target phase. The observation for determining the area ratio is preferably performed, for example, at least at least 10 fields of view. The entire cross section of any of the plating layers is imaged at about 1000 times using an SEM or the like, and a region surrounded by the tissue is formed on the image by a well-known image processing and binarization processing, and the area ratio is measured.

In more detail, for example, the plating layer can be confirmed as follows Metal organization. First, the cut surface parallel to the cutting direction in the thickness direction is the observation surface, and the quasi-crystalline plated steel sheet is cut and a sample is taken. The cut surface of the obtained sample was subjected to polishing or CP processing. After the polishing, the polished cross section is subjected to NITAL (nitric acid etching solution) etching. Subsequently, the obtained cross section was observed by an optical microscope, SEM, or the like, and a photograph of the metal structure was taken. Further, the chemical composition of the structural phase is as described above, and can be measured by EDX or EPMA. From the results of this chemical analysis, the structural phase can be easily identified. The area ratio of the structural phase can be measured by binarizing the obtained metal structure photograph by, for example, image analysis and measuring the area ratio of each portion of the plating layer. Further, the average circle equivalent diameter can be calculated from the area of the obtained individual region (structural phase). Alternatively, the metal structure of the plating layer may be observed by an EBSD (Electron Back Scattering Diffraction Pattern) method to identify the structural phase, and the area ratio of the structural phase and the average circle equivalent diameter may be obtained.

In order to identify the structural phase in more detail, the plating layer is observed as follows Metal organization. In other words, the cut surface in which the thickness direction is parallel to the cutting direction is the observation surface, and the quasi-crystalline plated steel sheet is cut and a sheet sample is taken. An ion etching method was applied to the obtained sheet sample. Alternatively, the quasi-crystalline plated steel sheet is subjected to FIB processing and a sheet sample is used so that the cut surface parallel to the cutting direction is the observation surface. The obtained sheet sample was observed by TEM and photographs of metal structures were taken. The structural phase can be correctly identified by electron beam diffraction images. Further, by performing image analysis on the obtained metal structure photograph, the area ratio of the structural phase and the average circle equivalent diameter can be obtained.

Also, although I don’t know the existence state in space, it is the easiest. It is also possible to confirm the presence of the structural phase based on the diffraction peak of the XRD of the plating layer.

The above description of the quasi-crystalline plated steel sheet according to the present embodiment will be described. A method for confirming various metal structures of a plating layer provided. Moreover, the above-described confirmation method can also be applied to confirm the structure of the alloy layer of the interface.

Further, in the plating layer containing the quasi-crystalline plated steel sheet of the present embodiment, it is also possible to further perform an organic chemical treatment or an inorganic chemical treatment to form a chemically treated coating layer. The plating layer of the present embodiment can be subjected to the same phosphoric acid chemical treatment, chromate treatment, or chromate-free treatment as the Zn-based plated steel sheet, and contains a certain concentration or more of Zn in the plating layer. Further, the chemical treatment of the film formed by the chemical treatment can be carried out in the same manner as the Zn-based plated steel sheet. Further, the quasi-crystalline plated steel sheet according to the present embodiment can also be used as an original sheet of a laminated steel sheet.

<Appearance mechanism for peeling resistance>

As described above, in the quasi-crystalline plated steel sheet according to the present invention, the structure of the plating layer is a multi-layer structure composed of a fine layer 1 which is located on the surface side (surface side) of the plating layer. And the compound layer 2, which is located closer to the mother steel sheet than the fine layer 1. By providing such a plating layer having a multi-layer structure, it is difficult to reach the interface between the plating layer and the mother steel sheet by peeling off the surface crack of the plating layer caused by the external pressure. Specifically, the relatively hard fine layer 1 located on the surface side of the plating layer is finely broken due to the external pressure, but when the generated crack reaches the interface between the fine layer 1 and the compound layer 2, along the interface And spread. That is, the crack generated on the surface of the plating layer does not propagate relatively to the soft compound layer 2, and thus does not reach the interface between the plating layer and the mother steel sheet. Therefore, even if the fine layer 1 which has been finely broken is peeled off due to the occurrence of cracks and cracks, the compound layer 2 having excellent adhesion to the mother steel sheet is less likely to be peeled off, and the mother steel sheet can be prevented from being exposed.

Here, the crack of the plating layer after the peeling test (peeling crack) An example in which the pattern 4 progresses along the interface between the fine layer 1 and the compound layer 2 is shown in FIG. As can be seen from FIG. 4, when the plating layer is provided with a multi-layer structure including the fine layer 1 and the compound layer 2, cracks generated along the surface of the plating layer, that is, the fine layer 1 are along with the compound. The interface of the layer 2 propagates and does not propagate to the inside of the compound layer 2 and does not reach the mother steel sheet. Such special crack (crack) propagation can be achieved by using the plating layer as a multi-layered structure as in the present invention. For example, even if the composition of the plating layer is the same as the above-described composition of the present invention, and the plating layer is a single-layer structure, the cracks are connected one after another in the structure, and a large peeling mark remains and the exposed portion of the mother steel sheet remains. Become bigger.

Also, in the case of a quasi-crystalline plated steel sheet, it is added to the plating layer. Al forms an interface alloy layer 3 at the interface between the steel sheet and the plating layer by an appropriate heat treatment to be described later, and an anchoring effect is exerted on the compound layer 2. Thereby, the adhesion between the plating layer and the mother steel plate is further improved.

Thus, the quasi-crystalline plated steel sheet of the present invention is even plated. In the case where a part of the coating layer is broken, the peeling marks are not conspicuous, and since the residual compound layer 2 exhibits an anti-corrosion function, it is possible to suppress the progress of corrosion without becoming red rust.

The quasi-crystalline plating of the present embodiment has been described in detail above. Steel plate.

(For the method of manufacturing a quasi-crystalline plated steel sheet)

Next, a method for producing a quasi-crystalline plated steel sheet according to the present invention, in particular, a method for forming a plating layer will be described in detail.

The formation of the plating layer can be applied by melt plating and spraying Method, sputtering method, vapor deposition method, plating method, and the like. However, in order to form a plating layer having a thickness which is generally used, such as an automobile, the hot-dip coating method is preferable in terms of the cost surface.

Further, in order to control the plating layer to have a phase structure and a layer structure specified in the present invention, a plurality of plating processes may be carried out using different conditions. However, in the present embodiment, after the plating layer having a uniform composition is formed first, the phase structure and the layer structure in the plating layer can be controlled to form a multi-layer structure by performing heat treatment described later on the plating layer. It is also advantageous for cost, but it is better. In this regard, the melt plating method is advantageous in that it can utilize the cooling process of the molten plating alloy as heat treatment.

Further, a specific composition is formed on the surface of the steel sheet by vapor deposition or the like in advance. After the metal coating layer is placed in a heating furnace or the like and heated to melt only the metal coating layer on the surface, and heat treatment is performed in the subsequent cooling process, plating with the hot plating method can also be formed. The same layer of plating. Further, in this case, only the plating layer (metal coating layer) is remelted, because the melting point of the metal coating layer containing Mg and Zn as main components is completely different from the melting point of the base material, that is, the melting point of the steel sheet, so that the manufacturer Optimizing temperature and time can be easily achieved. For example, when heated at 500 ° C, the metal coating layer containing Mg and Zn as main components is completely melted and the base material is not melted. In particular, rapid heating using a high-temperature environment is advantageous in that the surface of the steel sheet that is in contact with the environment is preferentially heated, so that it is advantageous for the coating layer to heat only the surface.

Hereinafter, a method of forming the phase structure of the plating layer by the heat treatment into the configuration of the present invention will be described in detail.

In order to obtain the phase structure of the present invention, first, a plating alloy having a molten state of the above-described chemical components is placed on a mother steel sheet (plating step). The plating method which can be utilized in the plating step is as described above, but it is preferable to use a molten plating method. Next, the molten alloy in a molten state on the mother steel sheet is cooled to 330 to 200 ° C at a cooling rate of 10 ° C /sec or less (first cooling step). Moreover, when the plating step is performed by the hot-dip plating method, after the removal from the plating bath, the first cooling process is performed. When the cooling rate in the first cooling process is large, the internal stress caused by the rapid solidification causes cracks to occur in the plating layer, and the peeling resistance is extremely lowered. Further, when the cooling rate is too fast, a large amount of quasi-crystalline phase precipitates in the plating layer and the precipitation form and the plating layer structure of the quasi-crystalline phase cannot be maintained in the subsequent thermal process.

Cracks and coarse precipitates so produced, as long as they are not added It is not suitable to form a plating layer having a multi-layer structure because it is heated to a temperature higher than the melting point of the plating alloy and the plating layer is remelted. In particular, since the cracking hinders the homogenization of the internal structure of the plating layer during the subsequent heat treatment, there is also a case where the composite layer is not formed. Since the formation of cracks causes the corrosion resistance of the present invention to be extremely deteriorated, it is preferable to suppress the formation as much as possible.

Moreover, from the viewpoint of further suppressing occurrence of cracks on the surface of the plating layer, The cooling rate of the molten alloy in the molten state is preferably 8 ° C / sec or less.

Here, the lower limit of the cooling rate of the plating alloy is not special. In the case where the crack is generated on the surface of the plating layer, the lower limit value may be appropriately determined in consideration of the operability such as cost.

Further, in the first cooling step, when the cooling reaching temperature is 330 ° C or lower, the plating layer is completely solidified once. After the plating layer is completely solidified, a temperature rising holding step of a reheating step of a plating layer to be described later is performed. However, when the temperature-maintaining step is performed without a process of completely solidifying the plating layer (that is, in a state where the plating layer is not completely solidified), the plating layer is a spherical coarse quasicrystal, MgZn. The phase-dispersed and Mg ₅₁ Zn ₂₀ fills up the remaining portion of the structure, and it becomes very difficult to form the above-mentioned compound layer 2. Further, there is a tendency that cracks are likely to occur in the plating layer. Therefore, it is important to set the cooling reaching temperature at the time of cooling the molten alloy in the molten state to 330 ° C or lower.

Moreover, from the viewpoint of stably forming the compound layer 2, the cooling reaching temperature is preferably 300 ° C or lower, and more preferably 250 ° C or lower. On the other hand, when the cooling reaching temperature is set to be less than 200 ° C and cooled, the surface texture of the plating layer is roughened in the subsequent temperature rising maintaining step. Since the surface appearance tends to be deteriorated, it is preferable to set the cooling reaching temperature to 200 ° C or higher. Further, when the cooling reaching temperature is set to less than 200 ° C and is cooled, more than necessary quasi-crystalline phase is precipitated in the plating layer. Growth causes the fine layer to be easily doped with a coarse quasi-crystalline phase. Since the control of the subsequent structure is slightly difficult, it is preferable to set the cooling reaching temperature to 200 ° C or higher from this viewpoint.

However, even if the cooling arrival temperature of the first cooling step is less than At 200 ° C, the plating performance itself is not affected, and the roughening of the surface texture described above is a means of eliminating it by smoothing by skin pass rolling, and the above-mentioned cooling can be solved. The problem of the appearance of the plating layer. Therefore, the lower limit of the cooling reaching temperature in the first cooling step is not necessarily strictly limited as the upper limit of the cooling reaching temperature. For example, even if the molten plating layer is cooled to room temperature, the structure of the present invention can be obtained as long as the subsequent heat treatment conditions can be satisfied.

Next, the plated steel sheet subjected to cooling in the first cooling step is The average heating rate (average heating rate) of 10 ° C / sec to 50 ° C / sec is reheated in a temperature rising temperature range of 350 ° C to 400 ° C and maintained in such a temperature range for 5 seconds to 30 seconds (temperature rising maintaining step) . By reheating and holding the plating layer in such a temperature range, the inside of the plating layer is changed from the solidified state to the semi-molten state, and the structure precipitated in the first cooling step can be substantially reorganized (however, depending on the situation) There is also a slight residual in the quasi-crystalline phase formed in the first cooling step). The temperature region of 350 ° C to 400 ° C is a state of the structure which does not have a specific precipitation phase and is substantially close to the liquid phase. Moreover, the crack generated in the initial cooling step is also recovered in a certain amount.

In the temperature range of 350 ° C ~ 400 ° C, first, the MgZn phase system The precipitate is deposited from the interface of the mother steel sheet, and then the Mg phase and the quasi-crystalline phase are sequentially grown to form the compound layer 2 having the composite phases. The material which is the easiest to grow in this temperature region is MgZn. As a result of segregation and separation of the components due to precipitation of MgZn, the dendritic quasicrystal system is subsequently precipitated and becomes a structure in which Mg fills the dendritic gap.

Also, when the average heating rate is too small and less than 10 ° C / sec, from the mother The MgZn phase precipitated at the steel sheet interface is excessively coarsened, so that the compound layer 2 cannot be a composite phase. Moreover, the crack formed in the first cooling step tends to remain directly. Further, when the average heating temperature is too large and is more than 50 ° C / sec, since the temperature rising temperature range is narrow, it is technically difficult in terms of temperature control.

On the other hand, when the retention time is less than 5 seconds, in the compound layer 2 The formation of the composite phase is insufficient, and the peeling resistance cannot be sufficiently improved. In addition, when the holding time is longer than 30 seconds, the ratio of the compound layer 2 in the plating layer is too large, so that it is difficult to sufficiently form the fine layer 1 in the second cooling step to be described later, and in this case, the composite layer is not formed and cannot be formed. Improve the peeling resistance.

In order to control the crystal grain size of MgZn, that is, to control the compound The thickness of the layer is preferably maintained in the range of 350 ° C to 400 ° C for about 10 seconds to 20 seconds. As time goes on, MgZn2 tends to grow.

Thus, the temperature rise in the range of 350 ° C to 400 ° C, and When the holding time of such a temperature rise temperature does not satisfy the above, the composite phase of the compound layer 2 is not sufficiently formed and the peeling resistance is not sufficiently improved. Further, when neither of the temperature rise nor the holding time is satisfied, the surface structure of the plating layer tends to be rough and the surface appearance tends to be deteriorated. Therefore, it is very important to control the temperature rise and hold time of reheating.

Moreover, at a temperature of 350 ° C, there is a composition of Mg-MgZn eutectic, The liquid phase appears in the plating layer above 350 °C. However, when the temperature is more than 400 ° C, the plating layer is completely molten, and there is also concern about the influence of the material of the ferrite iron. And the MgZn system grows extremely, and it is impossible to form a composite layer structure. Also, when the subsequent process is quenched, many cracks are generated because the temperature is too high. Further, when it is more than 400 ° C, since the plating surface is roughened and the appearance is poor in the subsequent temperature program, the upper limit temperature is preferably 400 ° C or lower. Further, when the temperature is more than 400 ° C, alloying occurs due to the reaction of Al with Fe or Zn and Fe, and the composition of the plating structure changes to cause deterioration. Therefore, in order to make the plating layer into a molten state, it is a very important condition to control the temperature rising temperature range within the range of 350 ° C to 400 ° C.

Also, in the temperature rise maintaining step, from the time of reaching 350 ° C Calculate the hold time.

After the temperature increase holding step, the plated steel sheet is cooled (quenched) at an average cooling rate of 20 ° C /sec or more (second cooling step). Whereby, in the step of maintaining the temperature rising, half-molten state of plating surface area-based cladding layer solidification from the liquid phase without the precipitation of Mg equilibrium phase, and is formed by a maximum grain size (circle equivalent diameter) of 1 μ The fine layer 1 composed of a fine structure of m or less. When the average cooling rate is less than 20 ° C / sec, the Mg phase is largely deposited on the surface of the plating layer, so that the corrosion resistance is extremely deteriorated.

Here, the upper limit of the average cooling rate in the second cooling step, There is no particular limitation, and for example, it is set to about 2000 ° C / sec. The cooling rate of the plated surface at the time of flooding cooling was about 2000 ° C / sec. At this time, it was confirmed that the composite phase disclosed in the present invention was formed. The higher the cooling rate, the more the hardness of the fine layer increases. When it is desired to intentionally increase the wear resistance and the damage, it is only necessary to increase the cooling rate during this period. In general, when coarse quasi-crystals are doped, although the hardness tends to partially increase, the average value of the hardness rises a little and the damage system does not change much.

Moreover, when manufacturing the quasi-crystalline plated steel sheet of this embodiment The method of measuring the temperature of the plating layer can be, for example, a contact type thermocouple (K-type). By mounting a contact type thermocouple on the mother steel sheet, the average temperature of the entire plating layer can be constantly monitored. Further, when mechanically controlling various speeds and thicknesses and unifying various operating conditions such as the preheating temperature of the steel sheet and the temperature of the molten plating bath, it is possible to substantially accurately monitor the plating layer at this point under such manufacturing conditions. The overall temperature. Therefore, the cooling process in the first cooling step and the second cooling step and the heat treatment in the temperature increasing holding step can be precisely controlled. Moreover, although the degree of correctness is not as good as that of the contact type, the surface temperature of the plating layer can also be measured using a non-contact radiation thermometer.

Moreover, it is also possible to perform advance calculation by performing simulation of heat conduction analysis. The relationship between the surface temperature of the plating layer and the average temperature of the entire plating layer is taken. Specifically, it is based on the preheating temperature of the steel sheet, the temperature of the molten plating bath, the drawing speed of the steel sheet from the plating bath, the thickness of the steel sheet, the layer thickness of the plating layer, and the heat exchange between the plating layer and the manufacturing equipment. Various types of heat, heat release of plating layer, etc. The surface temperature of the plating layer and the average temperature of the entire plating layer were determined under the manufacturing conditions. Then, the relationship between the surface temperature of the plating layer and the average temperature of the entire plating layer can be obtained by using the obtained results. Thereby, by measuring the surface temperature of the plating layer when manufacturing the quasi-crystalline plated steel sheet, the average temperature of the entire plating layer at this point under the manufacturing conditions can be estimated. As a result, the cooling process in the first cooling step and the second cooling step and the heat treatment in the temperature increasing holding step can be precisely controlled.

In addition, when the plating step is performed by the melt plating method, in order to perform the fusion For the melt plating, the temperature of the plating bath is usually set to the melting point of the plating alloy (in the plating composition of the present invention, 440 to 540 ° C) + 40 ° C or so. Therefore, in the present invention in which Al is contained in the plating alloy, the Al is instantaneously moved to the interface between the plating layer and the mother steel sheet and formed of an Al-Fe intermetallic compound at the time of initially immersing the plating original plate in the plating bath. The interface alloy layer formed. Once such an interface alloy layer is formed, since the melting point of the Al-Fe intermetallic compound constituting the interface alloy layer is high, then the interface alloy layer is not destroyed by the above heat treatment.

Hereinafter, the plating step of the method for producing a plated steel sheet according to the present invention will be described, and the molten plating method may be employed.

When a material of a plating alloy is produced, it is preferable to use a pure metal (purity of 99% or more) as an alloy material. First, a predetermined amount of the alloy metal is mixed so as to have the composition of the plating layer, and is completely melted by using a high-frequency induction furnace, an electric arc furnace or the like in a vacuum or inert gas substitution state to form an alloy. Further, a molten material obtained by melting the alloy obtained by mixing a predetermined component (composition of the above-mentioned plating layer) in the atmosphere is used as a plating bath.

Here, the bath temperature of the above plating bath is as described above, and is usually plated. The viewpoint of the application operation is preferably about 40 ° C higher than the melting point of the plating alloy, and is preferably 480 ° C to 520 ° C and 550 ° C or less.

Further, the plating alloy system as described above is not particularly limited. The pure Zn alloy, the Mg alloy, and the Al alloy may be dissolved and used. At this time, there is no problem as long as a predetermined composition alloy having less impurities is used.

Also, when applying the melt plating method, Senjimir can be applied. A well-known method such as a (Sendzimir) method, a pre-plating method, a two-stage plating method, a flux method, or the like. Before the plating step of forming the plating layer of the present invention, pre-plating treatment such as Ni pre-plating or Cu pre-plating can also be applied as a pre-treatment. Further, when a plating means such as vapor deposition or sputtering is applied to the plating step, it is not necessary to perform the pretreatment as described above, and a plating layer of a predetermined composition alloy may be formed on the steel sheet.

Further, when the melt plating method is applied to the plating step, in addition to the heat treatment described above, the usual plating operation conditions can be applied without requiring special equipment and conditions. For example, when the plating step is performed by the melt plating method, after immersing in the plating bath, the basis weight is adjusted by wiping with N ₂ gas, and then the above is performed by cooling with N ₂ gas or natural cooling. 1 cooling step can be.

Moreover, as a heating and cooling device for heat treatment, no special equipment and conditions are required. For example, in the heat treatment and the reheat treatment, it is sufficient to appropriately set the operating conditions of the apparatus by using a well-known apparatus such as an IH (Induction Heating) heating furnace or an infrared heating furnace and satisfying the above-described heat treatment conditions. Further, in the cooling treatment, a generally known method such as N ₂ gas cooling, mist cooling, or flooding cooling can be applied. In addition to the N ₂ gas, the cooling gas system may use a gas having a high heat-discharging effect such as He gas or hydrogen gas.

The method for producing a quasi-crystalline plated steel sheet according to the present embodiment has been described in detail above.

(Evaluation method for characteristics of quasi-crystalline plated steel sheets)

Next, a method for evaluating excellent corrosion resistance and peeling resistance exhibited by the quasi-crystalline plated steel sheet according to the present embodiment will be briefly described.

<Evaluation method of corrosion resistance>

In order to evaluate the corrosion resistance of the quasi-crystalline plated steel sheet, it is preferable to perform an exposure test capable of evaluating the corrosion resistance of the plating layer in an actual environment. The corrosion resistance can be evaluated by evaluating the corrosion reduction of the plating layer for a certain period of time.

When the corrosion resistance of the plating layer having high corrosion resistance is compared, it is preferable to carry out a long-term corrosion resistance test. The corrosion resistance was evaluated based on the magnitude of the period during which red rust was generated. Further, when evaluating the corrosion resistance, it is also considered that the corrosion resistance period of the steel sheet is important.

In order to evaluate the corrosion resistance more simply, a corrosion promotion test called a composite cyclic corrosion test, a warm water spray test, or the like can be used. The corrosion resistance can be judged by evaluating the corrosion reduction and the red rust prevention period. Further, when the corrosion resistance is compared with the plating layer having high corrosion resistance, it is preferable to carry out a corrosion promotion test using a NaCl solution having a high concentration (for example, about 5%). When using a concentrated aqueous solution (for example, less than 1%), most of the NaCl solution The situation is that it is not easy to judge the pros and cons of corrosion resistance.

<Evaluation method of peeling resistance>

In order to evaluate the peeling resistance of the quasi-crystalline plated steel sheet, for example, a method of visually evaluating the peeling area of the plating layer using a Gravelo tester is preferred. The test conditions may be appropriately set, for example, by using a Gravelo test machine to make the No. 7 crushed stone 100g from a distance of 30 cm and under an air pressure of 3.0 kg/cm 2 , and cooling to -20 at an angle of 90 degrees. The plating layer of °C may be subjected to conditions such as collision.

Moreover, the evaluation of the peeling resistance is compared to the direct use of the plating. In the evaluation of the steel sheet in the state, it is preferable to carry out the electrodeposition coating, the intermediate paint, and the coated steel sheet after the top coat coating, after the treatment with the phosphoric acid chemical method, which is close to the actual use condition.

<Evaluation method of area ratio>

In addition, the area ratio of MgZn contained in each of the plating layers is determined by TEM electron beam diffraction to identify the target phase as MgZn, and then the SEM field is replaced with the SEM field of view and evaluated according to the following method. That is, the image obtained from the SEM field of view is binarized into a white-black image, and the area occupied by the MgZn phase with respect to the entire plating layer can be calculated by computer image processing.

<Evaluation method of hardness of plating layer>

As a method of evaluating the hardness of the plating layer, it is simple to produce a plating layer having a thickness of 10 μm or more and to measure the Vickers hardness from the surface. However, in this method, if there is no plating thickness to some extent, it is necessary to be affected by the hardness of the ferrite, the interface alloy layer, and the compound layer. When the plating layer has a certain thickness, the hardness of the plating layer of the electrode surface layer is measured. The higher the hardness of the plating layer, the more excellent the abrasion resistance can be judged. It is preferred to use a cross section of the plating layer and to evaluate the hardness per phase using a nanoindenter or the like.

<Evaluation method of plating adhesion>

When the adhesion of the plating layer is evaluated, it is usually evaluated by peeling off the tape in the uneven portion after the ball impact test. The smaller the amount of peeling, the more excellent the adhesion. In addition, after the V-shaped bending test, the T-bend test, and the Erichsen test, the adhesion of the tape in the processed portion was evaluated in the same manner.

The evaluation method of the characteristics exhibited by the quasi-crystalline plated steel sheet according to the present embodiment has been briefly described above.

Example

Hereinafter, the effects of the present invention will be described by way of examples, but the present invention is not limited by the conditions used in the following examples.

First, a material having ingots having chemical compositions shown in Tables 1 to 8 as a plating alloy was produced and a plating bath was produced. Further, a cold-rolled steel sheet (plate thickness: 0.6 mm) was used as the original plate (plated original plate) of the plated steel sheet. After the cold-rolled steel sheet was cut into 10 cm × 17 cm, it was plated using a company-made batch type molten plating test apparatus. Further, as the cold-rolled steel sheet, low carbon steel (C: 0.1% or less, Si: 0.01% or less, Mn: 0.2% or less, P and S: 0.03% or less, and Fe: balance) is usually used.

Further, in the blank of the chemical composition of the plating alloy, the chemical component is not intentionally added.

Hereinafter, a method of forming the plating layer of the present embodiment will be specifically described in detail.

First, after the plated original plate is subjected to reduction annealing in a 5% H ₂ -N ₂ atmosphere at 800 ° C for 1 minute, the plated original plate is immersed in a plating bath having a melting point of +40 ° C of the original plate, and is pulled up by using N ₂ gas. Wipe to adjust the amount of plating adhesion (plating step).

The temperature of the specific plating bath and the subsequent temperature history of the plating production are shown in Tables 9 to 12 in detail.

Moreover, in order to confirm the structure of the plating layer, the obtained plating is performed. The cross-sectional direction of the steel sheet was subjected to CP processing and subjected to FE-SEM observation. Using the obtained FE-SEM image as the evaluation standard, it is possible to observe that the compound layer 2 and the multilayer structure formed by the fine layer 1 formed above the compound layer 2 are marked with "+", and can only be observed. "-" is attached to the person who has the fine layer 1 and the person who is composed of other organizations. In the case where the multi-layer structure cannot be confirmed, the ratio of the thickness of the entire plating layer 1 to the fine layer (second plating layer) 1 is measured.

For the cracking of the plating layer, the surface of the plating layer is observed by SEM. And select any 1 cm quadrilateral field of view of 5 fields of view. After one field of view is divided into 100 grid-shaped areas of 1 mm 2 , each region is observed, and a cracker attached "+" can be observed by 50% or more on the average value, and "-" can be attached to an unobservable person.

In addition, it is possible to confirm the multi-layer structure by observing the cross-section of the plating layer obtained by diffracting the image from the electron beam of the TEM, and confirming the compound layer 2 of the first plating layer and the fine layer 1 of the second plating layer. Plated tissue. Here, in the compound layer 2, "+" is attached to each of the plating structures in which MgZn, Mg, and quasicrystals can be observed. Similarly, in the fine layer 1, "+" is attached to each of the plating structures in which Mg ₅₁ Zn ₂₀ , Zn, and quasicrystals can be observed. Further, it can be observed that the interface alloy layer composed of the Al-Fe intermetallic compound is marked with "+", and the thickness of the interface alloy layer is measured, and "-" is attached to the non-existent one.

In addition, in the cross-sectional observation of the plating layer obtained by diffracting the image from the electron beam of the TEM, it is possible to confirm that the multi-layer structure is composed of the MgZn phase, the Zn phase, and the quasi-crystalline phase in the compound layer 2. The area ratio of the structure, and the area ratio of the structure composed of the Mg ₅₁ Zn ₂₀ phase, the Zn phase, and the quasi-crystalline phase in the fine layer 1. Moreover, the measurement of the area ratio of each layer is performed by image processing using a computer.

Moreover, for the obtained plated steel sheet, it is based on JASO (Nippon Automotive Technical Specifications) The cyclic corrosion promotion test of M609-91 was carried out to evaluate the bare corrosion resistance (plate corrosion resistance) of the plated steel sheet with a brine concentration of 0.5% NaCl. Specifically, the corrosion reduction after 60 cycles of more than 30 g/m2 is marked as "Poor", 30 to 10 g/m2 is marked as "Good", and less than 10 g/m2 is attached as " Excellent. The removal of the corrosion product of the plating layer was carried out by a method of "chromium oxide (VI) 200 g/l and immersing it at normal temperature for 1 minute".

In order to confirm the effect of suppressing red rust of the plating layer, a salt spray test according to JIS Z2371 was carried out. When the thickness of the plating ( μm ) is more than ×150 hours, it is impossible to observe that the red rust is produced, and the "Good" is attached, and it is possible to confirm that the person who produces the red rust is attached with "Poor". In particular, it is "Excellent" with respect to the plating thickness ( μm ), which is larger than ×200 hours.

The plating adhesion was evaluated by a ball impact test. In the ball In the impact test, a hemispherical convex core is disposed on the back side of the test surface, and a hemispherical concave tray is placed on the test surface side to make a steel 1/2 inch diameter (weight 2 kg) The hammer fell from a height of 70 cm and hit the core. After attaching a Cellophane tape made of NICHIBAN to the test surface after the core was pushed out, it was peeled off and observed to peel off from the surface of the plated steel sheet. It is impossible to observe that the stripper is attached to "Excellent". When the plating layer was slightly peeled off at the edge portion and the convex portion (less than 1% in area%), "Good" was attached, and 1% or more of the peeling was marked "Poor".

White rust is produced by salt water spray according to JIS Z2371:2000 The evaluation was carried out by a fog test (SST: Salt Spray Test). Specifically, using the produced plated steel sheet and performing a salt spray test (SST) using a 5% NaCl aqueous solution, it was investigated to test the white rust having an area % of more than 5% in the plane portion of the plated steel sheet. time. As a result of the evaluation of the white rust, the plated steel sheet which was unable to confirm the white rust after 120 hours was attached "Excellent", and the plated steel sheet which could not be confirmed after 24 hours was confirmed as "Good" In the plated steel sheet which is less than 24 hours and which can confirm the white rust, "Poor" is attached. In addition, "Excellent" means the most excellent evaluation of white rust.

Further, in the obtained plated steel sheet, wet-on-wet was used on a coated plate which was subjected to Zn phosphoric acid treatment and coated with an electrodeposition paint (Power top U-30 manufactured by PAINT Corporation, Japan). After coating the lacquer coating (Orga P-2, manufactured by PAINT AG, Japan), it was baked at 140 ° C for 30 minutes. As a topcoat paint, a metallic color coating (manufactured by Nippon PAINT Co., Ltd., trade name "Superlac M-155 Silver") is applied so as to have a dry film thickness of about 15 μm , and is wet. The transparent paint (manufactured by Nippon PAINT Co., Ltd., trade name "Superlac O-150 Clear") was applied so as to have a dry film thickness of about 40 μm . After setting for about 7 minutes, a laminated coating film was obtained by baking at 140 ° C for 25 minutes. Here, a solvent-based metallic base paint "Superlac M-90" manufactured by Japan PAINT Co., Ltd. was applied, and the clear coating was applied by wet-wet coating and baked at 140 ° C for 30 minutes.

Next, the peeling resistance was evaluated by performing the above-described series of coated plated steel sheets with a coating film. Specifically, a Gravelo test machine (manufactured by SUGA Test Machine Co., Ltd.) was used, and 100 g of No. 7 crushed stone was subjected to an air pressure of 3.0 kg/cm 2 from a distance of 30 cm, and was collided at an angle of 90 degrees to be cooled to - The film was coated at 20 ° C and the degree of peeling (peeling) was visually observed, and evaluated according to the following criteria. In addition, in the present embodiment, one evaluation is performed, and 3 is attached with "Good", 4 or more is attached to "Excellent", and 2 or less is attached with "Poor".

5 no peeling at all

4 Small peeling area and low frequency

3 The stripping area is small but the frequency is slightly higher

2 Large peeling area but low frequency

1 Large stripping area and high frequency

Further, after the Gravelo test, a salt spray test in accordance with JIS Z2371 was carried out. After 720 hours, it is confirmed that only white rust is attached to "Excellent", and in terms of frequency, it is based on white rust, and the area ratio of red rust is 0 to 10% or less. "Very Good" "10 to 20% or less will be marked with "Good", and those with more than 20% will be marked with "Poor".

The anti-glare effect was evaluated according to the spectrophotometric method. Originally, it is preferable to visually evaluate it, but after confirming that the visual correlation has a correlation with the L* value of the color meter, a spectrophotometer (D65 light source, 10° field of view) and SCI (including specular reflected light) are used. Way to evaluate. Specifically, it will be made The plated steel plate used was a spectrophotometer CM2500d manufactured by Konica Minolta, and the L* value was examined under the conditions of measuring the diameter of 8 Φ, the field of view of 10°, and the D65 light source.

For the anti-glare effect, a plated steel plate with an L* value of less than 75 is attached. "Excellent" is attached, and a plated steel plate having an L* value of not less than 75 is attached with "Poor". Moreover, "excellent" means that it has an excellent antiglare effect.

As an index for evaluating the damage resistance, the plating layer hardness (Vickers hardness) was measured. The sample was cut into 50 × 50 mm, and the Hv value of 30 points was measured in accordance with the lateral 2 mm interval, the longitudinal 7.5 mm interval, the load 10 gf, the AAV-504 manufactured by MITUTOYO, and the maritime test No. H-05TK225. The average Hv value is 250 or more, and the "Excellent" is attached, and the 200 or more is attached with "Good", and the less than 200 is attached to "Poor". Further, 1 gf is about 9.8 × 10 ^-3 N.

The appearance of the plated steel sheet is kept in a constant temperature and humidity chamber. Test to evaluate. Specifically, the produced plated steel sheet was stored in a constant temperature and humidity chamber at a temperature of 40° C. and a humidity of 95% for 120 hours, and the area % of the blackened portion in the plane portion of the plated steel sheet after storage was investigated.

In terms of appearance evaluation, it is 45 mm with respect to the evaluation area × For 70mm, the plated steel plate with a blackening portion of less than 1% is marked "Excellent", and the plated steel sheet with a blackening portion of less than 1% to 3% is marked "Good". The plated steel plate with a variation of 3% or more is marked with "Poor". Moreover, "Excellent" means the most excellent appearance evaluation.

Moreover, as a comparative material, in the case of a Zn-based plated steel sheet, a needle is used. The commercially available molten Zn plated steel was evaluated in the same manner for Zn-22%Al-7%Mg-0.2%Si.

The above evaluation results are shown together in Tables 13 to 20 below.

Heretofore, the preferred embodiments of the present invention have been described in detail with reference to the appended drawings, but the present invention is not limited by such examples. It is to be understood that various modifications and changes can be made without departing from the spirit and scope of the inventions. The technical scope.

1‧‧‧2nd plating layer (micro layer)

2‧‧‧1st plating layer (compound layer)

3‧‧‧ alloy layer (interface alloy layer)

Claims (11)

A quasi-crystalline plated steel sheet comprising: a plating layer on at least one surface of the steel sheet; and an alloy layer located at an interface between the plating layer and the steel sheet and composed of an Al-Fe intermetallic compound The chemical composition of the plating layer is in atom%, and contains: Zn: 28.5% to 50% Al: 0.3% to 12% La: 0% to 3.5% Ce: 0% to 3.5% Y: 0% to 3.5% Ca: 0% to 3.5% Sr: 0% to 0.5% Si: 0% to 0.5% Ti: 0% to 0.5% Cr: 0% to 0.5% Fe: 0% to 2% Co: 0% to 0.5% Ni :0%~0.5% V:0%~0.5% Nb:0%~0.5% Cu:0%~0.5% Sn:0%~0.5% Mn:0%~0.2% Sb:0%~0.5% Pb: 0% to 0.5%, and the remaining portion is composed of Mg and impurities; the plating layer sequentially has the first plating layer from the side of the steel sheet, which is composed of a structure containing a MgZn phase, a Mg phase, and a quasi-crystalline phase. And the second plating layer is formed on the first plating layer and is composed of a structure containing a Mg ₅₁ Zn ₂₀ phase, a Zn phase, and a quasi-crystalline phase. The quasi-crystalline plated steel sheet according to claim 1, wherein the chemical composition of the plating layer is in atomic %, and contains: Zn: 32% to 40% Al: 2% to 5% Ca: 1% to 2.5%, and The remaining part is composed of Mg and impurities; and the aforementioned chemical composition satisfies: Zn/Al=7.5~18 Ca/Al=0.4~1.1; and the maximum crystal grain size of the second plating layer is calculated by the circle equivalent diameter It is 1 μm or less. In the quasi-crystalline plated steel sheet according to claim 1 or 2, when the plating layer is viewed in a cross section parallel to the cutting direction in the thickness direction, the MgZn phase of the first plating layer is equivalent by a circle The crystal grains having a diameter of 1 μm or more are formed, and the quasi-crystalline phase of the first plating layer is along The structure is formed by the growth of the plate thickness direction. In the quasi-crystalline plated steel sheet according to claim 1, when the plating layer is viewed in a cross section parallel to the cutting direction in the thickness direction, the second plating is performed on the entire cross-sectional area of the second plating layer. The maximum crystal grain size of the coating layer is 90% or more in the area of the structure having a circle equivalent diameter of 1 μm or less. In the quasi-crystalline plated steel sheet according to claim 1, when the plating layer is viewed in a cross section parallel to the cutting direction in the thickness direction, the first plating is performed on the entire cross-sectional area of the first plating layer. The area of the aforementioned MgZn phase of the coating layer is 10% to 70%. The quasi-crystalline plated steel sheet according to claim 1, wherein the second plating layer does not contain a Mg phase. The quasi-crystalline plated steel sheet according to claim 1, wherein the average value of the Vickers hardness of the second plating layer is 250 to 350 Hv. The quasi-crystalline plated steel sheet according to claim 1, wherein the alloy layer contains at least one of Fe ₅ Al ₂ or Al _3.2 Fe as the Al—Fe intermetallic compound, and the alloy layer has a thickness of 10 nm to 200 nm. . A method for producing a quasi-crystalline plated steel sheet, comprising: a plating step of disposing a molten alloy in a molten state on at least one of the surfaces of the steel sheet, wherein the chemical composition of the plating alloy is in atom%, and :Zn: 28.5%~50% Al: 0.3%~12% La: 0%~3.5% Ce: 0%~3.5% Y: 0%~3.5% Ca: 0%~3.5% Sr: 0%~0.5% Si: 0%~0.5% Ti: 0%~0.5% Cr: 0%~0.5% Fe :0%~2% Co:0%~0.5% Ni:0%~0.5% V:0%~0.5% Nb:0%~0.5% Cu:0%~0.5% Sn:0%~0.5% Mn: 0%~0.2% Sb: 0%~0.5% Pb: 0%~0.5%, and the remaining part is composed of Mg and impurities; the first cooling step is to average the cooling rate of the molten alloy in the molten state. 10° C./sec or less is cooled to a temperature range of 330° C. or less to form a plating layer on the surface of the steel sheet, and a temperature increasing holding step is performed after the first cooling step, and the plating layer is heated at a temperature of 10 to 50. The temperature range of °C/sec is raised to a temperature range of 350 ° C to 400 ° C while maintaining 5 to 30 seconds; In the second cooling step, after the temperature increase holding step, the plating layer is cooled at a cooling rate of 20 ° C /sec or more. The method for producing a quasi-crystalline plated steel sheet according to claim 9, wherein the plating step is performed by a melt plating method, and after the steel sheet is taken out from the molten plating bath, the first cooling step is performed. . The method for producing a quasi-crystalline plated steel sheet according to claim 9 or 10, wherein the chemical composition of the molten alloy in the molten state is in atomic %, and contains: Zn: 32% to 40% Al: 2% to 5% Ca : 1% to 2.5%, and the remainder is composed of Mg and impurities; and the aforementioned chemical composition satisfies: Zn/Al = 7.5 to 18 Ca/Al = 0.4 to 1.1.