Hot-dip galvanized steel

Abstract

This hot-dip plated steel material has a plating layer having a desired average chemical composition, and when the distance from the surface of the plating layer to the interface between the base steel and the plating layer is taken as the thickness t of the plating layer, in a region from a thickness position 0.1×t from the surface of the plating layer to a thickness position where an Fe concentration of 40% of the Fe concentration in the base steel is detected, there is a region in which the total amount ΣA of Cr and Mo is 0.05 mass% or more, which extends continuously for 1.0 μm or more in the thickness direction of the base steel.

Description

[Technical field]

[0001] The present invention relates to a hot-dip galvanized steel material. [Background technology]

[0002] When steel materials are used for a long period of time, it is preferable to apply some kind of rust-proofing treatment to the steel materials to make them resistant to corrosion. Hot-dip galvanizing is used as a cheap method of rust-proofing steel materials in various fields where rust prevention is required, such as civil engineering, construction, and automotive fields.

[0003] The corrosion protection measures by the plating layer are determined by the inherent corrosion resistance and thickness of the plating layer. For example, Patent Document 1 describes the production of a plated steel sheet by a so-called continuous hot-dip plating method in which a steel sheet is continuously immersed in a hot-dip plating bath. The plated steel sheet is then processed into a part shape. The continuous hot-dip plating method is applied to form zinc plating or Zn alloy plating containing Al and Mg. In the continuous hot-dip plating method, the thickness of the plating layer is relatively thin compared to the post-plating method described later.

[0004] Patent Document 2 discloses a method of immersing a plated object processed into a predetermined shape in a plating bath. This method is also called a batch-type hot-dip plating method or a post-plating method. In the post-plating method, the plated object is immersed in the plating bath for one minute or more, so the plating layer tends to be thick, but compared with the continuous hot-dip plating method, there are greater restrictions on the alloy components, corrosion resistance tends to be inferior, and manufacturability is also significantly inferior.

[0005] However, in an environment where the time when the steel sheet is wetted with water is long, the steel sheet becomes extremely susceptible to corrosion. Therefore, in order to improve the corrosion resistance by wetness, it is important to increase the thickness of the plating layer in order to extend the service life of the steel sheet. If a Zn alloy plating layer containing a large amount of Al can be produced by the continuous hot-dip plating method to a thickness similar to that of the post-plating method, it will be possible to efficiently produce a steel sheet that provides long-term corrosion protection for steel materials.

[0006] Coated steel sheets manufactured by the continuous hot-dip galvanizing method are used in the civil engineering and building materials fields, and long-term corrosion resistance is required. The thickness of the coating layer of coated steel sheets manufactured by the continuous hot-dip galvanizing method is often about 20 to 30 μm. This is due to the process characteristics of the continuous hot-dip galvanizing method, such as lifting the molten metal when pulling the steel sheet out of the coating bath, gas wiping, and air-cooling solidification. If the pulling speed from the coating bath is increased, the coating layer becomes thicker, but since it becomes difficult to control the surface appearance, in reality, the upper limit of the coating layer thickness is strictly limited by wiping adjustment. For this reason, when a Zn alloy coating layer containing Al and Mg is manufactured by the continuous hot-dip galvanizing method, it is generally difficult to manufacture a coating layer with a thickness of 30 μm or more. This is because a coating bath containing a large amount of Al has a lighter specific gravity and a lower viscosity of the coating bath itself, and as a result, the amount of molten metal attached when the steel sheet is pulled out of the coating bath is reduced.

[0007] In recent years, various elements other than Al and Mg have been added to the Zn alloy plating bath in order to impart properties other than corrosion resistance to the plating layer. As shown in Patent Document 1, for example, Si, Sn, etc. may be added to the plating bath. These elements are likely to combine with Mg, Al, or Zn in the Zn alloy to form intermetallic compounds with high melting points. In addition, Si, Sn, etc. also combine with the steel components of the steel sheet passing through the plating bath to form intermetallic compounds with Fe, etc., which become fine particles (fine dross) and float or settle in the plating bath. Such micro-sized intermetallic compounds adhere to the steel sheet during hot-dip plating, causing non-plating (areas where the plating layer is not formed on the steel sheet) or making the plating layer surface uneven, which has become a problem of poor appearance. In order to suppress the precipitation of such fine intermetallic compounds, it is said that raising the plating bath temperature is effective. By using a high-temperature plating bath, fine dross is redissolved in the plating bath, making it possible to perform stable plating operations over a long period of time. However, increasing the temperature of the plating bath is likely to increase the thickness of the interfacial alloy layer, so there is a limit to how high the bath temperature can be.

[0008] In other words, considering that a plating bath with a high Al concentration has a low viscosity and a high melting point, when attempting to produce a thick plating layer with excellent corrosion resistance by a continuous hot-dip plating method, it is said to be difficult to produce due to the specific gravity and viscosity of the plating bath. Also, there has been no feasible means of operating for a long time without generating floating dross in a system where various alloy elements are added.

[0009] For example, Patent Document 3 discloses a surface-treated steel material in which a coating film is formed on the surface of the steel material via a base layer including at least an aluminum-zinc alloy plating layer. However, Patent Document 3 leaves room for improvement in terms of improving corrosion resistance and water-wet corrosion resistance. In addition, since the steel sheet provided with the plating layer is processed into parts of various shapes, it is also required to have excellent processability. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] International Publication No. 2018 / 139619 [Patent Document 2] Japanese Patent Publication No. 61-295361 [Patent Document 3] Japanese Patent Application Publication No. 2017-197795 Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hot-dip plated steel material excellent in corrosion resistance, water-wet corrosion resistance and workability. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention employs the following configuration. [1] A hot-dip plated steel material having a base steel material and a plating layer disposed on a surface of the base steel material, the average chemical composition of the plating layer being, in mass%, Al: over 10% and under 45% Mg: 4.0-15.0%, Si: 0 to 2.00%, Cr: 0-3.00%, Mo: 0-3.00%, Sn: 0-0.7%, Bi: 0 to 0.3%, In: 0 to 0.3%, Ca: 0-0.60%, Y: 0 to 0.3%, La: 0-0.3%, Ce: 0-0.3%, Sr: 0-0.3%, Li: 0~0.3%, Ni: 0-1.0%, Cu: 0-1.0%, Ag: 0~0.25%, Sb: 0-0.25%, Pb: 0~0.25%, B: 0 to 0.50%, P: 0-0.50%, Ti: 0 to 0.25%, Co: 0-0.25%, V: 0~0.25%, Nb: 0-0.25%, Mn: 0-0.25%, Zr: 0-0.25%, W: 0 to 0.25%, Fe: 0-5.0%, The balance is Zn and impurities, and Total amount of Cr and Mo ΣA: 0.03 to 3.00%, Total content of Sn, Bi and InΣX: 0~0.7% Total amount of Ca, Y, La, Ce, Sr and Li, ΣYa: 0~0.6%, Total amount of Ni, Cu, Ag, Sb and Pb ΣYb: 0~1.0%, Total amount of B and P ΣYc: 0 to 0.50% Total amount of Ti, Co, V, Nb, Mn, Zr and W ΣZ: 0~0.25% ΣYa≦Si+Cr+Mo, and In the element distribution profile obtained by performing GDS analysis in the thickness direction of the base steel material from the surface of the plating layer toward the base steel material, when the thickness position at which the Fe concentration of 95% of the base steel material Fe concentration is detected is defined as the interface between the plating layer and the base steel material, and the distance from the surface of the plating layer to the interface is defined as the thickness t of the plating layer, In the region from the thickness position of 0.1×t from the surface of the plating layer to the thickness position at which the Fe concentration of 40% of the base steel material Fe concentration is detected, a region where the total amount ΣA is 0.05% by mass or more continuously exists in the thickness direction of the base steel material for 1.0 μm or more, the hot-dip plated steel material. [2] The hot-dip plated steel material according to [1], wherein in the element distribution profile, the average value of the total amount ΣA in the region from the interface to 1.0 μm toward the surface of the plating layer is more than 0.50% by mass. [3] The hot-dip plated steel material according to [1] or [2], wherein in the cross section of the plating layer, the total area fraction of the Cr-containing compound and the Mo-containing compound is 1.0% or more. [4] When in the average chemical composition of the plating layer, the Ca concentration is 0.05% by mass or more, the Cr concentration or the Mo concentration is 0.05% by mass or more, and the relationship of ΣYa < Si + Cr + Mo is satisfied, In the X-ray diffraction pattern of the surface of the plating layer, the hot-dip plated steel material according to any one of [1] to [3], which satisfies the following formulas (1) and (2). (Imax(10.5°~11.0°) / (I(10.5°)+0.2×{(|I(11.0°)-I(10.5°)|})≧1.5 …(1) (Imax(20.2°~20.5°)) / (I(20.2°)+0.667×{|I(20.5°)-I(20.2°)|})≧1.5 …(2) Here, Imax(k~m°) is the maximum value of the X-ray diffraction intensity between diffraction angles k~m°, Imax(n°) is the X-ray diffraction intensity at diffraction angle n°, and k, m, and n are the diffraction angles shown in formulas (1) and (2), respectively. [5] The hot-dip plated steel material according to any one of [1] to [4], wherein the thickness t of the plated layer is 15 μm or more. Effect of the Invention

[0013] According to the present invention, it is possible to provide a hot-dip plated steel material having excellent corrosion resistance, water-wet corrosion resistance and workability. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a schematic diagram for explaining formulas (1) and (2) and showing the results of X-ray diffraction measurement. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present inventors have thoroughly investigated a hot-dip plated steel material having a plating layer containing Al, Mg and Zn and produced by a continuous hot-dip galvanizing method, which has a large plating layer adhesion, excellent corrosion resistance and water-wet corrosion resistance, and excellent workability, and a method for producing the same.

[0016] The melting point of a Zn alloy hot-dip plating bath, which contains elements such as Al or Mg in Zn, a low-melting-point metal, tends to increase as it moves away from a ternary eutectic composition or Zn-3%Al-3%Mg (the units of percentages are mass%). The melting point of a plating bath containing more than 10% Al and 4% or more Mg is higher than that of pure Zn (i.e., 100% Zn). When considering the hot-dip plating process, such a Zn alloy plating bath is operated at around 500°C, which is 50°C higher than the melting point of a pure Zn plating bath.

[0017] The specific gravity of alloying elements such as Al and Mg is smaller than that of Zn. The specific gravity of alloying elements is closely related to the viscosity in the molten state. In other words, molten metal containing high concentrations of Al, Mg, etc. has a smaller viscosity. For this reason, in the continuous hot-dip plating method, when a steel sheet is passed through a plating bath at about 500°C at a constant line speed, the amount of hot-dip plating bath that adheres to the steel sheet and rises with the steel sheet is significantly smaller than in the case of pure Zn plating. Therefore, in order to stably produce a plating layer with a thickness of more than 20 μm, it is essential to develop wiping technology, etc. However, since the specific gravity of the molten metal that constitutes the plating layer is small to begin with, the molten metal is light, so it is easily blown away during wiping blow. In addition, since it is prone to wrinkles, it is difficult to produce a thick plating layer even if wiping technology, etc. is improved.

[0018] In addition, silicon and other elements are sometimes added to the plating bath to enhance its performance. However, added elements such as silicon tend to combine with iron and magnesium, and furthermore, form floating dross that tends to settle in the plating bath. In particular, floating dross tends to form in plating baths at around 500°C.

[0019] Furthermore, when the plating bath contains Al, the reaction between Al and Fe becomes active, so that an Al-Fe-based interface alloy layer is easily formed when the base steel is passed through the plating bath. The Al-Fe-based interface alloy layer has large irregularities. Therefore, when the thickness of the Al-Fe-based interface alloy layer exceeds 1.0 μm, in the case of a thick plating layer, cracks originating from the Al-Fe-based alloy layer may propagate to the plating layer during bending tests, etc., and peeling of the plating layer may occur. This phenomenon becomes more noticeable as the temperature of the plating bath increases. For this reason, it becomes difficult to manufacture hot-dip plated steel with excellent workability under conditions of high Al concentration and high plating bath temperature.

[0020] Therefore, the present inventors have conducted extensive research to solve the above problems. In order to produce a coating layer with a large adhesion amount under conditions of a high Al concentration and high bath temperature in the coating bath, it is first necessary to increase the viscosity of the coating bath. This can be achieved by adding an element with a high specific gravity to the coating bath. In particular, the addition of Cr increases the specific gravity and viscosity of the coating bath, making it possible to increase the coating adhesion amount to the base steel material during threading. Note that Mo can be given as an element that exerts the same effect as Cr.

[0021] On the other hand, when Cr or Mo is added to the coating bath, floating dross tends to form in the coating bath because Cr or Mo easily combines with elements such as Si, Ca, and Mg. However, since these floating dross are fine, the floating dross can be redissolved in the coating bath by raising the temperature of the coating bath to around 600°C. On the other hand, in a coating bath at about 600°C, the Al-Fe alloying reaction is active, and a short immersion of the base steel can cause the Al-Fe-based interface alloy layer to grow thick, which can significantly impair the workability of the subsequent hot-dip coated steel. Therefore, it is necessary to control the immersion time of the base steel in the coating bath to be short.

[0022] In addition, by pre-coating the base steel with a high melting point metal such as Cr or Ni, the reaction between Al and Fe is suppressed, and the growth of the interface alloy layer can be significantly suppressed, making it possible to manufacture hot-dip plated steel that has excellent corrosion resistance, wet corrosion resistance, and workability, and has a relatively large coating weight of the plating layer.

[0023] Hereinafter, a hot-dip plated steel material according to an embodiment of the present invention will be described.

[0024] In the following description, the "%" used to indicate the concentration of each element in the chemical composition means "mass %." Furthermore, a numerical range expressed using "~" means a range that includes the numerical values ​​before and after "~" as the lower and upper limits. Furthermore, when the numerical values ​​before and after "~" are followed by "more than" or "less than," the numerical range does not include these numerical values ​​as the lower or upper limit.

[0025] The base steel material to be plated will now be explained. The base steel material is, for example, mainly a steel plate, but there is no particular limit to its size. The steel plate may be any steel plate that is applicable to a normal hot-dip galvanizing process. Specifically, this applies to steel plates that are applicable to processes in which the steel plate is immersed in molten metal and solidified, such as a continuous hot-dip galvanizing line (CGL). The size of the steel plate that can be applied is, for example, a plate thickness of 10 mm or less and a plate width of 2000 mm or less, but the size of the steel plate is not limited to this. The plate thickness of the base steel plate is preferably 0.25 to 10.00 mm, more preferably 0.40 to 10.00 mm, 0.50 to 10.00 mm, or 0.5 to 6.00 mm.

[0026] The material of the base steel material is not particularly limited. Examples of the base steel material that can be used include various steel plates, steel wire materials, and steel wires, such as general steel, pre-plated steel thinly plated with various metals, Al-killed steel, ultra-low carbon steel, high carbon steel, various high tensile steels, some high alloy steels (steels containing elements that enhance corrosion resistance, such as Ni and Cr), soft steel wire, hard steel wire, spring steel, steel cord, steel for bolts, and steel wire material for bridge cables. More specifically, for example, hot-rolled mild steel sheets and steel strips as specified in JIS G 3131:2018, cold-rolled steel sheets and steel strips as specified in JIS G 3141:2021, general structural rolled steel materials as specified in JIS G 3101:2020, various plated steels thinly plated with various metals such as JIS H 8641:2021, JIS G 3302:2022, JIS G 3303:2022, JIS G 3313:2021, JIS G 3314:2022, JIS G 3315:2022, JIS G 3317:2022, and JIS G 3321:2022 (hereinafter, plating to make a plated steel sheet into a base steel material is also referred to as "pre-plating", and a plated steel material or plated steel sheet as a base steel material is also referred to as a "pre-plated steel material or pre-plated steel sheet"). Applicable steels include rolled steel materials for architectural structures specified in JIS G 3136:2022, various high-tensile steels specified in JIS G 3113:2018, JIS G 3134:2018, JIS G 3135:2018, etc., and some high alloy steels (steels containing corrosion-resistant strengthening elements such as Ni and Cr, etc.).

[0027] As mentioned above, the surface of the base steel is pre-plated with 0.3 to 5.0 g / m 2 Alternatively, a Ni-plated layer, a Cr-plated layer or a Mo-plated layer may be provided in a coating amount of 0.01 to 0.01 mm. By using a base steel material provided with such a pre-plated layer, it is possible to suppress the growth of an Al-Fe-based interface alloy layer, suppress the occurrence of powdering, etc., and improve workability.

[0028] In addition, the manufacturing process of the base steel material includes general processes such as iron-making and steel-making processes using a blast furnace or electric furnace, a hot rolling process, a pickling process, a cold rolling process, and a heat treatment process. The base steel material of this embodiment may have undergone any of these processes, and the processing conditions of each process are not limited.

[0029] Next, the plating layer will be described. The plating layer according to this embodiment includes a Zn-Al-Mg alloy layer. When Zn contains alloy elements such as Al and Mg, corrosion resistance is improved, so that a thin plating layer with a small thickness, for example, about half the thickness of a normal Zn plating layer, has the same corrosion resistance. Therefore, in this embodiment, a thin plating layer also has corrosion resistance equal to or greater than that of a Zn plating layer. The plating layer may also include an Al-Fe interface alloy layer.

[0030] The Zn-Al-Mg alloy layer is made of a Zn-Al-Mg alloy, which means a ternary alloy containing Zn, Al, and Mg. The thickness of the Zn-Al-Mg alloy layer may be 4 to 80 μm. If necessary, the lower limit may be 7 μm, 10 μm, 15 μm, or 20 μm, and the upper limit may be 70 μm, 60 μm, or 50 μm.

[0031] The Al-Fe interfacial alloy layer is often an interfacial alloy layer between the base steel material and the Zn-Al-Mg alloy layer, and is in contact with the surface of the base steel material.

[0032] That is, the plating layer may be a single-layer structure of a Zn-Al-Mg alloy layer, or a laminate structure including a Zn-Al-Mg alloy layer and an Al-Fe interfacial alloy layer. In the case of a laminate structure, the Zn-Al-Mg alloy layer is preferably a layer constituting the surface of the plating layer.

[0033] Although the Al-Fe-based interface alloy layer has a small contribution to corrosion resistance, it ensures adhesion of the plating layer during processing of hot-dip plated steel material and affects workability (presence or absence of cracks). In particular, the Al-Fe-based interface alloy layer may affect powdering resistance, which indicates the degree of peeling of the plating layer during processing. Usually, the thinner the Al-Fe-based interface alloy layer, the fewer the crack initiation points of the plating layer during processing, and the better the powdering resistance. For this reason, in hot-dip plated steel material that may be subjected to high processing during use, it is preferable that the Al-Fe-based interface alloy layer is as thin as possible. Specifically, the thickness of the Al-Fe-based interface alloy layer is preferably less than 5.0 μm. The thickness of the Al-Fe-based interface alloy layer is more preferably 2.0 μm or less, and even more preferably 1.0 μm or less, 0.5 μm or less, or 0.3 μm or less. This makes it possible to suppress the generation of cracks during processing and to further improve powdering resistance. Furthermore, it is preferable that the thickness of the Al-Fe-based interface alloy layer accounts for less than 10% on average, and more preferably less than 5% of the entire plating layer.

[0034] As described above, when a pre-plated steel material pre-plated with Cr, Mo or Ni is used as the base material for plating (base steel material), the Al-Fe-based interface alloy layer in the hot-dip plated steel material according to this embodiment becomes extremely thin and may be barely visible. Also, when a pre-plated steel material that has been pre-plated in advance is used as the base material for plating, elements constituting the pre-plated layer may be taken into the base steel material side or the Al-Fe alloy layer.

[0035] The Al-Fe-based interface alloy layer is a layer in which the Al5Fe2 phase is the main phase in the structure. The Al-Fe-based interface alloy layer is formed by mutual atomic diffusion between the base steel (base steel material) and the plating bath. When a continuous hot-dip plating method is used as a manufacturing method, the Al-Fe-based interface alloy layer is likely to be formed in the plating layer containing the Al element. In this embodiment, since the plating bath contains Al at a certain concentration or more, the Al5Fe2 phase is formed most frequently in the Al-Fe-based interface alloy layer. However, since atomic diffusion takes time, the Fe concentration in the Al-Fe-based interface alloy layer is not uniform, and the Fe concentration may be high in the part close to the base steel. Therefore, the Al-Fe-based interface alloy layer may partially contain small amounts of the AlFe phase, the Al3Fe phase, the Al5Fe2 phase, etc. In addition, since the plating bath also contains a certain concentration of Zn, the Al-Fe-based interface alloy layer may also contain small amounts of Zn or Si, which is likely to accumulate at the interface.

[0036] In this embodiment, the plating layer may contain Si. A part of Si is incorporated into the Al-Fe-based interface alloy layer to form an Al-Fe-Si intermetallic compound phase. The intermetallic compound phase identified is the AlFeSi phase, and isomers include α, β, q1, q2-AlFeSi phases. Therefore, these AlFeSi phases may be detected in the Al-Fe-based interface alloy layer. The Al-Fe-based interface alloy layer containing these AlFeSi phases is also referred to as an Al-Fe-Si alloy layer.

[0037] The thickness of the entire plating layer depends on the plating conditions, so the upper and lower limits of the thickness of the entire plating layer are not particularly limited. Also, it is affected by the pulling speed of the steel material from the plating bath and the wiping conditions. That is, the thickness of the entire plating layer is affected by the viscosity and specific gravity of the plating bath in the continuous hot-dip plating method. Since the maximum value of the thickness of the plating layer formed by the continuous hot-dip plating method is often 100 μm or less, the thickness of the plating layer of the hot-dip plated steel material of this embodiment may be, for example, 100 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, or 50 μm or less. However, when a plating bath containing a high concentration of Al is usually produced at a bath temperature of around 600 ° C., the viscosity of the plating bath is low, so the thickness of the plating layer is often around 20 μm. In some cases, the immersion time can be increased to thicken the Al-Fe-based interface alloy layer and make the entire plating layer thick, but as described above, if the Al-Fe-based interface alloy layer is made thick, the workability is extremely deteriorated. The thickness of the plating layer is 20% or less of the thickness of the base steel material, but may be 15% or less, 10% or less, or 5% or less of the thickness of the base steel material, if necessary. The thickness of the plating layer may be 15 μm or more, 20 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, or 45 μm or more, if necessary.

[0038] Next, the average chemical composition of the plating layer will be described. When the plating layer has a single-layer structure of the Zn-Al-Mg alloy layer, the average chemical composition of the entire plating layer is the average chemical composition of the Zn-Al-Mg alloy layer. When the plating layer has a laminated structure of the Al-Fe interfacial alloy layer and the Zn-Al-Mg alloy layer, the average chemical composition of the entire plating layer is the average chemical composition of the Al-Fe interfacial alloy layer and the Zn-Al-Mg alloy layer combined.

[0039] Al: More than 10% and less than 45% Al is an element constituting the main part of the plating layer. When the Al concentration exceeds 10%, the melting point of the plating layer becomes higher than that of pure Zn. In addition, Cr, which is necessary to increase the thickness of the plating layer in this embodiment, is not solid-soluble in Zn and Mg. Therefore, a certain amount of Al is required to contain Cr. Since the minimum concentration required for this purpose is more than 10%, the Al concentration is set to more than 10%. Furthermore, Al is an essential element for forming a Cr-containing intermetallic compound or a Mo-containing intermetallic compound. The Al concentration is preferably 18% or more, and more preferably 25% or more. On the other hand, if the Al concentration is 45% or more, the reactivity between the plating bath and the base steel increases, making it difficult to suppress the Al-Fe interfacial alloy layer, and ensuring workability with a thick plating becomes difficult. In addition, the thickness of the Zn-Al-Mg alloy layer decreases by the amount that the Al-Fe interfacial alloy layer is formed thicker. Therefore, the Al concentration is set to less than 45%. The Al concentration is preferably 38% or less, and more preferably 35% or less.

[0040] Mg: 4.0-15.0% Like Zn, Mg is an element that constitutes the main part of the plating layer. Mg is necessary for high corrosion resistance, and forms a relatively hard MgZn2 phase in the Zn-Al-Mg alloy layer. Mg is an element necessary for ensuring water-wet corrosion resistance in a water-wet environment. If the Mg concentration is less than 4.0%, it will not form appropriate compounds with Cr, Mo, etc., and the plating layer will be thin regardless of the Cr content. Therefore, the Mg concentration is set to 4.0% or more. One of the reasons why high water-wet corrosion resistance can be obtained by including Mg is the MgZn2, Mg 32 (Zn, Al) 49 The Mg concentration is preferably 5.0% or more, more preferably 6.0% or more. On the other hand, if the Mg concentration exceeds 15.0%, it becomes difficult to form an intermetallic compound with Cr. In addition, the viscosity of the plating bath becomes extremely high, which significantly deteriorates the plating appearance. In addition, the plating bath does not pull up when pulling up, resulting in an extremely thin plating thickness. For this reason, the Mg concentration is set to 15.0% or less. The Mg concentration is preferably 13.0% or less, more preferably 10.0% or less.

[0041] Cr: 0~3.00% Mo: 0-3.00% Total amount of Cr and Mo ΣA: 0.03~3.00% When Cr is contained in a Zn-based plating bath containing Al, it increases the specific gravity of the plating bath and improves the viscosity of the plating bath. As a result, when the steel material is pulled out of the plating bath, the amount of molten metal that adheres to the steel material increases, and the plating layer becomes thicker. In addition, the presence of Cr in the plating bath increases the amount of Al in the early stages of solidification of the plating layer. 18 Cr-containing intermetallic compounds, such as Cr2Mg3, are formed, which promotes the increase in the thickness of the plating layer. It is difficult to distinguish which effect is greater, the effect of these intermetallic compounds or the effect of increasing specific gravity and viscosity, but both are considered to be the effects of the Cr content. When Al and Mg are in the appropriate concentration range, this effect tends to increase the plating adhesion weight when Cr is 0.03% or more. Therefore, it is preferable to set the Cr concentration to 0.03% or more. The Cr concentration is more preferably 0.10% or more, 0.30% or more, 0.50% or more, 0.70% or more, or 1.00% or more.

[0042] On the other hand, Cr-containing intermetallic compounds form floating dross in the coating bath. The floating dross generates coating defects such as non-coating and dross adhesion defects, which greatly affect the shape and performance of the product and deteriorate the corrosion resistance. Therefore, it is preferable to completely dissolve these floating dross in the coating bath, and for this reason, in this embodiment, the temperature of the coating bath when Cr is contained needs to be 600°C or higher. If the Cr concentration exceeds 3.00%, it is difficult to completely dissolve these floating dross even if the temperature of the coating bath is increased, and the viscosity of the coating bath becomes extremely high, reducing the amount of molten metal attached when the steel material is pulled out of the coating bath, and the thickness of the coating layer becomes extremely thin. In addition, the coating appearance is significantly deteriorated. For this reason, the Cr concentration is set to 3.00% or less. The Cr concentration is preferably 2.50% or less, 2.00% or less.

[0043] Mo, which is an element of the same group as Cr, exerts the same effect as Cr. Therefore, it is sufficient to contain at least one of Cr and Mo, and both may be contained. The Mo concentration is preferably 0.03% or more. The Mo concentration is more preferably 0.10% or more, 0.30% or more, 0.50% or more, 0.70% or more, or 1.00% or more. For the same reason as for Cr, the Mo concentration is set to 3.00% or less, and preferably 2.50% or less, and more preferably 2.00% or less. When Mo is added, the Mo-containing intermetallic compounds are Al 10 CaMo2 is produced. In this embodiment, in order to obtain the above-mentioned effects of containing Cr or Mo, the total concentration ΣA of Cr and Mo is set to 0.03 to 3.00%. It is not necessary to contain both Cr and Mo, and the concentration of either Cr or Mo may be within this range. Therefore, the lower limit of the concentration of Cr and Mo is 0%. The total amount ΣA is preferably more than 0.10%, more than 0.30%, 0.50% or more, 0.70% or more, or 1.00% or more. The total amount ΣA is preferably 2.50% or less, 2.00% or less.

[0044] Si: 0 to 2.00% Si suppresses the Al-Fe reaction, thereby suppressing the formation of an Al-Fe-based interface alloy layer. Also, Si is incorporated into a part of the Al-Fe-based interface alloy layer to form an Al-Fe-Si compound. If Si is not contained, the Al-Fe reaction becomes active, the thickness of the Al-Fe alloy layer becomes thick, powdering occurs during processing, and corrosion resistance is significantly impaired. Since Si is not necessary, the lower limit of the Si concentration is 0%. However, if Si is contained in an amount of 0.01% or more, the growth rate of the thickness of the interface alloy layer becomes slow. Therefore, the Si concentration is preferably 0.01% or more. The Si concentration is preferably 0.10% or more, 0.20% or more. On the other hand, if the Si concentration exceeds 2.00%, it bonds with Mg to form a large amount of intermetallic compound (Mg2Si). This causes the viscosity of the coating bath to become extremely high, reducing the amount of molten metal adhering to the base steel when the base steel is pulled out of the coating bath, and the thickness of the coating layer becomes extremely thin. In addition, the coating appearance is significantly deteriorated. For this reason, the Si concentration is set to 2.00% or less. The Si concentration is preferably 1.50% or less, 1.00% or less, 0.40% or less, or 0.30% or less. If the Si concentration is 2.00% or less, almost no Mg2Si is formed.

[0045] Element group X Sn: 0-0.7% Bi: 0 to 0.3% In: 0 to 0.3% Total content of Sn, Bi and InΣX: 0~0.7% Each element of element group X (Sn, Bi, In) is an element that promotes softening of the plating layer when contained in the plating layer. Since Sn, Bi, and In are elements that can be contained arbitrarily, the lower limit of each concentration is 0%. When Sn is contained, Mg9Sn5 tends to form in the plating layer. Bi forms Mg3Bi2, and In forms Mg3In, etc. These elements are softer than the MgZn2 phase and have good workability, and their inclusion can clearly improve the workability. At the same time, they exhibit very base electrochemical properties, so they have a high sacrificial anticorrosion effect. Therefore, the inclusion of these elements has the effect of improving the corrosion resistance of the processed part.

[0046] Each element has an upper limit of concentration, and if it is contained in a large amount, Mg is absorbed from the Cr-containing intermetallic compound, and the Cr-containing intermetallic compound is not formed, resulting in a thin plating thickness. Therefore, the Sn concentration is set to 0.7% or less, and the Bi and In concentrations are set to 0.3% or less. Furthermore, the total amount ΣX of the concentrations of Sn, Bi and In is set to 0.7% or less. The total amount ΣX is preferably 0.5% or less, 0.4% or less.

[0047] Next, each of the elements Ya, Yb, and Yc in the element group described below is an optional added element, and the lower limit thereof is 0%.

[0048] Element group Ya Ca: 0-0.60% Y: 0~0.3% La: 0 to 0.3% Ce: 0-0.3% Sr: 0-0.3% Li: 0~0.3% Total amount of Ca, Y, La, Ce, Sr and Li ΣYa: 0~0.6%

[0049] Ca, which is one of the element group Ya, is preferably contained because it brings about various effects in the plating bath. Among the elements in the plating bath, Ca is most likely to bond with Cr. Therefore, in a plating bath containing Cr, Al 10 CaCr2 is formed. When this intermetallic compound is formed, the viscosity of the plating increases, making it easy to obtain a thick plating layer.

[0050] When Ca>Cr, that is, when the Ca concentration exceeds the Cr concentration, the Ca that cannot bond with Cr bonds with Si and Al to form Ca-Al-Si compounds (Al2CaSi2, CaSi2, etc.). This compound is easier to form than Mg2Si, so the corrosion resistance deterioration of Mg2Si can be prevented by including Ca.

[0051] If the Ca concentration exceeds 0.60%, various floating dross is formed in the coating bath, resulting in an increase in coating defects. In addition, the viscosity of the coating bath becomes extremely high, which reduces the amount of molten metal attached to the base steel material when it is pulled out of the coating bath, making the coating layer extremely thin and deteriorating corrosion resistance. In addition, the coating appearance is significantly deteriorated. Therefore, the Ca concentration is set to 0.60% or less. The Ca concentration is preferably 0.50% or less, more preferably 0.40% or less.

[0052] Each element of the element group Ya other than Ca can have almost the same effect as Ca, so it can be contained as a substitute for Ca. However, elements other than Ca are expensive, and there is a concern that the inclusion of a large amount of Ca may impair economic efficiency, so it is not preferable for the total concentration of elements other than Ca to be equal to or greater than the Ca concentration. The intermetallic compounds formed by the inclusion of elements other than Ca, Ya, are Al 10 As a substitute for CaCr2, Al 10 (Ya) It also bonds with Cr2 and Si to form a Ya-Al-Si compound. If either Ca or any one of the elements is contained, almost no difference in corrosion resistance, workability, or performance is observed. If the concentration is high, as with Ca, Mg is absorbed from the Cr compound, and the compound is no longer formed, resulting in a thin plating thickness, so there is an upper limit to the concentration. Therefore, the concentration of each element in the element group Ya other than Ca is 0 to 0.3%. The concentration of each element in the element group Ya other than Ca is preferably 0.2% or less, and 0.1% or less, respectively. The total amount ΣYa of the concentrations of the elements in the element group Ya including Ca is set to 0 to 0.6%, and is preferably 0.5% or less, and more preferably 0.4% or less.

[0053] Total amount of Ca, Y, La, Ce, Sr and Li ΣYa≦Si+Cr+Mo The total amount ΣYa must be kept below the total concentration of Si, Cr, and Mo. If the total amount ΣYa exceeds the total concentration of Si, Cr, and Mo, Ca will form an Al-Zn-Ca compound, which will cause the viscosity of the plating bath to become extremely high. This will reduce the amount of molten metal adhering to the base steel when it is pulled out of the plating bath, making the plating layer extremely thin and deteriorating corrosion resistance. In addition, the appearance of the plating will be significantly deteriorated. In particular, when forming a thick plating, powdering is likely to occur, causing a large deterioration in corrosion resistance and other properties. Therefore, the total amount ΣYa≦Si+Cr+Mo must be satisfied.

[0054] Element group Yb Ni: 0-1.0% Cu: 0-1.0% Ag: 0-0.25% Sb: 0 to 0.25% Pb: 0~0.25% Total amount of Ni, Cu, Ag, Sb and Pb ΣYb: 0~1.0% The elements in the element group Yb have a common effect. When the concentration of any one of these elements is 0.10% or more, the effect of improving the water-wet corrosion resistance is obtained. Therefore, it is preferable that the concentration of any one of these elements is 0.10% or more. However, if the total concentration of these elements, ΣYb, becomes excessive, various intermetallic compounds are formed, and the viscosity of the coating bath becomes extremely high. As a result, when the base steel is pulled out of the coating bath, the amount of molten metal attached to the base steel is reduced, the thickness of the coating layer becomes extremely thin, and the corrosion resistance deteriorates. Therefore, the total concentration, ΣYb, is set to 1.0% or less. The total concentration, ΣYb, is preferably set to 0.5% or less, more preferably 0.3% or less. In order to prevent deterioration of corrosion resistance, the Ni and Cu concentrations are each set to 1.0% or less, and preferably 0.5% or less. In order to prevent deterioration of corrosion resistance, the concentrations of Ag, Sb and Pb are each set to 0.25% or less, and preferably, the concentrations of Ag, Sb and Pb are each set to 0.20% or less.

[0055] Element group Yc B: 0~0.50% P: 0~0.50% Total amount of B and P ΣYc: 0~0.50% The elements in the element group Yc have a common effect. If the concentration of any one of these elements is 0.05% or more, the effect of improving the corrosion resistance of the processed part is obtained. Therefore, it is preferable that the concentration of any one of these elements is 0.05% or more. On the other hand, if these elements are contained in large amounts, the viscosity of the plating bath becomes extremely high. As a result, when the base steel is pulled out of the plating bath, the amount of molten metal attached to the base steel decreases, the thickness of the plating layer becomes extremely thin, and the corrosion resistance deteriorates. Therefore, the concentrations of B and P are each set to 0.50% or less. The concentrations of B and P are preferably set to 0.30% or less and 0.20% or less, respectively. In order to prevent deterioration of corrosion resistance due to the above-mentioned action, the total concentration ΣYc of B and P is set to 0.50% or less, and preferably, the total concentration ΣYc of B and P is set to 0.30% or less, and more preferably, 0.20% or less.

[0056] Element group Z Ti: 0 to 0.25% Cobalt: 0 to 0.25% V: 0 to 0.25% Nb: 0 to 0.25% Mn: 0 to 0.25% Zr: 0 to 0.25% W: 0~0.25% Total amount of Ti, Co, V, Nb, Mn, Zr, and WΣZ: 0~0.25% The elements included in element group Z are elements that dissolve in the Al phase contained in the plating layer. When the elements in element group Z are contained in the plating bath, the water-wet corrosion resistance is improved. When the concentration of any one of these elements is 0.10% or more, or when the total amount ΣZ of these elements is 0.10% or more, the above effect can be obtained. Therefore, it is preferable that the concentration of any one of these elements is 0.10% or more, or when the total amount ΣZ of the concentrations of these elements is 0.10% or more. On the other hand, if these elements are contained in large amounts, various intermetallic compounds are formed, and the viscosity of the plating bath becomes extremely high. As a result, when the base steel is pulled out of the plating bath, the amount of molten metal attached to the base steel is reduced, the thickness of the plating layer becomes extremely thin, and the corrosion resistance is deteriorated. Therefore, the concentration of each element of the element group Z is set to 0.25% or less. The concentration of each element of the element group Z is preferably 0.20% or less and 0.10% or less, respectively. In order to prevent deterioration of corrosion resistance due to the above-mentioned action, the total amount ΣZ is set to 0.25% or less, and preferably 0.20% or less, and more preferably 0.10% or less.

[0057] Fe: 0 to 5.0% Since the hot-dip plated steel material according to this embodiment is manufactured by a continuous hot-dip plating method, Fe may diffuse from the plated base material to the plated layer during manufacturing. As described above, in this embodiment, the Al concentration of the plated layer is high, and an Al-Fe-based interface alloy layer may be formed, but its thickness is thin. As a result, the plated layer may contain Fe up to a maximum of 5.0%. The Fe concentration may be 0%, but if the Fe concentration is 5.0% or less, there is no effect on the frequency of cracks occurring in the plated layer. Therefore, the Fe concentration is set to 5.0% or less. The Fe concentration is preferably 4.0% or less, 3.0% or less, 2.0% or less, or 1.0% or less. The Fe concentration may be more than 0%.

[0058] Remainder: Zn and impurities The balance contains Zn and impurities. Since the hot-dip plated steel material of this embodiment is a Zn-based plated steel material with high versatility, the element constituting the main phase of the plated layer is Zn. There is no need to specify the concentration of Zn in particular, but the Zn concentration may be 30 to 96% by mass. If necessary, the upper limit may be 90%, 80%, 70%, or 60%, and the lower limit may be 35%, 45%, 50%, or 55%.

[0059] Impurities refer to elements contained in raw materials or elements mixed in during the manufacturing process, but not intentionally included. For example, trace amounts of elements other than Fe may be mixed into the plating layer as impurities due to mutual atomic diffusion between the base steel (base steel) and the plating bath. In addition, since metals with 3N purity (3N stands for Three Nines, meaning 99.9% purity) are usually used to manufacture plating alloys, the concentration of impurities may be approximately 0.03% or less in total.

[0060] To identify the average chemical composition of the plating layer, an acid solution containing an inhibitor that suppresses corrosion of the base steel (parent steel material) is used to strip and dissolve the plating layer. The average chemical composition can be obtained by measuring this acid solution using ICP atomic emission spectroscopy or ICP-MS. There are no particular limitations on the type of acid as long as it is an acid that can dissolve the plating layer. For example, an acid containing an inhibitor can be a solution in which IBIT (inhibitor) manufactured by Asahi Chemical Industry Co., Ltd. is dissolved in 10% by volume of HCl. If the area and mass are measured before and after stripping, the plating adhesion amount (g / m 2 ) can also be obtained at the same time.

[0061] Next, the intermetallic compounds and the like contained in the plating layer will be described. The plating layer according to the present embodiment is a Zn-Al-Mg alloy plating, and therefore contains a Zn phase, an Al phase, and an MgZn2 phase. The plating layer according to the present embodiment also contains one or both of a Cr-containing intermetallic compound and a Mo-containing intermetallic compound. Furthermore, the plating layer according to the present embodiment may contain other intermetallic compounds.

[0062] Cr-containing intermetallic compounds, Mo-containing intermetallic compounds The plating layer according to this embodiment includes Al 20 CaCr, Al 18 These include Cr-containing intermetallic compounds such as Cr2Mg3. These are formed in the plating layer when Cr is contained in the plating layer. Cr combines with Ca and Al to form Al 20 When Ca is insufficient, Cr combines with Al and Mg to form AlCr. 18 Cr2Mg3 is formed. In addition, since the atomic radii of Al and Zn, and Mg and Ca are close to each other, part of the Al is replaced by Zn in the plating layer, and part of the Mg is replaced by Ca (Al,Zn). 18 It may also exist as Cr2(Ca,Mg)3. In areas of the coating layer where Ca is insufficient, it may exist as (Al,Zn) 18 In some cases Cr2Mg3 may also form.

[0063] Furthermore, as described above, Cr can be substituted for Mo, which is a homologous element, so when Cr and Mo are both contained, a part of the Cr in the above-mentioned intermetallic compound may be substituted with Mo. Such a compound may be called either a Cr-containing intermetallic compound or a Mo-containing intermetallic compound.

[0064] In addition, when Cr is not contained and Mo is contained alone, it is classified as an intermetallic compound containing Mo, and is called Al. 10 CaMo2 is formed.

[0065] As described above, by including Cr or Mo in the plating layer, these intermetallic compounds are generated in the plating layer, the viscosity of the plating bath is significantly improved, and the lifting amount of the plating bath when the base steel is pulled up from the plating bath is increased. In addition, the formation of these intermetallic compounds in the plating layer improves the water-wet corrosion resistance and the corrosion resistance.

[0066] The presence of these intermetallic compounds can be indirectly confirmed by the GDS method (glow discharge optical emission spectroscopy), which is the most sensitive and quantitative detection method. These intermetallic compounds can also be confirmed by X-ray diffraction. However, for example, Al 18 Cr2Mg3 and (Al,Zn) 18 It is difficult to distinguish between Cr2(Ca,Mg)3 and Cr2(Ca,Mg)3 because their diffraction peaks are close to each other. Furthermore, when these intermetallic compounds are contained in large quantities in the plating layer, the cross section of the plating layer can be observed with a scanning electron microscope (SEM) to directly identify the intermetallic compounds, and the effect of the inclusion of the compounds can be determined by measuring the area fraction of the intermetallic compounds. These measurement methods are described later.

[0067] Other intermetallic compounds Ca is likely to bond with Cr and Mo in the plating layer, and then with Si. Therefore, when Ca is contained in the plating layer, it forms an Al-Ca-Si compound in addition to a Cr-containing intermetallic compound and a Mo-containing intermetallic compound.

[0068] Si easily forms Mg2Si, but when Ca is present, it forms an Al-Ca-Si compound. However, when the amount of Si contained exceeds the Ca concentration, Mg2Si is formed, and the corrosion resistance of this compound is not good. However, if the amount of Si contained is small, the deterioration of the corrosion resistance of the entire plating layer is small.

[0069] Sn and In tend to combine with Mg to form Mg2Sn, Mg9Sn5, and Mg3In, but these form independently of each other regardless of reactions with Cr and Mo.

[0070] Next, a method for confirming the element distribution profile of Cr and Mo in the plating layer according to this embodiment will be described.

[0071] A glow discharge optical emission spectroscopy (GDS) device is preferably used for the component analysis method in the depth direction inside the plating layer. The inventors use a LECO Japan 850A as a glow discharge optical emission spectroscopy device, but the measurement device is not limited to this. When performing the analysis in the depth direction, it is preferable to perform the analysis while performing Ar sputtering, and the analysis conditions are argon pressure: 0.27 MPa, output power: 30 W, output voltage: 1000 V, and discharge area: within a circular area with a diameter of 4 mm. The measurement is performed from the surface of the plating layer in the depth direction to a position at least 1 / 4 of the plate thickness away from the surface of the base steel sheet. Therefore, the analysis range of the depth direction analysis by GDS is a range that reaches from the plating surface to the Zn-Al-Mg alloy layer, the Al-Fe alloy layer, and a part of the base steel material. After the GDS analysis, the sputter depth of the cross section is measured using, for example, a surfcom130A manufactured by Tokyo Seimitsu Co., Ltd. The GDS analysis provides an element distribution profile in the depth direction of the plating layer. The element distribution profile shows the concentration distribution of each element in the depth direction, assuming the total amount of detected elements to be 100%.

[0072] In the coating layer according to this embodiment, in the element distribution profile when GDS analysis is performed from the surface of the coating layer toward the base steel to a position at least 1 / 4 of the plate thickness of the hot-dip plated steel, the Fe concentration at a position 1 / 4 of the plate thickness of the hot-dip plated steel from the surface of the hot-dip plated steel (hereinafter, the Fe concentration at this position is also referred to as the "base steel Fe concentration". Note: The thickness of the coating layer is 20% or less of the plate thickness of the base steel, and this position is always the thickness position at which 95% of the Fe concentration of the base steel (however, if the base steel is pre-plated steel, it is the base steel portion excluding the pre-plated layer) is detected is defined as the coating layer and the base steel. The evaluation range is defined as the interface between the coating layer and the base steel material. The distance from the surface of the coating layer to the interface is defined as the thickness t of the coating layer. The evaluation range is defined as the region from a thickness position 0.1×t from the surface of the coating layer (hot-dip plated steel) to a thickness position where an Fe concentration of 40% of the base steel material Fe concentration (i.e., the Fe concentration at a position ¼ of the sheet thickness of the hot-dip plated steel material from the surface of the hot-dip plated steel material) is detected. The inventors have found that when a region where the total amount ΣA is 0.05 mass% or more exists continuously for 1.0 μm or more in the thickness direction of the base steel material (hot-dip plated steel material) in the evaluation range, the water-wet corrosion resistance is improved.

[0073] When evaluating the Cr and Mo concentrations, the evaluation range is "the region from the thickness position 0.1×t from the surface of the coating layer (hot-dip coated steel) to the thickness position where 40% of the Fe concentration of the base steel (Fe concentration at a position 1 / 4 of the thickness of the hot-dip coated steel from the surface of the hot-dip coated steel) is detected." The region from the surface of the coating layer to the thickness position 0.1×t from the surface of the coating layer is excluded from the evaluation range because it is an area where the error of the GDS analysis can be large. In addition, the region close to the boundary between the coating layer and the base steel may be affected by the Al-Fe-based interface alloy layer. In addition, when a pre-coated base steel of Cr or Mo is used as the coating base material (base steel), it may be affected by the pre-coated layer. Therefore, the evaluation range is set to the thickness position where 40% of the maximum Fe concentration is detected, and the region on the base steel side beyond this is excluded from the evaluation range.

[0074] In the above evaluation range, if the region where the total amount ΣA of Cr concentration and Mo concentration is 0.05% or more exists continuously in the thickness direction of the base steel material for 1.0 μm or more, it can be said that a clear effect of increasing viscosity is observed during the production of the coating layer. Whether or not the region where the total amount ΣA of Cr concentration and Mo concentration is 0.05% or more exists continuously in the thickness direction for 1.0 μm or more is confirmed in the element distribution profile by the above-mentioned GDS analysis. As a result, when the pulling speed of the base steel material from the coating bath is constant, the thickness of the coating layer can be increased to 15 μm or more, preferably 20 μm or more, 25 μm or more, or more than 30 μm, when the region where the total amount ΣA of Cr and Mo is 0.03% or more exists continuously in the thickness direction for 1.0 μm or more. In contrast, the thickness of the coating layer was limited to about 30 μm when Cr and Mo were not contained. The region where the total amount ΣA of Cr and Mo is 0.03% or more is preferably continuous in the thickness direction and has a length of 10.0 μm or more, 20.0 μm or more, 30.0 μm or more, or 40.0 μm or more. The upper limit may be 90.0 μm or less, 80.0 μm or less, 70 μm or less, or 60 μm or less.

[0075] In addition, when a pre-plated steel material is used as the base material for plating, in an element distribution profile obtained by performing GDS analysis from the surface of the plating layer to a position at least 1 / 4 of the sheet thickness of the hot-dip plated steel, if the thickness position at which 95% of the Fe concentration of the base steel (Fe concentration at a position 1 / 4 of the sheet thickness of the hot-dip plated steel from the surface of the hot-dip plated steel) is detected is taken as the interface between the plating layer and the base steel, it is preferable that the average value of the total amount ΣA of the Cr concentration and Mo concentration is more than 0.50% in the region from the interface to 1.0 μm toward the surface of the plating layer. In this way, by having the average value of the total amount ΣA of the Cr concentration and Mo concentration be more than 0.50% in the region from the interface to 1.0 μm toward the surface of the plating layer, the diffusion of Fe of the base steel to the plating layer side during hot-dip plating is suppressed. This makes it possible to make the thickness of the Al-Fe-based interface alloy layer thinner. Specifically, the thickness of the Al-Fe-based interface alloy layer can be made 1.0 μm or less, and the workability of the hot-dip plated steel can be improved.

[0076] Furthermore, in the cross section of the plating layer, the total area fraction of the Cr-containing intermetallic compounds and the Mo-containing intermetallic compounds is preferably 1.0% or more. The area fraction is more preferably 1.5% or more, 2.0% or more, 3.0% or more, or 5.0% or more. This tends to enhance sacrificial corrosion protection, and improves the corrosion resistance of the bent portion in particular. The inventors speculate that the effect of sacrificial corrosion protection is that Mg, Cr, and Ca, which are inherently low electronegativity, are bonded to Al, making the oxide film covering the Al phase unstable, thereby enhancing sacrificial corrosion protection. It is believed that these intermetallic compounds, after dissolving due to corrosion, generate oxide films such as Cr, which improves the corrosion resistance after dissolving.

[0077] An electron probe microanalyzer (EPMA) is used to measure the area fraction of Cr-containing intermetallic compounds or Mo-containing intermetallic compounds. The cross section of the plating layer is exposed and observed with a scanning electron microscope attached to the EPMA to identify the areas where Cr and Mo exist. These identified areas are identified as Cr-containing intermetallic compounds or Mo-containing intermetallic compounds. The total area fraction of the Cr-containing compounds and Mo-containing compounds is then calculated.

[0078] More specifically, the following procedure is used: An element mapping image is obtained using an EPMA with a 200x observation field. In the element mapping image, Zn and other elements can be detected anywhere in the plating layer, except for certain small compounds. On the other hand, Cr, Mo, etc. are detected as certain intermetallic compounds (Al 18 Cr2Mg3, Al 20 CaCr, Al 10 In other words, the locations of Cr and Mo become the locations of intermetallic compounds.

[0079] Once the mapping images for each element have been obtained, they are analyzed using image analysis software such as ImageJ. For the Zn mapping image, they are binarized, a threshold is set so that the entire plating layer is white or black, and the number of pixels in the Zn map is calculated on a pixel-by-pixel basis.

[0080] Next, the Cr mapping image is also binarized to obtain the number of Cr pixels. The number of pixels in which Cr was detected is divided by the number of Zn pixels to obtain a value. This gives the area fraction of Cr-containing intermetallic compounds. The same operation is performed across 20 fields of view. That is, 20 different fields of view are randomly selected on the cross section of the plating layer, the area fraction is obtained in each field of view, and the average value is calculated. For Mo-containing intermetallic compounds, the area fraction is determined in the same manner as for Cr by using Mo mapping images.

[0081] Next, the indices of Cr-containing intermetallic compounds and Mo-containing intermetallic compounds by X-ray diffraction will be described.

[0082] Since the detection sensitivity of X-ray diffraction measurement is lower than that of GDS analysis, it is assumed that the plating layer contains a certain amount or more of Cr-containing intermetallic compounds or Mo-containing intermetallic compounds. Therefore, when the Ca concentration is 0.05% or more, the Cr concentration or the Mo concentration is 0.05% or more, and the relationship of ΣYa < Si + Cr + Mo is satisfied in the average chemical composition of the plating layer, it is preferable that the following equations (1) and (2) are satisfied in the X-ray diffraction pattern of the plating layer surface. (Imax(10.5°~11.0°) / (I(10.5°)+0.2×{(|I(11.0°)-I(10.5°)|})≧1.5 …(1) (Imax(20.2°~20.5°)) / (I(20.2°)+0.667×{|I(20.5°)-I(20.2°)|})≧1.5 …(2) Here, Imax(k~m°) is the maximum value of the X-ray diffraction intensity between diffraction angles k~m°, Imax(n°) is the X-ray diffraction intensity at diffraction angle n°, and k, m, n are the diffraction angles shown in equations (1) and (2), respectively.

[0083] When the Ca concentration is 0.05% or more, the Cr concentration or the Mo concentration is 0.05% or more, and the relationship of ΣYa < Si + Cr + Mo is satisfied, Al 18 Cr2Mg3, etc. can be detected by X-ray diffraction measurement. Al, which is a Cr-containing intermetallic compound 18 Cr2Mg3, Al 20 CaCr is an intermetallic compound with excellent corrosion resistance. When these metals are contained in the plating layer to the extent that they can be detected by X-ray diffraction, the corrosion resistance in a water-wetted environment is improved. When ΣYa < Si + Cr + Mo is not satisfied, the formation of Al-Zn-Ca compounds by Ca becomes dominant, and the effect of improving the corrosion resistance of Cr-containing intermetallic compounds cannot be confirmed. Since Ca and Cr are very likely to bond, if Ca ≦ Cr in terms of concentration, almost all of the Ca present in the plating bath binds to Cr, and the remaining Cr binds to Al18 It will form Cr2Mg3.

[0084] These intermetallic compounds can grow crystal phases in specific orientations by controlling solidification at an appropriate temperature after the crystal nuclei have grown.

[0085] In the X-ray diffraction measurement, Cu-Kα radiation is used, and the measurement is performed under conditions of an X-ray output of 50 kV and 300 mA.

[0086] The left sides of the above formulas (1) and (2) (here, the left side of formula (1) is referred to as I1, and the left side of formula (2) is referred to as I2) are regulations regarding the X-ray diffraction peaks of the Cr-containing intermetallic compound and the Mo-containing intermetallic compound. For example, in the case of the Cr-containing intermetallic compound, Al 18 Cr2Mg3 is an intermetallic compound defined in JCPDS card #01-071-5707. 20 CaCr2 is also an intermetallic compound defined in #01-081-2712. These intermetallic compounds have similar diffraction peaks and are difficult to distinguish from one another; that is, Al and Mg are in solid solution with each other, and Zn and Ca are in solid solution with each other, so they are assumed to have almost the same composition and structure, and the diffraction peaks appear at almost the same positions. Therefore, it is not necessary to distinguish between these Cr-containing intermetallic compounds in X-ray diffraction measurements.

[0087] Regarding Mo-containing intermetallic compounds, Al 20 CaMo2 is defined in JCPDS card #00-051-1061.

[0088] On the other hand, in the plating layer according to the present embodiment, many of the diffraction peaks of these Cr-containing intermetallic compounds overlap with the diffraction peaks of the other main constituent phases, namely MgZn2, Al, and Zn. Therefore, among the many diffraction peaks of the Cr-containing intermetallic compounds or the Mo-containing intermetallic compounds, it is necessary to pay attention to the diffraction peaks that do not overlap with the other constituent phases. One of them is a diffraction peak appearing near 2θ=10.6°, and the other is a diffraction peak appearing near 20.4°.

[0089] Equation (1) focuses on the diffraction peak near 2θ=10.6°. Imax(10.5°-11.0°) in equation (1) is the maximum value of the X-ray diffraction intensity between the diffraction angles of 10.5°-11.0°. I(10.5°) is the X-ray diffraction intensity at a diffraction angle of 10.5°, and Imax(11.0°) is the X-ray diffraction intensity at a diffraction angle of 11.0°.

[0090] Equation (2) focuses on the diffraction peak near 2θ=20.4°. Imax (20.2°-20.5°) in equation (2) is the maximum value of the X-ray diffraction intensity between the diffraction angles of 20.2°-20.5°. I(20.2°) is the X-ray diffraction intensity at a diffraction angle of 20.2°, and I(20.5°) is the X-ray diffraction intensity at a diffraction angle of 20.5°.

[0091] The numerators of formula (1) and formula (2) are the maximum diffraction intensities of the diffraction peaks including background intensity, which are intensities corresponding to the diffraction peaks of the Cr-containing compound or Mo-containing compound. Because the diffraction peaks may deviate from 10.6° or 20.4° due to measurement errors in X-ray diffraction, the maximum values ​​between 10.5° to 11.0° and 20.2° to 20.5° are obtained.

[0092] The denominators of equations (1) and (2) are the background intensities at diffraction angles of 10.6° or 20.4°, calculated from the diffraction intensities at 10.6° or 20.4°.

[0093] For example, for the denominator of formula (1), as shown in FIG. 1, a straight line is drawn connecting the diffraction line at 10.5° and the diffraction line at 11.0°. This straight line becomes the baseline of the diffraction peak. Next, the absolute value of I(10.5°)-I(11.0°) is calculated. Also, the ratio (0.1 / 0.5=0.2) of the difference (0.1°) between the diffraction angles 10.5° and 11.0° to the difference (0.5°) between the diffraction angles 10.5° and 10.6° is calculated. Then, the background intensity at the diffraction angle of 10.6° is calculated using the formula written in the denominator of formula (1) above.

[0094] For the denominator of formula (2), as in the case of FIG. 1, a straight line is drawn connecting the diffraction line at 20.2° and the diffraction line at 20.5°. This straight line becomes the baseline of the diffraction peak. Next, the absolute value of I(20.2°)-I(20.5°) is calculated. Also, the ratio (0.2 / 0.3=0.667) of the difference (0.2°) between the diffraction angles 20.2° and 20.5° to the difference (0.3°) between the diffraction angles 20.2° and 20.4° is calculated. Then, the background intensity at the diffraction angle of 20.4° is calculated using the formula written in the denominator of formula (2) above.

[0095] When formula (1) and formula (2) are satisfied, it indicates that the crystal phase of the Cr-containing intermetallic compound or Mo-containing intermetallic compound grows in a specific orientation, and the corrosion resistance of the processed part is improved. Although the cause is not fully understood, it is presumed that the form of the crack in the processed part changes with the specific crystal orientation.

[0096] The conditions for obtaining the X-ray diffraction image are as follows.

[0097] X-ray diffraction using Cu as the target as the X-ray source is the most convenient method because it can obtain average information on the constituent phases in the plating layer. As an example of the measurement conditions, the X-ray conditions are a voltage of 50 kV and a current of 300 mA. There are no particular limitations on the X-ray diffraction device, but for example, a horizontal sample type high-power X-ray diffraction device RINT-TTR III manufactured by Rigaku Corporation can be used.

[0098] The thickness of the Al-Fe-based interface alloy layer is measured as follows. When the cross section of the plating layer is observed using a backscattered electron image from an SEM, the base steel (parent steel), Al-Fe-based interface alloy layer, and Zn-Al-Mg-based alloy layer can be confirmed from the difference in color. If an observation field is obtained at a magnification of 1000 times or more, the thickness of the darkest Al-Fe-based interface alloy layer on the base steel can be confirmed in 0.1 μm increments. However, the Al-Fe-based interface alloy layer may not be confirmed if it is too thin. In addition, when pre-plated steel is used as the base material for plating, the Al-Fe-based interface alloy layer may not be clearly confirmed due to the influence of the pre-plated layer (Cr, Mo, Ni). The thickness of the Al-Fe-based interface alloy layer is obtained by measuring the thickness in any three fields of view using an SEM and calculating the average value. The thickness of the Zn-Al-Mg alloy layer can be obtained to the nearest 1 μm by calculating the average thickness of the plating layer obtained by observing three fields of view at 200x magnification, subtracting the average thickness of the Al-Fe interfacial alloy layer from the plating layer thickness, and rounding off the result.

[0099] Next, a method for producing a hot-dip plated steel material according to this embodiment will be described. The hot-dip plated steel material according to the present embodiment is preferably produced by a continuous hot-dip plating method. However, due to restrictions on the size of the base steel material, it may also be produced by a batch-type hot-dip plating method, if necessary.

[0100] In addition to the above-mentioned base steel material, a pre-plated steel material plated with Cr, Ni or Mo may be used as the base material for plating. The pre-plating may be an alloy plating of two or more of Cr, Mo and Ni. The plating may be formed by any method, such as electroplating or vapor deposition plating. The plating weight is 0.3 to 5.0 g / m 2 It is preferable to set the thickness to 0.3 g / m 2 This amount of adhesion is sufficient to suppress the Al-Fe reaction in the plating bath.

[0101] The continuous hot-dip galvanizing method is carried out by the Sendzimir method. That is, before immersing the base steel in the plating bath, the base steel is heated at the annealing temperature of the nitrogen-hydrogen mixed gas until the base steel temperature reaches or exceeds the plating bath temperature. The annealing atmosphere is usually a nitrogen atmosphere containing hydrogen, with a hydrogen concentration of 5%, and the base steel is heated and held at a temperature of around 800°C for about one minute to fully reduce the surface of the base steel. However, depending on the base material to be plated, the hydrogen concentration may be increased to 10%. In addition, when entering the plating bath, cooling is performed with N2 gas until the base steel temperature reaches the plating bath temperature, so that the plating bath temperature does not fluctuate during the manufacturing process.

[0102] Next, the base steel material with its surface sufficiently reduced is immersed in a reduced state in a plating bath. The temperature of the plating bath is 600°C or higher. The plating bath is stirred by bubbling N2 gas through it. The flow rate of the N2 gas bubbling is 0.05 m / sec or higher. If the plating bath is not stirred under these conditions, floating dross consisting of Cr compounds or Mo compounds will sink in the plating bath and become bottom dross, and these intermetallic compounds will not penetrate into the plating layer, making it impossible to obtain a plating layer with the desired components.

[0103] The immersion time of the base steel in the plating bath is in the range of 1 to 5 seconds. If the immersion time exceeds 5 seconds, a thick interface alloy layer will be formed, which is not preferable.

[0104] After immersion in the plating bath, the thickness of the plating layer is adjusted by wiping immediately. After wiping is completed, the plate is cooled so that the time from the plating bath temperature to 560°C is 3 to 5 seconds.

[0105] Between 600 and 560°C, Cr compounds or Mo compounds rapidly form solidification nuclei, and a milky white oxide film with high surface tension is instantly formed to cover the surface of the plating bath, causing a certain degree of viscosity in the molten metal. Therefore, it is easy to control the thickness of the plating layer, especially under conditions of weak wiping gas (slit width: 2 to 5 mm, distance between nozzle and base steel: 50 to 10 mm, gas pressure at nozzle outlet: 0.1 MPa or less). In general, in areas where the wiping gas pressure is weak, the plating thickness varies greatly with a slight fluctuation in the wiping gas pressure, making it difficult to control the thickness of the plating layer. However, in this embodiment, the viscosity of the plating bath is increased by including Cr or Mo in the plating bath, so that by controlling the wiping gas pressure and distance within the above ranges, a plating layer with a large amount of adhesion can be easily manufactured while accurately controlling its thickness. Therefore, there is no need to particularly limit the wiping conditions. However, when a cooling method such as rapid cooling by submerging in water or rapid cooling by spraying wiping gas from a wiping nozzle at a pressure exceeding 0.1 MPa is adopted, it is not preferable because it is not possible to favorably control the plating layer.

[0106] Regarding the Cr-containing intermetallic compounds and Mo-containing intermetallic compounds in the coating layer, if the cooling rate from the bath temperature to 560°C is too high, these may remain in the Al phase and become a solid solution. In particular, if the cooling rate is extremely high, solidification will be completed before these intermetallic compounds crystallize and grow. Therefore, the coating layer is cooled to pass 560°C within 3 to 5 seconds after being pulled out of the coating bath.

[0107] In addition, from the bath temperature until passing through 560°C, the product is manufactured in an environment with an oxygen concentration of 1000ppm or less. In the case of a plating layer with a large adhesion weight, wrinkles due to the oxide film are likely to occur, causing pattern defects in the horizontal axis direction, which may lead to poor thickness, poor plating, and poor corrosion resistance.

[0108] Regarding the cooling rate in the temperature range of 560°C or less, it is preferable to perform cooling under the following conditions according to the thickness of the plating layer to rapidly solidify it.

[0109] Plating layer thickness: Over 50μm Time required to reach 360℃ from 560℃: within 10 seconds

[0110] Plating layer thickness: Over 40 to 50 μm Time required to reach 360℃ from 560℃: within 20 seconds

[0111] Plating layer thickness: 30 to 40 μm Time required to reach 360℃ from 560℃: within 30 seconds

[0112] In addition, the cooling method from 560°C to 360°C must not involve submersion or water droplet collision that would leave indentations, and must not involve blowing at a close distance or with a gas pressure stronger than that of the wiping gas. In addition, it is preferable to use a mist-like mist or a gas with a high cooling effect such as hydrogen or helium as a cooling medium. Furthermore, the cooling gas temperature itself may be lowered.

[0113] After the plating layer is formed, various chemical conversion treatments and painting treatments may be carried out.

[0114] In the hot-dip plated steel material according to this embodiment, a coating may be formed on the plating layer. The coating may be formed in one layer or in two or more layers. Examples of the type of coating directly on the plating layer include a chromate coating, a phosphate coating, and a chromate-free coating. These coatings can be formed by known methods such as chromate treatment, phosphate treatment, and chromate-free treatment.

[0115] Chromate treatment includes electrolytic chromate treatment, which forms a chromate film by electrolysis, reactive chromate treatment, which forms a film by utilizing a reaction with the material and then washes away excess treatment liquid, and coating chromate treatment, which applies a treatment liquid to the substrate and then dries it without rinsing with water to form a film. Any of these treatments may be used.

[0116] Examples of electrolytic chromate treatments include electrolytic chromate treatments using chromic acid, silica sol, resins (phosphoric acid, acrylic resins, vinyl ester resins, vinyl acetate acrylic emulsions, carboxylated styrene butadiene latexes, diisopropanolamine-modified epoxy resins, etc.), and hard silica.

[0117] Examples of the phosphate treatment include zinc phosphate treatment, zinc calcium phosphate treatment, and manganese phosphate treatment.

[0118] Chromate-free treatments are particularly suitable because they do not place a burden on the environment. Chromate-free treatments include electrolytic chromate-free treatments that form a chromate-free film by electrolysis, reactive chromate-free treatments that form a film by utilizing a reaction with the material and then wash away excess treatment liquid, and coating-type chromate-free treatments that apply a treatment liquid to the substrate and dry it without rinsing with water to form a film. Any of these treatments may be used.

[0119] Furthermore, one or more organic resin films may be provided on the film directly on the plating layer. The organic resin is not limited to a specific type, and examples thereof include polyester resin, polyurethane resin, epoxy resin, acrylic resin, polyolefin resin, and modified products of these resins. The modified product here refers to a resin obtained by reacting a reactive functional group contained in the structure of these resins with another compound (monomer, crosslinking agent, etc.) containing a functional group capable of reacting with the functional group in the structure.

[0120] As such an organic resin, one or more organic resins (unmodified) may be mixed and used, or one or more organic resins obtained by modifying at least one other organic resin in the presence of at least one organic resin may be mixed and used. In addition, any coloring pigment or rust-preventive pigment may be contained in the organic resin film. Aqueous resins that have been dissolved or dispersed in water may also be used.

[0121] As described above, it is difficult to increase the adhesion weight of a plating layer with an increased Al concentration due to a decrease in the specific gravity of the plating bath. However, according to the hot-dip plated steel material according to the present embodiment, the viscosity of the plating bath is increased by containing Cr or Mo, and a hot-dip plated steel material having a plating layer with a large adhesion weight can be manufactured. Since the plating layer contains a Cr-containing intermetallic compound or a Mo-containing intermetallic compound, the corrosion resistance and wet corrosion resistance can be improved. Furthermore, the plating layer contains Cr or Mo, which results in a thinner thickness of the interface alloy layer, thereby improving the workability. Furthermore, since the adhesion weight of the plating layer is large, the corrosion resistance and wet corrosion resistance can be further improved.

[0122] In addition, while a coating bath containing Cr, Mo, etc. may generate floating dross, by increasing the temperature of the coating bath, the generation of floating dross can be suppressed and coating defects such as non-plating can be prevented. In addition, when the coating bath is heated to a high temperature, the reaction between Al and Fe may become active, causing the Al-Fe interfacial alloy layer to become thick, but by using a coating bath containing Cr and Mo, the Al-Fe interfacial alloy layer can be made thin. The hot-dip plated steel material produced in this manner has excellent corrosion resistance, water-wet corrosion resistance, workability, corrosion resistance of worked parts, and sacrificial corrosion protection. EXAMPLES

[0123] As the base sheets for plating, a hot-rolled steel sheet (symbol: H) measuring 100 mm x 200 mm and having a thickness of 1.6 mm, and a cold-rolled steel sheet (symbol: C) measuring 100 mm x 200 mm and having a thickness of 0.8 mm were prepared. In addition, pre-plated steel sheets were prepared by plating the hot-rolled steel sheet and the cold-rolled steel sheet with Cr, Ni, and Mo, respectively. The plating types and coating weights were as shown in Tables 1-1 to 1-8. The Cr plating (type: Cr) and the Ni plating (type: Ni) were formed by the electroplating method. The Mo plating (type: Mo) was formed by the vapor deposition plating method. A K thermocouple was spot-welded to the center of the back side of the base sheet for plating so that the temperature change during the plating process could be monitored.

[0124] The Sendzimir process was used as the hot-dip plating method. That is, before the plated original sheet was immersed in the plating bath, the base steel was heated at the annealing temperature of the nitrogen-hydrogen mixed gas until the base steel temperature reached the plating bath temperature or higher. The annealing atmosphere was a nitrogen atmosphere containing 5% hydrogen (N2-5%H2), and the base steel was heated and held at a temperature of around 800°C for about 1 minute to fully reduce the base steel surface. When entering the plating bath, cooling was performed with N2 gas until the base steel temperature reached the plating bath temperature, so that the plating bath temperature would not fluctuate during the manufacturing process.

[0125] The hot-dip plating method used a hot-dip plating simulator, and the base steel, whose surface had been sufficiently reduced, was immersed in the plating bath in a reduced state. The plating bath temperature was as shown in Tables 1-1 to 1-8. In addition, the plating bath was equipped with an N2 bubbling device capable of forming an upward flow velocity of 0.05 m / sec or more in the plating bath. During hot-dip plating, this bubbling device was controlled to be turned on and off. When it was turned off, the plating bath became an almost stationary bath. In addition, the oxygen concentration around the mechanism for pulling up the base steel was monitored. When the base steel was immersed in the plating bath, it was performed in a snout replaced with an atmosphere of N2-5% H2, and a small amount of oxygen was introduced into the snout as necessary.

[0126] The immersion time in the plating bath was uniformly set to 3 seconds. After the base steel material was pulled out of the plating bath, N2 gas wiping was performed with a slit width of 1 mm, a WP distance of 5 mm, and a WP pressure of 0.075 MPa (outlet). If the base steel was produced in an environment where the oxygen concentration was 1000ppm or less from the bath temperature until it passed through 560℃ when it was pulled up, the column for "Oxygen concentration at pulling position" in the table was marked "OK." On the other hand, if this condition was not met, it was marked "NG."

[0127] Thereafter, cooling was started, and the N2 gas flow rate and temperature were controlled to control the time required from when the plating bath was pulled up (bath temperature) to reach 560°C, and the time required from 560°C to reach 350°C. As for the cooling method, in some cases, a submerged cooling method and rapid cooling by spraying wiping gas at a pressure of 1.5 MPa from a wiping nozzle were performed. In Tables 1-1 to 1-8, examples of cooling by a submerged method are indicated as "submerged", and examples of rapid cooling by spraying wiping gas at a pressure of 1.5 MPa are indicated as "strong gas".

[0128] The hot-dip plated steel materials shown in Tables 1-1 to 4-8 were manufactured by the above-mentioned method. The average chemical composition of the plating layer was measured by the above-mentioned method. Furthermore, an element distribution profile was obtained by the above-mentioned method, and the thickness position at which 95% of the Fe concentration in the base steel (i.e., the Fe concentration at a position ¼ of the sheet thickness of the hot-dip plated steel material from the surface of the hot-dip plated steel material) was detected from the element distribution profile was determined as the interface between the plating layer and the base steel material, and the distance from the surface of the plating layer to the interface was determined as the thickness of the plating layer, thereby obtaining the thickness t of the plating layer.

[0129] The obtained hot-dip plated steel materials were subjected to various evaluations.

[0130] When obtaining the element distribution profile of the plating layer, a LECO Japan 850A glow discharge optical emission spectrometer (GDS) was used, and an element distribution profile in the depth direction of the plating layer was obtained by the above-mentioned method.

[0131] In the element distribution profile, in the region from the surface of the coating layer at a thickness position 0.1×t away to the thickness position where an Fe concentration of 40% of the Fe concentration in the base steel (i.e., the Fe concentration at a position 1 / 4 of the thickness of the hot-dip galvanized steel from the surface of the hot-dip galvanized steel) is detected, it was confirmed whether or not there exists a region in which the total concentration of Cr and Mo is 0.05 mass% or more, which extends continuously for 1.0 μm or more in the thickness direction of the base steel. In the above region, the continuous length of the region in which the total concentration of Cr and Mo is 0.05 mass% or more is shown in the column "Continuous length of region where ΣA is 0.05% or more" in the table.

[0132] In addition, in the element distribution profile obtained by GDS analysis, the average value of the total amount ΣA in the region from the interface between the coating layer and the base steel to 1.0 μm toward the surface of the coating layer was calculated. The obtained average value of the total amount ΣA is shown in the column of "Average value of ΣA" in the table.

[0133] The area fraction of the Cr-containing intermetallic compound or the Mo-containing intermetallic compound was measured by the above-mentioned method using an electron probe microanalyzer (EPMA) and ImageJ (image analysis software). The total area fraction of the obtained Cr-containing compound and Mo-containing compound is shown in the "Total of Cr-containing compound and Mo-containing compound" in the table.

[0134] Furthermore, I1 and I2 were obtained by performing X-ray diffraction measurement using the above-mentioned method using a horizontal sample type high-power X-ray diffractometer RINT-TTR III manufactured by Rigaku Corporation as the X-ray diffractometer. The obtained results are shown in the table.

[0135] (processability) The workability was evaluated by a 1t bending test. The sample size was 40mm x 120mm x 1.6mm for the case where a hot-rolled steel sheet was used as the plating base sheet, and 40mm x 120mm x 0.8mm for the case where a cold-rolled steel sheet was used as the plating base sheet. These samples were bent at the center of the 40mm width. Tape was firmly attached to both sides of the plated steel sheet in advance. A bending test piece with a space of one steel sheet on the inside was produced by sandwiching 1t (the thickness of one steel sheet) inside, bending it at 180° with a jig, and pressing it completely. After that, the inner steel sheet was removed, and the tape was pulled and peeled off vigorously. At this time, the inner and outer tapes were attached to black cardboard to check the presence or absence of plating peeling powder in the processed area. The evaluation criteria were as follows, with "G" being a pass and "B" being a fail. Tables 4-1 to 4-8 show the results as "powdering".

[0136] There is peeling powder on both sides... "B" No peeling powder on either side... "G"

[0137] (Corrosion resistance) The 1t bend test piece was subjected to a cyclic corrosion test to evaluate the corrosion resistance. The top of the 1t bend was subjected to severe processing, which caused cracks in the plating layer, and inevitably resulted in bare steel. The corrosion evaluation was performed using the artificial acid rain cycle test method defined in JIS H 8502:1999. That is, a photograph of the top of the 1t bend was taken for each specified cycle, and the evaluation was performed at the cycle when red rust occurred and the red rust area reached 50% at the center line of the top of the 1t bend. For the evaluation, t=1.6mm and 0.8mm were used. The evaluation criteria were as follows, with "S", "A+++", "A++", "A+", and "A" being considered as passing, and "B" being considered as failing. Tables 4-1 to 4-8 show the results as "corrosion resistance".

[0138] Red rust formation cycles exceed 900 cycles: "S" Red rust formation cycles exceed 750 cycles: "A+++" Red rust formation cycles exceed 600: "A++" Red rust formation cycles exceed 480 cycles: "A+" Red rust formation cycle exceeds 300 cycles: "A" Red rust formation cycles of 300 or less: "B"

[0139] The sample size for evaluating the water-wet corrosion resistance was 40 mm x 120 mm x 1.6 mm for the case where a hot-rolled steel sheet was used as the plating base sheet, and 40 mm x 120 mm x 0.8 mm for the case where a cold-rolled steel sheet was used as the plating base sheet. A 0.001 vol.% NaCl aqueous solution with pH=5.0±0.1 and room temperature was dropped at a height of 50 mm at a speed of 1 μl / sec on the center of the width and length of the sample. The period during which red rust of 1 mmφ or more was generated on the drop part was evaluated. The evaluation criteria were as follows, with "S", "A+++", "A++", "A+", and "A" being considered as pass, and "B" being considered as fail. The results are shown in Tables 4-1 to 4-8 as "water-wet corrosion resistance".

[0140] Red rust that has been present for more than 40 weeks: "S" If red rust occurs between 35 weeks and 40 weeks ago: "A+++" Red rust occurring between 30 and 35 weeks: "A++" If red rust occurs between 25 weeks and 30 weeks ago: "A+" Red rust that has developed over 20 to 25 weeks: "A" Those with rust for less than 20 weeks: "B"

[0141] The examples in the table were excellent in corrosion resistance, wet corrosion resistance and processability.

[0142] On the other hand, in the comparative examples in the table, one or more of the corrosion resistance, wet corrosion resistance, and workability were inferior.

[0143] [Table 1-1]

[0144] [Table 1-2]

[0145] [Table 1-3]

[0146] [Table 1-4]

[0147] [Table 1-5]

[0148] [Table 1-6]

[0149] [Table 1-7]

[0150]

Table 1-8

[0151]

Table 2-1

[0152]

Table 2-2

[0153]

Table 2-3

[0154]

Table 2-4

[0155]

Table 2-5

[0156]

Table 2-6

[0157]

Table 2-7

[0158]

Table 2-8

[0159]

Table 3-1

[0160]

Table 3-2

[0161]

Table 3-3

[0162]

Table 3-4

[0163]

Table 3-5

[0164]

Table 3-6

[0165]

Table 3-7

[0166]

Table 3-8

[0167]

Table 4-1

[0168]

Table 4-2

[0169]

Table 4-3

[0170]

Table 4-4

[0171]

Table 4-5

[0172]

Table 4-6

[0173]

Table 4-7

[0174]

Table 4-8

Claims

1. A hot-dip plated steel material having a base steel material and a coating layer disposed on a surface of the base steel material, wherein an average chemical composition of the coating layer is, in mass%, Al: more than 10% and less than 45%; Mg: 4.0 to 15.0%, Si: 0-2.00%, Cr: 0-3.00%, Mo: 0-3.00%, Sn: 0 to 0.7%, Bi: 0-0.3%, In: 0 to 0.3%, Ca: 0-0.60%, Y: 0 to 0.3%, La: 0 to 0.3%, Ce: 0-0.3%, Sr: 0-0.3%, Li: 0 to 0.3%, Ni: 0-1.0%, Cu: 0 to 1.0%, Ag: 0-0.25%, Sb: 0 to 0.25%, Pb: 0 to 0.25%, B: 0 to 0.50%, P: 0 to 0.50%, Ti: 0 to 0.25%, Co: 0-0.25%, V: 0 to 0.25%, Nb: 0 to 0.25%, Mn: 0 to 0.25%, Zr: 0 to 0.25%, W: 0 to 0.25%, Fe: 0 to 5.0%, The balance is Zn and impurities, and Total amount ΣA of Cr and Mo: 0.03 to 3.00% Total amount ΣX of Sn, Bi and In: 0 to 0.7% Total amount ΣYa of Ca, Y, La, Ce, Sr and Li: 0 to 0.6%, Total amount ΣYb of Ni, Cu, Ag, Sb and Pb: 0 to 1.0%; Total amount of B and P ΣYc: 0 to 0.50% Total amount ΣZ of Ti, Co, V, Nb, Mn, Zr and W: 0 to 0.25%, ΣYa≦Si+Cr+Mo, and In an element distribution profile obtained by GDS analysis from the surface of the coating layer toward the base steel in the thickness direction of the base steel, when a thickness position at which an Fe concentration that is 95% of the Fe concentration in the base steel is detected is defined as an interface between the coating layer and the base steel, and when a distance from the surface of the coating layer to the interface is defined as a thickness t of the coating layer, A hot-dip plated steel material in which, in a region from a thickness position 0.1×t from the surface of the plating layer to a thickness position at which an Fe concentration of 40% of the Fe concentration of the base steel is detected, a region in which the total amount ΣA is 0.05 mass% or more exists continuously for 1.0 μm or more in the thickness direction of the base steel material.

2. 2. The hot-dip plated steel material according to claim 1, wherein in the element distribution profile, an average value of the total amount ΣA in a region from the interface to 1.0 μm toward the surface of the plating layer exceeds 0.50 mass%.

3. 2. The hot-dip plated steel material according to claim 1, wherein a total area fraction of Cr-containing compounds and Mo-containing compounds in a cross section of the plated layer is 1.0% or more.

4. A hot-dip plated steel material as described in claim 2, wherein the total area fraction of Cr-containing compounds and Mo-containing compounds in the cross section of the plating layer is 1.0% or more.

5. In the average chemical composition of the plating layer, when the Ca concentration is 0.05 mass% or more, the Cr concentration or the Mo concentration is 0.05 mass% or more, and the relationship ΣYa<Si+Cr+Mo is satisfied, The hot-dip plated steel material according to any one of claims 1 to 4, wherein an X-ray diffraction pattern of the surface of the plating layer satisfies the following formulas (1) and (2): (Imax(10.5°~11.0°) / (I(10.5°)+0.2×{(|I(11.0°)−I(10.5°)|})≧1.5…(1) (Imax(20.2°~20.5°)) / (I(20.2°)+0.667×{|I(20.5°)−I(20.2°)|})≧1.5…(2) Here, Imax (k to m°) is the maximum value of the X-ray diffraction intensity between diffraction angles k and m°, Imax (n°) is the X-ray diffraction intensity at a diffraction angle n°, and k, m, and n are the diffraction angles shown in formula (1) and formula (2), respectively.

6. The hot-dip plated steel material according to any one of claims 1 to 4, wherein the thickness t of the plating layer is 15 µm or more.

7. Hot-dip plated steel material as described in claim 5, wherein the thickness t of the plating layer is 15 μm or more.

Images