Hot dipped steel material

Abstract

This hot dipped steel material has a plating layer that has a desired average chemical composition. When the distance from the surface of the plating layer to the interface between the base steel material and the plating layer is defined as the thickness t of the plating layer, a region in which the total amount ΣA of Cr and Mo is 0.05 mass% or more is present continuously in the thickness direction of the base steel material by 1.0 μm or more in a region from a thickness position of 0.1 × t from the surface of the plating layer to a thickness position at which an Fe concentration that is equal to 40% of the Fe concentration of the base steel material is detected.

Description

Hot-dip galvanized steel

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

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

[0003] The corrosion protection provided by a coating layer is determined by the inherent corrosion resistance and thickness of the coating layer. For example, Patent Document 1 describes the production of a coated steel sheet by a so-called continuous hot-dip coating method in which a steel sheet is continuously immersed in a hot-dip coating bath. The coated steel sheet is then processed into the shape of a part. The continuous hot-dip coating method is used to form zinc coatings and Zn alloy coatings containing Al and Mg. The continuous hot-dip coating method produces a relatively thinner coating layer than the post-coating method described below.

[0004] Patent Document 2 discloses a method of immersing a plated object that has been 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 thickness of the plated layer tends to be thick. However, compared to the continuous hot-dip plating method, the post-plating method has greater restrictions on alloy components, tends to have inferior corrosion resistance, and is significantly inferior in manufacturability.

[0005] In an environment where the time of wetting with water is long, plated steel sheets are extremely susceptible to corrosion. Therefore, increasing the thickness of the plating layer to improve the water corrosion resistance is an important factor in extending the life of plated steel sheets. Therefore, if a Zn alloy plating layer containing a large amount of Al can be produced by a continuous hot-dip plating method to a thickness comparable to that of a post-plating method, it will be possible to efficiently produce steel sheets that provide long-term corrosion protection for steel materials.

[0006] Coated steel sheets produced by continuous hot-dip galvanizing are used in the civil engineering and building materials fields and require long-term corrosion resistance. The thickness of the coating layer on coated steel sheets produced by continuous hot-dip galvanizing is often approximately 20 to 30 μm. This is due to process characteristics of continuous hot-dip galvanizing, such as lifting the molten metal when the steel sheet is pulled out of the coating bath, gas wiping, and air-cooling solidification. Increasing the pulling speed from the coating bath increases the thickness of the coating layer, but because it makes surface appearance control difficult, the upper limit of the coating layer thickness is strictly limited by wiping adjustment. For this reason, when producing a Zn alloy coating layer containing Al and Mg using the continuous hot-dip galvanizing method, it is generally difficult to produce 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 lower specific gravity and therefore a lower viscosity, resulting in a lower amount of molten metal adhering to the steel sheet when it is pulled out of the coating bath.

[0007] In recent years, various elements other than Al and Mg have been added to Zn alloy plating baths 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 easily combine with Mg, Al, or Zn in the Zn alloy to form intermetallic compounds with high melting points. Furthermore, 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., resulting in fine particles (fine dross) that float and settle in the plating bath. These micro-sized intermetallic compounds adhere to the steel sheet during hot-dip plating, causing unplated areas (areas where the plating layer is not formed on the steel sheet) and unevenness on the plating layer surface, resulting in poor appearance. Increasing the temperature of the plating bath is considered effective in suppressing the precipitation of such fine intermetallic compounds. Using a high-temperature plating bath allows the fine dross to redissolve in the plating bath, enabling 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 coating bath with a high Al concentration has a low viscosity and a high melting point, when an attempt is made to produce a coating layer with excellent corrosion resistance and a large thickness by a continuous hot-dip coating method, it is said to be difficult to produce due to the specific gravity and viscosity of the coating bath. Furthermore, there has been no feasible means for operating a system in which various alloy elements are added for a long period of time without generating floating dross.

[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. Furthermore, because steel sheets with plating layers are processed into parts of various shapes, they are also required to have excellent processability.

[0010] International Publication No. 2018 / 139619 Japanese Patent Application Laid-Open No. 61-295361 Japanese Patent Application Laid-Open No. 2017-197795

[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 that is excellent in corrosion resistance, water-wet corrosion resistance and workability.

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

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

[0014] FIG. 1 is a diagram for explaining formulas (1) and (2), and is a schematic diagram showing the results of X-ray diffraction measurement.

[0015] The present inventors have conducted extensive research into hot-dip plated steel materials that have a plating layer containing Al, Mg, and Zn and are produced by a continuous hot-dip galvanizing method, and that have a large coating weight of the plating layer, excellent corrosion resistance and water-wet corrosion resistance, and excellent workability, and a method for producing the same.

[0016] The melting point of a hot-dip galvanizing bath of a Zn alloy, in which Zn, a low-melting-point metal, is mixed with elements such as Al or Mg, tends to increase as the composition deviates from a ternary eutectic composition or Zn-3%Al-3%Mg (% expressed in 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). In consideration of the hot-dip galvanizing process, such a Zn alloy plating bath is operated at around 500°C, which is 50°C or more higher than the melting point of a plating bath of pure Zn.

[0017] Alloying elements such as Al and Mg have a lower specific gravity than Zn. The specific gravity of alloying elements is closely related to the viscosity in the molten state. That is, molten metal containing high concentrations of Al, Mg, etc. has a lower viscosity. Therefore, in a continuous hot-dip coating process, when a steel sheet is passed through a coating bath at approximately 500°C at a constant line speed, the amount of hot-dip coating bath that adheres to the steel sheet and is lifted up with the steel sheet is significantly less than in the case of pure Zn coating. Therefore, the development of wiping technology, etc. is essential to consistently produce coating layers with thicknesses exceeding 20 μm. However, because the molten metal that constitutes the coating layer is light due to its inherently low specific gravity, it is easily blown away during wiping blowing. Furthermore, due to the tendency for wrinkling, it is difficult to produce thick coating layers, even with improvements in wiping technology, etc.

[0018] In addition, Si and other elements may be added to the coating bath to enhance its performance. However, added elements such as Si tend to bond with Fe, Mg, and the like, and furthermore, form floating dross that easily settle in the coating bath. In particular, floating dross is likely to form in a coating bath at about 500°C.

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

[0020] Therefore, the present inventors conducted extensive research to solve the above problems. To produce a coating layer with a large adhesion weight 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, adding Cr increases the specific gravity and viscosity of the coating bath, thereby increasing the coating weight on the base steel during threading. Note that Mo can be cited as an element that exhibits the same effect as Cr.

[0021] On the other hand, when Cr or Mo is added to a coating bath, floating dross tends to form in the coating bath because Cr or Mo easily bonds with elements such as Si, Ca, and Mg. However, because 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 around 600°C, the Al-Fe alloying reaction is active, and a short immersion of the base steel may result in the growth of a thick Al-Fe-based interface alloy layer, which may 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 a short time.

[0022] Furthermore, by pre-plating the base steel with a high-melting-point metal such as Cr or Ni, the reaction between Al and Fe can be suppressed, and the growth of the interfacial alloy layer can be significantly suppressed, making it possible to produce a hot-dip plated steel material that has excellent corrosion resistance, water-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 %." A numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. When the numerical values ​​before and after "to" are followed by "greater 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 described. The base steel material is, for example, mainly a steel plate, but there are no particular restrictions on 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 continuous hot-dip galvanizing lines (CGLs). The applicable steel plate size is, for example, a plate thickness of 10 mm or less and a plate width of 2000 mm or less, but the steel plate size is not limited to these. 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 is not particularly limited, and examples of applicable base steel include various steel plates, steel wire rods, 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 strengthen corrosion resistance, such as Ni and Cr), soft steel wire, hard steel wire, spring steel, steel cord, steel for bolts, and steel wire rod for bridge cables. More specifically, for example, hot-rolled mild steel plates and steel strips specified in JIS G 3131:2018, cold-rolled steel plates and steel strips specified in JIS G 3141:2021, general structural rolled steel materials specified in JIS G 3101:2020, thinly plated steel sheets specified in 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, JIS G Applicable steels include various plated steels such as 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 plated steel or plated steel sheet as a base steel material is also referred to as "pre-plated steel or pre-plated steel sheet"); rolled steel for building 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 elements that strengthen corrosion resistance, such as Ni and Cr).

[0027] As mentioned above, the surface of the base steel is pre-plated in advance with a coating of 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. The use of a base steel material provided with such a pre-plated layer makes it possible to suppress the growth of an Al-Fe-based interfacial alloy layer, to suppress the occurrence of powdering, and to improve workability.

[0028] Furthermore, the manufacturing process for the base steel material includes common processes such as pig iron and steel making processes using a blast furnace or electric furnace, hot rolling processes, pickling processes, cold rolling processes, and heat treatment processes, but the base steel material of this embodiment may have undergone any of these processes, and the processing conditions for 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 alloying elements such as Al and Mg, corrosion resistance is improved, so a thin plating layer with a small thickness, for example, about half the thickness of a normal Zn plating layer, can provide equivalent corrosion resistance. Therefore, this embodiment also ensures corrosion resistance equivalent to or greater than that of a Zn plating layer with a thin film. The plating layer may also include an Al-Fe interfacial alloy layer.

[0030] The Zn—Al—Mg alloy layer is made of a Zn—Al—Mg alloy. The Zn—Al—Mg alloy refers to 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] In many cases, the Al--Fe interfacial alloy layer is an interfacial alloy layer that exists 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 have a single-layer structure of a Zn—Al—Mg alloy layer, or a laminated structure including a Zn—Al—Mg alloy layer and an Al—Fe interfacial alloy layer. In the case of a laminated structure, the Zn—Al—Mg alloy layer is preferably a layer that constitutes the surface of the plating layer.

[0033] Although the Al-Fe-based interface alloy layer only contributes to corrosion resistance, it influences the adhesion of the plating layer during processing of hot-dip galvanized steel and the 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. Generally, a thinner Al-Fe-based interface alloy layer reduces the number of crack initiation points in the plating layer during processing, thereby improving powdering resistance. Therefore, for hot-dip galvanized steel that may be subjected to high processing during use, it is preferable that the Al-Fe-based interface alloy layer be 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 can suppress the generation of cracks during processing and 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 of the entire plating layer, and more preferably less than 5%.

[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 interfacial alloy layer in the hot-dip plated steel material according to this embodiment becomes extremely thin and may be barely visible. Furthermore, 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 incorporated into the base steel material or the Al-Fe alloy layer.

[0035] The Al-Fe alloy layer has a structure of Al ５ Fe ２ The Al-Fe interfacial alloy layer is formed by mutual atomic diffusion between the base steel (base steel material) and the coating bath. When a continuous hot-dip coating method is used as the manufacturing method, the Al-Fe interfacial alloy layer is likely to be formed in the coating layer containing Al element. In this embodiment, since the coating bath contains Al at a certain concentration or more, the Al-Fe interfacial alloy layer contains Al. ５ Fe ２However, because atomic diffusion takes time, the Fe concentration in the Al-Fe system interface alloy layer is not uniform, and the Fe concentration may be higher in the area closer to the base steel. Therefore, the Al-Fe system interface alloy layer is partially composed of an AlFe phase, an Al ３ Fe phase, Al ５ Fe ２ In addition, since the plating bath also contains a certain concentration of Zn, the Al-Fe-based interface alloy layer may contain a small amount of Zn or Si, which tends to accumulate at the interface.

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

[0037] The thickness of the entire coating layer depends on the coating conditions, and therefore the upper and lower limits of the thickness of the entire coating layer are not particularly limited. Furthermore, it is affected by the withdrawal speed of the steel material from the coating bath and the wiping conditions. That is, in the continuous hot-dip coating method, the thickness of the entire coating layer is affected by the viscosity and specific gravity of the coating bath. Since the maximum thickness of the coating layer formed by the continuous hot-dip coating method is often 100 μm or less, the thickness of the coating layer of the hot-dip coated 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 coating bath containing a high concentration of Al is produced at a bath temperature of approximately 600°C, the viscosity of the coating bath is usually low, and therefore the thickness of the coating layer is often around 20 μm. Although extending the immersion time may thicken the Al-Fe interfacial alloy layer and thus the entire coating layer, as described above, a thick Al-Fe interfacial alloy layer significantly deteriorates workability. The thickness of the plating layer is set to 20% or less of the thickness of the base steel material, but may be set to 15%, 10%, or 5% or less of the thickness of the base steel material as needed. The thickness of the plating layer may be set to 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 as needed.

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

[0039] Al: More than 10% and Less than 45% Al is the main constituent element of the coating layer. When the Al concentration exceeds 10%, the melting point of the coating layer becomes higher than that of pure Zn. Furthermore, the Cr required to increase the thickness of the coating layer in this embodiment does not form a solid solution with Zn or 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 be more than 10%. Furthermore, Al is an essential element for forming Cr-containing intermetallic compounds or Mo-containing intermetallic compounds. The Al concentration is preferably 18% or more, and more preferably 25% or more. On the other hand, when the Al concentration is 45% or more, the reactivity between the coating bath and the base steel increases, making it difficult to suppress the formation of an Al-Fe-based interfacial alloy layer, and ensuring workability at a thick coating thickness becomes difficult. Furthermore, the thickness of the Zn-Al-Mg-based alloy layer decreases accordingly as the Al-Fe-based interfacial alloy layer is formed thicker. Therefore, the Al concentration is set to be less than 45%. The Al concentration is preferably 38% or less, and more preferably 35% or less.

[0040] Mg: 4.0 to 15.0% Mg, like Zn, is an element that mainly constitutes the plating layer. Mg is necessary for high corrosion resistance, and it is present in the Zn-Al-Mg alloy layer as a relatively hard MgZn. ２ Mg is an element necessary for ensuring wet corrosion resistance in a wet environment. If the Mg concentration is less than 4.0%, it will not form suitable 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 wet corrosion resistance can be obtained by including Mg is the MgZn ２ , Mg ３２ (Zn, Al) ４９ The presence of Zn-Mg compounds is a problem. The Mg concentration is preferably 5.0% or more, or 6.0% or more. On the other hand, if the Mg concentration exceeds 15.0%, it becomes difficult to form intermetallic compounds with Cr. Furthermore, the viscosity of the plating bath becomes extremely high, which significantly deteriorates the plating appearance. Furthermore, the plating bath does not lift up during lifting, 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, or 10.0% or less.

[0041] Cr: 0 to 3.00% Mo: 0 to 3.00% Total amount of Cr and Mo, ΣA: 0.03 to 3.00% When Cr is contained in a Zn-based coating bath containing Al, it increases the specific gravity of the coating bath and improves the viscosity of the coating bath. This increases the amount of molten metal adhering to the steel material when the steel material is pulled out of the coating bath, resulting in a thick coating layer. In addition, the presence of Cr in the coating bath increases the amount of Al adhering to the steel material during the initial solidification stage of the coating phase. １８ Cr ２ Mg ３ Cr-containing intermetallic compounds, such as those represented by the formula (I), are formed, further promoting an 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 the specific gravity and viscosity, but both are considered to be the effects of the Cr content. When Al and Mg are within the appropriate concentration range, this effect tends to increase the plating coating weight when the Cr content 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 causes coating defects such as non-coating and dross adhesion defects, significantly affecting the shape and performance of the product and degrading corrosion resistance. Therefore, it is preferable to completely dissolve the floating dross in the coating bath. For this reason, in this embodiment, the temperature of the coating bath containing Cr must be 600°C or higher. If the Cr concentration exceeds 3.00%, it is difficult to completely dissolve the floating dross even if the temperature of the coating bath is increased. Furthermore, the viscosity of the coating bath becomes extremely high, reducing the amount of molten metal adhering to the steel material when it is pulled out of the coating bath, resulting in an extremely thin coating layer. Furthermore, the coating appearance is significantly deteriorated. Therefore, the Cr concentration is set to 3.00% or less. The Cr concentration is preferably 2.50% or less, or 2.00% or less.

[0043] Mo, which is an element of the same group as Cr, exhibits the same effect as Cr. Therefore, it is sufficient to include at least one of Cr and Mo, and both may be included. 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 reasons as for Cr, the Mo concentration is 3.00% or less. The Mo concentration is preferably 2.50% or less, 2.00% or less. When Mo is contained, the Mo-containing intermetallic compound may be Al. １０ CaMo ２ is generated. In this embodiment, in order to obtain the above-mentioned effects of containing Cr or Mo, the total amount ΣA of the concentrations 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. Furthermore, 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. Furthermore, 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 increases, 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 slows. 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 will combine with Mg to form an intermetallic compound (Mg ２A large amount of Mg is formed. 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, resulting in an extremely thin coating layer. 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, most of the Mg ２ No Si is formed.

[0045] Element group X Sn: 0-0.7% Bi: 0-0.3% In: 0-0.3% Total amount of Sn, Bi, and In ΣX: 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, Mg ９ Sn ５ Bi tends to form Mg ３ Bi ２ In forms Mg ３ In etc. These elements form MgZn ２ It is softer than the Cr phase and has good workability, and its inclusion clearly improves workability. At the same time, it exhibits very base electrochemical properties, so it has a high sacrificial corrosion protection effect. Therefore, the inclusion of these elements improves the corrosion resistance of the processed parts.

[0046] Each element has an upper limit to its concentration, and if it is contained in a large amount, it will absorb Mg from the Cr-containing intermetallic compound, preventing the Cr-containing intermetallic compound from forming and 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 Sn, Bi, and In concentrations is set to 0.7% or less. The total amount ΣX is preferably set to 0.5% or less, or 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 to 0.60% Y: 0 to 0.3% La: 0 to 0.3% Ce: 0 to 0.3% Sr: 0 to 0.3% Li: 0 to 0.3% Total amount of Ca, Y, La, Ce, Sr and Li ΣYa: 0 to 0.6%

[0049] Ca, which is one of the elements of the Ya group, is preferably contained because it brings about various effects in the plating bath. Of the elements in the plating bath, Ca is most likely to bond with Cr. Therefore, in a plating bath containing Cr, Al １０ CaCr ２ 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 a Ca-Al-Si compound (Al ２ CaSi ２ , CaSi ２ This compound forms Mg ２ Mg because it is easier to form than Si ２ The deterioration of corrosion resistance in Si can be prevented by including Ca.

[0051] If the Ca concentration exceeds 0.60%, various floating dross will form in the coating bath, increasing the number of coating defects. Furthermore, the viscosity of the coating bath will become extremely high, reducing the amount of molten metal adhering to the base steel when the steel is removed from the coating bath, resulting in an extremely thin coating layer and a deterioration in corrosion resistance. Furthermore, the coating appearance will be significantly deteriorated. Therefore, the Ca concentration is set to 0.60% or less. The Ca concentration is preferably 0.50% or less, or 0.40% or less.

[0052] Each element of the element group Ya other than Ca can obtain 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 compound formed by the inclusion of the element group Ya other than Ca is Al. １０ CaCr ２As a substitute of Al １０ (Ya)Cr ２ , and further combines with Si to form a Ya-Al-Si compound. When either Ca or any one of these elements is present, almost no difference in corrosion resistance, workability, or performance is observed. At high concentrations, as with Ca, Mg is absorbed from Cr compounds, preventing the formation of these compounds and resulting in a thin plating thickness, so there is an upper limit to the concentration. Therefore, the concentrations of each element in the element group Ya other than Ca are set to 0 to 0.3%. The concentrations of each element in the element group Ya other than Ca are preferably 0.2% or less, 0.1% or less, respectively. Furthermore, the total concentration ΣYa of the elements in the element group Ya including Ca is set to 0 to 0.6%. The total concentration ΣYa is preferably 0.5% or less, 0.4% or less.

[0053] The total amount of Ca, Y, La, Ce, Sr, and Li, ΣYa≦Si+Cr+Mo, must be kept below the sum of the concentrations of Si, Cr, and Mo. If the total amount ΣYa exceeds the sum of the concentrations of Si, Cr, and Mo, Ca forms an Al-Zn-Ca compound, which significantly increases the viscosity of the coating bath. This reduces the amount of molten metal adhering to the base steel when the steel is removed from the coating bath, resulting in an extremely thin coating layer and poor corrosion resistance. Furthermore, the coating appearance is significantly impaired. In particular, when forming a thick coating, powdering is likely to occur, significantly deteriorating 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: 0-0.25% Pb: 0-0.25% Total Amount ΣYb of Ni, Cu, Ag, Sb, and Pb: 0-1.0% The elements in the element group Yb share common effects. When the concentration of any one of these elements is 0.10% or higher, the effect of improving wet corrosion resistance is obtained. Therefore, it is preferable that the concentration of at least one of these elements is 0.10% or higher. However, if the total concentration ΣYb of these elements becomes excessive, various intermetallic compounds are formed, resulting in extremely high viscosity of the coating bath. As a result, when the steel is removed from the coating bath, the amount of molten metal adhering to the base steel is reduced, the coating layer becomes extremely thin, and corrosion resistance is impaired. Therefore, the total amount ΣYb is set to 1.0% or less. The total amount ΣYb is preferably 0.5% or less, 0.3% or less. In order to suppress deterioration of corrosion resistance, the concentrations of Ni and Cu are each 1.0% or less. The concentrations of Ni and Cu are each preferably 0.5% or less. In order to suppress deterioration of corrosion resistance, the concentrations of Ag, Sb, and Pb are each 0.25% or less. The concentrations of Ag, Sb, and Pb are each preferably 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 share common effects. When the concentration of any one of these elements is 0.05% or more, the corrosion resistance of the processed portion is improved. 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 coating bath becomes extremely high. This reduces the amount of molten metal adhering to the base steel when withdrawn from the coating bath, resulting in an extremely thin coating layer and poor corrosion resistance. 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. Furthermore, to prevent deterioration of corrosion resistance due to the above effects, the total concentration ΣYc of B and P is set to 0.50% or less. The total amount ΣYc of B and P is preferably 0.30% or less, and more preferably 0.20% or less.

[0056] Element group Z Ti: 0-0.25% Co: 0-0.25% V: 0-0.25% Nb: 0-0.25% Mn: 0-0.25% Zr: 0-0.25% W: 0-0.25% Total amount ΣZ of Ti, Co, V, Nb, Mn, Zr, and W: 0-0.25% Elements included in element group Z are elements that form a solid solution in the Al phase contained in the plating layer. When elements of element group Z are included in the plating bath, water-wet corrosion resistance is improved. The above-mentioned effect can be achieved 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. Therefore, it is preferable that the concentration of any one of these elements is 0.10% or more, or the total amount ΣZ 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, causing the viscosity of the coating bath to become extremely high. As a result, when the base steel is pulled out of the coating bath, the amount of molten metal adhering to the base steel is reduced, the thickness of the coating layer becomes extremely thin, and corrosion resistance deteriorates. Therefore, the concentration of each element in element group Z is set to 0.25% or less. The concentrations of each element in element group Z are preferably 0.20% or less and 0.10% or less, respectively. Furthermore, to prevent deterioration of corrosion resistance due to the above-mentioned effects, the total amount ΣZ is set to 0.25% or less. The total amount ΣZ is preferably 0.20% or less and 0.10% or less.

[0057] Fe: 0 to 5.0% The hot-dip plated steel material according to this embodiment is manufactured by a continuous hot-dip plating method, so Fe may diffuse from the base material to be plated into 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 interfacial alloy layer may be formed, but its thickness is thin. As a result, the plated layer may contain up to 5.0% Fe. The Fe concentration may be 0%, but as long as the Fe concentration is 5.0% or less, there is no effect on the frequency of cracks 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 greater than 0%.

[0058] Balance: Zn and impurities The balance includes Zn and impurities. Since the hot-dip plated steel material of this embodiment is a highly versatile Zn-based plated steel material, the element constituting the main phase of the plated layer is Zn. There is no need to specify the Zn concentration, 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. Furthermore, since metals with 3N purity (3N stands for Three Nine, meaning 99.9% purity) are typically used to manufacture plating alloys, the total concentration of impurities may be approximately 0.03% or less.

[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 restrictions on the type of acid, as long as it can dissolve the plating layer. For example, a solution in which IBIT (inhibitor) manufactured by Asahi Chemical Industry Co., Ltd. is dissolved in 10% by volume of HCl can be used as an acid containing an inhibitor. If the area and mass before and after stripping are measured, the plating deposition amount (g / m ２ ) can also be obtained at the same time.

[0061] Next, the intermetallic compounds contained in the plating layer will be described. Since the plating layer according to this embodiment is a Zn-Al-Mg alloy plating, the plating layer contains a Zn phase, an Al phase, an MgZn phase, and the like. ２ The plating layer according to this embodiment contains one or both of a Cr-containing intermetallic compound and a Mo-containing intermetallic compound. Furthermore, the plating layer according to this embodiment may contain other intermetallic compounds.

[0062] Cr-containing intermetallic compound, Mo-containing intermetallic compound The plating layer according to this embodiment contains Al ２０ CaCr, Al １８ Cr ２ Mg ３ These include Cr-containing intermetallic compounds such as those shown in the following. 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 Al １８ Cr ２ Mg ３ In addition, since the atomic radii of Al and Zn, and Mg and Ca are close to each other, in the plating layer, part of Al is substituted with Zn and part of Mg is substituted with Ca, forming (Al, Zn). １８ Cr ２ It may also exist as (Ca, Mg)3. In areas where Ca is insufficient in the plating layer, it may exist as (Al, Zn) １８ Cr ２ Mg ３ may also be formed.

[0063] Furthermore, as described above, Cr can be substituted for Mo, which is a homologous element, and therefore, when Cr and Mo are both contained, there is a possibility that part of the Cr in the intermetallic compound described above will be substituted with Mo. Such a compound can 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, Al is contained as the Mo-containing intermetallic compound. １０ CaMo ２ is formed.

[0065] As described above, by including Cr or Mo in the coating layer, these intermetallic compounds are formed in the coating layer, the viscosity of the coating bath is significantly improved, and the amount of the coating bath lifted when the base steel is pulled up from the coating bath increases. Furthermore, the formation of these intermetallic compounds in the coating layer improves the water-wet corrosion resistance and 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 Cr ２ Mg3 and (Al, Zn) １８ Cr ２ (Ca, Mg) ３ However, since the diffraction peaks are close to each other, it is difficult to distinguish between them. Furthermore, when a large amount of these intermetallic compounds is contained in the plating layer, the intermetallic compounds can be directly identified by observing the cross section of the plating layer with a scanning electron microscope (SEM), and the effect of containing the compounds can be determined by measuring the area fraction of the contained intermetallic compounds. These measurement methods will be described later.

[0067] Other intermetallic compounds Ca tends 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 Al-Ca-Si compounds in addition to Cr-containing intermetallic compounds and Mo-containing intermetallic compounds.

[0068] Si is Mg ２ However, if the amount of Si exceeds the Ca concentration, Mg ２ Although the corrosion resistance of this compound is not favorable, if it is contained in a small amount, the deterioration of the corrosion resistance of the entire plating layer is small.

[0069] Sn and In tend to bond with Mg, ２ Sn, Mg ９ Sn ５ , Mg ３ In, but these are formed independently of each other regardless of the reaction 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 to analyze the components in the depth direction inside the plating layer. The inventors used a LECO Japan 850A glow discharge optical emission spectroscopy device, but the measurement device is not limited to this. When performing depth direction analysis, analysis is preferably performed while Ar sputtering is performed, under the following analysis conditions: argon pressure: 0.27 MPa, output power: 30 W, output voltage: 1000 V, and discharge area: a circular area with a diameter of 4 mm. 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 from the surface of the base steel sheet. Therefore, the analysis range of depth direction analysis using GDS extends from the plating surface to the Zn-Al-Mg alloy layer, the Al-Fe alloy layer, and a portion of the base steel. After GDS analysis, the sputter depth of the cross section is measured using, for example, a Surfcom 130A manufactured by Tokyo Seimitsu Co., Ltd. The GDS analysis provides an elemental distribution profile of the plating layer in the depth direction, which shows the concentration distribution of each element in the depth direction when the total amount of the detected elements is set to 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 material up to a position at least ¼ of the plate thickness of the hot-dip coated steel material, the Fe concentration at a position ¼ of the plate thickness of the hot-dip coated steel material from the surface of the hot-dip coated steel material (hereinafter, the Fe concentration at this position will also be 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 material, and this position is always the thickness position at which 95% of the Fe concentration of the base steel material (however, if the base steel material is pre-plated steel material, it will be the base steel portion excluding the pre-plated layer) is detected is defined as the coating layer and the base steel material. 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 plate 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 water-wet corrosion resistance is improved when, within the evaluation range, there is a region where the total amount ΣA is 0.05 mass% or more continuously present for 1.0 μm or more in the thickness direction of the base steel material (hot-dip plated steel material).

[0073] When evaluating the Cr and Mo concentrations, the evaluation range is defined as "the region from a thickness position 0.1 × t from the surface of the coating layer (hot-dip coated steel) to a thickness position where an Fe concentration of 40% of the base steel Fe concentration (Fe concentration at a position ¼ of the plate 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 a thickness position 0.1 × t from the surface of the coating layer is excluded from the evaluation range because it is a region where GDS analysis errors can be large. Furthermore, the region near the boundary between the coating layer and the base steel may be affected by an Al-Fe interfacial alloy layer. Furthermore, when a pre-coated base steel with Cr or Mo is used as the base steel for plating, it may be affected by the pre-coated layer. Therefore, the evaluation range is defined as the thickness position where an Fe concentration of 40% of the maximum Fe concentration is detected, and the region closer to the base steel than this is excluded from the evaluation range.

[0074] Within the above evaluation range, if a region where the total amount ΣA of Cr and Mo concentrations 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 viscosity increase effect is observed during the production of the coating layer. Whether a region where the total amount ΣA of Cr and Mo concentrations is 0.05% or more exists continuously in the thickness direction for 1.0 μm or more is confirmed by the element distribution profile obtained by the GDS analysis described above. As a result, when the rate at which the base steel material is pulled up from the coating bath is constant, by adjusting the wiping, the coating layer thickness can be increased to 15 μm or more, preferably 20 μm or more, 25 μm or more, or more than 30 μm, whereas in the case of a coating layer without Cr and Mo, the maximum thickness was limited to around 30 μm. If a 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, the coating layer thickness can be increased to 15 μm or more, preferably 20 μm or more, 25 μm or more, or more than 30 μm. 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] Furthermore, when pre-plated steel is used as the base material for plating, in an element distribution profile obtained by GDS analysis from the surface of the plating layer to a position at least ¼ of the 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 ¼ of the thickness of the hot-dip plated steel from the surface of the hot-dip plated steel) is detected is defined as the interface between the plating layer and the base steel, the average value of the sum of the Cr and Mo concentrations ΣA is preferably greater 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 sum of the Cr and Mo concentrations ΣA exceed 0.50% in the region from the interface to 1.0 μm toward the surface of the plating layer, diffusion of Fe from the base steel toward the plating layer during hot-dip plating is suppressed. This allows the thickness of the Al-Fe-based interface alloy layer to be made thinner. Specifically, the thickness of the Al-Fe-based interface alloy layer can be reduced to 1.0 μm or less, thereby improving the workability of the hot-dip plated steel.

[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, improving corrosion resistance, particularly in bent sections. The inventors speculate that the sacrificial corrosion protection effect is due to the fact that Mg, Cr, and Ca, which inherently exhibit low electronegativity, bond to Al, destabilizing the oxide film covering the Al phase and enhancing sacrificial corrosion protection. These intermetallic compounds are thought to form oxide films of Cr and the like after dissolution due to corrosion, improving corrosion resistance after dissolution.

[0077] An electron probe microanalyzer (EPMA) is used to measure the area fraction of Cr-containing intermetallic compounds or Mo-containing intermetallic compounds. A cross section of the plating layer is exposed, and the cross section is observed using 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 carried out: An elemental mapping image is obtained by EPMA at a 200x magnification. In the elemental mapping image, Zn and other elements can be detected anywhere in the plating layer, except for specific small compounds. On the other hand, Cr, Mo, and other elements can be detected in specific intermetallic compounds (Al １８ Cr ２ Mg ３ , Al ２０ CaCr, Al １０ CaMo ２ In other words, the locations of Cr and Mo are the locations of intermetallic compounds.

[0079] Once the mapping images for each element are obtained, they are analyzed using image analysis software such as Image J. For the Zn mapping image, the image is 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 in pixel units.

[0080] Next, the Cr mapping image is also binarized to obtain the number of Cr pixels. The number of pixels where Cr is 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 determined for each field of view, and the average value is calculated. For Mo-containing intermetallic compounds, the area fraction is calculated in the same manner as for Cr by using the Mo mapping image.

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

[0082] Since X-ray diffraction measurement has lower detection sensitivity than GDS analysis, it is presumed that a certain amount or more of Cr-containing intermetallic compounds or Mo-containing intermetallic compounds is contained in the plating layer. Therefore, when the average chemical composition of the plating layer has a Ca concentration of 0.05% or more, a Cr concentration or a Mo concentration of 0.05% or more, and satisfies the relationship ΣYa<Si+Cr+Mo, it is preferable that the X-ray diffraction pattern of the plating layer surface satisfies the following formulas (1) and (2): (Imax(10.5° to 11.0°) / (I(10.5°)+0.2×{(|I(11.0°)−I(10.5°)|})≧1.5 ... (1) (Imax(20.2° to 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 to 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 formulas (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 ΣYa<Si+Cr+Mo is satisfied, １８ Cr ２ Mg ３ It is possible to detect Al, which is a Cr-containing intermetallic compound, by X-ray diffraction measurement. １８ Cr ２ Mg ３ , Al ２０ CaCr is an intermetallic compound with excellent corrosion resistance. When these metals are contained in the plating layer to an extent that they can be detected by X-ray diffraction, corrosion resistance in a water-wet environment is improved. If ΣYa<Si+Cr+Mo is not satisfied, the formation of Al-Zn-Ca compounds by Ca becomes dominant, and the corrosion resistance-improving effect of Cr-containing intermetallic compounds is not confirmed. Note that, since Ca and Cr bond very easily, if the concentration is Ca≦Cr, almost all of the Ca present in the plating bath bonds with Cr, and the remaining Cr becomes Al. １８ Cr ２ Mg ３ It will form.

[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 rays are used and the measurement is performed under the conditions of an X-ray output of 50 kV and 300 mA.

[0086] The left side of the above formula (1) and formula (2) (where the left side of formula (1) is I １ The left side of equation (2) is called I ２ ) is a rule regarding the X-ray diffraction peaks of Cr-containing intermetallic compounds and Mo-containing intermetallic compounds. For example, when talking about Cr-containing intermetallic compounds, Al １８ Cr ２ Mg ３ is an intermetallic compound defined in JCPDS card #01-071-5707. ２０ CaCr ２is an intermetallic compound similarly defined in #01-081-2712. Note that these intermetallic compounds have similar diffraction peaks, making it difficult to distinguish them from one another; that is, Al and Mg form solid solutions, and Zn and Ca form solid solutions, so they are assumed to have almost the same components and structures, and the diffraction peaks appear at almost the same positions. Therefore, there is no need to distinguish these Cr-containing intermetallic compounds from one another in X-ray diffraction measurements.

[0087] Regarding Mo-containing intermetallic compounds, Al ２０ CaMo ２ is defined in JCPDS card #00-051-1061.

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

[0089] Equation (1) focuses on the diffraction peak near 2θ = 10.6°. Imax (10.5° to 11.0°) in equation (1) is the maximum value of the X-ray diffraction intensity between diffraction angles of 10.5° and 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° to 20.5°) in equation (2) is the maximum value of the X-ray diffraction intensity between diffraction angles of 20.2° and 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 in formulas (1) and (2) are the maximum diffraction intensities of the diffraction peaks, including background intensity, corresponding to the intensities of the Cr-containing compound or Mo-containing compound. Because measurement errors in X-ray diffraction can cause the diffraction peaks to deviate from 10.6° or 20.4°, the maximum values ​​between 10.5° and 11.0° and between 20.2° and 20.5° are obtained.

[0092] The denominators of the formulas (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 Figure 1, a straight line is drawn connecting the diffraction line at 10.5° and the diffraction line at 11.0°. This 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 between diffraction angles 10.5° and 11.0° (0.5°) to the difference between diffraction angles 10.5° and 10.6° (0.1°) is calculated. Then, the background intensity at a diffraction angle of 10.6° is calculated using the formula given in the denominator of formula (1) above.

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

[0095] When formula (1) and formula (2) are satisfied, it indicates that a crystal phase of a Cr-containing intermetallic compound or a Mo-containing intermetallic compound grows in a specific orientation, and the corrosion resistance of the processed part is improved. Although the reason for this is not fully understood, it is presumed that the form of cracks in the processed part changes depending on 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 X-ray source is the most convenient method, as it can obtain average information about the constituent phases of the plating layer. As an example of 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 coating layer is observed using a backscattered electron image of an SEM, the steel substrate (base steel), the Al-Fe-based interface alloy layer, and the Zn-Al-Mg-based alloy layer can be identified from the differences in color. When an observation field is obtained at a magnification of 1000x or more, the thickness of the darkest Al-Fe-based interface alloy layer on the steel substrate can be confirmed to the nearest 0.1 μm. However, if the thickness is too thin, the Al-Fe-based interface alloy layer may not be visible. Furthermore, when a pre-plated steel material is used as the base material for plating, the Al-Fe-based interface alloy layer may not be clearly visible 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 determined to the nearest 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 this embodiment is preferably produced by a continuous hot-dip plating method. However, due to size restrictions on the base steel material, it can also be produced by a batch-type hot-dip plating method, if necessary.

[0100] In addition to the above-mentioned base steel material, pre-plated steel material plated with Cr, Ni or Mo may also 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 density 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 coating method is carried out by the Sendzimir method. That is, before immersing the base steel in the coating bath, the base steel is heated at the annealing temperature of a nitrogen-hydrogen mixed gas until the temperature of the base steel reaches or exceeds the temperature of the coating bath. Usually, the annealing atmosphere is 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 1 minute to fully reduce the surface of the base steel. However, depending on the base material to be coated, the hydrogen concentration may be increased to 10%. Also, when entering the coating bath, N is added until the temperature of the base steel reaches the temperature of the coating bath. ２ Gas cooling is used to prevent fluctuations in the plating bath temperature during the manufacturing process.

[0102] Next, the base steel material whose surface has been sufficiently reduced is immersed in a reduced state in a plating bath. The temperature of the plating bath is 600°C or higher. ２ The plating bath is agitated by bubbling. ２ The bubbling flow rate is set to 0.05 m / sec or more. If the plating bath is not stirred under these conditions, floating dross consisting of Cr compounds or Mo compounds will settle 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 composition.

[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 interfacial 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 complete, the plate is cooled so that the time it takes to reach 560°C from the plating bath temperature is 3 to 5 seconds.

[0105] Between 600 and 560°C, Cr or Mo compounds rapidly solidify, forming a milky-white oxide film with high surface tension that covers the surface of the plating bath and imparts a certain degree of viscosity to the molten metal. This facilitates control of the plating layer thickness, particularly under conditions of weak wiping gas (slit width: 2 to 5 mm, distance between the nozzle and the base steel: 50 to 10 mm, gas pressure at the nozzle outlet: 0.1 MPa or less). Generally, in areas with weak wiping gas pressure, slight fluctuations in wiping gas pressure can significantly affect the plating layer thickness, making it difficult to control the plating layer thickness. However, in this embodiment, the inclusion of Cr or Mo in the plating bath increases the viscosity of the plating bath. Therefore, by controlling the wiping gas pressure and distance within the above ranges, a high-gas plating layer can be easily produced with precise control of its thickness. Therefore, wiping conditions do not need to be particularly limited. However, if a cooling method such as rapid cooling by submerging in water or rapid cooling by spraying wiping gas from a wiping nozzle at a high pressure exceeding 0.1 MPa is adopted, it is not desirable because the plating layer cannot be controlled favorably.

[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 form 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 removed from the coating bath.

[0107] Furthermore, production is carried out in an environment with an oxygen concentration of 1,000 ppm or less from the bath temperature until the temperature passes 560°C. In the case of a plating layer with a large coating 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] Thickness of plating layer: If it is more than 50 μm, the time required to reach 360°C from 560°C: Within 10 seconds

[0110] Thickness of plating layer: Over 40 to 50 μm Time required to reach 360°C from 560°C: Within 20 seconds

[0111] Plated layer thickness: 30-40 μm Time required to reach 360°C from 560°C: within 30 seconds

[0112] The cooling method from 560°C to 360°C must not involve submersion or water droplet collisions 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. It is also desirable to use a mist-like mist or a gas with a high cooling effect, such as hydrogen or helium, as the 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] The hot-dip plated steel material according to this embodiment may have a coating formed on the plating layer. One or more layers of the coating may be formed. Examples of the type of coating that may be formed directly on the plating layer include a chromate coating, a phosphate coating, and a chromate-free coating. These coatings may be formed by known methods such as chromate treatment, phosphate treatment, and chromate-free treatment.

[0115] Chromate treatments include electrolytic chromate treatments that form a chromate film by electrolysis, reactive chromate treatments that form a film by utilizing a reaction with the material and then wash away excess treatment solution, and paint-on chromate treatments that apply a treatment solution to the substrate and dry 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 latex, 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 paint-on 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 coatings may be provided on the coating directly on the plating layer. The organic resin is not limited to a specific type, and examples thereof include polyester resins, polyurethane resins, epoxy resins, acrylic resins, polyolefin resins, and modified versions of these resins. Here, the term "modified version" refers to a resin obtained by reacting a reactive functional group contained in the structure of these resins with another compound (such as a monomer or a crosslinking agent) containing a functional group capable of reacting with the functional group.

[0120] Such organic resins may be a mixture of one or more unmodified organic resins, or a mixture of one or more organic resins obtained by modifying at least one other organic resin in the presence of at least one organic resin. The organic resin film may also contain any coloring pigment or anti-rust pigment. Water-based organic resins obtained by dissolving or dispersing them in water may also be used.

[0121] As explained above, it is difficult to increase the coating weight of a coating layer with an increased Al concentration due to a decrease in the specific gravity of the coating bath. However, according to the hot-dip coated steel material of this embodiment, by adding Cr or Mo, the viscosity of the coating bath is increased, making it possible to produce a hot-dip coated steel material with a coating layer with a large coating weight. Furthermore, since the coating layer contains a Cr-containing intermetallic compound or a Mo-containing intermetallic compound, the corrosion resistance and wet corrosion resistance can be improved. Furthermore, by adding Cr or Mo to the coating layer, the thickness of the interfacial alloy layer can be reduced, thereby improving workability. Furthermore, since the coating weight of the coating layer is large, the corrosion resistance and wet corrosion resistance can be further improved.

[0122] Furthermore, while a coating bath containing Cr, Mo, etc. may generate floating dross, by increasing the bath temperature of the coating bath, it is possible to suppress the generation of floating dross and prevent coating defects such as non-coating. Furthermore, while a coating bath at a high temperature may activate the reaction between Al and Fe, resulting in a thick Al-Fe-based interfacial alloy layer, by using a coating bath containing Cr and Mo, it is possible to thin the Al-Fe-based interfacial alloy layer. The hot-dip coated steel material produced in this manner has excellent corrosion resistance, water-wet corrosion resistance, workability, corrosion resistance in processed parts, and sacrificial corrosion protection.

[0123] As the base sheets for plating, a hot-rolled steel sheet (designated H) measuring 100 mm x 200 mm and having a thickness of 1.6 mm and a cold-rolled steel sheet (designated C) measuring 100 mm x 200 mm and having a thickness of 0.8 mm were prepared. Pre-plated steel sheets were also 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 Ni plating (type: Ni) were formed by electroplating. The Mo plating (type: Mo) was formed by vapor deposition plating. A K-type thermocouple was spot-welded to the center of the backside of the base sheet for plating to enable monitoring of temperature changes during the plating process.

[0124] The Sendzimir method was used as the hot-dip plating method. That is, before immersing the base steel sheet in the plating bath, the base steel was heated at the annealing temperature of a nitrogen-hydrogen mixed gas until the temperature of the base steel reached the plating bath temperature or higher. The annealing atmosphere was a nitrogen atmosphere containing 5% hydrogen (N ２ -5% H ２ ) and heated to a temperature of about 800°C for about 1 minute to fully reduce the surface of the base steel material. ２ Gas cooling was used to prevent fluctuations in the plating bath temperature during the manufacturing process.

[0125] In the hot dip coating method, a hot dip coating simulator was used, and the base steel material, the surface of which had been sufficiently reduced, was immersed in a coating bath in a reduced state. The coating bath temperature was as shown in Tables 1-1 to 1-8. The coating bath contained N2O3, which is capable of forming an upward flow velocity of 0.05 m / s or more in the coating bath. ２ A bubbling device was installed. During hot dip coating, this bubbling device was turned on and off. When turned off, the coating bath became almost static. In addition, the oxygen concentration around the mechanism for lifting the base steel was monitored. When the base steel was immersed in the coating bath, N ２ -5% H ２ The test was carried out in a snout whose atmosphere had been replaced with that of 1000 kJ / cm 2 , and a trace amount of oxygen was introduced into the snout as required.

[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, it was subjected to N ２ Gas wiping was performed. When the base steel was pulled up, if it was produced in an environment where the oxygen concentration was 1000 ppm or less from the bath temperature until it passed through 560°C, it was marked as OK in the "Oxygen concentration at pulling up position" column in the table. On the other hand, if this condition was not met, it was marked as NG.

[0127] Then, cooling was started and N ２The gas flow rate and temperature were controlled to control the time required to reach 560°C from the time the plating bath was pulled up (bath temperature), and the time required to reach 350°C from 560°C. As a cooling method, some samples were quenched by submersion and by spraying wiping gas at a pressure of 1.5 MPa from a wiping nozzle. In Tables 1-1 to 1-8, examples where cooling was performed by submersion are indicated as "submersion," and examples where quenching was performed by spraying wiping gas at a pressure of 1.5 MPa are indicated as "strong gas."

[0128] The hot-dip galvanized steel materials shown in Tables 1-1 to 4-8 were produced using the above-mentioned method. The average chemical composition of the coating layer was measured using the above-mentioned method. Furthermore, an element distribution profile was obtained using the above-mentioned method, and the thickness t of the coating layer was obtained by defining the interface between the coating layer and the base steel from the element distribution profile as the thickness of the coating layer, and defining the distance from the surface of the coating layer to the interface as the thickness of the coating layer.

[0129] The obtained hot-dip plated steel material was 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 method described above.

[0131] In the element distribution profile, in the region from a thickness position 0.1 × t from the surface of the coating layer to a thickness position where an Fe concentration of 40% of the Fe concentration in the base steel (i.e., the Fe concentration at a position ¼ of the thickness of the hot-dip coated steel from the surface of the hot-dip coated steel) was detected, it was confirmed whether there was a region of 1.0 μm or more continuous in the thickness direction of the base steel where the total concentration ΣA of Cr and Mo was 0.05 mass% or more. In the above region, the continuous length of the region where the total concentration ΣA of Cr and Mo was 0.05 mass% or more is shown in the column of "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 was calculated 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. 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 using an electron probe microanalyzer (EPMA) and ImageJ (image analysis software) by the method described above. 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, by performing X-ray diffraction measurement using the horizontal sample type high-power X-ray diffractometer RINT-TTR III manufactured by Rigaku Corporation as the X-ray diffractometer according to the above-mentioned method, I １ and I ２ The results are shown in the table.

[0135] (Workability) Workability was evaluated by a 1-ton bending test. The sample size was 40 mm × 120 mm × 1.6 mm for samples using hot-rolled steel sheets as the base sheet for plating, and 40 mm × 120 mm × 0.8 mm for samples using cold-rolled steel sheets as the base sheet for plating. These samples were bent at the center of the 40-mm width. Tape was firmly attached to both sides of the plated steel sheets in advance. A 1-ton (the thickness of one steel sheet) was sandwiched inside, bent at 180° in a jig, and completely pressed to prepare a bending test specimen with a space equivalent to one steel sheet inside. The inner steel sheet was then removed, and the tape was forcefully pulled and peeled off. The inner and outer tapes were attached to black cardboard to check for the presence of peeled plating powder in the processed area. The evaluation criteria were as follows: "G" was considered pass, and "B" was considered fail. Tables 4-1 to 4-8 show the results as "powdering."

[0136] Peeling powder on both sides... "B" No peeling powder on both sides... "G"

[0137] (Corrosion Resistance) The corrosion resistance of the 1t bend test specimens was evaluated by subjecting them to a cyclic corrosion test as is. The top of the 1t bend was subjected to severe processing, which inevitably resulted in cracks in the plating layer, resulting in exposed areas of the base steel. Corrosion evaluation was performed using the artificial acid rain cycle test method specified in JIS H 8502:1999. That is, photographs of the top of the 1t bend were taken for each specified cycle, and evaluation was performed at the cycle in which red rust appeared and the red rust area reached 50% at the center line of the top of the 1t bend. The evaluation used t = 1.6 mm and 0.8 mm. The evaluation criteria were as follows: "S", "A+++", "A++", "A+", and "A" were considered pass, and "B" was considered fail. Tables 4-1 to 4-8 show the results as "corrosion resistance".

[0138] Those that develop red rust over 900 cycles... "S" Those that develop red rust over 750 cycles... "A+++" Those that develop red rust over 600 cycles... "A++" Those that develop red rust over 480 cycles... "A+" Those that develop red rust over 300 cycles... "A" Those that develop red rust 300 or fewer cycles... "B"

[0139] The sample size for evaluating water-wet corrosion resistance was 40 mm x 120 mm x 1.6 mm for samples using hot-rolled steel sheets as the base sheet for plating, and 40 mm x 120 mm x 0.8 mm for samples using cold-rolled steel sheets as the base sheet for plating. A 0.001 vol% NaCl aqueous solution at room temperature and pH 5.0±0.1 was dripped onto the center of the sample in the width and length directions from a height of 50 mm at a rate of 1 μl / sec. The time required for red rust of 1 mm diameter or greater to appear at the dripped area was evaluated. The evaluation criteria were as follows: "S," "A+++," "A++," "A+," and "A" were considered pass, and "B" was considered fail. The results are shown in Tables 4-1 to 4-8 as "water-wet corrosion resistance."

[0140] If red rust has appeared in more than 40 weeks... "S" If red rust has appeared in more than 35 weeks but within 40 weeks... "A+++" If red rust has appeared in more than 30 weeks but within 35 weeks... "A++" If red rust has appeared in more than 25 weeks but within 30 weeks... "A+" If red rust has appeared in 20 to 25 weeks... "A" If red rust has appeared in less than 20 weeks... "B"

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

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

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Claims

1. A hot-dip coated steel comprising a base steel material and a plated layer disposed on a surface of the base steel material, whereinan average chemical composition of the plated layer, in mass%, containsAl: more than 10% and less than 45%,Mg: 4.0 to 15.0%,Si: 0 to 2.00%,Cr: 0 to 3.00%,Mo: 0 to 3.00%,Sn: 0 to 0.7^Bi: 0 to 0.3%,In: 0 to 0.3%,Ca: 0 to 0.60%,Y: 0 to 0.3%,La: 0 to 0.3%,Ce: 0 to 0.3%,Sr: Oto 0.3%,Li: 0 to 0.3%,Ni: 0 to 1.0%,Cu: Oto 1.0%,Ag: Oto 0.25%,Sb: 0 to 0.25%,Pb: 0 to 0.25%,B: Oto 0.50%,P: 0 to 0.50%,Ti: Oto 0.25%,Co: Oto 0.25%,V: 0 to 0.25%,Nb: Oto 0.25%,Mn: 0 to 0.25%,Zr: 0 to 0.25%,W: 0 to 0.25%,Fe: 0 to 5.0%, andthe balance being Zn and impurities, and further satisfyinga total amount SA of Cr and Mo: 0.03 to 3.00%,a total amount LX of Sn, Bi, and In: 0 to 0.7%,a total amount SYa of Ca, Y, La, Ce, Sr, and Li: 0 to 0.6%,a total amount SYb of Ni, Cu, Ag, Sb, and Pb: 0 to 1.0%,a total amount SYc of B and P: 0 to 0.50%,a total amount SZ of Ti, Co, V, Nb, Mn, Zr, and W: 0 to 0.25%, andSYa < Si + Cr + Mo, andin a case where, in an elemental distribution profile obtained by GDS analysis in a thickness direction of the base steel material from a surface of the plated layer toward the base steel material, a thickness position at which a detected Fe concentration reaches 95% of an Fe concentration of the base steel material is defined as an interface between the plated layer and the base steel material, and a distance from the surface of the plated layer to the interface is defined as a thickness t of the plated layer,in a region from a thickness position of 0.1 x t from the surface of the plated layer to a thickness position at which a detected Fe concentration reaches 40% of the Feconcentration of the base steel material, a region in which the total amount SA is 0.05mass% or more exists continuously for 1.0 gm or more in the thickness direction of the base steel material.

2. The hot-dip coated steel according to claim 1, wherein in the elemental distribution profile, an average value of the total amount LA in a region from the interface to 1.0 gm toward the surface of the plated layer is more than 0.50 mass%.

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

4. The hot-dip coated steel according to any one of claims 1 to 3, whereinin a case where in the average chemical composition of the plated layer, a Ca concentration is 0.05 mass% or more, a Cr concentration or a Mo concentration is 0.05 mass% or more, and a relationship of LYa < Si + Cr ♦ Mo is satisfied,Expressions (1) and (2) are satisfied in an X-ray diffraction pattern of the surface of the plated layer,(lmax( 10.5 to 11.0°)) / (1(10.5°) + 0.2 x {(11(11.0°) - I(10.5°)l)}) > 1.5...(1),(Imax(20.2° to 20.5°)) / (I(20.2°) + 0.667 x {11(20.5°) - I(20.2°)l}) > 1.5...(2),where Imax(k° to m°) is a maximum value of X-ray diffraction intensities within a range of diffraction angles of k° to m°, Imax(n°) is an X-ray diffraction intensity at diffraction angle n°, and k, m, and n are diffraction angles represented by Expressions (1) and (2).

5. The hot-dip coated steel according to any one of claims 1 to 4, wherein thethickness t of the plated layer is 15 gm or more.

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