Hot-dip galvanized steel

Abstract

This hot-dip plated steel product has a steel material and a coating layer disposed on the surface of the steel material, and the coating layer has a chemical composition, in mass%, of Al: more than 10% and less than 40%, Mg: 4.0% to 15.0%, the balance being Zn and impurities, and a total amount ΣTR1 of V and Mn: 0.05% to 3.0%. In an element distribution profile obtained by GDS analysis from the surface of the coating layer toward the steel material in the thickness direction of the steel material, when the depth position at which the Fe concentration reaches 95% is defined as the interface between the coating layer and the steel material and the distance from the surface of the coating layer to the interface is defined as the thickness t of the coating layer, the proportion of the depth at which the total amount ΣTR1 shows 0.1% or more is 10% or more of the thickness t.

Description

[Technical Field]

[0001] The present disclosure relates to hot-dip galvanized steel products. This application claims priority based on Japanese Patent Application No. 2024-135644, filed on August 15, 2024, the contents of which are incorporated herein by reference. [Background technology]

[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 material to make it resistant to corrosion. Hot-dip galvanizing is an inexpensive method of rust prevention for steel materials and is used in various fields where rust prevention of steel materials is required, such as civil engineering, construction, and automotive.

[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 coating layer that is relatively thinner than the post-coating method described below.

[0004] Patent Document 2 describes a method in which a workpiece processed into a predetermined shape is immersed in a plating bath, and is called a batch-type hot-dip plating method or a post-plating method. The post-plating method involves immersing the workpiece in the plating bath for one minute or more, which tends to result in a thick plating layer. However, compared to the continuous hot-dip plating method, the post-plating method has greater restrictions on alloy components, tends to have poorer corrosion resistance, and is significantly less manufacturable.

[0005] However, in environments where the time spent wet with water (wet time) is long, corrosion of plated steel sheets becomes extremely severe. Therefore, increasing the thickness of the plating layer is important for extending the life of plated steel sheets. Therefore, if a Zn alloy plating layer containing a large amount of Al could be produced using a continuous hot-dip plating method with a thickness comparable to that of a post-plating method, it would be possible to efficiently produce steel sheets that provide long-term corrosion protection.

[0006] The thickness of the coating layer on coated steel sheets produced by continuous hot-dip galvanizing is often around 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. For example, increasing the pulling speed when pulling the steel sheet out of the coating bath increases the coating layer thickness, but it becomes difficult to control the surface appearance. Therefore, in practice, the upper limit of the coating layer thickness is strictly limited by adjusting the wiping rate. That is, 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, which results 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. For example, as shown in Patent Document 1, Sn may be added to the plating layer. These elements tend to bond with Mg, Al, or Zn in the Zn alloy to form intermetallic compounds with high melting points. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2018 / 139619 [Patent Document 2] Japanese Patent Publication No. 61-295361 Summary of the Invention [Problem to be solved by the invention]

[0009] One way to improve the lifespan of a plating layer, i.e., its corrosion resistance, is to increase the thickness of the plating layer. Increasing the viscosity of the plating bath is effective in obtaining a thicker plating layer, and this can be achieved, for example, by adding elements with a relatively heavy specific gravity to the plating bath. In other words, when elements with a heavy specific gravity are added to the plating bath, the specific gravity is restored, and it is expected that the plating coating weight can be increased.

[0010] However, when a heavy element is added to a coating bath, the heavy element is likely to change the reactivity between the elements in the coating bath and the base steel. For this reason, it has been difficult to obtain a thick, healthy coating layer by adding a heavy element to a coating bath while determining the effect of adding the heavy element.

[0011] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a hot-dip plated steel material that can increase the plating thickness even in the case of a plating layer that contains elements with a relatively high specific gravity. [Means for solving the problem]

[0012] To solve the above-mentioned problems, the present inventors investigated a technique for adding elements with a high specific gravity, such as V and Mn (transition metals), which are difficult to add to a plating bath. Furthermore, while transition elements such as V and Mn have relatively high melting points, substances with high melting points can frequently cause plating defects such as the generation of dross. Therefore, the inventors investigated a technique for stably adding metal elements with high melting points to the bath. As a result, they discovered a technique for stably producing plated steel products even when using a plating bath containing elements with a high specific gravity and a high melting point. They also discovered a plated steel product having a thick plating layer with excellent corrosion resistance. They also discovered that a plating layer containing these elements with a high specific gravity and a high melting point and exhibiting an appropriate morphology can achieve excellent corrosion resistance due to V, Mn, etc.

[0013] In order to solve the above problems, the present disclosure employs the following configuration. [1] A hot-dip galvanized steel material according to one embodiment of the present disclosure is a hot-dip galvanized steel material having a steel material and a plating layer disposed on a surface of the steel material, The plating layer is composed of, in mass %, Al: more than 10% and less than 40% Mg: 4.0% or more, 15.0% or less, Si: 0% or more, 2.0% or less, V: 0% or more, 3.0% or less, Mn: 0% or more, 3.0% or less, Cr: 0% or more, 3.0% or less, Mo: 0% or more, 3.0% or less, Sn: 0% or more, 0.7% or less, Bi: 0% or more, 0.3% or less, In: 0% or more, 0.3% or less, Ca: 0% or more, 0.6% or less, Y: 0% or more, 0.3% or less, La: 0% or more, 0.3% or less, Ce: 0% or more, 0.3% or less, Sr: 0% or more, 0.3% or less, Li: 0% or more, 0.3% or less, Ni: 0% or more, 3.0% or less, Co: 0% or more, 3.0% or less, Cu: 0% or more, 0.25% or less, Ag: 0% or more, 0.25% or less, Sb: 0% or more, 0.25% or less, Pb: 0% or more, 0.25% or less, B: 0% or more, 0.50% or less, P: 0% or more, 0.50% or less, Ti: 0% or more, 0.25% or less, Nb: 0% or more, 0.25% or less, Zr: 0% or more, 0.25% or less, W: 0% or more, 0.25% or less, Fe: 0% or more, 5.0% or less, The balance is Zn and impurities. Total amount of V and Mn ΣTR1: 0.05% or more, 3.0% or less, Total amount of Cr and Mo ΣTR1': 0% or more and 3.0% or less, ΣTR1+ΣTR1': 0.05% or more, 3.0% or less, Total content of Sn, Bi and InΣα: 0% or more and 0.7% or less, Total content of Ca, Y, La, Ce, Sr and Li Σβ: 0% or more, 0.6% or less, Total amount of Ni and Co ΣTR2: 0% or more, 3.0% or less, Total content of Cu, Ag, Sb, Pb, B, P, Ti, Nb, Zr and WΣγ: 0% or more, 1.00% or less, and having a chemical composition In an element distribution profile obtained by GDS analysis from the surface of the plating layer toward the steel material in the thickness direction of the steel material, the depth position at which the Fe concentration reaches 95% is defined as the interface between the plating layer and the steel material, and the distance from the surface of the plating layer to the interface is defined as the thickness t of the plating layer, the proportion of the depth at which the total amount ΣTR1 shows 0.1% or more is 10% or more of the thickness t. [2] When V and Mn in the chemical composition of the hot-dip plated steel material of [1] above are defined as TR1, the plated layer may contain TR1-containing intermetallic compounds, and the total area ratio of the TR1-containing intermetallic compounds may be 1% or more in a cross section of the plated layer. [3] In the hot-dip galvanized steel material of the above [1] or [2], when Ni and Co in the chemical composition are defined as TR2, the depth showing the maximum value of the TR2 concentration in the element distribution profile is defined as t(TR2), and the depth showing the maximum value of the TR1 concentration is defined as t(TR1), the following formula (1) may be satisfied: t(TR2)-t(TR1)≦0.30t (1) [4] In the hot-dip plated steel material of [1] or [2] above, in an X-ray diffraction pattern of the surface of the plated layer measured using Cu-Kα radiation under conditions of an X-ray output of 50 kV and 300 mA, I1 defined in the following formula (4) and I2 defined in the following formula (5) may satisfy the following formulas (2) and (3). 1.5≦I1…(2) 1.5≦I2…(3) I1=(Imax(10.5°~11.0°) / (I(10.5°)+0.2{|I(11.0°)-I(10.5°)|}) …(4) I2=(Imax(20.2°~20.5°)) / (I(20.2°)+0.667{|I(20.5°)-I(20.2°)|}) …(5) In equations (4) and (5), Imax (k to m°) is the maximum value of the X-ray diffraction intensity between diffraction angles k and m°, I(n°) is the X-ray diffraction intensity at a diffraction angle n°, and k, m, and n are the diffraction angles (2θ) shown in equations (4) and (5), respectively. [Effects of the Invention]

[0014] According to an embodiment of the present invention, a hot-dip plated steel material having a large coating thickness can be provided. Furthermore, according to the hot-dip plated steel material of this embodiment, the thickness of the coating layer can be increased, thereby improving the coating life (corrosion resistance). [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram showing the results of a GDS analysis of a coating layer of a hot-dip coated steel material according to an embodiment of the present invention, and is a graph showing an example of an element distribution profile. [Figure 2] FIG. 2 is a diagram showing the XRD analysis method. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, a hot-dip plated steel material according to one embodiment of the present invention will be described.

[0017] In this specification, the "%" used to indicate the content of each element in the chemical composition of the plating layer means "mass %" unless otherwise specified. Furthermore, the "%" used to indicate the composition of an intermetallic compound means "atomic %" unless otherwise specified. Furthermore, 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.

[0018] The present inventors have conducted extensive research into hot-dip galvanized steel material having a coating layer containing Al, Mg, and Zn and manufactured by a continuous hot-dip galvanizing method, which has a large coating layer thickness (adhesion amount), excellent corrosion resistance, and excellent adhesion during processing, and a method for manufacturing the same.

[0019] The melting point of a Zn alloy hot-dip bath, which contains elements such as Al or Mg in Zn, a low-melting-point metal, tends to increase as the composition deviates from a ternary eutectic composition or Zn-3%Al-3%Mg (% by 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. When considering the hot-dip plating process, such a Zn alloy plating bath is operated at around 500°C, which is more than 50°C higher than the melting point.

[0020] 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 continuous hot-dip galvanizing processes, when a steel sheet is passed through a coating bath at approximately 500°C at a constant line speed, the amount of hot-dip galvanizing bath that adheres to the steel sheet and lifts up with it is significantly less than in pure Zn coating. Therefore, the development of wiping technology is essential to consistently produce coating layers with thicknesses exceeding 20 μm. However, because the molten metal that makes up the coating layer is inherently light due to its low specific gravity, the molten metal is easily blown away during wiping blows, reducing the amount of hot-dip galvanizing bath that adheres to the steel sheet and lifts up.

[0021] Furthermore, when Al is present in the coating bath, the reaction between Al and Fe becomes more active, easily forming an Al-Fe interfacial alloy layer when steel is passed through the coating bath. In this case, cracks originating from the Al-Fe alloy layer may propagate through the coating layer during bending tests, resulting in peeling of the coating layer. This peeling becomes more pronounced as the temperature of the coating bath increases. Because of the immersion time and the loss of Al inside the coating layer due to Fe, using a coating bath with a high Al concentration and high temperature makes it difficult to produce hot-dip coated steel with a coating layer with high adhesion that can be processed into various products.

[0022] Therefore, the present inventors conducted extensive research to solve the above problems. To produce a coating layer with a high coating weight under conditions of a high Al concentration and high bath temperature, it is first necessary to increase the viscosity of the coating bath. This can be achieved by adding elements with a high specific gravity to the coating bath. In particular, the addition of transition metal elements such as V and Mn (TR1) increases the specific gravity and viscosity of the coating bath, thereby increasing the coating weight on the steel material during threading.

[0023] On the other hand, when these transition metal elements are added to a plating bath, floating dross tends to form in the plating bath because the transition metal elements easily bond with elements such as Si, Ca, and Mg. The coated steel product with this dross trapped in it will have reduced adhesion or contain coating defects. However, since this floating dross is very fine, it can be redissolved in the coating bath by raising the temperature of the coating bath to around 600°C if the concentration of the added transition metal elements is limited within a certain range.

[0024] On the other hand, in a plating bath at around 600°C, the Al-Fe alloying reaction is active, and even if the steel is immersed for a short period of time, a thick Al-Fe interfacial alloy layer can grow, which can significantly impair the adhesion of the subsequent hot-dip plated steel.

[0025] Furthermore, the added transition metal elements have a similar reaction pattern to Fe, and diffuse into the steel (Fe substrate). In particular, the accumulation of V and Mn on the steel surface immediately after immersion in the plating bath, which are elements that are more difficult to reduce than Fe, results in a large number of poorly plated areas and degraded areas such as non-plated areas (areas that have not reacted with the steel surface) due to poor reactivity with Fe. This is because fine oxides resulting from V and Mn formed below the surface of Zn-Al-Mg plated steel (i.e., in the surface layer of the steel) inhibit plating adhesion. Therefore, when a transition metal element is added to a plating bath, by taking measures to prevent excessive element diffusion into the steel material, the integrity of the plating layer can be maintained, and as a result, plated steel material with few defects and excellent corrosion resistance can be produced.

[0026] A hot-dip plated steel material according to one embodiment of the present invention, which has been made based on the above-mentioned new findings, will be described in detail below.

[0027] [Hot-dip galvanized steel] A hot-dip plated steel material according to an embodiment of the present invention will be described. The hot-dip plated steel material of this embodiment has a steel material and a plating layer disposed on the surface of the steel material.

[0028] The average chemical composition of the plating layer is, in mass%, Al: more than 10% and less than 40% Mg: 4.0% or more, 15.0% or less, Si: 0% or more, 2.0% or less, V: 0% or more, 3.0% or less, Mn: 0% or more, 3.0% or less, Cr: 0% or more, 3.0% or less, Mo: 0% or more, 3.0% or less, Sn: 0% or more, 0.7% or less, Bi: 0% or more, 0.3% or less, In: 0% or more, 0.3% or less, Ca: 0% or more, 0.6% or less, Y: 0% or more, 0.3% or less, La: 0% or more, 0.3% or less, Ce: 0% or more, 0.3% or less, Sr: 0% or more, 0.3% or less, Li: 0% or more, 0.3% or less, Ni: 0% or more, 3.0% or less, Co: 0% or more, 3.0% or less, Cu: 0% or more, 0.25% or less, Ag: 0% or more, 0.25% or less, Sb: 0% or more, 0.25% or less, Pb: 0% or more, 0.25% or less, B: 0% or more, 0.50% or less, P: 0% or more, 0.50% or less, Ti: 0% or more, 0.25% or less, Nb: 0% or more, 0.25% or less, Zr: 0% or more, 0.25% or less, W: 0% or more, 0.25% or less, Fe: 0% or more, 5.0% or less, The balance is Zn and impurities. Total amount of V and Mn ΣTR1: 0.05% or more, 3.0% or less, Total amount of Cr and Mo ΣTR1': 0% or more and 3.0% or less, ΣTR1+ΣTR1': 0.05% or more, 3.0% or less, Total content of Sn, Bi and InΣα: 0% or more and 0.7% or less, Total content of Ca, Y, La, Ce, Sr and Li Σβ: 0% or more, 0.6% or less, Total amount of Ni and Co ΣTR2: 0% or more, 3.0% or less, The total content Σγ of Cu, Ag, Sb, Pb, B, P, Ti, Nb, Zr, and W is 0% or more and 1.00% or less. Although V, Mn, Cr, and Mo are all transition metal elements, in this specification, V and Mn may be referred to as "transition metal element TR1," and Cr and Mo may be referred to as "transition metal element TR1'." Furthermore, V, Mn, Cr, and Mo may be collectively referred to as "transition metal element TR."

[0029] Furthermore, in the hot-dip coated steel material of this embodiment, in an element distribution profile obtained by GDS analysis in the thickness direction of the steel material from the surface of the coating layer toward the steel material, the proportion of depths at which ΣTR1 is 0.1% or more is 10% or more of the thickness t of the coating layer in the region from the surface of the coating layer to the interface between the coating layer and the steel material. In other words, the total depth at which ΣTR1 is 0.1% or more is 0.1t or more. Note that the "thickness t of the coating layer" here refers to the distance from the surface of the coating layer to the interface, assuming that the depth position at which the Fe concentration is 95% of the maximum Fe concentration in the aforementioned element distribution profile is the interface between the coating layer and the steel material.

[0030] (Steel) The steel material to be plated will now be explained. The steel material is, for example, mainly a steel plate, but there is no particular limitation on its size. The steel plate may be any steel plate that can be used in a normal hot-dip galvanizing process. Specifically, this applies to steel plates that can be used in processes such as continuous hot-dip galvanizing lines (CGLs) where the steel plate is immersed in molten metal and solidified. The size of the steel plate may be, for example, 10 mm or less in thickness and 2000 mm or less in width, but the steel plate size is not limited to these.

[0031] There are no particular limitations on the quality of the steel material, and examples of applicable steel materials include 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 for bridge cables. More specifically, for example, hot-rolled mild steel sheets and steel strips specified in JIS G 3131:2018, cold-rolled steel sheets and steel strips specified in JIS G 3141:2021, general structural rolled steel materials specified in JIS G 3101:2020, various plated steels thinly plated with various metals such as JIS H 8641:2021, JIS G 3302:2022, JIS G 3303:2022, JIS G 3313:2021, JIS G 3314:2022, JIS G 3315:2022, JIS G 3317:2022, and JIS G 3321:2022 (hereinafter, plating to make a plated steel sheet into a base steel material is also referred to as "pre-plating", and plated steel materials or plated steel sheets as base steel materials are also referred to as "pre-plated steel materials or pre-plated steel sheets"). Applicable materials include 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 corrosion-resistant strengthening elements such as Ni and Cr).

[0032] In addition, the surface of the steel material is pre-plated with 0.3 to 5 g / m 2 Alternatively, a Fe plating layer, a Ni plating layer, or a Co plating layer having a coating amount of 0.01 or less may be provided. By using a steel material provided with such a pre-plating layer, the plating layer containing the transition elements V and Mn in this embodiment can be stably formed. Details will be described later.

[0033] Furthermore, the manufacturing process of steel materials includes common processes such as iron and steel making processes using blast furnaces or electric furnaces, hot rolling processes, pickling processes, cold rolling processes, and heat treatment processes, but the steel materials of this embodiment may be those that have undergone any of these processes, and the processing conditions for each process are not limited.

[0034] (plating layer) Next, the plating layer provided on the steel material 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. Therefore, in the case of the plating layer according to this embodiment, which includes a Zn-Al-Mg alloy layer, even a thin plating layer with a thickness of, for example, about half the thickness of a typical Zn plating layer can exhibit corrosion resistance equal to or greater than that of a Zn plating layer. The plating layer may include an Al-Fe-based interface alloy layer.

[0035] The Zn-Al-Mg alloy layer is made of a Zn-Al-Mg alloy, which means a ternary alloy containing Zn, Al, and Mg.

[0036] The thickness of the Zn-Al-Mg alloy layer may be 4 to 100 μm. If necessary, the lower limit of the thickness of the Zn-Al-Mg alloy layer may be 7 μm, 10 μm, 15 μm, or 20 μm, and the upper limit of the thickness of the Zn-Al-Mg alloy layer may be 90 μm, 80 μm, or 70 μm.

[0037] In many cases, the Al-Fe interfacial alloy layer is an interfacial alloy layer between a steel material and a Zn-Al-Mg alloy layer, and is in contact with the surface of the steel material.

[0038] The thickness t of the entire coating layer depends on the coating conditions, and therefore the upper and lower limits of the thickness t of the entire coating layer are not particularly limited. Furthermore, the thickness of the entire coating layer 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 t of the entire coating layer is affected by the viscosity and specific gravity of the coating bath. Since the maximum thickness t of the coating layer formed by the continuous hot-dip coating method is often 100 μm or less, the coating thickness t 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, or 60 μm or less. The thickness t of the coating layer may be 30% or less of the sheet thickness of the steel material, or, if necessary, 20% or less of the sheet thickness of the steel material. The thickness t of the coating layer may be 15 μm or more, 20 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, or 45 μm or more, if necessary.

[0039] <Chemical composition> Next, the average chemical composition of the plating layer will be described. The average chemical composition of the entire coating layer is the average chemical composition of the Zn-Al-Mg alloy layer when the coating layer has a single-layer structure. Furthermore, when the coating layer has a laminated structure of an Al-Fe interfacial alloy layer and a Zn-Al-Mg alloy layer, it is the average chemical composition of the Al-Fe interfacial alloy layer and the Zn-Al-Mg alloy layer combined. Note that if a pre-coating layer is applied to the surface of the steel material (base sheet) before coating, Ni, Co, etc. derived from the pre-coating layer are also included in this chemical composition.

[0040] In the plating layer of this embodiment, the thickness of the Al-Fe-based interfacial alloy layer is small, preferably 10% or less of the total thickness of the plating layer, and therefore the Fe concentration in the plating layer is often 5.0% or less.

[0041] Al: Over 10% and under 40% Al is the element that mainly constitutes the plating layer. If the Al content exceeds 10%, the melting point of the plating layer becomes higher than that of pure Zn. Furthermore, the transition metal elements necessary to increase the thickness of the plating layer in this embodiment are hardly dissolved in Zn or Mg. Therefore, a certain amount of Al is required to contain the transition metal elements. Since the minimum concentration required for this purpose is more than 10%, the Al content is more than 10%. Furthermore, Al is an essential element for forming V-containing intermetallic compounds and / or Mn-containing intermetallic compounds (hereinafter, V-containing intermetallic compounds and Mn-containing intermetallic compounds are also collectively referred to as TR1-containing intermetallic compounds). The Al content is preferably 11% or more, more preferably 12% or more, even more preferably 18% or more, and even more preferably 25% or more. On the other hand, if the Al content is 40% or more, the reactivity between the coating bath and the base steel increases, making it difficult to suppress the formation of an Al-Fe interfacial alloy layer, and ensuring workability at a thick coating becomes difficult. Furthermore, the thickness of the Zn-Al-Mg alloy layer decreases by the amount of the thick Al-Fe interfacial alloy layer formed. Therefore, the Al content is set to less than 40%. The Al content is preferably 38% or less, and more preferably 35% or less.

[0042] Mg: 4.0% or more, 15.0% or less Like Zn, Mg is an element that mainly constitutes the coating layer. Mg is an element that ensures the corrosion resistance of the coating layer. Mg forms the MgZn2 phase, which has excellent corrosion resistance and is relatively hard, in the Zn-Al-Mg alloy layer. Mg also bonds with transition metal elements and is an effective element for improving various performances. If the Mg content is less than 4.0%, Mg does not form appropriate compounds with transition metal elements, etc., which promotes the formation of compounds between Al and transition metal elements, resulting in the generation of dross and the inability to form a sound coating layer. Therefore, the Mg content is set to 4.0% or more. The Mg content is preferably 4.5% or more, more preferably 4.8% or more, even more preferably 5.0% or more, and even more preferably 6.0% or more. On the other hand, if the Mg content exceeds 15.0%, the amount of dross generated increases, which may increase the number of unplated areas where the plating layer does not adhere. Therefore, the Mg content is set to 15.0% or less. The Mg content is preferably 13.0% or less, and more preferably 10.0% or less.

[0043] Si: 0% or more, 2.0% or less Si has the effect of suppressing the reaction between the plating bath and Fe. Generally, if a plating bath contains a large amount of transition metal element TR, the reaction will be excessive. Therefore, the use of Si or other additives can suppress the diffusion of transition metal elements to a certain extent. On the other hand, if a transition metal element and a large amount of Si are mixed, oxides may be generated partially at the interface or on the steel surface (Fe surface), causing the plating layer to lose adhesion, which is known as "bad plating." Therefore, the Si content is 2.0% or less. The Si content is preferably 1.5% or less, 1.0% or less, or 0.30% or less. When a pre-plating layer is used, reactivity with the substrate can be sufficiently suppressed even without Si. Since Si is not necessary, the lower limit of the Si content is 0%. The Si content is preferably 0.01% or more, more preferably 0.1% or more.

[0044] V: 0% or more, 3.0% or less Mn: 0% or more, 3.0% or less Total amount of V and Mn ΣTR1: 0.05% or more, 3.0% or less When V and Mn (transition metal element TR1) are contained in a Zn-based plating bath containing Al and Mg, they have the effect of increasing the specific gravity of the plating bath and improving the viscosity of the plating bath. As a result, when the steel material is pulled out of the plating bath, the amount of molten metal adhering to the steel material increases, and the thickness of the plating layer increases. In addition, the presence of the transition metal element TR1 in the plating bath increases the amount of Al in the initial stage of solidification of the plating layer. 18Al-Mg-TR1-based intermetallic compounds (TR1-containing intermetallic compounds), such as (TR1)2Mg3, are formed, further promoting an increase in the thickness of the coating layer. It is difficult to distinguish between the effect of increasing thickness due to the formation of such intermetallic compounds and the effect of increasing specific gravity and viscosity, but both effects are considered to be the effects of adding transition metals. When Al and Mg are within the appropriate concentration range, these effects tend to increase the coating weight when the transition metal element TR1 is 0.05% or more. Therefore, it is preferable that the content of each of V and Mn (transition metal element TR1) is 0.05% or more. More preferably, the content of each of the transition metal element TR1 is 0.1% or more, 0.3% or more, 0.5% or more, 0.7% or more, or 1.0% or more.

[0045] On the other hand, TR1-containing intermetallic compounds form floating dross in the coating bath. The floating dross causes coating defects such as non-coating and dross adhesion defects, which have a significant impact on the shape and performance of the product and deteriorate its corrosion resistance. Therefore, it is preferable to completely dissolve this floating dross in the coating bath. For this reason, in this embodiment, when the transition metal element TR1 is contained, the temperature of the coating bath needs to be 570°C or higher. Preferably, it is 600°C or higher. If the content of the transition metal element TR1 exceeds 3.0%, it is difficult to completely dissolve the floating dross even if the temperature of the coating bath is increased, and the viscosity of the coating bath becomes extremely high, reducing the amount of molten metal adhering to the steel when it is pulled out of the coating bath, resulting in an extremely thin coating layer. Furthermore, the coating appearance is significantly deteriorated. For this reason, the contents of V and Mn (transition metal element TR1) are each set to 3.0% or less. More preferably, the contents of the transition metal element TR1 are each set to 2.5% or less and 2.0% or less.

[0046] In this embodiment, the chemical composition of the plating layer may contain at least one of V and Mn, or may contain both. In this embodiment, in order to obtain the above-mentioned effects of V and Mn, the total concentration ΣTR1 of V and Mn is set to 0.03 to 3.0%. It is not necessary to include both V and Mn; the concentration of either V or Mn may be within this range. Therefore, the lower limit of the concentration of V and Mn is 0%. The total amount ΣTR1 is preferably 0.2% or more, 0.3% or more, 0.5% or more, 0.7% or more, or 1.0% or more, and is preferably 2.5% or less, or 2.0% or less.

[0047] In this embodiment, when Ca is contained in the plating layer, the TR1-containing intermetallic compound is Al. 10 Ca(TR1)2 may be generated. However, Al 10 Ca(TR1)2 has the same crystal structure and atomic arrangement as Al 18 It is difficult to distinguish from Mg3(TR1)2, and Al 18 It can also be considered a compound in which part of the Mg in Mg3(TR1)2 has been replaced with Ca. Therefore, in this embodiment, there is no problem in considering both as similar substances.

[0048] Cr: 0% or more, 3.0% or less Mo: 0% or more, 3.0% or less Cr and Mo (transition metal elements TR1') are elements that have effects similar to those of V and Mn. When V and Mn are contained, a portion of the V and Mn can be substituted for Cr and / or Mo, thereby exhibiting effects similar to those of V and Mn. Therefore, Cr and Mo are defined as transition metal elements TR1'. The Cr and Mo contents are each 3.0% or less, similar to V and Mn. More preferably, the Cr and Mo contents are 2.5% or less, 2.0% or less. The Cr and Mo contents may be 0%. The Cr and Mo contents are preferably 0.05% or more, more preferably 0.1% or more, 0.3% or more, 0.5% or more, 0.7% or more, or 1.0% or more.

[0049] The transition metal elements Cr, Mo, V, and Mn all form characteristically similar intermetallic compounds. However, when we examine the properties of each intermetallic compound focusing on the individual elements, we find that there are slight differences in their properties. Intermetallic compounds containing Cr and Mo (transition metal element TR1') tend to have a low sacrificial corrosion protection effect. This is thought to be because the formed intermetallic compounds are predicted to exhibit a high potential due to the Cr and Mo oxide film, which tends to delay the timing of dissolution into the plating layer during corrosion. On the other hand, V and Mn (transition metal element TR1) do not have the effect of strengthening the oxide film of the intermetallic compound, so they are dissolved at the appropriate time during corrosion of the plating layer, clearly contributing to corrosion resistance. It was also found that the delay in corrosion timing caused by the oxide film described above can be suppressed even in intermetallic compounds mainly composed of Cr and / or Mo by containing a certain amount of Mn and V. Therefore, the corrosion timing of intermetallic compounds can be controlled by incorporating V and Mn (transition metal element TR1) into intermetallic compounds mainly composed of Cr and / or Mo.

[0050] In this embodiment, in order to obtain the above-described effects of Cr and Mo, the total concentration ΣTR1′ of Cr and Mo is 0% or more and 3.0% or less. It is not necessary to include both Cr and Mo, and the concentration of either Cr or Mo may be within this range.

[0051] ΣTR1+ΣTR1': 0.05% or more, 3.0% or less As described above, when the transition metal elements TR, i.e., V, Mn, Cr, and Mo, are added to a Zn-based plating bath containing Al and Mg, the specific gravity of the plating bath increases, improving the viscosity of the plating bath and thereby increasing the thickness of the resulting plating layer. Therefore, the total content of the transition metal elements TR1 and TR1' is 0.05% or more. On the other hand, if the total content of the transition metal elements TR1 and TR1' (ΣTR1 + ΣTR1') exceeds 3.0%, the viscosity of the plating bath becomes extremely high, reducing the amount of molten metal adhering to the steel when it is pulled out of the plating bath and resulting in an extremely thin plating layer. For this reason, the total content of the transition metal elements TR1 and TR1' is set to 3.0% or less. More preferably, the total content of the transition metal elements TR1 and TR1' is 2.5% or less, or even 2.0% or less.

[0052] Element group α Sn: 0% or more, 0.7% or less Bi: 0% or more, 0.3% or less In: 0% or more, 0.3% or less Total content of Sn, Bi and InΣα: 0% or more, 0.7% or less Each element in element group α (Sn, Bi, In) promotes softening of the plating layer when contained in the plating layer. Sn, Bi, and In are elements that can be contained arbitrarily, and the lower limit of each content is 0%. When Sn is contained, Mg9Sn5 tends to form in the plating layer. Bi also forms Mg3Bi2, and In also forms Mg3In. Elements in element group α can be contained as needed to improve properties such as corrosion resistance and workability.

[0053] However, there is an upper limit to the content of each element in the element group α. If too much is added, Mg is absorbed from the TR1-containing intermetallic compound, preventing the TR1-containing intermetallic compound from forming, resulting in a deterioration in corrosion resistance and a poor appearance of the plating layer due to the formation of intermetallic compounds with the element group α. Therefore, the upper limit for the element group α is set to 0.7% or less for Sn, and 0.3% or less for Bi and In. Furthermore, the total amount Σα of these elements is also set to 0.7% or less. The total amount Σα is preferably set to 0.5% or less, or 0.4% or less.

[0054] Next, each element of element groups β and γ explained below is an optional added element, and the lower limit thereof is set to 0% or more.

[0055] element group β Ca: 0% to 0.6% 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 ΣY: 0% or more, 0.6% or less

[0056] Ca, one of the elements in element group β, 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 transition metal elements. Therefore, in a plating bath containing Ca and transition metal elements, a part of Mg is replaced by Ca, resulting in Al. 18 (Mg,Ca)3(TR1)2 and Al 10 Ca(TR1)2 is formed depending on the content of element group β. When such an intermetallic compound is formed, the viscosity of the plating increases, making it easy to obtain a thick plating layer.

[0057] If the Ca content exceeds 0.6%, 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 steel material when it 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 content should be 0.6% or less. The Ca content is preferably 0.5% or less, or 0.4% or less.

[0058] Each element of the element group β other than Ca can have almost the same effect as Ca, so it can be contained as a substitute for Ca. However, elements other than Ca are expensive, and there is a concern that the inclusion of a large amount of Ca may impair economic efficiency, so it is not preferable for the total content of elements other than Ca to be greater than or equal to the Ca content. The intermetallic compounds formed by the inclusion of the element group β other than Ca are Al 10 As a substitute for Ca(TR1)2, Al 10 (β)(TR1)2 is formed. When either Ca or one of the other elements is contained, almost no difference in corrosion resistance or performance is observed. As with Ca, if the concentration is high, Mg is absorbed from the TR1-containing intermetallic compound, and this compound is no longer formed, resulting in a thin plating thickness, so there is an upper limit to the concentration. Therefore, the concentration of each element in the element group β other than Ca is set to 0 to 0.3%. The concentration of each element in the element group β other than Ca is preferably 0.2% or less, and 0.1% or less, respectively. The total amount Σβ of the concentrations of the elements in the element group β including Ca is set to 0 to 0.6%, and is preferably 0.5% or less, and more preferably 0.4% or less.

[0059] Ni: 0% or more, 3.0% Co: 0% or more, 3.0% Total amount of Ni and Co ΣTR2: 0 to 3.0% Ni and Co are elements that can be used as materials for forming the pre-plating layer. When a pre-plating layer, such as a Ni layer or Co layer, is formed on a steel material (base sheet) before plating, these elements are ultimately contained in the plating layer. Typically, when a metal layer containing Ni or Co is formed on a base sheet for plating as a pre-plating layer, Ni or Co is often mixed into the plating layer in a range of 3.0% or less. Note that these pre-plating layers are often ultimately unevenly distributed as layers at the interface between the plating layer and the steel material, so the concentrations of Ni and Co are low as component concentrations in the Zn-Al-Mg alloy layer. Note that trace amounts of Ni and Co (e.g., 0.25% or less) can also be added to the plating bath in addition to the pre-plating layer.

[0060] element group γ Cu: 0% or more, 0.25% or less Ag: 0% or more, 0.25% or less Sb: 0% or more, 0.25% or less Pb: 0% or more, 0.25% or less B: 0% or more, 0.50% or less P: 0% or more, 0.50% or less Ti: 0% or more, 0.25% or less Nb: 0% or more, 0.25% or less Zr: 0% or more, 0.25% or less W: 0% or more, 0.25% or less Total content of Cu, Ag, Sb, Pb, B, P, Ti, Nb, Zr and WΣγ: 0% or more, 1.00% or less The elements in the element group γ are optional elements. When the concentration of one of these elements is 0.10% or more, the effect of improving corrosion resistance is obtained. Therefore, it is preferable that the concentration of at least one of these elements is 0.10% or more. However, if the total concentration of these elements Σγ becomes excessive, plating defects such as bare spots may occur. Therefore, the total concentration Σγ is set to 1.00% or less. The total concentration Σγ is preferably set to 0.50% or less. From the viewpoint of corrosion resistance, the concentrations of Cu, Ag, Sb, Pb, Ti, Nb, Zr and W shall each be 0.25% or less. The concentrations of B and P shall each be 0.50% or less.

[0061] Fe: 0% or more, 5.0% or less The hot-dip plated steel material of this embodiment is produced by a continuous hot-dip plating method, so Fe may diffuse from the base material to the plated layer during production. 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. Furthermore, when an Fe pre-plated layer or the like is used, Fe inevitably diffuses into the plated layer, and Fe is contained in the Zn-Al-Mg alloy layer. As a result, the plated layer may contain up to 5.0% Fe. Although the Fe concentration may be 0%, a Fe concentration of 5.0% or less does not affect the frequency of cracks in the plated layer. Therefore, the Fe content 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 content may be greater than 0%.

[0062] Remainder: Zn and impurities The balance contains 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 particular 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%.

[0063] Impurities are components contained in raw materials or components mixed in during the manufacturing process, but not intentionally added. For example, trace amounts of components other than Fe may be mixed into the plating layer as impurities due to atomic diffusion between the steel (base steel) and the plating bath. Furthermore, since metals with 3N purity are typically used to manufacture plating alloys, the total impurity concentration may be approximately 0.03% or less.

[0064] To identify the average chemical composition of the plating layer, the plating layer is stripped and dissolved using an acid containing an inhibitor that suppresses corrosion of the base steel (steel material) to obtain an acid solution. The resulting acid solution is then measured using ICP atomic emission spectroscopy or ICP-MS to obtain the chemical composition. There are no particular restrictions on the type of acid, as long as it can dissolve the plating layer. By measuring the area and weight before and after stripping, the plating adhesion amount (g / m 2 ) can also be obtained at the same time.

[0065] <Intermetallic compounds> Next, the intermetallic compounds contained in the plating layer will be described. The plating layer according to this embodiment is a Zn-Al-Mg alloy plating, and therefore contains a Zn phase, an Al phase, and an MgZn2 phase. The plating layer according to this embodiment also contains an intermetallic compound containing a transition metal element TR1 (TR1-containing intermetallic compound).

[0066] MgZn2 phase The MgZn2 phase is formed in the plating layer to improve the corrosion resistance of the plating layer. The MgZn2 phase is a hard phase that provides corrosion resistance to the plating layer.

[0067] Zn phase (Al-Zn phase, Zn-Al phase) The Zn phase is present in the coating layer, primarily as a ternary eutectic structure (Zn / Al / MgZn2 ternary eutectic structure). Furthermore, because the coating layer contains a large amount of Al, the Zn phase is composed of fine Al crystals intermixed with fine Zn crystals, and when the amount of Al phase is high, it exists as an Al-Zn phase (mixed phase). On the other hand, when the amount of Al phase is high within the Zn phase, it becomes a Zn-Al phase (mixed phase). Because the amount of this phase is small relative to the overall coating layer, corrosion resistance degradation and improvement effects are often not observed. Furthermore, the phase composed of Zn and Al is extremely workable.

[0068] Al phase The Al phase exists as fine grains in the Zn-Al and Al-Zn phases, and also in the ternary eutectic structure. In regions with high Al concentrations, grain growth can occur, resulting in the formation of coarse Al phases.

[0069] Intermetallic compounds containing transition metal elements (TR1) (TR1-containing intermetallic compounds) The plating layer according to this embodiment contains (Al, Zn) 18 These include TR1-containing intermetallic compounds, such as (Mg)3(TR1)2. Such TR1-containing intermetallic compounds are formed in the plating layer when TR1 is contained in the plating layer. When Ca is contained in the plating layer, TR1 bonds with Ca and Al to form Al. 10 In some cases, Ca(TR1)2 is formed. In addition, when Ca is insufficient, TR1 combines with Al and Mg to form Al 18 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 replaced by Zn, and part of Mg is replaced by Ca, forming (Al,Zn) 18 It may also exist as (Ca,Mg)3(TR1)2. In addition, in areas where Ca is insufficient in the plating layer, (Al, Zn) 18 (Mg)3(TR1)2 may also form.

[0070] These intermetallic compounds all have similar crystal structures and are difficult to distinguish from one another. These intermetallic compounds exhibit diffraction peaks at almost identical positions in XRD. However, from the perspective of enjoying the effects of this embodiment, it does not matter which intermetallic compound is formed, and the performance when contained in the plating layer is almost equivalent, so there is no need to distinguish between them. Details will be described later.

[0071] Adding TR1 to the coating bath significantly improves the viscosity of the coating bath, and increases the lifting amount of the coating bath when the steel material is pulled up from the coating bath. In other words, according to this embodiment, by using TR1 as a constituent element of the coating layer, it is possible to manufacture a thick coated steel sheet, and a coated steel sheet with an excellent coating life can be easily manufactured.

[0072] To achieve this effect, it is effective to contain a certain amount of TR1-containing intermetallic compounds in the plating layer. Specifically, it is preferable that the total area fraction of TR1-containing compounds is 1% or more in a cross section along the thickness direction of the plating layer. By increasing the total area fraction of TR1-containing compounds, it is possible to ensure sufficient plating thickness and obtain a plating layer with excellent adhesion. This area fraction in a plating layer produced by an appropriate manufacturing method is mainly proportional to the concentration of the transition metal TR1 added. TR1-containing compounds can be observed using a scanning electron microscope (SEM). Details of measuring the area fraction of intermetallic compounds such as TR1-containing compounds will be described later.

[0073] Furthermore, when a large amount of these TR1-containing intermetallic compounds is contained in the plating layer, the TR1-containing intermetallic compounds grow coarsely, and in this case, the intermetallic compounds can also be detected by XRD.

[0074] The role of TR1-containing intermetallic compounds is not only to increase the thickness of the plating layer, but also to incorporate transition metals into corrosion products during the corrosion process of the plating layer. The effect of corrosion products is particularly evident in sacrificial corrosion protection. For example, in plating layers containing these coarse TR1-containing intermetallic compounds, the coexistence of these coarse TR1-containing intermetallic compounds and Mg at the cut edge of plated steel allows corrosion products to form stably, making it possible to suppress the formation of red rust from the cut edge in the early stages of corrosion. Furthermore, as the TR1-containing intermetallic compounds grow coarse, unevenness appears on the plating surface, changing its appearance.

[0075] The presence of TR1-containing intermetallic compounds can be indirectly confirmed by the GDS method (glow discharge optical emission spectroscopy), which is a highly sensitive and quantitative detection method.

[0076] Transition metal elements remaining in the plating layer preferentially form these intermetallic compounds. On the other hand, because transition metal elements easily diffuse into Fe, diffusing a large amount of transition metal elements into the steel (inside the Fe) reduces the amount of transition metal elements in the plating layer. It is also possible to easily detect cases where the TR1 addition concentration is low, fine crystal grains are present, and TR1 is distributed throughout the plating layer.

[0077] Furthermore, when a large amount of the TR1 intermetallic compound is contained in the plating layer, the cross section of the plating layer can be observed with a scanning electron microscope (SEM) to directly identify the intermetallic compound, and the effect of containing the compound can be determined by measuring the area fraction of the contained intermetallic compound. These measurement methods will be described later.

[0078] Other intermetallic compounds When Ca and Si are contained, in addition to the TR1-containing metal compounds described above, Al-Ca-Si compounds may be formed. In addition, in the TR1-containing metal compounds, part of the Al may be substituted with Zn. Ca may also be substituted with part of the Mg.

[0079] Si easily forms Mg2Si, but when Ca is present, it forms an Al-Ca-Si compound. However, if the Si content exceeds the Ca concentration, Mg2Si is formed, but this Mg2Si reduces corrosion resistance, so it is not desirable to form large amounts. However, if the amount of Mg2Si is small, the deterioration of corrosion resistance of the entire plating layer is small.

[0080] Sn and In tend to bond with Mg, forming Mg2Sn, Mg9Sn5, and Mg3In. These are phases with excellent sacrificial corrosion protection, as described above. When Ni is contained, Al3Ni and the like may also be contained. In this embodiment, the elements constituting the plating layer are grouped according to atomic radius and properties. Therefore, when other elements are contained, there is a possibility that substitution products of these representative intermetallic compounds may be formed. Generally, these intermetallic compounds do not occupy the main phase in the plating layer, and therefore have little effect on its performance.

[0081] Next, a method for confirming the presence of intermetallic compounds containing the transition metal element TR1 in the plating layer according to this embodiment will be described. To eliminate the influence of solidification and structural characteristics of the plating layer during evaluation, it is preferable that the plating thickness of samples used for SEM, GDS, and XRD for cross-sectional observation of the plating layer be 25 μm (±2 μm). This allows for a relative evaluation between each plating component.

[0082] A glow discharge optical emission spectrometer (GDS) is preferably used to analyze the components in the depth direction within the coating layer. The inventors used a LECO Japan 850A glow discharge optical emission spectrometer, but this is not a limitation. Depth direction analysis is preferably performed while Ar sputtering is performed, under the following analytical 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 coating layer toward the depth direction until the Fe concentration reaches 100% (reaching the base steel). Therefore, the analysis range of depth direction analysis using GDS extends from the coating surface to the Zn-Al-Mg coating layer, and in some cases, alloy layers such as Fe-Al present between the coating layer and the pre-coating layer, and even to a portion of the steel material. After GDS analysis, the sputter depth of the cross section is measured using a Tokyo Seimitsu Co., Ltd. "surfcom130A." GDS analysis provides an element distribution profile in the depth direction of the coating layer. The element distribution profile shows the distribution of the content of each element in the depth direction, with the total amount of detected elements taken as 100%. The boundary (interface) between the coating layer and the steel is taken as the position (t) where the Fe content exceeds 95 mass%, and the region deeper than that position is considered to be the base steel (steel).

[0083] In this embodiment, in an element distribution profile obtained by GDS analysis from the surface of the coating layer toward the steel material, when the distance from the surface of the coating layer to the interface is defined as the thickness of the coating layer, a region of 0.1t or more (10% of the total thickness of the coating layer) exists in the region from the surface of the coating layer to the interface, where the total concentration ΣTR1 of the transition metal elements TR1 exhibits an intensity of 0.1% or more. Note that when two or more types of transition metal elements TR1 are contained in the coating layer, the total concentration ΣTR1 of the transition metal elements TR1 is used to obtain a total (concentration) intensity profile of the transition metal elements TR1 in the obtained element distribution profile.

[0084] Fig. 1 shows an example of the results of depth profile analysis by GDS for the plating layer according to this embodiment. The graph shown in Fig. 1 is an element distribution profile. In the example shown in Fig. 1, the plating thickness t is 26 µm.

[0085] Within the above evaluation range, i.e., from the surface to the interface of the coating layer, if a region showing ΣTR1 of 0.1% or more exists continuously for 0.1t or more in the depth direction, it can be said that a clear increase in viscosity has been observed during the production of the coating layer. Specifically, under the same coating conditions with constant wiping and strip threading speed, the thickness of the coating layer has increased. When considering the amount of corrosion of the coating layer, an increase in coating thickness is desirable from the perspective of corrosion resistance, as it leads to an extension of the corrosion protection period of the steel material.

[0086] In order to achieve the appropriate distribution of transition metal elements in the plating layer as described above, it is effective to appropriately control the production conditions, i.e., to appropriately manage the temperature of the plating bath, the base sheet to be plated, etc.

[0087] Furthermore, if the original plate has pre-plated layers such as Ni and Co layers, GDS can be used to confirm whether the Ni and Co layers remain even after plating.

[0088] In this embodiment, when Ni and Co in the chemical composition are the transition metal element TR2, it is preferable that the depth showing the maximum value of the TR2 concentration in the element distribution profile is t(TR2) and the depth showing the maximum value of the TR1 concentration is t(TR1), and that the following formula (1) is satisfied.

[0089] t(TR2)-t(TR1)≦0.30t (1)

[0090] It has been found that when formula (1) is satisfied, i.e., when layers of transition metal elements TR1 and TR2 remain near the interface, excellent adhesion and high sacrificial corrosion protection are obtained. This is thought to be because exposure of the base steel is suppressed and a large amount of intermetallic compounds containing TR1, which has excellent sacrificial corrosion protection, is present near the interface. To satisfy formula (1), it is effective to first form a Ni or Co layer and ensure a coating weight sufficient to sufficiently suppress the diffusion of transition metals.

[0091] The area ratio occupied by the intermetallic compound containing the transition metal element TR1 (TR1-containing intermetallic compound) is measured using an electron probe microanalyzer (EPMA). The cross section of the plating layer is exposed, and a vertical cross section in the depth direction of the plating layer is observed using a scanning electron microscope attached to the EPMA to identify the regions where V and Mn are present. These identified regions are then identified as intermetallic compounds containing TR1. Furthermore, these identified regions are quantitatively analyzed using point analysis or the like, and the intermetallic compound is identified from the atomic % ratio. For example, the intermetallic compound obtained in this embodiment contains Al 10 Ca(TR1)2, Al 18 Examples include Mg3(TR1)2, but it is fine as long as the atomic ratio is close to these. However, if the concentration of transition metal elements is low, the particles will be fine, which can make analysis with EPMA difficult. In such cases, it is best to identify intermetallic compounds from electron beam diffraction images using a TEM or similar. After identifying the intermetallic compounds, the total area fraction of the TR1-containing intermetallic compounds is determined.

[0092] More specifically, an elemental mapping image is obtained using an EPMA with a 1000x magnification. Because the map image of the transition metal to be detected corresponds to the position of the intermetallic compound, the area ratio of the intermetallic compound to the plating layer can be determined from the elemental mapping image. In this embodiment, the area ratio of the TR1-containing intermetallic compound in the cross section of the plating layer is 1% or more, which tends to increase the coating weight of the plating layer. More preferably, the area ratio of the TR1-containing intermetallic compound is 5% or more, 15% or more, or 25% or more. Furthermore, from the viewpoint of improving sacrificial corrosion protection, a content of 15% or more is preferable. The area ratio in the plating layer is correlated with the concentration of the added transition metal element.

[0093] Once the mapping images for each element are obtained, they are analyzed using image analysis software such as ImageJ. The Zn mapping image (in this embodiment, trace amounts of Zn are distributed in every part of the plating layer) 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 pixel by pixel.

[0094] Next, the transition metal element TR1 mapping image is also binarized, and the number of TR1 pixels is obtained so that the TR1-containing intermetallic compounds (the area where the detected position of TR1 corresponds to the location of the intermetallic compounds in the SEM image) can be identified. The number of TR1 pixels divided by the number of Zn pixels represents the area fraction of the TR1-containing intermetallic compounds. The same procedure 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.

[0095] Next, we will discuss the X-ray diffraction index of the TR1-containing intermetallic compounds.

[0096] X-ray diffraction measurement has lower detection sensitivity than GDS analysis, so it is assumed that the coating layer contains intermetallic compounds containing a certain amount of transition metal elements. Specifically, it is desirable that the area ratio of TR1-containing intermetallic compounds, as determined by the EPMA mentioned above, is 5% or more. In other words, when crystals large enough to exhibit specific orientations appear in the coating layer, these intermetallic compounds can also be detected by XRD. When nuclei within the coating layer grow and crystals with specific orientations grow within the coating layer, unevenness forms on the surface of the coating layer, suppressing metallic reflection and making it easier to achieve a uniform, concrete-like appearance. This reduces gloss appropriately, making it a desirable performance for coated steel sheets used in a variety of building materials.

[0097] In the X-ray diffraction measurement, Cu-Kα radiation is used and the X-ray diffraction pattern of the plating layer surface is measured under conditions of an X-ray output of 50 kV and 300 mA. In this case, it is preferable that I1 defined in the following formula (4) and I2 defined in the following formula (5) satisfy the following formulas (2) and (3), respectively.

[0098] 1.5≦I1…(2) 1.5≦I2…(3) I1=(Imax(10.5°~11.0°) / (I(10.5°)+0.2{|(I(11.0°)-I(10.5°)|}) …(4) I2=(Imax(20.2°~20.5°)) / (I(20.2°)+0.667{|I(20.5°)-I(20.2°)|}) …(5)

[0099] Here, Imax (k to m°) is the maximum value of the X-ray diffraction intensity between diffraction angles k and m°, I(n°) is the X-ray diffraction intensity at a diffraction angle n°, and k, m, and n are the diffraction angles (2θ) shown in equations (4) and (5), respectively.

[0100] I1 and I2 in formulas (4) and (5) are (TR1)2Mg3Al 18These are peaks related to intermetallic compounds, such as those in JCPDS card #00-040-1153 (V2Mg3Al8) and #04-007-9047 (Mn2Mg3Al 18 ), #04-008-7169(Cr2Mg3Al 18 ), but even if the elements of (TR1) and (TR1') change, the diffraction peak positions remain almost unchanged. Therefore, these intermetallic compounds can be treated as the same type, and the diffraction positions of I1 and I2 do not overlap with other diffraction peaks, making them suitable for detection. In other words, I1 and I2 represent the definition of the X-ray diffraction peaks of V-containing intermetallic compounds and Mn-containing intermetallic compounds. Furthermore, when it comes to Mo-containing intermetallic compounds, CaMo2Al 20 is as defined in JCPDS card #00-051-1061. These intermetallic compounds have similar diffraction peaks, making it difficult to distinguish them from one another. That is, Al and Mg are solid-solubilized together, and Zn and Ca are solid-solubilized together. Therefore, it is assumed that they have almost the same components and structures, and the diffraction peaks appear at almost the same positions. Therefore, it is not necessary to distinguish these transition metal-containing intermetallic compounds from one another in X-ray diffraction measurements.

[0101] On the other hand, in the plating layer according to this embodiment, many of the diffraction peaks of these TR1-containing intermetallic compounds overlap with those of the other major constituent phases, namely MgZn2, Al, and Zn. Therefore, among the many diffraction peaks of the TR1-containing intermetallic compounds, it is necessary to focus on those that do not overlap with those of other constituent phases. One of these is a diffraction peak near 2θ = 10.6°, and another is a diffraction peak that appears near 2θ = 20.4°.

[0102] Equation (4) focuses on the diffraction peak near 2θ = 10.6°. Imax (10.5° to 11.0°) in equation (4) is the maximum value of the X-ray diffraction intensity between diffraction angles of 10.5° and 11.0°. Imax (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°.

[0103] Furthermore, equation (5) focuses on the diffraction peak near 2θ=20.4°. Imax(20.2°-20.5°) in equation (4) is the maximum value of the X-ray diffraction intensity between diffraction angles of 20.2° and 20.5°. Imax(20.2°) is the X-ray diffraction intensity at a diffraction angle of 20.2°, and Imax(20.5°) is the X-ray diffraction intensity at a diffraction angle of 20.5°.

[0104] The numerators in equations (4) and (5) are the intensities corresponding to the diffraction peaks of the TR1-containing compound, and are the maximum diffraction intensities of the diffraction peaks, including the background intensity. Because measurement errors in X-ray diffraction can cause the diffraction peaks to deviate from 10.6° or 20.4°, we choose the maximum values ​​between 10.5° and 11.0° and between 20.2° and 20.5°.

[0105] The denominators of equations (4) and (5) are the background intensities at diffraction angles of 10.6° or 20.4°, calculated from the diffraction intensities at 10.6° or 20.4°.

[0106] For example, for the denominator of equation (4), as shown in Figure 2, 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. The ratio 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 (0.1 / 0.5 = 0.2). The background intensity at a diffraction angle of 10.6° is then calculated using the formula given in the denominator of equation (4).

[0107] For the denominator of equation (5), draw a straight line connecting the diffraction line at 20.2° and the diffraction line at 20.5°, as in the case of Figure 2. This straight 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 diffraction angles 20.2° and 20.4° (0.2°) to the difference between diffraction angles 20.2° and 20.5° (0.3°) is calculated (0.2 / 0.3 = 0.667). The background intensity at a diffraction angle of 20.4° is then calculated using the formula given in the denominator of equation (5) above.

[0108] The conditions for obtaining an X-ray diffraction image are as follows:

[0109] 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. For example, the measurement conditions are a voltage of 50 kV and a current of 300 mA. There are no particular limitations on the X-ray diffraction equipment, but for example, a horizontal-type high-power X-ray diffraction equipment RINT-TTR III manufactured by Rigaku Corporation can be used.

[0110] [Method of manufacturing hot-dip plated steel] Next, a method for producing the hot-dip plated steel material according to this embodiment will be described. The hot-dip plated steel material of this embodiment is preferably produced by a continuous hot-dip method. However, due to size restrictions of the steel material, it can also be produced by a batch-type hot-dip method, if necessary.

[0111] <Method A: Sendzimir method> In this embodiment, as described above, the diffusion of the transition metal element TR1 added to the bath is sufficiently suppressed, leaving the transition metal element TR1 inside the plating layer and forming a specific intermetallic compound (a TR1-containing intermetallic compound) within the plating layer. However, when the plating layer is formed using the conventional Sendzimir method, the diffusion of the transition metal element TR1 to the steel surface (Fe surface) becomes active, and the transition metal element TR1 collects on the Fe surface during immersion in the plating bath, which tends to cause a loss of the reduction effect and the formation of an oxide film consisting of the transition metal element TR1. A plating layer in this state is undesirable because it can lead to non-plating in non-plated areas and peeling during processing.

[0112] <Production method B> Therefore, the present inventors have investigated the optimum manufacturing conditions and found that forming a physical diffusion barrier on the original sheet for plating is effective in leaving the transition metal element TR1 in the plating layer. Note that the "physical diffusion barrier" means, for example, forming a mismatch plane with the Fe crystals deposited by electroplating on the Fe surface of the surface of the original sheet for plating. Specifically, an Fe plating layer (for example, 0.5 to 2.0 g / m) is formed on the Fe surface of the surface of the original sheet for plating. 2 ) is attached. This forms a continuous crystal grain between the Fe surface and the Fe plating layer, providing a temporary diffusion barrier. Then, when the base sheet with the Fe plating layer formed thereon is immersed in a high-temperature bath, the Fe dissolves and diffuses into the plating bath. Much of the Fe acts as a nucleus for transition-metal intermetallic compounds, promoting their growth and leaving almost no trace behind, effectively retaining the transition metal element TR1 in the plating layer. In this case, in Process B, the plating bath temperature is preferably in the range of 590–620°C to simultaneously promote the dissolution of the Fe layer. Temperatures outside this range may result in unplated areas or adverse effects on adhesion. Furthermore, because some of the transition metal element TR1 diffuses to the Fe surface, it is necessary to carefully control the oxidation conditions of the base sheet. Specifically, a dew point of 0°C or higher is effective in inhibiting the reaction between oxygen and the transition metal element TR1. On the other hand, in the case of the above-mentioned manufacturing method A (Sendzimer method), Cr, Mo, Mn, and V, which are the causes of non-plating, tend to gather at the interface during the reaction, which makes it easy for non-plating to occur.In addition, the above-mentioned manufacturing method A (Sendzimer method) is not preferable from a manufacturing standpoint because it cannot realize the function and effect of the Fe plating layer, which is to prevent these elements from gathering at the interface during the reaction and instead keep them offshore in the plating bath.

[0113] <Production method C> Furthermore, to more efficiently retain transition metal elements in the plating layer, it is preferable to form a Ni or Co pre-plating layer before forming the Fe plating layer as a pre-plating layer. The Ni or Co pre-plating layer acts as an additional barrier to the diffusion of transition metal elements into the Fe surface. As with Process B above, the Fe plating layer on top of the Ni or Co pre-plating layer reacts with the transition metal elements during plating and then rapidly diffuses into the plating layer. In other words, the reaction between the Fe plating layer and the transition metal elements during plating displaces the plating bath accumulated at the interface, regenerating a fresh Fe surface, resulting in a repeated reduction effect. This is thought to be due to the inconsistency of the crystal planes between the Fe in the base material and the Fe crystals (fine grains) in the Fe plating layer deposited by electroplating, which are involved in the reaction with the transition metal elements. The Ni in the Ni pre-plating layer and the Co in the Co pre-plating layer tend to diffuse toward the Fe surface of the base material rather than toward the plating bath, and are therefore more likely to remain on the Fe surface after immersion in the plating bath. On the other hand, the Fe in the Fe-plated layer formed on the upper surface tends to diffuse toward the plating bath. If the substrate has a Ni pre-plated layer or Co pre-plated layer, there is no need for dew point control as in Process B. The effective Ni or Co coating weight for Process C is 0.5 g / m 2 The coating amount is 2.0 g / m 2 In the above cases, the transition metal elements can be concentrated further near the interface, which is preferable in terms of sacrificial corrosion protection.

[0114] <Recipe D> On the other hand, when a Ni or Co pre-plated layer is used alone, immediately after immersion in the plating bath, Ni or Co diffuses into the steel material, and transition metals accumulate on the Ni or Co pre-plated layer, creating a situation where oxide films and other elements are likely to form. As a result, Fe-Ni-transition metal elements form, making reduction difficult and resulting in the formation of an oxide film. In this case, plating adhesion is poor and bare spots occur.

[0115] As explained above, the above-mentioned manufacturing method B and manufacturing method C are preferable as the manufacturing method of the plated steel material of this embodiment.

[0116] <Other manufacturing conditions> The continuous hot-dip galvanizing method is carried out by the Sendzimir method after preparing the base steel sheet to meet the requirements of the above-mentioned manufacturing methods B and C. That is, before immersing the steel in the galvanizing bath, the steel is heated at the annealing temperature of a nitrogen-hydrogen mixed gas until the steel temperature reaches or exceeds the galvanizing bath temperature. Typically, the annealing atmosphere is a hydrogen-containing nitrogen atmosphere with a hydrogen concentration of 5%, and the steel is heated to a temperature of approximately 600 to 800°C to sufficiently reduce the steel surface. If a pre-plating layer such as a Ni pre-plating layer or a Co pre-plating layer is not applied to the galvanized substrate, it is effective to humidify the atmosphere and adjust the dew point as described above. When the base steel sheet is immersed in the galvanizing bath, it is cooled with N2 gas until the steel temperature reaches the galvanizing bath temperature to prevent fluctuations in the galvanizing bath temperature during the manufacturing process.

[0117] Next, the steel material whose surface has been sufficiently reduced is immersed in a reducing state in a coating bath at a temperature of 570°C or higher, preferably 600°C or higher.

[0118] The immersion time of the steel material 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.

[0119] After immersion in the plating bath, the thickness of the plating layer is adjusted by wiping immediately. After wiping is complete, the workpiece is cooled.

[0120] If the cooling rate at high temperatures above 550°C is too slow, the Ni pre-plating layer, Co pre-plating layer, and Fe layer will dissolve excessively into the plating bath, affecting plating properties. Therefore, cooling from the bath temperature to 550°C should be completed within 10 seconds.

[0121] After immersion in the coating bath, the Fe in the Fe layer immediately diffuses, and these diffuse as nuclei to form intermetallic compounds containing transition metal elements. A fast cooling rate after immersion reduces the crystal size of each phase, while a slow cooling rate increases the crystal size. A large crystal size in the coating layer is preferable because it increases the coating thickness. In other words, a slow cooling rate after immersion is preferred. Furthermore, the coating structure is established by 350°C, where the liquid phase remains. For these reasons, the upper limit of the cooling rate to 350°C after removal from the coating bath is set to 100°C / s or less, and preferably 50°C / s or less. The lower limit of the cooling rate may be set to 1°C / s or more after removal from the coating bath, taking into account equipment constraints on the production line.

[0122] <Recipe E> Here, the cooling rate between 600 and 300°C while the liquid phase is present affects the process from nucleation by Fe in the Fe layer to growth. In other words, between 600 and 300°C, the higher the temperature, the easier the growth, while the lower the temperature, the more nuclei are generated and the more difficult the growth. Therefore, it is preferable to cool slowly in the high-temperature range between 600 and 450°C to suppress the amount of nuclei generated. Specifically, for example, it is preferable to suppress the cooling rate in this high-temperature range to between 5 and 20°C / second. It is also necessary to use a plating base sheet that promotes nucleus growth using pre-plated Fe.

[0123] After the plating layer is formed, various chemical conversion treatments and painting treatments may be carried out.

[0124] In the hot-dip plated steel material of this embodiment, a coating may be formed on the plating layer. One or more coatings may be formed. Examples of the type of coating directly on the plating layer include a chromate coating, a phosphate coating, and a chromate-free coating. These coatings can be formed by known methods such as chromate treatment, phosphate treatment, and chromate-free treatment.

[0125] 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.

[0126] Examples of electrolytic chromate treatments include those using chromic acid, silica sol, resin (phosphoric acid, acrylic resin, vinyl ester resin, vinyl acetate acrylic emulsion, carboxylated styrene butadiene latex, diisopropanolamine-modified epoxy resin, etc.), and hard silica.

[0127] Examples of the phosphate treatment include zinc phosphate treatment, zinc calcium phosphate treatment, and manganese phosphate treatment.

[0128] 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.

[0129] 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 include polyester resin, polyurethane resin, epoxy resin, acrylic resin, polyolefin resin, and modified versions of these resins. Here, the term "modified version" refers to a resin in which a reactive functional group contained in the structure of these resins is reacted with another compound (such as a monomer or a crosslinking agent) containing a functional group capable of reacting with the functional group.

[0130] Such organic resins may be a mixture of one or more organic resins (unmodified), 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. Aqueous solutions prepared by dissolving or dispersing in water may also be used.

[0131] As explained above, it is difficult to increase the coating weight of a coating layer with an increased Al content 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 V or Mn, 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 V-containing intermetallic compound or a Mn-containing intermetallic compound, corrosion resistance can be improved. Furthermore, by adding V or Mn to the coating layer, the thickness of the interfacial alloy layer can be reduced, thereby improving adhesion. Furthermore, since the coating weight of the coating layer is large, corrosion resistance can be further improved. [Example]

[0132] Next, examples of the present invention will be described, but the conditions in the examples are merely examples adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to these examples. Various conditions can be adopted in the present invention as long as they do not deviate from the gist of the present invention and the object of the present invention is achieved.

[0133] The details of the examples are shown in Tables 1 to 3. First, two types of cold-rolled steel sheets (JIS G 3141 (2017)) with different thicknesses of 100 mm x 200 mm x 0.8 mmt and 100 mm x 200 mm x 2.3 mm were prepared as the base steel sheets to be plated ("0.8 mm sheet" and "2.3 mm sheet" in the table).

[0134] These base steel materials were subjected to continuous hot-dip galvanization using the Sendzimir method. A K-type thermocouple was spot-welded to the center of the backside of the plated base sheet, allowing temperature changes during the plating process to be monitored. A hot-dip galvanization simulator manufactured by Rhesca was used.

[0135] [Plating layer manufacturing conditions] The plating layer was produced by employing one of the following production methods A to E. In each manufacturing method, pure metals (purity 3N or higher) of Zn, Al, and Mg were mixed to prepare a Zn-Al-Mg hot-dip plating bath so as to obtain a plating layer with the chemical composition shown in Table 1. The elements listed under "Base Sheet" in the table are the constituent elements of the pre-plating layer formed in advance on the base sheet to be plated, and the numerical values ​​attached to the elements indicate the coating weight (g / m 2 ) means

[0136] <Recipe A> The Sendzimir process was used as the hot-dip galvanizing method. That is, before immersing the original steel sheet in the plating bath, the steel sheet was heated at the annealing temperature of a nitrogen-hydrogen mixed gas until its temperature reached or exceeded the plating bath temperature. The annealing atmosphere was a nitrogen atmosphere containing 5% hydrogen (N2-5%H2), and the steel sheet was heated and held at a temperature of approximately 800°C for approximately 1 minute to fully reduce the steel surface. Humidification was not performed, and the dew point was set to -40°C. When the original steel sheet was immersed in the plating bath, it was cooled with N2 gas until its temperature reached the plating bath temperature to prevent fluctuations in the plating bath temperature during the manufacturing process. The plating bath temperature was set to 600°C. The immersion time in the plating bath was 3 seconds. The plating thickness t was set to 25 μm (±2) μm by adjusting the withdrawal speed and N2 gas wiping. After the plated original sheet was pulled up, it was cooled at a cooling rate of 10° C. / second in the temperature range of 600 to 200° C. Thereafter, it was allowed to cool naturally.

[0137] <Production method B> The Sendzimir method was used as the hot-dip plating method, but an Fe plating layer was formed on the base plate in advance. The Fe plating was performed using FeSO4·7H2O: 600g / L, 6.7A / dm 2 The test was carried out under the condition of a bath temperature of 47°C, with the current application time adjusted so as to obtain the desired Fe content. The subsequent plating conditions were the same as those in Process A, except that the dew point was set to 0°C.

[0138] <Production method C> The Sendzimir method was used as the hot-dip plating method, but a Ni layer or a Co layer was formed in advance as a pre-plating layer on the plating base sheet, and then Fe plating was carried out in the same manner as in Manufacturing Method B. Ni pre-plating was performed using NiSO4·6H2O: 340g / L, NiCl2·6H2O: 70g / L, and H3BO3: 40g / L, with a bath temperature of 50°C and a current of 5A / dm 2 The current application time was adjusted to obtain the specified Ni amount under the above conditions. Co pre-plating was performed using H2SO4: 0.5g / L, CoSO4·6H2O: 246g / L, H3BO3: 45g / L, bath temperature 50℃, 5A / dm 2 The current flow time was adjusted to obtain the desired Co content under the above conditions. The subsequent plating conditions were the same as those in Manufacturing Method A.

[0139] <Recipe D> The Sendzimir method was used as the hot-dip plating method, but only a Ni layer or a Co layer was formed in advance as a pre-plating layer on the original plate to be plated. The subsequent plating conditions were the same as those in Manufacturing Method A.

[0140] <Recipe E> Manufacturing method E is similar to manufacturing method C. In manufacturing method E, plating was performed using manufacturing method C, and after the base sheet was removed from the plating bath, mist cooling was performed, cooling it to 30°C at a cooling rate of 30°C / sec.

[0141] Plated steel materials were produced by the above manufacturing methods A to E. The area of ​​4cm from the center of the obtained plated steel 2 Samples were cut out. The plating layer was analyzed by GDS, XRD from the surface, and cross-sectional observation in the depth direction using an EPMA. The results are shown in Table 3. The "Equation (1)" column in Table 3 shows the calculation result of "(t(TR2)-t(TR1)) / t".

[0142] [Performance] Next, the properties of the resulting plated steel were evaluated using 0.8 mm and 2.3 mm plates. Specifically, the effects of plating thickness, adhesion, sacrificial corrosion protection, and gloss were investigated.

[0143] (effect of plating thickness) The effect on plating thickness was evaluated by the following test. Before immersing a sample of 100 x 200 x 0.8 mm of the plating base sheet in the plating bath, the sheet was annealed in a reducing atmosphere of N2-5%H2 to reduce the surface of the base sheet. After that, the sheet was immersed in the plating bath for at least 3 seconds and then pulled up vertically. The test was carried out at three lifting speeds of 10 mm / sec, 50 mm / sec, and 100 mm / sec. Wiping was not performed. The thickness of the plating layer was calculated from the amount of adhesion. Specifically, a 50mm diameter sample was taken from the center of the resulting plated steel sheet, immersed in 10% hydrochloric acid containing an inhibitor to peel off only the plating layer, and the plating adhesion amount was calculated from the difference in weight before and after peeling. The thickness of the plating layer was calculated by dividing the amount of adhesion by the theoretical density of the components. These three levels were tested repeatedly with N=3, and the average plating thickness was calculated from the average value of all samples. The evaluation criteria were as follows, with "S", "A", "B", "C" and "D" being considered pass and "E" being considered fail.

[0144] Average plating thickness over 31.5 μm... "S" Average plating thickness over 30 μm and 31.5 μm or less... "A" Average plating thickness over 27 μm and 30 μm or less: "B" Average plating thickness over 24 μm and 27 μm or less... "C" Average plating thickness over 21 μm and 24 μm or less... "D" Average plating thickness is 21 μm or less... "E"

[0145] (adhesion) The adhesion of the plating layer (unplated) was evaluated by a 1 ton bending test. First, a sample measuring 40 mm × 120 mm × 0.8 mm was taken from the obtained plated steel material so as to include the plated layer. Next, the sample was bent at the center in the longitudinal direction (120 mm) (single-sided length 60 mm). For the sample, tape was firmly attached to both sides of the plated steel sheet. A 1t (the thickness of one steel sheet) was sandwiched inside, bent 180° in a jig, and pressed completely to create a bending test specimen with a space the size of one steel sheet on the inside. The inner steel sheet was then removed, and the tape was forcefully pulled off. At this time, 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, with "G" being a pass and "B" being a fail.

[0146] There is peeling powder on both the front and back... "Bad (B)" No peeling powder on either the front or back... "Good (G)"

[0147] (Sacrificial corrosion protection) Three rectangular samples measuring 50 x 100 x 2.3 mm were taken from different positions on the resulting plated steel. The four edge surfaces were mirror-polished to eliminate the effects of shearing on the cut edges. The samples were then completely immersed in a 0.01 M NaCl solution for 10 seconds, and then placed horizontally at 45% humidity and 30°C for 240 hours. This cycle was repeated three times. After 240 hours, the red rust area ratio was measured on the four end faces. The same test was performed on three samples, and the average was taken as the red rust area ratio. The evaluation criteria were as follows, with "EX", "VG" and "G" being considered pass, and "B" being considered fail.

[0148] Red rust area rate is less than 10%... "Excellent (EX)" Red rust area ratio is 10% or more but less than 20%... "Very Good (VG)" Red rust area ratio: 20% or more, 30% or less... "Good (G)" Red rust area ratio is over 30%..."Bad(B)"

[0149] (glossiness) A sample for gloss testing was cut out from the center of the 2.3 mm plate sample, and the gloss level was measured using the sample. Specifically, the 60° gloss (G60) of the sample surface, as specified in JIS Z 8741:1997, was measured using a gloss meter. Samples manufactured with a thickness of 0.8 mm were used. The 60° gloss was measured at 10 random locations on the surface of the plated steel material, and the average value was calculated. The evaluation criteria were as follows: "FA" was considered good (i.e., low gloss).

[0150] 60° gloss (G60) is 40 or less... "favorable (FA)" 60° gloss (G60) is over 40... "dazzling (DZ)"

[0151] [Table 1]

[0152] [Table 2]

[0153] [Table 3] [Industrial Applicability]

[0154] According to the above-described aspects of the present invention, it is possible to provide a hot-dip plated steel material that can ensure a sufficient plating thickness even in the case of a plating layer containing elements with a relatively high specific gravity (particularly, transition metal elements), and as a result, it is possible to provide a hot-dip plated steel material that can exhibit good corrosion resistance over a long period of time and has a long life.

Claims

1. Steel and a plating layer disposed on a surface of the steel material, The plating layer comprises, in mass %, Al: more than 10% and less than 40% Mg: 4.0% or more, 15.0% or less, Si: 0% or more, 2.0% or less, V: 0% or more, 3.0% or less, Mn: 0% or more, 3.0% or less, Cr: 0% or more, 3.0% or less, Mo: 0% or more, 3.0% or less, Sn: 0% or more, 0.7% or less, Bi: 0% or more, 0.3% or less, In: 0% or more, 0.3% or less, Ca: 0% or more, 0.6% or less, Y: 0% or more, 0.3% or less, La: 0% or more, 0.3% or less, Ce: 0% or more, 0.3% or less, Sr: 0% or more, 0.3% or less, Li: 0% or more, 0.3% or less, Ni: 0% or more, 3.0% or less, Co: 0% or more, 3.0% or less, Cu: 0% or more, 0.25% or less, Ag: 0% or more, 0.25% or less, Sb: 0% or more, 0.25% or less, Pb: 0% or more, 0.25% or less, B: 0% or more, 0.50% or less, P: 0% or more, 0.50% or less, Ti: 0% or more, 0.25% or less, Nb: 0% or more, 0.25% or less, Zr: 0% or more, 0.25% or less, W: 0% or more, 0.25% or less, Fe: 0% or more, 5.0% or less, The balance is Zn and impurities. Total amount of V and Mn ΣTR1: 0.05% or more and 3.0% or less, Total amount of Cr and Mo ΣTR1′: 0% or more and 3.0% or less, ΣTR1+ΣTR1': 0.05% or more, 3.0% or less, Total amount Σα of Sn, Bi and In: 0% or more and 0.7% or less, Total amount Σβ of Ca, Y, La, Ce, Sr and Li: 0% or more and 0.6% or less, Total amount of Ni and Co ΣTR2: 0% or more and 3.0% or less, Total content Σγ of Cu, Ag, Sb, Pb, B, P, Ti, Nb, Zr and W: 0% or more and 1.00% or less, and having a chemical composition In an element distribution profile obtained by GDS analysis from the surface of the plating layer toward the steel material in the thickness direction of the steel material, the depth position at which the Fe concentration reaches 95% is defined as the interface between the plating layer and the steel material, and the distance from the surface of the plating layer to the interface is defined as the thickness t of the plating layer, the proportion of the depth at which the total amount ΣTR1 is 0.1% or more is 10% or more of the thickness t.

2. When V and Mn in the chemical composition are TR1, The plating layer contains a TR1-containing intermetallic compound, The hot-dip plated steel material according to claim 1, wherein a total area ratio of the TR1-containing intermetallic compounds in a cross section of the plated layer is 1% or more.

3. When Ni and Co in the chemical composition are TR2, 3. The hot-dip galvanized steel material according to claim 1, wherein, in the element distribution profile, when the depth showing the maximum value of the TR2 concentration is t(TR2) and the depth showing the maximum value of the TR1 concentration is t(TR1), the following formula (1) is satisfied: t(TR2)-t(TR1)≦0.30t...(1)

4. In the X-ray diffraction pattern of the surface of the plating layer measured using Cu-Kα rays under conditions of an X-ray output of 50 kV and 300 mA, I defined by the following formula (4) １ and I defined in the following formula (5) ２ The hot-dip plated steel material according to claim 1 or claim 2, wherein satisfies the following formulas (2) and (3): 1.5≦I １ …(2) 1.5≦I ２ …(3) I １ =(Imax(10.5°~11.0°) / (I(10.5°)+0.2{|I(11.0°)-I(10.5°)|}) …(4) I ２ =(Imax(20.2°~20.5°)) / (I(20.2°)+0.667{|I(20.5°)-I(20.2°)|}) …(5) In formulas (4) and (5), Imax (k to m°) is the maximum value of the X-ray diffraction intensity between diffraction angles k and m°, I(n°) is the X-ray diffraction intensity at a diffraction angle n°, and k, m, and n are the diffraction angles (2θ) shown in formulas (4) and (5), respectively.