Alloyed hot-dip galvannealed steel sheet and component

Abstract

The present invention provides: an alloyed hot-dip galvannealed steel sheet which has excellent bendability and hydrogen embrittlement resistance by virtue of a novel configuration; and a component containing the alloyed hot-dip galvannealed steel sheet.　The alloyed hot-dip galvannealed steel sheet of the present invention comprises a steel sheet and a plating layer that is arranged on at least a part of a surface of the steel sheet and contains Zn and 7%-18% by mass of Fe. The hot-dip galvannealed steel sheet is characterized in that: the steel sheet has a specific chemical composition; the thickness, from a surface of the steel sheet toward the depth direction, of a region that has a C concentration of 0.02% or more and less than 0.05% as determined by glow discharge optical emission spectrometry is 2.0 μm or more; and the concentration of Mn in solid solution in a ferrite phase within a 2.0 μm surface layer of the steel sheet is 1.0% or less.

Description

Alloyed hot-dip galvanized steel sheets and parts

[0001] This invention relates to alloyed hot-dip galvanized steel sheets and parts.

[0002] In recent years, there has been a trend towards increasing the strength of steel sheets used in various fields such as automobiles, home appliances, and building materials. For example, in the automotive sector, the use of thin, high-strength steel sheets is increasing in order to lighten vehicle bodies and components and improve fuel efficiency.

[0003] In high-strength steel plates like these, hydrogen embrittlement cracking can be a problem. Hydrogen embrittlement cracking is a phenomenon in which a steel component subjected to high stress under operating conditions suddenly fractures due to hydrogen entering the steel from the surrounding environment. This phenomenon is also called delayed fracture due to the manner in which the fracture occurs. Generally, it is known that hydrogen embrittlement cracking in steel plates is more likely to occur as the tensile strength of the steel plate increases. This is thought to be because the higher the tensile strength of the steel plate, the greater the stress remaining in the steel plate after the part is formed.

[0004] Various proposals have been made to improve the hydrogen embrittlement resistance of steel sheets to address this type of hydrogen embrittlement cracking.

[0005] For example, Patent Document 1 discloses a hot-dip galvanized steel sheet having a hot-dip galvanized layer on at least one surface of a base steel sheet, wherein the base steel sheet has a predetermined chemical composition, and the microstructure in the range of 1 / 8 to 3 / 8 thickness centered at a position 1 / 4 thickness from the surface of the base steel sheet contains, by volume fraction, ferrite: 0% to 50%, retained austenite: 0% to 30%, tempered martensite: 5% or more, fresh martensite: 0% to 10%, and the sum of pearlite and cementite: 0% to 5%, and if a remaining microstructure exists, the remaining microstructure consists of bainite, the concentration of B atoms at the prior austenite grain boundaries is 2.0 atm% or more, and the average effective grain size is 7.0 μm or less.

[0006] Furthermore, Patent Document 2 describes a material having a predetermined chemical composition and an area ratio of: polygonal ferrite: 10% or less, upper bainite: 20% or less, retained austenite: 5% or less, martensite: 70% or more, 1 × 10 ６ / mm ２ A hot-dip galvanized steel sheet is disclosed having a structure in which Fe carbides are present at the above number density in martensite: 50% or more of the total martensite, and the average effective grain size is 5.0 μm or less.

[0007] Furthermore, Patent Document 3 describes a material having a predetermined chemical composition, satisfying the relationship where the product of the amount of solid-solution B in the steel (solB [mass%]) and the prior austenite particle size Dγ [μm] is 0.0010 or more, and furthermore, in terms of area percentage, polygonal ferrite is 10% or less, bainite is 30% or less, retained austenite is 6% or less, and tempered martensite is 60% or more, and the number density of Fe carbides in the tempered martensite is 1 × 10⁻⁶ ６ / mm ２ Therefore, the average dislocation density of the entire steel is 1.0 × 10⁻⁶. １５ / m ２ The above is 2.0 x 10 １６ / m ２ The following discloses an ultra-high-strength cold-rolled steel sheet having a steel structure with an effective grain size of 7.0 μm or less, a tensile strength of 1300 MPa or more, and excellent resistance to hydrogen embrittlement.

[0008] The steel sheets disclosed in Patent Documents 1 to 3 are all described as high-strength steel sheets with excellent hydrogen embrittlement resistance.

[0009] International Publication No. 2020 / 162561, International Publication No. 2018 / 011978, Japanese Patent Publication No. 2016-50343

[0010] On the other hand, automotive parts are required to have not only strength and hydrogen embrittlement resistance, but also excellent collision performance. To improve collision performance, it is necessary to further improve the bendability of the steel sheets that make up automotive parts.

[0011] This invention has been made in view of the above circumstances, and aims to provide an alloyed hot-dip galvanized steel sheet with excellent bendability and hydrogen embrittlement resistance, as well as a component containing the same, through a novel configuration.

[0012] The present invention includes at least the following embodiments.

[0013] (Aspect 1) A steel plate and a plating layer containing Zn and 7 to 18 mass% Fe, disposed on at least a part of the surface of the steel plate, wherein the chemical composition of the steel plate is, in mass%, C: 0.05 to 0.40%, Mn: 1.0 to 5.0%, P: 0.0300% or less, S: 0.0300% or less, N: 0.0200% or less, Si: 0 to 0.65%, sol. It contains Al: 0-3.0%, O: 0-0.01%, B: 0-0.0100%, Ti: 0-0.1500%, Nb: 0-0.150%, V: 0-0.150%, Cr: 0-2.00%, Ni: 0-2.00%, Cu: 0-2.00%, Mo: 0-1.00%, W: 0-1.00%, Ca: 0-0.1000%, Mg: 0-0.100%, Zr: 0-0.500%, Hf: 0-0.100%, Sn: 0-0.100%, As: 0-0.100%, and REM: 0-0.100%, with the remainder being Fe and impurities. A hot-dip galvanized steel sheet characterized in that, as measured by glow discharge emission spectroscopy from the surface of the steel sheet toward the depth direction, the thickness of the region with a carbon concentration of 0.02% or more and less than 0.05% is 2.0 μm or more, and the solid solution Mn concentration in the ferrite phase within 2.0 μm of the surface layer of the steel sheet is 1.0% or less.

[0014] (Aspect 2) The chemical composition of the steel sheet is, in mass%, Si: 0.001 to 0.65%, sol. Al: 0.001-3.0%, O: 0.001-0.01%, B: 0.0001-0.0100%, Ti: 0.0001-0.1500%, Nb: 0.0001-0.150%, V: 0.001-0.150%, Cr: 0.001-2.00%, Ni: 0.001-2.00%, Cu: 0.001-2.00%, Mo: 0.001-1.00%, W: 0.0001-1.000%, Ca: 0.0001-0.1000%, Mg: 0.0001 to 0.100%, Zr: 0.001 to 0.500%, The alloyed hot-dip galvanized steel sheet according to embodiment 1, characterized by containing one or more of the following: Hf: 0.0001 to 0.100%, Sn: 0.0001 to 0.100%, As: 0.0001 to 0.100%, and REM: 0.0001 to 0.100%.

[0015] (Aspect 3) The alloyed hot-dip galvanized steel sheet according to aspect 1 or 2, characterized in that, as determined by the glow discharge emission spectroscopy analysis, the thickness of the region where the C concentration is 0.02% or more and less than 0.05% is 5.0 μm or more.

[0016] (Aspect 4) The alloyed hot-dip galvanized steel sheet according to aspect 1 or 2, characterized in that, as determined by the glow discharge emission spectroscopy analysis, the thickness of the region where the C concentration is 0.02% or more and less than 0.05% is 10.0 μm or more.

[0017] (Aspect 5) The alloyed hot-dip galvanized steel sheet according to any one of aspects 1 to 4, characterized in that the solid solution Mn concentration in the ferrite phase within 2.0 μm of the surface layer of the steel sheet is 0.4% or less.

[0018] (Aspect 6) The alloyed hot-dip galvanized steel sheet according to any one of aspects 1 to 4, characterized in that the solid solution Mn concentration in the ferrite phase within 2.0 μm of the surface layer of the steel sheet is 0.2% or less.

[0019] (Aspect 7) The alloyed hot-dip galvanized steel sheet according to any one of aspects 1 to 6, characterized in that the Vickers hardness at a depth of 1 / 4 of the thickness of the steel sheet is 360 Hv or more.

[0020] (Aspect 8) The alloyed hot-dip galvanized steel sheet according to any one of aspects 1 to 6, characterized in that the Vickers hardness at a depth of 1 / 4 of the thickness of the steel sheet is 460 Hv or more.

[0021] (Aspect 9) The alloyed hot-dip galvanized steel sheet according to any one of aspects 1 to 6, characterized in that the Vickers hardness at a depth of 1 / 4 of the thickness of the steel sheet is 550 Hv or more.

[0022] (Aspect 10) A component comprising an alloyed hot-dip galvanized steel sheet as described in any of aspects 1 to 9 above.

[0023] According to the present invention, it is possible to provide alloyed hot-dip galvanized steel sheets and parts that have excellent bendability and hydrogen embrittlement resistance.

[0024] Figure 1 is a graph showing the relationship between C concentration and depth in glow discharge emission spectroscopy analysis from the surface of a steel plate towards the depth direction.

[0025] To achieve the above objective, the inventors diligently studied means to improve the bendability and hydrogen embrittlement resistance of alloyed hot-dip galvanized steel sheets. As a result, the inventors found that in steel sheets containing 1.0 to 5.0% Mn by mass, excellent bendability and hydrogen embrittlement resistance can be obtained by decarburizing the surface layer of the steel sheet to a specific decarburized state and reducing the solid solution Mn concentration. Furthermore, the inventors discovered a new method in which, during the manufacturing of the steel sheet, a specific strain is applied to the surface layer of the steel sheet, and then the steel sheet is annealed under specific high dew point conditions, thereby promoting decarburization of the surface layer of the steel sheet and reducing the solid solution Mn concentration.

[0026] The present invention was completed based on the above findings and includes the following embodiments.

[0027] Preferred embodiments of the alloyed hot-dip galvanized steel sheet of the present invention will be described in detail below. In this specification, unless otherwise specified, numerical ranges enclosed by "~" include both a lower limit and an upper limit. However, if the lower limit and upper limit are described with numbers accompanied by "less than" or "greater than", they are not included in that numerical range.

[0028] <Steel Plate> One embodiment of the present invention is an alloyed hot-dip galvanized steel sheet comprising a steel plate (base steel plate) and a plating layer containing Zn and 7 to 18 mass% of Fe, disposed on at least a part of the surface of the steel plate. Here, alloyed hot-dip galvanizing is a plating formed by applying hot-dip galvanizing to the surface of the base steel plate and then performing a heat treatment to alloy iron and zinc. As described above, the plating layer formed by alloyed hot-dip galvanizing contains Zn and 7 to 18 mass% of Fe.

[0029] The alloyed hot-dip galvanized steel sheet according to this embodiment has a chemical composition in mass percent of: C: 0.05 to 0.40%, Mn: 1.0 to 5.0%, P: 0.0300% or less, S: 0.0300% or less, N: 0.0200% or less, Si: 0 to 0.65%, sol. It contains Al: 0-3.0%, O: 0-0.01%, B: 0-0.0100%, Ti: 0-0.1500%, Nb: 0-0.150%, V: 0-0.150%, Cr: 0-2.00%, Ni: 0-2.00%, Cu: 0-2.00%, Mo: 0-1.00%, W: 0-1.00%, Ca: 0-0.1000%, Mg: 0-0.100%, Zr: 0-0.500%, Hf: 0-0.100%, Sn: 0-0.100%, As: 0-0.100%, and REM: 0-0.100%. It has a specific chemical composition in which the remainder consists of Fe and impurities.

[0030] Furthermore, the alloyed hot-dip galvanized steel sheet of this embodiment has a characteristic configuration in which the thickness of the region with a carbon concentration of 0.02% or more and less than 0.05% is 2.0 μm or more, as measured by glow discharge emission spectroscopy from the surface of the steel sheet in the depth direction, and the solid solution Mn concentration in the ferrite phase within 2.0 μm of the steel sheet surface is 1.0% or less.

[0031] (Effects) As described above, the alloyed hot-dip galvanized steel sheet of this embodiment has a specific chemical composition and a unique decarburization state in which the thickness of the region with a C concentration of 0.02% or more and less than 0.05% is 2.0 μm or more, as determined by glow discharge emission spectroscopy (GDS analysis). This unique decarburization state is obtained, as will be described later, by applying a specific strain to the surface layer of the steel sheet during the manufacturing process and further annealing the steel sheet under specific high dew point conditions, thereby promoting the internal oxidation of Mn and suppressing the external oxidation of Mn on the surface of the steel sheet, that is, promoting the decarburization of the surface layer of the steel sheet. At this time, the internal oxidation of Mn is promoted, which reduces the solid solution Mn concentration in the ferrite phase within 2.0 μm of the surface layer of the steel sheet. Generally, decarburization and the decrease in solid solution Mn concentration are independent of each other, but in this invention, the decarburization of the surface layer of the steel sheet is promoted by the above-described method. As described above, in this embodiment, the alloyed hot-dip galvanized steel sheet exhibits excellent bendability and hydrogen embrittlement resistance because the decarburization of the steel sheet surface layer is promoted, and the solid solution Mn concentration in the ferrite phase of the steel sheet surface layer is reduced to 1.0% or less.

[0032] The following describes in detail each component of the alloyed hot-dip galvanized steel sheet of this embodiment with reference to the drawings. Here, Figure 1 is a graph showing the relationship between C concentration and depth in GDS analysis from the surface of the steel sheet in the depth direction. In Figure 1, the graph labeled "with shot blasting" is the graph of the alloyed hot-dip galvanized steel sheet of this embodiment, in which a specific strain is applied to the surface layer of the steel sheet by shot blasting during the manufacturing process, and then annealed under specific high dew point conditions. On the other hand, the graph labeled "without shot blasting" is the graph of the steel sheet that is annealed without shot blasting during the manufacturing process.

[0033] [Thickness of a region where the C concentration in GDS analysis is 0.02 mass% or more and less than 0.05 mass%: 2.0 μm or more] As shown in FIG. 1, the galvannealed steel sheet of the present embodiment is characterized in that, in GDS analysis conducted from the surface of the steel sheet (base steel sheet) toward the depth direction, the thickness of a region where the C concentration is 0.02% or more and less than 0.05% is 2.0 μm or more. Hereinafter, such a feature may be simply referred to as "the feature related to C concentration". In addition, in the graph labeled "with SB" shown in FIG. 1, the thickness of the region where the C concentration is 0.02% or more and less than 0.05% is approximately 20 μm.

[0034] The feature that the thickness of the region where the C concentration is 0.02% or more and less than 0.05% is 2.0 μm or more means that the surface layer of the steel sheet has been decarburized to an extent necessary for exhibiting excellent bendability.

[0035] The thickness of the region where the C concentration is 0.02% or more and less than 0.05% is preferably 5.0 μm or more, and more preferably 10.0 μm or more. In addition, the upper limit of the thickness of the region where the C concentration is 0.02% or more and less than 0.05% is not particularly limited, and is, for example, 40.0 μm.

[0036] Here, in the present specification, the "steel sheet surface layer" refers to a region near the outermost surface of the steel sheet (base steel sheet), and specifically means a region from the outermost surface of the steel sheet to a depth position of 5.0 μm in the thickness direction of the steel sheet.

[0037] Furthermore, regarding the outermost surface of the steel sheet which serves as the reference for the depth position of the steel sheet, the outermost surface of the steel sheet which serves as the reference for the depth position of the steel sheet is the outermost surface of the base steel sheet, that is, the interface between the base steel sheet and the plating layer. In the present specification, in GDS analysis, the depth position at which the emission intensity of Fe reaches 0.7 times or more of the internal Fe emission intensity is defined as the 0 μm position, and this 0 μm position is taken as the outermost surface of the steel sheet. The internal Fe emission intensity is the Fe emission intensity in a sufficiently deep region of the steel sheet. This region is a region where there is almost no change in Fe concentration in the depth direction, and is a region judged as "steel" according to common technical knowledge. The internal Fe emission intensity may be, for example, the Fe emission intensity at a sputtering time of 1000 seconds.

[0038] GDS analysis may be performed as follows.

[0039] (GDS analysis method) Glow discharge optical emission spectrometry (GD-OES) for elements in the steel sheet surface layer is performed by a method in accordance with JIS K0144:2018 *Surface chemical analysis - General rules for glow discharge optical emission spectrometry*. Specifically, using a glow discharge optical emission spectrometer, the surface of the steel sheet to be measured is placed in an Ar atmosphere, and after applying a voltage to generate glow plasma, analysis is performed in the depth direction while sputtering the steel sheet surface. Then, the element contained in the steel sheet, that is C (carbon), is identified from the emission spectral wavelength unique to the element emitted when atoms are excited in the glow plasma, and the emission intensity of the identified element is estimated.

[0040] Data in the depth direction can be estimated from the sputtering time. Specifically, by obtaining the relationship between sputtering time and sputtering depth in advance using a standard sample, sputtering time can be converted into sputtering depth. Therefore, the sputtering depth converted from the sputtering time can be defined as the depth from the steel sheet surface.

[0041] The C concentration is determined by converting the emission intensity of C obtained as described above into percent by mass. Specifically, by obtaining the relationship between emission intensity and C concentration in advance using a standard sample, emission intensity can be converted into C concentration. A calibration curve installed in a glow discharge optical emission spectrometer (model number "GDS850A") manufactured by LECO Japan G.K. can be used. For calibration of the calibration curve, "BS H-1B", a standard sample manufactured by Brammer Standard Company, can be used.

[0042] GDS analysis is performed at five measurement points spaced 5 mm or more apart from each other on the steel sheet surface, and the arithmetic mean value thereof is adopted.

[0043] A commercially available glow discharge emission spectrometer can be used for GDS analysis. In this embodiment, a glow discharge emission spectrometer (model number "GDS850A") manufactured by LECO Japan LLC is used. The measurement conditions are as follows: The detection pitch is 0.1 seconds. Background is removed from the obtained data. Subsequently, the arithmetic mean of the emission intensity of carbon on the surface of the steel plate is adopted as the average value of the emission intensity of carbon on the surface of the steel plate. On the other hand, for the emission intensity of carbon in the depth direction on the surface of the steel plate, a moving average of 11 points (center point + 5 points before and after each depth) is adopted. Anode diameter: 4 mmφ RF output: 30W Measurement time: 200 to 1500 seconds

[0044] [Solid-solution Mn concentration in the ferrite phase within 2.0 μm of the steel sheet surface: 1.0% or less] As described above, the alloyed hot-dip galvanized steel sheet of this embodiment has the characteristic that the solid-solution Mn concentration in the ferrite phase within 2.0 μm of the steel sheet surface is 1.0% or less. Hereinafter, this characteristic may simply be referred to as "characteristics relating to solid-solution Mn concentration".

[0045] The characteristic of having a solid solution Mn concentration of 1.0% or less in the ferrite phase within 2.0 μm of the steel sheet surface means that the internal oxidation of Mn was promoted during annealing, resulting in a sufficient reduction of the solid solution Mn concentration in the ferrite phase within 2.0 μm of the steel sheet surface. This characteristic also means that the steel sheet surface has been decarburized to the extent necessary to exhibit excellent bendability.

[0046] In this specification, "within 2.0 μm of the steel plate surface layer" means the region of the steel plate surface layer from the outermost surface of the steel plate (the interface between the base steel plate and the plating layer) to a depth of 2.0 μm.

[0047] The alloyed hot-dip galvanized steel sheet of this embodiment possesses both the above-mentioned characteristics regarding C concentration and the characteristics regarding solid-solution Mn concentration, that is, the surface layer of the steel sheet is sufficiently decarburized, thereby exhibiting excellent bendability and resistance to hydrogen embrittlement.

[0048] The galvannealed steel sheet according to the present embodiment preferably has a solid solution Mn concentration of 0.4% or less in the ferrite phase within 2.0 μm of the steel sheet surface layer, more preferably 0.2% or less, from the viewpoint of more reliably obtaining excellent bendability and hydrogen embrittlement resistance.

[0049] The solid solution Mn concentration in the ferrite phase within 2.0 μm of the steel sheet surface layer can be determined according to the following measurement method.

[0050] (Measurement Method for Solid Solution Mn Concentration) The solid solution Mn concentration in the ferrite phase within 2.0 μm of the steel sheet surface layer is determined by the STEM-EDS method. Specifically, first, a sample is collected from the steel sheet to be measured, with the thickness cross-section of the steel sheet used as the observation surface. Next, after mechanical polishing of the observation surface of the sample to obtain a mirror finish, electrolytic polishing is performed. In one or more observation fields of view within a range from the surface to a depth position of 2.0 μm on the observation surface, a total of 2.0×10 －９ m ２The above area is subjected to crystal structure and orientation analysis by SEM-EBSD to identify the ferrite phase. Next, the sample is thinned by FIB processing in a FIB-SEM combined system (model "NB5000", manufactured by Hitachi High-Tech Corporation). The acceleration voltage during FIB processing is set to 40-5kV. However, voltages below 10kV are considered finishing processes. In addition, the mesh used is made of molybdenum, and the protective film is made of carbon. Then, five points on the thinned sample are observed using a spherical aberration-corrected transmission electron microscope (Cs-TEM, model "JEM-ARM200F NEOARM", manufactured by JEOL Ltd.), and the Mn concentration is obtained by EDS analysis using an EDS analyzer (model "JED-2300Tx2 Dual EDS System", manufactured by JEOL Ltd.) mounted on the Cs-TEM. The arithmetic mean of the obtained Mn concentration measurements shall be taken as the solid-solution Mn concentration in the ferrite phase within 2.0 μm of the steel plate surface. The acceleration voltage during observation by Cs-TEM shall be 200 kV. The acceleration voltage during EDS analysis shall also be 200 kV, and the irradiation current (set value) shall be 1.0 nA. Furthermore, the irradiation time during EDS analysis shall be measured until the maximum peak intensity in the EDS analysis spectrum reaches 2000 counts or more. In addition, the measurement of the solid-solution Mn concentration shall be performed while avoiding areas other than the ferrite phase (e.g., internal oxides at grain boundaries, etc.).

[0051] In order for alloyed hot-dip galvanized steel sheets to possess the above-mentioned characteristics regarding C concentration and solid-solution Mn concentration, a specific strain should be applied to the surface layer of the steel sheet during the manufacturing process, and then the steel sheet should be annealed under specific high-dew-point conditions to promote decarburization of the surface layer and reduce the solid-solution Mn concentration. Specifically, this is done as follows.

[0052] First, a specific large strain is imparted to the surface of the steel sheet by applying a shot blast treatment to the surface of the steel sheet after the hot rolling process (hereinafter sometimes referred to as "hot-rolled black steel") or after pickling.

[0053] Next, in the cold rolling process, the convex parts of the uneven structure on the surface of the steel sheet are flattened, thereby introducing the large strain mentioned above into the outermost layer of the steel sheet (the area from the outermost surface to a depth of 4 μm or less).

[0054] Cold-rolled steel sheets with such specific strains are annealed under specific high dew point conditions. As the temperature rises during annealing, recrystallization occurs in the outermost layer where the specific strains were introduced, forming a fine ferrite phase. Furthermore, internal oxides of Mn are formed at the grain boundaries of this ferrite phase.

[0055] As the temperature rises further above the A1 transformation point, the fine ferrite phase transforms into the austenite phase, and the internal oxides pin the growth of austenite grains. Decarburization also begins above the A1 transformation point, but the formation of the internal Mn oxides mentioned above reduces the amount of metallic Mn in the solid solution (i.e., a Mn-depleted layer is formed), suppressing the external oxidation of Mn on the outermost surface of the steel. As a result, decarburization progresses further, that is, the inhibition of decarburization is suppressed.

[0056] In this way, by promoting decarburization of the steel sheet surface and reducing the solid-solution Mn concentration, it is possible to combine the characteristics related to C concentration and solid-solution Mn concentration described above. The specific manufacturing method and conditions for the alloyed hot-dip galvanized steel sheet of this embodiment will be described later.

[0057] [Chemical Composition] Next, the chemical composition of the base steel sheet in the alloyed hot-dip galvanized steel sheet of this embodiment will be described in detail. As described above, the steel sheet has the following composition in mass%, C: 0.05 to 0.40%, Mn: 1.0 to 5.0%, P: 0.0300% or less, S: 0.0300% or less, N: 0.0200% or less, Si: 0 to 0.65%, sol. It contains Al: 0-3.0%, O: 0-0.01%, B: 0-0.0100%, Ti: 0-0.1500%, Nb: 0-0.150%, V: 0-0.150%, Cr: 0-2.00%, Ni: 0-2.00%, Cu: 0-2.00%, Mo: 0-1.00%, W: 0-1.00%, Ca: 0-0.1000%, Mg: 0-0.100%, Zr: 0-0.500%, Hf: 0-0.100%, Sn: 0-0.100%, As: 0-0.100%, and REM: 0-0.100%. It has a specific chemical composition in which the remainder consists of Fe and impurities.

[0058] The following provides a more detailed explanation of each of these elements.

[0059] [C: 0.05-0.40%] Carbon (C) is an important element for controlling the strength of steel. To ensure the strength of the steel, the C content should be 0.05% or more. To prevent the C concentration on the surface of the steel plate from becoming too high, the C content should be 0.40% or less. The C content may be 0.08% or more, 0.10% or more, or 0.15% or more. The C content may be 0.37% or less, 0.35% or less, or 0.30% or less.

[0060] [Mn: 1.0-5.0%] Mn is an effective element for forming a hard structure and improving the strength of steel. Considering the strength of the steel, the Mn content should be 1.0% or more. Also, considering the decrease in workability such as bendability due to Mn segregation, the Mn content should be 5.0% or less. The Mn content may be 1.5% or more, 2.0% or more, or 2.5% or more. The Mn content may be 4.5% or less, 4.0% or less, or 3.5% or less.

[0061] [P: 0.0300% or less] P is an impurity commonly found in steel. P is an element that segregates at grain boundaries and promotes embrittlement of steel. A lower P content is preferable, so ideally it should be 0%. However, excessive reduction of the P content can lead to a significant increase in cost. For this reason, the P content may be 0.0001% or more, or 0.001% or more, or 0.005% or more. On the other hand, excessive P content can lead to embrittlement of steel due to grain boundary segregation, as described above. Therefore, the P content should be 0.0300% or less. The P content may also be 0.0250% or less, 0.0200% or less, 0.0150% or less, or 0.0100% or less.

[0062] [S: 0.0300% or less] S is an impurity commonly found in steel. S is an element that generates nonmetallic inclusions such as MnS in steel, leading to a decrease in the ductility of steel parts. A lower S content is preferable, so ideally it should be 0%. However, excessive reduction of the S content can lead to a significant increase in cost. For this reason, the S content may be 0.0001% or more, 0.0005% or more, 0.0010% or more, or 0.0020% or more. On the other hand, excessive S content can lead to a decrease in weldability and a decrease in workability such as bendability due to an increase in MnS precipitation. Therefore, the S content should be 0.0300% or less. The S content may be 0.0250% or less, 0.0200% or less, 0.0150% or less, or 0.0100% or less.

[0063] [N: 0.0200% or less] N is an impurity commonly found in steel. N forms coarse nitrides in steel, reducing the workability, such as bendability, and weldability of steel sheets. A lower N content is preferable, ideally it should be 0%. However, excessive reduction of the N content can lead to a significant increase in manufacturing costs. For this reason, the N content may be 0.0001% or more, 0.0005% or more, or 0.0010% or more. On the other hand, excessive N content can form coarse nitrides, reducing workability, such as bendability, and weldability. Therefore, the N content should be 0.0200% or less. The N content may also be 0.0150% or less, 0.0100% or less, or 0.0080% or less.

[0064] [Si: 0-0.65%] Si is an element that promotes ferrite stabilization and decarburization. When Si is present, decarburization proceeds more easily on the surface of the steel sheet, and the stabilization of the ferrite on the surface of the steel sheet improves bendability and hydrogen embrittlement resistance. These effects of including Si can also be obtained by including sol. Al, so Si is not an essential element in this invention. Therefore, the Si content may be 0%, but in order to sufficiently obtain the above effects, the Si content may be 0.001% or more. On the other hand, if Si is included in excess, external oxidation will proceed during high dew point annealing, and oxides (scale) will be formed on the surface of the steel sheet, which may suppress decarburization at the outermost surface and reduce the above effects. For this reason, the Si content should be 0.65% or less. The Si content may be 0.01% or more, 0.05% or more, or 0.10% or more. The Si content may be 0.60% or less, 0.55% or less, or 0.50% or less.

[0065] [sol. Al: 0-3.0%] Al is an element that promotes ferrite stabilization and decarburization by being dissolved in steel. Here, sol. Al means Al ２ O ３This refers to acid-soluble Al, which is not an oxide and is soluble in acid. The above effects obtained by including sol. Al can also be obtained by including Si, so sol. Al is not an essential element in this invention. Therefore, the sol. Al content may be 0%, but in order to sufficiently obtain the above effects, the sol. Al content may be 0% or more. On the other hand, if sol. Al is included in excess, external oxidation will progress during high dew point annealing, and oxides (scale) will be formed on the surface of the steel sheet, which may suppress decarburization at the outermost surface and reduce the above effects. For this reason, the sol. Al content should be 3.0% or less. The sol. Al content may be 0.01% or more, 0.05% or more, 0.1% or more, 0.3% or more, or 0.5% or more. The sol. Al content may be 2.0% or less, 1.5% or less, or 1.0% or less.

[0066] [O: 0-0.01%] O is an element that is mixed in during the manufacturing process and may be included as needed. Since O is not an essential element in the steel sheet of the present invention, the lower limit of the O content is 0%. The O content may be 0.001% or more, 0.003% or more, or 0.005% or more. On the other hand, from the viewpoint of suppressing the formation of coarse oxides and ensuring the ductility and formability of the steel sheet, the O content should be 0.01% or less. The O content may be 0.009% or less, 0.008% or less, or 0.007% or less.

[0067] [B: 0 to 0.0100%] B is an element that enhances hardenability and contributes to improved strength, as well as strengthening grain boundaries by segregating at them and improving toughness. By segregating on the surface of the steel plate in a solid solution state, B can suppress the penetration of Zn into the grain boundaries and improve LME resistance. B is an element that may be included as needed and is not an essential element in this invention, so the lower limit of the B content is 0%. In order to fully obtain each of the above effects, the B content may be 0.0001% or more. Also, from the viewpoint of ensuring sufficient toughness, the B content should be 0.0100% or less. The B content may be 0.0010% or more, 0.0020% or more, 0.0030% or more, or 0.0040% or more. The B content may be 0.0080% or less, 0.0070% or less, or 0.0060% or less.

[0068] [Ti: 0 to 0.1500%] Ti is an element that precipitates as TiC during the cooling of steel and contributes to improving its strength. Ti is an element that may be included as needed and is not an essential element in this invention, so the lower limit of the Ti content is 0%. In order to fully obtain the above effects, the Ti content may be 0.0001% or more. On the other hand, if Ti is included in excess, coarse TiN may be generated, which may impair toughness, so the Ti content should be 0.1500% or less. The Ti content may be 0.0002% or more, 0.0003% or more, 0.0004% or more, or 0.0005% or more. The Ti content may be 0.1200% or less, 0.1000% or less, or 0.0800% or less.

[0069] [Nb: 0-0.150%] Nb is an element that enhances the hardenability of steel and contributes to improving its strength. Nb is an element that may be included as needed and is not an essential element in this invention, so the lower limit of the Nb content is 0%. In order to fully obtain the above effects, the Nb content may be 0.0001% or more. Also, from the viewpoint of ensuring sufficient toughness, the Nb content should be 0.150% or less. The Nb content may be 0.001% or more, 0.010% or more, 0.020% or more, 0.030% or more, or 0.040% or more. On the other hand, the Nb content may be 0.120% or less, 0.100% or less, or 0.080% or less.

[0070] [V: 0-0.150%] V is an element that enhances hardenability and contributes to improved strength. V is an element that may be included as needed and is not an essential element in this invention, so the lower limit of the V content is 0%. In order to fully obtain the above effects, the V content may be 0.001% or more. Also, from the viewpoint of ensuring sufficient toughness, the V content should be 0.150% or less. The V content may be 0.005% or more, 0.010% or more, 0.030% or more, or 0.050% or more. The V content may be 0.120% or less, 0.100% or less, or 0.080% or less.

[0071] [Cr: 0-2.00%] Cr is an effective element for increasing the hardenability and strength of steel. Cr is an element that may be included as needed, and is not an essential element in this invention; therefore, the lower limit of the Cr content is 0%. To fully obtain the above effects, the Cr content may be 0.001% or more. On the other hand, if Cr is included in excess, a large amount of Cr carbide may be formed, impairing the hardenability; therefore, the Cr content should be 2.00% or less. The Cr content may be 0.01% or more, 0.05% or more, or 0.10% or more. The Cr content may be 1.80% or less, 1.50% or less, 1.20% or less, or 1.00% or less.

[0072] [Ni: 0-2.00%] Ni is an effective element for increasing the hardenability and strength of steel. Ni is an element that may be included as needed and is not an essential element in this invention, so the lower limit of the Ni content is 0%. In order to fully obtain the above effects, the Ni content may be 0.001% or more. On the other hand, excessive addition of Ni increases costs, so the Ni content should be 2.00% or less. The Ni content may be 0.005% or more, 0.01% or more, 0.05% or more, or 0.10% or more. The Ni content may be 1.80% or less, 1.50% or less, 1.20% or less, or 1.00% or less.

[0073] [Cu: 0-2.00%] Cu is an effective element for increasing the hardenability and strength of steel. Cu is an element that may be included as needed and is not an essential element in this invention, so the lower limit of the Cu content is 0%. In order to fully obtain the above effects, the Cu content may be 0.001% or more. On the other hand, in order to suppress the reduction of toughness and cracking of the slab after casting, the Cu content should be 2.00% or less. The Cu content may be 0.005% or more, 0.01% or more, 0.05% or more, or 0.10% or more. The Cu content may be 1.80% or less, 1.50% or less, 1.20% or less, or 1.00% or less.

[0074] [Mo: 0-1.00%] Mo is an element that enhances the hardenability of steel and contributes to improving its strength. Mo is an element that may be included as needed and is not an essential element in this invention, so the lower limit of the Mo content is 0%. In order to fully obtain the above effects, the Mo content may be 0.001% or more. Also, from the viewpoint of ensuring sufficient toughness, the Mo content should be 1.00% or less. The Mo content may be 0.005% or more, 0.010% or more, 0.015% or more, or 0.020% or more. On the other hand, the Mo content may be 0.80% or less, 0.70% or less, 0.60% or less, or 0.50% or less.

[0075] [W: 0-1.000%] W is an element effective in increasing the hardenability and strength of steel. W is an element that may be included as needed and is not an essential element in this invention, so the lower limit of the W content is 0%. In order to fully obtain the above effects, the W content may be 0.0001% or more. On the other hand, in order to suppress the decrease in toughness, the W content should be 1.000% or less. The W content may be 0.0005% or more, 0.001% or more, 0.005% or more, or 0.010% or more. The W content may be 0.800% or less, 0.700% or less, 0.600% or less, or 0.500% or less.

[0076] [Ca: 0 to 0.1000%] Ca is an element that contributes to controlling the morphology of nonmetallic inclusions, particularly to the fine dispersion of nonmetallic inclusions, and thereby enhances toughness. Ca is an element that may be included as needed and is not an essential element in this invention, so the lower limit of the Ca content is 0%. In order to fully obtain the above effects, the Ca content may be 0.0001% or more. On the other hand, if Ca is included in excess, deterioration of surface properties may become apparent, so the Ca content should be 0.1000% or less. The Ca content may be 0.0002% or more, 0.0003% or more, 0.0004% or more, or 0.0005% or more. The Ca content may be 0.0800% or less, 0.0700% or less, 0.0600% or less, or 0.0500% or less.

[0077] [Mg: 0-0.100%] Mg is an element that contributes to controlling the morphology of nonmetallic inclusions, particularly to the fine dispersion of nonmetallic inclusions, and thereby enhances toughness. Mg is an element that may be included as needed and is not an essential element in this invention, so the lower limit of the Mg content is 0%. To fully obtain the above effects, the Mg content may be 0.0001% or more. On the other hand, if Mg is included in excess, deterioration of surface properties may become apparent, so the Mg content should be 0.100% or less. The Mg content may be 0.0005% or more, 0.001% or more, 0.005% or more, or 0.010% or more. The Mg content may be 0.080% or less, 0.070% or less, 0.060% or less, or 0.050% or less.

[0078] [Zr: 0-0.500%] Zr is an element that contributes to controlling the morphology of nonmetallic inclusions, particularly to the fine dispersion of nonmetallic inclusions, and thereby enhances toughness. Zr is an element that may be included as needed and is not an essential element in this invention, so the lower limit of the Zr content is 0%. To fully obtain the above effects, the Zr content may be 0.001% or more. On the other hand, if Zr is included in excess, deterioration of surface properties may become apparent, so the Zr content should be 0.500% or less. The Zr content may be 0.003% or more, 0.005% or more, 0.008% or more, or 0.010% or more. The Zr content may be 0.450% or less, 0.400% or less, 0.350% or less, or 0.300% or less.

[0079] [Hf: 0-0.100%] Hf is an element that contributes to controlling the morphology of nonmetallic inclusions, particularly to the fine dispersion of nonmetallic inclusions, and thereby enhances toughness. Hf is an element that may be included as needed and is not an essential element in this invention, so the lower limit of the Hf content is 0%. To fully obtain the above effects, the Hf content may be 0.0001% or more. On the other hand, if Hf is included in excess, deterioration of surface properties may become apparent, so the Hf content should be 0.100% or less. The Hf content may be 0.0005% or more, 0.001% or more, 0.005% or more, or 0.010% or more. The Hf content may be 0.080% or less, 0.070% or less, 0.060% or less, or 0.050% or less.

[0080] [Sn: 0-0.100%] [As: 0-0.100%] Sn and As are elements that are effective in improving corrosion resistance. Sn and As are elements that may be included as needed, and are not essential elements in the steel sheet of the present invention, so the lower limit of the Sn and As content is 0% each. The Sn and As content may be 0.0001% or more, 0.0005% or more, and 0.001% or more, respectively. On the other hand, if Sn and As are included in excess, the above effect will saturate, and including more than necessary in the steel sheet will lead to an increase in manufacturing costs. Therefore, the Sn and As content should be 0.100% or less each. The Sn and As content may be 0.090% or less, 0.080% or less, 0.070% or less, or 0.060% or less, respectively.

[0081] [REM: 0-0.100%] REM (rare earth elements) are elements that contribute to controlling the morphology of nonmetallic inclusions, particularly to the fine dispersion of nonmetallic inclusions, and thereby enhance toughness. REM is an element that may be included as needed and is not an essential element in this invention, so the lower limit of the REM content is 0%. To fully obtain the above effects, the REM content may be 0.0001% or more. On the other hand, if REM is included in excess, deterioration of surface properties may become apparent, so the REM content should be 0.100% or less. The REM content may be 0.0005% or more, 0.001% or more, 0.005% or more, or 0.010% or more. The REM content may be 0.080% or less, 0.070% or less, 0.060% or less, or 0.050% or less. REM stands for Rare Earth Metal, and refers to the two elements Sr and Y, and the 15 elements belonging to the lanthanide series.

[0082] In the present invention, the remainder of the elements other than those mentioned above consists of Fe and impurities. Here, the impurities include components that are inevitably mixed in due to various factors in the manufacturing process, such as raw materials like ore and scrap, when steel sheets are manufactured industrially. The impurities can be included in a range that does not adversely affect the bendability and hydrogen embrittlement resistance of the steel sheet according to the present invention, that is, within a range that allows the bendability and hydrogen embrittlement resistance required for the alloyed hot-dip galvanized steel sheet of the present invention to be obtained.

[0083] Furthermore, regarding optional components, the chemical composition of the steel sheet is, in mass%, Si: 0.001-0.65%, sol. Al: 0.001-3.0%, O: 0.001-0.01%, B: 0.0001-0.0100%, Ti: 0.0001-0.1500%, Nb: 0.0001-0.150%, V: 0.001-0.150%, Cr: 0.001-2.00%, Ni: 0.001-2.00%, Cu: 0.001-2.00%, Mo: 0.001-1.00%, W: 0.0001-1.000%, Ca: 0.0001-0.1000%, Mg: 0.0001 to 0.100%, Zr: 0.001 to 0.500%, It may contain one or more of the following: Hf: 0.0001 to 0.100%, Sn: 0.0001 to 0.100%, As: 0.0001 to 0.100%, and REM: 0.0001 to 0.100%.

[0084] The chemical composition of steel sheets can be measured using general analytical methods. For example, the chemical composition of steel sheets can be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry) in accordance with JIS G 1201:2022. Specifically, a test piece with a width and length of 35 mm square (for example, a 35 mm square test piece with a sample thickness of 3 / 4 the thickness of the steel sheet) is obtained, machined so that the analysis surface is located 1 / 4 of the sheet thickness away from the surface of the steel sheet and parallel to the surface of the steel sheet. The chemical composition can then be determined by measuring it using a Shimadzu ICPS-8100 or similar (measuring device) under conditions based on a pre-established calibration curve. C and S, which cannot be measured by ICP-AES, can be measured using the combustion-infrared absorption method, and N can be measured using the inert gas fusion-thermal conductivity method. The sol. Al can be measured by atomic absorption spectrometry in accordance with JIS G1257-10-2:2013. When measuring the chemical composition of a steel sheet in areas where a plating layer is formed on the surface, the plating layer should be removed by methods such as pickling with a 10% HCl aqueous solution containing 0.06 volume% of an inhibitor (Asahi Chemical Co., Ltd., Ibit 710K) before measurement.

[0085] The thickness of the steel plate is not particularly limited, but generally it is between 0.2 and 8.0 mm. For example, the thickness may be 0.3 mm or more, 0.6 mm or more, 1.0 mm or more, 1.6 mm or more, or 2.0 mm or more. Similarly, the thickness of the steel plate may be 7.0 mm or less, 6.0 mm or less, 5.0 mm or less, or 4.0 mm or less.

[0086] [Vickers Hardness] In the alloyed hot-dip galvanized steel sheet of this embodiment, the hardness of the steel sheet is not particularly limited, but for example, the Vickers hardness of the steel sheet at a depth of 1 / 4 of the sheet thickness may be 360 ​​Hv or higher. Generally, as the strength and hardness of the steel sheet increase, it becomes more difficult to improve its bendability and hydrogen embrittlement resistance, but the present invention is particularly advantageous in that even with such a high-strength steel sheet, it can exhibit excellent bendability and hydrogen embrittlement resistance as described above. The Vickers hardness of the steel sheet at a depth of 1 / 4 of the sheet thickness may be 460 Hv or higher or 550 Hv or higher. The upper limit of the Vickers hardness is not particularly limited, but for example, the Vickers hardness of the steel sheet at a depth of 1 / 4 of the sheet thickness may be 950 Hv or less, 900 Hv or less, 850 Hv or less, or 800 Hv or less.

[0087] The Vickers hardness of steel plates can be measured in accordance with JIS Z 2244-1:2024 as follows: First, a test piece is cut from any position on the steel plate, excluding the edges, so that a cross-section perpendicular to the surface (a cross-section along the thickness direction) can be observed. The thickness cross-section of the cut test piece is polished using silicon carbide sandpaper of #600 to #1500 grit. Next, the thickness cross-section of the test piece is polished to a mirror finish using a liquid in which diamond powder with a particle size of 1 to 6 μm is dispersed in a diluent such as alcohol or pure water, and this thickness cross-section is used as the measurement surface. Then, using a micro-Vickers hardness tester, the Vickers hardness of the test piece is measured at intervals of at least three times the indentation depth with a load of 1 kgf. Specifically, a total of 20 points are measured randomly at a depth of 1 / 4 of the thickness of the test piece, and the arithmetic mean of these measurements is adopted as the Vickers hardness of the steel plate.

[0088] (Plating layer) In addition, the alloyed hot-dip galvanized steel sheet of this embodiment has a plating layer formed on at least a part of the surface of the steel sheet (base steel sheet) containing Zn and 7 to 18% by mass of Fe. The plating layer may be formed on only one side of the steel sheet surface, on both sides, or on only a part of the sheet surface.

[0089] The chemical composition of the plating layer is not particularly limited as long as it is an alloyed hot-dip galvanized (GA) plating containing Zn and 7 to 18% by mass of Fe. Examples of alloyed hot-dip galvanized plating include Zn-0.09%Al-10%Fe.

[0090] The thickness of the plating layer is not particularly limited, but may be, for example, 3 to 50 μm. The amount of plating layer applied is also not particularly limited, but may be, for example, 10 to 170 g / m² per side. ２ This may be the case. The amount of plating layer can be determined by dissolving the plating layer in an acid solution containing an inhibitor that suppresses corrosion of the steel plate, and measuring the weight change before and after dissolution of the plating layer.

[0091] <Parts> As described above, the alloyed hot-dip galvanized steel sheet of this embodiment is a steel sheet with excellent bendability and hydrogen embrittlement resistance. Therefore, the alloyed hot-dip galvanized steel sheet of this embodiment is useful as a raw material for parts that require excellent bendability and hydrogen embrittlement resistance. In particular, the alloyed hot-dip galvanized steel sheet of this embodiment is useful as a raw material for automobile parts.

[0092] In other words, one embodiment of the present invention is a part containing the alloyed hot-dip galvanized steel sheet of the above embodiment. Furthermore, examples of parts include automobile parts. Specific examples of automobile parts include the frame parts and bumpers of automobiles, as well as other structural and reinforcing parts that require strength. Further specific examples of automobile parts include exterior parts such as roofs, hoods, fenders, and doors, which require high aesthetic appeal. These parts only need to contain the alloyed hot-dip galvanized steel sheet of the above embodiment in at least a portion of the part. Therefore, these parts have the characteristics of the alloyed hot-dip galvanized steel sheet of the above embodiment in at least a portion of the part. It should be noted that in parts of the steel sheet that do not directly contact the mold during forming such as press forming, or that are in direct contact with the mold but undergo relatively little processing, the characteristics of the alloyed hot-dip galvanized steel sheet do not particularly change before and after forming.

[0093] When taking samples from automotive parts for various measurements and analyses, the following locations (i) to (iv) should be avoided: (i) Welded areas: within 20 mm of the toe of spot welds, and within 20 mm of the toe of arc / laser welds (ii) Machined areas: machined areas with a radius of curvature of less than 15 mm, and within 5 mm of the above machined areas (iii) Ends: ends within 5 mm of the cut end face of the part (iv) Red rust: within 5 mm of areas where red rust is visible

[0094] When taking samples from a coil for various measurements and analyses, the outermost part may have a changed surface condition. Therefore, samples should be taken from the third turn onwards from the outside of the coil, avoiding the end 100 mm away.

[0095] <Method for Manufacturing Steel Sheets> Next, a preferred method for manufacturing the alloyed hot-dip galvanized steel sheet according to one embodiment of the present invention will be described. The following description is intended to illustrate characteristic methods for manufacturing the alloyed hot-dip galvanized steel sheet of this embodiment, and is not intended to limit the alloyed hot-dip galvanized steel sheet to those manufactured by the manufacturing method described below.

[0096] The alloyed hot-dip galvanized steel sheet of this embodiment can be manufactured by a manufacturing method that includes a casting step of casting molten steel with an adjusted chemical composition to form a steel billet, a hot-rolling step of hot-rolling the steel billet to obtain a hot-rolled steel sheet, a shot-blasting step of applying shot blasting to the surface of the hot-rolled steel sheet (hot-rolled mill scale material) after the hot-rolling step or the hot-rolled steel sheet after pickling, a cold-rolling step of cold-rolling the hot-rolled steel sheet after shot-blasting to obtain a cold-rolled steel sheet, an annealing step of annealing the cold-rolled steel sheet after the cold-rolling step under specific high dew point conditions, a plating step of applying hot-dip galvanizing to the annealed steel sheet (base steel sheet), and an alloying step of applying an alloying treatment to the hot-dip galvanized steel sheet.Optionally, a pickling step of pickling the hot-rolled steel sheet after the hot-rolling step may also be performed.

[0097] The following will explain in detail the preferred conditions for these processes.

[0098] [Casting Process] In the method for manufacturing alloyed hot-dip galvanized steel sheets of this embodiment, the casting process is a process of casting molten steel with an adjusted chemical composition to form a steel billet. The conditions of the casting process are not particularly limited. For example, the casting process may involve melting in a blast furnace or electric furnace, followed by various secondary smelting processes, and then casting using methods such as conventional continuous casting or ingot casting.

[0099] [Hot Rolling Process] The hot rolling process is a process of obtaining hot-rolled steel sheets by hot rolling a steel billet. The hot rolling process is carried out by hot rolling the cast steel billet either directly or after it has been cooled and then reheated. When reheating is performed, the heating temperature of the steel billet may be, for example, 1100 to 1250°C. In the hot rolling process, rough rolling and finish rolling are usually performed. The temperature and reduction ratio of each rolling can be appropriately determined according to the desired metal structure and sheet thickness. For example, the finishing temperature of the finish rolling may be 900 to 1050°C, and the reduction ratio of the finish rolling may be 10 to 50%.

[0100] The hot-rolled steel sheet, after finish rolling, is wound at a predetermined winding temperature. The winding of the hot-rolled steel sheet is carried out at a winding temperature of 500°C or higher. The winding temperature may be 520°C or higher or 550°C or higher. The winding temperature may be 600°C or lower or 580°C or lower.

[0101] [Pickling Process] The pickling process is a process of pickling hot-rolled steel sheets after the hot-rolling process. In the pickling process, the hot-rolled steel sheets are pickled to remove surface oxides and internal oxides. The conditions for the pickling process are not particularly limited, and it is sufficient to carry it out under conditions appropriate for removing surface oxides and internal oxides using a commonly used pickling solution, for example, a hydrochloric acid solution of a predetermined concentration containing an inhibitor that suppresses corrosion of the steel sheet. Pickling may be carried out in one step, or it may be carried out in multiple steps to ensure that surface oxides and internal oxides are completely removed.

[0102] Since the pickling process is not essential for obtaining the alloyed hot-dip galvanized steel sheet of the present invention, the hot-rolled steel sheet after the hot-rolling process may be subjected to the subsequent shot-blasting process without going through the pickling process.

[0103] [Shot Blasting Process] The shot blasting process is a process of applying shot blasting to the surface of a hot-rolled steel sheet (hot-rolled mill scale material) after the hot-rolling process or after pickling. Shot blasting is a process in which spherical projectiles are projected onto the surface of the hot-rolled steel sheet. By applying such shot blasting to the surface of the steel sheet, a specific large strain can be imparted to the surface of the steel sheet. At this time, the surface roughness Ra of the steel sheet after shot blasting will be 0.8 μm or more. This surface roughness Ra may be 1.4 μm or more or 2.0 μm or more. Also, the surface roughness Ra of the steel sheet may be 5.0 μm or less. In this specification, surface roughness Ra means arithmetic mean roughness Ra. The surface roughness Ra of the steel sheet is measured in accordance with JIS B 0651:2022. Specifically, the surface roughness Ra is measured over a length of 0.4 mm at a position at least 10 mm away from the edge of the steel plate sample to be measured, using a needle-type roughness meter (needle tip diameter 2 μm) conforming to JIS B 0651:2022. The measurement is performed three times for each sample, and the average of the arithmetic mean roughness Ra obtained from the three measurements is calculated. The calculated average value is taken as the surface roughness Ra of the steel plate.

[0104] The abrasive material used in shot blasting is not particularly limited, but for example, steel balls (shots) with a central particle size of 40 to 450 μm can be used. Examples of such steel balls include WINOA IKK JAPAN's TSH30. The amount of abrasive material projected is, for example, 5 to 400 kg / m. ２ The projection rate is preferably 60 kg / m². ２ The above, and more preferably 100 kg / m ２ That concludes the explanation. The projection speed of the projection material is 5 kg / second or more, preferably 30 kg / second or more, and more preferably 60 kg / second or more.

[0105] [Cold Rolling Process] The cold rolling process is a process in which hot-rolled steel sheets, after shot blasting, are cold-rolled to obtain cold-rolled steel sheets. In the cold rolling process, the convex parts of the uneven structure on the surface of the steel sheet formed by shot blasting are crushed and flattened, thereby introducing the above-mentioned large strain into the outermost layer of the steel sheet (the range from the outermost surface to a depth of 4 μm or less). At this time, the surface roughness of the steel sheet becomes smaller than the surface roughness after shot blasting. The surface roughness Ra of the steel sheet after the cold rolling process is 0.1 to 2.0 μm. The change in surface roughness Ra of the steel sheet before and after the cold rolling process is, for example, 0.8 μm or more, and may be 1.4 μm or more or 2.5 μm or more. In particular, by setting the projection speed of the abrasive material in the shot blasting process to 30 kg / second or more, and the change in surface roughness Ra before and after the cold rolling process to 1.4 μm or more, the thickness of the region with a C concentration of 0.02% or more and less than 0.05% can be set to 5.0 μm or more, and the solid solution Mn concentration in the ferrite phase within 2.0 μm of the steel sheet surface can be set to 0.4% or less. Furthermore, by setting the projection speed of the abrasive material in the shot blasting process to 60 kg / second or more, and the change in surface roughness Ra before and after the cold rolling process to 2.5 μm or more, the thickness of the region with a C concentration of 0.02% or more and less than 0.05% can be set to 10.0 μm or more.

[0106] In the cold rolling process, the reduction ratio can be appropriately determined according to the desired metal structure and sheet thickness, and may be, for example, 20 to 80%. After the cold rolling process, the material may be cooled to room temperature by air cooling, for example.

[0107] [Annealing Process] The annealing process is a process in which the cold-rolled steel sheet, that is, the cold-rolled steel sheet into which the above-mentioned specific strain has been introduced, is annealed under specific high dew point conditions.

[0108] In the annealing process, first, as the temperature rises, recrystallization occurs in the outermost layer where the specific strain described above has been introduced, forming a fine ferrite phase. Furthermore, internal oxides of Mn are formed at the grain boundaries of this ferrite phase. Then, as the temperature rises further and exceeds the A1 transformation point, the fine ferrite phase transforms into an austenite phase, and the internal oxides pin the growth of austenite grains. Decarburization also begins above the A1 transformation point, but the formation of the internal oxides of Mn reduces the amount of metallic Mn in solid solution (i.e., a Mn-depleted layer is formed), suppressing external oxidation of Mn on the outermost surface of the steel. As a result, decarburization progresses further, that is, the inhibition of decarburization is suppressed.

[0109] In this way, the annealing process promotes decarburization of the surface layer of the steel sheet, thereby reducing the solid-solution Mn concentration. As a result, the steel sheet after the annealing process possesses both the above-mentioned characteristics regarding C concentration (a thickness of 2.0 μm or more in the region where the C concentration is 0.02% or more and less than 0.05%) and the characteristics regarding solid-solution Mn concentration (a solid-solution Mn concentration of 1.0% or less in the ferrite phase within 2.0 μm of the steel sheet surface).

[0110] The specific conditions for the annealing process are as follows: First, the steel sheet is heated from room temperature to the holding temperature in an atmosphere with a dew point of -20°C to 20°C. The holding temperature is in the range of 750°C to 900°C. The sheet is held at this holding temperature for 40 to 300 seconds. The holding time is preferably 80 to 200 seconds, and more preferably 100 to 200 seconds.

[0111] The atmosphere during the annealing process may be a reducing atmosphere, more specifically, a reducing atmosphere containing nitrogen and hydrogen. Examples of a reducing atmosphere include one containing 1 to 10 volume percent hydrogen (for example, 2 volume percent hydrogen and nitrogen in balance).

[0112] The steel sheet after the annealing process is then subjected to the next plating process.

[0113] [Plating Process] The plating process involves applying hot-dip galvanizing to the surface of the annealed steel sheet (base steel sheet). This plating process forms a hot-dip galvanized layer on at least a portion of the surface of the annealed steel sheet. In other words, a hot-dip galvanized steel sheet is obtained.

[0114] The plating process should be carried out according to methods known to those skilled in the art. The conditions for the plating process should be set appropriately, taking into consideration the chemical composition, thickness, and amount of the plating layer. The type and chemical composition of the plating layer are as described above.

[0115] For example, a hot-dip galvanized steel sheet may be obtained by immersing an annealed steel sheet in a molten zinc bath having an Al concentration of 0.155% by mass or more and less than 0.190% by mass for 1.0 to 15.0 seconds. The amount of Al in the plating film can be adjusted by the composition of the molten zinc bath, the bath temperature, and the immersion time in the molten zinc bath.

[0116] The hot-dip galvanized steel sheet obtained through the plating process is subjected to the next alloying process.

[0117] [Alloying Process] The alloying process is a process of applying an alloying treatment to a hot-dip galvanized steel sheet. By applying an alloying treatment to a hot-dip galvanized steel sheet, an alloyed hot-dip galvanized steel sheet is obtained.

[0118] The alloying treatment may be carried out according to methods known to those skilled in the art. The conditions for the alloying treatment should be set appropriately considering the chemical composition, thickness, and amount of adhesion of the plating layer. For example, the alloying treatment may be carried out by holding the plated surface at a temperature of 500 to 600°C for 5 to 30 seconds.

[0119] As described above, the alloyed hot-dip galvanized steel sheet of this embodiment can be obtained. In particular, by performing shot blasting on the hot-rolled steel sheet after the hot-rolling process at a projection speed of 5 kg / second or more, and then controlling the change in surface roughness before and after the cold-rolling process to 0.8 μm or more, a specific strain can be applied to the surface layer of the steel sheet. Furthermore, by annealing the steel sheet under specific high dew point conditions, namely, holding it in an atmosphere with a dew point of -20°C to 20°C at a holding temperature of 750°C to 900°C for 40 to 300 seconds, the internal oxidation of Mn can be promoted and the external oxidation of Mn on the surface of the steel sheet can be suppressed (i.e., decarburization of the surface layer of the steel sheet can be promoted). As described above, the alloyed hot-dip galvanized steel sheet obtained in this manner has a specific chemical composition and is characterized by having a thickness of 2.0 μm or more in the region where the C concentration is 0.02% or more and less than 0.05% as determined by GDS analysis, and a solid-solution Mn concentration of 1.0% or less in the ferrite phase within 2.0 μm of the steel sheet surface. In other words, as described above, the alloyed hot-dip galvanized steel sheet of this embodiment exhibits excellent bendability and hydrogen embrittlement resistance because the decarburization of the steel sheet surface is promoted and the solid-solution Mn concentration is reduced.

[0120] As described above, in this embodiment, the alloyed hot-dip galvanized steel sheet preferably has a thickness of 5.0 μm or more in the region where the C concentration is 0.02% or more and less than 0.05%. An alloyed hot-dip galvanized steel sheet that satisfies these characteristics can be obtained by further employing manufacturing conditions in which the projection speed of the abrasive material in the shot blasting process is 30 kg / second or more, and the change in surface roughness Ra before and after the cold rolling process is 1.4 μm or more.

[0121] Similarly, in this embodiment, it is more preferable that the alloyed hot-dip galvanized steel sheet has a thickness of 10.0 μm or more in the region where the C concentration is 0.02% or more and less than 0.05%. An alloyed hot-dip galvanized steel sheet satisfying these characteristics can be obtained by further employing manufacturing conditions in which the projection speed of the abrasive material in the shot blasting process is 60 kg / second or more, and the change in surface roughness Ra before and after the cold rolling process is 2.5 μm or more.

[0122] Furthermore, in this embodiment, the alloyed hot-dip galvanized steel sheet preferably has a solid solution Mn concentration of 0.4% or less in the ferrite phase within 2.0 μm of the steel sheet surface. An alloyed hot-dip galvanized steel sheet satisfying these characteristics can be obtained by further employing manufacturing conditions in which the projection speed of the shot blasting material is 30 kg / second or more, and the change in surface roughness Ra before and after the cold rolling process is 1.4 μm or more.

[0123] Furthermore, in this embodiment, it is more preferable that the solid solution Mn concentration in the ferrite phase within 2.0 μm of the steel sheet surface is 0.2% or less. An alloyed hot-dip galvanized steel sheet satisfying these characteristics can be obtained by further employing manufacturing conditions in which the projection speed of the abrasive material in the shot blasting process is 30 kg / second or more, the change in surface roughness Ra before and after the cold rolling process is 1.4 μm or more, and the holding time in the annealing process is 100 to 200 seconds.

[0124] In addition to the above steps, the method for manufacturing alloyed hot-dip galvanized steel sheets of this embodiment may further include any additional processing steps.

[0125] As described above, the alloyed hot-dip galvanized steel sheet of the present invention has excellent bendability and hydrogen embrittlement resistance, and can therefore be suitably used not only in the automotive field but also in a wide range of fields such as home appliances and building materials. It can be particularly suitably used as an automotive part.

[0126] The present invention is not limited to the embodiments described above or the following examples, and can be appropriately combined, substituted, or modified without departing from the purpose and spirit of the present invention.

[0127] The present invention will be described in more detail below with reference to examples, but the following examples are merely examples of the present invention, and the present invention is not limited in any way to these examples.

[0128] In the following examples, steel sheets according to embodiments of the present invention and steel sheets serving as comparative examples of the present invention were manufactured under various conditions, and the properties of the obtained steel sheets were investigated.

[0129] (Manufacturing of alloyed hot-dip galvanized steel sheet for Test No. 1) First, molten steel was cast using a continuous casting method to form a steel billet having the chemical composition shown in Test No. 1 in Table 1 below. Then, this steel billet was cooled, reheated to 1200°C, hot-rolled, and wound at a winding temperature of 520°C or higher. Hot rolling was carried out by rough rolling and finish rolling, with the finishing rolling ending temperature being 900-1050°C and the reduction ratio of the finish rolling being 30%.

[0130] Next, the surface of the obtained hot-rolled steel sheet (hot-rolled mill scale material) was subjected to shot blasting. Specifically, a projectile (WINOA IKK JAPAN, TSH30) was projected onto the surface of the hot-rolled steel sheet at a projection speed of 5 kg / second. The surface roughness Ra of the steel sheet surface after shot blasting was 1.2 μm.

[0131] A hot-rolled steel sheet that had undergone shot blasting was cold-rolled at a reduction ratio of 50% to obtain a cold-rolled steel sheet with a thickness of 1.6 mm. The surface roughness Ra of the steel sheet after cold rolling was 0.4 μm, and the change in surface roughness Ra before and after cold rolling was 0.8 μm.

[0132] The obtained cold-rolled steel sheet was annealed by heating it from room temperature to a holding temperature of 800°C in an atmosphere with a dew point of -5°C, and holding it at this temperature for 40 seconds.

[0133] Then, the annealed cold-rolled steel sheet was plated. In the plating process, the annealed steel sheet was immersed in a 450°C molten zinc plating bath for 3 seconds, then pulled out at 100 mm / second, and N ２ The plating adhesion rate was reduced to 50 g / m² by wiping gas. ２ The material was then adjusted. Subsequently, an alloying treatment was performed at 520°C for 30 seconds to obtain Test No. 1 alloyed hot-dip galvanized steel sheet (Zn-0.09%Al-10%Fe(GA)), which is an example of the present invention.

[0134] (Manufacturing of alloyed hot-dip galvanized steel sheet of Test No. 2) Except for changing the chemical composition to that shown in Test No. 2 in Table 1 below and changing the projection speed of the shot blasting treatment to 30 kg / second, an alloyed hot-dip galvanized steel sheet of Test No. 2, which is an example of the present invention, was obtained in the same manner as the steel sheet of Test No. 1.

[0135] (Manufacturing of alloyed hot-dip galvanized steel sheets for Tests No. 3-28 and 35-37) Except for changing the chemical composition to that shown in Table 1 below, and changing the projection speed and annealing conditions for the shot blasting treatment to those shown in Table 2 below, alloyed hot-dip galvanized steel sheets for Tests No. 3-28 and 35-37, which are examples of the present invention, were obtained in the same manner as in Test No. 1.

[0136] (Manufacturing of alloyed hot-dip galvanized steel sheets for Tests No. 29-34 and 38-42) Except for changing the chemical composition to that shown in Table 1 below and changing the projection speed of the shot blasting treatment or the annealing conditions to those shown in Table 2 below, alloyed hot-dip galvanized steel sheets for Tests No. 29-34 and 38-42, which serve as comparative examples, were obtained in the same manner as in Test No. 1.

[0137] Analysis of the chemical composition of each alloyed hot-dip galvanized steel sheet obtained in Tests No. 1 to 42 revealed that each was similar in chemical composition to the steel billet before hot rolling. Furthermore, in the chemical composition of each alloyed hot-dip galvanized steel sheet in Tests No. 1 to 42, the oxygen content was 0.01% or less in all cases.

[0138]

[0139] For each of the alloyed hot-dip galvanized steel sheets obtained as described above (Test Nos. 1 to 42), the thickness of the region with a carbon concentration of 0.02% or more and less than 0.05% determined by GDS analysis, the solid solution Mn concentration of the ferrite phase within 2.0 μm of the steel sheet surface, and the Vickers hardness were measured. Furthermore, the bendability and hydrogen embrittlement resistance of each alloyed hot-dip galvanized steel sheet (Test Nos. 1 to 42) were evaluated according to the following evaluation method. These measurement and evaluation results are shown in Table 2 below.

[0140] Note that the underlines next to the various numerical values ​​in Tables 1 and 2 below indicate that they are outside the scope of the present invention. Similarly, while manufacturing conditions that deviate from the manufacturing conditions envisioned by the inventors are underlined, this does not limit the alloyed hot-dip galvanized steel sheets according to the present invention.

[0141] <Evaluation of Bendability> The bendability of alloyed hot-dip galvanized steel sheets will be evaluated by performing a bending test in accordance with the VDA standard (VDA 238-100:2020-07) specified by the German Association of the Automotive Industry, and the maximum bending angle obtained from this bending test will be evaluated based on the evaluation criteria below. The conditions for the bending test will be as follows.

[0142] Specimen dimensions: 60 mm x 30 mm Specimen thickness: 1.6 mm Bending edge: Parallel to the width direction of the plate Test method: Roll support, punch pressing Roll diameter: φ30 mm Punch shape: Tip radius = 0.4 mm Distance between rolls: 2.0 x plate thickness (mm) + 0.5 mm Pressing speed: 20 mm / min Testing machine: SHIMADZU AUTOGRAPH 20kN

[0143] (Evaluation Criteria) AAA: Maximum bending angle is 30° or more AA: Maximum bending angle is 25° or more A: Maximum bending angle is 20° or more B: Maximum bending angle is less than 20°

[0144] The evaluation criteria are as follows: a rating of A or higher (i.e., ratings A, AA, and AAA) indicates excellent bendability, while a rating of B indicates poor bendability. A rating of AAA indicates extremely excellent bendability.

[0145] <Evaluation of Hydrogen Embrittlement Resistance> Two parallel longitudinal cuts reaching the base steel sheet were made in an alloyed hot-dip galvanized steel sheet. Then, a saltwater immersion test (SDT) was simulated by immersing the sheet in a 5% NaCl aqueous solution at 50°C for 480 hours. The amount of diffusible hydrogen in the alloyed hot-dip galvanized steel sheet after immersion was measured by the temperature rise desorption method. Specifically, the alloyed hot-dip galvanized steel sheet was heated to 400°C in a heating furnace equipped with gas chromatography, and the total amount of hydrogen released (amount of hydrogen desorption from the sample) was measured as the temperature dropped to 250°C. The measured amount of hydrogen was evaluated based on the following evaluation criteria.

[0146] (Evaluation Criteria) AAA: 0.2 ppm or less AA: greater than 0.2 ppm, 0.3 ppm or less A: greater than 0.3 ppm, 0.4 ppm or less B: greater than 0.4 ppm

[0147] The evaluation criteria are as follows: an evaluation of A or higher (i.e., evaluations A, AA, and AAA) indicates excellent resistance to hydrogen embrittlement, while an evaluation of B indicates poor resistance to hydrogen embrittlement. An evaluation of AAA indicates extremely excellent resistance to hydrogen embrittlement.

[0148]

[0149] The alloyed hot-dip galvanized steel sheets No. 1-28 and 35-37 are examples of the present invention, and as shown in Table 2, all of them exhibited excellent bendability and hydrogen embrittlement resistance. On the other hand, the alloyed hot-dip galvanized steel sheets No. 29-34 and 38-42, obtained under manufacturing conditions that did not yield the alloyed hot-dip galvanized steel sheets of the present invention, are comparative examples. Their chemical composition, the thickness of the region in the steel sheet surface layer with a C concentration of 0.02% or more and less than 0.05%, and the solid solution Mn concentration were all outside the range of the present invention, and all of them exhibited inferior bendability and hydrogen embrittlement resistance.

[0150] In Test No. 29, the high Si content and the low dew point and short holding time during annealing likely prevented sufficient internal oxidation of Mn during annealing, resulting in the formation of external Mn oxides on the steel sheet surface. In other words, decarburization was not sufficiently promoted on the surface of the steel sheet, and the concentration of solid-solution Mn could not be reduced. As a result, the bending properties and hydrogen embrittlement resistance were likely inferior.

[0151] In Test No. 30, the high Si content and excessively high dew point during annealing likely prevented sufficient internal oxidation of Mn during the annealing process, resulting in the formation of external Mn oxides on the steel sheet surface. This suggests that decarburization was not sufficiently promoted in the surface layer of the steel sheet, and the concentration of solid-solution Mn could not be reduced. Consequently, the bending properties and hydrogen embrittlement resistance were likely inferior.

[0152] In Test No. 31, the high Si content and low holding temperature during annealing likely prevented sufficient internal oxidation of Mn during the annealing process, resulting in the formation of external Mn oxides on the steel sheet surface. This suggests that decarburization was not sufficiently promoted in the surface layer of the steel sheet, and the concentration of solid-solution Mn could not be reduced. Consequently, the bending properties and hydrogen embrittlement resistance were likely inferior.

[0153] In test No. 32, the high Si content and short holding time during annealing likely prevented sufficient internal oxidation of Mn during annealing, resulting in insufficient decarburization on the steel sheet surface. Consequently, the bending properties and hydrogen embrittlement resistance were likely inferior.

[0154] In test No. 33, the high Si content and low projection speed of the shot blasting treatment likely prevented sufficient internal oxidation of Mn during annealing, resulting in insufficient decarburization of the steel sheet surface. Consequently, the bending properties and hydrogen embrittlement resistance were likely inferior.

[0155] In test No. 34, since shot blasting was not performed, it is thought that the internal oxidation of Mn during annealing was not sufficiently promoted, and decarburization on the surface of the steel sheet was not sufficiently promoted. As a result, the bending properties and hydrogen embrittlement resistance were inferior.

[0156] In Test No. 38, the annealing was performed at a low dew point, which likely prevented sufficient internal oxidation of Mn during annealing, resulting in the formation of external Mn oxides on the steel sheet surface. In other words, decarburization was not sufficiently promoted on the surface of the steel sheet, and the concentration of solid-solution Mn could not be reduced. As a result, the bending properties and hydrogen embrittlement resistance were likely inferior.

[0157] In Test No. 39, the annealing was performed at an excessively high dew point, which is thought to have prevented sufficient internal oxidation of Mn during annealing, resulting in the formation of external Mn oxides on the steel sheet surface. In other words, decarburization was not sufficiently promoted in the surface layer of the steel sheet, and the concentration of solid-solution Mn could not be reduced. As a result, the bending properties and hydrogen embrittlement resistance were deemed to be inferior.

[0158] In Test No. 40, the annealing was performed at a low holding temperature, which likely resulted in insufficient internal oxidation of Mn during annealing, leading to the formation of external Mn oxides on the steel sheet surface. In other words, decarburization was not sufficiently promoted on the surface of the steel sheet, and the concentration of solid-solution Mn could not be reduced. As a result, the bending properties and hydrogen embrittlement resistance were likely inferior.

[0159] In Test No. 41, the short holding time during annealing likely prevented sufficient internal oxidation of Mn during the annealing process, resulting in insufficient decarburization of the steel sheet surface. Consequently, the bending properties and hydrogen embrittlement resistance were likely inferior.

[0160] In Test No. 42, the shot blasting treatment was performed at a low projection speed, which is thought to have prevented sufficient internal oxidation of Mn during annealing, and thus insufficient decarburization on the surface of the steel sheet. As a result, the bending properties and hydrogen embrittlement resistance were deemed to be inferior.

Claims

1. A steel plate and a plating layer containing Zn and 7 to 18 mass% Fe, disposed on at least a portion of the surface of the steel plate, wherein the chemical composition of the steel plate is, in mass%, C: 0.05 to 0.40%, Mn: 1.0 to 5.0%, P: 0.0300% or less, S: 0.0300% or less, N: 0.0200% or less, Si: 0 to 0.65%, sol. It contains Al: 0-3.0%, O: 0-0.01%, B: 0-0.0100%, Ti: 0-0.1500%, Nb: 0-0.150%, V: 0-0.150%, Cr: 0-2.00%, Ni: 0-2.00%, Cu: 0-2.00%, Mo: 0-1.00%, W: 0-1.00%, Ca: 0-0.1000%, Mg: 0-0.100%, Zr: 0-0.500%, Hf: 0-0.100%, Sn: 0-0.100%, As: 0-0.100%, and REM: 0-0.100%, with the remainder being Fe and impurities. A hot-dip galvanized steel sheet alloyed with a glow discharge emission spectrometer, measured from the surface of the steel sheet in the depth direction, is characterized in that the thickness of the region with a C concentration of 0.02% or more and less than 0.05% is 2.0 μm or more, and the solid solution Mn concentration in the ferrite phase within 2.0 μm of the surface layer of the steel sheet is 1.0% or less.

2. The chemical composition of the steel sheet is, in mass%, Si: 0.001 to 0.65%, sol. Al: 0.001-3.0%, O: 0.001-0.01%, B: 0.0001-0.0100%, Ti: 0.0001-0.1500%, Nb: 0.0001-0.150%, V: 0.001-0.150%, Cr: 0.001-2.00%, Ni: 0.001-2.00%, Cu: 0.001-2.00%, Mo: 0.001-1.00%, W: 0.0001-1.000%, Ca: 0.0001-0.1000%, Mg: 0.0001~0.100%, Zr: 0.001~0.500%, The alloyed hot-dip galvanized steel sheet according to claim 1, characterized by containing one or more of the following: Hf: 0.0001 to 0.100%, Sn: 0.0001 to 0.100%, As: 0.0001 to 0.100%, and REM: 0.0001 to 0.100%.

3. The alloyed hot-dip galvanized steel sheet according to claim 1 or 2, characterized in that, as determined by glow discharge emission spectroscopy, the thickness of the region where the C concentration is 0.02% or more and less than 0.05% is 5.0 μm or more.

4. The alloyed hot-dip galvanized steel sheet according to claim 1 or 2, characterized in that, as determined by glow discharge emission spectroscopy, the thickness of the region where the C concentration is 0.02% or more and less than 0.05% is 10.0 μm or more.

5. The alloyed hot-dip galvanized steel sheet according to claim 1 or 2, characterized in that the solid solution Mn concentration in the ferrite phase within 2.0 μm of the surface layer of the steel sheet is 0.4% or less.

6. The alloyed hot-dip galvanized steel sheet according to claim 1 or 2, characterized in that the solid solution Mn concentration in the ferrite phase within 2.0 μm of the surface layer of the steel sheet is 0.2% or less.

7. The alloyed hot-dip galvanized steel sheet according to claim 1 or 2, characterized in that the Vickers hardness at a depth of 1 / 4 of the thickness of the steel sheet is 360 Hv or more.

8. The alloyed hot-dip galvanized steel sheet according to claim 1 or 2, characterized in that the Vickers hardness at a depth of 1 / 4 of the thickness of the steel sheet is 460 Hv or more.

9. The alloyed hot-dip galvanized steel sheet according to claim 1 or 2, characterized in that the Vickers hardness at a depth of 1 / 4 of the thickness of the steel sheet is 550 Hv or more.

10. A component comprising an alloyed hot-dip galvanized steel sheet as described in claim 1 or 2.

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