Galvanized steel sheet

Abstract

This zinc-plated steel sheet comprises a steel sheet and a zinc plating layer arranged on the steel sheet, in which a metal structure at a depth corresponding to 1 / 4 of the thickness of the steel sheet from the surface of the steel sheet comprises, in % by area, 2.0 to 25.0% of ferrite, 10.0% or less of bainite, more than 60.0% and 93.0% or less of tempered martensite and 5.0% or more of retained austenite, and the area ratio of the retained austenite that contacts with a 30° grain boundary, has an Mn concentration that is 1.2 times larger than the average Mn concentration, and also has a crystal grain diameter of 0.3 to 2.0μm is 3.0% or more.

Description

[Technical Field]

[0001] This invention relates to galvanized steel sheets. This application claims priority based on Japanese Patent Application No. 2021-191746, filed in Japan on November 26, 2021, and the contents of that application are incorporated herein by reference. [Background technology]

[0002] In recent years, efforts to reduce carbon dioxide emissions have been made in many fields from the perspective of protecting the global environment. Automobile manufacturers are also actively developing technologies to lighten vehicle bodies in order to improve fuel efficiency. However, since emphasis is also placed on improving collision resistance in order to ensure the safety of occupants, reducing vehicle body weight is not easy.

[0003] To achieve both vehicle weight reduction and collision resistance, the use of high-strength steel plates to thin components is being considered. Therefore, there is a strong demand for steel plates that possess both high strength and excellent workability. Several technologies have been proposed to meet these requirements. While the required formability varies depending on the component due to the various processing methods used for automotive components, ductility is considered a crucial indicator of workability.

[0004] Dual-phase steel sheets (DP steel sheets), which are composed of a composite structure of soft ferrite and hard martensite, and TRIP steel sheets, which utilize transformation-induced plasticity (TRIP), have been conventionally proposed as steel sheets that combine high strength and excellent workability.

[0005] For example, Patent Document 1 discloses a high-strength cold-rolled steel sheet having a structure in which the sum of the area ratios of ferrite and bainitic ferrite is 20% or more and 80% or less, the area ratio of retained austenite is more than 10% and 40% or less, the area ratio of tempered martensite is more than 0% and 50% or less, the proportion of retained austenite with an aspect ratio of 0.5 or less is 75% or more by area ratio, the proportion of retained austenite with an aspect ratio of 0.5 or less that is located at ferrite grain boundaries with an orientation difference of 40° or more is 50% or more by area ratio, and the average KAM value of the bcc phase is 1° or less. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2019 / 131189 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Generally, increasing the strength of a steel sheet makes it more prone to fracture in localized areas of high strain during impact deformation. Therefore, steel sheets used in automobiles are required to have properties that make them less susceptible to fracture in localized areas of high strain during impact deformation, i.e., excellent impact resistance.

[0008] However, as a result of our investigation, we found that the ductility and impact resistance properties of the material described in Patent Document 1 need to be further improved.

[0009] This invention was made in view of the above circumstances. The object of this invention is to provide a galvanized steel sheet having high strength, as well as excellent ductility and impact resistance. [Means for solving the problem]

[0010] The gist of this invention is as follows: (1) A zinc-plated steel sheet according to one aspect of the present invention comprises a steel sheet and a zinc-plated layer disposed on the steel sheet, wherein the chemical composition of the steel sheet is, by mass%, C: 0.150~0.350%, Si: 0.100~2.500%, Mn: 1.50~4.50%, sol.Al: 0.010~1.000%, P: 0.100% or less, S: 0.030% or less, N: 0.100% or less, O: 0.010% or less, Ti: 0~0.200%, Nb: 0~0.025%, V: 0~0.100%, B: 0~0.0100%, Cu: 0~2.00%, Cr: 0~2.00%, Mo: 0~1.00%, Ni: 0~2.00%, Ca: 0~0.0200%, Mg: 0~0.0200%, REM: 0~0.1000%, Bi: 0~0.0200%, One or more of Zr, Co, Zn, and W: total of 0-1.0000%, and Contains Sn: 0-0.100%, The remainder consists of Fe and impurities. The metallographic structure at a position 1 / 4 of the thickness from the surface of the steel plate is In area percentage, Ferrite: 2.0~25.0%, Baynite: 10.0% or less Tempered martensite: over 60.0%, 93.0% or less. Contains 5.0% or more of residual austenite. The area fraction of the retained austenite that is in contact with the 30° grain boundary, has a Mn concentration of 1.2 times or more the average Mn concentration, and has a crystal grain size of 0.3 to 2.0 μm is 3.0% or more. (2) The galvanized steel sheet according to (1) above, wherein the chemical composition of the steel sheet is, in mass %, Ti: 0.001 to 0.200%, Nb: 0.001 to 0.025%, V: 0.001 to 0.100%, B: 0.0001 to 0.0100%, Cu: 0.01 to 2.00%, Cr: 0.01 to 2.00%, Mo: 0.001 to 1.00%, Ni: 0.01 to 2.00%, Ca: 0.0005 to 0.0200%, Mg: 0.0005 to 0.0200%, REM: 0.0005 to 0.1000%, Bi: 0.0005 to 0.0200%, One or more of Zr, Co, Zn, and W: in total 0.0005 to 1.0000%, and Sn: 0.0005 to 0.100% may contain one or more of the group consisting of.

Advantages of the Invention

[0011] [[ID=3 six]] According to the above aspect of the present invention, a galvanized steel sheet having high strength, excellent ductility, and impact resistance characteristics can be provided.

Brief Description of the Drawings

[0012] [Figure 1] It is a diagram for explaining the test method of the three-point bending test.

Modes for Carrying Out the Invention

[0013] Hereinafter, the chemical composition and metal structure of the steel sheet constituting the galvanized steel sheet according to the present embodiment will be described more specifically. However, the present invention is not limited only to the configuration disclosed in the present embodiment, and various modifications are possible without departing from the gist of the present invention.

[0014] The numerical ranges indicated below, separated by a "~", include both a lower and upper limit. Numbers indicated as "less than" or "greater than" are not included in the numerical range. In the following explanation, percentages for the chemical composition of steel plates refer to mass percentages unless otherwise specified.

[0015] chemical composition The chemical composition of the galvanized steel sheet constituting this embodiment is, in mass%, C: 0.150~0.350%, Si: 0.100~2.500%, Mn: 1.50~4.50%, sol.Al: 0.010~1.000%, P: 0.100% or less, S: 0.030% or less, N: 0.100% or less, O: 0.010% or less, and the remainder: Fe and impurities. Each element is described in detail below.

[0016] C: 0.150~0.350% Carbon (C) is an element necessary to obtain the desired strength. If the C content is less than 0.150%, the desired strength cannot be obtained. Therefore, the C content should be 0.150% or more. Preferably, the C content is 0.170% or more, 0.180% or more, or 0.200% or more. On the other hand, if the carbon content exceeds 0.350%, the ductility of the galvanized steel sheet deteriorates, and the desired TS×El cannot be obtained. Therefore, the carbon content should be 0.350% or less. Preferably, the carbon content is 0.330% or less, or 0.300% or less.

[0017] Si: 0.100~2.500% Si has the effect of stabilizing retained austenite and improving ductility. Furthermore, Si has the effect of sounding down steel through deoxidation (suppressing the occurrence of defects such as blowholes in the steel). The above effects cannot be obtained if the Si content is less than 0.100%. Therefore, the Si content should be 0.100% or higher. Preferably, the Si content is 0.500% or higher, or 0.700% or higher. On the other hand, if the Si content exceeds 2,500%, the weldability of the galvanized steel sheet deteriorates. Therefore, the Si content should be 2,500% or less. Preferably, the Si content is 2,000% or less, 1,800% or less, or 1,500% or less.

[0018] Mn: 1.50~4.50% Mn is an element that concentrates in the carbides in the structure of hot-rolled sheets, delaying their dissolution during heating, and stabilizing retained austenite by remaining as Mn-concentrated regions after the carbides have dissolved. If the Mn content is less than 1.50%, the effect of stabilizing retained austenite by Mn concentration in the carbides cannot be obtained, and the desired amount of retained austenite area ratio (hereinafter sometimes referred to as "retained austenite area ratio at 30° grain boundaries") that is adjacent to the 30° grain boundary, has a Mn concentration of 1.2 times or more the average Mn concentration, and has a crystal grain size of 0.3 to 2.0 μm cannot be achieved. Therefore, the Mn content should be 1.50% or more. Preferably, the Mn content is 1.80% or more, 2.00% or more, or 2.30% or more. On the other hand, if the Mn content exceeds 4.50%, the carbides in the hot-rolled sheet structure become excessively concentrated with Mn, delaying the dissolution of the carbides during annealing, and as a result, the desired strength cannot be obtained. Therefore, the Mn content should be 4.50% or less. Preferably, the Mn content is 4.30% or less, 4.00% or less, 3.80% or less, or 3.50% or less.

[0019] sol.Al: 0.010~1.000% Al has the effect of sounding down steel through deoxidation and also has the effect of controlling ferrite transformation. If the sol.Al content is less than 0.010%, the effects of the above effects cannot be obtained. Therefore, the sol.Al content should be 0.010% or more. Preferably, the sol.Al content is 0.030% or more, 0.050% or more, 0.080% or more, or 0.100% or more. On the other hand, if the sol.Al content exceeds 1.000%, alumina precipitates in a cluster-like manner, degrading the ductility of the galvanized steel sheet. Therefore, the sol.Al content should be 1.000% or less. Preferably, the sol.Al content is 0.800% or less, 0.600% or less, 0.400% or less, or 0.200% or less. Note that sol.Al refers to acid-soluble Al, specifically solid-solution Al present in steel.

[0020] P:0.100% or less P is an element commonly found in steel as an impurity, and a lower P content is preferable. In particular, if the P content exceeds 0.100%, the workability and weldability of galvanized steel sheets deteriorate significantly, and the impact resistance also deteriorates. Therefore, the P content should be 0.100% or less. Preferably, the P content is 0.080% or less, 0.060% or less, or 0.040% or less. While a P content of 0% is preferable, it may be 0.001% or more from the viewpoint of refining costs.

[0021] S: 0.030% or less S is an element commonly found in steel as an impurity, and a lower S content is preferable. If the S content exceeds 0.030%, the ductility of the galvanized steel sheet decreases significantly. Therefore, the S content should be 0.030% or less. Preferably, the S content is 0.020% or less, or 0.010% or less. While a sulfur content of 0% is preferable, it may be 0.0001% or more from the viewpoint of refining costs.

[0022] N: 0.100% or less N is an element commonly found in steel as an impurity, and a lower N content is preferable. If the N content exceeds 0.100%, the ductility of the galvanized steel sheet decreases significantly. Therefore, the N content should be 0.100% or less. Preferably, the N content is 0.080% or less, 0.060% or less, or 0.040% or less. While it is preferable that the N content be 0%, it may be 0.0001% or more from the viewpoint of refining costs.

[0023] O: 0.010% or less O is an element that, when present in large quantities in steel, forms coarse oxides that act as fracture initiation points, leading to brittle fracture and hydrogen-induced cracking. When the O content exceeds 0.010%, brittle fracture and hydrogen-induced cracking are more likely to occur. Therefore, the O content should be 0.010% or less. Preferably, the O content is 0.008% or less, 0.006% or less, or 0.004% or less. In order to disperse a large number of fine oxides during the deoxidation of molten steel, the O content may be 0.0005% or more, or 0.001% or more.

[0024] The remainder of the chemical composition of the galvanized steel sheet constituting the galvanized steel sheet according to this embodiment may be Fe and impurities. In this embodiment, impurities are those introduced from raw materials such as ore, scrap, or the manufacturing environment. things It means.

[0025] The chemical composition of the steel sheet according to this embodiment may include the following elements as optional elements in place of a portion of Fe. The lower limit of the content when these optional elements are not included is 0%. The optional elements will be described in detail below.

[0026] Ti: 0.001~0.200% Ti precipitates in steel as carbides or nitrides, and enhances the strength of galvanized steel sheets through a pinning effect that refines the metal structure and precipitation strengthening. To reliably obtain this effect, it is preferable that the Ti content be 0.001% or higher. On the other hand, if the Ti content exceeds 0.200%, the strength of the galvanized steel sheet deteriorates due to excessive ferrite deposition. Therefore, the Ti content should be 0.200% or less.

[0027] Nb: 0.001~0.025% Nb is an element that precipitates as carbides and nitrides in steel, improving its strength through precipitation strengthening. To reliably obtain this effect, it is preferable that the Nb content be 0.001% or higher. However, if the Nb content exceeds 0.025%, the ductility of the galvanized steel sheet deteriorates. Therefore, the Nb content should be 0.025% or less.

[0028] V: 0.001~0.100% V, like Nb, is an element that precipitates as carbides and nitrides in steel, improving its strength through precipitation strengthening. To reliably obtain this effect, it is preferable that the V content be 0.001% or higher. However, if the V content exceeds 0.100%, the ductility of the galvanized steel sheet deteriorates. Therefore, the V content should be 0.100% or less.

[0029] B: 0.0001~0.0100% B has the effect of improving the hardenability of galvanized steel sheets. To reliably obtain this effect, it is preferable that the B content be 0.0001% or more. However, if the B content exceeds 0.0100%, the ductility of the galvanized steel sheet decreases significantly. Therefore, the B content should be 0.0100% or less.

[0030] Cu: 0.01~2.00% Cu has the effect of improving the hardenability of galvanized steel sheets and increasing the strength of galvanized steel sheets by precipitating as carbides in the steel at low temperatures. To reliably obtain these effects, it is preferable that the Cu content be 0.01% or more. However, if the copper content exceeds 2.00%, grain boundary cracking may occur in the slab. Therefore, the copper content should be 2.00% or less.

[0031] Cr: 0.01~2.00% Cr has the effect of improving the hardenability of galvanized steel sheets. To reliably obtain this effect, it is preferable to have a Cr content of 0.01% or more. However, if the chromium content exceeds 2.00%, the chemical conversion treatment properties of galvanized steel sheets are significantly reduced. Therefore, the chromium content should be 2.00% or less.

[0032] Mo: 0.001~1.00% Mo has the effect of increasing the hardenability of galvanized steel sheets and increasing the strength of galvanized steel sheets by precipitating as carbides in the steel. To reliably obtain these effects, it is preferable to have a Mo content of 0.001% or more. However, even if the Mo content exceeds 1.00%, the effects due to the above mechanism become saturated, making it economically undesirable. Therefore, the Mo content should be 1.00% or less.

[0033] Ni: 0.01~2.00% Ni has the effect of improving the hardenability of galvanized steel sheets. To reliably obtain this effect, it is preferable that the Ni content be 0.01% or more. However, since nickel is an expensive element, including large amounts of it is not economically desirable. Therefore, the nickel content should be 2.00% or less.

[0034] Ca: 0.0005~0.0200% Ca has the effect of improving the ductility of galvanized steel sheets by adjusting the shape of inclusions in the steel to a desirable shape. To reliably obtain this effect, it is preferable to have a Ca content of 0.0005% or more. However, if the Ca content exceeds 0.0200%, excessive inclusions are formed in the steel, degrading the ductility of the galvanized steel sheet. Therefore, the Ca content should be 0.0200% or less.

[0035] Mg: 0.0005~0.0200% Mg enhances the ductility of galvanized steel sheets by adjusting the shape of inclusions in the steel to a desirable shape. To reliably obtain this effect, it is preferable to have a Mg content of 0.0005% or more. However, if the Mg content exceeds 0.0200%, excessive inclusions are formed in the steel, degrading the ductility of the galvanized steel sheet. Therefore, the Mg content should be 0.0200% or less.

[0036] REM: 0.0005~0.1000% REM has the effect of improving the ductility of galvanized steel sheets by adjusting the shape of inclusions in the steel to a desirable shape. To reliably obtain this effect, it is preferable to have an REM content of 0.0005% or more. However, if the REM content exceeds 0.1000%, excessive inclusions are formed in the steel, degrading the ductility of the galvanized steel sheet. Therefore, the REM content should be 0.1000% or less. Here, REM refers to a total of 17 elements consisting of Sc, Y, and lanthanides, and the REM content mentioned above refers to the total content of these elements. In the case of lanthanides, they are added industrially in the form of mischmetal.

[0037] Bi: 0.0005~0.0200% Furthermore, Bi has the effect of improving the ductility of galvanized steel sheets by refining the solidification structure. To more reliably obtain the effect of this action, it is preferable that the Bi content be 0.0005% or more. However, if the Bi content exceeds 0.0200%, the effects from the above mechanism become saturated, which is economically undesirable. Therefore, the Bi content should be 0.0200% or less.

[0038] One or more of the following elements: Zr, Co, Zn, and W: Total of 0.0005-1.0000% Sn: 0.0005~0.100% Zr, Co, Zn, and W, as well as Sn, are elements effective in increasing the strength of steel sheets. To reliably obtain this effect, it is preferable that the total content of Zr, Co, Zn, and W be 0.0005% or more, or that the Sn content be 0.0005% or more. The inventors have confirmed that the effects of the zinc-plated steel sheet according to this embodiment are not impaired even if the total amount of Zr, Co, Zn, and W is 1.0000% or less. Therefore, one or more of Zr, Co, Zn, and W may be included in total at a concentration of 1.0000% or less. Furthermore, the inventors have confirmed that the effects of the galvanized steel sheet according to this embodiment are not impaired even if it contains 0.100% or less of Sn. Since a large amount of Sn may cause defects during hot rolling, the Sn content is kept to 0.100% or less.

[0039] The chemical composition of the steel sheet described above can be measured using general analytical methods. For example, it can be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Sol.Al can be measured by ICP-AES using the filtrate obtained after heating and decomposing the sample with acid.C and S can be measured using combustion-infrared absorption spectroscopy, N can be measured using inert gas fusion-thermal conductivity spectroscopy, and O can be measured using inert gas fusion-nondispersive infrared absorption spectroscopy. Furthermore, the chemical composition analysis is performed after grinding at least 150 μm of the zinc plating layer on both the front and back surfaces of the galvanized steel sheet by mechanical grinding.

[0040] Metal structure of steel plate Next, the metallographic structure of the steel sheet constituting the galvanized steel sheet according to this embodiment will be described. In this embodiment, the steel sheet has a metallic structure at a position 1 / 4 of the thickness from the surface of the steel sheet. In area percentage, Ferrite: 2.0~25.0%, Baynite: 10.0% or less Tempered martensite: over 60.0%, 93.0% or less. Contains 5.0% or more of residual austenite. The area fraction of the retained austenite that is in contact with the 30° grain boundary, has a Mn concentration of 1.2 times or more the average Mn concentration, and has a crystal grain size of 0.3 to 2.0 μm is 3.0% or more.

[0041] In this embodiment, the position 1 / 4 of the plate thickness from the surface of the steel plate refers to the region from 1 / 8 of the plate thickness to 3 / 8 of the plate thickness from the surface of the galvanized steel plate. The reason for defining the microstructure at this position is that the microstructure at this position represents the typical microstructure of the steel plate. The following explains each of the regulations.

[0042] Ferrite area ratio: 2.0~25.0% Ferrite is a structure formed when fcc transforms into bcc at relatively high temperatures. If the ferrite area ratio is less than 2.0%, the desired ductility cannot be obtained. Therefore, the ferrite area ratio should be 2.0% or more. Preferably, it should be 5.0% or more, 8.0% or more, or 10.0% or more. On the other hand, if the ferrite area ratio exceeds 25.0%, the desired strength cannot be obtained. Therefore, the ferrite area ratio should be 25.0% or less. Preferably, it should be 23.0% or less, 20.0% or less, or 18.0% or less.

[0043] Baynite: 10.0% or less Bainite is a structure composed of fine crystalline grains and carbides. If the area ratio of bainite exceeds 10.0%, the desired strength and ductility cannot be obtained. Therefore, the area ratio of bainite should be 10.0% or less. Preferably, it is 7.0% or less, 5.0% or less, or 3.0% or less. Since a lower area ratio of bainite is preferable, it may be set to 0%.

[0044] Tempered martensite: over 60.0%, 93.0% or less Tempered martensite is a structure that enhances the strength and ductility of galvanized steel sheets. If the area ratio of tempered martensite is 60.0% or less, the desired strength and ductility cannot be obtained. Therefore, the area ratio of tempered martensite should be greater than 60.0%. Preferably, it should be 63.0% or more, 65.0% or more, 68.0% or more, 70.0% or more, or 75.0% or more. On the other hand, if the area ratio of tempered martensite exceeds 93.0%, the desired ductility cannot be obtained. Therefore, the area ratio of tempered martensite should be 93.0% or less. Preferably, it should be 90.0% or less, 85.0% or less, or 80.0% or less.

[0045] Residual austenite: 5.0% or more Retained austenite is a metallic structure that exists as a face-centered cubic lattice even at room temperature. Retained austenite enhances the ductility of galvanized steel sheets through transformation-induced plasticity (TRIP). If the area ratio of retained austenite is less than 5.0%, the desired ductility cannot be obtained. Therefore, the area ratio of retained austenite should be 5.0% or more. Preferably, it should be 8.0% or more, or 10.0% or more. To obtain a large amount of retained austenite, it is necessary to include a large amount of alloying elements such as carbon, so the area ratio of retained austenite may be 20.0% or less. Preferably, it is 18.0% or less or 15.0% or less.

[0046] The steel sheet according to this embodiment may contain less than 5.0% fresh martensite and pearlite in total as the remaining structure.

[0047] The area ratio of each tissue is measured by the following method. First, a test piece is taken from the galvanized steel sheet with a thickness cross-section parallel to the rolling direction, so that the metallographic structure can be observed at a position 1 / 4 of the way from the surface of the steel sheet (the region from 1 / 8 of the way from the surface to 3 / 8 of the way from the surface) and at the center in the width direction of the sheet.

[0048] After polishing the cross-section of the above test specimen using silicon carbide paper ranging from #600 to #1500, it is finished to a mirror surface 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. Next, the specimen is polished at room temperature using colloidal silica that does not contain alkaline solutions to remove strain introduced into the surface of the sample. At any position in the longitudinal direction of the sample cross-section, the crystal orientation information is obtained by electron beam backscatter diffraction measurement at measurement intervals of 0.1 μm in a region with a length of 50 μm and a depth from 1 / 8 of the plate thickness from the surface to 3 / 8 of the plate thickness from the surface.

[0049] The measurement uses an EBSD analysis system consisting of a thermal field emission scanning electron microscope (JEOL JSM-7001F) and an EBSD detector (TSL DVC5 detector). The vacuum level inside the EBSD analysis system is 9.6 × 10⁻⁶. -5 The parameters are set to Pa or less, with an accelerating voltage of 15kV, an irradiation current level of 13, and an electron beam irradiation level of 62.

[0050] From the obtained crystal orientation information, the "Phase Map" function included in the "OIM Analysis®" software attached to the EBSD analyzer is used to identify regions with an fcc crystal structure. These regions are determined to be retained austenite, and their area fraction is calculated to obtain the area fraction of retained austenite.

[0051] Next, using the "Grain Orientation Spread" function installed in "OIM Analysis (registered trademark)," under the condition that boundaries with a crystal orientation difference of 15° or more are considered grain boundaries, regions where the "Grain Orientation Spread" is 1° or less are extracted as ferrite. The area ratio of the extracted ferrite is obtained by calculating the area ratio of the ferrite.

[0052] Next, the "Grain Average Misorientation" function is used to obtain a Grain Average Image Quality map (GAIQ map). In the obtained GAIQ map, regions surrounded by grain boundaries with a crystal orientation difference of 15° or more are defined as crystal grains. When the maximum "Grain Average Image Quality value (GAIQ value)" of the regions extracted as ferrite is defined as Iα, regions with a GAIQ value greater than Iα / 2 are extracted as bainite, and regions with a GAIQ value less than or equal to Iα / 2 are extracted as tempered martensite. By calculating the area fraction of the extracted bainite regions and the area fraction of the tempered martensite regions, the respective area fractions of bainite and tempered martensite are obtained. The area ratio of the remaining tissue is obtained by subtracting the area ratio of the above-mentioned tissue from 100%.

[0053] To remove contaminants from the surface of the observation area, buff polishing using alumina particles with a particle size of 0.1 μm or less, or methods such as Ar ion sputtering, can be used.

[0054] Area percentage of retained austenite adjacent to a 30° grain boundary, with a Mn concentration of 1.2 times or more the average Mn concentration, and a grain size of 0.3 to 2.0 μm: 3.0% or more The above-mentioned retained austenite can be rephrased as retained austenite that satisfies the following conditions (I) to (III). (I) Touches the grain boundary at 30°. (II) The Mn concentration is 1.2 times or more the average Mn concentration. (III) The crystal grain size is 0.3 to 2.0 μm. If the area ratio of retained austenite (area ratio of retained austenite at 30° grain boundaries) that satisfies the above conditions (I) to (III) is less than 3.0%, the impact resistance properties of the galvanized steel sheet will deteriorate. Therefore, the area ratio of retained austenite should be 3.0% or more. Preferably, it should be 4.0% or more, or 5.0% or more. There is no specific upper limit, but the area ratio of retained austenite may be set to 20.0% or less.

[0055] The area ratio of the retained austenite mentioned above is measured by the following method. First, the specimen is sampled and processed using the same method as when measuring the area fraction of the microstructure. The measurement position is 1 / 4 of the plate thickness from the surface of the steel plate (the region from 1 / 8 of the depth from the surface to 3 / 8 of the depth from the surface) and at the center in the width direction of the plate. Next, the 30° grain boundary is identified using the "Grain Orientation Spread" function installed in the "OIM Analysis®" software included with the EBSD analyzer. Next, the region with a crystal structure of fcc, i.e., retained austenite, is identified using the "Phase Map" function installed in "OIM Analysis®". This identifies the retained austenite adjacent to the 30° grain boundary (condition (I)). Note that retained austenite adjacent to the 30° grain boundary also includes retained austenite present on the 30° grain boundary.

[0056] The Mn concentration in the measurement area where the above measurements were performed is measured using an electron probe microanalyzer (EPMA). The measurement conditions are an acceleration voltage of 15kV and a magnification of 5000x to obtain a distribution image of the Mn concentration. More specifically, the measurement interval is set to 0.4μm, and the Mn concentration is measured at more than 40,000 locations. The average value of the Mn concentrations obtained from all measurement points is considered to be the average Mn concentration. Furthermore, retained austenite adjacent to the 30° grain boundary within the measurement area is identified if its Mn concentration is 1.2 times or more the average Mn concentration (Condition (II)).

[0057] The equivalent circular diameter of retained austenite satisfying conditions (I) and (II) within the above measurement area is calculated to obtain the grain size of the retained austenite. This identifies retained austenite with a grain size of 0.3 to 2.0 μm (condition (III)).

[0058] By calculating the area fraction of retained austenite that satisfies conditions (I) to (III) within the measurement area described above, the area fraction of retained austenite that is in contact with a 30° grain boundary, has a Mn concentration of 1.2 times or more the average Mn concentration, and has a grain size of 0.3 to 2.0 μm is obtained.

[0059] zinc plating layer The galvanized steel sheet according to this embodiment has a galvanized layer on at least one surface of the steel sheet described above. The galvanized layer may be a hot-dip galvanized layer, a hot-dip zinc alloy galvanized layer, or an alloyed zinc galvanized layer and an alloyed zinc alloy galvanized layer obtained by alloying these. It may also contain additive elements other than Zn, such as Al. Furthermore, the amount of the galvanized layer is not particularly limited and may be a general amount.

[0060] When the zinc plating layer is a hot-dip galvanized layer, the Fe content of the hot-dip galvanized layer is preferably 3.0% by mass or less in order to improve adhesion between the steel sheet surface and the hot-dip galvanized layer. The hot-dip galvanized layer and the hot-dip galvanized alloy layer may contain one or more of the following elements: Al, Ag, B, Be, Bi, Ca, Cd, Co, Cr, Cs, Cu, Ge, Hf, Zr, I, K, La, Li, Mg, Mn, Mo, Na, Nb, Ni, Pb, Rb, Sb, Si, Sn, Sr, Ta, Ti, V, W, Zr, and REM, to the extent that they do not impair the corrosion resistance and formability of the galvanized steel sheet. In particular, Ni, Al, and Mg are effective in improving the corrosion resistance of the steel sheet.

[0061] The hot-dip galvanized layer or hot-dip zinc alloy plated layer may be an alloyed zinc plated layer or an alloyed zinc alloy plated layer that has undergone an alloying treatment. When an alloying treatment is applied to the hot-dip galvanized layer or hot-dip zinc alloy plated layer, it is preferable that the Fe content of the alloyed zinc plated layer or alloyed zinc alloy plated layer after the alloying treatment be 7.0 to 13.0 mass% from the viewpoint of improving adhesion between the steel sheet surface and the alloyed plating layer. By applying an alloying treatment to a steel sheet having a hot-dip galvanized layer or hot-dip zinc alloy plated layer, Fe is incorporated into the plating layer, and the Fe content increases. As a result, the Fe content in the plating layer can be made 7.0 mass% or more. In other words, a zinc plated layer with an Fe content of 7.0 mass% or more is an alloyed zinc plated layer or an alloyed zinc alloy plated layer.

[0062] The Fe content in the zinc plating layer can be obtained by the following method: Dissolve and remove only the zinc plating layer using a 5 vol% HCl aqueous solution with an inhibitor added. By measuring the Fe content in the resulting solution using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry), the Fe content (mass%) in the zinc plating layer can be obtained.

[0063] Strength and ductility The galvanized steel sheet according to this embodiment may have a tensile strength of 1180 MPa or higher. A tensile strength of 1180 MPa or higher can contribute to weight reduction of the vehicle body. There is no specific upper limit for the tensile strength, but it may be 1780 MPa or lower. Furthermore, the product of tensile strength (TS) and total elongation (El) (TS × El) may be 16,500 MPa·% or higher. If TS × El is 16,500 MPa·% or higher, it can be determined that the galvanized steel sheet has high strength and excellent ductility. There is no specific upper limit for TS × El, but it may be 26,000 MPa·% or lower.

[0064] Tensile strength and total elongation shall be measured by tensile testing in accordance with JIS Z 2241:2011. The test specimen shall be a No. 5 specimen as specified in JIS Z 2241:2011. The tensile test specimen shall be taken from the 1 / 4 portion from the end in the width direction of the plate, with the longitudinal direction perpendicular to the rolling direction.

[0065] Impact resistance The galvanized steel sheet according to this embodiment may have an impact absorption energy of more than 1.0 kJ during a three-point bending test. If the impact absorption energy during the three-point bending test is more than 1.0 kJ, it can be determined that the galvanized steel sheet has excellent impact resistance. There is no upper limit specified, but it may be 3.0 kJ or less, 2.5 kJ or less, or 2.0 kJ or less.

[0066] The impact absorption energy during a three-point bending test is measured using the following method. First, a test specimen of 800 mm or longer is taken from a galvanized steel sheet, and a hat-shaped test specimen with the cross-section shown in Figure 1 is created. The units in Figure 1 are in mm. The test specimen shown in Figure 1 is obtained by spot welding a 60 mm x 80 mm hat member, which is made from a galvanized steel sheet by bending using a press brake, to a closing plate made from a galvanized steel sheet. The hat member and the closing plate are fastened together by spot welding at 40 mm intervals, with a nugget diameter of ≥ 5 × t / 2 (where t is the plate thickness), so that the center of the spot welds is located at the longitudinal center of the test specimen. This test specimen is placed on support rolls with a radius of 30 mm, which are set at 700 mm intervals, and a three-point bending test is performed by contacting it with an impactor with R=50 mm at a constant speed of 7.2 km / h. The displacement and load until the test specimen breaks are determined, and the product of these (displacement × load) is calculated to obtain the impact absorption energy during the three-point bending test.

[0067] plate thickness The thickness of the galvanized steel sheet according to this embodiment is not particularly limited, but may be 0.6 to 8.0 mm. By setting the thickness of the galvanized steel sheet to 0.6 mm or more, excessive rolling load can be suppressed, and hot rolling can be easily performed. Furthermore, by setting the thickness to 8.0 mm or less, the above-mentioned metallic structure can be easily obtained.

[0068] Manufacturing conditions In the preferred manufacturing method for galvanized steel sheets according to this embodiment, the following steps (1) to (7) are performed sequentially. In this embodiment, the slab temperature and steel sheet temperature refer to the surface temperature of the slab and the surface temperature of the steel sheet, respectively. (1) Heat the slab having the above chemical composition to a temperature of 1220°C or higher. (2) The final three stages of rough rolling are performed at a temperature of 1100°C or higher with a reduction ratio of 20% or more. (3) After rough rolling is completed and before finish rolling begins, the material is held at a temperature of 1000°C or higher for more than 50 seconds. (4) The finishing rolling completion temperature FT shall be in the temperature range of T1(°C)-80°C or higher, the cumulative reduction ratio in the temperature range of T1(°C) or higher shall be 75% or higher, and the cumulative reduction ratio of the final two stages of rolling shall be 20% or higher. Note that T1 (°C) is obtained by the following formula (A). In the following formula, the element symbols indicate the mass percentage content of each element, and 0 is substituted if the element is not present. T1=937+168×Ti+3545×Nb+4500×B...(A) (5) A temperature T of 500℃ or higher, and represented by the following formulas [1] and [2] C The winding temperature (CT) is below (°C). The elemental symbols in the following formulas indicate the mass percentage content of each element. CT≦T C =(C / 0.45+C γθ ) / 0.0019 ···[1] C γθ = 0.015 × Mn + 0.041 × Si + 0.671 ···[2] (6) After winding, the time t expressed by the following formula [3] is maintained at a post-winding holding temperature T that satisfies the winding temperature CT ± 50°C and Tc (°C) or less. C(h) or longer. t C ={a(Tp) 2 +q} / 3600 ···[3] In addition, a, p, and q in the above equation [3] are expressed by the following equations [4] to [6], where T is the holding temperature after winding. The elemental symbols in the following formulas indicate the mass percentage content of each element. In formula [6] below, FT indicates the finish rolling completion temperature, and T1 is expressed by formula (A) above. a=-1.516×C+0.0464×Mn+0.5257×Si+531.2×B...[4] p=680-195×C+23×Si-24×Mn...[5]

number

[0069] By a manufacturing method that controls the above processes in a closely interconnected and inseparable manner, galvanized steel sheets according to this embodiment can be manufactured stably. The following describes each step.

[0070] (1) Slab heating It is preferable to heat the slabs to be subjected to hot rolling to a temperature range of 1220°C or higher. Within this temperature range, the steel sheet temperature may be varied or kept constant. It is preferable to maintain this temperature range for 30 minutes or more. Heating to a temperature of 1220°C or higher allows for control of the shape and amount of prior austenite grains and sufficient dissolution of carbides. As a result, the area ratio of retained austenite and the area ratio of retained austenite at 30° grain boundaries can be increased.

[0071] Furthermore, there are no particular limitations on other manufacturing processes preceding hot rolling. Following melting in a blast furnace or electric furnace, various secondary smelting processes may be carried out, and then slabs may be cast using methods such as conventional continuous casting, ingot casting, or thin slab casting. In the case of continuous casting, the cast slab may be cooled to a low temperature once, then reheated and hot-rolled, or the cast slab may be hot-rolled immediately after casting without cooling to a low temperature. Scrap may be used as raw material. In addition, if necessary, materials that have undergone hot-working or cold-working may be used.

[0072] After the heating and holding described above, it is more preferable to perform slab width reduction at a temperature of 1200°C or higher with a reduction ratio of 10% or more. By performing slab width reduction with a reduction ratio of 10% or more, the retained austenite area ratio at the 30° grain boundary can be made 5% or more, thereby further improving the impact resistance. Although the detailed mechanism is unknown, this slab width reduction results in a higher retained austenite area ratio at the 30° grain boundary.

[0073] The reduction ratio for slab width reduction can be expressed as (1-w1 / w0)×100(%), where w0 is the widthwise length of the slab before reduction and w1 is the widthwise length of the slab after reduction. Methods for slab width reduction include rolling the slab using rolls installed so that the axis of rotation is perpendicular to the slab surface, or sequentially pressing the slab from the width direction.

[0074] (2)Rough rolling In rough rolling, it is preferable to perform the final three stages of rolling at a temperature of 1100°C or higher, and with a reduction ratio of 20% or more in each stage. Performing rough rolling under these conditions allows for the equiaxed arrangement of prior austenite grains through recrystallization. As a result, the area ratio of retained austenite at 30° grain boundaries can be increased. While a reduction ratio of 20% or higher is acceptable, a ratio of 60% or higher, for example, increases the rolling load, leading to roll wear and reduced productivity. Therefore, it is preferable that the reduction ratio in each stage be less than 60%.

[0075] (3) Holding after rough rolling is completed and before finish rolling begins It is preferable to hold the material at a temperature of 1000°C or higher for more than 50 seconds after rough rolling is complete and before finish rolling begins. Holding the material under these conditions promotes the growth of prior austenite grains. As a result, the area ratio of retained austenite at 30° grain boundaries can be increased.

[0076] Methods for maintaining the temperature within the above range include, for example, heating in a heating furnace or induction heating after rough rolling is complete, or using an insulating cover. In addition, the steel plate temperature may be kept constant or fluctuated within a temperature range of 1000°C or higher during the above-mentioned maintenance.

[0077] (4) Finish rolling The finish rolling completion temperature FT is set to a temperature range of T1 (°C) - 80 °C or higher, the cumulative reduction ratio in the temperature range of T1 (°C) or higher is set to 75% or higher, and the cumulative reduction ratio of the final two-stage rolling is preferably set to 20% or higher. By performing finish rolling under these conditions, the prior austenite grains can be controlled to be equiaxed by recovery and recrystallization. As a result, the residual austenite area ratio at 30° grain boundaries can be increased. Also, as long as the cumulative reduction ratio in the final two-stage rolling is 20% or higher, there is no problem even if it is high. However, for example, when it is set to 60% or higher, high-load rolling in a low-temperature range causes deterioration of the sheet shape and reduces productivity. Therefore, preferably, the cumulative reduction ratio of the final two-stage rolling is less than 60%.

[0078] After finish rolling, it is more preferable that the average cooling rate in the temperature range of the finish rolling completion temperature FT to 650 °C is 10 °C / s or higher. By cooling under these conditions, the formation of coarse ferrite in the high-temperature range can be suppressed. As a result, the residual austenite area ratio at 30° grain boundaries can be further increased.

[0079] In addition, in this embodiment, the average cooling rate refers to the value obtained by dividing the temperature drop width of the steel sheet from the start of cooling to the end of cooling by the required time from the start of cooling to the end of cooling.

[0080] (5) Coiling (6) Holding after coiling Coiling is preferably performed at a coiling temperature CT that satisfies 500 °C or higher and the temperature T C (°C) represented by the above formulas [1] and [2] or lower. Further, after coiling, at a holding temperature T that satisfies CT ± 50 °C and Tc (°C) or lower, the time t C (h) represented by the above formula [3] or longer. By performing coiling and holding after coiling under these conditions, the pearlite fraction at the stage before annealing can be controlled within a desired range, and the enrichment of Mn in the cementite in the pearlite can be promoted. As a result, after annealing, the residual austenite area ratio at 30° grain boundaries can be further increased. Furthermore, post-winding retention can be achieved by suppressing heat loss using a heat-insulating furnace or heat-insulating cover. When the coil is discharged from the furnace or the heat-insulating cover is removed and the coil surface is exposed, the end face temperature on the side of the coil can be measured with a radiation thermometer, and the obtained temperature can be considered as the retention temperature T for post-winding retention.

[0081] After winding and holding, pickling and cold rolling may be performed by conventional methods as needed. In cold rolling, the cumulative reduction ratio should be 50% or more.

[0082] (7) Annealing (a) Heating before the first soaking treatment In the heating before the first soaking treatment, it is preferable that the average heating rate in the temperature range of 600°C to Ac1+10°C be 10.0°C / s or less. Heating under these conditions promotes the recrystallization of ferrite while spheroidizing the cementite. As a result, the area ratio of retained austenite at 30° grain boundaries can be further increased. It is even more preferable that the average heating rate in the above temperature range be 5.0°C / s or less.

[0083] In this embodiment, the average heating rate refers to the value obtained by dividing the temperature rise of the steel plate from the start of heating to the completion of heating by the time required from the start of heating to the completion of heating.

[0084] (b) First soaking treatment It is preferable to hold the mixture at a maximum heating temperature of Ac1℃ + 30℃ to 900℃ for 1 to 1000 seconds. By performing the first soaking treatment in a temperature range of Ac1℃ or higher, the desired amount of ferrite and tempered martensite can be obtained. Alternatively, by performing the first soaking treatment in a temperature range of 900℃ or lower, the desired amount of ferrite can be obtained.

[0085] (c) Cooling after the first soaking treatment (first cooling) After the soaking treatment described above, it is preferable that the average cooling rate to the temperature range of 700-600°C be 20.0°C / s or less. Cooling under these conditions allows the ferrite-austenite interface to grow toward the austenite side and extend to the vicinity of the carbide, thereby increasing the area ratio of retained austenite at the 30° grain boundary. It is even more preferable that the average cooling rate to the above temperature range be 10.0°C / s or less.

[0086] (d) Second soaking treatment After the above cooling, it is preferable to hold the material at a temperature of 400-600°C for 60-300 seconds. Performing the second soaking treatment under these conditions allows the ferrite grain boundaries to move with a weak driving force, and the ferrite grain boundaries can be pinned by spherical carbides. As a result, the retained austenite area ratio at the 30° grain boundaries can be increased. If the second soaking treatment temperature exceeds 600°C, it may not be possible to obtain the desired amount of retained austenite area ratio at the 30° grain boundaries. If the second soaking treatment temperature is below 400°C, excessive bainite may be formed. If the holding time is outside the above range, it may not be possible to obtain the desired amount of retained austenite area ratio at the 30° grain boundaries.

[0087] Furthermore, if the second soaking treatment is performed after immersion in the plating bath, the powdering resistance of the plating layer deteriorates significantly. This is because if heat treatment is performed at a temperature of 480°C or higher for 80 seconds or more after immersion in the plating bath, the alloying reaction between the plating and the steel sheet proceeds excessively, and the structure within the plating layer changes from the δ phase, which has excellent ductility, to the Γ phase, which has inferior ductility. Therefore, from the viewpoint of ensuring powdering resistance, it is desirable to perform the second soaking treatment before immersion in the plating bath.

[0088] After the second soaking treatment, a hot-dip galvanized layer is formed on the steel sheet surface by a conventional method. For example, the plating bath temperature can be 440-470°C and the immersion time 5 seconds or less. A hot-dip galvanized bath containing 0.08-0.20% by mass of Al is preferred, but other impurities such as Fe, Si, Mg, Mn, Cr, Ti, and Pb may also be included. Furthermore, it is preferable to control the plating weight by a known method such as gas wiping. The plating weight should be 25-75 g / m² per side. 2 That's all you need to do.

[0089] A steel sheet with a hot-dip galvanized layer may be subjected to an alloying treatment as needed to form an alloyed zinc-plated layer or an alloyed zinc-alloy plated layer. In this case, if the alloying temperature is less than 460°C, the alloying rate will be slow, which will not only impair productivity but also cause unevenness in the alloying treatment. Therefore, it is preferable to set the alloying temperature at 460°C or higher. Furthermore, it is preferable to set the holding time at 460°C or higher to less than 80 seconds. On the other hand, if the alloying temperature exceeds 600°C, the alloying may proceed excessively, potentially degrading the plating adhesion of the steel sheet. Furthermore, the pearlite transformation may be accelerated, making it impossible to obtain the desired metallic structure. Therefore, it is preferable to keep the alloying temperature below 600°C.

[0090] (e) Cooling after the second soaking treatment (and after the plating layer has formed) (second cooling) Next, it is preferable to cool the mixture to a temperature range of over 100°C and 300°C or less. By cooling under these conditions, the desired amount of retained austenite can be obtained.

[0091] (f) Third soaking treatment After the above cooling, it is preferable to hold the material at a temperature of 300 to 420°C for 100 to 1000 seconds. Performing the third soaking treatment at a temperature of 300°C or higher stabilizes the retained austenite and ensures retained austenite at room temperature. Furthermore, performing the third soaking treatment at a temperature of 420°C or lower suppresses excessive decomposition of retained austenite and excessive formation of bainite.

[0092] After the third soaking treatment, the sheet should be cooled to room temperature. Temper rolling may be performed as needed to flatten the galvanized steel sheet and adjust its surface roughness. [Examples]

[0093] Next, the effects of one aspect of the present invention will be described in more detail with reference to examples. However, the conditions in the examples are merely examples of conditions adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to these examples of conditions. The present invention can adopt various conditions as long as they do not depart from the spirit of the invention and achieve the objectives of the present invention.

[0094] Steel having the chemical composition shown in Table 1 was melted down, and slabs with a thickness of 240 to 300 mm were produced by continuous casting. Using the obtained slabs, galvanized steel sheets (hot-dip galvanized steel sheets, hot-dip zinc alloy plated steel sheets, alloyed zinc plated steel sheets, or alloyed zinc alloy plated steel sheets) shown in Tables 4A to 4C were obtained under the manufacturing conditions shown in Tables 2A to 3C. After winding and holding, the material was pickled and cold-rolled using conventional methods. During cold rolling, the cumulative reduction ratio was set at 50% or more. The holding time at the alloying temperature was less than 80 seconds. After the third soaking treatment, the material was cooled to room temperature.

[0095] The obtained galvanized steel sheets were subjected to metallographic observation, tensile testing, and three-point bending testing using the method described above. The obtained measurement results are shown in Tables 4A to 4C.

[0096] If the tensile strength was 1180 MPa or higher, the galvanized steel sheet was deemed to have high strength and was judged to be acceptable. On the other hand, if the tensile strength was less than 1180 MPa, the galvanized steel sheet was deemed not to have high strength and was judged to be unacceptable.

[0097] If the product of tensile strength (TS) and total elongation (El) (TS × El) was 16,500 MPa·% or higher, the galvanized steel sheet was judged to be acceptable as it possessed high strength and excellent ductility. On the other hand, if the product of tensile strength (TS) and total elongation (El) (TS × El) was less than 16,500 MPa·%, the galvanized steel sheet was judged to be unacceptable as it did not possess high strength and excellent ductility.

[0098] If the impact absorption energy during the three-point bending test exceeded 1.0 kJ, the galvanized steel sheet was judged to be a good product with excellent impact resistance. On the other hand, if the impact absorption energy during the three-point bending test was 1.0 kJ or less, the galvanized steel sheet was judged to be a bad product with excellent impact resistance.

[0099] [Table 1]

[0100] [Table 2A]

[0101] [Table 2B]

[0102] [Table 2C]

[0103] [Table 3A]

[0104] [Table 3B]

[0105] [Table 3C]

[0106] [Table 4A]

[0107] [Table 4B]

[0108] [Table 4C]

[0109] Tables 4A to 4C show that the galvanized steel sheets according to the present invention have high strength, as well as excellent ductility and impact resistance. Furthermore, in the present invention, where slab width reduction was performed with a reduction ratio of 10% or more, the retained austenite area ratio at the 30° grain boundary was 5.0% or more, and an impact absorption energy of 1.7 kJ or more was obtained. On the other hand, it can be seen that the galvanized steel sheet in the comparative example does not possess one or more of the above characteristics. [Industrial applicability]

[0110] According to the above-described embodiment of the present invention, it is possible to provide a galvanized steel sheet having high strength, as well as excellent ductility and impact resistance properties.

Claims

1. A galvanized steel sheet comprising a steel sheet and a zinc plating layer disposed on the steel sheet, wherein the chemical composition of the steel sheet is, by mass%, C: 0.150-0.350%, Si: 0.100-2.500%, Mn: 1.50-4.50%, Sol. Al: 0.010–1.000%, P: 0.100% or less, S: 0.030% or less, N: 0.100% or less, O: 0.010% or less, Ti: 0-0.200%, Nb: 0 to 0.025%, V: 0 to 0.100%, B: 0 to 0.0100%, Cu: 0-2.00%, Cr: 0-2.00%, Mo: 0-1.00%, Ni: 0-2.00%, Ca: 0-0.0200%, Mg: 0 to 0.0200%, REM: 0-0.1000%, Bi: 0 to 0.0200%, One or more of Zr, Co, Zn, and W: total of 0 to 1.0000%, and Sn: Contains 0-0.100%, The remainder consists of Fe and impurities. The metallographic structure at a position 1 / 4 of the thickness from the surface of the steel plate is In area percentage, Ferrite: 2.0–25.0%, Baynite: 10.0% or less Tempered martensite: over 60.0%, 93.0% or less. Contains 5.0% or more of residual austenite. A galvanized steel sheet characterized by having retained austenite in contact with a 30° grain boundary, with a Mn concentration of 1.2 times or more the average Mn concentration, and a crystal grain size of 0.3 to 2.0 μm, with an area ratio of 3.0% or more.

2. The chemical composition of the steel plate is, in mass%, Ti: 0.001 to 0.200%, Nb: 0.001 to 0.025%, V: 0.001 to 0.100%, B: 0.0001 to 0.0100%, Cu: 0.01-2.00%, Cr: 0.01-2.00%, Mo: 0.001-1.00%, Ni: 0.01-2.00%, Ca: 0.0005-0.0200%, Mg: 0.0005-0.0200%, REM: 0.0005-0.1000%, Bi: 0.0005-0.0200%, One or more of Zr, Co, Zn, and W: total of 0.0005 to 1.0000%, and Sn: 0.0005-0.100% The zinc-plated steel sheet according to claim 1, characterized in that it contains one or more from the group consisting of the following.

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