Plated steel sheet and manufacturing method therefor

Abstract

The present invention relates to a plated steel sheet and a manufacturing method therefor and, more specifically, to a plated steel sheet and a manufacturing method therefor, the plated steel sheet being suitable for use as a steel material for automobile reinforcements such as bumper beams and sill side beams, and as a still material for the protection of electric vehicle battery cases such as side frames and cross members.

Description

galvanized steel sheet and method of manufacturing the same

[0001] The present invention relates to a galvanized steel sheet and a method for manufacturing the same, and more specifically, to a galvanized steel sheet suitable for use as steel for automotive reinforcement materials such as bumper beams and sill side beams, or steel for protecting electric vehicle battery cases such as side frames and cross members, and a method for manufacturing the same.

[0002] For steel materials primarily used as reinforcement components related to the crash safety of automobile passengers, it is required to possess high processing characteristics, particularly excellent bending characteristics, and ultra-high strength. Accordingly, ultra-high strength steel with a tensile strength of 1470 MPa or higher, manufactured using a single martensite phase, is already being mass-produced and applied as automotive reinforcement materials. However, there is a need to develop ultra-high strength steel with a tensile strength of 1700 MPa or higher to protect passengers and electric vehicle batteries.

[0003] Recently, the Hot Press Forming (HPF) method has been developed, in which a material is formed using a die at a high temperature—an environment conducive to forming—and then water-cooled to secure the required strength. Since the HPF method can secure high strength relative to the same thickness, it is widely used in the manufacture of parts; however, the HPF method has the disadvantage of requiring excessive equipment investment and increased process costs. Therefore, there is a need to develop materials for cold stamping and roll forming. Specifically, there is a need to develop cold-rolled steel sheets that are suitable for use in cold stamping and roll forming, possess ultra-high strength of 1700 MPa or higher and a high yield ratio to secure crash performance for the protection of passengers and electric vehicle batteries, and have excellent bending characteristics and shape for forming parts.

[0004] Patent Document 1 is a representative prior art of this method. Patent Document 1 relates to a steel having a single-phase martensitic structure containing C: 0.25~0.4%, Si: 1.0% or less, Mn: 1.5~2.5%, P: 0.02% or less, S: 0.003% or less, Al: 0.01~0.1%, N: 0.005% or less, B: 0.0005~0.005%, and also containing Ti: 0.005~0.1%, Nb: 0.005~0.1%, and a total of 0.005~0.1%. It discloses that the steel can be obtained by heating and holding the steel in a temperature range above the Ae3 transformation point and below 900°C, then rapidly cooling it to below 200°C at an average cooling rate of 300°C / s, and subsequently tempering it at below 250°C. However, in the case of Patent Document 1, there is a problem in that defects occur during molding because the shape (flatness) is inferior due to rapid cooling (water cooling).

[0005] Patent Document 2 relates to a thin steel sheet having a high-strength structure comprising C: 0.05% or more and 0.35% or less, Si: 0.01% or more and 2.0% or less, Mn: 0.8% or more and 3.0% or less, P: 0.05% or less, S: 0.005% or less, Al: 0.005% or more and 0.10% or less, and N: 0.0060% or less, with a ferrite area ratio of 0% or more and 90% or less, a bainite area ratio of 5% or less (including 0%), a martensite and tempered martensite area ratio of 10% or more (including 100%), and a retained austenite area ratio of 2.0% or less (including 0%), a standard deviation of yield strength in the width direction of 30 MPa or less, and a maximum bending amount of the steel sheet when sheared at a length of 1 m of 10 mm or less. However, in the case of Patent Document 2, there is a problem that shape defects occur due to rapid cooling after annealing.

[0006] Patent Document 3 contains, in weight percent, C: 0.2~0.4%, Si: 0.5% or less (excluding 0%), Mn: 1.0~2.0%, P: 0.03% or less (excluding 0%), S: 0.015% or less (excluding 0%), Al: 0.1% or less (excluding 0%), Cr: 0.5% or less (excluding 0%), Mo: less than 0.2% (excluding 0%), Ti: 0.1% or less (excluding 0%), Nb: 0.1% or less (excluding 0%), B: 0.005% or less (excluding 0%), N: 0.01% or less (excluding 0%), and the remainder being Fe and other unavoidable impurities; the microstructure consists of a tempered martensite single-phase structure or a mixed structure of martensite + tempered martensite, and the microstructure contains FHAGB per unit area of ​​45㎛ × 45㎛ This invention relates to an ultra-high strength cold-rolled steel sheet with excellent hole expansion properties, having an area of ​​60% or more and an LHAGB of 8mm or more. However, in the case of Patent Document 3, there is no specification regarding the improvement of part forming, impact characteristics, and hydrogen embrittlement of ultra-high strength steel.

[0007] Meanwhile, the introduction of martensite is essential for manufacturing ultra-high-strength steel with a tensile strength of 1,700 MPa or higher. Such steel is prone to brittle fracture caused by hydrogen remaining within or introduced from the outside; this phenomenon is referred to as hydrogen embrittlement. Hydrogen embrittlement causes material failure at a strength lower than the fracture threshold, meaning the material can fracture due to hydrogen embrittlement even when a very small stress is applied compared to the actual fracture strength. In particular, this hydrogen embrittlement becomes more sensitive as the strength of the steel increases. Furthermore, since resistance to hydrogen embrittlement improves with superior bending characteristics even with the same initial hydrogen content, it is necessary to improve the bending properties of the steel.

[0008] [Prior Art Literature]

[0009] (Patent Document 1) Japanese Patent Publication No. JP 2010-248565

[0010] (Patent Document 2) Japanese Patent Publication No. JP 2020-019992

[0011] (Patent Document 3) Korean Published Patent Application No. 2023-0043267

[0012] One aspect of the present invention is to provide a plated steel sheet and a method for manufacturing the same.

[0013] A preferred aspect of the present invention is to provide an ultra-high strength plated steel sheet with excellent hydrogen embrittlement resistance and a method for manufacturing the same.

[0014] The problems of the present invention are not limited to those described above. A person skilled in the art to which the present invention pertains will have no difficulty understanding additional problems of the present invention from the overall contents of this specification.

[0015] One embodiment of the present invention comprises: a base steel sheet; and a Zn plating layer formed on at least one surface of the base steel sheet; wherein the base steel sheet comprises, in weight percent, carbon (C): 0.180–0.330%, silicon (Si): 0.020–0.60%, manganese (Mn): 0.40–2.40%, phosphorus (P): 0.030% or less (excluding 0%), sulfur (S): 0.0050% or less (excluding 0%), boron (B): 0.00050–0.0050%, and the remainder being Fe and other unavoidable impurities; and wherein the base steel sheet has a GND average value (GNDave) of 255×10 12 m -2 ~325×10 12 m -2 The above Zn plating layer includes a Ni enrichment region, and provides a plated steel sheet having a diffusible hydrogen content (Hd) of 0.10 ppm or less.

[0016] The above-mentioned steel sheet may additionally include one or more of the following: aluminum (Al): 0.0050~0.080%, chromium (Cr): 0.0010~0.50%, molybdenum (Mo): 0.0010~0.40%, niobium (Nb): 0.0010~0.10%, titanium (Ti): 0.0050~0.250%, nitrogen (N): 0.010% or less (excluding 0%), copper (Cu): 0.0010~0.30%, and nickel (Ni): 0.0010~0.30%.

[0017] The above-mentioned steel sheet can satisfy the following relationship 1.

[0018] [Equation 1] 0.050 wt% ≤ Cr+Mo+Ni+Cu ≤ 1.0 wt%

[0019] The above-mentioned steel sheet may have a microstructure in area % comprising: a total of one or more of ferrite and bainite: 5% or less (including 0%), and the remainder being one or more of martensite and tempered martensite.

[0020] The above Zn plating layer may have an average thickness of 1.0 to 20.0 μm.

[0021] The above Ni enrichment range may have a maximum Ni content (Ni_max) of 0.010 to 0.40 wt%.

[0022] The above galvanized steel sheet can satisfy the following relationship 2.

[0023] [Equation 2] 0.010 wt% ≤ (Ni_max+Ni_nom) / 2 ≤ 0.350 wt%

[0024] (However, in the above Equation 2, Ni_max refers to the maximum Ni content within the Ni enrichment region, and Ni_nom refers to the average Ni content within the region up to 20㎛ in the thickness direction from the surface of the base steel sheet.)

[0025] The above Ni enrichment region may have an average thickness (Ni_Wave) of 0.40 to 10.0 μm in the region satisfying the above relationship 2.

[0026] The above-mentioned plated steel sheet may have a critical hydrogen content (Hc) of 0.14 ppm or more.

[0027] The above galvanized steel sheet may have a critical hydrogen content (Hc) / diffusible hydrogen content (Hd) of 2.5 or higher.

[0028] The above galvanized steel sheet may have a yield strength (YS): 1200 MPa or more, tensile strength (TS): 1470 MPa or more, total elongation (T_EL): 5.0% or more, and uniform elongation (U_EL): 2.7% or more.

[0029] The above galvanized steel sheet has a hydrogen embrittlement fracture time (Ft): 20 minutes or more, and a tensile strength (TS) / hydrogen embrittlement fracture time (Ft): 19~89 MPa·min -1 It could be.

[0030] Another embodiment of the present invention comprises the steps of: heating a slab comprising, in weight percent, carbon (C): 0.180~0.330%, silicon (Si): 0.020~0.60%, manganese (Mn): 0.40~2.40%, phosphorus (P): 0.030% or less (excluding 0%), sulfur (S): 0.0050% or less (excluding 0%), boron (B): 0.00050~0.0050%, and the remainder being Fe and other unavoidable impurities; finishing hot rolling the heated slab to obtain a hot-rolled steel sheet; coiling the hot-rolled steel sheet; cold rolling the coiled hot-rolled steel sheet to obtain a cold-rolled steel sheet; continuously annealing the cold-rolled steel sheet; first cooling the continuously annealed cold-rolled steel sheet; and second cooling the first cooled cold-rolled steel sheet. The present invention provides a method for manufacturing a plated steel sheet comprising: a step of reheating the secondarily cooled cold-rolled steel sheet and then overaging it; a step of forming a Ni coating layer on at least one surface of the overaged cold-rolled steel sheet; a step of tension leveling the cold-rolled steel sheet on which the Ni coating layer is formed; and a step of forming a Zn plating layer on the surface of the cold-rolled steel sheet on which the Ni coating layer is formed after tension leveling; wherein, during the second cooling, the Mf-second cooling end temperature (T2) is controlled to be 10°C or higher, and the method satisfies the following equation 3.

[0031] [Relationship 3] X = (TL_EL×W Zn ) / W Ni ≤ 1500

[0032] (However, in the above Equation 3, the above TL_EL represents the tension leveling elongation rate, and the above W Zn represents the amount of Zn attached to one side, and the above W Ni represents the amount of Ni deposited on one side.)

[0033] The heating of the above slab can be carried out at 1100~1300℃.

[0034] The above finishing hot rolling can be performed at Ar3 to Ar3+120℃.

[0035] The above winding can be performed at Ms~700℃.

[0036] The above cold rolling can be performed with a cold reduction rate of 35 to 70%.

[0037] The above continuous annealing can be performed at Ac3 to Ac3+120℃ for 50 to 200 seconds.

[0038] The above first cooling can be carried out at a first average cooling rate (CR1) of 0.5 to 6.0°C / s up to a first cooling end temperature (T1) of 620°C to Ac3.

[0039] The above secondary cooling can be carried out at a secondary average cooling rate (CR2) of 40 to 500°C / s up to a secondary cooling end temperature (T2) of 40 to 200°C.

[0040] The above overaging treatment can be performed at an overaging treatment temperature (HT) of 90 to 270°C for an overaging treatment time (ht) of 180 to 900 seconds.

[0041] During the above over-aging treatment, the over-aging treatment temperature (HT) - secondary cooling end temperature (T2) can be controlled to be 30℃ or higher.

[0042] When forming the above Ni coating layer, the amount of Ni attached on one side can be controlled to be 3 to 25 mg / m².

[0043] The above tension leveling can be performed with an elongation rate of 0.05 to 2.0%.

[0044] When forming the above Zn plating layer, the amount of Zn attached on one side can be controlled to be 5 to 120 g / m².

[0045] The following relationship 4 can be satisfied.

[0046] [Equation 4] Y = (CR2×TL_EL) / HT ≤ 1.0

[0047] (However, in the above Equation 4, CR2 represents the secondary average cooling rate, TL_EL represents the tension leveling elongation rate, and HT represents the overaging treatment temperature.)

[0048] According to one aspect of the present invention, a plated steel sheet and a method for manufacturing the same can be provided.

[0049] According to a preferred aspect of the present invention, an ultra-high strength plated steel sheet with excellent hydrogen embrittlement resistance and a method for manufacturing the same can be provided.

[0050] Figure 1 is the result of analyzing the surface layer of Invention Example 1 using GDS.

[0051] Advantageous embodiments of the present invention are described below. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0052] In addition, embodiments of the present invention are provided to more fully explain the present invention to those with average knowledge in the relevant technical field.

[0053] In describing the embodiments of the present invention, if it is determined that a detailed description of known technology related to the present invention may unnecessarily obscure the essence of the present invention, such detailed description will be omitted. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or conventions of the user or operator. Therefore, such definitions should be based on the content throughout this specification. The terms used in the detailed description are merely for describing the embodiments of the present invention and should not be limited in any way. Unless explicitly stated otherwise, expressions in the singular form include the meaning of the plural form.

[0054] In this description, expressions such as “include” or “equipped” are intended to refer to certain characteristics, numbers, steps, actions, elements, parts or combinations thereof, and should not be interpreted to exclude the existence or possibility of one or more other characteristics, numbers, steps, actions, elements, parts or combinations thereof other than those described.

[0055] Unless otherwise specifically defined in the specification of the present invention, % units mean weight %.

[0056] The present invention will be described in detail below through each embodiment or example of the invention. It should be noted that each embodiment or example described in this specification is not limited to a single embodiment or example, but may also be combined with other embodiments or examples. Accordingly, the citation of claims in the patent claims is merely an example of an embodiment, and the technical concept of the present invention should not be interpreted as being limited only to a combination with the cited claims; rather, combinations with various claims are also included within the scope of the technical concept of the present invention.

[0057] Hereinafter, a plated steel sheet according to one embodiment of the present invention will be described.

[0058] The plated steel sheet of the present invention may include a base steel sheet and a Zn plating layer formed on at least one surface of the base steel sheet.

[0059] The above-mentioned steel sheet may contain, in weight percent, carbon (C): 0.180~0.330%, silicon (Si): 0.020~0.60%, manganese (Mn): 0.40~2.40%, phosphorus (P): 0.030% or less (excluding 0%), sulfur (S): 0.0050% or less (excluding 0%), boron (B): 0.00050~0.0050%, and the remainder may consist of Fe and other unavoidable impurities.

[0060] The alloy composition of the base steel sheet of the present invention is described below. Unless otherwise specified, the alloy composition described below refers to weight percent.

[0061] Carbon (C): 0.180~0.330%

[0062] C is an interstitial solid solution element and is the most effective and important element for improving the strength of steel. If the content of C is less than 0.180%, it may be difficult to obtain the strength targeted in the present invention. If the content of C exceeds 0.330%, the strength increases rapidly, and the elongation may be inferior. In addition, hydrogen embrittlement resistance may decrease, and weldability may be inferior. Therefore, it is advantageous for the content of C to have a range of 0.180 to 0.330%. The lower limit of the C content is more advantageous at 0.185%, more advantageous at 0.190%, and most advantageous at 0.195%. The upper limit of the C content is more advantageous at 0.320%, more advantageous at 0.310%, and most advantageous at 0.30%.

[0063] Silicon (Si): 0.020~0.60%

[0064] Si is an element effective for improving resistance to tempering softening and is also effective for improving strength through solid solution strengthening. If the Si content is less than 0.020%, it may be difficult to sufficiently obtain the aforementioned effects. If the Si content exceeds 0.60%, there is a risk that excessive ferrite will be generated after continuous annealing and cooling, thereby weakening the strength of the steel. Furthermore, as Si is an element that increases resistivity, resistance spot weldability may be compromised. Therefore, it is advantageous for the Si content to be in the range of 0.020 to 0.60%. The lower limit of the Si content is more advantageous at 0.030%, more advantageous at 0.040%, and most advantageous at 0.050%. The upper limit of the Si content is more advantageous at 0.50%, more advantageous at 0.40%, and most advantageous at 0.30%.

[0065] Manganese (Mn): 0.40~2.40%

[0066] Mn is an element added to ensure strength. If the Mn content is less than 0.40%, the hardenability is low; consequently, if the cooling rate after continuous annealing is not sufficiently fast, martensite is not formed, making it difficult to secure the level of strength targeted in the present invention. If the Mn content exceeds 2.40%, the Ms temperature decreases during cooling after continuous annealing, and as the temperature at which cooling must end decreases, the shape of the steel sheet becomes defective. Furthermore, it is difficult to secure a martensite structure. In addition, Mn-based segregation zones occur along the longitudinal direction of the slab during steelmaking / continuous casting operations, degrading bending characteristics. That is, as manganese bands (Mn bands) are formed within the slab, cracks occur during continuous casting, and there is a problem of increased defect occurrence during the rolling process. Therefore, it is advantageous for the Mn content to be in the range of 0.40 to 2.40%. The lower limit of the Mn content is more advantageous at 0.45%, more advantageous at 0.50%, and most advantageous at 0.55%. The upper limit of the Mn content is more advantageous at 2.35%, more advantageous at 2.30%, and most advantageous at 2.25%.

[0067] Phosphorus (P): 0.030% or less (excluding 0%)

[0068] P is an impurity element contained in steel. If the content of P exceeds 0.030%, weldability deteriorates, and it is prone to segregation at grain boundaries, leading to intergranular embrittlement. Furthermore, the grain boundaries are prone to fracture due to hydrogen in the steel, raising concerns about brittleness in the steel. Meanwhile, while it is advantageous to exclude P from the steel as much as possible, 0% is excluded to account for cases where it is unavoidably included during the manufacturing process. Therefore, it is advantageous for the content of P to be 0.030% or less (excluding 0%). It is even more advantageous for the content of P to be 0.020% or less.

[0069] Sulfur (S): 0.0050% or less (excluding 0%)

[0070] S is an impurity element included in steel, similar to P. If the content of S exceeds 0.0050%, it can impair ductility and weldability, and a large amount of MnS precipitates may be formed, which can lead to inferior bending properties. Meanwhile, it is advantageous for S not to be included in steel as much as possible, but 0% is excluded to account for cases where it is unavoidably included during the manufacturing process. Therefore, it is advantageous for the content of S to be 0.0050% or less (excluding 0%). It is more advantageous for the content of S to be 0.0030% or less, and even more advantageous for it to be 0.0020% or less.

[0071] Boron (B): 0.00050~0.0050%

[0072] B is an element that inhibits ferrite formation. Accordingly, the present invention has the advantage of increasing resistance to hydrogen embrittlement by inhibiting the formation of ferrite upon cooling after continuous annealing and by strengthening the austenite grain boundaries to suppress hydrogen intrusion. If the content of B is less than 0.00050%, it is difficult to obtain the aforementioned effects sufficiently, and there is no hardenability effect at all, making it difficult to secure the strength targeted by the present invention. If the content of B exceeds 0.0050%, ductility may be significantly reduced. Therefore, it is advantageous for the content of B to have a range of 0.00050% to 0.0050%. The lower limit of the B content is more advantageous at 0.00070%, and more advantageous at 0.0010%. The upper limit of the B content is more advantageous at 0.0040%, and more advantageous at 0.0030%.

[0073] The remaining component is iron (Fe). However, since unintended impurities from raw materials or the surrounding environment may inevitably be incorporated during the ordinary manufacturing process, they cannot be excluded. As these impurities are known to any skilled person in the ordinary manufacturing process, all details thereof are not specifically mentioned in this specification.

[0074] The above-mentioned steel sheet may additionally include one or more of the following: aluminum (Al): 0.0050~0.080%, chromium (Cr): 0.0010~0.50%, molybdenum (Mo): 0.0010~0.40%, niobium (Nb): 0.0010~0.10%, titanium (Ti): 0.0050~0.250%, nitrogen (N): 0.010% or less (excluding 0%), copper (Cu): 0.0010~0.30%, and nickel (Ni): 0.0010~0.30%.

[0075] Aluminum (Al): 0.0050~0.080%

[0076] Al can be added to remove oxygen from the molten steel. If the Al content is less than 0.0050%, deoxidation is not sufficiently achieved, which impairs the cleanliness of the steel. If the Al content exceeds 0.080%, not only does the castability of the slab deteriorate, but the temperature required for single-phase heating during continuous annealing also increases, which may cause production and equipment problems. Therefore, it is advantageous for the Al content to be in the range of 0.0050% to 0.080%. The lower limit of the Al content is more advantageous at 0.010%, and more advantageous at 0.020%. The upper limit of the Al content is more advantageous at 0.070%, and more advantageous at 0.060%.

[0077] Chrome (Cr): 0.0010~0.50%

[0078] Cr is an element that facilitates securing a low-temperature transformation structure by suppressing ferrite transformation. Additionally, when utilizing a continuous annealing process involving slow cooling, as in the present invention, there is an advantage in suppressing ferrite formation. If the Cr content is less than 0.0010%, the hardenability is low; consequently, if the cooling rate after continuous annealing is not sufficiently fast, martensite is not formed, making it difficult to secure the strength level targeted in the present invention. If the Cr content exceeds 0.50%, resistance to delayed fracture may deteriorate, carbides such as CrC may form to reduce bending properties, and manufacturing costs may increase due to an excessive amount of alloy input. Therefore, it is advantageous for the Cr content to be in the range of 0.0010% to 0.50%. Regarding the lower limit of the Cr content, 0.0050% is more advantageous, 0.010% is more advantageous, and 0.020% is the most advantageous. The upper limit of the above Cr content is more advantageous at 0.40%, more advantageous at 0.30%, and most advantageous at 0.20%.

[0079] Molybdenum (Mo): 0.0010~0.40%

[0080] Mo is an element that exhibits effects such as improving the hardenability of steel, generating Mo-based fine carbides that serve as hydrogen trap sites, and improving resistance to delayed fracture through martensite refinement. If the content of Mo is less than 0.0010%, it may be difficult to sufficiently obtain the aforementioned effects. If the content of Mo exceeds 0.40%, the aforementioned effects do not increase significantly compared to the cost increase resulting from the addition of expensive alloying elements. Therefore, it is advantageous for the content of Mo to be in the range of 0.0010% to 0.40%. The lower limit of the Mo content is more advantageous at 0.0020%, more advantageous at 0.0030%, and most advantageous at 0.0040%. The upper limit of the Mo content is more advantageous at 0.350%, more advantageous at 0.30%, and most advantageous at 0.250%.

[0081] Niobium (Nb): 0.0010~0.10%

[0082] Nb is an element that segregates at austenite grain boundaries, suppresses the coarsening of austenite grains during continuous annealing, and contributes to strength improvement by forming fine precipitates. If the Nb content is less than 0.0010%, sufficient austenite grain refinement and precipitation strengthening effects cannot be obtained. If the Nb content exceeds 0.10%, the precipitation of coarse carbonitrides increases, and there is a risk that strength and elongation will decrease due to the reduction in carbon content in the steel. In addition, there are problems such as reduced workability of the base material and increased manufacturing costs. Therefore, it is advantageous for the Nb content to be in the range of 0.0010 to 0.10%. Regarding the lower limit of the Nb content, it is more advantageous for it to be 0.0020%, more advantageous for it to be 0.0030%, and most advantageous for it to be 0.0040%. The upper limit of the above Nb content is more advantageous at 0.090%, more advantageous at 0.080%, and most advantageous at 0.070%.

[0083] Titanium (Ti): 0.0050~0.250%

[0084] Ti is a nitride-forming element that scavenges dissolved N by precipitating it as TiN. If the Ti content is less than 0.0050%, it is difficult to obtain a strength-increasing effect, and the scavenging effect of dissolved N is reduced, leading to the formation of a large amount of AlN, which may cause cracks during continuous casting. If the Ti content exceeds 0.250%, the strength of the martensite may decrease as additional carbides are precipitated in addition to the removal of dissolved N, and the hole expansion and bending characteristics may be impaired due to the excessive formation of carbonitrides such as TiC and TiN. Therefore, it is advantageous for the Ti content to be in the range of 0.0050% to 0.250%. The lower limit of the Ti content is more advantageous at 0.010%, more advantageous at 0.0150%, and most advantageous at 0.020%. The upper limit of the above Ti content is more advantageous at 0.20%, more advantageous at 0.150%, and most advantageous at 0.10%.

[0085] Nitrogen (N): 0.010% or less (excluding 0%)

[0086] N is an impurity element, and if its content exceeds 0.010%, it significantly increases the risk of cracking during continuous casting due to the formation of AlN, etc. Although it is advantageous for the above N not to be included in the steel as much as possible, 0% is excluded to account for cases where it is unavoidably included during the manufacturing process. Therefore, it is advantageous for the above N content to have a range of 0.010% or less (excluding 0%). It is more advantageous for the above N content to be 0.0080% or less, and even more advantageous for it to be 0.0060% or less.

[0087] Copper (Cu): 0.0010~0.30%

[0088] Cu improves corrosion resistance in the operating environment of automobiles and also has the effect of suppressing hydrogen intrusion into the steel plate by coating the surface of the steel plate with corrosion products. In addition, as an element incorporated when utilizing scrap as a raw material, recycled materials can be utilized as raw materials, thereby reducing manufacturing costs. If the content of Cu is less than 0.0010%, it may be difficult to sufficiently obtain the aforementioned effects. If the content of Cu exceeds 0.30%, it may lead to the occurrence of surface defects. Therefore, it is advantageous for the content of Cu to have a range of 0.0010% to 0.30%. The lower limit of the Cu content is more advantageous at 0.0050%, and even more advantageous at 0.0070%. The upper limit of the Cu content is more advantageous at 0.20%, and even more advantageous at 0.10%.

[0089] Nickel (Ni): 0.0010~0.30%

[0090] Ni is an element that, like Cu, acts to improve corrosion resistance. Additionally, as an element incorporated when utilizing scrap as a raw material, recycled materials can be utilized as raw materials, thereby reducing manufacturing costs. If the Ni content is less than 0.0010%, it may be difficult to sufficiently obtain the aforementioned effects. If the Ni content exceeds 0.30%, it may lead to the occurrence of surface defects. Therefore, it is advantageous for the Ni content to be in the range of 0.0010% to 0.30%. The lower limit of the Ni content is more advantageous at 0.0050%, and more advantageous at 0.0070%. The upper limit of the Ni content is more advantageous at 0.20%, and more advantageous at 0.10%.

[0091] The substrate steel plate of the present invention satisfies the aforementioned alloy composition and can simultaneously satisfy the following relationship 1.

[0092] [Equation 1] 0.050 wt% ≤ Cr+Mo+Ni+Cu ≤ 1.0 wt%

[0093] The above Equation 1 is a compositional equation for improving hydrogen embrittlement through improved corrosion resistance. If the value of Cr+Mo+Ni+Cu is less than 0.050 wt%, there is a disadvantage that corrosion resistance is inferior and hydrogen embrittlement is inferior. If the value of Cr+Mo+Ni+Cu exceeds 1.0 wt%, there is a disadvantage that manufacturing costs increase. Therefore, it is advantageous for the value of Cr+Mo+Ni+Cu to have a range of 0.050 to 1.0 wt%. It is more advantageous for the lower limit of the Cr+Mo+Ni+Cu value to be 0.070 wt%, and more advantageous for it to be 0.090 wt%. It is more advantageous for the upper limit of the Cr+Mo+Ni+Cu value to be 0.90 wt%, and more advantageous for it to be 0.80 wt%.

[0094] The substrate steel sheet of the present invention may have a microstructure in area % comprising: a total of one or more types of ferrite and bainite: 5% or less (including 0%), and the remainder being one or more types of martensite and tempered martensite. That is, the total of one or more types of fresh martensite and tempered martensite may be 95% or more (including 100%). The fresh martensite and tempered martensite are structures that are highly advantageous for securing the strength and bending characteristics targeted by the present invention. However, one or more types of ferrite and bainite may inevitably be formed during the manufacturing process, and if the total fraction of one or more types of ferrite and bainite exceeds 5%, it may be difficult to secure the physical properties intended by the present invention. Therefore, it is advantageous for the total fraction of one or more types of ferrite and bainite to be 5% or less, and more advantageous for it to be 3% or less. The above tempered martensite may include auto-tempered martensite formed during the cooling process.

[0095] The substrate steel sheet of the present invention has an average GND value (GNDave) of 255×1012 m -2 ~325×10 12 m -2 It may be. The above GND (Geometrically Necessary Dislocations) is a value that can be calculated from the KAM value, which quantifies the dislocation density; a higher value indicates a higher dislocation density. The above average GND value (GNDave) is 255×10 12 m -2 If it is less than, it contains a large amount of excessively tempered martensitic structure, making it difficult to secure the target tensile strength. The above average GND value (GNDave) is 325×10 12 m -2 If it exceeds, the strength becomes excessively high due to the composition of a tissue with high dislocation density, which may result in inferior elongation. Therefore, the above average GND value (GNDave) is 255×10 12 m -2 ~325×10 12 m -2 It is advantageous to have a range. The lower limit of the above average GND value (GNDave) is 260×10 12 m -2 It is more advantageous to have this. The upper limit of the above average GND value (GNDave) is 320×10 12 m -2 It is more advantageous to do so. Meanwhile, the above KAM value is the average value of the crystal rotation amount (crystal orientation difference) between the target measurement point and surrounding measurement points, and the larger this value, the more deformation exists within the crystal.

[0096] The above Zn plating layer may have an average thickness of 1.0 to 20.0 μm. If the average thickness of the above Zn plating layer is less than 1.0 μm, there may be a disadvantage of inferior corrosion resistance. If the average thickness of the above Zn plating layer exceeds 20.0 μm, there may be a disadvantage of inferior weldability. Therefore, it is advantageous for the average thickness of the above Zn plating layer to have a range of 1.0 to 20.0 μm. It is more advantageous for the lower limit of the average thickness of the above Zn plating layer to be 1.5 μm, and more advantageous for it to be 2.0 μm. It is more advantageous for the upper limit of the average thickness of the above Zn plating layer to be 19.5 μm, and more advantageous for it to be 19.0 μm. Meanwhile, the present invention does not specifically limit the type of the above Zn plating layer, but as an example, the plating layer may be an electro-galvanized layer.

[0097] The above Zn plating layer may include a Ni enrichment region. By including a Ni enrichment region, the above Zn plating layer can secure the effect of preventing hydrogen penetration into the steel.

[0098] Referring to FIG. 1, the Ni enrichment region may refer to a region where the minimum Ni content is 0.05% or more. Additionally, the Ni enrichment region may be formed at a depth of 1.0 μm to 5.0 μm based on the depth in the thickness direction from the surface. In the embodiment of FIG. 1, it was formed at a depth range of 2.0 μm to 3.0 μm, but it is not necessarily limited thereto.

[0099] The above Ni enrichment region may have a maximum Ni content (Ni_max) of 0.010 to 0.40 wt%. If the maximum Ni content (Ni_max) of the above Ni enrichment region is less than 0.010 wt%, there may be a disadvantage of having a low effect in preventing hydrogen penetration. If the maximum Ni content (Ni_max) of the above Ni enrichment region exceeds 0.40 wt%, there may be a disadvantage of increased manufacturing costs. Therefore, it is advantageous for the maximum Ni content (Ni_max) of the above Ni enrichment region to have a range of 0.010 to 0.40 wt%. The lower limit of the maximum Ni content (Ni_max) of the above Ni enrichment region is more advantageous to be 0.020 wt%, and it is more advantageous to be 0.050 wt%. The upper limit of the maximum Ni content (Ni_max) of the above Ni enrichment region is more advantageous to be 0.38 wt%, and it is more advantageous to be 0.36 wt%.

[0100] The plated steel sheet of the present invention may satisfy the following relationship 2. If (Ni_max+Ni_nom) / 2 is less than 0.010 wt%, there may be disadvantages such as a low effect of preventing hydrogen penetration. If (Ni_max+Ni_nom) / 2 exceeds 0.350 wt%, there may be disadvantages such as an increase in manufacturing costs. The lower limit of (Ni_max+Ni_nom) / 2 is more advantageous at 0.012 wt%, and 0.014 wt% is more advantageous. The upper limit of (Ni_max+Ni_nom) / 2 is more advantageous at 0.330 wt%, and 0.310 wt% is more advantageous.

[0101] [Equation 2] 0.010 wt% ≤ (Ni_max+Ni_nom) / 2 ≤ 0.350 wt%

[0102] (However, in the above Equation 2, Ni_max refers to the maximum Ni content within the Ni enrichment region, and Ni_nom refers to the average Ni content within the region up to 20㎛ in the thickness direction from the surface of the base steel sheet.)

[0103] The above Ni enrichment region may have an average thickness (Ni_Wave) of the region satisfying the above Equation 2 ranging from 0.40 to 10.0 μm. If the average thickness (Ni_Wave) of the region satisfying the above Equation 2 is less than 0.40 μm, there may be a disadvantage of a low effect in preventing hydrogen penetration. If the average thickness (Ni_Wave) of the region satisfying the above Equation 2 exceeds 10.0 μm, there may be a disadvantage of increased manufacturing costs. Therefore, it is advantageous for the average thickness (Ni_Wave) of the region satisfying the above Equation 2 to have a range of 0.40 to 10.0 μm. It is more advantageous for the lower limit of the average thickness (Ni_Wave) of the region satisfying the above Equation 2 to be 0.50 μm, and even more advantageous for it to be 0.60 μm. The upper limit of the average thickness (Ni_Wave) of the region satisfying the above relationship 2 is more advantageous at 9.0㎛, and more advantageous at 8.0㎛.

[0104] The plated steel sheet of the present invention may have a diffusible hydrogen content (Hd) of 0.10 ppm or less. If the diffusible hydrogen content (Hd) exceeds 0.10 ppm, the hydrogen content in the steel may be high, which may result in a disadvantage of poor hydrogen embrittlement resistance. Therefore, it is advantageous for the diffusible hydrogen content (Hd) to have a range of 0.10 ppm or less. It is more advantageous for the diffusible hydrogen content (Hd) to be 0.095 ppm or less, and even more advantageous for it to be 0.090 ppm or less. Meanwhile, since a lower diffusible hydrogen content (Hd) is more advantageous, the present invention does not specifically limit the lower limit of the diffusible hydrogen content (Hd). However, as an example, the diffusible hydrogen content (Hd) may be 0.01 ppm or more.

[0105] The galvanized steel sheet of the present invention may have a critical hydrogen content (Hc) of 0.14 ppm or more. If the critical hydrogen content (Hc) is less than 0.14 ppm, it implies low hydrogen resistance, which may result in a disadvantage of inferior hydrogen embrittlement. Therefore, it is advantageous for the critical hydrogen content (Hc) to have a range of 0.14 ppm or more. It is more advantageous for the critical hydrogen content (Hc) to be 0.15 ppm or more, and even more advantageous for it to be 0.16 ppm or more. Meanwhile, since a higher critical hydrogen content (Hc) is advantageous, the present invention does not specifically limit the upper limit of the critical hydrogen content (Hc). However, as an example, the critical hydrogen content (Hc) may be 1 ppm or less. Meanwhile, the critical hydrogen content (Hc) refers to the amount of diffusible hydrogen at the point where cracks caused by hydrogen embrittlement begin to occur. In other words, a higher critical hydrogen amount (Hc) means that cracks caused by hydrogen embrittlement are less likely to occur, and if the diffusible hydrogen amount (Hd) is greater than the critical hydrogen amount (Hc), it means that cracks caused by hydrogen embrittlement have occurred.

[0106] The galvanized steel sheet of the present invention may have a critical hydrogen content (Hc) / diffusible hydrogen content (Hd) of 2.5 or higher. If the critical hydrogen content (Hc) / diffusible hydrogen content (Hd) is less than 2.5, there may be a disadvantage of lower resistance to hydrogen and inferior hydrogen embrittlement. Therefore, it is advantageous for the critical hydrogen content (Hc) / diffusible hydrogen content (Hd) to have a range of 2.5 or higher. It is more advantageous for the critical hydrogen content (Hc) / diffusible hydrogen content (Hd) to be 2.6 or higher, and even more advantageous for it to be 2.7 or higher. Meanwhile, since it is advantageous for the critical hydrogen content (Hc) / diffusible hydrogen content (Hd) to be higher, the present invention does not specifically limit the upper limit of the critical hydrogen content (Hc) / diffusible hydrogen content (Hd). However, as an example, the above critical hydrogen amount (Hc) / diffusible hydrogen amount (Hd) may be 5 or less.

[0107] As described above, the galvanized steel sheet of the present invention may have a yield strength (YS): 1200 MPa or more, a tensile strength (TS): 1470 MPa or more, a total elongation (T_EL): 5.0% or more, and a uniform elongation (U_EL): 2.7% or more. It is more advantageous for the yield strength to be 1210 MPa or more. In the present invention, the upper limit of the yield strength is not specifically limited, but as an example, it may be 1900 MPa. It is more advantageous for the tensile strength to be 1480 MPa or more. In the present invention, the upper limit of the tensile strength is not specifically limited, but as an example, it may be 2100 MPa. It is more advantageous for the total elongation to be 5.5% or more. In the present invention, the upper limit of the total elongation is not specifically limited, but as an example, it may be 10%. It is more advantageous for the above uniform elongation rate to be 2.9% or higher. In the present invention, the upper limit of the above uniform elongation rate is not specifically limited, but as an example, it may be 5%.

[0108] The plated steel sheet of the present invention provided as described above has a hydrogen embrittlement fracture time (Ft): 20 minutes or more, and a tensile strength (TS) / hydrogen embrittlement fracture time (Ft): 19~89 MPa·min -1 It may be. It is more advantageous for the above hydrogen embrittlement rupture time (Ft) to be 21 minutes or more. In the present invention, the upper limit of the above hydrogen embrittlement rupture time (Ft) is not specifically limited, but as an example, it may be 6000 minutes.

[0109] The thickness of the plated steel sheet of the present invention may be 0.6 to 2.5 mm. The lower limit of the thickness of the plated steel sheet is more advantageously 0.7 mm, and 0.8 mm. The upper limit of the thickness of the plated steel sheet is more advantageously 2.4 mm, and 2.3 mm.

[0110] Hereinafter, a method for manufacturing a plated steel sheet according to one embodiment of the present invention will be described.

[0111] First, a slab satisfying the aforementioned alloy composition is heated. The slab may satisfy the above-described relationship Equation 1. The slab heating process is performed to facilitate the subsequent hot rolling process and to sufficiently obtain the target physical properties of the steel sheet. The heating of the slab may be performed at 1100 to 1300°C. If the slab heating temperature is below 1100°C, a problem arises in which the hot rolling load increases rapidly. If the slab heating temperature exceeds 1300°C, the amount of surface scale increases, and the yield of the material decreases. The lower limit of the slab heating temperature is more advantageous at 1110°C, more advantageous at 1120°C, and most advantageous at 1130°C. The upper limit of the slab heating temperature is more advantageous at 1290°C, more advantageous at 1280°C, and most advantageous at 1270°C.

[0112] Subsequently, the heated slab is finished hot-rolled to obtain a hot-rolled steel sheet. The finish hot-rolling can be performed at a temperature of Ar3 to Ar3+120℃. If the finish hot-rolling temperature is below Ar3, rolling occurs in a two-phase region of ferrite + austenite or in a ferrite region, resulting in a mixed grain structure, and plate breakage may occur due to fluctuations in the hot-rolling load. If the finish hot-rolling temperature exceeds Ar3+120℃, a large amount of surface scale may form, which may degrade the surface quality. The lower limit of the finish hot-rolling temperature is more advantageous at Ar3+10℃, more advantageous at Ar3+20℃, and most advantageous at Ar3+30℃. The upper limit of the finish hot-rolling temperature is more advantageous at Ar3+110℃, more advantageous at Ar3+100℃, and most advantageous at Ar3+90℃. Meanwhile, the above Ar3 refers to the temperature at which austenite begins to transform into ferrite upon cooling, and can be calculated using the following Equation 1.

[0113] [Equation 1] Ar3(°C) = 910 - 203√C + 44.7Si + 31.5Mo

[0114] Subsequently, the hot-rolled steel sheet is coiled. The coiling may be performed at Ms to 700°C. If the coiling temperature exceeds 700°C, internal oxidation occurs on the surface of the steel sheet, causing the microstructure formed in the surface layer to become non-uniform, and consequently, the bending characteristics may deteriorate. Meanwhile, it is advantageous to manage the coiling temperature low to ensure material uniformity across the entire length and width by forming the microstructure of the hot-rolled steel sheet into a single-phase structure rather than a composite structure as much as possible. However, if the coiling temperature is below Ms, the strength of the hot-rolled steel sheet becomes excessively high, which may make actual production impossible due to the increased rolling load during the subsequent cold rolling process. It is more advantageous for the lower limit of the coiling temperature to be Ms + 10°C. It is more advantageous for the upper limit of the coiling temperature to be 600°C. Ms refers to the temperature at which austenite begins to transform into martensite upon cooling, and can be calculated using Equation 2 below.

[0115] [Equation 2] Ms(℃) = 521 - 379C - 15.1Si - 43.9Mn - 19.5Cr - 14.7Mo + 43.7Nb + 91.9Ti + 169B

[0116] Meanwhile, after the above coiling, it can be cooled by air cooling or water cooling. In addition, after the above cooling, a pickling process can be performed to remove the oxide layer formed on the surface of the hot-rolled steel sheet.

[0117] Subsequently, the coiled hot-rolled steel sheet is cold-rolled to obtain a cold-rolled steel sheet. The cold rolling may be performed with a cold reduction rate of 35 to 70%. If the cold reduction rate is less than 35%, it is difficult to secure the thickness desired in the present invention, and there is a concern that austenite may be formed during annealing heat treatment due to the persistence of crystal grains formed during hot rolling, which may affect the final physical properties. If the cold reduction rate exceeds 70%, the reduction amount in the length and width directions may become uneven due to work hardening occurring during cold rolling, which may lead to material variation in the steel sheet. In addition, it may be difficult to secure the thickness desired in the present invention due to the rolling load. The lower limit of the cold reduction rate is more advantageous at 36%, more advantageous at 37%, and most advantageous at 38%. The upper limit of the above cold rolling rate is more advantageous at 69%, more advantageous at 68%, and most advantageous at 67%.

[0118] Subsequently, the cold-rolled steel sheet is continuously annealed. The continuous annealing may be performed at Ac3 to Ac3+120°C for 50 to 200 seconds. If the continuous annealing temperature is below Ac3°C, a mixed grain structure may be formed as two-phase annealing, rather than a single-phase annealing, occurs over the entire length of the steel sheet. Consequently, it is difficult to secure the physical properties targeted by the present invention, and in particular, the difference in hardness between phases becomes large, which may significantly reduce hole expansion properties. If the continuous annealing temperature exceeds Ac3+120°C, equipment trouble may occur due to overloading of the annealing furnace. The lower limit of the continuous annealing temperature is more advantageous at Ac3+5°C, and more advantageous at Ac3+10°C. The upper limit of the continuous annealing temperature is more advantageous at Ac3+110°C, and more advantageous at Ac3+100°C. Meanwhile, the above Ac3 refers to the temperature at which the transformation from ferrite to 100% austenite is completed upon heating, and can be calculated using Equation 3 below. If the above continuous annealing time is less than 50 seconds, it may be difficult to secure a single-phase austenite structure, and as undissolved carbides remain and coarsen, bending characteristics and hydrogen embrittlement resistance may be reduced, and it may be difficult to sufficiently form a decarburized layer. If the above continuous annealing time exceeds 200 seconds, there is a disadvantage that the austenite size coarsen, making it difficult to secure strength. The lower limit of the above continuous annealing time is more advantageous at 60 seconds, and 70 seconds is more advantageous. The upper limit of the above continuous annealing time is more advantageous at 190 seconds, and 180 seconds is more advantageous.

[0119] [Equation 3] Ac3(℃) = 900 - 206C + 26.2Si - 25Mn - 12.3Cr + 9.12Mo + 50.2Nb + 148Ti - 131B

[0120] Subsequently, the above-mentioned continuous annealed cold-rolled steel sheet is cooled first. The first cooling may be performed at a first average cooling rate (CR1) of 0.5 to 6.0°C / s until a first cooling end temperature (T1) of 620°C to Ac3. If the first cooling end temperature (T1) is less than 620°C, the bending characteristics may deteriorate as a large amount of soft ferrite and bainite, in addition to martensite, is formed during the cooling process. If the first cooling end temperature (T1) exceeds Ac3°C, the temperature difference between the first cooling end temperature and the second cooling end temperature (T2) becomes severe, causing a rapid phase transformation and resulting in a defective product shape. It is more advantageous for the lower limit of the first cooling end temperature to be 630°C, and even more advantageous for it to be 640°C. The upper limit of the above first cooling end temperature is more advantageously Ac3-10℃, and the upper limit of Ac3-20℃ is more advantageous. If the above first average cooling rate is less than 0.5℃ / s, ferrite is formed during cooling, making it impossible to secure the level of strength targeted by the present invention. If the above first average cooling rate exceeds 6.0℃ / s, the average cooling rate during the subsequent second cooling decreases, increasing the fraction of low-temperature transformation phases other than martensite, making it impossible to secure the level of strength targeted by the present invention. The lower limit of the above first average cooling rate is more advantageously 1℃ / s. The upper limit of the above first average cooling rate is more advantageously 5℃ / s.

[0121] Subsequently, the first-cooled cold-rolled steel sheet is cooled a second time. The second cooling is intended to secure one or more of the main phases of the present invention, namely martensite and tempered martensite. The second cooling can be performed at a second average cooling rate (CR2) of 40 to 500°C / s until a second cooling end temperature (T2) of 40 to 200°C. If the second cooling end temperature (T2) is less than 40°C, shape defects are caused by rapid phase transformation, and there is a disadvantage that continuous production is difficult due to strip meandering problems. If the second cooling end temperature (T2) exceeds 200°C, it may be difficult to secure the strength targeted by the present invention. The lower limit of the second cooling end temperature is more advantageous at 50°C, more advantageous at 55°C, and most advantageous at 60°C. The upper limit of the above secondary cooling end temperature is more advantageous at 195°C, more advantageous at 190°C, and most advantageous at 185°C. If the above secondary average cooling rate is less than 40°C / s, soft ferrite transformation occurs during cooling, making it difficult to secure the target strength. If the above secondary average cooling rate exceeds 500°C / s, the product shape may become defective due to rapid phase transformation. The lower limit of the above secondary average cooling rate is more advantageous at 50°C / s, more advantageous at 60°C / s, and most advantageous at 70°C / s. The upper limit of the above secondary average cooling rate is more advantageous at 400°C / s, more advantageous at 300°C / s, and most advantageous at 200°C / s.

[0122] During the above secondary cooling, the Mf-secondary cooling termination temperature (T2) can be controlled to be 10°C or higher. If the Mf-T2 is less than 10°C, the martensite transformation may not occur sufficiently, making it difficult to secure the target strength. It is more advantageous for the Mf-T2 to be 15°C or higher, and even more advantageous for it to be 20°C or higher. In the present invention, the upper limit of the Mf-T2 is not specifically limited, but as an example, it may be 200°C. Meanwhile, the Mf represents the temperature at which the martensite transformation is terminated during cooling, and can be calculated using the following Equation 4.

[0123] [Equation 4] Mf(°C) = 371 - 412C - 17.4Si - 47.4Mn - 20.9Cr - 17Mo + 49.2Nb + 95Ti + 202B

[0124] Subsequently, the above-mentioned secondary cooled cold-rolled steel sheet is reheated and then subjected to overaging treatment. Through the reheating and overaging treatment, the martensite obtained by the aforementioned rapid cooling process is transformed into tempered martensite, thereby increasing the yield strength. The overaging treatment can be performed at an overaging treatment temperature (HT) of 90 to 270°C for an overaging treatment time (ht) of 180 to 900 seconds. If the overaging treatment temperature (HT) is below 90°C, there is a disadvantage in that tempering is not sufficiently performed, resulting in low yield strength and inability to secure sufficient toughness. If the overaging treatment temperature (HT) exceeds 270°C, there is a disadvantage in that bendability is degraded due to the precipitation and coarsening of large amounts of carbides. The lower limit of the above overaging treatment temperature is more advantageous at 100°C, more advantageous at 110°C, and most advantageous at 120°C. The upper limit of the above overaging treatment temperature is more advantageous at 265°C, more advantageous at 260°C, and most advantageous at 255°C. If the above overaging treatment time (ht) is less than 180 seconds, tempering is not sufficiently performed, and the yield strength may be lowered. If the above overaging treatment time (ht) exceeds 900 seconds, carbides may coarsen due to excessive tempering, and bending characteristics may deteriorate. The lower limit of the above overaging treatment time is more advantageous at 185 seconds, more advantageous at 190 seconds, and most advantageous at 195 seconds. The upper limit of the above over-aging processing time is more advantageous at 895 seconds, more advantageous at 890 seconds, and most advantageous at 885 seconds.

[0125] When the overaging treatment is performed, the overaging treatment temperature (HT) - secondary cooling end temperature (T2) can be controlled to be 30°C or higher. If the overaging treatment temperature (HT) - secondary cooling end temperature (T2) is less than 30°C, sufficient tempering is not achieved, making it difficult to secure the target yield strength. It is more advantageous for the overaging treatment temperature (HT) - secondary cooling end temperature (T2) to be 35°C or higher, and even more advantageous for it to be 40°C or higher.

[0126] Subsequently, a Ni coating layer is formed on at least one surface of the above-mentioned over-aged cold-rolled steel sheet. When forming the above-mentioned Ni coating layer, the amount of Ni deposited on one side can be controlled to be 3 to 25 mg / m². If the amount of Ni deposited on one side is less than 3 mg / m², there may be a disadvantage in that the hydrogen penetration inhibition during plating is weak, resulting in a high amount of hydrogen in the steel. If the amount of Ni deposited on one side exceeds 25 mg / m², there may be a disadvantage in that the manufacturing cost increases. It is more advantageous for the lower limit of the amount of Ni deposited on one side to be 4 mg / m², and more advantageous for it to be 5 mg / m². It is more advantageous for the upper limit of the amount of Ni deposited on one side to be 24 mg / m², and more advantageous for it to be 23 mg / m². In the present invention, the method of forming the above-mentioned Ni coating layer is not specifically limited, but as an example, electroplating may be used.

[0127] Subsequently, the cold-rolled steel sheet with the above-mentioned Ni coating layer is tension-leveled (T / L). The tension-leveling is intended to correct the shape of the steel sheet. The tension-leveling can be performed with an elongation of 0.05 to 2.0%. If the elongation is less than 0.05% during the tension-leveling, it may be difficult to correct the shape. If the elongation exceeds 2.0% during the tension-leveling, work hardening becomes severe, which may result in poor bending characteristics and hydrogen embrittlement resistance, and the difference in yield strength between the vertical and horizontal directions of the rolling direction becomes severe, which may adversely affect dimensional accuracy during part processing. It is more advantageous for the lower limit of the elongation during the tension-leveling to be 0.075%, and more advantageous for it to be 0.10%. When leveling the tension above, it is more advantageous for the upper limit of the elongation rate to be 1.8%, and more advantageous for it to be 1.5%.

[0128] After the above tension leveling, a Zn plating layer is formed on the surface of the cold-rolled steel sheet on which the above Ni coating layer is formed. When forming the above Zn plating layer, the amount of Zn deposited on one side can be controlled to be 5 to 120 g / m². If the amount of Zn deposited on one side is less than 5 g / m², there may be a disadvantage of inferior corrosion resistance. If the amount of Zn deposited on one side exceeds 120 g / m², weldability may be inferior. It is more advantageous for the lower limit of the amount of Zn deposited on one side to be 6 g / m², and more advantageous for it to be 7 g / m². It is more advantageous for the upper limit of the amount of Zn deposited on one side to be 115 g / m², and more advantageous for it to be 110 g / m². In the present invention, the method of forming the above Zn plating layer is not specifically limited, but as an example, electroplating may be used.

[0129] The manufacturing method of the present invention can satisfy the following equation 3. If X exceeds 1500, there may be disadvantages such as high residual stress due to surface work hardening caused by excessive tension leveling, easy hydrogen penetration, high Zn plating amount preventing hydrogen penetrating into the steel from escaping, and low Ni deposition amount resulting in weak inhibition of hydrogen penetration and inferior hydrogen embrittlement. It is more advantageous for X to be 1480 or less, and even more advantageous for X to be 1450 or less. In the present invention, the lower limit of X is not specifically limited, but as an example, it may be 1.

[0130] [Relationship 3] X = (TL_EL×W Zn ) / W Ni ≤ 1500

[0131] (However, in the above Equation 3, the above TL_EL represents the tension leveling elongation rate, and the above W Zn represents the amount of Zn attached to one side, and the above W Ni represents the amount of Ni deposited on one side.)

[0132] The manufacturing method of the present invention can satisfy the following relationship 4. If the following Y exceeds 1.0, the cooling rate is fast, which may result in a decrease in elongation due to increased strength and an increase in surface residual stress due to excessive tension leveling, leading to excessive hydrogen penetration into the steel during plating and a disadvantage of poor hydrogen embrittlement. It is more advantageous for the following Y to be 0.95 or less, and even more advantageous for it to be 0.90 or less. In the present invention, the lower limit of the above Y is not specifically limited, but as an example, it may be 0.0005.

[0133] [Equation 4] Y = (CR2×TL_EL) / HT ≤ 1.0

[0134] (However, in the above Equation 4, CR2 represents the secondary average cooling rate, TL_EL represents the tension leveling elongation rate, and HT represents the overaging treatment temperature.)

[0135] The present invention will be described in detail below through examples. However, it should be noted that the examples described below are intended merely to illustrate and embody the present invention and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the patent claims and matters reasonably inferred therefrom.

[0136] (Example)

[0137] After preparing slabs having the alloy compositions listed in Tables 1 and 2 below, galvanized steel sheets were manufactured using the conditions listed in Tables 3 to 5 below. At this time, the formation of the Ni coating layer and the Zn plating layer was performed using the electroplating method. Meanwhile, the temperature conditions listed in Tables 3 to 5 below were based on the surface temperature of the steel sheets.

[0138] The microstructure, Zn plating layer, Ni enrichment region, and mechanical properties of the plated steel sheet manufactured in this manner were measured, and the results are shown in Tables 6 and 7 below.

[0139] The types and fractions of the microstructure were observed using a scanning electron microscope (SEM) and an optical microscope (OM) at a position t / 4 (t: thickness of the steel plate) in the thickness direction of the steel plate, and the fractions of each phase were analyzed 20 times through image analysis to calculate the average value.

[0140] The average GND value (GNDave) was calculated by measuring 10 times at 2000x magnification using an EBSD (Backscattered Electron Diffraction Pattern Analyzer) at the 1 / 4 position in the thickness direction of the steel plate (Confidence Index (CI)≥0.3, measurement area: 45×45㎛, Step size: 80nm, Cleanup: Grain Dilation, Neighbor Orientation Correlation, Neighbor Phase Correlation), and quantifying it using OIM (Orientation Imaging Microscopy) Analysis software. In particular, when calculating GND, Phase Iron (Alpha), Preset Slip Systemps BCC Slip, Nearest 1st, and Maximum 5 were used.

[0141] The thickness of the Zn plating layer, Ni_max, Ni_nom, and Ni_Wave were measured using a GDS (Glow discharge spectrometer) after washing the plated steel sheet with methanol.

[0142] Yield strength (YS), tensile strength (TS), and elongation (EL) were measured by processing cold-rolled steel sheets according to JIS standards in a direction perpendicular to the rolling direction and then performing a tensile test under conditions of a test speed of 28 mm / min.

[0143] The amount of diffusible hydrogen (Hd) was measured using Thermal Desorption Spectroscopy (TDS), which quantitatively measures the gaseous release of hydrogen from the specimen according to temperature changes.

[0144] The hydrogen embrittlement fracture time (Ft) was measured under the following conditions. First, the steel plate was side-trimmed under conditions of a gap of 15% and a lap of 85%, and then cut to a length of 100mm and a width of 30mm. Afterward, it was bent according to ASTM G39 standards, and a current density of 7.5A / m² was applied in an aqueous solution of 30g / L NaCl + 3g / L NH4SCN, and the time at which fracture occurred was measured.

[0145] The critical hydrogen amount (Hc) was measured using a Thermal Desorption Spectroscopy (TDS) device after the sample was immediately removed from the solution and cut into a 10×10 mm section from the point of crack occurrence to a point 10 mm away while measuring the hydrogen embrittlement fracture time (Ft) under the above conditions.

[0146] Steel Grade No. Alloy Composition (Wet%) CSI Mn PS Al Cr Mo Invention Steel 10.2 30.0 91.9 50.0 100 0.0 100.0 300.1 10.0 8 Invention Steel 20.2 40.2 11.9 50.0 1100.0 0 90.0 320.0 60.0 5 Invention Steel 30.2 20.1 52.100.0 800.0 150.0 320.1 50.1 0 Invention Steel 40.2 10.3 52.2 50.0 900.0 150.0 420.0 50.0 5 Invention Steel 50.2 50.152.150.01200.00140.0200.150.05Comparison 10.150.051.250.01100.00110.0350.150.06Comparison 20.160.150.300.01100.00120.0410.050.05Comparison 30.210.251.760.01300.00140.0250.150.05Comparison 40.140.211.850.01500.00110.0390.030.06

[0147] Steel Grade No. Alloy Composition (Weight%) NbTiBNNiCuCr+Mo+Ni+Cu Invention Steel 10.0350.0250.00250.0040.0150.0150.220 Invention Steel 20.0320.0320.00200.00320.0210.0210.152 Invention Steel 30.0250.0310.00210.00350.0200.0250.295 Invention Steel 40.0210.0450.00190.00210.0520.1150.267 50.0360.0250.00260.00420.0520.0620.314Comparison 10.0210.0390.00240.00270.0350.0420.287Comparison 20.0350.0240.00210.00340.0390.0370.176Comparison 30.0250.0350.00020.00390.0320.0150.247Comparison 40.0250.0250.00030.00450.0510.0350.176

[0148] Classification Steel Grade No. Slab Heating Temperature (°C) Ar3 (°C) Finishing Hot Rolling Temperature (°C) Ms (°C) Coiling Temperature (°C) Cold Reduction Rate (%) Thickness (mm) Invention Example 1 Invention Steel 1 1 2 3 5 8 0 6 9 2 5 3 4 8 4 6 5 5 6 1.4 Invention Example 2 Invention Steel 2 1 2 1 5 8 0 8 9 1 5 3 4 4 4 7 5 5 6 1.4 Invention Example 3 Invention Steel 3 1 2 1 0 8 1 2 9 3 5 3 4 3 5 0 1 5 6 1 .4 Invention Example 4 Invention Lecture 4 123582290534148556 1.4 Invention Example 5 Invention Lecture 5 122280392433046556 1.4 Comparative Example 1 Comparative Lecture 1 123082591041048756 1.4 Comparative Example 2 Comparative Lecture 2 124282690244749056 1.4 Comparative Example 3 Comparative Lecture 3 124181791036147556 1.4 Comparative Example 4 Comparative Example 4 1252835925386435561.4 Comparative Example 5 Invention Example 11230806917348475561.4 Comparative Example 6 Invention Example 11241806912348482561.4 Comparative Example 7 Invention Example 11250806906348795561.4 Comparative Example 8 Invention Example 11230806899348502561.4 Comparison Example 9 Invention 11240806915348495561.4 Comparative Example 10 Invention 41235822921341482561.4 Comparative Example 11 Invention 41215822931341486561.4 Comparative Example 12 Invention 41205822915341476561.4 Comparative Example 13 Invention 41235822912341482561.4

[0149] Classification Steel Grade No. Ac3(°C) Annealing Temperature(°C) Annealing Time(sec) 1st Cooling End Temperature(T1)(°C) 1st Average Cooling Rate(CR1)(°C / s) Mf(°C) 2nd Cooling End Temperature(T2)(°C) Mf-T2(°C) 2nd Average Cooling Rate(CR2)(°C / s) Invention Example 1 Invention Steel 181184511571531831057879 Invention Example 2 Invention Steel 28138361327053179978280 Invention Example 3 Invention Lecture 381183511671231781027697 Invention Example 4 Invention Lecture 48178301257203176908695 Invention Example 5 Invention Lecture 580283716973031641055989 Comparative Example 1 Comparative Lecture 1844852152725325011413678 Comparative Example 2 Comparative Lecture 2868872142715329112516681 Comparative Example 3 Comparative Lecture 3824 7901367343197989987 Comparative Example 4 Comparative Lecture 483683710560032249512987 Comparative Example 5 Invention Lecture 18118251157153183450-26785 Comparative Example 6 Invention Lecture 28118531137353183958835 Comparative Example 7 Invention Lecture 381179012574031831057885 Comparative Example 8 Invention Lecture 4811777135735218 31216275 Comparative Example 9 Invention Steel 58118391657213183859891 Comparative Example 10 Invention Steel 181784020572131769086121 Comparative Example 11 Invention Steel 281784220674131769581560 Comparative Example 12 Invention Steel 3817835204735317610076550 Comparative Example 13 Invention Steel 481780121073931761057192

[0150] Classification Steel Grade No. Reheating / Overaging Treatment Temperature (HT) (°C) HT-T2 (°C) Overaging Treatment Time (Ht) (sec) Ni Single-sided Adhesion Amount (W Ni )(mg / m²)Tension Leveling Elongation (TL_EL)(%)ZnSingle-sided Adhesion Amount (W Zn)(g / ㎡)X(%)Y(% / s)Invention Example 1 Invention Steel 1 19590474110.20213820.08Invention Example 2 Invention Steel 2 17477546120.15202500.07Invention Example 3 Invention Steel 3 19593522110.15658860.07Invention Example 4 Invention Steel 4 197107450150.15555500.07Invention Example 5 Myeonggang515954492120.25255210.14Comparative Pre-1Comparative Lecture120187516150.10302000.04Comparative Pre-2Comparative Lecture219772450140.10251790.04Comparative Pre-3Comparative Lecture31878948690.25215830.12Comparative Pre-4Comparative Lecture41859048080.25226880. 12 Comparative Example 5 Invention Steel 1430-20522140.15222360.03 Comparative Example 6 Invention Steel 11101553450.453027000.14 Comparative Example 7 Invention Steel 119287474130.852516350.38 Comparative Example 8 Invention Steel 119574510140.654520890.25 Comparative Example 9 Invention Steel 1181965462 0.252531250.13 Comparative Example 10 Invention Steel 417888510150.2012516670.14 Comparative Example 11 Invention Steel 413540510140.556023572.28 Comparative Example 12 Invention Steel 419797450110.704528641.95 Comparative Example 13 Invention Steel 485-2053470.355025000.38X = (TL_EL×W Zn ) / W Ni Y = (CR2×TL_EL) / HT

[0151] Classification Microstructure (Area %) Ni_max (%) Ni_nom (%) (Ni_max + Ni_nom) / 2 (%) Ni_Wave (㎛) Zn Single-sided plating thickness (㎛) GNDave (×10 12 m -2) One or more of FM+TMF and B Invention Example 1 10000.1180.0040.0616.14.5274 Invention Example 2 10000.1010.0040.0535.95.1279 Invention Example 3 10000.0790.0040.0426.211.3281 Invention Example 4 9910.1210.0040.0636.59.5282 Invention Example 5 10000.0980.00 40.05 15.8 5.2 278 Comparative Example 1 73 270.1 200.00 40.06 26.4 4.9 225 Comparative Example 2 72 280.1 100.00 40.05 76.04 3210 Comparative Example 3 76 240.09 20.00 40.04 85.85.3 231 Comparative Example 4 72 280.09 70.00 40.05 15.6 5.4 245 Comparative Example 5 71290.1020.0040.0536.15.5225 Comparative Example 676240.1120.0040.0586.15.9252 Comparative Example 776240.0060.0040.0050.25.0211 Comparative Example 870300.0070.0040.0060.25.12201 Comparative Example 910000.0050.0040.00 50.25.2291 Comparative Example 1010000.1120.0040.0585.923.5282 Comparative Example 1110000.0050.0040.0050.211.9297 Comparative Example 1210000.0050.0040.0050.28.5299 Comparative Example 1373270.0050.0040.0050.29.8215 FM: Fresh Martensite, TM: Tempered Martensite, F: Ferrite, B: Bainite

[0152] Classification Yield Strength (YS) (MPa) Tensile Strength (YS) (MPa) Total Elongation (T_EL) (%) Uniform Elongation (U_EL) (%) Diffusible Hydrogen Content (Hd) (ppm) Critical Hydrogen Content (Hc) (ppm) Hc / Hd Time to Break (Ft) (min) TS / Ft (MPa / min) Invention Example 1 127315567.33.90.050.204.03643 Invention Example 2 129815827.03.70.040.215.34734 Invention Example 3127815457.34.00.060.254.24435 Invention Example 4130115807.03.80.040.256.34238 Invention Example 5127515467.54.10.050.275.45230 Comparative Example 1115214568.14.00.060.264.36424 Comparative Example 2113214468.24.20.030.279.06722 Comparative Example 3102514654 .32.50.050.091.81692 Comparative Example 4 110114357.64.10.060.254.24731 Comparative Example 5 108514257.84.20.050.204.04036 Comparative Example 6 117514647.53.90.040.256.35129 Comparative Example 7 136514664.22.30.190.201.115105 Comparative Example 8 130113994.32.40.180.2 01.11699 Comparative Example 9128715566.93.70.130.151.21792 Comparative Example 10128415647.23.90.150.171.11698 Comparative Example 11142516254.62.50.210.221.01986 Comparative Example 12152516354.22.60.190.211.114117 Comparative Example 13119714555.93.00.150.211.41890

[0153] Figure 1 shows the results of analyzing the surface layer of Invention Example 1 using GDS. As can be seen from Tables 1 to 7 and Figure 1, Invention Examples 1 to 5, which satisfy the alloy composition and manufacturing conditions proposed by the present invention, demonstrate that the mechanical properties and hydrogen embrittlement resistance are excellent as they secure the microstructure, average GND value, thickness of the Zn plating layer, composition related to the Ni enrichment region, diffusible hydrogen content, and critical hydrogen content desired by the present invention.

[0154] Comparative Example 1, which does not satisfy the C content proposed by the present invention, failed to secure the average microstructure and GND value, and thus the yield strength and tensile strength were found to be insufficient.

[0155] Comparative Example 2, which does not satisfy the C content and Mn content proposed by the present invention, failed to secure the average microstructure and GND value, and thus the yield strength and tensile strength were found to be insufficient.

[0156] In the case of Comparative Example 3, which does not satisfy the B content and annealing temperature proposed by the present invention, it can be seen that the yield strength, tensile strength, Hc / Hd, time to break, and TS / Ft are insufficient because the microstructure, average GND value, and critical hydrogen content are not secured.

[0157] In the case of Comparative Example 4, which does not satisfy the C content, B content, and first cooling end temperature proposed by the present invention, it can be seen that the yield strength and tensile strength are insufficient because the microstructure and GND average value intended by the present invention are not secured.

[0158] In the case of Comparative Example 5, which does not satisfy the secondary cooling termination temperature, Mf-T2, reheating / overaging treatment temperature, HT-T2 proposed by the present invention, it can be seen that the yield strength and tensile strength are insufficient because the microstructure and average GND values ​​intended by the present invention were not secured.

[0159] In the case of Comparative Example 6, which does not satisfy the second average cooling rate, HT-T2, and X value proposed by the present invention, it can be seen that the yield strength and tensile strength are insufficient because the microstructure and GND average value intended by the present invention were not secured.

[0160] In the case of Comparative Example 7, which does not satisfy the coiling temperature, annealing temperature, Ni single-sided coating amount, tension leveling elongation, and X value proposed by the present invention, it can be seen that the microstructure, GND average value, Ni_max, (Ni_max+Ni_nom) / 2, Ni_Wave, and diffusible hydrogen amount intended by the present invention were not secured, and thus the tensile strength, total elongation, uniform elongation, Hc / Hd, time to break, and TS / Ft were at an insufficient level.

[0161] In the case of Comparative Example 8, which does not satisfy the annealing temperature, Ni single-sided adhesion amount, tension leveling elongation, and X value proposed by the present invention, it can be seen that the microstructure, GND average value, Ni_max, (Ni_max+Ni_nom) / 2, Ni_Wave, and diffusible hydrogen amount intended by the present invention were not secured, and thus the tensile strength, total elongation, uniform elongation, Hc / Hd, time to break, and TS / Ft were at an insufficient level.

[0162] In the case of Comparative Example 9, which does not satisfy the Ni single-sided attachment amount and X value proposed by the present invention, it can be seen that the Ni_max, (Ni_max+Ni_nom) / 2, Ni_Wave, and diffusible hydrogen amount intended by the present invention were not secured, and thus the Hc / Hd, breakage time, and TS / Ft were at an insufficient level.

[0163] In the case of Comparative Example 10, which does not satisfy the Zn single-sided coating amount and X value proposed by the present invention, it can be seen that the Zn plating layer thickness and diffusible hydrogen amount intended by the present invention are not secured, and thus the Hc / Hd, breakage time, and TS / Ft are at an insufficient level.

[0164] In the case of Comparative Example 11, which does not satisfy the secondary average cooling rate, Ni single-sided coating amount, X value, and Y value proposed by the present invention, it can be seen that the total elongation, uniform elongation, Hc / Hd, and fracture time are at an insufficient level because the Ni_max, (Ni_max+Ni_nom) / 2, Ni_Wave, and diffusible hydrogen amount intended by the present invention are not secured.

[0165] In the case of Comparative Example 12, which does not satisfy the secondary average cooling rate, Ni single-sided coating amount, tension leveling elongation, X value, and Y value proposed by the present invention, it can be seen that the total elongation, uniform elongation, Hc / Hd, time to break, and TS / Ft are at an insufficient level because the Ni_max, (Ni_max+Ni_nom) / 2, Ni_Wave, and diffusible hydrogen amount intended by the present invention are not secured.

[0166] In the case of Comparative Example 13, which does not satisfy the reheat / overaging treatment temperature, HT-T2, and X value proposed by the present invention, it can be seen that the yield strength, tensile strength, Hc / Hd, time to break, and TS / Ft are insufficient because the microstructure, GND average value, Ni_max, (Ni_max+Ni_nom) / 2, Ni_Wave, and diffusible hydrogen content intended by the present invention were not secured.

Claims

1. A base steel plate; and a Zn plating layer formed on at least one surface of the base steel plate; comprising, The above-mentioned base steel sheet comprises, in weight percent, carbon (C): 0.180~0.330%, silicon (Si): 0.020~0.60%, manganese (Mn): 0.40~2.40%, phosphorus (P): 0.030% or less (excluding 0%), sulfur (S): 0.0050% or less (excluding 0%), boron (B): 0.00050~0.0050%, and the remainder consists of Fe and other unavoidable impurities. The above base steel plate has an average GND value (GNDave) of 255×10 12 m -2 ~325×10 12 m -2 And, The above Zn plating layer includes a Ni enrichment region, and Galvanized steel sheet with a diffusible hydrogen content (Hd) of 0.10 ppm or less.

2. In Paragraph 1, The above-mentioned base steel sheet is a plated steel sheet additionally comprising one or more of the following: aluminum (Al): 0.0050~0.080%, chromium (Cr): 0.0010~0.50%, molybdenum (Mo): 0.0010~0.40%, niobium (Nb): 0.0010~0.10%, titanium (Ti): 0.0050~0.250%, nitrogen (N): 0.010% or less (excluding 0%), copper (Cu): 0.0010~0.30%, and nickel (Ni): 0.0010~0.30%.

3. In Paragraph 1, The above-mentioned base steel plate is a galvanized steel plate satisfying the following relationship 1. [Equation 1] 0.050 wt% ≤ Cr+Mo+Ni+Cu ≤ 1.0 wt% 4. In Paragraph 1, The above-mentioned steel sheet is a plated steel sheet in which the microstructure, in area %, comprises a total of at least one type of ferrite and bainite: 5% or less (including 0%), and the remainder being at least one type of martensite and tempered martensite.

5. In Paragraph 1, The above Zn plating layer is a plated steel sheet having an average thickness of 1.0 to 20.0 μm.

6. In Paragraph 1, The above Ni enrichment region is a plated steel sheet having a maximum Ni content (Ni_max) of 0.010 to 0.40 wt%.

7. In Paragraph 1, The above galvanized steel sheet is a galvanized steel sheet satisfying the following relationship 2. [Equation 2] 0.010 wt% ≤ (Ni_max+Ni_nom) / 2 ≤ 0.350 wt% (However, in the above Equation 2, Ni_max refers to the maximum Ni content within the Ni enrichment region, and Ni_nom refers to the average Ni content within the region up to 20㎛ in the thickness direction from the surface of the base steel sheet.) 8. In Paragraph 7, The above Ni enrichment region is a plated steel sheet in which the average thickness (Ni_Wave) of the region satisfying the above relationship 2 is 0.40 to 10.0 μm.

9. In Paragraph 1, The above galvanized steel sheet is a galvanized steel sheet having a critical hydrogen content (Hc) of 0.14 ppm or more.

10. In Paragraph 1, The above galvanized steel sheet is a galvanized steel sheet having a critical hydrogen content (Hc) / diffusible hydrogen content (Hd) of 2.5 or higher.

11. In Paragraph 1, The above galvanized steel sheet is a galvanized steel sheet having a yield strength (YS): 1200 MPa or more, a tensile strength (TS): 1470 MPa or more, a total elongation (T_EL): 5.0% or more, and a uniform elongation (U_EL): 2.7% or more.

12. In Paragraph 1, The above galvanized steel sheet has a hydrogen embrittlement fracture time (Ft): 20 minutes or more, and a tensile strength (TS) / hydrogen embrittlement fracture time (Ft): 19~89 MPa·min -1 Phosphorized steel sheet.

13. A step of heating a slab comprising, in wt%, carbon (C): 0.180~0.330%, silicon (Si): 0.020~0.60%, manganese (Mn): 0.40~2.40%, phosphorus (P): 0.030% or less (excluding 0%), sulfur (S): 0.0050% or less (excluding 0%), boron (B): 0.00050~0.0050%, and the remainder being Fe and other unavoidable impurities: A step of obtaining a hot-rolled steel sheet by finishing hot-rolling the above heated slab; Step of winding the above hot-rolled steel sheet; A step of obtaining a cold-rolled steel sheet by cold-rolling the above-mentioned coiled hot-rolled steel sheet; Step of continuously annealing the above cold-rolled steel sheet; A step of first cooling the above continuously annealed cold-rolled steel sheet; A step of secondarily cooling the above first-cooled cold-rolled steel sheet; A step of reheating the above secondary cooled cold-rolled steel sheet and then over-aging it; A step of forming a Ni coating layer on at least one surface of the above-mentioned over-aged cold-rolled steel sheet; A step of tension leveling the cold-rolled steel sheet having the above Ni coating layer formed thereon; and The method includes the step of forming a Zn plating layer on the surface of the cold-rolled steel sheet having the Ni coating layer formed thereon after the tension leveling above. During the above secondary cooling, the Mf-secondary cooling end temperature (T2) is controlled to be 10℃ or higher, and A method for manufacturing a galvanized steel sheet satisfying the following relationship 3. [Relationship 3] X = (TL_EL×W Zn ) / W Ni ≤ 1500 (However, in the above Equation 3, the above TL_EL represents the tension leveling elongation rate, and the above W Zn represents the amount of Zn attached to one side, and the above W Ni represents the amount of Ni deposited on one side.) 14. In Paragraph 13, A method for manufacturing a galvanized steel sheet in which the heating of the above slab is performed at 1100~1300℃.

15. In Paragraph 13, The above finishing hot rolling is a method for manufacturing a galvanized steel sheet performed at Ar3 to Ar3+120℃.

16. In Paragraph 13, The above-mentioned coiling is a method for manufacturing a plated steel sheet performed at Ms~700℃.

17. In Paragraph 13, The above cold rolling is a method for manufacturing galvanized steel sheets, performed at a cold rolling reduction rate of 35 to 70%.

18. In Paragraph 13, The above continuous annealing is a method for manufacturing a plated steel sheet, performed at Ac3 to Ac3+120℃ for 50 to 200 seconds.

19. In Paragraph 13, A method for manufacturing a plated steel sheet, wherein the above first cooling is performed at a first average cooling rate (CR1) of 0.5 to 6.0℃ / s until a first cooling end temperature (T1) of 620℃ to Ac3.

20. In Paragraph 13, A method for manufacturing a plated steel sheet, wherein the above secondary cooling is performed at a secondary average cooling rate (CR2) of 40 to 500℃ / s until a secondary cooling end temperature (T2) of 40 to 200℃.

21. In Paragraph 13, A method for manufacturing a plated steel sheet in which the above overaging treatment is performed at an overaging treatment temperature (HT) of 90 to 270°C for an overaging treatment time (ht) of 180 to 900 seconds.

22. In Paragraph 13, A method for manufacturing a plated steel sheet in which, during the above overaging treatment, the overaging treatment temperature (HT) - secondary cooling end temperature (T2) is controlled to be 30℃ or higher.

23. In Paragraph 13, A method for manufacturing a plated steel sheet in which, when forming the above Ni coating layer, the amount of Ni attached on one side is controlled to be 3 to 25 mg / m².

24. In Paragraph 13, A method for manufacturing a plated steel sheet in which the above tension leveling is performed with an elongation rate of 0.05 to 2.0%.

25. In Paragraph 13, A method for manufacturing a plated steel sheet in which, when forming the above Zn plating layer, the amount of Zn attached on one side is controlled to be 5 to 120 g / ㎡.

26. In Paragraph 13, A method for manufacturing a galvanized steel sheet satisfying the following relationship 4. [Equation 4] Y = (CR2×TL_EL) / HT ≤ 1.0 (However, in the above Equation 4, CR2 represents the secondary average cooling rate, TL_EL represents the tension leveling elongation rate, and HT represents the overaging treatment temperature.)

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