Plated steel sheet and manufacturing method thereof

Abstract

One aspect of the present invention provides a plated steel sheet. The plated steel sheet comprises: a base steel sheet; a Zn-Ni plating layer disposed on at least one surface of the base steel sheet; a Ni plating layer disposed on one surface of the Zn-Ni plating layer; and an Fe-Ni-Zn diffusion layer disposed between the base steel sheet and the Zn-Ni plating layer, wherein the degree of alloying in the diffusion layer may be 30% or more and less than 80%.

Description

Galvanized steel sheet and its manufacturing method

[0001] The present invention relates to a plated steel sheet and a method for manufacturing the same. More specifically, the present invention relates to a plated steel sheet usable in secondary battery cases and the like, and a method for manufacturing the same.

[0002] Recently, as part of efforts to reduce CO2 emissions and protect the global environment, development and demand in the electric vehicle and electronic device industries have increased significantly. These technological advancements have led to a surge in the use of rechargeable secondary batteries, and their applications are diversifying, including mobile devices, power tools, energy storage devices, and electric vehicles.

[0003] In general, there is a growing demand for improved corrosion resistance in secondary battery case materials to withstand the alkaline properties of the battery contents. For example, aluminum, plastic, or nickel-plated steel with excellent corrosion resistance are trending as materials for these secondary battery cases.

[0004] Among these, nickel-plated steel sheets can be manufactured from cold-rolled steel sheets through processes such as nickel plating, diffusion heat treatment, and temper rolling. At this time, the amount of nickel plating, the alloying degree of the Fe alloy layer formed by heat treatment, or the hardness of the surface of the Ni plating layer are among the important factors that determine the quality of the case (e.g., corrosion resistance, workability, etc.).

[0005] Furthermore, nickel-plated steel sheets are manufactured into secondary battery cases through press processing. Therefore, a material that ensures not only corrosion resistance but also press workability is required. Specifically, the strength of the base steel sheet, its elongation, and / or the hardness of the nickel plating layer are among the factors determining press workability.

[0006] For example, if the hardness of the Ni plating layer is excessively high, it may cause defects or damage to the mold due to peeling or cracking of the plating layer during the press working process. In addition, for example, if the strength of the base steel sheet or the hardness of the Ni plating layer is excessively low, the plating layer may be fused to the mold during the press working process, resulting in severe burr generation and reduced productivity. Or, after manufacturing a secondary battery, a quality problem may occur, such as an electric short circuit or a loss of battery function due to burr fragments reacting with the charging solution inside the secondary battery.

[0007] As a prior art for manufacturing a case for a secondary battery, Patent Document 1 discloses a technology for improving the interfacial adhesion between a base steel sheet and a plating layer through a Ni-Fe alloy layer and improving corrosion resistance by filling in cracks formed on the surface layer of nickel, a hard metal.

[0008] However, research on materials with sufficient corrosion resistance and processability as materials for secondary battery cases using steel plates is still required.

[0009] (Patent Document 1) U.S. Patent Publication No. 5,587,248

[0010] One aspect of the present invention is to provide a plated steel sheet having excellent corrosion resistance and workability and a method for manufacturing the same.

[0011]

[0012] The objectives of the present invention are not limited to the above-described matters. Additional objectives of the present invention are described throughout the specification, and those skilled in the art will have no difficulty understanding the additional objectives of the present invention from the contents described in the specification.

[0013] One aspect of the present invention provides a plated steel sheet. The plated steel sheet includes: a base steel sheet; a Zn-Ni plating layer provided on at least one surface of the base steel sheet; a Ni plating layer provided on one surface of the Zn-Ni plating layer; and an Fe-Ni-Zn diffusion layer provided between the base steel sheet and the Zn-Ni plating layer, wherein the degree of alloying of the diffusion layer may be 30% or more and less than 80%.

[0014] Additionally, in the aforementioned plated steel sheet, the content of Ni with respect to the total weight of the Zn-Ni plating layer may be 5 to 30 wt%.

[0015] Additionally, in one of the aforementioned plated steel sheets, the thickness of the Zn-Ni plating layer may be 1 to 5 μm.

[0016] Additionally, in one of the aforementioned plated steel sheets, the thickness of the Ni plating layer may be 1 to 5 μm.

[0017] Additionally, in one of the aforementioned plated steel sheets, the average surface roughness (Ra) of the Ni plating layer may be 1.0 µm or more and less than 2.0 µm.

[0018]

[0019] Another aspect of the present invention provides a method for manufacturing a plated steel sheet. The method comprises the steps of: plating Zn-Ni on at least one surface of the base steel sheet; plating Ni on the Zn-Ni plated steel sheet; and annealing the Ni plated steel sheet, wherein in the annealing step, an Fe-Ni-Zn diffusion layer having an alloying degree of 30% or more and less than 80% can be formed.

[0020] In addition, in the method described above, if the steel sheet in the preparation step is a non-annealed steel sheet, the annealing step can be performed at 520 to 670°C.

[0021] In addition, in one of the above-described methods, if the steel sheet in the preparation step is an annealed steel sheet, the annealing step may be performed at 380 to 520°C.

[0022] In addition, in one of the above-described methods, the Zn-Ni plating step is performed with a plating adhesion amount of 3 to 20 g / m 2 It can be performed by Zn-Ni electroplating.

[0023] In addition, in one of the above-described methods, the Ni plating step is performed at a plating adhesion amount of 3 to 15 g / m 2 It can be performed by electroplating with Ni.

[0024] Additionally, in one of the aforementioned methods, the annealing step may be performed for a time period of more than 20 seconds and less than 100 seconds.

[0025] Additionally, in one of the above-described methods, a step of subjecting the annealed steel plate to temper rolling may be further included.

[0026] Additionally, in one of the aforementioned methods, the temper rolling step may be performed at an elongation of 0.7 to 1.5%.

[0027] According to the present invention, by including an Fe-Ni-Zn diffusion layer, processability and corrosion resistance are improved, and it can be used as a material for a secondary battery case.

[0028] In addition, according to the present invention, by including a Zn-Ni plating layer, the interfacial adhesion and ductility between the base steel sheet and the plating layer can be improved, thereby further improving press workability.

[0029]

[0030] The various advantageous and beneficial advantages and effects of the present invention are not limited to the above-described contents, and will be more easily understood in the course of explaining specific embodiments of the present invention.

[0031] In order to more fully understand the drawings cited in the detailed description of the present invention, a brief description of each drawing is provided.

[0032] Figure 1 is a flowchart of a method for manufacturing a plated steel sheet according to one embodiment of the present invention.

[0033] Figure 2 is a graph showing the GDS analysis of the plated steel sheet of Example 23.

[0034] Figure 3 is a graph showing the GDS analysis of the plated steel sheet of Comparative Example 4.

[0035] Hereinafter, preferred embodiments of the present invention will be described. However, the embodiments of the present invention may be modified in various other forms, and the terminology used herein is for the purpose of describing the present invention and is not intended to limit the present invention. Furthermore, the singular forms used herein also include plural forms, unless the relevant definition clearly indicates a contrary meaning.

[0036] In this specification, the term "including" is used to indicate that other components may be included rather than excluding other components unless specifically stated to the contrary.

[0037] Additionally, unless otherwise specifically provided in the specification of the present invention, the % unit means weight%.

[0038] Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which this invention pertains. Terms defined in the dictionary are to be interpreted to have meanings consistent with the relevant technical literature and the present disclosure.

[0039]

[0040] The present invention will be described in detail below.

[0041] A plated steel sheet according to one embodiment of the present invention may include: a base steel sheet; a Zn-Ni plating layer provided on at least one surface of the base steel sheet; a Ni plating layer provided on one surface of the Zn-Ni plating layer; and an Fe-Ni-Zn diffusion layer provided between the base steel sheet and the Zn-Ni plating layer.

[0042]

[0043] First, the substrate steel plate will be described. Regarding the substrate steel plate, the type of steel plate, the alloy composition, etc. are not particularly limited, and any steel plate commonly used for metal plating in the relevant technical field can be used. For example, the substrate steel plate can be an ultra-low carbon steel with excellent workability. Furthermore, for example, the substrate steel plate can be an annealed cold rolled steel plate (Cold Rolled; CR) or a non-annealed cold rolled steel plate (Full Hard; FH) that has not undergone an annealing process.

[0044]

[0045] The above alloying element may contain carbon (C), silicon (Si), manganese (Mn), and phosphorus (P). Below, each alloying element is briefly described. Unless otherwise specified, the content of the alloying element refers to weight percent.

[0046]

[0047] Carbon (C): 0.005 to 0.05%

[0048] Carbon (C) can improve the strength and hardenability of the steel sheet. If the C content is less than 0.005%, manufacturing may not be easy because C is included as a minimal impurity. In addition, if the C content exceeds 0.05%, processability may be reduced. That is, the C content may be 0.005 to 0.05%, specifically 0.005 to 0.050%, more specifically 0.015 to 0.050%, and even more specifically 0.025 to 0.050%.

[0049]

[0050] Silicon (Si): 0.03% or less (excluding 0%)

[0051] Silicon (Si) can improve strength as a solid-solution strengthening element. Furthermore, if the Si content exceeds 0.03%, the strength may increase excessively, making it ineffective in terms of processability. Specifically, the Si content may be 0.03% or less, specifically 0.030% or less, more specifically 0.025% or less, and even more specifically 0.020% or less.

[0052]

[0053] Manganese (Mn): 0.1 to 0.5%

[0054] The desired strength of the steel sheet can be secured through the solid solution strengthening effect of manganese (Mn), and manganese (Mn) can suppress hot-rolled embrittlement by forming MnS precipitates through combination with sulfur. When the content of Mn is less than 0.1%, MnS precipitation is not sufficient, and hot-rolled embrittlement may be induced by the remaining sulfur. In addition, when the content of Mn exceeds 0.5%, the strength may increase excessively, which may be undesirable in terms of workability. That is, the content of Mn may be 0.1 to 0.5%, specifically 0.10 to 0.50%, more specifically 0.1 to 0.4%, and even more specifically 0.1 to 0.3%.

[0055]

[0056] Phosphorus (P): 0.02% or less (excluding 0%)

[0057] Phosphorus (P) is a material reinforcing element that can improve the strength of steel plates. In addition, if the P content exceeds 0.02%, sufficient ductility cannot be secured. That is, the P content may be 0.02% or less, specifically 0.020% or less, more specifically 0.018% or less, and even more specifically 0.016% or less.

[0058]

[0059] The steel sheet may contain the above components, as well as iron (Fe) as a remaining component. Furthermore, during the typical manufacturing process, unintended impurities from raw materials or the surrounding environment may inevitably be mixed in, and thus cannot be excluded. Since these impurities are readily apparent to anyone skilled in the art of manufacturing, their full details are not specifically addressed in this specification.

[0060]

[0061] By incorporating the above alloy components in appropriate amounts, the steel sheet can secure strength and mechanical properties suitable for use as a secondary battery case. For example, the steel sheet can secure excellent strength and mechanical properties by having a tensile strength of 400 MPa or less and / or an elongation of 30% or greater.

[0062]

[0063] Below, the Zn-Ni plating layer is described.

[0064]

[0065] The Zn-Ni plating layer can improve the adhesion between the Ni plating layer and the base steel sheet and the corrosion resistance of the plated steel sheet. Specifically, the Zn-Ni plating layer can be formed by electroplating on at least one surface of the base steel sheet. In general, when Ni plating is performed on the base steel sheet, there is a problem that the Ni plating layer is too hard and thus the interfacial adhesion with the base steel sheet is somewhat poor. However, the plated steel sheet according to one embodiment of the present invention has the effect of improving the interfacial adhesion between the Ni plating layer and the base steel sheet and the ductility of the plated steel sheet, and also improving the press workability, by performing Zn-Ni plating on the base steel sheet before performing Ni plating.

[0066] The content of Ni relative to the total weight of the Zn-Ni plating layer may be 5 to 30 wt%. If the content of Ni is less than 5 wt%, sufficient corrosion resistance cannot be obtained. In addition, if the content of Ni exceeds 30 wt%, the hardness may be too high and the workability may be reduced. That is, the content of Ni may be 5 to 30 wt%, more specifically 7 to 25 wt%, and even more specifically 8 to 20 wt%.

[0067] The thickness of the Zn-Ni plating layer may be 1 to 5 μm. If the thickness of the Zn-Ni plating layer is less than 1 μm, sufficient corrosion resistance cannot be obtained. In addition, if the thickness of the Zn-Ni plating layer exceeds 5 μm, problems such as high manufacturing cost and difficulty in manufacturing may occur. That is, the thickness of the Zn-Ni plating layer may be 1 to 5 μm, more specifically 2 to 5 μm, and even more specifically 3 to 5 μm.

[0068] The Zn-Ni plating layer may contain zinc (Zn) as the remaining component. Furthermore, unintended impurities (e.g., iron (Fe)) may inevitably be mixed in during the typical manufacturing process from raw materials or the surrounding environment, and this cannot be ruled out. Since these impurities are readily apparent to anyone skilled in the art, their full content is not specifically addressed in this specification.

[0069]

[0070] Below, the Ni plating layer is described.

[0071]

[0072] A Ni plating layer can be formed on one surface of a Zn-Ni plating layer to improve the corrosion resistance of the plated steel sheet. For example, the Ni plating layer can be formed by electroplating on one surface of the Zn-Ni plating layer.

[0073] The thickness of the Ni plating layer may be 1 to 5 μm. If the thickness of the Ni plating layer is less than 1 μm, sufficient corrosion resistance cannot be obtained. In addition, if the thickness of the Ni plating layer exceeds 5 μm, problems such as high manufacturing costs and difficulty in manufacturing may occur. That is, the thickness of the Ni plating layer may be 1 to 5 μm, more specifically 1.5 to 4.5 μm, and even more specifically 2 to 4 μm.

[0074] The average surface roughness (Ra) of the Ni plating layer may be 1.0 ㎛ or more and less than 2.0 ㎛. If the average surface roughness of the Ni plating layer is less than 1.0 ㎛, it may not be easy to manufacture using a temper rolling method. In addition, if the average surface roughness of the Ni plating layer is 2.0 ㎛ or more, the characteristics required for a secondary battery (e.g., processability, corrosion resistance, etc.) cannot be sufficiently obtained. That is, the average surface roughness of the Ni plating layer may be 1.0 ㎛ or more and less than 2.0 ㎛, more specifically, may be 1.0 to 1.8 ㎛, and even more specifically, may be 1.0 to 1.6 ㎛.

[0075] The maximum roughness height (Ry) of the Ni plating layer may be 5 to 15 μm. If the maximum roughness height of the Ni plating layer is less than 5 μm, it may not be easy to manufacture using a temper rolling method. In addition, if the maximum roughness height of the Ni plating layer exceeds 15 μm, the characteristics required for a secondary battery (e.g., processability, corrosion resistance, etc.) cannot be sufficiently obtained. That is, the maximum roughness height of the Ni plating layer may be 5 to 15 μm, more specifically 5 to 12 μm, and even more specifically 6 to 10 μm.

[0076]

[0077] Below, the Fe-Ni-Zn diffusion layer is described.

[0078]

[0079] An Fe-Ni-Zn diffusion layer is formed between the base steel sheet and the Zn-Ni plating layer, thereby improving workability. Generally, the Ni plating layer has a problem of cracking during press processing due to its high hardness and low elongation. According to one embodiment of the present invention, the plated steel sheet forms an Fe-Ni-Zn diffusion layer through annealing treatment, thereby improving the formability of the plated steel sheet and minimizing problems during cutting processing (e.g., occurrence of burrs, chips, or dust, adhesion of the Ni plating layer to the mold, damage to the mold, etc.).

[0080] The alloying degree of the Fe-Ni-Zn diffusion layer may be 30% or more and less than 80%. Here, the alloying degree may be used synonymously with the alloying degree of (Fe+Zn) in the Fe-Ni-Zn diffusion layer, or the alloying degree of (Fe+Zn) / (Fe-Ni-Zn). In addition, the alloying degree may refer to the content fraction of (Fe+Zn) in the Fe-Ni-Zn diffusion layer. When the alloying degree is less than 30%, the workability and / or corrosion resistance may be insufficient. In addition, when the alloying degree is 80% or more, the Fe component may be exposed to the surface, resulting in insufficient corrosion resistance. That is, the alloying degree may be 30% or more and less than 80%, more specifically, may be 35 to 75%, and even more specifically, may be 35 to 65%.

[0081] In the Fe-Ni-Zn diffusion layer, the thickness of the Fe diffusion layer may be 30 to 80% of the total thickness of the Fe-Ni-Zn diffusion layer. Here, the Fe diffusion layer may be formed by the diffusion of the Fe component of the base steel sheet into the Zn-Ni plating layer. In addition, the thickness of the Fe diffusion layer here may mean the thickness of an area in the Fe-Ni-Zn diffusion layer where the Fe component is detected during GDS analysis. When the thickness of the Fe diffusion layer is less than 30%, the workability may be insufficient. In addition, when the thickness of the Fe diffusion layer exceeds 80%, the Fe component may be exposed to the surface, resulting in insufficient corrosion resistance. That is, the thickness of the Fe alloy layer may be 30 to 80%, more specifically, 35 to 75%, and even more specifically, 40 to 70%.

[0082]

[0083] Hereinafter, a method for manufacturing a plated steel sheet according to one embodiment of the present invention will be described.

[0084]

[0085] Figure 1 is a flow chart for a method for manufacturing a plated steel sheet of the present invention. Referring to Figure 1, the method for manufacturing a plated steel sheet may include a step of preparing a base steel sheet; a step of plating Zn-Ni on at least one surface of the base steel sheet; a step of plating Ni on the Zn-Ni plated steel sheet; and a step of annealing the Ni plated steel sheet.

[0086]

[0087] The steps of the manufacturing method of galvanized steel sheet are explained in more detail.

[0088]

[0089] [Preparation steps for the steel plate]

[0090] First, a base steel sheet is prepared. The base steel sheet is as described above, and the step of preparing the base steel sheet can be obtained by heating a slab that satisfies the alloy composition described above, and then hot-rolling, coiling, and cold-rolling it. There are no particular limitations on the conditions for slab heating, hot rolling, coiling, and cold rolling, and conditions commonly used in the relevant technical field can be applied. For example, a cold-rolled steel sheet (FH) can be annealed at a high temperature to produce a cold-rolled steel sheet (CR). The non-annealed cold-rolled steel sheet (FH) and the annealed cold-rolled steel sheet (CR) can be prepared as the base steel sheet.

[0091]

[0092] [Zn-Ni plating step]

[0093] Next, Zn-Ni plating can be performed on at least one surface of the base steel sheet. By performing Zn-Ni plating, a Zn-Ni plating layer can be formed on at least one surface of the base steel sheet. Specifically, the Zn-Ni plating step can be performed by electroplating the base steel sheet using a Zn-Ni plating solution. There are no particular limitations on the conditions for the electroplating, and conditions commonly used in the relevant technical field can be applied.

[0094] The Zn-Ni plating step is a plating deposition amount of 3 to 20 g / m 2 It can be performed by electroplating Zn-Ni. The plating amount of Zn-Ni is 3g / m 2 If it is less than 20g / m, excellent corrosion resistance cannot be secured. In addition, if the plating adhesion amount of the Zn-Ni is less than 20g / m 2 If it exceeds , the problem of increased manufacturing cost may occur. That is, the plating adhesion amount of the Zn-Ni is 3 to 20 g / m 2 may be, more specifically, 5 to 18 g / m 2 It can be, more specifically, 8 to 15 g / m 2 It could be.

[0095] For example, in the Zn-Ni plating step, the Zn-Ni plating solution can be prepared by dissolving 40 to 80 g / L of Zn metal and 40 to 80 g / L of Ni metal in sulfuric acid based on a total of 1 L, adjusting the pH to 0.8 to 2.0, and dissolving 20 to 50 g / L of sodium sulfate (Na2SO4). By adjusting the content of Zn metal, the content of Ni metal, the pH value, and / or the content of sodium sulfate within the above ranges, the content of Ni in the Zn-Ni plating layer and the plating weight of the Zn-Ni plating layer can be controlled.

[0096] For example, the Zn-Ni plating step may be performed at 50 to 80°C. If the Zn-Ni plating temperature is lower than 50°C, the plating speed may be slow, which may lower productivity. In addition, if the Zn-Ni plating temperature exceeds 80°C, the plating speed may be too fast, which may lower the quality of the plating layer. That is, the Zn-Ni plating temperature may be 50 to 80°C, more specifically 55 to 75°C, and even more specifically 60 to 70°C.

[0097] For example, in the Zn-Ni plating step, the deposition efficiency can be 85% or more. Here, the deposition efficiency can mean the actual plating amount relative to the theoretical plating amount that can be calculated based on the amount of current input.

[0098]

[0099] [Ni plating step]

[0100] Next, Ni plating can be performed on the Zn-Ni plated steel sheet. As Ni plating is performed, a Ni plating layer can be formed on one surface of the Zn-Ni plating layer. If the order of the Zn-Ni plating step and the Ni plating step is changed (i.e., if the Zn-Ni plating step is performed after the Ni plating step), since a Ni plating layer is formed on one surface of the base steel sheet, it may be difficult to secure the desired level of corrosion resistance.

[0101] For example, the Ni plating step can be performed by electroplating a base steel sheet using a Ni plating solution. There are no particular limitations on the conditions for the electroplating, and conditions commonly used in the relevant technical field can be applied.

[0102] The Ni plating step is to deposit a plating amount of 3 to 15 g / m 2 It can be performed by electroplating Ni. The plating amount of Ni is 3g / m 2 If it is less than 15g / m, not only can the processability and corrosion resistance required for secondary batteries not be secured, but the thickness of the Fe diffusion layer inside the Fe-Ni-Zn diffusion layer formed during subsequent annealing is insufficient, so cracks may occur in the plated steel sheet during press processing, or the thickness reduction rate of the plated steel sheet may significantly increase. If the plating adhesion amount of the Ni is less than 15g / m 2 If it exceeds , the manufacturing cost may increase excessively. That is, the plating adhesion amount of the Ni is 3 to 15 g / m 2 may be, more specifically, 5 to 13 g / m 2 may be, more specifically, 7 to 12 g / m 2 It could be.

[0103] The sum of the Zn-Ni plating adhesion amount and the Ni plating adhesion amount (hereinafter referred to as the total plating adhesion amount) is 5 to 40 g / m 2 The total plating adhesion amount may be 5g / m 2If the total plating amount is less than 40 g / m, it may be difficult to sufficiently protect the steel plate, which may result in reduced corrosion resistance. 2 If it exceeds , the production cost may increase or it may cause cracks in the hard Ni plating layer during press processing. That is, the total plating adhesion amount is 5 to 40 g / m 2 It can be, more specifically, 8 to 30 g / m 2 It can be, and more specifically, 10 to 25 g / m 2 It could be.

[0104] For example, in the Ni plating step, the Ni plating solution may contain 200 to 500 g / L of nickel sulfate (NiSO4), 30 to 100 g / L of nickel chloride (NiCl2), 20 to 80 g / L of boric acid (H3BO3), and the remainder of water, based on a total of 1 L. By adjusting the content of nickel sulfate, nickel chloride, and / or boric acid within the above ranges, the Ni plating layer can be implemented to have the target physical properties (e.g., corrosion resistance, processability, hardness, etc.).

[0105] For example, the Ni plating step may be performed at 40 to 80°C. If the temperature at which the Ni plating is performed is lower than 40°C, the plating speed may be excessively slow, thereby lowering the production speed. In addition, if the temperature at which the Ni plating is performed exceeds 80°C, the plating speed may be excessively fast, thereby reducing the adhesion of the plating layer to the base steel sheet. That is, the temperature at which the Ni plating is performed may be 40 to 80°C, more specifically 45 to 75°C, and even more specifically 50 to 70°C.

[0106] For example, the Ni plating step can be performed at pH 3.0 to 5.0. Additionally / alternatively, the Ni plating step can be performed at 5 to 40 A / dm 2It can be performed at a current density of . By adjusting the values ​​of pH and / or current density within the above range, excellent plating quality and an appropriate level of plating amount can be secured.

[0107]

[0108] [Annealing stage]

[0109] Next, the steel sheet on which the Ni plating layer is formed can be annealed. During the annealing step, an Fe-Ni-Zn diffusion layer can be formed between the base steel sheet and the Zn-Ni plating layer. The Fe-Ni-Zn diffusion layer is as described above.

[0110] For example, if the base steel sheet in the above-described preparation step is a slightly annealed base steel sheet (e.g., a slightly annealed cold-rolled steel sheet (Full Hard; FH)), the annealing step may be performed at 520 to 670°C. If the annealing temperature is less than 520°C, Fe diffusion is slow, and the desired degree of alloying cannot be obtained. In addition, if the annealing temperature exceeds 670°C, the thickness of the Fe diffusion layer inside the Fe-Ni-Zn diffusion layer may excessively increase, exposing Fe to the surface and reducing corrosion resistance. That is, the annealing temperature may be 520 to 670°C, more specifically, 540 to 650°C, and even more specifically, 560 to 630°C.

[0111] For example, if the base steel sheet in the above-described preparation step is an annealed base steel sheet (e.g., annealed cold rolled steel sheet (CR)), the annealing step may be performed at 380 to 520°C. If the annealing temperature is less than 380°C, Fe diffusion is slow, and the desired degree of alloying cannot be obtained. In addition, if the annealing temperature exceeds 520°C, the thickness of the Fe diffusion layer inside the Fe-Ni-Zn diffusion layer may excessively increase, exposing Fe to the surface and reducing corrosion resistance. That is, the annealing temperature may be 380 to 520°C, more specifically, 400 to 500°C, and even more specifically, 420 to 480°C.

[0112] The annealing step may be performed for a time exceeding 20 seconds and less than 100 seconds. If the annealing time is less than 20 seconds, Fe diffusion is slow, and the desired degree of alloying cannot be obtained. In addition, if the annealing time is more than 100 seconds, the thickness of the Fe diffusion layer inside the Fe-Ni-Zn diffusion layer may increase excessively, exposing Fe to the surface, which may deteriorate the corrosion resistance. That is, the annealing time may be more than 20 seconds and less than 100 seconds, more specifically, 30 to 90 seconds, and even more specifically, 40 to 80 seconds.

[0113] The thickness of the Fe-Ni-Zn diffusion layer formed in the annealing step may be 15 to 70% of the sum of the thickness of the Zn-Ni plating layer and the thickness of the Ni plating layer before annealing (hereinafter, the total plating layer thickness before annealing). If the thickness of the Fe-Ni-Zn diffusion layer is less than 15% of the total plating layer thickness before annealing, the workability may be inadequate. In addition, if the thickness of the Fe-Ni-Zn diffusion layer exceeds 70% of the total plating layer thickness before annealing, the corrosion resistance may be inadequate. That is, the thickness of the Fe-Ni-Zn diffusion layer may be 15 to 70% of the total plating layer thickness before annealing, more specifically, 20 to 65%, and even more specifically, 30 to 60%.

[0114]

[0115] [Temperature rolling stage]

[0116] For example, a step of temper rolling the annealed steel plate may be further included. Temper rolling can control the thickness, shape, and surface roughness of the steel plate, minimize residual stress in the steel plate, and ensure uniform material properties.

[0117] The temper rolling step can be performed at an elongation of 0.7 to 1.5%. If the elongation is less than 0.7%, the shape of the steel sheet may be poor. In addition, if the elongation exceeds 1.5%, the average surface roughness of the Ni plating layer may be somewhat low, which may deteriorate corrosion resistance or workability. That is, the elongation may be 0.7 to 1.5%, more specifically 0.8 to 1.3%, and even more specifically 0.8 to 1.2%.

[0118] Hereinafter, the present invention will be described in more detail through examples. However, it should be noted that the following examples are intended only to illustrate and further illustrate the present invention and are not intended to limit the scope of the invention. This is because the scope of the invention is determined by the matters set forth in the patent claims and matters reasonably inferred therefrom.

[0119]

[0120] (Example)

[0121] C: 0.03 wt%, Si: 0.01 wt%, Mn: 0.15 wt%, P: 0.008 wt%, a residual amount of iron (Fe) and other unavoidable impurities, and a 0.30 mm thick cold-rolled steel sheet containing annealed steel (CR) or non-annealed steel sheet (FH) were prepared as base steel sheets.

[0122] After alkaline degreasing, pickling and water rinsing using a sulfuric acid aqueous solution were performed on the above-mentioned base steel sheet, Zn-Ni electroplating was performed on the base steel sheet using a Zn-Ni plating solution. Specifically, the Zn-Ni plating solution was prepared by dissolving 60 g / L of Zn metal and 60 g / L of Ni metal in sulfuric acid for 1 L, adjusting the pH to 1.5, and then dissolving 40 g / L of sodium sulfate (Na2SO4). Zn-Ni plating was performed at 60°C, and the Zn-Ni plating amount and the Ni content relative to the total weight of the Zn-Ni plating layer were performed under the conditions described in Table 1 below.

[0123] Afterwards, Ni electroplating was performed on the steel plate on which the Zn-Ni plating layer was formed using a Ni plating solution. Here, the Ni plating solution contains 400 g / L of nickel sulfate (NiSO4), 80 g / L of nickel chloride (NiCl2), 60 g / L of boric acid (H3BO3), and the balance of water per 1 L. Ni plating was performed at pH 4.0, temperature 60°C, and current density 20 A / dm 2It was performed under the conditions of , and the Ni plating amount was performed under the conditions described in Table 1 below.

[0124] Finally, the steel sheet on which the Ni plating layer was formed was annealed under the conditions described in Table 1 below to form an Fe-Ni-Zn diffusion layer between the base steel sheet and the Zn-Ni plating layer, and then temper rolling was performed to manufacture the plating steel sheet.

[0125]

[0126] Types of steel plates Zn-Ni plating Ni plating weight (g / m) 2 )Total plating weight (g / m) 2 )Annealing temperature (℃)Annealing time (sec)Elongation during temper rolling (%)Zn-Ni coating amount (g / m) 2)Ni's Content (% by weight) Example 1 FH 5 5 5 10 5 5 0 4 0 0.8 Example 2 FH 5 5 5 10 5 5 0 8 0 1.3 Example 3 FH 5 5 5 10 6 5 0 4 0 0.8 Example 4 FH 5 5 5 10 6 5 0 8 0 1.3 Example 5 FH 5 5 10 1 5 5 0 4 0 0.8 Example 6 FH 5 5 10 1 5 5 0 8 0 1.3 Example 7 FH 5 5 10 1 5 6 5 0 4 0 0.8 Example 8 FH 5 5 10 1 5 6 5 0 8 0 1.3 Example 9 FH 5 2 0 5 10 5 5 0 4 0 0.8 Example 10 FH 5 2 0 5 10 5 5 0 8 0 1.3 Example 11 FH 5 2 0 5 10 6 5 0 4 0 0.8 Example 12 FH 5 2 0 5 10 6 5 0 8 0 1 .3 Example 13FH5201015550400.8 Example 14FH5201015550801.3 Example 15FH5201015650400.8 Example 16FH5201015650801.3 Example 17FH155520550400.8 Example 18FH155520550801.3 Example 19FH155520650400.8 Example 20FH155520650801.3 Example 21FH1551025550400.8 Example 22FH1551025550801.3 Example 23FH1551025650400.8 Example 2 4FH1551025650801.3Embodiment 25FH1520520550400.8Embodiment 26FH1520520550801.3Embodiment 27FH1520520650400.8Embodiment 28FH1520520650801.3Embodiment 29FH15201025550400.8Embodiment 30FH15201025550801.3Embodiment 31FH15201025650400.8Embodiment 32FH15201025650801.3Embodiment 33CR55510400400.9Embodiment 34CR55510400801.4Embodiment 35C R55510500400.8 Example 36CR55510500801.3 Example 37CR551015400400.8 Example 38CR551015400801.3 Example 39CR551015500400.8 Example 40CR551015500801.3 Example 41CR520510400400.8 Example 42CR520510400801.3 Example 43CR520510500400.8 Example 44CR520510500801.3 Example 45CR5201015400400.8 Example 46CR5201015400801.3Example 47CR5201015500400.8Example 48CR5201015500801.3Example 49CR155520400400.8Example 50CR155520400801.3Example 51CR155520500400.8Example 52CR155520500801.3Example 53CR1551025400400.8Example 54CR1551025400801.3Example 55CR1551025500400.8Example 56CR1551025500801. 3Example 57CR1520520400400.8Example 58CR1520520400801.3Example 59CR1520520500400.8Example 60CR1520520500801.3Example 61CR15201025400400.8Example 62CR15201025400801.3Example 63CR15201025500400.8Example 64CR15201025500801.3Comparative Example 1FH55510550200.8Comparative Example 2FH5551055010 01.3 Comparison Example 3 FH 5 5 5 1 0 7 0 0 4 0 0.8 Comparison Example 4 FH 5 5 5 1 0 7 0 0 8 0 1.3 Comparison Example 5 FH 2 0 2 0 4 0 7 0 0 4 0 0.8 Comparison Example 6 FH 2 0 2 0 4 0 7 0 0 8 0 1.3 Comparison Example 7 CR 5 5 5 1 0 4 0 0 2 0 0.8 Comparison Example 8 CR 5 5 5 1 0 4 0 0 1 0 1.3 Comparison Example 9 CR 5 5 5 1 0 5 5 0 4 0 0.8 Comparison Example 10 CR 5 5 5 1 0 5 5 0 8 0 1.3 Comparison Example 11 CR 2 0 2 0 5 5 0 4 0 0.8 Comparison Example 12 CR 2 0 2 0 5 5 0 8 0 1.3 Comparison Example 13 F H0-2020650801.3Comparative Example 14FH10151020450601.3Comparative Example 15FH10151020450600.5Comparative Example 16FH10151020700601.7Comparative Example 17CR0-2020500801.3Comparative Example 18CR10151020350601.3Comparative Example 19CR10151020350600.5Comparative Example 20CR10151020550601.7Comparative Example 21FH0-2020550801.3Comparative Example 22CR0-2020450601.3.

[0127]

[0128] For the above-mentioned manufactured examples and comparative examples, the alloying degree of the Fe-Ni-Zn diffusion layer, the average surface roughness (Ra) of the Ni plating layer, corrosion resistance, and workability were evaluated, and then listed in Table 2 below.

[0129] The degree of alloying was calculated using the formula [(Fe+Zn) / (Fe+Ni+Zn)×100] (where each element represents the content (weight %) in the Fe-Ni-Zn diffusion layer). Here, the content of each element was measured using GDS analysis.

[0130] The average surface roughness (Ra) was measured using a MITUTOYO SV502 2D surface roughness tester.

[0131] Corrosion resistance was evaluated through a 4-hour salt spray test based on JIS Z-2371. Specifically, each steel plate was processed into a cylindrical case for a 2170 grade battery (diameter 21 mm, height 70 mm), and then subjected to a salt spray test to evaluate corrosion resistance based on the presence or absence of white rust and red rust on the surface (◎: Excellent, ○: Good, △: Average, ×: Poor).

[0132] The workability was evaluated through a bending test for each steel plate. Specifically, after inserting a 25 mm thick specimen, it was bent 180° (1T bending), and the workability was evaluated by the presence or absence of cracks in the cross-section of the plating layer through FE-SEM (JEOL JSM-7000F) image analysis. If there were no cracks on the entire machined surface and the thickness reduction rate of the plating layer was less than 20%, it was evaluated as ◎ (excellent). If there were no cracks on the entire machined surface but the thickness reduction rate of the plating layer was 20% or more but less than 60%, it was evaluated as ○ (good). If there were no cracks on the entire machined surface but the thickness reduction rate of the plating layer was 60% or more, it was evaluated as △ (average). If cracks occurred on the entire machined surface, it was evaluated as × (bad).

[0133]

[0134] Classification Alloying degree (%) Average surface roughness (㎛) Corrosion resistance Machinability Example 1501.7 ◎◎ Example 2601.1 ◎◎ Example 3601.7 ◎◎ Example 4701.1 ◎◎ Example 5401.7 ◎◎ Example 6501.1 ◎◎ Example 7501.7 ◎◎ Example 8601.1 ◎◎ Example 9501.7 ◎◎ Example 10601.1 ◎◎Embodiment 11601.7◎◎Embodiment 12701.1◎◎Embodiment 13401.7◎◎Embodiment 14501.1◎◎Embodiment 15501.7◎◎Embodiment 16601.1◎◎Embodiment 17401.7◎◎Embodiment 18501.1◎◎Embodiment 19501.7◎◎Embodiment 20601.1◎◎ Example 21351.7◎◎ Example 22401.1◎◎ Example 23401.7◎◎ Example 24501.1◎◎ Example 25401.7◎◎ Example 26501.1◎◎ Example 27501.7◎◎ Example 28601.1◎◎ Example 29351.7◎◎ Example 30401.1◎◎ Example 31401.7◎◎ Example 32501.1◎◎ Example 33501.8◎◎ Example 34601.2◎◎ Example 35601.8◎◎ Example 36701.2◎◎ Example 37401.8◎◎ Example 38501.2◎◎ Example 39501.8◎◎ Example 40601.2◎◎ Example 4 1501.8◎◎Embodiment 42601.2◎◎Embodiment 43601.8◎◎Embodiment 44701.2◎◎Embodiment 45401.8◎◎Embodiment 46501.2◎◎Embodiment 47501.8◎◎Embodiment 48601.2◎◎Embodiment 49401.8◎◎Embodiment 50501.2◎◎Embodiment 51501.8◎◎Embodiment 52601.2◎◎Embodiment 53301.8◎◎Embodiment 54401.2◎◎Embodiment 55401.8◎◎Embodiment 56501.2◎◎Embodiment 57401.8◎◎Embodiment 58501.2◎◎Embodiment 59501.8◎◎Embodiment 60601.2◎◎Embodiment 61301 .8◎◎Embodiment 62401.2◎◎Embodiment 63401.8◎◎Embodiment 64501.2◎◎Comparative Example 1201.7△△Comparative Example 2801.1△△Comparative Example 3801.7△△Comparative Example 4901.1△△Comparative Example 5801.7◎△Comparative Example 6901.1◎△Comparative Example 7201.8△△Comparative Example 88 01.2△△Comparative example 9801.8△△Comparative example 10901.2△△Comparative example 11801.8◎△Comparative example 12901.2◎△Comparative example 13551.2△△Comparative example 14251.2△△Comparative example 15252.0△△Comparative example 16700.8△△Comparative example 17551.2△△Comparative example 18251.2△△Comparative example 19252.0△△Comparative example 20700.8△△Comparative example 21900.8△△Comparative example 22801.2△△.

[0135]

[0136] As can be seen from Tables 1 and 2 above, in the case of Examples 1 to 64 that satisfy the manufacturing conditions proposed by the present invention, an appropriate level of alloying degree and average surface roughness of the Ni plating layer were secured, and it was also found that corrosion resistance and processability were excellent.

[0137] In addition, a GDS analysis graph of Example 23 representing the embodiment is shown in Fig. 2. Specifically, (A) of Fig. 2 is a graph obtained by performing GDS analysis on the contents of Fe, Ni, and Zn in the entire plating layer (Zn-Ni plating layer and Ni plating layer) and the diffusion layer before annealing in Example 23. In addition, (B) of Fig. 2 is a graph obtained by performing GDS analysis on the contents of Fe, Ni, and Zn in the entire plating layer and the diffusion layer after annealing in Example 23.

[0138] Referring to Fig. 2, it was confirmed that the alloying degree of the diffusion layer after annealing was implemented at an appropriate level in the case of Example 23.

[0139]

[0140] On the other hand, Comparative Examples 1 and 7 had excessively short annealing times, resulting in insufficient alloying in the diffusion layer, which resulted in cracks occurring in the plating layer, and both corrosion resistance and workability deteriorated. In addition, Comparative Examples 2 and 8 had excessively long annealing times, resulting in excessive alloying in the diffusion layer, which resulted in both corrosion resistance and workability deteriorating.

[0141]

[0142] Comparative Examples 3, 4, 9, and 10 had excessively high annealing temperatures, which resulted in excessive increases in the alloying degree of the diffusion layer, resulting in deterioration in both corrosion resistance and workability. Furthermore, Comparative Examples 5, 6, 11, and 12 had inadequate workability because their annealing temperatures were excessively high.

[0143] In addition, a GDS analysis graph of Comparative Example 4 representing the comparative example is shown in Fig. 3. Specifically, (A) of Fig. 3 is a graph obtained by performing GDS analysis on the contents of Fe, Ni, and Zn in the entire plating layer (Zn-Ni plating layer and Ni plating layer) and the diffusion layer before annealing in Comparative Example 4. In addition, (B) of Fig. 3 is a graph obtained by performing GDS analysis on the contents of Fe, Ni, and Zn in the entire plating layer and the diffusion layer after annealing in Comparative Example 4.

[0144] Referring to Figure 3, it was confirmed that in the case of Comparative Example 4, the alloying degree of the diffusion layer after annealing was excessively large.

[0145]

[0146] Comparative Examples 13, 17, 21 and 22 showed that the degree of alloying after annealing was excessively high because the Zn-Ni plating layer was not formed, or the interfacial adhesion between the Ni plating layer and the base steel sheet was reduced, so that the press workability and corrosion resistance were also reduced.

[0147]

[0148] In Comparative Examples 14, 18, and 19, since the annealing temperature was set very low, the degree of alloying of the diffusion layer was insufficient and a sufficient alloy layer was not formed, so both the corrosion resistance and the workability were reduced.

[0149]

[0150] Comparative Examples 15 and 19 had extremely low elongation during temper rolling, resulting in excessively high average surface roughness, which deteriorated qualities such as corrosion resistance and workability. In addition, Comparative Examples 16 and 20 had extremely high elongation during temper rolling, which resulted in excessively low average surface roughness, which deteriorated qualities such as corrosion resistance and workability.

[0151]

[0152] The above embodiments are merely examples and the present invention is not limited thereto. Anything that has substantially the same configuration and achieves the same operational effects as the technical concepts described in the claims of the present invention is included within the technical scope of the present invention.

Claims

1. Steel plate; A Zn-Ni plating layer provided on at least one surface of the above steel plate; A Ni plating layer provided on one surface of the Zn-Ni plating layer; and Including an Fe-Ni-Zn diffusion layer provided between the above-mentioned steel plate and the Zn-Ni plating layer, A plated steel sheet having an alloying degree of the above diffusion layer of 30% or more and less than 80%.

2. In paragraph 1, A plated steel sheet having a nickel content of 5 to 30 wt% based on the total weight of the Zn-Ni plating layer.

3. In paragraph 1, A plated steel sheet having a thickness of the Zn-Ni plating layer of 1 to 5 ㎛.

4. In paragraph 1, A plated steel sheet having a thickness of the Ni plating layer of 1 to 5 ㎛.

5. In paragraph 1, A plated steel sheet having an average surface roughness (Ra) of the above Ni plating layer of 1.0 ㎛ or more and less than 2.0 ㎛.

6. Step for preparing the steel plate; A step of plating Zn-Ni on at least one surface of the above steel plate; A step of plating Ni on the Zn-Ni plated steel sheet; and Comprising a step of annealing the above Ni-plated steel sheet, A method for manufacturing a plated steel sheet, wherein, in the annealing step, an Fe-Ni-Zn diffusion layer having an alloying degree of 30% or more and less than 80% is formed.

7. In paragraph 6, A method for manufacturing a plated steel sheet, wherein when the base steel sheet in the above preparation step is a non-annealed base steel sheet, the annealing step is performed at 520 to 670°C.

8. In paragraph 6, A method for manufacturing a plated steel sheet, wherein when the base steel sheet in the above preparation step is an annealed base steel sheet, the annealing step is performed at 380 to 520°C.

9. In paragraph 6, The above Zn-Ni plating step is performed with a plating adhesion amount of 3 to 20 g / m 2 A method for manufacturing a plated steel sheet, the method comprising: electroplating a zinc-nickel layer; 10. In paragraph 6, The above Ni plating step is performed at a plating adhesion amount of 3 to 15 g / m 2 A method for manufacturing a plated steel sheet, the method comprising: electroplating a nickel (Ni) alloy; 11. In paragraph 6, A method for manufacturing a plated steel sheet, wherein the above annealing step is performed for a time of more than 20 seconds and less than 100 seconds.

12. In paragraph 6, A method for manufacturing a plated steel sheet further comprising the step of subjecting the annealed steel sheet to temper rolling.

13. In paragraph 12, A method for manufacturing a plated steel sheet, wherein the above-mentioned temper rolling step is performed at an elongation of 0.7 to 1.5%.

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