Ni-plated surface-treated steel sheet and battery container

Abstract

Provided is a Ni-plated surface-treated steel sheet provided with a steel sheet and an Fe-Ni-Cu-Cr layer formed on at least one surface of the steel sheet, the Ni-plated surface-treated steel sheet being characterized in that when Cu strength is continuously measured from the surface side of the Fe-Ni-Cu-Cr layer in the depth direction by high-frequency glow discharge emission spectroscopy (GDS), the Cu strength is less than the Cu strength in the depth direction. The ratio IRCu-0.1 d of the Cu strength InCu-0.1 d at a position 0.1 [mu] m from the surface side to the Cu strength InCu-steel of the steel sheet is 0.5 or more and less than 3.0.

Description

Technical Field

[0001] This invention relates to Ni-plated steel sheets and battery containers. Background Technology

[0002] Previously, Ni-plated steel sheets containing Ni were widely used as blanks for battery containers. Patent document 1 discloses a Ni-plated steel sheet for battery containers, which has an Fe-Ni diffusion layer formed by thermal diffusion treatment after forming a nickel-plated layer on the steel sheet, and controls the ratio of Ni to Fe in the outermost layer to prevent pitting corrosion and leakage.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2014-47359 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] However, with the increasing capacity of batteries, battery containers using the Ni-plated steel sheet disclosed in Patent Document 1 have the following problem: when over-discharge occurs due to an anomaly in the battery management system, the potential of the Fe-Ni diffusion layer approaches the positive electrode potential, and iron may sometimes dissolve from the Fe-Ni diffusion layer into the electrolyte, leading to corrosion of the inner wall of the battery container. In the future, with the increasing capacity of batteries, the positive electrode potential is expected to further increase, and there is a need for Ni-plated steel sheets with even better electrolyte resistance during over-discharge.

[0008] The purpose of this invention is to provide a Ni-plated surface-treated steel sheet with excellent resistance to electrolyte during over-discharge.

[0009] Solution for solving the problem

[0010] In order to achieve the above-mentioned objectives, the inventors conducted in-depth research and found that the above-mentioned objectives could be achieved by forming an Fe-Ni-Cu-Cr layer on a Ni-plated steel plate, thus completing the present invention.

[0011] [1] According to embodiment 1 of the present invention, a Ni-plated surface-treated steel sheet is provided, comprising: a steel sheet, and an Fe-Ni-Cu-Cr layer formed on at least one side of the aforementioned steel sheet, wherein when the Cu intensity is continuously measured from the surface side of the aforementioned Fe-Ni-Cu-Cr layer toward the depth direction by high-frequency glow discharge emission spectroscopy (GDS), the Cu intensity In at a depth of 0.1 μm from the surface side is... Cu-0.1d Compared to the Cu strength of the aforementioned steel plate, In Cu-steel The ratio of IR Cu-0.1d It is greater than 0.5 and less than 3.0.

[0012] [2] According to embodiment 2 of the present invention, a Ni-plated surface-treated steel sheet of embodiment 1 is provided, wherein, when the Cu intensity is continuously measured from the surface side of the aforementioned Fe-Ni-Cu-Cr layer toward the depth direction by high-frequency glow discharge emission spectroscopy (GDS), the Cu intensity In at a depth of 0.5 μm from the surface side is... Cu-0.5d Compared to the Cu strength of the aforementioned steel plate, In Cu-steel The ratio of IR Cu-0.5d It is greater than 0.5 and less than 3.0.

[0013] [3] According to embodiment 3 of the present invention, a Ni-plated surface-treated steel sheet of embodiment 1 or 2 is provided, wherein, when the Cr intensity is continuously measured from the surface side of the aforementioned Fe-Ni-Cu-Cr layer toward the depth direction by high-frequency glow discharge emission spectroscopy (GDS), the Cr intensity In at a depth of 0.5 μm from the surface side is... Cr-0.5d Compared to the aforementioned steel plate, the Cr strength In Cr-steel The ratio of IR Cr-0.5d It is greater than 0.2 and less than 2.0.

[0014] [4] According to embodiment 4 of the present invention, a Ni-plated surface-treated steel sheet of any one of embodiments 1 to 3 is provided, wherein, when the Cr intensity is continuously measured from the surface side of the aforementioned Fe-Ni-Cu-Cr layer toward the depth direction by high-frequency glow discharge emission spectroscopy (GDS), the Cr intensity In at a depth of 0.1 μm from the surface side is... Cr-0.1d Compared to the aforementioned steel plate, the Cr strength In Cr-steel The ratio of IR Cr-0.1d It is greater than 0.2 and less than 2.0.

[0015] [5] According to embodiment 5 of the present invention, a Ni-plated surface-treated steel sheet of any one of embodiments 1 to 4 is provided, wherein, when the Cu intensity is continuously measured from the surface side of the aforementioned Fe-Ni-Cu-Cr layer toward the depth direction by high-frequency glow discharge emission spectroscopy (GDS), the Cu intensity In at a depth of 0.3 to 0.7 μm from the surface side is... Cu-0.3d~0.7d Compared to the Cu strength of the aforementioned steel plate, In Cu-steel The ratio of IR Cu-0.3d~0.7d It is between 0.5 and 3.0.

[0016] [6] According to embodiment 6 of the present invention, a Ni-plated surface-treated steel sheet of any one of embodiments 1 to 5 is provided, wherein the aforementioned Fe-Ni-Cu-Cr layer has a Cu-rich region.

[0017] [7] According to embodiment 7 of the present invention, a Ni-plated surface-treated steel sheet of any one of embodiments 1 to 6 is provided, wherein, when the Cu intensity is continuously measured from the surface side of the aforementioned Fe-Ni-Cu-Cr layer toward the depth direction by high-frequency glow discharge emission spectroscopy (GDS), the maximum Cu intensity In at the depth up to the aforementioned steel sheet is... MAX Compared to the Cu strength of the aforementioned steel plate, In Cu-steel The ratio of IR Cu-MAX Above 0.8 and below 3.0.

[0018] [8] According to embodiment 8 of the present invention, a Ni-plated surface-treated steel sheet of any one of embodiments 1 to 7 is provided, wherein the aforementioned steel sheet is low-carbon steel or ultra-low-carbon steel.

[0019] [9] According to embodiment 9 of the present invention, a Ni-plated surface-treated steel sheet of any one of embodiments 1 to 8 is provided, wherein the steel sheet is low carbon steel, the Cu content of the steel sheet is 0.01 wt% to 1.0 wt%, and the Cr content of the steel sheet is 0.01 wt% to 1.0 wt%.

[0020]

[10] According to embodiment 10 of the present invention, a battery container is provided, which is made of Ni-plated surface-treated steel sheet of any one of embodiments 1 to 9.

[0021] The effects of the invention

[0022] According to the present invention, the dissolution of metals such as iron (Fe) into the electrolyte during over-discharge can be suppressed, and Ni-plated surface-treated steel sheets with excellent electrolyte resistance can be provided. Attached Figure Description

[0023] Figure 1 This is a schematic cross-sectional view showing the structure of the Ni-plated surface-treated steel sheet in an embodiment of the present invention.

[0024] Figure 2 This is an example of a temperature profile of a plated steel sheet used to represent the calculation method of the thermal history Y in the thermal diffusion process.

[0025] Figure 3 (a) is a graph obtained by high-frequency glow discharge emission spectrum analysis in Example 1. Figure 3 (b) is an enlarged view of the graph obtained by high-frequency glow discharge emission spectrum analysis in Example 1.

[0026] Figure 4 (a) is a graph obtained by high-frequency glow discharge emission spectrum analysis in Example 2. Figure 4 (b) is an enlarged view of the graph obtained by high-frequency glow discharge emission spectrum analysis in Example 2.

[0027] Figure 5 (a) is a graph obtained from the emission spectrum analysis of high-frequency glow discharge in Comparative Example 1. Figure 5 (b) is an enlarged view of the graph obtained by high-frequency glow discharge emission spectrum analysis of Comparative Example 1.

[0028] Figure 6 This is a schematic diagram of the measuring fixture used in evaluating the electrolyte resistance of Ni-plated surface-treated steel sheets based on the LSV method. Detailed Implementation

[0029] Figure 1 This is a schematic cross-sectional view showing the structure of the Ni-plated surface-treated steel sheet in this embodiment. (Example) Figure 1 As shown, the Ni-plated surface-treated steel sheet 1 in this embodiment includes: a steel sheet 2 formed of carbon steel, and an Fe-Ni-Cu-Cr layer 3 formed on at least one side of the steel sheet 2.

[0030] The steel sheet 2, which serves as the base material for the Ni-plated surface-treated steel sheet 1, is formed of carbon steel. The carbon steel used for the steel sheet 2 can be any carbon steel with excellent formability; there are no particular limitations. For example, low-carbon steel (carbon content 0.01% to 0.15% by weight) such as low-carbon aluminum-killed steel, where the carbon content is controlled by aluminum during steel manufacturing, ultra-low-carbon steel with a carbon content less than 0.01% by weight, or non-aging ultra-low-carbon steel made by adding Ti and / or Nb to ultra-low-carbon steel can be used.

[0031] As for the steel plate 2, from the viewpoint that Cu and Cr in the original plate used as the steel plate 2 can diffuse into the Ni coating to form an Fe-Ni-Cu-Cr layer 3, it is suitable to use a original plate made of carbon steel containing a specified amount of Cu and Cr. The Cu content of the steel plate 2 is preferably 0.01 wt% to 1.0 wt%, and from the viewpoint that increasing the Cu content in the Fe-Ni-Cu-Cr layer 3 can further improve the inhibition of metal dissolution, it is more preferably 0.05 wt% to 1.0 wt%, more preferably 0.05 wt% to 0.5 wt%, and particularly preferably 0.1 wt% to 0.4 wt%. In the case where the surface-treated steel plate 1 is used for cylindrical containers or the like that are subjected to deep drawing during forming, the Cu content of the steel plate 2 is preferably 0.05 wt% to 0.4 wt%.

[0032] The Cr content of the steel plate 2 is preferably 0.01 wt% to 1.0 wt%. From the viewpoint of increasing the Cr content in the Fe-Ni-Cu-Cr layer 3 to further improve the inhibition of metal dissolution, it is more preferably 0.03 wt% to 1.0 wt%. From the viewpoint of reducing the decrease in conductivity at the surface of the Fe-Ni-Cu-Cr layer 3 and inhibiting metal dissolution, it is even more preferably 0.03 wt% to 0.5 wt%, and particularly preferably 0.03 wt% to 0.4 wt%. There are no particular limitations on the method for adjusting the Cu and Cr content of the steel plate 2. For example, a method can be given by using steel made from raw materials such as scrap iron containing carbon steel and scrap iron containing SUS, Cu wire, etc., as the base plate of the steel plate 2.

[0033] In this embodiment, the following materials can also be used as the base plate for steel plate 2: hot-rolled carbon steel plate that has been pickled to remove surface oxide scale (oxide film), then cold-rolled, followed by electrolytic cleaning such as alkaline electrolytic degreasing, and then annealed and / or surface-finished; or cold-rolled, electrolytically cleaned, and then surface-finished without annealing. Furthermore, from a productivity perspective, continuous steel strip is preferred as steel plate 2. The hot-rolled plate can be manufactured using a blast furnace or an electric furnace.

[0034] It should be noted that in this embodiment, during the heat diffusion treatment process described later, Fe, Cu, and Cr diffuse from the surface of the original steel plate 2. Therefore, the Cu and Cr content near the boundary between the Fe-Ni-Cu-Cr layer 3 and the steel plate 2 decreases. However, relative to the overall thickness of the steel plate 2, the area where the Cu and Cr content decreases is only a very small portion and has almost no impact on the overall composition ratio of the steel plate 2. Therefore, it is acceptable to consider that the Cu and Cr content of the steel plate 2 is the same as that of the original plate. Furthermore, the same applies to components other than Cu and Cr; before and after the heat diffusion treatment process, the composition ratio of the original steel plate 2 and the composition ratio of the steel plate 2 can be considered to be the same. That is, the base plate of steel plate 2 is the same as steel plate 2, as long as it is carbon steel with excellent formability and there are no special restrictions. For example, low carbon steel such as low carbon aluminum killed steel (carbon content 0.01% to 0.15% by weight) that controls carbon content by aluminum during steel manufacturing, ultra-low carbon steel with carbon content less than 0.01% by weight, or non-aging ultra-low carbon steel made by adding Ti and / or Nb to ultra-low carbon steel can be used. From the point of view that Cu and Cr in the base plate can diffuse into the Ni coating to form Fe-Ni-Cu-Cr layer 3, it is suitable to use a base plate made of carbon steel containing a specified amount of Cu and Cr.

[0035] The thickness of the steel plate 2 can be appropriately selected according to the application of the Ni-plated surface-treated steel plate 1, and is not particularly limited. From the viewpoint of reducing manufacturing costs, it is preferably 1.5 mm or less, more preferably 1.25 mm or less, and even more preferably 0.9 mm or less. In addition, from the viewpoint of improving the mechanical properties of the Ni-plated surface-treated steel plate 1, the thickness of the steel plate 2 is preferably 0.03 mm or more, more preferably 0.1 mm or more, even more preferably 0.15 mm or more, and particularly preferably 0.2 mm or more.

[0036] The Ni-plated steel sheet 1 of this embodiment has an Fe-Ni-Cu-Cr layer 3 on a steel sheet 2. The Fe-Ni-Cu-Cr layer 3 is formed by forming a Ni plating layer on the steel sheet 2, and then subjecting the steel sheet 2 with the Ni plating layer to a thermal diffusion treatment, thereby allowing the iron (Fe), copper (Cu), and chromium (Cr) constituting the steel sheet 2 to thermally diffuse with the nickel (Ni) constituting the Ni plating layer. The Fe-Ni-Cu-Cr layer 3 can be formed on at least one side of the steel sheet 2, or it can be formed on both sides of the steel sheet 2. The Ni-plated steel sheet 1 of this embodiment has excellent electrolyte resistance during over-discharge by having the Fe-Ni-Cu-Cr layer 3.

[0037] The presence of an Fe-Ni-Cu-Cr layer 3 in the Ni-plated steel sheet 1 can be confirmed by elemental analysis of the surface layer. Specifically, this can be confirmed by surface composition analysis using high-frequency glow discharge emission spectroscopy (GDS), Auger electron spectroscopy (AES), or X-ray photoelectron spectroscopy (XPS). For example, for a standard sample with a Ni coating on low-carbon steel and the Ni-plated steel sheet 1, high-frequency glow discharge emission spectroscopy is performed from the surface towards the steel sheet 2 in the depth direction, continuously measuring the changes in Fe intensity, Ni intensity, Cu intensity, and Cr intensity relative to the measurement time. In the obtained data, when comparing the various intensities of the standard sample with those of the Ni-plated steel sheet 1, if the Fe intensity of the Ni-plated steel sheet 1 is more than 10% of the maximum Fe intensity of the standard sample, it can be determined that Fe is present. Similarly, if the Ni intensity of the Ni-plated steel sheet 1 is more than 10% of the maximum Ni intensity of the standard sample, it can be determined that Ni is present. Furthermore, if the Cu strength at any depth location of the Ni-plated steel sheet 1 is higher than the Cu strength at the same depth location in the Ni coating of the standard sample, it can be determined that Cu is present at that depth location. Similarly, if the Cr strength at any depth location of the Ni-plated steel sheet 1 is higher than the Cr strength at the same depth location in the Ni coating of the standard sample, it can be determined that Cr is present at that depth location. In cases where there are locations where it can be determined that Fe, Ni, Cu, and Cr are all present, it can be determined that an Fe-Ni-Cu-Cr layer 3 has been formed at that location. It should be noted that details regarding the standard sample will be described later.

[0038] It should be noted that the Cu and Cr in the Fe-Ni-Cu-Cr layer 3 diffused from the original plate used as steel plate 2. Therefore, the proportion of Cu and Cr in the Fe-Ni-Cu-Cr layer 3 is very small compared to the proportion of Fe and Ni. That is, the proportion of Fe and Ni is dominant in the metallic composition of the Fe-Ni-Cu-Cr layer 3. Specifically, the content of Cu and Cr in the Fe-Ni-Cu-Cr layer 3 is approximately the same as or less than the content of Cu and Cr in the steel plate 2. Therefore, the total amount of Cu and Cr is less than 2% by weight, and the total amount of iron and nickel is more than 98% by weight.

[0039] The Ni-plated steel sheet 1 only needs to have an Fe-Ni-Cu-Cr layer 3, but preferably the Cu intensity at a depth of 0.5 μm from the surface side is determined by high-frequency glow discharge emission spectroscopy. Cu-0.5d relative to the Cu strength In of steel plate 2 Cu-steel The ratio of IR Cu-0.5d (=In Cu-0.5d / In Cu-Steel The value is greater than 0.50 and less than 3.0. This is achieved by making the Cu intensity greater than the IR... Cu-0.5d Within the aforementioned range, the Ni-plated surface-treated steel sheet 1 exhibits superior electrolyte resistance during over-discharge. The reason for this is uncertain, but it is believed to be due to the formation of a mixed potential on the surface of the Fe-Ni-Cu-Cr layer 3, thereby suppressing localized dissolution upon contact with the electrolyte. If there is insufficient Cu near the surface, the number of Cu-containing grains in the surface of the Fe-Ni-Cu-Cr layer 3 decreases, or the area where Cu is present becomes smaller, potentially preventing the formation of a sufficient mixed potential. Conversely, if there is excessive Cu near the surface, areas with locally high potentials are created in the Fe-Ni-Cu-Cr layer 3, widening the potential difference with Fe and potentially increasing the dissolution of metals such as iron. From the viewpoint of further improving the suppression of iron and other metal dissolution during over-discharge, the intensity is higher than that of IR. Cu-0.5d The lower limit is more preferably 0.7 or higher, and even more preferably 0.8 or higher. Furthermore, the intensity ratio to IR... Cu-0.5d The upper limit is more preferably 2.5 or less, further preferably 2.0 or less, and particularly preferably 1.8 or less. Regarding the Cu strength In of steel plate 2... Cu-steel The method for determining this will be detailed later. Especially when the Ni adhesion is low, it is important to improve electrolyte resistance during over-discharge by making the strength higher than that of IR. Cu-0.5d Within the above range.

[0040] In high-frequency glow discharge emission spectroscopy analysis, the intensity of each element at various depth locations can be calculated by converting the measurement time (etching time) and the sputtering-based etching rate (unit: μm / s) to determine the depth from the sample surface, and then reading the intensity at that location. In this embodiment, the measurement time is converted to the measurement depth using the Ni etching rate. The method for converting the measurement time to the measurement depth is described in detail below.

[0041] First, the etching rate of Ni is determined. To determine the Ni etching rate, a standard sample is prepared from a steel sheet with Ni plating applied but without heat treatment, having a known coating thickness (or adhesion amount). For example, a standard Ni-plated steel sheet with a 1.1 μm thick matte Ni plating is prepared on a low-carbon steel sheet with a thickness of 0.3 mm. The plating treatment for the matte Ni plating of the standard Ni-plated steel sheet is not particularly limited; for example, a Watt's bath as described below can be used.

[0042] <Ni Plating Conditions>

[0043] Bath composition: Nickel sulfate hexahydrate 250 g / L, nickel chloride hexahydrate 45 g / L, boric acid 30 g / L

[0044] pH: 4.0~5.0

[0045] Bath temperature: 60℃

[0046] Current density: 10A / dm 2

[0047] The Ni plating thickness of a standard Ni-plated steel sheet can be determined by SEM-based cross-sectional observation of the Ni-plated steel sheet, converting the Ni adhesion amount obtained through fluorescence X-ray analysis into thickness using the Ni specific gravity. For this standard sample, a high-frequency glow discharge emission spectrometer was used to measure the Fe and Ni intensities in the standard Ni-plated steel sheet from the Ni-plated side until the Fe intensity reached saturation, resulting in a graph. Based on the obtained graph, the etching time for the Ni plating was determined. Specifically, the etching time of Ni is defined as the time from the start of the measurement until the Fe intensity reaches 10% of its saturation value. The Ni etching rate can be determined based on the Ni etching time and the Ni plating thickness. The saturation value of Fe intensity is determined by the rate of change of Fe intensity over time (Fe intensity change / second). The rate of change of Fe intensity over time increases sharply after the start of the measurement when Fe is detected, decreases after exceeding a maximum value, and stabilizes near zero. The value of Fe intensity when the rate of change of time stabilizes near zero is the saturation value of Fe intensity. Specifically, when the rate of change of Fe intensity over time is below 0.02 (Fe intensity / second), the Fe intensity is considered to have reached saturation.

[0048] The Ni etching rate calculated above represents a parameter relating the depth-time (based on the measurement time of the high-frequency glow discharge emission spectrometer) to the actual thickness, obtained by measuring the thickness of a Ni-coated steel sheet with a known Ni coating thickness that has not undergone thermal diffusion treatment using a high-frequency glow discharge emission spectrometer. Therefore, using the Ni etching rate calculated above, the measurement time of the high-frequency glow discharge emission spectrometer analysis of the Ni-coated steel sheet 1 can be converted into etching depth (thickness). It should be noted that in the measurements using the high-frequency glow discharge emission spectrometer, the etching rates of iron and nickel are known to be at the same level. Furthermore, the copper and chromium contained in the Fe-Ni-Cu-Cr layer 3 diffuse from the original carbon steel plate used as the substrate; therefore, the copper and chromium contained in the Fe-Ni-Cu-Cr layer 3 are present in trace amounts, and have almost no effect on the etching rate. Therefore, iron and nickel dominate the etching rate of the Fe-Ni-Cu-Cr layer 3, and the Ni etching rate calculated using a pure Ni coating can be used as the etching rate for both the Fe-Ni-Cu-Cr layer 3 and the steel sheet 2.

[0049] For example, calculating the Cu strength In at a depth of 0.5 μm from the surface side. Cu-0.5dTo obtain the Cu intensity at 0.5 μm, multiply the Ni etching rate by the measurement time. It should be noted that, depending on the etching rate, the intensity at a depth may not always match the target value. Therefore, it is sufficient to read the intensity within ±0.03 μm of the target value. For example, the intensity within 0.5 μm ± 0.03 μm can be treated as the intensity at a depth of 0.5 μm. The same method can be used to read the Cu intensity at other depths besides 0.5 μm, as described later.

[0050] In high-frequency glow discharge emission spectroscopy analysis, since the measurement is performed continuously from the surface of the sample towards the depth direction, when performing high-frequency glow discharge emission spectroscopy analysis on the Ni-plated surface-treated steel sheet 1 of this embodiment, as... Figure 3 As shown in (a), after obtaining data on the variations in Fe strength, Ni strength, Cu strength, and Cr strength, data is obtained where the depth variation (time variation) of any of the Fe strength, Ni strength, Cu strength, and Cr strength is close to 0, particularly where the Fe strength is approximately saturated. Furthermore, the Ni-plated steel sheet 1 has a structure where an Fe-Ni-Cu-Cr layer 3 is stacked with a steel sheet 2, and in the steel sheet 2, the concentration of each metal in the depth direction is generally constant. Therefore, the strength data at locations where the depth variation is close to 0 represents the strength data of each metal in the steel sheet 2. Additionally, if the results of high-frequency glow discharge emission spectroscopy analysis for the Ni-plated steel sheet 1 in this embodiment and the standard sample are compared, in the measurement results for the Ni-plated steel sheet 1, the depth at which the Ni strength of the Ni-plated steel sheet 1 becomes 2% of the maximum value of the Ni strength of the standard sample (hereinafter also referred to as D) is... Ni2% At point (), the depth variation of the strength data for each metal becomes close to 0. Therefore, in this embodiment, the depth D in the high-frequency glow discharge emission spectrum analysis results of the Ni-plated surface-treated steel sheet 1 is... Ni2% The strength of each metal at the specified location is used as data for the strength of each metal in steel plate 2. That is, the Cu strength In of the aforementioned steel plate 2... Cu-steel It can be in depth D Ni2% The strength of Cu at a given location is determined from the form of the strength of Cr at that location. The same applies to chromium; the strength of Cr is determined from the form of In. Cr-steel It can be in depth D Ni2% The strength of Cr at that location is determined by the form of the Cr intensity. It should be noted that... Figure 3 (a) is a graph obtained by high-frequency glow discharge emission spectrum analysis of Example 1 described later.

[0051] Furthermore, in this embodiment, the location where the boundary between the Fe-Ni-Cu-Cr layer 3 and the steel plate 2 serving as the substrate is defined as the point where the Ni strength measured in the Ni-plated surface-treated steel plate 1 is 10% of the maximum value of the Ni strength of a standard sample measured under the same conditions, and the depth at this point is defined as the thickness of the Fe-Ni-Cu-Cr layer 3. The thickness of the Fe-Ni-Cu-Cr layer 3 is preferably 0.5 to 3.5 μm, more preferably 0.7 to 3.0 μm.

[0052] The Cu strength In at a depth of 0.5 μm from the surface side obtained in this way Cu-0.5d relative to the Cu strength In of steel plate 2 Cu-steel The ratio (IR) Cu-0.5d =In Cu-0.5d / In Cu-Steel The ratio of Cu strength near the surface of Fe-Ni-Cu-Cr layer 3 to Cu strength of steel plate 2 is an indicator of the extent to which Cu in steel plate 2 diffuses to the surface.

[0053] In Ni-plated steel sheet 1, the Cu intensity In at a depth of 0.1 μm from the surface side was measured by high-frequency glow discharge emission spectroscopy (GDS). Cu-0.1d relative to the Cu strength In of steel plate 2 Cu-steel The ratio of IR Cu-0.1d (=In Cu-0.1d / In Cu-steel The value of Cu is greater than 0.50 and less than 3.0. The strength of Cu is greater than that of IR. Cu-0.1d The ratio of Cu intensity near the outermost surface of the Fe-Ni-Cu-Cr layer 3 to Cu intensity in the steel plate 2 indicates the extent to which Cu diffuses from the steel plate 2 to the outermost surface. If there is too little Cu near the outermost surface, the number of Cu-containing grains at the outermost surface of the Fe-Ni-Cu-Cr layer 3 will decrease, or the area where Cu exists will become smaller, potentially preventing the formation of a sufficient mixing potential. Conversely, if there is too much Cu near the outermost surface, metal dissolution may increase. From the viewpoint of further improving the suppression of metal dissolution during over-discharge, the intensity ratio is... Cu-0.1d The lower limit is more preferably 0.6 or more, further preferably 0.7 or more, and particularly preferably 0.8 or more. Additionally, the intensity ratio IR... Cu-0.1d The upper limit is more preferably 2.0 or less, further preferably 1.5 or less, and particularly preferably less than 1.0. This is achieved by making the Cu intensity ratio greater than that of the IR... Cu-0.1d Within the aforementioned range, the Ni-plated steel sheet 1 exhibits superior electrolyte resistance during over-discharge. Specifically, by increasing the strength compared to IR... Cu-0.1dWithin the above range, even with a low Ni adhesion amount, the Ni-plated surface-treated steel sheet 1 can still exhibit excellent electrolyte resistance during over-discharge.

[0054] In Ni-plated steel sheet 1, the Cu intensity In at a depth of 0.3 μm from the surface side was measured by high-frequency glow discharge emission spectroscopy analysis. Cu-0.3d relative to the Cu strength In of steel plate 2 Cu-steel The ratio of IR Cu-0.3d (=In Cu-0.3d / In Cu-steel The preferred value is 0.50 or higher and less than 3.0. From the viewpoint of further improving the suppression of metal dissolution during over-discharge, the intensity ratio is higher than that of IR. Cu-0.3d The lower limit is more preferably 0.7 or higher, further preferably 0.8 or higher, and particularly preferably 0.9 or higher. Additionally, the intensity ratio IR... Cu-0.3d The upper limit is more preferably 2.5 or less, further preferably 2.0 or less, and particularly preferably 1.8 or less. This is achieved by making the Cu intensity ratio lower than that of IR. Cu-0.3d Within the aforementioned range, the Ni-plated steel sheet 1 exhibits superior electrolyte resistance during over-discharge. Specifically, by increasing the strength compared to IR... Cu-0.3d Within the above range, even with a low Ni adhesion amount, the Ni-plated surface-treated steel sheet 1 can exhibit superior electrolyte resistance during over-discharge.

[0055] In Ni-plated steel sheet 1, the Cu intensity In at a depth of 0.7 μm from the surface side was measured by high-frequency glow discharge emission spectroscopy. Cu-0.7d relative to the Cu strength In of steel plate 2 Cu-steel The ratio of IR Cu-0.7d (=In Cu-0.7d / In Cu-steel The preferred value is 0.50 or higher and less than 3.0. From the viewpoint of further improving the suppression of metal dissolution during over-discharge, the intensity ratio is higher than that of IR. Cu-0.7d The lower limit is more preferably 0.7 or higher, further preferably 0.8 or higher, and particularly preferably 0.9 or higher. Additionally, the intensity ratio IR... Cu-0.7d The upper limit is more preferably 2.5 or less, further preferably 2.0 or less, and particularly preferably 1.8 or less. This is achieved by making the Cu intensity ratio lower than that of IR. Cu-0.7d Within the aforementioned range, the Ni-plated surface-treated steel sheet 1 can thus exhibit superior electrolyte resistance during over-discharge.

[0056] In Ni-plated steel sheet 1, the Cu intensity In at a depth of 0.9 μm from the surface side was measured by high-frequency glow discharge emission spectroscopy. Cu-0.9d relative to the Cu strength In of steel plate 2Cu-steel The ratio of IR Cu-0.9d (=In Cu-0.9d / In Cu-steel The preferred value is 0.50 or higher and less than 3.0. From the viewpoint of further improving the suppression of metal dissolution during over-discharge, the intensity ratio is higher than that of IR. Cu-0.9d The lower limit is more preferably 0.7 or higher, further preferably 0.8 or higher, and particularly preferably 0.9 or higher. Additionally, the intensity ratio IR... Cu-0.9d The upper limit is more preferably 2.5 or less, further preferably 2.0 or less, and particularly preferably 1.8 or less. This is achieved by making the Cu intensity ratio lower than that of IR. Cu-0.9d Within the aforementioned range, the Ni-plated surface-treated steel sheet 1 can thus exhibit superior electrolyte resistance during over-discharge.

[0057] In Ni-plated steel sheet 1, the maximum Cu intensity in the region from the surface to the boundary between the Fe-Ni-Cu-Cr layer 3 and the steel sheet 2, as determined by high-frequency glow discharge emission spectroscopy analysis, is [value missing]. Cu-MAX relative to the Cu strength In of steel plate 2 Cu-steel The ratio of IR Cu-MAX (=In Cu-MAX / In Cu-steel Preferably, the IR value is greater than 0.8 and less than 3.0. From the viewpoint of further improving the suppression of metal dissolution during over-discharge, IR... Cu-MAX More preferably, the value is 0.9 or higher and 2.5 or lower; even more preferably, it is 0.9 or higher and 2.0 or lower; and particularly preferably, it is 1.0 or higher and 1.8 or lower. This is achieved by making the Cu intensity ratio higher than that of the IR... Cu-MAX Within the aforementioned range, the Ni-plated surface-treated steel sheet 1 can thus exhibit superior electrolyte resistance during over-discharge.

[0058] Furthermore, in the Ni-plated steel sheet 1, the Cu intensity and In concentration in the region 0.3 μm to 0.7 μm from the surface depth were measured by high-frequency glow discharge emission spectroscopy analysis. Cu-0.3d~0.7d (That is, the Cu strength measured at any depth in the region 0.3 μm to 0.7 μm from the surface) relative to the Cu strength In of steel plate 2 Cu-steel The ratio of IR Cu-0.3d~0.7d (=In Cu-0.3d~0.7d / In Cu-steel The preferred value is 0.5 or higher and 3.0 or lower. This is achieved by making the Cu strength ratio higher than that of IR. Cu-0.3d~0.7dWithin the aforementioned range, fluctuations in the Cu content ratio along the depth direction of the Fe-Ni-Cu-Cr layer can be suppressed, leading to a more stable mixed potential state and improved suppression of metal dissolution during over-discharge. From the viewpoint of further enhancing the suppression of metal dissolution during over-discharge by stably maintaining a Cu-containing region not only at a specific depth location but also along the depth direction near the surface layer, the intensity is higher than that of IR. Cu-0.3d~0.7d The lower limit is more preferably 0.7 or higher, further preferably 0.8 or higher, and particularly preferably 0.9 or higher. Additionally, the intensity ratio IR... Cu-0.3d~0.7d The upper limit is more preferably 2.5 or less, further preferably 2.0 or less, and particularly preferably 1.8 or less. This is achieved by making the Cu intensity ratio lower than that of IR. Cu-0.3d~0.7d Within the aforementioned range, the Ni-plated surface-treated steel sheet 1 can thus exhibit superior electrolyte resistance during over-discharge.

[0059] The Fe-Ni-Cu-Cr layer 3 preferably has a Cu-rich region formed in the intermediate region (i.e., a region deeper than the outermost surface of the Ni-plated steel sheet 1 and shallower than the boundary between the Fe-Ni-Cu-Cr layer 3 and the steel sheet 2). The Cu-rich region in the Fe-Ni-Cu-Cr layer 3 can be achieved, for example, by using the Cu strength In at the location that forms the boundary between the Fe-Ni-Cu-Cr layer 3 and the steel sheet 2 as the substrate. Cu-boundary and the Cu strength In of the steel plate 2 Cu-steel Intensity than IR Cu-boundary (=In Cu-boundary / In Cu-steel The determination is made according to equations (1) and (2) below. When equations (1) and (2) are satisfied, it can be determined that the Fe-Ni-Cu-Cr layer 3 has a Cu-rich region in the middle region. It should be noted that, in this case, the location where the Cu strength reaches its maximum value is preferably between a position 0.3 μm from the surface depth and a position 0.1 μm shallower than the boundary between the Fe-Ni-Cu-Cr layer 3 and the steel plate 2 serving as the substrate. Furthermore, the location where the Cu strength reaches its maximum value is preferably at a depth from the surface that is less than 60% of the thickness of the Fe-Ni-Cu-Cr layer 3. By forming a Cu-rich region in the middle region of the Fe-Ni-Cu-Cr layer 3, the Ni-plated surface-treated steel plate 1 can exhibit better electrolyte resistance during over-discharge.

[0060] IR Cu-MAX -IR Cu-0.1d >0.05 (1)

[0061] IR Cu-MAX -IR Cu-boundary >0.05 (2)

[0062] In Ni-plated steel sheet 1, the Cu intensity In at any depth from the surface was measured by high-frequency glow discharge emission spectroscopy analysis. Cu-d The Cu intensity at a depth of 0.5 μm in the standard sample, as determined by high-frequency glow discharge emission spectroscopy, is compared to the In intensity at a depth of 0.5 μm. Cu-0.5d-ref The ratio of IR Cu-d-vref (=In Cu-d / In Cu-0.5d-ref Preferably, the IR is within a specified range. Within a depth of 0.1 μm to 0.5 μm from the surface... Cu-d-vref Preferably, the value is 2.0 or higher and 20 or lower. If the absolute amount of Cu near the surface layer closest to the outermost surface is too small, the number of Cu-containing grains in the Fe-Ni-Cu-Cr layer 3 will decrease, or the area where Cu exists will become smaller, which may prevent the formation of a sufficiently high mixing potential. Conversely, if the absolute amount of Cu near the surface layer closest to the outermost surface is too large, metal dissolution may increase. From the viewpoint of further improving the suppression of metal dissolution during over-discharge, within a depth range of 0.1 μm to 0.5 μm from the surface (the entire range of 0.1 μm to 0.5 μm from the surface), the IR... Cu-d-vref More preferably, the IR is 2.3 or higher and 10 or lower, and even more preferably 3.0 or higher and 10 or lower. On the other hand, in the range where the depth from the surface exceeds 0.5 μm but is 0.9 μm or lower, the IR... Cu-d-vref Preferably, the value is 2.0 or higher and 20 or lower, more preferably 2.5 or higher and 15 or lower, and even more preferably 3.0 or higher and 15 or lower.

[0063] In Ni-plated surface-treated steel sheet 1, compared to IR... Cu-MAX (=In Cu-MAX / In Cu-steel ) and IR Cu-0.1d (=In Cu-0.1d / In Cu-steel The difference between IR and IR Cu-MAX -IR Cu-0.1d Preferably, it is 1.0 or less; more preferably, 0.6 or less; even more preferably, 0.5 or less; and particularly preferably, 0.3 or less. IR Cu-MAX -IR Cu-0.1d The smaller the value, the more Cu diffuses to the vicinity of the surface in a state with small fluctuations in Cu intensity distribution within the Fe-Ni-Cu-Cr layer 3. This is achieved by adjusting the IR... Cu-MAX -IR Cu-0.1d Within the aforementioned range, especially when the amount of Ni attached is low, the Ni-plated surface-treated steel sheet 1 can exhibit superior electrolyte resistance during over-discharge.

[0064] In Ni-plated steel sheet 1, from the viewpoint of suppressing metal dissolution caused by the formation of mixed potential, the Cr intensity In at a depth of 0.1 μm from the surface side was measured by high-frequency glow discharge emission spectroscopy (GDS). Cr-0.1d The In strength relative to the Cr of steel plate 2 Cr-steel The ratio of IR Cr-0.1d (=In Cr-0.1d / In Cr-steel The Cr intensity is preferably 0.2 or higher and less than 2.0, more preferably 0.2 or higher and less than 1.0, and even more preferably 0.2 or higher and less than 0.95. This is achieved by making the Cr intensity ratio greater than the IR... Cr-0.1d Within the aforementioned range, the Ni-plated surface-treated steel sheet 1 can thus exhibit superior electrolyte resistance during over-discharge.

[0065] In Ni-plated steel sheet 1, the Cr intensity at a depth of 0.3 μm from the surface side was measured by high-frequency glow discharge emission spectroscopy (GDS). Cr-0.3d The In strength relative to the Cr of steel plate 2 Cr-steel The ratio of IR Cr-0.3d (=In Cr-0.3d / In Cr-steel Preferably, the Cr intensity is 0.2 or higher and less than 2.0, more preferably 0.2 or higher and less than 0.95, and even more preferably 0.2 or higher and less than 0.7. This is achieved by making the Cr intensity ratio greater than the IR... Cr-0.3d Within the aforementioned range, the Ni-plated surface-treated steel sheet 1 can thus exhibit superior electrolyte resistance during over-discharge.

[0066] In Ni-plated steel sheet 1, from the viewpoint of achieving a sufficiently high mixing potential to allow Cr to diffuse to the vicinity of the surface, the Cr intensity In at a depth of 0.5 μm from the surface side was measured by high-frequency glow discharge emission spectroscopy (GDS). Cr-0.5d The In strength relative to the Cr of steel plate 2 Cr-steel The ratio of IR Cr-0.5d (=In Cr-0.5d / In Cr-steel The Cr content is preferably 0.2 or higher and less than 2.0. If there is too little Cr near the surface layer, the number of Cr-containing grains in the surface layer of the Fe-Ni-Cu-Cr layer 3 may decrease, or the area where Cr exists may become smaller. Conversely, if there is too much Cr near the surface layer, localized areas of increased potential difference with Fe may occur. From the viewpoint of stably improving electrolyte resistance during over-discharge, a Cr content of 0.2 or higher and less than 0.95 is more preferred, and 0.2 or higher and less than 0.8 is even more preferred. This is achieved by making the Cr intensity ratio greater than the IR... Cr-0.5dWithin the aforementioned range, the Ni-plated surface-treated steel sheet 1 can thus exhibit superior electrolyte resistance during over-discharge.

[0067] In Ni-plated steel sheet 1, the Cr intensity at a depth of 0.7 μm from the surface side was measured by high-frequency glow discharge emission spectroscopy (GDS). Cr-0.7d The In strength relative to the Cr of steel plate 2 Cr-steel The ratio of IR Cr-0.7d (=In Cr-0.7d / In Cr-steel The Cr intensity is preferably 0.2 or higher and less than 2.0, more preferably 0.2 or higher and less than 0.95, and even more preferably 0.2 or higher and less than 0.8. This is achieved by making the Cr intensity ratio greater than the IR... Cr-0.7d Within the aforementioned range, the Ni-plated surface-treated steel sheet 1 can thus exhibit superior electrolyte resistance during over-discharge.

[0068] In Ni-plated steel sheet 1, the Cr intensity at a depth of 0.9 μm from the surface side was measured by high-frequency glow discharge emission spectroscopy (GDS). Cr-0.9d The In strength relative to the Cr of steel plate 2 Cr-steel The ratio of IR Cr-0.9d (=In Cr-0.1d / In Cr-steel The Cr intensity is preferably 0.2 or higher and less than 2.0, more preferably 0.2 or higher and less than 1.0, and even more preferably 0.2 or higher and less than 0.95. This is achieved by making the Cr intensity ratio IR... Cr-0.9d Within the aforementioned range, the Ni-plated surface-treated steel sheet 1 can thus exhibit superior electrolyte resistance during over-discharge.

[0069] In Ni-plated steel sheet 1, the maximum Cr intensity in the region from the surface to the boundary between the Fe-Ni-Cu-Cr layer 3 and the steel sheet 2, as determined by high-frequency glow discharge emission spectroscopy analysis, is [value missing]. Cr-MAX The In strength relative to the Cr of steel plate 2 Cr-steel The ratio of IR Cr-MAX (=In Cr-MAX / In Cr-steel Preferably, the chromium content is 0.3 or higher and 2.0 or lower, more preferably 0.3 or higher and 0.95 or lower. This is achieved by making the Cr intensity ratio higher than that of IR. Cr-max Within the aforementioned range, the Ni-plated surface-treated steel sheet 1 can thus exhibit superior electrolyte resistance during over-discharge.

[0070] Furthermore, in the Ni-plated steel sheet 1, the Cr intensity and In content in the region 0.3 μm to 0.7 μm deep from the surface were determined by high-frequency glow discharge emission spectroscopy analysis. Cu-0.3d~0.7d(That is, the Cr strength measured at any depth in the region 0.3 μm to 0.7 μm from the surface) relative to the Cr strength In of steel plate 2 Cr-steel The ratio of IR Cr-0.3d~0.7d (=In Cr-0.3d~0.7d / In Cr-steel The value is preferably 0.2 or higher and 2.0 or lower, more preferably 0.2 or higher and less than 0.95. This is achieved by making the Cr intensity ratio higher than the IR... Cr-0.3d~0.7d Within the aforementioned range, the Ni-plated surface-treated steel sheet 1 can thus exhibit superior electrolyte resistance during over-discharge.

[0071] In Ni-plated steel sheet 1, the Cr intensity In at any depth from the surface was determined by high-frequency glow discharge emission spectroscopy analysis. Cr-d The In intensity of Cr at a depth of 0.5 μm relative to that of a standard sample determined by high-frequency glow discharge emission spectroscopy. Cr-0.5d-ref The ratio of IR Cr-d-vref =(In Cr-d / In Cr-0.5d-ref Preferably, the IR is within a specified range. Within a depth range of 0.1 μm to 0.5 μm from the surface, Cr-d-vref Preferably, the Cr content is 2.0 or higher and 30 or lower. If there is too little Cr near the surface layer, the number of Cr-containing grains in the outermost surface of the Fe-Ni-Cu-Cr layer 3 will decrease, or the area where Cr is present will become smaller, which may prevent the formation of a sufficiently high mixing potential. Conversely, if there is too much Cr near the surface layer, the surface resistivity may increase excessively. Within a depth range of 0.1 μm to 0.5 μm from the surface, the IR... Cr-d-vref More preferably, the IR is 2.5 or higher and 30 or lower; even more preferably, 5.5 or higher and 30 or lower; and particularly preferably, 7.0 or higher and 20 or lower. On the other hand, in the range where the depth from the surface exceeds 0.5 μm but is 0.9 μm or lower, the IR... Cr-d-vref Preferably, the value is 2.0 or higher and 50 or lower, more preferably 5.5 or higher and 40 or lower.

[0072] In the Ni-plated steel sheet 1, from the viewpoint of improving electrolyte resistance during over-discharge and ensuring good battery performance, the Cu strength In at a depth of 0.5 μm from the surface side in the Fe-Ni-Cu-Cr layer 3 is preferred. Cu-0.5d relative to the Cu strength In of steel plate 2 Cu-steel The ratio of IR Cu-0.5d (=In Cu-0.5d / In Cu-Steel The value of Cr is greater than 0.50 and less than 3.0, and the strength of In is... Cr-0.5d The In strength relative to the Cr of steel plate 2Cr-steel The ratio of IR Cr-0.5d (=In Cr-0.5d / In Cr-steel The preferred values ​​are 0.2 or higher and less than 2.0. It is believed that by controlling the Cu intensity ratio and Cr intensity ratio to be within the above-mentioned ranges, the mixed potential resulting from the presence of Cu and Cr near the surface of the Fe-Ni-Cu-Cr layer 3 can be stabilized. Furthermore, even if Cr is present near the outermost surface, by including Cu in the Fe-Ni-Cu-Cr layer 3, the increase in contact resistance can be suppressed. Therefore, better battery characteristics can be obtained simultaneously with the suppression of metal dissolution.

[0073] In Ni-plated steel sheet 1, the Fe intensity In at a depth of 0.1 μm from the surface side of the standard sample (Ni-plated steel sheet) was measured by high-frequency glow discharge emission spectroscopy analysis from the surface towards the steel sheet. Fe-0.1d The maximum value of In relative to Fe strength Fe-MAX-ref The ratio of 10% of the value of IR Fe-0.1d (=In Fe-0.1d / (0.1×In Fe-MAX-ref The IR value is 1.0 or higher, preferably 2.0 or higher and less than 7.0. This is achieved by making the IR... Fe-0.1d Within the aforementioned range, even in wide, large-area surface-treated steel plates 1, a Fe-Ni-Cu-Cr layer can be formed across the entire surface, thereby stably improving electrolyte resistance.

[0074] In the Ni-plated steel sheet 1, from the viewpoint of appropriately forming the Fe-Ni-Cu-Cr layer 3 and controlling the Cu strength ratio and Cr strength ratio of the steel sheet 2 and the Fe-Ni-Cu-Cr layer 3 within an appropriate range, the lower limit of the Ni adhesion amount on the surface where the Fe-Ni-Cu-Cr layer 3 is formed as the outermost layer is preferably 0.45 g / m². 2 The above, more preferably 0.8 g / m 2 The above is further preferred to be 2.5 g / m 2 The above, especially preferred, is 3.0 g / m 2 The above. In the Ni-plated steel sheet 1, from the viewpoint that Fe is difficult to diffuse to the outermost surface, and that it is necessary to increase the heat treatment temperature or extend the heat treatment time in order to make Fe diffuse sufficiently, the upper limit of the Ni adhesion amount relative to the surface on which the Fe-Ni-Cu-Cr layer 3 is formed as the outermost layer is preferably 10.7 g / m. 2 Below, less than 8.9 g / m is preferred. 2 Further preferred is 8.0 g / m 2 The following is particularly preferred: 7.2 g / m 2The following should be noted: The amount of Ni deposited can be determined by fluorescence X-ray determination. In fluorescence X-ray determination, quantification can be performed using a standard curve method. Fluorescence X-ray determination can be performed on Ni-plated surface-treated steel sheet 1 with an Fe-Ni-Cu-Cr layer 3 formed through thermal diffusion treatment, or on steel sheet 2 with a Ni coating before thermal diffusion treatment.

[0075] It should be noted that, in this embodiment, as Figure 1 As shown, the Fe-Ni-Cu-Cr layer 3 is formed on only one side of the steel plate 2, but the composition of the Ni-plated surface-treated steel plate 1 is not particularly limited to this. The Fe-Ni-Cu-Cr layer 3 can be formed on at least one of the outermost surfaces of the steel plate 2, or it can be formed on both outermost surfaces of the steel plate 2.

[0076] The Ni-plated surface-treated steel sheet 1 in this embodiment can be manufactured as follows.

[0077] First, a Ni coating is formed on the original steel plate 2. As mentioned above, the original steel plate 2 can be made of carbon steel containing Cu and Cr in a specified ratio. The Cu content of the carbon steel used here is more preferably 0.05 to 1.0% by weight, and even more preferably 0.05 to 0.5% by weight. Furthermore, the Cr content of the carbon steel is more preferably 0.03 to 1.0% by weight, even more preferably 0.03 to 0.5% by weight, and particularly preferably 0.03 to 0.4% by weight. As the Ni plating bath for forming the Ni coating, commonly used plating baths can be used, such as Watt's baths, sulfamic acid baths, borofluoride baths, chloride baths, etc. For example, the Ni coating can be formed using a bath with a composition of 200 g / L to 350 g / L nickel sulfate hexahydrate, 20 g / L to 60 g / L nickel chloride hexahydrate, and 10 g / L to 50 g / L boric acid as a Watt's bath, at a pH of 3.0 to 5.0, a bath temperature of 40°C to 70°C, and a current density of 5 A / dm³. 2 ~40A / dm 2 It is formed under the following conditions. It should be noted that the Ni coating only needs to be formed on at least one side of the original plate of steel plate 2, but it is preferred to be formed on both sides.

[0078] In this embodiment, from the viewpoint of forming an Fe-Ni-Cu-Cr layer 3 by facilitating the diffusion of Cu and Cr contained in the original steel plate 2 during the heat diffusion treatment process described later, it is preferable to add a trace amount of a semi-glossy agent formed from aliphatic unsaturated alcohols such as polyoxyethylene adducts of unsaturated alcohols, unsaturated carboxylic acids, formaldehyde, and coumarin, which are sulfur-free compounds, to the Ni plating bath. Specifically, the amount of semi-glossy agent added is preferably 0.6 mL / L to 6.0 mL / L, more preferably 0.8 mL / L to 5.0 mL / L, and even more preferably 1.2 mL / L to 5.5 mL / L. One type of semi-glossy agent can be used, or multiple types can be used in combination. When multiple types are used in combination, it is preferable that the total amount of the various semi-glossy agents is within the above-mentioned range.

[0079] The amount of Ni adhering to the original steel plate 2 due to the formation of the Ni coating is not particularly limited, as long as it is sufficient to form an Fe-Ni-Cu-Cr layer 3 as the outermost surface of the Ni-plated steel plate 1 and its composition can be controlled. However, if the amount of adhering is too large, Fe, Cu, and Cr will have difficulty diffusing to the outermost surface, and in order to make Fe, Cu, and Cr diffuse sufficiently, it may be necessary to increase the heat treatment temperature or extend the heat treatment time, which may make it difficult to properly form the Fe-Ni-Cu-Cr layer 3. Therefore, 10.7 g / m is preferred. 2 The preferred value is 8.9 g / m³. 2 The following is a further preferred value of 8.0 g / m 2 The following is particularly preferred: 7.2 g / m 2 The following applies. On the other hand, if the amount of Ni attached, W, is too small, it will be difficult to properly form the Fe-Ni-Cu-Cr layer 3, and the electrolyte resistance during over-discharge may decrease. Therefore, the amount of Ni attached, W, is preferably 0.45 g / m³. 2 The above, more preferably 0.8 g / m 2 The above is further preferred to be 2.5 g / m 2 The above, especially preferred, is 3.0 g / m 2 The above is an explanation. It should be noted that when the Fe-Ni-Cu-Cr layer 3 is formed on the outermost surfaces of both sides of the steel plate 2, it is preferable that the Ni adhesion amount W on each side is within the range described above. Furthermore, when the Ni-plated steel plate 1 of this embodiment is used for a can-shaped battery container, it is preferable to form the Fe-Ni-Cu-Cr layer 3 on the outermost surface of the surface that becomes the inner surface of the battery container, and on the other hand, to form an Fe-Ni diffusion layer on the surface that becomes the outer surface of the battery container, and to form a Ni layer on the Fe-Ni diffusion layer. To achieve this configuration on the outer surface of the battery container, it is preferable that the Ni adhesion amount on the surface that becomes the outer surface of the battery container is 9.0 g / m². 2 ~90g / m 2 .

[0080] Next, the steel plate with a Ni coating formed on the surface of the original steel plate 2 (hereinafter referred to as the coated steel plate) is subjected to thermal diffusion treatment to form an Fe-Ni-Cu-Cr layer 3. By appropriately controlling the conditions of the thermal diffusion treatment, the Fe-Ni-Cu-Cr layer 3 can be formed on the steel plate.

[0081] The thermal diffusion treatment can be either continuous annealing or box annealing, without particular limitation. Preferably, the heat treatment atmosphere is a non-oxidizing atmosphere or a reducing protective gas atmosphere. When a reducing protective gas atmosphere is used, a mixture of H2 and N2, known as HNX gas, is preferred. In this embodiment, the thermal diffusion treatment includes an initial heating step, a final heating step, and a cooling step.

[0082] The initial heating process is the process of heating the coated steel sheet from room temperature to the starting temperature of the final heating process (the final heating start temperature), which will be described later. The heating rate in the initial heating process (hereinafter also referred to as the initial heating rate) is determined by calculating the slope of the temperature profile of the coated steel sheet in the initial heating process. That is, it can be calculated by dividing the temperature difference from the starting temperature of the initial heating process to the starting temperature of the final heating process by the required time. The initial heating rate is preferably greater than the heating rate in the final heating process, which will be described later. Specifically, the initial heating rate is preferably greater than 4°C / second and less than 14°C / second.

[0083] The maximum heating rate in the initial heating process (hereinafter also referred to as the maximum heating rate) is determined by calculating the maximum slope of the temperature curve of the plated steel sheet in the initial heating process, i.e., the temperature curve from room temperature to the starting temperature of the final heating process, and is preferably 4°C / second or more. Furthermore, from the viewpoint of appropriately forming the Fe-Ni-Cu-Cr layer 3 and controlling the Cu strength ratio and Cr strength ratio of the steel sheet 2 and the Fe-Ni-Cu-Cr layer 3 within an appropriate range, the maximum heating rate in the initial heating process is preferably 14°C / second or less, more preferably 12°C / second or less, and even more preferably 10°C / second or less. In particular, from the viewpoint of suppressing Fe diffusion to the outermost surface, the maximum heating rate in the temperature curve of 450°C or higher in the initial heating process is preferably 14°C / second or less, more preferably 12°C / second or less, and even more preferably 10°C / second or less.

[0084] The final heating process is the process of heating from the final heating start temperature to the highest temperature in the thermal diffusion treatment (hereinafter referred to as the arrival temperature). The final heating start temperature is preferably 600°C or higher, at which the Ni in the Ni plating and the Fe in the steel plate 2 begin to actively diffuse; more preferably, it is 650°C or higher, at which they begin to diffuse more actively; and from the viewpoint of easily promoting the active diffusion of Cu and Cr in the final heating process, it is further preferably 680°C or higher, and particularly preferably 710°C or higher. Furthermore, the final heating start temperature is preferably lower than 900°C, more preferably lower than 850°C. From the viewpoint of appropriately forming the Fe-Ni-Cu-Cr layer 3, the arrival temperature is preferably lower than 930°C, more preferably lower than 900°C, and even more preferably lower than 870°C. It should be noted that, as described later, the arrival temperature can be set based on the final heating start temperature, so that the temperature difference with the final heating start temperature is a predetermined temperature difference.

[0085] In this embodiment, as described below, from the viewpoint of improving the electrolyte resistance of the Ni-plated surface-treated steel sheet 1 during over-discharge, the heating rate (hereinafter also referred to as the final heating rate) in the final heating process is preferably 4°C / second or less, more preferably 3°C / second or less, and even more preferably 1°C / second or less. The heating rate in the final heating process is preferably 0.1°C / second or more, more preferably 0.2°C / second or more.

[0086] It should be noted that the temperature difference between the reached temperature and the final heating start temperature only needs to be 10°C or more, preferably 30°C or more, and more preferably 40°C or more. If the temperature difference is too small, the heating time in the final heating process (final heating time) will be insufficient, and the target Fe-Ni-Cu-Cr layer 3 alloy state may not be obtained. This is especially true when the Ni adhesion amount is 2.5 g / m 2 In the above cases, the temperature is preferably 30°C or higher, more preferably 40°C or higher, and even more preferably 60°C or higher. By maintaining a temperature difference of 60°C or higher, the target surface alloy state can be obtained, and the Ni-plated surface-treated steel sheet 1 with higher electrolyte resistance during over-discharge can be stably obtained. Regarding the aforementioned upper limit of the temperature difference, it is preferably 150°C or lower, more preferably 120°C or lower, and even more preferably 100°C or lower. In this embodiment, it is preferable to set the final heating rate to 4°C / second or lower, because if the temperature difference is too large, the time in the high-temperature region will be too long, and the target surface alloy state may not be obtained.

[0087] In the cooling process, the plated steel sheet heated to the required temperature is cooled to below 120°C. There are no particular limitations on the cooling rate, but from the viewpoint of suppressing deformities and wrinkles, a rate of 1°C / second to 20°C / second is preferred, and more preferably 1°C / second to 10°C / second.

[0088] Figure 2 This is an example of a temperature profile of a plated steel sheet used to represent the calculation method of the thermal history Y in the thermal diffusion process.

[0089] From the viewpoint of improving the electrolyte resistance of Ni-plated steel sheet 1 during over-discharge, in the thermal diffusion treatment, the thermal history Y experienced by the plated steel sheet through the initial heating step, the final heating step, and the cooling step is preferably 150,000 °C·s or less, more preferably 120,000 °C·s or less, and even more preferably 100,000 °C·s or less. Furthermore, from the viewpoint of achieving the target alloy state through sufficient thermal diffusion of Fe and Ni, the thermal history Y is preferably 15,000 °C·s or more, more preferably 35,000 °C·s or more, and even more preferably 45,000 °C·s or more. The thermal history Y can be calculated by integrating the changes in heating temperature (above 450 °C) and cooling temperature with respect to time. That is, Figure 2 The area of ​​the slanted portion in the figure corresponds to the thermal history Y in the heat diffusion process. In order to keep the thermal history Y of the coated steel sheet within the above range, the heating rate (including the maximum heating rate) of 450°C or higher in the initial heating process and the final heating process, the heating start temperature, the heating reach temperature, and the cooling rate in the cooling process can be appropriately adjusted.

[0090] If the thermal history Y in the thermal diffusion process is too large or too small, the target alloy state cannot be obtained, and there is a tendency for the electrolyte resistance to decrease during over-discharge.

[0091] Ni adhesion amount W (g / m 2 The ratio of W / Y to the thermal history Y is 10. 5 Preferably, it is 1.0 or higher. In W / Y×10 5 When the value is less than 1.0, the desired surface alloy state cannot be obtained, and the electrolyte resistance during over-discharge may deteriorate. Additionally, the Ni adhesion amount W (g / m²) 2 The ratio of W / Y to the thermal history Y is 10. 5 Preferably, it is 20.0 or less, more preferably 10.0 or less, and even more preferably 7.0 or less. W / Y×10 5 When the value exceeds 20.0, the diffusion of the metal becomes insufficient, and the target alloy state may not be obtained.

[0092] As described above, the inventors discovered that by controlling the amount of Ni attached to the steel plate W within the aforementioned range and performing a thermal diffusion treatment on the Ni-plated steel plate under the aforementioned conditions, the Ni in the Ni plating layer interdiffused with the Fe, Cu, and Cr of the steel plate 2, thereby forming an Fe-Ni-Cu-Cr layer 3 on the steel plate 2. The Ni-plated surface-treated steel plate 1 manufactured by the above method possesses the Fe-Ni-Cu-Cr layer 3, thereby exhibiting excellent electrolyte resistance during over-discharge.

[0093] Conventionally, to improve the electrolyte resistance of Ni-plated steel sheets, a method is known to form an Fe-Ni diffusion layer by performing a thermal diffusion treatment on the steel sheet with a Ni coating. In contrast, the inventors have discovered that by diffusing not only Fe but also Cu and Cr contained in the steel sheet 2, an Fe-Ni-Cu-Cr layer 3 can be formed on the steel sheet 2, thereby further improving the electrolyte resistance of the Ni-plated steel sheet 1.

[0094] While uncertain, the reasons for forming the Fe-Ni-Cu-Cr layer 3 via the aforementioned thermal diffusion treatment method are as follows: First, the diffusion coefficients of nickel and chromium in iron are similar, while the diffusion coefficient of copper is slightly higher but still approximately the same. Above 700°C, chromium diffuses more actively, while below 700°C, the diffusion rate decreases significantly. Above 700°C, copper also begins to diffuse more actively. Therefore, in the aforementioned thermal diffusion treatment method, by slowly increasing the temperature during the initial heating, the diffusion of copper and chromium can be suppressed, preventing a lack of copper and chromium near the interface. Furthermore, in the aforementioned thermal diffusion treatment method, by heating to above 700°C in the final heating process, the movement of copper and chromium from the interface to the surface can be promoted. It is believed that through this copper and chromium diffusion mechanism, an Fe-Ni-Cu-Cr layer 3 containing not only iron but also copper and chromium can be formed. Furthermore, it is believed that by continuing to raise the temperature in the final heating process, the abrupt change from the crystal structure of nickel to that of an iron-nickel alloy can be suppressed, thereby preventing the diffusion paths of copper and chromium from being blocked, and thus obtaining an Fe-Ni-Cu-Cr layer 3 containing sufficient and trace amounts of copper and chromium on the surface.

[0095] Furthermore, by using a Ni plating bath containing a trace amount of semi-glossy agent to form a Ni coating before thermal diffusion, a more preferred Fe-Ni-Cu-Cr layer 3 can be obtained. The Ni coating formed using a nickel plating bath containing a trace amount of semi-glossy agent contains more coating strain compared to a Ni coating formed using a matte Ni plating bath. Therefore, during the release of coating strain during thermal diffusion treatment, the atomic driving force accompanying the crystal structure change increases. As a result, it is believed that during diffusion from the steel sheet to the Ni coating, especially during diffusion in the final heating process, not only iron becomes more easily diffused, but copper and chromium also become more easily diffused, resulting in a more preferred Fe-Ni-Cu-Cr layer 3. On the other hand, if too much semi-glossy agent is added to the Ni plating bath, the grain size of the Ni coating becomes smaller, and considering copper and chromium, the Fe-Ni-Cu-Cr layer 3 may become too hard. Therefore, the amount of semi-glossy agent added is preferably 6.0 mL / L or less.

[0096] As described above, the Ni-plated surface-treated steel sheet 1 of this embodiment is manufactured.

[0097] It should be noted that after the heat diffusion treatment, the Ni-plated surface-treated steel sheet can be surface rolled as needed. By performing surface rolling, it is possible to control mechanical properties, correct shape, and impart surface roughness.

[0098] <Battery container>

[0099] The battery container in the present embodiment is obtained by forming the Ni-plated surface-treated steel sheet 1 in such a manner that the surface having the Fe-Ni-Cu-Cr layer 3 becomes the inner side of the battery container. Specifically, the Ni-plated surface-treated steel sheet 1 can be formed into the shape of a battery container by pressure forming such as drawing, thinning, DI (Drawing and Ironing), or DTR (Draw and Thin Redraw). In addition to cylindrical, square, bag-shaped, or cup-shaped, the shape of the battery container may also include shapes such as lids, current collectors, and terminals, which have concavities, convexities, and holes provided locally in the plate shape.

[0100] The battery container obtained by forming the Ni-plated surface-treated steel sheet 1 in the present embodiment has high electrolyte resistance during over-discharge because the Fe-Ni-Cu-Cr layer 3 is formed on the inner surface side, and can suppress the occurrence of corrosion caused by the dissolution of Fe.

[0101] Examples

[0102] Hereinafter, examples will be listed to describe the present invention more specifically, but the present invention is not limited to these examples.

[0103] It should be noted that the evaluation methods for each characteristic are as described below.

[0104] <Ni coating thickness>

[0105] In each of the examples and comparative examples, for the plated steel sheet having the Ni coating, measurement was performed using a fluorescence X-ray apparatus, and thereby the Ni adhesion amount per surface of the Ni-plated steel sheet was determined. As the fluorescence X-ray apparatus, ZSX100e (manufactured by Rigaku Corporation) was used, and measurement was performed by the standard curve method. By converting the Ni adhesion amount into thickness using the density of Ni (8.9 g / cm 3 )), the thickness of the Ni coating was obtained.

[0106] <Strength, strength ratio, and Fe-Ni-Cu-Cr layer thickness of each metal based on GDS>

[0107] Using a high-frequency glow discharge emission spectrometry analysis apparatus (Horiba Manufacturing Co., Ltd., model: GD-PROFILER2), firstly, using the method described above, a standard Ni-plated steel sheet (standard sample) with a 1.1 μm thick matte Ni plating applied to a 0.3 mm thick low-carbon steel sheet was used to determine the Ni etching rate as 0.035 μm / s. Furthermore, the maximum Ni intensity, as well as the Cu and Cr intensities at depths of 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, and 0.9 μm, were confirmed. Next, measurements were performed on the Ni-plated steel sheet 1, measuring the changes in Fe, Ni, Cu, and Cr intensities relative to the measurement time (etching time). Based on the Ni etching rate, the measurement time (etching time) of the high-frequency glow discharge emission spectrometry analysis of the Ni-plated steel sheet 1 was converted to depth. The resulting graph is shown below. Figure 3 (a)~ Figure 5 (b) Figure 3 (a) is a graph obtained by high-frequency glow discharge emission spectrum analysis in Example 1. Figure 3 (b) is Figure 3 Enlarged view of (a). Figure 4 (a) is a graph obtained by high-frequency glow discharge emission spectrum analysis in Example 2. Figure 4 (b) is Figure 4 Enlarged view of (a). Figure 5 (a) is a graph obtained from the emission spectrum analysis of high-frequency glow discharge in Comparative Example 1. Figure 5 (b) is Figure 5 Enlarged view of (a).

[0108] In the obtained graphs, the formation of the Fe-Ni-Cu-Cr layer 3 was confirmed by comparing it with a standard Ni-plated steel sheet using the above method. Furthermore, the Cu and Cr strengths at depths of 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, and 0.9 μm were determined. Additionally, the depth D at which the Ni strength becomes 2% of the maximum Ni strength of the standard sample was determined. Ni2% The Cu strength and Cr strength at point 2 are used as the Cu strength of steel plate 2. Cu-steel and Cr strength In Cr-steel Furthermore, the maximum value of Cu strength in each Ni-plated steel plate 1 was calculated. Cu-MAX And the maximum value of Cr strength In Cr-MAXAnd the depth at which the Ni strength reaches its maximum value. Furthermore, the Cu strength at the depth where the Ni strength reaches 10% is measured; this depth is the boundary point between the Fe-Ni-Cu-Cr layer 3 and the steel plate 2, and the thickness of the Fe-Ni-Cu-Cr layer 3 is determined from this depth. Furthermore, the Fe strength In at a depth of 0.1 μm from the surface side is calculated. Fe-0.1d The maximum value of Fe strength relative to the standard sample In Fe-MAX-ref The ratio of 10% of the value of IR Fe-0.1d .

[0109] Calculate the Cu intensity In at a location 0.1 μm below the surface. Cu-0.1d Cu strength In of steel plate 2 Cu-steel The ratio of IR Cu-0.1d Similarly, the Cu intensity ratio IR at depths of 0.3 μm, 0.5 μm, 0.7 μm, and 0.9 μm was calculated. Cu-0.3d IR Cu-0.5d IR Cu-0.7d and IR Cu-0.9d Similarly, the Cr intensity ratio to IR at depths of 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, and 0.9 μm were calculated. Cr-0.3d IR Cr-0.5d IR Cr-0.7d and IR Cr-0.9d Additionally, the maximum value of Cu strength, In, was calculated separately. Cu-MAX And the maximum value of Cr strength In Cr-MAX and their Cu strength relative to steel plate 2. Cu-steel The ratio of IR Cu-MAX and IR Cr-MAX Furthermore, the Cu strength In at a depth of 0.5 μm relative to the standard sample was calculated. Cu-0.5d-ref Cu intensity at various depths compared to IR Cu-d-vref and the Cr strength In at a depth of 0.5 μm relative to the standard sample. Cr-0.5d-ref Cr intensity ratio at various depths compared to IR Cr-d-vref .

[0110] It should be noted that the specific measurement conditions for the high-frequency glow discharge emission spectroscopy analyzer are set as follows.

[0111] • Measurement mode: HDD mode

[0112] • Excitation mode: RF (Normal)

[0113] Power: 35W

[0114] Pressure: 600Pa

[0115] Module: 7V

[0116] • Fuse: 5V

[0117] • Anode diameter: 4mm

[0118] • Gas replacement time: 30 seconds

[0119] • Pre-splashing time: 30 seconds

[0120] Background measurement time: 5 seconds

[0121] • Measurement time: 100 seconds

[0122] • Data acquisition interval: 0.1 seconds

[0123] <Evaluation of electrolyte resistance under over-discharge>

[0124] For Ni-plated steel sheet 1, the electrolyte resistance under over-discharge was evaluated using the LSV (Linear Sweep Voltammetry) method with a multifunctional electrochemical measurement system HZ-Pro (model: HAG-PROM12, manufactured by Hokuto Denko Co., Ltd.). During the measurement, the electrolyte was tested using... Figure 6 The measurement fixture shown. Figure 6 This is a schematic diagram of the measuring fixture used in evaluating the electrolyte resistance of Ni-plated surface-treated steel sheet 1 based on the LSV method. (See diagram for example.) Figure 6 As shown, a Ni-plated steel plate 1 is mounted at the bottom of the measuring fixture. An electrolyte (1 mol / L LiPF6, EC:DEC (1:1 v / v%), manufactured by Kishida Chemical Co., Ltd.) is added inside the fixture. Metallic lithium (manufactured by Honjo Metals Co., Ltd.) is mounted on the upper electrode of the fixture as both the counter electrode and the reference electrode. The surface area of ​​the measuring surface is set to 1.04 cm². 2 The surface area of ​​the electrode and the reference electrode is set at 1.2 cm². 2 The distance between the reference electrode and the working electrode was set to 2 mm, the distance between the counter electrode and the working electrode was set to 2 mm, and the distance between the counter electrode and the reference electrode was set to 12 mm. Measurements were performed in a dry chamber at a dew point below -40°C and a room temperature of 23°C. Measurements were taken from the spontaneous potential at a scan rate of 2 mV / s towards +4.1 V (vsLi / Li) equivalent to over-discharge. + Polarization was performed, and the current value (μA / cm) at 4.1V was measured. 2 The electrolyte resistance of Ni-plated steel sheet 1 under over-discharge was evaluated. The smaller the current value, the less metals such as Fe are dissolved, and the better the electrolyte resistance under over-discharge.

[0125] <Contact Resistance Value>

[0126] A 25mm square test piece was fabricated by cutting a Ni-plated steel sheet 1. Then, using an electrical contact simulator (manufactured by Yamazaki Precision Research & Development Co., Ltd., model: CRS-1), the contact resistance value [mΩ] of one of the fabricated test pieces was measured under a contact load of 150gf. A lower contact resistance value indicates better battery characteristics when the Ni-plated steel sheet 1 is used as a battery container.

[0127] <<Example 1>>

[0128] As the base plate for steel plate 2, a cold-rolled steel plate (low carbon steel A) with a thickness of 0.5 mm is prepared, which is made of low carbon aluminum killed steel with a Cu content of 0.2% to 0.4% by weight and a Cr content of 0.1% to 0.3% by weight.

[0129] Then, after alkaline electrolytic degreasing and sulfuric acid immersion pickling, the prepared cold-rolled steel sheet is electroplated (Ni plating) under the following conditions using a Ni plating bath with the following composition, resulting in a Ni adhesion amount W of 4.45 g / m on the surface of the cold-rolled steel sheet. 2 Ni coating is applied to obtain coated steel sheet.

[0130] <Ni Plating Conditions>

[0131] Bath composition: Nickel sulfate hexahydrate 250 g / L, nickel chloride hexahydrate 45 g / L, boric acid 30 g / L, semi-gloss agent (unsaturated alcohol polyoxyethylene adduct, unsaturated carboxylic acid, formaldehyde) 3.0 mL / L

[0132] pH: 4.0~5.0

[0133] Bath temperature: 60℃

[0134] Current density: 10A / dm 2

[0135] Next, the steel sheet with a Ni coating (coated steel sheet) is subjected to thermal diffusion treatment through continuous annealing in a reducing protective gas atmosphere to form an Fe-Ni-Cu-Cr layer 3. Following the thermal diffusion treatment, surface rolling with a reduction rate of 3% or less is performed to obtain a Ni-coated surface-treated steel sheet 1 having a steel sheet 2 and a Fe-Ni-Cu-Cr layer 3 on one side of the steel sheet 2. It should be noted that in the continuous annealing, in the initial heating step, the coated steel sheet is heated from room temperature to the final heating start temperature. The final heating start temperature is set within the temperature range of 660~694℃. The maximum heating rate in the initial heating step is 4.96℃ / second. Then, in the final heating step, the final heating start temperature and the final heating reach temperature are set within the temperature range of 695~729℃, with the temperature difference in the final heating reach temperature being 40℃, and the heating rate is 0.37℃ / second. Next, as a cooling process, cooling gases such as HNX gas are blown in to cool the steel sheet until the temperature of the plated steel sheet reaches below 120°C. The thermal history Y of the Ni-plated steel sheet after the initial heating process, the final heating process, and the cooling process is 57920°C·second.

[0136] The obtained Ni-plated surface-treated steel sheet 1 was evaluated according to the methods described above. The results are shown in Table 1. It should be noted that in Table 1, the Cu strength and Cr strength at each depth are collectively denoted as In. Cu-d and In Cr-d Furthermore, the ratio of Cu strength at each depth location to Cu strength of steel plate 2 is collectively denoted as IR. Cu-d The ratio of Cr strength at each depth location to the Cr strength of steel plate 2 is collectively referred to as IR. Cr-d .

[0137] <<Example 2>>

[0138] The original steel plate 2 was replaced with a 0.5 mm thick cold-rolled steel plate of low-carbon aluminum-killed steel (low-carbon steel B) with Cu and Cr contents of 0.01% to 0.05% by weight respectively. Otherwise, Ni-plated steel plate 1 was obtained in the same manner as in Example 1, and the evaluation was performed in the same manner. The results are shown in Table 1.

[0139] <<Example 3>>

[0140] The original steel plate 2 was replaced with a 0.5 mm thick cold-rolled steel plate (low-carbon steel C) of low-carbon aluminum killed steel with a Cu content of 0.1% to less than 0.2% by weight and a Cr content of 0.03% to less than 0.05% by weight. Heat diffusion treatment was performed under the conditions described in Table 5. Otherwise, Ni-plated surface-treated steel plate 1 was obtained in the same manner as in Example 1, and the same evaluation was performed.

[0141] <<Examples 4-5>>

[0142] The heat diffusion treatment was performed under the conditions described in Table 5. Otherwise, the Ni-plated steel sheet 1 was obtained in the same manner as in Example 3, and the evaluation was performed in the same manner.

[0143] <<Example 6>>

[0144] The Ni-based adhesion amount was changed to 0.89 g / m. 2 The heat diffusion treatment was performed under the conditions described in Table 5. Otherwise, the Ni-plated steel sheet 1 was obtained in the same manner as in Example 3, and the evaluation was performed in the same manner.

[0145] <<Examples 7-8>>

[0146] The Ni-based adhesion amount was changed to 2.67 g / m. 2 The heat diffusion treatment was performed under the conditions described in Table 5. Otherwise, the Ni-plated steel sheet 1 was obtained in the same manner as in Example 3, and the evaluation was performed in the same manner.

[0147] <<Example 9>>

[0148] The original steel plate 2 was replaced with a 0.5 mm thick cold-rolled steel plate (low-carbon steel D) of low-carbon aluminum killed steel with a Cu content of 0.05% or more and less than 0.1% by weight and a Cr content of 0.03% or more and less than 0.05% by weight. Heat diffusion treatment was performed under the conditions described in Table 5. Otherwise, Ni-plated surface-treated steel plate 1 was obtained in the same manner as in Example 1, and the same evaluation was performed.

[0149] <<Example 10>>

[0150] The Ni coating adhesion amount was changed to 6.68 g / m 2 The heat diffusion treatment was performed under the conditions described in Table 5. Otherwise, the Ni-plated steel sheet 1 was obtained in the same manner as in Example 3, and the evaluation was performed in the same manner.

[0151] <<Example 11>>

[0152] The original steel plate 2 was changed to low-carbon steel D. Otherwise, Ni-plated surface-treated steel plate 1 was obtained in the same manner as in Example 10, and was evaluated in the same manner.

[0153] <<Example 12>>

[0154] The original steel plate 2 was changed to low-carbon steel B. Otherwise, Ni-plated surface-treated steel plate 1 was obtained in the same manner as in Example 11, and the evaluation was carried out in the same manner.

[0155] <<Comparative Example 1>>

[0156] The Ni adhesion amount was changed to 8.9 g / m 2 Without thermal diffusion treatment, Ni-plated steel sheets were obtained in the same manner as in Example 2, and the evaluation was performed in the same way. The results are shown in Table 1. In Comparative Example 1, the intensities of each element in the high-frequency glow discharge emission spectrum analysis were the same as those of the standard Ni-plated steel sheet, therefore it was determined that the Fe-Ni-Cu-Cr layer 3 had not been formed. In addition, it was confirmed that the Cu intensity ratio and Cr intensity ratio of the Ni coating at each depth position in Comparative Example 1 were less than 0.5 and less than 0.2, respectively, compared with the steel sheet 2.

[0157] Comparative Example 2

[0158] The heat diffusion treatment was performed under the conditions described in Table 5, and the Ni-plated steel sheet was obtained in the same manner as in Example 10, and was evaluated in the same manner.

[0159] Comparative Example 3

[0160] The Ni coating adhesion amount was changed to 8.9 g / m. 2 Otherwise, a Ni-plated steel sheet was obtained in the same manner as in Example 10, and was evaluated in the same manner.

[0161] [Table 1]

[0162]

[0163] [Table 2]

[0164]

[0165] [Table 3]

[0166]

[0167] [Table 4]

[0168]

[0169] [Table 5]

[0170]

[0171] As shown in Tables 1 to 3, in Examples 1 to 12, when comparing the strengths of the standard nickel-plated steel sheet measured by high-frequency glow discharge emission spectroscopy with those of the Ni-plated surface-treated steel sheet 1, alloy regions were found where the Fe and Ni strengths were at least 10% of the maximum strength of the standard Ni-plated steel sheet, and the Cu and Cr strengths were higher than the strengths of the Ni coating of the standard Ni-plated steel sheet. Thus, it was confirmed that an alloy region, namely the Fe-Ni-Cu-Cr layer 3, containing Fe, Ni, Cu, and Cr, was formed. Specifically, it was determined that the aforementioned alloy region existed at depths of at least 0.1 μm, 0.3 μm, and 0.5 μm, and that the strength ratios of Cu and Cr relative to the standard Ni-plated steel sheet at each location were at least 2.0, i.e., more than twice the strength. Furthermore, in Examples 1 to 12, the strength ratio IR at depth 0.1 μm relative to the steel sheet 2 was confirmed. Cu-0.1d The strength is between 0.5 and 3.0. Furthermore, in Examples 1-12, the strength ratio IR at a depth of 0.5 μm to that of steel plate 2 was confirmed. Cu-0.5d IR is above 0.5 Cr-0.5d It is above 0.20.

[0172] As shown in Tables 1-3, the Ni-plated steel sheet 1 with Fe-Ni-Cu-Cr layer 3 exhibits a small current value caused by the dissolution of metals such as Fe at 4.1V, equivalent to over-discharge, and excellent electrolyte resistance during over-discharge (Examples 1-12). Particularly in Example 1, compared to Comparative Example 1 shown in Table 4, the current value is approximately 60% lower, and the electrolyte resistance is particularly excellent. Furthermore, compared to the Ni-plated steel sheet 2 of Example 2, the Ni-plated steel sheet 1 of Example 1 has a higher Cr strength (In) at a depth of 0.5 μm relative to the standard sample. Cr-0.5d-ref Cr intensity ratio at various depths compared to IR Cr-d-vref The contact resistance values ​​are high, but the contact resistance values ​​are similar. This is believed to be because, although there is also a lot of Cr in Example 1, Cu also diffuses sufficiently from the steel plate 2 and is contained within the Fe-Ni-Cu-Cr layer 3.

[0173] Furthermore, in Example 1, the strength ratio IR at a depth of 0.5 μm to that of steel plate 2 was confirmed. Cu-0.5d It is 0.5 or higher. Furthermore, in Example 1, the difference in Cu intensity ratio IR... Cu-MAX -IR Cu-0.1d If the value exceeds 0.05, it satisfies equation (1) above, and the difference in Cu intensity ratio IR Cu-MAX -IR Cu-boundaryThe value exceeds 0.05, satisfying equation (2) above. That is, in Example 1, it can be confirmed that a region of copper enrichment exists in the middle region of the Fe-Ni-Cu-Cr layer 3. This can also be confirmed by the fact that the depth of the maximum Cu intensity in Example 1 is 0.59 μm shallower than the boundary point with the steel plate 2; unlike Example 2 and Comparative Example 1, in the graph of Example 1, as shown Figure 3 As shown in (b), after the Cu strength reaches its maximum, the Cu strength decreases towards the boundary point with steel plate 2. Furthermore, in Example 1, the Cu strength ratio IR compared to the standard sample was [missing information - likely a specific value or characteristic]. Cu-d-vref The concentration is 2.3 or higher and 10 or lower, which is greater than that of Example 2. Therefore, it can be said that Example 1 has a higher absolute amount of Cu near the surface compared to Example 2. Compared to Example 2, Example 1 exhibits a lower current value at 4.1V during over-discharge due to the dissolution of metals such as Fe, and its electrolyte resistance during over-discharge is particularly excellent. It is believed that this result was obtained in Example 1 by using carbon steel with a significantly higher Cu content compared to Example 2.

[0174] As shown in Examples 3-5, when using carbon steel C with a Cu content of 0.1% or more and less than 0.2% by weight and a Cr content of 0.03% or more and less than 0.05% by weight, it is also possible to obtain Ni-plated surface-treated steel sheet 1 with excellent electrolyte resistance.

[0175] As shown in Table 2, even with a low Ni coating thickness, by using carbon steel containing specified amounts of Cu and Cr as the base plate, an Fe-Ni-Cu-Cr layer 3 is formed, achieving a strength ratio IR of 0.1 μm at the depth position relative to the steel plate 2. Cu-0.1d The electrolyte content is between 0.5 and 3.0, thus the electrolyte resistance of the Ni-plated surface-treated steel sheet 1 becomes excellent (Examples 6-9).

[0176] As shown in Table 3, when the Ni coating has a high adhesion amount, the strength ratio IR of the Cu in the steel plate is higher. Cu-d The Cu strength ratio IR compared to the standard sample Cu-d-vref Especially near the surface, the values ​​are relatively small (Examples 10-12). However, as can be seen from the comparison with Comparative Example 2 shown in Table 4, when the Ni coating adhesion is relatively large, by forming the Fe-Ni-Cu-Cr layer 3, the strength ratio IR at a depth of 0.1 μm to that of the steel plate 2 is improved. Cu-0.1d A value between 0.5 and 3.0 can also improve electrolyte resistance.

[0177] On the other hand, for Ni-plated steel sheets where the formation of the Fe-Ni-Cu-Cr layer was not confirmed, the current value caused by the dissolution of Fe at 4.1V during over-discharge is large, resulting in poor electrolyte resistance (Comparative Example 1).

[0178] Furthermore, even with the Fe-Ni-Cu-Cr layer 3 formed, the strength ratio IR at a depth of 0.1 μm is higher than that of the steel plate 2. Cu-0.1d When the concentration is below 0.5, insufficient diffusion of Cu into the vicinity of the surface layer also results in poor electrolyte resistance (Comparative Examples 2-3).

[0179] Explanation of reference numerals in the attached figures

[0180] 1…Ni-plated steel sheet

[0181] 2…steel plate

[0182] 3…Fe-Ni-Cu-Cr layer

Claims

1. A Ni-plated surface-treated steel sheet, comprising: a steel sheet formed of carbon steel, and an Fe-Ni-Cu-Cr layer formed on at least one side of said steel sheet. When the Cu intensity was continuously measured from the surface side to the depth direction of the Fe-Ni-Cu-Cr layer using high-frequency glow discharge emission spectroscopy (GDS), the Cu intensity In at a depth of 0.1 μm from the surface side was... Cu-0.1d The Cu strength In relative to the steel plate Cu-steel The ratio of IR Cu-0.1d It is greater than 0.5 and less than 3.

0.

2. The Ni-plated surface-treated steel sheet according to claim 1, wherein, When the Cu intensity was continuously measured from the surface side to the depth direction of the Fe-Ni-Cu-Cr layer using high-frequency glow discharge emission spectroscopy (GDS), the Cu intensity In at a depth of 0.5 μm from the surface side was... Cu-0.5d The Cu strength In relative to the steel plate Cu-steel The ratio of IR Cu-0.5d It is greater than 0.5 and less than 3.

0.

3. The Ni-plated surface-treated steel sheet according to claim 1 or 2, wherein, When the Cr intensity was continuously measured from the surface side to the depth direction of the Fe-Ni-Cu-Cr layer using high-frequency glow discharge emission spectroscopy (GDS), the Cr intensity In at a depth of 0.5 μm from the surface side was... Cr-0.5d The In relative to the Cr strength of the steel plate Cr-steel The ratio of IR Cr-0.5d It is greater than 0.2 and less than 2.

0.

4. The Ni-plated surface-treated steel sheet according to any one of claims 1 to 3, wherein, When the Cr intensity was continuously measured from the surface side to the depth direction of the Fe-Ni-Cu-Cr layer using high-frequency glow discharge emission spectroscopy (GDS), the Cr intensity In at a depth of 0.1 μm from the surface side was... Cr-0.1d The In relative to the Cr strength of the steel plate Cr-steel The ratio of IR Cr-0.1d It is greater than 0.2 and less than 2.

0.

5. The Ni-plated surface-treated steel sheet according to any one of claims 1 to 4, wherein, When the Cu intensity is continuously measured from the surface side of the Fe-Ni-Cu-Cr layer towards the depth direction using high-frequency glow discharge emission spectroscopy (GDS), the Cu intensity In at a depth of 0.3~0.7 μm from the surface side is... Cu-0.3d~0.7d The Cu strength In relative to the steel plate Cu-steel The ratio of IR Cu-0.3d~0.7d It is between 0.5 and 3.

0.

6. The Ni-plated surface-treated steel sheet according to any one of claims 1 to 5, wherein, The Fe-Ni-Cu-Cr layer has Cu-rich regions.

7. The Ni-plated surface-treated steel sheet according to any one of claims 1 to 6, wherein, The maximum Cu intensity In was measured by high-frequency glow discharge emission spectroscopy (GDS) from the surface of the Fe-Ni-Cu-Cr layer toward the depth direction, up to the steel plate. MAX The Cu strength In relative to the steel plate Cu-steel The ratio of IR Cu-MAX Above 0.8 and below 3.

0.

8. The Ni-plated surface-treated steel sheet according to any one of claims 1 to 7, wherein, The steel plate is low-carbon steel or very low-carbon steel.

9. The Ni-plated surface-treated steel sheet according to any one of claims 1 to 8, wherein, The steel plate is low-carbon steel. The Cu content of the steel plate is 0.01% to 1.0% by weight. The Cr content of the steel plate is 0.01% to 1.0% by weight.

10. A battery container made of a Ni-plated surface-treated steel sheet according to any one of claims 1 to 9.

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