Ni-PLATED SURFACE-TREATED STEEL SHEET, BATTERY CONTAINER, AND METHOD FOR PRODUCING Ni-PLATED SURFACE-TREATED STEEL SHEET

Abstract

Provided is a Ni-plated surface-treated steel sheet (1) comprising a steel sheet (10) and a metal layer (20) containing Ni and formed on the steel sheet (10), wherein: the metal layer (20) is positioned on an outermost surface of the Ni-plated surface-treated steel sheet (1); the skewness Ssk measured in accordance with ISO 25178 on the surface of the metal layer (20) is -1.44 to 2.0 inclusive; and the protruding peak height Spk [μm] measured in accordance with ISO 25178 satisfies formula (1).　(1): 0.493 × Ssk +0.919 ≤ Spk ≤ 5.0

Description

Ni-plated surface-treated steel sheet, battery container, and method for manufacturing Ni-plated surface-treated steel sheet

[0001] The present invention relates to a Ni-plated surface-treated steel sheet, a battery container, and a method for manufacturing the Ni-plated surface-treated steel sheet.

[0002] In recent years, portable devices such as audio equipment and mobile phones have come into wide use, and primary batteries such as alkaline batteries and secondary batteries such as nickel-metal hydride batteries and lithium-ion batteries are widely used as their operating power sources. Furthermore, secondary batteries such as nickel-metal hydride batteries and lithium-ion batteries are also used as in-vehicle power sources. As the performance and functionality of the devices in which they are installed become more advanced, longer life, higher performance, and higher capacity are required of such batteries. Therefore, the battery container, which is filled with power-generating elements such as positive and negative electrode active materials, is also required to have improved performance as an important component of the battery.

[0003] As a steel sheet used as a battery container for such a battery, a surface-treated steel sheet for battery containers is known, in which a nickel plating layer is formed on the steel sheet by performing a plating treatment under conditions of a bath temperature of 70°C or higher (for example, Patent Document 1).

[0004] International Publication No. 2016 / 148084

[0005] Conventional Ni-plated steel sheets with low nickel plating layer hardness have poor slipperiness on the surface that comes into contact with the press die during press forming, resulting in excessive heat generation due to friction during press forming. This locally heated Ni-plated steel sheet is prone to seizure on the press die during forming, resulting in the problem of nickel and iron on the surface layer of the Ni-plated steel sheet becoming easily attached to the die. If seizure occurs, defects may occur in the battery cans produced thereafter, and frequent mold maintenance and replacement may be required. Therefore, improved press formability is desired. On the other hand, the surface-treated steel sheet for battery containers disclosed in Patent Document 1 can reduce seizure, but the high hardness of the nickel plating layer increases die wear during press forming, resulting in frequent die replacement. Furthermore, the need for two nickel plating processes increases manufacturing costs and environmental impact, and improvements are desired.

[0006] An object of the present invention is to provide a Ni-plated surface-treated steel sheet having excellent press workability.

[0007] [1] According to a first aspect of the present invention, there is provided a Ni-plated surface-treated steel sheet comprising a steel sheet and a Ni-containing metal layer formed on the steel sheet, wherein the metal layer is located on the outermost surface of the Ni-plated surface-treated steel sheet, and the surface of the metal layer has a skewness Ssk measured in accordance with ISO 25178 of -1.44 or more and 2.0 or less, and a peak height Spk [μm] measured in accordance with ISO 25178 satisfies the following formula (1): 0.493 × Ssk + 0.919 ≦ Spk ≦ 5.0 (1)

[0008] [2] According to a second aspect of the present invention, there is provided a Ni-plated surface-treated steel sheet according to the first aspect, wherein the metal layer comprises an Fe—Ni diffusion layer and a Ni layer, and the Fe—Ni diffusion layer and the Ni layer are laminated in this order on the steel sheet.

[0009] [3] According to a third aspect of the present invention, there is provided the Ni-plated surface-treated steel sheet according to the first aspect, wherein the metal layer is an Fe—Ni diffusion layer.

[0010] [4] According to a fourth aspect of the present invention, there is provided the Ni-plated surface-treated steel sheet according to the first aspect, in which the metal layer is formed on both sides of the steel sheet.

[0011] [5] According to a fifth aspect of the present invention, there is provided a Ni-plated surface-treated steel sheet according to the fourth aspect, wherein the metal layers each comprise an Fe—Ni diffusion layer and a Ni layer, and the Fe—Ni diffusion layer and the Ni layer are laminated in this order on the steel sheet.

[0012] [6] According to Aspect 6 of the present invention, there is provided a Ni-plated surface-treated steel sheet according to Aspect 4, wherein the metal layer formed on one surface of the steel sheet is an Fe—Ni diffusion layer, and the metal layer formed on the other surface of the steel sheet comprises an Fe—Ni diffusion layer and a Ni layer, and in the metal layer formed on the other surface of the steel sheet, the Fe—Ni diffusion layer and the Ni layer are laminated in this order on the steel sheet.

[0013] [7] According to a seventh aspect of the present invention, there is provided the Ni-plated surface-treated steel sheet according to the fourth aspect, in which the metal layers are all Fe—Ni diffusion layers.

[0014] [8] According to an eighth aspect of the present invention, there is provided a Ni-plated surface-treated steel sheet according to any one of the first to seventh aspects, wherein the indentation hardness H ＩＴ is 3800N / mm ２ A Ni-plated surface-treated steel sheet having the following properties.

[0015] [9] According to a ninth aspect of the present invention, there is provided the Ni-plated surface-treated steel sheet according to any one of the first to eighth aspects, wherein the Ni coating weight in the metal layer on one surface of the steel sheet is 0.45 g / m ２ ~65.0g / m ２ The present invention provides a Ni-plated surface-treated steel sheet having the following properties.

[0016]

[10] According to a tenth aspect of the present invention, there is provided the Ni-plated surface-treated steel sheet according to any one of aspects 1 to 9, wherein the thickness of the steel sheet is 0.03 to 1.20 mm.

[0017]

[11] According to an eleventh aspect of the present invention, there is provided the Ni-plated surface-treated steel sheet according to any one of aspects 1 to 10, wherein the carbon content of the steel sheet is 0.01 to 0.15 wt %.

[0018]

[12] According to a twelfth aspect of the present invention, there is provided the Ni-plated surface-treated steel sheet according to any one of the first to eleventh aspects, wherein the metal layer contains at least one element selected from the group consisting of Co, Zn, and Sn.

[0019]

[13] According to a thirteenth aspect of the present invention, there is provided a battery container made using the Ni-plated surface-treated steel sheet according to any one of the first to twelfth aspects.

[0020]

[14] According to Aspect 14 of the present invention, there is provided a method for producing a Ni-plated surface-treated steel sheet according to any one of Aspects 1 to 12, the method comprising: a Ni-plating step of applying Ni plating to the steel sheet; a thermal diffusion step of performing a thermal diffusion treatment on the Ni-plated steel sheet; and a temper rolling step of temper rolling the Ni-plated steel sheet, wherein in the temper rolling step, temper rolling is performed using temper rolls having a surface skewness Rsk measured in accordance with JIS B 0601:2001 of −0.9 or more and 0.5 or less, and a surface protruding valley height Rvk [μm] measured in accordance with JIS B 0671:2001-2 of 1.4 or more and 6.0 or less.

[0021] According to the present invention, it is possible to provide a Ni-plated surface-treated steel sheet having excellent press workability.

[0022] Fig. 1 is a cross-sectional view showing the configuration of a Ni-plated surface-treated steel sheet according to an embodiment of the present invention. Fig. 2(a) and Fig. 2(b) are diagrams for explaining the skewness Ssk determined in accordance with ISO 25178, Fig. 2(a) is a graph showing the height distribution when the skewness Ssk is less than 0, and Fig. 2(b) is a schematic cross-sectional view showing the surface condition when the skewness Ssk is less than 0. Fig. 3(a) and Fig. 3(b) are diagrams for explaining the skewness Ssk determined in accordance with ISO 25178, Fig. 3(a) is a graph showing the height distribution when the skewness Ssk is greater than 0, and Fig. 3(b) is a schematic cross-sectional view showing the surface condition when the skewness Ssk is greater than 0. 4(a) to 4(c) are diagrams illustrating the protruding peak height Spk determined in accordance with ISO 25178. FIG. 4(a) is a graph showing a load curve determined from the area load ratio measured in accordance with ISO 25178. FIG. 4(b) is a graph showing an equivalent line determined from the load curve shown in FIG. 4(a). FIG. 4(c) is a graph showing the protruding peak height determined from the equivalent line shown in FIG. 4(b). FIG. 5 is a cross-sectional view showing the configuration of a first modified example of a Ni-plated surface-treated steel sheet according to an embodiment of the present invention. FIG. 6 is a cross-sectional view showing the configuration of a second modified example of a Ni-plated surface-treated steel sheet according to an embodiment of the present invention. FIG. 7 is a graph showing the relationship between the skewness Ssk and the protruding peak height Spk of Ni-plated surface-treated steel sheets 1 in examples and comparative examples according to an embodiment of the present invention. FIG. 8 is a graph showing the relationship between the surface hardness and the dynamic friction coefficient of Ni-plated surface-treated steel sheets 1 in examples and comparative examples according to an embodiment of the present invention.

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a schematic cross-sectional view showing the configuration of a Ni-plated surface-treated steel sheet according to this embodiment. The Ni-plated surface-treated steel sheet 1 according to this embodiment comprises a steel sheet 10 and a metal layer 20 containing Ni formed on the steel sheet 10.

[0024] <Steel Sheet 10> In this embodiment, the steel sheet 10 is not particularly limited as long as it has excellent formability. For example, low-carbon aluminum-killed steel (carbon content: 0.01 to 0.15 wt.%), ultra-low carbon steel with a carbon content of 0.003 wt.% or less, or non-aging ultra-low carbon steel obtained by adding Ti, Nb, or the like to ultra-low carbon steel can be used. In this embodiment, hot-rolled sheets of these steels are pickled to remove surface scale (oxide film), then cold-rolled, electrolytically cleaned, annealed, and temper-rolled. Alternatively, steel sheets that are cold-rolled and electrolytically cleaned without annealing or temper-rolling are used as the steel sheet 10. The type of annealing may be either continuous annealing or batch annealing, and is not particularly limited. The thickness of the steel sheet 10 may be appropriately selected depending on the application of the Ni-plated surface-treated steel sheet, but is preferably 0.03 to 1.20 mm. When used for a battery container, from the viewpoint of weight reduction and thinning, the upper limit is preferably 1.2 mm or less, more preferably 1.1 mm or less, and even more preferably 1.0 mm or less. From the viewpoint of workability and safety of the battery container, the lower limit is preferably 0.03 mm or more, more preferably 0.05 mm or more, even more preferably 0.15 mm or more, and particularly preferably 0.2 mm or more.

[0025] <Metal layer 20> The metal layer 20 is a layer containing Ni formed on the steel sheet 10, and is located on the outermost surface of the Ni-plated surface-treated steel sheet 1. As shown in Fig. 1 , in this embodiment, the metal layer 20 is composed of a Ni layer 30 and an Fe-Ni diffusion layer 40. The metal layer 20 is provided on both sides of the steel sheet 10.

[0026] The Ni layer 30 and the Fe—Ni diffusion layer 40 are obtained by subjecting the steel sheet 10, which has been nickel-plated to form a nickel-plated layer on its surface, to a thermal diffusion treatment. The Fe—Ni diffusion layer 40 is formed by subjecting the nickel-plated steel sheet 10 to a thermal diffusion treatment, thereby thermally diffusing the iron (Fe) constituting the steel sheet 10 and the nickel (Ni) constituting the nickel plating. The Ni layer 30 is obtained by subjecting the nickel-plated steel sheet 10 to a thermal diffusion treatment, leaving a layer made of nickel, without diffusing iron to the surface. In this embodiment, the Fe—Ni diffusion layer 40 and the Ni layer 30 are laminated in this order on the steel sheet 10. That is, the Ni layer 30 is located on the outermost surface of the Ni-plated surface-treated steel sheet 1. The Fe—Ni diffusion layer 40 is an intermediate layer located between the Ni layer 30 and the steel sheet 10.

[0027] The presence of the Ni-plated surface-treated steel sheet 1 in the Ni layer 30 and the Fe—Ni diffusion layer 40 can be confirmed by X-ray diffraction measurement, GDS measurement, or cross-sectional composition analysis using SEM and EDS. For example, when using X-ray diffraction measurement, confirmation can be performed using the following procedure. To confirm the presence of the Fe—Ni diffusion layer 40, first, X-ray diffraction measurement is performed on the Ni-plated surface-treated steel sheet 1 of this embodiment, and the range of diffraction angles 2θ of 43.00° or more and 44.30° or less is confirmed in the obtained diffraction chart. If either a diffraction peak with a maximum value exists within this range or the diffraction intensity within this range is sufficiently high, it can be confirmed that the Ni-plated surface-treated steel sheet 1 has the Fe—Ni diffusion layer 40.

[0028] The diffraction intensity in the range of the diffraction angle 2θ of 43.00° or more and 44.30° or less is ０．６４ Ni ０．３６ , FeNi, and FeNi ３ Therefore, a diffraction peak having a maximum value in this range indicates the presence of an Fe—Ni diffusion layer. In other words, if a diffraction peak having a maximum value exists in this range, it can be confirmed that the Ni-plated surface-treated steel sheet 1 has an Fe—Ni diffusion layer 40.

[0029] On the other hand, when the diffraction angle 2θ is 43.00° or more and 44.30° or less, the diffraction intensity value may be higher than the background value, but there may be no diffraction peak with a maximum value. Such a diffraction chart may be obtained when Ni-derived diffraction is present, such as when the Ni coating mass is relatively high and the Ni layer 30 on the Fe—Ni layer 40 is thick, or when the Ni plating thickness before heat treatment is 3 μm or more. In such cases, the presence of the Fe—Ni diffusion layer 40 can be confirmed if the ratio of the maximum diffraction intensity at a diffraction angle 2θ of 43.00° or more and 44.30° or less to the background diffraction intensity (maximum diffraction intensity at a diffraction angle 2θ of 43.00° or more and 44.30° or less / background diffraction intensity) is sufficiently high, such as 100 or more. The background diffraction intensity is a diffraction intensity within a range not affected by the diffraction of Fe—Ni, Ni, and Fe, for example, an average value at a diffraction angle 2θ of 86°±0.5°.

[0030] To confirm the presence of the Ni layer 30, X-ray diffraction measurement is performed on the Ni-plated surface-treated steel sheet 1 of this embodiment, and the range of the diffraction angle 2θ of 76° to 77° in the obtained diffraction chart is confirmed. If a diffraction peak with a maximum value exists within this range, it can be confirmed that the Ni-plated surface-treated steel sheet 1 has the Ni layer 30. The respective crystal structures and diffraction peaks are based on the following database. Fe ０．６４ Ni ０．３６ :ICDD PDF Card 00-047-1405 FeNi:ICDD PDF Card 01-071-8322 FeNi ３ :ICDD PDF Card 01-071-8323 Ni:ICDD PDF Card 01-087-0712

[0031] In this embodiment, the skewness Ssk on the surface of the metal layer 20 is −1.44 or more and 2.0 or less, and the protruding peak height Spk [μm] satisfies the following formula (1), whereby the coefficient of dynamic friction on the surface of the Ni-plated surface-treated steel sheet 1 is reduced, and the Ni-plated surface-treated steel sheet 1 has excellent press workability: 0.493×Ssk+0.919≦Spk≦5.0 (1)

[0032] 2(a), 2(b), 3(a), and 3(b) are diagrams for explaining the skewness Ssk determined in accordance with ISO. 2(a) and 2(b) are a graph showing the height distribution and a schematic cross-sectional view showing the surface condition when the skewness Ssk is less than 0, respectively. 3(a) and 3(b) are a graph showing the height distribution and a schematic cross-sectional view showing the surface condition when the skewness Ssk is greater than 0, respectively.

[0033] In this embodiment, skewness Ssk is a parameter that represents the symmetry of the height distribution measured in accordance with ISO 25178. A value of 0 indicates that the height distribution is symmetrical from top to bottom. Furthermore, when the Ssk value is less than 0, the surface height distribution is biased toward the higher side, as shown in FIG. 2( a), and the peaks are wider than the valleys, as shown in FIG. 2( b). On the other hand, when the Ssk value is greater than 0, the surface height distribution is biased toward the lower side, as shown in FIG. 3( a), and the valleys are wider than the peaks, as shown in FIG. 3( b).

[0034] Figures 4(a) to 4(c) are diagrams for explaining the protruding peak height Spk determined in accordance with ISO 25178. Figure 4(a) is a graph showing a load curve determined from the area load ratio measured in accordance with ISO 25178, Figure 4(b) is a graph showing an equivalent line determined from the load curve shown in Figure 4(a), and Figure 4(c) is a graph showing the protruding peak determined from the equivalent line shown in Figure 4(b).

[0035] In this embodiment, the average height Spk of the protruding peaks above the core portion is the average height measured in accordance with ISO 25178 and can be determined from the surface load curve. As shown in FIG. 4( a), the surface roughness load curve (hereinafter also referred to as the "load curve (surface)") is a curve measured in accordance with ISO 25178, showing the heights at which the area load ratio ranges from 0% to 100%. The area load ratio is a parameter that represents the proportion of the area of ​​the region above height c (the proportion of the solid portion that appears when the specimen is cut at height c) at a certain height c. As shown in FIG. 4( b), a secant line of the load curve (surface) is drawn along the load curve (surface) from an area load ratio of 0% to a difference of 40%, and the position where the slope of the secant line is the gentlest is referred to as the central portion of the load curve (surface). The line that minimizes the sum of squares of the deviations in the vertical direction from this central portion is referred to as the equivalent line. As shown in Figure 4(c), the part of the equivalent line that falls within the height range of areal load ratios from 0% to 100% is called the core. The parts higher than the core are called protruding peaks, and the parts lower than the core are called protruding valleys. Spk can be calculated by finding the average height of these protruding peaks.

[0036] The skewness Ssk of the surface of the metal layer 20, measured in accordance with ISO 25178, is −1.44 or more and 2.0 or less. By setting the skewness Ssk of the surface of the metal layer 20 within the above range, the height distribution of the surface of the metal layer 20 can be set within an appropriate range. As a result, when the Ni-plated surface-treated steel sheet 1 comes into contact with another member, such as a mold, the contact area of ​​the contact surface with the member can be appropriately reduced. Furthermore, by setting the skewness SSk within the above range, the number of contact points of the Ni-plated surface-treated steel sheet 1 with the other member can be appropriately reduced. This allows the Ni-plated surface-treated steel sheet 1 to contact the other member uniformly at points, resulting in the Ni-plated surface-treated steel sheet 1 having a low dynamic friction coefficient and excellent processability. From the viewpoint of more stably reducing the dynamic friction coefficient, the skewness Ssk is preferably −0.9 or more and 1.5 or less.

[0037] If the skewness Ssk is too small, the height distribution will be biased toward the higher side, resulting in a larger contact area, which will tend to generate friction and increase the dynamic friction coefficient. As a result, workability will be reduced and seizure will occur. On the other hand, if the skewness Ssk is too large, the height distribution will be biased toward the lower side, making the convex portions more likely to deform. As a result, the convex portions will deform upon contact with the mating material, i.e., the mold, or the convex portions will adhere to the mold, increasing the dynamic friction coefficient and reducing workability and seizure. This behavior is thought to be due to the fact that the newly formed surface of the metal layer 20 that appears on the surface due to the deformation of the convex portions is very unstable and active due to the absence of metal oxides or organic adsorbates, and therefore tends to bond firmly to the surrounding material, i.e., the mold in this case. The inventors focused on the skewness Ssk when examining the control of the contact state, which is essential for discussing the friction of metallic materials when plastic deformation occurs.

[0038] Furthermore, on the surface of the metal layer 20, the height Spk of the protruding peaks measured in accordance with ISO 25178 satisfies the following formula (1): 0.493×Ssk+0.919≦Spk≦5.0 (1)

[0039] The present inventors have investigated the reduction of the dynamic friction coefficient in a Ni-plated surface-treated steel sheet having a nickel plating layer with a low hardness on its surface, and have found that the dynamic friction coefficient does not simply depend on the height of the asperities, but that it is important to control the protruding peak height Spk within a suitable range depending on the skewness Ssk, which is the height distribution. In other words, the present inventors have found that by setting the protruding peak height Spk in accordance with the Ssk, which is the degree of deviation in the height distribution, the contact area with the mating material can be maintained in a suitable range, and as a result, the dynamic friction coefficient can be kept low and workability can be improved.

[0040] If the peak height Spk on the surface of the metal layer 20 is too low relative to the skewness Ssk, which is the height distribution, the contact area becomes large, which makes friction more likely to occur and increases the dynamic friction coefficient. This in turn makes it more likely for workability to deteriorate and seizure to occur. By setting the peak height Spk within an appropriate range relative to the skewness Ssk, the contact area can be reduced and more uniform point contact can be increased, resulting in the Ni-plated surface-treated steel sheet 1 having a low dynamic friction coefficient and excellent workability. If the peak height Spk is too large, the volume of the peaks increases relative to the valleys, making them more likely to deform due to contact with the mold, which in turn makes it more likely for workability to deteriorate and for seizure to occur due to adhesion to the mold.

[0041] The protruding peak height Spk is not particularly limited as long as it satisfies the above range, but is preferably 0.7 μm or more, and the upper limit is preferably 4.5 μm or less.

[0042] In general, the arithmetic mean roughness Ra, the maximum height Rz, and the surface hardness, which are typical indicators of surface quality, are said to be correlated with the coefficient of dynamic friction. For example, a technique is known in which a Ni-plated layer formed on a steel sheet is heat-treated and then re-plated with Ni to increase the surface hardness and thereby reduce the coefficient of dynamic friction. In contrast, the present inventors have found that adjusting the arithmetic mean roughness Ra, the maximum height Rz, and the surface hardness of a surface-treated steel sheet having a Ni-containing plating layer formed thereon does not necessarily reduce the coefficient of dynamic friction. As a result of extensive research, the present inventors have found that by controlling the skewness Ssk and the peak height Spk of the metal layer 20 constituting the outermost surface of the Ni-plated surface-treated steel sheet 1 in combination, the coefficient of dynamic friction on the surface of the Ni-plated surface-treated steel sheet 1 can be reduced, thereby improving the press workability of the Ni-plated surface-treated steel sheet 1.

[0043] The reason why adjusting the arithmetic mean roughness Ra does not necessarily reduce the dynamic friction coefficient is believed to be as follows. During processing of a surface-treated steel sheet, convex portions on the plating layer surface come into contact with other components, such as a mold. Therefore, controlling the convex portions on the surface, i.e., the contact points with other components, is believed to be important for reducing the dynamic friction coefficient of the surface of the surface-treated steel sheet. However, because the arithmetic mean roughness is an overall average value, it is a numerical value that includes information other than the contact points during processing, and the state of the contact points is not clearly reflected in the numerical value. Therefore, it is believed that controlling the arithmetic mean roughness Ra does not necessarily reduce the dynamic friction coefficient. In addition, the reason why adjusting the maximum height Rz does not necessarily reduce the dynamic friction coefficient is believed to be that the maximum height Rz is a numerical value for a single maximum point, whereas there are multiple convex portions that become contact points during press processing of the Ni-plated steel sheet 1, and information about these multiple convex portions is not reflected in the numerical value. As described above, the present inventors have found that controlling Ssk and Spk in combination, focusing on convex portions that are likely to be contact points with other members as peak portions, rather than controlling Ra and Rz, is effective in reducing the dynamic friction coefficient in a plating layer containing soft Ni, which has a conventional high dynamic friction coefficient.

[0044] Conventional Ni-plated steel sheets, which have a low hardness of the nickel plating layer, have poor slipperiness on the surface that comes into contact with the press die during press working. This leads to excessive heat generation due to friction during press working. As a result, the Ni-plated steel sheet, which is locally heated during forming, seizes and adheres to the press die during forming, causing scratches on the outer surface of the battery container manufactured from the Ni-plated steel sheet. Furthermore, when seizure occurs on the die, die maintenance is required, resulting in reduced productivity and a shortened die life. Furthermore, thermal expansion of the press die reduces the dimensional accuracy of the sidewall thickness of the battery container and makes it difficult for the battery container to be removed from the press die. In contrast, the Ni-plated surface-treated steel sheet 1 of this embodiment has a reduced dynamic friction coefficient by controlling the skewness Ssk and protruding peak height Spk of the metal layer 20 within specific ranges, thereby eliminating the above-mentioned problems that occur during press working.

[0045] When the hardness of the nickel plating layer is high, the coefficient of dynamic friction tends to be reduced, but the die wear amount increases, resulting in more frequent die replacement. Furthermore, in the conventional method of re-Ni-plating the Ni-plated layer after heat treatment to harden it, Ni-plating must be performed two or more times, which poses a problem of large carbon dioxide emissions and a heavy burden on the environment. In contrast, the Ni-plated surface-treated steel sheet 1 of this embodiment does not require Ni-plating two or more times, as will be described later, and therefore the burden on the environment in the manufacturing process can be reduced.

[0046] In this embodiment, since the Ni layer 30 is located on the outermost surface of the Ni-plated surface-treated steel sheet 1, it is sufficient that the skewness Ssk and the protruding peak height Spk on the surface of the Ni layer 30 satisfy the above conditions.

[0047] The Ni deposition amount in the metal layer 20, i.e., the Ni deposition amount relative to the steel sheet 10 on the surface on which the metal layer 20 is formed, is preferably 0.45 g / m ２ ~65.0g / m ２ When the metal layer 20 is made up of the Ni layer 30 and the Fe—Ni diffusion layer 40, from the viewpoint of corrosion resistance to the battery contents, the thickness is more preferably 4.5 g / m on the surface that becomes the inner surface of the battery container. ２ ~40.0g / m ２ and more preferably 8.9 g / m ２ ~35.0g / m ２ From the viewpoint of rust prevention on the outer surface of the battery container, it is more preferable that the thickness of the outer surface of the battery container is 8.9 g / m ２ ~65.0g / m ２ and more preferably 12.0 g / m ２ ~60.0g / m ２ and particularly preferably 16.0 g / m ２ ~55.0g / m ２ The Ni deposition weight relative to the steel sheet 10 refers to the total amount of Ni contained in the Ni layer 30 and the Fe—Ni diffusion layer 40. The Ni deposition weight refers to the amount of Ni deposited on one surface of the steel sheet 10. The Ni deposition weight can be measured, for example, by the method described in the examples below.

[0048] The thickness of the Ni-plated surface-treated steel sheet 1 may be appropriately selected depending on the application of the Ni-plated surface-treated steel sheet 1 and is not particularly limited, but is preferably 0.03 to 1.20 mm. When used for battery containers, from the viewpoint of weight reduction and thinning, the upper limit is preferably 1.2 mm or less, more preferably 1.1 mm or less, and even more preferably 1.0 mm or less. Furthermore, from the viewpoint of workability and safety of the battery container, the lower limit is preferably 0.03 mm or more, more preferably 0.05 mm or more, even more preferably 0.15 mm or more, and particularly preferably 0.2 mm or more. The thickness of the Ni-plated surface-treated steel sheet 1 is not particularly limited, but can be measured with a micrometer.

[0049] The hardness of the surface of the Ni-plated surface-treated steel sheet 1, i.e., the outermost surface of the metal layer 20, is determined by measuring the indentation hardness H ＩＴ The upper limit is 3800N / mm ２ Preferably, it is equal to or less than 3500 N / mm ２ The lower limit is not particularly limited, but from the viewpoint of reducing seizure on the press die, it is preferably 1500 N / mm ２ More preferably, 1600 N / mm ２ More preferably, it is 1700 N / mm ２ That's all. Indentation hardness H ＩＴThe hardness can be measured by the indentation method in accordance with ISO 14577-1 2002. By measuring with a small load of 10 mN, the hardness of the extremely shallow region of the outermost surface, which affects surface friction during processing, can be obtained, compared to Vickers hardness and the like. More specifically, if the indentation depth when measuring the hardness of the surface of the Ni-plated surface-treated steel sheet 1 using the indentation method with a load of 10 mN is approximately 0.4 μm, when the Vickers hardness of the same Ni-plated surface-treated steel sheet 1 is measured with a load of 10 gf, the indentation depth will be approximately 1.0 μm. Therefore, it can be said that the former method is more effective in obtaining hardness in an extremely shallow region. Furthermore, in general, the closer the measurement location is to the surface, i.e., the smaller the indentation depth, the more information is reflected from the location closer to the surface. Since the Ni-plated surface-treated steel sheet 1 in this embodiment has a surface hardness within the above range, the outermost layer is relatively soft. As described above, it has been conventionally believed that the coefficient of dynamic friction can be reduced by increasing the surface hardness, i.e., by hardening the outermost surface layer. In contrast, the Ni-plated surface-treated steel sheet 1 of the present embodiment has the skewness Ssk and the peak height Spk controlled within specific ranges, so that even if the outermost surface layer is relatively soft, the coefficient of dynamic friction is reduced and the sheet has excellent press workability.

[0050] One method for achieving the hardness of the outermost surface of the metal layer 20 within the above range is to perform a heat treatment after nickel plating. Furthermore, as long as the surface hardness falls within the above range, temper rolling may be performed after the heat treatment. If heat treatment is not performed after nickel plating, the hardness of the outermost surface will reflect the hardness of the nickel layer that has been distorted during plating, resulting in an extremely hard outermost surface of the Ni-plated surface-treated steel sheet. With such Ni-plated surface-treated steel sheets, die wear during press working increases, which tends to increase the frequency of die replacement. Therefore, it is important to perform a heat treatment after nickel plating.

[0051] The dynamic friction coefficient measured at a normal load of 1 N on the surface of the Ni-plated surface-treated steel sheet 1, i.e., the outermost surface of the metal layer 20, is preferably less than 0.70, and more preferably less than 0.3. There is no particular lower limit for the dynamic friction coefficient on the surface of the Ni-plated surface-treated steel sheet 1, but it is usually 0.10 or more. The dynamic friction coefficient can be measured, for example, by the method described in the examples below.

[0052] 5 and 6 are schematic cross-sectional views showing the configurations of first and second modified examples of the Ni-plated surface-treated steel sheet 1 according to this embodiment, respectively.

[0053] 1, the metal layer 20 includes the Ni layer 30 and the Fe—Ni diffusion layer 40, but the configuration of the metal layer 20 is not particularly limited thereto. For example, as shown in FIG. 5, the metal layer 20 may be composed of only the Fe—Ni diffusion layer 40. In FIG. 5, the metal layer 20 is composed of only the Fe—Ni diffusion layer 40, and therefore the Fe—Ni diffusion layer 40 is located on the outermost surface of the Ni-plated surface-treated steel sheet 1. Therefore, it is sufficient that the skewness Ssk and the protruding peak height Spk on the surface of the Fe—Ni diffusion layer 40 satisfy the above conditions.

[0054] When the metal layer 20 is composed of only the Fe—Ni diffusion layer 40, from the viewpoint of corrosion resistance and rust prevention against the battery contents, the Ni deposition amount on the steel plate 10 on the surface on which the metal layer 20 is formed is preferably 0.45 g / m ２ ~12.0g / m ２ and more preferably 0.8 g / m ２ ~8.9g / m ２ is.

[0055] 1, the two metal layers 20 formed on both sides of the steel plate 10 each include a Ni layer 30 and an Fe—Ni diffusion layer 40 and have the same configuration, but the configuration of the metal layer 20 is not particularly limited thereto, and the configurations of the two metal layers 20 may be different on each side of the steel plate 10. For example, as shown in FIG. 6, the metal layer 20 formed on one side of the steel plate 10 may be composed only of an Fe—Ni diffusion layer 40, and the metal layer 20 formed on the other side of the steel plate 10 may be composed of a Ni layer 30 and an Fe—Ni diffusion layer 40. In FIG. 6 as well, it is sufficient that the skewness Ssk and the protruding peak height Spk on the surface of the Fe—Ni diffusion layer 40 on the surface on which the Fe—Ni diffusion layer 40 is provided on the outermost surface satisfy the above conditions.

[0056] 1 , the metal layer 20 is formed on both sides of the steel sheet 10, and the Ni-plated surface-treated steel sheet 1 includes two metal layers 20, but the configuration of the Ni-plated surface-treated steel sheet 1 is not particularly limited to this. It is sufficient that the metal layer 20 is formed on at least one side of the steel sheet 10, that is, it is sufficient that the Ni-plated surface-treated steel sheet 1 includes at least one metal layer 20.

[0057] Furthermore, the metal layer 20 may contain at least Ni, but may also contain at least one element selected from the group consisting of Co, Zn, and Sn in addition to Ni. That is, the Ni layer 30 may contain one or more elements selected from Co, Zn, and Sn, and the Fe—Ni diffusion layer 40 may contain one or more elements selected from Co, Zn, and Sn. For example, an embodiment in which the Ni layer 30 and the Fe—Ni diffusion layer 40 each contain Co includes an embodiment in which the Ni layer 30 is made of a Ni—Co alloy and the Fe—Ni diffusion layer 40 is made of a Fe—Ni—Co alloy. Furthermore, for example, when the Ni layer 30 contains Co, the Ni layer 30 may be made of a layer made of only Ni stacked on the Fe—Ni diffusion layer 40 and a layer made of a Ni—Co alloy as the outermost layer.

[0058] The fact that the metal layer 20 includes the Ni layer 30 and the Fe—Ni diffusion layer 40, whether the outermost surface of the metal layer 20 is the Ni layer 30 or the Fe—Ni diffusion layer 40, and whether the metal layer 20 contains Co, Zn, or Sn can be confirmed by performing elemental analysis on the surface of the metal layer 20. For elemental analysis, radio frequency glow discharge optical emission spectroscopy (GDS), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), or the like can be used. For example, when radio frequency glow discharge optical emission spectroscopy is used, the analysis can be performed by the method described in the examples below.

[0059] <Method for Manufacturing Ni-Plated Surface-Treated Steel Sheet 1> The Ni-plated surface-treated steel sheet 1 in this embodiment can be manufactured by a method including a Ni-plating step of applying Ni plating to a steel sheet 10, a step of applying a thermal diffusion treatment to the Ni-plated steel sheet 10, and a temper rolling step of temper rolling the Ni-plated steel sheet 10 and imparting a surface texture to it. The surface texture is preferably imparted using rolls with controlled surface roughness. Examples of the temper rolling step using temper rolling equipment with controlled surface roughness for the temper rolling rolls are as described above. However, the process is not limited to this as long as the desired surface texture is obtained. For example, the surface texture imparting step may be performed before the thermal diffusion treatment step, or a step of imparting surface texture using temper rolling rolls or cold rolling rolls may be performed before the Ni-plating step. From the viewpoint of facilitating the attainment of the desired surface texture, it is preferable to perform the Ni-plating step, the thermal diffusion treatment step, and the temper rolling step in this order.

[0060] First, in the Ni plating step, Ni plating is applied to the steel sheet 10 to form a Ni plating layer. Ni plating may be applied to both sides of the steel sheet 10, or may be applied to only one side of the steel sheet 10. The Ni plating bath used for Ni plating may be a commonly used plating bath, such as a Watts bath, sulfamic acid bath, boron fluoride bath, or chloride bath. For example, Ni plating using a Watts bath uses a bath composition of 200 to 350 g / L of nickel sulfate hexahydrate, 20 to 60 g / L of nickel chloride hexahydrate, and 10 to 50 g / L of boric acid, at a pH of 3.0 to 5.0, a bath temperature of 40 to 70°C, and a current density of 10 to 40 A / dm ２ This can be done under the following conditions.

[0061] The thickness of the Ni plating layer formed on the steel sheet 10 by Ni plating is preferably 0.05 to 7.3 μm. The Ni coating amount is preferably 0.45 g / m ２ ~65.0g / m ２ When the metal layer 20 is made up of the Ni layer 30 and the Fe—Ni diffusion layer 40, from the viewpoint of corrosion resistance to the battery contents, the thickness is more preferably 4.5 g / m on the surface that becomes the inner surface of the battery container. ２ ~40.0g / m ２ and more preferably 8.9 g / m ２ ~35.0g / m ２ From the viewpoint of rust prevention on the outer surface of the battery container, it is more preferable that the thickness of the outer surface of the battery container is 8.9 g / m ２ ~65.0g / m ２ and more preferably 12.0 g / m ２ ~60.0g / m ２ and particularly preferably 16.0 g / m ２ ~55.0g / m ２ is.

[0062] When the metal layer 20 is composed of only the Fe—Ni diffusion layer 40, from the viewpoint of corrosion resistance and rust prevention against the battery contents, the Ni deposition amount on the steel plate 10 on the surface on which the metal layer 20 is formed is preferably 0.45 g / m ２ ~12.0g / m ２ and more preferably 0.8 g / m ２ ~8.9g / m２ is.

[0063] Next, the Ni-plated steel sheet 10 is subjected to a thermal diffusion treatment. The thermal diffusion treatment method may be either a continuous annealing method or a batch annealing method. Although not particularly limited, the heat treatment atmosphere is preferably a non-oxidizing atmosphere or a reducing protective gas atmosphere. When a reducing protective gas atmosphere is used, for example, H 2 O 3 , also known as HNX gas, is used. ２ and N ２ It is preferable to use a mixed gas of these. The thermal diffusion treatment conditions may be appropriately selected depending on the thickness and deposition amount of Ni plating. For example, in the case of continuous annealing, the heat treatment temperature is preferably 350 to 900 degrees Celsius and the heat treatment time is preferably 30 to 120 seconds, and in the case of batch annealing, the heat treatment temperature is preferably 450 to 600°C and the heat treatment time is preferably 15 minutes to 8 hours. From the viewpoint of ease of control over the imparting of surface texture in the temper rolling process, in the case of continuous annealing, the heat treatment temperature is more preferably 480°C or higher, even more preferably 600°C or higher, and particularly preferably 650°C or higher.

[0064] By carrying out the thermal diffusion treatment described above, an Fe—Ni diffusion layer 40 can be formed on the steel sheet 10, and the remaining portion of the Ni plating layer where Fe does not diffuse becomes a soft Ni layer 30 in which stress during plating is alleviated. In other words, the Ni-plated surface-treated steel sheet 1 obtained through the temper rolling process described below can be one in which the outermost metal layer 20 includes an Fe—Ni diffusion layer 40 and a soft Ni layer 30, and the Fe—Ni diffusion layer 40 and the Ni layer 30 are laminated in this order on the steel sheet 10. Furthermore, if the Ni plating is completely thermally diffused by the thermal diffusion treatment, a configuration can be achieved in which only the Fe—Ni diffusion layer 40 is formed on the steel sheet 10.

[0065] Next, in the temper rolling step, the steel sheet 10 that has been Ni-plated and then thermally diffused is subjected to temper rolling. For temper rolling, it is preferable to use a roll whose surface roughness is controlled by subjecting the roll surface to shot dulling, electrical discharge texturing (hereinafter also referred to as EDT (Electro Discharge Texturing) processing), brightening, or the like. Specifically, it is preferable that the skewness Rsk of the temper rolling roll surface measured in accordance with JIS B 0601:2001 is -0.9 or more and 0.5 or less, and that the protruding valley height Rvk of the temper rolling roll surface measured in accordance with JIS B 0671-2:2002 is 1.4 or more and 6.0 or less. It is more preferable to use a temper rolling roll whose skewness Rsk is -0.9 or more and 0.3 or less, and whose protruding valley height Rvk is 1.4 or more and 4.5 or less. By performing temper rolling using temper rolls having such surface properties, the skewness Ssk and protruding peak height Spk on the surface of the resulting Ni-plated surface-treated steel sheet 1 can be controlled within desired ranges, thereby providing the Ni-plated surface-treated steel sheet 1 with excellent press workability. The skewness Rsk and protruding valley height Rvk of the rolling roll surface can be determined by measuring the rolling roll surface in a direction perpendicular to the rolling direction using a stylus-type surface roughness tester. The surface treatment of the temper roll can be performed using the above-mentioned shot dulling, EDT, and brightening processes without any restrictions. However, shot dulling or EDT is preferred from the viewpoint of appropriately controlling the roughness of the roll surface. The roll material is not particularly limited, but temper rolls made of forged steel are preferred, and temper rolls made of forged steel containing 3 to 7 wt. % Cr are preferred. The temper rolling equipment can be one-stand or multiple-stand, but the surface roughness of the last roll to pass through is preferably within the above-mentioned range. When the temper rolling equipment is made up of multiple stands, it is preferable that the surface roughness of the last two rolling rolls is within the above range.

[0066] The elongation of the Ni-plated surface-treated steel sheet by temper rolling is preferably 0.3% to 5.0%, and more preferably 0.5% to 3.0%. The elongation by temper rolling is expressed by the following formula. In the formula, "sheet" refers to the steel sheet 10 that has been Ni-plated and then thermally diffused. Elongation (%) = (Length in the longitudinal direction of the sheet after temper rolling - Length in the longitudinal direction before temper rolling) / Length in the longitudinal direction of the sheet before temper rolling x 100

[0067] The reduction in temper rolling is preferably 5.0% or less, and more preferably 3.0% or less. The lower limit of the reduction is not particularly limited, and may be substantially 0.0%. The reduction is expressed by the following formula. In the following formula, "sheet" refers to a steel sheet 10 that has been Ni-plated and then thermally diffused. Reduction (%) = (sheet thickness after temper rolling - sheet thickness before temper rolling) / sheet thickness before temper rolling x 100

[0068] To achieve an embodiment in which the metal layer 20 contains at least one of Co, Zn, and Sn, the steel sheet 10 may be plated with these metals in the Ni plating step. For example, methods for providing the metal layer 20 with Ni and Co include a method of Co-plating the Ni-plated steel sheet 10 and then performing thermal diffusion treatment, a method of Ni-Co alloy plating the Ni-plated steel sheet 10, and a method of Ni-Co alloy plating the steel sheet 10. By such methods, the metal layer 20 can be obtained in which the Fe-Ni diffusion layer 40 is made of an Fe-Ni-Co alloy and the Ni layer 30 is made of an Ni-Co alloy.

[0069] The Ni-plated surface-treated steel sheet 1 of this embodiment is manufactured in the above manner. Thus, the present inventors have newly discovered that by temper rolling a steel sheet 10 having a Ni-containing metal layer 20 formed thereon using temper rolls in which the roll surface roughness, particularly the skewness Rsk and the protruding valley height Rvk, is appropriately controlled, a Ni-plated surface-treated steel sheet 1 in which the skewness Ssk and the protruding valley height Spk are appropriately controlled can be obtained. That is, according to the manufacturing method of the Ni-plated surface-treated steel sheet 1 of this embodiment, the skewness Ssk and the protruding valley height Spk are appropriately controlled, and a Ni-plated surface-treated steel sheet 1 having excellent press formability can be manufactured. Furthermore, according to the manufacturing method of the Ni-plated surface-treated steel sheet 1 of this embodiment, the surface texture can be controlled by temper rolling the steel sheet 10 after heat treatment, and two or more Ni plating processes are not required, thereby reducing manufacturing costs and environmental impact in the manufacturing process.

[0070] <Battery Container> The battery container of this embodiment is obtained by forming a Ni-plated surface-treated steel sheet 1. Although not particularly limited, when an Fe—Ni diffusion layer 40 is provided on the outermost surface of any side of the steel sheet 10, it is preferable to perform the processing so that the surface on which the Fe—Ni diffusion layer 40 is provided faces the inside of the battery container. Examples of forming methods include drawing, ironing, DI (Drawing and Ironing), and DTR (Draw and Thin Redraw). In the Ni-plated surface-treated steel sheet 1 of this embodiment, the skewness Ssk at the outermost surface of the metal layer 20 is −1.44 or more and 2.0 or less, and the protruding peak height Spk at the outermost surface of the metal layer 20 satisfies the above formula (1), thereby reducing the dynamic friction coefficient and providing excellent press workability. Therefore, the battery container in this embodiment has an excellent appearance and is less susceptible to scratches caused by heat generated by friction when pressing the Ni-plated surface-treated steel sheet 1. Furthermore, since the occurrence of seizure on the mold is reduced, factors that reduce productivity, such as mold maintenance, are less likely to occur.

[0071] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0072] <Ni deposition weight, Ni plating thickness> In each example and comparative example, the Ni deposition weight per one side of the Ni-plated steel sheet 10 was measured using an X-ray fluorescence spectrometer. The X-ray fluorescence spectrometer used was a ZSX100e (manufactured by Rigaku Corporation), and the measurement was performed using a calibration curve method. The Ni deposition weight was calculated based on the density of Ni (8.9 g / cm ３ ) was converted into thickness to determine the thickness of the Ni plating layer after the Ni plating step.

[0073] <Skewness Ssk and protruding peak height Spk of Ni-plated surface-treated steel sheet 1> Using a laser microscope (Olympus Corporation, 3D measuring laser microscope LEXT OLS5000) with a 20x objective lens (lens name: MPLAPON20XLEXT), the surface of the Ni-plated surface-treated steel sheet 1 was observed, and an analysis image with a field of view of 5295 μm × 1225 μm (the 1225 μm side was parallel to the rolling direction) was obtained. Next, the obtained analysis image was subjected to automatic correction processes, such as noise removal and tilt correction, using an analysis application. Thereafter, surface roughness analysis was performed, and the skewness Ssk and protruding peak height Spk of the Ni-plated surface-treated steel sheet 1 were determined.

[0074] <Skewness Rsk and protruding valley height Rvk of temper rolling roll> The temper rolling roll was measured in the direction perpendicular to the rolling direction using a stylus surface roughness measuring instrument (Mitutoyo, Surftest SJ-310). The measurement was performed under the following conditions: evaluation length: 4.0 mm, measurement speed: 0.5 mm / sec, cutoff value: 0.8 mm, filter type: Gaussian, measurement range: AUTO, tilt correction: linear, and cutoff ratio: 320, and the skewness Rsk and protruding valley height Rvk of the temper rolling roll were determined.

[0075] <Presence or Absence of Fe—Ni Diffusion Layer 40 and Ni Layer 30> X-ray diffraction measurement was performed on the Ni-plated surface-treated steel sheet 1, and the diffraction angle 2θ range of 43.00° to 44.30° was confirmed in the obtained diffraction chart. If a diffraction peak with a maximum value was present within this range or if the diffraction intensity was sufficiently high, the Ni-plated surface-treated steel sheet 1 was determined to have the Fe—Ni diffusion layer 40. If a diffraction peak with a maximum value was present within the diffraction angle 2θ range of 76° to 77°, the Ni-plated surface-treated steel sheet 1 was determined to also have the Ni layer 30. A Rigaku SmartLab was used as the X-ray diffraction measurement device. The Ni-plated surface-treated steel sheet 1 was cut into 20 mm × 20 mm pieces and used as samples. The configuration of the X-ray diffraction measurement device and measurement conditions were as follows. [Apparatus configuration] X-ray source: CuKα Goniometer radius: 300 mm Optical system: focusing method (incident side slit system) Soller slit: 5° Longitudinal limiting slit: 5 mm Divergence slit: 2 / 3° (receiving side slit system) Scattering slit: 2 / 3° Soller slit: 5° Receiving slit: 0.3 mm Monochromatization method: counter monochromator method Detector: scintillation counter [Measurement parameters] Target: Cu Tube voltage-tube current: 45 kV 200 mA Scanning axis: 2θ / θ (focusing method) Scanning mode: continuous Measurement range: 2θ 40 to 100° Scanning speed: 10° / min Step: 0.02°

[0076] <Method of Determining Layer Structure> When peaks of both the Fe—Ni diffusion layer 40 and the Ni layer 30 were confirmed in the X-ray diffraction measurement, the Fe intensity and Ni intensity in the Ni-plated surface-treated steel sheet 1 were measured using a radio-frequency glow discharge optical emission spectrometer (manufactured by HORIBA, Ltd., model number: GD-PROFILER2) until the Fe intensity was saturated, and the layer structure was determined. The specific measurement conditions for the radio-frequency glow discharge optical emission spectrometer were as follows: Measurement mode: HDD mode Excitation mode: RF (normal) Output: 35 W Pressure: 600 Pa Module: 7 V Fuse: 7 V Anode diameter: 4 mm Gas replacement time: 30 seconds Pre-sputtering time: 30 seconds Background measurement time: 10 seconds Measurement time: 80 seconds Capture interval: 0.1 seconds

[0077] In the obtained intensity data, if the point where the Ni intensity is maximum is near the outermost surface and the Ni intensity monotonically decreases thereafter, it was determined that the Ni layer 30 and the Fe—Ni diffusion layer 40 were formed in this order from the outermost surface (i.e., the Fe—Ni diffusion layer 40 and the Ni layer 30 were formed in this order on the steel sheet 10). The layer structure was determined using the measurement results from an X-ray diffraction device and a high-frequency glow discharge optical emission spectrometer.

[0078] <Dynamic Friction Coefficient> A ball-on-disk test was carried out on the Ni-plated surface-treated steel sheet 1 using a tribometer (manufactured by Anton Paar, model number TRB3, contact: SUJ-2 (chrome steel) ball with a diameter of 6 mm) at a rotation radius of 10 mm, a load of 1.0 N, and a rotation speed of 10 rpm, and the average value of the dynamic friction coefficients measured between 24 and 30 seconds after the start of the measurement was determined.

[0079] <Surface hardness> For the Ni-plated surface-treated steel sheet 1, the indentation hardness H ＩＴSpecifically, first, a Berkovich indenter was pressed vertically into the metal layer 20 of the Ni-plated surface-treated steel sheet 1 using an ultra-microindentation hardness tester (ENT-5, manufactured by Elionix), and the displacement h (nm) relative to the test load F (mN) was continuously measured. The measurement conditions were as follows:・Indenter used: Berkovich indenter ・Test mode: Load / unload test ・Loading conditions: Starting load = 0 mN, ending load = 10 mN, number of divisions = 500, step interval = 20 msec (applied for 10 seconds. 0 mN → 10 mN 0.02 mN / 20 msec) ・Holding conditions: No holding ・Unloading conditions: Starting load = 10 mN, ending load = 0 mN, number of divisions = 500, step interval = 20 msec (unloaded for 10 seconds. 10 mN → 0 mN -0.02 mN / 20 msec)

[0080] Before measuring the Ni-plated surface-treated steel sheet 1, fused quartz was measured under a load of 10 mN as a daily inspection, and after confirming that the result was within the standard and there was no abnormality (indentation hardness H ＩＴ : 9500 N / mm ２ ±15%, indentation elastic modulus E ＩＴ :73000N / mm ２ ±10%, maximum indentation depth h ｍａｘ The indentation width was 290 nm ± 5%). To eliminate the influence of the plastic deformation region around the indentation, the distance between indentations in the measurement was set to at least five times the diameter of the indentation. Furthermore, to reduce the influence of roughness, measurements were taken at 15 or more points on flat areas. After checking all the load-displacement curves and excluding those with peculiar profiles, load-displacement curves of 10 or more points were obtained.

[0081] Next, the load-displacement curve created from the measurement results was analyzed, and the maximum indentation load F ｍａｘ (N) is the projected area A where the indenter and the Ni-plated surface-treated steel sheet 1 are in contact at that time. ｐ (mm ２ ) is the indentation hardness H ＩＴ This calculation was performed in accordance with ISO 14577-1 2002. The correction of the indenter tip curvature was performed using the Oliver method, and the unloading fitting was performed using the power low fit method, with the analysis being performed under conditions of a minimum load of 20% and a maximum load of 95% of the power low fit.

[0082] Example 1 A cold-rolled sheet (thickness: 0.3 mm) of low-carbon aluminum-killed steel was prepared as the steel sheet 10. After alkaline electrolytic degreasing and acid pickling by immersion in sulfuric acid, electrolytic plating was performed under the following conditions to form a 1.0 μm-thick Ni plating film on the steel sheet 10. Bath composition: nickel sulfate hexahydrate 250 g / L, nickel chloride hexahydrate 45 g / L, boric acid 30 g / L, pH: 4.0 to 5.0, bath temperature: 60° C., current density: 20 A / dm ２ Power-on time: 35 seconds

[0083] Next, the steel sheet 10 on which the Ni-plated coating was formed was subjected to thermal diffusion treatment by continuous annealing at a temperature of 800°C for 50 seconds in a reducing atmosphere. Thereafter, the steel sheet 10 was temper rolled at an elongation of 1.0% using temper rolls made of forged steel with a 5% Cr content, the surface roughness of which had been adjusted to Rsk -0.6 to -0.3 and Rvk [μm] 2.0 to 2.3 by EDT processing or shotdulling, to obtain a Ni-plated surface-treated steel sheet 1. The reduction rate in temper rolling was 0%, which was a substantial value based on the measured thickness. The obtained Ni-plated surface-treated steel sheet 1 was evaluated using the methods described above. X-ray diffraction measurement confirmed the presence of an Fe—Ni diffusion layer 40, but not a Ni layer 30, confirming that the outermost layer of the Ni-plated surface-treated steel sheet 1 was the Fe—Ni diffusion layer 40. That is, the Ni-plated surface-treated steel sheet 1 was a steel sheet 10 having an Fe—Ni diffusion layer 40 formed on it as the outermost layer.

[0084] Examples 2 to 15 Ni-plated surface-treated steel sheets 1 were obtained and evaluated in the same manner as in Example 1, except that the Ni plating film amount, heat treatment conditions, and temper rolling roll roughness were changed to the conditions shown in Table 1. The results are shown in Table 1. In Examples 3 to 7 and 10 to 15, it was confirmed by X-ray diffraction measurement and high-frequency glow discharge optical emission spectroscopy that the outermost layer of the Ni-plated surface-treated steel sheet 1 was the Ni layer 30. It was also confirmed that an Fe—Ni diffusion layer 40 was formed between the steel sheet 10 and the Ni layer 30.

[0085] <Comparative Examples 1 to 5> Ni-plated surface-treated steel sheets 1 were obtained and evaluated in the same manner as in Example 1, except that the Ni-plated coating amount, heat treatment conditions, and temper rolling roll roughness were changed to the conditions shown in Table 1. The results are shown in Table 1.

[0086] Comparative Examples 6 to 11 Ni-plated surface-treated steel sheets 1 were obtained and evaluated in the same manner as in Example 1, except that temper rolls that had been surface-finished by brightening were used and the Ni-plated coating amount, heat treatment conditions, and temper roll roughness were changed to the conditions shown in Table 1. The results are shown in Table 1.

[0087] <Reference Example> A cold-rolled sheet of low-carbon aluminum-killed steel similar to that of Example 1 was prepared. The prepared steel sheet was then subjected to alkaline electrolytic degreasing and pickling by immersion in sulfuric acid, and then electrolytic plating was carried out under the following conditions to form a nickel plating layer of 0.25 μm in thickness on the steel sheet. Bath composition: nickel sulfate hexahydrate 250 g / L, nickel chloride hexahydrate 45 g / L, boric acid 45 g / L pH: 3.9 to 4.9 Bath temperature: 60°C Current density: 15 A / dm ２

[0088] Then, the steel sheet on which the nickel plating layer was formed was subjected to thermal diffusion treatment by continuous annealing under conditions of a heat treatment temperature of 720°C, a heat treatment time of 1 minute, and a reducing atmosphere, thereby forming an iron-nickel diffusion layer as a base layer.

[0089] Next, the steel sheet on which the underlayer (iron-nickel diffusion layer) was formed was subjected to electrolytic plating under the following conditions to form a nickel plating layer having a thickness of 0.5 μm on the steel sheet, thereby obtaining a surface-treated steel sheet having nickel plating layers formed on both main surfaces of the steel sheet 10. Bath composition: nickel sulfate hexahydrate 250 g / L, nickel chloride hexahydrate 45 g / L, boric acid 45 g / L, semi-brightener 4 ml / L, pH: 3.9 to 4.9, bath temperature: 70° C., current density: 15 A / dm ２

[0090] The obtained surface-treated steel sheet was subjected to the indentation hardness H ＩＴ was found to be 4190 N / mm ２ It was.

[0091]

[0092] 7 is a graph showing the relationship between the skewness Ssk and the peak height Spk of the Ni-plated surface-treated steel sheets 1 in the examples and comparative examples. The Ni-plated surface-treated steel sheets 1 obtained in Examples 1 to 15, in which the skewness Ssk measured in accordance with ISO 25178 was between −1.44 and 2.0 and the peak height Spk measured in accordance with ISO 25178 satisfied the above formula (1), i.e., the relationship between the skewness Ssk and the peak height Spk fell within the range surrounded by the solid line in FIG. 7, had a reduced dynamic friction coefficient and excellent press workability, as shown in Table 1.

[0093] On the other hand, the Ni-plated surface-treated steel sheets 1 obtained in Comparative Examples 1 to 11, in which the skewness Ssk and the protruding peak height Spk did not satisfy the above conditions, had a high dynamic friction coefficient and poor press workability.

[0094] 8 is a graph showing the relationship between the surface hardness and the dynamic friction coefficient of the Ni-plated surface-treated steel sheet 1 in the examples and comparative examples. As shown in Fig. 8, even when the surface hardness was approximately the same, the dynamic friction coefficient was significantly different, which indicates that adjusting the surface hardness of the Ni-plated surface-treated steel sheet 1 is not a sufficient method for reducing the dynamic friction coefficient.

[0095] 1...Ni-plated surface-treated steel sheet 10...Steel sheet 20...Metal layer 30...Ni layer 40...Fe—Ni diffusion layer

Claims

1. A Ni-plated surface-treated steel sheet comprising a steel sheet and a Ni-containing metal layer formed on the steel sheet, wherein the metal layer is located on the outermost surface of the Ni-plated surface-treated steel sheet, and the skewness Ssk on the surface of the metal layer measured in accordance with ISO 25178 is -1.44 or more and 2.0 or less, and the peak height Spk [μm] measured in accordance with ISO 25178 satisfies the following formula (1): 0.493 × Ssk + 0.919≦Spk≦5.0 (1) 2. A Ni-plated surface-treated steel sheet according to claim 1, wherein the metal layer comprises an Fe-Ni diffusion layer and a Ni layer, and the Fe-Ni diffusion layer and the Ni layer are laminated in this order on the steel sheet.

3. The Ni-plated surface-treated steel sheet according to claim 1, wherein the metal layer is an Fe-Ni diffusion layer.

4. The Ni-plated surface-treated steel sheet according to claim 1, wherein the metal layer is formed on both sides of the steel sheet.

5. A Ni-plated surface-treated steel sheet according to claim 4, wherein the metal layers each comprise an Fe-Ni diffusion layer and a Ni layer, and the Fe-Ni diffusion layer and the Ni layer are laminated in this order on the steel sheet.

6. A Ni-plated surface-treated steel sheet according to claim 4, wherein the metal layer formed on one surface of the steel sheet is an Fe-Ni diffusion layer, and the metal layer formed on the other surface of the steel sheet comprises an Fe-Ni diffusion layer and a Ni layer, and in the metal layer formed on the other surface of the steel sheet, the Fe-Ni diffusion layer and the Ni layer are laminated in this order on the steel sheet.

7. The Ni-plated surface-treated steel sheet according to claim 4, wherein the metal layers are all Fe-Ni diffusion layers.

8. The Ni-plated surface-treated steel sheet according to any one of claims 1 to 7, wherein the indentation hardness H measured by the indentation method under a load of 10 mN is ＩＴ is 3800N / mm ２ A Ni-plated surface-treated steel sheet having the following properties.

9. The Ni-plated surface-treated steel sheet according to any one of claims 1 to 8, wherein the Ni coating weight in the metal layer on one surface of the steel sheet is 0.45 g / m ２ ~65.0g / m ２ Ni-plated surface-treated steel sheet.

10. The Ni-plated surface-treated steel sheet according to any one of claims 1 to 9, wherein the thickness of the steel sheet is 0.03 to 1.20 mm.

11. A Ni-plated surface-treated steel sheet according to any one of claims 1 to 10, wherein the carbon content of the steel sheet is 0.01 to 0.15 wt %.

12. A Ni-plated surface-treated steel sheet according to any one of claims 1 to 11, wherein the metal layer contains at least one element selected from the group consisting of Co, Zn, and Sn.

13. A battery container made using the Ni-plated surface-treated steel sheet according to any one of claims 1 to 12.

14. A method for producing a Ni-plated surface-treated steel sheet according to any one of claims 1 to 12, comprising: a Ni-plating step of applying Ni plating to the steel sheet; a thermal diffusion step of applying thermal diffusion treatment to the Ni-plated steel sheet; and a temper rolling step of temper rolling the Ni-plated steel sheet, wherein in the temper rolling step, temper rolling is performed using temper rolls having a surface skewness Rsk measured in accordance with JIS B 0601:2001 of -0.9 or more and 0.5 or less, and a surface protruding valley height Rvk [μm] measured in accordance with JIS B 0671:2001-2 of 1.4 or more and 6.0 or less.

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