Surface-treated steel sheet and method for producing surface-treated steel sheet

Abstract

A surface-treated steel sheet according to one embodiment of the present invention is provided with a base steel sheet, an Ni-containing layer disposed on the surface of the base steel sheet, and an Ni-W alloy layer disposed on the surface of the Ni-containing layer, the Ni-containing layer having an Fe-diffused alloy layer, and the surface-treated steel sheet having a W-deficient layer within a range from the surface of the Ni-W alloy layer to a depth of 10 nm. In a method for manufacturing a surface-treated steel sheet according to another embodiment of the present invention, the dew point of the atmosphere during annealing is set to-25 DEG C to 5 DEG C, the soaking time during annealing is set to 10-180 seconds, and the maximum temperature during annealing is set to 630-860 DEG C.

Description

Technical Field

[0001] The present invention relates to a surface-treated steel plate and a method for manufacturing the surface-treated steel plate.

[0002] This application claims priority based on Japanese Patent Application No. 2023-016703 filed in Japan on February 7, 2023, the contents of which are incorporated herein by reference. Background Art

[0003] Conventionally, nickel-plated steel sheets have been used as surface-treated steel sheets for battery cans. Due to the excellent chemical stability of nickel, nickel-plated steel sheets are used in various battery containers, such as alkaline manganese dry batteries, lithium-ion batteries, and nickel-metal hydride batteries.

[0004] In recent years, Ni-W alloy-plated steel sheets mainly composed of an alloy of Ni and W have also begun to be used as materials for battery cans, etc. Examples of Ni-W alloy-plated steel sheets are described in Patent Documents 1 to 4.

[0005] Patent Document 1 discloses a plated steel sheet for a battery container, characterized in that an iron-nickel alloy layer, a nickel layer, and a nickel-tungsten alloy layer are formed in this order from the bottom on the steel sheet on the side of the steel sheet that becomes the inner surface of the battery container.

[0006] Patent Document 2 discloses a surface-treated steel sheet, which is a Ni-containing surface-treated steel sheet for containers formed by press forming, comprising: a steel sheet having a first surface that becomes the outer side of the container after the press forming; a Ni-containing layer disposed on the first surface of the steel sheet; and a Ni-W alloy plating layer disposed on the Ni-containing layer. The Ni-containing layer includes an Fe-Ni diffusion alloy layer, and the amount of Ni contained in the Ni-containing layer is 5 g / m 2 Above and 89g / m 2 the thickness of the Ni-W alloy plating layer is 0.02 μm or more and 2 μm or less; the W concentration in the Ni-W alloy plating layer is 10% or more and 65% or less by mass%.

[0007] Patent Document 3 discloses a steel plate for a non-aqueous electrolyte secondary battery case, comprising a steel plate and a Ni—W—Fe alloy plating layer formed on the surface of the steel plate. The Ni—W—Fe alloy plating layer contains a Ni—W—Fe alloy and serves as the inner surface of the non-aqueous electrolyte secondary battery case.

[0008] Patent document 4 discloses a steel plate for alkaline battery cans, which is used for battery cans of inside-out alkaline batteries. It is characterized in that a surface layer of one main surface of a substrate comprising a plate-shaped steel material has a plating layer selected from nickel-tungsten (Ni-W) and nickel-cobalt-tungsten (Ni-Co-W) alloys, and the above-mentioned plating layer has unevenness on the surface formed by the dissolution of the above-mentioned tungsten.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-51325

[0012] Patent Document 2: International Publication No. 2012 / 137823

[0013] Patent Document 3: International Publication No. 2017 / 006834

[0014] Patent Document 4: Japanese Patent Application Laid-Open No. 2020-155202 Summary of the Invention

[0015] Problems to be solved by the invention

[0016] In recent years, demand for rectangular battery cans has increased. Rectangular battery cans are used at a neutral potential. Therefore, surface-treated steel sheets for rectangular cans require high resistance to metal leaching from electrolytes. Ni-W alloy-plated steel sheets offer superior metal leaching resistance compared to Ni-plated steel sheets, which have been commonly used in battery cans. Therefore, Ni-W alloy-plated steel sheets are expected to be used as battery can materials.

[0017] However, Ni-W alloy coatings are harder and have lower workability than Ni coatings. When Ni-W alloy-coated steel sheets are used as materials for square cans, cracks are easily generated in the Ni-W alloy coatings during bending. Cracks are cracks that extend from the surface of the coating to the base material. Cracks expose the base material to the outside of the coating, promoting corrosion of the base material. Since Ni-W alloy coatings do not have a chemical corrosion protection effect, Ni-W alloy-coated steel sheets are easily corroded starting from cracks in the coating.

[0018] For the reasons described above, Ni—W alloy plated steel sheets having high workability are desired, but it is very difficult to meet this desire.

[0019] Patent Document 1 aims to suppress contact resistance and improve discharge characteristics, but no particular study has been conducted on the workability of the plated steel sheet.

[0020] Patent documentation 2 takes the corrosion resistance after improving press forming as a problem, and as its solution, proposes to form Fe-Ni diffusion alloy layer by heating at the interface of steel plate and Ni coating, and then, implements hard Ni-W alloy coating to the outermost surface.In the coating of record in patent documentation 2, use soft Fe-Ni diffusion alloy layer to prevent the crackle produced in Ni-W alloy coating from propagating to parent material steel plate.But, in the coating of record in patent documentation 2, for preventing the generation of crackle in Ni-W alloy coating, there is room for improvement.

[0021] The plated steel sheet disclosed in Patent Document 3 also has a Ni plating layer below the Ni-W-Fe alloy plating layer, which is relatively softer than the Ni-W-Fe alloy plating layer. However, the plating described in Patent Document 3 also has room for improvement in preventing cracks in the Ni-W alloy plating layer.

[0022] Patent Document 4 aims to improve the high-load discharge performance and long-term storage performance of steel sheets, but does not conduct any special research on the workability of plated steel sheets.

[0023] In view of the above circumstances, an object of the present invention is to provide a surface-treated Ni—W alloy-based steel sheet having excellent workability and a method for producing the same.

[0024] Means for solving problems

[0025] The gist of the present invention is as follows.

[0026] (1) A surface-treated steel sheet according to one embodiment of the present invention comprises: a base steel sheet, a Ni-containing layer arranged on a surface of the base steel sheet, and a Ni—W alloy layer arranged on a surface of the Ni-containing layer, wherein the Ni-containing layer has an Fe diffusion alloy layer, the Ni—W alloy layer has a thickness exceeding 10 nm, and the surface-treated steel sheet has a W-deficient layer within a range from the surface of the Ni—W alloy layer to a depth of 10 nm.

[0027] (2) It is preferred that in the surface-treated steel sheet described in (1), the surface-treated steel sheet has a W concentration valley in the range from the surface of the Ni-W alloy layer to a depth of 10 nm, the surface-treated steel sheet has a W concentration peak deeper than the W concentration valley, and the W concentration at the W concentration valley is W. B Relative to the W concentration at the W concentration peak W P The ratio W B / W P Below 0.5.

[0028] (3) Preferably, in the surface-treated steel sheet described in (1) or (2), the Fe diffusion alloy layer is arranged only in the Ni-containing layer, or in the entire Ni-containing layer and only a portion of the Ni-W alloy layer, the surface-treated steel sheet has a Ni concentration peak in the range from the surface of the Ni-W alloy layer to a depth of 10 nm, the surface-treated steel sheet has a Ni concentration valley deeper than the Ni concentration peak in the Ni-W alloy layer, and the Ni concentration at the Ni concentration peak is Ni. P Relative to the Ni concentration at the bottom of the Ni concentration, Ni B Ratio Ni P / Ni B is above 1.1.

[0029] (4) In the surface-treated steel sheet according to any one of (1) to (3) above, the Ni-containing layer preferably has a thickness of 0.2 to 4.0 μm.

[0030] (5) Preferably, in the surface-treated steel sheet according to any one of (1) to (4), the amount of Ni contained in the Ni-containing layer and the Ni-W alloy layer is 1.8 to 35.6 g / m 2 .

[0031] (6) In the surface-treated steel sheet according to any one of (1) to (5) above, the Fe diffusion alloy layer preferably has a thickness of 0.1 to 3.0 μm.

[0032] (7) In the surface-treated steel sheet described in any one of (1) to (6), it is preferred that the average W concentration in the Ni—W alloy layer is 10 to 45% by mass.

[0033] (8) In the surface-treated steel sheet according to any one of (2) to (7), it is preferable that the W concentration W at the W concentration valley bottom is B With respect to the W concentration W at the W concentration peak P The above ratio W B / W P It is 0.05 or above.

[0034] (9) In the surface-treated steel sheet according to any one of (1) to (8), preferably, only a portion of the Ni-containing layer is the Fe-diffused alloy layer.

[0035] (10) Preferably, in the surface-treated steel sheet described in any one of (1) to (9), the entire Ni-containing layer is the Fe-diffused alloy layer, and a portion of the Ni—W alloy layer is the Fe-diffused alloy layer.

[0036] (11) Another embodiment of the present invention relates to a method for manufacturing a surface-treated steel plate, comprising the following steps: a step of electroplating a base steel plate with Ni; a step of electroplating the base steel plate having the Ni-plated layer with a Ni-W alloy; and a step of annealing the base steel plate having the Ni-plated layer and the Ni-W alloy layer arranged thereon, wherein the dew point of the atmosphere during the annealing is set to -25 to 5°C, the soaking time during the annealing is set to 10 to 180 seconds, and the maximum temperature during the annealing is set to 630 to 860°C.

[0037] (12) In the method for manufacturing a surface-treated steel sheet described in (11), it is preferred that the amount of Ni deposited during the Ni electroplating be set to 1.5 to 33 g / m 2 .

[0038] (13) Preferably, in the method for manufacturing a surface-treated steel sheet according to (11) or (12), the total Ni deposition amount in the electroplated Ni and the electroplated Ni-W alloy is set to 1.8 to 35.6 g / m 2 .

[0039] Effects of the Invention

[0040] According to the present invention, a surface-treated Ni—W alloy steel sheet having excellent workability and a method for producing the same can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic cross-sectional view of an example (partial diffusion) of the surface-treated steel sheet according to the present embodiment.

[0042] Figure 2 It is a schematic cross-sectional view of another example (partial diffusion) of the surface-treated steel sheet according to the present embodiment.

[0043] Figure 3 It is a schematic cross-sectional view of another example (full diffusion) of the surface-treated steel sheet according to the present embodiment.

[0044] Figure 4 It is a schematic diagram of the W concentration curve of the Ni—W alloy layer in an example of the surface-treated steel sheet according to the present embodiment.

[0045] Figure 5 It is a schematic diagram of the Ni concentration curve of the Ni—W alloy layer in an example of the surface-treated steel sheet according to the present embodiment.

[0046] Figure 6 This is a flowchart illustrating an example of a method for producing a surface-treated steel sheet according to the present embodiment.

[0047] Figure 7 This is a cross-sectional view of the die used in the drawbead test. DETAILED DESCRIPTION

[0048] (1. Surface treated steel plate 1)

[0049] A surface treated steel plate 1 according to one embodiment of the present invention is as follows Figure 1 As shown in , etc., the surface-treated steel sheet 1 comprises a base steel sheet 11, a Ni-containing layer 12 disposed on the surface of the base steel sheet 11, and a Ni-W alloy layer 13 disposed on the surface of the Ni-containing layer 12. The Ni-containing layer 12 includes an Fe diffusion alloy layer 14. The thickness of the Ni-W alloy layer 13 exceeds 10 nm. The surface-treated steel sheet 1 includes a W-deficient layer 131 within a range from the surface of the Ni-W alloy layer 13 to a depth of 10 nm. The surface-treated steel sheet 1 according to this embodiment will be described in detail below. It should be noted that the entire coating layer including the Ni-containing layer 12 and the Ni-W alloy layer 13 may be simply referred to as the "coating layer."

[0050] (Base steel plate 11)

[0051] The surface-treated steel plate 1 includes a base steel plate 11. The base steel plate 11 is a steel plate serving as the base material of the surface-treated steel plate 1. The composition, thickness, and metal structure of the base steel plate 11 are not particularly limited and may be appropriately selected depending on the intended use of the surface-treated steel plate 1.

[0052] (Ni-containing layer 12)

[0053] The surface-treated steel sheet 1 includes a Ni-containing layer 12 disposed on the surface of a base steel sheet 11. The Ni-containing layer 12 is a layer containing Ni provided on the surface of the base steel sheet 11. The Ni-containing layer 12 may be provided on only one surface of the base steel sheet 11 or on both surfaces.

[0054] (Ni-W alloy layer 13)

[0055] The surface-treated steel sheet 1 further includes a Ni-W alloy layer 13 disposed on the surface of the Ni-containing layer 12. The Ni-W alloy layer 13 is an alloy plating layer composed primarily of Ni and further containing W. The Ni-W alloy plating layer is harder than Ni. By analyzing the compositional distribution of the plating layer using glow discharge emission spectroscopy, an analytical method capable of measuring the depth-wise distribution of chemical composition from the surface of the plating layer, it is possible to distinguish the Ni-W alloy layer 13, which has a high W concentration, from the Ni-containing layer 12, which has a low W concentration.

[0056] The thickness of the Ni-W alloy layer 13 is at least more than 10 nm. The thickness of the Ni-W alloy layer 13 is further preferably greater than 20 nm, greater than 50 nm, greater than 80 nm, greater than 100 nm or greater than 150 nm. The upper limit of the thickness of the Ni-W alloy layer 13 is not particularly limited, but the thickness is, for example, less than 350 nm, less than 320 nm or less than 300 nm. For example, in the case where the surface-treated steel plate 1 is a battery can, the thickness of the Ni-W alloy layer on the outer surface of the battery can is preferably in the range of 100 nm to 300 nm. In addition, the thickness of the Ni-W alloy layer on the inner surface of the battery can is preferably in the range of 20 nm to 40 nm.

[0057] The Ni—W alloy layer 13 may be provided on only one surface or on both surfaces of the base steel plate 11. A surface treatment layer such as a coating may be further provided on the surface of the Ni—W alloy layer 13.

[0058] (Fe diffusion alloy layer 14)

[0059] At least a portion of the Ni-containing layer 12 is an Fe-diffused alloy layer 14. That is, the Ni-containing layer 12 includes the Fe-diffused alloy layer 14. The Fe-diffused alloy layer 14 is an alloy layer formed by diffusion of Fe from the base steel plate 11 into the coating layer. The Fe-diffused alloy layer 14 is obtained, for example, by plating the surface of the base steel plate 11, followed by an alloying treatment such as annealing.

[0060] exist Figure 1 In the cross-sectional view shown in FIG, only a portion of the Ni-containing layer 12 is the Fe diffusion alloy layer 14 in contact with the base steel plate 11. Figure 2 and Figure 3 As shown in FIG, the entire Ni-containing layer 12 may be formed of the Fe diffusion alloy layer 14. Figure 2 and Figure 3 As shown in FIG, the Fe diffusion alloy layer 14 may also reach the Ni-W alloy layer 13. That is, the Ni-W alloy layer 13 may also have the Fe diffusion alloy layer 14. Figure 2 As shown in FIG, only a portion of the Ni-W alloy layer 13 may be formed as the Fe diffusion alloy layer 14. Figure 3 As shown in FIG, the entire Ni-W alloy layer 13 may be formed of the Fe diffusion alloy layer 14. Figure 3 As shown in the example, a plating layer in which the entire Fe diffusion alloy layer 14 including the Ni layer 12 and the Ni-W alloy layer 13 is sometimes referred to as a fully diffused plating layer. Figure 1 or Figure 2As shown in the example, the plating layer in which a portion of the Ni-containing layer 12 and the Ni-W alloy layer 13 is the Fe diffusion alloy layer 14 is sometimes referred to as a partially diffused plating layer. The Fe diffusion alloy layer 14 formed in the Ni-containing layer 12 may also be referred to as a Ni-Fe alloy layer, and the Fe diffusion alloy layer 14 formed in the Ni-W alloy layer 13 may be referred to as a Ni-W-Fe alloy layer. Generally speaking, a surface-treated steel sheet in which only a portion of the Ni-containing layer 12 is the Fe diffusion alloy layer 14 and a surface-treated steel sheet in which the entire Ni-containing layer 12 is the Fe diffusion alloy layer 14 and only a portion of the Ni-W alloy layer 13 is the Fe diffusion alloy layer 14 are referred to as partially diffused plated steel sheets. In addition, a surface-treated steel sheet in which the entire Ni-containing layer 12 and the Ni-W alloy layer 13 are the Fe diffusion alloy layer 14 is referred to as a fully diffused plated steel sheet.

[0061] (W-deficient layer 131 of Ni-W alloy layer 13)

[0062] The surface treated steel sheet 1 according to this embodiment is as follows Figure 4 As shown in the schematic diagram of FIG, a W-deficient layer 131 is provided from the surface of the Ni-W alloy layer 13 to a depth of 10 nm. The surface of the Ni-W alloy layer 13 does not refer to the interface between the Ni-W alloy layer 13 and the Ni-containing layer 12, but refers to the surface of the Ni-W alloy layer 13 on the opposite side of the Ni-containing layer 12. The W concentration in the W-deficient layer 131 is lower than the W concentration in the region of the Ni-W alloy layer 13 from the surface of the Ni-W alloy layer 13 to a depth exceeding 10 nm.

[0063] According to Fick's law, the concentration gradient of an element will cause the diffusion of the element. The diffusion rate of an element is proportional to the concentration gradient. In the stage before the alloying treatment, the W concentration of the Ni-W alloy layer 13 is high, while the W concentration of the Ni-containing layer 12 is substantially 0% by mass. It is expected that if the multilayer plating formed by overlapping the Ni-containing layer 12 and the Ni-W alloy layer 13 is alloyed, W atoms will diffuse from the Ni-W alloy layer 13 to the Ni-containing layer 12. Therefore, it is expected that in the plating layer after the normal alloying treatment, W will monotonically decrease from the Ni-W alloy layer 13 toward the Ni-containing layer 12. However, in the surface-treated steel sheet 1 involved in this embodiment, a phenomenon contrary to this expectation occurs. The Ni-W alloy layer 13 of the surface-treated steel sheet 1 involved in this embodiment has a W-deficient layer 131 with a low W concentration near the surface on the opposite side of the Ni-containing layer 12. The W-deficient layer 131 can be formed, for example, by appropriately controlling the dew point of the atmosphere during annealing for the alloying treatment. Furthermore, the present inventors analyzed various surface-treated steel sheets and found that W diffusion from the Ni—W alloy layer 13 to the Ni-containing layer 12 hardly occurred.

[0064] (Effect)

[0065] The surface-treated steel plate 1 involved in this embodiment has a Ni-W alloy layer 13. W has the function of improving the metal dissolution resistance of the Ni plating relative to the electrolyte. However, W will harden the Ni plating and impair its workability. In a plating with low workability, cracks are easily generated during press forming, etc. The so-called cracks are cracks that extend from the surface of the plating to the base material. The cracks expose the base material to the outside of the plating, promoting the corrosion of the base material. Since the Ni plating and the Ni-W alloy plating do not have a chemical corrosion protection effect, the Ni-plated steel plate and the Ni-W alloy-plated steel plate are easily corroded with the cracks in the plating as the starting point.

[0066] To improve the workability of the coating, the present inventors provided a Ni-containing layer 12 between the Ni-W alloy layer 13 and the base steel plate 11. Furthermore, at least a portion of the Ni-containing layer 12 was alloyed. The Ni-containing layer 12 and the Fe diffusion alloy layer 14 prevent cracks from propagating to the base steel plate 11, and even prevent the base steel plate 11 from being exposed to a corrosive environment.

[0067] However, the Ni-containing layer 12 and the Fe-diffused alloy layer 14 mitigate the adverse effects of cracking, but do not suppress the occurrence of cracks in the surface of the plated layer. The present inventors recognized the need to suppress the occurrence of cracks in the Ni-W alloy layer 13 and conducted research to achieve this goal. Furthermore, the present inventors discovered that the occurrence of cracks can be suppressed by disposing a W-deficient layer 131 near the surface of the Ni-W alloy layer 13.

[0068] Generally speaking, the hardness of the Ni-W alloy layer 13 increases in proportion to the W concentration. In the W-deficient layer 131, the hardness of the Ni-W alloy layer 13 is estimated to decrease. The vicinity of the surface of the Ni-W alloy layer 13 can serve as a starting point for cracks during bending of the surface-treated steel sheet 1. The present inventors estimate that the W-deficient layer 131 reduces the hardness near the surface of the Ni-W alloy layer 13, thereby suppressing the occurrence of cracks.

[0069] As described above, the surface-treated steel sheet 1 according to this embodiment uses the Ni-containing layer 12 and the Fe-diffused alloy layer 14 to prevent cracks from propagating to the base steel sheet 11. Furthermore, the surface-treated steel sheet 1 according to this embodiment uses the W-deficient layer 131 to suppress the occurrence of cracks. Therefore, the surface-treated steel sheet 1 according to this embodiment has excellent workability despite having the hard and crack-prone Ni-W alloy layer 13.

[0070] It should be noted that according to experimental results by the present inventors, the depth of the W-deficient layer 131 is within the range of 10 nm from the surface of the plated layer. If the thickness of the Ni-W alloy layer is 10 nm or less, the W-deficient layer 131 is not formed within the Ni-W alloy layer. Therefore, the thickness of the Ni-W alloy layer needs to be set to more than 10 nm.

[0071] The most basic aspect of the surface-treated steel sheet 1 according to the present embodiment has been described above. Next, a more preferred aspect of the surface-treated steel sheet 1 according to the present embodiment will be described.

[0072] (W concentration at the bottom of the W concentration valley W B Relative to the W concentration at the W concentration peak P ratio)

[0073] As described below, by using XPS, the W concentration of the Ni-W alloy layer 13 is continuously analyzed from the surface of the Ni-W alloy layer 13 along the depth direction, and the W concentration of the Ni-W alloy layer 13 can be obtained. Figure 4 In this W concentration curve, if there is a W concentration bottom in the region from the surface of the Ni-W alloy layer 13 to a depth of 10 nm, it is considered that there is a W-deficient layer 131. The size of the bottom in the W concentration curve, that is, the W concentration W at the W concentration valley bottom, is B There are no particular limitations, but for example, the content may be more than 0% by mass.

[0074] Alternatively, the W concentration at the W concentration valley W may be used. B Relative to the W concentration at the W concentration peak P The ratio W B / W P To define the size of the bottom of the W concentration curve. W concentration peak 13W P It refers to the place where the W concentration is the highest in the W concentration curve of the Ni-W alloy layer 13. P It refers to the W concentration at the peak of the W concentration. In other words, W P It refers to the maximum value of W concentration in the W concentration curve of the Ni-W alloy layer 13. W concentration valley 13W B It refers to the place where the W concentration is the lowest in the range from the surface to a depth of 10 nm in the W concentration curve of the Ni-W alloy layer 13. B It refers to the W concentration at the bottom of the W concentration valley. In other words, W BIt refers to the minimum value of the W concentration in the range from the surface to a depth of 10 nm in the W concentration curve of the Ni-W alloy layer 13. However, when the W concentration is substantially constant in the range from the surface to a depth of 10 nm or when the W concentration decreases monotonically from the surface toward the interior of the Ni-W alloy layer 13 within this range, it is considered that there is no W concentration valley 13W. B .

[0075] In the surface-treated steel sheet 1 according to the present embodiment, the W concentration W at the W concentration valley bottom is B Relative to the W concentration at the W concentration peak P The ratio W B / W P It is preferably 0.5 or less. This can further suppress the generation of cracks on the surface of the Ni-W alloy layer 13. B / W P More preferably, it is 0.4 or less, 0.3 or less, or 0.2 or less.

[0076] On the other hand, W B / W P Set to 0.05 or more, 0.07 or more, 0.1 or more, or 0.15 or more. B / W P , the metal dissolution resistance of the surface treated steel sheet 1 is further improved. For example, when the surface treated steel sheet 1 is used as a material for a battery can, W is added to the inner surface of the battery can. B / W P When the ratio is set to 0.05 or more, the electrolyte resistance of the battery can is further improved.

[0077] (Ni concentration peak 13Ni P )

[0078] As described above, the coating layer of the surface-treated steel sheet 1 according to this embodiment may be Figure 1 and Figure 2 The partial diffusion plating shown in the example may also be Figure 3 Furthermore, the present inventors have recognized that when the coating of the surface-treated steel sheet 1 is set to a partial diffusion coating, as shown in FIG. Figure 5 As shown in the figure, the Ni concentration peak 13Ni P It is arranged near the surface of the Ni—W alloy layer 13 .

[0079] That is, in the surface treated steel sheet 1 according to the present embodiment, the Fe diffusion alloy layer 14 is formed as follows. Figure 1 As shown in FIG, it is arranged in the Ni-containing layer 12, or as shown in FIG. Figure 2When the Ni-containing layer 12 is disposed in the entire Ni-containing layer 12 and only in a portion of the Ni-W alloy layer 13 as shown in FIG, the surface-treated steel sheet 1 preferably has a Ni concentration peak 13Ni in the range from the surface of the Ni-W alloy layer 13 to a depth of 10 nm. P , the peak Ni concentration of the surface treated steel sheet 1 in the Ni-W alloy layer 13 is 13Ni P Deep places have Ni concentration valley 13Ni B , Ni concentration at the peak Ni concentration P Relative to the Ni concentration at the bottom of the Ni concentration, Ni B Ratio Ni P / Ni B is above 1.1.

[0080] Ni concentration peak 13Ni P It refers to the place where the Ni concentration is the highest in the Ni concentration curve from the surface to a depth of 10 nm in the Ni-W alloy layer 13. P It refers to the Ni concentration at the Ni concentration peak. In other words, Ni P It refers to the maximum value of Ni concentration in the range from the surface to a depth of 10 nm in the Ni concentration curve of the Ni-W alloy layer 13. However, when the Ni concentration is substantially constant in the range from the surface to a depth of 10 nm or when the Ni concentration increases monotonically from the surface toward the inside of the Ni-W alloy layer 13 within this range, it is considered that there is no Ni concentration peak 13Ni. P . Ni concentration bottom 13Ni B It refers to the place where the Ni concentration is the lowest in the Ni concentration curve of the Ni-W alloy layer 13. B It refers to the Ni concentration at the bottom of the Ni concentration valley. In other words, Ni B It refers to the minimum value of the Ni concentration in the Ni concentration curve of the Ni—W alloy layer 13 .

[0081] If the diffusion law is considered, the Ni concentration peak 13Ni is the same as that of the W-deficient layer 131. PThe generation of is also a special phenomenon. In the stage before the alloying treatment, the Ni concentration of the Ni-W alloy layer 13 is lower than the Ni concentration of the Ni-containing layer 12. If the multilayer plating formed by overlapping the Ni-containing layer 12 and the Ni-W alloy layer 13 is alloyed, diffusion of Ni atoms from the Ni-containing layer 12 to the Ni-W alloy layer 13 will occur. Therefore, it can be expected that in the plating after the usual alloying treatment, Ni monotonically decreases from the Ni-containing layer 12 toward the Ni-W alloy layer 13. However, in the surface-treated steel sheet 1 involved in this embodiment, a phenomenon opposite to this expectation sometimes occurs. The Ni-W alloy layer 13 of the surface-treated steel sheet 1 involved in this embodiment sometimes has a Ni concentration peak near the surface on the opposite side of the Ni-containing layer 12 where the Ni concentration becomes higher. According to the knowledge of the present inventors, the Ni concentration peak can be formed, for example, by appropriately controlling the dew point of the atmosphere during annealing for the alloying treatment and setting the plating layer as a partial diffusion layer.

[0082] In the surface-treated steel sheet 1 according to the present embodiment, the Ni concentration at the Ni concentration peak is Ni P Relative to the Ni concentration at the bottom of the Ni concentration, Ni B Ratio Ni P / Ni B It is preferably 1.1 or more. The higher the Ni concentration, the lower the hardness of the Ni-W alloy layer 13 becomes. P / Ni B Setting the ratio to be 1.1 or greater can further suppress the occurrence of cracks in the surface of the Ni—W alloy layer 13. P / Ni B More preferably, it is 1.15 or more or 1.2 or more. P / Ni B The larger the value, the better. Although there is no need to limit the upper limit, for example, Ni P / Ni B Set to 1.4 or less, 1.35 or less, or 1.3 or less.

[0083] (Thickness of Ni-Containing Layer 12)

[0084] The thickness of the Ni-containing layer 12 is not particularly limited. Even with a very small thickness, the Ni-containing layer 12 has the effect of suppressing the progression of cracks. On the other hand, from the perspective of further improving the workability of the surface-treated steel plate 1, it is advantageous for the Ni-containing layer 12 to have a large thickness. Therefore, the thickness of the Ni-containing layer 12 can also be set to, for example, 0.2 μm or more. As a result, the workability of the surface-treated steel plate 1 is further improved. The thickness of the Ni-containing layer 12 can also be set to 0.7 μm or more, 1.0 μm or more, or 1.5 μm or more. The upper limit of the thickness of the Ni-containing layer 12 is not particularly specified. For example, the Ni-containing layer 12 can also be set to less than 4.0 μm, less than 3.0 μm, or less than 2.0 μm.

[0085] (Ni adhesion amount)

[0086] The amount of Ni contained in the plating layer (i.e., the Ni-containing layer 12 and the Ni-W alloy layer 13) is not particularly limited, but can be set to, for example, 1.8 to 35.6 g / m 2 The Ni adhesion amount is set to 1.8g / m 2 The above can further improve the corrosion resistance of the surface treated steel sheet 1 after processing. 2 The following can reduce the manufacturing cost of the surface-treated steel sheet 1. The Ni deposition amount may be 4.5 g / m 2 Above, 6.2g / m 2 Above or 8.9g / m 2 The Ni deposition amount can also be 26.7 g / m 2 Below, 17.8g / m 2 Below or 13.4g / m 2 the following.

[0087] It should be noted that the thickness of the plating layer (i.e., the total thickness of the Ni-containing layer 12 and the Ni-W alloy layer 13) is not particularly limited. For example, the thickness of the plating layer may be within the range of 0.2 μm to 5.0 μm. The thickness of the plating layer may also be 4.0 μm or less.

[0088] (Thickness of Fe Diffusion Alloy Layer 14)

[0089] The thickness of the Fe diffusion alloy layer 14 is not particularly limited. Even with a very small thickness, the Fe diffusion alloy layer 14 can suppress the progression of cracks, improve the workability of the surface-treated steel plate 1, and improve the corrosion resistance of the processed portion. On the other hand, the thickness of the Fe diffusion alloy layer 14 can also be, for example, 0.1 μm or more. In this way, the workability of the surface-treated steel plate 1 can be further improved. The thickness of the Fe diffusion alloy layer 14 can also be 0.5 μm or more, 0.6 μm or more, or 0.7 μm or more. The upper limit of the thickness of the Fe diffusion alloy layer 14 is not particularly specified. For example, the entire coating can also be the Fe diffusion alloy layer 14. On the other hand, the Fe diffusion alloy layer 14 can also be less than 3.0 μm, less than 2.0 μm, less than 1.5 μm, or less than 1.0 μm.

[0090] (Average W Concentration in Ni—W Alloy Layer 13)

[0091] The Ni-W alloy layer 13 contains Ni as a main component and further contains W. "Containing Ni as a main component" means that the Ni concentration is 50 mass % or higher. The average W concentration in the Ni-W alloy layer 13 is not particularly limited, but may be, for example, within a range of 10 to 45 mass %.

[0092] W improves the metal dissolution resistance of the Ni-W alloy layer 13. By setting the average W concentration within the above-mentioned range, the metal dissolution resistance of the Ni-W alloy layer 13 can be further improved. The average W concentration in the Ni-W alloy layer 13 can also be 15% by mass or more, 20% by mass or more, or 30% by mass or more. In addition, by reducing the W concentration in the Ni-W alloy layer 13, the workability of the Ni-W alloy layer 13 can be further improved. Therefore, the average W concentration in the Ni-W alloy layer 13 can also be 40% by mass or less, 37% by mass or less, or 35% by mass or less. For example, the Ni-W alloy layer 13 can also contain Cr and Mo, etc.

[0093] (Composition of Ni-Containing Layer 12)

[0094] The Ni-containing layer 12 is a layer having Ni and Fe diffused from the parent steel plate 11 as main components. For example, the total content of Ni and Fe in the Ni-containing layer 12 may be 98.0% by mass or more, 98.5% by mass or more, or 99.0% by mass or more. The total content of Ni and Fe in the Ni-containing layer 12 may be 100% by mass or less, 99.5% by mass or less, or 99.0% by mass or less. It should be noted that the ratio of Ni and Fe in the Ni-containing layer 12 is different in the thickness direction of the Ni-containing layer 12 (the thickness direction of the surface-treated steel plate 1). The reason is that, as described above, part or all of the Ni-containing layer 12 is made into the Fe diffusion alloy layer 14, and in the Fe diffusion alloy layer 14, the diffusion amount of Fe from the parent steel plate 11 is different in the thickness direction of the Fe diffusion alloy layer 14. In the Fe diffusion alloy layer 14, the closer to the parent steel plate 11, the greater the Fe content. In addition, the thickness of the Fe diffusion alloy layer 14 can be appropriately selected.

[0095] The Ni-containing layer 12 may also contain elements other than Ni and Fe. For example, the Ni-containing layer 12 may also contain Cr and Mo. For example, the Ni-containing layer 12 may also contain one or both of Cr and Mo, and their total content may be greater than 0 mass% and less than 0.1 mass%. In addition, the various alloying elements contained in the base steel plate 11 sometimes diffuse and invade into the Ni-containing layer 12 during the alloying treatment. Therefore, the Ni-containing layer 12 may also contain various impurity elements. In addition, there is also a case where W diffuses and invades into the Ni-containing layer 12 from the Ni-W alloy layer 13. However, the W content of the Ni-containing layer 12 is usually less than 1.0%.

[0096] (Composition of Ni-W Alloy Layer 13)

[0097] As described above, the Ni-W alloy layer 13 contains Ni as a main component and further contains W. Figure 2As shown in the example, when part or all of the Ni-W alloy layer 13 is an Fe diffusion alloy layer 14, the Ni-W alloy layer 13 may further contain Fe. When the Ni-W alloy layer 13 does not have an Fe diffusion alloy layer 14, the total content of Ni and W in the Ni-W alloy layer 13 may be 95.0 mass% or more, 96.0 mass% or more, or 97.0 mass% or more. When the Ni-W alloy layer 13 does not have an Fe diffusion alloy layer 14, the total content of Ni and W in the Ni-W alloy layer 13 may be 100 mass% or less, 99.0 mass% or less, or 98.0 mass% or less. When the Ni-W alloy layer 13 has an Fe diffusion alloy layer 14, the total content of Ni, W, and Fe in the Ni-W alloy layer 13 may be 95.0 mass% or more, 96.0 mass% or more, or 97.0 mass% or more. When the Ni—W alloy layer 13 includes the Fe diffusion alloy layer 14 , the total content of Ni, W, and Fe in the Ni—W alloy layer 13 may be 100 mass % or less, 99.0 mass % or less, or 98.0 mass % or less.

[0098] Similar to the Ni-containing layer 12, the Ni-W alloy layer 13 may also contain elements other than Ni, W, and Fe. As described above, the Ni-W alloy layer 13 may also contain, for example, Cr and Mo. For example, the Ni-W alloy layer 13 may contain one or both of Cr and Mo, with the total content exceeding 0% by mass and not more than 5% by mass. Furthermore, the Ni-W alloy layer 13 may also contain various impurity elements.

[0099] (Type of base steel plate 11, etc.)

[0100] The composition and metal structure of the base steel plate 11 are not particularly limited. The composition and metal structure of the base steel plate 11 can be appropriately selected depending on the intended use of the surface-treated steel plate 1. For example, the chemical composition of the base steel plate 11 may include, by mass%, C: 0.0001-0.08, Si: 0.001-0.03, Mn: 0.01-0.4, P: 0.001-0.03, and S: 0.000-0.03, with the remainder consisting of iron and impurities. The base steel plate 11 may also contain elements other than C, Si, Mn, P, and S.

[0101] When the surface treated steel sheet 1 is used as a material for a battery container, the base steel sheet 11 is preferably low carbon aluminum killed steel or IF steel (Interstitial Free Steel). Specific examples of the chemical composition (unit: mass %) of the base steel sheet 11 are as follows.

[0102] (Example 1) Low carbon aluminum killed steel

[0103] C: 0.057, Si: 0.004, Mn: 0.29, P: 0.014, S: 0.007, Al: 0.050, Cu: 0.034, Ni: 0.021, the remainder: includes iron and impurities

[0104] (Example 2) IF steel

[0105] C: 0.004, Si: 0.01, Mn: 0.16, P: 0.013, S: 0.006, Al: 0.029, Cu: 0.027, Ni: 0.022, Ti: 0.013, the remainder includes iron and impurities

[0106] (Example 3) IF steel

[0107] C: 0.0012, Si: less than 0.01, Mn: 0.16, P: 0.013, S: 0.006, Al: 0.029, Cu: 0.027, Ni: 0.022, Ti: 0.020, the remainder: includes iron and impurities

[0108] There is no particular limitation on the thickness of the base steel plate 11. When the surface-treated steel plate 1 is used as a material for a battery container, for example, the thickness of the base steel plate 11 is preferably 0.15 to 2.00 mm, for example.

[0109] (Measurement method)

[0110] The presence or absence of the W-deficient layer 131 is determined using XPS (X-ray Photoelectron Spectroscopy). By using XPS, the distribution of the W concentration of the Ni-W alloy layer 13 in the depth direction from the surface of the Ni-W alloy layer 13 can be obtained. Figure 4 The W concentration curve of the Ni—W alloy layer 13 is as shown in the schematic diagram of FIG. If the W concentration curve has a bottom in the range from the surface of the Ni—W alloy layer 13 to a depth of 10 nm, it is determined that the W-deficient layer 131 exists.

[0111] The W concentration at the bottom of the W concentration valley is W B Relative to the W concentration at the W concentration peak P The ratio W B / W P The measurement is also performed based on the W concentration curve of the Ni-W alloy layer 13 obtained by the above steps. Based on the shape of the W concentration curve of the Ni-W alloy layer 13, the W concentration valley 13 can be easily determined. B And W concentration peak 13W P The position of W and the W concentration at that position.

[0112] Ni concentration at the Ni concentration peak P Relative to the Ni concentration at the bottom of the Ni concentration, Ni B Ratio Ni P / Ni B XPS is also used for measurement. By using XPS, the distribution of Ni concentration in the Ni-W alloy layer 13 in the depth direction from the surface of the Ni-W alloy layer 13 can be obtained. Figure 5 The Ni concentration curve of the Ni-W alloy layer 13 is as shown in the schematic diagram of FIG. Based on the shape of the Ni concentration curve of the Ni-W alloy layer 13, the Ni concentration valley 13Ni can be easily determined. B and Ni concentration peak 13Ni P and the Ni concentration at that position.

[0113] The XPS measurement conditions are as follows: An ULVAC-PHI (PHI5600) X-ray source was set to MgKα. The analysis area was 800 μm. In addition to measuring W, Ni, and Fe, O and C were also measured simultaneously. Argon was used for depth analysis.

[0114] The amount of Ni deposited is measured by ICP optical emission spectrometry (ICP-OES). First, the coating of a specified area is dissolved with acid. Next, the total Ni content in the solution is quantitatively analyzed by ICP-OES. The total Ni content determined by ICP-OES is divided by the specified area to determine the amount of Ni deposited per unit area.

[0115] The thickness of the Ni-containing layer 12, the thickness of the Ni-W alloy layer 13, and the thickness of the Fe-diffused alloy layer 14 were measured by GDS (Glow Discharge Optical Emission Spectrometry). By using GDS, the element concentration distribution of the Ni-containing layer 12 and the Ni-W alloy layer 13 in the depth direction from the plated layer surface can be measured to obtain an element concentration curve.

[0116] For the measurement, a high-frequency glow discharge emission surface analyzer (manufactured by Horiba, Ltd., model: GD-Profiler 2) was used. The GDS measurement conditions were set as follows.

[0117] Anode diameter: φ4mm

[0118] Gas: Ar

[0119] Gas pressure: 600Pa

[0120] Output power: 35W

[0121] In the surface-treated steel sheet 1 according to this embodiment, a region in the coating layer having an Fe concentration of 5.0 mass% or greater is considered the Fe diffusion alloy layer 14. When component analysis is performed continuously along the depth direction from the surface of the coating layer, the Fe concentration increases as it approaches the base steel sheet 11. A region having an Fe concentration of 5.0 mass%, as determined by continuous component analysis along the depth direction from the surface of the coating layer, is considered the interface between the Fe diffusion alloy layer 14 and the coating layer other than the Fe diffusion alloy layer 14.

[0122] In the surface-treated steel sheet 1 according to this embodiment, the region having a Ni concentration of 1.0% by mass or greater is considered the plating layer, and the remaining region is considered the base steel sheet 11. In the plating layer of the surface-treated steel sheet 1 manufactured by alloying, the Ni concentration decreases as it approaches the base steel sheet 11. The region where the Ni concentration reaches 1.0% by mass, as determined by continuous component analysis from the surface of the plating layer in the depth direction, is considered the interface between the plating layer and the base steel sheet 11 (i.e., the interface between the Fe-diffused alloy layer 14 and the base steel sheet 11).

[0123] The distance between these interfaces is considered the thickness of the Fe diffusion alloy layer 14 in the sample obtained by the above-mentioned steps. This measurement is performed on 5 samples, and the average value is calculated. This average value is considered the thickness of the Fe diffusion alloy layer 14 of the surface-treated steel sheet 1.

[0124] Furthermore, in the surface-treated steel sheet 1 according to the present embodiment, a region in the plating layer where the W concentration is 1.0 mass % or more is regarded as the Ni-W alloy layer 13, and a region where the W concentration is less than 1.0 mass % is regarded as the Ni-containing layer 12. A portion where the W concentration is 1.0 mass %, as determined by continuous component analysis along the depth direction from the surface of the plating layer, is regarded as the interface between the Ni-W alloy layer 13 and the Ni-containing layer 12.

[0125] The distance from the interface between the Ni-W alloy layer 13 and the Ni-containing layer 12 to the interface between the coating and the base steel plate 11 is regarded as the thickness of the Ni-containing layer 12 in the sample obtained by the above steps. This measurement is performed on 5 samples, and the average value is calculated. This average value is regarded as the thickness of the Ni-containing layer 12 of the surface-treated steel plate 1. In addition, the distance from the surface of the coating to the interface between the Ni-W alloy layer 13 and the Ni-containing layer 12 is regarded as the thickness of the Ni-W alloy layer 13 in the sample obtained by the above steps. This measurement is performed on 5 samples, and the average value is calculated. This average value is regarded as the thickness of the Ni-W alloy layer 13 of the surface-treated steel plate 1.

[0126] The method for determining the average W concentration in the Ni-W alloy layer 13 is as follows. XPS (X-ray Photoelectron Spectroscopy) is used for measurement. First, the surface of the surface-treated steel plate 1 is sputtered using argon and / or xenon. Then, the composition of the Ni-W alloy layer 13 is measured from the surface of the Ni-W alloy layer 13 of the surface-treated steel plate 1 toward the inside. Repeat this cycle of sputtering again after the measurement is completed. The analysis results of the W concentration along the depth direction are plotted as a curve with the horizontal axis being the depth from the surface of the Ni-W alloy layer 13 and the vertical axis being the W concentration. Moreover, the value obtained by integrating the curve of the W concentration and dividing it by the width of the interval (i.e., the thickness of the Ni-W alloy layer 13) is regarded as the average W concentration. By applying the above-mentioned calculation for the W concentration to the Ni and Fe analysis results, the average Ni concentration and the average Fe concentration in the Ni-W alloy layer 13 can be obtained. It should be noted that the composition determination of the coating using XPS is implemented using a Mg radiation source. In the analysis using the Mg radiation source, there are no Auger peaks overlapping with the photoelectron peaks of Ni, W, and Fe. A peak due to the 2p orbital is observed for Fe, a peak due to the 2p orbital is observed for Ni, and a peak due to the 4f orbital is observed for W.

[0127] (2. Method for Manufacturing Surface-treated Steel Sheet 1)

[0128] Next, a method for producing the surface-treated steel sheet 1 according to the present embodiment will be described. For example, the production method according to the present embodiment can preferably produce the surface-treated steel sheet 1 having the above-mentioned components.

[0129] like Figure 6 As illustrated in FIG, a method for producing a surface-treated steel sheet 1 according to another embodiment of the present invention includes the following steps:

[0130] (S1) a step of electroplating the base steel plate 11 with Ni;

[0131] (S2) a step of electroplating the base steel plate 11 with a Ni-W alloy; and

[0132] (S3) a step of annealing the base steel plate 11 having the Ni plating layer and the Ni-W alloy layer 13 disposed thereon,

[0133] The dew point of the atmosphere during annealing is set to -25 to 5°C, the soaking time during annealing is set to 10 to 180 seconds, and the maximum temperature during annealing is set to 630 to 860°C.

[0134] (S1 Ni plating)

[0135] First, the base steel plate 11 is electroplated with Ni. The plated base material is the same as the base steel plate 11 of the surface treated steel plate 1 according to the present embodiment. Figure 6 As shown in , a Ni-containing layer 12 is provided on the surface of a base steel plate 11. Hereinafter, a plated steel plate obtained by Ni electroplating is referred to as a Ni-plated steel plate.

[0136] (S2 electroplating Ni-W alloy)

[0137] Next, the Ni-plated steel sheet is electroplated with Ni-W alloy. Figure 6 As shown in , a Ni-W alloy layer 13 is provided on the surface of the Ni-plated steel sheet. Hereinafter, a plated steel sheet obtained by electroplating the Ni-W alloy is referred to as a multilayer plated steel sheet.

[0138] (S3 annealing)

[0139] Next, the multi-layer plated steel sheet (i.e., the base steel sheet 11 having the Ni plated layer and the Ni-W alloy layer 13 disposed thereon) is annealed. Figure 6 As shown in , Fe in the base steel sheet 11 is diffused into a portion of the plating layer to form an Fe diffusion alloy layer 14. Thus, a surface-treated steel sheet 1 is obtained, comprising a base steel sheet 11, a Ni-containing layer 12 disposed on the surface of the base steel sheet 11, and a Ni-W alloy layer 13 disposed on the surface of the Ni-containing layer 12, wherein the Ni-containing layer 12 has the Fe diffusion alloy layer 14.

[0140] During the annealing, the dew point of the atmosphere is set to −25° C. to 5° C. Thus, the W-deficient layer 131 can be provided in the Ni—W alloy layer 13 .

[0141] The present inventors speculate as to why annealing performed with the dew point set within the above-mentioned range forms a W-deficient layer 131 in the Ni-W alloy layer 13 as follows. Ni is an element that is less easily oxidized than W. Under the above-mentioned conditions, the oxygen concentration is higher than in conventional alloying treatment atmospheres, making oxidation more likely. It is speculated that W, which was present in the outermost layer prior to the alloying treatment, is oxidized while diffusing throughout the coating layer during the alloying treatment in the high-dew-point atmosphere, thereby forming the W-deficient layer 131.

[0142] It should be noted that the present inventors investigated various surface-treated steel sheets and found that the diffusion of W from the Ni-W alloy layer to the Ni-containing layer was minimal. The thickness of the Ni-W alloy layer, as determined by the W concentration distribution in the depth direction from the coating surface, was substantially the same as the thickness of the Ni-W alloy layer before the alloying treatment.

[0143] (Annealing time and annealing temperature)

[0144] Furthermore, in the method for manufacturing the surface-treated steel sheet 1 according to this embodiment, the annealing time is set to 10 to 180 seconds, and the annealing temperature is set to 630 to 860°C. The longer the annealing time, the more alloying progresses, and the thickness of the Fe-diffused alloy layer 14 increases. Furthermore, the higher the annealing temperature, the more alloying progresses, and the thickness of the Fe-diffused alloy layer 14 increases. Furthermore, according to the findings of the present inventors, by setting the annealing time and the annealing temperature within the above-mentioned range, a W-deficient layer 131 can be formed in the Ni-W alloy layer 13. It is presumed that if the annealing time and the annealing temperature are insufficient, and the diffusion of the elements contained in the coating layer is insufficient, the migration of W becomes insufficient, and the W-deficient layer is not formed. On the other hand, an excessively long annealing time and the annealing temperature are disadvantageous from the perspectives of productivity and manufacturing costs.

[0145] The most basic aspect of the method for producing the surface-treated steel sheet 1 according to the present embodiment has been described above. Next, a more preferred aspect of the method for producing the surface-treated steel sheet 1 according to the present embodiment will be described.

[0146] In order to set the Ni concentration peak 13Ni in the range from the surface of the Ni-W alloy layer 13 to a depth of 10 nm, P , it is preferable to set the plating layer to a partially diffused plating layer obtained by alloying only a portion thereof. That is, it is preferable to set the annealing time and annealing temperature so that the Fe diffusion alloy layer 14 is arranged only in the Ni-containing layer 12, or in the entire Ni-containing layer 12 and only a portion of the Ni-W alloy layer 13. For example, a partially diffused plating layer can be obtained by setting the Ni-containing layer to 2 μm, setting the annealing soaking time during annealing to 10 seconds, and setting the annealing temperature during annealing to 750°C.

[0147] It is estimated that the Ni concentration peak 13Ni is obtained by setting the dew point within the above range and setting the plating layer as a partial diffusion layer. P The reason is that Ni is harder to oxidize than W, so W, which is easily oxidized, becomes internally oxidized, and Ni, which is difficult to oxidize, becomes externally oxidized.

[0148] As described above, the thickness of the Fe diffusion alloy layer 14 is preferably set to 0.1 to 3.0 μm. To obtain such a Fe diffusion alloy layer 14, for example, the soaking time during annealing is preferably set to 20 seconds and the annealing temperature is preferably set to 810°C.

[0149] (bath ingredients)

[0150] The Ni plating bath used in Ni electroplating contains Ni as its main component. For example, the ratio of Ni contained in the plating bath to all metal elements contained in the plating bath can be set to 95% by mass or more, 96% by mass or more, or 97% by mass or more. In addition to Ni, the Ni plating bath may also contain Cr, Mo, etc.

[0151] The Ni-W plating bath used for Ni-W alloy electroplating contains Ni and W as its main components. For example, the ratio of the W element contained in the plating bath to the total metal elements contained in the plating bath can be set within the range of 10-60 mass%. Furthermore, for example, the ratio of the total Ni and W elements contained in the plating bath to the total metal elements contained in the plating bath can be set to 95 mass% or more, 96 mass% or more, or 97 mass% or more. In addition to Ni and W, the Ni-W plating bath may also contain Cr, Mo, etc.

[0152] (Ni adhesion amount in Ni electroplating)

[0153] In the Ni electroplating, the Ni deposition amount is not particularly limited, and may be set to, for example, 1.5 to 33 g / m 2 Thus, the amount of Ni contained in the Ni-containing layer 12 can be set to 1.5 to 33 g / m 2 The more preferred Ni deposition amount in the electroplated Ni can also be set to be the same as the more preferred Ni deposition amount in the Ni-containing layer 12 of the surface-treated steel sheet 1 according to the present embodiment. The Ni deposition amount can be controlled by the composition and current flow of the Ni plating bath.

[0154] (Total Ni deposition amount in Ni electroplating and Ni-W alloy electroplating)

[0155] The total Ni deposition amount in the Ni electroplating and the Ni-W alloy electroplating is not particularly limited, but can be set to, for example, 1.8 to 35.6 g / m 2 Thus, the total deposition amount of Ni contained in the Ni-containing layer 12 and the Ni-W alloy layer 13 can be set to 1.8 to 35.6 g / m 2 The more preferred total Ni deposition amount of the Ni-containing layer 12 and the Ni-W alloy layer 13 can also be set to be the same as the more preferred total Ni deposition amount of the Ni-containing layer 12 and the Ni-W alloy layer 13 of the surface-treated steel sheet 1 according to the present embodiment described above. The total Ni deposition amount can be controlled by adjusting the composition and current flow of the Ni plating bath and the Ni-W plating bath.

[0156] Furthermore, the various aspects described with respect to the surface-treated steel sheet 1 according to this embodiment can be applied to the method for manufacturing the surface-treated steel sheet according to this embodiment. For example, the preferred aspects of the base steel sheet 11 in the surface-treated steel sheet 1 according to this embodiment can naturally be applied to the method for manufacturing the surface-treated steel sheet according to this embodiment.

[0157] Example

[0158] The effects of one embodiment of the present invention will be described in more detail using examples. However, the conditions in the examples are merely examples of conditions adopted to confirm the feasibility and effects of the present invention. The present invention is not limited to this example of conditions. Various conditions may be employed in the present invention as long as they achieve the purpose of the present invention without departing from the main purpose of the present invention.

[0159] The base steel sheets were subjected to Ni electroplating, Ni-W alloy electroplating, and annealing to produce various surface-treated steel sheets. The compositions of the base steel sheets are shown in Table 1. The compositions of the plating bath used for Ni-W alloy electroplating are shown in Table 2. The manufacturing conditions for the surface-treated steel sheets are shown in Table 3. The evaluation results of the surface-treated steel sheets are shown in Tables 4 and 5. It should be noted that the conditions not listed in the tables are the same for all examples and are as follows.

[0160] The composition of the plating bath for Ni electroplating was set to 240 g / L NiSO4·6H2O, 70 g / L NiCl2·6H2O, and 45 g / L H3BO3. The pH of the plating bath for Ni electroplating was set to 4, and the temperature was set to 50°C. The current density during Ni electroplating was set to 30 A / dm 2 The coating weight in Ni electroplating is controlled by the energization time.

[0161] The Ni ion source in the Ni-W alloy electroplating is set to NiSO4·6H2O, and the W ion source is set to Na2WO4·2H2O. The composition of the Ni-W alloy plating layer (W content) is adjusted by changing the ratio of the Ni ion concentration and the W ion concentration. In addition, in order to stabilize the W ions in the bath, 0.5 mol / L of citric acid is added to the plating bath for the Ni-W alloy electroplating. The pH of the plating bath for the Ni-W alloy electroplating is set to 6, and the temperature is set to 50°C. The current density in the Ni-W alloy electroplating is set to 20A / dm 2 The coating adhesion of Ni-W alloy electroplating is controlled by the energization time.

[0162] The thickness of the Fe diffusion alloy layer and the thickness of the Ni-containing layer were measured using the GDS method described above. The measurement results are recorded in Table 4. In addition, the thickness of the Ni-W alloy layer was also measured using the GDS method described above, but in all cases, it was confirmed that the thickness of the Ni-W alloy layer exceeded 10 nm. Therefore, the thickness of the Ni-W alloy layer is omitted in Table 5.

[0163] Determination of the presence of a W-deficient layer, W concentration at the bottom of the W concentration B Relative to the W concentration at the W concentration peak P The ratio W B / W P Determination of Ni concentration and Ni concentration peak P Relative to the Ni concentration at the bottom of the Ni concentration, Ni B Ratio Ni P / Ni B The measurement was performed by the above-mentioned XPS method. The measurement results are described in Table 4.

[0164] The average W concentration in the Ni—W alloy layer was measured by the XPS method described above. The measurement results are shown in Table 4.

[0165] The workability of the coating was evaluated by the drawbead test. The die 2 used in the test was set to Figure 7 The concave and convex mold 2 shown in . The material of mold 2 is set to SKD11. The lubricating oil is set to noxrust550HN. The thickness of the steel plate is set to 0.4 mm and the width is set to 30 mm. The drawing speed is set to 200 mm / min, the sliding distance is set to 100 mm, and the pressing load is set to 600 kgf. After the embossing stretching, the surface-treated steel plate 1 is alkali-degreased to remove the lubricating oil. Then, a 20 mm × 50 mm corrosion resistance evaluation test piece is cut out from the surface-treated steel plate 1 after the embossing stretching. The surface sliding with the convex side of the mold 2 is set as the corrosion resistance evaluation surface. The test piece is provided for a constant temperature and humidity test (60°C, 85% RH). After the constant temperature and humidity test, the area ratio of red rust generated in the corrosion resistance evaluation surface is measured and recorded in Table 5. Since corrosion resistance is related to the state of the coating cracks, the area ratio of red rust generation can be used to evaluate the processability. Samples with a red rust area ratio of 10% or less were judged as surface-treated steel sheets 1 with excellent workability and recorded as "Pass" in Table 5. Samples with a red rust area ratio exceeding 10% were recorded as "Fail" in Table 5.

[0166] The electrolyte resistance of the plating was evaluated by electrochemical measurement in an atmosphere-free environment within a glove box. The temperature of the measurement environment was set to 25°C, the dew point was set to below -80°C, and the oxygen concentration was set to below 0.7 ppm. In the electrolyte, the volume ratio of EC (ethylene carbonate) and EMC (ethyl methyl carbonate) was set to 1:3 (v / v%). In addition, 2 mass% of VC (vinyl carbonate) and 1 mol / L of LiPF6 were added to the electrolyte. The reference electrode and the counter electrode were set to 1 mmφ Li thin wire. During the electrochemical measurement, OCV (Open Circuit Voltage) was first performed for 5 minutes. Next, LSV (Linear Sweep Voltammetry) was performed to 4.5 V vs. Li. The scan rate in LSV was set to 20 mV / s. The anode current at 3.8 V vs. Li was recorded and reported in Table 5. The smaller the anode current, the higher the electrolyte resistance. The evaluation criteria are set as follows (unit: ×10 -6 A / cm 2 ).

[0167] S: Anode current is 0.50 or less

[0168] A: Anode current is more than 0.50 and less than 1.00

[0169] B: Anode current exceeds 1.00 and is less than 10.00

[0170] C: Anode current exceeds 10.00

[0171] It should be noted that the above evaluation method and criteria are stricter than those typically required for battery cans. Therefore, even samples classified as "C" based on the above evaluation criteria may still be usable as battery can inner surface materials. It can be understood that samples classified as B or higher based on the above evaluation criteria are extremely excellent as battery can inner surface materials.

[0172] [Table 1]

[0173]

[0174] [Table 2]

[0175]

[0176] [Table 3]

[0177]

[0178] [Table 4]

[0179]

[0180] [Table 5]

[0181]

[0182] The test pieces of Examples 23, 24, and 28 did not have a W-deficient layer within a depth of 10 nm from the surface of the Ni-W alloy layer. The red rust area ratio in these test pieces far exceeded the 10% pass / fail criterion, indicating poor workability. It should be noted that in the production of Example 23, the dew point of the annealing atmosphere was below the appropriate range. In the production of Example 24, the maximum annealing temperature was below the appropriate range. In the production of Example 28, the soaking time was below the appropriate range. In Examples 23, 24, and 28, it is presumed that the W-deficient layer was not formed due to inappropriate manufacturing conditions.

[0183] On the other hand, the test pieces obtained by the appropriate manufacturing method had a W-deficient layer from the surface of the Ni-W alloy layer to a depth of 10 nm. These test pieces had a red rust area ratio of 10% or less, indicating good workability.

[0184] In addition, it is confirmed that the W concentration W at the W concentration valley B Relative to the W concentration at the W concentration peak P The ratio W B / W P When W is high, the electrolyte resistance of the surface treated steel sheet is further improved. B / W P is 0, and the electrolyte resistance is judged as C. On the other hand, W B / W P The electrolyte resistance of the example with a value of 0.05 or more is more excellent than that of 37. B / W P As the value increases, the electrolyte resistance tends to be further improved.

[0185] Description of Reference Numerals

[0186] 1 Surface treated steel plate

[0187] 11 Base steel plate

[0188] 12 Ni-containing layer

[0189] 13 Ni-W alloy layer

[0190] 131 W deficiency layer

[0191] 13W B W concentration valley

[0192] 13W P W peak concentration

[0193] 13Ni B Ni concentration valley

[0194] 13Ni P Ni concentration peak

[0195] 14 Fe diffusion alloy layer

[0196] 2 Mold

[0197] W P W concentration at the W concentration peak

[0198] W B W concentration at the bottom of the W concentration valley

[0199] Ni P Ni concentration at the Ni concentration peak

[0200] Ni B Ni concentration at the bottom of Ni concentration valley

Claims

1. A surface-treated steel plate comprising: Base steel plate, The Ni-containing layer disposed on the surface of the base steel plate, and a Ni-W alloy layer disposed on the surface of the Ni-containing layer, The Ni-containing layer has an Fe diffusion alloy layer, The thickness of the Ni-W alloy layer exceeds 10 nm, The surface-treated steel sheet has a W-deficient layer in a range from the surface of the Ni—W alloy layer to a depth of 10 nm.

2. The surface-treated steel sheet according to claim 1, wherein: The surface-treated steel sheet has a W concentration valley in the range from the surface of the Ni—W alloy layer to a depth of 10 nm. The surface-treated steel sheet has a W concentration peak at a location deeper than the W concentration valley. The W concentration at the W concentration valley W B Relative to the W concentration W at the W concentration peak P The ratio W B / W P Below 0.

5.

3. The surface-treated steel sheet according to claim 1 or 2, characterized in that: The Fe diffusion alloy layer is arranged only in the Ni-containing layer, or arranged in the entire Ni-containing layer and only a portion of the Ni—W alloy layer. The surface-treated steel sheet has a Ni concentration peak in the range from the surface of the Ni—W alloy layer to a depth of 10 nm. The surface-treated steel sheet has a Ni concentration valley at a location deeper than the Ni concentration peak in the Ni—W alloy layer. The Ni concentration at the Ni concentration peak is Ni P Relative to the Ni concentration at the bottom of the Ni concentration, Ni B Ratio Ni P / Ni B is above 1.

1.

4. The surface-treated steel sheet according to claim 1 or 2, characterized in that: The thickness of the Ni-containing layer is 0.2-4.0 μm.

5. The surface-treated steel sheet according to claim 1 or 2, characterized in that: The Ni-containing layer and the Ni-W alloy layer contain Ni in an amount of 1.8 to 35.6 g / m 2 .

6. The surface-treated steel sheet according to claim 1 or 2, characterized in that: The thickness of the Fe diffusion alloy layer is 0.1-3.0 μm.

7. The surface-treated steel sheet according to claim 1 or 2, characterized in that: The average W concentration in the Ni—W alloy layer is 10 to 45% by mass.

8. The surface-treated steel sheet according to claim 2, wherein: The W concentration W at the W concentration valley B Relative to the W concentration W at the W concentration peak P The ratio W B / W P It is 0.05 or above.

9. The surface-treated steel sheet according to claim 1 or 2, characterized in that: Only a portion of the Ni-containing layer is the Fe-diffusion alloy layer.

10. The surface-treated steel sheet according to claim 1 or 2, characterized in that: The entire Ni-containing layer is the Fe diffusion alloy layer, and a portion of the Ni—W alloy layer is the Fe diffusion alloy layer.

11. A method for manufacturing a surface-treated steel plate, characterized in that: It has the following processes: The process of electroplating Ni on the base steel plate; a step of electroplating the base steel sheet having the Ni plating layer with a Ni-W alloy; and a step of annealing the base steel sheet having the Ni plating layer and the Ni-W alloy layer disposed thereon, The dew point of the atmosphere during the annealing is set to -25 to 5°C. The soaking time in the annealing is set to 10 to 180 seconds. The maximum temperature in the annealing is set to 630 to 860°C.

12. The method for manufacturing a surface-treated steel sheet according to claim 11, wherein: In the Ni electroplating, the Ni deposition amount is set to 1.5 to 33 g / m 2 .

13. The method for manufacturing a surface-treated steel sheet according to claim 11 or 12, wherein: In the Ni electroplating and the Ni-W alloy electroplating, the total Ni deposition amount is set to 1.8 to 35.6 g / m 2 .

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