Laminated metal plate, welded article, battery cell, method for manufacturing laminated metal plate, method for manufacturing welded article, and method for manufacturing battery cell

Abstract

This laminated metal plate comprises a base metal plate, and a resin coating film that covers one or both surfaces of the base metal plate. An exposed part in which the base metal plate is exposed is provided to a portion of the surface of the laminated metal plate on which the resin coating film is provided. The resin coating film has a main body part and a transition part provided around the exposed part. In the main body part, the interface between the base metal plate and the resin coating film and the surface of the resin coating film are substantially parallel. In the transition part, the surface of the resin coating film is inclined from the surface of the resin coating film in the main body part toward the surface of the base metal plate at the exposed part. A region on the surface of the base metal plate where the transition part is arranged and a region on the surface of the base metal plate where the exposed part is arranged are continuously linked.

Description

Laminated metal sheet, welded product, battery cell, method for manufacturing laminated metal sheet, method for manufacturing welded product, and method for manufacturing battery cell

[0001] This disclosure relates to a laminated metal sheet, a welded product, a battery cell, a method for manufacturing a laminated metal sheet, a method for manufacturing a welded product, and a method for manufacturing a battery cell. This application claims priority to Japanese Patent Application No. 2023-149240, filed on September 14, 2023, the contents of which are incorporated herein by reference.

[0002] Laminated metal sheets are manufactured by laminating a metal sheet and a resin film (resin coating). The resin coating enhances the corrosion resistance of the metal sheet (base metal sheet) of the laminated metal sheet. For this reason, laminated metal sheets are widely used as materials for mechanical structures that require corrosion resistance, such as battery cells and pails.

[0003] However, when laminated metal sheets are laser welded or resistance seam welded, defects are likely to occur in the weld. This is because, during welding, carbon and hydrogen constituting the resin film penetrate into the molten metal, or the resin film evaporates, causing bubbles to form in the molten metal. As a result, the weld bead formed by solidifying the molten metal suffers from excessive hardening, cracking, instability, and the like. Furthermore, in resistance seam welding, the resin coating prevents current flow, making it difficult to obtain a good weld. Therefore, when using laminated metal sheets as materials for welded products, it is necessary to remove the resin coating before welding.

[0004] The resin coating can be removed mechanically using a grinding tool. Alternatively, the resin coating can be removed by laser irradiation. From the viewpoint of shortening the time required for the resin coating, it is preferable to remove the resin coating by laser irradiation. Various proposals have been made so far regarding laser irradiation techniques for removing the resin coating.

[0005] Patent Document 1 discloses a method for manufacturing the top plate of an 18-liter can made of varnished resin-coated steel sheet and laminated steel sheet, characterized by irradiating two linear protrusions formed on the top plate with laser light from a carbon dioxide laser to remove only the resin layer necessary for surface welding.

[0006] Patent Document 2 discloses a coating removal method for removing a coating layer provided on the surface of a substrate, the method comprising: a destruction step for destroying a region of the coating layer that contacts the surface before the coating layer softens; a peeling step for peeling the coating layer from the surface after the destruction of the region; and a removal step for removing residue remaining on the surface exposed by the peeling step, in which a laser is irradiated onto the surface of the substrate exposed by the peeling step.

[0007] JP 2006-7225 A JP 2022-186272 A

[0008] However, the present inventors have found that conventional laser irradiation techniques may not be sufficient to remove resin coatings. For example, thick polypropylene coatings are difficult to remove even with conventional laser irradiation techniques. Experiments conducted by the present inventors have shown that when a carbon dioxide gas laser, such as that disclosed in Patent Document 1, is used to irradiate a resin coating made of polypropylene, the resin coating becomes thinner but remains on the base metal sheet. The resin coating remaining on the base metal sheet could not be removed without additional machining, such as grinding.

[0009] From the viewpoint of quickly removing the resin coating, it is preferable to remove the resin coating using only a laser. The technology of Patent Document 1 is not sufficiently effective for thick polypropylene coatings. The technology of Patent Document 2 removes the coating by combining induction heating and a laser, but does not disclose a method for removing the resin coating using only a laser.

[0010] In view of the above circumstances, an object of the present disclosure is to provide a method for manufacturing a laminated metal sheet, a method for manufacturing a welded product, and a battery cell, which make it easy to remove the resin coating from the laminated metal sheet to expose the base metal sheet, as well as a laminated metal sheet, a welded product, and a battery cell.

[0011] The gist of the present disclosure is as follows.

[0012] (1) A laminated metal sheet according to one aspect of the present disclosure is a laminated metal sheet comprising a base metal sheet and a resin coating covering one or both surfaces of the base metal sheet, wherein a portion of the surface of the laminated metal sheet where the resin coating is provided has an exposed portion where the base metal sheet is exposed, the resin coating has a main portion and a transition portion provided around the exposed portion, wherein in the main portion, the interface between the base metal sheet and the resin coating and the surface of the resin coating are approximately parallel, and in the transition portion, the surface of the resin coating is inclined from the surface of the resin coating in the main portion toward the surface of the base metal sheet in the exposed portion, and the region where the transition portion is located and the region where the exposed portion is located on the surface of the base metal sheet are continuously connected. (2) Preferably, in the laminated metal sheet described in (1) above, the resin coating is mainly composed of a polyolefin resin. (3) Preferably, in the laminated metal sheet described in (2) above, the resin coating is primarily composed of a polypropylene-based resin. (4) Preferably, in the laminated metal sheet described in any one of (1) to (3) above, the thickness of the resin coating in the main body portion is 18.0 μm or more. (5) Preferably, in the laminated metal sheet described in any one of (1) to (4) above, the exposed portion has a band-like shape extending along the edge of the laminated metal sheet. (6) Preferably, in the laminated metal sheet described in any one of (1) to (5) above, the angle between the surface of the base metal sheet and the surface of the resin coating in the transition portion is 5 to 70 degrees. (7) Preferably, in the laminated metal sheet described in any one of (1) to (6) above, the base metal sheet is a steel sheet.

[0013] (8) A welded product according to another aspect of the present disclosure comprises a laminated metal plate described in any one of (1) to (7) above, a workpiece joined to the laminated metal plate, and a welding portion provided on an exposed portion of the laminated metal plate and joining the laminated metal plate and the workpiece.

[0014] (9) A battery cell according to another aspect of the present disclosure includes the welded article described in (8) above.

[0015] (10) A method for manufacturing a laminated metal sheet according to another aspect of the present disclosure includes the steps of: irradiating a base metal sheet, which includes a base metal sheet and a resin coating covering one or both surfaces of the base metal sheet, with far-infrared laser light to modify the resin coating in the irradiated area; and irradiating the modified area with ultraviolet laser light and / or near-infrared laser light to remove the resin coating so as to expose the base metal sheet, wherein the thickness of the resin coating remaining in the irradiated area after the step of modifying the resin coating is less than 17 μm. (11) Preferably, in the method for manufacturing a laminated metal sheet described in (10) above, the resin coating is primarily composed of a polyolefin-based resin. (12) Preferably, in the method for manufacturing a laminated metal sheet described in (11) above, the resin coating is primarily composed of a polypropylene-based resin. (13) Preferably, in the method for producing a laminated metal sheet according to any one of (10) to (12) above, in the step of removing the resin coating, the resin coating is removed using near-infrared laser light. (14) Preferably, in the method for producing a laminated metal sheet according to any one of (10) to (13) above, the wavelength of the far-infrared laser light is 9.2 to 10.8 μm. (15) Preferably, in the method for producing a laminated metal sheet according to any one of (10) to (14) above, the wavelength of the ultraviolet laser light is 0.24 to 0.40 μm. (16) Preferably, in the method for producing a laminated metal sheet according to any one of (10) to (15) above, the wavelength of the near-infrared laser light is 0.79 to 1.09 μm. (17) Preferably, in the method for producing a laminated metal sheet according to any one of (10) to (16) above, the thickness of the resin coating is 18.0 μm or more. (18) Preferably, in the method for manufacturing a laminated metal sheet according to any one of (10) to (17), the resin coating is removed along the edge of the original sheet. (19) Preferably, in the method for manufacturing a laminated metal sheet according to any one of (10) to (18), the base metal sheet is a steel sheet.

[0016] (20) A method for manufacturing a welded product according to another aspect of the present disclosure includes a step of welding a laminated metal plate obtained by the method for manufacturing a laminated metal plate described in any one of (10) to (19) above to a workpiece, and welding the area where the resin coating has been removed.

[0017] (21) A battery cell manufacturing method according to another aspect of the present disclosure includes the method for manufacturing a welded product described in (20) above.

[0018] According to the present disclosure, it is possible to provide a method for manufacturing a laminated metal sheet, a method for manufacturing a welded product, and a method for manufacturing a battery cell, which make it easy to remove the resin coating from the laminated metal sheet to expose the base metal sheet, as well as a laminated metal sheet, a welded product, and a battery cell.

[0019] 9A is a schematic diagram of a method for manufacturing a laminated metal plate according to the present disclosure; FIG. 9B is a schematic diagram of a method for manufacturing a laminated metal plate by irradiating only far-infrared laser light; FIG. 9C is a schematic diagram of a method for manufacturing a laminated metal plate by irradiating only ultraviolet laser light and / or near-infrared laser light; FIG. 9D is a cross-sectional schematic diagram of an exposed portion of a laminated metal plate according to the present disclosure; FIG. 9E is a cross-sectional photograph of an exposed portion of an example of a laminated metal plate according to the present disclosure; FIG. 9F is a cross-sectional schematic diagram of an exposed portion of a laminated metal plate from which a resin coating has been removed by mechanical means; FIG. 9G is a plan view of an example of a laminated metal plate according to the present disclosure; FIG. 9H is a schematic diagram of another example of a laminated metal plate according to the present disclosure; FIG. 9H is a surface photograph of a laminated metal plate irradiated with various lasers; FIG. 9H is an explanatory diagram obtained by tracing the photograph of FIG. 9A; FIG. 9I is a cross-sectional photograph of an area A not irradiated with laser light; ２ This is a cross-sectional photograph of region B irradiated only with laser light. ２ 1 is a cross-sectional photograph of region C, which was irradiated with laser light and then with ultraviolet laser light; 2 is a cross-sectional photograph of region D, which was irradiated with only ultraviolet laser light; and 3 is a comparative diagram arranging cross-sectional photographs of regions A to D.

[0020] (1. Manufacturing method of laminated metal sheet 1) A manufacturing method of a laminated metal sheet 1 according to one embodiment of the present disclosure aims to provide a laminated metal sheet 1 having an exposed portion 13 where the base metal sheet 11 is exposed, and as illustrated in FIG. 1 , includes the steps of: (S1) irradiating an original sheet of the laminated metal sheet 1, which comprises the base metal sheet 11 and a resin coating 12 covering one or both surfaces of the base metal sheet 11, with far-infrared laser light L1 to alter the resin coating 12 in the irradiated area; and (S2) irradiating the area where the resin coating 12 has been altered with ultraviolet laser light and / or near-infrared laser light L2 to remove the resin coating 12 so as to expose the base metal sheet 11.

[0021] (Base Plate) In a manufacturing method of a laminated metal sheet 1 according to one embodiment of the present disclosure, first, a base plate for the laminated metal sheet 1 is prepared. The base plate for the laminated metal sheet 1 comprises a base metal sheet 11 and a resin coating 12 covering one or both surfaces of the base metal sheet 11. The resin coating 12 of the base plate covers one or both surfaces of the base metal sheet 11 of the base plate over its entirety. The base plate has the same configuration as the laminated metal sheet 1 to be finally obtained, except that it does not have an exposed portion 13. A commercially available ordinary laminated metal sheet 1 can be used as the base plate.

[0022] (S1 Irradiation of far-infrared laser light L1) Next, the original plate is irradiated with far-infrared laser light L1. In this embodiment, the far-infrared laser light L1 refers to laser light in a wavelength range that, when absorbed by a substance, is directly converted into vibrational energy or rotational energy of molecules or atoms without being converted into other forms of energy. The far-infrared laser light L1 is, for example, CO ２ The far-infrared laser light L1 may be emitted continuously or intermittently.

[0023] In the manufacturing method of the laminated metal sheet 1 according to this embodiment, the resin coating 12 is altered by irradiation with far-infrared laser light L1. The alteration of the resin coating 12 refers to a physical or chemical change in the state of the resin coating 12 from its original state. The "alteration of the resin coating 12" also includes the resin coating 12 being deteriorated and removed from the original sheet of the laminated metal sheet 1. That is, the irradiation of the far-infrared laser light L1 may remove part or all of the resin coating 12 at the irradiated portion from the laminated metal sheet 1. However, in the manufacturing method of the laminated metal sheet 1 according to this embodiment, the irradiation of the far-infrared laser light L1 is sufficient to cause some alteration in the resin coating 12. The thickness of the resin coating 12 remaining after irradiation with the far-infrared laser light L1 is set to be less than 17 μm. If the thickness of the resin coating 12 remaining after irradiation with far-infrared laser light L1 is less than 17 μm, the remaining resin coating 12 can be easily removed from the original plate by irradiating it with ultraviolet laser light and / or near-infrared laser light L2 in the next step.

[0024] (S2 Irradiation of ultraviolet laser light and / or near-infrared laser light L2) In the manufacturing method of the laminated metal sheet 1 according to this embodiment, the area where the resin coating 12 has been altered by irradiation with far-infrared laser light L1 is further irradiated with ultraviolet laser light and / or near-infrared laser light L2. Ultraviolet laser light is laser light having a wavelength shorter than that of visible radiation. Near-infrared laser light is laser light having a wavelength adjacent to the visible range that may cause a photochemical reaction when absorbed by a substance. The ultraviolet laser light and / or near-infrared laser light L2 may be irradiated continuously or intermittently.

[0025] In the manufacturing method of the laminated metal sheet 1 according to this embodiment, the resin coating 12 is removed from the original sheet by irradiation with ultraviolet laser light and / or near-infrared laser light L2. This forms an exposed portion 13 where the base metal sheet 11 is exposed. Note that the concept of "removing the resin coating 12" not only refers to completely separating the resin coating 12 from the laminated metal sheet 1, but also includes degrading the resin coating 12 so that it can be easily separated from the laminated metal sheet 1 by simple means such as blowing air.

[0026] (Effects) In the method for manufacturing a laminated metal sheet 1 according to this embodiment, far-infrared laser light L1 is combined with ultraviolet laser light and / or near-infrared laser light L2. This allows the resin coating 12 on the original sheet to be easily removed. The inventors speculate that the reason for this effect is as follows.

[0027] 2, the far-infrared laser light L1 alone may not be able to deteriorate the resin coating 12 to a degree that allows the resin coating 12 to be removed. The far-infrared laser light L1 can heat the resin coating 12 and reduce its thickness. However, if the resin coating 12 becomes thinner due to irradiation with the far-infrared laser light L1, the far-infrared laser becomes less absorbable by the resin coating 12. As a result, deterioration of the resin coating 12 due to irradiation with the far-infrared laser light L1 does not progress.

[0028] This tendency was particularly evident in the polypropylene coating. According to the results of experiments conducted by the inventors, the thickness of the polypropylene coating was reduced by irradiation with the far-infrared laser beam L1. However, the thinned polypropylene coating was firmly attached to the base metal plate 11. The polypropylene coating irradiated only with the far-infrared laser beam L1 could not be removed without using a powerful machining means such as a grinding tool.

[0029] As shown in FIG. 3 , the ultraviolet laser light and near-infrared laser light L2 alone may not be able to degrade the resin coating 12 to a degree that allows it to be removed. Experimental results by the inventors have shown that the ultraviolet laser light and near-infrared laser light L2 can peel the resin coating 12 from the base metal sheet 11. However, the ultraviolet laser light and near-infrared laser light L2 may not be able to separate the irradiated resin coating 12 from the surrounding non-irradiated resin coating 12. Furthermore, the energy of the ultraviolet laser light and near-infrared laser light L2 is easily absorbed by the base metal sheet 11. Therefore, when the ultraviolet laser light and near-infrared laser light L2 are increased in intensity, the base metal sheet 11 may melt before the resin coating 12 is sufficiently degraded.

[0030] This tendency was particularly pronounced in the polypropylene coating. According to the results of experiments conducted by the inventors, the polypropylene coating irradiated with ultraviolet laser light or near-infrared laser light L2 peeled off from the base metal sheet 11. However, the polypropylene coating that peeled off from the base metal sheet 11 was firmly connected to the surrounding polypropylene coating. The peeled off polypropylene coating could not be removed without using a powerful machining means such as a grinding tool.

[0031] However, the present inventors have found that, as shown in Fig. 1, first irradiating the resin coating 12 with far-infrared laser light L1 and then irradiating the resin coating 12 with ultraviolet laser light and / or near-infrared laser light L2 significantly deteriorates the resin coating 12, making it easy to remove from the original sheet. The present inventors presume that by thinning the resin coating 12 with far-infrared laser light L1 and then irradiating it with ultraviolet laser light and / or near-infrared laser light L2, the resin coating 12 peeled off from the base metal sheet 11 becomes easy to separate from the surrounding resin coating 12.

[0032] (2. Laminated Metal Sheet 1) A laminated metal plate 1 according to another aspect of the present disclosure is a laminated metal plate 1 comprising a base metal plate 11 and a resin coating 12 covering one or both surfaces of the base metal plate 11, wherein an exposed portion 13 in which the base metal plate 11 is exposed is provided on a portion of the surface of the laminated metal plate 1 on which the resin coating 12 is provided, and the resin coating 12 has a main body portion 121 and a transition portion 122 provided around the exposed portion 13, wherein in the main body portion 121, the interface between the base metal plate 11 and the resin coating 12 is approximately parallel to the surface of the resin coating 12, and in the transition portion 122, the surface of the resin coating 12 is inclined from the surface of the resin coating 12 in the main body portion 121 toward the surface of the base metal plate 11 in the exposed portion 13, and the area on the surface of the base metal plate 11 where the transition portion 122 is arranged and the area where the exposed portion 13 is arranged are continuously connected.

[0033] The laminated metal sheet 1 according to this embodiment comprises a base metal sheet 11 and a resin coating 12 covering one or both surfaces of the base metal sheet 11. The resin coating 12 of the laminated metal sheet 1 covers one or both surfaces of the base metal sheet 11 of the laminated metal sheet 1. However, a portion of the resin coating 12 has been removed from the laminated metal sheet 1. The area where the resin coating 12 has been removed and the base metal sheet 11 is exposed is an exposed portion 13.

[0034] (Aspect of Resin Coating 12 Around Exposed Portion 13) The resin coating 12 of the laminated metal sheet 1 according to this embodiment has a specific shape around the exposed portion 13. As shown in Fig. 4, the resin coating 12 is divided into a main body portion 121 and a transition portion 122 provided around the exposed portion 13.

[0035] In the main body portion 121, the interface between the base metal sheet 11 and the resin coating 12 is approximately parallel to the surface of the resin coating 12. That is, the thickness of the resin coating 12 is approximately constant in the main body portion 121. The resin coating 12 in the main body portion 121 is the same as the resin coating 12 of the laminated metal sheet 1 (i.e., the above-described original sheet) before the resin coating 12 is removed.

[0036] In the transition portion 122, unlike the main body portion 121, the interface between the base metal sheet 11 and the resin coating 12 is not approximately parallel to the surface of the resin coating 12. In the transition portion 122, the surface of the resin coating 12 is inclined from the surface of the resin coating 12 in the main body portion 121 toward the surface of the base metal sheet 11 in the exposed portion 13. That is, the thickness of the resin coating 12 in the transition portion 122 decreases as it approaches the exposed portion 13. The transition portion 122 separates the main body portion 121 from the exposed portion 13. The transition portion 122 is created by removing the resin coating 12 using laser light.

[0037] Figure 5 shows a cross-sectional photograph of the exposed portion 13 and its vicinity formed by first irradiating the resin coating 12 with far-infrared laser light L1 and then irradiating the resin coating 12 with ultraviolet laser light and / or near-infrared laser light L2. Figure 5 shows a photograph obtained by cutting the laminated metal sheet 1 at the exposed portion 13 of the laminated metal sheet 1 along a plane perpendicular to the direction in which the exposed portion 13 extends, embedding the laminated metal sheet 1 in a resin for cross-section observation 2, polishing the cut surface of the laminated metal sheet 1, and photographing the cut surface using an optical microscope. The angle and intensity of the illumination were optimized to clearly show the interface between the resin for cross-section observation 2 in which the laminated metal sheet 1 was embedded and the resin coating 12 of the laminated metal sheet 1. As a result, the cross section of the base metal sheet 11 in Figure 5 is whited out.

[0038] As shown in Figures 4 and 5, a transition portion 122 is formed around the exposed portion 13 formed using the laser beam. Furthermore, the region on the surface of the base metal sheet 11 where the transition portion 122 is disposed is continuously connected to the region on the surface of the base metal sheet 11 where the exposed portion 13 is disposed. Specifically, there is no step between the region on the surface of the base metal sheet 11 where the transition portion 122 is disposed and the region on the surface of the base metal sheet 11 where the exposed portion 13 is disposed, and the region on the surface of the base metal sheet 11 where the transition portion 122 is disposed and the region on the surface of the base metal sheet 11 where the exposed portion 13 is disposed are flat and connected. If the surface of the base metal sheet 11 of the original plate at the laser beam irradiation portion is flat, the surface of the base metal sheet 11 will also be flat at the exposed portion 13 formed using the laser beam. Furthermore, even if the surface of the base metal sheet 11 is not flat because it has been bent, for example, the exposed portion 13 formed using the laser beam will not have any irregularities (e.g., cutting marks) created by machining.

[0039] 6, no transition portion 122 is formed around the exposed portion 13 formed by machining such as grinding. When the resin coating 12 is removed by machining, some of the surface layer of the base metal sheet 11 is also removed. As a result, a recess is formed on the surface of the base metal sheet 11 at the exposed portion 13 formed by machining.

[0040] In a laminated metal sheet 1 in which a transition portion 122 is provided around the exposed portion 13 and the area where the transition portion 122 is provided and the area where the exposed portion 13 is provided are continuously connected on the surface of the base metal sheet 11, it is highly likely that the exposed portion 13 is formed by irradiation with laser light. Therefore, a laminated metal sheet 1 in which a transition portion 122 is provided around the exposed portion 13 can be easily manufactured.

[0041] The most basic aspects of the laminated metal sheet 1 and its manufacturing method according to this embodiment have been described above. More preferred aspects of the laminated metal sheet 1 and its manufacturing method according to this embodiment will be described below. Unless otherwise specified, the aspects described below are applicable to both the laminated metal sheet 1 and its manufacturing method.

[0042] (Type of resin coating 12) Preferably, the resin coating 12 is primarily composed of a polyolefin-based resin. Particularly preferably, the resin coating 12 is primarily composed of a polypropylene-based resin. Polyolefin-based resins and polypropylene-based resins have excellent corrosion resistance. Furthermore, polyolefin-based resins and polypropylene-based resins are easy to laminate onto the surface of a metal plate. By using a polyolefin-based resin or a polypropylene-based resin for the resin coating 12, the corrosion resistance of the laminated metal plate 1 can be improved and the manufacture of the laminated metal plate 1 can be made easier.

[0043] (Thickness of Resin Coating 12) There are no particular limitations on the thickness of the resin coating 12. A large thickness of the resin coating 12 is preferable to improve the corrosion resistance of the laminated metal sheet 1. For example, the thickness of the resin coating 12 on the original sheet and / or the thickness of the resin coating 12 on the main body portion 121 of the laminated metal sheet 1 is preferably 18.0 μm or more, 20.0 μm or more, or 30.0 μm or more.

[0044] It should be noted that thick polyolefin-based resins and polypropylene-based resins are difficult to remove using laser light. In conventional techniques, thick polyolefin-based resins and polypropylene-based resins have been removed by mechanical means such as grinding. However, in the manufacturing method of the laminated metal sheet 1 according to the present embodiment, by using far-infrared laser light L1 in combination with ultraviolet laser light and / or near-infrared laser light L2, the thick polyolefin-based resin and polypropylene-based resin can be easily removed from the original sheet to form the exposed portion 13.

[0045] (Shape of exposed portion 13 in plan view) The shape of exposed portion 13 in plan view is not particularly limited. Any shape of exposed portion 13 suitable for the use of laminated metal sheet 1 and the use of exposed portion 13 can be adopted.

[0046] For example, when the laminated metal sheet 1 is used as a material for battery cells of a lithium ion battery or an all-solid-state battery, the exposed portion 13 preferably has a band-like shape extending along the edge of the laminated metal sheet 1, as illustrated in Fig. 7. Furthermore, when manufacturing the laminated metal sheet 1, it is preferable to remove the resin coating 12 along the edge of the original sheet, thereby forming the exposed portion 13 having a band-like shape extending along the edge of the laminated metal sheet 1. By stacking two or more laminated metal sheets 1 illustrated in Fig. 7 and lap-welding (e.g., lap laser welding) the exposed portions 13 of these laminated metal sheets 1, it is possible to form a weld bead without welding defects.

[0047] (Coverage of resin coating 12 on laminated metal sheet 1) The coverage of resin coating 12 on laminated metal sheet 1 is not particularly limited. It can be set appropriately depending on the size and shape of laminated metal sheet 1 and the size and shape of exposed portion 13. In order to improve the corrosion resistance of laminated metal sheet 1, it is preferable that the coverage of resin coating 12 on laminated metal sheet 1 is large. For example, it is preferable that the coverage of resin coating 12 on laminated metal sheet 1 is 50% or more, 70% or more, or 90% or more. The coverage of resin coating 12 on laminated metal sheet 1 represents the proportion of the area of ​​resin coating 12 on each side of laminated metal sheet 1 after laser irradiation, when the area of ​​each side of the original sheet is 100%.

[0048] When the laminated metal sheet 1 is used as a material for a battery cell, the distance between the exposed portion 13 and the edge of the laminated metal sheet 1 is preferably greater than 0 mm and less than or equal to 15 mm. The smaller the distance between the exposed portion 13 and the edge of the laminated metal sheet 1, the larger the capacity of the battery cell can be and the lighter the weight of the battery cell can be. Furthermore, when the laminated metal sheet 1 is used as a material for a battery cell, the exposed portion 13 preferably extends continuously along the edge of the laminated metal sheet 1. However, in order to arrange electrodes on the battery cell, part of the edge of the laminated metal sheet 1 is not welded. Therefore, it is preferable that no exposed portion 13 be provided at part of the edge of the laminated metal sheet 1. The width of the exposed portion 13 is preferably 1.5 to 15 mm, for example.

[0049] When the laminated metal sheet 1 is used as the side wall of a pail can, the laminated metal sheet 1 has a rectangular shape. As illustrated in FIG. 8 , the laminated metal sheet 1 is rolled, and two opposing ends of the laminated metal sheet 1 are seam-welded. This results in the laminated metal sheet 1 being cylindrical. By providing strip-shaped exposed portions 13 extending along two parallel edges of the laminated metal sheet 1 and lap-welding these exposed portions 13, a weld bead without welding defects can be formed. In the example shown in FIG. 8 , both sides of the base metal sheet 11 are coated with resin coatings 12. Therefore, strip-shaped exposed portions 13 are provided on both sides of the laminated metal sheet 1. While FIG. 8 illustrates only the exposed portion 13 on the outward-facing surface of the laminated metal sheet 1, the exposed portion 13 on the inward-facing surface is similarly provided at the same position as the exposed portion 13 on the outward-facing surface.

[0050] (Laser Light Wavelength) In the manufacturing method of the laminated metal sheet 1, the wavelength of the far-infrared laser light L1 is not particularly limited, but is preferably 9.2 to 10.8 μm, for example. The wavelengths of the ultraviolet laser light and near-infrared laser light L2 are also not particularly limited, but are preferably 0.24 to 0.40 μm for the ultraviolet laser light and 0.79 to 1.09 μm for the near-infrared laser light, for example. According to the experimental results of the present inventors, laser light of the above wavelengths is most suitable for removing the resin coating 12 containing a polypropylene-based resin as a main component. Examples of near-infrared laser light include a fiber laser, a disk laser, and a semiconductor laser. Note that the irradiation conditions of the laser light other than the wavelength can be appropriately set depending on the type and thickness of the resin coating 12.

[0051] (Shape of transition portion 122) The shape of the transition portion 122 of the resin coating 12 is not particularly limited as long as the surface of the resin coating 12 is inclined from the surface of the resin coating 12 in the main body portion 121 toward the surface of the base metal sheet 11 in the exposed portion 13. The shape of the transition portion 122 changes depending on the irradiation conditions of the laser light when forming the exposed portion 13. For example, it is preferable that the angle between the surface of the base metal sheet 11 and the surface of the resin coating is 5 to 70 degrees. This makes it possible to remove the resin coating 12 more easily.

[0052] (Type of base metal sheet 11) The type of base metal sheet 11 is not particularly limited. Suitable examples of the base metal sheet 11 include a steel sheet, an aluminum sheet, a titanium sheet, and a stainless steel sheet. The base metal sheet 11 may be a plated steel sheet. Suitable examples of the plated steel sheet include a zinc-based plated steel sheet, an aluminum-based plated steel sheet, a nickel-based plated steel sheet, and a chromate-treated steel sheet.

[0053] (3. Welded Product) (4. Battery Cell) (5. Method for Manufacturing Welded Product) (6. Method for Manufacturing Battery Cell) A welded product according to another aspect of the present disclosure comprises a laminated metal sheet 1 according to the present embodiment, a workpiece joined to the laminated metal sheet 1, and a weld provided on the exposed portion 13 of the laminated metal sheet 1 to join the laminated metal sheet 1 and the workpiece. A battery cell according to another aspect of the present disclosure comprises a welded product according to the present embodiment. A method for manufacturing a welded product according to another aspect of the present disclosure comprises a step of welding the laminated metal sheet 1 obtained by the method for manufacturing a laminated metal sheet 1 according to the present embodiment to the workpiece, and welding the area where the resin coating 12 has been removed. A method for manufacturing a battery cell according to another aspect of the present disclosure comprises a method for manufacturing a welded product according to the present embodiment.

[0054] The type of welded product is not particularly limited. Various products that can be manufactured using the laminated metal sheet 1 as a material can be used as the welded product according to this embodiment. Suitable examples of welded products include battery cells, pails, beverage cans, roofs and walls of buildings, heat exchangers, and cooling devices for electric vehicles, etc.

[0055] The material to be welded can be any material that can be welded to the base metal sheet 11 of the laminated metal sheet 1. The material to be welded may be the laminated metal sheet 1. When the material to be welded is the laminated metal sheet 1, that is, when two laminated metal sheets 1 are joined to produce a welded product, it is preferable to provide an exposed portion 13 on each of the two laminated metal sheets 1 and to overlap these exposed portions 13 when welding.

[0056] When welding the laminated metal sheet 1 and the workpiece, it is preferable not to bring the molten metal into contact with the resin coating 12. In a welded product, it is preferable that the weld metal formed by solidifying the molten metal and the resin coating 12 are separated from each other. When observing the cross section of the weld in such a welded product, it is possible to confirm the presence of the following in the vicinity of the weld metal: (1) a region adjacent to the weld metal to which no resin is attached (corresponding to the exposed portion 13 of the laminated metal sheet), (2) a region adjacent to the region (1) to which a small amount of resin is attached (corresponding to the transition portion 122 of the resin coating 12 of the laminated metal sheet 1), and (3) a region adjacent to the region (2) to which more resin is attached than in the region (2) (corresponding to the main portion 121 of the resin coating 12 of the laminated metal sheet 1). When the resin coating 12 is sandwiched between the laminated metal sheet 1 and the workpiece, a gap is formed between the laminated metal sheet 1 and the workpiece at the position (2), whereas no gap is formed between the laminated metal sheet 1 and the workpiece at the position (3). A welded product having the welded portions at the positions (1), (2), and (3) is considered to be a welded product according to this embodiment.

[0057] Conventional laminated metal sheets 1 are often joined by thermal fusion. However, the fused portion may have poor liquid-tightness. For example, if the welded product is a battery cell, moisture may penetrate the battery cell through the fused portion, causing the battery cell to deteriorate. However, in the welded product and its manufacturing method according to the present embodiment, the joint is a welded portion. The welded portion prevents moisture from penetrating into the welded product. Furthermore, in the welded product and its manufacturing method according to the present embodiment, the welded portion is an exposed portion 13, and the resin coating 12 does not affect the welding. The exposed portion 13 can prevent welding defects from occurring in the weld bead of the weld. Furthermore, in the case of a battery, the laminated metal sheets are joined by surface fusion using thermal fusion, and the adjacent exposed portion is further joined using a joint structure that combines lap, fillet, or edge laser welding to more effectively prevent moisture from penetrating. In addition, by using heat conduction during laser welding, a heat fusion zone can be formed on the joining surface between the laminated metal plates away from the laser weld, thereby obtaining a joint structure with no welding defects and high moisture penetration prevention function that also uses heat fusion.

[0058] The effects of one embodiment of the present disclosure will be explained 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 disclosure. The present disclosure is not limited to this example of conditions. Various conditions may be adopted in the present disclosure as long as they do not deviate from the gist of the present disclosure and the object of the present disclosure is achieved.

[0059] (Experiment A) A base plate having a base metal plate and a resin coating covering one surface of the base metal plate was used as a sample for the experiment. The base metal plate was tin-free steel with a thickness of 0.3 mm. The resin coating was a polypropylene coating (PP) or a polyethylene terephthalate coating (PET). The type and thickness of the resin coating on the sample are listed in Table 1.

[0060] Attempts were made to remove the resin coatings of these samples using the removal methods listed in Table 1. For samples irradiated with two types of lasers, the laser light (S1) irradiated the first time and the laser light (S2) irradiated the second time are listed in the "Removal Method" column of Table 1. For other samples, the means for removing the resin coatings are also listed in the "Removal Method" column of Table 1.

[0061] The laser irradiation conditions listed in Table 1 were basically as follows. However, for the laser light irradiated to some samples, some of the irradiation conditions were changed, and the output and number of irradiations for these changes are listed in the "Removal method" column in Table 1. The "number of repetitions" refers to the number of irradiations.

[0062] CO ２ Laser light (far-infrared laser light) irradiation conditions: Wavelength: 9.4 μm, Focused light diameter: 0.5 mm, Output: 360 W, Pulse frequency: 10 kHz, Scan speed: 1000 to 4000 mm / s, Number of repetitions: 1 to 4, Galvano scanner processing range: 5 mm width

[0063] Irradiation conditions of fiber laser light (near-infrared laser light): Wavelength: 1.07 μm, Focused diameter: 0.68 mm, Output: 500 W, Pulse frequency: 60 kHz, Scan speed: 3000 to 9000 mm / S, Number of repetitions: 1, Galvano scanner processing range: 5 mm width

[0064] UV laser light irradiation conditions: Wavelength: 0.355 μm, Focused beam diameter: 38 μm, Output: 6 W, Pulse frequency: 10 kHz, Scan speed: 800 to 2000 mm / s, Number of repetitions: 1 to 4, Galvano scanner processing range: 5 mm width

[0065] After removing the resin coating, the sample was observed to confirm whether or not an exposed portion had been formed. For samples in which the resin coating had been removed to expose the base metal sheet, and for samples in which the resin coating had deteriorated sufficiently that the tester was able to remove the resin coating by spraying air to expose the base metal sheet, the column "Coating Removal Result" in Table 1 was marked "Pass." For samples in which the base metal sheet had not been removed and the tester was unable to remove the resin coating by spraying air, the column "Coating Removal Result" in Table 1 was marked "Fail."

[0066] Furthermore, for samples for which the coating removal result was "passed," it was confirmed whether or not a sloped portion had been formed in the resin coating near the exposed portion. The sample was embedded in resin, cut perpendicular to the direction of extension of the exposed portion, and the cross section was polished and observed under a microscope to make the sloped portion visible. Samples in which a transition portion such as that illustrated in Figure 5 was confirmed were determined to be samples in which a sloped portion had been formed, and the "Sloped portion" column in Table 1 was marked with "Present." Samples in which it was determined that a sloped portion had not been formed were marked with "Absent" in the "Sloped portion" column in Table 1.

[0067]

[0068] First, a far-infrared laser beam (CO ２ In samples in which the resin coating was irradiated with ultraviolet laser light and / or near-infrared laser light (fiber laser light), the resin coating was easily removed and an exposed portion was formed. When the cross sections of the exposed portions of these samples were observed, a sloped portion was formed. Furthermore, the surfaces of the base metal sheets of these samples were not deformed and were flat.

[0069] In Examples 6, 10, 12, 13, and 14, the samples were irradiated with far-infrared laser light, but not with ultraviolet laser light and / or near-infrared laser light. In the samples of Examples 6, 10, and 12, the thickness of the resin coating was reduced, but the resin coating was not degraded to the extent that it could be easily separated from the base metal sheet with air. In Example 13, the number of times the far-infrared laser light was irradiated was increased compared to the other examples, but the resin coating was not degraded to the extent that it could be easily separated from the base metal sheet with air. In Example 14, the output of the far-infrared laser light was increased compared to the other examples, resulting in the base metal sheet melting.

[0070] In Example 7, the resin coating was first irradiated with fiber laser light, and then irradiated with ultraviolet laser light. In Example 9, the resin coating was first irradiated with ultraviolet laser light, and then irradiated with fiber laser light. In Example 11, the resin coating was irradiated with only fiber laser light. That is, in Examples 7, 9, and 11, the samples were not irradiated with far-infrared laser light. In the samples of Examples 7, 9, and 11, the resin coating peeled off from the base metal sheet, but the resin coating was not deteriorated to the extent that it could be easily separated from the base metal sheet with air.

[0071] In Example 8, the resin film was first irradiated with ultraviolet laser light and then with far-infrared laser light. In the sample of Example 8, the resin film could not be completely removed.

[0072] In Example 17, the resin coating was mechanically cut. As a result, the resin coating was removed and an exposed portion was formed in Example 17. However, in Example 17, irregularities were formed on the surface of the base metal sheet. In Example 17, the strength of the base metal sheet may have been impaired. Furthermore, in Example 17, no inclined portion was formed around the exposed portion.

[0073] In Example 18, CO ２ The laser beam output was set to 120 W, and the number of irradiations was set to one. ２ After laser irradiation, CO ２The thickness of the resin coating remaining in the portion irradiated with the laser beam was 17 μm or more. In Example 18, the resin coating could not be removed from the master plate by irradiating the fiber laser beam, and an exposed portion could not be formed. In Example 19, the CO ２ The laser beam output was set to 360 W, and the number of irradiations was set to three. ２ After laser irradiation, CO ２ The thickness of the resin coating remaining in the portion irradiated with the laser beam was less than 17 μm. In Example 19, the remaining resin coating was successfully removed from the original plate by irradiating with the fiber laser beam to form an exposed portion.

[0074] (Experiment B) A 0.3 mm thick tin-free steel plate covered with a 150 μm thick polypropylene film was coated with CO ２ The irradiation conditions were as follows:

[0075] CO ２ Laser light (far-infrared laser light) irradiation conditions: Wavelength: 9.4 μm; Pulse width: 5.6 μs; Repetition rate: 10 kHz; Average output: 400 W (on work); fθ lens focal length: 482 mm; Focused light diameter: 494 μm; Galvano scanner processing range: 4 mm wide

[0076] UV laser light irradiation conditions: Wavelength: 0.355 μm Pulse width: 20 ns Repetition rate: 50 kHz Average output: 6 W (on work) fθ lens focal length: 250 mm Focal diameter: 38 μm Galvano scanner processing range: 4 mm width

[0077] A photograph of the resin coating 12 after irradiation is shown in Figure 9A. An explanatory diagram obtained by tracing the photograph of Figure 9A is shown in Figure 9B. In Figure 9B, the region marked with the symbol A is a region that was not irradiated with laser. The region marked with the symbol B is a region that was not irradiated with CO ２ The area marked with the symbol C is the area irradiated with only the laser beam. ２9A is a region irradiated with ultraviolet laser light after irradiation with laser light. The region marked with the symbol D is a region irradiated with only ultraviolet laser light. After taking the photograph of FIG. 9A , the sample was cut along the dashed dotted line shown in FIG. 9B , embedded in resin 2 for cross-section observation, and the cross section was polished. The cross section of the sample was then observed.

[0078] Figure 10A is a cross-sectional photograph of region A that was not irradiated with laser. ２ FIG. 10C is a cross-sectional photograph of region B irradiated with only laser light. ２ 10A to 10D are cross-sectional photographs of region C, which was irradiated with ultraviolet laser light after laser light irradiation. FIG. 10D is a cross-sectional photograph of region D, which was irradiated with only ultraviolet laser light. Note that the resin for cross-section observation 2 in which the sample is embedded is shown above in FIGS. 10A to 10D. FIG. 11 is a comparative diagram arranging cross-sectional photographs of regions A to D.

[0079] As shown in FIG. ２ In region B, which was irradiated only with the laser light, the resin coating 12 became thinner but remained on the surface of the base metal plate 11. In region D, which was irradiated only with the ultraviolet laser light, as shown in Figure 10D, the resin coating 12 peeled off from the base metal plate 11. As a result, when preparing a sample for cross-section observation, the resin 2 for cross-section observation entered between the resin coating 12 and the base metal plate 11.

[0080] On the other hand, as shown in FIG. ２ In the region C that was irradiated with the ultraviolet laser after the laser light irradiation, the resin coating 12 peeled off, and an exposed portion 13 where the base metal plate 11 was exposed was formed.

[0081] REFERENCE SIGNS LIST 1 Laminated metal sheet 11 Base metal sheet 12 Resin coating 121 Main body 122 Transition portion 13 Exposed portion L1 Far-infrared laser light L2 Ultraviolet laser light and / or near-infrared laser light 2 Resin for cross-section observation A Region not irradiated with laser B CO ２ Area irradiated only with laser light C CO ２ Area irradiated with laser light and then ultraviolet laser light D Area irradiated with ultraviolet laser light only

Claims

1. A laminated metal sheet comprising: a base metal sheet; and a resin coating covering one or both surfaces of the base metal sheet, wherein an exposed portion where the base metal sheet is exposed is provided on a portion of the surface of the laminated metal sheet on which the resin coating is provided, the resin coating has a main body portion and a transition portion provided around the exposed portion, wherein in the main body portion, the interface between the base metal sheet and the resin coating is approximately parallel to the surface of the resin coating, and in the transition portion, the surface of the resin coating is inclined from the surface of the resin coating in the main body portion toward the surface of the base metal sheet in the exposed portion, and a region on the surface of the base metal sheet where the transition portion is located and a region where the exposed portion is located are continuously connected.

2. The laminated metal sheet according to claim 1, wherein the resin coating is composed mainly of a polyolefin resin.

3. The laminated metal sheet according to claim 2, wherein the resin coating is composed mainly of a polypropylene resin.

4. The laminated metal sheet according to claim 1, characterized in that the thickness of the resin coating in the main body portion is 18.0 μm or more.

5. The laminated metal plate according to claim 1, wherein the exposed portion has a band-like shape extending along an edge of the laminated metal plate.

6. The laminated metal sheet according to claim 1, wherein the angle between the surface of the base metal sheet and the surface of the resin coating at the transition portion is 5 to 70 degrees.

7. The laminated metal sheet according to claim 1, wherein the base metal sheet is a steel sheet.

8. A welded product comprising: a laminated metal plate according to any one of claims 1 to 7; a workpiece joined to said laminated metal plate; and a weld portion provided on said exposed portion of said laminated metal plate for joining said laminated metal plate and said workpiece.

9. A battery cell comprising the welded product according to claim 8.

10. A method for manufacturing a laminated metal plate, comprising: a step of irradiating an original sheet of a laminated metal plate, the original sheet comprising a base metal sheet and a resin coating covering one or both surfaces of the base metal sheet, with far-infrared laser light to alter the resin coating in the irradiated area; and a step of irradiating the area where the resin coating has been altered with ultraviolet laser light and / or near-infrared laser light to remove the resin coating so as to expose the base metal sheet, wherein the thickness of the resin coating remaining in the irradiated area after the step of altering the resin coating is less than 17 μm.

11. The method for manufacturing a laminated metal sheet according to claim 10, wherein the resin coating is mainly composed of a polyolefin resin.

12. The method for manufacturing a laminated metal sheet according to claim 11, wherein the resin coating is mainly composed of a polypropylene resin.

13. The method for manufacturing a laminated metal sheet according to claim 10, characterized in that in the step of removing the resin coating, the resin coating is removed by the near-infrared laser light.

14. The method for producing a laminated metal sheet according to claim 10, wherein the wavelength of the far-infrared laser light is 9.2 to 10.8 μm.

15. The method for producing a laminated metal sheet according to claim 10, wherein the ultraviolet laser light has a wavelength of 0.24 to 0.40 μm.

16. The method for producing a laminated metal sheet according to claim 10, wherein the wavelength of the near-infrared laser light is 0.79 to 1.09 μm.

17. The method for manufacturing a laminated metal sheet according to claim 10, wherein the thickness of the resin coating is 18.0 μm or more.

18. The method for manufacturing a laminated metal sheet according to claim 10, characterized in that the resin coating is removed along the edges of the original sheet.

19. The method for manufacturing a laminated metal sheet according to claim 10, wherein the base metal sheet is a steel sheet.

20. A method for manufacturing a welded product, comprising a step of welding a laminated metal sheet obtained by the method for manufacturing a laminated metal sheet according to any one of claims 10 to 19 to a material to be welded, and welding the area from which the resin coating has been removed.

21. A method for manufacturing a battery cell comprising the method for manufacturing a welded product according to claim 20.

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