Aluminum alloy component for laser welding

Abstract

Provided is an aluminum alloy member for laser welding for firmly joining dissimilar materials of an aluminum alloy and copper by laser welding. The object of the present invention is achieved by an aluminum alloy member for laser welding having a nickel-plated layer on an aluminum alloy, the arithmetic average roughness Sa of the surface of the nickel-plated layer being 100 nm or more.

Description

Technical Field

[0001] This invention relates to aluminum alloy components for laser welding and welding structures for metal components using the aforementioned aluminum alloy components for laser welding. Within the scope of this specification and claims, an alloy of a certain metal M also includes pure metal M. For example, aluminum alloys also include pure aluminum (aluminum with a purity of 99.00% or higher) as specified in JIS standards. Copper alloys also include pure copper (copper with a purity of 99.90% or higher) as specified in JIS standards. Background Technology

[0002] As a busbar used to connect the positive electrode (aluminum alloy) and negative electrode (copper) of a battery, a cladding material made by pressing together an aluminum (Al) alloy and copper (Cu) is used. Since the cladding material is the same type of metal as each electrode, it is easy to perform laser welding. However, in order to reduce costs, a method is proposed to weld the positive and negative electrode sheets using a busbar made of aluminum alloy (for example, see Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Publication No. 2019-514694

[0006] The problem that the invention aims to solve

[0007] However, in the case of the welding method described in Patent Document 1, it is known that the negative electrode (copper) and the aluminum alloy busbar are dissimilar materials, making laser welding difficult. Specifically, the aluminum alloy and copper do not melt together and therefore lack strength. Furthermore, it is known that in the case of components of similar size as the busbar, gaps form between the opposing surfaces of the aluminum alloy component and the copper component (negative electrode) at the welding point due to material tolerances, making melting and mixing even more difficult. Summary of the Invention

[0008] Therefore, the object of the present invention is to provide an aluminum alloy component for laser welding, which is used to firmly join dissimilar materials such as aluminum alloy and copper by laser welding.

[0009] The aluminum alloy component for laser welding of the present invention is characterized in that a nickel plating layer is formed on the aluminum alloy, wherein the arithmetic mean roughness Sa of the surface of the nickel plating layer is set to 100 nm or more.

[0010] Invention Effects

[0011] According to the present invention, nickel (also referred to as Ni) has a higher laser absorption rate than aluminum in the substrate material irradiated by the laser, and the absorption rate can be improved more by roughening the surface than by a smooth surface. Therefore, it is possible to effectively melt and mix aluminum alloys and dissimilar metals other than aluminum alloys, and to obtain a strong bonded structure. Attached Figure Description

[0012] Figure 1 This is a schematic diagram illustrating the situation in existing laser-welded aluminum alloy parts where the material temperature rises due to laser irradiation and excessive energy is injected into the alloy parts.

[0013] Figure 2 This is a schematic diagram illustrating the situation in the aluminum alloy component for laser welding of the present invention, where the surface of the nickel plating layer is roughened and most of the incident and reflected light is absorbed inside the plating layer by laser irradiation.

[0014] Figure 3 This is a schematic diagram illustrating the use of an optical interference microscope to measure the arithmetic mean roughness Sa of the nickel plating layer on the surface of the laser-welded aluminum alloy component of the present invention. Figure 3 A and Figure 3 B is a black and white image representing a color image (two-dimensional and three-dimensional image) that uses different hues (colors) to represent the roughness of the coating surface (concave side: purple → blue → green → yellow → convex side: red). Figure 3 C and Figure 3 D is a black-and-white image representing a portion of an arbitrary 20μm×40μm region that is cut out from the aforementioned color image (two-dimensional image and three-dimensional image) to represent the color image (two-dimensional image and three-dimensional image).

[0015] Figure 4 This figure shows the measurement of the nickel plating thickness of the aluminum alloy component for laser welding according to the present invention using a field emission scanning electron microscope (FE-SEM).

[0016] Figure 5 This is a diagram showing the measurement of the nickel particle size of the nickel plating layer in the aluminum alloy component for laser welding of the present invention using a field emission scanning electron microscope (FE-SEM). Figure 5 A and Figure 5 B is a microscope photograph as shown in JIS G 0551:2020 "Steel - Microscopic Test Method for Grain Size". Figure 5 A is a graph that counts and represents the number of grains transversely cut by a line segment. Figure 5 B is a diagram that counts and represents the number of grain boundaries that are transversely cut by a line segment.

[0017] Figure 6 This is a diagram showing the gloss level of the nickel plating layer on the aluminum alloy component for laser welding according to the present invention, measured using a densitometer.

[0018] Figure 7 This diagram schematically illustrates a situation where an aluminum alloy component for laser welding and a metal component different from the aforementioned aluminum alloy are melted, mixed, and solidified to form a welded part.

[0019] Figure 8 This is a diagram schematically illustrating the determination of the welded structural strength (tensile stress) of a metal component. Detailed Implementation

[0020] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, in the description of the drawings, the same symbols are used to denote the same elements, and repeated descriptions are omitted. Additionally, for ease of explanation, the scale of the drawings is exaggerated and may sometimes differ from the actual scale.

[0021] <Aluminum alloy components for laser welding; First embodiment>

[0022] One embodiment (first embodiment) of the aluminum alloy component for laser welding of the present invention is characterized by having a nickel plating layer on the aluminum alloy, wherein the arithmetic mean roughness Sa of the surface of the nickel plating layer is 100 nm or more. This structure effectively achieves the aforementioned effects.

[0023] The reasons why the above-mentioned effects are achieved by the laser welding aluminum alloy component of this embodiment are not yet clear, but the following mechanism of action is considered. Furthermore, the following mechanism of action is derived by speculation, and this embodiment is not limited by the following mechanism of action.

[0024] For example, in welding dissimilar metals such as Al-Cu, heat energy is required to raise the materials to their melting points. However, because the intermetallic compounds formed by the reaction of dissimilar metals are brittle, there is a problem that when excessive energy is applied, the weld strength decreases, the resistance increases, and the electrical connection becomes a low-grade connection. Furthermore, as dissimilar metals, for example, in welding Al and Cu, AlCu, Al₂Cu, and Al₄Cu₉ are the main intermetallic compounds formed from Al and Cu.

[0025] In addition, such as Figure 1 As shown, when using a material with low absorptivity, such as aluminum alloy 11, which is common in existing laser welding aluminum alloy parts, surface reflection 13 occurs at the welding initiation point due to laser irradiation 12, allowing the target energy 14 to be applied. However, aluminum alloy 11 has the following problem: when the material temperature rises during welding, the laser absorptivity increases, resulting in the application of excessive energy 15 exceeding the target value.

[0026] To address the aforementioned issues, in this embodiment, the nickel in the nickel plating layer is a material that absorbs surface energy. Compared to aluminum, the base material for laser irradiation, nickel can improve laser absorption rate, and by roughening the surface of the nickel plating layer, the absorption rate is further improved compared to a smooth surface. That is, as... Figure 2 As shown, by roughening the surface 21 of the nickel plating layer, when laser 22 is irradiated onto the roughened surface 21, the incident light 22a is refracted and absorbed within the nickel plating layer, and the reflected light 22b is also absorbed again by the nickel plating layer. Most of the incident light 22a and the reflected light 22b are absorbed. On the other hand, on a smooth surface (not shown), even when laser is irradiated onto the surface, the incident light is absorbed by the nickel plating layer, but the reflected light is reflected in the opposite direction (light source side) at the surface of the nickel plating layer and is hardly absorbed by the nickel plating layer again. Therefore, by roughening the surface of the nickel plating layer, the absorption rate can be improved compared to a smooth surface. Therefore, it is believed that the molten mixing of dissimilar metals other than aluminum alloys (such as negative electrode sheets) such as aluminum alloys and copper can be effectively performed, resulting in a robust bonding structure.

[0027] Hereinafter, the aluminum alloy component for laser welding of this embodiment (hereinafter also referred to as aluminum alloy component) will be described according to its constituent elements.

[0028] [Material]

[0029] (Material of the base material)

[0030] The base material for the aluminum alloy component in this embodiment can be any aluminum alloy. The reason for this is that, due to the increased energy absorption rate resulting from plating, while there may be slight differences in melting point due to additives, this effect is applicable to all alloy systems. Therefore, alloys with low weldability are also included. As for aluminum alloys, the International Aluminum Alloy Name is commonly used, and in JIS (Japanese Industrial Standard), the four-digit International Aluminum Alloy Name is also included as part of the aluminum alloy name. The substances mixed according to No. 1000 are different, and the alloy can be identified by its number. Examples of the aforementioned aluminum alloys include A1050-H24, A1100-O, A1100-H24, A2011-T3, A2011-T8, A2017-T4, A2024-T3, A2024-T4, A2024-T6, A2024-T81, A5052-O, A5052-H34, A5052-H112, A5056-H34, A5056-H112, A5083-O, A6061-T6, A6061-T651, A6063-T5, A6082-T6, A6101-T6, and A7075-T651, but none of them are subject to any restrictions. The letter A at the beginning of the name indicates aluminum. The four digits following the A represent the material designation, and the number after the hyphen indicates the quality grade. Furthermore, the melting point of the base aluminum alloy itself hardly changes due to its type (material). Therefore, the amount of energy absorbed by the nickel (plating) that melts the base material and the dissimilar metal parts bonded to it has no effect on the type of aluminum alloy (6101, 1100, etc.). Thus, the type (material) of the base aluminum alloy can be appropriately selected based on the required properties for various applications, such as vibration and shock resistance, other than melting point.

[0031] (Material, shape, and size of the base material)

[0032] Regarding the material, shape, and size of the aforementioned base material, the same material, shape, and size as existing aluminum alloy parts for laser welding can be directly applied. That is, a structural component using an existing aluminum alloy part as the base material, and having a nickel-plated layer formed by surface roughening (arithmetic mean roughness Sa = 100 nm or more) on that base material, can be used as the aluminum alloy part for laser welding in this embodiment. However, while the base material in this embodiment can also be set to the same material, shape, and size as existing aluminum alloy parts for laser welding, from the viewpoint of lightweighting, any one or more of the material, shape, and size can be changed.

[0033] (Shape of the base aluminum alloy)

[0034] The shape of the aluminum alloy used as the base material can be directly applied to the same shape as existing laser-welded aluminum alloy parts, which is usually a flat plate shape.

[0035] (Thickness of the base aluminum alloy)

[0036] Furthermore, the size of the aforementioned base material aluminum alloy can be directly applied to the same size as existing laser-welded aluminum alloy parts. When the base material aluminum alloy has a thickness, such as a flat plate, the thickness is preferably in the range of 0.2 mm to 1 mm. If the aluminum alloy thickness is 0.2 mm or more, it is preferable in terms of adequately absorbing tolerances with mating parts during welding. On the other hand, if the aluminum alloy thickness is 1 mm or less, it is easier to melt using the absorbed energy, and it is also preferable in terms of being lightweight and inexpensive.

[0037] [Nickel plating]

[0038] (Location of nickel plating layer)

[0039] The aluminum alloy component described above features a nickel plating layer disposed on the aluminum alloy base material. Specifically, the nickel plating layer is disposed on one surface of the aluminum alloy base material. With this component structure, by configuring the nickel plating layer on the base material surface opposite the weld portion where the base material and the metal component different from the base material melt and solidify during welding, the following effects can be effectively achieved: Nickel, a component of the nickel plating layer, is a material that absorbs surface energy, and compared to aluminum, a component of the base material irradiated by the laser, nickel can improve the laser absorption rate. Furthermore, the nickel plating layer only needs to be disposed on at least the surface portion opposite the weld portion. For example, it can be disposed in the base material surface on the side opposite the weld portion, on the surface portion opposite the weld portion, and in its vicinity (e.g., from the outer edge of the surface portion opposite the weld portion to approximately 5-10 mm outwards). It can also be disposed over a wider range; the widest range is the entire surface of the base material on the side opposite the weld portion. From the viewpoint that it is easy to form the aforementioned nickel plating layer, and thus that the alignment of components can be made less precise during welding (allowing for a certain degree of misalignment), the aforementioned nickel plating layer is preferably provided on the entire surface of the base material on the side opposite to the weld portion. Furthermore, in order to produce a component structure with a nickel plating layer partially present on the surface of the base material opposite to the weld portion, for example, a peelable insulating film can be applied to the surface portion where the nickel plating layer is not provided before the plating process. Examples include, but are not limited to, peeling the insulating film off the base material after plating the portion of the base material covered with the insulating film. It is also preferable to provide the aforementioned nickel plating layer on one surface of the aluminum alloy base material, while leaving the other surface of the aluminum alloy base material unplated. Therefore, it is possible to use methods such as applying a peelable insulating film to the entire surface of the other aluminum alloy before plating, plating the base material covered with the insulating film, and then peeling the insulating film off the base material.

[0040] (The arithmetic mean roughness Sa of the nickel plating surface)

[0041] The surface with the aforementioned nickel plating layer has an arithmetic mean roughness Sa of 100 nm or more. This structure increases the surface energy absorption rate (laser absorption efficiency), avoiding unnecessary high energy input, thereby suppressing the formation of brittle intermetallic compounds caused by the reaction of dissimilar metals due to excessive energy input. This prevents brittleness (strength reduction) of the weld and improves weld strength (stability). Furthermore, since a higher arithmetic mean roughness Sa corresponds to a higher surface energy absorption rate, the arithmetic mean roughness Sa is preferably 185 nm or more. In this structure, because the absorption efficiency is further improved in the Sa region, welding can be performed even with less energy input. That is, because the surface energy absorption rate (laser absorption efficiency) is further improved, it can be laid out with less energy input, further suppressing the formation of intermetallic compounds and further improving weld strength (stability). Furthermore, the upper limit for the arithmetic mean roughness Sa is preferably 500 nm or less, more preferably 300 nm or less, and even more preferably 250 nm or less. This is because, although the aluminum alloy base material of the alloy component melts and penetrates the dissimilar metal (such as copper) component through energy absorption, the nickel plating layer thickness also increases in order to achieve a higher arithmetic mean roughness Sa. However, if the arithmetic mean roughness Sa is below the aforementioned upper limit (500 nm), it effectively prevents energy accumulation in only the nickel plating layer (the volume of the energy-absorbing nickel plating layer increases). Therefore, unnecessary large energy input can be avoided, the formation of intermetallic compounds can be suppressed, and the weld strength can be improved (stabilized).

[0042] (Method for determining the arithmetic mean roughness Sa of the nickel plating surface)

[0043] The arithmetic mean roughness Sa of the nickel plating surface can be determined and calculated using the following method.

[0044] The surface roughness of the coating was observed (measured) using a 115x optical interference microscope manufactured by Bruker, resulting in an image of the surface roughness. Specifically, the surface roughness (concavity / convexity) of the coating was measured using the aforementioned optical interference microscope, yielding color images (two-dimensional and three-dimensional images) representing the surface roughness (concavity / convexity) of the coating using different hues (colors) (concave side: purple → blue → green → yellow → convex side: red). Figure 3 A and Figure 3 B is a diagram representing these color images using black and white images. Regarding these color images, the arithmetic mean roughness (Sa) of three locations are measured, obtained by masking and cutting arbitrary 20μm × 40μm regions to eliminate the influence of ripples, and the average value is calculated. This average value is taken as the arithmetic mean roughness Sa of the nickel-plated surface. Figure 3 C and Figure 3 D is a graph representing a color image (two-dimensional and three-dimensional image) as a black-and-white image of a region obtained by masking and cutting out an arbitrary 20μm × 40μm area. Furthermore, the above example shows an optical interference microscope manufactured by Bruker Corporation, but this embodiment is not limited to optical interference microscopes manufactured by Bruker Corporation. That is, an optical interference microscope equipped with an image analysis device, etc., can be appropriately used, the image analysis device being equipped with software capable of performing the above-mentioned surface roughness measurement and analyzing the arithmetic mean roughness Sa of the image obtained by masking and cutting out an arbitrary 20μm × 40μm area.

[0045] (Thickness of the nickel plating layer)

[0046] The thickness of the aforementioned nickel plating layer is preferably 3 μm or more, and more preferably 5 μm or more. This is because the thicker the nickel plating layer, the coarser the surface roughness (the particle size of the nickel particles) becomes, making it easier to achieve the laser absorption enhancement effect brought about by surface roughening. Through this laser absorption enhancement effect, the welding strength is improved (stabilized). From this point of view, the thickness of the nickel plating layer is further preferably 8 μm or more. In addition, the thickness of the nickel plating layer is preferably 16 μm or less, and more preferably 14 μm or less. By melting and penetrating the dissimilar metal (copper) component, which is a welding mating part, due to the absorption of energy by the base material of the aluminum alloy component, the aluminum alloy and the dissimilar metal (copper) can be molten and mixed, the welding strength is improved (stabilized), and a strong welded structure can be obtained. If the thickness of the nickel plating layer is at the upper limit (16 μm) or less, it is possible to effectively prevent the volume of nickel (plating layer) that only stores energy and absorbs energy from increasing. Therefore, it is possible to avoid unnecessary large energy input, suppress the formation of fragile intermetallic compounds, and improve (stabilize) the welding strength.

[0047] (Method for measuring the thickness of nickel plating)

[0048] The thickness of the nickel plating layer can be determined by the following methods.

[0049] The cross-section of an aluminum alloy component sample (sample) that had undergone cross-sectional polishing was observed using a field emission scanning electron microscope (FE-SEM), and a cross-sectional image was obtained. The thickness of the nickel plating layer was measured from this cross-sectional image. More specifically, as... Figure 4 As shown, the thickness of the nickel plating layer can be measured using the image analysis apparatus of the FE-SEM from a cross-sectional image magnified 3000x. Furthermore, the surface count of the nickel plating layer is the lowest value measured, equal to the film thickness (the area of ​​surface irregularities).

[0050] (Particle size of nickel particles in the nickel plating layer)

[0051] The particle size of the nickel particles in the aforementioned nickel plating layer is preferably 0.5 μm or more, and more preferably 0.8 μm or more. This is because when the particle size of the nickel particles is enlarged to the above range, the surface roughness increases, resulting in improved laser absorption rate and enhanced (stable) welding strength. Furthermore, there is no particular upper limit to the particle size of the nickel particles in the nickel plating layer, but considering its relationship with the film thickness of the nickel plating layer, it is preferably 1.0 μm or less.

[0052] (Method for determining the particle size of nickel particles in nickel plating)

[0053] The particle size of nickel particles in a nickel plating layer can be determined by the following methods.

[0054] The cross-section of an aluminum alloy component sample (sample) that had undergone cross-section polishing was observed using a field emission scanning electron microscope (FE-SEM), and cross-sectional images were obtained. Specifically, a reflected electron image at 10,000x magnification was obtained. The number of nickel grains P in the nickel plating layer was measured from the obtained reflected electron image, and the number of grains N was calculated. Specifically, regarding the number of nickel grains N, as follows... Figure 5 A, Figure 5 As shown in Figure B, using JIS G0551:2020 "Steel - Microscopic Test Method for Grain Size", the number of grains located inside one end of the line segment is counted as 1 / 2, and this is considered as the grain number N ≒ grain boundary number P. Here, Figure 5 A and Figure 5 B. In the same microscope image, 5A is a diagram showing the count of grains transversely cut along a line segment. Figure 5 B is a graph that counts and displays the number of grains transected by the line segment. As mentioned above, the number of grains transected by the line segment is considered as the number of grain boundaries P measured from the reflected electron image. Next, the average grain size is calculated using the slicing method (cutting method) described in Takayama, Light Metals, 44, p.48, "Methods for Evaluating Grain Size" (1994). In detail, using the above-mentioned slicing method (cutting method), a line segment of total length L is drawn from the cross section (reflected electron image) of the sample (sample) to be targeted, and this line segment is used as the number of grains n transected by the line segment. L (N)≒Grain boundary number P, the average grain size l is obtained by the following formula (1). ave With this average grain size l ave This represents the particle size of the nickel particles in the nickel plating layer.

[0055] [Mathematical Expression 1]

[0056] l ave =L / n L (1)

[0057] Here, l ave Average grain size

[0058] L: Total length of the line segment

[0059] n L Number of grains in a cross section of a line segment

[0060] (Gloss of the nickel plating layer)

[0061] The gloss of the aforementioned nickel plating layer is preferably 0.40 or less, more preferably 0.38 or less. This is because the lower the gloss, the more light is scattered, resulting in increased absorption within the surface (increased laser absorption rate). Consequently, the welding strength is improved (stabilized). Furthermore, since a lower gloss of the nickel plating layer is better, there is no particular limitation on the lower limit of the gloss, but in practice, a gloss of 0.2 or more is preferred.

[0062] (Method for determining the gloss of nickel plating)

[0063] The gloss of nickel plating can be determined by the following methods.

[0064] Measurements can be performed using the ND-11 denier meter manufactured by Nippon Denshoku Kogyo Co., Ltd. More specifically, as... Figure 6 As shown, the incident angle of the light source is set to 0°, the light source 61 is a white light source with the spectral characteristics of a CIE standard light source, and the aperture angle of the light receiver 62 is set to 45°. Regarding the determination of gloss, a φ3mm section of the workpiece surface (measurement area) at the center of the specimen (nickel-plated surface of the aluminum alloy part) 63 is measured three times, and the average value is calculated. This average value is taken as the gloss of the nickel plating layer. The gloss is expressed as Log(I in / I out (I) in I represents the intensity of the incident light (illumination light) from the light source. out It is calculated as the intensity of the reflected light detected by the photodetector in the light reflected from the specimen.

[0065] (Methods for forming nickel plating)

[0066] As a method for forming a nickel plating layer with an arithmetic mean roughness Sa of 100 nm or more on an aluminum alloy, the following methods can be cited as examples. However, as a method for forming a nickel plating layer in this embodiment, it is not limited to the following methods, and existing known matte nickel plating techniques for roughening the surface can be appropriately used to form it.

[0067] The nickel plating layer of this embodiment can be formed by electrolytic nickel plating under the following conditions.

[0068] <Conditions for Electrolytic Nickel Plating>

[0069] Bath solution: Sulfamic acid bath, pH 3.5–4.8, 445–645 ml / L (60% nickel sulfamate)

[0070] • Impurities: Sulfur content below 0.1 wt%

[0071] • Current density is 2–10 A / dm 2 .

[0072] It has the following characteristics: The above-mentioned aminosulfonic acid bath uses nickel aminosulfonate, boric acid, and nickel chloride (or nickel bromide) as basic components. It has better flexibility than the Watt bath, can use high current density, and has less internal stress.

[0073] The aforementioned sulfamic acid bath consists of 445–645 ml / L (60% nickel sulfamic acid), 20–40 g / L boric acid, and 5–20 g / L nickel chloride (or nickel bromide). In most cases, only these three basic components are used for plating in the sulfamic acid bath, as the objective of this embodiment is to achieve a matte, rough surface, so gloss agents are not required. However, additives may be added without affecting the effectiveness of this embodiment. Furthermore, the film-forming time can be appropriately determined based on the target film thickness (e.g., 3–15 μm) (e.g., approximately 3–20 minutes). Additionally, the bath temperature can be appropriately determined based on factors such as the film-forming speed (e.g., approximately 35–45°C). However, conditions outside these ranges are acceptable as long as a nickel plating layer with the specified surface roughness can be formed using the matte nickel plating method. By adjusting these conditions to accommodate changes in concentration, pH, and impurities, the desired surface roughness (roughness) can be obtained.

[0074] (Welded mating parts for aluminum alloy components)

[0075] The aforementioned aluminum alloy components are preferably welded to copper alloy components. By welding with different types of materials, cost reduction is achieved. Furthermore, currently, by consistently welding with different types of materials with insufficient weld strength, weld strength is improved (stabilized). In principle, the material (type of material) of the welding mating parts for aluminum alloy components is effective for all metals containing aluminum; appropriate selection can be made according to the intended application.

[0076] The aforementioned aluminum alloy component is preferably separated from the aforementioned welded mating component, except for the welded portion. If a gap exists between the aluminum alloy component and the aforementioned welded mating component, it ensures a clearance for material vaporized during welding, prevents porosity, prevents strength reduction, and improves (stabilizes) the weld strength. The separation distance, excluding the welded portion, allows the use of a thin sheet of iron (approximately 0.2 mm thick) with an opening only at the welded portion (opening). This thin sheet component is preferably divided into two or more parts, left and right (front and back), centered on the welded portion (opening), allowing for easy removal after welding. Furthermore, it is preferable that each of the divided thin sheets has a portion overflowing from the aluminum alloy component (forming a handle), facilitating easy removal of the divided thin sheet.

[0077] (Thickness of welded mating parts)

[0078] The thickness of the welding mating parts (such as copper plates) can be appropriately determined according to the intended use (electrode sheet or other uses).

[0079] (Surface of welded mating parts)

[0080] As long as it does not impair the effectiveness of the invention, the welded mating parts (such as copper plates) may also have a glossy nickel plating layer on the weld side to the aluminum alloy parts. The purpose is to prevent oxidation of the surface of the welded mating parts (such as copper plates), because nickel is more difficult to oxidize than blanks such as copper plates, thus avoiding various negative environmental impacts.

[0081] <Welded structure of metal components; Second embodiment>

[0082] An embodiment (second embodiment) of the welding structure for metal components of the present invention provides a welding structure for metal components comprising a welded portion formed by melting and solidifying an aluminum alloy component for laser welding and a metal component different from the aforementioned aluminum alloy, characterized in that...

[0083] The aforementioned aluminum alloy component has a nickel plating layer on the side opposite to the welded portion, and the arithmetic mean roughness Sa of the nickel plating layer is 100 nm or more. With this structure, the laser absorption rate of nickel is higher than that of aluminum in the base material of the aluminum alloy component irradiated by the laser. Therefore, the energy absorption rate of the nickel plating layer on the surface of the alloy component increases, avoiding unnecessary high energy input and suppressing the formation of fragile intermetallic compounds. Furthermore, by roughening the surface, the absorption rate can be higher than that of a smooth surface. Therefore, the molten mixing of aluminum alloys and dissimilar metals other than aluminum alloys can be effectively carried out, the weld strength is improved (stabilized), and a robust welded structure can be obtained.

[0084] (Aluminum alloy components)

[0085] The aluminum alloy component for laser welding in this embodiment can be used in conjunction with the aluminum alloy component for laser welding described in the first embodiment. Therefore, the description of the aluminum alloy component for laser welding in this embodiment is as described in the first embodiment above, and to avoid repetition, further descriptions are omitted here.

[0086] In this embodiment, the aluminum alloy component is preferably a busbar that is joined to the electrode sheet. By using the aluminum alloy component of this embodiment as the busbar, the electrode sheet can be connected to ensure conductivity, while strength can be ensured as needed.

[0087] (Welded mating parts of aluminum alloy components; metal parts that are different from aluminum alloys)

[0088] The metal parts, which are different from the aluminum alloys mentioned above, are preferably made of copper alloys. These copper alloy parts, as welding fittings to the aluminum alloy parts (busbars), are suitable for use as negative electrodes in onboard batteries for electric vehicles (EVs) and other applications that serve both automotive and conductive purposes.

[0089] (Materials of welded components, etc.)

[0090] As described above, copper alloy is preferred as the material for metal parts that are different from aluminum alloys.

[0091] (The shape of the welded part)

[0092] Preferably, each of the aforementioned weldable components has a welded portion and is welded to the aforementioned aluminum alloy component. With this structure, it is not necessary to prepare multiple aluminum alloy components corresponding to the multiple weldable components; therefore, the number of parts is reduced, resulting in lower costs and easier parts management. Furthermore, since multiple weldable components can be welded without using multiple aluminum alloy components, the welding operation is not complicated, can be performed simply, and thus reduces costs.

[0093] (Methods for forming welded parts; welding methods)

[0094] As a method for forming a welded part by melting and mixing an aluminum alloy component for laser welding and a metal component different from the aforementioned aluminum alloy and solidifying them, the following methods can be cited, but are not limited to these methods.

[0095] like Figure 7 As shown, laser 74 is used to weld the aluminum alloy component 71, which serves as the upper plate, from the nickel-plated layer 71b side under the conditions shown below.

[0096] <Conditions for Laser Welding>

[0097] • Laser irradiation from the nickel-plated side of the aluminum alloy component on the upper plate under the following conditions

[0098] Laser type: YAG laser

[0099] • Welding speed: 100±20mm / second

[0100] The laser moves in a wobbling motion (drawing circles while moving forward).

[0101] • The weld length is determined by the length of the part to be welded (in the example, it is 21mm × 2).

[0102] For the welding of dissimilar materials such as aluminum alloy (busbar) and copper (negative electrode), and for addressing gaps between materials caused by manufacturing deviations (tolerance range), advancements in laser welding technology have been helpful. Specifically, while previous linear welding resulted in excessive heat input and low weld strength, techniques such as wobbling (circular welding) are being developed to avoid excessive heat input and melt the materials. Therefore, wobbling is preferred in laser welding. This is because, by using the aluminum alloy component for laser welding according to this embodiment and performing wobbling (circular welding), gaps between materials can be sealed while dissimilar materials are melted and mixed with lower energy. As a result, a stronger joint structure can be obtained. Furthermore, YAG lasers are preferred in laser welding. YAG lasers have better absorption of light energy relative to metals than CO2 lasers. Therefore, processing can be performed with less energy. As a result, a more robust joint structure can be obtained.

[0103] Example

[0104] The present invention will now be specifically described through examples, but the present invention is not limited to the following examples. In addition, unless otherwise specified, all examples and comparative examples are carried out under atmospheric pressure, at room temperature (25°C ± 3°C), and with a relative humidity of 50% ± 5% RH.

[0105] (Examples 1-5 and Comparative Examples 1-3)

[0106] (Fabrication of aluminum alloy components for laser welding)

[0107] Aluminum alloys A1100-H24 or A6101-T6 were used as the base material for aluminum alloy parts used in laser welding. The thickness of this base alloy was set to 0.6 mm. Regarding shape, rectangular plates were used for measuring the arithmetic mean roughness Sa, gloss, film thickness, and nickel particle size on the nickel plating surface. L-shaped plates (refer to...) were used... Figure 8 It is used to determine strength (tensile stress).

[0108] In Comparative Example 2, no coating was formed; the base material, aluminum alloy A1100-H24, was used directly as the aluminum alloy component for laser welding. The thickness of the alloy component was set to 0.6 mm, and regarding the shape, an L-shaped sheet material was used (see reference). Figure 8 It is used for strength (tensile stress) determination.

[0109] In Comparative Example 3, A6101-T6 aluminum alloy, without a coating film, was used directly as the aluminum alloy component for laser welding. The thickness of the alloy component was set to 0.6 mm, and an L-shaped plate was used (see reference). Figure 8 It is used for strength (tensile stress) determination.

[0110] A nickel plating layer was formed on one surface of the aluminum alloy base material of Examples 1-5 and Comparative Example 1 to obtain an aluminum alloy component for laser welding. The conditions for forming this nickel plating layer are described below. Furthermore, after the other surface of the aluminum alloy base material was covered with an insulating film with release properties in a manner that does not form a plating film, plating was performed. After plating was completed, the insulating film was peeled off.

[0111] <Conditions for Ni Plating>

[0112] Bath liquid: Aminosulfonic acid bath

[0113] • Concentration of components in the bath solution (aqueous solution): Nickel sulfamate (60% nickel sulfamate) 545 ml / L, nickel chloride 10 g / L, boric acid 30 g / L

[0114] • Bath liquid pH: 4.0

[0115] • Bath liquid temperature: 40℃

[0116] • Impurities in the bath solution: sulfur content less than 0.1 wt%.

[0117] • Current density: 3A / dm 2 .

[0118] In addition, in the glossy electrolytic nickel plating of Comparative Example 1, in addition to the above three components, 0.1% by mass of sulfur was added as a glossing agent in the above-mentioned aminosulfonic acid bath. Furthermore, the pH and film-forming time of the bath solutions in Examples 1-5 and Comparative Example 1 were set to the conditions shown in Table 1 below.

[0119] [Table 1]

[0120]

[0121] <Determination of the arithmetic mean roughness Sa of the nickel plating surface>

[0122] Regarding the plate-shaped aluminum alloy parts for laser welding obtained in Examples 1 to 5 and Comparative Example 1 above, the arithmetic mean roughness Sa of the nickel plating layer surface was measured and calculated using the above method. The obtained arithmetic mean roughness Sa of the nickel plating layer surface is shown in Table 2 below.

[0123] <Determination of Nickel Plating Thickness>

[0124] Regarding the plate-shaped aluminum alloy parts for laser welding obtained in Examples 1 to 5 and Comparative Example 1, the film thickness of the nickel plating layer was measured using the above method. The film thicknesses of the obtained nickel plating layers are shown in Table 2 below.

[0125] <Determination of the particle size of nickel particles in the nickel plating layer>

[0126] Regarding the plate-shaped aluminum alloy parts for laser welding obtained in Examples 1 to 5 and Comparative Example 1 above, the particle size of the nickel particles in the nickel plating layer was measured using the above method. The particle size of the nickel particles in the obtained nickel plating layer is shown in Table 2 below.

[0127] <Determination of the gloss of nickel plating>

[0128] Regarding the plate-shaped aluminum alloy parts for laser welding obtained in Examples 1 to 5 and Comparative Example 1, the gloss of the nickel plating layer was measured using the above method. The gloss of the obtained nickel plating layer is shown in Table 2 below.

[0129] (Fabrication of welded structures for metal components)

[0130] Using the plate-shaped aluminum alloy parts for laser welding obtained in Examples 1-5 and Comparative Examples 1-3 above, the aluminum alloy parts and metal parts different from the aluminum alloys are arranged as follows: Figure 7 The configuration shown is subjected to laser welding under the conditions described below. This results in a welded structure of a plate-shaped metal component having a welded portion formed by the melting and solidification of the aforementioned aluminum alloy component and a metal component different from the aforementioned aluminum alloy.

[0131] Specifically, as a metal component different from the aforementioned aluminum alloy, pure copper (oxygen-free copper) C1020-O is used. The thickness is set at 0.2mm, and regarding shape, rectangular and L-shaped sheet metal are used (see [reference]). Figure 8 This is used for strength (tensile stress) measurement. Furthermore, aluminum alloy parts and metal parts made of different aluminum alloys use sheet metal of the same size and shape. Similar to Example 1, a sheet metal with a glossy nickel plating layer formed on the surface of the metal part is used.

[0132] Next, press Figure 7The configuration is shown, and laser welding is performed under the conditions described below. Specifically, a structure is adopted in which a 0.2mm gap (73) is created between the aluminum alloy component 71 on the upper plate and the copper plate 72 on the lower plate, which is a metal component different from the aforementioned aluminum alloy. A 0.2mm thick SUS partition plate (φ10mm) (not shown) separates the two plates. The aluminum alloy component 71 on the upper plate is configured such that the side opposite to the welding side (the side opposite to the copper plate 72) (the upper side of the base material 71a = the laser incident side) becomes a nickel plating layer 71b. The copper plate 72 on the lower plate is configured such that the welding side becomes a glossy nickel plating layer (not shown).

[0133] The gap created by this separator is intentional. That is, gaps exist in each component due to manufacturing variations (within the allowable tolerance range). In the automotive battery, the median deviation between the busbar and the negative electrode is 0.1 mm, and the maximum is 0.2 mm. This gap is intentionally designed to ensure that even if gaps appear, they can be adequately sealed by welding. Therefore, although this separator was used in this test, it is not used in actual laser welding. In this test, the separator was assembled before welding and removed after welding.

[0134] Next, as Figure 7 As shown, laser 74 is used for welding from the nickel-plated layer 71b side of the base material 71a of the aluminum alloy component 71 on the upper plate, under the conditions shown below. In practice, an L-shaped sheet material is used instead of a rectangular sheet material, such as... Figure 8 As shown, the aluminum alloy component 81 is arranged with its 90° bent portion 81a facing upwards (nickel-plated side). On the other hand, the copper plate 82 is arranged with its 90° bent portion 82a facing downwards (unwelded back side). The aluminum alloy component 81 and the copper plate 82 are welded together at their facing portions, spaced 0.2 mm apart. The resulting weld is indicated by the symbol 83. Thus, as... Figure 8 As shown, when measuring strength (tensile stress), the following welding structure 80 is used: the portion 81a bent upwards at 90° towards the aluminum alloy component 81 and the portion 82a bent downwards at 90° towards the copper plate 82 are fixed together, and then the welded sections are positioned in the upward and downward directions respectively. Figure 8 (The arrow in the image indicates the direction of the stretching, which allows for the determination of strength.)

[0135] <Conditions for Laser Welding>

[0136] • Laser irradiation is performed from the nickel plating side of the upper plate under the following conditions.

[0137] Laser type: YAG laser

[0138] • Welding speed: 100mm / second

[0139] The laser moves in a wobbling motion (drawing circles while moving forward).

[0140] • Weld length: 21mm × 2.

[0141] Through the laser welding described above, a welded structure of a plate-shaped metal component with an L-shaped cross-section and a welded portion (not shown) is obtained (see reference). Figure 8 The aforementioned welded part is formed by melting and solidifying the aforementioned aluminum alloy component 71 and a metal component different from the aforementioned aluminum alloy, namely a copper plate 72.

[0142] [evaluate]

[0143] <Determination of Strength (Tensile Stress) of Welded Structures>

[0144] Regarding the welded structures of the metal parts in Examples 1-5 and Comparative Examples 1-3, the strength (tensile stress) of the welded structures was determined using a universal testing machine with an automatic plotter tensile testing machine. Specifically, as follows... Figure 8 As shown, portions 81a bent upwards at 90° towards the aluminum alloy component 81 and 82a bent downwards at 90° towards the copper plate 82 in the welded structure are fixed to a fixture, and tensile stress is applied in the peeling direction (arrow direction in the figure). The maximum load at fracture is recorded by an automatic plotter, and the strength (N) is the average of the data from N50 (50 specimens) minus 3σ. The strength of the resulting welded structure 80 is shown in Table 2 below.

[0145] [Table 2]

[0146]

[0147] Symbol Explanation

[0148] 11 Aluminum Alloy

[0149] 12 Laser irradiation

[0150] 13 Surface reflection

[0151] 14 Target Energy

[0152] 15. Excessive energy

[0153] 21. Surface of nickel plating

[0154] 22 lasers

[0155] 22a is the incident light that is refracted and absorbed into the coating.

[0156] 22b reflected light is absorbed again by the coating

[0157] 61 Light Source

[0158] 62. Photodetector

[0159] 63 specimens

[0160] 71 and 81 aluminum alloy components (busbars)

[0161] 71a base material

[0162] 71b nickel plating

[0163] 72 and 82 copper coins

[0164] 73 gap

[0165] 74 lasers

[0166] 80 Welded Structure

[0167] The sections 81a and 82a that are bent at 90°

[0168] 83 Welding Section

Claims

1. A welded structure for a metal component, comprising a welded part formed by laser welding an aluminum alloy component for laser welding and a copper alloy component for welding mating, wherein the welded part is formed by laser welding and solidification of the metal component, wherein... The aluminum alloy component has a nickel plating layer on the side opposite to the welded portion, and the arithmetic mean roughness Sa of the surface of the nickel plating layer is 100 nm or more and 250 nm or less. The gloss level of the nickel plating layer is below 0.

40. The nickel particles in the nickel plating layer have a particle size of 0.5 μm or larger. The thickness of the nickel plating layer is greater than 3 μm and less than 16 μm. The gloss of the nickel plating layer was measured using an ND-11 denier meter manufactured by Nippon Denshoku Kogyo Co., Ltd., with the light source incident angle set to 0° and the aperture angle of the light receiver set to 45°. The value is based on the incident light intensity as I. in The intensity of the reflected light from the surface of the nickel plating layer is I. out At that time, through Log(I) in / I out The calculated value.

2. The welded structure of the metal component as described in claim 1, wherein, The arithmetic mean roughness Sa of the nickel plating layer is above 100 nm and below 243 nm.

3. The welded structure of the metal component as described in claim 1, wherein, The arithmetic mean roughness Sa of the nickel plating layer is greater than 100 nm and less than 218 nm. The thickness of the nickel plating layer is greater than 5 μm and less than 14 μm.

4. The welded structure of the metal component as described in claim 1, wherein, The aluminum alloy component and the welded mating component are separated from each other at the part other than the welded part.

5. The welded structure of the metal component as described in claim 1 or 4, wherein, Multiple of the welded mating components are respectively welded to the aluminum alloy component via the welding section.

6. The welded structure of the metal component as described in claim 1 or 4, wherein, The aluminum alloy component is a busbar that is joined to the electrode sheet.

7. The welded structure of the metal component as described in claim 1 or 4, wherein, The laser used to form the welded portion is a YAG laser.

8. The welded structure of the metal component as described in claim 1 or 4, wherein, The gloss of the nickel plating layer is below 0.38.

Images