Patent Application
20240075556
The present invention relates to an aluminum alloy member for use in laser welding and a welded structure of a metal member using the same. In the present specification and claims, it is assumed that an alloy of a certain metal species M also encompasses pure metal M. For example, an aluminum alloy encompasses pure aluminum (aluminum having a purity of 99.00% or more) defined by JIS. A copper alloy encompasses pure copper (copper having a purity of 99.90% or more) defined by JIS.
As a bus bar for connecting a positive electrode tab (aluminum alloy) and a negative electrode tab (copper) of a battery, a clad material obtained by pressure-welding an aluminum (also referred to as Al) alloy and copper (also referred to as Cu) together has been used. Since the clad material is of the same type of metal as each electrode tab, laser welding is easily performed, but for the purpose of cost reduction, a method for welding a positive electrode tab and a negative electrode tab with a bus bar made of an aluminum alloy has been proposed (see, for example, Patent Literature 1).
It has been found, however, that the welding method disclosed in Patent Literature 1 has difficulty in performing laser welding because the negative electrode tab (copper) and the aluminum alloy bus bar are materials of different types. Specifically, the aluminum alloy and the copper are not melted and mixed, and sufficient strength is not obtained. It has been further found that a large member such as a bus bar has difficulty in being melted and mixed because a gap is formed, due to material tolerance, between their respective facing surfaces of the aluminum alloy member and the copper member (negative electrode tab) at a portion to be welded. It is therefore an object of the present invention to provide an aluminum alloy member for use in laser welding for firmly joining an aluminum alloy and copper, which are materials of different types, by laser welding.
An aluminum alloy member for use in laser welding according to the present invention includes a nickel plating layer formed on an aluminum alloy, and an arithmetic average roughness Sa of a surface of the nickel plating layer is greater than or equal to 100 nm.
According to the present invention, nickel (also referred to as Ni) is higher in laser absorptivity than aluminum in a base member to be irradiated with a laser and can increase the absorptivity with a roughened surface as compared with a smooth surface. It is therefore possible to efficiently melt and mix the aluminum alloy and a metal of a different type other than the aluminum alloy and obtain a strong joint structure.
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that, in the description of the drawings, the same elements are denoted by the same reference numerals, and no redundant description will be given. Further, dimensional ratios of the drawings are exaggerated for convenience of description, and may be different from actual ratios.
<Aluminum Alloy Member for Use in Laser Welding; First Embodiment>
An embodiment (first embodiment) of an aluminum alloy member for use in laser welding according to the present invention includes a nickel plating layer on an aluminum alloy, and an arithmetic average roughness Sa of a surface of the nickel plating layer is greater than or equal to 100 nm. With such a configuration, the above-described effects can be effectively obtained.
The reason why the above-described effects are obtained by the aluminum alloy member for use in laser welding of the present embodiment is not clear in detail, but the following action mechanism (mode of action) is conceivable. Note that the following action mechanism is based on a presumption, and the present embodiment is not limited to the following action mechanism at all.
For example, in order to weld metals of different types such as Al—Cu, thermal energy for heating the materials to a melting point is required. An intermetallic compound generated by reactions of the metals of different types, however, is brittle, so that there is a problem that when excessive energy is input, welding strength decreases, electrical resistance increases, and an electrical connection becomes poor in quality. Note that, for example, when Al and Cu are welded as the metals of the different types, AlCu, Al2Cu, and Al4Cu9 are intermetallic compounds of Al and Cu mainly produced.
Further, as illustrated in
In view of the above-described problem, according to the present embodiment, nickel of the nickel plating layer is a material that absorbs surface energy, nickel is higher in laser absorptivity than aluminum of a base member to be irradiated with a laser, and the surface of the nickel plating layer is roughened, so that the absorptivity can be increased as compared with a smooth surface. That is, as illustrated in
Hereinafter, the aluminum alloy member for use in laser welding of the present embodiment (hereinafter, also simply referred to as an aluminum alloy member) will be described for each configuration requirement.
[Base Member]
(Material of Base Member)
It is sufficient that the base member of the aluminum alloy member of the present embodiment be made of an aluminum alloy. That is, although a melting point slightly changes in a manner that depends on an additive due to an effect of increasing energy absorptivity by plating, all types of alloys can receive the effect. Therefore, an alloy having low weldability is also included. In general, an international aluminum alloy name is used for the aluminum alloy, and also in JIS (Japanese Industrial Standards), an international aluminum alloy name including a four-digit number is applied to a part of the name of the aluminum alloy. Mixed materials are different for each No. 1000, so that it is possible to determine what kind of materials an alloy contains by the number. Examples of the above-described aluminum alloy 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, A7075-T651, and the like, but the aluminum alloy is not limited to such examples. In each of the aluminum alloys, A at the head represents aluminum, a four-digit number following A represents a material designation, and a symbol after a slash represents a temper designation. Note that the melting point of the aluminum alloy itself of the base member hardly changes in a manner that depends on the type (component) of the base member. Therefore, the type (6101, 1100, or the like) of the aluminum alloy of the base member does not affect the melting of the base member and the metal member of a different type to be joined to the base member with the energy absorbed by the nickel (plating layer). Therefore, the type (component) of the aluminum alloy of the base member may be appropriately selected in accordance with required performance for each application other than melting properties (melting point), for example, vibration and impact resistance performance.
(Material, Shape, and Size of Base Member)
Regarding the material, shape, and size of the above-described base member, a member identical in material, shape, and size to an already available aluminum alloy member for use in laser welding can be applied as it is. That is, a structural member using the already available aluminum alloy member as the base member and having a nickel plating layer subjected to surface roughening (arithmetic average roughness Sa is greater than or equal to 100 nm) on the base member can be used as the aluminum alloy member for use in laser welding of the present embodiment. Note that the base member of the present embodiment may be identical in material, shape, and size as the already available aluminum alloy member for use in laser welding, but may be different in at least any one of material, shape, or size from the viewpoint of weight reduction or the like.
(Shape of Aluminum Alloy of Base Member)
Regarding the shape of the aluminum alloy of the base member, a member identical in shape as the already available aluminum alloy member for use in laser welding can be applied as it is, and in this case, a flat plate shape is common.
(Thickness of Aluminum Alloy of Base Member)
Regarding the size of the aluminum alloy of the base member, a member identical in size as the already available aluminum alloy member for use in laser welding can be applied as it is. In a case where the aluminum alloy of the base member is as thick as a flat plate shape or the like, the thickness of the aluminum alloy preferably falls within a range of 0.2 mm or greater and 1 mm or less. It is preferable that the thickness of the aluminum alloy be greater than or equal to 0.2 mm from the viewpoint that tolerance with respect to a mating member can be sufficiently absorbed at the time of welding. On the other hand, it is preferable that the thickness of the aluminum alloy be less than or equal to 1 mm from the viewpoint that the aluminum alloy is easily melted by the absorbed energy, and in addition, the aluminum alloy can be made light and low in cost.
[Nickel Plating Layer]
(Placement Position of Nickel Plating Layer)
The nickel plating layer of the aluminum alloy member is provided on the aluminum alloy of the above-described base member. Specifically, the nickel plating layer is provided on one surface of the aluminum alloy of the above-described base member. With such a member structure, the nickel plating layer is placed to serve as a base member surface side opposite from the welded portion where the base member and the metal member different from the base member are melted and solidified at the time of welding, thereby allowing the following effects to be effectively obtained. That is, nickel, which is a component of the nickel plating layer, is a material that absorbs surface energy, and nickel can be higher in laser absorptivity than aluminum, which is a component of the base member to be irradiated with a laser. Further, the nickel plating layer may be provided at least on a surface portion opposite from the welded portion. For example, the nickel plating layer may be provided on the surface portion opposite from the welded portion and the vicinity of the surface portion (for example, a range from an outer edge of the surface portion opposite from the welded portion to the outside by about 5 to 10 mm) in the base member surface on a side opposite from the welded portion. The nickel plating layer may be provided on a wider range, and the widest range corresponds to the entirety of the base member surface on the side opposite from the welded portion. It is preferable that the nickel plating layer be provided on the entirety of the base member surface on the side opposite from the welded portion from the viewpoint of easiness of formation of the nickel plating layer, and further, from the viewpoint that strict alignment between members need not be performed at the time of welding (allowing a certain degree of misalignment). Note that, in order to form a member structure having the nickel plating layer on a part of the base member surface opposite from the welded portion, for example, a removable insulating film is attached to a surface portion on which no nickel plating layer is provided to cover the surface portion before plating treatment. The method includes, but is not limited to, a method in which the base member partially covered with the insulating film is subjected to plating treatment, and then the insulating film is removed from the base member. Further, the nickel plating layer is provided on one surface of the aluminum alloy of the above-described base member, and it is preferable that nothing be provided on the other surface of the aluminum alloy of the above-described base member. It is therefore possible to employ a method in which the removable insulating film is attached to the entirety of the other surface of the aluminum alloy before plating treatment to cover the other surface, the base member covered with the insulating film is subjected to plating treatment, and then the insulating film is removed from the base member, or the like.
(Arithmetic Average Roughness Sa of Surface of Nickel Plating Layer)
The arithmetic average roughness Sa of the surface of the nickel plating layer is greater than or equal to 100 nm. With such a configuration, it is possible to increase the energy absorptivity (laser absorptivity) of the surface and to suppress, by preventing energy more than necessary from being input, the occurrence of a brittle intermetallic compound generated by reactions of metals of different types caused by the input of excessive energy. This makes it possible to prevent the welded portion from becoming brittle (reduction in strength) of and increase (stabilize) the welding strength. Further, the greater the arithmetic average roughness Sa of the surface, the higher the energy absorptivity of the surface, so that the arithmetic average roughness Sa of the surface is preferably greater than or equal to 185 nm. Such a configuration has a range of Sa that further increases the absorptivity, so that it is possible to perform welding even with the input of less energy. That is, the energy absorptivity (laser absorptivity) of the surface becomes higher, and welding can be performed even with the input of less energy, so that it is possible to further suppress the generation of the intermetallic compound and further increase (stabilize) the welding strength. Further, the upper limit of the arithmetic average roughness Sa of the surface is preferably less than or equal to 500 nm, more preferably less than or equal to 300 nm, and still more preferably less than or equal to 250 nm. This is because although the aluminum alloy base member of the alloy member melts to penetrate the metal member of a different type (copper or the like) due to energy absorption, the film thickness of the nickel plating layer needs to increase in order to coarsen (increase) the arithmetic average roughness Sa. However, when the arithmetic average roughness Sa is less than or equal to the upper limit value (500 nm), it is possible to effectively prevent energy from being accumulated only in nickel (plating layer) (prevent the volume of nickel (plating layer) that absorbs energy from being increased). It is therefore possible to prevent energy more than necessary from being input, suppress the generation of the intermetallic compound, and increase (stabilize) the welding strength.
(Method for Measuring Arithmetic Average Roughness Sa of Surface of Nickel Plating Layer)
The arithmetic average roughness Sa of the surface of the nickel plating layer can be measured and calculated by the following method.
The roughness of the surface of the plating layer is observed (measured) using a 115× lens of a light interference microscope manufactured by Bruker Corporation to obtain an image of the surface roughness. Specifically, the roughness (uneven state) of the surface of the plating layer is measured using the above-described light interference microscope, and a color image (two-dimensional image and three-dimensional image) in which the roughness (uneven state) of the surface of the plating layer is expressed by a difference in hue (color and tone) (lower side: purple->blue->green->yellow->higher side: red) is obtained.
(Film Thickness of Nickel Plating Layer)
The film thickness of the nickel plating layer is preferably greater than or equal to 3 μm, and more preferably greater than or equal to 5 μm. This is because the greater the film thickness of the nickel plating layer, the coarser surface roughness of a surface layer=plating grain size (grain size of nickel grains), thereby making it possible to easily obtain the effect of increasing laser absorptivity by surface roughening. Such an effect of increasing laser absorptivity increases (stabilizes) welding strength. From such a viewpoint, the film thickness of the nickel plating layer is more preferably greater than or equal to 8 μm. The film thickness of the nickel plating layer is preferably less than or equal to 16 μm, and more preferably less than or equal to 14 μm. The energy absorption causes the base member of the aluminum alloy member to melt to penetrate the metal member of a different type (copper) as a welding mating member, so as to allow the aluminum alloy and the metal of a different type (copper) to melt and mix and increase (stabilize) the welding strength, thereby making it possible to obtain a strong welded structure. When the film thickness of the nickel plating layer is less than or equal to the upper limit value (16 μm), energy is accumulated only in nickel (plating layer), and it is possible to effectively prevent an increase in the volume of nickel (plating layer) that absorbs energy. It is therefore possible to prevent energy more than necessary from being input, suppress the generation of a brittle intermetallic compound, and increase (stabilize) the welding strength.
(Method for Measuring Film Thickness of Nickel Plating Layer)
The film thickness of the nickel plating layer can be measured by the following method.
A cross section of a specimen (sample) of the aluminum alloy member having its cross section processed by a cross-section polishing machine is observed using a field emission scanning electron microscope (FE-SEM) to obtain an image of the cross section. The film thickness of the nickel plating layer is measured from the image of the cross section. Specifically, as illustrated in
(Grain Size of Nickel Grains in Nickel Plating Layer)
The grain size of the nickel grains in the nickel plating layer is preferably greater than or equal to 0.5 μm, and more preferably greater than or equal to 0.8 μm. This is because as the grain size of the nickel grains increases to reach the above-described range, the surface roughness increases; as a result, the laser absorptivity increases, and the welding strength increases (becomes stable). Note that the upper limit of the grain size of the nickel grains in the nickel plating layer is not particularly limited, but is preferably less than or equal to 1.0 μm from the viewpoint of a relation with the film thickness of the nickel plating layer.
(Method for Measuring Grain Size of Nickel Grains in Nickel Plating Layer)
The grain size of the nickel grains in the nickel plating layer can be measured by the following method.
A cross section of a specimen (sample) of the aluminum alloy member having its cross section processed by a cross-section polishing machine is observed using a field emission scanning electron microscope (FE-SEM) to obtain an image of the cross section. Specifically, a backscattered electron image with a magnification of 10,000 times is obtained. From the obtained backscattered electron image, a number P of crystal grain boundaries of nickel of the nickel plating layer is measured, and a number N of crystal grains is determined accordingly. Specifically, counting a crystal grain in which an end of a line segment is located as ½ as illustrated in
[Math. 1]
l
ave
=L/n
L (1)
wherein lave: the average crystal grain size,
(Degree of Luster of Nickel Plating Layer)
The degree of luster of the nickel plating layer is preferably less than or equal to 0.40, and more preferably less than or equal to 0.38. This is considered that when the degree of luster is low, light is scattered correspondingly, so that absorption in the surface increases (laser absorptivity increases). This is because the welding strength increases (becomes stable). Note that the degree of luster of the nickel plating layer is preferably as low as possible, so that the lower limit of the degree of luster is not particularly limited and is practically preferably greater than or equal to 0.2.
(Method for Measuring Degree of Luster of Nickel Plating Layer)
The degree of luster of the nickel plating layer can be measured by the following method.
The measurement can be performed using a densitometer ND-11 manufactured by Nippon Denshoku Industries Co., Ltd. Specifically, as illustrated in
(Method for Forming Nickel Plating Layer)
Examples of a method for forming, on the aluminum alloy, the nickel plating layer having an arithmetic average roughness Sa greater than or equal to 100 nm include the following method. Note that the method for forming the nickel plating layer of the present embodiment is not limited to the following method, and the nickel plating layer can be formed by appropriately using an already-known dull luster nickel plating technique for roughening a surface.
The nickel plating layer of the present embodiment can be formed by electrolytic nickel plating performed under the following conditions.
<Electrolytic Nickel Plating Conditions>
The above-described sulfamic acid bath primarily includes nickel sulfamate, boric acid, and nickel chloride (or nickel bromide), is excellent in flexibility than a watt bath, can use a high current density, and has less internal stress.
The above-described sulfamic acid bath is composed of 445 to 645 ml/L (60% nickel sulfamate), boric acid of 20 to 40 g/L, and nickel chloride (or nickel bromide) of 5 to 20 g/L. For the sulfamic acid bath, plating is often performed only with the three base components, and it is preferable not to use a brightener or the like because the purpose of the present embodiment is to roughen the surface with dull luster. Note that an additive may be added as long as the actions and effects of the present embodiment are not affected. Further, a film-forming time (for example, about 3 to 20 minutes) may be appropriately determined in accordance with a target film thickness (for example, 3 to 15 μm). Further, a bath temperature (for example, about 35 to 45° C.) may also be appropriately determined from a relation of the film-forming rate or the like. Note that these conditions may be conditions other than the above-described ranges as long as the nickel plating layer having the predetermined surface roughness described above can be formed by the dull luster nickel plating method. There is sensitivity to change in concentration, a change in pH, and impurities, and adjusting these allows desired surface roughness (graininess) to be obtained.
(Welding Mating Member of Aluminum Alloy Member)
The aluminum alloy member is preferably welded to a member made of a copper alloy. Allowing materials of different types to be welded together leads to cost reduction. Further, allowing materials of different types to be stably welded together, the welding conventionally leading to insufficient welding strength, makes it possible to increase (stabilize) the welding strength. Note that, as a material (type of material) of the welding mating member of the aluminum alloy member, all types of metals including aluminum are effective in principle, and the material may be appropriately selected according to the intended use.
The aluminum alloy member is preferably separated from the welding mating member except for the welded portion. A gap between the aluminum alloy member and the welding mating member makes it possible to provide an escape space for the material vaporized at the time of welding, to prevent the occurrence of a blowhole, to prevent a decrease in strength, and to increase (stabilize) the welding strength. For a separation distance other than the welded portion, a thin plate (about 0.2 mm in thickness) made of iron or the like having an opening only in a portion corresponding to the welded portion can be used. In order to allow the thin plate member to be easily removed after welding, the thin plate member is preferably divided into two or more portions, that is left and right (front and back) portions, with the welded portion (opening) as a center. Further, in order to allow the divided thin plates to be easily removed, each of the divided thin plates preferably has a portion protruding from the aluminum alloy member (portion serving as a handle).
(Thickness of Welding Mating Member)
A thickness of the welding mating member (copper plate or the like) may be appropriately determined according to the intended use (electrode tab or use other than the electrode tab).
(Surface of Welding Mating Member)
The welding mating member (copper plate or the like) may have a nickel plating layer with luster on a portion to be welded to the aluminum alloy member as long as the actions and effects of the present invention are not impaired. It is to prevent oxidation of the surface of the welding mating member (a copper plate or the like), and nickel is less prone to oxidation than the base such as a copper plate, so that it is possible to avoid various environmental negatives.
<Welded Structure of Metal Member; Second Embodiment>
An embodiment (second embodiment) of a welded structure of a metal member according to the present invention is a welded structure of a metal member including a welded portion where an aluminum alloy member for use in laser welding and a metal member different from the aluminum alloy are melted and solidified, the aluminum alloy member includes a nickel plating layer on a side opposite from the welded portion, and an arithmetic average roughness Sa of a surface of the nickel plating layer is greater than or equal to 100 nm. With such a configuration, nickel is higher in laser absorptivity than aluminum of a base member of the aluminum alloy member to be irradiated with a laser. This causes an increase in energy absorptivity of the nickel plating layer on the surface of the alloy member, so that it is possible to suppress, by preventing energy more than necessary from being input, the generation of a brittle intermetallic compound. Further, roughening the surface makes it possible to increase the absorptivity as compared with a smooth surface. It is therefore possible to efficiently melt and mix the aluminum alloy and a metal of a different type other than the aluminum alloy and increase (stabilize) the welding strength, thereby making it possible to obtain a strong welded structure.
(Aluminum Alloy Member)
The aluminum alloy member for use in laser welding of the first embodiment described above is applicable to the aluminum alloy member for use in laser welding of the present embodiment. Therefore, the aluminum alloy member for use in laser welding of the present embodiment is as described in the first embodiment, so that no description will be given below of the aluminum alloy member for use in laser welding to avoid the description from being redundant.
In the present embodiment, the aluminum alloy member is preferably a bus bar to be joined to an electrode tab. The use of the aluminum alloy member of the present embodiment as a bus bar makes it possible to obtain strength as necessary together with conductivity achieved by connecting electrode tabs.
(Welding Mating Member of Aluminum Alloy Member; Metal Member Different from Aluminum Alloy)
The metal member different from the aluminum alloy is preferably a metal member made of a copper alloy. The metal member made of a copper alloy is suitable as a member to be welded to the aluminum alloy member (bus bar), such as a negative electrode tab of a vehicle-mounted storage battery for an electric vehicle (EV) or the like, the negative electrode tab being used in automobiles and used to establish conduction.
(Material of Welding Mating Member and the Like)
As a material of the metal member different from the aluminum alloy, a copper alloy is preferable as described above.
(Mode of Welded Portion)
It is preferable that each of a plurality of welding mating members have the welded portion and be welded to the aluminum alloy member. Such a configuration eliminates the need for preparing a plurality of aluminum alloy members corresponding to the plurality of welding mating members, so that the number of components is reduced, cost is reduced, and component management is facilitated. Further, since it is not necessary to weld the plurality of welding mating members using the plurality of aluminum alloy members, the welding work is prevented from becoming complicated and can be easily performed, and the cost is reduced accordingly.
(Method for Forming Welded Portion; Welding Method)
Examples of a method for forming the welded portion where the aluminum alloy member for use in laser welding and a metal member different from the aluminum alloy are melted and mixed and then solidified include, but are not limited to, the following method.
As illustrated in
<Laser Welding Conditions>
The advance of laser welding technique also contributes to a gap between materials caused by welding of an aluminum alloy (bus bar) and copper (negative electrode tab), which are materials of different types, and manufacturing variations (range of tolerance). That is, linear welding used to make heat input excessive and make welding strength low, so that the linear welding has not been effective at all, but a technique of performing wobble welding called Wobbling to melt a material while preventing excessive heat input has been developed. Therefore, for the laser welding, wobble welding called Wobbling is preferably used. In order to solve the problem of the gap between the materials of different types, Wobbling (wobble welding) is performed using the aluminum alloy member for use in laser welding of the present embodiment, thereby making it possible to melt and mix the materials of different types with lower energy while filling in the gap between the materials. As a result, a stronger joint structure can be obtained. Further, for the laser welding, a YAG laser as a laser type is preferably used. The YAG laser makes metal high in absorbability of light energy as compared with a CO2 laser. Therefore, processing can be performed with less energy. As a result, a stronger joint structure can be obtained.
Hereinafter, the present embodiment will be described in detail with reference to examples, but the present invention is not limited to the following examples. Note that each of the example and comparative examples was performed, unless otherwise specified, under an atmospheric pressure, at room temperature (range of 25° C.±3° C.), and in a range of relative humidity of 50%±5% RH.
(Examples 1 to 5 and Comparative Examples 1 to 3)
(Preparation of Aluminum Alloy Member for Use in Laser Welding)
As a base member of the aluminum alloy member for use in laser welding, an aluminum alloy A1100-H24 or A6101-T6 was used. A thickness of the base alloy was set at 0.6 mm, and regarding a shape, a rectangular plate material for use in measurement of the arithmetic average roughness Sa, the degree of luster, and the film thickness of the surface of the nickel plating layer, and the grain size of nickel grains on the surface of the plating layer, and a plate material (see
In Comparative Example 2, an aluminum alloy A1100-H24 of the base member was used as it was as the aluminum alloy member for use in laser welding without forming a plating film. A thickness of the alloy member was set at 0.6 mm, and regarding a shape, a plate material (see
In Comparative Example 3, a plate-shaped aluminum alloy A6101-T6 of the base member was used as it was as the aluminum alloy member for use in laser welding without forming a plating film. A thickness of the alloy member was set at 0.6 mm, and regarding a shape, a plate material (see
A nickel plating layer was formed on one surface of the aluminum alloy of each of the base members of Examples 1 to 5 and Comparative Example 1, and a corresponding aluminum alloy member for use in laser welding was obtained. Ni plating conditions under which the nickel plating layer is formed were as follows. Note that the other surface of the aluminum alloy of the base member was coated with a removable insulating film so as to prevent a plating film from being formed and was then subjected to plating. After the end of the plating, the insulating film was removed.
<Ni Plating Conditions>
Note that, for the electrolytic nickel plating with luster of Comparative Example 1, sulfur of 0.1 mass % was added as a brightener to the above-described sulfamic acid bath in addition to the above-described three components. Note that the pH and film-forming time of each of the bath solutions of Examples 1 to 5 and Comparative Example 1 were set as shown in conditions in the following Table 1.
<Measurement of Arithmetic Average Roughness Sa of Surface of Nickel Plating Layer>
For each of the plate-shaped aluminum alloy members for use in laser welding of Examples 1 to 5 and Comparative Example 1 obtained as described above, the arithmetic average roughness Sa of the surface of the nickel plating layer was measured and calculated by the above-described method. The obtained arithmetic average roughness Sa of the surface of the nickel plating layer is shown in the following Table 2.
<Measurement of Film Thickness of Nickel Plating Layer>
For each of the plate-shaped aluminum alloy members for use in laser welding of Examples 1 to 5 and Comparative Example 1 obtained as described above, the thickness of the nickel plating layer was measured by the above-described method. The obtained film thickness of the nickel plating layer is shown in the following Table 2.
<Measurement of Grain Size of Nickel Grains in Nickel Plating Layer>
For each of the plate-shaped aluminum alloy members for use in laser welding of Examples 1 to 5 and Comparative Example 1 obtained as described above, the grain size of the nickel grains in the nickel plating layer was measured by the above-described method. The obtained grain size of the nickel grains in the nickel plating layer is shown in the following Table 2.
<Measurement of Degree of Luster of Nickel Plating Layer>
For each of the plate-shaped aluminum alloy members for use in laser welding of Examples 1 to 5 and Comparative Example 1 obtained as described above, the degree of luster of the nickel plating layer was measured by the above-described method. The obtained degree of luster of the nickel plating layer is shown in the following Table 2.
(Preparation of Welded Structure of Metal Member)
With each of the plate-shaped aluminum alloy members for use in laser welding of Examples 1 to 5 and Comparative Examples 1 to 3 obtained as described above, the aluminum alloy member and a metal member different from the aluminum alloy were arranged as illustrated in
Specifically, pure copper (oxygen-free copper) C1020-O was used as the metal member different from the aluminum alloy. A thickness was set at 0.2 mm, and regarding a shape, a rectangular plate material and a plate material having an L-shaped cross section (see
Next, laser welding was performed under the following conditions with the arrangement as illustrated in
The gap formed by the spacer is intentionally provided. That is, the gap is generated due to manufacturing variations of each member (range of tolerance). A median value of variations is 0.1 mm and MAX is 0.2 mm between the bus bar and the negative electrode tab of the vehicle-mounted storage battery, the gap was intentionally provided for verification that the gap can be sufficiently filled up by welding. Therefore, although used in this test, such a spacer is not used in actual laser welding. In this test, the spacer was set before welding and removed after welding.
Next, as illustrated in
<Laser Welding Conditions>
With the above-described laser welding, the welded structure (see
[Evaluation]
<Measurement of Strength (Tensile Stress) of Welded Structure>
The strength (tensile stress) of the welded structure of each of the metal members of Examples 1 to 5 and Comparative Examples 1 to 3 was measured using a universal tester, that is an Autograph tensile tester. Specifically, as illustrated in
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/048483 | 12/24/2020 | WO |
