JP6984240B2 - Aluminum member with laser weld - Google Patents

Description

The present invention relates to an aluminum member having a laser welded portion.

In electric vehicles and the like, the demand for bus bars used for batteries, inverters and the like is increasing. The bus bar is a conductive member obtained by processing a plate or strip of highly conductive metal such as copper or aluminum into various shapes for connecting a terminal tube such as a battery, depending on the structure of the place where the bus bar is used. Laser welding is known as a method of joining a device such as a bus bar and a battery, or the bus bars to each other.

Laser welding is a method of melting and bonding metals in a joint by laser light. Depending on the form of melting, it is divided into a heat conduction type with shallow melting and a keyhole type with deep melting, and it can be used properly according to the application. Laser welding does not require drilling or the like, has a high degree of freedom in bead shapes such as straight lines and curves, and can join a wide range in a short time.

Since aluminum is a material with high reflectance, most of the lasers are reflected when laser welding is attempted, making it difficult to generate sufficient heat in the welded portion, and it is easy to cause poor bonding. Therefore, aluminum was considered to be a material that is not suitable for laser welding.

In order to enhance the laser absorption of aluminum, laser welding is performed while supplying a wire rod of a low reflectance material such as vanadium, titanium, zirconium to the welded part (Patent Document 1), and the aluminum material is made of iron or titanium having a high laser absorption rate. Laser welding is performed after coating with, etc. (Patent Document 2), and electroless Ni-P plating with high laser absorption rate is applied to the welded portion of the aluminum member to perform laser welding (Patent Document 3). Proposed.
Japanese Unexamined Patent Publication No. 2001-198687 Japanese Unexamined Patent Publication No. 2008-274333 Japanese Unexamined Patent Publication No. 2017-94382

However, in the method of Patent Document 1, it is necessary to install a wire rod made of a low reflectance material in the condensing portion at the time of welding, the device configuration is complicated, and it is expected that the focal point of the laser and the tip position of the wire rod will deviate even slightly. It is difficult to construct because it cannot absorb the laser. In the method of Patent Document 2, specifically, iron and titanium are vapor-deposited, but the dry film on aluminum has poor adhesion due to the influence of the natural oxide film on aluminum, and a vacuum device is used. Since it is used, the device becomes expensive, and the shape and size of the member are also limited. Further, in the method of Patent Document 3, wet electroless Ni-P plating is shown, and although the problems of Documents 1 and 2 above are overcome, electroless Ni-P plating is poor in solder wettability. When laser welding and solder mounting are performed on the same member, the solder bondability may be impaired. Therefore, an aluminum member that can solve the above problem is desired.

An object of the present invention is to provide an aluminum member having a laser welded portion, which is also excellent in solder wettability.

As a result of conducting various studies to achieve the above problems, the present inventor not only improves the laser weldability of aluminum members by forming an electrolytic nickel plating film on an aluminum fabric material, but also electrolytic Ni plating. Has been found to have good solder wettability due to the high purity of nickel and less surface oxidation, and has completed the present invention.

That is, the present invention is an aluminum member having a laser welded portion, in which an electrolytic nickel plating film made of Ni having a purity of 99% by mass or more is formed on at least one surface in a thickness of 0.5 to 6.0 μm. Is.

According to one aspect of the present invention, there is provided an aluminum member having a laser welded portion in which the electrolytic nickel plating film has a crystalline structure.

According to one aspect of the present invention, there is provided an aluminum member having a laser welded portion having a bead width of 5 mm or less of the laser welded portion.

According to one aspect of the present invention, there is provided an aluminum member having a laser welded portion having an elongation rate of 8% or more of the electrolytic nickel plating film.

According to one aspect of the present invention, there is provided an aluminum member having a laser welded portion having an elongation rate of 10% or more of the electrolytic nickel plating film.

According to one aspect of the present invention, there is provided an aluminum member having a laser welded portion, wherein the aluminum member is a JIS standard 1000 series (pure Al) or 6000 series (Al-Mg-Si) alloy.

According to one aspect of the present invention, there is provided an aluminum member having a laser welded portion provided with a Zn plating layer as a base layer of an electrolytic nickel plating film.

According to one aspect of the present invention, there is provided an aluminum member having a laser welded portion having a bent portion.

According to the present invention, it is possible to provide an aluminum member having a laser welded portion, which is also excellent in solder wettability.

This is the relationship between the laser welding output and the penetration depth of the aluminum fabric material and the electrolytic Ni-plated aluminum material. 3 is a photomicrograph of a cross section of an electrolytic Ni-plated aluminum material irradiated with laser light at an output of 0.8 kW and an irradiation rate of 2 mm / min. It is a micrograph of the cross section of the aluminum cloth material irradiated with the laser beam at the output of 0.8 kW and the irradiation speed of 2 mm / min. It is a micrograph of a bead of an electrolytic Ni-plated aluminum material irradiated with a laser beam at a welding speed of 0.3 kW and a welding speed of 1 m / min. It is a micrograph of a bead of an electrolytic Ni-plated aluminum material irradiated with a laser beam at a welding speed of 2 m / min and an output of 0.3 kW. It is a micrograph of a bead of an aluminum cloth material having no electrolytic Ni plating film irradiated with a laser beam at a welding speed of 0.3 kW and a welding speed of 1 m / min. It is a micrograph of a bead of an aluminum cloth material having no electrolytic Ni plating film irradiated with a laser beam at a welding speed of 0.3 kW and a welding speed of 2 m / min. It is explanatory drawing about the solder wettability test. This is an example of a wetting force chart created with the solder wetting force (mN) obtained in the solder wetting property test as the vertical axis and the time (s) as the horizontal axis.

Hereinafter, one embodiment of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be carried out with appropriate modifications as long as the effects of the present invention are not impaired.

[Aluminum member]
The aluminum member according to the present embodiment is a member in which two or more aluminum materials are laser-welded, and has a laser-welded portion. The laser welded part is a part that has been laser welded, and the raised part of the weld mark is called a bead.

(Aluminum fabric material)
The aluminum fabric material is made of aluminum or an aluminum alloy, and is preferably a JIS standard 1000 series (pure Al) or 6000 series (Al-Mg-Si) alloy. The size and shape of the aluminum fabric material can be appropriately selected according to the size and shape required for the aluminum member.

(Electrolytic nickel plating film)
The aluminum member having a laser welded portion has an electrolytic nickel plating film (hereinafter, also simply referred to as “plating film”) having a purity of 99% by mass or more and having an electrolytic nickel plating film of 0.5 to 6.0 μm on the aluminum fabric material. It is formed on the surface by thickness. In general, an unplated aluminum fabric material has poor laser weldability due to its high reflectance, and also has poor solder wettability due to the formation of a dense natural oxide film on the surface. The aluminum member according to the present embodiment has good laser weldability because an electrolytic nickel plating film is formed. Further, since the electrolytic nickel plating film is made of Ni having a purity of 99% by mass or more, the surface is less oxidized and the solder wettability is good.

The purity of Ni constituting the electrolytic nickel plating film is preferably 99% by mass or more, and more preferably 99.5% by mass or more, in terms of further enhancing the laser weldability and the solder wettability. It can be confirmed, for example, by the electron probe microanalyzer (EPMA) method that the purity of Ni constituting the electrolytic nickel plating film is 99% by mass or more. The thickness of the electrolytic nickel plating film is preferably 0.5 to 6.0 μm, and more preferably 1.0 to 5.0 μm in terms of further enhancing the laser weldability and the solder wettability.

The electrolytic nickel plating film has a crystalline structure. Since the electrolytic Ni plating film has a crystalline structure, the elongation rate is high, so even if the aluminum material is bent after the plating film is formed on the aluminum fabric material, cracks may occur in the plating film. There is little concern that the plating film will peel off. Having a crystalline structure can be confirmed, for example, by an X-ray diffraction method. Further, since the electrolytic nickel plating film is formed by the electrolytic plating process, the aluminum fabric material wound in a coil shape is unwound, plated, and then wound again in a coil shape, that is, from the coil to the coil. It can be processed continuously and has high productivity in the plating process.

In the aluminum member having the laser welded portion according to the present embodiment, the elongation rate of the electrolytic nickel plating film is preferably 8% or more, more preferably 10% or more. Since the elongation rate is 8% or more, even if the plating film is formed on the aluminum fabric material and then bent, there is little concern that the plating film will be cracked or the plating film will be peeled off. The elongation of the electrolytic nickel plating film can be measured by a bending test according to ASTM B 489.

The electrolytic nickel plating film can be formed by an electrolytic plating process. Before forming the electrolytic nickel plating film, the aluminum fabric material may be subjected to pretreatment such as degreasing, pickling, and washing, if necessary. As the Ni plating treatment liquid to be brought into contact with the aluminum fabric material, an industrially used plating treatment liquid such as a Watt bath or a sulfamic acid bath can be used. It is preferable to perform the electrolytic plating treatment using a sulfamic acid bath having a pH of 3.5 to 4.8 or a watt bath having a pH of 4.0 to 5.5, but Zn plating is provided as a base layer on the aluminum fabric material. A sulfamic acid bath having a pH of 3.5 to 4.8 is preferable because it prevents the Zn plating layer from melting, the internal stress is small, and the moldability after plating is excellent. The current density at the time of forming the electroless nickel plating film by electrolytic plating process is preferably carried out at 2A / dm ² or more 10A / dm ² or less. A more preferable current density is 2 A / dm ² or more and 5 A / dm ² or less. Further, in order to increase the Ni ion concentration in the Ni plating treatment liquid, for example, in the case of a sulfamate Ni plating bath, the concentration of nickel sulfamate in the treatment liquid is 400 g / L or more and 500 g / L or less, or 450 g / L or more and 500 g. It is also preferable to set it to / L or less.

The aluminum member having the laser welded portion according to the present embodiment may be provided with a Zn plating layer as a base layer of the electrolytic nickel plating film. By providing the Zn plating layer, the adhesion of the nickel plating film can be improved. The thickness of the Zn plating layer is not particularly limited and may be 0.1 to 1.0 μm. The Zn-plated layer can be formed by a conventionally known zincate treatment.

(Aluminum member)
The aluminum member having the laser welded portion according to the present embodiment has good laser weldability and excellent solder wettability. Good laser weldability can be determined, for example, by the fact that the bead width is narrowly formed, the beads are formed in a series over the entire laser welded portion, and the like. Therefore, the bead width is preferably 5 mm or less, and more preferably 4 mm or less. The bead width can be measured by measuring the width of the raised portion of the weld mark using a microscope, if necessary. The solder wettability can be determined by a solder wettability test according to JIS C6000068-2-54, which will be described later.

The aluminum member having the laser welded portion according to the present embodiment has a bent portion. By having the bent portion, it is possible to take various shapes required for a bus bar or the like. The bent portion can be formed by edgewise bending, flatwise bending, hem bending, or the like.

[Production method]
The aluminum member having the laser welded portion according to the present embodiment can be obtained by laser welding two or more aluminum materials having an electrolytic nickel plating film formed on at least one surface. In laser welding, an electrolytic nickel plating film was formed by arranging two or more aluminum materials so that one surface was in contact with each other and the surfaces on which the electrolytic nickel plating film was formed faced in the same direction. It is performed by irradiating laser light from the surface side. The laser light source is not particularly limited, and a conventionally known light source such as a fiber laser, a YAG laser, or a CO _{2 laser can be used.} The output of the laser light source can be 0.1 to 5 kW, and the welding speed can be 0.5 to 5 m / min, depending on the output of the laser light source.

Hereinafter, the present invention will be described in more detail with reference to examples, but these examples do not limit the interpretation of the present invention.

[Electrolytic Ni plating process]
The electrolytic Ni plating treatment applied to the aluminum fabric material was carried out by a degreasing step, an alkali etching step, a desmat step, a primary zincating step, a zinc stripping step, a secondary zincating step, and a Ni plating step. The conditions (reagent, temperature, processing time, etc.) of each step are shown below.
Degreasing process: 20% by mass nickel, room temperature, 30 seconds Alkaline etching process: 5% by mass NaOH, 50 ° C, 30 seconds Desmat process: 20% by mass nickel, room temperature, 30 seconds Primary zincating process: AZ-301 (Uemura Kogyo Co., Ltd.) (Manufactured by the company), 25 ° C, 30 seconds Zinc peeling process: 20% by mass nitric acid, room temperature, 30 seconds Secondary zincating process: AZ-301 (manufactured by Uemura Kogyo Co., Ltd.), 25 ° C, 30 seconds Ni Plating process: Ni (NH) _{2 SO 3) 2 · 4H 2} O 450g / L, NiCl 2 ·
6H ₂ O 10g / L, H ₃ BO ₃ 35g / L, NP-A (stocks)
Company Murata, pit inhibitor) 3.0ml / L, 40 ℃, 5A
/ Dm ² , predetermined time Ion-exchanged water was used as the solvent for the treatment liquid in each step, and the aluminum material was washed with water for 30 seconds using ion-exchanged water at room temperature between each step.

[Electroless Ni plating process]
As a comparative example, an aluminum fabric material subjected to electroless Ni plating was prepared. In the electroless Ni plating treatment, each step other than the above electrolytic Ni plating treatment and the Ni plating step was carried out under the same conditions, and the Ni plating step was carried out under the following conditions.
Ni plating process: Top Nicolon SDB-LF (manufactured by Okuno Pharmaceutical Industry Co., Ltd.), 90 ° C.
10 minutes

[Plating composition analysis]
For the composition analysis of the plating applied to the aluminum fabric material, EPMA1610 (manufactured by Shimadzu Corporation) was used, and the plating surface was qualitatively and semi-quantitatively analyzed at an acceleration voltage of 15 kV. The results of the composition analysis are shown in Table 1. In the electrolytic Ni plating, P was less than the lower limit of quantification.

[Laser welding test]
Aluminum alloy 6101-T6 material (thickness 3 mm x 20 mm x 100 mm) (hereinafter referred to as "aluminum fabric material") and electrolytic Ni plating with a thickness of about 3 μm by the above-mentioned electrolytic Ni plating treatment on the aluminum alloy material. (Hereinafter referred to as "electrolytic Ni-plated aluminum material") were prepared, and laser welding was performed on each of them under the conditions shown below.
Oscillator: Multimode fiber laser output (kW): 0.3kW to 3kW
Welding speed (WS) (m / min): 1-2 m / min
Fiber diameter: 0.2 mm
Focal diameter: 0.2 mm
Shield gas type: N ₂
Shield gas flow rate: 20 to 30 L / min
Forward / backward angle: forward angle Defocus: just focus Pulse waveform: CW (continuous wave)

As shown in FIG. 1, the electrolytic Ni-plated aluminum material has a larger penetration depth on the lower output side than the aluminum fabric material. As shown in FIG. 2, the electrolytic Ni-plated aluminum material forms a bead that reaches the keyhole region at an output of 0.8 kW, while as shown in FIG. 3, the aluminum fabric material has 0.8 kW. At the output, the penetration is only about 0.15 mm and remains in the heat transfer region. That is, the electrolytic Ni-plated aluminum material is superior in weldability as compared with the aluminum fabric material.

As shown in FIGS. 4 and 5, in the electrolytic Ni-plated aluminum material, beads are stably formed even when the welding speed is high (the output density is low). On the other hand, as shown in FIGS. 6 and 7, the bead formation of the aluminum fabric material becomes unstable and intermittent as the welding speed increases (the output density decreases). That is, the electrolytic Ni-plated aluminum material is superior in weldability as compared with the aluminum fabric material.

[Solder wettability test]
Aluminum alloy 6101-T8 material (thickness 0.5 mm x 5 mm x 10 mm) subjected to electrolytic Ni plating or electroless Ni plating (both film thickness: about 3 μm) by the above-mentioned plating treatment (hereinafter, each). Prepare "electrolytic Ni plating material", "electroless Ni plating material") and untreated material (hereinafter referred to as "aluminum fabric material") for each test piece under the conditions shown below. , A solder wettability test according to JIS C6000068-2-54 shown in FIG. 8 was carried out.
Equipment: Solder Checker 5200TN (manufactured by Reska Co., Ltd.)
Solder: Lead-free solder M705 (manufactured by Senju Metal Industry Co., Ltd., composition: Sn3Ag
0.5Cu)
Flux: 2-propanol 30 g + rosin 10 g + diethylammonium chloride
Lido 61.7 mg (standard flux + 0.2% Cl flux)
Immersion speed: 5 mm / s
Immersion depth: 5 mm
Immersion time: 10s
Pulling speed: 5 mm / s
Each test piece was carried out at n = 3 and the zero cross time T ₀ (s) and the appearance of the test piece were evaluated. In FIG. 8, the zero cross time T ₀ means the time from the concave state of the molten solder liquid surface to the time when the angle θ formed by the test piece and the solder liquid surface becomes 90 °. It can be said that the smaller the zero cross time T ₀ is, the better the solder wettability is, and when the appearance of the test piece is well wet, the solder wettability is good.

Table 2 shows the results of the solder wettability test, and FIG. 9 shows an example of the solder wettability chart obtained in the solder wettability test. The electrolytic Ni-plated piece _{showed good solder wettability with T 0} of 3 seconds or less. On the other hand, neither the electroless Ni-plated piece nor the aluminum cloth material piece reached the buoyancy line, and T ₀ could not be measured. Moreover, when the appearance of the test piece was observed, only the portion of the electroless Ni-plated piece immersed in the solder bath was wet, and the aluminum fabric material was not wet at all. That is, it can be seen that the electrolytic Ni-plated aluminum material is superior in solder wettability to the electroless Ni-plated aluminum material and the untreated aluminum fabric material.

Claims (7)

On at least one surface, an electrolytic nickel plating film made of Ni having a purity of 99% by mass or more and having a crystalline structure is formed with a thickness of 0.5 to 6.0 μm, and is formed on JIS C6000068-2-54. An aluminum member having a laser welded portion having a zero cross time of 2.07 seconds or more and 3 seconds or less according to a compliant solder wettability test. The aluminum member having a laser welded portion according to claim 1, wherein the bead width of the laser welded portion is 5 mm or less. The aluminum member having a laser welded portion according to claim 1 or 2, wherein the elongation rate of the electrolytic nickel plating film is 8% or more. The aluminum member having a laser welded portion according to any one of claims 1 to 3, wherein the elongation rate of the electrolytic nickel plating film is 10% or more. The aluminum member having a laser welded portion according to any one of claims 1 to 4, wherein the aluminum member is a JIS standard 1000 series (pure Al) or 6000 series (Al-Mg-Si) alloy. The aluminum member having a laser welded portion according to any one of claims 1 to 5, wherein a Zn plating layer is provided as a base layer of the electrolytic nickel plating film. The aluminum member having a laser welded portion according to any one of claims 1 to 6, which has a bent portion.

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