JP6071010B2 - Welding method - Google Patents

Description

  The present invention relates to a welding method. More specifically, the present invention relates to a welding method capable of suitably welding while suppressing generation of voids.

  Conventionally, for example, power storage elements such as a lithium ion secondary battery, a sodium battery, an electric double layer capacitor, and a lithium ion capacitor are constructed by housing a power generation element that generates power in a case and sealing the power generation element. Such a case is typically composed of a case main body having an opening on one surface and a lid member having a shape corresponding to the opening. After the lid member is fitted into the case main body, the two are welded or the like. By joining by a technique, the opening is sealed with a lid member. Generally, laser welding (also referred to as laser beam welding) is employed for sealing the case. For example, Patent Documents 1 and 2 are known as conventional techniques relating to such laser welding.

JP 2011-092944 A JP 2011-204396 A

  In the above-mentioned Patent Document 1, for example, when the first member and the second member are butt-joined, it is disclosed to use superimposed laser light in which one low-intensity laser and two high-intensity lasers are superimposed. ing. Here, the low-intensity laser is irradiated such that the gap between the first member and the second member becomes the optical axis and the laser irradiation region is enlarged. In addition, the high-intensity laser light irradiates the first member and the second member with two high-intensity lasers having irradiation regions smaller than those of the low-intensity laser light. The first member and the second member are joined by filling the gap with the melt of the first member and the melt of the second member melted by the superimposed laser beam.

  By the way, in the case of the above-described storage element, etc., the plate-like constituent members constituting the case are being made thinner from the viewpoints of weight reduction and cost reduction. For example, in welding the case main body and the lid member, the lid member is fitted inside the opening of the case main body, and welding is performed by irradiating laser light from above the case. In this case, for the case main body, the side surface portion of the plate material constituting the case main body corresponds to a laser irradiation surface on which laser light is irradiated during welding. That is, in the case main body, a dimension in a direction perpendicular to the interface (which may be a joint surface) between the case main body and the lid member (hereinafter referred to as such dimension is simply referred to as a surface direction irradiated with laser light). , Sometimes referred to as “width” of the laser irradiation surface) corresponds to the thickness of the plate.

When welding the case main body and the lid member having such a small laser irradiation surface width, if the welding method disclosed in Patent Document 1 is applied, a void (blow hole, porosity) is formed in the weld deep portion between the case main body and the lid member. , Also referred to as pores). However, when such a void is formed in the case body having such a small size (width), there is a problem that the influence of the strength reduction of the plate material constituting the case body cannot be ignored and sufficient welding strength cannot be obtained. It was. On the other hand, when welding is performed by irradiating a low-intensity laser beam that does not form voids, a sufficient melting depth, and thus a sufficient joint surface depth cannot be ensured, and sufficient welding strength is obtained. I can't.
The present invention has been made in view of the above points, and the purpose thereof is to suppress the generation of voids, thereby suppressing a decrease in welding strength due to the voids and capable of stably realizing a high welding strength. Is to provide a method.

  In order to solve the above problems, the present invention provides a welding method for laser welding a plate-like first member and a plate-like second member. In this welding method, the first member and the second member are arranged in a direction in which the wide surfaces thereof are orthogonal to each other, and the side surface portion of the second member is substantially flush with the wide surface of the first member. So that the side surface portion of the first member and the wide surface end portion of the second member are abutted, and the side surface portion of the first member facing the second member is a first joint surface, When the wide surface end portion of the two members facing the first member is a second joint surface, the dimension of the first member in the direction orthogonal to the first joint surface is the second of the second member. The first laser beam is larger than the dimension in the direction perpendicular to the bonding surface; the first laser beam is irradiated along the first bonding surface with a first laser beam having an intensity capable of generating a keyhole on the wide surface of the first member. Forming a first molten pool that is melted by the first molten pool, wherein the first molten pool is A second laser beam having a lower intensity than that capable of generating a keyhole is irradiated along the second joint surface on the side surface of the second member; Forming a second molten pool that is melted by two laser beams, wherein the second molten pool is formed across the first member. The first molten pool and the second molten pool are integrated with each other to form a molten pool, and the first member and the second member are welded by a welded portion formed by solidifying the molten pool. It is characterized by doing.

  According to such a configuration, the keyhole-type first molten pool having a sufficient penetration depth can be formed in the first member by the first laser beam having a relatively high intensity (high luminance), and a sufficient amount of the first molten pool can be formed. Molten metal can be secured. In addition, for the second member having a thinner thickness, a heat conduction type second molten pool can be formed by a relatively low intensity (low luminance) second laser beam, resulting in a decrease in welding strength in the thin wall portion. The generation of voids to be obtained can be suppressed. At this time, the second molten pool is superposed on the first molten pool. Thereby, the ratio of the welding part which occupies for the joint surface which is a boundary of a 1st member and a 2nd member can be increased easily and stably. That is, for example, even when the keyhole-type first molten pool is displaced from a predetermined position due to, for example, an orbital shift of the first laser beam, the entire joint surface between the first member and the second member is sufficient. It is possible to connect with a welded portion having a large area, and to ensure a stable welding strength.

In a preferred aspect of the welding method disclosed herein, the output density I ₁ of the first laser beam is 5.6 × 10 ⁶ W / cm ² ≦ I ₁ <1.1 × 10 ⁸ W / cm ^2. It is characterized by being. In this manner, by roughly the range output density I ₁ of the first laser light, certainly it is possible to form a molten pool of keyhole type, suppressing the poor welding by laser excessive strength Can do. As a result, the welding strength can be more reliably increased and high-quality welding can be realized.

In a preferred aspect of the welding method disclosed herein, the output density I ₂ of the second laser beam is 2.8 × 10 ⁶ W / cm ² ≦ I ₂ <5.6 × 10 ⁶ W / cm ^2. It is characterized by being. According to this configuration, by adjusting the power density I ₂ of the second laser beam, it is possible to reliably form a molten pool of the heat conduction type having a sufficient penetration depth in the second member. Thereby, it can suppress reliably that a void generate | occur | produces in the 2nd member.

In a preferred aspect of the welding method disclosed herein, when the output density I ₂ of the second laser beam is 3.8 × 10 ⁶ W / cm ² or more and less than 5.6 × 10 ⁶ W / cm ^2. The scanning speed of the first laser beam and the second laser beam is 20 m / min or more. Thereby, high quality welding with higher bonding strength can be performed at a relatively high speed.

In a preferable aspect of the welding method disclosed herein, when the output density I ₂ of the second laser beam is 2.8 × 10 ⁶ W / cm ² or more and less than 3.8 × 10 ⁶ W / cm ^2. The scanning speed of the first laser light and the second laser light is less than 20 m / min. Thereby, even when a lower-intensity laser is used as the second laser light, sufficient welding heat can be input, and high-quality welding with higher joint strength can be performed.

In a preferred aspect of the welding method disclosed herein, the output density I ₁ of the first laser beam and the output density I ₂ of the second laser beam satisfy I ₁ ≧ 5 × I _2. It is said. According to such a configuration, the effect of the above welding method can be obtained more efficiently.

In a preferred aspect of the welding method disclosed herein, the irradiation diameter d ₁ of the first laser light and the irradiation diameter d ₂ of the second laser light satisfy d ₁ <d ₂ . . According to such a configuration, the above-described welding can be realized more efficiently.

In a preferred aspect of the welding method disclosed herein, the depth Dw of the welded portion of the joint surface in a cross section orthogonal to the first or second joint surface, and the second joint surface of the second member. The dimension L ₂ in the direction orthogonal to the direction satisfies Dw ≧ L ₂ . According to such a configuration, the welding strength can be increased more reliably.

  In another aspect, the invention disclosed herein provides a welded structure in which a plate-like first member and a plate-like second member are joined by a welded portion. In such a welded structure, the dimension of the first member in the direction orthogonal to the joint surface between the first member and the second member is larger than the dimension of the second member in the direction. Moreover, the said weld part has a 1st weld part and a 2nd weld part divided in the surface containing the said joint surface. The first welded portion is mainly constituted by a keyhole type welded portion formed by a laser applied to the first member, and includes a tip portion of the keyhole type welded portion. Further, the second welded portion is mainly constituted by a heat conduction type welded portion formed by a laser applied to the second member, and at least one of the portions excluding the tip portion of the keyhole welded portion. It is characterized by including at least one part of a part and the said heat conduction type welding part.

  According to such a configuration, it is possible to appropriately control the shape of the welded portion and the occurrence of defects by using a combination of two types of laser beams having different characteristics and applying them appropriately to the member to be welded. Thereby, for example, it is possible to stably secure a deep welding depth while suppressing the formation of blow holes (that may be voids). As a result, a welding structure in which the welding strength is stably secured can be realized.

In a preferred embodiment of the disclosed welded structures herein, the depth Dw of the welded portion of the joint surface in a cross section perpendicular to the junction plane, the dimensions L ₂ of the cross-sectional direction of the second member, Dw It is characterized by satisfying ≧ L _2. According to this configuration, the welding strength can be ensured more reliably.

FIG. 1 is a plan view for explaining an embodiment of a welding method disclosed herein. 2A is a schematic cross-sectional view illustrating a welded structure formed by the welding method of FIG. FIG. 2B is a schematic cross-sectional view illustrating a welded structure formed when only the first laser beam is irradiated on the first member. FIG. 3 is a view showing a state of a cross section in a welding direction in a welded portion formed by (1) welding method 1 and (2) welding method 2 in an example. FIG. 4 is a cross-sectional view illustrating a state in which a void is formed in the second member by the conventional welding method by the welding method 2 in the embodiment. FIG. 5 is a cross-sectional cutaway view illustrating the configuration of a lithium ion battery to which the welding method of the present invention is applied. FIG. 6 is a top view of FIG.

  Hereinafter, the electrode proposed here will be described in detail with reference to the drawings as appropriate based on a preferred embodiment. Note that matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention (for example, general matters such as the configuration and operation method of the welding machine) are the prior art in this field. It can be grasped as a design matter of those skilled in the art based on the above. Each drawing is schematically drawn, and the dimensional relationship (length, width, thickness, etc.) in each drawing does not reflect the actual dimensional relationship. Further, members / parts having the same action are denoted by the same reference numerals, and redundant description is omitted or simplified.

  FIG. 1 is a plan view for explaining an embodiment of a welding method according to the present invention. FIG. 2A is a diagram illustrating a welded structure formed by the welding method disclosed herein, and is a diagram illustrating a welded structure in a cross section perpendicular to the welding progress direction G. In the welding method according to the present embodiment, as shown in FIG. 1, the plate-like first member 10 and the plate-like second member 20 are abutted using the first laser beam 1 and the second laser beam 2. I try to join them. In the present specification, the expression “plate-like” regarding the shapes of the first member 10 and the second member 20 means that the cross section of each member perpendicular to the welding direction G is plate-like. However, the shape of each member other than the vicinity of the welded portion that affects the welding method (for example, a welded portion including the heat affected zone) is not limited at all.

In such a welding method, the first member 10 and the second member 20 are arranged so that the wide surfaces of the first member 10 and the second member 20 are orthogonal to each other, and the side surface portion of the second member 20 is substantially surface with respect to the wide surface of the first member 10. The side surface portion of the first member 10 and the wide surface end portion of the second member 20 are abutted so as to be one. Here, the side surface portion of the first member 10 facing the second member 20 is referred to as a first joint surface 12, and the wide surface end portion of the second member 20 facing the first member 10 is referred to as a second joint surface 22. Hereinafter, the dimension in the direction perpendicular to the bonding surface of the second member 20 (i.e., the width of the second member 20 in the laser irradiated surface) of the L _2. Here, the dimension in the direction orthogonal to the first joint surface 12 of the first member 10 is larger than the dimension L ₂ in the direction orthogonal to the second joint surface 22 of the second member 20. Although not particularly limited, typically, the first member 10 and the second member 20 having such a configuration may be such that the second member 20 is thinner than the first member 10.

  In addition, depending on the shape of the first member 10 and the second member 20, there is a configuration that realizes the matching by fitting both the members. Further, depending on the shapes of the first member 10 and the second member 20, a gap is provided between the first joint surface 12 and the second joint surface 22 for the purpose of facilitating the fitting of the two members. It can happen. Alternatively, a gap may occur due to various errors. For the purpose of narrowing or eliminating the gap between the first member 10 and the second member 20, both the first member 10 and the second member 20 are connected from the outside of the joining surfaces 12 and 22. There is also a case of pressing toward the inward contact. In this figure, an example in which there is no gap between the first member 10 and the second member 20 is shown, but the welding method disclosed herein can be similarly implemented even if there is a gap. In addition, when a clearance gap arises between the 1st member 10 and the 2nd member 20, what is necessary is just to implement this invention demonstrated below supposing that the center of this clearance gap is a joining surface.

[First laser beam]
The first laser beam 1 is a high-intensity (high power density) laser beam irradiated on the wide surface of the first member 10, and is mainly used to melt the first member 10. The first laser beam 1 has a laser intensity (power density) that can generate a keyhole for the first member 10. When a member to be welded is melted with a laser beam having a high output density, the welded member starts to evaporate simultaneously with the laser beam irradiation in the molten pool, and a repulsive force is generated on the material surface by the vapor, resulting in a depression in the molten pool. . The laser beam repeats irregular reflection in such a recess, so that the recess is rapidly deepened to form a cavity. This cavity is referred to as a keyhole, and it is important that the first laser beam 1 is constituted by a laser beam having an output density such that the keyhole is formed. The first laser beam 1 is irradiated on the laser irradiation surface (wide surface) of the first member 10 along the first bonding surface 12 and travels in the welding progress direction G. L _W1 in FIG. 1 illustrates the trajectory of the first laser beam 1.

Although the laser intensity of the first laser beam 1 depends on the material of the first member 10 and the like, it cannot be strictly stated. However, as an approximate guide, the output density I ₁ is 5.6 × 10 ⁶ W / cm ² ≦ The laser beam can be I ₁ <1.1 × 10 ⁸ W / cm ² . The power density I ₁ is preferably 10 × 10 ⁶ W / cm ² or more, more preferably 5.6 × 10 ⁷ W / cm ² or more. The upper limit of the output density I ₁ is not particularly limited. However, it is not preferable to input more laser energy than necessary because sputtering is likely to occur and poor welding may be caused. Therefore, the output density I ₁ can be set to an output density that does not penetrate the first member 10, for example, preferably 10 × 10 ⁷ W / cm ² or less, and more preferably 8 × 10 ⁷ W / cm ^2. cm ² or less. More preferably, it can be determined with reference to an output density shown in FIG. 2A that can stably secure a predetermined joint surface depth Dw. Here, the joining surface depth Dw is the depth direction (vertical direction in the drawing) of the welded portion 30 at the joining surfaces 12 and 22 formed by attaching the first joining surface 12 and the second joining surface 22 together. It is the dimension. For example, in the cross section orthogonal to the welding progress direction G shown in FIG. 2A, the joint surface depth Dw is the surface of the welded portion 30 on the surface including the interface (joint surface) between the first member 10 and the second member 20. It can be understood as a dimension. The joint surface depth Dw is an index that can reflect the weld area of the weld portion 30 on the surface including the interface (joint surface) between the first member 10 and the second member 20 when the entire weld portion 30 is considered. obtain.

  Here, the shape of the molten pool formed only by the 1st laser beam 1 is exhibiting what is called a keyhole type, as FIG. 2B refers, for example. Therefore, a weld width 16 'having a narrow bead width and a heat affected zone in a cross section perpendicular to the welding progress direction G and a deep penetration can be obtained. For example, in such a cross section, the dimensions of the first molten pool 14 ′ and the first welded portion 16 ′ on the surface of the first member 10 (for example, also referred to as the melt width) are a1, and the first molten pool 14 ′ of the first member 10 is the first molten pool 14 ′. When the melting depth of the first welded portion 16 ′ is b1, the aspect ratio of the first welded pool 14 ′ and the first welded portion 16 ′ represented by (b1 / a1) (referred to as the first aspect ratio). Can be a value exceeding 1. Typically, the first aspect ratio is 1.5 or more, more preferably 2 or more. Actually, the first member 10 is not only irradiated with the first laser beam 1 but also affected by the heat of the second laser beam 2. Therefore, it may be difficult to confirm the first aspect ratio during actual welding. In that case, for example, as illustrated in FIG. 2B, the first melt formed by using the same material as the first member 10 and the second member 20 in advance and irradiating the first laser beam 1 alone. A first aspect ratio can be determined for the pond 14 'and the first weld 16'.

[Second laser beam]
The second laser beam 2 is a low-intensity (low power density) laser beam applied to the side surface of the second member 20, and mainly melts the second member 20 and assists the melting by the first laser beam 1. It is used for the purpose. The second laser beam 2 has a laser intensity lower than that capable of generating a keyhole for the second member 20. When a laser beam having such a power density is irradiated onto a member to be welded, the laser beam is absorbed on the surface, and the absorbed light is converted into heat. And in the area | region which this heat energy conducted, the to-be-welded member is fuse | melted and a molten pool is formed. In this heat conduction type molten form, no keyhole is formed. The second laser beam 2 is irradiated on the laser irradiation surface (side surface portion) of the second member 20 along the second bonding surface 22 and proceeds in the welding progress direction G. _LW2 in FIG. 1 illustrates the trajectory of the second laser light 2.

Although the laser intensity of the second laser beam 2 depends on the material of the second member 20 and cannot be generally specified, as an approximate guide, the output density I ₂ is 2.8 × 10 ⁶ W / cm. can be ² ≦ _I 2 <laser light ^{5.6 × 10 6 W / cm 2} . The power density I ₂ is preferably 5.5 × 10 ⁶ W / cm ² or less, more preferably 4 × 10 ⁶ W / cm ² or less. The lower limit of the output density I ₂ is not particularly limited, but it is preferable to input laser energy that can provide a penetration depth that can assist melting by the first laser beam 1. Therefore, the laser intensity I ₂ of the second laser beam 2, for example, can be determined to measure the output density that can stably ensure a predetermined bonding surface depth Dw, preferably 3 × 10 6 ^{W /} cm ² or more, more preferably 3.2 × 10 ⁶ W / cm ² or more. More preferably, for example, as shown in FIG. 2A, in the cross section orthogonal to the welding progress direction G, the shape of the molten pool 24 formed in the second member 20 is a convex portion in the depth direction in the laser irradiation direction. The power density can be set so as to form (see the right end of the second welded portion 26 in the figure).

Note that the power density I ₁ of the first laser beam 1 and the output density I ₂ of the second laser, is not particularly limited, for example, preferably in the relationship satisfying I ₁ ≧ 5 × I ₂ . When the power density is in such a relationship, the shape of the welded portion 30 described later can be suitably adjusted. First output density _{I 1} of the laser beam 1 and the output density _{I 2} of the second laser, more preferably from _{I 1} ≧ 8 × _{I 2,} further, _{I 1} ≧ 10 × _{I 2,} for example, _{I 1} More preferably, ≧ 12 × I ₂ .

  The shape of the molten pool formed only by the second laser beam 2 is a so-called heat conduction type. Therefore, when the dimension of the second molten pool on the surface of the second member 20 (for example, it can be said to be a molten width) is a2, and the depth of the second molten pool in the second member 20 is b2, (b2 / a2) The expressed aspect ratio of the second molten pool (referred to as the second aspect ratio) may be a value of 1 or less. Typically, such second aspect ratio is 0.7 or less, more preferably 0.5 or less. In practice, the second member 20 is irradiated with the second laser beam 2 and a molten pool is formed by the first laser beam 1. Therefore, it may be difficult to confirm the second aspect ratio during actual welding. In such a case, although not shown, for example, similarly to the first aspect ratio, the same material as the first member 10 and the second member 20 is used in advance, and the second laser beam 2 is irradiated alone. The second aspect ratio can be obtained for the second molten pool and the second molten portion.

In the first laser beam 1 and the second laser beam 2, the irradiation diameter is not particularly limited. For example, the irradiation diameter of the first laser beam 1 can be adjusted so as to enable keyhole welding according to the output of the laser welding apparatus (laser oscillation apparatus) to be used, the accuracy of the optical system, and the like. . The irradiation diameter of the second laser beam 2 can also be a heat conduction type welding according to the output of the laser welding apparatus (laser oscillation apparatus) to be used, the accuracy of the optical system, etc. It can be adjusted so that melting by 1 can be assisted. Accordingly, since the first laser beam 1 realizes a high output density and the second laser beam 2 realizes a low output density, the irradiation diameter d ₁ of the first laser beam ₁ and the second laser beam are typically set. The irradiation diameter d _{2 of 2} can be in a relationship of d ₁ <d ₂ . For example, the irradiation diameter d ₁ of the first laser beam 1 and the irradiation diameter d ₂ of the second laser light 2, be adjusted such that the relation of 2d ₁ ≦ d _2, the balance of both lasers is the preferred embodiment As shown. The irradiation diameter _{d 1} of the first laser beam 1 and the irradiation diameter _{d 2} of the second laser beam 2 is preferably from 3d ₁ ≦ _{d 2,} and even more preferably 5d ₁ ≦ _{d 2.} The upper limit of the irradiation diameter d ₂ of the second laser beam 2 is not particularly limited, but can be determined in consideration of the thickness L ₂ of the second member that irradiates the second laser beam 2. For example, irradiation diameter _{d 2} of the second laser beam 2 is smaller than the thickness _{L 2} of the second member _(d 2 _{<L 2)} It is desirable. Furthermore, considering the orbital shift of the second laser light 2, d ₂ ≦ 0.8 × L ₂ (for example, 0.7 × L ₂ ≦ d ₂ ≦ 0.9 × L ₂ ) is set as a guide. Is preferred. Note that the first laser beam 1 and the second laser beam 2 may overlap the region (irradiation region) of the heat affected zone, but the laser beam itself does not necessarily have to be superimposed. Preferably, the first laser beam 1 and the second laser beam 2 can be irradiated alone without overlapping.

[Formation of welds]
The first laser beam 1 is applied to the wide surface (front surface) of the first member 10 at, for example, a position spaced from the bonding surface by a predetermined distance. Then, the first member 10 is moved in the welding progress direction G along the first joint surface 12. That is, the optical axis of the first laser beam 1 moves along the bonding surface at a predetermined distance from the bonding surface on the surface of the first member 10, as indicated by _LW1 in FIG. . Further, the second laser light 2 is applied to the side surface (surface) of the second member 20 at, for example, a position spaced a predetermined distance from the joint surface. Then, the second member 20 is moved in the welding progress direction G along the second joint surface 22. That is, the optical axis of the second laser beam 2 moves along the bonding surface at a position spaced from the bonding surface on the surface of the second member 20, as indicated by _LW2 in FIG. .

  Here, the first molten pool 14 is mainly configured by melting the first member 10 by the first laser beam 1. Such a molten pool is formed across the second member. In other words, the second member 20 is also melted by the first laser beam 1. Further, the second molten pool 24 is mainly configured by melting the second member 20 by the second laser light 2. Such a molten pool is formed across the first member. In other words, the first member 10 is also melted by the second laser beam 2. The first molten pool 14 and the second molten pool 24 are integrated with each other to form a single molten pool, which is solidified to form the welded portion 30. Thereby, the 1st member 10 and the 2nd member 20 can be joined by this welding part 30. FIG. Further, even when a gap is generated between the first member 10 and the second member 20, the first member 10 and the second member are filled while the gap is filled with the first molten pool 14 and the second molten pool 24. 20 can be joined to each other by the welded portion 30. In order to suitably form such a welded portion 30, the optical axes of the first laser beam 1 and the second laser beam 2 so that the first molten pool 14 and the second molten pool 24 can be integrated with each other. It is preferable to run parallel or substantially parallel.

[Shape of welded part]
Here, the first laser beam 1 essentially forms a keyhole-type first molten pool 14 ′ as shown in FIG. 2B, for example. Therefore, the cross section orthogonal to the joint surface (welding progress direction) of the first molten pool 14 ′ may include a shape similar to a sector having a sharp tip T. Here, by irradiating the first laser beam 1 closer to the first bonding surface 12, the bonding surface depth Dw ′ by the first laser beam 1 can be made deeper. Then, by superimposing the second molten pool 24 by the second laser beam 2 on the first molten pool 14 ', the symmetry of the keyhole type welded portion is disturbed, for example, as shown in FIG. The joint surface depth Dw can be easily realized.

  At this time, in the cross-sectional shape of the first molten pool 14 ′ by the first laser beam 1, the melting depth is abruptly decreased as the distance from the tip T is increased. That is, the melting depth is rapidly reduced. Also in the region of the second member 20, the depth suddenly decreases as the distance from the second joint surface 22 increases. Accordingly, the orbit of the first laser beam 1 is shifted to the center side (left side in the drawing) of the first member 10 due to some error, so that the first molten pool 14 ′ as a whole is also the first member than the first joint surface 12. 10 is shifted to the center side. At this time, due to the shape of the first molten pool 14 ′, the joint surface depth Dw ′ formed by the first laser beam 1 can be significantly reduced.

In the welding method disclosed here, the second molten pool by the second laser beam 2 is superimposed on the first molten pool 14 ′ by the first laser beam 1. Thereby, for example, as shown in FIG. 2A, the degree of decrease in the melting depth of the second molten pool 24 of the second member 20 when the second member 20 is separated from the tip portion T can be relaxed. Therefore, even when the trajectory of the first laser beam 1 is shifted to the more central side of the first member 10, a sufficient joint surface depth Dw can be stably secured.
Further, according to the second laser beam 2, the heat conduction type second molten pool 24 is formed, and therefore, a weld defect such as a void is hardly formed in the second member 20. Thereby, the strength of the welded portion 30 in the second member 20 can be maintained high.

The width dimension L ₂ is relatively small perpendicular to the second joint surface 22 of the second member 20, that is, in such case the thin, enters heat by the second laser beam 2 propagates to the second member 20 Further, it can reach the wide surface opposite to the second joint surface 22. For example, in the side surface portion of the second member 20, even the corner portion of the second member 20, which is the end portion on the opposite side to the second bonding surface 22, may be melted. In such a case, further heat input cannot propagate to the outside in the width direction of the second member 20 (on the side opposite to the second joint surface 22), and therefore propagates in the depth direction along the wide surface on the opposite side. Will be. Such heat input increases the joint surface depth Dw in the vicinity of the joint surface 22 and can transfer heat in the depth direction in the vicinity of the opposite surface to change the melt depth of the second molten pool 24. . As a result, for example, as shown in FIG. 2A, the shape of the welded portion 30 in the cross section orthogonal to the second joint surface 22 of the second member 20 can be characteristic. For example, as shown in FIG. 2A, the welded portion 30 is divided by the surfaces including the joint surfaces 12 and 22, and the welded portion located on the first member 10 side is placed on the first welded portion 16 and the second member 20 side. The welded portion that is positioned is referred to as a second welded portion 26. In other words, the melting depth of the second welded portion 26 once gradually becomes shallower as the distance from the second joint surface 22 increases, but the depth increases again as the distance from the second welded portion 26 increases further toward the opposite surface (see FIG. May be inclined downward) and may be convex in the depth direction (convex downward in the figure). By realizing such a characteristic shape of the second welded portion 26, the entire cross-sectional shape of the welded portion 30 includes a keyhole in the first member 10 and a convex portion in the depth direction in the second member 20. Have. That is, the welded portion 30 sandwiches the joint surface between the two convex portions in the direction parallel to the joint surface, and suppresses the first member 10 and the second member 20 from separating. Therefore, the bonding strength in the width direction orthogonal to the bonding surface can be even stronger. Further, even when the trajectory of the first laser beam 1 is shifted to the center side of the first member 10, the joint surface depth Dw of the welded portion 30 can be more stably ensured.

  The characteristic cross-sectional shape of the second welded portion 26 as described above can be suitably formed by appropriately adjusting the amount of heat input to the second member 20 by the second laser light. For example, it is preferable that a sufficient amount of welding heat is input to the second member 20 in a range where the heat conduction type second molten pool is formed, and this heat is transferred along the surface of the second member 20. As shown. The preparation of the input heat amount depends on the material and width (dimension in the direction orthogonal to the joint surface) of the second member 20 and the like. However, as an example, for example, the second member 20 has a width of 1 mm or less ( For example, in the case of a thin member having a thickness of 0.5 mm or less, welding can be performed using the following conditions as a guide.

Specifically, for example, (1) when the output density I ₂ of the second laser light is low brightness of 3.8 × 10 ⁶ W / cm ² or more and less than 5.6 × 10 ⁶ W / cm ² A sufficient amount of heat can be instantaneously supplied from the laser. Therefore, welding can be performed at a relatively high speed, such as a scanning speed of the second laser light of about 20 m / min or more. On the other hand, (2) when the output density I ₂ of the second laser beam is 2.8 × 10 ⁶ W / cm ² or more and less than 3.8 × 10 ⁶ W / cm ^2, which is even lower brightness, the laser beam is sufficient It is difficult to supply a large amount of heat instantaneously. Therefore, in order to surely form the characteristic sectional shape of the second welded portion 26, the scanning speed of the second laser beam is less than 20 m / min (preferably 15 m / min or less, for example, 10 m / min or less). It is preferable that the speed is relatively low. Thereby, even when the output of the second laser beam is low, the characteristic cross-sectional shape of the second welded portion 26 can be reliably formed.

The dimension L ₂ of the second member 20, that is, the thickness of the second member 20 is smaller than the dimension in the direction orthogonal to the bonding surface of the first member 10, that is, the dimension of the wide surface of the first member 10. As long as the effect of the welding method disclosed here is easily obtained, there is no particular limitation. However, voids with a diameter that significantly increases in the keyhole-type welded portion exceeding 0.1 mm or more can affect the strength reduction of the welded portion 30. In particular (in other words, the thickness is thin) dimension L ₂ smaller can result in significant strength reduction for difficult welds secure the welding strength. However, the welding method disclosed herein, in the case of welding such dimensions L ₂ smaller second member 20, preferably to its effect is particularly prominently expressed. Thus, in view of the decrease in the welding strength due to the presence of voids can become significant, in the welding method disclosed herein, the dimension L ₂ is a is 0.1mm or more, for example, 1 mm or less, more In a limited manner, the thin second member 20 having a thickness of 0.5 mm or less, for example, 0.4 mm or less, can be welded.

  In addition, as described above, the first member 10 and the second member 20 are formed on the first welded portion 16 including the keyhole-shaped welded portion formed on the first member 10 and the second member 20. By the second welded portion 26 including the welded portion convex in the depth direction, mechanical (structural) and firm fixation can be realized. In other words, the first member 10 and the second member 20 can be mechanically and firmly bonded to each other according to the form of the welded portion 30 in addition to the chemical bond at the interface accompanying solidification of the welded portion 30. Furthermore, although the influence of welding defects such as voids on the welding strength can be further increased with respect to the thin second member 20, voids are hardly formed on the second member 20. As a result, welding between the first member 10 and the second member 20 can be made higher in strength and more reliable, and a welded structure with higher strength and high reliability is provided. .

  The first laser beam 1 and the second laser beam 2 are preferably controlled so as not to irradiate the bonding surfaces 12 and 22 or the gap between the first member 10 and the second member 20. That is, as described above, the first laser beam 1 and the second laser beam 2 are irradiated on the surface of the first member 10 and the side surface of the second member 20, respectively. Especially the 1st laser beam 1 is irradiated to the surface of the 1st member 10 except the case where it is unavoidable. This is because when the first laser beam 1 having a high output intensity enters between the first member 10 and the second member 20, the first laser beam 1 is reflected through the gap and the first member 10 and the second member. 20 can be easily reached (penetrated) on the back surface side. Then, it is because the component member arrange | positioned at the back surface side of the 1st member 10 and the 2nd member 20 may be damaged by irradiation of the 1st laser beam 1. FIG. Therefore, it is particularly preferable to control the first laser beam 1 so that the first laser beam 1 is irradiated from the end of the first member 10 to the center side having a predetermined interval. Such a predetermined interval can be appropriately determined in consideration of the spot diameters of the first laser beam 1 and the second laser beam 2, mechanical errors due to the laser welding apparatus used, dimensional errors of the material to be welded, and the like. .

In addition, said joining surface depth Dw is preferable because welding strength is raised, so that this becomes large. The joint surface depth Dw can be determined as a target value in accordance with the material and dimensions of the first member 10 and the second member 20 as well as the welding strength required for the welded material by such welding. Although such a suitable value of the joining surface depth Dw is not generally determined, it is generally preferable that the joining surface depth Dw is equal to the dimension L ₂ in the direction orthogonal to the joining surface of the second member 20 or from L ₂ . Is preferably larger. Joint surface depth Dw is the dimension _{L 2} perpendicular to the joint surface of the second member 20, for example, be a Dw ≧ 0.8 × _{L 2} mm, is preferably from Dw ≧ _{L 2,} Furthermore, it is more preferable that Dw ≧ 1.2 × L ₂ .

[effect]
As described above, in the welding method disclosed herein, a sufficient penetration depth is ensured by the first laser beam 1 having a high output density. Then, the shape of the weld metal is controlled so that a predetermined joint surface depth Dw can be stably obtained by the second laser light 2 having a low output density. For this reason, even when there is a slight shift of the welding trajectory or when there is a gap between the first member 10 and the second member 20, the joint surface depth Dw is sufficiently and stably secured. can do. In addition, since heat conduction type melting is performed on the second member 20, generation of voids can be suppressed, and a decrease in welding strength due to the voids can be eliminated.

Further, the welding method disclosed herein, in particular, as the second member 20, more smaller member of the weld surface 22 in the direction perpendicular dimension L ₂ (for example, may be a thin member.) When adopting the In addition, the effect can be exerted. Such small member dimensions L ₂ is, for example, can also obtain sufficient melt by a small second laser power density, nor is essential to ensure the irradiation diameter extensive as in the prior art. Therefore, the laser output can be reduced, and the equipment cost can be kept low. For example, the present According to the inventors, by welding methods disclosed herein, as the second member 20, the thin plate of the following dimension _{L 2} is 0.5mm perpendicular to the bonding surface (e.g., about 0.4 mm) It has been confirmed that this welding can be suitably performed while suppressing the formation of voids.

  In the welded structure formed by such a welding method, for example, the shape of the welded portion in the cross section perpendicular to the joint surface has the following characteristics. In other words, (1) the first member includes a so-called keyhole-type acute-angle welded portion with a high aspect ratio. (2) In addition, the keyhole type first molten pool and the heat conduction type second molten pool are overlapped, and in the weld formed by this, the symmetry of the keyhole type welded portion is increased. Is disturbed, and a deeper joint surface depth Dw is stably realized at the joint surface. Furthermore, (3) the second welded portion formed on the second member may include a shape that slopes downward (a shape that protrudes downward) as the distance from the joint surface increases. Thereby, even when the orbital deviation of the first laser beam 1 occurs, the junction surface depth Dw can be secured more stably.

[Other aspects]
As the laser beam that can be used in the welding method disclosed herein, various types of laser beams can be used depending on the purpose without depending on the laser generation mechanism or the like. For example, various laser beams capable of realizing the above-described keyhole type and heat conduction type melting can be employed depending on the dimensions of the member to be welded. Specific examples of such laser light may include a CO ₂ laser, a YAG laser, a semiconductor laser (also referred to as a laser diode; LD), an LD-excited solid laser, a fiber laser, and the like.

  Moreover, there is no restriction | limiting in particular also about the 1st member and 2nd member which are the object of welding with the welding method disclosed here, The member which consists of various materials generally used for welding can be considered. Examples of such materials include metal materials, ceramic materials, and plastic materials. Especially preferably, it can apply suitably for the welding of the member which consists of metal materials. There is no restriction | limiting in particular also about this metal material, For example, aluminum, aluminum alloy, iron, iron alloy (including various stainless steels), copper, copper alloy etc. are illustrated as a representative thing. The first member and the second member may be made of the same material or different materials.

  As described above, according to the welding method disclosed herein, for example, the first member made of a relatively thick plate and the second member made of a thin plate can be suitably welded while maintaining a high welding strength. it can. Such a welding method can be particularly suitably applied to, for example, applications including welding of thin plate members that require highly reliable and airtight sealing. A typical example of the welding of a thin plate member that requires such reliability and airtightness is canned welding of a case of a storage element. Therefore, the present invention will be further described below by taking as an example a case where the welding method disclosed herein is applied to can welding of a case of a storage element.

EXAMPLES Examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples.
(Example 1)
[Case body welding]
The sealing process of the case 130 of the lithium ion battery 100 was performed according to the procedure described below. FIG. 5 is a partially cutaway front view showing the configuration of such a lithium ion battery, and FIG. 6 is a top view thereof. As shown in these drawings, the case 130 is a rectangular parallelepiped case having a small depth dimension. The upper surface of the case body 132 includes a case main body 132 and a substantially rectangular lid member 134 that is long in the horizontal direction corresponding to the opening. The case main body 132 is made of an aluminum alloy having an alloy number A3003 defined by JIS with a thickness of 0.4 mm. The lid member 134 is made of an aluminum alloy having an alloy number A1050 defined by JIS with a thickness of 1.4 mm. As shown in FIG. 6, the lid member 134 is provided with positive and negative external terminals 142 and 144, an injection hole 146, a safety valve 148, and the like. Since an external force can be applied to these portions during manufacture and use, the lid member 134 is made of a thicker plate material. The case main body 132 is made of a plate material that is slightly thicker and lighter than the lid member 134 but that is thinner.

  Although not shown in the drawing, support portions that can hold the lid member 134 flush with the upper end of the case body 132 are provided on the two short sides of the opening of the case body 132. After attaching the electrode body 120 as a power generation element of the lithium ion battery 100 to the lid member 134 in a predetermined procedure, the electrode body 120 is inserted into the case main body 132 and the lid member 134 is fitted into the opening of the case main body 132. And put the lid on. Next, the battery case 130 was sealed by welding with the lid member 134 as a first member and the case body 132 as a second member by the following welding method 1 or welding method 2.

[Welding method 1]
A high power fiber laser welder is used for welding, and the laser light oscillated from the welder is branched by an optical diffraction element (DOE) lens, so that a high power density laser light (first laser light) and a low power density are obtained. Laser light (second laser light) was generated.
Note that the oscillation conditions of the high power density laser light and the low power density laser light in this embodiment are five as shown in Table 1 below. Then, by combining the oscillation conditions of the first laser beam and the second laser beam, welding was performed under a total of 25 welding conditions.

First, as described above, the lid member as the first member was fitted into the case main body as the second member, and the respective joint surfaces were opposed to each other. Then, set the end of the surface of the lid member from the (joint surface) 0.15 mm only center side and the weld line L _W1, continuous the high power density laser beam along such weld line L _W1 (CW) irradiation did. At the same time, the upper surface of the case body, that is, the upper end surface of the side member of the case body is used as the laser irradiation surface, and the outer side of the case body is welded by 0.15 mm from the joint surface (that is, the inner surface of the case body). _LW2 was set, and the low power density laser beam was continuously (CW) welded along the weld line _LW2 . Each laser beam was made to run simultaneously at a speed of 24 m / min. Thus, on the upper surface of the case of the lithium ion secondary battery, the lid member and the case main body were sealed by welding around the periphery (around 240 mm).

[Welding method 2]
A high-power fiber laser welder is used for welding, and the first high-power density laser beam (first laser beam) is split by dividing the laser beam oscillated from the welder by an optical diffraction element (DOE) lens. Second high power density laser light (second laser light) and low power density laser light (third laser light) were generated.
The laser light oscillation conditions in this embodiment are as follows.

<First laser beam>
Spot diameter: φ0.04mm,
Laser output: 800W
Laser power density: 6.4 × 10 ⁷ W / cm ²

<Second laser beam>
Spot diameter: φ0.04mm,
Laser output: 540W
Laser power density: 4.3 × 10 ⁷ W / cm ²

<Third laser beam>
Spot diameter: φ0.5mm,
Laser output: 1000W
Laser power density: 5.1 × 10 ⁵ W / cm ²

First, as described above, the lid member as the first member 10 was fitted into the case main body as the second member 20, and the respective joining surfaces 12 and 22 were opposed to each other. Then, the center side by 0.15 mm from the end portion (joint surface 12) of the surface of the lid member is set as a weld line _LW1 , and the first laser light (first high power density) along the weld line _LW1 is set. Laser light) was continuously (CW) irradiated. The upper surface of the case body, that is, the upper end surface of the side member of the case body is a laser irradiation surface, and the outer side of the case body is welded line L _W2 by 0.15 mm from the joint surface (that is, the inner surface of the case body) The second laser beam (second high-power density laser beam) was continuously (CW) welded along the weld line _LW2 . Furthermore, the joint surface between the case body and the lid member was set as a weld line, and the third laser beam (low power density laser beam) was continuously (CW) welded along the weld line. In addition, when the clearance gap has arisen between the case main body and the cover member, the middle of both was made into the welding line. In addition, the respective laser beams were aligned in the direction orthogonal to the traveling direction, and were allowed to run at a speed of 24 m / min. Thus, on the upper surface of the case of the lithium ion secondary battery, the lid member and the case main body were sealed by welding around the periphery (around 240 mm).

[Evaluation of welding quality]
The welded part of the case sealed by welding method 1 (25 types) and welding method 2 (1 type) was evaluated for the following evaluation items [1] to [6]. And the quality as the whole welded part was evaluated from those results.

[1] to [3] Welding defect Nondestructive X-ray inspection apparatus (Corporation Co., Ltd.) determines whether or not welding defects (weld cracks and voids) have occurred in the welded portion of the case sealed by welding method 1 and welding method 2. Investigation was carried out using a microfocus X-ray transmission device SMX-225CT-F manufactured by Shimadzu Corporation.
FIG. 3 shows a cross-sectional image along the welding direction, showing the state of the weld formed on the case body by (1) welding method 1 (welding conditions; 1c × 2c) and (2) welding method 2. . Further, for the welding method 2, a cross-sectional observation view orthogonal to the welding progress direction showing a relatively large void observed in the case main body is shown in FIG. In FIG. 4, the portion surrounded by ○ is a void.
Thus, the X-ray fluoroscopic image of the cross section of the welded portion was subjected to image processing, and the presence or absence of weld cracks and the state of void generation in the case main body portion were examined.
The results are shown in the column of evaluation item [1] in Table 2 below regarding the presence or absence of weld cracks. In addition, about the number of voids, when the void with the diameter of 0.1 mm or more considered that the strength reduction could be brought about was confirmed, the number was counted. From the results, the number of voids per 1 mm of welding distance is calculated, and the number of voids per battery (case) is calculated in the column of evaluation item [2] in Table 2, and the evaluation item [3] in Table 2 is calculated. Shown in the column.

[4] to [5] Shape of welded portion A lid member as a first member based on the welded cross-sectional images of the respective examples obtained by cutting several portions of the welded portion of the case sealed as described above and obtained by cross-sectional observation. And the melted shape with the case main body as the second member was observed.
As a result, when the penetration depth of the lid member was shallow (that is, the keyhole was not formed), “shallow”, when penetrated through the lid member, “penetration”, and when the penetration shape was good, “○” is shown in the evaluation item [4] column of Table 2.
In addition, regarding the penetration shape of the case body, when the penetration depth is deep and voids are generated, it is `` void '', and it has a good penetration shape and has a convex part in the depth direction near the surface opposite to the joint surface. The case where the protrusion was not formed was “no protrusion”, and the case where the protrusion was formed with a good penetration shape was indicated as “◯”.

[6] Laser Output Density Ratio The output density ratio (I ₁ / I ₂ ) between the first laser beam and the second laser beam used in the welding methods 1 and 2 was calculated, and the evaluation item [6] in Table 2 It is shown in the column.
[Comprehensive] Comprehensive evaluation From the results of the above evaluation items [1] to [6], it was comprehensively evaluated whether or not the quality of the welded portion formed by each welding condition was good. As a result, the evaluation items in Table 2 are set as “◯” when judged good, “◎” when judged particularly good, and “×” when judged not good. It is shown in the “General” column. In this comprehensive evaluation, symbols ◯ and ◎ mean that the requirements for the technology disclosed herein are satisfied.

  As shown in the evaluation item [1] in Table 2, no superficial weld defects such as weld cracks were found in the welded portion by either welding method 1 or welding method 2. Therefore, it has been confirmed that the welding method 1 and the welding method 2 can be welded to a certain degree.

  Therefore, when further detailed examination is performed, in the present embodiment, the laser output density is weak in the present embodiment when the irradiation condition of the first laser irradiated to the lid member as the first member is 1a. It was found that a hole-type weld was not formed. It was found that if the keyhole type welded portion is not formed on the first member, the joint surface depth Dw becomes extremely shallow, and sufficient welding strength cannot be obtained. Conversely, it was found that when the irradiation condition of the first laser is 1e, the laser output density is too strong and the keyhole penetrates the lid member. And when the irradiation conditions of the 1st laser were 1b-1d, it was confirmed that the welding which formed the favorable keyhole is possible. In this case, it was also found that the junction surface depth Dw can be sufficiently secured.

  Moreover, when the irradiation condition of the 2nd laser irradiated to the case main body which is a 2nd member is 2a, the laser output density was enough and it was confirmed that the heat conduction type welding part is formed. However, a welded shape that protrudes downward is not formed outside the cross section of the case body. And when the irradiation conditions of the 2nd laser were 2b-2d, it turned out that the characteristic welding shape which becomes convex downward is formed in the cross section outer side of a case main body. In this respect, when the irradiation condition of the first laser is 1b to 1d and the irradiation condition of the second laser is 2a, the overall evaluation is “◯”, and similarly when the irradiation condition of the second laser is 2b to 2d The overall evaluation was “◎”. However, it was found that when the irradiation condition of the second laser was 2e, the laser output density was too strong, and a welded portion such as a keyhole was formed, causing many voids.

Therefore, in the present embodiment, it has been found that the irradiation condition of the first laser is preferably about 1b to 1d whose output density is higher than 1a and weaker than 1e. Further, it has been found that the irradiation condition of the second laser is preferably about 2a to 2d, more preferably about 2b to 2d, whose output density is weaker than 2e. Thus, when welding was performed according to the welding method 1 disclosed herein, it was confirmed that welding could be performed without generating a void having a diameter of 0.1 mm or more on a thinner case body.
On the other hand, when welding is performed by the conventional welding method 2, even if the first laser irradiation condition suitable in the welding method 1 is 1c, the conditions of the second and third lasers are not appropriate, and the thin laser beam is thin. It was confirmed that voids of 0.1 mm or more frequently occurred in the case body. Generation | occurrence | production of this big void in a thin member means that a case main body can be damaged with this void when unexpected external force is added to a welding part. That is, the welding strength was lowered, resulting in the deterioration of the welding quality and the reliability of the welded portion.

(Example 2)
The oscillation conditions of the first laser beam and the second laser beam were set to three as shown in Table 3 below. A total of nine welding conditions were obtained by combining the oscillation conditions of the first laser beam and the second laser beam. The first and second laser beams were allowed to run at a speed of 9 m / min, and other conditions were the same as in the welding method 1 of Example 1 above, and sealing welding of the lithium ion battery case was performed.
Moreover, the welded part was evaluated about evaluation item [1]-[6] similarly to the said Example 1, and the quality evaluation of the whole welded part was performed. The results are shown in Table 4.

As shown in Table 3, in the present embodiment, the output densities of the first laser light and the second laser light are set in a relatively lower range than in Example 1. However, even with such a relatively low power density, the case body has a good downward convexity by reducing the laser scanning speed and ensuring sufficient heat input to the welded member. It was confirmed that a weld could be formed. That is, the keyhole type welded portion is formed by chain reflection of laser light on the melted portion wall surface. Therefore, it is understood that the output density of the first laser beam may be low as long as a predetermined laser output density that can form a keyhole-type weld is secured. On the other hand, when the power density of the second laser beam is low, a general heat conduction type weld is formed in the heat conduction type weld. Here, when the output density of the second laser beam is low by applying a sufficiently large amount of heat according to the material and shape of the case body (dimension in the direction orthogonal to the joint surface, plate thickness), etc. In addition, it was confirmed that a well-protruding weld having a downward convexity can be formed. Specifically, for example, in Example 1 described above, even under the output condition 2a (I ₂ : 3.5 × 10 ⁶ W / cm ² ), the laser scanning speed is increased to 24 m / min. The amount of heat sufficient to form the welded portion could not be input to the case body. On the other hand, in Example 2, since the laser scanning speed was slowed down to 9 m / min, the output conditions 2f to 2h (I ₂ : 2.8 to 3.8 × 10 ⁶ W / cm ² ) are sufficient. It was shown that the amount of heat can be input to the case body and a convex weld can be formed below.

  In the thermal spraying method according to the present embodiment, it has been found that higher quality welding can be performed by variously changing the output conditions of the first laser beam and the second laser beam. For example, it can be seen that the shape of the welded portion can be suitably adjusted within the range of the output density described above by changing the scanning speed according to the welding mode of the first member and the second member, the shape of the weld line, and the like. . Then, a good keyhole type welded part is formed on the first member, and a good heat conduction type welded part is formed on the second member. It was also confirmed that higher strength and higher quality welding could be realized.

  In the above-described embodiment, the case main body and the lid member of the storage element are employed as the first welding member and the second welding member, and an example of welding them is shown. However, the use of the welding method proposed here is not limited to the welding of the case of the electric storage element, and can be used for welding of various welding members. Moreover, in embodiment mentioned above, the member which consists of aluminum alloys was used as a 1st welding member and a 2nd welding member. However, the welding method disclosed here can be used for welding various materials other than aluminum alloys. Examples of the material constituting the welding member include an iron alloy typified by a SUS material, other metal materials including pure metals and alloys, inorganic materials such as ceramics, and organic materials such as plastics. Therefore, the welding method disclosed here can be preferably used for butt welding of welding members made of various materials. In addition, it can apply especially preferably to welding of the welding member of the form where thickness was made thinner like the case main body in the case of the said electrical storage element.

DESCRIPTION OF SYMBOLS 1 1st laser beam 2 2nd laser beam 10 1st member 12 1st joining surface 14, 14 '1st molten pool 16, 16' 1st welding part 20 2nd member 22 2nd joining surface 24 2nd molten pool 26 Second weld 30 Weld

Claims (8)

A method of laser welding a plate-like first member and a plate-like second member,
The first member and the second member are arranged so that the wide surfaces of the first member and the second member are orthogonal to each other, and the side surface of the second member is substantially flush with the wide surface of the first member. The side surface portion of the first member and the wide surface end portion of the second member are abutted with each other. Here, the side surface portion of the first member facing the second member is defined as a first joint surface, and the first member is When the wide surface end portion of the second member facing each other is the second joint surface, the dimension of the first member in the direction perpendicular to the first joint surface is perpendicular to the second joint surface of the second member. Larger than the dimension in the direction of
A first laser beam having an intensity capable of generating a keyhole is irradiated along the first joint surface on the wide surface of the first member to form a first molten pool that is melted by the first laser beam. Wherein the first molten pool is formed across the second member; and the second laser light having a lower intensity than the second laser beam capable of generating a keyhole is formed on the side surface of the second member. Irradiating along the joining surface to form a second molten pool melted by the second laser beam, wherein the second molten pool is formed across the first member;
Including
The first molten pool and the second molten pool are integrated with each other to form a molten pool, and the first member and the second member are welded by a weld portion formed by solidifying the molten pool. Welding method. The welding method according to claim 1, wherein an output density I ₁ of the first laser light is 5.6 × 10 ⁶ W / cm ² ≦ I ₁ <1.1 × 10 ⁸ W / cm ² . 3. The welding method according to claim 1, wherein an output density I ₂ of the second laser light is 2.8 × 10 ⁶ W / cm ² ≦ I ₂ <5.6 × 10 ⁶ W / cm ² . When the output density I ₂ of the second laser light is 3.8 × 10 ⁶ W / cm ² or more and less than 5.6 × 10 ⁶ W / cm ² ,
The welding method according to claim 3, wherein a scanning speed of the first laser beam and the second laser beam is set to 20 m / min or more. When the output density I ₂ of the second laser light is 2.8 × 10 ⁶ W / cm ² or more and less than 3.8 × 10 ⁶ W / cm ² ,
The welding method according to claim 3, wherein a scanning speed of the first laser beam and the second laser beam is less than 20 m / min. Said first and output densities I ₁ of the laser beam and the power density I ₂ of the second laser light, satisfy I ₁ ≧ 5 × I _2, the method of welding according to claim 1 It said first and irradiation diameter d ₁ of the laser beam and the irradiation diameter d ₂ of the second laser beam, d 1 satisfy _{<d 2,} welding method according to any one of claims 1-6. Wherein the depth Dw of the welded portion of the joint surface of the first or section orthogonal to the second mating surface, the dimension L ₂ perpendicular to the second joint surface of said second member, Dw ≧ L The welding method according to any one of claims 1 to 7, which satisfies ₂ .