Laser welding method

Abstract

To provide a laser weld method capable of suppressing failure of joining.SOLUTION: A laser weld method is for radiating laser light, for welding a second member to a first member. The laser weld method comprises a preparing step and a weld step. In the preparing step, the second member is welded temporarily to the first member, thereby preparing a temporary weld member having a plurality of connection parts. In the weld step, laser light is radiated to the temporary weld member, for welding the second member to the first member. In the weld step, the first step is executed and then the second step is executed. In the first step, the laser light is radiated over a range from a prescribed position between a first connection part being one of the plurality of connection parts, and a second connection part adjacent to the first connection part, to the second connection part. In the second step, the laser light is radiated to the prescribed position from the first connection part.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] Embodiments of the present invention relate to a laser welding method.

Background Art

[0002] There is a laser welding method in which a plurality of members are welded by irradiating laser light. In the laser welding method, for example, after performing tack welding to form a connection part by welding a part of the welding part of the member, main welding for welding the entire welding part is performed to join the plurality of members. In the main welding, for example, laser light is continuously irradiated from one end side to the other end side of the welding part to weld the entire welding part.

[0003] In such a laser welding method, a gap may occur between a plurality of members after tack welding. In such a state with a gap, when laser light is continuously irradiated from the connection part on one end side to the connection part on the other end side in the main welding, the deflection of the member due to the gap becomes large around the connection part on the other end side, and a joining defect may occur.

Prior Art Documents

Non-Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide a laser welding method capable of suppressing joining defects.

Means for Solving the Problems

[0006] The laser welding method according to the embodiment is a method of welding a second member to a first member by irradiating laser light. The laser welding method according to the embodiment includes a preparation step and a welding step. In the preparation step, the second member is temporarily welded to the first member to prepare a temporarily welded member having a plurality of connection portions. In the welding step, the second member is welded to the first member by irradiating the temporarily welded member with laser light. In the welding step, a first step is performed, and then a second step is performed. In the first step, laser light is irradiated from a predetermined position between a first connection portion, which is one of the plurality of connection portions, and a second connection portion adjacent to the first connection portion to the second connection portion. In the second step, laser light is irradiated from the first connection portion to the predetermined position.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0008] Hereinafter, each embodiment of the present invention will be described with reference to the drawings. The drawings are schematic or conceptual, and the relationships between the thicknesses and widths of the respective parts, the size ratios between the parts, etc. are not necessarily the same as those in reality. Even when representing the same part, the dimensions and ratios may be represented differently in the drawings. In the present specification and each figure, the same reference numerals are assigned to elements similar to those described above with respect to the previously presented figures, and detailed descriptions are appropriately omitted.

[0009] Figures 1(a) and 1(b) are perspective views showing a laser welding method according to an embodiment. Figures 2(a) and 2(b) are perspective views showing a laser welding method according to an embodiment. Figure 3 is a plan view showing a welded portion in a laser welding method according to an embodiment. As shown in Figures 1(a), 1(b), 2(a), and 2(b), the laser welding method according to the embodiment includes a preparation step, a welding step, and a flattening step.

[0010] In the laser welding method according to the embodiment, first, a preparation step is performed. In the preparation step, first, as shown in Figure 1(a), a first member 10 and a second member 20 to be welded are prepared.

[0011] The first member 10 and the second member 20 include, for example, at least any one of aluminum, magnesium, and copper. The material of the second member 20 may be the same as or different from the material of the first member 10.

[0012] The first member 10 is, for example, a housing having an opening 16. The first member 10 has, for example, a substantially rectangular box-shaped structure with an open top. The first member 10 has, for example, a first side surface portion 11, a second side surface portion 12, a third side surface portion 13, a fourth side surface portion 14, and a bottom surface portion 15. The bottom surface portion 15 is located at the bottom of the first member 10. The first side surface portion 11, the second side surface portion 12, the third side surface portion 13, and the fourth side surface portion 14 are each a standing surface portion that rises upward from the bottom surface portion 15. The first side surface portion 11 and the third side surface portion 13 face each other. The second side surface portion 12 and the fourth side surface portion 14 face each other. The first member 10 has, for example, an opening 16 formed by the upper ends of the first side surface portion 11, the second side surface portion 12, the third side surface portion 13, and the fourth side surface portion 14.

[0013] The second member 20 is, for example, a lid that closes the opening 16 of the first member 10. The second member 20 has, for example, a flat plate-like structure. As shown in FIG. 3, the second member 20 has a welding portion 25. In FIG. 3, the welding portion 25 is shown hatched. The welding portion 25 is a portion that is welded (joined) to the first member 10 in the welding process. The welding portion 25 is, for example, a portion irradiated with a laser beam 220 in the welding process. The welding portion 25 is provided at a portion of the second member 20 that overlaps the first member 10. In this example, the welding portion 25 is provided at a position where the opening 16 and the second member 20 (lid) overlap.

[0014] Here, the case where the first member 10 is a housing and the second member 20 is a lid is described as an example, but the shapes of the first member 10 and the second member 20 are not limited to these. The shapes of the first member 10 and the second member 20 may be any shapes that can be welded by laser irradiation. The first member 10 and the second member 20 may both be, for example, flat plate-like.

[0015] In the preparation process, next, as shown in FIG. 1(b), a temporarily welded member 50 in which a second member 20 is temporarily welded to a first member 10 is prepared. The temporarily welded member 50 has a structure in which the second member 20 is welded to the first member 10 via a plurality of connecting portions 30 provided along the welding portion 25. That is, in the temporarily welded member 50, the first member 10 and the second member 20 are welded (joined) via a plurality of connecting portions 30.

[0016] The "temporary welding" mentioned here indicates that it is welding performed before the welding (main welding) in the subsequent welding process. In temporary welding, for example, in a state where the second member 20 is overlapped with the first member 10, the laser beam 210 is irradiated to a plurality of locations on the second member 20 along the welding portion 25, so that the second member 20 is melted at the plurality of locations irradiated with the laser beam 210 to form a plurality of connecting portions 30.

[0017] When the first member 10 is a housing having an opening 16 and the second member 20 is a lid, for example, in the preparation process, it is preferable to prepare a temporarily welded member in which the second member 20 (lid) is temporarily welded to the entire circumference of the opening 16 of the first member 10 (housing) via a plurality of connecting portions 30. In this case, for example, in the preparation process, by irradiating the laser beam 210 at equal intervals around the entire circumference of the opening 16 of the first member 10 (housing), the connecting portions 30 can be provided at equal intervals around the entire circumference of the opening 16 of the first member 10 (housing). Note that the intervals between the plurality of connecting portions 30 do not have to be equal intervals.

[0018] The laser device that irradiates the laser beam 210 used for the temporary welding in the preparation process may be, for example, a pulse laser that oscillates with a constant repetition frequency (pulse width) of a pulsed output, or a CW (Continuous Wave) laser that continuously oscillates with a constant output. In the case of a pulse laser, the pulse width is, for example, several femtoseconds, several picoseconds, or several milliseconds. The wavelength of the laser beam 210 is, for example, 300 nm or more and 5000 nm or less.

[0019] In the laser welding method according to the embodiment, next, a welding process is performed. The welding process is performed after the preparation process. In the welding process, as shown in Fig. 2(a), the second member 20 is welded to the first member 10 by irradiating the laser beam 220 along the welding portion 25 with respect to the temporary welding member 50. As a result, for example, as shown in Fig. 2(b), a sealed member 100 in which the opening 16 of the first member 10 (housing) is sealed by the second member 20 (lid) is manufactured. The welding process will be described later.

[0020] The laser device that irradiates the laser beam 220 used in the welding process may be, for example, a pulsed laser or a CW laser. In the case of a pulsed laser, the pulse width is, for example, several femtoseconds or several picoseconds. The wavelength of the laser beam 220 is, for example, 300 nm or more and 1070 nm or less. The laser beam 220 used in the welding process may be the same as or different from the laser beam 210 used in the temporary welding in the preparation process.

[0021] In the laser welding method according to the embodiment, next, a flattening process is performed. The flattening process is performed after the welding process. In the flattening process, as shown in Fig. 2(b), the surface of the welding portion 25 after the welding process is flattened by irradiating the laser beam 230 along the welding portion 25 of the sealed member 100. The flattening process is performed as necessary and can be omitted.

[0022] The laser device that irradiates the laser beam 230 used in the flattening process may be, for example, a pulsed laser or a CW laser. In the case of a pulsed laser, the pulse width is, for example, several femtoseconds or several picoseconds. The wavelength of the laser beam 230 is, for example, 300 nm or more and 1070 nm or less. The laser beam 230 used in the flattening process may be the same as or different from the laser beam 210 used in the temporary welding in the preparation process. The laser beam 230 used in the flattening process may be the same as or different from the laser beam 220 used in the welding process.

[0023] Hereinafter, the welding process will be described in more detail. Figure 4 is a plan view showing a welding process of the laser welding method according to the embodiment. Figure 4 is an enlarged view of the region R1 shown in FIG. 3. As shown in FIG. 4, in the welding process, the space between two adjacent connecting portions 30 is welded in two steps, i.e., the first step and the second step. In FIG. 4, the white arrows PR1 and PR3 indicate the first step, and the white arrows PR2 and PR4 indicate the second step.

[0024] Of the plurality of connecting portions 30, two adjacent ones are defined as a first connecting portion 31 and a second connecting portion 32, respectively. The first connecting portion 31a and the second connecting portion 32a are adjacent to each other. The first connecting portion 31b and the second connecting portion 32b are adjacent to each other. The second connecting portion 32a also serves as the first connecting portion 31b.

[0025] As represented by PR1 and PR3 in FIG. 4, in the first step, the laser beam 220 is irradiated from a predetermined position 35 between the first connecting portion 31 and the second connecting portion 32 to the second connecting portion 32. In the first step, for example, the laser beam 220 is continuously irradiated from the predetermined position 35 toward the second connecting portion 32. In the first step, the laser beam 220 is irradiated from the predetermined position 35 to at least a position overlapping the second connecting portion 32. In the first step, for example, it is preferable to irradiate the laser beam 220 from the predetermined position 35 to a position beyond the second connecting portion 32 (i.e., a position on the side opposite to the predetermined position 35 with respect to the second connecting portion 32).

[0026] As represented by PR2 and PR4 in FIG. 4, in the second step, the laser beam 220 is irradiated from the first connection part 31 to a predetermined position 35. In the second step, for example, the laser beam 220 is continuously irradiated from the first connection part 31 toward the predetermined position 35. In the second step, the laser beam 220 is irradiated at least from a position overlapping with the first connection part 31 to the predetermined position 35. In the second step, it is preferable to irradiate the laser beam 220 from a position not exceeding the first connection part 31 (i.e., a position on the opposite side of the predetermined position 35 with respect to the first connection part 31) to a position exceeding the predetermined position 35 (i.e., a position on the opposite side of the first connection part 31 with respect to the predetermined position 35). A part of the region irradiated with the laser beam 220 in the second step overlaps, for example, a part of the region irradiated with the laser beam 220 in the first step.

[0027] The distance L1 between the first connection part 31 and the second connection part 32 is, for example, 2 mm or more and 10 mm or less. The predetermined position 35 is located, for example, between the first intermediate point 41 and the second intermediate point 42. The first intermediate point 41 is located in the middle of the first connection part 31 and the second connection part 32. That is, the distance L2 between the first connection part 31 and the first intermediate point 41 is equal to the distance L3 between the first intermediate point 41 and the second connection part 32. The distance L2 and the distance L3 are half of the distance L1. The second intermediate point 42 is located in the middle of the first intermediate point 41 and the second connection part 32. That is, the distance L4 between the first intermediate point 41 and the second intermediate point 42 is equal to the distance L5 between the second intermediate point 42 and the second connection part 32. The distance L4 and the distance L5 are half of the distance L3.

[0028] In the welding process, the first step is performed, and then the second step is performed. In the welding process, at least the irradiation of the laser beam 220 at the position indicated by PR1 (the first step) is performed before the irradiation of the laser beam 220 at the position indicated by PR2 (the second step). In the welding process, at least the irradiation of the laser beam 220 at the position indicated by PR3 (the first step) is performed before the irradiation of the laser beam 220 at the position indicated by PR4 (the second step).

[0029] In the welding process, for example, the laser beam 220 is irradiated at the position indicated by PR1 (first step), then the laser beam 220 is irradiated at the position indicated by PR2 (second step), then the laser beam 220 is irradiated at the position indicated by PR3 (first step), and then the laser beam 220 is irradiated at the position indicated by PR4 (second step). That is, in the welding process, for example, the first step and the second step are alternately repeated.

[0030] Alternatively, in the welding process, for example, the laser beam 220 is irradiated at the position indicated by PR1 (first step), then the laser beam 220 is irradiated at the position indicated by PR3 (first step), then the laser beam 220 is irradiated at the position indicated by PR2 (second step), and then the laser beam 220 is irradiated at the position indicated by PR4 (second step). That is, in the welding process, for example, the first step may be performed collectively and then the second step may be performed collectively.

[0031] When the first member 10 is a housing having the opening 16 and the second member 20 is a lid, for example, in the welding process, between all the plurality of connection portions 30 provided on the entire circumference of the opening 16, by repeating the first step and the second step, it is preferable to weld the second member 20 (lid) to the entire circumference of the opening 16 of the first member 10. Also in this case, the first step and the second step may be alternately repeated, or the first step may be performed collectively and then the second step may be performed collectively.

[0032] Hereinafter, the effects of the laser welding method according to the embodiment will be described. FIGS. 5(a) and 5(b) are cross-sectional views showing the welding process of the laser welding method according to the embodiment. FIGS. 6(a) and 6(b) are cross-sectional views showing the welding process of the laser welding method according to the embodiment. FIGS. 5(a), 5(b), 6(a), and 6(b) are cross-sectional views taken along the line A1 - A2 shown in FIG. 4. FIG. 5(a) shows the irradiation of the laser beam 220 at the position indicated by PR1 in FIG. 4 (first step). FIG. 5(b) shows the irradiation of the laser beam 220 at the position indicated by PR2 in FIG. 4 (second step). FIG. 6(a) shows the irradiation of the laser beam 220 at the position indicated by PR3 in FIG. 4 (first step). FIG. 6(b) shows the irradiation of the laser beam 220 at the position indicated by PR4 in FIG. 4 (second step).

[0033] As shown in FIG. 5(a), in the temporary welding member 50, a gap G may occur between the first member 10 and the second member 20. The gap G is, for example, 10 μm or more and 50 μm or less.

[0034] In such a case, for example, in the welding process (main welding), when the laser beam 220 is continuously irradiated from the first connection portion 31a toward the second connection portion 32a, the deflection of the second member 20 due to the gap G becomes large around the second connection portion 32a, and a joining defect may occur. Further, such a joining defect may occur around the second connection portion 32 over the entire area of the welded portion 25.

[0035] On the other hand, in the laser welding method according to the embodiment, first, as shown in FIG. 5(a), a first step of irradiating the laser beam 220 from a predetermined position 35a between the first connection portion 31a and the second connection portion 32a to the second connection portion 32a is performed. Then, after the first step, as shown in FIG. 5(b), a second step of irradiating the laser beam 220 from the first connection portion 31a to the predetermined position 35a is performed.

[0036] In this way, by performing the irradiation of the laser beam 220 from the predetermined position 35a to the second connection portion 32a (first step) before the irradiation of the laser beam 220 from the first connection portion 31a to the predetermined position 35a (second step), it is possible to suppress an increase in the deflection of the second member 20 due to the gap G around the second connection portion 32a. Therefore, joining defects can be suppressed.

[0037] Further, in the laser welding method according to the embodiment, as shown in FIG. 6(a), a first step of irradiating the laser beam 220 from a predetermined position 35b between the first connection portion 31b and the second connection portion 32b to the second connection portion 32b is performed. Then, after the first step, as shown in FIG. 6(b), a second step of irradiating the laser beam 220 from the first connection portion 31b to the predetermined position 35b is performed.

[0038] By repeating the first step and the second step in this way, it is possible to suppress an increase in the deflection of the second member 20 due to the gap G around all the second connection portions 32. Therefore, joint failure can be suppressed over the entire welding portion 25.

[0039] Further, since the predetermined position 35 is located between the first intermediate point 41 (see FIG. 4) and the second intermediate point 42 (see FIG. 4), the length of irradiating the laser beam 220 in the first step does not become too long. Therefore, it is possible to suppress an increase in the deflection of the second member 20 due to the gap G around the second connection portion 32a when performing the first step. Therefore, joint failure can be suppressed.

[0040] Also, when the welding process is divided into the first step and the second step, unevenness may be formed in the welding portion 25 by the welding process. Therefore, in the laser welding method according to the embodiment, by performing a flattening process after the welding process, even if unevenness is formed in the welding portion 25 by the welding process, the surface of the welding portion 25 after the welding process can be flattened by the flattening process.

[0041] Further, when the first member 10 is a housing having an opening 16 and the second member 20 is a lid, in the preparation step, a temporarily welded member 50 in which the second member 20 (lid) is temporarily welded to the entire circumference of the opening 16 of the first member 10 (housing) via a plurality of connection portions 30 is prepared. In the welding step, the first step and the second step are repeated between all the plurality of connection portions 30 provided on the entire circumference of the opening 16, and the second member 20 (lid) is welded to the entire circumference of the opening 16, so that a sealed member 100 in which the opening 16 of the first member 10 is easily sealed with the second member 20 can be manufactured.

[0042] As described above, according to the embodiment, a laser welding method capable of suppressing joint failure is provided.

[0043] The laser welding method according to the embodiment is suitably used, for example, in the manufacture of devices such as secondary batteries, heat exchangers such as heat sinks, gas generators used in airbags, etc., and rotors for air conditioners.

[0044] As mentioned above, embodiments of the present invention have been illustrated. However, these embodiments are presented as examples and are not intended to limit the scope of the invention. This novel embodiment can be implemented in various other forms, and various omissions, replacements, changes, etc. can be made without departing from the gist of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0045] 10 First member 11 to 14 First to fourth side faces 15 Bottom face 16 Opening 20 Second member 25 Welded portion 30 Connection portion 31, 31a, 31b First connection portion 32, 32a, 32b Second connection portion 35, 35a, 35b Predetermined position 41 First intermediate point 42 Second intermediate point 50 Temporary welding member 100 Sealing member 210, 220, 230 Laser beam

Claims

1. A method for welding a second member to a first member by irradiating a laser beam, comprising: A preparation step of temporarily welding the second member to the first member to prepare a temporarily welded member having a plurality of connection portions; A welding step of welding the second member to the first member by irradiating the temporarily welded member with a laser beam; and in the welding step, performing a first step of irradiating a laser beam from a predetermined position between a first connection portion, which is one of the plurality of connection portions, and a second connection portion adjacent to the first connection portion to the second connection portion; After the first step, a second step of irradiating a laser beam from the first connection portion to the predetermined position is performed. A laser welding method.

2. The laser welding method according to claim 1, wherein the predetermined position is located between a first intermediate point located in the middle of the first connection portion and the second connection portion and a second intermediate point located in the middle of the first intermediate point and the second connection portion.

3. In the preparation step, in a state where the second member is stacked on the first member, by irradiating a plurality of locations of the second member with a laser beam, the second member is melted at the plurality of locations to form the plurality of connection portions, and the temporarily welded member is prepared. The laser welding method according to claim 1 or 2.

4. Further comprising a flattening step that is performed after the welding step and that flattens the surface of the portion welded in the welding step by irradiating a laser beam. The laser welding method according to any one of claims 1 to 3.

5. The first member is a housing having an opening, The second member is a lid that closes the opening, The housing and the lid are welded at a position where the opening and the lid overlap. The laser welding method according to any one of claims 1 to 4.

6. In the preparation step, a temporarily welded member in which the lid is temporarily welded to the entire circumference of the opening via the plurality of connection portions is prepared. In the welding step, the lid is welded to the entire circumference of the opening by repeating the first step and the second step between all of the plurality of connection portions provided on the entire circumference of the opening. The laser welding method according to claim 5.

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