Welding method and welded structure

Abstract

To provide a welding method that is applicable to a small part of an allowance of a hit point and can improve detachment strength of an object to be welded relative to a configuration of welding a plurality of objects to be welded with a single nugget, and to provide a weld structure.SOLUTION: A welding method forms a plurality of nuggets 22 and 24 by jointing welding objects 12 and 14 with laser welding. The plurality of nuggets 22 and 24 are formed in the plurality of welding objects 12 and 14 so as to be aligned at distance p between central axes along a virtual straight line or a virtual opening curve. The adjacent nuggets 22 and 24 are aligned at a pitch p. When a diameter of the nugget 22 of the welding objects 12 and 14 is denoted as d, a relationship 1.0<p / d≤1.6 is satisfied.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a welding method and a welded structure. [Background technology]

[0002] Patent Document 1 discloses a welded structure having a plurality of welded objects joined together by welds formed by laser welding. The welds have a plurality of nuggets formed along an imaginary closed curve on the welded objects. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-205323 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a welding method in which multiple nuggets arranged along a virtual closed curve are formed by laser welding, the weld bearing surface is larger than that in a method in which multiple nuggets arranged along a virtual straight line or a virtual open curve are formed by laser welding, and therefore this welding method cannot be applied when welding multiple objects with small welding spot allowances.

[0005] In consideration of the above-mentioned facts, the present invention aims to provide a welding method and welded structure that can be applied to areas with small welding spot widths and can improve the peel strength of the welded objects compared to a configuration in which multiple welded objects are welded with a single nugget. [Means for solving the problem]

[0006] The welding method according to the invention described in claim 1 is a method for joining a plurality of welding objects by laser welding, each of which has a welding spot length set to be equal to or larger than the diameter d of the nugget and equal to or smaller than 10 mm. Approximately circularA welding method for forming nuggets, wherein the adjacent nuggets are formed on the plurality of objects to be welded so as to be arranged at a distance p between central axes along a virtual straight line or a virtual open curve, and 1.0 < p / d ≤ 1.6 is satisfied for the diameter d of the nuggets of the plurality of objects to be welded.

[0007] In the welding method according to the invention described in claim 1, the nuggets are formed such that the ratio p / d is greater than 1.0. That is, the distance p between the central axes of adjacent nuggets is longer than the diameter d of the nuggets. For this reason, since the centers of the welding dots do not approach each other, it is possible to suppress the connection of solidification cracks in metals with large solidification shrinkage. As a result, it is possible to suppress welding defects such as an increased risk of cracking during fatigue or a poor appearance compared to a method in which the ratio p / d is 1.0 or less. Furthermore, by forming the nuggets such that the ratio p / d is 1.6 or less, it is possible to improve the peeling strength of the object to be welded while keeping the dotting cost small.

[0008] The welding method according to the invention described in claim 2 joins a plurality of objects to be welded, each having a dotting cost set to a length of not less than the diameter d of the nugget and not more than 10 [mm], by laser welding, thereby forming a plurality of Approximately circular A welding method for forming nuggets, wherein the adjacent nuggets are formed on the plurality of objects to be welded so as to be arranged at a distance p between central axes along a virtual straight line or a virtual open curve, and 1.0 < p / d ≤ 1.4 is satisfied for the diameter d of the nuggets of the plurality of objects to be welded.

[0009] The welded structure according to the invention described in claim 3 is a welded structure having a plurality of objects to be welded joined by laser welding and having a plurality of Approximately circular nuggets formed thereon, wherein the adjacent nuggets are arranged at a distance p between central axes along a virtual straight line or a virtual open curve, 1.0 < p / d ≤ 1.6 is satisfied for the diameter d of the nuggets of the plurality of objects to be welded, and further, each of the plurality of objects to be welded has a dotting cost set to a length of not less than the diameter d of the nugget and not more than 10 [mm].

[0010] In the welded structure according to the invention described in claim 3, the nuggets are formed such that the ratio p / d is greater than 1.0. That is, the distance p between the central axes of adjacent nuggets is longer than the diameter d of the nugget. For this reason, since the centers of the welding dots do not approach each other, in a metal with large solidification shrinkage, the connection of solidification cracks is suppressed. Thereby, compared with a configuration in which the ratio p / d is 1.0 or less, it is possible to suppress welding defects such as an increased risk of cracks during fatigue or poor appearance. Furthermore, by forming the nuggets such that the ratio p / d is 1.6 or less, it is possible to improve the peeling strength of the object to be welded while keeping the dotting cost small.

[0011] The welded structure according to the invention described in claim 4 is a welded structure having a plurality of Approximately circular welded objects having a plurality of formed nuggets joined by laser welding, wherein the adjacent nuggets are arranged at a distance p between the central axes along a virtual straight line or a virtual open curve, and as the diameter d of the nuggets of the plurality of welded objects, 1.0 < p / d ≦ 1.4, and further, each of the plurality of welded objects has a dotting cost set to a length of d or more and 10 [mm] or less of the diameter d of the nugget. The welding method according to the invention described in claim 5 is a welding method for forming a plurality of Approximately circular nuggets by joining a plurality of welded objects each having a dotting cost set to a length of d or more and 10 [mm] or less of the diameter d of the nugget by laser welding, wherein the adjacent nuggets are formed so as to be arranged at a distance smaller than the radius of the nugget. The welded structure according to the invention described in claim 6 is a welded structure having a plurality of Approximately circular welded objects having a plurality of formed nuggets joined by laser welding, wherein the adjacent nuggets are arranged at a distance smaller than the radius of the nugget, and further, each of the plurality of welded objects has a dotting cost set to a length of d or more and 10 [mm] or less of the diameter d of the nugget.

Advantages of the Invention

[0012] Claims 1 to claim 6According to the present invention, the welding can be applied to areas with small welding spot widths, and the peel strength of the welded objects can be improved compared to a configuration in which multiple welded objects are welded with one nugget. [Brief description of the drawings]

[0013] [Figure 1] 1A is a plan view of the welded structure according to the present embodiment, and FIG. 1B is a longitudinal cross-sectional view (cross-sectional view taken along line 1B-1B in FIG. 1A) of the welded structure according to the present embodiment. [Diagram 2] FIG. 2 is an explanatory diagram showing a welded state of the welded structure according to the embodiment; [Diagram 3] FIG. 2 is a perspective view showing a test specimen of the welded structure according to the present embodiment. [Figure 4] 1 is a graph showing the relationship between the ratio p / d of the pitch to the diameter of the nugget according to the present embodiment and the peel strength ratio of a test specimen. [Diagram 5] FIG. 2A is a plan view of a welded structure according to a first modified example of the present embodiment, and FIG. 2B is a plan view of a welded structure according to a second modified example of the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] FIG. 1(A) shows a welded structure 10 as an example of the present embodiment. The welded structure 10 has an object to be welded 12 and an object to be welded 14. The object to be welded 12 is, for example, a metal plate having a rectangular shape in a plan view. The object to be welded 14 is, for example, a metal plate having a rectangular shape in a plan view. The metal plate is a sheet material for automobiles, and for example, an aluminum alloy plate. In the following description, one direction in the in-plane direction of the object to be welded 12 and the object to be welded 14 is referred to as the "X direction", and a direction in the in-plane direction of the object to be welded 12 and the object to be welded 14 and perpendicular to the X direction is referred to as the "Y direction". Furthermore, the direction perpendicular to the X direction and the Y direction is referred to as the "Z direction".

[0015] 1(B), the work pieces 12 and 14 are overlapped. Moreover, the work pieces 12 and 14 are joined by a weld 20, for example. The weld 20 is formed by laser welding, as described below. During laser welding, the work pieces 12 are irradiated with a laser beam. The work pieces 14 are the side of the work pieces that is not irradiated with the laser beam.

[0016] The welded portion 20 is composed of nuggets 22 and 24, for example. When viewed in the Z direction, the nuggets 22 and 24 are each formed to have a substantially circular shape. When viewed in the Y direction, the nuggets 22 and 24 are each formed to have a drum-shaped XZ cross section. In FIG. 1(B), the central axis A of the nugget 22 and the central axis B of the nugget 24 are each indicated by a dashed line. The central axes A and B are aligned along the Z direction, for example.

[0017] As shown in FIG. 1A, a straight line passing through the central axis A of the nugget 22 and the central axis B of the nugget 24 is referred to as a "virtual straight line K1". The virtual straight line K1 is, for example, along the X direction. In the present embodiment, the nugget 22 and the nugget 24 are described as having the same shape and the same size. In the Y direction, the length of the area where the workpieces 12 and 14 contact each other is referred to as a "welding margin L". In the present embodiment, the portion with a small welding margin L means, for example, a portion where the welding margin L is 5 mm to 10 mm, or a portion where the welding margin L is smaller than 5 mm.

[0018] 1(B), the diameter of the nugget 22 in a plane (XY plane) perpendicular to the joining direction (Z direction) of the workpieces 12, 14 is defined as d [mm]. Specifically, the diameter of the nugget 22 between the workpieces 12, 14 (between the plates) is defined as d [mm]. The distance between the central axes of the welding points of adjacent nuggets 22, 24 (the distance in the X direction between central axis A and central axis B) is defined as p [mm]. In the following description, the distance p between the central axes of the nuggets 22, 24 is referred to as the "pitch p."

[0019] Here, the projections 22 and 24 are formed on the objects to be welded 12 and 14 such that the diameter d [mm] and the pitch p [mm] satisfy 1.0 < p / d ≤ 1.6. In other words, the projections 22 and 24 are formed on the objects to be welded 12 and 14 such that the ratio of the pitch p [mm] to the diameter d [mm] is greater than 1.0 and less than or equal to 1.6.

[0020] When the outer shapes of the projections 22 and 24 are elliptical, the diameter d [mm] may be the length in the X direction of the ellipse or the length obtained by averaging the major axis length and the minor axis length. In this embodiment, the projections 22 and 24 have the same shape and the same size. However, for example, when the diameters d of the projections 22 and 24 are different, an average value may be calculated from the respective diameters d and the average diameter d may be used.

[0021] FIG. 2 shows a welding method for welding the objects to be welded 12 and 14. The welding method in this embodiment is performed by a welding apparatus 100. The welding apparatus 100 includes an irradiation unit 102 that irradiates a laser beam LA toward the object to be welded 12, and a control unit 104 that controls the operation of the irradiation unit 102.

[0022] The irradiation unit 102 is configured, for example, by a laser scanner such as a galvanometer scanner, and irradiates the laser beam LA at a predetermined position of the object to be welded 12 by controlling the orientation of a built-in galvanometer mirror (not shown). Thereby, the projection 22 is formed at the position irradiated with the laser beam LA. The control unit 104 controls the orientation of the galvanometer mirror of the irradiation unit 102 so that the adjacent projections 22 and 24 are formed under the condition of 1.0 < p / d ≤ 1.6.

[0023] In this embodiment, as an example, a scanning-type forming method is used to form the nugget 22. In the scanning-type forming method, as an example, the nugget 22 is formed by scanning the laser light LA ​​along a circumferential path on the welding work-piece 12 as shown by an arrow C. In other words, the control unit 104 controls the operation of the irradiation unit 102 so that the laser light LA ​​is scanned along a circumferential path at a position on the welding work-piece 12 where the nugget 22 is to be formed. Note that, after the nugget 22 is formed, the control unit 104 controls the operation of the irradiation unit 102 so that the laser light LA ​​is irradiated to a position where the nugget 24 (see FIG. 1(A)) is to be formed.

[0024] <Peel strength test> The following describes a peel strength test performed on the welded workpieces 12 and 14 after welding. The peel strength test was performed using a testing machine AG-20kN / 50kNXDplus (Shimadzu Corporation).

[0025] The peel strength is a tensile load applied in a peel direction (thickness direction of the welded objects 12, 14) that causes the joined welded objects 12, 14 to peel off, and is indicated by the maximum tensile load that the welded objects 12, 14 can withstand without peeling. The peel strength ratio is the ratio of the peel strength of the welded portion 20 formed by the welding method of this embodiment to the peel strength of a welded portion in which the welded objects 12, 14 are joined by a single nugget of approximately the same size as the nugget 22 (see FIG. 1(A)).

[0026] (Test piece) As shown in Fig. 3, a 6000 series aluminum alloy plate material 30A having a thickness of 1.2 [mm] and a 6000 series aluminum alloy plate material 30B having a thickness of 0.9 [mm] were prepared, and each was bent into an L-shape and welded to form a test piece 30 (welded portion 20). The focused diameter φ of the laser beam LA (see Fig. 2) was about 0.4 [mm], and the laser beam LA was scanned in a circular shape. Note that the formation position of the nugget 22 was fixed, and the formation position of the nugget 24 was shifted in the X direction to prepare a plurality of test pieces 30 in which the ratio p / d of the pitch p to the diameter d was changed from 0.2 to 2.0.

[0027] In the peel strength test, a pair (two pieces) of test pieces 30 shown in Fig. 3 were prepared, and one test piece 30 was placed upside down relative to the other test piece, and the test was performed in a back-to-back state (cross state). The peel strength was determined by dividing the obtained test data by half. In addition, one nugget test piece was prepared as a comparison subject, and a peel strength test was performed in the same manner.

[0028] (Test Results) FIG. 4 shows the relationship between the ratio p / d of the pitch p to the diameter d of the nugget 22 (see FIG. 1(B)) and the peel strength ratio of the test piece 30 (see FIG. 3).

[0029] When the ratio p / d was in the range of 0.6 or less or more than 1.6, the peel strength ratio was approximately 1.0. In other words, in a welded structure in which welding (joining) was performed so that the ratio p / d was in the range of 0.6 or less or more than 1.6, the peel strength of the weld was approximately the same as the peel strength when joined with one nugget. In other words, it was confirmed that when the ratio p / d was 0.6 or less or more than 1.6, even if the weld was composed of two nuggets, the peel strength was unlikely to be high compared to when joined with one nugget.

[0030] On the other hand, when the ratio p / d was in the range of more than 0.6 and not more than 1.6, the peel strength ratio was greater than 1.0. In other words, in a welded structure in which welding (joining) was performed so that the ratio p / d was in the range of more than 0.6 and not more than 1.6, the peel strength of the weld was higher than the peel strength when joined with one nugget. In other words, it was confirmed that when the ratio p / d was in the range of more than 0.6 and not more than 1.6, when the weld 20 (see FIG. 1(A)) was composed of nuggets 22, 24 (see FIG. 1(A)), the peel strength was higher than when joined with one nugget.

[0031] When the ratio p / d was in the range of more than 0.2 and not more than 1.0, solidification cracks were confirmed between the nuggets 22 and 24 (see FIG. 3) by X-ray observation of the test piece 30 after welding (see FIG. 3). In other words, when the ratio p / d was in the range of more than 0.6 and not more than 1.0, the solidification cracks would connect, and this is not an appropriate condition for use. Specifically, if the solidification cracks connect, there is a high risk that these cracks will become cracks during fatigue of the welded structure 10 (see FIG. 1(A)) or the weld will be poor in appearance, and this is not an appropriate condition for use.

[0032] From the above results, the setting range of the ratio p / d in the welding method and welded structure 10 of this embodiment (see FIG. 1(A)) is 1.0 <p / d≦1.6となっている。

[0033] [Effect] Next, the operation of the welding method and the welded structure 10 of this embodiment will be described.

[0034] In the welded structure 10 and the welding method for obtaining the welded structure 10 shown in Figs. 1(A) and (B), the nuggets 22, 24 are formed so that the ratio p / d is greater than 1.0. That is, the pitch p of the nuggets 22, 24 is longer than the diameter d of the adjacent nuggets 22, 24. This prevents the centers of the welds in the objects to be welded 12, 14 from approaching each other, and prevents solidification cracks from connecting. This makes it possible to prevent welding defects such as a high risk of cracks during fatigue and poor appearance, compared to a method in which the ratio p / d is 1.0 or less. In addition, at the time of fracture, the parent material of the objects to be welded 12, 14 interposed between the nuggets 22, 24 can suppress the crack growth, thereby improving the peel strength.

[0035] Furthermore, by forming the nubs 22 and 24 such that the ratio p / d is 1.6 or less, the peel strength of the objects to be welded 12 and 14 is improved compared to the peel strength when forming a single nub. This is presumably because the stress applied to the single nub 22 or nub 24 is dispersed due to the interaction between the nubs 22 and 24. In other words, if the nubs 22 and 24 are too far apart, there is no interaction between the nubs 22 and 24 and they break one by one, so no improvement in the peel strength of the objects to be welded 12 and 14 is seen. Thus, by forming the nubs such that the ratio p / d is 1.6 or less, it is possible to improve the peel strength of the objects to be welded 12 and 14 while keeping the dotting cost L (see FIG. 1(A)) small.

[0036] In addition, in the present embodiment, the virtual straight line K1 of the welded structure 10 is arranged along the X direction, but the welded structure is not limited to this configuration.

[0037] <First Modified Example> FIG. 5(A) shows a welded structure 40 as a first modified example. In the welded structure 40, a welded portion 42 is formed in which a line passing through the central axes (not shown) of the six nubs 22 serves as the virtual straight line K1. The ratio p / d of two adjacent nubs 22 on the virtual straight line K1 is 1.0 < p / d ≤ 1.6. Thus, the number of nubs 22 may be a plurality of three or more. From the viewpoint of productivity, it is desirable that the number of nubs is two or three.

[0038] <Second Modified Example> FIG. 5(B) shows a welded structure 50 as a second modification. In the welded structure 50, a welded portion 52 is formed in which a line passing through the central axes (not shown) of the five studs 22 is a virtual open curve K2. The ratio p / d of two adjacent studs 22 on the virtual open curve K2 is 1.0 < p / d ≤ 1.6. Thus, a plurality of studs 22 may be arranged such that a line passing through the central axes of the plurality of studs 22 becomes the virtual open curve K2. Further, the number of studs 22 arranged on the virtual open curve K2 is not limited to five, and may be two, three, four, or six or more. From the viewpoint of productivity, it is desirable that the number of studs is two or three.

[0039] <Other Modifications> In this embodiment, as an example, the number of welding objects is two, but it is not limited thereto. The number of welding objects may be three or more. Further, the welding objects 12 and 14 are not limited to being stacked in the Z direction, and may be arranged at intervals in the Z direction. The welding method according to this embodiment is applicable to any welding object regardless of the presence or absence of surface treatment construction on the welding object.

[0040] The welding method for forming the studs 22 and 24 is not limited to the scanning formation method, and other formation methods such as the fixed-point formation method, the filling formation method, and the screw formation method can be used. In the fixed-point formation method, the studs 22 and 24 are formed by irradiating a laser beam for a certain period of time at a predetermined point on the welding object. In the filling formation method, first, an annular stud is formed by scanning a laser beam along a circular locus. Next, the studs 22 and 24 are formed by scanning the laser beam so as to fill the inside of the formed annular stud. In the screw formation method, the studs 22 and 24 are formed by scanning a laser beam along a spiral locus on the welding object.

[0041] The pitch between the dot groups (the welded portion 20 shown in FIG. 1(A)) is desirably set to 20 [mm] or more in order to make it difficult to be affected by the interaction between the dot groups due to welding.

[0042] The workpieces to be welded are not limited to aluminum alloys or high carbon steels, which have large solidification shrinkage and are prone to solidification cracking, but may be made of other materials.

[0043] The above describes the welding method and the welded structure according to the embodiment and each modification of the present invention. However, it is of course possible to use these embodiments and each modification in appropriate combination, and to implement the present invention in various forms without departing from the gist of the present invention. [Explanation of symbols]

[0044] 10 Welded Structure 12 Welding object 14 Welding object 22 Nugget 24 Nugget A center axis B Center axis d diameter K1 Virtual line K2 Virtual Open Curve p Distance between the central axes

Claims

1. A welding method for forming a plurality of substantially circular nuggets by laser welding a plurality of welding objects, each of which has a welding spot width set to be equal to or larger than a diameter d of the nugget and equal to or smaller than 10 mm in length, comprising: Adjacent nuggets are formed on the plurality of welding objects so as to be arranged along a virtual straight line or a virtual open curve with a distance p between their central axes, The welding method according to claim 1, wherein the diameter d of the nuggets of the plurality of welding objects is 1.0<p / d≦1.

6.

2. A welding method for forming a plurality of substantially circular nuggets by laser welding a plurality of welding objects, each of which has a welding spot width set to be equal to or larger than a diameter d of the nugget and equal to or smaller than 10 mm in length, comprising: Adjacent nuggets are formed on the plurality of welding objects so as to be arranged along a virtual straight line or a virtual open curve with a distance p between their central axes, The welding method according to claim 1, wherein the diameter d of the nuggets of the plurality of welding objects is 1.0<p / d≦1.

4.

3. A welded structure having a plurality of welded objects joined by laser welding to form a plurality of adjacent substantially circular nuggets, Adjacent nuggets are arranged along a virtual line or a virtual open curve with a distance p between their central axes, The diameter d of the nuggets of the plurality of welding objects is 1.0<p / d≦1.6, Furthermore, the plurality of welding objects are welded structures, each of which has a welding point width set to be equal to or larger than the diameter d of the nugget and to a length of 10 mm or less.

4. A welded structure having a plurality of welded objects joined by laser welding to form a plurality of adjacent substantially circular nuggets, Adjacent nuggets are arranged along a virtual line or a virtual open curve with a distance p between their central axes, The diameter d of the nuggets of the plurality of welding objects is 1.0<p / d≦1.4, Furthermore, the plurality of welding objects are welded structures, each of which has a welding point width set to be equal to or larger than the diameter d of the nugget and to a length of 10 mm or less.

5. A welding method for forming a plurality of substantially circular nuggets by laser welding a plurality of welding objects, each of which has a welding spot width set to be equal to or larger than a diameter d of the nugget and equal to or smaller than 10 mm in length, comprising: A welding method in which adjacent nuggets are formed side by side at a distance smaller than the radius of the nuggets.

6. A welded structure having a plurality of welded objects joined by laser welding to form a plurality of adjacent substantially circular nuggets, Adjacent nuggets are spaced apart from each other by a distance smaller than the radius of the nugget, Furthermore, the plurality of welding objects are welded structures, each of which has a welding point width set to be equal to or larger than the diameter d of the nugget and to a length of 10 mm or less.

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