Welded structure and welding method

Abstract

A welded structure according to the present invention is formed by generating and joining N welding beads at overlapping positions of a plurality of members. The N welding beads are formed in one direction in order from the first to the N-th welding beads. The relationship of the following formula (1) is satisfied, where: rN represents the radius of a welding spot which is a cross-section of the last welding bead formed in said one direction among the N welding beads; A represents the average of the radii of the respective welding spots at the overlapping positions of the members; B represents the average of the intersection heights of intersections where the outer edges of the welding spots overlap; and C represents the average of the center-to-center distances between adjacent welding spots.　(1): B / A≥((1 / rN)×√(rN 2-(C / 2)2))×0.95

Description

Welded structure and welding method

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

[0002] Conventionally, as a method for joining members using a laser, a method of welding by irradiating a laser beam is known (see, for example, Patent Document 1). In this laser welding, the laser beam is output intermittently (pulsed) to perform welding while suppressing thermal effects. In this type of laser welding, approximately circular welding spots are formed by a single irradiation and are continuously and overlappingly formed.

[0003] JP 2009-195948 A

[0004] However, in conventional laser welding such as that described in Patent Document 1, there is a risk that durability of the joint against load may be reduced due to variations in the diameter of each welding spot and insufficient penetration depth.

[0005] The present invention has been made in view of the above, and has an object to provide a welded structure and a welding method that can improve the durability of a joint.

[0006] In order to solve the above-mentioned problems and achieve the object, the welded structure according to the present invention is a welded structure formed by forming N weld beads at overlapping positions of a plurality of members to join the members together, the N weld beads being formed in one direction in order from the first to the Nth weld beads, and the radius of a weld spot, which is a cross section at the overlapping position of the last weld bead formed in the one direction, is defined as r N , where A is the average radius of each welding spot at the overlapping position, B is the average height of the intersections where the outer edges of the welding spots overlap, and C is the average distance between the centers of adjacent welding spots, the relationship of the following formula (1) is satisfied: B / A≧((1 / r N ) × √(r N 2 −(C / 2) 2 ) × 0.95 ... (1)

[0007] Furthermore, a welding method according to the present invention is a welding method for joining a plurality of components by generating N (>1) weld beads at overlapping positions of the components, and is characterized in that it includes a step of forming the N weld beads in one direction in order from 1 to N by laser welding, and in that the laser output is changed for each of the orders from 1 to N during the laser welding.

[0008] In addition, the welding method according to the present invention is characterized in that, in the above invention, the laser output is the largest in the first laser welding.

[0009] According to the present invention, it is possible to achieve an effect of improving the durability of the joint portion in a welded structure.

[0010] Fig. 1 is a diagram for explaining a welding mode in a welded structure according to an embodiment of the present invention. Fig. 2 is a diagram for explaining another example of a welding mode in a welded structure according to an embodiment of the present invention. Fig. 3 is a diagram for explaining a laser output mode in Examples. Fig. 4 is a diagram showing a cross-sectional image of a welded portion of a welded structure according to Example 1. Fig. 5 is a diagram showing a cross-sectional image of a welded portion of a welded structure according to Example 2. Fig. 6 is a diagram showing a cross-sectional image of a welded portion of a welded structure according to Example 3. Fig. 7 is a diagram showing a cross-sectional image of a welded portion of a welded structure according to Comparative Example 1. Fig. 8 is a diagram for explaining a peel test.

[0011] In the following description, a welded structure will be described as a form for carrying out the present invention (hereinafter referred to as an "embodiment"). However, the present invention is not limited to this embodiment. Furthermore, in the drawings, the same parts are given the same reference numerals. Furthermore, it should be noted that the drawings are schematic, and the relationship between the thickness and width of each member, the ratio of each member, etc., may differ from reality. Furthermore, the drawings may include parts with different dimensions and ratios.

[0012] (Embodiment) Fig. 1 is a diagram for explaining a welding mode in a welded structure according to one embodiment of the present invention. In the welded structure according to this embodiment, for example, a plurality of weld beads are formed to join two members. These members can be made of a metal material. Examples of metal materials include stainless steel, aluminum, aluminum alloys, copper, copper alloys, titanium, and titanium alloys.

[0013] FIG. 1 shows the cross section of a weld bead (weld spot) on the overlapping surface of the components (the surface where the components face each other and abut). In the example shown in FIG. 1, seven weld beads are formed, and weld spots S1 to S7 are shown, but the number of weld beads (weld spots) and the surface diameter of the weld spots are not limited to the example shown in FIG. 1. Furthermore, while the description will be given assuming that the outer edge of each weld bead cross section (weld spot) has a circular shape, in reality, due to distortion or the like, part of the outer edge may deviate from a perfect circle or may form an ellipse. In such cases, a virtual circle such as a circumscribing circle or an inscribing circle may be generated and applied.

[0014] The weld beads are formed sequentially in one direction, with adjacent weld beads partially overlapping in the formation direction. In the example shown in FIG. 1 , the weld beads are formed in the order of weld spot S1, weld spot S2, ..., weld spot S6, and weld spot S7. In this case, when weld beads are formed sequentially in one direction from the first to N (>1) weld spots, the laser output may be constant when forming each weld bead, or the laser output may be varied for each weld spot from the first to N. Because the temperature of the members increases as laser welding (bead formation) is performed continuously, from the perspective of heat input to the members, it is preferable that the laser output during later laser welding be lower than the laser output during earlier laser welding. For example, the laser output during the first laser welding bead is set to the highest and gradually decreased.

[0015] In this embodiment, for N (number of welding spots) weld beads, the welding spot of the last weld bead formed among the weld beads formed continuously in one direction is designated as S. N(In FIG. 1, the welding spot is S7), and the welding spots S1 to S N The radius of r1 to r N (In FIG. 1, the radius of the last weld bead formed is r7), and the center distance between adjacent welding spots is P1 to P N-1 , the height of the intersection where the outer edges of the welding spots overlap (intersection height) is H1 to H N-1 When the average radius of the welding spots is A, the average height of the intersections is B, and the average distance between the centers of the welding spots is C, the relationship of the following formula (1) is satisfied: B / A≧((1 / r N ) × √(r N 2 −(C / 2) 2 )) × 0.95 ... (1) where A, B, and C are as follows: A = (r1 + r2 + ... + r N-1 +r N ) / N B=(H1+H2+...+H N-2 +H N-1 ) / (N-1) C=(P1+P2+...+P N-2 +P N-1 ) / (N-1) Note that the intersection heights H1 to H N-1 is the center of the first welding spot (welding spot S1) and the last welding spot S N The distance between the line segment L0 connecting the center of the welding spot S7 (in FIG. 1) and the intersection of the outer edges of the welding spot is B / A. N ) × √(r N 2 −(C / 2) 2 )) should be 95% or more.

[0016] Here, when the weld bead is formed in more than one direction, for example, by bending in a plurality of different directions, the above formula (1) is applied to the weld beads arranged in one direction. Fig. 2 is a diagram for explaining another example of the welding mode in a welded structure according to an embodiment of the present invention. Fig. 2 shows a cross section of a weld bead (weld spot) at the overlapping position of the members. For example, as shown in Fig. 2, by forming a plurality of weld beads, the weld spot S 11 ~S 17 , S 21 ~S 27 However, welding spot S 11 , S 12 , ...S 17 , S 21 , S 22 , ...S 27 The welding spot S 17 , S 21 When the welding spots are formed in a V-shape by folding back at the same time, the above formula (1) is 21 ~S 27 The timing of forming the welding spot S 21 ~S 27 Forward welding spot S 11 ~S 17 The calculation of the above formula (1) may be performed for

[0017] In the above-described embodiment, the welded structure is configured such that the weld spots at the overlapping positions of the objects to be joined satisfy the relationship of formula (1) above. This makes it possible to obtain weld beads that suppress variation in the diameter of each weld spot and insufficient penetration depth, and the members are reliably joined together by the molten portions of the series of weld beads, thereby improving the durability of the joints in the welded structure.

[0018] Note that as long as the above formula (1) is satisfied, welding spots that do not overlap each other may be included. Furthermore, in the above-described embodiment, an example in which there are two components to be joined has been described, but three or more components may also be joined. In the case of three or more components, for example, the above formula (1) is applied to welding spots at overlapping positions of adjacent components in the stacking direction. Furthermore, in the above-described embodiment, if the shape of the welding spot is not a perfect circle, the center of gravity of the shape may be set as the center of the spot.

[0019] Examples of the bonded structure according to the present invention will be described below, but the present invention is not limited to these examples.

[0020] (Examples 1 to 3, Comparative Example 1) In Examples 1 to 3 and Comparative Example 1, two members were joined using the output (kW), welding point interval (mm), and number of welding points shown in Table 1. In Examples 1 to 3 and Comparative Example 1, welding was performed in a linear fashion. For example, in Example 1, a weld was formed in which 16 weld beads were arranged in a linear fashion. The members used in Examples 1 to 3 and Comparative Example 1 were stainless steel (SUS632J1).

[0021] In Examples 1 and 2, the laser output was varied depending on the number of hit points. FIG. 3 is a diagram illustrating the laser output patterns in the examples. In Example 1, as shown in FIG. 3, laser welding was performed using an output pattern F1 in which the output was reduced from the first hit point to the fourth hit point (0.41 kW → 0.38 kW), then maintained at the fourth hit point (0.38 kW) until the seventh hit point, and then reduced at the eighth hit point (0.38 kW → 0.37 kW) to a constant output (0.37 kW). In Example 3 and Comparative Example 1, laser welding was performed using a constant output (0.37 kW), as shown in the output pattern F2 in FIG. 3.

[0022] Table 2 shows the characteristics of the welding spots of Examples 1 to 3 and Comparative Example 1. Note that R indicates the radius of the welding spot at the overlapping position of the last formed weld bead.

[0023] FIG. 4 is a diagram showing a cross-sectional image of the welded portion of the welded structure according to Example 1. FIG. 5 is a diagram showing a cross-sectional image of the welded portion of the welded structure according to Example 2. FIG. 6 is a diagram showing a cross-sectional image of the welded portion of the welded structure according to Example 3. FIG. 7 is a diagram showing a cross-sectional image of the welded portion of the welded structure according to Comparative Example 1. Based on the welding spots shown in FIGS. 4 to 7, the B / A and ((1 / r N ) × √(r N 2 −(C / 2) 2 ) was calculated (see Table 2).

[0024] <Peel Test> The peel load was measured by measuring the load at which the bonded members peeled. If the load was equal to or greater than a predetermined load, it was marked as ◯, and if it was less than the predetermined load, it was marked as ×. In this peel test, if the load was 90 N, it was marked as ◯, and if it was less than 90 N, it was marked as ×. In the peel test, two test pieces formed by bending a portion of a strip-shaped member in the longitudinal direction were bonded, and the peel load was determined. FIG. 8 is a diagram for explaining the peel test. The test piece 101 has a bonded portion 101a having a bonded portion, and an erected portion 101b extending from one end of the bonded portion 101a so as to be perpendicular to the longitudinal direction of the bonded portion 101a. The test piece 102 has a bonded portion 102a having a bonded portion, and an erected portion 102b extending from one end of the bonded portion 102a so as to be perpendicular to the longitudinal direction of the bonded portion 102a. During joining, the test pieces 101 and 102 were joined by arranging the joints 101a and 102a facing each other so that the upstanding portions 101b and 102b extended in opposite directions, and then laser welding to form a weld 103. The test pieces 101 and 102 had the same shape. Here, in the test piece 101, the longitudinal length D1 of the joint 101a was 70 mm, the width D2 was 6.5 mm, and the extension length D3 of the upstanding portion 101b was 30 mm and the thickness D4 was 0.2 mm. Furthermore, the weld 103 was formed in the joints 101a and 102a at a position where the longitudinal distance D5 from the end opposite the upstanding portions 101b and 102b was 8 mm.

[0025] As shown in Table 2, in Examples 1 to 3, which satisfied the relationship of the above formula (1), welded structures with sufficient peel load were obtained. On the other hand, in Comparative Example 1, which did not satisfy the relationship of the above formula (1), the peel load was insufficient. The peel load was 104.7 N in Example 1, 100.6 N in Example 2, 95.0 N in Example 3, and 86.3 N in Comparative Example 1.

[0026] As such, the present invention may include various embodiments not described here, and various design changes may be made within the scope of the technical idea specified by the claims.

[0027] As described above, the welded structure and welding method according to the present invention are suitable for improving the durability of the joint.

[0028] H1 to H6 Intersection height L0 Line segment P1 to P6 Center distance r1 to r7 Radius S1 to S7 Welding spot

Claims

1. A welded structure formed by joining a plurality of members by generating N weld beads at overlapping positions of the members, wherein the N weld beads are formed in one direction in order from the first to the Nth, and the radius of the weld spot, which is a cross section at the overlapping position of the last weld bead formed in the one direction among the N weld beads, is defined as r N A welded structure characterized in that, when the average radius of each welding spot at the overlapping position is A, the average height of the intersection points where the outer edges of the welding spots overlap is B, and the average distance between the centers of adjacent welding spots is C, the relationship of the following formula (1) is satisfied. B / A≧((1 / r N ) × √(r N 2 −(C / 2) 2 ) × 0.95 ... (1) 2. A welding method for joining multiple components by generating N (>1) weld beads at overlapping positions of the components, comprising a step of forming the N weld beads in one direction in order from 1 to N by laser welding, and varying the laser output for each of the first to N weld beads in order during the laser welding.

3. The welding method according to claim 2, wherein the laser output is the largest in the first laser welding.

Images