JP2024103081A - Lap-welding joint, automobile skeleton component, and manufacturing method for lap-welding joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lap-welding joint having high breaking resistance and high torsional rigidity, which comprises a metal member having a vertical wall part and a flange and is reduced in heat strain, an automobile skeleton component, and a manufacturing method for a lap-welding joint.

SOLUTION: A lap-welding joint according to a first embodiment of the present invention comprises: a first metal member having a flat part; a second metal member having a flange overlapped with the flat part of the first metal member and a vertical wall part standing up from the flange; a plurality of spot-welding parts that weld the flat part of the first metal member to the flange of the second metal member; and a line-welding part that welds the flat part of the first metal member to the flange of the second metal member. The line-welding part is provided in an end of the flange. The plurality of spot-welding parts are arranged between the line-welding part and the vertical wall part, where a length of the line-welding part is equal to a diameter of the spot-welding part or more.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to lap welded joints, automobile frame parts, and methods for manufacturing lap welded joints.

The use of high-strength steel plates in automobile parts is being promoted in order to reduce the weight of automobiles and improve collision safety. High-strength steel plates can reduce the thickness of the components that make up an automobile part, thereby reducing the weight of the components, while ensuring the collision resistance of the automobile part. The collision resistance of an automobile part refers to the resistance of the automobile part to deformation when significant stress is applied. The greater the stress required to cause deformation or destruction in an automobile part, the higher the collision resistance of the automobile part is considered to be. In automobile parts made of high-strength steel plates, the starting point of destruction is the welded part. Therefore, technology to improve the fracture resistance of welded parts is desired. The fracture resistance refers to the resistance of a welded part to fracture when significant stress is applied.

In addition, for automotive parts, it is also necessary to improve the torsional rigidity and suppress thermal strain. The higher the torsional rigidity of an automotive part, the better the NVH (Noise, Vibration, Harshness) characteristics of the automobile and the stability of the automobile while it is running. However, reducing the thickness of the steel components to reduce the weight of the automotive parts may reduce the torsional rigidity of the automotive parts. Thermal strain is strain that occurs in the steel components due to welding heat. By suppressing thermal strain, the dimensional accuracy of the automotive parts can be improved.

Patent Document 1 discloses a laser-welded structural member that is constructed by overlapping one steel plate having a bent portion and a flange continuing from the bent portion with one or more other steel plates at the flange, and has a first laser welded portion and a second laser welded portion formed at the overlapped portion, the second laser welded portion being formed in a region near the first laser welded portion that is on the opposite side of the bent portion with respect to the first laser welded portion, and the hardness of the heat-affected zone of the first laser welded portion is 90% or less of the hardness of the heat-affected zone of the second laser welded portion.

Patent Document 2 discloses a lap welded component in which multiple steel members are joined together at overlapping portions, at least one of the multiple steel members containing a martensite structure, and the overlapping portion is formed with a spot weld having a nugget, and a molten solidification portion is formed between the nugget and a position 3 mm or more outward from the edge of the nugget by irradiation with a laser beam, the molten solidification portion crossing the edge of the nugget and having a depth at a position 1 mm outward from the edge of the nugget of 50% or more of the sheet thickness of each of the steel members containing the martensite structure.

Patent Document 3 discloses a method for welding a first steel member by overlapping it with a second steel member having a flange portion overlapping the first steel member and a vertical wall portion rising from the flange portion, the method comprising: a spot welding process for forming a nugget between the first steel member and the flange portion by spot welding the flange portion while overlapping it with the first steel member; and a laser welding process for forming a weld bead by laser welding in the area between the R end of the vertical wall portion and the nugget after the spot welding process; the weld bead is characterized in that the longitudinal dimension of the flange portion is equal to or greater than the diameter of the nugget and has a width dimension of 0.5 to 3.0 mm.

Patent Document 4 discloses a vehicle body structure in which a third plate-like member is spot-welded to the flange portion, which is formed by laser-welding a flange portion in the longitudinal direction of the plate-like members, in which the ends of the first and second plate-like members are overlapped so as to protrude outward, to form a closed cross-section body, and the flange portion has a laser weld mark that is adjacent to the base side of the flange portion width direction perpendicular to the longitudinal direction and continues in the longitudinal direction, and the third plate-like member is spot-welded so that the spot weld points are spaced apart in the longitudinal direction from the laser weld mark on the outer end side of the flange portion width direction, and a slit portion that penetrates in the thickness direction and has a predetermined length in the planar direction of the flange portion is opened between the spot weld point in the flange portion width direction and the laser weld mark in at least one of the parts of the first and second plate-like members that form the flange portion, in the thickness direction.

Patent Document 5 discloses an automobile framework part in which a flange portion of a frame part having a generally hat-shaped cross section is welded to another frame part or panel part arranged opposite the flange portion to form a closed cross section, wherein the welding position coordinates are expressed in a coordinate system in which the end portion of the contact position between the flange portion and the other frame part or panel part is set to 0, the flange outer end side of the flange portion is set to (-) and the vertical wall side of the generally hat shape is set to (+), and the radius of the arc-shaped portion connecting the vertical wall portion of the generally hat shape and the flange portion is set to R (mm), and the automobile framework part is characterized in that the automobile framework part is continuously welded using a one-sided welding method at position X expressed by the following formula:
+√(2Ra-a ² )≧X>1.5
However, R≧2 (unit: mm)
a: Weldable gap

Figure 32 of Non-Patent Document 1 discloses the dependency of LTS on the welding position. LTS is the maximum load of an L-shaped joint obtained by performing a peel test on the L-shaped joint. An L-shaped joint is a joint obtained by spot welding the flanges of two L-shaped members, each of which is made by bending a steel plate into an L shape and consists of a flange and a vertical wall rising from the flange (see Figure 3A and Figure 5 of Non-Patent Document 1). The vertical walls of the two steel members are arranged on the same plane, and in the peel test, a tensile load is applied to the vertical walls of the two steel members in a direction that peels off the spot welds. The tensile axis coincides with the extension direction of the vertical wall.

According to Non-Patent Document 1, the LTS can be increased by welding the R part of the L-shaped joint, i.e., near the boundary between the flange part and the vertical wall part. This is explained as being because the shorter the distance from the tensile axis to the weld toe, the lower the stress acting on the weld at the steel plate interface.

JP 2010-12504 A International Publication No. 2014/24997 International Publication No. 2017/47752 JP 2010-158983 A JP 2012-240118 A

"Advances and Prospects of Welding and Joining Technology in the Automotive Field" Miyazaki et al., Nippon Steel & Sumitomo Metal Technical Report, No. 409, 2017, pp. 10-22

In the technology disclosed in Patent Document 1, the combination of a linear first laser weld and a linear second laser weld increases the peel strength of the laser welded structural member. However, linear laser welding placed at or near the center of the flange causes thermal strain in the laser welded structural member. With regard to the dimensional accuracy of the laser welded structural member, the technology disclosed in Patent Document 1 leaves room for improvement.

In the technology disclosed in Patent Document 2, a laser beam is irradiated from the nugget of the spot weld across the edge of the nugget to form a molten solidified portion, which hardens the HAZ softened portion of the spot weld, suppresses fracture in the HAZ, and fully demonstrates the strength of the high-strength steel plate or hot stamped material. In the technology disclosed in Patent Document 3, a weld bead is formed in the region between the nugget and the vertical wall portion, improving torsional rigidity and joint strength. However, there is room for improvement in the technologies disclosed in Patent Documents 2 and 3 with regard to the irradiation position of the laser beam, etc.

According to the technology disclosed in Patent Document 4, it is possible to shorten the width of the flange portion by bringing the spot welding point and the laser welding mark closer to each other while lengthening the current path passing through the laser welding mark during spot welding. However, Patent Document 4 does not give any particular consideration to the joint strength and torsional rigidity, nor does it disclose any configuration that can improve these.

In the technology disclosed in Patent Document 5, the rigidity of the automotive frame parts is increased by moving the welding position closer to the vertical wall portion. Non-Patent Document 1 discloses that the peel strength of the L-joint is increased by moving the welding position closer to the vertical wall portion. However, Patent Document 5 and Non-Patent Document 1 do not consider the susceptibility of the L-joint to breaking during a collision or the structure of the flange end portion.

In view of the above, the present invention aims to provide a lap welded joint, an automobile frame part, and a method for manufacturing a lap welded joint that includes a metal member having a vertical wall portion and a flange, has reduced thermal strain, and has high fracture resistance and torsional rigidity.

The gist of the present invention is as follows:

(1) A lap welded joint according to a first embodiment of the present invention comprises a first metal member having a flat portion, a flange overlapping the flat portion of the first metal member, and a second metal member having a vertical wall portion rising from the flange, a plurality of spot welds joining the flat portion of the first metal member and the flange of the second metal member, and a line weld joining the flat portion of the first metal member and the flange of the second metal member, wherein the line weld is provided at an end of the flange, the plurality of spot welds are arranged between the line weld and the vertical wall portion, and the length of the line weld is greater than or equal to the diameter of the spot weld.
(2) Preferably, in the lap welded joint described in (1) above, the number of the line welds is two or more, and the line welds are spaced apart along the end of the flange.
(3) Preferably, in the lap welded joint described in (2) above, when the plurality of spot welds are projected onto the end of the flange, the centers of the projected portions of the plurality of spot welds overlap with the plurality of line welds.
(4) Preferably, in the lap welded joint described in (2) above, when the plurality of spot welds are projected onto the end of the flange, the center of the projected portions of the plurality of spot welds is between the plurality of line welds.
(5) In the lap welded joint according to any one of (1) to (4) above, the line weld has a width of 0.5 to 3.0 mm.
(6) Preferably, in the lap welded joint described in any one of (1) to (5) above, one or both of the first metal member and the second metal member are steel members.
(7) Preferably, in the lap welded joint described in (6) above, both the first metal member and the second metal member are steel members, and the hardness of the weld metal of the spot weld on the side of the line weld is 25 HV or more lower than the hardness of the weld metal of the spot weld on the side opposite the line weld.
(8) Preferably, in the lap welded joint according to any one of (1) to (7) above, the line weld is a laser weld or an arc weld.
(9) Preferably, in the lap welded joint according to any one of (1) to (8) above, the spot welds are spot welds or laser screw welds.
(10) In the lap welded joint according to any one of (1) to (9) above, the distance between the line weld and the vertical wall portion is preferably 10.0 mm or more.
(11) Preferably, in the lap welded joint according to any one of (1) to (10) above, a distance between an end of the spot weld on the side of the vertical wall portion and the vertical wall portion is 10.0 mm or less.

(12) The automobile frame component according to the second embodiment of the present invention has a lap weld joint described in any one of (1) to (11) above.

(13) A manufacturing method for a lap welded joint according to a third embodiment of the present invention is a method for manufacturing a lap welded joint from a first metal member having a flat portion, a flange, and a second metal member having a vertical wall portion rising from the flange, the method comprising the steps of: overlapping the flat portion of the first metal member and the flange of the second metal member; spot welding the flat portion of the first metal member and the flange of the second metal member multiple times; and line welding the flat portion of the first metal member and the flange of the second metal member, wherein the spot welding is performed between an end of the flange and the vertical wall portion, the line welding is performed at the end of the flange, and the length of the line weld obtained by the line welding along the end of the flange is greater than or equal to the diameter of the spot weld obtained by the spot welding.
(14) In the method for manufacturing a lap welded joint described in (13) above, the spot welding is preferably performed before the line welding.
(15) In the method for manufacturing a lap welded joint according to (13) or (14) above, the spot welding is preferably spot welding.

The present invention provides a lap welded joint, an automobile frame part, and a method for manufacturing a lap welded joint that includes a metal member having a vertical wall portion and a flange, reduces thermal strain, and has high fracture resistance and torsional rigidity.

FIG. 1 is a perspective view of an example of a lap weld joint. FIG. 2 is a plan view of an example of a flange. FIG. 2 is a plan view of an example of a flange. FIG. 2 is a plan view of an example of a flange. FIG. 13 is a schematic cross-sectional view of an L-shaped joint in which a tensile stress is applied to a vertical wall portion. FIG. 13 is a schematic cross-sectional view of an L-shaped joint in which compressive stress is applied to a vertical wall portion. 2 is a cross-sectional view of an example of a flange and a hardness distribution map of a spot weld. FIG. FIG. 2 is a cross-sectional view of an example of a flange. FIG. 2 is a cross-sectional view of an example of a flange. FIG. 2 is a cross-sectional view of an example of a flange. FIG. 13 is a perspective view of models of both hat members used for axial crush simulation. 1 is a graph showing the results of a simulation of axial crushing. FIG. 13 is a perspective view showing a method for simulating torsion. FIG. 13 is a perspective view of a model of the single-hat member, fulcrum, and impactor used for the three-point bending simulation.

Each embodiment of the present invention will be described in detail below with reference to the drawings.

(1. Lap weld joint 1)
First, a lap welded joint 1 according to a first embodiment of the present invention will be described with reference to Fig. 1 etc. The lap welded joint 1 according to the first embodiment includes a first metal member 11 having a flat portion 111, a second metal member 12 having a flange 121 overlapped on the flat portion 111 of the first metal member 11 and a vertical wall portion 122 rising from the flange 121, a plurality of spot welds 13 joining the flat portion 111 of the first metal member 11 and the flange 121 of the second metal member 12, and a line weld 14 joining the flat portion 111 of the first metal member 11 and the flange 121 of the second metal member 12, the line weld 14 being provided at an end 1211 of the flange 121, the plurality of spot welds 13 being arranged between the line weld 14 and the vertical wall portion 122, and the length of the line weld 14 being equal to or greater than the diameter D of the spot weld.

(First metal member 11)
The lap welded joint 1 is obtained by joining a first metal member 11 and a second metal member 12. The first metal member 11 has a flat portion 111. The flat portion 111 becomes a joining portion of the lap welded joint 1.

The simplest example of the first metal member 11 is a flat plate member as illustrated in FIG. 1. When the first metal member 11 is a flat plate member, the flat portion 111 can be considered to be provided over the entire first metal member 11. On the other hand, the first metal member 11 may have a flange 121 and a vertical wall portion 122, similar to the second metal member 12 described below, and this flange 121 may be considered to be the flat portion 111. For example, the first metal member 11 may be an L-shaped member or a hat member. In this case, the flange of the first metal member 11 can be considered to be the flat portion 111.

(Second metal member 12)
The second metal member 12 has at least a flange 121 and a vertical wall portion 122 rising from the flange 121. The flange 121 serves as a joining portion of the lap welded joint 1. The vertical wall portion 122 imparts a three-dimensional shape to the lap welded joint 1. Furthermore, when the lap welded joint 1 is an automobile frame part, the vertical wall portion 122 applies stress to the welded portion of the flange 121 during an automobile collision.

The simplest example of the second metal member 12 is an L-shaped member as illustrated in FIG. 3A etc. The L-shaped member is a member obtained by bending a metal plate and has one flat flange 121 and one flat vertical wall portion 122 rising approximately vertically from the flange 121. Another example of the second metal member 12 is a hat member as illustrated in FIG. 1. The hat member is a member obtained by bending a metal plate and has a pair of flanges 121, a pair of vertical wall portions 122 rising approximately vertically from the pair of flanges 121, and a horizontal wall portion 123 connecting the pair of vertical wall portions 122 and parallel to the flanges 121.

When the lap welded joint 1 includes a plurality of metal members having a vertical wall portion 122 and a flange 121, any of the metal members can be regarded as the second metal member 12. A joint including one or more second metal members 12 that satisfy the requirements of the lap welded joint 1 according to this embodiment is regarded as the lap welded joint 1 according to this embodiment. For example, the lap welded joint 1 in FIG. 4A and FIG. 4B includes two metal members having a vertical wall portion 122 and a flange 121. Of these metal members, the metal member arranged on the lower side of the paper does not have a line weld 14 at the end 1211 of the flange 121. If this is regarded as the second metal member 12, the lap welded joint 1 in FIG. 4A and FIG. 4B does not satisfy the requirements of the lap welded joint 1 according to this embodiment. However, in the metal member arranged on the upper side of the paper, the line weld 14 is provided at the end 1211 of the flange 121. If this is considered to be the second metal member 12, the lap welded joint 1 in Figures 4A and 4B satisfies the requirements of the lap welded joint 1 according to this embodiment. The lap welded joint 1 in Figures 4A and 4B is the lap welded joint 1 according to this embodiment because it includes one or more second metal members 12 that satisfy the requirements of the lap welded joint 1 according to this embodiment. In addition, in the lap welded joint 1 in Figures 4A and 4B, the metal member arranged on the lower side of the paper is considered to be the first metal member 11. The lap fillet joint in Figure 4C corresponds to the lap welded joint 1 according to this embodiment, regardless of whether the metal member on the upper side of the paper or the metal member on the lower side of the paper is considered to be the second metal member 12.

The number of metal members may be three or more. An example of a lap fillet joint having three or more metal members is shown in FIG. 4D. The lap fillet joint in FIG. 4D corresponds to the lap welded joint 1 according to this embodiment when the metal member on the upper side of the page is regarded as the second metal member 12 and the other metal members are regarded as the first metal member 11.

(Spot welds 13 and line welds 14)
The multiple spot welds 13 are welds that join the flat portion 111 of the first metal member 11 and the flange 121 of the second metal member 12. When the flat portion 111 or the flange 121 is viewed in plan, the spot welds 13 have a substantially circular shape. Examples of the spot welds 13 include the spot welds shown in Fig. 4A and the laser screw welds shown in Fig. 4B. The closer the spot welds are to the vertical wall portions, the more preferable the positions of the spot welds are, but the spot welds may be spaced from the vertical wall portions and slightly in contact with the line welds.

The line weld 14, together with the spot weld 13, is a weld that joins the flat portion 111 of the first metal member 11 and the flange 121 of the second metal member 12. When the flat portion 111 or the flange 121 is viewed in plan, the line weld 14 has a linear shape that extends along the edge of the flange 121. Examples of the line weld 14 include a laser weld and an arc weld.

The line weld 14 is provided at the end 1211 of the flange 121. Thus, the line weld 14 joins the end 1211 of the flange 121 to the flat portion 111 of the first metal member 11. In the lap weld joint 1 illustrated in FIG. 1, the line weld 14 is a lap fillet weld that joins the end face of the flange 121 to the surface of the flat portion 111. Meanwhile, a plurality of spot welds 13 are arranged between the line weld 14 and the vertical wall portion 122. Thus, the spot weld 13 joins the center of the flange 121 to the flat portion 111.

The length L of the line weld 14 is equal to or greater than the diameter D of the spot weld. Here, the length L of the line weld 14 refers to the dimension of the line weld 14 measured along the end 1211 of the flange 121 as shown in the plan view of FIG. 2A. The diameter D of the spot weld refers to the width of the weld metal measured in a cross section passing through the center of the spot weld 13 and perpendicular to the surface of the flange 121. Whether the spot weld 13 is a spot weld or a laser screw weld, the width of the spot weld 13 is measured along the mating surfaces of the flange 121 and the flat portion 111. As illustrated in FIG. 4D, when the number of members is three or more and the number of mating surfaces is two or more, the maximum value of the width of the spot weld 13 measured at each mating surface is regarded as the width of the spot weld 13.

The length L of the line weld 14 may vary depending on whether it is measured at the flat portion 111 of the first metal member 11 or at the flange 121 of the second metal member 12. In this case, the length L of the line weld 14 is measured on both sides, and it is sufficient that L≧D is satisfied on at least one side. There may also be two or more line welds and spot welds, and their sizes may not be uniform. In this case, the relationship between the diameter of the spot weld and the length of the line weld can be determined by examining an arbitrary spot weld and the line weld closest to the arbitrary spot weld, and it is sufficient that the relationship is satisfied for even one pair.

(Action and Effect)
In the lap welded joint 1 according to the first embodiment, the line weld 14 is provided at the end 1211 of the flange 121, and its length L is set to be equal to or greater than the diameter D of the spot weld. As a result, in the lap welded joint 1 according to the first embodiment, the fracture resistance characteristics of the weld are improved. Also, in the lap welded joint 1 according to the first embodiment, a plurality of spot welds 13 are arranged between the line weld 14 and the vertical wall portion 122. As a result, the lap welded joint 1 according to the first embodiment has high torsional rigidity and reduces thermal strain. The reason for this will be explained below.

First, the effect of the line weld 14 provided at the end 1211 of the flange 121 will be described. In the prior art, it has been thought that in order to improve the crash resistance of an automobile frame part, it is better to bring the weld that joins the flange 121 closer to the vertical wall 122. For example, the above-mentioned non-patent document 1 discloses the results of a peeling test of an L-shaped joint as shown in FIG. 3A. In this peeling test, a tensile load is applied to the vertical wall 122 of each of the two members to peel off the weld. Non-patent document 1 reports that the closer the weld is to the vertical wall 122, the less likely the weld is to peel off. However, when the present inventors performed various forms of crash evaluations on a lap weld joint 1 having a vertical wall 122, it became clear that the fracture resistance of the lap weld joint 1 is improved as the weld is farther away from the vertical wall 122.

The inventors have obtained new knowledge regarding the relationship between the fracture resistance of the lap welded joint 1 and the position of the weld. The inventors speculate as follows about the reason why it is preferable to separate the weld from the vertical wall portion.

In the peel test of FIG. 3A, tensile stress is applied to the vertical wall portion 122. At this time, the flange 121 functions as a lever. Here, the welded portion 13 is the point of application l, the end of the flange 121 is the fulcrum f, and the bent portion 124 between the vertical wall portion 122 and the flange 121 is the force point e. Therefore, when tensile stress is applied to the vertical wall portion 122 as shown in FIG. 3A, the further the welded portion 13, which is the point of application l, is from the end 1211 of the flange 121, which is the fulcrum f, the more difficult it is for the welded portion 13 to break.

On the other hand, when compressive stress is applied to the vertical wall portion 122 as shown in FIG. 3B, the bent portion 124 becomes the fulcrum f, and the welded portion 13 becomes the point of action l. Therefore, when compressive stress is applied to the vertical wall portion 122 as shown in FIG. 3B, the farther the welded portion 13, which is the point of action l, is from the bent portion 124, which is the fulcrum f, the less likely the welded portion 13 will break.

When the lap welded joint 1 is axially crushed or bent, the bend 124 between the vertical wall 122 and the flange 121 often functions as the fulcrum f of the lever, and it is presumed that this makes it advantageous to move the weld away from the bend 124.

For the above reasons, in the lap welded joint 1 according to the first embodiment, the line weld 14 is provided at the end 1211 of the flange 121. The end 1211 of the flange 121 is the location furthest from the vertical wall portion 122. This improves the fracture resistance of the lap welded joint 1. However, if the line weld 14 is too short, the fracture resistance of the line weld 14 cannot be guaranteed. Therefore, the length of the line weld 14 is set to be equal to or greater than the diameter D of the spot weld.

It is not preferable to join the end 1211 of the flange 121 with a spot weld 13. The area joined by the spot weld 13 is narrow, so the spot weld 13 does not ensure sufficient fracture resistance. In addition, if the spot weld 13 is a spot weld, the welding work becomes difficult because spatter is likely to fly from the end 1211 of the flange 121. For these reasons, the weld that joins the end 1211 of the flange 121 is a line weld 14.

Next, the effect of the spot welds 13 arranged between the vertical wall portion 122 and the line welds 14 will be described. The torsional rigidity of the lap welded joint 1 increases the closer the welds are to the vertical wall portion 122. Therefore, in the lap welded joint 1 according to the first embodiment, in addition to providing the line welds 14 at the end 1211 of the flange 121, a weld is also provided near the vertical wall portion 122, i.e., between the line welds 14 and the vertical wall portion 122.

However, according to the results of experiments conducted by the present inventors, it was found that line welding at a location close to the vertical wall portion 122 is not preferable. According to the results of simulations conducted by the present inventors, in the lap welded joint 1 in which the center of the flange or its vicinity was intermittently line welded, the effect of improving the fracture resistance characteristics was not obtained. Furthermore, when the center of the flange or its vicinity was continuously line welded, the thermal strain of the flange 121 became significant, and the dimensional accuracy of the lap welded joint 1 was impaired. In addition, line welding at the center of the flange or its vicinity is easily affected by plate gaps, and is prone to causing welding defects. On the other hand, spot welding is less susceptible to plate gaps, and the amount of thermal strain caused by spot welding is small. Therefore, the welded portion at the location close to the vertical wall portion 122 is designated as the spot welded portion 13.

Above, the most basic aspect of the lap welded joint 1 according to the first embodiment has been described. Next, a more preferred aspect of the lap welded joint 1 according to the first embodiment will be described.

(Number and Arrangement of Line Welds 14)
The number of line welds 14 may be one, as shown in Fig. 2C. A long, single line weld 14 as shown in Fig. 2C can most effectively suppress fracture of the weld of the lap weld joint 1. On the other hand, as shown in Fig. 2A or 2B, the number of line welds 14 may be two or more, and the line welds 14 may be spaced apart along the end 1211 of the flange 121. This can further suppress thermal strain of the flange 121 and the flat portion 111.

When the number of line welds 14 is two or more, the spot welds 13 and line welds 14 may be arranged side by side as shown in FIG. 2A. Specifically, the line welds 14 and spot welds 13 may be arranged so that when the multiple spot welds 13 are projected onto the end 1211 of the flange 121, the centers of the projections 13P of the multiple spot welds overlap with the multiple line welds 14. The arrangement in FIG. 2A can provide the tempering effect of the spot welds described below.

On the other hand, as shown in FIG. 2B, the spot welds 13 and line welds 14 may be arranged in a staggered manner. Specifically, the line welds 14 and spot welds 13 may be arranged so that when the multiple spot welds 13 are projected onto the end 1211 of the flange 121, the center of the projection 13P of the multiple spot welds is between the multiple line welds 14. The arrangement in FIG. 2B can ensure higher torsional rigidity than the arrangement in FIG. 2A.

(Width of Line Weld 14)
The width of the line weld 14 is not particularly limited, but is preferably within the range of 0.5 to 3.0 mm, for example. By making the width of the line weld 14 0.5 mm or more, the joint strength can be further improved. The width of the line weld 14 may be 0.6 mm or more, 0.8 mm or more, or 1.0 mm or more. On the other hand, by making the width of the line weld 14 3.0 mm or less, it is possible to prevent burn-through and thermal distortion during the manufacture of the line weld 14. The width of the line weld 14 may be 2.8 mm or less, 2.5 mm or less, or 2.0 mm or less. It should be noted that the width W of the line weld 14 refers to the dimension of the line weld 14 along a direction perpendicular to the end 1211 of the flange 121 in a planar view of the flange 121, as shown in FIG. 2A, when the line weld 14 is a lap fillet weld; and when the line weld 14 is an edge weld, it refers to the dimension of the line weld 14 along a direction perpendicular to the surface of the flange 121 in a cross-sectional view of the flange 121, as shown in FIG. 4C.

(Tempering of spot welds 13)
When both the first metal member 11 and the second metal member 12 are steel members, as shown in FIG. 4A, the hardness of the weld metal of the spot weld 13 on the line weld 14 side is preferably lower by 25 HV or more than the hardness of the weld metal of the spot weld 13 on the opposite side to the line weld 14. The cross-sectional view shown in the upper part of FIG. 4A is a cross-sectional view of the lap weld joint 1 perpendicular to the weld line direction of the line weld 14 and passing through the center of the spot weld 13, and the graph shown in the lower part of FIG. 4A is a hardness distribution graph of the spot weld 13 obtained by continuously measuring the hardness of the spot weld 13 in the lateral direction of the page. The hardness distribution of the spot weld 13 is usually uniform. However, the spot weld 13 can be partially softened by tempering the spot weld 13 with the welding heat when forming the line weld 14, for example. In this case, as shown in the graph at the bottom of FIG. 4A, the hardness of the spot weld 13 becomes smaller as it approaches the line weld 14. The toughness of the spot weld 13 can be increased by making the hardness of the weld metal of the weld on the line weld 14 side 25 HV or more lower than the hardness of the weld metal of the spot weld 13 on the side opposite the line weld 14. The difference in hardness between the weld metal of the spot weld 13 on the line weld 14 side and the side opposite the line weld 14 may be 30 HV or more, 35 HV or more, or 40 HV.

Tempering the spot welds 13 is particularly effective when one or both of the first metal member 11 and the second metal member 12 are high-strength steel plates. In general, the higher the tensile strength of the steel plate, the higher the peel strength of the welds. However, when the tensile strength exceeds 980 MPa, the higher the tensile strength of the steel plate, the more embrittled the welds become and the lower the peel strength becomes. By tempering the spot welds 13, the toughness of the spot welds 13 can be improved, and the fracture resistance of the lap welded joint 1 can be further improved.

The difference in hardness between the line weld 14 side and the opposite side of the line weld 14 of the spot weld 13 is obtained by the following procedure. First, the lap weld joint 1 is cut and the cross section is polished. The cross section is perpendicular to the weld line direction of the line weld 14 and passes through the center of the spot weld 13. Next, the Vickers hardness of the spot weld 13 is continuously measured along the surface of the flange 121 of the second metal member 12 arranged inside the joint. The load is 500 gf, and the measurement interval is 0.20 mm. This results in a hardness distribution of the spot weld 13 as shown in the lower part of FIG. 4A. Then, the minimum hardness value on the side closer to the line weld 14 than the center of the spot weld 13 and the maximum hardness value on the side farther from the line weld 14 than the center of the spot weld 13 are identified, and the difference between the two is calculated.

(Types of Line Welds 14)
The line welds 14 are preferably laser welds or arc welds. Laser welds can be manufactured with a small amount of heat input, so that thermal strain of the flange 121 and the flat portion 111 can be further suppressed. Arc welds have a large amount of heat input during manufacturing, so that the spot welds 13 can be easily tempered. The type of line welds 14 can be appropriately selected according to the shape, application, material, etc. of the lap welded joint 1. When the number of line welds 14 is two or more, both the laser welds and the arc welds may be adopted as the line welds 14. In addition, the line welds may be formed by hybrid welding of laser and arc or plasma welding, TIG welding, or MIG brazing, which is a type of arc welding (plasma welds, TIG welds, or MIG brazing).

(Types of spot welds 13)
The spot welds 13 are preferably resistance spot welds or laser screw welds. The spot welds can be formed in a short time. In addition, the spot welds can be easily formed even if there is a gap between the flange 121 and the flat portion 111. In addition, when the spot welds are formed and then the line welds 14 are formed, the line welds can be formed in a state where the gap between the end 1211 of the flange 121 and the flat portion 111 is closed, so that the line welds 14 can be easily formed. Therefore, when the spot welds 13 are spot welds, the manufacturing of the lap welded joint 1 becomes even easier. On the other hand, when the spot welds 13 are laser screw welds, the welds can be formed in an even shorter time than spot welding. In addition, unlike spot welding, no shunting occurs, so the interval between the welds can be made smaller. In addition, circumferential and C-shaped laser welds are also included in the spot welds.

(Space between line weld 14 and vertical wall 122)
The distance between the line weld 14 and the vertical wall 122 is preferably, for example, 10.0 mm or more. The larger the distance between the line weld 14 and the vertical wall 122, the less likely the weld of the lap welded joint 1 will break when crushed. The distance between the line weld 14 and the vertical wall 122 may be 12.0 mm or more, 14.0 mm or more, or 16.0 mm or more. On the other hand, the smaller the distance between the line weld 14 and the vertical wall 122, the smaller the width of the flange 121 can be, and the weight of the lap welded joint 1 can be reduced. Therefore, for example, the distance between the line weld 14 and the vertical wall 122 is preferably 40.0 mm or less. More preferably, the distance between the line weld 14 and the vertical wall 122 is 35.0 mm or less, 30.0 mm or less, or 25.0 mm or less. The distance between the line weld 14 and the vertical wall 122 is approximately equal to the width of the flange 121 before welding.

(Distance between spot weld 13 and vertical wall 122)
The distance between the end of the spot weld 13 on the vertical wall portion side and the vertical wall portion 122 is preferably, for example, 10.0 mm or less. The smaller the distance between the spot weld 13 and the vertical wall portion 122, the higher the torsional rigidity of the lap welded joint 1. More preferably, the distance between the spot weld 13 and the vertical wall portion 122 is 9.0 mm or less, 7.0 mm or less, or 5.0 mm or less. On the other hand, from the viewpoint of facilitating the manufacture of the spot weld 13, it is preferable that the distance between the spot weld 13 and the vertical wall portion 122 is large. Therefore, it is preferable that the distance between the spot weld 13 and the vertical wall portion 122 is, for example, 2.0 mm or more, 3.0 mm or more, or 4.0 mm or more.

(2. Automobile frame parts)
Next, an automobile frame part according to a second embodiment of the present invention will be described. The automobile frame part according to the second embodiment includes the lap welded joint 1 according to the first embodiment. Therefore, the automobile frame part according to the second embodiment is less likely to break at the welded portion during an automobile collision. Therefore, the automobile frame part according to the second embodiment can improve the collision safety of the automobile. In addition, the automobile frame part according to the second embodiment has high torsional rigidity. Therefore, the automobile frame part according to the second embodiment can improve the NVH (Noise, Vibration, Harshness) characteristics and the stability during the running of the automobile. In addition, the automobile frame part according to the second embodiment has the effect of thermal strain suppressed. Therefore, the automobile frame part according to the second embodiment has high dimensional accuracy.

Examples of automobile structural components include bumpers, A-pillars, B-pillars, side sills, roof rails, floor members, front side members, front side member kick portions, rear side members, front suspension towers, tunnel reinforcements, dash panels, torque boxes, seat frameworks, seat rails, battery case frames, and their joints. Examples of joints include the joint between the B-pillar and side sill, the joint between the B-pillar and roof rail, the joint between the roof cross member and roof rail, the joint between the side sill and A-pillar, the joint between the dash panel and tunnel, and the base of the front side member.

(3. Manufacturing method of lap welded joint 1)
Next, a manufacturing method of the lap welded joint 1 according to a third embodiment of the present invention will be described. A manufacturing method for a lap welded joint 1 in the third embodiment is a method for manufacturing a lap welded joint 1 from a first metal member 11 having a flat portion 111, a flange 121, and a second metal member 12 having a vertical wall portion 122 rising from the flange 121, and includes a step of overlapping the flat portion 111 of the first metal member 11 and the flange 121 of the second metal member 12, a step of spot welding the flat portion 111 of the first metal member 11 and the flange 121 of the second metal member 12 multiple times, and a step of line welding the flat portion 111 of the first metal member 11 and the flange 121 of the second metal member 12, wherein the spot welding is performed between an end 1211 of the flange 121 and the vertical wall portion 122, the line welding is performed at the end 1211 of the flange 121, and the length of the line weld portion 14 obtained by the line welding along the end 1211 of the flange 121 is greater than or equal to the diameter D of the spot weld portion obtained by the spot welding.

First, the flat portion 111 of the first metal member 11 and the flange 121 of the second metal member 12 are overlapped. Next, both spot welding and line welding are performed on the flat portion 111 and the flange 121. Spot welding is performed between the end 1211 of the flange 121 and the vertical wall portion 122, and line welding is performed at the end 1211 of the flange 121. This results in a line weld 14 provided at the end 1211 of the flange 121 and multiple spot welds 13 arranged between the line weld 14 and the vertical wall portion 122.

In line welding and spot welding, the length of the line weld 14 obtained by line welding along the end 1211 of the flange 121 is set to be equal to or greater than the diameter D of the spot weld obtained by spot welding. The diameter D of the spot weld can be freely controlled via the spot welding conditions. The length of the line weld 14 can be freely controlled via the travel distance of the welding torch, the laser irradiation length, etc.

The order in which spot welding and line welding are performed is not particularly limited, but it is preferable to perform spot welding first. Line welding is easily affected by the gap (plate gap) between the flat portion 111 and the flange 121, but spot welding is not affected as much by the plate gap. In addition, by performing spot welding, the plate gap can be reduced. Therefore, by performing spot welding and then line welding, the stability of the line welding can be further improved.

Spot welding includes, for example, spot welding and laser screw welding. From the viewpoint of reducing the plate gap during line welding, spot welding is preferred. Line welding includes, for example, laser welding and arc welding. From the viewpoint of suppressing thermal distortion, laser welding, which has a small heat input, is preferred. From the viewpoint of tempering the spot welded portion 13 and improving the toughness of the spot welded portion 13, arc welding, which has a large heat input, is preferred.

Furthermore, the preferred aspects of the lap welded joint 1 according to the first embodiment described above can be applied to the lap welded joint 1 according to the third embodiment.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be modified as appropriate without departing from the technical concept of the invention. Below, modified examples of the present invention are described. Note that unless otherwise specified, the aspects described below are applicable to all of the first, second, and third embodiments.

(Metal component material)
The material of the first metal member 11 and the second metal member 12 is not limited as long as it is a metal, and steel, aluminum, etc. can be applied. From the viewpoint of strength and rigidity, it is preferable that one or both of the first metal member 11 and the second metal member 12 are steel members, and from the viewpoint of light weight, it is preferable that one or both of the first metal member 11 and the second metal member 12 are aluminum members. The first metal member 11 and the second metal member 12 are made of, for example, a steel plate. It is desirable that one or both of the first metal member 11 and the second metal member 12 are made of a steel plate having a tensile strength of 780 MPa or more. This can further increase the strength and rigidity of the lap welded joint 1 and the automobile frame part. Note that the welded part of the high-strength steel plate is easily embrittled. However, in the lap welded joint 1 and the automobile frame part according to this embodiment, the fracture resistance characteristics are improved by optimizing the position and size of the line welded part 14.

Examples of high-strength steel sheets include DP steel sheets, TRIP steel sheets, dual-phase steel sheets, martensitic steel sheets, and hot-stamped steel sheets. The tensile strength of the steel sheet is preferably 1100 MPa or more, and optimally 1700 MPa or more. The steel sheet may be a cold-rolled steel sheet or a hot-rolled steel sheet.

The steel sheet may be a plated steel sheet or a non-plated steel sheet. Examples of plating that plated steel sheets have include GI plating, GA plating, Zn-Ni plating, Zn-Al plating, Zn-Mg plating, Zn-Mg-Al plating, etc. When the steel sheet constituting the first metal member 11 and/or the second metal member 12 is a zinc-based hot stamp steel sheet, zinc oxide may be contained in the surface layer of the Fe-Zn or Fe-Zn-Ni solid solution phase. When the steel sheet is an aluminum-based hot stamp steel sheet, multiple Al-Fe-Si intermetallic compound layers may be formed, and ZnO or a black coating may be formed on the intermetallic compound layer. When the steel sheet is a non-plated hot stamp steel sheet, it is preferable that the surface of the steel sheet is shot blasted to remove scale during the hot stamping process.

There are no particular limitations on the thickness of the high-strength steel plate. Generally, the thickness of steel plates used in automobile frame parts or vehicle bodies is 0.6 to 3.2 mm. This thickness may be applied to the steel plates constituting the first metal member 11 and/or the second metal member 12.

(Shape of flange 121)
From the viewpoint of further enhancing the fracture suppression effect, the width of the flange 121 of the second metal member 12 before welding is preferably 8 mm or more, and more preferably 10 mm or more, while from the viewpoint of reducing the weight of the lap welded joint 1, the width of the flange 121 is preferably 40 mm or less, and more preferably 30 mm or less. The width of the flange 121 before welding is approximately equal to the distance between the line weld portion 14 and the vertical wall portion 122 after welding. Therefore, the above-mentioned width of the flange 121 may be applied to the distance between the line weld portion 14 and the vertical wall portion 122.

(Spot welding conditions)
The conditions of spot welding performed as spot welding are not particularly limited, but the following are suitable examples. The tip of the electrode for spot welding can be DR type with a diameter of about 16 mm, a tip of 5 mm to 10 mm, and a tip curvature of 12 mm to 300 mm. The pressure can be 250 to 700 kgf, the current application time can be 0.2 to 1.0 seconds, the current application can be 5 to 11 kA, and the holding time can be 0.02 to 1.0 seconds. The current can be either a direct current or an alternating current. The current waveform can be either a single current or a multi-stage current of two or more stages, or a multi-stage current having an upslope or downslope. A post-segregation current that relieves solidification segregation of the spot welded portion by multi-stage current application, or a temper current that suppresses hardening of the spot welded portion can be performed. This can improve the joint strength and hydrogen embrittlement resistance of the spot welded portion.

(Laser screw welding conditions)
The conditions of the laser screw welding performed as the spot welding are not particularly limited, but the following are suitable examples. The welding device is preferably a remote laser welding device. A fiber laser or a semiconductor laser is used as an oscillator, and welding can be performed in a plurality of circumferential shapes with a beam diameter of 0.15 mm to 2.5 mm and an output of 2 kW to 20 kW. The shape of the spot weld 13 at this time may be circular or elliptical. Making it elliptical reduces stress concentration at the joint, leading to improved joint strength and reduced risk of delayed fracture. When the spot weld 13 is elliptical, the length of the spot weld 13 projected onto the flange end is defined as the diameter of the spot weld 13.

(Shape of Line Weld 14)
The line weld 14 provided at the end 1211 of the flange 121 may be a lap fillet weld that joins the end face of the flange 121 to the surface of the flat portion 111, as shown in Figures 4A and 4B. On the other hand, the line weld 14 may be an edge weld that joins the end face of the flange 121 to the end face of the flat portion 111, as shown in Figure 4C. In either case, the line weld 14 can be disposed at a position away from the vertical wall portion 122 to improve the fracture resistance of the lap welded joint 1.

(Laser welding conditions)
A preferred example of the line welding means is laser welding. The conditions of the laser welding are not particularly limited, but the following are preferred examples. Laser welding can be performed using a remote laser welding device. The remote laser welding device moves a laser beam between welding points at high speed using a galvanometer mirror attached to the tip of a robot arm. The remote laser welding device makes it possible to significantly reduce the welding work time. Lasers such as _CO2 lasers, YAG lasers, fiber lasers, DISK lasers, and semiconductor lasers can be used as the laser welding means. Laser welding can be performed under conditions of, for example, a laser output of 2 to 20 kW, a beam diameter at the focusing surface of 0.15 to 2.5 mm, and a welding speed of 0.1 to 20 m/min. In laser welding, wobbling, which oscillates the beam, may be used. By wobbling, even if the gap between the first metal member and the second metal member is large, both can be joined. A filler wire may be used during laser welding. By using an iron-based filler wire, line welding is possible even if there is a gap between the flange 121 and the flat portion 111. Laser brazing may also be performed using a filler wire made of a copper alloy such as Cu-Al or Cu-Si. The brazing portion is considered to be a type of welded portion. Welding may be performed by contact tracking using a filler. In order to prevent crater cracks, shrinkage cavities, holes, etc., crater treatment or a sacrificial bead treatment to extend the end of the laser weld may be performed. The line welding may also be laser-arc hybrid welding. Laser-arc hybrid welding is capable of joining both metal plates even when there is a large gap between them.

The effect of one aspect of the present invention will be explained in more detail using an example. However, the conditions in the example are merely one example of conditions adopted to confirm the feasibility and effect of the present invention. The present invention is not limited to this one example of conditions. Various conditions may be adopted in the present invention as long as they do not deviate from the gist of the present invention and the object of the present invention is achieved.

(Example 1: Simulation of axial crush and torsion of both hat members)
Simulations of axial collapse and torsion were carried out for a model of two hat members obtained by joining the flanges of hat members made of steel plates with a tensile strength of 1180 MPa and a plate thickness of 1.6 mm. The detailed configuration of the model used in the simulation is shown in Table 1.

In the simulation of axial collapse, as shown in Figure 5A, a compressive load was applied to both hat members from both ends along the axial direction (Z-axis direction) of both hat members. Figure 5B shows a graph showing the relationship between the displacement of both hat members and the stress required to cause the displacement. The value obtained by integrating the graph in Figure 5B by the displacement (integration interval: 0 to 200 mm) was calculated as the absorbed energy. Table 1 shows the ratio of the absorbed energy of each model based on the absorbed energy of Comparative Example 2, which is a conventional example.

In the torsion simulation, as shown in Figure 5C, one end of each hat component was fixed and a torsional stress was applied to the other end. The moment required to produce a torsion of 0.05 rad was calculated as the torsional rigidity. The ratio of the torsional rigidity of each model based on the torsional rigidity of Comparative Example 2, which is a conventional example, is shown in Table 1.

Comparative Example 2, which had only spot welds, and Invention Example 1, which had both spot welds and line welds, were superior in both energy absorption during axial collapse and torsional rigidity.

(Example 2: Simulation of three-point bending and twisting of a single hat member)
Simulations of static three-point bending and torsion were carried out for a model of a single-hat component obtained by joining a hat component and a flat component made of hot-stamped steel plate with a tensile strength of 1800 MPa and a thickness of 1.6 mm. The detailed configuration of the model used in the simulation is shown in Table 3.

In the three-point bending simulation, as shown in Figure 6, both ends of the single hat component were supported, a load was applied to the flat plate at the center of the single hat component, and the maximum load was measured. The ratio of the maximum load of each model based on the maximum load of Comparative Example 1, which is a conventional example, is shown in Table 4.

In the torsion simulation, one end of the single hat component was fixed and a torsional stress was applied to the other end. The moment required to produce a torsion of 0.05 rad was calculated as the torsional rigidity. The ratio of the torsional rigidity of each model based on the torsional rigidity of Comparative Example 1, which is a conventional example, is shown in Table 4.

Comparative Example 2, like Comparative Example 1, has a spot weld in the center of the flange, and further has a linear laser weld between the vertical wall and the spot weld. Comparative Example 2 has a higher torsional rigidity than the benchmark Comparative Example. Meanwhile, Comparative Example 2 and Comparative Example 1 are almost the same in terms of maximum load. The linear laser weld in Comparative Example 2 provided almost no effect in suppressing fracture of the weld in the event of a collision.

Invention examples 3 and 4, like comparative example 1, a spot weld is placed in the center of the flange, and linear laser welds are placed at the ends of the flange. In invention examples 3 and 4, both the maximum load and torsional load were increased.

Invention example 5, a laser screw weld is placed in the center of the flange, and a linear laser weld is placed at the end of the flange. In invention example 5, the spot weld in invention example 3 is replaced with a laser screw weld. In invention example 5, both the maximum load and torsional load were also increased.

In Example 6, a spot weld was provided 4 mm away from the center of the flange toward the end of the flange, and a linear laser weld was also provided at the end of the flange.
In Example 6, the spot weld of Example 3 was moved 4 mm closer to the end of the flange. Both the maximum load and the torsional load were also increased in Example 6. In Example 6, the hardness of the weld metal of the spot weld on the line weld side was 30 HV or more lower than the hardness of the weld metal of the spot weld on the opposite side to the line weld.

Comparative Example 7 has a linear laser weld in the center of the flange, and also has a linear laser weld between the vertical wall and the spot weld. Comparative Example 7 replaces the spot weld in Example 3 with a linear laser weld. The maximum load of Comparative Example 7 was significantly lower than that of Example 3, and also lower than that of the benchmark Comparative Example 1. The two linear laser welds in Comparative Example 7 did not provide the effect of suppressing breakage of the welds in the event of a collision. In Comparative Example 7, the laser weld in the center of the flange broke easily. This is presumably because the load was concentrated on the edge of the laser weld in the center of the flange.

1 Lap weld joint 11 First metal member 111 Flat portion 12 Second metal member 121 Flange 1211 End of flange 122 Vertical wall portion 123 Horizontal wall portion 124 Bending portion 13 Spot weld portion 13P Projection portion of spot weld portion 14 Line weld portion L Length of line weld portion (dimension of line weld portion along the end of the flange)
W Width of the weld line (the dimension of the weld line perpendicular to the flange edge)
D Diameter of spot weld f Support e Point of force l Point of action

Claims (15)

a first metal member having a flat portion;
a second metal member having a flange overlapping the flat portion of the first metal member and a vertical wall portion rising from the flange;
a plurality of spot welds joining the flat portion of the first metal member and the flange of the second metal member;
a line weld that joins the flat portion of the first metal member and the flange of the second metal member;
Equipped with
The line weld is provided at an end of the flange,
The spot welds are arranged between the line weld and the vertical wall portion,
A lap weld joint, wherein the length of the line weld is equal to or greater than the diameter of the spot weld. The number of the line welds is two or more,
The lap weld joint of claim 1 , wherein a plurality of said line welds are spaced apart along said edge of said flange. The lap welded joint according to claim 2, characterized in that when the plurality of spot welds are projected onto the end of the flange, centers of the projected portions of the plurality of spot welds overlap with the plurality of line welds. The lap welded joint according to claim 2, wherein when the plurality of spot welds are projected onto the end of the flange, the centers of the projections of the plurality of spot welds are between the plurality of line welds. The lap welded joint according to claim 1, characterized in that the width of the line weld is 0.5 to 3.0 mm. The lap weld joint of claim 1 , wherein one or both of the first metal member and the second metal member are steel members. both the first metal member and the second metal member are steel members;
7. The lap welded joint according to claim 6, wherein a hardness of the weld metal of the spot weld portion on the side of the line weld portion is lower by 25 HV or more than a hardness of the weld metal of the spot weld portion on the side opposite to the line weld portion. The lap welded joint according to claim 1, wherein the line weld is a laser weld or an arc weld. The lap weld joint according to claim 1 , wherein the spot welds are spot welds or laser screw welds. 2. The lap welded joint according to claim 1, wherein a distance between the line weld and the vertical wall portion is 10.0 mm or more. 2. The lap welded joint according to claim 1, wherein a distance between an end of the spot weld on the side of the vertical wall portion and the vertical wall portion is 10.0 mm or less. An automobile frame part having a lap weld joint according to any one of claims 1 to 11. A method for manufacturing a lap welded joint from a first metal member having a flat portion, and a second metal member having a flange and a vertical wall portion rising from the flange, comprising the steps of:
overlapping a flat portion of the first metal member with the flange of the second metal member;
spot welding the flat portion of the first metal member and the flange of the second metal member a plurality of times;
line welding the flat portion of the first metal member and the flange of the second metal member;
Equipped with
The spot welding is performed between an end of the flange and the vertical wall portion,
the line weld is at the end of the flange;
A method for manufacturing a lap welded joint, wherein the length of the line weld obtained by the line welding along the end of the flange is equal to or greater than the diameter of the spot weld obtained by the spot welding. The method for manufacturing a lap welded joint according to claim 13, wherein the spot welding is performed before the line welding. The method for manufacturing a lap welded joint according to claim 13 or 14, characterized in that the spot welding is spot welding.

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