JP6922753B2 - Welded joint structure and welded joint method - Google Patents

Description

The present invention relates to a welded joint structure and a welded joint method in which one part having a welded flange portion on the tip side and the other part having a contact surface portion with which the welded flange portion abuts are welded and joined.

Of the chassis parts of automobile bodies, many of the frame and suspension parts are welded joint structures assembled by arc welding. Of the performance required for chassis and suspension parts, durability and fatigue strength against input load from the road surface are one of the most important performance requirements. Therefore, the fatigue strength of chassis, suspension parts, etc. is required to be improved more than before.

When a welded joint structure assembled by arc welding breaks, most of it is due to fatigue cracks, and most of the fatigue cracks are welded joints, especially weld toes (welded metal and welded). It is said to occur from the boundary with the base metal) (Non-Patent Document 1).

In recent years, in order to improve the collision safety performance of automobiles and comply with fuel efficiency regulations, the weight of automobile bodies has been reduced. Therefore, recently, high-strength steel plates have been applied not only to the body frame members but also to chassis parts that have been required to secure the minimum wall thickness from the viewpoint of ensuring rust prevention, more than ever. Consideration is being given to thinning the wall. However, when a high-strength steel plate is applied, there is a concern that the fatigue strength may be further reduced due to gauge down, a large difference in strength from the weld metal, and a large residual stress during molding. .. Therefore, improving the fatigue strength at the welded joint is a major issue in reducing the weight of the automobile body by applying high-strength steel plates, and for that purpose, it is necessary to reduce the stress concentration at the welded joint, which directly affects the fatigue strength. is important.

Therefore, as a method of reducing stress concentration in the welded joint, measures by improving the welding method such as grinding the weld toe with a grinding machine, changing the welding wire or changing the shield gas at the time of welding have been proposed. Has been done. For example, Patent Document 1 discloses a technique for smoothing the shape of a weld toe by a peening process. However, these methods have a problem that extra cost and man-hours are required for post-treatment and improvement of the construction method.

Further, in Patent Document 2, a groove along the welding direction is formed in a part or all of the fillet welded portion of one part, and the groove is filled with a weld metal at the time of welding, and the leg length of the weld bead is the above groove. A method of welding so as to be larger than the width of is disclosed.

Further, in Patent Document 3, in order to suppress bending deformation of the steel plate joined by the fillet welded joint and reduce stress concentration in the vicinity of the welded portion, the steel plate in the vicinity of the weld bead is press-formed in advance before welding. A technique for forming a ribbed press bead so that a part of the press bead is in contact with or overlaps with a weld bead is disclosed.

WO2011 / 055848A1 Japanese Unexamined Patent Publication No. 2008-183569 WO2016 / 129690A1

Journal of the Welding Society, Vol. 62 (1993) No. 8, p. 595-598

Welded joint structure in which the welded flange portion provided on the tip end side of one component having a bent portion is brought into contact with the surface (contact surface portion) of the other component and the welded flange portion and the contact surface portion are welded and joined. Even in the body, when a load is repeatedly applied to the welded joint portion which is the welded joint portion, most of the fatigue cracks are generated from the welded joint portion, particularly the weld toe portion.

However, the welding method disclosed in Patent Document 2 is intended for a T-shaped welded joint portion, and the groove formed in one of the members is filled with a weld metal so that the leg length of the weld bead is larger than the width of the groove. Since welding is performed so that the size is large, a large amount of weld metal is required, and the weld toe is located on the surface of the lower member where no groove is formed, so the shape of the weld toe is There is a problem that the effect of improving the fatigue strength may not be sufficiently obtained without smooth relaxation.

Further, the welding method disclosed in Patent Document 3 does not cover a welded joint structure in which a welded flange portion is formed at the tip of a butt member and joined. Therefore, a welded joint structure in which the welded flange portion provided on the tip end side of one component having a bent portion is brought into contact with the contact surface portion of the other component and the welded flange portion and the contact surface portion are welded and joined. Also, a technique for improving fatigue strength has been desired.

The present invention has been made to solve the above-mentioned problems, and is excellent in fatigue strength without increasing the welding cost and the number of steps, and one part having a welding flange portion on the tip side and the welding. It is an object of the present invention to provide a welded joint structure and a welded joint method formed by welding and joining the other part having a contact surface portion with which the flange portion comes into contact.

(1) The welded joint structure according to the present invention is erected with one component having a continuous surface portion via a bent portion and the tip end side of each of the surface portions sandwiching the bent portion in contact with each other. Part The one part and the other part have a convex portion in the vicinity of the end portion of the adjacent welded flange portion on the abutting surface portion, and the welded flange portion and the abutting surface portion are welded and joined to each other and welded. It is characterized in that the weld toe portion of the bead is located on the inclined surface portion of the convex portion on the welding flange portion side.

(2) In the welded joint structure according to the present invention, in the above-mentioned (1), the portion where the tensile load acts is welded together with the convex portion provided, and the portion where only the compressive load acts is described above. It is characterized in that it is welded and joined without providing a convex portion.

(3) In the above-mentioned (1) or (2), the convex portion has an extending portion extending along the welded flange portion, and the protrusion height of the convex portion is h. When the radius of curvature in the height direction of the lower end of the convex portion is R, the overlapping length of the extending portion and the welded flange portion is L, and the plate thickness of the welded flange portion is t, R ≧ t, h It is characterized in that ≧ t and L ≧ 0 are satisfied.

(4) In the welding joining method according to the present invention, one part having a continuous surface portion via a bent portion is erected with the tip side of each of the surface portions sandwiching the bent portion abutting against the other part. The one part has a welded flange portion on the tip end side of each surface portion sandwiching the bent portion, and the one part is adjacent to the contact surface portion of the other part with which the welded flange portion abuts. A convex portion is formed in the vicinity of the end portion of the welded flange portion that fits, and the welded flange portion and the abutting portion are brought into contact with each other so that the weld toe portion of the weld bead is located on the inclined surface portion on the welded flange portion side of the convex portion. It is characterized by welding and joining with the surface portion.

(5) In the welding joining method according to the present invention, in the method described in (4) above, a tensile load acts in a state where the welding flange portion of the one part and the contact surface portion of the other part are welded and joined. The part to be applied and the part on which the compressive load is applied are specified, and the convex portion is provided on the part on which the specified tensile load is applied to weld and join the welded flange portion and the contact surface portion, and the specified compressive load is applied. The portion on which only acts is characterized in that the welded flange portion and the contact surface portion are welded and joined without providing the convex portion.

(6) In the above-mentioned (4) or (5), the convex portion has an extending portion extending along the welded flange portion, and the protrusion height of the convex portion is h. When the radius of curvature in the height direction of the lower end of the convex portion is R, the overlapping length of the extending portion and the welded flange portion is L, and the plate thickness of the welded flange portion is t, R ≧ t, h It is characterized in that ≧ t and L ≧ 0 are satisfied.

In the present invention, one part having a continuous surface portion via a bent portion and the other part erected with the tip side of each of the bent portions sandwiching the bent portion are welded and joined. The one part has a welded flange portion on the tip end side of each of the surface portions sandwiching the bent portion, and the other part is adjacent to each other on the contact surface portion with which the welded flange portion abuts. The one part and the other part have a convex portion in the vicinity of the end portion of the weld flange portion, the weld flange portion and the contact surface portion are welded and joined, and the weld toe portion of the weld bead is the weld toe. By being located on the inclined surface portion on the welding flange portion side of the convex portion, the stress concentration when a load is applied to the welding toe end portion is alleviated, and the fatigue strength is increased without increasing the welding cost and the number of steps. Excellent fatigue strength can be improved.

It is the schematic of the welded joint structure which concerns on embodiment of this invention. It is a figure which shows an example of one part provided in the welded joint structure which concerns on this embodiment. It is a figure explaining the position of the convex part provided in the other part provided with the welded joint structure which concerns on embodiment of this invention. It is a schematic diagram of the conventional welded joint structure. It is a figure explaining the fatigue test method of the welded joint structure which concerns on this invention. It is a figure explaining the shape of the weld toe portion of the weld bead in the conventional weld joint structure. It is a figure explaining the shape of the convex part provided on the contact surface part of the other part in the welded joint structure which concerns on this embodiment. It is a figure which shows the example of another aspect of the welded joint structure which concerns on this embodiment. It is the schematic of the other part in another aspect of the welded structure which concerns on this embodiment. It is a figure explaining the position of the convex part provided in the other part in the other aspect of the welded joint structure which concerns on this embodiment. It is a figure explaining the welding length of the weld bead in the weld-joint structure which concerns on this embodiment (the 1). It is a figure explaining the welding length of the weld bead in the weld-joint structure which concerns on this embodiment (the 2). It is a figure which shows the welded joint structure used in the Example of this invention. It is a figure explaining the repeated load acting on the welded joint structure in the fatigue test which concerns on embodiment of this invention. It is a graph which shows the measurement result of the fatigue life obtained in the fatigue test which concerns on Example of this invention.

The welded joint structure and the welded joint method according to the embodiment of the present invention will be described below. In the present specification and the drawings, elements having substantially the same function and configuration are designated by the same reference numerals, so that duplicate description will be omitted.

<Welded joint structure>
As shown as an example in FIG. 1, the welded joint structure 1 according to the present embodiment has one component 10 having surface portions 13 and 15 continuous via the bent portion 11, and the bent portion 11 in the surface portions 13 and 15. The component 10 is provided with the other component 20 to which the component 10 is erected by abutting the tip end side sandwiching the same.

The component 10 has welded flange portions 17 and 19 on the tip side of the surface portion 13 and the bent portion 11 of the surface portion 15 so as to sandwich the bent portion 11. In the present embodiment, as shown in FIG. 2, the part 10 has a closed cross-section in which two parts 10a having a U-shaped cross section made of a steel plate are welded and joined.

As shown in FIGS. 1 and 3, the component 20 is located in the vicinity of the contact surface portion 21 with which the welded flange portions 17 and 19 of the component 10 abut and the end portions of the adjacent welded flange portions 17 and 19 on the contact surface portion 21. It has a convex portion 23 provided. Here, the convex portion 23 is provided so as to project toward the component 10 across the ends of the welded flange portions 17 and 19 in the width direction (welding direction in each of the welded flange portions 17 and 19).

Then, in the parts 10 and 20, the welding flange portions 17 and 19 and the contact surface portion 21 are welded and joined, and the welding toe portion 31 of the welding bead 30 is an inclined surface portion on the welding flange portions 17 and 19 side of the convex portion 23. It is located at 23a (see the cross-sectional view in the dotted line ○ in FIG. 1).

≪Reason for improved fatigue strength≫
A convex portion 23 is provided on the contact surface portion 21 of the component 20, and the welding flange portions 17 and 19 of the component 10 and the component 20 are contacted so that the weld toe portion 31 of the weld bead 30 is located on the inclined surface portion 23a of the convex portion 23. The reason why the fatigue strength of the welded joint structure 1 is improved by welding and joining the contact surface portion 21 will be described below.

In the conventional welded joint structure 3 as shown in FIG. 4, the component 10 having the welded flange portions 17 and 19 on the tip side is brought into contact with the contact surface portion 41 of the component 40, and is in contact with the welded flange portions 17 and 19. The contact surface portion 41 is welded and joined.
Then, when a fatigue test is performed on the welded joint structure 3 by repeatedly applying a load to the upper part of the part 10 along the x direction as shown in FIG. 5, the portion where the tensile load acts (in the dashed elliptical shape in FIG. 5). Stress concentration occurs at the weld toe portion 31 of the weld bead 30 at the surrounding portion). In particular, in the welded joint structure 3, since the rigidity is increased by the bent portion 11 of the component 10, the vicinity of the widthwise end portions of the welded flange portions 17 and 19 adjacent to each other via the bent portion 11 (broken line in FIG. 4). High stress is concentrated on the weld toe 31 at the start and end 33 of the weld bead 30 (the portion surrounded by ◯), and fatigue cracks occur.

The reason why the stress is concentrated on the weld toe portion 31 in the welded joint structure 3 is that the welded joint portion formed by fillet welding the two parts 10 and 40 as described above is not a macroscopic structure. This is because it is continuous and the weld toe portion 31 has a small radius of curvature ρ and has a notched shape as shown in FIG.

In the welded joint structure 1 according to the present embodiment shown in FIG. 1, since the weld toe portion 31 at the start and end 33 of the weld bead 30 is located on the inclined surface portion 23a of the convex portion 23, the weld toe end portion The radius of curvature ρ of 31 is increased, and stress concentration is reduced. Further, in the component 20, since the convex portion 23 is formed near the ends of the weld flange portions 17 and 19 of the component 10, the rigidity around the start and end 33 of the weld bead 30 is increased and deformation is suppressed. Therefore, the stress concentration can be further reduced. As a result, the fatigue strength of the welded joint structure 1 is improved without increasing the welding cost and the number of steps.

≪About the shape of the convex part≫
Next, a suitable shape of the convex portion 23 formed on the contact surface portion 21 of the component 20 will be described.
As shown in FIG. 7, the convex portion 23 has an extending portion 23b extending along each of the welded flange portions 17 and 19, the protrusion height of the convex portion 23 is h, and the lower end portion of the convex portion 23. When the radius of curvature of 23c in the height direction is R, the overlapping length of the extension portion 23b and the welded flange portion 17 (or the welded flange portion 19) is L, and the plate thickness of the welded flange portions 17 and 19 is t. It is preferable to satisfy R ≧ t, h ≧ t, and L ≧ 0. It will be verified in Examples described later that the shape of the convex portion 23 is suitable for improving the fatigue strength by defining the shape in the above range.

Regarding the overlapping length L, even if L = 0 mm, there is a welding bead at the tip of the convex portion 23 and the end portion of the welding flange portion, and the welding toe is located on the inclined surface portion of the convex portion. , Stress concentration is relaxed and fatigue strength is improved.

≪About other aspects≫
The welded joint structure 1 in the above description has a closed cross-sectional shape in which the part 10 that comes into contact with the contact surface portion 21 of the part 20 is welded and joined with two parts 10a having a U-shaped cross section. As shown in FIG. 8A, the welded joint structure according to the above may be a welded joint between a part 10a having a U-shaped cross section and a part 50.

The component 10a has surface portions 13, 15a that are continuous via the bent portion 11, and welded flange portions 17, 19a on the tip side of the surface portions 13, 15a that sandwich the bent portion 11 (see FIG. 2).
On the other hand, the component 50 is provided with a convex portion 53 on the contact surface portion 51 near the ends of the welded flange portions 17 and 19a adjacent to each other with the bent portion 11 of the component 10a interposed therebetween (FIG. 8 (a), FIG. 9).

Then, in the component 10a and the component 50, the welding flange portions 17 and 19a and the contact surface portion 51 are welded and joined, and the welding toe portion 31 of the welding bead 30 is an inclined surface portion on the welding flange portion 17 and 19a side of the convex portion 53. It is located at 53a.

Further, the present invention may be a welded joint structure 7 including a part 10a and a part 55 as shown in FIG. 8B. The component 55 is provided with a convex portion 53 in the vicinity of the ends of the welded flange portions 17 and 19a adjacent to each other with the bent portion 11 interposed therebetween, and is convex in the vicinity of the end portion of the welded flange portions 17 and 19a opposite to the convex portion 53. A portion 57 is provided, and the component 10a and the component 55 are welded and joined so that the welding toe portion 31 of the welding bead 30 is located on the convex portion 57.

In such a welded joint structure 7, when a tensile load acts on an end portion opposite to the end portion of the welded flange portions 17 and 19a provided with the convex portion 53 and stress concentration occurs, the weld bead 30 Since the weld toe portion 31 of the above is located on the inclined surface portion 57a of the convex portion 57, the stress concentration is relaxed and the fatigue strength is improved.

Further, in the above description, for all the bent portions 11 of the one component 10 to which the tip side is welded and joined, the other component is near the end portion in the width direction of the welded flange portions 17 and 19 adjacent to each other with the bent portion 11 interposed therebetween. A convex portion 23 was provided on the contact surface portion 21 of the 20 (FIG. 1).

However, in the present invention, for example, as shown in FIG. 8C, a welded joint structure 9 including a part 10 and a part 50 is not provided with a convex portion 53 for all the bent portions 11. There may be. Regarding the position where the convex portion 53 is provided, for example, when a load is applied to the upper portion of the component 10 as shown in FIG. 4, the welding flange portion 17 side (left side in FIG. 10) on one side is provided. When a tensile load acts and only a compressive load acts on the welding flange portion 17 (right side in FIG. 10) on the other side, the welding flange portions 17 and 19 sandwiching the bent portion 11 on the side on which the tensile load acts. The convex portion 53 may be provided in the vicinity of the end portion in the width direction, and the convex portion may not be provided on the contact surface portion 51 on the welding flange portion 17 side on which only the compressive load acts.

The reason why the convex portion is not provided in the portion where only the compressive load acts is that even if the compressive load repeatedly acts on the weld toe, stress concentration and fatigue cracks due to this are unlikely to occur. ..

≪Welding bead length≫
Further, in the welded joint structure according to the present invention, as shown in FIG. 11A, the weld length of the weld bead 30 is the length in the width direction of the weld flange portions 17 and 19 (hereinafter, "base weld length"). It should be equal to). However, as shown in FIGS. 11 (b) and 12 (c), for example, the welding length of the weld bead 30 is such that the start and end 33 of the weld bead 30 is extended along the inclined surface portion 53a of the convex portion 53 to form a base. It may be longer than the welding length. In the weld bead 30 in which the start and end 33 is extended, the welding toe portion 31 at the start and end 33 is located on the inclined surface portion 53a, as in the case of the weld bead 30 having the base welding length shown in FIG. It is alleviated and fatigue strength is improved.

Further, as shown in FIG. 12D, the present invention may be a welded joint structure 9 in which the weld beads 60 are continuous over the entire circumference of the component 10. Also in the welded joint structure 9, since the weld toe portion 61 of the weld bead 60 is located on the inclined surface portion 53a of the convex portion 53, welding is performed as shown in FIGS. 11 (a), 11 (b) and 12 (c). Fatigue strength is improved as in the case where the weld beads 30 are provided on the flange portions 17 and 19 respectively.
The effect of the weld bead length on the fatigue strength will also be verified in Examples described later.

<Welding joining method>
Next, the welding joining method according to the embodiment of the present invention will be described.
In the welding joining method according to the present embodiment, as shown as an example in FIG. 1, a part 10 having continuous surface portions 13 and 15 via a bent portion 11 is sandwiched between the bent portions 11 in each of the surface portions 13 and 15. The side is brought into contact with the component 20 to be erected and welded.

As described above, the component 10 has the welded flange portions 17 and 19 on the tip side of the surface portions 13 and 15 sandwiching the bent portion 11, respectively.
On the other hand, in the component 20, the convex portion 23 is formed near the ends of the welded flange portions 17 and 19 on the contact surface portion 21 with which the welded flange portions 17 and 19 abut. Then, the welding flange portions 17 and 19 and the contact surface portion 21 are welded and joined so that the welding toe portion 31 of the welding bead 30 is located on the inclined surface portion 23a on the welding flange portions 17 and 19 sides of the convex portion 23.
By welding and joining the part 10 and the part 20 in this way, the stress concentration at the welding toe portion 31 of the start and end 33 of the welding bead 30 is alleviated, and the fatigue strength is increased without increasing the welding cost and the number of steps. Can be improved.

Further, in the welding joining method according to the present invention, for example, as shown in FIG. 4, when a load is repeatedly applied to the component 10 in a state where the component 10 and the component 40 are welded and joined, a portion on which a tensile load acts is used. A portion where only the compressive load acts is specified, and as shown in FIG. 10, a convex portion 53 is provided over the widthwise end of the welded flange portion 17 at the portion where the specified tensile load acts, and only the compressive load acts. A convex portion may not be provided in the vicinity of the widthwise end portion of the welded flange portion 17 at the portion to be welded.

The portion on which the tensile load acts and the portion on which only the compressive load acts may be specified based on the direction in which the load is applied, or may be specified by CAE analysis, fatigue test, or the like.

Further, the convex portion 23 provided by the welding joining method according to the present embodiment has an extending portion 23b extending along each of the welding flange portions 17 and 19, and the protrusion height of the convex portion 23 is set to h. When the radius of curvature of the lower end portion 23c of the convex portion 23 in the height direction is R, the overlapping length of the extension portion 23b and the welded flange portions 17 and 19 is L, and the plate thickness of the welded flange portions 17 and 19 is t. It is preferable that the shape satisfies R ≧ t, h ≧ t, and L ≧ 0.

Further, the welding length of the welding bead 30 may be longer than or equal to the length in the width direction of the welding flange portions 17 and 19, and as shown in FIGS. 11B and 12C, the start and end of the welding bead 30 The 33 may be extended and formed, or as shown in FIG. 12 (d), the weld bead 60 may be formed over the entire circumference of the component 10 to which the tip side is welded and joined.

An experiment for confirming the action and effect of the present invention has been carried out, which will be described below.
In this example, as an example of the invention, a fatigue test was performed on the welded joint structure 9 having the shape shown in FIG. 13 as a test object, and the fatigue strength was evaluated.

<Test material and part shape>
As shown in FIG. 13, the welded joint structure 9 is formed by welding and joining parts 10 and 50, and the parts 10 and 50 are hot-rolled steel plates having a plate thickness of t = 2.9 mm and a class of 780 MPa. Was used as a test material.

As shown in FIG. 2, the component 10 is formed by welding and joining the openings of the component 10a having a U-shaped cross section. Welded flange portions 17 and 19 are provided on the tip sides of the surface portion 13 and the bent portion 11 of the surface portion 15 so as to sandwich the bent portion 11.

As shown in FIG. 9, the component 50 has a U-shaped cross section, and the convex portion 53 is bent and formed on the contact surface portion 51. The lower end portion of the convex portion 53 (corresponding to the lower end portion 23c of the convex portion 23 in FIG. 7) has a curved shape in the height direction, and its radius of curvature R is 4 mm (> plate thickness t = 2.9 mm).

Parts 10 and 50 are welded using a 780 MPa class welding wire with a diameter of 1.2 mm under the conditions of welding current 205 A, voltage 23 V, speed 85 cm / min, Ar 80% -CO ₂ 20% shield gas 20 L / min. The flange portions 17 and 19 and the contact surface portion 51 were welded and joined. At the start and end 33 of the weld bead 30, the weld toe portion 31 is located on the inclined surface portion 53a of the convex portion 53 at the time of welding joint.

Further, in the present embodiment, the welded joint structure 3 (see FIG. 4) in which the welded flange portions 17 and 19 of the component 10 are welded and joined without providing the convex portion on the contact surface portion 41 of the component 40 is used as a comparative example, and the invention is made. A fatigue test was performed as in the example.

The welded joint structure 3 according to the comparative example has the same dimensions as the welded joint structure 9 shown in FIG. 13, and is the same as the welded flange portions 17 and 19 under the same welding conditions as the welded joint structure 9 according to the above-mentioned invention example. The contact surface portion 41 was welded and joined. However, in the welded joint structure 3, the weld toe portion 31 at the start and end 33 of the weld bead 30 is located on the flat portion of the contact surface portion 41.

<Fatigue test method and test conditions>
In the fatigue test method of the welded joint structure 9 according to the invention example, as in the fatigue test shown in FIG. 5, the part 50 is fixed and a load is repeatedly applied to the upper part of the part 10, and the welded joint structure 9 is cracked. Fatigue life was evaluated by measuring the number of cycles of repeated load until it occurred.
Here, the loading direction of the repetitive load applied to the welded joint structure 9 is the same as the x direction shown in FIG. 5, and as shown in FIG. 14 (a), the tension between 0 kN and 6 kN is applied to the convex portion 53 side. The load was one-sided swing with a load ratio (minimum load / maximum load) of 0.

In the fatigue test of the welded joint structure 3 according to the comparative example, as shown in FIG. 14B, a tensile load of 0 kN to 6 kN was applied to the flat portion where the welded flange portion 17 and the contact surface portion 51 were welded and joined. The load ratio was 0 (one-sided swing), and the number of cycles of repeated loading until cracks occurred was measured.
Table 1 shows the test conditions. Here, the overlapping length L = 0 mm has a convex portion 53 shown in FIG. 9, a welding bead is provided at the tip thereof and the ends of the weld flange portions 17 and 19, and the weld toe portion is a convex portion. This is the case when it is located on an inclined surface. Further, since the overlapping length L “−” does not have the convex portion 53, it is the case where only the welded flange portions 17 and 19 are provided.

In Table 1, No. 1-No. 7 is an example of the present invention, in which the protrusion height h of the convex portion 53 provided on the component 50 is changed to 3 mm or 5 mm, and the overlapping length L of the convex portion 53 and the welded flange portions 17 and 19 is changed in the range of 0 mm to 20 mm. It is a thing. The protrusion height h is equal to or larger than the plate thickness t (= 2.9 mm) of the welded flange portions 17 and 19.
On the other hand, No. Reference numeral 8 denotes a comparative example, in which the welded flange portions 17 and 19 of the component 10 are welded together without providing a convex portion on the contact surface portion 41 of the component 40 shown in FIG.

As shown in Table 1, No. 1 according to the comparative example. In No. 8, the radius of curvature of the weld toe portion 31 of the weld bead 30 was 0.2 mm. On the other hand, No. 1-No. In No. 7, the radius of curvature ρ of the weld toe portion 31 of the weld bead 30 was substantially constant at 1.5 to 1.6 mm regardless of the values of the protrusion height h and the overlap length L, and increased as compared with the comparative example.

<Fatigue test results>
FIG. 15 shows the fatigue test results.
No. which is an example of the present invention. 1-No. No. 7 is a comparative example. The result was that the fatigue life was improved as compared with 8. As a result, as shown in Table 1 above, the radius of curvature ρ of the weld toe portion 31 in the examples of the present invention (No. 1 to No. 7) is increased as compared with the comparative example (No. 8). Therefore, it is shown that the fatigue strength is improved because the stress concentration at the weld toe portion 31 is relaxed.

Next, the relationship between the shape of the convex portion 53 and the fatigue life in the welded joint structure 9 according to the example of the present invention shown in FIG. 13 will be examined.
First, No. 1 in which the protrusion height of the convex portion 53 was set to h = 3 mm. No. 1, 3 and h = 5 mm. Comparing 2 and 4, No. 2 with h = 5 mm. Fatigue life is improved in 2 and 4. It is considered that this is because increasing the protrusion height h of the convex portion 53 improves the rigidity in the vicinity of the weld toe portion 31 and reduces the stress concentration.

Next, the protrusion height h of the convex portion 53 was constant at 3 mm, and the overlapping length L was changed in the range of 0 mm to 20 mm. Comparing 2, 4, 5, 6 and 7, it was found that the fatigue life was improved by increasing the overlapping length L. It is considered that this is because the convex portion 53 becomes longer by increasing the overlapping length L, the rigidity in the vicinity of the weld toe portion 31 is improved, and the stress concentration is reduced.

As described above, in the welded joint structure according to the present invention, it has been shown that the stress concentration at the weld toe portion of the weld bead is relaxed, the fatigue strength is improved, and the fatigue life is increased.

1 Welded joint structure (invention)
3 Welded joint structure (conventional example)
5 Welded joint structure (invention)
7 Welded joint structure (invention)
9 Welded joint structure (invention)
10 Parts 10a Parts 11 Bending parts 13, 15 Faces 17 Welding flanges 19, 19a Welding flanges 20 Parts 21 Contact surface 23 Convex 23a Inclined surface 23b Extension 23c Lower end 30 Welding bead 31 Welding toe 33 End 40 Parts 41 Contact surface part 50 Parts 51 Contact surface part 53 Convex part 53a Inclined surface part 55 Parts 57 Convex part 57a Inclined surface part 60 Welding bead 61 Welding toe

Claims (6)

One part having a continuous surface portion via the bent portion and having a welding flange portion on the tip end side of each of the bent portions sandwiching the bent portion is brought into contact with the tip end side of each of the surface portions sandwiching the bent portion. The one part provided is provided with the other part to be welded and joined.
The other component is provided in the vicinity of the end portion of the adjacent welded flange portion on the contact surface portion with which the welded flange portion abuts , and a convex portion is provided at a portion where a tensile load acts when a repeated load is applied. is, the convex portion is not provided at the portion where only compressive load is applied,
In the one part and the other part, the welding flange portion and the contact surface portion are welded and joined, and the welding toe portion of the welding bead is welded on the convex portion at the portion where the convex portion is provided. A welded joint structure characterized in that it is located on an inclined surface portion on the flange portion side. The convex portion has an extending portion extending along the welded flange portion, the protrusion height of the convex portion is h, the radius of curvature in the height direction of the lower end portion of the convex portion is R, and the extending portion. The first aspect of claim 1 is that when the overlapping length of the protruding portion and the welded flange portion is L and the plate thickness of the welded flange portion is t, R ≧ t, h ≧ t, and L ≧ 0 are satisfied. The welded joint structure described. One part having a continuous surface portion via the bent portion and having a welding flange portion on the tip end side of each of the bent portions sandwiching the bent portion is brought into contact with the tip end side of each of the surface portions sandwiching the bent portion. The one part provided is provided with the other part to be welded and joined.
The other component has a convex portion in the vicinity of the end portion of the adjacent welded flange portion on the contact surface portion with which the welded flange portion abuts.
In the one part and the other part, the welded flange portion and the contact surface portion are welded and joined, and the weld toe portion of the weld bead is located on the inclined surface portion on the welded flange portion side of the convex portion. Welding
The convex portion has an extending portion extending along the welded flange portion, the protrusion height of the convex portion is h, the radius of curvature of the lower end portion of the convex portion in the height direction is R, and the extending portion. A welded joint structure characterized in that R ≧ t, h ≧ t, and L ≧ 0 are satisfied when the overlapping length of the protruding portion and the welded flange portion is L and the plate thickness of the welded flange portion is t. .. One part having a continuous surface portion via the bent portion and having a welded flange portion on the tip end side of each of the bent portions sandwiching the bent portion, and the tip end side sandwiching the bent portion on each of the surface portions corresponds to the other part. It is a welding joining method in which they are brought into contact with each other and erected and joined by welding.
Welding the welding flange portion of the one component and the contact surface portion of the other component in the vicinity of the end portions of the adjacent welding flange portions on the contact surface portion of the other component with which the welding flange portion abuts. When a load is repeatedly applied in the joined state, identify the part where the tensile load acts and the part where only the compressive load acts.
A convex portion is provided on the portion where the specified tensile load acts, and the welding flange portion and the contact surface portion are welded and joined, and the convex portion is not provided on the portion where only the specified compressive load acts. The welded flange portion and the contact surface portion are welded and joined to each other.
A welding joining method characterized by welding so that a welding toe portion of a welding bead is located on an inclined surface portion on the welding flange portion side of the convex portion at a portion where the convex portion is provided. The convex portion has an extending portion extending along the welded flange portion, the protrusion height of the convex portion is h, the radius of curvature in the height direction of the lower end portion of the convex portion is R, and the extending portion. The fourth aspect of claim 4 is that when the overlapping length of the protruding portion and the welded flange portion is L and the plate thickness of the welded flange portion is t, R ≧ t, h ≧ t, and L ≧ 0 are satisfied. The welded joining method described. One part having a continuous surface portion via the bent portion and having a welded flange portion on the tip end side of each of the bent portions sandwiching the bent portion, and the tip end side sandwiching the bent portion on each of the surface portions corresponds to the other part. It is a welding joining method in which they are brought into contact with each other and erected and joined by welding.
A convex portion is formed in the vicinity of the end portion of the adjacent welded flange portion on the contact surface portion of the other component with which the welded flange portion abuts.
The welding flange portion and the contact surface portion are welded and joined so that the welding toe portion of the welding bead is located on the inclined surface portion on the welding flange portion side of the convex portion.
The convex portion has an extending portion extending along the welded flange portion, the protrusion height of the convex portion is h, the radius of curvature of the lower end portion of the convex portion in the height direction is R, and the extending portion. A welding joining method characterized in that R ≧ t, h ≧ t, and L ≧ 0 are satisfied when the overlapping length of the protruding portion and the welding flange portion is L and the plate thickness of the welding flange portion is t.

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