Welded joint structure

Abstract

To solve such problems that in a conventional weld joint structure, the manufacturing cost and weight increase because of the use of a backing strip, and also stress concentration is easy to generate in a weld bead when load is applied to each component.SOLUTION: In a weld joint structure welded by lapping metal plates 1, 2 and melting a lapped portion, at least one of the plates 1, 2 has an exhaust groove 3 connecting to a weld root part P being a boundary of the lapped portion or a melting part Q at welding. By preparing the weld joint structure in which the exhaust groove 3 has an inclined plane S1 from one edge part 3a at a weld root part P side toward a bottom part on a cross section, a favorable weld bead B is obtained by eliminating a gas generating at the time of welding without increasing a production cost or weight and besides, stress concentration generating in the weld bead B is restrained.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a welded joint structure used when welding a plurality of overlapping metal plates. [Background technology]

[0002] A conventional welded joint structure is described in Patent Document 1 under the name of a backing metal for welding. The welded joint structure described in Patent Document 1 is a structure in which a backing metal is interposed between columns or a column and a diaphragm when they are butt-welded together. This backing metal has a gas venting slit for releasing gas, and by discharging gas generated during welding from the gas venting slit, it prevents bubbles from remaining in the molten metal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-291087 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional welded joint structure described above, a backing metal, which is a separate component, is interposed between the components to be joined, which increases manufacturing costs and weight. In addition, because the backing metal is simply inserted into the components, there is a problem that stress concentration is likely to occur in the weld bead when a load is applied to each component. Solving these problems was an issue.

[0005] The present invention has been made in consideration of the above-mentioned problems in the conventional art, and aims to provide a welded joint structure that can allow gas generated during welding to escape, thereby obtaining a good weld bead, without increasing manufacturing costs or weight, and that can suppress stress concentration in the weld bead. [Means for solving the problem]

[0006] The welded joint structure according to the present invention is 1st and 2nd The metal plates are stacked together, A corner portion formed by an end face of the first metal plate and a main surface of the second metal plate This welded joint structure is made by melting and welding. First and second At least one of the metal plates is The corners of the contact surface with the other metal plate are At the weld root or during welding Formed in the corner The exhaust groove is connected to the fusion zone, and the exhaust groove extends from one edge on the weld root side in the cross section. The exhaust ditch It is characterized by having a sloped surface toward the bottom. Effect of the Invention

[0007] The welded joint structure according to the present invention is 1st and 2nd The metal plates are stacked together, A corner portion formed by an end face of the first metal plate and a main surface of the second metal plate When melting and welding, Formed in the corner The gas generated in the molten part is discharged to the outside, while the gas that has entered between the metal plates is made to flow into the exhaust groove, and at that time, the gas is made to flow along the inclined surface to the bottom of the exhaust groove, thereby suppressing the backflow of the gas into the molten part. In the cross section, From one edge on the weld root side The exhaust ditch Since there is an inclined surface toward the bottom, the thickness of the metal plate decreases gradually, rather than abruptly, in the direction from the weld root toward the exhaust groove.

[0008] In this way, the above-mentioned welded joint structure can obtain a good weld bead by allowing gas generated during welding to escape using the exhaust groove without increasing manufacturing costs or weight, and the inclined surface of the exhaust groove gradually reduces the plate thickness of the metal plate, thereby suppressing stress concentration in the weld bead when a load is applied to the metal plate. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view illustrating a first embodiment of a welded joint structure according to the present invention. [Diagram 2] FIG. 2 is a perspective view showing the metal plate shown in FIG. [Diagram 3] FIG. 2 is a perspective view showing a suspension member which is an example of a metal plate. [Figure 4] 4 is a cross-sectional view taken along line AA in FIG. 3 and an enlarged view of a main portion. [Diagram 5] FIG. 11 is a perspective view illustrating a metal plate according to a second embodiment. [Figure 6] FIG. 11 is a perspective view illustrating a metal plate according to a third embodiment. [Figure 7] FIG. 13 is a cross-sectional view illustrating a metal plate according to a fourth embodiment. [Figure 8] FIG. 13 is a cross-sectional view illustrating a metal plate according to a fifth embodiment. [Figure 9] FIG. 13 is a cross-sectional view illustrating a metal plate according to a sixth embodiment. [Figure 10] FIG. 13 is a cross-sectional view illustrating a metal plate according to a seventh embodiment. [Figure 11] FIG. 13 is a cross-sectional view illustrating a metal plate according to an eighth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] First embodiment The welded joint structure shown in Fig. 1 is a structure in which multiple (two in the illustrated example) metal plates 1 and 2 are overlapped and melted at the overlapping portions to weld them. As shown in Fig. 2, the metal plates 1 and 2 are arranged in a shifted state relative to each other, and welding is performed at the corner portion formed by the end face of the first metal plate 1 shown on the upper side in each figure and the top surface of the second metal plate 2 shown on the lower side.

[0011] In addition, in the welded joint structure, the corner of the corner portion becomes a weld root portion P, which is the boundary between the overlapping portions of the first and second metal plates 1 and 2. In this embodiment, the weld root portion P has the entire width of the first metal plate 1 shown in Fig. 2, and welding is performed continuously from one end of the weld root portion P to the other end. Laser welding, electron beam welding, arc welding, etc. can be used for welding, and it does not matter whether a filler material is used or not.

[0012] In the welded joint structure, at least one of the first and second metal plates 1, 2 has an exhaust groove 3 that is connected to the weld root portion P or the molten portion Q during welding. In the welded joint structure of this embodiment, the second metal plate 2 has an exhaust groove 3 that is connected to the molten portion Q. This exhaust groove 3 is formed in a concave shape on the main surface (upper surface) of the second metal plate 2 with a reduction in the plate thickness of the second metal plate 2, and is not obtained by bending the metal plate.

[0013] In the cross section shown in Fig. 2, the exhaust groove 3 has an inclined surface S1 extending from one edge 3a on the side of the weld root P toward the bottom. The exhaust groove 3 in this embodiment also has a curved surface S2 extending from the inclined surface S1 toward the other edge 3b, and the inclined surface S1 and the curved surface S2 are smoothly continuous. Furthermore, the exhaust groove 3 is formed along the weld root P, as shown by the dotted line in Fig. 2.

[0014] 3 and 4 are diagrams showing specific examples of the first and second metal plates 1, 2. The first and second metal plates 1, 2 are components constituting the suspension member SM of the automobile shown in Fig. 3, in particular, components constituting the cross member CM connecting the left and right side members LM, RM. As shown in Fig. 4, the cross member CM is equipped with a main member M that is open on one side (upper side) and a flat stiffening plate R that closes the open part of the main member M, and the configuration consisting of the main member M and the stiffening plate R realizes improved rigidity and weight reduction.

[0015] The main member M has flanges F, F extending in opposite directions at the open portion, and can be manufactured by casting. The stiffening plate R is arranged overlapping both flanges F, F across the open portion of the main member M, and can be made of a plate material such as a blank material.

[0016] In the above-mentioned cross member CM, in the welded joint structure, the stiffening plate R corresponds to the first metal plate 1 and the main member M corresponds to the second metal plate 2, and an exhaust groove 3 is formed in the flange F of the main member M to join the flange (2)F and the stiffening plate (1)R. Here, the main member M (2) is a casting as described above, and since it is easy to form the exhaust groove 3 during casting, a separate process for forming the exhaust groove 3 is not required.

[0017] As shown in FIG. 1, the welded joint structure having the above configuration is welded with a welding torch To, centering on the weld root P. During this process, a molten zone Q is formed in the welded portion, where a portion of the first and second metal plates 1, 2 melts, and gas G is generated from the base material. Most of the gas G is released to the outside due to convection of the molten metal, but it may remain deep in the molten zone Q. The remaining gas G forms blowholes or wormholes, which are continuous holes, in the weld bead B where the molten zone Q has solidified, causing a decrease in weld strength and durability.

[0018] 1, gas G generated in the molten part Q is discharged to the outside by convection of the molten metal, and gas G that has entered between the metal plates 1, 2 is made to flow into the exhaust groove 3, as shown by dotted arrow A2 in the figure. At that time, the welded joint structure described above causes gas G to flow along the inclined surface S1 to the bottom of the exhaust groove 3, suppressing the backflow of gas G into the molten part Q.

[0019] In addition, in the above welded joint structure, the exhaust groove 3 has an inclined surface S1 extending from one edge 3a on the weld root P side toward the bottom, so that the plate thickness T of the second metal plate 2 gradually decreases without abrupt decrease in the direction from the weld root P toward the exhaust groove 3 (to the right in the figure), as shown in Fig. 1. As a result, the above welded joint structure suppresses stress concentration occurring in the weld bead B when a load is applied to the first and second metal plates 1, 2.

[0020] The suppression of the above-mentioned stress concentration will be explained using a specific example shown in Figure 4. The main component M (first metal plate 2) is subjected to a load in a direction A4 that closes the open portion and a direction A5 that opens the open portion. When a load in the closing direction A4 is applied to the main component M, a force acts in a direction that moves the flange F and the stiffener R (first metal plate 1) away from each other, causing a load on the weld bead B. When a load in the opening direction A5 is applied to the main component M, a force acts in a direction that moves the flange F and the stiffener R out of alignment, causing a load on the weld bead B.

[0021] In this case, if the exhaust groove 3 is rectangular, as shown by the virtual line in the enlarged view of Figure 4, the plate thickness T of the second metal plate 2 decreases rapidly at the edge of the exhaust groove 3 in the direction from the weld root portion P toward the exhaust groove 3, resulting in stress concentration in the deep portion C of the weld bead B.

[0022] In contrast, in the above-mentioned welded joint structure, the plate thickness T of the flange (second metal plate 2) F of the main component M is gradually reduced due to the inclined surface S1 of the exhaust groove 3, so that the stress generated in the deep part C of the weld bead B in response to a load in the closing direction A4 or the opening direction A5 on the main component M is dispersed and concentration is suppressed.

[0023] In this way, the above welded joint structure welds both metal plates 1, 2 while quickly exhausting gas G from the molten part Q using the exhaust groove 3 without using a separate member such as a backing metal for venting, so that the gas G generated during welding can be released to obtain a good weld bead B without increasing manufacturing costs or weight. Also, the above welded joint structure gradually reduces the plate thickness T of the metal plate 2 using the inclined surface S1 of the exhaust groove 3, thereby suppressing stress concentration that occurs in the weld bead B when a load is applied to the metal plate 2.

[0024] Furthermore, by using the above-described welded joint structure as a component of the suspension member SM, a suspension member SM with sufficient joint strength and high rigidity can be realized.

[0025] Furthermore, in the welded joint structure of this embodiment, the exhaust groove 3 has a curved surface S2 extending from the inclined surface S1 toward the other edge portion 3b. As shown by the dotted arrow A3 in Figure 1, the gas G that flows into the exhaust groove 3 becomes a vortex along the curved surface S2 and remains there, thereby more reliably suppressing the backflow of gas G into the molten part Q.

[0026] 5 to 11 are diagrams for explaining other embodiments of the welded joint structure according to the present invention. In the following embodiments, the same components as those in the first embodiment are given the same reference numerals, and detailed description thereof will be omitted.

[0027] Second Embodiment 5 has an exhaust groove 3 formed in the second metal plate 2, and this exhaust groove 3 is formed along the weld root P and is open to the outside air at least at one end. The exhaust groove 3 in the illustrated example is open at both ends of the second metal plate 2.

[0028] The welded joint structure of the first embodiment (see FIG. 2) has a structure in which both ends of the exhaust groove 3 are closed. In this welded joint structure, gas that has flowed into the exhaust groove 3 remains, but there is no risk of the gas affecting the metal plates 1 and 2, and the gas may be discharged to the outside over time.

[0029] In contrast, the welded joint structure of the second embodiment not only provides the same action and effect as the first embodiment, but also actively exhausts gas that has flowed into the exhaust groove 3 to the outside during welding, thereby more reliably preventing the gas from flowing back into the molten part (Q).

[0030] Third embodiment 6 is a structure in which an exhaust groove 3 formed in the second metal plate 2 is formed along the weld root portion P and is open to the outside air at least at one end. In the welded joint structure of the illustrated example, an exhaust groove 3 that does not reach the end is formed in the second metal plate 2, i.e., an exhaust groove 3 that is open only to the upper side, and a width dimension of the first metal plate 1 is smaller than a length dimension of the exhaust groove 3. As a result, the exhaust groove 3 is open to the upper surface of the second metal plate 2 on both sides of the first metal plate 1.

[0031] In the above welded joint structure, as in the second embodiment, the same actions and effects as in the first embodiment can be obtained, and in addition, during welding, gas can be quickly discharged to the outside, more reliably preventing gas from flowing back into the molten part (Q).

[0032] Fourth and Fifth Embodiments The welded joint structure shown in Fig. 7 has an exhaust groove 3 having an inclined surface S1 and a curved surface S2 formed in the first metal plate 1, whereas in the previous embodiments, the exhaust groove 3 is formed in the second metal plate 2. The welded joint structure shown in Fig. 8 has exhaust grooves 3, 3 formed in both the first and second metal plates 1, 2.

[0033] In the welded joint structure shown in FIG. 8, both exhaust grooves 3, 3 have the same shape and are arranged to coincide with each other, but as long as the structure is connected to the weld root portion P or the fusion zone Q, it is also possible for both exhaust grooves 3, 3 to have different shapes or to be arranged offset from each other.

[0034] In each of the above welded joint structures, as in the previous embodiments, the exhaust groove 3 can facilitate the discharge of gas during welding, and the inclined surface S1 of the exhaust groove 3 can suppress stress concentration in the weld bead B.

[0035] Sixth to Eighth Embodiments In the welded joint structure shown in Fig. 9, the exhaust groove 3 has, in its cross section, an inclined surface S1 extending from one edge 3a on the weld root P side toward the bottom, and a curved surface S2 extending from the inclined surface S1 toward the other edge 3b. In this embodiment, the inclined surface S1 is a curved surface. As a result, the exhaust groove 3 has a semicircular cross section.

[0036] 10, the exhaust groove 3 has an inclined surface S1 extending from one edge 3a on the weld root P side toward the bottom in its cross section, and the portion extending from the lower end of the inclined surface S1 to the other edge 3b is a vertical plane. This gives the exhaust groove 3 a triangular cross section. In this embodiment, an R may be formed at the corner between the inclined surface S1 and the vertical plane.

[0037] 11, the exhaust groove 3 has, in its cross section, an inclined surface S1 extending from one edge 3a on the weld root P side toward the bottom, and an inclined surface S3 extending from the bottom to the other edge 3b, with curved surfaces S2, S2 at the corners between the inclined surfaces S1, S3 and the bottom. As a result, the exhaust groove 3 has a trapezoidal cross section with R at the corners between the short side and both oblique sides.

[0038] In each of the above welded joint structures, similarly to the previous embodiments, the exhaust groove 3 can facilitate the discharge of gas during welding, and the inclined surface S1 of the exhaust groove 3 can suppress stress concentration in the weld bead B. In the embodiment in which the exhaust groove 3 has the inclined surface S1 and the curved surface S2, in addition to the above-mentioned actions and effects, a vortex of gas is formed along the curved surface S2, thereby further improving the effect of preventing backflow of gas into the molten part Q.

[0039] The configuration of the welded joint structure according to the present invention is not limited to the above-mentioned embodiments, and can be appropriately modified without departing from the gist of the present invention, and the configurations of the embodiments can also be combined. Furthermore, the above-mentioned welded joint structure can be applied to the joining of various metal plates in addition to the joining of the main member and stiffening plate that constitute a suspension member, and in particular, when applied to the joining of structural materials for automobiles, high-quality structural materials with sufficient joint strength can be obtained. [Explanation of symbols]

[0040] 1 1st metal plate 2 Second metal plate 3 Exhaust duct 3a One edge on the weld root side 3b The other edge B Weld bead CM Cross Member M Main member (second metal plate) SM Suspension Member S1 slope S2 Curved surface P Weld root Q Welding part R stiffening plate (first metal plate)

Claims

1. A welded joint structure in which a first and a second metal plate are overlapped and a corner portion formed by an end face of the first metal plate and a main surface of the second metal plate is melted and welded, At least one of the first and second metal plates has, on a contact surface with the other metal plate, an exhaust groove connected to a weld root portion which is a corner of the corner portion or a molten portion formed in the corner portion during welding, A welded joint structure, characterized in that the exhaust groove has, in its cross section, an inclined surface extending from one edge portion on the weld root side toward a bottom portion of the exhaust groove.

2. The welded joint structure according to claim 1, wherein the exhaust groove has a curved surface extending from the inclined surface to the other edge portion.

3. 3. The welded joint structure according to claim 1, wherein the exhaust groove is formed along the weld root portion and is open to the atmosphere at least at one end thereof.

4. the first and second metal plates are members constituting a suspension member, the second metal plate is a main member having an open portion on one side, and the first metal plate is a stiffening plate that closes the open portion of the main member, 4. The welded joint structure according to claim 1, wherein the exhaust groove is formed in at least the main member.

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