JP7633600B2 - Welded joint structure - Google Patents

Description

The present invention relates to a welded joint structure used when overlapping and welding multiple metal plates.

A conventional welded joint structure is described in Patent Document 1 under the name of a welding backing metal. The welded joint structure described in Patent Document 1 is a structure in which a backing metal is interposed between columns or between a column and a diaphragm when they are butt-welded together. This backing metal has a gas vent slit to allow gas to escape, and by discharging gas generated during welding from the gas vent slit, it prevents air bubbles from remaining in the molten metal.

JP 2004-291087 A

However, the conventional welded joint structure described above requires the insertion of a separate backing metal between the components to be joined, which increases manufacturing costs and weight. In addition, because the backing metal is simply inserted into the components, stress concentration is likely to occur in the weld bead when a load is applied to each component. The challenge was to solve these problems.

The present invention was made with a focus on the above-mentioned conventional problems, and aims to provide a welded joint structure that allows gas generated during welding to escape, resulting in a good weld bead, without increasing manufacturing costs or weight, and that can suppress stress concentration in the weld bead.

The welded joint structure according to the present invention is a welded joint structure formed by overlapping first and second metal plates and melting and welding 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 characterized in that at least one of the first and second metal plates has an exhaust groove on a contact surface with the other metal plate, the exhaust groove being connected to a weld root portion that is an edge of the corner portion or a molten portion that is formed in the corner portion during welding, and the exhaust groove has an inclined surface in a cross section from one edge portion on the weld root side toward the bottom of the exhaust groove .

In the welded joint structure according to the present invention, when 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 are melted and welded, gas generated in the molten portion formed in the corner portion is discharged to the outside, while gas that has entered between the metal plates is caused to flow into an exhaust groove, and at that time, the gas is caused to flow along the inclined surface to the bottom of the exhaust groove, thereby suppressing backflow of gas into the molten portion. In addition, in the above welded joint structure, the exhaust groove has an inclined surface in its cross section from one edge portion on the weld root side toward the bottom of the exhaust groove , so that the thickness of the metal plate is gradually reduced in the direction from the weld root toward the exhaust groove without abrupt reduction.

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

1 is a cross-sectional view illustrating a first embodiment of a welded joint structure according to the present invention. FIG. 2 is a perspective view showing the metal plate shown in FIG. 1 . FIG. 2 is a perspective view showing a suspension member which is an example of a metal plate. 4 is a cross-sectional view taken along line AA in FIG. 3 and an enlarged view of a main portion. FIG. 11 is a perspective view illustrating a metal plate according to a second embodiment. FIG. 11 is a perspective view illustrating a metal plate according to a third embodiment. FIG. 13 is a cross-sectional view illustrating a metal plate according to a fourth embodiment. FIG. 13 is a cross-sectional view illustrating a metal plate according to a fifth embodiment. FIG. 13 is a cross-sectional view illustrating a metal plate according to a sixth embodiment. FIG. 13 is a cross-sectional view illustrating a metal plate according to a seventh embodiment. FIG. 23 is a cross-sectional view illustrating a metal plate according to an eighth embodiment.

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 with respect 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 in each figure.

In addition, the welded joint structure has a corner of the corner portion that 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.

In the welded joint structure, at least one of the first and second metal plates 1, 2 has an exhaust groove 3 that connects 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 connects 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.

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. In addition, the exhaust groove 3 in this embodiment 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.

Figures 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 that make up the suspension member SM of the automobile shown in Figure 3, in particular, the cross member CM that connects the left and right side members LM, RM. As shown in Figure 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 portion of the main member M, and the configuration consisting of the main member M and the stiffening plate R improves rigidity and reduces weight.

The main member M has flanges F, F that extend in opposite directions at the open portion, and can be manufactured by casting. The stiffening plate R is placed over both flanges F, F, straddling the open portion of the main member M, and can be made of a plate material such as a blank material.

In the above cross member CM, the welded joint structure is such that 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.

As shown in FIG. 1, the welded joint structure having the above configuration is welded using a welding torch To, centering on the weld root portion P. During this process, a molten portion 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 portion Q. The remaining gas G becomes blowholes or wormholes that are connected to each other in the weld bead B where the molten portion Q has solidified, causing a decrease in weld strength and durability.

In contrast, the above welded joint structure releases gas G generated in the molten part Q to the outside by convection of the molten metal, as shown by dotted arrow A1 in Figure 1, and also allows gas G that has entered between the metal plates 1 and 2 to flow into the exhaust groove 3, as shown by dotted arrow A2 in the figure. At that time, the above welded joint structure allows gas G to flow along the inclined surface S1 to the bottom of the exhaust groove 3, suppressing backflow of gas G into the molten part Q.

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, as shown in FIG. 1, 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 a result, the above welded joint structure suppresses stress concentration that occurs in the weld bead B when a load is applied to the first and second metal plates 1 and 2.

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

At this time, if the exhaust groove 3 is rectangular, as shown by the virtual lines 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, causing stress concentration in the deep portion C of the weld bead B.

In contrast, in the above welded joint structure, the inclined surface S1 of the exhaust groove 3 gradually reduces the plate thickness T of the flange (second metal plate 2) F of the main member M, dispersing and suppressing the concentration of stress generated in the deep part C of the weld bead B in response to a load applied to the main member M in the closing direction A4 or opening direction A5.

In this way, the above welded joint structure welds the two metal plates 1, 2 while quickly exhausting the gas G from the molten part Q through 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. In addition, the above welded joint structure gradually reduces the plate thickness T of the metal plate 2 through 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.

Furthermore, by using the above welded joint structure as a component of the suspension member SM, a highly rigid suspension member SM with sufficient joint strength can be realized.

Furthermore, in the welded joint structure of this embodiment, the exhaust groove 3 has a curved surface S2 that extends 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, so that the backflow of gas G into the molten part Q can be more reliably suppressed.

Figures 5 to 11 are diagrams illustrating other embodiments of the welded joint structure according to the present invention. In the following embodiments, the same components as in the first embodiment are given the same reference numerals, and detailed descriptions are omitted.

Second Embodiment
5 has an exhaust groove 3 formed in the second metal plate 2, and the 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.

The welded joint structure of the first embodiment (see Figure 2) has both ends of the exhaust groove 3 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 it may be discharged to the outside over time.

In contrast, the welded joint structure of the second embodiment provides the same action and effect as the first embodiment, and can actively exhaust 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).

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, i.e., an exhaust groove 3 that is open only to the upper side, is formed in the second metal plate 2, and the width dimension of the first metal plate 1 is smaller than the 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.

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, gas can be quickly discharged to the outside during welding, more reliably preventing gas from flowing back into the molten part (Q).

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

In the welded joint structure shown in FIG. 8, both exhaust grooves 3, 3 have the same shape and are aligned 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 the exhaust grooves 3, 3 to have different shapes or to be offset from each other.

In each of the above welded joint structures, as in the previous embodiment, 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.

Sixth to Eighth Embodiments
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. The inclined surface S1 in this embodiment is a curved surface. As a result, the exhaust groove 3 has a semicircular cross section.

In the welded joint structure shown in FIG. 10, 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 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.

In the welded joint structure shown in FIG. 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 of 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.

In each of the above welded joint structures, as in the previous embodiment, the exhaust groove 3 can improve the exhaust of gas during welding, and the inclined surface S1 of the exhaust groove 3 can suppress stress concentration in the weld bead B. In an 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, which further enhances the effect of preventing backflow of gas into the molten part Q.

The configuration of the welded joint structure according to the present invention is not limited to the above-mentioned embodiments, and can be modified as appropriate without departing from the gist of the present invention, and the configurations of the various embodiments can also be combined. Furthermore, the above-mentioned welded joint structure can of course be applied to joining various metal plates in addition to joining the main members and stiffening plates that make up the suspension member, and in particular, when applied to joining structural materials for automobiles, high-quality structural materials with sufficient joint strength can be obtained.

1 First metal plate 2 Second metal plate 3 Exhaust groove 3a One edge portion on the weld root side 3b The other edge portion B Weld bead CM Cross member M Main member (second metal plate)
SM Suspension member S1 Inclined surface S2 Curved surface P Weld root Q Welded part R Stiffening plate (first metal plate)

Claims (4)

A welded joint structure in which a first metal plate and a second metal plate are overlapped and a corner portion formed by an end surface 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 . The welded joint structure according to claim 1, characterized in that the exhaust groove has a curved surface extending from the inclined surface to the other edge. The welded joint structure according to claim 1 or 2, characterized in that the exhaust groove is formed along the weld root and is open to the outside air at least at one end. 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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