JP7328525B2 - Welded structure - Google Patents

Description

The present invention relates to welded structures.

Girth-welded weld joints formed in tubular members are often found in civil engineering structures and machinery. Such welded joints are subjected to, for example, repeated external loads and repeated loads due to internal pressure when a pipe is filled with gas or liquid. In welded joints under such repeated stress, fatigue cracks may occur at intersections between the surface of the weld metal and the surface of the base material, specifically at the weld toe or weld root. Weld toes and weld roots tend to be the starting points of fatigue cracks because (1) stress concentrates because they are rapidly changing parts, and (2) tensile residual stress may be introduced by welding heat. and (3) the structure of the base material deteriorates due to welding heat. Of these, it has been proposed that the weld toe be subjected to post-treatment such as cutting and impact treatment to remove the above causes and suppress the occurrence of fatigue cracks.

On the other hand, it has been difficult to perform post-treatment as described above, especially for a weld root portion that is accessible only from one side, and therefore it has not been easy to suppress the occurrence of fatigue cracks. Therefore, for example, in Patent Document 1, another circumferential weld is applied to the cylinder surface in order to suppress the decrease in fatigue strength due to the stress concentration generated at the weld root portion of the circumferential weld between the head member and the cylinder tube in the fluid pressure cylinder. , and thereby introduce a compressive residual stress into the circumferential weld between the head member and the cylinder tube.

JP-A-2002-257238

However, in the technique described in Patent Document 1, the number of welds increases, and the effect is small when the residual stress due to the excessive stress is removed, and the potential crack starting point remains the weld root.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a welded structure capable of effectively suppressing the occurrence of fatigue cracks originating from the weld root portion of girth welding.

According to one aspect of the invention, a welded structure comprising a first tubular member, a second member, and a weld metal filled or laminated between the first tubular member and the second member, , a weld region filled or laminated with weld metal and a non-welded region not filled or laminated with weld metal are formed between the first tubular member and the second member, and the contact included in the non-welded region A welded structure is provided wherein contact between the first tubular member and the second member in the region transfers stress between each other.

At least one of the first tubular member and the second member may elastically deform near the contact area.

The second member has a convex shape toward the inner peripheral surface or the end surface of the first tubular member, and in the contact area, the convex portion of the second member and the first tubular member may come into contact.

The portion having a convex shape may be an edge of an oblique surface formed on at least a part of the surface of the second member facing the inner peripheral surface or the end surface of the first tubular member.

The second member is a plate-like member that at least partially closes the inner space of the first tubular member, and the welded area and the non-welded area are between the inner peripheral surface of the tubular member and the end surface of the second member. may be formed in

The second member is a plate-like member that at least partially closes the inner space of the first tubular member, and the welded region and the non-welded region are formed between the inner peripheral surface of the end of the first tubular member and the second tubular member. It may be formed between the stepped surface formed on the peripheral edge of the member.

The welded structure further includes a third tubular member, the second member abutting against inner peripheral surfaces of the first tubular member and the third tubular member, and the welded region and the non-welded region are: It may be formed between the inner peripheral surface of each of the first tubular member and the second tubular member and the second member.

The second member is a second tubular member, and the welded region and the non-welded region are formed between the inner peripheral surface of the end of the first tubular member and the outer peripheral surface of the second tubular member. good too. Alternatively, the second member may be a second tubular member and the welded region and non-welded region may be formed between the end face of the first tubular member and the end face of the second tubular member. Further, the end surface of the first tubular member has a convex shape toward the surface of the second member, and in the contact area, the convex portion of the first tubular member and the second member may come into contact.

At least one of the first tubular member and the second member may be formed of a fatigue-resistant steel material.

According to the above configuration, it is possible to effectively suppress the occurrence of fatigue cracks originating from the weld root portion of the girth weld.

1 is a perspective view of a welded structure according to a first embodiment of the present invention; FIG. FIG. 2 is a sectional view taken along line II of FIG. 1; 2 is an enlarged cross-sectional view showing a welded joint portion of the welded structure shown in FIG. 1; FIG. FIG. 4 is a diagram schematically showing stress transmission in the first embodiment of the present invention; FIG. 5 is a diagram schematically showing stress transmission in a comparative example; FIG. 4 is a cross-sectional view showing another example of a welded joint portion; FIG. 10 is a cross-sectional view showing yet another example of a welded joint portion; FIG. 5 is a cross-sectional view of a welded structure according to a second embodiment of the present invention; 9 is an enlarged view of the welded joint portion of the welded structure shown in FIG. 8; FIG. FIG. 5 is a cross-sectional view of a welded structure according to a third embodiment of the present invention; 11 is an enlarged view of the welded joint portion of the welded structure shown in FIG. 10; FIG. FIG. 5 is a cross-sectional view of a welded structure according to a fourth embodiment of the present invention; 13 is an enlarged view of the welded joint portion of the welded structure shown in FIG. 12; FIG. FIG. 5 is a cross-sectional view of a welded structure according to a fifth embodiment of the present invention; 15 is an enlarged view of the welded joint portion of the welded structure shown in FIG. 14; FIG. FIG. 16 is a diagram showing a modification of the example shown in FIG. 15; FIG. 11 is a cross-sectional view of a welded structure according to a sixth embodiment of the present invention; 18 is an enlarged view of the welded joint portion of the welded structure shown in FIG. 17; FIG. It is a figure which shows the testing apparatus based on the Example of this invention. It is a figure which shows the testing apparatus based on the Example of this invention. 4 is a graph showing test results in Examples of the present invention.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the present specification and drawings, constituent elements having substantially the same functional configuration are denoted by the same reference numerals, thereby omitting redundant description.

(First embodiment)
FIG. 1 is a perspective view of a welded structure according to a first embodiment of the present invention, and FIG. 2 is a sectional view taken along the line II of FIG. 3 is an enlarged view of a welded joint portion of the welded structure shown in FIG. 2; FIG. In this embodiment, the welded structure includes a steel pipe 1 having a circular cross section, which is a first tubular member, and a diaphragm 2, which is a plate-shaped member that at least partially closes the internal space of the steel pipe 1 . The planar shape of the diaphragm 2 is circular, and the peripheral end face 2E is circumferentially welded to the inner peripheral surface 1S of the steel pipe 1 . Specifically, the diaphragm 2 is joined to the steel pipe 1 by filling or laminating the weld metal 3 between the end surface 2E of the diaphragm 2 and the inner peripheral surface 1S of the steel pipe 1 . In this specification, circumferential welding means welding in the circumferential direction of the tubular member, and does not necessarily have to be welding over the entire circumference of the tubular member.

In the welded structure as described above, for example, when two diaphragms 2 are attached to the steel pipe 1, the space between these diaphragms 2 becomes a closed space. Access is only possible from one side, namely from the open side of the steel tube 1 to the diaphragm 2 . Therefore, the weld metal 3 is filled or laminated from the opening side of the steel pipe 1 between the inner peripheral surface 1S of the steel pipe 1 and the end face 2E of the diaphragm 2, and the post-treatment of the weld toes 3A and 3B is also performed in the same way. access only from the open side of the

In such a case, the intersection of the surface of the weld metal 3 located outside the diaphragm 2 and the surface of the base metal, that is, the weld toes 3A and 3B, is subjected to post-processing such as cutting as in the illustrated example. can suppress the occurrence of fatigue cracks. In addition, since post-processing of weld toe 3A, 3B is suitably performed by a well-known method in this embodiment, detailed description is abbreviate|omitted. The weld toes 3A and 3B may be post-treated by a method other than cutting, or the post-treatment may be omitted.

On the other hand, since it is difficult to access the intersection of the surface of the weld metal 3 located inside the diaphragm 2 and the surface of the base metal, that is, the weld root portion 3C, the generation of fatigue cracks should be suppressed by post-treatment. is not easy. Therefore, in the present embodiment, as described below, a structure is adopted in which the steel materials are in contact with each other in the non-welding region between the steel pipe 1 and the diaphragm 2, thereby allowing stress to be transmitted to each other. It effectively suppresses the occurrence of fatigue cracks originating from the root portion. For simplicity, the intersection point between the inner peripheral surface 1S of the steel pipe 1 and the weld metal 3 is shown as the weld root portion 3C, but the weld root portion, which is the intersection point between the end surface 2E of the diaphragm 2 and the weld metal 3, is also shown. Similarly, the occurrence of fatigue cracks is suppressed.

As shown in FIG. 3 , in the welded joint portion between the steel pipe 1 and the diaphragm 2 , the weld area between the steel pipe 1 and the diaphragm 2 is increased by filling or laminating the weld metal 3 from the outside of the diaphragm 2 . R1 and a non-welded region R2 are formed. Welding region R1 is a region where weld metal is filled or laminated between steel pipe 1 and diaphragm 2 . FIG. 3 shows a welded region R1 formed between the inner peripheral surface 1S of the steel pipe 1 and the end surface 2E of the diaphragm 2. As shown in FIG. In the welding region R1, the weld metal 3 is filled between the inner peripheral surface 1S of the steel pipe 1 and the end surface 2E of the diaphragm 2 from the design point of view. are melted, the inner peripheral surface 1S and the end surface 2E cannot always be clearly distinguished in the welded region R1 after welding.

On the other hand, the non-welded region R2 is a region where the weld metal is not filled or laminated between the steel pipe 1 and the diaphragm 2. As shown in FIG. FIG. 3 shows a non-welded region R2 formed between the inner peripheral surface 1S of the steel pipe 1 and the end surface 2E of the diaphragm 2. As shown in FIG. The edge of the weld metal 3 located between the inner peripheral surface 1S of the steel pipe 1 and the end surface 2E of the diaphragm 2 at the boundary between the welded region R1 and the non-welded region R2 is the welded root portion 3C. In this embodiment, stress is transmitted between the steel pipe 1 and the diaphragm 2 by contacting each other in the contact region R3 included in the non-welded region R2. More specifically, in the illustrated example, the entire end surface 2E of the diaphragm 2 is a beveled surface, and in the contact region R3, a portion including the edge 2G of the beveled surface and the inner peripheral surface 1S of the steel pipe 1 are separated. Contact.

In the example shown in FIG. 3, the steel pipe 1 and the diaphragm 2 are in contact with each other strongly enough to allow stress transmission in the contact region R3, so the steel pipe 1 is elastically deformed in the vicinity of the contact region R3. Although large elastic deformation is illustrated for explanation, such large elastic deformation does not necessarily occur. In addition to the steel pipe 1, the diaphragm 2 may be elastically deformed, or only the diaphragm 2 may be elastically deformed. Such elastic deformation occurs, for example, when the diaphragm 2 is pressed against the steel pipe 1 due to heat shrinkage after welding.

Further, in the example shown in FIG. 3, the diaphragm 2 has a convex shape toward the steel pipe 1, specifically, a beveled edge 2G formed on the entire end surface 2E. As a result, for example, even if the edge 2G does not come into contact with the inner peripheral surface 1S of the steel pipe 1 before welding, or even if it slightly comes into contact with the inner peripheral surface 1S of the steel pipe 1, the heat shrinkage after welding causes the end surface 2E and the inner peripheral surface 1S to contact each other. , the edge 2G is pressed against the inner peripheral surface 1S by shortening the distance between them, and a state in which stress is transmitted between the steel pipe 1 and the diaphragm 2 in the contact region R3 can be realized. Furthermore, in the present embodiment, in addition to thermal contraction of the steel pipe 1 in the radial direction, thermal contraction of the steel pipe 1 in the circumferential direction also occurs. Even so, the edge 2G is pressed against the inner peripheral surface 1S after welding, and a state in which stress is transmitted between the steel pipe 1 and the diaphragm 2 in the contact area can be realized.

FIG. 4 is a diagram schematically showing stress transmission in the first embodiment of the present invention, and FIG. 5 is a diagram schematically showing stress transmission in a comparative example. In the example shown in FIG. 4, the stress ST is intensively transmitted in the contact region R3 (see FIG. 3) where the portion including the edge 2G of the diaphragm 2 contacts the inner peripheral surface 1S of the steel pipe 1, thereby welding. Stress concentration on the root portion 3C is relieved. Although there is a possibility that the contact region R3 where stress concentrates may become the starting point of fatigue cracks, since the contact region R3 is in the non-welded region R2 as described above, residual stress due to welding heat and structural deterioration of the base material may occur. The influence is small, and therefore the possibility of occurrence of fatigue cracks starting from the contact region R3 is low compared to the weld root portion 3C. At least one of the base material, that is, the steel pipe 1 or the diaphragm 2, is formed of a steel material having high fatigue durability as described in, for example, Japanese Patent No. 4000049, Japanese Patent No. 4466196, and Japanese Patent No. 5304619. This can further reduce the possibility of fatigue cracks occurring from the contact region R3. Further, by separating the contact region R3 from the welding region R1, the effects of residual stress, structural deterioration of the base material, and the like may be reduced.

On the other hand, in the example shown in FIG. 5, since the steel pipe 1 and the diaphragm 2 are not in contact with each other in the non-welded region R2, stress ST is applied to the weld root portion 3C located at the boundary between the non-welded region R2 and the welded region R1. concentrate. As described above, the welding root portion 3C is susceptible to fatigue cracking due to the large influence of residual stress and structural deterioration of the base metal due to welding heat. 4 and 5, the stress ST in the direction parallel to the inner peripheral surface 1S of the steel pipe 1 is illustrated as an example, but the stress in the direction parallel to the plate surface of the diaphragm 2 and A similar trend is shown for the transmission of bending stress in the direction of .

FIG. 6 is a cross-sectional view showing another example of a welded joint portion. In the example shown in FIG. 6, a beveled surface 2B is formed on a part of the end surface 2E of the diaphragm 2, and the edge 2G of the beveled surface 2B is the contact region R3 included in the non-welding region R2. It contacts the peripheral surface 1S. In this way, the edge of the beveled surface formed on the end face 2E of the diaphragm 2 (the surface facing the inner peripheral surface of the steel pipe 1) has a convex shape toward the steel pipe 1, and the portion including this edge is Various modifications are possible for the configuration that is brought into contact with the inner peripheral surface 1S of the steel pipe 1 .

Further, for example, when the diaphragm 2 is concave as a whole and the end of the diaphragm 2 contacts the steel pipe 1 not at a right angle but at an angle (that is, when the inner peripheral surface 1S of the steel pipe 1 and the end surface of the diaphragm 2 2E), the edge of the end face 2E becomes convex toward the steel pipe 1 even if the beveled face is not formed on the end face 2E, and this edge By contacting the inner peripheral surface 1S of the steel pipe 1 with the portion including the , it is possible to realize a state in which stress is transmitted between the steel pipe 1 and the diaphragm 2 in the contact region R3.

FIG. 7 is a cross-sectional view showing still another example of a welded joint portion. In the example shown in FIG. 7, the end surface 2E of the diaphragm 2 is formed with a beveled surface 2B, but the end of the beveled surface forms a curved surface 2C rather than forming an angular edge. The curved surface 2C may be, for example, a cylindrical cross section. In this case as well, the curved surface 2C has a convex shape toward the steel pipe 1, and the stress is transmitted when the portion including the curved surface 2C of the diaphragm 2 contacts the steel pipe 1 at the contact region R3. As in this example, the convex shape formed on the diaphragm 2 does not necessarily have to be angular. The contact between the steel pipe 1 and the diaphragm 2 in the contact region R3 does not necessarily have to be a linear (point-like in cross section) contact, and may be a contact having a certain width. Further, the contact state between the steel pipe 1 and the diaphragm 2 in the contact region R3 may not be uniform in the direction along the weld line (the circumferential direction of the tubular member, the depth direction in FIG. 7). Specifically, for example, the width of the contact region R3 may change in the direction along the weld line, or the contact region R3 may be interrupted in some sections.

The first embodiment of the present invention has been described above. The configuration of this embodiment is not limited to a welded structure including the steel pipe 1 and the diaphragm 2, but also a joint configured by combining a first tubular member and a second member in a T-shaped cross section. It is possible to apply to various welded structures including

(Second embodiment)
FIG. 8 is a cross-sectional view of a welded structure according to a second embodiment of the present invention, and FIG. 9 is an enlarged view of a welded joint portion of the welded structure shown in FIG. In this embodiment, the welded structure includes a steel pipe 11 that is a first tubular member and a lid 12 that is a plate-like member that at least partially closes the internal space of the steel pipe 11 . The planar shape of the lid body 12 is circular, and a stepped surface 12P substantially perpendicular to the plate surface is formed on the peripheral edge. The steel pipe 11 is fitted to the lid 12 so that the inner peripheral surface 11S of the end faces the stepped surface 12P of the lid 12 . Here, in the example shown in FIG. 9, the end surface 11E of the steel pipe 11 includes an oblique surface, and the groove formed between the end surface 11E and the rising surface 12Q of the lid body 12 adjacent to the stepped surface 12P The weld metal 3 is filled or laminated. The weld metal 3 reaches the bottom of the groove, and a weld root portion 3C is formed between the inner peripheral surface 11S of the steel pipe 11 and the joint surface 12P of the lid body 12.

In the example shown in FIGS. 8 and 9 as described above, the welded region R1 and the non-welded region R2 are formed between the inner peripheral surface 11S of the steel pipe 11 and the stepped surface 12P of the lid body 12. Welding region R2 includes contact region R3. Here, the weld region R1 is formed by the weld metal 3 filled or laminated into the groove formed between the end surface 11E of the steel pipe 11 and the rising surface 12Q of the lid body 12. 11S and the stepped surface 12P of the lid body 12 are partially melted regions. In the illustrated example, the stepped surface 12P is a beveled surface as a whole. In the contact region R3, a portion including the edge 12G of the step joint surface 12P, which is an oblique surface, and the inner peripheral surface 11S of the steel pipe 11 come into contact with each other.

As a result, even in the examples shown in FIGS. 8 and 9, the stress concentration on the weld root portion formed between the inner peripheral surface 11S of the steel pipe 11 and the step joint surface 12P of the lid body 12 is alleviated, and welding is performed. It is possible to effectively suppress the occurrence of fatigue cracks originating from the root portion. As the configuration of the stepped surface 12P of the lid body 12, for example, it is possible to employ the example described above with reference to FIGS.

(Third embodiment)
FIG. 10 is a cross-sectional view of a welded structure according to a third embodiment of the present invention, and FIG. 11 is an enlarged view of a welded joint portion of the welded structure shown in FIG. In this embodiment, the welded structure is a butt pipe joint constructed by abutting the end surface 21E of the steel pipe 21, which is the first tubular member, and the end surface 23E of the steel pipe 23, which is the third tubular member. including. In the illustrated example, the fitting ring 22 is a fitting tubular member that abuts against the inner peripheral surfaces 21S, 23S of the steel pipes 21, 23 by fitting inside the steel pipes 21, 23, respectively. The end surface 23E of the steel pipe 23 includes a beveled surface, and the weld metal 3 is filled or laminated in the groove formed between the end surface 21E of the steel pipe 21 and the end surface 23E of the steel pipe 23 . The weld metal 3 reaches the bottom of the groove, and the weld root portion 3C is formed between the inner peripheral surface 21S of the steel pipe 21 and the outer peripheral surface 22S of the fitting ring 22, and between the inner peripheral surface 23S of the steel pipe 23 and the fitting ring 22. are formed between the outer peripheral surface 22S of the .

In the example shown in FIGS. 10 and 11 as described above, the welded region R1 and the non-welded region R2 are formed between the inner peripheral surface 21S of the steel pipe 21 and the outer peripheral surface 22S of the fitting ring 22. Weld region R2 includes contact region R3. Here, the weld region R1 is formed between the inner peripheral surface 21S of the steel pipe 21 and the inner peripheral surface 21S of the steel pipe 21 by the weld metal 3 filled or laminated into the groove formed between the end surface 21E of the steel pipe 21 and the end surface 23E of the steel pipe 23. It is a region where the outer peripheral surface 22S of the fitting ring 22 is partially melted. An oblique surface 22B is formed on a portion of the outer peripheral surface 22S of the fitting ring 22 facing the inner peripheral surface 21S of the steel pipe 21 (that is, the fitting ring 22 has a shape in which at least one side is widened at the bottom). ), the portion including the edge 22G of the beveled surface 22B contacts the inner peripheral surface 21S of the steel pipe 21 at the contact region R3.

10 and 11, the stress concentration on the weld root portion 3C formed between the inner peripheral surface 21S of the steel pipe 21 and the outer peripheral surface 22S of the fitting ring 22 is alleviated, It is possible to effectively suppress the occurrence of fatigue cracks originating from the weld root portion 3C. As the configuration of the outer peripheral surface 22S of the fitting ring 22, for example, it is possible to employ the example described above with reference to FIGS. Further, as shown in the figure, a welded region and a non-welded region are also formed between the inner peripheral surface 23S of the steel pipe 23 and the outer peripheral surface 22S of the fitting ring 22. Stress may be transmitted by bringing the surface 22S and the inner peripheral surface 23S into contact with each other, thereby suppressing the occurrence of fatigue cracks originating from the weld root portion on the steel pipe 23 side. It should be noted that the fitting ring may not be a member integrally formed over the entire circumference, and may be divided into, for example, two or three parts in the circumferential direction. In addition, welding is performed in a state in which a member that is not tubular or ring-shaped is brought into contact with the inner peripheral surfaces 21S, 23S of the steel pipes 21, 23 at a part of the circumferential direction of the butt pipe joint, so that the fitting ring As in the example of No. 22, the occurrence of fatigue cracks originating from the weld root portion may be suppressed.

(Fourth embodiment)
12 is a cross-sectional view of a welded structure according to a fourth embodiment of the present invention, and FIG. 13 is an enlarged view of a welded joint portion of the welded structure shown in FIG. In this embodiment, the welded structure includes a steel pipe 31 as a first tubular member and a steel pipe 32 as a second tubular member. A portion of the outer peripheral surface of the steel pipe 32 is notched at the end connected to the steel pipe 31 to form a stepped surface 32P. The steel pipe 31 is fitted to the end of the steel pipe 32 so that the inner peripheral surface 31S of the end faces the stepped surface 32P. Here, in the illustrated example, the end surface 31E of the steel pipe 31 includes an oblique surface, and the weld metal 3 is formed in the groove formed between the end surface 31E and the rising surface 32Q of the steel pipe 32 adjacent to the stepped surface 32P. Filled or laminated. The weld metal 3 reaches the bottom of the groove, and the weld root is formed between the inner peripheral surface 31S of the steel pipe 31 and the joint surface 32P of the steel pipe 32. In this embodiment, the stepped surface 32P is an oblique surface as a whole. A welded region R1, a non-welded region R2, and a contact region R3 similar to the form are formed. Stress concentration on the weld root portion can be alleviated by intensive transmission of stress in the contact region R3.

In the example shown in FIG. 12, since the outer diameter of the steel pipe 31 and the outer diameter of the steel pipe 32 are the same, a part of the outer peripheral surface of the steel pipe 32 is used as the stepped surface 32P. If the outer diameter of the steel pipe 31 is smaller than the inner diameter of the steel pipe 31, the lap joint-like welding is performed between the end surface 31E of the steel pipe 31 and the outer peripheral surface of the steel pipe 32 without forming the stepped surface 32P. may form a part. In this case, the above-described welded region R1, non-welded region R2, and contact region R3 are formed between the inner peripheral surface 31S of the steel pipe 31 and the outer peripheral surface (not the stepped surface) of the steel pipe 32.

(Fifth embodiment)
14 is a cross-sectional view of a welded structure according to a fifth embodiment of the present invention, and FIG. 15 is an enlarged view of a welded joint portion of the welded structure shown in FIG. In this embodiment, the welded structure includes a steel pipe 41 that is a first tubular member and a lid 42 that is a plate-like member that at least partially closes the internal space of the steel pipe 41 . The planar shape of the lid 42 is circular. The steel pipe 41 is brought into contact with the lid 42 so that the end face 41E faces the plate surface 42S of the lid 42 . Here, in the example shown in FIG. 15, the end surface 41E of the steel pipe 41 includes an oblique surface, and the groove formed between the end surface 41E and the plate surface 42S of the lid 42 is filled or laminated with the weld metal 3. be done. Therefore, the weld root portion 3C is formed between the end surface 41E of the steel pipe 41 and the plate surface 42S of the lid 42. As shown in FIG.

In the example shown in FIGS. 14 and 15 as described above, the welded region R1 and the non-welded region R2 are formed between the end surface 41E of the steel pipe 41 and the plate surface 42S of the lid 42, and the non-welded region R2 contains the contact region R3. Here, the welded region R1 is a region where the end surface 41E of the steel pipe 41 and the plate surface 42S of the lid 42 are partially melted by filling or laminating the weld metal 3 . In the illustrated example, the entire end surface 41E is an oblique surface, and the portion including the edge 41G of the end surface 41E, which is an oblique surface, and the plate surface 42S of the lid 42 come into contact with each other in the contact region R3.

FIG. 16 is a diagram showing a modification of the example shown in FIG. 15. In FIG. The example shown in FIG. 16 is the same as the example in FIG. 15 in that a groove is formed between the end surface 41E of the steel pipe 41 and the plate surface 42S of the lid body 42, but is different from the example in FIG. Conversely, a beveled surface is formed on a part of the plate surface 42S of the lid 42 . In this case, in the contact region R3, the end face 41E of the steel pipe 41 contacts the portion including the edge 42G of the beveled surface formed on the plate surface 42S.

14 to 16, by bringing the end surface 41E of the steel pipe 41 into contact with the plate surface 42S of the lid 42 in the contact area R3 included in the non-welding area R2, the welding root portion is Stress concentration can be alleviated, and the occurrence of fatigue cracks originating from the weld root portion can be effectively suppressed.

(Sixth embodiment)
17 is a cross-sectional view of a welded structure according to a sixth embodiment of the present invention, and FIG. 18 is an enlarged view of a welded joint portion of the welded structure shown in FIG. In this embodiment, the welded structure includes a steel pipe 51A as a first tubular member and a steel pipe 51B as a second tubular member. The steel pipes 51A, 52B are arranged so that their end faces 511E, 512E face each other. In the illustrated example, the end face 512E of the steel pipe 51B includes an oblique face, and the weld metal 3 is filled or laminated in the groove formed between the end face 512E and the end face 511E. The weld root portion 3C is formed between the end faces 511E, 512E of the steel pipes 51A, 51B. In the present embodiment, a portion including the beveled edge 512G of the end surface 512E of the steel pipe 51B contacts the end surface 511E of the steel pipe 51A, thereby forming a welded region R1, a non-welded region R2, and a welded region R1 between the steel pipes 51A and 51B. A contact region R3 is formed. Stress concentration on the weld root portion 3C can be alleviated by intensive transmission of stress in the contact region R3.

In the example shown in FIG. 17, steel pipe 51B is a tubular member continuous with steel pipe 51A, but in other examples, the second tubular member includes a short tubular portion and a lid portion joined to the tubular portion. , may close the internal space of the steel pipe 51A. Also in this case, if the steel pipe 51A and the second tubular member are joined at the end face of the tubular portion, it is possible to construct a welded structure similar to the examples shown in FIGS. 17 and 18 above. is.

Next, examples of the present invention will be described. 19A and 19B are diagrams showing a testing device according to an embodiment of the invention. As shown in FIG. 19A, the test used a specimen in which a material to be welded 82 was welded to the center of a beam 81 supported on both sides. This specimen corresponds to, for example, the welded joint portion of the welded structure including the steel pipe described above with reference to FIGS. The distance from the welded joint portion between the beam 81 and the material to be welded 82 to the fulcrums on both sides is shown as L1, and the distance from the welded joint portion to the loading point of the repeated load is shown as L2. A bending moment is generated in the beam 81 by applying a repeated load, and a tensile stress or a compressive stress is generated in the welded joint portion by the bending moment. As shown in FIG. 19B, the end surface 82E of the material to be welded 82 is not formed with a beveled surface, and the material to be welded 82 is positioned at an angle of 78° with respect to the beam 81 (that is, at an angle of 12° from the right angle). The beam 81 and the material 82 to be welded are brought into contact with each other in the non-welding region by welding using the weld metal 83 in the contact state.

FIG. 20 is a graph showing test results in Examples of the present invention. In the graph of FIG. 20, the stress ratio (the ratio of the minimum stress to the maximum stress) is -1 (a load that generates a tensile stress and a load that generates a compressive stress are alternately applied to the welded joint portion with the same magnitude). ) and 0.1 (the state where a predetermined load that generates a tensile stress in the welded joint portion and the state where a load of 1/10 of that load is alternately repeated), the stress range (N/mm ² ) and the fatigue life (the number of repetitions until the specimen loses its function as a structure due to fatigue cracks) is shown (both in logarithmic representation). The results indicated by arrows are the cases where the test was terminated because the predetermined number of repetitions was reached without causing fatigue cracks.

As shown in the graph, in the test results according to the examples of the present invention, the fatigue of the Japan Society of Steel Construction (JSSC), which defines the relationship between the stress range and fatigue life Corresponds to grade A. Since this fatigue grade A is generally used to evaluate the fatigue strength of the steel material itself rather than the welded joint portion (that is, the welded joint portion in general has a lower fatigue grade), the welded joint according to the embodiment of the present invention It can be said that the occurrence of fatigue cracks originating from the weld root portion is effectively suppressed in the welded structure in which the portion is formed. In addition, even when the stress ratio was set to 0.1, the occurrence of fatigue cracks was suppressed. It can be said that the occurrence of fatigue cracks can be effectively suppressed.

Further, as described above, for example, when a welded joint is formed on the inner peripheral surface of a steel pipe, it is affected by thermal contraction in the circumferential direction of the steel pipe in addition to thermal contraction in the radial direction of the steel pipe. Although the test apparatus according to the present embodiment does not take into consideration the thermal contraction of the steel pipe in the circumferential direction, in the actual welded joint formed on the inner peripheral surface of the steel pipe, the material to be welded 82 exerts a greater force on the beam 81. As a result of being brought into contact with each other and realizing contact in the non-welded region more reliably, the effect of suppressing the occurrence of fatigue cracks is enhanced.

Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention belongs can conceive of various modifications or modifications within the scope of the technical idea described in the claims. It is understood that these also naturally belong to the technical scope of the present invention.

1, 11, 21, 23, 31, 41, 51A, 51B... steel pipe, 1S, 11S, 21S, 23S, 31S... inner peripheral surface, 2... diaphragm, 2B... beveled surface, 2C... curved surface, 2E... end face, 2G, 12G... edge 3... weld metal 3C... weld root part 11E, 21E, 23E, 31E, 41E, 511E, 512E... end surface 12, 42... lid body 22... fitting ring 12G, 22G , 32G... edge, 12P... step joint surface, 12Q... rising surface, 22S... outer peripheral surface, 42S... plate surface, 81... beam, 82... material to be welded, 82E... end face, 83... weld metal.

Claims (8)

A welded structure comprising a first tubular member, a second member, and a weld metal filled or laminated between the first tubular member and the second member,
forming a weld region filled or laminated with the weld metal and a non-welded region not filled or laminated with the weld metal between the first tubular member and the second member;
contacting the first tubular member and the second member in a contact region included in the non-welded region to transmit stress between each other ;
the second member is a plate-like member that at least partially closes the internal space of the first tubular member;
The welded region and the non-welded region are formed between the inner peripheral surface of the first tubular member and the end surface of the second member,
A welded structure, wherein in the contact area, the edge of the beveled surface formed on the end surface of the second member contacts the inner peripheral surface of the first tubular member. A welded structure comprising a first tubular member, a second member, and a weld metal filled or laminated between the first tubular member and the second member,
forming a weld region filled or laminated with the weld metal and a non-welded region not filled or laminated with the weld metal between the first tubular member and the second member;
contacting the first tubular member and the second member in a contact region included in the non-welded region to transmit stress between each other;
the second member is a plate-like member that at least partially closes the internal space of the first tubular member;
The welded region and the non-welded region are formed between the inner peripheral surface of the end of the first tubular member and the stepped surface formed on the peripheral edge of the second member,
A welded structure, wherein in the contact area, an edge of the beveled surface formed on the stepped surface contacts the inner peripheral surface of the first tubular member. A welded structure comprising a first tubular member, a second member, and a weld metal filled or laminated between the first tubular member and the second member,
forming a weld region filled or laminated with the weld metal and a non-welded region not filled or laminated with the weld metal between the first tubular member and the second member;
contacting the first tubular member and the second member in a contact region included in the non-welded region to transmit stress between each other;
the welded structure further comprising a third tubular member;
the second member is in contact with the inner peripheral surfaces of the first tubular member and the third tubular member;
The welded structure, wherein the welded region and the non-welded region are formed between the inner peripheral surface of each of the first tubular member and the third tubular member and the second member. A welded structure comprising a first tubular member, a second member, and a weld metal filled or laminated between the first tubular member and the second member,
forming a weld region filled or laminated with the weld metal and a non-welded region not filled or laminated with the weld metal between the first tubular member and the second member;
contacting the first tubular member and the second member in a contact region included in the non-welded region to transmit stress between each other;
the second member is a second tubular member;
The welded region and the non-welded region are formed between the inner peripheral surface of the end of the first tubular member and the outer peripheral surface of the second tubular member,
The welded structure, wherein in the contact area, the edge of the beveled surface formed on the outer peripheral surface of the second tubular member contacts the inner peripheral surface of the first tubular member. A welded structure comprising a first tubular member, a second member, and a weld metal filled or laminated between the first tubular member and the second member,
forming a weld region filled or laminated with the weld metal and a non-welded region not filled or laminated with the weld metal between the first tubular member and the second member;
contacting the first tubular member and the second member in a contact region included in the non-welded region to transmit stress between each other;
the second member is a second tubular member;
The welded region and the non-welded region are formed between an end surface of the first tubular member and an end surface of the second tubular member;
A welded structure, wherein in the contact area, the edge of the beveled surface formed on the end face of the second tubular member contacts the end face of the first tubular member. A welded structure comprising a first tubular member, a second member, and a weld metal filled or laminated between the first tubular member and the second member,
forming a weld region filled or laminated with the weld metal and a non-welded region not filled or laminated with the weld metal between the first tubular member and the second member;
contacting the first tubular member and the second member in a contact region included in the non-welded region to transmit stress between each other;
the second member is a plate-like member that at least partially closes the internal space of the first tubular member;
the end surface of the first tubular member includes a beveled surface;
In the contact area, the edge of the oblique surface formed on the end surface of the first tubular member and the plate surface of the second member are in contact with each other, or the contact area is formed on the plate surface of the second member. Welded structure, wherein the edge of the beveled surface and the end face of the first tubular member are in contact. 7. The welded structure of any preceding claim, wherein at least one of the first tubular member or the second member is elastically deformed near the contact area. 8. The welded structure according to any one of claims 1 to 7 , wherein at least one of the first tubular member and the second member is made of steel having high fatigue durability.

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