JP2019104056A - Weld joint - Google Patents

Abstract

To provide a weld joint of which a fatigue strength can be improved.SOLUTION: A base material 2 comprises a second bulging part 21 which is formed at an end on a groove 3 side of a surface of the base material, and bulges in a thickness direction of the base material 2. Therefore, a rigidity of a toe part T can be improved in a state that a center of gravity G of a weld joint 1 does not too approach a load axis A side (a state maintaining decentration to a first bulging part 20 side). Consequently, since a moderate bending moment acts on a weld part 5 when a tensile load F is applied to the base material 2, a tensile stress Sb of a root part R of the weld zone 5 is reduced, and further, a rigidity of the toe part T of the weld zone 5 is improved, whereby also a tensile stress Sa acting on the toe part T can be reduced. Thus, since tensile stresses of the root part R and the toe part T can be suppressed, a fatigue strength of the weld joint 1 can be improved.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a welded joint, and more particularly to a welded joint capable of improving fatigue strength.

  When complete penetration welding is performed on the groove of the butt weld joint, there is a problem that stress concentration is likely to occur at the root portion of the weld (the end portion on the back surface side of the base material in the root surface of the groove). With respect to this problem, for example, Patent Document 1 discloses a welded joint including a protrusion (projecting portion) protruding from the back surface of a base material.

  Here, with reference to FIG. 2 (b), the case where the tensile load F acts on the conventional weld joint 201 will be described. FIG. 2B is a partially enlarged cross-sectional view of the welded joint 201 showing a case where a tensile load F acts on the conventional welded joint 201. As shown in FIG. In FIG. 2B, hatching is omitted for ease of understanding, and arrows of the compressive stress Sc2 and the tensile stress Sd2 resulting from the bending moment are schematically shown (with respect to the load axis A It is shown in the figure). Moreover, arrow U-D of FIG.2 (b) has shown the thickness direction of the weld joint 201. As shown in FIG.

  As shown in FIG. 2 (b), the weld joint 201 has a load axis A (protruding part 220) as the overhanging part 220 overhangs from the base material 202 in the thickness direction (direction of arrow D in FIG. 2B). The center of gravity G2 of the welded joint 201 is eccentric to the side of the overhanging portion 220 from the center in the thickness direction of the base material 202 in the region where it is not formed. When a tensile load F is applied to the welded joint 201, a bending moment is generated in the weld portion 205 because the center of gravity G2 is eccentric from the load axis line A.

  A compressive stress Sc2 is generated in the root portion R2 of the welded portion 205 (a portion where the root surface 230 of the groove 203 and the back surface of the overhang portion 220 are connected) by this bending moment. A part of the tensile stress Sb2 generated in R2 is offset by the compressive stress Sc2. Therefore, the stress generated in the root portion R2 can be reduced.

JP, 2002-144031, A (for example, paragraph 0027, FIG. 1)

  However, in the above-described conventional technique, the bending moment of the welded portion 205 causes the tensile stress Sd2 to be applied to the toe portion T2 of the welded portion 205 (a portion where the root surface 230 of the groove 203 and the surface of the base material 202 are connected). Works. That is, in addition to the tensile stress Sa2 caused by the tensile load F, a stress obtained by synthesizing the tensile stress Sd2 caused by the bending moment of the welded portion 205 acts on the toe portion T2, so that the fatigue fracture occurs at the toe portion T2. It tends to occur. Therefore, there is a problem that the fatigue strength of the welded joint 201 can not be sufficiently secured.

  The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a welded joint capable of improving the fatigue strength.

  In order to achieve this object, the welded joint of the present invention comprises a pair of base materials which are abutted against each other, and a groove formed between the pair of base materials facing each other and connecting the front and back surfaces of the base material. The base material includes a weld formed by single-sided welding from the surface side of the base material to the groove, and a backing metal disposed at the bottom of the weld part, the base material being the back side of the base material. It is provided with the 1st overhang | projection part which is formed in the edge part by the side of a groove side, and protrudes in the thickness direction of the said base material, and the said base material is formed in the edge part by the side of the said groove in the surface. And a second overhang portion projecting in the thickness direction of the base material.

  According to the welded joint according to claim 1, since the base material is provided at the end portion on the groove side in the surface and is provided with the second overhang portion projecting in the thickness direction of the base material, the center of gravity of the weld joint Can be brought closer to the load axis (the center in the thickness direction of the base material in the region where the first overhang and the second overhang are not formed) from the first overhang side. Thereby, when a tensile load is applied to the base material, the bending moment generated in the welded portion can be reduced, so that it acts on the toe portion of the welded portion (a portion where the surface of the second overhang portion and the welded portion are connected) Tensile stress can be reduced. Therefore, since it can suppress that fatigue failure arises in a toe part, it is effective in the ability to improve the fatigue strength of a welding joint.

  According to the weld joint of the second aspect, in addition to the effect of the weld joint of the first aspect, the overhang dimension of the second overhang portion is set to a value smaller than the overhang dimension of the first overhang portion. Thus, the center of gravity of the welded joint can be positioned closer to the first overhang than the load axis. Thereby, when a tensile load is applied to a base material, it can suppress that the bending moment which arises in a welding part reduces excessively.

  That is, since a compressive stress is generated at the root of the weld (the connection portion between the back surface of the first overhang and the weld) due to the bending moment generated at the weld, the tensile load on the base material acts on the root Some of the tensile stresses that occur can be offset by such compressive stresses. Therefore, since the tensile stress which acts on the root part of a welding part can be reduced and it can control that fatigue failure arises in a root part, it is effective in the ability to improve the fatigue strength of a welding joint.

  According to the weld joint of the third aspect, in addition to the effect of the weld joint of the second aspect, the following effect is exerted. The overhang dimension of the second overhang portion is set to 1% or more and 90% or less of the overhang dimension of the first overhang portion. Therefore, when a tensile load is applied to the base material, the bending moment generated in the weld portion is excessive Increase or decrease can be suppressed. Thereby, since the stress which arises in both the toe part of a welding part and a root part can be reduced, it can control that fatigue failure arises in those toe parts and a root part. Therefore, there is an effect that the fatigue strength of the welded joint can be improved.

(A) is a partial expanded sectional view which shows the state before welding of the weld joint in one Embodiment of this invention, (b) is a partial expanded sectional view which shows the state after welding of a weld joint. (A) is a partial expanded sectional view of a weld joint which shows the case where tensile load acts on the weld joint of the present invention, (b) shows the case where tensile load acts on the conventional weld joint. It is a partial expanded sectional view.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. First, with reference to FIG. 1, the whole structure of the weld joint 1 is demonstrated. Fig.1 (a) is a partial expanded sectional view which shows the state before welding of the weld joint 1 in one Embodiment of this invention, FIG.1 (b) is the partial expansion which shows the state after welding of the weld joint 1 FIG. Arrows U-D in FIG. 1 indicate the thickness direction of the welded joint 1.

  As shown in FIG. 1, the weld joint 1 is a butt weld joint that constitutes a part of a structure (in the present embodiment, a structure of a railway vehicle). Welded joint 1 is formed between a pair of base materials 2 which are abutted against each other and the pair of base materials 2 and extends in a direction perpendicular to the thickness direction of base material 2 (vertical direction in FIG. 1) And a back metal 4 disposed at the bottom of the groove 3 and a weld 5 formed in a space surrounded by the groove 3 and the back metal 4.

  The base material 2 is a plate-like body made of a metal material, and the pair of base materials 2 is formed in a symmetrical shape with the groove 3 interposed therebetween. The base material 2 is formed at the end on the side of the groove 3 on the back surface side, and at the same time, the first overhang portion 20 projecting in the thickness direction of the base material 2 (direction of arrow D in FIG. 1) The second tension is formed at the end of the groove 3 on the surface side and extends in the thickness direction of the base material 2 (direction of arrow U in FIG. 1) (opposite direction of extension of the first overhang 20). And an outlet 21. In addition, the area | region in which the 1st overhang | projection part 20 and the 2nd overhang | projection part 21 are not formed among the base materials 2 is defined as the base 22. FIG.

  The first overhanging portion 20 includes a first overhanging surface 20 a constituting the back surface thereof, and a first connection surface 20 b connecting the first overhanging surface 20 a and the back surface of the base 22. The first overhanging surface 20 a is configured as a flat surface parallel to the back surface of the base 22, and the first connection surface 20 b is configured as a gentle curved surface connecting the first overhang surface 20 a and the back surface of the base 22.

  The second overhanging portion 21 includes a second overhanging surface 21 a constituting the surface thereof, and a second connection surface 21 b connecting the surface of the second overhanging surface 21 a and the surface of the base 22. The second overhanging surface 21a is configured as a flat surface parallel to the first overhanging surface 20a, and the second connection surface 21b is configured as a gently curved surface connecting the second overhanging surface 21a and the surface of the base 22. .

  The thickness t of the base 22 is set to a predetermined size (4 mm in the present embodiment), and the projection dimension t1 (2 mm in the present embodiment) of the first overhanging portion 20 from the base 22 is from the base 22 The overhang dimension t2 (in the present embodiment, 1 mm) of the second overhang portion 21 is set larger.

  Further, ends of the first overhanging surface 20a and the second overhanging surface 21a on the base 22 side (opposite to the groove 3 side) are located on the same plane orthogonal to the butting direction of the base material 2, The width L2 (3.5 mm in the present embodiment) of the second overhang surface 21a is set smaller than the width L1 (8.5 mm in the present embodiment) of the first overhang surface 20a in the butting direction of the base material 2 Be done. That is, the cross-sectional area of the second overhanging portion 21 is set smaller than the cross-sectional area of the first overhanging portion 20 in a cross section cut along a plane orthogonal to the extending direction of the groove 3 (vertical direction in FIG. 1). Be done.

  Here, in a cross-sectional view cut along a plane orthogonal to the extending direction of the groove 3, a straight line passing through the center in the thickness direction of the base 22 (a straight line indicated by a two-dot chain line in FIG. Define as The overhang dimension t2 of the second overhang portion 21 is set smaller than the overhang dimension t1 of the first overhang portion 20 (the cross-sectional area of the second overhang portion 21 is smaller than the cross-sectional area of the first overhang portion 20 Is set smaller, so the center of gravity G of the welded joint 1 (the area where the first overhang 20 and the second overhang 21 are formed) is slightly closer to the first overhang 20 than the load axis A. It is eccentric.

  The groove 3 has a pair of root surfaces 30 facing each other at a predetermined distance in the butt direction (left and right direction in FIG. 1) of the base material 2 and the back surface (first overhanging surface 20a) side and the surface (base 1) It is configured as a V-shaped groove in communication with the second overhanging surface 21 a) side. The weld joint 1 is subjected to complete penetration welding by single-sided welding to form the weld portion 5, and the weld portion 5 is a portion where the weld metal is solidified by welding to the groove 3. The surface of the welding portion 5 is configured as a curved surface that connects the ends on the groove 3 side of the pair of second overhang surfaces 21 a.

  Next, with reference to FIG. 2A, the case where a tensile load F acts on the welded joint 1 will be described. Fig.2 (a) is the elements on larger scale sectional view of the weld joint 1 which shows the case where the tensile load F acts on the weld joint 1 of this invention. In FIG. 2A, hatching is omitted for ease of understanding, and arrows of a compressive stress Sc and a tensile stress Sd resulting from a bending moment described later are schematically shown (for the load axis A It is shown in the figure). Moreover, arrow U-D of Fig.2 (a) has shown the thickness direction of the welding joint 1. As shown in FIG.

  As shown in FIG. 2A, when stress (for example, 100 MPa) due to the tensile load F in the butt direction of the base material 2 is applied to the base material 2 (base 22), the toe portion T of the welded portion 5 ( A tensile stress Sa acts on the connection portion between the welded portion 5 and the second overhanging surface 21a. Similarly, the tensile stress Sb also acts on the root portion R of the welded portion 5 (the portion where the welded portion 5 and the first overhanging surface 20a are connected). In addition, since the center of gravity G of the welded joint 1 is eccentric to the first overhanging portion 20 side with respect to the load axis line A, a bending moment is generated in the welded portion 5.

  Since a compressive stress Sc acts on the root portion R by the bending moment of the welded portion 5, a part of the tensile stress Sb acting on the root portion R due to the tensile load F is due to the compressive stress Sc resulting from the bending moment Be offset. Therefore, the stress generated in the root portion R can be reduced. On the other hand, a tensile stress Sd is generated at the toe portion T by the bending moment of the welded portion 5. Therefore, in addition to the tensile stress Sa caused by the tensile load F, the tensile stress Sd caused by the bending moment acts on the toe portion T, the stress generated at the toe portion T is compared with the stress generated at the root portion R. growing.

  Here, as shown in FIG. 2 (b), since the overhanging portion 220 is provided only on the back surface side of the base material 202 in the conventional weld joint 201, the weld joint 201 (a region where the overhanging portion 220 is formed) The center of gravity G2 of the) is largely decentered from the load axis line A (larger than the center of gravity G of the welded joint 1 of the present embodiment). Therefore, while the stress which arises in root part R2 can be reduced comparatively greatly, the stress which arises in toe part T2 increases.

  On the other hand, according to the welded joint 1 of the present embodiment, the second overhanging portion 21 is formed at the end on the groove 3 side in the surface of the base material 2, and the second overhanging portion 21 is the base material It overhangs in the thickness direction of 2 and is formed. As a result, the center of gravity G of the welded joint 1 can be made closer to the load axis A side, as compared with a configuration in which the overhanging portion 220 is provided only on the back surface side of the base material 202 like the conventional welded joint 201. When a tensile load F is applied to No. 2, the bending moment generated in the welded portion 5 can be reduced. Moreover, the rigidity of the base material 2 in the toe part T side can be raised by forming the 2nd overhang | projection part 21. As shown in FIG. That is, by increasing the rigidity of the base material 2 on the toe side T while reducing the stress acting on the toe portion T of the welded portion 5, the stress generated at the toe portion T is allowed stress (for example, 100 MPa) It can be reduced to the following. Therefore, it is possible to suppress the occurrence of fatigue failure at the toe portion T, and to improve the fatigue strength of the welded joint 1.

  Here, when complete penetration welding is performed using the backing metal 4, stress tends to be concentrated on the root portion R due to thermal effects (for example, changes in shape and rigidity) of the base material 2 and the backing metal 4. When the tensile stress caused by the tensile load F acts on the root portion R, the stress generated in the root portion R exceeds the allowable stress (for example, 100 MPa). That is, while the stress acting on the toe portion T can be reduced by making the second overhang portion 21 overhang on the toe end T side, the overhang dimension t2 of the second overhang portion 21 is excessively large (for example, (2 mm or more), the center of gravity G of the welded joint 1 coincides with the load axis A (or eccentric to the side of the second overhang portion 21), and the compressive stress Sc is not generated in the root portion R (or The tensile stress in the opposite direction to the compressive stress Sc is generated). Therefore, the tensile stress Sb resulting from the tensile load F can not be offset, and the stress generated in the root portion R exceeds the allowable stress.

  On the other hand, according to the welded joint 1 of the present embodiment, the overhang dimension t2 of the second overhang portion 21 is set to a value smaller than the overhang dimension t1 of the first overhang portion 20 (first tension Since the cross-sectional area of the second overhang 21 is set smaller than the cross-sectional area of the overhang 20), the center of gravity G of the welded joint 1 is slightly eccentric to the first overhang 20 side than the load axis A. Can. Thereby, a part of tensile stress Sb which acts on root part R can be offset using bending moment (compression stress Sc) resulting from tensile load F.

  That is, the overhang dimension t2 of the second overhang portion 21 is set to a value smaller than the overhang dimension t1 of the first overhang portion 20 (the center G of the welded joint 1 is larger than the load axis A, the first overhang portion 20). By slightly decentering to the side, it is possible to reduce the stress acting on the toe portion T of the welded portion 5 while enhancing the rigidity of the base material 2 on the toe portion T side, and It can be made compatible with generating (preventing tensile stress due to bending moment from being generated at the root portion R). Thereby, since the stress generated in each of the root portion R and the toe portion T can be reduced to the allowable stress or less, the fatigue strength of the welded joint 1 can be improved.

  Further, although the stress generated in each of the root portion R and the toe portion T is reduced to the allowable stress or less, the stress generated in the toe portion T becomes slightly larger than the root portion R as described above. As a result, fatigue failure is likely to occur on the toe portion T side, so even if fatigue failure occurs, it can be easily found.

  As mentioned above, although the present invention was explained based on the above-mentioned embodiment, the present invention is not limited to the above-mentioned form at all, It is easy to be able to carry out various modification improvement in the range which does not deviate from the meaning of the present invention. It can be guessed. For example, the plate thickness t of the base 22, overhang dimensions t1 and t2 of the first overhang 20 and the second overhang 21, width dimensions L1 and L2 of the first overhang surface 20a and the second overhang surface 21a, and The numerical value of the groove angle of tip 3 is an example and can be set as appropriate.

  Specifically, depending on the thickness t of the base 22 and the material and weight of each portion (the first overhang 20, the second overhang 21, the backing metal 4 and the weld 5), the first overhang 20 may be used. By setting the overhang dimensions t1 and t2 and the width dimensions L1 and L2 of the second overhang portion 21 and the groove angle of the groove 3 appropriately, the center of gravity G of the welded joint 1 can be set to a desired position (load axis A It may be set to a position slightly eccentric to the first overhanging portion 20 side and a position at which the stress generated in the root portion R and the toe portion T becomes less than the allowable stress).

  Therefore, for example, in the above embodiment, the case where the plate thickness t of the base 22 is 4 mm, the overhang dimension t1 of the first overhang portion 20 is 2 mm, and the overhang dimension t2 of the second overhang portion 21 is 1 mm, respectively. Although explained, it is not necessarily limited to this. For example, the plate thickness t of the base 22 is 4 mm or more and 8 mm or less, the overhang dimension t1 of the first overhang portion 20 is 0.5 mm or more and 5 mm or less, and the overhang dimension t2 of the second overhang portion 21 is 0.005 mm or more 4.5 mm It may be set as follows.

  Further, in the above embodiment, the case where the overhang dimension t2 (1 mm) of the second overhang portion 21 is set to a value of 50% of the overhang dimension t1 (2 mm) of the first overhang portion 20 has been described. It is not limited to this. For example, the overhang dimension t2 of the second overhang portion 21 is preferably set to 1% or more and 90% or less of the overhang dimension t1 of the first overhang portion 20.

  As a result, excessive increase or decrease in bending moment generated in the welded portion 5 is suppressed (a moderate bending moment is generated in the welded portion 5), and the root portion R and the toe portion T of the welded portion 5 are The stress generated in each can be reduced to the allowable stress or less.

  The overhang dimension t2 of the second overhang portion 21 is more preferably set to 25% or more and 75% or less of the overhang dimension t1 of the first overhang portion 20, and the overhang dimension t1 of the first overhang portion 20. More preferably, it is set to 50% of By setting the overhang dimension t2 of the second overhang portion 21 to 25% or more and 75% or less of the overhang dimension t1 of the first overhang portion 20, a more appropriate bending moment is generated in the weld portion 5, and the weld portion The stress generated in each of the root portion R and the toe portion T of 5 can be reduced more effectively to the allowable stress or less.

  Further, by setting the overhang dimension t2 of the second overhang portion 21 to 50% of the overhang dimension t1 of the first overhang portion 20, a more appropriate bending moment is generated in the weld portion 5, and The stress generated at each of the root portion R and the toe portion T can be reduced more effectively below the allowable stress.

  In other words, as the overhang dimension t2 of the second overhang portion 21 approaches 50% of the overhang dimension t1 of the first overhang portion 20, the stresses generated in the root portion R and the toe portion T can be balanced. Therefore, while the overhang dimension t1 of the first overhang portion 20 and the overhang dimension t2 of the second overhang portion 21 are set as small values as possible, fatigue failure occurs in the root portion R and the toe portion T of the welded portion 5 As a result, the fatigue strength of the welded joint 1 can be improved while suppressing an increase in the weight of the base material 2.

  Although the said embodiment demonstrated the case where the weld joint 1 comprised a part of structure of a rail vehicle, it is not necessarily restricted to this. For example, as another structure to which the weld joint 1 is applied, a transport device (for example, a car, a tank trolley, a transport vehicle, etc.), a steel structure (for example, a bridge), a nonferrous metal structure (aluminum structure), etc. are exemplified. Ru. That is, the technical idea of the present invention can be applied as long as the structure has a portion in which base materials made of plate-like members are butted.

  Although the case where the base material 2 is comprised from a metal material was demonstrated in the said embodiment, it is not necessarily restricted to this, for example, the base material 2 may be comprised from a ceramic. That is, the technical concept of the present invention can be applied to any base material in which complete penetration welding is performed by butt welding.

  Although the said embodiment demonstrated the case where the 2nd overhang | projection surface 21a was comprised as a flat surface parallel to the 1st overhang | projection surface 20a, it is not necessarily restricted to this. For example, the second overhanging surface 21a may be configured as a surface inclined with respect to the first overhanging surface 20a, or part or all of the second overhanging surface 21a may be configured as a curved surface.

  In the said embodiment, although the description about the curvature of the 1st connection surface 20b and the 2nd connection surface 21b was abbreviate | omitted, the curvature radius and curved shape of the 1st connection surface 20b and the 2nd connection surface 21b can be set suitably. For example, the radius of curvature of the first connection surface 20b and the second connection surface 21b is preferably set larger than the thickness t of the base 22, but may be set equal to or less than the thickness t.

  Although the said embodiment demonstrated the case where overhang | projection dimension t1 (the overhang | projection dimension t2 of the 2nd overhang | projection part 21) of the 1st overhang | projection part 20 was set smaller than the plate thickness t of the base 22, It is not limited. For example, the plate thickness t of the base 22 and the overhang dimension t1 of the first overhang portion 20 (the overhang dimension t2 of the second overhang portion 21) may be set to the same value or the plate thickness t of the base 22 The projection size t1 of the first overhang portion 20 (the projection dimension t2 of the second overhang portion 21) may be set large.

  Although the said embodiment demonstrated the case where the groove 3 was comprised as a V-shaped groove, it is not necessarily restricted to this, for example, you may comprise the groove 3 as a U-shaped groove . Further, the groove 3 may be configured as a re-shaped groove or a J-shaped groove. That is, in the said embodiment, although the case where a pair of base material 2 was symmetrically formed on both sides of the groove 3, was demonstrated, it is not restricted to this. For example, if at least one of the pair of base materials is formed of a plate, the technical idea of the present invention can be applied.

  Although the said embodiment demonstrated the case where the whole backing metal 4 contact | abutted to the whole (the bottom face of the welding part 5) of the 1st overhang | projection surface 20a, it is not necessarily restricted to this. For example, an area not in contact with the backing metal 4 may be provided on the first overhanging surface 20a.

  Although the above-mentioned embodiment explained the case where the surface of welding part 5 was constituted as a curved surface, it is not necessarily restricted to this, for example, composition which makes the surface of welding part 5 a flat surface by grinder finish may be sufficient. .

DESCRIPTION OF SYMBOLS 1 Welded joint 2 base material 20 1st overhanging part 21 2nd overhanging part 3 groove 4 backing metal 5 welding part t1 overhanging dimension of 1st overhanging part t2 overhanging dimension of 2nd overhanging part

Claims (3)

A pair of base materials which are abutted against each other, a groove formed between the opposing surfaces of the pair of base materials and connecting the front and back surfaces of the base material, and one side to the groove from the surface side of the base material A welding portion formed by welding and a backing metal disposed on a bottom portion of the welding portion, the base material being formed at an end portion on the back side of the back surface and the base material In the welded joint including the first overhang portion that overhangs in the thickness direction of
The weld joint characterized in that the base material includes a second overhang portion formed at an end on the groove side of the surface and projecting in a thickness direction of the base material.   The weld joint according to claim 1, wherein the overhang dimension of the second overhang portion is set to a value smaller than the overhang dimension of the first overhang portion.   The weld joint according to claim 2, wherein the overhang dimension of the second overhang portion is set to 1% or more and 90% or less of the overhang dimension of the first overhang portion.

Images