JP6226814B2 - Manufacturing method of welded structure - Google Patents

Description

  The present invention relates to a method for manufacturing a welded structure having a first member and a second member welded to the first member along a preset welding line direction.

  Conventionally, it is known that in a welded portion of a welded structure between a first member and a second member, the fatigue strength of the welded portion decreases due to the stress concentration at the weld toe and the presence of tensile residual stress due to welding. ing.

  As a method for improving the fatigue strength of a welded structure, for example, a method described in Patent Document 1 is known.

  In the method described in Patent Document 1, the rib is hit by hammer peening on a base material welded along a circumferential direction (welding line direction) surrounding the rib.

  Specifically, a chipper having a flat tip is vibrated, and the tip of the chipper is collided in a direction perpendicular to the base material surface. In this state, the chipper is gradually moved from the position in the vicinity of the weld toe portion to the outside in the weld width direction orthogonal to the weld line direction.

  In this way, the chipper's flat surface collides perpendicularly with the base metal surface, so that the hitting force by the chipper is transmitted to the base material in the vertical direction, and in this state, the chipper is moved outward in the welding width direction. Within the range, the striking force is applied to the base material.

  Thereby, the compressive residual stress is introduced within a predetermined range in the weld width direction of the base material, and the fatigue strength of the base material can be improved.

JP 2011-131260 A

  However, Patent Document 1 discloses a method for introducing compressive residual stress into a predetermined range in the weld width direction with respect to the base material, but for improving the fatigue strength of the base material along the weld line direction. The method is not disclosed.

  The objective of this invention is providing the manufacturing method of the welded structure which can improve the fatigue strength of a weld part in a weld line direction and the weld width direction orthogonal to this.

  In order to solve the above-described problems, the present invention is a method for manufacturing a welded structure having a first member and a second member welded to the first member, along a preset welding line direction. A welding step of welding the second member to the first member, and a vibration member having a flat tip surface is vibrated in a vibration direction orthogonal to the tip surface, and the tip surface of the vibration member is moved to the first member. A striking step of colliding with the surface of the member in a direction parallel to the vibration direction. In the striking step, the welding width direction perpendicular to the welding line direction is outside the weld toe portion of the first member. A method for manufacturing a welded structure is provided in which the vibration member is moved in the weld line direction while the vibration member is reciprocated in the welding width direction within a set reciprocating range.

  According to the present invention, the striking force due to the vibration of the vibration member is moved to a predetermined range in the welding line direction and the welding width direction of the first member by moving the vibration member in the welding line direction while reciprocating in the welding width direction. Can be given over.

  Therefore, the fatigue strength of the welded portion in the first member can be improved in the weld line direction and the weld width direction.

  Here, when the second member is welded to the first member, a particularly high tensile residual stress exists at the boundary portion of the first member with respect to the weld toe.

  Therefore, in the method for manufacturing a welded structure, the reciprocating range is located outside the inner fold line located at a boundary portion of the first member with respect to the weld toe end and the inner fold line in the weld width direction. It is preferably set between the outer folding line.

  According to this aspect, since the compressive residual stress can be applied to the boundary portion with respect to the weld toe portion of the first member where the high tensile residual stress exists as described above, the fatigue of the first member is more effectively achieved. Strength can be improved.

  Here, the tensile residual stress generated in the first member during welding decreases as the distance from the weld toe portion increases to the outside in the weld width direction.

  Therefore, the manufacturing method of the welded structure further includes a preparation step of preparing stress information regarding the distribution of the tensile residual stress in the weld width direction generated in the first member by welding of the second member, It is preferable that the outer fold line is set at a position where the tensile residual stress in the first member becomes a preset reference stress in the stress information or on the outer side in the weld width direction than this.

  According to this aspect, since the compressive residual stress can be applied by the vibrating member to a range where the tensile residual stress in the first member is equal to or greater than the preset reference stress, the tensile residual stress generated in the first member by welding Can be suppressed below the reference stress.

  For example, if the reference stress is set to the value of the tensile residual stress of the first member before welding of the second member, the fatigue strength is improved with respect to the entire range of the first member in which the tensile residual stress is generated by welding. Can be achieved.

  In the manufacturing method of the welded structure, the period of the reciprocating motion of the vibration member is set as f, the moving speed of the vibration member in the welding line direction is set as v, and is parallel to the weld line direction of the tip surface of the vibration member. When the maximum length in the direction is A, it is preferable that the vibrating member is reciprocated so as to satisfy v / f <A in the striking step.

  According to this aspect, the trajectory of the forward path and the trajectory of the return path of the vibration member overlap each other in the weld line direction while the vibration member reciprocates once in the welding width direction. Can be applied evenly in the direction of the weld line.

  Here, the range on the first member in which the compressive residual stress is generated by a single collision of the vibration member has a predetermined width from the outer peripheral edge of the front end surface of the vibration member to the outer side and the front end surface of the vibration member around the entire periphery. It is a range that surrounds (hereinafter, this range is referred to as an effective range).

  Therefore, in the method for manufacturing a welded structure, the maximum width in the direction parallel to the weld width direction of the tip surface of the vibration member is ½ or less of the width of the reciprocating range in the direction parallel to the weld width direction. It is preferable that

  According to this aspect, since the effective ranges are continuously formed when the vibration member moves in the forward path and when the vibration path moves, the compressive residual stress is continuously introduced into the first member in the welding width direction. be able to.

  In the method for manufacturing a welded structure, the distal end surface of the vibration member preferably has a circular planar shape having a diameter of 1.5 mm or more and 4 mm or less.

  According to this aspect, compressive residual stress can be more effectively applied to the first member, and thereby the fatigue strength of the first member can be reliably improved.

  Specifically, when the diameter of the distal end surface of the vibration member is less than 1.5 mm, the wear of the vibration member progresses rapidly and the striking process cannot be performed stably.

  On the other hand, if the diameter of the tip surface of the vibration member exceeds 4 mm, the force from the vibration member to the first member is dispersed, and the compressive residual stress cannot be sufficiently introduced to the first member.

  According to the present invention, the fatigue strength of the welded portion can be improved in the weld line direction and the weld width direction orthogonal thereto.

It is a side view for demonstrating the manufacturing method of the welded structure which concerns on this invention, and shows the cross section of a welded structure. It is a graph which shows distribution of the residual stress of the weld width direction in a welded structure. It is a top view which shows the effective range which a compression residual stress produces on a 1st member by the collision of a vibration member. It is a top view which shows an example in case an effective range does not continue in a reciprocating range. It is a graph which shows the result of the fatigue test performed with respect to the welded structure by changing the conditions of a vibration member. It is a graph which shows the result of the fatigue test performed with respect to the welded structure by changing the conditions of a reciprocating range.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. The following embodiments are examples embodying the present invention, and are not of a nature that limits the technical scope of the present invention.

  With reference to FIG. 1, a welded structure 1 according to an embodiment of the present invention includes a first member 2 and a second member 3 welded to the first member 2. In addition, the code | symbol 4 is the weld metal located between the 1st member 2 and the 2nd member 3, and the code | symbol 4a is a welding toe part.

  The first member 2 and the second member 3 are welded to each other along a weld line direction D1 orthogonal to the paper surface of FIG. In addition, the direction (left-right direction of FIG. 1) orthogonal to the welding line direction D1 is demonstrated below as the welding width direction D2.

  Compressive residual stress is introduced into the welded portion of the first member 2 by the vibration member 5 of the ultrasonic peening apparatus, thereby improving the fatigue strength of the welded portion of the first member 2.

  That is, after the first member 2 and the second member 3 are welded, before the compressive residual stress by the vibration member 5 is introduced, the first member 2 is affected by the influence of heat during welding as shown in FIG. As shown, there is a distribution of tensile residual stress, and the fatigue strength of the first member 2 is reduced.

  Specifically, as shown in FIGS. 1 and 2, the tensile residual stress in the first member 2 is highest at the boundary portion in the weld toe portion 4a, and is separated from the weld toe portion 4a to the outside in the welding width direction D2. And becomes 0 at the position P1. On the other hand, a compressive residual stress exists in a range outside the weld width direction D2 of the position P1 in the first member 2. This compressive residual stress increases and peaks as the distance from the weld toe 4a starts from the position P1, and decreases to 0 as the distance from the weld toe 4a starts from the peak.

  And in the range in which the tensile residual stress exists in the 1st member 2, the compressive residual stress is introduce | transduced by the vibration member 5 of the ultrasonic peening apparatus. Specifically, a range E () between the inner fold line E1 located at the boundary portion of the first member with respect to the weld toe 4a and the outer fold line E2 located outside the inner fold line E1 in the welding width direction D2. Hereinafter, compressive residual stress is introduced into the reciprocating range E). That is, the outer fold line E2 is set at a position where the tensile residual stress in FIG. 2 becomes a preset reference stress (0 in this embodiment).

  The ultrasonic peening apparatus includes a vibration generator (not shown) that can vibrate the vibration member 5 along a vibration direction D3 orthogonal to the welding line direction D1 and the welding width direction D2. The vibration member 5 has a flat front end surface 5a orthogonal to the vibration direction D3. By causing the front end surface 5a of the vibration member 5 that vibrates in the vibration direction D3 to collide with the surface of the first member 2 in a direction parallel to the vibration direction D3, compressive residual stress can be introduced into the first member 2. it can.

  The front end surface 5a of the vibration member 5 is circular. As shown in FIG. 3, the range on the first member 2 where the compressive residual stress is generated by one collision of the tip surface 5a of the vibration member 5 is the outer periphery (diameter A in FIG. 3) of the tip surface 5a of the vibration member 5. A range R1 (hereinafter, referred to as an effective range R1) that has a predetermined width from the edge of the outer periphery and surrounds the entire end surface 5a.

  Therefore, the maximum width of the distal end surface 5a in the direction parallel to the welding width direction D2, that is, the diameter A is set to ½ or less of the width of the reciprocating range E in the direction parallel to the welding width direction D2. Thereby, when the vibration member 5 is moved from the inner folding line E1 to the outer folding line E2 or vice versa, an effective range R1 is continuously formed, and the compressive residual stress is applied to the first member 2 by the welding width. It can be introduced continuously in the direction.

  On the other hand, as shown in FIG. 4, when the diameter dimension of the tip surface 5 a is set to be larger than ½ of the reciprocating range, the compressive residual stress cannot be introduced in the non-overlapping range R <b> 2 of the first member 2.

  Hereinafter, the manufacturing method of the said welded structure 1 is demonstrated.

  First, information on the distribution of tensile residual stress in the welding width direction generated in the first member 2 when the second member is welded under preset welding conditions, for example, information on the stress distribution shown in FIG. 2 is prepared (preparation). Process). This information can be obtained, for example, by measuring the stress of the first member 2 after welding of the second member 3 and before peening, or by a simulation result based on the welding conditions.

  Moreover, the 2nd member 3 is welded with respect to the 1st member 2 along the welding line direction D1 (welding process). In addition, the order of a preparation process and a welding process is not specifically limited.

  After the preparation process and the welding process, the front end surface 5a of the vibration member 5 collides with the surface of the first member 2 in a direction parallel to the vibration direction D3 in a state where the vibration member 5 is vibrated along the vibration direction D3. (Blowing process)

  In this striking step, the vibration member 5 is moved to the first member 2 in a state where the vibration member 5 and the first member 2 are positioned so that the front end surface 5 a of the vibration member 5 is substantially parallel to the surface of the first member 2. Collide.

  Further, in the striking step, the vibration member 5 is welded while the vibration member is reciprocated in the welding width direction D2 within the reciprocation range E set outside the weld toe 4a of the first member 2 in the welding width direction D2. Move in the line direction D1.

  Specifically, in the striking step, the vibrating member is reciprocated so as to satisfy v / f <A. Here, f is the period of the reciprocating motion of the vibration member 5, v is the moving speed of the vibration member 5 in the weld line direction D1, and A is the direction parallel to the weld line direction D1 of the tip surface 5a of the vibration member 5. Is the maximum length (diameter).

  As a result, the trajectory of the forward path and the trajectory of the return path of the vibration member 5 overlap each other in the welding line direction D1 while the vibration member 5 reciprocates once in the welding width direction. However, the welding line direction D1 can be applied uniformly.

  Hereinafter, the result of the fatigue test (2 million times repeated strength test) performed on the welded structure manufactured by the above-described manufacturing method will be described.

  The conditions of the fatigue test are as follows. However, this test condition is an example and is not limited thereto.

  Steel materials (SM490A) are used as the first member 2 and the second member 3. MAG (metal active gas welding) welding is adopted as a welding method. A 50 kg class welding material is used in accordance with the steel material used for the first member 2 and the second member 3.

  In the first member 2 to which the second member 3 is welded under such conditions, it has been confirmed that a tensile residual stress exists within a range of 10 mm in the weld width direction starting from the weld toe portion 4a. . Therefore, this range is set to the reciprocating range E.

  The test results shown in FIG. 5 include a comparative example without peening (no striking process) and a comparative example in which the tip surface of the vibration member is a spherical surface.

  When the tip surface of the vibration member is a spherical surface, the stress amplitude (fatigue strength) is lower than in the embodiment in which the tip surface 5a of the vibration member 5 is a flat surface. This is because when the spherical surface collides with the surface of the first member 2, irregularities are formed on the surface of the first member 2, and the effect of improving the fatigue strength of the first member 2 varies. On the other hand, when the distal end surface 5a of the vibration member 5 is a flat surface, it is possible to suppress the formation of the unevenness as described above, and the fatigue strength is uniformly applied to the first member 2. Can be improved.

  Specifically, when the tip surface of the vibration member is spherical, the fatigue strength is improved by about 36% compared to the comparative example without peening, whereas the diameter of the flat tip surface 5a is 1.5 mm or more and 4 mm. In the following cases, the fatigue strength is more than doubled (about 218%) compared to the comparative example without peening.

  On the other hand, when the diameter of the flat front end surface 5a is 5 mm, the fatigue strength is lower than when the diameter is 4 mm. This is because if the diameter of the tip surface 5 a of the vibration member 5 exceeds 4 mm, the force from the vibration member 5 to the first member 2 is dispersed, and sufficient compressive residual stress is introduced into the first member 2. This is thought to be because it is impossible.

  Moreover, when the diameter of the flat front end surface 5a is less than 1.5 mm, it has been confirmed that the wear of the vibration member 5 proceeds rapidly and the hitting process cannot be performed stably.

  Next, with reference to FIG. 6, the result of the fatigue test (2 million times fatigue strength test) performed with respect to the welded structure 1 manufactured with the manufacturing method mentioned above is demonstrated. FIG. 6 shows a plurality of embodiments with different conditions for the round-trip range E. Further, FIG. 6 shows a test result when the diameter of the distal end surface 5a of the vibration member 5 is set to 3 mm.

  The test conditions other than the diameter of the tip surface 5a and the reciprocating range E are the same as the test conditions in the fatigue test shown in FIG. The range in which the tensile residual stress exists is the same in the range of 10 mm in the weld width direction starting from the weld toe 4a.

  FIG. 6 shows test results when the reciprocating ranges E of 2 mm, 4 mm, 10 mm, and 15 mm are set from the weld toe portion 4a (inner fold line E1), respectively.

  Stress amplitude (fatigue strength) when the reciprocating range E of 2 mm and 4 mm is set as compared to the case where the reciprocating range E of 10 mm and 15 mm including all of the range where the tensile residual stress exists is set. Is low.

  Further, fatigue occurs between the case where the reciprocating range E of 15 mm exceeding the range where the tensile residual stress exists is set and the case where the same reciprocating range E of 10 mm as the range where the tensile residual stress exists is set. There is no difference in strength.

  Therefore, it can be seen that the maximum fatigue strength improvement effect can be obtained by setting the range where at least the tensile residual stress exists to the reciprocating range E.

  As described above, by moving the vibration member 5 in the welding line direction D1 while reciprocating in the welding width direction D2, the striking force due to the vibration of the vibration member 5 is changed to the welding line direction D1 and the welding width in the first member 2. It can be given over a predetermined range in the direction D2.

  Therefore, the fatigue strength of the welded portion in the first member 2 can be improved in the weld line direction D1 and the weld width direction D2.

  Moreover, according to the said embodiment, there can exist the following effects.

  According to the embodiment, since the compressive residual stress can be applied to the boundary portion with respect to the weld toe portion 4a of the first member 2 where a high tensile residual stress exists, the fatigue of the first member 2 is more effectively achieved. Strength can be improved.

  According to the embodiment, since the compressive residual stress can be applied by the vibrating member 5 to a range in which the tensile residual stress in the first member 2 is equal to or higher than the preset reference stress (0), the first member 2 is welded. The tensile residual stress generated in the member 2 can be suppressed below the reference stress.

  In addition, if the said reference stress is set to the value of the tensile residual stress of the 1st member 2 before welding of the 2nd member 3, for example, with respect to the whole range of the 1st member 2 which the tensile residual stress produced by welding The fatigue strength can be improved.

  Further, the outer fold line E2 of the reciprocating range E can be set outside the welding width direction D2 from the position where the tensile residual stress becomes the reference stress (position P1 in FIG. 2). In this way, the tensile residual stress in the first member 2 can be suppressed to a reference stress or less more reliably.

  According to the embodiment, since the trajectory of the forward path and the trajectory of the return path of the vibration member 5 overlap each other in the welding line direction D1 while the vibration member 5 reciprocates once in the welding width direction D2, the impact of the vibration member 5 is reduced. It is possible to uniformly apply the welding line direction D1 to the surface of the one member 2.

  According to the embodiment, since the effective range R1 is continuously formed when the vibration member 5 moves in the forward path and when the vibration path 5 moves, the compressive residual stress is applied to the first member 2 in the welding width direction D2. It can be introduced continuously.

  According to the embodiment, since the tip surface 5a of the vibration member 5 has a circular planar shape with a diameter of 1.5 mm or more and 4 mm or less, the compressive residual stress is more effectively applied to the first member 2. Thus, the fatigue strength of the first member 2 can be reliably improved.

  Specifically, when the diameter of the distal end surface 5a of the vibration member 5 is less than 1.5 mm, the wear of the vibration member 5 progresses rapidly and the striking process cannot be performed stably.

  On the other hand, if the diameter of the distal end surface 5 a of the vibration member 5 exceeds 4 mm, the force from the vibration member 5 to the first member 2 is dispersed, and sufficient compressive residual stress can be introduced into the first member 2. Can not.

  In addition, the shape of the front end surface 5a of the vibration member 5 is not limited to a circle. For example, the front end surface 5a of the vibration member 5 can be polygonal or elliptical.

D1 Welding line direction D2 Welding width direction D3 Vibration direction E Reciprocating range E1 Inner folding line E2 Outer folding line R1 Effective range 1 Welded structure 2 First member 3 Second member 4a Weld toe 5 Vibration member 5a Tip surface

Claims (6)

A method for manufacturing a welded structure having a first member and a second member welded to the first member,
A welding step of welding the second member to the first member along a preset welding line direction;
In a state where a vibration member having a flat front end surface is vibrated in a vibration direction orthogonal to the front end surface, the front end surface of the vibration member collides with the surface of the first member in a direction parallel to the vibration direction. A striking process,
In the striking step, while reciprocating the vibrating member in the welding width direction within the reciprocating range set outside the weld toe portion in the first member in the welding width direction orthogonal to the welding line direction, A method for manufacturing a welded structure, wherein the vibration member is moved in the weld line direction.   The reciprocating range is set between an inner folding line positioned at a boundary portion of the first member with respect to the weld toe and an outer folding line positioned outside the inner folding line in the welding width direction. The manufacturing method of the welded structure of Claim 1. A preparatory step of preparing stress information related to a distribution of tensile residual stress in the weld width direction generated in the first member by welding of the second member;
The outer fold line of the reciprocating range is set at a position where the tensile residual stress in the first member becomes a preset reference stress in the stress information or outside the weld width direction than this. The manufacturing method of the welded structure as described in 1 ..   The period of the reciprocating motion of the vibration member is f, the moving speed of the vibration member in the weld line direction is v, and the maximum length of the vibration member in the direction parallel to the weld line direction is A. In this case, in the striking step, the vibration member is reciprocated so as to satisfy v / f <A. The method for manufacturing a welded structure according to any one of claims 1 to 3.   5. The maximum width in the direction parallel to the welding width direction of the distal end surface of the vibration member is one half or less of the width of the reciprocating range in the direction parallel to the welding width direction. 2. A method for manufacturing a welded structure according to item 1.   The method for manufacturing a welded structure according to any one of claims 1 to 5, wherein a tip surface of the vibration member has a circular planar shape having a diameter of 1.5 mm or more and 4 mm or less.

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