WO2013081015A1

WO2013081015A1 - Method for minimizing fatigue damage in welded structure, tool for forming strike mark, and welded structure

Info

Publication number: WO2013081015A1
Application number: PCT/JP2012/080768
Authority: WO
Inventors: 森影　康; 聡伊木
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2011-11-29
Filing date: 2012-11-28
Publication date: 2013-06-06
Also published as: IN2014CN03558A; KR20140066250A; CN103958116A; CN103958116B; KR101577261B1

Abstract

A method for minimizing fatigue damage in a welded structure by minimizing the fatigue damage produced in the welded portion of the welded structure. In this method, a substantially linear weld bead is curved in an arc-shape along a direction that transverses the weld bead at a right angle on the surface of a base material adjacent to the bead in the welded portion, and a strike mark is formed through hammer peening or ultrasonic shock peening using a tool for forming a strike mark having at the tip a strike-mark-forming surface with the center of curvature skewed to one side of two end surfaces mutually parallel along the weld bead; a strike mark is formed on the surface of the base material adjacent to the substantially linear and curved weld bead through hammer peening or ultrasonic shock peening using a tool for forming a strike mark having at the tip a planar strike-mark-forming surface with an overall circular or elliptical shape; and fatigue damage on the welded portion is minimized by introducing compressive residual stress in the vicinity of a weld bead toe with the tool for forming a strike mark.

Description

Fatigue damage suppressing method for welded structure, tool for forming impact mark, and welded structure

The present invention relates to a method for suppressing fatigue damage of a welded structure that suppresses occurrence of fatigue damage in a welded portion of a welded structure (also referred to as steel structure). It relates to preventing damage, tools for forming impact areas, and welded structures.

In recent years, reports of damage to steel bridges due to corrosion and fatigue have increased with the aging of steel bridges. In order to suppress damage to steel bridges, it is first necessary to establish an inspection system. However, especially in the case of fatigue damage, it is important to reduce the working external force such as passing vehicle and to improve the weld quality from the viewpoint of design and production. . In welded structures such as steel bridges, defects such as cracks occur in the weld zone or the weld bead shape is inadequate, so stress concentration is caused by the weld bead toe ( When it occurs in a weld toe, the effect of cyclic stress and the effect of weld residual stress are superimposed, also called fatigue crack (fatigue notch). ) Is likely to occur in the weld and may cause fatigue damage. The toe of the weld bead means a boundary where the surface of the weld metal forming the weld bead intersects the surface of the metal member as the base material.

In order to suppress such fatigue damage, Patent Documents 1 to 3 and Non-Patent Document 1 describe the fatigue strength (fatigue) of a welded portion by introducing compressive residual stress in the vicinity of the toe of the weld bead. A method for improving strength) is described.

Specifically, Patent Document 1 discloses that a specific dimension is obtained by using a processing equipment that performs plastic deformation by striking the vicinity of the toe end of the weld bead while being subjected to ultrasonic oscillation. Describes a method for improving the fatigue strength by processing the groove under predetermined hitting conditions.

In Patent Document 2, a pulsed laser beam from a laser source is used to instantaneously vaporize a surface coating that forms a thin layer of plasma or plasma. And a method of generating a compressive force locally on a part of the surface by the explosion power.

In Patent Document 3, the surface of a steel material is formed so that a groove having a specific dimension is formed by an impact area near the toe of the weld bead using an impact pin having a specific dimension at the tip. A method is described in which compressive residual stress is introduced into the weld by compression.

Non-Patent Document 1 examined a new hammer peening method that reduces stress concentration and residual stress in the vicinity of the toe of the weld bead because hammer peening may reduce fatigue strength. Results are listed.

JP 2006-175512 A JP 2006-159290 A JP 2010-29897 A

However, in the method described in Patent Document 1, as a means for introducing compressive residual stress in the vicinity of the toe of the weld bead, a tip (tip is a vibration terminal (transducer), chipper (chipper), striking pin, or It is also expensive and available compared to the conventional device that drives the tip with air pressure because it uses a device that processes a groove of a specific size near the toe end of the weld bead by ultrasonically vibrating the impact terminal) Have difficulty.

The method described in Patent Document 2 is a method in which compressive residual stress is introduced into the vicinity of the toe of the weld bead by laser shock peening. Therefore, pretreatment of the material is necessary, and the apparatus is expensive and large. It is difficult to apply to large welded structures such as steel bridges.

The method described in Patent Document 3 is a method of introducing a compressive residual stress by pressing a striking pin having a curvature radius of 2 to 10 mm on the surface of the base metal so as not to touch the weld metal. Therefore, it is difficult to introduce compressive residual stress.

Non-Patent Document 1 describes the results of studying a new hammer peening method for reducing stress concentration and residual stress in the vicinity of the toe of the weld bead. However, in hammer peening, an operator typically welds a peening tool (also referred to as a tip or chipper) to a tool tip (also referred to as a tipper (nib)). It is carried out by hitting the vicinity of the bead obliquely from above. Therefore, according to the method described in Non-Patent Document 1, as shown in FIG. 5, an out-of-plane gusset weld joint with ribs 2 standing upright on the surface of the base material 1 ) Is subjected to hammer peening, deep grooves that cause stress concentration are formed at the toe 4 of the weld bead 3, and a fatigue crack may occur from the toe 4 of the weld bead 3.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method for suppressing fatigue damage in a welded structure, which can suppress the occurrence of fatigue damage in a welded portion of the welded structure, and for forming impact marks. It is to provide a tool and a welded structure.

A method for suppressing fatigue damage of a welded structure according to the present invention is a method for suppressing fatigue damage of a welded structure that suppresses occurrence of fatigue damage in a welded portion of the welded structure, and is substantially straight among the welded portions. On the surface of the base material adjacent to the weld bead, a curved surface is formed in a circular arc shape along a direction perpendicular to the weld bead and is parallel to each other along the weld bead. Using the first impact scar forming tool with a tip for side impact forming area with a biased center of curvature, the impact scar is formed by hammer peening or ultrasonic impact peening. In addition, the surface of the base material adjacent to the substantially linear and curved weld beads has a flat impact mark forming surface formed in a round shape or an elliptical shape at the tip. 2 is used to form an impact mark by hammer peening or ultrasonic impact peening, and a compressive residual stress is applied in the vicinity of the toe of the weld bead by the first and second impact mark forming tools. It introduces and suppresses the fatigue damage of the said welding part.

The striking trace forming surface of the second striking trace forming tool has a length in the direction along the weld bead of 3.0 mm or more and 6.0 mm in a region of 5 mm from the toe of the weld bead to the base metal side. You may form continuously the impact trace which has the following dimensions and whose maximum depth is 0.03 mm or more and less than 0.50 mm with the said 2nd impact trace formation tool along the said weld bead.

As the second hitting mark forming tool, a hitting mark forming tool having a hitting mark forming surface formed at a tip having a flatness and a radius having a radius of 1.5 mm or more and 3.0 mm or less. It may be used.

As the second hitting mark forming tool, a hitting mark forming tool having a chamfer that is curved in an arc shape with a radius of curvature of 0.15 mm to 0.60 mm around the hitting mark forming surface is used. May be.

A striking mark having a maximum depth of 0.1 mm or more and 0.5 mm may be formed in a region from a position 0.5 mm away from the toe of the weld bead to the base material side to 3 mm.

As the second impact scar forming tool, a width along the direction perpendicular to the weld bead is 1.5 mm or more and 3.0 mm or less, a length along the weld bead is 3.0 mm or more and 6.0 mm or less, and You may use the striking trace formation tool which has the planar striking trace formation surface in which the whole shape was formed in the ellipse shape in the front-end | tip.

As the second hitting trace forming tool, a hitting trace forming tool having a chamfered portion curved in an arc shape with a radius of curvature of 0.15 mm or more and 0.60 mm or less around the hitting mark forming surface may be used. .

As the second hitting trace forming tool, a hitting trace forming tool formed in a truncated cone shape having a side surface inclined in a direction perpendicular to the hitting trace forming surface may be used.

The striking trace forming surface of the first striking trace forming tool is curved in an arc shape with a curvature radius of 1 mm or more and 5 mm or less along a direction perpendicular to the weld bead, and the first striking trace forming tool Striking marks having a maximum depth of 0.2 mm or more may be continuously formed along the weld bead.

As the first hitting mark forming tool, a hitting mark forming tool having a length of the hitting mark forming surface along the weld bead of 1 mm or more and 10 mm or less may be used.

As the first striking trace forming tool, there is provided a striking trace forming tool having two side surfaces perpendicular to the end face, and the shape of the side face is tapered with respect to the striking trace forming surface. It may be used.

As the first striking trace forming tool, a striking trace forming tool having an arc surface curved in an arc shape with a radius of curvature of 0.15 mm or more and 0.30 mm or less at a boundary portion between the striking trace forming surface and the side surface. May be used.

The hitting scar forming tool according to the present invention is used in the method for suppressing fatigue damage of a welded structure according to the present invention.

The welded structure according to the present invention is one in which fatigue damage is suppressed by the method for suppressing fatigue damage of a welded structure according to the present invention.

According to the present invention, it is possible to suppress the occurrence of fatigue damage in the welded portion of the welded structure.

FIG. 1 is a perspective view (diagrammatic perspective view) showing an example of a tool for forming an impact mark used when the fatigue damage suppressing method for a welded structure according to the first embodiment of the present invention is performed. FIG. 2A is a cross-section view of the tool for forming a hitting mark of FIG. 1 and cut along the XZ plane in FIG. FIG. 2B is a cross-sectional view taken along the YZ plane in FIG. FIG. 2C is a bottom view of the tool for forming an impact mark shown in FIG. FIG. 3A is a cross-sectional view taken along the XZ plane in FIG. 1, showing a modification of the hitting trace forming tool in FIG. 1. FIG. 3B is a cross-sectional view taken along the YZ plane in FIG. 1, showing a modification of the hitting trace forming tool in FIG. 1. FIG. 3C is a bottom view of a modified example of the hitting trace forming tool shown in FIG. 1. FIG. 4A is a perspective view showing a modified example of the tool for forming a hitting mark used when the fatigue damage suppressing method for a welded structure according to the first embodiment of the present invention is carried out. FIG. 4B is a cross-sectional view taken along the XZ plane in FIG. 4A, showing the hitting trace forming tool of FIG. 4A. FIG. 4C is a cross-sectional view taken along the YZ plane in FIG. FIG. 4D is a bottom view of the hitting trace forming tool shown in FIG. 4A. FIG. 5 is a view showing a hitting mark formed on the surface of the base material by the hitting mark forming tool shown in FIG. FIG. 6A is a plan view showing a welded portion welded with ribs standing upright on the surface of the steel plate. FIG. 6B is a side view showing the welded portion welded with the ribs standing upright on the surface of the steel plate. FIG. 7A is a cross-sectional view taken along the XZ plane in FIG. 1, showing a hitting tool for forming a hitting ball having a circular spherical hitting mark forming surface formed at the tip. FIG. 7B is a bottom view of the tool for forming a hitting mark in which a spherical hitting mark forming surface having a circular shape is formed at the tip. FIG. 8A is a cross-sectional view taken along the XZ plane in FIG. 1, showing a hitting trace forming tool having a square hitting trace forming surface forming a square at the tip. FIG. 8B is a cross-sectional view showing a hitting trace forming tool in which a flat hitting trace forming surface forming a square is formed at the tip. FIG. 9A is a photograph showing an end line of the hitting trace and a line of the weld toe when the hitting trace is formed on the surface of the base material using a hitting trace forming tool having a circular hitting trace forming surface. FIG. 9B is a photograph showing an end line of the hitting trace and a line of the weld toe when the hitting trace is formed on the surface of the base material using the hitting trace forming tool having a rectangular shape of the hitting trace forming surface. FIG. 10A is a perspective view showing an example of a tool for forming an impact mark used when the fatigue damage suppressing method for a welded structure according to the second embodiment of the present invention is carried out. FIG. 10B is a cross-sectional view taken along the XZ plane in FIG. 10A, showing the hitting trace forming tool of FIG. 10A. FIG. 10C is a cross-sectional view taken along the YZ plane in FIG. 10A, showing the hitting trace forming tool of FIG. 10A.

Hereinafter, a fatigue damage suppressing method for a welded structure according to the first and second embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
A striking scar forming tool 6 used when carrying out the fatigue damage suppressing method for a welded structure according to the first embodiment of the present invention is a high-strength steel having a tensile strength of 600 MPa or more. It is formed from (SM570 class or higher) and, as shown in FIGS. 1 and 2A to 2C, is provided with a striking mark forming surface 7 at the tip. The hitting mark forming surface 7 is for forming the hitting marks 5 on the surface of the base material 1 adjacent to the substantially linear and curved weld beads 3 (see FIG. 5). As shown in FIGS. 2A to 2C, the hitting mark forming surface 7 is flat and has a radius of 1.5 mm to 3.0 mm, that is, a diameter D of 3.0 mm to 6.0 mm. As the definition of “circular” of the impact mark forming surface 7 formed in a circle, the ratio of the major axis to minor axis (major axis / minor axis) is in the range of 1 to 1.1. If it is inside, it can be used as a substantially circular shape. The direction of the major axis is not particularly defined with respect to the weld line.

As described above, the reason for flattening the hitting mark forming surface 7 formed at the tip of the hitting mark forming tool 6 is that the hitting mark 5 formed on the base material 1 side varies in depth and width if it is not flat. This is because (variability) occurs. The width of the hitting trace 5 means a length B in a direction orthogonal to the direction orthogonal to the paper surface in FIG. 5, which is the moving direction of the hitting trace forming tool 7. Moreover, the reason why the hitting mark forming surface 7 is circular with a radius of 1.5 mm or more and 3.0 mm or less is that when the radius is less than 1.0 mm, the depth and width of the formed hitting mark 5 vary. This is because the shape is not obtained stably. On the other hand, when the radius is larger than 3.0 mm, the area of the hitting mark forming surface 7 becomes large, so that the hitting mark 5 having a sufficient depth cannot be formed with respect to the base material 1, and the weld bead 3. This is because the effect of improving the fatigue strength due to the introduction of compressive residual stress to the toe 4 is reduced.

As shown in FIGS. 2A and 2B, the hitting trace forming tool 6 is formed in a circular truncated cone shape having a side surface that is inclined in a direction perpendicular to the hitting trace forming surface 7. In this way, by forming the hitting trace forming tool 6 in the shape of a truncated cone, there is an effect that it is easy to maintain the shape of the tool even by repeated hitting. As shown in FIGS. 3A to 3C, the hitting trace forming tool 6 is not limited to the shape shown in FIGS. 2A and 2B, and is formed in a truncated cone shape having a side surface that is inclined in a direction perpendicular to the hitting trace forming surface 7. In addition, a chamfered portion 8 that is curved in an arc shape with a curvature radius r ₀ of 0.15 mm or more and 0.60 mm or less may be used around the hitting trace forming surface 7.

The reason why the radius of curvature r ₀ of the chamfered portion 8 is 0.15 mm or more and 0.60 mm or less is as follows. That is, when the radius of curvature r ₀ of the chamfered portion 8 is less than 0.15 mm, stress tends to concentrate on the bottom end portion of the hitting mark 5. Further, if the radius of curvature r ₀ of the chamfered portion 8 exceeds 0.60 mm, the contact area of the striking trace forming surface 7 that contacts the surface of the base material 1 becomes large. This is because it is not possible to form the striking trace 5 having a sufficient depth, and the effect of improving the fatigue strength by introducing the compressive residual stress to the toe 4 of the weld bead 3 is reduced. More preferably, they are 0.15 mm or more and 0.50 mm or less. More preferably, it is 0.15 mm or more and 0.30 mm or less.

Striking trace formed surface 7, the weld bead 3 in a direction crossing at a right angle width _{R X} along the (X direction shown in FIG. 4A) is 1.5mm or more 3.0mm or less, the length along the weld bead 3 _{R Y} (Figure 4A The length along the Y-direction) is 3.0 mm or more and 6.0 mm or less, and is formed in a flat shape at the tip of the hitting trace forming tool 6, and the entire shape may be formed in an elliptical shape. Also in this case, the hitting trace forming tool 6 may be formed in a truncated cone shape, or a chamfered portion 8 may be formed around the hitting trace forming surface 7. As the definition of the “elliptical shape” of the impact mark forming surface 7 formed in an elliptical shape, the ratio of the length of the major axis to the minor axis (major axis / minor axis) is in the range of 1.1 to 3.0. It is preferable. It is more preferable to use the hitting trace forming tool 6 so that the major axis is substantially parallel to the weld line because the number of hitting points can be reduced.

The reason for the width _{R X} striking trace formed surface 7 and 1.5mm or 3.0mm or less is as follows. That is, in the width of less than R _X striking trace formed surface 7 is 1.5 mm, variations occur in the width of the striking marks 5, hit mark 5 of stable shape from it is difficult to form on the surface of the base 1 It is. Also, the width R _X striking trace formed surface 7 becomes too large the area of the hitting marks 5 exceeds 3.0 mm, the maximum depth to form a striking mark 5 above 0.2mm on the surface of the base 1 This is because it becomes difficult.

The reason why the length _RY of the hitting mark forming surface 7 is set to 3.0 mm or more and 6.0 mm or less is as follows. That is, when the length _RY of the hitting mark forming surface 7 is less than 3.0 mm, the width of the hitting mark 5 becomes too narrow, and stress concentration occurs at the toe 4 of the weld bead 3 when a load is applied. This is because it tends to occur in the case of fatigue cracks. If the length _RY of the hitting mark forming surface 7 exceeds 6.0 mm, the area of the hitting mark forming surface 7 becomes too large, and the hitting mark 5 having a maximum depth of 0.2 mm or more is formed on the surface of the base material 1. This is because it becomes difficult to form.

The reason why the ratio of the length of the major axis to the minor axis (major axis / minor axis) exceeds 1.1 and is 3.0 or less is as follows. When the ratio of the length of the major axis to the minor axis exceeds 3.0, the width B of the impact mark becomes small even in the same area, and the introduction range of the compressive residual stress in the width direction of the impact mark becomes narrow, which is disadvantageous for fatigue characteristics. Because it becomes.

When the fatigue damage suppressing method for a welded structure according to the first embodiment of the present invention is carried out using such an impact mark forming tool 6, the base material 1 adjacent to the weld bead 3 in FIG. The striking trace forming tool 6 is vertically pressed against the surface of the striking surface to perform striking, and the striking trace forming tool 6 is relatively moved in the welding line direction. Is repeated, and hammer peening or ultrasonic impact treatment for forming a hitting mark 5 on the surface of the base material 1 is performed. The weld line direction indicates a direction orthogonal to the paper surface in FIG. 4 and an arrow Y direction in FIG. That is, after adjusting the position of the striking trace forming tool 6 so that the striking trace forming surface 7 is adjacent to the toe 4 of the substantially linear and curved welding beads 3, the striking trace formation of the striking trace forming tool 6 is performed. The surface 7 is struck perpendicularly to the surface of the base material 1 and is struck. A hitting mark 5 of 03 mm or more and less than 0.50 mm is formed.

Next, after the striking trace forming surface 7 of the striking trace forming tool 6 is separated from the surface of the base material 1, the striking trace forming tool 6 is moved a predetermined distance in the welding line direction of the substantially linear and curved welding beads 3. Just move. Then, the striking trace forming surface 7 of the striking trace forming tool 6 is again pressed against the surface of the base material 1 for impact, and the striking trace 5 is formed on the surface of the base material 1. A plurality of striking traces 5 are continuously formed along the substantially linear and curved weld beads 3 by repeating the striking and the movement of the striking trace forming tool 6. Thereby, a plurality of hitting marks 5 are formed with a maximum depth of 0.03 mm or more and less than 0.50 mm in a region from the toe 4 of the substantially linear and curved weld beads 3 to the base material 1 side up to 5 mm. A welded structure is obtained.

The reason why the hitting marks 5 are formed with a maximum depth of 0.03 mm or more and less than 0.50 mm in the region of 5 mm from the toe 4 of the weld bead 3 to the base metal 1 side is as follows. This is because if the maximum depth of the hitting mark 5 is more than 5 mm closer to the base material 1 than the toe 4 of the weld bead 3, the compressive residual stress is not sufficiently introduced in the vicinity of the toe. Further, the maximum depth of the hitting scar 5 is set to 0.03 mm or more and less than 0.50 mm. If the maximum depth of the hitting scar 5 is shallower than 0.03 mm, the compressive residual stress is not sufficiently introduced near the toe. This is because when the thickness is 0.50 mm or more, stress concentrates at the bottom of the impact mark during under tension load, and becomes a starting point of fatigue crack generation.

When the hitting mark 5 is formed with a maximum depth of 0.1 mm or more and less than 0.50 mm in a region from a position 0.5 mm away from the toe 4 of the weld bead 3 to the base material 1 side to 3 mm. preferable. This is because the compressive residual stress is sufficiently introduced in the vicinity of the toe.

[Example 1]
The inventors have welded the joint shown in FIGS. 6A and 6B under a welding condition of a welding current of 280 A, a welding voltage of 32 V, and a welding speed of 28 cpm. A test piece was prepared, and a compression residual stress introduction test was performed under the conditions shown in Table 1 using the prepared weld joint.

In Examples 1 to 4 in Table 1, the diameter D of the hitting mark forming surface 7 is 3 mm on the hitting mark 5 having a maximum depth of 0.03 mm or more and less than 0.50 mm on the surface of the base material 1 adjacent to the weld bead 3. The case where it forms continuously along the weld bead 3 with the tool 6 for impact mark formation of 4 mm, 5 mm, and 6 mm is shown. In Examples 5 to 8 of Table 1, the diameter D of the hitting mark forming surface 7 is 3 mm on the hitting mark 5 having a maximum depth of 0.03 mm or more and less than 0.50 mm on the surface of the base material 1 adjacent to the weld bead 3. It shows a case in which it is continuously formed along the weld bead 3 with the tool 6 for forming impact marks having a curvature radius r _{0 of} 4 mm, 5 mm, 6 mm and chamfered portion 8 of 0.15 mm, 0.20 mm, 0.30 mm. .

In Comparative Examples 1 to 3 of Table 1, a round (diameter D: 2 mm, 3 mm, 4 mm) hitting mark forming surface 11 is spherical (curvature radius r: 1) at the tip of the hitting mark forming tool 10 shown in FIGS. 7A and 7B. (5 mm, 2 mm, 4 mm) is used, and the impact mark 5 is formed on the surface of the base material 1 adjacent to the weld bead 3. In Comparative Examples 4 and 5 in Table 1, a strike mark forming surface 13 having a square shape (length L: 3 mm, 5 mm) is formed in a flat shape at the tip of the strike mark forming tool 12 shown in FIGS. 8A and 8B. The case where the hitting marks 5 are formed on the surface of the base material 1 adjacent to the weld bead 3 is shown. Ra in Table 1 indicates the maximum depth (mm) of the hitting mark 5, and in Examples 1 to 8 and Comparative Examples 1 to 5, hammer peening using the hitting mark forming tool is performed with an air pressure of about 6 kg / cm ² and a frequency (frequency). ): 90 Hz, moving speed: 0.25 mm / sec. The residual stress in Table 1 shows the result of measuring the residual stress by irradiating a 1 mm diameter X-ray (X-ray) at a position 1 mm away from the impact mark 5 formed on the surface of the base material 1.

Comparing Examples 1 to 8 and Comparative Examples 1 to 5, in Comparative Examples 1 to 5, the compressive residual stress introduced in the vicinity of the toe 4 of the weld bead 3 by the hitting marks 5 is in the range of 230 to 270 MPa. Met. On the other hand, in Examples 1 to 8, the compressive residual stress introduced in the vicinity of the toe 4 of the weld bead 3 by the hitting marks 5 was in the range of 300 to 330 MPa. Therefore, as in Examples 1 to 8, as a tool for forming a hitting mark that forms the hitting mark 5 on the surface of the base material adjacent to the weld bead 3 by hammer peening or ultrasonic impact peening, the tool is flat and has a radius of 1.5 mm. Using a striking trace forming tool 6 having a striking trace forming surface 7 formed in a circular shape of 3.0 mm or less at the tip, the maximum depth is 0.03 mm or more and less than 0.50 mm by this striking trace forming tool 6. By continuously forming the hitting marks 5 along the substantially linear and curved weld beads 3, it becomes possible to introduce a compressive residual stress exceeding 300 MPa in the vicinity of the toes 4 of the weld beads 3. Further, it is possible to reliably suppress the occurrence of fatigue damage such as fatigue cracks in the welded portion of a welded structure such as a steel bridge.

As in Examples 1 to 8, by using the hitting trace forming tool 6 formed in a truncated cone shape toward the hitting trace forming surface 7, the hitting trace having a maximum depth of 0.03 mm or more and less than 0.50 mm. 5 can be formed on the surface of the base material 1 adjacent to the weld bead 3 with a relatively small striking force, whereby a compressive residual stress can be easily introduced in the vicinity of the toe 4 of the weld bead 3. . By using the hitting trace forming tool 6 having the chamfered portion 8 that is curved in an arc shape with a radius of curvature of 0.15 mm or more and 0.30 mm or less around the hitting trace forming surface 7 as in Examples 5 to 8, It is possible to prevent stress concentration from occurring around the hitting mark 5.

When a striking trace is formed on the surface of the base material using a striking trace forming tool having a rectangular (3 × 4 mm) striking trace forming surface, as shown in FIG. A space of maximum 1.8 mm was generated between the end line and a residual stress of 300 MPa or more could not be left in the vicinity of the toe. On the other hand, when the impact mark forming surface is circular (diameter: 3.0 mm) and the impact mark is formed on the surface of the base material using a planar impact trace forming tool, as shown in FIG. The gap between the weld toe line and the end line of the hitting mark is 0.2 mm at the maximum, and the hitting mark is formed with almost no gap between the weld toe line and the end line of the hitting mark. did it.

[Example 2]
The inventors of the present invention used hammer peening (pneumatic: air pressure) to a steel plate having a thickness of 12 mm × 100 mm × 300 mm, using a tool for forming an impact mark shown in Table 2 (Examples 11 to 18, Comparative Examples 11 to 16). About 0.588 MPa (about 6 kg / cm ² ), frequency: 90 Hz, moving speed: according to 0.25 mm / second) over a length of 100 mm along the weld line up to 5 mm from the toe of the weld bead to the base metal side After repeatedly hitting the tool for forming a hitting mark vertically so that the maximum depth of the hitting mark becomes 0.02 to 0.50 mm in the region, it is 1 mm away from the end of the hitting mark 5 (end on the toe 4 side). The residual stress at the position was measured by X-ray. Measurement of residual stress using X-ray was performed at a beam diameter of 1 mmφ. The test results are shown in Table 2.

In Examples 11 to 14 in Table 2, the maximum depth is 0.03 mm or more in the region of 5 mm from the toe 4 of the weld bead 3 to the base metal side on the surface of the base metal 1 adjacent to the weld bead 3. The case is shown in which the hitting marks 5 of less than 50 mm are continuously formed along the weld bead 3 by the hitting mark forming tool 6 having a diameter D of the hitting mark forming surface 7 of 3 mm, 4 mm, 5 mm, and 6 mm. In Examples 15 to 18 in Table 2, the maximum depth is 0.03 mm or more in the region up to 5 mm from the vicinity of the toe 4 of the weld bead 3 to the surface of the base metal 1 adjacent to the weld bead 3. Stroke marks 5 having a diameter D of 3 mm, 4 mm, 5 mm, and 6 mm and a radius of curvature r ₀ of the chamfered portion 8 of 0.15 mm, 0.20 mm, and 0.50 mm are formed. The case where it forms continuously along the weld bead 3 with the tool 6 for a tool is shown.

In Comparative Examples 11 to 13 of Table 2, a round (diameter D: 2 mm, 3 mm, 4 mm) hitting mark forming surface 11 is spherical (curvature radius r: 1) at the tip of the hitting mark forming tool 10 shown in FIGS. 7A and 7B. 5 mm, 2 mm, and 4 mm) are used to show the impact mark 5 formed on the surface of the base material 1 adjacent to the weld bead 3, and Comparative Examples 14 and 15 show the impact shown in FIGS. 8A and 8B. A base material adjacent to the weld bead 3 by using a tool having a square (one side length L: 3 mm, 5 mm) hitting mark forming surface 13 formed in a flat shape at the tip of the mark forming tool 12. The case where it forms in 1 surface is shown. The comparative example 16 shows that the diameter D of the hitting mark forming surface 7 is 6 mm, but the maximum depth of the hitting mark is less than 0.03 mm. Ra in Table 2 indicates the maximum depth of the hitting mark 5.

When Examples 11 to 18 are compared with Comparative Examples 11 to 16, in Comparative Examples 11 to 16, the compressive residual stress introduced in the vicinity of the toe 4 of the weld bead 3 by the hitting marks 5 is in the range of 60 to 270 MPa. It was in. On the other hand, in Examples 11 to 18, the compressive residual stress introduced in the vicinity of the toe 4 of the weld bead 3 by the hitting marks 5 was in the range of 300 to 330 MPa. Therefore, as in Examples 11 to 18, the hitting trace forming tool 6 is formed as a hitting trace having a hitting trace forming surface 7 which is flat and has a radius of 1.5 mm or more and 3.0 mm or less. In the region from the toe 4 of the weld bead 3 to 5 mm on the base material 1 side, the impact depth 5 having a maximum depth of 0.03 mm or more and less than 0.50 mm is substantially reduced by using the impact tool 6. By continuously forming along the straight and curved weld beads 3, it becomes possible to introduce compressive residual stress exceeding 300 MPa in the vicinity of the toes 4 of the weld beads 3. It is possible to reliably suppress the occurrence of fatigue damage such as fatigue cracks in the welded portion of the welded structure. Further, as in Examples 15 to 18, as the hitting trace forming tool 6, the hitting having the chamfered portion 8 curved in an arc shape with a radius of curvature of 0.15 mm to 0.50 mm around the hitting trace forming surface 7. By using the trace forming tool 6, it is possible to prevent stress concentration from occurring around the hitting trace 5.

Example 3
4A to 4D, the impact mark 5 is formed along the weld bead 3 on the surface of the base material 1 adjacent to the weld bead 3 (for example, a steel plate of 12 mm thickness × 100 mm × 300 mm) using the impact trace forming tool 6 shown in FIGS. Table 21 shows Examples 21 to 28 together with Comparative Examples 21 to 25 when formed continuously over a length of 100 mm. Ra in Table 3 indicates the maximum depth of the hitting mark.

In Examples 21 to 24, the width R _X of the hitting mark forming surface 7 along the direction crossing the weld bead 3 is 2 mm, 2 mm, 2.5 mm, 3 mm, and the length R _Y of the hitting mark forming surface 7 along the weld bead 3. Shows a case where the impact mark 5 having a maximum depth Ra of 0.2 mm or more is formed on the surface of the base material 1 adjacent to the weld bead 3 using the impact mark forming tool 6 of 3 mm, 4 mm, 5 mm, and 6 mm. Yes. In Examples 25 to 28, the width R _X of the hitting mark forming surface 7 along the direction crossing the weld bead 3 is 2 mm, 2 mm, 2.5 mm, 3 mm, and the length R _Y of the hitting mark forming surface 7 along the weld bead 3. Is 3 mm, 4 mm, 5 mm, 6 mm, and the radius of curvature r ₀ of the chamfered portion 8 is 0.15 mm, 0.20 mm, 0.20 mm, 0.60 mm. The case where the depth Ra of the impact scar 5 of 0.2 mm or more is formed is shown, respectively.

In Comparative Examples 21 to 23, a spherical impact mark forming surface 11 (diameter R: 2 mm, 3 mm, 4 mm, curvature radius r: 1.5 mm, 2 mm, at the tip of the impact mark forming tool 10 shown in FIGS. 7A and 7B, 4 mm) is used, and the impact mark 5 having a maximum depth Ra of 0.2 mm or more is formed on the surface of the base material 1. In Comparative Examples 24 and 25, a flat hitting mark forming surface 13 is formed in a square shape (the length L of one side is 3 mm, 5 mm) at the tip of the hitting mark forming tool 12 shown in FIGS. 8A and 8B. In each of the drawings, the case where the impact mark 5 having the maximum depth Ra of 0.2 mm or more is formed on the surface of the base material 1 is shown. The residual stress in Table 3 shows the result of measuring the residual stress by irradiating the X-ray having a diameter of 1 mm at a position 1 mm away from the impact mark 5 formed on the surface of the base material 1. In Examples 21 to 28 and Comparative Examples 21 to 25, hammer peening with a tool for forming impact marks was performed under conditions of air pressure: about 6 kg / cm ² , frequency: 90 Hz, and moving speed: 0.25 mm / second.

Comparing Examples 21 to 28 with Comparative Examples 21 to 25, in Comparative Examples 21 to 25, the compressive residual stress introduced in the vicinity of the toe of the weld bead 3 by the hitting marks 5 was within a range of 230 to 270 MPa. It was. On the other hand, in Examples 21 to 28, the compressive residual stress introduced into the vicinity of the toe of the weld bead 3 by the hitting marks 5 was in the range of 305 MPa to 335 MPa. Therefore, as in Examples 21 to 28, the welding bead 3 is used as a tool for forming a hitting mark 5 by hammer peening or ultrasonic impact peening on the surface of the base material adjacent to the weld bead 3 of the welded portion. Formation of a planar hitting mark in which the width along the direction crossing at right angles is 1.5 mm or more and 3.0 mm or less, the length along the weld bead 3 is 3.0 mm or more and 6.0 mm or less, and the overall shape is formed in an elliptical shape. Using a striking trace forming tool 6 having a surface 7 at the tip, the striking trace forming tool 6 continuously strikes a striking trace 5 having a maximum depth of 0.2 mm or more along a substantially linear and curved weld bead 3. Since it is possible to introduce a compressive residual stress exceeding 300 MPa in the vicinity of the toe 4 of the weld bead 3 by forming the weld bead 3, fatigue such as fatigue cracks may occur in a welded portion of a welded structure such as a steel bridge. loss There can be reliably prevented from occurring.

As in Examples 21 to 28, by using the hitting trace forming tool 6 tapered toward the hitting trace forming surface 7, the hitting trace 5 having a maximum depth Ra of 0.2 mm or more is relatively It can be formed with a small striking force, whereby a compressive residual stress can be easily introduced in the vicinity of the toe 4 of the weld bead 3. As in Examples 25 to 28, by using the hitting trace forming tool 6 having the chamfered portion 8 curved in an arc shape with a radius of curvature of 0.15 mm or more and 0.60 mm or less around the hitting trace forming surface 7, It is possible to prevent stress concentration from occurring around the hitting mark 5.

[Second Embodiment]
As shown in FIG. 10A, the striking trace forming tool 21 used when carrying out the fatigue damage suppressing method for a welded structure according to the second embodiment of the present invention is formed of high strength steel such as SM570. And a striking mark forming surface 22 for forming the striking marks 5 on the surface of the base material 1 adjacent to the substantially linear weld bead 3 (see FIG. 5). The hitting mark forming surface 22 is curved in an arc shape with a radius of curvature r of 1 mm or more and 5 mm or less along a direction (X direction shown in FIG. 10A) that crosses the weld bead 3 at a right angle, and a length along the weld bead 3 The length L is a dimension of 1 mm or more and 10 mm or less, and is formed at the tip of the hitting trace forming tool 21.

The striking trace forming tool 21 has two end faces 23 a and 23 b that are parallel to each other along the weld bead 3. The hitting trace forming surface 22 is formed at the tip of the hitting trace forming tool 21 with the center of curvature C biased to one of the end faces 23a and 23b (for example, the end face 23a side). The hitting trace forming tool 21 has two

side surfaces

24a and 24b perpendicular to the end surfaces 23a and 23b. The front ends of the side surfaces 24a and 24b are formed in a taper shape that becomes narrower toward the end surface 23a. The striking trace forming tool 21 has two

arc surfaces

25a and 25b that are curved in an arc shape with a radius of curvature of 0.15 mm or more and 0.30 mm or less. The

arcuate surfaces

25a and 25b are formed at the boundary between the hitting mark forming surface 22 and the side surfaces 24a and 24b.

When the present invention is carried out using the striking trace forming tool 21, after adjusting the position of the striking trace forming tool 21 so that the end face 23 b is adjacent to the toe 4 of the substantially linear weld bead 3, the striking is performed. The trace forming surface 22 is pressed against the surface of the base material 1, and the impact mark 5 having a maximum depth of 0.2 mm or more is applied to the surface of the base material 1 adjacent to the substantially linear weld bead 3 by the hammer impact peening method or ultrasonic waves. It is formed by impact peening. Next, after the striking trace forming surface 22 is separated from the surface of the base material 1, the striking trace forming tool 21 is moved along the substantially linear weld bead 3 by a predetermined distance. Then, the striking trace forming surface 22 is again pressed against the surface of the base material 1, and the striking trace 5 is continuously formed on the surface of the base material 1 along the substantially linear weld bead 3.

The reason why the radius of curvature r of the hitting mark forming surface 22 is 1 mm or more and 5 mm or less is as follows. In other words, if the radius of curvature r of the hitting mark forming surface 22 is less than 1 mm, the width of the hitting mark 5 becomes too narrow, and stress concentration occurs in the hitting mark 5 when a load is applied to the toe 4 of the weld bead 3. It becomes easy to cause fatigue cracks. On the other hand, if the radius of curvature r of the hitting mark forming surface 22 exceeds 5 mm, the area of the hitting mark forming surface 22 becomes too large, and the hitting mark 5 having a maximum depth of 0.2 mm or more is formed on the surface of the base material 1. It becomes difficult. For this reason, the radius of curvature r of the hitting mark forming surface 22 is set to 1 mm or more and 5 mm or less.

The reason why the length L of the hitting mark forming surface 22 along the weld bead 3 is 1 mm or more and 10 mm or less is as follows. That is, when the length L of the hitting mark forming surface 22 is less than 1 mm, the length of the hitting mark 5 along the substantially linear weld bead 3 is less than 1 mm, and the hitting mark 5 having a stable shape is formed on the surface of the base material 1. It becomes difficult to form. On the other hand, when the length L of the hitting mark forming surface 22 exceeds 10 mm, the area of the hitting mark forming surface 22 becomes too large, and the hitting mark 5 having a maximum depth of 0.2 mm or more is formed on the surface of the base material 1. It becomes difficult. For this reason, the length L along the weld bead 3 of the hitting trace forming surface 22 is set to 1 mm or more and 10 mm or less.

The reason why the radius of curvature of the arc surfaces 25a and 25b is 0.15 mm or more and 0.30 mm or less is as follows. That is, when the radius of curvature of the circular arc surfaces 25a and 25b is less than 0.15 mm, stress concentration is likely to occur at the longitudinal ends of the hitting marks 5. On the other hand, when the radius of curvature of the arc surfaces 25a and 25b exceeds 0.30 mm, the contact area of the hitting mark forming surface 22 that comes into contact with the surface of the base material 1 becomes too large, and the hitting trace having a maximum depth of 0.2 mm or more. It becomes difficult to form 5 on the surface of the base material 1. For this reason, the curvature radius of the circular arc surfaces 25a and 25b is set to 0.15 mm or more and 0.30 mm or less.

〔Example〕
10A to 10D is used to form the striking trace 5 on the surface of the base material 1 adjacent to the weld bead 3 (for example, a steel plate having a thickness of 12 mm thick × 100 mm × 300 mm). Table 4 shows Examples 31 to 34 together with Comparative Examples 31 to 35 in the case of being continuously formed over a length of 100 mm along the weld bead 3. Ra in Table 4 indicates the maximum depth of the hitting mark.

In Example 31, a hitting trace forming tool 21 having a radius of curvature r of the hitting trace forming surface 22 of 1 mm, a length L of the hitting trace forming surface 22 of 4 mm, and an interval B between the end face 23a and the end face 23b of 3 mm was used. The case where the impact mark 5 having the maximum depth Ra of 0.2 mm or more is formed on the surface of the base material 1 adjacent to the weld bead 3 is shown. In Examples 32 to 34, the radius of curvature r of the hitting mark forming surface 22 is 3 mm and 5 mm, the length L of the hitting mark forming surface 22 is 5 mm and 6 mm, and the distance B between the end surface 23a and the end surface 23b is 4 mm and 5 mm. The case where the impact mark 5 having the maximum depth Ra of 0.2 mm or more is formed on the surface of the base material 1 by using the forming tool 21 is shown. An arc surface having a radius of curvature of 0.15 mm to 0.30 mm was provided at the boundary between the hitting mark forming surface 22 and the side surfaces 24a and 24b of Examples 31 to 34.

In Comparative Examples 31 to 33, a spherical impact mark forming surface 12 (diameter D: 2 mm, 3 mm, 4 mm, curvature radius r: 1.5 mm, 2 mm, at the tip of the impact mark forming tool 11 shown in FIGS. 7A and 7B, 4 mm) is used, and the impact mark 5 having a maximum depth Ra of 0.2 mm or more is formed on the surface of the base material 1. In Comparative Examples 34 and 35, a flat hitting mark forming surface 14 is formed in a square shape (the length L of one side is 3 mm and 5 mm) at the tip of the hitting mark forming tool 13 shown in FIGS. 8A and 8B. In each of the drawings, the case where the impact mark 5 having the maximum depth Ra of 0.2 mm or more is formed on the surface of the base material 1 is shown. The residual stress in Table 4 shows the result of measuring the residual stress by irradiating a 1 mm diameter X-ray at a position 1 mm away from the impact mark 5 formed on the surface of the base material 1. In Examples 31 to 34 and Comparative Examples 31 to 35, hammer peening with a tool for forming a striking mark was performed under the conditions of air pressure: about 6 kg / cm ² , frequency: 90 Hz, and moving speed: 0.25 mm / sec.

Comparing Examples 31 to 34 and Comparative Examples 31 to 35, in Comparative Examples 31 to 35, the compressive residual stress introduced in the vicinity of the toe 4 of the weld bead 3 by the hitting marks 5 is in the range of 230 to 270 MPa. Met. On the other hand, in Examples 31 to 34, the compressive residual stress introduced in the vicinity of the toe 4 of the weld bead 3 by the hitting marks 5 was in the range of 330 to 340 MPa. Therefore, as in Examples 31 to 34, the welding bead 3 is formed at a right angle as a tool for forming a hitting mark 5 by hammer peening or ultrasonic impact peening on the surface of the base material 1 adjacent to the weld bead 3. The center of curvature r ₀ is biased to one of the two end faces 23 a and 23 b that are curved in a circular arc shape with a radius of curvature r of 1 mm or more and 5 mm or less along the transverse direction, and parallel to each other along the weld bead 3. A striking trace forming tool 21 having a striking trace forming surface 22 at its tip is used, and this striking trace forming tool 21 causes a striking trace 5 having a maximum depth of 0.2 mm or more along a substantially linear weld bead 3. By continuously forming, it becomes possible to introduce compressive residual stress exceeding 300 MPa in the vicinity of the toe 4 of the weld bead 3, so that a fatigue crack is generated in a welded portion of a welded structure such as a steel bridge. The occurrence of fatigue damage such as can be reliably suppressed.

Two side surfaces perpendicular to the end surfaces 23a and 23b are obtained by biasing the center of curvature C of the striking trace forming surface 22 to one end surface side of the two

end surfaces

23a and 23b parallel to each other along the weld bead 3. Since the shape of 24a, 24b becomes a taper shape, the impact mark 5 is accurately formed on the surface of the base material 1 adjacent to the weld bead 3 even in a place where the vicinity of the toe 4 of the weld bead 3 is difficult to see or in a narrow space. Can do. As in Examples 31 to 34, the hitting marks having

arcuate surfaces

25a and 25b that are curved in an arc shape with a radius of curvature of 0.15 mm or more and 0.30 mm or less at the boundary between the hitting mark forming surface 22 and the side surfaces 24a and 24b. By using the forming tool 21, it is possible to prevent stress concentration from occurring at the longitudinal end portion of the hitting scar 5.

As mentioned above, although the embodiment to which the invention made by the present inventor is applied has been described, the present invention is not limited by the description and the drawings that form part of the disclosure of the present invention according to this embodiment. That is, other embodiments, examples, operational techniques, and the like made by those skilled in the art based on the present embodiment are all included in the scope of the present invention.

The present invention can be applied to a process for suppressing the occurrence of fatigue damage in a welded portion of a welded structure.

DESCRIPTION OF SYMBOLS 1 Base material 2 Rib 3 Welding bead 4 Toe 5

Impact mark

6, 10, 12, 21 Impact

trace formation tool

7, 11, 13, 22 Impact trace formation surface 8

Chamfer

23a,

23b End surface

24a,

24b Side surface

25a, 25b Arc surface

Claims

A method for suppressing fatigue damage of a welded structure that suppresses occurrence of fatigue damage in a welded portion of the welded structure,
Among the welds, two surfaces that are curved in an arc along a direction perpendicular to the weld bead and parallel to each other along the weld bead are formed on the surface of the base material adjacent to the substantially straight weld bead. Using the first striking trace forming tool having a striking trace forming surface with the center of curvature biased to one end face side of the end faces, a striking trace is formed by hammer peening or ultrasonic impact peening,
On the surface of the base material adjacent to the substantially linear or curved weld bead, a second hitting mark forming tool having a flat hitting mark forming surface formed in a circular or elliptical shape at the tip is used. To form a hitting mark by hammer peening or ultrasonic impact peening,
A method for suppressing fatigue damage of a welded structure, comprising introducing a compressive residual stress in the vicinity of the toe of the weld bead by the first and second tool for forming a hitting mark to suppress fatigue damage of the welded portion. .
The striking trace forming surface of the second striking trace forming tool has a length in the direction along the weld bead of 3.0 mm or more and 6.0 mm in a region of 5 mm from the toe of the weld bead to the base metal side. A striking mark having the following dimensions and having a maximum depth of 0.03 mm or more and less than 0.50 mm is continuously formed along the weld bead by the second striking mark forming tool. Item 2. A method for suppressing fatigue damage of a welded structure according to Item 1.
As the second hitting mark forming tool, a hitting mark forming tool having a hitting mark forming surface which is flat and formed in a circle having a radius of 1.5 mm or more and 3.0 mm or less is used. The method for suppressing fatigue damage of a welded structure according to claim 2.
As the second hitting mark forming tool, a hitting mark forming tool having a chamfered portion curved in an arc shape with a radius of curvature of 0.15 mm or more and 0.60 mm or less around the hitting mark forming surface is used. The method for suppressing fatigue damage of a welded structure according to claim 3.
The striking trace having a maximum depth of 0.1 mm or more and 0.5 mm is formed in a region from a position 0.5 mm away from the toe of the weld bead to the base metal side to 3 mm. The method for suppressing fatigue damage of a welded structure according to claim 4.
As the second impact scar forming tool, a width along the direction perpendicular to the weld bead is 1.5 mm or more and 3.0 mm or less, a length along the weld bead is 3.0 mm or more and 6.0 mm or less, and 3. The method for suppressing fatigue damage of a welded structure according to claim 2, wherein a tool for forming a hitting mark having a flat hitting mark forming surface formed in an elliptical shape at the tip is used.
As the second hitting mark forming tool, a hitting mark forming tool having a chamfered portion curved in an arc shape with a radius of curvature of 0.15 mm or more and 0.60 mm or less around the hitting mark forming surface is used. The method for suppressing fatigue damage of a welded structure according to claim 6.
The tool for forming an impact mark formed in a truncated cone shape having a side surface inclined in a direction perpendicular to the impact mark forming surface is used as the second impact mark forming tool. 7. The method for suppressing fatigue damage of a welded structure according to claim 1.
The striking trace forming surface of the first striking trace forming tool is curved in an arc shape with a curvature radius of 1 mm or more and 5 mm or less along a direction perpendicular to the weld bead, and the first striking trace forming tool The method for suppressing fatigue damage of a welded structure according to claim 1, wherein striking traces having a maximum depth of 0.2 mm or more are continuously formed along the weld bead.
The welding structure according to claim 9, wherein a tool for forming an impact mark having a length of the impact mark forming surface along the weld bead of 1 mm or more and 10 mm or less is used as the first impact mark forming tool. Fatigue damage control method.
As the first striking trace forming tool, there is provided a striking trace forming tool having two side surfaces perpendicular to the end face, and the shape of the side face is tapered with respect to the striking trace forming surface. The method for suppressing fatigue damage of a welded structure according to claim 9 or 10, wherein the method is used.
As the first striking trace forming tool, a striking trace forming tool having an arc surface curved in an arc shape with a radius of curvature of 0.15 mm or more and 0.30 mm or less at a boundary portion between the striking trace forming surface and the side surface. The method for suppressing fatigue damage of a welded structure according to claim 11, wherein:
A tool for forming an impact mark used in the fatigue damage suppression method for a welded structure according to any one of claims 1 to 12.
A welded structure in which fatigue damage is suppressed by the method for suppressing fatigue damage of a welded structure according to any one of claims 1 to 12.