JP7339511B2 - Welded joint and manufacturing method thereof - Google Patents

Description

The present invention relates to welded joints and methods of making same.

When butt-welding two butted metal plates from one side (front side), it is common to attach a backing metal to the back side of the metal plate (main plate) in advance before welding. When single-sided welding is performed using a backing metal, welding is performed at the tip of the slit between the backing metal and the main plate at the welding root portion where stress is concentrated. However, for hollow parts and containers where people cannot enter, such as transportation pipes and building steel pillars, it is possible to apply welding or measures to prevent fatigue cracks from the back side (inside) of the metal plate. Can not.

Therefore, for example, Patent Documents 1 to 4 below disclose a method of butt-welding a steel plate or steel pipe to be butted together by bending the ends of the steel plate or steel pipe to form a groove projecting out of the plane of the steel plate or steel pipe. It is Further, Patent Documents 5 and 6 below disclose a method of forming a groove into a shape protruding out of the surface of a steel plate and welding the steel plate. According to these techniques, since the projecting portion that becomes the backing metal is formed in a shape that smoothly projects from the main plate to the rear surface side, welding from the rear surface is not necessary. By the way, Patent Literature 7 discloses a method of bending a vertical plate and vertically butting it against a flat plate and performing fillet welding.

JP-A-09-164496 JP-A-2009-740 JP-A-11-10383 JP-A-59-92167 JP-A-2009-34696 JP-A-59-70466 JP 2010-221235 A

However, in the techniques described in Patent Literatures 1 to 6, it is necessary to precisely control the interval between the steel plates that are butted against each other in consideration of the dimensions of the projecting portions. For example, if the gap between the butted steel plates is too large, the arc will escape from the root side, making welding difficult. It may not be possible to fit the welded joint in place. L-shaped welded joints such as those disclosed in Patent Document 7, T-shaped joints, and cruciform joints may also have similar problems.

Accordingly, an object of the present invention is to provide a welded joint and a method of manufacturing the same that can reduce the influence on welding execution due to construction errors in the spacing between metal plates that are butted together when performing single-sided butt welding.

The gist of the present invention is the following welded joint and method for manufacturing the same.

(1) a first metal plate;
a second metal plate having a front surface and a back surface, and having an overhanging portion projecting toward the back surface at an end;
a groove formed between the surface of the first metal plate and an end face including the projecting portion of the second metal plate;
a insert disposed on the root side of the groove;
a weld metal filled in the groove;
a welded joint.
(2) the intersection of the boundary lines of the insert, the first metal plate and the weld metal is defined as a first triple point;
The second triple point is the intersection of the boundary lines of the insert, the second metal plate and the weld metal,
Let X1 be the component of the distance from the first triple point to the base of the projecting portion of the second metal plate parallel to the material axis direction of the second metal plate,
Let X2 be the component of the distance from the second triple point to the base of the projecting portion of the second metal plate parallel to the material axis direction of the second metal plate,
Letting Y1 be the distance between the back surface of the second metal plate and a plane parallel to the back surface including the first triple point,
When the distance between the back surface of the second metal plate and the plane parallel to the back surface including the second triple point is Y2,
Formula 1 below:
Y1/X1-(Y2/X2)/4≧0.34 and Y2/X2-(Y1/X1)/3≧0.25 (1)
The welded joint according to (1) above, which satisfies:
(3) The above, wherein the welding toe portion on the surface side of the second metal plate has a groove-shaped peening treatment portion having a depth of 0.1 mm or more and 0.5 mm or less and a width of 1.5 mm or more. The welded joint according to (1) or (2).
(4) A second metal plate having a front surface and a back surface, and having an overhanging portion projecting toward the back surface at an end, is provided between the surface of the first metal plate and the end surface including the overhanging portion of the second metal plate. A butting step of butting with the first metal plate so that a groove is formed therebetween;
an arrangement step of arranging a insert on the root side of the groove;
a welding step of filling the groove with a weld metal;
A method of manufacturing a welded joint comprising:
(5) A first triple point is defined as an intersection of boundary lines of the insert, the first metal plate and the weld metal;
The second triple point is the intersection of the boundary lines of the insert, the second metal plate and the weld metal,
Let X1 be the component of the distance from the first triple point to the base of the projecting portion of the second metal plate parallel to the material axis direction of the second metal plate,
Let X2 be the component of the distance from the second triple point to the base of the projecting portion of the second metal plate parallel to the material axis direction of the second metal plate,
Y1 is the distance between the back surface of the second metal plate and a plane parallel to the back surface including the first triple point;
When the distance between the back surface of the second metal plate and the plane parallel to the back surface including the second triple point is Y2,
Formula 1 below:
Y1/X1-(Y2/X2)/4≧0.34 and Y2/X2-(Y1/X1)/3≧0.25 (1)
The method for manufacturing a welded joint according to (4) above, which satisfies:
(6) After the welding step, a groove-shaped peening treatment having a depth of 0.1 mm or more and 0.5 mm or less and a width of 1.5 mm or more is performed on the weld toe portion on the surface side of the second metal plate. The method for manufacturing a welded joint according to (4) or (5) above, wherein a portion is formed.

ADVANTAGE OF THE INVENTION By this invention, the welding joint which can reduce the influence on welding work by the construction error of the space|interval of the metal plates which are butt|matched when performing single-sided butt welding, and its manufacturing method can be provided.

FIG. 1 is a side view schematically showing a welded joint according to an embodiment of the invention. FIG. 2 is a side view showing details of a welded portion of a welded joint according to an embodiment of the present invention. FIG. 3 is a side view schematically showing an example of a method of forming the projecting portion. FIG. 4 is a diagram showing the stress generated in the unwelded portion of the root when a backing metal is used. FIG. 5 is a side view schematically showing a welded joint when the conventional backing metal analyzed in FIG. 4 is used. FIG. 6 is a diagram showing the relationship between the nominal stress and the material axial stress at the first triple point. FIG. 7 is a diagram showing the relationship between the nominal stress and the material axial stress at the second triple point. FIG. 8 is a diagram showing the relationship between the determination index W and the determination index B and the stress concentration ratio of the triple point. FIG. 9 is a side view schematically showing stress distribution in the first metal plate and the second metal plate when a tensile load is applied to the second metal plate of the welded joint according to the embodiment of the present invention. 10 is a side view schematically showing stress streamlines near the weld root portion of the welded joint of FIG. 9. FIG.

A welded joint and a method for manufacturing the same according to embodiments of the present invention will be described below.

(welded joint)
The welded joint according to the present embodiment includes a first metal plate, a second metal plate having a front surface and a back surface, and a projecting portion projecting toward the back surface at an end, a surface of the first metal plate and the a groove formed between the second metal plate and an end surface including the projecting portion; a insert disposed on the root side of the groove; and a weld metal filling the groove. .

FIG. 1 is a side view schematically showing a welded joint according to an embodiment of the invention. A welded joint 100 shown in FIG. 1 includes a first metal plate 1, a second metal plate 2, a weld metal portion 3, and a insert 5 as main components.

The first metal plate 1 and the second metal plate 2 each have a front surface and a back surface, and are not particularly limited as long as they are made of a material that can be welded between the front surface of the first metal plate 1 and the end of the second metal plate 2. is, for example, plate-like or tubular. In the present application, the front surface and the back surface of the first metal plate 1 are not particularly distinguished. The second metal plate 2 is abutted against the surface of the first metal plate 1 so as to have a groove, and has an overhang portion 4 that overhangs the back side of the second metal plate 2 at the end on the abutting side. In FIG. 1 , the portion where the second metal plate 2 contacts the welded metal portion 3 is the end portion of the overhang portion 4 . The first metal plate 1 and the second metal plate 2 have grooves between the surface of the first metal plate and the end face including the projecting portion of the second metal plate.

The second metal plate 2 has a predetermined thickness except for the projecting portion 4 . Although the thicknesses of the first metal plate 1 and the second metal plate 2 are not particularly limited, they may have a thickness of 3 to 200 mm, for example. 1 and 2 show an example in which the thicknesses of the first metal plate 1 and the second metal plate 2 are the same, but the thicknesses of the first metal plate 1 and the second metal plate 2 are different from each other. may

1 and 2 show an example in which the first metal plate 1 and the second metal plate 2 are arranged vertically. It suffices if they are arranged non-parallel to each other so that the end faces abut each other. Although the materials of the first metal plate 1 and the second metal plate 2 are not particularly limited, they are made of, for example, steel, aluminum, stainless steel, or the like.

According to the welded joint of the present embodiment, when the surface of the first metal plate 1 and the end of the projecting portion 4 of the second metal plate 2 are butted against each other, even if there is an error in the size of the groove, welding The impact on construction can be reduced. Therefore, although the size of the groove is not particularly limited, it may be 1 to 100% of the plate thickness of the first metal plate 1 or the second metal plate 2, for example. The dimension of the groove is the shortest length in the direction parallel to the material axis direction of the second metal plate 2 .

The weld metal portion 3 is made of the weld metal filled in the groove formed by the surface of the first metal plate 1 and the end face of the second metal plate 2 which are butted as described above.

A insert 5 is placed on the root side of the groove. By arranging the insert 5 on the root side in the groove, it is possible to suppress leakage of the weld metal from the root side during welding.

The material constituting the insert 5 is not particularly limited as long as it is a material that can be joined by welding to the first metal plate 1 and the second metal plate 2 including the projecting portion 4. For example, it may be steel, aluminum, stainless steel, or the like. , preferably the same kind of material as the first metal plate 1 and the second metal plate 2 .

The shape of the insert 5 is not particularly limited as long as it can be arranged on the root side of the groove so that the weld metal does not leak from the root side during welding. It can have a shape or an inverted triangular cross-sectional shape, or an inverted trapezoidal, square, rhomboidal, circular, elliptical, etc. cross-sectional shape. In the present application, a cross section refers to a plane cut parallel to the material axis direction and plate thickness direction of the second metal plate 2 so as to pass through the central axis of the welded joint.

The dimensions of the insert 5 are particularly so that it can be arranged between the surface of the first metal plate 1 and the projecting portion 4 of the second metal plate 2 so that the weld metal does not leak from the root side during welding. Although not limited, the maximum length of the insert 5 in the direction parallel to the material axis direction of the second metal plate 2 is preferably 5 to 50% of the plate thickness of the second metal plate 2, The maximum length of the second metal plate 2 in the direction parallel to the thickness direction is preferably 12 to 125% of the thickness of the second metal plate 2 .

The insert 5 can be arranged in the groove so that the thin portion of the cross-sectional shape of the insert 5 is arranged on the back surface side of the second metal plate 2 .

The insert 5 preferably has a wedge-shaped or generally inverted trapezoidal cross-sectional shape. In FIG. 1, the tip of the thin side of the insert 5 is pointed, but the tip of the insert 5 does not necessarily have to be sharp, and the cross-sectional shape of the insert 5 may be substantially inverted trapezoid. When the insert 5 has a wedge-shaped or substantially inverted trapezoidal cross-sectional shape, the insert 5 has a groove shape, that is, a gap between the surface of the first metal plate 1 and the overhanging portion 4 of the second metal plate 2. It is easy to conform to the shape and can be fixed by filling the groove efficiently.

In FIG. 1 , the thick end face of the insert 5 is parallel to the surface of the second metal plate 2 , but the thick end face of the insert 5 is parallel to the first metal plate 1 and the second metal plate 2 . It may be non-parallel to the surface, or may be curved or the like.

A gap may be formed between the side surface of the insert 5 and the first metal plate 1 and the second metal plate 2 in the groove so that the weld metal does not leak from the root side during welding. A gap (slit) may be formed without welding the side surface of the insert 5 and the projecting portion 4 on the back surface side of the second metal plate 2 from the triple point described later.

The insert 5 preferably has a side surface of the insert 5 having an angle substantially equal to at least one of the surface of the first metal plate 1 and the groove angle of the second metal plate 2 . More preferably, the insert 5 has a side surface of the insert 5 having an angle substantially equal to the groove angle of the surface of the first metal plate 1 and the groove angle of the second metal plate 2, and the insert 5 It has a shape that is arranged without a gap between the surface of the plate 1 and the groove of the second metal plate 2 . Due to the preferred shape of the insert 5, the insert 5 can be fixed by filling the groove better.

The insert 5 need not be integral in the welding direction. The insert 5 may be divided in the welding direction as long as it can be packed into the groove to such an extent that the welding arc does not blow through from the root side of the groove. If the opening amount of the root portion (interval between the first metal plate 1 and the second metal plate 2) varies depending on the position due to construction error, prepare a plurality of inserts 5 with different dimensions and arrange them in the groove. Thus, a sufficient penetration depth of the weld metal can be ensured in all parts of the weld metal portion 3 .

Preferably, in the welded joint of the present embodiment, the intersection of boundary lines of the insert, the first metal plate and the weld metal is the first triple point, and the insert, the second metal plate and the weld metal The second triple point is defined as the intersection of the boundary lines, and the component parallel to the material axis direction of the second metal plate of the distance from the first triple point to the root of the overhanging portion of the second metal plate is X1 and the component parallel to the material axis direction of the second metal plate of the distance from the second triple point to the root of the overhanging portion of the second metal plate is X2, and the back surface of the second metal plate and , and the plane parallel to the back surface containing the first triple point, and the distance between the back surface of the second metal plate and the plane parallel to the back surface containing the second triple point is Y1. When the distance is Y2,
Formula 1 below:
Y1/X1-(Y2/X2)/4≧0.34 and Y2/X2-(Y1/X1)/3≧0.25 (1)
meet.

Next, the dimensions of the welded portion of the welded joint of this embodiment will be described.

FIG. 2 is a schematic side view showing the welded portion of the welded joint of this embodiment. FIG. 2 shows the dimensions of each portion of the welded portion of the welded joint in this embodiment.

In FIG. 2, P1 is the triple point, which is the intersection of the first metal plate 1, the weld metal part 3 and the insert 5. In FIG. P2 is the triple point that is the intersection of the second metal plate 2, the weld metal part 3 and the insert 5;

X1 is the material axial distance of the second metal plate 2 from the triple point P1 to the base P3 of the projecting portion 4 . X2 is the axial distance of the second metal plate 2 from the triple point P2 to the base P3 of the projecting portion 4; The base of the projecting portion 4 refers to the bending start position on the back surface of the metal plate.

θ is an acute angle of the groove of the second metal plate 2 (broken line in FIG. 2) before welding with respect to the surface of the first metal plate 1 (broken line in FIG. 2).

Y1 is the distance between the back surface of the second metal plate 2 and the plane parallel to the back surface of the second metal plate 2 including the triple point P1. Y2 is the distance between the back surface of the second metal plate 2 and the plane parallel to the back surface of the second metal plate 2 including the triple point P2. That is, Y1 and Y2 are the penetration depths of the weld metal.

In the vicinity of the triple points P1 and P2, stress is likely to concentrate, and fatigue cracks, ductile cracks, or brittle cracks are likely to occur. In order to suppress the initiation of fatigue cracks, ductile cracks, or brittle cracks, it is necessary to reduce the stress influx to the triple junction.

In order to reduce the influx of stress to the triple point, it is preferable to make the penetration of the weld metal as deep as possible on the root side of the weld metal portion 3 . The deeper the penetration of the weld metal, the deeper the triple point on the root side, making it difficult for stress to flow to the triple point (become less likely to wrap around).

The penetration depths Y1 and Y2 of the weld metal are preferably controlled by the insertion depth of the insert 5 so that the penetration of the weld metal becomes as deep as possible on the root side. From the viewpoint of facilitating control of the insertion depth of the insert 5, the welding groove angle θ is preferably 15° or more. Also, in order to reduce the dimensions X1 and X2 described below, the welding groove angle θ is preferably 45° or less, more preferably 30° or less.

In order to reduce the influx of stress to the triple point, it is preferable to reduce the thickness of the projecting portion 4 to the minimum required. That is, the dimensions X1 and X2 are preferably as small as possible. The smaller the dimensions X1 and X2, the less stress flows to the triple point. However, it is preferable that the dimensions X1 and X2 should be thick enough to prevent burn-through by welding.

As described above, in order to reduce the influx of stress to the triple point, it is preferable that the penetration depths Y1 and Y2 of the weld metal are as large as possible, and the dimensions X1 and X2 are as small as possible.

FIG. 9 shows a side view schematically showing the stress distribution of the first metal plate and the second metal plate when a tensile load is applied to the second metal plate of the welded joint according to the embodiment of the present invention. FIG. 10 shows a side view schematically showing stress streamlines near the weld root portion of the welded joint of FIG.

Based on FIG. 10(a), FIG. 10(b) shows the case where the triple point P1 is moved to the surface side of the metal plate, and FIG. is moved to .

In FIG. 10(b), the stress streamlines on the P1 side become dense near P1, increasing the stress concentration. In FIG. 10(c), the stress streamlines near P2 are dense. This is related to the secondary effect of the first term in Equation 1.

In addition, in FIG. 10(b), as the stress flows to the P1 side, the stress streamline on the P2 side becomes rougher, and the closer the position of P2 is to the back side of the second metal plate, the more the stress streamline on the P2 side becomes. becomes coarser and many streamlines are directed to the P1 side. In FIG. 10(c), as the stress flows to the P2 side, the stress streamline becomes rougher on the P1 side, which is in the shadow, and the closer the position of P1 is to the back side of the second metal plate, the more it is hidden behind P2. and the stress streamlines on the P2 side become dense. This is related to the secondary effect of the second term in Equation 1.

While changing the dimensions of Y1, Y2, X1, and X2, the material axial stress at the triple point against the nominal stress is analyzed using the finite element method (FEM), and the multiplier of the stress at the triple point against the nominal stress is calculated at the triple point It can be calculated as a stress magnification. Function W and function B that change with Y1/X1 and Y2/X2 normalized by Y as parameters for the triple point stress magnification range of 1 to 2 when the dimensions of Y1, Y2, X1, and X2 are changed can be asked for.

Function W and function B are functions whose parameters are the ratio Y1/X1 and the ratio Y2/X2 related to the stress flowing into the tip of the slit at the triple point (crack tip), and are represented by the following equation 1:
Y1/X1-(Y2/X2)/4≧0.34 and Y2/X2-(Y1/X1)/3≧0.25 (1)
It has been found that it is preferable to satisfy

The welded joint 100 is formed by adjusting Y1, Y2, X1, and X2 so as to satisfy the above formula, so that the stress inflow to the vicinity of the triple points P1 and P2 can be reduced. It is possible to suppress the occurrence of fatigue cracks, ductile cracks, and brittle cracks in the vicinity. That is, the fatigue strength and fracture strength of the welded joint 100 can be enhanced. Y1, Y2, X1, and X2 are represented by Formula 2 below:
Y1/X1-(Y2/X2)/4>0.40 and Y2/X2-(Y1/X1)/3>0.35 (2)
It is more preferable to satisfy

Formulas 1 and 2 above were derived based on the results of FEM analysis of the relationship between the dimensions of Y1, Y2, X1, and X2 and the stress in the material axial direction at the triple point with respect to the nominal stress. When the formula 1 is satisfied, the triple point stress magnification is 2 or less. When formula 2 is satisfied, the triple point stress magnification is 1 or less.

The plate thicknesses of the first metal plate 1 and the second metal plate 2 are not included in the influencing factors because they have little effect on the stress distribution at the weld root.

Regarding the groove angle θ, the value obtained by the function W and the function B in the region where the triple point stress magnification exceeds 2 (hereinafter also referred to as the W value, the B value, or the judgment index W and the judgment index B) It is not included in the influencing factor because it only has a slight effect on the variation in the linear relationship with the critical stress factor, and does not affect the overall trend in the range of groove angles used in actual welding.

The penetration depth Y1 of the weld metal is preferably 10 to 30% of the plate thickness of the second metal plate 2. When Y1 is within the above preferable range, the weld metal can be welded without excessively increasing its volume.

The penetration depth Y2 of the weld metal is preferably 5 to 20% of the plate thickness of the second metal plate 2. When Y2 is within the above preferred range, the weld metal can be welded without excessively increasing its volume.

Dimension X1 is preferably 15 to 100% of the plate thickness of second metal plate 2 . When the dimension X1 is within the preferred range, the insert 5 is not completely melted down, and the dimension of the projecting portion can be ensured.

Dimension X2 is preferably 5 to 50% of the plate thickness of second metal plate 2 . When the dimension X2 is within the above preferred range, welding can be performed without the overhanging portion 4 being melted down.

Although an example of a T-shaped joint is shown in FIG. A cruciform joint in which the back surface of the plate 1, ie, the side opposite to the second metal plate 2, is welded in the same manner as the second metal plate 2 may be used. On the back surface (opposite side) of the first metal plate 1, a cruciform joint may be formed by a method using a backing metal or a method of welding as a K groove.

Preferably, the welded joint 100 of this embodiment has a peening treated portion 6 at the weld toe portion on the surface side of the second metal plate 2 . The peening treated portion 6 is formed, for example, by performing a peening treatment on the weld toe portion on the surface side of the weld metal portion 3 .

The peening treated portion 6 preferably has a groove shape with a depth of 0.1 mm or more and 0.5 mm and a width of 1.5 mm or more.

Instead of the peening treated portion 6, a flattened portion of the weld toe may be formed by a grinding tool such as a grinder. If the surface side toe portion of the weld metal portion 3 is subjected to curvature processing with a grinder or the like to reduce stress concentration, or if a peening treatment portion 6 is formed to introduce compressive residual stress, the welded joint will be better. Fatigue strength is obtained.

Since the base of the projecting portion indicated by P3 on the back side of the second metal plate 2 and its vicinity are likely to become stress concentration portions, they preferably have a grinder-treated portion or a peening-treated portion. Grinding or peening of the base of the overhang on the back side and its vicinity can be performed before welding.

Y1, Y2, X1, X2, and θ, and the dimensions of the peened portion can be confirmed by macrostructure observation (JIS G 0553:2008). Specifically, a sample is taken from the welded joint, and the surface to be observed is mechanically polished and buffed to a mirror finish, and then etched to reveal the boundary between the weld metal and the base material (including the heat-affected zone). , observation with the naked eye or a magnifying glass. The triple point P1 and the triple point P2 are the boundaries between the portion (welded portion) where the first metal plate and the second metal plate and the insert are melted and integrated and the portion where they are not welded, respectively. Yes, and can be identified from the cross-sectional shape. Therefore, it is not always necessary to observe the macrostructure to identify the heat affected zone (HAZ) or the boundary of the weld metal.

(Manufacturing method of welded joint)
Next, a method for manufacturing a welded joint according to this embodiment will be described.

A method for manufacturing a welded joint according to the present embodiment includes a second metal plate having a front surface and a back surface and having an overhanging portion projecting toward the back surface at an end portion, by A butting step of butting against the first metal plate so that a groove is formed between the end face including the overhang portion of the groove, an arranging step of arranging a insert on the root side of the groove, and the groove and a welding step of filling a weld metal into the.

The manufacturing method of the welded joint of this embodiment has a butting process, an arrangement process, and a welding process. These steps are described below.

Prior to the butting step, first, the tip of the side of the second metal plate 2 to be butted is made to protrude to the back side to form the projecting portion 4 . FIG. 3 is a schematic side view showing an example of a method of forming the projecting portion 4 of the second metal plate. As a method for forming the projecting portion 4, for example, as shown in FIG. It is conceivable to prepare a groove in a shape extended parallel to and bend this extended portion to the back side by plastically deforming it. The method of forming the protruding portion 4 in this way does not require the bending of the entire thickness of the second metal plate 2, so it can be applied even if the second metal plate 2 is an extremely thick member.

As another method for forming the projecting portion 4, a method of welding a metal plate to be the projecting portion 4 to the rear surface side end portion of the second metal plate 2 is also conceivable.

In the butting step, the second metal plate 2 having the protruding portion 4 protruding toward the back side at the end as described above is placed on the surface of the first metal plate 1, and the surface of the first metal plate 1 and the second metal plate 2 and the end face including the projecting portion 4 are butted so as to form a bevel.

In the arranging step, the insert 5 is arranged on the root side of the groove formed between the surface of the first metal plate 1 and the end face of the second metal plate 2 including the projecting portion 4 . Preferably, the insert 5 is inserted from the surface side of the second metal plate 2 and arranged on the root side of the groove. In this manner, at least a portion of the groove is filled with the insert 5 so that the weld metal does not leak from the root side during welding. By arranging the insert 5, even if there is a slight error in the size of the groove, that is, the gap between the surface of the first metal plate 1 to be butted and the end face including the projecting portion 4 of the second metal plate 2, At least part of the groove can be filled so that the weld metal does not leak from the root side during welding.

After arranging the insert 5 as described above, in the welding process, the groove formed by the surface of the first metal plate 1 and the end face of the second metal plate 2 to be butted is filled with a weld metal, and the welding is performed. A metal part 3 is formed.

The welded metal part 3 is formed by melting a welding material on the insert arranged on the root side of the groove from the surface side of the second metal plate 2 and welding. The welding method is not particularly limited, and arc welding can be used, for example. Moreover, it is preferable that the weld metal is piled up on the front side and the back side of the second metal plate 2 so as to protrude to an out-of-plane position. In other words, the weld metal is preferably piled up so as to protrude outside the area sandwiched between a plane including the front surface of the second metal plate 2 and a plane including the back surface of the second metal plate 2 .

Preferably, in the method for manufacturing a welded joint of the present embodiment, the intersection of boundary lines of the insert, the first metal plate and the weld metal is set as a first triple point, and the insert, the second metal plate and The intersection of the boundary lines of the weld metal is defined as a second triple point, and the distance from the first triple point to the root of the projecting portion of the second metal plate is parallel to the material axis direction of the second metal plate. Let X1 be the component, let X2 be the component of the distance from the second triple point to the base of the projecting portion of the second metal plate, parallel to the material axis direction of the second metal plate, and let X2 be the component of the second metal plate. A distance between the back surface and a plane parallel to the back surface including the first triple point is Y1, and a distance between the back surface of the second metal plate and a plane parallel to the back surface including the second triple point is Y1. , is the distance Y2,
The formula below:
Y1/X1-(Y2/X2)/4≧0.34 and Y2/X2-(Y1/X1)/3≧0.25
meet.

Preferably, in the method for manufacturing a welded joint of the present embodiment, after the welding step, the weld toe on the surface side of the second metal plate has a depth of 0.1 mm or more and 0.5 mm or less and a width of 0.1 mm or more and 0.5 mm or less. includes forming a groove-shaped peened portion with a diameter of 1.5 mm or more.

The peening process is a process of forming the peening process part 6 after the welding process. A peening treatment step is not an essential step. Further, instead of the peening treatment step, the weld toe portion may be flattened by a grinding tool such as a grinder as described above.

(Effect of this embodiment)
According to the welded joint 100 according to the present embodiment, by using the insert 5, welding work due to a construction error in the gap between the first metal plate 1 and the second metal plate 2 that are butted when performing single-sided butt welding. can be mitigated.

Further, according to the preferred embodiment of the welded joint 100 according to the present embodiment, by using the metal plate having the insert 5 and the projecting portion 4 that satisfy the above formula 1, the penetration defect of the weld metal is further suppressed, A welded joint with higher fatigue strength and fracture strength can be obtained.

In examining the effects of welded joints of the present invention on fatigue cracks and ductile brittle fractures, FEM analysis was performed on welded joints of various sizes to evaluate the stress at the triple point.

FIG. 4 shows the result of a comparative example in which the stress at the tip of the unwelded portion of the weld root portion of a T-shaped welded joint using a common backing metal was calculated by FEM analysis. In this analysis example, when steel materials 11 and 12 having a strength of 590 MPa and a thickness of 20 mm having a yield stress of 452 MPa are used, as shown in FIG. It is an analysis result when a tensile load is applied in the axial direction of the steel plate 2 to which the ends are welded when jointed grooves are welded using a backing metal.

Fig. 4 shows the relationship between the nominal stress and the weld root, with the intersection of the steel plate 1, the weld metal part 3 and the backing metal as the triple point P1' and the intersection of the steel plate 2, the weld metal part 3 and the backing metal as the triple point P2'. It shows the relationship between triple points P1' and P2', which are the tips of unwelded portions, and stress in the material axial direction.

When 200 MPa, which is the maximum stress level generally considered in the fatigue design of a welded structure, is given in the axial direction of the steel plate 2 as a nominal stress, the axial direction stress at the triple points P1' and P2' is given to the steel plate 2. It shows 3 to 4 times the nominal stress, and a very high stress concentration occurs.

In order to confirm the effect of the present invention, when steel material 1 and steel material 2 having a strength of 590 MPa class with a yield stress of 452 MPa and a plate thickness of 20 mm were used, the penetration depths Y1 and Y2 and the first The relationship between the member nominal stress and the material axial stress at the tip of the weld root at the triple points P1 and P2 when changing X1 and X2, which are the distances to the triple point P1 and the second triple point P2, as parameters, It was obtained by two-dimensional plane strain elastic-plastic FEM analysis.

FIG. 6 shows the relationship between the member nominal stress and the member axial stress at the tip of the welding root at the first triple point P1. FIG. 7 shows the relationship between the member nominal stress and the member axial direction stress at the tip of the welding root at the second triple point P2. The stress in the material axial direction at the tip of the weld root was taken as the stress at the integration point (integration point closest to the triple point) of the FEM element closest to the tip of the weld root (the element at the tip of the unwelded portion).

The symbols in FIGS. 6 and 7 represent the dimensions of each part of the evaluated welded joint, and the two digits following M indicate the level of the penetration depth Y2 (04 is shallow and 44 is deep), and the last two digits indicates the level of penetration depth Y1 (+5 is shallow and 25 is deep).

Table 1 shows the symbols, the dimensions of each part of the specimen, and the analysis results.

The above analysis results in Table 1 are the relationship between the W value and B value based on the dimensions of each part of the specimen and the triple point stress ratio. The criteria for the triple point stress magnification and the method for calculating the W value and the B value will be described below.

Since the stress decreases when plastic deformation starts locally, the triple point stress ratio (triple point stress/nominal stress) was determined from the results for the severest nominal stress of 200 MPa. The stress at the root of the joint when using the conventional backing metal shown in FIG. 4 shows about 3 to 4 times the nominal stress. We thought that the following conditions were preferable. In addition, for example, in the fatigue design guideline for steel structures of the Japan Society of Steel Construction, the stress range in which 2 million cycles of load are allowed is 190 MPa even for a machined steel plate without welding. Therefore, fatigue design of joints is generally not designed in such a way that the stress range exceeds 200 MPa, regardless of the strength of the steel material.

The analysis results of FIGS. 6 and 7 are for a steel material with a strength of 590 MPa and a yield stress of 452 MPa. The following is set as a guideline for the effect. A more desirable condition is that the triple point stress is less than or equal to about 1.5 times the nominal stress of 200 MPa.

Based on the results of this analysis, the relationship between the penetration depths Y1 and Y2 and the dimensions X1 and X2 was examined as an influencing factor on the relationship between the stress at the triple points P1 and P2 and the nominal stress. A function W that changes in the form of a simple formula using Y1/X1 and Y2/X2 normalized by Y1 and Y2 as parameters in the range of 1.5 to 2.0 where the stress magnification of P1 is 1.5 to 2.0:
W=Y1/X1-(Y2/X2)/4
and a function B that changes in the form of a simple formula using Y1/X1 and Y2/X2 normalized by Y1 and Y2 as parameters in the range of 1.5 to 2.0 where the stress magnification at the triple point P2 is 1.5 to 2.0:
B=Y2/X2-(Y1/X1)/3
, and found that the stress levels at the triple points P1 and P2 can be determined from the W value and B value (determination index W and determination index B) obtained from the function W and the function B.

Function W and function B represent shape conditions necessary to prevent the stress acting on the second metal plate 2 from concentrating on the tip of the unwelded portion when there is an unwelded portion in the weld root. According to this determination method, the function W is used as the determination formula for the triple point P1, and the function B is used as the determination formula for the triple point P2.

As shown in FIG. 8, when W≧0.34, the stress concentration ratio with respect to the nominal stress at the triple points P1 and P2 is 2.0 or less, and when W≧0.40, the stress concentration ratio is 1.5 or less. That is, the function W is the following formula:
W=Y1/X1-(Y2/X2)/4≧0.34 (W≧0.40 is more desirable.)
meet. When B≧0.25, the stress concentration ratio with respect to the nominal stress at the triple points P1 and P2 is 2.0 or less, and when B≧0.35, the stress concentration ratio is 1.5 or less. That is, the function B is the following formula:
B=Y2/X2-(Y1/X1)/3≧0.25 (B≧0.35 is more desirable.)
meet. Since the fracture of the weld root portion occurs from either triple point P1 or P2, the function W and the function B must satisfy both conditions of the above equations. Therefore, assuming that the stress condition effective for fatigue is 400 MPa and the condition that does not break is 200 MPa, the following formula:
Y1/X1-(Y2/X2)/4≧0.34 and Y2/X2-(Y1/X1)/3≧0.25
is preferably satisfied.

More preferably
Y1/X1-(Y2/X2)/4≧0.40 and Y2/X2-(Y1/X1)/3≧0.35
meet.

Note that the plate thicknesses of the first metal plate 1 and the second metal plate 2 are not included in the influencing factors because they have little effect. Regarding the weld groove angle θ, there was only a slight effect on the variation in the linear relationship between the W value and B value and the triple point stress ratio in the region where the triple point stress ratio exceeds 2.0 in FIG. , the range of groove angles used in actual welding did not affect the overall trend.

According to the present invention, it is possible to easily construct single-sided butt welds with high fatigue strength and fracture strength even when there is a large root gap construction error and welding can only be performed from one side, such as on-site butt welding of various steel structures. Become.

1 First metal plate 2 Second metal plate 3 Weld metal part 4 Overhang part 5 Insert 6 Peening treatment part P1 First triple point (intersection of boundary lines of insert, first metal plate, and weld metal)
P2 Second triple point (intersection of insert, second metal plate (overhang is part of metal plate), and weld metal boundary)
P3 Root of overhang (second metal plate)
P1' The triple point of the first metal plate, the weld metal part and the backing metal P2' The triple point of the second metal plate, the weld metal part and the backing metal X1 The second point from the first triple point to the root P3 of the overhang part Metal plate axial distance X2 Second metal plate axial distance from the second triple point to the base P3 of the overhang Y1 Penetration depth (parallel to the back surface of the second metal plate and the back surface including the first triple point) and the distance between)
Y2 penetration depth (distance between the back surface of the second metal plate and a plane parallel to the back surface including the second triple point)
θ Groove angle 100 Weld joint

Claims (10)

a first metal plate;
a second metal plate having a front surface and a back surface, and having an overhanging portion projecting toward the back surface at an end;
a groove formed between the surface of the first metal plate and an end face including the projecting portion of the second metal plate;
a insert disposed on the root side of the groove and disposed between the tip of the projecting portion and the first metal plate;
a weld metal filled in the groove;
a welded joint. The intersection of the boundary lines of the insert, the first metal plate and the weld metal is defined as a first triple point,
The second triple point is the intersection of the boundary lines of the insert, the second metal plate and the weld metal,
Let X1 be the component of the distance from the first triple point to the base of the projecting portion of the second metal plate parallel to the material axis direction of the second metal plate,
Let X2 be the component of the distance from the second triple point to the base of the projecting portion of the second metal plate parallel to the material axis direction of the second metal plate,
Letting Y1 be the distance between the back surface of the second metal plate and a plane parallel to the back surface including the first triple point,
When the distance between the back surface of the second metal plate and the plane parallel to the back surface including the second triple point is Y2,
Formula 1 below:
Y1/X1-(Y2/X2)/4≧0.34 and Y2/X2-(Y1/X1)/3≧0.25 (1)
The welded joint of claim 1, wherein: A groove-shaped peening treated portion having a depth of 0.1 mm or more and 0.5 mm or less and a width of 1.5 mm or more is provided in the weld toe portion on the surface side of the second metal plate,
Welded joint according to claim 1 or 2. One insert is relatively thin on one side in the plate thickness direction of the second metal plate and relatively thick on the other side in a cross section perpendicular to the longitudinal direction of the welded portion, and the relatively thin one is the first. 2 Arranged on the back side of the metal plate,
The welded joint according to any one of claims 1-3. the side of the insert and the overhang are not welded to form a slit;
The welded joint according to any one of claims 1-4. A second metal plate having a front surface and a back surface and having an overhanging portion projecting toward the back surface at an end portion is opened between the surface of the first metal plate and an end surface including the overhanging portion of the second metal plate. a butting step of butting with the first metal plate so that the tip is formed;
an arrangement step of arranging a insert on the root side of the groove and between the tip of the projecting portion and the first metal plate;
a welding step of filling the groove with a weld metal;
A method of manufacturing a welded joint comprising: The intersection of the boundary lines of the insert, the first metal plate and the weld metal is defined as a first triple point,
The second triple point is the intersection of the boundary lines of the insert, the second metal plate and the weld metal,
Let X1 be the component of the distance from the first triple point to the base of the projecting portion of the second metal plate parallel to the material axis direction of the second metal plate,
Let X2 be the component of the distance from the second triple point to the base of the projecting portion of the second metal plate parallel to the material axis direction of the second metal plate,
Y1 is the distance between the back surface of the second metal plate and a plane parallel to the back surface including the first triple point;
When the distance between the back surface of the second metal plate and the plane parallel to the back surface including the second triple point is Y2,
Formula 1 below:
Y1/X1-(Y2/X2)/4≧0.34 and Y2/X2-(Y1/X1)/3≧0.25 (1)
The method for manufacturing a welded joint according to claim 6, wherein: After the welding step, a groove-shaped peened portion having a depth of 0.1 mm or more and 0.5 mm or less and a width of 1.5 mm or more is formed in the weld toe portion on the surface side of the second metal plate. do,
A method for manufacturing a welded joint according to claim 6 or 7. In a cross section perpendicular to the longitudinal direction of the welded part, the insert is relatively thin on one side in the plate thickness direction of the second metal plate, relatively thick on the other side, and the relatively thin side is the second metal plate. Placed on the back side of the board,
A method for manufacturing a welded joint according to any one of claims 6 to 8. the side of the insert and the overhang are not welded to form a slit;
A method for manufacturing a welded joint according to any one of claims 6 to 9.

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