CN110402175B

CN110402175B - Welding method and welded joint

Info

Publication number: CN110402175B
Application number: CN201880005543.9A
Authority: CN
Inventors: 樱木进
Original assignee: Sumitomo Heavy Industries Ltd
Current assignee: Sumitomo Heavy Industries Ltd
Priority date: 2017-03-15
Filing date: 2018-03-14
Publication date: 2021-06-01
Anticipated expiration: 2038-03-14
Also published as: CN110402175A; WO2018168896A1; JPWO2018168896A1; JP7043485B2

Abstract

The welding method of the present invention includes a step of forming a 1 st welding layer and a 2 nd welding layer between a 1 st member, a 2 nd member, and a backing plate. The 1 st part has a 1 st surface and the 2 nd part has a 2 nd surface. The No. 1 and No. 2 members are disposed so that the No. 1 and No. 2 surfaces are opposed to the backing plate. The 1 st weld layer intersects the 1 st surface of the 1 st part at an intersection point P1 and the 2 nd surface of the 2 nd part at an intersection point P2. When a straight line L passing through the intersection point P1 and the intersection point P2 is drawn, the tip of the 2 nd welding layer exceeds the straight line L. The 2 nd solder layer intersects the straight line L at an intersection point Q1 and an intersection point Q2, the intersection point Q1 is located inside the 1 st solder layer or coincides with the intersection point P1, and the intersection point Q2 is located inside the 1 st solder layer or coincides with the intersection point P2.

Description

Welding method and welded joint

Technical Field

The invention relates to a welding method and a welding joint.

Background

As a technique for joining two steel plates to each other, a welding technique such as a gas shielded arc welding method is known. In the gas-shielded arc welding method, an arc is generated between a welding wire and two steel plates, and the arc serves as a heat source, and the welding wire and the steel plates are melted, whereby the steel plates are welded to each other. At this time, since the shielding gas is supplied to the periphery of the arc, the welding can be performed in a state where the welding target portion is isolated from the external environment.

Prior art documents

Patent document

Patent document 1: japanese laid-open patent publication No. 6-79485

Disclosure of Invention

Technical problem to be solved by the invention

In the welding technique described above, when an oxide film called scale is present at the welded portion of the steel sheets, there is a possibility that a problem of weld defects occurring in the welded layer frequently occurs. In particular, when arc welding is performed with a large current, the possibility of occurrence of a large defect such as a tubular defect increases.

In order to prevent such a poor welding, a step of removing an oxide film is generally performed before the welding process (for example, patent document 1).

However, this oxide film removal step becomes a factor of lowering the work efficiency of welding. Therefore, a technique capable of performing stable welding by an efficient method is required.

The present invention has been made in view of such a background, and an object of the present invention is to provide a welding method capable of suppressing a large tubular defect without lowering the work efficiency. It is another object of the present invention to provide a welded joint in which large tubular defects are significantly suppressed.

Means for solving the technical problem

In the present invention, there is provided a welding method comprising:

(1) a step of forming a 1 st weld layer between the 1 st member, the 2 nd member and the backing plate by the 1 st weld bead,

said 1 st part having a 1 st surface, said 2 nd part having a 2 nd surface, said backing plate having an upper surface,

the 1 st and 2 nd members are configured such that the 1 st and 2 nd surfaces are opposite to or in contact with the upper surface of the backing plate,

when viewed from a cross section perpendicular to the extending direction of the 1 st welded layer,

the 1 st welding layer is formed to intersect the 1 st surface of the 1 st member at an intersection point P1 on the 1 st member side, and intersect the 2 nd surface of the 2 nd member at an intersection point P2 on the 2 nd member side; and

(2) a step of forming a 2 nd welding layer on the 1 st welding layer by a 2 nd welding pass,

when drawing a straight line L passing through the intersection point P1 and the intersection point P2,

the 2 nd solder layer is disposed such that a tip in a depth direction is introduced into the backing plate beyond the straight line L,

the 2 nd weld layer intersects the straight line L at an intersection Q1 and an intersection Q2, the intersection Q1 is located on the 1 st component side than the intersection Q2,

the intersection point Q1 is located inside the 1 st solder layer or coincides with the intersection point P1,

the intersection point Q2 is located inside the 1 st solder layer or coincides with the intersection point P2.

Further, in the present invention, there is provided a welded joint in which a 1 st member, a 2 nd member and a backing plate are joined to each other by a welded portion,

said 1 st part having a 1 st surface,

the 2 nd part has a 2 nd surface,

the 1 st and 2 nd members are configured such that the 1 st and 2 nd surfaces are opposite or in contact with an upper surface of the backing plate,

the welding part has a 1 st welding layer and a 2 nd welding layer from the side close to the backing plate in the depth direction,

when the welded portion is viewed from a cross section perpendicular to the extending direction of the welded portion,

the 1 st welding layer intersects the 1 st surface of the 1 st member at an intersection point P1 on the 1 st member side and intersects the 2 nd surface of the 2 nd member at an intersection point P2 on the 2 nd member side,

Effects of the invention

The present invention can provide a welding method capable of suppressing a large tubular defect without lowering the work efficiency. Also, in the present invention, a welded joint in which a tubular defect is significantly suppressed can be provided.

Drawings

Fig. 1 is a diagram schematically showing an example of a conventional welding method.

Fig. 2 is a schematic perspective view of a weld joint according to an embodiment of the present invention.

Fig. 3 is a schematic cross-sectional view along line a-a of the weld joint shown in fig. 2.

Fig. 4 is a view schematically showing a cross section of the 1 st welded layer and its vicinity.

Fig. 5 is a cross-sectional view schematically showing an embodiment of a welded portion that is not suitable for a welded joint.

Fig. 6 is a cross-sectional view schematically showing an embodiment of a welded portion that is not suitable for a welded joint.

Fig. 7 is a cross-sectional view schematically showing an embodiment of a welded portion suitable for a welded joint.

Fig. 8 is a diagram schematically showing a flow of a welding method according to an embodiment of the present invention.

Fig. 9 is a view schematically showing a step of a welding method according to an embodiment of the present invention.

Fig. 10 is a view schematically showing a step of a welding method according to an embodiment of the present invention.

Fig. 11 is a view schematically showing a step of a welding method according to an embodiment of the present invention.

Fig. 12 is a photograph showing an example of a cross section of a welded part after the first weld pass 1 is performed in example 1.

Fig. 13 is a photograph showing an example of a cross section of a welded part after the second weld pass in example 1 was performed.

Fig. 14 is a photograph showing an example of a cross section of the welded portion obtained in example 2.

Fig. 15 is a photograph showing the welded portion obtained in example 2 cut along the vicinity of the bead and obtained by transmission X-ray imaging from the side surface of the bead.

Detailed Description

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(problems of conventional welding methods)

In order to better understand the features of the present invention, a brief description of the problem points of the existing welding method will be first made with reference to fig. 1.

Fig. 1 schematically shows an example of a conventional welding method.

In the conventional welding method, first, as shown in fig. 1 (a), the 1 st steel plate 20, the 2 nd steel plate 30, and the backing plate 40 are prepared. These components are arranged in a predetermined relationship.

The 1 st steel plate 20 has an inclined end face 26 and the 2 nd steel plate 30 has an inclined end face 36. The 1 st steel plate 20 and the 2 nd steel plate 30 are disposed on the backing plate 40 so as to face the inclined end faces 26 and 36, respectively.

Next, in this arrangement state, the 1 st weld bead is performed between the inclined end surface 26 and the inclined end surface 36. Thereby, the solder layer 50 is formed as shown in fig. 1 (b).

Here, if an oxide film is present at or near the welded portions of the 1 st steel plate 20, the 2 nd steel plate 30, and the backing plate 40, defects may frequently occur in the weld layer 50.

In particular, when the input heat energy at the time of welding is large, for example, when arc welding is performed at a large current exceeding 500A, a tubular defect 70 called a wormhole as shown in fig. 1 (b) may be generated inside the welded layer 50. Here, the "tubular defect" means a hollow defect in an elongated tubular shape generated in the weld metal by the release of gas.

Such a tubular defect 70 may have an influence on the characteristics of the solder layer 50. Therefore, generally, a process of removing the oxide film existing in the 1 st steel plate 20, the 2 nd steel plate 30, and the backing plate 40 is performed before the welding process.

However, such a removal treatment of the oxide film has a problem of reducing the work efficiency of welding.

(welded joint according to one embodiment of the present invention)

Next, a welded joint according to an embodiment of the present invention will be described with reference to fig. 2 and 3. Fig. 2 is a schematic perspective view of a weld joint (hereinafter referred to as "1 st weld joint") according to an embodiment of the present invention. Also, fig. 3 shows a schematic cross-sectional view along the line a-a of the 1 st weld joint shown in fig. 2.

As shown in fig. 2, the 1 st welded joint 100 includes the 1 st member 120, the 2 nd member 130, the backing plate 140, and a welded portion 150 between the 1 st member 120 and the 2 nd member 130.

The 1 st component 120 has a 1 st surface 122 and a 2 nd surface 124 opposed to each other and an end surface 126 connecting the two surfaces. The 2 nd member 130 has a 3 rd surface 132 and a 4 th surface 134 which face each other, and an end surface 136 which connects both surfaces.

In the example shown in fig. 2, the welded portion 150 is not formed on the entire surfaces of the end surfaces 126 and 136, and as a result, the end surfaces 126 and 136 are partially observed.

However, unlike this, the welding portion 150 may be formed to cover the entire surfaces of the end surfaces 126 and 136. In this case, the end faces 126 and 136 cannot be observed.

In the 1 st welded joint 100, the 1 st member 120 and the 2 nd member 130 are arranged such that the two

end surfaces

126 and 136 are opposed to each other. The 1 st member 120 and the 2 nd member 130 are arranged such that the 1 st surface 122 and the 3 rd surface 132 face the same direction (face upward).

Backing plate 140 has an upper surface 142. The backing plate 140 is disposed under the welding portion 150 such that the upper surface 142 faces or contacts the 2 nd surface 124 of the 1 st member 120 and the 4 th surface 134 of the 2 nd member 130.

In the 1 st welded joint 100, the 1 st member 120, the 2 nd member 130, and the backing plate 140 are joined to each other by a welded portion 150.

As shown in fig. 3, welded portion 150 has 1 st welded

layer

151 and 2 nd welded layer 152 from the side close to backing plate 140 in the depth direction (Z direction in fig. 3). The 1 st solder layer 151 extends to the inner side of the backing plate 140 in the depth direction beyond the upper surface 142 of the backing plate 140. Similarly, the 2 nd solder layer 152 extends to the inner side of the backing plate 140 in the depth direction beyond the upper surface 142 of the backing plate 140.

For convenience of description, the names of the welded portion 150 of the 1 st welded joint 100, particularly, the portions of the 1 st welded layer 151 will be described with reference to fig. 4.

Fig. 4 schematically shows a cross section of the 1 st solder layer 151 and its vicinity.

In fig. 4, the 1 st welding layer 151 is schematically shown as a state before the 2 nd welding layer 152 is formed, and therefore, the 1 st welding layer 151 has a different cross-sectional form from the 1 st welding layer 151 shown in fig. 3. In fig. 4, the dotted line in the 1 st welding layer 151 shows a schematic outline before welding of each of the 1 st member 120, the 2 nd member 130, and the backing plate 140.

In fig. 4, the horizontal direction (X direction) is referred to as "(width direction of the welded layer") and the vertical direction (Z direction) is referred to as "(depth direction of the welded layer"). The width direction is oriented rightward as the forward direction, and the depth direction is oriented downward as the forward direction.

As shown in fig. 4, the 1 st solder layer 151 is formed to join the 1 st member 120, the 2 nd member 130, and the backing plate 140.

As a result, the 1 st solder layer 151 is on the 1 st member 120 side (left side in FIG. 4) and intersects the 2 nd surface 124 of the 1 st member 120 at the intersection point P₁Intersects the upper surface 142 of backing plate 140 at an intersection point P₃And (4) intersecting.

The 1 st solder layer 151 is on the 2 nd member 130 side (right side in fig. 4) and intersects the 4 th surface 134 of the 2 nd member 130 at a point P₂Intersects the upper surface 142 of backing plate 140 at an intersection point P₄And (4) intersecting.

In the example shown in fig. 4, gaps exist between the 2 nd surface 124 of the 1 st member 120 and the upper surface 142 of the backing plate 140 and between the 4 th surface 134 of the 2 nd member 130 and the upper surface 142 of the backing plate 140. However, as another mode, it is also possible that the 2 nd surface 124 of the 1 st member 120 and the upper surface 142 of the backing plate 140 and the 4 th surface 134 of the 2 nd member 130 and the upper surface 142 of the backing plate 140 are in contact. In this case, the intersection point P₃Point of intersection P₁Point of intersection P₄Is a crossPoint P₂。

In the 1 st welding layer 151, the secondary point P is to be formed₁To the point of intersection P₃The region (2) is called "1 st intersection region (160)", and will be from the intersection point P₂To the point of intersection P₄The region of (2) is referred to as "2 nd intersection region (162)". In the 1 st solder layer 151, the maximum position in the depth direction (Z direction) is referred to as a "tip (164)".

At the intersection point P₃Point of intersection P₁In the case of (1), the 1 st intersection region 160 is dotted when viewed in cross section as shown in fig. 4. However, in this case, the 1 st intersection region 160 also extends in the depth direction (direction perpendicular to the paper surface). At the point of intersection P₄Point of intersection P₂The same applies to the case of (1).

The tubular defect 70 shown in fig. 1 (b) tends to be generated from the 1 st intersection region 160 and/or the 2 nd intersection region 162.

Here, in the 1 st welded joint 100, when the welded portion 150 is viewed from a cross section (XZ plane in fig. 4) perpendicular to the extending direction of the welded portion, the following features are provided:

(1) at the point of intersection P₁And point of intersection P₂In the case of the straight line L of (2), the tip of the No. 2 solder layer 152 in the depth direction is arranged to be introduced into the backing plate 140 beyond the straight line L; and

(2) the 2 nd welding layer 152 is at the intersection point Q with the straight line L₁And intersection point Q₂Intersection, point of intersection Q₁Located at said intersection point Q₂Closer to the 1 st part side, an intersection point Q₁In the 1 st welding layer 151 or at the intersection point P₁Coincidence, intersection point Q₂In the 1 st welding layer 151 or at the intersection point P₂And (5) the consistency is achieved.

The effects of these features will be described below with reference to fig. 5 to 7.

Fig. 5 to 7 show a cross section of the 1 st welding layer that can be formed by the 1 st welding pass and a cross section of the 2 nd welding layer that can be formed by the 2 nd welding pass, overlapping each other.

In fact, since a part of the 1 st welding layer is melted by the 2 nd pass, the shape of the 1 st welding layer is not changed after the 2 nd pass is performed. Accordingly, fig. 5 to 7 schematically show the cross section of the 1 st welded layer before the 2 nd pass is performed.

In particular, fig. 5 and 6 show an example of an unsuitable welded portion, and fig. 7 shows an example of an appropriate welded portion.

In fig. 5 to 7, in order to avoid the complicated drawings, the 1 st member 120 and the backing plate 140 and the 2 nd member 130 and the backing plate 140 are shown in a state of being in contact with each other (i.e., in a state of having no gap).

First, referring to fig. 5, the 1 st welding layer 151 has a 1 st crossing region 160 and a 2 nd crossing region 162. Since fig. 5 is a cross-sectional view, the

intersection regions

160 and 162 are defined as the intersection points P₁And point of intersection P₂But are shown.

As described above, the tubular defect tends to be generated with the 1 st intersection region 160 and/or the 2 nd intersection region 162 as a starting point. Thus, fig. 5 schematically illustrates a tubular defect 170 extending from the 1 st intersection region 160 and the 2 nd intersection region 162.

The 2 nd welding layer 152A is formed by forming the 1 st welding layer 151 by the 1 st welding pass and then performing the 2 nd welding pass. The 2 nd solder layer 152A has a tip 168A.

In the example shown in fig. 5, the intersection point P is drawn₁And point of intersection P₂The tip 168A of the 2 nd solder layer 152A does not reach the straight line L. Namely, the feature (1) is not satisfied.

In the case where the 2 nd weld layer 152A is formed in this way, the possibility that the tubular defect 170 included in the 1 st weld layer 151 remains intact or hardly shortens after the 2 nd pass is performed is increased. As a result, the possibility of large tubular defects 170 remaining after the welding step is completed is increased.

Next, referring to fig. 6, in this example, after the 1 st welding layer 151 is formed, the 2 nd welding layer 152B is formed by the 2 nd pass.

As described above, the 1 st solder layer 151 has the intersection points P corresponding to the 1 st intersection region 160 and the 2 nd intersection region 162, respectively₁And point of intersection P₂。

The 2 nd solder layer 152B has a tip 168B. And, the 2 nd solder layer 152B is formed at an intersection Q with the 2 nd surface 124 of the 1 st part 120 in the width (X) direction₁Contact, at an intersection point Q, with the 4 th surface 134 of the 2 nd part 130₂And (4) contacting.

In the example shown in fig. 6, the intersection point P passing through the 1 st solder layer 151 is drawn₁And point of intersection P₂In the case of the straight line L, the 2 nd solder layer 152B is formed such that the tip 168B is introduced into the backing plate 140 beyond the straight line L in the depth direction.

That is, the 2 nd solder layer 152B satisfies the aforementioned characteristic (1).

When the 2 nd weld layer 152B is formed in this manner, at least a part of the tubular defect 170 existing in the 1 st weld layer 151 can be remelted when the 2 nd pass is performed. Therefore, after the 2 nd pass is performed, the tubular defect 170 in the 1 st welded layer 151 is shortened, and as a result, the tubular defect 170 can be removed or the tubular defect 170 can be reduced.

However, the 2 nd welding layer 152B is formed as an intersection Q with the straight line L₁Becomes a specific intersection point P₁Further to the left side (-X direction), and an intersection Q with the straight line L₂Becomes a specific intersection point P₂Further to the right (+ X direction).

That is, in the 2 nd solder layer 152B, the intersection Q₁And intersection point Q₂Are located outside the 1 st solder layer 151 and do not satisfy the aforementioned characteristic (2).

In this manner, the intersection point Q is caused to occur when the 2 nd pass is performed₁Becomes a new intersection region 180B, intersection point Q₂Becomes the new intersection region 182B. That is, the probability of the generation of a new tubular defect 171 in the 2 nd welded layer 152B starting from the new intersection regions 180B and 182B is increased.

On the other hand, referring to fig. 7, in this example, after the 1 st welding layer 151 is formed, the 2 nd welding layer 152C is formed by the 2 nd pass.

The 2 nd solder layer 152C has a tip 168C.

Here, in the example shown in fig. 7, as described above, the intersection point P is drawn through₁And point of intersection P₂In the case of the straight line L, the 2 nd solder layer 152C is formed such that the tip 168C is introduced into the backing plate 140 beyond the straight line L in the depth direction.

That is, the 2 nd solder layer 152C satisfies the aforementioned characteristic (1).

In this case, at least a part of the tubular defect 170 existing in the 1 st welded layer 151 can be remelted when the 2 nd pass is performed. Therefore, after the 2 nd pass is performed, the tubular defect 170 in the 1 st welded layer 151 is shortened, and as a result, the tubular defect 170 can be removed or the tubular defect 170 can be reduced.

In the example shown in fig. 7, the 2 nd welding layer 152C is formed at the intersection Q with the straight line L₁Becomes a specific intersection point P₁Further to the right (+ X direction), and an intersection Q with the straight line L₂Becomes a specific intersection point P₂Further to the left (X direction).

That is, in the 2 nd solder layer 152C, the intersection Q₁And intersection point Q₂Are located inside the 1 st welding layer 151, and satisfy the aforementioned characteristic (2).

In this embodiment, the intersection point Q can be passed when carrying out the 2 nd pass₁And intersection point Q₂To avoid creating new intersection regions in the 2 nd solder layer 152C. The reason for this is that at the intersection point Q₁And intersection point Q₂When formed inside the 1 st solder layer 151, the 2 nd solder layer 152C does not contact the 1 st member 120, the 2 nd member 130, and the backing plate 140 on the straight line L.

Therefore, in the mode shown in fig. 7, it is difficult to generate a new tubular defect starting from a new intersection region in the 2 nd welding layer 152C.

In this way, when the 2 nd welding layer 152C is formed so as to satisfy the characteristics of (1) and (2) described above at the same time, the tubular defect 170 existing in the 1 st welding layer 151 can be shortened, and the tubular defect 170 can be significantly removed or the tubular defect 170 can be reduced. Further, by forming the 2 nd solder layer 152C, it is also possible to avoid the generation of a new intersection region.

Therefore, in the 1 st welded joint 100 having both the features of the foregoing (1) and (2), a large tubular defect can be significantly suppressed.

(Components included in the welded joint according to one embodiment of the present invention)

Next, the features, structures, and the like of each member included in the welded joint according to the embodiment of the present invention will be described in more detail.

In order to clarify the description, reference numerals shown in fig. 2 to 4 and 7 are used to illustrate the respective members.

(1

st member

120 and 2 nd member 130)

The shape of the 1 st member 120 is not particularly limited as long as it is plate-like. For example, in the 1 st part 120, the 1 st surface 122 and the 2 nd surface 124 may have curved surfaces. The thickness of the 1 st member 120 may be, for example, in the range of 6mm to 60 mm.

The material of the 1 st member 120 is not particularly limited, and may be, for example, a steel material such as carbon steel.

The same applies to the 2 nd part 130. The 1 st member 120 and the 2 nd member 130 may be made of the same material or different materials.

(backing plate 140)

The backing plate 140 may be constructed of, for example, the 1 st component 120 or the same material as the 2 nd component 130.

The backing plate 140 may have a thickness of 6mm to 22mm, for example.

(weld part 150)

The welded portion 150 is formed of a plurality of welded layers. The number of layers is not particularly limited as long as it is 2 or more.

The 1 st welding layer 151 is present at the lowermost part of the welding part 150, and forms an interface with each of the 1 st member 120, the 2 nd member 130, and the backing plate 140.

More specifically, when the welded part 150 is viewed from a cross section perpendicular to the extending direction, the 1 st welded layer 151 intersects the 2 nd surface 124 of the 1 st member 120 at the 1 st member 120 side at the intersection point P as shown in fig. 4₁Intersects the upper surface 142 of backing plate 140 at an intersection point P₃And (4) intersecting.The 1 st solder layer 151 is on the 2 nd member 130 side and intersects the 4 th surface 134 of the 2 nd member 130 at a point P₂Intersects the upper surface 142 of backing plate 140 at an intersection point P₄And (4) intersecting.

Intersection point P on No. 1 solder layer 151₁And point of intersection P₂Width W between₁(see fig. 4 and 7) may be in the range of 3mm to 20 mm.

As described above, the 2 nd solder layer 152 passes through the intersection point P₁And point of intersection P₂Is formed as an intersection Q with the straight line L₁And intersection point Q₂Are contained in the inside of the 1 st welding layer 151.

Here, the point of intersection P₁And point of intersection Q₁The distance therebetween is preferably 2mm or less, more preferably 1mm or less. Likewise, the point of intersection P₂And point of intersection Q₂The distance therebetween is preferably 2mm or less, more preferably 1mm or less.

And, the intersection point Q₁And point of intersection Q₂Width W between₂(refer to fig. 7) may be in the range of 2mm to 20 mm. Especially, width W₂Relative to the width W₁The proportion of (b) is preferably 70% or more, more preferably 80% or more.

Such a welded portion 150 can be formed by the following method, for example.

(welding method according to one embodiment of the present invention)

Next, a welding method according to an embodiment of the present invention will be described with reference to fig. 8 to 11.

Fig. 8 schematically shows a flow of a welding method according to an embodiment of the present invention. Fig. 9 to 11 schematically show one step of the welding method according to the embodiment of the present invention.

As shown in fig. 8, a welding method according to an embodiment of the present invention (hereinafter referred to as "1 st welding method") includes:

(a) disposing the 1 st member, the 2 nd member and the backing plate at predetermined positions (step S110);

(b) a step (step S120) of forming a 1 st weld layer between the 1 st member, the 2 nd member and the backing plate by the 1 st weld bead; and

(c) and a step (step S130) of forming a 2 nd welding layer on the 1 st welding layer by the 2 nd welding pass.

Hereinafter, each step will be described with reference to fig. 9 to 11.

Here, a welding method in manufacturing the above-described first welded joint 100 will be described as an example. Therefore, in the case of showing each member, the reference numerals used in fig. 2 to 4 and 7 are used.

(step S110)

First, the 1 st member 120, the 2 nd member 130, and the backing plate 140 are prepared and arranged at appropriate relative positions.

Fig. 9 schematically shows a case where 3 members are arranged at appropriate positions.

As shown in fig. 9, the 1 st member 120 has a 1 st surface 122 and a 2 nd surface 124 opposed to each other and an end surface 126 connecting both surfaces. The 2 nd member 130 has a 3 rd surface 132 and a 4 th surface 134 facing each other, and an end surface 136 connecting the two surfaces. Backing plate 140 has an upper surface 142.

The 1 st member 120 and the 2 nd member 130 are arranged on the backing plate 140 so that the two

end surfaces

126 and 136 face each other. In this case, the 1 st member 120 and the 2 nd member 130 are arranged such that the 1 st surface 122 and the 3 rd surface 132 face the same direction (face upward). In other words, the 1 st and 2

nd members

120, 130 are disposed such that the 2 nd and 4 th surfaces 124, 134 are opposed to or in contact with the upper surface 142 of the backing plate 140.

In the example shown in fig. 3, the end surface 126 of the 1 st member 120 and the end surface 136 of the 2 nd member 130 are inclined at a predetermined angle. Therefore, when the 1 st member 120 and the 2 nd member 130 are appropriately arranged with respect to each other, the end surfaces 126 and 136 of the members form a V-groove shape with an angle θ. The angle θ is generally in the range of 30 ° to 90 °.

However, this is merely an example, and the inclination angles of the end surfaces 126 and 136 are not particularly limited. For example, at least one or at least a part of the end surface 126 of the 1 st member 120 and the end surface 136 of the 2 nd member 130 may be parallel to the thickness direction of the

members

120 and 130 without being inclined. The end surfaces 126 and 136 may have different inclination angles.

The minimum distance D (see fig. 9) between the 1 st member 120 and the 2 nd member 130 is, for example, in the range of 0mm to 20 mm.

As described above, the 1 st surface 122 and the 2 nd surface 124 of the 1 st part 120 do not necessarily have to be parallel, and they may have curved surfaces. The same applies to the 3 rd surface 132 and the 4 th surface 134 of the 2 nd member 130.

(step S120)

Then, arc welding using a filler metal such as a wire is performed. As a result, the 1 st weld bead forms the 1 st weld layer 151 between the 1 st member 120, the 2 nd member 130, and the backing plate 140.

Fig. 10 schematically illustrates a case where the 1 st welding layer 151 is formed by the 1 st bead.

As shown in fig. 10, the 1 st welding layer 151 is formed at the bottom between the end surface 126 of the 1 st member 120 and the end surface 136 of the 2 nd member 130. And, the 1 st welding layer 151 is formed such that the tip 164 enters the inside of the backing plate 140.

As described above, in the cross section of the 1 st welding layer 151, an intersection point where the 1 st welding layer 151 intersects the 2 nd surface 124 of the 1 st member 120 on the 1 st member 120 side is defined as P₁The intersection point of the No. 2 member 130 side and the No. 4 surface 134 of the No. 2 member 130 is defined as P₂。

In the 1 st pass, a large current exceeding 500A may be applied between the electrode wire and each

member

120, 130, or a smaller current may be applied.

(step S130)

Next, as shown in fig. 11, a 2 nd welding layer 152 is formed on the 1 st welding layer 151 by a 2 nd welding pass.

In general, the 2 nd pass is performed by applying a large current exceeding 500A between the electrode wire and each

member

120, 130.

Here, the 2 nd solder layer 152 has the characteristics as described above.

I.e. at the point of intersection P of the drawing₁And point of intersection P₂OfIn the case of line L, the 2 nd solder layer 152 is formed such that the tip 168 in the depth direction is introduced into the backing plate 140 beyond the straight line L.

And, the 2 nd welding layer 152 is formed as the intersection point Q₁In the 1 st welding layer 151 or at the intersection point P₁Coincide and intersect point Q₂In the 1 st welding layer 151 or at the intersection point P₂And (5) the consistency is achieved.

In addition, as described above, the intersection point Q₁And intersection point Q₂Is determined as the intersection point where the layer 152 intersects the straight line L in the cross section of the 2 nd welded layer 152. Here, the intersection point Q₁Is determined as a ratio crossing point Q₂Closer to the intersection of the 1 st part 120 side.

If necessary, the 3 rd and 4 th solder layers 4 … … may be provided on the 2 nd solder layer 152.

Through the above steps, the welded portion 150 is formed. Then, a 1 st welded joint 100 in which the 1 st member 120, the 2 nd member 130, and the backing plate 140 are joined to each other via the welded portion 150 can be obtained.

In the 1 st welding method, at least a part of the tubular defect 170 which may exist in the 1 st welded layer 151 can be remelted when the 2 nd pass in the step S130 is performed. Therefore, after the 2 nd pass is performed, the tubular defect 170 in the 1 st weld layer 151 can be removed or reduced.

In addition, in the 1 st welding method, it is possible to avoid the intersection point Q when the 2 nd welding layer 152 is formed by the 2 nd pass₁And Q₂A new intersection region is generated.

Therefore, in the 1 st welding method, even if an oxide film is present at the welded portion of the 1 st member 120, the 2 nd member 130, and/or the backing plate 140, large tubular defects can be significantly suppressed

In addition, in the first welding method, it is not necessary to perform a step of removing the oxide film existing on the 1 st member 120, the 2 nd member 130, and the backing plate 140, and thus the work efficiency can be improved.

In addition, the above-described 1 st welding method may be carried out using any welding technique as long as the characteristics as described above are obtained.

For example, the first1 the welding method may utilize the use of Ar with CO₂Mixed gas of (2), CO₂Gas Metal Arc Welding (GMAW), Flux Cored Arc Welding (FCAW), or Submerged Arc Welding (SAW).

Examples

Next, examples of the present invention will be explained.

(example 1)

The two steel plates and the backing plate were welded to each other by the welding method 1, and a welded joint was manufactured.

SM490 (rolled steel for welded structure) having a thickness of about 12mm was used for both steel sheets. The included angle θ of the V-shape formed by the end surfaces of the two steel plates was about 50 °, and the minimum distance D between the two steel plates was about 5mm (see fig. 9).

The backing plate is made of steel material similar to that of the steel plate.

The oxide film was not removed from both the steel sheet and the backing plate.

Moreover, a gas shielded arc welding machine is used for welding. The protective gas is Ar and CO₂As the mixed gas of (3), a solid wire having a diameter of 1.4mm corresponding to YGW15(JIS standard) was used.

The number of passes was set to two, and a weld composed of two weld layers was formed. In the 1 st pass, a current of less than 500A was applied between the electrodes. In contrast, in the 2 nd pass, a current exceeding 500A was applied between the electrodes.

As a result of inspecting the obtained welded joint, it was confirmed that the welded portion was in a stable state and the two steel plates and the backing plate were appropriately joined. Also, no tubular defect was confirmed in the welded portion.

Fig. 12 shows an example of a cross section of a welded part after the first weld pass is performed. Fig. 13 shows an example of a cross section of a welded part after the 2 nd pass is performed.

As can be seen from fig. 12, the 1 st weld layer extends from both steel plate sides to the inside of the backing plate. Similarly, as can be seen from fig. 13, the 2 nd solder layer is in the depth direction, and the tip reaches the inside of the backing plate.

From FIG. 13, and in accordance with the above definition, the intersection point P is obtained₁Point of intersection P₂Intersection point Q₁And intersection point Q₂. As a result, the intersection Q was confirmed₁And intersection point Q₂Are present inside the 1 st solder layer.

In addition, the intersection point P₁And point of intersection Q₁Is about 1mm, point of intersection P₂And point of intersection Q₂Is about 0.5 mm. And, the intersection point Q₁And point of intersection Q₂Width W between₂Relative to the intersection point P₁And point of intersection P₂Width W between₁The proportion of (c) is about 70%.

(example 2)

The two steel plates and the backing plate are welded to each other by a conventional welding method, and a welded joint is manufactured.

The same steel material as in example 1 was used for both the steel plate and the backing plate. Moreover, a gas shielded arc welding machine is used for welding. The protective gas is CO₂The same welding wire as in example 1 was used.

In example 2, a large current exceeding 500A was applied between the electrode wire and the steel plate, and a welded portion was formed by 1 pass. Thus, the weld has a single weld layer.

Fig. 14 and 15 show an example of the resulting welded portion.

Fig. 14 is a photograph in which a cross section of the welded portion is viewed (photographed) from a direction perpendicular to the extending direction. Fig. 15 is a photograph of a welded portion cut along a weld bead and subjected to transmission X-ray imaging from the side. In fig. 15, the upper portion corresponds to two steel plates, and the lower portion corresponds to a backing plate.

As can be seen from fig. 14, a tubular defect is generated at the intersection region on the left side of the welded layer. As is clear from fig. 15, a plurality of tubular defects starting from the intersection region are generated in the welded portion.

As described above, it is understood that in example 2, a plurality of tubular defects are included in the welded portion.

As is clear from the above, by forming the 2 nd welding layer on the 1 st welding layer so as to satisfy the characteristics of the above (1) and (2), it is possible to significantly suppress tubular defects that may occur in the welded portion.

The present application claims priority based on japanese patent application No. 2017-050152 of japanese application No. 2017, 3, 15, 2017, and the entire contents of the japanese application are incorporated by reference into the present application.

Description of the symbols

20-steel plate 1, 26-inclined end face, 30-steel plate 2, 36-inclined end face, 40-backing plate, 50-weld layer, 70-tubular defect, 100-1 st weld joint, 120-1 st part, 122-1 st surface, 124-2 nd surface, 126-end face, 130-2 nd part, 132-3 rd surface, 134-4 th surface, 136-end face, 140-backing plate, 142-upper surface, 150-weld, 151-1 st weld layer, 152A, 152B, 152C-2 nd weld layer, 160-1 st intersection region, 162-2 nd intersection region, 164-tip of 1 st weld layer, 168A, 168B, 168C-tip of 2 nd weld layer, 170-tubular defect, 171-new tubular defect, 180B-new intersection region, 182B-new intersection region.

Claims

1. A welding method, comprising:

the welding method is characterized in that,

2. The welding method according to claim 1,

the distance between the intersection point P1 and the intersection point Q1 is less than or equal to 2mm, and/or

The distance between the intersection point P2 and the intersection point Q2 is 2mm or less.

3. The welding method according to claim 1,

the ratio of the width W2 from the intersection point Q1 to the intersection point Q2 to the width W1 from the intersection point P1 to the intersection point P2, that is, W2/W1, is 70% or more.

4. A welded joint in which a No. 1 member, a No. 2 member and a backing plate are joined to each other by a welded portion,

said 1 st part having a 1 st surface,

the 2 nd part has a 2 nd surface,

said 1 st weld layer intersecting said 1 st surface of said 1 st part at an intersection point P1 on said 1 st part side, said 1 st weld layer intersecting said 2 nd surface of said 2 nd part at an intersection point P2 on said 2 nd part side,

5. The weld joint according to claim 4,

6. The weld joint according to claim 4,