Welding method

Abstract

To provide a welding method that can properly perform welding while suppressing the occurrence of unwelded areas when arc welding a second joint portion of a second member to a first joint portion of a first member by a partial penetration welding method.SOLUTION: A welding method of the present invention performs arc-welding by partial penetration welding, a second joint portion of a second member and a first joint portion of a first member, with the second member being butted against the first joint portion. The welding method includes the steps of: performing groove preparation on each of the first joint portion and the second joint portion; butting the second joint portion against the first joint portion to form a V-groove between the first joint portion and the second joint portion; fillet welding a location where the second joint portion is butted against the first joint portion on an opposite side of the V-groove as viewed from the second joint portion; and groove welding, with the V-groove, the location where the second joint portion is butted against the first joint portion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a welding method, and more particularly to a welding method for arc-welding a second joint portion of a second member to a first joint portion of a first member by partial penetration welding. [Background technology]

[0002] A welding method in which a groove is formed between two members having a joint (weld joint) and the joints are then arc-welded at the groove is already widely used. Groove welding methods include full penetration welding and partial penetration welding.

[0003] Full penetration welding requires the installation of a backing metal on the opposite side of the groove during welding, which requires additional work and is time-consuming. In contrast, partial penetration welding does not require the installation of a backing metal, which reduces the workload. For this reason, partial penetration welding is sometimes used when groove welding the joints of two members. For example, Patent Document 1 describes the use of partial penetration welding in a square groove welded joint. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-104882 Summary of the Invention [Problem to be solved by the invention]

[0005] When groove welding is performed using the partial penetration welding method, if the welding is not performed properly, there is a risk of non-welded areas occurring near the innermost part of the groove (the deepest part), which leads to a decline in construction quality. Meanwhile, in conventional welding work, whether or not non-welded areas at the innermost part of the groove can be prevented depends on the skill of the welder.

[0006] Furthermore, when groove welding is performed using the partial penetration welding method, there is a risk of defects occurring due to the component (base material) being welded bending during welding, and it is necessary to perform welding properly while avoiding such defects.

[0007] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a welding method that can appropriately weld while suppressing the occurrence of unwelded portions when arc welding a second joint portion of a second member to a first joint portion of a first member using partial penetration welding. [Means for solving the problem]

[0008] The above-mentioned problems are solved by a welding method of the present invention, which is a welding method in which a second joint portion of a second member is abutted against a first joint portion of a first member and the first joint portion and the second joint portion are arc-welded by partial penetration welding, the method comprising the steps of: performing groove preparation on each of the first joint portion and the second joint portion; abutting the second joint portion against the first joint portion and forming a V-groove between the first joint portion and the second joint portion; fillet welding the location where the second joint portion is abutted against the first joint portion on the opposite side of the V-groove as viewed from the second joint portion; and groove welding the location where the second joint portion is abutted against the first joint portion with the V-groove. According to the above method, when arc welding the second joint portion of the second member to the first joint portion of the first member by partial penetration welding, welding can be performed while suppressing the occurrence of unwelded portions, regardless of the skill of the welding worker. Furthermore, by using groove welding and fillet welding in combination, it is possible to suppress defects that can occur when groove welding is performed by partial penetration welding (the details of the defects will be described later), and as a result, the first joint portion and the second joint portion can be properly welded.

[0009] In the welding method of the present invention, it is more preferable to perform the step of fillet welding the area where the second joint part abuts the first joint part before the step of groove welding the area where the second joint part abuts the first joint part. In this case, the inner part of the groove can be sufficiently melted, and the occurrence of unwelded areas can be more effectively suppressed.

[0010] Furthermore, in the welding method of the present invention, in the step of performing groove preparation on each of the first joint part and the second joint part, it is even more preferable to perform groove preparation on each of the first joint part and the second joint part so that the angle formed by the pair of inclined surfaces provided in the V-shaped groove is 60° or more and 70° or less. According to the above configuration, the occurrence of unwelded portions during groove welding can be more effectively suppressed.

[0011] Furthermore, in the welding method of the present invention, in the step of performing groove preparation on each of the first joint part and the second joint part, it is even more preferable to perform groove preparation on each of the first joint part and the second joint part so that the inclination angle of at least one of the pair of inclined surfaces provided in the V-shaped groove relative to the surface of the first joint part against which the second joint part abuts is 30° or more. According to the above configuration, the occurrence of unwelded portions during groove welding can be more effectively suppressed.

[0012] In the welding method of the present invention, the first member may be a plate body, and the second joint portion may be a flat portion. Furthermore, in the welding method of the present invention, the second joint portion may be brought into contact with the first joint portion in a state in which the second joint portion intersects with the first joint portion. With the above configuration, the above-described effects of the present invention are effectively exhibited. [Effects of the Invention]

[0013] According to the present invention, when arc welding a second joint portion of a second member to a first joint portion of a first member using partial penetration welding, it is possible to suppress the occurrence of unwelded portions and to perform proper welding while suppressing defects that can occur during groove welding using partial penetration welding, regardless of the skill of the welding worker. [Brief explanation of the drawings]

[0014] [Figure 1] 1A to 1C are diagrams illustrating steps of a welding method according to an embodiment of the present invention. [Figure 2] 4 is an enlarged view of a first joint portion of a first member and a second joint portion of a second member, showing the state immediately before welding the two members together. FIG. [Figure 3] 4 is an enlarged view of a first joint portion of a first member and a second joint portion of a second member, showing the state immediately after the joint portions have been fillet welded together. FIG. [Figure 4] 4 is an enlarged view of a first joint portion of a first member and a second joint portion of a second member, showing the state after welding is completed. FIG. [Figure 5] FIG. [Figure 6] 1 is an image of a portion welded by a welding method according to one embodiment of the present invention. [Figure 7] 1 is an image showing the results of a tensile test performed on a test specimen made up of a plurality of members welded by a welding method according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] <<Welding method according to one embodiment of the present invention>> A welding method according to one embodiment of the present invention (hereinafter referred to as the present embodiment) will be described below with reference to the accompanying drawings. Note that in the drawings, each member is illustrated somewhat simplified and schematic for the sake of ease of understanding.

[0016] Furthermore, the embodiments described below are merely examples for facilitating understanding of the present invention and are not intended to limit the present invention. That is, the present invention may be modified or improved without departing from the spirit of the present invention. Furthermore, the present invention naturally includes equivalents thereof.

[0017] In this specification, the terms "orthogonal," "vertical," and "parallel" include the range of error permitted in the technical field to which the present invention pertains. For example, in this specification, "orthogonal," "vertical," and "parallel" mean that the deviation is within a range of less than ±10° from the strict orthogonal, vertical, or parallel state. The deviation from the strict orthogonal or parallel state is preferably 5° or less, and more preferably 3° or less. In addition, in this specification, the meanings of "same," "identical," "match," and "equal" may include a range of error generally accepted in the technical field to which the present invention belongs.

[0018] The welding method according to this embodiment (hereinafter also referred to as the present welding method) is a welding method in which a second joint portion of a second member is brought into contact with a first joint portion of a first member, and the first joint portion and the second joint portion are arc-welded by partial penetration welding. Except for the characteristic configuration described below, the present welding method is substantially the same as a known welding method in which joint portions are arc-welded by partial penetration welding.

[0019] The first member and the second member are base materials to be welded, and each has a joint portion as a weld joint. In this embodiment, the first member is a metal plate body having a rectangular or square outer shape in a plan view, and has a joint portion (i.e., a first joint portion) at an end portion in the longitudinal or lateral direction of the first member. The second member is a metal body having a flat plate-shaped joint portion (i.e., a second joint portion).

[0020] The uses of the first member and the second member are not particularly limited, but they may be, for example, members that form part of the skeleton of a building. More specifically, the first member may be an end plate fixed to a column of the skeleton, and the second member may be a beam member (strictly speaking, an H-shaped steel beam used as a beam). In this case, the vertical end (e.g., the upper end) of the end plate that forms the first member corresponds to the first joint, and the flange portion of the beam member that forms the second member corresponds to the second joint.

[0021] This welding method is performed according to the procedure shown in Fig. 1, specifically, a groove preparation step S001, a groove formation step S002, a fillet welding step S003, and a groove welding step S004 are performed in this order. Each step will be described below.

[0022] (Bevel processing process) In the groove preparation process, groove preparation is performed on each of the first joint part and the second joint part. Specifically, as shown in Fig. 2, groove preparation is performed on the end part of the first joint part (hereinafter, first joint part 11) facing the second joint part (hereinafter, second joint part 12) by cutting and chamfering the corners. Similarly, groove preparation is performed on the end part of the second joint part 12 facing the first joint part 11 by cutting and chamfering the corners.

[0023] In addition, in the groove processing step, groove processing is performed on each of the first joint portion 11 and the second joint portion 12 so that the angle formed by a pair of inclined surfaces 13a, 13b provided on the V-shaped groove 13 (see Figure 2) formed in the next step, the groove forming step, i.e., the groove angle θ, is 60° or more and 70° or less.

[0024] More specifically, in the groove preparation step, groove preparation is performed on each of the first joint part 11 and the second joint part 12 so that the inclination angle of at least one of the pair of inclined surfaces 13a, 13b provided on the V-shaped groove 13 with respect to the root face 14 is 30° or more. The root face 14 is a flat surface in the first joint part 11 against which the second joint part 12 abuts. Here, if the inclination angle of the inclined surface 13a on the first joint part 11 side with respect to the root face 14 is α and the inclination angle of the inclined surface 13b on the second joint part 12 side with respect to the root face 14 is β, in this embodiment, groove preparation is performed on each joint part so that the following formulas (1) and (2) are established. θ=α+β Equation (1) 30°≦α Equation (2)

[0025] In this embodiment, of the two inclination angles α and β, α is set to be 30° or greater, but this is not limited to this, and β may be 30° or greater, or both α and β may be 30° or greater.

[0026] (Groove formation process) In the groove forming step, as shown in FIG. 2, the second joint portion 12 after groove preparation is brought into contact with the surface of the first joint portion 11 after groove preparation, and a V-shaped groove 13 is formed between the first joint portion 11 and the second joint portion 12. At this time, the second joint portion 12 is brought into contact with the surface of the first joint portion 11 while being perpendicular to the first joint portion 11. As a result, the first joint portion 11 and the second joint portion 12 are arranged to form a substantially L-shape. More specifically, as shown in FIG. 2, the outer end surfaces of the first joint portion 11 and the second joint portion 12 are arranged so as to be positioned on the same plane. Here, the outer end surface refers to the end surface that does not face the mating joint portion, of the two end surfaces that form the corner where the groove preparation was performed in each joint portion.

[0027] The V-groove 13 has a pair of inclined surfaces 13a, 13b. The inclination angles α, β of the inclined surfaces 13a, 13b may be different from each other as shown in Fig. 2, or may be the same angle. The depth of the V-groove 13 (i.e., groove depth) is preferably set to an appropriate size depending on the plate thickness of the second joint portion 12 and the groove angle θ.

[0028] Furthermore, a root face 14 is provided at a position adjacent to the V-groove 13 in the depth direction of the V-groove 13. It is preferable that the length of the root face 14 (more specifically, the length in the direction along the depth direction of the V-groove 13) be 2 mm or more. This allows the welding current to be increased to a relatively high value (for example, about 250 A) in the subsequent fillet welding process, and as a result, sufficient penetration can be obtained during fillet welding, and the weld strength can also be a value that satisfies the required specifications.

[0029] (Filler welding process) In the fillet welding process, as shown in Fig. 3, the portion where the second joint portion 12 abuts against the first joint portion 11 is fillet welded on the opposite side of the V-groove 13 as viewed from the second joint portion 12. That is, a welding torch (not shown) is brought close to a recessed corner-shaped space formed by the first joint portion 11 and the second joint portion 12, which is formed at a portion adjacent to the root face 14 on the opposite side of the V-groove 13, and the second joint portion 12 is fillet welded to the first joint portion 11. The procedure and method of fillet welding are not particularly limited, and known procedures and methods may be used. In this embodiment, as shown in FIG. 1, the fillet welding step is performed before the groove welding step.

[0030] (groove welding process) In the groove welding process, the portion where the second joint portion 12 abuts against the first joint portion 11 is groove-welded at a V-groove 13. That is, the tip of a welding torch is positioned within the V-groove 13, and the second joint portion 12 is groove-welded to the first joint portion 11. The procedure and method of groove welding are not particularly limited, and any known procedure and method for groove welding at a V-groove may be employed. Furthermore, groove welding may be performed in one pass to form a single-layer weld (bead), or groove welding may be performed over multiple passes to form a weld (bead) having multiple layers.

[0031] <<Effectiveness of this embodiment>> In this embodiment, when the first joint portion 11 and the second joint portion 12 are arc-welded by partial penetration welding, the portion where the second joint portion 12 abuts against the first joint portion 11 is groove-welded with a V-shaped groove 13. This makes it possible to prevent the occurrence of a non-welded portion near the innermost portion of the groove as shown in Fig. 5 (the portion surrounded by a circle in Fig. 5).

[0032] To explain in more detail, for example, when the shape of the groove formed between the first joint part 11 and the second joint part 12 is a so-called checkerboard shape, it is necessary to adjust the groove depth, groove angle, welding current, etc. during groove welding. However, even if these are adjusted, depending on the skill of the welding worker, there is a possibility that a non-welded area as shown in Figure 5 may occur in the inner part of the groove. The verification data is shown in Table 1 below.

[0033] Table 1 shows the presence or absence of unwelded areas when groove welding was performed with a square groove under eight conditions, with the groove depth set to 12 mm and the groove angle and welding current varied. A circle in the table indicates "no unwelded areas" and a cross indicates "the presence of unwelded areas."

[0034] [Table 1]

[0035] As a result of the verification, as is clear from Table 1, the probability of occurrence of unwelded parts in the above test in which groove welding was performed with a square groove was approximately 63% (= 5 / 8 × 100).

[0036] Meanwhile, the presence or absence of unwelded areas when groove welding was performed on a V-shaped groove under six conditions in which the groove depth, groove angle, and welding current were changed is shown in Table 2 below. Note that in Table 2, a circle in the table indicates "no unwelded areas" and a cross indicates "the presence of unwelded areas."

[0037] [Table 2]

[0038] When groove welding is performed with a V-groove, the occurrence of unwelded areas near the inner part of the groove is suppressed, as shown in Figure 6. This is also clear from Table 2, where the probability of unwelded areas occurring during groove welding is approximately 17% (= 1 / 6 x 100), a significantly lower value than with a V-groove.

[0039] As described above, in this embodiment, the occurrence of unwelded portions near the innermost portion of the groove can be effectively suppressed by forming the groove formed for welding the first joint portion 11 and the second joint portion 12 as the V-shaped groove 13. This allows the second joint portion 12 to be appropriately groove-welded to the first joint portion 11 while suppressing the occurrence of unwelded portions, without depending on the skill of the welding worker.

[0040] Furthermore, when the groove shape is V-shaped, compared to a square groove, it is easier to insert the welding torch vertically into the groove during welding, allowing for more appropriate groove welding while holding the welding torch in a suitable position. Specifically, when groove welding, the torch is lowered from directly above the groove and moved in a straight line along the groove (rod operation). This makes the welding work easier, allowing for appropriate groove welding regardless of skill. As a result, the quality of welding work can be improved and stabilized.

[0041] In this embodiment, the groove angle θ of the V-shaped groove 13 is 60° or more and 70° or less, and the inclination angle of at least one of the pair of inclined surfaces 13a, 13b provided on the V-shaped groove 13 with respect to the root face 14 is 30° or more. With this configuration, the occurrence of unwelded portions near the innermost part of the groove can be more effectively suppressed.

[0042] In addition, in this embodiment, the portion where the second joint portion 12 abuts against the first joint portion 11 is fillet welded on the opposite side of the V-groove 13 as viewed from the second joint portion 12. That is, in this embodiment, groove welding and fillet welding are used in combination to weld the first joint portion 11 and the second joint portion 12. This makes it possible to suppress defects that may occur when the first joint portion 11 and the second joint portion 12 are groove welded by partial penetration welding, and as a result, the first joint portion 11 and the second joint portion 12 can be properly welded.

[0043] Specifically, when groove welding is performed using partial penetration welding, the heat generated during welding can cause the component to bend (base material) being welded, which can lead to defects caused by the deformation and a decrease in quality. In contrast, in the present embodiment, fillet welding is performed on the opposite side of the groove, thereby preventing the above-mentioned problems. As a result, in the present embodiment, the first joint part 11 and the second joint part 12 can be properly welded while preventing such problems.

[0044] Furthermore, in this embodiment, fillet welding is performed before groove welding, which allows the first joint portion 11 and the second joint portion 12 to be welded more appropriately.

[0045] Specifically, if fillet welding is performed after groove welding, back-cutting work for fillet welding must be performed after groove welding is completed. Furthermore, if the welding current is increased to ensure that the innermost part of the groove is melted in order to prevent the occurrence of unwelded areas near the innermost part of the groove, the welding current may become excessive. In this case, the molten part penetrates the root face 14, making welding impossible. On the other hand, if the welding current is reduced to avoid penetration of the molten part, sufficient penetration cannot be obtained. Therefore, the welding current is set to a high current value, but in that case, for example, a backing metal must be installed on the opposite side of the groove. As mentioned above, installing a backing metal requires additional work, which is time-consuming.

[0046] In contrast, in this embodiment, groove welding is performed after fillet welding on the opposite side of the groove where the second joint part 12 is in contact with the first joint part 11. This makes it possible to increase the welding current while avoiding the molten part from penetrating the root face without requiring a backing metal. This allows the inner part of the groove to be sufficiently melted, effectively suppressing the occurrence of unwelded parts near the inner part of the groove.

[0047] Furthermore, because fillet welding is performed prior to groove welding at the location where the second joint portion 12 is in contact with the first joint portion 11, the heat generated during fillet welding is retained and the area is in a state where it is easy to melt during groove welding. This makes it easier to melt the inner part of the groove, which makes it possible to more effectively prevent the occurrence of unwelded areas near the inner part of the groove.

[0048] Due to the effects described above, the first member and the second member (more specifically, the first joint portion 11 and the second joint portion 12) welded by this welding method are welded (joined) with sufficient weld strength. Specifically, when a tensile test is conducted on a test piece made up of a plurality of members (base materials) welded by this welding method, no fractures are observed at the welded portions, but fractures are confirmed in the members themselves, as shown in Figure 7. In other words, a strong joint is achieved across the board.

[0049] <<Other embodiments>> One embodiment of the welding method of the present invention has been described above, but the above embodiment is merely an example for facilitating understanding of the present invention and does not limit the present invention.

[0050] In the above embodiment, the first member is a plate and the second joint portion 12 of the second member is a flat portion, but this is not limiting. For example, the first member may be a columnar or cylindrical body, and the second joint portion 12 may be a rod-shaped, columnar, or cylindrical portion.

[0051] In the above embodiment, the first joint portion 11 and the second joint portion 12 are joined together by butting the second joint portion 12 against the surface of the first joint portion 11 while the first joint portion 11 and the second joint portion 12 are intersecting in a generally L-shape and welding the joint portions together. However, this is not limited to this. For example, the first joint portion 11 and the second joint portion 12 may be aligned in a straight line, and the end of the second joint portion 12 may be butted against the end of the first joint portion 11 and welded at that point. That is, each joint portion may be a butt joint. In this case, the length of the root face is shortened. Normally, the welding current for groove welding must be reduced as much as possible to prevent the molten portion from penetrating the root face. However, by applying the present invention and using fillet welding and groove welding together, the welding current can be increased for the reasons described above. As a result, the occurrence of unwelded areas near the innermost part of the groove can be suppressed, ensuring sufficient weld strength. [Explanation of symbols]

[0052] 11 First joint 12 Second joint 13 V-shaped bevel 13a, 13b Slope 14 Root surface

Claims

1. A welding method comprising: abutting a second joint portion of a second member against a first joint portion of a first member; and arc welding the first joint portion and the second joint portion by partial penetration welding, A step of performing groove processing on each of the first joint portion and the second joint portion; a step of abutting the second joint portion against the first joint portion to form a V-shaped groove between the first joint portion and the second joint portion; A process of fillet welding a portion where the second joint portion is abutted against the first joint portion on an opposite side of the V-shaped groove as viewed from the second joint portion; and groove welding the portion where the second joint portion is abutted against the first joint portion using the V-groove.

2. 2. The welding method according to claim 1, wherein a step of fillet welding a location where the second joint portion abuts against the first joint portion is performed before a step of groove welding a location where the second joint portion abuts against the first joint portion.

3. 3. The welding method according to claim 1, wherein in the step of performing groove preparation on each of the first joint portion and the second joint portion, the groove preparation is performed on each of the first joint portion and the second joint portion such that an angle formed by a pair of inclined surfaces provided in the V-shaped groove is 60° or more and 70° or less.

4. 3. The welding method according to claim 1, wherein in the step of performing the groove preparation on each of the first joint part and the second joint part, the groove preparation is performed on each of the first joint part and the second joint part so that an inclination angle of at least one of a pair of inclined surfaces provided in the V-groove with respect to a surface of the first joint part against which the second joint part abuts is 30° or more.

5. The welding method according to claim 1 or 2, wherein the first member is a plate body, and the second joint portion is a flat portion.

6. The welding method according to claim 1 or 2, wherein the second joint portion is brought into contact with the first joint portion in a state where the second joint portion crosses the first joint portion.

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