JPWO2020090939A1 - Welding method of square steel pipe and square steel pipe - Google Patents

Abstract

A square steel pipe is a steel pipe having a square cross-sectional view consisting of a plurality of steel plates thicker than the thickness of the steel pipes constituting the square steel pipe column and a welded metal (32) joined by welding the side edges of the steel plates. Welded metal (32) is a material that is formed at the corners of a square steel pipe and has a multi-layer structure in which different types of materials are laminated to form an inner material layer (321) located inside the multi-layer. The yield point of is higher than the yield point of the material forming the outer material layer (322) located on the outer side of the multilayer.

Description

The present invention relates to a square steel pipe and a method for welding a square steel pipe.

Conventionally, a diaphragm type (for example, a through diaphragm type, an inner diaphragm type, an outer diaphragm type, etc.) has been used at a joint portion between a square steel pipe column used for a column member of a steel structure and an H-shaped steel used for a beam member. It has been adopted. In recent years, a non-diaphragm type beam-column joint structure has also been adopted in which H-shaped steel can be directly welded to the pipe wall surface using a beam-column joint core made of a short thick-walled square steel pipe without providing this diaphragm. (For example, Patent Document 1).

As the thick-walled square steel pipe applied to the non-diaphragm type column-beam joint structure, for example, one made of cast steel or shaped steel is known to be joined by welding. In Patent Document 1, four rectangular steel plates are combined in a box shape, and the side edges of the steel plates are welded to each other to form a thick-walled square steel pipe having a quadrangular cross-sectional view. Specifically, four steel plates having grooves formed on both side edges are arranged in a box shape, side edges of each steel plate are adjacent to each other, and welding torches are arranged between the side edges, and welding of these steel plates is performed. Patent Document 1 describes a method of moving the torch from the lower side to the upper side of the steel plate and welding the side edges of the steel plate at the same time.

Japanese Unexamined Patent Publication No. 2014-024092

By the way, since the thick-walled square steel pipe applied to the non-diaphragm type beam-column joint structure has a structure in which H-shaped steel is directly joined to the side surface as described above, the strength that can withstand such a structure is high. Desired. When such a thick-walled square steel pipe is configured by welding the side edges of each steel plate as in Patent Document 1, stress is particularly likely to be concentrated on the joint portion, and the strength as designed can be obtained. Sometimes not. Although Patent Document 1 describes that the work efficiency is improved by welding the side edges of each steel plate at the same time, the strength of the thick-walled square steel pipe formed by joining by welding is improved. Was not considered and needed to be improved.

Therefore, an object of the present invention is to provide a technique capable of improving the strength of a square steel pipe used for a beam-column joint structure.

The square steel pipe according to one aspect of the present invention is a square steel pipe used for a beam-column joint between a column and a beam, and is welded by welding a plurality of steel plates and side edges of the steel plates. It is a steel pipe with a square cross-sectional view consisting of parts, and the welded part consists of a multi-layer structure in which different types of materials are laminated, and the yield point of the material forming the inner material layer located inside the multi-layer is multi-layer. It is higher than the yield point of the material forming the outer material layer located on the outer side.

According to the present invention, it is possible to provide a technique capable of improving the strength of a square steel pipe used for a beam-column joint structure.

It is a perspective view for demonstrating the main part of a steel structure. It is a perspective view which shows the schematic structure of the thick-walled square steel pipe which concerns on this embodiment. It is a side view which shows the schematic structure of the thick-walled square steel pipe which concerns on this embodiment. It is a top view which shows the schematic structure of the thick-walled square steel pipe which concerns on this embodiment. It is an enlarged view which shows the weld metal formed between adjacent steel plates in an enlarged manner. It is a figure for demonstrating the modification of the backing metal applied to a thick-walled square steel pipe. It is a figure for demonstrating the deformation example of the steel plate in a thick-walled square steel pipe.

Preferred embodiments of the present invention will be described with reference to the accompanying drawings. In each figure, those having the same reference numerals have the same or similar configurations.

First, the configuration of the beam-column joint structure to which the square steel pipe according to the present embodiment is applied will be described. When constructing a steel structure using a square steel pipe column and an H-shaped steel beam, a structure is adopted in which the square steel pipe column is erected and the H-shaped steel beam is attached to the square steel pipe column. When connecting an H-shaped steel beam to a square steel pipe column, a non-diaphragm type is adopted as the structure of the column-beam joint (column-beam joint structure). FIG. 1 shows a main part of a steel structure that employs this non-diaphragm type column-beam joint structure. FIG. 1 shows a state in which the quadrangular steel pipe column 10a joined to the upper side of the thick-walled square steel pipe 30 in the beam-column joining structure 1 is separated from the thick-walled square steel pipe 30. In FIGS. 1 to 7 described below, hatching may be added to a portion other than the cross section for convenience of illustration. FIG. 1 shows a main part of a steel frame structure adopting a non-diaphragm type beam-column joint structure, but the beam-column joint structure in the present embodiment is not limited to this aspect, and is, for example, a thick-walled square shape. A mode in which a hole is formed in the steel pipe 30 and the beam 20 is bolted is also included.

As shown in FIG. 1, the beam-column joint structure 1 is a thick-walled square steel pipe arranged between upper and lower square steel pipe columns 10a and 10b extending in the vertical direction and upper and lower square steel pipe columns 10a and 10b. It is composed of 30 (square steel pipe) and a beam 20 having one end fixed to the side surface of the thick-walled square steel pipe 30 and extending in the horizontal direction.

The beam 20 is made of H-shaped steel, and is composed of two flat plate-shaped flanges 20a facing each other and a web 20b formed between the flanges 20a facing each other. The beam 20 is welded to the thick-walled square steel pipe 30 so that the flange 20a faces in the vertical direction and one end surface of the web 20b abuts on the side surface of the thick-walled square steel pipe 30.

The square steel pipe columns 10a and 10b are members that serve as columns of a steel frame structure, and are long square steel pipes having a substantially quadrangular cross section. The lower end of the thick-walled square steel pipe 30 is joined to the upper end of the square steel pipe column 10b (lower floor column) extending downward, and the thick-walled square shape is joined to the lower end of the square steel pipe column 10a (upper floor column) extending upward. The upper ends of the steel pipe 30 are joined. Hereinafter, when the square steel pipe columns 10a and 10b are not individually distinguished and are collectively expressed, they are simply referred to as "square steel pipe columns 10".

The thick-walled square steel pipe 30 is a short square steel pipe having a substantially square cross-sectional view, which is arranged at a connection portion (column-beam joint portion) between the upper and lower square steel pipe columns 10 and the beam 20. In the beam-column joint structure 1, the upper and lower quadrangular steel pipe columns 10 and the thick-walled square steel pipe 30 are arranged so as to be positioned linearly. Since the non-diaphragm type thick-walled square steel pipe 30 capable of directly joining the beam 20 made of H-shaped steel to the side surface is used for the beam-column joining structure 1 in the present embodiment, the plate thickness of the thick-walled square steel pipe 30 is used. t _c is formed to be thicker than _{the plate thickness t p} of the square steel pipe column 10. The plate thickness t _c is, for example, 22 to 50 mm, and the plate thickness t _p is, for example, 6 to 25 mm. The length of the thick-walled square steel pipe 30 in the longitudinal direction is longer than the height of the beam 20 (height between the flanges 20a) joined to the side surface of the thick-walled square steel pipe 30.

The configuration of the thick-walled square steel pipe 30 will be further described with reference to FIGS. 2 to 5. FIG. 2 is a perspective view showing a schematic configuration of the thick-walled square steel pipe 30. FIG. 3 is a side view showing a schematic configuration of the thick-walled square steel pipe 30. FIG. 4 is a plan view showing a schematic configuration of the thick-walled square steel pipe 30. FIG. 5 is an enlarged view for explaining the weld metal 32 (welded portion) formed at the corner portion of the thick-walled square steel pipe 30.

As shown in FIG. 2, in the thick-walled square steel pipe 30, four rectangular steel plates 31a, 31a, 31b, and 31b, which are thicker than the thickness of the steel pipe constituting the square steel pipe column 10, are welded and joined to each other. It is molded by. Hereinafter, a step of welding the edges of the steel plates 31a, 31a, 31b, and 31b to each other to form the weld metal 32 will be described. In addition, in this specification, when each steel plate 31a, 31a, 31b, 31b is not distinguished individually and is expressed collectively, it is simply described as "steel plate 31".

First, the four steel plates 31 are arranged in a box shape so as to face each other. Grooves G having an inclination of a predetermined angle are formed on the side edges of the steel plates 31 arranged in a box shape adjacent to each other. In the present embodiment, groove G having an inclination of a predetermined angle is formed on both end edges of the steel plates 31b and 31b arranged so as to face each other in the width direction. Then, a predetermined welding device (for example, a welding torch (not shown)) is arranged in the groove G between the adjacent steel plates 31, and the steel plate 31 is formed along the vertical direction (vertical direction in FIG. 3) of the steel plate 31. Weld from one end to the other end (from the upper end to the lower end of the steel plate as shown in FIG. 3) to join the adjacent steel plates 31 to each other. In this way, the weld metal 32 is formed on the side edges of the adjacent steel plates 31 (inside the corners of the steel plates 31) and the steel plates 31 are joined to each other to manufacture a steel pipe having a substantially quadrangular cross section.

In the present embodiment, the weld metal 32 that has been multi-layer welded is formed on the groove G formed between the adjacent steel plates 31. FIG. 5 is an enlarged view showing the periphery of the weld metal 32 in an enlarged manner. The weld metal 32 is formed at the corners of the thick-walled square steel pipe 30 (near the four corners of a substantially quadrangular cross section), and has a multilayer structure in which a plurality of types of materials are laminated.

In the step of forming the weld metal 32 having a multi-layer structure shown in FIG. 5, in the welding forming step of the first layer, a backing metal is placed on the back of the groove G (inner surface side of the steel plate 31) formed between the adjacent steel plates 31. 35 is applied and _{welding is performed by CO 2} semi-automatic welding to form an inner material layer 321.

After forming the inner material layer 321, welding is performed by submerged arc welding to form the outer material layer 322. In this way, the weld metal 32 having a multi-layer structure composed of the inner material layer 321 and the outer material layer 322 is formed. In the present embodiment, in the first layer welding, the _{inner material layer 321 is formed by welding by CO 2} semi-automatic welding, and in the second and subsequent layers welding, the outer material layer 322 is welded by submerged arc welding. To form multiple layers. According to submerged arc welding, steel materials with a relatively long welding area, such as long members, can be welded continuously without human intervention, but because there is a large amount of heat input at one time, the base metal There is also a large effect of heat, such as the fact that the toughness may be impaired. In this regard, as in the present embodiment, if welding of a columnar four-sided box-shaped cross section in which a long area is to be continuously welded without manpower is performed in multiple layers, the amount of heat input at one time can be suppressed to a low level and the base metal can be welded. It is possible to reduce the heat effect of. In the present specification, the material layer located inside (the inner surface side of the thick-walled square steel pipe 30 (lower side of the weld metal 32 in FIG. 5)) of the weld metal 32 having a multi-layer structure is referred to as the inner material layer. It is referred to as 321 and the material layer located on the outside (the outer surface side of the thick-walled square steel pipe 30 (upper side of the weld metal 32 in FIG. 5)) is referred to as the outer material layer 322.

Among the weld metals 32 having a multi-layer structure as described above, a high-strength material is used for the inner material layer 321 formed by welding the first layer. Specifically, the yield point measured according to the tensile test specified in JIS Z 2241 of the material used for the inner material layer 321 is the tensile test specified in JIS Z 2241 of the material used for the steel plate 31. It is higher than the yield point measured according to JIS Z 2241 and higher than the yield point measured according to the tensile test specified in JIS Z 2241 of the material forming the outer material layer 322.

More specifically, the inner material layer 321 is a yield point is measured according to the tensile test defined in JIS Z 2241 is 460N / mm ² or more and a tensile strength of 550 N / mm ² or more numbers Formed using a range of materials. Further, in addition to satisfying the numerical values of the yield point and the tensile strength measured in accordance with the tensile test specified in JIS Z 2241, the impact absorption energy in the Charpy impact test specified in JIS Z 2242 is obtained. It is preferable to form the inner material layer 321 using a material having a temperature of 70 J or more at 0 ° C. As the welding material used for the inner material layer 321, for example, YGW18 or the like can be adopted. The welding material of the first layer may be a welding material having a strength (yield point, tensile strength) higher than that of the base material, and in order to ensure reliability, the welding material has a lower limit value exceeding the upper limit value of the base material standard. However, from the viewpoint of cost, a welding material having a lower limit value that probabilistically exceeds the upper and lower middle values of the base material standard is more preferable.

^{The outer material layer 322 has a yield point of 390 N / mm 2} or more measured in accordance with the tensile test specified in JIS Z 2241 and conforms to the tensile test specified in JIS Z 2241 of the inner material layer 321. ^{A material having a tensile strength in the numerical range of 490 N / mm 2} or more, which is lower than the yield point measured in the above, is used. As the welding material of the outer material layer 322 satisfying such conditions, for example, EH12K, EH14, S502-H and the like can be adopted.

^{The steel sheet 31 has a yield point in the numerical range of 325 to 445 N / mm 2} and a tensile strength of 490 to 610 N / mm ² measured in accordance with the tensile test specified in JIS Z 2241. Steel materials in the range are used. As such a steel material, for example, a rolled steel material for building structure SN490B, a TMCP steel plate for building structure TMCP325B, or the like can be adopted.

As described above, the inner material layer 321 formed by welding the first layer is measured in accordance with the tensile test specified in JIS Z 2241 of a high-strength material (steel plate 31, material used for the outer material layer 322). By using a material having a yield point higher than the yield point), the joint strength of the inside (inner surface side of the thick-walled square steel pipe 30) of the weld metal 32 formed by welding the side edges of the steel plate 31 can be increased. Can be improved. Since the beam 20 is directly joined to the side surface of the thick-walled square steel pipe 30 as shown in FIG. 1, the direction in which the inner corner portion of the thick-walled square steel pipe 30 is opened by receiving tensile stress from the beam 20 (FIG. 5). A force acts in the direction indicated by the broken line arrow F) to cause stress concentration at the inner corner of the thick-walled square steel pipe 30, particularly at the end of the gap between the backing metal 35 and the steel plate 31 on the weld metal 32 side. Since the inner material layer 321 is formed to improve the inner bonding strength of the weld metal 32, the proof stress against the stress concentration can be increased. Further, in the Charpy impact test specified in JIS Z 2242 described above, the toughness can be improved by using a material having an impact absorption energy of 70 J or more at 0 ° C. (for example, YGW18) for the inner material layer 321. Even when the above tensile stress acts, the possibility of breakage in the weld metal 32 can be suppressed. As one of the preferable combinations, the inner material layer 321 can be composed of YGW18, the outer material layer 322 can be composed of S502-H, and the steel plate 31 can be composed of SN490B.

As described above, the weld metal 32 forming step forms an inner material layer 321 made of a material higher than the yield point measured in accordance with the tensile test specified in JIS Z 2241 of the material used for the steel plate 31. After forming the inner material layer 321, the outer material layer 322 made of a material having a yield point lower than the yield point measured according to the tensile test specified in JIS Z 2241 of the material of the inner material layer 321 is formed. It has a process of welding. At the stage of forming the outermost layer in the welding metal 32 forming step (that is, the stage of forming the last layer of the outer material layer 322 composed of a plurality of layers), the welding voltage value and the welding current in the welding work in submerged arc welding. It is preferable to adjust the value and the welding speed value. That is, in the process of forming the outer material layer 322, only the stage of welding the outermost layer of the outer material layer 322, the welding voltage value, the welding current value, and the welding when welding the layers other than the outermost layer of the outer material layer 322. It is preferable to weld at a different speed value. By adjusting and welding only the outermost layer at the stage of welding in this way, it is possible to suppress the surplus that occurs when the weld metal 32 is formed. Preferably, the welding voltage value and the welding current value at the stage of forming the outermost layer of the weld metal 32 so that the height h of the surplus (FIG. 5) falls within the range of 0 to 1 mm from the outer surface of the steel plate 31. , It is preferable to adjust the welding speed value. By suppressing the surplus in this way, it is possible to eliminate the step of scraping the surface by a machine in order to smooth the surplus, and it is possible to reduce the manufacturing cost.

Also, considering the case of joining a beam to a square steel pipe with a welding surplus, it is difficult to join the beam as it is if the joint surface is not smooth. However, in contrast to this, in the beam-column joining structure 1 or welding method as in this embodiment, the surplus is removed by keeping the height of the surplus within a predetermined value. It is possible to join a beam to a square steel pipe at least. Moreover, in the present embodiment, the yield point is at the inner corner of the thick-walled square steel pipe 30 where stress concentration occurs when a force for deforming the pipe wall (steel plate) of the thick-walled square steel pipe is transmitted from the beam during an earthquake or the like. Is formed from a relatively high material to form the inner material layer 321 to improve the inner joint strength of the weld metal 32 and to increase the resistance to stress concentration. Therefore, even if the height of the weld surplus is reduced, In other words, even if the cross section of the welded portion is reduced, it is possible to secure the strength exceeding a predetermined level.

In the first place, in the case of post-joining, the post-joining portion is generally designed to have a strength higher than that of the base metal in consideration of defects due to welding (“base metal strength ≤ welding strength”). In this regard, in the beam-column joining structure 1 to the welding method of the present embodiment, after that, the strength at the post-joining portion by welding is set to "inner material layer ≥ outer material layer", and further, "inner material layer ≥ outer material layer". By designing the stress concentration point (inner material layer) with relatively high strength, it is possible to reduce the cross-sectional expansion that is secured by the surplus, that is, to reduce the surplus.

In the thick-walled square steel pipe 30 manufactured through the above welding steps, a rectangular backing metal 35 in a plan view is arranged inside the corners of the thick-walled square steel pipe 30 and formed outside the backing metal 35. The inclined groove G is welded to form the weld metal 32. As shown in FIG. 2, the backing metal 35 has a prismatic shape extending along the inside of the corner portion of the thick-walled square steel pipe 30, but is not limited to this shape and has various other shapes. It is possible to change to.

For example, as shown in FIG. 6A, the backing metal 35B arranged inside the corner portion of the thick-walled square steel pipe 30 can be formed in an L shape in a plan view. The backing metal 35B having an L-shape in a plan view shown in FIG. 6A extends from the upper end to the lower end of the thick-walled square steel pipe 30 along the inside of the corner portion of the thick-walled square steel pipe 30. As another modification, as shown in FIG. 6B, the backing metal 35C arranged inside the corner portion of the thick-walled square steel pipe 30 can be formed in a triangular shape in a plan view. The backing metal 35C having a triangular shape in a plan view also extends from the upper end to the lower end of the thick-walled square steel pipe 30 along the inside of the corner portion of the thick-walled square steel pipe 30. By arranging such backing metal 35B and 35C, the direction in which the steel plate 31 is opened by receiving tensile stress from the beam 20 (FIG. 1) welded and joined to the outside of the thick-walled square steel pipe 30 (broken line arrow F in FIG. 6). When a force acts in the direction shown in (1), the backing metal 35B and 35C can be easily followed. It is possible to alleviate the stress concentration that occurs at the inner corner of the thick-walled square steel pipe 30 and at the end of the gap between the backing metal 35 and the steel plate 31 on the weld metal 32 side.

In the embodiment described above, the groove G shape between the adjacent steel plates 31 on which the weld metal 32 is formed has a shape that expands from the inside to the outside of the thick-walled square steel pipe 30. The inclination angle θ (FIG. 5) of the groove G shape is set in the range of, for example, 20 ° to 40 °. If the inclination angle θ is 40 ° or more, the amount of welding increases, which reduces economic efficiency, and if it is 20 ° or less, it becomes difficult to ensure quality. In this way, the groove shape of the adjacent steel plates 31 is formed to expand from the inside to the outside of the thick-walled square steel pipe 30, so that the amount of material used for the inner material layer 321 in the weld metal 32 is formed. Can be suppressed. As described above, it is preferable to use a material having high strength and high toughness for the inner material layer 321. However, the material cost can be reduced by suppressing the amount of the material having such characteristics. can.

In this embodiment, an example is shown in which the shape of the groove G formed between the adjacent steel plates 31 is formed to expand from the inside to the outside of the thick-walled square steel pipe 30. It is possible to transform the groove shape into various other shapes without being limited to such a groove shape.

Further, in the embodiment described above, the side edges of the four flat steel plates 31 are welded together to manufacture the thick-walled square steel pipe 30 having a substantially quadrangular cross section. It is not limited to manufacturing the thick-walled square steel pipe 30 by using the flat steel plate 31.

For example, as shown in FIG. 7A, a cross section in which two steel plates 31d having a substantially L-shape in a plan view are used and the groove Gd between the edges of the steel plates 31d is welded and joined as a weld metal 32d. It is also possible to manufacture a thick-walled square steel pipe 30D having a substantially quadrangular shape. Further, as shown in FIG. 7B, two steel plates 31e having a substantially U-shaped plan view were used, and the groove Ge between the edges of the steel plates 31e was welded and joined as a weld metal 32e. It is also possible to manufacture a thick-walled square steel pipe 30E having a substantially quadrangular cross-sectional view. Further, as shown in FIG. 7C, a thick-walled square steel pipe 30F may be obtained by combining an H-shaped steel 31f and two flat steel plates 31g. Specifically, first, an H-shaped steel 31f composed of two flat plate-shaped flanges 31f1 facing each other and a web 31f2 formed between the facing flanges 31f1 is prepared. A flat plate-shaped steel plate 31g having groove Gf formed at both end edges in the width direction is arranged so as to connect between the flanges 31f1 facing each other in the H-shaped steel 31f. The groove Gf formed on both end edges of the steel plate 31g is welded to form a weld metal 32f, and the flange 31f1 of the H-shaped steel 31f and the steel plate 31g are joined. In this way, it is also possible to manufacture a thick-walled square steel pipe 30F (that is, a square steel pipe having a quadrangular cross-sectional view) having a quadrangular outer shape by combining the H-shaped steel 31f and the steel plate 31g.

The embodiments described above are for facilitating the understanding of the present invention, and are not for limiting and interpreting the present invention.

For example, in the embodiment described above, the inner material layer 321 is composed of a single layer, and the outer material layer 322 is composed of a plurality of layers made of the same material. Two or more layers of 321 may be formed. Further, the inner material layer 321 may be formed in a larger number than the outer material layer 322. The process described in the embodiment, each element included in the embodiment, its arrangement, material, condition, shape, size, and the like are not limited to those exemplified, and can be appropriately changed. In addition, the configurations shown in different embodiments can be partially replaced or combined.

1 ... Beam-beam joint structure, 10 ... Square steel pipe column, 20 ... Beam (H-shaped steel beam), 30 ... Thick-walled square steel pipe (square steel pipe), 31 ... Steel plate, 32 ... Welded metal (welded part), 35 ... Back Weld, 321 ... Inner material layer, 322 ... Outer material layer

Claims (11)

A square steel pipe used for column-beam joints between columns and beams.
The square steel pipe
It is a steel pipe having a quadrangular cross-sectional view, which consists of a plurality of steel plates and welded portions joined by welding the side edges of the steel plates.
The weld has a multi-layer structure in which different types of materials are laminated.
A square steel pipe characterized in that the yield point of the material forming the inner material layer located inside the multilayer is higher than the yield point of the material forming the outer material layer located outside the multilayer. The square steel pipe according to claim 1, wherein the yield point of the material forming the outer material layer is equal to or higher than the yield point of the material forming the steel plate. The square steel pipe includes four flat steel plates, and includes four flat steel plates.
The groove formed on the side edge of the flat steel plate has a shape that expands from the inside to the outside of the square steel pipe.
The inner material layer is a layer located on the innermost side of the welded portion formed by welding the groove portion.
The square steel pipe according to claim 1 or 2. The material constituting the inner material layer has an impact absorption energy of 70 J or more at 0 ° C. in the Charpy impact test.
The square steel pipe according to any one of claims 1 to 3. The inner material layer is composed of a single layer.
The outer material layer is composed of a plurality of layers made of the same material.
The square steel pipe according to any one of claims 1 to 4. The material constituting the inner material layer, yield point 460N / mm ² or more, and the tensile strength is at 550 N / mm ² or more,
The material constituting the outer material layer, yield point 390 N / mm ² or more, and is the tensile strength of 490 N / mm ² or more,
The square steel pipe according to any one of claims 1 to 5. A backing metal is arranged on the inner surface side of the corner of the square steel pipe.
The backing metal has a substantially L-shaped cross-sectional view or a substantially triangular cross-sectional view.
The square steel pipe according to any one of claims 1 to 6. The upper end of the lower floor column is joined to the lower end of the square steel pipe according to any one of claims 1 to 7.
The lower end of the upper floor column is joined to the upper end of the square steel pipe,
A beam-column joint structure in which a beam is joined to the side surface of the square steel pipe. This is a welding method for square steel pipes with a quadrangular cross-section used for column-beam joints between columns and beams.
The process of preparing multiple steel plates and
It has a welding process of welding the edge portions of the steel sheet to each other.
The welding process is
An inner material layer forming step of forming an inner material layer made of a material higher than the yield point of the material used for the square steel pipe, and
A method for welding a square steel pipe, comprising: after the inner material layer forming step, an outer material layer forming step of forming an outer material layer made of a material lower than the yield point of the material of the inner material layer. In the inner material layer forming step, one inner material layer is formed by CO ₂ semi-automatic welding.
The method for welding a square steel pipe according to claim 9. In the outer material layer forming step, a plurality of outer material layers are formed by submerged arc welding.
The method for welding a square steel pipe according to claim 9 or 10.

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