Welded box-shaped cross-sectional member and method for manufacturing the same

Abstract

To provide a weld assembly box type cross section member which does not require a large manufacturing facility, can suppress a heat input amount during welding, and can be manufactured with a small number of man-hours.SOLUTION: In a weld assembly box type cross section member 1 where corner weld is performed in a state where four skin plates are assembled so as to become a rectangular cross section, a first skin plate 11 and a second skin plate 12 are arranged on a pair of surfaces opposing to each other, and a third skin plate 13 and a fourth skin plate 14 are sandwiched by the first skin plate and the second skin plate on the other pair of surfaces opposing to each other, and grooves are provided on both ends in the width direction of the first skin plate, but grooves are not provided on the second skin plate. Out of both ends in a width direction of the third skin plate and the fourth skin plate, a groove is not provided on one end corner-welded with the first skin plate, and a groove is provided on an outside surface side of the weld assembly box type cross section member on the other end corner-welded with the second skin plate, and corner weld is performed at the groove.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a welded assembled box-shaped cross-sectional member formed by joining four skin plates so as to have a rectangular cross-section and a method for manufacturing the same.

Background Art

[0002] Square steel pipes such as cold-rolled formed square steel pipes, cold-pressed formed square steel pipes, and welded assembled box-shaped cross-sectional members are often used for column members of buildings. Among these, cold-rolled formed square steel pipes and cold-pressed formed square steel pipes, which are relatively inexpensive, are often used for column members of mid-rise and high-rise buildings. On the other hand, in the lower part of super high-rise buildings, welded assembled box-shaped cross-sectional members that can be made larger in cross-section, thicker, and higher in strength are often used because the rigidity and strength required for column members are very large.

[0003] Here, the welded assembled box-shaped cross-sectional member has a higher manufacturing cost than the cold-rolled formed square steel pipe and the cold-pressed formed square steel pipe. The factors include that a large number of man-hours are required for welding construction management and the like during the manufacture of the welded assembled box-shaped cross-sectional member. This will be described below.

[0004] As shown in FIGS. 4(a) and 4(b), the welded assembled box-shaped cross-sectional members 8 and 9 are manufactured by performing fillet welding W in a state where four skin plates 81 to 84 and 91 to 94 are combined so as to have a rectangular cross-section. Here, as a welding method for the fillet welding W of the welded assembled box-shaped cross-sectional members 8 and 9 having a large wall thickness, submerged arc welding is generally applied. Specifically, as shown in FIGS. 4(a) and 4(b), the skin plates on both sides or one side of the fillet welding W are cut obliquely to form a V-groove 81g to 84g or a J-groove 93g, 94g. Then, by performing submerged arc welding on this groove, the four skin plates 81 to 84 and 91 to 94 are joined to each other. Since the heat input amount by submerged arc welding is large, backing bars 85 and 95 are provided on the back side of the fillet welding W.

[0005] The submerged arc welding of the welded box-shaped cross section members 8 and 9 is performed in a downward position, as shown in Figures 4(a) and 4(b). Specifically, as shown in Figures 4(a) and 4(b), the grooves 81g, 82g, 84g, and 94g at both ends in the width direction of one of the four skin plates 81-84 and 91-94, are welded simultaneously in a downward position. Next, the welded box-shaped cross section members 8 and 9 are inverted, and the grooves 81g, 83g, 84g, and 93g at both ends in the width direction of skin plates 83 and 93 are welded simultaneously in a downward position.

[0006] Submerged arc welding of these welded box-section members is performed using equipment capable of two-electrode submerged arc welding with a gantry frame. Such equipment requires a movable gantry frame, flux and wire supply equipment, welding power supply, etc., making the equipment large and expensive. The number of steel fabricators with such equipment is limited, and the hurdles to introducing such equipment are high, resulting in a current shortage of welded box-section members.

[0007] Furthermore, since the equipment capable of performing two-electrode submerged arc welding using the aforementioned gantry frame is installed within the steel fabricator's factory, there is an upper limit to the size of the steel frame that can be accommodated in the gantry frame, which imposes constraints on the size of the welded assembly box-shaped cross-section members that can be manufactured.

[0008] Furthermore, when manufacturing four-sided welded box-shaped cross section members, the heat input by two-electrode submerged arc welding is a large amount, up to 500 kJ / cm. This can lead to a very slow cooling rate of the heat-affected zone and weld metal, potentially resulting in a decrease in the strength and toughness of the welded box-shaped cross section members.

[0009] In addition, submerged arc welding of the corners of the welded box-shaped cross-section members is performed in a downward welding position, requiring welding of one side of the welded box-shaped cross-section member at a time. Furthermore, the heat input from two-electrode submerged arc welding is large, which tends to lead to significant welding deformation. To keep this welding deformation within acceptable limits, it is necessary to attach numerous shape-retaining plates to the welded box-shaped cross-section member.

[0010] To address these issues, for example, Patent Document 1 proposes a method for manufacturing a welded box-shaped cross-sectional member, which involves fillet welding the corners of the welded box-shaped cross-sectional member from the inside to reduce the welding input. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Patent No. 5157556 [Overview of the project] [Problems that the invention aims to solve]

[0012] However, in the manufacturing method described in Patent Document 1, welding must be performed by a welder in the space inside the welded box-shaped cross-sectional member, which increases the workload of the welding work and may pose a risk to the welding process.

[0013] In view of the above-mentioned problems, the present invention aims to provide a welded assembly box-shaped cross section member and a method for manufacturing the same that does not require large-scale manufacturing equipment, can suppress the amount of heat input for welding, and can be manufactured with fewer man-hours. [Means for solving the problem]

[0014] To solve the above problems, the present invention has the following features.

[0015] [1] A welded box-shaped cross section member, comprising four skin plates assembled to form a rectangular cross section and then subjected to corner welding, wherein a first skin plate and a second skin plate are arranged on a pair of opposing faces, and a third skin plate and a fourth skin plate are arranged on another pair of opposing faces, sandwiched between the first skin plate and the second skin plate, grooves are provided at both ends of the first skin plate in the width direction, no grooves are provided on the second skin plate, of the ends of the third skin plate and the fourth skin plate in the width direction, one end which is corner-welded to the first skin plate is not provided, and the other end which is corner-welded to the second skin plate is provided on the outer surface side of the welded box-shaped cross section member, and the first to fourth skin plates are joined to each other by corner welding being performed on each groove.

[0016] [2] The welded assembly box cross section member according to [1], wherein each of the grooves is a V-groove.

[0017] [3] The welded assembly box-shaped cross section member according to [1] or [2], wherein the corner weld is a partial penetration weld.

[0018] [4] A method for manufacturing a welded box-shaped cross-sectional member according to [1] or [2], wherein the corner welding is performed on each groove by lateral welding.

[0019] A method for manufacturing a welded box-shaped cross-sectional member as described in [5] [3], wherein the corner welding is performed on each groove by lateral welding. [Effects of the Invention]

[0020] According to the welded box-shaped cross-sectional member and its manufacturing method of the present invention, even with a large wall thickness, a large manufacturing facility is not required, the amount of heat input for welding can be suppressed, and a welded box-shaped cross-sectional member can be manufactured with fewer steps. [Brief explanation of the drawing]

[0021] [Figure 1] FIG. 1(a) and FIG. 1(b) are cross-sectional views schematically showing an example of the welded and assembled box-shaped cross-sectional member of the present invention and a manufacturing method thereof. [Figure 2] FIG. 2 is a perspective view schematically showing a welding state of a groove in the manufacturing method of the welded and assembled box-shaped cross-sectional member of the present invention. [Figure 3] FIG. 3(a) and FIG. 3(b) are cross-sectional views schematically showing another example of the welded and assembled box-shaped cross-sectional member of the present invention and a manufacturing method thereof. [Figure 4] FIG. 4(a) and FIG. 4(b) are cross-sectional views schematically showing an example of a conventional welded and assembled box-shaped cross-sectional member and a manufacturing method thereof.

BEST MODE FOR CARRYING OUT THE INVENTION

[0022] Hereinafter, referring to the drawings, the welded and assembled box-shaped cross-sectional member of the present invention and a manufacturing method thereof will be described in detail. (First Embodiment) In FIG. 1(a) and FIG. 1(b), a cross-section of the welded and assembled box-shaped cross-sectional member 1 according to the first embodiment of the present invention and its manufacturing state are schematically shown.

[0023] As shown in FIG. 1(a), the welded and assembled box-shaped cross-sectional member 1 of the first embodiment is formed by performing fillet welding W in a state where four skin plates 11 to 14 are combined so as to have a rectangular cross-section. That is, the skin plates 11 to 14 are long thick steel plates constituting the four sides of the welded and assembled box-shaped cross-sectional member 1. The plate thickness of the skin plates 11 to 14 is about 9 mm to 100 mm, and particularly often 28 mm or more. Further, on the skin plates 11 to 14, a steel grade having a strength of 490 N / mm 2 class to 780 N / mm 2 class is often used.

[0024] The skin plates 11-14 consist of a pair of skin plates 11 and 12 arranged parallel to each other and facing each other, and another pair of skin plates 13 and 14 arranged parallel to each other and facing each other. These two pairs of skin plates 11-14 are arranged so that their longitudinal direction is along the material length direction of the welded box-shaped cross section member 1, and are combined to form a rectangular closed cross section, and are joined to each other by welding at the corners of the welded box-shaped cross section member 1. Specifically, the first skin plate 11 and the second skin plate 12 are arranged on a pair of faces of the welded box-shaped cross section member 1 that face each other. In addition, the third skin plate 13 and the fourth skin plate 14 are arranged on another pair of faces that face each other, sandwiched between the first skin plate 11 and the second skin plate 12.

[0025] Furthermore, as shown in Figure 1(b), both ends of the first skin plate 11 in the width direction are cut diagonally to provide a V-groove 11g. The second skin plate 12 does not have a groove. Also, of the two ends of the third skin plate 13 in the width direction, one end that is angularly welded to the first skin plate 11 (the upper end in Figure 1(b)) does not have a groove, while the other end that is angularly welded to the second skin plate 12 (the lower end in Figure 1(b)) is cut diagonally to provide a V-groove 13g. Similarly, of the two ends of the fourth skin plate 14 in the width direction, one end that is angularly welded to the first skin plate 11 (the upper end in Figure 1(b)) does not have a groove, while the other end that is angularly welded to the second skin plate 12 (the lower end in Figure 1(b)) has a V-groove 14g provided on the outer surface side of the welded assembly box-shaped cross section member 1 which is cut diagonally.

[0026] Then, corner welding W is performed on each of the aforementioned V-grooves 11g, 13g, and 14g by a welding robot 5, which will be described later, thereby joining the first to fourth skin plates 11 to 14 together to form a welded assembly box-shaped cross section member 1.

[0027] As shown in Figure 1(b), in the welded box-shaped cross section member 1 of the first embodiment, the aforementioned V-grooves 11g, 13g, and 14g are provided only in a portion of the thickness direction of the first, third, and fourth skin plates 11, 13, and 14. Furthermore, as shown in Figure 1(a), the corner welds W applied to the aforementioned V-grooves 11g, 13g, and 14g are partial penetration welds that do not reach the opposite side of the first, third, and fourth skin plates 11, 13, and 14. For this reason, no backing plate is provided on the back side of the corner welds W. The penetration depth of the partial penetration weld is determined according to the yield strength required for the welded box-shaped cross section member 1, but it is preferable to set it to more than half the thickness of the skin plate, as this reduces the risk of failure of the corner welds W.

[0028] The manufacturing method for the welded assembled box-shaped cross section member of this embodiment is a method for manufacturing the welded assembled box-shaped cross section member 1 described above, and is achieved by applying corner welds W to each of the above-mentioned V-grooves 11g, 13g, and 14g by lateral welding, as shown in Figure 1(b).

[0029] Figure 2 schematically shows the welding conditions of the V-grooves 11g, 13g, and 14g in the manufacturing method of the welded box-shaped cross section member of the first embodiment.

[0030] In the manufacturing method of the welded box-shaped cross section member of the first embodiment, various welding methods can be applied as the method of lateral welding, but as shown in Figure 2, it is preferable to apply MAG welding or MIG welding by automatic welding using a welding robot 5 that moves along guide rails 51. In this way, problems such as difficulty in supplying welding flux and dripping of molten metal, which occur when submerged arc welding is applied as the method of lateral welding, do not occur. The length of the welded box-shaped cross section member 1 used as a column member of a building can be up to nearly 10m, so the welding lengths of the V-grooves 11g, 13g, and 14g are also long, and the workload for semi-automatic welding by a welder is high. Therefore, as shown in Figure 2, by using a welding robot 5 that moves along guide rails 51 arranged along both sides of the welded box-shaped cross section member 1, lateral welding of the four V-grooves 11g, 13g, and 14g can be performed simultaneously, improving workability. This reduces the workload of the welder and allows the welded box-shaped cross section member 1 to be manufactured with fewer man-hours.

[0031] Here, in horizontal MAG welding or MIG welding, the amount of welding per pass is less compared to downward submerged arc welding as shown in Figures 4(a) and 4(b), which may increase the number of welding passes. Therefore, as shown in Figure 1(b), by making the horizontal corner welds W applied to each V-groove 11g, 13g, and 14g into partial penetration welds as described above, the amount of welding required to join the first to fourth skin plates 11 to 14 to each other can be suppressed. Furthermore, this eliminates the need to provide a backing plate on the back side of the corner welds W, and reduces the man-hours required to manufacture the welded assembly box-shaped cross section member 1.

[0032] Furthermore, by applying MAG welding or MIG welding, the amount of heat input can be reduced compared to welding methods with high heat input such as submerged arc welding, thereby suppressing the reduction in strength and toughness of the heat-affected zone of the corner weld W and preventing welding deformation.

[0033] Furthermore, in the manufacturing method of the welded box-shaped cross section member of the first embodiment, as described above, the four V-grooves 11g, 13g, and 14g can be welded horizontally simultaneously. Therefore, unlike submerged arc welding as shown in Figures 4(a) and 4(b), it is unnecessary to invert the welded box-shaped cross section members 8 and 9 vertically after welding the grooves 81g, 82g, 84g, and 94g on one side of the welded box-shaped cross section members 8 and 9 downwards, before welding the grooves 81g, 83g, 84g, and 93g on the opposite side downwards.

[0034] In addition, by simultaneously performing horizontal welding at four V-groove joints 11g, 13g, and 14g, the corner welds W on both sides of the welded box-shaped cross-sectional member 1 can be welded simultaneously and symmetrically. Therefore, compared to the case where downward submerged arc welding is used, welding deformation within the welded box-shaped cross-sectional member 1 can be suppressed. As a result, even if the number of shape-retaining plates welded into the welded box-shaped cross-sectional member 1 is reduced in order to keep the welding deformation within the allowable limit, the amount of deformation can be kept below a predetermined size, thus reducing the man-hours required to manufacture the welded box-shaped cross-sectional member 1.

[0035] Furthermore, in the manufacturing method of the welded box-shaped cross-sectional member of the first embodiment, by applying MAG welding or MIG welding, the welded box-shaped cross-sectional member 1 can be manufactured without introducing the large submerged arc welding equipment described above. Therefore, a new manufacturing line for the welded box-shaped cross-sectional member 1 can be set up with a relatively low investment. In addition, the manufacturing of the welded box-shaped cross-sectional member 1 can be carried out not only in the steel frame factory but also at the construction site, reducing the man-hours required for the manufacture of the welded box-shaped cross-sectional member 1, and enabling the manufacture of welded box-shaped cross-sectional member 1 of large sizes and special shapes that could not be manufactured with existing equipment. (Second Embodiment) Figures 3(a) and 3(b) schematically show a welded assembly box-shaped cross section member 2 according to a second embodiment of the present invention and its manufacturing process.

[0036] As shown in Figure 3(a), the welded assembly box-shaped cross section member 2 of the second embodiment is constructed in the same way as the first embodiment, by combining four skin plates 21 to 24 so that they form a rectangular cross section and then performing corner welding W.

[0037] As shown in Figure 3(b), both ends of the first skin plate 21 in the width direction are cut diagonally to provide a V-groove 21g. In addition, of the ends of the third skin plates 23 and 24 in the width direction, the end that is corner-welded to the second skin plate 22 (the lower end in Figure 3(b)) is cut diagonally to provide V-grooves 23g and 24g.

[0038] As shown in Figure 3(b), in the welded assembly box-shaped cross section member 2 of the second embodiment, the aforementioned V-grooves 21g, 23g, and 24g are provided over the entire thickness direction of the first, third, and fourth skin plates 21, 23, and 24. As shown in Figure 3(a), the corner welds W applied to the aforementioned V-grooves 21g, 23g, and 24g are full penetration welds that reach the opposite side of the first, third, and fourth skin plates 21, 23, and 24. For this reason, a backing plate 25 is provided on the back side of the corner welds W.

[0039] The method for manufacturing the welded assembled box-shaped cross section member of the second embodiment is a method for manufacturing the welded assembled box-shaped cross section member 2 described above, which is achieved by applying corner welds W to each of the above-mentioned V-grooves 21g, 23g, and 24g by lateral welding, as shown in Figure 3(b).

[0040] According to the welded box-shaped cross-sectional member and the manufacturing method of the welded box-shaped cross-sectional member of the second embodiment, the same effects as the first embodiment can be obtained.

[0041] In the embodiments described above, the case where each groove is a V-groove was explained, but the shape of each groove in the welded assembly box-shaped cross section member and its manufacturing method of the present invention is not limited to this. For example, the present invention can be applied to cases where each groove has other shapes such as J-grooves, and similar effects can be achieved. [Explanation of Symbols]

[0042] 1, 2, 8, 9 Welded assembly box-shaped cross section members 11, 21, 81, 91 First Skin Plate 12, 22, 82, 92 Second Skin Plate 13, 23, 83, 93 Third Skin Plate 14, 24, 84, 94 Fourth Skin Plate 11g, 13g, 14g, 21g, 23g, 24g, 81g, 82g, 83g, 84g, 93g, 94g Rectangular bevel 25, 85, 95 backing metal W-shaped welding 5. Welding robots 51 Guide rail

Claims

1. A welded box-shaped cross-sectional member is constructed by joining four skin plates together to form a rectangular cross-section and then applying corner welding, A first skin plate and a second skin plate are arranged on a pair of surfaces facing each other, and a third skin plate and a fourth skin plate are arranged on another pair of surfaces facing each other so as to be sandwiched between the first skin plate and the second skin plate. Bevels are provided at both ends in the width direction of the first skin plate. The second skin plate does not have a groove, Of the widthwise ends of the third and fourth skin plates, one end that is angularly welded to the first skin plate does not have a groove, while the other end that is angularly welded to the second skin plate has a groove on the outer surface side of the welded assembly box-shaped cross section member. A welded box-shaped cross-sectional member in which the first to fourth skin plates are joined to each other by applying angular welding to each of the grooves.

2. The welded assembly box-shaped cross section member according to claim 1, wherein each of the grooves is a V-groove.

3. The welded assembly box-shaped cross-sectional member according to claim 1 or claim 2, wherein the corner weld is a partial penetration weld.

4. A method for manufacturing a welded box-shaped cross-sectional member according to claim 1 or claim 2, wherein the corner welds are applied to each groove by lateral welding.

5. A method for manufacturing a welded box-shaped cross-sectional member according to claim 3, wherein the corner welds are applied to each groove by lateral welding.

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