JP2005095899A - Square steel tube manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a square steel tube manufacturing method capable of manufacturing a square steel tube of one seam by welding two times only. <P>SOLUTION: One butted portion 5 with grooves 2a and 2b butted to each other is formed by pressing the grooves from the outer side after folding a plate at a plurality of parts in the width direction 1B of the steel plate 1 with the grooves 2a and 2b formed at both edge portions 1C in the width direction 1B, and a square steel tube is manufactured by welding the butted portion 5. Welding is performed twice, in other words, an outer side welding 7 by an outer side welding machine 18 and an inner side welding 8 by an inner side welding machine 21 are performed by using MIG welding by the tandem DC system using mixed gas G of argon of about 90% and carbon dioxide of about 10%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing a rectangular steel pipe that is employed to manufacture a large-diameter, thick-walled rectangular steel pipe such as a rectangular parallelepiped shape or a rectangular parallelepiped shape that is used for, for example, a building column.

Conventionally, in order to manufacture this type of square steel pipe, a strip is conveyed in the length direction, and the groove is processed on both side edges in the width direction through a trimming groove processing machine. Then, the steel strip is put in the former forming press apparatus, and corners at right angles (90 degrees) are bent and formed at two locations near the side edge. Next, it is put in a subsequent forming press apparatus, and corners with an obtuse angle (about 105 degrees) are bent at two intermediate positions. And by pressurizing the four sides from the outside at the part of the tack welding machine, the obtuse corners are formed into a rectangular steel pipe by butting the grooves while forming a right-angled corner. Install. Next, after moving the rectangular steel pipe to the inner surface welder and performing inner surface welding, it is transferred to the outer surface welder and outer surface welding is performed, so that it has a large diameter and thick wall with a butt weld (seam weld) on one side. Can be manufactured (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 10-216839 (2nd page, FIG. 5-6)

  However, according to the above-described method for manufacturing a rectangular steel pipe, it is necessary to perform three times of welding, that is, tack welding, inner surface welding, and outer surface welding, which requires welding time. In addition, the square steel pipe must be rotated 180 degrees when moving to internal welding after tack welding, and the square steel pipe must be rotated 180 degrees again when moving to external welding after internal welding. Equipment is required and time is spent for the rotation work.

Accordingly, an object of the invention described in claim 1 of the present invention is to provide a method of manufacturing a rectangular steel pipe capable of manufacturing a one-seam rectangular steel pipe by only two welding operations.
The second aspect of the invention is to provide a method of manufacturing a rectangular steel pipe in which welding can be performed in a state in which a magnetic blow (arc blow) phenomenon is unlikely to occur.

  In order to achieve the above-mentioned object, a method for manufacturing a rectangular steel pipe according to claim 1 of the present invention is the outer side after bending a plurality of portions in the width direction of a steel sheet having grooves formed on both edges in the width direction. Is pressed to form a butt portion where the grooves are butted together, and this butt portion is welded to produce a square steel pipe. Welding is about 90% argon and about 10% carbon dioxide. The tandem direct current method MIG welding using a mixed gas is performed by two welding operations of outer surface welding by an outer surface welding machine and inner surface welding by an inner surface welding machine.

  Therefore, according to the invention of claim 1, after bending the corner corresponding to the product bending angle such as a right angle at a plurality of places, the two edges are brought into close contact with each other by pressurizing from the outside, so that the grooves are connected. It can be set as the square-shaped steel pipe which formed one butt | matching part made close to each other. Next, outer surface welding is performed between the grooves by an outer surface welding machine. Thereby, in the butt | matching part, outer surface welding can be constructed to about half of the outer side in the thickness direction.

  Next, after rotating the square steel pipe by 180 degrees, it is transferred to an inner surface welding machine, and inner surface welding is performed between the grooves by this inner surface welding machine. Thereby, in a butting | matching part, inner surface welding can be constructed to about the inner half in the thickness direction. By such outer surface welding and inner surface welding, a one-seam, large-diameter, thick-walled square steel pipe (product) can be manufactured. In this case, the outer surface welding and the inner surface welding can be easily controlled by MIG welding by a tandem direct current method using a mixed gas of about 90% argon and about 10% carbon dioxide.

  Further, in the method for manufacturing a rectangular steel pipe according to claim 2 of the present invention, in the configuration according to claim 1 described above, the MIG welding by the tandem direct current method is disposed with a torch interval of 120 to 300 mm in the welding direction. It has a pair of torches, the advance angle of these torches is set to 0-9 degrees, and welding is performed while a pair of wires are fed from each of the torches in the welding direction. It is.

  Therefore, according to the invention of the second aspect, the welding in the thickness direction at the butt portion can be performed efficiently by increasing the welding speed and in a state where the “magnetic blowing phenomenon” is less likely to occur. In other words, the “magnetic blowing phenomenon”, which is a defect due to the tandem (two-electrode) DC MIG method, has been solved by improving the equipment, etc., so that even if there is a slight gap in the butt portion (butt weld), welding is performed. Therefore, high-speed and complete continuous welding can be performed without falling off.

  The method for manufacturing a rectangular steel pipe according to claim 3 of the present invention is characterized in that, in the configuration according to claim 1 or 2, the welding direction is an approaching or separating direction with respect to the ground position. .

  Therefore, according to the invention of claim 3, when welding is performed in a direction away from the ground position, the bead shape can be finished with a succeeding torch. If the welding direction is changed to the approaching direction (approaching direction) for a short distance and then the separation direction, it will reduce the need to push the molten metal in front of the arc at the start, and further weld to the ground position. When the direction is the approaching direction, large penetration welding can be performed with the preceding torch.

  Furthermore, the manufacturing method of the square steel pipe according to claim 4 of the present invention is characterized in that, in the configuration according to any one of claims 1 to 3, the plate thickness of the steel sheet is 9 to 19 mm. It is.

  Therefore, according to the invention of claim 4, a thick square steel pipe (product) can be manufactured.

  According to the first aspect of the present invention described above, one butt portion in which the grooves are brought close to each other by pressurizing from the outside after bending a corner corresponding to the product bending angle such as a right angle at a plurality of positions. Can be formed into a square steel pipe. Next, by performing external surface welding between the grooves with the external surface welding machine, external surface welding can be performed on the outer half in the thickness direction at the butt portion. And after rotating a square-shaped steel pipe 180 degree | times, it moves to an inner surface welding machine, and by this inner surface welding machine, inner surface welding is performed between gaps, About half of the inner side in thickness direction in a butt | matching part Can be welded on the inside. By such outer surface welding and inner surface welding, it is possible to manufacture a square steel pipe (product) with a single seam and a large diameter and a thick wall.

  At that time, the outer surface welding and the inner surface welding are easy and easy to control by MIG welding by tandem direct current method using a mixed gas of about 90% argon and about 10% carbon dioxide gas. Quality (continuous) welding can be performed at low cost. Furthermore, the welding time can be shortened because only two welding operations, outer surface welding by the outer surface welding machine and inner surface welding by the inner surface welding machine, are required. Moreover, since it is only necessary to rotate the square steel pipe 180 degrees once when moving to the outer surface welding after the inner surface welding, the rotation facility can be simplified at one place, and the rotation work time can be shortened. It will be possible.

  According to the second aspect of the present invention described above, the welding in the thickness direction at the butt portion can be performed efficiently by increasing the welding speed and in a state where the “magnetic blowing phenomenon” is difficult to occur. In other words, the “magnetic blowing phenomenon”, which is a defect due to the tandem (two-electrode) DC MIG method, has been solved by improving the equipment, etc., so that even if there is a slight gap in the butt portion (butt weld) High-speed and complete continuous welding can be achieved without falling off by welding. Thereby, compared with the submerged arc welding conventionally employ | adopted for the seam welding of a steel pipe, it is cheap and can perform high quality welding with few heat inputs.

  According to the third aspect of the present invention described above, when welding is performed in a direction away from the ground position (a direction away from the ground), a good bead shape can be finished by the subsequent torch. In addition, when the welding direction is set to the approaching direction (approaching direction) for a short distance from the ground position and then the separation direction is performed, the start of the molten metal at the start of the arc is reduced and the start is reduced. It is possible to better control the partial welding, and when the welding direction is the approaching direction with respect to the ground position, welding with a large penetration can be performed with the preceding torch.

  Furthermore, according to claim 4 of the present invention described above, a thick square steel pipe (product) can be easily manufactured.

[Embodiment 1]
Below, Embodiment 1 of this invention is demonstrated based on FIGS. 1-4 as the state employ | adopted for manufacture of a square steel pipe.

  As shown in FIG. 1, a strip steel plate (an example of a steel plate) 1 having a thickness t of 9 to 19 mm is conveyed in the length direction 1A, passed through a trimming groove processing machine 11, and both edges in the width direction 1B. The grooves 2a and 2b are processed inside and outside 1C, and cut into a predetermined length before and after this.

  Then, as shown in FIG. 2, the strip steel plate 1 is put in the former forming press device 12, and the upper die 14 is moved up and down with respect to the lower die 13 so as to be perpendicular to the two positions near both edge portions 1C in the width direction 1B. The corner 3 of the shape (90 degrees) is bent and formed. Next, the steel strip 1 is placed in a subsequent forming press device 15, and the corner 4 having an obtuse angle (about 105 degrees) R is bent and formed at two intermediate positions by moving the upper mold 17 up and down relative to the lower mold 16. .

  As shown in FIG. 3, in the outer surface welding machine 18, the four sides are pressed from the outside by the rolls 19 and 20 groups (or cylinders) to form the corner 4 of the obtuse angle R into a right-angled shape r. A square steel pipe 6 having a single butted portion 5 in which the edge portion 1C is brought into substantial contact with each other so that the inner and outer grooves 2a, 2a, 2b, and 2b are brought close to each other can be obtained. Next, the outer surface welding machine 18 applies the outer surface welding 7 between the outer grooves 2 a and 2 a in the butt portion 5 of the rectangular steel pipe 6.

  At that time, the outer surface welding 7 uses a mixed gas G of 90% (about 90%) of argon and 10% (about 10%) of carbon dioxide as a shielding gas through the cover 25, and the cover 25 It is performed by MIG welding by a tandem direct current method used as a wire 2 electrode by passing two 1.3 mm and 1.6 mm wires W inside. Thereby, in the butt | matching part 5, the outer surface welding 7 can be constructed to about half of the outer side in the thickness direction.

  Next, the rectangular steel pipe 6 is rotated 180 degrees and then transferred to the inner surface welding machine 21, and the inner surface welding machine 21 performs inner surface welding 8 between the inner grooves 2 b and 2 b in the butt portion 5 of the rectangular steel pipe 6. Install. At that time, in the same manner as the outer surface welding 7 described above, the inner surface welding 8 passes a mixed gas G of 90% (about 90%) of argon and 10% (about 10%) of carbon dioxide through the cover 25. It is performed by MIG welding by a tandem direct current method that is used as a wire 2 electrode by passing two 1.3 mm and 1.6 mm wires W through the cover 25. Thereby, in the butt | matching part 5, the inner surface welding 8 can be constructed to about the inner half in the thickness direction.

  By such outer surface welding 7 and inner surface welding 8, as shown in FIG. 4, it is a one-seam having a butt weld portion 9 on one side, and has a large diameter with an outer dimension L of 250 to 1000 mm and a thickness t of 9 to 9 mm. A 19 mm thick rectangular steel pipe (product) 10 can be manufactured.

  At that time, the outer surface welding 7 and the inner surface welding 8 can be performed in a state where the mixed gas G is shield gas (inert gas) and the two wires W are positioned in the flow so as to be shielded from the air. The direct current type MIG welding makes control easy and enables high-speed and complete (high quality) continuous welding at low cost. Furthermore, the welding time can be shortened because only two welding operations of the outer surface welding 7 by the outer surface welding machine 18 and the inner surface welding 8 by the inner surface welding machine 21 are required. Moreover, since it is only necessary to rotate the rectangular steel pipe 6 once by 180 degrees when moving to the outer surface welding after the inner surface welding, the rotation facility can be simplified at one place and the time for the rotation work can be simplified. It can be shortened.

In other words, the “magnetic blowing phenomenon”, which is a defect due to the tandem (two-electrode) DC MIG method, has been solved by improving the equipment, etc., so that even if there is a slight gap in the butt portion (butt weld 9). High-speed and complete continuous welding is possible without falling off by welding. Thereby, compared with the submerged arc welding conventionally employ | adopted for the seam welding of a steel pipe, it is cheap and high quality welding with few heat inputs.
[Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 5, after being bent and formed by the forming press devices 12 and 15, in the portion of the outer surface welding machine 18, the four sides are pressurized from the outside by the rolls 19 and 20 groups (or cylinders), so that the obtuse angle R is increased. While forming the corner 4 into a right-angled shape r, the two edge portions 1C are brought into close contact with each other, so that a square steel pipe 6 having one butted portion 5 in which the grooves are brought close to each other can be formed. Here, the square steel pipe 6 has the groove 2 processed only on the outer side of both edge portions 1C, and therefore adopts a Y-type double-sided welding method. At that time, for example, when the plate thickness t is 12 mm, the groove angle C formed by the two grooves 2 is about 70 degrees, and the groove depth D is 6 to 7 mm.

Then, the outer surface welding machine 18 applies the outer surface welding 7 between the grooves 2 in the butt portion 5 of the rectangular steel pipe 6. That is, as shown in FIGS. 6 to 8, the outer surface welding machine 18 (same for the outer surface welding machine 21) that performs tandem direct current MIG welding is arranged with a torch interval A of about 180 mm apart in the welding direction B. It has a pair of torches, that is, a root pass torch 18A and a finishing pass torch 18B. And the advance angle θ of both torches 18A and 18B is set to 4 degrees, and a pair of wires WA ₁ , WA ₂ , WB ₁ and WB _{2 in} the welding direction B from each of both torches 18A and 18B, The welding is performed while being fed through the covers 25A and 25B.

Here, the leading wires WA ₁ and WB ₁ in both torches 18A and 18B are 1.6 mm, and the trailing wires WA ₂ and WB ₂ are 1.3 mm. And as cover 25A, 25B, it is about 37 mm in the welding direction B (side view direction), is about 20 mm in the direction (front view direction) orthogonal to the welding direction B, and an elliptical thing is used by planar view. Is done. The torch interval A between the pair of torches 18A and 18B is arranged at a distance of about 180 mm, and this is configured such that the interval can be adjusted within a range of 120 to 300 mm. Further, the advancing angle θ of the torches 18A and 18B is set to be inclined by 4 degrees, but this is configured such that the angle can be adjusted in the range of 0 to 9 degrees.

  As described above, when the plate thickness t of the rectangular steel pipe 6 is 12 mm, the groove angle C is about 70 degrees, and the groove depth D is 6 to 7 mm, the torch height HA of the root path torch 18A is The distance from the lower end of the cover 25A to the groove bottom is adjusted to 18 mm, and the torch height HB of the finishing pass torch 18B is adjusted to set the distance from the lower end of the cover 25B to the outer surface of the rectangular steel pipe 6 to 18 mm. Yes.

  On the rectangular steel pipe 6 side, as shown in FIG. 9 (a), the welding direction B is set as the separation direction, and the root path ground position 28A and the finish path ground position 28B are set, or as shown in FIG. 9 (b). In addition, the welding direction B is changed to the approach direction after a short distance and then the separation direction, and the root path ground position 28A and the finish path ground position 28B are set. As shown in FIG. 9C, the welding direction B is approached. The route path ground position 28A and the finish path ground position 28B are set.

According to the second embodiment, in the outer surface welder 18, the torch interval A between the two torches 18A and 18B is arranged at about 180 mm, and the advance angle θ of both the torches 18A and 18B is set to 4 degrees. The inclination is set. Then, for example, feed rate of the wire _{WA 1, WA 2, WB 1} , WB 2 is wire WA ₁ prior in root path torch 18A is 400～420Ipm, wire WA ₂ of the rear row is adjusted to 450Ipm, also finishing Pasutochi The leading wire WB ₁ in 18B is adjusted to 350 to 425 ipm, and the trailing wire WB ₂ is adjusted to 400 to 450 ipm.

First, as shown in FIG. 6 and FIG. 7, the outer surface welding 7 under such conditions is performed in the preceding stage while a pair of wires WA ₁ and WA ₂ are fed through the cover 15A in the preceding route path torch 18A. Next, as shown in FIGS. 6 and 8, in the subsequent finishing path torch 18B, a pair of wires WB ₁ and WB ₂ are fed through the cover 15B, and the latter welding is performed on the former welding 7a. This is done by constructing 7b.

At that time, welding uses a mixed gas G of 90% (about 90%) of argon and 10% (about 10%) of carbon dioxide gas as a shielding gas through the covers 25A and 25B, and the cover 25A. , 25B, two wires WA ₁ , WA ₂ , WB ₁ , WB ₂ are fed respectively to perform MIG welding by a tandem direct current method used as a wire 2 electrode.

  Then, as shown in FIG. 8A, when the outer surface welding 7 as described above is performed with the welding direction B as the separation direction (the direction away from the root path ground position 28A or the finish path ground position 28B), the finishing torch 18B is used. A better bead shape finish can be obtained. Further, as shown in FIG. 8B, when the welding direction B is set to the approach direction (approaching direction) for a short distance from the root path ground position 28A and the finish path ground position 28B, the arc is generated at the start. This will reduce the need to push the molten metal forward, giving better control of the start weld. Further, as shown in FIG. 8C, when the welding direction B is set as the approaching direction (the approaching direction) with respect to the root path ground position 28A and the finishing path ground position 28B, welding with a large penetration can be performed by the root path torch 18A.

  By these things, in the butt | matching part 5, the outer surface welding 7 can be efficiently performed by making the welding speed into 2 M / min in about half of the outer side in the thickness direction. Moreover, welding can be performed in a state where the magnetic blow (arc blow) phenomenon is less likely to occur. In other words, the “magnetic blowing phenomenon”, which is a defect due to the tandem (two-electrode) DC MIG method, has been solved by improving the equipment, etc., so that even if there is a slight gap in the butt portion (butt weld 9). High-speed and complete continuous welding is possible without falling off by welding. Thereby, compared with the submerged arc welding conventionally employ | adopted for the seam welding of a steel pipe, it is cheap and high quality welding with few heat inputs.

As shown in FIG. 5, the inner surface welding 8 can also be performed by an inner surface welding machine 21 of the same type.
In Embodiment 2 described above, the preceding wires WA ₁ , WB ₁ and the following wires WA ₂ , WB ₂ are fed through the respective covers 25A, 25B, which are all wires WA ₁ , WB. ₁ , WA ₂ , WB ₂ may be sent through a common cover.

  In both the above-described embodiments, a rectangular parallelepiped rectangular steel pipe (product) 10 having a butt weld portion 9 on one side is manufactured. However, this may be a manufacture of a rectangular parallelepiped rectangular steel pipe (product).

  In both of the above-described embodiments, a large-diameter and thick rectangular steel pipe (product) 10 having a butt weld portion (seam weld portion) 9 on one side is manufactured. This is a large-diameter and thin-walled rectangular steel pipe, The manufacturing may be a small diameter and thick rectangular steel pipe, a small diameter and thin rectangular steel pipe, or a hexagonal steel pipe or an octagonal steel pipe.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows Embodiment 1 of the present invention and is an explanatory view up to a groove forming step in a method for manufacturing a rectangular steel pipe. It is explanatory drawing to the 4 corner part formation process in the manufacturing method of the square steel pipe. It is explanatory drawing to the welding process in the manufacturing method of the square steel pipe. It is explanatory drawing of the square steel pipe manufactured in the manufacturing method of the square steel pipe. It is Embodiment 2 which shows Embodiment 2 of this invention, and is explanatory drawing to the welding process in the manufacturing method of a square steel pipe. It is a side view of the outer surface welding machine in the manufacturing method of the same square steel pipe. It is a front view of the root path torch part of the outer surface welding machine in the manufacturing method of the same square steel pipe. It is a front view of the finishing pass torch part of the outer surface welding machine in the manufacturing method of the same square steel pipe. It is a schematic plan view explaining the ground position in the manufacturing method of the same square steel pipe.

Explanation of symbols

1 Steel strip (steel)
1B Width direction 1C Edge 2a groove 2b groove 2 groove 3 corner 4 corner 5 butt 6 square steel pipe 7 outer surface welding 7a front welding 7b rear welding 8 inner surface welding 9 butt welding 10 rectangular steel pipe (product)
DESCRIPTION OF SYMBOLS 11 Trimming groove processing machine 12 Forming press apparatus 15 of a front | former stage Forming press apparatus 18 of a back | latter stage Outer surface welding machine 18A Root pass torch (torch)
18B Finishing Path Torch (Torch)
19 roll 20 roll 21 inner surface welding machine t plate thickness L outer size G mixed gas W wire A torch interval B welding direction θ advance angle WA ₁ wire WA ₂ wire WB ₁ wire WB ₂ wire

Claims (4)

After bending a plurality of locations in the width direction of the steel sheet with grooves formed on both edges in the width direction, by pressing from the outside, a single abutting portion that matches the grooves is formed. In order to produce a rectangular steel pipe by welding, welding is performed by MIG welding by a tandem direct current method using a mixed gas of about 90% argon and about 10% carbon dioxide gas. A method for manufacturing a rectangular steel pipe, characterized by performing welding twice with internal welding by a welding machine. The tandem DC method MIG welding has a pair of torches arranged with a torch interval of 120 to 300 mm in the welding direction, and the advance angle of these torches is set to 0 to 9 degrees. The method of manufacturing a rectangular steel pipe according to claim 1, wherein welding is performed while a pair of wires are fed in a welding direction. The method for manufacturing a square steel pipe according to claim 1 or 2, wherein the welding direction is a direction close to or away from the ground position. The plate thickness of a steel plate is 9-19 mm, The manufacturing method of the square steel pipe of any one of Claims 1-3 characterized by the above-mentioned.

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