JPH11123450A - Production of round steel tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method for a round steel tube having the reduced whole equipment cost and a good working efficiency. SOLUTION: By pressing from the outside after plural places in a width direction of a strip steel are bent and by welding at least part of a butt part of side edges 2, a polygon shaped steel tube 7 is formed, this polygon shaped steel tube 7 is formed round by a round tube forming machine 30. Pressing for forming the ploygon shaped steel tube 7 may be done several times. Because a welding part of tack welding 8, etc., is turned to a flat part, edge bending is not required. The round tube forming machine 30 passing the polygon shaped steel tube having tack welding 8 for round shape forming can be used for a polygon shaped steel tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a round steel pipe used for obtaining a large-diameter and thick-walled round steel pipe used for, for example, a column material for a building.

[0002]

2. Description of the Related Art Conventionally, this kind of round steel pipe has been manufactured as follows. That is, as shown in FIG. 9, the strip steel plate 50 is conveyed in the length direction, passed through a groove processing machine 60 to form grooves 51 on both side edges in the width direction, and cut to a predetermined length before and after this. . Then, the strip steel plate 50 is put into an end bending machine 61, and two places near the side edge are bent by elevating and lowering (pressing) the upper die with respect to the lower die. Next, the steel strip 50 is put into a press forming machine 62 and formed into an approximately circular steel pipe 52.

[0003] Then, the approximate circular steel pipe 52 is put into a tack welding machine 63 and press-formed from the outside, so that the grooves 51 are joined together while forming into a circular shape to form a circular steel pipe 53. Temporary welding 54 to butt
To construct. Next, the circular steel pipe 53 is connected to the inner surface welding machine 64.
To the inner surface welding 55 and then to the outer surface welding machine 65.
Then, the outer surface welding 56 is performed. After the bead is removed by the bead removing device 66, the bead is corrected by the straightening device 67 to produce a large-diameter, thick-walled round steel pipe (product) 58 having a seal portion 57 at one location in the circumferential direction. .

[0004] Or, as shown in FIG. 10, after two end bendings near the side edge are performed by an end bending forming machine 61, the resultant is put into a U bending forming machine 68 and formed into a U-shaped steel plate 59.
The U-shaped steel plate 59 is put into a round bending machine 69 and formed into a circular steel pipe 53. Thereafter, steps similar to those of the above-described conventional method (FIG. 9) are performed.

[0005]

However, according to the above-mentioned conventional manufacturing method, a dedicated line for manufacturing a round steel pipe (product) 58 is required, and thus a dedicated line for manufacturing a square steel pipe is required. When the line is provided, the total equipment cost increases. Also, in the step of forming the steel strip 50 into the approximate circular steel pipe 52 in the press forming machine 62, since it is pressed several tens of times with a press and gradually formed into a round shape, a considerable amount of time is required in this step. The efficiency was poor. In addition, since the welded portion such as the tack weld 54 becomes an arc portion, it is necessary to perform the end bending by the end bending machine 61, which increases the equipment cost and lowers the work efficiency.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a round steel pipe which can reduce the total equipment cost and has a high working efficiency.

[0007]

In order to achieve the above-mentioned object, a method for manufacturing a round steel pipe according to the first aspect of the present invention comprises bending a plurality of portions in a width direction of a steel strip, and then bending the steel strip from the outside. By pressure shaping, a butt portion of a side edge is formed on one side, and at least a part of the butt portion is welded to form a polygonal steel pipe, and the polygonal steel pipe is formed into a round shape by a round tube forming machine. It is characterized by the following.

According to the first aspect of the present invention, a strip steel plate is formed into a polygonal steel tube, and then the polygonal steel tube is formed into a round shape by a round tube forming machine, thereby forming a press into a polygonal steel tube. Pushing is only required several times. In addition, since the welded portion such as the tack welding becomes a flat portion, it is not necessary to perform the end bending. Further, when the round forming shape of the polygonal steel pipe on which the tack welding has been performed is passed (passed) by the round pipe forming machine, the square steel pipe can be manufactured using the same line.

According to a second aspect of the present invention, there is provided a method for manufacturing a round steel pipe, wherein a plurality of portions in the width direction of the steel strip are bent to form a bent steel plate, and the plurality of bent steel plates have abutting portions of side edges at the plurality of portions. After being arranged so as to be formed, at least a part of these butted portions is welded into a polygonal steel pipe, and the polygonal steel pipe is formed into a round shape by a round tube forming machine.

Therefore, according to the second aspect of the present invention, a round steel pipe having butt welds (seam welds) at a plurality of locations can be manufactured.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the strip steel plate 1 is transported in the length direction 1A, and
To form grooves 2 on both side edges in the width direction 1B,
Before and after this, it is cut to a predetermined length. Then, the steel strip 1 is put into the pre-forming press 21, and the upper die 2 with respect to the lower die 22.
By the lifting and lowering movement of 3, the large radius R-shaped corners 3 and 4 are bent and formed at two places near the side edge.

Then, as shown in FIG. 2, the upper mold 26 is put into a post-forming press 24, and the upper mold 26 is moved up and down with respect to the lower mold 25 to bend the large radius R-shaped corners 5 and 6 at two intermediate positions. Molding. Then, in the part of the tack welding machine 27, the four sides are pressed and shaped from the outside by the rolls 28 and 29 (or cylinders), so that the grooves 2 are butted together, and the square steel pipe (polygonal steel pipe) 7 After that, the tack welding 8 is performed on the butted portion.

Next, as shown in FIG.
Into the round tube forming machine 30 (see the solid line), and the upper die 32 is moved up and down with respect to the lower die 31 to form the square steel tube 7 into a round shape, thereby forming the round steel tube 9 (virtual line). reference). Thereafter, the round steel pipe 9 is transferred to the inner surface welding machine 33 to perform the inner surface welding 10, and then transferred to the outer surface welding machine 34 to perform the outer surface welding 11.

Then, as shown in FIG. 4, the round steel pipe 9 is transferred to a bead removing device 35 to remove the outer bead, and then the round steel pipe 9 is put into a straightening machine 36 to be straightened. A large-diameter and thick-walled round steel pipe (product) 13 having a butt weld (seam weld) 12 can be manufactured.

As shown in FIG. 5, the square steel pipe 7 on which the tack welding 8 has been performed is passed (passed) by the round forming machine 30 using a round pipe forming machine 30. When the inner welding 10 is performed by the welding machine 33 and the outer welding 11 is performed by the outer welding machine 34, the square steel pipe (product) 15 can be manufactured using the same line. As described above, since the square steel pipe 15 can be manufactured using the line for manufacturing the round steel pipe (product) 13, the overall equipment cost can be reduced.

Further, after the strip steel plate 1 is formed into a square steel pipe 7, the square steel pipe 7 is formed into a round shape by a round tube forming machine 30. Four (several) times are sufficient, and the time in the pressing process is shortened, and the work efficiency is improved. In addition, since the welded portion such as the tack weld 8 becomes a flat portion, it is not necessary to perform the end bending, and the equipment cost is reduced and the work efficiency is improved.

Next, a second embodiment of the present invention will be described with reference to FIG.
It will be described based on. That is, after the inner surface welding machine 33 performs the inner surface welding 10 on the square steel pipe 7 to which the tack welding 8 has been performed, the outer surface welding machine 34 performs the outer surface welding 11. Next, after the outer bead is removed by the bead removing device 35, the square steel pipe 7 is put into the round tube forming machine 30 (see the solid line), and the upper mold 32 is moved up and down with respect to the lower mold 31 so that the square steel pipe is moved. 7 is formed into a round shape, thereby forming a round steel pipe 9 (see a virtual line).
Then, the round steel pipe 9 is put into a straightening machine 36 and straightened, so that the butt weld portion (seam weld portion) 12 is formed at one place.
And a large-diameter, thick-walled round steel pipe (product) 13 having the following characteristics.

Next, a third embodiment of the present invention will be described with reference to FIG.
It will be described based on. That is, the strip steel plate 1 is
A is passed through the groove processing machine 20 to process the groove 2 on both side edges in the width direction 1B, and cut to a predetermined length before and after this. Then, the strip steel plate 1 is put into the forming press 40, and the large radii R-shaped corners 3 and 4 are bent and formed at two positions near the side edge by the ascending and descending movement of the upper die with respect to the lower die. The bent steel plate 15 has a shape (channel shape).

Next, in the part of the tack welding machine 27, the four sides are rolled in a state where a pair (plurality) of bent steel plates 15 are arranged so that a butt portion of the groove 2 is formed at two positions (plurality). The grooves 2 and 29 are pressed and shaped from the outside to butt the grooves 2 to each other to form a square steel pipe (polygonal steel pipe) 7, and then the temporary welding 8 is applied to the butt portion. After that, steps similar to those of the above-described first and second embodiments are performed.

According to the third embodiment, the butt-welded portion (seam-welded portion) 12
And a large-diameter, thick-walled round steel pipe (product) 13 having the following characteristics. Next, a fourth embodiment of the present invention will be described with reference to FIG.

That is, a hexagonal steel pipe 17 is shown as a polygonal steel pipe. As described above, as the polygonal steel pipe, a plurality of square steel pipes including the square steel pipe 7 and the hexagonal steel pipe 17 can be used.

In each of the above-described embodiments, the round steel pipe 13 (product) manufactured is put into a heating furnace or the like in a subsequent step, so that the round steel pipe 13 can be heated. In each of the embodiments described above, the press-type round tube forming machine 30 including the lower die 31 and the upper die 32 is shown, but this may be a roll-type round tube forming machine 30. In the round tube forming machine 30, for example, a lower die 31 and an upper die 32 having different sizes are prepared according to the diameter of the round steel pipe (product) 13 to be manufactured.

In each of the above-described embodiments, the round tube forming machine 30 and the straightening machine 36 are arranged in the line. However, the round tube forming machine 30 may serve as the straightening machine 36 as well. In each of the above-described embodiments, the former-stage forming press 21 and the latter-stage forming press 24 are arranged in the line. However, this may be of a type in which four moldings are performed by one molding press.

In each of the above-described embodiments, a large-diameter and thick-walled round steel pipe (product) 13 having a butt weld (seam weld) 12 at one or a plurality of places is manufactured. Production of a large-diameter thin-walled round steel pipe, a small-diameter thick-walled round steel pipe, a small-diameter thin-walled round steel pipe, or the like may be performed.

[0025]

According to the first aspect of the present invention, after the strip steel sheet is formed into a polygonal steel pipe, the polygonal steel pipe is formed into a round shape by a round pipe forming machine, thereby forming a polygonal steel pipe. Pressing for pressing may be performed only a few times, so that the time in the pressing process can be shortened and the working efficiency can be improved. In addition, since the welded portion such as the tack welding becomes a flat portion, it is not necessary to perform the end bending, so that the equipment cost can be reduced and the work efficiency can be improved. Further, when the round forming shape of the polygonal steel pipe subjected to tack welding is passed (passed) by the round pipe forming machine, the square steel pipe is manufactured using the line (the same line) for manufacturing the round steel pipe. Can be manufactured, and the total equipment cost can be reduced.

According to the second aspect of the present invention, a round steel pipe having butt welds (seam welds) at a plurality of locations can be manufactured with reduced equipment costs and improved work efficiency.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of the present invention and is an explanatory diagram up to a pre-press step in a method for manufacturing a round steel pipe.

FIG. 2 is an explanatory diagram up to a tack welding step in the method of manufacturing the round steel pipe.

FIG. 3 is an explanatory view up to a double-sided welding step in the method of manufacturing the round steel pipe.

FIG. 4 is an explanatory view up to a final step in the method of manufacturing the round steel pipe.

FIG. 5 shows a second embodiment of the present invention and is an explanatory diagram of steps in a method for manufacturing a round steel pipe.

FIG. 6 shows a third embodiment of the present invention and is an explanatory process diagram in a method of manufacturing a round steel pipe.

FIG. 7 is a view illustrating a fourth embodiment of the present invention and is a process explanatory view in a method of manufacturing a round steel pipe.

FIG. 8 shows a fifth embodiment of the present invention and is an explanatory view of a polygonal steel pipe.

FIG. 9 shows a conventional example and is an explanatory view of a process in a method of manufacturing a round steel pipe.

FIG. 10 is an explanatory view showing another conventional example and a process in a method of manufacturing a round steel pipe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Strip steel plate 1A Length direction 1B Width direction 2 Groove (side edge) 7 Square steel pipe (Polygonal steel pipe) 8 Temporary welding 9 Round steel pipe 12 Butt weld 13 Round steel pipe (product) 14 Square steel pipe (product) 15) Bent steel plate 17 Hexagonal steel pipe (polygonal steel pipe) 20 Groove processing machine 21 Pre-stage forming press 24 Post-stage forming press 27 Temporary welding machine 30 Round tube forming machine 33 Inner surface welding machine 34 Outer surface welding machine 35 Bead removing device 36 Straightening Machine 40 forming press

Claims (2)

[Claims] 1. After bending a plurality of portions in the width direction of a strip steel plate, by pressing and shaping from the outside, a butt portion of a side edge is formed on one side, and at least a part of the butt portion is welded. A method for producing a round steel pipe, comprising forming a polygonal steel pipe into a round shape using a round pipe forming machine. 2. A plurality of bent steel plates are bent at a plurality of positions in the width direction of the strip steel plate, and the plurality of bent steel plates are arranged so that the butt portions of the side edges are formed at the plurality of positions. Is formed into a polygonal steel pipe by welding, and the polygonal steel pipe is formed into a round shape by a round pipe forming machine.